Performance assessment of a ti6al4v(eli) light aircraft nose wheel fork produced through laser powder bed fusion

Thesis (Master: Engineering: Mechanical Engineering)--Central University of TechnologyA scaled-down nose wheel fork for a light aircraft was redesigned by applying topology optimization for manufacturing in Ti6Al4V(ELI) through laser powder bed fusion (LPBF). This scaled-down nose wheel fork was built together with the test specimens for tensile and fatigue testing in this study. The test specimens were quality checked, tested, and analyzed through standard procedures to obtain the porosity levels, tensile and fatigue properties, and fracture characteristics. The effect of the inherent surface roughness on the high-cycle fatigue properties of LPBF Ti6Al4V(ELI) test specimens was investigated. These test specimens were built to the standard geometry without subsequent machining in three orthogonal directions. They were tested under constant load in a tension–tension fatigue testing machine in accordance with the ASTM E 466 standard. The data was collected and complied with the ASTM F3001 – 14 standard for additive manufacturing (AM) Ti6Al4V(ELI) with laser powder bed fusion. The fatigue performance of the Ti6Al4V(ELI) specimens built to the standard geometry without subsequent machining was compared to that of machined test specimens. It was found that the inherent surface roughness of the specimens built to the standard geometry reduced their fatigue life by about half that of the machined specimens. A customized jig was designed and manufactured to simulate the operational conditions applicable to the scaled-down nose wheel fork. This jig allowed three critical load cases to be tested. The experimental results of the fatigue test specimens and the performance testing of the scaled-down nose wheel fork under static loading were used to evaluate the feasibility of LPBF for production of structural aircraft components, particularly the nose wheel fork. Based on the outcome of the study, it was concluded that it would be justifiable to build a fullscale prototype of the nose wheel fork for testing under operational conditions

Dental assistants` knowledge, attitude and practices of infection prevention and control measures in South-African Oral Health Care Facilities

Thesis (Master of Health Sciences in Environmental Health) (M_HSEN) --Central University of Technology, 2023Introduction: Due to the invasive nature of many dental procedures, the presence of blood, saliva, and intact mucous membranes and tissues are inevitable. Exposure to these substances that potentially contain pathogens puts oral health care workers (OHCWs), patients and significant others at risk of contracting infectious diseases. This lurking danger puts the obligation on each oral health care team (OHCT) member to ensure the utmost safety when providing oral health care (OHC) service to patients. The principal approach to attain safety within oral health care facilities (OHCFs) is to apply effective infection prevention and control (IPC) measures. Therefore, this study aimed to determine dental assistants’ knowledge, attitude, and practices (KAP) of IPC measures within OHCFs. Methods: A quantitative descriptive study was conducted at public OHCFs and within OHCFs under the management of a specific private health care service group, further referred to as private OHCFs. A validated questionnaire was used to collect data. A total of n = 197 dental assistants, of whom n = 76 were employed in the public sector, and n = 121 employed in the private sector, participated in the study. Of the total respondents, n = 84 were formally trained (FT), and n = 113 were in-service (IST) dental assistants. Results and discussion: IPC duties: Out of the fifteen (15) IPC tasks surveyed, more than 80% of the dental assistants were always responsible for performing twelve (12) of the IPC tasks. However, tasks such as preparing the clinical area, flushing the waterlines between patients, and changing the 3-in-1 tips after every patient were performed by less than 70% of the dental assistants. Significantly more dental assistants employed in the private sector were always responsible for the disinfection of working surfaces (p < 0.01), removing the local anaesthetic needles and ampules from the syringe and maintaining the clinical area (p=0.02). In contrast, significantly more IST dental assistants always flushed waterlines between patients (p < 0.01). Knowledge about IPC measures: A high percentage (81%) of dental assistants perceived their level of IPC knowledge as average and above. More than 80% were knowledgeable about aspects of infectious diseases and risks, sterilisation and disinfection, hand hygiene, personal protective equipment (PPE) and health care related waste. However, 77% of dental assistants were knowledgeable about aspects related to vaccination, and 62% of dental assistants were knowledgeable about aspects related to IPC training and continuous professional development. Dental assistants’ preferences for resources to obtain IPC information differed. In terms of IPC guidelines, less than 65% were aware of IPC guidelines, if it is available in their OHCFs, and were familiar with the content thereof. Significantly more private sector (p=0.001), and IST dental assistants (p=0.02), knew that IPC guidelines existed and were available within their OHCFs. Even though 89% of dental assistants were aware of transmitting Hepatitis B, HIV and TB within OHCFs, only 42% were knowledgeable about the possibility of transmitting prions within OHCFs. Furthermore, only 44% of dental assistants confirmed indirect contact as a disease transmission mode within OHCFs. Although dental assistants were aware of the risk of occupational exposure incidents (OEI), they were not knowledgeable about the correct management thereof. Furthermore, dental assistants lacked knowledge about the classification of endodontic instruments, mouth mirrors and dental handpieces; awareness about the vaccination against Hepatitis B was higher than that of Hepatitis A and Influenza. However, a misconception about the availability of a Hepatitis C vaccine exists among 74% of the dental assistants. Attitude towards IPC measures: More than 80% of dental assistants portrayed a positive attitude toward IPC training and continuous professional development, disinfection and sterilisation, infectious diseases and risks, vaccination, hand hygiene, personal protective equipment (PPE) and health care related (HCRW) management. Even though 90% agreed with the application of standard precautions to all patients, 43% of dental assistants indicated that they would consider changing their standard IPC routine when working on a patient with a known infectious disease, with significantly more respondents in the public sector who hold that stance (p=0.01). Furthermore, significantly more FT dental assistants portrayed a positive attitude towards the correct method to process orthodontic instruments. Significantly more FT dental assistants who portrayed a positive attitude towards Hepatitis B vaccination (p=< 0.01), vaccination against Influenza (p=0.01) and vaccination against Hepatitis C (p=0.01). Only 50% believed that protective clothing should always be used. However, less than 25% considered limited availability of PPE, comfortability of PPE, the time it takes to put on and remove PPE, the costs of PPE, patients fearing PPE and OHCWs being used to work without PPE as reasons that prevented them from wearing PPE. Practices of IPC measures: Overall, more than 70% of dental assistants reported acceptable practices in IPC training and continuous professional development, disinfection and sterilisation, infectious diseases and risks, vaccination, hand hygiene, personal protective equipment (PPE) and health care related waste (HCRW) management. However, the overall tendency was that significantly more dental assistants employed in the private sector confirmed performing the respective IPC practices. Dental assistants reported inadequate attendance of IPC training and ongoing professional development events, with only 40% receiving yearly IPC training within their respective OHCFs. Significantly more dental assistants in the private sector received IPC training when new IPC products and equipment arrived (p=0.01). On the other hand, more dental assistants in the public sector did not receive IPC training when new IPC equipment arrived (p=0.02). Factors that prevented dental assistants from attending CPD events were the cost of CPD events, unawareness of upcoming CPD events, and the date and time of the CPD event that clashed with their schedules. Significantly more FT dental assistants indicated that the costs of CPD events deterred them from attending the CPD events. Significantly dental assistants in the public sector were unaware of CPD events. Among the total dental assistants, 74% previously worked on a patient with a known infectious disease. A total of 48% once experienced an occupational exposure injury (OEI). The most common OEIs occurred during the instrument cleaning process (27%), as manual cleaning of instruments before sterilisation was done by 91% of the dental assistants. Splash into the eyes and face, and needle stick injuries were among the top OEI experienced. A further concern was that 37% of dental assistants who used cold/chemical sterilisation methods did not use a high-level disinfectant. Dental assistants' routine practices to clean dental handpieces require attention. Less than 40% run the dental handpiece for 20-30 seconds before removing it from the hose and disassembling it to reach the inner parts. Even though 88% confirmed being vaccinated against Hepatitis B, only 45% of the total respondents received all three Hepatitis B vaccination doses. Although visible hand hygiene instructions are available in 86% of OHCFs, only 67% of the dental assistants washed their hands before putting on gloves, and 77% always washed their hands after taking off their gloves and before leaving the clinical area. Furthermore, 60% did not use an alcohol-based hand sanitiser (ABHS) to supplement their hand hygiene practices. The average use of the individual PPE items across the listed procedures was 66% for gloves, 80% for masks, 5% for protective eyewear, and 50% for protective clothing. Regarding the use of PPE during different procedures, the tendency was that higher percentages of dental assistants used all the PPE items when assisting during surgical procedures, helping a patient with known infectious disease, and anticipating blood and splatter during procedures

Development and assessment of regionalised areal reduction factors for catchment design rainfall estimation in South Africa

Thesis (PhD: Engineering: Civil Engineering)--Central University of TechnologyDesign point rainfall depths converted to an average areal design rainfall depth using Areal Reduction Factors (ARFs) are regarded as fundamental input to various design flood estimation methods. The ARF estimation methods currently used in South Africa are regarded as being outdated and not being developed and/or verified using local data. The primary research objective is to estimate geographically-centred and probabilistically correct ARFs representative of the different rainfall regions associated with the Regional Linear Moment Algorithm and Scale Invariance (RLMA&SI) regionalisation scheme in South Africa. Merging of the 78 homogeneous RLMA&SI rainfall clusters was necessary to increase the size of the clusters and the number of rainfall stations within a particular cluster to meet the minimum required number of rainfall stations/km² criteria. The latter merging resulted in 46 delineated clusters. Long duration geographically-centred and probabilistically correct ARFs were estimated using a total of 2 053 artificial circular catchments and 1 779 daily rainfall stations located within the 46 clusters. Random combinations of the 46 clusters were used in an alternating fashion for calibration and/or verification purposes until all possible combinations were considered. Ultimately, it was noted that whether a dedicated set of clusters or all clusters are assigned to calibration, differences are regarded as insignificant, given that all ARF data sets, whether used for calibration or verification, remain only estimated sample values. Subsequently, five (5) ARF regions were deduced from the 46 clusters and all clusters in a particular ARF region were used for the final derivation of a non-linear (second-order polynomial) log-transformed empirical ARF equation. The new regional ARF equation performed similarly, and as expected, when compared to a selection of geographically-centred ARF estimation methods currently used in local and/or international practice in a range of catchment sizes. The estimated ARFs decreased with an increase in area and increased with an increase in both storm duration and return period. The ARF methodology developed in this research and the subsequent findings are new to the South African flood hydrology research community and practice: (i) ARFs were derived and are based on a regionalisation scheme utilising the daily rainfall data in the Daily Rainfall Extraction Utility (DREU) database, (ii) ARFs are probabilistically correct, i.e., vary with return period, and (iii) a web-based software application was developed to enable the consistent estimation of ARFs within the five (5) ARF regions of South Africa

Thyme oil and thyme oil hydrosol as alternative fungicides against Phyllosticta citricarpa (causative agent of citrus black spot)

Thesis (PhD: Environmental Health)--Central University of TechnologyThe South African citrus industry is one of the most important agricultural industries economically, as it contributes considerably to the country’s Gross Domestic Product (GDP) (Dlikilili and Van Rooyen, 2018; Venter, 2018). The citrus sector in the country also contributes greatly to employment opportunities, particularly for disadvantaged communities, as it currently employs over 125 000 people across the country (Genis, 2018). Over the years and despite the Covid 19 pandemic, the number of citrus trees planted in hectares (ha) has continued to increase. This is due to the high vitamin C content of citrus fruits, the increase in investments and aggressive new plantings of soft citrus, lemons, and new varieties of oranges (Cramer and Chisoro-Dube, 2021). Citrus cultivation for commercial purposes is reported mainly in Limpopo, Western Cape, Mpumalanga, Eastern Cape, KwaZulu-Natal, and Northern Cape. Within the Southern African Development Community (SADC), countries such as Zimbabwe, Swaziland and Mozambique also produce citrus fruits in much smaller quantities (Department of Agriculture and Fisheries, 2017). Most citrus fruits produced in South Africa are exported to countries such as Europe and the United States of America (USA) because of far greater returns from the export market than the domestic market. However, the spread of citrus black spot (CBS) has resulted in fears of a possible ban on South African citrus exports to other countries (Kau et al., 2018; Van Dyk and Maspero, 2004). Evidence that CBS affects the agricultural industry negatively regarding food production, security and trade is available. CBS is a citrus disease caused by the fungus Phyllosticta citricarpa, which affects almost all commercial citrus species externally but does not cause internal decay (Yonow et al., 2013; Roberts et al., 2012; Fialho et al., 2010). Almost all commercially sold citrus species are susceptible to Phyllosticta citricarpa infection, with lemons and Valencia oranges known to be highly susceptible. CBS was first discovered, recorded and described by Benson in Australia and was observed on Valencia oranges over 120 years ago (Paul, 2006; Kotzé, 2000; Kiely, 1948;). Phyllosticta citricarpa produces sexual and asexual spores, with each stage producing different spores responsible for spreading CBS using various modes of dispersion (Truter, 2010). Synthetic fungicides are currently used to minimize the spread of CBS; however, their use has raised health and environmental pollution concerns, including resistance to pathogens (Du Plooy et al., 2009). Hence, research into developing alternative agents for replacing synthetic fungicides for fungal disease control in agriculture continues, such as using essential oils (EOs) and their hydrosol. EOs are complex mixtures of secondary plant metabolites with relatively high vapour pressure and are poorly soluble in water. The EOs reported in various studies have shown to exhibit antifungal properties by targeting structures responsible for the life cycle of fungal organisms such as ascospores and conidia in vitro and in vivo in different fresh produce. The overall aim of the study was to investigate the in vivo effect of thyme oil and thyme oil hydrosol against citrus fungal pathogen Phyllosticta citricarpa (Feyaerts et al., 2018). Thyme oil characterization was done using gas chromatography-mass spectrometry GC-MS and GC × GC-TOFMS. Their effectiveness, together with that of hydrosol, was tested against Phyllosticta citricarpa (CBS causative agent) using methods such as broth microdilution assay (minimum inhibitory concentration (MIC) determination) and fungicidal or fungistatic activity. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to evaluate morphological changes that occurred due to EOs, while the inhibition of pathogen growth on leaves and fruits was also determined. The results of the study revealed that the pathogenic fungi P. citricarpa depend on increased mitochondrion activity, such as conidia, and these structures are sensitive to thyme oil used in the study. Furthermore, thyme oil hydrosol used in the study has indicated a moderate antifungal activity against this fungal pathogen

A roadmap for the reduction of carbon and ecological footprint of construction activity in Ghana

Thesis (Doctor of Engineering: Civil Engineering)--Central University of TechnologySustainable construction is acknowledged globally to be a viable means to reduce the negative environmental effects of construction projects. Sustainable construction utilises ecological and resource-saving concepts in executing projects. The reduction of carbon and ecological footprint of construction activity contributes to the achievement of sustainable construction. The sustainable construction practices are advanced in developed countries where governments have established legislation, codes, policies, and frameworks to promote the sustainability concept to reduce carbon and ecological footprint. However, sustainable construction implementation is immature in emerging countries like Ghana, because of implementation issues and unavailability of clear roadmap or government policies and legislation to promote the uptake. This study was motivated by a gap identified in the literature to develop a sustainable construction roadmap for the Construction Industry in Ghana to reduce carbon and ecological footprint of construction activity. Accordingly, the specific objectives of the research were: to determine why sustainability is a focus area that cannot be ignored by the Ghanaian Construction Industry; to determine how design should respond to sustainability requirements in the Ghanaian Construction Industry; to determine how construction materials should respond to sustainability requirements in the Ghanaian Construction Industry; to explore the effects of energy-efficiency on the construction process in the Ghanaian Construction Industry; to evaluate the modalities employed to reduce construction site solid waste in the Ghanaian Construction Industry; and to develop a sustainable construction roadmap that would reduce the carbon and ecological footprint of activities in the Ghanaian Construction Industry. The study was grounded in the pragmatist paradigm, and both qualitative and quantitative data were gathered using a mixed method strategy. The qualitative data collected from three rounds of a Delphi study were analysed descriptively and inferentially. The strong agreement reached on the key elements of sustainable construction is supported by the comparative analysis between the 18 Delphi panel experts. In order to better understand the phenomenon of sustainable construction in Ghana, 405 valid and completed questionnaires were received and retrieved. The data were then analysed using Partial Least Square - Structural Equation Modelling (PLS-SEM). According to the research, one of the benefits of implementing sustainable construction is to raise standard of living in general. The response of construction industry in Ghana to sustainable design requirements highlights resource conservation, adaptations, whole life-cycle designs, and cost efficiency as the main areas of concern for sustainable construction. Also, the renewable, recyclable, and re-usable materials; durable materials; and materials of minimum adverse impact on the environment are to be adopted to respond to sustainability requirements in Ghana. Some of the advantages of energy efficiency on the construction process identified include reduction in fuel usage of construction equipment, minimal energy consumption and reduction in energy cost, reduction of emission levels and protection of the environment. The just-in-time operations, careful handling of tools and equipment on site, early and prompt scheduling of deliveries, and use of more effective equipment are the primary construction waste management practices in the Ghanaian construction industry to achieve sustainability. The quantitative data provided a basis on which the roadmap evolved to serve as a guideline for carbon and ecological footprint reduction of construction activity in Ghana. Through semi-structured qualitative interviews, the developed roadmap was validated by academics and industry practitioners in Ghana, and the results indicated that the roadmap is useful and appropriate for application in the Ghanaian construction industry. Policy-makers, academics, developers, and investors who want to implement sustainable construction in the Ghanaian construction industry can use the study as a tool because it has practical, theoretical, and methodological relevance for sustainable construction. The Green Building Council in collaboration with the government should open offices in all the Assemblies to intensify the awareness creation and promotion of the roadmap to increase the adoption of the sustainable construction concept in Ghana. The government should implement financial incentives for construction companies and professinals that adopt sustainability practices to reduce carbon and ecological footprint of construction activity in Ghana. The study has contributed to sustainable construction body of knowledge since it reaffirmed the potential contributions to realising the relevant United Nations Sustainable Development Goals such as 9, 12 and 13

The effect of various clay nanoparticles and their synergy on the properties of polylactic acid for advanced applications

Thesis (Master: Health Sciences)--Central University of TechnologyThe study investigates the effect of clay(s) on the properties of the poly (lactic acid) (PLA). Nanocomposites having 3% of clays (viz. halloysite, montmorillonite (MMT), and kaolin) were fabricated using melt mixing method. Furthermore, zinc borate was added into the PLA/Clay(s) nanocomposites with the aim of enhancing the properties of nanocomposites. Techniques such as the transmission electron microscopy (TEM), X-ray diffractogram (XRD), thermogravimetric analysis (TGA), rheology, and UL-94 were adopted. TEM was used to investigate the dispersion of the clays within the PLA polymer matrix. The incorporation of the MMT into PLA resulted into an intercalation and exfoliation of the nanoclay within the polymer matrix when compared with kaolin and halloysite clays. As the ZnB was not modified, its nanoparticles were found to be agglomerated into the PLA matrix. Furthermore, the synergy of the other clays with MMT seems to have formed intercalation and exfoliation, which seems to verify that MMT acted as a modifier for other clays within the PLA matrix. It was further observed that the presence of ZnB and clays such as halloysite, and kaolin clays resulted in immiscibility between the nanoparticles and the PLA matrix. According to the XRD, the incorporation of the MMT in the PLA systems acted as a steric hindrance; and as a result, crystallization was restricted, thus causing a reduction in the intact crystalline region. Thermal stability of the tubular halloysite clay-based nanocomposite was found to be higher when compared with the silicate clay-based nanocomposites (viz. MMT and kaolin). One can realize that the synergistic effects of the nanoclays showed better thermal stability than all the single clays reinforced PLA matrix. Additionally, the majority of the synergistic nanoparticles were found to have a high thermal stability when compared with single filler-based nanoparticles/polymer composites. Halloysite in the PLA/ZnB system improved the complex viscosity of the system more than all the clays systems and PLA due to a stable and tubular structure of the halloysite. Halloysite, and its synergy with the other clays seemed to dominate in terms of improving the flammability resistance of the PLA matrix with V-0 UL-94 rating. The pollutant removal efficacy was found to be depended on the filler-type. Fillers with stronger interaction with PLA resulted in poor adsorption properties due to limited accessibility to the available active sites

Assessment of indirect estimation methods to extend observed stage-discharge relationships for above-structure-limit conditions at flow-gauging weirs

Thesis (Masters: Engineering: Civil Engineering)--Central University of TechnologyStreamflow is seldom directly measured; instead, the stage (flow depth) is continuously measured and converted into a discharge using a stage-discharge (SD) rating curve (RC) at a flow-gauging weir or specific river section. During flood events, flow-gauging weirs might be flooded with the water level beyond the gauging weir's designed measuring capacity, also referred to as the structural limit of the weir. Subsequently, the standard calibration of the flow-gauging weir will no longer be a true reflection of the actual discharges that occurred during the flood events, and the standard SD RC must then be extended beyond the highest stage reading to reflect these high discharges at above-structure-limit flow conditions. Direct measurements, e.g., conventional current gaugings, are also not always possible owing to various practical constraints associated with these high discharge events. As a result, various indirect methods for extending SD RCs are available; however, the impact of using these different methods varies significantly and highlights the need for a robust and reliable extension method. The overall aim of this research is to assess and compare a selection of indirect extension methods (e.g., hydraulic and one-dimensional modelling methods) with direct extension (benchmark) methods (e.g., at-site conventional current gaugings, hydrograph analyses and level pool routing techniques), in order to establish the best-fit and most appropriate SD extension method to be used in South Africa. As pilot case study, 10 flow-gauging sites in the Free State, Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga, and the Western Cape provinces were selected based on the range of possible site conditions present, e.g., type of flow-gauging weir, at-site and river geometry, flow conditions, type of hydraulics controls, and data availability. The following hydraulic methods were considered and applied at each site: (i) Simple extension (SE), (ii) Logarithmic extension (LE), (iii) Velocity extension simple approach (VE-SA), (iv) Velocity extension hydraulic radius approach (VEHRA), (v) Velocity extension Manning’s approach (VE-MA), (vi) Slope area method (SAM), and (vii) Stepped backwater analysis (SBA). In addition, one-dimensional modelling (1-D) was conducted using the Hydrologic Engineering Centre River Analysis System (HEC-RAS). Data were collected based on the hydrometric and geometric requirements for the extension of SD relationships. The processing of the geometric data, e.g., wetted perimeter, wetted area, and hydraulic radius, was done using the Windows CrossSection Professional (WinXSPRO), which is essentially a channel cross-section analyser. All the SD extensions were executed in the Microsoft Excel environment using semi-automated tools. The indirect extension methods’ results were compared and independently assessed against the direct SD measurements or estimates at each site by using a ranking-based selection procedure based on a selection of goodness-of-fit (GOF) criteria. In considering the overall GOF-based rankings, the SBA, SAM, and 1-D HEC-RAS steady flow modelling were identified as the most appropriate indirect estimation methods to reflect the hydraulic conditions during high discharges at a flow-gauging site. The other indirect extension methods were characterised by larger statistical differences between the at-site benchmark values and the modelled values. The VE-MA and SE methods are regarded as the least appropriate methods. In general, any extension method must be hydraulically correct if it is to be used as a robust approach to extend SD RCs beyond the structural limit. The extension of a RC is significantly more affected by the site (and river reach) geometry, initial hydraulic conditions, flow regimes and level of submergence at high discharges than the actual extension method used. Hence, there is no one-size-fits-all approach available for the extension of SD RCs in South Africa. By improving the quality of all input data and assigning more appropriate roughness coefficients, in conjunction with the implementation of new or alternative SD extension methods, the improved extension of SD RCs is warranted to result in consistent and acceptable results. Consequently, the improved and extended RCs will result in improved hydrological data sets, all of which, will contribute towards enhanced operational water resource planning, management, and allocation in South Africa. The recommendations for future research are towards the review of the current procedures used to estimate roughness coefficients for flash floods, and the consideration of alternative methods to extend SD relationships, e.g., hydrodynamic models, support vector machines (SVMs) and artificial neural network (ANN) methods

Modelling melt pool characteristics to predict process parameters for selective laser melting of titanium alloys

Thesis (Master: Engineering: Mechanical Engineering)--Central University of TechnologyThe time-consuming experimental process required to optimize process parameters for the selective laser melting (SLM) of new materials is a major hurdle in adopting this technology. For this reason, various methods in the literature attempt to shorten the time taken to optimise the process parameters for a specific material. One possible solution to this problem is the use of accurate numerical modelling to predict the required process parameters. Currently, melt pool modelling on part-scale is computationally expensive and not a feasible method for reducing the time required for the optimisation of process parameters. However, some studies have indicated that it is possible to effectively optimise process parameters through experimental investigation of the cross-sectional geometry of the molten region of single tracks created at various process parameters. It follows, therefore, that the accurate modelling of single tracks can be an effective way of determining optimal process parameters. This study reports on efforts to set up a numerical model of a single track of the SLM process that is accurate enough to be effectively used to optimise process parameters. Experimental and simulation results were obtained for a broad range of laser powers and scanning speeds to investigate the accuracy of the model. Thereafter, the effects of changing various simulation parameters on the accuracy of the model with respect to simulated melt pool dimensions were investigated to find parameters that could be responsible for inaccuracies in the developed model. These parameters included the temperature-dependent absorptivity of the material, the evaporation pressure coefficient, and to a lesser extent, the effect of temperature on the surface tension. It was concluded that provided that accurate values could be obtained for the simulation parameters discussed in this document, single-track SLM simulations could be a very powerful tool for quickly and effectively determining process parameters for any material

The impact of necessity entrepreneurship on the survival of hair salons in Mangaung metropolitan area

Thesis (MPhil: Business Administration)--Central University of Technology, 2023Despite the South African government’s effort to reduce unemployment, joblessness continues to increase. Some jobless people establish their own businesses in the face of adversity. Out of necessity and desperation, jobless people venture into establishing their own businesses despite the fact that they might not have the relevant resources. Often they lack funds. They venture into own business to accumulate money for survival purposes. One such business that has proliferated out of necessity are small hair salons. Many see this as quick and easy to initiate and run. However, no empirical evidence has been confirmed yet to substantiate the rationale for establishing hair salons and the impact thereof on the survival of the business. The objective of the study was, therefore, to establish whether hair salon owners start their businesses out of necessity or opportunity in the Mangaung Metropolitan area. Drawing from a positivist approach, this study adopted a quantitative research design with a sample size of 144 salon owners. A structured questionnaire with standardised questions was used to collect data. The findings show a statistically significant relationship between necessity entrepreneurship and business creation, business stakeholders and business creation business stakeholders and business survival and a minimal relationship between necessity entrepreneurship and business survival. The study concludes that necessity entrepreneurship is moderately related to business survival. The main recommendation is that necessity entrepreneurs need relevant information on small service business to achieve success. It is also recommended that government establish programs to support SMMEs by supporting innovation in small businesses and tax transparency

Enhancing spatial image datasets for utilisation in a simulator

Thesis (Master:Engineering:Electrical Engineering)--Central University of TechnologyThe introduction of Google Street View, which is an integral part of Google Maps, has brought to the surface a method of roof-mounted mobile cameras on vehicles. This is regarded as one of the highly known and adopted methodically for capturing street-level images. Computer vision as one of the frontier technologies in computer science has allowed for the use of building artificial systems to extract valuable information from images. This approach has a broad range of applications in various areas such as agriculture, business, and healthcare. This dissertation contributes to the development and implementation of Image-Based Rendering (IBR) techniques by presenting a method that makes use of hexagon-based camera configuration for image capturing. Upon the image capturing, each segmented image was stored in a specific folder relative to the camera number. Following this process, the images were chosen based on their timestamp and GPS coordinates and copied to a master folder where the rendering took place. However, before rendering can take place, the master folder was called inside Blender software. The reason for placing the master folder inside Blender3D was to ensure smooth blending of different image datasets with fewer resources and low computing power during the rendering process. This is feasible as all the image datasets are in one folder as compared to the calling of multiple datasets from different directories which might affect the processing power. Subsequently, OpenCV algorithms were utilised for the Structure from Motion and points of cloud simulation. These techniques and algorithms were based on the available image datasets that were created in the master folder. Following the optimal image rendering, a process of image blending took place inside the Blender3D software where the captured images (dataset) were rendered for utilisation in the simulator. The use of the Structure from Motion algorithm was utilised for the development of the dense point image, feature, and matching detection. Furthermore, the process for extraction of a depth map model from the three-dimensional (3D) mesh was also highlighted as well as the image restoration process utilising the 3D warping approach. In addition, after these processes were completed, the IBR technique was utilised again for rendering the scenes from the multiple datasets that were captured from the Hexagon Camera Configuration Model to present a scenery that can allow for bidirectional movement. It is therefore noted that the entire work done in this dissertation was substantiated using simulations, genuine data, and physical analysis based on the physically gathered raw data and results from the analysis. The study objectives were therefore achieved by presenting a framework that allows for virtual driving and bidirectional movement of the scene from a Hexagon Camera Configuration Model. Furthermore, the image datasets showed an improvement in the visuals, spatial details and quality of the panoramic images for location identification based on GPS coordinates. Additionally, the rendered images were observed to be smaller than the originally captured images. The study contribution was based on the GPS module which was utilised to observe and project the scene altitude and coordinates. Moreover, the contribution results process allows for free movement within the 3D-rendered scene to allow for back and forward motion as compared to a slide show that only allows for forwarding motion. In evaluating the efficacy of this research study, the objective argument highlights that through the use of a Hexagon Camera Configuration Model, the user is permitted to move in both the forward and reverse direction within a simulator as opposed to the one-directional movement. These results demonstrate the feasibility of utilising an alternative model for image capture as opposed to the utilisation of a 360o omnidirectional camera and image stitching protocol. Furthermore, the study results demonstrate that the more the input image data, the higher the realism of such a model. In contrast, for 364 image datasets, the output scene is high as a result of a large number of input image datasets with the scene realism observed for both points of cloud and mesh-based on 106110 points