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Total 398 records

#### On unimodular graphs

, Article Linear Algebra and Its Applications ; Volume 421, Issue 1 , 2007 , Pages 3-15 ; 00243795 (ISSN) ; Kirkland, S. J ; Sharif University of Technology
2007

Abstract

We study graphs whose adjacency matrices have determinant equal to 1 or -1, and characterize certain subclasses of these graphs. Graphs whose adjacency matrices are totally unimodular are also characterized. For bipartite graphs having a unique perfect matching, we provide a formula for the inverse of the corresponding adjacency matrix, and address the problem of when that inverse is diagonally similar to a nonnegative matrix. Special attention is paid to the case that such a graph is unicyclic. © 2006 Elsevier Inc. All rights reserved

#### Integration of symmetry and macro-operators in planning

, Article 6th Mexican International Conference on Artificial Intelligence, MICAI 2007, Aguascalientes, 4 November 2007 through 10 November 2007 ; Volume 4827 LNAI , 2007 , Pages 1056-1066 ; 03029743 (ISSN); 9783540766308 (ISBN) ; Ghassem Sani, G ; Nakhost, H ; Sharif University of Technology
Springer Verlag
2007

Abstract

Macro-operators are sequences of actions that can guide a planner to achieve its goals faster by avoiding search for those sequences. However, using macro-operators will also increase the branching factor of choosing operators, and as a result making planning more complex and less efficient. On the other hand, the detection and exploitation of symmetric structures in planning problems can reduce the search space by directing the search process. In this paper, we present a new method for detecting symmetric objects through subgraph-isomorphism, and exploiting the extracted information in macrooperator selection. The method has been incorporated into HSP2, and tested on a collection of...

#### Resource placement in networks using chromatic sets of power graphs

, Article 2nd International Symposium on Computer Science in Russia, CSR 2007, Ekaterinburg, 3 September 2007 through 7 September 2007 ; Volume 4649 LNCS , 2007 , Pages 158-167 ; 03029743 (ISSN); 9783540745099 (ISBN) ; Sarbazi Azad, H ; Akl, S.G ; Sharif University of Technology
Springer Verlag
2007

Abstract

In this paper, using the chromatic properties of power graphs we propose a new approach for placing resources in symmetric networks. Our novel placement scheme guarantees a perfect placement when such a solution is feasible in the topology. © Springer-Verlag Berlin Heidelberg 2007

#### Simplifying random satisfiability problems by removing frustrating interactions

, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 74, Issue 4 , 2006 ; 15393755 (ISSN) ; Moghimi Araghi, S ; Sharif University of Technology
2006

Abstract

How can we remove some interactions (generate shorter clauses) in a constraint satisfaction problem (CSP) such that it still remains satisfiable? In this paper we study a modified survey propagation algorithm that enables us to address this question for a prototypical CSP, i.e., random K -satisfiability problem. The average number of removed interactions is controlled by a tuning parameter in the algorithm. If the original problem is satisfiable then we are able to construct satisfiable subproblems ranging from the original one to a minimal one with minimum possible number of interactions. The minimal satisfiable subproblems will directly provide the solutions of the original problem. © 2006...

#### Duality in fuzzy number linear programming by use of a certain linear ranking function

, Article Applied Mathematics and Computation ; Volume 180, Issue 1 , 2006 , Pages 206-216 ; 00963003 (ISSN) ; Nasseri, S. H ; Sharif University of Technology
2006

Abstract

We explore some duality properties in fuzzy number linear programming problems. By use of a linear ranking function we introduce the dual of fuzzy number linear programming primal problems. We then present several duality results. © 2006 Elsevier Inc. All rights reserved

#### Application of neural network to find initial state of optimization parameters

, Article 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006, Chicago, IL, 5 November 2006 through 10 November 2006 ; 2006 ; 10716947 (ISSN); 0791837904 (ISBN); 9780791837900 (ISBN) ; Sayyaadi, H ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2006

Abstract

This paper derives an estimated function made by simple Neural Network to find initial state of optimization parameters. It changes a system of differential equations with boundary values to a system of equations with initial values. So a lot of time would be saved to solve it. As a result, the system with differential equations will reach the desired final state. Copyright © 2006 by ASME

#### Communication protocol evolution by natural selection

, Article CIMCA 2006: International Conference on Computational Intelligence for Modelling, Control and Automation, Jointly with IAWTIC 2006: International Conference on Intelligent Agents Web Technologies and International Commerce, Sydney, NSW, 28 November 2006 through 1 December 2006 ; 2006 ; 0769527310 (ISBN); 9780769527314 (ISBN) ; Shouraki, S. B ; Halavati, R ; Lesani, M ; Sharif University of Technology
IEEE Computer Society
2006

Abstract

One of the most important issues discussed in multi-agent systems, is communication between agents. Usually, a predefined communication protocol is used, but predefining a protocol between agents causes some problems; for example it is possible that agents recognize a subject that is not defined in their protocol so they can't express anything about it. In this paper we propose a new method for evolution of a communication protocol between intelligent agents by using natural selection mechanism. Experimental results will be discussed in detail. © 2006 IEEE

#### Evolution of a communication protocol between a group of intelligent agents

, Article 2006 World Automation Congress, WAC'06, Budapest, 24 June 2006 through 26 June 2006 ; 2006 ; 1889335339 (ISBN); 9781889335339 (ISBN) ; Shouraki, S. B ; Halavati, R ; Khameneh, E ; Sharif University of Technology
IEEE Computer Society
2006

Abstract

One of the most important issues that be discussed in multi-agent systems, is the communication between agents. In existing applications usually a communication protocol defined between agents. But defining a protocol between agents cause some problems; for example it is possible that agents recognize a subject, but because it is not defined in their protocol, they can't express any thing about that. In this paper we propose a new method for evolution of a communication protocol between intelligent agents, after that the experimental results will be discussed and at the end of the paper future works and conclusion. Copyright - World Automation Congress (WAC) 2006

#### Stochastic control of two-level nonlinear large-scale systems; Part II-Interaction balance principle

, Article 2006 IEEE International Conference on Systems, Man and Cybernetics, Taipei, 8 October 2006 through 11 October 2006 ; Volume 5 , 2006 , Pages 3856-3861 ; 1062922X (ISSN); 1424401003 (ISBN); 9781424401000 (ISBN) ; Dehghan Marvast, E ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2006

Abstract

In this paper a new two-level method for stochastic control of large-scale systems is presented. This two-level approach is based on Interaction Balance Principle (Goal coordination) for optimization problem and a two-level computational algorithm using extended Kalman filter for the estimation one. The two-level optimizer uses a new coordinator which works by the gradient of interaction errors that improves the convergence rate of the solution. The significance and the applicability of the theoretical developments of this paper are also shown by a numerical example. © 2006 IEEE

#### A genetic algorithm for resource investment problem with discounted cash flows

, Article Applied Mathematics and Computation ; Volume 183, Issue 2 , 2006 , Pages 1057-1070 ; 00963003 (ISSN) ; Akhavan Niaki, S. T ; Sharif University of Technology
2006

Abstract

A resource investment problem with discounted cash flows is a project scheduling problem in which the availability levels of the resources are considered decision variables and the goal is to find a schedule and resource requirement levels such that the net present value of the project cash flows optimizes. In this paper, we present a genetic algorithm to solve this problem. We explain the elements of the algorithm such as chromosome structure, fitness function, crossover, mutation, and local improvement operations and solve more than 220 problems with known optimal solutions to evaluate the performance of the proposed algorithm. The results of the experimentation are quite satisfactory. ©...

#### Problems and challenges for implementation of safety and HSE management rules in aged Iranian refineries and petrochemical complexes

, Article CHISA 2006 - 17th International Congress of Chemical and Process Engineering, Prague, 27 August 2006 through 31 August 2006 ; 2006 ; 8086059456 (ISBN); 9788086059457 (ISBN) ; Hashemi, V ; Rashtchian, D ; Sharif University of Technology
2006

Abstract

Nowadays "as everywhere in the world", so much attention is drawn to performing safety and HSE management rules in Iran. Considering the long life of oil and it's relevant industries in Iran (since 1908, first oil well in Middle East, Masjid Soleyman), many units with more than 50 years old are still in operation. This situation posed special problems in performing safety and HSE regulations that some of them are communal among these units. This paper reveals the result of industrial projects, collecting numerous technical checklists in such units and author's experiences in recent years in Iran, which is aimed to announce some of these major problems and also present solutions for them

#### A genetic algorithm approach to find the best regression/econometric model among the candidates

, Article Applied Mathematics and Computation ; Volume 183, Issue 1 , 2006 , Pages 337-349 ; 00963003 (ISSN) ; Akhavan Niaki, T ; Sharif University of Technology
2006

Abstract

Although statistical modeling is a common task in different fields of science, it is still difficult to estimate the best model that can accurately describe inherent characteristics of a system for which historical or experimental data are available. Since we may classify estimating techniques as optimizations, we can model this problem as an optimization problem and solve it by a new heuristic algorithm like neural networks, genetic algorithms, and tabu search or by classic ones such as regression and econometric models. In this paper, we propose a new type of genetic algorithm to find the best regression model among all suggested and evaluate its performances by an economical case study. ©...

#### Some sufficient conditions for the intersection with the vertical isocline in the Liénard plane

, Article Applied Mathematics Letters ; Volume 19, Issue 5 , 2006 , Pages 491-497 ; 08939659 (ISSN) ; Moradifam, A ; Sharif University of Technology
2006

Abstract

In this work we study the problem of whether all trajectories of the system ẋ=y-F(x) and ẏ=-g(x) cross the vertical isocline, which is very important for the existence of periodic solutions and oscillation theory. Sufficient conditions are given for all trajectories to cross the vertical isocline. © 2005 Elsevier Ltd. All rights reserved

#### An efficient simplified neural network for solving linear and quadratic programming problems

, Article Applied Mathematics and Computation ; Volume 175, Issue 1 , 2006 , Pages 452-464 ; 00963003 (ISSN) ; Mahdavi Amiri, N ; Sharif University of Technology
2006

Abstract

We present a high-performance and efficiently simplified new neural network which improves the existing neural networks for solving general linear and quadratic programming problems. The network, having no need for parameter setting, results in a simple hardware requiring no analog multipliers, is shown to be stable and converges globally to the exact solution. Moreover, using this network we can solve both linear and quadratic programming problems and their duals simultaneously. High accuracy of the obtained solutions and low cost of implementation are among the features of this network. We prove the global convergence of the network analytically and verify the results numerically. © 2005...

#### A recursive approach for analysis of snake robots using Kane's equations

, Article DETC2005: ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, Long Beach, CA, 24 September 2005 through 28 September 2005 ; Volume 7 B , 2005 , Pages 855-861 ; 0791847446 (ISBN) ; Pishkenari, H. N ; Meghdari, A ; Sharif University of Technology
2005

Abstract

This paper presents a recursive approach for solving kinematic and dynamic problem in snake-like robots using Kane's equations. An n-link model with n-nonholonomic constraints is used as the snake robot model in our analysis. The proposed algorithm which is used to derive kinematic and dynamic equations recursively enhances the computational efficiency of our analysis. Using this method we can determine the number of additions and multiplications as a function of n. The proposed method is compared with the Lagrange and Newton-Euler's method in three different aspects: Number of operations, CPU time and error in the computational procedures. Copyright © 2005 by ASME

#### Duality in fuzzy variable linear programming

, Article Wec 05: Fourth World Enformatika Conference, Istanbul, 24 June 2005 through 26 June 2005 ; Volume 6 , 2005 , Pages 115-117 ; 9759845857 (ISBN) ; Nasseri, S. H ; Sharif University of Technology
2005

Abstract

Recently, fuzzy variable linear programming problems have attracted some interests. We introduce the dual of fuzzy variable linear programming problem, and then deduce some important duality results. COPYRIGHT © ENFORMATIKA

#### A new stabilizing GPC for nonminimum phase LTI systems using time varying weighting

, Article Wec 05: Fourth World Enformatika Conference, Istanbul, 24 June 2005 through 26 June 2005 ; Volume 6 , 2005 , Pages 156-158 ; 9759845857 (ISBN); 9789759845858 (ISBN) ; Haeri, M ; Sharif University of Technology
2005

Abstract

In this paper, we show that the stability can not be achieved with current stabilizing MPC methods for some unstable processes. Hence we present a new method for stabilizing these processes. The main idea is to use a new time varying weighted cost function for traditional GPC. This stabilizes the closed loop system without adding soft or hard constraint in optimization problem. By studying different examples it is shown that using the proposed method, the closed-loop stability of unstable nonminimum phase process is achieved. COPYRIGHT © ENFORMATIKA

#### On the relevance of fair sampling assumption in the recent bell photonic experiments

, Article Journal of Modern Optics ; Volume 52, Issue 10 , 2005 , Pages 1405-1414 ; 09500340 (ISSN) ; Golshani, M ; Sharif University of Technology
2005

Abstract

In the experimental verification of Bell's inequalities in real photonic experiments, it is generally believed that the so-called fair sampling assumption (which means that a small fraction of results provide a fair statistical sample) has an unavoidable role. Here, we want to show that the interpretation of these experiments could be feasible, if some different alternative assumptions other than the fair sampling were used. For this purpose, we derive an efficient Bell-type inequality which is a CHSH-type inequality in real experiments. Quantum mechanics violates our proposed inequality, independent of the detection-efficiency problems. © 2005 Taylor & Francis Group Ltd

#### Biased random satisfiability problems: From easy to hard instances

, Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 71, Issue 6 , 2005 ; 15393755 (ISSN) ; Moghimi Araghi, S ; Sharif University of Technology
2005

Abstract

In this paper we study biased random K-satisfiability (K-SAT) problems in which each logical variable is negated with probability p. This generalization provides us a crossover from easy to hard problems and would help us in a better understanding of the typical complexity of random K-SAT problems. The exact solution of 1-SAT case is given. The critical point of K-SAT problems and results of replica method are derived in the replica symmetry framework. It is found that in this approximation αcp-(K-1) for p→0. Solving numerically the survey propagation equations for K=3 we find that for p

#### A practical exact algorithm for the shortest loop design problem in a block layout

, Article International Journal of Production Research ; Volume 43, Issue 9 , 2005 , Pages 1879-1887 ; 00207543 (ISSN) ; Laporte, G ; Sharifyazdi, M ; Sharif University of Technology
2005

Abstract

The problem of determining a shortest loop incident to each cell of a block layout is considered. A compact formulation is developed for this problem and a relatively simple algorithm is presented. It is shown that instances containing up to 60 cells can be solved optimally by using a commercial integer linear programming solver embedded within an iterative scheme. © 2005 Taylor & Francis Group Ltd