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Tehran, Iran

The Iran University of Science and Technology is a research institution and university of engineering and science in Iran, offering both undergraduate and postgraduate studies. Located on Hengam Street in the Narmak neighborhood in northeast Tehran, IUST and its surrounding communities provide a cultural and recreational environment suited to the work of a major research institution. The university consistently ranks among Iran's top three technical universities. Wikipedia.


Wang Y.,New York University | Jin J.,New York University | Kremkow J.,New York University | Lashgari R.,New York University | And 3 more authors.
Nature Neuroscience | Year: 2015

Images are processed in the primary visual cortex by neurons that encode different stimulus orientations and spatial phases. In primates and carnivores, neighboring cortical neurons share similar orientation preferences, but spatial phases were thought to be randomly distributed. We discovered a columnar organization for spatial phase in cats that shares similarities with the columnar organization for orientation. For both orientation and phase, the mean difference across vertically aligned neurons was less than one-fourth of a cycle. Cortical neurons showed threefold more diversity in phase than orientation preference; however, the average phase of local neuronal populations was similar through the depth of layer 4. We conclude that columnar organization for visual space is not only defined by the spatial location of the stimulus, but also by absolute phase. Taken together with previous findings, our results suggest that this phase-visuotopy is responsible for the emergence of orientation maps. © 2015 Nature America, Inc. All rights reserved.


Daeinabi K.,Islamic Azad University at Tehran | Korayem M.H.,Iran University of Science and Technology
Journal of Nanoparticle Research | Year: 2011

Atomic force microscopy is applied to measure intermolecular forces and mechanical properties of materials, nano-particle manipulation, surface scanning and imaging with atomic accuracy in the nano-world. During nano-manipulation process, contact forces cause indentation in contact area between nano-particle and tip/substrate which is considerable at nano-scale and affects the nano-manipulation process. Several nano-contact mechanics models such as Hertz, Derjaguin-Muller-Toporov (DMT), Johnson-Kendall-Roberts-Sperling (JKRS), Burnham-Colton-Pollock (BCP), Maugis-Dugdale (MD), Carpick-Ogletree-Salmeron (COS), Pietrement-Troyon (PT), and Sun et al. have been applied as the continuum mechanics approaches at nano-scale. In this article, indentation depth and contact radius between tip and substrate with nano-particle for both spherical and conical tip shape during nano-manipulation process are analyzed and compared by applying theoretical, semiempirical, and empirical nano-contact mechanics models. The effects of adhesion force, as the main contrast point in different nano-contact mechanics models, on nano-manipulation analysis is investigated for different contact radius, and the critical point is discussed for mentioned models. © 2010 Springer Science+Business Media B.V.


Shabannia R.,Iran University of Science and Technology
Journal of Materials Science: Materials in Electronics | Year: 2016

ZnO thin films were successfully produced on porous silicon (PS) substrates by a chemical bath deposition method. ZnO thin films were then annealed at 300, 500, and 700 °C for 20 min in nitrogen (N2) atmosphere. X-ray diffraction, field emission scanning electron microscopy (FESEM), and photoluminescence (PL) were utilized to investigate the effect of post-annealing temperature on the structural, optical, and electrical properties of ZnO thin films. The lattice constant, full width at half maximum, and strain (the grain size) of (0 0 2) peak of ZnO thin films decreased (increased) with increasing the annealing temperature, respectively. The FESEM images revealed that the ZnO thin films are compact array ZnO nanocolumns and were perpendicularly grown to the PS substrate. The biggest ratio of the PL intensity of UV emission to that of visible emission is observed from ZnO thin films annealed at 500 °C. The PL results of the ZnO thin films exhibit that the UV peak positions shift slightly toward lower wavelengths with increase of the annealing temperature. The current–voltage measurements demonstrate that the current level increases as the annealing temperature increases to 500 °C, and then decreases when the temperature further increases up to 700 °C. © 2016 Springer Science+Business Media New York


Farrokhabadi A.,Amirkabir University of Technology | Hosseini-Toudeshky H.,Amirkabir University of Technology | Mohammadi B.,Iran University of Science and Technology
Composite Structures | Year: 2011

The previously developed micromechanical approaches for the analysis of transverse cracking and induced delamination are limited for laminates with specific lay-ups such as cross-ply and specific loading conditions. In this paper a new micromechanical approach is developed to overcome such shortcomings. For this purpose, a unit cell in the ply level of composite laminate including transverse cracking and delamination is considered. Then, the governing equations for the stress and displacement fields of the unit cell are derived. The obtained approximate stress field is used to calculate the energy release rate for the propagation of transverse cracking and induced delamination. To show the capability of the new method, it is employed for the analyses of general laminates with [0/90]. s, [45/-45]. s, [30/-30]. s and [90/45/0/-45]. s lay-ups under combined loadings to calculate the energy release rate due to the transverse cracking and induced delamination. It is shown that the obtained energy release rates for transverse cracking and delamination initiation are in good agreement with the available results in the literature and finite element method. Furthermore, the occurrence priority of further transverse cracks and/or delamination at each damage state of the laminates will be discussed. © 2010 Elsevier Ltd.


Hedayati H.,Iran University of Science and Technology
Journal of Multiple-Valued Logic and Soft Computing | Year: 2011

The notion of implicative interval-valued intuitionistic fuzzy filter of a pseudo-BL algebra with respect to t-norm T and t-conorm S is introduced. The characteristic properties and connections are described. Also some natural equivalence relations and partitions defined on the set of implicative interval-valued intuitionistic (T, S)-fuzzy filters are analysed. © 2011 Old City Publishing, Inc.


Gheshlaghi B.,Islamic Azad University at Damavand | Hasheminejad S.M.,Iran University of Science and Technology
Applied Physics Letters | Year: 2012

The Timoshenko [S. S. Rao, Vibration of Continuous Systems (Wiley, New York, 2007)] beam model is used to derive the differential equations governing the free vibrations of thick nanowires (NWs) with dissipative surface stress effects. The natural frequencies are calculated as functions of NW length as well as thickness-to-length ratio, with the effects of dissipation, transverse shear deformation, and rotary inertia being included. The effects of latter two parameters are significant especially for higher modes of vibration and shorter NWs and are different from what is naively expected based on elementary mechanics for some specific dimensions. The results are also compared with the previous study using Euler-Bernoulli beam theory. © 2012 American Institute of Physics.


Farhadi S.,University of Kurdistan | Hosseini-Hashemi S.H.,Iran University of Science and Technology
International Journal of Mechanical Sciences | Year: 2011

Aeroelastic behavior of a supersonic rotating rectangular plate in the air medium is studied. For simulating the plate structure, the Mindlin first-order shear deformation plate theory along with Von Karman nonlinear terms is employed. Air dynamic pressure is modeled using first-order piston theory. The plate is placed inside a rigid baffle to remove shock waves generated by plate rotation and provide a uniform flow passing over the plate. Nonlinear dimensionless generalized equations of motion are presented based on the Kane dynamic method. After linearization of the nonlinear equations of motion, effect of different parameters including plate aspect ratio, thickness ratio, hub radius ratio and dimensionless rotation speed on aeroelastic behavior of the system are investigated. Frequency locking and high frequency flutter phenomenon are observed in the numerical results. © 2011 Elsevier Ltd. All rights reserved.


Kaveh A.,Iran University of Science and Technology | Farhoudi N.,K. N. Toosi University of Technology
Journal of Constructional Steel Research | Year: 2011

Meta-heuristic optimization algorithms have attracted many researchers in the last decade. Adjustment of different parameters of these algorithms is usually a time consuming task which is mostly done by a trial and error approach. In this study an index, namely convergence factor (CF), is introduced that can show the performance of these algorithms. CF of an algorithm provides an estimate of the suitability of the parameters being set and can also enforce the algorithm to adjust its parameters automatically according to a pre-defined CF. In this study GA, ACO, PSO and BB-BC algorithms are used for layout (topology plus sizing) optimization of steel braced frames. Numerical examples show these algorithms have some similarities in common that should be taken into account in solving optimization problems. © 2011 Elsevier Ltd. All rights reserved.


Farhadi S.,University of Kurdistan | Hosseini-Hashemi S.H.,Iran University of Science and Technology
JVC/Journal of Vibration and Control | Year: 2011

In the present work, active vibration suppression of moderately thick rectangular plates by means of piezoelectric actuators is investigated. Based on Lagrange energy method, a finite element formulation is presented for mathematical modeling of the system. Using modal controllability criterion, a simple method is offered for optimal placement of the piezoelectric actuator. For a cantilevered plate with specific characteristics, the optimal position of a piezoelectric patch is investigated. Then, for suppression of plate vibrations, an active damping controller is designed using modal velocity feedbacks. Numerical simulations are then performed for studying the performance of the designed controller. Presented simulations indicate the feasibility of vibration control of moderately thick plates by means of high voltage piezoelectric actuators. These simulations also show that, for a specific excitation force, the maximum required voltage for vibration suppression approaches to an asymptotic value as the values of modal feedback gains increase. This conclusion is of high importance in practical controller design. © The Author(s) 2011 Reprints and permissions.


Ramezani A.,Iran University of Science and Technology
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2011

In this paper, the pull-in instability of electrostatically actuated nanotweezers considering the dispersion forces is studied using distributed and lumped parameter models. By analogy to nanoswitches, closed-form solutions are obtained for electrostatic nanotweezers. The distributed and lumped parameter modeling of the tweezer result, respectively, in two coupled nonlinear boundary value problems and two coupled nonlinear equations, which are solved numerically in the cases of electrostatic microtweezers, freestanding nanotweezers, and electrostatic nanotweezers. In each case, analytical and numerical solutions are obtained and compared with those of the corresponding switch. In addition, the results of the distributed and lumped parameter models are compared. The detachment length and minimum initial gap of nanotweezers are determined. © 2011 Elsevier B.V.


Behzad S.,Iran University of Science and Technology
Optical and Quantum Electronics | Year: 2016

The full potential linearized augmented plane wave method with the generalized gradient approximation has been used to understand the electronic and optical properties of α-graphyne-like BN (α-BNyne) sheet. The total and partial density of states, electronic structure and optical constants for different light polarizations are obtained. The optical properties of α-BNyne are found to be strongly anisotropic. For electric field parallel to the α-BNyne sheet, strong optical adsorption and reflectivity are observed in the low-energy region, whiles for the electric field perpendicular to the α-BNyne sheet, the adsorption and reflectivity in the low-energy region are very weak. Also, the results of optical response property calculations show that α-BNyne sheet has broad spectral photoresponse. All of these properties indicate that α-BNyne is a new two-dimensional candidate for use in optoelectronic devices. © 2016, Springer Science+Business Media New York.


Torabi A.R.,University of Tehran | Ayatollahi M.R.,Iran University of Science and Technology
European Journal of Mechanics, A/Solids | Year: 2014

The aim of this research was to present a brittle fracture model for predicting the compressive failure load of engineering components weakened by V-notches with end holes (VO-notches). For this purpose, two well-known brittle fracture models in tension, namely the point stress (PS) and the mean stress (MS) were applied to the compressive stress field around the VO-notches and for each model a closed-form expression was obtained for the compressive mode I notch fracture toughness. In order to evaluate the validity of PS and MS criteria, the theoretical values of compressive notch fracture toughness were compared with the experimental results reported recently in literature dealing with fracture in fine-grained isostatic graphite plates containing V-notches with end holes subjected to pure compression. The results showed that while the MS model with a total discrepancy of 5% was an appropriate failure criterion, the PS model with about 86% accuracy could not predict the experimental results satisfactorily.©2013 Elsevier Masson SAS. All rights reserved.


Ghanbari B.,Iran University of Science and Technology
The Scientific World Journal | Year: 2014

We aim to study the convergence of the homotopy analysis method (HAM in short) for solving special nonlinear Volterra-Fredholm integrodifferential equations. The sufficient condition for the convergence of the method is briefly addressed. Some illustrative examples are also presented to demonstrate the validity and applicability of the technique. Comparison of the obtained results HAM with exact solution shows that the method is reliable and capable of providing analytic treatment for solving such equations. © 2014 Behzad Ghanbari.


Ayatollahi M.R.,Iran University of Science and Technology | Torabi A.R.,University of Tehran
Materials Science and Engineering A | Year: 2011

The fracture load and the fracture initiation angle were experimentally measured for a V-notched specimen made of polycrystalline graphite under combined tensile-shear loading. The experimental results were obtained for several specimens with different notch angles and various notch tip radii. The experimental observations showed that for a constant notch tip radius, the fracture load in pure tensile loading conditions decreases as the notch angle increases. Moreover, for a constant notch angle, as the notch tip radius increases the fracture load in graphite specimens enhances in the entire domain between pure tensile and pure shear loading conditions. A recently developed failure criterion was then used to estimate the experimental values of the notch fracture resistance and the fracture initiation angle for the tested graphite specimens. The experimental results could be estimated very well by using the results of the proposed criterion. © 2011 Elsevier B.V.


Pasdar A.,Iran University of Science and Technology | Mehne H.H.,Aerospace Research Institute
International Journal of Electrical Power and Energy Systems | Year: 2011

This paper studies the problem of current balancing in a three-phase, low-voltage distribution network. We assume that the network has an automatic metering system that communicates using the power line carrier technique. Each meter reports the customer's energy consumption and local current/voltage data to the central station at specified intervals. To maximize the efficiency of the grid, we wish to minimize the unbalanced current in the neutral phase. After framing this problem as a quadratic assignment problem, we use the "ant colony optimization" method to assign each customer to a phase. We confirm the effectiveness of the proposed method on an ensemble of simulated networks. Besides triggering point of high current relay is also decisive and should be consider in software commands output. © 2010 Elsevier Ltd. All rights reserved.


A new, efficient, one-pot multicomponent reaction for the synthesis of diazepine derivatives in excellent yields is described. The reactions of various 1,2-diamines, terminal alkynes, and an isocyanide take place in the presence of a catalytic amount of magnetically recoverable silica-supported superparamagnetic Fe3O4 nanoparticles in ethanol (as a green reaction medium) at ambient temperature. © 2013 Elsevier Ltd. All rights reserved.


Peyghambarzadeh S.M.,Islamic Azad University at Mahshahr | Hashemabadi S.H.,Iran University of Science and Technology | Jamnani M.S.,Islamic Azad University at Mahshahr | Hoseini S.M.,Islamic Azad University at Mahshahr
Applied Thermal Engineering | Year: 2011

In this paper, forced convective heat transfer in a water based nanofluid has experimentally been compared to that of pure water in an automobile radiator. Five different concentrations of nanofluids in the range of 0.1-1 vol.% have been prepared by the addition of Al 2O 3 nanoparticles into the water. The test liquid flows through the radiator consisted of 34 vertical tubes with elliptical cross section and air makes a cross flow inside the tube bank with constant speed. Liquid flow rate has been changed in the range of 2-5 l/min to have the fully turbulent regime (9 × 10 3 < Re < 2.3 × 10 4). Additionally, the effect of fluid inlet temperature to the radiator on heat transfer coefficient has also been analyzed by varying the temperature in the range of 37-49 °C. Results demonstrate that increasing the fluid circulating rate can improve the heat transfer performance while the fluid inlet temperature to the radiator has trivial effects. Meanwhile, application of nanofluid with low concentrations can enhance heat transfer efficiency up to 45% in comparison with pure water. © 2011 Elsevier Ltd. All rights reserved.


Mokhtari A.,Iran University of Science and Technology | Moghadas Nejad F.,Amirkabir University of Technology
Construction and Building Materials | Year: 2012

In this study, different additives such as mineral fiber, cellulose fiber and styrene-butadiene-styrene (SBS) were used to modify stone matrix asphalt (SMA) mixtures, and performance tests were performed for modified and unmodified mixtures. A mechanistic-empirical design procedure was employed to assess the effect of different additives in improving the service life of the pavement or reduction in thickness of pavement layers. Based on the results, SBS was more effective in improving the performance of asphalt mixtures compared to the fibers. According to the results of mechanistic-empirical design, the service life of the pavement system modified with mineral, cellulose and SBS were 1.07, 1.081 and 1.243 times more than unmodified mix, respectively. © 2012 Elsevier Ltd. All rights reserved.


Maleki A.,Iran University of Science and Technology | Rezayan A.H.,University of Tehran
Tetrahedron Letters | Year: 2014

A one-pot, three-component reaction for the synthesis of pyrido[2′,1′:2,3]imidazo[4,5-c]isoquinolines starting from 2-aminopyridines, phthalaldehyde, and trimethylsilyl cyanide in good to high yields is described. © 2014 Elsevier Ltd. All rights reserved.


Hasheminejad S.M.,Iran University of Science and Technology | Gheshlaghi B.,Islamic Azad University at Tehran
Composite Structures | Year: 2012

A three-dimensional semi-analytic analysis based on the linear elasticity theory is offered to study the transient vibration characteristics of an arbitrarily thick, simply supported, functionally graded (FGM) rectangular plate, resting on a linear Winkler-Pasternak viscoelastic foundation, and subjected to general distributed driving forces of arbitrary temporal and spatial variations. The problem solution is obtained by adopting a laminate model in conjunction with the powerful state space solution technique involving a global transfer matrix and Durbin's numerical Laplace inversion algorithm. Numerical calculations are carried out for the transient displacement and stress responses of aluminum-zirconia FGM square plates of selected thickness parameters and compositional gradients, resting on " soft" or " stiff" elastic foundations, under the action of moving transverse forces as well as uniformly distributed blast loads. Also, the response curves for the FGM plates are compared with those of equivalent bilaminate plates containing comparable total volume fractions of constituent materials. It is observed that the material gradient variation is substantially more influential on the dynamic stress concentrations induced across the plate thickness than on the displacement response of the inhomogeneous plates. In particular, the displacement response of the equivalent bilaminate plates can provide an accurate estimate for prediction of the dynamic response of the corresponding FGM plates, especially for thick plates resting on a stiff foundation. Limiting cases are considered and good agreements with the data available in the literature as well as with the computations made by using a commercial finite element package are obtained. © 2012 Elsevier Ltd.


Ahmadi R.,Iran University of Science and Technology
International Journal of Production Research | Year: 2016

Given a reward structure, this paper addresses an optimal replacement problem for complex multi-component systems. To maintain revenue stream resulting from system, the system is inspected according to a homogeneous Poisson process and certain actions are carried out in response to the system state. Decisions are based on a performance measure described by a Squared Bessel process. Given some assumption, we explore the inherent relation between the Squared Bessel process and an extended Gamma (EG) process. Since there are some flow of income and increasing costs due to inspections, the problem is to optimally stop processing the system and carrying out a renewal to maximize the reward functional. To this end, using the local characteristics of the EG process as a stopping criterion and the expected total discounted reward as a measure of policy, this paper aims at determining an optimal operating (stopping) time which truly balances both income and cost and so maximizes the expected discounted reward over a cycle. In support of the model a numerical example is provided to show feasibility of this programme in real application. Attention is restricted to perfect repair and inspection, but the paper provides the structure so that different scenarios can be explored. © 2016 Informa UK Limited, trading as Taylor & Francis Group


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Structural and Multidisciplinary Optimization | Year: 2011

The concept of the "fields of forces" is utilized as a general model of meta-heuristic algorithms from physics. This model is capable of representing the properties of different meta-heuristics and in this paper, it is used to enhance the recently developed meta-heuristic, the Charged System Search (CSS). The enhanced CSS is then applied to determine the configuration optimum design of structures. Comparison of the results for some examples, illustrates the efficiency of the enhanced CSS algorithm. © Springer-Verlag 2010.


Abiri M.B.,Mazandaran University of Science and Technology | Yousefli A.,Iran University of Science and Technology
International Journal of Advanced Manufacturing Technology | Year: 2011

This paper considers location-allocation problem in the real uncertain world and develops a possibilistic non-linear programming model to deal with this problem. Fuzzy decision making in fuzzy environment concept is used to determine possibility distribution of location and allocation variables. To solve this model, a novel approach based on genetic algorithm structure is developed. As the proposed model includes both deterministic (location) and uncertain (allocation) parameters, the developed solution algorithm uses a hybrid chromosome structure. Also, to cover continuous nature of the problem and prevent GA from early convergence, a new crossover operator is introduced. Finally, performance of the developed algorithm is evaluated by an example. © 2010 Springer-Verlag London Limited.


Alavi A.H.,Iran University of Science and Technology | Gandomi A.H.,Tafresh University
Engineering Computations (Swansea, Wales) | Year: 2011

Purpose - The complexity of analysis of geotechnical behavior is due to multivariable dependencies of soil and rock responses. In order to cope with this complex behavior, traditional forms of engineering design solutions are reasonably simplified. Incorporating simplifying assumptions into the development of the traditional models may lead to very large errors. The purpose of this paper is to illustrate capabilities of promising variants of genetic programming (GP), namely linear genetic programming (LGP), gene expression programming (GEP), and multi-expression programming (MEP) by applying them to the formulation of several complex geotechnical engineering problems. Design/methodology/approach - LGP, GEP, and MEP are new variants of GP that make a clear distinction between the genotype and the phenotype of an individual. Compared with the traditionalGP, the LGP, GEP, and MEP techniques are more compatible with computer architectures. This results in a significant speedup in their execution.These methods have a great ability to directly capture the knowledge contained in the experimental data withoutmaking assumptions about the underlying rules governing the system. This is one of their major advantages over most of the traditional constitutive modeling methods. Findings - In order to demonstrate the simulation capabilities of LGP, GEP, and MEP, they were applied to the prediction of: relative crest settlement of concrete-faced rockfill dams; slope stability; settlement around tunnels; and soil liquefaction. The results are compared with those obtained by other models presented in the literature and found to be more accurate. LGP has the best overall behavior for the analysis of the considered problems in comparison with GEP and MEP. The simple and straightforward constitutive models developed using LGP, GEP and MEP provide valuable analysis tools accessible to practicing engineers. Originality/value - The LGP, GEP, and MEP approaches overcome the shortcomings of different methods previously presented in the literature for the analysis of geotechnical engineering systems. Contrary to artificial neural networks and many other soft computing tools, LGP, GEP, and MEP provide prediction equations that can readily be used for routine design practice. The constitutive models derived using these methods can efficiently be incorporated into the finite element or finite difference analyses as material models. They may also be used as a quick check on solutions developed by more time consuming and in-depth deterministic analyses. © Emerald Group Publishing Limited.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Structural and Multidisciplinary Optimization | Year: 2011

Dome structures provide cost-effective solutions for covering large areas without intermediate supports. In this article, simple procedures are developed to reach the configuration of the geodesic domes. A new definition of dome optimization problems is given which consists of finding optimal sections for elements (size optimization), optimal height for the crown (geometry optimization) and the optimum number of elements (topology optimization) under determined loading conditions. In order to find the optimum design, the recently developed meta-heuristic algorithm, known as the Charged System Search (CSS), is applied to the optimum design of geodesic domes. The CSS takes into account the nonlinear response of the domes. Using CSS, the optimum design of the geodesic domes is efficiently performed. © 2010 Springer-Verlag.


Jalali Naini S.G.,Iran University of Science and Technology | Shafiee M.,University of Tehran
International Journal of Advanced Manufacturing Technology | Year: 2011

An upgrade action is a pre-sale procedure that brings the second-hand item to an improved functional state and effectively reduces its age. This action is usually costly and adds directly to the sale price of the second-hand product, but it improves the product reliability and can reduce the warranty servicing cost. In the present paper, we propose a decision model to determine the optimal price and upgrade strategy of a warranted second-hand product to maximize the dealer's expected profit. The objective function includes both demand and cost functions, where purchase price from an end user, upgrade cost, and warranty cost are involved. We illustrate our finding using real data on second-hand electric device. Also, a sensitivity analysis is conducted to evaluate the effect of model parameters on the optimal solution. © Springer-Verlag London Limited 2011.


Damghani K.K.,Islamic Azad University at Tehran | Sadi-Nezhad S.,Islamic Azad University at Tehran | Aryanezhad M.B.,Iran University of Science and Technology
Expert Systems with Applications | Year: 2011

In this paper, we have developed a modular Decision Support System (DSS) in order to select an optimum portfolio of several chances for investments in presence of uncertainty. The investments are considered as the projects so as their initial investment costs, profits, resource requirement, and total available budget are assumed to be uncertain. This uncertainty has been modeled using fuzzy concepts. The proposed DSS has two main modules. The first one is a fuzzy binary programming model which represents the mathematical model of the associated fuzzy capital-budgeting problem. It involves finding optimum combination of investment portfolio considering a multi-objective measurement function and subject to several set of constraints. The results of optimistic and pessimistic analysis of the aforementioned fuzzy binary programming model plus a managerial Confidence Level (CL) value are treated as input of a fuzzy rule based system which is the second module of the proposed DSS. Although some projects are simple to make a decision about at the final step of the first module but the unique output of the second module of the proposed DSS is Risk of Investment (ROI) for all remained project. The logic relations between precedence parts of the rules as well as CL value will work in favor of computational efforts in second module through diminishing some unessential rules. This will help to define a complete set of fuzzy IF-THEN rules more efficiently. The proposed DSS can help the decision makers to select an optimum investment portfolio with minimum risk in a complete ambiguous condition. © 2010 Elsevier Ltd. All rights reserved.


In this research, a new protocol for the one-pot multicomponent synthesis of diazepine derivatives using a 1,2-diamine, a linear or cyclic ketone, and an isocyanide in the presence of a catalytic amount of silica-supported iron oxide (Fe 3O 4/SiO 2) nanoparticles at ambient temperature in excellent yields is described. © 2012 Elsevier Ltd. All rights reserved.


Hosseini-Toudeshky H.,Amirkabir University of Technology | Ghaffari M.A.,Amirkabir University of Technology | Mohammadi B.,Iran University of Science and Technology
Composite Structures | Year: 2012

Fatigue crack growth analyses of aluminum panels with stiffeners repaired by composite patches have been rarely investigated. Generally, cracks may occur around the rivets which are capable to propagate under cyclic loadings. A composite patch can be used to stop or retard the crack growth rate. In this investigation, finite element method is used for the crack propagation analyses of stiffened aluminum panels repaired with composite patches. In these analyses, the crack-front can propagate in 3-D general mixed-mode conditions. The incremental 3-D crack growth of the repaired panels is automatically handled by a developed ANSYS Parametric Design Language (APDL) code. Effects of rivets distances and their diameters on the crack growth life of repaired panels are investigated. Moreover, the obtained crack-front shapes at various crack growth steps, crack trajectories, and life of the unrepaired and repaired panels with various glass/epoxy patch lay-ups and various patch thicknesses are discussed. © 2012 Elsevier Ltd.


Torabi A.R.,University of Tehran | Aliha M.R.M.,Iran University of Science and Technology
Engineering Solid Mechanics | Year: 2013

The aim of the present work was to develop a guideline for approving the railway axles made of C35 steel and containing surface and/or in-body defects after manufacturing. First, several through and part-through circular cracks were modeled on the surface and in the body of the axle at its critical cross-section. Then, the permissible size of such cracks was determined by using the fracture mechanics. To verify the validity of the guideline, the theoretical result for the semi-circular surface crack was compared with the allowable size prescribed by the international railway standard. A very good agreement was found to exist between the predicted and the standard values. © 2013 Growing Science Ltd. All rights reserved.


Kaupp G.,University of Oldenburg | Naimi-Jamal M.R.,Iran University of Science and Technology
Scanning | Year: 2010

The analysis of published loading curves reveals the exponent 3/2 to the depth for nanoindentations with sharp pyramidal or conical tips. This has geometric reasons, as it occurs independent on the bonding states and indentation mechanisms. Nevertheless, most mathematical deductions and finite element simulations of nanomechanical parameters in the literature continue using the experimentally not supported Hertzian exponent 2. Therefore, numerous published loading curves of various authors are plotted using the experimental exponent 3/2 to present unbiased proof for its generality with metals, oxides, semiconductors, biomaterials, polymers, and organics. Linearity is independent of equipment and valid for load controlled, or depth controlled, or continuous stiffness, or AFM force measurements. The linearity with exponent 3/2 often extends from the nano- into the microindentation ranges. The tip rounding and taper influence of the "geometrical similar" indenters are discussed. When kinks occur in such linear plots through the origin, these indicate change of the materials' mechanical properties under pressure by phase transition. These events are discussed for nanoindentations with respect to the known hydrostatic transformation pressures that are, of course, always higher than the necessary indentation mean pressure. Numerous Raman, as well as X-ray and electron diffraction results from the literature support the phase transitions that are now easily detected. Nanoporous materials first fill the pores upon indentation. Published loading curves exhibit more information than hitherto assumed. Copyright © 2010 Wiley Periodicals, Inc.


Moazami D.,University Putra Malaysia | Behbahani H.,Iran University of Science and Technology | Muniandy R.,University Putra Malaysia
Expert Systems with Applications | Year: 2011

With regard to limits in budget, inevitably, one must choose prioritized projects in pavements rehabilitation and maintenance process. This paper looks into prioritization based upon a model including all effects of important factors like pavement condition index, traffic volume, road width as well as rehabilitation and maintenance cost. Since defining a model that introduces all those factors was difficult, a more advanced modeling named fuzzy logic was referred for the problem of prioritization. Although analytical hierarchy process can be used for decision making process as well, fuzzy modeling lets one have more precise choices for the outcome. Finally with the help of MATLAB software and coded M-files, inference engines such as Product engine, Dienes-Rescher and Lukasiewicz were all tested and the logical favorite separation for this application was found in product inference engine. As a case study some streets located in district No. 6 of Tehran municipality were selected and the favorite mathematical model was executed on those streets. This model was used for prioritizing these 131 sections. © 2010 Elsevier Ltd. All rights reserved.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Engineering Computations (Swansea, Wales) | Year: 2011

Purpose: Meta-heuristic methods are powerful in obtaining the solution of optimization problems. Hybridizing of the meta-heuristic algorithms provides a scope to improve the searching abilities of the resulting method. The purpose of this paper is to provide a new hybrid algorithm by adding positive properties of the particle swarm optimization (PSO) algorithms to the charged system search (CSS) to solve constrained engineering optimization problems. Design/methodology/approach: The main advantages of the PSO consisting of directing the agents toward the global best (obtained by the swarm) and the local best (obtained by the agent itself) are added to the CSS algorithm to improve its performance. In the present approach, similar to the original CSS, each agent is affected by other agents considering the governing laws of electrical physics. However, the kind of the forces can be repulsive and attractive. In order to handle the constraints, the fly-to-boundary method is utilized as an improved feasible-based method. Findings: Four variants of hybrid methods are proposed. In these algorithms, the charged memory (CM) is changed to save the local best positions of agents. Utilizing this new CM to determine the direction and amount of movement of agents improve the power of the algorithms. When only this memory is utilized (method I), exploitation ability of the algorithm increases and when only two agents from CM in addition to other agents in the current iteration are used, then the exploration ability increases (method II). In order to have a good balance between exploration and exploitation of the algorithms, methods III and IV are proposed, where some agents of the memory and some other from the current agents are utilized. Method IV in which the numbers of used agents from the CM increase linearly, has a better search ability in addition to a powerful exploitation making this variant superior compared to the others. Originality/value: In this paper, four hybrid methods are presented and applied to some benchmark engineering optimization problems. The new algorithms are compared to those of the other advanced meta-heuristic methods to illustrate the effectiveness of the proposed methods. © Emerald Group Publishing Limited 0264-4401.


Alinejad H.,Iran University of Science and Technology | Mamun A.A.,Jahangirnagar University
Physics of Plasmas | Year: 2011

The nonlinear propagation of the dust-acoustic waves is studied in a strongly coupled inhomogeneous dusty plasma which consists of the strongly correlated negatively charged dust grains and weakly correlated electrons and ions. The Korteweg-de Vries equation with variable coefficients and an additional term due to the density gradient is deduced, and its solution is found by appropriate transformations. The propagation of two possible modes (fast and slow) and their evolution are investigated. Only the fast rarefactive solitary waves are found to propagate in such plasma with parameter ranges corresponding to the experimental conditions. It is shown that the special patterns of nonlinear DA waves (e.g., amplitude and width) are significantly modified in a way that depends upon the effects of polarization force (which arises due to the interaction between thermal ions and highly negatively charged dust grains), effective dust-temperature (which arises from the electrostatic interactions among highly negatively charged dust and from the dust thermal pressure), equilibrium electron density, and ion temperature. The amplitude of solitary waves also decreases as the wave propagates in the direction of increasing dust concentration. © 2011 American Institute of Physics.


Moradi A.,Iran University of Science and Technology
Physics of Plasmas | Year: 2011

A theoretical analysis of ionic electrostatic excitations of a charged biological membrane is presented within the framework of the fluid theory for surface ions inside and outside the cell, in conjunction with the Poisson's equation. General expressions of dispersion relations are obtained for electrostatic oscillations of intrinsic cellular with different shapes and symmetries. © 2011 American Institute of Physics.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Structural and Multidisciplinary Optimization | Year: 2010

A new meta-heuristic optimization algorithm is presented for design of skeletal structures. The algorithm is inspired by the Coulomb and Gauss's laws of electrostatics in physics, and it is called charged system search (CSS). CSS utilizes a number of charged particle (CP) which affects each other based on their fitness values and separation distances considering the governing laws of Coulomb and Gauss from electrical physics and the governing laws of motion from the Newtonian mechanics. Some truss and frame structures are optimized with the CSS algorithm. Comparison of the results of the CSS with those of other meta-heuristic algorithms shows the robustness of the new algorithm. © 2009 Springer-Verlag.


Alinejad H.,Iran University of Science and Technology | Alinejad H.,Research Institute for Astronomy and Astrophysics of Maragha
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2011

The properties of arbitrary amplitude dust-acoustic (DA) solitary waves (SWs) in a dusty plasma containing warm adiabatic dust fluid, isothermal electrons and ions following flat-topped velocity distribution is studied by the pseudo-potential approach. The effects of dust temperature and flat-trapped ions are found to significantly modify the basic features of DA-SWs as well modify the parametric regime for the existence of rarefactive solitary waves. The pseudo-potential for small amplitude limit is also analytically analyzed, and the numerical results are found to agree with analytical results. © 2011 Elsevier B.V.


Yasa R.,Iran University of Science and Technology
Journal of Coastal Research | Year: 2011

Scour around submarine pipelines is an aspect that can influence the stability of them. Scour around the pipeline over an erodible bed under the wave conditions is studied in this paper. There have been several experimental investigations on scour depth. However, due to the complexity of the scour process, proposed formulas do not result accurately. In this study, an effort made to propose a new simple formula for predicting scour depth under submarine pipelines. At first it tried to collect a wide dataset, by gathering all previous experimental data. This dataset can increase the accuracy of proposing formulas. After that the effects of different parameters on scour depth have been investigated. Then, multiple regression analysis was used to develop a simple and accurate model for prediction of scour depth in both live bed and clear water conditions. Results show that the proposed models are simple and accurate in comparison with previous models.


Moradi A.,Iran University of Science and Technology | Moradi A.,Institute for Studies in Theoretical Physics and Mathematics IPM
Physics of Plasmas | Year: 2011

We apply the plasmon hybridization method to a double-nano-wire system, providing a simple and intuitive description of the plasmon excitations in the system. We apply the two-center cylindrical coordinate system for mathematical convenience and find an explicit form of the surface plasmon oscillations, in terms of the interaction between the bare plasmon modes of the individual surfaces of the nano-wires. We present numerical results to display how the plasmon excitations of the system depend on nano-wire separation when there is no angular momentum transfer, i.e., when m=f0. © 2011 American Institute of Physics.


Ghamary Asl M.,K. N. Toosi University of Technology | Mobasheri M.R.,K. N. Toosi University of Technology | Mojaradi B.,Iran University of Science and Technology
IEEE Transactions on Geoscience and Remote Sensing | Year: 2014

Feature/band selection is a common technique to overcome the 'curse of dimensionality' posed by the high dimensionality of hyperspectral imagery. When the image is characterized by unknown phenomena, an unsupervised approach can be utilized to select the most distinctive and informative bands. The efficiency of an unsupervised feature selection (FS) depends on the criteria to be optimized and the space (e.g., feature space, pixel space, spectral space, etc.) in which the data are represented. Moreover, the determination of the initial feature and the determination of the optimal feature size (the optimal number of distinct bands to be selected) are other challenges faced in unsupervised approaches. In this paper, we propose two unsupervised FS methods by representing bands in the prototype space (PS). The first method proposes a way for selecting the initial feature based on the orthogonal distance from the PS diagonal and determines the optimal feature size by employing the HySime algorithm in the PS. The second method uses two criteria defined by the tangent of the angles between the band vectors in the PS in order to select the initial feature and to describe the band correlations. Meanwhile, the determination of the optimal feature size is embedded in this method. The experimental results on real and synthetic data sets show that our methods are more reliable and can yield a better result in terms of class separability and Friedman test than other widely used techniques. © 2013 IEEE.


Moradi A.,Iran University of Science and Technology
Physics of Plasmas | Year: 2010

The theoretical analysis of electrostatic sound wave modes in multiwalled carbon nanotubes is presented within the framework of the fluid theory in conjunction with the Poisson's equation. The electron and ion components of each wall of nanotubes are regarded as two-species plasma system, in which the perturbed electron number density is deduced by means of the quantum hydrodynamic model, while the ion density perturbation follows the classical expression. An analytical expression of the dispersion relation is obtained for the quantum ion-acoustic wave oscillations in the system. Numerical result is prepared for a two-walled carbon nanotube, giving rise to a splitting of the frequencies of the electrostatic oscillations due to the small coupling between the two cylinders. © 2010 American Institute of Physics.


Kamranzad B.,Iran University of Science and Technology | Etemad-Shahidi A.,Griffith University | Chegini V.,Iranian National Institute for Oceanography
Ocean Engineering | Year: 2013

Since wave energy has the highest marine energy density in the coastal areas, assessment of its potential is of great importance. Furthermore, long term variation of wave power must be studied to ensure the availability of stable wave energy. In this paper, wave energy potential is assessed along the southern coasts of Iran, the Persian Gulf. For this purpose, SWAN numerical model and ECMWF wind fields were used to produce the time series of wave characteristics over 25 years from 1984 till 2008. Moreover, three points in the western, central and eastern parts of the Persian Gulf were selected and the time series of energy extracted from the modeled waves were evaluated at these points. The results show that there are both seasonal and decadal variations in the wave energy trends in all considered points due to the climate variability. There was a reduction in wave power values from 1990 to 2000 in comparison with the previous and following years. Comparison of wind speed and corresponding wave power variations indicates that a small variation in the wind speed can cause a large variation in the wave power. The seasonal oscillations lead to variation of the wave power from the lowest value in summer to the highest value in winter in all considered stations. In addition, the seasonal trend of wave power changed during the decadal variation of wave power. Directional variations of wave power were also assessed during the decadal variations and the results showed that the dominant direction of wave propagation changed in the period of 1990 to 2000 especially in the western station. © 2013 Elsevier Ltd.


Moradi A.,Iran University of Science and Technology | Moradi A.,Institute for Studies in Theoretical Physics and Mathematics IPM
Applied Optics | Year: 2010

We derived simple sets of equations to describe the microwave response of the magnetized hydrogen plasma slab embedded inside carbon nanotubes, which were grown by iron-catalyzed high-pressure disproportionation. These equations, which are useful when interference effects due to multiple reflections between plasma film interfaces are small, were used to analyze the reflection, absorption, and transmission coefficients of the magnetized hydrogen plasma slab. A discussion on the effects of the continuously changing external magnetic field and hydrogen plasma parameters on the reflected power, absorbed power, and transmitted power in the system is presented. © 2010 Optical Society of America.


Mollahasani A.,Ferdowsi University of Mashhad | Alavi A.H.,Iran University of Science and Technology | Gandomi A.H.,Tafresh University
Computers and Geotechnics | Year: 2011

New empirical models were developed to predict the soil deformation moduli using gene expression programming (GEP). The principal soil deformation parameters formulated were secant (Es) and reloading (E) moduli. The proposed models relate Es and Er obtained from plate load-settlement curves to the basic soil physical properties. The best GEP models were selected after developing and controlling several models with different combinations of the influencing parameters. The experimental database used for developing the models was established upon a series of plate load tests conducted on different soil types at depths of 1-24m. To verify the applicability of the derived models, they were employed to estimate the soil moduli of a part of test results that were not included in the analysis. The external validation of the models was further verified using several statistical criteria recommended by researchers. A sensitivity analysis was carried out to determine the contributions of the parameters affecting Es and Er. The proposed models give precise estimates of the soil deformation moduli. The Es prediction model provides considerably better results in comparison with the model developed for Er. The simplified formulation for Es significantly outperforms the empirical equations found in the literature. The derived models can reliably be employed for pre-design purposes. © 2010 Elsevier Ltd.


Moradi A.,Iran University of Science and Technology
Physics of Plasmas | Year: 2010

A theory of electromagnetic wave scattering by metallic single-walled carbon nanotubes at oblique incidence is provided using modal techniques. Electronic excitations on the nanotube's surface are modeled by an infinitesimally thin layer of free-electron gas described previously by means of the linearized fluid theory. The current induced on the surface of the nanotube and the echo width of both transverse magnetic and transverse electric uniform plane wave by system at oblique incidences is obtained. Numerical results show that the optical wave scattering by carbon nanotubes strongly depends on the nanotube's radius and angle of incidence wave with system. © 2010 American Institute of Physics.


Khaburi D.A.,Iran University of Science and Technology
IEEE Transactions on Instrumentation and Measurement | Year: 2012

In this paper, a new resolver-to-digital conversion method is presented. This method is based on synchronous demodulation of resolver's output signals. A modified angle-tracking observer is proposed to extract the rotor angle in high speeds as well as in low speeds. An estimation algorithm, which is based on the sign and absolute values of sine and cosine of the rotor angle, is introduced to find an appropriate initial value for this observer. This method can be incorporated in a DSP-based motor drive system. The proposed method is simple and cost effective when an appropriate microcontroller is selected for motor control. This method has been successfully implemented in a DSP board. Several tests at different speeds and initial positions have been performed to evaluate the proposed method. © 2012 IEEE.


The purpose of this study was to develop quantitative structure-activity relationship models for N-benzoylindazole derivatives as inhibitors of human neutrophil elastase. These models were developed with the aid of classification and regression trees (CART) and an adaptive neuro-fuzzy inference system (ANFIS) combined with a shuffling cross-validation technique using interpretable descriptors. More than one hundred meaningful descriptors, representing various structural characteristics for all 51 N-benzoylindazole derivatives in the data set, were calculated and used as the original variables for shuffling CART modelling. Five descriptors of average Wiener index, Kier benzene-likeliness index, subpolarity parameter, average shape profile index of order 2 and folding degree index selected by the shuffling CART technique have been used as inputs of the ANFIS for prediction of inhibition behaviour of N-benzoylindazole derivatives. The results of the developed shuffling CART-ANFIS model compared to other techniques, such as genetic algorithm (GA)-partial least square (PLS)-ANFIS and stepwise multiple linear regression (MLR)-ANFIS, are promising and descriptive. The satisfactory results (r2 p = 0.845, Q2 LOO= 0.861, r2 L25%O = 0.829, RMSELOO = 0.305 and RMSEL25%O = 0.336) demonstrate that shuffling CART-ANFIS models present the relationship between human neutrophil elastase inhibitor activity and molecular descriptors, and they yield predictions in excellent agreement with the experimental values. © 2012 Copyright Taylor and Francis Group, LLC.


Effective electro-oxidation of glucose is critically important in developing analytical sensors and carbohydrate-based fuel cells. In this study, a template-free ZSM-5 nanozeolite was synthesized hydrothermally with spherical particle diameters of 40-60 nm, as characterized by scanning electron microscopy. Then, a carbon paste electrode (CPE) was modified by multi-walled carbon nanotubes (MWCNTs), ZSM-5 nanozeolite and Ni2+ ions (Ni-MW-ZSM-5/CPE). Electrochemical studies of this electrode were performed using cyclic voltammetry which exhibits the redox behavior of the Ni(iii)/Ni(ii) couple in alkaline medium. This modified electrode was used as an anode for the electrocatalytic oxidation of glucose in 0.1 mol L-1 NaOH solution. The results confirmed that ZSM-5 nanozeolite at the surface of the CPE improved the catalytic efficiency of the dispersed nickel ions toward glucose oxidation. The values of electron transfer coefficient, electrode surface coverage and charge-transfer rate constant for Ni(iii)/Ni(ii) redox couple were found to be 0.65, 4.04 × 10-8 mol cm-2 and 0.184 s-1, respectively. Also, the diffusion coefficient and the mean value of the catalytic rate constant for glucose and redox sites of the electrode were found to be 1.66 × 10-4 cm2 s-1 and 1.136 × 108 cm3 mol-1 s-1, respectively. The sensor showed an acceptable linear range of 0.5-6.1 mM with a detection limit of 0.14 mM (S/N = 3) by cyclic voltammetry technique. Moreover, differential pulsed voltammetry method revealed a linear range of 0.0001-0.01 mM with a detection limit of 3.5 × 10-5 mM. Based on the results, the fabricated electrode (Ni-MW-ZSM-5/CPE) showed good catalytic activity, good stability, high sensitivity and reproducibility. © The Royal Society of Chemistry.


Hamdy M.S.,MESA Institute for Nanotechnology | Hamdy M.S.,Helwan University | Amrollahi R.,MESA Institute for Nanotechnology | Amrollahi R.,Iran University of Science and Technology | Mul G.,MESA Institute for Nanotechnology
ACS Catalysis | Year: 2012

A one-step synthesis procedure at elevated temperature was used to prepare Ti3+-containing blue titania. The prepared material was characterized by X-ray powder diffraction (XRD), UV-vis, Raman, and X-ray photoelectron spectroscopy (XPS), and N2 adsorption and desorption measurements. The blue titania sample was found to be crystalline, with a surface area of 22 m2/g. Its phase composition consists of 85% rutile and 15% anatase with a multitude of defect surface VO-Ti3+ sites. The blue titania showed an absorption red-shifted as compared to that of rutile, with a calculated bandgap of 2.93 eV. The photocatalytic performance of the blue titania was evaluated in the liquid phase selective photo-oxidation of methylcyclohexane (MCH) by illumination at 375 ± 10 nm (UV) and 425 ± 10 nm (visible light). The activity was monitored by attenuated total reflectance-Fourier transform infrared analysis. A high activity was observed for blue TiO2, remarkably equal in magnitude at both investigated wavelengths. The activity of the blue titania surpassed the activity of other (commercial) titania catalysts (rutile and P25), in particular at 425 nm, and the obtained selectivity for ketones was also greater. The activity data are discussed in relation to the properties of the three catalysts investigated, i.e., the texture, phase composition, and presence or absence of surface defects, of which the latter appears to be dominant in explaining the performance of the blue titania. © 2012 American Chemical Society.


Ostadrahimi L.,University of California at Davis | Marino M.A.,University of California at Davis | Afshar A.,Iran University of Science and Technology
Water Resources Management | Year: 2012

Reservoir operation rules are intended to help an operator so that water releases and storage capacities are in the best interests of the system objectives. In multi-reservoir systems, a large number of feasible operation policies may exist. System engineering and optimization techniques can assist in identifying the most desirable of those feasible operation policies. This paper presents and tests a set of operation rules for a multi-reservoir system, employing a multi-swarm version of particle swarm optimization (MSPSO) in connection with the well-known HEC-ResPRM simulation model in a parameterization-simulation-optimization (parameterization SO) approach. To improve the performance of the standard particle swarm optimization algorithm, this paper incorporates a new strategic mechanism called multi-swarm into the algorithm. Parameters of the rule are estimated by employing a parameterization-simulation-optimization approach, in which a full-scale simulation model evaluates the objective function value for each trial set of parameter values proposed with an efficient version of the particle swarm optimization algorithm. The usefulness of the MSPSO in developing reservoir operation policies is examined by using the existing three-reservoir system of Mica, Libby, and Grand Coulee as part of the Columbia River Basin development. Results of the rule-based reservoir operation are compared with those of HEC-ResPRM. It is shown that the real-time operation of the three reservoir system with the proposed approach may significantly outperform the common implicit stochastic optimization approach. © 2011 Springer Science+Business Media B.V.


Derakhshan S.,Iran University of Science and Technology | Mohammadi B.,Montpellier University | Nourbakhsh A.,University of Tehran
Computers and Fluids | Year: 2010

In the present work, a centrifugal pump impeller's blades shape was redesigned to reach a higher efficiency in turbine mode using two different optimization algorithms: one is a local method as incomplete sensitivities-gradient based optimization algorithm coupled by 3D Navier-Stokes flow solver, and another is a global method as Genetic algorithms and artificial neural network coupled by 3D Navier-Stokes flow solver. New impeller was manufactured and tested in the test rig. Comparison of the local optimization method results with the global optimization method results showed that the gradient based method has detected the global optimum point. Experimental results confirmed the numerical efficiency improvement in all measured points. This study illustrated that the developed gradient based optimization method is efficient for 3D radial turbomachinery blade optimization. © 2010 Elsevier Ltd.


Moradi A.,Iran University of Science and Technology | Moradi A.,Institute for Studies in Theoretical Physics and Mathematics IPM
Optics Communications | Year: 2010

Propagation of surface plasma waves in a metallic single-walled carbon nanotube that either is encapsulated in a solid metallic channel or encapsulates a metallic nanowire are studied within the framework of the classical electrodynamics. The linearized hydrodynamic theory is used to describe the electronic excitations on the nanotube's surface, while the dielectric function of dielectric media is modeled on the basis of the Drude approximation. It is shown that for all wavelengths, only the transverse magnetic wave with no angular dependence can propagate in these systems and the dispersion relations of this mode are obtained. © 2009 Elsevier B.V. All rights reserved.


Mashadi B.,Iran University of Science and Technology
IEEE Transactions on Vehicular Technology | Year: 2010

In this paper, an innovative power-split device (PSD) is introduced, and its application in a hybrid powertrain system is studied. The new PSD is a mechanism that allows operation in two different power-split modes through locking/unlocking of two clutches. In one mode, the PSD operates similar to a standard planetary gear unit, and in the other mode, it works the same as a compound planetary set. A well-known analogous system is the Toyota Hybrid System (THS) and is used for comparison purposes. It is demonstrated that by the new system, the transmission losses are reduced by a considerable extent, and thus, the efficiency is improved. A controller is designed based on fuzzy logic, which receives the battery state of charge (SOC), the vehicle speed, and the power that is requested at the wheels to coordinate each component in such a way as to optimize the entire system efficiency. A numerical optimization algorithm is applied to sustain the SOC in high regions and shift engine operating points to higher efficiency regions. Simulation results demonstrate notable improvements in fuel economy and performance characteristics. © 2006 IEEE.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Computers and Structures | Year: 2010

A novel optimization method is presented based on a socio-politically motivated strategy, called imperialist competitive algorithm (ICA). ICA is a multi-agent algorithm with each agent being a country, which is either a colony or an imperialist. These countries form some empires in the search space. Movement of the colonies toward their related imperialist, and imperialistic competition among the empires, form the basis of the ICA. During these movements, the powerful imperialists are reinforced and the weak ones are weakened and gradually collapsed, directing the algorithm towards optimum points. Here, the ICA is utilized to optimize the skeletal structures. © 2010 Elsevier Ltd. All rights reserved.


Maleki A.,Iran University of Science and Technology
Helvetica Chimica Acta | Year: 2014

A one-pot multicomponent synthesis of imidazo[1,2-a]pyridine derivatives by using pyridin-2-amines, aldehydes, and terminal alkynes in the presence of a catalytic amount of silica-supported iron oxide (Fe3O 4@SiO2) nanoparticles in refluxing EtOH in good-to-excellent yields is reported. Copyright © 2014 Verlag Helvetica Chimica Acta AG, Zürich.


Vahedi Nouri B.,Bu - Ali Sina University | Fattahi P.,Bu - Ali Sina University | Ramezanian R.,Iran University of Science and Technology
International Journal of Production Research | Year: 2013

Job scheduling and maintenance activities scheduling are two important issues in production management, which are often addressed separately. In this paper, the non-permutation flow shop scheduling problem with learning effects and flexible maintenance activities is studied. Each machine has a number of preventive maintenance activities that should be finished within specific time intervals. The aim is to simultaneously determine the sequence of jobs and the finish time of maintenance activities for minimising the sum of tardiness costs and maintenance costs. A mixed integer linear programming model is proposed to formulate the problem. Owing to the high complexity of the problem, an improvement heuristic method and a hybrid meta-heuristic algorithm based on the simulated annealing algorithm and firefly algorithm is presented to find nearly optimal solutions for medium and large problems. To obtain better and more robust solutions, the Taguchi method is used in order to calibrate the hybrid algorithm parameters. Finally, the computational results are provided for evaluating the performance and effectiveness of the proposed solution approaches. © 2013 Taylor and Francis.


Ramezanianpour A.A.,Amirkabir University of Technology | Ghahari S.A.,Amirkabir University of Technology | Esmaeili M.,Iran University of Science and Technology
Construction and Building Materials | Year: 2014

In this study microscopic and mechanical properties of ordinary concrete exposed to CO2 gas, saline water, and the combination of CO 2 gas and saline water were investigated by an accelerated test method. Specimens with different water to cement ratio of 0.35, 0.4, and 0.45 were retained in an apparatus which was developed to provide an environment to simulate tide cycles. The CO2 gas pressure, NaCl solution concentration, temperature, and relative humidity were kept constant and controlled, and tide cycles were executed automatically each 6 h. Specimens were retained in CO2 gas and in NaCl solution with environment characteristics tantamount to that of the apparatus. Microscopic structure and interfacial transition zones of the specimens maintained in all three conditions were studied by implementing scanning electron microscope (SEM). In order to identify crystalline phases and morphological and structural characteristics, nanographs were obtained by transmission electron microscopy (TEM), and phase change due to carbonation and chloride ion ingress were studied along with X-ray diffraction analysis (XRD). Moreover, in order to signify the mechanical properties of specimens, compressive strength, surface resistivity, and CO 2 consumption were measured. It was found that more C-S-H gel and CH crystals has been formed in the presence of sole CO2 gas, and higher compressive strength is achieved compared to the combined CO2 gas and chloride ion ingress, and separate saline water. Besides, due to the presence of moisture in the pore solution of specimens maintained in the combined condition, less CO2 gas and chloride ion ingresses were observed. © 2014 Elsevier Ltd. All rights reserved.


Taraghi I.,Semnan University | Fereidoon A.,Semnan University | Taheri-Behrooz F.,Iran University of Science and Technology
Materials and Design | Year: 2014

In this article, the low-velocity impact response of woven Kevlar/epoxy laminated composites enhanced with different weight percentages (≤1%) of multi-walled carbon nanotubes (MWCNTs), was investigated under ambient (27. °C) and low temperature (-40. °C) conditions. Energy profile diagrams (EPDs) were employed to determine the penetration threshold of Kevlar/epoxy laminated composites. In addition, the effect of MWCNTs on laminate composites was evaluated by subjecting all specimens to the same level of energy, 45 J. The time history of absorbed energy, deflection and velocity are measured and some parameters such as stiffness bending, penetration limit and maximum deflection, for both composites and nanocomposites at ambient and low temperatures are reported. Results showed a remarkable dependency of damage formation on temperature and contents of MWCNTs. It was concluded that the MWCNTs was improved the impact response and was restricted the damage size in the woven Kevlar fiber composites at ambient and low temperature. The addition of 0.5% MWCNTs resulted in about 35% increase in energy absorption at ambient temperature, and the addition of 0.3% MWCNTs increased the absorbed energy capability about 34% at low temperature. © 2013 Elsevier Ltd.


Talebitooti M.,Iran University of Science and Technology
Archive of Applied Mechanics | Year: 2013

This paper focuses on the free vibration analysis of thick, rotating laminated composite conical shells with different boundary conditions based on the three-dimensional theory, using the layerwise differential quadrature method (LW-DQM). The equations of motion are derived applying the Hamilton's principle. In order to accurately account for the thickness effects, the layerwise theory is used to discretize the equations of motion and the related boundary conditions through the thickness of the shells. Then, the equations of motion as well as the boundary condition equations are transformed into a set of algebraic equation applying the DQM in the meridional direction. This study demonstrates the applicability, accuracy, stability and the fast rate of convergence of the present method, for free vibration analyses of rotating thick laminated conical shells. The presented results are compared with those of other shell theories obtained using conventional methods and a special case where the angle of the conical shell approaches zero, that is, a cylindrical shell and excellent agreements are achieved. © 2012 Springer-Verlag Berlin Heidelberg.


Dashti R.,Iran University of Science and Technology | Yousefi S.,Tarbiat Modares University
Reliability Engineering and System Safety | Year: 2013

Asset management (AM) is composed of distribution system activities that lead to realize the system administration targets based on the stakeholders' benefits and correspondingly satisfying them. In this paper, asset management structure is represented and employing the AM structure, asset management processes are proposed. Furthermore, corresponding revisory actions are represented based on distribution asset wastages in order to structure a novel reliability based asset assessment model. The proposed model has been applied in a real distribution company, which provides 1 million customers with their requisite electrical energy. Crown Copyright © 2012 Publishedby Elsevier Ltd.All rights reserved.


Naderpour H.,Semnan University | Kheyroddin A.,Semnan University | Amiri G.G.,Iran University of Science and Technology
Composite Structures | Year: 2010

Strengthening and retrofitting of concrete columns by wrapping and bonding FRP sheets has become an efficient technique in recent years. Considerable investigations have been carried out in the field of FRP-confined concrete and there are many proposed models that predict the compressive strength which are developed empirically by either doing regression analysis using existing test data or by a development based on the theory of plasticity. In the present study, a new approach is developed to obtain the FRP-confined compressive strength of concrete using a large number of experimental data by applying artificial neural networks. Having parameters used as input nodes in ANN modeling such as characteristics of concrete and FRP, the output node was FRP-confined compressive strength of concrete. The idealized neural network was employed to generate empirical charts and equations for use in design. The comparison of the new approach with existing empirical and experimental data shows good precision and accuracy of the developed ANN-based model in predicting the FRP-confined compressive strength of concrete. © 2010 Elsevier Ltd.


Bagheri A.,University of Pittsburgh | Amini F.,Iran University of Science and Technology
Structural Control and Health Monitoring | Year: 2013

A new methodology for optimal control of structures under uniform hazard earthquake excitation has been presented in this study. The proposed method for generation of uniform hazard earthquake accelerograms is based on the sets of ground motions developed for the SAC Steel Project. The proposed controller employs the decomposing capabilities of wavelet analysis on uniform hazard earthquake accelerograms and the ability of the pattern search method to optimize a cost function to control response of structure. The performance and effectiveness of the presented method are applied to both single degree of freedom and multiple degree of freedom systems for the response control of uniform hazard earthquake-excited systems. The results are compared with the linear quadratic regulator control algorithm; performance of the proposed control system has been found to be better than the linear quadratic regulator controller. Copyright © 2012 John Wiley & Sons, Ltd.


Fazlpour B.,Islamic Azad University at Babol | Banijamali A.,Iran University of Science and Technology
Advances in High Energy Physics | Year: 2015

We study dynamics of generalized tachyon scalar field in the framework of teleparallel gravity. This model is an extension of tachyonic teleparallel dark energy model which has been proposed by Banijamali and Fazlpour (2012). In contrast with tachyonic teleparallel dark energy model that has no scaling attractors, here we find some scaling attractors which means that the cosmological coincidence problem can be alleviated. Scaling attractors are presented for both interacting and noninteracting dark energy and dark matter cases. © 2015 Behnaz Fazlpour and Ali Banijamali.


Mohammad Reza A.P.,Iran University of Science and Technology | Ali M.H.,University of South Carolina
Energy | Year: 2010

Voltage source inverter (VSI) can produce single and three-phase (3P) AC voltages from a constant or variable DC voltage. There are many ways to control the VSI output voltage. Each control way produces some harmonics at the VSI output voltage. The space vector pulse width modulation (SVPWM) may be more effective than other modulation methods, e.g. harmonic injection, phase shifting, multi career pulse width modulation, in decreasing the low order harmonics (LOH). Different switching strategies (SSs) of power electronic devices in SVPWM have some specific advantages and disadvantages with regard to one another. In this paper, a comparative study between different SVPWM SSs is carried out by considering some objective functions such as total harmonic distortion (THD), power and switching losses, the ratio of the harmonic components to the fundamental component, distortion factor (DF). It is also shown that by selecting an optimized and appropriate SS for SVPWM, the harmonic orders, which are the multiples of the frequency index (FI), are eliminated. Then, to investigate the impact of variations of the capacitors voltage and switching frequency on power quality criteria, the most appropriate and optimized SS is applied to a 3P three-level (3L) neutral-point-clamped (NPC) VSI to supply a 3P load.This paper also presents a novel and optimized SS and control approach for a 3L two-quadrant (2Q) chopper in NPC VSI superconducting magnetic energy storage (SMES). Using the proposed SS, the voltage of the VSI capacitors in SMES can be independently controlled; also, the minimum power and switching losses - as well as the proper convection - can be achieved using this same strategy. The simulation results indicate that when combined with a proportional-integral (PI) control approach the proposed SS can be easily implemented in the power networks and can balance and stabilize the multi-level VSIs' capacitor voltage level. The voltage variation of the capacitors in the steady state condition is less than (0.062%) which is 15 times better than the IEEE standard requirement (1%). To investigate the effectiveness and reliability of the proposed approach in stabilizing capacitor voltage, SMES performance using the presented approach is compared with that of SMES when the capacitors of the 3L VSI are replaced with equal and ideal voltage sources. This comparison is carried out from the power quality point of view and it is shown that the proposed SS with a PI controller is highly reliable. © 2010 Elsevier Ltd.


Tolaminejad B.,Iran University of Science and Technology | Dehghani K.,University of Tehran
Materials and Design | Year: 2012

In the present research, equal channel angular extrusion (ECAE) of commercial purity aluminum (1070) was conducted using route BC. For ECAE processing a proper die set was designed and constructed. Electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) analyses were used to evaluate the microstructure and texture of the extruded materials. The results reveal two distinct processing regimes: from 1 to 4 passes the microstructure evolves from elongated subgrains to a rather equiaxed array of ultrafine grains and from 4 to 8 passes there is no strict change in the average grain size. The boundary misorientation angle and the fraction of high-angle boundaries increase rapidly up to 4 passes and at a slower rate from 4 to 8 passes. Also, the variation of hardness and yield stress with number of extrusion was documented up to 8 passes. The present results showed that first ECAE pass has resulted in enhancement of mechanical properties more than four times over the annealed condition. Further ECAE processing has resulted in slight improvement. Based on two strengthening mechanisms, variations of the strength as a function of the pass numbers were related to the calculated dislocation densities and the average boundary spacing. © 2011 Elsevier Ltd.


Kaveh A.,Iran University of Science and Technology | Shakouri Mahmud Abadi A.,Building Research Institute, Egypt
Journal of Constructional Steel Research | Year: 2010

In this study, cost optimization of a composite floor system is performed utilizing the harmony search algorithm and an improved harmony search algorithm. These algorithms imitate the musical performance process that takes place when a musician searches for a better state of harmony, similar to the optimum design process which looks for the optimum solution. A composite floor system is designed by the LRFD-AISC method, using a unit consisting of a reinforced concrete slab and steel beams. The objective function is considered as the cost of the structure, which is minimized subjected to serviceability and strength requirements. Examples of composite floor systems are presented to illustrate the performance of the presented algorithms. © 2010 Elsevier Ltd. All rights reserved.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Journal of Constructional Steel Research | Year: 2010

An optimum topology design algorithm based on the hybrid Big Bang-Big Crunch optimization (HBB-BC) method is developed for the Schwedler and ribbed domes. A simple procedure is defined to determine the Schwedler and ribbed dome configuration. This procedure includes calculating the joint coordinates and element constructions. The nonlinear response of the dome is considered during the optimization process. The effect of diagonal members on the results is investigated and the optimum results of Schwedler domes obtained by the HBB-BC method demonstrate the efficiency of these domes to cover large areas without intermediate supports. © 2009 Elsevier Ltd. All rights reserved.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Journal of Constructional Steel Research | Year: 2010

Grillage systems are widely used in structures to cover large areas in bridge decks, ship hulls and floors. In this paper, the charged system search (CSS) algorithm is utilized to obtain the optimum design of grillage systems. This algorithm is inspired by the Coulomb and Gauss laws of electrostatics in physics and the governing laws of motion from Newtonian mechanics. The cross-sectional properties of beams are considered as the design variables. Comparison of the results with those of some previous studies shows the robustness of the new algorithm. © 2010 Elsevier Ltd. All rights reserved.


Soltanpour M.R.,Iran University of Science and Technology | Khooban M.H.,Islamic Azad University
Nonlinear Dynamics | Year: 2013

In this paper, an optimal fuzzy sliding mode controller is used for tracking the position of robot manipulator, is presented. In the proposed control, initially by using inverse dynamic method, the known sections of a robot manipulator's dynamic are eliminated. This elimination is done due to reduction over structured and unstructured uncertainties boundaries. In order to overcome against existing uncertainties for the tracking position of a robot manipulator, a classic sliding mode control is designed. The mathematical proof shows the closed-loop system in the presence of this controller has the global asymptotic stability. Then, by applying the rules that are obtained from the design of classic sliding mode control and TS fuzzy model, a fuzzy sliding mode control is designed that is free of undesirable phenomena of chattering. Eventually, by applying the PSO optimization algorithm, the existing membership functions are adjusted in the way that the error tracking robot manipulator position is converged toward zero. In order to illustrate the performance of the proposed controller, a two degree-of-freedom robot manipulator is used as the case study. The simulation results confirm desirable performance of optimal fuzzy sliding mode control. © 2013 Springer Science+Business Media Dordrecht.


Kaveh A.,Iran University of Science and Technology | Tolou Kian M.J.,Building Research Institute, Egypt
Acta Mechanica | Year: 2013

This paper introduces an efficient method for the finite element analysis of models comprised of higher order triangular elements. The presented method is based on the force method and benefits graph theoretical transformations. For this purpose, minimal subgraphs of predefined special patterns are selected. Self-equilibrating systems are then constructed on these subgraphs leading to sparse and banded null basis. Finally, well-structured flexibility matrices are formed for efficient finite element analysis. © 2013 Springer-Verlag Wien.


Dargahi V.,Iran University of Science and Technology | Dargahi S.,University of Tabriz
IET Power Electronics | Year: 2013

This study proposes a mathematical model for stacked multicell (SM) converters (SMCs), to be exploited in the analytic determination of the natural voltage balancing dynamics of the SMCs, that is, investigation of the start-up behaviour, dynamic response and natural voltage balancing phenomenon. The crux of the proposed strategy is based on the closed-form analytic solution derivation for the switching functions used in the switching of the SMCs operated under phase disposition (PD) and phase-shifted carrier (PSC) pulse-width modulation (PD-PSC-PWM) technique. Hence, the suggested approach develops an analytic solution for the Fourier series and associated Fourier coefficients pertinent to the switching functions of the SMCs by obtaining the switching instants of the PD-PSC-PWM modulator in terms of -Kapteyn series- when the frequency of the triangular carrier waveform (fc) and that of the sinusoidal reference waveform (fr) have an integer ratio, that is, fcfr -1 = k, kεN{double struck}. This strategy results into a model ('first-order differential equation based model') which can be readily developed for the SMCs with any number of levels expediting the investigation of their performance. Numeric computation results of the proposed analytic model for the SMCs and simulation results as well as measurements taken from an experimental set-up are presented in order to validate the suggested approach and derived model.©The Institution of Engineering and Technology 2013.


Rikhtegar F.,Iran University of Science and Technology | Ketabchi M.,Amirkabir University of Technology
Materials and Design | Year: 2010

The thixoextrusion process is a new method for manufacturing complicated and net shape components through which high strength materials can be formed more easily. In this study 7075 Al alloy which has low extrudability has been thixoformed by forward extrusion process. As it is known conventional extrusion of 7075 Al alloy has been very difficult due to high strength and multi-phase microstructural characterization. In this research, by applying the advantages of semisolid processing, the applied pressure for extrusion is decreased and desired mechanical properties were reached near the standard predictable properties for wrought 7075 Al alloy under T6 tempering conditions, for example tensile and yield strength and hardness of samples of thixoextrusion product sufficiently agree with same expected properties of wrought 7075 Al alloy and only elongation is decreased along this process. © 2010 Elsevier Ltd.


Gandomi A.H.,Highest Prestige Scientific and Professional National Foundation | Alavi A.H.,Iran University of Science and Technology | Sahab M.G.,Tafresh University
Materials and Structures/Materiaux et Constructions | Year: 2010

This paper proposes a new approach for the formulation of compressive strength of carbon fiber reinforced plastic (CFRP) confined concrete cylinders using a promising variant of genetic programming (GP) namely, linear genetic programming (LGP). The LGP-based models are constructed using two different sets of input data. The first set of inputs comprises diameter of concrete cylinder, unconfined concrete strength, tensile strength of CFRP laminate and total thickness of utilized CFRP layers. The second set includes unconfined concrete strength and ultimate confinement pressure which are the most widely used parameters in the CFRP confinement existing models. The models are developed based on experimental results collected from the available literature. The results demonstrate that the LGP-based formulas are able to predict the ultimate compressive strength of concrete cylinders with an acceptable level of accuracy. The LGP results are also compared with several CFRP confinement models presented in the literature and found to be more accurate in nearly all of the cases. Moreover, the formulas evolved by LGP are quite short and simple and seem to be practical for use. A subsequent parametric study is also carried out and the trends of the results have been confirmed via some previous laboratory studies. © RILEM 2009.


Bolouri A.,Pusan National University | Shahmiri M.,Iran University of Science and Technology | Kang C.G.,Pusan National University
Journal of Alloys and Compounds | Year: 2011

The effects of compression ratios on the microstructure evolution of semisolid Al7075 alloy produced by the strain induced melt activation (SIMA) process were investigated. The samples were cold deformed by compression into the different heights up to 40% reduction. The isothermal holding treatments within mushy zone of the alloy were carried out at 610, 620 and 625 °C for predetermined time intervals. The results revealed that the average grain size gradually reduced with the increase in the compressive ratio. While the compressive ratio surpassed 30%, the descending trend above was not as evident as that of below 30% reduction. The optimum condition presenting the minimum grain size and the maximum shape factor with the highest uniformity is discussed. During the subsequent mushy zone heating, the recrystallization was induced in the deformed samples by the increasingly accumulated strain energy. © 2010 Elsevier B.V. All rights reserved.


Hosseini S.H.,Islamic Azad University at Tehran | Mohseni S.H.,Iran University of Science and Technology | Asadnia A.,Imam Hossein University | Kerdari H.,Islamic Azad University at Saveh
Journal of Alloys and Compounds | Year: 2011

Conductive polyaniline (PANi)-manganese ferrite (MnFe2O 4) nanocomposites with core-shell structure were synthesized by in situ polymerization in the presence of dodecyl benzene sulfonic acid (DBSA) as the surfactant and dopant and ammonium persulfate (APS) as the oxidant. The structure and magnetic properties of manganese ferrite nanoparticles were measured by using powder X-ray diffraction (XRD) and vibrating sample magnetometer (VSM), respectively. Its morphology, microstructure and DC conductivity of the nanocomposite were characterized by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR) and four-wire-technique, respectively. The microwave absorbing properties of the nanocomposite powders dispersing in resin acrylic coating with the coating thickness of 1.4 mm were investigated by using vector network analyzers in the frequency range of 8-12 GHz. A minimum reflection loss of -15.3 dB was observed at 10.4 GHz. © 2010 Elsevier B.V. All rights reserved.


Moradi A.,Iran University of Science and Technology | Moradi A.,Institute for Studies in Theoretical Physics and Mathematics IPM
Solid State Communications | Year: 2014

We study the extinction spectra of an isolated C60 molecule, within the framework of the vector wave function method. Electronic excitations on the C60 molecule surface are modeled by an infinitesimally thin spherical layer of the σ and π electrons, which is described by means of the two-dimensional two-fluid model. Numerical results show that a strong interaction between the fluids gives rise to the splitting of the extinction spectra into two peaks in a quantitative agreement with the π and σ+π plasmon energies. © 2014 Elsevier Ltd.


Sarkar A.,Iran University of Science and Technology
International Journal of Pavement Engineering | Year: 2015

A three-dimensional finite element model was utilised to examine the flexible pavement dynamic response under single, tandem and tridem axles at different speeds. Using two different hot-mix asphalt (HMA) layer thicknesses, 15.2 and 25.4 cm, the dynamic effects of moving axles were investigated on critical responses. These responses include the tensile strain at the bottom of asphalt layer, compressive strain on the top of subgrade and tensile and compressive strain on the surface layer. In this study, the HMA layer and other layers were characterised as linear viscoelastic and elastic material, respectively. Since this research focuses specifically on the time and dynamic effects, considering the transient dynamic loading and inertia forces, implicit dynamic analysis was done. The important findings are as follows. (1) Strains induced by tridem axles could be greater than tandem axles or even equal at different speeds. (2) It cannot be stated that axles always induce greater critical response value to road systems at lower speed because at higher speed they can also induce greater critical response value in pavements than that at lower speed. (3) Changing trend and changing rate of strains with speed are strongly affected by pavement thickness. In general, the effects of different axle configurations are strongly affected by moving speed and surface layer thickness. © 2015 Taylor & Francis


Eivani A.R.,Iran University of Science and Technology
Materials Letters | Year: 2015

Pure shear extrusion (PSE) is introduced as a new technique for severe plastic deformation of metals and alloys. In PSE, a sample with square cross section deforms to a rhombic alongside the diagonals and then, reversed back to its initial shape. The efficiency of pure shear for grain refinement is demonstrated by investigating the microstructure of two aluminum alloys, i.e., AA1050 and AA6063, after PSE. Formation of nanosized cell structures is resolved in both alloys. The percentage of high angle boundaries is found to be greater for the case of AA6063 alloy when compared to AA1050. © 2014 Elsevier B.V. All rights reserved.


Radmanesh H.,Iran University of Science and Technology
International Review on Modelling and Simulations | Year: 2010

Ferroresonance or nonlinear resonance is a complex electrical phenomenon, which may cause over voltages and over currents in the electrical power system which endangers the system reliability and continuous safe operating. The ability to predict or confirm ferroresonance depends primarily on the accuracy of the transformer model used by the computer simulation. An overview of available literature and contributors to this area is provided. This paper studies the effect of circuit breaker shunt resistance on the controlling chaotic ferroresonance in a voltage transformer while the core losses of the voltage transformer core are highly nonlinear. It is expected that this resistance generally can cause ferroresonance 'dropout'. For confirmation this aspect Simulation has been done on a one phase voltage transformer rated 100VA, 275kV. The magnetization characteristic of the transformer is modeled by a single-value two-term polynomial with q=7. The simulation results reveal that considering the shunt resistance on the circuit breaker in the case of nonlinear core losses, exhibits a great mitigating effect on ferroresonance over voltages. Significant effect on the onset of chaos, the range of parameter values that may lead to chaos along with ferroresonance over voltages has been obtained and presented. © 2010 Praise Worthy Prize S.r.l. - All rights reserved.


Kashani A.T.,Iran University of Science and Technology
Journal of injury & violence research | Year: 2012

Iran is a country with one of the highest rates of traffic crash fatality and injury, and seventy percent of these fatalities happen on rural roads. The objective of this study is to identify the significant factors influencing injury severity among drivers involved in crashes on two kinds of major rural roads in Iran: two-lane, two-way roads and freeways. According to the dataset, 213569 drivers were involved in rural road crashes in Iran, over the 3 years from 2006 to 2008. The Classification And Regression Tree method (CART) was applied for 13 independent variables, and one target variable of injury severity with 3 classes of no-injury, injury and fatality. Some of the independent variables were cause of crash, collision type, weather conditions, road surface conditions, driver's age and gender and seat belt usage. The CART model was trained by 70% of these data, and tested with the rest. It was indicated that seat belt use is the most important safety factor for two-lane, two-way rural roads, but on freeways, the importance of this variable is less. Cause of crash, also turned out to be the next most important variable. The results showed that for two-lane, two-way rural roads, "improper overtaking" and "speeding", and for rural freeways, "inattention to traffic ahead", "vehicle defect", and "movement of pedestrians, livestock and unauthorized vehicles on freeways" are the most serious causes of increasing injury severity. The analysis results revealed seat belt use, cause of crash and collision type as the most important variables influencing the injury severity of traffic crashes. To deal with these problems, intensifying police enforcement by means of mobile patrol vehicles, constructing overtaking lanes where necessary, and prohibiting the crossing of pedestrians and livestock and the driving of unauthorized vehicles on freeways are necessary. Moreover, creating a rumble strip on the two edges of roads, and paying attention to the design consistency of roads can be a helpful factor in order to prevent events such as "overturning" and improve the overall safety of freeways.


Sattari F.,University of Mohaghegh | Faizabadi E.,Iran University of Science and Technology
Solid State Communications | Year: 2014

We investigate the spin transport properties of magnetic graphene superlattice in the presence of Rashba spin-orbit interaction (RSOI). We consider two types of magnetic profiles: a sequence of N square magnetic barriers and a sequence of delta magnetic barriers. In the first case it is found that the angular range of the spin transmission through magnetic graphene superlattice can be efficiently controlled by the number of barriers and this renders the structure's efficient wavevector-dependent spin filters. As the number of magnetic barriers increases, the angular range of the spin transmission decreases, the gaps in transmission and conductivity versus energy become wider. In the second case, when the magnetic field is present, the spin polarization increase with increasing the magnetic field. In both cases, the magnetoresistance ratio shows a strong dependence on the number of magnetic barriers. © 2013 Elsevier Ltd.


Bahiraei M.,Kermanshah University of Technology | Hosseinalipour S.M.,Iran University of Science and Technology
Journal of Dispersion Science and Technology | Year: 2013

Convective heat transfer characteristics of water/Al2O3 nanofluid flow inside a tube were evaluated in this study. A non-uniform concentration distribution was used in thermal dispersion model. Meanwhile, an experimental study was done to find the dispersion coefficient in addition to assess the accuracy of simulation results. The accuracy of the results of thermal dispersion model was compared with the numerical solution using discrete phase modeling and homogenous method, while the effective parameters on particle migration were considered to find the particle distribution for being used in the dispersion model. Non-uniformity of the particle distribution is increased by raising volume fraction and Reynolds number. Concentration distribution was obtained using discrete phase method and was compared with the distribution employed for the dispersion model. When a uniform concentration is used in the dispersion model, error of prediction is expected to be increased. The thermal dispersion model, in which the particles have followed a non-uniform distribution, provides acceptable results in spite of its lower calculational time as compared to the two-phase approach. © 2013 Copyright Taylor and Francis Group, LLC.


Nikazad T.,Iran University of Science and Technology | Davidi R.,Stanford University | Herman G.T.,City University of New York
Inverse Problems | Year: 2012

We study the convergence of a class of accelerated perturbation-resilient block-iterative projection methods for solving systems of linear equations. We prove convergence to a fixed point of an operator even in the presence of summable perturbations of the iterates, irrespective of the consistency of the linear system. For a consistent system, the limit point is a solution of the system. In the inconsistent case, the symmetric version of our method converges to a weighted least-squares solution. Perturbation resilience is utilized to approximate the minimum of a convex functional subject to the equations. A main contribution, as compared to previously published approaches to achieving similar aims, is a more than an order of magnitude speed-up, as demonstrated by applying the methods to problems of image reconstruction from projections. In addition, the accelerated algorithms are illustrated to be better, in a strict sense provided by the method of statistical hypothesis testing, than their unaccelerated versions for the task of detecting small tumors in the brain from x-ray CT projection data. © 2012 IOP Publishing Ltd.


Mahmoudabadi A.,University of Tehran | Seyedhosseini S.M.,Iran University of Science and Technology
IATSS Research | Year: 2014

The present paper proposes an iterative procedure based on chaos theory on dynamic risk definition to determine the best route for transporting hazardous materials (Hazmat). In the case of possible natural disasters, the safety of roads may be seriously affected. So the main objective of this paper is to simultaneously improve the travel time and risk to satisfy the local and national authorities in the transportation network. Based on the proposed procedure, four important risk components including accident information, population, environment, and infrastructure aspects have been presented under linguistic variables. Furthermore, the extent analysis method was utilized to convert them to crisp values. To apply the proposed procedure, a road network that consists of fifty nine nodes and eighty two-way edges with a pre-specified affected area has been considered. The results indicate that applying the dynamic risk is more appropriate than having a constant risk. The application of the proposed model indicates that, while chaotic variables depend on the initial conditions, the most frequent path will remain independent. The points that would help authorities to come to the better decision when they are dealing with Hazmat transportation route selection. © 2013 International Association of Traffic and Safety Sciences.


Karimi-Nasab M.,Islamic Azad University at Tehran | Sabri-Laghaie K.,Iran University of Science and Technology
International Journal of Production Research | Year: 2014

This paper formulates a new imperfect production problem that generates defectives randomly. The production manager conducts total inspections to screen defectives (including reworkable and non-reworkable items) from non-defectives. But, the inspection is error-prone due to different sources. The model determines rates of main and rework processes, batch size and backlog. As the model is a nonlinear programme and it is difficult to obtain an algebraic closed-form solution, three randomised approximation algorithms are developed. Under certain conditions, the algorithms can find the global optimum in polynomial time. Finally numerical analyses are reported. © 2013 Taylor & Francis.


Herein, Alliphis geotrupes Ishikawa, 1979 is transferred to the genus Scarabacariphis Mašán, 1994 because of its free peritrematal shield (i.e. separated from the dorsal shield). The genus Scarabacariphis is redefined, and a key to the species of Scarabacariphis is provided, as well as additional morphological information for Scarabacariphis geotrupes comb. nov. © Kazemi S. et al.


Samavati V.,Iran University of Science and Technology
Carbohydrate Polymers | Year: 2013

Crude polysaccharide extraction from the Iranian Abelmoschus esculentus was performed using water decoction. Response surface methodology (RSM), based on a five level, four variable central composite rotatable design (CCRD), was employed to obtain the best possible combination of extraction time (X 1: 0.5-6.5 h), extraction temperature (X2: 80-100 °C), number of extraction (X3: 1-5), and water to the raw material ratio (X4: 4-28) for maximum polysaccharide extraction. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis and also analyzed by appropriate statistical methods (ANOVA). The optimum extraction conditions were as follows: extraction time of 4.94 h, extraction temperature of 94.97 °C, number of extraction of 4, and the ratio of water to raw material of 21.74. Under these conditions, the experimental yield was 16.895 ± 0.29%, which is well in close agreement with the value predicted by the model 16.916%. © 2013 Elsevier Ltd.


Samavati V.,Iran University of Science and Technology | Manoochehrizade A.,Islamic Azad University at Ahvaz
International Journal of Biological Macromolecules | Year: 2013

The effects of extraction temperature, extraction time, the ratio of water to raw material, and number of extraction on extraction yield of crude polysaccharides from the leaves of Malva sylvestris (MSLCP) were optimized by statistical analysis using response surface methodology. The response surface methodology (RSM) was used to optimize MSLCP extraction yield by implementing the CCD design. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis and also analyzed by appropriate statistical methods (ANOVA). Statistical analysis of the results showed that the linear and quadratic terms of these four variables had significant effects. The optimal conditions for higher extraction yield of MSLCP were extraction temperature: 90. °C, extraction time: 4. h, number of extraction: 2 and the ratio of water to raw material: 21. Under these conditions, the experimental yield was 8.377. ±. 0.38%, which is well in close agreement with the value predicted by the model 8.608%. The results demonstrated that MSLCP had strong scavenging activities in vitro on DPPH and hydroxyl radicals. Overall, MSLCP may have potential applications in the medical and food industries. © 2013 Elsevier B.V.


Taravati S.,Iran University of Science and Technology
Journal of Electromagnetic Waves and Applications | Year: 2012

In this article, a method to miniaturize the broadband rat-race couplers using microstrip nonuniform transmission lines (MNTLs) is presented. The proposed coupler features a compact size on a single circuit layer structure without reactive components and via-holes. The design formulas are developed using ABCD matrix and even-odd mode analysis. The theoretical analysis has been verified by measurement of the manufactured broadband MNTL rat-race coupler with center frequency of 1.35 GHz and 89% fractional bandwidth. The isolation, magnitude, imbalance and phase imbalance are less than -20 dB, 0.5 dB, and 4 degrees, respectively, within 0.75-1.95 GHz frequency bandwidth. © 2012 Taylor & Francis.


Moghaddam S.,Iran University of Science and Technology
International Journal of Applied Electromagnetics and Mechanics | Year: 2012

An analytical solution is found for equations of AC and DC-operated MHD micropump with circular channel. The kind of fluid is Newtonian and the flow generated by the Lorentz force is assumed to be laminar, unidirectional, and one-dimensional. The effect of Hartman number and radius is studied on the velocity and volumetric flow rate profiles and a relation for optimum Hartman number and radius which causing maximum volumetric flow rate is found. Finally DC-operated MHD micropump is compared with AC-operated. © 2012-IOS Press and the authors. All rights reserved.


Hashemi S.M.,Aalto University | Hashemi S.M.,Iran University of Science and Technology | Nefedov I.S.,Aalto University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

In this paper we discuss an interesting property of arrays of metallic carbon nanotubes, namely, the capability of perfect absorption in optically ultrathin layers. The carbon nanotube array is used in a regime where it possesses properties of a uniaxial indefinite medium. We show that if the optical axis is tilted with respect to an interface, a plane incident wave propagates inside a finite-thickness slab of the carbon nanotube array with a very small wavelength and small material losses cause the total wave absorption. We demonstrate that perfect matching with free space can be achieved in an optically ultrathin layer without a magnetic response and when the reflected wave is absent. Nonsymmetry appearing as a difference between wave numbers of waves propagating upward and downward with respect to the interface under oblique incidence leads to the absence of a thickness resonance. © 2012 American Physical Society.


Banijamali A.,Iran University of Science and Technology
Advances in High Energy Physics | Year: 2014

We consider a tachyon scalar field which is nonminimally coupled to gravity in the framework of teleparallel gravity. We analyze the phase-space of the model, known as tachyonic teleparallel dark energy, in the presence of an interaction between dark energy and background matter. We find that although there exist some late-time accelerated attractor solutions, there is no scaling attractor. So, unfortunately interacting tachyonic teleparallel dark energy cannot alleviate the coincidence problem. © 2014 Ali Banijamali.


Salamat-Talab M.,Iran University of Science and Technology | Nateghi A.,University of Tehran | Torabi J.,Amirkabir University of Technology
International Journal of Mechanical Sciences | Year: 2012

In this paper, Modified couple stress theory is developed for third-order shear deformation functionally graded (FG) micro beam. Classical Continuum theories are not able to capture size effects while higher order continuum theories consider material length scale parameters to improve the results in micro scales by interpreting size dependencies. By applying Hamilton's principle, governing equations, boundary and initial conditions are derived for a FG micro beam. It is assumed that properties of the FG micro beam follow a power law form through thickness. In addition, Poisson's ratio is assumed constant in the current model. Bending and free vibration of the simply supported FG micro beam is analyzed to illustrate size effects. It is observed that if the thickness of the beam is in the order of the material length scale parameter, size effects are more considerable. It is shown that size dependencies of FG micro beams are quite different from isotropic homogeneous beams as they have maximum and minimum size effects for certain values of power index of material distribution and Poisson's ratio. Moreover, it is shown that the results obtained by the present model deviates significantly from those in which Poissons effect is neglected. Also, the effect of Poisson's ratio on the deflection and natural frequency based on modified couple stress theory is proven to be different from Classical one. The numerical results for simply supported thin beams show that the first natural frequency estimated by the current model is higher than the classical one. In addition, it is observed that size effect is more significant for higher vibration modes. © 2012 Elsevier Ltd. All rights reserved.


Atashgar K.,Iran University of Science and Technology
International Journal of Advanced Manufacturing Technology | Year: 2013

When a control chart addresses an out-of-control condition, a root-cause analysis should be started to identify and eliminate the special cause(s) of variation manifested in the process. The change point refers to the time when a special cause(s) takes place in the process and leads it to a departure from the in-control condition to an out-of-control condition. Identification of the change point is considered as an essential step for a root-cause analysis in both univariate and multivariate processes. If a change manifests in a normally distributed process mean, variance, or both, then the change point should be identified in the process mean, variance, or both, respectively. This paper attempts to comprehensively review the researches that considered the mean change point in different environment corresponding to univariate and multivariate normal processes. © 2012 Springer-Verlag London Limited.


Khooban M.H.,Islamic Azad University at Garmsar | Soltanpour M.R.,Iran University of Science and Technology
Journal of Intelligent and Fuzzy Systems | Year: 2013

This paper provides an optimal controlling approach for a class of nonlinear systems with structured and unstructured uncertainties using fuzzy sliding mode control. First known dynamics of the system are eliminated through feedback linearization and then optimal fuzzy sliding mode controller is designed using an intelligent fuzzy controller based on Sugeno-Type structure. The proposed controller is optimized by a novel heuristic algorithm namely Particle Swarm Optimization with random inertia Weight (RNW-PSO). In order to handle, the uncertainties Lyapunov method is used. There are no signs of the undesired chattering phenomenon in the proposed method. The globally asymptotic stability of the closed-loop system is mathematically proved. Finally, this control method is applied to the inverted pendulum system as a case study. Simulation results show desirability of the system performance. © 2013-IOS Press and the authors. All rights reserved.


Ashtari A.H.,National University of Malaysia | Nordin M.J.,National University of Malaysia | Fathy M.,Iran University of Science and Technology
IEEE Transactions on Intelligent Transportation Systems | Year: 2014

In this paper, an Iranian vehicle license plate recognition system based on a new localization approach, which is modified to reflect the local context, is proposed, along with a hybrid classifier that recognizes license plate characters. The method presented here is based on a modified template-matching technique by the analysis of target color pixels to detect the location of a vehicle's license plate. A modified strip search enables localization of the standard color-geometric template utilized in Iran and several European countries. This approach uses periodic strip search to find the hue of each pixel on demand. In addition, when a group of target pixels is detected, it is analyzed to verify that its shape and aspect ratio match those of the standard license plate. In addition to being scale and rotation invariant, this method avoids time-consuming image algorithms and transformations for the whole image pixels, such as resizing and Hough, Fourier, and wavelet transforms, thereby cutting down the detection response time. License plate characters are recognized by a hybrid classifier that comprises a decision tree and a support vector machine with a homogeneous fifth-degree polynomial kernel. The performance detection rate and the overall system performance achieved are 96% and 94%, respectively. © 2014 IEEE.


Moghimi H.,Iran University of Science and Technology | Ahmadi A.,Islamic Azad University | Aghaei J.,Shiraz University of Technology | Rabiee A.,Shahrekord University
International Journal of Electrical Power and Energy Systems | Year: 2013

The environmental advantage of distributed energy resources (DERs) application has attracted lots of research attention and encouraged to implement clean power producers. In spite of the environmental benefits of renewable energy sources application as distributed power generation, the variability of renewable energy, e.g. wind power uncertainty, can potentially endanger the operation of electric power system. This paper presents a new techno-economic factor (TEF) for DERs based on the effect of their generation on network losses and the relationship between active/reactive power loss and generated power from thermal power plants. In order to simultaneously investigate these new factors and wind power uncertainty on power network operation, a stochastic Security Constrained Unit Commitment (SCUC) for 24 h is defined consisting of generation and emission costs. The simulation results of IEEE57-bus case study show the effective role of RES application on operational cost minimization. © 2012 Elsevier Ltd. All rights reserved.


Peyghambarzadeh S.M.,Islamic Azad University at Mahshahr | Hashemabadi S.H.,Iran University of Science and Technology | Naraki M.,Islamic Azad University at Mahshahr | Vermahmoudi Y.,Islamic Azad University at Mahshahr
Applied Thermal Engineering | Year: 2013

Heat transfer of coolant flow through the automobile radiators is of great importance for the optimization of fuel consumption. In this study, the heat transfer performance of the automobile radiator is evaluated experimentally by calculating the overall heat transfer coefficient (U) according to the conventional ε-NTU technique. Copper oxide (CuO) and Iron oxide (Fe 2O3) nanoparticles are added to the water at three concentrations 0.15, 0.4, and 0.65 vol.% with considering the best pH for longer stability. In these experiments, the liquid side Reynolds number is varied in the range of 50-1000 and the inlet liquid to the radiator has a constant temperature which is changed at 50, 65 and 80 °C. The ambient air for cooling of the hot liquid is used at constant temperature and the air Reynolds number is varied between 500 and 700. However, the effects of these variables on the overall heat transfer coefficient are deeply investigated. Results demonstrate that both nanofluids show greater overall heat transfer coefficient in comparison with water up to 9%. Furthermore, increasing the nanoparticle concentration, air velocity, and nanofluid velocity enhances the overall heat transfer coefficient. In contrast, increasing the nanofluid inlet temperature, lower overall heat transfer coefficient was recorded. © 2012 Elsevier B.V. All rights reserved.


Afshar M.H.,Iran University of Science and Technology
International Journal of Electrical Power and Energy Systems | Year: 2013

Three constrained versions of Particle Swarm Optimization (PSO) algorithm are presented in this paper for the efficient optimal operation of multi-reservoir systems using storage/release volumes as decision variables of the problem. Proposed algorithms are based on identifying and excluding the infeasible region of the search space before and during the search which has already proposed and used by the author for the operation of single reservoirs [5]. In the first version named Partially Constrained Particle Swarm Optimization I (PCPSO1), the sequential nature of the solution building procedure of PSO is used to explicitly enforce the release/storage constraints of the problem during solution construction. For this, the continuity equation is used at each period of the operation of each reservoir to define a new set of bounds for decision variable of the next period which satisfy release/storage constraints of the problem. Particles of the swarm are, therefore, forced to fly in the feasible region of the search space except for some rare cases. In the second version named Partially Constrained Particle Swarm Optimization Two (PCPSO2), the periods of the operations for upstream reservoirs, reservoirs with known inflow, are treated in a reverse order prior to the PCPSO1 search to define new set of bounds for storage volumes such that PCPSO1 algorithm is not given any chance of producing infeasible operations regarding upstream reservoirs. In the third version, the PCPSO2 search is augmented with a mechanism similar to that used in PCPSO2 for all downstream reservoirs by which all the infeasible operation of the downstream dams are also excluded from the search process and, hence, the name of Fully Constrained Particle Swarm Optimization (FCPSO) algorithm. Proposed methods are used to solve two benchmark problems of hydropower operations of multi-reservoir system namely Four and Ten reservoir systems and the results are presented and compared with those of the conventional unconstrained PSO and other methods in the literature. The methods are shown to be very effective in locating optimal or near optimal solutions and efficient in terms of the convergence characteristics of the resulting algorithms. Proposed algorithms are also shown to be relatively insensitive to the swarm size and initial swarm compared to the original algorithm. © 2013 Elsevier Ltd. All rights reserved.


Moradi A.,Iran University of Science and Technology | Moradi A.,Institute for Studies in Theoretical Physics and Mathematics IPM
Physics of Plasmas | Year: 2014

The extinction spectra of a single-walled carbon nanotube are investigated, within the framework of the vector wave function method in conjunction with the hydrodynamic model. Both polarizations of the incident plane wave (TE and TM with respect to the x-z plane) are treated. Electronic excitations on the nanotube surface are modeled by an infinitesimally thin layer of a two-dimensional electron gas represented by two interacting fluids, which takes into account the different nature of the σ and π electrons. Numerical results show that strong interaction between the fluids gives rise to the splitting of the extinction spectra into two peaks in quantitative agreement with the π and σ + π plasmon energies. © 2014 AIP Publishing LLC.


Photoperiod and stocking density are critical factors influencing the performance of decapod crustaceans in culture, however, their influence on growth; survival and biochemical physiology of crayfish broodstock have rarely been considered. Analysis of biochemical physiology in crayfish broodstock during the non-breeding season provides information on the energy storage requirements of broodstock for increased survival and reproductive output. Growth rate, moulting frequency, survival and biochemical physiology were measured in Astacus leptodactylus broodstock that were cultured at three different photoperiods (18L:6D; 12L:12D; and 6L:18D) and three stocking densities (10, 20 and 40 individuals m-2) during non-breeding season. Survival of crayfish was highest at 18L:6D photophase and 10 m-2 (100%) than other treatments. Survival in the high stocking density was high when combined with 18L:6D photophase, but weight gain (WG) and specific growth rate (SGR) were higher at shorter photophase and lower stocking density. Longer photophase (18L:6D) increased stress responses, characterized by increased haemolymph lactate and glucose levels. Stocking density did not affect proximate composition of crayfish; however, individuals cultured at 18L:6D photophase had higher lipid content than other photoperiod treatments. The study demonstrated that culturing A. leptodactylus at 18L:6D photophase and 10 m-2 is critical for increased survival of broodstock. © 2015 John Wiley & Sons Ltd.


Alinejad H.,Iran University of Science and Technology | Shahmansory M.,Arak University
Physics of Plasmas | Year: 2012

The properties of low intensity dust ion acoustic shock waves are studied in a charge varying dusty plasma with nonextensive electrons. Owing to the departure from the Maxwellian electron distribution to a nonextensive one, the modified electrostatic charging of a spherical dust particle in plasma with ion streaming speed is considered. Based on the weakly nonlinear analysis, a new relationship between the low intensity localized disturbances and nonextensive electrons is derived. It is found that both strength and steepness of shock structures arise as the electrons evolve far from their thermodynamic equilibrium in such plasma with parameter ranges corresponding to Saturn's rings. It is also shown that the ion temperature and population of electrons reduce the possibility of the formation of the shock profile. © 2012 American Institute of Physics.


Ghadiri M.,Iran University of Science and Technology | Shirazian S.,Iranian Research Organization for Science and Technology
Chemical Engineering and Processing: Process Intensification | Year: 2013

Theoretical study on extraction of alkali metals using a membrane contactor is carried out in this work. A novel model is built to simulate the flow and the concentration in a membrane extractor based on the finite element analysis. CFD model is applied by solving the 2D Navier-Stokes equations as well as mass conservation equations for steady state conditions in membrane extractors. The model predicts of the velocity field, the pressure and the concentration of alkali metal in the membrane module under laminar flow regime. The results of simulation were used for determination of concentration distribution and effect of extractant concentration on extraction efficiency and mass flux of cesium in the membrane extractor. Moreover, the simulation results for the extraction of cesium using the membrane extractor were compared with the experimental data in order to validate the proposed mass transfer model and showed great agreement. © 2013 Elsevier B.V.


Fazilat H.,Islamic Azad University at Tehran | Akhlaghi S.,Islamic Azad University at Tehran | Shiri M.E.,Iran University of Science and Technology | Sharif A.,Tarbiat Modares University
Polymer | Year: 2012

A multi-structured architecture of artificial intelligence techniques including artificial neural network (ANN), adaptive-neuro-fuzzy-interference system (ANFIS) and radial basis function (RBF) were developed to predict thermal degradation kinetics (TDK) of nylon6 (NY6)/feather keratin (FK) blend films. By simultaneous implementation of back-propagation ANN and feed-forward ANFIS modeling on the experimental data obtained from thermogravimetric analysis (TGA) method, thermal degradation behavior of various compositions of NY6/FK blends was successfully predicted with minimum mean square errors (MSE). RBF networks were then trained on the TGA data at one heating rate for predicting analogs information at different heating rates, providing sufficient feed for TDK modeling. According to the comparison made between experimental and predicted kinetic parameters of thermal degradation process calculated from Friedman and Kissinger methods, the proposed prediction effort could effectively contribute to the estimation of precise activation energy (E a) and reaction order (n) values with least amount of experimental work and most accuracy. © 2012 Elsevier Ltd. All rights reserved.


Aliha M.R.M.,Iran University of Science and Technology
Arabian Journal of Geosciences | Year: 2013

Indirect test methods are usually the preferred approach for determining the tensile strength of brittle and quasi-brittle materials such as ceramics, rocks, and concrete. In this paper, the tensile strength of a rock material (Iranian Harsin marble) was obtained indirectly by means of two disc type samples. The test samples were the well-known Brazilian disc and semi-disc specimen under three-point bend loading. Since the existing formula for determining the indirect tensile strength is based on 2-D stress assumption which ignores the effects of specimen thickness, a general 3-D tensile strength formulation was derived for each sample by employing finite element analysis. A series of tensile strength tests were conducted on Harsin white marble using disc and semi-disc specimens with different thicknesses in parallel to finite element analysis. The test results using 3-D formulation showed that the tensile strength of the tested marble depends on the thickness/diameter ratio of the specimen and generally decreases from 11.5 to 7 MPa on increasing the thickness of test samples. The average values of tensile strength were about 8.8 MPa for the Brazilian disc specimen and 9.8 MPa for the semi-disc specimen. The good agreement existing between the results of the two specimens suggests that the semi-disc specimen can also be used for determining the rock tensile strength in addition to using the conventional Brazilian test. © 2013 Saudi Society for Geosciences.


Shahmansouri M.,Arak University | Alinejad H.,Iran University of Science and Technology | Alinejad H.,Research Institute for Astronomy and Astrophysics of Maragha RIAAM
Physics of Plasmas | Year: 2012

The linear and nonlinear dust-ion-acoustic (DIA) wave propagating obliquely with respect to an external magnetic field is studied in a magnetized complex plasma which consists of a cold ion fluid, superthermal electrons, and static dust particles. The propagation properties of two possible modes (in the linear regime) are investigated. It is found that the electron suprathermality and the electron population decrease the phase velocities of both modes, while obliqueness leads to increase of separation between two modes. An energy-like equation derived to describe the nonlinear evolution of DIA solitary waves. The influences of electron suprathermality, obliqueness, and electron population on the existence domain of solitary waves and the soliton characteristics are examined. It is shown that the existence domain of the DIA soliton and its profile are significantly depending on the deviation of electrons from thermodynamic equilibrium, electrons population, and obliqueness. It is also found that the suprathermal plasma supports the DIA solitons with larger amplitude. © 2012 American Institute of Physics.


Naraki M.,Islamic Azad University at Mahshahr | Peyghambarzadeh S.M.,Islamic Azad University at Mahshahr | Hashemabadi S.H.,Iran University of Science and Technology | Vermahmoudi Y.,Islamic Azad University at Mahshahr
International Journal of Thermal Sciences | Year: 2013

In this research, the overall heat transfer coefficient of CuO/water nanofluids is investigated experimentally under laminar flow regime (100 ≤ Re ≤ 1000) in a car radiator. The experimental system is quite similar to cars' cooling system. The nanofluids in all the experiments have been stabilized with variation of pH and use of suitable surfactant. The results show that the overall heat transfer coefficient with nanofluid is more than the base fluid. The overall heat transfer coefficient increases with the enhancement in the nanofluid concentration from 0 to 0.4 vol.%. Conversely, the overall heat transfer coefficient decreases with increasing the nanofluid inlet temperature from 50 to 80 °C. The implementation of nanofluid increases the overall heat transfer coefficient up to 8% at nanofluid concentration of 0.4 vol.% in comparison with the base fluid. In addition, the results are statistically analyzed using Taguchi method by implementing Qualitek-4 software. The maximum value of the overall heat transfer coefficient with nanofluid, effect of each operating parameter on the overall heat transfer coefficient and the optimum values of each parameter are determined.© 2012 Elsevier Masson SAS. All rights reserved.


Moradi A.,Iran University of Science and Technology | Moradi A.,Institute for Studies in Theoretical Physics and Mathematics IPM
Physics of Plasmas | Year: 2012

The plasmon frequencies of a general double concentric metallic nanotube (NT) are obtained by using the plasmon hybridization method. Theoretical calculations indicate that there are four distinct plasmon modes for the system. It is shown that these two alternating layers of dielectric and metal have a greater geometrical tunability than the single metallic nanotubes of similar dimensions. © 2012 American Institute of Physics.


Shamsipur M.,Razi University | Najafi M.,Razi University | Hosseini M.-R.M.,Iran University of Science and Technology
Bioelectrochemistry | Year: 2010

Electrochemical oxidation of glucose on a glassy carbon disc electrode modified with multi-walled carbon nanotubes and nickel(II) oxide (GC/MWCNT/NiO) was examined by cyclic voltammetry and chronoamperometry in alkaline aqueous solutions. The results were compared with those obtained on a nickel(II) oxide modified glassy carbon electrode (GC/NiO). Both electrodes conditioned by potential cycling in a limited potential range (0.1-0.6 V vs. Ag/AgCl) in 0.10 M NaOH solution. It was found that the multi-walled carbon nanotubes improve remarkably the reactivity of nickel(II) oxide for glucose oxidation. The GC/MWCNT/NiO electrode exhibited good linear behavior in the concentration range from 2.0 × 10- 4 mol/L to 1.2 × 10- 2 mol/L for the quantitative analysis of glucose with a limit of detection of 1.6 × 10- 4 mol/L (3σ). The prepared electrode exhibits satisfactory stability and long life if stored at ambient conditions. Finally, it has been demonstrated that the proposed modified electrode can be successfully used for the assay of glucose in serum samples. © 2009 Elsevier B.V. All rights reserved.


Kaveh A.,Iran University of Science and Technology | Kaveh A.,Building and Housing Institute | Tolou Kian M.J.,Building and Housing Institute
Finite Elements in Analysis and Design | Year: 2012

In this paper an efficient method is presented for the analysis of finite element models (FEMs) composed of brick elements. In the present method, special graphs are associated with the considered FEM and minimal subgraphs are selected using these graph models. Localized self-equilibrating systems are constructed on these subgraphs, forming a suitable statical basis of the FEM. This basis corresponds to highly sparse and banded flexibility matrix. Finally the applicability and the efficiency of the present method are illustrated through some examples. © 2012 Elsevier B.V.


Rafee Nekoo S.,Iran University of Science and Technology
ISA Transactions | Year: 2013

The state-dependent Riccati equation (SDRE), as a controller, has been introduced and implemented since the 90s. In this article, the other aspects of this controller are declared which shows the capability of this technique. First, a general case which has control nonlinearities and time varying weighting matrix Q is solved with three approaches: exact solution (ES), online control update (OCU) and power series approximation (PSA). The proposed PSA in this paper is able to deal with time varying or state-dependent Q in nonlinear systems. As a result of having the solution of nonlinear systems with complex Q containing constraints, using OCU and proposed PSA, a method is introduced to prevent the collision of an end-effector of a robot and an obstacle which shows the adaptability of the SDRE controller. Two examples to support the idea are presented and conferred. Supplementing constraints to the SDRE via matrix Q, this approach is named a modified SDRE. © 2012 ISA.


Zandi F.,Iran University of Science and Technology
Applied Soft Computing Journal | Year: 2014

Nowadays, many healthcares are generating and collecting a huge amount of medical data. Due to the difficulty of analyzing this massive volume of data using traditional methods, medical data mining on Electronic Health Record (EHR) has been a major concern in medical research. Therefore, it is necessary to assess EHR architectures based on the capabilities of extracting useful medical knowledge from a huge amount of EHR databases. In this paper, we develop a bi-level interactive decision support framework to identify data mining-oriented EHR architectures. The contribution of this bi-level framework is fourfold: (1) it develops Interactive Simple Additive Weighting (ISAW) model from an individual single-level environment to a group bi-level environment; (2) it utilizes decision makers' preferences gradually in the course of interactions to reach to a consensus on an data mining-oriented EHR architecture; (3) it considers fuzzy logic and fuzzy sets to represent ambiguous, uncertain or imprecise information; and (4) it synthesizes a representative outcome based on qualitative and quantitative indicators in the EHR assessment process. A case study demonstrates the applicability of the proposed bi-level interactive framework for benchmarking a national data mining-oriented EHR. © 2014 Elsevier B.V.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Applied Soft Computing Journal | Year: 2012

The charged system search (CSS) algorithm is utilized for design of frame structures. The algorithm is inspired by the laws in physics. The CSS utilizes a number of charged particles which influence each other based on their fitness values and their separation distances considering the governing law of Coulomb. A comparison between the characteristics of the CSS algorithm and other well-known meta-heuristics is performed to indicate their similarities and differences. Some benchmark frame examples are optimized with the CSS algorithm. Comparison of the results of CSS with some other meta-heuristic algorithms shows the robustness of the new algorithm. © 2011 Elsevier B.V. All rights reserved.


Behbahani M.,Islamic Azad University at Tehran | Saghaee A.,Islamic Azad University at Tehran | Noorossana R.,Iran University of Science and Technology
Computers and Industrial Engineering | Year: 2012

Statistical process control (SPC) is a sub-area of statistical quality control. Considering the successful results of the SPC applications in various manufacturing and service industries, this field has attracted a large number of experts. Despite the development of knowledge in this field, it is hard to find a comprehensive perspective or model covering such a broad area and most studies related to SPC have focused only on a limited part of this knowledge area. According to many implemented cases in statistical process control, case-based reasoning (CBR) systems have been used in this study for developing of a knowledge-based system (KBS) for SPC to organize this knowledge area. Case representation and retrieval play an important role to implement a CBR system. Thus, a format for representing cases of SPC and the similarity measures for case retrieval are proposed in this paper. © 2012 Elsevier Ltd. All rights reserved.


Korayem M.H.,Iran University of Science and Technology | Esmaeilzadehha S.,Islamic Azad University at Tehran
International Journal of Advanced Manufacturing Technology | Year: 2012

Abstract Lacking real-time visual feedback is one of the main problems in working with AFM in a nanoenvironment. To overcome this problem, we begin to design a virtual reality environment. First, nano-image is enhanced by using image processing technique and genetic algorithms then the location and number of nano-particles and other properties are determined. A nano-manipulation environment is implemented and the forces between the tip of the probe and nano-particle are analyzed, so that we increase the ability of user in driving nano-particle in this environment. In the first step, nano-image quality will be improved by applying different filters that each one is appropriate to eliminate one type of noise. Genetic algorithms are applied to determine a suitable set of appropriate filters among filters bank, then the location and number of nano-particles will be extracted by using image processing technique. For nano-manipulation operation, the dimensions of the base plate and exact place of nano-particles on it should be defined, and the user can choose the primary and final location of the nano-particle. The second stage of simulation is driving the nano-particle in such a way that the tip of atomic force microscopy probe aims at nano-particle with constant velocity. At this moment, the movement of the tip of the probe begins, and the nano-particle moves to a chosen place, so that the user can see the manipulation process. ©Springer-Verlag London Limited 2012.


Moghaddam B.F.,Islamic Azad University at Parand | Ruiz R.,Polytechnic University of Valencia | Sadjadi S.J.,Iran University of Science and Technology
Computers and Industrial Engineering | Year: 2012

The Vehicle Routing Problem (VRP) has been thoroughly studied in the last decades. However, the main focus has been on the deterministic version where customer demands are fixed and known in advance. Uncertainty in demand has not received enough consideration. When demands are uncertain, several problems arise in the VRP. For example, there might be unmet customers' demands, which eventually lead to profit loss. A reliable plan and set of routes, after solving the VRP, can significantly reduce the unmet demand costs, helping in obtaining customer satisfaction. This paper investigates a variant of an uncertain VRP in which the customers' demands are supposed to be uncertain with unknown distributions. An advanced Particle Swarm Optimization (PSO) algorithm has been proposed to solve such a VRP. A novel decoding scheme has also been developed to increase the PSO efficiency. Comprehensive computational experiments, along with comparisons with other existing algorithms, have been provided to validate the proposed algorithms.


Karimi-Nasab M.,Iran University of Science and Technology | Konstantaras I.,University of Macedonia
Computers and Industrial Engineering | Year: 2012

Real world production planning is involved in optimizing different objectives while considering a spectrum of parameters, decision variables, and constraints of the corresponding cases. This comes from the fact that production managers desire to utilize from an ideal production plan by considering a number of objectives over a set of technological constraints. This paper presents a new multi-objective production planning model which is proved to be NP-Complete. So a random search heuristic is proposed to explore the feasible solution space with the hope of finding the best solution in a reasonable time while extracting a set of Pareto-optimal solutions. Then each Pareto-optimal solution is considered as an alternative production plan in the hand of production manager. Both the modeling and the solution processes are carried out for a real world problem and the results are reported briefly. Also, performance of the proposed problem-specific heuristic is verified by comparing it with a multi-objective genetic algorithm on a set randomly generated test data. © 2011 Elsevier Ltd. All rights reserved.


Talatahari S.,University of Tabriz | Kaveh A.,Iran University of Science and Technology | Sheikholeslami R.,Amirkabir University of Technology
Structural and Multidisciplinary Optimization | Year: 2012

The imperialist competitive algorithm is a new socio-politically motivated optimization algorithm which recently is applied for structural problems. This paper utilizes the idea of using chaotic systems instead of random processes in the imperialist competitive algorithm. The resulting method is called chaotic imperialist competitive algorithm (CICA) in which chaotic maps are utilized to improve the movement step of the algorithm. Some well-studied truss structures are chosen to evaluate the efficiency of the new algorithm. © 2012 Springer-Verlag.


Gheshlaghi B.,Islamic Azad University at Tehran | Hasheminejad S.M.,Iran University of Science and Technology
Current Applied Physics | Year: 2012

An analytical model for predicting surface effects on the free transverse vibrations of piezoelectric nanowires (NWs) is developed based on the non-local Euler-Bernoulli beam theory. The governing equation of motion for the piezoelectric NW with consideration of both surface and non-local effects is initially obtained, and the exact expressions for the natural frequencies and the fundamental buckling voltage are derived for simple support conditions. In addition, an explicit relationship between the residual surface tension and the small scale parameter of the piezoelectric NW, in terms of the critical electric potential at which the axial buckling occurs, is offered. Accordingly, a design chart is presented which may assist in experimental characterization of the mechanical properties of piezoelectric NW-based devices. © 2011 Elsevier B.V. All rights reserved.


Alinia Kashani A.H.,Iran University of Science and Technology | Maddahi A.,Tarbiat Modares University | Hajabdollahi H.,Vali e Asr University of Rafsanjan
Applied Thermal Engineering | Year: 2013

Thermodynamic modeling and optimal design of an air-cooled heat exchanger (ACHE) unit are developed in this study. For this purpose, ε-NTU method and mathematical relations are applied to estimate the fluids outlet temperatures and pressure drops in tube and air sides. The main goal of this study is minimizing of two conflicting objective functions namely the temperature approach and the minimum total annual cost, simultaneously. For this purpose, fast and elitist non-dominated sorting genetic-algorithm (NSGA-II) is applied to minimize the objective functions by considering ten design parameters. In addition, a set of typical constraints, governing on the ACHE unit design, is subjected to obtain more practical optimum design points. Furthermore, sensitivity analysis of change in the objective functions, when the optimum design parameters vary, is conducted and the degree of each parameter on conflicting objective functions has been investigated. Finally, a selection procedure of the best optimum point is introduced and final optimum design point is determined. © 2013 Elsevier Ltd. All rights reserved.


Alavi A.H.,Iran University of Science and Technology | Gandomi A.H.,Tafresh University
Geoscience Frontiers | Year: 2012

This study presents promising variants of genetic programming (GP), namely linear genetic programming (LGP) and multi expression programming (MEP) to evaluate the liquefaction resistance of sandy soils. Generalized LGP and MEP-based relationships were developed between the strain energy density required to trigger liquefaction (capacity energy) and the factors affecting the liquefaction characteristics of sands. The correlations were established based on well established and widely dispersed experimental results obtained from the literature. To verify the applicability of the derived models, they were employed to estimate the capacity energy values of parts of the test results that were not included in the analysis. The external validation of the models was verified using statistical criteria recommended by researchers. Sensitivity and parametric analyses were performed for further verification of the correlations. The results indicate that the proposed correlations are effectively capable of capturing the liquefaction resistance of a number of sandy soils. The developed correlations provide a significantly better prediction performance than the models found in the literature. Furthermore, the best LGP and MEP models perform superior than the optimal traditional GP model. The verification phases confirm the efficiency of the derived correlations for their general application to the assessment of the strain energy at the onset of liquefaction. © 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.


Shahmansouri M.,Arak University | Alinejad H.,Iran University of Science and Technology
Physics of Plasmas | Year: 2015

We give a theoretical investigation on the dynamics of nonlinear electrostatic waves in a strongly coupled dusty plasma with strong electrostatic interaction between dust grains in the presence of the polarization force (i.e., the force due to the polarized Debye sheath). Adopting a reductive perturbation method, we derived a three-dimensional Kadomtsev-Petviashvili equation that describes the evolution of weakly nonlinear electrostatic localized waves. The energy integral equation is used to study the existence domains of the localized structures. The analysis provides the localized structure existence region, in terms of the effects of strong interaction between the dust particles and polarization force. © 2015 AIP Publishing LLC.


Ghadiri M.,Iran University of Science and Technology | Fakhri S.,RAMPCO Group | Shirazian S.,Iranian Research Organization for Science and Technology
Industrial and Engineering Chemistry Research | Year: 2013

A two-dimensional comprehensive model was developed to predict the transport of water in the nanoporous membrane contactors. The considered membrane distillation device was a counter-current flat-sheet membrane contactor for production of pure water from saline water. The developed model formulates the fundamental transport equations of heat, mass, and momentum in the membrane contactor. The computational fluid dynamics techniques were applied for numerical simulation of model equations. The simulation results were compared with experimental data obtained from literature and showed great agreement with the measured values. A combination of the Knudsen flow and Poiseuille flow was used in the model for estimation of diffusion inside the membrane pores and increased the accuracy of the model. Simulation results revealed that, in the regions adjacent to the membrane wall, the temperature difference is significant. This could be attributed to the fact that a temperature boundary layer is formed near the membrane wall and causes a high temperature decline in this region. © 2013 American Chemical Society.


Mashhadi S.,Iran University of Science and Technology
International Journal of Network Security | Year: 2013

In 2004, Yang et al. proposed an efficient (t, n) threshold proxy signature scheme with known signers. However, Maimani et al. showed that a malicious original signer can forge a valid proxy signature for any message in Yang et al.'s scheme and further proposed an improvement to remedy such an attack. In this paper, we will show that in Maimani et al.s improvement, a malicious original or proxy signer can forge a valid threshold proxy signature for any message by different ways. Furthermore, we pro-pose a new threshold proxy signature scheme that reme-dies the weakness of Maimani et al.'s scheme.


Mosavi M.R.,Iran University of Science and Technology
Neural Processing Letters | Year: 2011

Accurate and reliable position determination is a vital componentin Global Positioning System (GPS). GPS positioning errors occur from the cumulative effects of receiver, satellite and atmosphere, and also due to the U.S. military intentionally such as Selective Availability (SA). In order to improve the accuracy of positions provided by GPS additional correction information may be used, such as Differential GPS (DGPS) or other sensors to enhance position reliability. The DGPS has the problem of slow updates. To overcome this limitation, DGPS corrections prediction has been proposed. The ability of Neural Networks (NNs) to discover nonlinear relationships in input data makes them ideal for modeling nonlinear dynamic systems. The Wavelet Neural Network (WNN) employing nonlinear wavelet basis function, which are localized in both the time and frequency space, has been developed as an alternative approach to nonlinear fitting problem. Particle Swarm Optimization (PSO), a global optimization method, is used to train the WNN. In this paper, a WNN trained by a PSO algorithm is proposed for DGPS corrections prediction in single-frequency GPS receivers. Experimental results show the feasibility and effectiveness of the proposed method. The results are analyzed and compared with WNN trained by Back Propagation (BP) algorithm. The experimental results show that WNN, trained by the PSO algorithm, is able to reduce RMS errors to less than 1 m with SA on and 0.6 m with SA off. © 2011 Springer Science+Business Media, LLC.


Fazlollahtabar H.,Iran University of Science and Technology | Mahdavi I.,Mazandaran University of Science and Technology | Mohajeri A.,Islamic Azad University at Tehran
Applied Soft Computing Journal | Year: 2013

Supply chain design problems have recently raised a lot of interest since the opportunity of an integrated management of the supply chain can reduce the propagation of undesirable events through the network and can affect decisively the profitability of the members. Often uncertainties may be associated with demand and relevant costs. In most of the existing models uncertainties are treated as randomness and are handled by appealing to probability theory. Here, we propose a fuzzy mathematical programming model for a supply chain which considers multiple depots, multiple vehicles, multiple products, multiple customers, and different time periods. In this work not only demand and cost but also decision variables are considered to be fuzzy. We apply two ranking functions for solving the model. The aim of the fuzzy mathematical program is to select the appropriate depots among candidate depots, the allocation of orders to depots and vehicles, also the allocation of the returning vehicles to depots, to minimize the total costs. To validate the model some numerical experiments are worked out and a comparative analysis is investigated. Also, a regression model is considered to analyze the applied fuzzy ranking methods. © 2012 Elsevier B.V.


Sadeghzadeh S.,Iran University of Science and Technology
Micro and Nano Letters | Year: 2016

To describe and analyse mechanical structures due to external loads, equation of motion must be supplemented with appropriate boundary conditions. When nanomechanical structures (especially layered systems) are considered, satisfying the boundaries is more challenging. It may be essential to develop a specific methodology for any system in such scale and configuration. This work introduces a general approach for boundary conditions of monolayer graphene sheets as the most important part of future sensors and resonators in nanoelectromechanical systems. Comparing with the experiments, it has been demonstrated that the graphene sheets on the adhesive surfaces should be assumed as a hinged edge condition and not as a clamped one. As a result, inaccuracy of the commonly used rigid base as a clamped condition is proven due to comparison with a reported experiment. It is suggested that a flexible substrate can be replaced to have better accordance. A flexible silicon base with equilibrium distance equal to s = 2.5 Å and depth of potential well equal to ϵ = 0.02 eV is obtained as the best substrate for a square graphene sheet under doubly clamped edge conditions. © The Institution of Engineering and Technology 2016.


Ashrafizadeh S.N.,Iran University of Science and Technology | Ameri Ghasrodashti A.,Tarbiat Modares University
Chemical Engineering Research and Design | Year: 2011

Miscible gas injection is generally used as one of the most efficient methods in the enhanced oil recovery. Minimum miscibility pressure (MMP) is an important parameter in the miscible gas injection projects, since local displacement efficiency in the reservoir media is highly dependent on the MMP. Therefore, an appropriate estimation of MMP would bring significant economic benefits. This paper presents a comparative study on five representative equations of state (EoSs) for predicting MMP using Parachor model together with the criterion of zero interfacial tension (IFT) at the miscibility conditions. The predicted MMP values are compared with the experimental data obtained from the most reliable measurement technique, so called slim tube method. Such a prediction would enables us to judge the accuracy of the results obtained from different equations of state as well as the capability of Parachor model to calculate the MMP. The results of predictions obtained for five oil-gas systems in this study reveal reliable MMP values within 5% of accuracy. © 2010 The Institution of Chemical Engineers.


Sohrabi M.R.,Islamic Azad University at North Tehran | Matbouie Z.,Islamic Azad University at Darab | Asgharinezhad A.A.,Shahid Beheshti University | Dehghani A.,Iran University of Science and Technology
Microchimica Acta | Year: 2013

We describe a novel magnetic metal-organic framework (MOF) for the preconcentration of Cd(II) and Pb(II) ions. The MOF was prepared from the Fe3O4-pyridine conjugate and the copper(II) complex of trimesic acid. The MOF was characterized by IR spectroscopy, elemental analysis, SEM and XRD. A Box-Behnken design through response surface methodology and experimental design was used to identify the optimal parameters for preconcentration. Extraction time, amount of magnetic MOF and pH value were found to be critical factors for uptake, while type, volume, concentration of eluent, and elution time are critical in the elution step. The ions were then determined by FAAS. The limits of detection are 0.2 and 1.1 μg L-1 for Cd(II), and Pb(II) ions, respectively, relative standard deviations are <4.5% (for five replicates at 50 μg L-1 of Cd(II) and Pb(II) ions), and the enrichment capacity of the MOF is at around 190 mg g-1 for both ions which is higher than the conventional Fe3O4-pyridine material. The magnetic MOF was successfully applied to the rapid extraction of trace quantities of Cd(II) and Pb(II) ions in fish, sediment, and water samples. © 2013 Springer-Verlag Wien.


Shokrieh M.M.,Iran University of Science and Technology | Rafiee R.,University of Tehran
Iranian Polymer Journal (English Edition) | Year: 2012

The main goal of this study was to develop a full range multi-scale modeling technique to extract Young's modulus and Poisson's ratio of carbon nanotube reinforced polymer (CNTRP) composites covering all nano, micro, meso and macro scales. The developed model consists of two different phases as top-down scanning and bottom-up modeling. At the first stage, the material region will be scanned from the macro level downward to the nano-scale. Effective parameters associated with each scale will be identified through this scanning procedure. Taking into account identified effective parameters of each specific scale, the suitable representative volume elements (RVE) will be defined for all nano, micro, meso and macro scales, separately. In the second stage of the modeling procedure, a hierarchical multi-scale modeling approach is developed. This modeling strategy would analyze the material at each scale and obtained results that were fed to the upper scale as input information. Due to involved random parameters, the developed modeling technique is implemented stochastically. It has been shown that the developed modeling procedure provides a clear insight to the properties of CNTRP and it is a very efficient tool for simulation of mechanical behavior of CNTRP composites. A sensitivity analysis was conducted to quantify the influence of the identified random parameters on the overall behavior of CNTRP. © Iran Polymer and Petrochemical Institute 2012.


Akbari T.,University of Tehran | Rahimikian A.,University of Tehran | Kazemi A.,Iran University of Science and Technology
Energy Conversion and Management | Year: 2011

This paper presents a multi-stage stochastic model for short-term transmission expansion planning considering the available transfer capability (ATC). The ATC can have a huge impact on the power market outcomes and the power system reliability. The transmission expansion planning (TEP) studies deal with many uncertainties, such as system load uncertainties that are considered in this paper. The Monte Carlo simulation method has been applied for generating different scenarios. A scenario reduction technique is used for reducing the number of scenarios. The objective is to minimize the sum of investment costs (IC) and the expected operation costs (OC). The solution technique is based on the benders decomposition algorithm. The N-1 contingency analysis is also done for the TEP problem. The proposed model is applied to the IEEE 24 bus reliability test system and the results are efficient and promising. © 2011 Elsevier Ltd. All rights reserved.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Engineering Structures | Year: 2010

This paper presents an improved ant colony optimization (IACO) for the design of planar steel frames. The algorithm consists of two phases: the global search phase and the local search phase. In the global search phase, IACO employs a sub-optimization mechanism (SOM) based on the principles of finite element methods to reduce the search space, the size of the trail matrix, the number of analyses and consequently the optimization time. In the local search phase, a final optimum design is obtained considering W-shaped sections from the available steel sections specified by the American Institute of Steel Construction (AISC) in the neighborhood of the result gained in the previous phase. The proposed method is tested on several frames from the literature. In order to verify the suitability of the present method, the results of optimum design for several planar steel frames are obtained by the present study and compared to those of the standard ant colony optimization, the genetic algorithm and the harmony search algorithm. The results indicate that the computational time required for the improved ant colony optimization is considerably reduced. © 2009 Elsevier Ltd. All rights reserved.


Sadeghi J.,Iran University of Science and Technology
Journal of Transportation Engineering | Year: 2010

In this paper, the statistical distribution of railway track geometry data is investigated using a significant volume of field data. Analyzing the results yields a general pattern for the statistical distribution of the track geometry data. This is used to develop new indexes for track geometry parameters including gauge, profile, alignment, and twist. An overall track geometry index is established by combining the new parameter's indexes. This combination is made by assigning a coefficient to each geometry parameter based on its role in the overall quality condition of the track. In comparison with the approaches previously used for the development of the track geometry indexes, this method has three distinguishing features. First, the mean values along with the SD of data are incorporated into the calculation of the new indexes. Second, the new indexes indicate not only the condition of the individual parameters but also the overall track geometry condition. Third, the track classification is considered, and an index is developed for each class of the tracks. A practical use of the new indexes is presented and discussed in the paper. © 2010 ASCE.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Asian Journal of Civil Engineering | Year: 2010

The Big Bang-Big Crunch (BB-BC) optimization algorithm is a new optimization method that relies on the Big Bang and Big Crunch theory, one of the theories of the evolution of the universe. In this paper, a discrete Big Bang-Big Crunch algorithm is presented for optimal design of structures. The BB-BC is employed to optimize different types of skeletal structures with discrete variables including trusses and frames. The results demonstrate the efficiency of the discrete BB-BC algorithm compared to other heuristic algorithms.


Cardenas-Barron L.E.,Monterrey Institute of Technology | Taleizadeh A.A.,Iran University of Science and Technology | Trevino-Garza G.,Monterrey Institute of Technology
Expert Systems with Applications | Year: 2012

Recently, in Expert Systems with Applications journal, Chen, Wu, Chiu, and Lee (2012) present an alternative optimization solution process to determine the optimal replenishment lot size with discontinuous issuing policy considering imperfect rework process and multiple shipments. Simultaneously, Chiu, Chiu, and Yang (2012) solve a multi-delivery policy into economic production quantity with partial rework. Both papers consider the number of shipments as a fixed and a given value. In this paper both the optimal replenishment lot size and the optimal number of shipments are derived jointly for the inventory models of Chen et al. (2012) and Chiu, Chiu, et al. (2012). Two easy to apply solution procedures are proposed. The solutions reported in this paper are better than the solutions of Chen et al. (2012) and Chiu, Chiu, et al. (2012). © 2012 Elsevier Ltd. All rights reserved.


Zohdi H.,Tarbiat Modares University | Shahverdi H.R.,Tarbiat Modares University | Hadavi S.M.M.,Iran University of Science and Technology
Electrochemistry Communications | Year: 2011

The corrosion behavior of Fe 55-xCr 18Mo 7B 16C 4Nb x (x = 0, 3, and 4 at.%) amorphous ribbons in Ringer's solution with pH value 6.5, open to air at 37 °C, was investigated by linear polarization and electrochemical impedance spectroscopy (EIS) methods, aiming to estimate the feasibility of Fe-based metallic glasses as potential biomaterials. It was shown that the corrosion resistance in Ringer's solution significantly increases with an increase in Nb content. The linear polarization and EIS measurements indicated that the Fe 51Cr 18Mo 7B 16C 4Nb 4 possesses larger polarization resistance value than that of 316L stainless steel and Ti-6Al-4V which are used in the human body in biomedical applications. In addition, the ICP test was carried out to measure the concentrations of ions which had dissolved into the electrolyte. It was seen that amorphous alloys do not release any significant ions into the Ringer's solution, implying good biocompatibility of these alloys. © 2011 Elsevier B.V. All rights reserved.


Akbari M.,Iran University of Science and Technology | Abdi Behnagh R.,Urmia University of Technology | Dadvand A.,Urmia University of Technology
Science and Technology of Welding and Joining | Year: 2012

Friction stir welding has been successfully used to weld the dissimilar metals. A few investigations have been carried out on the friction stir lap welding of Al to Cu, but the basic issue of how the position of the metals would affect the joint strength is still not resolved. In the present study, the 7070 Al and the commercially pure copper are lap joined using friction stir lap welding technology. Two test cases are considered. The distinction refers to the position of Al with respect to Cu. Microstructural analyses are carried out to gain intermetallic compounds and some microcracks. The effect of position of materials on the heat generation is investigated and justified through the temperature measurements. Mechanical properties of each sample are characterized using both shear and hardness tests. The results reveal that the maximum fracture load of the joint is obtained when Al is placed on the top of Cu. © 2012 Institute of MaterialsMaterials, Minerals and Mining.


Bahiraei M.,Kermanshah University of Technology | Hangi M.,Iran University of Science and Technology
Journal of Magnetism and Magnetic Materials | Year: 2015

Magnetic nanofluids (MNFs) are suspensions which are comprised of a non-magnetic base fluid and magnetic nanoparticles. In this modern set of suspensions which can be called smart or functional fluids, fluid flow, particles movement and heat transfer process can be controlled by applying magnetic fields. Regarding unique characteristics of MNFs, studies in this field have witnessed a phenomenal growth. This paper reviews and summarizes recent investigations implemented on MNFs including those conducted on thermophysical properties, natural convection, forced convection, boiling as well as their practical applications. Moreover, this review identifies the challenges and opportunities for future research. © 2014 Elsevier B.V.


Daliri M.R.,Iran University of Science and Technology | Daliri M.R.,Institute for Research in Fundamental Sciences | Torre V.,International School for Advanced Studies
Computer Vision and Image Understanding | Year: 2010

In this paper a kernel method for shape recognition is proposed. The approach is based on the edit distance between pairs of shapes after transforming them into symbol strings. The transformation of shapes into symbol strings is invariant to similarity transforms and can handle partial occlusions. Representation of shape contours uses the shape contexts and applies dynamic programming for finding the correspondence between points over shape contours. Corresponding points are then transformed into symbolic representation and the normalized edit distance computes the dissimilarity between pairs of strings in the database. Obtained distances are then transformed into suitable kernels which are classified using support vector machines. Experimental results over a variety of shape databases show that the proposed approach is suitable for shape recognition. © 2010 Elsevier Inc. All rights reserved.


Alinejad H.,Iran University of Science and Technology | Alinejad H.,Research Institute for Astronomy and Astrophysics of Maragha
Astrophysics and Space Science | Year: 2010

For an unmagnetized collisionless electron-positron-ion plasma, the effects of trapped and non-thermal electron distributions are incorporated in the study of arbitrary amplitude ion-acoustic solitary structures. Both highly and weakly analyses are examined by deriving an energy integral equation involving the Sagdeev potential for the large amplitude limit, and obtaining the non-linear partial-differential equations for the small but finite amplitude limit. It is shown that there exist ion-acoustic solitary waves with qualitatively different structures in a way that depend on the population of trapped and non-thermal electrons. In the presence of trapped electrons, fully non-linear analyses show that plasma can support only arbitrary amplitude compressive solitary waves. On the other hand, a consideration of the fast or non-thermal electron distribution provides the possibility of the coexistence of large amplitude compressive and rarefactive solitary waves, whereas both of them are decoupled in the small amplitude limit. It is found that the effects of such electron distributions and positron concentration change the maximum values of the Mach number and the amplitude for which solitary waves can exist. Furthermore, the non-thermally distributed electrons provide a KdV equation in the small amplitude limit, whereas the trapped electrons give rise to a modified KdV equation which exhibits a stronger non-linearity. © Springer Science+Business Media B.V. 2009.


Heshmati A.,Hamadan University of Medical Sciences | Milani J.M.,Iran University of Science and Technology
Food Control | Year: 2010

In this study the levels of aflatoxin M1 (AFM1) in UHT milk samples were determined in May, August and November and February. Two hundred and ten UHT milk samples were obtained from supermarkets in Tehran, Iran. The occurrence and concentration range of AFM1 in the samples were investigated by competitive enzyme-linked immunoabsorbent assay (ELISA) method. AFM1 was found in 116 (55.2%) of 210 UHT milk samples examined. The levels of AFM1 in 70 (33.3%) samples were higher than the maximum tolerance limit (0.05 μg/l) accepted by some European countries while none of the samples exceeded the prescribed limit of US regulations. The highest mean concentration of AFM1 was recorded in February (0.087 μg/l). The lowest mean concentration of AFM1 was recorded in August (0.021 μg/l). Statistical evaluation showed that there were significant difference (P < 0.01) between the mean concentrations of AFM1 of UHT milk samples taken in February with May and August. AFM1 contents of milk samples taken in February were not higher than UHT milk samples taken in November (P < 0.01). The AFM1 incidence of exceeding legal limit in UHT milk samples (33.3%) was relatively much higher than some other countries. It was therefore concluded that, the levels of AFM1 in UHT milk samples consumed in Iran were high and seemed to pose a threat to public health. © 2009 Elsevier Ltd. All rights reserved.


Mosavi M.R.,Iran University of Science and Technology
International Review of Electrical Engineering | Year: 2010

GPS measurements can be degraded by several type of error like unmodelled ionosphere and troposphere delays, satellite and receiver clocks inaccuracies, receiver noise, dilution of precision and multi-path effects, and also the U.S. military's intentionally such as Selective Availability (SA). These errors degrade the accuracy of GPS position. DGPS provides users with corrections to remove the correlated bias terms between receivers. The DGPS has the problem of slow updates. Any interruption of the DGPS service causes a loss of navigation guidance. This paper proposes the prediction of DGPS corrections using Neural Networks (NNs) trained by evolutionary algorithms such as the genetic algorithm and the Particle Swarm Optimization (PSO). A low cost commercial and single-frequency GPS receiver is utilized to demonstrate the DGPS positioning. The experimental results show the feasibility and effectiveness of the proposed methods. The results are analyzed and compared with NNs trained by the back propagation algorithm. The NNs trained by PSO gives better accuracy in estimating the DGPS corrections; so that the total RMS error reduces to less than 1.32 metre with SA on and 0.46 metre with SA off. © 2010 Praise Worthy Prize S.r.l. - All rights reserved.


Taleizadeh A.A.,Iran University of Science and Technology | Niaki S.T.A.,Sharif University of Technology | Nikousokhan R.,University of Tehran
Applied Soft Computing Journal | Year: 2011

An uncertain economic order quantity (UEOQ) model with payment in advance is developed to purchase high-price raw materials. A joint policy of replenishments and pre-payments is employed to supply the materials. The rate of demand is considered LR-fuzzy variables, lead-time is taken to be constant, and it is assumed that shortage does not occur in the cycles. The cycle is divided into three parts; the first part is the time between the previous replenishment-time to the next order-time (t0), the second part is the period between t0 to a payment-time (tk), and the third part is the period between tk to the next replenishment-time. At the start of the second part (t0), α% of the purchasing cost is paid. The (1 - α)% remaining purchasing cost is paid at the start of the third part (tk). The cost of the model is purchasing under incremental discount for each order with rough cost per unit, clearance cost, fixed-order cost, transportation cost, holding, and capital cost. Holding cost is for on-hand inventory and capital cost is for the capital that is paid for the next order. The constraints of the problem are space, budget, and the number of orders per year. Further, lead-time is considered less than a cycle time. We show that the model of this problem is a fuzzy integer-nonlinear-programming type and in order to solve it, a hybrid method of harmony search, fuzzy simulation, and rough simulation is proposed. In order to validate the results and examine the performance of the proposed method, a genetic algorithm, as well as a particle swarm optimization method is also employed. The results of a numerical example show that the proposed procedure has the best performance in terms of the mean of the objective function in different simulation runs. At the end, a case study along with a sensitivity analysis is given to demonstrate the applicability of the proposed methodology in real world inventory control problems and to provide some managerial insights. © 2011 Elsevier B.V. All rights reserved.


Alinejad H.,Iran University of Science and Technology | Alinejad H.,Research Institute for Astronomy and Astrophysics of Maragha
Astrophysics and Space Science | Year: 2010

A theoretical investigation of the one dimensional dynamics of nonlinear electrostatic dust ion-acoustic (DIA) waves in an unmagnetized dusty plasma consisting of ion fluid, non-thermal electrons and fluctuating immobile dust particles has been made by the reductive perturbation technique. The basic features of DIA solitary and shock waves are studied by deriving the Korteweg-de Vries (KdV) and KdV Burger equations, respectively. It is shown that the special patterns of nonlinear electrostatic waves are significantly modified by the presence of the non-thermal electron component. In particular, the rarefactive solitary and shock structures are found with smaller amplitude in comparison to the isothermal case. The transition from DIA solitary to shock waves is also studied which is related to the contributions of the dispersive and dissipative terms. It is found that the dust charge fluctuation is a source of dissipation, and is responsible for the formation of the dust ion-acoustic shock waves. Furthermore, the dissipative effect becomes important and may prevail over that of dispersion as the population of non-thermal electrons present decreases. The present investigation may be of relevance to electrostatic solitary structures observed in many space dusty plasma, such as Saturn's E-ring. © Springer Science+Business Media B.V. 2010.


Zakeri J.A.,Iran University of Science and Technology
Structure and Infrastructure Engineering | Year: 2012

One of the main problems of railway lines in sandy-dry areas is the sands flowing into the railway lines. This causes serious impact on the productivity and effectiveness of the railways and disturbs trains running safety. Compatibility of railways with this situation is very hard, imposing a dramatic sum of maintenance costs on railway industries. This research deals with the approaches and solutions for the maintenance of railways in these conditions and introduces an effective maintenance method based on long-term maintenance experiences in Iranian railway industries. In this paper, the current and most practical methods in confronting this phenomena including planting (artificial forest), constructing channels vertical to the wind direction, creating physical barriers vertical to the wind direction, stabilising sand areas with oil products, and constructing various water ways in the track infrastructures are discussed. Taking into consideration almost a decade of experience by Iranians of maintenance of railway in sandy-dry areas, the aforementioned methods are evaluated and the most practical approaches are introduced. © 2012 Taylor and Francis Group, LLC.


Hasheminezhad A.,Iran University of Science and Technology
Engineering Failure Analysis | Year: 2015

The B70 mono-block pre-stressed concrete sleeper is one of the most widely used types of concrete sleepers for railways. One of the most important defects of this type of sleepers is longitudinal cracks both before and during railway track operation, which usually begins at the rawlplugs positions and continues up to the central and regional area of the sleeper. In this research, creation of longitudinal cracks before track operation has been studied. For this purpose, effects of exerted applied loads on the sleeper including pre-stressed loading and cylindrical pressure loading in the circular hole of rawlplugs positions (four different types) in creating longitudinal cracks were investigated using the ABAQUS Finite Element software. In addition, a sensitivity analysis of the tensile stress in the rawlplugs positions of the B70 pre-stressed concrete sleeper was carried out against changes in the pre-stressing force as one of the most important parameters in the structural design of this type of sleeper. According to the research results, the cylindrical pressure inside the rawlplug holes increases the tensile stresses around the holes and eventually leads to extension of longitudinal cracks. Furthermore, the implementation of loadings on the B70 mono-block pre-stressed concrete sleeper increases the intensity of the damage significantly. The numerical model also shows the linear behaviour of the changes in the pre-stressing force and, as a result, high values of pre-stressing force can be a main factor in creating longitudinal cracks. © 2014 Elsevier Ltd.


Bakhshandeh-Chamazkoti R.,Iran University of Science and Technology
Mathematical Methods in the Applied Sciences | Year: 2015

In this research article, a complete analysis of symmetries and conservation laws for the charged squashed Kaluza-Klein black hole space-time in a Riemannian space is discussed. First, a comprehensive group analysis of the underlying space-time metric using Lie point symmetries is presented, and then the n-dimensional optimal system of this space-time metric, for n = 1,...,4, are computed. It is shown that there is no any n-dimensional optimal system of Lie symmetry subalgebra associated to the system of geodesic for n≥5. Then the point symmetries of the one-parameter Lie groups of transformations that leave invariant the action integral corresponding to the Lagrangian that means Noether symmetries are found, and then the conservation laws associated to the system of geodesic equations are calculated via Noether's theorem. © 2015 John Wiley & Sons, Ltd.


Moradi A.,Iran University of Science and Technology | Moradi A.,Institute for Studies in Theoretical Physics and Mathematics IPM
Plasmonics | Year: 2013

The propagation of the coupled surface plasmon-polariton modes in the metallic single-walled carbon nanotubes are investigated, taking into account the retardation effects. A simple model based on the classical electrodynamics and the two-fluid hydrodynamic theory is proposed. The dispersion relation of the surface polariton modes is obtained in order to survey the effects of the two-fluid model and the insulating dielectric media. © 2013 Springer Science+Business Media New York.


Moghaddam A.A.,Shiraz University | Seifi A.,Shiraz University | Niknam T.,Shiraz University of Technology | Alizadeh Pahlavani M.R.,Iran University of Science and Technology
Energy | Year: 2011

As a result of today's rapid socioeconomic growth and environmental concerns, higher service reliability, better power quality, increased energy efficiency and energy independency, exploring alternative energy resources, especially the renewable ones, has become the fields of interest for many modern societies. In this regard, MG (Micro-Grid) which is comprised of various alternative energy sources can serve as a basic tool to reach the desired objectives while distributing electricity more effectively, economically and securely. In this paper an expert multi-objective AMPSO (Adaptive Modified Particle Swarm Optimization algorithm) is presented for optimal operation of a typical MG with RESs (renewable energy sources) accompanied by a back-up Micro-Turbine/Fuel Cell/Battery hybrid power source to level the power mismatch or to store the surplus of energy when it's needed. The problem is formulated as a nonlinear constraint multi-objective optimization problem to minimize the total operating cost and the net emission simultaneously. To improve the optimization process, a hybrid PSO algorithm based on a CLS (Chaotic Local Search) mechanism and a FSA (Fuzzy Self Adaptive) structure is utilized. The proposed algorithm is tested on a typical MG and its superior performance is compared to those from other evolutionary algorithms such as GA (Genetic Algorithm) and PSO (Particle Swarm Optimization). © 2011 Elsevier Ltd.


Fallahi A.,Iran Power Generation, Transmission and Distribution Management Co. | Ebrahimi R.,Iran University of Science and Technology | Ghaderi S.F.,University of Tehran
Energy | Year: 2011

This paper provides an empirical analysis of the determinants of energy efficiency in 32 power electric generation management companies over the period 2005-2009. The study uses non-parametric Data Envelopment Analysis (DEA) to estimate the relative technical efficiency and productivity change of these companies. In order to verify the stability of our DEA model and the importance of each input variable, a stability test is also conducted. The results of the study indicate that average technical efficiency of companies decreased during the study period. Nearly half of the companies (14) are below this average level of 88.7% for five years. Moreover, it is shown that the low increase of productivity changes is more related to low efficiency rather than technology changes. © 2011 Elsevier Ltd.


The synthesis of pyrido[2′,1′:2,3]imidazo[4,5-c]isoquinolines via a one-pot three-component reaction by using benzene-1,2-dicarbaldehyde, trimethylsilylcyanide and various pyridin-2-amines in the presence of a catalytic amount of superparamagnetic nano-Fe3O4@SiO2 anchored sulfuric acid in ethanol in good-to-high yields is described. © 2014 The Royal Society of Chemistry.


Yaghoubi S.,Iran University of Science and Technology
International Journal of Systems Science | Year: 2015

In this paper, we attempt to present a constant due-date assignment policy in a multi-server multi-stage assembly system. This system is modelled as a queuing network, where new product orders are entered into the system according to a Poisson process. It is assumed that only one type of product is produced by the production system and multi-servers can be settled in each service station. Each operation of every work is operated at a devoted service station with only one of the servers located at a node of the network based on first come, first served (FCFS) discipline, while the processing times are independent random variables with exponential distributions. It is also assumed that the transport times between each pair of service stations are independent random variables with generalised Erlang distributions. Each product's end result has a penalty cost that is some linear function of its due date and its actual lead time. The due date is calculated by adding a constant to the time that the order enters into the system. Indeed, this constant value is decided at the beginning of the time horizon and is the constant lead time that a product might expect between the time of placing the order and the time of delivery. For computing the due date, we first convert the queuing network into a stochastic network with exponentially distributed arc lengths. Then, by constructing an appropriate finite-state continuous-time Markov model, a system of differential equations is created to find the manufacturing lead-time distribution for any particular product, analytically. Finally, the constant due date for delivery time is obtained by using a linear function of its due date and minimising the expected aggregate cost per product. © 2013 Taylor & Francis.


Agahi H.,Iran University of Science and Technology
Information Sciences | Year: 2015

Sugeno integral is a useful tool for many problems in several domains, especially in game theory, measure theory, decision making, probability, image processing and finance. In this paper, we introduce the concept of λ-generalized Sugeno integral. Then we establish general versions of Chebyshev type inequality for this kind of Sugeno integral by using a monotone measure. Our results generalize and improve the corresponding ones in the literature. Finally, some conclusions and problems for further investigations are given. © 2015 Elsevier Inc.


Rahbar-Kelishami A.,Iran University of Science and Technology | Bahmanyar H.,University of Tehran
Chemical Engineering Research and Design | Year: 2012

Developments in the area of packed columns, particularly structured packed columns, are ongoing, specifically in the area of liquid-liquid extractions in different industries. In the present study, mass transfer coefficients have been obtained experimentally in a structured packed extraction column to develop a new correlation for prediction of continuous phase Sherwood number. The experiments were carried out for toluene/acetic acid/water and n-butyl acetate/acetic acid/water systems with counter current flow in different heights of column. A new dimensionless parameter, d 32/h, is introduced in proposed equation. This number considers the effect of column height (h) and mean drop diameter (d 32) jointly. The main advantage of this approach is that the principal effect of column height is considered in correlation without which the experimental data could not be fitted with a acceptable accuracy. © 2011 The Institution of Chemical Engineers.


Naghshvarianjahromi M.,Iran University of Science and Technology
Journal of Electromagnetic Waves and Applications | Year: 2010

In this contribution, a compact ultra wideband band-pass filter with low insertion loss and good rejection using semi complementary split ring resonator is introduced. The 3.0 dB bandwidth is 2.9-8.2 GHz. The minimum and maximum insertion losses in passband are about 0.35 and 1.4 dB at frequencies of 5.4 GHz and 4 GHz respectively in measurement. The bandwidth is tunable via changing the upper 1.0 dB cutoff frequency from 5.0 to 9.0 GHz. The dimensions of this filter (excluding access line for connectors) are about 7.2 × 7.2 mm 2. The proposed filter is classified in DGS filters group without their problems such as radiation fields from DGS and requiring specific box. In addition, this filter can be used as conventional microstrip filters in commercial and military RF boards. Low-loss and compact behaviors in most frequency of pass-band are interpreted due to the presence of simultaneously negative εeff and μeff , and then left-handed wave propagation is permitted. © 2010 VSP.


Khalaj-Amirhosseini M.,Iran University of Science and Technology
IET Microwaves, Antennas and Propagation | Year: 2010

Dielectric inhomogeneous planar layers (IPLs) are optimally designed as microwave absorbers in a desired frequency range and incidence angle range. First, the lossy electric permittivity function of the IPL is expanded in a truncated Fourier series. Then, the optimum values of the coefficients of the series are obtained through an optimisation approach. The performance of the proposed structure is investigated and verified using two examples in the frequency range 8-12 GHz and 6-18 GHz. © 2010 The Institution of Engineering and Technology.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Asian Journal of Civil Engineering | Year: 2010

A discrete version of the Charged System Search algorithm (CSS) is developed to optimize truss structures with discrete variables. The discrete CSS algorithm, similar to its original version, is based on some laws from electrostatics and the Newtonian mechanics. Each agent in the CSS is considered as a charged sphere having a uniform volume charge density which can affect an electric force to the other ones. However, contrary to the original CSS, for the discrete CSS, the affected forces can be attractive or repulsive. In addition, a new approach is presented to handle the constraints, which is called the fly to boundary method. Some design examples are tested using the new method and the results are compared to those of other meta-heuristic algorithms to demonstrate the effectiveness of the present method. © 2009 by DotNetNuke Corporation.


Sadeghi J.,Iran University of Science and Technology
Advances in Structural Engineering | Year: 2010

A comprehensive field investigation was made with the aim of achieving a better understanding of the dynamics of railway track pre-stressed concrete sleepers. Modal analysis and free decay method were used to determine the natural frequencies, model shapes and damping of sleepers. The validity of the results is discussed by comparing the results obtained here with those available in the literature. In order to investigate the characteristics of the dynamics of the loads imposed on the sleepers, load cells were installed between the rail seat and the sleeper and beneath the sleeper, recording the interaction between both sleeper and rail, and sleeper and ballast. The loads transferred from the rail to the sleeper and from the sleeper to the ballast were measured as a function of train speed. The rail seat load and the contact pressure between the ballast and the sleepers versus train axle loads and train speeds were recorded. The effects of the sleeper supporting conditions on the sleeper dynamic behaviour were investigated. The ratios of the rail seat load and the ballast contact pressure to the wheel load were obtained from the analyses of the field test results. These ratios were used to calculate the dynamic impact factors and ballast-sleeper pressure distribution patterns required for the design of sleepers. The methods, the test procedures and the results are presented and discussed in this paper.


Barzegar Gerdroodbary M.,Iran University of Science and Technology
Shock Waves | Year: 2014

This study investigates a combined technique of both an active flow control concept that uses counterflowing jets and an aerodisk spike as a new method to significantly modify external flowfields and heat reduction in a hypersonic flow around a nose cone. The coolant gas (Carbon Dioxide and Helium) is chosen to inject from the tip of the nose cone to cool the recirculation region. The gases are considered to be ideal, and the computational domain is axisymmetric. The analysis shows that the counterflowing jet has significant effects on the flowfield and reduces the heat load over the nose cone. The Helium jet is found to have a relatively more effective cooling performance. © 2014 Springer-Verlag Berlin Heidelberg.


Shakeri K.,University of Mohaghegh | Shayanfar M.A.,Iran University of Science and Technology | Kabeyasawa T.,University of Tokyo
Engineering Structures | Year: 2010

In recent years some adaptive pushover methods have been proposed to include the effects of the higher modes and the changes in the vibration characteristics during the inelastic response. However, because of using the quadratic combination rules to combine the modal forces, the changes in the sign of the story components in the higher modes are removed. Consequently, the magnitudes of the applied loads in all story levels are positive and these adaptive methods are not superior to their non-adaptive counterparts. Here, an innovative adaptive pushover method, called "SSAP", is proposed based on the story shears which takes into account the reversal of sign in the higher modes. In each step, the applied load pattern is derived from the instantaneous combined modal story shear profile. The sign of the applied loads in consecutive steps are changed and the structure is simultaneously pushed and pulled in different story levels. Another aspect of the proposed method is that at each step an assumed fundamental mode shape is derived from the load profile. Based on this adaptive fundamental mode shape and the energy concept, the multi degree of freedom system is converted into a single degree of freedom system. The proposed method is applied to two steel moment-frame buildings. The results show an admirable accuracy in prediction of peak inelastic drift response, especially where the effects of the higher modes are important. A combination of this method with the conventional pushover approach, called "SS-M1", results in more accurate estimation of peak inelastic drift in all story levels compared to the other pushover approaches. © 2009 Elsevier Ltd. All rights reserved.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Acta Mechanica | Year: 2010

This paper presents a new optimization algorithm based on some principles from physics and mechanics, which will be called Charged System Search (CSS). We utilize the governing Coulomb law from electrostatics and the Newtonian laws of mechanics. CSS is a multi-agent approach in which each agent is a Charged Particle (CP). CPs can affect each other based on their fitness values and their separation distances. The quantity of the resultant force is determined by using the electrostatics laws and the quality of the movement is determined using Newtonian mechanics laws. CSS can be utilized in all optimization fields; especially it is suitable for non-smooth or non-convex domains. CSS needs neither the gradient information nor the continuity of the search space. The efficiency of the new approach is demonstrated using standard benchmark functions and some well-studied engineering design problems. A comparison of the results with those of other evolutionary algorithms shows that the proposed algorithm outperforms its rivals. © Springer-Verlag 2010.


Jafarian Y.,International Institute of Earthquake Engineering and Seismology | Vakili R.,Concordia University at Montreal | Sadeghi Abdollahi A.,Iran University of Science and Technology
Computers and Geotechnics | Year: 2013

Liquefaction resistance of granular soils is commonly characterized by the cyclic resistance ratio (CRR) in the simplified shear stress procedure of liquefaction potential assessment. This parameter is commonly estimated by cyclic tests on reconstituted samples or empirical correlations between liquefied/non-liquefied case histories. The current study employs results of cyclic triaxial tests on reconstituted soil specimens and presents a predictive equation for cyclic resistance ratio (CRR) of clean and silty sands. The CRR equation is a function of relative density, effective mean confining pressure, non-plastic fines content, number of harmonic cycles for liquefaction onset, and some other basic soil properties. It is demonstrated that the developed relationship obtains reasonable accuracy in the prediction of laboratory-based CRR. Based on the developed CRR model, new relationships are then presented for the coefficient of effective overburden pressure (Kσ) and magnitude scaling factor (MSF), two important modification factors in the simplified shear stress procedure. These new modification factors are then compared with those recommended by previous researchers. Finally, the possible application of the proposed CRR model in field condition is shown for a specific case. This study provides a preliminary insight into the liquefaction resistance of silty sands prior to the complementary laboratory studies. © 2013 Elsevier Ltd.


Oraizi H.,Iran University of Science and Technology | Fallahpour M.,Missouri University of Science and Technology
IEEE Transactions on Antennas and Propagation | Year: 2011

A design procedure for the synthesis of non-uniformly spaced linear arrays is presented, which uses the Poisson sum expansion of the array factor introduced in the literature. By considering the nonzero phase term in the existent formula and using the appropriate line source pattern synthesis methods, a general design procedure is obtained to synthesize any type of pattern, such as sum, difference and shaped beams. This approach converts the nonlinear complex problem of pattern synthesis for non-uniformly spaced linear arrays to a simple problem, which makes it fast and easy to implement. Moreover, an extra optimization process is added to the synthesis procedure to improve final pattern and provide control on computed parameters. © 2011 IEEE.


Nasiri-Gheidari Z.,University of Tehran | Tootoonchian F.,Iran University of Science and Technology
Energy Conversion and Management | Year: 2010

In this paper a novel optimization algorithm based on imperialist competitive algorithm (ICA) is used for the design of a low speed single sided linear induction motor (LIM). This type of motors is used increasingly in industrial process specially in transportation systems. In these applications having high efficiency with high power factor is very important. So in this paper the objective function of design is presented considering both efficiency and power factor. Finally the results of ICA are compared with the ones of genetic algorithm and conventional design. Comparison shows the success of ICA for design of LIMs. © 2010 Elsevier Ltd.


Soltani R.,Iran University of Science and Technology
International Journal of Industrial Engineering Computations | Year: 2014

The purpose of this paper is to discuss the state of the art on models and methods for reliability optimization problems (ROPs) including reliability allocation, redundancy allocation and reliability-redundancy allocation. There are literally few surveys for reviewing the literature of the ROPs. Tillman et al. (1980) classified the related papers by system structure, problem type, and solution methods, separately. In another work, Tzafestas (1980) reviewed system reliability optimization models and the optimization techniques. Yearout (1986) reviewed the literature related to standby redundancy. Kuo (2000) studied the system reliability optimization based on system structure and solution methods. Kuo and Prasad (2004) overviewed system reliability optimization methods. Later, Kuo (2007) reviewed recent advances in optimal reliability allocation problems. The present study adds to the previous literature surveys and focuses mainly on papers after year 2000 but with a quick review on the previous works so that the readers become familiar with the existing approaches. This research investigates the literature from system structure, system performance, uncertainty state and solution approach standpoints, simultaneously. © 2014 Growing Science Ltd. All rights reserved.


Zandi F.,Iran University of Science and Technology
International Journal of Production Research | Year: 2014

Outputs of each enterprise resource planning (ERP) process in an ERP system could constraint outputs of the next ERP processes. Therefore, it is necessary to determine the ability of ERP processes to support the orchestration of an ERP system. This paper presents a bi-level constraint-oriented outsourcing framework to identify any ERP process that effects on the orchestration of an ERP system. The contribution of the proposed bi-level constraint-oriented outsourcing framework for orchestration of ERP is twofold: (1) it develops the traditional constraints management from a crisp single-criteria environment to a fuzzy multi-criteria environment; and (2) it develops a linear programming technique for multidimensional analysis of preference (LINMAP) model to a fuzzy group bi-level LINMAP model. A case study demonstrates the applicability of the proposed constraint-oriented outsourcing framework for orchestration of ERP modules and processes. © 2013 Taylor & Francis.


Hedayati H.,Iran University of Science and Technology
Journal of Multiple-Valued Logic and Soft Computing | Year: 2013

Using a generalized version of the notion of quasi-coincidence of a fuzzy point, a generalization of (implicative) (∈,∈ vq)-fuzzy ideal, called (implicative) (∈,∈ vk)-fuzzy ideal, in a pseudo-MV algebra is introduced. Also (implicative) (∈,∈ vk)-fuzzy ideals are characterized in different ways. Specially, it is proved that, under certain conditions, an implicative (∈,∈ vk)-fuzzy ideal can be expressed as the union of two implicative (∈,∈ vk)-fuzzy ideals. Finally, a generalization of (implicative) implication-based fuzzy ideals is introduced and studied. © 2013 Old City Publishing, Inc.


Daneshmehr A.,University of Tehran | Rajabpoor A.,University of Tehran | Pourdavood M.,Iran University of Science and Technology
International Journal of Engineering Science | Year: 2014

This article presents a nonlocal higher order plate theory for stability analysis of nanoplates subjected to biaxial in plane loadings. It is assumed that the properties of the FG nanoplate follow a power law form through the thickness. Governing equations and corresponding boundary conditions are derived by using the principle of minimum potential energy. Generalized differential quadrature (GDQ) method is implemented to solve the size dependent buckling analysis according to the higher order shear deformation plate theories where highly coupled equations exist for various boundary conditions of rectangular plates. Some numerical results are presented to study the effects of the material length scale parameter, plate thickness, Poisson's ratio, side to thickness ratio and aspect ratio on size dependent buckling load. It is observed that buckling load predicted by higher order theory significantly deviates from classical ones, especially for thick plates. Also comparing the results obtained from different theories shows that as the material length scale parameter take higher values, the difference between the buckling load resulting from the first order shear deformation plate theory (FSDT), classical theory and higher order plate theory declines. © 2014 Elsevier Ltd. All rights reserved.


Khakzand M.,Iran University of Science and Technology
Journal of Asian Architecture and Building Engineering | Year: 2014

The value of socio-cultural aspects in the environmental design process and relevant issues are discussed in this paper. In addition, Alexander's Pattern Language theory is derived from human activity, perceptive and behavioural patterns and is associated with the Genius loci. Thus, the researcher considered the possibility of a relationship existing between Pattern Language and the field of Environmental Design (especially the socio-cultural dimension) that would arrive at a correlation model of A Pattern Language for Environmental Design. The research method was a survey implemented to collect data from 129 MS (related to the Environmental Design field) graduates and students studying at various universities in Tehran. The sampling method was based on stratified random sampling. A 49-item questionnaire was used to collect data and the reliability of all subscales was more than 0.80 estimated by the Cronbach alpha test. Hierarchical Confirmatory Factor Analysis was used to analyse data by LISREL 8.72 software. The results of the analysis statistically confirmed the correlation model of A Pattern Language for Environmental Design. While all correlations between pattern language components and their counterpart indicators were statistically significant, the correlation between the socio-cultural dimension and environmental design was the most powerful relationship in the model.


Daliri M.R.,Iran University of Science and Technology
Measurement: Journal of the International Measurement Confederation | Year: 2012

Here an approach for the diagnosis of neuro-degenerative diseases based on gait dynamics is proposed. The proposed method uses information from a time series of stride intervals, swing intervals, stance intervals and double support intervals of stride-to-stride measures of footfall contact times using force-sensitive resistors. Different features were extracted from these time series and the best of them were selected for the diagnosis. The support vector machines using different kernels were examined for the diagnosis. The radial basis function kernel obtained the best performance for this aim. The results show that features derived from double support intervals are common effective features for the diagnosis of neuro-degenerative diseases using the gait dynamics. © 2012 Published by Elsevier Ltd. All rights reserved.


Kaveh A.,Iran University of Science and Technology | Rahami H.,University of Tehran
International Journal for Numerical Methods in Engineering | Year: 2010

In this paper, an efficient method is developed for the analysis of regular structures. A structure is called regular if its model can be formed by a graph product. Here, instead of direct solution of the equations corresponding to a regular structure or finding the inverse of the stiffness matrix directly, modal analysis is used, and eigenvectors are employed for calculating the displacements and then internal forces of the structures. For this purpose, first an efficient method is developed for calculating the eigenvectors of the product graphs, and then a method is presented for using these eigenvectors for evaluating the displacements of a structure. © 2010 John Wiley & Sons, Ltd.


Vasquez J.C.,University of Aalborg | Guerrero J.M.,University of Aalborg | Savaghebi M.,Iran University of Science and Technology | Eloy-Garcia J.,Charles III University of Madrid | Teodorescu R.,University of Aalborg
IEEE Transactions on Industrial Electronics | Year: 2013

Power-electronics-based microgrids (MGs) consist of a number of voltage source inverters (VSIs) operating in parallel. In this paper, the modeling, control design, and stability analysis of parallel-connected three-phase VSIs are derived. The proposed voltage and current inner control loops and the mathematical models of the VSIs are based on the stationary reference frame. A hierarchical control scheme for the paralleled VSI system is developed comprising two levels. The primary control includes the droop method and the virtual impedance loops, in order to share active and reactive powers. The secondary control restores the frequency and amplitude deviations produced by the primary control. Also, a synchronization algorithm is presented in order to connect the MG to the grid. Experimental results are provided to validate the performance and robustness of the parallel VSI system control architecture. © 1982-2012 IEEE.


Taravati S.,Iran University of Science and Technology
International Journal of RF and Microwave Computer-Aided Engineering | Year: 2013

New designs of wide-band rat-race couplers are proposed. The wide-band operation is achieved with the use of the microstrip nonuniform transmission line sections for the branches of the conventional rat-race coupler. The design formulas are developed using ABCD matrix and the even- and odd-mode analysis. The theoretical analysis has been verified by measurements of the two manufactured wideband rat-race couplers, one operate within 0.85-1.92 GHz and other within 1.55-3.55 GHz frequency range with the equal normalized characteristic impedance functions. For both fabricated couplers, the isolation parameter is better than 15 dB over a 77% relative bandwidth. Also, it is shown that the designed wide-band rat-race coupler can be realized in higher frequency bands with the fixed fractional bandwidth. © 2012 Wiley Periodicals, Inc.


Pakzad M.A.,Islamic Azad University at Tehran | Moaveni B.,Iran University of Science and Technology
WSEAS Transactions on Systems and Control | Year: 2013

In this article, an observer with delay-dependent stability conditions has been presented for time delay systems with unknown inputs, where the time delay terms exist in the state and output of the system. The designing of this observer, whose performance index is the H2 norm, has been formulated as a nonlinear optimization problem. By using the finite characterization of a Lyapunov functional equation, sufficient conditions have been proposed to guarantee the existence of a desirable H2 filter. This finite characterization can be calculated by means of a matrix exponential function. Several numerical examples have also been simulated to show the effectiveness and simplicity of the proposed observer.


Vahidi B.,Amirkabir University of Technology | Esmaeeli E.,Iran University of Science and Technology
Computer Applications in Engineering Education | Year: 2013

Differential protection was already applied toward the end of the 19th century and was one of the first protection systems ever used. Faults are detected by comparison of the currents flowing into and out of the protected plant item. As a result of the fast tripping with absolute selectivity, it is suited as main protection of all important items of plant. The article presents an approach to teaching relay laboratory using specially designed exercises that can be done using MATLAB-SIMULINK. This article presents a MATLAB-SIMULINK- based technology to simulate differential relay for determining behavior of it during transformer internal fault protection. The results show that this simulation method can work properly and this design can be used for power system simulation in MATLAB-SIMULINK. Evaluation of the simulation with more than 60 students is very positive in terms of their developing confidence in and understanding of this kind of relay operation. © 2010 Wiley Periodicals, Inc.


Afshar M.H.,Iran University of Science and Technology
Proceedings of the Institution of Civil Engineers: Water Management | Year: 2013

A cellular automata (CA) method is proposed in this paper for the optimal operation of hydropower multi-reservoir systems. The beginning and the end of the operation periods are taken here as the CA cells leading to the storage volumes of the system being defined as the cell state. This choice naturally leads to a cell neighbourhood defined by the previous and next periods of the underlying cell. The objective function and constraints of the underlying optimal operational problem are projected on each cell to arrive at the local updating rule of the CA method. The resulting updating rule is, therefore, defined by an optimisation sub-problem of a size equal to the number of reservoirs in the system which is subsequently solved by NLP technique to get the updated values of the cell states, storage volumes of the reservoirs in the system. The efficiency and effectiveness of the proposed CA method is tested against two multi-reservoir systems, namely four-and ten-reservoir problems over 12, 60 and 240 monthly operation periods, and the results are presented and compared with those obtained by two of the most commonly used continuous heuristic search methods, namely genetic algorithm (GA) and particle swarm optimisation (PSO) algorithms. The results show that the proposed CA method is more efficient and effective than the GA and PSO algorithms, in particular for the solution of large-scale multi-reservoir hydropower operation problems.


Shojaei I.,University of Tehran | Kaveh A.,Iran University of Science and Technology | Rahami H.,University of Tehran
Computers and Structures | Year: 2013

In this paper an efficient method is presented for the analysis of those structures which can be converted to regular forms. The stiffness matrix for such regular structures can easily be inverted using their eigenvalues and eigenvectors. Many non-regular structures can be converted to regular forms. Here the presented method solves not only all the regular forms but also non-regular forms convertible to regular ones. The efficiency of the method is more significant when it is used in reanalyzing and rehabilitating structures where the stiffness matrix should be inverted in each step. © 2013 Elsevier Ltd. All rights reserved.


Farahani M.R.,Iran University of Science and Technology
Acta Chimica Slovenica | Year: 2013

Among topological descriptors connectivity topological indices are very important and they have a prominent role in chemistry. One of them is atom-bond connectivity (ABC) index defined as (Equation required) in which degree of vertex v denoted by dv. Recently, a new version of atom-bond connectivity (ABC4) index was introduced by M. Ghorbani et.al in 2010 and is defined as (Equation required) where (Equation required). In this paper we compute this new topological index for V-Phenylenic Nanotube and Nanotori.


Shabannia R.,Iran University of Science and Technology | Hassan H.A.,Universiti Sains Malaysia
Electronic Materials Letters | Year: 2014

Vertically aligned ZnO nanorods were synthesized on a polyethylene naphthalate (PEN) substrate using a chemical bath deposition method at a low temperature. The structural and optical investigations revealed the high quality of the fabricated ZnO nanorods on flexible substrate. A metal-semiconductor-metal UV photodetector based on ZnO nanorods was fabricated on the PEN substrate. The optoelectronic characteristics of fabricated UV photodetector were studied in the dark and under 325 nm UV light illumination at -3 V and 3 V bias voltages. The responsivity and photosensitivity of the ZnO nanorod UV photodetector were 2.856 A/W and 1175% at 3 V bias voltage, respectively. Moreover, the response and the recovery times measured during the turn-on and turnoff of UV illumination were 1.2 s and 1.8 s, respectively. © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.


Jalalvand M.,Amirkabir University of Technology | Hosseini-Toudeshky H.,Amirkabir University of Technology | Mohammadi B.,Iran University of Science and Technology
Composite Structures | Year: 2013

Diffuse delamination induced by transverse cracking is usually the secondary damage mode when a composite laminate experiences tensile loading. The fist damage mechanism in such a laminate is transverse cracking which has been widely investigated with both analytical methods and " mechanism-based" constitutive laws. Delamination induced by matrix cracking is already studied extensively by analytical approaches, however, a proper homogenization way has not been proposed yet. In this paper, a modification to an available cohesive constitutive law is proposed which is capable of considering the effect of diffuse delamination without the necessity of consideration of an actual discontinuity between the layers. The proposed constitutive law is then compared against its equivalent models containing interlaminar discontinuity and it is shown that the obtained results from both models are in good. Then the proposed modification is used in Double Cantilever Beam (DCB) specimen and the obtained results are found coincident with the equivalent model with diffuse discontinuities at the interface. Finally, a damaged cross-ply laminate is modeled under the boundary conditions of tensile loading and also 3-point bending with and without the proposed cohesive modification. In tensile loading, the results of both cases are similar; however, it is shown that in bending, the unmodified cohesive law predicts the lateral stiffness larger than the proposed modification. The lateral stiffness of the equivalent model with discontinuities as crack indicates that the proposed modification is able to properly consider the lateral stiffness decrease. © 2013 Elsevier Ltd.


Mosaddegh E.,Iran University of Science and Technology | Mosaddegh E.,Research Institute of Environmental science | Hassankhani A.,HIGH-TECH
Tetrahedron Letters | Year: 2011

A new, efficient, and environmentally benign protocol for the one-pot, four-component synthesis of 2,2-dimethyl-13-phenyl-2,3-dihydro-1H-indazolo[2,1- b]phthalazine-1,6,11(13H)-trione by condensation of phthalic anhydride, hydrazinium hydroxide, aromatic aldehydes, and dimedone catalyzed by Ce(SO 4)2·4H2O as an ecofriendly catalyst with high catalytic activity and reusability at 125 °C under solvent-free conditions is reported. The reaction proceeds to completion within 5-10 min in 71-95% yield. To the best of our knowledge, this new procedure provides the first example of an efficient synthetic method for 2H-indazolo[2,1-b] phthalazine-1,6,11(13H)-trione via a four-component reaction. © 2010 Elsevier Ltd. All rights reserved.


Eshaghi A.,Iran University of Science and Technology | Graeli A.,Iranian Academic Center for Education
Optik | Year: 2014

In this research, indium tin oxide (ITO) thin films of various thickness (200, 250, 300, 350, 400 nm) were deposited on polycarbonate polymer substrates using a magnetron sputtering technique. The structure, morphology, surface composition, optical and electrical properties of the thin films were investigated by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), X-ray Photoelectron Spectroscopy (XPS), UV-VIS-NIR spectrophotometer and four point probe method, respectively. The results indicated that grain size increased as the thickness increased. The transmittance and sheet resistance of the ITO thin films showed that ITO thin films with 200 nm thickness had the highest transmission whereas ITO thin film with 400 nm had the best conductivity.


Mokhtarian M.N.,Islamic Azad University at Tehran | Sadi-Nezhad S.,Islamic Azad University at Tehran | Makui A.,Iran University of Science and Technology
Computers and Industrial Engineering | Year: 2014

Facility location selection problem is one of the challenging and famous kinds of MCDM problems including both quantitative and qualitative criteria. For each Multiple Criteria Decision Making (MCDM) problem, when the ratings of alternatives with respect to the criteria and/or the values of criteria's weights are presented by Interval Valued Fuzzy Numbers (IVFNs), the conventional fuzzy MCDM methods (Type-1 fuzzy MCDM methods) tend to be less effective. Therefore, the IVF-MCDM (Interval Valued Fuzzy MCDM) methods should be applied for solving such fuzzy MCDM problems. In this paper, we propose an IVF-VIKOR (VlseKriterijumska Optimizacija I Kompromisno Resenje) method based on uncertainty risk reduction in decision making process. By using such method, the reliability of the captured decisions in an IVF decision making problem is significantly increased. The proposed method is applied for solving two numerical examples that the former of which is a real application problem related to selecting a suitable location for digging some pits for municipal wet waste landfill in one of the largest cities in Iran. The second numerical example is presented with an aim of comparing our method with the two other IVF-MCDM methods. As a result, we found out the proposed method is reliable and practical for the facility location selection problems and other MCDM problems. Moreover, the proposed method has a considerable accuracy and is flexible and easy to use. © 2014 Elsevier Ltd. All rights reserved.


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.


Mokhtari A.,Iran University of Science and Technology | Nejad F.M.,Amirkabir University of Technology
Journal of Materials in Civil Engineering | Year: 2013

Stone-matrix asphalt (SMA) is a type of hot-mix asphalt that can reduce the cost of maintenance and rehabilitation of pavements through decreasing the amount of permanent deformation during its service life. In addition, warm-mix asphalt (WMA) has been recently used to reduce the mixing and compaction temperatures of asphalt concrete and potentiallydecrease the initial cost of asphalt mixtures, especially in countries for which energy costs are high. The primary purpose of this research is to combine these technologies to produce more efficient asphalt mixtures. To this end, two different additives [cellulose fiber and styrene-butadiene-styrene (SBS)] were used to construct typical SMA mixtures, and a type of WMA additive (wax) was used to prepare warm SMA specimens. Modified binders were subjected to binder properties tests. Mixture performance tests, including the Marshall, indirect tensile strength, moisture susceptibility, dynamic creep, and resilient modulus tests were also performed to evaluate the performance properties of different types of SMA mixtures. A mechanisticempirical design procedure was conducted to investigate the benefit of modification. The results indicate that Fischer-Tropsch (FT) wax is capable ofenhancing the base binder properties. Although different percents of wax could reduce theamount of binder drain down, this reduction was not adequate. Consequently, the use of anadditional additive may be necessary. The effect of wax on the performance properties of SMA mixtures was also insignificant, although there were some improvements. Moreover, by comparing the test results, good correlations were obtained between various performance properties of SMA mixtures, all of which were significant. The use of cellulose fiber, SBS, and FTwax would respectively increase the service life of the pavement 1.08, 1.243, and1.154 times more than the corresponding unmodified mixtures. © 2012 American Society of Civil Engineers.


Nateghi A.,University of Tehran | Salamat-talab M.,Iran University of Science and Technology
Composite Structures | Year: 2013

Thermal effect on buckling and free vibration behavior of functionally graded (FG) microbeams based on modified couple stress theory is presented. Classical and first order shear deformation beam theories are adopted to count for the effect of shear deformations. Hamilton's principle is applied to give the governing equations, boundary and initial conditions of the FG microbeam. Using generalized differential quadrature (GDQ) method buckling load and natural frequency of FG microbeam with different boundary conditions are obtained. Some numerical results are presented to investigate effects of different parameters including temperature changes, material length scale parameter, beam thickness, Poisson's ratio and power index of material distribution on the FG microbeam behavior. Numerical results show that modified couple stress theory predicts higher values of buckling load and natural frequency for FG microbeams. In addition, it is observed that higher temperature changes signify size dependency of FG microbeam. It is shown that Poisson's effect on buckling load and natural frequency predicted by the current model differs significantly from classical one. Study of power index of material distribution proved that the behavior of FG microbeams differ considerably from homogeneous isotropic ones. © 2012 Elsevier Ltd.


Asgharifard Sharabiani P.,Iran University of Science and Technology | Haeri Yazdi M.R.,University of Tehran
Composites Part B: Engineering | Year: 2013

Nonlinear free vibration of functionally graded nanobeams is studied in this paper within the framework of Euler-Bernoulli beam model including the von Kármán geometric nonlinearity. It is assumed that material properties follow power law distributions through thickness direction. A second order nonlinear ordinary differential equation with quadratic and cubic nonlinear terms is obtained by using the free vibration modes of the corresponding linear problem. The direct numerical integration method is employed to find the natural frequencies of FG nanobeams with different boundary conditions. Numerical results demonstrate the normalized natural frequencies in different nanobeam dimensions, vibration amplitudes and volume fraction indices of FG material. Finally, the surface effects on the phase plane trajectory of fundamental mode time-dependent function have been shown. © 2012 Elsevier Ltd. All rights reserved.


Ghannadpour S.A.M.,Shahid Beheshti University | Mohammadi B.,Iran University of Science and Technology | Fazilati J.,Aerospace Research Institute
Composite Structures | Year: 2013

The present study is concerned with the bending, buckling and vibration analyzes of nonlocal Euler beams. Weak form of the governing equation of nonlocal Euler beams is outlined in this paper. Ritz method is selected in order to analyze the nonlocal beams with arbitrary boundary conditions along them. Analytical formulations are developed to find the stiffness matrix, buckling stiffness matrix and mass matrix. The results of the presented formulation for bending, vibration and buckling of nonlocal Euler beams with four classical boundary conditions are computed and compared, wherever possible. Finally, two types of beams with general boundary conditions are selected and new results are obtained which demonstrate the capability of the Ritz method to model such nonlocal beams. © 2012 Elsevier Ltd.


Eslamian M.,Iran University of Science and Technology
UPB Scientific Bulletin, Series A: Applied Mathematics and Physics | Year: 2014

In this paper, we consider Rockafellar's proximal point algorithm with viscosity method for a finite family of monotone operators. We obtain the strong convergence of the proposed algorithm to a common zero point for a finite family of monotone operators in Hilbert spaces. The results obtained in this paper extend and improve some recent known results.


Berto F.,University of Padua | Lazzarin P.,University of Padua | Ayatollahi M.R.,Iran University of Science and Technology
Carbon | Year: 2013

Brittle failure of isostatic polycrystalline graphite under pure compression loading is investigated experimentally by using prismatic specimens weakened by sharp and rounded-tip V-notches. The notched samples are characterised by different geometry parameters, i.e. notch opening angle and notch root radius, with the aim to provide a complete set of static strength data. While there are a number of papers dealing with compression of unnotched specimens made of different materials, very few results are available from notched components under compression and, in particular, no data can be found for isostatic graphite. After the description of the experimental activity, a criterion based on the strain energy density (SED) is proposed for the fracture assessment of notched graphite components under compression. The criterion, which averages SED over a control volume surrounding the notch tip, is an extension of what the present authors have proposed in previous papers dealing with the cases of in-plane tension-shear loading and torsion loading in notched graphite specimens. Good agreement is shown to exist between the experimental results and the theoretical predictions obtained for the fracture loads. © 2013 Elsevier Ltd. All rights reserved.


Rahmati A.,Sharif University of Technology | Ghaemi A.,Iran University of Science and Technology | Samadfam M.,Sharif University of Technology
Annals of Nuclear Energy | Year: 2012

Thermodynamic and kinetic studies have been carried out on the adsorption of uranium(VI) by Amberlite IRA-910 resin. The adsorption process has been investigated as a function of adsorbate concentration, solution acidity, contact time, adsorbent dosage, and temperature. The experiments were preformed in batch mode, where uranium initial concentration on the solution samples were 185.5, 277.6 and 456.8 (mg/lit), sulfuric acid concentration range was 0.02-9 (mol/lit) and sorbent dosages were 0.2, 0.3 and 0.5 g. Equilibrium isotherm data were analyzed using Freundlich and Dubinin-Radushkevich isotherm models. The results showed that the adsorption process was well described by Freundlich isotherm model. The kinetic data were analyzed using first-order and pseudo-second order kinetic models. The results indicated that adsorption fitted well with the pseudo-second order kinetic model. The thermodynamic parameters were determined at six (15, 30, 45, 45, 60 and 75 °C) different temperatures by plotting ln K L versus 1/T. The ΔH° and ΔG° values of uranium(VI) adsorption on Amberlite IRA-910 show endothermic heat of adsorption; higher temperatures favor the process. © 2011 Elsevier Ltd. All rights reserved.


Afshari K.,Islamic Azad University at Amol | Samavati V.,Iran University of Science and Technology | Shahidi S.-A.,Islamic Azad University at Amol
International Journal of Biological Macromolecules | Year: 2015

The effects of ultrasonic power, extraction time, extraction temperature, and the water-to-raw material ratio on extraction yield of crude polysaccharide from the leaf of Hibiscus rosa-sinensis (HRLP) were optimized by statistical analysis using response surface methodology. The response surface methodology (RSM) was used to optimize HRLP extraction yield by implementing the Box-Behnken design (BBD). The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis and also analyzed by appropriate statistical methods (ANOVA). Analysis of the results showed that the linear and quadratic terms of these four variables had significant effects. The optimal conditions for the highest extraction yield of HRLP were: ultrasonic power, 93.59. W; extraction time, 25.71. min; extraction temperature, 93.18. °C; and the water to raw material ratio, 24.3. mL/g. Under these conditions, the experimental yield was 9.66. ±. 0.18%, which is well in close agreement with the value predicted by the model 9.526%. The results demonstrated that HRLP had strong scavenging activities in vitro on DPPH and hydroxyl radicals. © 2014 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.


The method of wave function expansion is adopted to study the three dimensional scattering of a plane progressive harmonic acoustic wave incident upon an arbitrarily thick-walled helically filament-wound composite cylindrical shell submerged in and filled with compressible ideal fluids. An approximate laminate model in the context of the so-called state-space formulation is employed for the construction of T-matrix solution to solve for the unknown modal scattering coefficients. Considering the nonaxisymmetric wave propagation phenomenon in anisotropic cylindrical components and following the resonance scattering theory which determines the resonance and background scattering fields, the stimulated resonance frequencies of the shell are isolated and classified due to their fundamental mode of excitation, overtone and style of propagation along the cylindrical axis (i.e., clockwise or anticlockwise propagation around the shell) and are identified as the helically circumnavigating waves. © 2016, Pleiades Publishing, Ltd.


Jamalpoor A.,Iran University of Science and Technology | Hosseini M.,Sirjan University of Technology
Composites Part B: Engineering | Year: 2015

Background/purpose This paper deals with analysis of biaxial buckling behavior of double-orthotropic microplate system including in-plane magnetic field, using strain gradient theory. Methods Two Kirchhoff microplates are coupled by an internal elastic medium and also are limited to the external Pasternak elastic foundation. Utilizing the principle of total potential energy, the equilibrium equations of motion for three cases (out-of-phase buckling, in-phase buckling and buckling with a plate) are acquired. In this study, we assumed boundary conditions of all the edges are simply supported. In order to get exact solution for buckling load of system, Navier approach which satisfies the simply supported boundary conditions is applied. Results Variations of the buckling load of double-microplate system subjected to biaxial compression corresponding to various values of the thickness, length scale parameter, magnetic field, stiffness of internal and external elastic medium, aspect ratio, shear stiffness of the Pasternak foundation and biaxial compression ratio are investigated. Furthermore, influence of higher modes on buckling load is shown. By comparing the numerical results, it is found that dimensionless buckling load ratio for in-phase mode is more than those of out of phase and one microplate fixed. Also it is shown that the value of buckling load ratio reduces, when non-dimensional length scale parameter increases. Conclusion However, we found when properties of plate are orthotropic the buckling load ratio is more than isotropic state. Also, by considering the effect of magnetic field, non-dimensional buckling load ratio reduces. © 2015 Elsevier Ltd All rights reserved.


Samavati V.,University of Tehran | Adeli M.,Iran University of Science and Technology
Carbohydrate Polymers | Year: 2014

The present work is focused on the optimization of hydrophobic compounds extraction process from the carbohydrate matrix of Iranian Pistacia atlantica seed at laboratory level using ultrasonic-assisted extraction. Response surface methodology (RSM) was used to optimize oil seed extraction yield. Independent variables were extraction temperature (30, 45, 60, 75 and 90 C), extraction time (10, 15, 20, 25, 30 and 35 min) and power of ultrasonic (20, 40, 60, 80 and 100 W). A second order polynomial equation was used to express the oil extraction yield as a function of independent variables. The responses and variables were fitted well to each other by multiple regressions. The optimum extraction conditions were as follows: extraction temperature of 75 C, extraction time of 25 min, and power of ultrasonic of 80 W. A comparison between seed oil composition extracted by ultrasonic waves under the optimum operating conditions determined by RSM for oil yield and by organic solvent was reported. © 2013 Elsevier Ltd.


Janipour M.,Iran University of Science and Technology | Janipour M.,Sabanci University | Sendur K.,Sabanci University
Journal of Lightwave Technology | Year: 2016

In this study, we demonstrate enhanced transmission for out-of-plane stacked plasmonic apertures through the interaction of localized surface plasmons of apertures using both numerical and theoretical approaches. A dispersive finite-difference time-domain (D-FDTD) model is used to investigate the systems through the numerical simulations. To explain the results of the FDTD numerical simulations and to bring further insight to this interaction, we use a magnetic coupled dipole approximation as the theoretical basis. Our results demonstrate that near-field in-phase and out-of-phase interactions of the stacked nanoholes increase or decrease the optical transmission. Plasmon hybridization is discussed for stacked nanohole dimers on out-of-plane metallic films. © 2015 IEEE.


Haji Abdolvahab R.,Iran University of Science and Technology
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2016

Chaperone driven polymer translocation is an important model for biopolymer's translocation in vivo. Binding proteins spatial distribution is a significant factor in calculating the translocation time of the polymer in this type of translocation. Here using a dynamical Monte Carlo simulation we compare the results of the usual uniform distribution with the exponential distribution of different rates for a stiff polymer. Our simulation results show that just by changing the chaperones spatial distribution the translocation time of the biopolymer will change by as large as an order. It can change the translocation regime of the polymer completely from a diffusive to a ballistic one. Although generally increasing the exponential rate and the background concentration will increase the translocation velocity, it is not always true and one should consider both the sequence and the background concentration. We show that the results depend on the sequence and changing the distribution rates for increasing the translocation velocity will change the whole Probability Density Function (PDF) of the polymer translocation time accordance to its sequence. The translocation time sequence dependency will change in the extreme cases e.g. in the high exponential rate. Investigating the binding protein size, λ, also shows the importance of the so called parking lot effect in distribution dependency of the translocation velocity. Although there is not any important dependency for λ=1, translocation time depends clearly on the chaperone spatial distribution for the case of λ≥2. © 2016 Elsevier B.V. All rights reserved.


Moradi A.,Iran University of Science and Technology
Physics of Plasmas | Year: 2016

A theory of electrostatic surface waves on a quantum plasma half-space is developed with the inclusion of external magnetic field effects for the geometry in which the magnetic field is parallel to the surface and the direction of propagation is perpendicular to the magnetic field. A general analytical expression for dispersion relation of surface waves is obtained by solving Poisson and quantum magnetohydrodynamic equations with appropriate quantum boundary conditions. © 2016 AIP Publishing LLC.


Alinejad H.,Iran University of Science and Technology | Alinejad H.,Research Institute for Astronomy and Astrophysics of Maragha RIAAM
Astrophysics and Space Science | Year: 2013

The combined effects of the obliqueness and nonextensive electrons are incorporated in the study of ion-acoustic (IA) solitary waves in a magnetized electron-positron-ion (e-p-i) plasma. The nonlinear Korteweg-de Vries (KdV) equation is derived by using the reductive perturbation method. The plasma parameters such as, the degree of nonextensivity, obliqueness, positron concentration and temperature ratio are found to significantly affect the solitary waves characteristics. Also, a critical value of nonextensivity is found for which solitary structures transit from positive to negative potential. Our finding contributes to the physics of the nonlinear electrostatic excitation in astrophysical and cosmological scenarios like magnetosphere, polar cups region of pulsars, neutron stars and white dwarfs, etc., where magnetized e-p-i plasma can exist. © 2013 Springer Science+Business Media Dordrecht.


Kaveh A.,Iran University of Science and Technology | Rahami H.,University of Tehran
International Journal for Numerical Methods in Biomedical Engineering | Year: 2010

The graph model of many space structures and finite element models can be formed using graph products. These structures are known as regular structures. Methods for calculating the eigenvalues of the matrices corresponding to these models are already investigated. In practice for some structural models the addition of some nodes and members to the graph product is required. When such a node and the incident members are added to a regular model, it becomes a modified regular structure. In this paper the eigenproblem of the matrices corresponding to these models is studied. The necessary formulations are derived and examples are presented to illustrate the practical value of the presented approach. ©2009 John Wiley & Sons, Ltd.


Ahmadi N.,Iran University of Science and Technology
Engineering Applications of Artificial Intelligence | Year: 2010

The automatic recognition of the modulation format of a detected signal, the intermediate step between signal detection and demodulation, is a major task of an intelligent receiver, with various civilian and military applications. Obviously, with no knowledge of the transmitted data and many unknown parameters at the receiver, such as the signal power, carrier frequency and phase offsets, timing information, etc., blind identification of the modulation is a difficult task. This becomes even more challenging in real world. In this paper I develop a novel algorithm using Two Threshold Sequential Algorithmic Scheme (TTSAS) algorithm and pattern recognition to identify the modulation types of the communication signals automatically. I have proposed and implemented a technique that casts modulation recognition into shape recognition. Constellation diagram is a traditional and powerful tool for design and evaluation of digital modulations. In this paper, modulation classification is performed using constellation of the received signal by fuzzy clustering and consequently hierarchical clustering algorithms are used for classification of Quadrature-Amplitude Modulation (QAM) and Phase Shift Keying (PSK) modulations and also modulated signal symbols constellation utilizing TTSAS clustering algorithm, and matching with standard templates, is used for classification of QAM modulation. TTSAS algorithm used here is implemented by the Hamming neural network. The simulation results show the capability of this method for modulation classification with high accuracy and appropriate convergence in the presence of noise. © 2009 Elsevier Ltd. All rights reserved.


Alavi A.H.,Iran University of Science and Technology | Sahab M.G.,Tafresh University | Gandomi M.,University of Tehran
Engineering with Computers | Year: 2010

This paper presents an alternative approach to formulation of soil classification by means of a promising variant of genetic programming (GP), namely multi expression programming (MEP). Properties of soil, namely plastic limit, liquid limit, color of soil, percentages of gravel, sand, and fine-grained particles are used as input variables to predict the classification of soils. The models are developed using a reliable database obtained from the previously published literature. The results demonstrate that the MEP-based formulas are able to predict the target values to high degree of accuracy. The MEP-based formulation results are found to be more accurate compared with numerical and analytical results obtained by other researchers. © Springer-Verlag London Limited 2009.


Daliri M.R.,Iran University of Science and Technology | Daliri M.R.,Institute for Research in Fundamental Sciences
Brain Topography | Year: 2012

The functional magnetic resonance imaging (fMRI) provides very useful information about the activities from different brain areas during a task. This information can be used to train a classifier and predict the sensory and motor functions and also different mental states of the subject's brain in a particular task. Using a high resolution fMRI, normally the activities from many voxels are obtained with respect to time and not all of these voxels involve actively in a particular task. Here we propose a combination of feature selection strategies using an evolutionary computation algorithm and the support vector machines to find out those feature dimensions that are actively involved in representing the brain activities in a particular task. We show that using this lower dimensional space we can predict the cognitive state of the subjects in a particular task more accurately. © 2011 Springer Science+Business Media, LLC.


Koohestani K.,University of Tabriz | Kaveh A.,Iran University of Science and Technology
Finite Elements in Analysis and Design | Year: 2010

Eigenproblems play a key role in the stability and free vibration analysis of structures. In large structural models, the solutions of these problems need a considerable computational effort. There are special types of structures whose special properties can be utilized to achieve solutions in a much simpler way. In this paper, an efficient method is presented for buckling and free vibration analysis of cyclically repeated space truss type structures. First, for a three dimensional truss element, stiffness, geometric stiffness and mass matrices are expressed in cylindrical coordinate system and this leads to the formation of a special pattern for the related matrices of entire of such structures. Second, using this pattern where some concepts of Kronecker product, initial generalized eigenproblems are decomposed into some subproblems with smaller dimensions and their solutions can easily be obtained. Finally, the efficiency of the present method is illustrated through some examples. © 2010 Elsevier B.V.


Yang S.-S.,Jiangsu University | Derakhshan S.,Iran University of Science and Technology | Kong F.-Y.,Jiangsu University
Renewable Energy | Year: 2012

Insufficient understanding of the correlation between pump and pump as turbine (PAT) performance is a major problem encountered in the PAT selection and design. Therefore, establishment of accurate PAT performance prediction methods is necessary. In this paper, theoretical analysis of the relationship between pump and PAT performance was first performed. A theoretical method of predicting PAT performance is developed using theoretical analysis and empirical correlation. In the next step, computational fluid dynamics (CFD) was adopted in the direct and reverse modes performance prediction of a single stage centrifugal pump. To give a more accurate CFD result, all domains within the PAT control volume were modeled and hexahedral structured mesh was generated during CFD simulation. Complete performance curves of its pump and turbine modes were acquired. To verify the accuracy of theoretical and numerical prediction methods, the pump was manufactured and tested on a PAT open test rig. Results comparison and discussion of the theoretical, numerical and some other methods with experimental data were carried out. Eventually, relatively accurate theoretical and numerical PAT performance prediction methods were developed. © 2012 Elsevier Ltd.


Azadi M.,Sharif University of Technology | Azadi M.,Iran Khodro Powertrain Company IPCO | Shirazabad M.M.,Iran University of Science and Technology
Materials and Design | Year: 2013

In the present paper, the heat treatment effect on A356.0, a cast aluminum alloy which has been widely used in diesel engine cylinder heads, is investigated under out-of-phase thermo-mechanical fatigue and low cycle fatigue (at different temperatures) loadings. A typical heat treatment is applied to the material including 8. h solution at 535 °C, water quench and 3. h ageing at 180 °C. The experimental fatigue results show that the heat treatment process has considerable influence on mechanical and low cycle fatigue behaviors, especially at room temperature, but its effect on thermo-mechanical fatigue lifetime is not significant. The improvement in the strength can be explained by the dislocation theory. Under thermo-mechanical fatigue loadings, the difference between the fatigue lifetime of A356.0 alloy and A356.0-T6 alloy decreases when the temperature range increases. In this condition, plastic strain increases severely during the fatigue cycles in A356.0-T6 alloy due to over-ageing phenomenon and therefore, the amount of cyclic softening in heat treated alloy is more. © 2012 Elsevier Ltd.


Mashhadi S.,Iran University of Science and Technology
International Journal of Network Security | Year: 2012

Recently, Kim et al.'s proposed a new type of proxy signature scheme, called self proxy signature scheme. In their scheme, a signer, delegates his/her signing capability to himself/herself and uses the proxy private/public key pair as temporary keys. In this paper, we will demonstrate some security leaks inherent in Kim et al.'s scheme and show that an adversary can forge a valid self proxy signature for any message by using different ways. Finally, we will propose an improvement to eliminate the pointed out security leaks.


Lesani M.,University of Tehran | Bahaari M.R.,University of Tehran | Shokrieh M.M.,Iran University of Science and Technology
Composite Structures | Year: 2013

This paper presents the failure pattern, ultimate static strength and detailed behavior of steel tubular T-joints strengthened by fiber reinforced polymer (FRP) obtained from numerical investigations under an axial brace compressive loading. The joints were analyzed in two cases in which FRP was included and excluded considering typical glass/epoxy composite. The results obtained from the numerical modeling revealed the influence of the FRP wrap in joint ultimate capacity enhancement. In addition, the state of stresses and deflections of the steel substrate were all improved as a result of FRP application which clearly showed an upgrade in overall joint behavior. The orientation and extent of FRP reinforcement has been proposed based on practical applications. The modes of failure observed throughout the numerical analysis were local bending of the chord member, punching shear due to ovalization and plastic failure of the chord. The FRP-Strengthened joint hindered the occurrence of these failure modes. The FRP plies were capable to withstand a minimum of 50% of the joint ultimate load with no sign of failure. The critical regions of the plies were around the saddle point and the adjacent ovalized area of the chord shell. © 2012 Elsevier Ltd.


Farahani M.R.,Iran University of Science and Technology
Acta Chimica Slovenica | Year: 2012

Several topological indices are investigated in polyhex nanotubes: Randić connectivity index, sum-connectivity index, atom-bond connectivity index, geometric-arithmetic index, First and Second Zagreb indices and Zagreb polynomials. Formulas for calculating the above topological descriptors in polyhex zigzag TUZC6[m,n] and armchair TUAC6[m,n] nanotube families are given.


Rahimzadeh M.,Iran University of Science and Technology
Latin American Journal of Solids and Structures | Year: 2013

In the present study, efforts have been made to theoretically study the diffraction of plane harmonic compressional waves by a spherical nano-inclusion based on the Gurtin-Murdoch surface/interface elasticity theory in which the interface between the nano-inclusion and the matrix is considered as the material surface which has their own mechanical properties. Furthermore, a nano-composite has been considered in order to assess the size effect on the wave propagation characteristics of a plane compressional elastic wave containing the randomly distributed spherical nano-inclusions. Also, the phase velocities and attenuations of P and SV elastic waves along with the related dynamic effective elastic properties have been investigated for a wide variety of frequencies and volume fractions.


Lesani M.,University of Tehran | Bahaari M.R.,University of Tehran | Shokrieh M.M.,Iran University of Science and Technology
Journal of Constructional Steel Research | Year: 2013

This paper presents the failure pattern, ultimate static strength and detailed behavior of un-stiffened T and Y tubular joints under axial brace compressive loading using finite element method performed by ABAQUS software package. Properties of the un-stiffened tubular joints were extracted from the available experimental-based tubular joint database. Utilizing the Modified Riks Method in numerical analyses led to an accurate simulation of joint behavior and also helped to investigate its correct failure pattern. The modes of failure observed throughout the numerical analysis were local bending of the chord member, ovalization and plastic failure of the chord. The results obtained from the numerical modeling revealed the critical areas on the joint surface with respect to ovalization, deflections and stresses. Also, the ultimate strength predicted by the numerical analysis was compared and validated with available experiment results. Despite the fact that much research has been conducted on tubular joints which have mostly focused on the estimation of ultimate strength or stress concentration factors rather than detail study of joint behavior, the present detail investigation has provided a thorough understanding of joint behavior under axial compressive loads. Such an in-depth and detail tubular joint investigation has been rarely reported in the open literature. © 2012 Elsevier Ltd. All rights reserved.


Vermahmoudi Y.,Islamic Azad University at Mahshahr | Peyghambarzadeh S.M.,Islamic Azad University at Mahshahr | Hashemabadi S.H.,Iran University of Science and Technology | Naraki M.,Islamic Azad University at Mahshahr
European Journal of Mechanics, B/Fluids | Year: 2014

In this paper, the overall heat transfer coefficient of water based iron oxide nanofluid in a compact air-cooled heat exchanger has been measured experimentally under laminar flow conditions. The concentrations of 0.15, 0.4 and 0.65 vol.% of stabilized Fe2O3/water nanofluid have been examined with variation of flow rates in the range of 0.2-0.5 m 3/h. For better dispersion of iron (III) oxide nanoparticles in water, 0.8 wt% polyethylene glycol has been added and pH has been adjusted to 11.1. The air-cooled heat exchanger is consisted of 34 vertical tubes with stadium-shaped cross section and air makes a cross flow through the tube bank with variable flow rates ranging from 740 to 1009 m3/h. Also, hot working fluid enters the heat exchanger at different temperatures including 50, 65, and 80 C. The results demonstrate that increasing the nanofluid flow rate and concentration and the air Reynolds number can improve the overall heat transfer coefficient and heat transfer rate whereas enhancing the inlet temperature has a negative effect on the overall heat transfer coefficient and a positive effect on the heat transfer rate. Meanwhile, the maximum enhancements of the overall heat transfer coefficient and heat transfer rate compared with base fluid (distilled water) are respectively equal to 13% and 11.5% which is occurred at the concentration of 0.65 vol.%. © 2013 Elsevier Masson SAS. All rights reserved.


Afshar M.H.,Iran University of Science and Technology
Advances in Engineering Software | Year: 2010

This paper describes the application of the newly introduced Continuous Ant Colony Optimization Algorithm (CACOA) to optimal design of sewer networks. Two alternative approaches to implement the algorithm is presented and applied to a storm sewer network in which the nodal elevations of the network are considered as the decision variables of the optimization problem. In the first and unconstrained approach, a Gaussian probability density function is used to represent the pheromone concentration over the allowable range of each decision variable. The pheromone concentration function is used by each ant to randomly sample the nodal elevations of the trial networks. This method, however, will lead to solutions which may be infeasible regarding some or all of the constraints of the problem and in particular the minimum slope constraint. In the second and constrained approach, known value of the elevation at downstream node of a pipe is used to define new bounds on the elevation of the upstream node satisfying the explicit constraints on the pipe slopes. Two alternative formulations of the constrained algorithm are used to solve a test example and the results are presented and compared with those of unconstrained approach. The methods are shown to be very effective in locating the optimal solution and efficient in terms of the convergence characteristics of the resulting algorithms. The proposed algorithms are also found to be relatively insensitive to the initial colony and size of the colony used compared to the original algorithm. © 2009 Elsevier Ltd. All rights reserved.


Tehrani Dehkordi M.,Shahrekord University | Nosraty H.,Amirkabir University of Technology | Shokrieh M.M.,Iran University of Science and Technology | Minak G.,University of Bologna | Ghelli D.,University of Bologna
Materials and Design | Year: 2013

Low-velocity impact and compression after impact (CAI) tests were performed to investigate the impact behavior of hybrid composite laminates reinforced by basalt-nylon intraply fabrics. The purpose of using this hybrid composite is to combine the good mechanical property of basalt fiber as a brittle fiber with the excellent impact resistance of nylon fiber as a ductile fiber. Five different types of woven fabric with different contents of nylon (0%, 25%, 33.3%, 50% and 100%) were used as reinforcement. The effect of nylon/basalt fiber content on impact parameters, impact damage behavior and CAI strength was studied at different nominal impact energy levels (16, 30 and 40. J). The results indicate that at low impact energy, hybridization and variation in basalt/nylon fiber content cannot improve the impact performance of composite plates. With increasing impact energy, the impact performance becomes more and more dependent on the content of nylon and basalt. © 2012 Elsevier Ltd.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Engineering Computations (Swansea, Wales) | Year: 2010

Purpose - The computational drawbacks of existing numerical methods have forced researchers to rely on heuristic algorithms. Heuristic methods are powerful in obtaining the solution of optimization problems. Although they are approximate methods (i.e. their solution are good, but not provably optimal), they do not require the derivatives of the objective function and constraints. Also, they use probabilistic transition rules instead of deterministic rules. The purpose of this paper is to present an improved ant colony optimization (IACO) for constrained engineering design problems. Design/methodology/approach - IACO has the capacity to handle continuous and discrete problems by using sub-optimization mechanism (SOM). SOM is based on the principles of finite element method working as a search-space updating technique. Also, SOM can reduce the size of pheromone matrices, decision vectors and the number of evaluations. Though IACO decreases pheromone updating operations as well as optimization time, the probability of finding an optimum solution is not reduced. Findings - Utilizing SOM in theACO algorithm causes a decrease in the size of the pheromone vectors, size of the decision vector, size of the search space, the number of function evaluations, and finally the required optimization time. SOM performs as a search-space-updating rule, and it can exchange discrete-continuous search domain to each other. Originality/value - The suitability of using ACO for constrained engineering design problems is presented, and applied to optimal design of different engineering problems. © Emerald Group Publishing Limited.


Rezaie B.,Babol Noshirvani University of Technology | Jahed Motlagh M.-R.,Iran University of Science and Technology
Nonlinear Dynamics | Year: 2011

This paper addresses a new adaptive delayed feedback control technique for stabilizing a class of chaotic time-delayed systems with a variable parameter. In the proposed scheme, the feedback gain of a delayed feedback controller is automatically tuned according to an adaptation law in order to stabilize unstable fixed points of the system. Such a mechanism provides a way to cope with unexpected changes in the parameters of the system. The adaptation algorithm is constructed based on the Lyapunov-Krasovskii's stability theorem. The control technique provides the advantages of increased stability and optimality, adaptability to the changes in the parameters, high privacy, simplicity, and noninvasiveness. The effectiveness of the control scheme is demonstrated using numerical simulations for a well-known chaotic time-delayed system. © 2010 Springer Science+Business Media B.V.


Afshar M.H.,Iran University of Science and Technology
Scientia Iranica | Year: 2012

Application of standard binary coded genetic algorithms for the solution of problems with continuous design variables requires discretization of the continuous decision variables. Coarse discretization of the design variables could adversely affect the final solution, while finer discretization would increasingly enlarge the scale of the problem, leading to higher computation cost. A rebirthing procedure is used in this paper as a remedy for the problem just outlined. The method is based on the idea of limiting the originally wide search space to a smaller one once a locally converged solution is obtained. The smaller search space is designed to contain the locally optimum solution at its center. The resulting search space is refined and a completely new search is conducted to find a better solution. The procedure is continued until no refinement is necessary or no improvement could be made by further refinement. The method is applied to a benchmark problem of a storm water network design, and the results are compared with those of the existing method. The method is shown to be very effective, efficient and insensitive to the population size of the genetic search and the search space size of the optimization problem. © 2012 Sharif University of Technology. Production and hosting by Elsevier B.V. All rights reserved.


Salari M.,University of Tehran | Tabar M.M.,Iran University of Science and Technology | Tabar A.M.,Islamic Azad University at Tehran | Danesh H.A.,Islamic Azad University at Tehran
Numerical Heat Transfer; Part A: Applications | Year: 2012

This article presents the results of a numerical study on mixed convection within a square lid-driven which was heated simultaneously by two finite heat sources on the bottom and side walls, and also filled with nanofluids. The results were presented for different nanofluids. The governing equations were solved using a finite volume approach by the SIMPLE algorithm. The effects of the Rayleigh number, Reynolds number, the solid volume fraction, the dimensions of heaters, and their locations on the streamlines and isotherms contours were investigated accurately. Also, the effects of the above parameters on the average Nusselt number along two heat sources were precisely presented. Moreover, variations of the average Nusselt number of two heaters were considered whenever one heater was fixed and the location of the other heater was varied along the wall. In addition, variations of the length of one heater on the average Nusselt number were also studied whenever the length of the other heater was fixed. © 2012 Copyright Taylor and Francis Group, LLC.


Ayatollahi M.R.,Iran University of Science and Technology | Torabi A.R.,University of Tehran
Journal of Mechanical Science and Technology | Year: 2011

Fracture phenomenon was experimentally investigated in a soda-lime glass weakened by a V-notch under tensile-shear loading. Fracture tests were conducted using a new test sample called the V-notched Brazilian disc (V-BD) specimen. The fracture resistance and fracture initiation angle were obtained initially from the test results. Afterward, a fracture model was utilized to estimate the experimental results. Very good correlation was found between the experimental and theoretical results both for the fracture resistance and the fracture initiation angle in notches having different notch angles and various notch tip radii. Experimental results revealed that for a constant notch tip radius, the failure load under pure tensile loading conditions decreases as the notch angle increases. For a constant notch angle, as the notch tip radius increases, the fracture load in the soda-lime glass V-BD specimens enhances in the whole domain from pure tensile to pure shear loading. Moreover, for a constant notch tip radius, the notch angle has almost no effect on the fracture initiation angle when the specimen is predominantly under tensile loading conditions. © 2011 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.


Shahmansouri M.,Arak University | Alinejad H.,Iran University of Science and Technology
Astrophysics and Space Science | Year: 2013

The combined effects of the obliqueness and nonextensive electrons are incorporated in the study of ion acoustic (IA) waves in a magnetized plasma. The propagation properties of two possible modes (in the linear regime) are investigated. It is found that the electron nonextensivity decreases the phase velocities of both two modes. Also obliqueness leads to increase of separation between two modes. The nonlinear evolution of IA solitary waves is governed by an energy-like equation. The influence of electron nonextensivity, obliqueness and electron population on the existence domain of solitary waves and the soliton characteristics are examined. It is shown that the existence domain of the IA soliton and its profile is significantly depended on the deviation of electrons from thermodynamic equilibrium and obliqueness. Interestingly, the present model supports compressive as well as rarefactive IA solitary waves. Our finding should elucidate the nonlinear electrostatic structures that propagate in astrophysical and cosmological plasma scenarios where nonextensive and magnetized plasma can exist; like instellar plasma stellar polytropes, solar neutrino problem, peculiar velocities of galaxy clusters, dark-matter halos, protoneutron stars, hadronic matter, quark-gluon plasma, and magnetosphere, etc. © 2013 Springer Science+Business Media Dordrecht.


Kaupp G.,University of Oldenburg | Naimi-Jamal M.R.,Iran University of Science and Technology
Journal of Materials Chemistry | Year: 2011

Nut or seed hardshells' mechanical response is studied by vertical nanoindentation in the untreated surface with pyramidal tips. As in uniform materials the exponent of the loading curves is also determined to be 3/2 (but not 2 as Hertzian theory would predict) in all of the nanocomposites with correlation coefficients r > 0.999 (except two cases with r > 0.996 due to minor distortions) for the linear plots with slope k (N nm-3/2). Unlike hardness H and reduced elastic modulus Er, the pyramidal nanoindentation coefficient k reflects the total mechanical response. It allows for depth calculations according to FN = kh3/2. Thus, the k-values represent the penetration resistance, and k-1 represents the penetratability. Importantly, the penetration depth h follows F N 2/3 but not FN 1/2 what Hertzian theory had been claiming, despite the importance for wear, mar, mechanical treatments, and tribology. A quantitative mechanical rating is now possible for the first time. The values of k can be converted to different tip tapers. Reliable and repeatable vertical indentations with sharp cube corner were achieved by approaching sufficiently flat summit sites on the rough surfaces under AFM control. The surfaces were not previously destroyed by microtome cutting or abrading and polishing. Detailed knowledge of the architectures of the shells' sclerenchyma was obtained by 3D optical microscopy in color of clean natural surfaces and on fresh fracture surfaces in different directions. Multiple layers, fibrous structures in various alignments and several types of almost isodiametric cells were differentiated. The linearity of the F Nversush3/2 plots secures uniformity of the thick-walled cells notwithstanding initial minor deviations due to nanoroughness and surface layers. Comparison with published bone and nacre data is added and discussed. The nanomechanical response of unidirectional indentation at the cellular level influences the cracking resistance of the whole nuts/seeds, but the higher level of wood hierarchy has often the higher weight. The various stabilization tools governing the elastic and brittle responses towards the bending forces that apply upon cracking of the nuts/seeds with their different sizes and shapes are discussed on the basis of the structural data. Importantly, the combination of the mechanical and structural results reveals four new bionics models. These are possible improvements of Yacoe-Davis type dome constructions by stiffeners between the polygons, hedgehog effect for highly elastic materials by efficient interlocking, ellipsoidal cell effect for highly inelastic products, and vertical nanofiber arrays for highly light absorbing very dark surfaces. © 2011 The Royal Society of Chemistry.


Banijamali A.,Iran University of Science and Technology
Communications in Theoretical Physics | Year: 2016

We consider a tachyonic model of dark energy in which scalar field non-minimally coupled with curvature and kinetic part of its Lagrangian density. Additionally the model contains the Gauss-Bonnet coupling to the scalar field through an arbitrary function. The non-minimal Gauss-Bonnet coupling function and scalar field potential have been obtained for power-law solution and then for a dynamically varying equation of state. We have extracted the required condition for the so-called phantom divide line crossing in the model and represented such a crossing numerically. © 2016 Chinese Physical Society and IOP Publishing Ltd.


Namvar M.,Iran University of Science and Technology
ISMS 2010 - UKSim/AMSS 1st International Conference on Intelligent Systems, Modelling and Simulation | Year: 2010

Customer Segmentation is an increasingly significant issue in today's competitive commercial area. Many literatures have reviewed the application of data mining technology in customer segmentation, and achieved sound effectives. But in the most cases, it is performed using customer data from a special point of view, rather than from systematical method considering all stages of CRM. This paper, with the aid of data mining tools, constructs a new customer segmentation method based on RFM, demographic and LTV data. The new customer segmentation method consists of two phases. Firstly, with K-means clustering, customers are clustered into different segments regarding their RFM. Secondly, using demographic data, each cluster again is partitioned into new clusters. Finally, using LTV, a profile for customer is created. The method has been applied to a dataset from Iranian bank, which resulted in some useful management measures and suggestions. © 2010 IEEE.


Kaveh A.,Iran University of Science and Technology | Shakouri Mahmud Abadi A.,Building Research Institute, Egypt
International Journal of Civil Engineering | Year: 2011

Cost optimization of the reinforced concrete cantilever soil retaining wall of a given height satisfying some structural and geotechnical design constraints is performed utilizing harmony search and improved harmony search algorithms. The objective function considered is the cost of the structure, and design is based on ACI 318-05. This function is minimized subjected to design constraints. A numerical example of the cost optimization of a reinforced concrete cantilever retaining wall is presented to illustrate the performance of the presented algorithms and the necessary sensitivity analysis is performed.


Kaveh A.,Iran University of Science and Technology | Rahami H.,University of Tehran
Acta Mechanica | Year: 2011

In this paper, block circulant matrices and their properties are investigated. Basic concepts and the necessary theorems are presented and then their applications are discussed. It is shown that a circulant matrix can be considered as the sum of Kronecker products in which the first components have the commutativity property with respect to multiplication. The important fact is that the method for block diagonalization of these matrices is much simpler than the previously developed methods, and one does not need to find an additional matrix for orthogonalization. As it will be shown not only the matrices corresponding to domes in the form of Cartesian product, strong Cartesian product and direct product are circulant, but for other structures such as diamatic domes, pyramid domes, flat double layer grids, and some family of transmission towers these matrices are also block circulant. © 2010 Springer-Verlag.


Kaveh A.,Iran University of Science and Technology | Talatahari S.,University of Tabriz
Acta Mechanica | Year: 2011

A general model is presented to unify the explanation of different meta-heuristic algorithms. This model is based on the concept of fields of forces from physics and covers many meta-heuristic algorithms consisting of Genetic Algorithms, Ant Colony Optimization, Particle Swarm Optimization, Big Bang-Big Crunch algorithm and Harmony Search. The properties of these algorithms can be explained using the presented general model that is called the fields of forces (FOF) model. This extension provides efficient means to improve, expand, modify and hybridize the meta-heuristic algorithms. An improved and hybridized algorithm is then developed using the FOF model. © 2011 Springer-Verlag.


Shayeghi H.,University of Mohaghegh | Shayeghi H.,Iran University of Science and Technology | Sobhani B.,University of Mohaghegh
Energy Conversion and Management | Year: 2014

Due to increase of electrical power demand, several uncommon sources mainly voltage source converter (VSC) based distributed generations (DGs) have been included into the power systems which increased the systems complexity and uncertainty. One of the most problem of DGs is unwanted islanding. This paper addresses a reliable passive time-frequency islanding detection algorithm using the multi signal analysis method.