Faculty of Engineering and the Built Environment (ETDs)

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End date: 2024Subject: search.filters.subject.SDG-9: Industry, innovation and infrastructure

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    The Role of Chiefs in Land Management in Peri-Urban Customary Areas Of Blantyre, Malawi: The Case of Mpemba
    (University of the Witwatersrand, Johannesburg, 2022-04) Magwede, Chimwemwe Edith; Williamson, Amanda
    Peri-urbanisation is a new form of urbanisation and the peri-urban area is a new kind of multi-functional landscape for urban development. How peri-urban areas are managed matters because they are close to the city and due to high urbanisation rates in most developing countries, these areas will soon be part of the city. If urban peripheries are not well-managed, they will be a challenge for sustainable development. In Malawi, peri-urban areas fall under customary land and chiefs are the custodians of customary land. The study unpacks the role of chiefs in land management, how the National Land Policy and land-related legislation position customary leadership in the governance of land management and how municipal and customary land management systems interact with each other in the peri-urban areas. The study employed a qualitative approach. Semi-structured interviews were conducted and policy and legislation were reviewed. The 2002 National Land Policy of Malawi and land-related legislation were reviewed focusing on the role of chiefs in land management. Although the peri-urban areas fall under the jurisdiction of chiefs, the research reveals that this area is treated as no man's land as there exists an overlap of authorities in the peri-urban areas. The chiefs witness land transactions, advise their people on how to secure their land, and partially guide and manage land, although they are not aware of land regulations and standards. The findings also disclose that there is a lack of coordination within municipal land management systems and between municipal land management systems and customary land management systems. Although the legislation states that chiefs have to be incorporated in land management, these laws have not been fully implemented as there are still in the pilot phase.
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    Why do equity oriented, ‘progressive’ planning policies fail to redress the apartheid city? An examination of Planning Instrumentality in South Africa
    (University of the Witwatersrand, Johannesburg, 2023-09) Klug, Neil; Bénit-Gbaffou, Claire; Todes, Alison
    In the immediate post-apartheid period, the fields of urban planning and housing experienced what some have called a ‘golden era’ during which planning played a significant role in the Reconstruction and Development Programme of the government, through developing new and progressive planning and housing policy instruments. Some of these instruments were designed to expedite the release of serviced land and provide subsidised housing, address the apartheid legacy of spatial segregation and housing backlogs. Despite success in the large number of houses delivered to the poor and increased service delivery to previously disenfranchised communities, by the mid 2000s there was growing criticisms of the state’s failure to redress discriminatory apartheid spatial patterns. South Africa was also experiencing growth in unemployment and inequality between emerging elites on the one hand and the majority of previously disadvantaged in society. This study sought to examine what role planning policy instruments played in failing to address the spatial legacies of apartheid. Acknowledging the wide range of potential variables contributing to this lack of efficacy, the study took an in-depth grounded, research approach. Using three case studies on different planning and housing related policy instruments and suits of instruments, at different phases of the policy cycle framework, it examined whether or not the state had managed to address housing and other inequalities. The first case study involved the examination of the processes and practices in formulating a local eviction policy instrument, the second reflected on housing officials’ engagement with the National Housing Code suit of instruments, and the third examined the practices and processes of implementing the Upgrading of Informal Settlements Programme. The findings of these case studies were that equity oriented, ‘progressive’ planning policies fail to redress the apartheid spatial inequalities because they are either not being selected for use or, where they are being applied, had limited impact because they were being implemented in a watered-down fashion. My thesis shows that there are multiple factors, from broad and complex governance structures to the actions of individual actors, that affect the efficacy of policy instruments.
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    Developing of a parametrically resonw1t vibrating screen, modelling, simulation and dynamic testing
    (University of the Witwatersrand, Johannesburg, 2023-07) Mohanlal, Mishal; Li, Kuinian
    A novel coupled spring pendulum vibrating screen is proposed with the goal of developing efficient screening using parametric resonance. A simple spring pendulum is initially studied to provide the basis of the dissertation. The theoretical model of the proposed vibrating screen is developed using Lagrangian mechanics which includes damping and generalized forces. Two derivations of the vibrating screen are proposed, the first being a 4DOF (degree of freedom) system and the second being a 3DOF system. The 3DOF system is found to present better numerical stability and is thus utilized for the study. It is shown that the 3DOF system is comparable to the simple spring pendulum for the case where initial conditions are applied to similar coordinates. The proposed vibrating screen presents motion which is not indicative of traditional vibrating screens. It is found that a system where attributes are sized for parametric resonance requires far smaller excitation forces to achieve higher accelerations and displacements compared to traditional vibrating screens. The proposed vibrating screen is an unfeasible design due to the large displacements; high foundation loads and limitations on mechanical components. Discrete element method (DEM) simulations of the proposed vibrating screen are performed to study the efficiency with varying inclinations of the mesh deck. The results are compared to a linear motion vibrating screen. The proposed screen requires far less energy compared to traditional vibrating screens and achieves higher efficiencies with larger deck inclinations. The derived differential equations are verified by experimental testing using free vibrations. The numerical simulations and experimental tests present a good correlation. Signal processing is implemented to compare the natural frequencies from the experimental testing and numerical simulations, the results present a good correlation.
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    Support Design Approach for Crusher Chambers: A Case Study of Palabora Mining Company
    (University of the Witwatersrand, Johannesburg, 2023-01) Masole, Nyeleti Venus; Stacey, T.R.
    This report project aimed to design a support system for crusher chambers at Palabora. The research project focused mainly on the two crusher chambers (12m wide by 25m high and 61m long) planned for the Lift 2 project as part of the ore handling system. The main research questions that the researcher sought to answer were; what are the differences between Lift 1 & Lift 2 in rock mass characterisation, classification and the ground control district?; how suitable is the Lift 1 crusher chamber support system for Lift 2?; what could be support requirements for Lift 2 crusher chambers in terms of empirical, analytical and numerical design methods and what are the recommended support design approaches for Lift 2 crusher chambers? The methodology used to design support for the Lift 2 crusher chambers was based on determining the expected failure mode first and then selecting suitable design methods to cater for the extent of failure. This study combined empirical and analytical methods to determine the failure mode and required support system. The results were then validated using Finite Element Method numerical modelling software called RS2 (Phase 2) from RocScience. Research findings revealed that the ground control district, classification and characterisation of rock masses differ slightly between Lift 1 and Lift 2. Jointing in dolerite dykes (DOL) was slightly dense in Lift 2 compared to Lift 1 and was associated with increased mining depth. Furthermore, the Lift 1 crusher chamber support system was found to be suitable for Lift 2 but must incorporate dynamic support. Unwedge (RocScience) analysis simulated wedge type of failure in the crusher chamber walls. The empirical and analytical design approach proposed cable bolt lengths of between 6m and 9 m and 3-4 m for roof bolts with bolt spacing of 1.4 m and 1.0 m respectively. The simulation results using RS2 confirmed that the cable bolt length and spacing were appropriate. The recommended support system was expected to provide sufficient support to the crusher chamber in terms of controlling rock mass deformation and yielding. The general conclusion was that the design approach selected for crusher chambers must be able to adequately represent rock mass behaviour and the support required to maintain long-term stability.
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    Provision of personal protective equipment and sanitary facilities to female construction site workers
    (University of the Witwatersrand, Johannesburg, 2023-09) Nene, Simphiwe; Ozumba, Obinna; Sunjika, Bernadette
    The study was based on an aspect of social justice, namely gender equality in the workplace for the female workers who work on construction sites. The area covered in this study was the health and safety of women in construction in the form of the provision of personal protective equipment (PPE) and sanitary facilities to female workers. This specific focus is largely overlooked. The study explored, female workers’ (end-user) perceptions and experiences on the provisions of sanitary and personal protective equipment through a qualitative approach. The main source of data collection was through semi-structured interviews and further supported with site observations in order to triangulate the interview responses. The results of the study found that the availability of PPE for females in the construction industry has improved as women are provided with female size PPE. However, quality and advanced gender sensitive PPE still needs attention. Sanitary facilities at established sites are generally up to standard. However, female workers still share these facilities with their male counter parts. Sanitary facilities at unestablished sites still need attention.
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    Control of Aerial Manipulators for Contact Inspection
    (University of the Witwatersrand, Johannesburg, 2023-10) Matosse, James; Kuchwa-Dube, Chioniso
    Aerial manipulators are flying robotic systems that consist of a multi-rotor vehicle tailored with one or more manipulators. These systems are promising for contact inspection of chemical plants, boilers, tunnels and chimneys without human intervention. They require sophisticated control algorithms for control and stabilisation of complex varying dynamics due to the flying, manipulating and interacting with the environment. The dynamics of an aerial manipulator are treated as two subsystems, the quadrotor and the manipulator. The quadrotor dynamics are extracted through the Newton-Euler algorithm using quaternion-based orientation instead of Euler angles. The manipulator dynamics are extracted using the recursive Newton-Euler equations for purposes of handling the floating-base effect. A classic impedance control is a widely used effective control for contact force tracking but it requires the location of the environment relative to the end-effector and the environmental stiffness to be known precisely, and mostly- the desired force as a constant. In contact inspection without human intervention, the environmental properties (geometrical and mechanical) are uncertain, causing the classic impedance control method to be less effective. Presented in this study are: an adaptive variable impedance control (AVIC) for force tracking combined with the integral linear quadratic regulator (LQR) for the quadrotor and proportional-derivative (PD) for the manipulator’s navigation control. AVIC has the capability to counteract for environmental uncertainties by varying the impedance parameter (damping coefficient) on-line corresponding to the force tracking error. This control has been utilised effectively in industrial robot manipulators for a stable force tracking performance. So far in the literature, AVIC together with integral LQR and PD controllers have not been applied to aerial manipulators as a control strategy. Since the aerial manipulator is a coupled system, a linearisation process was performed on the quadrotor dynamics coupled with the manipulator to achieve a fair approximation of the non-linear model. This study has improved force tracking abilities through the implementation of AVIC that allows the aerial manipulator to achieve a desired contact force on the inspected contour while the quadrotor remains in a stable position. Finally, the developed system was simulated using MATLAB/SIMULINK program and the attained results proved the effectiveness of the strategy in comparison to the classic impedance control.
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    Model Propagation for High-Parallelism in Data Compression
    (University of the Witwatersrand, Johannesburg, 2023-10) Lin, Shaw Chian; Cheng, Ling
    Recent data compression research focuses on the parallelisation of existing algorithms (LZ77, BZIP2 etc.) by exploiting their inherent parallelism. Little work has been performed on parallelising highly sequential algorithms, whose slow compression speeds would benefit the most from parallelism. This dissertation presents a generalised parallelisation approach that can be potentially adopted by any compression algorithms, with model sequentiality in mind. The scheme presents a novel divide-and-conquer approach when dividing the data stream into smaller data blocks for parallelisation. The scheme, branching propagation, is implemented with prediction by partial matching (PPM), an algorithm of the statistical-modelling family known for their serial nature, which is shown to suffer from compression ratio increases when parallelised. A speedup of 5.2-7x has been achieved at 16 threads, with at most a 6.5% increase in size relative to serial performance, while the conventional approach showed up to a 7.5x speedup with an 8.0% increase. The branching propagation approach has been shown to offer better compression ratios over conventional approaches with increasing parallelism (a difference of 11% increase at 256 threads), albeit at slightly slower speeds. To quantify the speedup over ratio penalty, an alternate metric called speedup-to-ratio increase (SRI) is used. This shows that when serial dependency is maintained, branching propagation is superior in standard configurations, which offers substantial speed while minimising the compression ratio penalty relative to the speedup. However, at lower serial dependency, the conventional approach is generally preferable, with 9-16x speedup per 1% increase in compression ratio at maximal speed compared to branching propagation’s 6-13x speedup per 1%.
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    Evaluation and algorithmic adaptation of brain state control through audio entertainment
    (University of the Witwatersrand, Johannesburg, 2023-12) Cassim, Muhammed Rashaad; Rubin, David; Pantanowitz, Adam
    This dissertation presents the design and evaluation of a system that can alter the dominant brain state of participants through audio entrainment. The ‘rch broadly aimed to identify the possible improvements of a dynamic entrainment stimulus when compared to a set entrainment stimulus. The dynamic entrainment stimulus was controlled by a Q-Learning (QL) model. The experiment sought to build on previous research by implementing existing entrainment methods in Virtual Reality and dynamically optimising the entrainment stimulus. The neurological effects of the stimuli were evaluated by analysing electroencephalogram measurements. It was found that a set 24 Hz entrainment stimulus increased the power of Beta band brain waves relative to a control condition. Further, contrary to existing research, it was found that the entrainment stimulus did not have a notable effect on brainwave connectivity at the entrainment frequency. The study subsequently evaluated if the QL agent could learn to optimise the entrainment stimulus. The agent was allowed to switch between an 18 and 24 Hz entrainment stimulus and succeeded in learning an optimised policy. The QL driven stimulus yielded results that generally exhibited the same characteristics as the set entrainment stimulus when using power and connectivity analysis methods. Furthermore, the power analysis indicated that the QL driven stimulus was able to affect a broader range of frequencies within the targeted band. The QL driven stimulus, additionally, resulted in higher meta-analysis metric values in some aspects. These factors indicate that it was able to have a more consistent impact on targeted brain waves. Lastly, results from participants whose stimulus was controlled by a QL driven stimulus using optimal actions indicated that the optimised actions created a more sustained increase in Beta band activity when compared to any other results, indicating the impact of the optimised policy learned.
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    A Comparative Study of the Efficiencies of Vertical Bracing Practices
    (University of the Witwatersrand, Johannesburg, 2023-11) Saunders, Shawn Wayne Valintino; Elvin, Alex
    The efficiencies of cross sections and configurations applied to vertical bracing are investigated by evaluating reference configurations (RCs), composed of cross braced circular hollow section (CHS) members, against comparative configurations (CCs), consisting of cross-braced Angle members, and single-CHS members. The metrics used to evaluate efficiencies were mass, raw materials costs, and fabrication and erection costs. CCs were found to be more efficient than RCs for most analysed cases, metric and configuration dependent. The following results were found: i. Mass metric a. Crossed-Angle more efficient in 79% of analysed cases. b. Single CHS more efficient in 87% of analysed cases. ii. Raw materials costs metric a. Crossed-Angle more efficient in 92% of analysed cases b. Single CHS more efficient in 88% of analysed cases iii. Fabrication and erection costs metric a. Crossed-Angle more efficient in 90.4% of analysed cases b. Single CHS more efficient in 88.5% of analysed cases Inversions of the efficiency parameter findings, with RCs more efficient than CCs, were observed when: i. RC CHS member slenderness ratios were less than 80-90. ii. CC design loads were greater than 225 kN, 1200 kN and 1500 kN for mass, raw materials and total cost efficiency metrics, respectively
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    Alternative Tenure Options as a Stepping Stone for Urban Land Reform: The Case of Kwa Mai Mai Muthi Market
    (University of the Witwatersrand, Johannesburg, 2024-02) Mnguni, Thobeka; Maina, Miriam M.
    This research uses qualitative methods to investigate the case of the Kwa Mai Mai muthi market located in the central business district of Johannesburg where over the decades informal traders have converted their trading units into residential homes. This case is used to respond to the research question, ‘To what extent is taking administrative action to improve land tenure by offering communities rights to occupy urban land feasible and necessary for advancing the urban land reform agenda?.’ The research acknowledges that popular approaches to improving tenure by converting insecure tenure rights to statutory ownership through the Deeds office has had limited success and resulted in efficiencies due to the high costs and the resources intensive nature of this approach. Instead, the research recommends a necessary transition to improving tenure in innovative, context-specific ways that work to build on existing settlements through taking low-cost and low LOE administrative action.