Thesis (MComm)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Tsetse flies (Glossina spp), native to mid-continental Africa, are the vectors of trypanosomes that causes human (sleeping sickness) and animal (nagana) trypanosomiasis. Vector control plays a major role in alleviating the burden of the disease. Mathematical models of tsetse population dynamics provide insights into how best to manage these control efforts. A major mark-recapture experiment, carried out in Zimbabwe, provided valuable information on tsetse population dynamics, but the analyses so far published could be improved on because not all of the information available on the marking procedure was used. We have constructed an individual-based model that follows the life of individual tsetse flies, their progeny and, in particular, the sequence of occasions on which individual flies were captured and given distinctive marks. We have access to comprehensive data from the tsetse fly mark-release-recapture experiment carried out on Antelope Island, Lake Kariba, Zimbabwe. In order to calibrate or validate the model, we model both the growth of the introduced tsetse population and the mark-recapture process. We have compared the model outputs to the original data and recommend processes that may be followed for model calibration. It is possible to construct an individual-based model that adequately models tsetse fly populations. Whereas the focus of this study has been on modelling the mark-recapture study, the individual-based model could also be used in more general settings to model the growth, and reduction in fly numbers, changes in age structure, species and gender ratios and the acquisition of trypanosome infections by individual flies. This model can thus be used to investigate the effect of various factors on tsetse fly and trypanosome, population dynamics as well as on the performance of various control techniques effecting fly mortality and disease transmission. / AFRIKAANSE OPSOMMING: Tsetsevlieë (Glossina spp), inheems aan sentraalkontinentale Afrika, is die draers van trypanosomen wat trypanosomiasis by die mens (slaapsiekte) en by diere (nagana) veroorsaak. Die beheer van draers speel 'n belangrike rol om die las wat die siekte veroorsaak, te verlig. Wiskundige modelle van tsetse bevolkingsdinamika bied insigte oor hoe om beheerpogings die beste te bestuur. 'n Belangrike merk-hervang eksperiment, wat in Zimbabwe uitgevoer is, bevat waardevolle inligting oor tsetse bevolkingsdinamika. Die ontleding daarvan, wat tot dusver gepubliseer is, kan egter verbeter word aangesien nie al die inligting beskikbaar in die merkprosedure, gebruik is nie. Ons het 'n individu-gebaseerde model saamgestel wat die lewens van individuele tsetsevlieë en hul nageslagte volg, in besonder die volgorde waarop individuele vlieë gevang en herkenbaar gemerk is. Ons het toegang tot omvattende data van die tsetsevlieg merk-vrylaat-hervang eksperiment wat uitgevoer is op Antelope Eiland, Karibadam, Zimbabwe. Ten einde die model te kalibreer of om die model se geldigheid te bevestig, modelleer ons beide die groei van die ingevoerde tsetse bevolking en die merk-hervangs metode. Ons vergelyk die modeluitsette met die oorspronklike data en beveel prosesse aan wat gevolg kan word om die model te kalibreer. Dit is moontlik om 'n individu-gebaseerde model saam te stel wat tsetsevliegbevolkings voldoende moduleer. Terwyl hierdie studie die modellering van die merk-hervang data bestudeer, kan die individueel-gebaseerde model ook gebruik word in meer algemene gevalle vir die modellering van die vermeerdering en vermindering in vlieë getalle, veranderinge in die ouderdomstruktuur, spesies en geslagverhoudings en die verwerwing van trypanosomen infeksies deur individuele vlieë. Hierdie model kan dus gebruik word om die effek te ondesoek van verskeie faktore op die tsetsevlieg en trypanosomen, populasiedinamiek sowel as die prestasie van verskillende beheertegnieke rakende vliegsterftes en siekte-oordrag.

To survive in today's manufacturing environments companies must push the standards of accuracy and speed to the highest levels possible. Electro Discharge Machining (EDM) has been used for over 50 years and recent developments have seen the use of EDM become much more viable. The goal of this research is to produce and evaluate electrodes produced by different manufacturing methods. The use of electroforming and spray-metal deposition has only recently become viable methods of producing usable rapid tooling components. The speed and accuracy as well as the cost of manufacture play a vital role in the tool and mould manufacturing process. Electroforming and spray-metal deposition offer an alternate option to traditional machining of electrodes. Electroforming is one method of producing electrodes for EDM. The fact that electroforming can be used to produce multiple electrodes simultaneously gives it the advantage of saving on costs when multiple electrodes are needed. Spray-metal deposition offers another alternative that is much cheaper and relatively faster to manufacture. The used of these non-traditional manufacturing methods in this research are compared to the performance of traditional solid electrodes in terms of machining time, material removal rate, tool wear rates and surface roughness at several standard machining settings. The results of this research are presented in this thesis along with conclusions and comments on the performance of the different methods of electrode manufacture. The major findings of the research include the solid electrodes performed better than the electroformed electrodes in Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (Ra) at all machine settings. However it was found that the production cost of the solid electrodes was six times that of the electroformed electrodes. The production of spray metal electrodes was unsuccessful. The electrode shell walls were not an even thickness and the backing material broke through the shell making them unusable. It is concluded that with further refinements and research, electroforming and spray metal processes will become an extremely competitive method in electrode manufacture and other rapid tooling processes.

Plasma electrolytic Polishing (PeP) is a non-conventional technology for the surface treatment of electrically conductive materials. It is an effective machining technique for cleaning and polishing of metals and considered as a more environmentally friendly alternative to the electropolishing process. The electropolishing process uses aggressive media such as acids, whereas in PeP, acids or toxicants are replaced by low concentrated water solutions of various salts. In PeP, high DC voltage is applied to the electrodes in the aqueous electrolyte solution, which establishes a thin steam-gas layer around the surface of the work piece resulting in the generation of plasma. From the previous research, it is found that the formation of stable plasma generally takes place between 180-370 volts, where it results in better surface conditions. The aim of this study is to analyse the behaviour of current according to different voltages and their effects on surface roughness and material removal rate (MRR) of stainless steel in Plasma electrolytic Polishing process.

Compacted Graphite Iron offers mechanical properties in between of gray cast iron and ductile iron. Thus,the material is seen as a hopeful alternative for engine cylinder blocks and heads satisfying environmentaland performance objectives. Nevertheless, CGI is more difficult to machine than conventional gray castiron due to the presence of MnS and thin wall section of probing high strength. This problem of CGI thenled to the initiation of large Optima Sweden project to study machinability and optimization of related toCGI.The thesis is centered on a study of tool life, cutting force and MRR with regards to machining parametersmainly feed rate and cutting speed for CGI milling. Tool life is measured; flank-wear is observed andcompared between several combinations of cutting parameters.Similarly cutting forces were measured using LMS software for full factorial design experiments. Extensivemachining experiments were carried out. Machining tests was done based on Design of Experiment (DoE)for high cutting data and lower data are performed separately. Comparison is made for tool life and cuttingforces. After data collection, analysis of tool life and force has been followed. Once the data is analyzedand checked its consistency. An approximate model is developed using MODDE software. Further, multiobjective optimization of tool life and Material removal rate (MRR) using cutting parameters mainly feedrate and cutting speed are investigated. Working on optimal parameters will allow for CGI is to becompetitive in manufacturing with gray CI, aluminum alloy, magnesium.Keywords: Compacted Graphite Iron (CGI), face milling, tool life, MRR, optimization, cutting force

No description available.

No / Nickel alloys including Inconel 718 are considered as challenging materials for machining. Laser beam machining could be a promising choice to deal with such materials for simple to complex machining features. The machining accuracy is mainly dependent on the rate of material removal per laser scan. Because of the involvement of many laser parameters and complexity of the machining mechanism it is not always simple to achieve machining with desired accuracy. Actual machining depth extremely varies from very low to aggressively high values with reference to the designed depth. Thus, a research is needed to be carried out to control the process parameters to get actual material removal rate (MRRact) equals to the theoretical material removal rate (MRRth) with minimum surface roughness (SR) of the machined surfaces. In this study, five important laser parameters have been used to investigate their effects on MRR and SR. Statistical analysis are performed to identify the significant parameters with their strength of effects. Mathematical models have been developed and validated to predict the machining responses. Optimal set of laser parameters have also been proposed and confirmed to achieve the actual MRR close to the designed MRR (MRR% = 100.1%) with minimum surface roughness (Ra = 2.67 µm). / The authors extend their appreciation to the Deanship of Scientific Research at King Saud University for funding this work through research group number RG-1440-026.

Plasma electrolytic Polishing (PeP) is a non-conventional technology for the surface treatment of electrically conductive materials. It is an effective machining technique for cleaning and polishing of metals and considered as a more environmentally friendly alternative to the electropolishing process. The electropolishing process uses aggressive media such as acids, whereas in PeP, acids or toxicants are replaced by low concentrated water solutions of various salts. In PeP, high DC voltage is applied to the electrodes in the aqueous electrolyte solution, which establishes a thin steam-gas layer around the surface of the work piece resulting in the generation of plasma. From the previous research, it is found that the formation of stable plasma generally takes place between 180-370 volts, where it results in better surface conditions. The aim of this study is to analyse the behaviour of current according to different voltages and their effects on surface roughness and material removal rate (MRR) of stainless steel in Plasma electrolytic Polishing process.

This study linked to the line of research "Development of network educational technology", from the Professional Master course on Network Educational Technology, aims to contribute to the provision of Specialized Educational Service (SES). To do so, it was sought to develop a Digital Educational Material (DEM) to enhance SES; specifically the objectives were: 1) expand the SES, implementing a DEM in order to be used presentially and at a distance; 2) adapt the pedagogical model DEM, making it accessible to the target audience of the Special Education Student (SPES) and 3) validate the possibilities of motivation, autonomy and learning of DEM with SPES, under the assessment of SES teachers. On the basis of theories, it can include four axes: first, contemplating the special education; the second, with studies of digital educational materials, Learning objects; the third on Teaching Design (TD) in the construction of DEM and the fourth axis referring to the accessibility of digital educational materials. By applying a qualitative research, the focus was on teachers who work in Multifunctional Resource Rooms, performing the SES of state public schools in the city of Santa Maria, RS state. Data collected went through content analysis (Bardin, 2011), using three categories: motivation for the use of DEM, the autonomy in the use of DEM and potential for learning. The results of the analyzed categories allow evidence that the motivation to use DEM is present due to the context of illustrations, content and accessibility; as the autonomy, the results indicate that the non-linear path and affordable navigation possibilities are important characteristics for the development of a DEM, and finally, the potential for learning is present from the developed educational activities in accordance with the practices the SES and the possibilities of using DEM presentially and at distance. Thus, the study achieved its goals, understanding that the virtual room of multifunction resources gives SES greater potential. / O presente estudo vinculado à linha de pesquisa Desenvolvimento de tecnologias educacionais em rede , do Mestrado Profissional em Tecnologias Educacionais em Rede, pretendeu contribuir com a oferta do Atendimento Educacional Especializado (AEE). Para tanto, buscou desenvolver um Material Educacional Digital (MED) para potencializar o AEE; especificamente os objetivos foram: 1) ampliar o AEE, implementando um MED de forma a ser utilizado presencial e a distância; 2) adaptar o Modelo Pedagógico MED, tornando-o acessível ao Estudante Público-alvo da Educação Especial (EPAEE) e 3) validar as possibilidades de motivação, autonomia e aprendizagem do MED com os EPAEE, sob a avaliação dos professores do AEE. Nas teorias de base, referenciam-se quatro eixos: o primeiro, contemplando a Educação Especial; o segundo, apresentando estudos sobre Materiais Educacionais Digitais, objetos de Aprendizagem; o terceiro, sobre Design Pedagógico (DP) na construção dos MED e o quarto eixo referindo-se à acessibilidade em Materiais Educacionais Digitais. Com uma pesquisa qualitativa, aplicada, o foco recaiu sobre professores que atuam nas Salas de Recursos Multifuncionais, realizando o AEE de Escolas Públicas Estaduais, na cidade de Santa Maria, RS. Os dados coletados passaram pela análise de conteúdo (Bardin, 2011), por meio de três categorias: motivação para o uso do MED, autonomia no uso do MED e potencial para a aprendizagem. Os resultados das categorias analisadas permitem evidenciar que a motivação para uso do MED está presente devido à contextualização das ilustrações, conteúdos e acessibilidade; quanto à autonomia, os resultados apontam que o percurso não linear e as possibilidades de navegação acessíveis são características importantes para o desenvolvimento de um MED e, por fim, o potencial para aprendizagem se faz presente a partir das atividades pedagógicas elaboradas de acordo com as práticas do AEE e das possibilidades de uso do MED presencial e a distância. Assim, o estudo realizado contemplou os objetivos, entendendo que a Sala virtual de Recursos Multifuncionais potencializa o AEE.