Thesis (doctoral)--Universität Berlin.

Habil.-Schrift Jur. Fak. Univ. Basel, 2008. / Übers. von: Restitution von Kulturgut. Register. Originaltitel: Restitution von Kulturgut. Literaturverz.

Habil.-Schrift Jur. Fak. Univ. Basel, 2008. / Übers. von: Restitution von Kulturgut. Register. Originaltitel: Restitution von Kulturgut. Literaturverz.

Thesis (LLM) - University of Queensland, / Includes bibliography.

Erosion and deposition in gas turbine engines are functions of particle/wall interactions and the Coefficient of Restitution (COR) is a fundamental property of these interactions. COR depends on impact velocity, angle of impact, temperature, particle composition, and wall material. In the first study, a novel Particle Tracking Velocimetry (PTV) / Computational Fluid Dynamics (CFD) hybrid method for measuring COR has been developed which is simple, cost-effective, and robust. A Laser-Camera system is used in the Virginia Tech Aerothermal Rig to measure microparticles velocity. The method solves for particle impact velocity at the surface by numerical methods. The methodology presented here characterizes a difficult problem by a combination of established techniques, PTV and CFD, which have not been used in this capacity before. The current study characterizes the fundamental behavior of sand at different impact angles. Two sizes of Arizona Road Dust (ARD) and one size of Glass beads are impacted on to 304-Stainless Steel. The particles are entrained into a free jet of 27m/s at room temperature. Mean results compare favorably with trends established in literature. This technique to measure COR of microparticle sand will help develop a computational model and serve as a baseline for further measurements at elevated, engine representative air and wall temperatures. In the second study, ARD is injected into a hot flow field at temperatures of 533oK, 866oK, and 1073oK to measure the effects of high temperature on particle rebound. The results are compared with baseline measurements at ambient temperature made in the VT Aerothermal Rig, as well as previously published literature. The effects of increasing temperature and velocity led to a 12% average reduction in total COR at 533oK (47m/s), a 15% average reduction at 866oK (77m/s), and a 16% average reduction at 1073oK (102m/s) compared with ambient results. From these results it is shown that a power law relationship may not conclusively fit the COR vs temperature/velocity trend at oblique angles of impact. The decrease in COR appeared to be almost entirely a result of increased velocity that resulted from heating the flow. / Ph. D.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Le sujet de thèse concerne la réalisation et la caractérisation d’un simulateur dynamique de véhicule deux-roues. La thèse est organisée en plusieurs parties essentielles. D’abord, une étude bibliographique est menée pour cerner la problématique de la simulation de conduite d’une manière générale en se focalisant sur les simulateurs de point de vue conception. Dans cette partie, on a pris connaissance des différentes architectures mécaniques utilisées auparavant ainsi que les problèmes liés. Le choix de l'architecture du simulateur est guidé par les besoins nécessaires d'avoir une perception suffisante au cours de la simulation de conduite. Notre objectif est de reproduire les effets inertiels (accélération, effort,..) les plus pertinents perçus dans une conduite réelle. Le second chapitre aborde la dynamique des véhicules et compare celle des deux-roues contre les automobiles. Des adaptations pour des modèles dynamiques de moto ont été présentées pour répondre à nos besoins en termes de rendus privilégiés. Le troisième chapitre présente les aspects conception, réalisation, caractérisation et identification du simulateur de moto mis au point dans le cadre de cette thèse. Il constitue la principale contribution de ces travaux de recherche. Les deux derniers chapitres sont dédiés aux algorithmes de contrôle/commande ainsi qu’essais expérimentaux sur la plateforme. Ces tests ont été réalisés en vue de la caractérisation et la validation de performances de toute la chaîne de simulation. / This thesis deals with the design and realization of a dynamic mechanical platform intended to the motorcycle riding simulation. This dissertation is organized into several principal sections. First, a literature review is conducted to identify the driving simulation problematic in a general way by focusing on the simulator design. In this part, it was aware of the various mechanical architectures used previously as well as the related limitations. The choice of the simulator‘s mechanical architecture of is driven by the needs to have an sufficient perception during simulated driving situation. Our goal is to reproduce the most relevant inertial effects (acceleration, torque, ..) perceived in a real world driving. The second chapter discusses an exhaustive comparison between automotive vehicles dynamics against the two-wheeled vehicles against. Existing motorcycles dynamic models are adjusted and of have been adapted to meet our needs in terms of privileged inertial cues. The third chapter presents the design aspects, mechanical realization, characterization and identification of the motorcycle simulator developed within the framework of this thesis. It constitutes the main contribution of this research works. Finally, the last two chapters are dedicated to motion cueing /control algorithms and open-loop experimentation on the simulator’s platform. These tests were performed for the characterization and validation of performance of the entire simulation loop.

<p>Sudden death from arrhythmia is a major cause of mortality in the United States. Unfortunately, no current diagnostic test can accurately predict risk for sudden arrhythmic death. Because ventricular arrhythmias often result from abnormalities of repolarization, assessment of myocardial repolarization using the electrocardiogram (ECG) can aid in prediction of arrhythmia risk. Non-linear, rate-dependent changes in myocardial repolarization can promote the development of arrhythmia, but few studies examine how these dynamic changes in repolarization affect the ECG. This dissertation describes the use of a computer model to investigate the effect of dynamic changes in myocardial repolarization on the ECG T wave.</p><p>To simulate action potential conduction from the endocardium to the epicardium of the free wall of the canine left ventricle, 1-dimensional multicellular computer fiber models were created. Each fiber model was composed of endocardial, midmyocardial, and epicardial cells. For each cell type, existing mathematical models were modified to approximate experimental data for four types of dynamic repolarization behavior: (1) dynamic restitution, the response to steady-state pacing; (2) S1-S2 restitution, the response to a premature or postmature stimulus; (3) short-term memory (STM), the response to an abrupt change in pacing rate; and (4) repolarization alternans, beat-to-beat alternation in cellular repolarization time. Repolarization times were obtained from endocardial, midmyocardial, and epicardial regions in the fiber model and compared to parameters measured from a computed transmural ECG.</p><p>Spatial differences in repolarization created two voltage gradients that influenced the ECG: an endocardial-midmyocardial (endo-mid) gradient and a midmyocardial-epicardial (mid-epi) gradient. Epicardial dynamic restitution changes altered the mid-epi gradient, influencing the rising phase of the ECG T wave, and endocardial dynamic restitution changes altered the endo-mid gradient, influencing the falling phase of the T wave. Changes in epicardial or endocardial repolarization due to S1-S2 restitution or STM caused transient changes in the rising or falling phase of the T wave, respectively.</p><p>During repolarization alternans, an alternating, asymmetric distribution of extracellular potential around the fiber influenced the measurement of T-wave alternans (TWA) in the ECG. Presence of a resistive barrier in the fiber model altered the magnitude of repolarization alternans as well as the TWA amplitude in the ECG with effects dependent on barrier location. The resistive barrier also modified the relationship between cellular repolarization alternans magnitude and TWA amplitude.</p><p>The results presented in this dissertation explain basic mechanisms by which dynamic changes in myocardial repolarization affect the ECG T wave. These mechanisms form the foundation for the development of techniques to identify arrhythmogenic, dynamic changes in the myocardium using the ECG. Future studies in higher-dimensional, more complex models will build upon these results by considering the influence of additional voltage gradients, more realistic tissue geometries, and heterogeneities in the volume conductor.</p> / Dissertation

Texte remanié de: Th. doct.--Droit privé--Paris 1, 2002. / Bibliogr. p. 437-478. Index.

Texte remanié de: Thèse de doctorat--Droit romain--Paris 2, 2001. / Bibliogr. p. 305-320. Index.