Bibliography: leaves 119-124. / This thesis discusses the principles relating to the management of an Information Systems (IS) department. To be effective an IS service must support the ultimate goals of the organization directly. In this regard, user acceptance of the services offered is essential. In addition, economic justification and verification of the technical feasibility of an. IS project is essential to ensuring minimum wasted effort, management's commitment to the project.

Bibliography: leaves 93-100. / This thesis reports on investigations into the potential of off-the-shelf camcorder imagery for rapid mapping. Video technology was chosen as it has the advantage of continuous image capture, enabling quick acquisition times in environments where access may be limited. Video imagery is also very low cost compared to metric photography, and has the advantage of on-line control of the photography, which, for applications with low to medium mapping accuracies, make it an attractive and cheap alternative, well suited for application in developing countries and dynamic environments. Two case studies are presented. In the first, Hi-8 camcorder imagery was acquired for informal settlement mapping under the UrbanModeler project being run by the Department of Geomatics at the University of Cape Town. The informal settlement of Marconi Beam in Milnerton, Cape Town serves as an application for the UrbanModeler project, whose objective is the development of image exploitation tools for automating the geo-spatial modeling of urban settlements, primarily informal (or "squatter") settlements. Rapid production of georeferenced mosaics from the video imagery is reported on, and these mosaics were used in conjunction with a GIS database of Marconi Beam. This GIS database, containing an inventory of shacks and occupants of the settlement, would ultimately help in relocating the occupants of Marconi Beam to Joe Slovo Park, a low cost formal housing settlement nearby. An analysis of the mapping potential of this data source is made with respect to image interpretability, and three-dimensional point positioning accuracy. The second case study lies in the terrestrial photogrammetry domain, in a joint project between the Department of Geomatics and the Department of Archaeology at the University of Cape Town. In June 1996, the fieldwork for the photogrammetric mapping of a newly discovered shipwreck was carried out. A Sony Hi-8 camcorder was used for video image capture, and control for the imagery was obtained by a combination of GPS and theodolite survey. Retroreflective targets were placed along the surface of the wreck to tie the imagery together. This thesis reports on the mapping of one of the sections of the shipwreck, and discusses the use of video imagery for the production of surface maps.

Bibliography: leaves 132-137. / An overall process model is presented for the capture of sulphur dioxide by calcareous sorbents in a fluidised bed combustor for a feed of arbitrary size distribution. The description of sorbent sulphation kinetics, particle attrition and elutriation effects incorporated in this model is supported by experimental data for a wide range of South African sorbents. The sulphation of sorbent particles is described by a simple, two-parameter, kinetic model. No loss in physical relevance is incurred when the decrease in reaction rate with time is given by a negative exponential term. Both sulphation rate and capacity are shown to be functions of sorbent type. The sulphation propensity of the 16 South African samples is correlated against their geologic description. Sorbent properties such as porosity, crystallinity and topography, which affect sulphation capacity directly, are functions of geologic age. It is possible to make a first order assessment of sorbent potential simply from this geologic data. Sorbent attrition, caused by the continuous movement of particles within the combustor, is greatest for deep beds of soft friable material. Most of the attrition takes place in the distributor region where jetting action is important. The attrition model reflects an explicit dependence on fluidising velocity, bed depth, particle diameter, topography and structural strength. Measured values of attrition rate decrease with time to a steady state value, which, under normal FBC operating conditions, is attained after a time in the bed of 6 - 10 hours. The elutriation model considers the effect of fines, generated by attrition, on the carry-over of coarse particles from the bed. The overall process model confirms that choice of sulphation kinetics exerts the greatest influence on attainable sulphur capture,. although bed fluid dynamics, sorbent attrition and feed size distribution all play a role. The model is substantiated by extensive data from the performance of three dissimilar sorbents in a 10 MWth FBC. The contribution of sorbent attrition to the solids loading of downstream gas cleaning equipment is highlighted.

Includes bibliographical references. / The scope of this thesis project is the design and implementation of a digital quadrature demodulator for a stepped frequency ground penetrating radar. This dissertation presents a theoretical model of the demodulator, simulations characterising the demodulator performance as well as the design, construction, and measurement of the prototype demodulator. The demodulator estimates the amplitude and phase of the intermediate frequency signal of a time-interleaved dual-channel heterodyne radar receiver. A demodulator model is developed from a survey of the relevant literature, paying particular attention to errors introduced in sampling. Simulations predict the demodulator performance in the radar system, suggesting coherent integration improves accuracy by reducing the effect of random sampling errors. The design of the prototype and characterisation of its performance are briefly reported.

Includes bibliographical references (leaves 83-86). / The emergence of computerized medical imaging in early 1970s, which merged with digital technology in the 1980s, was celebrated as a major breakthrough in three-dimensional (3D) medicine. However, a recent South African innovation, the high speed scanning Lodox Stat scanCritical Digital Radiology modality, has posed challenges in X-ray photogrammetry. This is due to the system's imaging geometry. This research investigates the applicability of Direct Linear Transformation (DLT) method in Lodox Statscan 3D point localization. Static modelsdesigned from metal frames bearing targets of different contrast have been imaged on the Statscan system to generate experimental data. These models were used to eliminate distortions that arise from involuntary human body movements. A control frame for the 3D models has been generated at an accuracy of ± 0.5mm. Point positioning accuracy has been computed by comparing the acquired Statscan 3D point positions to the established control. Two different reference frames were used, showing that point positions could be established with RMS values in the mm range in the middle axis of the Statscan X-ray patient platform. This range of acceptable mm accuracies extends about 15 to 20 cm sideways towards the edge of the table and to about 20 cm above the table surface. Beyond this range, accuracy deteriorated significantly. The experiments further showed that the inclusion of control points close to the table edges and more than 20cm above the table resulted in lower accuracies for the L - parameters ofthe DLT solution than those derived from points close to the center axis only. As the accuracy of the L - parameters propagates into accuracy of the final coordinates of newly determined points, it becomes essential to restrict the space of the control points to the above described limits.

Includes abstract. / Includes bibliographical references. / This work has two main objectives, first to create a working energy model of South Africa’s electricity sector using the open source software; OSeMOSYS, and secondly, using this model to understand the unstudied effects of net metered capacity within the country and how this affects the planning of the energy sector in the future, which is done through processes such as the Integrated Resource Plan (IRP). Using a combination of electricity tariffs and solar PV price projections, and the Bass diffusion model, an estimated range of the total amount of installed MW capacity of rooftop solar PV within the residential sector of South Africa was determined.

Includes bibliographical references. / Research into ice crystallization processes is an important area of study. The desire to improve product quality and efficiency of processes involving ice crystallization in industries such as desalination by freezing, freeze drying, freeze concentration and freeze crystallization for food processing, requires insight into the ice growth mechanisms. More so, a novel technology called Eutectic Freeze Crystallization, where water is recovered in the form of ice, requires that ice crystals are of high purity as this directly determines the quality of the water obtained. During ice crystallization, ice growth mechanisms play an important role in determining the structure, size and morphology of ice which have an effect on separation processes and product purity. Heat and mass transfer play a fundamental role in ice growth processes as they affect the thermodynamics and kinetics of the crystallization process. Ice growth experiments were carried out in pure water, in 8.4 wt% and 16.8 wt% magnesium sulphate and in 8.4 wt% sodium nitrate using a 10x5x31 mm test cell made of Plexi-glass®. The Colour Schlieren optical technique was used to conduct the experiments. This is because of its capability to map refractive index gradients related to either temperature or/and concentration gradients of the solution during crystal growth.

Bibliography: leaves 141-147. / This thesis investigates the effect of introducing low elevation data (down to 5°), various a priori tropospheric delay models, mapping functions as well as the influence of tropospheric gradient parameters estimation on station position, precision and accuracy, in order to ascertain the optimal combination to use in routine processing of TrigNet station.

Bibliography: leaves 90-95. / The recovery of Platinum Group Minerals (PGM) and associated sulphides by froth flotation from the Bushveld Igneous Complex is complicated by the presence of naturally floatable gangue minerals such as talc. Although talc is present in small quantities it has a disproportionate effect on concentrate grade by enhancing froth stability and increasing the entrainment of other gangue minerals. However, there is an indication that some of the other gangue minerals, which are normally considered to be hydrophilic, such as chromite and pyroxene, report to the concentrate as floatable particles. Polysaccharide depressants, such as carboxymethyl cellulose (CMC) and modified guar gums are used to reduce the floatability of naturally floatable gangue and may also be able to reduce the floatability of activated gangue. This study examines the copper activation of a range of minerals found in the Bushveld Complex (namely pyroxene, feldspar, chromite and talc as well as the classical oxide, quartz) using zeta potential measurements, adsorption and microflotation tests. The effect on floatability is evaluated after activation and collector adsorption in the presence of a modified guar and a CMC depressant. Although quartz is not a major gangue component in PGM ores it was selected since it is a strongly negatively-charged mineral in the alkaline range and therefore likely to respond to copper activation. Steenberg and Harris, (1984) found that polymers such as guar and CMC did not appear to adsorb to a significant level on quartz.

Includes bibliographical references. / A mathematical model is formulated describing the mechanism of substrate removal by a microbial slime over which a film of liquid, containing the substrate as dissolved biodegradable material, is flowing. It is assumed that a lack of either organic carbon, oxygen, or both simultaneously, can limit the overall rate of the process. Basic chemical engineering principles of interfacial mass transfer, diffusion and biochemical reaction are used in the formulation of the model and the resulting set of equations is solved by digitial computer using typical kinetic parameters taken from the literature. Predictions of whether organic carbon, oxygen, or both simultaneously, limit the process, the substrate removal rate, and the active depth of the biofilm are made. Data were obtained in support of the model by measuring substrate removals on a vertically mounted experimental biofilm reactor over a range of hydraulic and organic loadings typical of industrial-scale operation.