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This thesis work presents a simple and practical technique for seamlessly texturing quadrilateral meshes. Using this technique, an isotropic homogeneous texture can be mapped to any quadrilateral mesh without any discontinuity or singularity in the resultant texturing. The method involves organizing a set of square texture tiles that satisfy specific boundary conditions into one texture image file which is called a tiled texture. Based on the tiled textures, we have developed an extremely simple texture mapping algorithm that randomly assigns one tile to every patch in any given quadrilateral mesh. The mapping technique developed yields singularity free textures, regardless of the singularities existing in the quadrilateral mesh, gives seamless and continuous boundaries across textures and provides an aperiodic and interesting look to the entire textured surface.

Osteoporosis is caused by loss of bone mineral content, which leads to bone fractures or structural deformations of bone. Osteoporosis usually occurs when people get older, after menopause in women, or it can be caused by a lack in the intake of a sufficient amount of calcium and vitamin D. Until recently, osteoporosis was considered to be an unavoidable part of aging, but today, approved and effective treatments can be used to deal with the consequences. At present, determination of risk of bone abnormalities is done by measuring the density of bone (largely determined by calcium content). Dual energy X-ray Absorptiometry (DXA) is the gold standard technique for measuring bone mineral density (BMD). Even though BMD is one of the principal determinants of bone strength, BMD measurements do not give information about variation of trabecular structure of bone. That's why DXA alone has limited ability to predict who will sustain an osteoporotic fracture. To predict fracture risk of patients, the texture analysis of the DXA images is of interest as a measure to predict fracture in addition to BMD. This thesis focuses on the application of texture analysis to digital images of bone scans of patients at risk of fracture and osteoporosis. Texture analysis was performed by analyzing the variation of grey level patterns of pixels of DXA images. Texture analysis of such images will give an idea of the variation of grey scale patterns of pixels between normal and osteoporotic DXA images of bone. Existing texture analysis measures such as contrast measures of co-occurrence matrices and mean slope value of fractal dimension based measure are used to analyze the texture of DXA images. An alternative partitioning technique is proposed as a measure of the texture analysis.

Magnesium and its alloys have been considered as alternatives to aluminum alloys and steels for structural applications in automotive and aerospace applications due to their superior specific strength and light-weight. However, they have hexagonal-close packed (hcp) structure, and thus have a small number of deformation systems resulting in low ductility and formability near room temperature, anisotropic thermo-mechanical response and strong deformation textures. The aim of this work is to investigate experimentally the effect of crystallographic texture generated during severe plastic deformation (SPD), on the subsequent formability and mechanical flow anisotropy in AZ31B Mg alloy. The proper control of grain size and texture through SPD is expected to result in better low temperature formability and better control of mechanical flow anisotropy. AZ31B Mg alloy has been successfully processed using equal channel angular extrusion (ECAE) following different processing routes, multiple passes, and different processing temperatures, in order to obtain samples with a wide variety of grain sizes, ranging from ~370 nm up to few microns, and crystallographic textures. Low temperature processing of the AZ31B Mg alloy was successful after initial high temperature processing. Smaller grain sizes were achieved using the temperature step-down method leading to incremental reduction in grain size at each ECAE pass. The temperature step-down method was utilized to develop hybrid ECAE routes to obtain specific crystallographic textures. Optimized hybrid ECAE routes were developed which resulted in a high strength/high ductility material with the average grain size of ~370 nm. The ECAE processed alloy showed a high tensile yield strength of ~380 MPa that has never been reported so far in AZ31 ingot metallurgy Mg alloys. The influence of grain size on the critical stress for the activation of individual deformation mechanisms was also investigated by systematically controlling the texture and grain size, and assuming the activation of mainly a single deformation mechanism through the careful selection of the loading direction on the processed samples. It was revealed that the Hall-Petch slope for the basal slip was much smaller than those of prismatic slip and tensile twinning.

Osteoporosis is caused by loss of bone mineral content, which leads to bone fractures or structural deformations of bone. Osteoporosis usually occurs when people get older, after menopause in women, or it can be caused by a lack in the intake of a sufficient amount of calcium and vitamin D. Until recently, osteoporosis was considered to be an unavoidable part of aging, but today, approved and effective treatments can be used to deal with the consequences. At present, determination of risk of bone abnormalities is done by measuring the density of bone (largely determined by calcium content). Dual energy X-ray Absorptiometry (DXA) is the gold standard technique for measuring bone mineral density (BMD). Even though BMD is one of the principal determinants of bone strength, BMD measurements do not give information about variation of trabecular structure of bone. That's why DXA alone has limited ability to predict who will sustain an osteoporotic fracture. To predict fracture risk of patients, the texture analysis of the DXA images is of interest as a measure to predict fracture in addition to BMD. This thesis focuses on the application of texture analysis to digital images of bone scans of patients at risk of fracture and osteoporosis. Texture analysis was performed by analyzing the variation of grey level patterns of pixels of DXA images. Texture analysis of such images will give an idea of the variation of grey scale patterns of pixels between normal and osteoporotic DXA images of bone. Existing texture analysis measures such as contrast measures of co-occurrence matrices and mean slope value of fractal dimension based measure are used to analyze the texture of DXA images. An alternative partitioning technique is proposed as a measure of the texture analysis.

Visual perception of images is closely related to the recognition of the different texture areas within an image. Identifying the boundaries of these regions is an important step in image analysis and image understanding. This thesis presents supervised and unsupervised methods which allow an efficient segmentation of the texture regions within multi-texture images. The features used by the methods are based on a measure of the fractal dimension of surfaces in several directions, which allows the transformation of the image into a set of feature images, however no direct measurement of the fractal dimension is made. Using this set of features, supervised and unsupervised, statistical processing schemes are presented which produce low classification error rates. Natural texture images are examined with particular application to the analysis of sonar images of the seabed. A number of processes based on fractal models for texture synthesis are also presented. These are used to produce realistic images of natural textures, again with particular reference to sonar images of the seabed, and which show the importance of phase and directionality in our perception of texture. A further extension is shown to give possible uses for image coding and object identification.

Typescript (photocopy) / xxv, 179 leaves : ill. (part col), maps ; 30 cm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1982

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Soil Science, 1982. / Typescript (photocopy).

Thesis (M.Ag.Sc.)--University of Adelaide, 1939. / Typewritten. Includes bibliographical references.