Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 145-160).

Thesis--Catholic University of America. / Bibliography: leaves 120-129.

Th. 3e cycle--Sci. pour les ind. chim.--Nancy--I.N.P.L., 1983.

Dielectric dispersion has been observed in the symmetric-top molecules CHF₃ and CH₃­F in the gas phase over a density range from 10­³ to 40 amagats at a temperature of 309°K and a frequency of 30 MHz. The absorption (related to the dispersion by the Kramers-Kronig relations) has been expressed in terms of a simple correlation function of the permanent electric dipole moment which is the product of the correlation function for free motion and an exponentially decaying "reduced" correlation function. The effects of molecular collisions were described by a single correlation time which measures the apparent molecular diameter. The results were compared with microwave nonresonant absorption and nuclear spin relaxation experiments done on the same molecules. At low densities (<.l amagats) a dispersion curve of the Debye type was observed. At high densities (>1 amagat) the dependence of the dielectric susceptibility on density deviated from that expected from the Clausius-Mossotti equation. The origin of this effect is not understood at present. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

Ce travail de thèse porte sur deux parties relativement distinctes de problématiques liées à l'optimisation de forme. Dans la première moitié de cette thèse, nous développons une librairie permettant la modélisation et l'optimisation de problèmes issus du calcul des variations. Nous illustrons l'efficacité de cet outil en l'appliquant à des exemples variés : le contrôle optimal, le problème de Steiner, le problème des surfaces minimales et enfin la régularisation de contours discrets par minimisation de l'énergie de Willmore. Dans une deuxième partie nous nous intéressons à la mise en œuvre d'un processus de génération aléatoire d'objets de largeur constante en dimension quelconque. La motivation d'un tel travail repose sur la conjecture de Meissner qui est un problème de géométrie convexe ouvert depuis le début du siècle dernier. / This thesis is dedicated to the regularization of discrete images by the minimization of second order energies. More precisely, assuming that the original image is a digital picture of a smooth object, we propose to reconstruct its boundary by the minimization of Willmore's energy under suitable constraints given by the image.Our objective in the present work is to extend their approach in three different directions:• the efficient reconstruction of 3D objects,• the reconstruction of cartoons images,• none smooth objects, sharp edges.

Le procédé de grenaillage permet d’améliorer la durée de vie en fatigue des pièces mécaniques dans l’industrie. La mise en compression de la surface par les billes introduit un gradient de déformations inélastiques hétérogènes qui engendre un champ de contraintes résiduelles. Ce sont principalement ces contraintes résiduelles de compression qui sont à l’origine du gain de durée de vie. Les contraintes résiduelles générées évoluent lors des sollicitations thermomécaniques des composant mécaniques après grenaillage. La relaxation et la fatigue ont été étudiées à l’échelle des phases sur l’acier de type TRIP780, acier multiphasé (ferrite, bainite, austénite) possédant une phase austénitique résiduelle susceptible de se transformer en martensite sous un chargement thermomécanique. Pour cet acier, le gain de durée de vie dû au grenaillage est dépendant de la stabilité des contraintes résiduelles de compression dans les différentes phases au cours des chargements mécaniques généralement cyclique. Des essais de flexion cycliques ont été réalisés sur des éprouvettes planes afin de déterminer les durées de vie en fonction des conditions de grenaillage. Avec l’aide d’essais cycliques interrompus, l’évolution des profils de contraintes, de dosage de phase et des largeurs intégrales ont été caractérisée par diffraction des rayons X dans les phases ferritiques et austénitique montrant ainsi la relaxation des contraintes résiduelles en fonction du chargement mécanique appliqué (niveau des contraintes et nombre de cycles). A partir de ces différents résultats, des simulations utilisant la méthode des éléments finis ont été développées pour prédire la relaxation. Après génération numérique des champs de contraintes dans l’éprouvette (méthode thermique fictive), des modèles de comportement élastoplastiques globaux et par phases ont été proposés dans le cas de faibles nombres de cycle. Dans une dernière partie, un post-traitement global par critère de fatigue multiaxial de type Crossland intégrant les résultats sur la relaxation a été proposé. Les résultats ont alors été comparés aux courbes expérimentales de fatigue. / Shot peening process aim at enhancing life duration of mechanical parts in industry. Balls introduce a compressive state on the surface of the part by strain hardening the subsurface which must be accommodated by elastic strain. Compressive residual stresses are mainly the origin of the enhancing life duration. These residual stresses evolve during thermomechanical solicitations after shot-peening. Relaxation and life duration are studied at the phase scale in the TRIP780 steel – a multiphased steel (bainite, ferrite and austenite) owning a metastable austenitic phase which can transform in martensite under thermomechanical solicitations. In this steel, life duration gain depends on the compressive residual stresses stability in the different phases during cyclic loads. Bending test were carried out on thick samples to determine life duration in function of shot-peening conditions. With interrupted cyclic test, the evolution of the residual stress profile, phase partition and integral width were characterized by X-ray diffraction in ferritic and austenite phases showing the relaxation of residual stresses following the mechanical loads (loading level and number of cycle). With these experimental results, finite element simulations were carried out to forecast the relaxation. After residual stress numerical generation (fictive thermal method), global and by-phase comportment models were proposed in the case of the low number cycles. In the last part, a post-treatment by multiaxial fatigue criterion like Crossland one integrating relaxation results was proposed. The results were compared to the experimental fatigue curves.

O papel das tÃcnicas de relaxamento fÃsico e mental no controle da pressÃo arterial permanece mal definido em funÃÃo de aspectos como efeito placebo, nÃmero pequeno de estudos com grandes populaÃÃes e dificuldades tÃcnicas e metodolÃgicas. Este estudo examinou o impacto de uma sessÃo de relaxamento fÃsico e mental sobre a pressÃo arterial de 64 pacientes portadores de hipertensÃo arterial grau I. Os pacientes foram divididos em 2 grupos. O primeiro grupo foi constituÃdo per 41 pacientes que alÃm do relaxamento usaram medicaÃÃo antihipertensiva (betabloqueadores ou diurÃticos). O segundo foi composto per 23 pacientes que sà realizaram o relaxamento. A pressÃo arterial dos pacientes foi aferida atravÃs de um sistema de monitorizaÃÃo ambulatorial da pressÃo arterial (MAPA) nas 24 horas subsequentes ao relaxamento. Os resultados mostraram que houve reduÃÃo da pressÃo arterial sistÃlica e diastÃlica nos dois grupos (PAS=27mmHg PAD=20mmHg no primeiro grupo e PAS=20mmHg e PAD=15mmHg no segundo) com valores mais acentuados no grupo que usou medicaÃÃo hipotensora. NÃs concluÃmos que as tÃcnicas de relaxamento reduziram os nÃveis da pressÃo arterial em valores que variaram em funÃÃo do fenÃmeno estresse de IigaÃÃo. Recomendamos novos estudos comparando intervenÃÃes comportamentais e farmacolÃgicas combinadas, alÃm de se procurar delinear a magnitude do efeito placebo e determinar a influencia das caracterÃsticas de personalidade dos pacientes nos resultados obtidos. / The role of the phisical and mental relaxation thecnics in blood pressure control remains ill-defined because of placebo effects, small study numbers and technical and methodological limitations. This study examined the impact of a phisical and mental relaxationâs session on the blood pressure of 64 subjects with hipertension type I. The patients were alocated in 2 groups. The first one with 41 subjects that used antihypertensive medication (betablockers or diuretics) and relaxation; the second group with 23 patients that used only relaxation technics. Blood pressure was evaluated using a 24-hr ambulatory blood pressure monitoring (ABPM). Results showed blood pressure reduction of the components sistolic and diastolic in the two groups. The results were improved in the first group. (SBP=27mmHg DBP=20mmHg and SBP=20mmHg DBP=15mmHg) We concluded that the relaxation technics reduced blood pressure with a large variation because the linkstress phenomenon. We recomend future research with combined behavioral and pharmacological interventions and further explorations trying to determine the capability of placebo effects and personality characteristics to alter the outcome.

No description available.