Thesis (MEng) -- University of Stellenbosch, 1991. / ENGLISH ABSTRACT: A two-dimensional Coupled Element Method (CEM) for solving electromagnetic scattering problems involving lossy, inhomogeneous, arbitrarily shaped cylinders, was investigated and implemented. The CEM uses the Finite Element Method (FEM) to approximate the fields in and around the scatterer and the Boundary Element Method (BEM) to approximate the far-field values. The basic CEM theory is explained using the special, static electric field problem involving the solution of Laplace's equation. This theory is expanded to incorporate scattering problems, involving the solution of the Helmholtz equation. This is done for linear as well as quadratic elements. Some of the important algorithms used to implement the CEM theory are discussed. Analytical solutions for a round, homogeneous- and one layer coated PC cylinder are discussed and obtained. The materials used in these analytical solutions can be lossy as well as chiral. The CEM is validated by comparing near- and far-field results to the analytical solution. A comparison between linear and quadratic elements is also made. The theory of the CEM is further expanded to incorporate scattering from chiral media / AFRIKAANSE OPSOMMING: 'n Gekoppelde Element Metode (GEM) wat elektromagnetiese weerkaatsingsprobleme, van verlieserige, nie-homogene, arbitrere voorwerpe kan oplos, is ondersoek en geimplimenteer. Die GEM gebruik die Eindige Element Metode (EEM) om die velde in en om die voorwerp te benader. 'n Grenselementmetode word gebruik om die vervelde te benader. Die basiese teorie van die GEM word verduidelik deur die toepassing daarvan op die spesiale geval van 'n statiese elektriese veld- probleem. Hierdie probleem verlang die oplossing van Laplace se vergelyking. Die teorie word uitgebrei om weerkaatsingsprobleme te kan hanteer. Die weerkaatsingsprobleme verlang die oplossing van 'n Helmholtz-vergelyking. Hierdie teorie word ontwikkel vir lineere sowel as kwadratiese elemente. Van die belangrike algoritmes wat gebruik is om die GEM-teorie te implimenteer, word bespreek. Analietise oplossings vir ronde, homogene en eenlaag bedekte perfek geleidende silinders word bespreek en verkry. Die material wat in die oplossings gebruik word, kan verlieserig of kiraal wees. Die GEM word bekragtig deur naby- en verveld resultate te vergelyk met ooreenkomstige aitalitiese oplossings. Die lineere en kwadratiese element- resultate word ook met mekaar vergelyk. Die GEM-teorie is verder uitgebrei sodat weerkaatsing vanaf kirale materiale ook hanteer kan word.

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Lights is almost always detected by its interaction with matter. One of these interaction phenomena is the scattering of light by small particles. A model is developed that estimates the amount of energy that is scattered towards a detector from a beam given the locations of the source, detector and particle. This collection of particles is allowed to be very dense so that a photon scattered from the beam can be scattered several times before leaving the scattering medium. By considering the single-scatter component and multiple-scatter component separately, the model retains the characteristics of both types.

In this dissertation, a novel approach to modeling the scattered field of a periodic corrugated cylinder, from an oblique incident planewave, is presented. The approach utilizes radial waveguide approximations for fields within the corrugations, which are point matched to approximated scattered fields outside of the corrugation to solve for the expansion coefficients. The point matching is done with TMz and TEz modes simultaneously, allowing for hybrid modes to exist. The derivation of the fields and boundary conditions used are discussed in detail. Axial and radial propagating modes for the scattered fields are derived and discussed. Close treatment is given to field equations summation truncation and conversion to matrix form, for numerical computing. A detailed account of the modeling approach using Mathematica® and NCAlgebra for the noncommutative algebra, involved in solving for the expansion coefficients, are also given. The modeling techniques offered provide a full description and prediction of the scattered field of a periodic corrugated cylinder. The model is configured to approximate a smooth cylinder, which is then compared against that of a textbook standard smooth cylinder. The methodology and analysis applied in this research provide a solution for computational electromagnetics, RF communications, Radar systems and the like, for the design, development, and analysis of such systems. Through the rapid modeling techniques developed in this research, early knowledge discovery can be made allowing for better more effective decision making to be made early in the design and investigation process of an RF project. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection

In this dissertation, a novel approach to modeling the scattered field of a periodic corrugated cylinder, from an oblique incident planewave, is presented. The approach utilizes radial waveguide approximations for fields within the corrugations, which are point matched to approximated scattered fields outside of the corrugation to solve for the expansion coefficients. The point matching is done with TMz and TEz modes simultaneously, allowing for hybrid modes to exist. The derivation of the fields and boundary conditions used are discussed in detail. Axial and radial propagating modes for the scattered fields are derived and discussed. Close treatment is given to field equations summation truncation and conversion to matrix form, for numerical computing. A detailed account of the modeling approach using Mathematica® and NCAlgebra for the noncommutative algebra, involved in solving for the expansion coefficients, are also given. The modeling techniques offered provide a full description and prediction of the scattered field of a periodic corrugated cylinder. The model is configured to approximate a smooth cylinder, which is then compared against that of a textbook standard smooth cylinder. The methodology and analysis applied in this research provide a solution for computational electromagnetics, RF communications, Radar systems and the like, for the design, development, and analysis of such systems. Through the rapid modeling techniques developed in this research, early knowledge discovery can be made allowing for better more effective decision making to be made early in the design and investigation process of an RF project. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2017. / FAU Electronic Theses and Dissertations Collection