Motivated by the existence of complex behaviors arising from interactions between chemistry and fluid dynamics in numerous research problems and every-day life situations, we theoretically investigate the dynamics resulting from the interplay between chemistry, diffusion, and fluid motions in a reactive aqueous solution. As a chemical reaction induces changes in the temperature and in the composition of the reactive medium, such a reaction can modify the properties of the solution (density, viscosity, surface tension,…) and thereby trigger convective motions, which in turn affect the reaction. Two classes of convective flows are commonly occurring in solutions open to air, namely Marangoni flows arising from surface tension gradients and buoyancy flows driven by density gradients. As both flows can be induced by compositional changes as well as thermal changes and in turn modify them, the resulting experimental dynamics are often complex. The purpose of our thesis is to gain insight into these intricate dynamics thanks to the theoretical analysis of model systems where only one type of convective flow is present. In particular, we numerically study the spatio-temporal evolution of model chemical fronts resulting from the coupling between reactions, diffusion, and convection. Such fronts correspond to self-organized interfaces between the products and the reactants, which typically have different density and surface tension. Fluid motions are therefore spontaneously induced due to these differences across the front. In this context, we first address the propagation of a model autocatalytic front in a horizontal solution layer, in the presence of pure Marangoni convection on the one hand and of pure buoyancy convection on the other hand. We evidence that, in both cases, the system attains an asymptotic dynamics characterized by a steady fluid vortex traveling with the front at a constant speed. The presence of convection results in a deformation and acceleration of the chemical front compared to the reaction-diffusion situation. However we note important differences between the Marangoni and buoyancy cases that could help differentiate experimentally between the influence of each hydrodynamic effect arising in solutions open to the air. We also consider how the kinetics and the exothermicity of the reaction influence the dynamics of the system. The propagation of an isothermal front occurring when two diffusive reactants are initially separated and react according to a simple bimolecular reaction is next studied in the presence of chemically-induced buoyancy convection. We show that the reaction-diffusion predictions established for convection-free systems are modified in the presence of fluid motions and propose a new way to classify the various possible reaction-diffusion-convection dynamics./En induisant des changements de composition et de température, une réaction chimique peut modifier les propriétés physiques (densité, viscosité, tension superficielle,…) de la solution dans laquelle elle se déroule et ainsi générer des mouvements de convection qui, à leur tour, peuvent affecter la réaction. Les deux sources de convection les plus courantes en solution ouverte à l’air sont les gradients de tension superficielle, ou effets Marangoni, et les gradients de densité. Comme ces deux sources sont en compétition et peuvent toutes deux résulter de différences de concentration ou de température, les dynamiques observées expérimentalement sont souvent complexes. Le but de notre thèse est de contribuer à la compréhension de telles dynamiques par une étude théorique analysant des modèles réaction-diffusion-convection simples. En particulier, nous étudions numériquement l’évolution spatio-temporelle de fronts chimiques résultant du couplage entre chimie non-linéaire, diffusion et hydrodynamique. Ces fronts constituent l’interface auto-organisée entre les produits et les réactifs qui typiquement ont des densités et tensions superficielles différentes. Des mouvements du fluide peuvent dès lors être spontanément initiés dus à ces différences au travers du front. Dans ce contexte, nous étudions la propagation d’un front chimique autocatalytique se propageant dans une solution aqueuse horizontale, d’une part en la seule présence d’effets Marangoni, et d’autre part en présence uniquement d’effets de densité. Nous avons montré que dans les deux cas, le système atteint une dynamique asymptotique caractérisée par la présence d’un rouleau de convection stationnaire se propageant à vitesse constante avec le front. Ce front est à la fois déformé et accéléré par les mouvements convectifs par rapport à la situation réaction-diffusion. Nous avons mis en évidence d’importantes différences entre les deux régimes hydrodynamiques qui pourraient aider les expérimentateurs à différencier les effets de tension superficielle de ceux de densité générés par la propagation de fronts chimiques en solution. Nous avons également considéré l’influence de la cinétique de réaction ainsi que de l’exothermicité sur la dynamique de ces fronts. Enfin, nous avons étudié la propagation en présence de convection d’un front de réaction impliquant deux espèces de densités différentes, initialement séparées et réagissant selon une cinétique bimoléculaire. Nous avons montré que la convection modifie les propriétés réaction-diffusion du système et nous proposons de nouveaux critères pour classifier les dynamiques réaction-diffusion-convection.

Les travaux de cette thèse s’articulent autour des « problèmes d’ordonnancement multiagent avec une fonction objectif globale ». Ces modèles considèrent différents agents associés à des sous-ensembles de travaux disjoints, chacun d’eux vise à minimiser un objectif qui ne dépend que de ses propres travaux. Un critère global est aussi considéré, qui est appliqué à la totalité des travaux. La résolution de ces problèmes revient à trouver les meilleurs compromis entre les critères des agents et le critère global. Ces problèmes sont une classe particulière des problèmes d’ordonnancement « multi-agents » qui ont connu une grande expansion, reflétant leurs intérêts dans le domaine de l’ordonnancement. / This thesis addresses the multi-agent scheduling problems with a global objective function. We consider the problems featured by various agents, each of which is associated with a distinct subset of jobs. Each agent aims at minimizing a certain objective function, which only operates on its assigned jobs. A global criterion associated with a global agent is applied on the whole set of the jobs. Solving these problems involves finding the best compromises between the requirements of agents and that of the global agent. These problems belong to a particular class of multi-criteria scheduling problems. Such a class has drawn a significant interest to researchers in the area of scheduling and operational research.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-10-22T19:41:10Z No. of bitstreams: 4 Dissertação - Douglas Hilário da Cruz - 2013 - PARTE 01.pdf: 20946472 bytes, checksum: 1f5cc7eeda54593cff53f3c563b23faa (MD5) Dissertação - Douglas Hilário da Cruz - 2013 - PARTE 02.pdf: 20125557 bytes, checksum: 9c30c03de1a6b7fb3f356cc931d61534 (MD5) Dissertação - Douglas Hilário da Cruz - 2013 - PARTE 03.pdf: 266901 bytes, checksum: 97410256533198e3a3b180056a740526 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2014-10-22T20:18:04Z (GMT) No. of bitstreams: 4 Dissertação - Douglas Hilário da Cruz - 2013 - PARTE 01.pdf: 20946472 bytes, checksum: 1f5cc7eeda54593cff53f3c563b23faa (MD5) Dissertação - Douglas Hilário da Cruz - 2013 - PARTE 02.pdf: 20125557 bytes, checksum: 9c30c03de1a6b7fb3f356cc931d61534 (MD5) Dissertação - Douglas Hilário da Cruz - 2013 - PARTE 03.pdf: 266901 bytes, checksum: 97410256533198e3a3b180056a740526 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-10-22T20:18:04Z (GMT). No. of bitstreams: 4 Dissertação - Douglas Hilário da Cruz - 2013 - PARTE 01.pdf: 20946472 bytes, checksum: 1f5cc7eeda54593cff53f3c563b23faa (MD5) Dissertação - Douglas Hilário da Cruz - 2013 - PARTE 02.pdf: 20125557 bytes, checksum: 9c30c03de1a6b7fb3f356cc931d61534 (MD5) Dissertação - Douglas Hilário da Cruz - 2013 - PARTE 03.pdf: 266901 bytes, checksum: 97410256533198e3a3b180056a740526 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-04-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we study asymptotic lines in the neighborhood of a singular point, lines of curvature in the neighborhood of singular curves of ellipsoid wave fronts and the lines of curvature in the neighborhood of the Darbouxian umbilic points. / Neste trabalho estudamos as linhas assintóticas na vizinhança de um ponto singular, as linhas de curvatura na vizinhança das curvas de pontos singulares das frentes de ondas do elipsóide e as linhas de curvatura na vizinhança dos pontos umbílicos Darbouxianos das frentes de ondas de uma superfície regular.

L'apparition de structures spatiales est un phénomène universel. En optique non linéaire, générer des structures transverses et contrôler leur dynamique est important non seulement d'un point de vue fondamental mais aussi d'un point de vue des applications. Ce travail de thèse s'inscrit dans cette logique de caractérisation et manipulation des structures spatiales optiques, engendrées dans une expérience de valve à cristaux liquides. Une première partie est consacrée aux effets de forçages spatiaux sur la propagation de fronts, induits avec un modulateur spatial de lumière. Une étude unidimensionnelle, incluant des comparaisons avec des modèles analytiques et des résultats numériques, montre l'existence d'une région d'agrafage à l'intérieur de laquelle des états localisés de taille différente peuvent être générés. Une extension à deux dimensions est aussi présentée pour différentes géométries du forçage spatial. La seconde partie s'intéresse aux effets d'une rétroaction non locale sur les structures localisées, apparaissant en présence simultanée de diffraction et d'interférence de polarisation. Dans le cas d'un effet de translation, un phénomène d'advection des structures est observé, associé à l'apparition de singularités de phase dans leur sillage. Au-delà d'un certain taux de translation, un autre régime est atteint avec une périodicité le long de la direction de translation. Dans le cas où rotation et translation sont présentes simultanément, les modes d'auto-organisation des structures localisées présentent des analogies avec certains modes de croissance des végétaux. L'influence des différents paramètres, dont la rotation, est caractérisée sur les motifs obtenus.

Les systèmes de réaction-diffusion interviennent pour décrire les transitions de phase dans de nombreux champs d'application. Cette thèse porte sur l'analyse mathématique de modèles de propagation dans des milieux diffusifs, non bornés et hétérogènes, et s'inscrit ainsi dans la lignée d'une recherche particulièrement active. La première partie concerne l'équation simple: on s'y intéressera à la structure interne des fronts, mais on exhibera aussi de nouvelles dynamiques où la vitesse d'un profil de propagation n'est pas unique. Dans la seconde partie, on s'intéresse aux systèmes à deux équations, pour lesquels l'absence de principe du maximum pose de nombreuses difficultés. Ces travaux, en portant sur un vaste éventail de situations, offrent une meilleure compréhension des phénomènes de propagation, et mettent en avant de nouvelles propriétés des problèmes de réaction-diffusion, aidant ainsi à améliorer l'analyse théorique comme alternative à l'approche empirique. / Reaction-diffusion systems arise in the description of phase transitions in various fields of natural sciences. This thesis is concerned with the mathematical analysis of propagation models in some diffusive, unbounded and heterogeneous media, which comes within the scope of an active research subject. The first part deals with the single equation, by looking at the inside structure of fronts, or by exhibiting new dynamics where the profile of propagation may not have a unique speed. In a second part, we take interest in some systems of two equations, where the lack of maximum principles raises many theoretical issues. Those works aim to provide a better understanding of the underlying processes of propagation phenomena. They highlight new features for reaction-diffusion problems, some of them not known before, and hence help to improve the theoretical approach as an alternative to empirical analysis.

L’émergence du concept d’un avion plus électrique implique une refonte en profondeur des réseaux embarqués. L’axe principalement développé repose sur une augmentation de la tension du réseau et un passage au bus continu. Le contrôle des actionneurs électriques embarqués passe alors par l’utilisation massive de convertisseurs électroniques qui vont imposer des fronts de tension très raides et des contraintes particulières aux enroulements des machines. Les oscillations pseudopériodiques qui suivent ces fronts raides sont à l’origine de champs électriques intenses qui peuvent dépasser le seuil d’apparition des décharges partielles (PDIV) et de ce fait provoquer une dégradation rapide des isolants classiques qui sont à base de polymères. Le travail effectué dans cette thèse est centré sur l’étude d’une nouvelle méthode de conception des bobinages permettant la réduction des problèmes de décharges partielles. Un dispositif expérimental mis au point dans ce cadre reproduit les contraintes imposées par des convertisseurs modernes et permet de mesurer les tensions inter-spires d’une bobine. L’étude expérimentale met en évidence les phénomènes àprendre en compte avec ce type d’alimentation et donne une première idée des axes d’optimisation envisageables. Un modèle prédictif capable de donner la distribution des tensions inter-spires, en réponse à un front raide de tension, aide à identifier les points critiques. Les paramètres constitutifs de ce modèle ont été déterminés en utilisant des méthodes analytiques, expérimentales et numériques. Compte tenu de la complexité du modèle, un outil numérique automatisé a été élaboré afin de simuler le modèle des bobines étudiées. Plusieurs types de bobinage ont été analysés et optimisés avec succès. Cette optimisation consiste à diminuer la tension inter-spires en agissant sur l’arrangement des fils dans les encoches. L’utilisation des bobines optimisées avec cette méthode permet d’envisager une nette amélioration de la fiabilité des machines électriques. / The emergence of the concept of a more electric aircraft requires a major overhaul of onboard grid. The main developed axis is based on an increase in the grid voltage and a switch to DC bus. In this context, the onboard electric actuators are supplied through power electronic converters that will impose very fast voltage fronts and particular constraints in the windings of the machines. The transient over-voltages that follow the steep-fronted pulses are the source of intense electric fields which may exceed the partial discharge inception voltage (PDIV) and cause a rapid deterioration of polymer based insulators. This thesis focuses on the study of a new design method of the windings in order to reduce problems of partial discharges. An experimental device developed in this framework reproduces the constraints of modern converters and allows measuring the turn-to-turn voltages of a coil. The experimental study shows the phenomena to be considered with this type of power supply and gives an idea of possible areas for optimization. A predictive model able to give the distribution of turn-to-turn voltages, in response to a steep-fronted voltage, helps to identify critical points. The constitutive parameters of this model were determined using analytical, experimental and numerical methods. Given the complexity of the model, an automated numerical tool has been developed in order to simulate the model of studied coils. Several types of coil have been analyzed and optimized successfully. This optimization consists in reducing the turn-to-turn voltages by acting on the arrangement of the wires in the slots. The use of optimized coils with this method allows envisaging a significantimprovement in the reliability of electrical machines.

Ce travail de thèse est constitué de l'étude de deux problèmes inverses associés à des équations paraboliques à coefficients périodiques. Dans la première partie, on a considéré une équation parabolique à coefficients et condition initiale périodiques. Notre travail a consisté à aborder le cas de coefficient à régularité faible et à minimiser les contraintes d'observations requises pour établir notre résultat de reconstruction du potentiel. On a commencé par établir un résultat d'existence et d'unicité de la solution dans un espace d'énergie adéquat. Ensuite, on a énoncé un principe du maximum adapté aux hypothèses du problème étudié et on a travaillé avec des coefficients mesurables et bornés. Enfin, on a reconstruit le potentiel en établissant une inégalité de Carleman. Le résultat d'identification a été obtenu via une inégalité de stabilité de type Lipschitz. Dans le second travail, on s'est intéressé à la détermination d'un coefficient périodique en espace du terme de réaction dans une équation de réaction-diffusion définie dans l'espace entier $mathbb{R}$. On établit un résultat d'unicité en utilisant un nouveau type d'observations. La nature du problème étudié, posé dans l'espace $mathbb{R}$, nous a permis d'utiliser la notion de vitesse asymptotique de propagation. On a prouvé l'existence de cette vitesse et on l'a caractérisé. On a surdéterminé le problème inverse en choisissant une famille de conditions initiales à décroi-ssance exponentielle. Notre principal résultat est que ce coefficient est déterminé de façon unique, à une symétrie près, par l'observation d'un continuum de vitesses asymptotiques de propagation. / This thesis consists in the study of two problems associated to inverse para-bolic equations with periodic coefficients. We are interested in identifying one coefficient by using two different methods. In the first part, we consider a parabolic equation with periodic coefficients and periodic initial condition. Our work consists to consider the case of coefficient with weak regularity and to minimize the constraints of observations which are required to establish our reconstruction result. We establish a result of existence and uniqueness of the solution in adequate energy space. Then we prove a maximum principle adapted to the hypothesis of the problem studied and we work with measurable and bounded coefficients. Finally, we reconstruct the potential by establishing a Carleman estimate. The identification result was achieved via an inequality of stability. In the second work, we are interested to determine a periodic coefficient of the reaction term defined in the whole space $mathbb{R}$. We establish a uniqueness result by using a new type of observations. The nature of the studied problem allowed us to use the notion of asymptotic speed of propagation. We prove the existence of this speed and we give its characterization. We overdetermin the inverse problem by choosing a family of initial conditions exponentially decaying. Our main result is that the coefficient is uniquely determined up to a symmetry, by the observation of a continuum of asymptotic speed of propagation.

Approved for public release; distribution is unlimited / Results of a highly vectorized and multitasked model of the world ocean circulation were analyzed. This model which uses realistic physics, geometry, and forcing on a high-resolution grid, was run on the NCAR Cray X-MP/48 using a robust-diagnostic strategy. Twenty years of model integration using one-half degree horizontal resolution and 20 levels of vertical resolution were accomplished after 200 wall-clock hours at a maximum FORTRAN performance speed of 450 megaflops. Seven key regions of the world ocean were analyzed using an ocean model processor. A representation of the global ocean circulation emerged that compared well with observations and that included strong advective features, fronts, and subtropical meanders. A diagnostic analysis program was developed to analyze meridional heat and volume transports. The results in all basins appear to be reasonable when compared to the results of other studies. For example, an anomalous northward heat transport of 3.8 x 10 to the 14th power W at 30 deg in the South Atlantic compares favorably with the estimate of 4.2 x 10 to the 14th power W at 32 deg S by Bennett (1978) using hydrographic data. The results of simulations conducted in this study can be compared and contrasted against the results of future eddy-resolving simulations. Keywords: Digital simulation, Advection, Heat transport, Meridional volume transport, Oceanographic fronts, Meanders, Thermoclines, Finite difference analysis. Theses. (EDC) / http://archive.org/details/analysisofresult00bart / Lieutenant Commander, United States Naval Reserve

Os padrões de circulação do Atlântico Sudoeste são caracterizados por uma diversidade de massas de água. A presença das correntes associadas ao giro subtropical e a incursão para norte da Corrente Circumpolar Antártica (CCA) determinam extensas regiões de largo gradiente de Temperatura da Superfície do Mar (TSM). Ao mesmo tempo, circulações de mesoescala geram intensos gradientes setorizados, ou reforçam o contraste de larga-escala. Consequentemente, frentes oceânicas de diferentes escalas são formadas ao longo desses gradientes. Quando o vento sopra sobre essas frentes, os fluidos trocam calor e momentum alterando suas propriedades dinâmicas e termodinâmicas. Nesse trabalho visamos caracterizar as alterações no campo de vento superficial que podem ser atribuídas a essas trocas. Para isso, foi aplicado um algoritmo de detecção de frentes em campos de Temperatura da Superfície do Mar (TSM) derivados do conjunto OSTIA. Em situações de escoamento atmosférico sinótico homogêneo, foram calculados o divergente e rotacional do vento medido pelo escaterômetro QuickSCAT ao longo das zonas frontais, bem como suas componentes perpendicular e paralela às frentes. Ao longo de 8 anos mais 96.000 frentes oceânicas foram detectadas, co-localizadas com a disponibilidade de dados de vento dando origem a 40.000 composições. O sistema de coordenadas dessas composições foi rotacionado para que as frentes oceânicas tivessem a mesma orientação. Nós empilhamos as composições em um arranjo 3D e foram obtidas médias das circulações atmosféricas induzidas. As perturbações médias obtidas indicaram que há convergência do vento quando este sopra do lado quente para o lado frio da frente com a frenagem do escoamento. De forma oposta, há divergência e aceleração do vento quando este sopra no sentido oposto. Nós identificamos alterações locais no rotacional do campo de vento capazes de induzir o bombeamento de Ekman no oceano. Esse processo pode gerar mecanismos de retroalimentação no sistema. Nossos resultados corroboram o de diversos estudos sobre o tema presentes literatura. / The southwest Atlantic circulation patterns are characterized by a diversity of water masses. The presence of currents associated with the subtropical gyre and the northward incursion of Antarctic Circumpolar Current (ACC) determine extensive regions of strong sea surface temperature gradient (SST). At the same time, mesoscale circulations generate intense local gradients, or reinforce the large-scale contrast. Consequently, oceanic fronts are formed along these gradients on different scales. When the wind blows over these fronts, the fluids exchange heat and momentum, and that changes their dynamic and thermodynamic properties. In this work we aim to characterize the changes in the surface wind field that might be attributed to these exchanges. To do it, a frontal detection algorithm was applied to the SST field derived from OSTIA set. We selected situations of synoptic homogeneous atmospheric flow and calculated the divergent and rotational wind, in addition to its perpendicular and parallel components to the oceanic fronts. We used wind measurements recorded by the QuickSCAT scatterometer along the frontal zones. More than 96,000 oceanic fronts were detected along 8 years of data. We matched them to available wind data and formed more than 40,000 SST-WIND compositions. The coordinate system of these compositions was rotated so that all oceanic fronts have the same horizontal orientation. We piled up the compositions in a 3D array and the temporal mean of the induced circulations was calculated. The average disturbance obtained indicated that there is wind convergence when it blows from the warm side of the front to the cold side because the flow is slowed down. Conversely, there is wind divergence when it blows in the opposite direction due to speeding up flow. We identified local changes in wind field curl capable of inducing Ekman pumping over the ocean. This process can generate feedback mechanisms in the system. Our results were consistent with the literature.

Made available in DSpace on 2016-08-10T10:49:47Z (GMT). No. of bitstreams: 1 Jesse Goncalves Cutrim.pdf: 2774161 bytes, checksum: c360b9a9826d2517b584fa34250e4579 (MD5) Previous issue date: 2011-03-18 / This study examines in a broader perspective, the territorial changes produced in the Amazonico Maranhense Savannah . These are strongly related to the expansion fronts and development of the agricultural frontier in evidence. From the years 1980 accelerate the process of implementation of large agricultural projects and development in the region, which is part of the legal Amazon, in an area geographically related to the savannah, the area of the plateau and the forest. Hence the name "Amazonico Maranhense Savannah." The way some of these appropriations of Maranhense Savannah in the legal Amazon territory in large scale involves conflicts and contradictions within the sustainable territorial development. In the last three decades came to this region large agribusiness conglomerates of South-Central. It changed its territory, causing in the passage of a rural complex for agro-industrial complex. The region of "Amazonico Maranhense Savannah" established itself as agriculture frontier area and territorial development in the light of implementation of public policies and institutional logistical contributions. As well, favorable natural conditions, fertile land and abundant water, for example. Large projects and agribusiness contributed to highlight the effects of development about society and nature, contributing to increasing population densities and the region's economic dynamism. Therefore, this study examines more strictly the socioeconomic and environmental relationship of sugarcane industry in the city of Campestre of Maranhão. / O presente estudo analisa numa perspectiva mais ampla, as transformações territoriais produzidas no cerrado amazônico maranhense . Estas estão intensamente relacionadas às frentes de expansão e a concepção de fronteira agrícola em evidência. A partir dos anos 1980 se acelera o processo de implantação dos grandes projetos agropecuários e de desenvolvimento na região, que é parte integrante da Amazônia Legal, numa área geograficamente relacionada com o cerrado, a zona da chapada e a floresta. Daí a denominação cerrado amazônico maranhense . O modo como algumas dessas apropriações do cerrado maranhense em território da Amazônia Legal em larga escala implica em conflitos e contradições no âmbito do desenvolvimento territorial sustentável. Nas últimas três décadas vieram para essa região grandes conglomerados agroindustriais do Centro-Sul. Isso modificou o seu território, saindo da condição de complexo rural para um complexo agroindustrial. A região do cerrado amazônico maranhense consolidou-se como área de fronteira agrícola e de desenvolvimento territorial em função da implantação de políticas públicas e de aportes logísticos institucionais. Bem como, condições naturais favoráveis, terras férteis e água em abundância, por exemplo. Os grandes projetos e as agroindústrias contribuíram para dar visibilidade aos efeitos do desenvolvimento sobre a sociedade e a natureza, concorrendo para o aumento da densidade demográfica e para o dinamismo econômico da região. Portanto, esta pesquisa analisa de maneira mais estrita a relação socioeconômica e ambiental da agroindústria canavieira no município de Campestre-MA.