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Item A covariance based method to describe power processing in power electronics converters(2022) Eardley, ArloThis paper explores the use of a new topology evaluation framework to describe the internal power processing of a power electronics converter. This method is called the matrix method and leverages off a covariance matrix to describe power processing patterns in a power electronics converter. Covariance measures how two signals interact with each other. The covarianc between the power waveforms of the components in a converter describes how these components interact in terms of power. These are called “power interactions”. These power interactions between component powers provide insight into the power processing of a topology. The covariance matrix contains all combinations of component power pairs. This aims to describe all the power interactions components have in the entire converter. The covariance matrix is interpreted as describing the power processing inside a converter, where circulating power is occurring and which components are most involved in power processing. The covariance matrices of converters are able to be compared in a quantitative manner with the aim of providing a more justifiable reason for topology selection rather than personal bias. The matrix method is shown to be aligned with the principles of differential power theories. The matrix method is shown to be useful in comparing topologies, aiding in the topology selection processItem The Positioning of electromagnetic near field hotspots within a resonant cavity for applications in microwave thermal ablation(2022) Young, Graeme Robin; Clark, Alan; Rubin, DavidThe investigation into moving electromagnetic near field hotspots inside a resonant cavity is presented. The investigation is focused on providing an alternative approach to thermal ablation of tumours, by inducing a hotspot over a tumour instead of using an interstitial antenna. The methodology comprised comparing various electromagnetic solvers, verifying the simulation techniques, characterising the resonance within a rectangular resonant cavity, and attempting to control the movement of its hotspots by introducing a phase shift between its sources and modifying their frequency. The effects of dielectric media of the field were also investigated. It was determined that incremental frequency shifts only progressively moved the system’s hotspots between 2.6 and 2.7 GHz and phase shifting only worked between 2.55 and 2.7 GHz when the feeds were on opposite walls. At the system’s eigenfrequencies, no pattern change was evident, indicating that when the chamber was resonating, the field pattern was set. Further, it was determined that the bandwidth of the characteristic modes of the system were very narrow, such that the addition of dielectric material completely altered the resonance of the system and the eigenfrequencies shifted. Therefore, the application of this method to thermal ablation, which requires high precision, accuracy and control, was deemed impractical. Future recommendations include using adjustable cavity geometry and directive microwave sources to design for specific field patterns. Additionally, it is recommended to investigate the validity of the ‘reverse problem’ to create a specific current distribution around the resonant cavity. This is reminiscent of the three-dimensional Green’s Theorem, which would induce the desired hotspot pattern from the surrounding current distribution.