Graduation - 2024 - December (Open Access)
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- ItemFoundations of the triplet unravelling algorithm(Stellenbosch : Stellenbosch University, 2024-12) Woithe, Gerhard Gustav; Petruccione, F.; Pleasance, G.; Stellenbosch University. Faculty of Science. Dept. of Physics.Finding the ground state of a quantum many-body system is a notoriously difficult problem, and clever numerical strategies are indispensable in order to solve it. Triplet unravelling is a recently-introduced method that performs this task. This algorithm is the result of the confluence of a number of ideas from previous, and in some cases, unrelated fields, like the theory of open quantum systems, a recent reformulation of quantum field theory known as dissipative quantum field theory, and diffusion quantum Monte Carlo methods. In this thesis, we review the necessary aspects of these constituent fields so as to show in detail how triplet unravelling follows from all of them. We describe our own implementation of this algorithm, which we then use to investigate the ground state of a certain Heisenberg chain.
- ItemWho Cares? Work in South African Farmworker Homes: A Dialectical Materialist Methodology(Stellenbosch : Stellenbosch University, 2024-12) Wiltshire, Anne Hilda; Fakier, Khayaat; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Sociology and Social Anthropology.This dissertation investigates the social issue surrounding farmworkers who transition out of temporary employment for work in homes. It employs Social Reproduction Theory (SRT) as both eminent social theory of work in homes (Hopkins, 2017) and as dialectical materialist methodology (Davis, 1981; Federici, 1998; Bhattacharya, 2017a,b; McNally, 2017). The findings suggest that despite SRT’s neglect to research workers in homes as inclusive of children, given the advancements in Childhood Studies and Social Reproduction Feminism (SRF) SRT has begun theorising child work in homes. The philosophical analyses examine the underpinnings of SRT’s dialectical materialist methodology. The ontological analysis argues dialectical materialism excels at rendering the best understandings of social phenomena. This is because dialectical materialism is not only a social theory, but also a method of enquiry. The epistemological analysis finds dialectical materialism further distinguished as social scientific methodology for its comparative method, empirical grounding, and scientific evidence-based pursuit of knowledge. The theoretical and conceptual analyses reveal SRT’s methodological limitations. SRT has significantly broadened its narrowly concrete theorisation of work in homes of white Anglo-American middle-class adult women. Yet, SRT's 'strategic essentialism' (Hochschild, 2003) conceptualises concretes of work, has yet to reach conceptual consensus, and a rigorous conceptualisation of work, in homes. This dissertation theorises work abstractly. This heeds Marx methodology and suggestion that work in the social economy “be treated and analysed according to the existing empirical data” (1932: 49) to derive concrete social theories. The research design was informed by the comparative method SRT’s dialectical materialism methodology. Qualitative data was collected at three points in time over one year from quotas of 12 farmworking women stratified by residence (farm/town) and employment (permanent/temporary). Validation of the findings necessitated an abductive analysis to triangulate the empirical findings with parallel data from Childhood Studies, SRF, and Social Reproduction in Education (SRE), in addition to SRT. The historical analyses reveal a social reorganisation of work, workers, and workplaces, emphasising the importance of contextualising social research. Nineteenth century ‘child workers’ have been reconceived adult ‘workers’; and, ‘child scholars’ and whom without adult supervisionary ‘care’ are ‘neglected’ children. The contemporary analysis finds despite prohibition of child employment, even in agriculture, the hours of child work in schools have yet to be renegotiated in over 200 years, especially for the youngest most vulnerable scholars. This dissertation emphasises the value of dialectical materialism as social scientific methodology. It raises concern for the Social State of Neglect of vulnerable children, especially during employment hours. It proposes urgent national and international social policy reforms to address the social disjunctures in the social organisation of work, achieve the ‘Social’ objectives of the Sustainable Development Goals (SDGs), and ensure the fundamental and paramount Rights of children to ‘care’ and protection from ‘neglect’.
- ItemMoving towards a transformative diaconia in the Christian Dependency Ministry of the Uniting Reformed Church in Southern Africa: A Practical Theological approach(Stellenbosch : Stellenbosch University, 2024-12) Williams, Claudette; Bowers Du Toit, Nadine; Stellenbosch University. Faculty of Theology. Dept. of Practical Theology and Missiology.South Africa finds itself in a crisis when it comes to substance dependency and, although rehabilitation centres are available, addicts from disadvantaged communities face numerous challenges. What compounds the problem is that, if an addict has attended a rehabilitation centre and been discharged, there is not always an aftercare group that they can attend. The study aims to make recommendations to the Christian Dependency Ministry (CDM), which is an organisation of the Uniting Reformed Church in Southern Africa (URCSA), in order to facilitate more effective interventions with regards to this issue. It is important to note that the findings of the study reveal that URCSA, as a denomination, still largely functions in what may be termed charity mode. After a thorough examination of the terms diaconia and more especially, transformative diaconia, the researcher argues for a more constructive theological engagement based on the notion of transformative diaconia, which moves beyond mere charity as a theological framework for the church’s public engagement with societal issues such as substance abuse. The study also calls for the URCSA to view the CDM as an integral part of its ministry in context. The findings of the qualitative empirical research indicate that, while CDM branches could hold significant value in terms of the aftercare of substance abuse addicts, the CDM branches are not yet working as effectively as they could in order to make a sustainable difference. The research reveals that, while many challenges remain, there are also workable solutions. These solutions are mirrored in the recommendations made by the researcher, which are directed at the Executive Committees and members of the CDM branches, family members who have a relative who is addicted, local church councils, the General Synod of URCSA, and rehabilitation centres. There are many URCSA congregations spread throughout South Africa and Namibia. The researcher is, therefore, of the opinion that if each URCSA congregation has a CDM branch which functions effectively, the church and CDM would be optimally positioned to address the issues of substance abuse and related issues in many socio-economically marginalised local communities.
- ItemInvestigation of Module Temperatures in Floating Photovoltaic Arrays(Stellenbosch : Stellenbosch University, 2024-12) Willemse, Brendan; Pretorius, Hannes; Owen, Michael; Rix, Arnold; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.This study aimed to simulate the thermal behaviour and performance of floating photovoltaic modules under varying plane-of-array irradiance, wind speed, air temperature, and water temperature conditions. A one-dimensional finite difference method transient model was developed to calculate cell temperature, efficiency, and power output for ground-mounted fixed-tilt, single-axis tracking, and floating photovoltaic configurations. A comprehensive literature review guided the model development, ensuring reliable approximations and identifying areas for improvement. The model is validated against measured data from two test sites—Mariendahl (open-rack) and Marlenique (floating photovoltaic)—utilising CS3W (420W) and CS6U (330W) modules, respec- tively. Validation results demonstrated that the model achieved a root mean square error < 4 °C and a R² of 0.89 for 72048 open-rack fixed-tilt data points. Similar accuracy was achieved for single-axis tracking configurations (9758 data points), with a root mean square error of 3.08 °C and a R² of 0.91. For the floating photovoltaic system (33326 data points), the model predicted tem- peratures with a root mean square error of 4.00 °C and a R² of 0.91 based on a calibrated pontoon temperature of TP = 1.3 · Tₐir. This demonstrates that model predictions are reliable for varying environmental conditions. A sensitiv- ity analysis was conducted to evaluate the impact of design parameters (mod- ule tilt angle, module height above water, pontoon surface area, and pontoon emissivity) on floating photovoltaic cell temperatures. The analysis found that pontoon surface area and emissivity affect cell temperature by 0.22 °C per %
- ItemA Walk-Forward Multi-Factor Machine Learning Investment Process(Stellenbosch : Stellenbosch University, 2024-12) Wessels, Zander; Engelbrecht, Andries P.; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.It can be said that traditional asset management modelling lacks true empiricism due to the difficulty of accurate simulation of investment strategies through time. This is often demonstrated by positively biased academic results that do not reflect real-world outcomes. This thesis addresses this problem by developing a walk-forward platform that is inspired by the blackboard-expert architecture and that can simulate investment processes through time, providing reliable repeatability, which is the essence of good science. The proposed platform accounts for common biases, such as survivorship bias and forwardlooking bias, to create a true hypothesis-testing engine. When considering the investment process as it pertains to equities, this thesis argues that the process can be fully closed under the questions of “what should I buy?”, “when should I buy?”, and “how much should I buy?”. The thesis then aims to use the hypothesis engine to build an example investment pipeline that can test and automate a whole investment process. The proposed investment pipeline will answer the questions of “what”, “when”, and “how much”, respectively. Traditional factor models and machine learning models for stock selection will be explored to answer the “what” question. The thesis argues that training models using the proposed engine is the correct way to do so in a non-stationary time series setting. The “how much” question will be addressed using portfolio optimisation, with particular consideration given to particle swarm optimisation. The “when” question will be briefly discussed as a further research idea.