The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform

Richard Barakat - One of the best experts on this subject based on the ideXlab platform.

  • Plane wave scattering by a finite array of conducting cylinders partially buried in a ground plane: TM polarization
    Pure and Applied Optics: Journal of the European Optical Society Part A, 1994
    Co-Authors: Tenneti C. Rao, Richard Barakat
    Abstract:

    The problem of scattering by a finite array of infinitely long perfectly conducting circular cylinders located on the surface of a conducting ground plane or partially buried into it due to an obliquely incident plane electromagnetic wave is solved by an exact Procedure based on the method of images. The incident field, the reflected field from the ground plane in the absence of cylinders and the scattered fields from different cylinders and their images are expressed in terms of cylindrical vector wavefunctions. The boundary conditions of the vanishing of the tangential electric field on each one of the cylinders are then imposed and this Procedure leads to a set of coupled infinite systems of equations for the even and odd mode expansion coefficients of the scattered fields originating from each cylinder. These equations are truncated at a large fixed number and the coefficients are determined by a Gaussian Elimination Procedure. The scattered far field from the array is then determined by summing contributions from each cylinder. The variation of the scattered field with the different parameters of the array like the electrical radius, spacings between cylinders, height parameter and the angle of incidence is studied in detail. Numerical results are presented for the TM polarization in a three-cylinder configuration for those cylinders whose electrical radius is in the Rayleigh and lower resonance regions.

  • Plane-wave scattering by a conducting cylinder partially buried in a ground plane II: TE case
    Journal of the Optical Society of America A, 1991
    Co-Authors: Tenneti C. Rao, Richard Barakat
    Abstract:

    The problem of plane-wave scattering by an infinitely long perfectly conducting circular cylinder that is partially buried in a perfectly conducting ground plane is studied by the method of images, for which the incident electric-field vector is assumed to be in a plane perpendicular to the axis of the cylinder (TE polarization). The incident field, the reflected field from the ground plane in the absence of the cylinder, and the scattered field from the cylinder and its image are expressed in terms of cylindrical vector wave functions. By imposing the boundary conditions on the surface of the cylinder, we obtain a set of two coupled infinite systems of equations for the even–and odd–mode expansion coefficients of the scattered field. We solve these equations numerically by truncating the infinite summations and using a subsequent Gaussian Elimination Procedure. The scattered power patterns in the far–field region are obtained, and their variations with the angle of incidence, height (or depth) above (or below) the ground plane, and the electrical radius are studied. Comparisons with the corresponding TM–case results are made.

Raja Nassar - One of the best experts on this subject based on the ideXlab platform.

  • A HYBRID FINITE ELEMENT-FINITE DIFFERENCE METHOD FOR SOLVING THREE-DIMENSIONAL HEAT TRANSPORT EQUATIONS IN A DOUBLE-LAYERED THIN FILM WITH MICROSCALE THICKNESS
    Numerical Heat Transfer Part A: Applications, 2000
    Co-Authors: W Eizhong Dai, Raja Nassar
    Abstract:

    W e develop a finite element?finite difference method for solving three-dimensional heat transport equations in a double-layered thin film with microscale thickness. The implicit scheme is solved by using a preconditioned Richardson iteration, so that only two block tridiagonal linear systems with unknowns at the interface are solved for each iteration. W e then apply a parallel Gaussian Elimination Procedure to solve these two block tridiagonal linear systems and develop a domain decomposition algorithm for thermal analysis of the double-layered thin film. Numerical results for thermal analysis of a gold layer on a chromium padding layer are obtained.

  • A domain decomposition method for solving thin film elliptic interface problems with variable coefficients
    International Journal for Numerical Methods in Engineering, 1999
    Co-Authors: W Eizhong Dai, Raja Nassar
    Abstract:

    A domain decomposition method is developed for solving thin film elliptic interface problems with variable coefficients. In this study, the elliptic equation with variable coefficients is discretized using second-order finite differences while a discrete interface equation is obtained using the immersed interface method in order to obtain a second-order global accuracy. The obtained linear system is solved using a preconditioned Richardson iteration, which is shown to converge fast when the grid size in the thickness direction is much smaller than the grid sizes in both the length and width directions. To simplify the computation, a domain decomposition algorithm is obtained based on a parallel Gaussian Elimination Procedure. The method is illustrated by a numerical example. Copyright © 1999 John Wiley & Sons, Ltd.

Tenneti C. Rao - One of the best experts on this subject based on the ideXlab platform.

  • Plane wave scattering by a finite array of conducting cylinders partially buried in a ground plane: TM polarization
    Pure and Applied Optics: Journal of the European Optical Society Part A, 1994
    Co-Authors: Tenneti C. Rao, Richard Barakat
    Abstract:

    The problem of scattering by a finite array of infinitely long perfectly conducting circular cylinders located on the surface of a conducting ground plane or partially buried into it due to an obliquely incident plane electromagnetic wave is solved by an exact Procedure based on the method of images. The incident field, the reflected field from the ground plane in the absence of cylinders and the scattered fields from different cylinders and their images are expressed in terms of cylindrical vector wavefunctions. The boundary conditions of the vanishing of the tangential electric field on each one of the cylinders are then imposed and this Procedure leads to a set of coupled infinite systems of equations for the even and odd mode expansion coefficients of the scattered fields originating from each cylinder. These equations are truncated at a large fixed number and the coefficients are determined by a Gaussian Elimination Procedure. The scattered far field from the array is then determined by summing contributions from each cylinder. The variation of the scattered field with the different parameters of the array like the electrical radius, spacings between cylinders, height parameter and the angle of incidence is studied in detail. Numerical results are presented for the TM polarization in a three-cylinder configuration for those cylinders whose electrical radius is in the Rayleigh and lower resonance regions.

  • Plane-wave scattering by a conducting cylinder partially buried in a ground plane II: TE case
    Journal of the Optical Society of America A, 1991
    Co-Authors: Tenneti C. Rao, Richard Barakat
    Abstract:

    The problem of plane-wave scattering by an infinitely long perfectly conducting circular cylinder that is partially buried in a perfectly conducting ground plane is studied by the method of images, for which the incident electric-field vector is assumed to be in a plane perpendicular to the axis of the cylinder (TE polarization). The incident field, the reflected field from the ground plane in the absence of the cylinder, and the scattered field from the cylinder and its image are expressed in terms of cylindrical vector wave functions. By imposing the boundary conditions on the surface of the cylinder, we obtain a set of two coupled infinite systems of equations for the even–and odd–mode expansion coefficients of the scattered field. We solve these equations numerically by truncating the infinite summations and using a subsequent Gaussian Elimination Procedure. The scattered power patterns in the far–field region are obtained, and their variations with the angle of incidence, height (or depth) above (or below) the ground plane, and the electrical radius are studied. Comparisons with the corresponding TM–case results are made.

Liguo Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Stability analysis for a class of switched nonlinear systems
    Automatica, 2011
    Co-Authors: A. Yu. Aleksandrov, Yawei Chen, Alexey V. Platonov, Liguo Zhang
    Abstract:

    This paper addresses the stability analysis of a class of switched nonlinear systems. The switched systems have uncertain nonlinear functions constrained in a sector set, which are called admissible sector nonlinearities. A sufficient condition in terms of linear inequalities is presented to guarantee the existence of a common Lyapunov function, and thereby to ensure that the switched system is stable for an arbitrary switching signal and any admissible sector nonlinearities. A constructive algorithm based on the modified Gaussian Elimination Procedure is given to find the solutions of the linear inequalities. The obtained results are applied to a population model with switchings of parameter values and the conditions of ultimate boundedness of its solutions are investigated. Another example of an automatic control system is considered to demonstrate the effectiveness of the proposed approaches.

  • Stability analysis and design of uniform ultimate boundedness control for a class of nonlinear switched difference systems
    2010 8th World Congress on Intelligent Control and Automation, 2010
    Co-Authors: A. Yu. Aleksandrov, Yawei Chen, Alexey V. Platonov, Liguo Zhang
    Abstract:

    This paper addresses the problems of stability analysis and synthesis of uniform ultimate boundedness (UUB) control for a class of nonlinear switched difference systems. This kind of discrete-time systems could be regarded as the digitization systems induced from the corresponding continuous-time switched system in virtue of the numerical integration approach, such as Euler or Runge-Kutta method. A sufficient stability condition in terms of linear inequalities is presented to ensure that for prescribed digitalized steps the switched difference system is stable for an arbitrary switching signal. Moreover, a constructive algorithm based on the modified Gaussian Elimination Procedure is given to find the solutions to the linear inequalities. Finally, continuous state feedback control methods are developed to guarantee uniform ultimate boundedness of the switched systems with nonlinear and time-varying parameter uncertainties and unknown input disturbances. A numerical example illustrates the effectiveness of the proposed approach.

M. Ghanbari - One of the best experts on this subject based on the ideXlab platform.

  • FINDING AN INNER ESTIMATION OF THE SOLUTION SET OF A FUZZY LINEAR SYSTEM
    Applied Mathematical Modelling, 2013
    Co-Authors: Rahele Nuraei, T. Allahviranloo, M. Ghanbari
    Abstract:

    Abstract In this paper, we consider the problem of finding an inner estimation of the solution set of a fuzzy linear system with a real-valued coefficient matrix and a fuzzy-valued right-hand side vector. The proposed idea is based on the utilization of interval Gaussian Elimination Procedure to produce an inner estimation of the solutions set. To this end, firstly we apply interval Gaussian Elimination Procedure to obtain the solution set of a fuzzy linear system and secondly, by limiting it via solving a crisp linear system, we find an inner estimation of the solutions set, such that it satisfies the related fuzzy linear system. Finally, several numerical examples are given to show the efficiency and ability of our method.

  • Estimation of algebraic solution by limiting the solution set of an interval linear system
    Soft Computing, 2012
    Co-Authors: M. Ghanbari, T. Allahviranloo, E. Haghi
    Abstract:

    In this paper, we introduce a new method for estimating the algebraic solution of an interval linear system (ILS) whose coefficient matrix is real-valued and right-hand side vector is interval-valued. In the proposed method, we first apply the interval Gaussian Elimination Procedure to obtain the solution set of an interval linear system and then by limiting the solution set of related ILS by the limiting factors, we get an algebraic solution of ILS. In addition, we prove that the obtained solution by our method satisfies the related interval linear system. Finally, based on our method, an algorithm is proposed and numerically demonstrated.