Showing papers on "Computational electromagnetics published in 1983"
Journal Article•
TL;DR: An algorithm based on the method of integral equations to simulate the electromagnetic responses of three‐dimensional bodies in layered earths and finds that tabulation and interpolation of the six electric and five magnetic Hankel transforms defining the secondary Green’s functions is preferable to any direct Hankel transform calculation using linear filters.
Abstract: An algorithm based on the method of integral equations to simulate the electromagnetic responses of three-dimensional bodies in layered earths has been developed. The inhomogeneities are replaced by an equivalent current distribution which is approximated by pulse basis functions. A matrix equation is constructed using the electric tensor Green's function appropriate to a layered earth, and it is solved for the vector current in each cell. Subsequently, scattered fields are found by integrating electric and magnetic tensor Green's functions over the scattering currents. Efficient evaluation of the tensor Green's functions is a major consideration in reducing computation time. We find that tabulation and interpolation of the six electric and five magnetic Hankel transforms defining the secondary Green's functions is perferable to any direct Hankel transform calculation using linear filters. A comparison of responses over elongate three-dimensional (3-D) bodies with responses over two-dimensional (2-D) bodies of identical cross-section using plane wave incident fields is the only check available on our solution. Agreement is excellent; however, the length that a 3-D body must have before departures between 2-D transverse electric and corresponding 3-D signatures are insignificant depends strongly on the layering. The 2-D transverse magnetic and corresponding 3-D calculations agree closely regardless of the layered host. (Author)
250 citations
TL;DR: To investigate the potentialities of hyperthermia as a cancer therapy, computer simulations have been performed and numerical results pertaining to the temperature distribution in a model of the human pelvis are presented.
Abstract: To investigate the potentialities of hyperthermia as a cancer therapy, computer simulations have been performed. This simulation consists of two tuccessive steps. First, the heat generated in a distribution of biological tissue when irradiated by a source of electromagnetic radiation is computed. The mathematical tool for determining the disbution of generated heat is the domain-integral-equation technique. This technique enables us to determine in a body with arbitrary distribution of permittivity and conductivity the electromagnetic field due to prescribed sources. The integral equation is solved numerically by an iterative minimization of the integrated square error. From the computed distribution of generated heat, the temperature distribution follows by solving numerically the pertaining heat transfer problem. The relevant differential equation together with initial and boundary conditions is solved numerically using a finite-element technique in space and a finite-difference technique in time. Numerical results pertaining to the temperature distribution in a model of the human pelvis are presented.
121 citations
TL;DR: In this paper, a rigorous integral formalism for the problem of scattering of electromagnetic radiation from a cylindrical, perfectly conducting rough surface of arbitrary shape is introduced, and the computer code obtained from this theory enables us to show that the range over which the incident field affects the surface current density is of the order of the radiation wavelength.
Abstract: A rigorous integral formalism for the problem of scattering of electromagnetic radiation from a cylindrical, perfectly conducting rough surface of arbitrary shape is introduced. The computer code obtained from this theory enables us to show that the range over which the incident field affects the surface current density is of the order of the radiation wavelength. This phenomenon is explained using a new approximate theory, able to express the scattered field in the form of an integral whose integrand is known in closed form. Using the rigorous computer code, we show that the new approximate theory is better than the Kirchhoff approximation in the resonance region. Finally, it is shown that the phenomenon of short interaction range of the incident field permits the rigorous computation of the field scattered from a rough surface of arbitrary width.
73 citations
TL;DR: The analytical approach used in this paper is based on the network analytical method of electromagnetic fields, and the formulation process is straightforward for complicated structures, and some numerical results are presented and comparison is made with the results available in the literature.
Abstract: Various types of striplines with anisotropic media are analyzed. The analytical approach used in this paper is based on the network analytical method of electromagnetic fields, and the formulation process is straightforward for complicated structures. Some numerical results are presented and comparison is made with the results available in the literature.
50 citations
TL;DR: In this article, the electromagnetic radiation of an electric dipole in a medium with three layers was examined using dyadic Green's functions, and it was shown that the excitation of this wave may be reinforced through a dipole inclination and an optimum position may be determined.
Abstract: The electromagnetic radiation of an electric dipole in a medium with three layers is examined using dyadic Green's functions. The far zone field for problems of this nature is primarily determined from the lateral wave. It is shown that the excitation of this wave may be reinforced through a dipole inclination and an optimum position may be determined. The radio losses for typical forests were calculated for vertical and horizontal dipoles and for dipoles with an optimum inclination. The theoretical results are in good agreement with the available experimental data.
49 citations
TL;DR: In this paper, the Fredholm integral equation method is applied to the scattering of electromagnetic waves by finite dielectric cylinders of circular cross-section, and good agreement has been obtained with the experimental backscatter measurements of McCormick and Hendry.
Abstract: The Fredholm integral equation method is applied to the scattering of electromagnetic waves by finite dielectric cylinders of circular cross section. The method is applied to a wide range of diameter/length ratios, including both rods and discs. Generally good agreement has been obtained with the experimental backscatter measurements of McCormick and Hendry.
25 citations
TL;DR: In this paper, an entire-domain Galerkin expansion along one dimension of the body and a piecewise continuous one along the other are used to represent the unknown current variations.
Abstract: Electromagnetic scattering from finite, conducting bodies of translation (BOT) is examined using a formulation based on the electric field integral equation (EFIE) and solved by the method of moments (MM). The present approach provides a systematic, unified treatment for a wide class of finite, thin scatterers at all angles of illumination and polarization. Both concave and convex surfaces are considered. An entire-domain Galerkin expansion along one dimension of the body and a piecewise continuous one along the other are used to represent the unknown current variations. The scattering cross sections, obtained with this formulation, are compared with published results using more specialized methods and further confirmed by experimental measurements.
22 citations
TL;DR: In this article, an integral equation method is proposed for analyzing scattering and mode conversion of guided modes by boundary deformations of a dielectric slab waveguide, where the tangential electromagnetic fields on the deformed boundaries are derived using the integral expressions of fields and the fundamental properties which the integral over a closed path has.
Abstract: An integral equation method is proposed for analyzing scattering and mode conversion of guided modes by boundary deformations of a dielectric slab waveguide. Integral equations are derived for the tangential electromagnetic fields on the deformed boundaries only, using the integral expressions of fields and the fundamental properties which the integral over a closed path has. Mode conversion coefficients for guided and radiation modes are easily obtained from the solutions of the integral equations. Using the mode conversion coefficients, physical quantities such as radiation loss, reflected mode power, and total scattered power, are calculated. Numerical examples are presented for the two-dimensional models of the typical boundary deformations in optical fibers caused by a fusion splice.
20 citations
TL;DR: In this paper, the coupled set of differential equations describing the electromagnetic perturbations in tokamak plasmas is reduced to a single simple integral equation with a symmetric kernel.
Abstract: The coupled set of differential equations describing the electromagnetic perturbations in tokamak plasmas is reduced to a single simple integral equation with a symmetric kernel. Obvious analytical and computational advantages are discussed.
6 citations
6 citations
01 Sep 1983
TL;DR: In this article, a new method for dimensioning a multiple layer Frequency Selective Surface (F.S.) based on an appropriate electromagnetic model was examined. But the authors focused on the accuracy of the measurement technique.
Abstract: A new method for dimensioning a multiple layer Frequency Selective Surface (F.S.S.) based on an appropriate electromagnetic model will be examined. Feasibility and performance I imitations of F.S.S. having a single grid of Jerusalem crosses packed with several dielectric slabs will be analyzed. The technique of waveguide simulators is proposed as an attractive alternative to the radiation measurement technique. Experimental and theoretical results, in the frequency range of 8÷18Qk, are discussed in order to point out: the val idity of the measurement technique and the accuracy of the electromagnetic model.
TL;DR: In this article, a heuristic definition of far field is given for time-domain two-dimensional scattering that simplifies the expression of the scattered far field as an integral over the sources.
Abstract: A heuristic definition of far field is given for time-domain two-dimensional scattering that simplifies the expression of the scattered far field as an integral over the sources. The meaning of this definition and of the ensuing simplifications is clarified by Fourier transforming the approximate time-domain result to compare it with well-known frequency-domain expressions in the Fresnel and Fraunhofer approximations.
23 May 1983
01 Jan 1983
TL;DR: This paper describes the application of the finite element method to electrical machine modeling taking into account iron saturation, eddy currents in conducting parts and the distributed nature of materials and sources.
Abstract: The need for design optimization and operational reliability of electrical machinery necessitates accurate performance prediction at the design stage. This in turn requires the detailed evaluation of the magnetic field distribution in the machine geometry. The finite element method offers a stable numerical solution technique with a good deal of precision. This method requires the formulation of the partial differential equations in variational terms or by a weighted residual procedure. In the case of the former an energy related expression called a functional is minimized with respect to a set of trial solutions. This paper describes the application of the finite element method to electrical machine modeling taking into account iron saturation, eddy currents in conducting parts and the distributed nature of materials and sources. Some of the areas surveyed are utility generators, skin-effect in busbars, eddy current losses in transformers, and others.
23 May 1983
TL;DR: In this article, an expansion technique for the dipole interaction of a spin-J system with a quantized monochromatic electromagnetic field is developed, where the energy levels are equally spaced and the rotating-wave approximation is used.
Abstract: An expansion technique for the dipole interaction of a spin-J system with a quantized monochromatic electromagnetic field is developed. The energy levels are equally spaced and the rotating-wave approximation is used. Particular results of the application of the method are presented.
TL;DR: In this paper, it is argued that these generalizations are essentially a generalization of the 1859 and 1882 Kirchhoff integration of the scalar and vector wave equations, respectively, as well as a generalisation of the 1938 Stratton-Chu integration of Maxwell's equations.
Abstract: The conventional formulations of the acoustic and electromagnetic scattering integral equations, which are valid only for surfaces with continuous and differentiable curvature, are generalized to surfaces containing curvature discontinuities. It is argued that these generalizations are essentially a generalization of the 1859 and 1882 Kirchhoff integration of the scalar and vector wave equations, respectively, as well as a generalization of the 1938 Stratton–Chu integration of Maxwell’s equations.
TL;DR: Scattering and depolarization of electromagnetic waves in irregular stratified, spheroidal structures (bodies of revolution) were investigated in this paper. But the results were limited to the case of the body of revolution.
Abstract: Scattering and depolarization of electromagnetic waves in irregular stratified, spheroidal structures (bodies of revolution) are investigated. Using complete expansions for the electromagnetic fiel...
29 Mar 1983
TL;DR: The direct implicit PIC simulation approach is applied to simulations that include full electromagnetic fields and the resulting algorithm offers advantages relative to moment implicit electromagnetic algorithms and may help in the quest for robust and simpler implicit codes.
Abstract: Interesting modelling of intense electron flow has been done with implicit particle-in-cell simulation codes. In this report, the direct implicit PIC simulation approach is applied to simulations that include full electromagnetic fields. The resulting algorithm offers advantages relative to moment implicit electromagnetic algorithms and may help in our quest for robust and simpler implicit codes.
01 Jan 1983
TL;DR: In designing and in evaluating finite element packages for industrial electromagnetics applications, the following questions are typical: how easy is the package to use?
Abstract: In designing and in evaluating finite element packages for industrial electromagnetics applications. the: following questions are typical:
How easy is the package to use?
How accurate is the solution?
Can I get smooth flux plots?
What about the electric and magnetic fields?
23 May 1983
22 Jun 1983
TL;DR: Simulation results show that control energy consumption is reduced to approximately one third of the energy used to achieve the same RF performance with traditional control strategies.
Abstract: A general approach to the optimal control of large space antennas based on their RF/structural characteristics is described. The approach consists of defining a cost functional based on the degradation of the RF performance of the antenna and using the structural model as the dynamic system. The method is applied to the design of an optimal controller for a 55-m, wraprib offset-fed antenna. Simulation results show that control energy consumption is reduced to approximately one third of the energy used to achieve the same RF performance with traditional control strategies.
23 May 1983
TL;DR: In this article, a quaternion formulation of the generalized equations of macroscopic electrodynamics is given and a discussion of possible physical applications of these generalized equations is given.
Abstract: A quaternion formulation of Maxwell equations in a medium is given. Adding gradient terms to these equations, they become invariant under the transformations of field variables forming a representation of the group S0(3, 3) — the group of external transformations of electromagnetic field variables. A discussion of possible physical applications of the generalized equations of macroscopic electrodynamics is given.