Faculty of Engineering and the Built Environment (ETDs)
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Item An investigation into equity market timing practices by South African mining companies(University of the Witwatersrand, Johannesburg, 2024) Matumba, LindelaniThis research examines the practice of equity market timing among 30 Johannesburg Stock Exchange (JSE)-listed mining companies from 2006 to 2022. Mining companies, characterised by their capital-intensive nature, rely on management for optimal capital management, which includes both the acquisition of capital through debt or equity and its optimal allocation. The concept of equity market timing, introduced by Wurgler and Baker in the 1990s, suggests that company management may engage in timing the equity market when they perceive their stock to be mispriced. This study incorporated control variables such as market-to-book value (a relative valuation metric that investors use to assess a company's market value in relation to its book value), asset tangibility, degree of leverage, and profitability. Panel regression analysis, utilising both fixed effects and random effects, revealed that market-to-book value was not statistically significant at the 5% level. The overall R-squared value was 58.8%. Given the lack of significance for market-to- book value and asset tangibility, it is recommended to consider other capital structure theories, such as the pecking order or trade-off theory. Additionally, incorporating variables like interest rates and other macroeconomic factors could help address the potential for omitted variable bias.Item Assessing the policies for legalising artisanal and small-scale mining in south africa(University of the Witwatersrand, Johannesburg, 2024) Komape, Ledile Jane; Marshall, T. R.This research examines the regulatory framework of artisanal and small-scale mining in South Africa, discussing issues around whether the current policies are up to the challenge of managing the realities and expectations of artisanal and small-scale miners. The research was conducted through a survey of three focus groups across four areas in South Africa using structured questionnaires and interviews. Data collection involved contacting individuals at the Department of Mineral Resources and Energy, Mine Health and Safety Council, and Mining Qualifications Authority, as well as Artisanal and Small-Scale Miners and mine representatives, and conducting interviews at their offices, homes, or workplaces based on their preferences. Data collected from the three focus groups reveal a disconnect between the goals of the policies and how the artisanal and small miners’ communities experience them, emphasising the need for effective policy implementation, comprehensive education initiatives, and avoidance of unrealistic expectations. Key recommendations of the research include the adoption of digital technologies for monitoring, fostering cooperative models, and encouraging international collaboration between local and foreign operators. It underscores the importance of creating and applying inclusive, equitable and sustainable policies to improve the socio-economic and environmental conditions of artisanal and small-scale miners in South Africa.Item Assessing the Challlenges in the Valuation of Early-Stage Secondary Diamond Deposits(University of the Witwatersrand, Johannesburg, 2024) Ganda, Nair da Conceição de Oliveira Gavião; Marshall, Tania R.Diamond mining is a fundamentally important part of the economy in many countries. Globally, some of these countries are home to early-stage alluvial diamond projects that attract significant interest from investors. Often, these investors need to understand the project’s value to make informed decisions. However, valuing early-stage alluvial projects is a complex and challenging process. This research report identifies and assesses the challenges associated with the valuation of early-stage alluvial projects through a case study of a project in Angola. For the case study, a valuation exercise was conducted using both the Cost Approach and the Market Approach. The research identified challenges specific to the Cost Approach, such as data availability and compliance with internationally recognised Resources and Reserves reporting codes. Likewise, challenges specific to the Market Approach included estimating current commodity prices and checking the performance of alluvial diamond properties on an applicable stock exchange. Additionally, it became clear that complications related to both approaches, such as experience and resource estimation methodologies, need to be addressed before a final valuation range can be determined. Although there are several difficulties, the valuation of early-stage alluvial projects is still possible. Nonetheless, these challenges impact the accuracy, consistency, and interpretation of the valuation results. Therefore, becoming familiar with these challenges and the recommendations made in the report will help valuators avoid potential pitfalls and contribute significantly to the field by guiding more informed decision-making in the valuation of early-stage alluvial diamond projects.Item An assessment of the Angolan mineral taxation regime: considerations for possible improvements on government´s revenue(University of the Witwatersrand, Johannesburg, 2024) Africano, N´djamila Hilifavale Borges; Mtegha, HudsonAngola is host to 36 of the 51 critical minerals in the world and ranks third in mineral exports, totalling over USD 1 billion in 2020, and third in diamond production; Botswana and South Africa hold the top two slots, respectively. These untapped opportunities make the Angolan mining industry an excellent place to invest despite the mining industry contributing less than 1% to GDP and has yet to become a driver of economic diversification. In June 2022, Angola joined the EITI, bringing a welcome improvement in the transparency of the sector´s governance and reform, intended to attract new investors. The study evaluates the effectiveness of the Angolan mineral fiscal system as a tool for maximising revenue for the benefit of its citizens and securing investment (local and foreign) to promote linkages and broad-based national growth and development. Four objectives were examined in this study: (i) Conduct a situational analysis of the current fiscal regime through a comparative analysis of headline rates in regional and international countries; (ii) Qualitative evaluation of the effectiveness and efficiency of the mineral fiscal regime; (iii) Analyse the tax revenues raised by the mining industry between 2011-2021; (iv) Make possible recommendations to improve the current mining tax regime. The study employed a descriptive survey design with a qualitative and quantitative approach for data collection and analysis. The main findings include: (i); Angola's political economy setting resembles that of a hegemonic government characterised by an institutionalised one-party regime whereby the implications on the mineral fiscal regime are multifaceted, affecting investment, regulation, revenue sharing, and sustainability; (ii) Both mineral royalty and corporate income tax rates, are within regional and international norms and have consistently contributed a significant share of the government's direct tax revenues over the last eleven years; (iii) Prevailing fiscal regime can be improved through a combination of tax instruments such as resource rent-tax or profit-based royalty with a basic ad valorem tax system; (iv) However, Angola’s primary challenges point to a possible absence of enforcement and compliance mechanisms for both the mining code iii and the sector fiscal framework, as well as the need to strengthen government agency capacity to oversee and gather fiscal contributions from the sector. In light of these findings, it is recommended to (i) Improve the sector's mining code and fiscal legislative framework and enforce it; (ii) Conduct a study to analyse the effects of all government taxes (direct tax, indirect tax and non-tax instruments and tax incentives) on both the industry and the government´s treasury; and (iii) Conduct further studies on the proposed optimal mineral fiscal regime. Finally, an effective, efficient, and transparent mineral fiscal system can only exist first and foremost through intentional collaboration and alignment of objectives among the sector’s stakeholders.Item Systems approach to improve utilisation of autonomous drilling at an open pit mine in South Africa(University of the Witwatersrand, Johannesburg, 2024) Talane, Tabotabo; Botha, AndriesMining companies have opportunities to feed the continuously growing global economy. However, these opportunities come with challenges. Technologies like drilling automation can help combat these challenges while improving operational efficiency. Although the importance of investing in technology is well appreciated, mining houses still struggle with the sustainable and effective use of introduced technologies. This study looks at the challenges faced by one of the open pit mines in South Africa. The case study mine has introduced ADS (autonomous drilling system) to aid in improving both health and safety, and operational efficiency, but utilisation of the system remains low. The aim of this study is to investigate potential causes of the problem and to come up with an actionable solution to tackle the challenges faced and improve the use of ADS. Six semi-structured interviews were conducted where experts in the field of autonomous drilling shared their insights into factors affecting the adoption of ADS. The interview data were recorded, transcribed and analysed using thematic content analysis. The analysis of the interview data yields seven themes: stakeholder engagement and buy-in; management support and trust; process management and KPIs (key performance indicators); ownership, accountability and influence; site capability; culture and attitude shift; and implementation approach. Using the systems approach and soft systems methodologies (SSM), the study found that effective stakeholder engagement and communication with workers early in the project can lead to a positive attitude towards the introduced system, improving its adoption. Further, management support becomes vital to build trust and team resilience, especially during challenging times. Additionally, the way of managing processes must evolve and adapt to accommodate the technology system introduced, and this requires a mindset shift from a leadership perspective. Operating standards and procedures of the entire drilling process, from planning to execution, also need to evolve with the introduction of technology to ensure that upstream processes become enablers of the effective use of the technology. Like standards and procedures, key performance indicators are those metrics that managers track, and they also need to be updated to allow accountability and ownership around the use of technologies like ADS. With commitment and drive from operational leaders, technology implementation can succeed. The correct implementation approach will increase the chances of success. The approach must be guided by an effective stakeholder engagement and requirements analysis. A proper approach in tandem with both management support and team commitment can result in the sustainable adoption of new technologies, including ADS.Item An Investigation Into The Propulsive Force Generation Of Multiple Flapping Surfaces(University of the Witwatersrand, Johannesburg, 2024) Mabvuu, Never; Ho, WeihuaThe aerodynamic performance of flapping NACA0012 airfoils was analyzed through numerical simulation, focusing on the effects of stagger, gap, phase difference, and the number of airfoils. The simulation was conducted under specific conditions: 𝑈∞ = 0.2𝑚/𝑠, f=2Hz, 𝛼0=200, C=0.04m, St=0.2 and Re= 8000). The problem was modeled in ANSYS Fluent using a transient viscous approach with absolute velocity formulation, employing the pressure-based coupled solver (PBCS). PRESTO! interpolation and second-order upwind discretization were applied for pressure, momentum, intermittency, turbulent kinetic energy, and specific dissipation rate. Mesh validation and independence studies confirmed that the results were driven by the physics setup, independent of mesh configuration. It was discovered that small stagger and gap at φ=1800 is not good for thrust production as the airfoils produced thrust less than a single airfoil with ∆Ctav = -0.94. However, lift production is increased and ∆Clav =1.2. At larger spacing ∆Ct, ∆Cl and η generally become constant. One of the worst performing cases (X=1.0C;Y=0.5C; ϕ= 1800 ) was improved by making the aft airfoil lead ( φ= -450 ). This explains why insects alter φ or frequency depending on the situation and flight requirements. The most effective X-Y- ϕ were found to be the ones at which flow separation is suppressed. For the 4 airfoils cases the fore pair performed better than the aft pair for the small spacing case. When spacing was increased the aft pair performed better than the aft pair.Item Factors influencing innovation in public healthcare in South Africa: A critical analysis(University of the Witwatersrand, Johannesburg, 2024) Nkosi, Mbali Rosemary; Siriram, RajenlallHealthcare innovation has proven to reduce morbidity and mortality rates by enhancing healthcare delivery. Most of the South African population depends on the public healthcare system for health needs. The morbidity and mortality rates in South Africa are much higher compared to other middle-income countries in the world. To enhance healthcare delivery in South Africa, understanding the factors that influence innovation in public healthcare is important. Therefore, this research aims to provide a comprehensive understanding of the factors influencing innovation in public healthcare in South Africa and the potential impact of innovation on the country's healthcare system. The main objectives of this study are to determine the level of successfully implemented innovation in public healthcare and the factors influencing it. Existing literature identifies several factors that influence innovation in public healthcare, including design empathy, technological infrastructure, decision-makers, human capital, and organisational culture. This study also investigates the readiness of the public health sector to embrace innovation and the strategies in place for implementing innovation in public healthcare. A gap was identified in the existing literature. There is evidence in literature is that healthcare innovation centres in South Africa and their impact on the adoption of innovation in public healthcare were only covered marginally by existing literature. To bridge this gap, this study provides results on the status of suitable research and development hubs for testing healthcare innovation prototypes in South Africa and their impact on the adoption of innovation in public healthcare. Currently, there are limited health innovation centres in South Africa. This study posits that an increase in the number of healthcare innovation centres would increase evidence-based innovation which would increase the uptake of innovation in public healthcare. A qualitative research approach was used to acquire descriptive information on the factors that influence innovation in healthcare through interviewing participants. Semi-structured interviews were used as the primary instruments of data collection. The interviews were then subjected to a thematic analysis. One of the significant findings of this research is that the lack of funding in public healthcare hinders innovation in the public healthcare system. Also, the rigorous regulatory requirements pertaining to healthcare innovation tend to cause uncertainty and delays, which in turn reduces the funding available for innovative projeItem The techno-economic impact of a high penetration of embedded generators on South African, Brazilian, Australian and Ugandan distribution networks: A comparative review(University of the Witwatersrand, Johannesburg, 2024) Rakgalakane, Motladitseba Dorcas; Jandrell, IanOwing to current electricity capacity shortages and rising electricity prices in South Africa, customers are opting for self-generation to mitigate the effects of load shedding and offset their electricity bills. In June 2021, the South African government removed the licensing requirement for private generation to encourage the uptake of self- generation, close capacity shortages and promote investment in private generation. While the increase in private generation is seen by the electricity industry as a positive step towards meeting energy supply demands, there are concerns about the impact that high numbers of embedded generation facilities will have on the distributors, i.e., their networks and revenues. The aim of this study was to conduct a review of the technical, economic and regulatory impact of a high number of embedded generators on distributors and their networks. The impact in South Africa is compared with the impact in Brazil, Australia and Uganda. The research study seeks to identify some of the success strategies implemented by these countries to address challenges associated with private embedded generation, and to provide recommendations for South Africa. South Africa compares well with Brazil and Australia in terms of electricity access and installed generation capacity vs population; however, in terms of embedded generation, particularly from variable renewable energy sources, South Africa’s penetration levels are still lower than those of Brazil and Australia, although higher than those of Uganda. The review highlights that the impact of embedded generation is largely driven by technical, economic and regulatory policy changes. The absence of a clear market structure or market direction, enabling legislation and policies, regulatory tools (such as national rules for integration or compensation and unbundled tariffs for some customer categories) make it difficult to minimise the negative effects of a high penetration of embedded generation and to capitalise on potential positive effects. In Brazil and Australia, the success of renewable energy embedded generation is largely a result of clear policy and regulations, which lead and drive positive changes in their electricity industries. Recommendations are made for legislation, policy and regulation changes to support embedded generation, the creation of a clear market structure, and the publication of national guidelines for embedded generation management. In addition, tariffing mechanisms should be reviewed to ensure a fair distribution of costs.Item Improving Iterative Soft Decision Decoding of Reed Solomon Codes Using Deep Learning(University of the Witwatersrand, Johannesburg, 2024) Nkiwane, Kimberly NtokozoTelecommunications in the current information age is increasingly dependent on efficient transmission of data through a noisy channel. Therefore, utilizing For- ward Error Correction (FEC) in the development of decoding algorithms is an active area of research. This dissertation work focuses on exploiting deep learn- ing techniques and error correction techniques to improve iterative soft decision decoding of Reed Solomon codes (RS). The parity check matrix of RS codes is characterized by a dense structure. This directly affects the exchange of soft information during the iterative decoding process. Therefore, to counter this issue, a bit-level implementation is utilized with the proposed decoding approach. Furthermore, additional techniques to add sparsity to the parity check matrix are presented in this research work. The proposed method for adding sparsity leverages the cyclical properties of RS codes to add low rate rows to the parity check matrix. This sparse implementation aids with the exchange of soft information during the message passing stage of the proposed iterative decoding process. The implementation of deep learning techniques to improve iterative soft decision decoders are also presented in this dissertation. The proposed approach makes adjustments to the Neural Belief Propagation (NBP) algorithm for RS codes. The proposed NBP utilizes the sparse implementation presented in this research to improve exchange of soft information. This in turn leads to gains in error correction performance without further adding complexity which is one of the main advantages of incorporating neural networks in the iterative decoding process. Additionally, this dissertation proposes a Graph Neural Network (GNN) imple- mentation for iterative soft decision decoding of RS codes. The approach employs the GNN architecture to construct a fully connected graph. This graph represents a message passing algorithm based on the Tanner graph, with trainable weights assigned to the graph nodes. This implementation improves the error correction performance of the proposed iterative soft decision decoder while reducing the number of iterations required to decode the received vector.Item A linear vibration isolator integrating a non-linear energy sink (nes)(University of the Witwatersrand, Johannesburg, 2024) Waite, Clinton; Li, KuinianThis report investigates the integration of traditional linear vibration isolators with non-linear energy sinks (NES) to enhance vibration control in structures subjected to dynamic loading. Structures often respond to dynamic loads—such as machinery vibrations, seismic activity, and environmental factors—by vibrating at their natural frequencies, potentially leading to resonance and structural failure. Vibration isolation and damping systems, such as linear isolators and NES, mitigate these effects. Linear isolators are effective at higher frequencies but have limited performance at lower frequencies, while NES systems offer broader frequency- range effectiveness. This study explores the effectiveness of combining these systems to optimize vibration control. Through simulation of both simple and complex setups, the research compares the vibration response of traditional linear isolators, NES-integrated isolators, and NES systems combined with additional damping elements. Key findings demonstrate that integrating NES with linear isolators significantly reduces peak transmissibility and improves vibration reduction under harmonic and seismic loading. However, the integration's effectiveness varies depending on system configuration and specific loading conditions, highlighting the need for further optimization. The study also presents a parametric analysis for designing vibration control systems tailored to diverse applications, offering valuable insights for engineering practice in reducing structural vibrations.