L'allumage d'ergols injectés dans une chambre de combustion, la propagation du noyau de flamme puis sa stabilisation sont autant de paramètres déterminants pour la conception d'un moteur fusée. Pour ce type d'application, il est nécessaire - du point de vue de la modélisation - de tenir compte du couplage existant entre les effets de compressibilité, les processus de mélange turbulent ainsi que de cinétique chimique, dans un environnement diphasique puisque les ergols sont injectés à l'état liquide. Un modèle Lagrangien a été implanté dans le code de calcul compressible N3S-Natur afin de disposer d'un outil numérique capable de simuler le transitoire d'allumage d'un moteur fusée. La physique représentative de chacun des processus physiques impliqués pendant la phase d'allumage a été incorporée puis validée sur des configurations académiques. Ce travail a permis de mettre en évidence l'importance de la description du mélange à petites échelles pour capturer correctement le développement de la flamme. Il a aussi mis en exergue la nécessité de prendre en compte le transitoire thermique des gouttes d'oxygène liquide afin de reproduire fidèlement sa stabilisation. Enfin, il a nécessité l'extension de la notion de fraction de mélange à des cas pratiques présentant plus de deux entrées afin d'être en mesure de simuler la propagation de l'allumage sur la plaque d'injection. Cette approche basée sur l'introduction d'un injecteur fictif est non seulement utile pour la simulation de l'allumage des moteurs-fusées mais peut aussi être employée dans tout autre système impliquant le mélange entre des courants de réactifs issus de deux entrées ou plus. / In the field of liquid rocket propulsion, ignition, propagation and stabilization of the flame are of first importance for the design of the engine. Computational fluid dynamics (CFD) solvers may provide a great deal of help to proceed with the primary design choice but need to be fed with suited physical models. Important modelling efforts are therefore required to provide reliable computational representations able to take into account compressibility effects, turbulent mixing and chemical kinetics in two-phase flows since ergols are injected at the liquid state. A Lagrangian model has been implemented in the compressible solver N3S-Natur so as to obtain a computational tool able to compute the transient ignition of rocket engines. The physical processes involved at each step of this ignition sequence have been integrated and validated on academically configurations. Three significant contributions rose from this work. First of all, it is highlighted that the description of the micro-mixing is of first importance to correctly capture the flame development. This study also emphasized the need to consider the transient heating of liquid oxygen droplets in order to accurately compute the flame stabilization. Finally, the notion of mixture fraction must be extended to practical devices implying more than two inlets. The proposed approach which is based on the introduction of a fictive injector is not only well suited to rocket engine ignition application but also to deal with other practical devices implying two inlets and more.

>Magister Scientiae - MSc / The growth of structure in the Universe proceeds via the collapse of dark matter and baryons. This process is retarded by dark energy which drives an accelerated expansion of the late Universe. In this thesis we use cosmological perturbation theory to investigate structure formation for a particular class of dark energy models, i.e. interacting dark energy models. In these models there is a non-gravitational interaction between dark energy and dark matter, which alters the standard evolution (with non-interacting dark energy) of the Universe. We consider a simple form of the interaction where the energy exchange in the background is proportional to the dark energy density. We analyse the background dynamics to uncover the e ect of the interaction. Then we develop the perturbation equations that govern the evolution of density perturbations, peculiar velocities and the gravitational potential. We carefully account for the complex nature of the perturbed interaction, in particular for the momentum transfer in the dark sector. This leads to two di erent types of model, where the momentum exchange vanishes either in the dark matter rest-frame or the dark energy rest-frame. The evolution equations for the perturbations are solved numerically, to show how structure formation is altered by the interaction.

Pendant les deux dernières décennies l'idée d'une nature holographique de la gravité a pris forme à travers la correspondance AdS/CFT, aussi connue sous le nom de dualité jauge/gravité. CFT correspond à « conformal field theory », théorie conforme des champs, et dans la dualité il s'agit d'une théorie de jauge dans la limite de grand N 1. AdS représente l'espace d'anti-de Sitter, une solution maximalement symétrique des équations d'Einstein avec une constante cosmologique négative, et correspond au côté gravitationnel de la dualité. Dans certaines limites, des théories sur AdS avec de la gravité en d+1 dimensions peuvent être associées à des CFTs sans gravité en d dimensions, d'où le nom « dualité ». Cette dualité est aussi dite « holographique » par analogie avec le concept optique homonyme qui indique la possibilité de générer une image tridimensionnelle comme la projection d'un écran ou d'un film bidimensionnel. Le terme holographie vient des mots grecs holos, « en entier », et graphe, « écriture. Une telle projection, malgré le fait que l'information est stockée en 2 dimensions, contiendrait toute l'information pour reconstruire l'image tridimensionnelle. Dans la dualité jauge/gravité, la théorie de jauge se comporte comme un film d-dimensionnel qui contient la même information que l'image gravitationnelle (d+1)-dimensionnelle. Cette dualité relie la théorie gravitationnelle à la théorie quantique de champs (TQC) dual à travers des conditions aux limites sur des champs qui vivent dans AdS. Dans ce sens-là, la théorie de jauge peut être considérée comme définie sur le bord d'AdS, ce qui renforce l'analogie optique et, pour cela, la dualité est aussi connue comme la correspondance « bulk/boundary » ou « intérieur/bord ». Une de ses principales propriétés est l'association d'une TQC fortement couplée à une théorie gravitationnelle faiblement couplée et vice-versa. Pour cette raison, dans cette thèse j'utilise un intérieur faiblement couplé pour explorer et identifier des propriétés non-perturbatives de TQCs dans la limite de couplage fort. Cette thèse explore l'holographie à température nulle et finie. Nos objets d'intérêt sont des TQCs générées par la brisure de l'invariance d'échelle de CFTs et qui peuvent être étudiées à travers le groupe de renormalisation (GR). Le profil des champs au long de la dimension supplémentaire à l'intérieur est dual à des flots du GR sur la TQC vivant sur le bord, car la dimension supplémentaire est en correspondance avec l'échelle d'énergie. La correspondance va plus loin en identifiant les champs de l'intérieur comme duaux aux couplages renormalisés de la TQC, ce qui mène au concept du GR holographique. Avec le GR holographique, dans cette thèse je vais explorer des comportements qui sont d'une nature intrinsèquement non-perturbatifs du point de vue de la QFT. Les principaux résultats sont les suivants. A température nulle, pour un seul couplage, nous avons classifié toutes les solutions de notre système et identifié trois types de flots exotiques correspondant à des solutions qui inversent leur direction au long du flot, d'autres qui sautent des points fixes et des flots qui interpolent entre des minima du potentiel. Ces résultats ont été généralisés à plusieurs couplages à température nulle. Je présente également la relation entre la fonction principale de Hamilton et la nature du champ de vitesses des couplages: gradient ou non. À température finie nous avons considéré un seul couplage et exploré la thermodynamique des trois types de solutions exotiques mentionnées ci-dessus. Nous avons identifié une transition de phase entre des solutions qui sautent et qui ne sautent pas des points fixes, une discontinuité de l'énergie libre pour un potentiel admettant des solutions qui inversent le sens du flot à température nulle et la non-existence de solutions à température finie associées à un flot entre minima pour un potentiel qui admet une telle solution à température nulle. / Over the past twenty years the idea that gravity is holographic has become progressively concrete, materialised through the AdS/CFT correspondence, also known as the gauge/gravity duality. CFT stands for conformal field theory and in the correspondence it is a gauge-theory in the large N limit1. AdS stands for anti-de Sitter space-time, a maximally symmetric solution of Einstein’s equations with negative cosmological constant, it corresponds to the gravitational side of the duality. In some limits, theories on AdS with gravity in d + 1 dimensions can be mapped to CFTs without gravity in d dimensions and vice-versa, hence the name “duality”. Another term for the gauge/gravity duality is holographic duality. The term holography comes from the Greek words holos, “whole”, and graphe, “writing” or “drawing”. In physics, the term holography originates in optics, referring to the possibility of generating a 3-dimensional image as a projection from a bi- dimensional screen or film. In such a projection, despite of the fact that the film has one spatial dimension less than the projection, the film would contain all the information to recover the three-dimensional image. In the gauge/gravity duality, the gauge-theory behaves as a d-dimensional film which contains the same information as the (d + 1)-dimensional gravitational image. This analogy is reinforced by the fact that the duality relates the gravitational theory to the dual resulting quantum field theory (QFT) via boundary conditions of the fields living in the AdS bulk. In this sense, the gauge theory can be thought of as living at the boundary of AdS and the duality is also know as the bulk/boundary correspondence. One of the most important features of the correspondence is the mapping of a strongly coupled QFT into a weakly coupled gravitational theory and vice-versa. For this reason, in this thesis I will use a weakly coupled bulk theory to explore and identify non-perturbative features of QFT in the strong coupling regime. This thesis explores holography at zero and finite temperature. Our main concern are the CFTs in which scale invariance is either spontaneously or explicitly broken and the resulting QFT can be studied via the renormalisation group (RG). The profile of fields along the extra-dimension in the bulk is dual to renormalisation group flows in the QFT side (boundary), as the extra-dimension can be mapped to an energy scale. The mapping goes further by identifying bulk fields as dual to QFT running couplings, leading to the so-called holographic renormalisation group. With the holographic RG in what follows I will explore behaviours that are of an intrinsically non-perturbative nature from the QFT standpoint. The main results are as follows. At zero temperature, for a single coupling, we classified all possible solutions in our setup and identified three kinds of exotic flows corresponding to solutions reversing direction along the flow (bounces), flows skipping fixed points and solutions interpolating between minima of the potential. These results are generalised to many couplings at zero temperature. I also present a complete map between forms of the Hamilton's principal function and the gradient or non-gradient nature of the solutions. At finite temperature we considered a single coupling setup and explored the thermodynamics of the three kinds of above-mentioned exotic flows. We identified a phase transition between skipping and non-skipping solutions, a discontinuous free energy for a bouncing potential and the non-existence of a finite-temperature solutions for a chosen potential admitting a minimum-to-minimum solution.

[pt] Em um sistema de comunicações, procura-se representar a informação gerada de forma eficiente, de modo que a redundância da informação seja reduzida ou idealmente eliminada, com o propósito de armazenamento e/ou transmissão da mesma. Este interesse justifica portanto, o estudo e desenvolvimento de técnicas de compressão que vem sendo realizado ao longo dos anos. Este trabalho de pesquisa investiga o uso de códigos de permutação para codificação de fontes segundo um critério de fidelidade, mais especificamente de fontes sem memória, caracterizadas por uma distribuição uniforme e critério de distorção de erro médio quadrático. Examina-se os códigos de permutação sob a ótica de fontes compostas e a partir desta perspectiva, apresenta-se um esquema de compressão com duplo estágio. Realiza-se então uma análise desse esquema de codificação. Faz-se também uma extensão L- dimensional (L > 1) do esquema de permutação apresentado na literatura. Os resultados obtidos comprovam um melhor desempenho da versão em duas dimensões, quando comparada ao caso unidimensional, sendo esta a principal contribuição do presente trabalho. A partir desses resultados, busca-se a aplicação de um esquema que utiliza códigos de permutação para a compressão de imagens. / [en] In communications systems the information must be represented in an efficient form, in such a way that the redundancy of the information is either reduced or ideally eliminated, with the intention of storage or transmission of the same one. This interest justifies the study and development of compression techniques that have been realized through the years. This research investigates the use of permutation codes for source encoding with a fidelity criterion, more specifically of memoryless uniform sources with mean square error fidelity criterion. We examine the permutation codes under the view of composed sources and from this perspective, a project of double stage source encoder is presented. An analysis of this project of codification is realized then. A L-dimensional extension (L > 1) of permutation codes from previous research is also introduced. The results prove a better performance of the version in two dimensions, when compared with the unidimensional case and this is the main contribution of the present study. From these results, we investigate an application for permutation codes in image compression.

This diploma thesis deals with the design of the asynchronous mathematical model, and creation its model in MATLAB Simulink. And by creating different types of asynchronous motor control. At the beginning of the work there are theoretical knowledge about transformation of quantities into coordinates, which are needed for creation of mathematical model and further for machine control. Furthermore, control logarithms are created from these transformed quantities, which can be used to control the torque or engine speed. It is a constant magnetic flux control, scalar control, vector control, and ultimately direct torque control. All derived control algorithms have been tested in MATLAB Simulink. Where were simulations of investigated quantities.

The diploma thesis deals with the simulation of induction motor control with respect to high efficiency. The theory of an induction motor is described here, with emphasis on its losses. Scalar and vector control are also described here. Vector control is optimized for higher efficiency. Subsequently, the creation of a model in the program đť‘€đť´đť‘‡ đťżđť´đťµâ’𝑆𝑖𝑚𝑢𝑙𝑖𝑛𝑠is described here, for the comparison of scalar and vector control with optimization.

Proyecto FONDECYT de iniciación N°11150789 “Glocal urban governance between neoliberalism, risk and resilience: re-assembling urban strategies in three chilean cities” Memoria para optar al título de Geógrafo / Memoria para optar al título de Geógrafo / “Urbanya Ciudad Global” y “Praderas de Lo Aguirre” en Pudahuel serán las urbanizaciones privadas más grandes que se desarrollarán en Chile, y al mismo tiempo, son megaproyectos inmobiliarios cuyos procesos de aprobación han tomado largos 24 años, pasando por la participación de asociaciones públicas-privadas y por desarticulaciones en niveles de gobierno regional y local. En esta investigación, se realiza un análisis cualitativo de la evolución de las formas de gobernanza en Pudahuel asociado a estos megaproyectos inmobiliarios, a través del lente de la gobernanza urbana analítica (Pierre, 1999; DiGaetano & Strom, 2003; Martí-Costa & Tomás, 2016, Lukas, 2018) y las relaciones de poder (Lukes, 2007; Howarth, 2010), concebidas como micropolíticas y macrodiscursos. Se identifican en los resultados cuatro grandes fases de gobernanza entre 1994 y 2018, en las cuales es posible reconocer una transición desde un régimen urbano (Stone, 1989) y un régimen pluralista de carácter corporacionista a escala local, en los que existe una fuerte presencia de la Comisión Mixta como asociación pública-privada, hacia una forma de gobernanza de carácter regional, con mixturas entre formas gerencialistas y clientelistas, donde la burocracia estatal y las diferentes visiones de los servicios públicos implicados retrasan el proceso. Se concluye que existen tres lógicas transversales que articulan los 24 años de gobernanza en Pudahuel: i) una fragmentación en los espacios de toma de decisiones de carácter multiescalar, ii) diferentes estrategias escalares de los desarrolladores inmobiliarios para afrontar las fases de gobernanza y iii) una improvisación de carácter reactiva por parte del diseño institucional chileno en lo que respecta a planificación y gestión urbana en Pudahuel. / "Urbanya Ciudad Global" and "Praderas de Lo Aguirre" in Pudahuel will be the largest private urbanizations to be developed in Chile, and at the same time, are real estate megaprojects whose approval processes have taken 24 long years, with the participation of public-private partnerships and several disarticulations at regional and local government levels. In this research, a qualitative analysis of the evolution of the ways of governance in Pudahuel associated with these real estate megaprojects is made, through the lens of analytical urban governance (Pierre, 1999, DiGaetano & Strom, 2003, Martí-Costa & Tomás, 2016, Lukas, 2018) and power relations (Lukes, 2007; Howarth, 2010), conceived as micro-politics and macro-discourses. In the results, four governance stages are identified between 1994 and 2018, in which it is possible to recognize a transition from an urban regime (Stone, 1989) and a pluralist corporatist regime at local scale, with a strong presence of the Comisión Mixta as a public-private partnership until 2003, towards a form of regional governance since 2004, with mixtures between managerialist and clientelist forms, where the state bureaucracy and the different visions of the public services involved delay the process. It is concluded that there are three transversal logics that articulate the 24 years of governance in Pudahuel: i) a multi scalar fragmentation in decision-making spaces, ii) different scalar strategies from real estate developers to face the governance stages and iii) the presence of a reactive improvisation on Chilean institutional design in both urban planning and urban management in Pudahuel.

The present thesis deals with a number of challenges in the field of large eddy simulation (LES). These include the performance of subgrid-scale (SGS) models at fairly high Reynolds numbers and coarse resolutions, passive scalar and stochastic modeling in LES. The fully-developed turbulent channel flow is used as the test case for these investigations. The advantage of this particular test case is that highly accurate pseudo-spectral methods can be used for the discretization of the governing equations. In the absence of discretization errors, a better understanding of the subgrid-scale model performance can be achieved. Moreover, the turbulent channel flow is a challenging test case for LES, since it shares some of the common important features of all wall-bounded turbulent flows. Most commonly used eddy-viscosity-type models are suitable for moderately to highly-resolved LES cases, where the unresolved scales are approximately isotropic. However, this makes simulations of high Reynolds number wall-bounded flows computationally expensive. In contrast, explicit algebraic (EA) model takes into account the anisotropy of SGS motions and performs well in predicting the flow statistics in coarse-grid LES cases. Therefore, LES of high Reynolds number wall-bounded flows can be performed at much lower number of grid points in comparison with other models. A demonstration of the resolution requirements for the EA model in comparison with the dynamic Smagorinsky and its high-pass filtered version for a fairly high Reynolds number is given in this thesis. One of the shortcomings of the commonly used eddy diffusivity model arises from its assumption of alignment of the SGS scalar flux vector with the resolved scalar gradients. However, better SGS scalar flux models that overcome this issue are very few. Using the same methodology that led to the EA SGS stress model, a new explicit algebraic SGS scalar flux model is developed, which allows the SGS scalar fluxes to be partially independent of the resolved scalar gradient. The model predictions are verified and found to improve the scalar statistics in comparison with the eddy diffusivity model. The intermittent nature of energy transfer between the large and small scales of turbulence is often not fully taken into account in the formulation of SGS models both for velocity and scalar. Using the Langevin stochastic differential equation, the EA models are extended to incorporate random variations in their predictions which lead to a reasonable amount of backscatter of energy from the SGS to the resolved scales. The stochastic EA models improve the predictions of the SGS dissipation by decreasing its length scale and improving the shape of its probability density function. / QC 20110615

The diploma thesis deals with the simulation of induction motor control with respect to high efficiency. The theory of an induction motor is described here, with emphasis on its losses. Scalar and vector control are also described here. Vector control is optimized for higher efficiency. Subsequently, the creation of a model in the program MATLAB - Simulink is described here, for the comparison of vector control with and without optimization.

Selon Asher (2013), la cohérence discursive force l’inférence de (1c) dans les exemples (1a)-(1b), expliquant ainsi l’(in)acceptabilité des exemples. (1) a. ‘John a un nombre pair d’enfants. Il en a 4.’ b. ‘ ? ?John a un nombre pair d’enfants. Il en a 3.’ c. +> John a n enfants et pas plus Nous avons tenté de déterminer si les implicatures nécessaires au maintien de la cohérence discursive sont systématiquement inférées en nous appuyant sur les théories de la RST et de la SDRT. Des tests linguistiques et la vérification du respect des contraintes sémantiques associées aux relations de discours ont mis en évidence deux catégories d’exemples contenant le quantificateur certains : ceux de type- RenfNA, dont les implicatures ne sont pas nécessaires à la cohérence et ceux de typeRenfA dans lesquels elles le sont. Nos tests ayant révélé que le renforcement est nécessaire dans les exemples de typeRenfA, nous avons conclu que les implicatures ne sont pas systématiquement inférées. Nous avons tenté d’apporter une explication à ce phénomène en effectuant des analyses de la structure discursive de nos exemples et avons démontré que dans les exemples de typeRenfNA, les relations de discours visent le constituant π∃ (certains), tandis que dans ceux de typeRenfA, le constituant π¬∀ (mais pas tous) est visé. Nos travaux ont démontré que les implicatures scalaires ne sont pas systématiquement inférées rendant parfois leur renforcement obligatoire. Nous avons également proposé un modèle à granularité fine prenant en compte la structure discursive et la pragmatique afin d’expliquer ce phénomène. / According to Asher (2013), discourse coherence forces the inference of (2c) in examples (2a)-(2b), thus explaining the (in)acceptability of these examples. (2) a. ‘John has an even number of children. He has 4.’ b. ‘??John has an even number of children. He has 3.’ c. +> John has n children and not more We attempted to determine whether the implicatures that are necessary to maintain discourse coherence are systematically inferred by drawing on the theories of RST and SDRT. Through linguistic tests and checking the respect of semantic constraints associated with discourse relations, we identified two categories of examples containing the quantifier some: typeRenfNA examples, in which implicatures are not necessary for discourse coherence, and typeRenfA examples in which they are. As our tests revealed that reinforcement is necessary in typeRenfA examples, we concluded that implicatures are not systematically inferred. We then attempted to explain this phenomenon. We performed analyses of the discourse structure of our examples and showed that in typeRenfNA examples, the discourse relations target the π∃ (some) constituent, while in typeRenfA examples, the π¬∀ (but not all) constituent is targeted. Thus, our work has shown that scalar implicatures are not systematically inferred, making implicature reinforcement sometimes mandatory. We also proposed a fine-grained model taking discourse structure and pragmatics into account to explain this phenomenon.