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Total 398 records

#### Applying robust predictive functional control to mass transmission benchmark

, Article EUROCON 2005 - The International Conference on Computer as a Tool, Belgrade, 21 November 2005 through 24 November 2005 ; Volume I , 2005 , Pages 294-297 ; 142440049X (ISBN); 9781424400492 (ISBN) ; Haeri, M ; Sharif University of Technology
IEEE Computer Society
2005

Abstract

Predictive functional controller originally developed based on a first order reference model. In this paper the related equation of the predictive functional control is derived for an arbitrary reference model and then a simple approach to tune different parameters of the controller is examined by applying the controller on a benchmark problem. Finally, the robustness of the design is improved using the so called Youla parameterization approach. © 2005 IEEE

#### On some combinatorial properties of the star graph

, Article 8th International Symposium on Parallel Architectures, Algorithms and Networks, I-SPAN 2005, Las Vegas, NV, 7 December 2005 through 9 December 2005 ; Volume 2005 , 2005 , Pages 6-11 ; 0769525091 (ISBN); 9780769525099 (ISBN) ; Sarbazi Azad, H ; Akl, S. G ; Sharif University of Technology
IEEE Computer Society
2005

Abstract

The star graph, as an interesting network topology, has been extensively studied in the past. In this paper, we address some of the combinatorial properties of the star graph. In particular, we consider the problem of calculating the surface area of the star graph, answering an open problem previously posed in [12]. © 2005 IEEE

#### A modified pressure-based algorithm to solve flow fields with shock and expansion waves

, Article Numerical Heat Transfer, Part B: Fundamentals ; Volume 46, Issue 5 , 2004 , Pages 497-504 ; 10407790 (ISSN) ; Mokarizadeh, V ; Sharif University of Technology
2004

Abstract

The use of collocated grid schemes in control-volume-based methods has resulted in developing different strategies for coupling mass and momentum governing equations. Defining two different velocity components at cell faces is one remedy to suppress the possible checkerboard problem in the solution domain. These velocity components are widely known as convected and convecting velocities which are normally used in the momentum and mass governing equations, respectively. However, the linearization of the nonlinear governing equations generates a number of lagged velocity components which must be carefully treated in a manner to preserve the conceptual definition of the convected and convecting...

#### Iterative detection for V-BLAST MIMO communication systems based on expectation maximisation algorithm

, Article Electronics Letters ; Volume 40, Issue 11 , 2004 , Pages 684-685 ; 00135194 (ISSN) ; Nasiri Kenari, M ; Sharif University of Technology
2004

Abstract

By applying the expectation maximisation algorithm to the maximum likelihood detection of layered space-time codes, the conditional log-likelihood of a single layer is iteratively maximised, rather than maximising the intractable likelihood function of all layers. Computer simulations demonstrate the efficiency of the proposed detection scheme

#### A generalized regression neural network to inverse scattering from cylindrical conducting targets

, Article IEEE Antennas and Propagation Society Symposium 2004 Digest held in Conjunction with: USNC/URSI National Radio Science Meeting, Monterey, CA, 20 June 2004 through 25 June 2004 ; Volume 1 , 2004 , Pages 213-216 ; 15223965 (ISSN) ; Barkeshli, K ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2004

Abstract

In this paper, we use the generalized regression neural network (GRNN) for the inverse scattering from perfectly conducting cylindrical targets illuminated by the transverse magnetic to z polarization

#### Parallelization of the Lattice Boltzmann model in simulating buoyancy-driven convection heat transfer

, Article 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE, Anaheim, CA, 13 November 2004 through 19 November 2004 ; Volume 375, Issue 1 , 2004 , Pages 305-312 ; 02725673 (ISSN) ; Darbandi, M ; Schneider, G. E ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2004

Abstract

The main objective of the current work is to utilize Lattice Boltzmann Method (LBM) for simulating buoyancy-driven flow considering the hybrid thermal lattice Boltzmann equation (HTLBE). After deriving the required formulations, they are validated against a wide range of Rayleigh numbers in buoyancy-driven square cavity problem. The performance of the method is investigated on parallel machines using Message Passing Interface (MPI) library and implementing domain decomposition technique to solve problems with large order of computations. The achieved results show that the code is highly efficient to solve large scale problems with excellent speedup. Copyright © 2004 by ASME

#### Parallel computation of a mixed convection problem using fully-coupled and segregated algorithms

, Article 2004 ASME International Mechanical Engineering Congress and Exposition, IMECE, Anaheim, CA, 13 November 2004 through 19 November 2004 ; Volume 375, Issue 1 , 2004 , Pages 313-322 ; 02725673 (ISSN) ; Banaeizadeh, A ; Schneider, G. E ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2004

Abstract

In this work, parallel solution of the Navier-Stokes equations for a mixed convection heat problem is achieved using a finite-element-based finite-volume method in fully coupled and semi coupled algorithms. A major drawback with the implicit methods is the need for solving the huge set of linear algebraic equations in large scale problems. The current parallel computation is developed on distributed memory machines. The matrix decomposition and solution are carried out using PETSc library. In the fully coupled algorithm, there is a 36-diagonal global matrix for the two-dimensional governing equations. In order to reduce the computational time, the matrix is suitably broken in several...

#### Optimal fuel core loading pattern design in PWR nuclear power reactors using genetic algorithms and fuzzy nonlinear programming

, Article Journal of Intelligent and Fuzzy Systems ; Volume 14, Issue 2 , 2003 , Pages 85-93 ; 10641246 (ISSN) ; Ghofrani, M. B ; Lucas, C ; Sharif University of Technology
2003

Abstract

In pressurized water reactors, the fuel reloading problem has significant meaning in terms of both safety and economics. An optimal loading pattern is defined as a pattern in which the local power peaking factor (Pq) is lower than a predetermined value during one cycle and the effective multiplication factor (keff) is maximized to extract the maximum energy. This article presents a specialized genetic algorithm for loading pattern design. The tests on well-researched cases have shown that the genetic algorithm is capable of finding better loading patterns than solutions found by direct search methods. However, most of the previous researchers have considered simple fitness (cost) functions;...

#### Analysis of a dissimilar finite wedge under antiplane deformation

, Article Mechanics Research Communications, Exeter ; Volume 27, Issue 1 , 2000 , Pages 109-116 ; 00936413 (ISSN) ; Fariborz, S. J ; Sharif University of Technology
Elsevier Science Ltd
2000

Abstract

The dissimilar wedge with finite radius under antiplane shear deformation is analyzed. The finite Mellin transform is used to solve the governing differential equation. By simply letting the wedge radius approaches infinity, the solution is obtained

#### The minimum vulnerability problem

, Article Algorithmica ; Volume 7676 LNCS , 2012 , Pages 382-391 ; 14320541(ISSN) ; 9783642352607 (ISBN) ; Emamjomeh Zadeh, E ; Norouzi Fard, A ; Yazdanbod, S ; Zarrabi Zadeh, H ; Sharif University of Technology
2012

Abstract

We revisit the problem of finding k paths with a minimum number of shared edges between two vertices of a graph. An edge is called shared if it is used in more than one of the k paths. We provide a ⌊k/2⌋-approximation algorithm for this problem, improving the best previous approximation factor of k - 1. We also provide the first approximation algorithm for the problem with a sublinear approximation factor of O(n3/4), where n is the number of vertices in the input graph. For sparse graphs, such as bounded-degree and planar graphs, we show that the approximation factor of our algorithm can be improved to O(√n). While the problem is NP-hard, and even hard to approximate to within an O(log n)...

#### Density and power graphs in graph homomorphism problem

, Article Discrete Mathematics ; Volume 308, Issue 17 , 6 September , 2008 , Pages 4027-4030 ; 0012365X (ISSN) ; Hajiabolhassan, H ; Sharif University of Technology
2008

Abstract

We introduce two necessary conditions for the existence of graph homomorphisms based on the concepts of density and power graph. As corollaries, we obtain a lower bound for the fractional chromatic number, and we set forward elementary proofs of the facts that the circular chromatic number of the Petersen graph is equal to three and the fact that the Coxeter graph is a core. © 2007 Elsevier B.V. All rights reserved

#### Total domination and total domination subdivision number of a graph and its complement

, Article Discrete Mathematics ; Volume 308, Issue 17 , 6 September , 2008 , Pages 4018-4023 ; 0012365X (ISSN) ; Karami, H ; Sheikholeslami, S. M ; Sharif University of Technology
2008

Abstract

A set S of vertices of a graph G = (V, E) with no isolated vertex is a total dominating set if every vertex of V (G) is adjacent to some vertex in S. The total domination numberγt (G) is the minimum cardinality of a total dominating set of G. The total domination subdivision numbersdγt (G) is the minimum number of edges that must be subdivided in order to increase the total domination number. We consider graphs of order n ≥ 4, minimum degree δ and maximum degree Δ. We prove that if each component of G and over(G, -) has order at least 3 and G, over(G, -) ≠ C5, then γt (G) + γt (over(G, -)) ≤ frac(2 n, 3) + 2 and if each component of G and over(G, -) has order at least 2 and at least one...

#### A simple relation in elastic contact problems

, Article Tribology International ; Volume 41, Issue 5 , 2008 , Pages 341-347 ; 0301679X (ISSN) ; Sharafbafi, F ; Sharif University of Technology
2008

Abstract

In this paper, a new relation is introduced that simplifies the determination of the Muskhelishvili's potential function in plane contact problems. The relation is Φ (z) = 1 / 2 [p (z) - i q (z)], which is correct for all uncoupled contact problems. The new relation is proved in a mathematical way and utilized to obtain the potential function in several contact problems. A complete agreement has been observed between our results and the potential functions that have been obtained from complicated methods in the past. Utilization of the new relation simplifies the solution of contact problems and analytical calculation of the stress and displacement fields, which may lead to the design of...

#### Coupling between microring resonators in presence of Kerr effect

, Article Optics Communications ; Volume 281, Issue 9 , 2008 , Pages 2644-2650 ; 00304018 (ISSN) ; Bahrampour, A. R ; Farrahi Moghaddam, R ; Taraz, M ; Sharif University of Technology
2008

Abstract

The high degree of intensity values in microring resonators needs a careful treatment of nonlinear phenomena. Nonlinear effects are analyzed in coupling problem of ring-ring directional couplers. It has been observed that the nonlinearity affects the coupling device dramatically, and can be used as controlling techniques in such as coupled resonator optical waveguides. © 2007 Elsevier B.V. All rights reserved

#### Implementation of geometrical domain decomposition method for solution of axisymmetric transient inverse heat conduction problems

, Article Heat Transfer Engineering ; Volume 29, Issue 3 , 2008 , Pages 255-271 ; 01457632 (ISSN) ; Kazemzadeh Hannani, S ; Farhanieh, B ; Sharif University of Technology
2008

Abstract

The objective of this article is to study the performance of iterative parameter and function estimation techniques to solve simultaneously two unknown functions (quadratic in time, and linear in time and space) using transient inverse heat conduction method in conjunction with a geometrical domain decomposition approach, in cylindrical coordinates. For geometrical decomposition of physical domain, a multi-block method has been used. The numerical scheme for the solution of the governing partial differential equations is the finite element method. The results of the present study for a configuration composed of two joined disks with different heights are compared to those of exact heat...

#### A genetic algorithm approach to optimize a multi-products EPQ model with discrete delivery orders and constrained space

, Article Applied Mathematics and Computation ; Volume 195, Issue 2 , 2008 , Pages 506-514 ; 00963003 (ISSN) ; Akhavan Niaki, S. T ; Sharif University of Technology
2008

Abstract

The economic production quantity (EPQ) is one of the most applicable model in production and inventory control environments. Like other classical production and inventory control models, it is derived based upon assumptions that cause limited real-world applications. Continuous and constant-rate delivery of orders, infinite availability of warehouse spaces, and applicability on a single product are some of these assumptions. In order to make the EPQ model more applicable to real-world production and inventory control problems, in this paper, we expand this model by assuming that the orders may be delivered discretely in the form multiple pallets. In addition, we may have more than one...

#### Data mining with a simulated annealing based fuzzy classification system

, Article Pattern Recognition ; Volume 41, Issue 5 , 2008 , Pages 1824-1833 ; 00313203 (ISSN) ; Habibi, J ; Saniee Abadeh, M ; Saadi, H ; Sharif University of Technology
Elsevier Ltd
2008

Abstract

In this paper, the use of simulated annealing (SA) metaheuristic for constructing a fuzzy classification system is presented. In several previous investigations, the capability of fuzzy systems to solve different kinds of problems has been demonstrated. Simulated annealing based fuzzy classification system (SAFCS), hybridizes the learning capability of SA metaheuristic with the approximate reasoning method of fuzzy systems. The objective of this paper is to illustrate the ability of SA to develop an accurate fuzzy classifier. The use of SA in classification is an attempt to effectively explore and exploit the large search space usually associated with classification problems, and find the...

#### Query-point visibility constrained shortest paths in simple polygons

, Article Theoretical Computer Science ; Volume 389, Issue 1-2 , 2007 , Pages 1-11 ; 03043975 (ISSN) ; Ghodsi, M ; Sharif University of Technology
2007

Abstract

In this paper, we study the problem of finding the shortest path between two points inside a simple polygon such that there is at least one point on the path from which a query point is visible. We provide an algorithm which preprocesses the input in O (n2 + n K) time and space and provides logarithmic query time. The input polygon has n vertices and K is a parameter dependent on the input polygon which is O (n2) in the worst case but is much smaller for most polygons. The preprocessing algorithm sweeps an angular interval around every reflex vertex of the polygon to store the optimal contact points between the shortest paths and the windows separating the visibility polygons of the query...

#### A novel multi-agent evolutionary programming algorithm for economic dispatch problems with non-smooth cost functions

, Article 2007 IEEE Power Engineering Society General Meeting, PES, Tampa, FL, 24 June 2007 through 28 June 2007 ; July , 2007 ; 1424412986 (ISBN); 9781424412983 (ISBN) ; Hosseini, S. H ; Sharif University of Technology
2007

Abstract

This paper presents a new approach to economic dispatch (ED) problem with non-continuous and non-smooth cost functions using a hybrid evolutionary programming (EP) algorithm. In the proposed method the concept of multi-agent (MA) systems and EP are integrated together to form a new multi-agent evolutionary programming (MAEP) approach. In MAEP, an agent represents a candidate solution to the optimization problem in hand, and all agents live together in a global environment. Each agent senses its local environment, competes with its neighbors, and also learns by using its own knowledge. MAEP uses these agent-agent interactions and the evolutionary mechanism of EP to obtain the optimal...

#### Hybrid meta-heuristic algorithms for solving network design problem

, Article European Journal of Operational Research ; Volume 182, Issue 2 , 2007 , Pages 578-596 ; 03772217 (ISSN) ; Rouhani, O. M ; Sharif University of Technology
2007

Abstract

Network design problem has been, and is, an important problem in transportation. Following an earlier effort in designing a meta-heuristic search technique by an ant system, this paper attempts to hybridize this concept with other meta-heuristic concepts such as genetic algorithm, simulated annealing, and tabu search. Seven hybrids have been devised and tested on the network of Sioux Falls. It has been observed that the hybrids are more effective to solve the network design problem than the base ant system. Application of the hybrid containing all four concepts on a real network of a city with over 2 million population has also proved to be more effective than the base network, in the sense...