Tesi sul tema "Encre de carbone"
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Mohamadi, Parian Sadat. "Système innovant de détection du colmatage des filtres à air basé sur les e-textiles". Electronic Thesis or Diss., Centrale Lille Institut, 2023. http://www.theses.fr/2023CLIL0012.
Testo completoIn this study, thermoplastic polyurethane (TPU) nanofibers were fabricated by optimizing electrospinning parameters. In order to make the membranes conductive, the carbon ink was printed on the surface of TPU nanofibers membranes using different patterns. Mechanical tests, electromechanical measurements, and cycle testing demonstrated suitable mechanical properties, resistance changes during stretching, andrepeatability of the sensor performance. To optimize the sensor ability, membranes with structured holeswere fabricated to minimize the pressure drop. Then, the pressure drop and resistance change of the sensorswith various printing patterns were measured in a ventilation tunnel. Comparison with M5 filters showedthat the pressure drop of these printed structured membranes was similar to air filters, and did not cause anincrease in the pressure drop of the system. Moreover, the resistance change of the sensor under differentair velocities indicated high sensitivity. In conclusion, this study successfully developed a facile andscalable technique to fabricate textile sensors for detecting air velocity in air filters
Bertran, Xavier. "Comportement en milieu oxydant d’un composite carbone/carbone pour applications structurales entre 150 et 400°c dans l’aéronautique civile". Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14922/document.
Testo completoA 2D Carbon/Carbon composite is envisaged for structural parts, operating between 150 and 400°C, in civil aircraft. In this temperature range, the durability of these materials remains unknown because they have never been developed for this kind of applications. A first approach allowed us to correlate the chemical reactivity of the elemental constituents (fiber and matrix) to their structural organization. Then, thermal ageing tests performed on the composite material have demonstrated that a low rate of oxidation could be responsible to a significant reduction of residual mechanical properties. Cracks and fiber/matrix debonding resulting to the elaboration process create an extended pathway to a preferential oxidation of the most reactive compound. This latter is followed by a premature failure by delamination. The reduction of the material properties over long periods is finally discussed in order to evaluate its ability to replace metallic materials in aircraft structural parts
Danhiez, François-Pierre. "Relations entre les propriétés optiques de la matière organique dissoute colorée et le carbone organique dissous dans des eaux côtières aux caractéristiques contrastées". Thesis, Littoral, 2015. http://www.theses.fr/2015DUNK0395/document.
Testo completoThe coastal ocean represents an important component of the global carbon cycle however its participation to the overall carbon flux is currently not well constrained. Information on DOC stock and its variability in the coastel ocean is however still very scarce and its represents a strong limitation to our current understanding of the exact role of these ecosystems in the oceanic carbon cycle. In this context, the general aims of this study was to get more insights on dissolved organic carbon dynamics in the coastal ocean through the optical properties of dissolved organic matter (CDOM) that present the advantage to be easily measured from in situ or satellite observations. In practice, in situ data gathered during several sampling cruises conducted in three constrasted continental margins (Eastern Channel, French Guiana, Vietnam) have allowed : (i) the characterization of the strong regional discrepancies in the CDOM-DOC relationships between the three coastal sites investigated, (ii) the possible use of a generalized parameterization to retrieve DOC concentrations from CDOM optical properties (estimated in situ or from ocean color remote sensing)over a large range of coastal sites dominated by terrestrial imput of DOM. A further objective of this work was to investigate the impact on DOM dynamics of the phytoplankton bloom event of Phaeocystis.globosa known to affect the coastal waters of the eastern English Channel during the spring period. In practice, this DOM production was investigated during a 45 days mesocom experiment coupled to field survey data (2012-1014) leading to the identification of an optical marker of this marine CDOM production (i.e. S320-412). We further demonstrated that this optical parameter provides useful information to enhance our ability to retrieve DIC 1 from CDOM optical properties in a context of an algal bloom event
Maffre, Pierre. "Interactions entre tectonique, érosion, altération des roches silicatées et climat à l'échelle des temps géologiques : rôle des chaînes de montagnes". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30287.
Testo completoThis thesis explores how orogenies may affect the Earth climate through the quantification of the interactions between climate dynamics, continental erosion, silicate rock weathering rate and geological carbon cycle. The first chapter describes the mechanisms linking the continental topography and its impacts on the atmospheric and oceanic circulations, with emphasis on the thermohaline circulation. The second chapter compares the effects on continental weatherability of climate dynamics and erosional changes related to the presence of mountains. The third chapter describes a dynamic model of regolith designed for global scale simulations, and describes its transient behavior, as well as its response to a CO2 degassing. Finally, the last chapter presents a numerical model of the continental isotopic cycle of lithium, so that its reliability as a proxy of the past weathering can be tested. The model explores the case study of the Amazon lithium cycle
Sirat, Abdelkader. "Etude de l'électrohydrogénation du dioxyde de carbone entre 400°C et 600°C". Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20184.
Testo completoThe electrical energy storage is one of the main challenges of the century. The conversion of electrical energy into chemical energy is one of the several possibilities to store electrical energy. As CO2 is the most important gas responsible of greenhouse effect, the compilation of electrical energy storage and CO2 utilization in a process could be of particular interest. In the so-called electrohydrogenation process of CO2, a PCEC (Proton conductor electrolysis Cells) functioning at medium temperature (400°C and 600°C) is used to convert CO2 into organic compounds, like CH4 or CH3OH, to assess electrical energy transformation into chemical energy. The electrolyzer is a conversion tool which creates hydrogen protons that will react with CO2 at the cathode of the electrolyte/electrodes assembly.In this process, experimental parameters like the temperature, the pressure, the CO2 flow, and the power (U and I) applied at the assembly influence the nature and ratio of the different chemical products formed. Mainly, a low CO2 flow will promote the synthesis of products with a low melting point (alcools) even if these compounds are minor relative to CO formation.A co-electrolysis side reaction, caused by the oxygen vacancies in the perovkite (electrolyte), has been identified
Torres-Canas, Fernando José. "Tintas y materiales compuestos anisotrópicos basados en nanotubos de carbono". Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS142/document.
Testo completoThis thesis focus on the study of inks, composites and deposits of single-wall carbon nanotubes (SWNT). The control of dispersion and orientation of nanotubes in such nanostructured composites materials allows to optimize their properties, and especially their electrical and optical properties.The first part of the work is devoted to the optimization of dispersion of SWNT in aqueous suspensions stabilized by bile salts surfactants, and to the study of their optical properties, and especially their near infrared photoluminescence (PL). Dispersion of the nanotubes is probed by absorption spectroscopy. We show that their absorption coefficient is very sensitive to the individualization of the nanotubes. On the other hand, we revisit the interpretation of the PL spectra excited in the near infrared (especially at 1.17 and 1.58 eV), and we assign the different peaks to different mechanisms, namely direct excitonic transitions, exciton-phonon coupling, and energy transfer between nanotubes. We show that the evolution of PL intensity as a function of individualization allows to distinguish the different mechanisms.The second part of the work is dedicated to the preparation of aqueous suspensionsstabilized by hydrosoluble polymers (PVA and PVP), and SWNT/polymer composites, without surfactants. SWNT suspensions are mixed with polymer solutions, and then the surfactant is removed by dialysis. The yield, i.e. the relative concentration of SWNT in the dialyzed suspension, is ~75 times higher than for a suspension prepared directly with polymers. On the other hand, PL signatures are sensitive to the dielectric environment of the nanotubes which allows to evidence an exchange between the dispersing agents bile salts/PVA on the nanotube surface, such an exchange is not observed in the case of PVP.In the third part of the thesis, we use the inkjet printing technique to print continuous micrometric lines of SWNT, and we propose original methods to study their morphology and their anisotropy. The morphology of the deposits varies between two limit cases, an homogeneous deposit and a ‘‘pair of tracks'', by varying nanotube concentration in the inks, inter-drop distance and substrate temperature. The orientation of the nanotubes is very high at the edge of the deposits (orientational order parameter S between 0.6 y 0.9), the nanotubes are well-oriented as well in the tracks (S~0.5) and to a lesser extent in the homogeneous lines (S~0.3)
Marini, Marcio Vinicius. "Avaliação da aderência entre o concreto e o sistema de reforço com fibra de carbono". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258422.
Testo completoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
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Resumo: O reforço de estruturas de concreto armado ou protendido têm sido necessário na construção civil devido às falhas causadas por erros em projetos e execuções de obras, corrosões de armaduras, reabilitação após incêndios ou mudanças na utilização das estruturas projetadas. Os métodos convencionais para reforço de estruturas de concreto estão relacionados ao reforço pela adição de barras de aço e de concreto na estrutura ou, ainda, pela instalação de chapas de aço. O uso de fibras de carbono para reforços estruturais é recente, apresentando vantagens em relação aos métodos tradicionais, tais como: fácil manuseio na aplicação, alta aderência entre as fibras de carbono e o concreto e aumento na resistência à corrosão. Sendo assim, o objetivo deste trabalho é avaliar a aderência entre o sistema de reforço com as fibras de carbono e concretos com resistência à compressão de 15 MPa, 40 MPa e 60 MPa. A aderência concreto/fibra foi avaliada por meio de ensaios pull-out em pequenas placas de concreto com fibras de carbono aplicada superficialmente. Do concreto, foram obtidos resultados de sua porosidade e rugosidade; por meio de estereomicroscópia, foram avaliadas características como a textura superficial. Os resultados demonstraram que os concretos com menor relação água/cimento (a/c), ou seja, com maior resistência à compressão apresentaram maior aderência entre si e o sistema de reforço com fibras de carbono e menores valores de porosidade e rugosidade com maior homogeneidade superficial. Em relação aos concretos com maior relação água/cimento (a/c), observou-se o comportamento inverso nas propriedades citadas. De acordo com esses resultados, pôde-se concluir que a resistência à compressão do concreto (substrato) alterou a resistência de aderência com o sistema de reforço com fibras de carbono e também a porosidade; a rugosidade e a característica de superfície não influíram significativamente nestas propriedades
Abstract: Strengthening of conventional or prestressed concrete structures has been used due to failure occurred by design errors, erroneous methods and executives process, corrosion of steel bars of concrete pieces, rehabilitation after damages caused by fire or variations of structure type utilization. Conventional strengthening methods of concrete structure are used adding new steel bars to structure or installing steel plates. However more recent reinforcement methods based on carbon fiber use had been demonstrated advantages, such as: easy and fast application to substrate, high adhesion between carbon fiber and concrete and method to increase corrosion of bars of concrete structures. Thus, this work aims to evaluate adhesion process between strengthening concrete system employing carbon. In the experimental study was used concrete specimens with compressive strength of 15 MPa, 40 MPa and 60 MPa. The interface adherence of concrete/fiber was evaluated through pull-out test type on concrete slabs, where carbon fiber was superficially applied. Results of concrete porosity and roughness were obtained through a stereo microscope that assesses characteristics as the superficial texture. The obtained results showed that concretes with lower water/cement ratio (w/c) had higher values of adhesion between carbon fiber and concrete, lower porosity values and higher superficial homogeneity. Opposite behavior was observed in concretes with higher water/cement ratio (w/c). According to the obtained results was possible to note that the compressive strength concrete (substrate) modified the adherence resistance between concrete and carbon fiber, where higher compression strength increased adherence between concrete and carbon fiber. Also the results indicated that both the concrete surface characteristics and the roughness were not influenced significantly
Mestrado
Estruturas
Mestre em Engenharia Civil
Leal, Carla Camargo. "Fatores determinantes da eficiência de carbono das empresas participantes do carbon disclosure project entre 2006 e 2009". Universidade Presbiteriana Mackenzie, 2012. http://tede.mackenzie.br/jspui/handle/tede/797.
Testo completoFundo Mackenzie de Pesquisa
In just over 20 years of systematic studies on climate change, there are still many questions about its causes and its effects in environmental, social and economical terms. Various global institutions are involved with the issue, including among them, national governments, companies, and non-governmental organizations. The Carbon Disclosure Project collects information annually on carbon emissions from business; the project is due to the initiative of environmental organizations, which inserted the concern about the impact of climate change over business on the agenda of institutional investors. The objective of this thesis is to investigate, among the possible factors that influence the positioning of companies and business attitudes, which are those that are associated with significantly higher or lower greenhouse gases emissions, as well as major changes, a) in proportion to the company's growth, b) regarding industry peers and c) in relation to the emissions of previous periods, taking as basis the information reported by companies to the Carbon Disclosure Project between 2006 and 2009. The potential influence factors analyzed include: a) financial aspects; b) issues related to financial risks; c) issues related to climatic risks; d) certified processes of environmental management; e) forms of reporting the information on climate change adopted by the companies; e) the location; f) the industry. Regarding the volume of emissions, the results indicated two factors of influence: the location, i.e., the fact that the company is headquartered in a country listed in Annex I of the Kyoto Protocol; and the industry, i.e., the industrial activity to which the company belongs. As for efficiency relative to sales and to industry peers, the results indicated that we can not statistically reject the influence of the following factors: a) age of assets; b) level of financial leverage; c) level of assets intangibility; d) headquarters established in a country signatory to the Kyoto Protocol. The results of the analysis of possible factors influencing the variation in emissions compared to previous periods, however, failed to identify the influence of any factor.
Em pouco mais de 20 anos de estudos sistemáticos sobre as mudanças climáticas, restam ainda muitas dúvidas sobre suas causas e seus efeitos em termos ambientais, sociais e econômicos. Diversas instituições mundiais estão envolvidas com a questão, incluindo-se dentre elas, os governos nacionais, as empresas e organizações não governanamentais. O Carbon Disclosure Project coleta anualmente informações sobre emissões de carbono das empresas e seu surgimento se deu por iniciativa de organizações ambientalistas, que inseriram a preocupação com o impacto das mudanças climáticas sobre os negócios nas agendas dos investidores institucionais. O objetivo dessa pesquisa é investigar, dentre os possíveis fatores de influência sobre o posicionamento e as ações das empresas, quais são aqueles que se associam significativamente a maiores ou menores emissões de gases de efeito estufa, bem como a maiores variações, tanto proporcionalmente ao crescimento da empresa, quanto comparativamente aos pares do setor e ainda relativamente às emissões dos períodos anteriores, tomando-se como base as informações relatadas pelas empresas ao Carbon Disclosure Project entre 2006 e 2009. Os fatores potenciais de influência analisados incluem aspectos financeiros, aspectos relacionados a riscos financeiros e climáticos, os processos certificados de gestão ambiental, as formas de publicidade das informações relativas as mudanças climáticas adotadas pelas empresas, a localização geográfica e o setor. Quanto ao volume de emissões, os resultados apontaram dois fatores de influência: o fato da empresa estar sediada em um país listado no Anexo I do Protocolo de Quioto e o setor de atividade ao qual a empresa pertence. Quanto à eficiência, relativamente a vendas e aos pares do setor, os resultados indicaram que estatisticamente não se pode rejeitar a influência dos seguintes fatores: a) idade dos ativos: b) do nível de alavancagem financeira; c) do nível de intangibilidade e d) do fato da sede estar estabelecida em país signatário do Protocolo de Quioto. Os resultados da análise de possíveis fatores de influência na variação das emissões em relação aos períodos anteriores, no entanto, não permitiram identificar influência de qualquer fator.
Lamboley, Xavier. "Apparition de rugosités de surface lors de l'ablation d'un matériau composite en régime de transition entre laminaire et turbulent". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0334.
Testo completoDuring the descent of an atmopheric reentry vehicle, very high pressure and heat flux (> 2000 K) is reached at the surface of the body. In order to withstand these extreme conditions, thermal protective systems are used. These are composed of carbon-carbon composite materials. Numerous phenomena will occur at the material surface, including heterogeneous chemical reactions of oxidation and nitriding of the carbon. In the most extreme cases, sublimation will also occur. These reactions will lead to the ablation of the thermal protection.Along the different flow regimes from laminar to turbulent, a multiscale roughness will be developed on the material. The laminar regime is associated with a microscopic roughness due to the architecture of the carbonated composite. This surface condition will then favour locally the laminar to turbulent transition, leading to macroscopic structures, of the centimeter scale. Finally when the turbulence is fully developed, regular waves appear no more localised but this time generalised to the whole surface. These characteristic patterns are known as "scallops". They are able to multiply the heat transfer and the recession rate by more than 2; therefore understanding their formation and behaviour is a necessity for a better design of the thermal protection.A numerical approach has been considered in order to identify the stability regimes of a surface perturbation according to the flow regime, the micro-roughness of the material, and its reactivity. The code SURRF, based on the open-source software OpenFOAM was developed in this context. Thanks to the turbulence model gamma-Re_th which models the laminar-turbulence transition, the parameters which enable the development and growth of the scallops at the material surface were determined
Souza, André Luis Rocha de. "Perfil do mercado de carbono no Brasil: análise comparativa entre os mercados regulado e voluntário". Universidade Federal da Bahia, 2012. http://www.adm.ufba.br/sites/default/files/publicacao/arquivo/andre_luis_rocha_de_souza_0.pdf.
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Essa pesquisa teve por objetivo geral investigar as principais diferenças entre o mercado de carbono regulado e voluntário no Brasil, no período de 2004 a 2011. Para alcançar o objetivo proposto, realizou-se uma pesquisa exploratória, de caráter bibliográfica e documental. Além disso, realizou-se o mapeamento de projetos no mercado de carbono voluntário no Brasil por meio de busca em bancos de dados e sites institucionais dos Padrões Internacionais (PIs) e dos proponentes, enquanto que os projetos do mercado de carbono regulado foram extraídos do banco de dados já existente no site do Ministério da Ciência e Tecnologia (MCT). Os dados secundários foram coletados por meio de analise de conteúdo dos Documentos de Concepção dos Projetos (DCP) mapeados e extraídos dos sites e banco de dados visitados. Verificam-se diferenças e semelhanças entre os mercados de carbono regulado e voluntário no Brasil, estando o primeiro mercado com 499 projetos, enquanto o segundo possui 111 projetos até o momento. Constatou-se que o mercado de comercialização de créditos de carbono brasileiro, seja ele na categoria regulada, seja na voluntária pode constituir-se em um instrumento econômico de extrema importância na viabilização da redução das emissões de GEE, contribuindo, assim, para a mitigação das mudanças climáticas e para o alcance das metas nacionais de redução de emissão de GEE fixadas na Política Nacional de Mudanças Climáticas (PNMC). Constatou-se também que o uso desses projetos como instrumentos de políticas públicas poderá contribuir significativamente para o cumprimento das metas fixadas pela PNMC e requer a criação de fundos de financiamentos voltados para esses mercados, viabilizando o aumento do número de projetos e suas contribuições para mitigar as mudanças climáticas, bem como a consolidação desses mercados no Brasil. Além disso, faz-se necessário que o governo estimule a iniciativa privada a investir em tecnologias ambientalmente seguras, viabilizando o aumento de energias renováveis para o país, que contribuam para a transição para uma economia de baixo carbono, além da criação de incentivos fiscais que motivem as empresas a desenvolverem os projetos de redução de emissão de GEE. Enfim, recomenda-se como novas investigações futuras a realização de pesquisa com o objetivo de verificar de que forma os créditos de carbono são comercializado no Brasil, identificando as características dos contratos fechados no mercado financeiro nacional, como também a realização de estudos de caso em projetos representativos do mercado de carbono voluntário no Brasil, visando confrontar os dados secundários obtidos via análise de dados com os dados primários obtidos através de pesquisa de campo.
Salvador
Neu, Vania. "O ciclo do carbono na bacia do Alto Xingu: interações entre ambientes terrestre, aquático e atmosférico". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/91/91131/tde-17042009-141320/.
Testo completoThe objective of this research was to quantify the fluxes of carbon (C) input and output in a watershed during a hydrological year that represent important components for the C budget in an ecosystem. The watershed studied covered an area of 1319 ha, and is drained by the Darro River tributary, Xingu Basin, Mato Grosso state - Brazil. The area is characterized by a typical transition from evergreen tropical forest to Cerrado. In order to estimate the input and transport of C in the system, samples from 12 rain events were collected over the year and measured for dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the rainwater, throughfall, stemflow, overlandflow, soil solution, and groundwater. C fluxes were quantified in 13 sampling events for carbon dioxide (CO2) and methane (CH4) emissions from the stream and soil, and for DOC, DIC and particulate organic carbon (POC) exported by the stream. Mean annual DOC concentration in the rainwater was 6.7 ± 3.7 mg L-1 representing an input of 82.3 Kg C ha-1 yr-1. Throughfall represented the largest flow path of DOC in the system with an annual transport of 142.6 Kg C ha-1 yr-1. Stemflow and overlandflow contributed to 1 and 2% of the total DOC transported in the system. For dissolved inorganic carbon, the concentrations in aboveground compartments were very low, similar to what is expected as result of the equilibrium whith the atmosphere. In contrast, DIC concentration in the belowground flow paths was high due to supersaturation in relation to the CO2 concentrations in the atmosphere. Soil C emission was the largest carbon flow path in the basin, more than 6000 Kg C ha-1 yr-1, which represented 99% of C losses in the watershed. In the case of CH4 the soil acted as a C sink with a sequestration rate of 4.37 ± 0.09 Kg C ha-1 yr-1. The stream showed elevated fluxes of CO2 and CH4 of more than 63000 Kg C ha-1 yr-1 . However, compared to the entire basin area the losses from the stream were small (56.2 ± 0.07 Kg C ha-1 yr-1). Although the DOC concentration in the stream was low, it represented the main organic carbon loss component, with a flux of 1.6 Kg C ha-1 yr-1. Losses of DIC and POC from the stream amounted around 0.9 Kg C ha-1 yr-1 and 0.01 Kg C ha-1 yr-1, respectively. The high DOC concentrations in aboveground flow paths exibited clear seasonal variations, in part problably as a result of massive human activities in the region. Also, the high concentrations of DIC in the soil solution and in groundwater during the rainy season, associated with the highest CO2 fluxes, indicated the strong connectivity between terrestrial and aquatic environments.
Launois, Thomas. "Modélisation de la composition isotopique des cernes d'arbres (13C et 18O) et des transferts de COS entre l'atmosphère et la biosphère continentale pour quantifier les flux bruts de carbone". Thesis, Versailles-St Quentin en Yvelines, 2014. http://www.theses.fr/2014VERS0039/document.
Testo completoIn the context of global climate change, the behavior of the terrestrial biosphere can be durably affected by the increased frequency and intensity of extreme climatic events, which can decrease the photosynthetic assimilation of carbon and/or increase the respiration rate of the ecosystems. Therefore, quantifying the carbon storage capacity of the ecosystems and predicting their sensitivity to climate changes strongly rely on our capacity to separately estimate the photosynthesis and respiration rates at different scales. The gross primary productivity (GPP) is however not directly measurable. Indirect approaches have been proposed to estimate the biospheric gross fluxes (GPP and respiration), combining for instance stable isotopologues of CO2 (13C and 18O), and, more recently, the measure of carbonyl sulfide (COS) concentrations in the atmosphere. In this context, my PhD work followed two complementary approaches. In the first approach, isotopic measurements and tree-ring widths were used, because both of them are linked to the photosynthetic activity. The inter-annual variations of the photosynthetic fluxes simulated with the ORCHIDEE continental biosphere model were evaluated and compared with in situ measurements. The second approach consisted in using atmospheric measurements of OCS concentrations and in exploring their potential to constrain the current estimates of the GPP in dynamic global vegetation models (DGVM), by (1) establishing a new global budget of sources and sinks of this gas, (2) optimizing the source and sink terms of this cycle and (3) estimating the potential of this new tracer to validate/invalidate the simulated GPP when using current DGVMs
Hennequin, Salomé. "Étude des couplages entre l'évolution géologique des cycles biogéochimiques, du climat, et de la biodiversité océanique". Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30197.
Testo completoThe main objective of this thesis is to understand the co-evolution of biogeochemical cycles, climate and ocean biodiversity at the geological time scale through numerical modeling. Currently numerical models simulating the geological evolution of climate and long-term geochemical cycles simulate the oceanic primary bioproductivity, this component being either forced by the inversion of the delta(13)C signal measured on sedimentary carbonates, or modelled in a totally deterministic way by making it only dependent on the available nutrient fluxes. It therefore appears impossible to compare the geochemical evolution of the atmosphere and oceans (e.g. CO2, delta(13)C) with the evolution of its biodiversity (fossil record). In order to contribute to the filling of this gap between paleontological data and numerical biogeochemical-climate models, an ecological module is introduced in the GEOCLIM model. It allows the calculation of productivity and individual biomass for a prescribed number of primary producers, primary and secondary consumers and predators. The random selection of some of the parameters used in this calculation allows the creation of a unique assembly of groups for each simulation. The simulations were carried out in a dynamic way across the Permian-Trias boundary, with the massive degassing of CO2 linked to the onset of the Siberian large igneous province. The temperature sensitivity of the different assemblages of primary producers leads to a variety of responses to the perturbation, in the intensity of the extinction rates, of the excursion in delta(13)C and of the variation in primary bioproductivity. Among the full set of simulations, primary bioproductivity can either increase or decrease in response to global warming, despite a significant loss of biodiversity for all simulations. The response of primary producer groups amplifies or reduces the magnitude of global warming. The biomass of the groups in the upper trophic levels evolves according to the biomass of the primary producers at the base of the trophic chain. Despite limited comparisons with geological data, the ecological module coupled with GEOCLIM has made possible the investigation of the feedbacks between the evolution of biodiversity and the evolution of the carbon cycle and climate over geological time scales
Coelho, João Paulo. "Interação não covalente entre nanotubos de carbono de paredes múltiplas e a proteína ovalbumina e o oligonucleotídeo CpG". CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2013. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=300.
Testo completoDiversos estudos têm sido realizados utilizando proteínas e oligonucleotídeos adsorvidos em nanotubos de carbono para inúmeras aplicações como, por exemplo, em nanomedicina, catálise, biosensores etc. No entanto, os tipos de interações que ocorrem entre essas biomoléculas e os nanotubos de carbono, as quais certamente influenciam ou mesmo determinam o desempenho desses híbridos, ainda não estão bem entendidos. Esse entendimento é muitas vezes dificultado pela complexidade tanto da estrutura das biomoléculas (a estrutura secundária das proteínas e os diversos resíduos de aminoácidos e bases nitrogenadas contendo diferentes grupos funcionais), quanto da superfície dos nanotubos de carbono quimicamente processados. O presente trabalho aborda o estudo da interação não covalente entre a proteína ovalbumina (OVA) e o oligonucleotídeo CpG (sequência de bases T*C*G*T*C*G*T*T*T*T*G*T*C*G*T, onde * representa uma ligação do tipo fosforotioato) e nanotubos de carbono de paredes múltiplas (MWNT), visando ao entendimento da atuação desse sistemas híbridos como nanocarreadores em formulações vacinais. Inicialmente, amostras de MWNT e MWNT oxidados (Ox-MWNT) foram caracterizadas por termogravimetria, espectrometria de energia dispersiva, espectroscopias Raman e no infravermelho (IV), microscopia eletrônica de transmissão (MET) e titulação potenciométrica. O processo de purificação/oxidação adotado resultou em amostras com pureza de 88% em massa de nanotubos, contendo tubos de até 2 μm (após dispersos), com paredes pouco defeituosas e a superfície funcionalizada com 0,78 mmol.g-1 de grupos ácidos carboxílicos e 0,92 mmol.g-1 de grupos fenólicos. Foram obtidos quatro sistemas híbridos dispersos em solução aquosa, MWNT-OVA, Ox-MWNT-OVA, MWNT-CpG e Ox-MWNT-CpG, os quais foram caracterizados por espectroscopia Raman, no IV e no ultravioleta-visível, potencial Zeta (ξ), MET e dicroísmo circular. De maneira geral, os híbridos obtidos apresentaram alta estabilidade em meio aquoso e seletividade no sítio ligante. Enquanto o CpG interage com ambos MWNT e Ox-MWNT via empilhamento-π, a interação entre a OVA e os nanotubos parece ocorrer principalmente via empilhamento-π com o MWNT e ser dominada por um caráter eletrostático com o O-MWNT. A interação com os nanotubos de carbono altera a liberdade conformacional das biomoléculas estudadas, principalmente a OVA, tendo como consequência o enfraquecimento das ligações de hidrogênio na biomolécula e uma maior definição das bandas vibracionais associadas a cada uma das estruturas secundárias da proteína.
Several studies have been conducted using protein and oligonucleotides adsorbed onto carbon nanotubes for many applications such as nanomedicine, catalysis, biosensors etc. However, the types of interactions that occur between these biomolecules and carbon nanotubes, which certainly influence or even determine the performance of these hybrids, are not yet well understood. This understanding is often hindered by the complexity of both the structure of biomolecules (the secondary structure of proteins and several residues of amino acids and nitrogen bases containing different functional groups), and the chemically processed surface of the carbon nanotubes. Herein, we describe the non-covalent interaction between the protein ovalbumin (OVA) and oligonucleotide CpG (with specific bases sequence T * C * G * T * C * G * T * T * T * T * G * T * C * G * T, where * is a phosphorothioate bond) and multi-walled carbon nanotubes (MWNT), aimed at understanding the hybrid systems performance as nanocarriers for vaccine formulations. Firstly, MWNT and oxidized MWNT (Ox-MWNT) samples were characterized by thermogravimetry, energy dispersive spectrometry, Raman and infrared (IV) spectroscopies, transmission electron microscopy (MET) and potentiometric titration. The purification/oxidation process resulted in 88% purity samples by mass of nanotubes containing tubes up to 2 micrometers (after dispersed) with slightly defective walls and functionalized surface with 0.78 mmol.g-1 of carboxylic acidic groups and 0.92 mmol.g-1 of phenolic groups. We obtained four hybrids dispersed in aqueous solution, MWNT-OVA, Ox-MWNT-OVA, MWNT-CpG and Ox-MWNT-CpG, which were characterized by Raman, IV, circular dichroism and ultraviolet-visible spectroscopies, Zeta potential (ξ) and MET. All the hybrids obtained showed high stability in aqueous media and selectivity binding site. While CpG interacts with both MWNT and Ox-MWNT via π-stacking, the interaction between the nanotubes and the OVA seems to occur mainly via π-stacking with MWNT and be dominated by an electrostatic character with Ox-MWNT. The interaction with the carbon nanotubes alters the conformational freedom of biomolecules here studied, mainly the OVA, weakening of the intramolecular hydrogen bonds of biomolecule and a higher definition of the vibrational bands associated each one of the protein secondary structure.
Boeira, Carla Daniela. "Comparação entre diferentes intercamadas contendo silício para adesão de filmes de DLC sobre substrato de aço AISI 4140". reponame:Repositório Institucional da UCS, 2016. https://repositorio.ucs.br/handle/11338/1758.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES.
Diamond-like carbon (DLC) films research has a high academic appeal, is being developed for more than four decades. Nowadays, the industrial needs in their properties, such as high wear resistance and superlow friction coefficient, boosted the development of different applications in large scales and many fields [1]. However such applications are restricted by the low adhesion of this material on steel. An alternative for solving this problem is the deposition of a silicon-containing interlayer [2]. However, there are few methodical studies of dependence on key parameters such as temperature and process use of silicon-containing liquid precursors such as tetramethylsilane (TMS), hexamethyldisiloxane (HMDSO) and tetraethoxysilane (TEOS). In this work, different interlayer were deposited by using these three precursors on AISI 4140 steel substrates in order improve the DLC film adhesion. The treatments were done in bipolar pulsed-DC PECVD equipment with electrostatic confinement. The samples were characterizes in details by means of FEG-SEM, EDS, GD-OES and nanoscratch tests. On the one hand, FEG-SEM images revealed an interlayers thickness dependence on deposition temperature, which is quite similar in the all samples. On the other hand, EDS and GDOES analysis identified and quantified intensities variation of iron, silicon, hydrogen, oxygen and carbon intensities that are elements responsible for the structure DLC/interlayer/substrate. The GD-OES analyzes allowed to identify the variation of concentration the elements present in the interlayer for each precursor used. Corroborating these results, linear nanoscratch tests showed delamination to DLC in different loads, indicating the influence of concentration to elements on the adhesion of the film. The critical delamination load for DLC films deposited on interlayers deposited by HMDSO at 300 °C is greater than 500 mN (equipment limit). Finally, the critical load for TMS at 300 °C is 313.8 mN and for TEOS at 300°C is 306 mN, where the concentration of the oxygen and silicon elements present in the interlayer impaired adhesion of the DLC film. The interlayer deposited by the precursor HMDSO points to the greater amount of C, consequently the greater number of C–C bonds promotes better adhesion of the DLC film to a temperature of 300 °C.
Minchetti, Inaê Mayor [UNESP]. "Mercado de carbono: um estudo comparado entre Brasil, China e Índia". Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/89997.
Testo completoCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
As questões ambientais nos últimos anos têm adquirido cada vez mais importância no cenário econômico mundial, sobretudo em razão de evidências sobre graves problemas ambientais de impacto global. Em 2005 entrou em vigência o Protocolo de Quioto da Convenção Quadro das Nações Unidas sobre Mudança do Clima, estabelecendo metas de redução da emissão de gases causadores do efeito estufa (GEE) para os países desenvolvidos, assim como mecanismos de flexibilização para auxiliar os países no cumprimento dessas metas. O mecanismo de flexibilização que pode ser utilizado por países como Brasil, China e Índia é o Mecanismo de Desenvolvimento Limpo (MDL), o qual pode gerar “créditos de carbono” comercializáveis. O objeto do presente estudo é o estudo comparado do desempenho do Brasil, China e Índia no marcado de carbono, de acordo com a metodologia de cálculo do fator de emissão baseada na matriz energética para a obtenção dos Certificados de Emissões Reduzidas (CERs), e com a legislação ambiental nacional voltada para a regulamentação desse mercado. A metodologia aqui utilizada para cada um dos três países compreende: a) estatísticas descritivas sobre o número de projetos aprovados; b) caracterização dos projetos no que se refere a sua localização setorial, porte (custos econômicos e benefícios ambientais); tempo de maturação e respectivos CERs gerados; origem da iniciativa (se pública ou privada, se nacional ou estrangeira); e, c) inventário das informações sobre o contexto nacional no que diz respeito à matriz e política energética de cada país, o marco regulatório na área ambiental, as linhas de financiamento e fundos de investimentos disponíveis para projetos MDL. As oportunidades econômicas e ambientais propiciadas pelas iniciativas de projetos MDL nos três países concentram-se...
Environmental issues in recent years have acquired increasing importance in the global economic scenario, especially because serious environmental problems of global impact. In 2005 enter in vigor the Kyoto Protocol of the Convention United Nations Framework on Climate Change, setting targets for reducing the emissions of greenhouse gases (GHG) for developed countries, as well as flexibility mechanisms for helping the countries to comply with these targets. The flexibility mechanism that can be used by countries like Brazil, China and India is the Clean Development Mechanism (CDM), which can earn saleable “carbon credits”. The object of this study is a comparative analysis of the performance of Brazil, China and India in the carbon market, according to the methodology of calculation of emission factor based on the energy matrix to obtain the Certified Emission Reductions (CERs), and with the national environmental legislation focused in the regulation of this market. The methodological approach applied here for each of these three countries includes: a) descriptive statistics on the number of approved projects; b) characterization of the projects regarding the location industry, business (economic costs and environmental benefits), duration of maturation and their CERs generated; origin of the initiative (public or private, whether domestic or foreign); and, c) the inventory of information on the national context in relation to the energy matrix and policy of each country, the regulatory framework in the environmental area, the financial support and investment funds available for CDM projects. The economic and environmental opportunities provided by the initiatives setup as CDM projects in all three countries it’s concentrated in the sectors of renewable energy, especially biomass and wind power, where investments in China... (Complete abstract click electronic access below)
Bairam, Emna. "Etude des processus écophysiologiques caractérisant la distribution du carbone entre les sources et les puits au sein de la charpentière du pommier. Eléments pour un modèle fonction-structure". Thesis, Rennes, Agrocampus Ouest, 2017. http://www.theses.fr/2017NSARC129/document.
Testo completoThe synthesis and the transport of carbon in apple are basedon a whole host of complex and interlaced mechanisms thatdepend on endogenous and exogenous factors. An approachthat combines the ecophysiological characterisation with theuse of a Functional-Structural Plant Model (FSPM) representsan interesting method in this fi eld of research, inasmuch assuch an FSPM allows integrating the topology and the geometryof the plant and its constituting organs with the entiretyof factors involved in assimilation as well as water andcarbon transport. The present study has contributed to thebetter understanding of the source-sink relations characterizingthis system but also to the elaboration of a multi-scaledFSPM. First, the development of models for the prediction ofthe architecture of different shoot types in apple from simplevariables provides a novel way to simplify the simulationof theinitial structure of branches but also to quantify leaf area in arobust manner. Second, the creation of a network of correlationsamong morphometric variables of the different organsformed by the mixed bud of apple clearly shows the functionalrelations among the spur organs. In the end, the study ofsource-sink relations at the branch scale has allowed, on theone hand, to characterize the regulation of net photosynthesisas a function of a changed source/sink ratio but also asa function of leaf type and, on the other hand, to shed somelight on the infl uence that the competition among fruits hason increasing sink strength and thus regulating the leaf
Minchetti, Inaê Mayor. "Mercado de carbono : um estudo comparado entre Brasil, China e Índia /". Araraquara : [s.n.], 2009. http://hdl.handle.net/11449/89997.
Testo completoBanca: Rogério Gomes
Banca: Ademar Ribeiro
Resumo: As questões ambientais nos últimos anos têm adquirido cada vez mais importância no cenário econômico mundial, sobretudo em razão de evidências sobre graves problemas ambientais de impacto global. Em 2005 entrou em vigência o Protocolo de Quioto da Convenção Quadro das Nações Unidas sobre Mudança do Clima, estabelecendo metas de redução da emissão de gases causadores do efeito estufa (GEE) para os países desenvolvidos, assim como mecanismos de flexibilização para auxiliar os países no cumprimento dessas metas. O mecanismo de flexibilização que pode ser utilizado por países como Brasil, China e Índia é o Mecanismo de Desenvolvimento Limpo (MDL), o qual pode gerar "créditos de carbono" comercializáveis. O objeto do presente estudo é o estudo comparado do desempenho do Brasil, China e Índia no marcado de carbono, de acordo com a metodologia de cálculo do fator de emissão baseada na matriz energética para a obtenção dos Certificados de Emissões Reduzidas (CERs), e com a legislação ambiental nacional voltada para a regulamentação desse mercado. A metodologia aqui utilizada para cada um dos três países compreende: a) estatísticas descritivas sobre o número de projetos aprovados; b) caracterização dos projetos no que se refere a sua localização setorial, porte (custos econômicos e benefícios ambientais); tempo de maturação e respectivos CERs gerados; origem da iniciativa (se pública ou privada, se nacional ou estrangeira); e, c) inventário das informações sobre o contexto nacional no que diz respeito à matriz e política energética de cada país, o marco regulatório na área ambiental, as linhas de financiamento e fundos de investimentos disponíveis para projetos MDL. As oportunidades econômicas e ambientais propiciadas pelas iniciativas de projetos MDL nos três países concentram-se... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Environmental issues in recent years have acquired increasing importance in the global economic scenario, especially because serious environmental problems of global impact. In 2005 enter in vigor the Kyoto Protocol of the Convention United Nations Framework on Climate Change, setting targets for reducing the emissions of greenhouse gases (GHG) for developed countries, as well as flexibility mechanisms for helping the countries to comply with these targets. The flexibility mechanism that can be used by countries like Brazil, China and India is the Clean Development Mechanism (CDM), which can earn saleable "carbon credits". The object of this study is a comparative analysis of the performance of Brazil, China and India in the carbon market, according to the methodology of calculation of emission factor based on the energy matrix to obtain the Certified Emission Reductions (CERs), and with the national environmental legislation focused in the regulation of this market. The methodological approach applied here for each of these three countries includes: a) descriptive statistics on the number of approved projects; b) characterization of the projects regarding the location industry, business (economic costs and environmental benefits), duration of maturation and their CERs generated; origin of the initiative (public or private, whether domestic or foreign); and, c) the inventory of information on the national context in relation to the energy matrix and policy of each country, the regulatory framework in the environmental area, the financial support and investment funds available for CDM projects. The economic and environmental opportunities provided by the initiatives setup as CDM projects in all three countries it's concentrated in the sectors of renewable energy, especially biomass and wind power, where investments in China... (Complete abstract click electronic access below)
Mestre
Walcker, Romain. "Dynamique spatiale des mangroves de Guyane entre 1950 et 2014 : forçage atmosphérique et conséquence pour le stock de carbone côtier". Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30318/document.
Testo completoMangroves in French Guiana are characterized by their spatial dynamism. This specificity is the result of intense coastal sedimentary processes. The goals of this study are to: (1) quantify mangrove spatial dynamics on a regional level and a multi-decadal timescale using archives of remote sensing images; (2) test the hypothesis of the role played by the atmosphere using correlations with time series of atmospheric and ocean surface reanalysis datasets; (3) quantify consequence of this spatial dynamism on coastal carbon storage. Results showed that approximatively 15 000 ha of mangroves fluctuate on a multi-decadal timescale in opposition to the North Atlantic Oscillation (NAO) phases, the main mode of atmospheric multi-decadal variability in the North Atlantic. This relation is operated by ocean waves whose energy is modulated by NAO phases. The study suggests that, on the one hand, decrease of mangrove surface areas is due to periods of high wave energy (NAO+) which favour coastal erosion and mangrove retreat, sediment resuspension and transport. On the other hand, the study suggests that periods of low wave energy (NAO-) favour sediment deposition on the coast and is at the origin of mangrove surface area expansion. Results also showed that alternation between phases of retreat and expansion generates the demographic structure of mangrove ages, which determines the mangrove carbon storage capacity. The study finally suggests that through time mangrove can switch from a source to a sink of carbon, and vice and versa, for the ocean and the atmosphere
Nsouadi, Clarda. "Analyse multi-échelle du comouvement entre les prix du quota carbone, du crédit carbone, et des produits énergétiques". Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTD052/document.
Testo completoThe purpose of this thesis is to contribute to the understanding of the carbon price quota structure, the analysis of its fluctuation, and the interactions that may exist between on the one hand the EU system of emission quota exchange (ETS) and the mechanism for clean development (CDM) and on the other hand between carbon quota market and the quota in the energy sector. For this study, we introduced the hypothesis of heterogeneity of agents' behavior on the carbon market where coexist multiple scales of investments.To achieve this, we used a time-frequency approach (wavelets) that can analyze the local behavior of a signal by isolating the components related to the agents’ trading frequency. This method allows variance decomposition of a time series into different frequency components. The time investment horizons are assigned to each frequency band associated with a degree of market risk. High frequency bands obtained by wavelet decomposition contain information pertaining to the short-term time series structure; the medium and the low frequencies respectively capture the structures of the time series in the medium and long term.To complete this project we proposed developing of our research in 3 chapters:The first chapter presents the carbon market, its creation, its operation, and the various actors who animate it. The formation of the CO2 price, its evolution and its determinants were also analyzed during this chapter.The second chapter develops a multi-scale analysis of the co-movement between price of quota (ETS) and carbon credit (CDM). This particular study was based on two assumptions:- The first assumption was the homogeneity of the various agents’ behaviors. The co-movement relationship between the price of quota (ETS) and carbon credit (CDM) assumes that market participants have the same investment strategy especially since all stakeholders agents invest in these markets on the same horizons. This relationship is studied using standard econometric tools such as Analysis of Co-integration of causality and Vector Autoregressive modeling.The main result of this specific part highlights the existence of a unidirectional causality from the ERC to the EUA with an observed acceleration of the mechanism for clean development (CDM). Manufacturers have a strong interest in the CDM which has had a direct impact on the price of EUAs on the European carbon market. We also observed a dynamic interconnection through the VAR (1) between EUA and CER.- The second assumption is the heterogeneity of agents' behavior. We highlighted the relationship of co-movement between price of quota (ETS) and carbon credit (CDM) to a multi-scale analysis derived from wavelet theory. We show that whatever the different investment horizons retained (short, medium and long term), there is a significant positive relationship between the two sets of prices. The more dynamic causal wavelet on each pair of frequency bands detects an unstable relationship between EUA and CER which confirms our working hypothesis.And finally, a third chapter that complements the previous analysis by the co-movement between multi-scale carbon allowance prices resulting from the ETS to those energy markets (oil, coal and gas). Using coherence wavelet, it examined the simultaneous dependence (co-movement) between two price series in time and frequency. It can be interpreted as a local measurement of correlation calculated non-parametrically. Overall, this study is the first attempt at a multi-scale analysis of the co-movement relationship between the CO2 market, Oil, Gas and Coal which is based on the hypothesis of heterogeneity of agents using a template from wavelet algorithm. The model used in this study will allow stakeholders agents on the carbon market to have a great range of choices for their strategies to be able to anticipate wisely because of the high volatility of carbon prices on their different investment horizons
Lejeune, Michaël. "Etudes des corrélations entre la microstructure locale et les propriétés des couches minces de carbone amorphe hydrogéné et de carbone amorphe nitruré". Amiens, 2002. http://www.theses.fr/2002AMIE0202.
Testo completoFrançois, Raoul. "Beton arme : correlation entre fissuration et corrosion". Toulouse 3, 1987. http://www.theses.fr/1987TOU30153.
Testo completoLaunois, Thomas. "Modélisation de la composition isotopique des cernes d'arbres (13C et 18O) et des transferts de COS entre l'atmosphère et la biosphère continentale pour quantifier les flux bruts de carbone". Electronic Thesis or Diss., Versailles-St Quentin en Yvelines, 2014. http://www.theses.fr/2014VERS0039.
Testo completoIn the context of global climate change, the behavior of the terrestrial biosphere can be durably affected by the increased frequency and intensity of extreme climatic events, which can decrease the photosynthetic assimilation of carbon and/or increase the respiration rate of the ecosystems. Therefore, quantifying the carbon storage capacity of the ecosystems and predicting their sensitivity to climate changes strongly rely on our capacity to separately estimate the photosynthesis and respiration rates at different scales. The gross primary productivity (GPP) is however not directly measurable. Indirect approaches have been proposed to estimate the biospheric gross fluxes (GPP and respiration), combining for instance stable isotopologues of CO2 (13C and 18O), and, more recently, the measure of carbonyl sulfide (COS) concentrations in the atmosphere. In this context, my PhD work followed two complementary approaches. In the first approach, isotopic measurements and tree-ring widths were used, because both of them are linked to the photosynthetic activity. The inter-annual variations of the photosynthetic fluxes simulated with the ORCHIDEE continental biosphere model were evaluated and compared with in situ measurements. The second approach consisted in using atmospheric measurements of OCS concentrations and in exploring their potential to constrain the current estimates of the GPP in dynamic global vegetation models (DGVM), by (1) establishing a new global budget of sources and sinks of this gas, (2) optimizing the source and sink terms of this cycle and (3) estimating the potential of this new tracer to validate/invalidate the simulated GPP when using current DGVMs
Qiu, Kehui. "Transfert de silicium et de carbone entre un gaz CO-SiO-CO2 et un alliage Fe-Si-C : étude de laboratoire". Châtenay-Malabry, Ecole centrale de Paris, 1993. http://www.theses.fr/1993ECAP0301.
Testo completoDouthe, Cyril. "Relations entre échanges gazeux foliaires et discrimination isotopique du carbone-13 pendant la photosynthèse : estimations et variations rapides de la conductance mésophyllienne au CO2". Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10125/document.
Testo completoThis work was focused on the relationship between isotopic discrimination of 13C during photosynthesis (delta13C) and leaf gas exchange. The model of Farquhar and colleagues (Farquhar et al. 1982) predicts delta13C by accounting for diffusion, carboxylation and decarboxylation processes during the photosynthesis. This relationship is widely used and delta13C is frequently considered as a proxy water use efficiency (WUE, the amount of water required to fix a amount of carbon), an interesting parameter in the context of climate change, crop production and sylviculture. The delta13C model is also used to assess mesophyll conductance to CO2 (gm), that strongly limits photosynthesis via the availability of carbon in the chloroplast. Along this work we analyzed the delta13C model and identified the most important parameters, and highlighted that using the "simple form" of the model (which ignores gm and the decarboxylations) could lead to misestimating WUE. We also focused on the possible rapid variations of gm, a subject still under debate. We confirmed that gm was sensitive to rapid variations of CO2 and irradiance in all species tested in this study. We also showed that apparent rapid variations of gm could not be induced by variations of other parameters in the model, with the exception of parameter b (discrimination during carboxylation). We propose that future studies should focus on (i) the possible environmental and genetic variability of parameter b, and (ii) the physiological processes able to change gm at short time scales (aquaporins and carbonic anhydrase)
Chevarin, Francois, e Francois Chevarin. "Relation entre les propriétés physico-chimiques de l'anode en carbone et sa vitesse de réaction sous CO2". Doctoral thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/26633.
Testo completoL’aluminium de première fusion est, de nos jours, produit principalement par l’électrolyse de l’alumine à 960 °C appelé procédé Hall-Héroult. L’électrolyse est réalisée par le passage du courant électrique entre des anodes en carbone et une cathode en carbone par l’intermédiaire d’un électrolyte (cryolithe : Na3AlF6). Ces anodes sont composées de coke de pétrole et d’anodes usagées (mégots) collés ensemble par du pitch (brai de houille). Dans ce procédé, les anodes sont attaquées lors de l’électrolyse mais également en raison de réactions parasites avec l’air et le CO2 provoquant une surconsommation de ces anodes et créant de la charbonnaille. La charbonnaille est définie par l’ensemble des particules d’anode tombant dans le bain électrolytique et générant de nombreux problèmes électriques. Ce projet de recherche porte sur la compréhension de la consommation (réactivité) des anodes en carbone, utilisées dans le procédé électrochimique, par le CO2 à 960 °C. Dans le but de mieux comprendre cette consommation des anodes, l’étude de la réactivité est divisée en trois sections principales; la réaction du CO2 avec l’anode dite de Boudouard en régime chimique, la réactivité avec de grosses particules et la proposition d’une nouvelle représentation de l’anode. La réaction de Boudouard (CO2 + C → 2 CO) sous régime chimique est contrôlée par les propriétés intrinsèques du matériau carboné (impuretés et niveau de graphitisation). Dans ce projet, les paramètres (taille des particules, masse initiale, débit) du régime chimique, c'est-à-dire sans limitation du transport de masse, ont été déterminés pour des particules d’anode broyées. Le test de réactivité utilisé pour ces particules est un réacteur thermogravimétrique (TGA). La vitesse de réaction apparente obtenue à partir des données brutes du TGA permet d’évaluer la réactivité de l’anode en fonction du pourcentage de gazéification. Les conditions obtenues sont une masse initiale de 2 mg, un temps de broyage des particules de 10 minutes, un débit de 100 ml/min de CO2 et une température de 960 °C. Avec une préparation similaire à l’échantillon d’anode, des particules cuites provenant de chaque constituant d’une anode (coke, pitch et mégot) ont été placés dans le TGA et leur vitesse de réaction apparente a été mesurée. La détermination de la réactivité sous régime chimique de ces matériaux démontre que la vitesse de réaction apparente du pitch (pour un pitch ayant un niveau de graphitisation similaire au coke et pour des matières premières utilisées dans ce projet) n’est pas plus élevée que celles du coke et du mégot (ce qui est en contradiction par rapport à la littérature), ainsi le phénomène de charbonnaille, attribué à une supposée sélectivité du CO2 sur le pitch n’est pas confirmée. La consommation de l’anode en carbone dans la cuve d’électrolyse est contrôlée par les impuretés, par le niveau de graphitisation mais également par le transport de masse à travers sa structure poreuse. Dans ce projet, la gazéification des grosses particules pourrait se rapprocher de la consommation de l’anode industrielle dans une cuve d’électrolyse. La vitesse de réaction apparente mesurée pour 9 tailles de particules d’anode (allant de 33 µm à 4 380 µm de diamètre) a permis de révéler l’effet de la taille, de la porosité et de la masse de l’échantillon sur la réactivité. Trois tailles de particules comprises entre 725 et 2 190 µm ont particulièrement été étudiées car elles sont proches de la taille standardisée (ISO 12981-1; - 1 400 + 1 000 µm). Les surfaces et les volumes spécifiques différentiels de ces trois tailles de particules gazéifiées à 5 pourcentages (0; 15; 25; 35 et 50%) déterminés par adsorption d’argon et par infiltration de mercure ont permis d’évaluer les contributions des gazéifications sous-critique (taille de pores inférieure à la taille critique des pores) et sur-critique (taille de pores supérieure à la taille critique des pores) sur la gazéification totale des anodes sous CO2 à 960 °C. La détermination de la taille critique des pores (TC) pour les 3 tailles de particules (20 µm pour 725 µm et 40 µm pour les particules de 1 200 et 2 190 µm) et la mesure des contributions sous-critique et sur-critique ont permis de révéler que les pores ayant une taille supérieure à cette taille critique jouerait un rôle prépondérant dans la réactivité au CO2 des anodes. En se basant sur une dimension intermédiaire de cet intervalle de taille de particules et sur la norme ISO 12981-1 (utilisée pour mesurer la réactivité au CO2 des particules de coke), les particules comprises entre - 1 400 + 1 000 µm ont été choisies pour mettre en évidence l’effet de la porosité sur la réactivité de l’anode et de ses constituants (coke, pitch, mégot et matrice liante) sous CO2 à 960 °C. La matrice liante est un mélange de fines particules de coke (inférieur à 150 µm) et le pitch. La mesure de la vitesse de réaction apparente de ces matériaux permet d’évaluer que la matrice liante semble avoir une réactivité légèrement plus grande que celles du coke, du mégot et de l’anode et très largement supérieure à celle du pitch (valable pour les matériaux utilisés dans ce projet). Ces différences peuvent s’expliquer par le ratio des impuretés catalysantes et inhibitrices, (Vanadium + Nickel) / Soufre, qui est très élevé dans le cas de la matrice liante et du coke mais également à un niveau de graphitisation légèrement plus faible. L’utilisation du facteur d’efficacité apparent permet de mettre en évidence l’effet de la structure du matériau sur la réactivité de particules de grandes tailles par rapport à la vitesse de réaction en régime chimique. En associant les vitesses de réaction apparente des deux régimes (chimique et particules de grandes tailles) pour les 5 matériaux (anode, coke, pitch, mégot et matrice liante), il est possible de révéler l’effet de la structure. Ainsi, pour l’anode et le pitch, le facteur d’efficacité est très faible (inférieure à 0,3) indiquant par conséquent qu’une structure adaptée de l’anode peut diminuer la réactivité globale. Lors de la caractérisation de ces matériaux afin de comprendre leurs réactivités, il a été révélé que la surface spécifique initiale de l’anode ne peut être estimée par la moyenne pondérée des surfaces de ses constituants (coke, pitch, mégot et matrice liante). Ainsi, malgré une similitude chimique, une division par matière première (coke, pitch et mégot) ou physique (coke, mégot et matrice liante) ne semble pouvoir expliquer cette grande surface spécifique et une nouvelle représentation de l’anode doit être envisagée. En raison d’un manque de support lors de la cuisson, le pitch, cuit seul ou bien cuit sous forme de matrice liante, ne peut pas s’étaler lors de sa pyrolyse. Ainsi, le mixage et la cuisson de trois recettes de coke et de pitch (coke/pitch : 100/0, 95/5 et 85/15 en masse/masse) révèlent une très grande surface spécifique initiale pour la recette 95/5. La réactivité de cette recette et celle de 100/0 sont très similaires alors que celle de 85/15 est très faible alors que celle de l’anode se situe à un niveau intermédiaire. En conséquence, en se basant sur les surfaces spécifiques initiales et sur les réactivités de ces trois recettes, il est possible d’estimer qu’une anode entière est composée de particules de coke partiellement enrobé de pitch (95/5) et totalement enrobé (85/15).
Primary aluminum is mainly produced by electrolysis of alumina at 960 °C by the Hall-Héroult process. The electrolysis is carried out by passing the electric current between carbon anodes and a carbon cathode through molten cryolite (Na3AlF6) that acts as electrolyte. The anodes are consisted of petroleum coke and anode butts bonded together by coal tar pitch. The anodes are consumed in the cell by the electrolysis reaction but also by air and CO2 gas reactions. The anode-gas reactions cause an overconsumption of the anodes and create dusting phenomenon. The dusting is defined by the falling out of anode particles in the electrolytic bath that generates many electrical problems. This research project focuses on the understanding of CO2 consumption (reactivity) of carbon anodes at 960 °C to increase the service life of anodes. In order to reveal the mechanism of the CO2 reactivity of anodes, the present study was divided into three main sections; 1) the reaction of CO2 and carbon, called Boudouard reaction, under chemical regime, 2) the CO2 reactivity of large particles under mass transport limitations and 3) the proposal of a new representation of the anode. The Boudouard reaction (CO2 + C → 2 CO) under chemical regime is controlled by the intrinsic properties of the carbonaceous materials, i.e. the impurities and of graphitization levels. In this project, the parameters (particle size, initial mass and CO2 flow) of chemical regime (without mass transport limitations) were determined for milled anode particles. A Thermo-Gravimetric Analyzer (TGA) was used to measure the CO2 reactivity of anode particles. The apparent reaction rate versus gasification percentage was obtained from the TGA raw data to estimate the carbon activity under CO2 atmosphere. The experimental conditions for chemical regime with TG instrument included an initial mass of 2 mg, 10 minutes of milling and a CO2 flow rate of 100 ml/min at 960 °C. A similar preparation was applied to the anode samples and each constituent of anode (coke, pitch and butt) was prepared and baked separately. The anode constituents were placed in the TGA and their apparent reaction rate was measured. The chemical reactivity of anode constituents showed that the apparent reaction rate of the pitch material (with a similar level of graphitization than that of coke material and for the raw materials used in this project) was not higher than that of the coke and the butt particles (which is in contradiction to the literature) and thus the dusting phenomenon which is attributed to a supposed selectivity of CO2 on pitch constituent was not confirmed. The consumption of the industrial carbon anodes in the electrolytic bath is controlled by the impurities, the level of graphitization and also by the mass transport through its porous structure. In this project, the gasification of large particles could be assimilated at the consumption of industrial anodes. The apparent reaction rates were measured for 9 particle sizes of anode (between 33 µm and 4380 µm of diameter). A larger particle size decreased the reaction rate. Three sizes of anode particles (725, 1200 and 2190 µm) were specifically studied because they are close to the particle sizes recommended by the ISO standard 12981-1 where - 1400 + 1000 µm is used to measure the CO2 reactivity of coke particles. The specific differential surface areas and volumes measured by argon adsorption and mercury infiltration were determined for the 3 particle sizes consumed at 5 gasified percentages (0; 15; 25; 35 and 50%). With the pore volumes, it was possible to weight the internal and external gasification on overall gasification. The determination of the critical pore size (TC) for the 3 particle sizes (20 µm to 725 µm particles and 40 µm for 1200 and 2190 µm particles) and the weights of internal and external gasifications revealed that the pores having a size greater than this critical size could have an essential weight on the overall CO2 reactivity of the anodes. Based on the ISO standard 12981-1, the particles between - 1400 + 1000 µm were chosen to demonstrate the effect of porosity on the CO2 reactivity of the anode and its constituents (coke, pitch, butt and binder matrix) under CO2 at 960 °C. The measurement of apparent reaction rates of these materials revealed the reactivity of binder matrix was slightly higher than those of the coke, butt and anode samples and was much greater than the reactivity of pitch material (considering the materials studied). These differences could be explained by the ratio of catalysts/inhibitor, (Vanadium + Nickel) / Sulfur, which was very high for the binder matrix and coke samples, used in this project and a lower level of graphitization for binder matrix. The butt was also highly reactive because the catalyst effect of sodium on the Boudouard reaction at 960 °C is very important. The apparent effectiveness factor allowed to highlight the effect of structure on the reactivity of large particle sizes compared to the reaction rate under chemical regime. The ratio of apparent reaction rate under mass transport limitations over the rate under chemical regime for the 5 materials (anode, coke, pitch, butt and binder matrix) indicated the porosity impact. The apparent effectiveness factor for anode and pitch samples was very low (less than 0.3 for 4 gasification percentages of 15; 25; 35 and 50%) revealing that a suitable structure of carbon material may decrease the overall reactivity. After characterization of anode and its constituents, it was assumed that the initial surface area of the anode could be estimated by the weighted average of the surface areas of its components (coke + butt + pitch and coke + butt + binder matrix). The binder matrix is a mixture of the fine particles of coke and the pitch material. In spite of similar chemical compositions, classification of raw materials as coke + pitch + butt and coke + butt + binder matrix could not explain the large specific area of anode. Consequently, a new representation of the anode should be considered. Due to the lack of support during baking, the pitch material, baked alone or baked in binder matrix, could not be spread during its pyrolysis. Thus, three recipes of pitch/coke mixtures (coke/pitch: 100/0, 95/5 and 85/15 w/w) were mixed and baked, separately. The 95/5 mixture presented a very large initial surface area (similar to that of anode). The CO2 reactivity was measured in TG instrument at 960 °C. The reactivity of 95/5 composition was very similar to that of 100/0 while the reactivity of 85/15 composition was very low. The anode reactivity had an intermediate level. According to the initial specific surface area and the CO2 reactivity of these three recipes, it was possible to approximate the surface area and the CO2 reactivity of the carbon anode with a mixture of coke particles partially coated (95/5) and fully coated (85/15) with pitch. Consequently, this new assembly could be useful to better understand the wetting of coke by pitch during baking.
Primary aluminum is mainly produced by electrolysis of alumina at 960 °C by the Hall-Héroult process. The electrolysis is carried out by passing the electric current between carbon anodes and a carbon cathode through molten cryolite (Na3AlF6) that acts as electrolyte. The anodes are consisted of petroleum coke and anode butts bonded together by coal tar pitch. The anodes are consumed in the cell by the electrolysis reaction but also by air and CO2 gas reactions. The anode-gas reactions cause an overconsumption of the anodes and create dusting phenomenon. The dusting is defined by the falling out of anode particles in the electrolytic bath that generates many electrical problems. This research project focuses on the understanding of CO2 consumption (reactivity) of carbon anodes at 960 °C to increase the service life of anodes. In order to reveal the mechanism of the CO2 reactivity of anodes, the present study was divided into three main sections; 1) the reaction of CO2 and carbon, called Boudouard reaction, under chemical regime, 2) the CO2 reactivity of large particles under mass transport limitations and 3) the proposal of a new representation of the anode. The Boudouard reaction (CO2 + C → 2 CO) under chemical regime is controlled by the intrinsic properties of the carbonaceous materials, i.e. the impurities and of graphitization levels. In this project, the parameters (particle size, initial mass and CO2 flow) of chemical regime (without mass transport limitations) were determined for milled anode particles. A Thermo-Gravimetric Analyzer (TGA) was used to measure the CO2 reactivity of anode particles. The apparent reaction rate versus gasification percentage was obtained from the TGA raw data to estimate the carbon activity under CO2 atmosphere. The experimental conditions for chemical regime with TG instrument included an initial mass of 2 mg, 10 minutes of milling and a CO2 flow rate of 100 ml/min at 960 °C. A similar preparation was applied to the anode samples and each constituent of anode (coke, pitch and butt) was prepared and baked separately. The anode constituents were placed in the TGA and their apparent reaction rate was measured. The chemical reactivity of anode constituents showed that the apparent reaction rate of the pitch material (with a similar level of graphitization than that of coke material and for the raw materials used in this project) was not higher than that of the coke and the butt particles (which is in contradiction to the literature) and thus the dusting phenomenon which is attributed to a supposed selectivity of CO2 on pitch constituent was not confirmed. The consumption of the industrial carbon anodes in the electrolytic bath is controlled by the impurities, the level of graphitization and also by the mass transport through its porous structure. In this project, the gasification of large particles could be assimilated at the consumption of industrial anodes. The apparent reaction rates were measured for 9 particle sizes of anode (between 33 µm and 4380 µm of diameter). A larger particle size decreased the reaction rate. Three sizes of anode particles (725, 1200 and 2190 µm) were specifically studied because they are close to the particle sizes recommended by the ISO standard 12981-1 where - 1400 + 1000 µm is used to measure the CO2 reactivity of coke particles. The specific differential surface areas and volumes measured by argon adsorption and mercury infiltration were determined for the 3 particle sizes consumed at 5 gasified percentages (0; 15; 25; 35 and 50%). With the pore volumes, it was possible to weight the internal and external gasification on overall gasification. The determination of the critical pore size (TC) for the 3 particle sizes (20 µm to 725 µm particles and 40 µm for 1200 and 2190 µm particles) and the weights of internal and external gasifications revealed that the pores having a size greater than this critical size could have an essential weight on the overall CO2 reactivity of the anodes. Based on the ISO standard 12981-1, the particles between - 1400 + 1000 µm were chosen to demonstrate the effect of porosity on the CO2 reactivity of the anode and its constituents (coke, pitch, butt and binder matrix) under CO2 at 960 °C. The measurement of apparent reaction rates of these materials revealed the reactivity of binder matrix was slightly higher than those of the coke, butt and anode samples and was much greater than the reactivity of pitch material (considering the materials studied). These differences could be explained by the ratio of catalysts/inhibitor, (Vanadium + Nickel) / Sulfur, which was very high for the binder matrix and coke samples, used in this project and a lower level of graphitization for binder matrix. The butt was also highly reactive because the catalyst effect of sodium on the Boudouard reaction at 960 °C is very important. The apparent effectiveness factor allowed to highlight the effect of structure on the reactivity of large particle sizes compared to the reaction rate under chemical regime. The ratio of apparent reaction rate under mass transport limitations over the rate under chemical regime for the 5 materials (anode, coke, pitch, butt and binder matrix) indicated the porosity impact. The apparent effectiveness factor for anode and pitch samples was very low (less than 0.3 for 4 gasification percentages of 15; 25; 35 and 50%) revealing that a suitable structure of carbon material may decrease the overall reactivity. After characterization of anode and its constituents, it was assumed that the initial surface area of the anode could be estimated by the weighted average of the surface areas of its components (coke + butt + pitch and coke + butt + binder matrix). The binder matrix is a mixture of the fine particles of coke and the pitch material. In spite of similar chemical compositions, classification of raw materials as coke + pitch + butt and coke + butt + binder matrix could not explain the large specific area of anode. Consequently, a new representation of the anode should be considered. Due to the lack of support during baking, the pitch material, baked alone or baked in binder matrix, could not be spread during its pyrolysis. Thus, three recipes of pitch/coke mixtures (coke/pitch: 100/0, 95/5 and 85/15 w/w) were mixed and baked, separately. The 95/5 mixture presented a very large initial surface area (similar to that of anode). The CO2 reactivity was measured in TG instrument at 960 °C. The reactivity of 95/5 composition was very similar to that of 100/0 while the reactivity of 85/15 composition was very low. The anode reactivity had an intermediate level. According to the initial specific surface area and the CO2 reactivity of these three recipes, it was possible to approximate the surface area and the CO2 reactivity of the carbon anode with a mixture of coke particles partially coated (95/5) and fully coated (85/15) with pitch. Consequently, this new assembly could be useful to better understand the wetting of coke by pitch during baking.
Bertran, Xavier. "Comportement en milieu oxydant d'un composite carbone/carbone pour applications structurales entre 150 et 400°c dans l'aéronautique civile". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2013. http://tel.archives-ouvertes.fr/tel-00933566.
Testo completoAlencar, Rafael Silva. "Estudo de fônons em nanotubos de carbono e dissulfeto de molibdênio: efeito do acoplamento entre camadas". reponame:Repositório Institucional da UFC, 2016. http://www.repositorio.ufc.br/handle/riufc/18134.
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In this work we present the studies on Double (DWCNTs) and Triple Wall Carbon Nanotubes, on molybdenum disulfide in the bulk form and on few layer of MoS_2 under hydrostatic high pressure conditions. Theoretical calculations were performed in collaboration to support the experimental results. For the DWCNTs samples, changes in the G-band frequency vs. pressure plot and the disappearance of the radial breathing modes (RBM) between 2 GPa and 5 GPa indicate the beginning and ending of the radial collapse of the nanotubes. Theoretical calculations based on Density-Functional Tight-Binding (DFTB) shown that the collapse pressure (P_c) for DWCNTs follows a d^{-3}_{in} law, in excellent agreement with the experimental results. The P_c dependence on number of tube-walls and on the inter-wall distance is also investigated. For the TWCNTs samples, pressure screening effects are observed for the innermost tubes of TWCNTs similar to what has been already found for DWCNTs. However, using the RBM pressure coefficients in conjunction with the histogram of the diameter distribution, we were able to separate the RBM Raman contribution related to the intermediate tubes of TWCNTs from that related to the inner tubes of DWCNTs. By combining Raman spectroscopy and high pressure measurements, it was possible to identify these two categories of inner tubes even if the two tubes exhibit the same diameters, since their pressure response is different. Furthermore, it was possible to observe similar RBM profiles of the innermost tubes of TWCNTs using different resonance laser energies but also under different pressure conditions. This is attributed to changes in the electronic transition energies caused by small pressure-induced deformations. Theoretical calculations based on ab initio were performed for support the experimental results. By using Raman spectroscopy, it was possible to estimate the displacement of the optical energy levels with pressure. For the exfoliated MoS_2 samples, we studied the effect of the stacking on the E^1_{2g} and A_{1g} vibrational modes at high pressures. New components for both modes were observed with increasing pressure. It was also observed that the pressure coefficient of the E^1_{2g} mode decreases exponentially with MoS_2 thickness is increased, differently of the A_{1g} mode and the new components, which do not present a significant dependence on the variation of the number of layers. These results were attributed to deformations in the MoS_2 structure induced by a biaxial strain (dependent on the number of layers), resulting from the deformation of the SiO_2 substrate. Such adhesion decreases with the increasing of the MoS_2 thickness due to the increasing on the unbinding regions between MoS_2 and SiO_2. As result, a higher pressure is needed to improve the adhesion and consequently, a higher pressure is required to achieve the biaxial strain. For the MoS_2 microcrystalline powder, except for the B_{1u}, E^2_{2g}, E_{1g}, E^1_{2g} and A_{1g} modes, the behavior of all other modes was studied for the first time in high pressure conditions. For all modes, a linear variation of the Raman frequency and positive pressure coefficient was observed. Moreover, the differences in the behavior of the intensity profiles of the A_{1g}, 2LA(M) and A_{2u} modes in resonance and off-resonance were attributed to variations in the energy of direct optical transitions induced by pressure.
Nesta Tese apresentamos os estudos de espectroscopia Raman em condições extremas de pressão hidrostática realizados em nanotubos de carbono de parede dupla (DWCNTs) e tripla (TWCNTs), em dissulfeto de molibdênio na forma bulk e em poucas camadas. Cálculos teóricos foram usados para dar suporte aos resultados experimentais. Para as amostras de DWCNTs, as mudanças no coeficiente de pressão da banda G e o desaparecimento dos modos de respiração radial (RBMs) entre 2 GPa e 5 GPa foram interpretados como um indicativo do início e fim do colapso radial dos nanotubos de carbono (CNTs). Os cálculos teóricos usando Tight-Binding baseado no Funcional da Densidade (DFTB) mostraram que a pressão de colapso (P_c) para os DWCNTs segue uma lei de potência do tipo d^{-3}_{in}, em excelente acordo com os resultados experimentais. A dependência de P_c em relação ao número de paredes do tubo, como também a distância inter-paredes também foram investigadas. Para a amostra contendo TWCNTs, através da análise dos coeficientes de pressão dos modos RBMs em conjunto com o histograma da distribuição de diâmetros da amostra, foi possível separarmos as contribuições dos RBMs nos espectros Raman relacionados aos tubos internos dos TWCNTs e DWCNTs, embora possuam a mesma distribuição de diâmetro, a resposta das propriedades vibracionais à pressão são diferentes. Adicionalmente, foi possível observar perfis de intensidades semelhantes para os modos RBMs dos tubos mais internos dos TWCNTs usando diferentes energias de LASER, mas sob diferentes condições de pressão. Atribuímos este resultado à mudanças nas energias de transições eletrônicas causadas por pequenas deformações estruturais nos nanotubos induzidas pela pressão. Cálculos teóricos baseados em ab initio foram realizados para dar suporte às interpretações dos resultados experimentais. Para as amostras de MoS_2 esfoliadas, estudamos o efeito do empilhamento nos modos vibracionais E^1_{2g} e A_{1g} em altas pressões. Novas componentes para esses modos foram observadas com o aumento da pressão. Foi também observado que o coeficiente de pressão do modo E^1_{2g} diminui exponencialmente com o aumento do número de camadas, diferentemente do modo A_{1g} e das novas componentes, que não apresentam uma dependência significativa com a variação da espessura do MoS_2. Atribuímos estes resultados às deformações estruturais do MoS_2 induzidas por uma tensão biaxial (dependente da adesão entre SiO_2 e MoS_2) resultante da deformação do substrato de SiO_2. O aumento do número de camadas diminui a adesão entre o MoS_2 e o SiO_2 devido ao aumento da porcentagem de regiões em não-contato com o substrato, e como consequência, uma pressão mais elevada é necessária para aumentar a adesão, resultando no aumento da pressão para deformar a estrutura do MoS_2. Para o pó microcristalino de MoS2, com exceção dos modos B_{1u}, E^2_{2g}, E1g, E^1_{2g} e A_{1g}, o comportamento de todos os outros modos foi também estudado em condições de altas pressões hidrostáticas. Todos os modos apresentaram uma variação linear de suas frequências Raman com a pressão e coeficientes de pressão positivos. Além disso, as diferenças no comportamento dos perfis de intensidade dos modos A_{1g}, 2LA(M) e A_{2u} em ressonância e fora de ressonância foram interpretados como sendo devido às variações nas energias das transições ópticas direta induzidas pela pressão.
Freixes, Sandra. "Disponibilité en carbone et architecture racinaire : relations entre teneur locale en sucres et élongation ou ramification et interaction avec le déficit hydrique". Montpellier, ENSA, 2003. http://www.theses.fr/2003ENSA0022.
Testo completoTo test the role of sugar in the control of root growth, we have looked for relationships between local sugar concentration in regions involved in elongation and branching and these processes. An original culture method was developed to allow an easy root growth study and a correct development of leaves. Positive and robust relationships between local hexose concentration and root growth were obtained using a large spectrum of environmental conditions (irradiance, external sucrose). These relationships accounted for plant-to-plant variability within treatments as well as root-to-root variability within plants. Similar relationships were identified in various genotypes. In case of soil water deficit, as well as in case of other sink limitation of root growth, an accumulation of sugar was observed together with a decrease of root elongation. This suggests that in theses case, root elongation is not source but rather sink limited
Simar, Aline. "Impact du vieillissement humide sur le comportement d'un composite à matrice organique tissé fabriqué par injection RTM : Mise en évidence d'un couplage entre absorption d'eau et thermo-oxydation de la matrice". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2014. http://www.theses.fr/2014ESMA0021/document.
Testo completoThe initiative of this work is based on weight saving European program of aeronautic structures. It takes part of PRC-Composites project and aim to develop processes and new materials. This thesis belong with this whole project and wants to highlight, to analyze, to understand, then to modelize water absorption phenomena in an organic composite (carbon/epoxy) 2D woven, manufactured by RTM process. The final objective is to evaluate the effect of moisture on the mechanical behavior.The method consists in studying the effect of water ageing on components: neat resin, interface/interphase resin/tow, and composite.For the neat resin (RTM6), a complicated coupling between water sorption and thermo-oxidation of the matrix at 70°C has been demonstrated, uncoupled and then experimentally quantified using a coupled diffuso-mechanical model. A study based on the use of “mono-tow” samples, specially manufactured for this work, has shown – on the microscopic scale – the presence of interface/interphase resin/tow has no significant effect on the diffusion kinetic through the matrix. In moist/oxidant environment, the composite behavior (RTM6/AS7) has been explored relaying on established ideas related to components. Water diffusion has been modelized through an explicit representation of the microstructure and by including neat resin established model. The aged composite behavior has been evaluated with uni-axial tensile tests in 3 directions (0°, 90° and 45°). These experiments show the interest of the component pre-study
Bigarani, Fernando Artico. "Relação entre renda e emissão de dióxido de carbono". Universidade Estadual de Londrina. Centro de Estudos Sociais Aplicados. Programa de Pós-Graduação em Economia Regional, 2015. http://www.bibliotecadigital.uel.br/document/?code=vtls000207948.
Testo completoThe objective of this work is to verify the existence of relationship between per capita carbon dioxide emissions and income growth and also determine the format of the Environmental Kuznets Curve (EKC). The methodology consists of exploratory spatial data analysis for the years 1994 and 2009 using geoda program and also using the same program for regression through the classical model and the spatial autoregressive error model. Through maps and Moran Index seeks to observe the existence of spatial autocorrelation, per capita, between carbon dioxide emissions and gross domestic product of the countries of Europe and Africa, identifying the existence of spatial clusters, since the regressions It is intended to determine the CKA format. The results showed significant spatial autocorrelation between variables and allowed the identification of spatial clusters in Europe and Africa. The regression results were significant to indicate a possible existence of CKA in the inverted U-shaped in the short term and in the long run assuming a format N. The conclusion confirms that the Environmental Kuznets Curve took an inverted U-shaped in the short term and in the long run a C shape and also identifies that the Kyoto protocol was able to promote changes in univariate analysis clusters. The suggestion of new research is in order to further explore the literature of long-term CKA and include in the regression model the Kyoto protocol.
Vialla, Fabien. "Interaction entre les nanotubes de carbone et leur environnement physico-chimique : vers un contrôle des propriétés optiques". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2014. http://tel.archives-ouvertes.fr/tel-00971753.
Testo completoGomes, Daniela Caio André. "Modelagem termodinâmica do equilíbrio de fases entre componentes graxos e dióxido de carbono supercrítico". [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256357.
Testo completoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Corrigiu-se empiricamente o parâmetro a da equação de estado de Peng-Robinson para o CO2 em função da temperatura e pressão, para que a equação pudesse calcular corretamente a fugacidade do dióxido de carbono em condições supercríticas. Em princípio, o intuito foi verificar se a modelagem termodinâmica com esta correção poderia correlacionar melhor os dados de equilíbrio de fases de sistemas constituídos de dióxido de carbono supercrítico e substâncias de interesse presentes em alimentos. Para testar esta hipótese, os seguintes sistemas bifásicos constituídos de dióxido de carbono supercrítico e componentes graxos foram selecionados da literatura: CO2 ¿ esqualeno, CO2 ¿ ácido oleico, CO2 ¿ tricaprilina, CO2 ¿ éster etílico de EPA, CO2 ¿ éster etílico de DHA, CO2 ¿ alfa-tocoferol, CO2 ¿ alfa-tocoferol, CO2 ¿ trioleína, CO2 ¿ tripalmitina. Tais escolhas são decorrentes do crescente interesse de se recuperar esses componentes minoritários de óleos brutos ou dos subprodutos resultantes do processamento convencional de óleos e gorduras, devido a sua importância na manutenção da saúde humana. Além disso, tem crescido o interesse por produtos naturais isentos de solventes orgânicos indesejáveis. Nesse sentido, os processos de extração com dióxido de carbono supercrítico vêm suprir esta demanda atual, pois é um solvente inerte que não agride o meio ambiente. Os resultados mostraram que as propriedades críticas que são estimadas por métodos de contribuição de grupos influenciaram mais no desempenho da modelagem termodinâmica que a correção do parâmetro a da equação de estado de Peng-Robinson. As maiores correções do parâmetro foram obtidas nas condições de maiores valores de temperatura e menores de pressão. No geral, a correção do parâmetro a não diminuiu o desvio em relação aos valores experimentais quando comparados aos valores obtidos sem a correção do parâmetro. No entanto, em alguns sistemas observou-se que a correção deste parâmetro para as condições de pressões elevadas modificou o comportamento dos valores de solubilidade calculados, produzindo valores mais próximos aos experimentais
Abstract: Corrected empirically the parameter a of the Peng- Robinson equation of state of for CO2 as a function of temperature and pressure, so that the equation could correctly calculate the fugacity of carbon dioxide in supercritical conditions. In principle, the aim was to verify whether the thermodynamic modeling with this correction could better correlate the phase equilibrium data from system consisting of supercritical carbon dioxide and substances of interest in food. To test this hypothesis, the following two-phase systems consisting of supercritical carbon dioxide and fatty components were selected from the literature: CO2 - squalene, CO2 - oleic acid, CO2 - tricaprylin, CO2 - ethyl ester of EPA, CO2 - DHA ethyl ester, CO2 - ?-tocopherol, CO2 - ?-tocopherol, CO2 - triolein, CO2 - tripalmitin. Such choices are the result of growing interest to recover these minor components of crude oils or byproducts resulting from conventional processing of oils and fats, due to its importance in maintaining human health. In addition, interest has grown in natural products free of undesirable organic solvents. In this sense, the processes of extraction with supercritical carbon dioxide come meet this current demand, it is an inert solvent that does not harm the environment. The results showed that the critical properties are estimated by group contribution methods of influence over the performance of thermodynamic modeling that the correction of the parameter to the equation of state of Peng-Robinson. The larger corrections of the parameter were obtained under conditions of higher temperatures and under pressure. In general, the correction of the parameter a does not diminish the deviation from the experimental values when compared to values obtained without the correction parameter. However, in some systems it was observed that the correction of this parameter for the conditions of high pressures changed the behavior of the solubility values calculated, yielding values closer to experimental
Mestrado
Engenharia de Alimentos
Mestre em Engenharia de Alimentos
LAMY, MARIE-NOELLE. "L'intoxication oxycarbonee dans le secteur sanitaire de montlucon : d'apres 112 cas survenus entre le 1er avril 1986 et le 31 mars 1991". Clermont-Ferrand 1, 1991. http://www.theses.fr/1991CLF13025.
Testo completoWaisman, H. "Les politiques climatiques entre prix du carbone, rentes pétrolières et dynamiques urbaines". Phd thesis, Ecole des Hautes Etudes en Sciences Sociales (EHESS), 2012. http://tel.archives-ouvertes.fr/tel-00799199.
Testo completoWaisman, Henri. "Les politiques climatiques entre prix du carbone, rente pétrolière et dynamiques urbaines". Paris, EHESS, 2012. https://hal.archives-ouvertes.fr/tel-00799199.
Testo completoThis thesis investigates the effects of constraints imposed on economic interactions by limitations due to natural resources, among which oil and urban land play a curcial role in the context of climate change. These dimensions, often neglected in existing analyses, have an ambiguous effect since they suggest both the risk of enhanced costs if carbon limitations reinforce the sub-optimalities caused by pre-existing constraints, but also, conversely, the possibility of co-benefits if the climate policy helps to correct some pre-existing imperfections of socio-economic trajectories. To investigate this issue, an innovative modeling framework of the energy-economy interactions is elaborated that embarks the specificities of the deployment of oil production capacities and the issues related to the spatial organization in urban areas. We demonstrate that, beyond the carbon price, the costs of climate policy essentially depend on the sequencing of complementary measures, with a crucial role of spatial policy designed to control transport-related emissions through mobility
Cadule, Patricia. "Modélisation des interactions entre le système climatique et le cycle du carbone". Paris 6, 2009. http://www.theses.fr/2009PA066142.
Testo completoNeto, Sérgio Candido de Gouveia. "\"Concentrações e balanços de carbono orgânico dissolvido em duas bacias do Estado de Rondônia: uma comparação entre floresta e pastagem\"". Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/64/64132/tde-04102006-192006/.
Testo completoDissolved Organic Carbon (DOC) is one of the main fractions of organic carbon exported in rivers and other flow paths in watersheds. In the Amazon, studies of DOC in waters focus mainly on the large basins of the central region, with few analyses of changes in its dynamics after the replacement of forests by pastures, one of the most important land use changes in the region. This objective of this study was to obtain more information about these processes, by comparing dynamics in several flowpaths, exports and budgets of DOC during rain events in two first-order watersheds, one with forest and another with pasture. The study was conducted near city of Cacaulândia in the State of Rondônia. Samples were collected in the transition from dry to wet (August to November of 2004) and in the wet seasons (January to April of 2005). The results demonstrate that during the transition from dry to wet seasons, statistically significant differences in DOC concentrations between forest and pasture occur only in the inputs from precipitation in pasture and throughfall in forest and in the outputs in streams and groundwater. During the wet season the remaining flowpaths analyzed, soil solution at 20 and 100cm depth and overland flow, also showed statistically significant differences in DOC concentrations between forest and pasture. In terms of the periods of the year, in both watersheds DOC concentrations were higher during the transition from dry to wet seasons. The only exception to this pattern was observed in forest groundwater, with higher concentrations during the wet season. In the pasture, increases in discharge resulted in higher DOC export than in forest. As a consequence of this, DOC budgets, both in individual events and annually, showed a larger retention in the latest. Although in this study it was not possible, among others, to quantify the fluxes of DOC in groundwater, the results demonstrate that the conversion of forest into pasture causes a significant increase of DOC export in streams, both in individual rain events and on an annual basis.
Tresonne, Nathalie. "Etude expérimentale des équilibres isotopiques entre CO#2, CO, CH#4, H#2, H#2O : applications à la géothermométrie des aquifères profonds". Paris 6, 1991. http://www.theses.fr/1991PA066370.
Testo completoThery, Alexandre. "Relations entre l'organisation multi échelles des aérogels de carbone et leurs propriétés de stockage électrochimique de l'hydrogène". Orléans, 2004. http://www.theses.fr/2004ORLE2057.
Testo completoLargeot, Céline. "Développement de supercondensateurs carbone/carbone : relation entre la taille des ions de l'électrolyte et la taille des pores de la matière active". Toulouse 3, 2009. http://thesesups.ups-tlse.fr/529/.
Testo completoThe aim of this work is to study ion/porous carbon interactions in supercapacitor electrodes to improve their electrochemical performances. Titanium Carbide Derived Carbon (TiC-CDC) are microporous carbon with monodisperse porosity. They allowed us to finely study the interactions between electrolyte's ion size and active material pore size during the electrochemical double layer formation in two different kind of electrolyte (organic and ionic liquid). Unlike to traditional views, in order to maximise capacitance, carbon pore size must be close to electrolyte ions size. It was demonstrated that ions adsorbed on carbon's surface are at least partially desolvated. As carbon porosity is well adapted to electrolyte ions size, the capacity is improved of 40 % in acetonitrile and 60 % in ionic liquid. This corresponds respectively to an enhancement by two and by three of the energy of supercapacitors
BOUNOUH, YAHYA. "Relations entre microstructure et proprietes electroniques de couches minces de carbone amorphe hydrogene". Paris 6, 1993. http://www.theses.fr/1993PA066037.
Testo completoAlencar, Rafael Silva. "ESTUDO DE FÃNONS EM NANOTUBOS DE CARBONO E DISSULFETO DE MOLIBDÃNIO: EFEITO DO ACOPLAMENTO ENTRE CAMADAS". Universidade Federal do CearÃ, 2016. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=17226.
Testo completoNesta Tese apresentamos os estudos de espectroscopia Raman em condiÃÃes extremas de pressÃo hidrostÃtica realizados em nanotubos de carbono de parede dupla (DWCNTs) e tripla (TWCNTs), em dissulfeto de molibdÃnio na forma bulk e em poucas camadas. CÃlculos teÃricos foram usados para dar suporte aos resultados experimentais. Para as amostras de DWCNTs, as mudanÃas no coeficiente de pressÃo da banda G e o desaparecimento dos modos de respiraÃÃo radial (RBMs) entre 2 GPa e 5 GPa foram interpretados como um indicativo do inÃcio e fim do colapso radial dos nanotubos de carbono (CNTs). Os cÃlculos teÃricos usando Tight-Binding baseado no Funcional da Densidade (DFTB) mostraram que a pressÃo de colapso (P_c) para os DWCNTs segue uma lei de potÃncia do tipo d^{-3}_{in}, em excelente acordo com os resultados experimentais. A dependÃncia de P_c em relaÃÃo ao nÃmero de paredes do tubo, como tambÃm a distÃncia inter-paredes tambÃm foram investigadas. Para a amostra contendo TWCNTs, atravÃs da anÃlise dos coeficientes de pressÃo dos modos RBMs em conjunto com o histograma da distribuiÃÃo de diÃmetros da amostra, foi possÃvel separarmos as contribuiÃÃes dos RBMs nos espectros Raman relacionados aos tubos internos dos TWCNTs e DWCNTs, embora possuam a mesma distribuiÃÃo de diÃmetro, a resposta das propriedades vibracionais à pressÃo sÃo diferentes. Adicionalmente, foi possÃvel observar perfis de intensidades semelhantes para os modos RBMs dos tubos mais internos dos TWCNTs usando diferentes energias de LASER, mas sob diferentes condiÃÃes de pressÃo. AtribuÃmos este resultado à mudanÃas nas energias de transiÃÃes eletrÃnicas causadas por pequenas deformaÃÃes estruturais nos nanotubos induzidas pela pressÃo. CÃlculos teÃricos baseados em ab initio foram realizados para dar suporte Ãs interpretaÃÃes dos resultados experimentais. Para as amostras de MoS_2 esfoliadas, estudamos o efeito do empilhamento nos modos vibracionais E^1_{2g} e A_{1g} em altas pressÃes. Novas componentes para esses modos foram observadas com o aumento da pressÃo. Foi tambÃm observado que o coeficiente de pressÃo do modo E^1_{2g} diminui exponencialmente com o aumento do nÃmero de camadas, diferentemente do modo A_{1g} e das novas componentes, que nÃo apresentam uma dependÃncia significativa com a variaÃÃo da espessura do MoS_2. AtribuÃmos estes resultados Ãs deformaÃÃes estruturais do MoS_2 induzidas por uma tensÃo biaxial (dependente da adesÃo entre SiO_2 e MoS_2) resultante da deformaÃÃo do substrato de SiO_2. O aumento do nÃmero de camadas diminui a adesÃo entre o MoS_2 e o SiO_2 devido ao aumento da porcentagem de regiÃes em nÃo-contato com o substrato, e como consequÃncia, uma pressÃo mais elevada à necessÃria para aumentar a adesÃo, resultando no aumento da pressÃo para deformar a estrutura do MoS_2. Para o pà microcristalino de MoS2, com exceÃÃo dos modos B_{1u}, E^2_{2g}, E1g, E^1_{2g} e A_{1g}, o comportamento de todos os outros modos foi tambÃm estudado em condiÃÃes de altas pressÃes hidrostÃticas. Todos os modos apresentaram uma variaÃÃo linear de suas frequÃncias Raman com a pressÃo e coeficientes de pressÃo positivos. AlÃm disso, as diferenÃas no comportamento dos perfis de intensidade dos modos A_{1g}, 2LA(M) e A_{2u} em ressonÃncia e fora de ressonÃncia foram interpretados como sendo devido Ãs variaÃÃes nas energias das transiÃÃes Ãpticas direta induzidas pela pressÃo.
In this work we present the studies on Double (DWCNTs) and Triple Wall Carbon Nanotubes, on molybdenum disulfide in the bulk form and on few layer of MoS_2 under hydrostatic high pressure conditions. Theoretical calculations were performed in collaboration to support the experimental results. For the DWCNTs samples, changes in the G-band frequency vs. pressure plot and the disappearance of the radial breathing modes (RBM) between 2 GPa and 5 GPa indicate the beginning and ending of the radial collapse of the nanotubes. Theoretical calculations based on Density-Functional Tight-Binding (DFTB) shown that the collapse pressure (P_c) for DWCNTs follows a d^{-3}_{in} law, in excellent agreement with the experimental results. The P_c dependence on number of tube-walls and on the inter-wall distance is also investigated. For the TWCNTs samples, pressure screening effects are observed for the innermost tubes of TWCNTs similar to what has been already found for DWCNTs. However, using the RBM pressure coefficients in conjunction with the histogram of the diameter distribution, we were able to separate the RBM Raman contribution related to the intermediate tubes of TWCNTs from that related to the inner tubes of DWCNTs. By combining Raman spectroscopy and high pressure measurements, it was possible to identify these two categories of inner tubes even if the two tubes exhibit the same diameters, since their pressure response is different. Furthermore, it was possible to observe similar RBM profiles of the innermost tubes of TWCNTs using different resonance laser energies but also under different pressure conditions. This is attributed to changes in the electronic transition energies caused by small pressure-induced deformations. Theoretical calculations based on ab initio were performed for support the experimental results. By using Raman spectroscopy, it was possible to estimate the displacement of the optical energy levels with pressure. For the exfoliated MoS_2 samples, we studied the effect of the stacking on the E^1_{2g} and A_{1g} vibrational modes at high pressures. New components for both modes were observed with increasing pressure. It was also observed that the pressure coefficient of the E^1_{2g} mode decreases exponentially with MoS_2 thickness is increased, differently of the A_{1g} mode and the new components, which do not present a significant dependence on the variation of the number of layers. These results were attributed to deformations in the MoS_2 structure induced by a biaxial strain (dependent on the number of layers), resulting from the deformation of the SiO_2 substrate. Such adhesion decreases with the increasing of the MoS_2 thickness due to the increasing on the unbinding regions between MoS_2 and SiO_2. As result, a higher pressure is needed to improve the adhesion and consequently, a higher pressure is required to achieve the biaxial strain. For the MoS_2 microcrystalline powder, except for the B_{1u}, E^2_{2g}, E_{1g}, E^1_{2g} and A_{1g} modes, the behavior of all other modes was studied for the first time in high pressure conditions. For all modes, a linear variation of the Raman frequency and positive pressure coefficient was observed. Moreover, the differences in the behavior of the intensity profiles of the A_{1g}, 2LA(M) and A_{2u} modes in resonance and off-resonance were attributed to variations in the energy of direct optical transitions induced by pressure.
Petitprez, Jérôme. "La relation entre les concentrations sanguines en monoxyde de carbone (CO) et les symptômes lors d'intoxications pures au CO". Paris 5, 1998. http://www.theses.fr/1998PA05P153.
Testo completoTILLIETTE, JEAN-FRANCOIS. "Intoxication par l'oxyde de carbone dans la region nord/pas-de-calais : resultats d'une enquete a propos de 136 cas survenus entre le 18 et 21 septembre 1988". Lille 2, 1989. http://www.theses.fr/1989LIL2M247.
Testo completoCornetta, Andrei. "Entre o clima e a terra: uma abordagem geográfica da \'economia de baixo carbono\' na Amazônia Legal". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/8/8136/tde-10052017-125617/.
Testo completoFrom a critical perspective, this research examines the ways in which political programs on climate change and compensatory activities of greenhouse gases become reality in Brazil. The research analyzes the establishment of a low carbon economy in the Amazon, more specifically on its consequences on land issues in the Amazonian states, and present two illustrative cases of carbon projects involving forests in the state of Pará. It discusses about the coexistences and antagonisms in relations established between the regular activities of rural communities - their economic uses and ways of living together with the Amazon rainforest (specifically wood and agriculture) - and the introduction of the current projects \"deforestation avoided\". On the complexity that presents the current context of climate change, the research relies on an analysis from fundamental concepts for contemporary geography, as \"accumulation by dispossession\", \"uneven geographical development\" and \"production of nature\". Thus, it presents, along the thesis, the central question about how the Amazon forest is replaced by new use-value and exchange in the context of climate change and how their resignification comes to represent new strategies of accumulation of capital.
PEYRON, LAURENCE. "Intoxication par l'oxyde de carbone : etude de 100 cas recus au service d'accueil des urgences de l'hopital d'aix-en-provence entre le 1er decembre 1988 et le 30 novembre 1991". Aix-Marseille 2, 1992. http://www.theses.fr/1992AIX20057.
Testo completoHONARJOU, MADJID. "Intoxication par l'oxyde de carbone dans la region nord/ pas-de-calais : resultats d'une enquete a propos de 753 cas survenue entre le 15 octobre 1986 et le 14 octobre 1987". Lille 2, 1989. http://www.theses.fr/1989LIL2M324.
Testo completoSilva, Euclides Castorino da. "Correlação entre os métodos tradicionais de quantificação de fases e o método que utiliza o sistema de análise de imagens em aços ao carbono comum". Universidade de São Paulo, 1997. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-14092016-123118/.
Testo completoThe evaluation of the metallographic parameters in metallic materials has been carried out by many methods and they have been used extensively in the metallographic practice. However, the best method to be adopted has been a subject of many discussion. Nowadays, with the fast advance of computerisation, it has been possible to create semi-automatic or completely automatic systems for evaluation of these metallographic parameters, which are very important in determining the mechanical strength of carbon steels. In this work nine samples were removed from carbon steel plates with carbon content varying from 0,05 to 0,56 for evaluation of the correlation between the traditional methods, as well as with the method which use a digitised image analysis. This late method emphasise to the difference on the grey levels of the phases present. The results from this work are one of the first in this area, and they exploited the particularity of each method. Also, they demonstrated that the image analysis method, when compared with the traditional ones, gives a rapid and precise evaluation of the metallographic parameters, with a very good results reproducibility.
Leconte, Arnaud. "Combler l'écart entre la gestion de l'information et du risque social : : le marché européen du carbone, un modèle pour un marché global du carbone?" Nice, 2010. http://www.theses.fr/2010NICE0012.
Testo completoThe development of a new emerging market of carbon emission rights, the EU ETS (European Trading Scheme), since 2005 represents the first empirical attempt to capture new information (the carbon price) in climate risk management. A future global and efficent carbon price set by the market system assumes the existence of financial and technological transfer mechanisms to developing countries under the equity principle. The fair distribution of resources and risks is critical in the carbon market, and issues of equity are central to securing a global action programme to deal with climate change. Most economic studies consider that the carbon market is superior to other instruments (such as the carbon tax) in terms of efficiency and effectiveness. Formal modelisation in economics focuses on neo-classical models where perfect information is assumed. However, even a small amount of information imperfection has a profound effect on the nature of the equilibrium. The loss of confidence in the market mechanism observed in the current crisis leads to propose a new way of analysing financial markets. Under a framework of interactions between imperfect information and speculative flows, the new model developed in the present thesis, called PRISME, identifies and addresses the six key functions of financial markets: Price, Risk, Incentives, Social, Multiplier and Effectiveness. .