Submitted by WELLINGTON PINE OMORI null (wpomori@hotmail.com) on 2018-03-02T14:43:37Z No. of bitstreams: 1 Tese_Wellington_Pine_Omori.pdf: 3601697 bytes, checksum: 300108bd7832f7e80a842293e639462a (MD5) / Approved for entry into archive by Alexandra Maria Donadon Lusser Segali null (alexmar@fcav.unesp.br) on 2018-03-05T18:02:24Z (GMT) No. of bitstreams: 1 omori_wp_dr_jabo.pdf: 3601697 bytes, checksum: 300108bd7832f7e80a842293e639462a (MD5) / Made available in DSpace on 2018-03-05T18:02:24Z (GMT). No. of bitstreams: 1 omori_wp_dr_jabo.pdf: 3601697 bytes, checksum: 300108bd7832f7e80a842293e639462a (MD5) Previous issue date: 2018-02-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A torta de filtro apresenta bagaço residual oriundo do processo de extração do caldo de cana-de-açúcar e quando armazenada por longos períodos, se torna um habitat ideal para o desenvolvimento de comunidades microbianas que atuam na desconstrução da lignocelulose. Nossas análises de dados de sequenciamento de DNA metagenômico sugerem que a torta de filtro armazenada por 40 dias possui uma microbiota com características funcionais e ecológicas exclusivas em relação a outros ambientes com elevada disposição de material lignocelulósico. Assim como em ambientes de compostagem, os filos mais abundantes são Actinobacteria, Proteobacteria, Firmicutes e Bacteroidetes. Dentre os principais genes que estes micro-organismos possuem, estão Glicosiltransferases, Carboidrato Esterases e Glicosil Hidrolases, que atuando em conjunto, são passíveis de desconstruírem a lignocelulose e participarem na liberação de açúcares menores, ácidos orgânicos e outros nutrientes. Neste trabalho, identificamos novas enzimas da família AA10 que oxidam a celulose cristalina, demostrando o potencial deste ambiente em possibilitar a adaptação de micro-organismos que expressam enzimas capazes de desestruturar a celulose altamente condensada, possibilitando a liberação de moléculas de glicose. A comunidade microbiana pode acessar nutrientes como Fósforo e Nitrogênio através da despolimerização da biomassa vegetal ou decomposição da microbiota morta. No ciclo biogeoquímico do nitrogênio, a evaporação de amônia é reduzida pela assimilação desta substância pela comunidade microbiana, sendo que a amônia é produzida pela via de amonificação de nitrato e nitrito. Outro ciclo biogeoquímico identificado na torta de filtro foi o do carbono, ocorrendo diminuição da emissão de metano e gás carbônico devido ao uso destas moléculas no metabolismo microbiano. Por apresentar muitas espécies de micro-organismos termofílicos e funções ecológicas similares a compostagens que alcançaram fase termofílica, a torta de filtro armazenada por 40 dias não aparenta conter micro-organismos patogênicos em elevada abundância, o que poderia ser um indício de sua segurança biológica se usado como adubo no solo. No entanto, recomenda-se que novos estudos sejam realizados neste tipo de ambiente agrícola, afim de avaliar como se comportam principalmente os fungos Neosartorya fumigata e Paracoccidioides brasiliensis, os quais são identificados como agentes patogênicos mas que também são encontrados vivendo na natureza como organismos saprofíticos e em interação com alguns mamíferos, sem causar doença. / The filter cake presents residual bagasse from the process of extracting the sugarcane juice and when stored for long periods, it becomes an ideal habitat for the development of microbial communities that act in the deconstruction of lignocellulose. Our analyzes of metagenomic DNA sequencing data suggest that the filter cake stored for 40 days has a microbiota with unique functional and ecological characteristics compared to other environments with high lignocellulosic material. Thus in composting environments, the most abundant phyla are Actinobacteria, Proteobacteria, Firmicutes, and Bacteroidetes. Glycosyltransferases, Carbohydrate Estersases and Glycoside Hydrolases, which act together, are capable of deconstructing lignocellulose and participate in the release of smaller sugars, organic acids and other nutrients. In this work, we identify new enzymes of the AA10 family that oxidize crystalline cellulose, demonstrating the potential of this environment to enable the adaptation of microorganisms that express enzymes capable of destabilizing highly condensed cellulose, allowing the release of glucose molecules. The microbial community can access nutrients such as Phosphorus and Nitrogen through the depolymerization of the plant biomass or decomposition of the dead microbiota. In the biogeochemical cycle of nitrogen, the evaporation of ammonia is reduced by the assimilation of this substance by the microbial community, and ammonia is produced by ammonification of nitrate and nitrite. Another biogeochemical cycle identified in the filter cake was that of carbon, with a decrease in the emission of methane and carbon dioxide due to the use of these molecules in microbial metabolism. Because it contains many species of thermophilic microorganisms and ecological functions similar to composting that reached the thermophilic phase, the filter cake stored for 40 days does not appear to contain pathogenic microorganisms in high abundance, which could be an indication of its biological safety if used as soil fertilizer. However, it is recommended that new studies be carried out in this type of agricultural environment, in order to evaluate the behavior of the fungi Neosartorya fumigata and Paracoccidioides brasiliensis, which are identified as pathogens but are also found living in nature as saprophytic organisms and in interaction with some mammals, without causing disease.

Submitted by BRUNO ZANON ENGELBRECHT null (bruno_zenon2@hotmail.com) on 2017-05-29T15:14:19Z No. of bitstreams: 1 engelbrecht_bz_me_rcla.pdf: 5854576 bytes, checksum: c42f1bd84eff53bf59926b2392253d96 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-05-31T16:34:17Z (GMT) No. of bitstreams: 1 engelbrecht_bz_me_rcla.pdf: 5854576 bytes, checksum: c42f1bd84eff53bf59926b2392253d96 (MD5) / Made available in DSpace on 2017-05-31T16:34:17Z (GMT). No. of bitstreams: 1 engelbrecht_bz_me_rcla.pdf: 5854576 bytes, checksum: c42f1bd84eff53bf59926b2392253d96 (MD5) Previous issue date: 2017-04-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O sistema aquífero cristalino estende-se por cerca de 62.000 km² no estado de São Paulo, correpondendo a aproximadamente 25% de sua área. A prospecção desses aquíferos, contudo, baseia-se majoritariamente na delimitação de feições lineares nas unidades geológicas e sua correlação com a evolução tectônica regional. Modelos hidrogeológicos conceituais proporcionam a compreensão dos mecanismos que governam a circulação e o armazenamento de água em subsuperfície, permitindo aprimorar e subsidiar a prospecção e gestão dos recursos hídricos subterrâneos. Com este objetivo, o presente estudo apresenta um modelo hidrogeológico conceitual do aquífero cristalino no município de Itu (SP), fundamentado em levantamentos por imageamento elétrico e valores de permeabilidade da zona não-saturada, bem como em análises químicas e isotópicas, tendo como principal enfoque a porção rasa do aquífero e suas interações com as águas superficiais. O modelo embute a ocorrência do manto de alteração e as descontinuidades do maciço rochoso na avaliação do potencial hídrico, prevendo expressiva conectividade hidráulica entre os compartimentos hidráulicos do manto de alteração e do embasamento cristalino fraturado. Os resultados obtidos mostram que a presença de depósitos sedimentares recentes e a ação de processos intempéricos, que resultam em horizontes porosos e na abertura de estruturas preexistentes, favorecem a infiltração, ocorrência e circulação de água em subsuperfície. As características mineralógicas e geométricas do manto de alteração, sua extensão e continuidade regional, redundam em aquíferos heterogêneos e complexos. A constante renovação das águas subterrâneas e sua conectividade com águas superficiais proporcionam a captação das águas de aquíferos cristalinos como fonte hídrica complementar para o abastecimento público, desde que sejam apropriadamente estudadas e geridas. / In São Paulo state the crystalline aquifer system occupies about 62,000 km², corresponding to approximately 25% of its area. However, the prospection of these aquifers is based on the delimitation of linear features in the geological units and their correlation with the regional tectonic evolution. Conceptual hydrogeological models provide an understanding of the mechanisms that govern the circulation and storage of groundwater, allowing to improve and subsidize the exploration and management of groundwater resources. For this purpose, this study presents a conceptual hydrogeological model of the crystalline aquifer in the city of Itu (SP), based on electrical imaging surveys and permeability values of the unsaturated zone, as well as chemical and isotopic analyzes focused on the shallow portion of the aquifer and its interactions with surface water. The hydrogeological model incorporates the occurrence of the weathered zone and the discontinuities of the rock mass in the evaluation of the hydraulic potential, predicting expressive hydraulic connectivity between the hydraulic compartments of the alteration mantle and the fractured crystalline basement. The results show that the presence of recent sedimentary deposits and the processes, which result in porous horizons and the opening of preexisting structures, favor the infiltration, occurrence and circulation of subsurface water. The mineralogical and geometric characteristics of the weathered zone, its extension and regional continuity, results in heterogeneous and complex aquifers. The constant renewal of groundwater and its connectivity with surface water provides the usage of groundwater as a complementary water source for public supply, provided that they are properly studied and managed.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Em geral, o efeito magnetocalórico (EMC) é caracterizado pela variação adiabática da temperatura (ΔTad) e a variação isotérmica da entropia (ΔST) sob variações do campo magnético. Devido as aplicações tecnológicas do EMC na refrigeração magnética, que não apresentam efeitos perigosos para o meio ambiente e tem o potencial para reduzir o consumo de energia, os estudos sobre o EMC tem crescido ao longo dos anos . Neste trabalho, estudamos as propriedades magnéticas e magnetocalóricos da série Gd (1-Y) Pr (Y) Ni2 com Y = 0; 0,25; 0,5; 0,75 e 1 A série dos compostos RNi2 compostos cristalizam na fase de Laves cúbico C15, o que torna o Campo Elétrico Cristalino cúbico um quadro adequado para descrever a anisotropia magnética sobre estes compostos . Além do modelo hamiltoniano inclui contribuições do efeito Zeeman e as interações de troca indireta entre Gd-Gd, Gd-Pr e íons Pr-Pr. Vale a pena notar que o GdNi2 apresenta um arranjo ferromagnético com temperatura de transição de cerca de 78 K e o composto PrNi2 é paramagnético. Os potenciais magnetocalóricos foram calculados e comparados com os dados experimentais. Além disso, investigamos a influência da direção do campo magnético sobre as quantidades magnéticas e no EMC investigada. / In general, the magnetocaloric effect (MCE) is characterized by the adiabatic temperature change, (ΔTad) , and the isothermal entropy change, (ΔST) , under changes of the magnetic field intensity. Due to technological applications of the MCE on magnetic refrigeration, which do not present hazardous effects to the environmental and has the potential to lower energy consumption, the interest on the MCE had grown over the years . In this work, we have studied the magnetic and magnetocaloric properties in the series Gd(1-Y)Pr(Y)Ni2 with Y = 0, 0.25, 0.5, 0.75 and 1. The RNi2 (R = Rare-earth) compounds crystallize in the cubic laves phase, which makes the cubic CEF an appropriate framework to describe the magnetism on these compounds . Besides CEF, the model Hamiltonian includes contributions of the Zeeman effect, and the indirect exchange interactions among Gd-Gd, Gd-Pr and Pr-Pr ions. It is worth noticing that the GdNi2 presents a ferromagnetic arrangement with transition temperature around 78 K and the PrNi2 compound is paramagnetic. The temperature dependences of the magnetocaloric potentials were simulated and compared with the experimental data. Furthermore, the influence of the magnetic field direction on the magnetocaloric quantities was theoretically investigated.

Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / Neste trabalho foram investigados os comportamentos térmico e mecânico e as características morfológicas de amostras de policarbonato de bisfenol-A (PC) com cristalinidade induzida por exposição ao vapor de solvente. A técnica de indução de cristalização foi empregada em três amostras de policarbonato de bisfenol-A de diferentes massas molares. Filmes vazados a partir de soluções de PC em clorofórmio e amostras moldadas por compressão foram expostos a um ambiente contendo vapor de acetona. Os filmes foram expostos por diferentes períodos de tempo e analisados em equipamentos de Calorimetria Diferencial de Varredura, Microscopia Óptica com luz polarizada e Espectroscopia na Região do Infravermelho com Transformada de Fourier, para caracterizar a indução de cristalinidade. A indução de cristalinidade foi confirmada e a fase cristalina apresentou estrutura esferulítica. As amostras de maior massa molar mostraram maior teor de cristalinidade. O desempenho mecânico das amostras cristalinas de policarbonato mostrou diferenças, com a mudança de seu comportamento mecânico de dúctil para frágil, independente da massa molar / In this work were investigated the thermal and mechanical behaviors and the morphological characteristics of bisphenol-A polycarbonate (PC) samples with crystalline induction by solvent vapor exposure. The crystallization induction technique was employed on three samples of bisphenol-A polycarbonate of different molar mass. Films cast from PC solutions in chloroform and compression molded samples were exposed to an environment containing acetone vapor. The films were exposed for different periods of time and analyzed on Differential Scanning Calorimeter, Polarized Light Optical Microscope and Fourier Transform Infra Red devices to characterize crystalline induction. The crystalline induction was confirmed and the crystalline phase has presented spherulitic structure. The highest molar mass samples have shown higher crystallinity degrees. Mechanical performance of crystalline samples has shown differences with the change of its mechanical behavior from ductile to fragile, independently of the molar mass

abstract: The objective of this thesis is to achieve a detailed understanding of the loss mechanisms in SHJ solar cells. The working principles of these cells and what affects the cell operation, e.g. the IV characteristics at the maximum power point (MPP) and the correspondingly ll factor (FF) are investigated. Dierent loss sources are analyzed separately, and the weight of each in the total loss at the MPP are evaluated. The total series resistance is measured and then compared with the value obtained through summation over each of its components. In other words, series resistance losses due to recombination, vertical and lateral carrier transport, metalization, etc, are individually evaluated, and then by adding all these components together, the total loss is calculated. The concept of ll factor and its direct dependence on the loss mechanisms at the MPP of the device is explained, and its sensitivity to nearly every processing step of the cell fabrication is investigated. This analysis provides a focus lens to identify the main source of losses in SHJ solar cells and pave the path for further improvements in cell efficiency. In this thesis, we provide a detailed understanding of the FF concept; we explain how it can be directly measured; how it can be calculated and what expressions can better approximate its value and under what operating conditions. The relation between FF and cell operating condition at the MPP is investigated. We separately analyzed the main FF sources of losses including recombination, sheet resistance, contact resistance and metalization. We study FF loss due to recombination and its separate components which include the Augur, radiative and SRH recombination is investigated. We study FF loss due to contact resistance and its separate components which include the contact resistance of dierent interfaces, e.g. between the intrinsic and doped a-Si layers, TCO and a-Si layers. We also study FF loss due to lateral transport and its components that including the TCO sheet resistance, the nger and the busbars resistances. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2018

It is well-known that concrete permeability is a good indicator of its expected durability until it remains uncracked. However, in various stages of its service life, different types of cracking in concrete can be developed due to exposure to different deterioration processes such as early plastic shrinkage or chloride-induced reinforcement corrosion. Although these cracks may not endanger concrete’s structural performance from the mechanical point of view, they create a pathway for aggressive ions that can initiate degradation processes, lead to increase in concrete permeability and thus reduce its durability. Cracking in concrete might not be preventable, but its capability to naturally seal small cracks, named autogenous self-healing (SH), provides an additional feature to manufacture more durable concrete structures. However, natural self-healing capability of concrete is limited and therefore it is typically omitted in the design of concrete structures. Hence, more attention has been recently paid to Engineered Self-healing Concrete (EShC) which is associated with artificially triggered healing mechanisms into the cementitious matrix by incorporating various substances such as crystalline products. EShC helps in reducing concrete permeability; thus, increasing its service-life and durability. Due to formation of needle-shaped pore-blocking crystals, Crystalline Admixtures (CA), as a candidate from the Permeability-Reducing Admixtures (PRA) category, can be implemented into concrete mixtures to fabricate EShC concretes. Crystalline waterproofing technology is not new, but still is unknown to many researchers, engineers, and construction industry professionals. The lack of knowledge of its microstructure and self-healing properties limits CA’s proper usage in the construction industry. The techniques to assess the self-healing capability of mortar and concrete are not well-standardized yet. No research work has been done to address certain durability characteristics of this material (i.e. electrical resistivity (ER) or chloride diffusivity) especially when combined with Supplementary Cementitious Materials (SCM) and Portland Limestone Cement (PLC). Since the resistance of concrete against ions’ penetration is a function of its permeability, it might be a straightforward and reliable parameter to rapidly evaluate concrete’s durability during its intended service life. Hence, electrical resistivity measurement is considered as an indirect and alternative tool for other time-consuming permeability testing techniques to examine the CA’s efficiency as it modifies the concrete’s microstructure by crystals’ deposition; thus, leads to permeability improvement. In comparison to previous studies, on a larger scale, this thesis aims to systematically study the effects of CA on the microstructural features, self-healing properties and long-term durability and resistivity of cement-based materials and in addition, draw some comprehensive conclusions on the use of CA in new and repair applications. This study is divided into three major phases to propose all-inclusive work on using CA in construction industry. To satisfy the goals of each individual phase, a test matrix consisting of a series of four mixes with variables such as use of PLC or presence of CA in powder form is considered. In order to address to the lack of research and industry knowledge discussed above, this PhD thesis includes the following phases: Phase (I) In this phase, the main focus is on the microstructural properties and the changes in the pore structure and chemical compositions of the cement phase of mortar mixes when treated with CA. These microstructural features are studied using Scanning Electron Microscope (SEM) and Scanning Transmission Electron Holography Microscope (STEHM). Moreover, physical and chemical characteristics of the hydration products are determined using image analysis and Energy Dispersive X-ray (EDX) Spectroscopy, respectively. Phase (II) This phase is allocated to macro-level investigation of durability characteristics such as chloride/water permeability and electrical resistivity of concrete structures containing CA and PLC cement. To non-destructively measure the chloride ion concentration in the field conditions, both changes in corrosion potential of rebars and concrete electrical resistivity in treated circular hollow-section steel reinforced columns exposed to simulated marine environment is monitored and compared over a 2-year period with control samples. In addition, laboratory-size concrete samples are studied to investigate the effects of CA presence on long-term resistivity, rapid chloride permeability, water permeability and chloride diffusivity of concrete. Later, a resistivity-based model is developed to predict long-term performance of concretes incorporating slag or metakaolin, studied in various environmental conditions. The long-term goal of this phase is to develop a standard design guideline and durability-based model. Phase (III) Using an innovative self-healing testing method [1], quantitative analysis of crack closure ability and self-healing potential of CA treated and control concretes with OPC or PLC cement is accomplished during this phase. The obtained results from first phase showed that hydrated CA particle revealed fine, compact, homogenous morphology examined by STEHM and its diffraction pattern after water-activation indicated nearly amorphous structure, however, diffuse rings, an evidence for short-range structural order and sub-crystalline region, were observed which requires further investigation. The SEM micrographs taken from specimen’s fractured surface showed formation of pore-blocking crystals for all treated mixes while similar spots in un-treated sections were left uncovered. Although needle-shaped crystals were observed in the treated mortar specimens, but not all of them had shapes and chemical compositions other than ettringite (well-known to form needle-like crystals). Using backscatter SEM images and EDX spectrums, examination of polished mortar sections with and without CA also showed typical hydration phases, forming in the control system. Results from phase II showed that concretes treated with CA had almost 50% lower water penetration depth and thus smaller permeability coefficient when compared with the virgin OPC or PLC concretes. According to salt ponding test results, the use of CA helped in enhancing the resistance to chloride penetration compared to control concrete. This improvement increases with increasing in concrete age. Strong linear relationship between Surface Resistivity (SR) and Bulk Resistivity (BR) data was observed which indicates that these test methods can be used interchangeably. The presence of SCM in concrete indicated considerable increase in both SR and BR compared to control concrete. Concretes incorporating slag or metakaolin have tendency to react more slowly (or rapidly in MK case), consume calcium hydroxide over time, form more Calcium Silicate Hydrate (C-S-H) gel, densify internal matrix, and also reduce OH- in the pores’ solution; thus, increase concrete electrical resistivity. For laboratory specimens, environmental conditions such as temperature variation and degree of water saturation indicated considerable effects on electrical resistivity measurements. As temperature or water content of concrete decreases, its electrical resistivity greatly increases by more than 2-3 times from reference environmental condition. This is mostly because of variation or accessibility in electron mobility. Experimental results from field investigation showed that electrical resistivity readings were highly influenced by the presence of rebar and concrete moisture conditions. In addition, concrete cover thickness and CA addition into cementitious matrix had a negligible effect on its resistivity. In the last phase, an optical microscope was used to measure the average crack width. OPC samples had an average measured crack width of 0.244 mm as compared to 0.245 mm for OPC-CA, 0.251 mm for PLC, and 0.247 mm for PLC-CA. Self-healing test results also showed 90% self-healing ratio for CA modified mix within few days after starting experiment. Addition of CA into the mix led to higher rates of healing and full crack closure (width up to 250 µm) when compared to reference concrete. An empirical equation that relates water initial flow rate to the crack width (Q∝〖CW〗^3) was also proposed in this phase. Presence of PLC and CA in the mixture resulted in positive improvement in crack-closing capability and self-healing ratio. / Graduate / 2019-09-11

abstract: As crystalline silicon solar cells continue to get thinner, the recombination of carriers at the surfaces of the cell plays an ever-important role in controlling the cell efficiency. One tool to minimize surface recombination is field effect passivation from the charges present in the thin films applied on the cell surfaces. The focus of this work is to understand the properties of charges present in the SiNx films and then to develop a mechanism to manipulate the polarity of charges to either negative or positive based on the end-application. Specific silicon-nitrogen dangling bonds (·Si-N), known as K center defects, are the primary charge trapping defects present in the SiNx films. A custom built corona charging tool was used to externally inject positive or negative charges in the SiNx film. Detailed Capacitance-Voltage (C-V) measurements taken on corona charged SiNx samples confirmed the presence of a net positive or negative charge density, as high as +/- 8 x 1012 cm-2, present in the SiNx film. High-energy (~ 4.9 eV) UV radiation was used to control and neutralize the charges in the SiNx films. Electron-Spin-Resonance (ESR) technique was used to detect and quantify the density of neutral K0 defects that are paramagnetically active. The density of the neutral K0 defects increased after UV treatment and decreased after high temperature annealing and charging treatments. Etch-back C-V measurements on SiNx films showed that the K centers are spread throughout the bulk of the SiNx film and not just near the SiNx-Si interface. It was also shown that the negative injected charges in the SiNx film were stable and present even after 1 year under indoor room-temperature conditions. Lastly, a stack of SiO2/SiNx dielectric layers applicable to standard commercial solar cells was developed using a low temperature (< 400 °C) PECVD process. Excellent surface passivation on FZ and CZ Si substrates for both n- and p-type samples was achieved by manipulating and controlling the charge in SiNx films. / Dissertation/Thesis / Ph.D. Electrical Engineering 2013

Si l'amorçage des fissures de fatigue est aujourd'hui bien compris dans le cas de monocristaux de métaux purs, ce phénomène s'avère plus complexe à cerner et à prédire dans le cas d'alliages métalliques polycristallins tels que l'acier AISI 316LN.D'un point de vue expérimental, notre étude s'est concentrée sur la caractérisation du comportement mécanique et l'étude, à différentes échelles, des phénomènes liés à l'amorçage des fissures de fatigue oligocyclique dans l'acier 316LN. Pour des niveaux de déformation appliquée de Δε/2 = 0,3 et 0,5%, l'adoucissement cyclique observé au cours des essais coïncide avec l'organisation des dislocations sous forme de bandes. Ces bandes sont liées à l'activation des systèmes de plus haut facteur de Schmid. Elles portent la majeure partie de la déformation et provoquent en surface des intrusions et extrusions favorisant l'apparition et la coalescence de fissures.D'un point de vue modélisation, nous avons proposé un nouveau modèle de plasticité cristalline intégrant des dislocations géométriquement nécessaires (GND) directement calculées à partir du second gradient de la rotation élastique. Implémenté dans les codes d'éléments finis AbaqusTM et Cast3mTM, ce modèle s'inspire des travaux sur le monocristal en transformations finies de Peirce et al. (1983) et de Teodosiu et al. (1993). Adapté au cas des polycristaux par Hoc (1999) et Erieau (2003), il a été enrichi par l’introduction GND selon la théorie proposée par Acharya et Bassani (2000). Les simulations réalisées sur des différents types d'agrégats (2D extrudé et 3D) montrent que la prise en compte de GND permet :- de reproduire les effets de taille de grains au niveau macroscopique et local,- de décrire plus finement les champs de contraintes calculés.Ces simulations ont permis de mettre en évidence l'influence des matrices d'élasticité et d'écrouissage sur les valeurs et l'évolution des contraintes macroscopique effective et cinématique moyenne et le rôle important des conditions aux limites lors des calculs d'agrégats. / If fatigue crack initiation is currently quite well understood for pure single crystals, its comprehension and prediction in cases of polycrystal alloys such as AISI 316LN stainless steel remain complicated.Experimentally our study focuses on the characterisation of the mechanical behaviour and on the study at different scales of the phenomenon leading to low cycle fatigue crack initiation in 316LN stainless steel. For straining amplitudes of Δε/2 = 0,3 and 0,5%, the cyclic softening observed during testing has been related to the organisation of dislocations in band structures. These bands, formed due to the activation of slip systems having the greatest Schmid's factor, carry the most part of the deformation. Their emergence at free surfaces leads to the formation of intrusions and extrusions which help cracks initiate and spread.Numerically we worked on the mesoscopic scale, proposing a new model of crystalline plasticity. This model integrates geometrically necessary dislocations (GND) directly computed from the lattice curvature. Implemented in the finite element code AbaqusTM and Cast3mTM, it is based on single crystal finite deformations laws proposed by Peirce et al. (1983) and Teodosiu et al. (1993). Extended for polycrystals by Hoc (2001) and Erieau (2003), it has been improved by the introduction of GND (Acharya and Bassani, 2000). The simulations performed on different types of aggregates (2D/3D) have shown that taking GND into account enables:- the prediction of the grain size effect on a macroscopic and on a local scale,- a finer computation of local stress field.The influence of the elasticity and interaction matrices on the values and the evolution of the isotropic and kinematic mean stresses has been shown. The importance of boundary conditions on computed mechanical fields could also be pointed out.

O presente trabalho apresenta um amplo estudo das propriedades espectroscópicas de fibras cristalinas de CMO:NdNbO4 e CVO:Nd3+, visando aplicações como novos meios ativos excitados por laser de diodo. As fibras em estudo, foram crescidas pela técnica de LHPG (Laser Heated Pedestal Growth) a qual permitem uma rápida obtenção de fibras, em dimensões já apropriadas para a confecção de mini lasers, sem a utilização de cadinhos, com excelente qualidade cristalina e baixa perda de material. Para uma completa caracterização, foram realizados os cálculos de Judd Ofelt, baseando-se nos espectros de absorção óptica, como ferramenta para a calibração e interpretação dos experimentos de luminescência, emissão estimulada (SE), absorção do estado excitado (ESA) obtido por duas técnicas: (a) pela técnica de bombeio e feixe de prova contínuos em um esquema de dupla modulação e (b) pela técnica de excitação do estado excitado (ESE). Estes resultados mostraram que ambos os materiais possuem baixos valores de seção de choque ESA na principal região de emissão laser de materiais dopados com Nd3+ 4F3/2 &#8594; 4I11/2 (~1070nm). A presença de bandas largas observadas nos espectros de luminescência e absorção óptica e um número de transições maior do que esperado observado nos espectros de absorção óptica a baixa temperatura, indicaram a provável existência de multisítios em ambos cristais de CVO:Nd3+ e CMO:NdNbO4. Para quantificar e caracterizar os multisítios de Nd3+ nas amostras, foram realizados experimentos de excitação óptica, seleção de sítios por excitação laser e luminescência seletiva, demonstrando que a amostra de CVO:Nd3+ possui um grande numero de sítios e a amostra de CMO:NdNbO4 possui sete sítios diferentes, justificando o comportamento de bandas largas observado nos espetros de absorção óptica e luminescência. Os valores das seções de choque de absorção óptica (&#963;GSA=4,1x\'10-20cm2 para o CVO e &#963;GSA=5,5x10-20cm2 para o CMO:NdNbO4) e de emissão estimulada, para ambos os materiais (&#963;e=5,5x10-20cm2 para o CMO:NdNbO4 e 13,3x10-20cm2 para o CVO:Nd3+), estão na faixa de importantes meios ativos laser que exibem propriedades multisítios e uma largura de linha de absorção óptica em 810nm (&#916;&#955;GSA=11nm para o CVO e &#916;&#955;GSA=11,5nm para o CMO) maior que muitos importantes meios ativos como YAG:Nd3+ ou GGG:Nd3+ colocando-os em vantagem em relação a estes e muitos outros materiais, para excitação com laser de diodo, justificando a importância do trabalho apresentado e o estudo desses materiais. / The present work release an extensive study of spectroscopic properties on CMO:NdNbO4 and CVO:Nd3+ single crystal fibers, in searching for new laser materials activated with diode laser. The fibers were grown by LHPG (laser Heated Pedestal Growth) technique that permits a fast production of fibers with appropriate dimension for mini laser construction, without the use of crucible, with excellent crystalline quality and low waste of material. For a full optical characterization, it was performed the Judd Ofelt analysis based on the measured absorption spectra as a tool for calibration and interpretation of the experiments of luminescence, stimulated emission (SE), excited-state absorption (ESA) using two different techniques: (a) by the double modulate pump and probe continuous wave technique and (b) by the excited-state excitation (ESE) technique. These results show that both materials have low ESA cross-section values in the main expected laser region 4F3/2 &#8594; 4I11/2 of Nd3+ - doped materials (-1070nm). The existence of broad bands in the luminescence and optical absorption spectra and a number of transitions more than expected as observed in the low temperature absorption spectra suggest the existence of multisites in both crystals of CVO:Nd3+ e CMO:NdNbO4. In order to quantify and characterize the multisites of Nd3+ in the samples, experiments were realized of optical excitation, site selective laser excitation and selective luminescence. These experiments shown that CVO:Nd3+ has a large number of different sites and the CMO:NdNbO4 has seven different sites, justifying the broad band behavior observed on the luminescence and optical absorption experiments. The values of absorption cross-sections (&#963;GSA=4,1x\'10-20cm2 for CVO and &#963;GSA=5,5x10-20cm2 for CMO:NdNbO4) and emission cross-sections (&#963;e=5,5x10-20cm2 for the CMO:NdNbO4 and 13,3x10-20cm2 for CVO:Nd3+) among important laser materials that have multisites properties and a FWHM of absorption at 810nm (&#916;&#955;GSA=11nm for CVO and &#916;&#955;GSA\'=11,5nm for CMO) broader than many other active laser medium like YAG:Nd3+ or GGG:Nd3+ suggesting these materials to be on advantage from many others lasers materials using diode laser excitation, justifj4ng the important of the present work and the study of these material.

O estudo hidrogeoquímico dos aquíferos Tubarão (sedimentar, granular) e Cristalino (granítico, fissural) na Região de Salto (SP), tem como proposta avaliar os processos da interação água-solo-rocha que influem na composição química das águas e discutir a origem de anomalias de fluoreto e salinidade. Para averiguar a relação dessas anomalias com fontes naturais ou antropogênicas, foram estudados processos geoquímicos envolvidos nos níveis rasos e profundos de duas microbacias hidrográficas, onde se têm instaladas várias industriais. As águas dos aquíferos apresentam concentrações iônicas, pH e condutividade elétrica mais elevados em relação às águas subterrâneas rasas, sendo predominantemente bicarbonatadas cálcicas e sódicas no Aquífero Cristalino e bicarbonatadas e sulfatadas sódicas no Tubarão. A salinidade, pH e concentração de sódio destas águas tende a aumentar com a profundidade e no sentido do fluxo subterâneo das áreas de recarga para as de descarga nos principais rios da região. As anomalias geoquímicas ocorrem somente nas águas profundas. A origem do fluoreto é atribuída a alteração de biotita nos granitos e de micas e argilominerais nas rochas sedimentares. O F- está associado a águas bicarbonatadas e sulfatadas sódicas e a valores alcalinos de pH. Os focos de maior salinidade ocorrem em localidades próximas ao Rio Tietê e ao Rio Jundiaí. Ela pode estar associada a lineamentos estruturais de direção NE e NW, mas não se descarta a hipótese de águas residuais aprisionadas durante a deposição marinha dos sedimentos ou à circulação restrita da água subterrânea no Aquífero Tubarão. O sistema profundo encontra-se relativamente isolado em relação aos níveis subsuperficias rasos/superficiais, constatado pelos distintos fluxos subterrâneos e características físico-químicas e químicas. Os solos, sedimentos e águas superficiais e de poços cacimba apresentam evidências de degradação ocasionada por lançamento de esgotos e de um antigo lixão. / The hydrogeochemical study of Tubarão (sedimantary, granular) and Cristallyne (Granitic, fissural) aquifers in Salto Region, evaluates water-soil-rock interaction processes that have influence on water chemical composition and discuss the origin of fluoride and salinity anomalies in ground waters. To investigate the correlation between these anomalies with natural or antropogenic sources, geochemical process studies considering shallow and deep portions were conducted in two small watersheds, where several industries are installed. Deep ground waters present higher ionic concentrations, pH and electrical conductivity when compared to shallow ground waters; they are mainly bicarbonated calcic and sodic in the Crystalline Aquifer and bicarbonated or sulfated sodic in Tubarao Aquifer. The salinity, pH and sodium concentration of these water rise with deepness and from recharge to discharge areas in the main regional rivers. Geochemical anomalies only occur in deep waters. The origin of fluoride is attributed to biotite alteration in granites and to micas and clayminerals in sedimentary rocks. The fluoride is associated to bicarbonated and sulfated sodic waters and alcaline pH values. Focal points of high salinity occur in places near Tietê River and Jundiaí River. It can be associated to structural lineaments with NE and NW directions, but the hypothesis of residual waters that remained in the pore spaces of rocks during marine deposition of sediments cannot be rejected, as well as restrict portions of ground water circulation in the Tubarão Aquifer. The deep system is relatively isolated to the superficial and shallow subterraneous levels, verified by their distinct water flow and physicochemical and chemical properties. Soils, sediments and superficial waters and shallow groun dwater present evidences of degradation, caused by sewerage and an old waste dump.