4. Electronic Theses and Dissertations (ETDs) - Faculties submissions
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Item South Africa’s earliest giant: The systematics and palaeobiology of a new species of sauropodomorph(University of the Witwatersrand, Johannesburg, 2023) Moopen, Atashni; Choiniere, Jonah N.; Botha, JenniferSauropodomorph dinosaurs are characterized by their gigantic body size and quadrupedal postures, but they evolved from small, bipedal ancestors. Transitional non sauropodan sauropodomorphs from the Norian are key to understanding this evolutionary transition. A new Norian sauropodomorph (BP/1/8469) discovered in 2018 in the lower Elliot Formation of Qhemegha, Eastern Cape consists of a well-preserved, well-represented associated postcranial skeleton of a relatively large individual. This specimen provides novel information about the Norian transition in sauropodomorph body plan. This study presents the results of BP/1/8469, using comparative anatomical study, quantitative body mass and postural estimation, osteohistological enquiry, and phylogenetic systematics assessment. BP/1/8469 is a 1.8 to 3.1 metric tonne, facultative quadrupedal sauropodomorph. It was an adult that displays rapid, interrupted growth, similar to other sauropodiforms. Phylogenetic analysis of BP/1/8469 highlights incongruencies in sauropodomorph character datasets, flags considerable homoplasy in sauropodomorph evolution, and underscores the need for accurate homology statements.Item Project Reality - Imagining the symbiotic relationship between virtual reality and the human narrative(University of the Witwatersrand, Johannesburg, 2024) Peneda, MichaelWith virtual reality technology being ever more integrated in our daily lives, through the accessibility to technology such as smartphones, personal computers, the internet, and social media. The potential possibilities for exploration, education, historical preservation, spatial exploration and how we define reality are endless. With the Newtown precinct having historical, educational, and recreational facilities within the heart of Johannesburg yet not functioning as a true representation of a cultural precinct. It provides the perfect catalyst for a virtual reality centre that enables the public to access this technology and explore its vast potential whilst reviving and transforming Newtown into a functional cultural precinct. Whilst being supported by the surrounding public infrastructure as well as creating a new pillar to support the precinct. This virtual reality centre provides the ability for users to explore both the virtual realm and the physical, while being able to easily transition from one to the other. With new ways of engaging with spatial exploration, immersive education, and new representations of historical narratives. With the building functioning as an amalgamation of new representations of classical typologies such as museums, exhibition spaces, galleries, research development and education facilities. By housing the functionalities of these typologies within the centre yet representing them in new ways with unique ways of engaging with them.Item [T]read Between the Lines Unraveling and Upskilling Hidden Communities in Orange Grove and Norwood(University of the Witwatersrand, Johannesburg, 2023) Moshe, Khumo; Francis, LialeThis research explores the historical tension and socio-economic differences between Orange Grove and Norwood, which are neighbouring suburbs characterized by a diverse culture and a mixed-income profile. These tensions lie between and along major arterial nodes Louis Botha Avenue and Grant Avenue, which serve communities. Louis Botha Avenue is a transit route and Grant Avenue, is a local retail high street. The study investigates the potential of Patterson Park, located between Louis Botha and Grant Avenue, as a mediating space for these neighbourhoods. The park offers the opportunity for connection between these neighbourhoods through urban principles that create safe and comfortable public connections. The proposed intervention neighbours Paterson Park and is driven by the imitiate human interactions. It aims to establish a maker’s guild and trade training centre, providing opportunities and possibilities for marginalized individuals, local entrepreneurs, businesses, and the community. The facility will impart essential urban principles for successful neighbourhoods and emphasize the significance of public art, craft in construction, along with facilitating better contractor-client relationships.Item Shaping Coverage of #Feesmustfall: Investigation of Facebook and Twitter as agenda-setters for South African Newspapers The Times, Daily Sun and The Star(University of the Witwatersrand, Johannesburg, 2018) Mthembu, Vuyo; Cowling, LesleyThe purpose of this research is to investigate social media as an agenda-setter and source of news for print media. The #FeesMustFall student protests, which began on 14 October 2015, is used as a case study for the purposes of the research. The first phase of the project involved collecting and analyzing news articles from the Daily Sun, Times and The Star newspapers. Additional data was collected from Twitter and Facebook to identify the top posters around #FeesMustFall and analyze whether any issues pertinent in social media were covered by the print publications mentioned above. The second phase drew on information from journalists and newspaper editors at the three newspapers. The findings were that social media did play a role as an agenda-setter in varying degrees in the respective newspapers and that there are implications for Journalists in South Africa, in utilizing the platform, in their day to day work.Item Optimisation of Kick Latency for Enhanced Performance of Robots in the RoboCup Three-Dimensional League through Proximal Policy Optimisation (PPO)(University of the Witwatersrand, Johannesburg, 2024-07) Nekhumbe, Humbulani Colbert; Ranchod, PraveshThis study aimed to enhance the kicking ability of Nao robots in the three-dimensional RoboCup simulation by addressing a crucial challenge observed in the University of Witwatersrand RoboCup team. The focal challenge revolved around a noticeable delay and slow movement manifested by the robot during ball kicks, leading to vulnerabilities in ball possession against opposing teams. To surmount this challenge, the implementation of Proximal Policy Optimisation (PPO), a methodology pioneered by OpenAI, was advocated. The precise objective was to optimise kick parameters, with a primary emphasis on curtailing kick latency. This optimisation aimed to ensure swift and accurate execution across various kicking scenarios, encompassing actions like propelling the ball into the opponent’s territory to bolster ball possession and thwart adversary manoeuvres. Harnessing the iterative advancements embedded in PPO, the successor to Trust Region Policy Optimisation (TRPO), the endeavour was to refine the kicking behaviour of Nao robots. This optimisation process significantly reduced the observed kick delay, and this made the robot more agile and effective at competing in the complex three-dimensional RoboCup simulation environment. The study’s outcomes highlighted substantial progress in reducing kick latency and improving the adaptability of robotic soccer players, opening up possibilities for further exploration in reinforcement learning for autonomous agents.Item Search for high-mass resonances in the Zgamma channel and Quality assurance of Scintillation detector modules of Tile Calorimeter Phase-I Upgrade of the ATLAS detector(University of the Witwatersrand, Johannesburg, 2024-09) Mokgatitswane, Gaogalalwe; Ruan, Xifeng; Solovyanov, Oleg; Mellado, BruceThis thesis presents a search for narrow, high-mass resonances decaying to a Z boson and a photon (Zy) in the final state. The analysis utilizes the full Run 2 dataset collected by the ATLAS experiment at the CERN Large Hadron Collider (LHC), corresponding to an integrated luminosity of 140 fb-1 of proton-proton col- lisions at a center-of-mass energy of ps = 13 TeV. The search focuses on a mass range of 220 GeV and 3400 GeV, aiming to identify deviations from the expected background arising from Standard Model processes. A small excess is observed at 250 GeV within the area of interest, with a combined significance of 2.1 standard deviations, indicating the need for further investigation with more data. Upper limits are set on the production cross-section times branching ratio for resonances decaying to Zy across the investigated mass range. When considering spin-0 resonances produced through gluon-gluon fusion, the observed limits at a 95% confidence level range from 65.5 fb to 0.6 fb. For spin-2 resonances produced via gluon-gluon fusion (with quark-antiquark initial states), the limits vary between 77.4 (76.1) fb and 0.6 (0.5) fb. The thesis also highlights the successful Phase-I upgrade of the Tile Calorimeter in the ATLAS detector, ensuring its continued performance. This involved the replacement of degraded Gap-Crack scintillators and Minimum Bias Trigger Scintillators (MBTS) with non-irradiated ones, along-side optimising their geometry, all in preparation for data taking during LHC Run 3. These upgrade endeavors encompassed the design of new Gap-Crack and MBTS counters, including extensions to higher rapidity, the assembly of these counters, their rigorous qualification, and characterization using radioactive sources (90Sr and 137Cs), along with their seamless integration onto the ATLAS detector.Item Magnetic field strength estimations for the main phases of solar cycles 13-24 using magnetohydrodynamic Rossby waves in the lower tachocline(University of the Witwatersrand, Johannesburg, 2024-09) Morris, Tania Mari; Duba, ThamaThe magnetic field strength (MFS) estimates used by the existing space weather prediction models (SWPMs) are inaccurate. Consequently, it has been indicated that there is a need to find solutions to rectify the wrong assumption that the magnetic field remains constant in strength and location throughout the solar cycle. This study explores a solution to this problem by increasing the granularity and accuracy of the previous MFS estimations by calculating them for the main phases of the solar cycle (solar minimum and maximum) per hemisphere for solar cycles 13-24. A dispersion relation of the fast magnetohydrodynamic (MHD) Rossby wave was derived analytically in spherical coordinates that included a toroidal magnetic field and latitudinal differential rotation, which adequately captures the dynamics of the lower tachocline. Secondly, a change to the methodology of calculating the MFS that utilises the established connection between the observed Rieger-type periodicity (RTP) in solar activity of 150-190 days and the fast MHD Rossby wave in the lower tachocline was proposed. Furthermore, a new magnetic field profile (MFP) of Bφ = B0 sin(6Θ) was introduced to improve the model results. This MFP has a maximum and minimum value at the same latitudes associated with sunspot appearances during these extreme solar cycle phases. Consequently, the MFS values were calculated at a latitude of 29◦ (solar min) and 16◦ (solar max) using the hemispheric RTP data. The average MFS (RTP) for the solar min and solar max in the dominant hemisphere was established to be 8 kG (212 days) and 76 kG (163 days), respectively. For the non-dominant hemisphere, the average MFS was established to be 5 kG (213 days) and 50 kG (183 days) for the solar min and max, respectively. The results of this study show a significant difference in the results based on latitude. The findings have also revealed that the periodicity of increased solar activity associated with a specific MFS is affected not only by the solar cycle strength and hemispheric asymmetry but also by the solar cycle phase (or latitude) considered. Additionally, we strongly argue that this study’s MFS results represent reality more closely than previously calculated results. Therefore, we propose that the MFS estimates reported in this study should be considered for the input to various existing space weather prediction models.Item Towards Lifelong Reinforcement Learning through Temporal Logics and Zero-Shot Composition(2024-10) Tasse, Geraud Nangue; Rosman, Benjamin; James, StevenThis thesis addresses the fundamental challenge of creating agents capable of solving a wide range of tasks in their environments, akin to human capabilities. For such agents to be truly useful and be capable of assisting humans in our day-to-day lives, we identify three key abilities that general purpose agents should have: Flexibility, Instructability, and Reliability (FIRe). Flexibility refers to the ability of agents to adapt to various tasks with minimal learning; instructability involves the capacity for agents to understand and execute task specifications provided by humans in a comprehensible manner; and reliability entails agents’ ability to solve tasks safely and effectively with theoretical guarantees on their behavior. To build such agents, reinforcement learning (RL) is the framework of choice given that it is the only one that models the agent-environment interaction. It is also particularly promising since it has shown remarkable success in recent years in various domains—including gaming, scientific research, and robotic control. However, prevailing RL methods often fall short of the FIRe desiderata. They typically exhibit poor sample efficiency, demanding millions of environment interactions to learn optimal behaviors. Task specification relies heavily on hand-designed reward functions, posing challenges for non-experts in defining tasks. Moreover, these methods tend to specialize in single tasks, lacking guarantees on the broader adaptability and behavior robustness desired for lifelong agents that need solve multiple tasks. Clearly, the regular RL framework is not enough, and does not capture important aspects of what makes humans so general—such as the use of language to specify and understand tasks. To address these shortcomings, we propose a principled framework for the logical composition of arbitrary tasks in an environment, and introduce a novel knowledge representation called World Value Functions (WVFs) that will enable agents to solve arbitrary tasks specified using language. The use of logical composition is inspired by the fact that all formal languages are built upon the rules of propositional logics. Hence, if we want agents that understand tasks specified in any formal language, we must define what it means to apply the usual logic operators (conjunction, disjunction, and negation) over tasks. The introduction of WVFs is inspired by the fact that humans seem to always seek general knowledge about how to achieve a variety of goals in their environment, irrespective of the specific task they are learning. Our main contributions include: (i) Instructable agents: We formalize the logical composition of arbitrary tasks in potentially stochastic environments, and ensure that task compositions lead to rewards minimising undesired behaviors. (ii) Flexible agents: We introduce WVFs as a new objective for RL agents, enabling them to solve a variety of tasks in their environment. Additionally, we demonstrate zero-shot skill composition and lifelong sample efficiency. (iii) Reliable agents: We develop methods for agents to understand and execute both natural and formal language instructions, ensuring correctness and safety in task execution, particularly in real-world scenarios. By addressing these challenges, our framework represents a significant step towards achieving the FIRe desiderata in AI agents, thereby enhancing their utility and safety in a lifelong learning setting like the real world.Item Beneath These Saline Stars(University of the Witwatersrand, Johannesburg, 2024) Wilhelm-Solomon, MatthewA plague of drowning strikes an unnamed lakeside city. Hospitals are flooded with patients – primarily Black youth – who have died on soccer pitches, in their homes, and on the streets. A disgraced and divorced white journalist, now working on the arts pages of his newspaper, named Lüderitz Edward Leveza writes a profile on a performing artist and medical doctor, Isiwa: they are tattooed with black lightning, and walk as if on the point of falling. Isiwa is searching for the childhood song stolen from them when police arrested their mother—an activist against the former dictatorship—as a child. They provide Lüderitz information on deaths at the hospital where they work. Lüderitz’s investigation of the drownings takes him deeper into his past, his documentation of torture during the dictatorship, and his entanglement with Isiwa’s life. Together, Isiwa and Lüderitz see inexplicable visions in the city’s sky: men-of-war pass over his apartment block, a shoal of sardines weaves through the tower blocks, and whales arrive to mourn the dead. Isiwa leads an occupation of the city’s Freedom Square in protest against the deaths, but they are increasingly isolated and then arrested. Lüderitz is removed from his job and is mainly alone, punctured by Isiwa’s absence and left longing for them. During this time, he helps a young journalist called Zé in his investigations into the protests and drownings, which lead to a terrifying outcome. Beneath These Saline Stars is an aesthetic reworking of post-colonial journalistic realism and surrealism. It explores moral complicity with violence, loss and queer desire, rebellion and mourning, and the search for healing in a time of concatenated ecological, public health, and political catastrophes. A reflective essay follows the novel, in the form of crônicas – a Brazilian style of fragmentary essay. These explore diverse themes, both theoretical and personal, related to the context, influences and resonances of the novel: transatlantic literature and music; magical realism; créolité and postcolonial thought; Candomblé and climate change. The juxtaposition of these fragments aims to illuminate the personal, literary and political tides from which Beneath these Saline Stars took form.Item Bridging the Gap: Achieving Professionalization Through Memes(University of the Witwatersrand, Johannesburg, 2024) Greaves, Megan; Parkins-Maliko, Natasha‘Bridging the Gap: Achieving Professionalization through Memes’ focuses on how social media is a useful marketing tool that South African Sign Language interpreters can use to promote the professionalism of interpreting. Up to now, there has been little focus on the ways South African Sign Language interpreters can use social media memes/behaviours to promote and advocate for the mainstream recognition of interpreters. This research bridges that gap by conducting a discourse analysis of the various hashtags South African Sign Language interpreters can employ to promote their personal brands as well as the brands of interpreting agencies. It also looks at the various social media strategies individuals and companies use to reach wider audiences. Although social media is a useful tool to promote professionalism, it does not come without its risks and ethical concerns. These risks are discussed in depth, and it is imperative that interpreters keep these risks in mind when using social media.