Cette thèse de doctorat concerne l’étude de la distillation membranaire sous vide pour l’élimination de l’arsenic contenu dans les eaux souterraines. En effet, la contamination des nappes phréatiques par l’arsenic est une problématique majeure dans de nombreux pays, et en particulier au Vietnam. Dans ce pays, choisi comme cas d’étude pour ce travail, environ 13% de la population est empoisonnée par des eaux souterraines contaminées par l’arsenic. De plus, ces eaux souterraines présentent des salinités élevées (5-10 g.L-1) dues à des infiltrations d’eau de mer dans les nappes. Ce travail de thèse a permis de démontrer la faisabilité de la distillation membranaire sous vide (DMV) pour éliminer l’arsenic contenu dans ces eaux et réduire leur salinité afin de les rendre propres à la consommation humaine. Les concentrations en As(III) dans le perméat de DMV sont toujours inférieures aux limites de la norme en eau potable (10 μg.L-1), même pour de très fortes concentrations en As(III) dans l’alimentation (jusqu’à 2000 μg.L-1). La DMV ne nécessite pas de pré-oxydation de l’As(III) en As(V), étape nécessaire dans de nombreux procédés conventionnels de traitement. De plus, un couplage entre l’osmose inverse (OI) et la DMV a été étudié : l’étape d’OI permet une pré-concentration en NaCl et As(III), puis ce rétentat est alors sur-concentré grâce à laDMV. La DMV a montré de très bonnes performances pour traiter un concentrat contenant de très fortes concentrations en As(III) (7000 μg/L). La DMV permet toujours de limiter les teneurs en arsenic dans le perméat à des valeurs en-dessous de la norme. Enfin, unesimulation d’un procédé global, incluant OI et DMV, et fonctionnant à un taux de conversion global de 96%, a été effectuée. Ce couplage ouvre la voie vers un traitement global de l’arsenic permettant de générer de très faibles quantités d’effluents finaux / This PhD work deals with vacuum membrane distillation (VMD) for arsenic removal from groundwaters. Contamination of water resources with arsenic was identified in 105 countries. Approximately 150 million people are being exposed to arsenic contamination, and 147 million of these people live in Asia. In Vietnam, chosen as the case study of this work, 13% of the population is being in risk of arsenic poisoning. Drinking water resources present not only high arsenic concentration (1 – 3050 ppb) but also high salinity (5 – 15 g/L). This work allowed demonstrating the feasibility of VMD to remove arsenic and also salts contained in groundwaters. As(III) concentration in the permeate of VMD was always lower than the standard level for drinking water (10 μg.L-1), even for high As(III) concentrations in the feed (up to 2000 μg.L-1). With VMD, a pre-oxidation step was not necessary to convert As(III) into As(V), as it is the case for other conventional treatment processes. Moreover, a coupling between reverse osmosis (RO) and VMD was studied. RO was considered as a first step to concentrate NaCl and As(III) before this retentate stream was further concentrated by the VMD. VMD could work efficiently with 99.9% of As(III) andNaCl rejections at a very high RO retentate concentrations ([NaCl] = 300 g/L and [As(III)] = 7000 ppb). Arsenic in the permeate was still lower than the required standard for drinking water. Finally, a simulation of the coupling was performed. By coupling of RO and VMD, ahigh global recovery of 96% could be achieved

Made available in DSpace on 2014-06-11T19:32:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-06-26Bitstream added on 2014-06-13T19:43:38Z : No. of bitstreams: 1 zanfolim_aa_dr_bauru.pdf: 2078904 bytes, checksum: 89fecc6406c0fe251fffb9f3101d20dd (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho foram preparados filmes finos de ftalocianinas de zinco (ZnPc) e de níquel (NiPc) através da técnica de evaporação térmica à vácuo (PVD - physical vapor deposition) em diversas espessuras e em escala nanométrica com o objetivo de determinar a arquitetura molecular destes filmes bem como suas propriedades ópticas e elétricas. Em última análise buscam-se gerar subsídios para as possíveis aplicações, especialmente dispositivos eletrônicos a base de semicondutores orgânicos e sensores de gás. A ZnPc e a NiPc em pó foram caracterizadas utilizando-se as técnicas de termogravimetria (TG), calorimetria exploratória diferencial (DSC) e os filmes PVD por espectroscopias de absorção no ultravioleta-visível (UV-vis), no infravermelho com transformada de Fourier (FTIR), espalhamento Raman, difração de raios-X, microscopias óptica e de força atômica (AFM) e caracterização elétrica cc (tensão x corrente). Os resultados mostraram que é possível a fabricação de filmes PVD de ZnPc e NiPc, uma vez que estas moléculas não são termicamente degradadas durante o processo de evaporação térmica a vácuo, e que o crescimento dos filmes pode ser controlado em escala nanométrica para ambos os materiais. Em termos estruturais, os filmes PVD de ZnPc e NiPc são cristalinos (forma α) e possuem as moléculas arranjado-se na forma de agregados e monômetros e ordenadas com o anel macrociclo inclinado em relação à superfície do substrato. Tais agregados podem ser vistos em escala nanométrica, porém, em escala micrométrica os filmes apresentam-se morfologicamente homogêneos. Em relação às propriedades ópticas e elétricas, observou-se que ambos os filmes PVD absorvem na região do visível com a ZnPc apresentando fotoluminescência quando irradiado com laser 785 nm. A condutividade elétrica é de 1,2x'10 POT. -10' S/m para a ZnPc e de 72x'10 POT... / In this work thin films of phthalocyanines of zinc (ZnPc) and nickel (NiPc) were fabricated through the vacuum thermal evaporation technique (PVD - physical vapor deposition) for different thicknesses at nanometric scale with the objective of determining the molecular architecture of these films as well as their optical and electrical properties. The final idea is to generate subsidies for applications of these films in electronic devices based on organic semiconductors and gas sensors. The PVD films were characterized using thermogravimetry (TG), differential scanning calorimetry (DSC), ultraviolet-visible (UV-vis) and Fourier transform infrared (FTIR) absorption spectroscopies, Raman scattering, X-ray diffraction, optical and atomic force (AFM) microscopies, and electrical characterization (tension x current dc). The results showed that the fabrication of ZnPc and NiPc films is possible since these molecules are not thermally degraded during the process of vacuum thermal evaporation and that the growth of the films can be controlled at nanometric scale for both materials. Structurally, the PVD films of ZnPc and NiPc possess the molecules organized with the macrocycle ring tilted in relation to the substrate surface. They are crystalline (α form) and possess molecular aggregates in the form of dimmers or higher order of aggregates and monomers. Such aggregates can be seen at nanometric scale, however, at micrometric scale the films are morphologically homogeneous. In relation to the optical and electrical properties, it was observed that boh PVD films absorb in the visible region with the ZnPc presenting photoluminescence when irradiated with the 785 nm laser line. The electric conductivity at 1,2x'10 POT. -10' S/m for ZnPc and 72x'10 POT. -10' S/m for NiPc. They also presented photoconductivity with the ZnPc more photoconductor than NiPc. Finally, after thermal treatment... (Complete abstract click electronic access below)

The Eulerian description of dispersed two-phase flows results in a system of partial differential equations describing characteristics of the flow, namely volume fraction, density and velocity of the two phases, around any point in space over time. When pressure forces are neglected or a same pressure is considered for both phases, the resulting system is weakly hyperbolic and solutions may exhibit vacuum states (regions void of the dispersed phase) or localized unbounded singularities (delta shocks) that are not physically desirable. Therefore, it is crucial to find a physical way for preventing the formation of such undesirable solutions in weakly hyperbolic Eulerian two-phase flow models. This thesis focuses on the mathematical analysis of an Eulerian model for air- droplet flows, here called the Eulerian droplet model. This model can be seen as the sticky particle system with a source term and is successfully used for the prediction of droplet impingement and more recently for the prediction of particle flows in air- ways. However, this model includes only one-way momentum exchange coupling, and develops delta shocks and vacuum states. The main goal of this thesis is to improve this model, especially for the prevention of delta shocks and vacuum states, and the adjunction of two-way momentum exchange coupling. Using a characteristic analysis, the condition for loss of regularity of smooth solutions of the inviscid Burgers equation with a source term is established. The same condition applies to the droplet model. The Riemann problems associated, respectively, to the Burgers equation with a source term and the droplet model are solved. The characteristics are curves that tend asymptotically to straight lines. The existence of an entropic solution to the generalized Rankine-Hugoniot conditions is proven. Next, a way for preventing the formation of delta shocks and vacuum states in the model is identified and a new Eulerian droplet model is proposed. A new hierarchy of two-way coupling Eulerian models is derived. Each model is analyzed and numerical comparisons of the models are carried out. Finally, 2D computations of air-particle flows comparing the new Eulerian droplet model with the standard Eulerian droplet model are presented.

La thèse est consacrée à la modélisation et à l'analyse par voie numérique de l'écoulement dans une pompe à vide turbomoléculaire hybride, combinant une succession d'étages de type rotor et stator et un Holweck. Une approche de type Test Particle Monte Carlo 3D a été développée pour des configurations de pompes industrielles (géométries complexes d'aubes, gestion des étages rotor et stator) dans un souci d'optimisation des coûts de simulation. L'outil numérique développé a été validé pour des configurations académiques et industrielles, en s'appuyant notamment sur des résultats expérimentaux obtenus grâce au banc d'essai de l'entreprise aVP. L'apport de l'approche TPMC3D par rapport aux méthodes de design disponibles en début de thèse a été clairement démontré pour le régime moléculaire libre. Quelques préconisations de design ont également pu être formulées en utilisant le code développé. Le potentiel d'une approche de type Direct Simulation Monte Carlo, prenant en compte les interactions entre molécules du gaz, a également été établi en 2D pour le régime de transition. / The thesis is devoted to the modeling and the numerical analysis of the flow in a turbomolecular vacuum pump of hybrid type, that is combining a succession of rotor and stator stages with an Holweck. A 3D Test Particle Monte Carlo approach has been developed for simulating industrial pump configurations (complex blade geometries, management of rotor and stator stages), with attention paid to the optimization of the computational cost. The numerical tool developed in the thesis has been validated for academic and industrial test cases, relying in particular on reference experimental results obtained on the test rig of the aVP company. The prediction improvement brought by the TPMC 3D approach with respect to the design tools available at the start of the thesis has been clearly demonstrated for the free molecular flow regime. Some design recommendations have also been formulated using the developed solver. The potential of a Direct Simulation Monte Carlo approach, taking into account the interactions between gas molecules, has also been established in 2D for the transition regime.

In an attempt to improve the quality in finite element analysis of thermoformed components, a method for predicting the thickness distribution is presented. The strain induced anisotropic material behaviour in the amorphous polymers of concern is also taken into account in the method. The method comprises of obtaining raw material data from experiments, followed by a simulation of the vacuum thermoforming process where hyperelastic material behaviour is assumed. The theory of hyperelasticity that was applied was based on the Ogden model and implemented in the FE-software LS-DYNA. Material behaviour from thermoformed prototypes is examined by experiments and implemented together with the mapped results from the thermoforming simulation in a succeeding FE-model. For the latter, the three-parameter Barlat model was suggested, giving the possibility to account for anisotropic material behaviour based on an initial plastic strain.

Made available in DSpace on 2014-10-09T12:41:57Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:43Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-12-17T15:03:24Z (GMT). No. of bitstreams: 1 YTCS_DISSERT.pdf: 5384825 bytes, checksum: aa8710a0ccd842fef87d4421af582dca (MD5) Previous issue date: 2009-12-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Only 32% of the population of Natal is attended by sewage, while the remaining population use pits and septic tanks. The characterization of the contents of septic tanks and pits contributes to the performance of such system and may guide the decision on treatment of these contents. The main of this research is to characterize the contents of interior residential pits and septic tanks in the greater Natal, with the following specific goals: to develop and manufacture a sampler capable of collecting a representative sample of the entire column (the surface scum, the clarified liquid and sludge bottom); to compare the contents of the tanks with the pits; to compare the contents of the septage from vacuum trucks; to relate the composition content with socioeconomic characteristics of households; to compare the content in both chambers of the septic tanks in series; to assess the situation of the content before and six months after the cleanness; and ultimately propose a pilot scale plant for treatment of septage. Once the sampler was developed, samples were collected within 14 septic tanks and 10 pits in many districts of Natal. Medians of the 24 systems were obtained: temperature, pH, conductivity, oil and grease, total solids, total suspended solids and sediments of 28.0 ?C, 6.95; 882 mS/cm, 75.2 mg/L; 10,169 mg/L, 6,509 mg/L and 175 mL/L respectively; 111.0 mgN/L for ammonia, 130.5 mgN/ L for organic nitrogen, 0.2 mgN/L for nitrite, 0.4 mg/L for nitrate; 8935 mgO2/L for COD, 29.2 mgP/L for total phosphorus, thermotolerant coliforms from 9.95 E +06 CFU/100mL helminth eggs and 9.2 eggs/L with a maximum concentration of 688 eggs/L and minimum of 0 eggs/L. Medians of organic nitrogen and TKN were significantly different between groups of tanks and pits. The systems with cleanness gap from 11 and 20 years presented the higher concentrations for most variables. The effluent from the toilets and bathrooms participate more effectively in contributing fractions of solids, alkalinity, nitrogen, COD, total phosphorus, thermotolerant coliforms and helminth eggs. The systems used by socioeconomics class with income from R$ 3,700.00 to R$ 7,600.00, presented higher concentrations for COD, nitrogen, solids and helminth eggs. The first of the two chambers had always presented higher concentrations over the second compartment. The analysis of variance for most variables, showed that the values of septic tanks, pits and septage from vacuum trucks belong to the same group. In the samples taken after cleanness, the median of pH and temperature increased, while alkalinity, COD, organic nitrogen, total phosphorus, ammonia and helminth eggs decreased. The oils and greases and thermotolerant coliforms had slightly varied due to the continuous release of sewage into the systems that maintained their steady state concentrations. / Apenas 32% da popula??o de Natal ? coberta por rede coletora de esgotos, sendo as fossas e tanques s?pticos os mecanismos de disposi??o de esgotos comumente utilizados pelo restante da popula??o. A caracteriza??o do conte?do de fossas e tanques colabora para o conhecimento sobre o tratamento desses res?duos no pr?prio domic?lio, al?m de enriquecer as informa??es a respeito deste conte?do. O objetivo geral desta pesquisa ? caracterizar o conte?do do interior de fossas e tanques s?pticos residenciais da cidade de Natal, tendo como metas espec?ficas desenvolver e fabricar um amostrador capaz de coletar uma amostra representativa de toda a coluna dos tanques s?pticos e fossas, que contemple a escuma da superf?cie, o l?quido clarificado e o lodo presente no fundo; comparar o conte?do dos tanques com os das fossas; comparar o conte?do com os res?duos dos caminh?es limpa-fossa; avaliar a composi??o do conte?do e relacionar com as caracter?sticas s?cio-econ?micas dos domic?lios; comparar a qualidade do conte?do nas duas c?maras dos tanques s?pticos em s?rie; avaliar a situa??o do conte?do antes e decorridos seis meses ap?s o esgotamento e, por fim, propor uma esta??o, em escala piloto, para o tratamento dos res?duos gerados por tanques s?pticos e fossas. Com o amostrador desenvolvido foram coletadas amostras do interior de 14 tanques s?pticos e 10 fossas em bairros de Natal. O conte?do dos 24 sistemas obteve medianas para temperatura, pH, condutividade el?trica, ?leos e graxas, s?lidos totais, s?lidos suspensos totais e sediment?veis de 28,0?C; 6,95; 882 mS/cm; 75,2 mg/L; 10.169 mg/L; 6.509 mg/L e 175 mL/L respectivamente; 111,0 mgN/L para am?nia, 130,5 mgN/L para nitrog?nio org?nico, 0,2 mgN/L para nitrito, 0,4 mg/L para nitrato; 8.935 mgO2/L para DQO, 29,2 mgP/L para f?sforo total; coliformes termotolerantes de 9,95E+06 UFC/100mL e ovos de helmintos 9,2 ovos/L com concentra??o m?xima de 688 ovos/L e m?nima de 0 ovos/L. Houve diferen?a estat?stica significativa para nitrog?nio org?nico e NTK entre os grupos dos tanques e fossas. A classe com tempo de esgotamento entre 11 a 20 anos apresentou para a maioria das vari?veis concentra??es bem mais elevadas. O efluente oriundo dos banheiros e sanit?rios participou mais efetivamente na contribui??o das fra??es dos s?lidos, alcalinidade, fra??es nitrogenadas, DQO, f?sforo total, coliformes termotolerantes e ovos de helmintos. A classe com renda entre R$ 3.700,00 a R$ 7.600,00, apresentou maiores concentra??es para DQO, nitrog?nio, s?lidos e ovos de helmintos. A primeira c?mara dos tanques s?pticos de duas c?maras em s?rie apresentou conte?do mais concentrado em rela??o ao segundo compartimento. Nas an?lises de vari?ncia a maioria das vari?veis apontou que os valores de fossas, tanques s?pticos e res?duos de carros limpa-fossa pertencem ao mesmo grupo. Na amostragem ap?s o esgotamento, o pH e temperatura aumentaram suas medianas, enquanto que alcalinidade, DQO, nitrog?nio org?nico, f?sforo total, am?nia e ovos de helmintos diminu?ram. Os ?leos e graxas e coliformes termotolerantes variaram pouco devido ao lan?amento cont?nuo de esgoto dentro dos sistemas que mantinham suas concentra??es est?veis

Les transistors organiques à effet de champ (OFETs) ont aujourd’hui des performances qui permettent d’envisager la réalisation de circuits électroniques plus ou moins complexes. Cependant, ces dispositifs doivent encore être améliorés en termes de performance et de stabilité sous air avant d’être commercialisés. Le premier objectif de cette thèse est de réaliser des OFETs stables à l’air avec des performances atteignant l’état de l’art, tout en simplifiant leur procédé de fabrication. Le dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT),petite molécule référence, a été choisie comme couche active des dispositifs pour chaque étude. En insérant une couche interfaciale d’oxyde entre le matériau de contact et le SCO de nos OFETs, une étude a été menée sur la réduction de la résistance de contact, qui affecte la mobilité effective des porteurs de charge mais peut également compliquer l’élaboration de circuits. Dans le but de réaliser des OFETs sur substrats flexibles opérant à de faibles tensions,un travail a été réalisé sur le dépôt d’un diélectrique à forte capacité dont la surface a ensuite été passivée et lissée par un polymère. Les transistors de type p obtenus présentent des performances hautes en termes de mobilité (2,4 cm2.V-1.s-1) et de ratio des courant On/Off (>106) avec une faible tension de seuil et aucune hystérésis. Le second objectif a été de réaliser des simulations sur ces OFETs optimisés avec le logiciel GoldenGate dans l’environnement Cadence Virtuoso®, pour obtenir les paramètres nécessaires à l’élaboration d’un circuit amplificateur. Enfin, des composants passifs (résistances) ont été développés et un circuit détecteur d’amplitude sur substrat flexible a été élaboré et testé. / Organic field effect transistors (OFETs) have huge potential in the applications of future electronics, such as flexible circuits and displays or medical application. However, stability and performances of OFETs need to be improved, so as to reach the real market applications.First objective of this work is to realize air stable OFETs with state of the art performance. To that end, several approaches have been applied with special focus on process simplification. Small molecule, dinaphtho[2,3-b:2',3‘-f]thieno[3,2-b]thiophene (DNTT) has been chosen as the active layer for all devices studies. Metal electrodes in combination with oxide interfacial layers were investigated to decrease the contact resistance, which not only affects eventual mobility that can be achieved but also complicates circuit design. A systematic study was carried out to fabricate high capacitance dielectric layer and passivating the surface with proper interfacial layers. These approaches allowed to obtain high performance OFET on plastic substrate with high mobility (2.4cm2.V-1.s-1), high current on/off ratio (> 106), low threshold voltage and no hysteresis As the second objective, OFET devices were simulated using GoldenGate (with Cadence Virtuoso® environment) to derive relevant parameters, which helped to design amplifier circuit. Finally, passive component (resistance) has been developed and final circuit was realized and characterized.

As observações astronômicas dos últimos 15 anos revelaram que o universo atualmente está expandindo aceleradamente. No contexto da relatividade geral se acredita que a energia escura, cujo melhor candidato é a densidade do vácuo ($\\Lambda/8\\pi G$), é o agente responsável por este estado acelerado. No entanto, o termo $\\Lambda$ tem duas sérias dificuldades: o problema da constante cosmológica e o problema da coincidência. Com o objetivo de aliviar o problema da constante cosmológica, muitos modelos adotam um termo $\\Lambda$ dinâmico, permitindo seu decrescimento ao longo de toda a história cósmica. Neste tipo de modelo, a equação de conservação do tensor momento energia total exige uma troca de energia entre a densidade do vácuo e as outras componentes energéticas do universo; o que também alivia o problema da coincidência. Neste trabalho discutimos diferentes consequências de um vácuo dinâmico no âmbito cosmológico e no processo de colapso gravitacional. Em particular, analisamos o caso em que a densidade do vácuo possui uma dinâmica não trivial com a escala de energia típica do universo, que depende monotonamente do parâmetro de Hubble, decrescendo ao longo de toda a história cósmica. Nos referiremos a este modelo como modelo deflacionário. Nesse contexto, utilizando os primeiros termos da expansão para a densidade do vácuo, sugerida pela teoria do grupo de renormalização em espaço-tempos curvos, propomos um novo cenário cosmológico baseado numa densidade do vácuo dinâmica. O cenário proposto é completo no sentido de que o mesmo vácuo é responsável pelas duas fases aceleradas do universo, conectadas por uma fase de radiação e um estágio de domínio da matéria. Neste cenário o universo plano é não singular, iniciando sua evolução a partir de um estágio do tipo de Sitter e, portanto, toda a história cósmica ocorre entre duas fases de Sitter limites. Este modelo não apresenta o problema de horizonte, e nele a nucleossíntese cosmológica ocorre como no modelo de Friedmann, e embora este modelo seja muito próximo do modelo $\\Lambda$CDM, o grande acúmulo de observações no estágio recente do universo permitirão que este poda ser testado. Adicionalmente, mostraremos que generalizações do modelo deflacionário incluindo curvatura espacial apresentam propriedades e vantagens similares. Usando observações de $H(z)$, da luminosidade de supernovas tipo Ia, da função de crescimento linear das perturbações escalares, e da posição do pico das oscilações acústicas de bárions conseguimos vincular um dos parâmetros do modelo. Por outro lado, analisando a física do universo primordial, assumindo um vácuo não perturbado, conseguimos limitar um segundo parâmetro fazendo uso do índice espectral das perturbações escalares. Com o objetivo de fazer uma análise mais completa do modelo no âmbito cosmológico, analisamos também as possíveis restrições oriundas da validade da segunda lei da termodinâmica em sua forma generalizada (GSLT). Para isto investigamos a evolução tanto da entropia associada ao horizonte aparente do universo, que é um horizonte atrapante devido a que o escalar de Ricci é positivo, como do seu conteúdo material. Motivados pela forma como a singularidade primordial do universo é evitada devido aos efeitos do decaimento do vácuo, incluímos no presente trabalho outra linha de desenvolvimento: a análise dos estágios finais do processo de colapso gravitacional em presença de uma densidade do vácuo dinâmica. Centraremos esta análise na determinação de modelos que possam ou não evitar a formação de um buraco negro. Mostraremos que modelos com um termo de vácuo proporcional à densidade de energia total do sistema, não podem evitar a formação de uma singularidade no estágio final do processo de colapso. Adicionalmente obteremos correções para a massa colapsada, para o tempo de formação do horizonte e para o tempo de colapso como função dos parâmetros do modelo e da curvatura espacial. Por último analisaremos a influência de uma densidade do vácuo capaz de dominar sobre as outras componentes no regime de altas energias, mostrando que este tipo de dinâmica na densidade do vácuo evita a formação de um estado final singular. / The astronomical observations of the last 15 years revealed that the universe is currently undergoing an expanding accelerating phase. In the general relativity context is believed that dark energy, whose best candidate is the vacuum energy density $ho_v \\equiv \\Lambda/8\\pi G$, is the fuel responsible for the present accelerating stage. However, the so-called $\\Lambda$-term has two serious drawnbacks, namely: the cosmological constant problem and the coincidence problem. In order to alleviate the cosmological constant problem, many models adopt a dynamical $\\Lambda$ term, thereby allowing its decreasing throughout the cosmic history. In this kind of model, the total energy conservation law defined in terms of the energy momentum tensor requires an energy exchange between the vacuum and the material components of the universe, which also contributes to alleviate the coincidence problem. In the present thesis we discuss different consequences of an interacting vacuum component both in the cosmological scenario as well as in the process of gravitational collapse. In particular, in the cosmological domain, we examine the case where the vacuum has a nontrivial dynamics dependent on a typical energy scale, the Hubble parameter, that decreases in the course of the cosmic history. We will refer to this model as deflationary model. In this context, by using a truncated expansion for the vacuum energy density, as suggested by the renormalization group theory in curved space-time, we propose a new cosmological scenario based on a dynamical $\\Lambda$-term. The proposed scenario is complete in the sense that the same vacuum is responsible for both accelerating phases of the universe, which are linked by two subsequent periods of radiation and non-relativistic matter domination. In this scenario the flat universe is nonsingular and starts its evolution from an asymptotic de Sitter stage, so that the cosmic story takes place between two extreme de Sitter phases. The model is free of the horizon problem as well as of the \"graceful exit\" problem plaguing many inflationary variants. In addition, the cosmological nucleosynthesis occurs as in the Friedmann model and the observations in the latest stages of the universe can potentially differentiate between the deflationary and the standard $\\Lambda$CDM model. The generalizations including spatial curvature are aslo discussed in detail. On the other hand, by using the late time tests like type Ia supernovae, the redshift dependence of the Hubble parameter, $H(z)$, the linear growth function of scalar perturbations, and the peak position of baryon acoustic oscillations we have constrained the basic parameters of the model. Conversely, analyzing the physics of the primordial universe and assuming that the vacuum is a smooth component, we have also constrained the spectral index of scalar density perturbations. In order to establish a more complete analysis of our cosmological scenario, we also discuss the possible constraints arising from the validity of the generalized second law of thermodynamics, that is, by including the horizon thermodynamics. Since the apparent horizon of the universe behaves like a trapped horizon because the Ricci scalar is positive, we investigate the evolution of both the entropy of the material components and the entropy associated to the horizon. Motivated by the avoidance of the Big-Bang singularity due to the decaying vacuum effects, we have explored another line of development: the analysis of the final stages of gravitational collapse process in the presence of a dynamic vacuum. This analysis focused on the determination of models able to prevent or not the formation of a black hole. In this connection, we shown that the presence of an interacting vacuum proportional to the total energy density of the system does not prevent the formation of a singularity in the final stages of the collapsing process. In addition, we obtain corrections for the collapsed mass, the horizon time formation and the collapsing time as a function of the free parameters and the spatial curvature of the models. Finally, we have also analyzed the influence of a vacuum contribution which dominates the other components into the high energy limit (due to the presence of higher orders terms in the contraction rate), and shown that for this kind of models the growth of the vacuum energy density prevents the formation of the singularity.

Este trabalho estuda as variáveis que influenciam as estimativas de recalques em aterros sobre solos moles com drenos verticais e pré-carregamento com vácuo. É realizada revisão bibliográfica em duas vertentes. Primeiro sobre as teorias de adensamento vertical, radial e com sobrecarga de sucção a vácuo, aplicadas no Estudo de Caso e necessárias para a estimativa dos recalques. Segunda sobre probabilidade e estatística aplicada à geotecnia, utilizada para contemplar a variabilidade e a incerteza dos parâmetros geotécnicos de forma científica. Na prática, a dificuldade interposta por custo e prazo para determinação dos parâmetros geotécnicos necessários para o desenvolvimento do projeto determinaram se a propriedade geotécnica buscada seria definida diretamente ou estimada por meio de propriedades índice, ambos os casos apresentando incertezas. Lambe (1973) discutiu a acurácia dos projetos geotécnicos e concluiu que somente com a compatibilidade entre dados e métodos é que se obtêm previsões geotécnicas acuradas. Análises de recalques são realizadas a partir dos dados do Estudo de Caso, de acordo com as questões práticas importantes: a magnitude dos recalques e o tempo necessário para o seu desenvolvimento. São interpretados ensaios de adensamento em laboratório do Estudo de Caso a respeito da sua qualidade, dos parâmetros geotécnicos medidos e da representatividade da amostra em relação ao solo aluvionar heterogêneo tratado. Dois métodos de cálculo da sobrecarga a vácuo são utilizados, a saber: constante com a profundidade, de uso corrente e mais simples; e decrescente com a profundidade, conforme teoria recente e mais sofisticada. Os parâmetros geotécnicos inferidos pelas sondagens e ensaios realizados são comparados com os parâmetros aferidos de melhor ajuste à instrumentação por meio de retroanálise paramétrica. Para melhor compreender a importância e influência das variáveis que afetam a acurácia das análises realizadas são utilizados métodos probabilísticos a partir das informações disponíveis. Por fim, os resultados obtidos em ambos os locais e com os métodos de previsão utilizados são confrontados quanto à acurácia obtida. / The present research studies the variables that influence settlement estimates in embankments on soft soil with vertical drains and vacuum preloading. The analysis of the existing literature on the topic is twofold. Firstly, it concerns the theories on vertical and radial consolidation, as well as consolidation under vacuum overload, applied in the Case Study and necessary for estimating settlements. Secondly, it regards probability and statistics applied to geotechnics, used to take into account the variability and uncertainty of geotechnical parameters in a scientific manner. In practice, the difficulty posed by costs and deadlines when defining the geotechnical parameters that are necessary for developing the project determined whether the geotechnical property sought would be either directly defined or estimated through index properties, with both scenarios presenting uncertainty. Lambe (1973) discussed the accuracy of geotechnical predictions and concluded that it is only possible to obtain accurate geotechnical forecasts when data and methods are compatible. Settlement analyses are performed based on data from the Case Study, according to important practical issues: settlement levels and the time that is necessary for its development. Consolidation laboratory tests concerning the Case Study are interpreted regarding their quality, the geotechnical parameters measured and sample representativeness in relation to the heterogeneous alluvial soil that has been treated. Two methods for calculating vacuum overload are used, namely, one that is constant with depth (simpler and more broadly used) and one that decreases with depth (following a more recent and more sophisticated theory). The geotechnical parameters inferred through borings and tests that have been carried out are compared with the parameters that best suit instrumentation through parametric back analysis. With a view to better understanding the importance and influence of the variables that affect the accuracy of the analyses performed, probabilistic methods are employed based on the information available. Finally, the results obtained in both sites and through the forecast methods used are compared in regard to the accuracy obtained.