Made available in DSpace on 2014-06-12T15:56:56Z (GMT). No. of bitstreams: 2 arquivo3093_1.pdf: 6869100 bytes, checksum: 84babf04dc9aa424f94c497c190576d6 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Nós apresentamos um método eficiente para síntese de padrões definidos como uma coleção de elementos vetoriais bidimensionais, a partir de uma amostra do padrão. Soluções recentes para este problema fazem uso de triangulação da entrada ou de medidas estatísticas da amostra para controlar o estágio de síntese. Nós propomos um método aplicável a texturas coloridas, desde regular até estocásticas, e que provê controle local sobre a densidade dos elementos. A amostra é segmentada em grupos de elementos similares e definimos uma nova métrica, que não ignora elementos isolados, para cálculo de distância entre vizinhanças de elementos, para comparar vizinhanças diferentes e incompletas. O laço principal de síntese consiste em um crescimento procedural, onde sementes são substituídas por referências a elementos da amostra, gerando novas sementes até que o espaço de síntese seja preenchido. Os resultados mostram a mesma qualidade visual de trabalhos anteriores, e resolvem padrões não abordados em trabalhos anteriores. Nós também mostramos que este método pode ser estendido para sintetizar padrões vetoriais sobre malhas poligonais

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The focus of this thesis is the definition of a complete framework for texture-based annotation and retrieval. This framework is centred on the concept of "texture codes", so called because they encode the relative energy levels of Gabor filter responses. These codes are pixel-based, robust descriptors with respect to illumination variations, can be generated efficiently, and included in a fast retrieval process. They can act as local or global descriptors, and can be used in the representations of regions or objects. Our framework is therefore capable of supporting a wide range of queries and applications. During our research, we have been able to utilise results of psychological studies on the perception of similarity and have explored non-metric similarity scores. As a result, we have found that similarity can be evaluated with simple measures predominantly relying on the information extracted from the query, without a drastic loss in retrieval performance. We have been able to show that the most simple measure possible, counting the number of common codes between the query and a stored image, can for some algorithmic parameters outperform well-proven benchmarks. Importantly also, our measures can all support partial comparisons, so that region-based queries can be answered without the need for segmentation. We have investigated refinements of the framework which endow it with the ability to localise queries in candidate images, and to deal with user relevance feedback. The final framework can generate good and fast retrieval results as demonstrated with a databases of 3723 images, and can therefore be useful as a stand-alone system. The framework has also been applied to the problem of high-level annotation. In particular, it has been used as a cue detector, where a cue is a visual example of a particular concept such as a type of sport. The detection results show that the system can predict the correct cue among a small set of cues, and can therefore provide useful information to an engine fusing the outputs of several cue detectors. So an important aspect of this framework is that it is expected to be an asset within a multi-cue annotation and/or retrieval system.

Alzheimer's Disease (AD) is a major concern for the elderly population, currently affecting over 670,000 people in the UK. With the continual increase in the age of the population the problem is expected to rise. There is no known cure to the condition and a definite diagnosis cannot be made in life. Clinical diagnosis is considered to be approximately 80% - 90% accurate, sometimes taking up to a year to assess. Early detection could aid in the care and possible development of better treatments or even a cure. AD has been shown to alter the structure and global texture of the brain. Studies using Magnetic Resonance imaging (MRI) and Computerised Tomography (CT) have been used to detect these changes with some success by some researchers. Positron Emission Tomography (PET) imaging is a functional imaging modality and in theory before structural changes are evident functional changes should be apparent. Therefore we utilise PET images for this study. This thesis will exploit the fact that AD alters the global texture of the brain. Texture features extracted from fluoro-deoxy-glucose (FDG) PET images and sinograms of the brain will be used. Most texture feature extraction methods fail, due to poor signal to noise ratio so we will use a novel texture feature extraction method known as the Trace transform - triple features, which can extract features directly from raw data acquired by PET scanners. Classifiers will be used to aid in the separation of the two groups, namely AD patients and normal controls. The Trace transform - triple feature method has proven its potential as a good feature extraction technique. It enabled us to achieve classification accuracy of up to 93% on raw sinogram data using a combination of five features. This result is very good compared with the clinical accuracy of 80% reported by most researcher. It is comparable to results obtained by Kippenhan et al [52, 53, 51, 50], who used regional metabolic activity using PET and a neural network classifier. Monomial features extracted from images achieved accuracies as high as 87%. These features are good discriminators, however, they suffer from lack of scaling invariance. This is problematic as brain sizes do vary considerably. The use of registration and extraction of regional information failed to produce fruitful results. This is principally due to poor registration. The registration failed primarily because a very small cross section of the brain was available. Also the effect of AD alters the structure of the brain. Since the registration relies on matching structure, it becomes questionable whether one can actually register automatically a very degraded AD brain. Gender and age are crucial to the progress of Alzheimer's disease. Age and gender matching is not sufficient to get the best results. This thesis has shown that performance gains of up to 11% can be attained by simply incorporating age and/or gender into the classification model. However, the maximum classification accuracy was not improved any further.

Irradiation sterilization of precooked, hermetically sealed meat provides a shelf-stable, ready-to-eat product that can be stored for long periods of time without refrigeration. The Atomic Energy Corporation of South Africa started to develop precooked, shelf-stable meat products during the late 1970’s, using gamma radiation from a 60Co source at dose levels of at least 45 kGy. A number of meat dishes were successfully developed though problems were experienced with the texture of dry-packed roast beef slices, as these were found to be slightly dry. Polyphosphates can possibly be used to alleviate the textural problems found in precooked irradiation-sterilized meat because polyphosphates are known to increase the water binding properties of meat proteins, resulting in a juicy, tender product. The choice of cattle breed used for the preparation of precooked meat dishes may also affect cooked meat texture, due to genotypic differences in the amount and especially the solubility of collagen. Biceps femoris and semitendinosus muscles obtained from Afrikaner (Bos Indicus), Hereford (Bos Taurus) and Simmental (Bos Taurus) steers were treated with low levels of sodium tripolyphosphate (0.3% and 0.5%) and tetrasodium pyrophosphate (0.22% and 0.36%) in combination with 0.7% salt. The precooked meat was vacuum packed in flexible pouches and irradiated in the frozen state (-40°C) with a 60Co gamma source until a minimum target dose of 45 kGy was reached. Various physico-chemical tests as well as descriptive generic sensory evaluation were performed on the samples to determine the effect of breed, polyphosphate treatment and irradiation on the physico-chemical and sensory properties of irradiated precooked beef. Cattle breed affected the texture of precooked, irradiated, shelf-stable beef, with Afrikaner biceps femoris giving a more tender, juicy product than that of Hereford and Simmental. The low levels of polyphosphates used in combination with salt successfully increased the juiciness and tenderness of precooked, shelf-stable beef. There was little difference in the physico-chemical and sensory results obtained from samples treated with the two different polyphosphates, or the level at which the polyphosphates were administered. Irradiation sterilization of precooked beef resulted in a tender product. Comparison of irradiated and non-irradiated samples revealed that the irradiated samples had longer sarcomere and I-band lengths, and shorter A-band lengths, which explained the increased tenderness in irradiated samples. An increase in both soluble collagen and % collagen solubility after irradiation sterilization further substantiated the tenderness results. Treatment of the biceps femoris with low levels of sodium tripolyphosphate or tetrasodium pyrophosphate in combination with salt, prior to cooking and irradiation, resulted in a juicy, shelf-stable product. Irradiation sterilization did, however, produce a detectable wet dog flavour and aroma, and more research is required into improving the flavour and aroma of irradiation sterilized beef. Although this research indicated that irradiation of cooked, polyphosphate treated Afrikaner meat resulted in the most tender and juicy end-products, it is recommended that sensory evaluation using a consumer panel also be conducted, in order to determine if this level of tenderness is acceptable, or if it is over tender due to excessive degradation of the connective tissue. / Dissertation (MSc)--University of Pretoria, 2005. / Food Science / unrestricted

Le zirconium et de titane sont des métaux de structure hexagonale. Ils présentent donc une plus faible symétrie cristalline que les métaux usuels (Fer, Aluminium,...) et par conséquent une anisotropie de propriété très marquée. Malgré cette forte anisotropie et les applications exigeantes dans lesquelles sont employés leurs alliages, les mécanismes de recristallisation et de changement de texture dans ces métaux ont été peu étudiés en comparaison de leurs homologues cubiques. L'étude de l'évolution de texture au cours du recuit après différents chargement initiaux nous a permis d'établir les mécanismes d’évolutions de texture dans le Zirconium. Nous avons notamment montré que pour des faibles taux de déformation en laminage croisé, la texture de recristallisation évolue très vite, en raison de la distribution d'orientation spécifique des germes dans la microstructure initiale, après laminage transverse, la texture évolue également rapidement en raison d'une corrélation entre énergie de déformation et orientation, qui accroît l'effet de la croissance orientée, de plus, les mécanismes de changement de texture au cours de la croissance normale et anormale des grains ont été élucidés, notamment grâce à l’utilisation de simulations numériques (type Monte-Carlo) / Zirconium and Titanium are hexagonal metals. Thus, they have a weaker symmetry than cubic metals, and a stronger crystalline anisotropy. Despite this strong anisotropy, the fundamental mechanisms of the texture evolution of these metals has not been deeply investigated yet. We studied here the texture and microstructure evolution during annealing after several conditions of deformation, and showed that : slow texture change is expected in grain growth after severe rolling, because of oriented growth rapid texture change after low reductions is due to oriented nucleation transverse rolling gives rise to a correlation between orientation and stored energy in the deformed material, which also induces fast texture changes. These mechanisms have been explained on the basis of microstructure specificities. In addition, texture evolution during normal and abnormal grain growth have been studied in details, and moddeling was used to confirm some hypotheses on boundary mobility anisotropy

The origin of texture components associated with rare-earth (RE) element additions in wrought magnesium (Mg) alloys is a long-standing problem in magnesium technology. The objective of this research is to identify the mechanisms accountable for rare-earth texture during dynamic recrystallization (DRX). Towards this end, we designed binary Mg-Cerium and Mg-Gadolinium alloys along with complex alloy compositions containing zinc, yttrium and Mischmetal. Binary alloys along with pure Mg were designed to individually investigate their effects on texture evolutions, while complex compositions are designed to develop randomized texture, and be used in automotive and aerospace applications. We selected indirect extrusion to thermomechanically process our materials. Different extrusion ratios and speeds were designed to produce partially and fully recrystallized microstructures, allowing us to analyze DRX from its early stages to completion. X-ray diffraction, electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) were used to conduct microstructure and texture analyses Our analyses revealed that rare-earth elements in zinc-containing magnesium alloys promote discontinuous dynamic recrystallization at the grain boundaries. During nucleation, the effect of rare earth elements on orientation selection was explained by the concomitant actions of multiple Taylor axes in the same grain. Isotropic grain growth was observed due to rare earth elements segregating to grain boundaries, which lead to texture randomization. The nucleation in binary Mg-RE alloys took place by continuous formation of necklace structures. Stochastic relaxation of basal and non-basal dislocations into lowangle grain boundaries produced chains of embryos with nearly random orientations. Schmid factor analysis showed a lower net activation of dislocations in RE textured grains compared to ones on the other side of the stereographic triangle. Lower dislocation densities within RE grains favored their growth by setting the boundary migration direction toward grains with higher dislocation density, thereby decreasing the system energy. We investigated the influence of RE elements on extension twinning induced hardening. RE addition enhanced tensile twinning induced hardening significantly. EBSD analysis illustrated that tensile twins cross low angle grain boundaries in Mg-RE alloys, which produced large twins and facilitated transmutation of basal to prismatic dislocations. Higher activity of pyramidal II dislocations in Mg-RE alloys resulted in higher twinning induced hardening.

With increasing meat goat production in the United States, it is necessary to examine carcass composition and quality parameters of goats at various stages of growth. In this study, intact male Boer and Kiko Goats (n = 48) were harvested after 0, 4, 8, or 12 wk on feed. Increased feeding duration led to increased final live and carcass weight, and increased dressing percent. Leg and shoulder circumferences and body wall thickness increased, but 12th rib fat and Longissimus muscle area did not change across all feeding durations. Percent carcass fat increased and percent bone decreased, but percent muscle did not differ across feeding durations. Boer carcasses were composed of more fat and less muscle than Kiko carcasses. Increased feeding duration increased the weight of all primal cuts, but also increased the percentage of fat in the shoulder, breast, rack, loin, sirloin, leg, hindshank, ribs, neck, and trim. Shoulder composition produced the strongest correlations with entire side composition compared to all other primal cuts and may be useful for predicting carcass composition. Increasing feeding duration led to decreased Warner-Bratzler shear force of Longissimus, Semitendinosus, and Infraspinatus muscles, suggesting that cold shortening may have caused toughening of these muscles in smaller, leaner carcasses. Entire boneless carcass sides were ground, mixed, and formed into patties to evaluate cook loss, texture profile analysis, and descriptive sensory characteristics. Increasing feeding duration increased percent fat and decreased moisture in raw ground meat, but breed and feeding duration did not affect cook loss. Springiness, hardness, and cohesiveness were not affected by breed or feeding duration. Increased feeding duration increased aroma intensity and goaty, bloody, musty, and liver/organy aromas; salty, bitter, umami, grassy, goaty, fat, liver/organy, metallic, earthy, and chemical tastes; and juiciness and oiliness, while decreasing chewiness and crumbliness. Results indicate that younger, smaller goats produced leaner carcasses with less intense aroma and flavor attributes, however muscles from smaller carcasses may be tougher.

At low temperatures, glide twinning activates in HCP structures easier than non-close packed slip necessary to accommodate strain along the c-axis. In contrast to slip, twinning occurs as an accumulation of successive stacking faults that properly report reconstruction of the stacking sequence in a new crystal-reorientated lenticular lamella. These faults are spread by partial dislocations known as twinning dislocations, forcing atoms to switch positions by shear into new crystal planes. As the twinning dislocations thread the faults, the new crystal lamella grows at the expense of the parent. Grain texture changes upon strain, and a strong non-linear trend marks the strain hardening rate. The strain hardening rate changes to a point where it switches sign upon strain. Since activation of these twinning dislocations obey Schmid’s law, twinning could be precluded or exhaustively promoted in sharp textures upon slight changes in loading orientations, so strong anisotropy arises. Moreover, a twinning shear can only reproduce the stacking sequence in one direction, unless the twin mode changes or the c/a ratio crosses a certain ratio. When a twin mode arises with reversed sign, the reorientation is different and more importantly, the strength is different and also the growth rate. Therefore, in addition to strain anisotropy, twin polarity induces a strong asymmetry in textured HCP structures, e.g. wrought HCP metals. This anisotropy/asymmetry is still a barrier to the great economic gain expected from the industrialization of low density, high specific strength and stiffness, HCP Magnesium. This barrier has stimulated efforts to identify the missing links in current scientific knowledge to proper prediction of Magnesium anisotropy. The effect of twinninginduced texture change on the mechanical response is of a major concern. Mesoscale modelers still struggle, without success to predict simultaneously twinning and strain hardening rates upon arbitrary loading directions. We propose a new mechanism that relies on admitting dislocation populations of the twin by dislocations transmuted from the parent when they intersect twinning disconnections. These dislocations interact with original dislocations created in the twin to cause hardening able to faithfully capture anisotropy upon any loading orientation and any initial texture.