COMPEL - The international journal for computation and mathematics in electrical and electronic engineering
Purpose The purpose of this study is to develop an efficient model to solve the electromagnetic f... more Purpose The purpose of this study is to develop an efficient model to solve the electromagnetic forward problem using a novel semi-analytical approach to compute the electromagnetic fields because of the presence of a scatterer. Design/methodology/approach The proposed model involves a novel formulation of a complete orthonormal set of radiating/nonradiating polarization currents. Furthermore, an integral equation-based representation is derived, and the appropriate boundary conditions are imposed to get the scattered electromagnetic field. An error term is introduced to evaluate the obtained results. Findings The proposed model was tested using several examples at different frequencies. The results of this study show that the novel representation exhibits fast convergence behavior and achieves highly accurate results, when compared to the results provided by the transmission line method. Originality/value The derived formulations presented in this study are significant in the elect...
Journal of Electromagnetic Engineering and Science
Electromagnetic measurements are widely used to gain information about an object through interact... more Electromagnetic measurements are widely used to gain information about an object through interaction of electromagnetic fields with the physical properties of this object. The inversion problem is the process of estimating object parameters from electromagnetic records. This problem has a nonlinear nature and can be formulated as an optimization scheme. In this paper, we introduce an inversion methodology to estimate the electrical properties of a two-dimensional inhomogeneous layered scattering object. The proposed methodology deals with the inversion problem as a learning process through two multilayer perceptron artificial neural network designs. Several neural network design parameters were tuned to achieve the best inversion performance. Moreover, the proposed neural networks were tested against noise presence in terms of error criteria and proved to be effective in solving the inverse scattering problem.
Published online 10 April 2008The concept of left-handed material (LHM) was proposed by Veselago ... more Published online 10 April 2008The concept of left-handed material (LHM) was proposed by Veselago in (1968), where both the dielectric constant and the magnetic permeability are negative. Much attention has been received recently on the study of LHM on theory, experiments and potential applications (IEEE 2003). To mention a few of their applications, LHMs can be used to focus electromagnetic energy; they have the potential to form highly efficient, low reflectance surfaces by cancelling the scattering properties of other materials. The methods based on the Kontorovich–Lebedev transform (Lebedev 1965) have been successfully applied in the past to a number of problems of diffraction by wedges (Oberhettinger 1954; Forristall & Ingram 1971, 1972; Rawlins 1972, 1999; Osipov 1993; Salem et al. 2006). A strategy has been presented by Salem et al. (2006) to solve the problem of diffraction by an ordinary material wedge. This paper extends the strategy of Salem et al. (2006) to metamaterial w...
Introduction: To investigate the features of various media by means of electromagnetic radiation ... more Introduction: To investigate the features of various media by means of electromagnetic radiation it is necessary to know the field scattered by inhomogeneties of these media. This problem can be tackled by using as a basis a rigorous solution of a basic structure. One of the basic structures is the one considered in this letter. The problem under consideration has also acquired practical relevance in fields of optical engineering such as the study of contaminated surfaces and the detection of defects. Additionally the solution of canonical problems such as the one under consideration is important in the sense of scattering and diffraction theories. The aim of this letter is to present solutions, in terms of a discrete index of Hankel function transform, to the problem of the scattering of TM waves by a circular impedance cylinder immersed halfway between two half spaces of different electromagnetic properties. Other configurations of cylinder and two half spaces have been dealt with...
2013 International Symposium on Electromagnetic Theory, 2013
The scattering of the electromagnetic field by an impedance cylinder immersed halfway between two... more The scattering of the electromagnetic field by an impedance cylinder immersed halfway between two different half-spaces is considered. One of the half-spaces is composed of a dielectric material, and the other a metamaterial. In addition to the general case, several special cases are also considered. These cases include scattering by a thin wire, the limiting values for the surface impedance on the cylinder (PEC and PMC), and the reverse isovelocity case.
The presence of edges on the surface of a target may considerably influence the scattered field. ... more The presence of edges on the surface of a target may considerably influence the scattered field. The corresponding edge corrections are derived from the solution of the canonical problem of diffraction by an infinite wedge. If the refraction index takes different values inside and outside the wedge, no closed-form solution has been found so far despite multiple attempts and the use of a broad variety of methods. The Kontorovich-Lebedev transform has been successfully applied in the past to a number of scalar problems of diffraction by wedges. This paper applies the method to a vector problem of electromagnetic diffraction by a dielectric wedge. The boundary-value problem is reduced to a system of singular integral equations. It is shown that the equations can be approximately solved by perturbation method when the refraction index is near unity.
The manner in which boundary conditions are approximated and introduced into finite-difference sc... more The manner in which boundary conditions are approximated and introduced into finite-difference schemes has an important influence on the stability and accuracy of the results. The standard von Neumann stability condition applies only for points which are not in the vicinity of the boundaries. This stability condition does not take into consideration the effects caused by introducing the boundary conditions to the scheme. In this paper, we extend the von Neumann condition to include boundary conditions. The method is based on studying the time propagating matrix which governs the space-time behavior of the numerical grid. Examples of applying the procedure on schemes with different boundary conditions are given.
We consider the boundary-value problem for the Helmholtz equation connected with an in...nite cir... more We consider the boundary-value problem for the Helmholtz equation connected with an in...nite circular cone with an impedance boundary on its face. The scheme of solution includes applying the Kontorovich-Lebedev (KL) transform, derivation of an integral equation satis...ed by the KL spectral amplitude and obtaining alternative near and far ...eld representations together with the conditions of validity of these representations for a given set of problem parameters. As such, this article presents a second application to a problem solving strategy that was proposed in [1].
The presence of edges on the surface of a target may considerably influence the scattered field. ... more The presence of edges on the surface of a target may considerably influence the scattered field. The corresponding edge corrections are derived from the solution of the canonical problem of diffraction by an infinite wedge. If the refraction index takes different values inside and ...
COMPEL - The international journal for computation and mathematics in electrical and electronic engineering
Purpose The purpose of this study is to develop an efficient model to solve the electromagnetic f... more Purpose The purpose of this study is to develop an efficient model to solve the electromagnetic forward problem using a novel semi-analytical approach to compute the electromagnetic fields because of the presence of a scatterer. Design/methodology/approach The proposed model involves a novel formulation of a complete orthonormal set of radiating/nonradiating polarization currents. Furthermore, an integral equation-based representation is derived, and the appropriate boundary conditions are imposed to get the scattered electromagnetic field. An error term is introduced to evaluate the obtained results. Findings The proposed model was tested using several examples at different frequencies. The results of this study show that the novel representation exhibits fast convergence behavior and achieves highly accurate results, when compared to the results provided by the transmission line method. Originality/value The derived formulations presented in this study are significant in the elect...
Journal of Electromagnetic Engineering and Science
Electromagnetic measurements are widely used to gain information about an object through interact... more Electromagnetic measurements are widely used to gain information about an object through interaction of electromagnetic fields with the physical properties of this object. The inversion problem is the process of estimating object parameters from electromagnetic records. This problem has a nonlinear nature and can be formulated as an optimization scheme. In this paper, we introduce an inversion methodology to estimate the electrical properties of a two-dimensional inhomogeneous layered scattering object. The proposed methodology deals with the inversion problem as a learning process through two multilayer perceptron artificial neural network designs. Several neural network design parameters were tuned to achieve the best inversion performance. Moreover, the proposed neural networks were tested against noise presence in terms of error criteria and proved to be effective in solving the inverse scattering problem.
Published online 10 April 2008The concept of left-handed material (LHM) was proposed by Veselago ... more Published online 10 April 2008The concept of left-handed material (LHM) was proposed by Veselago in (1968), where both the dielectric constant and the magnetic permeability are negative. Much attention has been received recently on the study of LHM on theory, experiments and potential applications (IEEE 2003). To mention a few of their applications, LHMs can be used to focus electromagnetic energy; they have the potential to form highly efficient, low reflectance surfaces by cancelling the scattering properties of other materials. The methods based on the Kontorovich–Lebedev transform (Lebedev 1965) have been successfully applied in the past to a number of problems of diffraction by wedges (Oberhettinger 1954; Forristall & Ingram 1971, 1972; Rawlins 1972, 1999; Osipov 1993; Salem et al. 2006). A strategy has been presented by Salem et al. (2006) to solve the problem of diffraction by an ordinary material wedge. This paper extends the strategy of Salem et al. (2006) to metamaterial w...
Introduction: To investigate the features of various media by means of electromagnetic radiation ... more Introduction: To investigate the features of various media by means of electromagnetic radiation it is necessary to know the field scattered by inhomogeneties of these media. This problem can be tackled by using as a basis a rigorous solution of a basic structure. One of the basic structures is the one considered in this letter. The problem under consideration has also acquired practical relevance in fields of optical engineering such as the study of contaminated surfaces and the detection of defects. Additionally the solution of canonical problems such as the one under consideration is important in the sense of scattering and diffraction theories. The aim of this letter is to present solutions, in terms of a discrete index of Hankel function transform, to the problem of the scattering of TM waves by a circular impedance cylinder immersed halfway between two half spaces of different electromagnetic properties. Other configurations of cylinder and two half spaces have been dealt with...
2013 International Symposium on Electromagnetic Theory, 2013
The scattering of the electromagnetic field by an impedance cylinder immersed halfway between two... more The scattering of the electromagnetic field by an impedance cylinder immersed halfway between two different half-spaces is considered. One of the half-spaces is composed of a dielectric material, and the other a metamaterial. In addition to the general case, several special cases are also considered. These cases include scattering by a thin wire, the limiting values for the surface impedance on the cylinder (PEC and PMC), and the reverse isovelocity case.
The presence of edges on the surface of a target may considerably influence the scattered field. ... more The presence of edges on the surface of a target may considerably influence the scattered field. The corresponding edge corrections are derived from the solution of the canonical problem of diffraction by an infinite wedge. If the refraction index takes different values inside and outside the wedge, no closed-form solution has been found so far despite multiple attempts and the use of a broad variety of methods. The Kontorovich-Lebedev transform has been successfully applied in the past to a number of scalar problems of diffraction by wedges. This paper applies the method to a vector problem of electromagnetic diffraction by a dielectric wedge. The boundary-value problem is reduced to a system of singular integral equations. It is shown that the equations can be approximately solved by perturbation method when the refraction index is near unity.
The manner in which boundary conditions are approximated and introduced into finite-difference sc... more The manner in which boundary conditions are approximated and introduced into finite-difference schemes has an important influence on the stability and accuracy of the results. The standard von Neumann stability condition applies only for points which are not in the vicinity of the boundaries. This stability condition does not take into consideration the effects caused by introducing the boundary conditions to the scheme. In this paper, we extend the von Neumann condition to include boundary conditions. The method is based on studying the time propagating matrix which governs the space-time behavior of the numerical grid. Examples of applying the procedure on schemes with different boundary conditions are given.
We consider the boundary-value problem for the Helmholtz equation connected with an in...nite cir... more We consider the boundary-value problem for the Helmholtz equation connected with an in...nite circular cone with an impedance boundary on its face. The scheme of solution includes applying the Kontorovich-Lebedev (KL) transform, derivation of an integral equation satis...ed by the KL spectral amplitude and obtaining alternative near and far ...eld representations together with the conditions of validity of these representations for a given set of problem parameters. As such, this article presents a second application to a problem solving strategy that was proposed in [1].
The presence of edges on the surface of a target may considerably influence the scattered field. ... more The presence of edges on the surface of a target may considerably influence the scattered field. The corresponding edge corrections are derived from the solution of the canonical problem of diffraction by an infinite wedge. If the refraction index takes different values inside and ...
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Papers by Aladin Kamel