Graduation - 2024 - December (Open Access)
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- ItemAutomated Pre-impact Fall Detection(Stellenbosch : Stellenbosch University, 2024-12) Swanepoel, Mia; Coetzer, J.; Stellenbosch University. Faculty of Science. Dept. of Applied Mathematics.The global population is aging rapidly, with individuals aged 60 and older now outnum- bering children under five. As a result, age-related injuries, including falls, have become increasingly common. Falls are the second leading cause of injury and death in the elderly. Systems such as cameras and wearable devices have been developed to monitor movement and detect falls. Research is now focusing on detecting falls before impact to enable possible interventions, such as wearable airbags, to reduce injuries. Current systems use methods like thresholding techniques and machine learning models to detect falls before they occur. This study examines various models that utilise time series data from a wearable device to detect falls before impact. The models include a thresholding technique, a support vector machine (SVM), a convolutional neural network (CNN), a convolutional long short term memory (ConvLSTM) network, a transformer, and the state of the art iTransformer. The data used in this study to train and test the models is the KFall dataset which includes 2729 activities of daily living (ADLs) and 2346 falls. The ConvLSTM model achieved the longest lead time of 391 ± 109 ms and the largest area under the receiver operating characteristic curve (AUC) of 0.94 as well as the best sensitivity and specificity trade off. The iTransformer showed promising results with an AUC of 0.84 and lead time of 375 ± 111 ms as well as a notable specificity of 91.22%. This research demonstrates the capability of a thresholding technique and deep learning models to accurately detect falls before impact in order to improve reaction time and reduce fall-related injuries.
- ItemNatural Draft Direct Dry Cooling System Performance at Various Application Scales Under Steady and Transient Conditions(Stellenbosch : Stellenbosch University, 2024-12) Strydom, Wian; Pretorius, J. P.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.Natural draft direct dry cooling systems (NDDDCSs) provide an efficient alternative to traditional forced draft air-cooled condensers and indirect nat- ural draft dry cooling systems. NDDDCSs combine the advantages of these systems, including reduced system complexity, direct condensing, and lower auxiliary power consumption. This study developed 1-Dimensional (1-D) numerical, 3-Dimensional (3-D) computational fluid dynamics (CFD), and co-simulation models to character- ize the steady-state and transient performance of NDDDCSs with vertically arranged heat exchanger bundles. These models were applied to three appli- cations: a large coal-fired power plant (900 MWt), a concentrated solar power plant (100 MWt), and a water desalination plant (1 MWt). The steady-state 1-D and 3-D CFD models were validated against 3-D CFD results from lit- erature, which in turn matched large-scale experimental data under no-wind conditions. The transient models were validated against their steady-state counterparts. Steady-state 1-D simulation results show that increasing the ratio of to- tal tower height to inlet diameter (H₅/d₃) enhances NDDDCS performance. Larger outlet diameter to inlet diameter ratios (d₅/d₃) can also improve perfor- mance, although this reduces outlet air velocities, possibly resulting in cold in- flow effects. Lower inlet diameter to inlet height ratios (d₃/H₄) increase steam velocity through the condenser tubes, whereas higher ratios reduce steam-side pressure drops, leading to higher average saturated steam temperatures. Thus, optimal NDDDCS design parameters vary with scale. Steady-state 3-D CFD simulations reveal that recirculation reduces ND- DDCS performance. Air streams from the upper and lower tower regions converge to create low-velocity vortices in front of most heat exchanger deltas, causing localised reductions in air mass flow rates and increased inlet air tem- peratures, resulting in reduced outlet air temperatures. Under a 6 m/s cross- wind, NDDDCS performance decreases at all scales, with medium- and small- scale systems losing 40-50% in heat transfer rate. Wind mitigation measures are recommended for all scales. Novel performance recovery points are identi- fied as crosswind speeds reach 18 m/s, 15 m/s, and 9 m/s for large-, medium-, and small-scale NDDDCSs, respectively. Transient 1-D simulations indicate that NDDDCS start-up performance does not constrain overall power plant start-up. Step inputs in steam flow admission of 6.25% and 18% from cold start conditions can be managed by large- and medium-scale systems without exceeding statutory pressure limits. Industry-standard thermal load ramps are also effectively managed. Addition- ally, results highlight substantial full and partial load turbine islanding capa- bilities, with load increases of 150% and 135%, respectively, being managed without exceeding typical dry-cooled turbine pressure protection limits. Transient co-simulation results demonstrate substantial reductions in the permissible cold start-up steam flow admission step input for large- (0.8%) and medium-scale (3.25%) NDDDCSs compared to 1-D results. A no-wind, cold start load ramp presents the worst case for NDDDCS start-up performance, exceeding the statutory pressure limit before plant start-up is achieved. How- ever, NDDDCSs achieve start-up effectively under crosswind conditions. Ad- justment of the selected tower-to-heat exchanger arrangement is recommended to improve start-up performance. Finally, co-simulation results confirm the considerable turbine islanding capacity of the system.
- ItemThe effects of climate change on aquaculture in the Western Cape of South Africa(Stellenbosch : Stellenbosch University, 2024-12) Stopforth, Judith-May; Salie, Khalid; Malgas, RhodaThis thesis investigates the impacts of climate change on the aquaculture sector in the Western Cape, South Africa, focusing on both marine and freshwater systems. With global wild fish stocks under significant pressure due to overfishing and climate change, aquaculture has emerged as a critical sector for ensuring food security. However, aquaculture itself is not immune to climate-related challenges, including in regions like the Western Cape, where rising temperatures, erratic rainfall, and shifts in marine conditions are becoming more frequent. The study's primary objectives are to evaluate the effects of climate change on aquaculture production, explore the perceptions of climate change among aquaculture farmers, and assess their adaptive capacity. The thesis is divided into three key chapters: an introduction to the Western Cape's aquaculture sector and climate challenges, a literature review of climate trends and their effects on aquaculture, and a detailed results-discussion based on primary data collected from aquaculture farms. Chapter 1 provides a comprehensive overview of aquaculture in the Western Cape, tracing its origins from early attempts at cultivating oysters in the 17th century to the present-day operations. It outlines the historical context, the current state of the sector, and highlights some of the pressing environmental challenges that threaten its sustainability. Various production systems and value chains associated with each cultured species are discussed, emphasizing the sector's economic importance. Chapter 2 reviews existing literature on climate change's effects on aquaculture, particularly in the context of the Western Cape. Key climate change risks include rising temperatures, shifting rainfall patterns, and the growing occurrence of harmful algal blooms. These changes have adverse impacts on fish growth, mortality rates, feed requirements, and the sustainability of aquaculture operations. The review also examines potential adaptation strategies, including selective breeding for thermal tolerance, changes in feed management, and infrastructure modifications to mitigate environmental stressors, among others. Chapter 3 presents the findings of a survey conducted among 32 aquaculture sector participants across the Western Cape. The survey captures farmers' perceptions of climate change, its impacts on their operations, and the strategies they are adopting to cope with climate variability. Marine farmers, particularly those involved in mussel, oyster, and abalone farming, report significant impacts from ocean warming, increased acidity, and harmful algal blooms. Freshwater farmers, including those cultivating trout and tilapia, face challenges related to droughts, water scarcity, and rising temperatures. While many farmers have taken adaptive measures-such as water conservation, changing feed practices, and diversifying production, among others- some of these strategies may be standard operating procedures rather than direct responses to climate change. Additionally, there remain considerable barriers to further adaptation, including financial constraints and socio-economic issues like load shedding which may overshadow the gradual effects of climate change. This thesis concludes that the aquaculture sector in the Western Cape is vulnerable to climate change yet holds significant potential for adaptation and growth. With targeted support, innovative technologies, and a focus on building resilience, the sector can continue to contribute to food security and economic development in the province. The study emphasizes the importance of strong coordination among all stakeholders and fostering collaboration between government, sector participants, and academia to ensure the sector's sustainability. By addressing these challenges, the Western Cape can position itself as a leader in climate-resilient aquaculture, contributing to both local food security and global sustainability efforts.
- ItemDeveloping and Assessing the Feasibility of a Psychosocial Intervention for Persistent Fatigue for Women with Endometriosis(Stellenbosch : Stellenbosch University, 2024-12) Spyrelis, Alexandra; Roomaney, Rizwana; Loades, Maria; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Psychology.Endometriosis is a complex, poorly understood disease that affects approximately 2% to 10% of women globally. Persistent fatigue renders many endometriosis patients unable to engage in daily life, yet has not received much attention in the academic literature and treatment protocols are almost non-existent. Persistent fatigue is a common symptom of other long-term diseases and the evidence for cognitive behavioural therapy (CBT)-based treatment is strong. This study involved the development of a CBT-based intervention for endometriosis-related persistent fatigue and investigated its feasibility among a group of South African patients. Phase I of the study aimed to describe the lived experiences of fatigued endometriosis patients, utilising existing data attained from a prior qualitative study involving semi-structured interviews with 25 participants. A deductive analytical approach was used to code the data according to five research questions to inform the development of the intervention, namely what it was like for participants to live with persistent fatigue, the impact that endometriosis had in their lives, what they knew about the cause and treatment of fatigue, how they coped with fatigue, and how the people in their lives reacted to their fatigue. The second aim was to develop a psychosocial intervention using the existing evidence base from other diseases for which fatigue is a common symptom and informed by the qualitative findings. An interventionist manual and workbook were created for the Managing Fatigue in Endometriosis (MEND) programme, based on key CBT principles. The intervention was originally intended to be offered face-to-face but given the COVID-19 pandemic, it was adapted to be offered online. The draft programme manuals underwent a review process by expert stakeholders, including my doctoral supervisors, specialised health and mental health professionals, as well as several endometriosis patients, to ensure the relevance and appropriateness of the content. Phase II of the study involved an exploratory, single arm within-subjects evaluation of the MEND intervention utilising mixed methods. The study assessed the feasibility, acceptability, and preliminary indications of effectiveness of MEND among 21 participants. The intervention was offered virtually by trained Registered Counsellors. The study findings demonstrate that the appropriate participants could be recruited from the target group and that the eligibility criteria were feasible, with a high recruitment rate (83%). A lower enrolment rate (49%) was noted, which was mostly due to non-response to communication about the study. Session attendance was relatively low (between 43% to 76% per session), with a 57% completion rate and 28% drop out rate, which was predominantly due to crippling countrywide power outages during implementation. The intervention was well received and found to be acceptable by participants and interventionists alike. While not sufficiently powered to determine effectiveness, the study findings indicate preliminary improvements in fatigue severity, depressive symptomology, quality of life, and cognitive and behavioural responses to symptoms, many of which can be considered to be clinically meaningful, although the improvements were not fully sustained at follow-up. A randomised controlled trial is required to assess the outcomes and treatment gains more definitively, with several recommendations for improvement made.
- ItemPraktiese inklusiwiteit: ’n Hulpbron vir inklusiwiteit in graad 12-Afrikaans Huistaal(Stellenbosch : Stellenbosch University, 2024-12) Solomon, Lynn-Mari; Swart, Marius; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Afrikaans and Dutch.South Africa has a history of segregation and racial discrimination that has drastically affected the socio-economic circumstances and capital (in the sense used by Bourdieu) of previously marginalised groups. The school system and language were both used in promoting the Afrikaner’s political agendas in their attempt to enforce their culture, language (Afrikaans) and ideologies. However, the notion of segregation and (racial) discrimination was not only a problem in South Africa. There was a global inclusivity movement at an international level in response to segregation and discrimination, and South Africa followed in those footsteps. This study looked at the context-appropriateness of the definition of inclusivity in South Africa and proposed a practical resource (lesson template) to promote an inclusive Afrikaans Home Language classroom in the South African context. This was done by largely using secondary resources to formulate a definition appropriate to the South African context. Inclusivity was investigated at micro and macro level and the demographics of Afrikaans in South Africa and South African schools were investigated. Subsequently, a lesson template was compiled that guides teachers to think more intentionally about the inclusion of all learners, whether previously marginalised or not, to provide a truly transformative learning experience to all South African learners in the Afrikaans Home Language classroom. It turned out that the already existing definitions are indeed quite appropriate for the South African context, possibly indicating that the implementation of inclusive teaching practices is the challenge. It therefore underlines the creation of a practical resource to guide teachers in the implementation process. After applying the lesson plan to a hypothetical context with hypothetical learners, the importance of teacher attitudes and pedagogy is again highlighted. However, the actual effectiveness of the lesson plan will only be confirmed with certainty with its application in a real and existing South African Afrikaans Home Language classroom. The findings of this study are of such a nature that they can be applied in all subjects and therefore have the potential to effect large-scale change. It also opens discussions around the role of pedagogy in the successful implementation of inclusive education and possible other avenues for South Africa to realise inclusive education.