3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item The affective black experience: struggles with conformity for young black professionals in corporate South Africa(2017-09) Bokala, Kutlwano TlameloSouth Africa’s democratic transition was cultured by, amongst others, the mythical ideology of Rainbowism. Rooted in happiness and the promises thereof, the renowned national metaphor was utilised by the state to radically shift the country’s narrative around nationhood towards a shared understanding of identity, belonging, citizenship, and diversity. Today, the influence of Rainbowism within state-led efforts towards social change has slowly deemed under much public scrutiny. Persistent poverty, inequality and violence have fostered the emergence of, what many are calling, an “End of the Rainbow” discourse. As integral and lurid entities within post-apartheid nation-building, black youth and institutionalised spaces have affected and been affected by the shortcomings of Rainbowism. Their shared history and intersecting significance in fuelling collective action amongst South Africans have been well depicted in recent times where youth-led movements have highlighted the inequality and unhappiness that exists in institutions spaces like the university. However, little mention has been made about how black youth are making sense of institutional life within spaces like the workplace, against the backdrop of promised happiness. Through the conversations had with eight young black professionals, this research report centres Rainbowism as a project of happiness that governs institutional life for black youth in South Africa. Happiness is revealed as a dominant discourse operating along axes of power that shape ‘happy’ employees based on various forms of corporeal differentiation.Item Item Laser shock peening in friction stir welded joints with lack of penetration defects(2016) Leering, Mitchell PatrickThis experimental work was conducted in order to assess the influence of the application of Laser Shock Peening (LSP) to Friction Stir Welded (FSW) joints. LSP has the ability to potentially recover the reduction in joint mechanical properties that arose due to the presence of a common FSW defect known as Lack of Penetration (LOP). The material used throughout this study was 3 mm thick AA6082-T6 Aluminium. This specific material was selected due to its weldability and common use in the manufacturing of aircraft structures. A 20 mm diameter, spiralled profile shoulder and 5 mm diameter, tapered, three facetted pin was used in the manufacturing of the FSW joints. Experimental assessment and optimisation of the FSW parameters window consisted of the varying the tool rotational speed from 630 to 1600 RPM, at five increments and the feed rate from 200 to 600 mm/min, 200 mm/min intervals. The joints were assessed on the overall quality, microstructure, ductility and static strength. The parameter combinations produced joints with ultimate tensile joint efficiencies which ranged from 48% to 74% that of the base material. The initial study showed that higher welding rates, typically associated with low feed rates, resulted in the highest quality joints. This was attributed to the sufficient thermal softening of the material during welding. The increased welding temperatures improved the joint formation, material flow and mechanical properties. Due to the elevated welding temperatures and material flow, substantial flash formation was observed on all joints manufactured with a welding rate of 5 rev/mm and higher. These results formed the foundation of the multi-objective optimisation in order to determine the most suitable parameters for this welding configuration. The optimisation simulation determined the optimum parameters to be, a tool rotational speed of 1433 RPM, feed rate of 196 mm/min and a welding rate of 7.3 rev/mm. Due to the fixed gearing of the CNC FSW machine the required tool rotational speed could not be achieved, thus, all FSW completed after the optimisation was completed at 1600 RPM, 200 mm/min and 8.00 rev/mm. This parameter combination produced a joint of high structural integrity, high ductility and with no visual sign of internal voids, defects or lack of penetration. The performance of the defect free joint formed the foundation of the characterisation of the influence of intentionally introduced LOP defects. LOP was defined as a pre-initiated crack which formed at the root surface during the fabrication of a FSW joint. Controlled and consistent LOP was introduced into the joints, manufactured with welding parameters of 1600 RPM and 200 mm/min, by offsetting the welding tool in combinations of the normal and lateral directions relative to the joint line. The defects originated at the root surface and extended at various lengths through the thickness of the joints due to the numerous offsets. The defects lengths ranged from a few microns to as much as 954.5 μm. A number of defects affected as much as 43% of the joint thickness. The presence of the defects negatively affected the joints structural static strength by as much as 9% to 27% (dependent on the size of the defect) and dynamic fatigue life of as much as 36%. Laser Shock Peening (LSP) is a novel post manufacturing technique, which has been used to introduce compressive residual stresses within the near surface of the metallic components. A LSP processing was completed without a protective ablative coating (LSPwC), at a wavelength of 1064 nm and pulsed nano-second laser at 10 Hz. The characterisation of varying the laser power intensity and processed coverage to the base of FSW AA6082-T6 Aluminium was completed through extensive parameter window exploration. Factors such as the quality of the energy delivery, sample deflection, strain hardening, penetration of effects through the FSW joint thickness and the improvement of the fatigue life of the base material were used to define the appropriate parameters. A multi-objective optimisation strategy was implemented in the attempt to fully explore the regions between tested parameter combinations; to provide an optimum set of LSP parameters which would be used in combination of the optimum FSW parameters. The simulation predicted two optimum sets of parameters dependent on the desired outcome of either maximising component fatigue or LSP depth of penetration effect. Due to the nature of this research requiring both fatigue and penetration depth, a parameter set was selected based on parameters that would theoretically provide the maximum for both desired outcomes. The optimum power intensity and coverage was specified as 3.33 GW/cm2 and 1067 spots/cm2. The optimum parameters of each process was combined in an attempt to recover the drop in fatigue life of the joints due to the presence of the LOP defect. LSP was capable of altering the near surface residual stress states of approximately 100 MPa tensile to -150 to -200 MPa compressive across the three measurement ranges. It was found that LSP had minimal effect on the fatigue life of the components in the low cycle fatigue due to the applied stress relaxing the introduced stress thus having minimal effect on the life of the joints. LSP was found to increase the fatigue life of the non-defective joints by as much as 68%. LSP showed a life improvement of approximately 20% in a joint which had a defect length of roughly 175μm. After the application of LSP the samples in the low cycle fatigue tended to fail at a closed cycles to failure as the non-defective unpeened samples. Application of a LSP to a FSW was found to shift the fracture position of the flawed components from the region of the defect to that of the Heat Affected Zone (HAZ) on the advancing side of the weld. It is suggested that, the shift in fracture position was due to critical relocation of the tensile stress during LSP into the HAZ on the advancing side. The results did not conclusively show that LSP was capable of recovering the effects of the LOP but was plausible that it could possible. This has been said due to some samples exhibiting an increase and due to the change in location of the fracture position.Item A preliminary description of South African Sign Language syntax(2017) Wright, DonovanThis study is a preliminary investigation into the syntax of South African Sign Language. Utilising narrative data within a case study approach, signing is observed and analysed in terms of Radical Construction Grammar. An emphasis is placed on signs as form-meaning pairings, in which information of form is drawn from previous research on the phonology and morpho-syntax of signed languages. Meaning is explained within the same sphere, drawing on established literature regarding meaning in signed languages – with the addition of Mental Space and Conceptual Blending theories. The aim is to describe the signing elicited as in-depth as possible while covering a broad number of relevant aspects. The efficacy of Radical Construction Grammar as a theoretical framework in signed language is also considered. Results include descriptions of different construction types and a holistic view of signing. Schemas are proposed for common constructions, and Radical Construction Grammar is posited as a viable alternative to a traditional understanding of syntax.Item Teachers’ perceptions of school-based support teams in the Johannesburg East School District(2015) Schneiderman, FarrynThe aim of this research study was to explore how teachers in a sample of primary schools in the Johannesburg East school district of Gauteng perceive the school-based support teams (SBST) at their schools. These support teams are supposed to be existing structures within public schools in South Africa according to the policy outlined in Education White Paper 6 (Department of Education, 2001). Teachers in South African government schools often face considerable challenges in the implementation of inclusive education. These include catering to the individual needs of all learners within classrooms that contain a large number of learners. A mixed-method exploratory descriptive design was used to carry out the exploration of this study. Five government primary schools in the Johannesburg East school district participated in this study and there were fifty-four educators that voluntarily completed a questionnaire that consisted of both open- and closed-ended questions. Data from the questionnaires were analysed by using frequency and descriptive analysis, as well as thematic content analysis. Results from this questionnaire indicated that the majority of the respondents have a positive outlook on the school-based support team approach and would like this approach to continue within their school. They do however require additional support from the district support team and would need assistance from both the district and school-based support teams in order to constructively deal with specific barriers to learning. This will improve the collaborative support and emotional well-being of the educators, thereby improving the quality of education provided to the learners.Item A geometallurgical strategy for improving ore quality and mineral processing efficiency at Kansanshi Mine in Zambia(2016) Beaumont, ChristopherThe Kansanshi mine is located in north-western Zambia. It is a copper and gold bearing, vein hosted, structurally controlled, ore deposit, which is exploited using conventional open pit mining methods. A series of highly complex mineralogical suites have formed through the interaction of the in-situ geological, weathering and oxidation processes. Some of these mineralogical suites are extremely difficult for effective extraction of copper and gold. Currently ore is classified into 22 different quality categories using a system called “Mat_Type”. Only the “best quality” ore is directed to the metallurgical process plant, while the remaining “poor quality” ore is directed to long term stockpiles. These stockpiles are unlikely to be processed until the end of the life of mine despite containing metal quantities of significant value. A systematic investigation of Kansanshi’s mine value chain was carried out to determine if this value could be realised sooner. It was found that, due to a lack of integration between technical silos that form the mine value chain, the Mat_Type system does not take due consideration of geological, mineralogical nor metallurgical processes. Ore quality control factors are incorrect and economic data to determine suitable cut-off grades is both outdated and applied in an inappropriate manner. As a result 12 of the 22 Mat_Type ore categories are unnecessary, while a further six categories are inaccurately defined, leaving only four categories that can be considered to be correct. It is because of these errors, that so much ore is being directed to long term stockpiles. Through the research study presented in this report it was found that five key factors determine an effective ore classification system for Kansanshi mine. These factors can be defined as: Spatial distribution of mineralogical relationships between in-situ geological, oxidation and weathering domains; The impact of mineralogical groupings on copper recovery in each metallurgical process; The size, statistical distribution, range and accuracy of available data sets; The application of appropriate economic factors in the mineral resource to mineral reserve conversion process; and, The practicality of overcoming physical constraints at various stages of the mining process A more appropriate geo-metallurgical ore classification system can be developed that will consider the above listed factors. Three mineralogical groupings naturally exist in the deposit. Using total copper and acid soluble copper assay data, these mineralisation categories can be defined by a specific range of oxidation ratio. These ranges can be listed as: Primary copper sulphide minerals, with oxidation ratio < 0.1 ; Secondary copper sulphide minerals, with an oxidation ratio between 0.1 to 0.8; and , Primary copper oxide minerals, with an oxidation ratio between 0.8 to 1.0. Each mineralogical grouping can be assigned to a specific metallurgical process. Further subdivisions of these groupings can be made based upon economic grade ranges and appropriate metallurgical quality control factors which are linked to a specific metallurgical process. By implementing the proposed geo-metallurgical ore classification system, 12 of the erroneous ore categories in the Mat_Type system can be removed. The remaining 10 categories would be accurately and consistently defined. This will lead to a significant reduction in the quantity of ore directed to long-term stockpile, thereby releasing previously lost value. The new ore classification methodology proposed would be supported by a systematic process to manage regular, periodic updates, based on new data and developments in technical understanding across all functional areas of the mine value chain. A continued dialogue and sharing of knowledge between the main technical silos is critical when promoting a robust and integrated ore classification system. Such a system has the potential to remain relevant throughout the life of Kansanshi mine.Item The industrial viability and characterization of WC-Co alloys produced by acid leaching and recycling techniques(2016) Freemantle, Christopher StuartIn the current study, the well-established zinc recycling process and a prototype acetic acid recycling plant were successfully employed to recycle cemented tungsten carbide scrap material for re-use as production powders. The recycled materials were studied and compared to new materials at each stage along the cemented carbide manufacturing route, in a production environment. Analysis of by-product materials from the zinc recycling process revealed that while some by-product material can be readily converted into powder using the supplementary acetic acid method, the rest is most efficiently recovered by using a second zinc recycling run and by controlling the size and purity of the scrap material introduced into the process. Various analytical techniques, including the novel use of proton induced x-ray emission studies were used to characterize the materials in both the powder and sintered form. The analyses revealed that the recycled materials possessed superior microstructural homogeneity than new materials, and greater than 99% purity. Studies of milling behavior and slurry rheology revealed no adverse effects of using recycled materials, provided that the slurry properties prior to powder spray drying were appropriately controlled. Polymer binder integrity remained intact despite the longer milling times associated with the use of recycled materials, and the superior slurry stability of recycled materials was demonstrated. The flow behavior and powder rheology of the spray dried powders was found to depend on the precursor slurry rheology and particle grain size. This was controlled predominantly by the formation of a sufficient yield stress to produce ideal, dense granules for greater ease of manufacturing, in both new and recycled powders. The acetic acid recycling technique can be used as a complimentary recycling process to the existing zinc recycling process, and can produce useable recycled material at low cost.Item A review of packed red cell transfusions in the neonatal unit at Charlotte Maxeke Johannesburg Academic hospital(2017) Song XiaojunBackground: Packed red cell transfusion (PRT) is a common therapeutic option in neonates with anaemia. Objectives: The aim of this study is to review the use of PRT in the neonatal unit, and identify any associations with specific complications. Methods: This is a retrospective descriptive study of all neonates who were admitted to the neonatal unit of Charlotte Maxeke Johannesburg Academic Hospital, younger than 72 hours, from 1 January 2013- 31 December 2014. Neonates older than 72 hours, or with missing data, were excluded from the study. The timing and number of transfusions given to each neonate could not be established with the available data and were therefore not included in this study. Neonates were divided according to weight into 2 groups, those weighing less than 1500g, and those 1500g or larger. Within the groups, neonates who were not transfused were compared with babies who were transfused. By means of univariate and multivariate analysis, the characteristics of the neonates and the incidence of complications were reported. Results: The study sample included 3432 neonates. Of these, 2395 were ?:1500g and 1037 neonates were< 1500g. The total number of PRT was 435/3432 neonates ( 12. 7% ). The incidence of necrotizing enterocolitis (NEC) in the smaller transfused group was 11.9% versus 4.6% in the smaller non-transfused (P<0.001). The incidence of NEC in the larger transfused group was 14.1 % versus 0.7% larger non-transfused group (P<0.001). The incidence of late-onset sepsis (LOS) in the smaller transfused group was 49.4% versus 12.0% in the smaller non-transfused group (P<0.001). The incidence of LOS was 3 7.3 % in the larger transfused group versus 2. 8% in the larger non-transfused group (P<0.001). The incidence of bronchopulmonary dysplasia (BPD) in the smaller transfused group was 50.2% versus 5.5% in the smaller non-transfused group (P<0.001 ). The incidence of BPD larger transfused group was 21.2% in the group transfused versus 0.5% in the larger non-transfused group (P<0.001). The incidence of intraventricular hemorrhage (IVH) in the smaller transfused group was 22.0% versus 6.1 % small non-transfused group (p<0.001 ). The incidence of IVH in the larger transfused group was 7.0% versus 0.2% in the larger non-transfused group (p<0.001 ). The incidence of ROP in the smaller transfused group was 9.8% versus 2.0% in the smaller non-transfused group (p<0.001 ). The incidence of conventional mechanical ventilation (CMV) in the smaller transfused group was 40.8% versus 9.1% in the smaller non-transfused group (p<0.001). The incidence of CMV in the the larger transfused group was 60.6% versus 8.0% in the larger non-transfused group. The lengths of stay as well as the duration of CMV in the transfused group were more than double the duration of those who were not transfused. In both groups, after multivariate regression analysis, a significant association was found between PRT and CMV, LOS, BPD, IVH, and birth weight. NEC and ROP were no longer significantly associated with PRTs. Conclusion: 12.7% of neonates admitted to the CMJAH neonatal unit received a PRT. However, the exact timing and number of PRT per neonate were not known. Very low birth weight neonates are 8 times more likely to be transfused compared to larger babies. Future prospective studies are needed to determine whether PR T cause LOS, BPD, IVH, and longer duration of CMV; and also to determine that NEC is not associated with PRT.Item An evaluation of preimplantation genetic diagnosis outcomes in Johannesburg, South Africa(2017) Carzis BiancaPreimplantation genetic diagnosis (PGD) involves testing embryos that were created using artificial reproductive technology for a familial genetic condition before being transferred to a woman's uterus. The aim of this study was to determine the number and nature of PGD cases managed through the Division of Human Genetics at the University of the Witwatersrand and National Health Laboratory Service, and assess the outcomes at various stages of the PGD process, including a cost estimation of PGD. The files of 22 PGD couples were included in a retrospective case review. In total, there were 42 IVF/ICSI cycles included in the analysis. The clinical pregnancy rate per embryo transfer was 29.3%. Overall, 10/22 (45.5%) couples had a successful cycle resulting in a liveborn baby. On average, one cycle of PGD costs USO 9,525 (ZAR 125,578). This study shows that our PGD success rates are comparable to those achieved globally.Item Oral health status among Nyaope users at drug rehabilitation clinics in Johannesburg(2017) Tetarwal AnitaIntroduction: Nyaope, an extremely addictive drug, has devastating effects on the health of its users. This comparative cross-sectional analytical study sought to assess the oral health status and behavior of nyaope users against a matched cohort of nondrug users. Methods: This study was conducted at Empilweni and Nishtara drug rehabilitation clinics in Johannesburg from 1 September to 29 December 2016. A total of 51 nyaope users and 25 matched non-drug users were recruited. Oral Health status was compared between the groups the decayed, filled, and missing teeth (DMFT) score, pulpal involvement, ulceration caused by dislocated tooth fragments, fistula and abscess (PUFA) score, bleeding on probing (BOP) and periodontal pocket depth (POD) scores. A validated questionnaire that assessed sociodemographic, diet, and dental behavior was administered to all participants. Results: The mean age of nyaope users (n=51) was 26.4 years (SD 4.84) and nondrug users (n=25) was 26.04 (SD 4.09) years (p= 0.75). Nyaope users had a mean DMFT score significantly higher than non-drug users [3.97 (SD 4.1 1) vs. 2.04 (SD 2.81) (p=0.03)]. Caries prevalence was significantly higher in nyaope users compared to non-drug users (82.35% vs. 48.0%; p=0.03). There was no significant difference in the prevalence of BOP [users 19.61 % vs non-users 16.0% (p=0.50)] and PDD (~4mm) [nyaope users 13.73 % vs. non-drug users 16.0 % (p=0.53)) between two groups. The PUFA score among nyaope users and non-drug users were similar [1.19 (SD 3.03) vs. 0.68 (SD 1.28) p= 0.42]. Only 51% of nyaope users (vs. 100% non-drug users) reported daily brushing and 100% (vs. 56% of non-drug users) had a highly cariogenic diet. Conclusion: Nyoape users had significantly higher cariogenic diets, caries prevalence, and DMFT scores compared to non-drug users. Additionally, Nypoape users were also significantly less likely to practice daily brushing than non-drug users