Although the general principles of biomass gasification are broadly understood, at a larger scale of operation (e.g. > 200 kg/h) there is a lack of confidence in the translation of the basic scientific concepts into a financially viable operation that satisfies regulatory requirements. Looking in particular at the operation of a down-draft type of gasifier, a number of challenges were identified and studied in greater detail. Gasification experiments were performed on wood and straw pellets in a small scale, 21 mm i.d. quartz-tube reactor. These provided useful insight into what was occurring inside the gasifier, and the complexity and roles of the various reaction zones. In order to perform on-line gas analysis measurements in real time, a method was developed which enabled a quadrupole mass spectrometer (QMS) to be used. This was tested in a laboratory environment, and then used on a commercial pilot-plant gasifier (150 to 250 kg/h). This enabled the composition of the gas to be monitored while the plant was started up, and then operated at various levels of gas flow through the plant. In general the concentrations measured during a stable operation were as follows: CO = 16.0 vol.%, H2 = 11.9 vol.%, CO2 = 15.8 vol.%, N2 = 54.1 vol.%, CH4 = 1.9 vol.%, O2 = 0.3 vol.%. Measurements of O2 concentrations in the gas stream on start-up provide useful information on conditions when a flammable atmosphere could exist in the lines/vessels. To help with the development of suitable gas clean-up strategies, the presence of two key sulphur species, H2S and carbonyl sulphide (COS), was studied in more detail. Experimental measurements were taken on the laboratory reactor (e.g. H2S = 286 ppmv, COS = 28 ppmv for gasification of refuse-derived fuel (RDF) pellets), and the commercial pilot-scale gasifier (e.g. H2S = 332 ppmv, COS = 12 ppmv). This data was also compared with theoretical thermodynamic predictions. The steam gasification of char was also studied in a laboratory 9.5 mm i.d. reactor, and kinetic expressions were determined for RDF-derived char. It was shown that high concentrations of H2 (20 vol.%) and CO (15 vol.%) can be achieved, and the temperature at which reactions were initiated was > 700 ºC, and significant at 900 ºC. Interestingly, the RDF-derived char (at carbon conversion from 10 to 70 %) appears to be more reactive than other biochars reported in the literature. However, at high conversion (> 50 %), its apparent reactivity decreases with carbon conversion, behaving in a similar manner to coal chars.

Este trabalho foi dividido em duas grandes partes principais, a primeira relacionada ao estudo da luminescência de quatro espécimes de quartzo naturais brasileiros (verde, hialino, rosa e azul) e a segunda trata da confecção e caracterização de amostras sintéticas, baseadas na estrutura do SiO2, obtidas pelo método de sol-gel para fins de dosimetria das radiações ionizantes ambientais. Através da Análise por Ativação com Nêutrons Instrumental (AANI) e Fluorescência de Raios X por Reflexão Total (TXRF), foram determinadas as principais impurezas em concentrações maiores, menores e traços de forma quantitativa e qualitativa, respectivamente. Os espécimes verde e azul foram os que apresentaram as maiores quantidades de impurezas, incluindo metais e elementos terras raras, enquanto que o hialino e rosa são praticamente puros. Suas emissões de TL foram distintas, em termos de intensidade e posição dos picos. Testes de recuperação de dose por luminescência opticamente estimulada (LOE), através dos protocolos de alíquotas múltiplas (MAR) e única (SAR) com doses regenerativas, foram realizados e o espécime verde foi o único que apresentou resultados satisfatórios nesses testes, seguido do azul. Os cristais hialino e rosa apresentaram saturação e curva de crescimento fora da linearidade, onde o primeiro mostrou o efeito da fototransferência para a maioria das análises de SAR. Como os cristais verde e hialino apresentaram resultados opostos, em termos de quantidades de impurezas e emissões luminescentes, foi realizado um tratamento térmico em alta temperatura (1600 °C) para observar o efeito da mudança de fase (cristobalita) nas suas emissões luminescente. Ajustes teóricos das curvas de emissão de LOE contínua, linearmente modulada e TL mostraram que elas seguem o modelo teórico de cinéticas de ordens gerais. Na segunda parte deste trabalho, 32 amostras artificiais, do polimorfo de alta temperatura do quartzo, a cristobalita, foram sintetizadas com diferentes quantidades e tipos de dopantes, baseado nas impurezas determinadas no quartzo verde, utilizando duas rampas de aquecimento nas calcinações (3 e 15 °C/min). Essa parte do trabalho teve como finalidade o estudo do efeito do Fe na emissão luminescente das amostras sintéticas, a reprodução de uma das amostras naturais e produção e caracterização de dosímetros para radiações ionizantes ambientais. A utilização das duas rampas de aquecimento na emissão de TL, de forma geral, não desempenhou papel determinante na intensidade dos picos de altas temperaturas. Já na LOE foi observado que as amostras calcinadas com a rampa de maior temperatura apresentaram resposta à dose mais elevadas. O Fe como dopante em maior quantidade atuou como um inibidor de luminescência tanto na TL quanto na LOE. Uma amostra com características qualitativas semelhante ao quartzo verde, na fase da cristobalita, foi obtida com relativo sucesso utilizando como dopante todas as doze principais impurezas adquiridas para realização deste projeto. Quatro amostras foram sintetizadas com diferentes tipos e quantidades de dopantes para aplicação em dosimetria das radiações. Somente uma destas apresentou resposta linear às doses de radiação utilizando estimulação térmica (TL), cuja mínima dose de detecção (MDD) foi de 172 µGy. Utilizando estimulação óptica (LOE), duas amostras apresentaram comportamento linear com as doses de radiação, em que valores de MDD de ~440 µGy e 405 µGy foram obtidos. / This work was divided into two major parts, the first one related to the study of the luminescence of four Brazilian natural quartz specimens (green, hyaline, pink and blue) and the second one deals with the confection and characterization of synthetic samples, based on SiO2 structure, obtained by means of sol-gel method to environmental ionizing radiation dosimetry. Through Instrumental Neutron Activation Analysis (INAA) and Total Reflection X-ray Fluorescence (TXRF), the main impurities in major, minor and trace concentrations were determined quantitative and qualitatively respectively. The green and blue specimens presented the highest amounts of impurities, including metals and rare earth elements, whereas hyaline and pink are practically pure. Their TL emissions were distinct, in terms of intensity and peak position. OSL dose recovery tests, using multiple (MAR) and single aliquots regeneration (SAR) dose protocols were performed and the green specimen was the only one which presented satisfactory results in these tests, followed by blue. The hyaline and pink crystals showed saturation and growth curve out of linearity, where the first one showed the effect of phototransference for most SAR analysis. As green and hyaline crystals presented opposite results, in terms of impurities quantities and luminescent emissions, a high temperature (1600 °C) heat treatment was performed to observe the effect of the phase change (cristobalite) on its luminescent emissions. Theoretical adjustments of the CW-OSL, LM-OSL and TL emission curves showed that they follow the theoretical model of general order kinetics. In the second part of this work, 32 artificial samples of the high temperature polymorph of the quartz, cristobalite, were synthesized with different amounts and types of dopants, based on impurities determined in green quartz, making use of two heating rates in the calcinations (3 and 15 °C/min). This part of the work had as purpose the study of the effect of Fe in the luminescent emission of the synthetic samples, the reproduction of one of the natural samples and production and characterization of dosimeters for environmental ionizing radiation. The use of the two heating rates in TL emission, in general, did not play a determining role in the intensity of the high temperature peaks. In the OSL, it was observed that samples calcined with higher heating rate temperature showed higher response to dose. The Fe as a dopant in greater quantities acted as a quencher of luminescence both in TL and OSL. A sample with qualitative characteristics similar to the green quartz, in the cristobalite phase, was obtained with relative success using as dopants all the twelve main impurities acquired for this project. Four samples were synthesized with different types and amounts of dopants for application in ionizing radiation dosimetry. Only one of these showed a linear response to radiation doses using thermal stimulation (TL), with a minimum detectable dose (MDD) of 172 µGy. Using optical stimulation (OSL), two samples showed linear behavior with radiation doses, in which MDD values of ~440 µGy and 405 µGy were obtained.

O quartzo é um mineral abundante na crosta terrestre e pode ser valorizado através do design. A cor é um importante elemento de design e algumas gemas são incolores ou possuem cores e tonalidades pouco atrativas, necessitando de tratamento para serem revalorizadas. O intuito desta pesquisa é usar o recurso tecnológico da irradiação industrial para estudar parâmetros desse processo, a fim de gerar contribuições aos desenvolvedores de materiais gemológicos exclusivos e diferenciados ou de joias de arte (design autoral). Para isso, foram realizados experimentos com fonte panorâmica de Cobalto-60 estocada a seco, com aproximadamente 33398,34 TBq de atividade. Foram selecionadas variedades de quartzo de diferentes regiões brasileiras a fim de gerar materiais bicolores para futuro estudo do desenvolvimento de desenhos pela técnica de irradiação seletiva. A pesquisa foi dividida em duas etapas: 1) A primeira etapa consistiu no desenvolvimento de diretrizes, seleção de materiais e experimentos piloto. Foram testados principalmente variedades de quartzo provenientes do Rio Grande do Sul, 2) A segunda etapa consistiu na irradiação homogênea e seletiva do quartzo rosa de Águas vermelhas-MG e rosa-pálido límpido de Pedra Lavrada-PB. Com relação à irradiação homogênea, foi estudada a variação de tonalidade de cor obtida após a irradiação em amostras com diferentes espessuras e dose mínima e máxima da irradiação para alteração cromática; já com relação à irradiação seletiva, foi estudada a relação da espessura de amostras de chumbo para atenuação da irradiação, contraste de tonalidade resultante da atenuação, espessura de fresta entre as amostras de chumbo, afastamento da amostra em relação à atenuação provocada pelo chumbo, altura do experimento em relação à fonte de irradiação e sobreposição de doses para o desenvolvimento de efeito estético “xadrez”. A irradiação seletiva foi realizada através da atenuação da radiação gama com amostras de diferentes espessuras de chumbo, 20, 10, 5 e 3 cm. As espessuras das fatias polidas de quartzo para visualização da cor foram de 2 mm e 4 mm. Os resultados foram analisados por sistema de cores hue, saturation e brigh (HSB) de modo experimental, por espectrometria no Infravermelho (FTIR) e na região de luz visível (UV-Vis). Nesta pesquisa pôde-se destacar alguns parâmetros para a irradiação seletiva do quartzo rosa-pálido de Pedra Lavrada, PB, pois as outras variedades de quartzo não apresentaram aspectos tão interessantes. / Quartz is an abundant mineral in the earth's crust and can be enhanced by design. The color is an important design element and some gems are colorless or have unattractive colors and shades, requiring treatment to be enhanced. Among various ways to change or improve the color of a gem, gamma irradiation Cobalt-60 has been approved in the world trade. The purpose of this research is to use the installed resources of Brazilian industrial irradiation, to study parameters of this process to apply in design, in order to generate contributions to develop unique gemological materials or art jewelry (authorial design). For this, experiments were conducted with a dry stored panoramic source of Cobalt-60, with approximately 33,398.34 terabecquerel (TBq) activity. Different quartz varieties of several Brazilian regions were selected in order to produce bi-colored materials, for development of future drawing studies by selective irradiation techniques. The research was separated into two stages: 1) The first step was the development of guidelines, materials selection and pilot experiments, being tested mainly quartz varieties from Rio Grande do Sul, 2) The second step was of homogeneous and selective irradiation of massive pink quartz of Águas Vermelhas-MG and clear pale pink quartz of Pedra Lavrada-PB. In the homogeneous irradiation studies, the variation in shade obtained after irradiation (in different thicknesses of samples) and maximum and minimum dose of radiation to color change was analyzed; In the selective irradiation, it was studied the relation between the thickness of lead samples to the radiation attenuation, the final color tone contrast attenuation, thickness gap between the lead samples, the sample distance from the lead, in relation to the radiation attenuation, elevations of the experiment samples relative to the irradiation source, and overlapping doses to the development of a “chess” aesthetic effect. Selective irradiation was performed through the attenuation of gamma radiation with lead samples of thickness of, 10, 20, 5 and 3 cm. The thicknesses of quartz polished slices for color visualization was of 2 mm and 4 mm. The results were analyzed by experimental color systems that include hue, saturation and bright (HSB) analysis, by Infrared (FT-IR) and visible light region (UV-Vis) spectrometry. In this research it was possible to point out some parameters for selective irradiation of pale pink quartz of Pedra Lavrada-PB, once the other quartz varieties tested did not present such interesting results.

O presente trabalho teve como objetivo avaliar as interações entre bolhas com distintos tamanhos (diâmetros) e partículas minerais e o efeito de combinações destas bolhas na flotação de minérios, em escala de bancada. As bolhas empregadas nesses estudos foram: i) Nanobolhas – NBs, diâmetro médio de 150 – 200 nm; ii) Microbolhas – MBs, diâmetro médio de 70 μm; e iii) Macrobolhas – MaBs, diâmetro médio de 1 mm. As dispersões de NBs e MBs foram geradas a partir da despressurização de água saturada com ar e cavitação hidrodinâmica em válvula agulha. As pressões de saturação foram, respectivamente, 2,5 e 4,0 bar. Os estudos de interação bolhas-partícula mineral foram desenvolvidos utilizando um sistema fotográfico que permitiu avaliar a adesão de bolhas às partículas de quartzo (grão de alta pureza) e apatita em função do tipo de bolhas injetadas. Os resultados mostraram que a maior adesão de bolhas no grão de apatita ocorreu com a combinação de NBs + MBs + MaBs e, no caso do quartzo, uma expressiva concentração de MaBs aderidas foi obtida após “condicionamento” do mineral com NBs. As NBs ficaram confinadas às superfícies dos grãos minerais devido à dissipação da energia livre superficial dos sólidos em função de sua rugosidade e, desta forma, aumentaram o mecanismo de adesão de outras bolhas (MBs e/ou MaBs). O estudo de avaliação das associações de bolhas na flotação foi realizado com os sistemas minerais quartzo e minério fosfático. No caso do minério fosfático, constituído por 35% de partículas finas (< 37 μm), os estudos avaliaram a combinação de i) NBs + MaBs; ii) MBs + MaBs; e iii) NBs + MBs + MaBs, nos parâmetros cinéticos e de separação na flotação, em relação ao ensaio standard, que emprega o uso de apenas MaBs. Os efeitos foram avaliados em quatro situações que compreenderam variação de porcentagem de sólidos (28 e 35% em peso) e concentração de reagentes (1000 g.t-1 de coletor + 600 g.t-1 de depressor; e 500 g.t-1 de coletor + 300 g.t-1 de depressor; sendo que o coletor de apatita empregado foi óleo de soja saponificado com hidróxido de sódio e o depressor das partículas de ganga - magnetita, carbonatos, micas, quartzo, diopsídio e perovskita/anatásio - foi amido de milho gelatinizado com hidróxido de sódio). O emprego combinado de bolhas apresentou incrementos na recuperação de P2O5, com pequena queda no teor de P2O5 e elevada cinética, em relação aos ensaios STD em praticamente todas as condições estudadas, com valores variando entre 0,2 e 8.9%. Os incrementos quando a porcentagem de sólidos foi de 35% p/p (até 2,7%) foram consideravelmente menores que os obtidos com 28% de sólidos (até 8,9%). Em algumas condições, o uso concomitante de MBs + MaBs e NBs + MBs + MaBs foi capaz de superar, já na primeira coleta (1,5 min de ensaio), a recuperação total de fosfato obtida no ensaio standard. No caso do quartzo, os ensaios de microflotação (realizados em tubo de Hallimond modificado) com e sem a presença de NBs mostraram que a associação de NBs às MaBs aumentou a recuperação de quartzo (até 39%) em praticamente todas as condições estudadas, mostrando sua efetividade tanto com partículas finas quanto com as mais grossas. Já os ensaios realizados em célula mecânica com e sem adição de NBs, mostraram que o emprego de NBs foi responsável pelo aumento de 23 pontos percentuais na recuperação de quartzo. Ainda, a cinética de flotação aumentou significativamente e já no primeiro min do ensaio com NBs obteve-se cerca do dobro da recuperação de quartzo do ensaio standard. Os resultados obtidos na dissertação mostram o elevado potencial das NBs combinadas a outras distribuições de tamanhos de bolhas na melhoria do processo de adesão bolha-partícula e na flotação de minérios fosfáticos finos e de frações granulométricas distintas de quartzo, principalmente em tempos curtos. / The objective of this work was to evaluate the interactions between bubbles with different sizes (diameters) and mineral particles and the effect of the combinations of these bubbles on the flotation of ores, on a bench scale. The bubbles used in these studies were: i) Nanobubbles - NBs, mean diameter of 150-200 nm; ii) Microbubbles - MBs, average diameter of 70 μm; and iii) Macrobubbles - MaBs, average diameter of 1 mm. Dispersions of NBs and MBs were generated after depressurizing-cavitation of the saturated water in air. The saturation pressures were, respectively, 2.5 and 4.0 bar. The bubble-particle mineral interaction studies were developed using a photographic system that allowed to evaluate the adhesion of bubbles to the particles of quartz (high purity grain) and apatite according to the type of bubbles injected. The results showed that the highest adhesion of bubbles in the apatite grain occurred with the combination of NBs + MBs + MaBs and, in the case of quartz, an expressive concentration of adhered MaBs was obtained after "conditioning" of the mineral with NBs. The NBs were confined to the surfaces of the mineral grains as a result of the dissipation of the free surface energy of the solids due to their roughness and, therefore, it increased the adhesion mechanism of other bubbles (MBs and / or MaBs). The study of the evaluation of the associations of bubbles in the flotation was carried out with the mineral systems quartz and phosphate ore. In the case of phosphate ore, consisting of 35% fine particles (<37 μm), the studies evaluated the combination of i) NBs + MaBs; ii) MBs + MaBs; and iii) NBs + MBs + MaBs, in the kinetics and flotation separation parameters, in relation to the standard test, which employs the use of only MaBs. The effects were evaluated in four situations involving percentage of solids (28 and 35% by weight) and concentration of reagents (1000 g·t-1 collector + 600 g·t-1 depressant and 500 g·t-1 collector + 300 g·t-1 of depressor; the apatite collector used was a saponified soybean oil with sodium hydroxide and the depressant of the ganga - magnetite, carbonates, micas, quartz, diopside and perovskite / anatase particles - was a gelatinized corn starch with sodium hydroxide). The combined use of bubbles presented increases in the recovery of P2O5, with a small drop in P2O5 content and high kinetics, in relation to the STD tests in practically all the studied conditions, with values varying between 0.2 and 8.9%. The increments when the percentage of solids was 35% w/w (up to 2.7%) were considerably lower than those obtained with 28% solids (up to 8.9%). In some conditions, the concomitant use of MBs + MaBs and NBs + MBs + MaBs was able to overcome, in the first min and a half of the test, the total phosphate recovery obtained in the standard tests. Regarding the quartz, the microflotation tests (performed in modified Hallimond tube) with and without the presence of NBs showed that the association of NBs with MaBs increased the recovery of quartz (up to 39%) in practically all the studied conditions, showing its effectiveness with both fine and coarse particles. However, the tests performed in mechanical cell with and without addition of NBs showed that the use of NBs was responsible for the increase of 23 percentage points in quartz recovery. Also, flotation kinetics increased significantly and ealier in the first min of the NBs test, about twice the quartz recovery of the standard test was achieved. The results obtained in the dissertation show the high potential of NBs combined with other bubble size distributions in the improvement of the bubble-particle adhesion process and the flotation of fine phosphatic or quartz granulometric fractions, especially in short times.

Thesis. 1978. M.S.--Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 67-68. / M.S.

Many countries intend to achieve the safe management of their radioactive wastes through geological disposal. In addition, radioactively contaminated land is of global concern. To address both of these technical challenges it is imperative to understand the behaviour and subsequent migration of radionuclides in the subsurface. This thesis addresses uncertainties in the behaviour of the long-lived, risk-driving radionuclides U and Np in their most mobile and environmentally relevant oxidation states, U(VI) and Np(V). The formation the U(VI) colloidal nanoparticles is identified under the high pH, low carbonate conditions expected within the near field of a cementitious Geological Disposal Facility (GDF). XAS, SAXS, and TEM have been used to characterise these U(VI) colloids as 60-80 nm clusters of 1-2 nm clarkeite-like (Na uranate) nanoparticles, which are stable in cement leachate for a period of at least 5 years. The reactivity of these U(VI) colloids towards a range of mineral phases was investigated. In the presence of the common rock-forming minerals biotite, orthoclase, and quartz, only limited reactivity was observed with > 80 % of the U(VI) remaining in the filtered fraction after up to 5 years of reaction. In contact with cement, > 97 % of the U(VI) was removed from solution within 1 month. Reversibility studies, luminescence spectroscopy, and XAS suggest that a large portion of the cement associated U(VI) is in a uranophane-like coordination environment, likely incorporated into the C-S-H interlayers or as a stable surface precipitate. Together, this suggests that while U(VI) colloids could form in high pH (> 13) cement leachate, providing an additional pathway for migration, many of them are likely to be removed from suspension by the presence of solid cement, although 2.4 % (1.0 IμM) U(VI) remained in the filtered fraction even after 21 months of reaction. The interaction of aqueous U(VI) and Np(V) with a range of environmentally relevant Mn minerals has also been studied under circumneutral to alkaline conditions. Here, extensive (up to 99 %) uptake of U(VI) and Np(V) was observed in systems containing δ-Mn(IV)O2, triclinic (Na)-birnessite [Na0.5Mn(IV/III)2O4 · 1.5H2O], hausmannite [Mn(III/II)3O4], and rhodochrosite [Mn(II)CO3]. The uptake of U(VI) by δ-MnO2 and hausmannite was found to be partially irreversible, suggesting that these minerals could be particularly important in determining radionuclide migration. XAS indicated that both U(VI) and Np(V) formed edge-sharing bidentate adsorption complexes on the surface of δ-MnO2 and hausmannite, implying that these complexes are responsible for the observed reversibility. These complexes were also identified on triclinic (Na)-birnessite; however, after 1 month of reaction U(VI) was found to have migrated into the triclinic (Na)-birnessite interlayer, replacing Na+. Reaction with all three investigated Mn oxide phases was rapid, with equilibrium being reached within at least 2 weeks. However, whilst U(VI) and Np(V) were both extensively removed from solution in systems containing rhodochrosite, these reactions were much slower, with equilibrium taking up to 4 months to be established. XAS suggested that this was due to the formation of a U(VI) or Np(V) containing precipitate on the rhodochrosite surface.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

La conception des oscillateurs à quartz a été longtemps basée sur des méthodes empiriques ou des techniques de modélisation approximatives ou inappropriées. Bien que ces méthodes permettent de réaliser des oscillateurs stables, leur procédure de conception reste lourde et fastidieuse et le comportement du circuit oscillateur n'est pas toujours déterminé avec une précision optimale. Le logiciel ADOQ (Analyse Dipolaire des Oscillateurs à Quartz) a été développé pour remédier aux limitations de ces méthodes. Cet outil fondé sur l'analyse dipolaire consiste à modéliser un oscillateur à quartz en tenant compte des non linéarités de la partie amplificateur séparément de celles du résonateur. Grâce à cette séparation, on s'affranchit du temps de calcul prohibitif imposé par le coefficient de qualité très élevé du résonateur. Le comportement non linéaire de l'amplificateur est déterminé en boucle ouverte par une analyse temporelle réalisée à l'aide d'un simulateur électrique de type SPICE. Les résultats fournis par ce simulateur permettent de déterminer avec précision l'impédance non linaire équivalente de l'amplificateur, c'est-à-dire son impédance en fonction de la fréquence et de l'amplitude. L'analyse consiste ensuite à rechercher de manière itérative la solution en boucle fermée à partir d'une série d'analyses dipolaires en boucle ouverte et de définir avec précision les conditions de fonctionnement de l'oscillateur : fréquence, amplitude, puissance d'excitation du résonateur en régime permanent, régime transitoire et spectres de bruit d'amplitude et de phase. ADOQ permet également de déterminer la sensibilité des caractéristiques de l'oscillateur en fonction des variations de la valeur des composants ou d'autres paramètres tels que la tension d'alimentation ou la température. La méthode dipolaire nécessite de calculer l'impédance non linaire de l'amplificateur en fonction de l'amplitude de la source harmonique en régime permanent. Bien que la séparation du résonateur et de l'amplificateur permette un gain de temps appréciable, l'utilisation d'un simulateur temporel tel que SPICE nécessite tout de même d'attendre que le régime permanent soit atteint ce qui reste pénalisant pour la méthode. D'autres méthodes d'analyses utilisées dans certains simulateurs industriels permettent d'obtenir le régime permanent d'un circuit non linaire beaucoup plus rapidement : équilibrage harmonique (harmonic—balance) ou méthode balistique (shooting—method). D'autre part les modèles des composants utilisés par SPICE sont assujettis aux bibliothèques de composants fournies par le concepteur de l'outil ou le fabricant des composants. La plus grande partie du travail effectué dans cette thèse consiste à exploiter les fonctionnalités de l'outil de conception Cadence pour étendre les performances en termes de calculs (SpectreRF) et les possibilités en termes de modèles de composants (Dracula) pour optimiser le logiciel ADOQ. Des tests et des simulations ont été réalisés et les résultats ont permis de mettre en évidence les améliorations acquises ainsi que leurs limites.

Le but de ce travail est de trouver des relations entre les caractères acquis par les cristauxde quartz :-morphologie externe, morphologie interne, teneur en impuretés, dimension de la maille élémentaire, d'une part,. et les conditions de leur croissance d'autre part. Les deux types de filons choisis pour cette étude sont le filon de La Gardette (Bourg d'Oisans) et les cavités à cristaux du massif du Mont-Blanc . Ils sont habituellement classés parmi les filons "de type alpin" . Pourtant leurs cristaux sont très différents, ceux de La Gardette possèdent une structure lamellaire (Weil, 1930 ; Bambauer, Brunner et Laves, 1961) alors que ceux du Mont Blanc possèdent une structure macromosaique (Weil, 1930 ; Laemmlein, 1937). La démarche scientifique suivie présente trois aspects différents : - étude des cristaux, qui fait l'objet du chapitre premier: observation de la morphologie externe et de la morphologie interne, détermination de la teneur en impuretés et des dimensions de la maille élémentaire. - caractérisation des milieux fluides de croissance par l'étude des inclusions fluides (chap.II). La méthode employée consiste en l'observation des transformations de phases, sous le microscope. au cours du chauffage et de la réfrigération . - caractérisation de l'environnement géologique des filons (chap. III ). Dans le as de La Gardette cela entraîne l'étude du socle cristallin et de sa couverture sédimentaire puisque le filon est post- triasique. Pour les cavités à cristaux du Mont-Blanc on se limite à l 'étude du granite et de ses modifications au contact des cavités . Les résultats de cette recherche se situent sur les trois plans de la croissance du quartz, de la géochimie des fluides profonds et de la géologie des régions où se trouvent ces filons. a - Croissance du quartz. Les cristaux de quartz lamellaire sont des cristaux impurs qui croissent avec des vitesses alternativement élevées et faibles, et ensevelissent des quantités d 'impuretés différentes en fonction de ces vitesses. Les cristaux de quartz à structure macromosaique sont des cristaux très purs. La différence de faciès des deux types de cristaux (allongés ou trapus) s'explique par la différence des contenus en impuretés . Lorsque le cristal ensevelit beaucoup d'impuretés on observe un freinage préférentiel de l'avancement des faces du prisme ce qui entraine l'allongement des cristaux. L'origine de cet ensevelissement d'une grande quantité d'impuretés à La Gardette n'a pu être déterminée de façon sûre. Deux paramètres en' effet conjuguent leurs effets : la température et la nature du milieu fluide de croissance. A La Gardette la température devait être plus basse qu'au Mont- Blanc, et la phase fluide n' était pas en équilibre avec des minéraux silicatés mais avec des sédiments carbonatés. b - Géochimie des fluides profonds . L'apport de ce travail découle en partie de la découverte de fluides tardifs riches en CO2 : au cours de la rétromorphose du granite du Mont-Blanc. Cela oblige à considérer que les températures de cette rétromorphose sont beaucoup plus élevées que ne l'indiquent les températures d'homogénéisation des inclusions fluides aqueuses du quartz enfumé, et sont proches des températures actuellement admises pour le faciès schistes verts. Les températures d'homogénéisation ne nous donnent donc que la densité du fluide et de telles inclusions sont alors plus utiles comme manomètres que comme thermomètres géologiques . c - Géologie de l'Oisans et du massif du Mont-Blanc. Pour la région de Bourg d'Oisans nous pouvons dire que la densité des fluides inclus dans les minéraux du Trias et du Lias est telle qu'on doit envisager un recouvrement épais de la région entre la fin du Lias et la période actuelle, recouvrement qui a disparu maintenant. Ceci s'accorde avec l'existence d'une schistosité dans le Lias du synclinal d'Ornon et avec la découverte par Martini et Vuagnat (1965) d'un faciès à zéolite à l'ouest des massifs cristallins externes. Le filon de La Gardette apparaît alors comme un filon formé en profondeur avec du matériel (fluides, silice, sulfures) issu essentiellement des sédiments qui le recouvrent . Dans le massif du Mont-Blanc, outre la mise en évidence des hautes pressions, on montre que le CO2 a joué un rôle perturbateur durant la rétromorphose. Par l'acidité qu'il provoque il règle l' équilibre entre certains minéraux et en particulier entre orthose et muscovite. Ceci conduit à un schéma de rétromorphose en système ouvert au cours duquel la température a dû jouer un rôle moindre que la composition de la phase fluide.

The aim of this work is to better understand the factors and mechanisms leading to the supramolecular organization of collagen layers adsorbed on polymers. Native collagen adsorption on polystyrene (PS) and plasma-oxidized polystyrene (PSox) substrates revealed that the adsorbed layer consists in two parts: a dense and thin sheet (~ 10 nm) in which fibrils are formed, as revealed by atomic force microscopy, and an overlying thick layer (~ 200 nm) which contains protruding molecules, as revealed by quartz crystal microbalance with dissipation monitoring. The protruding molecules are in low density but modify noticeably the local viscosity. Faster and enhanced fibril formation takes place on hydrophobic compared to hydrophilic substrate. As a result of drastic thermal denaturation, the ability of collagen to assemble into fibrils is lost and the number of protruding molecules responsible for higher viscosity is reduced. Radiochemical measurements showed that collagen molecules are more easily displaced when adsorbed on a hydrophobic substrate compared to a hydrophilic substrate. This may explain why fibril formation occurs more readily on the more hydrophobic substrate, but is in contrast with higher surface affinity. The possible explanation of this paradox by the quick formation of a dense layer of collagen molecules having a smaller number of contact points with a very hydrophobic surface could not be demonstrated by a comparison of adsorption procedures. Comparing different collagen sources revealed various modes of aggregation with different characteristics regarding size and order (large fibers in solution, smaller fibrils to featureless underneath layer in the adsorbed phase). Moreover, collagen aggregation in the solution is a process competing with adsorption: more aggregated solutions behave like less concentrated solutions regarding the adsorbed amount and fibril formation in the adsorbed phase. It must be emphasized that interpretation of the QCM-D data, which is based on fitting physical quantities according to a model, has to be performed very carefully, and requires the examination of the sensitivity of the fitted data to the fitting parameters.