La durabilité des structures en béton est désormais intégrée dans la démarche de conception des ouvrages de Génie Civil. En effet, quel que soit le type de sollicitation (mécanique, thermique, hydrique) une fissuration est susceptible de se produire risquant d'impacter la durée de vie de l'ouvrage par la pénétration d'agents agressifs. L'aptitude au service peut elle-même être affectée pour les structures où une étanchéité est requise (enceinte de confinement de centrales nucléaires, réservoirs de gaz naturel liquéfié, barrages, stockages des déchets radioactifs ou de CO2, etc.). Dans ce contexte industriel, la prédiction du débit de fuite traversant des éléments composés de matériaux à base cimentaire est donc un enjeu scientifique et industriel majeur. Pour parvenir à cet objectif de simulation numérique, il est nécessaire de mettre en place un couplage hydro-mécanique. L'anisotropie de la fissuration induite par les sollicitations mécaniques complexes conduit à un tenseur de perméabilité macroscopique anisotrope. La détermination de ce tenseur est un enjeu important dans l'objectif de mener des calculs à l'échelle macroscopique avec des modèles phénoménologiques. De plus, les calculs de perméabilité sont un moyen de comparer les volumes fissurés obtenus par les différents modèles mécaniques. La modélisation de la fissuration pour les matériaux quasi-fragiles hétérogènes à l'échelle mésoscopique tels que le béton est complexe et suivant les approches utilisées, les résultats peuvent fortement varier. C'est pourquoi l'étude numérique proposée dans la thèse comporte une comparaison entre deux approches mécaniques : - une première basée sur une modélisation mécanique de type E-FEM (Embedded Finite Element Method) [Benkemoun et al., 2010] - - une seconde basée sur une modélisation mécanique d'endommagement [Mazars, 1984] régularisée en énergie de fissuration [Hillerborg et al., 1976]. Le travail numérique associé à cette thèse consiste donc à développer un modèle couplant de manière faible un modèle mécanique à un modèle de transfert en 3D à l'échelle mésoscopique. En se basant sur le concept de « double porosité », la perméabilité du milieu fissuré est vue comme la combinaison d'une perméabilité diffuse et isotrope (liée au réseau poreux initial du béton et à son degré de saturation) et d'une perméabilité « discrète » et orientée au sein des fissures (le calcul de cette dernière étant basé sur les ouvertures de fissures données par le modèle mécanique et sur les équations de la mécanique des Navier-Stokes en régime permanent). La comparaison des résultats obtenus sur différents résultats expérimentaux issus de la littérature (un tirant traversé par de l'eau [Desmettre et Charron, 2011] et un élément structurel traversé par de l'air sec [Nahas et al., 2014]) permet de comparer la pertinence des deux modèles mécaniques utilisés ainsi que l'approche utilisée pour estimer le débit traversant des éléments en béton fissurés. / The durability of concrete structures is nowadays fully integrated in the civil engineering constructions design process. Whatever the loading is (mechanical, thermic, hydric), cracks may appear and impact the structure lifespan by the infiltration of aggressive agents. The serviceability can be directly impacted for the structures playing an air/water tightness role (containment building nuclear power plants, liquefied natural gas storage tanks, dams, radioactive waste disposal, etc.). The prediction of the flow going through elements composed of a cementitious material is therefore a major scientific and industrial issue. To achieve this goal, a hydro-mechanical coupling must be implemented. The anisotropic cracking induced by complex mechanical loadings leads to an anisotropic macroscopic permeability tensor. This tensor computation is an important issue dealing with phenomenological models for macroscopic problems. The cracking modelling of quasi-brittle materials, heterogeneous at the mesoscopic scale like concrete, is complex and different mechanical approaches can lead to various results. Therefore, permeability calculations are an elegant way to examine cracking patterns obtained with several mechanical models. Consequently, this study compares two mechanical approaches: - the first one is based on an Embedded Finite Element Method (E-FEM) mechanical model [Benkemoun et al., 2010] - - the second one is based on a damage mechanical model [Mazars, 1984] regularised by the fracture energy of the material [Hillerborg et al., 1976]. This thesis presents a hydro-mechanical approach weakly coupling a mechanical model with a permeation model in 3D at the mesoscopic scale. This work is based on the “double porosity” concept splitting the permeability into two parts: the first one is isotropic and corresponds to flows within the porosity of the material- the second one, based upon a set of cracks with different orientations and openings, is anisotropic. For the latter, each crack is a path for mass flow according to the fluid laws considering two infinite planes. In order to check this approach relevance, numerical results are compared to experimental results extracted from the literature (an experiment where water goes through a specimen made of a steel reinforcing bar covered with concrete under load [Desmettre et Charron, 2011] and a device where dry air goes through a structural element made of reinforced concrete [Nahas et al., 2014]). The computation of the flow going to those cracked concrete elements helps to understand the presented approach efficiency and the differences between the two used mechanical models.

This thesis deals with application of optimisation methods based on linear and mixed-integer linear programming to various problems in the power sector related to electricity production. The thesis goal is to test the applicability of such methods to formulating and solving various instances from the class of real-world electricity production problems, and to find the advantages and disadvantages associated with using these methods. Introductory chapters describe the main characteristics of power markets, including the historical and regulatory context. Fundamental properties of power markets on both demand and supply side are also described, both from a real-world and a modelling point of view. Benefits of optimisation and modelling are discussed, in particular the solution feasibility and optimality as well as insights gained from sensitivity analysis which is often difficult to replicate with the original system. In the core of the thesis, optimisation techniques are applied to three case studies, each of which deals with a specific problem arising during electricity production. In the first problem, the profit of gas-fired power plant in Slovakia from selling power on the day-ahead market is maximised. The model is set up using both technical and commercial constraints. The second problem deals with the problem of representing a two-dimensional production function which primarily arises for a hydro generator with large variations in the level of its reservoir. Several representations of the original function using piecewise linear subsets are presented, compared, and characterised by their computational intensity both theoretically and practically. In the third problem, the prices on the German day-ahead market in 2011 are modelled. Contrary to the previous two models, the model does not capture an optimisation problem faced by a single producer, but incorporates a large subset of the whole market instead. Consequently the model is formed out of generic constraints relevant to all power plants whose parameters are estimated. By combining information about the aggregate availability of power plants with the estimated efficiencies a full supply curve for each day is created. Different scenarios are analysed to test the impact of uncertain inputs such as unknown or estimated constraints. The choice of the investigated problems stems from the attempt to cover electricity production problems from the point of view of multiple criteria. The three investigated electricity production problems span a broad range from the decisions of a single power plant to the modelling a power market as a whole. Formulations of the production function with different level of detail are presented ranging from a simple linear relationship to several bivariate function formulations. While each problem answers a specific question, they all illustrate the ease with which various electricity production problems can solved using optimisation methods based on linear and mixed-integer linear programming. This is mainly due to the ability of these methods to approximate even non-linear functions and constraints over non-convex domains and find global solutions in reasonable time. Moreover, models formulated with these methods allow sensitivity and scenario analyses to be carried out easily as is illustrated in each of the case studies.

O trabalho apresenta uma discussão sobre o nível de contratação ótima dos geradores hidroelétricos participantes do Mecanismo de Realocação de Energia (MRE), considerando a influência dos Procedimentos Operativos de Curto Prazo (POCP). O assim denominado POCP é um conjunto de procedimentos realizados pelo Operador Nacional do Sistema (ONS) para proporcionar mais segurança no atendimento à carga do Sistema Interligado, sendo realizado no período de abril a novembro, durante o Programa Mensal de Operação (PMO). O gerador hidráulico, em função do despacho centralizado e normativo adotado no Brasil, dependendo da quantidade de água que aflui aos reservatórios e do consequente despacho das usinas determinado pelo ONS, fica sujeito às exposições no mercado de curto prazo, decorrentes da diferença entre os contratos de venda do gerador e o montante de garantia física (GF) alocada mensalmente após a realização do MRE. Como o POCP não está incorporado nos modelos de despacho das usinas do setor elétrico, uma alternativa de simulação foi construída e, a partir dos seus resultados, pode-se perceber a interferência do mecanismo em tela nas exposições no mercado de curto prazo e no patamar de risco incorrido. A aplicação do POCP traz um efeito líquido de redução da geração hidrelétrica, pois se diminui a possibilidade de utilizar a capacidade de regularização dos reservatórios, evitando riscos de eventual não recuperação dos reservatórios no período chuvoso. Por outro lado, o procedimento conservador hoje utilizado pode gerar um volume muito maior de vertimentos durante o período úmido, limitando a chance de recuperação financeira dos geradores hidrelétricos que tiveram sua geração reduzida no período seco devido ao despacho antecipado de termelétricas, fatalmente com rebatimentos traduzidos por exposições ao PLD. Por conta de todos os fatores de risco citados, os agentes geradores precisam ajustar sua estratégia ótima de contratação, mantendo a função objetivo de maximizar a receita, condicionado a critérios de risco, que ponderem os fatores citados. Nessa perspectiva, foi analisada a aplicação do POCP no ano de 2010 e seus impactos, além de simular a receita esperada e o risco futuro com e sem a aplicação deste mecanismo. Os resultados mostram o quanto o POCP interfere na receita esperada dos agentes, agregando maiores riscos e alterando-se o nível de contratação ótima. Sendo assim, dependendo do risco que cada agente gerador está disposto a assumir, uma revisão de seu nível de contratação torna-se imperiosa. / This work presents a discussion about the optimal level of energy contracting of the Hydroelectric Generators participants of the Energy Reallocation Mechanism, (MRE - Mecanismo de Realocação de Energia), considering the influence of Short Term Operating Procedures (POCP - Procedimentos Operativos de Curto Prazo). The POCP is a set of procedures performed by the National System Operator (ONS - Operador Nacional do Sistema) to provide more security in the Interconnected System, being carried out from April to November, during the Monthly Programme Operation (PMO - Programa Mensal de Operação). Hydro plants are subject to exposure in short-term market due to the centralized dispatch adopted in Brazil, which depends on the amount of water that flows to the reservoir and on the subsequent dispatch of plants determined by the ONS. The exposure in short-term market, arises from the difference between the Generator sales contracts and the amount of assured energy (GF - Garantia Física) monthly allocated after the MRE. As the POCP is not incorporated into the dispatch models of the electricity sector, an alternative simulation was built and, from its results, we can notice the interference of the mechanism displayed in the short-term market and in the incurred risk level. The application of the POCP brings a net reduction in hydropower generation, because it decreases the possibility of using the regularization capacity of the reservoirs, avoiding any risk of non recovery of the reservoirs during the rainy season. On the other hand, the conservative procedure used today can generate a much larger volume of spilling water during the wet season, limiting the chance of financial recovery of hydroelectric dams that had their generation reduced in the dry season due to the anticipated dispatch of thermoelectric plants, inevitably with repercussions represented by exposure to the PLD (SPOT). Considering all risk factors mentioned, the generating agents have to adjust their optimal strategy for contract level, retaining the objective function to maximize revenue, conditional to risk criteria, which consider the factors mentioned. From this perspective, we analyzed the application of the POCP in 2010 and its impacts, as well as simulated the expected revenue and the future risk with and without the application of this procedure. The results show how the POCP interferes in the expected revenue of the agents, adding greater risks and changing the optimal level of energy contracting. Thus, depending on the risk that each generating agent is willing to take, a review of their contracting level becomes imperative.

Le concept d’habitat, qui définit le lieu de vie des organismes par des conditions abiotiques et biotiques, est déterminant pour étudier les relations entre les organismes et leur environnement. La sélection d’habitat est le processus à travers lequel l’organisme va choisir l’habitat où il se trouve en fonction des différents habitats disponibles autour de lui. Cette sélection va dépendre d’un choix individuel, qui est propre à l’organisme (ex. son comportement), et d’un choix commun, qui est observable chez des organismes qui partagent des traits communs (ex. les individus d’une même espèce). Les modèles spécifiques de sélection d’habitat cherchent à expliquer et prédire ce choix commun, et sont notamment utilisés pour les cours d’eau dans les outils d'aide à la définition de débits écologiques. Pour les poissons de rivière, la plupart des modèles spécifiques à l’échelle du microhabitat sont peu transférables à d’autres rivières. En effet, ils sont construits à partir de données d’abondance échantillonnées dans le même site pendant quelques campagnes. Afin d’améliorer la qualité prédictive de ces modèles, j’ai développé une approche prometteuse de modélisation multi-sites et multi-campagnes permettant à la fois de considérer la réponse non linéaire de la sélection et la surdispersion des données d’abondance. A partir de suivis individuels par télémétrie, j’ai montré la pertinence des modèles de sélection spécifiques malgré la forte variabilité individuelle observée. Finalement, la sélection d’habitat étant dépendante de processus structurant les communautés et agissant à l’échelle du paysage, telle que la dispersion des individus, j’ai mis en évidence l’intérêt d’utiliser des techniques légères d’échantillonnage comme les observations par plongée pour caractériser les structures des communautés et leurs répartitions spatiales. Ces techniques permettront alors d’étudier l’influence des processus du paysage sur les modèles de sélection d’habitat / The habitat concept, which defines the place where organisms live, is composed by abiotic and biotic conditions and differs for examples between species or activities. The habitat selection is the process where organisms choose the habitat to live in function of all habitats available around them. This habitat selection depends on an individual choice related to the organism, for example its behavior and a common choice related to organisms sharing common traits as individuals from the same species. Specific habitat selection models are developed to understand and represent this common choice and used to build ecological flow tools. For freshwater fish, most of specific habitat selection models have low transferability between reaches and rivers. Indeed, they are built from abundance data and sampled in the same study reach during few numbers of surveys. In order to improve predictive quality of models, I developed an attractive modelling approach, both multi-reach and multi-survey, involving the non-linear response of habitat selection and abundance data overdispersion. Then, despite the high individual variability of habitat selection, I showed, from telemetry data, the relevance of developing specific habitat selection models. Finally, as the habitat selection is also depending on processes which influence community structures at the landscape scale (e.g. dispersal), I demonstrate the benefits of sampling methods such as snorkeling to characterize community structures and their longitudinal distributions at a large spatial scale. These techniques will allow studying the influence of landscape processes on habitat selection models.

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This diploma thesis deals with the design of hydraulic cleaning machine of fine screens located in the supply channel of small hydropower plant. The part of this thesis is also the design of hydraulic circuit and strength analysis using finite element method. The thesis also deals with the optimal debris removal. The thesis is attached by drawing documentation of selected parts of the mechanism.

This thesis focused on creating a model of a small hydropower plant model (SHPP) and a part of the electricity network in the simulation software "PSCAD" (basing on real sources). The model will be specified on the basis of the data obtained from the measurements to correspond with the real equipment.

The aim of the diploma thesis is to create an algorithm by which it will be possible to devise management rules. These management rules will be able to advise a more efficient use of the hydroenergetic potential of reservoirs with run-of-river small hydro. The actual algorithm will be created with a view to maximizing the profit from the operation of the hydropower plant and using the time course of electricity prices on the market. The rules designed by algorithm will be tested in a simplified way in selected period using simulation model.