nÃo hà / O presente trabalho tem como principal objetivo investigar as condiÃÃes mais adequadas para o estudo da difusividade de n-parafinas em um catalisador tÃpico para a sÃntese de Fischer-Tropsch (SFT), utilizando o mÃtodo cromatogrÃfico ZLC (coluna de comprimento zero), e avaliando-se a repetitividade e a reprodutibilidade desta metodologia. Objetiva, ainda, verificar o desempenho do catalisador em um reator de leito fixo, em escala piloto, e observar o efeito da difusÃo na seletividade a hidrocarbonetos de alta massa molar. O catalisador foi caracterizado, com Ãnfase nos ensaios de microscopia e anÃlise textural. Quanto à difusividade dos n-alcanos (n-C7, n-C9, n-C12, n-C16), foram utilizados dois sistemas ZLC, sendo um na Universidade Federal do Cearà (UFC) e o outro na Universidade de Edimburgo, empregando-se amostras de diferentes granulometrias (forma pà e pellet). Investigou-se, tambÃm, a influÃncia da temperatura, da vazÃo do gÃs de purga, da massa de catalisador e da concentraÃÃo do sorbato no gÃs de purga. Quanto à etapa reacional, esta ocorreu em uma unidade piloto para a SFT a 20 bar, nas temperaturas de 210 ÂC e 230 ÂC e em diferentes velocidades espaciais. O catalisador apresentou-se como mesoporoso, com um pouco de microporosidade, e com a fase ativa (Co) bem distribuÃda. Em relaÃÃo à difusividade efetiva, o diÃmetro de partÃcula mais adequado para o uso na coluna ZLC, dentre os testados, foi de 214 Âm para o catalisador na forma pÃ, com 5 mg de amostra. Comparando-se os experimentos realizados nas duas universidades, percebeu-se uma boa repetitividade, porÃm a reprodutibilidade, nÃo foi satisfatÃria. Observou-se ainda, a influÃncia da constante de Henry nos resultados obtidos para difusividade efetiva, em diferentes tamanhos de catalisador, entretanto, nÃo se perceberam mudanÃas significativas na difusividade efetiva em funÃÃo da variaÃÃo da temperatura e da concentraÃÃo de sorbato no gÃs de purga. Em se tratando da reaÃÃo, os resultados indicaram um forte efeito da temperatura na conversÃo de CO e na seletividade a C5+. O mecanismo difusivo à afetado pela difusividade de superfÃcie, e, a partir deste resultado, pode-se justificar o aumento da seletividade a metano com o incremento da relaÃÃo H2/CO. Com base nos resultados apresentados, o mÃtodo ZLC mostrou-se adequado para o estudo da difusividade efetiva de n-parafinas em um catalisador convencional para a SFT. / The main goal of the present research is to establish the most appropriate conditions for studying the diffusivity of n-paraffins in the presence of a typical catalyst for Fischer-Tropsch synthesis (FTS), by using the chromatographic method ZLC (zero length column) and evaluating the repeatability and reproducibility of this method. It also aims to verify the catalyst performance in a fixed bed reactor, at a pilot-scale, and observe the effect of diffusion in the selectivity of high molar mass hydrocarbons. At first, the catalyst characterization was done with emphasis on the microscopy studies and textural analysis with N2. Regarding the n-alkanes diffusivity (n-C7, n-C9, n-C12, n-C16), two ZLC equipments were used, one at the Federal University of Ceara (UFC) and the another one at the University of Edinburgh, with different particle size samples. This work has also evaluated the influence of temperature, the purge gas flow rate, the catalyst mass and sorbate concentration in the purge gas. The reaction step was done at a Fisher-Tropsch pilot-scale unit at 20 bar, with 210ÂC and 230ÂC in different space velocities. As a result, the catalyst was presented as mesoporous, with small microporosity, and with active phase (Co) well distributed. Concerning the effective diffusivity, the most appropriate particle diameter to be used at the ZLC column, among the tested diameters, is 214 Âm (dust form), with 5 mg of catalyst. Comparing the studies that were held at the two universities, it was noticed a good repeatability, however, the reproducibility was not satisfactory. It was observed a strong influence of the HenryÂs constant at the results of effective diffusivity, for different catalyst sizes; however, no significant changes at the effective diffusivity were noted due to temperature variation and sorbate concentration. Regarding the reaction, the results indicated a strong effect of temperature at the CO conversion and at the C5+ selectivity. The diffusive mechanism is strongly affected by the catalyst surface effects. Based on this result, the raise of methane selectivity by increasing H2/CO ratio can explained. As final result, the ZLC is found as a suitable method for surface diffusion estimation using typical Fischer-Tropsch catalyst.

INTRODUÇÃO: Epilepsia do lobo temporal mesial (ELTM) por esclerose hipocampal (EH) é a forma de epilepsia focal mais comum na idade adulta e a causa mais frequente de refratariedade ao tratamento clínico. Apesar de se tratar de uma patologia da substância cinzenta, alguns estudos, por meio da imagem por tensor de difusão (diffusion tensor imaging-DTI), têm demonstrado alteração da substância branca temporal e extratemporal nestes pacientes. O corpo caloso (CC) é a maior comissura cerebral conectando áreas corticais homólogas de ambos os hemisférios cerebrais e tem sido implicado na propagação da atividade epiléptica. O objetivo principal do presente estudo foi avaliar possíveis alterações no CC de pacientes com ELTM-EH pela técnica de DTI e verificar se essas dependem da lateralidade da EH e da concordância entre os exames de ressonância magnética (RM) e os exames de vídeo-eletroencefalograma (EEG). Como objetivo secundário, também avaliou-se se estas alterações se correlacionavam com alguma variável clínica ou com as medidas volumétricas do CC. MÉTODOS: 42 pacientes com ELTM-EH (idades: 20-54 anos) e 30 voluntários saudáveis como grupo controle (idades: 18-53 anos) realizaram exame de RM de crânio, sendo obtidas sequências de DTI com 32 direções de gradiente e imagens volumétricas ponderadas em T1. Os pacientes foram também divididos em subgrupos: EH à direita e EH à esquerda, e em pacientes concordantes e discordantes. Os valores de anisotropia fracionada (AF), difusividade média (DM), difusividade axial (DA), difusividade radial (DR) e os dados volumétricos foram extraídos a partir de cinco segmentos obtidos automaticamente na secção sagital do CC. Foram realizadas comparações dos parâmetros de DTI no CC entre os grupos de pacientes e controles, e entre os subgrupos de pacientes. Foram investigadas correlações entre os parâmetros do tensor de difusão e as variáveis clínicas. As alterações volumétricas no CC dos pacientes com ELTM-EH bem como a correlação dessas alterações com as anormalidades de difusão também foram avaliadas. Considerou-se um valor de p < 0,05 como estatisticamente significativo. RESULTADOS: Nas regiões anterior, médio-posterior e posterior do CC dos pacientes, observaram-se redução da AF e aumento da DM e da DR, em relação aos controles. A DA manteve-se inalterada. Não foram demonstradas diferenças nos padrões de alteração de difusão entre os pacientes com EH à direita e com EH à esquerda, nem entre pacientes concordantes e discordantes. Não foram observadas correlações significativas entre os parâmetros do tensor de difusão com a idade ao evento inicial, idade de início da epilepsia, tempo de doença, tempo de epilepsia, período de latência e frequência de crises. No entanto, pacientes que apresentaram crise febril como evento precipitante inicial exibiram maior intensidade e extensão das alterações de difusão. Observou-se redução volumétrica difusa do CC, sendo demonstrada correlação negativa significativa entre DM e DR, e o volume nos segmentos central, médio-posterior e posterior, e, ainda, entre DA e volume do segmento posterior. Nós observamos, ainda, correlação negativa significativa entre o volume e o tempo de epilepsia, e o tempo de doença. CONCLUSÕES: Houve alteração dos parâmetros de DTI em áreas específicas do CC e redução volumétrica difusa desta estrutura. Tais anormalidades parecem ser secundárias à propagação das crises epilépticas ao longo de vias específicas anatômica ou funcionalmente relacionadas aos lobos temporais promovendo alterações secundárias na substância branca cerebral. O histórico de crise febril está relacionado a maior intensidade e extensão de acometimento do CC / INTRODUCTION: Mesial temporal lobe epilepsy (MTLE) with hippocampal sclerosis (HS) is the most common form of focal epilepsy in adults and it is frequently associated with refractoriness to medical treatment. Although epilepsy is considered a grey-matter disease, abnormalities in the temporal and extra-temporal white matter have been identified in these patients with diffusion tensor imaging (DTI). The corpus callosum (CC) is the major white matter tract connecting both cerebral hemispheres and has been implicated as an important route of spread of epileptic activity. The first goal of this study was to detect DTI abnormalities in specific areas of the CC in patients with MTLE-HS and to verify if these abnormalities depend on the laterality of the HS and on the concordance between the magnetic resonance imaging (MRI) and video-electroencephalogram (EEG). As a second goal we assessed if DTI results were correlated with any clinical variable or volumetric changes of the CC. METHODS: 42 patients (age: 20-54 years) and 30 healthy controls (age:18-53 years) were submitted to brain MRI. DTI sequences with 32 gradient encoding directions and volumetric T1-weighted images were obtained. Additionally, we grouped the patients in left sided and right sided HS and in concordant and discordant HS. Mean values of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) and volumetric results were extracted from five segments at the midsagittal section of the CC obtained through automatic segmentation. Comparisons of DTI parameters of the CC were performed between patients and controls and between subgroups of patients. Correlations between DTI parameters and clinical findings were calculated. We also evaluated volume abnormalities of the CC in MTLE-HS patients and the correlations between these abnormalities and DTI changes. We considered a value of p <0.05 statistically significant. RESULTS: Our study showed that, when HS patients was compared to controls, the FA was lowest in the anterior, mid-posterior and posterior subregions of the CC. MD and RD were higher in these same segments. No changes were observed in AD. No differences in the CC DTI parameters were detected between right-sided HS and left-sided HS or between concordant and discordant HS patients. Age at initial event, age at epilepsy onset, duration of disease, duration of epilepsy, latency period and seizure frequency were not significantly correlated with the DTI parameters. However, patients who had febrile seizures as initial event exhibited greater intensity and extent of DTI changes. All segments demonstrated volume reduction compared to controls. Significant negative correlation was demonstrated between MD and RD and the volume in the central, midposterior and posterior segments of the CC, and between AD and volume of the posterior segment. We also demonstrated negative correlation between volume and duration of disease and duration of epilepsy. CONCLUSIONS: This study showed diffusion abnormalities in specific areas of the CC and diffuse atrophy in patients with unilateral HS, which may be secondary to seizures propagation along specific pathways leading to secondary changes in brain white matter. The history of febrile seizure is related to greater involvement of the CC

INTRODUÇÃO: Epilepsia do lobo temporal mesial (ELTM) por esclerose hipocampal (EH) é a forma de epilepsia focal mais comum na idade adulta e a causa mais frequente de refratariedade ao tratamento clínico. Apesar de se tratar de uma patologia da substância cinzenta, alguns estudos, por meio da imagem por tensor de difusão (diffusion tensor imaging-DTI), têm demonstrado alteração da substância branca temporal e extratemporal nestes pacientes. O corpo caloso (CC) é a maior comissura cerebral conectando áreas corticais homólogas de ambos os hemisférios cerebrais e tem sido implicado na propagação da atividade epiléptica. O objetivo principal do presente estudo foi avaliar possíveis alterações no CC de pacientes com ELTM-EH pela técnica de DTI e verificar se essas dependem da lateralidade da EH e da concordância entre os exames de ressonância magnética (RM) e os exames de vídeo-eletroencefalograma (EEG). Como objetivo secundário, também avaliou-se se estas alterações se correlacionavam com alguma variável clínica ou com as medidas volumétricas do CC. MÉTODOS: 42 pacientes com ELTM-EH (idades: 20-54 anos) e 30 voluntários saudáveis como grupo controle (idades: 18-53 anos) realizaram exame de RM de crânio, sendo obtidas sequências de DTI com 32 direções de gradiente e imagens volumétricas ponderadas em T1. Os pacientes foram também divididos em subgrupos: EH à direita e EH à esquerda, e em pacientes concordantes e discordantes. Os valores de anisotropia fracionada (AF), difusividade média (DM), difusividade axial (DA), difusividade radial (DR) e os dados volumétricos foram extraídos a partir de cinco segmentos obtidos automaticamente na secção sagital do CC. Foram realizadas comparações dos parâmetros de DTI no CC entre os grupos de pacientes e controles, e entre os subgrupos de pacientes. Foram investigadas correlações entre os parâmetros do tensor de difusão e as variáveis clínicas. As alterações volumétricas no CC dos pacientes com ELTM-EH bem como a correlação dessas alterações com as anormalidades de difusão também foram avaliadas. Considerou-se um valor de p < 0,05 como estatisticamente significativo. RESULTADOS: Nas regiões anterior, médio-posterior e posterior do CC dos pacientes, observaram-se redução da AF e aumento da DM e da DR, em relação aos controles. A DA manteve-se inalterada. Não foram demonstradas diferenças nos padrões de alteração de difusão entre os pacientes com EH à direita e com EH à esquerda, nem entre pacientes concordantes e discordantes. Não foram observadas correlações significativas entre os parâmetros do tensor de difusão com a idade ao evento inicial, idade de início da epilepsia, tempo de doença, tempo de epilepsia, período de latência e frequência de crises. No entanto, pacientes que apresentaram crise febril como evento precipitante inicial exibiram maior intensidade e extensão das alterações de difusão. Observou-se redução volumétrica difusa do CC, sendo demonstrada correlação negativa significativa entre DM e DR, e o volume nos segmentos central, médio-posterior e posterior, e, ainda, entre DA e volume do segmento posterior. Nós observamos, ainda, correlação negativa significativa entre o volume e o tempo de epilepsia, e o tempo de doença. CONCLUSÕES: Houve alteração dos parâmetros de DTI em áreas específicas do CC e redução volumétrica difusa desta estrutura. Tais anormalidades parecem ser secundárias à propagação das crises epilépticas ao longo de vias específicas anatômica ou funcionalmente relacionadas aos lobos temporais promovendo alterações secundárias na substância branca cerebral. O histórico de crise febril está relacionado a maior intensidade e extensão de acometimento do CC / INTRODUCTION: Mesial temporal lobe epilepsy (MTLE) with hippocampal sclerosis (HS) is the most common form of focal epilepsy in adults and it is frequently associated with refractoriness to medical treatment. Although epilepsy is considered a grey-matter disease, abnormalities in the temporal and extra-temporal white matter have been identified in these patients with diffusion tensor imaging (DTI). The corpus callosum (CC) is the major white matter tract connecting both cerebral hemispheres and has been implicated as an important route of spread of epileptic activity. The first goal of this study was to detect DTI abnormalities in specific areas of the CC in patients with MTLE-HS and to verify if these abnormalities depend on the laterality of the HS and on the concordance between the magnetic resonance imaging (MRI) and video-electroencephalogram (EEG). As a second goal we assessed if DTI results were correlated with any clinical variable or volumetric changes of the CC. METHODS: 42 patients (age: 20-54 years) and 30 healthy controls (age:18-53 years) were submitted to brain MRI. DTI sequences with 32 gradient encoding directions and volumetric T1-weighted images were obtained. Additionally, we grouped the patients in left sided and right sided HS and in concordant and discordant HS. Mean values of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) and volumetric results were extracted from five segments at the midsagittal section of the CC obtained through automatic segmentation. Comparisons of DTI parameters of the CC were performed between patients and controls and between subgroups of patients. Correlations between DTI parameters and clinical findings were calculated. We also evaluated volume abnormalities of the CC in MTLE-HS patients and the correlations between these abnormalities and DTI changes. We considered a value of p <0.05 statistically significant. RESULTS: Our study showed that, when HS patients was compared to controls, the FA was lowest in the anterior, mid-posterior and posterior subregions of the CC. MD and RD were higher in these same segments. No changes were observed in AD. No differences in the CC DTI parameters were detected between right-sided HS and left-sided HS or between concordant and discordant HS patients. Age at initial event, age at epilepsy onset, duration of disease, duration of epilepsy, latency period and seizure frequency were not significantly correlated with the DTI parameters. However, patients who had febrile seizures as initial event exhibited greater intensity and extent of DTI changes. All segments demonstrated volume reduction compared to controls. Significant negative correlation was demonstrated between MD and RD and the volume in the central, midposterior and posterior segments of the CC, and between AD and volume of the posterior segment. We also demonstrated negative correlation between volume and duration of disease and duration of epilepsy. CONCLUSIONS: This study showed diffusion abnormalities in specific areas of the CC and diffuse atrophy in patients with unilateral HS, which may be secondary to seizures propagation along specific pathways leading to secondary changes in brain white matter. The history of febrile seizure is related to greater involvement of the CC

Le travail exposé dans ce mémoire propose un examen, selon une approche multiéchelle, de la relation entre l’évolution de l’endommagement et la perte de conductibilité thermique de Compositesà Matrice Céramique. Les recherches sont menées à la fois sur le plan expérimental et sur le plan théorique. La démarche mise en oeuvre consiste à examiner deux échelles significatives (Microet Meso) auxquelles agissent des mécanismes d’endommagement différents et à évaluer pardes techniques d’homogénéisation l’effet sur les propriétés thermiques effectives.Une attention particulière a été donnée à l’élaboration d’une démarche expérimentale approfondieassociant des moyens de caractérisation mécanique, thermique et microstructurale. Aux deuxéchelles étudiées, un banc expérimental a été conçu pour réaliser des mesures thermiques sur des CMC sollicités mécaniquement. La diffusivité thermique longitudinale du mini composite est estimée par thermographie à détection synchrone. Des variantes de la méthode flash en face arrière sont mises en oeuvre pour l’étude du composite tissé. Par ailleurs, la progression de l’endommagementest déduite de l’enregistrement des signaux acoustiques et d’observations microstructurales post-mortem. Les résultats expérimentaux sont systématiquement comparés à des simulations. A l’échelle Micro, un modèle micromécanique est proposé afin de simuler la perte de conductivité thermique d’un mini composite en traction. A l’échelle Méso, une stratégie multiéchelle de calcul numérique de l’effet de l’endommagement sur les propriétés thermiques d’un CMC tissé est présentée. / In this work the relationship between the evolution of damage and the loss of thermal propertiesof Ceramic Matrix Composites is investigated by a multiscale approach. Research are conductedboth experimentally and theoretically. The implemented approach is to consider two significantscales (micro and meso) where different damage mechanisms are operating and then assess theeffect on the effective thermal properties by homogenization techniques.Particular attention has been given to the development of a thorough experimental work combiningvarious characterization tools (mechanical, thermal and microstructural). At the two aforementionedscales, an experimental setup was designed to perform thermal measurements onCMC under tensile test. Thermal diffusivity of minicomposites is estimated using Lock-in thermography.Also, tranverse diffusivity mapping as well as global in-plane diffusivity of woven CMCare determined by suitable rear face flash methods. The evolution of damage is then derived fromacoustic emission activity along with postmortem microstructural observations. Experimental resultsare systematically compared to simulations. At microscale, a micromechanical-based modelis used to simulate the loss of thermal conductivity of a minicomposite under tensile test. At mesoscale,a multiscale Finite ElementModel is proposed to compute the effect of damage on thermalproperties of woven CMC.

No presente trabalho, as propriedades termofísicas do pão francês durante o assamento foram determinadas. Os pães foram feitos na Padaria Piloto do Laboratório de Engenharia de Alimentos do Departamento de Engenharia Química da Escola Politécnica da Universidade de São Paulo, com formulação semelhante aos pães comercializados. Durante o assamento, mudanças profundas ocorreram nos pães como diminuição do conteúdo de água de 44,1 para 30,8 % e aumento do volume de 382 para 420 cm3. Devido ao aumento do volume e diminuição da massa, a densidade aparente do pão francês variou de 0,231 g/cm3 para o pão sem assamento a 0,324 g/cm3 para o pão com 14 minutos de assamento. A difusividade térmica efetiva do pão francês foi determinada a partir das curvas de penetração de calor considerando o pão como um cilindro bidimensional. As curvas foram registradas a uma taxa de 30 aquisições/minuto durante o assamento dos pães em um forno turbo com dispositivo de vaporização. O valor médio da difusividade térmica encontrada para o pão francês durante o assamento foi de 4,1 ´ 10-7 m2/s. A condutividade térmica efetiva do pão francês foi determinada pelo método da sonda linear de aquecimento em diferentes tempos de assamento. A sonda linear utilizada nos ensaios foi dimensionada e construída no laboratório para o pão francês. A condutividade térmica efetiva do pão francês variou de 0,283 W/m K para o pão sem assamento a 0,136 W/m K para o pão com 14 minutos de assamento. Os resultados foram comparados com dados existentes na literatura. Um modelo empírico foi proposto para correlacionar a condutividade térmica do pão francês com o seu conteúdo de água e sua densidade aparente. / In this work, thermophysical properties of the french bread during baking were determined. Breads were produced at the Pilot Bakery of the Food Engineering Laboratory of the Chemical Engineering Department of Escola Politécnica of São Paulo University, with a formulation similar to breads purchased at the market. During baking, deep changes ocurred in the breads such as a water content decrease from 44,1 to 30,8 % and an increase of volume from 382 to 420 cm3. Due to the increase of volume and mass decrease, the bulk density of french bread changed from 0,324 g/cm3 for the dough to 0,231 g/cm3 for the bread with 14 minutes of baking. Effective thermal diffusivity of french bread was determined through heat penetration curves in a bidimensional cylinder. Temperature history was registred at a rate of 30 samples/minute during bread baking in a turbo oven with a vaporization device. The average value of thermal diffusivity to the french bread during baking was 4,1´10-7 m2/s. The effective thermal conductivity of the french bread was determined by the line heat source method in different times of baking. The thermal conductivity probe used was designed and built at the laboratory for french bread. The effective thermal conductitivy of the french bread changed from 0,283 W/m K for the dough without baking to 0,136 W/m K for the bread with 14 minutes of baking. Results were compared with literature data. An empiric model was proposed to correlate the french bread thermal conductivity with its water content and bulk density.

Computer simulations of the growth of binary alloy thin films in two and three dimensions were performed using an extension of the Solid on Solid model. Snapshots for a range of interactions and diffusion rates are presented and critically compared to experiment. A wide variety of distinct phases is identified and their growth conditions analyzed. These findings are summarized in a phase diagram. In addition, a fractal analysis of the domains is performed. It is found that for negative interactions the islands are two-dimensional, while for positive interactions, regardless of diffusion rate, a fractal dimension of 1.78 is obtained. / by Mark R. Bouwens. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

"Gas carburizing is an important heat treatment process used for steel surface hardening of automotive and aerospace components. The quality of the carburized parts is determined by the hardness and the case depth required for a particular application. Despite its worldwide application, the current carburizing process performance faces some challenges in process control and variability. Case depth variability if often encountered in the carburized parts and may present problems with i) manufacturing quality rejections when tight tolerances are imposed or ii) insufficient mechanical properties and increased failure rate in service. The industrial approach to these problems often involves trial and error methods and empirical analysis, both of which are expensive, time consuming and, most importantly, rarely yield optimal solutions. The objective for this work was to develop a fundamental understanding of the mass transfer during gas carburizing process and to develop a strategy for the process control and optimization. The research methodology was based on both experimental work and theoretical developments, and included modeling the thermodynamics of the carburizing atmosphere with various enriching gasses, kinetics of mass transfer at the gas-steel interface and carbon diffusion in steel. The models accurately predict: 1) the atmosphere gas composition during the enriching stage of carburizing, 2) the kinetics of carbon transfer at the gas-steel surfaces, and 3) the carbon diffusion coefficient in steel for various process conditions and steel alloying. The above models and investigations were further combined to accurately predict the surface carbon concentration and the carbon concentration profile in the steel during the heat treatment process. Finally, these models were used to develop a methodology for the process optimization to minimize case depth variation, carburizing cycle time and total cycle cost. Application of this optimization technique provides a tradeoff between minimizing the case depth variation and total cycle cost and results in significant energy reduction by shortening cycle time and thereby enhancing carburizing furnace capacity."

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 269-271. / Ph.D.

Orientador: Roberto Naves Domingos / Banca: Jorge Roberto Pimentel / Banca: Edson Salvador Octaviano / Resumo: O descarte de resíduos industriais constitui-se num problema para os agentes produtores e para a sociedade. O volume de resíduo produzido é bastante grande e, normalmente, são poluidores ambientais. Pesquisadores afirmam que a determinação das propriedades térmicas de um solo e do resíduo, pode colaborar na decisão de incorporar este ao solo, visando melhorar sua capacidade de difundir a energia necessária ao processo de crescimento das plantas. O presente trabalho foi desenvolvido com o propósito de obter a medida da difusividade térmica de um solo incorporado um resíduo industrial de silicato, em várias proporções. O método utilizado foi aquele proposto por CLIVATI (1991), adaptado para as condições da pesquisa. A partir dos valores obtidos para a temperatura com o tempo, as difusividades térmicas das amostras foram determinadas, comparadas entre si e com a literatura. Dos resultados concluiu-se que amostras de solo com resíduo incorporado na proporção de 10%, em massa, apresentaram valores de difusividade térmica muito próximos daqueles obtidos para o solo. Tais resultados indicam a possibilidade de se descartar esse resíduo no solo, em condições semelhantes àquelas propostas neste trabalho. / Abstract: The dump of industrial residue, constitutes a problem for the agents that produce them and for the society. The amount of residue produced is quite voluminous and they are generally environment polluters. Researchers state that the determination of the thermal properties of the soil and of the residue can cooperate in the decision to the incorporate the residue into the soil, thus improving its capacity to diffuse the necessary energy for the growth process of the plants. This work has been developed with the purpose of determining the value of the thermal diffusivity of a soil in which an industrial residue of silicate was incorporated in various proportions. The method used was the one proposed by CLIVATI (1991) and adequate for the actual conditions. From the values obtained for the temperature in time function, the thermal diffusivities of the samples were determined, compared among themselves and with the current literature. The obtained results allow us to conclude that the soil samples with the residue incorporated at the proportion of 10% in weight, presented values of thermal diffusivities very close to those obtained from the barren soil. These results point out for the possibility of dumping this residue into the soil, in the conditions closed to those proposed in this work. / Mestre

In this thesis, we have used a phase field model for studying the effect of atomic mobility inside the precipitate phase on coarsening behaviour in two dimensional (2D) systems. In all the available coarsening theories, the diffusivity inside the precipitate phase is not explicitly taken into account; this would imply that there is no chemical potential gradient inside the precipitate. This assumption is valid if (a) the atomic mobility inside the precipitate is much higher than that in the matrix, or (b) the precipitate volume fraction is small (i.e. the interparticle spacing is far higher than the average particle size). We undertook this study to evaluate the potential effect of diffusivity in the precipitate on coarsening in situations where conditions (a) and (b), above, do not hold, by studying systems with moderate volume fractions (20% and 30%) and with low atomic mobilities in the precipitate. In our study, we have fixed the atomic mobility in the matrix at a constant value. We have used the well known Cahn-Hilliard model in which the microstructure is described in terms of a composition field variable. The evolution of microstructure is studied by numerically solving a non-classical diffusion equation known as the Cahn-Hilliard equation. We have used a semi-implicit Fourier spectral technique for solving the CH equation using periodic boundary conditions. The coarsening behaviour is tracked and analyzed using number density of particles, their average size and their size distribution. The main conclusion from this study is that, contrary to expectations, the atomic mobility in the precipitate phase has only a small effect on coarsening behavior. Specifically, with decreasing atomic mobility in the precipitate phase, we report a small increase in the number density, a slightly wider size distribution and a slightly smaller coarsening rate. We also add that these effects are too small to allow experimental verification. These results indicate that the need for chemical potential equilibration within each precipitate is not an important factor during coarsening.