Aladin Kamel - Academia.edu (original) (raw)
Papers by Aladin Kamel
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...
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...
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].
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2006
Electromagnetic fields excited by a line source in the presence of an infinite dielectric wedge w... more Electromagnetic fields excited by a line source in the presence of an infinite dielectric wedge with refractive index N are determined by application of the Kontorovich–Lebedev transform. Singular integral equations for spectral functions are solved by perturbation procedure, and the solution is obtained in the form of a Neumann series in powers of . The devised numerical scheme permits evaluation of the higher-order terms and, thus, extends the perturbation solution to values of N not necessarily close to unity. Asymptotic approximations for the near and far fields inside and outside the dielectric wedge are derived. The combination of the Neumann-type expansion of the transform functions with the representation of the field as a Bessel function series extends solutions derived with the Kontorovich–Lebedev method to the case of real-valued wavenumbers and arbitrarily positioned source and observer. Numerical results showing the influence of wedges with various values of dielectric ...
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.
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 ...
Bulletin of the Seismological Society of America
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.
Journal of Electromagnetic Waves and Applications
SEG Technical Program Expanded Abstracts 1990
The International Conference on Electrical Engineering
In this paper we propose a nanoscale planar lens structure for generating Bessel beam like fields... more In this paper we propose a nanoscale planar lens structure for generating Bessel beam like fields to achieve large focal lengths and depth of fields. The structure consists of sub wavelength slits of different widths constructed on a thin metallic slab that is surrounded by air on both sides. The proposed structure is simulated using a modal technique that represents the structure as a waveguide and solves for the modes of the waveguide. Although diffraction affects the behavior of the generated beam from that of conventional Bessel beams, the simulation results show that the proposed structure is very promising for obtaining a very compact Bessel beam generator.
2013 International Symposium on Electromagnetic Theory, 2013
ABSTRACT The scattering of the electromagnetic field by an impedance cylinder immersed halfway be... more ABSTRACT 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 ...
Journal of Electromagnetic Waves and Applications
In practical calculations it is often essential to truncate the computational domain by introduci... more In practical calculations it is often essential to truncate the computational domain by introducing artificial boundaries. The manner in which boundary conditions are approximated has an important influence on the accuracy of the results. In this paper we present a time domain technique to quantify the spurious reflection of waves from an artificial boundary, obtained by using a nonreflecting boundary condition based on rational approximations.
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...
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...
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].
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2006
Electromagnetic fields excited by a line source in the presence of an infinite dielectric wedge w... more Electromagnetic fields excited by a line source in the presence of an infinite dielectric wedge with refractive index N are determined by application of the Kontorovich–Lebedev transform. Singular integral equations for spectral functions are solved by perturbation procedure, and the solution is obtained in the form of a Neumann series in powers of . The devised numerical scheme permits evaluation of the higher-order terms and, thus, extends the perturbation solution to values of N not necessarily close to unity. Asymptotic approximations for the near and far fields inside and outside the dielectric wedge are derived. The combination of the Neumann-type expansion of the transform functions with the representation of the field as a Bessel function series extends solutions derived with the Kontorovich–Lebedev method to the case of real-valued wavenumbers and arbitrarily positioned source and observer. Numerical results showing the influence of wedges with various values of dielectric ...
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.
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 ...
Bulletin of the Seismological Society of America
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.
Journal of Electromagnetic Waves and Applications
SEG Technical Program Expanded Abstracts 1990
The International Conference on Electrical Engineering
In this paper we propose a nanoscale planar lens structure for generating Bessel beam like fields... more In this paper we propose a nanoscale planar lens structure for generating Bessel beam like fields to achieve large focal lengths and depth of fields. The structure consists of sub wavelength slits of different widths constructed on a thin metallic slab that is surrounded by air on both sides. The proposed structure is simulated using a modal technique that represents the structure as a waveguide and solves for the modes of the waveguide. Although diffraction affects the behavior of the generated beam from that of conventional Bessel beams, the simulation results show that the proposed structure is very promising for obtaining a very compact Bessel beam generator.
2013 International Symposium on Electromagnetic Theory, 2013
ABSTRACT The scattering of the electromagnetic field by an impedance cylinder immersed halfway be... more ABSTRACT 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 ...
Journal of Electromagnetic Waves and Applications
In practical calculations it is often essential to truncate the computational domain by introduci... more In practical calculations it is often essential to truncate the computational domain by introducing artificial boundaries. The manner in which boundary conditions are approximated has an important influence on the accuracy of the results. In this paper we present a time domain technique to quantify the spurious reflection of waves from an artificial boundary, obtained by using a nonreflecting boundary condition based on rational approximations.