La formation de la structure de grains dans les métaux pendant la solidification est déterminante pour les propriétés mécaniques et électroniques des pièces coulées. En plus de la texture donnée au matériau, la germination et la croissance des grains sont liées en particulier avec la formation des phases thermodynamiques et les inhomogénéités en composition d'éléments d'alliage. La structure de grains est rarement modélisée à l'échelle macroscopique, d'autant plus que l'approximation 2D est très souvent injustifiée. Dans ces travaux, la germination et la croissance de chaque grain individuel sont suivies avec un modèle macroscopique 3D CAFE. La microstructure interne des grains n'est pas explicitement résolue. Pour valider les approximations faites sur cette microstructure, une comparaison directe avec un modèle microscopique "champ de phase" a été réalisée. Celle-ci a permis de valider les hypothèses de construction du modèle CAFE, de mettre en avant le lien entre données calculées par les modèles microscopiques et paramètres d'entrée des modèles à plus grande échelle, et les domaines de validité de chaque modèle. Dans un deuxième temps, un couplage avec la ségrégation chimique et les bases de données thermodynamiques a été mise en place et appliquée sur un alliage binaire étain-plomb. Une expérience de macroségrégation par convection naturelle a été simulée. L'accord entre les courbes de température expérimentales et simulées atteint une précision de l'ordre de 1K, et la recalescence est correctement prédite. Les cartes de compositions sont comparables qualitativement, ainsi que la structure de grains. Les avantages du suivi de la structure ont été mis en évidence par rapport à une simulation par éléments finis classique. De plus, il a été montré que le calcul 3D était ici indispensable. Enfin, une implémentation parallèle optimisée du code a permis d'appliquer le modèle CAFE à un lingot de silicium polycristallin industriel de dimensions 0,192 x 0,192 x 2,08m, avec une taille de cellules de 250µm. Au total, 4,9 milliards de cellules sont représentées sur le domaine, et la germination et la croissance de 1,6 million de grains sont suivies. / Grain structure formation during solidification of metal parts has a big impact on the final mechanical and electronic properties. Besides determining the crystallographic texture, the nucleation and growth of grains are linked and interact with the appearance of thermodynamic phases and inhomogeneities in the alloy's chemical elements distribution. Grain structure is very rarely modeled on the macro scale, especially because the 2D approximation is often not justified. In this work, the nucleation and growth of each individual grain is tracked with the 3D CAFE macroscopic model. The internal microscopic structure is not explicitly solved. In order to validate the assumptions concerning this microstructure, a direct comparison has been done with a microscopic "phase field" model. That comparison led to the validation of some of the hypothesis on which the CAFE model is built. Moreover, the various data computed in microscopic models that can be used as input parameters of the macroscopic models have been identified, and the limits of each model clearly shown. Secondly, coupling with macrosegregation and thermodynamic databases was achieved, and applied to a binary tin-lead alloy. An experiment featuring macrosegregation induced by natural convection was modeled. The agreement between the experimental and the predicted cooling curves is within 1K, and the recalescence is found to be correctly predicted. The composition maps and the grain structure agree qualitatively with the experiment. The improvement due to structure tracking was demonstrated, regarding a standard finite elements resolution. It was also shown that the 3D simulation is mandatory to reach a good description. Finally, the model was implemented through an optimized parallel algorithm. This permitted to apply the CAFE model on an industrial scale polycrystalline silicon ingot, which dimensions are 0,192 x 0,192 x 2,08m. The cell size is chosen to be 250µm. In total, 4,9 billions of cells were represented, and the nucleation and growth of 1,6 million of grains were tracked.

Dans cette thèse, on s'intéresse aux automates cellulaires en tant que modèle de calcul permettant de reconnaître des langages. Dans un tel domaine, il est toujours difficile d'établir des résultats négatifs, typiquement de prouver qu'un langage donné n'est pas reconnu en une certaine fonction de temps par une certaine classe d'automates. On se focalisera en particulier sur les classes de faible complexité comme le temps réel, au sujet desquelles de nombreuses questions restent ouvertes.Dans une première partie, on propose plusieurs manières d'affaiblir encore les classes de langages étudiées, permettant ainsi d'obtenir des exemples de résultats négatifs. Dans une seconde partie, on montre un théorème d'accélération par automate cellulaire d'un modèle séquentiel, les automates finis oublieux. Ce modèle est une version a priori affaiblie, mais non triviale, des automates finis à plusieurs têtes de lecture. / This document deals with cellular automata as a model of computation used to recognise languages. In such a domain, it is always difficult to provide negative results, that is, typically, to prove that a given language is not recognised in some function of time by some class of automata. The document focuses in particular on the low-complexity classes such as real time, about which a lot of questions remain open since several decades.In a first part, several techniques to weaken further still these classes of languages are investigated, thereby bringing examples of negative results. A second part is dedicated to the comparison of cellular automata with another model language recognition, namely multi-head finite automata. This leads to speed-up theorem when finite automata are oblivious, which makes them a priori weaker than in the general case but leaves them a nontrivial power.

Interface automaton is a model of software component behaviour based on finite state machines. It describes component's provided interface, the supported usage, and required interface, the usage of other components. A considerable number of components can be used in parallel with no bound on the level of parallelism. It is not necessary for the model to attempt to capture such unboundedness. An alternative approach is to allow an increment of the level of parallelism on- demand. This thesis analyses on a theoretical level and proposes a final form of an operation to perform such replication to allow creation of models of an arbitrary level of parallelism of certain parts of its behaviour.

Modelar a dinâmica de neurônios é relevante em estudos de neurociências. Neste trabalho, propõe-se um modelo computacional de neurônio baseado no comportamento dos canais iônicos presentes na sua membrana. O modelo combina elementos microscópicos, como o comportamento dos canais individuais, com elementos macroscópicos, como a tensão ao longo de um trecho de membrana. Simulações foram realizadas com o objetivo de reproduzir dados biológicos e resultados obtidos de modelos teóricos clássicos da área. Foi possível reproduzir com boa concordância o potencial de ação, o fenômeno da adaptação, a curva da corrente de entrada versus a frequência de disparos e o potencial excitatório pós-sináptico. / Modelling the dynamics of neurons is relevant in studies on neurosciences. In this work, a computational model of neuron based on the behavior of the ionic channels found in its membrane is proposed. The model comprises microscopic elements, as the behavior of the individual channels, and macroscopic elements, as the tension along a membrane patch. Simulations were performed with the aim of reproducing biological data and results derived from classical theoretical models of the field. It was possible to reproduce with good agreement the action potential, the phenomenon of adaptation, the curve of the input current versus the spike frequency, and the excitatory postsynaptic potential.

Durante a solidificação de ligas metálicas, a decantação de grãos equiaxiais pode causar: macrossegregação, mudança na posição da transição colunar-equiaxial e alteração no tamanho de grão equiaxial. O objetivo do presente trabalho é a implementação e análise de um modelo matemático para simular a solidificação sob efeito da decantação de grãos. Este modelo combina: (a) a técnica do autômato celular bi-dimensional em escala microscópica considerando a decantação de grãos, (b) um submodelo microscópico baseado em equações de conservação para simular os processos internos aos grãos e (c) um submodelo macroscópico também baseado em equações de conservação para simular os processos importantes da escala de tamanho macroscópica. Os submodelos macroscópico e microscópico compartilham informações correspondentes às suas escalas características de tamanho através de um método de acoplamento. O modelo matemático completo foi examinado inicialmente através da simulação de diversas situações idealizadas como: a decantação de uma esfera sólida, a decantação de um conjunto de esferas porosas e a decantação e solidificação simultânea de um grão dendrítico isolado e imerso em um líquido super-resfriado. Posteriormente, compararam-se os resultados do modelo para a solidificação isotérmica e para a solidificação unidirecional com resultados disponíveis na literatura obtidos por outros modelos numéricos e por técnicas experimentais. Os resultados do modelo mostraram que a decantação de grãos resulta nos seguintes efeitos no caso da solidificação unidirecional: variação de tamanho médio de grãos e macrossegregação ao longo do lingote e alteração ou até eliminação na posição da transição colunar-equiaxial. / During solidification of metallic alloys, the settling of equiaxed grains can cause macrosegregation, change the position of the columnar-to-equiaxed transition, and change the grain size of equiaxed grains. The objective of the present work is to implement and analyze a mathematical model to simulate the solidification under the effect of grain settling. The present model combines: (a) the cellular automaton technique in two dimensions applied in the microscopic lengthscale to account for the movement of grains; (b) a microscopic submodel based on conservation equations to simulate important phenomena occurring within the grains, and (c) a macroscopic submodel, also based on conservation equations, to simulate important phenomena of the macroscopic lengthscale. Using a strong coupling scheme, the macroscopic and microscopic submodels share important information specific to their typical lengthscales. The complete mathematical model was initially examined in several idealized conditions: the settling of a single solid sphere; the settling of a group of porous spheres; and the growth of a single dendritic grain settling in an undercooled liquid. The model was also used to simulate the isothermal solidification and the unidirectional solidification. For these cases, the outcome of the model was compared with experimental and calculated results available in the literature. For the unidirectional solidification, the model results showed that the settling of grains can cause a variation in the macrosegregation and grain size along the ingot and can change the position or even eliminate the columnar-to-equiaxed transition region.

Durante a solidificação de ligas metálicas, a decantação de grãos equiaxiais pode causar: macrossegregação, mudança na posição da transição colunar-equiaxial e alteração no tamanho de grão equiaxial. O objetivo do presente trabalho é a implementação e análise de um modelo matemático para simular a solidificação sob efeito da decantação de grãos. Este modelo combina: (a) a técnica do autômato celular bi-dimensional em escala microscópica considerando a decantação de grãos, (b) um submodelo microscópico baseado em equações de conservação para simular os processos internos aos grãos e (c) um submodelo macroscópico também baseado em equações de conservação para simular os processos importantes da escala de tamanho macroscópica. Os submodelos macroscópico e microscópico compartilham informações correspondentes às suas escalas características de tamanho através de um método de acoplamento. O modelo matemático completo foi examinado inicialmente através da simulação de diversas situações idealizadas como: a decantação de uma esfera sólida, a decantação de um conjunto de esferas porosas e a decantação e solidificação simultânea de um grão dendrítico isolado e imerso em um líquido super-resfriado. Posteriormente, compararam-se os resultados do modelo para a solidificação isotérmica e para a solidificação unidirecional com resultados disponíveis na literatura obtidos por outros modelos numéricos e por técnicas experimentais. Os resultados do modelo mostraram que a decantação de grãos resulta nos seguintes efeitos no caso da solidificação unidirecional: variação de tamanho médio de grãos e macrossegregação ao longo do lingote e alteração ou até eliminação na posição da transição colunar-equiaxial. / During solidification of metallic alloys, the settling of equiaxed grains can cause macrosegregation, change the position of the columnar-to-equiaxed transition, and change the grain size of equiaxed grains. The objective of the present work is to implement and analyze a mathematical model to simulate the solidification under the effect of grain settling. The present model combines: (a) the cellular automaton technique in two dimensions applied in the microscopic lengthscale to account for the movement of grains; (b) a microscopic submodel based on conservation equations to simulate important phenomena occurring within the grains, and (c) a macroscopic submodel, also based on conservation equations, to simulate important phenomena of the macroscopic lengthscale. Using a strong coupling scheme, the macroscopic and microscopic submodels share important information specific to their typical lengthscales. The complete mathematical model was initially examined in several idealized conditions: the settling of a single solid sphere; the settling of a group of porous spheres; and the growth of a single dendritic grain settling in an undercooled liquid. The model was also used to simulate the isothermal solidification and the unidirectional solidification. For these cases, the outcome of the model was compared with experimental and calculated results available in the literature. For the unidirectional solidification, the model results showed that the settling of grains can cause a variation in the macrosegregation and grain size along the ingot and can change the position or even eliminate the columnar-to-equiaxed transition region.

XML stream applications bring the challenge of efficiently processing queries on sequentially accessible token-based data streams. The automaton paradigm is naturally suited for pattern retrieval on tokenized XML streams, but requires patches for implementing the filtering or restructuring functionalities common for the XML query languages. In contrast, the algebraic paradigm is well-established for processing self-contained tuples. However, it does not traditionally support token inputs. This dissertation proposes a framework called Raindrop, which accommodates both the automaton and algebra paradigms to take advantage of both. First, we propose an architecture for Raindrop. Raindrop is an algebra framework that models queries at different abstraction levels. We represent the token-based automaton computations as an algebraic subplan at the high level while exposing the automaton details at the low level. The algebraic subplan modeling automaton computations can thus be integrated with the algebraic subplan modeling the non-automaton computations. Second, we explore a novel optimization opportunity. Other XML stream processing systems always retrieve all the patterns in a query in the automaton. In contrast, Raindrop allows a plan to retrieve some of the pattern retrieval in the automaton and some out of the automaton. This opens up an automaton-in-or-out optimization opportunity. We study this optimization in two types of run-time environments, one with stable data characteristics and one with fluctuating data characteristics. We provide search strategies catering to each environment. We also describe how to migrate from a currently running plan to a new plan at run-time. Third, we optimize the automaton computations using the schema knowledge. A set of criteria are established to decide what schema constraints are useful to a given query. Optimization rules utilizing different types of schema constraints are proposed based on the criteria. We design a rule application algorithm which ensures both completeness (i.e., no optimization is missed) and minimality (i.e., no redundant optimization is introduced). The experimentations on both real and synthetic data illustrate that these techniques bring significant performance improvement with little overhead.

Made available in DSpace on 2017-07-21T19:25:58Z (GMT). No. of bitstreams: 1 Caroline Martins.pdf: 2933587 bytes, checksum: 3b47c87334757fd35f267d132590b3b7 (MD5) Previous issue date: 2010-03-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work we considered cellular automaton model with time delay. The time delay reflects the delay between the time at which the site is affected and the time at which its variable is updated. We analyzed the effect of the rules on the dynamics through the cluster counting. According to this cluster counting, the dynamics behaviour is investigated. We verified the same periodic oscillations as the delay differential equation. / Nessa dissertação consideramos um modelo de automato celular com um tempo de atraso. O tempo de atraso incluso reflete a diferença existente entre o tempo que o sıtio é afetado e o tempo em que sua variável é afetada. Analizamos o efeito das regras na dinâmica através da contagem de cluster. O procedimento dinamico é investigado de acordo com essa contagem de cluster. Verificamos as mesmas oscilações periódicas das equações diferenciais com atraso.

As variáveis de processo determinam as propriedades dos produtos resultantes dos processos de fundição ou de soldagem, que são função da sua macro e microestrutura bruta de solidificação. Um dos parâmetros importantes para se determinar as propriedades de um produto é a posição da transição colunarequiaxial (CET) e, por este motivo, o entendimento dos fenômenos físicos que causam esta transição é essencial. Com o intuito de se prever a formação da CET, surgiram os métodos empíricos e os modelos matemáticos, que são divididos em dois grandes grupos: modelos determinísticos e modelos estocásticos. Estes dois grupos foram bem estudados, porém nunca foram comparados entre si, particularmente em relação à previsão da posição da CET. O presente trabalho tem como um primeiro objetivo preencher esta lacuna através da comparação entre estes modelos. No entanto, o objetivo principal é apresentar, implementar e validar um novo modelo matemático, denominado de híbrido estocástico-determinístico (CADE -\"Cellular Automaton Deterministic\"), que combine características importantes e vantajosas de cada um dos dois grupos de modelos. Inicialmente, um modelo representante do grupo dos modelos estocásticos foi implementado e validado frente a resultados disponíveis na literatura. Durante esta validação, foi necessária a elaboração de um critério baseado na razão de aspecto dos grãos para a identificação da CET nas macroestruturas calculadas pelo modelo. Estes resultados foram então comparados com os resultados de modelos determinísticos para, após cuidadosa discussão, possibilitar a proposta e implementação do modelo híbrido. Os modelos determinísticos que utilizam o critério mecânico para prever o bloqueio de grãos colunares e a ocorrência da CET mostram regiões colunares em geral maiores que as previstas pelo modelo estocástico. Por outro lado, os modelos determinísticos que utilizam um critério de bloqueio a partir da interação do campo de concentração de soluto ao redor dos grãos prevêem uma CET em posições semelhantes às calculadas pelos modelos estocásticos. O modelo implementado no presente trabalho é capaz de prever a macroestrutura bruta de solidificação e ainda utilizar as equações tradicionalmente empregadas nos modelos determinísticos, sem a necessidade de qualquer método extra para prever a posição da frente de crescimento colunar ou o seu bloqueio por grãos equiaxiais. / The processing variables determine many properties of the products obtained by casting and welding processes and these properties, on the other hand, are strongly affected by the as-cast micro and macrostructure. Particularly the position of the columnar-to-equiaxed transition (CET), which determines the amount of columnar and equiaxed grains in the macrostructure, has an important effect on the properties of as-cast parts. Therefore, understanding the important physical phenomena that cause and affect the formation of the CET plays a crucial role in predicting the ascast macrostructure. To predict the CET formation, empirical methods and mathematical models have been developed. These models are frequently divided into two main groups: deterministic and stochastic. Both groups have been thoroughly studied, but a comparison between them was never attempted, especially regarding the prediction of the CET position. One of the main objectives of the present work is to fulfill this gap by carefully comparing these models. Nevertheless, the most important objective is to propose, implement, and validate a hybrid stochastic-deterministic model, referred to as CADE (Cellular Automaton Deterministic), that combines some important and well-known features of each model. Initially, a model from the stochastic group was implemented and validated using results available in the literature and then used to analyze the effects of some processing variables on the CET prediction. To carry out this analyzes, a criteria based on the aspect ratio of the grains was proposed and developed to identify the CET region from macrostructure images calculated by the model. The results were compared with those obtained by deterministic models and finally led to the development of the new proposed model. This new model has some characteristics from each group of mathematical models and, for this reason, was denoted as hybrid. A deterministic model based on a mechanical blocking criterion to block columnar grains and define the CET position showed, for the most part, larger columnar regions than those predicted by the stochastic model. A deterministic model with a solutal blocking criterion to predict the CET showed results similar to those calculated with the stochastic model. The model proposed in the present work (CADE) was able to predict the as-cast macrostructure using the well-established deterministic equations, without the need for a new method to track columnar grains or predict their blocking by equiaxed grains.

Cette recherche vise à élaborer une théorie de la pratique et une philosophie morale qui n’accorderaient aucune réalité à des possibles ou à des virtualités. Si l’inspiration bourdieusienne hante notre propos, c’est à partir de Spinoza que nous tentons dans un premier temps de construire un concept de disposition qui soit débarrassé de toute connotation indéterministe en référant les dispositions à des états de corps actuels et en clarifiant le sens de la notion, trop souvent confondue avec d’autres (aptitude, capacité, habitus). Nous montrons dans une deuxième partie que l’incorporation de l’extériorité dans des dispositions actuelles s’accompagne, conformément à la philosophie spinoziste, d’un effort nécessaire et déterminé pour accomplir aussitôt ce que l’agent est condamné à accomplir. La disposition désigne une puissance qui va au bout de ce qu’elle peut, abstraction faite de contrariétés internes ou externes. Si la puissance d’agir peut augmenter ou diminuer, l’effort ne peut être qu’aidé ou contrarié. L’agent est un automate, mais un automate qui s’efforce d’effectuer de gré et nécessairement ce qu’il est forcé d’effectuer, même s’il s’avère que c’est pour le pire. Cela nous conduit dans une troisième partie à contester les interprétations de la philosophie pratique spinoziste en terme d’aliénation. Nous montrons aussi que l’intellectualisme spinoziste doit être largement redéfini, la libération ne pouvant s’effectuer sans compter sur les « dispositions du dehors », y compris l’imagination d’un progrès possible. Enfin, si l’agent automate se signale par la grande inconstance de ses dispositions, il faut le disposer à agir dans un sens favorable à la raison. Le fonctionnement de l’État doit reposer sur la seule mécanique des institutions, puisqu’il est acquis qu’on ne peut vraiment compter sur personne. / This research aims at developing a theory of practice and a moral philosophy that leaves no place for what is merely possible and virtual. While inspired by the sociology of Bourdieu, I first draw on Spinoza to develop a concept of disposition that is freed of all indeterminist connotations by referring dispositions to actual states of the body so as to clarify the meaning of the term, which is so often confused with concepts such as aptitude, capacity, habitus. In the second part of this work, I show that the incorporation of the exteriority comes with the necessary effort to immediately accomplish what the agent is condemned to accomplish. « Disposition » refers to a power that sees through to the end what it can, notwithstanding internal and external impediments. If the power to act increases or diminishes, effort itself can only be helped or hindered. Thus, the agent is an automaton, but one that willingly strives to do what it is compelled to do, even if it is for the worst. Consequently, in the third part, I contest interpretations that relate human bondage in Spinoza’s ethics to alienation. I argue that Spinoza’s intellectualism must be redefined : emancipation cannot occur without relying on the dispositions we receive from the common order of Nature, including imagining possible progress. Finally, although the automaton is characterized by the inconstancy of his dispositions, he has to be disposed in a way that is favorable to reason. The workings of the state should rest solely on the mechanism of the institutions, as it has been established that we really cannot rely upon anyone.