Esfahan, Iran

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

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Aghajani A.,Isfahan University of Technology
Materials Performance | Year: 2017

A 56-in.-diameter gas pipeline was monitored using a magnetic flux leakage pig. Significant local corrosion close to a compressor station was diagnosed before the gas pipeline experienced a failure. A field study showed that cathodic protection (CP) potentials in the corroded area failed to satisfy established criteria for protection due to concentration cells and CP interference. Replacing the gas pipeline with a new coated pipeline resulted to effective CP potentials through adding local CP. The results suggest that local variations in soil resistivity can affect the CP potentials of a pipeline and sometimes cause local underprotection. Therefore, the type of soil layers located around and under the pipeline must be considered in CP design. Also, segmenting a pipeline that traverse soils with varying conditions offers the option of providing effective corrosion control with separate CP systems.

Shafizadeh M.,ACECR Institute of Higher Education | Rezai A.,Isfahan University of Technology
Journal of Computational Electronics | Year: 2017

The scaling of MOSFETs is an important and effective way for achieving high performance and low power consumption. One of the bottlenecks for scaling is the physical gate oxide thickness. This paper presents and evaluates a new method for scaling carbon nanotube field-effect transistors (CNTFETs) using (Formula presented.) as a new gate dielectric, which has excellent electrical properties. The proposed CNTFET is simulated using HSPICE. Some of the main digital and analog parameters such as current ratio, subthreshold swing (SS), transconductance, and intrinsic gain have been studied. The simulation results show that the proposed CNTFET outperforms present CNTFETs in terms of current ratio, transconductance, and intrinsic gain. © 2017 Springer Science+Business Media New York

Aboueian J.,Isfahan University of Technology | Sohankar A.,Isfahan University of Technology
Theoretical and Computational Fluid Dynamics | Year: 2017

The flow over two square cylinders in staggered arrangement is simulated numerically at a fixed Reynolds number ((Formula presented.)) for different gap spacing between cylinders from 0.1 to 6 times a cylinder side to understand the flow structures. The non-inclined square cylinders are located on a line with a staggered angle of (Formula presented.) to the oncoming velocity vector. All numerical simulations are carried out with a finite-volume code based on a collocated grid arrangement. The effects of vortex shedding on the various features of the flow field are numerically visualized using different flow contours such as (Formula presented.) criterion, vorticity, pressure and magnitudes of velocity to distinguish the distinctive flow patterns. By changing the gap spacing between cylinders, five different flow regimes are identified and classified as single body, periodic gap flow, aperiodic, modulated periodic and synchronized vortex shedding regimes. This study revealed that the observed multiple frequencies in global forces of the downstream cylinder in the modulated periodic regime are more properly associated with differences in vortex shedding frequencies of individual cylinders than individual shear layers reported in some previous works; particularly, both shear layers from the downstream cylinder often shed vortices at the same multiple frequencies. The maximum Strouhal number for the upstream cylinder is also identified at (Formula presented.) for aperiodic flow pattern. Furthermore, for most cases studied, the downstream cylinder experiences larger drag force than the upstream cylinder. © 2017 Springer-Verlag Berlin Heidelberg

Davari N.,Isfahan University of Technology | Gholami A.,Isfahan University of Technology
IEEE Sensors Journal | Year: 2017

In the conventional integrated navigation systems, such as direct Kalman filter, the statistical information of the process and measurement noises is considered constant. In real applications, due to the variation of vehicle dynamics, the environmental conditions and imperfect knowledge of the filter statistical information, the process and measurement covariance matrices are unknown and time dependent. To improve performance of the direct Kalman filter algorithm, this paper presents an asynchronous adaptive direct Kalman filter (AADKF) algorithm for underwater integrated navigation system. The designed navigation system is composed of a high-rate strapdown inertial navigation system along with low-rate auxiliary sensors with different sampling rates. The auxiliary sensors consist of a global positioning system (GPS), a Doppler velocity log (DVL), a depthmeter, and an inclinometer. Performance of the proposed algorithm is investigated using real measurements. The experimental results indicate the proposed AADKF algorithm outperforms asynchronous direct Kalman filter (ADKF) algorithm, i.e., the relative root mean square error (RMSE) of the estimated position is reduced by 61% on average. © 2016 IEEE.

Behfarnia K.,Isfahan University of Technology | Shirneshan A.,Isfahan University of Technology
Computers and Concrete | Year: 2017

Concrete shear walls are one of the major structural lateral resisting systems in buildings. In some cases, due to the change in the occupancy of the structure or functional requirements like architectural and even mechanical ones, openings need to be provided and installed in structural walls after their construction. Providing these openings may significantly influence the structural behavior of the constructed wall. This paper considers the results of a nonlinear finite element analysis of shear walls with opening strengthened by carbon fiber reinforced polymer (CFRP) strips with different configurations. Details of bond-slip constitutive model of link elements to simulate the connections of FRP strips to concrete surface is presented. The proposed model in this research has been validated using experimental results available in the literature. The results indicated that the proposed configuration of CFRP strips significantly improved the lateral resistance and deformation capacity of the shear walls with opening. Copyright © 2017 Techno-Press, Ltd.

Mallakpour S.,Isfahan University of Technology | Zadehnazari A.,Isfahan University of Technology
Bulletin of Materials Science | Year: 2017

Ascorbic acid has been covalently linked to multi-walled carbon nanotubes (MWCNTs). The structures of the functionalized MWCNTs were characterized with Fourier-transform infrared spectroscopy. Thermogravimetric analysis results also demonstrated the presence of organic portions of the functionalized MWCNTs. Polymer composites based on a nanostructured poly(amide-imide) (PAI) were fabricated by an ex situ technique with 5, 10 and 15% loading by weight. Composite films were made by the solvent casting method. The thermal stability of the composites increased with even a small amount of modified MWCNT added. Tensile tests were conducted and depicted an increase in the elastic modulus with increasing MWCNTs content. X-ray diffraction study of the composites also indicated that the composites incorporated MWCNTs in the polymer chain. © 2017 Indian Academy of Sciences.

Hosseini Balam N.,Isfahan University of Technology | Mostofinejad D.,Isfahan University of Technology | Eftekhar M.,Isfahan University of Technology
Construction and Building Materials | Year: 2017

This paper presents the results of an experimental investigation carried out to evaluate the influence of two types of bacteria, namely Sporosarcina pasteurii and Bacillus subtilis, with different cell concentrations (106, 107, 108−1) on the water absorption of four types of concrete aggregates. Surface deposition of calcium carbonate crystals was found to decrease water absorption by 20–30%, depending on the type of bacteria and aggregate porosity. The use of ureolytic gram-positive bacteria S. pasteurii resulted in a more pronounced decrease in the uptake of water by the aggregates. The reduced water absorption observed was possibly due to deposition on the bacteria cell walls in the pores. The results show that the aggregates retained their properties and yielded the same results after about 20 days, indicating that the deposits remained over this time period. The XRD and SEM analysis indicated the formation of calcite in bacterial aggregates. © 2017 Elsevier Ltd

Aghaeipour A.,Isfahan University of Technology | Madhkhan M.,Isfahan University of Technology
Construction and Building Materials | Year: 2017

Having recorded a profile of success in mass concrete applications such as in dam building, roller compacted concrete has recently stimulated a growing interest in road pavement construction as a novel application. The present study was designed to investigate the effects of ground granulated blast furnace slag (GGBFS) used in concrete mixtures on durability properties of roller compacted concrete pavements as water absorption, permeability and freeze-thaw cycles. For this purpose, eight principal concrete mixes were designed containing four blast furnace slag levels (0, 20, 40, and 60% relative to the weight of the cementitious materials) and two cementitious material levels (12 and 15% relative to the aggregate weight) at an optimum moisture content. Results showed that the moisture content required for the concrete to reach its maximum compaction increased with increasing slag content. Moreover, cracking and porosity declined with increasing slag content up to a certain level beyond which both took a rising trend. This was evidenced by the minimum and maximum levels of concrete cracks and porosity for slag contents of 40% and 60%, respectively, compared to the levels observed in plain concrete lacking GGBFS. Concrete permeability was also observed to decline with the experimental concrete mix designs containing 20 and 40% GGBFS but increased for a GGBFS content of 60%. Finally, increasing cementitious materials from 12 to 15% was observed to reduce concrete permeability. The highest destructive effect due to 150 and 300 freeze-thaw cycles was observed with mix designs having a GGBFS content of 40%; however, mix designs containing a GGBFS of 60% exhibited relatively improved resistance against the effects of freeze-thaw cycles. © 2017

Gholinezhad H.,Isfahan University of Technology | Zeinal Hamadani A.,Isfahan University of Technology
Reliability Engineering and System Safety | Year: 2017

This paper develops a new model for redundancy allocation problem. In this paper, like many recent papers, the choice of the redundancy strategy is considered as a decision variable. But, in our model each subsystem can exploit both active and cold-standby strategies simultaneously. Moreover, the model allows for component mixing such that components of different types may be used in each subsystem. The problem, therefore, boils down to determining the types of components, redundancy levels, and number of active and cold-standby units of each type for each subsystem to maximize system reliability by considering such constraints as available budget, weight, and space. Since RAP belongs to the NP-hard class of optimization problems, a genetic algorithm (GA) is developed for solving the problem. Finally, the performance of the proposed algorithm is evaluated by applying it to a well-known test problem from the literature with relatively satisfactory results. © 2017 Elsevier Ltd

Mallakpour S.,Isfahan University of Technology | Hatami M.,Isfahan University of Technology
European Polymer Journal | Year: 2017

Recently nanocomposites (NCs) based on layered double hydroxide (LDH) and condensation polymers have attracted a huge deal of attention; because these compounds offer a great and important potential to provide grander behaviors in contrast to uncombined materials. These materials demonstrate good properties such as great heat deflection temperature, great dimensional stability, cheap gas absorbency, enhance in thermal, flame retardancy, and mechanical properties. Such enhancements happen due to interfacial effects resulting from uniform and homogenous dispersion of great aspect ratio LDH nanofillers in condensation polymeric matrixes, and of their tunable behaviors of LDHs. This review provides a summary of condensation polymers with LDH incorporated NCs and characterization of these NCs by morphological, mechanical, thermal and barrier properties, flame retardancy, and reduced gas permeability in contrast to the neat polymeric matrix. So, at first, a summary of the basic structure and how to modification of LDH nanofillers will be presented, then, the potential applications of LDH nanofillers incorporation in condensation polymers matrix and the effects of them on the properties of NCs will be briefly discussed. © 2017 Elsevier Ltd

Kianfar A.H.,Isfahan University of Technology | Dostani M.,Isfahan University of Technology
Journal of Materials Science: Materials in Electronics | Year: 2017

Two novel tridentate N2O Schiff base ligands, H2L1 ((E)-3-((2-amino-5-nitrophenylimino)methyl)benzene-1,2-diol) and H2L2 ((E)-4-((2-amino-5-nitrophenylimino)methyl)benzene-1,3-diol) and metal complexes [ML(DMF)] (where M = Ni2+, Cu2+ and VO2+) were synthesized. All new materials were studied by spectroscopic methods. The Schiff base complexes were loaded over TiO2 nano-particles and calcined at 450 °C. The MOX/TiO2 structure and morphology were characterized by IR, UV, TEM, SEM and XRD techniques. The effect of the photocatalytic activity of MOX/TiO2 semiconductor nano-particles on the degradation of methylene blue was investigated via visible light in the aqueous solution. Based on the results, incorporation of metal Schiff base complexes was found to improve the activation of mixed oxide nano particles with visible light. © 2017 Springer Science+Business Media New York

Saadat M.,Isfahan University of Technology | Asghari K.,Isfahan University of Technology
Water Resources Management | Year: 2017

Stochastic Dynamic Programming (SDP) is widely used in reservoir operation problems. Besides its advantages, a few drawbacks have leaded many studies to improve its structure. Handling the infeasible conditions and curse of dimensionality are two major challenges in this method. The main goal of this paper is proposing a new method to avoid infeasible conditions and enhance the solution efficiency with new discretization procedure. For this purpose, an optimization module is incorporated into regular SDP structure, so that, near optimal values of state variables are determined based on the available constraints. The new method (RISDP) employs reliability concept to maximize the reservoir releases to satisfy the downstream demands. Applying the proposed technique improves the reservoir operating policies compared to regular SDP policies with the same assumptions of discretization. Simulation of reservoir operation in a real case study indicates about 15% improvement in objective function value and elimination of infeasible conditions by using RISDP operating policies. © 2017, Springer Science+Business Media Dordrecht.

Kangazian J.,Isfahan University of Technology | Shamanian M.,Isfahan University of Technology
Journal of Manufacturing Processes | Year: 2017

This research work articulated a comparative study on Incoloy 825 Ni-based alloy and SAF 2507 super duplex stainless steel dissimilar joints. Welding was accomplished by ER2594 and ERNiFeCr-1 filler wires, pulsed current (PCGTAW) and continuous current gas tungsten arc welding (CCGTAW) techniques. Characterizations were conducted by optical microscopy, scanning electron microscopy equipped with an energy dispersive spectroscopy and X-ray diffraction. In order to investigate the evolution of mechanical properties of the weld joints’ micro-hardness, impact and tensile tests were employed. The results showed that Ti-rich phase was formed in weld zones employing ERNiFeCr-1 filler metal. On the other hand, Cr-rich phase was characterized in the weld zone of ER2594 sample employing CCGTAW. The welds of PCGTAW method displayed finer microstructure, lower ferrite contents and lack of Cr-rich phase formation. In tensile tests, fracture occurred at weaker base metals (Incoloy 825) in all cases. The use of ER2594 caused higher hardness and lower toughness than ERNiFeCr-1 filler metal. Based upon comparative investigations, ERNiFeCr-1 filler metal and PCGTAW technique were recommended to improve dissimilar joint efficiency. © 2017 The Society of Manufacturing Engineers

Imani M.,Isfahan University of Technology | Enayati M.H.,Isfahan University of Technology
Journal of Alloys and Compounds | Year: 2017

In recent years, amorphous alloys have received a considerable attraction because of their physical, mechanical and magnetic properties. Fe-Co alloy system has good soft magnetic properties (high magnetic saturation and high Curie point) which makes it suitable for high temperature magnetic applications. In this paper, the effect of different elements on glass forming ability (GFA) of Fe-Co system was evaluated based on Meidema semi-empirical model and the results were compared to mechanical alloying (MA) experiments. Si, B and P seem to be good elements to be added to Fe-Co alloys with respect to thermodynamics and kinetics requirements. Calculations based on extended Miedema model showed that enthalpy and Gibbs free energy changes for solid state amorphisation of Fe70Co7Si8B8P7 were −179 (kJ mol−1) and −181 (kJ mol−1) respectively, but MA experiments in three different routes did not lead to amorphisation in this system. Also comparison between MA and melt spinning (MS) techniques showed GFA in both techniques are completely different. © 2017 Elsevier B.V.

Gholami E.,Isfahan University of Technology | Lashkami Z.M.,University of Zanjan
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2017

As an unusual type of anomalous diffusion behavior, namely (transient) superballistic transport, has been experimentally observed recently, but it is not yet well understood. In this paper, we investigate the white noise effect (in the Markov approximation) on quantum diffusion in one-dimensional tight-binding models with a periodic, disordered, and quasiperiodic region of size L attached to two perfect lattices at both ends in which the wave packet is initially located at the center of the sublattice. We find that in a completely localized system, inducing noise could delocalize the system to a desirable diffusion phase. This controllable system may be used to investigate the interplay of disorder and white noise, as well as to explore an exotic quantum phase. © 2017 American Physical Society.

Kazemi A.,Isfahan University of Technology | Mehrabani-Zeinabad A.,Isfahan University of Technology | Beheshti M.,University of Isfahan
Energy | Year: 2017

Application of vapor recompression systems can result in enhanced energy efficiency and reduced energy requirements of distillation systems. In vapor recompression systems, temperature and dew point temperature of the top product of the column are increased through compression. By transferring heat from top to bottoms product, required boil up and reflux streams for the column are provided. In this paper, a new system is proposed for efficient stripping of sour water based on vapor recompression. Ammonia and H2S are the contaminants of sour water. Initially, based on a certain specifications of products, a sour water stripping system is implemented. A novel processing system is then developed and simulated to reduce utility requirements. The two processing systems are economically evaluated by Aspen Economic Evaluation software. There are 89.0% and 83.7% reduction of hot and cold utility requirements for the proposed system in comparison to the base processing system. However, the new processing system requires new equipment such as compressor and corresponding mechanical work that increases its capital and operating costs in comparison to the base case. However, the results indicate that the proposed system results in reduction of 11.4% of total annual costs and 14.9% of operating costs. © 2017 Elsevier Ltd

Zargar T.,Isfahan University of Technology | Kermanpur A.,Isfahan University of Technology
Ceramics International | Year: 2017

Effects of hydrothermal temperature and time on physical, magnetic and thermal properties of Zn-substituted magnetite nanoparticles (Zn0.3Fe2.7O4) were assessed. The magnetic nanoparticles were synthesized via citric acid-assisted hydrothermal reduction route at temperatures of 150, 175 and 200C for duration of 10, 15 and 20h. The nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and specific loss power (SLP) measurements. The results showed that temperature and time of the hydrothermal process both had significant effects on nanoparticles composition and properties. It was observed that at 150C, heat generation was insufficient to produce activation energy required for nucleation of Zn0.3Fe2.7O4 spinel nanoparticles, even after a long time. At 175C, although temperature was low, but the suitable condition for nucleation of nanoparticles was made and spinel nanoparticles with the size of about 13nm were formed after 15h. Nonetheless, since crystallinity and SLP of the nanoparticles was low, they showed weak performance for magnetic hyperthermia. At 200C, the required activation energy was provided for nanoparticles nucleation; however, the spinel was oxidized to hematite, resulting in a decrease in thermal and magnetic properties. In overall, the nanoparticles synthesized at 200C for 15h possessed the best characteristics of reasonable purity, saturation magnetization of about 35.9emu/g and SLP of 18.7W/g. © 2017.

Safari A.,Isfahan University of Technology | Karimi K.,Isfahan University of Technology | Shafiei M.,University of Isfahan
Bioresource Technology | Year: 2017

Dilute alkali pretreatment was performed on softwood pine to maximize ethanol and biogas production via a biorefinery approach. Alkali pretreatments were performed with 0–2% w/v NaOH at 100–180 °C for 1–5 h. The liquid fraction of the pretreated substrates was subjected to anaerobic digestion. The solid fraction of the pretreatment was used for separate enzymatic hydrolysis and fermentation. High ethanol yields of 76.9‒78.0% were achieved by pretreatment with 2% (w/v) NaOH at 180 °C. The highest biogas yield of 244 mL/g volatile solid (at 25 °C, 1 bar) was achieved by the pretreatment with 1% (w/v) NaOH at 180 °C. The highest gasoline equivalent (sum of ethanol and methane) of 197 L per ton of pinewood and the lowest ethanol manufacturing cost of 0.75 €/L was obtained after pretreatment with 1% NaOH at 180 °C for 5 h. The manufacturing cost of ethanol from untreated wood was 4.12 €/L. © 2017 Elsevier Ltd

Noormohammadi N.,Isfahan University of Technology | Boroomand B.,Isfahan University of Technology
Computers and Mathematics with Applications | Year: 2017

In this paper a novel method is presented to construct singular basis functions for solving harmonic and bi-harmonic problems with weak singularities. Such bases are found without any knowledge of the singularity order. The singular bases are constructed by choosing a series as a tensor product of Chebyshev polynomials and trigonometrical functions, in radial and angular directions respectively, and applying weak form of the governing equation. With such features, the singular bases are categorized as the equilibrated basis functions. The constructed singular functions can be utilized as a complementary part to the smooth part of the approximation in the solution of problems with singularities. To demonstrate the efficiency of employing such singular bases, they are used in a boundary node method. Through the solution of some examples, selected from the well-known literature, the capability of the method is shown. It will be demonstrated that the main function and its derivatives are excellently approximated at very close neighborhood of the singular point. The method may especially be found useful for those who research on the eXtended Finite Element Method or similar ideas. © 2017 Elsevier Ltd

Jafari R.,Isfahan University of Technology | Hasheminasab S.,Isfahan University of Technology
Environmental Monitoring and Assessment | Year: 2017

This study aimed to analyze the impact of Zayandehrood Dam on desertification using the spatio-temporal dynamics of land use/land cover (LULC) and land surface temperature (LST) in an arid environment in central Iran from 1987 to 2014. The LULC and LST images were calculated from Landsat TM, ETM+, and OLI data, and their accuracies were assessed against reference data using error matrix and linear regression analysis. Results showed that salty and bare lands increased up to 57,302 ha, while agricultural lands declined substantially (28,275.58 ha) in the region. The changes in LULC classes resulted in dramatic variations in LST values. The average temperature showed a 5.03 °C increase, and the minimum temperature increased by 5.66 °C. LST had an increasing trend in bare lands (8.74 °C), poor rangelands (6.8 °C), agricultural lands (9.46 °C), salty lands (9.6 °C), and residential areas (3.18 °C) in this 27-year period. Rainfall and temperature trend analysis revealed that the main cause of these extreme changes in LULC and LST was largely attributed to the drying up of Zayandehrood River due to dam construction and allocating water mainly for industrial sectors. Results indicate that in addition to LULC changes, the spatio-temporal variations of LST can be used as an effective index in desertification assessment and monitoring in arid environments. © 2017, Springer International Publishing Switzerland.

Kabiri-Samani A.,Isfahan University of Technology | Naderi S.,Isfahan University of Technology
Proceedings of the Institution of Civil Engineers: Water Management | Year: 2017

In some cases, the flow head loss is not the main concern of design engineers, who instead prefer to exclude the hydraulic jump from super-to subcritical flow due to unfavourable flow conditions. The present study investigates the flow field and hydrodynamic aspects of the transitional region from super-to subcritical flow without a hydraulic jump. It is found that inside the transitional region the velocity and pressure profiles deviate slightly from uniform flow velocity and hydrostatic pressure. According to evaluation of the velocity measurements in conjunction with the continuity equation, the characteristics of the transitional region are determined. Furthermore, Reynolds stresses are analysed and the mechanisms of transition from super-to subcritical flow without a jump are demonstrated qualitatively. Results relating to the profiles of shear stresses, vorticity and the total angular momentum along the transition are developed. Results indicate that the first short part of the flow field downstream of the transition structure floats on the incoming high-speed fluid where the shear stress is maximal. It is observed that, downstream of the structure, both the shear stresses and the vorticity are maximal along the streamlines. Inside the shear layer, the vorticity spreads upward by diffusive mechanisms. © ICE Publishing: All rights reserved.

Motahar S.,Islamic Azad University at Shahreza | Alemrajabi A.A.,Isfahan University of Technology | Khodabandeh R.,KTH Royal Institute of Technology
Energy Conversion and Management | Year: 2017

The solidification process of n-octadecane as a phase change material (PCM) with dispersed titanium dioxide (TiO2) nanoparticles was experimentally studied. Experiments were performed in a rectangular enclosure cooled from one vertical side corresponding to the solid Stefan numbers in the range 0.17–0.239. The Rayleigh numbers at the initial of experiment were in the range 0.92–18.3 × 106. The rheological behavior of liquid PCM/TiO2 samples at higher concentrations tended to Bingham fluids, thus the solidification experiments were conducted for Bingham numbers in the range 0–2.17. The solidification process was characterized by visualizing the progression of solid-liquid interface as well as recording the temperature distribution inside the enclosure. Experimental results showed that heat conduction was the dominant mode of heat transfer during the solidification. Dispersing TiO2 nanoparticles led to enhance in thermal conductance and consequently the increase in solidified volume. An increase of 7%, 9% and 18% in solidified volume fraction was observed at the end of solidification for the mass fractions of 1 wt.%, 2 wt.% and 4 wt.%, respectively. A universal correlation was proposed to predict the solidified volume fraction as a function of Fourier number, Rayleigh number, solid Stefan number, Bingham number and mass fraction of nanoparticles with an error below 11%. © 2017 Elsevier Ltd

FUREDI Z.,Alfred Renyi Institute of Mathematics | MALEKI Z.,Isfahan University of Technology
Combinatorics Probability and Computing | Year: 2017

We give an asymptotic formula for the minimum number of edges contained in triangles among graphs with n vertices and e edges. Our main tool is a generalization of Zykov's symmetrization method that can be applied to several graphs simultaneously. Copyright © Cambridge University Press 2017

Givchi A.,Isfahan University of Technology | Palhang M.,Isfahan University of Technology
Soft Computing | Year: 2017

In this paper, we investigate the possibility of covariate shift adaptation in off-policy temporal difference learning for the class of fast mixing Markov chains. Off-policy evaluation algorithms in reinforcement learning such as off-policy least squares temporal difference (LSTD) deal with the problem of evaluating a target policy different from the sampling (or behavior) policy. Off-policy LSTD may result in poor quality of solution due to the shift among stationary distributions of the chains induced by following the target and behavior policies. Previous works—least squares temporal difference–distribution optimization (LSTD-DO) and the recently proposed emphatic TD—each tackles this problem by mapping distribution of states collected following the behavior policy (i.e. off-policy samples) to a new different distribution with better LSTD solution. In this paper, we consider off-policy LSTD in the class of target Markov chains with fast mixing time. For this class of problems, we propose adapting the distribution of off-policy state samples to the distribution of state samples after transition model adaptation, using a regularized covariate shift adaptation algorithm called least squares importance fitting. Empirical evaluations of our proposed approach on two classes of fast mixing chains show promising results in comparison with LSTD-DO and unadapted off-policy LSTD as the number of samples increases. © 2017 Springer-Verlag Berlin Heidelberg

Gharakhlou A.R.,Isfahan University of Technology | Sarvi M.N.,Isfahan University of Technology
Materials Research Express | Year: 2017

In this study, a surfactant assisted hydrometallurgical procedure was proposed from preparation of mesoporous nanoparticles of titanium dioxide (TiO2) from ilmenite concentrate. Initially, Fe was removed from ilmenite concentrate using HCl and then the titanium was dissolved from the remaining solid in an alkaline condition of NH3 or NaOH in assistance of H2O2 as oxidizing agent in order to prepare the titanium solution (Ti-sol). Afterwards, the prepared Ti-sol was used as titanium source from preparation of a mesoporous nanoparticles of TiO2 in assistance of hexadecyltrimethyl ammonium bromide (HDTMA-Br) as structure directing agent. Different methods were used to characterize the mesoporous nanoparticles of TiO2 structures such as XRD, SEM, and BET. The results showed that the HDTMA helps the formation of slit-shaped mesopores in the range of 1.5 nm when the synthesis was carried out at room temperature despite the media which Ti-sol was prepared, NH3 or NaOH. When a hydrothermal treatment was added to the synthesis process similar mesoporous structure was formed when the Ti-sol was prepared in NH3 with nitrogen sorption hysteresis of H3 type. However, when the NaOH prepared Ti-sol was used the nitrogen sorption hysteresis loop changed to H4 type showing existence of large mesopores (12 nm) in addition to smaller mesopores (2-5 nm). The HRTEM results showed mesoporous structure with nano-rod like particles with particle size around 30-60 nm. © 2017 IOP Publishing Ltd.

Ebrahimi J.,Isfahan University of Technology | Karshenas H.R.,Isfahan University of Technology
IEEE Transactions on Industrial Electronics | Year: 2017

This paper presents a new multicell topology based on flying capacitor (FC) structure suitable for multilevel converters. The proposed topology employs the concept of phase-shifted carrier pulse width modulation (PWM) with modified modulating signals to generate appropriate PWM signals. The modulation strategy along with all possible switching states are explained. The implementation of the proposed PWM technique is shown by the help of illustrating waveforms. To show the advantages of the proposed structure, different performance criteria are compared with other FC multicell (FCM) structures. Simulation results are used to further evaluate the potential merits of the proposed topology. It is shown that the proposed structure is superior to other FCM-based structures from different standpoints. Specifically, it reduces the number of high-frequency switches, the number of FCs, and at the same time improves the quality of output voltage. A laboratory-type experimental setup is used to validate the modulation strategy and other theoretical findings. © 2016 IEEE.

Hajipour A.R.,University of Wisconsin - Medical School | Tavangar-Rizi Z.,Isfahan University of Technology
Applied Organometallic Chemistry | Year: 2017

The preparation of an efficient heterogeneous catalyst system based on the immobilization of palladium nanoparticles on a magnetic nanoparticle core (ImmPd(0)-MNPs) is described. The new catalytic system was characterized using transmission and scanning electron microscopies, X-ray diffraction, energy-dispersive X-ray and Fourier transform infrared spectroscopies, thermogravimetric analysis, vibrating sample magnetometry and inductively coupled plasma analysis. We have demonstrated that ImmPd(0)-MNPs is an efficient and reusable catalyst for the Suzuki-Miyaura and Sonogashira coupling reactions of various types of aryl halides in water as a green and environmentally acceptable solvent. Moreover, the reactions were carried out efficiently at room temperature. The catalyst was easily separated using an external magnet from the reaction mixture and recycled ten times without significant loss of activity. © 2017 John Wiley & Sons, Ltd.

Bahadormanesh N.,Isfahan University of Technology | Salimpour M.R.,Isfahan University of Technology
Applied Thermal Engineering | Year: 2017

This study documents geometrical optimization of inserts with high-emissivity applied for cooling a disk-shaped body with heat generation based on constructal theory. The high-emissivity inserts used for cooling purposes are located in radial direction in three structures: radial structure, radial structure with one level of discontinued pairing and radial structure with two levels of discontinued pairing. An analytical method is proposed for calculating the maximum temperature of the disk which is verified by the numerical results of a commercial program. The aim of design and optimization is obtaining the best configuration so that thermal resistance is minimized. The degrees of freedom are the radius of pairing the aspect of inserts' thickness. Results show that the percentage of area which is allocated to high-emissivity inserts has the most significant effect on thermal resistant. Secondly, the factor that affects the maximum temperature of the disk is number of inserts in center of the disk. In other word, increasing the high-emissivity area and number of inserts lead to reduction of the thermal resistance. Moreover, by evaluating the results, it is apprehended that by adding pairing to the structure even in same number of inserts the thermal resistance reduced significantly. © 2016 Elsevier B.V. All rights reserved.

Mohammadifard H.,Isfahan University of Technology | Amiri M.C.,Isfahan University of Technology
Chemical Engineering Communications | Year: 2017

Removal of heavy metals from water and wastewaters has recently gained a great deal of attention due to their serious environmental problems. In this study, novel synthesized calcium carbonate nanoparticles, prepared in a colloidal gas aphron (CGA) system, were used as adsorbents for the removal of Cu2+ ions from aqueous solutions under different conditions. A developed pseudo-second-order (PSO) model well described the adsorption kinetics of the process. Langmuir and Freundlich adsorption isotherms have been examined and the maximum adsorption capacity from the Langmuir isotherm equation was found to be 666.67 mg Cu/g adsorbent. The effects of temperature, Cu2+ initial concentration, and CaCO3 dosage on the removal capacity were also investigated using the three-level Box–Behnken experimental design method. The response surface modeling results demonstrated that under certain experimental conditions (i.e., T = 26°C, [Cu2+] = 200 mg/L, and [CaCO3] = 0.5 g/L), maximum removal capacity value (393.52 mg/g) was achieved. © 2017, Copyright © Taylor & Francis Group, LLC.

Aghili S.J.,Islamic Azad University at Najafabad | Hajian-Hoseinabadi H.,Isfahan University of Technology
International Journal of Electrical Power and Energy Systems | Year: 2017

This paper focuses on material that is required for the practical application of fuzzy reliability; impacts of repair and data uncertainty. For this purpose, a holistic solution is presented to measure and manage the degree of uncertainty in the reliability indices of repairable systems. First, a flexible form of Markov Processes (MPs) namely Equivalent Transition Rate (ETR) is introduced in order to obtain an analytical formalism. Second, we delve deeply into the issues of fuzzy arithmetic by providing an intuitive, methodic and computational discussion of feasible approaches; Standard Fuzzy Arithmetic (SFA), Intermediate Variables (IMVs) and Taylor Series (TS). Specific emphasis is then placed upon Fuzzy Transformation Method (FTM). Third, we evaluate the performance of proposed techniques in case of a reliability problem involving fuzzy complexity. Consequently, the reader is given useful insights into the nature of fuzzy computations and practical impediments when measuring uncertain data. Given materials and methods, current paper provides a broad perspective by evaluating the reliability characteristics of a repairable Substation Automation System (SAS) that is one of the fundamental elements in Smart Grids (SGs). In this regard, quantitative results and diagrammatic outputs are supported by a detailed analysis under different assumptions. Our findings demonstrate that fuzzy outputs are computationally tractable and properly estimated. Besides, this investigation shows how the objective SAS can respond to the variations in reliability data. The framework proposed here encourages the continuation of the work towards more applications in electric power components and systems. As far as we know, there are no studies on these techniques, results and remarks. © 2016 Elsevier Ltd

Amiri-Rad A.,Isfahan University of Technology | Mashayekhi M.,Isfahan University of Technology | van der Meer F.P.,Technical University of Delft
Composite Structures | Year: 2017

This paper deals with high cycle fatigue delamination in composite materials. The cohesive zone approach along with the level set method is used to simulate fatigue-driven delamination growth. The cohesive zone method is used for calculation of the energy release rate at the crack front because of its superiority over the virtual crack closure technique (VCCT) for bi-material interfaces and non self-similar crack growth. Evolution of the crack front in 3D during fatigue growth is handled with the level set method. The damage variable in the cohesive zone formulation is changed according to the updated level set field. Benchmarks are used to evaluate the performance of the proposed approach in simulation of 3D delamination growth under fatigue loading. © 2016 Elsevier Ltd

In this work, the adsorption of the adenine (AD) and cytosine (CY) on the Au(111) nano surface (AD@Au and CY@Au) have been examined in the framework of combined quantum mechanics/molecular mechanics (QM/MM) methodology using two-layer ONIOM method and different density functional theory (DFT) functionals in the absence of periodic boundary conditions (PBC). It was found by selecting an appropriate size for the Au surface, the results obtained using QM/MM method were in good agreement with those obtained via the periodic DFT calculations with the same functional. The calculated adsorption energies (Ead) using M06-2X and M06-L functional were in good agreement with those, recently, obtained using periodic DFT calculations considering PBC and employing van der Waals (vdW) DFT functionals. The correlation diagram between the molecular orbitals of isolated deformed AD (AD-D) and CY (CY-D) and their molecular orbitals in AD@Au and CY@Au systems have also been investigated in this work. © 2017 Elsevier B.V.

Madani S.R.,Isfahan University of Technology | Rasti-Barzoki M.,Isfahan University of Technology
Computers and Industrial Engineering | Year: 2017

Despite the considerable influence of the governmental regulations on the green supply chain, in the most of the studies in the literature of green supply chain, almost the role of the government and interactions between the government and supply chains members’ decisions are disregarded. In this study, a competitive mathematical model of government as the leader and two competitive green and non-green supply chains as the followers is developed and for the first time in this paper, pricing policies, greening strategies and governance tariffs determining in supply chains competition under government financial intervals are discussed. In the presented framework, the government seeks social benefits and determines subsidy and tax rates for green and non-green products respectively. The sale prices of products and the green degree of the green product are supply chains’ decision variables. In centralized and decentralized models, the optimal values of decision variables are gained and some important sensitivity analyses of governance decisions are done. In the governmental decisions area, it is observed that the impact of raising subsidy rate is significantly more than tax rate and it leads to increase in profits of government and supply chains and sustainability of products. Also among the competition of supply chains, cooperating between members makes more profit for them and leads to produce more eco-friendly products. © 2017 Elsevier Ltd

Mallakpour S.,Isfahan University of Technology | Sadeghzadeh R.,Isfahan University of Technology
Polymers for Advanced Technologies | Year: 2017

The present work describes preparation of modified alumina with biocompatible, water soluble, and treating agents such as citric acid and ascorbic acid. Also, the influence of the modified nanoparticles (NPs) into the blend of poly(vinyl alcohol)@poly(vinyl pyrrolidone) (50/50) matrix was studied. At first, citric acid and ascorbic acid as environmental friendly agents were grafted on the surface of Al2O3 NPs. Then, nanocomposites (NCs) with different amounts of modified Al2O3 NPs were prepared via a simple ultrasonic method. The characterizations of the molecular structure of the NCs specified that chemical and physical interactions happened between inorganic and organic counterparts. The mutual effect of modified NPs into the polymer matrix was investigated on the structural, interfacial interaction, thermal stability, and optical properties. The results from morphological characterization confirmed changes in morphology of poly(vinyl alcohol) and poly(vinyl pyrrolidone) after loading NPs. Uniform dispersion of modified spherical Al2O3 NPs powders into the matrix of 50/50 polymers was detected by field emission scanning electron microscopy and energy-dispersive X-ray. Adding M-NPs into the polymer matrix expressively improved the thermal stability of NCs. Peaks in ultraviolet-visible spectra were shifted to the higher absorption. © 2017 John Wiley & Sons, Ltd.

Enshaee A.,Isfahan University of Technology | Enshaee P.,Payame Noor University
Journal of Energy Engineering | Year: 2017

In a deregulated electric power system, it is important to distribute transmission losses between market participants fairly. This paper presents an effective method for active loss allocation by tracing power flow. In this method, after obtaining the alternating current (AC) load flow results of the system, it is first converted to a system in which the power flow is constant along each branch. A new matrix (i.e., power adjacency matrix) is then constructed for the system. The matrix is decoupled, and matrix operations are carried out using the submatrices to derive three other matrices. The contributions of the generators and loads of the main system to active losses of its branches and the shares of the generators in active power consumption of the loads are specified using these matrices. The proposed method is implemented on a four-bus system and several standard test systems. The results show that the method can be applied to any transmission system, and the loss allocation results are preferable to that of previous methods. © 2016 American Society of Civil Engineers.

Dehdashti-Jahromi M.,Isfahan University of Technology | Farrokhpour H.,Isfahan University of Technology
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2017

Ionization and excitation energies, IR and Raman spectra of sulfur hexafluoride (SF6), located inside helium (He) nanoclusters with different sizes (SF6@Hen; n = 20, 40, 60), were calculated. The effect of the cluster size on the spectroscopic properties of the SF6 was investigated and found that the Hen-SF6 interaction in the He clusters with large number of atoms is small so that the ionization and absorption energies of SF6 are not affected while for small He nanoclusters the Hen-SF6 interaction is more important. The effect of Hen-SF6 interaction and deformation of the fragments on the photoelectron and absorption spectra of SF6@Hen were separated theoretically and discussed in details. It was deduced that the effect of the cluster size on the IR and Raman vibrational frequencies of the SF6 is negligible for the cluster size range considered in this work. Density functional theory (DFT) employing M06-2X functional and 6-31 + G(df) basis set were used for optimizing the structures of SF6@Hen. Symmetry adapted cluster-configuration interaction (SAC-CI) methodology, with the same basis set, were used to calculate the ionization and excitation energies of the SF6@Hen structures. Using the calculated ionization and absorption energies and their intensities, the photoelectron and absorption spectra of the considered SF6@Hen structures were simulated and compared with the experiment. © 2016 Elsevier B.V.

Mallakpour S.,Isfahan University of Technology | Nezamzadeh Ezhieh A.,Isfahan University of Technology
Carbohydrate Polymers | Year: 2017

The attempt of this study was to modify chitosan/poly(vinyl alcohol) (CS/PVA) matrix properties using Starch/Multi-Walled Carbon Nanotube (MWCNT)-Valine (SMV) nanocomposite (NC) as a new filler. To prevent aggregation and obtain homogeneous dispersion of MWCNT into the matrix, at first the surface of MWCNTs was covalently modified by Valine as a natural amino acid. Then, modified MWCNT was incorporated into the starch matrix for the preparation of SMV NC. In the second step, different concentrations of prepared SMV NCs (30, 50 and 70 wt.%) were embedded to the CS-PVA matrix by ultrasonication technique for the fabrication of CS-PVA/SMV NC films. The effect of SMV NC on the properties of CS-PVA was studied by different techniques. Thermogravimetric analysis indicated that the thermal stability of the CS-PVA was enhanced after incorporation with nanofillers. The results indicated that prepared NCs were promising adsorbents for the removal of Cd(II) ions from the aqueous solution. © 2017 Elsevier Ltd

Zhiani M.,Isfahan University of Technology | Chitsazzadeh F.,Isfahan University of Technology
Electrocatalysis | Year: 2017

A new electrochemical method for gram quantitative amount preparation of Li-doped graphene nanosheets was presented based on the one-pot cathodic exfoliation of a graphite electrode in an organic environment. Structural characterizations of synthesized graphene by FE-SEM and AFM indicate that graphene nanosheets have thickness lower than 4 nm, with a typical worm-like shape. Li-doped graphene nanoparticles show a superior electrocatalytic activity toward oxygen reduction reaction (ORR) without using any novel metals and losing stability during 3000 cycles. With a modification of the graphite configuration, the process can be used in a continuous manner, presenting a potentially scalable method for high-yield synthesis of few-layer graphene. [Figure not available: see fulltext.] © 2017, Springer Science+Business Media New York.

Spanani S.,Isfahan University of Technology | Majidi M.M.,Isfahan University of Technology
Plant Breeding | Year: 2017

Inbreeding depression is the reduction in the fitness of inbred offspring relative to progeny from unrelated parents. In orchardgrass (Dactylis glomerata L.), limited efforts have been made to evaluate the effects of deliberate selfing on agro-morphological traits and to estimate the genetic variation of traits. Twenty-five genotypes of orchardgrass, along with 25 S1 (full-sibs) and 25 families of half-sibs, were created in 2012 and used to assess the consequences of the first generation of inbreeding and outcrossing for offspring fitness and to estimate heritabilities, genetic parameters and correlations of agro-morphological traits during the period of 2013–2014 in the field. Different levels of inbreeding depression were observed for the traits, with higher values for plant height, days to inflorescence emergence and dry matter yield. The degree of inbreeding or outbreeding effects varied among the studied genotypes. This facilitates the development of inbred lines for further studies. The results showed that some of the studied genotypes were self-fertile, thereby indicating the possibility of developing inbred lines from these genotypes. Heritabilities ranged from 0.10 for the number of stems per plant to 0.64 for spread among the studied populations. Spread had high heritability as well as high correlation with forage yield, thereby indicating that this trait could be used to improve forage yield indirectly. © 2017 Blackwell Verlag GmbH

Marzban H.R.,Isfahan University of Technology
International Journal of Control | Year: 2017

In this paper, we are concerned with the parameter identification of linear time-invariant systems containing multiple delays. The approach is based upon a hybrid of block-pulse functions and Legendre's polynomials. The convergence of the proposed procedure is established and an upper error bound with respect to the L2-norm associated with the hybrid functions is derived. The problem under consideration is first transformed into a system of algebraic equations. The least squares technique is then employed for identification of the desired parameters. Several multi-delay systems of varying complexity are investigated to evaluate the performance and capability of the proposed approximation method. It is shown that the proposed approach is also applicable to a class of nonlinear multi-delay systems. It is demonstrated that the suggested procedure provides accurate results for the desired parameters. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Dinari M.,Isfahan University of Technology | Haghighi A.,Isfahan University of Technology
Polymers for Advanced Technologies | Year: 2017

s-Triazine containing dicarboxylic acid was synthesized. Then, it was reacted with 1,3-phenylenediamine in molten tetrabutylammonium bromide to formed soluble aromatic polyamide with good yield and moderate inherent viscosity of 0.35 dL g-1. The solubility and flexibility of polyamides are low. So, we used ether group such as di(4-aminephenyl) ether in building polyamide. The structure of monomer and polymer was confirmed by Fourier transform infrared spectroscopy, elemental analysis, and proton nuclear magnetic resonance techniques. Thermogravimetric analysis was used to evaluate the thermal properties of synthesized polyamide, and their results show that this polymer had a good thermal stability. The surface morphology of s-triazine containing polyamide was studied by field emission-scanning electron microscopy and transmission electron microscopy, and the results show that it has a porous morphology and moderate Brunauer-Emmett-Teller specific surface (367 m2 g-1). It was further investigated for Pb (II) and Cr(VI) ion removal by optimizing the parameters including pH and contact time. The maximum uptakes of Pb(II) and Cr(VI) at pH 5.0 and pH 4.0 are 57% and 76%, respectively. Also, sorption kinetics of this polymer was investigated. © 2017 John Wiley & Sons, Ltd.

Khanbabapour S.,Isfahan University of Technology | Hamedani Golshan M.E.,Isfahan University of Technology
IEEE Transactions on Power Delivery | Year: 2017

The deployment of the distributed generation (DG), especially the synchronous distributed generation (SDG), as the energy infrastructure of smart grid in the distribution systems has drawn the attention of the distribution utilities to improve system performance through DG planning. In this paper, a methodology has been proposed for the planning of SDG units in the distribution system in an attempt to optimize a multiobjective index including the active energy losses during the planning period, the active and reactive power losses at the peak demand, voltage deviations from a reference value, the network investment deferral, the overcurrent protection system speed, and the anti-islanding protection speed. The constraints include the feeders' capacity, the maximum penetration limit due to anti-islanding protection requirements, the voltage limit, the preservation of the overcurrent protection system coordination, and the discrete size of SDG units. The proposed method has been applied to IEEE 14-bus test system with different cases including the different sets of weighting coefficients and the anti-islanding protections. © 2016 IEEE.

Dinari M.,Isfahan University of Technology | Haghighi A.,Isfahan University of Technology
Journal of Polymer Research | Year: 2017

In this work, cyanuric chloride was reacted with morpholine to obtain 2,4-dichloro-6-morpholino-1,3,5-triazine, which was then reacted with 4-aminobenzoic acid, yielding a new triazine monomer containing dicarboxylic acid. The chemical structure and purity of this monomer was confirmed by different techniques. Direct polycondensations of this diacid with several aromatic diamines were carried out in a molten ionic liquid, tetrabutylammonium bromide. Polyamides (PAs) with moderate inherent viscosities in the range 0.32–0.38 dL g−1 were obtained in high yields. These PAs were characterized by Fourier transform infrared spectroscopy, 1H NMR spectroscopy, X-ray powder diffraction, inherent viscosity measurements, and elemental analysis. All of the PAs were found to be amorphous, to possess outstanding solubilities, and to be easily dissolved in amide-type polar aprotic solvents. The thermal properties of the PAs were evaluated by thermogravimetric analysis and differential scanning calorimetry. These polymers showed good thermal stability with glass transition temperatures (Tg) of 223–248°C, and their 10% weight loss temperatures were around 448°C and 460°C, confirming their good thermal stability. The char yields of these polymers were 53–59%, and, given their LOI values of 39–41, these polymers also show good flame retardancy. © 2017, Springer Science+Business Media Dordrecht.

Enayati M.H.,Isfahan University of Technology
KONA Powder and Particle Journal | Year: 2017

Al5083 powder was subjected to ball milling in liquid nitrogen for 8 h using an attrition ball milling. The evolution of morphology of powder particles and the refinement of grain size were studied by scanning and transmission electron microscopies. The results showed that during cryomilling the morphology of powder particles changed from spherical to equiaxed shape. Additionally, the size of powder particles increased from ~10 μm to ~20 μm with narrower distribution. Simultaneously the cryomilling was associated with a significant reduction of grain size so that the final product after 8 h of cryomilling had a nanocrystalline microstructure (~25 nm) with well-developed high angle grain boundaries. These features were discussed in terms of severe plastic deformation, cold-welding and fracturing of powder particles which occur simultaneously during cryomilling process. © 2017 The Authors.

Khavari S.,Isfahan University of Technology | Ghane M.,Isfahan University of Technology
Fibers and Polymers | Year: 2017

Viscoelastic models composing of different combination of spring and dashpot are usually used to explain the mechanical behavior of textile materials. In this study, three different models were analyzed for explaining the compression, decompression and recovery of cut pile carpets under constant rate of compression. The carpet samples were compressed by the Zwick tester under constant rate of compression. The experiments were performed for just one cycle of compression-decompression. Maxwell mechanical model as well as the standard linear and nonlinear three-element models was employed for simulating the compression behavior and recovery of the carpet samples. Curve fitting method based on least square method was used to adapt the experimental data to the theoretical models. The results showed that the three element model consists of a Maxwell body paralleled with a non-linear spring can describe the compression and decompression behavior of more significantly in compression to Maxwell and standard linear models. Several attributes of compression can be described by the model parameters including work of compression, work of recovery and initial modulus. The results also showed that the Maxwell model is not capable of explaining the recovery property of the carpet as it shows some residual deformation after load removal. This is in contrary to the experimental results where all sample recovered to initial thickness after just one cycle of compression-decompression. The standard linear and nonlinear three-element models showed acceptable compliance with the recovery. The result suggests that the nonlinear three-element model provides the best fit for the experimental data. © 2017, The Korean Fiber Society and Springer Science+Business Media Dordrecht.

Moradi M.,Isfahan University of Technology
2016 6th International Conference on Computer and Knowledge Engineering, ICCKE 2016 | Year: 2016

One of the main challenges in Grid systems is designing an adaptive, scalable, and model-independent method for job scheduling to achieve a desirable degree of load balancing and system efficiency. Centralized job scheduling methods have some drawbacks, such as single point of failure and lack of scalability. Moreover, decentralized methods require a coordination mechanism with limited communications. In this paper, we propose a multi-agent approach to job scheduling in Grid, named Centralized Learning Distributed Scheduling (CLDS), by utilizing the reinforcement learning framework. The CLDS is a model free approach that uses the information of jobs and their completion time to estimate the efficiency of resources. In this method, there are a learner agent and several scheduler agents that perform the task of learning and job scheduling with the use of a coordination strategy that maintains the communication cost at a limited level. We evaluated the efficiency of the CLDS method by designing and performing a set of experiments on a simulated Grid system under different system scales and loads. The results show that the CLDS can effectively balance the load of system even in large scale and heavy loaded Grids, while maintains its adaptive performance and scalability. © 2016 IEEE.

Asadinezhad A.,Isfahan University of Technology | Kelich P.,Isfahan University of Technology
Applied Surface Science | Year: 2017

The effects of nanofiller chemistry and geometry on static and dynamic properties of an aromatic polyester, poly (trimethylene terephthalate), were addressed thanks to long-run classical molecular dynamics simulation. Two carbon nanofillers, graphene and carbon nanotube, were employed, where graphene was used in pristine and functionalized forms and carbon nanotube was used in two different diameters. The nanofiller geometry and chemistry were found to exert significant effects on conformation and dynamic behavior of PTT chain at the interface within the time scale the simulation was performed. It was found that PTT chain underwent interaction of van der Waals type with nanofiller via two subsequent phases, adsorption and orientation. The former stage, with definite characteristic time, involved translation of polymer chain toward interface while the latter was controlled by vibrational motions of chain atoms. The consequence of interaction was an increase in conformational order of polymer chain by transition to folded shape being favorable for any subsequent structural ordering (crystallization). The interaction of polymer with nanofiller gave rise to a reduction in overall mobility of polymer chain characterized by crossover from normal diffusive motion to subdiffusive mode. © 2016 Elsevier B.V.

Mousavi S.M.,Isfahan University of Technology | Zadhoush A.,Isfahan University of Technology
Journal of Membrane Science | Year: 2017

This study displays that the lacy structure could be effectively formed and retained in polysulfone (PSf) membrane morphology, prepared by non-solvent induced phase inversion process, by the adoption of poorer solvent as an additive. With 2-pyrrolidone (2P) as a solvent, the PSf membrane comprised a porous skin layer, lacy structure and fewer macrovoids, while with N-methyl pyrrolidone (NMP) a dense skin layer, finger-like macrovoids and cellular structure were dominant. The addition of 2P and water to PSf/NMP solution increased the viscoelasticity of the polymer solution. When water added to the PSf/NMP solution, the fully cellular structure formed in the PSf membranes due to the enhanced viscosity of the solution and occurring the delayed liquid-liquid demixing process. The enhanced viscoelasticity of the PSf/NMP solution with the utilization of 2P at various ratio slowed down the growth rate of demixed domains during the liquid-liquid demixing process due to the formation of hydrogen bonding between PSf chains and 2P molecules in the solution. The gelation of polymer-rich phase inhibited the coarsening of the phase-separated domains, and consequently, the lacy structure formed and locked in the nascent PSf membrane. The lacy structure formation, as well as the size and shape of the macrovoids in the PSf membranes, were controlled by the amounts of 2P presented in the systems. Also, the performance results showed that the flux is enhanced and salt rejection is declined with 2P content in the dope solution. While, the addition of water yielded reverse results, which they are in good agreement with the membrane morphology. © 2017 Elsevier B.V.

Nosoohi I.,Isfahan University of Technology | Nookabadi A.S.,Isfahan University of Technology
International Transactions in Operational Research | Year: 2017

This paper investigates a supply contract design by a dominant manufacturer who faces a stochastic demand during a selling season. The manufacturer has several estimations of the supplier's cost with corresponding probabilities, that is, asymmetric cost information. The manufacturer designs a menu of call option contracts that include three variables: a supply order, an option, and an exercise price. We determine the optimal negative correlation between option and exercise prices as well as closed-form formulas for the optimal supply orders. The results show that in the optimal menu of contracts either the option or the exercise price may be omitted from the menu, whereas the supply orders should always be customized for each supplier type. We show that in this problem, optimal profit assignment between contract partners under put and bidirectional option contracts is the same as call option contract studied. Numerical analysis including managerial insights is presented. © 2017 The Authors.

Razavi M.S.,Isfahan University of Technology | Shirani E.,Foolad Institute of Technology | Salimpour M.R.,Isfahan University of Technology | Kassab G.S.,Indiana University – Purdue University Indianapolis
PLoS ONE | Year: 2014

Diverse tree structures such as blood vessels, branches of a tree and river basins exist in nature. The constructal law states that the evolution of flow structures in nature has a tendency to facilitate flow. This study suggests a theoretical basis for evaluation of flow facilitation within vascular structure from the perspective of evolution. A novel evolution parameter (Ev) is proposed to quantify the flow capacity of vascular structures. Ev is defined as the ratio of the flow conductance of an evolving structure (configuration with imperfection) to the flow conductance of structure with least imperfection. Attaining higher Ev enables the structure to expedite flow circulation with less energy dissipation. For both Newtonian and non-Newtonian fluids, the evolution parameter was developed as a function of geometrical shape factors in laminar and turbulent fully developed flows. It was found that the non-Newtonian or Newtonian behavior of fluid as well as flow behavior such as laminar or turbulent behavior affects the evolution parameter. Using measured vascular morphometric data of various organs and species, the evolution parameter was calculated. The evolution parameter of the tree structures in biological systems was found to be in the range of 0.95 to 1. The conclusion is that various organs in various species have high capacity to facilitate flow within their respective vascular structures. © 2014 Razavi et al.

Safavi H.R.,Isfahan University of Technology | Falsafioun M.,Isfahan University of Technology
Journal of Irrigation and Drainage Engineering | Year: 2017

In this study, a genetic algorithm optimization model is applied to two different scenarios of deficit irrigation in an attempt to develop an appropriate plan for the conjunctive use of surface and ground water resources in Nekouabad irrigation zone located in Zayandehrud Basin, Iran. The study aims to reduce water consumption, define an optimal cropping pattern, decrease the annual decline in the local water table, and to maximize the farmers' net financial returns. Scenario I is based on normal conditions in terms of both water resources and weather parameters in the region while Scenario II is implemented to develop a 5-year irrigation plan for the study area. For the 5-year period in Scenario II, all possible weather (i.e., dry, normal, and wet) conditions are considered. Results show that water consumption would reduce by almost 24 million cubic meters and the net financial return would decline by 22% under Scenario I. Scenario II reveals that the decline in net revenues would be less under normal and wet conditions than it would be under drought conditions. © 2016 American Society of Civil Engineers.

Hassanzadeh S.,Isfahan University of Technology | Hasani H.,Isfahan University of Technology
Journal of Industrial Textiles | Year: 2017

Importance of solving the environmental pollution has attracted lots of designers and engineers’ attentions towards finding different available solutions such as substituting polymer-based raw materials with the natural ones. Thus, significant efforts applied by the researchers are generally involved to find new recourses of natural fibers instead of using the petroleum-based synthetic fibers. Among the variety of newly known natural resources, Milkweed is categorized as a versatile substitutive fiber with numerous unique properties which are mainly attributed to their hollowness structures. The presence of hollow channel along the fiber length is responsible for their lightweight and good insulation properties. Because of the fibers’ ecological and chemical benefits, numerous technical application fields could be considered for the eco-friendly and nonallergenic textiles made of Milkweed fibers especially in production of medical goods. Since morphological aspects as well as physical and mechanical properties of the Milkweed fibers significantly affect their functional behavior during their end uses, here in this review paper it is aimed to summarize all the available information regarding the fibers’ characteristics and properties. Having fundamental knowledge about the spin-ability of Milkweed fibers as well as finding the optimized process condition for their carding operation is considered to be the important points for obtaining such applicable textile products with desired properties. © The Author(s) 2015.

Fallah M.,Isfahan University of Technology | Zamani-Ahmadmahmoodi R.,Shahrekord University
Wetlands Ecology and Management | Year: 2017

In the present study, the water quality of the Anzali Wetland, located southwest of the Caspian Sea in Iran, was compared for the years 1985, 2007, and 2014, using a weighted arithmetic mean function (National Sanitation Foundation Water Quality Index: NSFWQIa), a weighted geometric mean function (NSFWQIm), and the Oregon Water Quality Index (OWQI). To that end, nine water quality parameters [pH, turbidity (TURB), temperature (T), dissolved oxygen (DO), nitrate (NO3), total solids (TS), phosphate (PO4), biological oxygen demand (BOD5), and fecal coliforms (FC)] were analyzed at eight selected stations. According to the proposed classification for water quality indices (higher value (0–100), better water quality), the Wetland water quality was classified as the mean values of the three indices for the three sampled years, as follows: NSFWQIa (13.72, 12.81, 12.07); NSFWQIm (63.049, 52.388, 49.108); and OWQI (26.867, 14.477, 15.53). The values of NSFWQIa, NSFWQIm, and OWQI for the western stations were better than for the other stations in the region over the 29-year span of investigation; however, the remainders of the stations’ values were very poor. Because wastewaters discharged from industrial and agricultural areas are more concentrated in the eastern part of the Anzali Wetland, the eastern stations of the Wetland showed lower water quality compared to the central and western stations. The water of the Anzali Wetland has different quality classes according to the aggregation methods employed. It is concluded that when evaluating water quality of aquatic ecosystems, several indices should be used to obtain more comprehensive results. © 2017 Springer Science+Business Media Dordrecht

Mirsalehi M.,Isfahan University of Technology | Azhari M.,Isfahan University of Technology | Amoushahi H.,University of Isfahan
European Journal of Mechanics, A/Solids | Year: 2017

In the present article the mechanical instability and free vibration of FGM micro-plate based on the modified strain gradient theory were studied using the spline finite strip method. By daily increase in the application of micro-scale structures, developing theories were become essential to account in a way for the size-reduction effect. The modified strain gradient theory based on three length scale parameters, has the capability of evaluating structures at the micro size level. Considering the obtained results, it was clear that increasing the length-scale parameter would increase the critical buckling load and the vibration frequency, similar to the macroscopic case. In addition, increasing the power of volume fraction module decreases the critical load and the natural frequency of micro plate. Finally, the effect of length-scale parameter, boundary conditions, volume fraction module and dimensions of the micro-plate on critical loading and natural frequency of micro-plate were studied. © 2016 Elsevier Masson SAS

Fakhari Z.,Isfahan University of Technology | Kabiri-Samani A.,Isfahan University of Technology
Journal of Hydraulic Research | Year: 2017

Local scour in the transition from super- to sub-critical flow without a hydraulic jump is investigated based on model experimentation. Supercritical flow was enforced by a box-culvert, passed a curved bed, and then flowed over the sediment bed. The scour processes and the initiation of sediment motion are discussed. Attempts are also made to explain similarities among scour processes and profiles. The temporal development of the maximum scour depth is evaluated. Results indicate that the maximum equilibrium scour depth and scour hole geometry in the transition from super- to sub-critical flow without a hydraulic jump significantly depend on the upstream supercritical approach flow, and the densimetric Froude numbers. Scour profiles were also compared with those resulting from equivalent hydraulic jumps, indicating that the geometrical characteristics of the scour holes are significantly smaller than those of the corresponding hydraulic jumps. Finally, relationships characterizing the equilibrium scour hole geometry are derived based on the experimental results. © 2017 International Association for Hydro-Environment Engineering and Research

Abasaltian A.,University of Isfahan | Ghandil M.,Isfahan University of Technology
Journal of Earthquake Engineering | Year: 2017

The unexpected damages in structures during severe earthquakes have been reported frequently so far. In this study, the damage-based inelastic behavior of special moment resisting frame (SMRF) structures designed according to the new versions of general earthquake loading codes (International building code [IBC] 2012 & American Society of Civil Engineers [ASCE] 7-2010) and seismic design references (National Earthquake Hazards Reduction Program [NEHRP] 2009 & Federal Emergency Management Agency [FEMA] P-750) has been investigated. The final results presented based on distinctive shear and flexural failure modes show that a non-uniform distribution of severe damage in structural height occurs during design level seismic excitations. Also it is observed that the shear and flexural damages are more critical in short and tall MRF structures, respectively. © 2017 Taylor & Francis Group, LLC

Mallakpour S.,Isfahan University of Technology | Motirasoul F.,Isfahan University of Technology
Ultrasonics Sonochemistry | Year: 2017

Alpha manganese dioxide (α-MnO2) nanorods have been covalently functionalized with stearic acid by solvothermal method. The α-MnO2-stearic acid nanorods were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The amount of stearic acid grafted onto α-MnO2 surface was determined about 41 wt% by thermogravimetric analysis. The α-MnO2-stearic acid nanorods was used as nanofiller for the preparation of poly(vinyl alcohol) (PVA) nanocomposites (NCs). The NCs with 1, 3, and 5 wt% of nanofiller were prepared through ultrasound assisted technique as an economical, fast, eco-friendly, and effective method. The PVA/α-MnO2-stearic acid NCs were characterized by different techniques. The results showed that with increasing the α-MnO2-stearic acid content, the thermal stability and tensile properties were improved. Besides, the NC 5 wt% was used as adsorbent for sorption of Cd (II) ion. The adsorption efficiency of NC 5 wt% in different initial concentrations of Cd (II) ion (20–100 mg L−1) was 58–95%. All the isotherm data were well fitted by both Langmuir and Freundlich equations. The adsorption kinetics study demonstrated that pseudo-second-order model was the best fit with the experimental data. The results indicated that prepared NCs are promising adsorbents for the removal of Cd (II) ion from the aqueous solution. © 2017 Elsevier B.V.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The main objective of this research was to evaluate the potential of electrochemical bioleaching to extract copper from pyritic chalcopyrite concentrates. Bacterial and chemical (uninoculated) shake flask leaching of Sarcheshmeh copper concentrate at 15% (w/v) pulp density, 150 rpm and stirred tank electrochemical bioleaching of the concentrate at ORP (oxidation reduction potential) ranging from 400 to 430 mV (vs. Ag/AgCl), 20% pulp density and 600 rpm were conducted with and without pyrite addition. A mixed culture of moderately thermophilic microorganisms was used in all bioleaching experiments at an initial pH of 1.5, 50 °C, Norris nutrient medium and 0.02% (w/w) yeast extract addition. The results of leaching experiments in shake flasks showed that the addition of pyrite to the concentrate significantly increased the efficiency of copper extraction especially in the presence of microorganisms. In electrochemical bioleaching process, both the rate and extent of copper extraction were selectively (with respect to iron) enhanced in the pyritic copper concentrate in which about 90% copper recovery was achieved from the concentrate after 10 days. Analyses of optical microscopy and SEM/EDS revealed that pyrite remained unaffected in the electro-biochemical system while chalcopyrite was preferentially dissolved. It can also be concluded that at low levels of solution ORP, pyrite remains inert, which acts as a cathode site relative to chalcopyrite and other copper sulfide minerals (galvanic interaction) leading to enhance the anodic dissolution of the copper bearing minerals. Electrochemical system regulates the ratio of ferric to ferrous iron at an optimum level where the dissolution rate of chalcopyrite is maximum. Sulfur oxidizer microorganisms intensify the galvanic interactions and the rate of electron transfer among sulfides by removing the insulating sulfur product. © 2012 Elsevier Ltd. All rights reserved.

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Ghiaci M.,Isfahan University of Technology | Zarghani M.,Isfahan University of Technology | Khojastehnezhad A.,Islamic Azad University at Mashhad | Moeinpour F.,Islamic Azad University at Bandar Abbas
RSC Advances | Year: 2014

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

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

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

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

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

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

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

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

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

News Article | December 15, 2015

Home > Press > Biosensor Produced in Iran to Diagnose Agents Harmful to DNA Abstract: Iranian researchers from Isfahan University of Technology produced a nanobiosensor to study the effects of various elements on DNA degradation and the methods to prevent it. The sensor is able to sense and measure the amount of DNA degradation in the presence of pharmaceutical materials. Since DNA degradation is the source of cancers, mutations and gene diseases, many researchers have studied the effective parameters on DNA degradation in recent years, and they have tried to find effective methods to prevent the degradation. Therefore, researchers produced a nanobiosensor at laboratorial scale to study the subject. The biosensor has been manufactured through a simple, quick and cost-effective method, and carbon nanotubes have been used in the production of the sensor. In this research, DNA degradation by using dopamine in absence and presence of a few metal ions was investigated and a few methods were suggested to prevent the degradation. The aim of the research was to present and study a sensor that enables the investigation of DNA degradation by dopamine in the absence and presence of metal ions. The researchers also studied the effect of the presence of some antioxidants such as ascorbic acid and glutathione on the prevention of DNA degradation. Results showed that compounds such as dopamine and copper and iron ions are not able to degrade DNA by themselves. However, the simultaneous presence of dopamine and copper ion or iron ion degrades DNA. The effectiveness of the two antioxidants showed that prevention of glutathione is two times higher than that of ascorbic acid. Results of the research have been published in Bioelectrochemistry, vol. 104, 2015, pp. 71-78. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Mirzadeh H.,Isfahan University of Technology | Najafizadeh A.,Isfahan University of Technology
Materials and Design | Year: 2010

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Mirzadeh H.,Isfahan University of Technology | Najafizadeh A.,Isfahan University of Technology
Materials and Design | Year: 2010

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

Mostofinejad D.,Isfahan University of Technology | Mahmoudabadi E.,Isfahan University of Technology
Journal of Composites for Construction | Year: 2010

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

Khatoonabadi A.,Isfahan University of Technology
Information Technology and Applications - Proceedings of the 2014 International Conference on Information technology and Applications, ITA 2014 | Year: 2015

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

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

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

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

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

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

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

Mazrooei-Sebdani R.,Isfahan University of Technology | Farjami S.,Isfahan University of Technology