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published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

An integrated circuit processing schedule is presented that enables fabrication of both high speed I²L gates and high voltage linear type transistors on the same silicon starting substrate material. This process design circumvents conflicting processing requirements normally encountered in considering an I²L/Linear compatible structure by providing two separate epitaxial thicknesses for the I²L and linear section of the chip. The electrical characteristics of the I²L cells and the linear transistors are presented to illustrate their dependence on the doping conditions and are shown to be in contrast to each other. As a consequence of the separate epitaxial thicknesses, independence of the processing constraints is achieved. Experimental results of linear transistors and I²L devices fabricated using this processing schedule are presented and compared to calculated and computer simulations. Modifications to the basic process design is shown possible and enhanced performance of I²L devices results.

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An important fraction of the reservoirs in the Outer Continental Shelf of the Gulf of Mexico is comprised of thin-bedded deposits from channel-levee systems. These reservoirs are particularly difficult to describe. Not only is their architecture complex but the quality of the reservoir is determined by connection and length of beds below the resolution of usual reflection data. Improved characterization is needed to improve development and production of these reservoirs. This study presents an integrated approach to build a geologically consistent reservoir model, based on the 8 sand reservoir in Northern Green Canyon block 18. The underlying idea of the construction of this model is that reservoir quality is influenced more by the internal architecture than by the statistical values of petrophysical parameters. Seismic interpretation and attribute extraction provided the reservoir geometry and stratigraphy. The structural framework and the limits of the reservoir have been determined, showing the preeminent role of salt and faults in the constitution of this reservoir. Seismic attributes are calibrated to extract areal information on reservoir architecture. Gross thickness and net thickness maps have been estimated using geostatistical methods. Lateral variations in the quality of the 8 sand and the definition zones with different average properties were inferred from geostatistical results. Lithofacies characterization from core showed that 3 facies could be used to describe the internal variability. The fine-scale heterogeneity is described in each zone from vertical facies distribution determined from wells. A truncated Gaussian sequential simulation was performed to reflect both the regional trend and the internal variability on a 150*150*1 ft grid. The major contribution of this work is to show the efficiency of this approach to describe complex reservoirs where the impact of internal variability is a major control of flow efficiency. This is especially valuable when the well information is scarce or not uniformly distributed. This model will be used for flow simulation and sensitivity analysis to improve the field description.

In order for the Vredefort Dome to be declared, and to exist as a World Heritage site, it is imperative that the tourism product owners in the area realise their roles as custodians of this precious site. This proposition leads to the main aim of this study, namely to develop an integrated tourism development strategy for the Vredefort Dome as a proposed World Heritage site. In order to achieve the above-mentioned aim, a thorough literature review was conducted. The goal of the literature study was to investigate the birth and growth of sustainable development based on Agenda 21. This literature review revealed that the three-legged chair of sustainable development has more profound foundations than the obvious economical, social and environmental aspects. Each one of these aspects consists of various elements that are interrelated. In order to formulate a strategy for sustainable tourism development, this interrelation between aspects was analysed and the following conclusions were drawn: Sustainable tourism development is an integrated system Education, poverty alleviation, health and insight into human settlements and demographics are the cornerstones of social well-being Climate change, land resources, deforestation, drought, mountain development, agriculture, biodiversity, freshwater resources, toxic chemicals and waste are central concerns in environmentally sensitive development 0 Institutions involved such as the different levels of Government, as well as aspects such as fair trade, economic enhancement programmes and economic measuring are essential elements of economic sustainability. The custodians of the present generation in the Vredefort Dome should realise their role in this complicated and integrated system and therefore the practices at present were evaluated as well as the future view regarding sustainable practices. In order, then, for sustainable tourism development to realise in the Vredefort Dome, the following strategies were formulated to assist product owners to achieve sustainability: Assisting to alleviate poverty in the VFD with a view to a sustainable future and supporting sustainable livelihoods Improving participation that would be true to the demographic composition in the VFD Protecting and promoting human health in the VFD Promoting education and training in the VFD Promoting sustainable human settlement development in the VFD-area Following an integrated approach to the planning and management of land resources Promoting sustainable agriculture and rural development Conserving the biological diversity in the VFD Acquiring support from national, provincial and local levels of government Establishing a system that guarantees supply that is coherent with fair trade in tourism Establishing an economic enhancement system that will contribute to the well-being of the VFD community Reducing leakage and other purchasing practices. The results of the empirical study indicated that tourism stakeholders are prepared to improve the present situation in the Vredefort Dome and are willing to adjust their businesses practices in the future. These changed practices addressed some strategic issues and the strategies above would give direction to this proposed World Heritage site to become more sustainable. / Thesis (Ph.D. (Tourism))--North-West University, Potchefstroom Campus, 2004.