Thesis (MSc)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 103-105). Also available via the Internet.

This thesis describes a research investigation into novel designs of high voltage pulse transformers using magnetic insulation, which is the only practicable form of insulation for much of the equipment presently used in ultrahigh voltage pulsed-power work, including transmission lines and plasma opening switches. Although its use in transformers would bring important advantages in both size and weight reductions, a number of seemingly insurmountable problems have however so far prevented this. Two novel arrangements are presented in this thesis: one of these is a 500 kV transformer with self-magnetic insulation, and the other one is a 1 MV 'Tesla' transformer with external magnetic insulation. It is shown that both of these overcome the problems inherent in earlier designs and also offer considerable scope for further development in a number of important areas. It is believed that they represent the first working examples of magnetically-insulated transformers anywhere in the world. Modelling considerations of the transformers developed include both theoretical models and predicted characteristics. The filamentary technique used to describe mathematically the arrangements being investigated involves decomposition of the main conducting components into filamentary elements. The resulting equivalent electrical network includes all the mutual interactions that exist between the different filamentary elements, takes magnetic diffusion fully into account and enables the resistances and self and mutual inductances that are effective under fast transient conditions to be calculated. Theoretical results provided by the resulting mathematical models have been successfully validated by comparison with reliable experimental data. Much of the work detailed in the thesis has already been presented in high quality academic journals and at prestigious international conferences, and a solid theoretical and experimental basis has been laid down for future development and new progress into pulsed power system research.

The theory of operation of a controlled transformer is described. A PWM controlled transformer is proposed and implemented in a forward converter to provide post regulation. Experimental results are presented to verify the new control scheme. Overall efficiency of 82%-86% is achieved in a 200khz, 500-watt, 5V-output off-line regulator. A discussion of design issues of the controlled transformer is also presented. / Master of Science

Thesis (MSc (Mathematical Sciences))--University of Stellenbosch, 2007. / Data analysis frequently involves the extraction (i.e. recognition) of parts that are important at the expense of parts that are deemed unimportant. Many mathematical perspectives exist for performing these separations, however no single technique is a panacea as the de nition of signal and noise depends on the purpose of the analysis. For data that can be considered a sampling of a smooth function with added 'well-behaved' noise, linear techniques tend to work well. When large impulses or discontinuities are present, a non-linear approach becomes necessary. The LULU operators, composed using the simplest rank selectors, are non-linear operators that are comparable to the well-known median smoothers, but are computationally e cient and allow a conceptually simple description of behaviour. De ned using compositions of di erent order LULU operators, the discrete pulse transform (dpt) allows the interpretation of sequences in terms of pulses of di erent scales: thereby creating a multi-resolution analysis. These techniques are very di erent from those of standard linear analysis, which renders intuitions regarding their behaviour somewhat undependable. The LULU perspective and analysis tools are investigated with a strong emphasis on practical applications. The LULU smoothers are known to separate signal and noise ef- ciently: they are idempotent and co-idempotent. Sequences are smoothed by mapping them into smoothness classes; which is achieved by the removal, in a consistent manner, of block-pulses. Furthermore, these operators preserve local trend (i.e. they are fully trend preserving). Di erences in interpretation with respect to Fourier and Wavelet decompositions are also discussed. The dpt is de ned, its implications are investigated, and a linear time algorithm is discussed. The dpt is found to allow a multi-resolution measure of roughness. Practical sequence processing through the reconstruction of modi ed pulses is possible; in some cases still maintaining a consistent multi-resolution interpretation. Extensions to two-dimensions is discussed, and a technique for the estimation of standard deviation of a random distribution is presented. These tools have been found to be e ective in the analysis and processing of sequences and images. The LULU tools are an useful alternative to standard analysis methods. The operators are found to be robust in the presence of impulsive and more 'well-behaved' noise. They allow the fast design and deployment of specialized detection and processing algorithms, and are possibly very useful in creating automated data analysis solutions.