Made available in DSpace on 2016-04-29T14:16:40Z (GMT). No. of bitstreams: 1 Valeria de Oliveira Albuquerque.pdf: 1204119 bytes, checksum: f224a058d3a86ee6a6a32a0c384a8cfe (MD5) Previous issue date: 2015-03-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / This thesis discusses the teaching in higher education Private institutions in the city of São Paulo (IPES), and aims to analyze the conditions and relations in which this work is done, individualising its implementation, especially in the context of growth private education. With regard to the object of this study, we consider teaching a type of work inserted in capitalist relations of production and their living subjects - teachers - employed in the service sector. We tried to understand how higher education facing the market and the capitalist sociability conditions, determines and features the work of social worker in teaching, and to identify current strategies of labor precarization ties and intensification of the teaching workload social worker in IPES. For the unveiling of the thesis subject, bibliographical and documentary research has been done, and access to other sources as major newspapers and internet research, considering the rapid changes in the nature of the sponsors of the IPES, in these last five years have engaged in intense economic processes of sale, merger, acquisition and opening of capital in the stock market, which imposed new elements for teaching and research. To collect empirical data, there was qualitative research, based on semi-structured interviews and form, and personal contacts, by email or by phone. Direct observation was due to some interviews have taken place in the space of IPES, where interviewed on assignment. The research sample comprised 14 Private Institutions of Higher Education (IPES), offering classroom course of social work in the city of São Paulo. The subject of research were 13 social workers teachers, with bond of at least 3 semesters in a row in the same IPES. The analysis, based on the studies and the results of empirical research, pointed out that the main factor of precarization and intensification of teaching is the incompatibility between the procurement regime hourly and own demands of teaching in university teaching / Esta tese discute o trabalho docente nas Instituições Privadas de Ensino Superior na cidade de São Paulo (IPES), e tem o objetivo de analisar as condições e relações em que este trabalho se concretiza, particularizando a sua realização, sobretudo, no contexto de crescimento da educação privada. No que se refere ao objeto deste estudo, consideramos a docência um tipo de trabalho inserido nas relações capitalistas de produção e seus sujeitos vivos os professores trabalhadores assalariados do setor de serviços. Buscou-se entender como a educação superior voltada para o mercado e para a sociabilidade capitalista condiciona, determina e caracteriza o trabalho do assistente social na docência, bem como apontar as estratégias atuais de precarização dos vínculos trabalhistas e de intensificação da carga de trabalho do docente assistente social nas IPES. Para o desvendamento do objeto da tese, foram realizadas pesquisas bibliográfica e documental, além do acesso a outras fontes como jornais de grande circulação e pesquisa na internet, considerando as rápidas mudanças na natureza das mantenedoras das IPES, que nesses últimos cinco anos se envolveram em intensos processos econômicos de venda, fusão, aquisição e abertura de capitais na bolsa de valores, o que impôs novos elementos para o trabalho docente e para a pesquisa. Para a coleta de dados empíricos, realizou-se pesquisa de natureza qualitativa, tendo como base entrevistas semiestruturadas e formulário, além de contatos pessoais, por e-mail ou por telefone. A observação direta se deu em razão de algumas entrevistas terem se realizado no espaço da IPES, onde a entrevistada realizava seu trabalho. O universo da pesquisa compreendeu 14 Instituições Privadas de Ensino Superior (IPES), com oferta de curso presencial de Serviço Social na cidade de São Paulo. Os sujeitos da pesquisa foram 13 assistentes sociais professoras, com vínculo de pelo menos 3 semestres seguidos na mesma IPES. A análise realizada, a partir dos estudos e dos resultados da pesquisa empírica, apontou que o principal fator de precarização e intensificação do trabalho docente é a incompatibilidade entre o regime de contratação horista e as demandas próprias do trabalho docente no magistério superior

La maîtrise de la température des composants à forte dissipation, notamment dans les systèmes électroniques nomades, constitue un verrou à leurs développements. Que ce soit pour l'électronique de puissance ou les calculateurs, les densités de puissance requièrent l'utilisation de systèmes de refroidissement de plus en plus performants, en particulier dans le cas des microprocesseurs qui associent miniaturisation et augmentation des fréquences d'horloge. Les conséquences sont multiples, limitation des performances, augmentation de la consommation et du taux de défaillance. C'est dans ce contexte que le projet CANOPEE, réunissant un consortium de partenaire industriel et académique, propose de développer et démontrer les avantages d'une solution technologique active récemment brevetée et appelée OnduloTrans. Elle consiste en un dispositif échangeur-pompe, permettant à la fois d'obtenir un excellent transfert thermique et d'assurer le pompage du fluide caloporteur. OnduloTrans est une solution active de refroidissement basée sur la déformation dynamique d'une paroi d'un canal. Le dispositif est fixé directement à l'aplomb du composant à refroidir. Le canal est déformé suivant une onde progressive pour créer un pompage péristaltique. L'intensification des transferts est obtenue lorsque les variations dynamiques des dimensions du canal viennent perturber la couche limite à l'interface conduction/convection. Le travail de la thèse consiste à concevoir et développer une solution d'actionnement intégrée permettant de mouvoir la paroi souple. Il s'accompagnera d'essais concrets témoignant des performances thermiques de cette solution. L'actionnement mis en oeuvre doit respecter les contraintes hydrauliques et thermiques de l'application embarquée visée, tout particulièrement le faible encombrement et une consommation électrique minimale. La difficulté réside dans les critères antagonistes que sont la production d'une onde progressive de grande amplitude dans un milieu aux dimensions centimétriques. Le manuscrit s'articule en trois parties. Dans un premier temps les solutions d'actionnement envisageables seront explorées. Pour ce faire, la solution OnduloTrans est d'abord décrite. Un état de l'art des solutions de conversion électromécanique, puis des micropompes péristaltiques est entrepris. Les phénomènes hydrauliques propres au micropompage péristaltique sont abordés pour cerner la problématique du développement de l'actionnement. Ensuite les deux chapitres suivants détaillent l'étude de deux solutions piézoélectriques distinctes. Une première solution piézoélectrique à onde discrète est développée dans le second chapitre. Elle consiste en une répartition d'actionneurs flextensionnels le long de la paroi souple. Une méthodologie de prédimensionnement basée sur des modèles mécaniques simples est présentée. L'onde progressive créée étant très particulière, une méthode analytique de calcul du débit, validée par simulations numériques, permet d'étudier l'influence de la commande des actionneurs. Un prototype est finalement réalisé avec l'aide des partenaires. De nombreux essais sont ensuite réalisés afin de valider les différentes hypothèses et déterminer les premières performances hydrauliques et thermiques du dispositif. Le troisième chapitre aborde une solution à onde progressive continue et actionnement intégré à la membrane. Le but est ici de prouver le concept de pompage péristaltique par flexion contrôlée d'une plaque intégrant une couche piézoélectrique. Un modèle de dimensionnement 1D constitué de tronçons piézoélectriques répartis à la surface est tout d'abord présenté. La répartition des segments piézoélectriques fait ensuite l'objet d'une étude paramétrique afin de définir judicieusement leur disposition, ceci en vue de maximiser le débit théorique. Cette étude paramétrique est finalement couplée à une optimisation des commandes électriques, évaluée par les résultats d'un prototype. / Controlling the temperature of components with high thermal dissipation is a constraining factor in their developments, especially in embedded electronic systems. Power density, whether in computing or power electronics, requires the use of ever more efficient cooling systems. This is especially true for microprocessors in which increasingly miniaturization and clock frequency are combined. Consequently, without the adequate cooling, the performance is severely limited and its power consumption increased as well as the failure rate. In this challenging context a consortium of industrial and academic partners created the CANOPEE project. CANOPEE focus is to develop and prove the advantages of a recently patented solution called OnduloTrans. The solution is an exchanger-pump device, ensuring at the same time an excellent heat transfer and the pumping of the coolant. OnduloTrans is an active cooling solution based on the dynamic deformation of a thin wall. This deformation is in the manner of a pseudo travelling wave to satisfy a peristaltic pumping. The device is fixed directly above the component to be cooled, thus the liquid flows on its surface. The enhancement in heat transfer is obtained when the dynamic variations of the channel thickness disturb the boundary layer near the conduction / convection interface. The purpose of this thesis was to study the capability of such active pumping system and to design an integrated actuation solution to move the flexible wall. It will result to experimental tests showing the thermal performance of this solution. The implemented actuation system must respect the constraints for on-board applications, especially compactness and minimal power consumption. The challenge stands in the trade-off between the production of a large amplitude travelling wave and the limited volume available. The manuscript is divided into three parts. Initially, the different actuation solutions will be explored. To do this, the OnduloTrans solution is first described. Then, a state of the art of electromechanical conversion solutions and peristaltic micropumps is undertaken. After that, the specific hydraulic phenomena involved in peristaltic micropumps are discussed to determine the difficulties in the development of such actuation system. Then the two next chapters detail the study of two distinct piezoelectric solutions. A discrete wave piezoelectric solution is presented in the second chapter. It consists of a distribution of flextensional actuators along the flexible wall. A pre-dimensioning methodology based on simple mechanical models is presented. The created wave is very particular, so an analytical method is developed to evaluate the flow rate and making possible to study the impact of the actuator control strategy. This algorithmic method is validated by comparison with finite element numerical simulations. A prototype is finally made with the support of partners. Several tests are then carried out in order to validate the hypotheses and evaluate the preliminary hydraulic and thermal performances of the prototype. The third chapter addresses a continuous travelling wave solution and an actuation system integrated into the membrane. The purpose here is to prove the concept of peristaltic pumping by controlled bending of a plate incorporating a piezoelectric layer. A 1D dimensioning model consisting of piezoelectric segments distributed on the surface is first presented. The distribution of the piezoelectric segments is then the subject of a parametric study to judiciously define their arrangement, in order to maximize the theoretical flow. This parametric study is finally coupled with an optimization of electrical controls, and compared to the experimental results of a prototype.

Les systèmes diphasiques à pompage capillaire sont couramment utilisés pour contrôler la température de l'électronique embarquée. Ces systèmes sont fiables et performants, mais ils présentent certaines limites associées essentiellement à la vaporisation dans le milieu poreux (limite capillaire, limite d'ébullition). Une façon d'étendre leurs performances en termes de longueur de transport de la chaleur et d'intensification des transferts serait de les coupler avec un système mécaniquement actif. Un des moyens pour réaliser cela est d'utiliser les forces électro-hydro-dynamiques (EHD) se développant dans le fluide lorsqu'on applique un champ électrique. Les travaux proposés sont une contribution à la compréhension de l'interaction entre une interface liquide-vapeur et un champ électrique afin de déterminer quels sont les mécanismes qui dans ces conditions contrôlent le pompage et le transfert de chaleur. La première partie se focalise sur l'étude expérimentale d'une interface liquide-vapeur sous un champ électrique avec ou sans flux de chaleur dans une configuration très académique (deux électrodes planes et verticales) tout en étant proche de ce qui se passe dans une cannelure de caloducs par exemple. L'objectif est d'observer, de quantifier et d'analyser les effets (forces, structures, instabilités) se développant sur l'interface. Une analyse a ensuite été menée à partir de modèles 1D et 2D. Nous avons ainsi pu vérifier que parmi l'ensemble des forces s'exerçant sur l'interface, la force diélectrophorétique est celle qui contrôle sa position et sa forme avec ou sans vaporisation. On a montré cependant qu'il existait des effets de couplage avec la conduction électrique dans le liquide pouvant sensiblement agir sur la courbure de l'interface. Enfin, les résultats en vaporisation ont confirmé que le champ électrique, en donnant des moyens de contrôle de la position et de la structure de l'interface de vaporisation, peut être effectivement mis à profit pour une intensification des transferts de chaleur proches d'une paroi chauffée. Dans un dernier volet, les travaux se sont concentrés sur la mise en mouvement d'un liquide diélectrique en mettant à profit le régime de conduction. Une étude expérimentale permettant d'étudier l'influence des différents paramètres (géométrie des électrodes, distance inter électrodes, nombre de modules) a été réalisée dans les fluides HFE-7000 et HFE-7100. Les résultats ont montré une faible reproductibilité des performances de la pompe pour ces fluides suggérant une forte sensibilité des phénomènes à l'état de surface des électrodes et aux régimes parasites d'injection de charge. / Two-phase systems based on the capillary pumping are widely used for electronics cooling. These systems are reliable and efficient, but the maximum heat load is given by the porous medium characteristics (pore size and conductivity) and the fluid properties. The use of an additional source of energy to actively control the heat transport and the heat transfers is a way to extend the performance. Electro-hydrodynamic forces (EHD) could fulfill this objective. This work proposed a contribution to the understanding of the interaction between a liquid-vapor interface and an electric field in order to determine which mechanisms control the pumping and heat transfer. The first part focused on the experimental study of a liquid-vapor interface under an electric field with or without heat flux in a very academic configuration while being close to the operating conditions of the vaporization in a groove of a heat pipe for example. The objective was to observe, quantify and analyze the effects (forces, structures, instabilities) developing on the interface. On top of that, analysis based on 1D and 2D models were made. We found that the dielectrophoretic force mainly controlled the position and the shape of the interface with or without vaporization. However, some effects of coupling with the electrical conduction in the liquid were proved to substantially modify the interface curvature. Finally, the results confirmed that the electric field can effectively be used to the heat transfer enhancement close to a heated wall. In a final section, the work is related to the pumping of a dielectric liquid based on the conduction regime. An experimental study was carried out in HFE-7000 and HFE-7100 fluids to investigate the role of different parameters (electrode geometry, inter-electrode distance, number of modules). For these fluids, the repeatability of results was not satisfactorily suggesting a high sensitivity of the phenomena according to the surface state of the electrodes and parasitic charge injection.

O ambiente de terras baixas no sul do Brasil é predominantemente explorado com a cultura do arroz irrigado. Baseado em um sistema agrícola pouco diversificado, é comum o uso sucessivo das mesmas áreas ano após ano, com práticas de manejo que envolvem o revolvimento do solo. Isto acarreta em prejuízos tais como a degradação do solo e recursos naturais, além de recorrente baixa rentabilidade da atividade. O cultivo de espécies forrageiras hibernais, associado com o não revolvimento do solo, pode trazer melhorias ao sistema produtivo, seja com seu uso como plantas de cobertura ou com o pastejo animal. O objetivo deste trabalho foi avaliar os benefícios e potencialidades que a utilização destas espécies podem proporcionar e, para tanto, dois estudos principais foram realizados. O primeiro, conduzido no município de Cachoeirinha, RS, avaliou o estado de agregação e o incremento do teor de carbono orgânico do solo, comparando cultivos sucessivos de arroz irrigado em um experimento de longa duração. Os tratamentos foram um sistema manejado na forma convencional, com revolvimento do solo, e outros três sob semeadura direta, com coberturas de: azevém, cornichão e vegetação espontânea. Os resultados indicaram que, na camada de 0 a 5 cm de profundidade, os tratamentos sob semeadura direta apresentaram maiores teores de carbono orgânico e agregação do que o convencional. Já na camada de 5 a 10 cm, para os agregados, o tratamento azevém se destacou em relação aos demais. O segundo estudo foi conduzido no município de Cristal, RS. Foram avaliadas a produção animal e de forragem durante três anos no período hibernal, em diferentes combinações de sistemas integrados de produção agropecuária (SIPA). Os cultivos estivais trataram-se de arroz irrigado, soja, capim sudão e campo de sucessão, enquanto as pastagens hibernais consistiram de azevém e consórcios desta espécie com trevo branco e cornichão. Os resultados confirmaram a adaptabilidade destas espécies forrageiras ao ambiente de terras baixas e demonstraram as potencialidades que a exploração pecuária possui, sendo necessários, porém, novos estudos para o melhor ajuste do manejo das áreas. Por fim, foi realizado um terceiro estudo, comparando a relação entre a massa de forragem e altura de pastos hibernais em SIPA conduzidos em terras altas com SIPA em terras baixas. A relação no ambiente de terras baixas é menor, corroborando a necessidade de maiores estudos neste ambiente, visto que as alturas ótimas preconizadas para o manejo do pasto se originam de estudos conduzidos em terras altas. / The lowland environment in Southern Brazil is predominantly explored with the irrigated rice crop. Based on a very low diversified system, in such environment is very common the successive use of the same areas year after year, with management practices that involve soil tillage. This leads to damages such as the degradation of soil and natural resources, in addition to recurrent profitability problems. The insertion of winter pasture species associated with the no-till, as cover crops or for animal grazing, may bring improvements to the system. The objective of the current work was to evaluate the benefits and potentialities that the utilization of such plants can provide. For this, two main studies were performed. The first, conducted in the Cachoeirinha County (Rio Grande do Sul State – RS), evaluated the soil aggregation status and its organic carbon content, by comparing successive irrigated rice croppings in a long-term experiment. The treatments consisted of one system under conventional soil tillage and three others under no-till, being the treatments the following cover crops: Italian ryegrass, birdsfoot trefoil and spontaneous vegetation. The results indicated that, in 0 to 5 cm soil layer, the treatments under no-till presented higher organic carbon contents and greater aggregation, as compared to the conventional system. In the 5 to 10 cm soil layer, the treatment with Italian ryegrass has its aggregation highlighted among the others. The second study was conducted in the Cristal County (RS). The animal and pasture production was evaluated during three years in the winter season, under different combinations of integrated crop-livestock systems (ICLS). The summer croppings were irrigated rice, soybean, Sudan grass and a succession field (native pasture), while the winter pastures consisted of Italian ryegrass and its mix with white clover and birdsfoot trefoil. The results confirmed the adaptability and potentiality of such pasture species and livestock exploration in the lowland environment. However, it is needed further studies for a better management adjustment of the areas. Finally, a third study was performed, comparing the relationship between forage mass and winter pasture height in ICLS conducted in highland and lowland. It was demonstrated that in lowland such relationship is lower, corroborating the necessity of more studies in these conditions, because the optimum heights preconized for pasture management are originated from studies conducted in highlands.

As mudanças na organização, nos processos e nas relações de trabalho, que estão no bojo do processo de reestruturação produtiva capitalista, se intensificaram a partir das últimas décadas do século XX, resultando em um quadro de agravamento das condições de trabalho que interfere diretamente nas condições de saúde dos trabalhadores de forma geral. Esta pesquisa se debruça sobre estas questões, tomando como objeto de investigação a atividade laboral dos trabalhadores do setor de alimentos empregados em uma unidade de processamento de aves, pertencentes a uma das maiores empresas deste ramo no país, localizada na região oeste do Estado do Paraná. A metodologia adotada para esta pesquisa foi de cunho qualitativo e foram utilizadas como instrumento de coleta de dados, entrevistas abertas. Ao todo foram entrevistados dez trabalhadores, de ambos os sexos, que foram contatados através da técnica de indicação sucessiva, somando aproximadamente 5h e 30m de gravação. Foram também realizadas entrevistas com a psicóloga e com o presidente do sindicato a qual estão vinculados os trabalhadores desta indústria avícola. A partir das informações obtidas com os trabalhadores foi realizada a reconstituição do processo de trabalho observando a sua dinâmica (destacando as questões referentes à organização e divisão do trabalho e aquelas relacionadas ao uso de tecnologias), e a descrição do ambiente de trabalho; visando compreender como são as condições de trabalho para saber se as mesmas interferem na saúde dos trabalhadores. A análise dos conteúdos das entrevistas revelou que a organização do trabalho fundada nos preceitos taylorista/fordista predominante naquele setor, foi acrescida por outras técnicas de organização da produção e do trabalho, inspiradas no modelo japonês ou toyotista, e que estão interferindo nas condições de saúde dos trabalhadores tanto física quanto psíquica. O crescimento de casos de LER na categoria aparece de forma destacada nos depoimento colhidos. / The changes in organization, in work processes and relationships that are basic for the capitalist productive restructuring process, which have been intensified for the last decades in the 20th century, have resulted in a state of working conditions aggravation, which directly interferes in the workers´ health conditions, in general. This paper delves into these questions, having as its investigation object the workers´ labor activities in the food sector, who were employed in a poultry processing plant which belongs to one of the country´s largest companies in its field, located in the west of Paraná state. The adopted methodology for this research was qualitative, and it was used as an instrument for data collection in open interviews. Altogether, ten employees of both sexes were interviewed, who were contacted through the successive indication technique, logging approximately a 5-hour-and-30-minute recording. There was also an interview with the psychologist and the president of the union these poultry plant´s workers are associated with. Based on the information obtained from the workers, the reconstitution of the work process was conducted, observing its dynamics (pointing out the issues referring to work organization and division and those related to the use of technologies), and the description of the work setting, with a view to understand what the working conditions are like and discover if they interfere in the employees´ health. The analysis done on the contents of the interviews revealed that the work organization fashioned around Taylorist/Fordist precepts, predominant in that sector, was increased by other organization techniques for production and work, inspired by the Japanese model (or Toyotist), and that they have been interfering in the workers´ physical and mental health conditions. The increasing number of LRE cases in this category is outstandingly apparent in the testimonies.

O escopo deste trabalho foi o desenvolvimento de microrreatores em tecnologia LTCC para produção de biodiesel, com foco na otimização de uma geometria de micromisturador. Esta proposta é resultado das oportunidades identificadas em três áreas do conhecimento: Microtecnologia, Intensificação de processos e Biocombustíveis. A principal ferramenta de desenvolvimento desta proposta é a fluidodinâmica computacional. Os microcanais baseados em geometrias com sucessivos cotovelos foram os escolhidos, para a investigação computacional e experimental. A metodologia computacional desenvolvida para alcançar os objetivos propostos envolve as etapas de: definição de um padrão de comparação, projeto das distâncias entre cotovelos, escolha de uma geometria com base na comparação entre diversas geometrias baseadas em sucessivos cotovelos e a otimização da geometria em função dos parâmetros fluidodinâmicos. Paralelamente, ensaios para a produção de biodiesel foram realizados, bem como, a investigação da produção de emulsões para avaliar como uma etapa do processo de produção do biodiesel. A geometria escolhida e otimizada foi a serpentina 3D, o que permitiu a otimização do módulo de tempo de residência e o projeto do microrreator. Finalizando, um microrreator foi projetado com parâmetros ótimos, obtendo assim a intensificação de processo por meio de conceitos de microtecnologia, para aplicação na produção de biocombustíveis. / The scope of this work was the development of microreactors in LTCC technology for biodiesel production, with a focus on the optimization of a micromixer geometry. This proposal is resulted from the opportunities identified in three areas of knowledge: Microtechnology, processes intensification and Biofuels. The main tool for development of this proposal is the computational fluid dynamics (CFD). The microchannels geometry with successive elbows were chosen for computational and experimental research. The computational methodology developed to achieve the proposed goals involves the following steps: defining a standard of comparison, a project of the distances between elbows, a choice of geometry based on the comparison between different geometries based on successive elbows and geometry optimization for the parameters hydrodynamic. In addition, tests for the production of biodiesel were being made and the investigations of production of emulsions to evaluate a step in the producing of biodiesel process. The geometry was chosen and optimized serpentine 3D, allowing the optimization of residence time module and the design of the microreactor. Finally, a microreactor was designed with optimal parameters, thus obtaining the intensification process through microtechnology concepts for application in the biofuels production.

The area of vegetable production is growing rapidly world-wide, as are efforts to increase production on existing lands in these labor- and input-intensive systems. Yet information on nutrient losses, greenhouse gas emissions, and input efficiency is lacking. Sustainable intensification of these systems requires knowing how to optimize nutrient and water inputs to improve yields while minimizing negative environmental consequences. This work characterizes soil nitrogen (N) dynamics, nitrate (NO3¯) leaching, greenhouse gas emissions, and crop yield in five diversified vegetable systems spanning a gradient of intensification that is characterized by inputs, tillage and rotational fallow periods. The study systems included a low input organic system (LI), a mechanized, medium scale organic system (CSA), an organic movable high tunnel system (MOV), a conventional system (CONV) and an organic stationary high tunnel system (HT). In a three-year vegetable crop rotation with three systems (LI, HT and CONV), key N loss pathways varied by system; marked N2O and CO2 losses were observed in the LI system and NO3– leaching was greatest in the CONV system. Yield-scaled global warming potential (GWP) was greater in the LI system compared to HT and CONV, driven by greater greenhouse gas flux and lower yields in the LI system. The field data from CONV system were used to calibrate the Root Zone Water Quality Model version 2 (RZWQM2) and HT and LI vegetable systems were used to validate the model. RZWQM2 simulated soil NO3¯-N content reasonably well in crops grown on bare ground and open field (e.g. beet, collard, bean). Despite use of simultaneous heat and water (SHAW) option in RZWQM2 to incorporate the use of plastic mulch, we were not able to successfully simulate NO3¯-N data. The model simulated cumulative N2O emissions from the CONV vegetable system reasonably well, while the model overestimated N2O emissions in HT and LI systems.

In recent years there has been a growing demand to produce lightweight high pressure die cast (HPDC) parts for structural applications to decrease vehicle mass and to reduce manufacturing costs. Due to the coupled rapid heat flow and complex flow/deformation that occur in the process, the formation of microstructure and defects in HPDC are still not fully understood. Developing a better understanding of microstructure formation is essential to enable advances in die design and process optimisation, as well as alloy development, to improve the quality and productivity of HPDC components. Therefore, this thesis aims to enhance this understanding by conducting detailed microstructural analysis of samples produced in controlled HPDC experiments. In the first series of experiments, various microstructure characterisation techniques were used to study salient HPDC microstructural features. The microstructures of castings were characterised at different length scales, from the scale of the casting to the scale of the eutectic interlamellar spacing. The results show that the salient as-cast microstructural features, e.g. externally solidified crystals (ESCs), defect bands, surface layer, grain size distribution, porosity and hot tears were similar for both two HPDC-specific Al alloys used, AlSi4MgMn and AlMg5Si2Mn. The formation of these features has been explained by considering the influence of flow and solidification during each stage of the HPDC process. The formation of defect bands is further studied by investigating the ratio between band thickness ( ) and average grain size in the band ( ). Suitable methods for measuring w and dsb in HPDC have been developed. The w/dsb relationship of defect bands has been investigated in HPDC specimens from a range of alloys, casting geometries and band locations within castings. The bands were measured to be 7-18 mean grains wide. This is substantial evidence that defect bands form due to strain localisation in partially solidified alloys during cold-chamber and hot-chamber HPDC. At the end of solidification, dilatant shear bands contain a higher eutectic volume fraction and/or porosity content than adjacent material. In the cross-section of the AM50 Mg alloy, the centrally-located band contains a much higher volume fraction of concentrated porosity than the second-outermost band and insignificant porosity was found in the outermost band. The level of porosity in bands was attributed to the relative difficulty of feeding shrinkage for each band location. As the feeding of material during the intensification stage is important for the reduction of porosity, the influence of intensification pressure (IP) and gate thickness on the transport of material through the gate during the latter stages of HPDC were investigated. Microstructural characterisation of the gate region indicated a marked change in feeding mechanism with increasing IP and gate size. Castings produced with a high IP and/or thick gate contained a relatively low fraction of total porosity and shear band-like features existed through the gate, suggesting that semi-solid strain localisation in the gate is involved in feeding during the pressure intensification stage. When a low IP is combined with a thin gate, no shear band was observed in the gate and feeding was less effective, resulting in a higher level of porosity in the HPDC component. As equiaxed primary crystals are subjected to intense shear during HPDC, their agglomeration and bending behaviour were investigated in the last series of experiment. Samples produced by near-static cooling, HPDC and Thixomoulding®, where the solidifying crystals experience different levels of mechanical stresses, were characterised. The electron backscatter diffraction (EBSD) technique was used to acquire grain misorientation data which is linked to the crystal agglomeration and bending behaviour during solidification. The number fraction of low-energy grain boundaries in HPDC and Thixomoulded samples was substantially higher than in ‘statically cooled’ samples. This is attributed to the much higher shear stresses and pressure applied on the solidifying alloy in HPDC and Thixomoulding, which promote crystal collisions and agglomeration. In-grain misorientations were found to be significant only in branched dendritic crystals which were subjected to significant shear stresses. This is related to the increased bending moment acting on long protruding dendrite arms compared to more compact crystal morphologies.

This dissertation explores the theoretical and methodological implications involved in the policy framework needed to intensify urban residential areas in a developing country. Metropolitan Khartoum, Sudan, has been chosen as a case study. The aim of the study is to further our understanding of the implications of transforming a sprawling city form to an intensified form. The objectives are: to identify the factors that have shaped Sudanese urban form in general and Metropolitan Khartoum in specific; to identify the policies that can intensify the urban residential neighborhoods in Metropolitan Khartoum; and, to influence both the demand and requisite housing needs for this intensified form. This research is qualitative in its nature: the complexity of the study problematic required the adoption of a constructivist paradigm as the fundamental set of beliefs. Inductive arguments are used in conjunction with a wide range of methods, including detailed descriptions of Sudan and metropolitan Khartoum, with special emphasis on how local environment, urban challenges, policy, legislation and practices affect the study problematic. The theoretical premises of intensification are reviewed along with development issues, urban infrastructure challenges and opportunities in developing countries and local acceptability of intensification. The different forces that can shape urban forms have been described and the suitability of metropolitan Khartoum, with different general urban intensification policies and practices and of urban management tools in large African cities has been investigated. The outcome of the study provides detail for a discussion of results that work to explain some of the cause and effect of urban sprawl in Metropolitan Khartoum. It also suggests possible change in both policy and regulation to induce successful city reform towards intensification. / QC 20110121

Urban economic theory states that transit improvements result in travel time savings and consequently warrant higher rents particularly with proximity to surrounding stations. This research uses the Sheppard subway corridor as a case study to test the established theories by measuring the changes to residential intensification and property values (1) as a function of time before and after the construction, and (2) as a function of distance to subway stations. Two metrics are established to observe residential intensification and property value: Dwelling Density and Value Density respectively. Dwelling Density is the number of dwellings contained in its property parcel divided by property area; Value Density is total property value of a given property parcel divided by its property area. Using obtained property sales data in four identified analysis years (1991, 1996, 2001, and 2006) and ArcGIS, spatial interpolation surfaces are generated to visualize the changes on a geographical plane through time. Dwelling and Value Density scatterplots are generated by extracting values from the interpolated surfaces and computing its distance to the nearest subway station and to major development nodes. The generated interpolated surfaces show a strong increase in Dwelling and Value Density in North York Centre which suggest that (1) planning policies succeeded in guiding residential growth, (2) a time lag is present of which the full benefits of rapid transit construction are realized, and (3) there may be positive network effects associated with the completion of the Sheppard subway. The scatterplot results demonstrated moderate change in Dwelling and Value Density at the Bayview station area and little change for the remaining stations (Bessarion, Don Mills, and Leslie) based on observations up to December 2006. The results warrant a degree of optimism about Sheppard subway’s ability to attract residential intensification and raise property values, especially given that data was analyzed only up to four years after the subway corridor began revenue service. It is recommended that a similar methodology be performed at a later date when the corridor’s ridership and surrounding development reaches maturity. A preliminary forecasting exercise determined that Dwelling and Value Density will rise, particularly surrounding stations that have since demonstrated little change in residential land use.