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Power electronics are becoming established in ever broadening areas of industry. The transition from previous generation technology is driven by the oportunity for improvements in controllability, efficiency, and longevity. A wide variety of power semiconductors are available, however power handling capacity is still a significant limitation for many applications. An increase in the capacity of a single device is usually accompanied by a drop in switching frequency, and hence achievable system bandwidth. Increased capacity can be attained without this loss in bandwidth by using multiple lower power devices in parallel. Products based on parallel device topologies are already present in the marketplace, however there are many associated complications. The nature of these complications depends on the control method and topology used, but no system combines high performance and high power with high reliability and easy maintainability. This research aims to identify and develop a method that would provide a system of voltage source inverters with a total capacity in excess of 10MVA, with effective control bandwidth comparable to a 100kVA system. Additionally, the method should be equally applicable at still higher power levels in the future with the anticipated development of higher capacity power semiconductors. The primary goal when using paralleled devices is to achieve an even distribution of system load between them, as unbalanced load leads to poor system utilisation. Devices can be paralleled either passively, in which devices are controlled in common and characteristics inherent to the device are relied upon to balance load; or actively, in which devices are individually controlled and monitored to improve load balance. A key component of the thesis is the identification and analysis of the inadequacies inherent to passively paralleled systems. It is the limitations of passive paralleling that provide the motivation to develop an active parallel control mechanism. Following the analysis, an active control algorithm is developed and implemented on a paralleled system. The proposed system topology consists of an array of medium power Voltage Source Inverter (VSI) modules operating in parallel. Each module is controlled semi-independently at a local level, with an inter-module communications network to enable active equalisation of module load, and redundant fault management. An innovative load equalisatiion algorithm is developed and proven, the key feature of which is this inclusion of a synthetic differential resistance between modules within the system. The result is a modular expandable structure offering the potential for very high power capacity combined with quality of response usually only found in low power systems. The system as a whole is extremely reliable as any module can be isolated in the event of a fault without significantly affecting the remainder of the network. Performance results from both simulation and experimentation on a two module small scale prototype are given. Using the developed topology and control method extremely accurate load balancing can be achieved without degradation of the response characteristics. The system is tested up to only 2.4kW in the course of this research, but the correlation with simulation is high and gives confidence that the developed mechanism will allow the 10MV A goal to be achieved. Following the developmental stage of this research the technology has been applied to a commercial system comprising parallel structures of up to 8 modules with a total power handling capacity of 1MVA with no deterioration in performance. 2MVA systems are deliverable with the current technology without any changes, and higher power levels are expected to be easily achieved.

River ice is an important component of the traditional way of life for the communities along the Slave River both culturally and economically. During the winter, a stable ice cover provides local residents with safe access to their traditional hunting, trapping, and fishing grounds along the river. Periodic spring ice breakup flooding is required to maintain the ecological balance along the Slave River Delta. Recently, however, local observations have indicated changes in ice cover characteristics (e.g. air pocket formation, double layer ice, ice cover flooding) during the winter, which increase the risks of travelling on the ice. Also prolongs dry periods during the spring are leading to rapid growth of invasive vegetation that reduces the lake and channel areas of the Delta. Although some attempts have been made to understand the patterns of spring flood frequency in the Delta, very little is known about the Slave River’s ice cover characteristics and behaviour. Remote sensing techniques and field surveys were used in this study to understand the ice cover progression and to examine ice cover characteristics along the river during the winters of 2013-2014 and 2014-2015. RADARSAT-2 satellite imagery captured the changes in the ice cover and identified different types of ice during the winter seasons at two primary study sites – downstream of Fort Smith and the Slave River Delta. The mechanism of ice cover growth, with the formation of air pockets and layers underneath the ice cover was investigated. Steeper channels and several open water sections appear to be contributing to significant amounts of air entrainment into the water in winter. Changes in the hydraulic characteristics due to flow regulation and ice cover progression can also change the quantity and distribution of air pockets along the river ice cover. Additionally, the impact of flow fluctuations on the ice cover (e.g. ice cover flooding) was also observed. Increases in discharge cause the ice cover to crack or dislodge from the river banks, leading to water seeping onto the ice and flooding it, which has implications for the muskrat and beaver populations. A geospatial model was developed to determine the spatial patterns of ice cover breakup along the river from Fort Fitzgerald to the delta. This model successfully identified the areas of breakup initiation and persistence of ice until the end of the breakup. MODIS satellite imagery was used to describe the temporal patterns and evolution of breakup events between the years 2008 and 2011. In addition to geomorphological influences, air temperature and flow conditions also have strong impacts on the spatial and temporal patterns of the ice cover breakup.

This thesis interrogates how Lawrence Hill’s The Book of Negroes represents histories of violence ethically by utilizing Emmanuel Lévinas’s philosophy of ethics as a methodology for interpretation. Traditional slave narratives like Olaudah Equiano’s autobiography and postmodern neo-slave narratives like Toni Morrison’s Beloved animate the violence endemic to slavery and colonialism in an effort to emphasize struggles in conscience, the incomprehensible atrocities, and strategies of rebellion. However, this project illustrates how The Book of Negroes supplements these literary goals with Hill’s own imagination of how slaves contested the inhumanities thrust upon them. Through his aesthetic choices as a realist, Hill foregrounds the possibilities of pacifism, singular identities, and altruistic agency through his protagonist Aminata Diallo. These three narrative elements constitute Lévinas’s ethical peace, which means displaying a profound sensitivity towards the historical Other whom imperial discourses and traditional representations of catastrophes in Black history might obscure. / Graduate / 0325 / 0328 / 0352 / jaslife12@hotmail.com

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The oxidation state, reflected in the oxygen fugacity (fO2), of the lithospheric mantle is both laterally and vertically heterogeneous. Depth-fO2 profiles from kimberlite-borne peridotitic mantle xenoliths from the Bultfontein kimberlite, Kimberley, South Africa and the A154-N and A154-S kimberlites of the Diavik Mine, NWT, Canada were constructed by measuring ferric iron concentrations in garnets using the flank method. These data demonstrate that mantle metasomatic re-enrichment processes had a significant effect on fO2. In the garnet stability field, the Kaapvaal lithospheric mantle becomes progressively more reducing with increasing depth from Δlog fO2 (FMQ) of -2 at 110 km to -4 at 210 km. The lithospheric mantle beneath Diavik is vertically layered with respect to its bulk and trace-element composition. The shallow ‘ultradepleted’ layer is oxidized, to the point that carbonate rather than graphite is the anticipated carbon host. The deeper layer is more fertile and has fO2 conditions extending down to Δlog fO2 (FMQ) -3.8. Deviations from predicted depth-fO2 trends in both xenolith localities result from metasomatic re-enrichment caused by transient fluids and melts. Diamond formation in the Kaapvaal lithospheric mantle may have occurred through the infiltration of reduced fluids into relatively more oxidized mantle. Trace-element concentrations in garnets preserve evidence of two distinct melt metasomatic enrichment events. One was a craton-wide event that is commonly observed in garnet peridotite xenoliths and xenocrysts worldwide; the other was melt infiltration event, preserved as MARID xenoliths, related to the eruption of the Group 2 kimberlites in the western portion of the Kaapvaal craton. The effect of the former melt metasomatism on fO2 is unclear ambiguous whereas the MARID event was clearly oxidizing. Diavik xenoliths preserve evidence for events similar to the fluid and ‘common’ melt metasomatism seen in the Bultfontein samples. Fluid metasomatism affected the entire depth range of xenoliths sampled from Diavik and was oxidizing. A stage of melt metasomatism affected only the deeper (>140 km) portion of the lithospheric mantle and had an overall reducing effect. The observation of sharp-edged octahedral diamonds in microxenoliths affected by the fluid metasomatic event may indicate that this was a major diamond-forming event in the mantle beneath Diavik.

"A doctoral dissertation (Radcliffe College, 1924)"--Pref. / At head of title: The American Historical Association. "This volume is published from a fund contributed to the American Historical Association by the Carnegie Corporation of New York."--P. [iv]. Bibliography: p. 431-451.

"A doctoral dissertation (Radcliffe College, 1924)"--Pref. / At head of title: The American Historical Association. "This volume is published from a fund contributed to the American Historical Association by the Carnegie Corporation of New York."--P. [iv]. Bibliography: p. 431-451.

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 (leaves 402-423).

This thesis asserts that the slave narratives are a significant resource for philosophers. Following Lewis Gordon, I argue that the slave narratives should not be understood merely as experiential evidence by which to validate Western thought. Instead, the narratives should be read as moments in which Black narrators shared their unique insights on the Western world. In line with Angela Davis, I argue that these critiques are still relevant to philosophers of this day and age. However, I argue that Davis' Marxist reading of Frederick Douglass' Narrative of the Life of Frederick Douglass, an American Slave is still vulnerable to Gordon's criticism. Using the narrative Olaudah Equiano, I demonstrate that by reading the slave narratives as expressing unique thoughts, philosophers can discover new resources to invigorate their philosophical inquiries.