Mon travail de thèse a porté sur la simulation numérique du comportement dynamique de poussières et de petits corps autour d’étoiles, appliqué à deux grands domaines de localisation : les disques de débris et les exozodis.Concernant les disques de débris, je me suis plus particulièrement intéressé aux arches mouvantes observées sur une période de 15 ans au sein du disque d’AU Mic. En supposant qu’elles proviennent toutes d’un corps parent unique et que les grains composant les arches ont la même dynamique que les arches elles-mêmes, j’ai montré que le corps parent doit être plus interne que la ceinture de planétésimaux (<25 UA) et qu’il peut être sur une orbite circulaire ou fixe par rapport à l’observateur. Afin d’expliquer la vitesse apparente des arches, il est nécessaire que les grains les composant soient submicrométriques pour être suffisamment sensibles à la pression du vent stellaire. Le champ magnétique à grande échelle de cette étoile est suffisant pour expliquer l’élévation verticale des arches, mais l’interaction des grains avec ce champ nécessite des études plus approfondies.D’autre part, j’ai développé un code numérique permettant de tester l’origine dynamique des poussières constituant les exozodis, en comparant les résultats de mes simulations aux observations. J‘ai montré que le scénario classique de migration par PR-drag de grains provenant d’une ceinture externe froide produit trop de flux dans le moyen infrarouge en regard du proche infrarouge, et cet effet n’est pas suffisamment contrebalancé par l’accumulation proche de la distance de sublimation. En revanche, le scénario cométaire, avec un apport de matière au plus près de l’étoile, permet de modérer le flux en moyen infrarouge. Les observations peuvent être reproduites avec une dizaine de comètes kilométriques autour de chaque étoile. Le code que j’ai conçu est capable d’appréhender de nombreux effets physiques, et il est possible de tester l’influence du DDE, de la pression du vent stellaire ou encore du champ magnétique.Par mon travail, j’ai montré que la prise en compte de la dynamique des grains de poussière permet de contraindre les propriétés physiques des grains, et j’ai développé des outils numériques adaptables à de nombreux cas de figures afin de pouvoir caractériser la diversité et la complexité de la poussière observée autour des étoiles. / During my thesis, I numerically simulated the dynamical behaviour of dust and small grains around stars, applied to two ranges of stellar distance : debris disks and exozodis.Concerning debris disks, I focused on the fast moving arch-like structures observed over 15 years inside the disk of AU Mic. Supposing that they all come from a single parent body and that the dust composing the arches have the same dynamics, I showed that the parent body must be closer-in than the planetesimal belt (<25 au), on a circular orbit or static with respect to the observer. Grains must be submicronic in order to explain the apparent velocity of the arches, gained by means of stellar wind pressure. Large-scale magnetic field of the star is large enough to explain the vertical extent of the arches, but require further investigations.I also developped a numerical code in order to test the dynamical origin of dust composing exozodis, to compare its results to the observations. I showed that the classical PR-drag scenario involving grains drifting inward from a distant cold parent belt produce an excess flux in mid-infrared compared to the near-infrared, unbalanced by the pile-up. The cometary scenario, by producing dust very close to the star, emits less in mid-infrared. A ten of kilometric comets can reproduce the flux levels observed around all stars. This numerical code is also able to handle the DDE, the stellar wind pressure or the magnetic field.During my work, I showed that taking into account the dust dynamics can constrain the dust physical properties. I developped adaptative numerical tools that can handle the variety and complexity of dust observed around stars.

L’entreprise Subsea Tech développe un ROV (véhicule sous-marin téléopéré - Remotely OperatedVehicle) léger (40 kg), nommé Tortuga 500, dont la particularité est la capacité de reconfiguration de ses actionneurs. Ses quatre propulseurs horizontaux, dits azimutaux, peuvent en effet pivoter autour de leur axe vertical en cours de mission pour permettre une optimisation de la poussée ou de la manœuvrabilité du véhicule. Le but de cette thèse est de maximiser, à chaque instant de la mission effectuée, la propulsion du ROV dans une direction souhaitée qui peut évoluer en cours de mission. Pour ce faire, une méthode d’optimisation locale et déterministe est utilisée pour calculer en ligne l’orientation optimale de chaque propulseur. Elle est initialisée par une méthode de recherche globale effectuée en amont. Les perturbations dues aux interactions entre les flux des propulseurs sont prises en compte dans la méthode d’optimisation. La poussée du véhicule est alors maximisée à chaque instant, et pour chaque direction souhaitée, tout en conservant un minimum de commandabilité latérale pour faire face aux perturbations extérieures (traînée de l’ombilical, courant). Plusieurs simulations, portant sur la poussée maximale atteignable par le véhicule, sa puissance consommée, et sa vitesse maximale lors d’un transit, permettent de comparer les performances de la méthode d’optimisation proposée avec celles de la traditionnelle configuration fixe dite "vectorielle" observée sur la majorité des autres ROVs du commerce. / The Subsea Tech company is developing a lightweight (40 kg) Remotely Operated Vehicle (ROV) called Tortuga 500, which can online reconfigure its four horizontal thrusters. These thrusters, also called "azimuth thrusters", can steer around their vertical axis during a mission in order to optimize the thrust or the manoeuvrability of the vehicle. This thesis focuses on the online thrust maximization of the ROV, along a variable desired direction. To do so, a local and deterministic optimization method is used and allows to get the optimal orientation of each thruster in real time. It is initialized by values previously computed by a sparse and offline research method. The interactions between thrusters due to cross flows are modelled and integrated into the optimization method. Thus, the vehicle thrust is maximized at every iteration step, and for every desired direction. Furthermore, a fixed minimum ratio of manoeuvrability is preserved during this process, to cope with external disturbances such as the tether’s drag and currents. Several simulations have been made and allow to compare the maximal reachable thrust, the consumed power, and the maximal achievable velocity, when it is configured with the proposed optimization method or with the "vectorized configuration" found on most other commercial ROVs.

La thèse décrit l'essentiel de la notion de la simulation. La première partie sert à la description des dispositions du droit du travail qui permettent d'appliquer le droit civil dans le rapport d'emploi. En le faisant une analyse des vices des déclarations d'engagement dans le sens du droit polonais et les vices du consentement dans le sens du droit civil français est envisagé ensemble avec l'analyse des conceptions de la simulation et les critères du contrat de travail selon deux systèmes juridiques respectifs. La première partie contient également la description des contrats qui permettent aux parties de cacher le rapport du travail. La deuxième partie parle des conséquences de la simulation dans les relations de travail et analyse les différences entre la simulation et la fraude. La description des moyens disponibles dans la bataille contre le contournement des règles du droit du travail mène aux remarques de lege ferenda en proposant l'adoption des solutions disponibles dans le droit polonais. / The dissertation describes the essentials of the concept of simulation. The first part describes the labour law provisions that make it possible to apply civil law in the employment relationship. By doing so, an analysis of the defects of the declarations of commitment in the sense of Polish law and the defects of consent in the sense of French civil law is envisaged together with the analysis of the concepts of simulation and the criteria of the employment contract under two respective legal systems. The first part also contains a description of the contracts that allow the parties to hide the employment relationship.The second part discusses the consequences of simulation in labour relations and analyses the differences between simulation and fraud. The description of the means available in the battle against the circumvention of labour law rules leads to the remarks de lege ferenda by proposing the adoption of the solutions available in Polish law.

Dans cette recherche doctorale, une enquête approfondie et une revue de la littérature concernant la collaboration de la chaîne d'approvisionnement ont été menées. Plusieurs paradigmes et stratégies émergents de collaboration dans la chaîne d'approvisionnement ont été identifiés, ce qui a fourni une base théorique et une direction de recherche pour mes recherches ultérieures. En conséquence, trois modèles innovants de chaîne d'approvisionnement avec des stratégies d'optimisation correspondantes ont été développés: (1) un nouveau mécanisme de partage des ressources pour optimiser la fabrication des vêtements dans la chaîne d'approvisionnement textile; (2) un système central de traitement des commandes pour l'optimisation de la chaîne d'approvisionnement textile axée sur la demande, et (3) une plate-forme collaborative de services cloud pour l'optimisation de la chaîne d'approvisionnement textile da la fabrication à la commande. Stratégies de collaboration identifiées pour la chaîne d'approvisionnement, à savoir, le partage des ressources, le partage de l'information, la prise de décision conjointe, le partage des bénéfices, ont été utilisés pour développer les trois modèles de collaboration. Des heuristiques d'optimisation ont également été conçues pour différents objectifs dans trois modèles respectivement. Les trois stratégies collaboratives de la chaîne d'approvisionnement proposées ont été réalisées dans trois modèles de simulation en utilisant la technologie de simulation à événements discrets ou la technologie de simulation multi-agents. Plusieurs expériences ont été menées pour démontrer les avantages d'une telle structure collaborative dans différentes conditions. / In this PhD research, a thorough investigation and literature review regarding supply chain collaboration was conducted. Several emerging supply chain collaboration paradigms and strategies were identified, which provided a theoretical foundation and research direction for my subsequent research. Consequently, three innovative supply chain models with corresponding optimization strategies were developed: (1) a novel resource sharing mechanism for optimizing garment manufacturing echelon in textile supply chain, (2) a central order processing system for optimizing demand-driven textile supply chain, and (3) a collaborative cloud service platform for optimizing make-to-order textile supply chain. Identified supply chain collaboration strategies, viz. resource sharing, information sharing, joint decision-making, profit sharing, were employed for developing the three collaborative models. Optimization heuristics were also designed for different objectives in three models respectively. The three proposed supply chain collaboration strategies were realized in three simulation models by employing discrete-event simulation technology or multi-agent simulation technology. Several experiments were conducted to demonstrate the advantages of such collaborative structure under different conditions.

Graduation date: 1983

This thesis presents a discussion of motion of a six-legged walking machine following removal of one leg constraint. To take a step, one leg must be lifted and placed at some other position. As soon as the constraint provided by the leg is removed, however the machine begins to fall. This falling motion can be represented as screw motion of the body center of mass and of body-leg attachments. First a study of body workspace of the machine was done with all six feet on the ground. Body workspace is the intersection of kinematic and force workspaces. Kinematic workspace is the volume in space where the center of mass can be placed such that all joint angles of legs are within specified limits; and force workspace is the volume in space where the force in all legs is compressive. The affect of various foot positions, pitches and heights of the center of mass were investigated to find a set of three symmetric foot positions that might constitute acceptable intermediate positions in a walking sequence. Motion of the center of mass in the forward direction is limited in the force workspace by two points at which the force on a pair of legs goes to zero. With the center of mass at each of these two positions, the screw parameters resulting from the release of force on one leg (front, middle and hind individually) could be determined. Dynamic simulation of these body and foot positions used the commercial software SD/FAST. Code was written in C to do both static and dynamic simulation of machine and merged with code generated by SD/FAST. Code was also written in Auto Lisp to plot the falling motion of machine. Screw parameters found in this study were such that sustained forward motion of the body could not be achieved using the falling motion alone. Other measures such as extending one or more of the remaining five legs would be needed for effective forward body motion. / Graduation date: 1994

The exponential growth of information demands the automated movement of data and software via new software models that are able to integrate data and components on their own without scientists’ direct involvement. However, current stand-alone software modeling environments do not support a secure software execution, nor do client server applications allow user customization of the software running on the servers. To address this problem, a biological pathway modeling environment was built as a stand-alone Rich Internet Application (RIA). The modeling environment was tested by constructing a simulation of the glycolysis pathways in the human erythrocytes, and the results were compared against one of the latest and richest erythrocyte metabolism models developed by Kuchel and Mulquiney. The working simulation was able to settle into a quasi-stable state, with substrate concentrations close to what Kuchel and Mulquiney presented. It was also found that while the browser environment does allow for dynamic applications to be developed, speed and performance do become major issues. In later versions, it is hoped that the performance of the simulator can be increased and that it will become possible to link models together and add collaboration tools.

The exponential growth of information demands the automated movement of data and software via new software models that are able to integrate data and components on their own without scientists’ direct involvement. However, current stand-alone software modeling environments do not support a secure software execution, nor do client server applications allow user customization of the software running on the servers. To address this problem, a biological pathway modeling environment was built as a stand-alone Rich Internet Application (RIA). The modeling environment was tested by constructing a simulation of the glycolysis pathways in the human erythrocytes, and the results were compared against one of the latest and richest erythrocyte metabolism models developed by Kuchel and Mulquiney. The working simulation was able to settle into a quasi-stable state, with substrate concentrations close to what Kuchel and Mulquiney presented. It was also found that while the browser environment does allow for dynamic applications to be developed, speed and performance do become major issues. In later versions, it is hoped that the performance of the simulator can be increased and that it will become possible to link models together and add collaboration tools.

I propose a particle-based technique for simulating incompressible uid that includes adaptive re nement of particle sampling. Each particle represents a mass of uid in its local region. Particles are split into several particles for ner sampling in regions of complex ow. In regions of smooth ow, neghboring particles can be merged. Depth below the surface and Reynolds number are exploited as our criteria for determining whether splitting or merging should take place. For the uid dynamics calculations, I use the hybrid FLIP method, which is computationally simple and e cient. Since the uid is incompressible, each particle has a volume proportional to its mass. A kernel function, whose e ective range is based on this volume, is used for transferring and updating the particle's physical properties such as mass and velocity. In addition, the particle sampling technique is extended to a fully adaptive approach, supporting adaptive splitting and merging of uid particles and adaptive spatial sampling for the reconstruction of the velocity and pressure elds. Particle splitting allows a detailed sampling of uid momentum in regions of complex ow. Particle merging, in regions of smooth ow, reduces memory and computational overhead. An octree structure is used to compute inter-particle interactions and to compute the pressure eld. The octree supporting eld-based calculations is adapted to provide a ne spatial reconstruction where particles are small and a coarse reconstruction where particles are large. This scheme places computational resources where they are most needed, to handle both ow and surface complexity. Thus, incompressibility can be enforced even in very small, but highly turbulent areas. Simultaneously, the level of detail is very high in these areas, allowing the direct support of tiny splashes and small-scale surface tension e ects. This produces a nely detailed and realistic representation of surface motion.

Thèse doctorat : Génie Civil : INSA LYON : 2002. / Titre provenant de l'écran-titre. Bibliogr. p. 201-206.