L'hydraulique est la principale énergie renouvelable produite en France. Elle apporte une réserve d'énergie et une flexibilité intéressantes dans un contexte d'augmentation de la part des énergies intermittentes dans la production. Sa gestion soulève des problèmes difficiles dus au nombre des barrages, aux incertitudes sur les apports d'eau et sur les prix, ainsi qu'aux usages multiples de l'eau. Cette thèse CIFRE, effectuée en partenariat avec Electricité de France, aborde deux questions de gestion hydraulique formulées comme des problèmes d'optimisation dynamique stochastique. Elles sont traitées dans deux grandes parties.Dans la première partie, nous considérons la gestion de la production hydroélectrique d'un barrage soumise à une contrainte dite de cote touristique. Cette contrainte vise à assurer une hauteur de remplissage du réservoir suffisamment élevée durant l'été avec un niveau de probabilité donné. Nous proposons différentes modélisations originales de ce problème et nous développons les algorithmes de résolution correspondants. Nous présentons des résultats numériques qui éclairent différentes facettes du problème utiles pour les gestionnaires du barrage.Dans la seconde partie, nous nous penchons sur la gestion d'une cascade de barrages. Nous présentons une méthode de résolution approchée par décomposition-coordination, l'algorithme Dual Approximate Dynamic Programming (DADP). Nousmontrons comment décomposer, barrage par barrage, le problème de la cascade en sous-problèmes obtenus en dualisant la contrainte de couplage spatial ``déversé supérieur = apport inférieur''. Sur un cas à trois barrages, nous sommes en mesure de comparer les résultats de DADP à la solution exacte (obtenue par programmation dynamique), obtenant desgains à quelques pourcents de l'optimum avec des temps de calcul intéressants. Les conclusions auxquelles nous sommes parvenu offrent des perspectives encourageantes pour l'optimisation stochastique de systèmes de grande taille / Hydropower is the main renewable energy produced in France. It brings both an energy reserve and a flexibility, of great interest in a contextof penetration of intermittent sources in the production of electricity. Its management raises difficulties stemming from the number of dams, from uncertainties in water inflows and prices and from multiple uses of water. This Phd thesis has been realized in partnership with Electricité de France and addresses two hydropower management issues, modeled as stochastic dynamic optimization problems. The manuscript is divided in two parts. In the first part, we consider the management of a hydroelectric dam subject to a so-called tourist constraint. This constraint assures the respect of a given minimum dam stock level in Summer months with a prescribed probability level. We propose different original modelings and we provide corresponding numerical algorithms. We present numerical results that highlight the problem under various angles useful for dam managers. In the second part, we focus on the management of a cascade of dams. We present the approximate decomposition-coordination algorithm called Dual Approximate Dynamic Programming (DADP). We show how to decompose an original (large scale) problem into smaller subproblems by dualizing the spatial coupling constraints. On a three dams instance, we are able to compare the results of DADP with the exact solution (obtained by dynamic programming); we obtain approximate gains that are only at a few percents of the optimum, with interesting running times. The conclusions we arrived at offer encouraging perspectives for the stochastic optimization of large scale problems

Cette thèse est dediée à l'alanyse numérique de méthodes numériques dans le domaine du contrôle optimal, et est composée de deux parties. La première partie est consacrée à des nouveaux résultats concernant des méthodes numériques pour le contrôle optimal de systèmes hybrides, qui peuvent être contrôlés simultanément par des fonctions mesurables et des sauts discontinus dans la variable d'état. La deuxième partie est dédiée è l'étude d'une application spécifique surl'optimisation de trajectoires pour des lanceurs spatiaux avec contraintes en probabilité. Ici, on utilise des méthodes d'optimisation nonlineaires couplées avec des techniques de statistique non parametrique. Le problème traité dans cette partie appartient à la famille des problèmes d'optimisation stochastique et il comporte la minimisation d'une fonction de coût en présence d'une contrainte qui doit être satisfaite dans les limites d'un seuil de probabilité souhaité. / This thesis is devoted to the analysis of numerical methods in the field of optimal control, and it is composed of two parts. The first part is dedicated to new results on the subject of numerical methods for the optimal control of hybrid systems, controlled by measurable functions and discontinuous jumps in the state variable simultaneously. The second part focuses on a particular application of trajectory optimization problems for space launchers. Here we use some nonlinear optimization methods combined with non-parametric statistics techniques. This kind of problems belongs to the family of stochastic optimization problems and it features the minimization of a cost function in the presence of a constraint which needs to be satisfied within a desired probability threshold.

[pt] O planejamento hidrotérmico estocástico multi-etapa se destaca como um dos problemas mais importantes do setor elétrico, principalmente devido à sua grande relevância na operação do sistema. Este problema refere-se a determinar o despacho ótimo das usinas que minimizam o custo de operação sob as restrições físicas do sistema. Uma das principais dificuldades do problema reside nas representações de incerteza, pois a decisão de despacho deve considerar os diferentes cenários possíveis de afluência de água, geração renovável e demanda. Mais recentemente, o grande aumento de fontes renováveis variáveis trouxe a atenção dos pesquisadores para como melhorar a granularidade do modelo sem aumentar muito o tempo computacional. Neste trabalho é proposto uma nova formulação para um despacho econômico estocástico multi-etapa com unit-commitment. O modelo usa regras de decisão afins para ser computacionalmente tratável. A relação entre regras de decisão e o scenario approach é explorada e, ao construir o conjunto de incertezas, tanto a viabilidade da política da regra de decisão quanto a restrição probabilística do balanço de carga são automaticamente respeitadas. / [en] Multi-stage stochastic hydrothermal planning stands as one of the most critical problems in the power systems industry, mostly due to its vast implication in the system operation. The multi-stage stochastic hydrothermal scheduling refers to determining the economic dispatch of the power plants that minimize the global operation cost under the system s physical constraints. One of the main difficulties of the problem lies in the representations of uncertainty, as the dispatch decision must consider the different possible scenarios of water inflow, renewable generation, and the demand. More recently, we have seen a worldwide speed up in the integration of variable renewable sources. Nonetheless, these sources have a greater uncertainty in the short-term than the world has ever experienced. Therefore, to support the dispatch scheduling, the models must accurately represent the uncertainties without increasing computational time. In this work it is proposed a novel formulation for a multistage stochastic week-ahead economic dispatch with unit-commitment. The model uses affine decision rules to be computationally tractable. The relationship between the decision rules and the scenario approach is explored, and by building the uncertainty set with the scenario approach, both the feasibility of the decision rule policy and the chance-constraint on the load balance are respected.

As energy demands increase and energy resources change, the traditional energy system has been upgraded and reconstructed for human society development and sustainability. Considerable studies have been conducted in energy expansion planning and electricity generation operations by mainly considering the integration of traditional fossil fuel generation with renewable generation. Because the energy market is full of uncertainty, we realize that these uncertainties have continuously challenged market design and operations, even a national energy policy. In fact, only a few considerations were given to the optimization of energy expansion and generation taking into account the variability and uncertainty of energy supply and demand in energy markets. This usually causes an energy system unreliable to cope with unexpected changes, such as a surge in fuel price, a sudden drop of demand, or a large renewable supply fluctuation. Thus, for an overall energy system, optimizing a long-term expansion planning and market operation in a stochastic environment are crucial to improve the system's reliability and robustness. As little consideration was paid to imposing risk measure on the power management system, this dissertation discusses applying risk-constrained stochastic programming to improve the efficiency, reliability and economics of energy expansion and electric power generation, respectively. Considering the supply-demand uncertainties affecting the energy system stability, three different optimization strategies are proposed to enhance the overall reliability and sustainability of an energy system. The first strategy is to optimize the regional energy expansion planning which focuses on capacity expansion of natural gas system, power generation system and renewable energy system, in addition to transmission network. With strong support of NG and electric facilities, the second strategy provides an optimal day-ahead scheduling for electric power generation system incorporating with non-generation resources, i.e. demand response and energy storage. Because of risk aversion, this generation scheduling enables a power system qualified with higher reliability and promotes non-generation resources in smart grid. To take advantage of power generation sources, the third strategy strengthens the change of the traditional energy reserve requirements to risk constraints but ensuring the same level of systems reliability In this way we can maximize the use of existing resources to accommodate internal or/and external changes in a power system. All problems are formulated by stochastic mixed integer programming, particularly considering the uncertainties from fuel price, renewable energy output and electricity demand over time. Taking the benefit of models structure, new decomposition strategies are proposed to decompose the stochastic unit commitment problems which are then solved by an enhanced Benders Decomposition algorithm. Compared to the classic Benders Decomposition, this proposed solution approach is able to increase convergence speed and thus reduce 25% of computation times on the same cases.

In the U.S., Black childhood has been underimagined. The representational vocabulary of Black childhood is fraught with dehumanizing and adultifying imagery and sounds—from representations of “Topsy” and “Black Sambo” to caricatures of pickaninnies and their many (re)iterations in U.S. popular culture. Popular music is one expressive domain wherein artists and audiences alike have contested and reinforced the peculiar adultification and infantilization that have long haunted Black American life. In the years surrounding the Trump presidency, numerous Black popular music artists made childhood a primary feature of their artistic output through vocal technique, lyrical content, merchandise, music videos, social media, and more. At the precise moment when white innocence was wielded most violently and obviously on the national stage, these artists challenged the assumed goodness and whiteness of innocence and its relation to childhood, performing capacious versions of free Black childhoods to various ends. This dissertation turns to the performance of childhood as a productive domain of inquiry and focuses on four artists/groups—Tank and the Bangas, Chance the Rapper, Jamila Woods, and Noname—all of whom chart a liberatory politics of Black childhood through sound. Through the poetics and aesthetics of their work, I theorize and historicize four interrelated, childhood-adjacent concepts: nostalgia, vulnerability, innocence, and freedom. Methodologically, I attempt to turn the tables on how vulnerability has normally been rendered in ethnographies. I blend (auto)ethnography about my own experiences as a white father of a multi-racial child with critical theory to analyze live and mediated performances of popular music. I look to music as a poetic and aesthetic space with which to not only grapple with the realities faced by Black children in the United States, but also to affirm Black childhood as a space of freedom, play, possibility, and joy. Ultimately, I make two interrelated assertions: (1) foregrounding Black childhood in our social analysis urges the necessity of abolition and (2) popular music is a primary conduit through which we can imagine an abolitionist future free of police, prisons, and the carceral logics that undergird their imagined necessity.

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Last chance tourism (LCT) is defined as an endangered place due to climate change which creates motivations for tourists to travel to these places before they vanish. These trips also involve interaction with and observation of rare species that is about to disappear due to climate change. By integrating the Value-Belief-Norm and cognitive dissonance theory models, the main purpose of this research was to investigate psychological antecedents of engaging in LCT in higher educational institutions in Sweden. A survey was administered to 234 academics on seven universities in Sweden consisting of items measuring beliefs, pro-environmental personal norms, cognitive dissonance, and intentions to engage in Last Chance Tourism. The data was later analyzed using Partial Least Square-Structural Equation (PLS-SEM) approach. The results revealed a significant impact of cognitive dissonance on intentions to engage in LCT. These findings are important since they support the advantage of using cognitive dissonance theory within the context of LCT. The implications will hopefully spark an interest among academics to develop a sustainable tourism rescue plan and transfer this knowledge to a younger generation. For practitioners, this could be food for fought for organizations that are operating within the field of LCT.

Lost&Found Videothek is the concept for an interactive video library thought for users engaged in an exploratory research mode, in which content is organized according to a collaborative, subjective and implicit indexing system for the enhancement of serendipity. This idea was the result of a design-based research with a user-centered approach in the field of information retrieval. With the use of design methods such as heuristic UX evaluation, co-sketching, and other original design experiments, the project aimed at identifying the most valuable qualities of physical and digital libraries in order to integrate them within one retrieval system.

Em um contexto de demandas sociais tendencialmente crescentes, uma das alternativas para o aumento da arrecadação de receitas pelo Estado reside no manejo de aplicações financeiras. Os investimentos financeiros estatais, a rigor, já acontecem, mas nem sempre o objetivo claro e explícito de obtenção de resultados financeiramente interessantes e, eventualmente ou mesmo por isso , sob gestão economicamente ineficiente. Às vezes, até se enxerga o foco na obtenção de rendimentos relevantes na ação estatal, mas sem uma disciplina específica, o que pode abrir espaço a uma gestão de ativos desqualificada ou mesmo fraudulenta, com sérios prejuízos aos cofres públicos e, em situações extremas, ampliação ainda maior das despesas públicas. O objetivo desta tese, portanto, é reconhecer que nem sempre o Estado atua na economia com propósito interventivo e que, na qualidade de investidor institucional vale dizer, de ente que tem o dever de proceder aos investimentos e às aplicações financeiras que digam com as melhores práticas de administração dos ativos públicos , precisa atuar sob o jugo de normas jurídicas claras, que permitam ao Estado ampliar suas receitas dentro de limites razoáveis de exposição a risco financeiro e disponibilizem aos órgãos de fiscalização e controle da Administração Pública as ferramentas necessárias para, também quanto a esse aspecto, aferir a eficiência da ação estatal. Para tanto, têm-se como pressupostos o anacronismo da resistência cultural às aplicações financeiras dos entes da Administração Pública e a noção de que quaisquer ferramentas de obtenção de receitas pelo Estado estão sujeitas a algum grau de risco. Com base nas bem-sucedidas experiências nacionais e internacionais, será possível concluir, ao final, que é admissível, do ponto de vista constitucional e legal, a ação do Estado como investidor nos mercados financeiro e de capitais e que é viável a formulação de parâmetros gerais para a disciplina jurídica do Estado investidor. / In a context of growing social demands, financial investments become one of the alternatives for the State to increase its revenues. State investments, as a matter of fact, already do happen, but not always with the clear and explicit objective of obtaining financially interesting earnings, often due economically inefficient management. Sometimes it is possible to see in government investments some focus on obtaining relevant income, but not under a specific regulation, which can lead to an unqualified or even fraudulent management that may cause serious damage to the exchequer and, in extreme situations, expansion of the government spending. Hence the intent of this thesis is to acknowledge that the State does not always act in the economy with regulatory purposes and that, as an institutional investor i.e., an organization which has the duty of making financial investments in accordance to the best practices in public asset management , it must be framed by clear legal rules, which should allow the State to maximize its revenues within reasonable limits of financial risk exposure and the oversight and control agencies to assess the State efficiency and compliance. It is assumed that the cultural resistance to state financial investments is anachronistic as well as every state means of obtaining revenues is subject to some level of financial risk. Based on well succeeded experiences in Brazil and abroad, it will be possible to conclude, in the end, that it is constitutionally and legally admissible that the State acts as an investor in financial and stock markets and that it is possible to suggest some standards on legal regulation for this issue.

Em um contexto de demandas sociais tendencialmente crescentes, uma das alternativas para o aumento da arrecadação de receitas pelo Estado reside no manejo de aplicações financeiras. Os investimentos financeiros estatais, a rigor, já acontecem, mas nem sempre o objetivo claro e explícito de obtenção de resultados financeiramente interessantes e, eventualmente ou mesmo por isso , sob gestão economicamente ineficiente. Às vezes, até se enxerga o foco na obtenção de rendimentos relevantes na ação estatal, mas sem uma disciplina específica, o que pode abrir espaço a uma gestão de ativos desqualificada ou mesmo fraudulenta, com sérios prejuízos aos cofres públicos e, em situações extremas, ampliação ainda maior das despesas públicas. O objetivo desta tese, portanto, é reconhecer que nem sempre o Estado atua na economia com propósito interventivo e que, na qualidade de investidor institucional vale dizer, de ente que tem o dever de proceder aos investimentos e às aplicações financeiras que digam com as melhores práticas de administração dos ativos públicos , precisa atuar sob o jugo de normas jurídicas claras, que permitam ao Estado ampliar suas receitas dentro de limites razoáveis de exposição a risco financeiro e disponibilizem aos órgãos de fiscalização e controle da Administração Pública as ferramentas necessárias para, também quanto a esse aspecto, aferir a eficiência da ação estatal. Para tanto, têm-se como pressupostos o anacronismo da resistência cultural às aplicações financeiras dos entes da Administração Pública e a noção de que quaisquer ferramentas de obtenção de receitas pelo Estado estão sujeitas a algum grau de risco. Com base nas bem-sucedidas experiências nacionais e internacionais, será possível concluir, ao final, que é admissível, do ponto de vista constitucional e legal, a ação do Estado como investidor nos mercados financeiro e de capitais e que é viável a formulação de parâmetros gerais para a disciplina jurídica do Estado investidor. / In a context of growing social demands, financial investments become one of the alternatives for the State to increase its revenues. State investments, as a matter of fact, already do happen, but not always with the clear and explicit objective of obtaining financially interesting earnings, often due economically inefficient management. Sometimes it is possible to see in government investments some focus on obtaining relevant income, but not under a specific regulation, which can lead to an unqualified or even fraudulent management that may cause serious damage to the exchequer and, in extreme situations, expansion of the government spending. Hence the intent of this thesis is to acknowledge that the State does not always act in the economy with regulatory purposes and that, as an institutional investor i.e., an organization which has the duty of making financial investments in accordance to the best practices in public asset management , it must be framed by clear legal rules, which should allow the State to maximize its revenues within reasonable limits of financial risk exposure and the oversight and control agencies to assess the State efficiency and compliance. It is assumed that the cultural resistance to state financial investments is anachronistic as well as every state means of obtaining revenues is subject to some level of financial risk. Based on well succeeded experiences in Brazil and abroad, it will be possible to conclude, in the end, that it is constitutionally and legally admissible that the State acts as an investor in financial and stock markets and that it is possible to suggest some standards on legal regulation for this issue.