Sharif Digital Repository

The use of traffic information in the form of radio reports, as a solution to the problem of congestion, is one of the issues, which are of particular importance for large cities like Tehran. In this study, factors affecting the use of traffic information in the context of a developing country are examined for commuters in the city of Tehran using ordered logit models. Results based on the particular survey designed for this purpose are compared to those of a developed country. Regarding the use of information in the form of listening to the radio traffic reports, the models show that older commuters, commuters who adjust their departure time according to traffic conditions (those who are... 

In this paper, Analytic Hierarchy Process and Data Envelopment Analysis are introduced as multi attribute decision making techniques in planning of standalone micro-power systems. The objective of the planning framework is to select the best configuration and capacity of different generating technologies in micro-power systems to minimize certain economical and environmental attributes. The economical attributes are capital cost and net present cost and the environmental attribute is emission. The proposed framework is illustrated by a case study on a real network in northern region of Iran  

The necessity of dynamic equivalents for power system analysis has been well known since the expansion of large interconnected power networks, and has been discussed during the last decades. The present paper proposes a new method for constructing dynamic equivalents of power systems. In this method, at the first step the "study system" is modeled completely via a single machineinfinite bus modeling procedure. Then the "external system" is identified as a MIMO feedback block of this model in such a manner that can include dynamic effects of the latter on the behavior of the former. The method is successfully experimented on a part of the Iranian southern network. Copyright © 2007 The... 

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... 

The Ising model with nearest-neighbor interactions on the edge dual of uncorrelated random networks was discussed. It was found that in the thermodynamic limit, the networks have a finite clustering. Low- and high-temperature expansions of Ising model on the edge dual of random networks were derived. A comparison of the critical behavior of Ising model on scale free random networks and their edge dual was performed. A simple relation was given between the partition function of an Ising model with nearest- and next-nearest-neighbor interactions on a tree like network and its edge dual  

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  

We consider the Ising model on the edge dual of uncorrelated random networks with arbitrary degree distribution. These networks have a finite clustering in the thermodynamic limit. High- and low-temperature expansions of Ising model on the edge dual of random networks are derived. A detailed comparison of the critical behavior of Ising model on scale free random networks and their edge dual is presented. © 2004 The American Physical Society  

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  

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  

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... 

In maintenance and replacement planning of an industry, the purchasing of new equipment on the market with some kind of technological improvement over existing equipment should be taken into account. Because of operating cost, ordinary and preventive maintenance expenses may be lower, production rate may be higher and the quality of output may be better, etc. The industry to be considered in this paper is the mining industry and the replaced equipment is the mine shovel. It is assumed that, at most, one new shovel can be purchased before the mine is exhausted. It is possible that the mine is given up before exhausted, because of the disadvantage of the expense and loss of the salvage value... 

In this paper, the third order differential equation x‴ + ψ (x′)x″ + (κ2 +ø (x))x′ + f(t, x = e(t) is considered. Under certain conditions on the functions appearing in the differential equation, the existence of periodic solutions is proved. Similar problems have been treated by authors in [4,6,7]. However, the method employed here is used by Reissig [1] and the results obtained are, in fact, a generalization of those in [1-3]. The conditions imposed on the nonlinear terms do not require the ultimate boundedness of all solutions. © Sharif University of Technology  

A new methodology has been proposed to enhance inverse dynamics applications in the process of trajectory planning and optimization in Terrain Following Flights (TFF). The new approach uses least square scheme to solve a general two-dimensional (2D) Terrain Following Flight in a vertical plane. In the mathematical process, Chebyshev polynomials are used to model the geographical data of the terrain in a given route in a manner suitable for the aircraft at hand. The aircraft then follows the modeled terrain with sufficient clearance. In this approach the TF problem is effectively converted to an optimal tracking problem. Results show that. this method provides a flexible approach to solve the... 

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;... 

In this paper, we present the most general form for error control coding using finite field multi-rate filters. This method shows how different types of codes can easily be generated by multi-rate filters and filter banks. In all previous works, codes and syndromes were generated using prefilters. Here we present simple multi-rate structures for encoding and generating syndrome. We show that all kinds of arbitrary rate K/L, circulant linear codes can be generated by these structures. Then we claim that a similar simple structure for syndrome generation in all presented cases exist  

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  

Sometimes, in our capacity as professionals, and under certain circumstances, we find ourselves faced with an ethical problem such as a conflict of interest in which codes of ethics or available ethical problem-solving methods cannot help us decide upon the moral course of action to take. Hence, either the codes or methods are flawed, or we are not using them appropriately. A method claimed to be helpful in such situations is The New York Times Test (NYTT). © 1982-2012 IEEE  

This communication addresses the focusing problem in the millimeter-wave imaging systems. We categorize the focusing problem into the frequency focusing for wideband systems and the range focusing for narrowband systems. In an out-of-focus wideband system, a shifted shadow of the object is present in the reconstruction, whereas for a range out of the focused system, the recovered images are blurred. To overcome these issues, first, we theoretically show that the defocusing variations for both categories are bounded. Then, we present a universal formulation for focusing problem, which covers both wideband and narrowband systems. As the true focused images are sharp at the boundaries of the... 

In this letter, the problem of non-coherent direction of arrival (DOA) estimation is investigated exploiting the sign of the measurements in order to resolve the inherent ambiguity of the problem. Although the phase values are inaccurate, the sign of real and imaginary parts of the measurements will most likely remain correct under limited phase errors. Furthermore, a new approach for solving the problem is proposed employing a modified version of the Majorization-Minimization (MM) technique, without any prior information about the number of incident signals. Some theoretical analyses of our proposed algorithm are also provided in the paper. Finally, the simulation results are presented,...