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Thèse (M.Sc.)--Université Laval, 2007. / Bibliogr.: f. 180-185. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

Th. doct.--Paris--École supérieure des mines, 2001. / Bibliogr. p. 131-135. Résumé en français et en anglais. L'ouvrage porte par erreur : ISSN 0078-3780.

Orientador: José Carlos Peraçoli / Coorientador: Maria Teresinha de Oliveira Cardoso / Banca: Adriano Bueno Tavares / Banca: Francisco Diogo Rios Mendes / Resumo: A taxa de sucesso de ovulação com uso do citrato de clomifene é excelente, alcançando valores entre 80% e 85%, porém a taxa de gravidez é de apenas 20% a 40%. Quando o citrato de clomifene é usado como indutor de ovulação, em mulheres portadoras de síndrome dos ovários policísticos, a literatura não define qual o momento ideal de ruptura folicular que se correlaciona com sucesso de gravidez. Identificar o diâmetro de ruptura folicular de pacientes com síndrome de ovários policísticos (SOP) estimuladas com citrato de clomifeno que melhor se correlacione com ocorrência de gravidez. Estudo corte transversal realizado entre janeiro a dezembro de 2010, que incluiu 104 pacientes com ciclos ovulatórios após uso de citrato de clomifeno, acompanhadas com ultrassonografia até determinar-se o diâmetro de ruptura folicular, que foi posteriormente correlacionado com a ocorrência ou não de gravidez. Para o estudo da associação entre as variáveis aplicou-se o teste do qui-quadrado e para as variáveis quantitativas a análise de variância seguida do método de Tukey ou teste t de Student, com valor de p <0,05. No grupo de pacientes com ruptura folicular com menos de 25 mm (n: 54) a taxa de gravidez foi de 35,2% e no grupo com ruptura folicular com mais de 25 mm (50) essa taxa foi de 34%, sem diferencia estatística significativa. Quando relacionamos aleatoriamente os diferentes diâmetros de ruptura folicular com a ocorrência de gravidez também não houve diferença significativa. O presente estudo permitiu concluir que, a taxa de gravidez de mulheres portadoras de síndrome dos ovários policísticos estimuladas com citrato de clomifene, não tem correlação com o diâmetro de ruptura folicular / Abstract: The success rate of ovulation using clomiphene citrate is excellent, reaching values between 80% and 85%, but the pregnancy rate is only 20% to 40%. When clomiphene citrate is used to induce ovulation in women with polycystic ovary syndrome (PCOS), the literature does not define what the optimal timing of follicular rupture that correlates with successful pregnancy is. To identify the diameter of follicular rupture in patients with PCOS stimulated with clomiphene citrate that best correlates with the occurrence of pregnancy. Cross-sectional study conducted between January and December 2010, which included 104 patients with ovulatory cycles after the use of clomiphene citrate, followed by ultrasound to determine the diameter of follicular rupture, which was later correlated with the occurrence of pregnancy or not. To the study of the association between variables the chi-square test for quantitative variables and the analysis of variance followed by Tukey's method or Student's t test, with p <0.05 was applied. In patients with follicular rupture less than 25mm (n = 54) the pregnancy rate was 35.2%, in the group with follicular rupture with more than 25mm (50) this rate was 34%, no statistically significant difference was found. When relating the different diameters of randomly follicular rupture with the occurrence of pregnancy there was no significant difference. This study concluded that the pregnancy rate of women with PCOS stimulated with clomiphene citrate does not correlate with the diameter of follicular rupture / Mestre

L'objectif de ce travail de thèse a été de modéliser avec une méthode aux éléments discrets la fracturation en tension, et plus particulièrement la fragmentation dynamique, sur des matériaux fragiles pour de hautes vitesses de déformation. La fragmentation est un phénomène irréversible, non linéaire et aléatoire. Elle intervient dans de nombreux domaines de la vie courante, quelque soit l'échelle considérée. La modélisation numérique de ce phénomène permettrait une prédiction de certains paramètres statistiques de la fragmentation, comme le nombre de fragments, la taille des fragments, la distribution de la taille des fragments, etc. Pour cette thèse, la Méthode des Éléments Discrets (DEM) s'est révélée être un excellent moyen pour simuler la fracturation en raison de sa nature discrète. Toutefois, une bonne méthode de simulation numérique ne suffit pas à elle seule pour modéliser la fragmentation dynamique. Un critère de rupture doit également être inséré, afin d'introduire un endommagement. Ce critère de rupture s'écrit au niveau d'un lien entre deux particules et il engendre un dommage, en faisant décroître la contrainte locale jusqu'à l'obtention d'une fissuration discrète. Dans un premier temps, un critère de rupture de Camacho-Ortiz |24| a été introduit dans une méthode aux éléments discrets. Ce critère se traduit par un endommagement en fonction d'une ouverture de fissure. Ce premier critère a donné de bons résultats comparé à ceux de |69, 88, 97, 143-147| sur la convergence des paramètres de la fragmentation sur des cas simples, mais nécessite un grand nombre de particules. Dans un second temps, afin d'envisager la modélisation de la fragmentation sur des cas plus complexes en trois dimensions à de hautes vitesses de déformation, un second critère de rupture a été introduit. Ce critère de rupture s'appuie sur une approche physique différente, qui prend en compte l'hétérogénéité des matériaux fragiles avec leurs défauts susceptibles d'évoluer et de provoquer une rupture locale. Pour cela, il fait intervenir une loi probabiliste de Weibull afin d'introduire des défauts par élément de volume. Ce critère a été développé par C. Denoual, P. Forquin et F. Hild |29, 33, 42-44|. Tout d'abord, ce second critère de rupture a été testé sur des cas simples en obtenant une convergence des paramètres statistiques de la fragmentation avec un nombre environ $10$ fois moins important de particules que pour la première méthode. Un cas plus complexe en trois dimensions de modélisation de barre d'Hopkinson en trois dimensions a permis de tester de manière « qualitative » la méthode. / The objective of this thesis work is to model the high-strain rate and dynamic fragmentation of brittle materials using the Discrete Element Method. Fragmentation is an irreversible, nonlinear and random phenomenon.It can be found in many practical applications in engineering and can take place at various length scales. This research work takes advantages of computer simulations to model this phenomenon and to predict a few statistical parameters related to fragmentation including number, size, and size distribution of fragments. To this effect, the Discrete Element Method was found to simulate efficiently fracturing, which is a discrete phenomenon by nature. However, an efficient computer simulation is not sufficient for representing fragmentation. It also needs to account for a rupture criterion and a damage criterion. This rupture criterion is defined at the contact points between particles where it generates a local damage that decreases the local stress until a discrete crack appears. In a first step, the rupture criterion of Camacho-Ortiz |24| has been introduced in the Discrete Element Method. This criterion expresses damage as a function of crack opening. When the local stress reaches a rupture threshold, it decreases linearly with the crack opening until the rupture is obtained. This first criterion gives good results on the convergence of fragmentation parameters in simple cases |69, 88, 97, 143-147|, but requires a great number of particles. In a second step, another rupture criterion has been introduced for simulating the fragmentation of more complex three-dimensional structures for high-strain rates. This rupture criterion is based on a different physical approach that accounts for heterogeneous brittle materials with defects. These defects can evolve and cause local failure. They are introduced per unit volume elementusing a Weibull probability distribution |29, 33, 42-44|. This distribution depends on the local stress until the local stress reaches an activation threshold. After that, the defects propagate and form areas of relaxation in which defect cannot evolve. The damage evolves as these areas of relaxation evolve. This second rupture criterion has been validated in simple cases by examining the convergence of the statistical parameters of fragmentation. Compared to the first criterion, the second criterion requires ten times fewer particles. After, a more complex three-dimensional case, dynamic tensile tests in Hopkinson bars, has been treated.

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Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

New Insights on the Uncertainties in Finite-Fault Earthquake Source Inversion Hoby Njara Tendrisoa Razafindrakoto Earthquake source inversion is a non-linear problem that leads to non-unique solutions. The aim of this dissertation is to understand the uncertainty and reliability in earthquake source inversion, as well as to quantify variability in earthquake rupture models. The source inversion is performed using a Bayesian inference. This technique augments optimization approaches through its ability to image the entire solution space which is consistent with the data and prior information. In this study, the uncertainty related to the choice of source-time function and crustal structure is investigated. Three predefined analytical source-time functions are analyzed; isosceles triangle, Yoffe with acceleration time of 0.1 and 0.3 s. The use of the isosceles triangle as source-time function is found to bias the finite-fault source inversion results. It accelerates the rupture to propagate faster compared to that of the Yoffe function. Moreover, it generates an artificial linear correlation between parameters that does not exist for the Yoffe source-time functions. The effect of inadequate knowledge of Earth’s crustal structure in earthquake rupture models is subsequently investigated. The results show that one-dimensional structure variability leads to parameters resolution changes, with a broadening of the posterior 5 PDFs and shifts in the peak location. These changes in the PDFs of kinematic parameters are associated with the blurring effect of using incorrect Earth structure. As an application to real earthquake, finite-fault source models for the 2009 L’Aquila earthquake are examined using one- and three-dimensional crustal structures. One- dimensional structure is found to degrade the data fitting. However, there is no significant effect on the rupture parameters aside from differences in the spatial slip extension. Stable features are maintained for both structures. In the last part of this work, a multidimensional scaling method is presented to compare and classify earthquake slip distributions. A similarity scale to rank them are thus formulated. Dissimilarities among slip models (from various parameterizations) are computed using two different distance metrics, normalized squared and gray-scale metrics. Multidimensional scaling is then used to visualize the differences among the models. The analyzes are done for 2 case studies; one based on artificial scenarios with a known answer and another one based on the published rupture models of the 2011 Tohoku earthquake.

We investigate the influence of rupture complexity on directivity effects. We consider, in particular, how variations in the hypocenter location, the slip distribution and the rupture speed affect the amplitudes of near-field directivity pulses. To that end, we generate a suite of 15 bilateral-rupture models for an Mw 7 event and simulate the corresponding velocity waveforms at a number of sites in the vicinity of the fault. To quantify the influence of the hypocenter location and the rupture speed, we rely on a measure of the isochrone velocity on the fault along a path we term the “closest path”. Our simulations reveal that the peak amplitudes of the directivity pulses largely correlate with the isochrone velocity and that both increase with increasing rupture speed. We also examine the effect of the slip distribution and conclude that the presence of a region of high slip along the “closest path” leads to the amplification of the directivity pulse. Our findings primarily serve to inform empirical ground motion models on the rupture parameters of relevance to directivity.