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No description available.

The goal of this thesis is to determine the relationship between the macroscopic stress and the macroscopic strain for a variety of complex multiphase materials exhibiting rate-independent non-linear response at the micro-scale, based on experimental data obtained both at the local and macroscopic scales. A micro-macro secant mean field model (SMF model) based on the result of Eshelby and the approach of Mori and Tanaka is developed to model the behaviour of three particular systems which we have worked out by ourselves: 1) a ferrite-martensite steel produced by rolling in which we quantify the plastic anisotropy due to the morphological texture in terms of the Lankford's coefficient and pseudo yield surface; 2) a composite made of two continuous and interpenetrating phases: an aluminium matrix reinforced by a preform of sintered Inconel601 fibres. We quantify the coupled effects of temperature and phases co-continuity on the phases and overall stresses; 3) a TRIP-aided multiphase steel, in which the dispersed metastable austenite phase transforms to martensite. We derive the relationship between the overall uniaxial elastoplastic response and the progress of phase transformation, itself influenced by the thermodynamical, microstructural and mechanical properties. The stress-state dependence of the martensitic transformation is enlightened and explained. We demonstrate the existence of thermomechanical treatments leading to optima of ductility and strength-ductility balance. Finally, we show that the formability of TRIP-aided multiphase steels depends on the stability criterion.

To deploy a large group of autonomous robots in dynamic multi-tasking environments, a suitable multi-robot task-allocation (MRTA) solution is required. This must be scalable to variable number of robots and tasks. Recent studies show that biology-inspired self-organized approaches can effectively handle task-allocation in large multi-robot systems. However most existing MRTA approaches have overlooked the role of different communication and sensing strategies found in selfregulated biological societies. This dissertation proposes to solve the MRTA problem using a set of previously published generic rules for division of labour derived from the observation of ant,human and robotic social systems. The concrete form of these rules, the attractive field model (AFM), provides sufficient abstraction to local communication and sensing which is uncommon in existing MRTA solutions. This dissertation validates the effectiveness of AFM to address MRTA using two bio-inspired communication and sensing strategies: "global sensing - no communication" and "local sensing - local communication". The former is realized using a centralized communication system and the latter is emulated under a peer-topeer local communication scheme. They are applied in a manufacturing shop-floor scenario using 16 e-puck robots. A robotic interpretation of AFM is presented that maps the generic parameters of AFM to the properties of a manufacturing shopfloor. A flexible multi-robot control architecture, hybrid event-driven architecture on D-Bus, has been outlined which uses the state-of-the-art D-Bus interprocess communication to integrate heterogeneous software components. Based-on the organization of task-allocation, communication and interaction among robots, a novel taxonomy of MRTA solutions has been proposed to remove the ambiguities found in existing MRTA solutions. Besides, a set of domainindependent metrics, e.g., plasticity, task-specialization and energy usage, has been formalized to compare the performances of the above two strategies. The presented comparisons extend our general understanding of the role of information exchange strategies to achieve the distributed task-allocations among various social groups.

The air-water flow reqime transitions in a horizontal pipe under the influence of a stronq electric field perpendicular to the interface are studied. The separated flow model to predict flow regime transitions has been developed. The present version of the model is a modification of Taitel and Dukler's separated flow model. This assumes that all flow reqimes are perturbations from stratified smooth flow. Expressions for the electrical force are derived and added to the conservation and constitutive equations to obtain new transition criteria. The theoretical results are compared with observations of air-water flow in a 1.27 cm. and 1.9 cm. internal diameter pipe. Good agreement was found when no electric field was applied, however, the experimentally observed effect of the electric field was not as pronounced as predicted by theory. Further experiments to refine the theoretical model are presented. / Thesis / Master of Engineering (ME)

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Les propriétés finales des alliages métalliques sont directement liées à la microstructure de fin de mise en forme. Les mécanismes de recristallisation dynamique (DRX) et post-dynamique (PDRX) jouent un rôle important sur les évolutions microstructurales intervenant pendant et après les étapes de déformation à chaud. Dans ce contexte, un défi majeur pour les industriels et les chercheurs est de prédire la microstructure obtenue en fonction des conditions de mise en forme. Cela implique de bien connaître les mécanismes de DRX et PDRX et leur cinétique. Les modèles en champ complet permettent de modéliser explicitement la microstructure des alliages métalliques et ses possibles évolutions à l’échelle du polycristal. Ces modèles sont précis comparativement aux modèles œuvrant aux plus grandes échelles, mais ils sont généralement très couteux en termes de temps de calcul. Les modèles à champ moyen sont quant à eux basés sur une description implicite de la microstructure, conduisant à des temps de calcul considérablement réduits, mais ils reposent sur un grand nombre d’hypothèses, notamment topologiques. Cette thèse propose un nouveau modèle champ complet de DRX/PDRX et croissance de grains, capable de fonctionner en 2D comme en 3D, et une nouvelle approche en champ moyen, s'appuyant sur ces simulations en champ complet. La nouvelle approche champ moyen prend notamment mieux en compte les effets topologiques pour une meilleure prédiction des distributions de tailles de grains. Ce travail inclut une procédure de calibration et une validation des deux modèles s'appuyant sur une campagne d’essais expérimentaux sur un acier austénitique 304L. / Final properties of metal alloys are directly related to their microstructure, inherited from the processing route. Dynamic (DRX) and post-dynamic recrystallization (PDRX) mechanisms play a primordial role in microstructure evolutions occurring during and after hot-deformation. Within this context, predicting microstructures depending on the applied thermomechanical conditions is a major challenge for both industrials and researchers. This requires a good knowledge of recrystallization mechanisms and kinetics. Full field models are based on an explicit description of the microstructure of a metallic alloy, and its possible evolutions at a polycrystalline scale. These models are accurate compared to models operating at larger scales, but they generally lead to prohibitive numerical costs. On the other hand, mean field models are based on an implicit description of the microstructure, leading to considerably reduced numerical costs, but they are based on many assumptions, notably with regards to topology. The outcome of this PhD work is a new full field model of DRX/PDRX and grain growth, working in 3D as well as in 2D, and a new DRX/PDRX mean field approach which better accounts for topological effects, and provides better predictions for grain size distributions. This work also includes a calibration procedure and a validation of these two new models, using experimental data obtained from compression tests performed on the 304L austenitic steel.

A presente pesquisa for desenvolvida junto a pacientes hipertensos cadastrados em um Programa de Exercício Aeróbio de um Centro de Saúde do Município de Toluca - México, tendo por objetivo caracterizá-los de acordo com as variáveis do Modelo de Campo de Saúde de Lalonde: biologia humana, meio ambiente, estilo de vida e organização dos serviços de saúde e, analisar o sentir e o pensar destes pacientes sobre sua doença e os cuidados com a mesma. Participaram da pesquisa quarenta e oito pacientes, cujos dados foram obtido em duas fases; primeiramente obteve-se os dados referentes aos quatro elementos do Modelo de Campo de Saúde de Lalonde em seguida, por meio de cinco questões orientadoras foi possível identificar a experiência dos hipertensos com a doença, enfocando o pensar e o sentir destes pacientes, desde o diagnóstico até as mudanças e cuidados impostos pela doença; após a obtenção dos valores da PA, os pacientes, foram classificados em dois grupos: aqueles com PA controlada e aqueles de PA não controlada, de acordo com as recomendações do JNC-7 (2006). Entre os pacientes do grupo de PA controlada 77,08% eram mulheres: 54,16% tinham idade superior a 60 anos; 81,25% estavam com a PA controlada; 27,08% apresentavam sobrepeso e 68,75% possuíam RCQ maior que 90; 45,83% não sabiam indicar antecedentes familiares para a doença; 20,83% indicaram ser hipertensos há mais de dez anos; 72,91% faziam tratamento para a hipertensão arterial, 43,73% indicaram conhecer os valores de PA; 39,59% eram viúvos; 52,08% procediam do meio urbano; 68,75% possuíam nível de escolaridade baixo; 54,16% ocupavam-se dos afazeres domésticos; 70,83% indicaram realizar exercício físico, sendo a caminhada indicada por 66,67% deles; 75,0% não fumavam e 68,75% não consumiam bebida alcoólica; 66,67% indicaram apresentar estresse, sendo este mais freqüente em função de problemas familiares e no lar; 72,91% indicam fazer em média três refeições diárias e consumir alimentos com pouco sal (68,75%); 68,75% indicaram usar os serviços de saúde do sistema público, sendo que 54,16% indicaram procurar o serviço somente quando não se sentissem bem. Em relação ao que pensavam sobre sua doença e o cuidado, pode-se identificar que os hipertensos percebem como necessária a mudança de comportamento a partir da descoberta da doença, embora o início da doença não tenha gerado nenhuma mudança significativa. Os resultados deste estudo são importantes para o universo dos serviços de saúde do México, uma vez que demanda a necessidade de aprofundar estudos que gerem novos conhecimentos que possam contribuir para a melhoria do cuidado ao hipertenso. / This study was developed with hypertensive patients registered in an Aerobic Exercise Program in a Health Care Center in the city of Toluca-Mexico. The study objective is to characterize these individuals according to the Lalonde\'s Health Field Model variables: human biology, environment, life style, and health service organization. The study also aimed to analyze these patients\' feelings and considerations regarding their illness and their care towards it. Forty-eight patients took part in the study. Patient data was obtained in two phases: first, the data regarding the four Lalonde\'s Health Field Model elements were obtained, and, then, using five guiding questions, it was possible to identify the hypertensive patients\' experience with the illness, focusing on their thoughts and feelings from the moment of diagnosis to the changes imposed by the illness. After obtaining the patients\' blood pressure (BP) values, they were classified in two groups, according to JNC-7 (2006) recommendations: those with BP under control, and those with uncontrolled BP. Among patients in the controlled BP group, 77.08% were women, 54.16% were aged above 60 years, 81.25% did not have the BP under control, 27.08% were overweight, and 68.75% had a waist-hip ration (WHR) above 90. Among the hypertensive patients, 45.83% were unable to report any family history for the illness, 20.83% reported being hypertensive for over 10 years, 72.91% were under hypertension treatment, 43.73% reported knowing their BP values, 39.59% were widowed, 52.08% originated from the urban environment, 68.75% had a low educational level, 54.16% performed household chores, 70.83% reported doing physical exercises, with 66.67% reporting walking regularly, 75.0% are non-smokers, 68.75% do not drink alcoholic beverages, 66.67% reported having stress, which is rather often due to family problems, 72.91% reported eating at least three meals a day and eating foods with littlesalt (68.75%), 68,75% indicated using the public system\'s health care service, of which54.16% reported seeking the service only when they did not feel well. Regarding what the patients considerations about the illness and health care, is was possible to identify that they perceived that the change in behavior as something necessary for the change in behavior from as of the moment the illness is identified, regardless if the onset has not yet caused any significant change. The study results are important for the universe of health services in Mexico, since the requires the need for more profound studies that would generate new knowledge that could enhance the care offered to hypertensive individuals.

An analytical dispersion model has been derived to determine the distribution of velocities and concentrations of a tracer in a two-dimensional jet in a coflowing ambient fluid. The particular novelty of this model is that it bridges the gap between near-field (where initial momentum dominates behaviour) and far-field (where ambient turbulence is more important) domains. We describe this domain as the ???intermediate field???. In a literature review of coflowing jets we find several laboratory studies and models which can predict the velocities (and in some cases concentrations) in a 2D jet, however they all have shortcomings. None could fully account for ambient turbulence, and all were strictly near-field, i.e. they are unable to describe behaviour when ambient turbulence dominates the initial shear. A brief review of analytical far-field models was also undertaken. There are standard solutions for the dispersion of a 2D continuous source but none that allow for an initial source momentum or non-uniform velocity. As opposed to the near-field coflow approach used by other researchers we start from the far-field, modifying the simple diffusion models by perturbing the governing equations to allow for the initial momentum. Models are developed for both along-stream velocity and the concentration field of a tracer. From the velocity model, a comparison is made with experimental data available from one researcher (Wang, 1996) and an existing near-field coflow model PJCMERG (Davidson, 1989). The initial conditions (width and excess velocity) for our model are determined by Gaussian curve fitting to an arbitrary point in the near-field. The diffusivity parameter is used to adjust (tune) the model until the centreline velocity profile matches. We can always achieve this match and to a much closer degree than PJCMERG. There are no available laboratory or field data for concentrations of a tracer in a 2D coflowing jet although the near-field model PJCMERG does have a tracer component. We demonstrate how PJCMERG cannot converge to any far-field model, while our model provides a neat transition between the near-field and far-field. We have started the extension of the 2D model to the more common 3D situation although we have yet to carry out any comparisons with other models or data. The model development is included in an appendix for other researchers to pick up.