Résolution du contact frottant déformable-déformable par lagrangien augmenté et GCR préconditionné

Ce document traite le problème de l’élasticité en grandes déformations avec contact frottant. Dans le premier chapitre, nous présentons un rappel des lois auxquelles nous ferons référence : lois de comportement matériau, conditions aux limites, contact et frottement selon la loi de Coulomb. Le coeur de la thèse commence par la discrétisation des conditions de bord. L’imposition en moyenne de la non-pénétration et de la loi de Coulomb est explicitée dans le but de se ramener en dimension finie. C’est dans ce domaine que les algorithmes sont développés. Les conditions d’optimalité sont donc calculées pour le problème déjà discrétisé et sont linéarisées par la suite selon le paradigme des contraintes actives. Suivant cette stratégie, l’état de contact est fixé à chaque itération de la méthode de Newton, transformant les conditions de contact en contraintes d’égalité. Le système de conditions d’optimalité ainsi obtenu peut alors être linéarisé. La résolution de ce nouveau système linéaire constitue l’autre partie importante de cette thèse. Les méthodes de pénalisation et d’Uzawa sont d’abord exposées ; elles serviront de point de comparaison. Nous construisons par la suite un algorithme basé sur un GCR préconditionné par une factorisation faisant apparaître un complément de Schur. Le tout est présenté d’abord dans le cas plus simple du contact sans frottement, puis en ajoutant le frottement. Des résultats numériques, parfois académiques (des cubes) et parfois industriels (des lamelles de pneus), viennent finalement appuyer les convictions que non seulement ces méthodes sont rapides, mais qu’elles sont aussi robustes.This thesis addresses the problem of large deformation elasticity with frictional contact. In the first chapter, we recall the laws to which we refer: material behavior laws, boundary conditions, contact and friction according to Coulomb’s law. The heart of the thesis begins with the discretization of boundary conditions. Mortar formulations for non-penetration and Coulomb’s law are explained in order to set the problem in a finite dimensional space. Optimality conditions are calculated for the discretized problem and are subsequently linearized according to the paradigm of active set strategy. Under this approach, the contact state is set at each iteration of Newton’s method, transforming the contact conditions in equality constraints. The system of optimality conditions thus obtained can then be linearized. The resolution of this new linear system is another important part of this thesis. Methods of penalization and Uzawa are first exposed; they serve as a comparison point. Thereafter, we introduce a preconditioned GCR algorithm based on a factorization using a Schur complement. The whole problem is presented first in the simplest case of contact without friction, and, in the last chapter, with friction. Numerical results, sometimes academic (cubes) and sometimes industrial (slides tires) finally support the belief that not only these methods are efficient, but they are also robust

Measuring Patient and Clinician Perspectives to Evaluate Change in Health-Related Quality of Life Among Patients with Chronic Obstructive Pulmonary Disease

CONTEXT: Many treatments aim to improve patients’ health-related quality of life (HRQoL), and many care guidelines suggest assessing symptoms and their impact on HRQoL. However, there is a lack of consensus regarding which HRQoL outcome measures are appropriate to assess, and how much change on those measures depict significant HRQoL improvement. OBJECTIVE: We used triangulation methods to identify and understand clinically important differences (CIDs) for the amount of change in HRQoL that reflects both health professionals and patients’ values, among patients with chronic obstructive pulmonary disease (COPD). DESIGN, SETTING, AND PARTICIPANTS: We incorporated three perspectives: (1) an expert panel of physicians familiar with the measurement of HRQoL in COPD patients; (2) 610 primary care COPD outpatients who completed baseline and bimonthly follow-up HRQoL interviews over the 12-month study; and (3) the primary care physicians (PCPs; n = 43) of these outpatients who assessed their patients’ disease at baseline and at subsequent PCP visits during the year long study. MEASUREMENTS: The Chronic Respiratory Disease Questionnaire (CRQ), the Medical Outcomes Study Short Form 36-item survey (SF-36, version 2.0), and global assessments of change from each of the three perspectives for all HRQoL domains. RESULTS: With few exceptions, the CRQ was able to detect small changes at levels reported by the patients (1–2 points) and their PCPs (1–5 points). These results confirm minimal important difference standards developed in 1989 by Jaeschke et al. anchored on patient-perceived changes in HRQoL. In general, the expert panel and PCP CIDs were larger than the patient CIDs. CONCLUSION: This triangulation methodology yielded improved interpretation, understanding, and insights on stakeholder perspectives of CIDs for patient-reported outcomes

ICE COLD ERIC – International collaborative effort on chronic obstructive lung disease: exacerbation risk index cohorts – Study protocol for an international COPD cohort study

<p>Abstract</p> <p>Background</p> <p>Chronic Obstructive Pulmonary Disease (COPD) is a systemic disease; morbidity and mortality due to COPD are on the increase, and it has great impact on patients' lives. Most COPD patients are managed by general practitioners (GP). Too often, GPs base their initial assessment of patient's disease severity mainly on lung function. However, lung function correlates poorly with COPD-specific health-related quality of life and exacerbation frequency. A validated COPD disease risk index that better represents the clinical manifestations of COPD and is feasible in primary care seems to be useful. The objective of this study is to develop and validate a practical COPD disease risk index that predicts the clinical course of COPD in primary care patients with GOLD stages 2–4.</p> <p>Methods/Design</p> <p>We will conduct 2 linked prospective cohort studies with COPD patients from GPs in Switzerland and the Netherlands. We will perform a baseline assessment including detailed patient history, questionnaires, lung function, history of exacerbations, measurement of exercise capacity and blood sampling. During the follow-up of at least 2 years, we will update the patients' profile by registering exacerbations, health-related quality of life and any changes in the use of medication. The primary outcome will be health-related quality of life. Secondary outcomes will be exacerbation frequency and mortality. Using multivariable regression analysis, we will identify the best combination of variables predicting these outcomes over one and two years and, depending on funding, even more years.</p> <p>Discussion</p> <p>Despite the diversity of clinical manifestations and available treatments, assessment and management today do not reflect the multifaceted character of the disease. This is in contrast to preventive cardiology where, nowadays, the treatment in primary care is based on patient-specific and fairly refined cardiovascular risk profile corresponding to differences in prognosis. After completion of this study, we will have a practical COPD-disease risk index that predicts the clinical course of COPD in primary care patients with GOLD stages 2–4. In a second step we will incorporate evidence-based treatment effects into this model, such that the instrument may guide physicians in selecting treatment based on the individual patients' prognosis.</p> <p>Trial registration</p> <p>ClinicalTrials.gov Archive NCT00706602</p

An Overview on Principles for Energy Efficient Robot Locomotion

Despite enhancements in the development of robotic systems, the energy economy of today's robots lags far behind that of biological systems. This is in particular critical for untethered legged robot locomotion. To elucidate the current stage of energy efficiency in legged robotic systems, this paper provides an overview on recent advancements in development of such platforms. The covered different perspectives include actuation, leg structure, control and locomotion principles. We review various robotic actuators exploiting compliance in series and in parallel with the drive-train to permit energy recycling during locomotion. We discuss the importance of limb segmentation under efficiency aspects and with respect to design, dynamics analysis and control of legged robots. This paper also reviews a number of control approaches allowing for energy efficient locomotion of robots by exploiting the natural dynamics of the system, and by utilizing optimal control approaches targeting locomotion expenditure. To this end, a set of locomotion principles elaborating on models for energetics, dynamics, and of the systems is studied

A Selective Sampling Strategy for Label Ranking

We propose a novel active learning strategy based on the compression framework of [9] for label ranking functions which, given an input instance, predict a total order over a predefined set of alternatives. Our approach is theoretically motivated by an extension to ranking and active learning of Kääriäinen’s generalization bounds using unlabeled data [7], initially developed in the context of classification. The bounds we obtain suggest a selective sampling strategy provided that a sufficiently, yet reasonably large initial labeled dataset is provided. Experiments on Information Retrieval corpora from automatic text summarization and question/answering show that the proposed approach allows to substantially reduce the labeling effort in comparison to random and heuristic-based sampling strategies

Novel Plant Virus-Based Vaccine Induces Protective Cytotoxic T-Lymphocyte-Mediated Antiviral Immunity through Dendritic Cell Maturation▿

Currently used vaccines protect mainly through the production of neutralizing antibodies. However, antibodies confer little or no protection for a majority of chronic viral infections that require active involvement of cytotoxic T lymphocytes (CTLs). Virus-like particles (VLPs) have been shown to be efficient inducers of cell-mediated immune responses, but administration of an adjuvant is generally required. We recently reported the generation of a novel VLP system exploiting the self-assembly property of the papaya mosaic virus (PapMV) coat protein. We show here that uptake of PapMV-like particles by murine splenic dendritic cells (DCs) in vivo leads to their maturation, suggesting that they possess intrinsic adjuvant-like properties. DCs pulsed with PapMV-like particles displaying the lymphocytic choriomeningitis virus (LCMV) p33 immunodominant CTL epitope (PapMV-p33) efficiently process and cross-present the viral epitope to p33-specific transgenic T cells. Importantly, the CTL epitope is also properly processed and presented in vivo, since immunization of p33-specific T-cell receptor transgenic mice with PapMV-p33 induces the activation of large numbers of specific CTLs. C57BL/6 mice immunized with PapMV-p33 VLPs in the absence of adjuvant develop p33-specific effector CTLs that rapidly expand following LCMV challenge and protect vaccinated mice against LCMV infection in a dose-dependent manner. These results demonstrate the efficiency of this novel plant virus-based vaccination platform in inducing DC maturation leading to protective CTL responses