Showing papers by "Amirkabir University of Technology published in 2006"
TL;DR: In this article, a fuzzy multiobjective linear model is developed to overcome the vagueness of the information for the first time in a fuzzy supplier selection problem, an asymmetric fuzzy-decision-making technique is applied to enable the decision-maker to assign different weights to various criteria.
424 citations
TL;DR: Several finite difference schemes are discussed for solving the two-dimensional Schrodinger equation with Dirichlet's boundary conditions with the unique advantage of the Barakat and Clark technique, which is unconditionally stable and is explicit in nature.
400 citations
TL;DR: In this article, an attempt is made to introduce a new parameter that could be easily extracted with no error in calculation, theta at high frequencies has very good agreement with other extracted parameters.
275 citations
TL;DR: An immune algorithm approach to the scheduling of a SDST hybrid flow shop is described and it was established that IA outperformed RKGA.
239 citations
TL;DR: A stable neural network (NN)-based observer for general multivariable nonlinear systems is presented in this paper and the stability of the recurrent neural network observer is shown by Lyapunov's direct method.
Abstract: A stable neural network (NN)-based observer for general multivariable nonlinear systems is presented in this paper. Unlike most previous neural network observers, the proposed observer uses a nonlinear-in-parameters neural network (NLPNN). Therefore, it can be applied to systems with higher degrees of nonlinearity without any a priori knowledge about system dynamics. The learning rule for the neural network is a novel approach based on the modified backpropagation (BP) algorithm. An e-modification term is added to guarantee robustness of the observer. No strictly positive real (SPR) or any other strong assumption is imposed on the proposed approach. The stability of the recurrent neural network observer is shown by Lyapunov's direct method. Simulation results for a flexible-joint manipulator are presented to demonstrate the enhanced performance achieved by utilizing the proposed neural network observer.
229 citations
TL;DR: It is proved that finding all of the real solutions which satisfy in a system with interval coefficients is NP-hard, and some heuristics based methods on Dubois and Prade’s approach are employed, finding some positive fuzzy vector x which satisfies A ˜ x ˜ = b ˜, where A and b are a fuzzy matrix and a fuzzy vector respectively.
207 citations
TL;DR: In this article, the numerical solution of the one-dimensional parabolic equation subject to the specification of mass, which have been considered in the literature, is reported. And the performance of the proposed algorithm, considering a test problem, is investigated.
Abstract: Certain problems arising in engineering are modeled by nonstandard parabolic initial-boundary value problems in one space variable, which involve an integral term over the spatial domain of a function of the desired solution. Hence, in the past few years interest has substantially increased in the solutions of these problems. As a result numerous research papers have also been devoted to the subject. Although considerable amount of work has been done in the past, there is still a lack of a completely satisfactory computational scheme. Also, there are some cases that have not been studied numerically yet. In the current article several approaches for the numerical solution of the one-dimensional parabolic equation subject to the specification of mass, which have been considered in the literature, are reported. Finite difference methods have been proposed for the numerical solution of the new nonclassic boundary value problem. To investigate the performance of the proposed algorithm, we consider solving a test problem. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006
154 citations
TL;DR: In this article, the equilibrium, stability, and compatibility equations of an imperfect functionally graded plate are derived using the classical plate theory, assuming that the nonhomogeneous mechanical properties of the plate, graded through thickness, are described by a power function of the thickness variable.
150 citations
TL;DR: A general fuzzy linear system using the embedding approach, has been investigated and then several well-known numerical algorithms for solving system of linear equations such as Richardson, Extrapolated Richardson, Jacobi, JOR, Gaus are extended for solving FLS.
134 citations
TL;DR: Based on the petrography and geochemistry, it is suggested that the Sungun deposit as a composite stock comprising an early monzonite/quartzmonzonite and a later diorite/granodiorite phase as discussed by the authors.
134 citations
TL;DR: In this article, a nanocomposite type of hydrogels (NC gels) were prepared by crosslinking the polyacrylamide/montmorillonite (Na-MMT) clay aqueous solutions with chromium (III).
Abstract: In the present work, attempts have been made to prepare nanocomposite type of hydrogels (NC gels) by crosslinking the polyacrylamide/montmorillonite (Na-MMT) clay aqueous solutions with chromium (III). The X-ray diffraction patterns of the NC gels exhibited a significant increase in d001 spacing between the clay layers, indicating the formation of intercalated as well as exfoliated type of morphology. Exfoliation of the clay layers through out the gel network was found to be predominated, which evidences the high interaction between the polyacrylamide segments and montmorillonite layers. Gelation time as well as variation of viscoelastic parameters such as storage modulus (G′) of the gel network during gelation process at 75°C was studied and followed by rheomechanical spectroscopy (RMS). The NC gels prepared with lower crosslinker concentration showed higher strength and elastic modulus compared with the similar but unfilled polyacrylamide gel. This distinct characteristic of the NC gels yields a gel network structure with high resistance towards syneresis at high temperature in the presence of the oil reservoir formation water. The effects of the composition, such as clay content, crosslinker concentration, and also water salinity upon the gelation rate, gel strength as well as rate of syneresis have been investigated. To optimize the injectivity of the intercalated polyacrylamide solution before the onset of gelation with the gel strength of the final developed gel, sodium lactate was employed as retarder. This was found to be effective to balance these two characteristics of the NC gels, which are aimed to be used for water shut-off and as profile modifier in enhanced oil recovery (EOR) process during water flooding process. The nanocomposite gels showed much more elasticity and extensibility at low crosslinker concentration compared with the similar but unfilled gel, which makes the NC gels suitable as an in-depth profile modifier, and also as an oil displacing agent in the heterogeneous oil reservoir in chemical EOR. Effects of the clay content on the thermal stability of the gel network have also been investigated by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) has been performed upon the NC-gel samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2096–2103, 2006
TL;DR: In this article, the authors examined the use of independent and continuous pier collars in combination with riprap for reducing local scour around bridge pier groups and found that independent collars showed better efficiency than a continuous collar around both piers.
Abstract: The present study examines the use of independent and continuous pier collars in combination with riprap for reducing local scour around bridge pier groups. The efficiency of collars was studied through experiments. The data from the experiments were compared with data from earlier studies on single piers with collars and bridge pier groups without collars. The data showed that in the case of two piers in line, combination of continuous collars and riprap results in the most significant scour reduction of about 50 and 60% for the front and rear piers, respectively. In other cases for two piers in line, independent collars showed better efficiency than a continuous collar around both piers. It was also shown that efficiency of collars is more on a rectangular pier aligned with the flow than two piers in line. Experiments however, indicated that collars are not so effective in reduction of scouring around two transverse piers.
TL;DR: This paper introduces a method to construct high coding gain lattices with low decoding complexity based on LDPC codes and applies Construction D', due to Bos, Conway, and Sloane, to a set of parity checks defining a family of nestedLDPC codes to construct such lattices.
Abstract: Low-density parity-check codes (LDPC) can have an impressive performance under iterative decoding algorithms. In this paper we introduce a method to construct high coding gain lattices with low decoding complexity based on LDPC codes. To construct such lattices we apply Construction D', due to Bos, Conway, and Sloane, to a set of parity checks defining a family of nested LDPC codes. For the decoding algorithm, we generalize the application of max-sum algorithm to the Tanner graph of lattices. Bounds on the decoding complexity are derived and our analysis shows that using LDPC codes results in low decoding complexity for the proposed lattices. The progressive edge growth (PEG) algorithm is then extended to construct a class of nested regular LDPC codes which are in turn used to generate low density parity check lattices. Using this approach, a class of two-level lattices is constructed. The performance of this class improves when the dimension increases and is within 3 dB of the Shannon limit for error probabilities of about 10-6. This is while the decoding complexity is still quite manageable even for dimensions of a few thousands
TL;DR: In this article, an approach based on fuzzy logic and mathematical morphology is proposed, to extract main road centrelines from pansharpened IKONOS images. But the method is more accurate at road intersections and on curves than on straight sections of road.
Abstract: Automatic extraction of geospatial features has been the subject of extensive research in the past three decades. Here, an approach based on fuzzy logic and mathematical morphology is proposed, to extract main road centrelines from pansharpened IKONOS images. In the IKONOS images, a standard deviation of 10 grey levels has been measured for the road classes. In the proposed fuzzy logic system, just one arbitrary pixel (up to a maximum of 3 pixels) provides an adequate initial value. Road identification requires neither the numbers of the classes nor the corresponding mean values; then, using advanced morphological concepts, the road centreline is extracted. The method is applied to pan-sharpened IKONOS images of urban, suburban and rural areas around the Pyramids in Egypt, and Rasht City and Kish Island in Iran. The extracted road centrelines have an average error of 0AE504 pixel and root mean square error of 0AE036 pixel. The method is more accurate at road intersections and on curves than on straight sections of road. The extracted road is then used as a direct input to a geographical information system (GIS).
TL;DR: In this article, the analysis of functionally graded thick hollow cylinders under dynamic load is presented, where each subcylinder is considered as an isotropic layer and material properties in each layer are constant and functionally graded properties are resulted by suitable arrangement of layers in multilayer cylinder.
TL;DR: The Sar-Cheshmeh porphyry Cu-Mo deposit is located in Southwestern Iran (∼65 km southwest of Kerman City) and is associated with a composite Miocene stock, ranging in composition from diorite through granodiorite to quartz-monzonite as discussed by the authors.
TL;DR: A new mixed integer nonlinear program (MINLP) and an optimal enumeration method to solve the lot and delivery scheduling problem in a simple supply chain where a single supplier produces multiple components on a flexible flow line (FFL) and delivers them directly to an assembly facility (AF).
TL;DR: The decolorization and degradation of triazinic ring-containing azo dye by using TiO(2)-immobilized photoreactor is reported and Kinetics analysis indicates that the dye photocatalyticDecolorization rates followed first order model.
TL;DR: Several computational techniques based on finite-difference schemes and the product trapezoidal numerical integration rule are constructed for determining the solution of a partial integro-differential equation subject to an initial condition and given boundary conditions.
Abstract: Partial integro-differential equations occur in many fields of science and engineering. This study presents various numerical schemes for solving a partial integro-differential equation with a weakly singular kernel. These schemes are presented for determining the solution of a partial integro-differential equation subject to an initial condition and given boundary conditions. We construct several computational techniques based on finite-difference schemes and the product trapezoidal numerical integration rule. This problem can be found in the modelling of physical phenomena involving viscoelasticity forces. The finite-difference procedures developed are based on the forward Euler explicit scheme, the backward Euler implicit technique, the Crank–Nicolson implicit formula and Crandall’s implicit method. Three of the methods have second-order accuracy with respect to the space variable. The order of accuracy of the Crandall’s scheme is higher than that of the others. The numerical results of a test problem ...
TL;DR: In this paper, the decolorization and mineralization of reactive dyes by heterogeneous nanophotocatalysis using an immobilized TiO2 nanoparticle photocatalytic reactor was investigated.
TL;DR: It is shown that the shortest path is found with a probability as close as to unity by proper choice of the parameters of the proposed algorithms.
Abstract: In this paper, we first introduce a network of learning automata, which we call it as distributed learning automata and then propose some iterative algorithms for solving stochastic shortest path problem These algorithms use distributed learning automata to find a policy that determines a path from a source node to a destination node with minimal expected cost (length) In these algorithms, at each stage distributed learning automata determines which edges to be sampled This sampling method may result in decreasing unnecessary samples and hence decreasing the running time of algorithms It is shown that the shortest path is found with a probability as close as to unity by proper choice of the parameters of the proposed algorithms
TL;DR: The proposed approach to find the optimal solutions of a class of fuzzy linear programming problems called fully fuzzified linear programming (FFLP), where all decision parameters and variables are fuzzy numbers, is constructed on the basis of comparison of mean and standard deviation of fuzzy numbers.
Abstract: In this paper, we propose a two-phase approach to find the optimal solutions of a class of fuzzy linear programming problems called fully fuzzified linear programming (FFLP), where all decision parameters and variables are fuzzy numbers. Our approach is constructed on the basis of comparison of mean and standard deviation of fuzzy numbers. In this approach, the first phase maximizes the possibilistic mean value of fuzzy objective function and obtains a set of feasible solutions. The second phase minimizes the standard deviation of the original fuzzy objective function, by considering all basic feasible solutions obtained at the end of the first phase. The advantage of the proposed approach is its simplicity in programming and computation. Moreover, we also generalize the concept of linear programming duality and extend the duality as well as the weak duality theory to FFLP.
TL;DR: The Adomian decomposition method for solving fully fuzzy linear systems ( shown as FFLS) is extended and Dubois and Prade's approximate arithmetic operators on LR fuzzy numbers are employed.
TL;DR: In this article, the photocatalytic degradation of acid red 14 (AR 14) was investigated using a simple and effective method for immobilization of titanium(IV) oxide nanoparticles.
Abstract: Immobilized titanium(IV) oxide nanoparticles were used for the photocatalytic degradation of Acid Red 14 (AR 14). A simple and effective method was used for immobilization of titanium(IV) oxide nanoparticles. Photocatalytic degradation processes were performed using pilot scale (7 L) colored dye solutions. UV–vis and ion chromatography (IC) analyses were employed to obtain the details of the photocatalytic degradation of AR 14. It has been found that adsorption has a negligible effect on the aqueous dye concentration and the photocatalytic process occurred at solution bulk. The effects of operational parameters such as H 2 O 2 , dye concentration, anions (NO 3 − , Cl − , SO 4 2− , HCO 3 − and CO 3 2− ) and pH were investigated. Reaction rate was drastically inhibited by carbonate. Produced aromatic intermediates were not studied. Formate, acetate and oxalate anions were detected as dominant aliphatic intermediates where, they were further oxidized slowly to CO 2 . Nitrate and sulfate anions were detected as the photocatalytic mineralization of AR 14. Kinetics analysis indicates that the photocatalytic decolorization rates can usually be approximated first-order model for AR 14. Results show that the employment of optimal operational parameters may lead to complete decolorization and mineralization of dye solutions.
TL;DR: The results indicate the potential of P300-based GKT for detecting concealed information, although further research is required to increase its accuracy and precision and evaluating its vulnerability to countermeasures.
20 Aug 2006
TL;DR: A feature-based license plate localization algorithm that copes with multi-object problem in different image capturing conditions and outperforms the other available approaches in the literature is presented.
Abstract: This paper presents a feature-based license plate localization algorithm that copes with multi-object problem in different image capturing conditions. The proposed algorithm is robust against illumination, shadow, scale, rotation, and weather condition. It extracts license plate candidates using edge statistics and morphological operations and removes the incorrect candidates according to the determined features of license plates. We have formed a rather complete database of 269 images in different conditions. The proposed algorithm successfully detecteds the accurate location of the license plates in 96.5% cases, which outperforms the other available approaches in the literature.
TL;DR: The radial basis functions (RBF) method is used for finding the solution of an inverse problem with source control parameter and some comparisons are made with several well-known finite difference schemes.
TL;DR: The main idea behind this work is the use of the well-known Adomian decomposition method, and in this technique, the solution is found in the form of a rapid convergent series.
Abstract: In this paper, a method for solving multipoint boundary value problems is presented. The main idea behind this work is the use of the well-known Adomian decomposition method. In this technique, the solution is found in the form of a rapid convergent series. Using this method, it is possible to obtain the solution of the general form of multipoint boundary value problems. The Adomian decomposition method is not affected by computation round off errors and one is not faced with the necessity of large computer memory and time. To show the efficiency of the developed method, numerical results are presented.
TL;DR: In this article, the effects of surrounding members (i.e. beams and columns) on the overall behavior of thin steel plate shear walls are studied, and it is shown that the flexural stiffness of the surrounding members has no significant effect, either on elastic shear buckling or on the post-buckling behaviour of shear wall.
TL;DR: In this paper, the effects of a cutout on the buckling behavior of rectangular plates made of polymer matrix composites (PMC) are investigated. And the buckler behavior of these plates is modeled in clamped and simply supported boundary condition.