Nous concentrons notre intérêt sur l'Équation du Bilan de la Population (PBE). Cette équation décrit l'évolution, au fil du temps, des systèmes de particules en fonction de sa fonction de densité en nombre (NDF) où des processus d'agrégation et de rupture sont impliqués. Dans la première partie, nous avons étudié la formation de groupes de particules et l'importance relative des variables dans la formation des ces groupes en utilisant les données dans (Vlieghe 2014) et des techniques exploratoires comme l'analyse en composantes principales, le partitionnement de données et l'analyse discriminante. Nous avons utilisé ce schéma d'analyse pour la population initiale de particules ainsi que pour les populations résultantes sous différentes conditions hydrodynamiques. La deuxième partie nous avons étudié l'utilisation de la PBE en fonction des moments standard de la NDF, et les méthodes en quadrature des moments (QMOM) et l'Extrapolation Minimale Généralisée (GME), afin de récupérer l'évolution, d'un ensemble fini de moments standard de la NDF. La méthode QMOM utilise une application de l'algorithme Produit- Différence et GME récupère une mesure discrète non-négative, étant donnée un ensemble fini de ses moments standard. Dans la troisième partie, nous avons proposé un schéma de discrétisation afin de trouver une approximation numérique de la solution de la PBE. Nous avons utilisé trois cas où la solution analytique est connue (Silva et al. 2011) afin de comparer la solution théorique à l'approximation trouvée avec le schéma de discrétisation. La dernière partie concerne l'estimation des paramètres impliqués dans la modélisation des processus d'agrégation et de rupture impliqués dans la PBE. Nous avons proposé une méthode pour estimer ces paramètres en utilisant l'approximation numérique trouvée, ainsi que le Filtre Étendu de Kalman. La méthode estime interactivement les paramètres à chaque instant du temps, en utilisant un estimateur de Moindres Carrés non-linéaire. / We center our interest in the Population Balance Equation (PBE). This equation describes the time evolution of systems of colloidal particles in terms of its number density function (NDF) where processes of aggregation and breakage are involved. In the first part, we investigated the formation of groups of particles using the available variables and the relative importance of these variables in the formation of the groups. We use data in (Vlieghe 2014) and exploratory techniques like principal component analysis, cluster analysis and discriminant analysis. We used this scheme of analysis for the initial population of particles as well as in the resulting populations under different hydrodynamics conditions. In the second part we studied the use of the PBE in terms of the moments of the NDF, and the Quadrature Method of Moments (QMOM) and the Generalized Minimal Extrapolation (GME), in order to recover the time evolution of a finite set of standard moments of the NDF. The QMOM methods uses an application of the Product-Difference algorithm and GME recovers a discrete non-negative measure given a finite set of its standard moments. In the third part, we proposed an discretization scheme in order to find a numerical approximation to the solution of the PBE. We used three cases where the analytical solution is known (Silva et al. 2011) in order to compare the theoretical solution to the approximation found with the discretization scheme. In the last part, we proposed a method for estimate the parameters involved in the modelization of aggregation and breakage processes in PBE. The method uses the numerical approximation found, as well as the Extended Kalman Filter. The method estimates iteratively the parameters at each time, using an non- linear Least Square Estimator.

L’efficacité du système visuel est permise par un complexe réseau d’élaboration, qui s’appuie sur des structures corticales, sous-corticales et périphériques. Le but de la présente recherche est de mieux comprendre le processus de perception visuelle du mouvement, et réaliser un modèle computationnel capable de reproduire les fonctionnalités humaines du tracking (suivi) d'un objet en mouvement. Ce travail de thèse comprend une ample recherche bibliographique, ainsi qu’une série d’expérimentations ; la thèse se compose de deux parties :La première partie a pour objet la détermination des performances dans l’inférence « vers le passé », d’un mouvement partiellement visible. Il s’agit de définir l’implication des informations exogènes (les signaux rétiniens) et endogènes (les modèles internes de l’action observée) dans la reconstruction de la cinématique d’une cible en mouvement et partiellement occultée. Nos résultats supportent l’hypothèse que le Système Nerveux Central adopte un mécanisme basé sur le recours aux modèles internes dans la reconstruction du passé de cinématiques biologiques. La deuxième partie complémente la première, et vise à identifier la structure et les caractéristiques fonctionnelles du système de poursuite, ainsi que à comprendre l’origine des erreurs systématiques présentes dans la localisation d’une cible chez l’homme. Nous avons développé un modèle computationnel en langage Matlab, basé sur le mécanisme d’extrapolation du mouvement, qui est capable de reproduire les données expérimentales dans la tâche de localisation / The effectiveness of the visual system is permitted by a complex processing network, which relies on cortical, sub-cortical and peripheral structures. The purpose of this research is to improve the knowledge of the process sustaining the visual perception of motion, and to produce a computational model able to reproduce the features of human visual tracking of a moving object.This work includes an extensive bibliographic research, and a series of experiments. The thesis consists of two parts:The first part pertains to the determination of performance in the "backward" inference of a partially visible movement. It consist of defining the involvement of exogenous information (retinal signals) and endogenous information (internal models of observed action) in the kinematic reconstruction of a partially hidden trajectory of a moving target. Our results support the hypothesis that the CNS adopts a mechanism based on the use of internal models in the reconstruction of past biological kinematics.The second part complements the first one, and aims to identify the structure and the functional characteristics of the tracking system; it also aims to understand the origin of systematic errors present in the location of a target, in humans.We developed a computational model in Matlab, based on the extrapolation mechanism of movement, which is capable of reproducing the experimental data for the localization task

Ce projet traite de la restitution par Wave Field Synthesis (WFS) d’un champ sonore mesuré par une antenne microphonique. L’importance de la reproduction de champ sonore de milieux industriels ou d’intérieurs de véhicule a pris son essor depuis ces dernières années. Ainsi la capacité de pouvoir synthétiser fidèlement un champ mesuré dans une salle dédiée à l’écoute faciliterait son analyse dans le cadre de mesures objectives (études suivant des métriques prédéfinis) et subjectives (études de perception). La WFS s’impose comme une technologie de reproduction de champ capable d’assurer une grande résolution spatiale, une restitution étendue du champ d’écoute ainsi qu’une bonne précision physique du champ sonore. L’objectif principal est de reproduire un champ fidèle en terme de : 1) réponses en fréquences de la chaîne complète de reproduction, 2) d’erreurs de spectre réduites, 3) bonne restitution du champ d’un point de vue des caractéristiques spatiales. Des simulations appuyées par une campagne expérimentale ont été menées pour valider les algorithmes de restitution proposés et définir l’approche type problème inverse régularisé par formation de voies comme étant le plus performant. Cette recherche est le fruit de deux ans de travaux effectués au Groupe d’Acoustique de l’Université de Sherbrooke (GAUS).

Transfer of drugs into milk and the clearance of drugs in neonates are critical determinants of the exposure of infants to drugs in breast milk. Models predicting both parameters have been proposed. The objective of this dissertation is to test two models predicting milk to serum ratio and an ontogeny clearance model predicting clearance in the neonate. Predicted milk to serum ratio (M/S) values were generated according to the Atkinson and Begg model. The model did not adequately predict M/S when comparing the predicted values to observed values in the literature. The Fleishaker model was also tested. The model was able to predict whether the drugs appeared in milk by passive diffusion only or whether active transport processes were involved. This model, together with appropriate animal models, is useful in understanding the mechanism of drug transfer into milk. An ontogeny model that predicts clearance was proposed earlier by our laboratory. In order to test the model prediction and assumptions of constant microsomal protein and constant Km for an enzyme-substrate system with age, the male rat was used as an animal model. The ontogeny of Cyp3a1, Cyp3a2, Mdr1a and Mdr1b mRNA was examined in the male rat liver and intestine. The ontogeny pattern of Cyp3a2 mRNA, protein and in vitro Cyp3a activity were found to be similar in male rat liver. The microsomal protein content was found to vary with age in the liver. Km was found to be constant with age for the midazolam 4-hydroxylation by male rat liver microsomes. Scaling factors that extrapolate adult clearance to infant clearance were calculated from in vitro data. The model did not predict the in vivo oral clearance of midazolam for day 7 and 21 age groups from the 112 day age group (adult). The assumption that intestinal availability in the rat pups and adults was equal to unity might not be true resulting in overprediction of rat pup clearance when compared to the adult. Intestinal first pass effect for midazolam in adult rats might be significant. More experiments are needed to further test the model adequacy in clearance prediction.

This thesis presents new boundary element formulations for solution of bending problems in plates and shells. Also presented are the dual boundary element formulations for analysis of crack problems in plates and shells. Reissner plate theory is adopted to represent the bending and shear, and two dimensional (2-D) plane stress is used to model the membrane behaviour of the plate. New set of boundary element formulations to solve bending problems of shear deformable shallow shells having quadratic mid-surface is derived based on the modified Reissner plate and two dimensional plane stress governing equations which are now coupled due to the curvature of the shell. Dual Boundary Element Methods (DBEM) for plates and shells are developed for fracture mechanics analysis of structures loaded in combine bending and tension. Five stress intensity factors, that is, two for membrane and three for bending and shear are computed. The JIntegral technique and Crack Surface Displacements Extrapolation (CSDE) technique are used to compute the stress intensity factors. Special shape functions for crack tip elements are implemented to represent mom accurately displacement fields close to the crack tip. Crack growth processes are simulated with an incremental crack extension analysis. During the simulation, crack growth direction is determined using the maximum principal stress criterion. The crack extension is modelled by adding new boundary elements to the previous crack boundaries. As a consequence remeshing of existing boundaries is not required, and using this method the simulation can be effectively performed. Finally, a multi-region boundary element formulation is presented for modelling assembled plate-structures. The formulation enforces the compatibility of translations and rotations as well as equilibrium of membrane, bending and shear tractions. Examples are presented for plate and shell structures with different geometry, loading and boundar-y conditions to demonstrate the accuracy of the proposed formulations. The results obtained are shown to be in good agreement with analytical and other numerical results. Also presented are crack growth simulations of flat and curved panels loaded in combine bending and tension. The DBEM results are in good agreement with existing numerical and experimental results. Assembled plate-structure and a non-shallow shell bending problems are also analysed using a multi-region formulation developed in this thesis.

As câmaras de extrapolação são câmaras de ionização com volume variável e são utilizadas principalmente como detectores de radiação beta. Neste trabalho foram caracterizadas duas câmaras de extrapolação, uma comercial da marca PTW, e uma outra desenvolvida no Laboratório de Calibração do IPEN, para aplicação como sistemas de referência em feixes de mamografia, radiodiagnóstico convencional e radioterapia. Os resultados obtidos nos testes de caracterização da resposta das câmaras de extrapolação: corrente de fuga, estabilidade de curto e médio prazos, determinação das correntes de saturação e das eficiências de coleção de íons, dependência angular e energética, mostram que estas câmaras de extrapolação podem ser utilizadas em dosimetria de feixes de radiação X de energias baixas. Os fatores de transmissão no tecido e os fatores de calibração foram também determinados para todas as qualidades de radiação citadas. Finalmente, foi estabelecido um procedimento de calibração de detectores de radiação em feixes padronizados de radiação X, utilizando as câmaras de extrapolação. / The extrapolation chambers are ionization chambers with variable volume, and they are mainly utilized as beta radiation detectors. In this work two extrapolation chambers were characterized, a commercial PTW extrapolation chamber and another extrapolation chamber developed at the Calibration Laboratory of IPEN, for application as reference systems in mammography, conventional diagnostic radiology and radiotherapy beams. The results obtained from the characterization tests of the chamber response: leakage current, short- and medium terms stability, determination of the saturation currents and the ion collection efficiencies, angular and energy dependence, show that these extrapolation chambers may be utilized for low-energy X radiation beam dosimetry. The transmission factors in tissue and the calibration factors were also determined for all cited radiation qualities. Finally, a procedure was established for calibration of radiation detectors in standard X radiation beams, using the extrapolation chambers.

As câmaras de extrapolação são câmaras de ionização com volume variável e são utilizadas principalmente como detectores de radiação beta. Neste trabalho foram caracterizadas duas câmaras de extrapolação, uma comercial da marca PTW, e uma outra desenvolvida no Laboratório de Calibração do IPEN, para aplicação como sistemas de referência em feixes de mamografia, radiodiagnóstico convencional e radioterapia. Os resultados obtidos nos testes de caracterização da resposta das câmaras de extrapolação: corrente de fuga, estabilidade de curto e médio prazos, determinação das correntes de saturação e das eficiências de coleção de íons, dependência angular e energética, mostram que estas câmaras de extrapolação podem ser utilizadas em dosimetria de feixes de radiação X de energias baixas. Os fatores de transmissão no tecido e os fatores de calibração foram também determinados para todas as qualidades de radiação citadas. Finalmente, foi estabelecido um procedimento de calibração de detectores de radiação em feixes padronizados de radiação X, utilizando as câmaras de extrapolação. / The extrapolation chambers are ionization chambers with variable volume, and they are mainly utilized as beta radiation detectors. In this work two extrapolation chambers were characterized, a commercial PTW extrapolation chamber and another extrapolation chamber developed at the Calibration Laboratory of IPEN, for application as reference systems in mammography, conventional diagnostic radiology and radiotherapy beams. The results obtained from the characterization tests of the chamber response: leakage current, short- and medium terms stability, determination of the saturation currents and the ion collection efficiencies, angular and energy dependence, show that these extrapolation chambers may be utilized for low-energy X radiation beam dosimetry. The transmission factors in tissue and the calibration factors were also determined for all cited radiation qualities. Finally, a procedure was established for calibration of radiation detectors in standard X radiation beams, using the extrapolation chambers.

Melatonin, a nontoxic natural antioxidant, is of interest as a possible spin trap for use in spectroscopic methods to observe and identify short-lived free radicals, which have been linked to oxidative stress that may result in serious health problems. However, the reaction mechanisms for the oxidation of melatonin to form the product N1-acetyl-N2-formyl-5-methoxykynuramine are still not well understood. Computational quantum chemistry studies have been done on four proposed reaction mechanisms, involving the following major intermediate structures: a dioxetane, an epoxide, a melatonin radical cation, and a spin radical adduct. Molecular geometries were optimized at the DFT/B3LYP/cc-pVTZ level of theory, and single point energies were extrapolated to the complete basis set limit at the Hartree-Fock and second-order Møller-Plesset perturbation levels of theory using the cc-pVXZ (X = D, T, Q) basis sets. The lowest energy pathway was found to be the single electron transfer pathway, involving the melatonin radical cation intermediate.

De nos jours, les émulsions doubles se trouvent dans de nombreuses applications dans différents domaines, tels que le domaine alimentaire, les produits cosmétiques, les produits chimiques ou biochimiques. Dans les produits alimentaires par exemple, les émulsions doubles peuvent permettre d’encapsuler des arômes ou de réduire la teneur en matières grasses. La littérature manque cependant de compréhension globale de ces systèmes. La modélisation peut améliorer la compréhension d'un système et permettre d'optimiser les conditions de fonctionnement afin d'améliorer la qualité du produit. Dans ces systèmes, la qualité du produit est déterminée par l'efficacité de l'encapsulation et la distribution de la taille des gouttes internes et externes, qui peuvent affecter la stabilité physique pendant le stockage. L'objectif de ce travail est de réaliser une étude théorique et expérimentale approfondie des phénomènes intervenant à la fois lors de la préparation et du stockage des émulsions doubles. La contribution du travail peut donc être divisée en deux parties. Dans un premier temps, nous étudions les paramètres affectant l’étape de préparation des émulsions doubles et nous proposons des modèles pour les décrire. Trois procédés ont été considérés pour l’émulsification des émulsions doubles, l’ultra-sonication, l’Ultra-Turrax et un réacteur agité. Le modèle est basé sur un modèle de bilan de population des gouttelettes externes, incluant les phénomènes de rupture et de coalescence, associé à un modèle de relargage des gouttes internes. Le relargage des gouttes internes est supposé être régi par la rupture des gouttes externes. Pour être applicables aux différents procédés, les modèles de rupture ont été adaptés aux différentes échelles de turbulence, de dissipation pour ultra-sonication et inertielle pour Ultra-Turrax. La deuxième contribution de ce travail concerne l’étude des phénomènes ayant lieu lors du stockage des émulsions doubles, notamment le gonflement et le relargage des gouttes. Dans ce cas, deux modèles de bilan de population des gouttelettes internes et externes ont été développés, comprenant les phénomènes de gonflement des gouttelettes internes, et donc externes, ainsi que le relagage des gouttelettes internes par diffusion et coalescence avec la phase continue externe. Le modèle de gonflement prend en compte la pression de Laplace qui contrebalance le gradient de pression osmotique et arrête le gonflement. Dans les différentes étapes de préparation ou de stockage, les modèles développés permettent de prédire les distributions de la taille des gouttelettes et le taux de libération / Double emulsions can nowadays be found in a number of applications in different domains, like food, cosmetics, chemicals or biochemical. In food for instance, double emulsions may allow to encapsulate flavors or reduce the fat content. Yet, the literature is still lacking a comprehensive understanding of these systems. Modelling may improve the understanding of a system and allow optimizing the operating conditions in order to improve the product quality. In these systems, the product quality is determined by the encapsulation efficiency and the inner and outer droplet size distribution, which may affect the physical stability during storage. The objective of this work is to handle theoretical and experimental investigations of the phenomena occurring during both the preparation and the storage of double emulsions. The contribution of the work can therefore be divided into two parts. First of all, investigations of the parameters affecting the preparation step of double emulsions are handled, and models are proposed to describe them. Three processes were considered for the emulsification of the double emulsions, ultrasonication, Ultra-Turrax and a stirred vessel. The model is based on a population balance model of the outer droplets, including the kernels of breakage and coalescence combined with a leakage model of the inner droplets. The leakage of inner droplets is assumed to be governed by the breakage of the outer droplets. In order to be applicable in the different processes, the breakage models were adapted to different scales of turbulence, the dissipation subrange for ultrasonication and the inertial subrange for the Ultra-Turrax. The second contribution of the work concerns the investigation of the phenomena taking place during the storage of the double emulsions, including swelling and release. In this case, two population balance models of the inner and outer droplets were considered, including the phenomena of swelling of the inner, and so of the outer, droplets as well as the escape of the inner droplets by diffusion and coalescence with the external continuous phase. The swelling model takes into account the Laplace pressure that counterbalances the osmotic pressure which is the driving force for swelling. In the different steps of preparation or storage, the developed models allow the prediction of the droplet size distributions and the release rate

O problema da dosimetria beta está ligado a indivíduos que manipulam fontes radioativas a pequenas distâncias ou em contato. O objetivo principal da dosimetria beta é a determinação da dose na pele e no cristalino do olho. A câmara de extrapolação Böhm foi caracterizada em feixes de radiação beta das fontes de 85Kr e 147Pm e ela foi estabelecida como sistema de padronização primária. Foram determinadas as taxas de dose absorvida no ar e no tecido à profundidade nula e de 0,07 mm das fontes de 85Kr e 147Pm e os seus fatores de transmissão. Além disso, foi caracterizado e estabelecido um sistema de transferência ou método alternativo/complementar de dosimetria beta. Foram aplicadas as técnicas de termoluminescência e de luminescência opticamente estimulada, para a caracterização de detectores de SOL-GEL α-Al2O3 em campos padrões de radiação beta, e foram determinados os parâmetros cinéticos do processo termoluminiscente. O material estudado mostrou-se adequado para a dosimetria beta. Foi estabelecido um modelo computacional pelo método Monte Carlo para a câmara de extrapolação e para as fontes de radiação; foram determinadas as taxas de dose absorvida, os fatores de correção de Bremsstrahlung, os fatores de correção pelo retroespalhamento do eletrodo coletor e do anel de guarda da câmara de extrapolação e os fatores de dependência angular. Para o sistema de transferência de dosimetria beta, foram determinados os fatores de correção pela atenuação no ar e o espalhamento da radiação no suporte de irradiação dos detectores pelo método Monte Carlo. Todas os testes de caracterização, assim como o modelo de Monte Carlo, foram também realizados e implementados com a fonte de 90Sr/90Y por ser a fonte de referência da radiação beta e para fins comparativos. / The problem of beta dosimetry is linked to individuals who manipulate radioactive sources at small distances or in contact. The main objective of beta dosimetry is to determine the dose on the skin and in the lens of the eye. The Böhm extrapolation chamber was characterized in beta radiation beams from 85Kr and 147Pm sources, and a primary standard system was established. The absorbed dose rates in air and tissue at null depth and at 0.07 mm for 85Kr and 147Pm sources and the transmission factors were determined. In addition, a transfer system or alternative/complementary beta dosimetry method was characterized and established too. The thermoluminescence and optically stimulated luminescence techniques were applied for the characterization of the SOL-GEL α-Al2O3 detectors in standard beta radiation fields, and the kinetic parameters of the thermoluminescent process were determined. The studied material was shown to be suitable for beta dosimetry. A model by the Monte Carlo method for the extrapolation chamber and the radiation sources was established. The absorbed dose rates, the Bremsstrahlung correction factors, the correction factors for the backscattering of the collecting electrode and the guard ring of the extrapolation chamber, and the angular dependence factors were determined. For the beta dosimetry transfer system, the correction factors by attenuation in air and the scattering of the radiation in the irradiation holder of the detectors were determined by the Monte Carlo method. All the characterization and tests, as well as the Monte Carlo model, were performed and implemented with the 90Sr/90Y source, because it is the reference source for beta radiation and for comparative purposes.