Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Thomas David Burleigh. / M.S.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / Includes bibliographical references (leaves 70-74). Also available in electronic version.

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Bibliography: leaves 260-302. / viii, 302 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / An investigation into the development of numerical models of the Gas Metal Arc Welding (GMAW) process. Models that solve the full equations of motion within the pool are very computationally expensive and their accuracy is limited by the available turbulence and free surface models. An approximate heat-conduction only model has therefore been developed which uses enhanced thermal conductivity to simulate convection within the pool. This model requires several orders of magnitude less computational resources than full cnvection solutions and much less empirical tuning than the modified conduction solutions. As such it appears to be a valuable method for accurate practical prediction of new weld thermal behaviour. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1996?

Bibliography: leaves 260-302. / viii, 302 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / An investigation into the development of numerical models of the Gas Metal Arc Welding (GMAW) process. Models that solve the full equations of motion within the pool are very computationally expensive and their accuracy is limited by the available turbulence and free surface models. An approximate heat-conduction only model has therefore been developed which uses enhanced thermal conductivity to simulate convection within the pool. This model requires several orders of magnitude less computational resources than full cnvection solutions and much less empirical tuning than the modified conduction solutions. As such it appears to be a valuable method for accurate practical prediction of new weld thermal behaviour. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1996?

Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1999. / Bibliography: leaves 191-198.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2009. / Includes bibliographical references (p. 73-75).

Este trabalho propõe um novo método para a detecção automática de cordões de solda em imagens radiográficas de juntas soldadas de tubulações. A metodologia proposta baseia-se na otimização de parâmetros que controlam e adaptam o posicionamento, tamanho e formato de uma janela de imagem, de modo a enquadrar a região da imagem que mais se assemelha à representação visual de um cordão de solda radiografado. A busca por parâmetros ótimos é conduzida por um algoritmo genético, que parte de soluções aleatoriamente geradas e as avalia com base em um conceito de similaridade entre imagens, oriundo de técnicas de casamento de protótipos. Além de se tratar de uma proposta inédita, a solução apresentada cobre uma diversidade de situações, incluindo problemas de detecção do cordão de solda para os quais ainda não havia sido encontrada uma solução automatizada que a literatura tenha referenciado. Os resultados dos testes realizados alcançaram um desempenho entre 93 e 100%, para um total de 478 imagens consideradas, que incluem exemplos de praticamente todas as técnicas de exposição radiográfica recomendadas pelo código ASME V, para inspeção de juntas soldadas de tubulações. Entrementes, uma técnica já existente de segmentação de imagens foi adaptada para desempenhar a detecção automática de defeitos de soldagem. Para tais testes, foram utilizados padrões radiográficos das principais classes de defeitos, provenientes do International Institute of Welding (IIW). Após modificações agregadas à técnica de segmentação utilizada, foi possível detectar exemplos de todas as classes de defeitos testadas. Tais resultados contribuem para a análise automática de radiografias industriais e visa melhorar a qualidade e eficiência na inspeção radiográfica de soldas. / This work proposes a new method for the automatic detection of the weld seam in radiographic images of pipeline welded joints. The proposed methodology is based on the optimization of parameters that are used to control and modify the position, size and shape of an image window, in order to enclose the image region that best matches the radiographic representation of a reinforced weld seam. The search for the best matching is managed by a genetic algorithm and uses an image similarity concept that is commonly applied on template matching procedures. The proposed technique solved weld seam detection problems for which no other automatic detection method was successful. The test results achieved an accuracy between 93% and 100%, regarding different tests circumstances, for a total of 478 radiographic images. The images data set included radiograph samples that cover all the recommended radiographic exposure techniques that are recommended, in the ASME V code, for inspection of pipeline welded joints. Meanwhile, a known image segmentation technique was modified and applied to perform the automatic detection of welding defects. For that test series, radiographic patterns from the International Institute of Welding (IIW) were used, including samples of the most popular classes of welding defects. After the used segmentation technique has been properly modified, defect detection samples were achieved for all the tested defect classes. Such results contribute with advancements in the automatic analysis of industrial radiographs and, as a final goal, aim at aggregating quality and efficiency to the radiographic inspection of welded joints.

Este trabalho propõe um novo método para a detecção automática de cordões de solda em imagens radiográficas de juntas soldadas de tubulações. A metodologia proposta baseia-se na otimização de parâmetros que controlam e adaptam o posicionamento, tamanho e formato de uma janela de imagem, de modo a enquadrar a região da imagem que mais se assemelha à representação visual de um cordão de solda radiografado. A busca por parâmetros ótimos é conduzida por um algoritmo genético, que parte de soluções aleatoriamente geradas e as avalia com base em um conceito de similaridade entre imagens, oriundo de técnicas de casamento de protótipos. Além de se tratar de uma proposta inédita, a solução apresentada cobre uma diversidade de situações, incluindo problemas de detecção do cordão de solda para os quais ainda não havia sido encontrada uma solução automatizada que a literatura tenha referenciado. Os resultados dos testes realizados alcançaram um desempenho entre 93 e 100%, para um total de 478 imagens consideradas, que incluem exemplos de praticamente todas as técnicas de exposição radiográfica recomendadas pelo código ASME V, para inspeção de juntas soldadas de tubulações. Entrementes, uma técnica já existente de segmentação de imagens foi adaptada para desempenhar a detecção automática de defeitos de soldagem. Para tais testes, foram utilizados padrões radiográficos das principais classes de defeitos, provenientes do International Institute of Welding (IIW). Após modificações agregadas à técnica de segmentação utilizada, foi possível detectar exemplos de todas as classes de defeitos testadas. Tais resultados contribuem para a análise automática de radiografias industriais e visa melhorar a qualidade e eficiência na inspeção radiográfica de soldas. / This work proposes a new method for the automatic detection of the weld seam in radiographic images of pipeline welded joints. The proposed methodology is based on the optimization of parameters that are used to control and modify the position, size and shape of an image window, in order to enclose the image region that best matches the radiographic representation of a reinforced weld seam. The search for the best matching is managed by a genetic algorithm and uses an image similarity concept that is commonly applied on template matching procedures. The proposed technique solved weld seam detection problems for which no other automatic detection method was successful. The test results achieved an accuracy between 93% and 100%, regarding different tests circumstances, for a total of 478 radiographic images. The images data set included radiograph samples that cover all the recommended radiographic exposure techniques that are recommended, in the ASME V code, for inspection of pipeline welded joints. Meanwhile, a known image segmentation technique was modified and applied to perform the automatic detection of welding defects. For that test series, radiographic patterns from the International Institute of Welding (IIW) were used, including samples of the most popular classes of welding defects. After the used segmentation technique has been properly modified, defect detection samples were achieved for all the tested defect classes. Such results contribute with advancements in the automatic analysis of industrial radiographs and, as a final goal, aim at aggregating quality and efficiency to the radiographic inspection of welded joints.

M.Ing. / The product of switching frequency and output power of solid state converters has increased dramatically during the past few years. This progress can mainly be attributed to the recent developments in power electronic switching devices. These developments are mainly responsible for a reduction in the physical size of the converter, especially that of the reactive components, and an increase in the dynamic response of the converter ...