Theses / Dissertations

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Open Access
1+1+2 covariant approach to gravitational lensing in f(R) gravity
(2009) Nzioki, Anne Marie; Dunsby, Peter
In this thesis, we develop the 1 + 1 + 2 formalism, a technique originally devised for General Relativity, to treat spherically symmetric spacetimes in for fourth order theories of gravity. Using this formalism, we derive equations for a static and spherically symmetric spacetime for general f(R) gravity. We apply these master eqautions to derive some exact solutions, which are used to gain insight on Birkhoff's theorem in this framework. Additionally, we derive a covariant form of the lensing angle for a specific spherically symmetric solution in f(R) = Rn gravity.
Open Access
1. When to cry, "Sham!" 2. Residence of a trust as defined by its place of effective management
(2013) Stephens, Anthea Louise
Open Access
A 12 week pre-season fitnes training programme for senior male high school rugby players : the effect of supervision on anthropometric, physiological and physical performance variables
(1998) Clark, David Rodney; Lambert, Michael I
The study comprises of two sections; i) a survey to determine the attitude towards fitness training for rugby and the current fitness training habits of elite high school rugby players in their penultimate year at school, ii) a training study on a sample of the same population group, to measure the effect of a 12 week fitness training programme, based on scientific principles, on anthropometric, physiological and performance variables. The training study also measured the efficacy of training supervision compared no supervision on these variables.
Open Access
14 ways to remember Nzira gumi nena dzekuyeuka : exploring and preserving memories
(2009) Matindike, Tashinga; Zaayman, Carine
My project is one of memorialisation, expressed as a creative process. A core theme throughout my work concerns the notions of absence and presence, as the project is founded on a personal loss and inspired by a desire to sustain the memories of my late brother. My investigation involves the exploration and preservation of the memories of my brother. The body of work manifests as the residue of my reflections on grief and memory that I have chosen to exhibit in a commemorative manner. In turn, my practice has functioned as a source of comfort in the course of my mourning.
Open Access
A 14C and 15N study of the effects of ammonium or nitrate nutrition on carbon allocation in Triticum aestivum L. and Zea mays L
(1991) Van der Leij, Martina
The poor response of some plant species, e.g. wheat, to ammonium nutrition has been attributed to a diversion of carbon allocation from structural material for root extension to functions associated with the assimilation and translocation of ammonium in the root. The aim of this research was to investigate carbon allocation in response to ammonium or nitrate nutrition in wheat, an ammonium intolerant species, and maize, which exhibits ammonium tolerance. Experiments were carried out at 4mM and 12mM nitrogen feeding levels in sand and hydroponic culture respectively. pH of growth media was maintained at 6.0 to 6.5. Measurements made included shoot : root ratios, photosynthetic and root respiratory rates, plant water content, xylem sap analysis, and ¹⁴C and ¹⁵N allocation to soluble and bound nitrogen compounds, and soluble, storage and structural carbohydrates. Stunted root growth occurred in ammonium-fed wheat, which was exacerbated by increasing the NH4 concentration. No difference in growth response was evident between ammonium- and nitrate-fed maize. Photosynthetic rates of ammonium- and nitrate-fed plants within both species were similar but maize showed a 3-fold higher photosynthetic rate than wheat. Root respiration of ammonium- and nitrate-fed wheat was similar, while nitrate-fed maize appeared to have a higher root respiratory rate than ammonium-fed maize. Xylem sap analysis showed that for both species, ammonium-fed plants translocated more amino compounds and more carbon to the shoots than nitrate-fed plants, although maize appeared to have a more rapid translocation-rate than wheat. ¹⁴C allocation to nitrogenous compounds in roots of ammonium-fed plants was greater than that in nitrate-fed counterparts for both species. In wheat this increase appeared to be accommodated by a larger initial diversion of ¹⁴C to the root. In maize, reserve carbon in the root appeared to accommodate this increase. A reduction in ¹⁴C allocation to structural material in ammonium-fed plants compared to nitrate-fed counterparts was not evident in either species. ¹⁵N tracing in maize showed that significantly more nitrogen was taken up by ammonium-fed plants in comparison to nitrate-fed plants. The difference in total N between plants fed ammonium or nitrate was, however, not nearly as pronounced, suggesting that ammonium may be cycled out of the plant again. The response of wheat and maize to ammonium or nitrate nutrition is discussed independently, and suggestions for further research are made.
Open Access
An 15N study of the effects of nitrate, ammonium, and nitrate + ammonium nutrition on nitrogen assimilation in Zea Mays L.
(1984) Murphy, Andrew Telfer; Lewis, O A M
A brief review of the literature on the effects of nitrate and ammonium nitrogen sources on plant growth, and the assimilation of those nitrogen sources, has been presented. A water culture technique for the growth of maize was developed. The use of a gravel rooting medium with nutrients recycling through the rooting medium, and an iron supplement in the form of ferric citrate, resulted in superior growth of nitrate-fed plants in comparison to that observed with a hydroponic growth technique and a standard Long Ashton nutrient solution. The effects of nitrogen source on plant growth, organic nitrogen and inorganic nitrogen contents, and the rates of incorporation into nitrogenous compounds were studied. The observed differences were explained with reference to the effects of the various nitrogen sources on the physiology of the plants. The experimental techniques included assays of the enzymes nitrate reductase and glutamine synthetase, whole plant growth studies, and the analysis of nitrogenous compounds of xylem exudate and those extracted from the leaf blade, leaf base, and root regions of maize plants after feeding with a nutrient solution containing nitrogen as 15N.
Open Access
The 1985 school crisis in the Western Cape
(1992) Nekhwevha, Fhulufhuwani Hastings; Molteno, Frank; Jubber, Ken
The thesis is an exploratory and primarily empirical study with the objective to construct a detailed chronology of the events of the 1985 school crisis particularly in African schools in the Western Cape and to reflect on the relationship between the school crisis and the organic crisis in South Africa and the Western Cape in particular. The data for the thesis were derived from primary and secondary documentary sources and in-depth interview material. A total of 51 interviewees were selected principally on the basis of the specific role they played particularly within the Department of Education and Training institutions as well as in community, political, workers', parents', teachers' and student organisations during the 1985 school crisis in the Western cape. Interviews were open-ended with a semi-structured interview schedule which consisted of topical headings. The thesis's theoretical framework was informed by Gramsci's Marxism am the key concepts employed in the analysis included Gramsci's notions of hegemony and organic crisis as well as Freire's concept of conscientisation. Utilising Gramsci's Marxism, the historical transformations in economic, political and ideological spheres which affected the development of student struggles and the crisis in the Department of Education and Training schools in 1985 were examined. Chapter 1 deals with .the 'Total strategy' as a form of state "formative action" to overcome the general crisis. It also documents in chronological order the main events of the school boycotts and both political and economic struggles on a national level from 1953 to 1984 and early 1985 in order to provide a sound background for the 1985 school crisis in the Western Cape. Chapter 2 which is offered as an empirical contribution to sociology of education covers a series of complex events and processes which constituted the core of the 1985 school crisis in the Western Cape in a chronological order. In the conclusion, Gramsci's concepts of 'hegemony' and 'organic crisis' supplemented by Freire's notion of conscientisation were directly utilised to analyse the slogan 'People's education for people's power'. One crucial observation explicit in the thesis am expressed through verbatim interview extracts was that the school crisis could only be resolved when the apartheid capitalist system in its entirety has been abolished.
Open Access
19th century glass trade beads : from two Zulu royal residences
(1990) Saitowitz, Sharma Jeanette
Open Access
2-Aminophenazine carboxylic acids
(1962) Brock, David John Henry; Holliman, F G
Open Access
The 2010 Fifa world cup: Perceptions of its sports and development legacy potential
(2010) Mills, Lucy Caroline; De Wet, Jacques
Sport mega-events are a contemporary phenomenon which embody and unify global processes in an increasingly globalised world. Whilst the sport industry has grown exponentially as a result of global market forces envisaging extensive economic opportunities, hosting a mega-event has also been economically attractive for cities and countries. In aiming to be globally competitive and world-class, mega-events derive from an economic-growth centred model of urban development, whereby benefits will 'trickle-down' to the poor and marginalised (Pillay and Bass, 2008). The 2010 FIFA World Cup typifies such an event as it encompasses historical, geopolitical, economic and socio-cultural processes that have intensified and been intensified by, globalisation. South Africa's bid for the 2010 FIFA World Cup however, has differed from other mega-event bids. Official World Cup discourses boast that the World Cup will produce lasting socio-economic impacts to South Africa and indeed the rest of Africa. FIFA and the South African government have labelled the 2010 World Cup an 'African World Cup' with promises of stimulating pan-African economic and sociocultural opportunities. There is significant emphasis on providing social benefits to underprivileged populations. One of the anticipated social legacies is the development of sport structures and increased participation of sport in disadvantaged areas where barriers to sport are most entrenched. The aim of the research project was to determine whether a sport and development legacy is in fact materialising in both South Africa and Zambia as a result of South Africa hosting the World Cup. I employed a qualitative research design and conducted 20 semi-structured in-depth interviews with representatives from a wide variety of sport and development related organisations in Cape Town and Lusaka. I regarded this cross-section of people as best positioned to provide evidence of a legacy. v Findings demonstrate that the official World Cup discourses generated by FIFA and the South African government pledging benefits continent-wide, have infiltrated everyday discourse of people in townships in Lusaka and Cape Town. There is however a discrepancy between this rhetoric and the reality. Respondents from smallscale, community-based sports structures rarely perceive themselves or their organisations to benefit from World Cup opportunities due to a lack of access to information and resources. Despite limited tangible gains or involvement, a sense of pride in South Africa, and indeed Africa, is evident. This alone is contributing to the support of the World Cup rather than visible positive changes in disadvantaged communities. In contrast to these organisations, representatives from larger, wealthier sport for development NGOs record increased funding and activities. This research has therefore exposed a dual system of sports delivery present in South Africa and Zambia. Whilst sport for development NGOs thrive, community sports structures struggle to the point of being near dysfunctional or even non-existent. Given the problematic history of donor-driven, Northern-based development programmes, we must be wary of perpetuating the marginalisation of local voices. This thesis suggests that pitfalls of globalisation at large are reproduced in globalised sport. It substantiates existing literature that doubts the potential of the World Cup to generate development among poorer populations.
Open Access
20th-century serial thought and its development from performed to electronic music.
(1966) Mears, Guy Edgar Frank
Unable to copy abstract from PDF document
Open Access
21st century tertiary design education in post-apartheid South Africa : a question of quality
(2007) Leroux, Allen; Crawhall, Nigel T
The dissertation explores the question of; what drives excellence in tertiary design education in 21st Century post-Apartheid South Africa? Is it what the state does in terms of policy and regulation or is it what the higher educational providers do in terms of curriculum and methodology that creates excellence? In the first part the dissertation traces the development of higher education policy in South Africa following the political changes from Apartheid to Democracy after 1994. It explores the development of a regulatory framework for higher education provision in post-Apartheid South Africa, due to the disparate levels of quality higher education developed under the Apartheid system for different racial groups and also the proliferation of poor quality private higher education during the first decade of democracy. It follow s the view that while the state set the regulatory control for higher education a n d bench marked educational excellence against public institutions, the realisation that market demands for access to quality higher education would require private education provision to form part of the institutional mix was soon reached. In the second part of the dissertation a case study of a newly established private higher education provider is developed. Created within the new regulatory framework for higher education in South Africa, FEDISA (Future Excellence Design Institute of South Africa) of which this author is the academic director, endeavours to show that private providers of higher education can, when pursuing excellence, become viable partners to the stat e in education provision and may even surpass the state institutions, now burdened with massification, in terms of quality education provision. The study goes on to develop an understanding of how changes in the economic markets have created change demand within design. It then considers the four tenets on which FEDISA's programme for achieving excellence is based in order to comply academically with the highest quality of 21st Century design education. This is as much in answer to the requirements of the new regulatory framework as to the institution's own analysis of what the market now wants. These tenets include the concept of what a curriculum is, drawing on Stenhouse and Smith's views of the curriculum as 'a blueprint for action'. Next, the importance of integrating the component elements of the design curriculum by drawing parallels between the 'collection type and integrated curriculum' theory of Bernstein is considered. In the third instance, an analysis of 'Knowing, Acting and Being', after the curriculum theory of Barnett and Coates is developed through the addition of a liberal arts component to the design curriculum. Special focus is afforded the importance of 'Being' development of design students in 21st Century design education. Finally, Brookfield's notion of becoming a critically reflective practitioner and how the concept of critical reflection has found its place in the 21st Century design classroom through the use of the 'tools of critical reflection' is brought into focus. The dissertation concludes that while the shift in the design markets from craft through mass production to an understanding of ethical considerations in new millennium design dictates what kind of design professionals should now be educated and that this awareness may be achieved through the refocusing of inherently simple means inside the design classroom of the 21st Century, excellence in tertiary design education, while primarily based on what happens inside our design institutions, goes hand in hand with compliance to the demands of state regulation in order to ensure the viability of our tertiary institutions.
Open Access
25cc HCCI engine fueled with Diethyl Ether
(2009) Lemberger, Ian; Floweday, Gareth; Yates, Andrew
This research forms part of an ongoing HCCI study at the SASOL Advanced Fuels Laboratory to investigate and understand engine configuration and fuel chemistry effects on combustion in HCCI engines. This project continues from a previous project where a small Progress Aero Works (PAW) 6.5cc high speed model "diesel" aeroplane engine was found to operate in HCCI mode with surprising ease and flexibility. A 25cc, four-stroke, single cylinder Honda GX25 engine, possessing 2-valves with an overhead cam and separate oil sump lubrication system was used. This research aimed to provide insight with respect to which engine characteristics such as size, heat transfer, speed and fuel blending effects, play the primary role in operational differences between the Honda GX25, conventional HCCI engines and the remarkable operational flexibility of the PAW engine.
Open Access
3-month bond option strategies: an analysis of performance from 1998 to 2010 in the South African market
(2011) Ndebele, Ndumiso; Jones, Samantha; Touna-Mama, Albert
Due to the 2008 financial crisis, investors have become more risk averse in investing in equities and have increased their holdings in bonds as they are believed to be less risky. However, South African interest rates have been volatile over the past decade due to changes in the inflation rate. This has caused the returns of bond portfolios to be uncertain since bond prices are inversely related to interest rates. It is thus imperative to manage the interest rate risk inherent in bond portfolios so that institutional investors can achieve their mandates and targeted returns.
Open Access
3-Phase gate-turn off thyristor inverter
(1986) Kleyn, D A
The requirements of a standard 3-phase Induction Motor driven by a Voltage Source Inverter (VSI) are studied. A full 3-phase Variable Speed Drive (VSD) and its controller have been designed, constructed and tested. Gate Turn-Off Thyristors (GTO's) are used as the main switching elements in the Inverter stage of the Drive. The drive requirements of GTO's are studied in detail.
Open Access
A 3-phase Z-source inverter driven by a novel hybrid switching algorithm
(2007) Malengret, Jean-Claude; Braae, Martin
A 3-phase Z-source inverter has been researched, designed, simulated, builtand tested. The purpose of the inverter is to deliver 3-phase 400 VAC from aDC supply that can vary over a range of 20 to 70 Vdc. This is done with a Zsourceinverter topology which is a single conversion method with no additionalDC to DC boost converter. A novel DSP control algorithm allows the inverter toachieve the following:Â· Run Space Vector Pulse Width Modulation (SV-PWM) for maximum DCbus voltage utilization while boosting the DC bus during zero space vectorstates using shoot through.Â· Seamless transition between modulation control and modulation / shootthrough control.Â· Optimised efficiency and DC bus utilisation using Hybrid Space VectorBoost Pulse Width Modulation (HSVB PWM) which is unique to thisdissertation.Such a system is particularly suited to fuel cell and particularly wind turbineapplications where the DC bus voltage is varies over a wide range resulting inthe need for a DC to DC buck/boost to regulate the DC bus to maintain a steady3-phase sinusoidal output. A further application could be for general purpose 3-phase inverter capable of operating on different DC standard bus voltages ( e.g.24, 36, 48 VDC).The benefits of a Z-source topology for the above purposes are a reduction inhigh power semi-conductor components (e.g. power MOSFET). There is also areduction in switching losses and inherent shoot through protection.Furthermore, the inverter is more robust in the sense that it is not vulnerable to spurious shoot through, which could be disastrous in the case of a traditionalvoltage fed inverter.
Open Access
3D approximation of scapula bone shape from 2D X-ray images using landmark-constrained statistical shape model fitting
(2016) Wasswa, William; Mutsvangwa, Tinashe E M; Douglas, Tania S
Two-dimensional X-ray imaging is the dominant imaging modality in low-resource countries despite the existence of three-dimensional (3D) imaging modalities. This is because fewer hospitals in low-resource countries can afford the 3D imaging systems as their acquisition and operation costs are higher. However, 3D images are desirable in a range of clinical applications, for example surgical planning. The aim of this research was to develop a tool for 3D approximation of scapula bone from 2D X-ray images using landmark-constrained statistical shape model fitting. First, X-ray stereophotogrammetry was used to reconstruct the 3D coordinates of points located on 2D X-ray images of the scapula, acquired from two perspectives. A suitable calibration frame was used to map the image coordinates to their corresponding 3D realworld coordinates. The 3D point localization yielded average errors of (0.14, 0.07, 0.04) mm in the X, Y and Z coordinates respectively, and an absolute reconstruction error of 0.19 mm. The second phase assessed the reproducibility of the scapula landmarks reported by Ohl et al. (2010) and Borotikar et al. (2015). Only three (the inferior angle, acromion and the coracoid process) of the eight reproducible landmarks considered were selected as these were identifiable from the two different perspectives required for X-ray stereophotogrammetry in this project. For the last phase, an approximation of a scapula was produced with the aid of a statistical shape model (SSM) built from a training dataset of 84 CT scapulae. This involved constraining an SSM to the 3D reconstructed coordinates of the selected reproducible landmarks from 2D X-ray images. Comparison of the approximate model with a CT-derived ground truth 3D segmented volume resulted in surface-to-surface average distances of 4.28 mm and 3.20 mm, using three and sixteen landmarks respectively. Hence, increasing the number of landmarks produces a posterior model that makes better predictions of patientspecific reconstructions. An average Euclidean distance of 1.35 mm was obtained between the three selected landmarks on the approximation and the corresponding landmarks on the CT image. Conversely, a Euclidean distance of 5.99 mm was obtained between the three selected landmarks on the original SSM and corresponding landmarks on the CT image. The Euclidean distances confirm that a posterior model moves closer to the CT image, hence it reduces the search space for a more exact patient-specific 3D reconstruction by other fitting algorithms.
Open Access
3D cine DENSE MRI: ventricular segmentation and myocardial stratin analysis
(2013) Auger, Daniel A; Spottiswoode, Bruce S
Includes abstract. Includes bibliographical references.
Open Access
A 3D fault seal analysis study conducted in the Ibhubesi Gas Field Offshore the West Coast of South Africa
(2018) Ntombela, Nondumiso; Kahle, Beth
A three dimensional fault seal analysis study of the AK fault situated offshore of the West Coast of South Africa is presented. This study is aimed at informing the development plan of the Ibhubesi gas field with regards to the compartmentalization of the reservoirs, by understanding whether a key fault, the AK fault facilitates hydrocarbon migration to the Ibhubesi field reservoirs or whether it provides a seal. In order to address this research aim, a seismic interpretation of the area was carried out and combined with an interpretation of well data to construct a 3D structural model from which the fault seal analysis was carried out. Juxtaposition analysis was used to determine the lithologies that had been juxtaposed across the fault. Fault clay was determined using the Shale Gouge Ratio (SGR) algorithm and permeability and threshold pressure were also used to quantify the fault seal capacity. The results from the SGR were correlated to the across fault pressure difference and plotted on a reference diagram which is a comparison of sealing faults vs. leaking faults. This diagram indicates that faults with an SGR greater than 25% and threshold pressures greater than 8bars, have a high potential to seal. The AK fault SGR results range between 25 and 55 % with a threshold pressure of up to 20bars. These results indicate that the AK fault is likely to be a sealing fault.
Open Access
3D model reconstruction using photoconsistency
(2007) Joubert, Kirk Michael; Nicolls, Fred; De Jager, Gerhard
Model reconstruction using photoconsistency refers to a method that creates a photohull, an approximate computer model, using multiple calibrated camera views of an object. The term photoconsistency refers to the concept that is used to calculate the photohull from the camera views. A computer model surface is considered photoconsistent if the appearance of that surface agrees with the appearance of the surface of the real world object from all camera viewpoints. This thesis presents the work done in implementing some concepts and approaches described in the literature.

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