Loading...

**Search for:**problem-solving

0.008 seconds

Total 398 records

#### Dynamic behavior and modal control of beams under moving mass

, Article Journal of Sound and Vibration ; Volume 306, Issue 3-5 , 2007 , Pages 712-724 ; 0022460X (ISSN) ; Rahimzadeh Rofooei, F ; Shadnam, M. R ; Sharif University of Technology
Academic Press
2007

Abstract

The constitutive equation of an Euler-Bernoulli beam under the excitation of moving mass is considered. The dynamics of the uncontrolled system is governed by a linear, self-adjoint partial differential equation. A Dirac-delta function is used to describe the position of the moving mass along the beam and its inertial effects. An approximate formulation to the problem is obtained by limiting the inertial effect of the moving mass merely to the vertical component of acceleration. Having defined a "critical velocity" in terms of the fundamental period and span of the beam, it is shown that for smaller velocities, the approximate and exact approaches to the problem almost coincide. Since, the...

#### Unit commitment using particle swarm-based-simulated annealing optimization approach

, Article 2007 IEEE Swarm Intelligence Symposium, SIS 2007, Honolulu, HI, 1 April 2007 through 5 April 2007 ; 2007 , Pages 297-302 ; 1424407087 (ISBN); 9781424407088 (ISBN) ; Hajian, M ; Zamani, M ; Sharif University of Technology
2007

Abstract

In this paper, a new approach based on hybrid Particle Swarm-Based- Simulated Annealing Optimization (PSO-B-SA) for solving thermal unit commitment (UC) problems is proposed. The PSO-B-SA presented in this paper solves the two sub-problems simultaneously and independently; unit-scheduled problem that determines on/off status of units and the economic dispatch problem for production amount of generating units. Problem formulation of UC is defined as minimization of total objective function while satisfying all the associated constraints such as minimum up and down time, production limits and the required demand and spinning reserve. Simulation results show that the proposed approach can...

#### NN-RED: An AQM mechanism based on neural networks

, Article Electronics Letters ; Volume 43, Issue 19 , 2007 , Pages 1053-1055 ; 00135194 (ISSN) ; Sadati, N ; Sharif University of Technology
2007

Abstract

A novel active queue management (AQM) method is proposed. This method, named NN-RED, is based on the use of a neural network for early congestion prediction. By simulations, it is demonstrated that the performance of the proposed approach is better than the random early detection (RED) method that is currently known as one of the best AQM methods in solving congestion problems. © The Institution of Engineering and Technology 2007

#### Capturing an intruder in product networks

, Article Journal of Parallel and Distributed Computing ; Volume 67, Issue 9 , 2007 , Pages 1018-1028 ; 07437315 (ISSN) ; Sarbazi Azad, H ; Zomaya, A. Y ; Sharif University of Technology
2007

Abstract

In this paper, we propose a solution to the problem of capturing an intruder in a product network. This solution is derived based on the assumption of existing algorithms for basic member graphs of a graph product. In this problem, a team of cleaner agents are responsible for capturing a hostile intruder in the network. While the agents can move in the network one hop at a time, the intruder is assumed to be arbitrarily fast in a way that it can traverse any number of nodes contiguously as far as no agents reside in those nodes. Here, we consider a version of the problem where each agent can replicate new agents. Thus, the algorithm starts with a single agent and new agents are created on...

#### A new wave equation for MHD instabilities in aluminum reduction cells

, Article TMS 2007 Annual Meeting and Exhibition, Orlando, FL, 25 February 2007 through 1 March 2007 ; 2007 , Pages 345-349 ; 01470809 (ISSN) ; 0873396596 (ISBN); 9780873396592 (ISBN) ; Saboohi, Y ; Sharif University of Technology
2007

Abstract

To overcome the problem of magneto hydrodynamic instabilities at the aluminum-cryolite interface in aluminum reduction cells, the use of a simple and efficient model has been suggested. In this paper a new model for evaluation of magneto hydrodynamic instabilities in aluminum reduction cells is proposed. This model is in the form of a wave equation for interfacial oscillations and is constructed based on Shallow Water approximation and linear stability analysis. In this model two terms for linear friction in each molten layer of aluminum and cryolite has been considered and also Lorentz forces in cryolite layer have not been neglected. By accounting of these additional terms in our model,...

#### A genetic algorithm for resource investment project scheduling problem, tardiness permitted with penalty

, Article European Journal of Operational Research ; Volume 181, Issue 1 , 2007 , Pages 86-101 ; 03772217 (ISSN) ; Kianfar, F ; Sharif University of Technology
2007

Abstract

In this paper a genetic algorithm for solving a class of project scheduling problems, called Resource Investment Problem, is presented. Tardiness of project is permitted with defined penalty. Elements of algorithm such as chromosome structure, unfitness function, crossover, mutation, immigration and local search operations are explained. The performance of this genetic algorithm is compared with the performance of other published algorithms for Resource Investment Problem. Also 690 problems are solved and their optimal solutions are used for the performance tests of the genetic algorithm. The tests results are quite satisfactory. © 2006 Elsevier B.V. All rights reserved

#### Solving the discrete time/resource trade-off problem in project scheduling with genetic algorithms

, Article Applied Mathematics and Computation ; Volume 191, Issue 2 , 2007 , Pages 451-456 ; 00963003 (ISSN) ; Kianfar, F ; Sharif University of Technology
2007

Abstract

In this paper, we develop a metaheuristic procedure for solving the discrete time/resource trade-off problem in the field of project scheduling. In this problem, a project contains activities interrelated by finish-start-type precedence constraints with a time lag of zero, which require a single constrained renewable resource. Each activity has a specified work content and can be performed in different modes, i.e. with different durations and resource requirements; as long as the required work content is met. The objective is to schedule each activity in one of its modes in order to minimize the project makespan. To tackle this problem, we use a genetic algorithm in which a new method based...

#### The impact of stationary nodes on the performance of wireless mobile networks

, Article Third International Conference on Wireless and Mobile Communications 2007, ICWMC '07, Guadeloupe, 4 March 2007 through 9 March 2007 ; 2007 ; 0769527965 (ISBN); 9780769527963 (ISBN) ; Khosravi, A ; Sarbazi Azad, H ; Sharif University of Technology
2007

Abstract

In this paper, impact of the stationary nodes on the link excess life as an important performance parameter of wireless mobile networks is investigated First, a model for the link excess life is introduced. Based on this model, the relation between the probability density function (PDF) of the link excess life and the PDF of relative velocity is explored. In fact, the PDF of relative velocity is divided into three PDFs according to the three categories of links. The effect of each group on the resultant PDF of global link excess life for different percentages of stationary nodes is explored. Moreover, an approximation method defined in our previous work is proposed as a tool to evaluate the...

#### Optimal solution for a two-level inventory system with information exchange leading to a more computationally efficient search

, Article Applied Mathematics and Computation ; Volume 189, Issue 2 , 2007 , Pages 1341-1349 ; 00963003 (ISSN) ; Haji, R ; Sharif University of Technology
2007

Abstract

In this paper we consider a two-level inventory system with one warehouse and one retailer with information exchange. The retailer applies fixed order size continuous review policy. The supplier starts with m initial batches of the same order size of the retailer, and places an order to an outside source immediately after the retailer's inventory position reaches an amount equal to the retailer's order point plus a fixed value s. Transportation times are constant and the retailer faces independent Poisson demand. In a recent paper it was pointed out that the optimal supplier policy in this inventory system is an open question. To obtain the optimal policy for this system, first we find the...

#### Lebesgue function for multivariate interpolation by radial basis functions

, Article Applied Mathematics and Computation ; Volume 187, Issue 1 SPEC. ISS , 2007 , Pages 306-314 ; 00963003 (ISSN) ; Jokar, S ; Sharif University of Technology
Elsevier Inc
2007

Abstract

Multivariate interpolation and approximation is a powerful tool for intuition of real world. In this paper we study Lebesgue function and Lebesgue constant for multivariate interpolation by conditionally positive definite RBFs. Also we give a conjecture about similar Bernstein and Erdös problem to multivariate case. © 2006 Elsevier Inc. All rights reserved

#### Adaptive regulation and set-point tracking of the Lorenz attractor

, Article Chaos, Solitons and Fractals ; Volume 32, Issue 2 , 2007 , Pages 832-846 ; 09600779 (ISSN) ; Shahrokhi, M ; Mahboobi, S. H ; Sharif University of Technology
2007

Abstract

In this paper, an approach is proposed for controlling the uncertain Lorenz system. Based on an identification technique, a controller is designed that guarantees the regulation of all states in the presence of system uncertainty. Since in some applications the challenging problem of output tracking is desired, we have proposed several effective set-point tracking control techniques. The control schemes that are based on the feedback linearization method, can stabilize the internal dynamics of the system. Simulation results have illustrated the effectiveness of the proposed schemes. © 2005 Elsevier Ltd. All rights reserved

#### Extended reduced rank two Abaffian update schemes in the ABS-type methods

, Article Applied Mathematics and Computation ; Volume 185, Issue 1 , 2007 , Pages 255-265 ; 00963003 (ISSN) ; Mahdavi Amiri, N ; Peyghami, M. R ; Sharif University of Technology
2007

Abstract

The ABS methods, introduced by Abaffy, Broyden and Spedicato, are direct iteration methods for solving a linear system where the ith iterate satisfies the first i equations, therefore a system of m equations is solved in at most m steps. Recently, we have presented a new approach to devise a class of ABS-type methods for solving full row rank systems [K. Amini, N. Mahdavi-Amiri, M. R. Peyghami, ABS-type methods for solving full row rank linear systems using a new rank two update, Bulletin of the Australian Mathematical Society 69 (2004) 17-31], the ith iterate of which solves the first 2i equations. Here, to reduce the space and computation time, we use a new extended rank two update formula...

#### On pancyclicity properties of OTIS networks

, Article 3rd International Conference on High Performance Computing and Communications, HPCC 2007, Houston, TX, 26 September 2007 through 28 September 2007 ; Volume 4782 LNCS , 2007 , Pages 545-553 ; 03029743 (ISSN); 9783540754435 (ISBN) ; Sarbazi Azad, H ; Sharif University of Technology
Springer Verlag
2007

Abstract

The OTIS-Network (also referred to as two-level swapped network) is composed of n clones of an n-node original network constituting its clusters. It has received much attention due to its many favorable properties such as high degree of scalability, regularity, modularity, package-ability and high degree of algorithmic efficiency. In this paper, using the construction method, we show that the OTIS-Network is Pancyclic if its basic network is Hamiltonian- connected. The study of cycle embeddings with different sizes arises naturally in the implementation of a number of either computational or graph problems such as those used for finding storage schemes for logical data structures, layout of...

#### Fast sparse representation based on smoothed ℓ0norm

, Article 7th International Conference on Independent Component Analysis (ICA) and Source Separation, ICA 2007, London, 9 September 2007 through 12 September 2007 ; Volume 4666 LNCS , 2007 , Pages 389-396 ; 03029743 (ISSN); 9783540744931 (ISBN) ; Babaie Zadeh, M ; Jutten, C ; Sharif University of Technology
Springer Verlag
2007

Abstract

In this paper, a new algorithm for Sparse Component Analysis (SCA) or atomic decomposition on over-complete dictionaries is presented. The algorithm is essentially a method for obtaining sufficiently sparse solutions of underdetermined systems of linear equations. The solution obtained by the proposed algorithm is compared with the minimum ℓ1-norm solution achieved by Linear Programming (LP). It is experimentally shown that the proposed algorithm is about two orders of magnitude faster than the state-of-the-art ℓ1-magic, while providing the same (or better) accuracy. © Springer-Verlag Berlin Heidelberg 2007

#### Estimating the mixing matrix in sparse component analysis based on converting a multiple dominant to a single dominant problem

, Article 7th International Conference on Independent Component Analysis (ICA) and Source Separation, ICA 2007, London, 9 September 2007 through 12 September 2007 ; Volume 4666 LNCS , 2007 , Pages 397-405 ; 03029743 (ISSN); 9783540744931 (ISBN) ; Babaie Zadeh, M ; Jutten, C ; Sharif University of Technology
Springer Verlag
2007

Abstract

We propose a new method for estimating the mixing matrix, A, in the linear model x(t) = As(t),t = 1,...,T, for the problem of underdetermined Sparse Component Analysis (SCA). Contrary to most previous algorithms, there can be more than one dominant source at each instant (we call it a "multiple dominant" problem). The main idea is to convert the multiple dominant problem to a series of single dominant problems, which may be solved by well-known methods. Each of these single dominant problems results in the determination of some columns of A. This results in a huge decrease in computations, which lets us to solve higher dimension problems that were not possible before. © Springer-Verlag...

#### Valuation of dynamic reactive power support in multitransaction power systems

, Article European Transactions on Electrical Power ; Volume 17, Issue 1 , 2007 , Pages 61-79 ; 1430144X (ISSN) ; Vakilian, M ; Feuillet, R ; Hadj Said, N ; Sharif University of Technology
2007

Abstract

This paper presents a reactive power valuation method with regard to its effect on realization of MW transactions. The security constraint optimization model in which the objective function is maximization of transactions is solved by the genetic algorithm approach. The proposed scheme allocates a specific amount of MW transactions to each dynamic reactive power source. An index is introduced to derive VAr value from the calculated optimal parameters of power network. This index represents the system-wide effect of MVAr sources on MW transactions implementations. Application of proposed method has been illustrated using IEEE 30 and 14 bus test systems. Results are discussed and compared in...

#### Corotational analysis of elastic-plastic hardening materials based on different kinematic decompositions

, Article ASME PVP2006/ICPVT-11 Conference, Vancouver, BC, 23 July 2006 through 27 July 2006 ; Volume 2006 , 2006 ; 0277027X (ISSN) ; 0791837823 (ISBN); 9780791837825 (ISBN) ; Naghdabadi, R ; Sharif University of Technology
2006

Abstract

In this paper, two corotational modeling for elastic-plastic, mixed hardening materials at finite deformations are introduced. In these models, the additive decomposition of the strain rate tensor as well as the multiplicative decomposition of the deformation gradient tensor is used. For this purpose, corotational constitutive equations are derived for elastic-plastic hardening materials with the non-linear Armstrong-Frederick kinematic hardening and isotropic hardening models. As an application of the proposed constitutive modeling, the governing equations are solved numerically for the simple shear problem with different corotational rates and the stress components are plotted versus the...

#### NORTA and neural networks based method to generate RANDOM vectors with arbitrary marginal distributions and correlation matrix

, Article 17th IASTED International Conference on Modelling and Simulation, Montreal, QC, 24 May 2006 through 26 May 2006 ; Volume 2006 , 2006 , Pages 234-239 ; 10218181 (ISSN) ; 0889865949 (ISBN); 9780889865945 (ISBN) ; Abbasi, B ; Sharif University of Technology
2006

Abstract

Growing technology, escalating capability, and increasing complexity in many real world systems demand the applications of multivariate statistical analysis approaches by simulation. In these approaches, generating multivariate random vectors is a crucial part of the system modeling and analyzing. The NORTA algorithm, in which generating the correlation matrices of normal random vectors is the most important task, is one of the most efficient methods in this area. To do this, we need to solve some complicated equations. Many researchers have tried to solve these equations by three general approaches of (1) solving nonlinear equations analytically, (2) solving equations numerically, and (3)...

#### Semi-decentralized control of multi-agent systems based on redundant manipulator optimization methods

, Article 9th IEEE International Workshop on Advanced Motion Control, 2006, Istanbul, 27 March 2006 through 29 March 2006 ; Volume 2006 , 2006 , Pages 278-283 ; Elhamifar, E ; Sharif University of Technology
2006

Abstract

In this paper, a new approach for online reactive path generation and control of multi-agent systems is proposed. This method is based on local optimization techniques used for solving the inverse kinematic problem of redundant manipulators. Convergence of the agents' velocities to the desired values in the null-space of the primary task is guaranteed by introducing a new control law. The efficacy of the proposed algorithm is demonstrated through simulation experiments. © 2006 IEEE

#### Edge sensitive block motion estimation employing partial ridgelet distortion search

, Article 6th IEEE International Symposium on Signal Processing and Information Technology, ISSPIT 2006, Vancouver, BC, 27 August 2006 through 30 August 2006 ; 2006 , Pages 902-907 ; 0780397541 (ISBN); 9780780397545 (ISBN) ; Fatemizadeh, E ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2006

Abstract

Motion estimation is an important field of video processing. Conventional block motion estimation methods consider all pixels equally. In this paper a new edge sensitive algorithm is proposed in which distortion of ridgelet coefficients is calculated partially and compared over all candidates. Using an edge boosting distortion function, edge pixels will have more important role since they introduce larger ridgelet coefficients. Inherent ability of ridgelet in representing edges with various directions in multi scale, makes it a powerful tool for edge pursuit. Proposed partial ridgelet distortion search (PRDS) do not reject any candidate without assessment while performs relatively fast since...