Esfahan, Iran
Esfahan, Iran

Isfahan University of Technology is one of the most prestigious engineering universities in Iran. It is located 15 Kilometers north west of Isfahan and is one of the major universities and research poles in Iran in the fields of science, engineering and agriculture. It has its own dorms, shopping center, sports & recreation centers and medical centers on the campus. This university enjoys the advantages of being situated in the vicinity of the historical, industrial, and commercial city of Isfahan; a city with a long-standing tradition in science, art and culture as well as a leading center of technological activities in present-day Iran.Isfahan university of technology is not to be confused with University of Isfahan which is located in southern Isfahan. Wikipedia.

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Prabhakaran M.P.,National University of Singapore | Vatankhah E.,National University of Singapore | Vatankhah E.,Isfahan University of Technology | Ramakrishna S.,National University of Singapore
Biotechnology and Bioengineering | Year: 2013

Nerve regeneration following the injury of nerve tissue remains a major issue in the therapeutic medical field. Various bio-mimetic strategies are employed to direct the nerve growth in vitro, among which the chemical and topographical cues elicited by the scaffolds are crucial parameters that is primarily responsible for the axon growth and neurite extension involved in nerve regeneration. We carried out electrospinning for the first time, to fabricate both random and aligned nanofibers of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate; PHBV) and composite PHBV/collagen nanofibers with fiber diameters in the range of 386-472nm and 205-266nm, respectively. To evaluate the potential of electrospun aligned nanofibers of PHBV and composite scaffolds as a substrate for nerve regeneration, we cultured nerve cells (PC12) and studied the biocompatibility effect along with neurite extension by immunostaining studies. Cell proliferation assays showed 40.01% and 5.48% higher proliferation of nerve cells on aligned PHBV/Coll50:50 nanofibers compared to cell proliferation on aligned PHBV and PHBV/Col75:25 nanofibers, respectively. Aligned nanofibers of PHBV/Coll provided contact guidance to direct the orientation of nerve cells along the direction of the fibers, thus endowing elongated cell morphology, with bi-polar neurite extensions required for nerve regeneration. Results showed that aligned PHBV/Col nanofibers are promising substrates than the random PHBV/Col nanofibers for application as bioengineered grafts for nerve tissue regeneration. © 2013 Wiley Periodicals, Inc.

Ghaedamini H.,Isfahan University of Technology | Salimpour M.R.,Isfahan University of Technology | Mujumdar A.S.,National University of Singapore
Applied Thermal Engineering | Year: 2011

In this investigation, svelteness is introduced as an important factor which illustrates the importance of bifurcation angle effect on pressure drop and flow distribution uniformity in tree-shaped networks. Moreover, the influence of mass flow rate and Reynolds number is also discussed. Results show that as svelteness increases, flow uniformity is enhanced while the effect of bifurcation angle on the pressure drop is diminished. The power-law relationship between Bejan number and dimensionless mass flow rate shows that the power component increases at higher values of svelteness which is in agreement with previously published works. Numerical simulations of the proposed networks showed that flow distribution uniformity and thermal uniformity are achieved at low Reynolds numbers. Thus, in addition to Svelteness, Reynolds number is also an important factor which should be considered when uniformity is desired. © 2010 Elsevier Ltd. All rights reserved.

Dini G.,Isfahan University of Technology | Najafizadeh A.,Isfahan University of Technology | Ueji R.,Kagawa University | Monir-Vaghefi S.M.,Isfahan University of Technology
Materials and Design | Year: 2010

The tensile deformation behavior and microstructural evolutions of twinning induced plasticity (TWIP) steel with the chemical composition of Fe-31Mn-3Al-3Si and average grain sizes in the range of 2.1-72.6μm have been analyzed. For each grain size, the Hollomon analysis and also the Crussard-Jaoul (C-J) analysis as an alternative method to describe the work hardening behavior were investigated. The results indicated that the optimum mechanical properties as a function of work hardening capacity can be obtained by changing the grain size. The microstructural observations showed that the pile-ups of planar dislocations are necessary for triggering the mechanical twinning and grain refinement suppresses the mechanical twinning in TWIP steel. Furthermore, the mechanical twinning increases with increasing applied strain. As a result, a high instantaneous work hardening due to the mechanical twin boundaries enhances the uniform elongation. The contribution from the strain of twinning and hardening due to an increase in the hardness of the twinned regions (i.e., the Basinski mechanism) may be also useful in achieving the high strength-ductility in TWIP steels. © 2010 Elsevier Ltd.

Falsafain A.,Shahid Bahonar University of Kerman | Taheri S.M.,Isfahan University of Technology
Soft Computing | Year: 2011

In several works, Buckley (Soft Comput 9:512-518, 2005a; Soft Comput 9:769-775 2005b; Fuzzy statistics, Springer, Heidelberg, 2005c) have introduced and developed an approach to the estimation of unknown parameters in statistical models. In this paper, we introduce an improved method for the estimation of parameters for cases in which the Buckley's approach presents some drawbacks, as for example when the underlying statistic has a non-symmetric distribution. © 2010 Springer-Verlag.

Silani M.,Isfahan University of Technology | Ziaei-Rad S.,Isfahan University of Technology | Esfahanian M.,Isfahan University of Technology | Tan V.B.C.,National University of Singapore
Composite Structures | Year: 2012

Due to increasing use of clay/epoxy nanocomposites in industry, investigation of mechanical properties of clay nanocomposites has become of great interest. While the stiffening mechanism of clay nanocomposites is well documented, there is still not a clear understanding about how addition of clays affect the fracture behavior of clay/epoxy nanocomposites. The main aim of this paper is to measure and explain the effect of clays on ductility reduction of these nanocomposites. First, epoxy and clay/epoxy nanocomposites with different clay weight ratio were built. Then, the damage parameters of epoxy and clay/epoxy nanocomposites were measured by variation of the elasticity modulus. Based on loading-unloading experiments, the Lemaitre damage parameters for epoxy and clay/epoxy nanocomposites were extracted. Crack initiation and propagation in dog-bone sample were simulated for epoxy and clay/epoxy nanocomposites using the eXtended Finite Element Method (XFEM). The comparison between experimental and numerical results shows that the proposed method can predict the crack initiation location and propagation path in clay/epoxy nanocomposites. © 2012 Elsevier Ltd.

Casadio R.,University of Bologna | Casadio R.,National Institute of Nuclear Physics, Italy | Hsu S.D.H.,University of Oregon | Mirza B.,Isfahan University of Technology
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

Asymptotic safety (an ultraviolet fixed point with finite-dimensional critical surface) offers the possibility that a predictive theory of quantum gravity can be obtained from the quantization of classical general relativity. However, it is unclear what becomes of the singularities of classical general relativity, which, it is hoped, might be resolved by quantum effects. We study dust collapse with a running gravitational coupling and find that a future singularity can be avoided if the coupling becomes exactly zero at some finite energy scale. The singularity can also be avoided (pushed off to infinite proper time) if the coupling approaches zero sufficiently rapidly at high energies. However, the evolution deduced from perturbation theory still implies a singularity at finite proper time. © 2010 Elsevier B.V.

Mahdavi M.,Islamic Azad University at Khorasgan | FarzanehFard H.,Isfahan University of Technology
IET Power Electronics | Year: 2014

In this study, a new zero-voltage transition (ZVT) bridgeless single-ended primary inductance converter power factor correction converter is introduced. The proposed converter has only two semiconductor elements in the current path at any time. Therefore the conduction losses in this converter are reduced in comparison with conventional SEPIC PFC rectifier. Also, in the proposed converter, ZVT soft switching technique is applied to improve the efficiency. The principle of the operation, design procedure and simulation results are presented. A 450 W prototype of this converter is implemented and the experimental results are presented to demonstrate the feasibility of the proposed technique. © The Institution of Engineering and Technology 2014.

Naghsh M.M.,Isfahan University of Technology | Modarres-Hashemi M.,Isfahan University of Technology | Shahbazpanahi S.,University of Ontario Institute of Technology | Soltanalian M.,Uppsala University | Stoica P.,Uppsala University
IEEE Transactions on Signal Processing | Year: 2013

In this paper, we study the problem of code design to improve the detection performance of multi-static radar in the presence of clutter (i.e., a signal-dependent interference). To this end, we briefly present a discrete-time formulation of the problem as well as the optimal detector in the presence of Gaussian clutter. Due to the lack of analytical expression for receiver operation characteristic (ROC), code design based on ROC is not feasible. Therefore, we consider several popular information-theoretic criteria including Bhattacharyya distance, Kullback-Leibler (KL) divergence, J-divergence, and mutual information (MI) as design metrics. The code optimization problems associated with different information-theoretic criteria are obtained and cast under a unified framework. We propose two general methods based on Majorization-Minimization to tackle the optimization problems in the framework. The first method provides optimal solutions via successive majorizations whereas the second one consists of a majorization step, a relaxation, and a synthesis stage. Moreover, derivations of the proposed methods are extended to tackle the code design problems with a peak-to-average ratio power (PAR) constraint. Using numerical investigations, a general analysis of the coded system performance, computational efficiency of the proposed methods, and the behavior of the information-theoretic criteria is provided. © 1991-2012 IEEE.

Jafari R.,Isfahan University of Technology | Lewis M.M.,University of Adelaide
International Journal of Applied Earth Observation and Geoinformation | Year: 2012

The low spectral resolution of multispectral satellite imagery limits its capability for extracting information in arid environments with sparse vegetation cover. The higher spectral resolution of hyperspectral imagery may improve discrimination of different vegetation types, even with low cover. The aim of this study was to evaluate the potential of Earth Observing 1 (EO-1) Hyperion hyperspectral data to discriminate arid landscape components in the southern rangelands of South Australia. Hyperion imagery was analysed with spectral mixture analysis to discriminate spectrally distinct land cover components. Five distinct end-members were extracted: two associated with vegetation cover and the remaining three associated with different soils and surface gravel and stone. The end-members were characterised with field spectra collected by ASD Fieldspec Pro spectrometer. To confirm the identity of the end-members we also investigated relationships between their abundance and field cover data collected at 54 sample sites using a step-point technique. One vegetation end-member was significantly correlated with Cottonbush (Maireanaaphylla) vegetation cover (R2 = 0.89) that was distributed as patches throughout the study area. The second vegetation end-member mapped green and grey-green perennial shrubs (e.g. Mulga, Acacia aneura) and was significantly correlated with total vegetation cover (R2 = 0.68). The soil and surface gravel and stone were not significantly correlated with the field estimates of these physical components. Despite the high spectral resolution of the Hyperion scene, spectral mixture analysis was unable to identify more than five meaningful spectral end-members in this arid environment. This may be the result of low vegetation cover of the region (28%), the lack of spectral contrast in arid vegetation types, and the ground resolution of Hyperion (900 m2) that reduced the ability to identify spectrally pure end-members to represent different land cover components. © 2012 Elsevier B.V.

Ahmadi A.,Isfahan University of Technology | Ranjbar M.,Shahid Bahonar University of Kerman | Schaffie M.,Shahid Bahonar University of Kerman
Minerals Engineering | Year: 2012

Ghaei A.,Isfahan University of Technology | Green D.E.,University of Windsor | Aryanpour A.,General Motors
Materials and Design | Year: 2015

Derakhshandeh S.Y.,Isfahan University of Technology | Masoum A.S.,Transmission Maintenance Delivery | Deilami S.,Curtin University Australia | Masoum M.A.S.,Curtin University Australia | Hamedani Golshan M.E.,Isfahan University of Technology
IEEE Transactions on Power Systems | Year: 2013

Conventional industrial microgrids (IMGs) consist of factories with distributed energy resources (DERs) and electric loads that rely on combined heat and power (CHP) systems while the developing IMGs are expected to also include renewable DERs and plug-in electric vehicles (PEVs) with different vehicle ratings and charging characteristics. This paper presents an electricity and heat generation scheduling method coordinated with PEV charging in an IMG considering photovoltaic (PV) generation systems coupled with PV storages. The proposed method is based on dynamic optimal power flow (DOPF) over a 24-hour period and includes security-constrained optimal power flow (SCOPF), IMG's factories constraints, PV storage constraints and PEVs dynamic charging constraints. It will utilize the generators waste heat to fulfill thermal requirements while considering the status of renewable DERs to decrease the overall cost of IMGs. To demonstrate the effectiveness of the proposed method, detailed simulation results are presented and analyzed for an 18-bus IMG consisting of 12 factories and 6 types of PEVs without/with PV generation systems operating in grid-connected and stand-alone modes. The main contribution is including PEVs with dynamic constraints that have changed the nature of scheduling formulation from a simple hourly OPF to a dynamic OPF. © 1969-2012 IEEE.

Bakhtari A.,University of California at Davis | Bakhtari A.,Isfahan University of Technology | Ross P.J.,University of California at Davis
Epigenetics | Year: 2014

Dppa3 has been described in mice as an important maternal factor contributed by the oocyte that participates in protecting the maternal genome from oxidation of methylated cytosines (5mC) to hydroxymethylated cytosines (5hmC). Dppa3 is also required for normal mouse preimplantation development. This gene is poorly conserved across mammalian species, with less than 32% of protein sequence shared between mouse, cow and human. RNA-seq analysis of bovine oocytes and preimplantation embryos revealed that DPPA3 transcripts are some of the most highly abundant mRNAs in the oocyte, and their levels gradually decrease toward the time of embryonic genome activation (EGA). Knockdown of DPPA3 by injection of siRNA in germinal vesicle (GV) stage oocytes was used to assess its role in epigenetic remodeling and embryo development. DPPA3 knockdown resulted in increased intensity of 5hmC staining in the maternal pronucleus (PN), demonstrating a role for this factor in the asymmetric remodeling of the maternal and paternal PN in bovine zygotes. Also, DPPA3 knockdown decreased the developmental competence of parthenogenetic and in vitro fertilized embryos. Finally, DPPA3 knockdown embryos that reached the blastocyst stage had significantly fewer ICM cells as compared with control embryos. We conclude that DPPA3 is a maternal factor important for correct epigenetic remodeling and normal embryonic development in cattle, indicating that the role of DPPA3 during early development is conserved between species. © 2014 Landes Bioscience.

Salavati-Niasari M.,University of Kashan | Ghanbari D.,Islamic Azad University of Arak | Loghman-Estarki M.R.,Isfahan University of Technology
Polyhedron | Year: 2012

Nanocrystalline PbS with different morphologies and particle sizes was obtained via a simple hydrothermal reaction between Pb(NO 3) 2 and thioglycolic acid (TGA) at relatively low temperature. Products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) spectroscopy, photoluminescence (PL) and Fourier transform infrared (FT-IR) spectroscopy. Depending on the reactant concentration and molar ratio of TGA to the lead nitrate, the morphologies of the PbS crystals varied and the crystals with shapes of nanoparticles, star-like dendrite and nanorods were obtained. The effect of reaction temperature and reaction time on the morphology and particle sizes of nanocrystalline PbS products has been investigated. © 2012 Elsevier Ltd. All rights reserved.

Baharlouei Z.,Isfahan University of Technology | Hashemi M.,Isfahan University of Technology | Narimani H.,Isfahan University of Technology | Mohsenian-Rad H.,University of California at Riverside
IEEE Transactions on Smart Grid | Year: 2013

Autonomous demand response (DR) programs are scalable and result in a minimal control overhead on utilities. The idea is to equip each user with an energy consumption scheduling (ECS) device to automatically control the user's flexible load to minimize his energy expenditure, based on the updated electricity pricing information. While most prior works on autonomous DR have focused on coordinating the operation of ECS devices in order to achieve various system-wide goals, such as minimizing the total cost of generation or minimizing the peak-to-average ratio in the load demand, they fall short addressing the important issue of fairness. That is, while they usually guarantee optimality, they do not assure that the participating users are rewarded according to their contributions in achieving the overall system's design objectives. Similarly, they do not address the important problem of co-existence when only a sub-set of users participate in a deployed autonomous DR program. In this paper, we seek to tackle these shortcomings and design new autonomous DR systems that can achieve both optimality and fairness. In this regard, we first develop a centralized DR system to serve as a benchmark. Then, we develop a smart electricity billing mechanism that can enforce both optimality and fairness in autonomous DR systems in a decentralized fashion. © 2010-2012 IEEE.

Rafiee M.,Islamic Azad University of Arak | Mohammadi M.,Isfahan University of Technology | Sobhani Aragh B.,Islamic Azad University of Arak | Yaghoobi H.,Islamic Azad University at Tehran
Composite Structures | Year: 2013

Nonlinear vibration and dynamic response of simply supported piezoelectric functionally graded material (FGM) shells under combined electrical, thermal, mechanical and aerodynamic loading are studied in this paper. The material properties of the shell are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of volume fractions of the constituents. The third-order piston theory is employed to evaluate the aerodynamic pressure. The governing equations are derived using improved Donnell shell theory ignoring the shallowness of cylindrical shells and kinematic nonlinearity and the physical neutral surface concept are taken into consideration. The Galerkin method, Volmir's assumption and the multiple time scales perturbation methods are used for the nonlinear dynamical analysis of shells to give the expression of natural frequencies, the nonlinear dynamic responses and the primary resonance phenomena. The influences of the shell geometry and piezoelectric thickness, temperature change, external constant electric voltage and aerodynamic loads on the nonlinear dynamic behavior of the piezoelectric functionally graded shells through a comprehensive parametric study are discussed in details. © 2013 Elsevier Ltd.

Rafiee M.,Islamic Azad University of Arak | Mohammadi M.,Isfahan University of Technology | Sobhani Aragh B.,Islamic Azad University of Arak | Yaghoobi H.,Islamic Azad University at Tehran
Composite Structures | Year: 2013

Nonlinear vibration and dynamic response of the simply supported piezoelectric functionally graded material (FGM) shells under combined electrical, thermal, mechanical and aerodynamic loading are studied in this paper. The material properties of the shell are assumed to be graded in the thickness direction according to a simple power-law distribution in terms of volume fractions of the constituents. The third-order piston theory is employed to evaluate the aerodynamic pressure. The governing equations are derived using improved Donnell shell theory ignoring the shallowness of cylindrical shells and kinematic nonlinearity and the physical neutral surface concept are taken into consideration. The Galerkin method, Volmir's assumption and the multiple time scales perturbation methods are used for the nonlinear dynamical analysis of shells to give the expression of natural frequencies, the nonlinear dynamic responses and the primary resonance phenomena. The influences of the shell geometry and piezoelectric thickness, temperature change, external constant electric voltage and aerodynamic loads on the nonlinear dynamic behavior of the piezoelectric functionally graded shells through a comprehensive parametric study are discussed in details. © 2013 Elsevier Ltd.

Khosravifard M.,Isfahan University of Technology | Halabian H.,Isfahan University of Technology | Gulliver T.A.,University of Victoria
IEEE Transactions on Information Theory | Year: 2010

A greedy scheme called Greedy Codeword Assignment Scheme (GCAS) is proposed to assign D-ary codewords to the given code-lengths ℓ1ℓ 2,...,ℓn, so that they satisfy the fix-free property. This scheme guarantees that a D-ary fix-free code can be obtained whenever ∑i=1 n D-ell;i ≤ Υ(D), where Υ(D) is equal to 5/8 for D even and very close to 5/8 for D odd. This result can be regarded as an extension of Yekhanin's theorem on the existence of binary fix-free codes. In the special case D = 2, the greediness of GCAS enables us to prove that if miniℓi = 2, the inequality ∑i = 1n 2-ℓi ≤ 21/32 implies the existence of a binary fix-free code with code-lengths ℓ1,ℓ2,... ℓn. © 2010 IEEE.

Emadi A.,Isfahan University of Technology | Saboonchi A.,Isfahan University of Technology | Taheri M.,Rayan Tahlil Sepahan Company | Hassanpour S.,Rayan Tahlil Sepahan Company
Applied Thermal Engineering | Year: 2014

The heating characteristics of billet in a walking hearth type reheating furnace were studied by developing a mathematical heat transfer model. Radiation calculations were conducted by means of zone method and considering all radiation exchange paths. The weighted-sum-of-gray-gas-model was used for better accuracy of gas radiation prediction. Convective heat flux was calculated by considering suitable value of convective heat transfer coefficient at any location of the furnace. The model was substantiated through its comparison to experimental data. A comparison was drawn to evaluate the effect of constant and variable convective coefficient on convective flux distribution and billet thermal behavior. The effect of furnace wall's emissivity of each zone and whole of the furnace on the billet thermal behavior was investigated. The obtained results revealed that by increasing furnace wall's emissivity for a determined residence time, billet's temperature in primary zones rises but it has no significant effect on its final temperature. However, by increasing wall's emissivity from 0.7 to 0.95, the residence time can be declined by about 5%. Moreover, emissivity increase in non-firing and preheating zones as compared to heating and soaking zones has greater impact on the billet thermal behavior. © 2013 Elsevier Ltd.

Ayoubi S.,Isfahan University of Technology | Mokhtari Karchegani P.,Islamic Azad University at Khorasgan | Mosaddeghi M.R.,Isfahan University of Technology | Honarjoo N.,Islamic Azad University at Khorasgan
Soil and Tillage Research | Year: 2012

The study was conducted to investigate the effects of slope gradient and land use change on soil structural stability, and soil organic carbon (SOC) and total nitrogen (TN) pools in aggregate-size fractions in western Iran. Three land uses in the selected site were natural forest (NF), disturbed forest (DF) and cultivated land (CL); and three classes of slope gradient (0-10%, S 1; 10-30%, S 2; and 30-50%, S 3) were used as a basis for soil sampling. The results showed that DF and CL treatments significantly decreased soil structural stability indices in the three slope classes. The highest percentages of macro-aggregates (i.e. 2.00-4.75mm) and meso-aggregates (0.25-2.00mm) were found in the lowest slope class (S 1) which was related to high SOC stock in this position. The highest percentage of macro-aggregates was observed in the NF soil; but the highest percentages of micro-aggregates (0.053-0.25mm) were observed in the CL treatment. Micromorphological observations confirmed that topsoil under natural forest mainly consisted of highly-porous crumb microstructure, excremental pedo-features or passage features, which are indicators of enhanced SOC and biological activity. The lowest values of SOC and TN were observed at the steep slope class (S3) presumably coincided with accelerated soil erosion. Overall, enhanced aggregation and aggregate-associated organic carbon pools were observed in the forest soils on the steep slopes indicating the importance of land management on C sequestration in natural environments. © 2012 Elsevier B.V.

Narimani H.,Isfahan University of Technology | Khosravifard M.,Isfahan University of Technology | Gulliver T.A.,University of Victoria
IEEE Transactions on Information Theory | Year: 2013

In order to determine how suboptimal the Shannon code is, one should compare its performance with that of the optimal code, i.e., the corresponding Huffman code, in some sense. It is well known that in the worst case the redundancy of both the Shannon and Huffman codes can be arbitrarily close to 1. Beyond this worst case viewpoint, very little is known. In this paper, we compare the performance of these codes from an average point of view. The redundancy is considered as a random variable on the set of all sources with n symbols and its average is evaluated. It is shown that the average redundancy of the Shannon code is very close to 0.5 bits, whereas the average redundancy of the Huffman code is less than n-1(1+ln n)+0.086bits. It is also proven that the variance of the redundancy of the Shannon code tends to zero as n increases. Therefore, for sources with alphabet size n, the redundancy of the Shannon code is approximately 0.5 bits with probability approaching 1 as nto ∞ . © 2012 IEEE.

Yazdani M.R.,Islamic Azad University at Khorasgan | Farzanehfard H.,Isfahan University of Technology
IET Power Electronics | Year: 2012

Switching power converters cause electromagnetic interference (EMI), which can disturb the normal operation of the converter itself and other adjacent systems. Power converters must comply with electromagnetic compatibility (EMC) standards to guarantee proper operation of converters and nearby systems. Soft switching methods can be employed as EMI mitigation techniques in power converters. Although, soft switching converters are commonly addressed to have lower EMI than hard switching counterparts, they may not satisfy EMC regulations. In this study, spread spectrum by the means of pseudorandom modulation is applied to a zero-current transition (ZCT) flyback converter. By extracting the converter EMI model, the effect of using ZCT soft switching method is simulated and compared to its hard switching counterpart. The reduced amount of conducted electromagnetic emission is demonstrated via the proposed simulation method. To justify the theoretical analysis, the experimental results are presented. © 2012 The Institution of Engineering and Technology.

Delshad M.,Islamic Azad University at Khorasgan | Farzanehfard H.,Isfahan University of Technology
Energy Conversion and Management | Year: 2011

In this paper a new zero voltage switching current fed push pull dc-dc converter is proposed for fuel cell generation system. The auxiliary circuit in this converter, not only absorbs the voltage surge across the switches at turn off instance, but also provides zero voltage switching condition for all converter switches. Therefore, the converter efficiency is increased and size and weight of the converter can be decreased. Also implementation of control circuit is very simple since the converter is PWM controlled. In this paper, the proposed dc-dc converter operating modes are analyzed and to verify the converter operation a laboratory prototype is implemented and the experimental results are presented. © 2010 Elsevier Ltd. All rights reserved.

Shahbazi M.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology | Soghrati S.,University of Illinois at Urbana - Champaign
Composite Structures | Year: 2011

In this part of the paper, we introduce a meshfree approach for static analysis of isotropic/orthotropic cross-ply laminated plates with symmetric/non-symmetric layers. In this method, the solution is first split into homogenous and particular parts and then the homogenous part is approximated by the summation of an appropriately selected set of exponential basis functions (EBFs) that are restricted to satisfy the governing partial differential equation (PDE). The particular solution is derived using a similar approach and another series of EBFs. The imposition of the boundary conditions is performed by a collocation method through a discrete transformation technique. The solution method allows us to obtain semi-analytical solution of plate problems with various shapes and boundary conditions. Although implemented for cross-ply laminates in this work, the proposed method is applicable to more general lamination cases as long as the governing PDEs are of constant coefficient type. This part of the paper is devoted to the basic features of the formulation and the evaluation of the EBFs using classical, first and third order shear deformation theories. Explicit expressions are given for special cases for further use. © 2011 Elsevier Ltd.

Shahbazi M.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology | Soghrati S.,University of Illinois at Urbana - Champaign
Composite Structures | Year: 2011

In this part of the paper we give the details of the implementation of the method presented in the first part. Also the solutions of several benchmark plate problems with various geometries are presented to validate the results. It has been observed that the method can perform excellently in a wide range of problems defined for the bending analysis of laminated plates based on various plate theories. For further use, some explicit expressions are given for the exponential basis functions suitable for the solution of symmetric cross-ply laminates. © 2011 Elsevier Ltd.

Shahbazi M.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology | Soghrati S.,University of Illinois at Urbana - Champaign
Composite Structures | Year: 2012

In this paper we present some results from the application of a mesh-free method introduced previously (Compos Struct 2011;93:3112-9 and 94:84-91) for bending analysis of laminated composite plates. This method is applicable to a wide range of bending problems without limitation in the stacking sequence of the laminated plates and the boundary conditions. Herein, two specific types of problems, having traction free boundaries, are examined and the issues related to the solution of them are addressed. Also as new benchmark problems, some more results for cross-ply and angle-ply composites are presented. © 2012 Elsevier Ltd.

Manshaei M.H.,Isfahan University of Technology | Zhu Q.,University of Illinois at Urbana - Champaign | Zhu Q.,Isfahan University of Technology | Alpcan T.,University of Melbourne | And 2 more authors.
ACM Computing Surveys | Year: 2013

This survey provides a structured and comprehensive overview of research on security and privacy in computer and communication networks that use game-theoretic approaches. We present a selected set of works to highlight the application of game theory in addressing different forms of security and privacy problems in computer networks and mobile applications. We organize the presented works in six main categories: security of the physical and MAC layers, security of self-organizing networks, intrusion detection systems, anonymity and privacy, economics of network security, and cryptography. In each category, we identify security problems, players, and game models. We summarize the main results of selected works, such as equilibrium analysis and security mechanism designs. In addition, we provide a discussion on the advantages, drawbacks, and future direction of using game theory in this field. In this survey, our goal is to instill in the reader an enhanced understanding of different research approaches in applying gametheoretic methods to network security. This survey can also help researchers from various fields develop game-theoretic solutions to current and emerging security problems in computer networking. © 2013 ACM.

Movahedian B.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology | Soghrati S.,University of Illinois at Urbana - Champaign
Engineering Analysis with Boundary Elements | Year: 2013

In this paper we present a Trefftz method based on using exponential basis functions (EBFs) to solve one (1D) and two (2D) dimensional transient problems. We focus on direct and inverse heat conduction problems, the latter being the more challenging ones, to show the capabilities of the method. A summation of exponential basis functions (EBFs), satisfying the governing equation in time and space, with unknown coefficients is considered for the solution. The unknown coefficients are determined by the satisfaction of the prescribed time dependent boundary and initial conditions through a collocation method. Several 1D and 2D direct and inverse heat conduction problems are solved. Some numerical evidence is provided for the convergence and sensitivity of the method with respect to the noise levels of the measured data and time steps. © 2013 Elsevier Ltd.

Mirzadeh H.,Isfahan University of Technology | Cabrera J.M.,Polytechnic University of Catalonia | Cabrera J.M.,Fundacio Center Tecnologic | Najafizadeh A.,Isfahan University of Technology
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2012

The modeling of hot flow stress and prediction of flow curves for unseen deformation conditions are important in metal-forming processes because any feasible mathematical simulation needs accurate flow description. In the current work, in an attempt to summarize, generalize, and introduce efficient methods, the dynamic recrystallization (DRX) flow curves of a 17-4 PH martensitic precipitation hardening stainless steel, a medium carbon microalloyed steel, and a 304 H austenitic stainless steel were modeled and predicted using (1) a hyperbolic sine equation with strain dependent constants, (2) a developed constitutive equation in a simple normalized stress-normalized strain form and its modified version, and (3) a feed-forward artificial neural network (ANN). These methods were critically discussed, and the ANN technique was found to be the best for the modeling available flow curves; however, the developed constitutive equation showed slightly better performance than that of ANN and significantly better predicted values than those of the hyperbolic sine equation in prediction of flow curves for unseen deformation conditions. © 2011 The Minerals, Metals & Materials Society and ASM International.

Boroomand B.,Isfahan University of Technology | Soghrati S.,University of Illinois at Urbana - Champaign | Movahedian B.,Isfahan University of Technology
International Journal for Numerical Methods in Engineering | Year: 2010

In this paper, exponential basis functions (EBFs) are used in a boundary collocation style to solve engineering problems whose governing partial differential equations (PDEs) are of constant coefficient type. Complex-valued exponents are considered for the EBFs. Two-dimensional elasto-static and time harmonic elasto-dynamic problems are chosen in this paper. The solution procedure begins with first finding a set of appropriate EBFs and then considering the solution as a summation of such EBFs with unknown coefficients. The unknown coefficients are determined by the satisfaction of the boundary conditions through a collocation method with the aid of a consistent and complex discrete transformation technique. The basis and various forms of the transformation have been addressed and discussed. We shall propose several strategies for selection of EBFs with the aid of the basis explained for the transformation. While using the transformation, the number of EBFs should not necessarily be equal to (or less than) the number of boundary information data. A library of EBFs has also been presented for further use. The effect of body forces is included in the solution via construction of particular solution by the use of the discrete transformation and another series of EBFs. A number of sample problems are solved to demonstrate the capabilities of the method. It has been shown that the time harmonic problems with high wave number can be solved without much effort. The method, categorized in meshless methods, can be applied to many other problems in engineering mechanics and general physics since EBFs can easily be found for almost all problems with constant coefficient PDEs. © 2009 John Wiley & Sons, Ltd.

Zandi S.M.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology | Soghrati S.,University of Illinois at Urbana - Champaign
Journal of Computational Physics | Year: 2012

In this paper exponential basis functions (EBFs) satisfying the governing equations of elastic problems with incompressible materials are introduced. Due to similarity between elasticity problems and steady state fluid problems the bases found for the former problems are used for latter problems. We discuss on using single field form known as displacement/velocity based formulation and also on using a two-field form known as u-p formulation. In the first formulation we find the pressure bases through performing a limit analysis using a fictitious bulk modulus while in the second formulation the bases are found directly by considering the pressure as a separate variable. In the second formulation we directly apply the condition of incompressibility. It is shown that both formulations yield identical bases meaning that the first one may be used in a standard approach. However, it is also shown that when the incompressibility condition is applied by a Laplacian of pressure in the second formulation, some additional spurious EBFs may be obtained. Having defined appropriate bases, we follow the solution strategy recently introduced by the authors for other engineering problems. Some well-known benchmark problems are solved to show the capabilities of the method. © 2012 Elsevier Inc.

Zandi S.M.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology | Soghrati S.,University of Illinois at Urbana - Champaign
Journal of Computational Physics | Year: 2012

In this paper, a new simple meshless method is presented for the solution of incompressible inviscid fluid flow problems with moving boundaries. A Lagrangian formulation established on pressure, as a potential equation, is employed. In this method, the approximate solution is expressed by a linear combination of exponential basis functions (EBFs), with complex-valued exponents, satisfying the governing equation. Constant coefficients of the solution series are evaluated through point collocation on the domain boundaries via a complex discrete transformation technique. The numerical solution is performed in a time marching approach using an implicit algorithm. In each time step, the governing equation is solved at the beginning and the end of the step, with the aid of an intermediate geometry. The use of EBFs helps to find boundary velocities with high accuracy leading to a precise geometry updating. The developed Lagrangian meshless algorithm is applied to variety of linear and nonlinear benchmark problems. Non-linear sloshing fluids in rigid rectangular two-dimensional basins are particularly addressed. © 2011 Elsevier Inc.

Mirzadeh H.,Polytechnic University of Catalonia | Mirzadeh H.,Isfahan University of Technology | Cabrera J.M.,Polytechnic University of Catalonia | Cabrera J.M.,Fundacio Center Tecnologic | Najafizadeh A.,Isfahan University of Technology
Acta Materialia | Year: 2011

Constitutive equations were used to derive the flow stress of a 17-4 PH stainless steel during hot compression testing. Two general methods were used: (i) a conventional method of finding apparent materials constants; and (ii) a physically based approach which accounts for the dependence of the Young's modulus and the self-diffusion coefficient of austenite on temperature. Both methods were critically discussed and some modifications and easy-to-apply methods were also introduced. The second approach was also performed for peak and critical stresses to find out the effect of dynamic recrystallization on the ideal theoretical values. The discussion of results proved that when the deformation mechanism is controlled by the glide and climb of dislocations, a constant creep exponent (n) of 5 can be used in the classical hyperbolic sine equation, and the self-diffusion activation energy can be used to describe the appropriate stress. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Soltanizadeh N.,Isfahan University of Technology | Mirmoghtadaie L.,Shahid Beheshti University of Medical Sciences
Comprehensive Reviews in Food Science and Food Safety | Year: 2014

Phenylketonuria (PKU) is one of the most widespread dysfunctions caused by an inheritable problem in the phenylalanine metabolism. In this metabolic disease, gene mutations in phenylalanine hydroxylase (PAH) result in phenylalanine accumulation that causes varying degrees of mental retardation. The most effective treatment is restriction of phenylalanine in diet provided through different strategies including combination of low-protein foods, hydrolyzing of protein-rich foods, or use of protein substitutes. Meat and meat products, sea foods, milk and infant formula, cereal products, and beans are among the modified foods for PKU management. Elimination of phenylalanine from food presents major technological, nutritional, and organolleptic challenges because protein, as an essential structure-building and nutritional element, is removed. In addition, following this program is laborious, boring, and restrictive for both patients and their families. This paper reviews the current findings about PKU and the recent developments in the production of phenylalanine-free foods. Also, the nutritional requirements and challenges encountered by PKU individuals and food technologists are finally discussed. © 2014 Institute of Food Technologists®.

Karimi-Ghartemani M.,Queen's University | Khajehoddin S.A.,Sparq Systems | Jain P.K.,Queen's University | Bakhshai A.,Queen's University | Mojiri M.,Isfahan University of Technology
IEEE Transactions on Power Electronics | Year: 2012

This paper presents a method for addressing the dc component in the input signal of the phase-locked loop (PLL) and notch filter algorithms applied to filtering and synchronization applications. The dc component may be intrinsically present in the input signal or may be generated due to temporary system faults or due to the structure and limitations of the measurement/conversion processes. Such a component creates low-frequency oscillations in the loop that cannot be removed using filters because such filters will significantly degrade the dynamic response of the system. The proposed method is based on adding a new loop inside the PLL structure. It is structurally simple and, unlike an existing method discussed in this paper, does not compromise the high-frequency filtering level of the concerned algorithm. The method is formulated for three-phase and single-phase systems, its design aspects are discussed, and simulations/experimental results are presented. © 2011 IEEE.

Jannesari H.,Isfahan University of Technology | Jannesari H.,Albert Ludwigs University of Freiburg | Emami M.D.,Isfahan University of Technology | Ziegler C.,Albert Ludwigs University of Freiburg
Journal of Power Sources | Year: 2011

In this work, for the first time, we model the variation of solid electrolyte interface (SEI) across the depth of anode electrode of lithium ion battery. It is anticipated that due to higher thickness of SEI layer at the electrode side connected to the separator, a more critical condition prevails there. The present work also investigates the effects of variations in the morphological parameters including porosity, interfacial surface area and active particle radius across anode electrode on the uniformity of side reaction. Moreover, the sensitivity of the side reaction uniformity to electrolyte parameters, such as diffusion and ionic conductivity, is studied. Results show that the ionic conductivity has a major role on the uniformity, and could reduce critical conditions in the part of electrode next to the separator. Moreover, simulation results show that increasing ionic conductivity could significantly prolong the lifetime of the battery. An increase in electrolyte diffusion improves side reaction uniformity. Results also show that positive gradients of morphological parameters across anode electrode, when parameters are changed independently, have considerable effects on uniformity of side reaction. This could be a criterion in choosing new morphologies for the part of anode electrode connected to separator. © 2011 Elsevier B.V.

Karimi-Maleh H.,Kerman Graduate University of Technology | Tahernejad-Javazmi F.,Kerman Graduate University of Technology | Ensafi A.A.,Isfahan University of Technology | Moradi R.,Islamic Azad University at Qaemshahr | And 2 more authors.
Biosensors and Bioelectronics | Year: 2014

This study describes the development, electrochemical characterization and utilization of novel modified N-(4-hydroxyphenyl)-3,5-dinitrobenzamide-FePt/CNTs carbon paste electrode for the electrocatalytic determination of glutathione (GSH) in the presence of piroxicam (PXM) for the first time. The synthesized nanocomposite was characterized with different methods such as TEM and XRD. The modified electrode exhibited a potent and persistent electron mediating behavior followed by well-separated oxidation peaks of GSH and PXM. The peak currents were linearly dependent on GSH and PXM concentrations in the range of 0.004-340 and 0.5-550μmolL-1, with detection limits of 1.0nmolL-1 and 0.1μmolL-1, respectively. The modified electrode was successfully used for the determination of the analytes in real samples with satisfactory results. © 2014 Elsevier B.V.

Amini K.,Islamic Azad University at Tehran | Nategh S.,Islamic Azad University at Tehran | Shafyei A.,Isfahan University of Technology
Materials and Design | Year: 2010

This experimental study investigated the effect of cryogenic treatments on the wear behavior of 80CrMo12 5 tool steel. For this purpose, two different cryogenic temperatures were used: -80 °C as the shallow cryogenic temperature and -196 °C as the deep cryogenic temperature. The results showed that the cryogenic treatments decrease retained austenite, which is more effective in the case of the deep cryogenic treatment (DCT). As a result, a remarkable improvement in the wear resistance of the cryogenically treated specimens was observed. In addition, DCT increases the percentage of carbides and their homogeneity in distribution. An optimum holding time was found in the deep cryogenic temperature, in which the hardness and wear resistance show maximum values. Moreover, the wear debris and worn surfaces showed that the dominant mechanism in the wear test is adhesive. © 2010 Elsevier Ltd.

Arefmanesh A.,University of Kashan | Najafi M.,Islamic Azad University at Tehran | Musavi S.H.,Isfahan University of Technology
Engineering Analysis with Boundary Elements | Year: 2013

The meshless local Petrov-Galerkin method is implemented to simulate the buoyancy-driven flow and heat transfer in a differentially-heated enclosure having a baffle attached to its higher temperature side wall. To execute the proposed numerical treatment, the stream function-vorticity formulation is employed and a unity weighting function is applied for the weak form of the governing equations. In this meshless numerical approach, the field variables are approximated using the MLS interpolation technique. Being attested through comparing the results of two test case simulations with the results of either an analytical or a conventional numerical approach, the MLPG method is applied to investigate the buoyancy-driven flow and heat transfer in the baffled cavity. The present analyses involve a parametric study to implicate the effects of the baffle undulation number, amplitude, location on the wall, and the system Rayleigh number. The investigation reveals the eminent participation of the baffle in transferring heat from the hot wall. The analyses disclose an increase of the hot wall average Nusselt number by elevating the location of the baffle on the hot wall. This average Nusselt number descends with increasing the baffle amplitude. The cold wall average Nusselt number increases as the baffle number of undulation augments. © 2012 Elsevier Ltd.

Mostafavi E.S.,Isfahan University of Technology | Ramiyani S.S.,Sharif University of Technology | Sarvar R.,Islamic Azad University at Tehran | Moud H.I.,Chalmers University of Technology | Mousavi S.M.,Islamic Azad University at Tehran
Energy | Year: 2013

This paper presents an innovative hybrid approach for the estimation of the solar global radiation. New prediction equations were developed for the global radiation using an integrated search method of genetic programming (GP) and simulated annealing (SA), called GP/SA. The solar radiation was formulated in terms of several climatological and meteorological parameters. Comprehensive databases containing monthly data collected for 6 years in two cities of Iran were used to develop GP/SA-based models. Separate models were established for each city. The generalization of the models was verified using a separate testing database. A sensitivity analysis was conducted to investigate the contribution of the parameters affecting the solar radiation. The derived models make accurate predictions of the solar global radiation and notably outperform the existing models. © 2012 Elsevier Ltd.

Moghim M.N.,Isfahan University of Technology | Alizadeh F.,Islamic Azad University at Tehran
Coastal Engineering | Year: 2014

An empirical new berm recession formula is derived based on the assumption that the maximum wave force causing armor movement and berm recession is proportional to the maximum wave momentum flux near the structure toe. This concept introduces a more physics-based first principles approach to estimate the berm recession. Recession seems well predicted by the new formula for reshaping berm breakwaters. The results from this formula show a better estimation than earlier formulae used for estimating the berm recession. © 2013 Elsevier B.V.

Mokhtari A.,Golestan University | Karimi-Maleh H.,Islamic Azad University | Ensafi A.A.,Isfahan University of Technology | Beitollahi H.,Research Institute of Environmental science
Sensors and Actuators, B: Chemical | Year: 2012

A novel modified carbon paste electrode with vinylferrocene/multiwall carbon nanotubes was fabricated. The electrochemical response of the modified electrode toward morphine was studied by means of cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The structural morphology of the modified electrode was characterized by SEM technique. The prepared electrode showed an excellent electrocatalytic activity in the oxidation of morphine, leading to remarkable enhancements in the corresponding peak currents and lowering the peak potential. Using square wave voltammetry (SWV), we could measure morphine and diclofenac in one mixture independently from each other by a potential difference of about 300 mV for the first time. Square wave voltammetric peaks current of morphine and diclofenac increased linearly with their concentrations in the ranges of 0.2-250.0 μmol L -1, and 5.0-600.0 μmol L -1, respectively. The detection limits of 0.09 and 2.0 μmol L -1 were achieved for morphine and diclofenac, respectively. The proposed voltammetric sensor was successfully applied to the determination of morphine and diclofenac in real samples. © 2012 Elsevier B.V. All rights reserved.

Hajmohammadi M.R.,Amirkabir University of Technology | Salimpour M.R.,Isfahan University of Technology | Saber M.,Islamic Azad University at Tehran | Campo A.,University of Texas at San Antonio
Energy Conversion and Management | Year: 2013

Maintaining the peak temperature of a heat source under an allowable level has always been a major concern for engineers engaged in the design of cooling systems for electronic equipment. The primary goal of this paper is to examine the advantages and/or disadvantages of placing a conductive thick plate as a heat transfer interface between a heat source and a cold flowing fluid. In such arrangement, the heat source is cooled under the thick plate instead of being cooled in direct contact with the cooling fluid. It is demonstrated that the thick plate can significantly improve the heat transfer between the heat source and the cooling fluid by way of conducting the heat current in an optimal manner. The two most attractive advantages of this method are that no additional pumping power and no extra heat transfer surface area, that is quite different from fins (extended surfaces). Unlike related archival papers in the literature, the present paper allows open spaces toward optimization. The objective is to minimize the maximum temperature, the 'hot spot'. Detailed analytical expressions are presented and a numerical analysis is carried out on the conservation equations based on the SIMPLEC algorithm. It is categorically proved that there exists an optimal thickness of the thick plate, which minimizes the peak temperature. Also, it is shown that the efficiency of the optimized plate on minimizing the target peak temperature depends upon the Reynolds number of the fluid flow and the material thermal conductivity. © 2013 Elsevier Ltd. All rights reserved.

Shojaeian S.,Islamic Azad University at Tehran | Soltani J.,Islamic Azad University at Khomeinishahr | Soltani J.,Isfahan University of Technology | Arab Markadeh G.,Shahrekord University
IEEE Transactions on Power Systems | Year: 2012

In this paper, damping of the low frequency oscillations of multi-machine multi-UPFC power systems is investigated based on adaptive input-output feedback linearization control (AIFLC) approach. Considering a three-phase symmetrical fault, ignoring the subtransient states of the synchronous machines, the nonlinear state equations of the system are derived in order to obtain the UPFC reference control signals as well as the system parameters estimation laws. The stability of the system controller is proved by Lyapunov theory. Moreover using the six reduced order model of synchronous machine, some simulation results are presented in order to verify the validity and effectiveness of the proposed control approach. © 1969-2012 IEEE.

Farajpour A.,Islamic Azad University at Tehran | Farajpour A.,Isfahan University of Technology | Dehghany M.,Iran University of Science and Technology | Shahidi A.R.,Isfahan University of Technology
Composites Part B: Engineering | Year: 2013

In this paper, the axisymmetric buckling analysis of circular single-layered graphene sheets is studied by decoupling the basic constitutive equations based on the nonlocal theory of Eringen. The influences of temperature change, surface parameters and nonlocality on the buckling response of single-layered graphene sheet are investigated considering size-dependent material properties. Numerical solutions for buckling loads are computed using differential quadrature method (DQM). For comparison purpose, Galerkin method is also used to solve the nonlocal governing differential equation. DQM results are successfully verified with those of Galerkin method. The comparison of present results with the available molecular dynamics simulation data from the literature shows that the present formulation with appropriate values of surface and nonlocal parameters provides more accurate results than those obtained by the classical plate model. The results of present work can be used as benchmarks to evaluate future analyses of the circular nanoplates. © 2013 Elsevier Ltd. All rights reserved.

Bina M.H.,Iranian Research Organization for Science and Technology | Dehghani F.,Islamic Azad University at Tehran | Salimi M.,Isfahan University of Technology
Materials and Design | Year: 2013

In this investigation, explosive welding and heat treatment processes provided an effective method for manufacturing high-strength and high-ductility copper/ austenitic stainless steel couple. In order to improve diffusion in the interface of copper/stainless steel, first the tensile samples were provided from the welded part, then they were subjected to annealing at 300 °C (below recrystallization temperature) for 8-32. h with 8. h intervals and then samples were cooled in the furnace. Optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to evaluate the possibility of diffusion in the joints. Moreover, in order to measure the hardness of the samples, microhardness test was performed. Microstructural evaluations showed that the stainless steel 304L had a wavy interface. Furthermore, the post heat treatment process resulted in great enhancement of diffusion. Microhardness measurements showed that the hardness of the sample near to the interface is greatly higher than other parts; this is due to plastic deformation and work hardening of copper and stainless steel 304L in these regions. The interface of samples with and without the post heat treatment was exhibited ductile and brittle fracture, respectively. © 2012 Elsevier Ltd.

Yazdani M.R.,Islamic Azad University at Tehran | Farzanehfard H.,Isfahan University of Technology | Faiz J.,University of Tehran
IEEE Transactions on Power Electronics | Year: 2011

Switching power supplies are sources of noise for sensitive circuits. Converters should comply with electromagnetic compatibility (EMC) rules so that the electromagnetic interference (EMI) caused by switching cannot interfere with the normal operation of adjacent circuits and also the converter itself. The produced interference can be in the form of conduction or radiation. In this paper, some techniques are used in switching converters to suppress EMI with emphasis on the conduction form. EMI analysis and evaluation of a conventional flyback converter and a proposed zero-current transition (ZCT) flyback converter is achieved by simulation and experimental results. In addition to evaluating some EMI suppression techniques, the main objective of this paper is to improve EMI in the topology design stage. The operating modes of the improved ZCT flyback are discussed. In addition to the efficiency improvement, the amount of EMI reduction of this ZCT flyback and the effectiveness of some EMI reduction techniques are shown by practical implementation. © 2011 IEEE.

Tatari M.,Isfahan University of Technology | Dehghan M.,Amirkabir University of Technology
JVC/Journal of Vibration and Control | Year: 2012

In this work, multi-point boundary value problems are considered. These problems have important roles in the modelling of various problems in physics and engineering. Although numerous works have been carried out on the existence and uniqueness to the solution of these problems, the numerical or analytical methods are not established for solving them. In this paper the well-known He's variational iteration method is applied for solving the multi-point boundary value problems. The method is modified and the results are shown using some test problems. These results show the efficiency of the new approach. © 2011 The Author(s).

Amini M.,Isfahan University of Technology | Kravtsov V.E.,Abdus Salam International Center For Theoretical Physics | Kravtsov V.E.,L D Landau Institute for Theoretical Physics | Muller M.,Abdus Salam International Center For Theoretical Physics
New Journal of Physics | Year: 2014

We study the interaction-driven localization transition, which a recent experiment (Richardella et al 2010 Science 327 665) in Ga1-xMnxAs has shown to come along with the multifractal behavior of the local density of states (LDoS) and the intriguing persistence of critical correlations close to the Fermi level. We show that the bulk of these phenomena can be understood within a Hartree-Fock (HF) treatment of disordered, Coulomb-interacting spinless fermions. A scaling analysis of the LDoS correlation demonstrates multifractality with the correlation dimension d2 ≈ 1.57, which is significantly larger than at a non-interacting Anderson transition and is compatible with the experimental value dexp2 = 1.8 ± 0.3. At the interaction-driven transition, the states at the Fermi level become critical, while the bulk of the spectrum remains delocalized up to substantially stronger interactions. The mobility edge stays close to the Fermi energy in a wide range of disorder strength, as the interaction strength is further increased. The localization transition is concomitant with the quantum-to-classical crossover in the shape of the pseudo-gap in the tunneling density of states, and with the proliferation of metastable HF solutions that suggest the onset of a glassy regime with poor screening properties. © 2014 IOP Publishing and Deutsche Physikalische Gesellschaft.

Farahbod F.,Building Research Institute, Egypt | Mostofinejad D.,Isfahan University of Technology
Composite Structures | Year: 2011

The present paper describes an experimental investigation of moment redistribution of continuous beams in 6 two-span RC frames strengthened with CFRP laminates. Design variables were the number of CFRP layers, and the configuration of the laminates. To prevent debonding of the CFRP laminates at the end region and at the beam-column connection, U-shaped CFRP anchorages were provided for all of the frame specimens. Furthermore, mechanical anchorages of steel plate strips and bolts were added to the laminates in one frame of these specimens. Test results showed that a maximum moment redistribution of 56% occurred in the strengthened frames. Furthermore, the load carrying capacities of the strengthened frames increased from 20% to 38%, while the flexural capacities had an increase of 9% to 20% and 35% to 55% at the negative and positive moment regions, respectively. © 2010 Elsevier Ltd.

Malekzadeh S.,University of Yazd | Malekzadeh S.,Islamic Azad University at Shabestar | Sohankar A.,Isfahan University of Technology
International Journal of Heat and Fluid Flow | Year: 2012

This study focuses on the reduction of the fluid forces acting on a square cylinder in a laminar flow regime by a passive control, i.e. a flat plate placed upstream of the cylinder. The Reynolds numbers based on the width of the square cylinder (W) and the inlet flow velocity are selected from Re = 50 to Re = 200. The width of the control plate (h) is varied from 0.1. W to 0.9. W and the distance between the control plate and the cylinder (S) is chosen within the range of 1.1-7. W. In these ranges of h and S, the different flow patterns and the magnitude of the reduction of the fluid forces in order to identity the optimum conditions are studied. The results of the heat transfer from a cylinder in the presence of a control plate are also provided for S= 1.1-7. W, h= 0.5-0.9. W, Re = 160, Pr = 0.71. The results show that the optimum position and width for the control plate are a distance of 3. W away from the cylinder and a width of 0.5. W, respectively, where the almost maximum reduction of the fluid forces and the minimum reduction of the heat transfer are provided. It is also found that the total Nusselt number of the cylinder in the presence of the control plate decreases for different gap spacings, except for S/. W= 1.1. © 2011 Elsevier Inc.

Akbarzadeh M.,Isfahan University of Technology | Wilmot C.G.,Louisiana State University
Natural Hazards Review | Year: 2015

In this research, the factors affecting route choice in hurricane evacuation are investigated. Two hypotheses are tested. First, it is hypothesized that contrary to common practice where travel time is considered the sole or main determinant of route choice, other variables such as familiarity with the route, availability of fuel and shelter, road type, and accessibility of the route have an effect on an evacuees' route choice as well. The second hypothesis is that as time passes and storm conditions change, the impact each variable has on route choice changes. That is, it is hypothesized that the importance evacuees assign to the factors determining route choice is not static but varies with time. The logit structure was used for modeling the choice process and stated choice data previously collected from the New Orleans area on hypothetical storms was used to calibrate the model. The study found that accessibility to a route, familiarity with the route, road type, length of a route, and availability of services (gas stations and hotels) had an effect on evacuation route choice. The magnitude of the coefficients of perceived service, accessibility, and distance differed among those evacuating in the first half of the evacuation period versus those that evacuated in the second half, but coefficients of road type were not significantly different between the two time intervals. Observed traffic count data from hurricane Katrina evacuation were used to validate the model. Comparison of traffic volumes predicted by the model with actual traffic volumes from hurricane Katrina shows error percentages of 17.5, 0.01, and 28% of error for volumes on I-10, I-55, and US-61 respectively. © 2014 American Society of Civil Engineers.

Fereidouni A.R.,Amirkabir University of Technology | Vahidi B.,Amirkabir University of Technology | Hosseini Mehr T.,Isfahan University of Technology
IEEE Transactions on Smart Grid | Year: 2013

In this paper, it is aimed to investigate the impact of the various solid-state fault current limiters (SSFCLs) on several electric power networks with the wind-turbine power generation (WTPG). Distributed generations (DGs) are predicted to perform an increasing role in the future electrical power system. Expose of the DG, can change the fault current during a grid disturbance and disturb the existing distribution system protection. Fault current limiters (FCLs) can be sorted into L-types (inductive) and R-types (resistive) by the fault current limiting impedance. In this paper, a new SSFCL has been proposed. SSFCLs can provide the fast system protection during a rigorous fault. The act of dynamic damping enhancement via the SSFCL is appraised in the presence of the wind-turbine power generation. Hence, its efficiency as a protective device for the wind-turbine system is confirmed via some case studies by time-domain simulation based on the PSCAD/EMTDC. © 2010-2012 IEEE.

Tatari M.,Isfahan University of Technology | Dehghan M.,Amirkabir University of Technology
Engineering Analysis with Boundary Elements | Year: 2010

In this work a technique is proposed for solving partial differential equations using radial basis functions. The approach is different from the traditional schemes. The radial basis functions are very suitable instruments for solving partial differential equations of various types. However, the matrices which result from the discretization of the equations are usually ill-conditioned especially in higher-dimensional problems. In the current paper, a stable method will be proposed for solving the partial differential equations and will be generalized to solve higher-dimensional problems. To the contrast of most existing methods, the new technique provides a closed form approximation for the solution. Another advantage of the developed method is that it can be applied to problems with nonregular geometrical domains. © 2009 Elsevier Ltd. All rights reserved.

Hasanbeigi A.,CA Technologies | Hasanabadi A.,Isfahan University of Technology | Abdorrazaghi M.,Amirkabir University of Technology
Journal of Cleaner Production | Year: 2012

The textile industry is a complicated manufacturing industry because it is a fragmented and heterogeneous sector dominated by small and medium enterprises (SMEs). Energy is one of the main cost factors in the textile industry. This paper contributes to the understanding of energy use in the textile industry. In this study, thirteen textile plants from five major sub-sectors of the textile industry in Iran, i.e. spinning, weaving, wet-processing, worsted fabric manufacturing, and carpet manufacturing, were studied. The energy intensity of each plant was calculated and compared against other plants within the same sub-sector. The results showed the range of energy intensities for plants in each sub-sector. It also showed that energy saving/management efforts should be focused on motor-driven systems in spinning plants, whereas in other textile sub-sectors thermal energy is the dominant type of energy used and should be focused on. For conducting a fair and proper comparison/benchmarking studies, factors that significantly influence the energy intensity across plants within each textile sub-sector (explanatory variables) are discussed. © 2011 Elsevier Ltd. All rights reserved.

Kianfar K.,Isfahan University of Technology | Fatemi Ghomi S.M.T.,Amirkabir University of Technology | Oroojlooy Jadid A.,Sharif University of Technology
Engineering Applications of Artificial Intelligence | Year: 2012

A flexible flow shop is a generalized flow shop with multiple machines in some stages. This system is fairly common in flexible manufacturing and in process industry. In most practical environments, scheduling is an ongoing reactive process where the presence of real time information continually forces reconsideration of pre-established schedules. This paper studies a flexible flow shop system considering non-deterministic and dynamic arrival of jobs and also sequence dependent setup times. The problem objective is to determine a schedule that minimizes average tardiness of jobs. Since the problem class is NP-hard, a novel dispatching rule and hybrid genetic algorithm have been developed to solve the problem approximately. Moreover, a discrete event simulation model of the problem is developed for the purpose of experimentation. The most commonly used dispatching rules from the literature and two new methods presented in this paper are incorporated in the simulation model. Simulation experiments have been conducted under various experimental conditions characterized by factors such as shop utilization, setup time level and number of stages. The results indicate that methods proposed in this study are much better than the traditional dispatching rules. © 2011 Published by Elsevier Ltd. All rights reserved.

Mirzaei A.,Isfahan University of Technology | Rahmati M.,Amirkabir University of Technology
IEEE Transactions on Fuzzy Systems | Year: 2010

Clustering-combination methods have received considerable attentions in recent years, and many ensemble-based clustering methods have been introduced. However, clustering-combination techniques have been limited to "flat" clustering combination, and the combination of hierarchical clusterings has yet to be addressed. In this paper, we address and formalize the concept of hierarchical-clustering combination and introduce an algorithmic framework in which multiple hierarchical clusterings could be easily combined. In this framework, the similarity-based description matrices of input hierarchical clusterings are aggregated into a transitive consensus matrix in which the final hierarchy could be formed. Empirical evaluation, by using popular available datasets, confirms the superiority of combined hierarchical clustering introduced by our method over the standard (single) hierarchical-clustering methods. © 2006 IEEE.

Faez K.,Amirkabir University of Technology | Amirfattahi R.,Isfahan University of Technology
10th International Conference on Information Sciences, Signal Processing and their Applications, ISSPA 2010 | Year: 2010

In this paper, a novel multimodal biometric recognition system using three modalities including face, ear and gait, based on Gabor+ PCA feature extraction method with fusion at matching score level is proposed. The performance of our approach has been studied under three different normalization methods (min-max, medianMAD and z-score) and two different fusion methods (weighted sum and weighted product). Our new method has been successfully tested using 360 images corresponding to 120 subjects from three databases including ORL face database, USTB ear database, and CASIA gait database. Because of these biometric traits, our proposed method requires no significant user co-operation and also can work from a long distance. According to the experimental results our proposed method exhibits excellent recognition performance and outperforms unimodal systems. The best recognition performance that our proposed method achieved is %97.5. © 2010 IEEE.

Dehghan M.,Amirkabir University of Technology | Tatari M.,Isfahan University of Technology
International Journal of Computer Mathematics | Year: 2010

Third-order boundary value problems (BVPs) were discussed in many papers in recent years. The existence of solutions to these problems is shown under certain conditions. Finding the exact or approximate solution of these problems is not easy especially when the boundary conditions are non-linear. In this paper, we present a method for solving a class of third-order BVPs with non-linear boundary conditions. The decomposition procedure of Adomian is used for solving these problems and the advantages of this method over the other existing methods are shown. Numerical results are presented to show the efficiency of the developed method.

Khosravi R.,Isfahan University of Technology | Janbazi M.,Islamic Azad University at Shiraz
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

The strong form factors and coupling constants of VDs0* Ds1 and VDsDs*(V=&phi, J/ψ) vertices in the framework of the three-point QCD sum rules are considered. Taking into account the nonperturbative part contributions of the correlation functions, the quark-quark, gluon-gluon, and quark-gluon condensate as important terms are evaluated. Considering the SUf(3) symmetry, we compare our results with the values obtained in other methods. © 2014 American Physical Society.

Hajihashemi A.,University of Memphis | Mostofinejad D.,Isfahan University of Technology | Azhari M.,Isfahan University of Technology
Journal of Composites for Construction | Year: 2011

In this research, concrete beams were strengthened with carbon-fiber-reinforced polymer (CFRP) laminate strips that were placed in precut grooves on the concrete surface. Five simple-span RC beams were tested. Among these specimens, one served as a reference beam and was not strengthened, one was tested after being strengthened with nonprestressed near-surface-mounted (NSM) CFRP laminates, and the remaining three were strengthened with NSM CFRP laminates that had been prestressed to 5, 20, and 30% of the nominal ultimate strain of the strips. The test results indicate that the prestressed beams more effectively improved the cracking and yielding loads than the nonprestressed strengthened specimen. In addition to a higher cracking load, the prestressed strengthened specimens had cracks with a more limited distribution and width. Furthermore, the prestressed strengthened beams had up to a 15% higher ultimate load-carrying capacity than the nonprestressed specimen, and their failures corresponded to lower deflections. © 2011 American Society of Civil Engineers.

Tarkesh M.,Isfahan University of Technology | Jetschke G.,Friedrich - Schiller University of Jena
Environmental and Ecological Statistics | Year: 2012

A variety of statistical techniques has been used in predictive vegetation modelling (PVM) that attempt to predict occurrence of a given community or species in respect to environmental conditions. We compared the performance of three profile models, BIOCLIM, GARP and MAXENT with three nonparametric models of group discrimination techniques, MARS, NPMR and LRT. The two latter models are relatively new statistical techniques that have just entered the field of PVM. We ran all models on a local scale for a given grassland community (Teucrio-Seslerietum) using the same input data to examine their performance. Model accuracy was evaluated both by Cohen's kappa statistics (κ) and by area under receiver operating characteristics curve based both on resubstitution of training data and on an independent test data set. MAXENT of profile models and MARS of group discrimination techniques achieved the best prediction. © 2012 Springer Science+Business Media, LLC.

Taghian Dinani S.,Islamic Azad University at Shahreza | Hamdami N.,Isfahan University of Technology | Shahedi M.,Isfahan University of Technology | Havet M.,French National Center for Scientific Research
Energy Conversion and Management | Year: 2014

Researches about mathematical modeling of electrohydrodynamic (EHD) drying are rare. In this study, hot air combined with electrohydrodynamic (EHD) drying behavior of thin layer mushroom slices was evaluated in a laboratory scale dryer at voltages of 17, 19, and 21 kV and electrode gaps of 5, 6, and 7 cm. The drying curves were fitted to ten different mathematical models (Newton, Page, Modified Page, Henderson and Pabis, Logarithmic, Two-term exponential, Midilli and Kucuk, Wang and Singh, Weibull and Parabolic models) and a proposed new empirical model to select a suitable drying equation for drying mushroom slices in a hot air combined with EHD dryer. Coefficients of the models were determined by non-linear regression analysis and the models were compared based on their coefficient of determination (R2), sum of square errors (SSE) and root mean square error (RMSE) between experimental and predicted moisture ratios. According to the results, the proposed model that contains only three parameters provided the best fit with the experimental data. It was closely followed by the Midilli and Kucuk model that contains four parameters. Therefore, the proposed model can present comfortable usage and excellent predictions for the moisture content changes of mushroom slices in the hot air combined with EHD drying system. © 2014 Elsevier Ltd. All rights reserved.

Zamani F.,Islamic Azad University at Shahreza | Zamani F.,Isfahan University of Technology | Hosseini S.M.,Islamic Azad University at Shahreza
Catalysis Communications | Year: 2014

In this paper, Fe3O4 nanoparticles were coated by a number of amino acids, e.g. cysteine, serine, glycine and β-alanine, via a simple method. Because of the surface modification of the magnetic nanoparticles with amino acid, the obtained magnetic nanocomposite is able to trap palladium nanoparticles through a strong interaction between the metal nanoparticles and the functional groups of amino acids. Among the synthesized nanocomposites, Fe3O4/cysteine-Pd exhibited the highest catalytic performance and excellent selectivity in the solvent-free aerobic oxidation of various alcohols, along with high level of reusability. © 2013 Elsevier B.V.

Mallakpour S.,Isfahan University of Technology | Rafiee Z.,Yasouj University
Progress in Polymer Science (Oxford) | Year: 2011

The purpose of this review is to provide appropriate details concerning the application of ionic liquids (IL)s associated with microwave-assisted polymer chemistry. From the viewpoint of microwave chemistry, one of the key significant advantages of ILs is their high polarity, which is variable, depending on the cation and anion and therefore can effectively be tuned to a particular application. Hence, these liquids offer a great potential for the innovative application of microwaves for organic synthesis as well as for polymer science. ILs efficiently absorb microwave energy through an ionic conduction mechanism, and thus are employed as solvents and co-solvents, leading to a very high heating rate and a significantly shortened reaction time. Since an IL-based and microwave-accelerated procedure is efficient and environmentally benign, we believe that this method may have some potential applications in the synthesis of a wide variety of vinyl and non-vinyl polymers. This review describes application of combination of ILs with microwave irradiation as a modern tool for the addition and step-growth polymerization as well as modification of polymers and it was compared with ILs alone and conventional polymerization method. © 2011 Elsevier Ltd. All rights reserved.

Gholami A.,Isfahan University of Technology | Molin D.,Draka Communications France | Sillard P.,Draka Communications France
Journal of Lightwave Technology | Year: 2011

A physical model of 10 Gigabit Ethernet (GbE) optical communications systems based on 50-$\mu$ m graded-index multimode fibers (MMFs) is presented in this paper. It includes a model of vertical cavity surface emitting lasers (VCSELs) that accounts for the spatiotemporal dynamic of such transversally multimode lasers, commonly used in 10 GbE optical systems, and an accurate MMF model. This complete model is compared to the 10 GBASE-S Link Budget Spreadsheet developed within the IEEE P802.3ae 10 GbE Task Force and to experimental transmissions. Finally, VCSEL-to-MMF interactions and their impacts on 10 GbE transmissions are detailed and explained. © 2011 IEEE.

Tabatabaei S.M.K.,Isfahan University of Technology | Behbahani S.,Isfahan University of Technology | Mirian S.M.,Iran University of Science and Technology
Journal of Materials Processing Technology | Year: 2013

Ultrasonic assisted machining (UAM) is an advanced technology for improving the machining process, especially for hard materials. This paper presents an experimental and theoretical study toward the effect of UAM on chatter. Theoretical explanation of the effect of UAM on chatter is not fully presented in the available literature yet. In this paper, considering fixed tool geometry, theoretical dynamic equations for UAM are represented. The approach is demonstrated by deriving dynamic formulation of UAM in turning, considering both turning equation and Merchants ultrasonic machining equations. A time domain analysis is fulfilled on each machining condition to verify whether it has a stable vibration or an unstable chatter vibration. Subsequently, an experimental setup is designed and manufactured to investigate UAM effect on regenerative chatter. Special conical shape for workpiece is designed to experimentally generate different points of stability lobe. The generated oscillation by a piezoelectric actuator is transferred, amplified, and concentrated on the tip of the tool by appropriate design of a cutting tool, which is vibrated in its bending mode. The obtained results are encouraging, and indicating good agreement between experimental and theoretical results. © 2012 Elsevier B.V.

Karimi-Maleh H.,Kerman Graduate University of Technology | Moazampour M.,Kerman Graduate University of Technology | Ensafi A.A.,Isfahan University of Technology | Mallakpour S.,Isfahan University of Technology | Hatami M.,Islamic University
Environmental Science and Pollution Research | Year: 2014

In this study, we report preparation of a high sensitive electrochemical sensor for determination of hydrazine in the presence of phenol in water and wastewater samples. In the first step, we describe synthesis and characterization of ZnO/CNTs nanocomposite with different methods such as transmission electron microscopy (TEM) and X-ray diffraction (XRD). In the second step, application of the synthesis nanocomposite describes the preparation of carbon paste electrode modified with n-(4-hydroxyphenyl)-3,5-dinitrobenzamide as a high sensitive and selective voltammetric sensor for determination of hydrazine and phenol in water and wastewater samples. The mediated oxidation of hydrazine at the modified electrode was investigated by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS). Also, the values of catalytic rate constant (k) and diffusion coefficient (D) for hydrazine were calculated. Square wave voltammetry (SWV) of hydrazine at the modified electrode exhibited two linear dynamic ranges with a detection limit (3σ) of 8.0 nmol L-1. SWV was used for simultaneous determination of hydrazine and phenol at the modified electrode and quantitation of hydrazine and phenol in some real samples by the standard addition method. © 2014 Springer-Verlag Berlin Heidelberg.

Jafari M.T.,Isfahan University of Technology | Badihi Z.,Isfahan University of Technology | Jazan E.,Islamic Azad University at Shahreza
Talanta | Year: 2012

This paper deals with a method based on negative electrospray ionization ion mobility spectrometry (ESI-IMS) as a detection technique. The method was used to determine the salicylic acid in human urine and plasma after selective separation of salicylic acid (SA) via molecular imprinted polymer (MIP). The ion mobility spectrum of salicylic acid in negative mode and the reduced mobility value for its ion peak is reported in this paper for the first time. In order to combine the technique with negative ESI-IMS, suitable experimental conditions related to MIP (e.g., Soxhlet extraction) were selected. The method was exhaustively validated in terms of sensitivity, imprinting factor, enrichment factor, and sorption capacity. The linear dynamic range of 0.02-2.00 μg mL-1 and the relative standard deviation (RSD) below 6% were obtained for the analysis of SA through this method. The average recovery was calculated about 92% for the analyzed drug. Finally, human urine and plasma were analyzed and the feasibility of the proposed method was successfully verified by the efficient clean-up of the samples using MIP separation before the analysis by ESI-IMS. © 2012 Elsevier B.V.

Kurd F.,Isfahan University of Technology | Samavati V.,Iran University of Science and Technology
International Journal of Biological Macromolecules | Year: 2015

Polysaccharides from Spirulina platensis algae (SP) were extracted by ultrasound-assisted extraction procedure. The optimal conditions for ultrasonic extraction of SP were determined by response surface methodology. The four parameters were, extraction time (X1), extraction temperature (X2), ultrasonic power (X3) and the ratio of water to raw material (X4), respectively.The experimental data obtained were fitted to a second-order polynomial equation. The optimum conditions were extraction time of 25min, extraction temperature 85°C, ultrasonic power 90W and ratio of water to raw material 20mL/g. Under these optimal conditions, the experimental yield was 13.583±0.51%, well matched with the predicted models with the coefficients of determination (R2) of 0.9971. Then, we demonstrated that SP polysaccharides had strong scavenging activities in vitro on DPPH and hydroxyl radicals. Overall, SP may have potential applications in the medical and food industries. © 2015 Elsevier B.V.

Eshraghi M.,Najafabad Payamenoor University | Kameli P.,Isfahan University of Technology
Current Applied Physics | Year: 2011

We developed a simple synthesis method for production of CoFe 2O4 nanoparticles. The method is based on the solid state ball-milling and calcinations of acetate precursors and citric acid. The samples were characterized using X-ray diffraction, transmission electron microscope, Fourier transform infrared and energy-dispersive X-ray spectroscopy. Magnetic properties of the samples were studied using vibrating sample magnetometer and ac susceptibility measurements. The results show that the products mainly consist of CoFe2O4 nanoparticles. Magnetization measurements demonstrate the effect of calcination temperature on particle size and hence, on the magnetic properties of the CoFe2O4 nanoparticles. By increasing the particle size from 3.5 to 7.2 nm, the room temperature coercivity and magnetization increase from 0 to 152 Oe and from 8 to 30 emu/g respectively. Also, the low temperature calcinated samples, C250 and C30 are superparamagnetic in nature due to its near-zero coercivity and remanence. We estimated the mean value of the effective anisotropy constant, Keff = 9.2 × 106 erg/cm3. This value is much larger than the bulk value, due to the surface effects. © 2010 Elsevier B.V. All rights reserved.

Zamani F.,Islamic Azad University at Shahreza | Zamani F.,Isfahan University of Technology | Izadi E.,Islamic Azad University at Shahreza
Catalysis Communications | Year: 2013

Abstract In this paper, we wish to report the synthesis and characterization of sulfonated-phenylacetic acid coated on Fe3O 4 nanoparticles by a simple method. This catalyst was effectively employed as a novel acid magnetic catalyst for the one-pot synthesis of different 3,4-dihydropyrimidin-2(1H)-ones under mild and solvent-free conditions. This catalyst was easily prepared and showed excellent level of reusability. © 2013 Elsevier B.V.

Zamani F.,Islamic Azad University at Shahreza | Zamani F.,Isfahan University of Technology | Kianpour S.,Isfahan University of Technology
Catalysis Communications | Year: 2014

In this study, Ni nanoparticles incorporated β-alanine-acrylamide (Ala-AA) was successfully prepared by a simple method. The obtained magnetic nanocomposite exhibited excellent activity as a new heterogeneous magnetic catalyst for the reduction of a number of nitro aromatic compounds under mild conditions along with high level of reusability. © 2013 Elsevier B.V.

Mirhadi S.M.,Islamic Azad University at Shahreza | Tavangarian F.,Isfahan University of Technology | Emadi R.,Isfahan University of Technology
Materials Science and Engineering C | Year: 2012

Single-phase nanocrystalline bredigite powder was successfully synthesized by mechanical activation of talc, calcium carbonate, and amorphous silica powder mixture followed by annealing. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS),and Fourier transform infrared spectroscopy (FT-IR) techniques were employed to characterize various powders. Single-phase nanostructure bredigite powder with crystallite size of about 65 nm was synthesized by 20 h of mechanical activation with subsequent annealing at 1200 °C for 1 h. The bredigite formation mechanism was studied. During the formation process of nanostructure bredigite powder some intermediate compounds such as wollastonite (CaSiO 3), larnite (Ca 2SiO 4), merwinite (Ca 3MgSi 2O 8), and calcium magnesium silicate (Ca 5MgSi 3O 12) were formed. It was found that bredigite was not produced directly and that the formation of merwinite, enstatite and Ca 5MgSi 3O 12was unavoidable during the synthesis of bredigite. © 2011 Elsevier B.V. All rights reserved.

Mallakpour S.,Isfahan University of Technology | Rafiee Z.,Yasouj University
Journal of Polymers and the Environment | Year: 2011

With the increasing emphasis on the environment and the need to find environmentally friendly solvent systems, ionic liquids (IL)s have been emerging as promising green solvents to replace conventional solvents in recent years. They possess unique properties such as nonvolatility, low toxicity, ease of handling, nonflammability and high ionic coductivity; thus they have received much attention as green media for various chemistry processes. This report provides an extensive overview of use of ILs in polymers chemistry and technology. © 2011 Springer Science+Business Media, LLC.

Mallakpour S.,Isfahan University of Technology | Rafiee Z.,Yasouj University
Journal of Polymers and the Environment | Year: 2011

With the increasing emphasis on the environment and the need to find environmentally friendly solvent systems, ionic liquids (IL)s have been emerging as promising green solvents to replace conventional solvents in recent years. They possess unique properties such as nonvolatility, low toxicity, ease of handling, nonflammability and high ionic conductivity; thus they have received much attention as green media for various chemistry processes. This report provides an extensive overview of use of ILs in polymers chemistry and technology. © 2011 Springer Science+Business Media, LLC.

Khosravi R.,Isfahan University of Technology | Janbazi M.,Shiraz University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We investigate the strong form factors and coupling constants of vertices containing the strange charmed mesons Ds0*, Ds, Ds*, and Ds1 with the vector mesons and J/ψ in the framework of the three point QCD sum rules. Taking into account the nonperturbative part contributions of the correlation functions, the condensate terms of dimension 3, 4 and 5 related to the contributions of the quark-quark, gluon-gluon, and quark-gluon condensate, respectively, are evaluated. The present work can give considerable information about the hadronic processes involving the strange charmed mesons. © 2013 American Physical Society.

Kheradmand S.,Shiraz University | Karimi-Jashni A.,Shiraz University | Sartaj M.,Isfahan University of Technology
Waste Management | Year: 2010

The main objective of this study was to assess the feasibility of treating sanitary landfill leachate using a combined anaerobic and activated sludge system. A high-strength leachate from Shiraz municipal landfill site was treated using this system. A two-stage laboratory-scale anaerobic digester under mesophilic conditions and an activated sludge unit were used. Landfill leachate composition and characteristics varied considerably during 8months experiment (COD concentrations of 48,552-62,150mg/L). It was found that the system could reduce the COD of the leachate by 94% at a loading rate of 2.25g COD/L/d and 93% at loading rate of 3.37g COD/L/d. The anaerobic digester treatment was quite effective in removing Fe, Cu, Mn, and Ni. However, in the case of Zn, removal efficiency was about 50%. For the rest of the HMs the removal efficiencies were in the range 88.8-99.9%. Ammonia reduction did not occur in anaerobic digesters. Anaerobic reactors increased alkalinity about 3.2-4.8% in the 1st digester and 1.8-7.9% in the 2nd digester. In activated sludge unit, alkalinity and ammonia removal efficiency were 49-60% and 48.6-64.7%, respectively. Methane production rate was in the range of 0.02-0.04, 0.04-0.07, and 0.02-0.04 L/g CODrem for the 1st digester, the 2nd digester, and combination of both digesters, respectively; the methane content of the biogas varied between 60% and 63%. © 2010 Elsevier Ltd.

Khosravi R.,Isfahan University of Technology | Falahati F.,Shiraz University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

The semileptonic Bs→ανν̄, and B s→αl+l-, l=τ, μ, e transitions are investigated in the framework of the three-point QCD sum rules in the standard model. These rare decays take place at loop level by electroweak penguin and weak box diagrams in the standard model via the flavor-changing neutral current transition of b→s. Considering the quark condensate contributions, the relevant form factors as well as the branching fractions of these transitions are calculated. The longitudinal lepton polarization and forward-backward asymmetries are also investigated. © 2013 American Physical Society.

Farajpour A.,Isfahan University of Technology | Shahidi A.R.,Isfahan University of Technology | Mohammadi M.,Isfahan University of Technology | Mahzoon M.,Shiraz University
Composite Structures | Year: 2012

Buckling response of orthotropic single layered graphene sheet (SLGS) is investigated using the nonlocal elasticity theory. Two opposite edges of the plate are subjected to linearly varying normal stresses. Small scale effects are taken into consideration. The nonlocal theory of Eringen and the equilibrium equations of a rectangular plate are employed to derive the governing equations. Differential quadrature method (DQM) has been used to solve the governing equations for various boundary conditions. To verify the accuracy of the present results, a power series (PS) solution is also developed. DQM results are successfully verified with those of the PS method. It is shown that the nonlocal effects play a prominent role in the stability behavior of orthotropic nanoplates. Furthermore, for the case of pure in-plane bending, the nonlocal effects are relatively more than other cases (other load factors) and the difference in the effect of small scale between this case and other cases is significant even for larger lengths. © 2012 Elsevier Ltd.

Sarlak H.,Isfahan University of Technology | Atapour M.,Isfahan University of Technology | Esmailzadeh M.,Shiraz University
Materials and Design | Year: 2015

The corrosion behavior of a friction stir welded lean duplex stainless steel was investigated in H2SO4 solution. Friction stir welding (FSW) was performed at a constant rotation speed of 800rpm and welding speeds of 50, 100 and 150mmmin-1 using WC-based tool. The corrosion evaluations were carried out through open circuit potential measurements, potentiodynamic polarization and immersion tests. Also, the semiconducting properties of the passive films were studied by Mott-Schottky analysis. It was demonstrated that increasing the welding speed decreased the grain size of the α and γ phases and improved the corrosion resistance of the stir zone (SZ). According to Mott-Schottky analysis, it was found that the calculated donor density decreased with decreasing the grain size of the stir zone. These observations were consisted with the results of the immersion tests, evidencing that the passivation behavior of the stir zone enhanced with decreasing the grain size. © 2014 Elsevier Ltd.

Karami Horastani Z.,Isfahan University of Technology | Sayedi S.M.,Isfahan University of Technology | Sheikhi M.H.,Shiraz University
Sensors and Actuators, B: Chemical | Year: 2014

The effect of single wall carbon nanotube (SWCNT) additive on electrical conductivity and methane sensitivity of SnO2 gas sensor has been investigated. Sensors were prepared through powder pressing procedure and the morphology and microstructure of the materials were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The electrical resistivity and methane sensitivity of the samples were examined in the temperature interval of 100 to 450 °C. Results show that in the air ambient the electrical resistivity of the samples increases with the increase of SWCNT concentration. Also, comparative results show that by increasing of SWCNT concentration up to 1.2 wt%, the methane sensitivity of the samples increases, and after that by further increase of SWNT concentration the sensitivity decreases. Based on the SEM images of the sensors, and also the measurement results, three types of resistance, related to metal oxide, SWCNT bundle, and SWCNT/SnO2 grain junction, were realized in the sensors and based on that, a simple electrical circuit model is proposed. Results show that SWCNT/SnO2 grain junction resistance is the main reason for the higher electrical resistivity of the samples with higher SWCNT concentrations. © 2014 Elsevier B.V.

Davar F.,Isfahan University of Technology | Loghman-Estarki M.R.,Islamic Azad University at Kashan
Ceramics International | Year: 2014

Pure monoclinic zirconia nanosheets were successfully prepared by the polymeric complex method. In this approach, zirconium acetylacetonato, Zr(acac)4, citric acid (CA) and ethylene glycol (EG) were used as the source of Zr4+ and the chelating and polymerization agent, respectively. The effects of heat treatment and EG:CA ratios on the structure, morphology and zirconia particle size were investigated. UV-vis spectra illustrated that ZrO2 nanosheets did not show any extrinsic states aroused from surface trap states, defect states, or impurities. © 2014 Elsevier Ltd and Techna Group S.r.l.

Samet H.,Shiraz University | Hamedani Golshan M.E.,Isfahan University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2012

Prediction of electric arc furnace (EAF) reactive power is an appropriate solution to compensate for static VAr compensator delay and improve its performance in flicker reduction. A linear autoregressive moving average (ARMA) can only pull out the linear deterministic (LD) component of EAF reactive power time series. For the prediction to be made through both nonlinear deterministic (ND) and LD components, employing nonlinear models is necessary. However, before developing the nonlinear models for prediction, the necessity of the employing them should be verified by investigating the significance of the ND components in the process. This paper presents a novel approach for wide analysis of nonlinear behavior of EAFs reactive power time series related to eight ac EAFs installed in Mobarakeh steel industry, Isfahan, Iran to answer the question about the importance of their ND components. In the approach, a suitable linear auto regressive moving average (ARMA) model with order (4,4) is used for the time series to extract the residual time series. Then, a number of well established nonlinear analysis techniques such as time delay reconstruction, surrogate data, delay vector variance and recurrence plot methods are applied to the original and residual time series. To describe the nonlinear characteristics of the time series, some new indices are defined. They quantify the significance of the ND component in compare with LD component. © 2011 Elsevier Ltd. All rights reserved.

Alemohammad H.R.,University of Waterloo | Foroozmehr E.,Isfahan University of Technology | Cotten B.S.,University of Waterloo | Toyserkani E.,University of Waterloo
Journal of Lightwave Technology | Year: 2013

Coupled sensitivity of optical fiber sensors to structural strain and temperature has been a long lasting problem for reliable measurements in environments where both parameters are varying. This problem has been a driving force for the employment of methods to compensate the effect of one parameter. In this paper, a packaged dual-parameter optical fiber Bragg grating (FBG) sensor for the simultaneous measurement of structural strain and temperature using a single FBG is presented. The sensor consists of FBGs with on-fiber silver thin films synthesized by a laser direct write method. The new sensor design, fabrication, packaging, and calibration are addressed. A customized test rig and a sensor calibration package are designed and built. The performance of the sensor for the concurrent measurement of strain and temperature is investigated by analyzing the experimental data, and the characteristic curves for the calibration of the sensor are presented. © 1983-2012 IEEE.

Zarei M.,Isfahan University of Technology | Zarei M.,Institute for Research in Fundamental Sciences
European Physical Journal C | Year: 2015

In this work we consider a dipole asymmetry in tensor modes and study the effects of this asymmetry on the angular power spectra of CMB. We derive analytical expressions for the $$C_{l}^{TT}$$ClTT and $$C_{l}^{BB}$$ClBB in the presence of such dipole modulation in tensor modes for $$l<100$$l<100. We also discuss on the amplitude of modulation term and show that the $$C_{l}^{BB}$$ClBB is considerably modified due to this term. © 2015, The Author(s).

Soleimani M.,Isfahan University of Technology | Farhoudi M.,Safir e Sabz Co. Isfahan Science and Technology Town | Christensen J.H.,Copenhagen University
Journal of Hazardous Materials | Year: 2013

Bioremediation is a promising technique for reclamation of oil polluted soils. In this study, six methods for enhancing bioremediation were tested on oil contaminated soils from three refinery areas in Iran (Isfahan, Arak, and Tehran). The methods included bacterial enrichment, planting, and addition of nitrogen and phosphorous, molasses, hydrogen peroxide, and a surfactant (Tween 80). Total petroleum hydrocarbon (TPH) concentrations and CHEMometric analysis of Selected Ion Chromatograms (SIC) termed CHEMSIC method of petroleum biomarkers including terpanes, regular, diaromatic and triaromatic steranes were used for determining the level and type of hydrocarbon contamination. The same methods were used to study oil weathering of 2 to 6 ring polycyclic aromatic compounds (PACs). Results demonstrated that bacterial enrichment and addition of nutrients were most efficient with 50% to 62% removal of TPH. Furthermore, the CHEMSIC results demonstrated that the bacterial enrichment was more efficient in degradation of n-alkanes and low molecular weight PACs as well as alkylated PACs (e.g. C3-C4 naphthalenes, C2 phenanthrenes and C2-C3 dibenzothiophenes), while nutrient addition led to a larger relative removal of isoprenoids (e.g. norpristane, pristane and phytane). It is concluded that the CHEMSIC method is a valuable tool for assessing bioremediation efficiency. © 2013 Elsevier B.V.

Sadeghi S.-H.,Isfahan University of Technology | Peters T.,Washington State University
Irrigation Science | Year: 2013

A new method for calculating total friction head loss in center-pivots with an operational end-gun was developed. The proposed methodology is based on adjusting the previous friction correction factors for center-pivots with end-guns in order to correct their paradoxes and shortcomings. Equations presented in the current work are developed for center-pivots with a finite number of outlets along the lateral and constant outlet spacing and discharge as well as constant discharge and variable spacing. The proposed formulas depend on the number of outlets along the supply pipeline, the exponent of velocity term in the friction formula used and the distance that water is jetted by the end-gun. All equations reduce to the well-established equations for the friction correction factor when the end-gun is turned off. The equations presented here compare well to the stepwise friction calculation method, yet correct slight errors in the way that these friction correction factors were calculated in the past. © 2011 Springer-Verlag.

Maleknejad A.,Institute for Research in Fundamental Sciences | Zarei M.,Institute for Research in Fundamental Sciences | Zarei M.,Isfahan University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We present an exhaustive analysis on the background inflationary solutions of the chromo-natural model. We show that starting from an arbitrary axion field value χ0 (0,fπ), it is possible to have slow-roll inflation with enough number of e-folds and determine the allowed region of the parameters corresponding to each χ0 value. Having the available parameter space, we then study the behavior of the solutions with respect to the initial value of the axion field. © 2013 American Physical Society.

Loran F.,Isfahan University of Technology | Sheikh-Jabbari M.M.,Institute for Research in Fundamental Sciences
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2010

Banados-Teitelboim-Zanelli (BTZ) black holes are constructed by orbifolding AdS3 geometry by boost transformations of its O(2,2) isometry group. Here we construct a new class of solutions to AdS3 Einstein gravity, orientifolded BTZ or O-BTZ for short, which in general, besides the usual BTZ orbifolding, involve orbifolding (orientifolding) by a Z2 part of O(2,2) isometry group. This Z2 is chosen such that it changes the orientation on AdS3 while keeping the orientation on its 2D conformal boundary. O-BTZ solutions exhaust all un-oriented AdS3 black hole solutions, as BTZ black holes constitute all oriented AdS3 black holes. O-BTZ, similarly to BTZ black holes, are stationary, axisymmetric asymptotically AdS3 geometries with two asymptotic charges, mass and angular momentum. © 2010 Elsevier B.V.

Loran F.,Isfahan University of Technology | Sheikh-Jabbari M.M.,Institute for Research in Fundamental Sciences | Vincon M.,Institute for Research in Fundamental Sciences
Journal of High Energy Physics | Year: 2011

As shown by Cardy [1], modular invariance of the partition function of a given unitary non-singular 2d CFT with left and right central charges cl and cr, implies that the density of states in a microcanonical ensemble, at excitations δ and δ and in the saddle point approximation, is ρ0(δ, δmacr;;cl, cr) = cl exp(2π√cLδ/6) · cr exp(2 π √crδ̄/6). In this paper, we extend Cardy's analysis and show that in the saddle point approximation and up to contributions which are exponentially suppressed compared to the leading Cardy's result, the density of states takes the form ρ(δ, δ̄; cl, c r) = f (clδ) f (crδ̄) ρ0(δ, δ̄; cl, cr), for a function f(x) which we specify. In particular, we show that (i) ρ(δ, δ̄; cl, cr) is the product of contributions of left and right movers and hence, to this approximation, the partition function of any modular invariant, non-singular unitary 2d CFT is holomorphically factorizable and (ii) ρ(δ, δ̄; cl, c r)/(clcr) is only a function of c Lδ and crδ̄. In addition, treating ρ(δ, δ̄; cl, cr) as the density of states of a microcanonical ensemble, we compute the entropy of the system in the canonical counterpart and show that the function f(x) is such that the canonical entropy, up to exponentially suppressed contributions, is simply given by the Cardy's result lnρ0(δ, δ̄; c l, cr). © SISSA 2011.

Bevrani H.,University of Kurdistan | Habibi F.,University of Kurdistan | Babahajyani P.,Isfahan University of Technology | Watanabe M.,Kyushu Institute of Technology | Mitani Y.,Kyushu Institute of Technology
IEEE Transactions on Smart Grid | Year: 2012

Modern power systems require increased intelligence and flexibility in the control and optimization to ensure the capability of maintaining a generation-load balance, following serious disturbances. This issue is becoming more significant today due to the increasing number of microgrids (MGs). The MGs mostly use renewable energies in electrical power production that are varying naturally. These changes and usual uncertainties in power systems cause the classic controllers to be unable to provide a proper performance over a wide range of operating conditions. In response to this challenge, the present paper addresses a new online intelligent approach by using a combination of the fuzzy logic and the particle swarm optimization (PSO) techniques for optimal tuning of the most popular existing proportional-integral (PI) based frequency controllers in the ac MG systems. The control design methodology is examined on an ac MG case study. The performance of the proposed intelligent control synthesis is compared with the pure fuzzy PI and the Ziegler-Nichols PI control design methods. © 2010-2012 IEEE.

Ghiaci M.,Isfahan University of Technology | Zarghani M.,Isfahan University of Technology | Khojastehnezhad A.,Islamic Azad University at Mashhad | Moeinpour F.,Islamic Azad University at Bandar Abbas

A novel silica functionalized N-heterocyclic carbene palladium complex was found to be a very efficient and reusable catalyst in the Suzuki and Sonogashira coupling reactions. The synthesized catalyst was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption analysis (BET), thermal gravimetric analysis (TGA) and inductively coupled plasma/atomic emission spectroscopy (ICP/AES). The catalysts showed excellent performance in these two reactions including various aryl halide derivatives (except aryl chloride derivatives) with phenylboronic acid and phenylacetylene under green conditions (H2O). Moreover, the catalyst was recycled for several runs without any significant loss of catalytic activity. This journal is © the Partner Organisations 2014.

Emami R.,Institute for Research in Fundamental Sciences | Firouzjahi H.,Institute for Research in Fundamental Sciences | Zarei M.,Institute for Research in Fundamental Sciences | Zarei M.,Isfahan University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

In this work we study models of anisotropic inflation with the generalized nonvacuum initial states for the inflaton field and the gauge field. The effects of the non-Bunch-Davies initial condition on the anisotropic power spectrum and bispectrum are calculated. We show that the non-Bunch-Davies initial state can help to reduce the fine-tuning on the anisotropic power spectrum while reducing the level of anisotropic bispectrum. © 2014 American Physical Society.

Sadegh M.,Isfahan University of Technology | Shirzad A.,Isfahan University of Technology | Shirzad A.,Institute for Research in Fundamental Sciences
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

Constraint analysis of the three-dimensional massive gravity, the so-called new massive gravity, is studied in the Palatini formalism. We show that amongst 6 components of the metric, 2 are dynamical, which is compatible with the existence of one vector massive graviton in the linearized theory (Fierz-Pauli theory). © 2011 American Physical Society.

Fathi M.,Isfahan University of Technology | Martin T.,University of Valladolid | McClements D.J.,University of Massachusetts Amherst
Trends in Food Science and Technology | Year: 2014

Natural and modified polysaccharides are promising vehicles for nano- and micro-encapsulation of active food ingredients. This article reviews the state of the art of carbohydrate-based delivery systems for utilization in the food, pharmaceutical and other industries. Initially, an overview of the different kinds of carbohydrates used to assemble delivery systems is given, including starch, cellulose, pectin, guar gum, chitosan, alginate, dextrin, cyclodextrins, new sources of native gums, and their combinations and chemically modified forms. Their molecular and physicochemical properties, functional performance, and advantages and disadvantages for encapsulation are given. Various approaches for fabrication of carbohydrate-based delivery systems are then discussed, including coacervation, spray drying, electrospinning, electrospray, supercritical fluid, emulsion-diffusion, reverse micelle, emulsion-droplet coalescence, emulsification/solvent evaporation, salting-out, ultrasonication and high pressure homogenization. The biological fate of carbohydrate nanocarriers during digestion, absorption, metabolism and excretion are discussed, and some notes about their bioavailability and potential toxicity are provided. Finally, the functional performances of different carbohydrate-based delivery systems are discussed, and future developments are highlighted. © 2014 Elsevier Ltd.

Mousavi S.R.,Isfahan University of Technology | Babaie M.,Isfahan University of Technology | Montazerian M.,University of London
Journal of Heuristics | Year: 2012

The Far From Most Strings Problem (FFMSP) asks for a string that is far from as many as possible of a given set of strings. All the input and the output strings are of the same length, and two strings are far if their Hamming distance is greater than or equal to a given threshold. FFMSP belongs to the class of sequence consensus problems which have applications in molecular biology, amongst others. FFMSP is NP-hard. It does not admit a constant-ratio approximation either, unless P = NP. In the last few years, heuristic and metaheuristic algorithms have been proposed for the problem, which use local search and require a heuristic, also called an evaluation function, to evaluate candidate solutions during local search. The heuristic function used, for this purpose, in these algorithms is the problem's objective function. However, since many candidate solutions can be of the same objective value, the resulting search landscape includes many points which correspond to local maxima. In this paper, we devise a new heuristic function to evaluate candidate solutions. We then incorporate the proposed heuristic function within a Greedy Randomized Adaptive Search Procedure (GRASP), a metaheuristic originally proposed for the problem by Festa. The resulting algorithm outperforms state-of-the-art with respect to solution quality, in some cases by orders of magnitude, on both random and real data in our experiments. The results indicate that the number of local optima is considerably reduced using the proposed heuristic. © Springer Science+Business Media, LLC 2011.

News Article | December 15, 2015
Site: www.nanotech-now.com

Ashiri R.,Sharif University of Technology | Ashiri R.,Isfahan University of Technology | Ashiri R.,Islamic Azad University at Dezful
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2014

In the present work, an improved method is developed for preparing highly pure ultrathin barium titanate nanostructured films with desired structural and morphological characteristics. In contrast to other approaches, our method can be carried out at a relatively lower temperature to obtain barium titanate ultrathin films free from secondary phases, impurities, and cracks. To reach an in-depth understanding of scientific basis of the proposed process, and in order to disclose the mechanism of formation and growth of barium titanate ultrathin film, in-detail analysis is carried out using XRD, SEM, FE-SEM, and AFM techniques aided by theoretical calculations. The effects of calcining temperature on the nanoscale structure development, phase transition, morphology evolution, and growth mechanism of the ultrathin barium titanate nanostructured films are studied. XRD results indicate that the reaction leading to the formation of the barium titanate initiates at about 873 K (600 °C) and completes at about 1073 K (800 °C). Moreover, secondary phases are not detected in the XRD patterns of the ultrathin films which this observation ensures the phase purity of the ultrathin films. The results show that the ultrathin films are nanothickness and nanostructured leading to the enhancement of rate of diffusion by activating short-circuit diffusion mechanisms. The high rate of the diffusion enhances the rate of the formation of barium titanate and also prevents from the formation of the secondary phases in the final products. SEM and AFM results indicate that the deposited ultrathin films are crack-free exhibiting a dense nanogranular structure. The results indicate that the root-mean square (RMS) roughness of the ultrathin films is in the range of 1.66 to 6.71 nm indicating the surface of the ultrathin films is smooth. RMS roughness also increases with an increase in the calcining temperature which this observation seems to be related to the grain growth process. Finally, based on the observed results, the mechanism of the formation and growth of the ultrathin barium titanate nanostructured films is deeply disclosed. © The Minerals, Metals & Materials Society and ASM International 2014.

Sanati A.L.,Kerman Graduate University of Technology | Karimi-Maleh H.,Kerman Graduate University of Technology | Badiei A.,University of Tehran | Biparva P.,Sari University of Agricultural Sciences and Natural Resources | Ensafi A.A.,Isfahan University of Technology
Materials Science and Engineering C | Year: 2014

A novel ionic liquid modified NiO/CNTs carbon paste electrode (IL/NiO/CNTCPE) had been fabricated by using hydrophilic ionic liquid 1-methyl-3-butylimidazolium chloride [MBIDZ]Cl as a binder. The cyclic voltammogram showed an irreversible oxidation peak at 0.61 V (vs. Ag/AgCl sat), which corresponded to the oxidation of morphine. Compared to common carbon paste electrode, the electrochemical response was greatly improved for morphine electrooxidation. This modified electrode exhibited a potent and persistent electron mediating behavior followed by well separated oxidation peaks of morphine and diclofenac. Detection limit of morphine was found to be 0.01 μM using square wave voltammetry (SWV) method. The proposed sensor was successfully applied for the determination of morphine in human urine and pharmaceutical samples. © 2013 Elsevier B.V.

Journal of Mechanical Science and Technology | Year: 2013

This paper is concerned with a quasi-3D design method for the radial and axial diffusers of a centrifugal compressor on the meridional plane. The method integrates a novel inverse design algorithm, called ball-spine algorithm (BSA), and a quasi-3D analysis code. The Euler equation is solved on the meridional plane for a numerical domain, of which unknown boundaries (hub and shroud) are iteratively modified under the BSA until a prescribed pressure distribution is reached. In BSA, unknown walls are composed of a set of virtual balls that move freely along specified directions called spines. The difference between target and current pressure distributions causes the flexible boundary to deform at each modification step. In validating the quasi-3D analysis code, a full 3D Navier-Stokes code is used to analyze the existing and designed compressors numerically. Comparison of the quasi-3D analysis results with full 3D analysis results shows viable agreement. The 3D numerical analysis of the current compressor shows a huge total pressure loss on the 90° bend between the radial and axial diffusers. Geometric modification of the meridional plane causes the efficiency to improve by about 10%. © 2013 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

Bayareh M.,Islamic Azad University | Mortazavi S.,Isfahan University of Technology
Advances in Engineering Software | Year: 2011

The collision of two equal-size drops in an immiscible phase undergoing a shear flow is simulated over a range of viscosity ratios (λ) and different geometries. The full Navier-Stokes equations are solved by a finite difference/front tracking method. Based on experimental data, different cases were simulated by changing the offset, size of drops, and viscosity ratio. The distance between drop centres along the velocity gradient direction (z) was measured as a function of time. It was found that Δz increases after collision and reaches a new steady-state value after separation. The values of Δz, during the interaction, increases with increasing initial offset. Our results show that the time of approaching of drops at low initial offset is greater than the other cases, but the maximum deformation is the same for equal drop sizes. The deformation decreases with decreasing the size of drops. As the initial offset increases, the drops rotate more quickly and the available contact time for film drainage decreases. We found that the trajectories of drops in the approaching stage are different owing to the different initial offsets. However, after the drops come into contact, it observed that they follow the same trajectories. As λ increases, the drops rotate more slowly, and the point at which the drops separate is delayed. The trajectories of drops become more symmetric with the increased λ. © 2011 Elsevier Ltd. All rights reserved.

Fahimpour V.,Sharif University of Technology | Sadrnezhaad S.K.,Sharif University of Technology | Karimzadeh F.,Isfahan University of Technology
Materials and Design | Year: 2012

Wrought aluminum sheets with thickness of 13. mm were square butt-welded by friction stir welding (FSW) and gas tungsten arc welding (GTAW) methods. Corrosion behavior of the welding zone was probed by Tafel polarization curve. Optical metallography (OM) and scanning electron microscopy together with energy dispersive spectroscopy (SEM-EDS) were used to determine morphology and semi-quantitative analysis of the welded zone. FSW resulted in equiaxed grains of about 1-2 μm, while GTAW caused dendritic structure of the welded region. Resistance to corrosion was greater for the FSW grains than the GTAW structure. In both cases, susceptibility to corrosion attack was greater in the welded region than the base metal section. T6 heat treatment resulted in shifting of the corrosion potential towards bigger positive values. This effect was stronger in the welded regions than the base metal section. © 2012 Elsevier Ltd.

Madhkhan M.,Isfahan University of Technology | Azizkhani R.,Isfahan University of Technology | Torki Harchegani M.E.,Sharif University of Technology
Construction and Building Materials | Year: 2012

Effects of pozzolans and fibers on mechanical properties of RCC are addressed. The mechanical properties were evaluated using optimum moisture with different amounts of pozzolans, steel and polypropylene fibers. Using pozzolans, maximum increase in compressive strength was observed to occur between 28 and 90 days of age, rupture modulus was found to decrease; but toughness indices did not change considerably. The influence of steel fibers on compressive strength was often more significant than that of PP fibers; but neither steel nor PP fibers did contribute to increase in the rupture modulus independently from pozzolans. Also, the toughness indices increased when steel fibers were used. © 2011 Elsevier Ltd. All rights reserved.

Khoeini D.,Isfahan University of Technology | Akhavan-Behabadi M.A.,University of Tehran | Saboonchi A.,Isfahan University of Technology
International Communications in Heat and Mass Transfer | Year: 2012

This experimental study is performed to investigate condensation heat transfer coefficient of R-134a flow inside corrugated tube with different inclinations. Different inclinations of test condenser ranging from -90 ° to +90 ° and various flow mass velocities in the range of 87 to 253 [kg/m 2s] are considered in this study. Data analysis showed that change in the tube inclination had a significant effect on condensation heat transfer behavior. At low mass velocities, and low vapor qualities, the highest condensation heat transfer coefficient was obtained for α=+30 ° which was 1.41 times greater than the least one obtained for α=-90 °. The results also showed that at all mass velocities, the highest average heat transfer coefficients were achieved for α=+30 °. Based on the experimental results, a new empirical correlation is proposed to predict the condensation heat transfer coefficient of R134a flow in corrugated tubes with different inclinations. © 2011 Elsevier Ltd.

Chachi J.,Semnan University | Taheri S.M.,University of Tehran | Taheri S.M.,Isfahan University of Technology
International Journal of Intelligent Systems | Year: 2013

Two general classes of similarity measures between intuitionistic fuzzy sets (hereafter IFSs) are introduced. Some properties of these measures are investigated with respect to some well-known reasonable axioms. It is shown that several similarity measures between IFSs introduced elsewhere can be expressed by these definitions as special cases. Some illustrative and practical examples from the areas of pattern recognition, fuzzy clustering analysis, and decision making will be used to investigate the performance of the proposed measures with respect to some common measures. The results indicate that these measures can provide a useful way for measuring the degree of similarity between IFSs and that the proposed approach performs well in pattern recognition, fuzzy clustering, and decision making. © 2013 Wiley Periodicals, Inc.

Geranian H.,Birjand University | Mokhtari A.R.,Isfahan University of Technology | Cohen D.R.,University of New South Wales
Science of the Total Environment | Year: 2013

Mining activities may contribute significant amounts of metals to surrounding soils. Assessing the potential effects and extent of metal contamination requires the differentiation between geogenic and additional anthropogenic sources. This study compares the use of conventional probability plots with two forms of fractal analysis (number-size and concentration-area) to separate geochemical populations of ore-related elements in agricultural area soils adjacent to Pb-Zn mining operations in the Irankuh Mountains, central Iran. The two general approaches deliver similar spatial groupings of univariate geochemical populations, but the fractal methods provide more distinct separation between populations and require less data manipulation and modeling than the probability plots. The concentration-area fractal approach was more effective than the number-size fractal and probability plotting methods at separating sub-populations within the samples affected by contamination from the mining operations. There is a general lack of association between major elements and ore-related metals in the soils. The background populations display higher relative variation in the major elements than the ore-related metals whereas near the mining operations there is far greater relative variation in the ore-related metals. The extent of the transport of contaminants away from the mine site is partly a function of the greater dispersion of Zn compared with Pb and As, however, the patterns indicate dispersion of contaminants from the mine site is via dust and not surface/groundwater. A combination of geochemical and graphical assessment, with different methods of threshold determination, is shown to be effective in separating geogenic and anthropogenic geochemical patterns. © 2013 Elsevier B.V.

Talebi H.,Bauhaus University Weimar | Silani M.,Isfahan University of Technology | Bordas S.P.A.,University of Cardiff | Kerfriden P.,University of Cardiff | Rabczuk T.,Korea University
Computational Mechanics | Year: 2014

We present an open-source software framework called PERMIX for multiscale modeling and simulation of fracture in solids. The framework is an object oriented opensource effort written primarily in Fortran 2003 standard with Fortran/C++ interfaces to a number of other libraries such as LAMMPS, ABAQUS, LS-DYNA and GMSH. Fracture on the continuum level is modeled by the extended finite element method (XFEM). Using several novel or state of the art methods, the piece software handles semi-concurrent multiscale methods as well as concurrent multiscale methods for fracture, coupling two continuum domains or atomistic domains to continuum domains, respectively. The efficiency of our open-source software is shown through several simulations including a 3D crack modeling in clay nanocomposites, a semi-concurrent FE-FE coupling, a 3D Arlequin multiscale example and an MD-XFEM coupling for dynamic crack propagation. © Springer-Verlag Berlin Heidelberg 2013.

ISIJ International | Year: 2013

The hot deformation behavior of a 17-4 PH stainless steel was investigated by compression tests. The typical single-peak dynamic recrystalization (DRX) behavior and also a transition state between single and multiple peak (cyclic) behaviors were seen in the resultant flow curves. The application of constitutive equations for determination of hot working constants was critically discussed. As a result, the deformation activation energy and the stress multiplier in the hyperbolic sine equation were determined as 337 kJ/mol and 0.011, respectively. The Zener-Hollomon parameter (Z) exponents for peak stress and peak strain based on the power relationships were determined as 0.18 and 0.11, respectively. The normalized critical stress and strain for initiation of DRX were respectively found to be 0.89 and 0.47. The prior austenite grain boundaries (PAGB) were revealed by electrolytic etching of the martensite in order to study the microstructure of hot deformed samples. Significant grain refinement occurred as a result of necklace DRX mechanism. The average dynamically recrystallized grain size was related to Z and peak stress by power equations with exponents of -0.25 and -1.24, respectively. A DRX map was developed to show the effect of deformation conditions on the occurrence of DRX and on the final grain size. © 2013 ISIJ.

Nejati A.,Isfahan University of Technology | Shahrokhi M.,Sharif University of Technology | Mehrabani A.,Isfahan University of Technology
Journal of Process Control | Year: 2012

In this work performances of adaptive backstepping controller (BSC) and globally linearizing controller (GLC) are compared for pH control. First, based on the system full order model a GLC has been designed and it has been shown that this controller is identical to BSC proposed in the literature. Next in order to avoid state estimator design, BSC and GLC are designed based on pH reduced order model and their identities have been established. Through computer simulations, it has been shown that the performance of non-adaptive GLC designed based on reduced order model is better than that of adaptive BSC designed based on pH full order model which requires state measurement for implementation. Finally, the effectiveness of GLC designed based on the reduced order model in load rejection and set-point tracking has been demonstrated through simulation and experimental studies. © 2011 Elsevier Ltd. All Rights Reserved.

Shokouhmand H.,University of Tehran | Meghdadi Isfahani A.H.,University of Tehran | Shirani E.,Isfahan University of Technology
International Communications in Heat and Mass Transfer | Year: 2010

Invoking the velocity slip and temperature jump, numerical simulation of Darcy-Brinkman-Forchheimer flow model and forced convection in a circular micro/nano channel filled with porous media are presented. Relating the viscosity to the local Knudsen number, Kn, a generalized diffusion coefficient is obtained in such a way that it can model wide range of Kn regimes of flow. The effect of Kn and Darcy coefficient on velocity and temperature distribution is described. It is shown that despite of the fact that in most of previous researches it is assumed that Kn is constant along the channel, the variations of Kn due to the pressure variations, have considerable effects on heat transfer and temperature distribution across the channel cross section. © 2010 Elsevier Ltd.

Jamshidian M.,Isfahan University of Technology | Jamshidian M.,Bauhaus University Weimar | Rabczuk T.,Bauhaus University Weimar | Rabczuk T.,Korea University
Journal of Computational Physics | Year: 2014

We establish the correlation between the diffuse interface and sharp interface descriptions for stressed grain boundary migration by presenting analytical solutions for stressed migration of a circular grain boundary in a bicrystalline phase field domain. The validity and accuracy of the phase field model is investigated by comparing the phase field simulation results against analytical solutions. The phase field model can reproduce precise boundary kinetics and stress evolution provided that a thermodynamically consistent theory and proper expressions for model parameters in terms of physical material properties are employed. Quantitative phase field simulations are then employed to investigate the effect of microstructural length scale on microstructure and texture evolution by stressed grain growth in an elastically deformed polycrystalline aggregate. The simulation results reveal a transitional behaviour from normal to abnormal grain growth by increasing the microstructural length scale. © 2014 Elsevier Inc.

Babaesmailli M.,Isfahan University of Technology | Arbabshirani B.,Isfahan University of Technology | Golmah V.,Islamic Azad University
Expert Systems with Applications | Year: 2012

SWOT analysis is the most important tool for decision makers in strategic management process, because it enables the managers to discover and collect the facts that resulted from internal and external analysis. This analysis can be a good base for strategy formulation, but it is not non-defect. It includes no means of analytically determining the importance of factors or assessing the fit between SWOTS factors and decision alternatives and is mainly based on the qualitative analysis. Many researchers develop different techniques to quantify the SWOT analysis, but these methods are not comprehensive. In this study, we develop a fuzzy method model for quantitative weighing of SWOT strategies. The decision maker's imprecise information is regarded by fuzzy numbers in this model. To consider dependency among factors and sub-factors, we use ANP technique in our research. We demonstrate our model with a case study example and compare results of our research with prior research. © 2011 Elsevier Ltd. All rights reserved.

Mirmohammadi H.S.,Isfahan University of Technology | Eshghi K.,Sharif University of Technology
Computers and Operations Research | Year: 2012

We propose an efficient optimal algorithm for determining the lot sizes for purchase component in Material Requirement Planning (MRP) environments with deterministic time-phased demand and zero lead time. In this model, backlog is not permitted, the unit purchasing price is based on the all-units discount system with single price break point and resale of the excess units is acceptable at the ordering time. The problem is divided into the sub-plans with specific properties by the dynamic programming (DP) method already presented. By modifying the main structure of the DP method, we present a branch-and-bound algorithm to obtain the optimal ordering policy for each sub-plans. Furthermore, we prove some useful fathoming rules to make the branch-and-bound algorithm very efficient. It has also been shown that the worst-case time complexity function of the presented algorithm is O(N4) where N is the number of periods in the planning horizon. Finally, we show the efficiency of the presented algorithm and its fathoming rules by solving some test problems which are randomly generated in various environments. © 2011 Elsevier Ltd. All rights reserved.

Feyzi T.,Islamic Azad University | Safavi S.M.,Isfahan University of Technology
International Journal of Advanced Manufacturing Technology | Year: 2013

In this paper, by joining three non-traditional machining methods - plasma-enhanced machining, cryogenic machining, and ultrasonic vibration assisted machining - a new hybrid machining technique for machining of Inconel 718 is presented. Cryogenic machining reduces the temperature in the cutting zone, and therefore decrease tool wear and increases tool life, while plasma-enhanced machining helps to increase the temperature in the workpiece to make it softer. Also, applying ultrasonic vibrations to the tool helps to improve cutting quality and to prolong tool life by lowering, mainly, the cutting force and improving the dynamic cutting stability. This study experimentally investigates the effect of cutting parameters on cutting performance in the machining of Inconel 718 and compares the results of hybrid machining and conventional machining (CM). It is found that the hybrid method results in better surface finish and improves tool life in hard cutting at low cutting speeds as compared to the CM method. © 2012 Springer-Verlag London Limited.

Ekramian M.,University of Isfahan | Sheikholeslam F.,Isfahan University of Technology | Hosseinnia S.,Islamic Azad University at Najafabad | Yazdanpanah M.J.,University of Tehran
Systems and Control Letters | Year: 2013

The problem of adaptive observer synthesis for Lipschitz nonlinear systems is addressed. In the case of known parameters, the convergence property of state observer is first discussed. Based on a generalized Lipschitz condition, the sufficient conditions to ensure the stability of observer error dynamics are presented in terms of some LMIs. In the case of system dynamics with some unknown parameters, the proposed conditions along with an equality constraint are then employed to guarantee the convergence property of an adaptive state observer. Moreover, an adaptive observer form is derived which can be utilized in designing the reduced order state observer. The simulation results are finally given to exhibit the effectiveness of proposed synthesis approaches in dealing with the practical systems. © 2013 Elsevier B.V. All rights reserved.

Kakaei Lafdani E.,University of Zabol | Moghaddam Nia A.,University of Tehran | Ahmadi A.,Isfahan University of Technology
Journal of Hydrology | Year: 2013

In recent decades, development of artificial intelligence, as a predictor for hydrological phenomenon, has created a great change in predictions. This paper investigates the abilities of Support Vector Machine (SVM) and Artificial Neural Network (ANN) models to predict daily suspended sediment load (SSL) in Doiraj River, located in the west part of Iran. An 11-year data (1994-2004) was applied for predicting SSL. Streamflow and rainfall were used as the model inputs and SSL as the model output. The best input of SVM and ANN models was identified using combination of Gamma Test and Genetic Algorithm (GT-GA). Its results accuracy was compared with the results of conventional correlation coefficient analysis between input and output variables and the best combination was identified. Also, the present study explores Gamma Test to identify the length of the training dataset. Finally, in order to predict SSL, we used the nu-SVR (using the four kernels including linear, polynomial, sigmoid and Radial Basis Function (RBF)) and ANN models (based on BFGS algorithm and Conjugate algorithm). The reliability of SVM and ANN models were evaluated based on performance criteria such as Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Efficiency Index (EI) and correlation coefficient (R2). The obtained results show that ANN models and nu-SVR model using Gamma Test for input selection has better performance than regression combination. Also, the performance BFGS-ANN model were better than other models with RMSE value and R2 equal to 0.34 (ton) and 0.99, respectively. The nu-SVR model with RBF kernel has more capability in prediction of SSL than the other kernels (RMSE=0.96 (ton) and R2=0.98). In addition, the results show M-test can be used as a new method to determine the number of required data for network training for creating a smooth model by nu-SVR and ANN models. © 2012 Elsevier B.V.

Zhiani M.,Isfahan University of Technology | Gharibi H.,University of Tehran | Kakaei K.,Islamic Azad University at Maragheh
Journal of Power Sources | Year: 2012

In this work, a novel nanostructure membrane-electrode assembly (MEA) has been successfully prepared by employing of the polyaniline (PANI) modified anode for DMFC and characterized by SEM and polarization curves in DMFC under different conditions. PANI modified anode made by electro-polymerization of aniline and trifluoromethane sulfonic acid (TFMSA) under galvanostatic conditions on the surface of conventional DMFC's anode. The DMFC test results under steady state conditions indicate that the novel nanostructure MEA exhibits higher performance compared to the conventional MEA in term of maximum power density and resistivity against methanol crossover from the anode side to the cathode side. Maximum power density of 105 mW cm -2 was obtained by new PANI modified anode compared to 75 mW cm -2 by conventional anode in the same conditions. The enhanced performance could be attributed to the higher activity of the PANI modified anode and lower methanol crossover caused by the PANI as barrier in the modified anode. © 2012 Elsevier B.V. All rights reserved.

Naghsh M.M.,Isfahan University of Technology | Soltanalian M.,Uppsala University | Stoica P.,Uppsala University | Modarres-Hashemi M.,Isfahan University of Technology | And 2 more authors.
IEEE Transactions on Signal Processing | Year: 2014

In this paper, we study the joint design of Doppler robust transmit sequence and receive filter to improve the performance of an active sensing system dealing with signal-dependent interference. The signal-to-noise-plus- interference (SINR) of the filter output is considered as the performance measure of the system. The design problem is cast as a max-min optimization problem to robustify the system SINR with respect to the unknown Doppler shifts of the targets. To tackle the design problem, which belongs to a class of NP-hard problems, we devise a novel method (which we call DESIDE) to obtain optimized pairs of transmit sequence and receive filter sharing the desired robustness property. The proposed method is based on a cyclic maximization of SINR expressions with relaxed rank-one constraints, and is followed by a novel synthesis stage. We devise synthesis algorithms to obtain high quality pairs of transmit sequence and receive filter that well approximate the behavior of the optimal SINR (of the relaxed problem) with respect to target Doppler shift. Several numerical examples are provided to analyze the performance obtained by DESIDE. © 1991-2012 IEEE.

Aubry A.,University of Naples Federico II | De Maio A.,University of Naples Federico II | Naghsh M.M.,Isfahan University of Technology
IEEE Journal on Selected Topics in Signal Processing | Year: 2015

Assuming unknown target Doppler shift, we focus on robust joint design of the transmit radar waveform and receive Doppler filter bank in the presence of signal-dependent interference. We consider the worst case signal-to-interference-plus-noise-ratio (SINR) at the output of the filter bank as the figure of merit to optimize under both a similarity and an energy constraint on the transmit signal. Based on a suitable reformulation of the original non-convex max-min optimization problem, we develop an optimization procedure which monotonically improves the worst-case SINR and converges to a stationary point. Each iteration of the algorithm, involves both a convex and a generalized fractional programming problem which can be globally solved via the generalized Dinkelbach's procedure with a polynomial computational complexity. Finally, at the analysis stage, we assess the performance of the new technique versus some counterparts which are available in open literature. © 2015 IEEE.

Habibi Khoshmehr H.,Isfahan University of Technology | Saboonchi A.,Isfahan University of Technology | Shafii M.B.,Sharif University of Technology
International Journal of Thermal Sciences | Year: 2014

It is well established that nanofluids increase or decrease heat transfer in boiling phenomenon. The study acquired Quenching curve and boiling curve in two different surface roughnesses in two fluids: deionized water and the nanofluid MWCNT-water with four different concentrations. The cylinder was made of silver and two surface roughnesses of 129 and 690 nm. It was heated up and soaked in the fluid mentioned above. Temperature was recorded by a drilled to install thermocouple. The experiment was replicated in five times. To calculate the heat transfer quotient, assuming the cylinder to be thermally homogeneous, the Lumped capacity method was applied. The obtained results during quenching process indicated that CHF in nanofluids was less than deionized water. It was also observed that in identical circumstances by repeating the test, the quenching time of the sample in both deionized water and CNT nanofluid decreased. The comparison between the two surface roughnesses revealed that the cylinder with higher surface roughness quenched faster and roughness had a significant effect. The subsequent test was conducted in order to investigate the effect of surfactant dissolved in deionized water. The result indicated that the quenching time increased. © 2013 Elsevier Masson SAS. All rights reserved.

Mehdipourghazi M.,Isfahan University of Technology | Moheb A.,Isfahan University of Technology | Kazemian H.,University of Western Ontario
Microporous and Mesoporous Materials | Year: 2010

The isomorphous substitution of trivalent boron in MFI zeolite structure by applying a novel microwave-assisted "two-stage varying temperature" hydrothermal synthesis method was investigated in this study. The effects of template concentration in the batch composition, aging/stirring time, Si/B ratio and second stage time and temperature on the size, morphology and zeolite formation yield were of interest. At the first stage, nucleation and maturation of zeolite precursors was carried out at 80 °C for 90 min, whereas, the crystallization was done during the second stage at temperature range of 120-175 °C and crystallization time in the range of 30-60 min. The homogeneity and morphology of particles were specified by SEM and the framework vibration spectra and crystallinity of the samples were recorded by FT-IR and XRD test results. Crystallites size and powder recovery varied from 75 to 410 nm and from 26.9% to 100% (w/w), respectively for 120 and 175 °C. Also, crystallinity of MFI phase reached 100% after 60 min crystallization at 140 °C. © 2010 Elsevier Inc. All rights reserved.

Nabavitabatabayi M.,Isfahan University of Technology | Shirani E.,Isfahan University of Technology | Rahimian M.H.,University of Tehran
International Communications in Heat and Mass Transfer | Year: 2011

This work investigates the heat transfer performance in an enclosure including nanofluids with a localized heat source. The velocity field is solved by multiple relaxation time lattice Boltzmann modeling (MRT) which has superior numerical advantages to single relaxation time lattice Boltzmann modeling (SRT); however, heat transfer is simulated separately using SRT-lattice Boltzmann modeling. The hydrodynamics and thermal fields are then coupled together using the Boussinesq approximation. The main objective of this study is to investigate the influence of several pertinent parameters such as Rayleigh number, solid particle volume fraction of nanoparticles, and the geometry as well as location of the localized heat source on the heat transfer performance of nanofluids. The results obtained from lattice Boltzmann modeling clearly indicate that heat transfer augmentation is possible using nano-fluids in comparison to conventional fluids, resulting in the compactness of many industrial devices. © 2010 Elsevier Ltd.

Daemi T.,Isfahan University of Technology | Ebrahimi A.,Isfahan University of Technology | Fotuhi-Firuzabad M.,Sharif University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2012

In this paper, Bayesian Network (BN) is used for reliability assessment of composite power systems with emphasis on the importance of system components. A simple approach is presented to construct the BN associated with a given power system. The approach is based on the capability of the BN to learn from data which makes it possible to be applied to large power systems. The required training data is provided by state sampling using the Monte Carlo simulation. The constructed BN is then used to perform different probabilistic assessments such as ranking the criticality and importance of system components from reliability perspective. The BN is also used to compute the frequency and duration-based indices without time sequential simulation based inferences. The proposed approach provides the possibility of assessing the components importance in view of different load points. The validity and efficiency of the proposed approach is verified by application to the IEEE-Reliability Test System (RTS). © 2012 Elsevier Ltd. All rights reserved.

Ashiri R.,Sharif University of Technology | Ashiri R.,Isfahan University of Technology | Ashiri R.,Islamic Azad University at Dezful
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2012

In the current research, a cost-effective and modified method with a high degree of reproducibility was proposed for the preparation of fine nanoscale and high-purity BaTiO3. In contrast to the other established methods, in this research, carbonate-free BaTiO3 nanopowders were prepared at a lower temperature and in a shorter time span. To reach an in-depth understanding of the scientific basis of the proposed process, an in-detail analysis was carried out for characterization of nanoscale BaTiO3 particles via differential thermal analysis (DTA)/thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques aided by theoretical calculations. The effects of the temperature and time of calcination process on the preparation mechanism, phase transformation, tetragonality, and particle size of BaTiO3 were examined. The reaction that results in the formation of barium titanate initiated at approximately 873 K (600 °C) and seemed to be completed at approximately 1073 K (800 °C) and the polymorphic transformation of cubic to tetragonal initiated at approximately 1173 K (900 °C). It seemed to be completed at approximately 1373 K (1100 °C). According to the reaction mechanism, the formation of BaTiO3 in the initial stage of the interfacial reaction between BaCO3 and TiO2 depends on the BaCO3 decomposition. In the second stage, the BaTiO3 formation is controlled by barium diffusion through the barium titanate layer. In this stage, in contrast to the literature, no secondary phase was detected. The overall characterizations showed the temperature is more effective than time on the progress in process of preparation because of its diffusion-controlled nature. © 2012 The Minerals, Metals & Materials Society and ASM International.

Norouzi N.,University of Tehran | Sadegh-Amalnick M.,University of Tehran | Alinaghiyan M.,Isfahan University of Technology
Measurement: Journal of the International Measurement Confederation | Year: 2015

This paper presents a new mathematical model for measuring and evaluating efficiency of periodic vehicle routing problem (PVRP) that arises in a competitive environment. In the competitive environment several distributors are in competition and arriving to the customers earlier than other competitors affect amount of the sale. The main objectives are to minimize the travel cost and maximize the sale to serve customers before other rival distributors. To measuring the efficiency of the problem an improved particle swarm optimization (IPSO) algorithm is proposed and it compared with an original PSO algorithm in terms of accuracy. Computational results indicate that the improved PSO algorithm performs well in terms of accuracy but the original PSO performs better in computational time. © 2014 Elsevier Ltd. All rights reserved.

Shokouhmand H.,University of Tehran | Jam F.,University of Tehran | Salimpour M.R.,Isfahan University of Technology
International Communications in Heat and Mass Transfer | Year: 2011

In the present work, the effect of porous insert position on enhanced heat transfer in a parallel-plate channel partially filled with a fluid-saturated porous medium was studied. The fully-developed laminar flow and convective heat transfer in the channel were simulated using Lattice Boltzmann Method (LBM). The walls of the channel were subject to a uniform constant temperature. The flow field and thermal performance of the channel were investigated and compared for two configurations: first the porous insert was attached to the channel walls, and second the same amount of the porous material was positioned in the channel core. Comparing the results of the present study to the analytical solutions, a reasonable agreement was observed. The effects of various parameters like Darcy number, porous medium thickness, etc. on the conduit thermal performance were investigated in both channel configurations. It was found that the position of the porous insert has significant influence on the thermal performance of the channel. © 2011 Elsevier Ltd.

Sadeghian H.,University of Isfahan | Villani L.,University of Naples Federico II | Keshmiri M.,Isfahan University of Technology | Siciliano B.,University of Naples Federico II
IEEE Transactions on Robotics | Year: 2014

In this paper, the problem of controlling a robot manipulator in task space, while guaranteeing a compliant behavior for the redundant degrees of freedom, is considered. This issue may arise in the case where the robot experiences an interaction on its body, especially in the presence of humans. The proposed approach guarantees correct task execution and compliance of the robot's body during intentional or accidental interaction in the null space of the main task, simultaneously. The asymptotic stability of the task-space error is ensured by using suitable observers to estimate and compensate the generalized forces acting on the task variables, without using joint torque measurements. Two different controller-observer algorithms are designed, and they are based on the task-space error and on the generalized momentum of the robot, respectively. The performance of the proposed algorithms is verified in experiments on a 7R lightweight robot arm. © 2004-2012 IEEE.

Helmi A.,Isfahan University of Technology | Keshavarzi E.,Isfahan University of Technology
Chemical Physics | Year: 2014

We investigate the effects of concavo-convex walls of a nanopore on the structure and certain thermodynamic properties of confined fluids. Adsorption, solvation force, and capillary condensation in a nanopore formed between two homocentric spheres will be determined using the MFMT. For hard sphere fluids, contact density is greater at the concave wall than it is at the convex wall. In Yukawa fluids, for the thermodynamic state in which the energy effect is the dominant factor, contact density at a concave wall is less than that at a convex wall; this will be reversed for the thermodynamic state in which the entropy effect is the dominant factor. It is possible to find thermodynamic states in which contact densities at concave and convex walls become identical. The adsorption and solvation force of hard sphere fluid show an oscillatory behavior versus H. Capillary condensation is in certain cases observed for Yukawa fluids. © 2014 Elsevier B.V. All rights reserved.

Yazdian N.,Isfahan University of Technology | Karimzadeh F.,Isfahan University of Technology | Tavoosi M.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2010

This work focuses on structural changes of nanostructure 7075 aluminum alloy (Al7075) during isothermal annealing. Nanostructured Al7075 was synthesized by mechanical alloying. The produced structure was isothermally heat-treated at 125-500 °C for 1-3 h under argon atmosphere. The as-milled and annealed powders were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that after 15 h of milling, an Al-Zn-Mg-Cu supersaturated solid solution with a grain size of 35 nm was obtained. By increasing the milling time up to 15 h, the MgZn phase precipitated from supersaturated solid solution. Large variety of precipitants including MgZn, MgZn2 (at temperatures range between 200 and 400 °C), AlCuMg and Al2Cu (at temperatures range between 300 and 500 °C) were formed during isothermal annealing. © 2010 Elsevier B.V. All rights reserved.

Mohammad Sharifi E.,Isfahan University of Technology | Karimzadeh F.,Isfahan University of Technology | Enayati M.H.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2010

Al2O3-TiC nanocomposite was synthesized by ball milling of aluminum, titanium oxide and graphite powder mixtures. Effect of the milling time and heat treatment temperatures were investigated. The structural evolution of powder particles after different milling times was studied by X-ray diffractometry and scanning electron microscopy. The results showed that after 40 h of ball milling the Al/TiO2/C reacted with a self-propagating combustion mode producing Al2O3-TiC nanocomposite. In final stage of milling, alumina and titanium carbide crystallite sizes were less than 10 nm. After annealing at 900 °C for 1 h, Al2O3 and TiC crystallite sizes remained constant, however increasing annealing temperature to 1200 °C increased Al2O3 and TiC crystallite size to 65 and 30 nm, respectively. No phase change was observed after annealing of the synthesized Al2O3-TiC powder. © 2009.

Farzaneh M.A.,Isfahan University of Technology | Raeissi K.,Isfahan University of Technology | Golozar M.A.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2010

The nanostructure Ni-Co-W alloy coatings were electrodeposited onto a copper substrate using different applied current densities, in a modified Watts-type bath. The coatings were single-phase solid solutions with average grain sizes about 6-11 nm, calculated from X-ray diffraction patterns using the Scherrer equation. EIS results showed that the adsorption and reduction of W-containing ion complexes dominated at all applied current densities. However, the diffusion of the ion complexes reached to a limitation at higher current densities. The W and Co contents of the coatings decreased with an increase in the applied current density. A homogeneous nodular surface morphology was obtained at all current densities. The coatings produced at low current densities, containing higher amount of alloying elements, showed lower corrosion resistance. © 2009 Elsevier B.V. All rights reserved.

Materials and Design | Year: 2010

Both the critical stress and strain for initiation of dynamic recrystallization (DRX) were determined using: (1) the strain hardening rate versus stress curve, (2) the natural logarithm of strain hardening rate versus strain curve, and (3) the constitutive equations. In order to perform these analyses, the behavior of a 17-4 PH stainless steel during hot compression test was investigated at temperatures of 950-1150 °C and strain rates of 0.001-10 s-1. The first and second methods were found to be the best ones for determining the critical stress and strain, respectively. The Cingara constitutive equation was also used to model the flow curves up to the peak point and subsequently was used for predicting the critical strain. In summary, for 17-4 PH stainless steel, the DRX was found to start when the normalized stress and strain reach to the values of 0.89 and 0.47, respectively. © 2009 Elsevier Ltd. All rights reserved.

Tavangarian F.,Isfahan University of Technology | Emadi R.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2010

Synthesis of nanocrystalline magnesium aluminate spinel (MgAl2O4) by mechanical activation of a powder mixture containing Al2O3 and MgCO3 with subsequent annealing was investigated. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques were utilized to characterize the as-milled and annealed samples. Results showed that pure nanocrystalline spinel could be fabricated completely by 5 h of mechanical activation with subsequent annealing at 1200 °C for 1 h with a crystallite size of about 45 nm. Further milling had no significant effects on structure or phase composition of spinel phase after subsequent annealing. The nanocrystalline spinel powder obtained after 60 h of milling and subsequent annealing at 1200 °C for 1 h had a crystallite size of about 25 nm according to Williamson-Hall approach and particle sizes smaller than 200 nm. Enhanced mechanical properties were observed in samples prepared from the powder mixture and milled for a longer period. © 2009 Elsevier B.V. All rights reserved.

Arezoomand M.,Islamic Azad University at Majlesi | Taeri B.,Isfahan University of Technology
Match | Year: 2013

In this paper the first and the second Zagreb indices of generalized hierarchical product of graphs, which is generalization of standard hierarchical and Cartesian product of graphs, is computed. As a consequence we compute the Zagreb indices of some chemical graphs.

Moradi-Shahrbabak Z.,Isfahan University of Technology | Tabesh A.,Isfahan University of Technology | Yousefi G.R.,Isfahan University of Technology
IEEE Transactions on Industrial Electronics | Year: 2014

This paper presents an algorithm for the economical design of a utility-scale photovoltaic (PV) power plant via compromising between the cost of energy and the availability of the plant. The algorithm inputs are the plant peak power and the price of inverters with respect to their power ratings. The outputs are the optimum inverter ratings and the interconnection topology of PV panels. This paper introduces the effective levelized cost of energy (LCOE) (ELCOE) index as the core of the proposed design algorithm. ELCOE is an improved index based on the conventional LCOE that includes the availability of a power plant in economical assessments. The conventional LCOE index determines centralized topology (e.g., 1-MW inverter for a 1-MW PV power plant) for minimizing the energy generation cost, whereas based on ELCOE, a multistring topology (e.g., a 1-MW PV plant consists of fifty 20-kW inverters) despite of higher investment cost becomes the economically winning topology. Given the price of commercially available PV inverters at present, the case studies in this paper show that, for 0.1-100-MW PV power plants, the economical ratings of inverters range from 8 to 100 kW. The recently installed PV power plants confirm the feasibility of the calculations based on the suggested algorithm. © 2013 IEEE.

Mirramezani M.,Isfahan University of Technology | Mirdamadi H.R.,Isfahan University of Technology | Ghayour M.,Isfahan University of Technology
Computer Methods in Applied Mechanics and Engineering | Year: 2014

In this article, the nonlocal but linear vibrations of carbon nano-tubular shells are analyzed subjected to both internal and external flows. This analysis is addressed for both separate flows as well as concurrent flows by considering slip condition. We observe that both nonlocal parameter and Kn could decrease the eigen-frequency and critical velocity of the first-mode divergence. It is observed that the existence of quiescent fluid does not impress the value of divergence velocity. Nonetheless, the frequencies are declined substantially. Besides, we perceive that CNT subjected to both internal and external flows loses its stability drastically sooner as compared with that subjected to each flow separately. Furthermore, it is observed that an increase in the value of mass density of the external flow results in a greater decrease in the eigen-frequencies as well as the divergence velocity. © 2014 Elsevier B.V.

Nikfarjam F.,University of Yazd | Sohankar A.,Isfahan University of Technology
Acta Mechanica | Year: 2013

The low-Reynolds numbers free-stream flow of power-law fluids and forced convection heat transfer around a square cylinder and two square cylinders in a tandem arrangement are numerically investigated. In the single cylinder case, the power-law index and Reynolds numbers range from n = 0.7-1.4 and Re = 60-160 at Pr = 0.7. In the tandem case, the spacing between the cylinders is four widths of each cylinder side and the power-law index ranges from 0.7 to 1.6 at Re = 40, 100, 160 and Pr = 0.7. All simulations are performed with a finite volume code based on the SIMPLEC algorithm and a non-staggered grid. The effect of spatial resolution on the results is also studied for a single cylinder and tandem cylinders. The mean and instantaneous streamlines, vorticity and temperature contours, the global quantities such as pressure and friction coefficients, the rms lift and drag coefficients, Strouhal and Nusselt numbers are determined and discussed for various power-law indexes at different Reynolds numbers. A comparison between the results of the single cylinder case and the two cylinders in tandem arrangement shows that there are relatively similar results for the single cylinder and the upstream cylinder of the tandem case. © Springer-Verlag Wien 2013.

Sharifi E.M.,Isfahan University of Technology | Karimzadeh F.,Isfahan University of Technology
Wear | Year: 2011

In the present article, the dry sliding wear behavior of aluminum matrix nanocomposites containing various amounts of Al2O3-AlB12 (5, 10 and 15wt.%) particles was investigated. All specimens were prepared by mechanical milling of Al and Al2O3-AlB12 nanocomposite powders, followed by hot pressing. Wear tests were carried out at room temperature in air using the pin-on-disc machine under variable normal loads. The counterface was an AISI 52100 steel pin with the hardness of 780HV. Friction values and wear mechanisms are discussed based on scanning electron microscopy observations and energy-dispersive spectroscopy analysis of wear tracks and wear debris morphology. The average hardness of the nanocomposite increased with the percentage of added Al2O3-AlB12 particles. Results confirmed that worn surfaces of all nanocomposite samples tested under variable loads, covered by a mechanically mixed layer (MML), contained a considerable amount of oxygen and iron. The results indicated that higher Al2O3-AlB12 content in the nanocomposite promotes stronger material transfer from the counterface and oxidation reaction and, consequently, causes formation of protective MML with higher amount of oxide compounds content on the worn surface of nanocomposite, leading to the lower wear rate. After a certain sliding distance, the friction coefficient of the nanocomposites reduced and tended to attain a constant value. The formation of MML on the worn surface which can act as a lubricant seems to be responsible for this trend. © 2011 Elsevier B.V.

Shahriari-Kahkeshi M.,Isfahan University of Technology | Sheikholeslam F.,Isfahan University of Technology
IET Control Theory and Applications | Year: 2014

Fault is an undesired and unexpected event that changes the system behaviour resulting in performance degradation or even instability, so how to detect and diagnose fault become a great deal in engineering community. In this study, an adaptive fuzzy wavelet network-based fault detection and diagnosis (AFWN-FDD) scheme is proposed for non-linear systems subject to unstructured uncertainty. The proposed scheme is composed of a diagnostic estimator and an adaptive fuzzy wavelet network (AFWN). Diagnostic estimator is designed for residual generation and fault detection and AFWN based on multiresolution analysis of wavelet transform and fuzzy concept is proposed to approximate the model of fault. Learning algorithm of the proposed AFWN-FDD scheme is derived in the Lyapunov stability sense. The proposed scheme can simultaneously detect and estimate multiple incipient and abrupt faults in the presence of uncertainty. Stability analysis for the presented fault detection and diagnosis (FDD) scheme is provided. Furthermore, an extension of the proposed scheme for a class of non-linear systems with unmeasured states is presented. The efficiency and performance of the proposed scheme is evaluated through simulations that are performed for two well-known case studies. Comparison results highlight the superiority and capability of the proposed scheme. © 2014 The Institution of Engineering and Technology.

Verdian M.M.,Isfahan University of Technology
Surface Engineering | Year: 2011

Ni-3Al and Ni-3Ti alloys were deposited on AISI 1045 steel substrate using air plasma spraying process. In this regard, mechanically alloyed feedstock powders were used. Open circuit potential EOCP measurements and Tafel polarisation tests were carried out to study corrosion behaviour of the coatings in 3?5%NaCl solution. These tests indicated that the corrosion performance of the Ni-3Ti coating is better than that of the Ni-3Al coating. The corrosion current densities were three times lower in the Ni-3Ti coating than in Ni-3Al coating. In addition, Ni-3Ti coating showed better passive behaviour than Ni-3Al coating. After 10 h of immersion, the surface of Ni-3Al coating became pitted, and rust spots appeared on the surface. In contrast, there was no rusting and pitting on the surface of Ni-3Ti coating even after 10 h of immersion. © 2011 Institute of Materials, Minerals and Mining.

Shafiei N.,Islamic Azad University at Najafabad | Pahlevaninezhad M.,Queen's University | Farzanehfard H.,Isfahan University of Technology | Bakhshai A.,Queen's University | Jain P.,Queen's University
IEEE Transactions on Power Electronics | Year: 2013

Power transformer is one of the most complex parts of power converters. The complicated behavior of the transformer is usually neglected in the power converter analysis and a simple model is mostly used to analyze the converter. This paper presents a precise analysis of a fifth-order resonant converter which has incorporated the resonant circuit into the transformer. The derived model, which is based on the accurate model of the power transformer, can fully predict the behavior of the fifth-order resonant converter. The proposed fifth-order resonant converter is able to effectively reduce the range of phase-shift angle from no load to full load for a fixed-frequency phase-shift control approach. Therefore, the converter is able to operate under zero voltage switching during entire load range with a fixed-frequency control method. Also, the proposed converter offers a high gain which leads to a lower transformer turns ratio. A 10-kVDC, 1.1-kW prototype has been prepared to evaluate the performance of the proposed converter. The experimental results exhibit the excellent accuracy of the proposed model and the superiority of the performance compared to the lower order resonant converters, especially for high-voltage applications. © 1986-2012 IEEE.

Halabian A.M.,Isfahan University of Technology | Erfani M.,Isfahan University of Technology
Structural Design of Tall and Special Buildings | Year: 2013

Current force-based design procedure adopted by most seismic design codes allows the seismic design of building structures to be based on static or dynamic analyses of elastic models of the structure using elastic design spectra. The codes anticipate that structures will undergo inelastic deformations under strong seismic events; therefore, such inelastic behaviour is usually incorporated into the design by dividing the elastic spectra by a factor, R, which reduces the spectrum from its original elastic demand level to a design level. The most important factors determining response reduction factors are the structural ductility and overstrength capacity. For a structure supporting on flexible foundation, as Soil Structure Interaction (SSI) extends the elastic period and increases damping of the structure-foundation elastic system, the structural ductility could also be affected by frequency-dependent foundation-soil compliances. For inelastic systems supporting on flexible foundations, the inelastic spectra ordinates are greater than for elastic systems when presented in terms of flexible-base structure's period. This implies that the reduction factors, which are currently not affected by the SSI effect, could be altered; therefore, the objective of this research is to evaluate the significance of foundation flexibility on force reduction factors of RC frame structures. In this research, by developing some generic RC frame models supporting on flexible foundations, effects of stiffness and strength of the structure on force reduction factors are evaluated for different relative stiffnesses between the structure and the supporting soil. Using a set of artificial earthquake records, repeated linear and nonlinear analyses were performed by gradually increasing the intensity of acceleration time histories to a level, where first yielding of steel in linear analysis and a level in which collapse of the structure in nonlinear analysis are observed. The difference between inelastic and elastic resistance in terms of displacement ductility factors has been quantified. The results indicated that the foundation flexibility could significantly change the response reduction factors of the system and neglecting this phenomenon may lead to erroneous conclusions in the prediction of seismic performance of flexibly supported RC frame structures. © 2010 John Wiley & Sons, Ltd.

Mallakpour S.,Isfahan University of Technology | Hatami M.,Isfahan University of Technology
Polymer - Plastics Technology and Engineering | Year: 2012

Optically active zinc oxide/poly(amide-imide) (PAI) nanocomposites (NC)s were synthesized by using ultrasonic assisted technique. The polymers and zinc oxide (ZnO) nanoparticles were physically and/or chemically connected with each other through different kinds of interactions such as physical van der Waals forces, hydrogen bonding and/or covalent interactions. ZnO/PAI NCs were characterized by Fourier transform infrared spectra, X-ray diffraction patterns, and field emission scanning electron microscopy. The thermal stability studies indicated an enhancement of thermal stability of new NC materials compared with the pure polymer. © 2012 Copyright Taylor and Francis Group, LLC.

Zamani A.,Isfahan University of Technology | Taherzadeh M.J.,University of Borås
Iranian Polymer Journal (English Edition) | Year: 2012

Superabsorbent polymers (SAPs) were prepared from fungal chitosan through three steps of carboxymethylation, cross-linking, and freeze drying. The alkali-insoluble material (AIM) of the cell wall of zygomycetes fungus Rhizomucor pusillus was first pretreated with 72 mM sulfuric acid at room temperature to release the phosphates from the cell wall. The phosphate-free AIM was then either subjected directly to carboxymethylation, or treated with 72 mM sulfuric acid at 120 °C to extract and recover the fungal chitosan prior to carboxymethylation. The carboxymethylated derivative of pretreated AIM (CM-P-AIM) and carboxymethyl fungal chitosan (CM-f- CS) exhibited 50 and 100 % water solubility, respectively. Glutaraldehyde was subsequently added to aqueous mixtures of CM-f-CS and CM-P-AIM to cross-link the water-soluble fractions. These mixtures were then frozen at -20 °C and freeze dried. The water-binding capacity (WBC) of the final product obtained from CM-f-CS (30 % of AIM) was 77, 30, 33 and 45 g/g after 10 min of immersion in water, urine, 0.9 % NaCl and artificial blood solutions, respectively. The respective WBCs of the product obtained from CM-P-AIM (90 % of AIM) were 73, 22, 24 and 37 g/g at identical conditions. SEM micrographs indicated that the SAPs prepared from CM-f-CS and CM-P-AIM had porous sheet-like structures. © Iran Polymer and Petrochemical Institute 2012.

Rezaei A.,Isfahan University of Technology | Nasirpour A.,Isfahan University of Technology | Fathi M.,Isfahan University of Technology
Comprehensive Reviews in Food Science and Food Safety | Year: 2015

Cellulose is the most abundant and a low-cost biodegradable by-product in the food and agricultural industries. Electrospun cellulosic nanofibers have remarkable physicochemical properties that make them attractive for many applications in the food sector. In this review, electrospinning is investigated as an easy method for producing nanofibers from polymers. Moreover, the most important applications of cellulosic nanofibers in food science are presented. These applications are (a) immobilization of bioactive substances such as enzymes, vitamins, and antimicrobials; (b) nutraceutical delivery systems and controlled release of materials; (c) as biosensors; (d) filtration; and (e) for reinforcing composites and in films. Finally, some potential risks of using electrospinning in food science are reviewed. © 2015 Institute of Food Technologists®.

Mirfendereski E.,Isfahan University of Technology | Jahanian R.,Isfahan University of Technology
Poultry Science | Year: 2015

The present study was carried out to investigate the effects of dietary supplementation of chromium-methionine (CrMet) and vitamin C (VC) on performance, immune response, and stress status of laying hens subjected to high stocking density. A total of 360 Hy-Line W-36 leghorn hens (at 26 wk old) were used in a 2×3×2 factorial arrangement that had 2 cage densities (5 and 7 hens per cage), 3 Cr levels (0, 500, and 1,000 ppb as CrMet), and 2 dietary VC levels (0 and 500 ppm as L-ascorbic acid). The trial lasted for 12 wk. The first 2 wk were for adaptation (26 to 28 wk of age), and the remaining 10 wk served as the main recording period. In addition to performance, immune response to Newcastle disease virus (NDV) was assessed at d 7 and 14 postvaccination. Also, the birds' stress status was evaluated by analyzing appropriate plasma metabolites. The results showed that hens in cages with higher stocking density had lower hen-day egg production, egg mass, and feed intake compared with those in normal density cages (P<0.05). Dietary CrMet supplementation caused significant increases in egg production and egg mass (P<0.01). There were significant Cr×VC interactions related to egg production and feed conversion efficiency (P<0.01); dietary CrMet supplementation was more effective in improving egg production and feed conversion ratio in VC-unsupplemented diets. Although plasma concentrations of triglycerides and high-density lipoproteins were not influenced by dietary treatments, supplemental CrMet decreased plasma cholesterol levels (P<0.05). Plasma insulin and glucose levels of hens kept at a density of 7 hens/cage were significantly higher than those of hens in normal cage density (P<0.01), and dietary CrMet supplementation decreased plasma concentrations of insulin (P<0.001) and glucose (P<0.01), with higher impacts in high stocking density-challenged hens. While high stocking density caused a marked increase in plasma corticosterone (P<0.01), both supplemental CrMet and VC decreased it to near normal levels. There were significant stocking density × Cr interactions related to plasma insulin and corticosterone concentrations (P<0.01); supplemental CrMet was more effective in lowering these hormones in high stocking density-challenged hens. The high stocking density challenge suppressed NDV antibody response (P<0.001), while dietary supplementation of CrMet improved antibody titers against NDV at d 14 post vaccination particularly in hens kept at a density of 7 hens/cage (P<0.01). From the present observations, it can be concluded that CrMet can improve laying performance largely because it alleviates harmful responses to stressful conditions. © 2015 Poultry Science Association Inc.

Saraji M.,Isfahan University of Technology | Boroujeni M.K.,Isfahan University of Technology
Analytical and Bioanalytical Chemistry | Year: 2014

During the past 7 years and since the introduction of dispersive liquid-liquid microextraction (DLLME), the method has gained widespread acceptance as a simple, fast, and miniaturized sample preparation technique. Owing to its simplicity of operation, rapidity, low cost, high recovery, and low consumption of organic solvents and reagents, it has been applied for determination of a vast variety of organic and inorganic compounds in different matrices. This review summarizes the DLLME principles, historical developments, and various modes of the technique, recent trends, and selected applications. The main focus is on recent technological advances and important applications of DLLME. In this review, six important aspects in the development of DLLME are discussed: (1) the type of extraction solvent, (2) the type of disperser solvent, (3) combination of DLLME with other extraction methods, (4) automation of DLLME, (5) derivatization reactions in DLLME, and (6) the application of DLLME for metal analysis. Literature published from 2010 to April 2013 is covered. © 2013 Springer-Verlag Berlin Heidelberg.

Soltani P.,Isfahan University of Technology | Zerrebini M.,Isfahan University of Technology
Textile Research Journal | Year: 2012

The amount of research conducted on sound absorption properties of woven fabrics in comparison to nonwoven and spacer textile fabrics is very limited. The main aim of this research is to study acoustical and sound absorption properties of woven fabrics. Normal incident sound absorption coefficient was determined via the impedance tube method. To achieve the objective of the research, general acoustical properties of textiles together with existing standards were thoroughly studied. Samples of woven fabrics having varying structural elements, such as weave type, weft yarn linear density, thickness created by layering of test fabrics, yarn spinning system and depth of air space at the back of samples were tested. Results showed that, for most samples while the maximum value of the sound absorption coefficient occurred at a frequency of 1000 Hz, the minimum value was observed at frequencies of 250 and 2000 Hz. Results showed that, the sound absorption coefficient of woven fabrics is influenced by both density and porosity of fabrics. It was found that, plain fabric absorbed sound wave more than the other weave types. Results also indicated that, for a given weft density, fabrics produced with weft yarn linear density of 24.5 tex has a higher absorption than fabrics woven with weft yarns of other counts. It was found that, finer weft yarn and higher thickness of fabric causes the noise reduction coefficient or NRC of the fabric to be increased. It was established that, fabrics woven using rotor-spun yarns exhibited the highest absorption in comparison to samples woven using ring-spun or compact yarns. © The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Mallakpour S.,Isfahan University of Technology | Dinari M.,Isfahan University of Technology
Journal of Polymers and the Environment | Year: 2012

Biodegradable nanocomposites comprising of biodegradable polymers and bioactive organically modified layered silicates commonly reveal extremely enhanced mechanical and various other properties when compared to those of virgin polymers. This work was undertaken with a view to preparation of polymer bionanocomposites consisting of biodegradable poly(vinyl alcohol) (PVA) and organo-nanoclay. Cloisite Na + and ammonium salt of l-isoleucine amino acid was used for the preparation of the novel chiral organo-nanoclay via an intercalation reaction in an aqueous solution. PVA/organo-nanoclay bionanocomposites of various compositions were created through the solution intercalation method by ultrasound-assisted technique. The resulting novel materials were characterized by X-ray diffraction and Fourier transform infrared spectroscopy techniques. Thermogravimetric analysis (TGA) and UV/vis spectroscopy were applied to test the properties of PVA bionanocomposites. TGA indicate that the thermal stability is enhanced distinctly, without a sacrifice in optical clarity. The improvement of thermal properties was attributed to the homogeneous and good dispersion of organo-nanoclay in polymeric matrix and the strong hydrogen bonding between O-H groups of PVA and the oxygen atoms of silicate layers or carbonyl group as well as OH group of intercalated amino acid. The morphology of the organo-nanoclay and PVA bionanocomposites was examined by scanning electron microscopy and transmission electron microscopy techniques. Uniform distribution of clay due to intimate interaction between clay and polymer appears to be the cause for improved properties. © 2012 Springer Science+Business Media, LLC.

Mirmahboub B.,Isfahan University of Technology | Samavi S.,Isfahan University of Technology | Karimi N.,Isfahan University of Technology | Shirani S.,McMaster University
IEEE Transactions on Biomedical Engineering | Year: 2013

Population of old generation is growing in most countries. Many of these seniors are living alone at home. Falling is among the most dangerous events that often happen and may need immediate medical care. Automatic fall detection systems could help old people and patients to live independently. Vision-based systems have advantage over wearable devices. These visual systems extract some features from video sequences and classify fall and normal activities. These features usually depend on camera's view direction. Using several cameras to solve this problem increases the complexity of the final system. In this paper, we propose to use variations in silhouette area that are obtained from only one camera. We use a simple background separation method to find the silhouette. We show that the proposed feature is view invariant. Extracted feature is fed into a support vector machine for classification. Simulation of the proposed method using a publicly available dataset shows promising results. © 1964-2012 IEEE.

Hojjat M.,Isfahan University of Technology | Etemad S.G.,Isfahan University of Technology | Bagheri R.,Isfahan University of Technology | Thibault J.,University of Ottawa
International Journal of Thermal Sciences | Year: 2011

Three kinds of nanofluids were prepared by dispersing γ-Al 2O3, CuO, and TiO2 nanoparticles in an aqueous solution of carboxymethyl cellulose (CMC). The forced convective heat transfer of these nanofluids through a uniformly heated circular tube under turbulent flow conditions was investigated experimentally. The base fluid and all nanofluids show pseudoplastic (shear-thinning) rheological behavior. Results reveal that the local and average heat transfer coefficients of nanofluids are larger than that of the base fluid. Heat transfer enhancement of nanofluids increases with an increase in nanoparticle concentration. Similar trend are demonstrated for Nusselt number of nanofluids. For a given nanoparticle concentration and Peclet number, the local heat transfer coefficient of the base fluid and that of the nanofluids decreases with the axial distance from the tube inlet. A new correlation is proposed to predict successfully the Nusselt number of non-Newtonian nanofluids as a function of the Reynolds and the Prandtl numbers. © 2010 Elsevier Masson SAS. All rights reserved.

Azimi G.,Isfahan University of Technology | Shamanian M.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2010

Three Fe-based alloys, namely 55Fe39Cr6C, 49Fe39Cr6C6Si, and 45Fe39Cr6C10Si (wt.%), were fabricated on AISI St52 using a tungsten-inert gas (TIG) heat source. Microstructure, microhardness, and electrochemical corrosion behavior of the TIG clad composite coatings were investigated. It was found that as-deposited coatings consisted of higher volume fractions of carbides (Cr 7C3). Potentiodynamic polarization studies in the 3.5 wt.% NaCl solution showed that the corrosion resistance of the substrate was remarkably improved by TIG surface coating (TSC) with 55Fe39Cr6C and 49Fe39Cr6C6Si, while 45Fe39Cr6C10Si had a lower effect on this same property. The formation of silicides (Fe3Si) in the clad with 45Fe39Cr6C10Si was taken as the reason for the reduced corrosion resistance observed as compared to those of the other clads. © 2010 Elsevier B.V.All rights reserved.

Majdzadeh-Ardakani K.,Islamic Azad University at Majlesi | Nazari B.,Isfahan University of Technology
Composites Science and Technology | Year: 2010

Thermoplastic starch/poly(vinyl alcohol) (PVOH)/clay nanocomposites, exhibiting the intercalated and exfoliated structures, were prepared via melt extrusion method. The effects of clay cation, water, PVOH and clay contents on clay intercalation and mechanical properties of nanocomposites were investigated. The experiments were carried out according to the Taguchi experimental design method. Montmorillonite (MMT) with three types of cation or modifier (Na+, alkyl ammonium ion, and citric acid) was examined. The prepared nanocomposites with modified montmorillonite indicated a mechanical improvement in the properties in comparison with pristine MMT. It was also observed that increases in tensile strength and modulus would be attained for nanocomposite samples with 10%, 5% and 4% (by weight) of water, PVOH and clay loading, respectively. The clay intercalation was examined by X-ray diffraction (XRD) patterns. The chemical structure and morphology of the optimum sample was also probed by FTIR spectroscopy and transmission electron microscopy (TEM). © 2010 Elsevier Ltd.

Fadavi Boostani A.,Isfahan University of Technology | Tahamtan S.,Isfahan University of Technology
Materials and Design | Year: 2010

In the present study, a novel thixoforming process for semi-solid deformation of A356 aluminum alloy is introduced using a continuous hot deformation process to the temperature being lower than the eutectic temperature of the alloy. A new hypothesis was introduced and the deformation mechanism of the alloy was investigated using the presented hypothesis. Microstructure and fracture surfaces of thixoformed samples were investigated using image analyzing technique and scanning electron microscopy. Obtained results indicated that this novel thixoforming process produces fine and compact silicon particles, dispersed uniformly in the microstructure of the alloy, compared to those produced by conventional thixoforming and gravity-cast processes with large and integrated morphology for silicon particles. The production stages of these silicon particles in this process were well documented by mentioned hypothesis. In order to investigate the effect of this novel process on mechanical properties of A356 alloy, tensile tests were conducted on produced samples. It was found that morphological changes of silicon particles as well as increasing the density ratio of samples in this process have a remarkable effect on enhancing the mechanical properties of produced alloy in comparison with other production routes. A new combination parameter, i.e. silicon density ratio (SDR) index was introduced. This parameter correlates the mechanical properties of samples to morphological properties of silicon particles and density ratio of them. Results of the study also indicated that samples with low SDR index have superior mechanical properties and consequently intergranular fracture mode. © 2010 Elsevier Ltd.

Sepahi O.,Isfahan University of Technology | Forouzan M.R.,Isfahan University of Technology | Malekzadeh P.,Persian Gulf University
Composite Structures | Year: 2010

The effects of three-parameter elastic foundations and thermo-mechanical loading on axisymmetric large deflection response of a simply supported annular FGM plate are investigated. An annular FGM plate, resting on a three-parameter elastic foundation under a transverse uniform loading and a transverse non-uniform temperature, is considered. The mechanical and thermal properties of the FGM plate are assumed to be graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. The mathematical modeling of the plate and the resulting nonlinear governing equations of equilibrium are derived based on the first-order shear deformation theory (FSDT) in conjunction with nonlinear von Karman assumptions. A polynomial-based differential quadrature method is used as a simple but powerful numerical technique to discretize the nonlinear governing equations and to implement the boundary conditions. Finally, the effects of certain parameters, such as nonlinear foundations stiffness, volume fraction index, and temperature, on the axisymmetric large deflection response of the FGM plate are obtained and discussed in detail. © 2010 Elsevier Ltd.

Verdian M.M.,Isfahan University of Technology
Materials and Manufacturing Processes | Year: 2010

In this study, mechanically activated Al/TiO2 powders were heated in molten (NaCl +KCl) salts to obtain TiAl3-Al 2O3 composite powders. The morphology and phase composition of the samples were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. It was shown that the milled powders reacted completely after 15min at 800C. Further investigations indicated that synthesized TiAl3-Al2O3 powders have a particle size of 400nm to 800nm. The consolidation of synthesized powders led to the formation of a composite structure composed of a continuous network of Al 2O3 phase interpenetrated by a continuous network of TiAl3 phase. Copyright © Taylor & Francis Group, LLC.

Kheradmandfard M.,Isfahan University of Technology | Fathi M.H.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2010

Properties of hydroxyapatite (HA) or fluorapatite (FA), such as bioactivity, biocompatibility, solubility, and adsorption properties can be tailored over a wide range by modifying the composition via ionic substitutions. This research aimed to prepare and characterize Mg-doped FA (Mg-FA) nanopowders. Mg-FA nanopowders with different Mg contents were prepared by sol-gel method. The designated degree of substitution of Ca2+ by Mg2+ in the mixture was determined by the x value in the general formula of (Ca10-xMgx(PO4)6F 2), where x = 0, 0.25, 0.5, 0.75, and 1. X-ray diffraction (XRD), scanning electron microscopic (SEM), transmission electron microscopy (TEM), atomic absorption spectrophotometer (AAS) and Fourier transform infrared spectroscopy (FTIR) techniques were utilized to characterize the obtained powders. Results showed that Mg ions entered into the fluorapatite lattice and occupied Ca2+ sites. The incorporation of Mg ions into the fluorapatite resulted in the decrease of the lattice parameters. The obtained powders had crystallite size of about 30-100 nm. © 2010 Elsevier B.V. All rights reserved.

Jamaati R.,Isfahan University of Technology | Toroghinejad M.R.,Isfahan University of Technology
Materials and Design | Year: 2010

The anodizing and accumulative roll bonding (ARB) processes are used in this paper as a new, effective alternative for manufacturing high-strength and highly-uniform aluminum/alumina composites. Four different thicknesses of alumina layers are grown on the substrate using an anodizing process and the microstructural evolution and mechanical properties of the resulting aluminum/alumina composite are investigated. Microscopic investigations of the composite show a uniform distribution of alumina particles in the matrix. It is found that alumina layers produced by the anodizing process neck, fracture, and depart as the number of accumulative roll bonding passes increases. During ARB, it is observed that as strain increases with the number of passes, the strength and elongation of the produced composites correspondingly increase. Also, by increasing alumina quantity, tensile strength improves so that the tensile strength of the Al/3.55vol.% Al2O3 composite becomes ∼3.5 times greater than that of the annealed aluminum used as raw material. © 2010 Elsevier Ltd.

Verdian M.M.,Isfahan University of Technology
Materials and Manufacturing Processes | Year: 2010

A supersaturated NiTi(Al) alloy powder was produced from NiTi and Al powders by solid-state synthesis utilizing high-energy mechanical alloying with times up to 8h. The microstructure and phase composition of the milling products were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results indicated that the diffraction lines corresponding to B2-NiTi shift toward higher angles with increasing milling time, which means that the lattice parameter of NiTi decreases and NiTi(Al) solid solution is formed. Further investigations showed that the lattice parameter of NiTi reaches a constant value after 8h of milling, indicating that alloying of NiTi and Al is completed. Copyright © Taylor & Francis Group, LLC.

Materials and Design | Year: 2010

The hot working behavior of 17-4 PH stainless steel (AISI 630) was studied by hot compression test at temperatures of 950-1150°C with strain rates of 0.001-10s-1. The progress of dynamic recrystallization (DRX) was modeled by the Johnson-Mehl-Avrami-Kolmogorov (JMAK) kinetics equation. The flow softening was directly related to the DRX volume fraction and the DRX time was determined by strain rate. For quantification of recrystallization rate, the reciprocal of the time corresponding to the DRX fraction of 0.5% or 50% was used. Analysis of the sigmoid-shaped recrystallization curves revealed that the rate of DRX increases with increasing deformation temperature and strain rate. The Zener-Hollomon parameter (Z) was found to be inappropriate for analysis of DRX kinetics. Therefore, the dynamic recrystallization rate parameter (DRXRP) was introduced for this purpose. The DRXRP may be determined readily from the Avrami analysis and can precisely predict the rate of DRX at hot working conditions. © 2010 Elsevier Ltd.

Abbasi A.R.,Isfahan University of Technology | Shamanian M.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2010

The α-Mo/Mo5SiB2 nanocomposite was synthesized by mechanical alloying of the elemental powders. The structural evolutions of powder particles during mechanical alloying were studied by X-ray diffractometry, scanning electron microscopy and microhardness measurements. After 10 h of milling, a supersaturated solid solution of Si and B in Mo was formed and a composite microstructure consisting of fine boron and silicon particles distributed into molybdenum solid solution matrix was observed. In addition, the crystallite size of Mo reached to less than 23 nm. After 20 h of milling, new peaks related to Mo5SiB2 appeared in X-ray diffractograms. The microstructure of 20 h milled samples showed a composite structure in which intermetallic phases were embedded in a continuous α-Mo matrix. At this time, molybdenum crystallite size was 14 nm and a considerable increase in hardness value of powder particles was yielded due to the formation of Mo5SiB2. By further increase of milling time to 40 h, the molybdenum content of Mo5SiB2 increased whereas the crystallite size decreased. The 40 h milled powders had microhardness up to 1200 HV0.1 due to refinement of crystallite size. © 2010 Elsevier B.V. All rights reserved.

Journal of Composites for Construction | Year: 2010

Structural repair and strengthening have long been dynamic and challenging activities in construction work. One of the most commonly used methods for such repairs is the application of fiber-reinforced polymer (FRP) sheets to strengthen RC or even steel structure members. A major issue of concern in flexural strengthening of RC beams with FRP laminates is the debonding of the concrete substrate, which leads to premature failure of the structural member thus strengthened. One reason for this premature rupture may be the lack of proper preparation of the concrete surface in contact with the FRP sheet. Surface preparation is typically associated with such constraints as adverse environmental impacts, economic losses due to stoppage of activities, repair costs, or even inaccessibility of the member(s) to be strengthened. This study aims to investigate surface preparation for application of FRP sheets in an attempt to develop substitute methods for conventional surface preparation methods. The experimental specimens used for the purposes of this study included a minimum of 100 prism specimens of dimensions 100×100×500 mm subjected to four-point flexural loading. The specimens were divided into the two control and experimental groups. The control group lacked FRP sheets, while the experimental one had FRP sheets tested for their ultimate failure strength as a result of both surface preparation and transverse, longitudinal, and diagonal grooves as substitutes for surface preparation. The results indicated that surface preparation prior to bonding of FRP sheets increased ultimate rupture strength. It was also found that the substitute preparation methods greatly compensated for the lack of conventional surface preparation such that they changed, in some cases, the ultimate failure behavior of the member. © 2010 ASCE.

Mazrooei-Sebdani R.,Isfahan University of Technology
Mathematical Methods in the Applied Sciences | Year: 2015

This paper is concerned to additive and multiplicative systems of homogeneous difference equations of non-negative degree. We apply a reduction in order for both additive and multiplicative systems. Then, we consider convergence and monotony of positive solutions. In fact, using convergence results on factor maps, we obtain convergence results on homogeneous systems. We will conclude that monotonic behaviour on the invariant ray (i.e. x=r¯y for multiplicative systems and x=s¯+y for additive systems) may or may not be the representative of other solutions. To illustrate our results, some examples are presented by multiplicative and additive homogeneous systems of rational equations. Copyright © 2014 John Wiley & Sons, Ltd.

Kharaziha M.,Isfahan University of Technology | Fathi M.H.,Isfahan University of Technology
Journal of the Mechanical Behavior of Biomedical Materials | Year: 2010

This work deals with the fabrication and characterization of nanostructured forsterite bulk. This material may have better biocompatibility and mechanical properties than coarse grain forsterite for the development of bone tissue engineering materials. Nanostructured forsterite bulks were prepared by two step sintering of sol-gel derived forsterite nanopowder. Their sinterability and mechanical properties were then studied. Biocompatibility of the nanostructured forsterite bulk was also evaluated by cell attachment and proliferation experiments. In addition, the effects of ionic products from forsterite nanopowder dissolution on osteoblasts were studied. Results show that dense nanostructured forsterite bulk was prepared with hardness and fracture toughness of about 1102 Hv and 4.3 MPa m1/2, respectively. Nanostructured forsterite was biocompatible and the MTT test confirmed that the products from forsterite nanopowder dissolution significantly promoted osteoblast proliferation within a certain concentration range. In addition, cells attached to and spread on the surface of nanostructured forsterite bulks. Mechanical properties of the nanostructured forsterite were much higher than that of hydroxyapatite. It was concluded that nanostructured forsterite is a bioactive ceramic with good biocompatibility that can be used as a bone tissue engineering material. © 2010 Elsevier Ltd.

Jamaati R.,Isfahan University of Technology | Toroghinejad M.R.,Isfahan University of Technology
Materials and Design | Year: 2010

Layered materials have become an increasingly interesting topic in industrial development. Cold roll bonding (CRB) process, as a solid phase method of bonding same or different metals by rolling at room temperature, has been widely used in manufacturing process. In this paper, characteristics such as bond strength and threshold deformation of as-received commercial pure aluminum (AA1100) strips prepared by the cold roll bonding process are investigated. Bond strength is evaluated by the peeling test. The main factors evaluated included effects of different annealing time, annealing temperature, hardness, and the effect of friction coefficient on bond strength. It is found that bond strength is enhanced by increasing annealing time, friction coefficient, and annealing temperature but that it is inversely proportional to hardness. © 2010 Elsevier Ltd.

Baharlouei Z.,Isfahan University of Technology | Hashemi M.,Isfahan University of Technology
IEEE Transactions on Smart Grid | Year: 2014

Demand side management (DSM) programs are designed to encourage users to shift the use of their non-critical appliances to off-peak hours. Autonomous DSM programs have recently been proposed to achieve this goal by coordinating the users' energy consumption, using smart meters. On the other hand, this objective can be achieved only when the users actively contribute in DSM programs. Devising a fair billing mechanism is important to encourage the users to keep their contribution in the programs to achieve system optimality in the sense of minimum cost of the system. Another important issue in implementing DSM programs is protecting the users' privacy which is short addressed in DSM literature. In this paper, we introduce the concept of fairness, optimality and privacy in DSM systems. Next, we introduce a class of optimal billing mechanisms. We propose a subclass of optimal billing mechanisms which is fair in terms of distributing the energy cost across the users based on their contribution in minimizing the total cost of system. We show that fairness axioms which have been previously introduced in resource allocation algorithms are achievable in the proposed billing subclass. Next, we apply the secure sum algorithm to protect the users' privacy in implementing this billing mechanism. © 2014 IEEE.

Ghaziof S.,Isfahan University of Technology | Golozar M.A.,Isfahan University of Technology | Raeissi K.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2010

Amorphous Cr-C alloy coatings were electrodeposited from a trivalent chromium bath containing formic acid. The effects of plating parameters such as pH and current density on composition, structure, morphology and corrosion behaviour of as-deposited coatings were investigated. Results showed that the suitable current density for Cr-C alloy electrodeposition is increased as the pH is decreased. Furthermore, by decreasing the pH, higher amount of carbon was introduced into the coatings. The Cr-C alloy coatings deposited at lower pH showed higher passive current density on Tafel plot. By annealing the amorphous Cr-C alloy coatings at 300 °C, a nanocrystalline structure having higher hardness was obtained. However, the corrosion resistance was seen to be impaired. Annealing at 600 °C led to the precipitation of Cr23C6 which resulted in a higher hardness. The formation of Cr23C6 enhanced the corrosion resistance of coatings due to an increase in corrosion potential. However, formation of micro-cells between the Cr23C6 precipitates and bulk chromium prevented the passive film formation. © 2010 Elsevier B.V. All rights reserved.

Shamanian M.,Isfahan University of Technology | Abarghouie S.M.R.M.,Isfahan University of Technology | Pour S.R.M.,Isfahan University of Technology
Materials and Design | Year: 2010

In this research, the effect of austenitic stainless steel cladding on improving the wear behavior of ductile iron was studied. Samples made of ductile iron were coated with steel electrodes (E309L) by manual shielded metal arc welding. The effect of coated layer thickness on microstructure, hardness, and wear resistance of the surface were investigated. Wear resistance of the samples was measured using the pin-on-plate technique. Optical microscopy and scanning electron microscopy were used to investigate microstructure and wear mechanisms. The phases in the interface of both the coating and the substrate were studied by X-ray diffraction. The results showed that a film of white chromium-enriched iron formed at the interface between the substrate and coating which contained iron-chromium complex carbides. It was, therefore, concluded that enhanced properties would be obtained if the coating thickness and the carbides deposited on the surface were reduced. In samples with a thin coating, surface hardness rose to above 1150 HV (five times higher than that of the substrate) and wear resistance increased significantly. © 2010 Elsevier Ltd. All rights reserved.

Rezaei M.R.,Isfahan University of Technology | Toroghinejad M.R.,Isfahan University of Technology | Ashrafizadeh F.,Isfahan University of Technology
Journal of Materials Processing Technology | Year: 2011

Accumulative roll bonding (ARB) has been used as a severe plastic deformation process for the production of high-strength materials. Ageing treatment has been found to enhance the strength of alloys by precipitation of a second phase. In the present work, ARB followed by the ageing process was used for the fabrication of the high-strength 6061 aluminum alloy. Samples of the alloy thus made were subjected under annealed and ARBed conditions to ageing treatment at different temperatures for different times and their mechanical properties were evaluated. It was found that the microhardness and tensile strength of the specimens increased with the number of ARB cycles but their elongation values decreased. After the ageing treatment, the mechanical properties of the ARBed specimens improved in terms of both strength and ductility. Based on TEM observations, it may be concluded that the improved mechanical properties after the duplex ARB-ageing process can be attributed to the precipitation of very fine particles with a slight decrease in dislocation density and limited structure coarsening. SEM observation of fracture surfaces of aged specimens indicated that the fracture was predominantly caused by microvoid coalescence at constituent particles. © 2011 Elsevier B.V. All rights reserved.

Mazaheri Y.,Isfahan University of Technology | Karimzadeh F.,Isfahan University of Technology | Enayati M.H.,Isfahan University of Technology
Journal of Materials Processing Technology | Year: 2011

A356/Al2O3 surface nanocomposite was produced by friction stir processing (FSP) method. X-ray diffractometery, optical and scanning electron microscopy, microhardness and nanoindentation tests were used to characterize the samples. The results indicated that the uniform distribution of Al2O3 particles in A356 matrix by FSP process can improve the mechanical properties of specimens. The hardness and elastic modulus of the as-received A356, the sample treated by the FSP without Al 2O3 particles, surface micro- and nanocomposite specimens were about 75 Hv and 74 GPa, 69 Hv and 73 GPa, 90 Hv and 81 GPa, 110 Hv and 86 GPa, respectively. © 2011 Elsevier B.V. All rights reserved.

Chachi J.,Isfahan University of Technology | Taheri S.M.,Isfahan University of Technology
Expert Systems with Applications | Year: 2011

A new approach to construct the two-sided and one-sided fuzzy confidence intervals for the fuzzy parameter is introduced, based on normal fuzzy random variables. Fuzzy data, that are observations of normal fuzzy random variables, are used in constructing such fuzzy confidence intervals. We invoke usual methods of finding confidence intervals for parameters obtained form h-level sets of fuzzy parameter to construct fuzzy confidence intervals. The crisp data that are used in constructing these confidence intervals come form h-level sets of fuzzy observations. Combining such confidence intervals yields a fuzzy set of the class of all fuzzy parameters, which is called the fuzzy confidence interval. Then, a criterion is proposed to determine the degree of membership of every fuzzy parameter in the introduced fuzzy confidence interval. A numerical example is provided to clarify the proposed method. Finally, the advantages of the proposed method with respect to some common methods are discussed. © 2010 Elsevier Ltd. All rights reserved.

Reisi M.,Isfahan University of Technology | Moslehi G.,Isfahan University of Technology
International Journal of Advanced Manufacturing Technology | Year: 2011

Nowadays, the importance of timely delivery, which is based on the just in time concept, has caused a number of criteria related to scheduling problems to be taken into consideration. One of the most important of these criteria is maximum earliness to control final costs and number of tardy jobs in an attempt to win customer satisfaction. In this paper, the strongly NP-hard problem of the single machine scheduling with two criteria, i.e., maximum earliness and number of tardy jobs, has been considered. For this purpose, artificial immune system which is inspired by the immunology theory in biology has been used. This algorithm is applied to different instances of small to large sizes and the obtained results is compared with those obtained from a heuristic method and a genetic algorithm reported in the literature. Computational results show a significant preference for the algorithm proposed in this paper. © Springer-Verlag London Limited 2010.

Saeedi-Sourck H.,Isfahan University of Technology | Wu Y.,TU Eindhoven | Bergmans J.W.M.,TU Eindhoven | Sadri S.,Isfahan University of Technology | Farhang-Boroujeny B.,University of Utah
IEEE Transactions on Signal Processing | Year: 2011

We compare filter bank multicarrier (FBMC) and orthogonal frequency-division multiplexing (OFDM) in the uplink of a multiple access network. Our study reveals that the high sensitivity of OFDM to carrier frequency offset (CFO) among different users and the need for interference cancellation methods to reduce this sensitivity leads to very complex and yet not very high performance systems. In FBMC-based networks, on the other hand, near-perfect performance is achieved without any need for interference cancellation, thanks to the excellent frequency localized filters used in the realization of FBMC systems. © 2010 IEEE.

Hashemi S.H.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology | Movahedian B.,Isfahan University of Technology
Journal of Computational Physics | Year: 2013

In this paper we present a method based on using exponential basis functions (EBFs) to solve well-known two-dimensional time dependent engineering problems such as elasto-dynamic ones. The formulation has much in common with those in three dimensional problems while time is taken as the third axis. The solution is first approximated by a summation of EBFs and then completed by satisfying the time dependent boundary conditions as well as the initial conditions through a collocation method. This is performed by considering a series of spatial and time dependent boundary points to satisfy the boundary conditions through a mixed collocation method. The solution method is presented in a time marching form which is capable of solving variety of problems such as transient heat conduction and wave propagation in solids. Several problems are solved to demonstrate the capabilities of the method. © 2013 Elsevier Inc.

Hosseini S.M.,Isfahan University of Technology | Najafizadeh A.,Isfahan University of Technology | Kermanpur A.,Isfahan University of Technology
Journal of Materials Processing Technology | Year: 2011

In this study, a simple experimental method was developed to produce the nano/ultrafine grained structure in a low carbon steel. This method involved cold plane strain compression of martensite starting structure and subsequent annealing. The martensitic specimens were first plane strained to 75% reduction in thickness (equivalent strain of 1.5), followed by subsequent annealing at the temperature range of 400-550 °C for 0-180 min. The microstructures and mechanical properties of specimens were characterized. The microstructure of the specimen annealed at 500 °C for 65 min showed cementite precipitates in the ferritic microstructure with the grain size of about 145 nm. The results showed superior mechanical properties with the estimated values of ultimate strength of 1135 MPa and uniform elongation of 11.6% for the fully recrystallized specimen. © 2010 Elsevier B.V. All rights reserved.

Mahdavi M.,Isfahan University of Technology | Farzanehfard H.,Isfahan University of Technology
IEEE Transactions on Industrial Electronics | Year: 2011

In this paper, a new bridgeless single-ended primary inductance converter power-factor-correction rectifier is introduced. The proposed circuit provides lower conduction losses with reduced components simultaneously. In conventional PFC converters (continuous-conduction-mode boost converter), a voltage loop and a current loop are required for PFC. In the proposed converter, the control circuit is simplified, and no current loop is required while the converter operates in discontinuous conduction mode. Theoretical analysis and simulation results are provided to explain circuit operation. A prototype of the proposed converter is realized, and the results are presented. The measured efficiency shows 1% improvement in comparison to conventional SEPIC rectifier. © 2010 IEEE.

Vaziri Sereshk M.,Isfahan University of Technology | Salimi M.,Isfahan University of Technology
International Journal for Numerical Methods in Biomedical Engineering | Year: 2011

Finite element method is a commonly used method in the simulation of plate and shell deformation. Usually, researchers in this field establish elements based on displacements of nodes and gradients of displacements with respect to a reference configuration as nodal variables. Recently, a new formulation, absolute nodal coordinate formulation (ANCF), has been developed. In this formulation, the gradients of the global position vector are used as nodal coordinates and no rotations are interpolated over the finite element. In this paper, the application, efficiency and domain of the application of these two formulations have been studied by considering some numerical examples. These examples show that high nonlinearity and very large computation time and extra wrinkling in the predicted deformed shape of plate are some disadvantages of the ANCF models in comparison with the classical finite element method models. The major discussion is about the performance of ANCF shape functions for rectangular elements. © 2009 John Wiley & Sons, Ltd.

Amini M.R.,Isfahan University of Technology | Farzanehfard H.,Isfahan University of Technology
IEEE Transactions on Industrial Electronics | Year: 2011

In this paper, a novel three-phase soft-switching inverter is presented. The inverter-switch turn on and turn off are performed under zero-voltage switching condition. This inverter has only one auxiliary switch, which is also soft switched. Having one auxiliary switch simplifies the control circuit considerably. The proposed inverter is analyzed, and its operating modes are explained in details. The design considerations of the proposed inverter are presented. The experimental results of the prototype inverter confirm the theoretical analysis. © 2010 IEEE.

Hejazi S.R.,Isfahan University of Technology | Doostparast A.,Isfahan University of Technology | Hosseini S.M.,Isfahan University of Technology
Expert Systems with Applications | Year: 2011

This paper presents a novel method of fuzzy risk analysis based on a new similarity measure of generalized fuzzy numbers. This similarity measure considers many features of generalized fuzzy numbers such as the area, perimeter, height and geometric distance of these kinds of fuzzy numbers. Using some sets of generalized fuzzy numbers, we show the power of this similarity measurement method to overcome the drawbacks that other methods are suffering. Applying the proposed method, we present an improved fuzzy risk analysis method which develops the capability of fuzzy risk analysis methods to deal with sophisticated problems. In the proposed method we use new factors such as probability of failure detection and economic disbenefits of failure occurrence which have not been used in fuzzy risk analysis methods before. © 2011 Published by Elsevier Ltd.

Sami S.,Isfahan University of Technology | Etesami N.,Isfahan University of Technology | Rahimi A.,University of Isfahan
Energy | Year: 2011

In the present study, using a previously developed dynamic mathematical model for performance analysis of an indirect cabinet solar dryer [1], a microscopic energy and exergy analysis for an indirect solar cabinet dryer is carried out. To this end, appropriate energy and exergy models are developed and using the predicted values for temperature and enthalpy of gas stream and the temperature, enthalpy and moisture content of the drying solid, the energy and exergy efficiencies are estimated. The validity of the model for predicting variations in gas and solid characteristics along the time and the length of the solar collector and/or dryer length was examined against some existing experimental data. The results show that in spite of high energy efficiency, the indirect solar cabinet dryer has relatively low exergy efficiency. Results show that the maximum exergy losses are in midday. Also the minimums of total exergy efficiency are 32.3% and 47.2% on the first and second days, respectively. Furthermore, the effect of some operating parameters, including length of the collector, its surface, and air flow rate was investigated on the exergy destruction and efficiency. © 2011 Elsevier Ltd.

Loran F.,Isfahan University of Technology | Mostafazadeh A.,Koç University
Annals of Physics | Year: 2015

For a pair of real or complex scattering potentials vj:R→C (j=1, 2) with support Ij and transfer matrix Mj, the transfer matrix of v1+v2 is given by the product M2M1 provided that I1 lies to the left of I2. We explore the prospects of generalizing this composition rule for the cases that I1 and I2 have a small intersection. In particular, we show that if I1 and I2 intersect in a finite closed interval of length ℓ in which both the potentials are analytic, then the lowest order correction to the above composition rule is proportional to ℓ5. This correction is of the order of ℓ3, if v1 and v2 are respectively analytic throughout this interval except at x=ℓ and x=0. We use these results to explore the superposition of a pair of unidirectionally invisible potentials with overlapping support. © 2015 Elsevier Inc.

Hojjat M.,Isfahan University of Technology | Etemad S.G.,Isfahan University of Technology | Bagheri R.,Isfahan University of Technology | Thibault J.,University of Ottawa
International Communications in Heat and Mass Transfer | Year: 2011

γ-Al2O3, TiO2 and CuO nanoparticles were dispersed in a 0.5wt.%. aqueous solution of carboxymethyl cellulose (CMC) to prepare three types of non-Newtonian nanofluids. Rheological characteristics of the base fluid and nanofluids with various nanoparticle concentrations at different temperatures were measured. Results show that all nanofluids as well as the base fluid exhibit pseudoplastic (shear thinning) behavior. The rheological characteristics of nanofluids and those of the base fluid are functions of temperature and particle concentrations. © 2010 Elsevier Ltd.

Hojjat M.,Isfahan University of Technology | Etemad S.G.,Isfahan University of Technology | Bagheri R.,Isfahan University of Technology | Thibault J.,University of Ottawa
International Journal of Heat and Mass Transfer | Year: 2011

Three different types of nanofluids were prepared by dispersing γ-Al2O3, TiO2 and CuO nanoparticles in a 0.5 wt% of carboxymethyl cellulose (CMC) aqueous solution. Thermal conductivity of the base fluid and nanofluids with various nanoparticle loadings at different temperatures were measured experimentally. Results show that the thermal conductivity of nanofluids is higher than the one of the base fluid and the increase in the thermal conductivity varies exponentially with the nanoparticle concentration. In addition to increase with the nanoparticle concentration, the thermal conductivity of nanofluids increases with the temperature. Neural network models were proposed to represent the thermal conductivity as a function of the temperature, nanoparticle concentration and the thermal conductivity of the nanoparticles. These models were in good agreement with the experimental data. On the other hand, the Hamilton Crosser model was only satisfactory for low nanoparticle concentrations. © 2010 Elsevier Ltd. All rights reserved.

Mokhatab Rafiei F.,Isfahan University of Technology | Manzari S.M.,Tarbiat Modares University | Bostanian S.,Tarbiat Modares University
Expert Systems with Applications | Year: 2011

The purpose of this study is to design a model to predict financial health of companies. Financial ratios for 180 manufacturing companies quoted in Tehran Stock Exchange for one year (year ended March 21, 2008) have been used. Three models; based on artificial neural networks (ANN), genetic algorithm (GA), and multiple discriminant analysis (MDA) are utilized to classify the bankrupt from non bankrupt corporations. ANN model achieved 98.6% and 96.3% accuracy rates in training and holdout samples, respectively. To evaluate the reliability of the model, the data were examined with genetic algorithm and Multivariate discriminate analysis method. GA model attained only 92.5% and 91.5% accuracy rates and MDA reached 80.6% and 79.9 in training and holdout samples, respectively. © 2011 Published by Elsevier Ltd.

Abedi M.,Isfahan University of Technology | Farrokhpour H.,Isfahan University of Technology
Dalton Transactions | Year: 2013

The calculations of the acidity constants (pKa) of a series of sulfur oxoacids including H2SOn (n = 1-5) and H 2S2On (n = 1, 3, 4, 6 and 7) are presented for the first time. The calculations were performed using two expensive correlated levels of theory including MP2/6-311++G(3df,3pd) and CCSD/6-311++G(d,p) in both gas and aqueous phases. The new continuum solvation model, SMD, based on the quantum mechanical charge density of a solute molecule interacting with a continuum description of the solvent, used to account the solvent effects. The calculated pKas were corrected using the different correlation equations (Zimmermann and Tossell, J. Phys. Chem. A, 2009, 113, 5105-5111) to improve the accuracy of results. Also, the calculated results showed the effect of the intramolecular hydrogen bonding on the acidity strength. © 2013 The Royal Society of Chemistry.

Norouzzadeh M.S.,Isfahan University of Technology | Ahmadzadeh M.R.,Isfahan University of Technology | Palhang M.,Isfahan University of Technology
Applied Intelligence | Year: 2012

Optimization plays a critical role in human modern life. Nowadays, optimization is used in many aspects of human modern life including engineering, medicine, agriculture and economy. Due to the growing number of optimization problems and their growing complexity, we need to improve and develop theoretical and practical optimization methods. Stochastic population based optimization algorithms like genetic algorithms and particle swarm optimization are good candidates for solving complex problems efficiently. Particle swarm optimization (PSO) is an optimization algorithm that has received much attention in recent years. PSO is a simple and computationally inexpensive algorithm inspired by the social behavior of bird flocks and fish schools. However, PSO suffers from premature convergence, especially in high dimensional multi-modal functions. In this paper, a new method for improving PSO has been introduced. The Proposed method which has been named Light Adaptive Particle Swarm Optimization is a novel method that uses a fuzzy control system to conduct the standard algorithm. The suggested method uses two adjunct operators along with the fuzzy system in order to improve the base algorithm on global optimization problems. Our approach is validated using a number of common complex uni-modal/multi-modal benchmark functions and results have been compared with the results of Standard PSO (SPSO2011) and some other methods. The simulation results demonstrate that results of the proposed approach is promising for improving the standard PSO algorithm on global optimization problems and also improving performance of the algorithm. © 2011 Springer Science+Business Media, LLC.

Khazaeli R.,Isfahan University of Technology | Mortazavi S.,Isfahan University of Technology | Ashrafizaadeh M.,Isfahan University of Technology
Journal of Computational Physics | Year: 2013

In this paper, a ghost fluid (GF) method is utilized to propose a numerical approach to enhance the capability of thermal lattice Boltzmann method (TLBM) in dealing with complex geometries. A ghost fluid approach is imposed on a double-population thermal lattice Boltzmann method. A Cartesian grid handles the flow and the boundaries are imposed by a ghost fluid approach. The essence of this method is to decompose the unknown distribution functions into equilibrium and non-equilibrium parts at each ghost points. The major quantities are extrapolated from the image points to the corresponding ghost points to form the equilibrium parts. The non- equilibrium parts are then determined by using the bounce-back scheme. The method is relatively easy to apply, and second order accurate. There is no need to modify the original governing equations, and both Dirichlet and Neumann boundary conditions can be handled. The method is applied to Couette flow between two concentric circular cylinders, natural convection in a square cavity, natural convection in an annulus, and a forced convection in a lid-driven semi-circular cavity. The results obtained are generally in good agreement with that predicted by other theoretical and numerical efforts. © 2013 Elsevier Inc.

Goshadrou A.,Isfahan University of Technology | Karimi K.,Isfahan University of Technology | Taherzadeh M.J.,University of Borås
Industrial Crops and Products | Year: 2011

The present work deals with production of ethanol from sweet sorghum bagasse by a zygomycetes fungus Mucor hiemalis. The bagasse was treated with phosphoric acid and sodium hydroxide, with or without ultrasonication, prior to enzymatic hydrolysis by commercial cellulase and β-glucosidase enzymes. The phosphoric acid pretreatment was performed at 50°C for 30. min, while the alkali treatment performed with 12% NaOH at 0°C for 3. h. The pretreatments resulted in improving the subsequent enzymatic hydrolysis to 79-92% of the theoretical yield. The best hydrolysis performance was obtained after pretreatment by NaOH assisted with ultrasonication. The fungus showed promising results in fermentation of the hydrolyzates. In the best case, the hydrolyzate of NaOH-ultrasound pretreated bagasse followed by 24. h fermentation resulted in about 81% of the corresponding theoretical ethanol yield. Furthermore, the highest volumetric ethanol productivity was observed in the hydrolyzates of NaOH pretreated bagasse, especially after ultrasonication in pretreatment stage. © 2011 Elsevier B.V.

Sayed Razavi M.,Isfahan University of Technology | Shirani E.,Foolad Institute of Technology
Journal of Biomechanics | Year: 2013

In the present study, theoretical formulations for calculation of optimal bifurcation angle and relationship between the diameters of mother and daughter vessels using the power law model for non-Newtonian fluids are developed. The method is based on the distribution of wall shear stress in the mother and daughter vessels. Also, the effect of distribution of wall shear stress on the minimization of energy loss and flow resistance is considered. It is shown that constant wall shear stress in the mother and daughter vessels provides the minimum flow resistance and energy loss of biological flows. Moreover, the effects of different wall shear stresses in the mother and daughter branches, different lengths of daughter branches in the asymmetric bifurcations and non-Newtonian effect of biological fluid flows on the bifurcation angle and the relationship between the diameters of mother and daughter branches are considered. Using numerical simulations for non-Newtonian models such as power law and Carreau models, the effects of optimal bifurcation angle on the pressure drop and flow resistance of blood flow in the symmetric bifurcation are investigated. Numerical simulations show that optimal bifurcation angle decreases the pressure drop and flow resistance especially for bifurcations at large Reynolds number.© 2013.

Boroomand B.,Isfahan University of Technology | Noormohammadi N.,Isfahan University of Technology
Engineering Analysis with Boundary Elements | Year: 2013

In this paper weakly equilibrated basis functions (EqBFs) are introduced for the development of a boundary point method. This study is the extension of the one in (Int. J. Numer. Methods Engng. 81 (2010) 971-1018) using exponential basis functions (EBFs) which are available just for partial differential equations (PDEs) with constant coefficients. Here the EqBFs are evaluated numerically to solve more general PDEs with non-constant coefficients. The EqBFs are found through weighted residual integrals defined over a fictitious domain embedding the main domain. A series of Chebyshev polynomials are used for the construction of the basis functions. By properly choosing the weight functions as the product of two unidirectional functions, here with Gaussian distribution, the main 2D integrals are written as the product of the simpler 1D ones. The results of the integrals can be stored for further use; however in some particular cases the EqBFs may be stored as a set of library functions. The results may also be found useful for those who are interested in residual-free functions in other numerical methods. For the verification, we discuss on the validity of the solution through an essential and comprehensive test procedure followed by several numerical examples. © 2013 Elsevier Ltd.

Az'Hari S.,Isfahan University of Technology | Ghayeb Y.,Isfahan University of Technology
Molecular Simulation | Year: 2014

We carried out molecular dynamics simulations to study the adsorption of all the 20 amino acids (AAs; aromatic, polar and non-polar) on the surface of chiral, zigzag and armchair single-walled carbon nanotubes. The adsorption was occurring in all systems. In the aromatic AAs, the π-π stacking and the semi-hydrogen bond formation cause a strong interaction with the carbon nanotubes (CNTs). We also investigated the chirality, length and diameter dependencies on adsorption energies. We found that all AAs have more tendency to adsorption on the chiral and zigzag CNTs over the armchair. The results show that increasing both the diameter and the length causes the enhancement of the adsorption energy. But, the effect of the length is more than of the diameter. For example, the adsorption energy of Trp on the surface of CNT (4,1), with 2 nm length, is 20.4 kcal/mol. When the length of CNT becomes twice, the adsorption energy increases by 24 ± 0.3%. But by doubling the diameter, the adsorption energy increased only by 9.8 ± 0.25%. © 2013 Taylor & Francis.

Keshmiri M.,Isfahan University of Technology
2010 15th International Conference on Methods and Models in Automation and Robotics, MMAR 2010 | Year: 2010

In this paper a comparative analysis is represented on various navigation guidance methods used for intercepting fast maneuvering moving objects. A glancing revision is introduced on relevant works within the introduction section. Four common methods for navigation guidance known as PNG, APNG, IPNG and AIPNG are under investigation. Results demonstrate their infirmity on smoothly intercepting a moving object. Hence, to improve the navigation guidance methods and to adapt them with robotic problems a modified version of AIPNG is proposed for 2D problems and is developed for 3D problems utilization. ©2010 IEEE.

Momeni M.M.,Isfahan University of Technology | Hosseini M.G.,University of Tabriz
Journal of Materials Science: Materials in Electronics | Year: 2014

In the present work we reported the fabrication of different TiO2 nanotube arrays (TiO2 NTs) by anodization method. When used in dye-sensitized solar cells, the TiO2 NTs prepared in the two-step anodization process (2-step TiO2 NTs) showed better efficiency than those of TiO2 NTs prepared in one step anodization process (1-step TiO2 NTs). The 2-step TiO2 NTs show a remarkable efficiency of 1.56 %. This is higher than those of TiO2 NTs prepared in one step anodization process. Electrochemical impedance spectroscopy has been performed for qualitative analysis of charge transport process in dye-sensitized solar cells. © 2014, Springer Science+Business Media New York.

Mallakpour S.,Isfahan University of Technology | Barati A.,Isfahan University of Technology
Progress in Organic Coatings | Year: 2011

In the present investigation, at first, the surface of titanium dioxide (TiO2) nanoparticles was modified with γ-aminopropyltriethoxy silane as a coupling agent. Then a new kind of poly(vinyl alcohol)/titanium dioxide (PVA/TiO2) nanocomposites coating with different modified TiO2 loading were prepared under ultrasonic irradiation process. Finally, these nanocomposites coating were used for fabrication of PVA/TiO 2 films via solution casting method. The resulting nanocomposites were fully characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), thermogravimetric analysis/derivative thermal gravimetric (TGA/DTG), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The TEM and SEM results indicated that the surface modified nanoparticles were dispersed homogeneously in PVA matrix on nanoscale and based on obtained results a possible mechanism was proposed for ultrasonic induced nanocomposite fabrication. TGA confirmed that the heat stability of the nanocomposite was improved. UV-vis spectroscopy was employed to evaluate the absorbance and transmittance behavior of the PVA/TiO2 nanocomposite films in the wavelength range of 200-800 nm. The results showed that this type of films could be used as a coating to shield against UV light. © 2011 Elsevier B.V. All rights reserved.

Ebrahimi Serest A.,Isfahan University of Technology | Akbarzadeh S.,Isfahan University of Technology
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology | Year: 2014

Helical gears are widely used in power transmission systems, and hence any improvement in their design and also the ability to predict their performance is of great importance. The key issues related to gears are their film thickness, which represents the lubricant ability to protect the surfaces from wear, and friction coefficient, which reflects the power loss. Since the pinion and gear mesh is usually under mixed-elastohydrodynamic lubrication, the effect of asperities should also be considered. The goal of this research is to present a model for predicting the performance of helical gears with consideration of surface roughness. Initially, the pinion and gear engagement analysis is performed considering non-uniform load distribution on gear's tooth. In this model, each of the contact points on the gear flank is replaced with two cylinders, and lubrication analysis will be executed on these cylinders. The load-sharing concept has been employed to account for lubricant and surface roughness contribution in carrying the applied load. The predicted results are compared to other published data, and an acceptable agreement is seen. Acceptable accuracy, short execution time, and consideration of surface roughness are among the features of this model. It is shown that increasing the applied load results in an increase in the portion of the load that is carried by asperities as well as the friction coefficient. © IMechE 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Panahandeh-Shahraki D.,Isfahan University of Technology | Amiri Rad A.,Isfahan University of Technology
International Journal of Mechanical Sciences | Year: 2014

Buckling of cracked functionally graded plates resting on Pasternak foundation under tension has been studied. Classical plate theory in framework of the finite element method has been used. Shape functions for elements surrounding crack tips have been derived using previous solutions of displacement fields around crack tips. In-plane loads have been obtained by a pre-buckling solution using quarter-point elements around crack tips. Results show that an increase of foundation stiffness, leads to greater values of buckling loads. For longer cracks the effect of foundation stiffness on buckling load diminishes. For bi-axial loading such stiffness has less effect on buckling compared to uni-axial case. © 2014 Elsevier Ltd.

Mehrabi R.,Vali e Asr University of Rafsanjan | Mehrabi R.,University of Toledo | Kadkhodaei M.,Isfahan University of Technology | Elahinia M.,University of Toledo
International Journal of Solids and Structures | Year: 2014

In microplane theory, it is assumed that a macroscopic stress tensor is projected to the microplane stresses. It is also assumed that 1D constitutive laws are defined for associated stress and strain components on all microplanes passing through a material point. The macroscopic strain tensor is obtained by strain integration on microplanes of all orientations at a point by using a homogenization process. Traditionally, microplane formulation has been based on the Volumetric-Deviatoric-Tangential split and macroscopic strain tensor was derived using the principle of complementary virtual work. It has been shown that this formulation could violate the second law of thermodynamics in some loading conditions. The present paper focuses on modeling of shape memory alloys using microplane formulation in a thermodynamically-consistent framework. To this end, a free energy potential is defined at the microplane level. Integrating this potential over all orientations provides the macroscopic free energy. Based on this free energy, a new formulation based on Volumetric-Deviatoric split is proposed. This formulation in a thermodynamic-consistent framework captures the behavior of shape memory alloys. Using experimental results for various loading conditions, the validity of the model has been verified. © 2014 Elsevier Ltd. All rights reserved.

Sarrami-Foroushani S.,Isfahan University of Technology | Azhari M.,Isfahan University of Technology
International Journal of Mechanical Sciences | Year: 2014

In the present work, the buckling and vibration of rectangular single-layered graphene sheets is analyzed based on the nonlocal theory of elasticity which takes the small scale effects into account. The graphene sheet is assumed as a thin plate, and the classical plate theory is applied to obtain the differential equation of the sheet. For the first time, the complex finite strip method is employed to study the vibration and buckling behavior of graphene sheets. The weighted residual method is employed to obtain the stiffness, stability and the mass matrices of the graphene sheet which is assumed to be an isotropic nanoplate. A sinusoidal displacement function is used for the longitudinal direction, which satisfies the simply supported boundary condition, while piecewise interpolation polynomials including the Hermitian and bubble functions are assumed for the other direction. A matrix eigenvalue problem is solved to find the vibration frequency and buckling load of graphene sheets subjected to different types of in-plane loadings including the uniform and non-uniform uniaxial and biaxial compressions as well as shear loading. The accuracy of the proposed model is validated by comparing the results with those reported by the available references. Furthermore, a number of examples are presented to investigate the effects of various parameters (e.g., boundary conditions, nonlocal parameter, aspect ratio, and type of loading) on the results. © 2014 Elsevier Ltd.

Mallakpour S.,Isfahan University of Technology | Zeraatpisheh F.,Isfahan University of Technology
Colloid and Polymer Science | Year: 2011

A new class of chiral and potentially biodegradable poly(ester-imide)s (PEI)s as pseudo-poly(amino acid)s (PAA)s bearing natural amino acids in the main chain was synthesized. In this investigation, N,N′-(pyromellitoyl)- bis-(L-tyrosine dimethyl ester) as a biodegradable optically active diphenol and synthesized trimellitic anhydride-derived dicarboxylic acids containing different natural amino acids such as S-valine, L-methionine, L-leucine, L-isoleucine, and L-phenylalanine were used for direct polyesterification. With the aim of tosyl chloride/pyridine/N,N′-dimethylformamide system as a condensing agent, the new optically active PEIs were obtained in good yields and moderate inherent viscosity up to 0.42 dL/g. The obtained polymers were characterized with FT-IR, 1H-NMR, X-ray diffraction (XRD), field emission scanning electron microscopy, elemental, and thermogravimetric analysis techniques. These polymers show high solubility in organic solvents, such as N,N′-dimethyl acetamide, N-methyl-2-pyrrolidone, and sulfuric acid at room temperature, and are insoluble in solvents, such as methylene chloride, cyclohexane, and water. Morphology probes showed these pseudo-poly(amino acid)s were noncrystalline and nanostructured polymers. On the basis of thermogravimetric analysis data, such PAAs are thermally stable and can be classified as self-extinguishing polymers. In addition due to the existence of amino acids in the polymer backbones these pseudo-PAAs not only are optically active but also are expected to be biodegradable and therefore could be classified under eco-friendly polymers. © 2011 Springer-Verlag.

Sarrami-Foroushani S.,Isfahan University of Technology | Azhari M.,Isfahan University of Technology
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2014

Detailed studies on the nanoscale vibration and buckling characteristics of rectangular single and multi-layered graphene sheets (SLGSs and MLGSs) are carried out using semi-analytical finite strip method (FSM), based on the classical plate theory (CPT). The displacement functions of the sheets are evaluated using continuous harmonic function series which satisfy the boundary conditions in one direction and a piecewise interpolation polynomial in the other direction. Nonlocal continuum mechanics is employed to derive the differential equation of the system. The weighted residual method is employed to obtain stiffness, stability and mass matrices of the graphene sheets. The effects of van der Waals (vdW) forces which are present as bonding forces between the layers are considered in the stiffness matrix of the system. The analysis of MLGSs is much more complex due to the influence of vdW forces. The mechanical properties of the graphene sheet are assumed in two ways as orthotropic or isotropic materials. A matrix eigenvalue problem is solved to find the natural frequency and critical stress of GSs subjected to different types of in-plane loadings including uniform and non-uniform uniaxial loadings. The accuracy of the proposed model is validated by comparing the results with those reported by the available references. Furthermore, a comprehensive parametric study is performed to investigate the effects of various parameters such as boundary conditions, nonlocal parameter, aspect ratio and the type of loading on the results. © 2013 Elsevier B.V.

Jannesari M.,Isfahan University of Technology
International journal of nanomedicine | Year: 2011

The aim of this study was to develop novel biomedicated nanofiber electrospun mats for controlled drug release, especially drug release directly to an injury site to accelerate wound healing. Nanofibers of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and a 50:50 composite blend, loaded with ciprofloxacin HCl (CipHCl), were successfully prepared by an electrospinning technique for the first time. The morphology and average diameter of the electrospun nanofibers were investigated by scanning electron microscopy. X-ray diffraction studies indicated an amorphous distribution of the drug inside the nanofiber blend. Introducing the drug into polymeric solutions significantly decreased solution viscosities as well as nanofiber diameter. In vitro drug release evaluations showed that both the kind of polymer and the amount of drug loaded greatly affected the degree of swelling, weight loss, and initial burst and rate of drug release. Blending PVA and PVAc exhibited a useful and convenient method for electrospinning in order to control the rate and period of drug release in wound healing applications. Also, the thickness of the blend nanofiber mats strongly influenced the initial release and rate of drug release.

Nasresfahani M.R.,Isfahan University of Technology | Niroumand B.,Isfahan University of Technology
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2014

A new criterion for prediction of hot tearing susceptibility of cast alloys is suggested which takes into account the effects of both important mechanical and metallurgical factors and is believed to be less sensitive to the presence of volume defects such as bifilms and inclusions. The criterion was validated by studying the hot tearing tendency of Al-Cu alloy. In conformity with the experimental results, the new criterion predicted reduction of hot tearing tendency with increasing the copper content. © The Minerals, Metals & Materials Society and ASM International 2014.

Ashiri R.,Isfahan University of Technology | Ashiri R.,Islamic Azad University at Dezful
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2014

In the present work, we have tried to study and develop the processing of amorphous BaTiO3 nanothin films, which have amorphous structure and nanometric thickness. It was seen that they exhibit enhanced optical responses. An improved method was used to prepare amorphous BaTiO3 nanothin films, which, compared to other approaches, is simple, cost-effective, and environmentally friendly. It was found that amorphous BaTiO3 films exhibit better optical transmittance in contrast to the similar nanocrystalline, polycrystalline, or thick films. This finding is due to the absence of grain boundaries, which have an important role in light scattering processes. AFM and SEM results indicate that the surface of the nanothin film is uniform, smooth, and amorphous. Moreover, the surface of the nanothin film exhibits a dense structure with no crack and voids. RMS roughness of the prepared nanothin film was quite small and equal to 0.7 nm. This value is very less than other reported RMS roughness values which were in the range of 5 to 11 nm. XRD results indicate that all of the prepared thin films in this work are amorphous, independent of number of dip-coated layers and preparation conditions. The work also aims to study and develop the processing of the amorphous BaTiO3 nanothin films deeply. The results showed that annealing temperature has a more pronounced effect on transmittance, thickness, and shift in the absorption edge of the thin films than annealing time. It was found that the viscosity of the sol has remarkable influence on the transmission spectrum and shift in the absorption edge of the films. The transparency of the films decreases with an increase in the viscosity and concentration of the sol. It was found that size of particle within the sol and rate of the sol-gel reactions have important roles on the transmittance of the films. © 2014 The Minerals, Metals & Materials Society and ASM International.

Mallakpour S.,Isfahan University of Technology | Hatami M.,Isfahan University of Technology
Designed Monomers and Polymers | Year: 2011

Bionanocomposites (BNCs) containing 4, 8 and 12% (w/w) modified ZnO nanoparticles (NPs) were successfully prepared by homogenous dispersion of these NPs in an optically active poly(amide-imide) (PAI) matrix through an ultrasonic process. PAI was synthesized via solution polycondensation of 3,5-diamino-N-(4-hydroxyphenyl) benzamide and N,N-(pyromellitoyl)-bis-L- phenylalanine diacid chloride at low temperature. The ZnO NPs were treated with γ-aminopropyltriethoxysilane (KH550) as a coupling agent to change the surface property of NPs from hydrophilic to hydrophobic nature for better dispersion in PAI matrix. The obtained BNCs were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetry analysis. AFM studies of the BNCs suggest that the ZnO NPs of 20-50 nm in diameter were dispersed in polymer matrices. FE-SEM and TEM results also confirmed the formation of well-dispersed nano ZnO in the PAI matrix. © 2011 Koninklijke Brill NV, Leiden.

Tavangarian F.,Isfahan University of Technology | Emadi R.,Isfahan University of Technology
Materials Research Bulletin | Year: 2010

This study investigates the synthesis of single-phase nanocrystalline forsterite powder by mechanical activation with subsequent annealing. To produce forsterite powder, a mixture of talc and magnesium oxide powders was first milled by a planetary ball mill, and then annealed at 1000 and 1200 °C for 1 h. The synthesized powder was characterized by X-ray diffraction (XRD), simultaneous thermal analysis (STA), scanning electron microscopy (SEM), and atomic absorption spectrometry (AAS). The initial temperature of forsterite crystallization was reduced to about 825 °C after 20 h of mechanical activation. The forsterite powder synthesized by 5 h of mechanical activation with subsequent annealing at 1000 °C for 1 h had crystallites 40 nm in size. The particle size of this sample was less than 500 nm. © 2010 Elsevier Ltd. All rights reserved.

Tabesh A.,Isfahan University of Technology | Frechette L.G.,Université de Sherbrooke
IEEE Transactions on Industrial Electronics | Year: 2010

An adaptive energy-harvesting circuit with low power dissipation is presented and demonstrated, which is useful for efficient ac/dc voltage conversion of a piezoelectric micropower generator. The circuit operates stand-alone, and it extracts the piezoelectric strain energy independent of the load and piezoelectric parameters without using any external sensor. The circuit consists of a voltage-doubler rectifier, a step-down switching converter, and an analog controller operating with a single supply voltage in the range of 2.515 V. The controller uses the piezoelectric voltage as a feedback and regulates the rectified voltage to adaptively improve the extracted power. The nonscalable power dissipation of the controller unit is less than 0.05 mW, and the efficiency of the circuit is about 60% for output power levels above 0.5 mW. Experimental verifications of the circuit show the following: 1) the circuit notably increases the extracted power from a piezoelectric element compared to a simple full-bridge diode rectifier without control circuitry, and 2) the efficiency of the circuit is dominantly determined by its switching converter. The simplicity of the circuit facilitates the development of efficient piezoelectric energy harvesters for low-power applications such as wireless sensors and portable devices. © 2006 IEEE.

Karami K.,Isfahan University of Technology | Ghasemi M.,Isfahan University of Technology | Naeini N.H.,Isfahan University of Technology
Tetrahedron Letters | Year: 2013

In this Letter the dimeric palladacycle [Pd(μ-C1)(P (OPh) 2(OC6H4)]2 containing a phosphorus donor atom is prepared and its catalytic activity was tested in the Suzuki reaction of phenylboronic acid at room temperature, and the Heck reaction of styrene at 130 °C with aryl halides of varying electron density. All reactions were monitored by GC and generally gave high yields of coupled products. Copyright © 2012 Elsevier Ltd.

Ensafi A.A.,Isfahan University of Technology | Heydari-Bafrooei E.,Isfahan University of Technology | Rezaei B.,Isfahan University of Technology
Biosensors and Bioelectronics | Year: 2013

In this study, the interaction between codeine and morphine with dsDNA was assessed at pH 7.0. Poly(diallyldimethylammonium chloride), PDDA, was used as a dispersant of MWCNTs. Using differential pulse voltammetry (DPV) at pencil graphite electrode (PGE) showed that both molecules were electrochemically oxidized due to the presence of phenolic and amino groups in their structures. When DNA was added to the solution, the electrochemical signal of codeine and morphine was decreased and shifted to more negative and positive potentials, respectively. The interaction modes were respectively electrostatic for codeine and intercalation for morphine with two anodic peaks of codeine being merged into them when DNA concentration was increased. At high DNA concentrations, a sharp anodic wave for codeine and a clear discrimination of codeine and morphine oxidation peaks were observed. Finally, a pencil graphite electrode was modified with carbon nanotubes and DNA was tested in order to determine codeine and morphine in solution. Electrochemical oxidation of codeine and morphine bonded on dsDNA/MWCNTs-PDDA/PGE was used to obtain an analytical signal. Allowing five min as an accumulation time, a linear dependence was observed between 0.05 and 40μgmL-1 for codeine and 0.05 and 42μgmL-1 for morphine. Detection limits of 0.041 and 0.043μgmL-1 were obtained for codeine and morphine, respectively. The biosensor was applied to validate its capability for the analysis of codeine and morphine in blood serum, urine samples and pharmaceutical formulations. © 2012 Elsevier B.V.

Meghdadi S.,Isfahan University of Technology | Amirnasr M.,University of California at Santa Barbara | Ford P.C.,University of California at Santa Barbara
Tetrahedron Letters | Year: 2012

The cyclocondensation of 2-aminothiophenol and carboxylic acids to give benzothiazoles has been carried out under mild conditions using tetrabutylammonium bromide (TBAB) as the reaction medium and triphenyl phosphite as the catalyst. Shorter reaction times, rapid isolation of the products, and excellent yields are advantages of this method. The reaction is found to be general and quite tolerant to the nature of the substituted carboxylic acids. © 2012 Elsevier Ltd. All rights reserved.

Razavi M.,Isfahan University of Technology | Fathi M.H.,Isfahan University of Technology | Meratian M.,Isfahan University of Technology
Materials Characterization | Year: 2010

Recent studies indicate that there is a high demand for magnesium alloys with adjustable corrosion rates, suitable mechanical properties, and the ability for precipitation of a bone-like apatite layer on the surface of magnesium alloys in the body. An approach to this challenge might be the application of metal matrix composites based on magnesium alloys. The aim of this work was to fabricate and characterize a nanocomposite made of AZ91 magnesium alloy as the matrix and fluorapatite nano particles as reinforcement. A magnesium- fluorapatite nanocomposite was made via a blending-pressing-sintering method. Mechanical, metallurgical and in vitro corrosion measurements were performed for characterization of both the initial materials and the composite structure. The results showed that the addition of fluorapatite nano particle reinforcements to magnesium alloys can improve the mechanical properties, reduce the corrosion rate, and accelerate the formation of an apatite layer on the surface, which provides improved protection for the AZ91 matrix. It is suggested that the formation of an apatite layer on the surface of magnesium alloys can contribute to the improved osteoconductivity of magnesium alloys for biomedical applications. © 2010 Elsevier Inc. All rights reserved.

Bagheri S.,Isfahan University of Technology | Heidarpour M.,Isfahan University of Technology
Journal of Irrigation and Drainage Engineering | Year: 2012

In this study, water flow over rectangular sharp-crested side weirs of various heights and widths was investigated. The distribution of the three-dimensional velocity over the crest and in the vicinity of the side weir was obtained using an acoustic Doppler velocity (ADV) meter. The structure of each component of velocity was examined separately. The velocity distributions showed that longitudinal velocity peaked near the beginning of the side weir, whereas velocity in the direction of spill flow was highest at the end of the weir. The observed values of vertical velocity showed that the direction of flow near the crest was upward, but at the highest depths, the flow direction was reversed and a downward flow was generated near the water surface. Analysis of the velocity profiles indicated that the local discharge increased along the crest of the weir; local discharge also increased as the relative width of the weir decreased. Since the angle of the spilling jet (φ) plays a large role in shaping the hydraulic characteristics of a side structure, variation in this angle was investigated, and an expression for estimating φ was developed. © 2012 American Society of Civil Engineers.

Khorsand S.,Isfahan University of Technology | Raeissi K.,Isfahan University of Technology | Ashrafizadeh F.,Isfahan University of Technology
Applied Surface Science | Year: 2014

A super-hydrophobic nickel film with micro-nano structure was successfully fabricated by electrodeposition process. By controlling electrodeposition parameters and considering different storage times for the coatings in air, various nickel films with different wettability were fabricated. Surface morphology of nickel films was examined by means of scanning electron microscopy (SEM). The results showed that the micro-nano nickel film was well-crystallized and exhibited pine cone-like microstructure with nano-cone arrays randomly dispersed on each micro-protrusion. The wettability of the micro-nano nickel film varied from super-hydrophilicity (water contact angle 5.3°) to super-hydrophobicity (water contact angle 155.7°) by exposing the surface in air at room temperature. The corrosion resistance of the super-hydrophobic film was estimated by electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. The potentiodynamic curves revealed that the corrosion rate of superhydrophobic surface was only 0.16% of the bare copper substrate. Moreover, EIS measurements and appropriate equivalent circuit models revealed that the corrosion resistance of nickel films considerably improved with an increase in the hydrophobicity. The superhydrophobic surface also exhibited an excellent long-term durability in neutral 3.5 wt.% NaCl solution. © 2014 Elsevier B.V.

Latifi M.,Islamic Azad University at Khomeinishahr | Farhatnia F.,Islamic Azad University at Khomeinishahr | Kadkhodaei M.,Isfahan University of Technology
European Journal of Mechanics, A/Solids | Year: 2013

Mallakpour S.,Isfahan University of Technology | Zadehnazari A.,Isfahan University of Technology
Synthetic Metals | Year: 2013

Functionalization of multi-walled carbon nanotubes (MWCNTs) with amino acid molecule using microwave irradiation, followed by reaction with a carboxylic acid moiety allows direct attachment by an amide bond. The process is fast, one-pot, simple and resulted in a high degree of functionalization as well as dispersibility in organic solvents like N,N'-dimethylacetamide. Surface functionality groups and morphology of MWCNTs were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction, field emission and transmission electron microscopy (TEM), and thermogravimetric analysis. The results consistently confirmed the formation of amino acid functionalities on MWCNTs. After that, functionalized MWCNTs (f-MWCNTs) were dispersed throughout a thiadiazol and amino acid containing poly(amide-thioester-imide) (PATEI). Through casting of these dispersions, f-MWCNT/PATEI composite films were successfully fabricated on substrates and showed no signs of macroscopic aggregation. The f-MWCNTs were dispersed homogeneously in the PATEI matrix while the structure of the polymer and the MWCNTs structure were stable in the preparation process as revealed by TEM. The PATEI and the composites were characterized by the aforementioned techniques. Tensile tests and thermal analysis were also carried out on free-standing composite films for different f-MWCNT loading levels. The results indicated that thermal and mechanical properties of the composites can be improved by hydrogen bonding interaction between the modified f-MWCNT and PATEI matrix. © 2013 Elsevier B.V. All rights reserved .

Abdollahi R.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology
International Journal of Solids and Structures | Year: 2014

In this paper we consider a nonlocal elasticity theory defined by Eringen's integral model and introduce, for the first time, a boundary layer method by presenting the exponential basis functions (EBFs) for such a class of problems. The EBFs, playing the role of the fundamental solutions, are found so that they satisfy the governing equations on an unbounded domain. Some insight to the theory is given by showing that the EBFs satisfying the Navier equations in the classical elasticity theory also satisfy the governing equations in the nonlocal theory. Some additional EBFs are particularly obtained for the nonlocal theory. In order to use the EBFs on bounded domains, the effects of the boundary conditions are taken into account by truncating the kernel/attenuation function in the constitutive equations. This leads to some residuals in the governing equations which appear near the boundaries. A weighted residual approach is employed to minimize the residuals near the boundaries. The method presented in this paper has much in common with Trefftz methods especially when the influence area of the kernel function is much smaller than the main computational domain. Several one/two dimensional problems are solved to demonstrate the way in which the EBFs can be used through the proposed boundary layer method. © 2014 Elsevier Ltd. All rights reserved.

Mahboubi Soufiani A.,Isfahan University of Technology | Karimzadeh F.,Isfahan University of Technology | Enayati M.H.,Isfahan University of Technology
Materials and Design | Year: 2012

In recent years, researches on properties of nanocrystalline materials in comparison with coarse-grained materials have attracted a great deal of attention. The present investigation has been based on production of nanocrystalline Ti6Al4V powder from elemental powders by means of high energy mechanical milling. In this regard, Ti, Al and V powders were milled for up to 90. h and heat treated at different temperatures. The structural and morphological changes of powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA) and microhardness measurements. The results demonstrated that Ti(Al) and Ti(Al, V) solid solutions with grain size of 95 and 20. nm respectively form during mechanical alloying. In addition, an amorphous structure was obtained at longer milling times. The crystallization of amorphous phase upon annealing led to the formation of nanostructured Ti6Al4V phase with a grain size of 20-50. nm. The as-milled Ti6Al4V powder with amorphous structure exhibited a high microhardness of ∼720. Hv. Upon crystallization the hardness value reduced to ∼630. Hv which is higher than those reported for Ti6Al4V alloys processed by conventional routes. © 2012 Elsevier Ltd.

Asgari M.,Isfahan University of Technology | Masoomi M.,Isfahan University of Technology
Composites Part B: Engineering | Year: 2012

In this paper, two grafted copolymers, Glycidyl Methacrylate grafted polypropylene (PP) (PP-g-GMA) and Maleic Anhydride grafted PP (PP-g-MA) were used in PP reinforced with short poly(ethylene terephthalate) (PET) fibre composites. Transcrystallization (TC) of PP on PET fibres was investigated using a polarized optical microscope, which revealed no TC for either of the modified composites at the fibre-matrix interface. Heat deflection temperature (HDT) results of GMA modified composites revealed more enhancement than HDT of MA modified samples. The composite strength results showed enhancement for both modified composites up to 10 wt.%, and this growth was bigger for GMA modified composites. The morphological analysis of GMA modified PP/PET composites pointed out a marked improvement of fibre dispersion and interfacial adhesion as compared to non-compatibilized PP/PET composites. The results of impact strength showed about 43% enhancement for 15 wt.% PET fibre composites. It was found that at low fibre percentages, using either of the modifiers reduces the impact strength a little in comparison to impact strength of the unmodified samples. According to linear elastic fracture mechanics LEFM, impact fracture toughness (G c) and critical stress intensity factor (K c) were evaluated for these composites based on the fracture energy obtained from impact tests. © 2011 Elsevier Ltd. All rights reserved.

Johari N.,Isfahan University of Technology | Fathi M.H.,Isfahan University of Technology | Golozar M.A.,Isfahan University of Technology
Composites Part B: Engineering | Year: 2012

The aim of this study was to prepare and characterize the novel poly (-caprolactone)/nano-fluoridated hydroxyapatite (PCL-FHA100) nanocomposite scaffolds and, to investigate the mechanical properties of the scaffolds in order to obtain an optimized composition. These polymer-matrix composite (PMC) scaffolds were produced by solvent casting/particulate leaching method. The chemical composition of the FHA100 was Ca 10(PO 4) 6OH 2-xF x (x = 2.0). 10, 20, 30 and 40 wt.% of the FHA100 were added to the PCL. Sodium chloride (NaCl) particles with diameters of 300-500 μm were used as porogen. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM) were used to identify the phase structure, functional groups, and distribution of pores in the scaffolds, respectively. Mechanical properties of the scaffolds were also evaluated. Results showed that compressive strength of scaffolds increased by increasing the weight ratio of FHA100 (e.g. in constant porosity (∼60%), compressive strength of PCL-10FHA100 was ∼52 kPa and compressive strength of PCL-40FHA100 was ∼100 kPa) and decreased by increasing the porosity (e.g. in constant ratio of FHA100 (40%), compressive strength of PCL-40FHA100 for ∼60% and ∼80% porosity was ∼100 and ∼50 kPa, respectively). © 2011 Elsevier Ltd. All rights reserved.

Mallakpour S.,Isfahan University of Technology | Madani M.,Isfahan University of Technology
Bulletin of Materials Science | Year: 2012

A series of novel poly(amide-imide)/ZnO nanocomposites with modified ZnO nanoparticles contents was prepared by ultrasonic irradiation. For this purpose, surface of ZnO nanoparticle was modified with γ - aminopropyltriethoxysilane as a coupling agent. Then the effect of surface modification on dispersion of nanoparticles, thermal stability and UV absorption property of the obtained nanocomposites were investigated. The resulting novel nanocomposites were characterized by several techniques. Field emission scanning electron microscopy and transmission electron microscopy analyses of the nanocomposites were performed in order to study the dispersion of nanofillers in the polymer matrix. According to thermogravimetry analysis results, the addition of ZnO nanoparticles improved thermal stability of the obtained nanocomposites. Since the resulting nanocomposites contain phenylalanine amino acid and ZnO, they are expected to be biocompatible as well as biodegradable. © Indian Academy of Sciences.

Jamaati R.,Isfahan University of Technology | Toroghinejad M.R.,Isfahan University of Technology
Journal of Materials Engineering and Performance | Year: 2012

In this study, Al/Al 2O 3 composite strips were produced by the cold roll bonding (CRB) process. Microhardness, tensile strength, and elongation of composite strips were investigated as a result of changes in thickness reduction, quantity of alumina particles, and the production method used. It was found that higher values of reduction and quantities of alumina improved microhardness and tensile strength but decreased elongation. Furthermore, as-received strips exhibited the highest values for microhardness and tensile strength but the lowest for elongation. In contrast, post-rolling annealed strips recorded the lowest values for microhardness and tensile strength but the highest for elongation. Finally, it was found that pre-rolling annealing was the best method for producing this composite via the CRB process. © 2011 ASM International.

Nouri N.,Isfahan University of Technology | Ziaei-Rad S.,Isfahan University of Technology | Adibi S.,Isfahan University of Technology | Karimzadeh F.,Isfahan University of Technology
Materials and Design | Year: 2012

The use of carbon nanotubes (CNTs) in nanotechnology and leading industries is of extreme importance due to its various applications. One such application is producing Aluminum reinforced nanocomposites which may find applications in the aerospace and automobile industries. Scientists and engineers have, recently, concentrated increasing attention on the manufacturing and modeling of such materials. This paper deals with preparing Carbon Nanotube Reinforced Aluminum Nanocomposite (CNRAN) and predicting its mechanical and surface properties using the finite element method (FEM). To prepare the reinforced nanocomposite, a pre-alloyed powder was milled in a planetary ball mill under the argon atmosphere. Multi-wall carbon nanotubes (MWCNTs) were then added to the powder in a particular procedure. Next, a finite element model consisting of MWCNTs as the fibers and Aluminum as the matrix was constructed. A series of nano-indentation tests were carried out to obtain the mechanical and surface properties of the constructed material. The finite element models were then used to predict the results obtained from real indentation tests. The predicted hardness and elastic modulus from the FE model show good agreement with experimental findings. © 2011 Elsevier Ltd.

Mostofinejad D.,Isfahan University of Technology | Reisi M.,Isfahan University of Technology | Shirani A.,Isfahan University of Technology
Construction and Building Materials | Year: 2012

Structures in which γ-ray production instruments are located are made of heavyweight concrete. To determine roof and wall thickness of such structures, it is necessary to measure amount of radiation absorbed. The present study was designed to investigate the effects of mix design parameters such as water to cementations materials ratio, type of aggregates and cement and pozzolanic material contents on γ-ray absorption. This paper determines attenuation coefficient of normal and heavyweight concrete. Absorption of γ-ray was both measured by experimental tests and XCOM software. Results also showed that using barite aggregates increases attenuation coefficient by 30%. Comparison of the compressive strength of normal concrete made of limestone aggregates with that of heavyweight concrete made of barite aggregates showed very close compressive strengths in both types of concrete at high W/CM values. For low W/CM values, however, compressive strength of normal concrete was higher than that of heavyweight. © 2011 Elsevier Ltd. All rights reserved.

Shabani A.,Isfahan University of Technology | Toroghinejad M.R.,Isfahan University of Technology | Shafyei A.,Isfahan University of Technology
Materials and Design | Year: 2012

In this study, the effect of coating nickel and also its different thicknesses on the bond strength of Al-Ni-Cu layers was investigated. Furthermore, the effect of reduction in thickness and post-rolling annealing on the bond strength was evaluated in order to achieve the optimum parameter in rolling Al/Cu/Ni composites. So, after preparing samples, using peeling test, we investigated the bond strength of Al-Cu strips. The results showed that coating copper with nickel reduces the bond strength of Al-Cu strips. However, by increasing the thickness of coating, the bond strength was increased, reaching the highest level compared with the strips without coating. Also, the increase in the reduction enhanced the bond strength of the layered strips. Yet, a decrease in bond strength was achieved by post-rolling annealing of the layered strips. © 2012 Elsevier Ltd.

Mirshahi F.,Isfahan University of Technology | Meratian M.,Isfahan University of Technology
Materials and Design | Year: 2012

Non-reactive in situ process is one of the newly emerged routes for metal matrix composite manufacturing, in which recycling of their scraps has been found to be advantageous. In the present work, the Mg/Mg2Si composite was synthesized using non-reactive in situ method. Improving coarse and dendritic structure of primary Mg2Si precipitates was a reason for modification of primary Mg2Si particles. By adding 0.5wt.% bismuth to the melt, the primary Mg2Si particles were formed in polygonal morphologies while their average size decreased. Tensile tests in different temperatures were conducted on non-modified and modified composite specimens. Tensile properties of the modified composites in different temperatures were enhanced compared to those of non-modified ones. © 2011 Elsevier Ltd.

Parsapour A.,Isfahan University of Technology | Khorasani S.N.,Isfahan University of Technology | Fathi M.H.,Isfahan University of Technology
Journal of Materials Science and Technology | Year: 2012

Surface engineering technology is a suitable method for coatings on the metal surfaces or performing surface modification treatment, which can improve corrosion resistance and biocompatibility of metals. In this research, corrosion behavior of Nb coating on H 2SO 4 and HNO 3 treated AISI stainless steel 316L (SS) was evaluated. Nb coating was carried out using physical vapor deposition process on the SS. Characterization techniques including scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) technique were used to investigate the microstructure and morphology of the coated and treated SS. Electrochemical potentiodynamic tests were performed in two types of physiological solutions and compared with the pristine SS specimens. Cyclic polarization tests were performed to evaluate resistivity against pitting. Experimental results indicate that Nb coating and surface treatment of the SS had a positive effect on improvement of corrosion behavior. The decrease in corrosion current densities was significant for coated and treated specimens. The corrosion current density was much lower than the values obtained for pristine specimens. © 2012 The Chinese Society for Metals.

Mostofinejad D.,Isfahan University of Technology | Reisi M.,Isfahan University of Technology
Construction and Building Materials | Year: 2012

The grading and shape of aggregates have significant effects on the performance of fresh and hardened concrete. Aggregate blends with maximum packing density (PD) require lower amounts of paste to fulfill voids between aggregates and as a result, they are less expensive and have less durability problems. Different methods have been presented by researchers and codes to determine PD of aggregates considering grading; however, there are a few methods that consider the shapes of aggregates. In the current research, using computer simulation software based on discrete element method (DEM), a new method was developed to predict PD of coarse aggregates with regard to grading and shape of aggregates. In this method, all aggregates are modeled as sphere but, as for the shape of aggregates, a friction coefficient, μ is determined for each aggregate. Effectiveness of this method has been substantiated by different computer modeling and laboratory experiments. © 2012 Elsevier Ltd. All rights reserved.

Saraji M.,Isfahan University of Technology | Ghani M.,Isfahan University of Technology
Journal of Chromatography A | Year: 2014

A magnesium-aluminum layered double hydroxide coated on magnetic nanoparticles was synthesized and used as a sorbent to extract some phenolic acids including p-hydroxy benzoic acid, caffeic acid, syringic acid, p-coumaric acid and ferulic acid from fruit juices. After extraction, the elution step was performed through dissolving double hydroxide layers containing the analytes by changing the solution pH. The extracted phenolic acids were separated and quantified using high performance liquid chromatography-photodiode array detection. Experimental parameters such as sorbent amount, solution pH, desorption solvent volume and extraction time were studied and optimized. The linearity range of the method was between 2 and 500μgL-1 with the determination coefficient (r2) higher than 0.991. Relative standard deviations for intra- and inter-day precision for the analytes at 100μgL-1 were in the range of 4.3-9.2% and 4.9-8.6%, respectively. Batch-to-batch reproducibility at 100μgL-1 concentration level was in the range of 7.8-11% (n=3). The limits of detection were between 0.44 and 1.3μgL-1. Relative recoveries higher than 81% with RSDs in the range of 4.2-9.7% were obtained in the analysis of fruit juice samples. © 2014 Elsevier B.V.

Moradlou M.,Isfahan University of Technology | Karshenas H.R.,Isfahan University of Technology
IEEE Transactions on Power Delivery | Year: 2011

This paper is concerned with calculating the optimum rating for two dynamic voltage restorers (DVRs) when used in an interline DVR (IDVR) structure. An IDVR consists of two or more DVRs which have a common dc link and, thus, can exchange active power. This can increase the compensation range of an IDVR compared with separate but otherwise similar DVRs. The basic operation of the DVR and IDVR is briefly explained. The limitations of IDVR operation in terms of active power exchange are explained and, based on that, the expressions governing the steady-state operation of IDVR are derived. The compensation range of an IDVR is compared with that of two separate DVRs. This paper also explores how the limitations in absorbing power from a healthy feeder can narrow the compensation range of an IDVR. After identifying and formulating various limitations in IDVR operation, a design procedure is presented to determine the optimum size (or rating) of the DVRs in an IDVR structure. In the proposed approach, all possible scenarios concerning healthy and faulty feeders are taken into consideration. Examples along with graphs and tables aid in conveying the proposed approach. © 2010 IEEE.

IEEE Transactions on Power Delivery | Year: 2011

Automation can significantly enhance substation reliability by speeding up service restoration. Although much research works has been done in reliability assessment of substation control systems, there are still several aspects that need to be considered in automated substation reliability evaluation. The impacts of automation system on substation reliability indices have not been comprehensively covered in the literature so far. This paper aims at presenting a comprehensive technique to quantitatively assess the reliability of the automated substations. The technique is based on the event tree methodology and the concepts of conditional probability technique. A step by step evaluation procedure is presented using a typical substation automation architecture known as simple star. The proposed technique is applied to some conventional substation configurations to examine the effectiveness of the technique and also to examine the level of reliability improvement achieved by automation. Furthermore, different sensitivity analyses have been carried out for both automatic switching action and a specific automated substation. The proposed strategy is easy to implement and suitable to analyze for an automated substation reliability with arbitrary automation architectures. Also, automated substation reliability assessment tools can be developed in detail, and can be catered to the specific needs of substation design. © 2011 IEEE.

Jafari M.T.,Isfahan University of Technology | Riahi F.,Isfahan University of Technology
Journal of Chromatography A | Year: 2014

The capability of corona discharge ionization ion mobility spectrometry (CD-IMS) for direct analysis of the samples extracted by dispersive liquid-liquid microextraction (DLLME) was investigated and evaluated, for the first time. To that end, an appropriate new injection port was designed and constructed, resulting in possibility of direct injection of the known sample volume, without tedious sample preparation steps (e.g. derivatization, solvent evaporation, and re-solving in another solvent...). Malathion as a test compound was extracted from different matrices by a rapid and convenient DLLME method. The positive ion mobility spectra of the extracted malathion were obtained after direct injection of carbon tetrachloride or methanol solutions. The analyte responses were compared and the statistical results revealed the feasibility of direct analysis of the extracted samples in carbon tetrachloride, resulting in a convenient methodology. The coupled method of DLLME-CD-IMS was exhaustively validated in terms of sensitivity, dynamic range, recovery, and enrichment factor. Finally, various real samples of apple, river and underground water were analyzed, all verifying the feasibility and success of the proposed method for the easy extraction of the analyte using DLLME separation before the direct analysis by CD-IMS. © 2014 Elsevier B.V.

Ensafi A.A.,Isfahan University of Technology | Amini M.,Isfahan University of Technology | Rezaei B.,Isfahan University of Technology
Biosensors and Bioelectronics | Year: 2014

An electrochemical protocol is described for direct monitoring of anti-cancer properties of MMC. Using electrochemical impedance spectroscopy, a pretreated pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs) and poly(diallyldimethylmmonium chloride), PDDA, decorated with ds-DNA was employed in this study to identify DNA damages induced by MMC. The change in charge transfer resistance after incubation of the DNA-biosensor in MMC solution for a known time was used as indication of DNA damage. It was found that MMC did not interact with DNA. As MMC does not inherently possess any anti-cancer activity, it is, therefore, necessary to activate it by either of two ways: activation in acidic media or electrochemical activation. Incubation of DNA-modified electrode in activated MMC led to alterations in DNA and changes in its electrochemical properties (which forms the theme of the present study). Acid and electroreductive MMC activations were compared and different adducts were subsequently generated, suggesting that the drug can bind to DNA in more than one way. Impedance spectroscopy was used for the first time as a novel technique for detecting DNA-drug adducts. © 2014 Elsevier B.V.

Momeni M.M.,Isfahan University of Technology
Bulletin of Materials Science | Year: 2016

This study compares different Fe-doped TiO2 nanostructures in terms of their photocatalytic performance. Iron-doped TiO2 nanostructures (FeTNs) were prepared by in situ anodizing of titanium in a single-step process in the presence of 3, 9, 15 and 21mMK3Fe(CN)6. Potassium ferricyanide was used as the iron source. Prepared films are amorphous, so these layers were thermally annealed. The effect of iron doping on the photoelectrochemical properties (including dye-sensitized solar cells) and photocatalysis properties (decomposition of methomyl) was investigated. In all investigated cases, the sample C, which was formed by anodizing in a ethylene glycol electrolyte containing 9 mM K3Fe(CN)6, exhibited better performance than the bare TiO2 and FeNTs fabricated using other iron concentrations. This study demonstrated a feasible and simple anodizing method to fabricate an effective, reproducible and inexpensive photocatalyst for various applications. © Indian Academy of Sciences.

Information Technology and Applications - Proceedings of the 2014 International Conference on Information technology and Applications, ITA 2014 | Year: 2015

This paper aims to demonstrate the results and achievements of an action research project on the application of ICT in a participatory manner within four Iranian villages. The action research process involved: action planning, determination of stakeholders to participate in action program in an integrated manner, establishment and implementation of ICT centers, and evaluation of the behavioral changes among rural beneficiaries for further reflections. As a result four pilot ICT centers for rural communities were established through a participatory process. Consequently, the results of the survey study on the changes in the behavioral patterns of the local users in terms of socio-cultural, economical and technical was significant. One of the peripheral objectives of the project was to study the impacts of such ICT centers in order to be used in developing a comprehensive model for extending information technologies to all rural areas across Iran. The results from the studies conducted and the analyses thereupon indicate that the mere establishment of single ICT centers in scattered points in villages will not suffice to address the demand for ICT and that it is crucially necessary to develop local ICT networks. It was also concluded that sustainability of rural ICT centers greatly depends in their initial stages of support from local institutions and companies in neighboring urban centers. The logistic provisions for rural IT centers must be provided in an organized manner. © 2015 Taylor & Francis Group, London.

Habibi N.,Isfahan University of Technology
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2014

Zinc oxide was coated on Fe2O3 nanoparticles using sol-gel spin-coating. Caulobacter crescentus have a crystalline surface layer (S-layer), which consist of one protein or glycoprotein species. The immobilization of bacterial S-layers obtained from C. crescentus on zincite-coated nanoparticles of iron oxide was investigated. The SDS PAGE results of S-layers isolated from C. crescentus showed the weight of 50 KDa. Nanoparticles of the Fe2O3 and zinc oxide were synthesized by a sol-gel technique. Fe2O3 nanoparticles with an average size of 50 nm were successfully prepared by the proper deposition of zinc oxide onto iron oxide nanoparticles surface annealed at 450 C. The samples were characterized by field-emission scanning electron microscope (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR).© 2014 Elsevier B.V. All rights reserved.

Rezaei B.,Isfahan University of Technology | Khalili Boroujeni M.,Isfahan University of Technology | Ensafi A.A.,Isfahan University of Technology
Biosensors and Bioelectronics | Year: 2014

In the present study, a novel sensitive and selective nanocomposite imprinted electrochemical sensor for the indirect determination of caffeine has been prepared. The imprinted sensor was fabricated on the surface of pencil graphite electrode (PGE) via one-step electropolymerization of the imprinted polymer composed of conductive polymer, sol-gel, gold nanoparticles (AuNPs), and caffeine. Due to such combination like the thin film of molecularly imprinted polymer (MIP) with specific binding sites, the sensor responded quickly to caffeine. AuNPs were introduced for the enhancement of electrical response by facilitating charge transfer processes of [Fe(CN)6]3-/[Fe(CN)6]4- which was used as an electrochemical active probe. The fabrication process of the sensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Several important parameters controlling the performance of the sensor were investigated and optimized. The imprinted sensor has the advantages of high porous surface structure, inexpensive, disposable, excellent stability, good reproducibility and repeatability. The linear ranges of the MIP sensor were in the range from 2.0 to 50.0 and 50.0 to 1000.0nmolL-1, with the limit of detection (LOD) of 0.9nmolL-1 (S/N=3). Furthermore, the proposed method was successfully intended for the determination of caffeine in real samples (urine, plasma, tablet, green tea, energy and soda drink). © 2014 Elsevier B.V.

Ensafi A.A.,Isfahan University of Technology | Amini M.,Isfahan University of Technology | Rezaei B.,Isfahan University of Technology
Biosensors and Bioelectronics | Year: 2014

The potential toxicity of catecholics is a big concern, because the catechol-derived semiquinone radical after the oxidation of catechol (CA) can donate an H-atom to generate quinone, and during this process a superoxide anion radical may be produced. Considering the fact that catecholics are highly consumed in our daily life and some drugs also contain one or more CA moieties, we speculate that CA's toxicity might not be insurmountable. Therefore, finding approaches to investigate catecholics potential toxicity is of great significance. Here in, an electrochemical protocol for direct monitoring of genotoxicity of catecholics is described. CA encapsulated on MWCNTs (CA@MWCNT) through continuous cyclic voltammetric on the surface of pencil graphite electrode (PGE). Subsequently, a DNA functionalized biosensor (DNA/CA@MWCNT/PGE) was prepared and characterized for the detection and the investigation of DNA damage induced by radicals generated from catecholics. The change in the charge transfer resistance (Rct) after the incubation of the DNA biosensor in the damaging solution for a certain time was used as an indicator for DNA damage. Incubation of DNA-modified electrode with CA solution containing Cu(II), Cr(VI) and Fe(III) has been shown to result in oxidative damage to the DNA and change in the electrochemical properties. It was found that the presence of Cu(II), Cr(VI) and Fe(III) in solution caused damage to DNA. The inhibitory effect of glutathione and plumbagin on the CA-mediated DNA damage has also been investigated using the biosensor. The minimum concentration of the metal ions for CA induced DNA damage was investigated. Recognition of suitable matrixes for CA-mediated DNA damage can be assessed using proposed DNA biosensor. Such direct monitoring of the DNA damage holds great promise for designing new biosensors with modification of the biosensor with different damaging agents. © 2013 Elsevier B.V.

Mazrooei-Sebdani R.,Isfahan University of Technology | Farjami S.,Isfahan University of Technology
Neurocomputing | Year: 2013

In this paper, a discrete-time-delayed Hopfield type neural network model consisting of p neurons with ring architecture and different internal decays is considered. The stability domain of the null solution is found, the values of characteristic parameter for which bifurcations occur at the origin are identified and the existence of Fold/Cusp, Neimark-Sacker and Flip bifurcations are proved. These bifurcations are analyzed by applying the center manifold theorem and the normal form theory. Probability of resonant 1:3 and 1:4 bifurcations also are proved. It is shown that the dynamics in a neighborhood of the origin become more and more complicated as the characteristic parameter grows in magnitude and passes through the bifurcation values. The occurrence of chaos in the sense of Marotto is shown, if the magnitude of the interconnection coefficients are large enough and at least one of the activation functions has two simple real roots. Some numerical simulations are carried out to illustrate the analytical results. © 2012 Elsevier B.V.

Khodaverdizadeh H.,Isfahan University of Technology | Niroumand B.,Isfahan University of Technology
Materials and Design | Year: 2011

In this study, the effects of applied pressure during solidification on the microstructure and mechanical properties of cylindrical shaped ductile iron castings were investigated. Magnesium treated cast iron melts were solidified under atmospheric pressure as well as 25, 50 and 75. MPa external pressures. Microstructure features of the castings were characterized using image analysis, optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques. Tensile properties, toughness and hardness of the castings were also measured. The results showed that average graphite nodule size, free graphite content and ferrite content of the castings decreased and pearlite and eutectic cementite contents increased as the applied pressure was raised from 0 to 75. Mpa. Graphite nodule count was first increased by raising the applied pressure up to 50. MPa and then decreased. The highest graphite nodule count was obtained at 50. MPa applied pressure. The microstructural changes were associated with the improved cooling rate and the expected changes in the corresponding phase diagram of the alloy under pressure. The ultimate tensile strength (UTS), yield point strength (0.2% offset) and fracture toughness of the castings were improved when the applied pressure was raised from 0 to 50. MPa. Further increase of the applied pressure resulted in slight decrease of these properties due to the formation of more cementite phase in structures as well as reduced graphite nodule count. Hardness of the castings continuously increased with increasing the applied pressure. © 2011 Elsevier Ltd.

Afzalimehr H.,Isfahan University of Technology
Hydrological Processes | Year: 2010

Non-uniform flows encompassing both accelerating and decelerating flows over a cobble-bed flume have been experimentally investigated in a flume at a scale of intermediate relative submergence. Measurements of mean longitudinal flow velocity u, and determinations of turbulence intensities u', v', w', and Reynolds shear stress -ufwf have been made. The longitudinal velocity distribution was divided into the inner zone close to the bed and the outer zone far from the bed. In the inner zone of the boundary layer (near the bed) the velocity profile closely followed the 'Log Law'; however, in the outer zone the velocity distribution deviated from the Log Law consistently for both accelerating and decelerating flows and the changes in bed slopes ranging from -2% to +2% had no considerable effect on the outer zone. For a constant bed slope (S = ±0.015), the larger the flow rate, the smaller the turbulence intensities. However, no detectable pattern has been observed for u', v' and w' distributions near the bed. Likewise, for a constant flow rate (Q = 0.040 m3/s), with variation in bed slope the longitudinal turbulent intensity profile in the longitudinal direction remained concave for both accelerating and decelerating flows; whereas vertical turbulent intensity (w') profile presented no specific form. The results reveal that the positions of maximum values of turbulence intensities and the Reynolds shear stress depend not only on the flow structure (accelerating or decelerating) but also on the intermediate relative submergence scale. © 2009 John Wiley & Sons, Ltd.

Tavangarian F.,Isfahan University of Technology | Emadi R.,Isfahan University of Technology
Materials Letters | Year: 2011

Recently, forsterite (Mg2SiO4) has been introduced as a possible bioceramics due to its good biocompatibility. It has a better bending strength and fracture toughness than those of commercially available hydroxyapatite ceramics. In this study, nanostructure effects on the bioactivity of forsterite powder were investigated. For synthesizing forsterite powder, talc and magnesium carbonate powders were mechanically activated for various times. Then, the prepared powders were mixed with ammonium chloride (as a catalyst) and annealed at different temperatures. For bioactivity evaluation, the obtained forsterite powders were pressed in the form of tablets and then immersed in simulated body fluid (SBF). The results showed that nanostructure forsterite powder with crystallite size of about 31 nm, unlike micrometer-sized forsterite, possessed apatite formation ability and its bioactivity, biocompatibility, and good mechanical properties make it a suitable candidate for load bearing application in bone implant materials and open new horizons in tissue engineering. © 2010 Elsevier B.V.

Sebdani M.M.,Isfahan University of Technology | Fathi M.H.,Isfahan University of Technology
International Journal of Applied Ceramic Technology | Year: 2011

Despite considerable bioactivity of bioactive ceramics such as hydroxyapatite, their poor mechanical properties have hindered their clinical applications. It is expected that the incorporation of a ceramic reinforcement with reduced grain size below 100 nm improves their properties. The aim of this work was fabrication, characterization, and bioactivity evaluation of a novel hydroxyapatite-forsterite-bioglass composite nanopowder via a sol-gel method. Results showed that suitable temperature for calcination was 600°C and the particle size was about 60-70 nm. During immersion in simulated body fluid, apatite layer was formed. It seems that prepared composite nanopowder could be a good candidate for biomedical applications. © 2010 The American Ceramic Society.

Mallakpour S.,Isfahan University of Technology | Dinari M.,Isfahan University of Technology
Journal of Polymers and the Environment | Year: 2010

A short and green method for the preparation of optically active aromatic polyamides (PAs) using tetrabutylammonium bromide (TBAB) as a molten ionic liquid is reported. Polycondensation reactions of amino acid containing diacid (2S)-5-(4-methyl-2-phthalimidylpentanoylamino)isophthalic acid with various commercially available diisocyanates in molten TBAB as a green medium or in N-methylpyrrolidone as common organic solvent with or without dibutyltin dilaurate as a catalyst under microwave irradiation were carried out. Various PAs were obtained with high yields and moderate inherent viscosities in the rang of 0. 30-0. 57 dL/g. The obtained polymers were characterized by FT-IR, specific rotation measurements, and representative of them by 1H NMR and elemental analysis techniques. Thermal properties of PAs were evaluated by thermogravimetric analysis and the results showed that the 10% weight loss temperature in a nitrogen atmosphere for four representative samples were more than 258 °C, which indicates that the resulting PAs have good thermal stability as well as excellent solubility. © 2010 Springer Science+Business Media, LLC.

Tavangarian F.,Isfahan University of Technology | Emadi R.,Isfahan University of Technology
Materials Letters | Year: 2011

This paper reports the positive effects of chlorine ion on the forsterite formation rate. The influence of mechanical activation of talc and magnesium carbonate mixture on the formation of forsterite structure was studied in the presence of chlorine ion. Mechanical activation increased the contact surface area of the reacting phases as a consequence of intensively reduced particle size, which is very important in the case of diffusion-controlled reactions. Besides, the presence of chlorine ion affected the forsterite formation rate following annealing. The single-phase nanostructure forsterite powder with a crystallite size of about 20 nm was obtained by 5 h of mechanical activation and subsequent annealing at 1000 °C for 2 min in the presence of the chlorine ion. © 2010 Elsevier B.V. All rights reserved.

Diba M.,Isfahan University of Technology | Fathi M.H.,Isfahan University of Technology | Kharaziha M.,Isfahan University of Technology
Materials Letters | Year: 2011

Novel highly porous nanocomposite scaffolds consisting of polycaprolactone (PCL) and forsterite nanopowder were prepared by a solvent-casting/particle- leaching method. In addition, the effects of forsterite nanopowder contents on the structure of the scaffolds were investigated to provide an appropriate composite for bone regenerative medicine. Results showed that the scaffolds exhibited high porosity (up to 92%) with open pores of 100-300 μm average diameters. This porosity increased with decreasing forsterite nanopowder content. In addition, the pore walls contained numerous micropores. Microstructure studies showed that the pores were well distributed throughout the structures. Furthermore, the bioactive forsterite nanoparticles were homogenously distributed within the PCL matrix of the scaffolds, which contained up to 30 wt.% forsterite nanopowder. This porous structure with micropores provides the properties required for bone tissue engineering applications. © 2011 Elsevier B.V. All rights reserved.

Shah Hosseini H.,Isfahan University of Technology | Shamanian M.,Isfahan University of Technology | Kermanpur A.,Isfahan University of Technology
Materials Characterization | Year: 2011

The microstructure and mechanical properties of Inconel 617/310 austenitic stainless steel dissimilar welds were investigated in this work. Three types of filler materials, Inconel 617, Inconel 82 and 310 austenitic stainless steels were used to obtain dissimilar joint using the gas tungsten arc welding process. Microstructural observations showed that there was no evidence of any possible cracking in the weldments achieved by the nickel-base filler materials. The welds produced by 617 and 310 filler materials displayed the highest and the lowest ultimate tensile strength and total elongation, respectively. The impact test results indicated that all specimens exhibited ductile fracture. Among the fillers, Inconel 617 exhibited superlative fracture toughness (205 J). The mechanical properties of the Inconel 617 filler material were much better than those of other fillers. © 2011 Elsevier Inc. All rights reserved.

Ensafi A.A.,Isfahan University of Technology | Karimi-Maleh H.,Isfahan University of Technology | Mallakpour S.,Isfahan University of Technology | Hatami M.,Isfahan University of Technology
Sensors and Actuators, B: Chemical | Year: 2011

A new dopamine-derivative, i.e. N-(3,4-dihydroxyphenethyl)-3,5- dinitrobenzamide (N-DHPB), was synthesized and its application was investigated for the simultaneous determination of N-acetylcysteine (NAC) and acetaminophen (AC) using modified multiwall carbon nanotubes paste electrode. This modified electrode exhibited a potent and persistent electron mediating behavior followed by well separated oxidation peaks of NAC and AC. The peaks current of differential pulse voltammograms of NAC and AC increased linearly with their concentration in the ranges of 0.5-200 μmol L-1 NAC and 15.0-270 μmol L-1 AC. The detection limits for NAC and AC were 0.2 μmol L-1 and 10.0 μmol L-1, respectively. The relative standard deviation for seven successive assays of 1.0 and 30.0 μmol L -1 NAC and AC were 1.7% and 2.2%, respectively. The proposed sensor was successfully applied for the determination of NAC in human urine, tablet, and serum samples. © 2010 Elsevier B.V.

Tavangarian F.,Isfahan University of Technology | Emadi R.,Isfahan University of Technology
Materials Letters | Year: 2011

This paper reports the successful synthesis of nanostructure bredigite powder by mechanical activation with subsequent annealing. Talc, calcium carbonate, and amorphous silica were used as initial reactants. The initial materials were milled for various times and then annealed in order to obtain single-phase nanostructure bredigite powder. The results showed that during the formation of bredigite powder some intermediate compounds such as wollastonite and larnite were formed. Single-phase nanostructure bredigite powder was synthesized by 10-60 h of mechanical activation with subsequent annealing at 1200 °C for 1 h. The bredigite powder obtained after 60 h milling and subsequent annealing at 1200 °C for 1 h had a mean crystallite size of about 50 nm and mean particle size of about 779 nm. © 2011 Elsevier B.V. All rights reserved.

Abedi H.R.,Isfahan University of Technology | Salehi M.,Isfahan University of Technology
Materials and Design | Year: 2011

In this study, the effect of temperature of post-oxidation process on tribological and corrosion behavior of AISI 316 plasma nitrided stainless steel has been studied. Plasma nitriding was carried out at 450°C for 5h with gas mixture of N2/H2=1/3. The plasma nitrided samples were post-oxidized for 1h with gas mixture of O2/H2=1/5 at different temperature of 400, 450 and 500°C. The structural, tribological and corrosion properties were analyzed using XRD, SEM, microhardness testing, pin-on-disk tribotesting and electrochemical polarization. The results indicated that the nitride layer was composed of S-phase. The amount of S-phase decreased as the treatment temperature rose from 400°C to 500°C. In addition, it was found that oxidation treatment reduces wear resistance of plasma nitrided sample. It was demonstrated that the corrosion characteristics of the nitrided sample were further improved by post-oxidation treatment. The difference in corrosion resistance is mainly attributed to the thickness of the oxide top layer, which is governed by the post-oxidizing temperature. © 2010 Elsevier Ltd.

Shamsaei B.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology
Composite Structures | Year: 2011

In this paper a new method for solution of static two-dimensional laminates has been proposed. A series of Exponential Basis Functions (EBFs) have been used to satisfy the governing equations within each layer. Compatibility and equilibrium conditions at the interfaces of the layers, with isotropic or orthotropic properties, are rigorously satisfied through defining a characteristic problem. The solution of such a characteristic problem yields to a set of spectral basis functions through which one may obtain a clear insight to the modes governing the displacement field. For further use, we present simplified relations for single-layer and two-layer laminates. The boundary conditions at the ends of the laminate are satisfied by a suitable discrete transformation in a collocation style. With such an approach one can solve problems with variety of end conditions. Excellent agreement is observed between the results of this work and some benchmark problems. Some more problems are solved as new benchmarks for further studies. © 2011 Elsevier Ltd.

Verdian M.M.,Isfahan University of Technology
Materials and Manufacturing Processes | Year: 2011

A supersaturated Ni-10Ti alloy powder was produced from Ni and Ti elemental powders by solid state synthesis utilizing high energy mechanical alloying with times up to 5h. Then, the milled powders were deposited on AISI 304 stainless steel substrate using air plasma spraying (APS) process. The microstructure and phase composition of the products were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results indicated that the coatings contain Ni-Ti supersaturated solid solution and small amounts of oxides. The microhardness value for the deposited layer was comparable to that of as-milled powder. Further investigation showed that the corrosion performance of Ni-10Ti coating was comparable to that of AISI 304 stainless steel substrate. Copyright © Taylor & Francis Group, LLC.

Rahmati S.,Isfahan University of Technology | Ghaei A.,Isfahan University of Technology
Journal of Thermal Spray Technology | Year: 2014

Cold spray is a coating deposition method in which the solid particles are accelerated to the substrate using a low temperature supersonic gas flow. Many numerical studies have been carried out in the literature in order to study this process in more depth. Despite the inability of Johnson-Cook plasticity model in prediction of material behavior at high strain rates, it is the model that has been frequently used in simulation of cold spray. Therefore, this research was devoted to compare the performance of different material models in the simulation of cold spray process. Six different material models, appropriate for high strain-rate plasticity, were employed in finite element simulation of cold spray process for copper. The results showed that the material model had a considerable effect on the predicted deformed shapes. © 2013 ASM International.

Sepahi O.,Isfahan University of Technology | Forouzan M.R.,Isfahan University of Technology | Malekzadeh P.,Persian Gulf University
Materials and Design | Year: 2011

As a first endeavor, the thermal buckling and postbuckling analysis of functionally graded (FG) annular plates with material properties graded in the radial direction is presented. The formulation is derived based on the first-order shear deformation theory (FSDT) and the geometrical nonlinearity is modeled using Green's strain in conjunction with von Karman's assumptions. The material properties are temperature-dependent and graded according to the power law distribution. It is assumed that the temperature varies along the radial direction. Using the virtual work principle, the pre-buckling and postbuckling equilibrium equations and the related boundary conditions are derived. Differential quadrature method (DQM) as an efficient numerical technique is adopted to solve the governing equations. The presented formulation and the method of solution are validated by performing convergence and comparison studies with available results in the literature. Finally, the effects of volume fraction index, geometrical parameters, mechanical/thermal properties of the constituent materials and boundary conditions on the thermal buckling and postbuckling behavior of the radially graded annular plate are evaluated and discussed. © 2011 Elsevier Ltd.

Mohammad Sharifi E.,Isfahan University of Technology | Karimzadeh F.,Isfahan University of Technology | Enayati M.H.,Isfahan University of Technology
Materials and Design | Year: 2011

In this study, fabrication and characterization of bulk Al-B4C nanocomposites were investigated. B4C nanoparticles were mixed with pure Al powder by ball milling to produce Al-B4C powder. Al-B4C powders containing different amounts of B4C (5, 10 and 15wt.%) were subsequently hot pressed to produce bulk nanocomposite samples. Consolidated samples were characterized by hardness, compression and wear tests. Results showed that the sample with 15wt.% B4C had the optimum properties. This sample had a value of 164HV which is significantly higher than 33HV for pure Al. Also, ultimate compressive strength of the sample was measured to be 485MPa which is much higher than that for pure Al (130MPa). The wear resistance of the nanocomposites increased significantly by increasing the B4C content. Dominant wear mechanisms for Al-B4C nanocomposites were determined to be formation of mechanical mixed layer on the surface of samples. © 2011 Elsevier Ltd.

Amirkhanlou S.,Isfahan University of Technology | Niroumand B.,Isfahan University of Technology
Materials and Design | Year: 2011

One of the great challenges of producing cast metal matrix composites is the agglomeration tendency of the reinforcements. This would normally result in poor distribution of the particles, high porosity content, and low mechanical properties. In the present work, a new method for uniform distribution of very fine SiC particles with average size of less than 3μm was employed. The key idea was to allow for gradual in situ release of properly wetted SiC particles in the liquid metal. For this purpose, SiC particles were injected into the melt in three different forms, i.e., untreated SiCp, milled particulate Al-SiCp composite powder, and milled particulate Al-SiCp-Mg composite powder. The resultant composite slurries were then cast from either fully liquid (stir casting) or semisolid (compocasting) state. Consequently, the effects of the casting method and the type of the injected powder on the microstructural characteristics as well as the mechanical properties of the cast composites were investigated. The results showed that the distribution of SiC particles in the matrix and the porosity content of the composites were greatly improved by injecting milled composite powders instead of untreated-SiC particles into the melt. Casting from semisolid state instead of fully liquid state had similar effects. The average size of SiC particles incorporated into the matrix was also significantly reduced from about 8 to 3μm by injecting milled composite powders. The ultimate tensile strength, yield strength and elongation of Al356/5vol.%SiCp composite manufactured by compocasting of the (Al-SiCp-Mg)cp injected melt were increased by 90%, 103% and 135%, respectively, compared to those of the composite manufactured by stir casting of the untreated-SiCp injected melt. © 2010 Elsevier Ltd.

Arabi Jeshvaghani R.,Tarbiat Modares University | Shamanian M.,Isfahan University of Technology | Jaberzadeh M.,Isfahan University of Technology
Materials and Design | Year: 2011

This paper deals with the improvement of the wear resistance of ductile iron surface alloyed by a hypoeutectic stellite 6 alloy. In this regard, the surface alloyed layer with 3. mm thickness deposited on ductile iron using tungsten inert gas (TIG) surface processing. The microstructure, hardness and wear resistance of surface alloyed layer were investigated using optical microscopy, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis, Vickers hardness (HV0.3) and pin-on-plate tests. The results showed that the microstructure of the surface alloyed layer consisted of carbides dispersed in a Co-based solid solution matrix with dendritic structure. This microstructure was responsible for the improvement of the hardness and wear resistance of the coating. Further investigations showed that the dominant mechanism of the wear in the coated and uncoated samples was delamination wear. © 2010 Elsevier Ltd.

Amirkhanlou S.,Isfahan University of Technology | Rezaei M.R.,Isfahan University of Technology | Niroumand B.,Isfahan University of Technology | Toroghinejad M.R.,Isfahan University of Technology
Materials and Design | Year: 2011

Silicon carbide reinforced aluminum alloy composite materials produced by casting methods are increasingly used in many engineering fields. However, these materials suffer from poor distribution of the reinforcement particles in the matrix and high content of porosity. The effect of subsequent cold rolling process with different reductions on the porosity, microstructure and mechanical properties of cast Al6061/10 vol.% SiCp composite was investigated in this study. Composites fabricated by compocasting method were rolled at five different reductions of 30, 60, 75, 85 and 95%. The rolled specimens exhibited reduced porosity as well as a more uniform particle distribution when compared with the as-cast samples. Microscopic investigations of the composites after 95% reduction showed an excellent uniform distribution of silicon carbide particles in the matrix. During cold rolling process it was observed that the tensile strength and ductility of the samples increased by increasing the reduction content. After 95% reduction, the tensile strength and elongation values reached 306.7MPa and 7.9%, which were 4.6 and 3.3 times greater than those of the as-cast composite, respectively. © 2010 Elsevier Ltd.

Eshraghi-Kakhki M.,Mississippi State University | Golozar M.A.,Isfahan University of Technology | Kermanpur A.,Isfahan University of Technology
Materials and Design | Year: 2011

Success or failure of a quenching process is determined by selecting an appropriate quenchant. In this work, the quenching process of the automobile tie rods in different media including water, oil, and a polymeric solution was investigated. The microstructures and mechanical properties of the rods were predicted by a finite element simulation model. Several specimens were cut from the tie rods and heat treated by quenching in five different quenching media including water, oil, and PAG aqueous solutions with polymer concentrations of 10, 20, and 30%. The hardness tests and metallographic analyses were performed on the specimens. Considering the results of the simulations and the experiments, the optimum quenchant was selected and the tie rods were heat treated using this quenchant. The results showed that the use of Poly Alkylene Glycol (PAG) solution quenchants, with respect to its unique cooling mechanism, outperformed water and oil quenchants. The distortion and cracking was reduced compared to water quenching and, on the other hand, the mechanical properties which were not achievable by oil quenching were resulted using polymer-based quenching medium. © 2010 Elsevier Ltd.

Rezaei B.,Isfahan University of Technology | Rahmanian O.,Isfahan University of Technology
Sensors and Actuators, B: Chemical | Year: 2011

In this work, nanolayer MIP (molecularly imprinted polymer) is used to achieve suitable conformation for catalyzing AP (allopurinol) redox reaction. Also, a sensitive electrochemical sensor was fabricated for AP based on MIP immobilized on multiwall carbon nanotube (MWCNT) surface. Thin film of MIP immobilized on MWCNT surface (MIPCNT) with specific recognition sites for AP was cast on glassy carbon electrode (GCE). The morphology and features of the film were characterized by field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometric measurements (I-t) in detail. The near equilibrium time to adsorb AP on the surface of electrode is about 9 min. The modified electrode was used to detect the concentration of AP with a linear range and detection limit (S/N = 3) of 0.01-1.0 μM and 6.88 nM, respectively. The MIPCNT film displayed an excellent selectivity toward AP. Finally, the modified electrode was successfully applied to determine AP in the human serum sample and two brand tablets. © 2011 Elsevier B.V. All rights reserved.

Farajpour A.,Isfahan University of Technology | Danesh M.,Isfahan University of Technology | Mohammadi M.,Isfahan University of Technology
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2011

This paper presents an investigation on the buckling characteristics of nanoscale rectangular plates under bi-axial compression considering non-uniformity in the thickness. Based on the nonlocal continuum mechanics, governing differential equations are derived. Numerical solutions for the buckling loads are obtained using the Galerkin method. The present study shows that the buckling behaviors of single-layered graphene sheets (SLGSs) are strongly sensitive to the nonlocal and non-uniform parameters. The influence of percentage change of thickness on the stability of SLGSs is more significant in the strip-type nonoplates (nanoribbons) than in the square-type nanoplates. © 2011 Elsevier B.V.

Bazarganipour M.,Isfahan University of Technology
Ceramics International | Year: 2016

Rod-like and sphere-like barium molybdate (BaMoO4) nanostructures have been synthesized by a large scale and simple sonochemical method by using Ba(Sal)2 (Sal=salicylidene) and Na2MoO4·2H2O for the first time. The effects of sonochemical irradiation time, sonochemical power, temperature, solvent, surfactant and barium source were considered to obtain a controlled shape. It was established that morphology, particle size and phase composition of the final products could be greatly affected by these parameters. The photocatalytic activity of the synthesized products has been compared for the photodegradation activity of methylene blue (MB). © 2016 Elsevier Ltd and Techna Group S.r.l.

Sarhadi A.,Isfahan University of Technology | Soltani S.,Isfahan University of Technology | Modarres R.,INRS - Institute National de la Recherche Scientifique
Journal of Hydrology | Year: 2012

This study presents an exhaustive methodology of floodplain mapping at ungauged rivers. To present our methodology, we selected the Halilrud basin and Jiroft city in southeastern Iran as an example of hazardous regions. To estimate flood quantiles in different return periods at ungauged reaches, we used regional flood frequency analysis. By using the well-known L-moments approach and related criteria, a homogeneous region was formed and the 3-parameter Log normal distribution was identified as the robust regional frequency distribution. The hydro-geomorphic characteristics and the land use properties of the catchments were then extracted using RS&GIS techniques to establish multivariate regional regression models between hydro-geomorphic characteristics and flood quantiles. After delineation of the catchments for the ungauged reaches, flood quantiles as an important factor in flood inundation at outlets of these reaches with different probabilities were estimated using the regional regression models. To delineate flood hazard maps and to enhance the accuracy of the hydraulic modeling, we applied satellite stereoscope images of Cartosat-1 along with the Rational Polynomial Coefficients to extract a high resolution DTM and detailed parameterization of the channel required by 1D hydraulic model HEC-RAS. The GIS-based HEC-Geo RAS pre- and post-processor were also used for careful optimization of the geometry features for real visualization of the flood prone areas. Information of some historical flood events was also used to evaluate the hydraulic model performance in predicting flood inundations. Finally, vulnerable areas were crossed with extracted land use mapping from IRS-P6 satellite images to differentiate the critical infrastructures and the valuable land use classes affected by floods in different return periods. © 2012 Elsevier B.V.

Jamaati R.,Isfahan University of Technology | Toroghinejad M.R.,Isfahan University of Technology
Journal of Materials Engineering and Performance | Year: 2011

It is the objective of this article to investigate the influence of surface preparation on the cold roll bonding (CRB) process. In this context, the effects of surface preparation parameters consisting of surface preparation method, surface roughness, scratch-brushing parameters, and the delay time between surface preparation and rolling are investigated on the bond strength of aluminum strips. The bond strength of two adjacent aluminum strips produced by the CRB process is evaluated by the peeling test. Furthermore, the interface region is investigated by metallographic observations. Our findings indicate that higher surface roughness values and shorter delay times improve the bond strength. It is also found that degreasing followed by scratch-brushing yield the best bonding properties. © 2010 ASM International.

Arabi Jeshvaghani R.,Tarbiat Modares University | Harati E.,Tarbiat Modares University | Shamanian M.,Isfahan University of Technology
Materials and Design | Year: 2011

In this study, the effect of surface alloying on the microstructure and wear behavior of ductile iron was studied. In this regard, ductile iron samples were coated by single and double pass welds of a nickel-based electrode (ENiCrFe3) using shielded metal arc welding. The effects of number of passes on microstructure, hardness and wear resistance of cladded layers were investigated. Optical microscopy and X-ray diffractometry were used to identify the microstructure and phase composition of cladded layers and interfaces. The results revealed that cladded layers consist of austenite (Fe, C), γ(Fe, Ni) and small quantities of carbides such as Cr7C3. It was also found that the hardness of the cladded layers was higher than that of substrate. In samples processed with a single and double passes, hardness reached up to 500 and 450 HV, respectively. Pin-on-plate wear tests showed that the wear mechanism is predominantly delamination in the cladded layers and substrate. © 2010 Elsevier Ltd.

Eskandari K.,Isfahan University of Technology | Lesani M.,Isfahan University of Technology
Chemistry - A European Journal | Year: 2015

When R is sufficiently electron withdrawing, the fluorine in the R-F molecules could interact with electron donors (e.g., ammonia) and form a noncovalent bond (F•••N). Although these interactions are usually categorized as halogen bonding, our studies show that there are fundamental differences between these interactions and halogen bonds. Although the anisotropic distribution of electronic charge around a halogen is responsible for halogen bond formations, the electronic charge around the fluorine in these molecules is spherical. According to source function analysis, F is the sink of electron density at the F•••N BCP, whereas other halogens are the source. In contrast to halogen bonds, the F•••N interactions cannot be regarded as lump-hole interactions; there is no hole in the valence shell charge concentration (VSCC) of fluorine. Although the quadruple moment of Cl and Br is mainly responsible for the existence of s -holes, it is negligibly small in the fluorine. Here, the atomic dipole moment of F plays a stabilizing role in the formation of F•••N bonds. Interacting quantum atoms (IQA) analysis indicates that the interaction between halogen and nitrogen in the halogen bonds is attractive, whereas it is repulsive in the F•••N interactions. Virial-based atomic energies show that the fluorine, in contrast to Cl and Br, stabilize upon complex formation. According to these differences, it seems that the F•••N interactions should be referred to as "fluorine bond" instead of halogen bond. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dinari M.,Isfahan University of Technology | Mallakpour S.,Isfahan University of Technology
Journal of Polymer Research | Year: 2014

In this contribution, polyvinylpyrrolidone (PVP) nanocomposites (NCs) with novel chiral diacid intercalated layered double hydroxides (LDHs) as nanofillers were prepared via ultrasonic irradiation. Chiral LDH was synthesized in one step via a co-precipitation reaction in aqueous solution under ultrasonic irradiation. The modified Mg-Al LDH shows an increase in interlayer distance as compared to the unmodified Mg-Al LDH by X-ray diffraction (XRD). Different NCs of organo-modified chiral LDHs and PVP were constructed by means of an ultrasonic process. The structures of these new materials were investigated by XRD, Fourier transform infrared, field emission scanning electron microscopy and transmission electron microscopy techniques. XRD and electron microscopy results confirmed the delaminated state of the LDH in the PVP matrix. Furthermore, thermal analysis was evaluated and the prepared NCs show significantly improved thermal stability at higher temperature because of the homogeneous and good dispersion of modified LDH in polymeric matrix. © 2014 Springer Science+Business Media Dordrecht.

Mallakpour S.,Isfahan University of Technology | Zadehnazari A.,Isfahan University of Technology
Polymer Bulletin | Year: 2014

An amino acid containing poly(amide-thioester-imide) (PATEI) possessing a conjugated thiadiazol ring was shown to be effective for dispersing multiwall carbon nanotubes (MWCNTs) in N,N′-dimethylacetamide. Through casting of these dispersions, MWCNT/PATEI composite films were successfully fabricated on substrates and showed no signs of macroscopic aggregation. To increase the compatibility between PATEI matrix and MWCNTs, carboxyl-functionalized MWCNTs (f-MWCNTs) were used in this study. The f-MWCNTs were dispersed homogeneously in the PATEI matrix while the structure of the polymer and the MWCNTs structure were stable in the preparation process as revealed by transmission electron microscopy. Tensile tests and thermal analysis were carried out on free-standing composite films for different MWCNT loading levels. Results showed that overall mechanical and thermal properties of the composites were greatly improved as compared with the neat PATEI film. Fourier transform infrared spectroscopy, powder X-ray diffraction, and field emission electron microscopy were also used to evaluate the MWCNT/PATEI composite system. © 2013 Springer-Verlag Berlin Heidelberg.

Mallakpour S.,Isfahan University of Technology | Zeraatpisheh F.,Isfahan University of Technology
Designed Monomers and Polymers | Year: 2011

In this paper, we investigated the synthesis of an optically active poly(ester-imide) containing two aminoacid residues in the main chain. This macromolecule was synthesized by polycondensation of N,N- (pyromellitoyl)-bis-L- tyrosine dimethyl ester as a diphenolic monomer and a chiral trimellitic anhydride-derived diacid monomer containing L-methionine. The direct step-growth polymerization of this diacid with aromatic diol was carried out in a system of tosyl chloride (TsCl), pyridine (Py) and N,N-dimethylformamide (DMF) as a condensing agent. The obtained polymer has a useful level of thermal stability. Thereafter, the surface of zinc oxide nanoparticles (ZnO-NPs) was treated with a silane coupling agent, γ-methacryloxypropyltrimethoxysilane (KH570), which introduces functional groups on the surface of ZnO-NPs. Then, PEI/zinc oxide bionanocomposites (PEI/ZnO BNCs) containing 4, 8 and 12% of NPs were successfully prepared by an ultrasonic method as a simple and inexpensive route. In modified ZnO-NPs, the organic chains of KH570 can fulfill strict hindrance between inorganic NPs and prevent their aggregation. The obtained polymer BNCs were characterized by FT-IR, XRD, FE-SEM, TEM and TGA. The FT-IR spectroscopy indicated that the silane coupling agent was anchored on the surface of ZnO-NPs. Direct proof for the formation of the true polymer BNCs was provided by TEM investigation. Also, a morphology study of the synthesized polymer BNCs using FE-SEM analysis showed well-dispersed ZnO-NPs in the polymer matrix. TGA confirmed that the heat stability of the polymer BNCs was enhanced in the existence of modified nanostructure ZnO particles. © 2011 Koninklijke Brill NV, Leiden.

Baninasab B.,Isfahan University of Technology
Journal of Horticultural Science and Biotechnology | Year: 2010

Salicylic acid (SA) is a common, plant-produced signal molecule that is responsible for inducing tolerance to a number of biotic and abiotic stresses. An experiment was therefore conducted to test whether the application of SA at various concentrations (0,0.25,0.50,0.75, or 1.00 mM) by seed soaking, or as a foliar spray would protect cucumber (Cucumis sativus L.) seedlings subjected to drought stress. Thirty-six-day-old seedlings (n = 12 seedlings per treatment) were exposed to drought stress for 14 d. Pretreatment with SA improved the majority of the physiological (e.g., relative chlorophyll content and chlorophyll fluorescence ratio) and morphological parameters (e.g., shoot and root fresh and dry weights) measured in cucumber seedlings subjected to drought stress. SA ameliorated the injuries caused by drought stress by increasing shoot tissue proline contents and preventing an increase in leaf electrolyte leakage. SA was more effective at increasing the drought tolerance of cucumber seedlings when applied using the seed-soaking method, rather than as a foliar spray. The best drought protection appeared to be obtained when seeds were soaked in 0.50 mM SA.

Mallakpour S.,Isfahan University of Technology | Khadem E.,Isfahan University of Technology
High Performance Polymers | Year: 2014

In the present study, novel optically active poly(amide-imide)/alumina nanocomposites (PAI/Al2O3 NCs) containing different amounts of modified α-Al2O3 nanoparticles (NPs) were synthesized using the ultrasonic-assisted technique. To improve NPs dispersion and increase the possible interaction between NPs and PAI matrix, the surface of α-Al2O3 NP was modified with bioactive diacid coupling agent. The PAI chains were formed from the polycondensation of N-trimellitylimido-l-phenylalanine diacid with 1,5-diamino naphthalene under green conditions. The obtained polymer and inorganic metal oxide NPs were used to prepare chiral PAI/Al2O3 NCs through the ultrasonic irradiation. PAI/Al2O3 NCs were characterized by Fourier transform infrared spectra, x-ray diffraction patterns, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and ultraviolet-visible (UV-Vis). TGA results confirmed that the heat stability of the prepared NP-reinforced composites was improved compared with the pure polymer. In addition, TEM and FESEM images showed that NPs were dispersed into the polymer matrix at nanoscale. © The Author(s) 2014.

Mohammadi M.,Isfahan University of Technology | Zamani A.,Isfahan University of Technology | Karimi K.,Isfahan University of Technology
Journal of Agricultural and Food Chemistry | Year: 2012

Glucosamine (GlcN) is a major and valuable component in the cell wall of zygomycetes fungi. In this study, a time independent and accurate method was developed for the determination of GlcN. In this method, the cell wall was treated via a two-stage sulfuric acid process, and chitin and chitosan were fully deacetylated, partially depolymerized, and converted to GlcN oligosaccharides. Then, the oligosaccharides were deaminated to 2,5-anhydromannose using nitrous acid. Finally, 2,5-anhydromannose was analyzed by high performance liquid chromatography (HPLC). The determinations of pure GlcN solutions were stable at least for 10 days, while those of the conventional colorimetric method were not stable for more than one hour. The alkali insoluble material (AIM) of biomass of purely yeast-like, mostly yeast-like, and filamentous forms of the fungus Mucor indicus was analyzed by the developed method. The respective GlcN content of AIM of the fungus was 0.232, 0.204, and 0.458 (g/g). © 2012 American Chemical Society.

Mallakpour S.,Isfahan University of Technology | Soltanian S.,Isfahan University of Technology
Journal of Polymer Research | Year: 2014

This study aims at characterizing the thermal and morphological properties of multi-walled carbon nanotubes (MWCNT)s reinforced poly(ester-imide) (PEI) bionanocomposites (BNC)s containing amino acid group which were prepared through ultrasonication technique. To enhance the interfacial interaction between MWCNTs and PEI, carboxylic functionalized MWCNTs were embedded with PEI chains. By applying a step-growth polymerization method, biodegradable and chiral PEI was synthesized from a reaction of natural amino acid based diacid (4) with 4,4′-thiobis(2-tert-butyl-5-methylphenol) (5) promoted by tosyl chloride in pyridine and N,N-dimethyl formamide solution. The prepared BNCs were studied with Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The microstructure study of the BNCs containing 5, 10, and 15 wt.% MWCNT-COOH exhibited rather homogeneous dispersion of MWCNTs throughout PEI matrices on the macroscopic scale. In comparison with neat PEI, the MWCNTs reinforced BNCs revealed higher thermal stability as confirmed by TGA results. © 2014 Springer Science+Business Media Dordrecht.

Goshadrou A.,Isfahan University of Technology | Goshadrou A.,McGill University | Karimi K.,Isfahan University of Technology | Taherzadeh M.J.,University of Borås
Biomass and Bioenergy | Year: 2013

Birch wood was pretreated with N-methylmorpholine-N-oxide (NMMO or NMO) followed by enzymatic hydrolysis and fermentation to ethanol or digestion to biogas. The pretreatments were carried out with NMMO (wNMMO = 85%) at 130 °C for 3 h, and the effects of drying after the pretreatment were investigated. Enzymatic hydrolysis of the untreated wood resulted in 8%-10% of theoretical glucose yield after 4 days hydrolysis, while the NMMO pretreatment improved this yield to 91%. Consequently, ethanol production yield from NMMO-pretreated materials resulted in around 9-fold improvement compared to the untreated wood. On the other hand, drying of the pretreated wood had a negative impact and decreased the yield of enzymatic hydrolysis by 4%-10%. Digestion of the untreated wood with thermophilic bacteria resulted in maximum methane yield of 158 cm3 g-1 of VS in 30 days, while the NMMO pretreatment improved the methane yield up to 232 cm3 g-1 of VS (80% of the theoretical biogas yield) in just 9 days. © 2012 Elsevier Ltd.

Hamadani A.Z.,Isfahan University of Technology | Khorshidi H.A.,Isfahan University of Technology
International Journal of Advanced Manufacturing Technology | Year: 2013

In the recent years, many significant methods for evaluation of structural system reliability and its improvement have been evolved. First step for improving the longevity of system is to estimate the system reliability. After that, improving actions can be employed in an optimized way. This paper tries to evaluate the reliability of system during function period. Also, the optimization model has been developed to make a best decision on component's number and improving actions' level. To achieve this goal, reliability value and engineering economic tools have been useful to model a multiobjective problem. At last, an illustrative example is presented, and genetic algorithm, as the most applicable meta-heuristic method in the field of reliability optimization, has been used. © 2012 Springer-Verlag London Limited.

Tavakol H.,Isfahan University of Technology | Shahabi D.,Isfahan University of Technology
Journal of Physical Chemistry C | Year: 2015

In this work, the interactions of S-doped single-wall carbon nanotubes (SCNTs) with rare gases (RGs) were fully considered using density functional theory (DFT), quantum theory of atom in molecule (QTAIM), and natural bond order (NBO) calculations. Different numbers of doped atoms and four RGs (He, Ne, Ar, and Kr) were considered for their adsorption on the surface of and into the SCNTs. The adsorption energies indicated that RGs could be adsorbed on the surface of the S-doped CNTs in endothermic process. Partial charges showed the small charge transfer from RGs to SCNTs. The calculated Ead values showed that first He and then Ar are the best RGs for adsorption by SCNTs. QTAIM calculations confirmed the close-shell (non-covalent) interactions between SCNTs and RGs. In accordance with the results of QTAIM, both NBO charges and E2 interaction energies showed the interaction of SCNTs with RGs. Moreover, population analyses were performed to obtain electronic properties, reactivity parameters, and density of states plots of all structures. © 2015 American Chemical Society.

Javanbakht V.,Isfahan University of Technology | Zilouei H.,Isfahan University of Technology | Karimi K.,Isfahan University of Technology
International Biodeterioration and Biodegradation | Year: 2011

Biosorption characteristics of Pb+2 ions from aqueous solution were investigated using fungus Mucor indicus biomass treated with NaOH. Biosorption was measured as a function of biomass morphology, pH, biomass concentration, contact time, and metal concentration. The morphology of M. indicus biomass was manipulated towards filamentous or yeast-like forms. The highest and lowest biosorption capacities were observed for purely filamentous and yeast-like forms, respectively. Models of Langmuir, Freundlich, Temkin, and Scachard were applied to describe adsorption isotherm and fitted appropriately. Biosorption kinetics was successfully described using Ho's pseudo-second-order model. Maximum and minimum values of biosorption capacity of Pb2+ were 22.1 and 12.1 mg g-1 for purely filamentous and yeast-like morphologies, respectively. Increasing pH resulted in higher biosorption of Pb+2 ions up to pH 5.5. Biosorption capacity of individual Pb+2 ions was reduced in the presence of other metal ions in bi- or multi-metal ion experiments. Metal ions adsorption by the biomass could be eluted effectively with HNO3. © 2010 Elsevier Ltd.

Ensafi A.A.,Isfahan University of Technology | Amini M.,Isfahan University of Technology | Rezaei B.,Isfahan University of Technology
Sensors and Actuators, B: Chemical | Year: 2013

Ensafi A.A.,Isfahan University of Technology | Jafari-Asl M.,Isfahan University of Technology | Rezaei B.,Isfahan University of Technology | Allafchian A.R.,Isfahan University of Technology
Sensors and Actuators, B: Chemical | Year: 2013

An electrochemical sensor was developed for guanine and adenine detection using multiwall carbon nanotubes (MWCNTs) decorated with NiFe2O 4 magnetic nanoparticles on a glassy carbon electrode. Incorporation of MWCNT/NiFe2O4 nanohybrid on the surface of the electrode significantly increases oxidation the peaks currents but reduces the peaks potential of guanine and adenine. The modified electrode was employed for detecting purine bases using linear sweep voltammetry and hydrodynamic amperometry. With hydrodynamic amperometry, the peaks current of both guanine and adenine showed linear dependence on their concentrations in the range of 3.0-45.0 μmol L-1 for guanine and 3.0-40.0 μmol L-1 for adenine. When linear sweep voltammetry was used, the peak currents exhibited linear dependence on guanine in the concentration range of 0.05-3.0 μmol L-1 and on adenine in the concentration range of 0.1-4.0 μmol L-1. The limit of detection (S/N = 3) was found to be 0.006 and 0.01 μmol L-1 for guanine and adenine, respectively. Linear sweep voltammetry was also used for simultaneous determination of adenine and guanine. Finally, the proposed electrochemical sensor was employed to determine guanine and adenine in single-strand deoxyribonucleic acid (ssDNA) samples with satisfactory results. © 2012 Elsevier B.V.

Mazrouei-Sebdani Z.,Isfahan University of Technology | Khoddami A.,Isfahan University of Technology
Progress in Organic Coatings | Year: 2011

For the fabrication of the "lotus-type" fibers a combination of two major requirements, low surface energy and the magnified of the degree of roughness, should be utilized. In this research, the possible surface roughening effect of alkaline hydrolysis of the polyester fibers was applied to manipulate surface topography while fluorocarbon polymer layer generates low surface energy. The results were compared with the method which created variety of surface roughness by changing the size of the nano-silica particles using the 3 M water/oil repellency test, sliding (tilt) angle, microscopy (SEM), decay of hydrophobicity, self-cleaning, tensile properties, abrasion fastness, and air permeability. The results indicated the usefulness of the conventional polyester weight reduction process to control surface roughness for engineering superhydrophobic fabric with sliding angle as low as 7°. Due to the applied conditions this process presents new facile procedure for industrial scale manufacturing of ultrahydrophobic polyester fabric. © 2011 Elsevier B.V. All rights reserved.

Ensafi A.A.,Isfahan University of Technology | Bahrami H.,Isfahan University of Technology | Rezaei B.,Isfahan University of Technology | Karimi-Maleh H.,Isfahan University of Technology
Materials Science and Engineering C | Year: 2013

An ionic liquid-TiO2 nanoparticle modified carbon paste electrode (IL-TiO2/CPE) was used as a fast and sensitive tool for the investigation of the electrochemical oxidation of benserazide using voltammetry. This modified electrode has been fabricated using hydrophilic ionic liquid (n-hexyl-3-methylimidazolium hexafluoro phosphate) as a binder. The modified electrode offers a considerable improvement in voltammetric sensitivity toward benserazide, compared to the bare electrode. Using differential pulse voltammetry (DPV), the electrocatalytic oxidation peak current of benserazide shows a linear calibration curve in the range of 1.0-600 μmol L- 1 benserazide. The limit of detection was equal to 0.4 μmol L- 1. The relative standard deviation (RSD%) for eight successive assays of 10 μmol L- 1 benserazide was 1.1%. Finally, the proposed method was successfully applied to the determination of benserazide in real samples such as blood serum and urine. © 2012 Elsevier B.V.

Ensafi A.A.,Isfahan University of Technology | Taei M.,Isfahan University of Technology | Rahmani H.R.,Isfahan University of Technology | Khayamian T.,Isfahan University of Technology
Electrochimica Acta | Year: 2011

A simple and sensitive DNA impedance sensor was prepared for the detection of chronic lymphocytic leukemia. The DNA electrochemical biosensor is worked based on the electrochemical impedance spectroscopic (EIS) detection of the sequence-specific DNA related to chronic lymphocytic leukemia. The ssDNA probe was immobilized on the surface of the gold nanoparticles. Compared to the bare gold electrode, the gold nanoparticles-modified electrode could improve the density of the probe DNA attachment and hence the sensitivity of the DNA sensor greatly. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy were performed in a solution containing 1.0 mmol L-1 K 3[Fe(CN)6]/K4[Fe(CN)6] and 50 mmol L-1 phosphate buffer saline pH 6.87 plus 50 mmol L-1 KCl. In the CV studied, the potential was cycled from 0.0 to +0.65 V with a scan rate of 50 mV s-1. Using EIS, the difference of the electron transfer resistance (ΔRet) was linear with the logarithm of the complementary oligonucleotides sequence concentrations in the range of 7.0 × 10-12-2.0 × 10-7 mol L-1, with a detection limit of 1.0 × 10-12 mol L-1. In addition, the DNA sensor showed a good reproducibility and stability during repeated regeneration and hybridization cycles. © 2011 Elsevier Ltd.

Anvari S.R.,Isfahan University of Technology | Karimzadeh F.,Isfahan University of Technology | Enayati M.H.,Isfahan University of Technology
Wear | Year: 2013

Al-Cr-O hybrid nano-composites have been fabricated in-situ on the surface of Al6061 plate by friction stir processing (FSP) and their wear resistance has been investigated and compared with Al6061-T6 and friction stir processed (FSPed) Al6061-T6. A new procedure was introduced for applying the reinforcement particles, in which Cr2O3 powder was applied on Al6061 plate by atmosphere plasma spray and then the FSP was performed on the plate. During FSP due to thermomechanical condition, Cr2O3 was reduced with aluminum so pure Cr and Al2O3 were produced and as a result of reaction between Al and Cr, intermetallic compounds including Al13Cr2 and Al11Cr2 appeared. Dry sliding wear tests were applied using a reciprocating wear test. Results showed improved wear resistance in nano-composite samples. Al6061-T6 plate after FSP showed lower wear resistance than Al6061-T6 and nano-composites. This is due to the loss of hardening precipitates as a result of FSP. © 2013 Elsevier B.V.

Hajipour A.R.,University of Wisconsin - Medical School | Hajipour A.R.,Isfahan University of Technology | Pourkaveh R.,Isfahan University of Technology
Synlett | Year: 2014

Palladium-catalyzed cross-coupling reaction of arylboronic acids with acid chlorides at room temperature under phosphine-free conditions affords the corresponding aromatic ketones in excellent yields within short times. This synthetic method overcomes common disadvantages of Friedel-Crafts acylation procedures and is compatible with both electron-donating and electron-withdrawing substituents on the aryl ring of the acyl chlorides. © Georg Thieme Verlag Stuttgart New York.

Kadkhodapour J.,Isfahan University of Technology | Butz A.,Fraunhofer Institute for Mechanics of Materials | Ziaei Rad S.,Isfahan University of Technology
Acta Materialia | Year: 2011

A detailed analysis of the microstructure and failure mechanism of a dual-phase steel material as a function of strain was conducted. Accordingly, three tensile tests were performed and interrupted at different strain levels in order to investigate void nucleation, void growth and void coalescence. Scanning electron microscopy analysis revealed that void nucleation occurs by ferrite grain-boundary decohesion in the neighborhood of martensite grains. Further, void initiation could be observed between closely situated martensite grains. Martensite morphology and distribution has a significant impact on the accumulation of damage. The mechanism of failure was found to be influenced by deformation localization due to microstructural inhomogeneity. Based on the experimental observations and simulation results, a model describing the failure mechanism is proposed for dual-phase steel material. © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Faqeeh A.,Isfahan University of Technology | Aghababaei Samani K.,Isfahan University of Technology
Physica A: Statistical Mechanics and its Applications | Year: 2012

The "clumpiness" matrix of a network is used to develop a method to identify its community structure. A "projection space" is constructed from the eigenvectors of the clumpiness matrix and a border line is defined using some kind of angular distance in this space. The community structure of the network is identified using this borderline and/or hierarchical clustering methods. The performance of our algorithm is tested on some computer-generated and real-world networks. The accuracy of the results is checked using normalized mutual information. The effect of community size heterogeneity on the accuracy of the method is also discussed. © 2011 Elsevier B.V. All rights reserved.

Mallakpour S.,Isfahan University of Technology | Barati A.,Isfahan University of Technology
Amino Acids | Year: 2012

In this investigation, poly(vinyl alcohol) was chemically modified by the introduction of different amounts of N-phthaloyl-L-phenylalanine. The modification was carried out by the reaction of PVA hydroxyl groups with (2S)-3-phenyl-2-phthalimidylpropanoyl chloride using N,N-dimethyl acetamide/lithium chloride as a reaction media. The novel copolymers obtained were characterized by spectroscopic techniques, elemental analysis, Xray diffraction and thermal methods. Optical rotation and viscosities were also measured. The degree of esterification was determined by 1H-NMR. The influence of reagent molar ratio on the degree of modification was also evaluated. The vinyl(3-phenyl-2-phthalimidopropanoate) content in the copolymer was attained up to 52%. Thermal stability of the copolymers was checked by thermogravimetric analysis and differential thermogravimetric analysis. All copolymers displayed improved thermal stability compared to the parent polymer. © Springer-Verlag 2010.

Momeni M.M.,Isfahan University of Technology
Surface Engineering | Year: 2016

Platinum nanoparticle-multi-walled carbon nanotube (Pt-MWCNT) nanocomposite films supported on titanium substrate were prepared by the co-electrodeposition method. This nanocomposite catalyst was characterised by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy and electrochemical methods. The SEM images reveal that nanostructures are distributed at the surface of the titanium plate. Electro-oxidation of methanol was investigated in acidic media on Pt-MWCNTs/Ti electrodes via cyclic voltammetric analysis in the mixed 0.1 M methanol and 0.1 M H2SO4 solutions. The Pt-MWCNTs/Ti catalyst has good electro-catalytic activity for methanol oxidation. This novel Pt-MWCNTs/Ti catalyst can be used repeatedly and exhibits stable electro-catalytic activity for the methanol oxidation. © 2016 Institute of Materials, Minerals and Mining

Kadkhodapour J.,Isfahan University of Technology | Butz A.,Fraunhofer Institute for Mechanics of Materials | Ziaei-Rad S.,Isfahan University of Technology | Schmauder S.,University of Stuttgart
International Journal of Plasticity | Year: 2011

Both experimental and numerical methods were employed to investigate the mechanism of failure in dual phase steels. The tensile test was interrupted in different steps to capture the mechanism of void initiation and void growth during material failure. The results can be considered as a first report for the commercial DP800 steel. Numerical simulations, which were carried out using the real micro-structure, are able to predict the void initiation in the material. In addition, through the numerical simulation a new understanding of the deformation localization was gained. Deformation localization, which causes severely deformed regions in the material, is most probably the main source of rupture in the final stages of the failure. In the SEM micrographs of the material after failure some voids are observable which can validate the results obtained by the simulation. © 2010 Elsevier Ltd. All rights reserved.

Modarres R.,INRS ETE | Sarhadi A.,Isfahan University of Technology
Global and Planetary Change | Year: 2011

Iran is a large country with diverse geophysical and climatic conditions which are influenced by both large atmospheric circulation patterns and local effects. The density of rainfall station network of Iran is not enough for rainfall estimation at ungauged regions.Therefore, rainfall regionalization should be used to extend rainfall data to regions where rainfall data are not available. The aim of this study is to use cluster analysis and L-moment methods together to quantify regional rainfall patterns of Iran using annual rainfall of 137 stations for the period of 1952-2003. The cluster analysis follows "Ward's method" and shows eight regions of rainfall in Iran. The homogeneity test of L-moments shows that most of these regions are homogeneous. Using the goodness-of-fit test, Z Dist, the regional frequency distribution functions for each group are then selected. The 3-parameter Log Normal (LN3), Generalized Extreme Value (GEV) and generalize logistic (GLOG) distributions are selected for the first, second and the remaining 6 regions of rainfall over Iran, respectively. However, because of different rainfall generating mechanisms in Iran such as elevation, sea neighborhood and large atmospheric circulation systems, no parent distribution could be found for the entire country. © 2010 Elsevier B.V.

Reza Sabzalian M.,Isfahan University of Technology | Mirlohi A.,Isfahan University of Technology
Journal of Plant Nutrition and Soil Science | Year: 2010

Infection with Neotyphodium spp. endophytes increases resistance to drought stress and soil mineral imbalances in tall fescue (Festuca arundinacea Schreb. = Lolium arundinaceum (Schreb.) S. J. Darbysh.) and meadow fescue (Festuca pratensis Huds. = Lolium pratense (Huds.) Darbysh.). We hypothesized that resistance of these grasses to salinity stress may also be attributed to endophyte infection. Two tall fescue genotypes, Fa75 and Fa83, and one meadow fescue genotype, Fp60, infected (E+) with their endophytic fungi, Neotyphodium coenophialum (Glenn, Bacon and Hanlin) and N. uncinatum (Glenn, Bacon and Hanlin), respectively, and their noninfected counterparts (E-) were cultured in nutrient solution at three salinity levels of 0, 85, and 170 mM NaCl. Except for genotype Fa75, E+ plants exhibited higher leaf survival rates than E- clones at a high salinity level (170 mM). Root dry matter was higher in E+ than in E- plants, but shoot dry matter was not affected by endophyte infection. This resulted in a lower shoot-to-root ratio in E+ plants (1.63) compared with E- plants (2.40). Sodium (Na+) and chloride (Cl-) concentrations were greater in roots of E- than in E+ clones. In shoots, Na+ and Cl- concentrations were not affected by the endophyte. In contrast, E+ plants accumulated more potassium (K+), which resulted in a greater K+ Na+ ratio in shoots of E+ than in those of E- plants. Our results show that endophyte infection reduced Na+ and Cl- concentrations in tall fescue and meadow fescue roots but increased K+ concentrations in the shoots. Based on these results, we conclude that endophyte-infected grasses may thrive better in salinity-stress environments. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Norouzi S.,Isfahan University of Technology | Khademi H.,Isfahan University of Technology
Plant and Soil | Year: 2010

Nonexchangeable soil K trapped between interlayers of clay minerals is an important source of K for plants grown on many soils. In this study, the ability of alfalfa, as the most important forage crop worldwide, to take up K from some micaceous minerals and to promote the transformation of micaceous minerals were investigated. Alfalfa was cultivated in pots that consisted of a mixture of Hamadan quartz sand and Amlash biotite, Hamadan muscovite and Hamadan phlogopite. Plants were irrigated with distilled water and complete or K-free nutrient solutions. After 90 days, K uptake by plants was measured by flame photometer. Also, the clay size particles in each pot were analyzed using x-ray diffraction. It was found that alfalfa was able to induce a significant release of interlayer K during cropping. The amount of K taken up by alfalfa was significantly higher for Hamadan phlogopite. X-ray diffractometry showed a strong vermiculitization of Hamadan phlogopite and Amlash biotite, but no X-ray detectable transformation of muscovite was recognized. © Springer Science + Business Media B.V. 2009.

Karami K.,Isfahan University of Technology | Rizzoli C.,University of Parma | Salah M.M.,Isfahan University of Technology
Journal of Organometallic Chemistry | Year: 2011

The ortho-metallated complex [Pd(μ-Cl){κ2(C,C)-[C 6H4(PPh2CHC(O)C6H 4-Ph-4)}]2 (2a) was prepared by refluxing of Pd(OAc) 2 and {(Ph)3PCHCOC6H4-Ph-4} (PhBPPY) of in CH2Cl2 followed by addition of an excess of KCl in MeOH Complex (2a) reacts with triphenylphosphine to give the mononuclear derivative [Pd(Cl)(PhC6H4COCHPPh2C 6H4)(PPh3)] (3a) whose crystal structure has been determined by single crystal X-ray diffraction. The Suzuki reactions of aryl bromides and chlorides of varying electron density using complex (3a) as an efficient catalyst were performed, giving the cross-coupling products in good to excellent yields. © 2010 Elsevier B.V. All rights reserved.

Gharibi H.,Tarbiat Modares University | Kakaei K.,Tarbiat Modares University | Zhiani M.,Isfahan University of Technology
Journal of Physical Chemistry C | Year: 2010

A film of PANI nanowires (PANI (NWs)) was deposited onto the surface of a stainless steel electrode via cyclic voltammetry. During the polymerization of aniline (ANI), PANI(NWs) were doped with trifluoromethane sulfonic acid, and the doped PANI were utilized for the fabrication of a Vulcan (C) PANI composite. Pt particles were subsequently deposited by reduction onto the C-PANI composite to produce a Pt/C-PANI electrocatalyst. The current peak during methanol oxidation, the electrochemical surface area, and the stability of the Pt/C-PANI electrocatalysts were better than those observed using Pt/C+PANI (commercial Pt/C composites containing PANI) or Pt/C electrodes. The ionic resistance of the two electrodes containing PANI were only slightly larger than those of the Pt/C and Nafion solution catalysts, but electrochemical impedance spectroscopy measurements using the modified electrodes did not show a negative impedance after measurement of the open current voltage. The methanol diffusion coefficients in the Pt/C-PANI and Pt/C+PANI electrocatalysts were found to be 2.5 and 2 times higher than in the Pt/C electrode. X-ray diffractometer and scanning electron microscopy technique have been applied to investigate the crystallite size and the surface morphologies respectively. The Pt/C-PANI modified catalysts is more suitable for applying in the direct methanol fuel cells in comparison with the standard Pt catalysts. © 2010 American Chemical Society.

Farrokhpour H.,Isfahan University of Technology | Fathi F.,Isfahan University of Technology
Chemical Physics Letters | Year: 2014

The comments of Plekan et al. (2013) on the Letter 'Valence ionization of l-proline amino acid: experimental and theoretical study, Chem. Phys. Lett. 565 (2013) 102' are entirely replied to. We strongly confirm our experimental and theoretical results on the photoelectron spectroscopy of l-proline in our published Letter. © 2014 Elsevier B.V. All rights reserved.

Mallakpour S.,Isfahan University of Technology | Dinari M.,Isfahan University of Technology
Amino Acids | Year: 2012

In the present work, several novel optically active nanostructure poly(amide-imide)s (PAI)s were synthesized via step-growth polymerization reaction of chiral diacids based on pyromellitic dianhydride-derived dicarboxylic acids containing different natural amino acids such as l-Alanine, S-valine, l-leucine, l-isoleucine, l-methionine, and l-phenylalanine with 2-(3,5-diaminophenyl)-benzimidazole under green conditions using molten tetrabutylammonium bromide. The new optically active PAIs were achieved in good yields and moderate inherent viscosity up to 0.41 dL/g. The synthesized polymers were characterized with FT-IR, 1H-NMR, X-ray diffraction, field emission scanning electron microscopy (FE-SEM), elemental and thermogravimetric analysis (TGA) techniques. These polymers show high solubility in organic polar solvents due to the presence of amino acid and benzimidazole pendant group at room temperature. FE-SEM results show that, these chiral nanostructured PAIs have spherical shapes and the particle size is around 20-80 nm. On the basis of TGA data, such PAIs are thermally stable and can be classified as self-extinguishing polymers. In addition due to the existence of amino acids in the polymer backbones, these macromolecules are not only optically active but also could be biodegradable and thus may well be classified under environmentally friendly materials. © 2012 Springer-Verlag.

Jafari M.T.,Isfahan University of Technology | Saraji M.,Isfahan University of Technology | Yousefi S.,Isfahan University of Technology
Journal of Chromatography A | Year: 2012

A novel method based on microextraction in packed syringe (MEPS) coupled with negative electrospray ionization-ion mobility spectrometry (ESI-IMS) was developed for simultaneous and direct determination of phenoxyacid herbicides in water samples. The effects of various parameters such as pH of the sample solution, sample loading rate, the nature of elution solvent and its volume, and the number of extraction cycles were investigated. The method was exhaustively validated in terms of sensitivity, recovery, reproducibility, and enrichment factor. The detection limits of the method for 2,4-D, silvex, and haloxyfop were found to be 60, 70, and 90ngL-1, respectively. The recovery of the analyzed herbicides was in the range 73-102%, and the relative standard deviation (RSD) was lower than 10% for all the experiments. Various real samples were analyzed with the proposed method, and the obtained results revealed the efficient extraction of the analytes using MEPS extraction before the analysis by negative ESI-IMS. © 2012 Elsevier B.V.

Mallakpour S.,Isfahan University of Technology | Soltanian S.,Isfahan University of Technology
Amino Acids | Year: 2012

Four derivatives of N-trimellitylimido-l-amino acid (4a-4d) were prepared by the reaction of trimellitic anhydride (1) with the l-amino acids (2a-2d) in acetic acid as diacid monomers and were used with the aim to obtain a new family of amino acid based poly(ester-imide)s (PEI)s. The polymerization was performed by direct polycondensation of chiral diacids (4a-4d) with 4,4′-thiobis(2- tert-butyl-5-methylphenol) (5) in the presence of tosyl chloride (TsCl), pyridine and N,N-dimethyl formamide (DMF). Step-growth polymerization was carried out by varying the time of heating and the molar ratio of TsCl/diacid and the optimum conditions were achieved. The synthesized polymers were characterized by means of specific rotation experiments, FT-IR, 1H-NMR, X-ray diffraction techniques and elemental analysis. The surface morphology of the obtained polymers was studied by field emission scanning electron microscopy. The result showed nanostructure morphology of the resulting polymers. The obtained PEIs were soluble in polar aprotic solvents such as DMF, N,N-dimethyl acetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and protic solvents such as sulfuric acid. Thermal stability and the weight-loss behavior of the PEIs were studied by thermal gravimetric analysis (TGA) techniques. TGA showed that the 10% weight loss temperature in a nitrogen atmosphere was more than 402°C, therefore they had useful levels of thermal stability associated with excellent solubility. © 2011 Springer-Verlag.

Loghman-Estarki M.R.,Isfahan University of Technology | Edris H.,Isfahan University of Technology | Shoja Razavi R.,Malek-Ashtar University of Technology
Ceramics International | Year: 2013

Non-transformable tetragonal scandia, yttria doped zirconia (SYDZ) nanopowders were prepared in large scale by the citric acid (CA) based gel method. The effect of ethylene glycol monobutyl ether (EGM):CA ratios and pH on the structure, morphology and SYDZ particle size was investigated. The microstructure of SYDZ was characterized by XRD, Raman scattering, TG-DTA, SEM, TEM, and FTIR analyses. The SYDZ nanopowders, synthesized with 1Zr 4+:4EGM:4CA mole ratio in acidic medium (pH ∼1) at 700° C, had an average diameter of 15±2 nm. Finally, air plasma spray (APS) coatings were produced from nanostructured SYDZ agglomerated powders. © 2013 Elsevier Ltd and Techna Group S.r.l.

Polymer (United Kingdom) | Year: 2014

In this study, the synthesis, morphology, and thermal properties of new poly(ether imide)/titania nanohybrid films were investigated. The novel diamine containing functional nitrile groups was prepared in two steps by the nucleophilic substitution reaction and it was fully characterized by different techniques. Reaction of this diamine with pyromellitic dianhydride and 4-aminobenzoic acid gave poly(ether imide) with carboxylic acid end groups. This acid functionalized poly(ether imide) was condense with different amount of TiO2 nanoparticles to provide organic-inorganic bonding, and the flexible films of these hybrid were prepared. The obtained materials were characterized by Fourier transform-infrared spectroscopy, thermogravimetry analysis (TGA), differential scanning calorimetry, X-ray powder diffraction, UV-Vis spectroscopy, field emission-scanning electron microscopy, and transmission electron microscopy (TEM) techniques. TEM of the nanohybrid films with 12% of TiO2 contents confirms well dispersion of nanoparticles in the polymer matrix. TGA data indicated that the thermal behavior of the hybrid materials was increased with an increasing the content of TiO2 nanoparticles. The tensile stress-strain of the hybrids was investigated and the resulting nanocomposites showed good mechanical properties. The permeability and selectivity of the PEI/TiO2 membranes as a function of the titania weight percentage were study and the results indicated that the permeabilities of CO2 and N2 increase with increasing the titania content. © 2014 Elsevier B.V. All rights reserved.

Mallakpour S.,Isfahan University of Technology | Zadehnazari A.,Isfahan University of Technology
Journal of Solid State Chemistry | Year: 2014

Multi-walled carbon nanotubes (MWCNTs) were functionalized by ascorbic acid by a fast strategy under microwave irradiation to improve interfacial interactions and dispersion of CNTs in a poly(amide-imide) (PAI) matrix. This technique provides a rapid and economically viable route to produce covalently functionalized CNTs. The as-prepared, new type of functionalized CNTs were analyzed by several techniques. The thermal stabilities and mechanical interfacial properties of CNT/PAI composites were investigated using several techniques. The dispersion state of CNTs in the PAI matrix was observed by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The mechanical interfacial property of the composites was significantly increased by the addition of ascorbic acid treated CNTs. The FE-SEM and TEM results showed that the separation and uniform dispersion of CNTs in the PAI matrix. The overview of these recent results is presented. © 2014 Elsevier Inc.

Ensafi A.A.,Isfahan University of Technology | Karimi-Maleh H.,Isfahan University of Technology | Ghiaci M.,Isfahan University of Technology | Arshadi M.,Isfahan University of Technology
Journal of Materials Chemistry | Year: 2011

In this work a new sensor in nano size containing Mn-nanoparticles decorated organo-functionalized nanosized SiO2-Al2O 3 mixed-oxide support was developed as a new electrocatalysis for oxidation of organic compounds such as captopril. SiO2-Al 2O3 mixed-oxide were functionalized with Schiff base ligand and thereatfer, in the next step, Mn-nanoparticles were prepared over the organo-functionalized SiO2-Al2O3 mixed-oxide. The synthesized materials were characterized with different methods such as FT-IR spectroscopy, UV-vis, CHN elemental analysis, TEM, ICP-OES, cyclic voltammetry, and electrochemical impedance spectroscopy. Under the optimum conditions (pH 7.0) in cyclic voltammetry, the oxidation of the captopril was occurred at a potential about 650 mV at a surface of the modified electrode. Linear sweep voltammetry exhibited two wide linear dynamic ranges of 0.30-5.0 and 5.0-340 μmol L-1 captopril. The detection limit was found to be 0.095 μmol L-1 captopril. The kinetic parameters such as electron transfer coefficient and catalytic reaction rate constant were also determined. Finally, the modified electrode used as a novel electrochemical sensor for the determination of captopril in real samples such as pharmaceutical, patient and safe human urine. This journal is © The Royal Society of Chemistry.

Gholipour A.,Isfahan University of Technology | Shamanian M.,Isfahan University of Technology | Ashrafizadeh F.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2011

This paper deals with the investigation of the microstructure and wear behavior of the stellite 6 cladding on precipitation hardening martensitic stainless steel (17-4PH) using gas tungsten arc welding (GTAW) method. 17-4 PH stainless steel is widely used in oil and gas industries. Optical metallography, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to study the microstructure and wear mechanisms. X-ray diffraction analysis was also used to identify phases formed in the coating. The results showed that the microstructure of the surface layer consisted of carbides embedded in a Co-rich solid solution with a dendritic structure. In addition, the dendritic growth in the coating was epitaxial. Primary phases formed during the process were Co (fcc), Co (hcp), lamellar eutectic phases, M 23C6 and Cr7C3 type carbides. The results of the wear tests indicated that the delamination was the dominant mechanism. So, it is necessary to apply an inter-layer between the substrate and top coat. © 2011 Elsevier B.V. All rights reserved.

Mokhtari A.R.,Isfahan University of Technology
Journal of Geochemical Exploration | Year: 2014

Hydrothermal alterations play a key role in the formation of different mineralization types and zones of economic interests. In mineral exploration industry, the identification of such alterations is usually carried out by visual inspection of specimen through mineral assemblage study. In the following study, it is attempted to identify the alteration type mathematically, based on chemical analysis of the samples. However, modeling of alteration types due to its categorical nature requires special techniques that could handle such variables. The present research employs logistic regression analysis to propose a model for the classification of alteration types (argilic and propilitic) over part of the geological-geochemical dataset, collected at the Kuh Panj porphyry copper mineralization. Logistic regression is applied in a stepwise manner, and the final model has successfully classified the samples in the training dataset (90.50% of a correct classification). The model is also examined by the test dataset and it has concluded to an acceptable result, similar to training set with 90% of a correct classification in the differentiation of alteration types. The final model includes a constant and 9 explanatory variables, including: As, Cr, Cu, Fe, Na, Ni, Sc, Tl and Y. The Wald statistic has suggested that the selected variables are significant and the model itself is evaluated to be significant trough chi-square and Hosmer and Lemeshow tests (all in 5% of significance level).Application of this technique can then effectively be used where powder samples are taken from an ore body. Additionally, training a model where microscopic studies are available can more precisely separate the alteration types, leading to lower cost of exploration program and consequently, more efficient programming at exploration, exploitation and mineral processing stages. © 2014 Elsevier B.V.

Ensafi A.A.,Isfahan University of Technology | Dadkhah M.,Isfahan University of Technology | Karimi-Maleh H.,Isfahan University of Technology
Colloids and Surfaces B: Biointerfaces | Year: 2011

An electrochemical method is described for the voltammetric determination of isoproterenol in the presence of uric acid using p-chloranil-carbon nanotubes paste electrode. Cyclic voltammetric, chronoamperometric, and electrochemical impedance spectroscopic methods have used to investigate the suitability of p-chloranil as a mediator for the electrocatalytic oxidation of isoproterenol at pH=10.5. Using differential pulse voltammetry, isoproterenol (ISPT) and uric acid (UA) in a mixture can be measured simultaneously and individually with a potential difference of 360mV. The electrocatalytic currents increase linearly with ISPT and UA concentrations over the concentration ranges of 0.015-100μmolL-1 ISPT and 3.0-310μmolL-1UA. The detection limits for ISPT and UA were equal to 0.009 and 2.3μmolL-1, respectively. The diffusion coefficient and the kinetic parameters such as electron transfer coefficient and heterogeneous rate constant were determined for ISPT, using the electrochemical approaches. The proposed method was successfully applied to the determination of isoproterenol in both ampoule and urine samples. © 2011 Elsevier B.V.

Saraji M.,Isfahan University of Technology | Bidgoli A.A.H.,Isfahan University of Technology
Analytical and Bioanalytical Chemistry | Year: 2010

A novel and efficient surfactant-assisted dispersive liquid-liquid microextraction combined with high-performance liquid chromatography-photodiode array detection was developed for the determination of phenylurea herbicides in water samples. Based on this procedure, which is a dispersive-solvent-free technique, the extractant is dispersed in the aqueous sample using methyltrialkylammonium chloride. Compared with the conventional dispersive liquid-liquid microextraction, the new extraction method has many advantages such as higher extraction efficiency, low cost, reduced environmental hazards, and consumption of less extracting solvent. A few microliters of chloroform containing an appropriate amount of methyltrialkylammonium chloride (mixture of C8-C10) was used to extract the analytes from water samples. The main parameters relevant to the extraction process (namely, type of surfactant, selection of extractant solvent, extractant volume, surfactant concentration, ionic strength, and extraction time) were investigated. The performed analytical procedure showed limits of detection ranging from 2.3 to 18 ng/L, and precision ranges from 0.6% to 2.0% (as intra-day relative standard deviation, RSD) and from 1.3% to 8.3% (as inter-day RSD) depending on the analyte. The method showed good linearity between 0.0