Cette thèse porte sur la caractérisation du milieu des think tanks aux États-Unis à travers l’étude de leur discours et de leur culture professionnelle dans le cadre d’une recherche en anglais de spécialité. L’objectif est de démontrer que ce milieu hétérogène peut être envisagé comme un milieu spécialisé, caractérisé par un discours et une culture spécifiques qui répondent aux impératifs de son objectif d’influence. Dans une première partie, nous exposons les fondements épistémologiques de la thèse : nous présentons les défis soulevés par l’étude de cet objet du point de vue de la recherche en anglais de spécialité, et proposons une approche de sa spécialisation fondée sur sa raison d’être. Une définition opératoire est élaborée, et le cadre méthodologique de la thèse à la croisée de l’histoire institutionnelle et politique des États-Unis, de l’ethnographie, de l’analyse du discours et de la pragmatique est exposé. La deuxième partie porte sur les modalités notamment culturelles de la spécialisation ; nous montrons comment le milieu s’est structuré en réponse à un besoin d’expertise dans la société américaine, et s’organise autour de missions, pratiques, valeurs et genres communs. Une topographie de ces genres est proposée pour éclairer les modalités communicationnelles de la stratégie programmatique des think tanks. La troisième partie explore les modalités discursives de cette stratégie dans deux genres, les blogs et les policy briefs, pris individuellement, puis en vis-à-vis ; l’analyse des modules péritextuels, structurels et interpersonnels révèle un ensemble de choix argumentatifs qui reflètent les enjeux de captation et de crédibilité de l’intervention des experts. / This dissertation aims to characterize the milieu of think tanks in the United States through their discourse and professional culture from the French point of view of research on English for Specific Purposes. We contend that this heterogeneous milieu may nonetheless be considered a specialized milieu, as its discourse and its culture are shaped by its programmatic aim. Part 1 presents the epistemological foundations of our research: it sheds light on the theoretical challenges raised by the study of think tanks in the framework of English for Specific Purposes and offers an approach to specialization based on its raison d’être. We suggest a working definition for the milieu and explain the methodology for this study situated at the crossroads between US institutional and political history, ethnography, the French approach to discourse analysis, and pragmatics. Part 2 focuses on the cultural manifestations of think tanks’ programmatic aim; it shows how the milieu has crystallized in response to a need for expertise in US society and is characterized by similar aims, practices, values and genres. A topography of these genres is offered to cast light on the milieu’s discursive strategy. Part 3 explores the discursive manifestations of this strategy and concentrates on two genres, blog posts and policy briefs, which are studied first individually and then jointly. The analysis of peritextual, structural and interpersonal modules reveals the argumentative choices experts make to remain credible and attractive in the marketplace of ideas.

Cylindrical shells are widely used in civil engineering. Examples include cooling towers, pipelines, nuclear containment vessels, steel silos and tanks for storage of bulk solids and liquids, and pressure vessels. The loading condition for these shells is quite varied depending on the function of the shell. Axial compression, global bending, external or internal pressure and wind loading are some of the most common loading forms for realistic structures. The failure of these cylindrical shell structures is often controlled by elastic or elastic-plastic buckling failure. Yield failure may occur in thick cylinders in some situations. A cylindrical shell under different loading conditions may display quite different buckling behaviour. The objective of this thesis is to investigate the characteristics of different buckling behaviours of cylindrical shell structures under axial compression, global bending, uniform external pressure and wind pressure. Some challenging practical problems in the design of these shell structures are explored. This thesis is expected to have some far-reaching impacts in defining how to design cylindrical shell structures to give them adequate strength to resist extreme events. Many aspects will be based on the latest Eurocode (EN 1993-1-6, 2007) and Recommendations (ECCS EDR5, 2008). The results show both some strength and some weaknesses in the Eurocode in design of shell structures. New methods are proposed for some practical problems. Some new conclusions and suggestions are derived and are expected to provide some useful knowledge for the improvement of the Eurocode in cylindrical shell design in general.

The provision of sanitation services during the apartheid era in South Africa was minimal or non-existent in the previous "black" areas and for farm workers. Whatever service that was provided was often in a bad state of disrepair. One of the priorities established in the post 1994 elections was to improve the quality of lives for the previously marginalised and neglected communities. This was done through the development and implementation of a policy for reducing the sanitation backlog, and for the provision of a basic level of sanitation. The principles encompassed in the policies developed for poverty alleviation and sustainable development had many points in common with the United Nations Millennium Development Goals and targets declared in 2000. The provision of Ventilated Improved Pit (VIP) latrines by municipalities satisfies the minimum requirements for basic sanitation. This provision together with the awareness programs are seen to offer communities an improved environment and hence living conditions. Problems arise however, due to the rapid filling, blockages and even the overflow of these pits. The emptying of these pits is also hazardous due to the nature of the waste. One of the solutions proposed by entrepreneurs was to supply additives that would enhance the degradation processes in the pit thereby increasing the Iifespan of these pits as well as offering other benefits; reduced odours, and flies. The aim of this research work was to test the claim of enhanced degradation by determining the effectiveness of an additive, M, which was deemed to be representative of a group of additive; made up of aerobic microbes and enzymes. The objective was to supply information to the municipality planners and decision makers in municipalities to assist them in their planning for improved management of pits. Waste was removed from suitable VIPs and used as samples for laboratory scale experiments. Reactor vessels were designed to simulate pit conditions. The additive was tested on the waste as recommended by the supplier and compared in activity against waste tested as references. The reference tests had (i) no addition of additive or water, as well as (ii) varying the volume of water added and (iii) varying the frequency of water addition, no additive added. Measurements were made of the following variables: • Total mass • Chemical oxygen demand. • Total solids • Volatile solids. • Ash. The results of the experimental vessels were analysed and compared with the reference vessels to reveal any differences. The results obtained did not present enough precision and reliability to make any conclusive decision as to whether the additive is effective or not. Recommendations made were to improve the test methodology using the same additive, to obtain results that would make a conclusive decision possible. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2008.

The focus of this thesis is the study of turbulent solid-liquid stirred suspensions, which are involved in many common unit operations in the chemical, pharmaceutical and food industries. The studies of two-phase flows present a big challenge to researchers due to the complexity of experiments; hence there is a lack of quantitative solid and liquid hydrodynamic measurements. Therefore, an investigation of turbulence modulation by dispersed particles on the surrounding fluid in stirred vessels has been carried out, via two-phase fluorescent Particle Image Velocimetry (FPIV) and micromixing experiments. The main property of interest has been the local dissipation rate, as well as root-mean-square (rms) velocities and turbulent kinetic energy (TKE) of the fluid. Initially a single-phase PIV study was conducted to investigate the flow field generated by a sawtooth (EkatoMizer) impeller. The purpose of this study was to gain insight into various PIV techniques before moving on to more complex two-phase flows. Subsequently stereo-, highspeed and angle-resolved measurements were obtained. The EkatoMizer formed a good case study as information regarding its hydrodynamics is not readily available in literature, hence knowledge has been extended in this area. An analysis of the mean flow field elucidated the general structure of fluid drawn into the impeller region axially and discharged radially; the latter characterised the impeller stream. The radial rms velocity was considered to represent best the system turbulence, even though the tangential rms velocity was greater close to the blade; however the radial component was more prevalent in the discharge stream. Due to differences in rms velocities, TKE estimates obtained from two and three velocity components deviated, being greater in the latter case. Integral (1-D and 2-D) length scales were overestimated by the quantity W / 2 in the impeller region. Ratios of longitudinal-to-lateral length scales also indicated flow anisotropy (as they deviated from 2:1). The anisotropy tensor showed that the flow was anisotropic close to the blade, and returned to isotropy further away from the impeller. Instantaneous vector plots revealed vortices in the discharge stream, but these were not associated with flow periodicity. Alternatively, the vortex structures were interpreted as low frequency phenomena between 0-200 Hz; macro-instabilities were found to have a high probability of occurrence in the discharge stream. Dissipation is the turbulent property of most interest as it directly influences micromixing processes, and its calculation is also the most difficult to achieve. Its direct determination from definition requires highly resolved data. Alternative methods have been proposed in the literature, namely dimensional analysis, large eddy simulation (LES) analogy and deduction from the TKE balance. All methods were employed using 2-D and 3-D approximations from stereo-PIV data. The LES analogy was deemed to provide the best estimate, since it accounts for three-dimensionality of the flow and models turbulence at the smallest scales using a subgrid scale model. (Continues...).

The performance of settling tanks depends on several interrelated processes and factors that include: hydrodynamics, settling, turbulence, sludge rheology, flocculation, temperature changes and heat exchange, geometry, loading, the nature of the floc, the atmospheric conditions and the total dissolved solids concentration. A Quasi-3D (Q3D) clarifier model has been developed to include the following factors: axisymmetric hydrodynamics (including the swirl component), five types of settling (nonsettleable particles, unflocculated discrete settling, flocculated discrete settling, hindered settling and compression), turbulence, sludge rheology, flocculation with four classes of particles, temperature changes and surface heat exchange with the atmosphere, various external and internal geometry configurations, unsteady solids and hydraulic loading, the nature of the floc settling/interaction. The model includes: shear flocculation, differential settling flocculation and sweep flocculation. The Q3D model reproduces the major features of the hydrodynamic processes and solids distribution on secondary clarifiers. When the model is executed with the field derived settling characteristics, it can accurately predict the effluent and recirculation suspended solids concentrations. The model has been formulated to conserve fluid, tracer and solids mass. The model has been developed and tested using field data from the UNO Pilot Plant and the Jefferson Parish Waste Water Treatment Plant located at Marrero, Louisiana. A field testing procedure is presented that addressees all of the settling regimes that are encountered in a Secondary Settling Tank. Results obtained with the Q3D model indicate that the flocculation process plays a major role in the effluent suspended solids (ESS) on secondary clarifiers. The extent of actual flocculation depends on the design of the center well and on the concentration of the incoming mixed liquor suspended solids (MLSS). The center well promotes flocculation, but its most important benefit is the improvement on the tank hydrodynamics. The changes in temperature on secondary clarifiers play an important role on the performance of secondary settling tanks. The gravity induced radial velocities in the sludge blanket are higher than the radial velocities of the scraper in the region near the hopper, therefore the blades are not highly effective in conveying the solids in this region.

本論文探討智庫的定義及起源，並依其性質與功能將美國的智庫做分類，另介紹著名的美國外交智庫。本論文亦說明美國外交政策的決策環境，探討為何智庫得以參與美國外交政策，以及參與決策過程的方式，並討論智庫在決策過程中所扮演的角色以及智庫在美國興盛的原因。最後分析智庫在發展上可能受到的限制，及探討智庫如何因應未來的挑戰。 / This paper explores the definition and origin of think tanks, classifies American think tanks according to their nature and functions, and introduces some famous think tanks on US foreign policy. This paper also explains the decision-making environment of US foreign policy, discusses why think tanks can participate in the making of US foreign policy, and examines the roles of think tanks in the decision-making process and the reasons why think tanks flourish in the United States. This paper also tries to find out the development restrictions of American think tanks and explores how they meet future challenges.

Neste trabalho estuda-se a elaboração dos projetos estruturais dos reservatórios paralelepipédicos de concreto armado, comumente usados no armazenamento de água. Para facilitar as análises, estes reservatórios são separados segundo as formas de suas cubas em três grupos, denominados reservatórios achatados, alongados e cúbicos. Para cada um destes grupos apresentam-se indicações para a escolha dos arranjos estruturais bem como dos prováveis carregamentos que devem ser considerados na obtenção dos esforços máximos. Fornecem-se também critérios para a determinação dos esquemas estáticos, correspondentes a cada um destes carregamentos. Incluem-se ainda critérios práticos para o dimensionamento dos elementos estruturais com verificações de fissuração e de estabilidade da estrutura. Sugerem-se, no final, os arranjos das armaduras mais adequados para toda a estrutura e em particular para as ligações das lajes com as paredes e destas entre si. / In this work, the elaboration of structural designs of parallelepiped form water reservoirs is studied. To facilitate the analysis, these reservoirs are separated into three groups according to their tank forms, namely flat, elongated and almost cubic. For each one of these groups, adequate structural arrangements are indicated as well as probable loads that must be considered in order to obtain maximum efforts. Criteria are proposed to specify static schemes in agreement with each one of the loads. Practical criteria for the design of structural elements, verification of cracking, and the study of the stability of structures have also been included. Finally, suggestions for the most adequate reinforcement arrangements for the whole structure and in particular for the slab-wall and wall-wall connections.

Esta pesquisa teve como objetivo quantificar a emissão de metano (CH4) proveniente da vinhaça presente em diferentes sistemas de armazenamento e transporte e, adicionalmente, avaliar, por técnicas independentes de cultivo, a microbiota funcional relacionada à produção deste gás. Para atingir esta meta foram realizados três estudos complementares. O primeiro abordou a caracterização dos sistemas de armazenamento e transporte de vinhaça encontrados no Brasil baseado em um questionário aplicado às usinas produtoras de etanol. O segundo visou quantificar as emissões de CH4 em condições de campo provenientes da vinhaça nos canais e tanques e também em laboratório em um estudo de incubação. O terceiro estudo avaliou a microbiota funcional associada à emissão de CH4 através de técnicas independentes de cultivo, como PCR em tempo real (qPCR) e pirosequenciamento. As análises microbiológicas indicaram que as emissões de CH4 são produzidas, preferencialmente, através da decomposição anaeróbia do material orgânico dissolvido da vinhaça depositados no fundo dos sistemas. Estas emissões não são desprezíveis e devem ser consideradas nos cálculos de pegada de carbono do etanol. Nos canais sem revestimento a emissão média em dois anos safras consecutivos apresentou valor de 0,75 kg CO2 eq m-3 de vinhaça, aproximadamente 5 vezes superior às emissões na parte revestida. Nos tanques a emissão foi aproximadamente setenta vezes inferior quando comparada ao canal revestido. O experimento de incubação auxiliou no entendimento de que a vinhaça sozinha não produz quantidades significativas de CH4. Entende-se que os nichos microbianos metanogênicos provavelmente são formados no sedimento, enquanto que a vinhaça mantém as condições de anaerobiose do sedimento necessárias à metanogênese e fornece nutrientes para acelerar a reação. O gênero Methanobrevibacter se mostrou dominante na comunidade microbiana metanogênica, conforme demonstrado pelo pirosequenciamento do gene 16S rRNA. Houve correlação positiva entre a abundância do gene 16S rRNA de Arquéia e dos genes funcionais mcrA e mba com a emissão de CH4. As informações sobre produção e emissão de CH4 e das características da vinhaça constituem informações importantes para tomada de decisão sobre a mitigação e/ou aproveitamento do CH4 gerado para fins econômicos e ambientais. / This research aimed to quantify methane (CH4) emissions from the vinasse in different storage and transportation systems and, additionally, to evaluate the functional microbiota associated with the production of this gas by molecular biology approaches. Three complimentary studies were performed to reach this goal. The first one was related to the characterization of main vinasse storage and transportation systems adopted in Brazil based on a survey administered to the mills, in south-central region of Brazil, producing sugarcane etanol. The second aimed to quantify the CH4 emissions from vinasse in both, field - channels and thanks - and laboratory conditions. The third study evaluated the functional microbiota associated with the CH4 emission by molecular biology approaches like real time PCR ans pyrosequencing. Microbial analysis indicated that CH4 emissions are produced preferably by anaerobic decomposition of the organic material dissolved in the vinasse and deposited on the bottom of the systems. These emissions are not negligible and should be considered in ethanol\'s carbon footprint calculations. At the uncoated part of the channel, the average emission from two crop years was 0.75 kg CO2 eq m-3 of vinasse, about 5 times greater than the emissions at the coated part. Methane emissions from the tank were about seventy times lower than from the uncoated channel. The laboratory experiment supported the understanding that the vinasse alone produces no significant emission of CH4. The microbial methanogenic niches were probably formed in the sediment, while the vinasse keeps sediment anaerobic conditions necessary for methanogenesis and provides nutrients to speed up the reaction. The Methanobrevibacter genus showed dominant in methanogenic microbial community, as demonstrated by pyrosequencing of the 16S rRNA gene. There was a positive correlation between the abundance of 16S rRNA gene Archaea and the functional mcrA and mba genes with the emission of CH4. Information on production and emission of CH4 and vinasse characteristics are important for decision making on mitigation and/or use of gas generated for economic and environmental purposes.

Em doze anos de atuação profissional no desenvolvimento de projetos específicos para a indústria sucro-alcooleira, observou-se a pouca informação encontrada para o projeto de equipamentos utilizados neste setor, sendo de grande utilidade aos profissionais que nele atuam, algo introdutório, para auxiliar na análise estrutural de reservatórios metálicos elevados utilizados na fabricação de açúcar e álcool. Objetivou-se, utilizar a teoria de estruturas em casca de revolução e programa \"comercial\" de análise de estruturas por elementos finitos, como ferramentas, no cálculo estrutural de cascas cilíndrica e cônica que compõem um equipamento com dimensões \"típicas\" utilizadas na área de processos da indústria sucro-alcooleira. O estudo de forma comparativa com o método dos elementos finitos permitiu calibrar a solução teórica aproximada desenvolvida. As equações obtidas, para cascas cilíndricas e cônicas com bordas engastadas ou apoiadas fixas sob a ação de pressão hidrostática, podem ser utilizadas para prever o seu comportamento estrutural, desde que observadas hipóteses e recomendações básicas. Mesmo distantes da simulação do comportamento real das cascas, já que em campo, encontram-se inúmeros outros parâmetros não considerados neste trabalho, procurou-se apresentar um melhor esboço do comportamento estrutural das mesmas com equacionamento acessível aos engenheiros não acadêmicos envolvidos com problemas de projeto estrutural. / In twelve years of professional performance in the development of specific projects for the sugar and alcohol industry, the little information for equipments used in this sector design was observed, and it would be of great usefulness to the design engineers of this area, something introductory in the structural analysis of elevated steel tanks used in the production of sugar and alcohol. This work had as objective to use the shell of revolution theory and \"commercial\" programs for finite element analysis of structures, as tools, in the calculation of cylindrical and conical shells that compose a typical \"dimensions\" equipment used in the sugar industry processes area. The study in a comparative way with the finite elements method allowed to gauge the approximate theoretical solution developed. The equations developed for cylindrical and conical shells with fixed or supported borders under liquid pressure action, can be used to anticipate the structural behavior of the same ones, since fundamental hypotheses and basic recommendations wil have observed. In spite o f far from the real behavior simulation of the shells, because of the countless others in field parameters existence and that had not considered in this work, we tried to present a better sketch of the structural behavior of the shells with useful equations for the non academics\' engineers involved with structural design problems.

Este trabalho estudou a aplicação de oito métodos clássicos de escalonamento de tanques condicionadores, testando sua validade para dois tanques de geometria semelhante, mas com diferentes volumes (V1=10 e V2=49 decímetros cúbicos). No interior dos tanques, operavam impulsores (diâmetro D1=0,078m x D2=0,132m) que exibiam três distintos desenhos (2 pás versus 4 pás inclinadas em 45 graus versus turbina de Rushton). Sua rotação (N1 no tanque menor x N2 no tanque maior) visava à suspensão de partículas grossas de apatita (diâmetro médio = 254 micrometros) em polpas com 40% de sólidos em massa. Para balizar o escalonamento, adotou-se como variável de controle a mínima rotação do impulsor (Njs) que é capaz de fazer com que nenhuma partícula repouse no fundo do tanque por mais do que 1 ou 2 segundos (Critério 1-s), além de perfis axiais de distribuição de sólidos e a extensão da Zona Turbulenta versus Zona Quiescente no interior dos tanques. A diferença entre o valor previsto de Njs para o tanque de 49 decímetros cúbicos (N2) pelos métodos de escalonamento versus o valor de Njs (N2) determinado experimentalmente foi expressa como erro percentual (E). Consideraram-se como adequados para a aplicação que constitui o objetivo desta dissertação todos os métodos que exibiram E menor que 10%. Para o impelidor de 2 pás inclinadas, a adequação do método baseado na constância da razão potência/volume (E=2%) e também do método empírico de Rautzen (E=6%), indica a expressão N2=N1.(D1/D2) com seu expoente da relação entre os diâmetros variando entre 0,67 e 0,75 para a aplicação desejada. Considerando o impulsor de 4 pás inclinadas, a adequação do método da constância da razão potência/volume (E=4%); assim como dos métodos empíricos de Rautzen (E=0%) e Zwietering (5%), sugere o uso da expressão N2=N1.(D1/D2) com seu expoente da relação entre os diâmetros variando entre 0,67 e 0,85. Para a turbina de Rushton, o único método que exibiu E menor que 10% foi o da constância da relação potência/volume (E=8%), cuja expressão é N2=N1.(D1/D2) com seu expoente da relação entre os diâmetros igual a 0,67. Uma vez que a determinação do valor real de N2 foi baseada numa técnica experimental influenciada pelas limitações do observador, pode-se inferir que uma expressão geral de escalonamento do tipo N2=N1.(D1/D2) com seu expoente da relação entre os diâmetros igual a 0,75 atende aos propósitos desta aplicação. Por outro lado, o uso da relação P/V provê um critério mais objetivo para se balizar o escalonamento, haja vista que ele se adequou a todos os três tipos de impelidores contemplados por este estudo. / This work has studied the application of eight classical methods appointed by literature to accomplish the scale-up of stirred tanks which aimed to suspend slurries of 40% of solids, containing coarse (mean diameter=254 micrometers) apatite particles. The validity of the methods was accomplished by using two tanks of similar geometry but different capacity (V1=10 e V2=49 cubic decimeter), together with impellers of different diameter (D1=0,078m versus D2=0,132m) and design (turbine of 2 or 4 blades inclined at 45 degrees and Rushton turbine). To assist the process of validation, the impeller speed (Njs) under which no particle rests on the bottom of the tank for more than 1-2 seconds (1-s Criterium) was used together with the axial profile of solids percent distribution plus the extension of the turbulent versus quiescent zones within the two tanks. For any of the eight scale-up methods, the difference between the predicted value of Njs (N2) for the 49 cubic decimeter tank and the actual value (experimental) of the same variable was determined and its magnitude was expressed in terms of the percent error (E). The methods that yielded E less than 10% were considered as suitable for the aimed application. Considering the 2-inclined blade impeller, low value of E yielded by the method based on the constancy of the ratio power/volume (E=2%) and also by the empiric method of Rautzen (E=6%) indicate that the expression N2=N1.(D1/D2) with its exponent of the relation between diameters ranging between 0,67 and 0,75 is suitable for the desired application. Regarding the 4-inclined blade impeller, because the method based on the constancy of the ratio power/volume (E=4%) and also the empiric methods of Rautzen (E=0%) and Zwietering (E=5%) yielded the lowest values of E, the expression N2=N1.(D1/D2) with its exponent of the relation between diameters ranging between 0,67 and 0,85 is suitable for the aimed application. Moreover, for the Rusthon turbine, only the method based on the constancy of the ratio power/volume (E=8%) was adequate for the aimed application and, thus, the expression N2=N1.(D1/D2) with its exponent of the relation between the diameters equal to 0,67 is suitable for the purpose of this dissertation. Once the actual value of N2 is determined by visual observation, it is not possible to get very accurate results. This way, a generic scale-up expression is proposed: N2=N1.(D1/D2) with its exponent of the relation between the diameters equal to 0,75. On the other hand, the ratio P/V may provide a more objective criterium for scale-up, because the three sort of impellers used in this study yielded E less than 10% when the power/volume method was applied for the purpose of scale-up.