Electronic Theses and Dissertations (Masters)
Permanent URI for this collectionhttps://hdl.handle.net/10539/37972
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Item Modelling the badminton jump smash for injury prevention and performance enhancement(University of the Witwatersrand, Johannesburg, 2023) Chohan, Raees Ghalib; Mangera, TaahirahBadminton is considered the fastest competitive racket sport. To gain a competitive edge, athletes commonly execute a forward jump smash to return the shuttlecock with high speeds and steep angles. Research has shown that common injuries in badminton, resulting from incorrect landing during the execution of the jump smash, include rupture of the Achilles tendon and Anterior Cruciate Ligament (ACL). There is a need to identify safe landing techniques to minimise risk of injury while preserving the performance of the manoeuvre. This study involved assessing four different landing techniques. The techniques involved varying the initial contact with the ground upon landing. The landing techniques assessed were the Normal Landing Technique (NLT), Toe-First (TF) technique, Flat Foot (FF) technique and the Heel First (HF) technique. Data was obtained using an Xsens motion capture suit which uses inertial sensors placed on body segments to capture kinematic and kinetic data. Sixteen athletes from the South African Badminton team participated, however, only data from ten athletes were considered due to the experimental obstacles identified during the analysis of the data. Kinematic data, Newton- Euler equations and inverse kinematics were used to model the ground reaction forces and moments at the foot, ankle, knee and hip joints. The ground reaction forces were validated alongside data collected from a Bertec Force Plate. By use of the Stretch-Shortening Cycle, the force vs time profile of each landing technique was assessed to classify if a landing technique was “good,” “moderate” or “poor.” The angular velocity of body segments was also assessed at various phases of the jump smash to determine the effect on performance. The study found that there are no statistical differences in the ground reaction forces when varying the landing technique. When analysing the force vs time profiles during landing, the Normal Landing Technique (NLT), which typically involves landing on the ball of the foot, and the Toe- First (TF) technique exhibited spring like characteristics and were therefore classified as good landing techniques. The Flat Foot (FF) and Heel First (HF) techniques displayed impact peaks and were therefore considered poor landing techniques. The Heel First and Flat Foot techniques produced the largest reaction moment at the floor and in all lower limb joints, therefore contributing to a higher risk of injury. There were no statistical differences in segment angular velocity when varying the landing technique. Further analysis on differences in biomechanical responses between male and female athletes is advised.Item Magnetically Enhanced Vacuum Arc Thruster for Nanosatellites(University of the Witwatersrand, Johannesburg, 2024) Rencken, Tristan MarkThis dissertation describes the development and testing of a magnetically-enhance Vacuum Arc Thruster (VAT) with various cathode materials and magnetic field strengths. The thruster uses a Power Processing Unit (PPU) used to generate a high-voltage spike to initiate and maintain a high current arc discharge. A multi-layer solenoid coil is placed around the arc discharge to investigate the effects of pulsed magnetic fields on the ion density distribution. The VAT produces consistent arc discharges with a peak arc current of IApk ≈ 270 A with a pulse length of tp ≈ 3.5 ms for three cathode materials, Fe (iron), Al (aluminium), and Cu (copper). The magnetic field generator uses a separate capacitive discharge circuit which produces field strengths between⃗ B = 0 - 250 mT along the center line of the thruster. Research was conducted to determine the effects of applied magnetic fields to the ion density distribution of ions with the VAT plasma plume. Ion-to-arc current ratios were normalised to a baseline VAT to directly compare qualitative distributions for the various materials and magnetic field strengths. The application of a magnetic field results in the increase in peak ion-to-arc current ratios with a decrease in ion-to-arc ratios at higher angles from the center line. The increased peak and narrowing of the ion distribution suggests that the magnetic field causes ion collimation within the plasma plume. For 0 <⃗ B < 250mT, performance increase over the non-magnetic case is observed with the best percentage increase in thrust factor of 16.4% for Al, 10.8% for Cu, and 6.3% for Fe, obtained at⃗ B ≈ 150 mT. For⃗ B > 150 mT, the ion distribution is shown to result in higher ion-to-arc ratios at higher angles perpendicular to the center line resulting in greater momentum loss. The greatest thrust factor increase of Al was found to be as a result of the mass-to-charge ratio of the Al ion which is subjected to greater accelerations due to Lorentz forces. The application of an axial magnetic field was found to increase the thrust factor and result in improved VAT thrust performances.Item Uncontrolled aerobatic tumble manoeuvre mechanics(University of the Witwatersrand, Johannesburg, 2024) Piccolo, Stefano FabrizioDespite advancements in aerobatic aircraft, the issues concerning aerobatic flight safety remain largely unresolved with incidents occurring at airshows, during training and during private flights, even with stable, predictable and reliable aircraft. The likelihood of aerobatic incidents has increased as aircraft are now capable of being flown in even more dangerous, low energy scenarios. Spins or tumble manoeuvres are typically the origin of loss-of-control accidents. Such scenarios occur generally in manoeuvres that result in low energy states. This dissertation aims to understand the mechanics behind a low energy aerobatic manoeuvre. The positive 𝑔 tumble manoeuvre was selected as the manoeuvre to analyse, as it is one of the most difficult aerobatic manoeuvres to recover from. The Extra 330SC was selected as the model aircraft as it is one of the most popular aerobatic aircraft across all pilot skill levels. Additionally, the Extra Aircraft Corporation provided more information about the aircraft than any other aerobatic aircraft manufacturer. Methods to develop mass, inertial and aerodynamic data were explored. The aerodynamic data was extended to high angles of attack. Aerodynamic models for the wing, fuselage, horizontal stabiliser and propeller were considered. Generated mass and inertial data were compared to reference data and demonstrated good correlation. Static aerodynamic data was compared to published experimental data (where possible). Good agreement was shown between the generated data and test data. Considerations for surfaces exposed to propeller slipstream and rotational dynamics were considered. No literature was available for direct comparison of these considerations. A non-linear three degree of freedom model was developed to simulate the tumble manoeuvre. This was achieved by simplifying the equations of motion in the velocity axes. The velocity axes were appropriate in determining the flight path of the manoeuvre along with all affiliated parameters. The aircraft body axes were utilised in determining the rotational parameters during the tumble manoeuvre. Force components at high angles of attack were modelled in both the velocity and body axes. The current model does not include any lateral-directional forces or moments, assuming the manoeuvre is purely in the longitudinal plane. A tumble manoeuvre is possible for a very specific aircraft configuration. An upgraded engine and propeller slipstream effects are essential in performing the tumble manoeuvre. It was shown the entire manoeuvre could be completed in a horizontal distance of ≈ 50 m and a vertical distance of ≈ 15 m for manoeuvre entry velocities of 25 m/s, 30 m/s, 35 m/s and 40 m/s. Each of the minimum radius tumble manoeuvres occurred at the most rearward centre of mass location. An entry velocity of 30 m/s provided the smallest possible radius tumble. The entry to the manoeuvre requires large decelerations and normal forces that were beyond the lift limits of the wing. Both these requirements were met by orientating the aircraft at large pitch angles and subsequently large angles of attack. The large angles of attack resulted in large decelerating forces and orientated various aircraft force components, other than iii the wing, in the lift direction. Significant energy loses are seen through the manoeuvre resulting in large losses in airspeed and ultimately altitude. The risks associated with a tumble manoeuvre could be minimised by adjusting the normal forces and moments acting on the aircraft. By altering the propeller blade pitch angle, the normal forces and subsequently the moments from the propeller could be changed, altering the overall normal forces and moments acting on the aircraft. This resulted in a slightly larger overall manoeuvre but illustrated increased velocity values throughout the manoeuvre. A form of validation of the results was performed by comparing model results of tumble manoeuvres that were generated through a patchwork of images compiled from video footage of the manoeuvre. Good correlation was shown between the model data and video footage.Item Water Management Practices of South African Electricity Power Plants(University of the Witwatersrand, Johannesburg, 2024) Mkhize, Zama; Sunjka, BernadetteSouth African (SA) power plants are experiencing several challenges when managing water usage and containing it within their clean and dirty water dams (leading to water wastage and pollution). Numerous reasons have been provided to explain the increased water usage. However, the key issue is understanding the causes of high-water use that leads to dam overflows and pollution of the natural water streams/rivers and groundwater system. The main aim of this research, thus, sought to establish the causes of high-water usage in thermal power plants in South Africa. The objective to identify where and how water wastage occurs in the system, any variations from the power plants' standard operating procedures (SOPs) contributing to water wastage and finally, recommend solutions to address the gaps. Qualitative research was conducted through semi-structured interviews at two power plants (namely Power Plant 1 and Power Plant 2) to provide an understanding and detailed information on water use at thermal power plants in South Africa. The standard operating procedures and policies that govern and control water processes were analysed. As a result, the study showed that the most significant cause that came out of the interviews was leadership, followed by financial constraints, negligence (of the plant and water) and lastly, maintenance. Water management is failing and needs to be improved, with the primary challenges being maintenance and a lack of leadership decision-making. Further research on the remaining power plants will be required to determine the generalisability of the findings.Item Supply Chain Risk Management in Manufacturing Small and Medium Enterprises: A Systematic Literature Review(University of the Witwatersrand, Johannesburg, 2024) Pungula, Vusumuzi; Sunjka, B.Background: Small and Medium Enterprises (SMEs) are becoming major actors in the manufacturing sector due to the rising complexity of global supply chains. However, they still face enormous risks from supply chain disruptions and market dynamics, which can have costly effects. SMEs sometimes lack the means and expertise to execute comprehensive risk management plans intended for larger businesses, despite their significance. Research on Supply Chain Risk Management (SCRM) specifically for small and medium-sized enterprises (SMEs) is noticeably lacking, especially in the manufacturing sector. Purpose: The aim of the study was to systematically review how SCRM has been developing in manufacturing SMEs globally over the past two decades, and provide insights for policymakers, industry associations, and SMEs themselves. Method: A Systematic Literature Review (SLR) was conducted by utilizing a qualitative research approach. Seven key phrases were formulated to guide the search for relevant articles published between 2000 and 2023. A thorough screening process was employed to select 38 articles that met inclusion criteria, and data analysis was performed using NVivo software on these articles. Following this, thematic analysis and textual narrative synthesis methods were employed for data analysis and synthesis. The discussion of the identified themes provides comprehensive insights to policymakers, industry associations, and SMEs into the current status of SCRM research in manufacturing SMEs globally. It highlights the importance of effectively addressing risk variables, developing tailored SCRM approaches, and striking a balance between risk reduction efforts and strategic opportunities within supply chains to enhance resilience and ensure operational continuity. Results: The review revealed a significant increase in SCRM research pertaining to manufacturing SMEs over the past decade. Trends analysis indicated a growing emphasis on SCRM in various disciplines, highlighting its increasing significance. Thematic analysis identified eight key themes, including the current status of SCRM research and factors influencing SCRM strategies in manufacturing SMEs. Conclusion: Based on the comprehensive review of literature, several key conclusions can be drawn. There is prevalent recognition of the importance of SCRM within SMEs, emphasizing the need for proactive risk mitigation strategies tailored to the SME context. While formal risk management approaches are increasingly adopted, the context-specific nature of risk management practices highlights the importance of tailored approaches. Technological advancements play a significant role in enhancing SCRM strategies, alongside the integration of green supply chain management practices.Item The improvement of the on-time delivery for “company x” e-commerce orders during the golden quarter(University of the Witwatersrand, Johannesburg, 2024) Sukazi, Thobile Nomalungelo; Sunjka, BernadetteE-commerce has revolutionized global business and consumer interactions, offering convenience and accessibility across various domains like Business-to-Business (B2B), Business-to-Consumer (B2C), and Consumer-to-Consumer (C2C). The COVID-19 pandemic has accelerated digital transformation, with South Africa's e-commerce market showing robust growth projections, fuelled by factors such as improved internet penetration and shifting consumer behaviours. The Omni-channel strategy has become standard, with leading players leveraging digital capabilities to maintain market share. Notably, the "Golden Quarter" of retail, encompassing events like Black Friday and Singles Day, presents a pivotal opportunity for retailers to boost profits through strategic promotional efforts. As the market matures, focus shifts to optimizing the final mile of delivery, aiming to improve efficiency and reduce costs. This project seeks to explore tailored strategies for final mile optimization in Company X, aligning with the broader goal of enhancing efficiency and customer experiences in South Africa's growing e-commerce sector. Despite being the second-largest wholesale food distributor in South Africa, Company X experienced significant on-time delivery performance declines, particularly in its discount retailer brand, Banner 3. The analysis identified logistical bottlenecks in the final mile as the primary contributor to these challenges, resulting in an average delay of 4.3 days in the order fulfilment process. Additionally, the study highlighted the importance of addressing these challenges to maintain customer satisfaction, loyalty, and competitiveness in the rapidly evolving South African e-commerce landscape. This study employs a comprehensive framework and systematic approach to investigate the research questions and objectives. A qualitative research design involves one-on-one interviews conducted digitally via Microsoft Teams. Ethics clearance (MIAEC 099/23) was obtained, ensuring transparency and participant understanding. The sampling strategy prioritizes quality over quantity, with six diverse participants selected to provide rich qualitative data. Data analysis follows Braun and Clarke's thematic analysis approach, incorporating triangulation methods and emphasizing thorough documentation to ensure validity and reliability. This research has thoroughly investigated Company X's final mile delivery challenges during the Golden Quarter, providing comprehensive insights and recommendations for enhancement. Key findings underscore the significance of accurate forecasts, planning collaboration, proximity to customers, fleet and technology utilization, customer service levels, and delivery types in optimizing delivery performance. Recommendations encompass advanced forecasting models, collaborative planning efforts, tailored customer promises, technological enhancements, and automation to address identified challenges and capitalize on opportunities for improvement. The proposed strategies offer a strategic roadmap for Company X to enhance efficiency, customer satisfaction, and competitiveness in the e-commerce landscape, aligning with the study's objectives and concluding the project successfully. The tailored recommendations contribute valuable strategies for improving efficiency, customer satisfaction, and competitiveness. Future research could focus on evaluating the implementation of these strategies and exploring emerging technologies to further optimize the delivery process and adapt to evolving market dynamics.Item Characterisation, Modelling, Finite element analysis, and optimisation of hyperelastic materials for Non-Pneumatic Wheels(University of the Witwatersrand, Johannesburg, 2024) Bhartu, Saahil; Pietra, FrancescoThis abstract concludes the exploration of hyperelasticity within the context of mechanical engineering. Through this section, we have delved into the substantial elastic deformations characteristic of hyperelastic materials, their capacity for energy conservation during deformation, and their inherently non-linear behaviour. The calibration of non-linear material models has been informed by a rigorously designed experimental regimen, where preferred methodologies and necessary precautions were identified to ensure the integrity of the data obtained. Theoretical foundations for the development of constitutive models have been established, with a discussion of prevalent models frequently employed in engineering applications. Practical modelling applications introduced have provided a tangible context for the utilization of hyperelastic material models. While our focus was predominantly on nearly or fully incompressible materials, foundational concepts for compressible behaviour were also addressed, setting the stage for further investigative pursuits. Polyurethane (PU) materials exemplify hyperelastic behaviour. Through computational simulation, we assessed the deformation in a structured wheel to be 4.6mm, utilizing a 9;5 and 2 parameter Mooney-Rivlin model for the PU material. Experimental testing was conducted measuring deformation to be 4.1mm From the results, the deformation patterns, stress distributions, and contact pressures were analysed, indicating the wheel’s ability to endure a contact pressure of 7.36MPa, deformation of 4.6mm, Von-Mises stress of 3.9MPa. This investigation not only corroborates the distinctive properties of hyperelastic materials but also illustrates how analysis results can inform and optimize design iterations. It demonstrates the practical applications of hyperelastic material models in design engineering, providing a comprehensive understanding that is indispensable for the modelling and analysis of hyperelastic components.Item The assessment of exploration processes in the Upstream Industry to increase exploration efficiency and promote accelerated drilling decisions.(University of the Witwatersrand, Johannesburg, 2024) Tshikovhi, Rilwele Mikovhe Muditambi; Botha, A.During petroleum exploration, petroleum companies (operators) require efficient hydrocarbon detection and delineation methods to locate petroleum prospects and promote drilling (Selley, 1998). The two pre-drill surveys under investigation in this study are seismic surveys and controlled source electro-magnetic (CSEM) surveys which are used to study the subsurface during offshore petroleum exploration. Drilling dry holes is inevitable, however, a proper and thorough prospect evaluation can significantly increase the chance of success of a prospect (Milkov & Samis, 2020). The purpose of the research is to evaluate seismic and CSEM surveys as secondary hydrocarbon detection tools used to recommend drilling, and to also determine if any of these methods can encourage accelerated drilling decisions and significantly reduce exploration risk. A total of 49 seismic-based samples and 41 CSEM-based samples were used in the study. Survey anomalies were assessed against drilling results to determine the predictive strength of each survey. The Chi-test confirmed that there is a significant association between survey anomalies and attributes such as well results, predictive strength, fluid type and trap style. The researcher analysed the two datasets to determine the probability of an anomaly in each survey and the chance of success if each well is drill based on these surveys. The presence of an anomaly was defined as a positive anomaly (PA) and the absence of an anomaly was defined as a negative anomaly (NA). Fluid type and trap style were used to analyse the predictive ability of the survey anomalies. Seismic and CSEM surveys have indicated a high probability of discovering charged reservoirs in a structural trap as compared to stratigraphic traps, however, CSEM is slightly better than seismic surveys in defining these reservoirs. Both surveys have a low probability of predicting a charged stratigraphic reservoir, although seismic surveys have indicated higher chance of success as compared to CSEM. Positive anomalies observed in both surveys proved to be good indicators of gas-bearing reservoirs as compared to other hydrocarbon fluid. CSEM has a slightly higher chance of predicting oil than seismic surveys. A simplified process mapping for the current offshore exploration processes was conducted. A decision tree was used to analyse seismic and CSEM surveys as secondary tools with emphasis given to their hydrocarbon detection capabilities. Bayesian Theorem was used to calculate the posterior probabilities given that a well is drilled on a positive iii anomaly. The same was applied for wells drilled on negative anomalies. The results have indicated that CSEM has a higher probability of detecting hydrocarbon accumulations as compared to seismic surveys.Item Investigating the impact of Railway Signalling Performance on Railway Operations & Performance in South Africa(University of the Witwatersrand, Johannesburg, 2024) Naidoo, Pranell; Sunjka, BernadetteThe South African railway was once an attractive and thriving industry, serving as a catalyst for socio-economic growth and opportunities (George, Mokoena and Rust, 2018). However, in the past decade, the South African freight rail service has become uncompetitive, unreliable, and ineffectively integrated to other modes of freight transportation (The World Bank, 2023). Railway signalling systems are a vital component of the rail network as it ensures that trains travel safely and the rail network is operating at optimal capacity (Zhang et al., 2021). This research focuses on investigating the critical factors contributing to poor railway signalling performance in South Africa, and the impact that these risk factors have on the performance of railway operations, safety and the organization. A critical literature review revealed a gap in the knowledge and understanding of the systemic factors contributing to poor signalling performance. In the effort to close this literature gap, a holistic approach was adopted to develop a conceptual framework which presented factors identified from literature which affects the performance of railway signalling systems. This research adopted a qualitative research approach to achieve the objectives of this research. Semi-structured interviews were conducted with railway signalling and operations professionals. Thematic analysis was used to identify emergent themes from the collected data. The findings identified several factors contributing to poor signalling performance, some of the major identified factors were theft and vandalism, loss of critical skills, lack of investment and budget, managerial issues, ageing infrastructure, inadequate maintenance, human factors, etc. The research findings concluded by outlining the recommendations for future research to address theft and vandalism through collaborative strategies and initiatives, obtaining investments through public-private partnerships, addressing the skills shortage through effective skills retention programs, upgrading the freight rail signalling systems, optimizing the maintenance philosophy, and expanding the research into the passenger rail network to improve railway signalling systems in South Africa.Item An analysis of factors leading to the production of defective wagons in Transnet Engineering(University of the Witwatersrand, Johannesburg, 2024) Nemakhavhani, Pfananani Thelma; Dewa, Mncedisi TrinityRail manufacturing industries play a crucial role in many countries by developing cost-effective transportation solutions to move freight more efficiently. To date, the industry has seen the implementation of traditional quality management practices that are critical in driving efficiencies and better-managed operations to improve the quality of their freight wagons. Despite the conventional quality management techniques, the rail industry continues to manufacture defective rolling stock due to design changes, errors and omissions, and inadequate skills. Over the past few decades, industry and academia have identified various factors contributing to rolling stock manufacturing defects. Nevertheless, which factors were predominantly responsible for the defective wagon production at the Transnet Engineering (TE) Bloemfontein factory remained unclear. Identifying the most prevalent causes of defects is essential in addressing the organisation's quality issues. The primary purpose of this study was to gain insights into the root causes of the defects and recommend strategies to minimise them. The study used an interpretive methodology to identify the root cause of defective wagons produced at TE. Data was collected using purposive sampling. Ten experienced TE employees actively engaged in freight wagon manufacturing were selected for face-to-face interviews. During the research study, the interviews were conducted with the employees using a semi-structured format that allowed for open-ended questions. Investigative techniques, such as cause-and-effect diagrams and the Five "Whys" root cause analysis tool, were used to investigate defects' root causes on the customer complaints register. Additionally, thematic analysis was applied to thoroughly analyse the interviews conducted with the employees, which allowed for a deeper understanding of the issues at hand. The findings showed that inadequate skills, human errors and omissions, a lack of quality culture, time constraints, management's failure to enforce accountability, and poor workshop maintenance/machinery all contribute to defective wagon production. The research provided recommendations, including adopting innovative technology and skills transfer programs to enhance the company's quality management practices.