Cette thèse porte sur l'étude de milieux granulaires constitués de particules molles. Elle s'appuie d'une part sur la méthode de corrélation d'images numériques (DIC) et d'autre part sur des simulations associant la méthode des éléments finis (FEM) et la méthode de Dynamique des Contacts (CD) permettant de tenir compte de la déformabilité élevée des particules et des interactions entre particules. Pour une large gamme de matériaux complexes (élastique, plastique et mousse solide), l'étude préliminaire de particules uniques comprimées radicalement valide la technique de DIC pour les mesures des champs de déformation, et pour la détermination de l'énergie de déformation pour des matériaux élastiques. Des grandeurs macroscopiques et micro-structurales tels que la compacité, la coordinence, l'énergie élastique, la densité de la probabilité de force de contact ainsi que de la densité d'énergie sont mesurées, et comparées entre les résultats numériques et expérimentaux en particulier dans le régime où les déformations des particules sont d'amplitudes finies. L'accord quantitatif entre ces approches permet de valider à la fois la méthode expérimentale pour l'étude de milieux granulaires à particules déformables, et d'autre part l'approche numérique. Forts de ces résultats, nous avons mené une étude numérique de la compression uniaxiale d'un assemblage de cylindres Néo-Hookéens. L'effet du frottement sur les paramètres macroscopiques et mico-structuraux est déterminé, y compris lorsque la compacité du système est proche de 100% / This thesis deals with the study of granular media composed of soft particles. It relies on the one hand on the method of Digital Image Correlation(DIC) and on the other hand, on simulations coupling the Finite Element Method and the Contact Dynamics method, taking into account the high deformability of particles and interactions between particles. For a wide range of complex materials (elastic, plastic and solid foam), the preliminary study of radially compressed single particles validates the DIC technique for strain field measurements, and for the determination of the strain energy for elastic materials. Macroscopic and micro-structural quantities such as packing fraction, coordination, elastic energy, probability density of the contact force as well as strain energy density, are measured and compared between the numerical and experimental results in particular in the regime where the deformations of the particles are large. The quantitative agreement between these approaches makes it possible to validate both the experimental method for the study of granular media with deformable particles, and the numerical approach. Based on these results, we conducted a numerical study of the uniaxial compression of a Neo-Hookean cylinder assembly. The effect of friction on the macroscopic and mico-structural parameters is determined, even when the packing fraction of the system is close to 100%.

Submitted by Vinicius de Godoi Contessoto null (vinicius@sjrp.unesp.br) on 2016-09-09T18:11:23Z No. of bitstreams: 1 Tese-Vinícius_Contessoto-Final.pdf: 17297320 bytes, checksum: f601c338b5bf6436dc595bad581418f5 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-09-13T13:26:05Z (GMT) No. of bitstreams: 1 contessoto_vg_dr_sjrp.pdf: 17297320 bytes, checksum: f601c338b5bf6436dc595bad581418f5 (MD5) / Made available in DSpace on 2016-09-13T13:26:05Z (GMT). No. of bitstreams: 1 contessoto_vg_dr_sjrp.pdf: 17297320 bytes, checksum: f601c338b5bf6436dc595bad581418f5 (MD5) Previous issue date: 2016-08-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Entender a contribuição das interações eletrostáticas no processo de enovelamento e na estabilidade do estado nativo de proteínas é de grande relevância em biofísica molecular. Este trabalho possui duas frentes de estudos. Na primeira etapa é apresentado o estudo das interações eletrostáticas no processo de enovelamento utilizando modelos baseados em estruturas com cargas em dinâmica molecular com pH constante. O estudo foi realizado na parte N-terminal da proteína ribossomal L9 (NTL9), uma proteína com o mecanismo de enovelamento de 2 estados, reversível e realizado desde pH 1.0 até 12.0. Foi possível comparar os resultados das simulações com os resultados experimentais presentes na literatura e os dados obtidos indicam que o modelo proposto é capaz de capturar informações fundamentais sobre o processo de enovelamento referentes à estabilidade e dependência com pH. Na segunda etapa é apresentado o estudo sobre as interações eletrostáticas na estabilidade de enzimas com interesse na produção de bioetanol de segunda geração. O objetivo final deste trabalho é adequar as enzimas às condições do reator para a produção de bioetanol. Neste trabalho foi utilizada uma metodologia capaz de indicar possíveis mutações, pela otimização da interação carga–carga na superfície da proteína, que levam ao aumento de termostabilidade. Este trabalho conta com a colaboração do grupo experimental do Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE) que realizam os testes experimentais e as validações das mutações propostas. / The understanding of electrostatic interactions in protein folding process and in native state stability is important to molecular biophysics area. This work has two areas of interest. At first step it is presented the study about electrostatic interactions in the protein folding process using structure-based models in a constant pH molecular dynamics. It was used the N-terminal domain of ribosomal protein L9 (NTL9), which folding mechanism is a two-state pathway, fully reversible and foldable in a pH range from 1.0 to 12.0. The simulation results were compared with experimental results from literature and the obtained data indicates that the proposed model is capable of capturing essential features of folding mechanism about stability and pH dependence. At second step, it is presented the study about electrostatic interactions in stability of enzymes related with second generation bioethanol production. The final goal of this work is to adjust the enzymes to reactor conditions of bioethanol production. It was employed a method that can suggest rational mutation, based on optimization of charge-charge interactions, that leads to thermostability increase. This work can count on the collaboration of an experimental group of Brazilian Bioethanol Science and Technology Laboratory (CTBE) that performs the wet lab tests and validates the suggested mutations.

El concentrador solar Fixed Mirror Solar Concentrator (FMSC) apareció en los años 70 con la finalidad de reducir costes en la producción de energía termoeléctrica. Este diseño consiste en un concentrador de reflector estacionario y foco móvil, presenta buena integrabilidad en cubiertas, y es capaz de alcanzar temperaturas entre 100 y 200ºC manteniendo una eficiencia aceptable. En esta tesis se expone una metodología para determinar el comportamiento del FMSC. Se ha desarrollado una herramienta de cálculo basada en el método de ray-tracing, que simula el trazado de los rayos solares en el sistema óptico. Con esta herramienta se ha analizado el comportamiento óptico y térmico del FMSC, y de la versión con espejos curvos Curved Slats Fixed Mirror Solar Concentrator (CSFMSC). Se ha realizado un análisis paramétrico para conocer la influencia de los distintos parámetros en el modificador de ángulo (IAM), y para obtener los diseños óptimos a una temperatura de 200ºC para tres climas en diferentes latitudes. Se han comparado los valores teóricos obtenidos mediante ray-tracing con dos prototipos ensayados, obteniendo un buen ajuste en ambos casos. Los ensayos han sido utilizados para determinar la curva de rendimiento de uno de los prototipos. Se ha hecho uso del método propuesto en la norma EN-12975-2:2006, combinado con valores de IAM obtenidos mediante ray-tracing. Se prueba que esta combinación puede ser útil para obtener la curva de rendimiento de colectores complejos con un modelo biaxial para el IAM. / The Fixed Mirror Solar Concentrator (FMSC) appeared during the 70s with the aim of reducing costs in the production of electricity in solar thermal power plants. This design consists of a concentrator with fixed reflector and moving receiver, has a very good integrability into building roofs and can reach temperatures between 100 and 200ºC with an acceptable efficiency. In this Thesis a methodology is presented for the determination of the behaviour of the FMSC. A simulation tool based on the forward ray-tracing method has been developed. The optical and thermal behaviour of the FMSC and its curved mirror variation called the Curved Slats Fixed Mirror Solar Concentrator (CSFMSC), have been analyzed with this tool. A parametric analysis has been carried out in order to determine the influence of the different parameters on the Incidence Angle Modifier (IAM) and to determine the optimal designs at a temperature of 200ºC for three different climates at different latitudes. The theoretical values obtained from the ray-tracing code have been compared with two experimental prototypes. The experimental and numerical results obtained show a good fit. The efficiency curve of one of the prototypes has been determined from the experimental tests. The methodology proposed in the norm EN-12975-2:2006 has been used in combination with IAM values obtained by ray-tracing. It has been shown that this combination can be effectively used to obtain the efficiency curve of complex collectors with a bi-axial IAM model.