This thesis presents the development of a set of novel graphical tools Known as 'virtual primitives' that allow the user of a stereoscopic telepresence system to actively and intuitively model features in a remote environment. The virtual primitives provide visual feedback during the model creating process in the form of a dynamic wireframe of the primitive overlaid and registered with the real object. The operator can immediately see the effect of his decisions and if necessary make minor corrections to improve the fit of the primitive during its generation. Virtual primitives are a generic augmented reality (AR) tool and their applications extend past the modelling of a workspace for telerobot operation to other remote tasks such as visual inspection, surveying and collaborative design. An AR system has been developed and integrated with the existing Surrey Telepresence System. The graphical overlays are generated using virtual reality software and combined with the video images. To achieve a one-to-one correspondence between the real and virtual worlds the AR system is calibrated using a simple pinhole camera model and standard calibration algorithm. An average RMS registration error between the video and graphical images of less than one framegrabber pixel is achieved. An assessment of a virtual pointer confirms that this level of accuracy is acceptable for use with the virtual primitives. The concept of the virtual primitives has been evaluated in an experiment to model three test objects. The results show that using a virtual primitive was superior in accuracy and task completion time to using a pointer alone. Finally, a case study on the remote inspection of sewers demonstrates the advantages of virtual primitives in a real application. It confirms that the use of virtual primitives significantly reduces the subjective nature of the task, offers an increase in precision by an order of magnitude over conventional inspection methods, and provides additional useful data on the characteristics of the sewer features not previously available.

A study has been made of the respective performance of cubic boron nitride (CBN) and polycrystalline diamond (PCD) cutting tool materials and compared to various coated and uncoated tungsten carbide grades when cutting titanium alloy workpieces. Two important experimental techniques were employed during the course of this work, firstly a quasi-static contact method was employed to establish the workpiece/tool interfacial temperature above which strongly adherent layers may be formed. This technique revealed that the critical temperatures which marked adhesion and welding, were 740, 820 and 800 °C for coated and uncoated carbides, and 760 and 900 °C for PCD and CBN tools respectively. Furthermore, the technique has been used to study the integrity of the bulk tool material, and/or individual coatings on their substrates, when welded junctions formed between the tool and workpiece are separated. With regard to the latter it was observed that in all cases fracture was initiated in the bulk of the harder tool material rather than in the workpiece or at the welded junction interface. Secondly, a quick-stop technique was used to study chip formation and tool wear when cutting with carbides, CBN and PCD tools under nominally the same conditions. The predominant wear mechanisms for each of the tool materials was found to be based on a diffusion/dissolution process. The wear process is discussed in detail for each of the tool materials and reasons advanced for observed differences in performance when removing material from a titanium alloy workpiece. The wear resistance and quality of the machined surface was found to be superior when cutting with the ultra-hard materials than with the carbide grades and in particular the PCD tool was found to produce exceptionally good surface finish. In the case of coated carbide tool grades rapid removal of the coated layers occurred leaving the substrate vulnerable to reaction with the workpiece material and this is considered to explain the seeming absence of beneficial effects when cutting with these grades.

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Made available in DSpace on 2014-10-09T12:49:22Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:29Z (GMT). No. of bitstreams: 0 / O desenvolvimento tecnológico e a ampliação da infra-estrutura das telecomunicações propiciou um aumendo do número de usuários na Internet. Dentre as imensas possibilidades de utilização, a aprendizagem constitui-se num dos temas mais atrativos. A aprendizagem à distância – EAD consolida-se como uma opção atrativa ao considerar-se principalmente as variáveis custo e comodidade. O trabalho visa avaliar alguns modelos para educação a distância e desenvolver um modelo para instituições de ensino.. Inicialmente, busca-se ampliar o conhecimento teórico acerca do tema com pesquisas bibliográficas que envolvem temas como a Internet, a tecnologia, modelos internacionais e nacionais e o processo de aprendizagem. A etapa seguinte, promove o desenvolvimento de modelos, utilizando a técnica da prototipação de modelos de ensino à distância, nesta etapa são consideradas como vertentes: tecnologia, mercado, cliente e metodologia utilizada. Os modelos são apresentados e analisados qualitativamente e seqüencialmente, sob o prisma dos seus pontos fortes e pontos fracos, os resultados são considerados e tornam-se subsídios para o desenvolvimento dos modelos posteriores. Para coleta de dados são utilizados métodos de questionários, entrevistas e observação direta durante o transcorrer dos cursos. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Decay kinetics of bacteria in biological wastewater treatment systems are vital to efficient design and operation of treatment plants.  Of special concern are decay characteristics of fecal indicator organisms, which can aid design of wastewater treatment processes to eliminate fecal pathogens.  This study focuses on characterizing the decay of three strains of the key fecal indicator bacterium, Escherichia coli, and comparing microbial techniques for quantifying decay rates.  Traditional metrics for monitoring decay include volatile solids and plate counts, which may not provide the full picture of specific decay dynamics. In particular, the viable-but-not-culturable growth phase is challenging to assay.  Recently, more specific molecular techniques have been developed, such as DNA and RNA extraction with qPCR and RT-qPCR, ATP assays and live/dead cell-staining.  However, these assays have not been widely accepted or bench-marked against traditional techniques.  It is expected that molecular assays will generate kinetic constants that better reflect the viability and activity of the bacteria as they decay, generating a more integrated understanding of the decay process.  Cells grown in pure culture were spiked into microreactors and subjected to a variety of time/temperature treatments in both buffered pure culture and sludge matrices.  These scenarios were intended to mimic on a small scale typical waste treatment processes, more specifically pasteurization, thermophilic digestion and land application.  Results indicate decay curves similar to traditional curves but with constants that vary with respect to the strains and the characterization methods used.  The foundation laid by this work can be utilized in further studies involving other organisms in a variety of environmental scenarios. / Master of Science

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Thesis (M.Sc. (Palaeoarchaeology))--University of the Witwatersrand, Faculty of Science, 2003 / This project was inspired by the identification of 108 bone tools (dated roughly to between 2 and 1 Mya) from sites in the Cradle of Humankind World Heritage Site, Gauteng. An experimental study was lUldertaken in an attempt to answer the basic question of "what caused modification marks on early hominid bone tools?" Five experimental tools were used in each of seven different task oriented experiments. The purpose of this project was to broaden the existing database of experimentally employed bone tools and the associated process-pattern relationships. Analysis was based on an optical comparison of primarily microscopically, but also macroscopically visible usewear patterns observed on the experimental tools. The experimental data were then used to make inferences on a middle range theoretical level regarding the use of the fossil specimens and comment on the currently held opinions.

<p> This thesis sets out to examine how street youth use art as a mode of voice and what messages they choose to bring forward in their art. To complete this research a critical, post-modern framework was consulted. Alongside this a threeday, art-based research activity was planned and developed for street youth to participate in. Six street youth gathered at a drop-in centre/shelter to work on a collective art piece. Once the art piece was finished, messages from the art were analyzed through interview discussions with the youth, the literature, field notes and my own interpretations of what I was seeing. Findings of the street youth's messages were categorized as follows: public perception of street youth, being ignored/not being heard, expressions of hunger, sadness/pain, and coping/strengths. Art as a tool for voice was explored in the literature, and it was found that it has the ability to send powerful messages that can have consciousness-raising abilities, and even has instances of impacting organizational/structural changes. This research contributes to knowledge in various ways. First the community can learn from street youth voices that were gathered by an alternative medium. Also art-based methods can prove to be a more accessible way of collecting and interpreting data depending on the population you are working with. Finally, in the field of social work, it could be that art-based research is an alternative way to engage communities in research while at the same time challenging dominant knowledge processes.</p> / Thesis / Master of Social Work (MSW)

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