Showing items 241 - 260 of 31619

Your selections:

Self-attentive vision in evolutionary robotics

  • Authors: Botha, Bouwer
  • Date: 2024-04
  • Subjects: Evolutionary robotics , Robotics , Neural networks (Computer science)
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63628 , vital:73566
  • Description: The autonomy of a robot refers to its ability to achieve a task in an environment with minimal human supervision. This may require autonomous solutions to be able to perceive their environment to inform their decisions. An inexpensive and highly informative way that robots can perceive the environment is through vision. The autonomy of a robot is reliant on the quality of the robotic controller. These controllers are the software interface between the robot and environment that determine the actions of the robot based on the perceived environment. Controllers are typically created using manual programming techniques, which become progressively more challenging with increasing complexity of both the robot and task. An alternative to manual programming is the use of machine learning techniques such as those used by Evolutionary Robotics (ER). ER is an area of research that investigates the automatic creation of controllers. Instead of manually programming a controller, an Evolutionary Algorithms can be used to evolve the controller through repeated interactions with the task environment. Employing the ER approach on camera-based controllers, however, has presented problems for conventional ER methods. Firstly, existing architectures that are capable of automatically processing images, have a large number of trained parameters. These architectures over-encumber the evolutionary process due to the large search space of possible configurations. Secondly, the evolution of complex controllers needs to be done in simulation, which requires either: (a) the construction of a photo-realistic virtual environment with accurate lighting, texturing and models or (b) potential reduction of the controller capability by simplifying the problem via image preprocessing. Any controller trained in simulation also raises the inherent concern of not being able to transfer to the real world. This study proposes a new technique for the evolution of camera-based controllers in ER, that aims to address the highlighted problems. The use of self-attention is proposed to facilitate the evolution of compact controllers that are able to evolve specialized sets of task-relevant features in unprocessed images by focussing on important image regions. Furthermore, a new neural network-based simulation approach, Generative Neuro-Augmented Vision (GNAV), is proposed to simplify simulation construction. GNAV makes use of random data collected in a simple virtual environment and the real world. A neural network is trained to overcome the visual discrepancies between these two environments. GNAV enables a controller to be trained in a simple simulated environment that appears similar to the real environment, while requiring minimal human supervision. The capabilities of the new technique were demonstrated using a series of real-world navigation tasks based on camera vision. Controllers utilizing the proposed self-attention mechanism were trained using GNAV and transferred to a real camera-equipped robot. The controllers were shown to be able to perform the same tasks in the real world. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
  • Full Text:
  • Date Issued: 2024-04

South Africa’s regulation of mineral mining activities in the area: lessons from the United Kingdom

  • Authors: Karomo, Adelaide Aquiline
  • Date: 2024-04
  • Subjects: Mineral mining activities , Mining law , Deep Sea mining Act
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/64411 , vital:73700
  • Description: As they anticipate the benefits associated with mining polymetallic nodules, polymetallic sulphides and ferromanganese crusts, several States are currently exploring or sponsoring State-owned enterprises and private persons to explore for these mineral resources in the seabed, ocean floor and subsoil beyond national jurisdiction (the Area). However, Africa remains the only region that is not actively participating. To guide South Africa in developing a deep seabed mining regime the thesis begins by identifying the international law regulating the Area and the activities therein. Since the mineral resources in the Area have been declared the common heritage of mankind, this principle as regulated by Part XI of the United Nations Convention on the Law of the Sea (UNCLOS), and modified by the Agreement relating to the implementation of Part XI of the United Nations Convention on the Law of the Sea of 10 December 1982 forms an essential component of this study. As such, the thesis determines, amongst others, the requirements for participating in mining activities in the Area (as set out in Part XI of UNCLOS) and establishes that developing a legislative framework is crucial to exempt UNCLOS States parties from liability associated with the damage caused by sponsored activities. Based on the obligations in international law, the thesis zooms in on three aspects concerning the regulation of the activities in the Area: (i) mining concessions, (ii) the relevant payment system, and (iii) environmental protection measures. In terms of these aspects, how the United Kingdom’s deep seabed mining regime regulates activities in the Area is examined. For this assessment, the thesis pays particular attention to the Deep Sea Mining Act and the domestic licences granted to UK Seabed Resources Ltd (UKSRL). In identifying lessons for South Africa, the thesis assesses the extent to which the United Kingdom’s regime complies with the international law framework and highlights the inconsistencies and legislative gaps. Thereafter, the thesis examines the South African legislative instruments regulating mining activities at sea, such as the Mineral and Petroleum Resources Development Act and the National Environmental Management Act, to determine whether their scope should be amended to regulate mining activities in the Area. As per the observations from international law and the lessons learnt from the United Kingdom's regulatory framework, the thesis argues that South Africa’s current mining framework should not be amended; separate deep seabed mining-specific legislation must be adopted. The thesis concludes by setting out the recommendations for developing such legislation. , Thesis (LLD) -- Faculty of Law, 2024
  • Full Text:
  • Date Issued: 2024-04

Spatiotemporal recharge determination in response to episodic rainfall events within the Central Karoo, South Africa

  • Authors: Williams, Aarifah
  • Date: 2024-04
  • Subjects: Groundwater -- South Africa -- Beaufort West , Groundwater recharge , Hydrogeology
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64459 , vital:73735
  • Description: With inadequate and unpredictable rainfall patterns resulting in a mean annual precipitation of 464 mm, South Africa is classified as a water-stressed semi-arid country. Consequently, between 2015 and 2021, the majority of South Africa was confronted with severe drought conditions, with numerous dams running dry across the country. The Beaufort West Municipality is a prime example of the adverse effects of South Africa's inadequate and erratic rainfall patterns. In Beaufort West, a town located within the Central Karoo region of the Western Cape, groundwater is the primary source of water. Since recharge within the region is episodic, occurring irregularly, understanding the dynamics surrounding recharge in the area is essential for achieving sustainable long-term water resource management. This study aimed to gain a better understanding of how the aquifers within the Beaufort West Municipality Well Fields respond to extended periods of drought, extreme episodic precipitation events and excessive abstraction. This study aimed to quantify extreme recharge in the Beaufort West municipal wellfields using the water-table fluctuation (WTF) method. Additionally, it sought to deepen comprehension of the local climate's interaction with groundwater levels, surface water dynamics, and recharge through a 32-year historical data analysis (1990 to 2022) encompassing precipitation, evaporation, and surface water parameters. Findings revealed the complex relationship between precipitation, evaporation, regional geology, and water abstraction, influencing recharge periods, duration, and mechanisms across different regions within the aquifer system. Groundwater levels exhibited rapid declines during droughts due to extensive well field abstraction, but recovery was evident following episodic high precipitation events in 1993, 1996, 2010/2011, and 2019/2020. This comprehensive analysis serves as a valuable foundation for informed water resource management strategies, emphasizing the need for diversified approaches ensure the long-term water security and resilience of the Beaufort West Municipality. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
  • Full Text:
  • Date Issued: 2024-04

Statistical learning methods for photovoltaic energy output prediction

  • Authors: Magaya, Aphiwe
  • Date: 2024-04
  • Subjects: Photovoltaic power generation , Mathematical statistics , Statistics
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64138 , vital:73656
  • Description: Predicting solar energy accurately is important for the integration of more renewable energy into the grid, which can help to alleviate the energy demand on traditional coal-powered sources in South Africa. This study aims to assess several statistical learning models to predict the energy output of a 1MW photovoltaic system installed on the Nelson Mandela University South Campus in Gqeberha. Weather data (including temperature, wind speed, wind direction, precipitation, air pressure, and humidity) and solar irradiance data (including global horizontal radiation, diffuse radiation, and direct radiation) are used to predict the energy output of this system using Artificial Neural Networks (ANN), Support Vector Machines (SVM), Multiple Linear Regression (MLR), and Regression Trees (RT). The performance of each of the models was compared and the results indicated that the ANN model performed best. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2024
  • Full Text:
  • Date Issued: 2024-04

Statutory conciliation as a labour-dispute-resolution mechanism

  • Authors: Masaya, Ruvimbo Cheryl
  • Date: 2024-04
  • Subjects: Labor disputes -- South Africa , South Africa. -- Labour Relations Act, 1995 , Labor -- Law and legislation -- South Africa , Industrial relations -- South Africa South Africa. -- Commission for Conciliation, Mediation, and Arbitration
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/65701 , vital:74229
  • Description: South African labour dispute resolution is a product of the country’s problematic past which was based on inequality and division. The new political dispensation led to the adoption of the Constitution of the Republic of South Africa in 1996, which enshrined a variety of basic human rights for all people within the Republic. Amongst these rights was section 23, which provided for and still protects the right to fair labour practices for all. In order to further give effect to this right, the Labour Relations Act was promulgated, with section 112 of the Act establishing the Commission for Conciliation, Mediation and Arbitration (hereafter referred to as the CCMA). One of the main mandatory functions of the CCMA is that of statutory conciliation. Statutory conciliation must also be performed by any other accredited bodies such as bargaining councils. The term statutory conciliation refers to a process that occurs under the direction of an impartial third party where parties to a dispute endeavour to reach an agreement in order to settle the dispute. The process is without prejudice and proceedings are intended to help the parties find an amicable solution. It can be a very powerful tool to settle disputes in the labour law context where there are disputes between employers and employees where internal procedures have been exhausted and a deadlock has been reached. Statutory conciliation is the first step where a case has been referred to the CCMA. According to the CCMA, 3 844 169 cases have been referred to it since its establishment in 1996.1 In the 2021/22 financial year thus far, the number of case referrals to the CCMA sits at 156 777, a reflection of how well utilised the mechanism is. The main aim of this treatise is to explore the role of statutory conciliation as a mechanism of labour dispute resolution. The history and development of labour dispute resolution in South Africa will be examined; briefly followed by an explanation of the process of conciliation. The treatise will also consider the limitations of the process of statutory conciliation, as the process is not immune to abuse by parties. Since the advent of the Labour Relations Act, the courts have had to consider various aspects of conciliation, in particular concerning the confidentiality of the process and whether a commissioner may be compelled to testify on the conciliation process at arbitration or the Labour Court. In addition, the ambit of the conciliation commissioner’s functions and powers will also be considered. , Thesis (LLM) -- Faculty of Law, Department of Mercantile law, 2024
  • Full Text:
  • Date Issued: 2024-04

Strategies for amplifying street vendors’ contribution to local economic development in Limpopo: a case study of vendors in Thohoyandou Plaza

  • Authors: Motalaota, Tumiso Molatelo
  • Date: 2024-04
  • Subjects: Street vendors -- South Africa -- Limpopo -- Thohoyandou , Street vendors -- South Africa -- Limpopo -- Thohoyandou -- Economic conditions , Economic development -- South Africa -- Limpopo -- Thohoyandou
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/65241 , vital:74064
  • Description: The study investigated strategies for amplifying street vendors' contribution to local economic development at Thohoyandou Plaza in Limpopo Province. Street vendors have been acknowledged as a critical component of global and South African socioeconomic growth. Nonetheless, very little study has been undertaken in Thohoyandou Plaza with the primary goal of identifying the problems and potential for increasing the number of street vendors. Consequently, this study adds to current knowledge by focusing on approaches for raising the number of street vendors in the area. Access to finance, infrastructure, laws and licensure were among the barriers noted in this study. The sample comprised 23 participants selected through purposive sampling techniques. The study population included street vendors and municipal officers. The study interviewed 18 vendors and 5 government officials who met the criteria and were willing to participate. A literature review was conducted and found that the constraints include partial access to storage services, which explains the inadequate options for street vendors to succeed. The study used qualitative research methodology to attain intended goals. Furthermore, the study used an interview guide to obtain data from individual participants using a face-to-face method. To acquire information from important informants, open and closed-ended questionnaires were also used. Recruitment was done to street vendors who showed interest in contributing to the study. Data were collected through questionnaires and interview schedules. Atlas ti. Version 23 was used in coding and categorising the data according to emerging themes for qualitative data. Views and perspectives of various individuals and previous studies were considered to give a tangible outcome, conclusion and recommendations. Street vendors have challenges such as poor literacy and limited access to financial assistance. Therefore, training on financial literacy, marketing and managerial abilities is required for them to improve their market opportunities. Private organisations should invest in the infrastructure required for the success of street vendors. This will in turn help street vendors to contribute significantly to local economic development while also alleviating unemployment. The recommendation of the current study aimed to advance the working conditions of street vendors, particularly those selling fruits and vegetables. The study's outcomes may aid street vendors by decreasing the obstacles connected with street trade. The findings of the study can support policymakers to address relevant restrictions faced by these street vendors by making it easier to access critical raw materials, which might be challenging owing to financial and seasonal concerns. , Thesis (MA) -- Faculty of Business and Economic Sciences, School of Economics, Development and Tourism, 2024
  • Full Text:
  • Date Issued: 2024-04

Supporting competitive robot game mission planning using machine learning

  • Authors: Strydom, Elton
  • Date: 2024-04
  • Subjects: Machine learning , High performance computing , Robotics , LEGO Mindstorms toys Computer programming
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64841 , vital:73929
  • Description: This dissertation presents a study aimed at supporting the strategic planning and execution of missions in competitive robot games, particularly in the FIRST LEGO® League (FLL), through the use of machine learning techniques. The primary objective is to formulate guidelines for evaluating mission strategies using machine learning techniques within the FLL landscape, thereby supporting participants in the mission strategy design journey within the FLL robot game. The research methodology encompasses a literature review, focusing on the current practices in the FLL mission strategy design process. This is followed by a literature review of machine learning techniques on a broad level pivoting towards evolutionary algorithms. The study then delves into the specifics of genetic algorithms, exploring their suitability and potential advantages for mission strategy evaluation in competitive robotic environments within the FLL robot game. A significant portion of the research involves the development and testing of a prototype system that applies a genetic algorithm to simulate and evaluate different mission strategies, providing a practical tool for FLL teams. During the development of the evaluation prototype, guidelines were formulated aligning with the primary research objective which is to formulate guidelines for evaluating mission strategies in robot games using machine learning techniques. Key findings of this study highlight the effectiveness of genetic algorithms in identifying optimal mission strategies. The prototype demonstrates the feasibility of using machine learning to provide real-time, feedback to participating teams, enabling more informed decision-making in the formulation of mission strategies. , Thesis (MIT) -- Faculty of Engineering, the Built Environment, and Technology, School of Information Technology, 2024
  • Full Text:
  • Date Issued: 2024-04

Sustainable management of the back sourcing of service functions at South African universities

  • Authors: Hashatse, Lebogang
  • Date: 2024-04
  • Subjects: Contracting out -- South Africa , Education, Higher -- South Africa -- Economic aspects , Universities and colleges -- South Africa -- Economic aspects , Universities and colleges -- Management Universities and colleges -- South Africa -- Employees
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/64996 , vital:74004
  • Description: This study employed a three-phase qualitative case study research method to determine whether backsourcing and reintegration of previously outsourced services and workers could be managed in ways that contributed to the long-term sustainability of institutions. To achieve this goal, the study developed a framework for the sustainable management of university-based resources. The framework was a response in support of institutional sustainability after South African public universities were compelled to implement involuntary backsourcing in response to the ongoing #FeesMustFall (#FMF) and #OutsourcingMustFall (#OMF) protests that commenced in the latter part of 2015. An extensive literature review was conducted as part of the study’s phase one. The goal was to obtain insight into management practises used in outsourcing and backsourcing as well as to gain a thorough grasp of the concept of sustainability and its application in resource management in the settings of operations, organisations and universities. The literature demonstrated that there were well-established theoretical frameworks supporting the concepts of backsourcing and sustainability management. These frameworks provided clear outlines of how successful backsourcing and remunicipalisation processes could be effectively managed. Moreover, they highlighted that these management processes could be used by profitable sustainable businesses. This contributed to the development of a theoretical framework for the study. A conceptual framework together with the outcome of the literature review, served as a guide for conducting a qualitative case study at a selected Higher Education Institution (HEI) in South Africa, which was chosen as the primary research site. This constituted phase two of the study. The selected HEI case study established its efficacy in managing the process of backsourcing and reintegration. Furthermore, it demonstrated sustainable ways that contributed to the institution’s overall sustainability. In conjunction with the established theoretical framework and the developed conceptual framework, the selected HEI , Thesis (PhD) -- Faculty of Business and Economic Sciences, School of Management Sciences, 2024
  • Full Text:
  • Date Issued: 2024-04

Synthesis and applications of hydroxyl-functionalized chemosensors for selective detection of ions in aqueous systems

  • Authors: Hamukoshi, Simeon Shiweda
  • Date: 2024-04
  • Subjects: Molecular recognition , Solution (Chemistry) , Water chemistry
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63787 , vital:73613
  • Description: Fluorescent molecular chemosensors are crucial tools for monitoring toxic metal ions and environmental compounds that pose risks to both humans and wildlife. Continuous sensing is essential for early detection, and chemosensors offer a sensitive and straightforward approach by detecting challenging analyte’s through optical absorption and fluorescence. Current detection methods, such as flame photometry and mass spectrometry, can be expensive, destructive, and impractical for continuous monitoring. Consequently, fluorescent-based methods present a promising, simple, and highly sensitive alternative for chemical recognition and monitoring. In this project, we successfully synthesized ten highly selective small hydroxyl containing molecule fluorescent and colorimetric sensors; Oxime Dye (OD), Small Sensor 1 (SS1), Small Sensor 2 (SS2), Quinoline Dye 1 (QD1), Quinoline Dye 2 (QD2), Quinoline Dye 3 (QD3), Coumarin Dye 1 (CD1), Coumarin Dye 2 (CD2), Naphthalene Dye 1 (ND1), Naphthalene Dye 2 (ND2). These chemosensors contained benzothiazole, naphthalene, quinoline, and coumarin fluorophores. These sensors facilitate both quantitative and qualitative assessment of cationic and anionic species in aqueous organic media. The chemosensors were synthesized using modified Schiff base, azo dye, and oxime-based reactions, enhancing binding and selectivity with analyte’s. They exhibited selectivity towards various metal ions (Cu2+, Fe2+, Ni2+, and Hg2+) and anions (hydroxyl and cyanate), characterized by distinct absorption bands and significant fluorescent quenching and enhancement. While some sensors were selective towards both cations and anions, others exclusively targeted cations, showing lower selectivity or sensitivity towards anions upon further testing. Conversely, certain sensors were selective towards anions, demonstrating reduced sensitivity or selectivity towards the tested cations. The oxime-based chemosensor, OD, was obtained through an oxime-based reaction. The sensor demonstrates remarkable selectivity for Cu2+ and cyanate ions. During titration experiments, the interaction of Cu2+ with OD resulted in a noticeable fluorescence quenching effect, while the presence of OCN ions led to fluorescence enhancement. These distinct behaviors strongly suggest the formation of specific 1:1 complexes between OD and Cu2+ or OCN ions, a conclusion supported by detailed analysis using the Jobs plot technique. In addition to the fluorescence studies, investigations into the influence of pH on the sensor OD, as well as its complexes with Cu2+ and OCN, were conducted to determine the optimum pH conditions for their operation. Moreover, reversible behavior of the complexes was explored in the presence of EDTA, revealing that only the OD-OCN complex displayed reversibility. Furthermore, molecular modeling studies were performed to validate the binding units and calculate the energy differences between the sensor and its respective complexes. Additionally, four chemosensors (SS1, SS2, CD2, and QD2) were synthesized and characterized using Schiff-based reactions, showcasing their unique absorption behaviors. SS1 and SS2, characterized by benzothiazole fluorophores, demonstrated high sensitivity to hydroxyl anions. Jobs plot studies revealed a stable 1:1 binding stoichiometry. Chemosensor CD2, incorporating a coumarin fluorophore, was structurally confirmed but showed no significant spectral changes when screened with various ions. Chemosensor QD2 exhibited remarkable selectivity for Fe2+ ions, and stable 1:1 complexes were confirmed. Further molecular modeling studies were conducted to identify potential binding sites. Furthermore, five chemosensors (CD1, CD3, QD1, ND1, and ND2) were synthesized and characterized using azo dye reactions, revealing their unique absorption behaviors. Chemosensor CD1 showed high selectivity towards Hg2+ under both absorption and emission spectroscopy. Job's plot studies confirmed a stable 1:1 complex formation. The presence of competing cations did not affect complex formation, emphasizing its stability and selectivity. Another coumarin-containing dye chemosensor, CD3, was synthesized as a novel chemosensor. In the presence of TBA anionic solutions, CD3 exhibited strong absorption bands and selectivity for OH- ions, forming a stable complex with them. Quantitative studies, including the determination of LOD and LOQ, were also conducted. The binding stoichiometry of 1:1 between CD3 and OH- was established through Job's plot analysis. Lastly, two naphthalene dyes were synthesized. However, they did not exhibit selectivity towards cations or anions. Interestingly, their absorption spectra were affected by the change in solvent system, a concept worth exploring in future work. Chemosensor ND1 and ND2 did not show any cation or anion selectivity. However, they demonstrated different spectra and colour responses to cations and anions in different water-DMSO solvent systems. , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
  • Full Text:
  • Date Issued: 2024-04

Synthesis and applications of novel coumarin-based chemosensors for the detection of metal ions using UV-visible spectroscopy

  • Authors: Myburgh, Lisa
  • Date: 2024-04
  • Subjects: Biosensors , Molecular recognition , Chemical detectors
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64239 , vital:73668
  • Description: Current methods for ion detection are expensive and require trained personnel to operate the instruments. This led to the desire for alternative techniques that are quicker, easier to operate, cheaper, and highly efficient. With this in mind, coumarinbased derivatives were designed and synthesised using Knoevenagel condensation. These compounds were designed to incorporate different functional groups at the 3- position. Compounds S1, S2, and S3 contained keto, ester, and carboxylic acid groups, respectively. The structures of these compounds were confirmed using NMR, FT-IR, and X-ray crystal structures. During UV-Vis analysis, these compounds displayed a maximum absorption band between λmax= 289 and 295 nm, attributed to the coumarin moiety. Furthermore, the absorption behaviour of S2 was analysed in different solvent systems. It was noted that when S2 was dissolved in toluene, a significant absorbance increase and a hypsochromic shift were observed. The chemosensing capabilities of S1, S2 and S3 were investigated using UV-Vis for metal cations in acetonitrile. S1 and S3 showed selectivities towards Fe²⁺ ions, with S2 being selective for Fe³⁺ ions in a 1:1 binding ratio. Reversibility studies were performed using EDTA and revealed that S1 and S3 were partially reversible, with S2 showing nonreversibility properties. Lastly, the binding modes of these compounds with metal ions were determined using molecular modelling studies. These calculations concluded that the complexation occurs via the two carbonyl moieties from the coumarin ring and the ester group and is stabilised by nitrate counterions and water molecules. To change the selectivity of S2 towards Hg2+ ions, thiocarbonyl analogues of this compound were synthesised using Lawessons reagent. The reagent replaced the carbonyl oxygen of the coumarin backbone and the ester moiety with sulphur to form their respective analogues, S5 and S6. A switch in the selectivity of S5 and S6 was noted when tested as potential chemosensors for metal ions. S5 showed a high affinity for Hg²⁺, whereas S6 strongly interacted with both Hg²⁺ and Cu²⁺ ions in a 1:1 binding ratio. The mode of interaction was confirmed to occur between the thiocarbonyl and ester carbonyl group for S5 and between the two thiocarbonyl functional groups in S6. The viability of these novel chemosensors for detecting metal ions was then further tested in water samples obtained from local dams with positive results. , Thesis (MSc) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
  • Full Text:
  • Date Issued: 2024-04

Synthesis of gatifloxacin, an important fluoroquinolone antibiotic using continuous flow technology

  • Authors: Moyo, McQuillan
  • Date: 2024-04
  • Subjects: Antibiotics , Drug resistance in microorganisms , Chemical processes
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/64204 , vital:73664
  • Description: Gatifloxacin belongs to an important class of antibiotics known as fluoroquinolones (the fourth generation). Bristol-Myers Squibb (BMS) introduced gatifloxacin to the market in 1999 under the brand name Tequin® for treating respiratory tract infections. It has recently been widely employed as an ophthalmic solution for treating bacterial conjunctivitis. There is limited literature describing the complete synthesis of gatifloxacin; however, ciprofloxacin, a similar fluoroquinolone, has received much attention recently and is a good guide in the synthesis. Even though there are several similarities between ciprofloxacin and gatifloxacin, key reactions towards the synthesis of gatifloxacin have not been reported, which forms a knowledge gap, for instance, the three steps leading to the synthesis of the benzoyl chloride intermediate. It is estimated that 70-90 % of the active pharmaceutical ingredients (APIs) in drugs consumed in sub-Saharan Africa are imported, mainly from India, China and Europe. To reduce dependence and improve access to life-saving drugs, Africa needs to develop cutting-edge technology that is more advanced than traditional means. We envisage that employing continuous flow technology in synthesising gatifloxacin, previously developed in a batch setup, will offer an improved, future-proof process. Thus, this research aimed to create a more efficient multi-step continuous flow process for synthesising gatifloxacin compared to the current batch methods. The first chapter of this thesis provides an extensive literature review on the synthesis of gatifloxacin and its sister drug, ciprofloxacin. The foreground is based on the manufacture and consumption of APIs, particularly antibiotics. Continuous flow technology is also introduced and discussed as the solution to bridging the gap in Africa’s demand for API manufacturing, which significantly lags. Chapter two describes the results and discusses findings on the continuous flow synthesis of gatifloxacin. A seven-step process is described with reaction optimisation studies for each step, starting from 2,4,5-trifluoro-3-hydroxybenzoic acid. An alternative shorter route (with six steps) is also offered, incorporating microwave-assisted technology instead of the traditional batch process. We also describe several elegant multistep processes for synthesising gatifloxacin and its intermediates, achieved by combining several compatible, optimised steps. Subsequently, Chapter 3 describes all the experimental details of our research. In this study, efficient continuous flow procedures were developed to synthesise gatifloxacin. The seven-step continuous flow procedure we developed afforded gatifloxacin (54 % overall isolated yield) in a total residence time of 15.6 mins, a significant improvement from the reported batch process (52 % overall yield and over 103 hours reaction time). , Thesis (PhD) -- Faculty of Science, School of Biomolecular & Chemical Sciences, 2024
  • Full Text:
  • Date Issued: 2024-04

Technological Pedagogical Content Knowledge (TPACK): investigating senior primary mathematics teachers’ integration of technology in the classroom in Okahao educational circuit

  • Authors: Shikesho, Hilya Ndahambelela
  • Date: 2024-04
  • Subjects: Technological Pedagogical Content Knowledge , Cultural-historical activity theory , Educational technology , Mathematics Study and teaching (Primary) Namibia Okahao , Mediated learning experience , Social interaction
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/423913 , vital:72104
  • Description: The overwhelming advancement of ICT devices in the contemporary Namibian education system has led to their praise for supporting differentiated instruction, fostering collaboration, and engaging multiple intelligences in teaching and learning. Consequently, the compulsory incorporation of ICTs into the teaching and learning process becomes imperative across various fields of study, including Mathematics. However, the integration of technology-based teaching proves to be a complex and challenging issue, often considered a wicked problem. To explore this matter, a qualitative case study was conducted to investigate how Senior Primary Mathematics Teachers integrated technology to develop their TPACK. The study was conducted among the twenty-seven senior primary mathematics teachers in the Okahao educational circuit in the Omuasti region. The study utilized Vygotsky‘s (1978); Socio-cultural Theory, together with Mishra and Koehler (2006), and; the Technological Pedagogical Content Knowledge (TPACK) framework was used as a lens to analyse the data. The data were gathered through semi-structured questionnaires, semi-structured interviews, focus group interviews, and lesson observations. The study findings indicate that senior primary mathematics teachers utilize the available resources at their respective schools during their classroom instruction. The study further reveals that mathematics teachers exhibit a positive attitude toward the integration of technology. The study uncovers the intricate interplay between technological knowledge, pedagogical expertise, and content knowledge within the context of mathematics education. The findings reveal that while participants demonstrate a high level of proficiency in certain TPACK components such as CK, TK, PK, TPK, and PCK, they expressed a moderate level of expertise in TCK and TPCK. The study also identified challenges in TPACK development, particularly the need for subject specific technology training, lack of technological infrastructure, particularly advanced technology, as well as a deficiency in ICT knowledge. The importance of access to various technologies was emphasized, enabling teachers to seamlessly integrate technology into their practices and address diverse learning styles. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
  • Full Text:
  • Date Issued: 2024-04

The Algoa Bay region groundwater cycle – linking source to coast

  • Authors: Dodd, Carla
  • Date: 2024-04
  • Subjects: Ecohydrology , Hydrology , Groundwater -- Management
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63722 , vital:73592
  • Description: Groundwater is a crucial component of freshwater supply globally, especially in water-scarce regions such as semi-arid climatic areas where surface water resources are climatically limited and further constrained during droughts. Groundwater resources are also important from an ecological perspective as they support numerous surface ecosystems including wetlands and rivers. Coastal groundwater discharge along the South African coast sustains supratidal spring-fed living microbialite ecosystems (SSLiME). These systems act as potential analogues for Earth’s earliest ecosystems and are therefore useful from a palaeoscientific and evolutionary perspective. The Southern Cape coast of South Africa is characterised by both fractured and intergranular aquifers and hosts the most extensive network of SSLiME reported globally. However, the region is frequently affected by water scarcity crises and consequently groundwater development and usage has increased. Yet, it is unclear to what extent coastal discharge is linked to inland aquifers and whether anthropogenic activities influence the quantity and quality of groundwater that flows into SSLiME. This thesis aims to assess the groundwater cycle of the Algoa Bay region along the Southern Cape coast by means of a multi-tracer study. Specifically, it endeavours to develop a better understanding of the hydrogeochemical connectivity between inland groundwater resources and coastal microbialite ecosystems. To achieve this, four groups of hydrochemical tracers were used: H- and O-isotope ratios, major cations and anions, organic micropollutants and macronutrients. Sampling strategies included monthly precipitation collection over twelve months (stable water isotopes), once-off groundwater collection from boreholes, inland springs and coastal discharge (all tracers). In addition, coastal groundwater discharge was sampled during a once-off repeat campaign (all tracers) and seasonally at selected sites (macronutrients). A local meteoric water line (LMWL) for the region was established and compared to the isotopic signature of groundwater. The results indicate that groundwater is likely recharged directly and with little evaporation. Furthermore, similarities in isotopic signatures between inland and coastal aquifer systems suggest some level of hydrogeological connectivity or similar environmental drivers of recharge, such as precipitation amount and moisture source. This is also supported by the physico-chemistry and major ionic composition of the groundwater samples. However, the major ion composition of groundwater is variable and, although it predominantly reflects the sodium-chloride nature of precipitation, lithological and spatial trends are apparent. For example, coastward trends such as increasing conductivity, calcium, total alkalinity, and nitrogen is evident. While isotopes and major ions inform on the environmental drivers and geogenic influence on groundwater recharge, the organic micropollutants and macronutrients provide insight into the nature of anthropogenic impacts on groundwater quality. Micropollutants quantified in the groundwater samples included artificial sweeteners, pharmaceuticals, a biocide, and an illicit drug. These compounds are mostly classed as wastewater indicators and indicate aquifer contamination from leaking reticulation systems and septic tanks. The highest concentrations are associated with the urban and coastal peri-urban areas, while groundwater from rural areas is often devoid of any micropollutants except sulfamic acid, which may be introduced during recharge from precipitation. Furthermore, the presence of selected compounds in groundwater discharge signifies that at least a component of the groundwater is derived from recent infiltration. Similarly, the macronutrient content of groundwater reflects the proximal land use. As such, coastal groundwater discharge sites adjacent to coastal villages reflect higher concentrations compared to rural sites. In addition, the nutrient load supplied to and discharged from SSLiME systems is quantified and the nutrient attenuation is estimated. This thesis contributes recent hydrogeochemical information for a structurally complex semi-arid area under both natural (drought conditions) and human (increased water use, degradation of aquifers) pressures. Collectively, the results indicate that coastal groundwater discharge is likely a mixture of both the intergranular and fractured aquifers and that anthropogenic activities in the hinterland is contaminating the groundwater. This study is an important addition to the baseline hydrological information available for the region and may be useful in terms of sustainable groundwater management strategies and development toward a socio-ecological optimum, especially as related to coastal microbialite system. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2024
  • Full Text:
  • Date Issued: 2024-04

The asymmetric effects of the exchange rate on bilateral trade between the United Kingdom and Germany

  • Authors: Kamwiyo, Craig
  • Date: 2024-04
  • Subjects: Foreign exchange rate , Foreign trade regulation -- Great Britain , Foreign trade regulation -- Germany , Commercial treaties
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/65086 , vital:74021
  • Description: Brexit has given the United Kingdom greater autonomy over its international trade policies and as a result, there is a need to understand the dynamics around the effects of exchange rate on trade balances. Therefore, this study sought to investigate the effects of the pound to euro exchange rate on trade between the United Kingdom and Germany. In so doing, the study investigated the existence of the J-curve phenomenon in the bilateral trade balance. While most existing studies focus on aggregating the trade balance, this study considers disaggregating the trade balance at industrial level. Therefore, the disaggregated trade balance led to several unique studies catering for the twelve biggest industries that make up the trade balance. In addition, the study also does away with the assumption of linearity in the effects of exchange rate changes on the trade balance by making use of asymmetric analysis. For this purpose, the study uses the linear autoregressive distributed lag (ARDL) and the nonlinear autoregressive distributed lag (NARDL) models to analyse monthly data over the period of January 2010 to August 2022. The results provide evidence supporting the existence of the J-curve effect among linear ARDL and NARLD models. Furthermore, it was found that the exchange rate had an asymmetric effect on trade both in the short run and long run. All in all, the results in this study are industry-specific, indicating that the effects of both an appreciation and depreciation of the exchange rate on the bilateral trade balances vary across industries. Considering the J-curve effect identified in six cases, and greater trade elasticities following a depreciation, the government should advocate for expansionary monetary policy by lowering interest rates to improve the trade balance. , Thesis (MCom) -- Faculty of Business and Economic Sciences, School of Economics, Development and Tourism, 2024
  • Full Text:
  • Date Issued: 2024-04

The Camdeboo-Mountain Zebra mega-reserve as an opportunity to protect viable populations of medium- to large-sized mammals

  • Authors: Davis, Kristen
  • Date: 2024-04
  • Subjects: Mammals -- Ecology -- South Africa -- Eastern Cape , Conservation of natural resources -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63711 , vital:73590
  • Description: Conservation planning has focused extensively on representation of species in protected areas (PAs), rather than achieving the persistence of these species in PAs. Consequently, most PAs do not support viable populations of many species represented within them, particularly large mammals, resulting in extinction debt risks. The challenge is therefore to identify opportunities to achieve viable populations and to develop and implement conservation plans to achieve this, e.g., expand and connect existing PAs. A recent meta-analysis provides a minimum viable population (MVP) estimate of 5 000 individuals for mammals. This value was used as the target for modelling conservation opportunities for the South African endemic Cape mountain zebra (Equus zebra zebra), blesbok (Damaliscus pygargus phillipsi), black wildebeest (Connochaetes gnou) and co-existing medium- and large-sized mammal species. This study focused on the region between the Camdeboo and Mountain Zebra national parks (ca. 736 000 ha). Within the envisaged Camdeboo-Mountain Zebra (C-MZ) mega-reserve, a spreadsheet model was used to estimate potential herbivore population sizes, spatial requirement data were used to estimate potential omnivore and insectivore population sizes, and herbivore densities were used to estimate potential large carnivore population sizes. I show that 12 (the three endemic grazers and nine co-existing species) of the 28 modelled medium- and large-sized mammal species will potentially exceed 5 000 individuals, the MVP target, within the envisaged mega-reserve. The remaining 16 species show potential to reach substantial population sizes, however, will likely require ongoing metapopulation management. Using a conservation planning approach, I identify priority areas for the conservation of suitable habitat for Cape mountain zebra, blesbok, and black wildebeest within the envisaged mega-reserve, thus indirectly identifying priority areas for the conservation of these endemic species. I show that the potential incorporation of these priority areas within the envisaged mega-reserve will contribute considerably to the conservation of all focal species. In addition, the potential incorporation of these priority areas will contribute to PA expansion and significantly improve connectivity between existing PAs within the envisaged C-MZ mega-reserve. The importance of adequately-sized PAs to support viable populations of focal species is thus evident, and will ensure their long-term survival and ability to persist by allowing population and evolutionary scale processes. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
  • Full Text:
  • Date Issued: 2024-04

The curious case of Albert Ellis: a psychobiographical case study

  • Authors: van Rensburg, Philip
  • Date: 2024-04
  • Subjects: Psychotherapy , Ellis, Albert -- Interviews , Rational emotive behavior therapy
  • Language: English
  • Type: Doctoral theses , text
  • Identifier: http://hdl.handle.net/10948/63928 , vital:73627
  • Description: Although much has been written on the life and work of American psychologist Albert Ellis, none of the literature adopts a specific psychobiographical framework and no instrumental case studies on the life of Ellis exist. The primary aim of this psychobiographical case study is to provide a psychobiographical exploration and description of aspects of Albert Ellis’ life within his sociohistorical context. More specifically, Ellis’ upbringing with an immigrant past and the role this has played relating to Ellis’ curiosity towards issues of sex and women. The findings of this psychobiographical case study will also be conveyed to inform on the role that culture and cultural diversity has on how an individual experiences and deals with conflict in their life. A specific area of interest in this study is the culture of the twentieth century, with a special focus on the relationship individuals had with sex, as well as examining the lived experience of immigrants during this time. Aspects of Albert Ellis' life within the sociohistorical context of the twentieth century is illustrated by using certain psychological techniques to the available biographical data. This is accomplished by looking at Ellis' experiences and how they influenced the creation of his own paradigm of rational emotive behaviour therapy. Furthermore, Ellis is conceptualised using Karen Horney’s theory of the dynamic relationship, which exists between cultural processes and conflicting human character traits and their impact on behavioural motivation. This study adopts an inductive research approach. Therefore, it implements an instrumental, single-case research design and is exploratory-descriptive in nature. The subject was chosen through purposive sampling and data will be analysed utilising three linked subprocesses theorised by Miles and Huberman. , Thesis (DPhil) -- Faculty of Health Science, School of Behavioural & Lifestyle Sciences, 2024
  • Full Text:
  • Date Issued: 2024-04

The demographic-specific prey preferences of lions and cheetahs, and potential impacts on prey populations

  • Authors: Dreyer, Nicola Bondi
  • Date: 2024-04
  • Subjects: Predation (Biology) , Animal populations , Animal ecology
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/63733 , vital:73593
  • Description: Understanding prey selection offers predictive insights into predator-prey interactions, which can be extended to explore the impacts of predators on prey populations. Prey availability and vulnerability vary across species, demographic classes, body sizes, and seasons. Traditional prey selection models for large carnivores, based on estimates of prey body size, assume uniform vulnerability across prey demographic classes and seasons, failing to account for these variations. This study aims to contrast seasonal shifts in demographic-specific prey preferences between lions and cheetahs and examine the potential impact of their demographic-specific predation patterns on a range of prey species across a body size spectrum. It was predicted that cheetahs would shift their selection from adults and juveniles of smaller prey species in the dry season to neonates and juveniles of both smaller and larger prey species in the wet season, while lions would select adults irrespective of the season. Additionally, predation focusing on adults would have a greater impact on prey populations compared to predation focusing on non-adults. Furthermore, it was predicted that prey populations experiencing demographic-specific selection from both lions and cheetahs would be impacted more than species selected by only one predator. Degrees of preference (DOP) were estimated based on prey availability (camera traps) and prey use (GPS clusters) for lion and cheetah populations in Lapalala Wilderness Reserve. Generalized Additive Models for Location, Scale, and Shape (GAMLSS) were used to determine seasonal shifts in demographic-specific prey preferences. The seasonal-demographic specific predation patterns of lion and cheetah, along with prey vital rates extracted from the literature, were then used to model potential predation impacts on prey populations using both Leslie-Usher and Lefkovitch matrix models. Lions preferred larger adult prey such as blue wildebeest, eland, and buffalo, while cheetahs preferred smaller prey, particularly juveniles of small to intermediate-sized species like impala, kudu, blue wildebeest, and zebra. Both predators showed seasonal shifts in demographic-specific prey preferences, with lions selecting adult buffalo during the dry season and juvenile buffalo in the wet season, and cheetahs selecting juveniles in the dry season and neonates and juveniles during the wet season. Lions and cheetahs exerted the highest degree of top-down limitations on their preferred prey. Predation on adult prey had a greater effect on prey population growth rates than predation on non-adults, especially in the dry season. Intermediate-sized prey species experienced the highest predation pressures, while larger prey species were more affected than smaller ones, contrary to the size-nested predation hypothesis. My study represents a first effort in the southern hemisphere to model the demographic impacts of multiple predators on diverse prey species, incorporating seasonal and demographic-specific prey preferences. The findings emphasise the importance of incorporating prey demographics and seasonality in predator-prey studies as these refined studies have implications for the management and conservation of both predator and prey populations. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2024
  • Full Text:
  • Date Issued: 2024-04

The determinants of foreign direct investment inflows into South Africa

  • Authors: Campher, Renate
  • Date: 2024-04
  • Subjects: Investments, Foreign -- South Africa , Economic development -- South Africa , South Africa -- Foreign economic relations
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64907 , vital:73958
  • Description: Through mechanisms such as knowledge transfer and productivity spillovers, foreign direct investment (FDI) is viewed as a critical driver of growth in developing economies. The flow of FDI into a country can benefit both the investing entity and the host government. This study employed ordinary least square (OLS) regression to examine the factors that determine FDI in South Africa using time series data from 1996 to 2021. The results demonstrate that gross domestic product (GDP), institutional quality, trade openness, the regulatory environment, and the real effective exchange rate (REER) all have positive effects on FDI flows into South Africa. To sustain and promote FDI inflows, the government of South Africa must ensure that the country remains attractive for investment by better promoting good governance, creating jobs to increase growth, maintaining free and fair elections in 2024, forging alliances with trading partners outside of Africa, speeding up all policy processes that may hinder the inflow of FDI, and decreasing government debt. , Thesis (MPhil) -- Faculty of Business and Economic Sciences, School of Economics, Development and Tourism, 2024
  • Full Text:
  • Date Issued: 2024-04

The determinants of job satisfaction in the renewable energy sector in South Africa

  • Authors: Mienie, Alice
  • Date: 2024-04
  • Subjects: Job satisfaction -- South Africa , Work ethic -- South Africa , Work -- Psychological aspects
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/65175 , vital:74041
  • Description: Small and medium enterprises (SMEs) within South Africa face unique challenges, including the quality of education of prospective employees, ailing educational infrastructure and a lack of financial support. In addition, the COVID-19 pandemic has resulted in the phenomenon, known as the great resignation. During this time a significant number of people quit their jobs, citing various reasons, including poor working conditions, lack of recognition and a toxic work culture. This has highlighted the importance of effective organisational talent management strategies across various industries. The renewable energy sector in South Africa plays a vital role in the government’s National Development Plan 2030, in particular, as it relates to the elimination of poverty. At the same time, employees in all sectors, including the renewable energy sector, are continuously assessing whether their employer is meeting their professional and personal needs. Therefore, ensuring their job satisfaction is a crucial organisational consideration, as job satisfaction has been linked to positive employee outcomes, including motivation, and retention. It is also important for organisations to have a clear idea of the factors that promote job satisfaction. Studies on job satisfaction is limited in the renewable energy sector, specifically in the South African context. For this reason, this study was deemed important in filling this gap. The purpose of this study was to identify the determinants of job satisfaction in an organisation in the renewable energy sector in South Africa. In the past, job satisfaction had been assessed in this organisation using an employee net promotor score (eNPS). It was believed that this measure was limited, as it did not provide an indication of the factors contributing to job satisfaction. A detailed literature review was conducted to understand what job satisfaction entails, the determinants thereof, how it is measured and its impact on , Thesis (MBA) -- Faculty of Business and Economic Sciences, Business School, 2024
  • Full Text:
  • Date Issued: 2024-04

The development of a continuous improvement culture causal framework to enhance effectiveness in a South African port environment

  • Authors: Schoeman, Nicole Therese
  • Date: 2024-04
  • Subjects: Continuous improvement process , Organizational change , Corporate culture
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10948/64786 , vital:73908
  • Description: Significant competition challenges confront South Africa's port sector. The sector is also essential to the Eastern Cape Province's economic and social standing. This study was conducted with the objective of helping the port industry in South Africa apply the continuous improvement (CI) philosophy more successfully. The formation of an organisational culture that was conducive to CI was accomplished via the identification of key leadership practices and behaviours. The principal objective of the study was to ascertain, examine, and conduct an empirical examination of the potential impact of diverse leadership practices and behaviours on the culture of the organisation. As a result, the goal of the study was to combine well-researched theories and findings about general organisational culture with more recent findings and firsthand knowledge about CI culture and its significance for the effective execution of CI methodology. Formulating a causal framework for CI culture was the main objective of this work. A literature study was conducted on organisational culture, CI principles, and the port industry. This assessment clearly supported CI as a proven strategy for port industry improvement. One of the main reasons why so many organisations are unable to properly deploy CI is the misalignment of their organisational cultures. Furthermore, there was proof of the crucial part that the conduct and behaviour of leaders might play in the formation of a CI culture. Based on the research study, a framework was created to direct these activities and behaviours. The research methodology used to ultimately create the framework was through an empirical study using a quantitative approach. This quantitative approach was used to evaluate eight hypotheses of this study. Additionally, the validity and reliability of the study was also assessed. The eight major types of leadership actions addressed in this framework, and was tested through the hypotheses, included supportive leadership, process management, employee empowerment, organisational values, reward system, external interaction, customer focus, and future orientation. The association between the eight criteria and the existence of CI culture was then investigated empirically using a structured questionnaire. After this, the data was extensively analysed and statistically scrutinised. The findings showed a substantial positive correlation between the degree of CI culture that was presently in place (dependent variable) and four of the eight categories (independent variables). The four categories were external interaction, process management, organisational values, and supportive leadership. After illustrating these connections, the study's recommendations and conclusions were presented in accordance with the data. The recommendations include improving the framework even more by giving additional information about the precise leadership behaviors connected to each variable and increasing the scope of the study to more than just one sample from one port in South Africa. , Thesis (MEng) -- Faculty of Engineering, the Built Environment, and Technology, School of Engineering, 2024
  • Full Text:
  • Date Issued: 2024-04
  • Disclaimer
  • Privacy
  • Copyright
  • Contact