En radiologie interventionnelle, l’assistance robotisée permet de limiter l’exposition du praticien aux rayons X et d’apporter plus de précision pour effectuer des opérations complexes. La présence de robots dans un environnement humain pose alors la question de la sécurité du patient et de l’équipe médicale, que ce soit lors d’interactions ou de manipulations. Dans cette thèse, nous nous intéressons dans un premier temps aux problématiques de sûreté. Une structure d’actionnement intrinsèquement sûre est proposée. Le prototype réalisé permet d’effectuer des tâches de positionnement en mode automatique. Parallèlement, une stratégie de guidage basée sur une approche passive est proposée. Un système à raideur variable permet d’imposer un effort résistif variable à l’utilisateur en vue de contraindre son geste. Dans une deuxième partie, nous étudions la possibilité d’intégrer de tels systèmes sur un dispositif à plusieurs degrés de liberté, répondant au problème de placement d’aiguille. / In the context of interventional radiology, robotic-assisted surgery limits practitioners’ exposure to radiations and brings more accuracy to perform complex interventions. However, the presence of robot in the environment is a potential danger for the patient and the medical staff in case of unexpected interactions and manipulations.In this PhD thesis, we first focus on safety problems. An intrinsically safe mechanism is proposed. The achieved prototype allows to follow both planned trajectories and moving environments.Secondly, a guidance mechanism based on a passive approach is suggested. With a variable stiffness system, using a compliant mechanism, a resistive force is applied to the user which allows him to be guided in his gesture.Based on medical needs, we then study the possibility to integrate and generalize such systems to multiple degrees of freedom.

We introduce a new class of measures for testing independence between two random vectors, which uses expected difference of conditional and marginal characteristic functions. By choosing a particular weight function in the class, we propose a new index for measuring independence and study its property. Two empirical versions are developed, their properties, asymptotics, connection with existing measures and applications are discussed. Implementation and Monte Carlo results are also presented. We propose a two-stage sufficient variable selections method based on the new index to deal with large p small n data. The method does not require model specification and especially focuses on categorical response. Our approach always improves other typical screening approaches which only use marginal relation. Numerical studies are provided to demonstrate the advantages of the method. We introduce a novel approach to sufficient dimension reduction problems using the new measure. The proposed method requires very mild conditions on the predictors, estimates the central subspace effectively and is especially useful when response is categorical. It keeps the model-free advantage without estimating link function. Under regularity conditions, root-n consistency and asymptotic normality are established. The proposed method is very competitive and robust comparing to existing dimension reduction methods through simulations results.

Recently, covering arrays have been the subject of considerable research attention as they hold both theoretical interest and practical importance due to their applications to testing. In this thesis, we perform the first comprehensive study of a generalization of covering arrays called variable strength covering arrays, where we dictate the interactions to be covered in the array by modeling them as facets of an abstract simplicial complex. We outline the necessary background in the theory of hypergraphs, combinatorial testing, and design theory that is relevant to the study of variable strength covering arrays. We then approach questions that arise in variable strength covering arrays in a number of ways. We demonstrate their connections to hypergraph homomorphisms, and explore the properties of a particular family of abstract simplicial complexes, the qualitative independence hypergraphs. These hypergraphs are tightly linked to variable strength covering arrays, and we determine and identify several of their important properties and subhypergraphs. We give a detailed study of constructions for variable strength covering arrays, and provide several operations and divide-and-conquer techniques that can be used in building them. In addition, we give a construction using linear feedback shift registers from primitive polynomials of degree 3 over arbitrary finite fields to find variable strength covering arrays, which we extend to strength-3 covering arrays whose sizes are smaller than many of the best known sizes of covering arrays. We then give an algorithm for creating variable strength covering arrays over arbitrary abstract simplicial complexes, which builds the arrays one row at a time, using a density concept to guarantee that the size of the resultant array is asymptotic in the logarithm of the number of facets in the abstact simplicial complex. This algorithm is of immediate practical importance, as it can be used to create test suites for combinatorial testing. Finally, we use the Lovasz Local Lemma to nonconstructively determine upper bounds on the sizes of arrays for a number of different families of hypergraphs. We lay out a framework that can be used for many hypergraphs, and then discuss possible strategies that can be taken in asymmetric problems.

Conventional vehicle suspensions consist of a spring and a damper, while mass is rarely used. A mass, if properly used, can also create a damping-like effect. However, a mass has only one terminal which makes it difficult to be incorporated into a suspension. In order to use a mass to achieve the damping-like effect, a two-terminal mass (TTM) has to be designed. However, most of the reported TTMs are of fixed moment of inertia (TTM-CMI), which limits the further improvement of the suspension performance and responsiveness to changes in environment and driving conditions. In this study, a TTM-based vibration absorber with variable moment of inertia (TTM-VMI) is proposed. The main component of the proposed TTM absorber contains a hydraulic-driven flywheel with sliders. The moment of inertia changes with the positions of the sliders in response to the driving conditions. The performance of the proposed TTM-VMI absorber has been analyzed via dynamics modeling and simulation and further examined by experiments. The analysis results indicate that the TTM-VMI absorber outperforms the TTM-CMI design in terms of body displacement; and ride comfort, tire grip and suspension deflection for zero and impulse inputs with comparable performance for sinusoidal input.

La réduction de la consommation des véhicules est un enjeu majeur pour les constructeurs. Parmi les stratégies employées, l’utilisation de lois de levée de soupape variables est en voie de démocratisation.Le premier objectif de cette thèse est de présenter la recherche et le pré dimensionnement d’un mécanisme offrant à la soupape trois levées distinctes : une pour la pleine charge, une pour les faibles charges et une permettant de désactiver un ou plusieurs cylindres pour les charges intermédiaires. Le pré dimensionnement comprend notamment les conditions d’usinabilité des cames, le calcul des ressorts de distribution et la contrainte de pression de contact entre les cames et les poussoirs.Le mode de fonctionnement de ce mécanisme est piloté par la position de deux actionneurs électromagnétiques choisis pour leur temps de réponse faible. Le deuxième objectif de la thèse est de proposer une optimisation afin de réduire leurs dimensions et faciliter leur intégration. Cette optimisation nécessite une modélisation multi-physique (magnétique, électrique, mécanique) du comportement de l’actionneur et permet de définir le profil de commande et les ressorts.Compte tenu du nombre de paramètres d’entrée et du temps de calcul d’une itération, l’optimisation présente un coût de calcul important. Nous présentons donc deux algorithmes de création de modèles de substitution par krigeage. Le premier permet d’approximer une fonction fine dans tout le domaine d’étude à un coût limité. Le second est inclus dans une boucle d’optimisation et n’utilise le modèle fin que lorsque l’approximation n’est pas suffisamment fiable. Ils permettent tout deux de réduire le coût d’optimisation. / Abstract : As the constraint on vehicle consumption tightens, variable valve lift strategies are used to increase engines efficiency. This thesis focuses on issues related to the design of a three-stage electromagnetic valve tappet. First of all, the tappet has to fit inside the engine and has to offer three different valve lifts: a full lift for high speed and torque requirements, a low lift for small loads and a lift allowing cylinder deactivation for medium loads. The tappet dimensioning includes, for example, cams feasibility, spring parameters and contact pressure between cams and tappets. Valve lift selection is made by two electromagnetic actuators in order to obtain a short transition time. Their size, however, hinders their integration. Hence, we realize an optimization aiming to reduce its volume and define the command profile and its return springs. This optimization requires a multi-physics model (electric, magnetic and dynamic) to simulate the actuator behavior. Due to the parameter number and the computational time needed per iteration, the optimization is expensive. Hence we suggest two metamodels algorithms to be used in the optimization. The first algorithm, off-line, is able to create iteratively a predictor precise in the entire domain studied with a lesser cost than Latin Hypercube Sample. The second, in-line, refines the predictor inside the optimization loops and uses it when the predicted error is small.

Das Ziel der Masterarbeit ist es zu klären, ob private Haushalte variable Strompreise akzeptieren und die Stärke der charakteristischen Merkmale zu ermitteln. Der dazu benötigte Datensatz wurde mit Hilfe einer Stated Choice Befragung im Internet ermittelt. Dafür wurden drei Gerätekategorien und ein Dreitarifmodell formuliert. Für die Auswertung wurde ein additiv verknüpftes Teilwert-Nutzenmodell und ein binäres Logit-Choice-Modell verwendet. Signifikante Variablen wurden über das Top-down-Verfahren bestimmt. Das Modell und die Schätzer der Preise wurden im Anschluss durch Hypothesentest getestet. Als signifikante Schätzer, mit stark negativen Werten, stellten sich in allen Kategorien die Preise heraus. Die Hypothesentests ergaben, dass es sinnvoll ist, die Schätzer der Preise für die ersten beiden Gerätetypen zusammenzufassen. Es stellte sich eine unterproportionale Preiselastizität der Nachfrage heraus und eine hohe Akzeptanz ein Teil der Geräte in den Nachtstunden zu nutzen. Insgesamt sprachen sich mehr Teilnehmer für ein Smart-Meter-Gateway aus als dagegen. / The aim of the master thesis is to clarify whether private households accept variable electricity prices and determine the strength of the characteristic attributes. The data set was determined with a Stated Choice survey on the Internet. For this purpose, three device categories and a three-tariff model were formulated. An additive-linked partial-value model and a binary logit choice model were used for the evaluation. Significant variables were determined by using the top-down method. Afterwards the model and the estimators of the prices were tested with statistical hypothesis testings. The price emerged as a significant estimator, with strongly negative values in all categories. The hypothesis tests showed that it is useful to conclude the estimators of the prices for the first two device types. The results showed an inelastic price elasticity of demand and a high acceptance of the subjects to use a part of the devices in the night hours. Overall, more participants decide to use a smart meter gateway than to refuse it.

In many applications, the success probability 𝜋 of a Bernoulli distributed variable 𝑌 is influenced by another variable 𝑋. For example for loans granted, it is necessary to rate debtors in different rating classes, where the probability of default (PD) 𝜋 of 𝑌 is assumed to be homogeneous within and heterogeneous between the rating classes. The PD of a debtor is largely influenced by macroeconomic and individual variables (𝑋). In this work, we study a Bernoulli mixture model for 𝑌, where the success probability of 𝑌 changes systematically at the breakpoints. We focus on cross-sectional data and our main objective is to estimate all 𝑘 breakpoints with 𝑘 either known or unknown and their corresponding success probabilities between each pair of neighbouring breakpoints. To the best of our knowledge, an estimator for estimating multiple breakpoints has not yet been developed in this context. Thus, we develop an approach with a view to closing this research gap. We show that our estimator works for independent and identically distributed (i.i.d.) 𝑋 as well as for a linear one-factor model for 𝑋. A theoretical foundation for this estimator is also presented. In practice, the number of breakpoints 𝑘 is often unknown a priori. As the multiple estimator is based on an iterative procedure, we propose stopping criteria for estimating 𝑘 correctly. We conduct a simulation study in the context of credit rating to demonstrate the performance of the developed estimator. Furthermore, we apply the new estimator on credit risk data from the Sächsische Aufbaubank, the Development Bank of Saxony. To simplify the use of the new estimator, we also develop an R package called MultipleBreakpoints.

The purpose of this thesis is to design the key parameters of the high-powered Walkel engine and to design a chamber side on the base of computed parameters so that it enables variable change of the intake and exhaust port geometry. Consequently, to carry out a flow simulation in both ports in designed chamber side in order to find out its flow character and geometry change reaction.

Dans cette thèse nous nous intéressons à l'étude et à la résolution de problèmes d'optimisation dans le domaine du transport. La première problématique concerne le problème d'élaboration de tournées avec gestion des stocks, et nous considérons dans une seconde partie le problème du voyageur de commerce avec tirant d'eau. Nous avons développé des approches basées sur la recherche à voisinage variable pour résoudre ces problèmes NP-Difficiles, en proposant différentes structures de voisinages et schémas de résolution efficaces. L'évaluation globale des approches proposées sur des instances de la littérature montre leur efficacité. En particulier, nos algorithmes ont amélioré les résultats obtenus par les meilleures approches existantes pour ces deux problèmes. / This thesis deals with the study of optimization problems in the transportation domain. We first address the inventory routing problem and we consider the traveling salesman problem with draft limits in a second part. In both cases we have developed methods based on the variable neighborhood search to solve these NP-hard problems. We have proposed several efficient neighborhood structures and solving frameworks. The global evaluation of the proposed approach on sets of benchmarks available in the litterature shows a remarkable efficency and effectiveness. In particular, our algorithms have improved the results obtained by the current best approaches for these two problems.

Background. Hardware-accelerated ray tracing has enabled ray traced reflections for real-time applications such as games. However, the number of rays traced each frame must be kept low to achieve expected frame rates. Therefore, techniques such as rendering the reflections at quarter resolution are used to limit the number of rays traced each frame. The new hardware features inline ray tracing, and hardware variable rate shading (VRS) could be combined to limit the rays even further. Objectives. The first goal is to use hardware VRS to limit the number of rays even further than rendering the reflections at quarter resolution, while maintaining the visual quality in the final rendered image. The second goal is to determine if inline ray tracing provides better performance than using ray generation shaders. Methods. Experiments are performed on a ray traced reflections pipeline using different techniques to generate rays. The techniques use inline ray tracing, inline ray tracing combined with VRS, and ray generation shaders. These are compared and evaluated using performance tests and the image evaluator \FLIP. Results. The results show that limiting the number of rays with hardware VRS result in a performance increase. The difference in visual quality between using inline ray tracing with VRS and previous techniques remain comparable. The performance tests show that inline ray tracing performs worse than ray generation shaders with increased scene complexity. Conclusions. The conclusion is that hardware VRS can be used to limit the number of rays and achieve better performance while visual quality remain comparable to previous techniques. Inline ray tracing does not perform better than ray generation shaders for workloads similar to ray traced reflections. / Bakgrund. Hårdvaruaccelererad strålspårning har möjliggjort strålspårade reflektioner för realtidsapplikationer såsom spel. Däremot måste antalet strålar som spåras hållas lågt för att förväntade bildfrekvenser ska uppnås. Därför används renderings-tekniker som att rendera reflektioner i en fjärdedels upplösning för att begränsa mängden strålar. De nya teknikerna inline strålspårning och hårdvarubaserad variable rate shading (VRS) kan användas för att minska antalet strålar ytterliggare. Syfte. Det första målet är att använda hårdvarubaserad VRS för att minska antalet strålar ytterligare jämfört med att rendera reflektioner i en fjärdedels upplösning, men samtidigt upprätthålla den visuella kvalitén. Det andra målet är att avgöra om inline strålspårning ger bättre prestanda än att använda strålgenererings shaders för reflektioner. Metod. För att svara på forskningsfrågorna ufördes experiment på en strålspårad reflektionspipeline med olika tekniker för att generera strålar. Teknikerna som testas är inline strålspårning, inline strålspårning kombinerat med VRS, samt strålgenererings shaders. Dessa jämförs och evalueras med prestandatester och bild-evaulatorn \FLIP. Resultat. Resultaten visar att minska mängden strålar med hårdvarubaserad VRS resulterar i en prestandaökning. Skillnaden i visuell kvalité mellan inline strålspårning kombinerat med VRS och tidigare tekniker är jämförbara. Prestandatesterna visar att inline strålspårning presterar värre än strålgenererings shaders vid ökad scenkomplexitet. Slutsatser. Slutsatsen är att hårdvarubaserad VRS kan användas för att minska antalet strålar och resultera i bättre prestanda, medan den visuella kvalitén är jämförbar med tidigare tekniker. Inline strålspårning ger inte bättre prestanda än strålgenererings shaders vid strålspårade reflektioner och liknande arbetsbelastning.