Mount Moorosi Village, located within the Senqu River Valley in Lesotho, has experienced significant damage to its buildings over the last several years, due to severe cracking. The cause of these cracks has been attributed to the local soil, which presents itself as an ideal building and founding material, while it may in fact be to the contrary. A previous investigation by Damane (2019), into the underlying soil profile of Mount Moorosi Village concluded that the village was underlain by a top layer of silty-sandy loess, a windblown soil of at least 3 m in thickness, with the majority of its grains falling within the siltsized particle range. The material demonstrated significant warping potential as well as a high hydrocollapse potential. To attempt to mitigate the hydrocollapse potential of the soil, linear low-density polyethylene (LLDPE) pellets, made from recycled plastic waste, were blended with the soil at concentrations of 3, 6 and 9 % by mass, before being subjected to pycnometer, oedometer and triaxial tests, to determine the specific gravity of the blended soil as well as the settlement and shear strength parameters, respectively. Test results showed that the addition of the LLDPE chips, at 6 % concentration by mass, resulted in the maximum improvement in both the settlement and shear strength parameters. The soil's collapse and hydrocollapse coefficients were reduced by 54 and 40 % respectively, with the overall classification of the soil going from ‘severe' to ‘moderately severe'. The cohesion of the soil was improved by 8 and 400 % for field and saturated moisture contents, respectively. The internal angle of friction of the soil was increased by 97 and 150 % for field and saturated moisture contents, respectively. Collapse and settlement calculations, conducted on Settle3D, showed that the soil's overall settlement was reduced by 34 and 54 % for field moisture and saturated soil conditions, respectively. The total settlement of the strip foundations with their current dimensions, however, was still outside of the acceptable ranges. The total settlement was lowered to within acceptable range of under 50 mm when the width of the strip footings was widened to 750 mm, and their depth increased to 200 mm.

In recent times, the dry reforming of methane has received significant interest as an alternative process through which synthesis gas can be produced. This is because dry reforming combines methane and carbon dioxide which are both greenhouse gases into synthesis gas which is used in the production of synthetic fuels and chemicals. The main problem faced by the dry reforming reaction is the formation carbon which causes catalyst deactivation. Noble metal catalysts such as ruthenium and rhodium have shown great promise as dry reforming catalysts because of their resistance to carbon formation, but they are expensive making their use on an industrial scale unlikely. This has led to nonnoble metals such as nickel and cobalt being considered as potential catalysts. Bimetallic nickel-cobalt (Ni-Co) catalysts have garnered a lot of interest as dry reforming catalysts as combining these two metals is believed to produce catalysts that would be more stable than monometallic nickel and cobalt catalysts. The objectives of the project were to investigate the suitability of nickel-cobalt (Ni-Co) alloy catalysts with different compositions as well as monometallic nickel and cobalt catalysts as dry reforming catalysts. In doing so, special emphasis was placed on understanding the effect of the Ni-Co ratio on catalyst activity, stability, and deactivation mechanisms. In the study, seven catalysts with varying Ni-Co ratios were prepared. The catalysts had a 10 wt.% active metal (nickel and cobalt combined) loading and were supported on magnesium aluminate (MgAl2O4). Catalyst testing was carried out on all the catalysts at 700 °C for a period of 12 hours to compare their performance in the dry reforming reaction. The results from catalyst testing showed that the Ni-Co catalysts that were nickel rich (70% and 90% nickel in terms of active metal) were the most active catalysts. This was because these catalysts achieved higher methane and carbon dioxide conversions in comparison to the rest of the catalysts. The most surprising result from catalyst testing was that the monometallic nickel catalyst showed very limited activity and was unstable. Post run catalyst characterisation using Raman spectroscopy showed that the Ni-Co composition of the catalysts influenced the type of carbon deposited on the catalysts during catalyst testing. This was because the carbon deposits on the cobalt rich Ni-Co catalysts were found to be more graphitic in nature compared to those on the nickel rich Ni-Co catalysts. However, the Ni-Co composition of the catalysts was found to have no influence on the amount of carbon deposited on the catalysts based on the results obtained from TGA analysis. In addition, post run catalyst characterisation showed that there was carbon formation on all the catalysts studied except for the monometallic nickel catalyst. This showed that there is a need to investigate additional means through which the carbon formation can be limited during catalyst testing. The co-feeding of water in the dry reforming of methane is one such measure that should be investigated.

Cogeneration is a core part of the SA sugar industry operations. Most factories in SA already cogenerate, but not to their full potential. Improving cogeneration through better energy utilisation than the usual status-quo can potentially enhance profitability. However, investment in cogeneration in the sugar industry is not taking place and although factories have proven to be able to produce excess power, many are not selling it back to the national grid. This research aimed to further the understanding of the SA sugar industry cogeneration options with the use of techno-economic modelling methods over a planning horizon extending to 2040. The methodological approach adopted for the study, configures the industry's cogenerating system, and allowed the adoption of additional options likely to play a role in assisting cogenerating performance in 2025. Some cogenerating technologies that were explored were back-pressure and condensing extraction steam turbines, as well as, high-efficiency gas engines in open and closed cycles. The least-cost optimizing TIMES modelling framework was used to evaluate the cogeneration investment decision for different cogeneration configurations under different scenarios, and to capture some of the uncertainties faced by the industry. Each scenario was evaluated using a set of techno-economic indicators, justifying the viability of technological implementations in cogenerating system pathways. Focusing on these transformative pathways highlighted diversification cogenerating options, whilst simultaneously ensuring the fulfilment of the industry's sugar production obligations, for the domestic as well as foreign market under pressure from competitive forces. Input data for model parameters stemmed from literature and information sources applied to Microsoft excel spreadsheets calculations. Analysed outcomes were scrutinised using tableau, which generated output data from iterating modelled power purchase agreement (PPA) and break-even tariff determinations. The assessment of generated transformative pathways was compared to metrics from other sugar-producing countries, with successfully diversified mills, using evaluated scenarios to emphasize the unit costs per energy in R2015/KWh. Research findings showed cogeneration feasibility at subsidised tariffs of between 1.20 and 1.76 R/kWh for steam turbines and gas turbines in open cycles, with combinedcycling from intergrated bagasse gasification being feasible from 1.20 to 1.37 R/KWh. Feasibly installed CHP technologies were concluded to have potential magnitudes of between 350 up to 800 MWe depending on the scenario.

Reinforcement corrosion is the main cause of deterioration in concrete structures. Condition assessment tests help to predict whether reinforcement corrosion is occurring and aid in the prevention of its consequences. The results of these condition assessment tests can, however, be affected by certain factors. A set of experiments that included carrying out four of these tests, namely the half-cell potential (HCP), cover depth, carbonation and resistivity tests was performed on several concrete structures on upper campus at UCT. The half-cell potential and resistivity tests were carried out across a four-month period between August and November 2018 during both dry and wet periods and on days with different temperatures. This was done to assess how changing weather conditions can affect the test results. The results from these tests were also used to do a comparison between HCP and cover depth results and HCP and resistivity results. A second set of experiments involved taking cover depth measurements and cores for carbonation testing from different locations across a building and assessing how variations in measurement location and sample size can affect the results. The HCP and resistivity results showed changes due to the effects of rain and temperature. Rainy weather caused the values to become more negative, while dry weather led to more positive values. An increase in temperature showed a slight decrease in the values of both the half-cell potential and resistivity measurements. The changes suggest that using prescribed value ranges to interpret the risk of corrosion may prove to be too simplistic. Contour plots of the HCP results proved to be a more stable method for assessing reinforcement corrosion than using prescribed value ranges. The overall trend for the comparison between HCP and cover depth results showed that HCP values decrease as cover depths decrease. The comparison between HCP and resistivity results was expected to show an overall decrease in HCP values as resistivity values decrease, but this did not hold true for some of the test locations. The results of the cover depth analysis showed significant changes in calculated statistics due to both changes in location and sample size. A cover depth analysis should thus be widespread and include a large number of measurements in order to provide useful results. The variation in results for the carbonation testing was contradictory for the two buildings that were tested, with one building showing significant variations with measurement location and the other building showing very little variation.

The current manufacturing of clay-fired and cement bricks has contributed greatly to anthropogenic global emissions and environmental damages. A possible solution that could be used to alleviate such environmental pressures is through the adoption of carbon neutral, microbial induced calcium carbonate precipitation (MICP) bio-bricks as a replacement for traditional bricks. MICP produced bio-bricks are formed by exploiting the ability of the microorganism, Sporosarcina pasteurii, to produce a biocement capable of binding sand particles (or any aggregate) together into a solid. Furthermore, such bio-bricks can be grown from otherwise ‘waste' resources such as human urine. This significantly reduces energy inputs whilst creating value by ‘upcycling' waste streams, resulting in a product which is sustainable whilst promoting the modern ethos of implementing environmentally friendly circular economies. However, the environmental benefits of MICP bio-bricks are hindered by the use of sand in their production. Sand, after water, is by volume the worlds most exploited and traded raw material and as such the supply of sand is being rapidly depleted globally. Added to this, sand extraction processes are known to cause extensive environmental damages. A possible solution to this issue is to replace the sand aggregate used to grow bio-bricks with mine tailings. The increasing global demand for metal products has resulted in the concurrent production of vast volumes of waste mine tailings which, if left untreated, pose a potential risk of leaching toxins into surrounding populations and biota. As such it was postulated that this risk to surrounding populations and the environment could be mitigated by repurposing mine tailings, as a replacement for sand, into MICP bio-bricks. Both a technical and economic study was conducted to determine the feasibility of repurposing copper mine tailings into bio-bricks. As bio-bricks were resource intensive to produce (reagents, chemicals etc.), bio-columns were used as a proxy in studying the technical feasibility of such a process. The technical aspect of this study involved characterising copper mine tailings received from Columbia in terms of physiochemical make-up, particle size distribution and the development of a MICP submergent technique used in growing the bio-columns. This was necessitated by the fact that it was noted during the characterisation of the mine tailings that the cementation media could not be pumped through the columns filled with mine tailings aggregate, resulting in the traditional pumping method used to grow MICP bio-solids being impractical. The submergent technique was used to compare the MICP efficiency of growing biocolumns from either beach sand or copper mine tailings. In addition, the toxicity of copper to S. pasteurii was investigated and an attempt was made to acclimate a culture of S. pasteurii to the copper concentration found within copper mine tailings. Furthermore, the copper mine tailings were screened to determine if there were any indigenous, anaerobic and copper tolerant ureolytic extremophiles contained within, which had the potential to grow more robust bio-columns.

3D motion-capture is essential for research in biomechanics and biomedical engineering. It can provide insight into performance and injury prevention in sport, diagnosis of illnesses and disorders as well as help biologists to study animals and help engineers to design bio-inspired robots. Researchers studying animal locomotion often study humans and dogs due to the difficulty associated with studying other animals; however, the cheetah (Acinonyx jubatus) is a particularly compelling animal to study due to its various cursorial adaptions. In recent years, there have been significant improvements in computer-based pattern recognition in deep learning, specifically convolutional neural networks (CNNs). This project will explore the use of computer vision techniques including CNNs, extended Kalman filters (EKFs), non-linear optimisation and sparse bundle adjustment (SBA) to remove the need for markers to be used in recovering a subject's location from video footage. The result of the project will be the development of a markerless 3D motion-capture system. The thesis discusses the theory behind and describes the development of tools for video synchronisation and processing, camera calibration, pose estimation, robust 3D reconstruction and 3D pose visualisation. Results are shown for motion capture performed on video footage of cheetahs. Visualisations and 3D motion data of these agile animals are also shown. The system developed is an enabling tool in the study of biomechanics and biomedical research.

Bibliography: p. 173-182. / The objective of this dissertation was to investigate compressed air energy storage as an alternative generation capacity for the South African electricity industry. In chapter one, an introduction to energy storage, electrical energy storage was introduced as an alternative generation option. Various energy storage technologies were discussed with their characteristics and applications. Compressed air energy storage was identified as a competitive energy storage option to pumped hydro in particular, and a suitable contender for the South African electricity market. In chapter two, the literature review, an in-depth study into compressed air energy storage was conducted. Many aspects of CAES were covered including CAES variants, underground pressurised air storage, projects and pre-feasibility studies, and operational plants. Due to the additional fuelling that certain CAES variants require, a Charge Energy Factor and a Fuel Heat Rate were defined. From the literature review it was seen that to date, only two CAES plants are still in operation. They are both of the conventional CAES type and use fuel-oil or alternatively natural gas for combustion In chapter three, an analysis of Eskom's demand, Eskom's future demand growth was analysed. A prediction in load growth, based on several economic scenarios, was made and the capacity of a suitable CAES plant, to meet this future demand, was determined. Chapter four, underground air storage reservoirs, focused on the aspects and prospects of storing compressed air underground in South Africa. Past underground air storage in South Africa was discussed and unused goldmines were identified as the most convenient and cost effective storage volumes available. The uniqueness of individual underground air storage volumes in mines were discussed as well as techniques necessary for the conversion of existing cavities. Both constant volume and constant pressure systems were investigated and mine cavern conversion costs where estimated per electric energy generated (R/kWh). Two of the most likely CAES turbo-machinery configurations suitable for South Africa were evaluated in chapter five, conceptual designs and cost analysis. The two types of CAES were conventional CAES and CAES with pressurised fluidised bed combustors (CAESIPFBC). Available plant was discussed and future generating capacities of individual CAES turbo-machinery trains were predicted. Costs per kW for CAES plants, excluding the cavern, were estimated through the escalation of costs from other plants and sources.

Includes bibliographical references (p. 80-82). / This study explores the potential of concentrated solar thermal technologies for high temperature industrial processes in South Africa which makes a significant contribution to global Greenhouse Gas emissions and it whose electricity supply is under pressure. It is thus required to explore reliable technologies that can provide low-carbon renewable energy at competitive costs. Few studies have investigated the economic and other benefits of using solar-generated heat for large-scale industrial process heat applications to replace or support conventional heating methods. Parabolic trough collectors are the most mature technology for both power and process heat, or steam generation. Linear Fresnel collectors could become an attractive alternative in terms of cost in the not too distant future.

The catalyst used plays a pivotal role in the optimization of the Fischer Tropsch (FT) synthesis. Cobalt (Co)-based catalysts have been widely used in low temperature Fischer Tropsch synthesis for the production of longer chain olefins [1]. The interaction between the support and the active metal, Co, has been observed to affect the activity and selectivity of the FT synthesis [2]. In order to investigate metal support interactions independent of other support effects, the inverse method was used in the synthesis of model catalysts [3]. The inverse method mimics the interface bond between the support and the active metal, resulting in CoO-Si bond formation. By exposing Co nanoparticles (NPs) to a dilute solution of an alkoxide, tetraethyl orthosilicate (TEOS) or triphnyl ethoxy silane (TPEOS), Co-O-Si bond (ligand) is expected to form until it reaches equilibrium state. The concentration of the dilute alkoxide solution can be varied to observe its effect on the surface coverage of the Co NPs with the alkoxide. XRD analysis of the modified cobalt nanoparticles showed that there was no evidence of the formation of a crystalline silica phase as those characteristic diffraction lines were absent. The TPR profiles showed a shift to higher reduction temperatures with increasing silica loading suggesting that the surface modification results in retardation of reduction of the cobalt nanoparticles. CO-TPD studies of the model catalyst indicated that the total number of active sites available for CO adsorption and bond cleavage decreases upon surface modification, but it leads to a more facile CO bond cleavage as evidenced by decrease in energy of dissociation. The activity of these materials in the Fischer Tropsch synthesis decreased with increasing silicon content for the oxidized cobalt nanoparticles. This was attributed to the decline in the total number of active site available for CO bond cleavage with increasing silicon content. The methane selectivity passes a minimum with increasing silicon content. This may be related to the carbon coverage on the surface of the nanoparticles affecting the chain growth. It is recommended that Fischer Tropsch synthesis studies be conducted on the modified as-synthesized cobalt nanoparticles to compare the performance of the two catalysts.

The Aeroswift machine is a novel high-speed powder bed fusion machine developed through a collaborative effort between the CSIR, Aerosud and the DSI. Its novelty lies in the substantial increase in build rate achieved through the implementation of a 5kW IPG laser and faster laser scanning speeds employed during processing. It is capable of producing Ti6Al4V low volume, high value and high integrity components required by the aerospace industry. Commercial selective laser melting (SLM) systems are a good benchmark for the type of quality needed in the integrity of aerospace components although they don't always meet them. The biggest difference between commercial systems and the Aeroswift machine is the amount of heat input used to make components based on the laser powers. Heat input is the ratio of the laser power to the scanning speed and it plays a role in the thermal history of a built part, its thermal gradients and therefore its residual stress. Heat input also has a big influence on the microstructure produced which determines the resultant mechanical properties. The focus of this project was to investigate the effect of increased heat input on residual stress, the development of microstructure and mechanical properties of Ti6Al4V specimens produced by the Aeroswift high (400 J/m) heat input system and commercial SLM Solution M280 low (150 J/m) heat input machine. This was to be accomplished by comparing the tested results of Aeroswift built specimens (High Heat Input) to those built by a commercial SLM machine (Low Heat Input). The effect of preheating on these properties was also studied. The low heat input specimens had two sets of test specimens, where one set was built without preheating and the other built at a preheating temperature of 200°C. This was the maximum preheating temperature for the commercial system used in this study. Firstly, the cantilever specimen were used to measure the amount of distortions that processing caused for both systems. The measured spread of the cantilever gave an indication of the amount of distortion caused by each processing condition. Distortion was found to be similar between the high heat specimen and the low heat specimen. Preheating at 200°C also did not give an appreciable difference in the amount of distortion. X-ray Diffraction was used to measure very near surface residual stresses up to a penetration depth of 5 microns. Blocks of 20X20X22 mm3 for each processing condition were used with measurements taken at the top surface center of the blocks. The very near surface stresses were higher with an increase in heat input, where high heat input specimens had average tensile residual stress in excess of 650 MPa while the low heat input specimens had average tensile residual stresses below 400 MPa. The Incremental hole drilling technique was utilised to measure the stresses in the blocks up to a depth of 1 mm from the top surface. Holes were drilled at the top surface center of each block. The stress distribution for both the high heat input specimens and the low heat specimens increased from 0.2 mm to a similar range of 500-600 MPa between 0.3 mm to 0.8 mm depth. Preheating at 200 °C yielded the same amount of stress. The microstructural analysis involved imaging from Optical Microscopy, Scanning Electron Microscopy and Electron Backscattered Diffraction. This combination of techniques confirmed a martensitic microstructure morphology of α' laths within prior β grains for all the specimens. The α' laths were arranged in the form of basket-weaves as well as colonies. The high heat input specimen prior β grains were columnar having grown across several layers in the build direction. For the low heat input specimens both with no preheating and with 200°C preheating, the prior β grains were atypically discontinuous. A hexagonal-titanium phase was identified in all the specimens as the dominant phase, with essentially no presence of the cubic phase. Dog-bone tensile specimens built in the z-direction (build direction) were used to test for static mechanical properties. The Yield Strength and the Ultimate Tensile Strength were above 1000 MPa and 1200 MPa respectively for all specimens. The average elongation of 11.2% in the low heat input specimen with no preheating was significantly higher than the 4.3% achieved by the high heat input specimen. The effect of the observed micro porosity under the microscope is thought to have contributed to this behaviour. Compact tension specimens for fracture toughness and fatigue crack growth rate testing were built in the ZX direction as per ASTM E399-17 labelling. The high heat input specimens had an average fracture toughness of 43 MPa√m compared to the less than 38 MPa√m achieved by the low heat input specimens. The high heat input specimens also had a better crack growth resistance than the low heat input specimens. The low heat input specimens without preheating had better crack initiation resistance. The results show that an increase in heat input does not have a substantial effect on the integrity and quality of parts. In fact, it produces comparable results to commercial SLM processing deployed in this study with respect to the properties studied, with the exception of a lower ductility. This brings about even more confidence on the advantage of high-speed processing. Future work should include testing at other orientations as well as testing higher preheating temperatures.