No description available.

No description available.

Thesis (Ph.D.)--University of Western Australia, 2006.

Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 104-111).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Mathematics." Includes bibliographical references (p. 183-189).

Thesis (M.Eng.) -- Memorial University of Newfoundland, 1984. / Bibliography: leaves 118-121. Also available online.

No description available.

Numerical modeling of electromagnetic fields is becoming an important topic in such diverse areas as microwave and RF engineering, antenna design, bio-electromagnetics, and electromagnetic compatibility and interference (EMC/EMI). Among several techniques, time-domain schemes are of particular interest, due to their high flexibility and ease of implementation. This thesis is focused on the Transmission Line Matrix (TLM) method, based on a space and time discrete formulation of Maxwell's equations. The objective of this thesis is to develop, implement and test a number of techniques aimed to the enhancement of the accuracy of the method without increasing the computational load. The link between the electromagnetic theory and the TLM updating equations is first investigated, creating a solid background for the implementation of hybrid schemes characterized by better accuracy. The problem of coarseness error is in particular addressed. Two methods are proposed and analyzed. In the first approach the knowledge of the relationship between field equations and TLM equations is exploited to incorporate the static field behavior in the vicinity of singularities into the three-dimensional TLM mesh. Secondly, the field distribution around a corner is represented in terms of an equivalent circuit derived from a quasi-static approximation of the Green's functions for an infinite conductive wedge. As a result, relatively coarse TLM meshes, in combination with hybrid schemes, can be used to obtain highly accurate results, within the dispersion error margin, across a wide frequency range. By taking advantage of these techniques it is possible to incorporate more information of the structure under study into the TLM solution, thus creating an accurate and efficient CAD tool. / Graduate

Short resumés of the theories of propagation of electromagnetic waves in an anisotropic medium, of the Faraday effect, and of the influence of paramagnetic resonance on the Faraday effect are given. The Poincaré sphere is introduced to describe polarized light. A paramagnetic resonance spectrometer is described, which was modified so as to allow the study of magneto-optical phenomena under the influence of paramagnetic resonance. The spectrometer operated in the X-band using a 2K39 Klystron. The samples were located in a transmission type cavity operating in the TE 101 mode, and immersed in liquid helium. The cavity was provided with holes allowing the passage of light through the sample in a direction parallel to the external magnetic field. An optical system provided plane-polarized monochromatic light ( ג = 5461 Å ) incident on the sample. The light emerging from the sample passed through a Glan-Thompson prism analyzer. The relative intensity of the light passing the analyzer could be measured by a photomultiplier circuit and could be displayed as a function of time on an oscilloscope. Experiments are described in detail in which the spin-lattice relaxation time was measured as a function of temperature and external magnetic field. In these experiments, for a given temperature and magnetic field, the Faraday rotation was reduced by pulses of microwave power of varying length applied to the cavity. The return of the Faraday rotation as a function of time to its equilibrium value after the microwave power was cut off could be inferred from the intensity versus time relationship of the light transmitted by the analyzer. Photographic records of this intensity versus time relationship were obtained and the relaxation time was deduced from these records. Results of the measurement of the spin-lattice relaxation time of neodymium ethylsulfate for fields between 780 and 2540 Oerstedt and temperatures between 1.38°K and 4.22°K are given. The relaxation times measured were of the order of .001 to .1 seconds. The relaxation time appeared to be inversely proportional to the third power of the temperature and showed only small field dependence, except for a large dip at a field corresponding to the resonance field for the microwave frequencies used. Within the accuracy of the experiments no effect of the length of the microwave pulses on the relaxation time could be observed. An experiment on cerium ethylsulfate is described, which showed that the spin-lattice relaxation time must be smaller than 1 millisecond for this salt. No accurate determination of the relaxation time could be made in this case. Mention is made of an "overshoot effect" observed in one particular crystal of neodymium ethylsulfate. A possible explanation for this effect is given, by assuming that the crystal in question was twinned. In this case one may infer that the relaxation time is strongly dependent on the orientation of the optical axis of the crystal with respect to the external magnetic field The results were found to disagree with present-day theories of paramagnetic relaxation. Assumptions of doubtful validity in the theory are discussed as possible reasons for such disagreement. / Science, Faculty of / Physics and Astronomy, Department of / Graduate