Kharagpur, India

The Indian Institutes of Technology is a prestigious group of autonomous public engineering and management institutes of India. The IITs are governed by the Institutes of Technology Act, 1961 which has declared them as "institutions of national importance", and lays down their powers, duties, framework for governance etc. The Institutes of Technology Act, 1961 lists sixteen institutes located at Bhubaneswar, Chennai, Delhi, Gandhinagar, Guwahati, Hyderabad, Indore, Jodhpur, Kanpur, Kharagpur, Mandi, Mumbai, Patna, Ropar, Roorkee and Varanasi. Each IIT is an autonomous institution, linked to the others through a common IIT Council, which oversees their administration. The IITs award degrees ranging from B.Tech to PhD.The IITs have a common admission process for undergraduate admissions. It was called IIT-JEE, which was replaced by Joint Entrance Examination in 2013. The post-graduate level program that awards M.Tech degree in engineering is administered by the older IITs . M.Tech admission is done on the basis of Graduate Aptitude Test in Engineering . In addition to B.Tech and M.Tech programs IITs also award other graduate degrees such as M.Sc in Engineering, Maths, Physics and Chemistry, MBA, PhD etc. Admission to these programs of IITs is done through Common Admission Test, Joint Admission Test for Masters and Common Entrance Examination for Design . Wikipedia.

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Chakraborty S.,Indian Institute of Technology Kharagpur | Chattopadhyay S.,Indian Institute of Technology Kharagpur
ECCE 2016 - IEEE Energy Conversion Congress and Exposition, Proceedings | Year: 2016

This paper proposes a dual-active bridge (DAB)-based isolated microinverter topology with integrated energy storage capability. A control strategy involving dynamic variation of the phase-shift allows twice line frequency energy buffering to be handled on the high-voltage secondary side, resulting in considerable reduction in decoupling capacitance requirement. Being a DAB-derived structure, most of the devices have the possibility of undergoing zero-voltage-switching (ZVS) turn-on. The topology has further advantages of the battery and PV port currents having very less high frequency ripple on account of them being inductively interfaced. Working principle of the circuit is first described followed by an explanation of the control scheme. Circuit operation is verified through simulations and open-loop experimental tests on a 250 W hardware prototype. © 2016 IEEE.

Sreehari V.M.,Indian Institute of Technology Kharagpur | Maiti D.K.,Indian Institute of Technology Kharagpur
Structural and Multidisciplinary Optimization | Year: 2017

Optimization with Unified Particle Swarm Optimization (UPSO) method is performed for the enhancement of buckling load capacity of composite plates having damage under hygrothermal environment which has received little or no attention in the literature. Numerical results are presented for effect of damage in buckling behavior of laminated composite plates using an anisotropic damage model. Optimized critical buckling temperature of laminated plates with internal flaw is computed with the fiber orientation as the design variable by employing a UPSO algorithm and results are compared with undamaged case for various aspect ratios, ply orientations, and boundary conditions. FEM formulation and programming in the MATLAB environment have been performed. The results of this work will assist designers to address some key issues concerning composite structures. It is observed that the degradation of buckling strength of a structural element in hygrothermal environment as a result of internal flaws can be avoided to a large extent if we use these optimized ply orientations at design phase of the composite structure. This specific application proves the contribution of present work to be of realistic nature. © 2016, Springer-Verlag Berlin Heidelberg.

Kumar Y.S.,Indian Institute of Technology Kharagpur | Poddar G.,Indian Institute of Technology Kharagpur
IEEE Transactions on Industrial Electronics | Year: 2017

For the application of variable speed drive, submodule capacitors of the modular multilevel converter (MMC) suffer from large voltage fluctuations at low frequencies. This paper presents a control technique that regulates this fluctuation to a constant value at all speeds with rated load torque. Transformerless configuration of this drive is as follows. An MMC is used as a front-end converter and is directly connected to the grid. It keeps the grid current sinusoidal and is in phase with the grid voltage. It generates regulated dc current at the output. Another MMC, connected in cascade with the earlier one, drives a three-phase induction motor. Therefore, the input to this rear-end MMC is constant dc current, the output is variable magnitude and frequency voltage source that drives the motor. This paper proposes a control strategy for this drive. The proposed control method and its performance have been analyzed and verified through experimental results in this paper. © 2016 IEEE.

Laha P.,Indian Institute of Technology Kharagpur | Chakraborty B.,Indian Institute of Technology Kharagpur
Renewable and Sustainable Energy Reviews | Year: 2017

Energy model, a systematic data-intensive multi-objective framework replicating the energy sector of the country or globe, constitutes of energy resource supply, energy consumption sector-by-sector, energy transformation technologies, greenhouse gas emission and energy pricing. Considering the atypical weather pattern yearly and geographical diversity, the challenges and benefits of designing an energy model have been summarized. The paper has documented the tremendous jeopardy of drastic climate change, energy crisis on the global economy, requirement for transition to low carbon economy and rural electrification which have been impetus for the evolution of legitimate energy model. Special emphasis has been provided on the types of energy models that have been developed and practiced throughout the world followed by a comparative analysis of a few. The requirement to configure a unique energy model in India followed by certain recommendations has been proposed in this paper. © 2017 Elsevier Ltd

Das S.,Indian Institute of Technology Kharagpur | Das D.,Indian Institute of Technology Kharagpur | Patra A.,Indian Institute of Technology Kharagpur
Renewable and Sustainable Energy Reviews | Year: 2017

This paper presents the reconfiguration of the distribution network in the presence of distributed generations (DGs) by considering two bus types i.e., P bus and PQV bus (remotely voltage controlled bus). The ‘P’ bus is represented by active power specification only whereas the PQV bus is one whose voltage is remotely controlled by the P bus. A methodology is proposed to select the P bus for controlling the voltage magnitude of remotely located PQV bus. A sensitivity analysis approach is used for selecting the buses for the placement of DGs operating at unity power factor. The placement of DGs is done in two ways i.e., non-sequential placement and sequential placement of DG in a distribution network. Genetic algorithm (GA) technique is used for the optimization of DGs followed by network reconfiguration. The objective function for network reconfiguration in this paper is considered to be real power loss reduction. Effectiveness of the proposed method is demonstrated through examples of 33 bus and 69 bus distribution networks. © 2017 Elsevier Ltd

Sahu S.,Indian Institute of Technology Kharagpur | Banerjee A.,Indian Institute of Technology Kharagpur | Maji M.S.,Indian Institute of Technology Kharagpur
Organic Letters | Year: 2017

The synthesis of sensitive β-alkyl 3-vinylindoles having diverse functional groups with good selectivity remains a challenging task. Keeping the synthetic utility of 3-alkenylindoles in mind, we explored a unique approach to synthesize them from unprotected indoles in a domino fashion. A transition-metal-free C3-alkenylation of indole is reported by using sequential Brønsted acid/base catalysis. Several β-substituted 3-alkenylindoles and conjugated 1,3-dienes are synthesized by direct coupling of indole and readily available aliphatic aldehydes. Excellent scalability and recycling of benzenesulfinic acid for successive alkenylation reactions up to five times make this method economically viable. © 2017 American Chemical Society.

Pahar G.,Indian Institute of Technology Kharagpur | Dhar A.,Indian Institute of Technology Kharagpur
Journal of Hydrology | Year: 2017

A robust Incompressible Smoothed Particle Hydrodynamics (ISPH) framework is developed to simulate specified inflow and outflow boundary conditions for open-channel flow. Being purely divergence-free, the framework offers smoothed and structured pressure distribution. An implicit treatment of Pressure Poison Equation and Dirichlet boundary condition is applied on free-surface to minimize error in velocity-divergence. Beyond inflow and outflow threshold, multiple layers of dummy particles are created according to specified boundary condition. Inflow boundary acts as a soluble wave-maker. Fluid particles beyond outflow threshold are removed and replaced with dummy particles with specified boundary velocity. The framework is validated against different cases of open channel flow with different boundary conditions. The model can efficiently capture flow evolution and vortex generation for random geometry and variable boundary conditions. © 2017 Elsevier B.V.

Saha N.,Indian Institute of Technology Kharagpur | Dutta Gupta S.,Indian Institute of Technology Kharagpur
Journal of Hazardous Materials | Year: 2017

Chemically synthesized silver nanoparticles (chem-AgNPs) have been assessed extensively to show adverse effects on plant cells but the role of biologically synthesized nanoparticles (bio-AgNPs) at lower concentrations and their toxicological impact on plant cells have not been sufficiently studied. In this study, bio-AgNPs were prepared using aqueous leaf extracts of Swertia chirata. This AgNPs showed absorption peak at 440 nm of the visible spectrum. TEM analysis revealed that the average size of AgNPs were 20 nm and mainly spherical in shape. AFM topographic images depicted the three dimensional aspects of AgNPs. XRD analysis confirmed the crystalline nature. FTIR spectrum of the AgNPs revealed the possible biomolecules involved in bioreduction and efficient stabilization of the particles. Low-dose of bio-AgNPs concentrations (5, 10 and 20 μg ml−1) were used for toxicity studies on Allium cepa. The studies revealed that various chromosomal aberrations were induced in both mitotic and meiotic cells of Allium cepa even at lower concentrations of bio-AgNPs. Abnormalities in post meiotic products were also observed. Both mitotic and meiotic indexes decreased with increasing concentrations of bio-AgNPs in the treated cells. These findings implied that low dose bio-AgNPs can induce significant clastogenic effects on both meristematic and reproductive plant cells. © 2017 Elsevier B.V.

Basak B.,Indian Institute of Technology Kharagpur | Gupta S.,Indian Institute of Technology Kharagpur
Computers, Environment and Urban Systems | Year: 2017

Religious mass gatherings require proper movement planning for pilgrims in crowded situations. Most religious towns are old and have informal infrastructure with haphazard road networks, which results in improper connectivity. However, the sacredness of religious festivals calls for gatherings of millions of pilgrims within a limited space and duration. The annual Ratha Yatra at Puri is an event that is manually controlled by the logistics provided by the district authorities. Pedestrian crowds move along a 3-kilometre stretch of the road to witness the manual dragging of three chariots for around 4 h. The objective of this paper is to understand crowd characteristics at a particular location during the event and suggest for crowd evacuation in emergencies through identified exit routes. In Ratha Yatra 2015, a single-camera video recording of the event was performed from an overhead location. The individual video frames were perspective-rectified and analyzed to detect human shapes and extract parameters of crowd density, flow, and speed. The results were simulated through an agent-based model to trigger an evacuation process at critical crowd densities. A similar approach using multiple cameras at multiple locations in a large mobility network can provide a decision-making tool to adopt safety measures in mass gatherings. © 2017 Elsevier Ltd

Dutta S.,Indian Institute of Technology Kharagpur
Concurrency Computation | Year: 2017

Transformations for high-performance superscalar, vector, and parallel processors maximize parallelism and memory locality. Often parallelizing compilers apply transformations, such as loop parallelization and loop vectorization, to convert a sequential array-handling program into a parallel program. Validation of such transformations is extremely useful in the prevalent high-performance computing environment. This paper proposes a novel algorithm for construction of the dependence graph of the generated parallel programs. These transformations are validated by checking equivalence of the dependence graphs of the original sequential program and the transformed parallel program using a standard algorithm reported in the literature. The above equivalence checker works even when the above parallelizing transformations are preceded by various enabling transformations except for loop collapsing transformation that changes the dimensions of the arrays. In the present paper, the scope of the equivalence checker has been expanded to handle this special case by informing it of the correspondence between the index spaces of the corresponding of input and output arrays in the sequential and the parallel programs. The proposed methods are implemented and tested against a set of available benchmark programs that are parallelized by the polyhedral auto-parallelizer LooPo and the auto-vectorizer Scout. © 2017 John Wiley & Sons, Ltd.

Debnath S.K.,Indian Institute of Technology Kharagpur | Dutta R.,Indian Institute of Technology Kharagpur
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2017

The availability of electronic information is necessary in our everyday life. Progressively, often, data needs to be shared among the unreliable entities. In this field, one interesting and common problem occurs when two parties want to secretly determine the intersection or cardinality of intersection of their respective private sets. PSI or its variants are ideal to solve the aforementioned problems. Existing solutions of mPSI and mPSI-CA mainly use trusted third party to achieve fairness. However, in real life, the unconditional trust is fraught with security risks as the trusted third party may be unfaithful or corrupted. As a consequence, construction of an efficient mPSI-CA preserving fairness remains a challenging problem. In this paper, we address this issue by employing an off-line third party, called arbiter, who is assumed to be semi-trusted in the sense that he does not have access to the private information of the entities while he will follow the protocol honestly. In this work, we design a construction of fair and efficient mPSI-CA utilizing Bloom filter. Our mPSI-CA is proven to be secure in the random oracle model (ROM) and achieves linear communication and computation overheads. A concrete security analysis is provided in malicious environments under the Decisional Diffie-Hellman (DDH) assumption. © Springer International Publishing AG 2017.

Biswas R.,Indian Institute of Technology Roorkee | Bhowmick P.,Indian Institute of Technology Kharagpur
Journal of Mathematical Imaging and Vision | Year: 2017

This paper presents a novel study on the functional gradation of coordinate planes in connection with the thinnest and tunnel-free (i.e., naive) discretization of sphere in the integer space. For each of the 48-symmetric quadraginta octants of naive sphere with integer radius and integer center, we show that the corresponding voxel set forms a bijection with its projected pixel set on a unique coordinate plane, which thereby serves as its functional plane. We use this fundamental property to prove several other theoretical results for naive sphere. First, the quadraginta octants form symmetry groups and subgroups with certain equivalent topological properties. Second, a naive sphere is always unique and consists of fewest voxels. Third, it is efficiently constructible from its functional-plane projection. And finally, a special class of 4-symmetric discrete 3D circles can be constructed on a naive sphere based on back projection from the functional plane. © 2017 Springer Science+Business Media New York

Roy Chowdhury S.,Indian Institute of Technology Kharagpur | Mishra S.,Indian Institute of Technology Kharagpur
European Journal of Inorganic Chemistry | Year: 2017

Linear or near-linear bicoordinate mononuclear CoII complexes are studied as potential single-molecule magnets owing to the strong spin–orbit coupling constant of CoII and its low coordination number, which results in the retention of the unquenched metal-orbital angular momentum. The spin–orbit-coupled unquenched orbital angular momentum of the metal center produces strong magnetic anisotropy through ligand-field interactions. The role of the ligand environment, structural distortions, and conformational changes on the magnetic anisotropy of CoII complexes are investigated through ab initio electronic-structure calculations. The zero-field splitting parameters, g tensors, and transition-magnetic-moment matrix elements among the Kramers pairs are evaluated to obtain the effective anisotropy barriers (Ueff) and the mechanism for the relaxation of magnetization in a series of CoII complexes, for which the estimated values of Ueff range between 394 and 974 cm–1 and include the largest effective anisotropy barriers reported for transition-metal complexes. The calculations reveal that the ligand-field strength, structural distortion, and conformational changes not only affect the magnetic anisotropy barrier but also significantly alter the mechanism of relaxation of the magnetic moments. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Kundu A.,Indian Institute of Technology Kharagpur | Kundu A.,National Institute of Plant Genome Research
Planta | Year: 2017

Main conclusion: The present review compiles the up-to-date knowledge on vanillin biosynthesis in plant systems to focus principally on the enzymatic reactions ofin plantavanillin biosynthetic pathway and to find out its impact and prospect in future research in this field.Vanillin, a very popular flavouring compound, is widely used throughout the world. The principal natural resource of vanillin is the cured vanilla pods. Due to the high demand of vanillin as a flavouring agent, it is necessary to explore its biosynthetic enzymes and genes, so that improvement in its commercial production can be achieved through metabolic engineering. In spite of significant advancement in elucidating vanillin biosynthetic pathway in the last two decades, no conclusive demonstration had been reported yet for plant system. Several biosynthetic enzymes have been worked upon but divergences in published reports, particularly in characterizing the crucial biochemical steps of vanillin biosynthesis, such as side-chain shortening, methylation, and glucoside formation and have created a space for discussion. Recently, published reviews on vanillin biosynthesis have focused mainly on the biotechnological approaches and bioconversion in microbial systems. This review, however, aims to compile in brief the overall vanillin biosynthetic route and present a comparative as well as comprehensive description of enzymes involved in the pathway in Vanilla planifolia and other plants. Special emphasis has been given on the key enzymatic biochemical reactions that have been investigated extensively. Finally, the present standpoint and future prospects have been highlighted. © 2017 Springer-Verlag Berlin Heidelberg

Yedla N.,National Institute of Technology Rourkela | Ghosh S.,Indian Institute of Technology Kharagpur
Intermetallics | Year: 2017

To identify the atomistic mechanism of plastic deformation in metallic glasses (MGs), classical molecular dynamics (MD) simulation of plastic deformation of amorphous Cu50Zr50 alloy is carried out for the strain rates varying from 10−3 s−1 to 1011 s−1 and for two states of stress viz. pure shear and uniaxial tension. Although MD studies of plastic deformation in MGs have been widely reported previously, atomic movements have seldom been studied. In the present study, random movement of atoms, as observed in diffusion, is observed irrespective of the strain rate and state of stress. The average ratio of distance traveled to the magnitude of net displacement by an atom, within a time interval, is found to increase with strain rate. It suggests that the randomness in the atomic trajectories, although present, decreases with the strain rate. At high strain rates, control masses are observed to translate (convective flow) and exchange atoms with their neighboring control masses, losing their individuality within a short time. These observations clearly suggest that there is no such thing as shear transformation zone (STZ), and the atomistic mechanism of plastic deformation in MGs is exactly like that in liquid. © 2016 Elsevier Ltd

Guha A.,Indian Institute of Technology Kharagpur | Pradhan K.,Indian Institute of Technology Kharagpur
International Journal of Thermal Sciences | Year: 2017

Similarity analysis shows that Nux varies as Grx 1/4 for natural convection on an isothermal vertical surface but Nux varies as Grx 1/5 for isothermal horizontal surfaces. It is thus difficult to develop a rigorously-derived, closed-form solution for Nux on a surface with arbitrary inclination. In the present study we have formulated, for the first time, a unified integral theory for laminar natural convection on an arbitrarily inclined surface, both for specified variation in surface temperature (Tw(x) = T∞ + f1(x)) and surface heat flux (qw = f2(x)), such that the Nusselt number matches with results obtained from the similarity analysis in the limiting cases of vertical and horizontal surfaces. The predictions of the present formulation also agree well with previous computational and experimental results at intermediate angles of inclination between the vertical and the horizontal. f1(x) or f2(x) can be any arbitrary function, including power law variation, and represents a differentially heated surface. Another important feature of the present integral theory is that the developed generalized equations can accommodate arbitrary orders of polynomials (λ and χ) representing the velocity and temperature profiles, and optimum values for λ and χ have been systematically determined for various boundary conditions (i.e. λ = 4, χ = 2 for isothermal case and λ = 3, χ = 2 for constant-heat-flux case). Because of the simplicity of the present theory, it is easy to generate results for combinations of Grashof number, Prandtl number and inclination angle not presented here. The different physical mechanisms for natural convection on vertical and horizontal surfaces (buoyancy versus indirect pressure difference) are explained with the help of the present analysis. It is shown that for moderate to high Prandtl number fluids, the natural convection mechanism for vertical surface is the dominating factor for a large range of inclination angles except for near horizontal configurations. The range of inclination angles for which the vertical solution predominates decreases as the Prandtl number decreases. For very low Prandtl number fluids at low Grashof number, the vertical mechanism applies only to nearly vertical surfaces. A physical explanation for such behaviour is discovered here, for the first time, in terms of the relative magnitudes of the buoyancy and indirect pressure difference. Compact scaling laws for significant data reduction are proposed and explained. New algebraic correlations have been developed that give Nusselt number as explicit functions of Grashof number, Prandtl number and inclination angle. A new methodology for the representation of the results brings out more powerfully the role of inclination angle in determining the heat transfer rate as well as the mechanism of natural convection. © 2016 Elsevier Masson SAS

Pal A.K.,Indian Institute of Technology Kharagpur | Datta S.N.,Indian Institute of Technology Bombay
Chemical Physics Letters | Year: 2017

Six diradicals designed from imino nitroxide, verdazyl and nitronyl nitroxide monoradicals coupled via the ferrocene moiety and six corresponding triradical cations are quantum chemically investigated. The transoid conformation is employed for considerations of general stability. All biradicals are found as very weakly and antiferromagnetically coupled. This agrees with experiment. The cations have strong antiferromagnetic spin-coupling. The charge and spin population distributions, spin alternation pattern, and the disjoint nature of SOMOs can be used to explain the nature and extent of magnetic interaction. Calculated EPR characteristics identify the neutral species as well as their cations as possible single molecule magnets. © 2017 Elsevier B.V.

Pal P.,Indian Institute of Technology Kharagpur | Nanda S.,Indian Institute of Technology Kharagpur
Organic Letters | Year: 2017

A short and flexible asymmetric synthesis of ramariolides A and C was accomplished. A bimetallic catalytic system consisting of Pd-Cu-mediated cascade cyclization, unprecedented Z-E isomerization by a Ru-based metathesis catalyst, and late-stage stereoselective epoxidation are the key steps involved in the synthesis. © 2017 American Chemical Society.

Garai M.,Indian Institute of Technology Kharagpur | Biradha K.,Indian Institute of Technology Kharagpur
Crystal Growth and Design | Year: 2017

The coordination polymers (CPs) of bis(3-pyridyl-Acrylamido)ethane (L) with nitrate, acetate, and perchlorate salts of Cu(II), Cd(II), and Zn(II) were synthesized, and their crystal structures have been analyzed with respect to the influence of anions, hydrogen bonding, and their solid state [2 + 2] photochemical reactivity. Four out of the six CPs (1-4) containing NO3 -and AcO- ions were found to form one-dimensional chains and exhibit solid state [2 + 2] reactivity. Two CPs (5-6) containing ClO4 - ions were found to form ML2 discrete complexes which are photostable. The CPs 1 and 4 were found to form single [2 + 2] dimers, while 2 and 3 resulted in the formation of polymers via solid state [2 + 2] polymerization upon irradiation. The photoproducts are characterized by 1H NMR, electrospray ionization mass spectrometry, and matrix-Assisted laser desorption/ ionization-Time of flight (MALDI-TOF) spectra. The dimer was charecterized by single crystal X-ray structure determination. The MALDI-TOF analyses of polymers indicate the highest degree (29-mer) of polymerization. ©2016 American Chemical Society.

Jana A.K.,Indian Institute of Technology Kharagpur
Applied Thermal Engineering | Year: 2017

In this contribution, a thermally coupled dividing tower batch rectifier (TCDTBR) is proposed. Aiming to boost the fuel efficiency and economic performance, the cylindrical shell of the batch column is horizontally divided into two diabatic sections. A compressor is installed in such a way that one section operates at sufficiently higher pressure than the other one to create a positive thermal driving force between them for feasible heat exchange. The internal heat integration between these two coupled sections in TCDTBR arrangement can be accomplished by using the sequential heat exchangers in the trays. Proposing a variable manipulation policy, this thermal intensification mechanism is demonstrated by a batch rectifier that separates a binary mixture of wide boiling constituents, showing a substantial improvement in both fuel consumption (i.e., energy) and cost savings. Finally, the proposed TCDTBR has shown its superiority over an existing heat integrated batch rectifier with a jacketed reboiler (HIBRJR) on the same example system. © 2017 Elsevier Ltd

Raj S.,Indian Institute of Technology Kharagpur
1st IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems, ICPEICES 2016 | Year: 2016

Non-linear system such as Double Inverted Pendulum has been balanced using Reinforcement Learning. Reinforcement Learning has been utilized to develop a controller for stabilization of a Double Inverted Pendulum. A physics based simulation model has been constructed using the bond graphs in the simulations to develop the controller. The input, output and control parameters are defined using bond graph model making it easier to associate with the physical model. Reinforcement Learning does not require training set of data and linearization of equation of motion. It is valid over wide range of angle variation. Simulation results show the effectiveness of the Reinforcement Learning as compared to Linear Quadratic Regulator. © 2016 IEEE.

Ray M.C.,Indian Institute of Technology Kharagpur
Composite Structures | Year: 2017

This paper is concerned with the development of a mesh free model for the static analysis of smart nanobeams. The top surface of the substrate nanobeam is integrated with a flexoelectric layer which acts as the distributed actuator of the nanobeam. A layer wise displacement theory has been used to derive the model. Both thick and thin substrate nanobeams are considered for presenting the numerical results. The responses of the smart nanobeams computed by the present new mesh free model based on the layer wise displacement theory excellently match with those obtained by the exact solutions. The performance of the active flexoelectric layer either as an axial or as a shear actuator has been investigated. Variation of the control authority of the active flexoelectric layer with its thickness has also been investigated. The model derived here suggests that the mesh free method can be efficiently used for the numerical analysis of smart nanostructures coupled with flexoelectric actuator layer. © 2016 Elsevier Ltd

Bhowmik A.,Indian Institute of Technology Kharagpur | Dutta N.N.,Auburn University | Roy S.,Ben - Gurion University of the Negev
Astrophysical Journal | Year: 2017

The present work reports transition line parameters for Xe viii, which are potentially important for astrophysics in view of recent observations of multiply ionized xenon in hot white dwarfs. The relativistic coupled-cluster method is employed here to calculate the E1, E2, and M1 transition line parameters with high accuracy. The E1 oscillator strengths and probabilities of E2 and M1 transitions are determined using theoretical amplitudes and experimental energy values. The calculated branching ratios and the lifetimes are supplemented to the transition parameters. The accurate presentation of these calculated data is crucial for density estimation in several stellar and interstellar media. © 2017. The American Astronomical Society. All rights reserved.

Upadhyay S.,Indian Institute of Technology Kharagpur
EPL | Year: 2017

A massive Aharony-Bergman-Jafferis-Maldacena (ABJM) model in N = 1 superspace is analysed by considering a Proca-type mass term into the most general Faddeev-Popov action in a covariant gauge. The presence of a mass term breaks the original BRST and anti-BRST invariance of the model. Further, the symmetry of the massive ABJM model is restored by extending the BRST and anti-BRST transformations. We show that the supergauge dependence of the generating functional for connected diagrams occurs in the presence of mass and ghost-anti-ghost condensates in the theory. © EPLA, 2017.

Rajeshwari P.,Indian Institute of Technology Kharagpur | Dey T.K.,Indian Institute of Technology Kharagpur
Materials Chemistry and Physics | Year: 2017

The inclusion of inorganic nano-fillers with high mechanical strength in polymers could enhance efficiently the nano-mechanical properties of polymer-matrix (nano) composites. In this article, low-cost, high mechanical strength and stable crystal structured Aluminum nitride (nano) particles were incorporated into a High-density polyethylene (HDPE) thermoplastic polymer-matrix fabricated by melt-blending, compression moulding followed by hot pressing for investigation of nano-mechanical properties of HDPE/AlN nanocomposites. Nano-mechanical properties of HDPE/AlN (nano) composites (0-20 vol%) were measured by Quasi-static nanoindentation technique. A standard Berkovich indenter was used to make indentations under four different normal loads viz., 700, 1000, 3000 and 5000 μN, respectively. The surface topographies of the indented regions were monitored by AFM. The micro-structure of AlN (nano)/HDPE composites were characterized by intermittent tapping mode AFM, XRD, FEG-SEM and HR-TEM. The results showed that the homogenous distribution of AlN (nano) particles in the HDPE polymer-matrix affected the nano-mechanical properties of AlN (nano)/HDPE composites significantly. Nano-mechanical properties of the composites display substantial improvement with increasing AlN (nano) content in HDPE. The results are discussed with reference to AlN (nano) particles dispersion, interfacial adhesion and effective load transfer in AlN (nano) particles filled HDPE polymer composites. © 2017 Elsevier B.V.

Mondal S.,Indian Institute of Technology Kharagpur | Khastgir D.,Indian Institute of Technology Kharagpur
Polymer Testing | Year: 2017

The paper reveals the influence of different methods of carbon black (CB) incorporation in the compatible blend of 50/50 (wt %) Ethylene vinyl acetate (EVA) and Acrylonitrile butadiene elastomer (NBR) on different properties of vulcanized blend compounds. The partitioning of two types of CB in two different phases of the blend was estimated from dynamic mechanical analysis (DMA). The distribution of CBs due to preferential addition in different phases of the blend affects property variations in different degrees. From the analysis of SEM, TEM, AFM and electrical property measurements, it is found that mixing method significantly affects the electrical properties, morphology, and surface topography. The variation in AC conductivity and surface resistance study confirms the formation of different conductive network of CB with variation in mixing technique and it is supported by morphology analysis. The DMA have shown that CB has higher affinity towards less viscous EVA phase. This is further corroborated by the surface energy measurement, which in turn controls the electrical conductivity behaviour as well as mechanical properties of the blends. © 2017

Ghosh I.,Indian Institute of Technology Kharagpur
IOP Conference Series: Materials Science and Engineering | Year: 2017

In compressor driven solid sorption process, cooling obtained from a desorbing bed (equivalent to an evaporator), is intermittent in nature. Intermittency can be avoided using multiple adsorbent columns. However, connecting a desorbing bed to heat source and adsorbing beds to heat sink in alternate cycles enhances operational complexity and constructional disadvantages. In a recent development, it has been seen that rapid and successive pressurization and depressurization of an adsorbent (solid) bed with adsorbate (gas) creates temperature differential across the column length. The presence of an orifice at the end opposite to gas entrance enhances the temperature gradient. By connecting the hot end to heat sink and the cold end to heat source permanently, one can substantially reduce the operational hazards associated with the intermittent sorption cooling processes. More recently, it has seen that the introduction of a regenerator in the process makes the cooling process more effective. Though the proposed sorption cooling process apparently looks similar to orifice type 'pulse tube' cooler, the former is intrinsically different than the other. In the present manuscript, experimental sorption cooling studies using of metal foam as regenerator has been discussed. Tests have been conducted near room temperature in activated carbon-nitrogen system. © Published under licence by IOP Publishing Ltd.

Ray S.K.,Indian Institute of Technology Kharagpur
Optics InfoBase Conference Papers | Year: 2016

We shall present the fabrication of 2D-materials heterojunctions on silicon for photonic devices. Electrical and optical characteristics of devices using luminescent MoS2 quantum dots, plasmonic graphene oxide and a few-layer WS2 will be reviewed. © OSA 2016.

Varshney S.K.,Indian Institute of Technology Kharagpur
Optics InfoBase Conference Papers | Year: 2016

Mid-IR fiber parametric and supercontinuum sources, based on capillary-assisted chalcogenide optical fibers-providing great design space and tunability feature to achieve wideband parametric gain and tunable multi-peaks dispersive-wave generation, would be presented and discussed. © OSA 2016.

Rawat S.,Indian Institute of Technology Kharagpur | Mitra N.,Indian Institute of Technology Kharagpur
Computational Materials Science | Year: 2017

We perform molecular dynamics simulations to simulate the c-axis compression of single crystal Ti at high strain rates under uniaxial strain conditions. Since it is well known that molecular dynamics simulations heavily rely upon the type of potential used, a comprehensive study is presented in which four different commonly utilized potentials for Ti (Ackland, Mishin, Kim and Hennig) are evaluated against their abilities to demonstrate different variants of compression twins, dislocation structures and structural phase transformation. We find that {101¯1} and {112¯2} twins activate for Ackland and Mishin potentials, while only {101¯1} twins activate for Kim potential. No compression twin systems activate for Hennig potential. The c-vector analysis of unknown structure generated with Ackland, Mishin and Kim potentials shows that the unknown structure has {101¯1} twin-like orientations and the structure factor analysis gives a signature of pressure-induced ω phase for the twin-like oriented unknown structure. No signature of twin-like oriented unknown structure and ω phase is observed for Hennig potential. The large amount of dislocation density is observed for Ackland potential followed by Mishin, Kim and Hennig potentials. The presence of compression twins and high dislocation density for Ackland, Mishin and Kim potentials suggest that the c-axis deformation is accommodated by twins and slip together, while only slip accommodates the c-axis deformation for Hennig potential. Based on these observations and as well as on the formulation of the above mentioned potentials, Kim potential is being recommended for use under c-axis uniaxial compressive strain loading situations. © 2016 Elsevier B.V.

Panicker S.S.,Indian Institute of Technology Kharagpur | Panda S.K.,Indian Institute of Technology Kharagpur
Journal of Manufacturing Science and Engineering, Transactions of the ASME | Year: 2017

Automotive industries are very much interested in implementing warm forming technology for fabrication of light weight auto-body panels using aluminum alloys without localized thinning or splitting. A nonheat treatable and low formable AA5754-H22 aluminum alloy sheet was selected in the present work, and a laboratory scale warm deep drawing test set-up and process sequences were designed to improve material flow through independent heating of punch and dies. Significant enhancement in cup depth was observed when the temperature of punch and dies were set to 30 °C and 200 °C, respectively. Thermo-mechanical finite-element (FE) model of the nonisothermal deep drawing test was developed successfully to study the improvement in material flow incorporating Barlat-89 yield theory using temperature dependent anisotropy coefficients and Cowper-Symonds hardening model. It was found that a nonisothermal temperature gradient of approximately 93 °C was established within the blank from the center to flange at the start of deformation, and subsequent evolution of temperature gradient helped in improving material flow into the die cavity. The effect of temperature gradient on forming behavior in terms of cup height, ear profile, and thinning development across flange, cup wall, and blank center were predicted and validated with experimental results. © 2017 by ASME.

Saha G.,Indian Institute of Technology Kharagpur | Biligiri K.P.,Indian Institute of Technology Kharagpur
Materials and Structures/Materiaux et Constructions | Year: 2017

The study utilized response surface methodology and optimized fracture toughness characteristics that affect the cracking performance of different asphalt mixtures in respect of four parametric variables. The experimental investigation included determination of fracture toughness KIC of nine conventional dense graded asphalt mixes with four replicates per mix type totalling 96 specimens using the static semicircular bending (SCB) test. The statistical response modelling on experimental results showed a good agreement with the predicted data, which certified the appropriateness of the optimization process. Further, the statistical optimization indicated that the measure of fracture resistance of an asphalt mix could be optimized (maximized) at lower test temperatures for thicker specimens prepared with high asphalt content and low air voids. A significant contribution of this study was to devise and use a methodology to optimize the cracking resistance (here, KIC) of asphalt mixes based on a rational test method such as SCB, which could potentially become an algorithm for characterizing any other response parameter in future. © 2016, RILEM.

Rose L.,Indian Institute of Technology Kharagpur | Bhaskaran P.K.,Indian Institute of Technology Kharagpur
Estuarine, Coastal and Shelf Science | Year: 2017

The Head Bay of Bengal is highly vulnerable to flooding events caused due to monsoons, cyclones and sea-level rise, owing to its funnel-like shape, high tidal range, presence of numerous river drainage systems, low-lying topography, and shallow bathymetry. Tides dominate the hydrodynamic behaviour and coastal processes in this region and its propagation is quite distinct. The present study uses ADCIRC hydrodynamic model customized for the Head Bay of Bengal, discretized using unstructured finite elements and validated against limited available observations in this data sparse region. The water-level elevations derived from ADCIRC simulation was used to understand the pattern of non-linear tidal propagation with respect to complex coastal geomorphology prevalent in this region. The study finds a marginal amplification of diurnal tide, nearly double amplification of semi-diurnal components, and existence of a degenerate amphidromic point near Meghna delta consistent with previous studies. The spatial and temporal variability of tidal spectral components were examined by applying the techniques of wavelet, harmonic, and time-series analysis at various locations. Maximum amplification of tides occurs at the head of the bay, along a zone enclosing the mouth of tidal inlets; and for regions northward, the tides decay with progressively increasing phase lags. The study signifies dominance of a forced fortnightly tide and tidal asymmetry leading to flood-dominance in the rivers Hooghly, Meghna, and Tetulia. The non-linear properties of tides have been elucidated, and their origin and spatio-temporal variability in these riverine systems were further investigated. Shallow depth and sharp depth gradients were discerned to be the important conditions for the origin of non-linear components. It has been deduced that non-linear tides are generated in regions where propagating tides are accumulated, and amplified in regions where they are funneled. A study of tidal energetics show that maximum rate of tidal energy dissipation is deep inside the rivers at head of the bay. The spatial variability analysis of tidal form factor shows an overall semi-diurnal dominance in the Head Bay. © 2017 Elsevier Ltd

Venudharan V.,Indian Institute of Technology Kharagpur | Biligiri K.P.,Indian Institute of Technology Kharagpur
Materials and Structures/Materiaux et Constructions | Year: 2017

The objective of this study was to evaluate the effect of various crumb rubber (CR) gradations on asphalt binder performance leading to the development of a rational asphalt-rubber (AR) binder selection procedure. The scope encompassed advanced asphalt binder rheological characterization and statistical analyses in order to formulate a methodical procedure to select an optimum AR material. A total of twenty asphalt binders covering over 5000 data points were utilized, including two virgin binders, and eighteen laboratory prepared AR binders at one CR dosage of 20% but with varying CR gradations. Temperature-frequency oscillation and multiple stress creep and recovery (MSCR) tests were conducted on all the twenty asphalts. G* shear modulus master curves developed from the oscillation test results indicated that AR binders with finer CR particles in the gradation produced flatter master curves that had high G* magnitudes, which are indicative of high strength, better rutting resistance, and reduced viscosity-temperature susceptibility than those with coarser gradation. MSCR test findings complemented the oscillation test results. Analyses of Variance and Dunnett’s statistical tests were performed on the binder rheological properties. From statistical analyses, it was concluded that the variation in CR gradations could significantly affect the binders’ properties and resistance to distresses. Based on the results of rheological experimentation and statistical analyses, a methodical selection procedure for AR binders was devised by developing Ashby plots for the binder rheological parameters. These Ashby plots are envisioned to assist the pavement engineers and contractors in choosing the best suitable AR binder with the essential properties required to satisfy the performance criteria. © 2017, RILEM.

Datta N.,Indian Institute of Technology Kharagpur | Verma Y.,Indian Institute of Technology Kharagpur
International Journal of Mechanical Sciences | Year: 2017

A semi-analytical approach to understand the manifestation of plate modeshapes associated with twin frequencies has been presented. Square Mindlin's plate, clamped on all sides, has been considered here. It highlights the importance of efficacy of the beam-wise trial functions in an energy-based plate vibration analysis method, in terms of (a) accuracy, (b) orthogonality, (c) sense (plus/minus) and (d) interference. The inconsistency in the modeshapes of repeated frequencies, seen extensively in literature, has been attempted to be removed, through superior closed-form orthogonal set of Timoshenko admissible functions into the Rayleigh-Ritz method. The constructive/destructive interferences of the admissible functions, which are the products of the beam-wise modeshapes, give the final nodal patterns and the prominence of the anti-nodes. Also, the pairs of ‘very close’ but distinct frequencies, which were often considered as ‘numerical errors’, have been counter-intuitively justified through their Eigenvectors, which are either symmetric or skew-symmetric in the matrix form. Nodal patterns for CCCC plate modeshapes are accurately investigated; i.e. chess-board and diagonal nodal patterns. © 2017

Gupta N.,Indian Institute of Technology Kharagpur | Bhaskaran P.K.,Indian Institute of Technology Kharagpur
Theoretical and Applied Climatology | Year: 2017

The present study reports a low-rank and sparse decomposition method that separates the mean and the variability of a climate data field. Until now, the application of this technique was limited only in areas such as image processing, web data ranking, and bioinformatics data analysis. In climate science, this method exactly separates the original data into a set of low-rank and sparse components, wherein the low-rank components depict the linearly correlated dataset (expected or mean behavior), and the sparse component represents the variation or perturbation in the dataset from its mean behavior. The study attempts to verify the efficacy of this proposed technique in the field of climatology with two examples of real world. The first example attempts this technique on the maximum wind-speed (MWS) data for the Indian Ocean (IO) region. The study brings to light a decadal reversal pattern in the MWS for the North Indian Ocean (NIO) during the months of June, July, and August (JJA). The second example deals with the sea surface temperature (SST) data for the Bay of Bengal region that exhibits a distinct pattern in the sparse component. The study highlights the importance of the proposed technique used for interpretation and visualization of climate data. © 2017 Springer-Verlag Wien

Karan C.K.,Indian Institute of Technology Kharagpur | Sau M.C.,Indian Institute of Technology Kharagpur | Bhattacharjee M.,Indian Institute of Technology Kharagpur
Chemical Communications | Year: 2017

A copper(ii) metal-organic hydrogel has been synthesised and characterised. This hydrogel is an efficient, reusable precatalyst for CuAAC reactions and chemical fixation of CO2 under solvent free conditions. © The Royal Society of Chemistry.

Pahar G.,Indian Institute of Technology Kharagpur | Dhar A.,Indian Institute of Technology Kharagpur
Transport in Porous Media | Year: 2017

A divergence-free moving particle semi-implicit method is introduced for free-surface flow through porous media. Numerical incompressibility is conserved by solving additional pressure Poisson equation (PPE). Depending on current particle coordinates, a porosity-based factor is introduced to incorporate the effect of solid volume inside the porous domain. A hybrid formulation containing specified boundary condition and PPE is utilized on free-surface particles. The current framework is tested for four different problems. The first problem shows the effect of the proposed factor in vertical flow through a rectangular porous block and its representative volume change for different phases. Second and third problems validate the numerical model for dam break through a rectangular block of homogeneous porous media. In the fourth problem, flow through a trapezoidal porous block consisting of different porous media with variable effective porosity and permeability is simulated. © 2017 Springer Science+Business Media Dordrecht

Maity S.K.,Indian Institute of Technology Kharagpur
CSCW 2017 - Companion of the 2017 ACM Conference on Computer Supported Cooperative Work and Social Computing | Year: 2017

With the evolution of social media over the years, entities like hashtags, tags, topics have also evolved and adopted traits that are very similar to various natural language units. One of the interesting and prevalent linguistic phenomena is compounding. Like natural language compounding, hashtag compounding also takes place and we study the factors behind their adoption in social media. Similar compounding phenomena can also be seen in Quora topics and other non-English languages used in social media.

Bose T.,National Institute of Technology Meghalaya | Mohanty A.R.,Indian Institute of Technology Kharagpur
International Journal of Mechanical Sciences | Year: 2017

Here, the large amplitude axisymmetric vibration of a circular plate having a circumferential crack is studied considering the simply supported and clamped boundary conditions. Exact modal functions are generated by satisfying the boundary conditions and constraints along the crack. The inplane or membrane forces resulting from the large deflection are derived from the Berger's formulation. Next, the Galerkin's method is used to transform the differential equation into the Duffing equation with cubic nonlinearities. The amplitude and phase curves are generated using the Method of multiple scales. Natural frequency variations of axisymmetric modes are studied for a change in crack depth and crack position, considering both boundary conditions. Some natural frequencies are also compared with the finite element results and they are found to be in good agreement. For clamped boundary conditions, the natural frequency of a cracked plate is shown to approach that of an uncracked plate for a particular crack position independent of different crack depths. The amplitude and phase curves are shown for different crack parameters. Finally, the phase plane plot variations are presented for different crack depths, positions and boundary conditions. © 2017

Basak S.,Indian Institute of Technology Kharagpur | Guha P.,Indian Institute of Technology Kharagpur
LWT - Food Science and Technology | Year: 2017

The present study aimed at characterization of betel leaf (Piper betle L.) essential oil based microemulsion (BLEO-ME) and modelling its effect on growth of Aspergillus flavus in tomato paste. The microemulsion was formulated using betel leaf essential oil, Tween 20 and water by low energy emulsification method. The average droplet size of formulated emulsions having different concentration of surfactant (5%, 10% and 15%) and BLEO (2.5%, 5% and 10%) was evaluated. The formulated BLEO-ME was observed to be kinetically and thermodynamically stable for at least 90 days at 4 °C. Primary modelling estimated maximum growth rate (μmax) and apparent lag time (λ) of the selected mould in tomato paste. Secondary modelling was performed to evaluate the effect of different concentration of BLEO on estimated growth parameters. Estimated Emax (minimum concentration of oil at which mould growth was inhibited) and MIC (minimum inhibitory concentration of BLEO at which lag time is infinite) value against A. flavus was estimated to be 2.01 ppm and 3.55 ppm in tomato paste, respectively. Accuracy and bias factor of the fitted secondary models suggested good similarity between observed and estimated values of μmax and λ. The formulated BLEO-ME exhibited antifungal efficacy in tomato paste, which suggests its potential as natural preservative. © 2016 Elsevier Ltd

Choudhary A.K.,Indian Institute of Technology Kharagpur | Dash S.K.,Indian Institute of Technology Kharagpur
International Journal of Geomechanics | Year: 2017

An experimental study on the load-carrying mechanism of vertical plate anchors is presented and discussed. It was found that, with a shallow anchor, the rupture surface reached the ground surface, leading to a general shear failure, whereas with deeper embedment, the rupture surface was localized around the anchor. Anchors placed close to the ground surface failed in linear rupture but, when embedded within the failure mechanism, were very close to the polar curve of a logarithmic spiral, which, however, tends to be nearly circular for deeper depths of embedment. The size of rupture surface increases with an increase in density of fill soil that mobilizes higher resistance, leading to enhanced anchor capacity. The critical embedment depth beyond which the anchor breakout factor does not change much is found to be approximately 7 times the anchor height for dense soil, whereas it is approximately 5 times the anchor height for loose soil. The anchor when placed below the critical depth, settlement, and heave on the fill surface tend to be marginal. © 2016 American Society of Civil Engineers.

Basak S.,Indian Institute of Technology Kharagpur | Guha P.,Indian Institute of Technology Kharagpur
LWT - Food Science and Technology | Year: 2017

The present study describes the effect of betel leaf (Piper betle L.) essential oil (BLEO) on spore inactivation and cell viability of Aspergillus flavus and Penicillium expansum using predictive model and its antifungal activity in raw apple juice. Survival curve of the spores under minimum fungicidal concentration of BLEO was modelled by a modified Weibull model: logN=logN0−(t/δ)β. The forward and side-scatter parameters of flow cytometer suggested differences in size and complexity of spores. Propidium iodide was used as fluorescent stain to distinguish between viable and non-viable spores. Scanning electron microscopic images revealed morphological alterations of treated spores. The cell viability effect of BLEO on mycelial matrix of A. flavus and P. expansum was measured using tetrazolium salt MTT and the inhibition was fitted to dose-response curves. Mycelial biomass of a selected mould in raw apple juice treated with BLEO based microemulsion (BLEO-ME) having different concentration of BLEO was determined based on ergosterol content. BLEO-ME exhibited fungal growth inhibition in raw apple juice, which suggests potential of BLEO as antifungal agent in food system. © 2017 Elsevier Ltd

Murmu S.B.,Indian Institute of Technology Kharagpur | Mishra H.N.,Indian Institute of Technology Kharagpur
LWT - Food Science and Technology | Year: 2017

Edible coating formulations based on Arabic gum (AG) (0–15 g/100 mL), sodium caseinate (SC) (0–2 g/100 mL) and tulsi extract (TE) (0–5 mL/100 mL) were developed using central composite rotatable design and its effect on quality of guava was studied at 28 ± 2 °C for seven days. The guava peel and pulp color, respiration rate, and weightloss were analyzed after 3rd and 7th days of storage. After seven days pulp firmness, mold growth, and overall acceptability were additionally evaluated. The OTR, CTR, and WVTR of the coated guava with AG concentration in the range of 7.5–12 g/100 mL in the coating formulation was lower than those of the control samples (coated with water). The SC showed significant (p < 0.001) positive effect on CTR, and WVTR; TE showed a significant effect on the carbon dioxide evolution rate; its interaction with AG showed significant effects on the oxygen consumption rates of coated guava. The optimized coating formulation (5 g/100 mL AG, 1 g/100 mL SC and 2.5 mL/100 mL TE) maintained suitable internal gas composition to delay ripening, showed higher overall acceptability and shelf-life of 7 days at 28 ± 2 °C compared to 4 days of control. © 2017 Elsevier Ltd

Jadhav D.A.,Indian Institute of Technology Kharagpur | Ghosh Ray S.,Advanced Technology Development Center | Ghangrekar M.M.,Indian Institute of Technology Kharagpur
Renewable and Sustainable Energy Reviews | Year: 2017

Bio−electrochemical system (BES) mainly focused on bio−energy generation in the form of methane and bio−hydrogen while treating wastewater in anodic chamber. The potential of BES to produce intermittent chemicals and high-value derivatives has been immensely explored since last decade by adopting modified reaction kinetics. This review article deals with the mechanism of recovery of resources and by-products during redox reactions in BES. The BES offers flexible platform for both oxidation and reduction processes. Development of BES for product synthesis via bio-electrochemical pathway has greatly extended the new horizon in bioenergy research. Microbial fuel cell and microbial electrolysis cell, the major two variants of BES, are useful to convert the energy present in wastewater to recover resources like bio-electricity, hydrogen, nutrients, heavy metals, minerals and industrial chemicals. Thus, after improving the performance of BES, widening the scope for products recovery by developing better understanding of the process and with efforts to reduce its production cost, it can become a sustainable technology for treatment of wastewater with added advantage of recovery of resources and bio-energy generation. © 2017 Elsevier Ltd

Mishra S.,Indian Institute of Technology Kharagpur | Roy G.G.,Indian Institute of Technology Kharagpur
Ironmaking and Steelmaking | Year: 2017

The effect of CaO on the reduction behaviour of iron ore–coal composite pellets has been studied in a laboratory scale multi-layer bed rotary hearth furnace at 1250°C for 20 min. Reduced pellets have been characterised through weight loss, porosity measurement, phase analysis by XRD, and morphology study by SEM. The addition of CaO to the composite pellets showed different effects at different carbon levels. For higher carbon-containing pellets (C/Fe2O3 molar ratio at the upper stoichiometric level of 3), the addition of CaO increased the extent of reduction for all three layers significantly up to a certain limit (4 wt-%); and thereafter the degree of reduction is decreased with a further increase in CaO percentage in the pellets. For low carbon-containing pellets (C/Fe2O3 molar ratio of 1.66), the addition of CaO to the pellets did not show any beneficial effect. © 2017 Institute of Materials, Minerals and Mining

Chakraborty S.,Indian Institute of Technology Kharagpur | Chattopadhyay S.,Indian Institute of Technology Kharagpur
IEEE Transactions on Power Electronics | Year: 2017

This paper presents a comprehensive steady-state analysis of asymmetrically operated dual active half-bridge (DAHB) dc-dc converters, i.e, DAHB converters operated with a non 0.5 duty-ratio. Such asymmetric operation presents an additional control handle, which may be used to optimize converter performance. The different possible modes of operation are introduced followed by detailed analysis of active power and rms current variation and zero-voltage-switching (ZVS) performance in each mode. Using this information, closed-form expressions corresponding to two control strategies are derived which minimise rms value of transformer current at a given power with and without ZVS operation. The accuracy of the theoretical predictions are verified using numerical optimisation approaches and also through MATLAB Simulink-based simulations. Finally, experimental results on a 625Wlaboratory prototype are presented which validate the discussed ideas. Both simulation and experimental results indicate that the proposed strategies potentially offer significant efficiency advantages compared to simple square-wave control, especially under light-load conditions for converters operating with nonunity effective voltage conversion ratios. © 2016 IEEE.

Kapat S.,Indian Institute of Technology Kharagpur
IEEE Transactions on Power Electronics | Year: 2017

The inductor current ripple under hysteresis current control is sensitive to system as well as controller parameters, which often deviates from the desired band. Thus, a phase-locked-loop (PLL) is employed to regulate the switching frequency over the operating range. Digital platform drastically simplifies this using an all-digital PLL (ADPLL) and offers the controller-tuning flexibility for improved performance. However, the use of uniform voltage-sampling often leads to multilimit cycle instability. This paper proposes a mixed-signal hysteretic current controller (MSHCC) with the digital voltage-loop and the analog current-loop. A digital-to-analog converter is sufficient to generate time-multiplexed current references. This achieves robust stability and parameter-insensitive current ripple by sampling the error-voltage at the rising edge of the high-side gate signal. Stability analysis is carried out using discrete-time models. The proposed MSHCC can be configured to either of the peak, average, or valley current-mode techniques along with the flexibility to adjust the switching frequency using an ADPLL for real-time energy-optimization. The proposed scheme is implemented using an FPGA device and tested on a buck converter prototype. The MSHCC scheme can be extended to a multiphase buck converter. © 1986-2012 IEEE.

Raha R.,Indian Institute of Technology Kharagpur
2016 20th International Conference on System Theory, Control and Computing, ICSTCC 2016 - Joint Conference of SINTES 20, SACCS 16, SIMSIS 20 - Proceedings | Year: 2016

Adaptive regulation of sampling period has gained significant attention in research community in recent times and some encouraging techniques has been reported in this research direction. One such promising technique is commonly referred as multi-rate sampling. A linear control system that uses multi-rate sampling contains a collection of sampling periods and appropriately designed controllers for the corresponding sampling modes. Further, the switching between the sampling modes may depend upon some switching guards. In this paper, we address the problem of the multi-rate sampling associated with linear time invariant control systems, by formalizing the basis of selecting the sampling periods for the different sampling modes, such that overall system stability under arbitrary switching can be guaranteed. We also present a framework for controller synthesis in a multi-rate setting, such that our primary goal is achieved. Further, we present a case study using standard academic example and provide results in support of our proposed methodology. © 2016 IEEE.

Das D.,Indian Institute of Technology Kharagpur
Bioresource Technology | Year: 2011

Biohydrogen is a sustainable energy resource due to its potentially higher efficiency of conversion to usable power, non-polluting nature and high energy density. The purpose of modeling and optimization is to improve, analyze and predict biohydrogen production. Biohydrogen production depends on a number of variables, including pH, temperature, substrate concentration and nutrient availability, among others. Mathematical modeling of several distinct processes such as kinetics of microbial growth and products formation, steady state behavior of organic substrate along with its utilization and inhibition have been presented. Present paper summarizes the experimental design methods used to investigate effects of various factors on fermentative hydrogen production, including one-factor-at-a-time design, full factorial and fractional factorial designs. Each design method is briefly outlined, followed by the introduction of its analysis. In addition, the applications of artificial neural network, genetic algorithm, principal component analysis and optimization process using desirability function have also been highlighted. © 2011 Elsevier Ltd.

Roy N.,Indian Institute of Technology Kharagpur | Bhowmick A.K.,Indian Institute of Technology Kharagpur | Bhowmick A.K.,Indian Institute of Technology Patna
Journal of Physical Chemistry C | Year: 2012

This work holds significance in designing biomimetic implants where biocompatibility and strength are two critical concerns. In the work mentioned herein, hydroxyapatite nanofibers of varying aspect ratios have been synthesized by the soft template assisted method. These nanoparticulates have been successfully introduced into the polydimethylsiloxane (PDMS) matrix through a solution casting technique, and this is probably the first successful attempt made. Nanocomposites prepared with longer nanofibers (300-500 nm length) showed more improvement in various physicomechanical and thermal properties compared with those prepared with lower aspect ratio nanofibers (10.3 versus 4.5). In-depth analysis revealed that a combined effect of several factors leads to these differences. Besides the most important factor, viz., aspect ratio of the nanofibers, the amorphicity of nanofibers and adherence of polymer on the nanofiller surface, i.e., noncovalent surface modification of nanofiller and restriction of microcrystalline domain formation by the nanofiller, also owe their responsibility. © 2012 American Chemical Society.

Biradha K.,Indian Institute of Technology Kharagpur | Su C.-Y.,Sun Yat Sen University | Vittal J.J.,National University of Singapore | Vittal J.J.,Gyeongsang National University
Crystal Growth and Design | Year: 2011

In recent years, Asian countries, especially China and India, are making significant progress in the field of crystal engineering. The recent surge of publications in this area from these countries in high impact journals is a tangible measure of this activity. An important milestone in this direction was the China-India-Singapore Symposium on Crystal Engineering recently held at the National University of Singapore. This symposium brought researchers working in this field to meet, discuss, present, and exchange their research work and has generated momentum to further accelerate the growth of this field. This perspective highlights the recent advances discussed by the researchers at this symposium in the fast growing field of crystal engineering.(Figure Presented) © 2011 American Chemical Society.

Gogurla N.,Indian Institute of Technology Kharagpur | Ray S.K.,Indian Institute of Technology Kharagpur
Current Applied Physics | Year: 2015

We have investigated the resistive switching mechanism in solution processed Au-reduced graphene oxide-polyvinyl alcohol (PVA) nanocomposites on flexible substrates. Monodispersed gold nanoparticles (Au NPs) attached to reduced graphene oxide (RGO) in aqueous PVA solution have been synthesized using a novel one pot technique. The fabricated hybrid device showed high On/Off switching ratio more than 103 with low operating voltages. The performance of hybrid device can be effectively enhanced over control RGO device. The switching mechanism occurs from the electrochemical reduction/oxidation process of partially reduced graphene oxide. The proposed devices reveal superior asymmetric bipolar resistive switching characteristics attractive for solution processable flexible and transparent non-volatile memory applications. © 2015 Elsevier B.V. All rights reserved.

Misra R.,Indian Institute of Technology Patna | Mandal C.,Indian Institute of Technology Kharagpur
IEEE Transactions on Parallel and Distributed Systems | Year: 2010

A minimum connected dominating set (MCDS) is used as virtual backbone for efficient routing and broadcasting in ad hoc sensor networks. The minimum CDS problem is NP-complete even in unit disk graphs. Many heuristics-based distributed approximation algorithms for MCDS problems are reported and the best known performance ratio has (4.8+ln 5). We propose a new heuristic called collaborative cover using two principles: 1) domatic number of a connected graph is at least two and 2) optimal substructure defined as subset of independent dominator preferably with a common connector. We obtain a partial Steiner tree during the construction of the independent set (dominators). A final postprocessing step identifies the Steiner nodes in the formation of Steiner tree for the independent set of G. We show that our collaborative cover heuristics are better than degree-based heuristics in identifying independent set and Steiner tree. While our distributed approximation CDS algorithm achieves the performance ratio of (4.8+ln 5)opt + 1.2, where opt is the size of any optimal CDS, we also show that the collaborative cover heuristic is able to give a marginally better bound when the distribution of sensor nodes is uniform permitting identification of the optimal substructures. We show that the message complexity of our algorithm is O(nΔ2), Δ being the maximum degree of a node in graph and the time complexity is O(n). © 2010 IEEE.

Roy N.,Indian Institute of Technology Kharagpur | Bhowmick A.K.,Indian Institute of Technology Kharagpur | Bhowmick A.K.,Indian Institute of Technology Patna
Polymer | Year: 2010

A series of novel in situ polydimethylsiloxane (PDMS)-sepiolite nanocomposites were synthesized by anionic ring opening polymerization of octamethylcyclotetrasiloxane. These nanocomposites were characterized by Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy, Wide Angle X-Ray Diffraction (WAXD), Transmission Electron Microscopy (TEM), mechanical and dynamic mechanical properties and thermogravimetry. This paper highlights the structure-property relationship of in situ PDMS-sepiolite nanocomposites and a way to improve the mechanical, dynamic mechanical and thermal properties of silicone rubber. Comparison of these physico-mechanical properties with those of the ex situ nanocomposites reflects greater degree of filler dispersion for the in situ nanocomposites. Increasing amount of the filler reduced the size of the crystalline domains in PDMS matrix, which was evident from the X-Ray and the dynamic mechanical analysis. However, the polymer-filler interaction was even more prominent to negate the effect of the deterioration of the properties due to decrease in size of the microcrystallites. The polymer-filler interaction was reflected in the improved mechanical and thermal properties which were the consequences of proper dispersion of the filler in the polymer matrix. The modulus improvement of the rubber-clay nanocomposites was examined by using Guth and Halpin-Tsai model. The temperature of maximum degradation was raised by 167 °C and improvement of 210% in tensile strength and 460% in modulus at 100% elongation was observed. These results were correlated with the data obtained from WAXD and TEM studies. © 2010 Elsevier Ltd.

Agency: European Commission | Branch: FP7 | Program: CP | Phase: ENERGY.2010.5&6.2-1 | Award Amount: 2.45M | Year: 2011

Coal mining and utilisation results in release of significant amounts methane and represent an important threat to the fight against climate change. Coal Mine Methane drainage processes can be set up to recover methane from the emissions during coal production. Methane can also be extracted from virgin coal seams trough primary and enhanced coalbed methane recovery. The main objective of the proposed research project is to contribute to the global GHG emissions reduction objective by addressing the key challenges facing the industry and emerging economies which also are major coal mining counties worlwide. This objective canbe expanded upon as follows: - to achieve significant improvements in methane drainage efficiency and purity in coal mines in the emerging economies of China and India, where methane drainage is employed with relatively low yields of gas and purity. - to develop a novel and effective gas drainage techniques for the ultra-thick seam and gassy mining operations in Europe - to investigate the benefits of implementing horizontal wells for coalbed methane (CBM) and coupling horizontal wells with the injection of CO2 and/or CO2 enriched flue gas to enhance methane recovery and CO2 storage - to disseminate the know-how developed across the coal sector internationally

Maiti J.,Indian Institute of Technology Kharagpur | Ray P.K.,Indian Institute of Technology Kharagpur
Safety Science | Year: 2012

In this paper, a comprehensive review of the concepts of occupational injury and accident causation and prevention is presented. Starting with hazard identification, the issues on risk assessment, accident causation, and intervention strategies are discussed progressively. The distinctiveness and overlaps in accident and injury research are highlighted. Both empirical research in terms of hypotheses tested and theoretical research such as accident causation models are compared and contrasted. Finally, based on the critical appraisal of the comprehensive review, future research directions on occupational injury research are delineated. © 2011 Elsevier Ltd.

Agency: European Commission | Branch: FP7 | Program: CP-SICA | Phase: ENV.2008. | Award Amount: 4.29M | Year: 2009

The hydrological system of Northern India is based on two main phenomena, the monsoon precipitation in summer and the growth and melt of the snow and ice cover in the Himalaya, also called the Water Tower of Asia. However, climate change is expected to change these phenomena and it will have a profound impact on snow cover, glaciers and its related hydrology, water resources and the agricultural economy on the Indian peninsula (Singh and Kumar, 1996, Divya and Mehrotra, 1995). It is a great challenge to integrate the spatial and temporal glacier retreat and snowmelt and changed monsoon pattern in weather prediction models under different climate scenarios. Furthermore, the output of these models will have an effect on the input of the hydrological models. The retreat of glaciers and a possible change in monsoon precipitation and pattern will have a great impact on the temporal and spatial availability of water resources in Northern India. Besides climate change, socio-economic development will also have an influence on the use of water resources, the agricultural economy and the adaptive capacity. Socio-economic development determines the level of adaptive capacity. It is a challenge to find appropriate adaptation strategies with stakeholders for each of the sectors agriculture, energy, health and water supply by assessing the impact outputs of the hydrological and socio-economical models. The principal aim of the project is to assess the impact of Himalayan glaciers retreat and possible changes of the Indian summer monsoon on the spatial and temporal distribution of water resources in Northern India and to provide recommendations for appropriate and efficient response strategies that strengthen the cause for adaptation to hydrological extreme events.

Meena N.K.,Wadia Institute of Himalayan Geology | Maiti S.,Indian Institute of Technology Kharagpur | Shrivastava A.,University of Delhi
Journal of Applied Geophysics | Year: 2011

In this paper magnetic property of the Delhi topsoil has been used to characterize the potentially polluted areas in terms of magnetic minerals and grain (Magnetic Domain) concentration as a factor of toxic metals and other mutagenic pollutant concentration. The Saturation magnetisation (Ms) and Saturation remanence (Mrs) has been taken as proxy for ferrimagnetic mineral concentration. However, delineation of anthropogenic magnetic fraction from lithogenic (geogenic) magnetic fraction has been done by the paramagnetic/diamagnetic contribution of soil with the fact that the fresh soil contains higher paramagnetic and diamagnetic minerals than polluted. Predominantly, the topsoils of Delhi are dominated with ferrimagnetic minerals (Magnetite and Maghemite phase). Significantly the industrial areas contain highest concentration of the ferrimagnetic minerals with negligible paramagnetic/diamagnetic fraction which leads to anthropogenic contribution. Heavy traffic and densely populated areas of the Delhi exhibit moderate to low soil pollution while green areas show lowest with higher paramagnetic/diamagnetic contribution. The soils in Delhi are dominated with Pseudo-Single Domain (PSD) magnetic grain, though the industrial areas in Delhi show coarser Multidomain (MD) grains in comparison to Stable Single Domain (SSD) in forest areas. Our study reveals that the fine grain particle does not show significant link with higher concentration of ferrimagnetic minerals at least in soils. The presence of the lithogenic magnetite crystal in the forest soil and anthropogenically produced spherules in industrial areas and higher concentration of the heavy metal in Delhi soil strengthen our findings. © 2011 Elsevier B.V.

Misra S.,Indian Institute of Technology Kharagpur | Krishna P.,Vellore Institute of Technology | Saritha V.,Vellore Institute of Technology | Obaidat M.,Monmouth University
IEEE Communications Magazine | Year: 2013

The rapid growth of smart grid systems demands efficient management of smart grid services. Smart grids are expected to enable the delivery and management of electricity in a more reliable, efficient, economical, and secured manner. Thus, the development of effective power management solutions for smart grids to meet these challenges is an important area of research in recent times. In this article, we propose using learning automata (LA), a computational learning utility, for efficient power management in smart grids (LAPM). The proposed system, LAPM, helps in identifying the electricity required for various distribution substations and controls the usage of power by various devices (i.e., preventing unauthorized use of power). The use of LA enables performing a dynamic analysis of power usage and providing decision making for its effective usage. The system is evaluated on a real-life-resembling environment, with respect to parameters such as power utilization and customer satisfaction. © 1979-2012 IEEE.

Kapat S.,Indian Institute of Technology Kharagpur | Krein P.T.,University of Illinois at Urbana - Champaign
IEEE Transactions on Power Electronics | Year: 2012

Time optimal control (TOC) is a technique to provide fast transient recovery in dc-dc converters. Prior published approaches are incomplete in the formulation of TOC because they ignore voltage-deviation effects on inductor-current and load-current dynamics during a large-signal recovery. An accurate TOC algorithm based on capacitor current is presented. This method achieves minimum transient recovery time for load transients and tracking in a buck converter. The minimum recovery time is preserved even with a transient-detection delay. This control configuration ensures large-signal stability in a sense similar to that of sliding-mode control. The results are demonstrated in an experimental buck converter that uses a digital control algorithm. © 2011 IEEE.

Kapat S.,Indian Institute of Technology Kharagpur | Krein P.T.,University of Illinois at Urbana - Champaign
IEEE Transactions on Power Electronics | Year: 2012

The output voltage derivative term associated with a PID controller injects significant noise in a dc-dc converter. This is mainly due to the parasitic resistance and inductance of the output capacitor. Particularly, during a large-signal transient, noise injection significantly degrades phase margin. Although noise characteristics can be improved by reducing the cutoff frequency of the low-pass filter associated with the voltage derivative, this degrades the closed-loop bandwidth. A formulation of a PID controller is introduced to replace the output voltage derivative with information about the capacitor current, thus reducing noise injection. It is shown that this formulation preserves the fundamental principle of a PID controller and incorporates a load current feedforward, as well as inductor current dynamics. This can be helpful to further improve bandwidth and phase margin. The proposed method is shown to be equivalent to a voltage-mode-controlled buck converter and a current-mode-controlled boost converter with a PID controller in the voltage feedback loop. A buck converter prototype is tested, and the proposed algorithm is implemented using a field-programmable gate array. © 2011 IEEE.

Kapat S.,Indian Institute of Technology Kharagpur | Shenoy P.S.,University of Illinois at Urbana - Champaign | Krein P.T.,University of Illinois at Urbana - Champaign
IEEE Transactions on Power Electronics | Year: 2012

The maximum closed-loop bandwidth of a dc-dc converter is restricted to a fraction of its switching frequency when governed by a conventional average-based pulsewidth modulation (PWM) controller. Even an advanced geometric control is limited by internal slew rates. The bandwidth can reach or exceed the switching frequency through converter augmentation; however, this requires a nonlinear control algorithm and circuit arrangements. This paper considers methods of augmentation and control for a fast buck converter. Conditions for time-optimal transient recovery are obtained for both instantaneous and delayed transient disturbance detection. Design tradeoffs and control issues related to augmentation are considered here. The main switch is controlled using a fixed frequency PWM current-mode control with load current feedforward, and augmented switches are controlled using frequency-limited bang-bang control based on a geometric approach. A small-signal model is obtained and extended control bandwidth is demonstrated. Fast transient recovery is achieved for both single- and two-resistance augmentation. A prototype augmented buck converter is tested. Output voltage and inductor current overshoot and undershoot can be lowered more than with previous methods. It is possible to achieve near-null response in the sense of ripple band to a large-signal transient. © 1986-2012 IEEE.

Sinha K.,Honeywell | Sinha B.P.,Indian Statistical Institute | Datta D.,Indian Institute of Technology Kharagpur
IEEE Transactions on Wireless Communications | Year: 2011

We propose a redundant radix based number (RBN) representation for encoding and transmitting data for applications which typically utilize low cost devices and demand low power operations with simple modulation techniques like ASK, OOK and FSK. Coupled with silent periods for communicating the digit zero, this encoded communication scheme, called as RBNSiZeComm, provides a highly energy-efficient technique for data transmission. Considering an n-bit data representation and assuming that each of the 2n binary strings is equally likely to occur, theoretically obtainable fraction of energy savings by using our proposed RBNSiZeComm transmission protocol is, on an average, 1 - n+2/4n. A hybrid modulation scheme using FSK and ASK with non-coherent detection based receiver for the RBNSiZeComm protocol has been presented. Assuming equal likelihood of all possible binary strings of a given length, there is nearly 53% savings in energy on an average at the transmitter relative to binary FSK, over additive white gaussian noise (AWGN) channels. Simulation results demonstrate that compared to binary FSK, our proposed implementation can extend the battery life of devices from about 33% to 62% on an average in applications like remote healthcare and wireless sensor networks for agriculture. © 2011 IEEE.

News Article | November 29, 2016

A team of researchers from India have created a model to explain how liquid diffuses through paper which has applications in medical testing and perfume manufacturing WASHINGTON, D.C., November 29, 2016 - Molecules move randomly, colliding with each other in continual motion. You can even smell this process at times; it's how perfume spreads across a room when the air is still. The process is termed diffusion and the theory of diffusion can be applied to liquid spreading through paper, too - a process at work in a range of everyday products, from ink pens to paper sampling patches for medical tests. Now, a team of researchers in India have developed a model that deepens their conceptual grasp of how liquids spread through paper. "Liquid spreading in a paper is essentially random liquid motion through a randomly distributed network of fibers," said Suman Chakraborty, lead researcher of the investigation at the Indian Institute of Technology Kharagpur, and the Advancement Technology Development Centre, both located in Kharagpur, India. Results are published this week in Applied Physics Letters, from AIP Publishing. Diffusion is a well-known process. But the team's elaboration of diffusion theory in the context of paper-liquid interactions, which pose tortuous fiber networks to transport dynamics, is novel and reveals new theoretical detail. In their experiment, the researchers observed ink spreading on filter paper using a scanning electron microscope. The team mapped liquid spreading dynamics from a single fiber capillary to a larger network of the fibers. They then computed the resulting transport characteristics, with results confirming a generalized unified perspective of diffusion at work in the process of liquid moving through a paper matrix. Scanning micrographic images show paper fiber distributions, along with the micro-particle-image-velocimetry measure of random liquid movement through the network. "Our study reveals that, despite such diversified uses of paper interacting with liquids, there is a fundamental uniqueness of liquid spreading through paper leading toward a general and unified theory about it," Chakraborty said. The theory holds that molecules of a liquid move through the fiber network of paper following the principles of universal diffusive dynamics. "Paper is constituted of a network of fibers distributed randomly," said Chakraborty. "As a consequence, random motion of the liquid in all possible directions occurs. We know molecules move randomly and collide with each other, and this is the premise of diffusion." Despite wide use of liquid-infused paper technologies, there are gaps in the understanding of the basic science behind its behavior. Chakraborty and his students, Kaustav Chaudhury and Shantimoy Kar, help fill that gap. By understanding liquid spread in the paradigm of diffusion, scientists can control it more precisely to create and refine new products that involve liquid spreading through paper. For example, current markets have validated an important potential property of paper: acting as the essential building block of a rapid diagnostic kit in an ultra-low-cost paradigm. Examples of this application include pregnancy test strips; alkalinity or acidity tests of beauty and baby soaps using a paper strip; paper-strips for checking water quality; and medical diagnosis aided by paper-strip tests of urine, saliva and blood. The author's diffusion model of liquid spreading in paper can also improve papers and inks used for writing, drawing and painting. Next, the investigators plan to develop smart and compact technologies for diagnostic purposes, advancing the existing paper based platforms. "The key objectives are to obtain rapid results at the expense of low costs. To this end, the paper shows a promising prospect of being a tool to serve both the objectives. The present work, as we believe, will pave the way for the design and development of the paper-based technologies to serve a wider public," Chakraborty said. The article, "Diffusive dynamics on paper matrix," is authored by Kaustav Chaudhury, Shantimoy Kar and Suman Chakraborty. The article will appear in the journal Applied Physics Letters on November 29, 2016 (DOI: 10.1063/1.4966992). After that date, it can be accessed at: http://scitation. Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology.

Ravi Teja A.V.,Indian Institute of Technology Kharagpur | Chakraborty C.,Indian Institute of Technology Kharagpur | Maiti S.,Corporate Research Center | Hori Y.,University of Tokyo
IEEE Transactions on Industrial Electronics | Year: 2012

In this paper, a new model reference adaptive controller (MRAC) for the speed estimation of the vector-controlled induction motor drive is presented. The proposed MRAC is formed using instantaneous and steady-state values of X (=ν →*× i → where v = ν = voltage and i = = current vector in synchronously rotating reference frame), which is a fictitious quantity and has no physical significance. This formulation is not only simply realizable but also made the sensorless drive stable in all the four quadrants of operation. Speed estimation does not involve computation of stator or rotor flux. Requirement of no additional sensors makes the drive suitable for retrofit applications. A simple modification of the controller can estimate the stator resistance in all the four quadrants of operation, if speed signal is available. The proposed MRAC-based speed sensorless vector control drive as well as the stator resistance estimation technique has been simulated in MATLAB/SIMULINK and experimentally validated through a dSPACE-1104-based laboratory prototype. A study on stability of such systems is also added. © 2012 IEEE.

Paul G.,Indian Institute of Technology Kharagpur | Chopkar M.,National Institute of Technology Raipur | Manna I.,Indian Institute of Technology Kharagpur | Das P.K.,Indian Institute of Technology Kharagpur
Renewable and Sustainable Energy Reviews | Year: 2010

There has been a rapid progress in research activities concerning nanofluids since a large enhancement in their thermal conductivity has been reported a decade ago. While this extraordinary thermal conductivity of nanofluids deserves scientific investigation, the inconsistency and controversy of the results reported by different groups for identical nanofluids across the world raises fundamental doubts and poses a hindrance in the potential applications of nanofluids. This paper presents a critical review of the several techniques for the measurement of thermal conductivity of nanofluids employed by the researchers. Additionally, a detailed description of a unique thermal conductivity measurement device based on the thermal comparator principle, developed by the present authors has been described. Besides the principle of this measurement device, the constructional details have been elaborated. Finally, some suggestions have been made for improving the reliability of the measurement of thermal conductivity. © 2010 Elsevier Ltd. All rights reserved.

Bassani J.L.,University of Pennsylvania | Racherla V.,Indian Institute of Technology Kharagpur
Progress in Materials Science | Year: 2011

In non-close-packed crystalline lattices, e.g. of bcc metals and intermetallic compounds, the stress-state dependence of the Peierls barrier for the motion of a screw dislocation violates Schmid's law and leads to non-associated plastic flow at the continuum level. Plasticity models based upon distinct yield and flow functions are developed for both single crystals and polycrystalline aggregates that build upon atomic-level simulations of single dislocations. For a random polycrystal, isotropic forms for those functions are proposed and used to study mechanisms of macroscopic deformation. Non-associated flow is shown to have a significant effect on strain localization. Intermittent strain bursts are predicted to arise as a consequence of non-associated flow, particularly for deformations close to the plane strain state and for nearly rate-insensitive response. © 2011 Elsevier Ltd. All rights reserved.

Biligiri K.P.,Indian Institute of Technology Kharagpur | Way G.B.,Consulpav
Road Materials and Pavement Design | Year: 2014

The purpose of this research investigation was to conduct field and laboratory noise evaluation of 36 laboratory-blended and 49 field pavement cores encompassing 11 pavement types collected from Arizona and California in the USA and Sweden in Europe mainly to characterise their acoustical properties. Furthermore, a new and unique parameter referred to as damping acoustical measurement parameter (DAMP) was conceptualised and developed as part of this study to characterise noise-damping properties of the different road materials. Laboratory acoustical evaluation was performed on the samples covering nine conventional and modified asphalt and two non-asphaltic mixtures using the ultrasonic pulse velocity technique and Impedance (Z) was estimated. DAMP was established for the mixes which were inversely related to Z. Theoretically, lower Z and higher DAMP exemplified higher noise-damping capacity of the pavement. Amongst the asphaltic mixes, asphalt rubber friction course had the highest DAMP (∼20%) compared to the other mixes indicative of being the quietest pavement material, also confirmative of the field noise measurement findings. Within the non-asphaltic mixtures, poroelastic road surface showed the highest DAMP (37%), while Portland cement concrete exhibited the lowest DAMP (12%). © 2014, © 2014 Taylor & Francis.

Nath S.,Indian Institute of Technology Kharagpur | Pityana S.,South African Council for Scientific and Industrial Research | Dutta Majumdar J.,Indian Institute of Technology Kharagpur
Surface and Coatings Technology | Year: 2012

In the present study, laser surface alloying of aluminium with WC+Co+NiCr (in the ratio of 70:15:15) has been conducted using a 5kW continuous wave (CW) Nd:YAG laser (at a beam diameter of 0.003m), with the output power ranging from 3 to 3.5kW and scan speed from 0.012m/s to 0.04m/s by simultaneous feeding of precursor powder (at a flow rate of 1×10 -5kg/s) and using He shroud at a gas flow rate of 3×10 -6m 3/s. The effect of laser power and scan speed on the characteristics (microstructures, phases and composition) and properties (wear and corrosion resistance) of the surface alloyed layer have been investigated in details. Laser surface alloying leads to development of fine grained aluminium with the dispersion of WC, W 2C, Al 4C 3, Al 9Co 2, Al 3Ni, Cr 23C 6, and Co 6W 6C. The microhardness of the alloyed zone is significantly improved to a maximum value of 650 VHN as compared to 22 VHN of the as-received aluminium substrate. The mechanism of microhardness enhancement has been established. The fretting wear behavior of the alloyed zone was evaluated against WC by Ball-on-disc wear testing unit and the mechanism of wear was established. © 2012 Elsevier B.V.

Machiwal D.,Indian Central Arid Zone Research Institute | Jha M.K.,Indian Institute of Technology Kharagpur
Hydrological Processes | Year: 2014

The aim of this study was to investigate rainfall-groundwater dynamics over space and annual time scales in a hard-rock aquifer system of India by employing time series, geographic information system and geostatistical modelling techniques. Trends in 43-year (1965-2007) annual rainfall time series of ten rainfall stations and 16-year (1991-2006) pre-monsoon and post-monsoon groundwater levels of 140 sites were identified by using Mann-Kendall, Spearman rank order correlation and Kendall rank correlation tests. Trends were quantified by Kendall slope method. Furthermore, the study involves novelty of examining homogeneity of pre-monsoon and post-monsoon groundwater levels, for the first time, by applying seven tests. Regression analysis between rainfall and post-monsoon groundwater levels was performed. The pre-monsoon and post-monsoon groundwater levels for four periods - 1991-1994, 1995-1998, 1999-2002 and 2003-2006 - were subjected to geographic information system-based geostatistical modelling. The rainfall showed considerable spatiotemporal variations, with a declining trend at the Mavli rainfall station (p-value<0.05). The Levene's tests revealed spatial homogeneity of rainfall at α=0.05. Regression analyses indicated significant relationships (r2>0.5) between groundwater level and rainfall for eight rainfall stations. Non-homogeneity and declining trends in the groundwater level, attributed to anthropogenic and hydrologic factors, were found at 5-61 more sites in pre-monsoon compared with post-monsoon season. The groundwater declining rates in phyllite-schist, gneiss, schist and granite formations were found to be 0.18, 0.26, 0.21 and 0.14myear-1 and 0.13, 0.19, 0.16 and 0.02myear-1 during the pre-monsoon and post-monsoon seasons, respectively. The geostatistical analyses for four time periods revealed linkages between the rainfall and groundwater levels. © 2013 John Wiley & Sons, Ltd.

Ghosh S.,Defence Research and Development Organisation | Mukhopadhyay S.,Indian Institute of Technology Kharagpur
IEEE Transactions on Aerospace and Electronic Systems | Year: 2011

In this paper an acceleration model and a jerk model are proposed for estimation of the kinematic state of reentry ballistic targets (RBTs) using extended Kalman filters (EKF). The models proposed here use the equations of target kinematics only and do not assume any model parameterization for variation of the ballistic coefficient and air density a priori, as found in the literature. The novelty lies in estimation of the ratio (γ) of air density and ballistic coefficient and its time derivatives using a separate Kalman filter (KF) (γ-filter) which utilizes pseudo measurements of γ computed from the velocity and acceleration estimated by the EKF at each time step. The parameter γ and its derivatives estimated by the γ-filter are, in turn, used for the estimation of position, velocity, acceleration, and jerk in the EKF. The use of the pseudo measurements of γ makes the algorithms inherently adaptive to variations of the ballistic coefficient and air density during reentry. A comparative assessment of several dynamic models for reentry of ballistic targets reported in the literature and those proposed here demonstrates that the estimation errors in velocity and acceleration are significantly less for the proposed models compared with the existing ones. © 2011 IEEE.

Mondal C.,Indian Institute of Technology Kharagpur | Ganguly M.,Indian Institute of Technology Kharagpur | Manna P.K.,Bhabha Atomic Research Center | Yusuf S.M.,Bhabha Atomic Research Center | Pal T.,Indian Institute of Technology Kharagpur
Langmuir | Year: 2013

A facile, cost-effective, surfactant-free chemical route has been demonstrated for the fabrication of porous β-Co(OH)2 hierarchical nanostructure in gram level simply by adopting cobalt acetate as a precursor salt and ethanolamine as a hydrolyzing agent at room temperature. A couple of different morphologies of β-Co(OH)2 have been distinctly identified by varying the mole ratio of the precursor and hydrolyzing agent. The cyclic voltammetry measurements on β-Co(OH)2 displayed significantly high capacitance. The specific capacitance obtained from charge-discharge measurements made at a discharge current of 1 A/g is 416 F/g for the Co(OH)2 sample obtained at room temperature. The charge-discharge stability measurements indicate retention of specific capacitance about 93% after 500 continuous charge-discharge cycles at a current density of 1 A g-1. The capacitive behavior of the other synthesized morphology was also accounted. The nanoflower-shaped porous β-Co(OH) 2 with a characteristic three-dimensional architecture accompanied highest pore volume which made it promising electrode material for supercapacitor application. The porous nanostructures accompanied by high surface area facilitates the contact and transport of electrolyte, providing longer electron pathways and therefore giving rise to highest capacitance in nanoflower morphology. From a broad view, this study reveals a low-temperature synthetic route of β-Co(OH)2 of various morphologies, qualifying it as supercapacitor electrode material. © 2013 American Chemical Society.

Karemore A.,Indian Institute of Technology Kharagpur | Pal R.,University of Calcutta | Sen R.,Indian Institute of Technology Kharagpur
Algal Research | Year: 2013

Algal biomass can serve as rich source of bioproducts including lipids for diverse commercial applications. Both biomass production and lipid accumulation are limited by several factors, of which nutrients play a vital role. In the present investigation, the nutritional requirement for the growth by a (an autotrophic) Chlorococcum infusionum was determined using a Plackett-Burman based statistical screening experiment. Five out of the fifteen factors of a reported production medium were found to be significantly affecting the biomass growth. The components NaNO3, K2HPO4, FeSO4.7H2O and KOH had direct proportional correlation with biomass production, while MgSO4 showed inverse proportional relationship in the selected experimental range. Nitrogen was the most influential factor with an effect contribution of 45.77% and a very low p-value of <0.001. The most favorable nitrogen source was potassium nitrate which could replace both sodium nitrate and potassium hydroxide. More than two fold increase in biomass concentration was achieved by screening and standardizing the media components of Bold Basal Medium. Lipid accumulation under normal condition was 12-15% dry cell weight (dcw). Under nitrogen starvation condition, it was 30-35% dcw. However, a semi-starvation condition at 1.75mM of sodium nitrate induced lipid production as high as 40±2% dcw. FAME analysis in GC showed the presence of more saturated fatty acids. Results obtained in this work can further be applied to optimize production of algal biomass and lipid for applications like biofuel, fish or animal feed, fertilizer, etc. Also information obtained could be exploited for wastewater treatment processes. © 2013 Elsevier B.V.

Chatterjee D.,Indian Institute of Technology Kharagpur | Ghosh A.,Queensland University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2011

This paper discusses the use of trajectory sensitivity analysis (TSA) in determining the transient stability margin of a power system compensated by a shunt FACTS device. The shunt device used is static synchronous compensator (STATCOM). It is shown that TSA can be used for the design of controller for the STATCOM. The preferable locations for the placement of the STATCOM for different fault conditions are also identified. The effects of STATCOM in maintaining different bus voltages in the post-fault condition are studied. The STATCOM is modeled by a voltage source connected to the system through a transformer. The systems used for the study are the WSCC 3-machine 9-bus system and the IEEE 16-machine 68-bus system. © 2010 Elsevier Ltd. All rights reserved.

Pan S.,Indian Institute of Technology Kharagpur | Merino G.,Research Center Estudios Avanzados | Chattaraj P.K.,Indian Institute of Technology Kharagpur
Physical Chemistry Chemical Physics | Year: 2012

Prompted by the stability of some lithium decorated star-like clusters and super-alkali systems, their hydrogen trapping potential is assessed at the M06/6-311+G(d,p) and the M052X/6-311+G(d) levels, respectively. The effect of an applied electric field is also analyzed. Most of these systems are found to have the potential to become effective hydrogen storage materials with high gravimetric weight percent owing to the charges on the Li centers. The presence of an external electric field improves the situation. © 2012 The Owner Societies.

Mishra D.P.,Indian School of Mines | Das S.K.,Indian Institute of Technology Kharagpur
Materials Characterization | Year: 2010

This study examines the suitability of Talcher coal fly ash for stowing in the nearby underground coal mines based on their physico-chemical and mineralogical analysis. The physical properties such as bulk density, specific gravity, particle size distribution, porosity, permeability and water holding capacity etc. have been determined. From the chemical characterization it is found that the ash samples are enriched predominantly in silica (SiO 2), alumina (Al 2O 3) and iron oxides (Fe 2O 3), along with a little amount of CaO, and fall under the Class F fly ash category. In addition, the mineral phases identified in the ash samples are quartz, mullite, magnetite, and hematite. The particle morphological analysis revealed that the ash particles are almost spherical in shape and the bulk ash porous in nature. From the particle size and permeability point of view, pond ash may be considered a better stowing material than fly ash. © 2010 Elsevier Inc.

Gupta A.,Indian Institute of Technology Kharagpur | O'Malley M.K.,Rice University
Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME | Year: 2011

In this paper, we propose the use of a nonlinear disturbance-observer for estimation of contact forces during haptic interactions. Most commonly used impedance-type haptic interfaces employ open-loop force control under the assumption of pseudostatic interactions. Advanced force control in such interfaces can increase simulation fidelity through improvement of the transparency of the device. However, closed-loop force feedback is limited both due to the bandwidth limitations of force sensing and the associated cost of force sensors required for its implementation. Using a disturbance-observer, we estimate contact forces at the tool tip, then use these estimates for closed-loop control of the haptic interface. Simulation and experimental results, utilizing a custom single degree-of-freedom haptic interface, are presented to demonstrate the efficacy of the proposed disturbance-observer (DO)-based control approach. This approach circumvents the traditional drawbacks of force sensing while exhibiting the advantages of closed-loop force control in haptic devices. Results show that the proposed disturbance-observer can reliably estimate contact forces at the human-robot interface. The DO-based control approach is experimentally shown to improve haptic interface fidelity over a purely open-loop display while maintaining stable and vibration-free interactions between the human user and virtual environment. Copyright © 2011 by ASME.

Pradhan P.M.,Indian Institute of Technology Kharagpur | Panigrahi K.L.,Indian Institute of Technology Kharagpur | Panigrahi K.L.,Abdus Salam International Center For Theoretical Physics
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We derive the energy of pulsating strings, as a function of oscillation number and angular momenta, which oscillates in AdS3 with an extra angular momentum along S1. We find similar solutions for the strings oscillating in S3 in addition to extra angular momentum. Furthermore, we generalize the result of the oscillating strings in anti-de Sitter space in the presence of both spin and angular momentum in AdS5×S1. © 2013 American Physical Society.

Mondal P.K.,Indian Institute of Technology Kharagpur | Deb B.,Indian Association for The Cultivation of Science | Majumder S.,Indian Institute of Technology Kharagpur
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

The exchange of orbital angular momentum between a Laguerre-Gaussian beam of light and the center-of-mass motion of an atom or molecule is well known. We show that the orbital angular momentum of light can also be transferred to the internal electronic or rotational motion of an atom or a molecule provided the internal and center-of-mass motions are coupled. However, this transfer does not happen directly to the internal motion, but via center-of-mass motion. If atoms or molecules are cooled down to the recoil limit, then an exchange of angular momentum between the quantized center-of-mass motion and the internal motion is possible during the interaction of cold atoms or molecules with the Laguerre-Gaussian beam. The orientation of the exchanged angular momentum is determined by the sign of the winding number of the Laguerre-Gaussian beam. We present selective results of numerical calculations for the quadrupole transition rates in the interaction of the Laguerre-Gaussian beam with an atomic Bose-Einstein condensate to illustrate the underlying mechanism of light orbital angular momentum transfer. We discuss how the alignment of diatomic molecules will facilitate exploration of the effects of light orbital angular momentum on the electronic motion of molecules. © 2014 American Physical Society.

Dey K.,Indian Institute of Technology Kharagpur | Murthy V.M.S.R.,Indian School of Mines
Tunnelling and Underground Space Technology | Year: 2012

Drilling and blasting is the predominant rock excavation technique in driving horizontal tunnels. This often results in large overbreak. One of the prime reasons for overbreak is the unacceptable levels of ground vibration generated in blasting. From the literature survey and practical experience, it was found that threshold levels of PPV for overbreak depends on rock properties, namely, rock strengths, P-wave velocity, specific gravity, Poisson's ratio and rockmass parameters. Determination of threshold level of peak particle velocity (PPV) is crucial for controlling blast-induced overbreak and can be approximated by extrapolating the vibration predictor established from near-field vibration monitoring. This paper reports the experiments carried out in five horizontal tunnels for monitoring near-field ground vibration using accelerometer-based-seismograph planted in roof/sidewalls to establish ground vibration predictors. Blast-induced overbreak for each blast has been measured using a telescopic profiler. The threshold levels of PPV for overbreak have been estimated from the extrapolated vibration predictors to the overbreak zone and also using near field approximation technique. The estimated threshold levels of PPV for overbreak ranged between 590 and 1050. mm/s in extrapolation model and 410-890. mm/s in near-field HP model. Apart from these, a relationship between the percentage overbreak and rock/rockmass, charge and blast design parameters has been established through multivariate regression analysis of the data pertaining to five investigating sites. The result has been validated for four blasts within reasonable accuracy. © 2011 Elsevier Ltd.

Mitra S.,Indian Institute of Technology Kharagpur | Washington S.,Queensland University of Technology
Accident Analysis and Prevention | Year: 2012

Advances in safety research - trying to improve the collective understanding of motor vehicle crash causes and contributing factors - rest upon the pursuit of numerous lines of research inquiry. The research community has focused considerable attention on analytical methods development (negative binomial models, simultaneous equations, etc.), on better experimental designs (before-after studies, comparison sites, etc.), on improving exposure measures, and on model specification improvements (additive terms, non-linear relations, etc.). One might logically seek to know which lines of inquiry might provide the most significant improvements in understanding crash causation and/or prediction. It is the contention of this paper that the exclusion of important variables (causal or surrogate measures of causal variables) cause omitted variable bias in model estimation and is an important and neglected line of inquiry in safety research. In particular, spatially related variables are often difficult to collect and omitted from crash models - but offer significant opportunities to better understand contributing factors and/or causes of crashes. This study examines the role of important variables (other than Average Annual Daily Traffic (AADT)) that are generally omitted from intersection crash prediction models. In addition to the geometric and traffic regulatory information of intersection, the proposed model includes many spatial factors such as local influences of weather, sun glare, proximity to drinking establishments, and proximity to schools - representing a mix of potential environmental and human factors that are theoretically important, but rarely used. Results suggest that these variables in addition to AADT have significant explanatory power, and their exclusion leads to omitted variable bias. Provided is evidence that variable exclusion overstates the effect of minor road AADT by as much as 40% and major road AADT by 14%. © 2012 Elsevier Ltd.

Lal A.,Sardar Vallabhbhai National Institute of Technology, Surat | Singh B.N.,Indian Institute of Technology Kharagpur | Patel D.,Sardar Vallabhbhai National Institute of Technology, Surat
Composite Structures | Year: 2012

This paper present the second ordered statistics of first-ply failure response of laminated composite plate with random material properties under random loading. The basic formulation is based on higher order shear deformation plate theory (HSDT) with the geometrically nonlinearity in the von-Karman. The direct iterative based C 0 nonlinear finite element method combined with mean centered first order perturbation technique developed by the authors are extended and successfully applied nonlinearity for failure problem with a reasonable accuracy to predict the second order statistics (standard deviation) of first-ply failure response using Tsai-Wu and Hoffman failure criterion with macroscopic analysis. Typical numerical results for various combinations of boundary conditions, plate thickness ratios, aspect ratios, laminates scheme and layers, elastic modulus ratios have been presented to illustrate the application of developed procedure. Some new results are presented and examined which clearly demonstrated the importance of the randomness in the system parameters in the failure response of the structures subjected to transverse loadings. © 2011 Elsevier Ltd.

Sinha S.,Tata Consultancy Services Ltd. | Sarmah S.P.,Indian Institute of Technology Kharagpur
Computers and Industrial Engineering | Year: 2010

This paper analyzes the coordination and competition issues in a two-stage supply-chain distribution system where two vendors compete to sell differentiated products through a common retailer in the same market. The demand of a product not only depends on its own price, but also on the price of the other. Mathematical models have been developed to analyze the coordination issues under three different contexts: (i) price competition without channel coordination; (ii) price competition with channel coordination; and (iii) global coordination. It has been shown that under certain conditions, price competition through the dynamic process of price adjustment reaches the Nash-Bertrand equilibrium. Conditions have been derived for the Nash-Bertrand equilibrium to be dynamically stable. Further, it has been shown that duopoly competition can make consumers better-off or worse-off depending on the degree of product differentiation and the type of the product; while coordination enhances overall supply-chain profitability. The model is illustrated with suitable numerical examples. © 2010 Elsevier Ltd. All rights reserved.

Nagesh D.S.,Delhi Technological University | Datta G.L.,Indian Institute of Technology Kharagpur
Applied Soft Computing Journal | Year: 2010

This paper explains an integrated method with a new approach using experimental design matrix of experimental designs technique on the experimental data available from conventional experimentation, application of neural network for predicting the weld bead geometric descriptors and use of genetic algorithm for optimization of process parameters. The properties of the welded joints are affected by a large number of welding parameters. Modeling of weld bead shape is important for predicting the quality of welds. In an attempt to model the welding process for predicting the bead shape parameters (also known as bead geometry parameters) of welded joints, modeling and optimization of bead shape parameters in tungsten inert gas (TIG) welding process has been tried in the present work. Multiple linear regression technique has been used to develop mathematical models for weld bead shape parameters of TIG welding process, considering the effects of main variables as well as two factor interactions. Also by using the same experimental data, an attempt has been made to predict the bead shape parameters using back-propagation neural network. To optimize the process parameters for the desired front height to front width ratio and back height to back width ratio, genetic algorithmic approach has been applied. © 2009 Elsevier B.V. All rights reserved.

Sinha S.,Tata Consultancy Services Ltd. | Sarmah S.P.,Indian Institute of Technology Kharagpur
Computers and Industrial Engineering | Year: 2010

In this paper, a single-vendor multi-buyer discount pricing model has been developed under stochastic demand information. The vendor offers multiple pricing schedules to encourage the buyers to adopt the global optimal policy instead of their individual optimal ordering policy. The global optimal solution ensures that each buyer is assigned to the best schedule with maximum benefit. The results show that coordination benefit increases with increase in the number of pricing schedules. However, the system performance deteriorates with increasing demand variability and service level. Hence, if the system contains high degree of uncertainty or each buyer sets her service level too high, coordination through discount policy may not be an efficient mechanism to enhance channel profitability. © 2010 Elsevier Ltd. All rights reserved.

Debnath J.,University of Memphis | Dasgupta S.,Indian Institute of Technology Kharagpur | Pathak T.,Indian Institute of Technology Kharagpur
Chemistry - A European Journal | Year: 2012

Ribonuclease A (RNase A) serves as a convenient model enzyme in the identification and development of inhibitors of proteins that are members of the ribonuclease superfamily. This is principally because the biological activity of these proteins, such as angiogenin, is linked to their catalytic ribonucleolytic activity. In an attempt to inhibit the biological activity of angiogenin, which involves new blood vessel formation, we employed different dinucleosides with varied non-natural backbones. These compounds were synthesized by coupling aminonucleosides with dicarboxylic acids and amino- and carboxynucleosides with an amino acid. These molecules show competitive inhibition with inhibition constant (K i) values of (59±3) and (155±5) μM for RNase A. The compounds were also found to inhibit angiogenin in a competitive fashion with corresponding K i values in the micromolar range. The presence of an additional polar group attached to the backbone of dinucleosides was found to be responsible for the tight binding with both proteins. The specificity of different ribonucleolytic subsites were found to be altered because of the incorporation of a non-natural backbone in between the two nucleosidic moieties. In spite of the replacement of the phosphate group by non-natural linkers, these molecules were found to selectively interact with the ribonucleolytic site residues of angiogenin, whereas the cell binding site and nuclear translocation site residues remain unperturbed. Docked conformations of the synthesized compounds with RNase A and angiogenin suggest a binding preference for the thymine-adenine pair over the thymine-thymine pair. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DuttaMajumdar J.,Indian Institute of Technology Kharagpur | Li L.,University of Manchester
Materials Letters | Year: 2010

The present study aims at development of TiB dispersed α-Ti matrix composite by laser melting of Ti-2 wt.% B alloy powder (of particle size ranging from 50-100 μm) using a high power diode laser with argon shroud and depositing the molten alloy on a Ti-6Al-4 V substrate in a layer by layer fashion (up to a maximum of 5 layers were built). Followed by direct laser cladding, the characteristics and mechanical properties of the clad layer were investigated in details. Laser cladding led to formation of TiB dispersed α-Ti matrix composite with an average microhardness of 290 VHN to 500 VHN for different conditions of lasing. The average Young's modulus was considerably improved to 155-165 GPa. © 2009 Elsevier B.V. All rights reserved.

Mukherjee R.,Indian Institute of Technology Kharagpur | Sharma A.,Indian Institute of Technology Kanpur
Soft Matter | Year: 2015

The free surface of a thin soft polymer film is often found to become unstable and self-organizes into various meso-scale structures. In this article we classify the instability of a thin polymer film into three broad categories, which are: category 1: instability of an ultra-thin (<100 nm) viscous film engendered by amplification of thermally excited surface capillary waves due to interfacial dispersive van der Waals forces; category 2: instability arising from the attractive inter-surface interactions between the free surface of a soft film exhibiting room temperature elasticity and another rigid surface in its contact proximity; and category 3: instability caused by an externally applied field such as an electric field or a thermal gradient, observed in both viscous and elastic films. We review the salient features of each instability class and highlight how characteristic length scales, feature morphologies, evolution pathways, etc. depend on initial properties such as film thickness, visco-elasticity (rheology), residual stress, and film preparation conditions. We emphasize various possible strategies for aligning and ordering of the otherwise isotropic structures by combining the essential concepts of bottom-up and top-down approaches. A perspective, including a possible future direction of research, novelty and limitations of the methods, particularly in comparison to the existing patterning techniques, is also presented for each setting. © The Royal Society of Chemistry.

Chattaraj P.K.,Indian Institute of Technology Kharagpur | Duley S.,Indian Institute of Technology Kharagpur | Domingo L.R.,University of Valencia
Organic and Biomolecular Chemistry | Year: 2012

A local reactivity difference index Rk is shown to be able to predict the local electrophilic and/or nucleophilic activation within an organic molecule. Together with the electrophilic and/or nucleophilic behavior of the center k given by the sign, the magnitude of the Rk index accounts for the extent of the electronic activation, a behavior that allows for the use of the Rk index as a measure of the molecular reactivity especially in polar processes. © The Royal Society of Chemistry 2012.

Kumar K.D.,Indian Institute of Technology Kharagpur | Tsou A.H.,ExxonMobil | Bhowmick A.K.,Indian Institute of Technology Kharagpur
Macromolecules | Year: 2010

Adhesion between two unvulcanized rubber surfaces of the same material is termed autohesive tack. Interdiffusion of polymer chains that takes place across the interface and their bulk properties controls the strength of the interface. In this work, for the first time, we have studied the influence of sepiolite nanoclay on the autohesive tack strength of brominated isobutylene-co-p- methylstyrene (BIMS) rubber. The tack strength of BIMS rubber dramatically increases with nanoclay concentration. For example, the tack strength of 8 phr of nanoclay loaded sample is nearly 300% higher than the tack strength of neat BIMS rubber. Various tack governing factors such as green strength, creep compliance, entanglement molecular weight, relaxation times, self-diffusion coefficient, average penetration depth of rubber chains, and monomer friction coefficient have been analyzed. The addition of nanoclay reduces the extent of molecular diffusion across the interface by reducing the chain mobility; however, the diffusion level is still sufficient to form entanglements on either side of the interface. The entanglements arising from the diffused chains of the nanocomposite samples show greater resistance to separation due to an increase in cohesive strength, onset of transition zone relaxation time, and monomer friction coefficient value of the BIMS rubber matrix by the nanoclay reinforcement. On the other hand, the diffused chains of the unfilled sample exhibit facile chain separation due to the less cohesive strength of the BIMS rubber matrix. © 2010 American Chemical Society.

Mukherjee R.,Indian Institute of Technology Kharagpur | Sharma A.,Indian Institute of Technology Kanpur
ACS Applied Materials and Interfaces | Year: 2012

The surface of a thin elastic bilayer becomes spontaneously unstable when it is brought in proximity to another rigid contactor. The instability patterns, which are random and isotropic, exhibit a dominant lateral length scale of instability λ, which linearly scales with the bilayer thickness (h) as: λ = R Fh. It is known that for an elastic bilayer, R F exhibits a nonlinear dependence on the ratios of individual film thicknesses (H) and shear moduli (M) of the two constituent layers, and can have values as low as 0.5 under specific conditions. This is in contrast to a near constant value of R F ≈ 3 for a single layer elastic film.(1) These isotropic contact instability patterns in a bilayer can be ordered, aligned and modulated using a topographically patterned stamp. The precise morphology of the aligned structures depends on commensuration between λ and the stamp periodicity (λ P), and on the intersurface separation distance. A variety of patterns, like an array of circular holes, double periodic channels, etc., in addition to a positive and a negative replica of the stamp pattern, can be engineered with a simple stamp having 1D grating structure. A lower value of R F in a bilayer allows generating patterns with sub 500 nm lateral resolution, which is impossible to create by elastic contact lithography (ECL) of a single layer film due to strong surface tension effects in ultrathin films. Thus, control of elastic instability in a bilayer with a patterned stamp represents a flexible soft lithography tool allowing modulation of length scales, morphology, and order. © 2011 American Chemical Society.

Mittal R.,Indian Institute of Technology Kharagpur | Kansal A.,Microsoft | Chandra R.,Microsoft
Proceedings of the Annual International Conference on Mobile Computing and Networking, MOBICOM | Year: 2012

Battery life is a critical performance and user experience metric on mobile devices. However, it is difficult for app developers to measure the energy used by their apps, and to explore how energy use might change with conditions that vary outside of the developer's control such as network congestion, choice of mobile operator, and user settings for screen brightness. We present an energy emulation tool that allows developers to estimate the energy use for their mobile apps on their development workstation itself. The proposed techniques scale the emulated resources including the processing speed and network characteristics to match the app behavior to that on a real mobile device. We also enable exploring multiple operating conditions that the developers cannot easily reproduce in their lab. The estimation of energy relies on power models for various components, and we also add new power models for components not modeled in prior works such as AMOLED displays. We also present a prototype implementation of this tool and evaluate it through comparisons with real device energy measurements. Copyright © 2012 ACM.

Mondal S.,Jadavpur University | De S.,Indian Institute of Technology Kharagpur
Separation and Purification Technology | Year: 2010

A generalized theory has been proposed for a crossflow membrane filtration process, comprising of intermediate pore blocking followed by cake formation, in sequence. A phase space plot has been generated to identify the three filtration domains namely, pore blocking dominant, comparable resistances and cake dominating process. It is found that the crossflow velocity (in terms of steady state flux) has significant effect on the onset of the cake formation. It is observed that the intermediate pore blocking has very narrow region of dominance, so most experimental data are likely to lie in the cake controlling region. The operator can effectively control the characteristics of filtration by changing the crossflow velocity and transmembrane pressure. © 2010 Elsevier B.V. All rights reserved.

Jha J.K.,Indian Institute of Technology Kharagpur | Shanker K.,Indian Institute of Technology Kanpur
International Journal of Production Research | Year: 2013

This study considers a two-echelon system in which a vendor produces a product at a finite production rate and supplies it to several buyers facing independent normally-distributed demands. The product is delivered to the buyers using a set of different speed vehicles with identical capacity and different operating costs. The issues of lead time reduction and the service level constraint on the buyers have been incorporated in the model. A model is formulated to determine the optimal production-inventory policy, vehicle routes and vehicle type for each route by minimising the related production, inventory, lead time crashing and transportation costs of the system while satisfying the service level constraint on each buyer. A coordinated two-phase iterative approach is proposed to solve the model. Finally, a numerical example is included to describe the solution approach and illustrate the results. © 2013 Taylor & Francis.

Giri B.K.,Indian Institute of Technology Kharagpur | Hakanen J.,University of Jyväskylä | Miettinen K.,University of Jyväskylä | Chakraborti N.,Indian Institute of Technology Kharagpur
Applied Soft Computing Journal | Year: 2013

A new bi-objective genetic programming (BioGP) technique has been developed for meta-modeling and applied in a chromatographic separation process using a simulated moving bed (SMB) process. The BioGP technique initially minimizes training error through a single objective optimization procedure and then a trade-off between complexity and accuracy is worked out through a genetic algorithm based bi-objective optimization strategy. A benefit of the BioGP approach is that an expert user or a decision maker (DM) can flexibly select the mathematical operations involved to construct a meta-model of desired complexity or accuracy. It is also designed to combat bloat - a perennial problem in genetic programming along with over fitting and under fitting problems. In this study the meta-models constructed for SMB reactors were compared with those obtained from an evolutionary neural network (EvoNN) developed earlier and also with a polynomial regression model. Both BioGP and EvoNN were compared for subsequent constrained bi-objective optimization studies for the SMB reactor involving four objectives. The results were also compared with the previous work in the literature. The BioGP technique produced acceptable results and is now ready for data-driven modeling and optimization studies at large. © 2012 Elsevier B.V. All rights reserved.

News Article | March 2, 2017

Play Shifu Technologies, Inc., a Wyoming-based startup, is no stranger to augmented and virtual reality. The team at Play Shifu has developed a number of educational VR and AR games for children. Now, the startup is turning to the Kickstarter community to rally support for their newest product, Orboot. This smart globe uses augmented reality to teach children about different cultures, cuisines, monuments, inventions and animals from all over the world. “Globes have always been a great tool for teaching children and adults about countries from all over the world. The great thing about Orboot is that we’re able to enhance that experience for children,” said Vivek Goyal, Co-Founder at Play Shifu Technologies. Play Shifu Technologies’ other Co-Founder, Dinesh Advani, added, “By engaging children, we’re hoping to foster curiosity and help build a foundation for geography, as well as social and cultural norms across the world.” Orboot is a 10” globe that can easily fit on a child’s bedside table, desk or shelf. To use Orboot, children can scan the globe with an iOS or Android tablet to learn about countries all over the world. With hundreds of immersive 3D content pieces across eight categories, children can pick and choose which country they wish to learn more about. Within the Orboot app, children can learn about animals native to that country, monuments, cuisines, inventions, nature’s wonders, culture, language and arts, political maps and weather. Orboot launches on Kickstarter today with a $15K funding goal. The team is offering a limited number of early bird deals starting at only $29 with free shipping to most countries worldwide. Backers can expect their rewards to ship this August. Those who are interested in backing the project are encouraged to visit the Orboot campaign at About Play Shifu Technologies, Inc. Founded in 2016, Play Shifu Technologies is a startup with offices in Wyoming and India. The startup was co-founded by Vivek Goyal and Dinesh Advani, graduates of Stanford Graduate School of Business and the Indian Institute of Technology Kharagpur. As a whole, the Play Shifu team consists of parents, early learning experts, innovators and technologists. Play Shifu’s aim is to make every experience exciting and meaningful for kids. For more information, visit the website at

Dholey S.,Tdb College | Gupta A.S.,Indian Institute of Technology Kharagpur
Physics of Fluids | Year: 2013

Using group-theoretic method, an analysis is presented for a similarity solution of boundary layer equations which represents an unsteady two-dimensional separated stagnation-point (USSP) flow of an incompressible fluid over a porous plate moving in its own plane with speed u0(t). It is observed that the solution to the governing nonlinear ordinary differential equation for the USSP flow admits of two solutions (in contrast with the corresponding steady flow where the solution is unique): one is the attached flow solution (AFS) and the other is the reverse flow solution (RFS). A novel result of the analysis is that in the case of stationary plate (u0(t) = 0), after a certain value of the magnitude of the blowing d (<0) at the plate, only the AFS exists and the solution becomes unique. For a stationary plate (u0(t) = 0), the USSP flow is found to be separated for all values of d in both the cases of AFS and RFS. It is also observed that when u0(t) = 0, in the RFS flow with wall suction d (>0), there are two stagnation-points in the flow but in the presence of blowing d (<0), there is only one stagnation-point in the flow which moves further and further up with increase in |d|. Suction is shown to increase the wall shear stress while blowing has an opposite effect. Streamlines for an USSP flow when u0(t) ≠ 0 are also plotted. It is found that in this case, the USSP flow is not in general separated. © 2013 American Institute of Physics.

Kumar M.,Indian Central Research Institute for Dryland Agriculture | Raghuwanshi N.S.,Indian Institute of Technology Kharagpur | Singh R.,Indian Institute of Technology Kharagpur
Irrigation Science | Year: 2011

The use of artificial neural networks (ANNs) in estimation of evapotranspiration has received enormous interest in the present decade. Several methodologies have been reported in the literature to realize the ANN modeling of evapotranspiration process. The present review discusses these methodologies including ANN architecture development, selection of training algorithm, and performance criteria. The paper also discusses the future research needs in ANN modeling of evapotranspiration to establish this methodology as an alternative to the existing methods of evapotranspiration estimation. © 2010 Springer-Verlag.

Marchang N.,North Eastern Regional Institute of Science and Technology | Datta R.,Indian Institute of Technology Kharagpur
IET Information Security | Year: 2012

Mobile ad hoc networks (MANETs) were originally designed for a cooperative environment. To use them in hostile environments, trust-based routing can be used, where instead of establishing the shortest routes as done in traditional routing protocols, most trusted routes are established. In this study, the authors present a light-weight trust-based routing protocol. It is light-weight in the sense that the intrusion detection system (IDS) used for estimating the trust that one node has for another, consumes limited computational resource. Moreover, it uses only local information thereby ensuring scalability. Our light-weight IDS takes care of two kinds of attacks, namely, the blackhole attack and the grey hole attack. Whereas our proposed approach can be incorporated in any routing protocol, the authors have used AODV as the base routing protocol to evaluate our proposed approach and give a performance analysis. © 2012 The Institution of Engineering and Technology.

Kumar G.V.P.,North Eastern Regional Institute of Science and Technology | Raheman H.,Indian Institute of Technology Kharagpur
Biosystems Engineering | Year: 2011

A 9.75 kW walk-behind type hand tractor powered 2-row fully automatic vegetable transplanter for individual paper pot seedlings was developed by considering the power availability, paper pot dimensions and space availability in the hand tractor after the complete removal of rotavator tillage assembly. It consisted of two sets of feeding conveyor, metering conveyor, seedling drop tube, furrow opener, soil covering device, an automatic feeding mechanism, a depth adjustment wheel and hitching arrangement. Horizontal slat-type chain conveyor was used as feeding conveyor and horizontal pusher type chain conveyor was used as metering conveyor. The automatic feeding mechanism, with a timing shaft, cam and clutch, was used to coordinate the working of feeding and metering conveyors. The vegetable transplanter carried 108 seedlings on two feeding conveyors in upright orientation, fed them to the metering conveyors and planted them in upright orientation in furrows. The performance of the vegetable transplanter was evaluated for transplanting tomato at 45 × 45 cm spacing in the field at a forward speed of 0.9 km h-1. Field capacity of the transplanter was found to be 0.026 ha h-1. It resulted in the saving of 68% labour and 80% time over the conventional method of manual transplanting. The planting rate of the transplanter was found to be 32 pot seedlings min-1 with 4% missed planting and 5% tilted planting. The soil covering efficiency of the developed vegetable transplanter was about 81% and the quality of transplanting was satisfactory. © 2011 IAgrE.

Shekhar S.,Indian Defence Research And Development Laboratory | Sarkar R.,Indian Defence Research And Development Laboratory | Kar S.K.,Indian Institute of Technology Kharagpur | Bhattacharjee A.,Indian Defence Research And Development Laboratory
Materials and Design | Year: 2015

Ti-5Al-5V-5Mo-3Cr is one of the latest high strength β titanium alloys to be used for larger size components in aircraft structures replacing Ti-10V-2Fe-3Al. In the present study, a double VAR melted ingot was thermo-mechanically processed and it's microstructure and tensile properties determined as a function of β as well as α + β solution treatment and aging. The β solution treatment and aging resulted in higher strength and α + β solution treatment and aging resulted in an optimum combination of strength and ductility. Its aging behavior was studied as a function of time and temperature and corresponding microstructure as well as fractographs of tensile tested specimens were recorded. This systematic study should help in further modeling its mechanical behavior. © 2014 Elsevier Ltd.

Sahoo N.C.,Petronas University of Technology | Ganguly S.,Indian Institute of Technology Kharagpur | Das D.,Indian Institute of Technology Kharagpur
Swarm and Evolutionary Computation | Year: 2012

A multi-objective planning approach for electrical distribution systems using particle swarm optimization is presented in this paper. In this planning, the number of feeders and their routes, number and locations of sectionalizing switches, and number and locations of tie-lines of a distribution system are optimized. The multiple objectives to determine optimal values for these planning variables are: (i) minimization of total installation and operational cost and (ii) maximization of network reliability. The planning optimization is performed in two steps. In the first step, the distribution network structure, i.e., number of feeders, their routes, and number and locations of sectionalizing switches are determined. In the second step, the optimum number and locations of tie-lines are determined. Both the objectives are minimized simultaneously to obtain a set of non-dominated solutions in the first step of optimization. The solution strategy used for the first step optimization is the Strength Pareto Evolutionary Algorithm-2 (SPEA2) based multi-objective particle swarm optimization (SPEA2MOPSO). In the second step, the solutions/networks obtained from the previous step are further optimized by placement of tie-lines. SPEA2-based binary MOPSO (SPEA2BMOPSO) is used in the second step of optimization. The proposed planning algorithm is tested and evaluated on different practical distribution systems. © 2011 Elsevier B.V. All rights reserved.

Mukherjee D.,Indian Institute of Technology Kharagpur | Ray S.,Indian Statistical Institute
Palaeontology | Year: 2014

A new species of the rhynchosaur genus Hyperodapedon, namely H. tikiensis, is described from well-preserved skeletal elements that were collected from the Upper Triassic Tiki Formation of India. Hyperodapedon tikiensis is diagnosed on the basis of several cranial and postcranial features including longer than wide basipterygoid process, crest-shaped maxillary cross section lateral to the main longitudinal groove, deeply excavated neural arches of mid-dorsal vertebrae, long scapular blade, a pronounced deltopectoral crest, proximal humeral end much broader than distal end, iliac length greater than iliac height, equal pre- and postacetabular iliac lengths and circular femoral cross section. Two distinct morphotypes of the maxillary tooth plates can be discerned, which are attributed to ontogenetic variations. A maximum-parsimony analysis was carried out to show that the order Rhynchosauria is characterized by nine cranial and one postcranial character states. The analysis reveals that Otischalkia elderae is invalid and the basal forms, Howesia and Mesosuchus, are closely related. The Mid-Triassic genus Ammorhynchus is more derived and forms a sister group to the Late Triassic subfamily Hyperodapedontinae. Isalorhynchus and Teyumbaita are basal to the pandemic genus Hyperodapedon. Twenty-four characters that are not homoplasious document major patterns of skeletal evolution in rhynchosaurs. From laterally oriented scapula and slender propodials, the postcranial skeleton evolved into a more robust form as is evident from nearly vertical scapula and increase in the robustness of the propodials. Shortening of the femur is noted in the derived Late Triassic forms as exemplified in Hyperodapedon gordoni, Hyperodapedon huxleyi and H. tikiensis. © The Palaeontological Association.

Mukherjee S.,Mentor Graphics | Dasgupta P.,Indian Institute of Technology Kharagpur
International Journal of Approximate Reasoning | Year: 2013

High-level descriptions of real-time systems often use fuzzy notions of time that are left open to domain specific interpretations. In order to verify that a given implementation conforms to such loosely defined specifications, the typical approach is to verify the implementation to be correct within well defined limits of time tolerance. This approach determines whether the real-time requirements are met, but does not reflect how well it is met. Our goal in this paper is to prescribe the development of timed specifications using fuzzy notions of time, and to present a methodology for computing the quality of satisfaction of the specification on a given implementation using domain specific fuzzy membership functions. With this objective, we combine the notions of real-time interval temporal logic (like Metric Interval Temporal Logic) and fuzzy logic to derive FRTL, a fuzzy real-time temporal logic. The novelty of the proposed logic is in introducing the notion of fuzzy time intervals into the core fabric of conventional metric temporal logic. We present a method for evaluating the fuzzy truth of FRTL properties on finite traces. We discuss the motivation of computing the fuzzy truth towards evaluating the quality of control in time critical embedded control system applications. We also show that two important related problems from the domain of mixed-signal design verification, are subsumed by the proposed framework of analysis. © 2013 Elsevier Inc. All rights reserved.

Ganguly S.,National Institute of Technology Rourkela | Sahoo N.C.,Petronas University of Technology | Das D.,Indian Institute of Technology Kharagpur
Fuzzy Sets and Systems | Year: 2013

This paper presents a multi-objective planning approach for electrical distribution systems under uncertainty in load demand incorporating distributed generation (DG). Both radial and meshed systems are considered. The overall influence of load demand uncertainty on planned networks is investigated in detail. Uncertainty in load demand is possibilistically modeled using a fuzzy triangular number. The two objectives in system planning are: (i) minimization of total installation and operational costs, and (ii) minimization of the risk factor. The risk factor is a function of the contingency load-loss index (CLLI), which measures load loss under contingencies, and the degree of network constraints violations. CLLI minimization improves network reliability. The network variables optimized are: (i) the network structure type (radial or meshed), (ii) the number of feeders and their routes, and (iii) the number and location of sectionalizing switches. The optimization tool is a multi-objective particle swarm optimization (MOPSO) variant that uses heuristic selection and assignment of leaders or guides for efficient identification of non-dominated solutions. The optimal number, location, and size of the DG units are determined in another planning stage. Performance comparisons between the planning approaches with possibilistic and deterministic load models highlight the relative merits and demerits. The advantages of networks obtained using the proposed planning approach in the context of DG integration are described. The proposed planning approach is validated using three typical distribution systems. © 2012 Elsevier B.V.

Rahut D.B.,Wheat Improvement Center | Behera B.,Indian Institute of Technology Kharagpur | Ali A.,Agricultural Economist
Renewable and Sustainable Energy Reviews | Year: 2016

This paper uses data from three Bhutan Living Standard surveys (BLSS 2003, BLSS 2007, and BLSS 2012) to examine the trends and patterns of household energy consumption, and identify and analyze the factors that influence household energy choices, consumption intensity and the per capita household expenditure on energy sources in Bhutan. During the last decade significant numbers of Bhutanese households have switched to cleaner energy sources. Empirical results show that a household's choice of cleaner energy sources is driven by income level and household wealth, the age, gender and education of the household heads, access to electricity, and location. Education and income have a differential role on the choice of clean or dirty fuel; wealthier and more educated households use and rely more on clean sources of energy like electricity and liquid petroleum gas while poorer households use and rely on dirty fuel such as fuelwood and kerosene. The study shows that female-headed households are more likely to choose cleaner fuels and, above all, the availability of a clean and cost-effective source of energy within proximity to the household is an important factor in the adoption of clean energy. Several models using a variety of alternative independent variables, such as proxies for education and wealth, were estimated and confirmed the robustness of the results. © 2015 Elsevier Ltd. All rights reserved.

Roy S.,Indian Institute of Technology Kharagpur | Bhattacharya B.B.,Indian Statistical Institute | Chakrabarty K.,Duke University
Proceedings -Design, Automation and Test in Europe, DATE | Year: 2011

A key challenge in design automation of digital microfluidic biochips is to carry out on-chip dilution/mixing of biochemical samples/reagents for achieving a desired concentration factor (CF). In a bioassay, reducing the waste is crucial because the waste droplet handling is cumbersome and the number of waste reservoirs on-chip needs to be minimized to use limited volume of sample and expensive reagents and hence to reduce the cost of a biochip. The existing dilution algorithms attempt to reduce the number of mix/split steps required in the process but focus little on minimization of sample requirement or waste droplets. In this work, we characterize the underlying combinatorial properties of waste generation and identify the inherent limitations of two earlier mixing algorithms (BS algorithm by Thies et al., Natural Computing 2008; DMRW algorithm by Roy et al., IEEE TCAD 2010) in addressing this issue. Based on these properties, we design an improved dilution/mixing algorithm (IDMA) that optimizes the usage of intermediate droplets generated during the dilution process, which in turn, reduces the demand of sample/reagent and production of waste. The algorithm terminates in O(n) steps for producing a target CF with a precision of 1/2n. Based on simulation results for all CF values ranging from 1/1024 to 1023/1024 using a sample (100% concentration) and a buffer solution (0% concentration), we present an integrated scheme of choosing the best waste-aware dilution algorithm among BS, DMRW, and IDMA for any given value of CF. Finally, an architectural layout of a DMF biochip that supports the proposed scheme is designed. © 2011 EDAA.

Pande S.,Indian Institute of Technology Kharagpur | Chowdhury J.,Sammilani Mahavidyalaya | Pal T.,Indian Institute of Technology Kharagpur
Journal of Physical Chemistry C | Year: 2011

Adsorption of 1,10-phenanthroline (PHEN) on the Aucore-Ag shell (Au@Ag) bimetallic nanocolloid surface has been investigated. Bimetallic nanocolloids have been synthesized using β-cyclodextrin (β-CD) in alkaline solution. Nanocolloids of different Au core:Agshell ratio were synthesized keeping the same Aucore size. Again, for the preparation, the total metal concentrations were always kept constant. The structure and composition of the bimetallic particles were characterized by UV-vis and high-resolution transmission electron microscopy. Detailed normal Raman (NRS) and surface-enhanced Raman spectra (SERS) of PHEN in aqueous solution have been studied. The relative contributions of the electromagnetic (EM) and charge-transfer (CT) mechanism to the overall enhancement of the SERS bands of the PHEN molecule have been estimated. PHEN molecules are adsorbed on the Agshell surface through both the nitrogen atoms with the molecular plane almost perpendicular to the surface, which has been confirmed from Ag-N stretching vibration. The three-dimensional finite difference time domain (3D-FDTD) method has been applied to simulate the local electric field on the spherical Au@Ag nanocolloid for various core/shell ratios. Comparative spectral information revealed the highest SERS effect from the 1:4 Aucore- Agshell bimetallic nanocolloid of 29 nm size. This observation has also been supported by theory. Thus, experiment and theory keep abreast the attachment of PHEN molecules on a new substrate from SERS studies. © 2011 American Chemical Society.

Rekha S.,Indian Institute of Technology Kharagpur | Viswanath T.A.,Goa University | Bhattacharya A.,Indian Institute of Technology Kharagpur | Prabhakar N.,Indian Institute of Technology Kharagpur
Precambrian Research | Year: 2013

Synthesis of mesoscopic structures and microscopic analyses of fabric superposition and deformation microstructures are combined with Th-U-Pb (total) ages in monazites to constrain the Meso/Neoarchean crustal domains in the Western Dharwar Craton (WDC) along the western coast of India; the domains are correlated with those in NE Madagascar to configure the assembly of crustal domains in the East Gondwanaland prior to the Mesozoic break up. In the WDC, para-schists and phyllites of the Shimoga schist belt, SSB (unmixed age components, 3067. ±. 26 and 3158. ±. 110. Ma) and the Peninsular gneisses (3138. ±. 35. Ma) are intruded by granitoid plutons (2924. ±. 50. Ma) deformed at low-T. Five generations of deformation events are identified in the SSB and Peninsular gneisses. But the two early tectonic fabrics in Peninsular gneisses formed at anatectic amphibolite facies conditions are in sharp contrast to fabrics in SSB formed at greenschist facies. The two lithodemic units are inferred to share a pre-3.2. Ga tectonic contact.By contrast, in the Goa schist belt (GSB), phyllites/schists (unmixed ages - 2436. ±. 34, 2543. ±. 66 and 2625. ±. 36. Ma) and polymict conglomerates (unmixed ages - 2458. ±. 34 and 2566. ±. 53. Ma) possess two generations of tectonic fabrics and are the youngest dated metamorphic unit in the WDC. The deformed Quepem granitoid pluton located along the axial zone of the regional-scale N-trending gently plunging upright folds in GSB yields comparable chemical age (2565. ±. 33. Ma). Angular to sub-rounded and boulder to granule sized polymict clasts of Peninsular gneisses (3128. ±. 60. Ma), foliated granitoids, amphibolites, BIFs and low-grade quartzite/chlorite-muscovite schists in GSB para-conglomerates suggest the sediments deposited in shallow basin were derived from neighboring sources, e.g. the Peninsular gneisses and SSB supracrustals. The Neoarchean deformation-metamorphism marks the closure of the Goa basin synchronous with the 2.4-2.6. Ga accretion of the West and the East Dharwar Cratons.Based on the results of this study, the following correlation among Mesoarchean-Neoarchean crystallites in the Western Dharwar Craton and the Antongil-Masora Block, NE Madagascar (in italics below) appears realistic, e.g. 2.4-2.6. Ga Goa schist belt. ≈. Mananara Group; 2.5. Ga Quepem granitoid. ≈. Masoala Suite; 3.1. Ga Shimoga schist belt. ≈. Fenerivo Group; 3.1. Ga Peninsular gneiss suite. ≈. Nosy Boraha suite. © 2013 Elsevier B.V.

Rekha S.,Indian Institute of Technology Kharagpur | Bhattacharya A.,Indian Institute of Technology Kharagpur | Viswanath T.A.,Goa University
Geochimica et Cosmochimica Acta | Year: 2013

In a deformed para-conglomerate (western India), monazites occur as discrete grains (50-250μm long axis) in tonalite clasts, in the warping chlorite-biotite-calcite schist layers, and as disseminated grains (<5μm) along with xenotime and huttonite forming veins in schist layers. The veins are absent in clasts. Chlorite and biotite defining schistosity in schist layers and in synchronously-formed extensional veins/fractures in clasts are chemically identical. δ18O (VSMOW) and δ13C (VPDB) in calcite in schistosity, in clasts, and in "beards" in pressure shadow zones around clasts are tightly bracketed, 11.4-12.2‰ and -3.1 to -3.6‰ respectively. Margins of clast-hosted monazites are partly altered to fluorapatite-huttonite ± allanite ± Y-xenotime. By contrast, monazite alteration in schist layers is extensive. In schist layers, rafts of embayed monazite occur in fluorapatite-dominated corona studded with idiomorphic huttonite, Y-xenotime ± allanite. Mass balance calculation in a well-defined alteration zone around monazite in schist layer with P conserved indicate large gain in mass fraction of lower-abundance, less soluble HREEs, Y and Th in the alteration zone was compensated by minor loss in mass fraction of higher abundance elements (LREEs, MREEs) resulting in negligible net mass change. Monazite decomposition was associated with ∼50% dilation strain. Yb, Th and U abundances in alteration zones around decomposed monazites in schist layer are computed to be manifold higher than average schists. The contemporaneous formation of pore microstructures, the chemical homogeneity among ferromagnesian minerals and C-O isotope data in calcite in different textural domains, and results of mass balance calculations are compatible with deformation-aided porosity generation, synchronous fluid-mediated advection transport of elements, and dissolution-re-precipitation of mica-calcite aggregates at upper crustal conditions, ∼500 °C, ∼4 kbar. Monazite instability was induced by strain-focused influx of HREE, Y, Th and U rich fluids from external sources. The better preservation of within-clast monazite relative to the ones in weak-to-shear schist layers is attributed to limited fluid access through fewer porosity networks in actively deforming clasts. © 2012 Elsevier Ltd.

Kundu J.,Indian Institute of Technology Kharagpur | Poole-Warren L.A.,University of New South Wales | Martens P.,University of New South Wales | Kundu S.C.,Indian Institute of Technology Kharagpur
Acta Biomaterialia | Year: 2012

Hydrogels are three-dimensional polymer networks widely used in biomedical applications as drug delivery and tissue engineered scaffolds to effectively repair or replace damaged tissue. In this paper we demonstrate a newly synthesized cytocompatible and drug releasing photo-crosslinked hydrogel based on poly(vinyl alcohol) methacrylate and silk fibroin which possesses tailorable structural and biological properties. The initial silk fibroin content was 0%, 10%, 20%, 30%, 40% and 50% with respect to the weight of poly(vinyl alcohol) methacrylate. The prepared hydrogels were characterized with respect to morphology, crystallinity, stability, swelling, mass loss and cytotoxicity. FITC-dextrans of different molecular weights were chosen as model drugs molecules for release studies from the hydrogels. The hydrogels containing different silk fibroin percentages showed differences in pore size and distribution. X-ray diffraction analysis revealed that amorphous silk fibroin in poly(vinyl alcohol) methacrylate is crystallized to β-sheet secondary structure upon gelation. The sol fraction increased with increasing fibroin concentration in the co-polymer gel (from 18% to 45%), although the hydrogel extracts were non-cytotoxic. Similarly, the addition of silk fibroin increased water uptake by the gels (from 7% to 21%). FITC-dextran release from the hydrogels was dependent on the silk fibroin content and the molecular weight of encapsulated molecules. The study outlines a newer type of photo-crosslinked interpenetrating polymer network hydrogel that possess immense potential in drug delivery applications. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Krithivasan S.,Jawaharlal Nehru Centre for Advanced Scientific Research | Wahal S.,Indian Institute of Technology Kharagpur | Ansumali S.,Jawaharlal Nehru Centre for Advanced Scientific Research
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

A solid-fluid boundary condition for the lattice Boltzmann (LB) method, which retains the simplicity of the bounce-back method and leads to positive definite populations similar to the diffusive boundary condition, is presented. As a refill algorithm, it is proposed that quasi-equilibrium distributions be used to model distributions at fluid nodes uncovered due to solid movement. The method is tested for flow past an impulsively started cylinder and demonstrates considerable enhancement in the accuracy of the unsteady force calculation at moderate and high Reynolds numbers. Furthermore, via simulations, we show that momentum exchange procedure used in LB to compute forces is not Galilean invariant. A modified momentum exchange procedure is proposed to reduce the errors due to violation of Galilean invariance. © 2014 American Physical Society.

Bhowmik S.K.,Indian Institute of Technology Kharagpur | Bernhardt H.-J.,Ruhr University Bochum | Dasgupta S.,Indian Institute of Science
Precambrian Research | Year: 2010

In this study, we deduce the age of the collisional orogeny in the Aravalli-Delhi Mobile Belt, using electron microprobe (EMP) dating of monazites of two suites of metapelitic to metapsammitic rocks from the Banded Gneissic Complex of Central Rajasthan. These metasediments of the Sandmata and the Mangalwar Complexes record a high-pressure, upper amphibolite (P ∼ 10.3 ± 0.8 kbar, T ∼ 675 ± 60 °C) to granulite facies (P ∼ 12-14 kbar, T ∼ 815 °C) peak metamorphism (M2P stage) and a post-peak decompression to ∼5 kbar, 575-660 °C (M2R stage), following a clockwise P-T path (M2 event). The metapelites of the Sandmata Complex, however, record an older, medium-pressure, sillimanite-facies granulite metamorphism (M1 event). Electron microprobe dating of monazites, occurring in the different textural settings of three metapelite granulite samples of the Sandmata Complex yields three mean spot age populations at ∼1700 ± 3 to ∼1733 ± 15 Ma, ∼1597 ± 6 to ∼1629 ± 23 Ma and ∼882 ± 15 Ma. While Late Palaeoproterozoic age populations are correlated with the timing of the M1 metamorphism, the Early Neoproterozoic ages from garnet-breakdown textural domain constrain the timing of the overprinting M2R event. Interpretation of the Late Mesoproterozoic age component is problematic. It may reflect either a mixed age due to partial Pb loss of the Palaeoproterozoic monazites by a younger high-grade event or may define the timing of a high-grade tectonothermal event, the imprints of which have been registered in the Proterozoic mobile belts of central, eastern, north-eastern and south-eastern India. Monazites from the metapelites of the Mangalwar Complex yield characteristic Late Mesoproterozoic to Neoproterozoic ages with clusters at 946 ± 6, 909 ± 9 and 865 ± 10 Ma. The metagranites intrusive into the M1 granulites additionally register an emplacement age of ∼978 ± 18 Ma. The age span of ∼0.98-0.95 to ∼0.88-087 Ga is taken as the age of the M2 event. Based on these geochronologic and metamorphic findings, we assign a Grenvillian age for the collisional orogeny in the Aravalli-Delhi Mobile Belt. The extent of propagation of the Grenvillian orogenic front in the Aravalli-Delhi orogen and its implication in Rodinia reconstruction are also discussed. © 2010 Elsevier B.V. All rights reserved.

Sarkar U.,Assam University | Khatua M.,Indian Institute of Technology Kharagpur | Chattaraj P.K.,Indian Institute of Technology Kharagpur
Physical Chemistry Chemical Physics | Year: 2012

Quantum fluid density functional theory has been used to study the time evolution of various reactivity parameters such as hardness, electrophilicity, entropy, chemical potential, polarizability, electronegativity etc. in a confined environment during time dependent processes like atom-ion collision and atom-field interaction. Responses in the reactivity parameters of the helium atom, in the dynamical context, for ground state as well as in excited state, have been reported. The confinement is incorporated through a Dirichlet type boundary condition. With a decrease in the size of the cylindrical box, the system gets harder and less polarizable. Simultaneous excitation and confinement may bring back the ground state behavior. © the Owner Societies 2012.

Reddy G. U.,Indian Central Salt and Marine Chemicals Research Institute | Das P.,Indian Central Salt and Marine Chemicals Research Institute | Saha S.,Indian Central Salt and Marine Chemicals Research Institute | Baidya M.,Indian Institute of Technology Kharagpur | And 2 more authors.
Chemical Communications | Year: 2013

A new "turn-on" luminescence probe for imaging the uptake of 0.2 ppm inorganic CN- in live HeLa cells as well as for probing the CN- generation through an enzymatic process in a virtual aqueous medium at appropriate pH. This journal is © 2013 The Royal Society of Chemistry.

Barai M.,Indian Institute of Technology Kharagpur | Sengupta S.,Indian Institute of Technology Kharagpur | Biswas J.,International Institute of Information Technology Bangalore
IEEE Transactions on Power Electronics | Year: 2010

A high-frequency digital controller that includes an optimized analog-digital converter (ADC) with a novel formulation of digital error value based on target clock frequency and converter output voltage is presented in this paper. A programmable look-up table-based digital compensator is implemented for fast processing the feedback error. Limitations of a hybrid digital pulsewidth modulator (DPWM) at high frequency are addressed and solved by an edge-triggered logic. Support for process, voltage, and temperature variations is incorporated in the integrated design. Target clock frequency denotes the frequency of the signal which is driven by dynamic voltage scaling (DVS) processor and corresponds to the reference value of the regulated output voltage. This work realizes the classical digital controller design implementation of a target frequency to minimum required regulated voltage for DVS-enabled adaptive dc-dc converter. A synchronous buck converter of 1 MHz switching frequency and the proposed delay-line-based optimized ADC have been fabricated for realizing and verifying the complete digital controller on a field-programmable gate array-based closed-loop prototype. Experimental results are presented, which demonstrate the fast dynamic response achieved for target clock frequency in the range of 6-16 MHz, corresponding to the regulated output voltage range of 1.6-3.2 V. The complete design of digital controller has been implemented in 0.5 μm CMOS technology using Cadence and Synopsys tools. The active on-chip area of the proposed delay-line ADC, digital compensator, and edge-triggered hybrid DPWM are 0.08, 0.28, and 0.07 mm2respectively. © 2009 IEEE.

Rekha S.,Indian Institute of Technology Kharagpur | Bhattacharya A.,Indian Institute of Technology Kharagpur | Chatterjee N.,Massachusetts Institute of Technology
Precambrian Research | Year: 2014

New structural-mineralogical data and U-Th-total Pb monazite chemical ages in 27 samples in a 430. km long corridor along the west coast of India are combined with existing data to reconstruct the tectonic set up of the Meso/Neoarchean crystalline rocks in the Western Dharwar Craton (WDC). The data helps to delineate two NW-trending Paleoproterozoic ductile shear zones that limit the southern and the northern margins of the WDC. The southern shear zone (metamorphic age: 2.3-2.4 Ga) separates the greenschist facies supracrustal belts (2.5 and 3.3 Ga), foliated granitoids (2.5 and 2.9 Ga) and amphibolite facies anatectic gneisses (>3.0 Ga) of the WDC from the >2.9 Ga granulite facies ortho/para-gneisses of the Coorg Block. This shear zone is correlated with the ~2.4 Ga Betsimisaraka suture zone in east-central Madagascar that demarcates the accretion zone between the Antongil Block (≈WDC) and the granulite facies lithologies of the Antananarivo domain (≈Coorg Block). The northern shear zone system (metamorphic age: 2.2-1.8 Ga) extending NW into Madagascar possibly exists as a hitherto undiscovered tectonic zone forming the basement of the Mesoproterozoic Sahantaha Formation underlying the Neoproterozoic Bemarivo Belt supracrustals in NE Madagascar. Within the WDC, the Meso/Neoproterozoic ages retrieved from poorly-defined margins in monazite are uncommon, dispersed within the craton, and do not define localized zones within the craton. The chemical ages of metamorphic monazites formed at greenschist/amphibolite facies conditions preclude metamorphism-deformation associated with accretion of crustal blocks within the WDC during the Rodinia assembly. © 2014 Elsevier B.V.

Chinnasamy S.S.,University of KwaZulu - Natal | Mishra B.,Indian Institute of Technology Kharagpur
Economic Geology | Year: 2013

Gold mineralization at Jonnagiri is hosted in laminated quartz veins within sheared granodiorite in a typical Archean greenstone-granitoid ensemble. The greenstones and the intrusive granodiorite have been affected by two folding and shearing events, respectively. THERMOCALC-aided P-T calculations suggested that lower amphibolite-grade metamorphism affected the greenstones, involving peak conditions at ~5 kbar and 500°C. Gold mineralization is characterized by a chlorite + biotite-rich proximal alteration zone and a muscovitedominant inner zone among laminated auriferous quartz veins. Whereas the proximal zone had significant gain in S, C, K, Si, and Rb and depletion of Ca, Mg, and Fe, the inner alteration zone is typified by major addition of Si, K, S, C, and Au. General depletion of rare earth elements in the altered granodiorites is ascribed to high ambient fluid/rock during hydrothermal alteration. Results of the computed (aMg 2+/aH +2) vs. (aK +/aH +) and (aNa +/aH +) vs. (aK +/a H +) diagrams, along with an increase in carbonation and alkali enrichment indices in the altered rocks, explain the observed hydrothermal alteration-induced mineralogical changes and constrain the possible fluid composition. Gold occurs as fracture fillings in the quartz matrix and pyrite grains, together with other sulfides, and associated with the f S2-buffering assemblage pyrite + pyrrhotite. Arsenopyrite compositions in the pyrite-arsenopyrite assemblage yielded temperature and log fS2 ranges of 305° to 335°C and -10.9 to -8.6, respectively. These temperature estimates compare well with the published results of chlorite thermometry (263°-323°C). Mineral-fluid equilibrium computations place narrow constraints on the ore fluid fO2 (and aH2S). Gold precipitation was a consequence of postpeak metamorphic fluid phase separation involving immiscibility of gaseous spies, fluid-rock interaction, and decrease in fO2 of the fluid. Published δ34S values in pyrite fall in a narrow range of 1.4 to 7.1‰, and the calculated δ34S H2S varies from 0.2 to 5.8‰, at log f O2 = -32.6 and pH = 5.15 to 5.95; these imply that Au(HS)2 - was the dominant gold complex. The narrow range of δ34SPy values is indicative of magmatic (± mantle) source, or involvement of fluid with an average crustal sulfur composition. The geologic events responsible for Jonnagiri started with accretion of the greenstone package at the subduction boundary between the eastern and western blocks of the Dharwar craton, followed by their deformation, shearing, and metamorphism, with subsequent emplacement of the Pagadarayi granodiorite and continued shearing, culminating with fluid flow focused along the shear fractures, which resulted in postpeak metamorphic hydrothermal alteration and precipitation of gold-bearing quartz lodes. From the observed craton-scale uniformity in the chemical and sulfur isotope compositions of the ore fluids, we propose a model involving contamination of an auriferous metamorphic fluid with crustal sulfur during its upward transport. ©2013 Society of Economic Geologists, Inc.

Kameswaran P.K.,University of KwaZulu - Natal | Narayana M.,University of KwaZulu - Natal | Sibanda P.,University of KwaZulu - Natal | Murthy P.V.S.N.,Indian Institute of Technology Kharagpur
International Journal of Heat and Mass Transfer | Year: 2012

We investigate the convective heat and mass transfer in nanofluid flow over a stretching sheet subject to hydromagnetic, viscous dissipation, chemical reaction and Soret effects. Two types of nanofluids, namely Cu-water and Ag-water were studied. A similarity transformation was used to obtain a system of non-linear ordinary differential equations, which was then solved numerically using the Matlab "bvp4c" function. Numerical results were obtained for the skin friction coefficient, Nusselt number, Sherwood number as well as for the velocity, temperature and concentration profiles for selected values of the governing parameters, such as the nanoparticle volume fraction φ, the magnetic parameter M. For a fixed Prandtl number Pr=6.2 (corresponding to water) and different values of the magnetic field parameter and the nanoparticle volume fraction, we have shown that a good agreement exists between the present results and those in the literature. It was shown that the Cu-water nanofluid exhibits higher wall heat and mass transfer rates as compared to a Ag-water nanofluid. The influence of a magnetic field is to reduce both wall heat and mass transfer rates. © 2012 Elsevier Ltd. All rights reserved.

Kundu B.,Indian Institute of Technology Kharagpur | Saha P.,Jawaharlal Nehru University | Datta K.,Jawaharlal Nehru University | Kundu S.C.,Indian Institute of Technology Kharagpur
Biomaterials | Year: 2013

Microenvironment around tumor cells plays an important role in its malignancy or invasiveness. Hyaluronan (HA), a major component of extracellular matrix is found to be elevated in most of cancerous niche/microenvironment and performs regulatory role in the progression of tumors and metastasis. Overexpression of the hyaladherin, hyaluronan-binding protein 1 (HABP1) in the hepatocarcinoma cells (HepG2) termed as HepR21 leads to enhanced cell proliferation with increased HA 'pool' associated with HA 'cables' indicating elevated tumorous potential under 2D culture conditions. For invitro experimentation, scaffold based three dimensional niche modeling may have greater acceptance than conventional 2D culture condition. Thus, we have examined the influence of intrinsic properties of non-mulberry tropical tasar silk fibroin on the HepR21 cells in order to develop a 3D hepatocarcinoma construction to act as model. The scaffold of tasar silk fibroin of Antheraea mylitta when efficiently loaded with transformed hepatocarcinoma cells, HepR21; exhibits enhanced adhesiveness, viability, metabolic activity, proliferation and enlarged cellular morphology in 3D compared to its parent cell line HepG2, supporting the earlier observation made in 2D system. In addition, formation of multicellular aggregates, the indicator of tumor progression is also revealed in silk based 3D culture conditions. Further, the use of 4-MU (a hyaluronan synthase inhibitor) on HepR21 cells reduces the HA level and downregulates the expression of growth promoting factors like pAKT and PKC; while upregulating the expression of the tumor suppressor p53. Thus, 4-MU efficiently reduces the tumor potency associated with increased HA pool as well as HA cables and the effect of 4-MU doubling up as an anticancer agent in 2D and 3D are also comparable. The invitro 3D multicellular model demonstrates the insight of hepatocarcinoma progression and offers the predictability of cellular response to transfection efficacy, drug treatment and therapeutic intervention. © 2013 Elsevier Ltd.

Sahu D.,Indian Central Salt and Marine Chemicals Research Institute | Dey S.,Indian Institute of Technology Kharagpur | Pathak T.,Indian Institute of Technology Kharagpur | Ganguly B.,Indian Central Salt and Marine Chemicals Research Institute
Organic Letters | Year: 2014

DFT (M06-L) calculations on the transition state for the 1,3-dipolar cycloadditions between substituted vinyl sulfones with sugar azide have been reported in conjunction with new experimental results, and the origin of reversal of regioselectivity has been revealed using a distortion/interaction model. This study provides the scientific justification for combining organic azides with two different types of vinyl sulfones for the preparation of 1,5-disubstituted 1,2,3-triazoles and 1,4-disubstituted triazolyl esters under metal-free conditions. © 2014 American Chemical Society.

Jha R.K.,Indian Institute of Information Technology, Design and Manufacturing | Chouhan R.,Indian Institute of Technology Kharagpur
Signal, Image and Video Processing | Year: 2014

In this paper, a dynamic stochastic resonance (DSR)-based technique in singular value domain for contrast enhancement of dark images has been presented. The internal noise due to the lack of illumination is utilized using a DSR iterative process to obtain enhancement in contrast, colorfulness as well as perceptual quality. DSR is a phenomenon that has been strategically induced and exploited and has been found to give remarkable response when applied on the singular values of a dark low-contrast image. When an image is represented as a summation of image layers comprising of eigen vectors and values, the singular values denote luminance information of each such image layer. By application of DSR on the singular values using the analogy of a bistable double-well potential model, each of the singular values is scaled to produce an image with enhanced contrast as well as visual quality. When compared with performance of some existing spatial domain enhancement techniques, the proposed DSR-SVD technique is found to give noteworthy better performance in terms of contrast enhancement factor, color enhancement factor and perceptual quality measure. © 2012 Springer-Verlag London Limited.

Sahoo M.P.K.,Indian Institute of Technology Kharagpur | Choudhary R.N.P.,Institute of Physics, Bhubaneswar
Materials Letters | Year: 2012

A solid-solution of PbMg1/3Nb2/3O3- BiFeO3 (60:40) was prepared by a high-temperature solid-state reaction technique. Rietveld structural analysis using high-resolution X-ray diffraction data/pattern of the above system unfolds a rhombohedral crystal structure with R3m space group. Detailed studies of dielectric properties of the material in wide temperature range (30-420 °C) exhibit a dielectric anomaly at 300 °C which may be related to the magnetic transition. Increase in relative permittivity above this transition temperature is supported by thermally activated transport of oxygen vacancies and hopping of electrons. The temperature response of ac conductivity in this material is found to be governed by the motion of ionized oxygen vacancies, polarons and lead (Pb) vacancies. © 2011 Elsevier B.V. All rights reserved.

Barekar N.S.,Brunel University | Dhindaw B.K.,Indian Institute of Technology Kharagpur
Materials and Manufacturing Processes | Year: 2014

Since its invention by Sir Henry Bessemer in 1865, twin-roll casting (TRC) has been the subject of extensive research, not only to develop the technology but also to achieve an understanding of microstructural evolution. The present review confines itself to the literature on process aspect, modeling, and quality issues. Initially, the principles of the process are outlined. Modeling of fluid flow, heat transfer, and microstructural evolution, surface and internal defects in TRC of aluminum alloys are next discussed. The role of process parameters on solidification during casting is reviewed. The controls of grain structure by melt treatment are also discussed in brief. Copyright © 2014 Taylor & Francis Group, LLC.

Sharma S.P.,Indian Institute of Technology Kharagpur | Verma S.K.,National Geophysical Research Institute
Geophysical Prospecting | Year: 2011

The problem of equivalence in direct current (DC) resistivity and electromagnetic methods for a thin resistive and conducting layer is well-known. Attempts have been made in the past to resolve this problem through joint inversion. However, equivalence still remains an unresolved problem. In the present study, an effort is made to reduce non-uniqueness due to equivalence using global optimization and joint inversion by successive refinement of the model space. A number of solutions derived for DC resistivity data using very fast simulated annealing global inversion that fits the observations equally well, follow the equivalence principle and show a definite trend. For a thin conductive layer, the quotient between resistivity and thickness is constant, while for a resistive one, the product between these magnitudes is constant. Three approaches to obtain very fast simulated annealing solutions are tested. In the first one, layer resistivities and thicknesses are optimized in a linear domain. In the second, layer resistivities are optimized in the logarithmic domain and thicknesses in the linear domain. Lastly, both layer resistivities and thicknesses are optimized in the logarithmic domain. Only model data from the mean models, corresponding to very fast simulated annealing solutions obtained for approach three, always fit the observations. The mean model defined by multiple very fast simulated annealing solutions shows extremely large uncertainty (almost 100%) in the final solution after inversion of individual DC resistivity or electromagnetic (EM) data sets. Uncertainty associated with the intermediate resistive and conducting layers after global optimization and joint inversion is still large. In order to reduce the large uncertainty associated with the intermediate layer, global optimization is performed over several iterations by reducing and redefining the search limits of model parameters according to the uncertainty in the solution. The new minimum and maximum limits are obtained from the uncertainty in the previous iteration. Though the misfit error reduces in the solution after successive refinement of the model space in individual inversion, it is observed that the mean model drifts away from the actual model. However, successive refinement of the model space using global optimization and joint inversion reduces uncertainty to a very low level in 4-5 iterations. This approach works very well in resolving the problem of equivalence for resistive as well as for conducting layers. The efficacy of the approach has been demonstrated using DC resistivity and EM data, however, it can be applied to any geophysical data to solve the inherent ambiguities in the interpretations. © 2011 European Association of Geoscientists & Engineers.

Bandopadhyay A.,Advanced Technology Development Center | Chakraborty S.,Advanced Technology Development Center | Chakraborty S.,Indian Institute of Technology Kharagpur
Electrophoresis | Year: 2013

Electrokinetics in salt-free media (in which counterions are only present) is central to the performance of many systems of modern technological relevance, ranging from ion-selective nanopores to electronic papers. Here, we introduce an analytical theory to describe the size dependence of electroosmosis in such typical scenarios, exhibiting an interesting confluence of the implications of interdependence of the electroosmotic transport mechanisms, ionic sizes, and confinement dimensions along with the counterion concentration. Our results do reveal that the concerned mobility parameter, describing the strength of electroosmotic transport, increases simultaneously with increments in the surface charge density as well as an ionic size factor (also known as the steric factor), bearing far-ranging consequences in microfluidic and nanofluidic technology. © 2013 WILEY-VCH Verlag GmbH & Co.

Dey P.,Advanced Technology Development Center | Banerjee J.,Indian Institute of Technology Kharagpur | Maiti M.K.,Advanced Technology Development Center | Maiti M.K.,Indian Institute of Technology Kharagpur
Bioresource Technology | Year: 2011

Lipid accumulation abilities of two endophytic fungal isolates - Colletotrichum sp. and Alternaria sp. grown under optimum and nutrient-stress conditions were investigated and compared. Significant variations in lipid contents, ranging from 30% to 58% of their dry biomass were found in liquid culture using various carbon sources. Since, >50% of the total lipid was estimated to be neutral lipid for both the fungal species, predicted biodiesel properties were theoretically calculated based upon the determined fatty acid profiles; and the values were found to be comparable to those of commonly used plant oils for biodiesel production. The two endophytes grew successfully on the combined rice straw and wheat bran as substrate that was degraded by their secretory enzymes including cellulase [1.21-2.51. FPU/g dry substrate (gds)] in solid state fermentation and produced substantial amount of lipid (60.32-84.30. mg/gds). Our study highlights the potential utilities of these two novel endophytic fungi as biodiesel feedstock. © 2011 Elsevier Ltd.

Kamwa I.,Hydro - Quebec | Pradhan A.K.,Indian Institute of Technology Kharagpur | Joos G.,McGill University
IEEE Transactions on Power Delivery | Year: 2011

The steady-state performance of phasor measurement units (PMUs) is well standardized in the recently issued revised IEEE Std. C37.118. The Western Electricity Coordinating Council (WECC) has developed dynamic performance requirements for PMU filters as a means to guarantee better, uniform PMU response under dynamic conditions, such as power swings and changing harmonics. These have been endorsed by North American Synchrophasor Initiative (NASPI) for its wide-area monitoring infrastructure. The main purpose of this paper is to present a new framework for designing PMU filtering algorithms capable of meeting or exceeding the WECC/NASPI requirements, while achieving an optimum transient response time. To this end, an adaptive complex bandpass filter derived from the exponentially modulated filter bank theory has been devised. It is built from freely chosen low-pass filter prototypes that fulfill the WECC requirements. The static and dynamic performances of two specific schemes dedicated to control and monitoring with 4- and 7-cycle response-time, respectively, are ascertained under noisy waveforms and changing harmonics with system frequency varying from 40 to 80 Hz. The center-frequency adaptation approach is shown to be intrinsically superior to the frequency compensation scheme, especially under fast varying frequency and changing harmonics. © 2010 IEEE.

Kamwa I.,Hydro - Quebec | Pradhan A.K.,Indian Institute of Technology Kharagpur | Joos G.,McGill University
IEEE Transactions on Power Systems | Year: 2011

Critical to real-time oscillations monitoring is early detection when otherwise dormant natural modes become a serious threat to grid stability. The next urgent issue is to determine the frequency and damping of the problematic modes when the signal is embedded in noise and the system contains closely spaced natural modes. The present paper addresses the detection issue using the Teager-Kaiser energy operator (TKEO) which has shown to be a fast predictor of the instability onset time when applied to the output signals of an orthogonal filter bank. In the system stability context, linear filter decomposition (LFD) is preferred rather than empirical mode decomposition (EMD), well known for its tendency to generate artificial modes with no physical meaning. A narrowband LFD with a less than 0.2-Hz bandwidth is achieved in the range 0.05 to 3 Hz through a cosine-modulated filter bank design. The effectiveness of the scheme in accurately detecting and tracking the frequency and damping of oscillatory modes is demonstrated using Monte Carlo simulations of three closely spaced modes and a detailed analysis of an actual event recorded by Hydro-Québec's WAMS in 2006. © 2010 IEEE.

Bhattacharya A.,Advanced Technology Development Center | Bhattacharyya T.K.,Indian Institute of Technology Kharagpur
IEEE Transactions on Electron Devices | Year: 2014

This paper reports the implementation and wafer-level mechanical and RF testing of three types of MEMS inductor - octagonal, square, and circular; the latter over a temperature range 30°C to 150°C. The devices were fabricated using a silicon on insulator process with deep reactive ion etching (DRIE) trench on a low-resistivity substrate (ρ=1-10Ω cm and contains gold bond wire overpass to complete the inductance loop. The three inductors exhibited nominal inductance of 3.36, 12.15, and 3.29 nH with peak quality factor of 9.51, 6.91, and 7.26, respectively, and self-resonance frequency more than 10 GHz. Afterward, the inductors were packaged in a pin grid array package and postpackaging RF testing was carried out to analyze the effect of packaging on RF performance of the inductors. © 2013 IEEE.

Ghosh Ray S.,Advanced Technology Development Center | Ghangrekar M.M.,Indian Institute of Technology Kharagpur
Bioresource Technology | Year: 2015

For enhancing organic matter removal from cereal-based distillery stillage two-stage treatment consisting of fermentation by Aspergillus awamori followed by microbial fuel cell (MFC) is proposed. Considerable reduction in total and soluble chemical oxygen demand (COD) up to 70% and 40%, respectively, along with 98% reduction of suspended solids (SS) has been achieved during fungal pretreatment. The process generated chitosan, a useful fermentation byproduct from fungal mycelia, as 0.6-0.7g/l of settled sludge with mycelium (3.8% solids). Prior treatment of wastewater with fungal strain enhanced the power generation in MFC by 2.9 times at an organic loading rate of 1.5kgCOD/m3day, demonstrating soluble COD reduction of 92% in MFC. While treating distillery wastewater, this two-stage integrated biological process demonstrated overall 99% COD removal and almost complete removal of SS, delivering ample scope for scale-up and industrial application to offer effective solution for distillery wastewater treatment. © 2014 Elsevier Ltd.

Patra P.K.,Advanced Technology Development Center | Bhattacharya B.,Indian Institute of Technology Kharagpur
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

The widely used Nose-Hoover chain (NHC) thermostat in molecular dynamics simulations is generally believed to impart the canonical distribution as well as quasi- (i.e., space-filling) ergodicity on the thermostatted physical system (PS). Working with the standard single harmonic oscillator, we prove analytically that the two-chain Nose-Hoover thermostat with unequal thermostat masses approaches the standard Nose-Hoover dynamics, and hence the PS loses its canonical and quasiergodic nature. We also show through numerical simulations over substantially long times that for certain Poincaré sections, for both the equal and unequal thermostat mass cases, the bivariate distribution function of position and momentum (x,p) and of reservoir degrees of freedom (ξ,η) lose their Gaussian nature. Further, the four-dimensional x-p-ξ-η extended phase space exhibits two holes of nonzero measure. The NHC thermostat therefore does not generate the canonical distribution or preserve quasiergodicity for the PS. © 2014 American Physical Society.

Prasad M.V.D.,Advanced Technology Development Center | Bhattacharya B.,Indian Institute of Technology Kharagpur
Nano Letters | Year: 2016

Using phonon wave packet molecular dynamics simulations, we find that anomalous longitudinal acoustic (LA) mode phonon scattering in low to moderate energy ranges is responsible for initiating thermophoretic motion in carbon nanotube oscillators. The repeated scattering of a single mode LA phonon wave packet near the ends of the inner nanotube provides a net unbalanced force that, if large enough, initiates thermophoresis. By applying a coherent phonon pulse on the outer tube, which generalizes the single mode phonon wave packet, we are able to achieve thermophoresis in a carbon nanotube oscillator. We also find the nature of the unbalanced force on end-atoms to be qualitatively similar to that under an imposed thermal gradient. The thermodiffusion coefficient obtained for a range of thermal gradients and core lengths suggest that LA phonon scattering is the dominant mechanism for thermophoresis in longer cores, whereas for shorter cores, it is the highly diffusive mechanism that provides the effective force. © 2016 American Chemical Society.

Saha S.,Indian Institute of Technology Kharagpur | Pal A.,Indian Institute of Technology Kharagpur | Kundu S.,Texas A&M University | Basu S.,Indian Institute of Technology Kharagpur | Pal T.,Indian Institute of Technology Kharagpur
Langmuir | Year: 2010

Silver and gold nanoparticles have been grown on calcium alginate gel beads using a green photochemical approach. The gel served as both a reductant and a stabilizer. The nanoparticles were characterized using UV-visible spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), energy dispersive X-ray (EDS), and selected area electron diffraction (SAED) analyses. The particles are spherical, crystalline, and the size ranges for both Ag and Au nanoparticles are <10 nm. It is noticed from the sorption experiment that the loading of gold on calcium alginate beads is much more compared to that of Ag. The effectiveness of the as-prepared dried alginate-stabilized Ag and Au nanoparticles as a solid phase heterogeneous catalyst has been evaluated, for the first time, on the well-known 4-nitrophenol (4-NP) reduction to 4-aminophenol (4-AP) in the presence of excess borohydride. The reduction was very efficient and followed zero-order kinetics for both Ag and Au nanocomposites. The effects of borohydride, initial 4-NP concentration, and catalyst dose were evaluated. The catalyst efficiency was examined on the basis of turnover frequency (TOF) and recyclability. The catalytic efficiency of alginate-based Ag catalyst was much more compared to that of the Au catalyst. The as-prepared new solid-phase biopolymer-based catalysts are very efficient, stable, easy to prepare, eco-friendly, and cost-effective, and they have the potential for industrial applications. © 2009 American Chemical Society.

Bandopadhyay A.,Advanced Technology Development Center | Chakraborty S.,Advanced Technology Development Center | Chakraborty S.,Indian Institute of Technology Kharagpur
Langmuir | Year: 2012

In this work, we investigate the effects of local permittivity variations, induced by a preferential orientation and exclusion of water dipoles close to channel walls, and the effects of finite-sized ions on the induced streaming potential in nanochannels. We make a detailed analysis of the underlying physicochemical interactions by considering combinations of cases where ions are considered to be point sized/finite sized and permittivity variation effects to be present/absent. By accounting for the dielectric friction (which in turn is a function of the local permittivity) in addition to the classical Stokes friction, we show that for high interfacial potentials and narrow confinements, the induced streaming potential field for the cases in which the polarization effects are considered for finite-sized ions is remarkably higher than for the cases in which the polarization effects are neglected. Thus, by coupling the nonlinear effects of finite-sized ions and water dipole polarization along with the dielectric friction, we open a new paradigm of streaming potential predictions for narrow fluidic confinements, bearing far-ranging scientific and technological consequences in nanoscale science and technology. © 2012 American Chemical Society.

Neogi A.,Advanced Technology Development Center | Mitra N.,Indian Institute of Technology Kharagpur
Physics of Fluids | Year: 2016

Molecular dynamics simulations were carried out using numerous force potentials to investigate the shock induced phenomenon of pure bulk liquid water. Partial phase transition was observed at single shock velocity of 4.0 km/s without requirement of any external nucleators. Change in thermodynamic variables along with radial distribution function plots and spectral analysis revealed for the first time in the literature, within the context of molecular dynamic simulations, the thermodynamic pathway leading to formation of ice VII from liquid water on shock loading. The study also revealed information for the first time in the literature about the statistical time-frame after passage of shock in which ice VII formation can be observed and variations in degree of crystallinity of the sample over the entire simulation time of 100 ns. © 2016 AIP Publishing LLC.

Routray W.,McGill University | Mishra H.N.,Indian Institute of Technology Kharagpur
Comprehensive Reviews in Food Science and Food Safety | Year: 2011

Yogurt is a basic dairy product that has been consumed for centuries as a part of the diet, even when its beneficial effects were neither fully known nor scientifically proven. With time, yogurt has been continuously modified to obtain a product with better appeal and nutritional effects. The flavor components of yogurt are affected because of these modifications. The present review article is focused on the influence of the different parameters and modifications on aroma and taste components of yogurt. Extensive work has been done to explore the effect of chemical components as well as the microbial, processing, and storage aspects. The popularity of yogurt as a food component depends mainly on its sensory characteristics, of which aroma and taste are most important. This review also outlines the effects of the different modifications attempted in the composition of yogurt. © 2011 Institute of Food Technologists®.

Hati M.K.,Advanced Technology Development Center | Bhattacharyya T.K.,Indian Institute of Technology Kharagpur
Proceedings - 2011 IEEE Computer Society Annual Symposium on VLSI, ISVLSI 2011 | Year: 2011

This paper presents a low-power, high speed complementary input folded regulated cascode operational transconductance amplifier (OTA) designed for the 10bit, 150MSPS parallel pipeline ADC. The OTA plays an important role in the ADC, because of its conversion rate and power consumption are limited by the performance of the OTA. The designed ADC in this paper employs parallel pipeline architecture based on double sampling sampled hold (DSSH) technique, and shares the OTA between two channels of the ADC. The folded cascode OTA consists of fully differential and regulated cascode gain boosting technique. Besides, a Common Mode Feed Back (CMFB) circuit was introduced and some methods are concerned to improve the performance. Then, by proper optimization of the layout design, OTA's mismatch was reduced up-to a great extent. With 1.8V power supply, using the CMOS9T5V 180nm process technology, the simulation shows that the open-loop gain of the OTA is 90.39 dB, the phase margin (PM) is 63.85° with the unity gain bandwidth (UGB) of 700.7 MHz. The power consumption of this OTA is only 3.24 mW, which significantly reduces the whole power consumption of the parallel pipeline ADC. © 2011 IEEE.

Samanta P.K.,Ghatal Rabindra Satabarsiki Mahavidyalaya | Chaudhuri P.R.,Indian Institute of Technology Kharagpur
Materials Letters | Year: 2012

A wet chemical method has been used to grow rarely observed ZnO octahedrons at room temperature without using any surfactant. The X-ray diffraction data confirmed the formation of hexagonal phase of ZnO. The size variation of the octahedrons indicates that the growth unit is not arbitrary but octahedron one. Formation of the octahedral nanostructures depends on the precursor concentrations, growth kinetics, growth temperature and duration of the chemical growth process. This type of octahedral structure occurs due to the electrostatic interaction between different basal polar planes of ZnO. The absorption spectrum studies revealed the band gap enhancement due to quantum size effect. The fabricated ZnO octahedron shows strong violet emission due to recombination of electron at Zn-interstitial and hole in the valence band. © 2011 Elsevier B.V. All rights reserved.

Maity A.K.,Indian Institute of Technology Kharagpur | Maity A.K.,University of Texas at El Paso | Roy S.,Indian Institute of Technology Bhubaneswar
Advanced Synthesis and Catalysis | Year: 2014

The multimetallic iridium-tritin (Ir-Sn3) complex [Cp*Ir(SnCl3)2{SnCl2(H2O) 2}] (1) proved to be a highly effective catalyst towards C-OH bond activation of γ-hydroxylactams, leading to a nucleophilic substitution reaction known as the α-amidoalkylation reaction. Catalyst 1 can be easily synthesized from the reaction of (pentamethylcyclocyclopentadienyl)iridium dichloride dimer {[Cp*IrCl2]2} and tin(II) dichloride (SnCl2). In terms of catalyst loading, reaction conditions and yields of the product formed, 1 is found to be superior compared to classical Lewis acid catalysts. Different carbon (arenes, heteroarenes, allyltrimethylsilane, 1,3-dicarbonyls) and heteroatom (alcohols, thiols, amides and sulfonamides) nucleophiles have been successfully employed in the intramolecular and intermolecular alkylations, as well as in heterocyclization reactions. In the majority of cases good to excellent yields of 3-substituted isoindolinones and 5-substituted pyrrolidin-2-ones have been obtained. Besides, the reactions are also atom economical and salt free. It is proposed that the multimetallic Ir-Sn3 catalyst behaves as a mild and selective Lewis acid to activate the γ-hydroxylactam towards the formation of the N-acyliminium ion; the latter being trapped by potent nucleophiles leading to the desired products. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Raul S.K.,Anand Agricultural University | Panda S.N.,Indian Institute of Technology Kharagpur
Water Resources Management | Year: 2013

The canal water supply, which is the only source of irrigation, in the rice-dominated cropping system of the Hirakud canal command (eastern India) is able to meet only 54 % of the irrigation demand at 90 % probability of exceedance. Hence, considering groundwater as the supplemental source of irrigation, conjunctive use management study by combined simulation-optimization modelling was undertaken in order to predict the maximum permissible groundwater pumpage from the command area. Further, optimal land and water resources allocation model was developed to determine the optimal cropping pattern for maximizing net annual return. The modelling results suggested that 2. 0 and 2. 3 million m3 of groundwater can be pumped from the bottom aquifer during monsoon and non-monsoon seasons, respectively, at 90 % probability of exceedance of rainfall and canal water availability (PERC). Optimal cropping patterns and pumping strategies can lead to about 51. 3-12. 5 % increase in net annual return from the area at 10-90 % PERC. The sensitivity analysis of the model indicates that the variation in the market price of crops has very high influence on the optimal solution followed by the cost of cultivation and cultivable area. Finally, different future scenarios of land and water use were formulated for the command area. The adoption of optimal cropping patterns and optimal pumping strategies is strongly recommended for sustainable management of available land and water resources of the canal command under hydrological uncertainties. © 2013 Springer Science+Business Media Dordrecht.

Karmakar R.,Indian Institute of Technology Kharagpur | Karmakar R.,TU Braunschweig | Pahari P.,Indian Institute of Technology Kharagpur | Pahari P.,CSIR - Central Electrochemical Research Institute | Mal D.,Indian Institute of Technology Kharagpur
Chemical Reviews | Year: 2014

Small molecule natural products have been the mainstay of research in organic chemistry since its early development. The established classes of natural products, like alkaloids, amino acids, flavonoids, quinonoids, steroids, and terpenoids, have played vital roles in the discovery of new drugs. Research on the chemistry of natural products is continuing to generate new leads in medicinal chemistry. A case in point is the emerging class of compounds called isobenzofuranones, commonly termed as phthalides. NBP is a viscous oil and occurs as the major component of celery oil. It also exhibits antibacterial, antiviral, and antihypertensive activity. Mycophenolic acid is in clinical trial for the prevention and reversal of transplant rejection and anticancer. Dimeric forms of this core structure feature a few natural products.

Bindumadhavan K.,Indian Institute of Technology Kharagpur | Srivastava S.K.,Indian Institute of Technology Kharagpur | Mahanty S.,CSIR - Central Electrochemical Research Institute
Chemical Communications | Year: 2013

Molybdenum disulfide (MoS2)-multiwalled carbon nanotube (MWCNT) hybrids have been prepared by simple dry grinding. Excellent initial charge capacity (1214 mA h g-1) and ∼85% retention after 60 discharge-charge cycles at different current densities (100-500 mA g -1) make MoS2-MWCNT (1:1) hybrids a superior anode in Li-ion batteries. © 2013 The Royal Society of Chemistry.

Bhargava V.,Indian Institute of Technology Kharagpur | Fateen S.E.K.,Cairo University | Bonilla-Petriciolet A.,Aguascalientes Institute of Technology
Fluid Phase Equilibria | Year: 2013

In this study, Cuckoo Search is introduced for performing phase equilibrium and stability calculations for the first time. Cuckoo Search is a population-based method that mimics the reproduction strategy of cuckoos. This meta-heuristics have been successfully used for solving some engineering design and optimization problems with promising results. However, this emerging optimization method has not been applied in chemical engineering problems including thermodynamic calculations. This study reports the application of Cuckoo Search and its modified version for phase equilibrium and stability calculations in both reactive and non-reactive systems. Performance of this nature-inspired optimization method has been analyzed using several phase stability, phase equilibrium and reactive phase equilibrium problems. Results show that Cuckoo Search offers a reliable performance for solving these thermodynamic calculations and is better than other meta-heuristics previously applied in phase equilibrium modeling. © 2012 Elsevier B.V.

Jana M.,National Institute of Technology Rourkela | Bandyopadhyay S.,Indian Institute of Technology Kharagpur
Journal of Physical Chemistry B | Year: 2013

Atomistic molecular dynamics (MD) simulations of host-guest inclusion complexes of β-cyclodextrin (BCD) and zwitterionic phenylalanine (zPHE) following two possible orientations of zPHE in aqueous solutions have been carried out. The guest induced structural changes of BCD and the microscopic properties of surrounding water have been explored. The results obtained for the complex molecules were compared with those obtained for free BCD and free zPHE molecules. It is found that irrespective of the orientation, the complexation of BCD and zPHE (1:1) is associated with loss of configurational entropy. Besides, the net configurational entropy is found to differ depending upon its orientation inside the BCD cavity. Interestingly, within the simulation length scale it is found that the relatively hydrophobic aromatic moiety of zPHE prefers to stay within the hydrophobic cavity of BCD, irrespective of its orientation. Further, nonuniform distribution and altered tetrahedral ordering of hydration water molecules around the complex molecules as compared to that around the free forms are correlated well with their conformational flexibilities. © 2013 American Chemical Society.

Chatterjee S.,National Institute of Technology Rourkela | Bhattacherjee A.,Indian Institute of Technology Kharagpur
Engineering Applications of Artificial Intelligence | Year: 2011

Measuring the quality parameters of materials at mines is difficult and a costly job. In this paper, an image analysis-based method is proposed efficiently and cost effectively that determines the quality parameters of material. The image features are extracted from the samples collected from a mine and modeled using neural networks against the actual grade values of the samples generated by chemical analysis. The dimensions of the image features are reduced by applying the genetic algorithm. The results showed that only 39 features out of 189 features are sufficient to model the quality parameter. The model was tested with the testing data set and the result revealed that the estimated grade values are in good agreement with the real grade values (R 2=0.77). The developed method was then applied to a case study mine of iron ore. The case study results show that proposed image-based algorithm can be a good alternative for estimating quality parameters of materials at a mine site. The effectiveness of the proposed method was verified by applying it on a limestone deposit and the results revealed that the method performed equally well for the limestone deposit. © 2010 Elsevier Ltd. All rights reserved.

Chakradhara Rao M.,Indian Institute of Technology Kharagpur | Bhattacharyya S.K.,CSIR - Central Electrochemical Research Institute | Barai S.V.,Indian Institute of Technology Kharagpur
Construction and Building Materials | Year: 2011

This paper presents the experimental results of recycled aggregate concrete (RAC) beams prepared with different amount of recycled coarse aggregate (RCA) subjected to low velocity impact. The recycled coarse aggregates are obtained from a demolished RCC culvert. Four concrete mixes with 0%, 25%, 50% and 100% RCA respectively are prepared. With each mix three beam specimens of size 1.15 × 0.1 × 0.15 m are prepared and tested under drop weight impact load. The behavior of the RAC beams are studied in terms of acceleration, strains and support reaction histories under impact load in addition to the physical and mechanical characteristics of RCA and RAC. It is observed that 25% RCA does not influence the strength of concrete. In addition, it is found that for a given impact energy (the energy imparted by the hammer per blow) the reactions and strains of RAC with 50% and 100% RCA are significantly lower and higher respectively than those of normal concrete and RAC with 25% RCA. © 2010 Elsevier Ltd. All rights reserved.

Sarkar J.,Indian Institute of Technology BHU Varanasi | Bhattacharyya S.,Indian Institute of Technology Kharagpur
Energy | Year: 2015

India has great potential to employ the ORC (organic Rankine cycle) technology for conversion of low temperature waste heat and renewable energy. In this study, available waste heat and relevant renewable heat sources in India are reviewed and suitable working fluids for ORC have been selected based on operational, environmental and safety criteria. A feasibility study and comparison of selected fluids for ORC is also presented for Indian climates along with discussions on component, operation and cost related aspects. A comprehensive review on available heat sources and sinks shows that India has plenty of waste heat and renewable energy sources for electricity generation by means of ORC; however, condenser operation may be challenging due to wide ambient temperature variation. Appropriate performance comparison among selected working fluids shows that ammonia is the best fluid in terms of net power generation and compactness of turbo-machineries, whereas n-Pentane is the best fluid in terms of thermal efficiency and heat exchanger compactness. Both are recommended as working fluids for ORC installations in India. The study reveals that there is a great opportunity to employ this technology in India provided we have to overcome some challenges related to component selection, finance and maintenance. © 2015 Elsevier Ltd.

Deck O.,University of Lorraine | Singh A.,Indian Institute of Technology Kharagpur
International Journal for Numerical and Analytical Methods in Geomechanics | Year: 2012

The objective of this study is to develop an analytical model that can predict the building-relevant deflections induced by tunnelling or mining subsidence. The model takes into account soil-structure interactions due to differences in stiffness between the ground and the building. The ground is modelled by the Winkler model with an initial ground curvature equivalent to the free-field ground movements. The building is modelled by a horizontal beam with uniform loading. The static and cinematic equilibrium of both the ground and the building are then calculated to assess the final building and ground shape, and the building deflection is derived. The resulting analytical model is used to investigate the influence of the ground and the building's mechanical properties, the building load and the initial value of the free-field ground curvature (hogging or sagging). The model appears to be more comprehensive than those reported elsewhere that address the problem with numerical models. In particular, the analytical model makes it possible to distinguish two different final situations-with continuous or discontinuous contact between the ground and the building. The model is compared with numerical results and used to analyse a case study. © 2010 John Wiley & Sons, Ltd.

Panda S.K.,National Institute of Technology Rourkela | Singh B.N.,Indian Institute of Technology Kharagpur
Aerospace Science and Technology | Year: 2013

Numerical investigation of nonlinear free vibration of thermally post-buckled laminated composite spherical shell panel embedded with shape memory alloy (SMA) fibre is presented. The mathematical model is proposed for the first time by taking the geometric nonlinearity in Green-Lagrange sense and the panel kinematics based on higher order shear deformation theory. In addition to the above the material nonlinearity in SMA fibres due to the temperature field is also considered in the present analysis. The system governing differential equation of the shell panel is obtained using Hamilton's principle. A direct iterative method in conjunction with nonlinear finite element is used to discretise and solve the system of equations. Effects of various parameters such as curvature ratios, thickness ratios, amplitude ratios, aspect ratios, support conditions, lamination schemes, SMA prestrains and SMA volume fractions on the nonlinear free vibration behaviour on post-buckled laminated panels are examined in detail and discussed. The results obtained are compared with those available in the literature. © 2013 Elsevier Masson SAS. All rights reserved.

Pattnaik M.,National Institute of Technology Rourkela | Pattnaik M.,Indian Institute of Technology Kharagpur | Kastha D.,Indian Institute of Technology Kharagpur
IEEE Transactions on Industrial Electronics | Year: 2013

Doubly fed induction generator (DFIG)-based stand-alone variable-speed constant-frequency systems reported so far cannot supply nonlinear unbalanced load current containing cophasor components. This paper presents three topologies of a stand-alone DFIG which can handle this type of load. The harmonic/imbalance component of the load current in each case is supplied by the stator-side converter. In the first option, a ΔY transformer with neutral connection supplies the load. However, the harmonic current circulating in the delta winding still distorts the load phase voltage beyond the acceptable limit. As a solution, the zero-sequence load voltage is actively controlled through the stator-side converter with the load neutral connected to the midpoint of the dc-link capacitor. However, this configuration also fails when the load current contains dc component as in half-wave rectifiers. Finally, a configuration with an additional inverter leg connected to the load neutral is proposed in conjunction with the zero-sequence stator voltage controller. Simulation and experimental results from this last configuration demonstrate its excellent load voltage regulation property while supplying various nonlinear and unbalanced loads. The control algorithm is implemented without any speed/position sensor. © 1982-2012 IEEE.

Manna B.,National Institute of Technology Rourkela | Baidya D.K.,Indian Institute of Technology Kharagpur
Soil Dynamics and Earthquake Engineering | Year: 2010

The influence of nonlinearity on the dynamic response of cast-in-situ reinforced concrete piles subjected to strong vertical excitation was studied. Forced vibration test of single piles (L/d=10, 15, 20) and 2×2 pile groups (s/d=2, 3, 4 for each L/d) were conducted in the field for two different embedded conditions of pile cap. From the measured nonlinear response curves, the effective pile-soil system mass, stiffness and damping were determined and the nonlinear response curves were back-calculated using the theory of nonlinear vibration. The test results were compared with the continuum approach of Novak with dynamic interaction factor approach using both linear and linear-equivalent numerical methods. Reasonable match between the measured and predicted response was found for linear-equivalent methods by introducing a weak boundary-zone around the pile to approximately account for the nonlinear behaviour of pile-soil system. The test data were used to establish the empirical relationship in order to estimate the extent of soil separation around the pile with soil under vertical vibration. © 2010 Elsevier Ltd. All rights reserved.

Sahu S.,National Institute of Technology Rourkela | Behera B.,Indian Institute of Technology Kharagpur | Maiti T.K.,Indian Institute of Technology Kharagpur | Mohapatra S.,National Institute of Technology Rourkela
Chemical Communications | Year: 2012

Highly photoluminescent carbon dots with a PL quantum yield of 26% have been prepared in one step by hydrothermal treatment of orange juice. Due to high photostability and low toxicity these carbon dots are demonstrated as excellent probes in cellular imaging. © 2012 The Royal Society of Chemistry.

Indian Institute of Technology Kharagpur and Gm Global Technology Operations Llc | Date: 2011-05-10

A method and system for using Equivalent Time Sampling to improve the effective sampling rate of sensor data, and using the improved-resolution data for diagnosis and control. Data samples from existing sensors are provided, where the sampling rate of the existing sensors is not sufficient to accurately characterize the parameters being measured. High-resolution data sets are reconstructed using Equivalent Time Sampling. High-resolution input data sets are used in a system model to simulate the performance of the system being measured. Results from the system model, and high-resolution output data sets from Equivalent Time Sampling, are provided to an estimator, which provides accurate estimation of measured quantities and estimation of quantities not measured. Output from the estimator is used for fault diagnosis and control of the system being measured.

Hazra J.,IBM | Sinha A.K.,Indian Institute of Technology Kharagpur
European Transactions on Electrical Power | Year: 2011

This paper presents a multi-objective optimal power flow technique using particle swarm optimization. Two conflicting objectives, generation cost, and environmental pollution are minimized simultaneously. A multi-objective particle swarm optimization method is used to solve this highly nonlinear and non-convex optimization problem. A diversity preserving technique is incorporated to generate evenly distributed Pareto optimal solutions. A fuzzy membership function is proposed to choose a compromise solution from the set of Pareto optimal solutions. The algorithm is tested on IEEE 30 and 118 bus systems and its effectiveness is illustrated. © 2010 John Wiley & Sons, Ltd.

Vignesh R.,Indian Institute of Technology Kharagpur | Oh B.T.,University of Southern California | Kuo C.-C.J.,University of Southern California
IEEE Signal Processing Letters | Year: 2010

A speed up technique for the non-local means (NLM) image denoising algorithm based on probabilistic early termination (PET) is proposed. A significant amount of computation in the NLM scheme is dedicated to the distortion calculation between pixel neighborhoods. The proposed PET scheme adopts a probability model to achieve early termination. Specifically, the distortion computation can be terminated and the corresponding contributing pixel can be rejected earlier, if the expected distortion value is too high to be of significance in weighted averaging. Performance comparative with several fast NLM schemes is provided to demonstrate the effectiveness of the proposed algorithm. © 2010 IEEE.

Samal A.K.,Sambalpur University | Mall R.,Indian Institute of Technology Kharagpur | Tripathy C.,Veer Surendra Sai University of Technology
Swarm and Evolutionary Computation | Year: 2014

Conventional methods for fault-tolerant scheduling of real-time tasks based on traditional heuristic approach offer poor performance and inefficient system utilization. The primary-backup (PB) approach is often used as a fault-tolerant scheduling technique to guarantee RT tasks to meet their deadline despite the presence of fault. We propose a novel scheduling algorithm using optimization approach based on genetic algorithm (GA) hybridized with knowledge from the real-time task scheduling domain for providing fault-tolerance (FT) in multiprocessor environment. Exhaustive simulation reveals that the new GA based primary-backup fault-tolerant scheduling (PBFTS) approach outperforms other fault-tolerant scheduling schemes in terms of system utilization and efficiency. © 2013 Elsevier B.V.

Pal P.,Motilal Nehru National Institute of Technology | Bhattacharyya S.K.,Indian Institute of Technology Kharagpur
Journal of Sound and Vibration | Year: 2010

This paper deals with the numerical and experimental studies of sloshing of liquid in partially filled prismatic containers subjected to external excitation. Meshless local Petrov-Galerkin (MLPG) method is used for computing the nonlinear sloshing response of liquid in a two-dimensional rigid prismatic tank. At every instant of time, velocity potential is computed at each node and the nodal positions are updated. A local symmetric weak form (LSWF) for nonlinear sloshing of liquid is developed, and a truly meshless method, based on LSWF and moving least squares (MLS) approximation, is presented for the solution of Laplace equation with the requisite boundary conditions. An experimental set-up is also designed to study the behavior of liquid sloshing in partially filled prismatic tank. The resulting slosh heights for various excitation frequencies and amplitudes are compared with the data obtained from the numerical studies. The numerical results are close to that obtained experimentally and little variations in the data are due to ineptness of the experimental set-up and the input parameters. © 2010 Elsevier Ltd. All rights reserved.

Dalai T.K.,Indian Institute of Technology Kharagpur | Ravizza G.,University of Hawaii at Manoa
Geochimica et Cosmochimica Acta | Year: 2010

Osmium isotope composition (187Os/188Os) and concentrations of Os, Ir and Pt are reported for an early Pleistocene section from the ODP Site 849 in the eastern equatorial Pacific. Using the data obtained in this study, the contributions from detrital and extraterrestrial particulate matter to Os concentration and 187Os/188Os of sediment are estimated. Our calculations show that detrital contributions to sedimentary Os are too small (<2%) to significantly shift measured bulk sediment 187Os/188Os away from seawater values. A moderate but significant negative correlation between 187Os/188Os and 3He/188Os indicate that the average particulate extraterrestrial Os flux to this site is 1.21±0.47pgcm2kyr1, which constitutes 3% of total Os burial flux. The estimates of detrital and extraterrestrial Os are used to calculate the seawater 187Os/188Os in the early Pleistocene. The most notable features of this early Pleistocene 187Os/188Os record are: (1) glacial-interglacial 187Os/188Os differences are insignificant within errors of estimates, (2) glacial 187Os/188Os values are higher compared to those reported for the late Pleistocene glacials. Comparison of 187Os/188Os values at Site 849 to the late Pleistocene records suggests that average seawater 187Os/188Os change has been modest (∼5%) since the early Pleistocene. Assuming that 187Os/188Os difference between the glacial periods of the late and the early Pleistocene results solely from temperature dependence of weathering rates, it has been calculated that average surface temperature during the late Pleistocene glacials was 0.8±0.2°C lower than glacials in the early Pleistocene. This inference is consistent with temperature estimates based on a recent study of pCO2 reconstruction in the Pleistocene. This observation based on limited studies of marine 187Os/188Os records seems to suggest that temperature played an important role in influencing chemical weathering during the Pleistocene glacials. However, more studies are needed to confirm if this temperature-weathering feedback was operational throughout the Pleistocene. A significant down core Ir-3He co-variation coupled with similar burial fluxes of Ir at Site 849 and at LL44 GPC-3 in the north Pacific point to the utility of Ir concentration as a point paleoflux tracer. However, a twofold difference in Ir burial fluxes between the eastern and the western equatorial Pacific suggests that calibration in space and time is required to use Ir concentration as a robust indicator of paleoflux through time. Significant co-variation of concentrations of Os and total alkenone during the glacials coupled with lighter δ13C of benthic foraminifera indicates that productivity and carbon burial played a dominant control on scavenging of Os at Site 849. In a broader context, this data set encourages future investigation of response of PGE behavior to paleoceanographic processes. © 2010 Elsevier Ltd.

Mehta C.R.,Central Institute of Agricultural Engineering | Tewari V.K.,Indian Institute of Technology Kharagpur
International Journal of Industrial Ergonomics | Year: 2015

A biomechanical model is important for prediction of loads likely to arise in specific body parts under various conditions. The biomechanical model was developed to predict compressive and shear loads at L4/L5 (lumbar vertebra) of a tractor operator seating on seats with selected seat pan and backrest cushion materials. A computer program was written to solve the model for various inputs viz. stature and weight of the tractor operators, choice of operating conditions, and reaction forces from seat pan and backrest cushions. It was observed that maximum compressive and shear forces ranged 943-1367N and 422-991N, respectively at L4/L5 of tractor operators steering the tractor with leg and hand control actions and occasionally viewing the implement at back. The compressive forces were maximum (1202-1367N) with coir based composite seat backrest cushion materials (thickness of 80mm, density of 47.19kg/m3) and were minimum (943-1108N) with high density polyurethane foam (thickness of 44mm, density of 19.09kg/m3) for the seats. Relevance to industry: The biomechanical model of a tractor operator is important for theoretical understanding the problem of sitting and is also valuable in prediction of compressive and shear loads at L4/L5 of operator under various operating conditions. It will help in design of tractor seat for operator's comfort. © 2015 Elsevier B.V.

Majumdar S.,Indian Institute of Technology Kharagpur | Majumdar S.,The Oskar Klein Center | Bharadwaj S.,Indian Institute of Technology Kharagpur | Choudhury T.R.,National Center for Radio Astrophysics
Monthly Notices of the Royal Astronomical Society | Year: 2013

We have used seminumerical simulations of reionization to study the behaviour of the power spectrum of the epoch of reionization 21-cm signal in redshift space. We have considered two models of reionization, one which has homogeneous recombination (HR) and the other incorporating inhomogeneous recombination (IR). We have estimated the observable quantities - quadrupole and monopolemoments ofHI power spectrum at redshift space from our simulated data. We find that the magnitude and nature of the ratio between the quadrupole and monopole moments of the power spectrum (Ps 2/Ps 0) can be a possible probe for the epoch of reionization. We observe that this ratio becomes negative at large scales for x̄HI = 0.7 irrespective of the reionization model, which is a direct signature of an inside-out reionization at large scales. It is possible to qualitatively interpret the results of the simulations in terms of the fluctuations in the matter distribution and the fluctuations in the neutral fraction which have power spectra and cross-correlation Pδδ(k), Pxx(k) and Pδx(k), respectively. We find that at large scales the fluctuations in matter density and neutral fraction are exactly anticorrelated through all stages of reionization. This provides a simple picture where we are able to qualitatively interpret the behaviour of the redshift-space power spectra at large scales with varying x̄HI entirely in terms of a just two quantities, namely x̄HI and the ratio Pxx/Pδδ. The nature of Pδx becomes different for HR and IR scenarios at intermediate and small scales. We further find that it is possible to distinguish between an inside-out and an outside-in reionization scenario from the nature of the ratio Ps 2/Ps 0 at intermediate length scales. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Ganguly S.,Tata Steel | Chakraborty S.,Indian Institute of Technology Kharagpur
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011

A theoretical model is developed to study the sedimentation characteristics of nanoscale colloidal suspensions (nanofluids). The influences of various deterministic and stochastic forcing parameters in the transport characteristics of the suspended nanoparticles are investigated by employing a Langevin formalism of particle transport. The role of collective particle interaction phenomena in the sedimentation of nanoparticles is analyzed by invoking the fundamental considerations of agglomeration-deagglomeration kinetics of the particulate phases. The model demonstrates the effect of particle volume fraction, particle size, and aggregate structure on the sedimentation velocity of the suspended nanoparticles. Predictions from the present model agree well with the experimental results reported in the literature. © 2011 Elsevier B.V. All rights reserved.

Mejia C.A.,University of Southern California | Dutt A.,Indian Institute of Technology Kharagpur | Povinelli M.L.,University of Southern California
Optics Express | Year: 2011

We explore a technique which we term light-assisted templated self-assembly. We calculate the optical forces on colloidal particles over a photonic crystal slab. We show that exciting a guided resonance mode of the slab yields a resonantly-enhanced, attractive optical force. We calculate the lateral optical forces above the slab and predict that stably trapped periodic patterns of particles are dependent on wavelength and polarization. Tuning the wavelength or polarization of the light source may thus allow the formation and reconfiguration of patterns. We expect that this technique may be used to design all-optically reconfigurable photonic devices. ©2011 Optical Society of America.

Dash S.K.,Indian Institute of Technology Kharagpur | Bora M.C.,Indian Institute of Technology Guwahati
Geotextiles and Geomembranes | Year: 2013

A series of experiments have been carried out to develop an understanding of the performance improvement of soft clay foundation beds using stone column-geocell sand mattress as reinforcement. It is found that with the provision of stone columns, of adequate length and spacing, about three fold increases in bearing capacity can be achieved. While with geocell-sand mattress it is about seven times that of the unreinforced clay. But if combined together, the stone column-geocell mattress composite reinforcement, can improve the bearing capacity of soft clay bed as high as by ten fold. The optimum length and spacing of stone columns giving maximum performance improvement are, respectively, 5 times and 2.5 times of their diameter. The critical height of geocell mattress can be taken equal to the diameter of the footing, beyond which, further increase in bearing capacity of the composite foundation bed is marginal. © 2013 Elsevier Ltd.

Dash S.K.,Indian Institute of Technology Kharagpur | Bora M.C.,Indian Institute of Technology Guwahati
Canadian Geotechnical Journal | Year: 2013

This paper investigates the influence of geosynthetic encasement on the performance of stone columns floating in soft clay. It was found that with unencased columns the bearing capacity improvement is about 3.5 fold, but with geogrid encasement the improvement increases to 5 fold, where 60% of the column length is encased. With full-length encasement (i.e., 100%), the improvement is only about 3 fold. It is therefore evident that partially encased floating columns are superior to the fully encased ones. In contrast, with end-bearing stone columns, full-length encasement is reported to have exhibited better performance improvement than the partially encased ones. In the former case (floating columns), it is the bulge formation at a deeper depth that enhances the bearing capacity, while in the latter case (end-bearing columns), it is the stiffening effect of the encasement that enables the column to transmit the surcharge pressure onto the competent strata below.

Pala P.,Motilal Nehru National Institute of Technology | Bhattacharyya S.K.,Indian Institute of Technology Kharagpur
Journal of Fluids and Structures | Year: 2013

This paper deals with the studies of sloshing of liquid in partially filled rectangular composite containers subjected to external excitation. The governing equation for inviscid fluid is written as pressure variable form. At each time step, the pressure is evaluated using the meshless local Petrov-Galerkin (MLPG) approach. A local symmetric weak form (LSWF) for linearized sloshing is developed, and a truly meshless method, based on LSWF and moving least squares (MLS) approximation, is presented for the solution of Laplace equation with the requisite boundary conditions. The effectiveness of the developed algorithm is demonstrated through few numerical examples. The comparison of results in terms of natural slosh frequencies, sloshing amplitudes and hydrodynamic pressures obtained in the present investigation are made with those available in the reported literature. To observe the change in the total liquid response due fluid-structure interaction effects, parametric studies are carried out for different cases by varying the fibre orientations and wall thicknesses in the laminated container wall. The present meshless method based on LSWF is found to be simple and attractive with a great potential in engineering applications. © 2013 Elsevier Ltd.

Bhar A.,Motilal Nehru National Institute of Technology | Satsangi S.K.,Indian Institute of Technology Kharagpur
European Journal of Mechanics, A/Solids | Year: 2011

An efficient method for accurate evaluation of through-the-thickness distribution of transverse stresses in thick composite and sandwich laminates, using a displacement-based C0 higher-order shear deformation theory (HSDT), is presented. The technique involves a least square of error (LSE) method applied to the 3D equilibrium equations at the post-processing phase, after a primary finite element analysis is performed using the HSDT. This is distinctly different from the conventional method of integrating the 3D equilibrium equations, for transverse stress recovery in composite laminates during post-processing. Competence of the technique is demonstrated in the numerical examples through comparison with results from first-order shear deformation theory (FSDT), another HSDT and those from analytical and 3D elasticity solutions available in literature. © 2010 Elsevier Masson SAS. All rights reserved.

Mandal S.M.,Indian Institute of Technology Kharagpur | Barbosa A.E.A.D.,Catholic University of Brasília | Franco O.L.,Catholic University of Brasília
Biotechnology Advances | Year: 2013

Lipopeptides are compounds that are formed by cyclic or short linear peptides linked with a lipid tail or other lipophilic molecules. Recently, several lipopeptides were characterized, showing surfactant, antimicrobial and cytotoxic activities. The properties of lipopeptides may lead to applications in diverse industrial fields including the pharmaceutical industry as conventional antibiotics; the cosmetic industry for dermatological product development due to surfactant and anti-wrinkle properties; in food production acting as emulsifiers in various foodstuffs; and also in the field of biotechnology as biosurfactants. Some lipopeptides have reached a commercial antibiotic status, such as daptomycin, caspofungin, micafungin, and anidulafungin. This will be the focus of this review. Moreover, the review presented here will focus on the biotechnological utilization of lipopeptides in different fields as well as the functional-structure relation, connecting recent aspects of synthesis and structure diversity. © 2013 Elsevier Inc.

Ghosh A.,Indian Institute of Technology Kharagpur | Kundu S.,Tata Steel | Chakrabarti D.,Indian Institute of Technology Kharagpur
Scripta Materialia | Year: 2014

The effect of crystallographic texture on impact transition behavior has been studied in a low-carbon steel. Crystallographic texture was found to influence the general yield temperature through its effect on the plastic constraint factor. The effective grain size depends on the angle between the {001} cleavage planes of the neighbouring crystals, rather than the grain boundary misorientation angle as determined from electron backscattered diffraction analysis considering the angle-axis pair. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Vallabhaneni V.,Indian Institute of Technology Guwahati | Maity D.,Indian Institute of Technology Kharagpur
Procedia Engineering | Year: 2011

Methods to assess damage in a structure and to evaluate their life are very important to ensure the structural integrity of operating plants and structures. The difficulties faced in implementing traditional procedures and the need to develop computer based automated evaluation process motivates the application of soft-computing tools like artificial neural network. The present works focus on development of a computer code to assess structural damages from curvature damage factor using radial basis neural network (RBNN). Comparative study on damage assessment of structures has been carried out between RBNN and the well established back propagation neural network. The structural damage has been introduced by incorporating a stiffness reduction factor. The inverse problem in the damage assessment technique is formulated as optimization problem. The basic idea applied in case of neural network is to train a suitable network to recognize the behavior of the structure with various possible damage scenarios. The steepest descent gradient algorithm is used to train the simple neural network. The developed code has been implemented on a cantilever beam. The results obtained from both the neural network techniques showed the efficiency of the developed code using RBNN. The outcomes of the results are quite encouraging.

Biswal M.,Veer Surendra Sai University of Technology | Pati B.B.,Veer Surendra Sai University of Technology | Pradhan A.K.,Indian Institute of Technology Kharagpur
International Journal of Electrical Power and Energy Systems | Year: 2013

Distance relay protecting series compensated line has limitations with metal oxide varistor (MOV) operation, prefault system condition, high resistance fault and shunt capacitance. This paper proposes an adaptive first-zone distance protection scheme for line with fixed series compensation connected at one end using local measurements. Impedance offered by series capacitor and MOV combination is estimated using relay end fault current. The method has ability to compensate the error due to high resistance fault. The technique is tested for different system operating condition, level of compensation and fault resistance of a 400 kV series compensated line and simulated through EMTDC/PSCAD. Simulation results demonstrate the effectiveness of the proposed method. © 2013 Elsevier Ltd. All rights reserved.

Pal A.,IBM | Maiti J.,Indian Institute of Technology Kharagpur
Expert Systems with Applications | Year: 2010

Mahalanobis-Taguchi System (MTS) is a pattern recognition method applied to classify data into categories - "healthy" and "unhealthy" or "acceptable" and "unacceptable". MTS has found applications in a wide range of problem domains. Dimensionality reduction of the input set of attributes forms an important step in MTS. The current practice is to apply Taguchi's design of experiments (DOE) and orthogonal array (OA) method to achieve this end. Maximization of Signal-to-Noise (S/N) ratio forms the basis for selection of the optimal combination of variables. However the DOE-OA method has been reviewed to be inadequate for the purpose. In this research study, we propose a dimensionality reduction method by addressing the problem as feature selection exercise. The optimal combination of attributes minimizes a weighted sum of total fractional misclassification and the percentage of the total number of variables employed to obtain the misclassification. Mahalanobis distances (MDs) of "healthy" and "unhealthy" conditions are used to compute the misclassification. A mathematical model formulates the feature selection approach and it is solved by binary particle swarm optimization (PSO). Data from an Indian foundry shop is adopted to test the mathematical model and the swarm heuristic. Results are compared with that of DOE-OA method of MTS. © 2009 Elsevier Ltd. All rights reserved.

Mandal S.K.,Indian National Institute of Foundry and Forge Technology | Chan F.T.S.,Hong Kong Polytechnic University | Tiwari M.K.,Indian Institute of Technology Kharagpur
Expert Systems with Applications | Year: 2012

The generation of leak along the pipeline carrying crude oils and liquid fuels results enormous financial loss to the industry and also affects the public health. Hence, the leak detection and localization problem has always been a major concern for the companies. In spite of the various techniques developed, accuracy and time involved in the prediction is still a matter of concern. In this paper, a novel leak detection scheme based on rough set theory and support vector machine (SVM) is proposed to overcome the problem of false leak detection. In this approach, 'rough set theory' is explored to reduce the length of experimental data as well as generate rules. It is embedded to enhance the decision making process. Further, SVM classifier is employed to inspect the cases that could not be detected by applied rules. For the computational training of SVM, this paper uses swarm intelligence technique: artificial bee colony (ABC) algorithm, which imitates intelligent food searching behavior of honey bees. The results of proposed leak detection scheme with ABC are compared with those obtained by using particle swarm optimization (PSO) and one of its variants, so-called enhanced particle swarm optimization (EPSO). The experimental results advocate the use of propounded method for detecting leaks with maximum accuracy. © 2011 Elsevier Ltd. All rights reserved.

Dey R.S.,Indian Institute of Technology Kharagpur | Hajra S.,Indian Institute of Technology Kharagpur | Sahu R.K.,Indian National Metallurgical Laboratory | Raj C.R.,Indian Institute of Technology Kharagpur | Panigrahi M.K.,Indian Institute of Technology Kharagpur
Chemical Communications | Year: 2012

A rapid and facile route for the synthesis of reduced graphene oxide sheets (rGOs) at room temperature by the chemical reduction of graphene oxide using Zn/acid in aqueous solution is demonstrated. © 2012 The Royal Society of Chemistry.

Kim W.J.,Yeungnam University | Pradhan D.,Indian Institute of Technology Kharagpur | Min B.-K.,Yeungnam University | Sohn Y.,Yeungnam University
Applied Catalysis B: Environmental | Year: 2014

BiOCl and BiOClxI1-x were synthesized in two different solvents of ethylene glycol (EG) and water, and their natures were examined by scanning electron microscopy (SEM), electron transmission microscopy (TEM), X-ray diffraction, UV-vis absorption and Raman, Fourier-transform infrared, and photoluminescence spectroscopy. The Ag and Au-doping effects on the fundamental nature and photocatalytic activity of BiOCl and BiOClxI1-x were investigated in detail. SEM revealed that 3D flower-like and 2D plate-like microstructures were formed with EG and water solvents, respectively. The as-synthesized samples were tested for the adsorption and photocatalytic degradation of methyl orange and Rhodamine B, with the flower-like 3D-structure showing superior adsorption performance relative to the stacked 2D plate-like structures. Upon introducing iodine into BiOCl, we observed a dramatic increase in the adsorption ability and Brunauer-Emmett-Teller surface area, with an order of 2D BiOCl<3D BiOCl≪BiOClxI1-x (x=0.8, 0.6 and 0.4). The dye degradation performance was further markedly enhanced under irradiation by visible light. However, a small amount of Ag and Au-doping drastically negated the adsorption and photocatalytic performance. The photocatalytic mechanism was elucidated by an indirect chemical probe method using active species scavengers, and photoluminescence spectroscopy. On the basis of the results obtained, we propose a dye-sensitized photodegradation mechanism, and the active species play roles in the order of OH≪O2 -≈h+ under visible light irradiation. © 2013 Elsevier B.V.

Thakur A.K.,Indian Institute of Technology Kharagpur | Hashmi S.A.,University of Delhi
Solid State Ionics | Year: 2010

Fourier transform infra-red (FTIR) spectroscopic studies have been carried out to probe, at the microscopic level, the effect of filler concentration on poly ethylene oxide (PEO) based composite polymer electrolytes complexed with sodium salts (NaClO4 and NaI) dispersed with inorganic fillers, Na2SiO3 and SnO2. The FTIR results correlate very well with macroscopic changes such as glass transition temperature (T g), electrical conductivity and mechanical properties in the composite polymeric systems due to the dispersion of filler particles. The striking observation of the two maxima feature in electrical conductivity (σ) variation versus filler concentration is satisfactorily explained in terms of variation of Tg and degree of crystallinity of the polymer composites. Although, few such observations have been reported by other earlier workers in some composite systems no explanation is available at the microscopic level. A mechanism at microscopic level from FTIR results involving ion-polymer, ion-ion, ion-filler and polymer-filler interactions has been proposed by us to explain the variations of σ and Tg as a function of filler concentration. The initial increase in free anions due to the interaction of fillers with ether oxygen of PEO and/or ClO4- anions followed by ion-pair formation results in the first maxima in the variations of σ vs. filler concentration. The second maxima results from the additional generation of free anions due to weakening of filler-anion interactions followed by the cluster formation on addition of fillers. The improvements in mechanical properties of the composite polymer electrolytes have also been explained on the basis of the proposed mechanism. © 2010 Elsevier B.V. All rights reserved.

Ghosh S.,Indian Institute of Technology Kharagpur | Sahu R.K.,Indian National Metallurgical Laboratory | Retna Raj C.,Indian Institute of Technology Kharagpur
Nanotechnology | Year: 2012

We describe the decoration of multiwalled carbon nanotubes (MCNTs) with Pt-Pd alloy nanoelectrocatalysts of three different compositions and their electrocatalytic performance toward the oxygen reduction reaction (ORR). The decoration of the MCNTs involves polymer-assisted impregnation of metal precursors PtCl 6 2- and PdCl 4 2- and the subsequent reduction of the impregnated precursors by a modified polyol route. The composition of the catalyst was controlled by tuning the molar ratio of the precursors during their impregnation. Electron probe microscopic analysis shows that the catalysts have compositions of Pt 46Pd 54; Pt 64Pd 36 and Pt 28Pd 72. The Pt 46Pd 54 and Pt 64Pd 36 catalysts have truncated octahedral and icosahedral shapes with a size ranging from 8 to 10 nm. On the other hand, the catalyst of Pt 28Pd 72 composition has a spherical/quasispherical shape with a size distribution of 1 2 nm. The XPS measurement confirms the signature of metallic Pt and Pd. The Pt 46Pd 54 catalyst has a pronounced electrocatalytic activity toward the ORR with a specific and mass activity of 378 μcm -2 Pt Pd and 64 μA μg -1 PtPd, respectively at 0.8 V. Moreover, the Pt 46Pd 54 nanoelectrocatalyst is highly durable and it retains its initial catalytic activity even after 1000 extensive cycles. Interestingly, this catalyst has a very high tolerance toward methanol and it does not favor the oxidation of methanol in the potential window of 0.11.4 V. The electrocatalytic activity of the alloy electrocatalyst is compared with commercially available Pt black and MCNT-supported spherical Pt nanoparticles. The catalytic activity of the Pt 46Pd 54 nanoelectrocatalyst is higher than the other catalysts. The Pt 46Pd 54 catalyst outperforms the electrocatalytic activity of all other catalysts. © 2012 IOP Publishing Ltd.

Ghosh S.,Indian Institute of Technology Kharagpur | Sahu R.K.,Indian National Metallurgical Laboratory | Raj C.R.,Indian Institute of Technology Kharagpur
Journal of Materials Chemistry | Year: 2011

We describe a shape regulated synthesis of branched Pt nanostructures (nPts) by a simple polyol method using 1,3-propanediol as solvent and poly(diallyldmethylammonium chloride) (PDDA) as stabilizing agent and their electrocatalytic activity in the oxygen reduction and methanol oxidation reactions. The transmission electron microscopic measurements show that the nanoparticles have multiple branches. The size of the branched nanostructures ranges from 10 to 15 nm and the branches have the width of 3-5 nm. The X-ray diffraction measurement indicates the existence of face centered cubic structure of Pt. UV-vis spectroscopic measurement suggests that the reduction of Pt(iv) proceeds through the formation of Pt(ii) species. The solvent and the stabilizing agent plays vital role in the growth of nPts. Aggregated nanoparticles were obtained in the absence of PDDA. The traditional solvent ethylene glycol in the presence of PDDA yields only spherical nanoparticles. The nPts were loaded onto the walls of multiwall carbon nanotube (MWCNT) to examine their electrocatalytic activity. The nanoparticles on MWCNT retain their initial shape, size and morphology. The electrocatalytic activity of nPts toward oxygen reduction reaction (ORR) was evaluated in terms of kinetic current density using rotating-ring-disk electrode (RRDE) system. The nanostructured electrocatalyst favors the 4-electron pathway for the reduction of oxygen at a more positive potential with a kinetic current density of 11.97 mA cm -2. The electrocatalytic performance of the catalyst in the methanol oxidation reaction (MOR) was studied with chronoamperometry and potential dependent electrochemical impedance spectroscopy measurements. The nPts show high specific activity in the ORR and MOR. The electrocatalytic activity of nPts towards ORR and MOR is compared with the commercial catalyst and spherical nanoparticles. © The Royal Society of Chemistry 2011.

Saha S.,Indian Institute of Technology Kharagpur | Wang J.M.,Hungkuang University | Pal A.,Indian Institute of Technology Kharagpur
Separation and Purification Technology | Year: 2012

Commercial TiO 2 was impregnated with silver nanoparticles at 1 and 2 mol% Ag using a simple 'liquid impregnation followed by heat treatment' method and the material was characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM)/energy dispersive X-ray (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, diffusive reflectance spectroscopy (DRS), and BET surface area/pore volume analysis. Impregnation of silver nanoparticles on P25 TiO 2 was done using the same procedure. Commercial TiO 2 was also modified under simple heat treatment to make combusted TiO 2. To probe the challenge of photodegradation of a known carcinogen, malachite green (MG), we have investigated the UV-induced photodegradation of MG in aqueous medium using all these modified TiO 2 catalysts in order to evaluate the effect of silver impregnation. We report that the presence of silver in TiO 2 enhances the photon induced mineralization of MG but reduces the decolorization efficiency. Based on both decolorization and mineralization, and also on the cost and availability, 1% silver impregnated commercial TiO 2 was found the optimal. The degradation of MG using this catalyst has been investigated in a more detail, and the effect of pH, stirring, initial MG concentration, catalyst dose, nature of light, and the presence of interfering ions/organics are examined. The dye (∼25 mg/l) is bleached almost completely upon 1 h of light irradiation under experimental conditions. The degradation follows zero-order kinetics over the entire MG concentration range (25-125 mg/l), and we presume that the degradation occurs via step-wise N-demethylation. Most importantly, we observe high turn over frequency (TOF) for our catalyst. This makes the catalytic process cost-effective and the catalyst recycle able. Further, a cost-analysis is made to evaluate the proper selection of the catalyst in terms of efficiency and economy. © 2012 Elsevier B.V. All rights reserved.

Roy N.,Indian Institute of Technology Kharagpur | Sohn Y.,Yeungnam University | Pradhan D.,Indian Institute of Technology Kharagpur
ACS Nano | Year: 2013

Controlled crystal growth determines the shape, size, and exposed facets of a crystal, which usually has different surface physicochemical properties. Herein we report the size and facet control synthesis of anatase TiO2 nanocrystals (NCs). The exposed facets are found to play a crucial role in the photocatalytic activity of TiO2 NCs. This is due to the known preferential flow of photogenerated carriers to the specific facets. Although, in recent years, the main focus has been on increasing the surface area of high-energy exposed facets such as {001} and {100} to improve the photocatalytic activity, here we demonstrate that the presence of both the high-energy {001} oxidative and low-energy {101} reductive facets in an optimum ratio is necessary to reduce the charge recombination and thereby enhance photocatalytic activity of TiO2 NCs. © 2013 American Chemical Society.

Arora C.,Indian Institute of Technology Kharagpur | Bhaskaran P.K.,Indian Institute of Technology Kharagpur
Ocean Engineering | Year: 2012

A comprehensive knowledge of the wave climate is an essential pre-requisite for practical applications in coastal and near-shore region. In coastal areas the dominant dissipative mechanism appears to be bottom friction where the relative strength depends on bottom characteristics, sediment type and bottom ripple geometry. The present state-of-art version SWAN wave model uses three popular formulations for dissipative mechanism due to bottom interaction. The bottom friction coefficient as in SWAN cannot be a constant and needs to be tuned based on prevailing hydrodynamic conditions when applied for a tidal dominant region. A combined wave-current interaction study should take into account varying water levels, reversal of current system and associated shear on the sea-bed. The present work reports on development of a new resistance law for bottom friction under the combined action of waves and currents. This new formulation has been implemented in the SWAN model and further its implication on variability of significant wave height for the Hooghly estuary located in the Bay of Bengal, East coast of India was investigated by comparison with ENVISAT satellite measurement. Based on this study, it could be ascertained that new friction formulation has potential for wind-wave modeling studies in near-shore and coastal waters. © 2012 Elsevier Ltd. All rights reserved.

Kashid S.S.,Walchand Institute of Technology | Maity R.,Indian Institute of Technology Kharagpur
Journal of Hydrology | Year: 2012

Prediction of Indian Summer Monsoon Rainfall (ISMR) is of vital importance for Indian economy, and it has been remained a great challenge for hydro-meteorologists due to inherent complexities in the climatic systems. The Large-scale atmospheric circulation patterns from tropical Pacific Ocean (ENSO) and those from tropical Indian Ocean (EQUINOO) are established to influence the Indian Summer Monsoon Rainfall. The information of these two large scale atmospheric circulation patterns in terms of their indices is used to model the complex relationship between Indian Summer Monsoon Rainfall and the ENSO as well as EQUINOO indices. However, extracting the signal from such large-scale indices for modeling such complex systems is significantly difficult. Rainfall predictions have been done for 'All India' as one unit, as well as for five 'homogeneous monsoon regions of India', defined by Indian Institute of Tropical Meteorology. Recent 'Artificial Intelligence' tool 'Genetic Programming' (GP) has been employed for modeling such problem. The Genetic Programming approach is found to capture the complex relationship between the monthly Indian Summer Monsoon Rainfall and large scale atmospheric circulation pattern indices - ENSO and EQUINOO. Research findings of this study indicate that GP-derived monthly rainfall forecasting models, that use large-scale atmospheric circulation information are successful in prediction of All India Summer Monsoon Rainfall with correlation coefficient as good as 0.866, which may appears attractive for such a complex system. A separate analysis is carried out for All India Summer Monsoon rainfall for India as one unit, and five homogeneous monsoon regions, based on ENSO and EQUINOO indices of months of March, April and May only, performed at end of month of May. In this case, All India Summer Monsoon Rainfall could be predicted with 0.70 as correlation coefficient with somewhat lesser Correlation Coefficient (C.C.) values for different 'homogeneous monsoon regions'. © 2012 Elsevier B.V.

Das A.K.,Indian Institute of Technology Kharagpur | Raj C.R.,Indian Institute of Technology Kharagpur
Journal of Colloid and Interface Science | Year: 2011

We describe a facile route for the one-pot room temperature synthesis of anisotropic Au nanostructures in aqueous solution in the absence of seeds or surfactants and their electrocatalytic activity. The Au nanostructures were synthesized using piperazine derivatives 1-(2-hydroxyethyl)piperazine and 1,4-Bis(2-hydroxyethyl)piperazine as reducing agents. The Au nanostructures were characterized by spectral, transmission electron microscopic (TEM), X-ray diffraction and electrochemical measurements. The absorption spectrum of colloidal nanoparticles displays two bands ~580 and ~930. nm, corresponding to the dipole and quadrupole plasmon resonance, respectively. TEM measurements show that the Au nanostructures have penta-twined polyhedral shape with an average size of 52. nm. X-ray and selected area electron diffraction patterns reveal the existence of face centered cubic nanocrystalline Au. The concentration of Au(III) controls the stability of the nanoparticles. The nanoparticles were immobilized on 3-D silicate network pre-assembled on a conducting support to examine their electrocatalytic activity. The nanoparticle-based electrochemical interface was characterized by spectral, voltammetric and impedance measurements. The nanoparticle shows high catalytic activity in the oxidation of NADH and reduction of oxygen. Unique inverted 'V' shape voltammogram was obtained for the oxidation of NADH at less positive potential. The nanoparticle-based interface favors two-step four-electron reduction of oxygen to water in neutral pH. Significant decrease in the overpotential for the oxidation of NADH and reduction of oxygen with respect to the polycrystalline Au electrode was observed. The electrocatalytic performance of the polyhedral nanoparticle is compared with the conventional citrate stabilized spherical nanoparticles. © 2010 Elsevier Inc.

Sahoo B.,Indian Institute of Technology Kharagpur | Sahu S.K.,Indian Institute of Technology Kharagpur | Pramanik P.,Indian Institute of Technology Kharagpur
Journal of Molecular Catalysis B: Enzymatic | Year: 2011

The development of simple and reliable technique for the immobilization of enzymes is an important part of biotechnology. We demonstrate herein the modification of magnetic nanoparticles and its use in the immobilization of the urease enzyme. Magnetite particles were prepared by simple co-precipitation method in aqueous medium and then subsequently coated with phosphonomethyl iminodiacetic acid. Urease was immobilized on the magnetic nanoparticles through a carbodiimide reaction. Surface functional groups and surface composition were analyzed by Fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis (TGA), respectively. The structural characteristics of the powders were studied by XRD. These modified nanoparticles were characterized by dynamic light scattering (DLS) and high resolution transmission electron microscopy (HRTEM). Vibration sample magnetometry (VSM) measurements showed the superparamagnetic nature of the particles at room temperature. The catalytic activity of the immobilized urease was comparable to that of the free enzyme in solution. The immobilized urease exhibited excellent catalytic activity over six times successive reuse as well as the stability. By using immobilization technique on this magnetic nanoparticle it is easy to isolate product from reaction mixture enabling to control the reaction and simultaneously lowers the cost of enzyme. © 2011 Elsevier B.V. All rights reserved.

Gazi S.,Indian Institute of Technology Kharagpur | Ananthakrishnan R.,Indian Institute of Technology Kharagpur
Applied Catalysis B: Environmental | Year: 2011

Reduction of 4-nitrophenol (4-NP) with NaBH4 in the aqueous medium is a kinetically inert reaction, and generally the reaction occurs in the presence of metal/metal oxide nanoparticles. In the present study, the reduction of 4-nitrophenol (4-NP) has been carried out photocatalytically using the visible irradiation under a metal-free (eco-friendly) condition. By systematic screening, Eosin Y loaded resin is identified to be efficient in the reduction of 4-NP under the visible light. The effectiveness of the catalytic process depends upon the adsorption and the electron transfer. The adsorption favours the reaction molecules to come closer on the resin surface, and then reduction occurs by transfer of electrons. Gradual decrease in the absorbance at 400nm confirms the decrease in concentration of the 4-NP. Simultaneously, there is an increase in absorbance at 300nm infers the formation of 4-aminophenol (4-AP) during the photolysis. Results obtained from the irradiation on-off experiment suggests that the visible light irradiation is essential for the above processes, and also it indicates the sensitivity of the photocatalyst. The optimized reaction condition had been arrived from the results obtained after a series of experiments, including variation of catalytic dose, concentrations of 4-NP and the reducing agent (NaBH4). The rate of the reaction is found to be pseudo first order kinetics, and the rate constant (k) value is 6.90×10-2min-1, under the experimental condition. From the control experiments, it is identified that the photocatalyst is primarily serving as an electron carrier in the reaction mechanism. © 2011 Elsevier B.V.

Ghosh S.,Indian Institute of Technology Kharagpur | Dey J.,Indian Institute of Technology Kharagpur
Journal of Colloid and Interface Science | Year: 2011

The interaction of sodium N-lauroylsarcosinate (SLS) with N-cetylpyridinium chloride (CPC) and N-dodecylpyridinium chloride (DPC) was investigated in aqueous mixtures. A strong interaction between the anionic and cationic surfactants was observed. The interaction parameter, β was determined for a wide composition range and was found to be negative. The mixed systems were found to have much lower critical micelle concentration (cmc) and surface tension at cmc. The surfactant mixtures exhibit synergism in the range of molar fractions investigated. The self-assembly formation in the mixtures of different compositions and total concentrations were studied using a number of techniques, including surface tension, fluorescence spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), confocal fluorescence microscopy (CFM). Thermodynamically stable unilamellar vesicles were observed to form upon mixing of the anionic and cationic surfactants in a wide range of composition and concentrations in buffered aqueous media. TEM as well as DLS measurements were performed to obtain shape and size of the vesicular structures, respectively. These unilamellar vesicles are stable for periods as long as 3 months and appear to be the equilibrium form of aggregation. Effect of pH, and temperature on the stability was investigated. The vesicular structures were observed to be stable at pH as low as 2.0 and at biological temperature (37°C). In presence of 10. mol% of cholesterol the mixed surfactant vesicles exhibited leakage of the encapsulated calcein dye, showing potential application in pH-triggered drug release. © 2011 Elsevier Inc.

Datta S.,Indian Institute of Technology Kharagpur | Mahapatra N.,Indian Institute of Technology Kharagpur | Halder M.,Indian Institute of Technology Kharagpur
Journal of Photochemistry and Photobiology B: Biology | Year: 2013

Here we have investigated the binding of carmoisine, a water-soluble azo food colorant, with serum proteins (HSA and BSA) by fluorescence and UV-VIS spectroscopy, circular dichroism and molecular docking studies. Results indicate that fluorescence quenching of protein has been due to site-specific binding of the dye with biomacromolecules. Site marker competitive binding and molecular docking explorations show that interaction occurs in the sub-domain IIA of HSA and the sub-domains IIA and IB in the case of BSA. Conformational investigation indicates that dye binding modifies the secondary structure of proteins and this also alters the microenvironment of the tryptophan(s). The interaction is found to be pH-insensitive which can have relevance to the toxicological profiles of the dye, and ionic strength dependence of binding can be exploited in protein purification mediated by such food colorants. © 2013 Elsevier B.V. All rights reserved.

Khilari S.,Indian Institute of Technology Kharagpur | Pandit S.,Indian Institute of Technology Kharagpur | Das D.,Indian Institute of Technology Kharagpur | Pradhan D.,Indian Institute of Technology Kharagpur
Biosensors and Bioelectronics | Year: 2014

Manganese cobaltite nanorods (MnCo2O4 NRs) were prepared and tested as potential air-cathode catalyst for the single-chambered microbial fuel cells (sMFC). The power generation of sMFC increases with MnCo2O4 NRs loading to the cathode. The Polypyrrole (PPy) and Vulcan XC were used as conducting support to the MnCo2O4 NRs to form composites either by in situ or by mechanical mixing in the cathode fabrication. The cyclic voltammetry, linear sweep voltammetry and electrochemical impedance studies reveal that the in situ-MnCo2O4 NRs/PPy composite has higher catalytic activity than that of mechanically mixed-MnCo2O4NRs/PPy composite because of higher interfacial contact between MnCo2O4 NRs and PPy. The maximum volumetric power density with in situ-MnCo2O4 NRs/PPy, mechanically mixed-MnCo2O4 NRs/PPy, MnCo2O4 NRs/Vulcan XC and catalyst-free (only Vulcan XC) cathode was measured to be 6.11, 5.05, 4.22, and 1.77W/m3, respectively, in the sMFC. This suggests that PPy is not only a better conducting support than that of conventionally used Vulcan XC but also the cathode composite fabrication process is important for enhanced performance. The synergetic effect of MnCo2O4 NRs and PPy was found to play an important role for the improved energy recovery and it could be applied as an efficient and inexpensive cathode catalyst for the sMFC. © 2013 .

Dey R.S.,Indian Institute of Technology Kharagpur | Raj C.R.,Indian Institute of Technology Kharagpur
Biosensors and Bioelectronics | Year: 2014

A new approach for the one-pot synthesis of reduced graphene oxide-dendritic Pd nanoparticle (rGO-nPd) hybrid material and the development of biosensing scaffold for the amperometric sensing of H2O2 and total cholesterol in human serum are described. In situ reduction of both graphene oxide (GO) and PdCl4 2- in acidic solution was achieved with Zn to obtain rGO-nPd hybrid material. The oxygen containing functionalities of GO were reduced by the liberated atomic hydrogen in 20min. The formal potential of Zn/Zn2+ and PdCl4 2-/Pd couples favor the facile reduction of PdCl4 2-. The in situ produced Pd nanoparticles behave like hydrogen sponge and increase the local concentration of atomic hydrogen. Biosensing platforms for H2O2 and cholesterol in human serum and butter sample were developed using the hybrid material. Amperometric sensing of H2O2 at 0.2nM level without any redox mediator or enzymes in neutral pH is demonstrated. The cholesterol biosensing platform was developed by integrating cholesterol oxidase and cholesterol esterase with the hybrid material. The biosensor is highly sensitive (5.12±0.05μA/μMcm2) and stable with a fast response time of 4s; it could detect cholesterol ester as low as 0.05μM (S/N=3). The biosensor is successfully used for the analysis of total cholesterol in human serum and butter. © 2014 Elsevier B.V.

Wagenmakers E.-J.,University of Amsterdam | Lodewyckx T.,Catholic University of Leuven | Kuriyal H.,Indian Institute of Technology Kharagpur | Grasman R.,University of Amsterdam
Cognitive Psychology | Year: 2010

In the field of cognitive psychology, the p-value hypothesis test has established a stranglehold on statistical reporting. This is unfortunate, as the p-value provides at best a rough estimate of the evidence that the data provide for the presence of an experimental effect. An alternative and arguably more appropriate measure of evidence is conveyed by a Bayesian hypothesis test, which prefers the model with the highest average likelihood. One of the main problems with this Bayesian hypothesis test, however, is that it often requires relatively sophisticated numerical methods for its computation. Here we draw attention to the Savage-Dickey density ratio method, a method that can be used to compute the result of a Bayesian hypothesis test for nested models and under certain plausible restrictions on the parameter priors. Practical examples demonstrate the method's validity, generality, and flexibility. © 2009 Elsevier Inc. All rights reserved.

Haldar R.,Indian Institute of Technology Kharagpur | Das S.,Indian Institute of Technology Kharagpur | Varshney S.K.,Indian Institute of Technology Kharagpur
Journal of Lightwave Technology | Year: 2013

In this paper, we have developed a theory of an off-axis microring resonator (MRR) with single and multiple off-axis rings. The off-axis inner ring introduces tunable extra notches with many striking features in the transmission spectrum which facilitates its use as efficient modulators and sensors. A few such notches when closely packed have been used to design a compact band rejection filter with improved bandwidth (>10 nm). Moreover, these closely packed extra notches achieved by serially coupled MRRs with off-axis inner rings are tunable to reject arbitrarily chosen WDM channels. Through numerical simulations, based on both transfer matrix method and finite difference time domain method, it has been examined that off-axis MRRs cater superior performances in comparison to the serially coupled conventional MRR with respect to the device size, faster response, and low dispersion. The proposed off-axis MRRs may be used for cluster to cluster interconnects and can have other potential on-chip photonic applications in network layer. Necessary design parameters are computed from the coupled mode theory. © 1983-2012 IEEE.

Hota A.R.,Indian Institute of Technology Kharagpur | Juvvanapudi M.,Indian Institute of Technology Kharagpur | Bajpai P.,Indian Institute of Technology Kharagpur
Renewable and Sustainable Energy Reviews | Year: 2014

Successful integration of plug-in hybrid electric vehicles (PHEVs) into the power system is a major challenge for the future smart grid. As a result, this topic has attracted the attention of researchers from different communities in the past few years. Recent research progress has addressed different technical aspects of PHEV integration into the smart grid; such as charging and control strategies of PHEVs, vehicle-to-grid (V2G) technology, and several application domains, such as wind energy integration, frequency regulation, design of parking areas and participation in electricity markets. Most of these works require formulation of mathematical models which extensively use artificial intelligence techniques, intelligent methods and agent-based computing approaches to solve the computational problems. This paper presents a comprehensive survey of different research problems and their solution approaches in the context of PHEV integration to the smart grid. © 2013 Elsevier Ltd. All rights reserved.

Singh A.,Indian Institute of Technology Kharagpur
Water Resources Management | Year: 2014

Proper planning and management of irrigation is vital in achieving food security for the burgeoning global population and sustaining livelihoods. Because irrigated agriculture is expected to provide more food, if managed properly. The comprehensive reviews on the use of various programming techniques used for planning and management of irrigation have been provided in this paper. The literature review revealed that the management models used in the past mainly considered the objectives of maximization of net farm income, minimization of waterlogging, and minimization of groundwater depletion. These objectives were achieved by optimizing the allocation of available land and water resources. The past reviews are grouped into four sections based on the programming techniques adopted. The sections include: linear programming, nonlinear programming, dynamic programming, and genetic algorithms. This review provides the basis for the selection of appropriate methodology for the planning and management of irrigation. © 2013 Springer Science+Business Media Dordrecht.

Singh A.,Indian Institute of Technology Kharagpur
Journal of Hydrology | Year: 2014

The continuous increase in global population and simultaneous decrease in good quality water resources emphasizes the need of using surface water and groundwater resources conjunctively for irrigation. The conjunctive use allows the utilization of poor quality water, which cannot be used as such for the crop production due to its harmful effect on soil and crop health. This paper presents an overview on issues and methods of the conjunctive use of surface water and groundwater resources for sustainable irrigated agriculture. The background of the conjunctive water use and its applications for the management of poor quality water and management of rising watertable are presented. The management of conjunctive water use through the computer-based models is also covered in this review. The advantages and disadvantages of the approach have been described. Conclusions are provided based on this review which could be useful for all the stakeholders. © 2014 Elsevier B.V.

Singh A.,Indian Institute of Technology Kharagpur
Journal of Hydrology | Year: 2014

The coastal aquifers of the world are facing environmental problem of seawater intrusion. This problem is the results of indiscriminate and unplanned groundwater exploitation for fulfilling the growing need of freshwater for the burgeoning global population. There is a need to develop appropriate management models for assessing the maximum feasible pumping rates which protects seawater intrusion in coastal aquifers. The comprehensive reviews on the use of various programming techniques for the solution of seawater intrusion management problem of coastal aquifers have been provided in this paper. The literature review revealed that the management models used in the past mainly considered the objectives of maximization of pumping rate, minimization of drawdown, minimization of pumped water, minimization of seawater volume into the aquifer, and/or minimization of pumping cost. The past reviews are grouped into five sections based on the programming techniques adopted. The sections include: linear programming, nonlinear programming, genetic algorithms, artificial neural networks, and multiobjective optimization models. Conclusions are drawn where gaps exist and more research needs to be focused. This review provides the basis for the selection of appropriate methodology for the management of seawater intrusion problems of coastal aquifers. © 2013 Elsevier B.V.

Bhati R.,Indian Institute of Technology Kharagpur | Mallick N.,Indian Institute of Technology Kharagpur
Journal of Chemical Technology and Biotechnology | Year: 2012

Background: Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] co-polymer has immense potential in the field of environmental and biomedical sciences as biodegradable and biocompatible material. The present study examines a filamentous N 2-fixing cyanobacterium, Nostoc muscorum Agardh as a potent feedstock for P(3HB-co-3HV) co-polymer production and characterization of co-polymer film for commercial applications. Results: Under photoautotrophic growth conditions, N. muscorum Agardh accumulated the homopolymer of poly-β-hydroxybutyrate (PHB), whereas synthesis of P(3HB-co-3HV) co-polymer was detected under propionate- and valerate-supplemented conditions. Exogenous carbons such as acetate, fructose and glucose supplementation with propionate/valerate was found highly stimulatory for the co-polymer accumulation; the content reached 58-60% of dry cell weight (dcw) under P-/N-deficiencies with 0.4% acetate + 0.4% valerate supplementation, the highest value reported so far for P(3HB-co-3HV) co-polymer-producing cyanobacterial species. The material properties of the films were studied by mechanical tests, surface analysis and differential scanning calorimetry (DSC). CONCLUSION: N. muscorum Agardh, a photoautotrophic N 2-fixing cyanobacterium, emerged as a potent host for production of P(3HB-co-3HV) co-polymer with polymer content 60% of dry cell weight. The material properties of the films were found to be comparable with that of the commercial polymer, thus advocating its potential applications in various fields. © 2012 Society of Chemical Industry.

Rao J.G.,Indian Institute of Technology Kharagpur | Pradhan A.K.,Indian Institute of Technology Kharagpur
IEEE Transactions on Power Delivery | Year: 2012

Distance relays are blocked during power swing to ensure reliability of the power system. However, if a fault occurs during a power swing, it should be detected and the unblocking function should be invoked to clear the fault as soon as possible. Due to the symmetric nature of signals during the power swing, symmetrical faults are difficult to be detected. In this paper, a differential power-based fault detection technique is proposed for the detection of symmetrical faults during power swings. The differential power is calculated from the difference in predicted and actual samples of voltage and current. The predicted voltage and current samples are obtained using the autoregression technique. The proposed method is tested for different fault conditions and the results are compared with the available method. The proposed method is found to identify symmetrical faults accurately during slow and fast power swings for different power systems. © 2012 IEEE.

Kiran B.,Indian Institute of Technology Kharagpur | Jana A.K.,Indian Institute of Technology Kharagpur | Samanta A.N.,Indian Institute of Technology Kharagpur
Energy | Year: 2012

In this contribution, a novel intensified heat integrated ternary distillation column (int-HITDiC) is introduced. The objective is to show the superiority of the int-HITDiC over its general form, namely the HITDiC and the conventional standalone column on the basis of two criteria: energy consumption and economics. The concept of pinch technology has been applied to identify the feasibility region for internal thermal coupling between two diabatic sections, namely the rectifying section and stripping section. In this study, the influence of system parameters on the behavior of HITDiC is examined. The optimum compression ratio is arrived at by taking into account the energetic and economic aspects. Performing a detailed analysis, it is observed that the general HITDiC scheme shows lower energy consumption and better economic figure compared to its conventional counterpart. Aiming to improve the overall efficiency further, the int-HITDiC scheme has been explored. The proposed intensified strategy gets the advantage of both HIDiC and direct vapor recompression column (VRC). © 2012 Elsevier Ltd.

Ganguly M.,Indian Institute of Technology Kharagpur | Pal A.,Indian Institute of Technology Kharagpur | Pal T.,Indian Institute of Technology Kharagpur
Journal of Physical Chemistry C | Year: 2012

Straight chain amines of variable chain length offer steric stabilization to gold nanoparticles (AuNPs), and thereby, gold organosol is produced in nonpolar solvent. We have found that dodecylamine (DDA) becomes a preferred ligand over other amines, for extraction, stabilization, and preparation of gold organosol in hexane. In the same context, straight chain thiols also provide steric stabilization to the AuNPs and compete with amines. But, the extracting power of thiols is dramatically reduced while the size of AuNPs is increased, and amines accomplish success for variable sizes of AuNPs. Organosol system always remains admixed with excess free ligands, and it is true for amines also. Hence, free amines (unbound) conjecture false information and pose a problem during further course of investigation. Excess unbound ligands in the organosol system limit application of AuNPs in the organic medium. A simple heterogeneous separation technique is reported here to prepare amine stabilized organosol devoid of unbound (free) amine. A greenish blue solid copper stearate [Cu(St) 2] has been introduced as the best suited reagent that endorses quantitative removal (97.3 ± 0.12%) of free amine. The solid reagent [Cu(St) 2] in turn produces a violet solid. The greenish blue to violet color change of the solid reagent indicates selective removal of excess amine from the organosol keeping the properties of amine stabilized organosol unaltered. © 2012 American Chemical Society.

Bhattacharjee P.,Indian Institute of Technology Kharagpur | Ray P.K.,Indian Institute of Technology Kharagpur
Computers and Industrial Engineering | Year: 2014

Analysis of hospital processes is essential for development of improved methods, policies and decision tools for overall performance improvement of the hospital system. Amidst the current scenario of continuously increasing healthcare costs and scarcity of resources, optimal utilization of resources without hampering the quality of care has gained importance in any country. Modelling, analysis and management of patient flows, in this context, plays a key role in performance analysis and improvement of hospital processes as appropriate modelling of patient flows may help healthcare managers make decisions related to capacity planning, resource allocation and scheduling, appointment scheduling and for making necessary changes in the process of care. The concept of patient flow and its modelling has gained much attention in healthcare management literature over past few decades. In this paper, the existing approaches pertaining to modelling of patient flows in hospital systems have been classified and critically appraised focussing on the recent advancements in order to identify future research avenues. A generic framework for patient flow modelling and performance analysis of hospital systems that may serve as a guide for the practitioners dealing with similar kinds of problems to improve healthcare delivery has also been provided. © 2014 Elsevier Ltd. All rights reserved.

Ghosh A.K.,Indian Institute of Technology Kharagpur | Ray D.,Indian Institute of Technology Kharagpur
Polyhedron | Year: 2013

Dinuclear [Cu2(μ-OH)] fragment and its self-assembled tetranuclear part [Cu2(μ4-O)Cu2] are found in two copper(II) complexes of ligand H3bpmp: [Cu2(μ 2-OH)(μ-H2bpmp)(μ1,3-NO 3)][Cu2(μ2-OH)(μ-H2bpmp) (NO3)(H2O)](NO3)2·2H 2O (1·2H2O) and [Cu4(μ4-O) (μ-H2bpmp)2(μ1,3-O2CCH 2Ph)4] (2) [H3bpmp = 2,6-bis-[(3-hydroxy- propylimino)-methyl]-4-methylphenol]. These complexes have been synthesized and characterized by single crystal X-ray crystallography. Complex 1 showed unique reactivity with phenylacetate anions to provide 2 in which two [Cu 2(μ2-OH)] units available within same crystal lattice collapsed to give [Cu4(μ4-O)] hub. Formation of the [Cu4] compound is also achieved from individual components and phenylacetate ligands, which allows an effective tuning of the self-assembly of two ligand bound [Cu2] fragments and removal of H+ from hydroxido bridges to provide oxido nucleus.

Chakraborty S.,Indian Institute of Technology Kharagpur | Raj C.R.,Indian Institute of Technology Kharagpur
Sensors and Actuators, B: Chemical | Year: 2010

Electrochemical sensing of hydrazine using a highly sensitive platform based on nanosized Pt (nPt) particles is described. The sensing platform is developed by the pre-organization of metal precursor on multiwalled carbon nanotubes (MCNT) modified conducting substrate and subsequent chemical reduction of the precursor in aqueous solution. The Pt nanoparticles are characterized by transmission electron microscope, X-ray diffraction (XRD), spectral and electrochemical measurements. The nPt on MCNT modified electrode has spherical shape with 5-10 nm size. XRD and selected area electron diffraction pattern reveal the existence of (1 1 1), (2 0 0) and (2 2 0) planes of face centered cubic structure. The electrocatalytic activity of nPt on the MCNT modified electrode toward oxidation of hydrazine is examined. The nPt on the MCNT modified electrode exhibit significantly high electrocatalytic activity with respect to the polycrystalline Pt electrode. The nanoparticle coverage on the electrode has strong influence on the electrocatalytic activity. Gradual negative shift in the oxidation peak potential and increase in the peak current are observed while increasing the particle coverage. The nanoparticle-based electrode is highly stable and sensitive and it can sense as low as 0.5 nM hydrazine sulfate at the potential of -0.35 V without any redox mediator. The co-existence of hydrazine derivative N,N-dimethylhydrazine does not interfere the electrochemical sensing of hydrazine. © 2010 Elsevier B.V. All rights reserved.

Singh A.,Indian Institute of Technology Kharagpur
Water Resources Management | Year: 2012

Direct measurement of groundwater recharge is nearly impossible. So there are various direct and indirect methods and sophisticated models have been used for its estimation. However, the use of multiple approaches has been recommended to estimate the groundwater recharge since each individual approach is associated with some limitations. In many cases, different approaches complement each other and help refine the conceptual model of recharge processes. In this study, a simple watertable model, which is a combination of the groundwater budget and watertable fluctuation, was developed. The model is unique, simple, cost effective, and easy to apply. The model requires input parameters that are readily available or obtainable and which can be accurately measured. The model was applied to estimate the seasonal long-term (30 years, e. g., from 1981 to 2011) groundwater recharge of a canal command located in Jhajjar district of Haryana State (India), where watertable is rising. The results were analysed to provide an overview of the process dynamics that led to watertable rise in the command area. The calculated watertable depths reasonably matched with the observed ones for all the seasons which were confirmed by the high R-squared value of 0. 963. The mean error and root mean squared error were low at -0. 0068 and 0. 2548 m, respectively, while the model efficiency was 0. 83. Different water management alternatives were studied to examine the effect of variation in model parameters on its output. Among the alternatives studied, increased tubewell draft had a higher impact on the overall water balance followed by reduced rice area and canal lining, respectively. © 2012 Springer Science+Business Media Dordrecht.

Maity R.,Indian Institute of Technology Kharagpur
Hydrological Processes | Year: 2012

In this paper, Split Markov Process (SMP) is developed to assess one-step-ahead variation of daily rainfall at a rain gauge station. SMP is an advancement of general Markov Process and specially developed for probabilistic assessment of change in daily rainfall magnitude. The approach is based on a first-order Markov chain to simulate daily rainfall variation at a point through state/sub-state transitional probability matrix (TPM). The state/sub-state TPM is based on the historical transitions from a particular state to a particular sub-state, which is the basic difference between SMP and general Markov Process. The cumulative state/sub-state TPM is represented in a contour plot at different probability levels. The developed cumulative state/sub-state TPM is used to assess the possible range of rainfall in next time step, in a probabilistic sense. Application of SMP is investigated for daily rainfall at four rain gauge stations - Khandwa, Jabalpur, Sambalpur, and Puri, located at various parts in India. There are 99years of record available out of which approximately 80% of data are used for calibration, and 20% of data are used to assess the performance. Thus, 80years of daily monsoon rainfall is used to develop the state/sub-state TPM, and 19years data are used to investigate its performance. Model performance is assessed in terms of hit rate (HR), false alarm rate (FAR), and percentage captured. It is found that percentage captured is maximum for Khandwa (70%) and minimum for Sambalpur (44%) whereas hit rate is maximum for Sambalpur and minimum for Khandwa (73%). FAR is around 30% or below for Jabalpur, Sambalpur, and Puri. FAR is maximum for Khandwa (37%). Overall, the assessed range, particularly the upper limit, provides a quantification possible extreme value in the next time step, which is a very useful information to tackle the extreme events, such as flooding, water logging and so on. © 2011 John Wiley & Sons, Ltd.

Mukherjee G.,Indian Institute of Technology Kharagpur | Biradha K.,Indian Institute of Technology Kharagpur
Crystal Growth and Design | Year: 2013

The reactions of bis(pyridylcarboxamido)propane (L1, 4-pyridyl and L2, 3-pyridyl), and bis(pyridylcarboxamido)pentane (L 3, 4-pyridyl and L4, 3-pyridyl) with Cu(I/II), Co(II), and Cd(II) salts in the presence of various anions resulted in one-dimensional (1D) and two-dimensional (2D) coordination polymers containing M2L 2 and M4L4 metallacycles. Reactions of L 1 and L2 with CuI afforded the formation of two different kinds of SBUs as Cu2I2 and Cu4I4, and both complexes form 1D chains, which are assembled further by α-sheet hydrogen bonding. The reactions of M(II) salts in the absence of guest molecules lead to the formation of 1D chains containing M2L2-type metallacycles. These 1D chains are found to be of two types: in one type adjacent metallacycles are in plane with each other and in the second type they are nonparallel to each other. The reaction of Cu(II) with L1 in the presence of guest molecules such as benzonitrile or nitrobenzene leads to the formation of corrugated 2D layers containing M4L4 metallacycles. These 2D layers exhibit 2-fold interpenetration as well as guest inclusion simultaneously and also exhibit preferential guest-exchange dynamics. The self-complementary amide groups of the ligands assembled these coordination networks into higher dimensional architectures via amide-to-amide (α-sheet), amide-to-water, amide-to-anions, and N-H⋯O or O-H⋯O hydrogen bonds. The alkyl spacers are found to exhibit various conformations depending on the coordination network geometries, anions, and guest molecules. © 2013 American Chemical Society.

Roy S.,Indian Institute of Technology Kharagpur | Biradha K.,Indian Institute of Technology Kharagpur
Crystal Growth and Design | Year: 2013

Several complexes of 2,2′,6,6′-tetracarboxybiphenyl (H 41) with various N-containing heterocycles and N-oxides were synthesized and their crystal structures were analyzed in terms of salt/cocrystal, deprotonation, synthons, and network geometries. The tetra carboxylic acid, H41, was found to act as a host for the inclusion of acetic acid dimers. For complexation reactions with bases, the mono basic compounds such as pyridine, quinoline, and acridine; the dibasic compounds such as 9,10-phenanthrolene, 4,4′-bipyridylethane, 4,4′- bipyridyldisulfide, phenazine, and 1,4-diazabicyclooctane (dabco); and N-oxides of 4,4′-bipyridine and dabco are considered. In the crystal structures of these complexes, the H41 was found to exist as H21 (double deprotonation of H41), H31 (mono deprotonation of H 41), or H41 (cocrystals) forms depending on the basicity of the complexing agent and other factors. Out of 13 complexes studied here the more probable acid-pyridine synthon was observed in one complex, the COO -⋯HOOC- synthon was found to be dominant as it was observed in seven complexes. The assembling of anions and cations produced versatile network architectures including discrete, one-dimensional, two-dimensional, and three-dimensional networks in terms of strong and conventional hydrogen bonds. In some cases, the cations acted as pillars to assemble the layers of anions into three-dimensional networks containing huge channels that are filled by self-interpenetration. Only phenazine was found to form a neutral complex, cocrystal, with H41 among all of the bases used. The weak bases such as N-oxides of 4,4′-bipyridine and dabco were found to be doubly protonated and form polar hydrogen bonded networks. © 2013 American Chemical Society.

Mukherjee G.,Indian Institute of Technology Kharagpur | Biradha K.,Indian Institute of Technology Kharagpur
Chemical Communications | Year: 2014

Four iso-structural layered coordination polymers (CPs) of Cd(ii) and Zn(ii) were shown to exhibit breathing transitions with N2/H 2 gases. Furthermore, the solid solutions containing Zn(ii)/Cd(ii) have shown better uptake capacities of gas than parent CPs. These results give some insights into the role of metal ions and anions for fine-tuning the porosity of CPs. © 2014 The Royal Society of Chemistry.

Das A.,Indian Institute of Technology Kharagpur | Paul S.K.,Indian Institute of Technology Kharagpur
Energy Economics | Year: 2014

CO2 emission from anthropogenic activities is one of the major causes of global warming. India being an agriculture dependent country, global warming would mean monsoon instability and consequent food scarcity, natural disasters and economic concerns. However with proper policy interventions, CO2 emissions can be controlled. Input-output analysis has been used to estimate direct and indirect CO2 emissions by households for 1993-94, 1998-99, 2003-04 and 2006-07. Complete decomposition analysis of the changes in CO2 emissions between 1993-94 and 2006-07 has been done to identify the causes into pollution, energy intensity, structure, activity and population effects according to broad household consumption categories. Results indicate that activity, structure and population effects are the main causes of increase in CO2 emission from household fuel consumption. To identify the causes at the sectoral level a second decomposition has been done for changes between 2003-04 and 2006-07 to identify the causes in the next stage. Finally alternative energy policy options have been examined for each consumption category to reduce emissions. Combined strategies of technology upgradation, fuel switching and market management in order to reduce CO2 emissions for sectors like Batteries, Other non-electrical machinery, Construction and Electronic equipments (including Television), for which all the effects are positive, need to be adopted. © 2013 Elsevier B.V.

Kundu J.,Indian Institute of Technology Kharagpur | Pradhan D.,Indian Institute of Technology Kharagpur
ACS Applied Materials and Interfaces | Year: 2014

A simple, template-free and mild solution chemistry route was employed to synthesize diverse copper sulfide (CuS) nanostructured assemblies at 70 C by varying the solvent (water or ethylene glycol, or their ratios (3:1, 1:1 and 1:3)). The CuS structures in the shape of spheres and nanotubes were found to be assemblies of either nanoplates or nanoparticles. The nanotube formation was elaborately studied by varying the synthesis parameters such as temperature, reaction duration, precursor's ratio, and counterions. Counterions such as NO3- and SO42- were found to be suitable for nanotube formation whereas in the presence of Cl- and OAc- ions, CuS flake-like and nanoparticle assemblies are obtained, respectively. The optical bandgaps for the CuS with different morphologies were measured to be in the range of 1.88-2.16 eV. The bandgap of CuS in the visible region of electromagnetic radiation prompted it to be used as photocatalyst in the past under natural light. However, we demonstrate here the similar catalytic performance of as-synthesized CuS nanostructures for the degradation of methylene blue in the dark, suggesting that light does not play a role in its catalytic behavior. © 2014 American Chemical Society.

Dey R.S.,Indian Institute of Technology Kharagpur | Raj C.R.,Indian Institute of Technology Kharagpur
ACS Applied Materials and Interfaces | Year: 2013

We describe the redox functionalization of graphene oxide (GO) and the development of versatile amperometric biosensing platforms for clinically important analytes such as cholesterol ester, uric acid and glucose. Ferrocene (Fc) redox units were covalently tethered onto the GO backbone using diamine sigma spacers of different chain lengths (C3-, C6-, and C9-diamines). The functionalized GO (Fc-GO) displays a pair of redox peak corresponding to Fc/Fc+ redox couple at ∼0.225 V. The surface coverage and heterogeneous electron transfer rate constant of Fc-GO depends on the length of sigma spacer. Amperometric biosensors for cholesterol (total), uric acid and glucose have been developed by integrating Fc-GO and the respective redox enzymes with screen printed electrode. Fc-GO efficiently mediates the bioelectrocatalytic oxidation of the substrates in the presence of the redox enzymes. The spacer length of Fc-GO controls the bioelectrocatalytic response of the biosensing platforms. The sensitivity of the biosensors based on C9 sigma spacer is significantly higher than the others. The detection limit (S/N = 3) of the biosensors for cholesterol and uric acid was 0.1 μM and for glucose it was 1 μM. Excellent stability, reproducibility, selectivity and fast response time were achieved. Biosensing of cholesterol, uric acid and glucose in human serum sample is successfully demonstrated with the biosensors, and the results are validated with the clinical laboratory measurement. © 2013 American Chemical Society.

Maiti S.,Indian Institute of Technology Kharagpur | Shrivastava N.K.,Indian Institute of Technology Kharagpur | Suin S.,Indian Institute of Technology Kharagpur | Khatua B.B.,Indian Institute of Technology Kharagpur
ACS Applied Materials and Interfaces | Year: 2013

Today, we stand at the edge of exploring carbon nanotube (CNT) and graphene based polymer nanocomposites as next generation multifunctional materials. However, irrespective of the methods of composite preparation, development of electrical conductivity with high electromagnetic interference (EMI) value at very low loading of CNT and (or) graphene is limited due to poor dispersion of these nanofillers in polymer matrix. Here, we demonstrate a novel technique that involves in-situ polymerization of styrene/multiwalled carbon nanotubes (MWCNTs) in the presence of suspension polymerized polystyrene (PS)/graphite nanoplate (GNP) microbeads, for the preparation of electrically conducting PS/MWCNT/GNP nanocomposites with very high (∼20.2 dB) EMI shielding value at extremely low loading of MWCNTs (∼2 wt %) and GNP (∼1.5 wt %). Finally, through optimizing the ratio of PS-GNP bead and MWCNTs in the nanocomposites, an electrical conductivity of ∼9.47 × 10-3 S cm -1 was achieved at GNP and MWCNTs loading of 0.29 and 0.3 wt %, respectively. The random distribution of the GNPs and MWCNTs with GNP-GNP interconnection through MWCNT in the PS matrix was the key factor in achieving high electrical conductivity and very high EMI shielding value at this low MWCNT and GNP loadings in PS/MWCNT/GNP nanocomposites. With this technique, the formation of continuous conductive network structure of CNT-GNP-CNT and the development of spatial arrangement for strong π-π interaction among the electron rich phenyl rings of PS, GNP, and MWCNT could be possible throughout the matrix phase in the nanocomposites, as evident from the field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) studies. © 2013 American Chemical Society.

Basak N.,National Institute of Technology Jalandhar | Jana A.K.,National Institute of Technology Jalandhar | Das D.,Indian Institute of Technology Kharagpur | Saikia D.,National Institute of Technology Jalandhar
International Journal of Hydrogen Energy | Year: 2014

Hydrogen is green fuel for the future, mainly due to its recyclability. Biohydrogen production processes are less energy intensive and environmental friendly in compared to chemical processes. Fermentative biohydrogen production can be broadly classified as: dark and photo fermentation. Two enzymes, nitrogenase and hydrogenase play important role in biohydrogen production. Purple Non-Sulfur bacteria (PNS) are mainly used in photofermentative hydrogen production through which the overall yield can be improved manifolds. The scope and objective of this review paper is to investigate the performance of various light driven photofermentative hydrogen production by PNS bacteria along with several developmental works related to batch, repeated batch, feed batch and continuous operation. However the study of Photobiological process by microalgae or cyanobacteria is outside the scope of this review. Optimization of suitable process parameters such as carbon and nitrogen ratio, illumination intensity, bioreactor configuration, immobilization of active cells in specific continuous mode and inoculum age may lead to higher yield of hydrogen generation. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Singh A.,Indian Institute of Technology Kharagpur
Agricultural Water Management | Year: 2014

Good quality surface water and groundwater resources are limited furthermore they are shrinking because of the urbanization, contamination, and climate change impacts. In this backdrop, the proper allocation and management of these resources is a critical challenge for satisfying the rising water demands of agricultural sector. Because irrigated agriculture is the largest user of all the developed water resources and consumes over 70% of the abstracted freshwater globally. The computer-based models are useful tools for achieving the optimal allocation of limited water resources for the conjunctive use planning and management in irrigated agriculture. Various simulation and optimization modeling approaches have been used to solve the water allocation problems. Optimization models have been shown to be of great importance when used with simulation models and the combined use of these two approaches gives the best results. The reviews on the combined applications of simulation and optimization modeling for the conjunctive use planning and management of surface water and groundwater resources for sustainable irrigated agriculture are done and presented in this paper. Conclusions are provided based on this review which could be useful for all the stakeholders. © 2014 Elsevier B.V.

Ghosh D.,Indian Institute of Technology Kharagpur | Giri S.,Indian Institute of Technology Kharagpur | Das C.K.,Indian Institute of Technology Kharagpur
Nanoscale | Year: 2013

One-dimensional NiMoO4·nH2O nanorods and their graphene based hybrid composite with good electrochemical properties have been synthesized by a cost effective hydrothermal procedure. The formation of the mixed metal oxide and the composite was confirmed by XRD, XPS and Raman analyses. The morphological characterizations were carried out using FESEM and TEM analyses. The materials were subjected to electrochemical characterization through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies with 6 M KOH as the supporting electrolyte. For NiMoO4·nH2O, a maximum specific capacitance of 161 F g-1 was obtained at 5 A g-1 current density, accompanied with an energy density of 4.53 W h kg-1 at a steady power delivery rate of 1125 W kg-1. The high utility of the pseudocapacitive NiMoO4·nH2O was achieved in its graphene based composite, which exhibited a high specific capacitance of 367 F g-1 at 5 A g-1 current density and a high energy density of 10.32 W h kg-1 at a power density of 1125 W kg -1 accompanied with long term cyclic stability. © 2013 The Royal Society of Chemistry.

Saha Roy B.K.,Indian Institute of Technology Kharagpur | Sinha A.K.,Indian Institute of Technology Kharagpur | Pradhan A.K.,Indian Institute of Technology Kharagpur
International Journal of Electrical Power and Energy Systems | Year: 2012

Power system state estimation with exclusive utilization of synchronous phasor measurements demands that the system should be completely observable through PMUs only. To have minimum number of PMUs, the PMU placement issue in any network is an optimization problem. A three stage optimal PMU placement method is presented in this paper using network connectivity information. The method initially considers PMU in all buses of the network. Stage I and Stage II of the algorithm iteratively determine (i) less important bus locations from where PMUs are eliminated and (ii) strategically important bus locations where PMUs are retained. Stage III of the algorithm further minimizes the number of PMU using pruning operation. The set of PMUs obtained after Stage III is an optimal set of PMU locations for network observability. Proposed method is further extended for assuring complete observability under single PMU outage cases. Simulation results for IEEE 14-bus, 24-bus, 30-bus, 57-bus, 118-bus and New England 39-bus test systems are presented and compared with the existing techniques. Results show that the proposed method is simple to implement and accurate compared to other existing methods. © 2012 Elsevier Ltd. All rights reserved.

Bag S.,Indian Institute of Technology Kharagpur | Roy K.,CSIR - National Chemical Laboratory | Gopinath C.S.,CSIR - National Chemical Laboratory | Raj C.R.,Indian Institute of Technology Kharagpur
ACS Applied Materials and Interfaces | Year: 2014

Development of efficient electrocatalyst based on non-precious metal that favors the four-electron pathway for the reduction of oxygen in alkaline fuel cell is a challenging task. Herein, we demonstrate a new facile route for the synthesis of hybrid functional electrocatalyst based on nitrogen-doped reduced graphene oxide (N-rGO) and Mn3O4 with pronounced electrocatalytic activity towards oxygen reduction reaction (ORR) in alkaline solution. The synthesis involves one-step in situ reduction of both graphene oxide (GO) and Mn(VII), growth of Mn3O4 nanocrystals and nitrogen doping onto the carbon framework using a single reducing agent, hydrazine. The X-ray photoelectron (XPS), Raman and FTIR spectral, and X-ray diffraction measurements confirm the reduction of GO and growth of nanosized Mn3O4. The XPS profile reveals that N-rGO has pyridinic (40%), pyrrolic (53%), and pyridine N oxide (7%) types of nitrogen. The Mn 3O4 nanoparticles are single crystalline and randomly distributed over the wrinkled N-rGO sheets. The hybrid material has excellent ORR activity and it favors the 4-electron pathway for the reduction of oxygen. The electrocatalytic performance of the hybrid catalyst is superior to the N-rGO, free Mn3O4 and their physical mixture. The hybrid material shows an onset potential of -0.075 V, which is 60-225 mV less negative than that of the other catalyst tested. It has excellent methanol tolerance and high durability. The catalytic current density achieved with the hybrid material at 0.1 mg cm-2 is almost equivalent to that of the commercial Pt/C (10%). The synergistic effect of N-rGO and Mn3O4 enhances the overall performance of the hybrid catalyst. The nitrogen in N-rGO is considered to be at the interface to bridge the rGO framework and Mn 3O4 nanoparticles and facilitates the electron transfer. © 2014 American Chemical Society.

Babu G.U.B.,Indian Institute of Technology Kharagpur | Aditya R.,Indian Institute of Technology Kharagpur | Jana A.K.,Indian Institute of Technology Kharagpur
Energy | Year: 2012

It has long been recognized that the highly irreversible operation of batch distillation involves more wastage of energy compared to continuous flow distillation. For boosting its energy efficiency, the middle vessel batch distillation (MVBD) column has been invented. In this paper, a rigorous model for an MVBD process for the separation of a ternary hydrocarbon system is developed to simulate its transient behavior. In order to obtain the products at their maximum achievable purities, we device the two operating policies for the representative configuration.This contribution introduces a heat pumping system in the MVBD aiming to further improve its energetic and economic potentials. This novel heat integration technique is operated with a variable speed compressor for pressurizing the overhead vapor before thermally coupling it with the reboiler liquid. Interestingly, along with the compression ratio (CR), the other two manipulated variables are the inflow rate of overhead vapor to the compressor and that of an external medium (here, steam) that provides makeup heat to the reboiler. The operation of this adaptive heat pump assisted column originally involves the simultaneous adaptation of two variables throughout the entire batch processing. The simulation results show that a cost savings predicted in the heat integrated MVBD scheme can be achieved along with a substantial reduction in energy consumption. © 2012 Elsevier Ltd.

Biswal R.C.,Indian Institute of Technology Kharagpur | Biswas K.,Indian Institute of Technology Kharagpur
Journal of the European Ceramic Society | Year: 2013

In the present study, LSGM (La0.8Sr0.2Ga0.8Mg0.2O2.8) powder has been synthesized using precipitation route followed by hydrothermal treatment. Quantitative phase analyses of different powders, have been done by Rietveld analyses of the XRD data and they reveal formation of single phase orthorhombic LSGM at 1400°C, 8h. Morphology of the calcined powder and microstructure of the sintered pellets are observed by transmission electron microscope (TEM) and scanning electron microscope (SEM), respectively. Thermal analysis has been carried out to find out the thermal expansion co-efficient. Successive electrical characterization of the 99% dense sintered pellet has been done by impedance spectroscopic analysis. The diffused semicircles observed in the Nyquist plots have been simulated as (RQ)(RQ) circuit and the total ionic conductivity obtained is found to be the highest for LSGM synthesized by similar routes. © 2013 Elsevier Ltd.

Dutta N.N.,Indian Institute of Technology Kharagpur | Majumder S.,Indian Institute of Technology Kharagpur
Astrophysical Journal | Year: 2011

In this paper, we report on weighted oscillator strengths of E1 transitions and transition probabilities of E2 transitions among different low-lying states of triply ionized germanium using highly correlated relativistic coupled cluster (RCC) method. Due to the abundance of Ge IV in the solar system, planetary nebulae, white dwarf stars, etc., the study of such transitions is important from an astrophysical point of view. The weighted oscillator strengths of E1 transitions are presented in length and velocity gauge forms to check the accuracy of the calculations. We find excellent agreement between calculated and experimental excitation energies. Oscillator strengths of few transitions, wherever studied in the literature via other theoretical and experimental approaches, are compared with our RCC calculations. © 2011. The American Astronomical Society. All rights reserved..

Ghosh N.,Indian Institute of Technology Kharagpur | Ghosh S.K.,Indian Institute of Technology Kharagpur
Applied Intelligence | Year: 2012

In the present scenario, even well administered networks are susceptible to sophisticated cyber attacks. Such attack combines vulnerabilities existing on different systems/ services and are potentially more harmful than single point attacks. One of the methods for analyzing such security vulnerabilities in an enterprise network is the use of attack graph. It is a complete graph which gives a succinct representation of different attack scenarios, depicted by attack paths. An attack path is a logical succession of exploits, where each exploit in the series satisfies the preconditions for subsequent exploits and makes a causal relationship among them. Thus analysis of the attack graph may help in assessing network security from hackers' perspective. One of the intrinsic problems with the generation and analysis of such a complete attack graph is its scalability. In this work, an approach based on Planner, a special purpose search algorithm from artificial intelligence domain, has been proposed for time-efficient, scalable representation of the attack graphs. Further, customized algorithms have been developed for automatic generation of attack paths (using Planner as a low-level module). The analysis shows that generation of attack graph using the customized algorithms can be done in polynomial time. A case study has also been presented to demonstrate the efficacy of the proposed methodology. © Springer Science+Business Media, LLC 2010.

Kole M.,Indian Institute of Technology Kharagpur | Dey T.K.,Indian Institute of Technology Kharagpur
Journal of Applied Physics | Year: 2013

Stable and well dispersed functionalized graphene-ethylene glycol (EG) + distilled water nanofluids having graphene nano-sheets (GnS) volume concentration between 0.041 and 0.395 vol. % are prepared without any surfactant. Graphene nano-sheets are prepared from high purity graphite powder by Hummers method followed by exfoliation and reduction by hydrogen gas. Thus, obtained hydrogen exfoliated graphene (HEG) is then functionalized using acid. The graphene nano-sheets are characterized using XRD, TEM, Raman spectroscopy, and FTIR spectroscopy. Thermal conductivity and viscosity measurements are performed both as a function of graphene loading and temperature between 10 and 70 °C. Thermal conductivity enhancement of ∼15% for a loading of 0.395 vol. % f-HEG is observed at room temperature. The measured nanofluid's thermal conductivity is explained well in terms of the expression derived by Nan (J. Appl. Phys. 81, 6692 (1997)), which considers matrix-additive interface contact resistance of mis-oriented ellipsoidal particles. The viscosity of the prepared f-HEG nanofluids and the base fluid (EG + distilled water) displays non-Newtonian behaviour with the appearance of shear thinning and nearly 100% enhancement compared to the base fluid (EG + DI water) with f-HEG loading of 0.395 vol. %. Known theoretical models for nanofluid's viscosity fail to explain the observed f-HEG volume concentration dependence of the nanofluid's viscosity. Temperature dependence of the studied nanofluid between 10 and 70 °C is explained well by the correlations proposed earlier for nanofluids with spherical nanoparticles. Electrical conductivity of the f-HEG nanofluids shows significant enhancement of ∼8620% for 0.395 vol. % loading of f-HEG in a base fluid of 70:30 mixture of EG and distilled water. © 2013 American Institute of Physics.

Chakraborty S.,Indian Institute of Technology Kharagpur | Chatterjee D.,Indian Central Mechanical Engineering Research Institute | Bakli C.,Indian Institute of Technology Kharagpur
Physical Review Letters | Year: 2013

We discover a nonlinear coupling between the hydrophobicity of a charged substrate and electrokinetic pumping in narrow fluidic confinements. Our analyses demonstrate that the effective electrokinetic transport in nanochannels may get massively amplified over a regime of bare surface potentials and may subsequently get attenuated beyond a threshold surface charging condition because of a complex interplay between reduced hydrodynamic resistance on account of the spontaneous inception of a less dense interfacial phase and ionic transport within the electrical double layer. We also show that the essential physics delineated by our mesoscopic model, when expressed in terms of a simple mathematical formula, agrees remarkably with that portrayed by molecular dynamics simulations. The nontrivial characteristics of the initial increment followed by a decrement of the effective zeta potential with a bare surface potential may open up the realm of hitherto-unexplored operating regimes of electrohydrodynamically actuated nanofluidic devices. © 2013 American Physical Society.

Choudhuri D.,Indian Institute of Technology Kharagpur | Raja Sekhar G.P.,Indian Institute of Technology Kharagpur
Physics of Fluids | Year: 2013

The problem of non-isothermal fluid flow in and around a liquid drop has been studied. The temperature of the fluid is assumed to be non-constant, steady and hence is governed by the Laplace's equation. The thermal and hydrodynamic problems have been solved under nonisothermal boundary conditions assuming Stokes equations for the flow inside and outside the drop. The drag and torque on the droplet in the form of Faxen's laws are presented. The use of the drag formula has been demonstrated by few particular cases. Some important asymptotic limiting cases have been discussed. © 2013 American Institute of Physics.

Behera H.,Indian Institute of Technology Kharagpur | Mandal S.,Indian Institute of Technology Kharagpur | Sahoo T.,Indian Institute of Technology Kharagpur
Physics of Fluids | Year: 2013

Trapping of obliquely incident surface waves by permeable flexible barriers placed near a vertical rigid wall in a two-layer fluid having free surface and an interface is studied for both surface-piercing and bottom-standing partial barriers. For the surface-piercing permeable flexible barrier, the barrier is assumed to be fixed near the free surface and is free at the submerged end. On the other hand, for the bottom standing permeable flexible barrier, the barrier is assumed to be fixed at the bottom and the other end is free. As special cases of the permeable flexible barrier, the results associated with surface-piercing and bottom-standing permeable membrane barriers are obtained by assuming that the two ends of the barriers are fixed. Appropriate continuity conditions are used to deal with the interface-piercing flexible/membrane barriers. The mathematical problem is handled for solution using a generalized orthogonal relation suitable for two-layer fluid along with the least square approximation method. Explicit relations are derived to ensure full reflection by porous flexible barriers of any configuration placed near a vertical rigid wall for waves in surface and internal modes, which are validated through numerical computations in various cases. The effect of critical angle of incidence on wave reflection and trapping by barriers, surface and interface wave elevations, deflection of the flexible barrier under wave action, pressure distribution on the barrier, wave loads on barrier and rigid wall are analyzed. The finding of the present study is likely to play a significant role in the design of marine facilities with less wave force on the infrastructure. The present concept and methodology can be easily extended to similar problems in acoustic-structure interactions. © 2013 AIP Publishing LLC.

Chakraborty S.,Indian Institute of Technology Kharagpur | Kaushik N.,Indian Institute of Technology Kharagpur | Rao P.S.,Indian Institute of Technology Kharagpur | Mishra H.N.,Indian Institute of Technology Kharagpur
Comprehensive Reviews in Food Science and Food Safety | Year: 2014

In the last 2 decades high-pressure processing (HPP) has established itself as one of the most suitable nonthermal technologies applied to fruit products for the extension of shelf-life. Several oxidative and pectic enzymes are responsible for deterioration in color, flavor, and texture in fruit purees and juices (FP&J). The effect of HPP on the activities of polyphenoloxidase, peroxidase, β-glucosidase, pectinmethylesterase, polygalacturonase, lipoxygenase, amylase, and hydroperoxide lyase specific to FP&J have been studied by several researchers. In most of the cases, partial inactivation of the target enzymes was possible under the experimental domain, although their pressure sensitivity largely depended on the origin and their microenvironmental condition. The variable sensitivity of different enzymes also reflects on their kinetics. Several empirical models have been established to describe the kinetics of an enzyme specific to a FP&J. The scientific literature in the last decade illustrating the effects of HPP on enzymes in FP&J, enzymatic action on those products, mechanism of enzyme inactivation during high pressure, their inactivation kinetics, and several intrinsic and extrinsic factors influencing the efficacy of HPP is critically reviewed in this article. In addition, process optimization of HPP targeting specific enzymes is of great interest from an industrial approach. This review will give a fair idea about the target enzymes specific to FP&J and the optimum conditions needed to achieve sufficient inactivation during HPP treatment. © 2014 Institute of Food Technologists.

Savier J.S.,Indian Institute of Technology Kharagpur | Das D.,Indian Institute of Technology Kharagpur
International Journal of Electrical Power and Energy Systems | Year: 2012

This paper presents an exact method for real power loss allocation to consumers connected to radial distribution networks in a deregulated environment. The proposed method has the advantage that no assumptions are made in the allocation of real power losses as opposed to the algorithms available in the literature. A detailed comparison of the real loss allocation obtained with the proposed 'Exact method' with two alternative algorithms, namely, pro rata (PR), and quadratic loss allocation schemes are presented. Pro rata procedure is based on the load demand of each consumer, quadratic allocations are based on identifying the real and reactive parts of current in each branch and the losses are allocated to each consumer, and the proposed 'exact method' is based on the actual contribution of real power loss by each consumer. A case study based on 30 node distribution system is provided. © 2011 Elsevier Ltd. All rights reserved.

Bakli C.,Indian Institute of Technology Kharagpur | Chakraborty S.,Indian Institute of Technology Kharagpur
Soft Matter | Year: 2015

We investigated the filling dynamics in closed-end capillaries of sub-micron length scale, in which the displacing phase advances at the expense of the entrapped phase. Contrary to common intuition, we reveal that the existence of a displaced phase in a closed-end nano-scale system does not necessarily retard the meniscus advancement over all temporal regimes, unlike what is observed in cases of macro-scale capillaries, but can also sometimes augment the local filling rates. We determined that the combined effect of surface wettability and the displaced phase molecules resulted from the pinning-depinning of the meniscus, and hence, from the local dynamics of capillary filling. We also employed a simple force balance-based model to capture the essential interfacial phenomena governing this behavior, and benchmarked the same with our molecular dynamics simulations. Our results suggest a possible mechanism for modifying the effective wettabilities of nano-scale capillaries without any modification of the surface architecture or chemical treatment of the surface. This journal is © The Royal Society of Chemistry.

Kole M.,Indian Institute of Technology Kharagpur | Dey T.K.,Indian Institute of Technology Kharagpur
Applied Thermal Engineering | Year: 2012

Surfactant free and fairly stable ZnO-ethylene glycol (EG) nanofluids are prepared using prolonged sonication (>60 h). Extended period of sonication results in superior fragmentation and dispersion of ZnO nanoparticles, as is evident from the DLS data. Thermal conductivity of the prepared nanofluid displays a maximum enhancement of 40% for 3.75% volume fractions of ZnO loading in EG at 30 °C. The nucleate pool boiling heat transfer characteristics of ZnO-EG nanofluids with various loading of ZnO nanoparticles are measured at atmospheric pressure employing a cylindrical polished copper heater surface. The boiling heat transfer coefficient enhances with ZnO concentration and attains a maximum of 22% compared to that of base fluid for ZnO volume fraction of 1.6%. However, further loading of ZnO nanoparticles in EG decreases the heat transfer coefficient. Critical heat flux measurements are performed with a thin Constantan wire. CHF value appreciably increases with increasing ZnO loading and displays a maximum enhancement of ∼117% for nanofluid containing 2.6% volume fractions of ZnO. © 2011 Elsevier Ltd. All rights reserved.

Raheman H.,Indian Institute of Technology Kharagpur | Mondal S.,Indian Institute of Technology Kharagpur
Biomass and Bioenergy | Year: 2012

Jatropha seed cake (JSC) was anaerobically digested at different total solid contents (TS) and carbon to nitrogen (C:N) ratios in batch type digesters with 40 days hydraulic retention time (HRT). Biogas production from kg of TS was found to be maximum i.e. 0.17m 3 at 20% TS of JSC slurry followed by 15%, 25% and 10% TS in that order as compared to 0.166m 3 in case of cow dung (CD) slurry alone. Higher gas production from JSC slurry was observed when the carbon to nitrogen ratio (C:N) ratio was between 22:1 to 27:1 (by adding different quantity of paddy straw). Further gas production from kg of TS of the mixture of JSC and CD was higher than that produced from JSC/CD slurry alone and was maximum when JSC percentage in the mixture was within 25%. The Nitrogen content in the biodigested JSC slurry was increased by 5.9% as compared to JSC alone and its use as fertilizer produced better growth of maize and tomato crops. © 2012 Elsevier Ltd.

Bag S.,Indian Institute of Technology Kharagpur | Raj C.R.,Indian Institute of Technology Kharagpur
Journal of Materials Chemistry A | Year: 2014

We describe a facile one-step strategy for the synthesis of a novel layered hybrid material of reduced graphene oxide (rGO) and α-Ni(OH)2 by non-hydrothermal route and the supercapacitive performance of the material. The hybrid material rGO/α-Ni(OH)2 was synthesized using glucose as a templating agent for the growth of layered α-Ni(OH)2 and a reducing agent for the reduction of graphene oxide (GO). The templating agent partially reduces GO to rGO and assists the growth of α-Ni(OH)2 layers in between the rGO sheets. The electron microscopy measurements show the stacking of layered α-Ni(OH)2 over rGO sheets. The activity of the hybrid material was evaluated by voltammetric, electrochemical impedance and charge-discharge measurements in alkaline pH in terms of specific capacitance, internal resistance and capacitance retention. The hybrid material has superior performance, which is comparable to rGO, free α-Ni(OH)2 and the physical mixture of rGO and free α-Ni(OH)2. A high specific capacitance of 1671.67 F g-1 was obtained at a current density of 1 A g-1. The hybrid material retains 81% of its initial capacitance after 2000 continuous charge-discharge cycles. The large surface area and high electronic conductivity of the hybrid material favor a facile charge transport, whereas the layer structure ensures the easy diffusion of electrolytes ions and enhances the overall performance. An asymmetric supercapacitor device was made by pairing the hybrid material with rGO, and it delivers a high energy density of 42.67 W h kg-1 at a power density of 0.4 kW kg-1. This journal is © the Partner Organisations 2014.

Datta P.,Indian Institute of Technology Kharagpur | Dhara S.,Indian Institute of Technology Kharagpur | Chatterjee J.,Indian Institute of Technology Kharagpur
Carbohydrate Polymers | Year: 2012

In this work, N-methylene phosphonic chitosan (NMPC) based hydrogels and electrospun nanofibrous scaffolds are reported with objective to obtain osteoconductive and osteoinductive matrixes for bone grafting applications. NMPC, a phosphorylated derivative of chitosan, is known to mimic the function of non collagenous phosphoproteins in providing nucleation sites for biomineralization. NMPC hydrogels were prepared by crosslinking between NMPC and genipin. A detailed investigation of physicochemical properties of NMPC solutions is also carried out in order to obtain beads free nanofibers. Both NMPC gels and nanofibers were further evaluated for their biomineralization potential and biocompatibility with human osteoblast like cells. Results indicated that hydrogels and nanofibrous scaffolds NMPC are biocompatible and significantly osteoinductive compared to tissue culture plate controls. However, cells seeded on nanofibrous scaffolds exhibited greater proliferation measured by MTT assay, and higher expression of early markers for osteogenic differentiation proving the superior applicability of nanofibrous scaffolds for bone grafting applications. © 2011 Elsevier Ltd. All rights reserved.

Sarkar S.,Indian Institute of Technology Kharagpur | Rao K.S.,Indian Institute of Technology Kharagpur
Applied Soft Computing Journal | Year: 2014

This paper explores the significance of stereo-based stochastic feature compensation (SFC) methods for robust speaker verification (SV) in mismatched training and test environments. Gaussian Mixture Model (GMM)-based SFC methods developed in past has been solely restricted for speech recognition tasks. Application of these algorithms in a SV framework for background noise compensation is proposed in this paper. A priori knowledge about the test environment and availability of stereo training data is assumed. During the training phase, Mel frequency cepstral coefficient (MFCC) features extracted from a speaker's noisy and clean speech utterance (stereo data) are used to build front end GMMs. During the evaluation phase, noisy test utterances are transformed on the basis of a minimum mean squared error (MMSE) or maximum likelihood (MLE) estimate, using the target speaker GMMs. Experiments conducted on the NIST-2003-SRE database with clean speech utterances artificially degraded with different types of additive noises reveal that the proposed SV systems strictly outperform baseline SV systems in mismatched conditions across all noisy background environments. © 2014 Elsevier B.V.

Kapat S.,Indian Institute of Technology Kharagpur
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2015

Pulse train (PT) control improves light load efficiency in a DC-DC converter and also enables to achieve spread spectrum using bi-frequency operation (BFO). However, existing PT control shows existence of sub-harmonic oscillations; thus periodic BFO cannot be ensured. This paper proposes digital voltage-mode PT control in DC-DC converters, in which on-time of an active pulse is generated from DPWM output (similar to voltage mode control) for a predefined sequence of pulses. Discrete-time models are derived, which confirm stable BFO with predictable spectral behavior. This enables to further optimize efficiency, to meet EMI compliance, and to achieve smooth PT/PWM transition because of sharing the outer voltage loop. A buck converter prototype is made, and the proposed scheme is implemented using an FPGA device. © 2015 IEEE.

Bhattacharjee K.K.,Indian Institute of Technology Kharagpur | Sarmah S.P.,Indian Institute of Technology Kharagpur
Applied Soft Computing Journal | Year: 2014

This paper proposes a modified discrete shuffled frog leaping algorithm (MDSFL) to solve 01 knapsack problems. The proposed algorithm includes two important operations: the local search of the 'particle swarm optimization' technique; and the competitiveness mixing of information of the 'shuffled complex evolution' technique. Different types of knapsack problem instances are generated to test the convergence property of MDSFLA and the result shows that it is very effective in solving small to medium sized knapsack problems. Further, computational experiments with a set of large-scale instances show that MDSFL can be an efficient alternative for solving tightly constrained 01 knapsack problems. © 2014 Elsevier B.V.

Chiranjeevi P.,Indian Institute of Technology Kharagpur | Sengupta S.,Indian Institute of Technology Kharagpur
IEEE Transactions on Image Processing | Year: 2014

We propose a new algorithm for moving object detection in the presence of challenging dynamic background conditions. We use a set of fuzzy aggregated multifeature similarity measures applied on multiple models corresponding to multimodal backgrounds. The algorithm is enriched with a neighborhood-supported model initialization strategy for faster convergence. A model level fuzzy aggregation measure driven background model maintenance ensures more robustness. Similarity functions are evaluated between the corresponding elements of the current feature vector and the model feature vectors. Concepts from Sugeno and Choquet integrals are incorporated in our algorithm to compute fuzzy similarities from the ordered similarity function values for each model. Model updating and the foreground/background classification decision is based on the set of fuzzy integrals. Our proposed algorithm is shown to outperform other multi-model background subtraction algorithms. The proposed approach completely avoids explicit offline training to initialize background model and can be initialized with moving objects also. The feature space uses a combination of intensity and statistical texture features for better object localization and robustness. Our qualitative and quantitative studies illustrate the mitigation of varieties of challenging situations by our approach. © 1992-2012 IEEE.

Pradhan B.,Indian Institute of Technology Kharagpur | Srivastava S.K.,Indian Institute of Technology Kharagpur
Polymer International | Year: 2014

The homogeneous dispersion of nanofillers and filler-matrix interfacial interactions are important factors in the development of high-performance polymer materials for various applications. In the present work, a simple solution-mixing method was used to prepare multi-walled carbon nanotube (MWCNT)-graphene (G) (3:1, 1:1, 1:3) hybrids followed by their characterization through wide-angle X-ray diffraction, transmission electron microscopy and thermogravimetric analyses. Subsequently, MWCNT-G (1:1) hybrid was used as reinforcing filler in the formation of silicone rubber (VMQ) nanocomposites by solution intercalation, and their morphology and properties were investigated. Our findings showed that MWCNT-G (0.75wt%)/VMQ composite exhibited significant improvements in tensile strength (110%) and Young's modulus (137%) compared to neat VMQ. The thermal stability of MWCNT-G (1wt%)/VMQ was maximally improved by 154°C compared to neat VMQ. Differential scanning calorimetry demonstrated the maximum improvement of glass transition temperature (4°C), crystallization temperature (8°C) and melting temperature (5°C) for MWCNT-G (1wt%)/VMQ nanocomposite with respect to neat VMQ. Swelling measurements confirmed that the crosslink density and solvent resistance were a maximum for hybrid nanocomposites. Such improvements in the properties of MWCNT-G/VMQ nanocomposites could be attributed to a synergistic effect of the hybrid filler. © 2014 Society of Chemical Industry.

Krishna Murthy J.,Indian Institute of Technology Kharagpur | Venimadhav A.,Indian Institute of Technology Kharagpur
Applied Physics Letters | Year: 2013

We report a giant zero field cooled exchange bias (ZEB) effect (∼0.65 T) in La1.5Sr0.5CoMnO6 sample. Magnetic study has revealed a reentrant spin glass ∼90 K, phase separation to spin glass and ferromagnetic phases below 50 K and canted antiferromagnetic transition ∼10 K. A small conventional exchange bias (CEB) is established with the advent of spontaneous phase separation down to 10 K. Giant ZEB and enhanced CEB effects are found only below 10 K and are attributed to the large unidirectional anisotropy at the interface of isothermally field induced ferromagnetic phase and canted antiferromagnetic background. © 2013 AIP Publishing LLC.

Tiwari K.N.,Indian Institute of Technology Kharagpur | Bhadoria P.B.S.,Indian Institute of Technology Kharagpur
Environmental Monitoring and Assessment | Year: 2011

Universal soil loss equation (USLE) was used in conjunction with a geographic information system to determine the influence of land use and land cover change (LUCC) on soil erosion potential of a reservoir catchment during the period 1989 to 2004. Results showed that the mean soil erosion potential of the watershed was increased slightly from 12.11 t ha-1 year -1 in the year 1989 to 13.21 t ha-1 year-1 in the year 2004. Spatial analysis revealed that the disappearance of forest patches from relatively flat areas, increased in wasteland in steep slope, and intensification of cultivation practice in relatively more erosion-prone soil were the main factors contributing toward the increased soil erosion potential of the watershed during the study period. Results indicated that transition of other land use land cover (LUC) categories to cropland was the most detrimental to watershed in terms of soil loss while forest acted as the most effective barrier to soil loss. A p value of 0.5503 obtained for two-tailed paired t test between the mean erosion potential of microwatersheds in 1989 and 2004 also indicated towards a moderate change in soil erosion potential of the watershed over the studied period. This study revealed that the spatial location of LUC parcels with respect to terrain and associated soil properties should be an important consideration in soil erosion assessment process. © 2010 Springer Science+Business Media B.V.

Sinha S.K.,Indian Institute of Technology Kharagpur | Bandyopadhyay S.,Indian Institute of Technology Kharagpur
Physical Chemistry Chemical Physics | Year: 2012

Water present near the surface of a protein exhibits dynamic properties different from that of water in the pure bulk state. In this work, we have carried out atomistic molecular dynamics simulation of an aqueous solution of hen egg-white lysozyme. Attempts have been made to explore the correlation between the local heterogeneous mobility of water around the protein segments and the rigidity of the hydration layers with the microscopic dynamics of hydrogen bonds formed by water molecules with the protein residues. The kinetics of breaking and reformation of hydrogen bonds involving the surface water molecules have been calculated. It is found that the reformations of broken hydrogen bonds are more frequent for the hydration layers of those segments of the protein that are more rigid. The calculation of the low-frequency vibrational modes of hydration layer water molecules reveals that the protein influences the transverse and longitudinal degrees of freedom of water around it in a differential manner. These findings can be verified by appropriate experimental studies. © 2011 The Owner Societies.

Jaganathan S.K.,Indian Institute of Technology Kharagpur | Mandal M.,Indian Institute of Technology Kharagpur
Investigational New Drugs | Year: 2010

Summary: Honey is a complex mixture of different biologically active constituents. Honey possesses anti-inflammatory, antioxidant and antitumor properties. Our chief investigation was to assess the honey induced apoptosis and its molecular mechanism in colon cancer cell growth inhibition. Honey exerted antiproliferative potential against the HCT-15 and HT-29 colon cancer cells as assessed by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay. Flow cytometric analysis showed the increasing accumulation of hypodiploid nuclei in the sub-G1 phase of cell cycle indicating apoptosis. Honey transduced the apoptotic signal via initial depletion of intracellular non protein thiols, consequently reducing the mitochondrial membrane potential (MMP) and increasing the reactive oxygen species (ROS) generation. An increasing earlier lipid layer break was observed in the treated cells compared to the control. Honey induced apoptosis was accompanied by up-regulating the p53 and modulating the expression of pro and anti-apoptotic proteins. Further apoptosis induction was substantiated using DNA fragmentation assay and YO-PRO-1 staining. Results showed honey as a plausible candidate for induction of apoptosis through ROS and mitochondria-dependent mechanisms in colon cancer cells. This will promote honey as a potential chemotherapeutic agent against colon cancer. © 2009 Springer Science+Business Media, LLC.

Goswami D.,Indian Institute of Technology Kharagpur | Basu J.K.,Indian Institute of Technology Kharagpur | De S.,Indian Institute of Technology Kharagpur
Critical Reviews in Biotechnology | Year: 2013

Lipase (triacylglycerol acylhydrolase) is a unique enzyme which can catalyze various types of reactions such as hydrolysis, esterification, alcoholysis etc. In particular, hydrolysis of vegetable oil with lipase as a catalyst is widely studied. Free lipase, lipase immobilized on suitable support, lipase encapsulated in a reverse micelle and lipase immobilized on a suitable membrane to be used in membrane reactor are the most common ways of employing lipase in oil hydrolysis. Castor oil is a unique vegetable oil as it contains high amounts (90%) of a hydroxy monounsaturated fatty acid named ricinoleic acid. This industrially important acid can be obtained by hydrolysis of castor oil. Different conventional hydrolysis processes have certain disadvantages which can be avoided by a lipase-catalyzed process. The degree of hydrolysis varies widely for different lipases depending on the operating range of process variables such as temperature, pH and enzyme loading. Immobilization of lipase on a suitable support can enhance hydrolysis by suppressing thermal inactivation and estolide formation. The presence of metal ions also affects lipase-catalyzed hydrolysis of castor oil. Even a particular ion has different effects on the activity of different lipases. Hydrophobic organic solvents perform better than hydrophilic solvents during the reaction. Sonication considerably increases hydrolysis in case of lipolase. The effects of additives on the same lipase vary with their types. Nonionic surfactants enhance hydrolysis whereas cationic and anionic surfactants decrease it. A single variable optimization method is used to obtain optimum conditions. In order to eliminate its disadvantages, a statistical optimization method is used in recent studies. Statistical optimization shows that interactions between any two of the following pH, enzyme concentration and buffer concentration become significant in presence of a nonionic surfactant named Span 80. © 2013 Informa Healthcare USA, Inc.

Kapat S.,Indian Institute of Technology Kharagpur
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2015

Dynamic voltage scaling (DVS) is an useful technique to optimize performance and efficiency of CMOS digital processors using DC-DC converters that require to meet extremely fast slew rate demand. This paper formulates time optimal performance of existing buck-derived DVS architectures, such as using (a) a synchronous buck converter, (b) a multi-phase buck converter, and (c) multiple dedicated buck converter topologies. Thereafter, time optimal performance is formulated using a single-inductor-multiple-output (SIMO) buck converter based DVS architecture. It is shown that a SIMO-derived DVS architecture can achieve performance much beyond system physical limits of that using existing architectures for a step-change in the reference voltage and/or the load current. The proposed architecture and existing power converter architectures are fabricated, and time optimal control is implemented using an FPGA device. Test results demonstrate significant reduction in time and energy overheads using the proposed DVS architecture. © 2015 IEEE.

Kapat S.,Indian Institute of Technology Kharagpur
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2015

Majority of spread spectrum techniques employ chaos-based PWM schemes in a switching power converter, in which neither dynamic performance nor ripple parameter can be correctly predicted so as for efficiency. This paper proposes a bifrequency DPWM controller which uses two discrete frequencies as guided by a modulating signal fm(t). Fourier analysis shows that discrete frequencies only contribute to power spectrum at fundamental and harmonic contents of fm(t). The controller can be easily reconfigured to achieve custom spread spectrum with predictable ripple parameters and insignificant performance impact. Discrete-time models are derived for stability analysis. Design guidelines are discussed for a synchronous buck converter. The proposed method has been implemented using an FPGA device. © 2015 IEEE.

Jana M.,Indian Institute of Technology Kharagpur | Bandyopadhyay S.,Indian Institute of Technology Kharagpur
Physical Chemistry Chemical Physics | Year: 2012

Protein-carbohydrate non-covalent interactions are important to understand various biological processes in living organisms. One of the important issues in protein-carbohydrate binding is how the protein identifies the target carbohydrate and recognizes its conformational features. Surrounding water molecules are expected to play a critical role not only in mediating the recognition process but also in maintaining the structure of the complex. We carried out atomistic molecular dynamics (MD) simulations of an aqueous solution of the protein-carbohydrate complex formed between the hyaluronan binding domain (HABD) of the murine Cd44 protein and the octasaccharide hyaluronan (HA 8). The conformational flexibilities of the protein and the carbohydrate, and the microscopic structure and ordering of water molecules around them in the complexed form have been explored. It is revealed that the formation of the complex is associated with significant immobilization of the monosaccharide units of the carbohydrate moiety that are involved in binding. Further, reduction in water densities around the binding residues of the two molecules in the complex with respect to their free forms clearly demonstrated that the recognition between the protein and the carbohydrate is facilitated by removal of a fraction of water molecules from regions around the binding domains. © the Owner Societies 2012.

Kiran Kumar K.,Vignans Institute of Engineering for Women | Ram Gopal M.,Indian Institute of Technology Kharagpur
Applied Thermal Engineering | Year: 2011

In this paper, experimental results obtained on a natural circulation loop operating with CO2 as loop fluid and water as the external fluid are presented. The instrumented test rig consists of two end heat exchangers that act as heat source and heat sink and two insulated vertical legs which act as downcomer and riser. Experiments are conducted with the loop fluid (CO 2) in vapour phase, liquid phase and liquid-vapour phases by varying the amount of CO2 charged into the loop as well as the external fluid temperatures. In line with the theoretical predictions, it is observed from the experimental results that for a given loop, operating at given external fluid temperatures, there exist an optimum value of CO2 inventory in the loop at which the heat transfer rate is maximum. Results also show that the time required to reach steady state is more in case of two-phase loops compared to single phase loops. The experimental data are compared with the results obtained from a theoretical model. By normalising the experimental results comparison is also made between the results obtained from the present study and with those available in the literature, and a reasonably good agreement is found between them. © 2011 Elsevier Ltd.

Savier J.S.,Indian Institute of Technology Kharagpur | Das D.,Indian Institute of Technology Kharagpur
International Journal of Electrical Power and Energy Systems | Year: 2011

This paper presents allocation of power losses to consumers connected to radial distribution network before and after network reconfiguration in a deregulated environment. Loss allocation is made in a quadratic way, which is based on identifying the real and imaginary parts of current in each branch and losses are allocated to consumers. Comparison of loss allocation after multi-objective approach based distribution network reconfiguration is made with those before reconfiguration. For network reconfiguration, multiple objectives are considered for minimization of system real power loss, deviations of nodes voltage, branch current constraint violation and transformer loading imbalance and they are integrated into an objective function through appropriate weighting factors which is minimized for each tie-switch operation. The effectiveness of the proposed approach is demonstrated through an example. © 2010 Elsevier Ltd. All rights reserved.

Gilbert J.J.,Indian Institute of Technology Kharagpur | Ray S.,Indian Institute of Technology Kharagpur | Das D.,Indian Institute of Technology Kharagpur
International Journal of Hydrogen Energy | Year: 2011

Photofermentative hydrogen production is challenged by the photobioreactor design that can overcome poor light penetration, agitation and temperature control. Flat panel reactors have been reported to have several advantages over other reactors. But they are limited to a suitable type of agitation system when using it for hydrogen production. The aim of the present study is to develop and improve a flat panel reactor that can overcome the problem of agitation with a rocking motion. Studies with Rhodobacter sphaeroides O.U. 001 resulted in a cumulative hydrogen production of 492 ± 10 mL with maximum production rate of 11 mL L-1 h-1, substrate (malic acid) conversion efficiency of 44.4% and light conversion efficiency of 3.31%. The mixing time of the reactor was found to be around 17 s with a power input of 100-275 W/m 3. Though the entire reactor was in motion the energy spent for the rocking motion was found to be quite low. © 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Banerjee N.,Indian Institute of Technology Kharagpur | Sharma P.,Indian Institute of Science
Monthly Notices of the Royal Astronomical Society | Year: 2014

We study the interplay between turbulent heating, mixing, and radiative cooling in an idealized model of cool cluster cores. Active galactic nuclei (AGN) jets are expected to drive turbulence and heat cluster cores. Cooling of the intracluster medium (ICM) and stirring by AGN jets are tightly coupled in a feedback loop. We impose the feedback loop by balancing radiative cooling with turbulent heating. In addition to heating the plasma, turbulence also mixes it, suppressing the formation of cold gas at small scales. In this regard, the effect of turbulence is analogous to thermal conduction. For uniform plasma in thermal balance (turbulent heating balancing radiative cooling), cold gas condenses only if the cooling time is shorter than the mixing time. This condition requires the turbulent kinetic energy to be ≳ the plasma internal energy; such high velocities in cool cores are ruled out by observations. The results with realistic magnetic fields and thermal conduction are qualitatively similar to the hydrodynamic simulations. Simulations where the runaway cooling of the cool core is prevented due to mixing with the hot ICM show cold gas even with subsonic turbulence, consistent with observations. Thus, turbulent mixing is the likely mechanism via which AGN jets heat cluster cores. The thermal instability growth rates observed in simulations with turbulence are consistent with the local thermal instability interpretation of cold gas in cluster cores. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Saha P.,Indian Institute of Technology Kharagpur | Mishra P.K.,College of Engineering, Pune
International Journal of Advanced Manufacturing Technology | Year: 2010

Electro-discharge machining (EDM) is a widely accepted nontraditional machining process used mostly for machining materials difficult to machine by conventional shearing process. Surface modification by powder metallurgy sintered tools is an uncommon aspect of EDM. Of late, it is being explored by many researchers. In the present paper, attempts have been made to model the surface modification phenomenon by EDM with artificial neural networks. Two output measures, material transfer rate and average layer thickness, have been correlated with different process parameters and presented in the form of plots. The predicted results are matching well with the experimental results. © 2010 Springer-Verlag London Limited.

Datta S.N.,Indian Institute of Technology Kharagpur | Chakrabarti S.,Indian Institute of Technology Kharagpur
IEEE Communications Letters | Year: 2010

Using the unified expression as devised by Wojnar, an analytical framework is presented to determine the end-to-end error performance of coherent and non-coherent binary modulation schemes with dual-hop relay transmission in amplify-and-forward (AF) mode under average power scaling (APS) and instantaneous power scaling (IPS) constraints and operating over independent, non-identical flat Nakagami-m fading channels. Generalized closed-form expressions for the bit error probability (BEP) have been obtained following the cumulative distribution function (cdf)-based approach for a dual-hop relay link with single antenna nodes. Moreover, we derive a unified closed-form solution for the BEP when selection combining (SC) is employed at the IPS based multi-antenna relay to diversity process the signals. © 2006 IEEE.

Sadhukhan A.K.,National Institute of Technology Durgapur | Gupta P.,National Institute of Technology Durgapur | Saha R.K.,Indian Institute of Technology Kharagpur
Fuel | Year: 2011

Single particle devolatilization followed by combustion of the residual coal char particle has been analyzed in a batch-fluidized bed. The kinetic scheme with distributed activation energy is used for coal devolatilization while multiple chemical reactions with volume reaction mechanism are considered for residual char combustion. Both the models couple kinetics with heat transfer. Finite Volume Method (FVM) is employed to solve fully transient partial differential equations coupled with reaction kinetics. The devolatilization model is used to predict the devolatilization time along with residual mass and particle temperature, while the combined devolatilization and char combustion model is used to predict the overall mass loss and temperature profile of coal. The computed results are compared with the experimental results of the present authors for combustion of Indian sub-bituminous coal (15% ash) in a fluidized bed combustor as well as with published experimental results for coal with low ash high volatile matter. The effects of various operating parameters like bed temperature, oxygen mole fraction in bulk phase on devolatilization time and burn-out time of coal particle in bubbling fluidized bed have been examined through simulation. © 2011 Elsevier Ltd. All rights reserved.

Chakraborty D.,Indian Institute of Technology Kharagpur | Ghosh D.,Indian Institute of Technology Kharagpur
Fuzzy Sets and Systems | Year: 2014

This paper formulates fuzzy lines in a fuzzy geometric plane. We construct a fuzzy line passing through several fuzzy points whose cores are collinear. Consecutively four different forms for fuzzy lines: a two-point form, a point-slope form, a slope-intercept form, and an intercept form are proposed. Their properties and interrelations are also investigated. We demonstrate the construction of the membership function of all four forms and illustrate this with suitable examples. It is shown that the two-point form and intercept form are equivalent. However, the two-point form or intercept form cannot, in general, be equivalent to the point-slope form or the slope-intercept form. To define and analyze all the proposed ideas, the concepts of same and inverse points in fuzzy geometry are used. All our discussions are supported by suitable examples.© 2013 Elsevier B.V.

Santra R.,Indian Institute of Technology Kharagpur | Biradha K.,Indian Institute of Technology Kharagpur
Crystal Growth and Design | Year: 2010

Ag⋯Ag interactions were shown to template [2 + 2] photochemical reactions of unsymmetrically substituted olefin molecules, namely 4-pyridyl acrylic acid (1), 4-pyridyl acryl amide (2), and methyl ester of 4-pyridyl acrylic acid (3) in their Ag(I) complexes [Ag(1)2(NO 3)]·MeOH (4); [Ag(2)2(NO3)] (5); and [Ag(3)2(NO3)]·MeOH (6). Nitrate ions were found to bridge these Ag⋯Ag interactions in two ways: as a discrete dimer in 4 and 5 and as a zigzag 1D-polymer in the case of 6. Irradiation of these complexes in UV/sunlight produced respective head-to-head dimers in nearly 100% yields, as supported by 1H NMR spectroscopy. In the case of 5, the transformation was shown to occur in single crystal to single crystal fashion by determining the crystal structure of partially irradiated materials of 5. Further, we have also found that the irradiation of mechanically grounded samples of AgNO3 with 2 or 3 produces a similar [2 + 2] reaction, to result in respective head-to-head dimers in good yields. © 2010 American Chemical Society.

Malviya R.,Indian Institute of Technology Kharagpur | Pratihar D.K.,Indian Institute of Technology Kharagpur
Swarm and Evolutionary Computation | Year: 2011

Particle swarm optimization technique has been used for tuning of neural networks utilized for carrying out both forward and reverse mappings of metal inert gas (MIG) welding process. Four approaches have been developed and their performances are compared to solve the said problems. The first and second approaches deal with tuning of multi-layer feed-forward neural network and radial basis function neural network, respectively. In the third and fourth approaches, a back-propagation algorithm has been used along with particle swarm optimization to tune radial basis function neural network. Moreover, in these two approaches, two different clustering algorithms have been utilized to decide the structure of the network. The performances of hybrid approaches (that is, the third and fourth approaches) are found to be better than that of the other two. © 2011 Elsevier B.V. All rights reserved.

Shukla N.,Indian Institute of Technology Kharagpur | Thakur A.K.,Indian Institute of Technology Kharagpur
Solid State Ionics | Year: 2010

Transport properties of ion conducting polymer-clay nanocomposites (PNCs) are reported. Experimental results indicate the possibility of exfoliation at lower clay loading and intercalation with increase in clay concentration in the composite matrix. The intercalation of cation coordinated polymer into the nanometric clay galleries has been confirmed by XRD and TEM analyses. Convincing evidences of polymer-ion, polymerclay, ion-ion and ion-clay interactions have been observed in FTIR results. The estimated fraction of free charge carriers has shown excellent correlation with measured conductivity. Substantial enhancement in d.c. conductivity in the PNC films relative to the polymer salt complex (PS) is attributed to clay induced interaction among the composite components. A model for conductivity enhancement is proposed to understand the ion transport process in exfoliated and intercalated PNCs. The conceptual basis of the model seems consistent with the experimental results. The ion transport number (tion) for all the PNC films has been estimated to be >99%. An improvement in voltage stability has been observed with addition of clay. © 2010 Elsevier B.V. All rights reserved.

Majumdar J.D.,Indian Institute of Technology Kharagpur
Surface and Coatings Technology | Year: 2010

In the present study, an attempt has been made to develop in-situ iron silicide dispersed surface on mild steel substrate by laser surface alloying with silicon using a high-power continuous wave CO 2 laser. The effect of laser surface remelting of the alloyed surface using argon and nitrogen (with and without graphite coating) as shrouding environment has also been studied. The microstructure of laser surface alloyed mild steel with silicon consists of uniformly dispersed iron silicide in grain refined α-iron matrix with an improved microhardness to 575 VHN as compared to 150 VHN of as-received mild steel substrate. Surface remelting in Ar atmosphere coarsened the microstructure and reduced the area fraction of silicide and hence, reduction in the microhardness to 450 VHN. Surface remelting in nitrogen increased the microhardness to 740 VHN due to the formation of iron nitrides in addition to the presence of silicides. Graphite coating prior to remelting improved the microhardness to 800 VHN due to the presence of martensites along with nitrides and silicides. A maximum enhancement in wear resistance was achieved when remelting was done in nitrogen environment with carbon deposition. The mechanism of wear was found to be predominantly abrasive in nature as compared to adhesive and oxidative in as-received mild steel. © 2010.

Kotal M.,Indian Institute of Technology Kharagpur | Srivastava S.K.,Indian Institute of Technology Kharagpur | Paramanik B.,Indian Institute of Technology Kharagpur
Journal of Physical Chemistry C | Year: 2011

The current work deals with enhancements in conductivity and thermal stabilities of thermoplastic polyurethane (TPU)/dodecylbenzenesulfonic acid doped polypyrrole (PPy.DBSA) nanoblends prepared by solution intercalation (SB) and in situ (IS) methods. It is observed that the electrical conductivity (δdc) of nanoblends is influenced by interaction between PPy.DBSA and TPU as well as homogeneous nanolevel dispersion and content of PPy.DBSA in TPU matrix. The maximum value of δdc has been found at 30 wt % PPy.DBSA for the SB (0.26 S cm-1) nanoblend due to the presence of the hexagonal network. The percolation threshold is attained at 2.5 wt % of PPy.DBSA for IS and SB nanoblends. The temperature variation of conductivity for different nanoblends follows one-dimensional variable range hopping (VRH) model. A significant improvement (32 °C) in thermal stability has been observed at 50% wt loss for SB nanoblend containing 30 wt % PPy.DBSA. The PL peak of the TPU nanoblend is red-shifted with increasing wt % of PPy.DBSA. © 2011 American Chemical Society.

Dey R.T.,Indian Institute of Technology Kharagpur | Sarkar T.K.,Indian Institute of Technology Kharagpur
Journal of Organic Chemistry | Year: 2010

(Figure presented) Improved conditions were found to trigger [3 + 2] annulation of cyclic allylsilanes with N-phenyltriazolinedione (PTAD); the products from this reaction were readily tailored into cis-1,3-diaminocyclitols in highly enantioenriched form with full stereochemical control of up to four contiguous stereogenic centers. © 2010 American Chemical Society.

Majumder A.K.,Indian Institute of Technology Kharagpur | Barnwal J.P.,Advanced Materials and Processes
Fuel | Year: 2011

It is reported in the literature that a water-only cyclone (WOC), a centrifugal gravity concentrator, is an alternative to froth flotation to treat coal fines (below 0.5 mm). This unit overcomes the inherent limitations of froth flotation and the dense-medium cyclone techniques as it requires no chemicals or artificial medium. The literature dealing with WOC performance to treat coal fines is also limited and as a result it is not well established how the design variables affect the performance of a WOC while treating coal fines. Therefore, an attempt has been made to develop regression models based on factorial design of experiments to quantify the effects of major design variables of a WOC on the beneficiation characteristics of a typical coal fine sample. Further attempts have been made to provide possible explanations on the observed trends of the data based on simple hydrodynamic analyses. © 2010 Elsevier Ltd. All rights reserved.

Jose N.,Indian Institute of Technology Kharagpur | Sengupta S.,Indian Institute of Technology Kharagpur | Basu J.K.,Indian Institute of Technology Kharagpur
Fuel | Year: 2011

The oxidative desulfurization of thiophene in a synthetic mixture of thiophene and iso-octane was investigated with copper loaded titanium silicate-1 (TS-1) catalyst in presence of hydrogen peroxide as oxidising agent and the conversion was enhanced by 22% at 240 min on addition of 1.05 wt.% copper in TS-1. The optimal design of experiments using box-behnken method was employed to evaluate the effects of individual process variables such as, reaction temperature, amount of catalyst and moles of hydrogen peroxide per mole of thiophene and their optimum values were found to be 70 °C, 0.45 g (22.5 mol/L of iso-octane) and 19.9 mol (in 20 ml of iso-octane), respectively, to achieve a conversion of 93%. The influence of mass transfer effects on the desulfurization reaction was minimized by selecting proper degree of agitation and catalyst size. An empirical kinetic model was used to interpret the rate data. The apparent activation energy was found to be 28.67 kJ/mol. © 2010 Elsevier Ltd. All rights reserved.

Maji K.,Indian Institute of Technology Kharagpur | Pratihar D.K.,Indian Institute of Technology Kharagpur
Expert Systems with Applications | Year: 2010

Input-output relationships of an electrical discharge machining process have been established both in forward as well as reverse directions using adaptive network-based fuzzy inference system. Three input parameters, such as peak current, pulse-on-time and pulse-duty-factor, and two outputs, namely material removal rate and surface roughness have been considered for the said mappings. A batch mode of training has been adopted with the help of 1000 data for the developed adaptive network-based fuzzy inference system, which has been designed using linear (say triangular) and non-linear (bell-shaped) membership function distributions of the input variables, separately. The performances of the developed models have been tested for both forward and reverse mappings with the help of some test cases collected through the real experiments. Adaptive network-based fuzzy inference system is found to tackle the problems of forward and reverse mappings efficiently. The fuzzy inference system utilizing non-linear membership functions is seen to perform slightly better than that with linear membership functions for the input variables. © 2010 Elsevier Ltd. All rights reserved.

Jena P.,Indian Institute of Technology Kharagpur | Pradhan A.K.,Indian Institute of Technology Kharagpur
IEEE Transactions on Power Delivery | Year: 2011

In this paper, a directional relaying technique is proposed for the protection of a double-circuit line. The directional relaying issues during the cross country fault, far-end fault, as well as voltage and current inversions in a double-circuit line with series compensation are addressed. Four features using positive-sequence components are selected and an integrated solution scheme is proposed using a multicriteria fuzzy decision approach. The technique is evaluated using data simulated with EMTDC/PSCAD for a double-circuit line with and without the series compensation condition, and the dynamic performance of the algorithm is studied. © 2011 IEEE.

Maiti D.,Indian Institute of Technology Kharagpur | Jana A.K.,Indian Institute of Technology Kharagpur | Samanta A.N.,Indian Institute of Technology Kharagpur
Applied Energy | Year: 2011

Published studies have been focused mainly on the energy integration of continuous distillation columns. In this contribution, a novel heat integrated batch distillation column (HIBDC) is proposed. Aiming to improve the thermodynamic efficiency and reduce the total annual cost (TAC), a thermally coupled column configuration is explored with introducing heat integration between the rectifying tower and concentric reboiler. A compressor is employed to provide the necessary temperature driving force for the heat transferred from the rectifier to the reboiler. Investigating the feasibility of energy integration in the simulated batch process, a number of sensitivity tests have been conducted to select the value of operating compression ratio. An economic comparison between the proposed HIBDC and the conventional stand alone column is also performed. It is observed that the HIBDC system appears overwhelmingly superior to its conventional counterpart providing about an energy savings of 56.1% and cost (TAC) savings of 40.53%. © 2011 Elsevier Ltd.

Kole M.,Indian Institute of Technology Kharagpur | Dey T.K.,Indian Institute of Technology Kharagpur
Experimental Thermal and Fluid Science | Year: 2011

Copper oxide nanoparticles (~40. nm) are dispersed in gear oil (IBP Haulic-68) at different volume fractions (0.005-0.025) with oleic acid added as a surfactant to stabilize the system. Prepared nanofluids are characterized by Fourier Transform Infrared spectroscopy (FTIR) and Dynamic light scattering (DLS) measurements. DLS data confirmed the presence of agglomerated nanoparticles in the prepared nanofluids. Thermal conductivity measurements are performed both as a function of CuO volume fraction and temperature between 5 and 80°C. An enhancement in thermal conductivity at 30°C of 10.4% with 0.025 volume fraction of CuO nanoparticle loading is observed. Measured volume fraction dependence of the thermal conductivity enhancement at room temperature is predicted fairly well considering contributions from both nanolayer at the solid-liquid interface and particle agglomeration in the suspension, as visualized by Feng et al. © 2011 Elsevier Inc.

Ganguly M.,Indian Institute of Technology Kharagpur | Pal A.,Indian Institute of Technology Kharagpur | Pal T.,Indian Institute of Technology Kharagpur
Journal of Physical Chemistry C | Year: 2011

Diiminic Schiff bases (DSBs) with a variety of spacers in between the two imine bonds have been prepared from salicylaldehyde and different diamines. Gold and silver nanoparticles (NPs) are photoproduced as stable hydrosol from the respective metal salts in the presence of alkaline DSBs. In solution, the capping capability of DSBs renders stability toward both the NPs. The phenomenon of capping of noble metal by DSBs is gifted with surprising alteration of the fluorescence property of DSBs. Varying concentration of the local field on the fluorophore as well as the coupling between the molecular dipole of the fluorophore and the surface plasmon band of the metal have been ascribed to be the key point of these stunning phenomena in solution phase. © 2011 American Chemical Society.

Das A.K.,Indian Institute of Technology Kharagpur | Raj C.R.,Indian Institute of Technology Kharagpur
Journal of Physical Chemistry C | Year: 2011

The surfactant-assisted seed-mediated growth approach has been widely used for the synthesis of anisotropic Au nanoparticles. Interestingly, it has been shown that the iodide impurities present in the surfactant ions can control the shape and surface structure of Au nanoparticles. In this article, we describe a different role of iodide ions in the surfactant-free synthesis of single crystalline polyhedral Au nanostructures and their electrocatalytic activity. This new green route for the synthesis of Au nanostructures involves the reduction of Au(III) complex by iodide ions to a metastable Au(I) complex and the subsequent disproportionation of Au(I) at room temperature to metallic Au. The quasispherical Au nanoparticles produced at the initial stage of the reaction autocatalyze the disproportionation and produce Au nanoparticles of polyhedral shape with an average size of 45 nm. The concentration of iodide ions play a crucial role in controlling the shape and surface structure of the nanoparticles. The surface of the nanoparticles obtained at low concentration (10 μM) is exclusively (111) plane. The unreduced Au(III) ions stabilize the Au nanoparticles. Aggregated nanoparticles with irregular shape were obtained at a high concentration of iodide ions. The presence of either silver ions or naked Au nanoseeds facilitate/catalyze the disproportionation of Au(I) complex; significant enhancement in the growth of Au nanoparticle was observed in the presence of silver ions. Silver ions induce the growth of dendritic Au nanostructures. The dendritic nanostructures have multiple arms with an average size of 190 nm. The naked Au nanoseeds catalyze the disproportionation and favor the growth of twined Au nanoparticles with size ranging from 50 to 85 nm. The disproportionation of Au(I) does not occur in the presence of coordinating ligands. The coordinating ligands completely inhibit the disproportionation reaction. The electrochemical characteristics of the single crystalline nanoparticles was examined with the surface-sensitive electrode reaction of As(III). The single crystalline Au nanoparticles show excellent electrocatalytic activity toward the detection of As(III). The nanoparticle-based electrode could detect as low as 10 ppb of As(III), and it has very high sensitivity with respect to the polycrystalline Au and the electrode modified with other nanoparticles. © 2011 American Chemical Society.

Mahata G.,Indian Institute of Technology Kharagpur | Roy S.,Indian Institute of Technology Kharagpur | Biradha K.,Indian Institute of Technology Kharagpur
Chemical Communications | Year: 2011

The selective inclusion of aromatic guest molecules in host frameworks formed by 3-sulfophthalic acid or 4-sulfophthalic acid and 4,4′-bipyridine has been effectively utilized for the separation of sulfophthalic acid isomers. © 2011 The Royal Society of Chemistry.

Hajra S.,Indian Institute of Technology Kharagpur | Bar S.,Indian Institute of Technology Kharagpur
Tetrahedron Asymmetry | Year: 2011

A concise asymmetric synthesis of first, high affinity domaine D1 full agonist, dihydrexidine has been accomplished via catalytic enantioselective aziridination and subsequent one-pot Friedel-Crafts cyclization of an in situ generated tethered aziridine with high diastereo- and enantioselectivities. © 2011 Elsevier Ltd. All rights reserved.

Hajra S.,Indian Institute of Technology Kharagpur | Bar S.,Indian Institute of Technology Kharagpur
Chemical Communications | Year: 2011

A-86929, a dopamine D1 agonist was synthesized with 95% ee in five steps with overall yield of 56% via catalytic enantioselective one-pot aziridination followed by Friedel-Crafts cyclization and a mild Pictet-Spengler cyclization protocol. © The Royal Society of Chemistry.

Patil D.,Indian Institute of Technology Kharagpur | Nag A.,Indian Institute of Technology Kharagpur
JAOCS, Journal of the American Oil Chemists' Society | Year: 2011

In fish and poultry processing, viscera are generally considered as a waste product and often discarded. Chicken and hilsa fish (Hilsa ilisa) viscera were used for the production of polyunsaturated fatty acids (PUFA) linoleic (18:2n-6), eicosapentaenoic (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). Free fatty acids (FFA) were extracted by alkaline hydrolysis of chicken and fish viscera; yields were 5.2 and 5.9% (w/w) respectively. PUFA concentrates were obtained by a two step process-deduction of saturated fatty acids (FA) by low temperature crystallization in acetone followed by urea inclusion compound-based fractionation. Acetone treatment removed 90 and 96% of saturated FA in chicken and fish viscera respectively with FA to acetone ratio of 1:12 (w/v). Using an urea to FA ratio (w/w) of 4.0, chicken viscera produced a maximum of 84.1% of PUFA concentrates containing 82.1% of linoleic acid with a yield of 10% where as in the case of fish viscera the maximum PUFA concentrates were 91.3% containing 78.2% of EPA-DHA with the yield of 11%. Thus, the utilization of poultry and fish processing waste into the production of PUFA concentrates has been shown. © 2010 AOCS.

Patil A.,Indian Institute of Technology Kharagpur | Dasgupta A.,Indian Institute of Technology Kharagpur
European Journal of Mechanics, A/Solids | Year: 2013

In this paper, finite axisymmetric inflation of an initially stretched flat circular hyperelastic membrane has been analyzed. The membrane material has been assumed to be a homogeneous and isotropic Mooney-Rivlin solid. The inflation problem has been reduced to a set of three first order ordinary differential equations using a set of appropriately defined variables. An interesting method based on the invariance of these equations to scaling has been used to solve the two point boundary value problem without much effort. This method does not require any special technique for negotiating the limit points in the pressure-stretch relations of the membrane. Several inflation results of an initially unstretched and pre-stretched circular membrane for various material parameters are obtained. The roles of pre-stretch and internal pressure on the inflation mechanics are clearly delineated. The initial stretch is observed to have some interesting counter-intuitive effects on the inflation of the membrane. © 2013 Elsevier Masson SAS. All rights reserved.

Roy S.,Indian Institute of Technology Kharagpur | Anoop A.,Indian Institute of Technology Kharagpur | Biradha K.,Indian Institute of Technology Kharagpur | Basak A.,Indian Institute of Technology Kharagpur
Angewandte Chemie - International Edition | Year: 2011

Let's get radical: A general synthetic route toward angularly ortho-fused polyaromatic [4]helicenes starting from aryl alkenyl N-substituted cyclic enediynes is described (see scheme; DMSO=dimethyl sulfoxide, Ns=4-nitrobenzenesulfonyl). The process involved a Bergman cyclization (BC) as the key step of an unprecedented tandem radical reaction. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Singh A.,Indian Institute of Technology Kharagpur | Panda S.N.,Indian Institute of Technology Kharagpur
Journal of Irrigation and Drainage Engineering | Year: 2012

Irrigated agriculture faces serious threats of waterlogging and soil salinization in the arid and semiarid regions of the world. In this paper, an integrated spatial-agro-hydro-salinity model (SAHYSMOD) was used to analyze water and salt balances of an irrigated semiarid area located in the Haryana State of India where the groundwater level is rising continuously. The calibration, validation, error analysis, and sensitivity analysis of the model parameters were performed. The sensitivity analysis revealed that hydraulic conductivity is the most sensitive model parameter for both groundwater levels and salinities, followed by effective porosity of the aquifer. The leaching efficiency of the soil is sensitive only to the groundwater salinities. The results show a good agreement between the simulated and observed groundwater levels and salinities for almost all the nodes during the calibration and validation periods. The results are also substantiated by the high R-squared values and low mean error (ME) and root mean square error (RMSE) values. On the basis of the results, it could be concluded that the SAHYSMOD performed very well in predicting groundwater levels and salinities during the calibration and validation periods. © 2012 American Society of Civil Engineers.

Santra R.,Indian Institute of Technology Kharagpur | Banerjee K.,Indian Institute of Technology Kharagpur | Biradha K.,Indian Institute of Technology Kharagpur
Chemical Communications | Year: 2011

Synthesis of a stereospecific four-twelve-four fused tricyclic compound containing a tetraamide macrocycle has been achieved by the solid state [2+2 reaction through utilization of Ag⋯Ag interaction. The influence of anions on crystal packing has been utilized for the synthesis of a regioselective mono cyclobutane compound via the Ag⋯π interactions. © 2011 The Royal Society of Chemistry.

Chakraborty D.,Indian Institute of Technology Kharagpur | Madou M.,University of California at Irvine | Chakraborty S.,Indian Institute of Technology Kharagpur
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2011

We analyse the characteristics of two-fluid mixing in T-shaped microchannels on rotating platforms (Lab-on-a-Compact-Disk framework). Three regimes of mixing were identified based on the distinct flow behaviour in each of these regimes. A diffusion-based mixing regime was obtained for low rotation speeds. A Coriolis force based mixing regime was observed for intermediate rotation speeds, which introduced some nontrivial aspects in the mixing behaviour, which was explained through scaling analysis. At very high rotational speeds, rapid mixing close to the junction was achieved by exploiting flow instabilities (instability based mixing). A good agreement between the theoretical calculations and the experimental observations was obtained. © 2011 The Royal Society of Chemistry.

Singh A.,Indian Institute of Technology Kharagpur
Journal of Irrigation and Drainage Engineering | Year: 2012

Good quality soil and water resources are often limited in arid and semi-arid regions; however, poor quality groundwater can be used conjunctively with good quality canal water to fulfill crop water demand in these areas. In the present study, a linear programming model was developed for the optimal land and water resources allocation to maximize net annual returns from a command area located in Jhajjar district of Haryana, India. The water production functions were developed and incorporated in the model to estimate the crop yield under different qualities of irrigation water. A groundwater balance constraint was imposed on the model, which mitigated the waterlogging problems while making optimal use of land and water resources. The model results show a reduction in rice and mustard areas against an increase in cotton, sugarcane, and wheat under optimal conditions. Under the optimal land and water allocation the groundwater use increases, which in turn mitigates the waterlogging and salinity problems of the command area. The net annual return from the command area increased by more than 20% under optimal allocations. The sensitivity analysis of the model parameters show that better price of crops is the most sensitive parameter followed by the crop area and cost of cultivation. State agencies and farmers involved in the actual agricultural production process are advised to practice conjunctive use of canal water and groundwater to maximize their farm income. This strategy could also mitigate further rise in the water table in the command area without installing expensive drainage systems, which is also not feasible because the groundwater quality is poor and the drainage water may pose a serious disposal problem. © 2012 American Society of Civil Engineers.

Bera R.K.,Indian Institute of Technology Kharagpur | Anoop A.,Indian Institute of Technology Kharagpur | Raj C.R.,Indian Institute of Technology Kharagpur
Chemical Communications | Year: 2011

A nonenzymatic method for the selective detection and quantification of serum uric acid (UA) using 2-thiouracil (2-TU) tailored Au nanoparticles is developed. The H-bonding interaction of UA with functionalized Au nanoparticles brings instantaneous visible color change and paves the way for the visible sensing of UA. © 2011 The Royal Society of Chemistry.

Ganguly S.,Indian Institute of Technology Kharagpur
Chemical Engineering Research and Design | Year: 2011

Water is injected into oil-bearing porous rock for displacement of oil. Water tends to flow through high permeablity streaks, leaving significant amount of oil in place, unless the streaks are plugged by structure-forming fluids such as, polymer-gels. Cr(III)-polyacrylamide gel finds an use even in production well, as this gel structure offers easy flow of oil, apart from restricting water flow. The resistances that water and oil encounter, while flowing through the gel structure are characterized in this paper. The permeability of Cr(III)-polyacrylamide gel, held in tubes was evaluated as function of oil and water flow rates. This was observed that immediately after the rupture, a new pore space was created by the injec