Time filter

Source Type

Suresh Kumar N.,Naval Physical and Oceanographic Laboratory | Bhattacharya C.,Defense Institute of Advanced Technology
2012 Annual IEEE India Conference, INDICON 2012 | Year: 2012

In this paper, we have broadened the scope of Direction of Arrival (DoA) estimation using compressive sampling in free space to a shallow ocean scenario, considering the complexities that arise due to the formation of modes in shallow ocean, along with the use of acoustic vector sensor array. We use compressive sampling of the array elements, followed by compressive beamforming, which helps in greatly reducing the complexity of the front-end circuitry and the size of array correlation matrix that is used in DoA estimation in MUSIC/MVDR algorithms. Also, in shallow ocean, the plane-wave DoA estimators generally yield biased estimates, due to the multimode nature of acoustic propagation. To solve this problem, the normal mode based MUSIC (NM-MUSIC) method is modified to be used with AVS array and compressive beamforming. In this paper, we propose a method that takes a very small set of informative measurements from an AVS array deployed in a shallow ocean, that still allow us to estimate DoA's. Simulation results for the Pekeris model of the ocean show that resolution obtained using the compressed AVS array is similar to that obtained using a conventional AVS array in which larger number of sensors with higher snapshots are used. © 2012 IEEE.

Harikrishnan G.,Indian Institute of Technology Kharagpur | Patro T.U.,Indian Institute of Technology Bombay | Patro T.U.,Defense Institute of Advanced Technology | Unni A.R.,Huntsman Polyurethanes | Khakhar D.V.,Indian Institute of Technology Bombay
Soft Matter | Year: 2011

Remarkable evolutionary changes in cell morphology during reactive polymer nanocomposite foaming are observed by controlled foaming of suspensions of montmorillonite clay in the oligomeric polyurethane component. Delaminated nanoplatelets, when present as a networked cluster in suspensions, are shown to have very high efficiency in generating gas embryos for bubble nucleation. In the post-nucleation foaming period, clay nanoplatelets show an additional de-wetting behavior. The packing fraction of clay platelets in suspension and the consequent suspension rheology affect the final foam morphology. © 2011 The Royal Society of Chemistry.

Devaraju A.,National Institute of Technology Warangal | Kumar A.,National Institute of Technology Warangal | Kumaraswamy A.,Defense Institute of Advanced Technology | Kotiveerachari B.,National Institute of Technology Warangal
Materials and Design | Year: 2013

In this investigation, the influence of rotational speed and reinforcement particles such as silicon carbide (SiC), alumina (Al2O3) on wear and mechanical properties of aluminum alloy based surface hybrid composites fabricated via friction stir processing (FSP) was studied. Taguchi method was employed to optimize the rotational speed and volume percentage of reinforcement particles for improving the wear and mechanical properties of surface hybrid composites. The fabricated surface hybrid composites have been examined by optical microscope for dispersion of reinforcement particles. Microstructures of all the surface hybrid composites revealed that the reinforcement particles (SiC and Al2O3) are uniformly dispersed in the nugget zone. It also revealed that the microhardness at optimum condition is increased due to presence and pining effect of hard SiC and Al2O3 particles. It is found that the reinforcement particles (i.e. SiC and Al2O3) reduced in size (~5μm) than the as received particles size and also observed that the wear resistance at optimum condition is immensely improved. The observed wear and mechanical properties have been correlated with microstructures and worn micrographs. © 2013 Elsevier Ltd.

Ghosh S.,University of Pune | Patil S.,University of Pune | Ahire M.,University of Pune | Kitture R.,Fergusson College | And 8 more authors.
Journal of Nanobiotechnology | Year: 2012

Background: Novel approaches for synthesis of gold nanoparticles (AuNPs) are of utmost importance owing to its immense applications in diverse fields including catalysis, optics, medical diagnostics and therapeutics. We report on synthesis of AuNPs using Gnidia glauca flower extract (GGFE), its detailed characterization and evaluation of its chemocatalytic potential.Results: Synthesis of AuNPs using GGFE was monitored by UV-Vis spectroscopy and was found to be rapid that completed within 20 min. The concentration of chloroauric acid and temperature was optimized to be 0.7 mM and 50°C respectively. Bioreduced nanoparticles varied in morphology from nanotriangles to nanohexagons majority being spherical. AuNPs were characterized employing transmission electron microscopy, high resolution transmission electron microscopy. Confirmation of elemental gold was carried out by elemental mapping in scanning transmission electron microscopic mode, energy dispersive spectroscopy and X-ray diffraction studies. Spherical particles of size ~10 nm were found in majority. However, particles of larger dimensions were in range between 50-150 nm. The bioreduced AuNPs exhibited remarkable catalytic properties in a reduction reaction of 4-nitrophenol to 4-aminophenol by NaBH4 in aqueous phase.Conclusion: The elaborate experimental evidences support that GGFE can provide an environmentally benign rapid route for synthesis of AuNPs that can be applied for various purposes. Biogenic AuNPs synthesized using GGFE exhibited excellent chemocatalytic potential. © 2012 Ghosh et al; licensee BioMed Central Ltd.

Ghosh S.,University of Pune | Patil S.,University of Pune | Ahire M.,University of Pune | Kitture R.,Fergusson college | And 7 more authors.
International Journal of Nanomedicine | Year: 2012

Background: Development of an environmentally benign process for the synthesis of silver nanomaterials is an important aspect of current nanotechnology research. Among the 600 species of the genus Dioscorea, Dioscorea bulbifera has profound therapeutic applications due to its unique phytochemistry. In this paper, we report on the rapid synthesis of silver nanoparticles by reduction of aqueous Ag + ions using D. bulbifera tuber extract. Methods and results: Phytochemical analysis revealed that D. bulbifera tuber extract is rich in favonoid, phenolics, reducing sugars, starch, diosgenin, ascorbic acid, and citric acid. The biosynthesis process was quite fast, and silver nanoparticles were formed within 5 hours. Ultraviolet-visible absorption spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectroscopy, and x-ray diffraction con-frmed reduction of the Ag + ions. Varied morphology of the bioreduced silver nanoparticles included spheres, triangles, and hexagons. Optimization studies revealed that the maximum rate of synthesis could be achieved with 0.7 mM AgNO 3 solution at 50°C in 5 hours. The resulting silver nanoparticles were found to possess potent antibacterial activity against both Gram-negative and Gram-positive bacteria. Beta-lactam (piperacillin) and macrolide (eryth-romycin) antibiotics showed a 3.6-fold and 3-fold increase, respectively, in combination with silver nanoparticles selectively against multidrug-resistant Acinetobacter baumannii. Notable synergy was seen between silver nanoparticles and chloramphenicol or vancomycin against Pseudomonas aeruginosa, and was supported by a 4.9-fold and 4.2-fold increase in zone diameter, respectively. Similarly, we found a maximum 11.8-fold increase in zone diameter of streptomycin when combined with silver nanoparticles against E. coli, providing strong evidence for the synergistic action of a combination of antibiotics and silver nanoparticles. Conclusion: This is the frst report on the synthesis of silver nanoparticles using D. bulbifera tuber extract followed by an estimation of its synergistic potential for enhancement of the antibacterial activity of broad spectrum antimicrobial agents. © 2012 Ghosh et al.

Tahmouresi F.,University of Pune | Tahmouresi F.,Islamic Azad University at Kermānshāh | Das S.K.,Defense Institute of Advanced Technology
Journal of Fluids Engineering, Transactions of the ASME | Year: 2014

The paper presents an analytical solution of velocity, mass flow rate, and pressure distribution for fully developed gaseous slip flow in nonsymmetric and symmetric parabolic microchannels. The flow is considered to be steady, laminar, and incompressible with constant fluid properties. Fully developed gaseous slip flow in microchannels of parabolic cross section is solved analytically for various aspect ratios using a parabolic cylindrical coordinate system on applying the method of separation of variables. Prior to apply separation of variables, Arfken transform [Arfken, 1970, Mathematical Methods for Physicists, Academic Press, Orlando, FL, Ch. 2] was used on momentum equations and first-order slip boundary conditions at each channel wall were imposed. A simple model is proposed to predict the friction factor and Reynolds number product fRe for slip flow in parabolic microchannels. Through the selection of a characteristic length scale, the square root of cross-sectional area and the effect of duct shape have been minimized. The results of a normalized Poiseuille number for symmetric parabolic microchannels (ε = 1) shows good agreement with the previous results [Morini et al., 2004, "The Rarefaction Effect on the Friction Factor of Gas Flow in Micro/Nano-Channels," Superlattices Microstruct., 35(3-6), pp. 587-599; Khan and Yovanovich, 2008, "Analytical Modeling of Fluid Flow and Heat Transfer in Microchannel/Nanochannel Heat Sinks" J. Thermophys. Heat Transf., 22(3), pp. 352-359] for rectangular microchannels. The developed model can be used to predict mass flow rate and pressure distribution of slip flow in parabolic microchannels. Copyright © 2014 by ASME.

Arora S.,Govind Ballabh Pant University of Agriculture & Technology | Sharma P.,Govind Ballabh Pant University of Agriculture & Technology | Kumar S.,Govind Ballabh Pant University of Agriculture & Technology | Nayan R.,Govind Ballabh Pant University of Agriculture & Technology | And 2 more authors.
Plant Growth Regulation | Year: 2012

Experiments were carried out to determine the effect of Gold-nanoparticles on the growth profile and yield of Brassica juncea, under field conditions. Five different concentrations (0, 10, 25, 50 and 100 ppm) of Gold-nanoparticles were applied through foliar spray. Presence of Gold-nanoparticles in the leaf tissues was confirmed through atomic absorption spectroscopy. Various growth and yield related parameters, including plant height, stem diameter, number of branches, number of pods, seed yield etc. were positively affected by the nanoparticle treatment. Gold-nanoparticle treatment increased the number of leaves per plant; however the average leaf area was not affected. Optimal increase in seed yield was recorded at 10 ppm of Gold-nanoparticle treatment. Reducing as well as total sugar contents increased up to 25 ppm of Gold-nanoparticle treatment. Application of nanoparticles also improved the redox status of the treated plants. The results, for the first time, demonstrate successful use of Gold-nanoparticles in enhancing growth and yield of B. juncea, under actual field conditions and present a viable alternative to GM crops for ensuring food security. © 2011 Springer Science+Business Media B.V.

Nalawade S.M.,Defense Institute of Advanced Technology | Harnol S.S.,Defense Institute of Advanced Technology | Thakur H.V.,Defense Institute of Advanced Technology
IEEE Sensors Journal | Year: 2012

An all-fiber modal interferometric torsion sensor based on simple splicing configuration is presented wherein a photonic crystal fiber is spliced in between multimode fiber and single mode fiber. Appreciable torsion sensitivity of ∼ 79.83 pm/° is obtained in the long dynamic range of 180°. It is also found that there is no effect of strain and temperature on torsion sensitivity in the range of 0-4500 με and 30-200° C, respectively, leading to zero cross-sensitivity of torsion with strain and temperature. © 2012 IEEE.

Dewangan M.K.,Defense Institute of Advanced Technology | Panigrahi S.K.,Defense Institute of Advanced Technology
Journal of Mechanical Science and Technology | Year: 2015

Residual stress analysis of swage autofrettaged gun barrel is performed in this study via finite element (FE) method. The swage autofrettage technique is one of the modernized pre-stressing methods to enhance the load bearing capacity and fatigue life of all gun barrels. An oversized moving mandrel is forced inside the gun barrel, which deforms the material through physical interference. The process is analyzed by evaluating residual stresses using a commercially available software package. The deformation effects caused by the mandrel and the geometrical variation of the mandrel on the gun barrel are analyzed in this study. This field has been insufficiently researched, but the effect of pre-stressing on the barrel, and at the start and mid-length for the swaging process, is not well examined. Thus, further analysis is required. The variations and effectiveness of the designed pressure band model are shown to define the problem easily. Results are evaluated at mid-length using a fixed fringe width percentage (A defined percentage of gun barrel axial length). The desired effects are well validated through numerical investigation using FE analysis. This study reveals that the geometry should be designed very thoroughly to determine the after effects. If too many variations occur, then the initial force requirement is extremely high; otherwise, the desired swaging effect cannot be achieved. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

Nene M.J.,Defense Institute of Advanced Technology | Deodhar R.S.,Armament Research and Development Establishment | Patnaik L.M.,Indian Institute of Science
IEEE Sensors Journal | Year: 2015

In this paper, sensing coverage by wireless camera-embedded sensor networks (WCSNs), a class of directional sensors is studied. The proposed work facilitates the autonomous tuning of orientation parameters and displacement of camera-sensor nodes in the bounded field of interest (FoI), where the network coverage in terms of every point in the FoI is important. The proposed work is first of its kind to study the problem of maximizing coverage of randomly deployed mobile WCSNs which exploits their mobility. We propose an algorithm uncovered region exploration algorithm (UREA-CS) that can be executed in centralized and distributed modes. Further, the work is extended for two special scenarios: 1) to suit autonomous combing operations after initial random WCSN deployments and 2) to improve the network coverage with occlusions in the FoI. The extensive simulation results show that the performance of UREA-CS is consistent, robust, and versatile to achieve maximum coverage, both in centralized and distributed modes. The centralized and distributed modes are further analyzed with respect to the computational and communicational overheads. © 2001-2012 IEEE.

Loading Defense Institute of Advanced Technology collaborators
Loading Defense Institute of Advanced Technology collaborators