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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.


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. Source


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. Source


Hajian-Hoseinabadi H.,Isfahan University of Technology
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. Source


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. Source


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). Source


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. Source


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. Source


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. Source


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. Source


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. Source


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. Source


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. Source


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. Source


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. Source


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. Source


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 Source


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. Source


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. Source


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. Source


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. Source


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

In this paper, the buckling problem of thin rectangular functionally graded plates subjected to proportional biaxial compressive loadings with arbitrary edge supports is investigated. Classical plate theory (CPT) based on the physical neutral plane is applied to derive the stability equations. Mechanical properties of the FGM plate are assumed to vary continuously along its thickness according to a power law function. The displacement function is considered to be in the form of a double Fourier series whose derivatives are determined using Stokes' transformation. The advantage of this method is capability of considering any possible combination of boundary conditions with no necessity to be satisfied in the Fourier series. To give generality to the problem, the plate is assumed to be elastically restrained by means of rotational and translational springs at the four edges. Numerical examples are presented, and the effects of the plate aspect ratio, the FGM power index, and the loading proportionality factor on the buckling load of an FGM plate with different usual boundary conditions are studied. The present results are compared with those have been previously reported by other analytical and numerical methods, and very good agreement is seen between the findings indicating validity and accuracy of the proposed approach in the buckling analysis of FGM plates. © 2013 Elsevier Masson SAS. All rights reserved. Source


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. Source


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. Source


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. Source


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. Source


Tabesh A.,Isfahan University of Technology | Frechette L.G.,Universite 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. Source


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. Source


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. Source


Shafiei N.,Islamic Azad University at Najafabad | Pahlevaninezhad M.,Queens University | Farzanehfard H.,Isfahan University of Technology | Bakhshai A.,Queens University | Jain P.,Queens 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. Source


Haghighi M.,Isfahan University of Technology
Journal of the Science of Food and Agriculture | Year: 2012

Background: This paper reports for the first time the influence of partially replacing the nitrogen (N) source of a nutrient solution with amino acids and humic acid on the physiological and antioxidant activities and N metabolism in lettuce. A hydroponic experiment was designed to replace 25 and 50% of the N in nutrient solutions (NSs) with glutamic acid (GA) and humic acid (HA) and evaluate the effects on growth, nitrate (NO3) assimilation, protein content, nitrate reductase (NR) activity and antioxidant changes in lettuce. Results: The results showed that, when a portion of the N was replaced with GA and HA, the fresh and dry weights of lettuce shoots did not change significantly compared with the full NO3 treatment. The titratable acidity was not affected by adding HA and/or GA to the NS. The nitrite concentration and NR activity decreased with reductions in the N concentration of the NS and improved with the addition of GA and HA. GA enhanced the NO3 uptake and protein content more than HA. Changes in the superoxide dismutase (SOD) and peroxidase (POD) activities and malondialdehyde content were inconclusive: SOD and POD activities decreased with decreasing N content of the NS, and HA addition improved the SOD and POD activities. Conclusion: When HA and GA were substituted for NO3 in an NS, the acids effectively adjusted the N metabolism and growth in lettuce and decreased the N consumption of the NS. © 2012 Society of Chemical Industry. Source


Enayati M.H.,Isfahan University of Technology | Mohamed F.A.,University of California at Irvine
International Materials Reviews | Year: 2014

Mechanical alloying (MA) and mechanical milling (MM) techniques have been widely utilised over the past two decades for synthesis of various alloys and composites with equilibrium or metastable structure at room temperature. One of the most interesting features of MA/MM is the ability to produce nanocrystalline and amorphous materials. Several mechanisms for formation of nanocrystalline and amorphous structures have been introduced based on experimental findings and similarity of MA/MM to other solid-state processing routes. In this paper, the recent experimental observations reported on development of nanocrystalline and amorphous structures using ball mill technique are selectively examined and critically reviewed to provide further insight into the key issues related to this solid-state technique. The review includes four major parts. It begins with a brief introduction to MA/MM and the principles of ball milling process for synthesis of materials. The second part is devoted to the formation of nanocrystalline structure by ball milling process. The earlier studies are summarised with special emphasis on the minimum grain size obtainable by ball milling, besides the recent progresses on the prediction of minimum grain size based on dislocation models are analysed and discussed in detail. The third part deals with the amorphisation reaction induced by ball milling. This section includes the thermodynamic and kinetic aspects, the criteria developed for amorphisation reaction and microstructural evolution of powders during MA leading to the amorphisation reaction. The last part is devoted to the bulk amorphous/nanocrystalline alloys produced from precursor powder. © 2014 Institute of Materials, Minerals and Mining and ASM International. Source


Fathi M.,Isfahan University of Technology | Varshosaz J.,Isfahan University of Medical Sciences
Journal of Functional Foods | Year: 2013

The objective of this research was to encapsulate hesperetin as a natural antioxidant in order to enhance its functionality for food fortification. Hesperetin loaded nanostructure lipid carriers (NLC) were coated with different biopolymers (chitosan, alginate, and low methoxypectin) and some features of the developed nanocarriers, including size, zeta potential, morphology, release kinetics, stability, thermal behaviour, chemical structure, and sensory properties were studied. The developed nano size carries showed high zeta potential and excellent stability against aggregation. Thermal analysis indicated that hesperetin was well incorporated into nanoparticles. The Fourier transform infrared spectroscopy revealed no chemical reaction between encapsulating materials and hesperetin. Sensory analysis also showed that developed nanoparticles could be applied for milk fortification to mask bitterness, inhibit colour change and enhance its solubility. © 2013 Elsevier Ltd. Source


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. Source


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. Source


Zamani A.,Isfahan University of Technology | Taherzadeh M.J.,University of Boras
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. Source


Mokhtari R.,Isfahan University of Technology
Communications in Theoretical Physics | Year: 2011

The aim of this paper is to generate exact travelling wave solutions of the Harry-Dym equation through the methods of Adomian decomposition, He's variational iteration, direct integration, and power series. We show that the two later methods are more successful than the two former to obtain more solutions of the equation. © 2011 Chinese Physical Society and IOP Publishing Ltd. Source


Khosravi R.,Isfahan University of Technology
European Physical Journal C | Year: 2015

We investigate the structure of the (Formula presented.) mesons via analyzing the semileptonic (Formula presented.) transition in the frame work of the three-point QCD sum rules and the heavy-quark effective theory. We consider the (Formula presented.) meson in three ways: as a pure (Formula presented.) state, as a mixture of the two (Formula presented.) states with a mixing angle (Formula presented.), and as a combination of the two mentioned states with mixing angle (Formula presented.) in the heavy-quark limit. Taking into account the gluon condensate contributions, the relevant form factors are obtained for the three above conditions. These form factors are numerically calculated for (Formula presented.) and the heavy-quark limit cases. The obtained results for the form factors are used to evaluate the decay rates and the branching ratios. Also for mixed states, all of the mentioned physical quantities are plotted with respect to the unknown mixing angle $$\theta $$θ. © 2015, The Author(s). Source


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). Source


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. Source


Khosravi R.,Isfahan University of Technology
European Physical Journal C | Year: 2015

We analyze the semileptonic $$B \rightarrow a_1 \ell ^+\ell ^-$$B→a1ℓ+ ℓ-, $$\ell =\tau , \mu , e$$ℓ=τ,μ,e transitions in the framework of the three-point QCD sum rules in the standard model. These rare decays are governed by the flavor-changing neutral current transition of $$b \rightarrow d$$b→d. Considering the quark condensate contributions, the relevant form factors as well as the branching fractions of these transitions are calculated. © 2015, The Author(s). Source


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. Source


Hasani H.,Isfahan University of Technology
Indian Journal of Fibre and Textile Research | Year: 2010

The influence of different processing stages on the low stress mechanical and surface properties of cotton knitted fabrics has been studied. The KES-FB system has been used for the measurements of low stress tensile, shear, bending, compression and surface properties. The results show remarkable changes in mechanical and surface properties of knitted fabrics after processing stages, such as bleaching, dyeing and softening. Source


Mohammadikish M.,Islamic Azad University at Kermanshah | Davar F.,Razi University | Loghman-Estarki M.R.,Isfahan University of Technology | Hamidi Z.,Islamic Azad University at Kermanshah
Ceramics International | Year: 2013

Spherical ZnS based nanoparticles (hierarchical architectures) were successfully synthesized using Zinc bis(salicyle aldehitato), Zn(Sal) 2, thioacetamide (TAA) and thioglycolic acid (TGA) as Zn 2+, sulfur source and capping agent, respectively. The hierarchical ZnS structure was produced from the self-assembly of nanoparticles with diameters of 21±4 nm. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and Fourier transform infrared (FT-IR) spectra. The influence of temperature on the morphology of the products was also investigated. The possible formation mechanism and optical properties of these architectures were also reported. © 2012 Elsevier Ltd and Techna Group S.r.l. Source


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. Source


Ashiri R.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2014

In pressurized solidification, the air gap formation due to shrinkage eliminated and heat transfer and cooling rate increased considerably. This effect resulted in a significant microstructure refinement and improvements in the mechanical properties of castings. Pressure also affects the freezing temperature of the alloy. A new version of the Clausius-Clapeyron equation was proposed to determine the extra pressure- induced undercooling. The results showed that pressurized sample exhibit a much stronger tendency to return to its equilibrium state. Improvement the wear response of pressurized cast sample is another effect of applied pressure. © 2013 Elsevier B.V. All rights reserved. Source


Amoushahi H.,University of Isfahan | Azhari M.,Isfahan University of Technology
Composites Part B: Engineering | Year: 2014

A linear finite strip plate element based on the first order shear deformation theory is considered for the analysis of viscoelastic plates. The plate end conditions are considered to be simply supported and the polynomial shape functions are used to evaluate the deflection of plates in transverse direction. The mechanical properties of the material are considered to be linear viscoelastic by expressing the relaxation modulus in terms of Prony series. The time history of maximum deflection of viscoelastic plates subjected to loading and unloading is calculated. In addition, a nonlinear procedure is used to calculate the changing of in-plane critical load of plate with time. Moreover, the effect of thickness and the interaction of biaxial loading on critical load of plate are studied. © 2013 Elsevier Ltd. All rights reserved. Source


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. Source


Salarvand A.,University of Isfahan | Mirzaeian B.,University of Isfahan | Moallem M.,Isfahan University of Technology
IET Generation, Transmission and Distribution | Year: 2010

A problem of concern in the deregulated electricity market is to obtain a global power quality (PQ) index for the supply and load side to estimate the cost of PQ in order to include it in the contracts between customers and utility companies. Existing PQ indices are usually isolated and lack the cost impact of bad PQ. This study presents an intelligent method based on artificial neural network (ANN) and fuzzy logic to obtain a quantitative global index for PQ evaluation and pricing in competitive electricity market. Taking into account the cost of PQ phenomena with their relative weights in this index, it can be used as a PQ measure in electricity tariffs by utility companies. Although individual cost assignments used in this study are subject to approximation, once the assignments are made, the calculation is consistent and gives a useful and unique measure of quality of electricity for both supply side and customer side. The proposed algorithm has been implemented on real measured data of a distribution network. The results show the capability of this method to obtain an accurate measure for PQ evaluation and pricing. © 2010 The Institution of Engineering and Technology. Source


Hasani H.,Isfahan University of Technology
Fibres and Textiles in Eastern Europe | Year: 2010

In this paper, the ability ofthe pulling-through method with a distance plate for measuring the shearing properties of knittedfabrics was studied. The conventional extraction method does not have a good correlation with the shearing properties ofwoven fabrics due to the complex deformation of the fabrics during testing. This study investigated a modified approach very similar to the conventional extraction method in order to evaluate the shearing behaviour of knittedfabrics. In this technique, the test is performed by a special pulling device mounted on a tensile testing machine consisting oftwo transparent horizontal plates: a replaceable base plate with a hole in the center, and a distance plate placed at a specified distance from the base plate. The shear properties of different knitted fabrics were measured by KES and the pulling-through method. The results reveal a high correlation between the pulling-through curve features and shear properties of the knitted fabrics. Source


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. Source


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. Source


Nili-Ahmadabadi M.,Isfahan University of Technology | Poursadegh F.,Sharif University of Technology
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. Source


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. Source


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. Source


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. Source


Mortezaie A.,Islamic Azad University at Najafabad | Shamanian M.,Isfahan University of Technology
International Journal of Pressure Vessels and Piping | Year: 2014

In the present study, dissimilar welding between Inconel 718 nickel-base superalloy and 310S austenitic stainless steel using gas tungsten arc welding process was performed to determine the relationship between the microstructure of the welds and the resultant mechanical and corrosion properties. For this purpose, three filler metals including Inconel 625, Inconel 82 and 310 stainless steel were used. Microstructural observations showed that weld microstructures for all filler metals were fully austenitic. In tension tests, welds produced by Inconel 625 and 310 filler metals displayed the highest and the lowest ultimate tensile strength, respectively. The results of Charpy impact tests indicated that the maximum fracture energy was related to Inconel 82 weld metal. According to the potentiodynamic polarization test results, Inconel 82 exhibited the highest corrosion resistance among all tested filler metals. Finally, it was concluded that for the dissimilar welding between Inconel 718 and 310S, Inconel 82 filler metal offers the optimum properties at room temperature. © 2014 Elsevier Ltd. Source


Mazrooei-Sebdani R.,Isfahan University of Technology
Mathematical Methods in the Applied Sciences | Year: 2014

Consider the non-autonomous equations: xn+1=xnAnxn+Bnxn- 1αnxn+βnxn-1,αnxn+βnxn-1>0, xn+1=xn-1Bnxn+Dnxn- 2αnxn+γnxn-2,αnxn+γnxn-2>0, xn+1=xnBnxn-1+Cnxn- 2βnxn-1+γnxn-2,βnxn-1+γnxn-2>0, where An≥0,Bn≥0,Cn≥0,αn≥0,βn≥0,γn≥0,n=0,1,2,., and also limn→∞An=A≥0,limn→∞Bn=B≥0,limn→∞Cn= C≥0,limn→∞αn=α>0,limn→∞βn= β>0,limn→∞γn=γ>0.These are some non-autonomous homogeneous rational difference equations of degree one. A reduction in order is consi-dered. Convergence and monoton character of positive solutions are studied. Copyright © 2013 John Wiley & Sons, Ltd. Copyright © 2013 John Wiley & Sons, Ltd. Source


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. Source


Jabbari M.,Isfahan University of Technology
IET Power Electronics | Year: 2010

This study presents a new resonant inverting step-down DC-DC converter. A half-bridge inverter and an LC resonant tank are employed. The resonant tank is the medium of energy transfer and provides soft-switching conditions at turn-on and turn-off switching instants for all active elements. The voltage conversion ratio is adjustable, and the converter is automatically shut down at output short circuit. Its characteristics are very similar to half-bridge series-resonant converter, except that input and output terminals possess common ground and voltage gain up to unity can be achieved at discontinuous conduction mode. Practical results from a laboratory prototype verify the presented theoretical analysis. © 2010 © The Institution of Engineering and Technology. Source


Kabiri-Samani A.R.,Isfahan University of Technology
Scientia Iranica | Year: 2010

Flow discharge over an oblique weir is greater than that over a straight or plain weir for the same water head due to its extra length with respect to the channel width or fully extended plain weir. In this study, a new theoretical approach is used for the hydraulics of oblique weirs. The main objective is to investigate the effect of different hydraulic and geometric properties of the flow and the weir on the flow deflection angle and discharge coefficients for free and submerged flow over oblique weirs. This approach is based on energy, momentum and continuity equations. For improving the performance of this kind of weir, one approach is to increase the flow deflection until it is perpendicular to the oblique weir for maximum use of the weir length. The submerged guide vanes have also been used and investigated theoretically. The data for calibration of the models are taken from Borghei et al. (2003). It is shown that by employing guide vanes, for some cases, the discharge coefficient can be increased up to 33%. Finally, new relations were developed for practical purposes. © Sharif University of Technology. Source


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. Source


Marzban H.R.,Isfahan University of Technology
Optimal Control Applications and Methods | Year: 2015

This paper presents a novel approximation scheme to the numerical treatment of linear time-varying multi-delay systems with a quadratic performance index. A direct approach based on a hybrid of block-pulse functions and Chebyshev polynomials is successfully developed. The operational matrix of delay associated to multi-delay systems is constructed by an efficient manner. The excellent properties of hybrid functions together with the operational matrices of integration, delay, and product are then used to transform the optimal control problem into a mathematical optimization problem whose solution is much more easier than the original one. The procedure described in the current paper can be regarded as a multi-interval decomposition scheme. The convergence of the proposed method is verified numerically. A wide variety of multi-delay systems are investigated to demonstrate the effectiveness and computational efficiency of the proposed numerical scheme. The method has a simple structure, is easy to implement, and provides very accurate solutions. © 2015 John Wiley & Sons, Ltd. Source


Safian R.,Isfahan University of Technology
IEEE Transactions on Antennas and Propagation | Year: 2010

In a dispersive medium excited by a wideband pulse, the appearance of the steady-state part of the propagated signal is preceded by oscillations known as precursors. Precursor fields in lossy Debye media have been shown to present a sub-exponential attenuation rate, thus becoming good candidates for applications requiring field penetration into such media. This communication aims to study the performance of a pulse consisting of two mutually delayed precursors for the detection of dielectric objects inside triply distilled water. Finite-difference time-domain (FDTD) simulations are employed to evaluate the strength of the scattered field obtained by illuminating the targets with the precursor-based pulse excitation and to compare it with other conventional alternatives, namely, Gaussian, rectangular and sinusoidal pulses. © 2006 IEEE. Source


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. Source


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. Source


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. Source


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

The stress-strain response of some materials, such as advanced high strength steels, during unloading is nonlinear after the material has been loaded into the plastic deformation region. Upon reloading, the response shows a nonlinear elastic response that is different from that in unloading. Therefore, unloading-reloading of these materials forms a hysteresis loop in the elastic region. The Quasi-plastic-elastic model (Sun and Wagoner, 2011) was modified and combined with both isotropic-nonlinear kinematic hardening and two-surface plasticity models to simultaneously describe the nonlinear unloading response and complex cyclic response of sheet metals in the plastic region. The model was implemented as user-defined material subroutines, i.e. UMAT and VUMAT, for ABAQUS/Standard and ABAQUS/Explicit finite element codes, respectively. Uniaxial loading-unloading tests were performed on three common grades of automotive sheet steel: DP600, DP980 and TRIP780 steel. The model was verified by comparing the predicted material response with the corresponding experimental response. Finally, the model was used to predict the springback of a U-shape channel section formed in a plane-strain channel draw process. The results showed that the model was able to considerably improve springback predictions compared to the usual assumption of linear elastic unloading. © 2015 Elsevier Ltd. Source


Basiry M.,Shahrekord University | Esehaghbeygi A.,Isfahan University of Technology
Journal of Electrostatics | Year: 2010

The drying rate and germination parameters of rapeseeds (PF variety) treated by a high-voltage electrostatic field (HVEF) were investigated. The experiment was laid out as a factorial arrangement based on a completely randomized design with three replications. The results showed that the electrostatic field had a significant effect (P< 0.01) on decreasing rapeseed moisture content. Average drying rate for 8, 9, and 10. kV electrostatic fields over a time of 270. min increased by 1.78, 2.11, and 2.47 times, respectively, compared with that of the control. Drying rate increased with increasing voltage. Moreover, the results obtained from the germination experiment showed that the EHD had significant effects on the stemlet and radicle lengths of the rapeseed sprouts compared to that of the control. No significant effects were observed on the seed germination percentage and speed. © 2010 Elsevier B.V. Source


(Graph Presented) The preparation and characterization of functional biocompatible magnetite-cellulose nano-composite fibrous material is described. Magnetite-cellulose nano-composite was prepared by a combination of the solution-based formation of magnetic nano-particles and subsequent coating with amino celluloses. Characterization was accomplished using X-ray powder diffraction (XRD), fourier transformed infrared (FTIR) and field emission scanning electron microscopy (FESEM) analysis. The peaks of Fe3O4 in the XRD pattern of nanocomposite confirm existence of the nanoparticles in the amino cellulose matrix. Magnetite-cellulose particles exhibit an average diameter of roughly 33 nm as demonstrated by field emission scanning electron microscopy. Magnetite nanoparticles were irregular spheres dispersed in the cellulose matrix. The vibration corresponding to the N-CH3 functional group about 2850 cm-1 is assigned in the FTIR spectra. Functionalized magnetite-cellulose nano-composite polymers have a potential range of application as targeted drug delivery system in biomedical field. © 2014 Elsevier B.V. All rights reserved. Source


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. Source


Jafari M.T.,Isfahan University of Technology
Analytical Chemistry | Year: 2011

In this research work, the capability of low-temperature plasma (LTP) as an ionization source for ion mobility spectrometry (IMS) has been investigated for the first time. This new ionization source enhances the potential of IMS as a portable analytical tool and allows direct analysis of various chemical compounds without having to evaporate the analyte or seek a solvent or reagent whatsoever. The effects of parameters such as the flow rate of the discharge gas, plasma voltage, and positioning of the LTP on the IMS signal were investigated. The positive reactant ions generated by the LTP ionization source were similar to those created in a corona discharge ionization source, where the proton clusters (H2O), H+)are the most abundant reactant ion, and in the negative mode, in addition to a saturated electron peak, several negative reactant ions (e.g., NOx) were observed too. These reactant ions subsequently ionized the gaseous samples directly and liquids or solids after evaporation by plasma desorption. The ion mobility spectra of a few selected compounds, including explosives, drugs, and amines, were obtained to evaluate the new ionization source in positive and negative modes, and the reduced mobility values (K0) of the originated ions were calculated. Furthermore, the method has also been applied to obtain the figures of merit for acetaminophen as a test compound. The results obtained are promising enough to ensure the use of LTP as a desorption/ionization source in IMS for analytical applications. © 2010 American Chemical Society. Source


Bonakdar E.,Isfahan University of Technology
Genetics and molecular research : GMR | Year: 2010

We estimated the allele and genotype frequencies of IGF-I/SnaBI gene polymorphism and the concentration of this protein in Holstein dairy cows. We also examined the association with milk yield (305-day milk yield) and milk components (fat and protein percentage, and 305-day milk protein and fat yield). Blood IGF-I levels were measured and genotyping was performed on 250 Holstein cows of four different herds. In the association studies, traits of interest were analyzed using the GLM procedure of SAS; means of the IGF-I level among genotypes were compared by the LSMeans test. The AB and AA genotypes were the most (0.583-0.661) and least (0.083-0.192) frequent in the herds, respectively; the frequency of the BB genotype ranged from 0.201 to 0.333. The frequency of the A allele ranged from 0.375 to 0.495, while the frequency of the B allele ranged from 0.504 to 0.625, being the dominant allele. The mean level of IGF-I was 107 +/- 22 ng/mL for all groups, without any significant correlation with the production traits. Association of IGF-I/SnaBI genotypes with percentage of fat and protein in the milk was relatively high (P < 0.1 and P < 0.05, respectively); the AB genotype was superior to AA and BB genotypes. We concluded that this marker should be considered for milk component selection in Holstein dairy cattle. Source


Mousavi Anijdan S.H.,McGill University | Rezaeian A.,Isfahan University of Technology | Yue S.,McGill University
Materials Characterization | Year: 2012

In this investigation, by using continuous cooling torsion (CCT) testing, the transformation behavior of four microalloyed steels under two circumstances of austenite conditioning and non-conditioning was studied. A full scale hot-rolling schedule containing a 13-pass deformation was employed for the conditioning of the austenite. The CCT tests were then employed till temperature of ~ 540 °C and the flow curves obtained from this process were analyzed. The initial and final microstructures of the steels were studied by optical and electron microscopes. Results show that alloying elements would decrease the transformation temperature. This effect intensifies with the gradual increase of Mo, Nb and Cu as alloying elements added to the microalloyed steels. As well, austenite conditioning increased the transformation start temperature due mainly to the promotion of polygonal ferrite formation that resulted from a pancaked austenite. The final microstructures also show that CCT alone would decrease the amount of bainite by inducing ferrite transformation in the two phase region. In addition, after the transformation begins, the deformation might result in the occurrence of dynamic recrystallization in the ferrite region. This could lead to two different ferrite grain sizes at the end of the CCT. Moreover, the Nb bearing steels show no sign of decreasing the strength level after the transformation begins in the non-conditioned situation and their microstructure is a mix of polygonal ferrite and bainite indicating an absence of probable dynamic recrystallization in this condition. In the conditioned cases, however, these steels show a rapid decrease of the strength level and their final microstructures insinuate that ferrite could have undergone a dynamic recrystallization due to deformation. Consequently, no bainite was seen in the austenite conditioned Nb bearing steels. The pancaking of austenite in the latest cases produced fully polygonal ferrite structures. © 2011 Elsevier Inc. Source


Nasibi M.,Petroleum University of Technology of Iran | Golozar M.A.,Isfahan University of Technology | Rashed G.,Petroleum University of Technology of Iran
Materials Letters | Year: 2012

In this research, nano iron oxide (Fe 2O 3)/carbon black electrodes are prepared by mechanical pressing method and evaluated as possible electrodes for electrochemical capacitors. Electrochemical properties of the produced electrodes are studied using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests in 2 M KCl electrolyte at different scan rates. Scanning electron microscopy (SEM) is also used to characterize the microstructure and nature of the produced electrodes. Electrochemical stability of the electrodes is investigated by switching the electrode back and forth for 500 cycles at 20 mV s -1.The results obtained show a specific capacitance of as high as 40.07 F g -1 for 30:60:10 (carbon black:Fe 2O 3:polytetrafluoroethylene) electrode in 2 M KCl at 10 mV s -1. The proposed electrode exhibits good cyclic stability and maintains 80% of the capacitance after 500 cycles. SEM images confirm the porous structure of Fe 2O 3/carbon black electrodes. Crown Copyright © 2012 Published by Elsevier B.V. All rights reserved. Source


Modarres R.,INRS - Institute National de la Recherche Scientifique | Sarhadi A.,Isfahan University of Technology
Journal of Hydrologic Engineering | Year: 2010

Hydrologic drought is a type of drought which directly affects the water supply of a region. Long streamflow dry spells or streamflow under a specific threshold are usually considered as hydrologic drought. The annual extreme hydrologic dry spell length (AEHDSL) data of the Halilrud basin in the southeastern semiarid region of Iran were considered to estimate the return period of hydrologic drought and the associated risk in this region. The method of L-moments was applied to check discordant stations and test the homogeneity of the region which consists of 15 gauging watersheds. One discordant station was found and the region was homogeneous according to the homogeneity measure after removing the discordant station. The three-parameter lognormal distribution was found to be representative of the regional distribution for the entire region based on the goodness-of-fit test. For prediction in ungauged basins, the AEHDSL regional regression was developed for the region. The regression model indicates that the vegetation cover and relief of watersheds play important roles in the hydrologic drought length of the Halilrud basin. These two variables control the infiltration and hydraulic slopes of a watershed, respectively. © 2010 ASCE. Source


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. Source


Behbahani S.,Isfahan University of Technology | De Silva C.W.,University of British Columbia
IEEE/ASME Transactions on Mechatronics | Year: 2013

A typical mechatronic problem (modeling, identification, and design) entails finding the best system topology as well as the associated parameter values. The solution requires concurrent and integrated methodologies and tools based on the latest theories. The experience on natural evolution of an engineering system indicates that the system topology evolves at a much slower rate than the parametric values. This paper proposes a two-loop evolutionary tool, using a hybrid of genetic algorithm (GA) and genetic programming (GP) for design optimization of a mechatronic system. Specifically, GP is used for topology optimization, while GA is responsible for finding the elite solution within each topology proposed by GP. A memory feature is incorporated with the GP process to avoid the generation of repeated topologies, a common drawback of GP topology exploration. The synergic integration of GA with GP, along with the memory feature, provides a powerful search ability, which has been integrated with bond graphs (BG) for mechatronic model exploration. The software developed using this approach provides a unified tool for concurrent, integrated, and autonomous topological realization of a mechatronic problem. It finds the best solution (topology and parameters) starting from an abstract statement of the problem. It is able to carry out the process of system configuration realization, which is normally performed by human experts. The performance of the software tool is validated by applying it to mechatronic design problems. © 1996-2012 IEEE. Source


Khatoon-Abadi A.,Isfahan University of Technology
Journal of Agricultural Science and Technology | Year: 2011

Diversity, accessibility and reliability are the three main factors governing the adoption of information sources by farmers in rural areas. Based on the research hypothesis, the existing knowledge and information delivery system in the agricultural sector, functions far below the ever changing nature and tangible needs of existing farming systems. The main objective in this study is to determine and prioritize farmers' information channels and their communication networks within rural areas of 19 townships of Isfahan Province - the central part of Iran. After exploratory field visits of several villages, a questionnaire was designed and pre-tested for its validity and reliability (Alpha= 82%). The statistical society included all farmers who had regular contacts with the local extension offices. The sample population was 228 farmers who were selected through a two-step random sampling method from the villages with an extension office. The results showed that extension system disregarded farmers' local media and did not meet their actual needs. The extension system failed to build trust among the local communities. Moreover, farmers' trust in one information source had a synergic effect on the others. The sources were categorized in three groups based on the farmers' preferences. The printed materials did not play any significant role in the knowledge and information processes. There was also a significant correlation between dependent variables (determination of information source by farmers) and the independent variables (for example: farming land size and farmers educational level). Finally, most farmers claimed that visiting 'local extension service offices' was mainly in response to their urgent needs to acquire subsidized agricultural input such as fertilizer, rather than acquisition of information and were yet disappointed. Source


Behnamfar F.,Isfahan University of Technology
Bulletin of Earthquake Engineering | Year: 2016

In this paper maximum response of a single degree of freedom system resting on a flexible base is determined under consistent earthquakes and the results are presented as acceleration spectra including soil–structure interaction (SSI). Flexibility of base is modeled using frequency-dependent springs and dampers. The spring–damper coefficients are calculated for the desired natural mode of vibration of a multi-degree-of-freedom system. Consistency of earthquakes is maintained considering their magnitude, distance, local soil type, and return period. The latter parameter is accounted for by the use of earthquake categories identified by their similar spectral values. Ratio of spectral acceleration modification factors with SSI from this study to those calculated using the ASCE 7-10 procedure are determined for each case. Examination of the resulting curves shows that the mentioned code is conservative/non-conservative in estimation of spectral responses with SSI in certain cases for the lower/higher modes of vibration. The code’s procedure is modified using the developed curves for a conversion factor. © 2016 Springer Science+Business Media Dordrecht Source


Behnamfar F.,Isfahan University of Technology
Bulletin of Earthquake Engineering | Year: 2016

In this study a new method for nonlinear static analysis based on the relative displacements of stories is proposed that is able to be implemented in a single stage analysis and considers the effects of an arbitrary number of higher modes. The method is called the extended drift pushover analysis procedure (EDPA). To define the lateral load pattern, values of the relative displacements of stories are calculated using the elastic modal analysis and the modal combination factors introduced. For determining the combination factors, six different approaches are examined. Buildings evaluated in this study consist of four special steel moment-resisting frames with 10–30 stories. Responses including relative displacements of stories, story shear forces and rotation of plastic hinges in each story are calculated using the proposed approaches in addition to modal pushover analysis and nonlinear dynamic time history analyses. The nonlinear dynamic analysis is implemented using ten consistent earthquake records that have been scaled with regard to ASCE7-10. Distribution of response errors of story shears and plastic hinge rotations show that a major part of error corresponds to the second half of the buildings studied. Thus, the mentioned responses are corrected systematically. The final results of this study show that implementing the EDPA procedure using the third approach of this research is able to effectively overcome the limitations of both the traditional and the modal pushover analyses methods and predict the seismic demands of tall buildings with good accuracy. © 2016 Springer Science+Business Media Dordrecht Source


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. Source


Mousavi S.R.,Isfahan University of Technology
Journal of Theoretical Biology | Year: 2012

Given a set of aligned fragments, haplotype assembly is the problem of finding the haplotypes from which the fragments have been read. The problem is important because haplotypes contain SNP information, which is essential to many genomic analyses such as the analysis of potential association between certain diseases and genetic variations. The current state-of-the-art haplotype assembly algorithm, HapSAT, does not exploit genotype information and only receives a read matrix as input. However, the imminent importance of haplotypes and inexpensiveness of genotype information motivate for exploiting genotype information to obtain more accurate haplotypes. In this paper, an improved haplotype assembly method, xGenHapSAT, is proposed, which exploits xor genotype information for more accurate haplotype assembly. Xor genotype information is even less expensive than full genotype information, e.g., using the Denaturing High-Performance Liquid Chromatography (DHPLC) technique. It is shown that using this inexpensively obtainable information significantly improves the accuracy of the assembled haplotypes. In addition, a new, more efficient, Max-2-SAT formulation is adopted in xGenHapSAT, which, on average, increases the speed of the algorithm. Moreover, the proposed xGenHapSAT method replaces the current state-of-the-art haplotype assembly method based on genotype information. Finally, our state-of-the-art haplotype assembly software, HapSoft, which includes both xGenHapSAT and HapSAT, is made freely available for research purposes. © 2012 Elsevier Ltd. Source


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®. Source


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. Source


Mousavi S.M.,Islamic Azad University at Tehran | Mostafavi E.S.,Isfahan University of Technology | Hosseinpour F.,Islamic Azad University at Central Tehran
Computers and Industrial Engineering | Year: 2014

This study proposes a new gene expression programming (GEP) approach for the prediction of electricity demand. The annual population, gross domestic product, stock index, and total revenue from exporting industrial products were used to predict the electricity demand of the same year in Thailand. Several statistical criteria were used to verify the validity of the model. Further, the contributions of the influencing variables to the prediction of the electricity demand were analyzed. Correlation coefficient, root mean squared error and mean absolute percent error were used to evaluate the performance of the model. In addition to its high accuracy, the derived model outperforms regression and other soft computing-based models. © 2014 Elsevier B.V. All rights reserved. Source


Copper decorated WO3-TiO2 nanotubes (Cu/WTNs) with a high photocatalytic activity were prepared by anodizing and photochemical deposition. Highly ordered WO3-TiO2 nanotubes (WTNs) on pure titanium foils were successfully fabricated by electrochemical anodizing and copper deposited on these nanotubes (Cu/WTNs) by photoreduction method. The resulting samples were characterized by various methods. Only the anatase phase was detected by X-ray diffraction analysis. The presence of copper in the structure of thin films was confirmed by energy dispersive X-ray spectrometry and X-ray diffraction. The extension of optical absorption into the visible region of as-prepared films was indicated by UV/Vis spectroscopy. The degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of the obtained samples. Results showed that the photocatalytic activity of Cu/WTNs samples is higher than bare WTNs sample. Kinetic research showed that the reaction rate constant of Cu/WTNs is approximately 2.5 times higher than the apparent reaction rate constant of bare WTNs. These results not only offer an economical method for constructing Cu/WTNs photocatalysts, but also shed new insight on the rational design of a low cost and high-efficiency photocatalyst for environmental remediation. © 2015 Elsevier B.V. All rights reserved. Source


This research was conducted to study the genetic variation among eighteen genotypes of sesame (Sesamum indicum L.) collected from various agro-climatic regions of Iran along with six exotic genotypes from the Asian countries using both agro-morphological and ISSR marker traits. The results showed significant differences among genotypes for all agro-morphological traits and a relatively high genetic coefficient of variation observed for number of fruiting branches per plant, capsules per plant, plant height and seed yield per plant. Cluster analysis based on these traits grouped the genotypes into five separate clusters. Larger inter- than intra cluster distances implies the presence of higher genetic variability between the genotypes of different groups. Genotypes of two clusters with a good amount of genetic divergence and desirable agronomic traits were detected as promising genotypes for hybridization programs. The 13 ISSR primers chosen for molecular analysis revealed 170 bands, of which 130 (76.47%) were polymorphic. The generated dendrogram based on ISSR profiles divided the genotypes into seven groups. A principal coordinate analysis confirmed the results of clustering. The agro-morphological traits and ISSR markers reflected different aspects of genetic variation among the genotypes as revealed by a non significant cophenetic correlation in the Mantel test. Therefore the complementary application of both types of information is recommended to maximize the efficiency of sesame breeding programs. The discordance among diversity patterns and geographical distribution of genotypes found in this investigation implies that the parental lines for hybridization should be selected based on genetic diversity rather than the geographical distribution. Source


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. Source


A continuum model based on the nonlocal theory of elasticity is developed for buckling analysis of embedded orthotropic circular and elliptical micro/nano-plates under uniform in-plane compression. The nanoplate is considered to be rested on two-parameter Winkler-Pasternak elastic foundation. The principle of virtual work is used to derive the governing vibration and stability equations. The weighted residual statements of the equations of motion are performed and the well-known Galerkin method is employed to obtain the nonlocal "Quadratic Functional" for embedded micro/nano-plates. The Ritz functions are taken to form an expression for transverse displacement which satisfies the kinematic boundary conditions. In this way, the entire nanoplate is considered as a single super-continuum element. Employing the Ritz functions eliminates the need for mesh generation and thus large number of degrees of freedom arising in discretization methods such as finite element (FE). The results show obvious dependency of critical buckling loads on the non-locality of the micro/nano elliptical plate, especially, at very small dimensions. © 2012 Springer Science+Business Media Dordrecht. Source


Bidram A.,University of Texas at Arlington | Hamedani-Golshan M.-E.,Isfahan University of Technology | Davoudi A.,University of Texas at Arlington
IEEE Transactions on Power Systems | Year: 2012

This paper proposes an algorithm for designing a fixed shunt capacitive compensator to improve first swing stability margin of a micro-grid including synchronous machine-based distributed generators (SMDGs). The notion of trajectory sensitivity analysis is used to determine the sensitivity of the SMDGs' relative rotor angles and velocities with respect to the compensator susceptance. For a given fault contingency, the minimum required susceptance and compensator location are determined to maintain the first swing stability of SMDGs. The proposed methodology can be used for a micro-grid with an arbitrary number of SMDGs, various fault scenarios, and both grid-connected and autonomous (islanded) modes of operation. The proposed algorithm is verified using time-domain simulation of a modified benchmark system of the IEEE standard 399-1997. © 1969-2012 IEEE. Source


Sohankar A.,Isfahan University of Technology
International Journal for Numerical Methods in Fluids | Year: 2012

This paper describes a numerical study of the two-dimensional and three-dimensional unsteady flow over two square cylinders arranged in an in-line configuration for Reynolds numbers from 40 to 1000 and a gap spacing of 4D, where D is the cross-sectional dimension of the cylinders. The effect of the cylinder spacing, in the range G=0.3D to 12D, was also studied for selected Reynolds numbers, that is, Re=130, 150 and 500. An incompressible finite volume code with a collocated grid arrangement was employed to carry out the flow simulations. Instantaneous and time-averaged and spanwise-averaged vorticity, pressure, and streamlines are computed and compared for different Reynolds numbers and gap spacings. The time averaged global quantities such as the Strouhal number, the mean and the RMS values of the drag force, the base suction pressure, the lift force and the pressure coefficient are also calculated and compared with the results of a single cylinder. Three major regimes are distinguished according to the normalized gap spacing between cylinders, that is, the single slender-body regime (G<0.5), the reattach regime (G<4) and co-shedding or binary vortex regime (G ≥4). Hysteresis with different vortex patterns is observed in a certain range of the gap spacings and also for the onset of the vortex shedding. © 2011 John Wiley & Sons, Ltd.. Source


Ghasemi E.,Isfahan University of Technology
Neural Computing and Applications | Year: 2016

One of the most challenging safety problems in open pit mines is backbreak during blasting operation, and its prediction is very important for a technically and economically successful mining operation. This paper presents application of particle swarm optimization (PSO) technique to estimate the backbreak induced by bench blasting, based on major controllable blasting parameters. Two forms of PSO models, linear and quadratic, are developed based on blasting data from Sungun copper mine, Iran. According to obtained results, both models can be used to predict the backbreak, but the comparison of two models, in terms of statistical performance indices, shows that the quadratic form provides better results than the linear form. © 2016 The Natural Computing Applications Forum Source


Varmaghani F.,Bu - Ali Sina University | Nematollahi D.,Bu - Ali Sina University | Mallakpour S.,Isfahan University of Technology | Esmaili R.,Bu - Ali Sina University
Green Chemistry | Year: 2012

Electrochemical synthesis of some new sulfonamide derivatives was carried out via the electrooxidation of 4-substituted urazoles in the presence of arylsulfinic acids. The results show that electrogenerated 4-alkyl-4H-1,2,4- triazole-3,5-diones participated in a Michael-type reaction with arylsulfinic acids and, via an "electron transfer + chemical reaction" (EC) mechanism, were converted to the corresponding sulfonamide derivatives. In this work, some new sulfonamide derivatives with high yields in aqueous solutions, without toxic reagents and solvents at a carbon electrode using an environmentally friendly novel method, are provided. © 2012 The Royal Society of Chemistry. Source


Ahmadi A.,Isfahan University of Technology | Han D.,University of Bristol
Journal of Hydroinformatics | Year: 2013

Downscaling methods are utilized to assess the effects of large scale atmospheric circulation on local hydrological variables such as precipitation and runoff. In this paper, a methodology of statistical downscaling using a support vector machine (SVM) approach is presented to simulate and predict the precipitation using general circulation model (GCM) data. Due to the complexity and issues related to finding a relationship between the large scale climatic parameters and local precipitation, the climate variables (predictors) affecting monthly precipitation variations over Wales are identified using a combination of the methods including the principal component analysis (PCA), fuzzy clustering, backward selection, forward selection, and Gamma test (GT). The effectiveness of those tools is illustrated through their implementations in the case study. It has been found that although the GT itself fails to identify the best input variable combination, it provides useful and narrowed-down options for further exploration. The best input variable combination is achieved by the GT and forward selection method. This approach can be a useful way for assessing the impacts of climate variables on precipitation forecasting. © IWA Publishing 2013. Source


Esehaghbeygi A.,Isfahan University of Technology
Drying Technology | Year: 2012

The effects of high-voltage electrostatic field (10 kV), batch drying (45°C), and natural air-drying (26°C) on the impact strength of a brown rice kernel (Oryza Sativa L.) variety of Khazar were investigated under three levels of kinetic impact loading (10, 23, and 37 mJ) with 10 replications. Results showed that the effects of kinetic impact loading on the breakage susceptibility index (BSI) of artificially dried rice grains were significant at 1% confidence level. With increasing kinetic impact loading, the average value of BSI increased. The sound brown rice grains became stronger in natural air-drying as the drying duration increased at low drying temperatures. High-voltage electrostatic field and batch drying considerably increased the rate of breakage susceptibility but the EHD drying was inherently energy efficient with a low surface drying temperature. © 2012 Copyright Taylor and Francis Group, LLC. Source


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. Source


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. Source


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. Source


Firooz A.R.,University of Isfahan | Movahedi M.,University of Isfahan | Ensafi A.A.,Isfahan University of Technology
Sensors and Actuators, B: Chemical | Year: 2012

A reversible optical membrane sensor for detection of Hg(II) was developed based on the colorimetric determination of tetrathia-12-crown-4-Hg(II), incorporating chromoionophore I (ETH5294) as a lipophilic H +- selective indicator, and sodium tetra phenyl borate (NaTPB) as a lipophilic anionic site. A decrease in absorption of the membrane at 664 nm and/or increase at 555 nm could be used as a suitable wavelength for quantitative determination of Hg(II). This membrane is capable of determining mercury(II) ions over a wide linear dynamic range 1.0 × 10 -9 to 9.5 × 10 -5 mol L -1 Hg(II) at pH 7.0 with detection limits of 8.1 × 10 -10 mol L -1 Hg(II) and response time of 100 s. The optode reveals a very good selectivity toward Hg(II) ions over a wide variety of other metal ions in solution and the response to Hg(II) is fully reversible. Performance characteristics of the sensor evaluated as good reversibility, wide dynamic range, long life span, long-term response stability, and high reproducibility. The optode was applied to the determination of mercury(II) in water samples. The accuracy of the results was comparable to those obtained by cold vapor atomic absorption spectrometry. © 2012 Elsevier B.V. All rights reserved. Source


Ghaei A.,Isfahan University of Technology
International Journal of Mechanical Sciences | Year: 2012

Several studies have reported that the elastic modulus decreases during elastoplastic deformation. However, the return mapping algorithms commonly used to implement the elastoplastic constitutive equations into finite element programs assume that the elastic modulus remains constant during plastic deformation. In order to consider the decrease of elastic modulus in elastoplastic constitutive models, the return mapping algorithms need to be generalized. In this study, a numerical procedure was developed for implementation of elastoplastic constitutive laws assuming that the elastic modulus was defined as a function of effective plastic strain. Using the developed numerical procedure, the Hill's quadratic yield function and the combined isotropic-nonlinear kinematic hardening model was implemented as a user subroutine for ABAQUS commercial finite element package. Different numerical tests were carried out to evaluate the performance of the developed algorithm. The results showed that the algorithm was robust and as accurate as the other return mapping algorithms. Finally, the model was used to simulate both the forming stage and the subsequent springback of a U-shaped part made of DP600 steel. The results showed that the accuracy of springback simulation considerably improved when the decrease of elastic modulus was described in the model. © 2012 Elsevier Ltd. Source


Ghari M.,Isfahan University of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

In this paper, we introduce justification counterparts of distributed knowledge logics. Our justification logics include explicit knowledge operators of the form [[t]] iF and , which are interpreted respectively as "t is a justification that agent i accepts for F", and "t is a justification that all agents implicitly accept for F". We present Kripke style models and prove the completeness theorem. Finally, we give a semantical proof of the realization theorem. © 2012 Springer-Verlag. Source


Momeni M.M.,Isfahan University of Technology
Applied Physics A: Materials Science and Processing | Year: 2015

The degradation of 4-nitrophenol (4-NP) in aqueous solution with different processes was investigated. Tungsten-loaded titania nanotubes (WT-NTs) were used as electrode in photocatalytic (PC), sonophotocatalytic (SPC), photoelectrocatalytic (PEC), and sonophotoelectrocatalytic (SPEC) processes. WT-NTs electrode was fabricated by in situ anodization of titanium in a single-step process using sodium tungstate as the tungsten source. The morphology and structure were characterized by FE-SEM, XRD, and EDX. Experimental results showed that the hybrid processes could efficiently enhance the degradation efficiency of 4-NP and followed pseudo-first-order kinetics. At the optimized experimental conditions, the rate constants of degradation of 4-NP were 0.0594 min−1 for SPEC process, 0.0293 min−1 for PEC process, 0.0211 min−1 for SPC process, and 0.0116 min−1 for PC process. The rate constants indicated that there existed synergistic effect in the ultrasonic, electro-assisted, and photocatalytic processes. © 2015, Springer-Verlag Berlin Heidelberg. Source


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. Source


Kakaei K.,Islamic Azad University at Maragheh | Zhiani M.,Isfahan University of Technology
Journal of Power Sources | Year: 2013

We report a Pt/graphene catalyst for the methanol oxidation. Graphene is synthesized from graphite electrodes using ionic liquid-assisted electrochemical exfoliation. Graphene-supported Pt electrocatalyst is then reduced by sodium borohydride with ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) as a stabilizing agent to prepare highly dispersed Pt nanoparticles on carbon graphene to use as methanol oxidation in direct methanol fuel cell (DMFC) catalysts. X-ray diffractometer and scanning electron microscopy technique are used to investigate the crystallite size and the surface morphologies respectively. The electrochemical characteristics of the Pt/graphene and commercial Pt/C catalysts are investigated by cyclic voltammetry (CV) in nitrogen saturated sulfuric acid aqueous solutions and in mixed sulfuric acid and methanol aqueous solutions. The catalytic activities of the Pt/graphene and Pt/C electrodes for methanol oxidation is 1315 A g-1 Pt and 725 A g-1 Pt, which can be revealed the particular properties of the exfoliated graphene supports. Furthermore, Pt/graphene exhibited a better sensitivity, signal-to-noise ratio, and stability than commercial Pt/C. © 2012 Elsevier B.V. All rights reserved. Source


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. Source


Falahati F.,Shiraz University | Khosravi R.,Isfahan University of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In this paper, the dependency of P ij's on the dilepton invariant mass, q2, and the model III two-Higgs-doublets model (2HDM) parameters for B→K0*(1430)ℓ +ℓ - decay were investigated, and the results were compared to those of the standard model (SM) and Appelquist, Cheng and Dobrescu model. Also, for this decay, the effects of model III 2HDM parameters on the averages of double-lepton polarization asymmetries, P ijs, were studied, and by taking into account the corresponding theoretical and experimental errors in the SM, the results of the SM and 2HDM were compared to each other. In addition, by comparing the averages of double-lepton polarization asymmetries in 2HDM to those of SM4 and obtaining the required number of events for detecting each asymmetry at the LHC or the Super Large Hadron Collider, we present a comprehensive discussion regarding the lepton polarizations of B→K0*ℓ +ℓ - decay. We discovered that the study of the double-lepton polarization asymmetries and the corresponding averages in the B→K0*(1430) ℓ +ℓ - decay can provide good signals for probing new physics beyond the SM in the future B-physics experiments. © 2012 American Physical Society. Source


Chu U.B.,University of Wisconsin - Madison | Ramachandran S.,University of Wisconsin - Madison | Hajipour A.R.,Isfahan University of Technology | Ruoho A.E.,University of Wisconsin - Madison
Biochemistry | Year: 2013

The sigma-1 receptor is a ligand-regulated endoplasmic reticulum (ER) resident chaperone involved in the maintenance of cellular homeostasis. Coupling of the sigma-1 receptor with various ER and/or plasma membrane ion channels is associated with its ability to regulate the locomotor activity and cellular proliferation produced in response to sigma-1 receptor ligands. A number of endogenous small molecules bind to the sigma-1 receptor and have been shown to regulate its activity; these include progesterone, N,N-dimethyltryptamine, d-erythro-sphingosine, and/or other endogenous lipids. We previously reported the synthesis of long chain N-alkylamine derivatives and the characterization of the structure-activity relationship between the chain length of N-alkylamine and affinities at the sigma-1 receptor. Here, we present data demonstrating the photoincorporation of one of these N-alkylamine derivatives, N-[3-(4-nitrophenyl)propyl]-N-dodecylamine (4-NPPC12), to the sigma-1 receptor. Matrix-assisted laser desorption ionization time-of-flight and tandem mass spectrometry showed that 4-NPPC12 photoinserted at histidine 154 of the derivatized population of the sigma-1 receptor. Interestingly, light-dependent photoinsertion of 4-NPPC12 resulted in an enhanced electrophoretic mobility of only 50% of the derivatized receptor molecules as assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The proposed binding and reactivity of 4-NPPC12 evoke a ligand binding model for the sigma-1 receptor that likely involves a receptor dimer and/or oligomer. © 2013 American Chemical Society. Source


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. Source


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. Source


Shoja Razavi R.,Malek-Ashtar University of Technology | Loghman-Estarki M.R.,Isfahan University of Technology
Journal of Cluster Science | Year: 2012

Copper oxide nanoparticles within zeolite Y have been synthesized by a procedure comprising (i) ion-exchange of copper ions into the zeolite, (ii) precipitation of copper ions with sodium hydroxide within the supercages of the zeolite, and (iii) calcination. The products were characterized by X-ray diffraction, scanning electron microscope, energy-dispersive X-ray spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The particle size of CuO products are 20 nm. © 2012 Springer Science+Business Media, LLC. Source


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. Source


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. Source


Orthopalladated binuclear complexes (1) have been prepared by refluxing a mixture of the phosphorus ylide (ClBPPY) with Pd(OAc)2 in CH 2Cl2. Complex 1 reacts with ligands (L) to give (L = PPh3 (2), Me3Py (3)). Cyclopalladated complexes are highly efficient catalysts for the Suzuki reactions of aryl bromide with aryl boronic acid. The monomeric complexes 2 and 3 are more active than the dimer 1. Palladium mirror was observed, indicating the involvement of classic Pd(0)/Pd(II) catalytic cycle using these cyclopalladated complexes. The coupling of aryl bromide with aryl boronic acid gave the desired biphenyl congeners in good to excellent yields. We tested the various bases, finding that inorganic bases work better than organic ones. © 2010 Taylor & Francis. Source


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. Source


Valipour M.,Islamic Azad University at Kermanshah | Eslamian S.,Isfahan University of Technology
International Journal of Hydrology Science and Technology | Year: 2014

The evapotranspiration was estimated using 11 temperature-based models and was compared with the FAO Penman-Monteith model. The results showed that the modified Hargreaves-Samani models estimate the evapotranspiration better than the other models in the most provinces of Iran. However, the values of R2 were less than 0.98 for 15 provinces of Iran. Therefore, the models were calibrated and precision of estimation was increased (the values of R2 were less than 1.00 (with respect to two decimal numbers) for only five provinces in the modified models). The temperaturebased models estimated the evapotranspiration in the north east and south west provinces of Iran better than other provinces. The best precise methods were the modified Hargreaves-Samani 1 method for AL (before calibration) and the Hargreaves-Samani method for AR, the Modified Hargreaves-Samani 2 method for SE and GH, the modified Hargreaves-Samani 1 for FA, and the modified Hargreaves-Samani 3 for MZ (after calibration). Copyright © 2014 Inderscience Enterprises Ltd. Source


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. Source


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. Source


Hajipour A.R.,Isfahan University of Technology | Hajipour A.R.,University of Wisconsin - Medical School | Azizi G.,University of Wisconsin - Medical School
Green Chemistry | Year: 2013

An environmentally friendly iron-based catalyst supported on acac-functionalized silica was successfully prepared and evaluated as a heterogeneous catalyst for Mizoroki-Heck reaction of aryl iodides and olefins. Our catalytic system showed good activities that were comparable to that of palladium catalysts. The catalyst was simply recovered from the reaction mixture and recycled five times. Furthermore, the reaction was carried out in poly(ethylene glycol) as a green solvent. Interestingly, using this catalyst, aryl iodides were selectively olefinated in the presence of aryl bromides. © 2013 The Royal Society of Chemistry. Source


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. Source


this study, a low-power and high performance architecture for finite impulse response digital filter based on the ring topology which is modelled from recurrent neural network is presented. The proposed structure is based on a ring topology reduced number of multipliers, adders and also CLK cycles. In the design, all the operators including multipliers and adders have been designed at gate level. Multiplication is a very important operation in many digital filters hence, the authors designed a novel and modified retiming serial multiplier. To increase the performance, the authors use two types of adders, a proposed high-speed logarithmic carry look ahead adder and a carry save adder with four inputs. The proposed structure is modelled and verified using FPGA and simulation results. It has been successfully synthesised and implemented with Xilinx ISE 7.1 and Virtex IV FPGA, target device Xc4vf100. The results demonstrate that the proposed method has high performance and low-power consumption. © The Institution of Engineering and Technology 2013. Source


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. Source


Soltanalian M.,Uppsala University | Naghsh M.M.,Isfahan University of Technology | Stoica P.,Uppsala University
Signal Processing | Year: 2013

In this paper, we introduce a fast computational frequency-domain approach for designing complementary sets of sequences. Following the basic idea of CAN-based algorithms, we propose an extension of the CAN algorithm to complementary sets of sequences (which we call CANARY). Moreover, modified versions of the proposed algorithm are derived to tackle the complementary set design problems in which low peak-to-average-power ratio (PAR), unimodular or phase-quantized sequences are of interest. Several numerical examples are provided to show the performance of CANARY. © 2013 Elsevier B.V. Source


Davar F.,Isfahan University of Technology | Loghman-Estarki M.R.,Malek-Ashtar University of Technology | Ashiri R.,Islamic Azad University at Dezful
Journal of Industrial and Engineering Chemistry | Year: 2015

The aim of this work is to synthesis and characterization of cadmium sulfide/ thioglycolic acid nanocomposite and its conversion to pure CdS nanoparticles. The products were characterized by X-ray diffraction (XRD), SEM, TEM, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectra. The CdS/organic nanocomposite was decomposed into pure wurtzite CdS nanoparticles through hydrothermal treatment at 200. °C. UV-vis spectra were used to study the optical properties of CdS/organic nanocomposites and pure CdS. It was found that the absorption maximum of the CdS/TGA nanocomposite was significantly blue-shifted as compared to pure CdS nanoparticles. © 2014 The Korean Society of Industrial and Engineering Chemistry. Source


Relative energies and optimized structures of uracil tautomers and their complexes with silver ions were obtained using B3LYP calculations and more properties were investigated using AIM and NBO calculations. The interactions between all uracil tautomers and silver ions in different ways were investigated. Nine tautomers for uracil (U) and twenty U-Ag+ complexes were considered in this study. The IR spectra for three most stable tautomers and complexes were graphically presented, showing significant differences between their spectra. Analyzing the IR spectra of tautomers and complexes revealed that the frequency of C{double bond, long}O π-bond near the silver ion increases and it decreased while being away from the silver ion. The di-keto tautomer (pyrimidine-2,4(1H,3H)-dione) is the most stable tautomer but their complexes with silver ions are not the most stable because they are coordinated to silver ions only via oxygen atom. Moreover, binding energies in the gas phase and different solvents were obtained. In all solvents except water, with the increase of the solvent's dielectric constant, the binding energy decreased. A linear-like relationship was found between the binding energies in all solvents and in the gas phase and the frequency of stretching vibrations of U-Ag+. AIM (based on atom in molecular theory) values at the critical points confirm the effective interaction between silver ions and oxygen or nitrogen atoms of uracil tautomers. Natural bond orbital (NBO) calculations were employed to obtain the interaction energies for the charge transfer between uracil tautomers and silver ions. At last, UV-Vis absorptions and NMR chemical shifts of two most stable tautomers and complexes were calculated and compared with experimental data. © 2012. Source


Jabbari M.,Isfahan University of Technology
IEEE Transactions on Power Electronics | Year: 2011

A mechanism for power processing is presented, in which a certain amount of energy is transferred from the source to the output in each cycle. The result is establishing a family of resonant converters so-called switched-resonator converters. The basic nonisolated formation presented in this paper exhibits a collection of 23 simple dcdc converters. All topologies are inherently soft switched and systematically synthesized. A plenary analysis of the proposed converters is presented. © 2011 IEEE. Source


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. Source


Matinnejad R.,Isfahan University of Technology
Proceedings - 2011 9th International Conference on Software Engineering Research, Management and Applications, SERA 2011 | Year: 2011

Both the model-driven and agile development approaches have significantly enhanced productivity and predictability of software development in practice. Agile Model Driven Development or AMDD is an attempt to effectively bring together the fast pace of agile development and the guaranteed quality of model-driven development. Despite the proliferation of processes claim to comply with AMDD principles, there has been little academic research examining merits and demerits of such an approach. This paper first presents the underlying theoretical foundations of AMDD and then reviews, classifies and compares existing AMDD processes. The results indicate significant disparity between compared processes that implies the AMDD concepts are still in their infancy. © 2011 IEEE. Source


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. Source


Eskandari K.,Isfahan University of Technology | Mahmoodabadi N.,Damghan University
Journal of Physical Chemistry A | Year: 2013

Although, most of the authors classify the pnicogen bonds as σ-hole bonding, there are some evidence that show they do not require any positive electrostatic potential around interacting molecules. In this work, the Laplacian of electron density is used to study pnicogen bonds in different dimer and trimer complexes. It is shown that the noncovalent P·· ·P, P···N, and N···N bonds can be categorized as lump-hole interactions; a region of charge depletion and excess kinetics energy (hole) in the valence shell charge concentration (VSCC) of pnicogen atom combines with a region of charge concentration and excess potential energy (lump) in the VSCC of another molecule and form a pnicogen bond. In fact, since the full quantum potential (according to the local statement of virial theorem) has been used in the definition of the Laplacian, the lump-hole concept is more useful than the σ-hole in which the electrostatic part of potential is only considered. It is shown that the existence of hole in the VSCC of pnicogen atom is responsible for formation and (in the absence of other interactions) geometry of pnicogen bonded complexes. Because there is (at least) one hole in their VSCC, the pnicogen atoms in PH3, PH2F, H2C=PH, H2C=PF, and NH2F can engage in direct pnicogen-pnicogen interactions. However, the VSCC of nitrogen atom in the NH3 is devoid of hole and hence cannot act as an electron acceptor in pnicogen-bonded complexes. © 2013 American Chemical Society. Source


Tavakol H.,Isfahan University of Technology
Journal of Physical Chemistry A | Year: 2013

DFT calculations were employed to study tautomers of 2,2-di(pyrimidin-2-yl) acetic acid (DPA) in the gas phase and in the presence of water, methanol, DMSO (microsolvation models), and proton (H+). In the gas phase, all three tautomers were in equilibrium with each other (T2 was slightly more favorable); but, in microsolvation with protic solvent, T3 was a major isomer. Moreover, unexpectedly enough, T1 (common form of DPA) was the least stable tautomer in the gas phase, while, in the water (as solvent), T1 was the most stable one. The calculated energy values indicated a very special barrierless tautomeric system between T2 and T3. In the gas phase, ΔG# for T2 → T3 was only 0.30 kcal/mol, while it was 56.4 and 44.8 kcal/mol for T2 → T1 and T3 → T1, respectively. Rate constants for conversion of T2 into T3 were high in all cases, and their values in the gas phase and in the presence of water, methanol, DMSO, and proton were 3.6 × 1012, 3.3 × 10 9, 2.7 × 1011, 2.3 × 1012, and 2.3 × 1012 s-1, respectively. All types of microsolvation slightly decreased the rate constant of this conversion. The rate constant for conversion of T2 into T1 (1,3-H shift) in the gas phase and in the presence of water, methanol, DMSO, and proton was 3.0 × 10-29, 2.2 × 105, 1.1 × 10-34, 5.2 × 10 -40, and 4.2 × 10-26 s-1, respectively. These values showed that only microsolvation with water strongly increased rate constants of tautomerism for T2 → T1 and this type of tautomerism was impossible in the gas phase or other microsolvation models. Although using water as the solvent enhanced rate constants of all types of tautomeric interconversions, its enhancement was less than that of microsolvation with water. © 2013 American Chemical Society. Source


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. Source


Sohankar A.,Isfahan University of Technology
Theoretical and Computational Fluid Dynamics | Year: 2014

The results of an investigation on the interference effects of the tandem square cylinders exposed to a uniform flow are presented in this paper. Time-dependent and three-dimensional flow simulations are carried out using large eddy simulation with a one-equation subgrid model. An incompressible three-dimensional finite volume code with a collocated grid arrangement is used for solving filtered Navier–Stokes equations. These equations are solved with an implicit fractional two-step method. Simulations are conducted with different Reynolds numbers between 103 and 105. The longitudinal spacing between the cylinders is selected 4D for the chosen Reynolds numbers, where D is the side of the cylinders. Also the effect of the spacing between cylinders, ranging from 1D to 12D, is studied for the selected Reynolds numbers. The instantaneous flow field is studied by analyzing the vortices, pressure, streamlines and Q-criterion to assist understanding of the various flow patterns, vortical structures and Kelvin–Helmholtz vortices in the separating shear layers. The hysteresis is observed in a certain range of the gap spacing, which this range depends on the selected Reynolds number. The global results are also computed and compared with available experimental results. The results indicate that there is a satisfactory agreement between the predictions and available experimental data considering the fine grid adopted. © 2014, Springer-Verlag Berlin Heidelberg. Source


Hajiannia I.,Islamic Azad University at Najafabad | Shamanian M.,Isfahan University of Technology | Kasiri M.,Islamic Azad University at Najafabad
Materials and Design | Year: 2013

In the present study, microstructure and mechanical properties of AISI 347 austenitic stainless steel/ASTM A335 low alloy steel dissimilar joint were investigated. For this purpose, two filler metals including ER309L and ERNiCr-3 were selected to be used during the gas tungsten arc welding process. In tension tests, all weldments failed in the HAZ of A335. The impact test results indicated that all specimens exhibited ductile fracture. The maximum fracture energy was related to the ERNiCr-3 weld metal specimen. The maximum and minimum hardness corresponded to the ERNICr-3 and ER309L. Finally, it was concluded that ERNiCr-3 filler metal was the best choice for the joint between 347 austenitic stainless steel and A335 low alloy steel. © 2013 Elsevier Ltd. Source


Nejati H.R.,Tarbiat Modares University | Ahmadi M.,Tarbiat Modares University | Hashemolhosseini H.,Isfahan University of Technology
Tunnelling and Underground Space Technology | Year: 2012

The purpose of this study is the simulation of train movement and calculation of ground surface vibration induced by train movement in the subway tunnel. Tehran metro line 4 that is located in a populated area was considered as a case study. For simulation of train movement, effective factors on dynamic load magnitude and frequency have been studied and variation of wagon force in a longitude model is considered. Then Fourier amplitude spectrum was computed by means of Fast Fourier Transformation (FFT) of the dynamic train load and then the frequency range of train load was determined. In the next step, low energy frequencies were filtered and the dynamic load as a point load was applied on the numerical model of the tunnel and the ground surface vibration was determined. Finally, the result of the numerical model is verified by Metrikine and Vrouwenvelder's analytical model. Comparisons of numerical and analytical solutions shows that the numerical results have a good agreement with the analytical output and the maximum displacement in the horizontal and vertical directions are 3.75 and 5.25. mm, respectively. © 2011 Elsevier Ltd. Source


Shahri Z.,University of Kashan | Bazarganipour M.,Isfahan University of Technology | Salavati-Niasari M.,University of Kashan
Superlattices and Microstructures | Year: 2013

Zinc molybdate rod-like nanostructures have been successfully synthesized by precipitation method process and using a solid organometallic molecular precursor [bis(salicylaldehydato)zinc(II)], Zn(sal)2, and (NH 4)6Mo7O24·4H2O as starting materials. Some parameters including time effect, temperature effect, and surfactant effect were investigated to reach the optimum conditions. The as synthesized nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmittance electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectra. Facile preparation and separation are important features of this route. This work has provided a general, simple, and effective method to control the composition and morphology of zinc molybdate in aqueous solution, which will be important for inorganic synthesis methodology. © 2013 Elsevier Ltd. All rights reserved. Source


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. Source


Mirzadeh H.,University of Tehran | Najafizadeh A.,Isfahan University of Technology
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. Source


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. Source


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. Source


Hashemifar S.J.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2013

On the basis of ab initio pseudopotential calculations, we study structural, magnetic, dynamical, and mechanical properties of the hypothetical CaC ionic compound in the rock-salt (RS), B2, zinc-blende (ZB), wurtzite (WZ), NiAs (NA), anti-NiAs (NA*), and CrB (B33) structures. It is argued that the ZB, WZ, NA, and RS structures are more ionic while the NAz.ast;, B2, and B33 structures are more covalent systems. As a result of that, the nonmagnetic B33.CaC is the energetically preferred system, while the more ionic structures prefer a ferromagnetic ground state with high Fermi level spin polarization. The observed ferromagnetism in the more ionic systems is attributed to the sharp partially filled p states of carbon atom in the system. In the framework of density functional perturbation theory, the phonon spectra of these systems are computed and the observed dynamical instabilities of the NA. and B2 structures are explained in terms of the covalent bonds between carbon atoms. The calculated Helmholtz and Enthalpy free energies indicate the highest stability of the B33 structure in a wide range of temperatures and pressures. Among the ferromagnetic structures, RS.CaC and ZB.CaC are reported, respectively, to be the most and the least metastable systems in various thermodynamics conditions. Several mechanical properties of the dynamically stable structures of CaC are determined from their phonon spectra. © 2013 Elsevier B.V. All rights reserved. Source


Andani M.T.,University of Toledo | Alipour A.,Isfahan University of Technology | Eshghinejad A.,University of Toledo | Elahinia M.,University of Toledo
Journal of Intelligent Material Systems and Structures | Year: 2013

In this article, a semi-analytical modeling approach is presented to study the pseudoelastic response of shape memory alloy rods and tubes subjected to combined tension-torsion loading states. A three-dimensional phenomenological shape memory alloy constitutive model is used to obtain the corresponding two-dimensional constitutive relations. The rod is partitioned into a finite number of narrow annular regions, and the equilibrium equations are found in each region for both loading and unloading paths. The derived equations are then solved based on an iterative algorithm. A set of experiments is conducted on a shape memory alloy thin-walled tube, and the results are then used to evaluate the performance of the modeling approach. Several numerical examples along with a finite element analysis are finally presented to demonstrate the capabilities of the proposed method. Using this approach, it is possible to design active biomedical devices with shape memory alloy actuators under combined loading conditions. © The Author(s) 2013. Source


Andani M.T.,University of Toledo | Alipour A.,Isfahan University of Technology | Elahinia M.,University of Toledo
Journal of Intelligent Material Systems and Structures | Year: 2013

In this article, the coupled thermomechanical response of superelastic shape memory alloy bars and tubes in combined tension and torsion is studied both analytically and experimentally. Using the Gibbs free energy as the thermodynamic potential and choosing appropriate internal state variables, a three-dimensional phenomenological macroscopic constitutive model for shape memory alloys is derived. Taking into account the effect of latent heat during the forward and reverse martensitic phase transformation, the appropriate form of the energy balance relation is obtained. The three-dimensional coupled relations for the energy balance in the presence of the internal heat flux and the constitutive equations are reduced to a two-dimensional form for the tension-torsion case. An explicit finite difference approach is utilized to discretize the governing boundary conditions of bars. An empirical expression for the free heat convection from the surface of a shape memory alloy bar was proposed and experimentally validated. Several sets of experiments were then carried out to evaluate the mechanical and thermal responses of the model for a shape memory alloy tube subjected to uniaxial, pure torsion and non-proportional tension and torsion loading-unloading conditions. The approach could be used in the design of shape memory alloy devices undergoing combined loads with high strain rates or in the fatigue design of shape memory alloy devices subjected to cyclic loading. © The Author(s) 2013. Source


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. Source


Akbari M.,Isfahan University of Technology | Madani S.M.,University of Isfahan
IET Renewable Power Generation | Year: 2014

Increase in doubly fed induction generator (DFIG)-based wind farms degrades the short-term frequency regulation of power systems. However, such wind farms may have large amount of kinetic energy which can be rapidly injected into the power system to support system frequency by using an appropriate supplementary control loop. This study first analyses the impacts of DFIGs and their supplementary loop on power system short-term frequency regulation. Then, the average power system frequency model is modified to include the participation of wind farms in frequency control. Moreover, a new method is proposed to derive an analytical expression for minimum frequency of a power system, as an important index of frequency regulation, after a power imbalance occurrence. This analytical expression provides a tool for better insight into frequency behaviour of power systems with high levels of wind generation. The results of the analysis are verified by simulation of the nine-bus test system, using MATLAB/SIMULINK. © The Institution of Engineering and Technology 2014. Source


Sedaghat A.,Isfahan University of Technology
Renewable Energy | Year: 2014

One of attracting concepts has been the use of Magnus effect to produce lift from rotating cylinders in various engineering applications. With emerging innovative Magnus type wind turbine technology, it is important to determine power performance and characteristics of such generators as correctly as possible. As stressed by Seifert, there is lack of theories in design and modelling of using Magnus force in engineering which is particularly noticed for the horizontal axis Magnus type wind turbines. In this study, the importance of research carried out for determining lift and drag forces of rotating circular cylinders is highlighted and reviewed. Then, the theoretical methods used in designing commercial aerofoil type wind turbines are extended to apply on the Magnus types. New formulation is presented for potential flow around the Magnus blades. The blade element momentum (BEM) theory is formulated for the Magnus wind turbines. A cubic function for angular induction factor is found from the BEM analysis which is strongly dependant on the drag to lift ratio. It is also observed that the relative wind incidence angle and the local power coefficient of the Magnus cylinder are independent functions of spin ratio. © 2013 Elsevier Ltd. Source


Mostafaeipour A.,University of Yazd | Jadidi M.,University of Yazd | Mohammadi K.,University of Kashan | Sedaghat A.,Isfahan University of Technology
Renewable and Sustainable Energy Reviews | Year: 2014

Most people would produce their own clean local energy if it were easy and affordable. When a renewable energy system is installed, there is an upfront cost that can be partially or completely offset by various ways. Purpose of this study is to assess wind energy potential for the city of Zahedan in southeast part of Iran. Five-year (2003-2007) wind data has been analyzed to obtain wind power density and wind energy potential. Weibull density function has been used to determine the wind power density and energy of the region. Yearly mean Weibull parameters, k and c, were 1.155 and 3.401 (m/s). Obtained wind power and energy densities are 89.184 W/m2, and 781.252 kWh/m2 respectively. In short, economic evaluation and analysis of four different wind turbines are presented in this paper. In order to utilize wind energy, it is recommended to install Proven 2.5 kW model wind turbine in the region which is the most cost efficient option. © 2013 Elsevier Ltd. All rights reserved. Source


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. Source


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. Source


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. Source


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. Source


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. Source


Babakhani D.,University of Isfahan | Soleymani M.,Isfahan University of Technology
Journal of the Taiwan Institute of Chemical Engineers | Year: 2010

Current study reveals an analytical solution of coupled heat and mass transfer processes in a packed bed liquid desiccant regenerator. This solution showed good accuracy when compared with reliable experimental data available in the literature. In order to maintain the mass transfer gradient on the interface, a high liquid desiccant flow rate is often applied in the regenerator. Hence, the solution flow rate and concentration change very little in the whole processes. The experimental results confirmed the validation of this topic. Therefore, for narrow range of operating conditions in practical regeneration process, with acceptable error we can assume that equilibrium humidity ratio is constant on the interface. The assumption of constant humidity ratio was applied in this paper for derivation of analytical solution. The effects of variables such as air and liquid desiccant flow rate, air temperature and humidity, desiccant temperature and concentration were investigated on the evaporation rate. Furthermore, a comparison is made between the present study and analytical solution given in the literature. The results showed that the present analytical solution can give better results than other analytical solutions that presented in the literature. © 2009 Taiwan Institute of Chemical Engineers. Source


Thamburaja P.,National University of Malaysia | Jamshidian M.,Isfahan University of Technology
Journal of the Mechanics and Physics of Solids | Year: 2014

In this work, we have developed a thermodynamically consistent, three-dimensional, finite-deformation-based constitutive theory to describe grain growth due to stress-driven grain boundary motion in polycrystalline cubic metals. The constitutive model has been formulated in a multiscale setting using the Taylor-type homogenization scheme (Taylor, 1938), and it has also been implemented into a computational framework. In our numerical scheme, the mechanical response of a structure at the macroscale level is modeled using the finite-element method whereas at the mesoscale level, the stress-driven grain growth process within a polycrystalline aggregate is handled by phase-field-like simulations. Using our multiscale constitutive theory and computational framework, we model several boundary value problems involving grain growth in polycrystalline cubic metals. From our coupled finite-element and phase-field simulations, we obtain the following trends: (a) sufficiently stressed polycrystalline metals result in the preferential growth of elastically soft crystal orientations at the expense of elastically hard crystal orientations, and (b) grain growth stagnation effects can be responsible for preventing a polycrystalline aggregate from evolving into a single crystal under stress-driven grain growth conditions. These observations agree well with previously conducted experimental and simulation results available in the literature. © 2013 Elsevier Ltd. Source


Golestani N.,Isfahan University of Technology | EtehadTavakol M.,Isfahan University of Medical Sciences | Ng E.Y.K.,Nanyang Technological University
EXCLI Journal | Year: 2014

Breast thermography is a physiological test that provides information based on the tempera-ture changes in breast. It records the temperature distribution of a body using the infrared ra-diation emitted by the surface of that body. Precancerous tissue and the area around a cancer-ous tumor have higher temperature due to angiogenesis, and higher chemical and blood vessel activity than a normal breast; hence breast thermography has potential to detect early abnor-mal changes in breast tissues. It can detect the first sign of forming up cancer before mam-mography can detect. The thermal information can be shown in a pseudo colored image where each color represents a specific range of temperature. Various methods can be applied to extract hot regions for detecting suspected regions of interests in the breast infrared images and potentially suspicious tissues. Image segmentation techniques can play an important role to segment and extract these regions in the breast infrared images. Shape, size and borders of the hottest regions of the images can help to determine features which are used to detect ab-normalities. In this paper, three image segmentation methods: k-means, fuzzy c-means and level set are discussed and compared. These three methods are tested for different cases such as fibrocystic, inflammatory cancer cases. The hottest regions of thermal breast images in all cases are extracted and compared to the original images. According to the results, level set method is a more accurate approach and has potential to extract almost exact shape of tumors. Source


The density functional theory is used to investigate the effects of a tiny sphere (TS) inserted in the center of a nanospherical pore (SP) on the interfacial tension and surface adsorption behavior of confined fluids. Results show that the size and type (hard or attractive) of the inserted TS play important roles in the fluid interfacial tension. The perturbation created in the structure of the confined fluid due to the insertion of a hard TS is not capable of changing the positive sign of the interfacial tension although it does give rise to changes in the interfacial tension and surface adsorption behavior of the pore depending on its size. If, on the other hand, an attractive TS is inserted, the sign may become negative or positive depending on the TS-fluid interactions and TS size. Insertion of a hard TS in the SP, however, causes the interfacial tension to exhibit a positive deviation from its value for the fluid in the SP while this deviation will be negative if an attractive TS is inserted. Investigation of surface adsorption and interfacial tension reveals that, for large SPs, fluid interfacial tension in each thermodynamic state has a linear relationship with adsorption when a TS is inserted. This is while this linear relationship fails for small SPs. Also, it is shown that the locus of deviation from linearity, H, is shifted to higher values of H or Rs as a result of increasing TS radius and bulk density. Finally, it is found that the type (hard or attractive) of the fluid and the inserted TS, however, cannot change the locus of the break point. © 2016 Elsevier B.V. All rights reserved. Source


Eskandari K.,Isfahan University of Technology | Van Alsenoy C.,University of Antwerp
Journal of Computational Chemistry | Year: 2014

The nature of H-H interaction between ortho-hydrogen atoms in planar biphenyl is investigated by two different atomic energy partitioning methods, namely fractional occupation iterative Hirshfeld (FOHI) and interacting quantum atoms (IQA), and compared with the traditional virial-based approach of quantum theory of atoms in molecules (QTAIM). In agreement with Bader's hypothesis of H-H bonding, partitioning the atomic energy into intra-atomic and interatomic terms reveals that there is a net attractive interaction between the ortho-hydrogens in the planar biphenyl. This falsifies the classical view of steric repulsion between the hydrogens. In addition, in contrast to the traditional QTAIM energy analysis, both FOHI and IQA show that the total atomic energy of the ortho-hydrogens remains almost constant when they participate in the H-H interaction. Although, the interatomic part of atomic energy of the hydrogens plays a stabilizing role during the formation of the H-H bond, it is almost compensated by the destabilizing effects of the intra-atomic parts and consequently, the total energy of the hydrogens remains constant. The trends in the changes of intra-atomic and interatomic energy terms of ortho-hydrogens during H-H bond formation are very similar to those observed for the H 2 molecule. © 2014 Wiley Periodicals, Inc. Source


Emissions of nitrogen oxides (NOx) in fuel combustion from stationary and mobile sources contribute to the greenhouse effects and cause a variety of environmentally harmful results. Meanwhile, the selective catalytic reduction (SCR) of NOx using ammonia over a vanadia-based catalyst in heterogeneous reactors is still a well-proven technique for NOx abatement. However, to meet forthcoming restrictive legislation, greater De-NOx performance can be achieved by eliminating operational setbacks such as diffusion resistance, poor catalyst activity at low temperatures, etc. In this study, an electrohydrodynamic (EHD)-SCR model was developed to evaluate the enhancing effect of the EHD technique on NH 3-SCR of NO through a hollow cylindrical catalyst. Computational investigations were performed based on the proposed model in different operational conditions to examine the effect of various operating parameters on SCR enhancement. Simulation results showed that catalyst utilization was intensified significantly by EHD application and generation of additional flow known as EHD-induced secondary flow through the catalyst porous layer, which undermined the proposed drawbacks of the catalyst medium and provided higher catalyst effectiveness with greater NO conversion. Results also indicated that the maximum enhancement of almost 4.2-fold could be obtained for NO conversion with electric potentials and operating temperatures of 150-270 V and 150-165 °C, respectively. © 2014 American Chemical Society. Source


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. Source


Momeni M.M.,Isfahan University of Technology
Materials Research Innovations | Year: 2016

The effect of tungsten trioxide doping on the photovoltaic efficiency of dye-sensitized solar cells (DSSCs) with anodized TiO2 nanotubes was investigated. Tungsten-doped TiO2 nanotubes with different amounts of tungsten were obtained directly by the electrochemical anodizing of titanium in a single-step process using sodium tungstate as the tungsten source. Nanocomposite films features were investigated by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and ultraviolet-visible spectroscopy. The photovoltaic efficiencies of fabricated DSSCs were characterized by a solar cell measurement system via the photocurrent-voltage (I-V) curves. It was found that the photovoltaic efficiency of DSSCs with tungsten-doped TiO2 nanotubes (sampleWT2)was improved compared to DSSCs with as-prepared TiO2 nanotubes andWT samples fabricated using other tungsten concentrations. This improvement is ascribed to increased dye loading and photocurrent density. © 2016 Informa UK Limited, trading as Taylor & Francis Group. Source


Sodeifian G.,University of Kashan | Azizi J.,University of Kashan | Ghoreishi S.M.,Isfahan University of Technology
Journal of Supercritical Fluids | Year: 2014

In this study, the essential oil of aerial parts of a species of a plant called Smyrnium cordifolium Boiss (SCB) was extracted by supercritical CO 2. The essence was analyzed by the method of GC/MS. Design of experiments was carried out with response surface methodology by Minitab 16 software to optimize four operating variables of supercritical carbon dioxide (SC-CO2) extraction (pressure, temperature, CO2 flow rate and extraction dynamic time). This is the first report announcing optimization of the operation of supercritical extraction of SCB in laboratorial conditions. Optimizing process was done to achieve maximum yield extraction. Independent variables were dynamic time (td), pressure (P), temperature (T) and flow rate of SC-CO2 (Q) in the range of 30-150 min, 10-30 MPa, 40-60 °C and 0.5-1.7 ml/min, respectively. The experimental optimal recovery of essential oil (0.8431, w/w%) was obtained at 13.43 MPa, 40 °C, 150 min (dynamic) and 1.7 ml/min (CO2 flow rate). © 2014 Elsevier B.V. Source


Mokhtari A.,Golestan University | Rezaei B.,Isfahan University of Technology
Analytical Methods | Year: 2011

A flow injection chemiluminescence (FI-CL) method was developed for the rapid and sensitive determination of two phenothiazine derivatives including chlorpromazine hydrochloride (CPH) and fluphenazine hydrochloride (FPH). The method is based on the CL reaction of phenothiazines with Ru(phen) 3 2+ and Ce(iv) in acidic medium. Effects of chemical variables were investigated employing central composite design (CCD) and response surface methodology (RSM). Under the optimum conditions, the calibration curves were linear over the range 0.030-36 g mL -1 for CPH, and 0.030-0.50 and 0.50-20 g mL -1 for FPH. The limits of detection (S/N = 3) were 0.020 g mL -1 and 0.015 g mL -1 for CPH and FPH, respectively. The method was successfully applied to the determination of CPH and FPH in pharmaceutical formulations and human serum with good recoveries (94.5-106.4%). Sample throughput was 90 h -1. © 2011 The Royal Society of Chemistry. Source


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. Source


Davar F.,Razi University | Mohammadikish M.,Islamic Azad University at Kermanshah | Reza Loghman-Estarki M.,Isfahan University of Technology | Hamidi Z.,Islamic Azad University at Kermanshah
CrystEngComm | Year: 2012

In this paper, we report a facile hydrothermal method for the preparation of spherical ZnS based nanocrystals (flower-like architectures), using Zn(acac) 2 and thioacetamide (TAA) as the Zn 2+ and sulfur sources and thioglycolic acid (TGA) as the capping agent. The influence of temperature and polyethylene glycol (PEG), as a surfactant, on the morphology of the products was investigated. The flower-like ZnS were produced from self-assembly of nanoparticles with diameters of 40 ± 5 nm. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SEAD), and Fourier transform infrared (FT-IR) spectra. The influence of temperature and surfactant (polyethylene glycol) on the morphology of the products was investigated. The possible formation mechanism and optical properties of these architectures were also reported. This journal is © 2012 The Royal Society of Chemistry. Source


Baniasadi E.,Southern Illinois University Carbondale | Alemrajabi A.A.,Isfahan University of Technology
International Journal of Hydrogen Energy | Year: 2010

Today's concern regarding limited fossil fuel resources and their contribution to environmental pollution have changed the general trend to utilization of high efficiency power generation facilities like fuel cells. According to annual reducing capital cost of these utilities, their entrance to commercial level is completely expected. Hot exhaust gases of Solid Oxide Fuel Cells (SOFC) are potentially applicable in heat recovery systems. In the present research, a SOFC with the capacity of 215 kW has been combined with a recovery cycle for the sake of simultaneous of electric power, cooling load and domestic hot water demand of a hotel with 4600 m2 area. This case study has been evaluated by energy and exergy analysis regarding exergy loss and second law efficiency in each component. The effect of fuel and air flow rate and also current density as controlling parameters of fuel cell performance have been studied and visual software for energy-exergy analysis and parametric study has been developed. At the end, an economic study of simultaneous energy generation and recovery cycle in comparison with common residential power and energy systems has been done. General results show that based on fuel lower heating value, the maximum efficiency of 83 percent for simultaneous energy generation and heat recovery cycle can be achieved. This efficiency is related to typical climate condition of July in the afternoon, while all the electrical energy, cooling load and 40 percent of hot water demand could be provided by this cycle. About 49 percent of input exergy can be efficiently recovered for energy requirements of building. Generator in absorption chiller and SOFC are the most destructive components of exergy in this system. © 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. Source


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. Source


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. Source


Golkar P.,Isfahan University of Technology
Australian Journal of Crop Science | Year: 2014

Safflower (Carthamus tinctorius L.) is an oil seed crop that is grown not only for its edible oil but also for its applications as animal feed and plant-made pharmaceuticals. Historically, biometrical genetics played a crucial role in the improvement of safflower seed yield and its components, phenologic and morphologic traits, and nutritional properties including oil, fatty (linoleic, oleic, stearic, and palmitic) acids, protein, and fiber. Breeding methods based on gene action of different traits has a significant role in releasing high-yield genotypes. In recent years, biotechnological methods have played a supplementary role in safflower breeding, but breeding programs are not being complemented adequately with molecular tools. In this review article, efforts are made to investigate and review the different genetic studies thus far conducted on the genetic control of different traits and molecular markers used for germplasm identification in safflower. The studies reviewed have left their mark on safflower improvement in recent years. Source


Karimi M.,Isfahan University of Medical Sciences | Esrafilian A.,Isfahan University of Technology
Prosthetics and Orthotics International | Year: 2013

Background: Stability during standing is achieved by a complex coordination process between various human systems. The stability of normal subjects and patients with various neuromuscular disorders has been evaluated by common methods based on force plate data analysis for one minute. However, most of the people frequently stand for a prolonged period during daily activities. Objectives: This study aimed to evaluate the stability of subjects during a longer period of time. Moreover, the new method was introduced to analyze the stability of subjects with musculoskeletal disorders. Study Design: Experimental. Methods: Four groups of normal adults and children, individuals with spinal cord injury (SCI) and Perthes disease were recruited in this study. Stability of the subjects was evaluated by using parameters collected from centre of pressure (COP) sways obtained while subjects standing on force plate for one and then five minutes based on the old and new methods. Two sample t-test was used to compare the stability of the subjects by the commonly used method. The number of stable to unstable frames was selected for final analysis based on the new method. Results: Based on the traditional method, the SCI and Perthes patients were more stable than normal subjects (p < 0.05). Moreover, children were more unstable in the anteroposterior plane than adults. However, based on the new method, SCI and patients with Perthes disease were more unstable than normal adults. Moreover, in mediolateral direction the results of stability analysis with the new method differed from that of the traditional method. Conclusion: The new method of stability analysis seems to be more sensitive and accurate than that of the traditional commonly used method. Based on the new method, stability is the ability of a subject to return from an unstable position to a stable one and to remain in a stable one for a certain period of time. © 2012 The International Society for Prosthetics and Orthotics. Source


In this study, an optically active diamine, N,N′-(pyromellitoyl)- bis{N-[4(4-aminophenoxy)phenyl]-2-(4-methyl)pentanamide} (1) containing amino acid l-leucine was prepared in three steps. The step-growth polymerization of this chiral diamine with several diisocyanates in room temperature ionic liquid (IL), 1,3-dipropylimidazolium bromide as an environmentally friendly solvent and in a volatile organic solvent, is investigated. The polymerization yields and inherent viscosities of the resulting poly(amide-ether-imide-urea)s are compared in both solvents. The results show that the IL to be the superior polymerization media. All of the obtained polymers exhibited good solubility in some polar aprotic organic solvents such as N,N-dimethyacetamide, N,N-dimethyformamide, dimethyl sulfoxide while thermal stability was not disturbed based on thermogravimetric analysis and differential scanning calorimetry experiments. X-ray diffraction analysis of polymers shows that they are amorphous. The observation of optical rotation confirms the optical activity of prepared polymers. © 2010 Springer-Verlag. Source


Momeni M.M.,Isfahan University of Technology
Materials Research Innovations | Year: 2016

The photoelectrochemical water splitting into hydrogen and oxygen using solar light is a promising method to provide clean energy carriers in the future. Here, we report a simple but efficient way to fabricate iron-decorated tungsten-titania nanotube photoanodes for photoelectrochemical water splitting. These photoanodes were fabricated through electrochemical anodising in combination with chemical bath deposition. The morphology, crystal phase, chemical composition and photocatalytic activity of the prepared samples were evaluated using various characterisation techniques. Results showed that these films have nanotubular morphology and iron was successfully anchored on tungsten-titania nanotubes, which enhanced the photocatalytic activity of these samples. Iron-decorated photoanodes exhibited an excellent and stable photocatalytic activity in the solar water splitting compared to the unmodified photoanode. After irradiation under xenon light illumination for 120 min, the total amount of hydrogen evolved on the iron-decorated sample was approximately 3.5 times higher than that on the unmodified sample and 6.3 times higher than that on bare titania. © 2016 Informa UK Limited, trading as Taylor & Francis Group. Source


Morshedi M.,Institute for Advanced Studies in Basic Sciences | Hadadzadeh H.,Isfahan University of Technology
Journal of Fluorescence | Year: 2013

Two novel, mixed ligand complexes of cobalt(III) and nickel(II), [Co(phen)2(taptp)]3+ (1) and [Ni(phen)2(taptp)] 2+ (2) (phen = 1,10-phenanthroline and taptp = 4,5,9,18- tetraazaphenanthreno [9,10-b]triphenylene), were synthesized and characterized by elemental analyses, UV-visible and NMR spectroscopies. The binding interactions of the two complexes with DNA have been investigated using absorption and emission spectroscopy methods and electrophoresis measurement mode. The intrinsic binding constants for these complexes to DNA are in the order of 105. In Tris buffer, the Co(III) complex shows a moderate luminescence which was enhanced after binding to DNA. However for complex Ni(II), no emission was observed in Tris buffer. The [Co(phen) 2(taptp)]3+ and [Ni(phen)2(taptp)]2+ can cause the photocleavage of DNA supercoiled pBR322 upon irradiation by 360 nm light. Based on the data, an intercalative mode of DNA binding is suggested for the two complexes. © 2012 Springer Science+Business Media New York. Source


Levitas V.I.,Iowa State University | Javanbakht M.,Iowa State University | Javanbakht M.,Isfahan University of Technology
Journal of the Mechanics and Physics of Solids | Year: 2015

Abstract A thermodynamically consistent, large strain phase field approach to dislocation nucleation and evolution at the nanoscale is developed. Each dislocation is defined by an order parameter, which determines the magnitude of the Burgers vector for the given slip planes and directions. The kinematics is based on the multiplicative decomposition of the deformation gradient into elastic and plastic contributions. The relationship between the rates of the plastic deformation gradient and the order parameters is consistent with phenomenological crystal plasticity. Thermodynamic and stability conditions for homogeneous states are formulated and satisfied by the proper choice of the Helmholtz free energy and the order parameter dependence on the Burgers vector. They allow us to reproduce desired lattice instability conditions and a stress-order parameter curve, as well as to obtain a stress-independent equilibrium Burgers vector and to avoid artificial dissipation during elastic deformation. The Ginzburg-Landau equations are obtained as the linear kinetic relations between the rate of change of the order parameters and the conjugate thermodynamic driving forces. A crystalline energy coefficient for dislocations is defined as a periodic step-wise function of the coordinate along the normal to the slip plane, which provides an energy barrier normal to the slip plane and determines the desired, mesh-independent height of the dislocation bands for any slip system orientation. Gradient energy contains an additional term, which excludes the localization of a dislocation within a height smaller than the prescribed height, but it does not produce artificial interface energy. An additional energy term is introduced that penalizes the interaction of different dislocations at the same point. Non-periodic boundary conditions for dislocations are introduced which include the change of the surface energy due to the exit of dislocations from the crystal. Obtained kinematics, thermodynamics, and kinetics of dislocations at large strains are simplified for small strains and rotations, as well. © 2015 Elsevier Ltd. Source


Javanbakht M.,Isfahan University of Technology | Javanbakht M.,Iowa State University | Levitas V.I.,Iowa State University
Journal of the Mechanics and Physics of Solids | Year: 2015

The complete system of phase field equations for coupled martensitic phase transformations (PTs), dislocation evolution, and mechanics at large strains is presented. Finite element method (FEM) is utilized to solve this system for two important problems. The first one is related to the simulation of shear strain-induced PT at the evolving dislocation pile-ups in a nanosized bicrystal. Plasticity plays a dual part in the interaction with PT. Dislocation pile-ups produce strong stress tensor concentrators that lead to barrierless martensite (M) nucleation. On the other hand, plasticity in the transforming grain relaxes these stress concentrators suppressing PT. The final stationary M morphology is governed by the local thermodynamic equilibrium, either at the interfaces or in terms of stresses averaged over the martensitic region or the entire grain. This is very surprising because of strong heterogeneity of stress fields and is in contrast to previous statements that phase equilibrium conditions do not enter the description of strain-induced PTs. The second problem is devoted to martensitic plate propagation through a bicrystal during temperature-induced PT. For elastic growth (without dislocations) and a large thermal driving force, a complex transformation path with plate branching and direct and reverse PTs is observed, which still ends with the same stationary nanostructure as for a smaller driving force and a traditional transformation path. Sharp grain boundary arrests plate growth at a relatively small driving force, exhibiting an athermal friction. For elastoplastic growth, the generation of dislocations produces athermal friction and arrests the plate below some critical driving force, leading to a morphological transition from plate to lath M. The width of the martensitic plate increases in comparison with elastic growth due to internal stress relaxation. Plate growth is accompanied by the nucleation of dislocations within M and remaining in M, the nucleation of dislocations at the tip of a plate and spreading them in austenite (A), and passing some dislocations through M, then through a M-A interface, and then through A. Due to the existence of a stationary equilibrium M nanostructure and concentration for each temperature, for a large enough observation time one observes athermal, rate- and time-independent kinetics, even while local kinetics is rate dependent. In the final structure, most dislocations are in M despite its having a yield strength three times larger than for A, which is consistent with experiments. © 2015 Elsevier Ltd. All rights reserved. Source


Levitas V.I.,Iowa State University | Javanbakht M.,Isfahan University of Technology | Javanbakht M.,Iowa State University
Journal of the Mechanics and Physics of Solids | Year: 2015

Thermodynamically consistent, three-dimensional (3D) phase field approach (PFA) for coupled multivariant martensitic transformations (PTs), including cyclic PTs, variant-variant transformations (i.e., twinning), and dislocation evolution is developed at large strains. One of our key points is in the justification of the multiplicative decomposition of the deformation gradient into elastic, transformational, and plastic parts. The plastic part includes four mechanisms: dislocation motion in martensite along slip systems of martensite and slip systems of austenite inherited during PT and dislocation motion in austenite along slip systems of austenite and slip systems of martensite inherited during reverse PT. The plastic part of the velocity gradient for all these mechanisms is defined in the crystal lattice of the austenite utilizing just slip systems of austenite and inherited slip systems of martensite, and just two corresponding types of order parameters. The explicit expressions for the Helmholtz free energy and the transformation and plastic deformation gradients are presented to satisfy the formulated conditions related to homogeneous thermodynamic equilibrium states of crystal lattice and their instabilities. In particular, they result in a constant (i.e., stress- and temperature-independent) transformation deformation gradient and Burgers vectors. Thermodynamic treatment resulted in the determination of the driving forces for change of the order parameters for PTs and dislocations. It also determined the boundary conditions for the order parameters that include a variation of the surface energy during PT and exit of dislocations. Ginzburg-Landau equations for dislocations include variation of properties during PTs, which in turn produces additional contributions from dislocations to the Ginzburg-Landau equations for PTs. A complete system of coupled PFA and mechanics equations is presented. A similar theory can be developed for PFA to dislocations and other PTs, like reconstructive PTs and diffusive PTs described by the Cahn-Hilliard equation, as well as twinning and grain boundaries evolution. © 2015 Elsevier Ltd. All rights reserved. Source


Arezoomand M.,Islamic Azad University at Majlesi | Taeri B.,Isfahan University of Technology
Match | Year: 2010

Let e be an edge of a graph G with endpoints u and v. Define two sets G1 (e) and G2(e), Gi1(e) is the set of vertices closer to u than to v while G2(e) consists of those vertices that are closer to v. Then the Szeged index of G is defined as mathemetical represented. The generalized hierarchical product of graphs was defined by Barriere et. al. (L. Barrière, C. Dalfó, M. A. Fiol and M. Mitjana, Discrete Math., 309 (2009) 3871-3881.) In this paper we compute the Szeged index of hierarchical product of graphs. As a consequence of our results, these indices were computed for some chemical structures such as regular dicentric dendrimers, linear phenylenes, dimer fullerene C60, truncated cube and truncated cuboctahedron. Source


Firooz A.R.,University of Isfahan | Ensafi A.A.,Isfahan University of Technology | Hajyani Z.,University of Isfahan
Sensors and Actuators, B: Chemical | Year: 2013

A new optical sensor for highly sensitive and selective determination of ultra-trace amounts of mercury(II) ions is developed. This optode is based on the interaction of 1,15-diaza-3,4,12,13-dibenzo-8-oxa-16,18-pyridin-5,1- dithiacyclo octadecane-2,14-dione with Hg(II) in plasticized (2-nitrophenyloctyl ether (o-NPOE)) polyvinyl chloride (PVC) membrane incorporating chromoionophore V as a lipophilic H+-selective indicator. By increasing Hg(II) concentration, the absorbance of chromoionophore V in the membrane decreased at 668 nm whereas the absorbance at 567 nm increased. With the proposed sensor at pH 6.3, mercury(II) can be measured in the range of 1.0 × 10 -12-8.6 × 10-4 mol L-1 with a limit of detection 5.3 × 10-13 mol L-1. The relative standard deviation for eight determination of 1.0 × 10-10 mol L -1 Hg(II) was 2.8%. The results obtained for the determination of mercury ions in water samples, SRM, and tomato leaves using the proposed optode were found to be comparable with the well-established cold vapor atomic absorption spectrometry. © 2012 Elsevier B.V. Source


Malekzadeh P.,Persian Gulf University | Farajpour A.,Isfahan University of Technology
Acta Mechanica | Year: 2012

As a first endeavor, the axisymmetric free and forced vibrations of circular single- and doublelayered nanoplates under initial in-plane radial stresses and embedded in an elastic medium are investigated. The governing equations are derived by decoupling the nonlocal constitutive equations of the Eringen theory in polar coordinates in conjunction with the classical plate theory. The elastic medium is modeled as a twoparameter elastic foundation (Pasternak type). Galerkin's method is employed to solve the resulting equation for vibration frequencies and dynamic response. The effects of small scale together with the other parameters such as initial in-plane load, Winkler and shear elastic foundation coefficients and the radius of the nanoplate are investigated. It is shown that the corresponding natural frequencies obtained by nonlocal elasticity theory are very different from those predicted by classical elasticity theory when the radius of the nanoplate is less than an approximate limit value. © Springer-Verlag 2012. Source


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. Source


Mostafaeipour A.,University of Yazd | Sedaghat A.,Isfahan University of Technology | Dehghan-Niri A.A.,University of Yazd | Kalantar V.,University of Yazd
Renewable and Sustainable Energy Reviews | Year: 2011

Climate change, global warming, and the recent worldwide economic crisis have emphasized the need for low carbon emissions while also ensuring economic feasibility. In this paper, the status and wind power potential of the city of Shahrbabak in Kerman province in Iran was investigated. The technical and economical feasibility of wind turbine installation is presented. The potential of wind power generation was statistically analyzed. The mean wind speed data of three-hour interval long term period from 1997 to 2005 was adopted and analyzed in order to determine the potential of wind power generation. The numerical values of the dimensionless Weibull shape parameter (k) and Weibull scale parameter (c) were determined. Annual values of "k" ranged from 1.725 to 1.930 with a mean value of 1.504, while annual values of "c" were in the range of 4.848-6.095 with a mean value of 5.314 (m/s). With the average wind power density of 100 W/m2, it is found that the city is not an appropriate place for construction of large-scale wind power plants, but is suitable for employment of off-grid electrical and mechanical wind driven systems. An economic evaluation was done in order to show feasibility of installing small wind turbines. It was concluded that it costs 18 cents for 1 kW h which is 5 cents more than the market price. Each turbine of 10 kW can supply power for icebox, washer, water pump, TV, lighting, electrical fan, charger, and air conditioning units for small houses. In order to utilize wind energy in the region, it is recommended to install small size wind turbines for electricity supply of public and public buildings and private houses. © 2011 Elsevier Ltd. All rights reserved. Source


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. Source


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. Source


Rahimmalek M.,Isfahan University of Technology
Plant OMICS | Year: 2012

ISSR and morphological markers were used to detect genetic diversity in several genotypes of Achillea tenuifolia from different geographical regions of Iran. Fifteen primers revealed 247 polymorphic bands, out of which 214 (86.78%) were polymorphic. The dendrogram was constructed using SM coefficient and UPGMA method. The generated dendrogram revealed three groups. The accessions originated from central regions of the country separated from others in group 3. The principle coordinate analysis (PCoA) confirmed the results of clustering (>90%). For morphological traits, North-western (NW) accessions had the highest values of leaf length, leaf width, leaf area, essential oil yield and the latest flowering time, while the Northern one (AtN76) had the highest flower diameter and number of florets in main inflorescence. Results showed the relatively broad genetic base of in most of the accessions evaluated in this study. The lowest and the highest gene diversity were obtained in North-western (AtNW) group (0.18) and Northern (AtN) accession (0.28) respectively. High genetic variation of A. tenuifolia might be attributed to its reproductive propagation and seed dispersal. So, conservation strategies should be provided to maintain such diversity aiming to improve future breeding programs. Source


Bagheri A.,Isfahan University of Technology | Saraee M.,University of Salford | De Jong F.,INTERACTION MEDIA GROUP
Knowledge-Based Systems | Year: 2013

With the rapid growth of user-generated content on the internet, automatic sentiment analysis of online customer reviews has become a hot research topic recently, but due to variety and wide range of products and services being reviewed on the internet, the supervised and domain-specific models are often not practical. As the number of reviews expands, it is essential to develop an efficient sentiment analysis model that is capable of extracting product aspects and determining the sentiments for these aspects. In this paper, we propose a novel unsupervised and domain-independent model for detecting explicit and implicit aspects in reviews for sentiment analysis. In the model, first a generalized method is proposed to learn multi-word aspects and then a set of heuristic rules is employed to take into account the influence of an opinion word on detecting the aspect. Second a new metric based on mutual information and aspect frequency is proposed to score aspects with a new bootstrapping iterative algorithm. The presented bootstrapping algorithm works with an unsupervised seed set. Third, two pruning methods based on the relations between aspects in reviews are presented to remove incorrect aspects. Finally the model employs an approach which uses explicit aspects and opinion words to identify implicit aspects. Utilizing extracted polarity lexicon, the approach maps each opinion word in the lexicon to the set of pre-extracted explicit aspects with a co-occurrence metric. The proposed model was evaluated on a collection of English product review datasets. The model does not require any labeled training data and it can be easily applied to other languages or other domains such as movie reviews. Experimental results show considerable improvements of our model over conventional techniques including unsupervised and supervised approaches. © 2013 Elsevier B.V. All rights reserved. Source


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. Source


Dehghani R.,Isfahan University of Technology
IET Circuits, Devices and Systems | Year: 2016

A divide-by-3 injection locked frequency divider is presented. The divider works based on a two-stage differential ring oscillator in which two quadrature signals are used as injection signals. The analytical relationship for the divider locking range is derived and the main factors impacting on this parameter are discussed. The circuit has been designed in a 0.18 μm CMOS technology with a supply voltage of 1.8 V. Post layout simulation on the divider including all layout wiring parasitic elements such as resistance, capacitance and inductance shows that the typical locking range of the divider is over 3 GHz from 1 to 4.2 GHz for -0.5 dBm injection signal level while its total power dissipation for 4.2 GHz input injection signal is 505 μW at the supply of 1.8 V. © 2016. The Institution of Engineering and Technology. Source


Hanifi A.,Isfahan University of Technology
Journal of materials science. Materials in medicine | Year: 2010

Gene therapy provides a unique approach to medicine as it can be adapted towards the treatment of both inherited and acquired diseases. Recently, calcium phosphate vectors as a new generation of the non viral gene delivery nano carriers have been studied because of their biocompatibility and DNA condensation and gene transfer ability. Substituting cations, like magnesium, affects physical and chemical properties of calcium phosphate nano particles. In this study, Mg(2+) substituted calcium phosphate nano particles have been prepared using the simple sol gel method. X-ray diffraction analysis, Fourier transform infra red spectroscopy, transmission electron microscopy, specific surface area analysis, zeta potential measurement and ion release evaluation were used for characterization of the samples. It was concluded that presence of Mg ions decrease particle size and crystallinity of the samples and increase positive surface charge as well as beta tricalcium phosphate fraction in chemical composition of calcium phosphate. These properties result in increasing the DNA condensation ability, specific surface area and dissolution rate of the samples which make them suitable particles for gene delivery application. Source


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. Source


Zadehgol A.,Isfahan University of Technology
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

In this work, minimal kinetic theories based on unconventional entropy functions, H∼lnf (Burg entropy) for 2D and H∼f1-2n (Tsallis entropy) for nD with n≥3, are studied. These entropy functions were originally derived by Boghosian et al. [Phys. Rev. E 68, 025103 (2003)1063-651X10.1103/PhysRevE.68.025103] as a basis for discrete-velocity and lattice Boltzmann models for incompressible fluid dynamics. The present paper extends the entropic models of Boghosian et al. and shows that the explicit form of the equilibrium distribution function (EDF) of their models, in the continuous-velocity limit, can be identified with the Poisson kernel of the Poisson integral formula. The conservation and Navier-Stokes equations are recovered at low Mach numbers, and it is shown that rest particles can be used to rectify the speed of sound of the extended models. Fourier series expansion of the EDF is used to evaluate the discretization errors of the model. It is shown that the expansion coefficients of the Fourier series coincide with the velocity moments of the model. Employing two-, three-, and four-dimensional (2D, 3D, and 4D) complex systems, the real velocity space is mapped into the hypercomplex spaces and it is shown that the velocity moments can be evaluated, using the Poisson integral formula, in the hypercomplex space. For the practical applications, a 3D projection of the 4D model is presented, and the existence of an H theorem for the discrete model is investigated. The theoretical results have been verified by simulating the following benchmark problems: (1) the Kelvin-Helmholtz instability of thin shear layers in a doubly periodic domain and (2) the 3D flow of incompressible fluid in a lid-driven cubic cavity. The present results are in agreement with the previous works, while they show better stability of the proposed kinetic model, as compared with the BGK type (with single relaxation time) lattice Boltzmann models. © 2015 American Physical Society. Source


Momeni M.M.,Isfahan University of Technology
Rare Metals | Year: 2016

The effect of chromium doping on the photovoltaic efficiency of dye-sensitized solar cells (DSSCs) with anodized TiO2 nanotubes followed by an annealing process was investigated. Cr-doped TiO2 nanotubes (CrTNs) with different amounts of chromium were obtained by anodizing of titanium foils in a single-step process using potassium chromate as the chromium source. Film features were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and ultraviolet–visible (UV–Vis) spectroscopy. It is clearly seen that highly ordered TiO2 nanotubes are formed in an anodizing solution free of potassium chromate, and with a gradual increase in the potassium chromate concentration, these nanotube structures change to nanoporous and compact films without porosity. The photovoltaic efficiencies of fabricated DSSCs were characterized by a solar cell measurement system via the photocurrent–voltage (I–V) curves. It is found that the photovoltaic efficiency of DSSCs with CrTNs1 sample is improved by more than three times compared to that of DSSCs with undoped TNs. The energy conversion efficiency increases from 1.05 % to 3.89 % by doping of chromium. © 2016 The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg Source


Goudarzi M.,University of Kashan | Bazarganipour M.,Isfahan University of Technology | Salavati-Niasari M.,University of Kashan
RSC Advances | Year: 2014

The synthesis and characterization of Co3O4 nanoparticles via solid state thermal decomposition of a binuclear cobalt(iii) complex, as a new precursor is reported. Solid state thermal decomposition of the complex at 450 °C for 3 h produces Co3O4 nanoparticles which are characterized by FT-IR spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). SEM and TEM images exhibit the quasi-spherical shape of the Co3O4 nanoparticles of between 20 and 30 nm. Moreover, adsorption of methylene orange dye on Co3O4 nanoparticles was investigated and the uptake% was determined to be >45% in 200 min. © 2014 the Partner Organisations. Source


Aghabarari B.,Iranian Materials and Energy Research Center | Dorostkar N.,Isfahan University of Technology
Journal of the Taiwan Institute of Chemical Engineers | Year: 2014

In this study, bentonite was modified with acidic ionic liquid (modified bentonite with ionic liquid 8B: MBIL8B) and characterized with XRD, BET, SEM and TGA analyses. The esterification of oleic acid with ethanol was studied over this modified bentonite and the effect of reaction temperature, type and amount of catalyst, molar ratio and reaction time was investigated. The results showed that the MBIL8B had higher catalytic activity than sulfuric acid and able to catalyze the esterification of oleic acid to its ethyl ester in 6.5. h with yield greater than 93%. Finally, we studied the catalytic activity of MBIL8B in the esterification of other fatty acids with different alcohols. © 2014 Taiwan Institute of Chemical Engineers. Source


Loran F.,Isfahan University of Technology
Classical and Quantum Gravity | Year: 2013

By applying the holographic renormalization method to the metric formalism of f(Ric) gravity in three dimensions, we obtain the Brown-York boundary stress tensor for backgrounds which asymptote to the locally AdS3 solution of Einstein gravity. The logarithmic divergence of the on-shell action can be subtracted by a non-covariant cut-off-independent term which exchanges the trace anomaly for a gravitational anomaly. We show that the central charge can be determined by means of Banados-Teitelboim-Zanelli holography or in terms of the Hawking effect of a Schwarzschild black hole placed on the boundary. © 2013 IOP Publishing Ltd. Source


Koofigar H.R.,University of Isfahan | Sheikholeslam F.,Isfahan University of Technology | Hosseinnia S.,Islamic Azad University at Najafabad
Chaos | Year: 2011

The synchronization problem for a general class of uncertain chaotic systems is addressed. The underlying systems may be perturbed by unknown time-varying parameters, unstructured uncertainties, and external disturbances. Meanwhile, the time-varying parameters and disturbances are neither required to be periodic nor to have known bounds. Assuming the disturbances are L2 signals, an adaptive control incorporated with H∞ control technique is employed to construct a robust adaptive synchronization algorithm. Then, removing such assumption, a novel adaptive-based method is developed to achieve the goal of synchronization. In order to demonstrate the effectiveness of the proposed algorithms, such methods are applied to solve the synchronization problem of uncertain chaotic Chua's circuits. © 2011 American Institute of Physics. Source


A key issue in designing an effective multilevel inverter is to generate high quality output waveform with low-order harmonics to meet grid codes. Selective harmonic mitigation (SHM) fulfills the grid code requirement and eliminates or reduces bulky and costly tuned filters. SHM becomes complex when the dc links of a cascaded H-bridge (CHB) inverter are varied over time (when PVs are used as dc links). This paper presents a new multi-objective selective harmonic mitigation formula for a CHB inverter connected to a photovoltaic system. This multi-objective formulation considers the supply voltage requirements of standard EN 50160 to choose optimal switching angles. To predict optimal switching angles for all possible input intervals, dc link voltages, and modulation index variations, a learning algorithm called the hierarchical multi-output support vector regression is proposed. Simulation results are presented that validate the advantages of the proposed structure. © 2013 IEEE. Source


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. Source


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. Source


Momeni M.M.,Isfahan University of Technology
Materials Research Innovations | Year: 2016

WO3-TiO2 nanotube films on pure titanium substrates were successfully fabricated by one-step electrochemical anodizing and copper deposited on these nanotubes by photo-Assisted deposition method. The morphology, structure and composition of synthesized films were characterized by SEM, XRD, EDX and UV-vis, respectively. Results showed that the films have the ordered nanotubes with average pore diameter of 70-100 nm and wall thickness of 20-25 nm. Diffuse reflectance spectra showed an increase in the visible absorption relative to bare WO3-TiO2 nanotubes. Photocatalytic activity of samples was evaluated by testing the solar water splitting. After irradiated under xenon light illumination for 360 min, the total amount of H2 evolved on the Cu/WO3-TiO2 sample was 55 mL/cm2, which is approximately 6.9 times higher than that on the bare WO3-TiO2 (8 mL/cm2). The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photocatalytic activity. © 2016 Taylor &Francis. Source


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. Source


Karimi-Ghartemani M.,Queens University | Khajehoddin S.A.,Sparq Systems | Jain P.K.,Queens University | Bakhshai A.,Queens 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. Source


Hoseinieh S.M.,Petroleum University of Technology of Iran | Ashrafizadeh F.,Isfahan University of Technology | Maddahi M.H.,Petroleum University of Technology of Iran
Journal of the Electrochemical Society | Year: 2010

Deactivation of a RuO2 - IrO2 - TiO02 /Ti oxide anode was investigated during an accelerated life test in 0.5 mol dm-3 NaCl by use of cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy/energy-dispersive X-ray analysis. The variations in double-layer capacitance, film resistance, and charge-transfer resistance during electrolysis were recorded at different potentials. A comprehensive deactivation mechanism of titanium anodes has been proposed by the growth of an insulating TiO2 layer at the coating-substrate interface due to the titanium substrate oxidation. The impedance interpretation of the deactivation mechanism in chloride solutions changes with an increase in potential due to an increase in oxygen evolution on the anode surface at higher potentials. © 2010 The Electrochemical Society. Source


The various embodiments herein provide a method and system for reducing Out of Band Radiation in Orthogonal Frequency Division Multiplexing (OFDM). The method includes transmitting a plurality of signals with a plurality of modulated symbols on each subcarrier. The method includes introducing a controlled amount of correlation among the consecutive modulated symbols across time. Further the method includes removing the controlled amount of correlation among the plurality of modulated symbols. The method also includes reducing an out of band radiation in OFDM. The system for reducing Out of Band Radiation in Orthogonal Frequency Division Multiplexing (OFDM) includes a transmitter to transmit one or more signals with a plurality of modulated symbols on each subcarrier. The system includes a transmitter with digital filters and a receiver. The receiver includes a Maximum Likelihood Sequence Detector (MLSD) to remove the controlled amount of correlation among the plurality of modulated symbols.


Mojiri M.,Isfahan University of Technology | Karimi-Ghartemani M.,Queens University | Bakhshai A.,Queens University
IEEE Transactions on Power Delivery | Year: 2010

A method for real-time detection and extraction of individual harmonic and interharmonic components in a power signal with potentially time-varying characteristics is presented. The proposed method, which is based on the concept of adaptive notch filter (ANF), adaptively decomposes the measured power signal into its constituting components independent of where their frequencies are located. The algorithm provides instantaneous values of the various estimated frequency components in addition to the values of their frequencies, amplitudes, and phase angles. The structure and mathematical formulation of the proposed technique, including guidelines for its parameter tuning, are presented and its performance is studied in a variety of scenarios where the power signal attributes, such as fundamental frequency and amplitude, undergo variations over time. This study confirms the desirable transient and steady-state performances of the proposed method. Compared with its recently proposed counterpart, the proposed method of this paper obviates the need for using a phase-locked loop (PLL), and hence, offers a more simplified structure which makes it more attractive from an implementation point of view. © 2010 IEEE. Source


News Article
Site: http://www.nanotech-now.com/

Abstract: Iranian researchers from Isfahan University of Technology produced a highly sensitive and accurate sensor which can measure a type of blood anti-coagulation drug. Story: The sensor was produced through a simple and cost-effective method and its application does not require advanced skills. Protamine is an important drug that is used as an anti-heparin agent to prevent blood coagulation during cardiovascular surgeries. Excess consumption of protamine causes undesirable effects, including sudden reduction in blood pressure, shortness of breath and feeling hot. Therefore, researchers have recently paid special attention to quick and exact methods to measure protamine. In this research, a simple but very sensitive sensor based on fluorescence spectroscopy was presented by using cadmium – telluride quantum dots to quickly measure protamine drug. Taking into account the fact that this sensor presents a simple and quick method for the measurement of protamine, it is able to prevent excess consumption of the drug without wasting time. Therefore, the required medical actions can be taken before it gets too late. In addition to its high speed, this sensor minimizes environmental pollution due to the use of very low concentration of quantum dots in the production of the sensor and the lack of the need for toxic and organic solvents. Researchers believe that the results of the research can be commercialized due to the advantages of the sensor, including quick and fast measurement, low production cost and the availability of the devices required for tracing signal (fluorescence spectroscopy device). Results of the research have been published in Biosensors and Bioelectronics, vol. 71, issue 1, 2015, pp. 243-248.


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. Source


Jamaati R.,Islamic Azad University at Amol | Naseri M.,Isfahan University of Technology | Toroghinejad M.R.,Isfahan University of Technology
Materials and Design | Year: 2014

In the present work, wear behavior of nanostructured aluminum and composite performed by accumulative roll bonding (ARB) process was investigated. The wear characteristics were studied by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). Also, transmission electron microscopy (TEM) and crystallographic texture investigations were performed. The results indicated that the ARB process led to the decrease in wear resistance of the monolithic and composite samples compared with as-received aluminum strip. The adhesive, abrasive and delaminating wear mechanisms occurred in the monolithic and composite samples simultaneously. At higher number of ARB cycles, delamination was the dominant wear mechanism. It was found that the surface damage of the composite was more extensive than that of the monolithic sample due to the occurrence of spalling mechanism. It was suggested that the intense Rotated Cube {0. 0. 1}〈1. 1. 0〉 texture component of composite helped to crack nucleation and propagation greatly. The role of delamination and especially, spalling in decreasing the wear resistance of composite was very important such that it eliminated the role of reinforcing particles and grain size on the wear resistance. © 2014 Elsevier Ltd. Source


Jamaati R.,Isfahan University of Technology | Jamaati R.,Islamic Azad University at Amol | Toroghinejad M.R.,Isfahan University of Technology | Edris H.,Isfahan University of Technology | Salmani M.R.,Islamic Azad University at Saveh
Materials and Design | Year: 2014

In the present work, a comparison of microparticles and nanoparticles effects on the microstructure and mechanical properties of steel-based composite and nanocomposite fabricated via accumulative roll bonding (ARB) process was studied. The microstructure of the fabricated composite and nanocomposite after fourth cycle of the ARB process exhibited an excellent distribution of SiC micro/nano particles in the IF steel matrix without any porosity. Unlike the nanocomposite, the particle breaking (cracking) was one of the most important phenomena that occurred during ARB process of composite. The findings revealed that with increasing the number of ARB cycles, the tensile strength of the ARB-processed composite and especially nanocomposite improved, but their elongation decreased at first step and then increased at second step. In addition, the ARB-processed composite and especially nanocomposite exhibited a higher hardness than the annealed IF steel so that the hardness values of the composite and nanocomposite were 4.18 and 4.44 times higher than that of the annealed IF steel, respectively. © 2013. Source


Jamaati R.,Isfahan University of Technology | Jamaati R.,Islamic Azad University at Amol | Toroghinejad M.R.,Isfahan University of Technology | Edris H.,Isfahan University of Technology
Materials and Design | Year: 2014

In the present work, the effect of SiC nanoparticles on the mechanical properties of steel-based nanocomposite produced by accumulative roll bonding (ARB) process was investigated. The microstructure of the fabricated nanocomposites after fourth ARB cycle was exhibited an excellent distribution of SiC nanoparticles in the interstitial free (IF) steel matrix without any porosity. The findings revealed that with increasing the number of ARB cycles, the tensile strength of the ARB-processed pure IF steel and also nanocomposites was improved, but their elongation was decreased at first step and then was increased at second step. The tensile strength of the ARB-processed pure IF steel and nanocomposites was 4.5 and 6. times higher than the same value was obtained for annealed IF steel, respectively. In addition, the ARB-processed pure IF steel and nanocomposite was exhibited a higher hardness than the annealed IF steel so that the hardness values of the pure IF steel and nanocomposite were 3.78 and 4.44. times higher than that of the annealed IF steel. © 2013 Elsevier Ltd. Source


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. Source


Jamaati R.,Isfahan University of Technology | Toroghinejad M.R.,Isfahan University of Technology | Dutkiewicz J.,Polish Academy of Sciences | Szpunar J.A.,University of Saskatchewan
Materials and Design | Year: 2012

In this study, the accumulative roll bonding (ARB) process was used for manufacturing nanostructured aluminum/15. vol.% alumina composites. Microstructural characterization by transmission electron microscopy (TEM) identified the severe shear deformation, however, the grain growth was restrained by particles of oxide film and recrystallization produced the nanograins with an average size <100. nm after the 13th cycle of composite strip. The findings also indicated that the presence of large particles and deformation structure in the vicinity of the particles made the particle stimulated nucleation (PSN) of recrystallization possible. The Williamson-Hall method was used to calculate the grain size from the X-ray diffraction (XRD) patterns, which were 150. nm for pure aluminum and 63. nm for aluminum/alumina composite after 13 cycles of the ARB process. The findings also revealed that after the first cycle, hardness rapidly increased, then dwindled, and finally reached saturation as the number of ARB cycles increased. © 2011 Elsevier Ltd. Source