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A dynamical system approach is utilized to reduce the representation order of unsteady fluid flows and fluid-structure interaction systems. This approach allows for significant reduction in the computational cost of their numerical simulations, implementation of optimization and control methodologies and assessment of their dynamic stability. In the first chapter, I present a new Lagrangian function to derive the equations of motion of unsteady point vortices. This representation is a reconciliation between Newtonian and Lagrangian mechanics yielding a new approach to model the dynamics of these vortices. In the second chapter, I investigate the flutter of a helicopter rotor blade using finite-state time approximation of the unsteady aerodynamics. The analysis showed a new stability region that could not be determined under the assumption of a quasi-steady flow. In the third chapter, I implement the unsteady vortex lattice method to quantify the effects of tail flexibility on the propulsive efficiency of a fish. I determine that flexibility enhances the propulsion. In the fourth chapter, I consider the stability of a flapping micro air vehicle and use different approaches to design the transition from hovering to forward flight. I determine that first order averaging is not suitable and that time periodic dynamics are required for the controller to achieve this transition. In the fifth chapter, I derive a mathematical model for the free motion of a two-body planar system representing a fish under the action of coupled dynamics and hydrodynamics loads. I conclude that the psicform fish family are inherently stable under certain conditions that depend on the location of the center of mass. / Ph. D. / We present modeling approaches of the interaction between flying or swimming bodies and the surrounding fluids. We consider their stability as they perform special maneuvers. The approaches are applied to rotating blades of helicopters, fish-like robots, and micro-air vehicles. We develop and validate a new mathematical representation for the flow generated by moving or deforming elements. We also assess the effects of fast variations in the flow on the stability of a rotating helicopter blade. The results point to a new stable regime for their operation. In other words, the fast flow variations could stabilize the rotating blades. These results can also be applied to the analysis of stability of rotating blades of wind turbines. We consider the effects of flexing a tail on the propulsive force of fish-like robots. The results show that adding flexibility enhances the efficiency of the fish propulsion. Inspired by the ability of some birds and insects to transition from hovering to forward motion, we thoroughly investigate different approaches to model and realize this transition. We determine that no simplification should be applied to the rigorous model representing the flapping flight in order to model transition phenomena correctly. Finally, we model the forward-swim dynamics of psciform and determine the condition on the center of mass for which a robotic fish can maintain its stability. This condition could help in designing fish-like robots that perform stable underwater maneuvers.

[EN] Atrial tachyarrhythmias present a high prevalence in the developed world, and several studies predict that in the coming decades it will be increased. Micro or macro-reentrant mechanisms of the electrical wavefronts that govern the mechanical behavior of the heart are one of the main responsibles for the maintenance of these arrhythmias. Atrial flutter is maintained by a macro-reentry around an anatomical or functional obstacle located in the atria. In the case of atrial fibrillation, the hypothesis which describes high frequency rotors as dominant sources of the fibrillation and responsible for the maintenance of the arrhythmia, has been gaining relevance in the last years. However, the therapies that target high frequency sources have a limited efficacy with current techniques. Radiofrequency ablation allows the destruction of parts of the cardiac tissue resulting in the interruption of the reentrant circuit in case of macro-reentries or the isolation of micro-reentrant circuits. The non-invasive location of reentrant circuits would increment the efficacy of these therapies and would shorten surgery interventions. In parallel, pharmacological therapies modify ionic expressions associated to the excitability and electrical refractoriness of the cardiac tissue with the objective of hindering the maintenance of reentrant behaviors. These therapies require a deep knowledge of the ionic mechanisms underlying the reentrant behavior and its properties in order to be effective. The research in these mechanisms allows the evaluation of new targets for the treatment and thus may improve the efficacy in atrial fibrillation termination. In this thesis, mathematical modeling is used to go forward in the minimization of the limitations associated to these treatments. Body surface potential mapping has been evaluated, both clinically and by means of mathematical simulations for the diagnosis and location of macro-reentrant circuits. The analysis of phase maps obtained from multiple lead electrocardiographic recordings distributed in the whole torso allowed the discrimination between different reentrant circuits. It is the reason why this technique is presented as a tool for the non-invasive location of macro and micro-reentrant circuits. A population of mathematical models designed in this thesis based on the action potentials recordings of atrial cardiomyocites from 149 patients, allowed the evaluation of the ionic mechanisms defining the properties of reentrant behaviors. This study has allowed us defining the blockade of ICaL as a target for the pharmacological treatment. The blockade of this current is associated with the increase of the movement in the core of the rotor which easies the collision of the rotor with other wavefronts or anatomical obstacles promoting the extinction of the reentry. The variability observed between patients modeled in our population has allowed showing and explaining the mechanisms promoting divergent results of a single treatment. This is why the introduction of populations of models will allow the prevention of side effects associated to inter-subject variability and to go forward in the development of individualized therapies. These works are built through a simulation platform of cardiac electrophysiology based in Graphic Processing Units (GPUs) and developed in this thesis. The platform allows the simulation of cellular models, tissues and organs with a realistic geometry and shows features comparable to that of the platforms used by the most relevant electrophysiology research groups at the moment. / [ES] Las taquiarritmias auriculares tienen una alta prevalencia en el mundo desarrollado, además diversos estudios poblacionales indican que en las próximas décadas ésta se verá incrementada. Los mecanismos de micro o macro-reentrada de los frentes de onda eléctricos que rigen el comportamiento mecánico del corazón, se presentan como una de las principales causas del mantenimiento de estas arritmias. El flutter auricular es mantenido por un macro-reentrada alrededor de un obstáculo anatómico o funcional en las aurículas, mientras que en el caso de la fibrilación auricular la hipótesis que define a los rotores de alta frecuencia como elementos dominantes y responsables del mantenimiento de la arritmia se ha ido imponiendo al resto en los últimos años. Sin embargo, las terapias que tienen como objetivo finalizar o aislar estas reentradas tienen todavía una eficacia limitada. La ablación por radiofrecuencia permite eliminar zonas del tejido cardiaco resultando en la interrupción del circuito de reentrada en el caso de macro-reentradas o el aislamiento de comportamientos micro-reentrantes. La localización no invasiva de los circuitos reentrantes incrementaría la eficacia de estas terapias y reduciría la duración de las intervenciones quirúrgicas. Por otro lado, las terapias farmacológicas alteran las expresiones iónicas asociadas a la excitabilidad y la refractoriedad del tejido con el fin de dificultar el mantenimiento de comportamientos reentrantes. Este tipo de terapias exigen incrementar el conocimiento de los mecanismos subyacentes que explican el proceso de reentrada y sus propiedades, la investigación de estos mecanismos permite definir las dianas terapéuticas que mejoran la eficacia en la extinción de estos comportamientos. En esta tesis el modelado matemático se utiliza para dar un paso importante en la minimización de las limitaciones asociadas a estos tratamientos. La cartografía eléctrica de superficie ha sido testada, clínicamente y con simulaciones matemática,s como técnica de diagnóstico y localización de circuitos macro-reentrantes. El análisis de mapas de fase obtenidos a partir de los registros multicanal de derivaciones electrocardiográficas distribuidas en la superficie del torso permite diferenciar distintos circuitos de reentrada. Es por ello que esta técnica de registro y análisis se presenta como una herramienta para la localización no invasiva de circuitos macro y micro-reentrantes. Una población de modelos matemáticos, diseñada en esta tesis a partir de los registros de los potenciales de acción de 149 pacientes, ha permitido evaluar los mecanismos iónicos que definen las propiedades asociadas a los procesos de reentrada. Esto ha permitido apuntar al bloqueo de la corriente ICaL como diana terapéutica. Ésta se asocia al incremento del movimiento del núcleo que facilita el impacto del rotor con otros frentes de onda u obstáculos extinguiéndose así el comportamiento reentrante. La variabilidad entre pacientes reflejada en la población de modelos ha permitido además mostrar los mecanismos por los cuales un mismo tratamiento puede mostrar efectos divergentes, así el uso de poblaciones de modelos matemáticos permitirá prevenir efectos secundarios asociados a la variabilidad entre pacientes y profundizar en el desarrollo de terapias individualizadas. Estos trabajos se cimientan sobre una plataforma de simulación de electrofisiología cardiaca de basado en Unidades de Procesado Gráfico (GPUs) y desarrollada en esta tesis. La plataforma permite la simulación de modelos celulares cardiacos así como de tejidos u órganos con geometría realista, mostrando unas prestaciones comparables con las de las utilizadas por los grupos de investigación más potentes en el campo de la electrofisiología. / [CA] Les taquiarítmies auriculars tenen una alta prevalença en el món desenvolupat, a més diversos estudis poblacionals indiquen que en les pròximes dècades aquesta es veurà incrementada. Els mecanismes de micro o macro-reentrada dels fronts d'ona elèctrics que regeixen el comportament mecànic del cor, es presenten com una de les principals causes del manteniment d'aquestes arítmies. El flutter auricular és mantingut per una macro-reentrada al voltant d'un obstacle anatòmic o funcional en les aurícules, mentre que en el cas de la fibril·lació auricular la hipòtesi que defineix als rotors d'alta freqüència com a elements dominants i responsables del manteniment de l'arítmia s'ha anat imposant a la resta en els últims anys. No obstant això, les teràpies que tenen com a objectiu finalitzar o aïllar aquestes reentrades tenen encara una eficàcia limitada. L'ablació per radiofreqüència permet eliminar zones del teixit cardíac resultant en la interrupció del circuit de reentrada en el cas de macro-reentrades o l'aïllament de comportaments micro-reentrants. La localització no invasiva dels circuits reentrants incrementaria l'eficàcia d'aquestes teràpies i reduiria la durada de les intervencions quirúrgiques. D'altra banda, les teràpies farmacològiques alteren les expressions iòniques associades a la excitabilitat i la refractaritat del teixit amb la finalitat de dificultar el manteniment de comportaments reentrants. Aquest tipus de teràpies exigeixen incrementar el coneixement dels mecanismes subjacents que expliquen el procés de reentrada i les seues propietats, la recerca d'aquests mecanismes permet definir les dianes terapèutiques que milloren l'eficàcia en l'extinció d'aquests comportaments. En aquesta tesi el modelatge matemàtic s'utilitza per a fer un pas important en la minimització de les limitacions associades a aquests tractaments. La cartografia elèctrica de superfície ha sigut testada, clínicament i amb simulacions matemàtiques com a tècnica de diagnòstic i localització de circuits macro-reentrants. L'anàlisi de mapes de fase obtinguts a partir dels registres multicanal de derivacions electrocardiogràfiques distribuïdes en la superfície del tors permet diferenciar diferents circuits de reentrada. És per açò que aquesta tècnica de registre i anàlisi es presenta com una eina per a la localització no invasiva de circuits macro i micro-reentrants. Una població de models matemàtics, dissenyada en aquesta tesi a partir dels registres dels potencials d'acció de 149 pacients, ha permès avaluar els mecanismes iònics que defineixen les propietats associades als processos de reentrada. Açò ha permès apuntar al bloqueig del corrent ICaL com a diana terapèutica. Aquesta s'associa a l'increment del moviment del nucli que facilita l'impacte del rotor amb altres fronts d'ona o obstacles extingint-se així el comportament reentrant. La variabilitat entre pacients reflectida en la població de models ha permès a més mostrar els mecanismes pels quals un mateix tractament pot mostrar efectes divergents, així l'ús de poblacions de models matemàtics permetrà prevenir efectes secundaris associats a la variabilitat entre pacients i aprofundir en el desenvolupament de teràpies individualitzades. Aquests treballs es fonamenten sobre una plataforma de simulació de electrofisiologia cardíaca basat en Unitats de Processament Gràfic (GPUs) i desenvolupada en aquesta tesi. La plataforma permet la simulació de models cel·lulars cardíacs així com de teixits o òrgans amb geometria realista, mostrant unes prestacions comparables amb les de les utilitzades per els grups de recerca més importants en aquesta área. / Liberos Mascarell, A. (2016). Mathematical modeling approaches for the diagnosis and treatment of reentrant atrial tachyarrhythmias [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62166

Les aubes des turbomachines modernes sont de plus en plus fines, légères et chargées aérodynamiquement. Cette tendance accroît l'apparition de phénomènes aéroélastiques tel que le flottement qui conduit à la rupture si l'amortissement est insuffisant. Bien que les outils numériques soient de plus en plus robustes, la fiabilité de sa prédiction demeure insuffisante. La nature critique du phénomène et le manque de données expérimentales pour des écoulements typiques de l'industrie encouragent des travaux de recherche. Dans ce contexte, la présente thèse est dédiée à l'étude du flottement dans des configurations récentes de turbine à travers l'analyse aérodynamique des écoulements subsoniques ou supersoniques soumis à un mode de structure vibratoire imposé. L'objectif est de fournir des éléments de compréhension des mécanismes potentiellement générateurs de flottement pour une meilleure intégration lors de la conception des aubes. L’approche consiste à mener des travaux expérimentaux et numériques. La partie expérimentale s'appuie sur un secteur de grille annulaire constitué de sept aubes dont une peut osciller de manière contrôlée. Les fluctuations de pressions instationnaires générées sont mesurées avec la technique dite des coefficients d'influence pour différents paramètres mécaniques et aérodynamiques : déformées modales pures et combinées, fréquence réduite, nombre de Mach, angle d'incidence. Complétée par des mesures de niveau de turbulence, la base de données vise à évaluer l'influence de ces paramètres sur la réponse aéroélastique, à valider le principe de superposition linéaire et à soutenir les codes numériques. La partie numérique se base sur des calculs instationnaires linéarisés dans le domaine fréquentiel en utilisant la technique dite des "ondes propagatives" (traveling wave mode).Deux cas de turbines spatiales industrielles sont étudiés.• Des calculs 2D sont réalisés sur une turbine monobloc ou blisk. L'amortissement mécanique quasi-nul entraîne des déformées complexes avec couplage de modes et des fréquences réduites très élevées. Bien que les aubes soient prédites stables, une méthodologie basée sur des décompositions géométriques élémentaires est présentée afin d'identifier les contributions déstabilisantes. Les résultats aboutissent étonnamment aux conclusions de la théorie du flottement classique : la torsion est une source potentielle d'instabilité. De plus, le coefficient d'amortissement aérodynamique a été trouvé extrêmement sensible au déphasage interaube et aux fréquences de coupure (modes cut-on/cut-off).• Des calculs 3D sont ensuite réalisés sur une turbine supersonique. L'écoulement présente des ondes de chocs avec décollement de la couche limite et le mouvement de l'aube est de nature élémentaire, i.e. purement axial. Les aubes ont été prédites instables pour les modes rétrogrades et stables pour les modes propagatifs. En dépit des fortes hypothèses, des analyses quasi-stationnaires rendent compte des mécanismes de flottement : la phase entre le mouvement du choc et l'excitation établit la frontière entre configurations stable et instable. / Modern turbomachines are designed towards thinner, lighter and highly loaded blades. This gives rise to increased sensitivity to flow induced vibrations such as flutter, which leads to structure failure in a short period of time if not sufficiently damped. Although numerical tools are more and more reliable, flutter prediction still depends on a large degree on simplified models. In addition, the critical nature of flutter, resulting in poor welldocumented real cases in the open literature, and the lack of experimental database typical of engine flows make its apprehension even more challenging. In that context, the present thesis is dedicated to study flutter in recent turbines through aerodynamic analysis of subsonic or supersonic flows in response to a prescribed vibratory mode of the structure. The objective is to highlight some mechanisms potentially responsible for flutter in order to be in better position when designing blades. The strategy consists in leading both experimental and numerical investigations. The experimental part is based on a worldwide unique annular turbine sector cascade employed for measuring the aeroelastic response by means of the aerodynamic influence coefficient technique. The cascade comprises seven low pressure gas turbine blades one of which can oscillate in a controlled way as a rigid body. Aeroelastic responses are measured at various mechanical and aerodynamic parameters: pure and combined modeshapes, reduced frequency, Mach number, incidence angle. In addition to turbulence level measurements, the database aims at assessing the influence of these parameters on the aerodynamic damping, at validating the linear combination principle and at providing input for numerical tools. The numerical part is based on unsteady computations linearized in the frequency domain and performed in the traveling wave mode. The focus is put on two industrial space turbines: 2D computations are performed on an integrally bladed disk, also called blisk; its very low viscous material damping results in complex motions with combined modes and extremely high reduced frequency. The blisk operates at low subsonic conditions without strong non-linearities. Although the blades have been predicted aeroelastically stable, an original methodology based on elementary decompositions of the blade motion is presented to identify the destabilizing movements. The results suggest that the so-called classical flutter is surprisingly prone to occur. Moreover, the aerodynamic damping has been found extremely sensitive to the interblade phase angle and cut-on/cut-off conditions.• 3D computations are then performed on a supersonic turbine, which features shockwaves and boundary layer separation. In contrast, the blade motion is of elementary nature, i.e. purely axial. The blades have been predicted aeroelastically unstable for backward traveling waves and stable for forward traveling waves. The low reduced frequencies allow quasi-steady analysis, which still account for flutter mechanisms: the shock wave motion establishes the boundary between stable and unstable configurations.

The thesis focuses on modern methods of traffic sign detection and traffic lights detection directly in traffic and with use of back analysis. The main subject is convolutional neural networks (CNN). The solution is using convolutional neural networks of YOLO type. The main goal of this thesis is to achieve the greatest possible optimization of speed and accuracy of models. Examines suitable datasets. A number of datasets are used for training and testing. These are composed of real and synthetic data sets. For training and testing, the data were preprocessed using the Yolo mark tool. The training of the model was carried out at a computer center belonging to the virtual organization MetaCentrum VO. Due to the quantifiable evaluation of the detector quality, a program was created statistically and graphically showing its success with use of ROC curve and evaluation protocol COCO. In this thesis I created a model that achieved a success average rate of up to 81 %. The thesis shows the best choice of threshold across versions, sizes and IoU. Extension for mobile phones in TensorFlow Lite and Flutter have also been created.

[pt] Este trabalho tem como objetivo principal estudar o comportamento de flambagem lateral de vigas através de modelos de elementos finitos baseados nas teorias de placas de Kirchhoff e de Mindlin–Reissner. Esses modelos foram combinados com efeitos de membrana, possibilitando a análise de cascas. Foi desenvolvido um código MATLAB para analisar cargas críticas estáticas e dinâmicas, modos de flambagem, frequências e modos de vibração de placas finas e espessas sujeitas a cargas conservativas e cargas não conservativas (também chamadas de seguidoras ou circulatórias). O programa ANSYS foi usado para validação e comparação. Para o cálculo das frequências naturais foram usadas as matrizes de massa e a matriz de rigidez. Para o cálculo da carga crítica estática com carga conservativa, implementa-se a matriz geométrica. Quando há carregamento seguidor não conservativo, é necessário adicionar uma matriz de correção de cargas que é uma matriz assimétrica, achando assim a carga crítica dinâmica, também denominada de flutter. Diferentes condições de contorno e diferentes carregamentos são aplicados em vigas e analisados os casos de flambagem lateral. Valores teóricos encontrados na literatura são comparados com os valores achados usando o método de elementos finitos. A instabilidade lateral de vigas esbeltas tem grande interesse prático, pois em alguns casos pode ocorrer o esgotamento da resistência da peça antes mesmo que seja atingido o estado limite último de flexão. Por isso, o tema flambagem lateral é mencionado em diversas normas nacionais e internacionais, tendo sido feitas algumas comparações com os resultados do programa implementado neste trabalho. / [en] The main objective of this paper is to present results on the lateral buckling of beams using finite elements based on Kirchhoff and Mindlin-Reissner Plate theories, merged with membrane elements in order to include the analysis of shells. A MATLAB code was developed to calculate static and dynamic critical loads, buckling modes, frequencies, and vibration modes of thin and thick plates subjected to conservative and non-conservative (also called follower or circulatory) loads. Mass and stiffness matrices are employed to determine natural frequencies. In the case of conservative loads, static critical loads are calculated by adding a so-called geometric matrix. However, in case of displacement-dependent applied forces, it is necessary to implement a matrix that will correct the loads, designated as load matrix. In the case of conservative forces, the load matrix is symmetric, and in the case of non-conservative forces, it is non-symmetric. In the latter case, the critical load usually will correspond to dynamic behavior designated as flutter. Different boundary conditions and loads are considered and several cases of lateral buckling are investigated. Theoretical values when found in the literature are compared with values determined by Finite Element Method (FEM). The lateral instability of slender beams is very important in practice, because in some situations it may occur prior to ultimate plastic limit state in bending. Therefore, lateral buckling is mentioned in a wide variety of national and international rules, and some comparisons with the results of the computer code developed herein are presented.

<p align="justify">This work deals with the development of numerical methods for compressible flow simulation with application to the interaction of fluid flows and structural bodies.</p> <p align="justify">First, we develop numerical methods based on multidimensional upwind residual distribution (RD) schemes. Theoretical results for the stability and accuracy of the methods are given. Then, the RD schemes for unsteady problems are extended for computations on moving meshes. As a second approach, cell centered and vertex centered finite volume (FV) schemes are considered. The RD schemes are compared to FV schemes by means of the 1D modified equation and by the comparison of the numerical results for scalar problems and system of Euler equations. We present a number of two and three dimensional steady and unsteady test cases, illustrating properties of the numerical methods. The results are compared with the theoretical solution and experimental data.</p> <p align="justify">In the second part, a numerical method for fluid-structure interaction problems is developed. The problem is divided into three distinct sub-problems: Computational Fluid Dynamics, Computational Solid Mechanics and the problem of fluid mesh movement. The problem of Computational Solid Mechanics is formulated as a system of partial differential equations for an anisotropic elastic continuum and solved by the finite element method. The mesh movement is determined using the pseudo-elastic continuum approach and solved again by the finite element method. The coupling of the problems is achieved by a simple sub-iterative approach. Capabilities of the methods are demonstrated on computations of 2D supersonic panel flutter and 3D transonic flutter of the AGARD 445.6 wing. In the first case, the results are compared with the theoretical solution and the numerical computations given in the references. In the second case the comparison with experimental data is presented.</p>

As características arquitetônicas e o desempenho estrutural de pontes suspensas, estaiadas ou pênseis, têm determinado a sua crescente utilização em obras de arte destinadas a vencer grandes vãos. Essa utilização crescente que ocorreu no mundo nas últimas décadas se repete agora nos últimos anos no país. Várias dessas obras estão em execução e em projeto. Um dos aspectos relevantes na análise estrutural das pontes suspensas é o de seu comportamento quando submetidas à ação do vento. Apresenta-se o sistema computacional ANA-PSp desenvolvido especialmente para o estudo do movimento de tabuleiros de pontes suspensas sujeitas a esforços aeroelásticos e aerodinâmicos. Esse sistema computacional formado por um conjunto de subsistemas, é elaborado para a análise aeroelástica de pontes suspensas sob a ação de vento e permite análises paramétricas extensas dos fenômenos de drapejamento (flutter) e de martelamento (buffeting). A discretização da estrutura é efetuada pelo método dos elementos finitos e a redução dos graus de liberdade é realizada por superposição modal com modos selecionados que melhor descrevem os movimentos do tabuleiro. Utiliza-se modelo matemático reduzido para a análise multimodal no domínio do tempo e da freqüência. A velocidade crítica ou velocidade de drapejamento é determinada por procedimento de autovalores complexos com a obtenção de freqüências e taxas de amortecimentos modais para várias velocidades do vento. Adicionalmente, o fenômeno do drapejamento é estudado por séries temporais de respostas de coordenadas generalizadas e de deslocamentos selecionados e por análise espectral dessas séries temporais, que permitem a verificação das características de vibração do tabuleiro da ponte no domínio da freqüência. O estudo do fenômeno de martelamento considera esforços aeroelásticos determinísticos e esforços aerodinâmicos estocásticos e apresentam-se resultados em espectros de potência de deslocamentos e em desvios padrão de deslocamentos ao longo do tabuleiro. Para validar o sistema ANA-PSp, apresentam-se estudos de caso para a ponte estaiada da Normandia, para a ponte pênsil colapsada de Tacoma Narrows e para a ponte estaiada projetada, mas não executada, sobre o Rio Tietê e localizada na extremidade do complexo viário Jacu-Pêssego. / The architectonic characteristics and the structural performance of suspension bridges and cable-stayed bridges have determined their growing use on large span bridges. This growing usage, which has occurred world-wide during the last decades, is now being repeated in Brazil during the last few years. Several such bridges are presently either undergoing construction or being designed. One of the outstanding aspects in the structural analysis of suspension bridges is their behavior under wind action. This paper presents the computer system ANA-PSp, specially developed for studying the movement of suspended bridge decks under aeroelastic and aerodynamic forces. This computer system is formed by a group of subsystems and is created for aeroelastic analysis of suspended bridges under wind action. It allows extended parametric analyses of the flutter and the buffeting phenomena. Structural discretization is done by the finite element method and the reduction of degrees of freedom is obtained by modal superposition of the selected modes which best describe the deck movements. A reduced mathematical model is used for the multimodal analysis in the time and frequency domains. Critical velocity or flutter velocity is determined by a procedure of complex eigenvalues which obtains frequencies and damping ratios for different wind speeds. Additionally, the flutter phenomenon is studied by temporal series of answers to generalized coordinate responses and of selected displacements by spectral analysis of such temporal series, which allow us to verify the characteristics of the vibrations of the bridge deck in the frequency domain. The study of the buffeting phenomenon considers deterministic aeroelastic and stochastic aerodynamic forces. The paper presents results in displacement power spectra and in the standard deviation of displacements along the deck. In order to validate system ANA-PSp, case studies are presented for the cable-stayed Ponte de Normandie in Le Havre (France), for the collapsed suspension bridge on Tacoma Narrows and for the cable-stayed bridge, already designed but not built, on Tietê River, located at one end of the highway complex Jacu-Pêssego (São Paulo, SP, Brazil).

In the past decade, camera manufacturers have offered smaller form factors, smaller pixel sizes (leading to higher resolution images), and faster processing chips to increase the performance of consumer cameras. However, these conventional approaches have failed to capitalize on the spatio-temporal redundancy inherent in images, nor have they adequately provided a solution for finding $3$D point correspondences for cameras sampling different bands of the visible spectrum. In this thesis, we pose the following question---given the repetitious nature of image patches, and appropriate camera architectures, can statistical models be used to increase temporal, structural, or spectral resolution? While many techniques have been suggested to tackle individual aspects of this question, the proposed solutions either require prohibitively expensive hardware modifications and/or require overly simplistic assumptions about the geometry of the scene. We propose a two-stage solution to facilitate image reconstruction; 1) design a linear camera system that optically encodes scene information and 2) recover full scene information using prior models learned from statistics of natural images. By leveraging the tendency of small regions to repeat throughout an image or video, we are able to learn prior models from patches pulled from exemplar images. The quality of this approach will be demonstrated for two application domains, using low-speed video cameras for high-speed video acquisition and multi-spectral fusion using an array of cameras. We also investigate a conventional approach for finding 3D correspondence that enables a generalized assorted array of cameras to operate in multiple modalities, including multi-spectral, high dynamic range, and polarization imaging of dynamic scenes.

Les instabilités aéroélastiques de bandes d’acier constituent aujourd’hui l’un des problèmes majeurs dans les sections de refroidissement par jets impactants des lignes de recuit continues.En effet, le traitement thermique des nouveaux aciers nécessite de très fortes pentes de température impliquant constamment des augmentations de vitesse de soufflage susceptibles de mettre en jeu des instabilités aéroélastiques. Des flottements ainsi que des divergences de bande ont déjà été constatées et identifiées. Ces deux instabilités impliquent dans la plupart des cas des chocs entre la bande et les buses de soufflage ce qui engendre des défauts de surface sur la bande.Un banc d’essai a été conçu et fabriqué dans le but d’analyser ces instabilités et d’anticiper leur apparition. A partir d’observations, la dynamique structurelle de la bande a été simplifiée à un mode de rotation rigide. Le banc comporte une plaque oscillante en mouvement forcé.Celle-ci est impactée par un dispositif de plusieurs jets axisymétriques turbulents ayant une disposition identique à celle des tours industrielles. Les efforts aérodynamiques stationnaires et instationnaires agissant sur la plaque sont mesurés au moyen de capteurs de pression.L’impact de plusieurs jets en interaction crée de très importants gradients de pression sur la plaque il est donc nécessaire que la grille de prises de pression soit très fine pour que l’estimation des efforts aérodynamiques soit correcte. La plaque est donc instrumentée de 91capteurs de pression sur une surface de 18 cm². Elle peut également être translatée dans les ois directions de l’espace, ce qui permet d’obtenir la distribution des efforts instationnaires ainsi que des coefficients aéroélastiques sur une grande surface de plaque et à différentes distances d’impact.Les mesures de pression stationnaires ont permis d’établir les courbes d’évolution des efforts d’impact des jets sur la plaque en fonction de la distance jet-plaque ainsi que de la géométrie des buses. Les résultats ont permis de déterminer la stabilité statique de la plaque en mouvement de pompage. Les mesures de vitesses des jets libres ont été effectuées paranémométrie à fil chaud et ont permis de déterminer leurs propriétés statistiques.Les mesures de coefficients aéroélastiques sur la plaque en rotation ont été effectuées surune seule géométrie de soufflage, pour différentes vitesses réduites. Les résultats mettent en évidence l’importance des effets de bords sur la stabilité de plaque. Des méthodes de post traitements ont proposées afin d’extrapoler les résultats à différentes largeurs de bande. Ils sont confrontés aux travaux de Regardin et al. (réf. [1]) et mettent en évidence des désaccords avec le cas réel. Des suggestions sont apportées afin d’améliorer la représentativité du banc vis-à-vis des bandes industrielles. / Aeroelastic instabilities of steel strips impinged by arrays of cooling gas jets have becomeone of the main issues in cooling sections of continuous annealing lines. Indeed, the new steeltreatments require very high temperature variation rates which involve increases in jetvelocities that are likely to onset some aeroelastic instabilities. Strip flutter and divergencehave already been observed and identified. These two aeroelastic instabilities imply a strongrisk of contact with the blowing boxes, which can seriously blemish the strip.An experimental test rig was designed and built in order to analyze and predict of theseinstabilities. From observations, the strip’s structural dynamics was simulated by a rigidrotation mode. The rig included a forced oscillating plate which is impinged by an array ofaxisymmetric jets having the exact industrial geometry. The plate was instrumented withpressure sensors to measure the steady and unsteady surface pressures. The impingement ofinteracting jets creates very large pressure gradients on the plate and therefore a tight mesh ofpressure taps (91 over an 18cm² jet impingement surface) was necessary to allow a goodestimation of the aerodynamic loads The plate could also be moved in the three coordinatedirections as to obtain surface mappings of the unsteady jet forces and aeroelastic coefficientscan be obtained over a wide area and different jet-to-plate distances.The variation of the impinging aerodynamic forces was established as a function of the jetto-plate distance for different nozzle geometries. These results were used to determine the jetstatic stability in plunging motion. Velocity and turbulence measurements in free jets werecarried out using hot wire anemometry in order to determine their statistical properties.Aeroelastic coefficient measurements were carried out on the oscillating plate with onlyone nozzle geometry and different reduced velocities. Results show that the plate’s stability ismainly dependent on the boundary effects. Post processing methods are suggested in order toapply the results to larger plates. Results are compared to the data of Regardin et al. (réf. [1])and emphasize some discrepancies with respect to the real case. Finally some improvementsto the test-rig are suggested for it to be more representative of the industrial situation.