O etanol, produto proveniente da indústria sucroalcooleira, um dos setores mais importantes da economia brasileira, atrai a atenção dos países desenvolvidos. O aumento de sua demanda em todo o mundo, motivado por razões econômicas e ambientais, impulsiona sua exportação. O volume exportado passou de 750 milhões de litros em 2003 para 3,5 bilhões de litros em 2006 e os produtores estimam que em cinco anos este volume alcance 6,5 bilhões de litros. Diante da perspectiva de acréscimo nas exportações, e do fato de quase 90% da produção brasileira concentra-se no Centro-Sul, esta dissertação tem por objetivo analisar as alternativas de transporte de etanol para exportação no médio prazo, baseado no plano de investimentos proposto pelo projeto do corredor de exportação de etanol da Transpetro, um dos investimentos propostos para melhorar a eficiência logística do transporte de etanol. Tais investimentos pretendem atender a demanda instalada pelo mercado internacional de forma satisfatória, garantindo o suprimento do combustível e prevenindo o surgimento de gargalos logísticos motivados por falta de infra-estrutura suficiente para o escoamento da produção. Foram avaliadas três alternativas de transporte que representam a movimentação de etanol das unidades produtoras aos portos: alternativa rodoviária, alternativa rodo-dutoviária, e alternativa rodo-hidro-dutoviária. Definidas as alternativas, foram identificadas as trinta principais zonas produtoras de etanol e analisadas as alternativas específicas para cada uma. Assim, foi possível identificar as principais vantagens competitivas das alternativas de transporte por região produtora e verificar os ganhos derivados do transporte por dutos e pela hidrovia no escoamento da produção de etanol até os principais portos. / Ethanol, a product originated from the sugarcane and ethanol industry, one of the most important sectors in the brazilian economy is attracting the interest of the developed countries. The exportation of ethanol is stimulated by the increasing worldwide demand driven by economic and environmental reasons. The exported volume increased from more than 750 million liters in 2003 to 3.5 billion liters in 2006 and, in the next five years, the brazilian producers expect that this volume will reach 6.5 billion liters. Because of this expectation in increasing exportations of ethanol, and being aware that the center-south region of Brazil produces almost 90% of the brazilian ethanol, the objective of this dissertation is to analyze the alternatives of transportation of ethanol for exportation in the medium term. This study is based in the Transpetro´s corridor of ethanol exportation investment plan, which is one of the proposed investments to increase the logistic efficiency of the transportation of ethanol. These investments intend to satisfactorily fulfill the demand of the international market, guaranteeing the supply of ethanol and preventing the appearance of logistic gaps due to lacks of infra-structure for transporting the product. Three alternatives of transportation were evaluated, representing the transportation of ethanol from the manufacturing units to the ports: roadway alternative, road-pipeline alternative and road-waterway-pipeline alternative. After the definition of these alternatives, the thirty major manufacturing zones of ethanol were defined and each zone had these alternatives analyzed. As a result, the major competitive advantages of the transportation alternatives by zone were identified. Also, the potential gains of transporting ethanol to the major seaports by pipelines and waterways were evaluated.

The rapidly increasing number of cores available in multicore processors does not necessarily lead directly to a commensurate increase in performance: programs written in conventional languages, such as C, need careful restructuring, preferably automatically, before the benefits can be observed in improved run-times. Even then, much depends upon the intrinsic capacity of the original program for concurrent execution. Using software techniques to parallelize the sequential application can raise the level of gain from multicore systems. Parallel programming is not an easy job for the user, who has to deal with many issues such as dependencies, synchronization, load balancing, and race conditions. For this reason the role of automatically parallelizing compilers and techniques for the extraction of several threads from single-threaded programs, without programmer intervention, is becoming more important and may help to deliver better utilization of modern hardware. One parallelizing technique that has been shown to be an effective for the parallelization of applications that have irregular control flow and complex memory access patterns is Decoupled Software Pipeline (DSWP). This transformation partitions the loop body into a set of stages, ensuring that critical path dependencies are kept local to a stage. Each stage becomes a thread and data is passed between threads using inter-core communication. The success of DSWP depends on being able to extract the relatively fine-grain parallelism that is present in many applications. Another technique which offers potential gains in parallelizing general purpose applications is slicing. Program slicing transforms large programs into several smaller ones that execute independently, each consisting of only statements relevant to the computation of certain, socalled, (program) points. This dissertation explores the possibility of performance benefits arising from a secondary transformation of DSWP stages by slicing. To that end a new combination method called DSWP/Slice is presented. Our observation is that individual DSWP stages can be parallelized by slicing, leading to an improvement in performance of the longest duration DSWP stages. In particular, this approach can be applicable in cases where DOALL is not. In consequence better load balancing can be achieved between the DSWP stages. Moreover, we introduce an automatic implementation of the combination method using Low Level Virtual Machine (LLVM) compiler framework. This combination is particularly effective when the whole long stage comprises a function body. More than one slice extracted from a function body can speed up its execution time and also increases the scalability of DSWP. An evaluation of this technique on six programs with a range of dependence patterns leads to considerable performance gains on a core-i7 870 machine with 4-cores/8-threads. The results are obtained from an automatic implementation that shows the proposed method can give a factor of up to 1.8 speed up compared with the original sequential code.

Stop-motion animation is a traditional form of animation that has been practised for over 100 years. While the unique look and feel of stop-motion animation has been retained in modern productions, the production process has been modernised to take advantage of technological advancements. Modern stop-frame animation production integrates digital imaging technology and computational methods with traditional hand-crafted skills. This portfolio documents three projects undertaken at Aardman Animations, each investigated with the aim of improving efficiency in the stop-motion production process: - Rig removal is the removal of equipment, or ‘rigging’, used on set during stop-motion animation to hold characters or objects in unstable positions. All rigging captured in frames must be removed in post-production and currently manual methods are used which can be very time-consuming. The key task is to separate the character from the rig. In Chapter 2, I present a novel spatio-temporal segmentation algorithm for segmenting characters from stop-motion footage. The algorithm has been designed to work with stop-motion animated content, in contrast to other state of the art algorithms which struggled when tested on stop-motion footage. - Set shift is a problem which occurs when background items on set move subtly over the time taken to shoot a scene. For example, temperature and humidity changes can cause wood to warp during a weekend, changing the position of a background object the following week. These small ‘shifts’ are recorded in the footage and must be corrected in post-production. Chapter 3 describes the problem in detail, investigates potential solutions and explains why solving set shift automatically is a significant challenge. - Plasticine shading is required when a plasticine model has to be generated computationally. One motivation for producing footage computationally is that problems such as rig removal and set shift do not arise. In order to simulate plasticine accurately, the distinct reflectance model of this material must be known and reproduced. By collecting experimental data from plasticine samples and fitting parametric models, I have developed a bespoke surface shading model for plasticine (Chapter 4). This new model provides the best fit to the measured data when compared to existing state of the art surface shaders. It has been implemented into commercially used production systems, for use with existing rendering software. Advancing state of the art research is only one of the challenges when working in a production studio such as Aardman Animations. Additionally, findings must be integrated into the production pipeline. Chapter 5 discusses the challenges and constraints faced when conducting research in this environment. In order for stop-motion animation to remain competitive it is vital that production companies stay up-to-date with technological advancements in research areas that can contribute to their production processes. I conclude by discussing whether technological advancements can help Aardman Animations in improving the efficiency of their stop-motion production pipeline.

O reparo em dutos defeituosos é previsto por normas e literatura, porém existe grande espaço para definição dos parâmetros ideais para aplicação prática e avaliação do desempenho destes reparos em fadiga. O presente trabalho tem por objetivo a definição dos parâmetros ideais para aplicação de reparos eficientes do tipo dupla calha sem solda circunferencial e com carregamento externo em escala real em dutos com defeitos de mossa com cava. O reparo é baseado na instalação de duas calhas concêntricas ao duto a ser reparado, preenchendo-se o defeito com resina e aplicando carga de compressão através de atuadores hidráulicos com correntes a fim de induzir tensões compressivas na região do defeito e, por fim, as calhas são unidas longitudinalmente pelo processo de soldagem. Para este trabalho, foi realizada uma modelagem numérica utilizando o método de elementos finitos de modo a simular a reprodução do defeito, ensaios de fadiga sem reparo, parâmetros para aplicação do reparo, ensaios de fadiga com reparo e, por fim, ensaio hidrostático. O procedimento proposto foi a reprodução do defeito, primeiramente o duto foi deformado com uma esfera metálica, de modo a formar uma mossa de profundidade igual a 6 % do diâmetro externo e, em seguida, a cava foi usinada com a utilização de um disco abrasivo. Após a produção do defeito, três amostras foram ensaiadas em fadiga, de modo a produzir uma amostra de referência sem reparo a ser comparada com os corpos de prova com reparo. O reparo dupla calha foi aplicado em duas amostras com defeito, sendo essas então submetidas a ensaios de fadiga. Esses ensaios indicaram que ambas as amostras resistiram a um número de ciclos correspondentes a 100 anos de vida em serviço. Por fim, as amostras reparadas após o ensaio de fadiga foram submetidas a ensaios hidrostáticos até a ruptura, a fim de avaliar a vida remanescente. Ambos os dutos romperam fora da região reparada, com uma pressão 2,1 %, menor que a pressão calculada analiticamente. Como principal resultado, foram obtidos parâmetros ideais para aplicação do reparo dupla calha em dutos com defeito tipo mossa com cava. Os resultados experimentais mostram convergência em relação aos dados do modelo numérico, provando que a modelagem por elementos finitos pode ser uma ferramenta útil no desenvolvimento deste tipo de trabalho. / Defective duct repairs are envisaged by norms and by the literature, yet there is enough space left to define ideal parameters for practical application and performance evaluation of these fatigue repairs. This work’s objective is to define the ideal parameters for the application of efficient repairs in double spouts without circumferential welding and real scale external loading in ducts with dent and gouge defects. The repair is based on the installation of two concentric spouts in the duct, filling the defect with resin and applying compression loading through hydraulic actuators with currents to induce compressive stresses in the defective area. Afterwards, the spouts are united lengthwise through the process of welding. To develop this work, we conducted a numerical modelling by using the finite element method to simulate the reproduction of the defect, as well as fatigue tests with no repairs, parameters for the application of repairs, fatigue tests with repairs, and finally a hydrostatic test. The proposed procedure was the reproduction of the defect. At first the duct was deformed with a metallic sphere, to form a dent whose depth was equal to 6 % of the external diameter and, subsequently, the gouge was machined with the help of an abrasive disk. Following the production of a defect, three samples were tested in fatigue to produce a reference sample without repair which would be compared to the samples with repairs. The double spout repair was applied in two samples with defects, which were then subjected to fatigue tests. These tests showed that both samples resisted to a number of cycles corresponding to a 100-year use lifespan. At last, the samples repaired after fatigue tests were subjected to hydrostatic tests until rupture, in order to evaluate their remaining lifespan. Both ducts ruptured outside of the repaired region, with a stress rate of 2.1 %, lower than the stress calculated analytically. The main result of this study was obtaining ideal parameters for the application of double spout repair in ducts with dents and gouge defects. The experimental results show convergence in relation to the numerical model data, proving that finite element modelling can be a useful tool when conducting this kind of work.

Métodos acurados de avaliação de tenacidade à fratura, incluindo curvas de resistência ao rasgamento dúctil de juntas soldadas de dutos e risers rígidos, tornam-se essenciais em procedimentos de avaliação de defeitos em regiões de soldas e zonas termicamente afetadas, nas quais defeitos não detectados podem se propagar devido às grandes tensões e deformações envolvidas na instalação e/ou operação dessa classe de estruturas. Este trabalho apresenta uma investigação experimental da tenacidade à fratura de uma junta soldada de um duto rígido de aço API 5L X80 (curvas J-Ãa). A motivação para este trabalho decorre da demanda crescente na aplicação de dutos de alta resistência na indústria de óleo e gás, em particular dutos submarinos e risers rígidos em catenária. Para tal, foram empregados corpos de prova de tração SE(T) fixados por garras, e flexão três pontos SE(B) contendo entalhe no centro da solda, para determinação das curvas J-R pelo método do corpo de prova único utilizando a técnica da flexibilidade no descarregamento, além das funções de flexibilidade e fatores n referentes aos corpos de prova SE(T) e SE(B) em função do nível de dissimilaridades mecânicas, o que permite obter valores mais assertivos das propriedades de tenacidade à fratura de juntas soldadas. / Accurate measurements of fracture resistance properties, including crack growth resistance curves for pipeline girth welds, become essential in defect assessment procedures of the weldment region and the heat affected zone, where undetected crack-like defects (such as lack of penetration, deep undercuts, root cracks, etc.) may exhibit further crack extension due to high tensile stresses and strains during installation and in-service operation. This work presents an investigation of the ductile tearing properties for a girth weld made of an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves (J-Ãa curves). Use of these materials is motivated by the increasing demand in the number of applications for manufacturing high strength pipes for the oil and gas industry including marine applications and steel catenary risers. Testing of the pipeline girth welds utilized sidegrooved, clamped SE(T) specimens and 3P bend SE(B) specimens with a weld centerline notch to determine the crack growth resistance curves based upon the unloading compliance (UC) method using a single specimen technique. Recently developed compliance functions and n-factors applicable for SE(T) and SE(B) fracture specimens with homogeneous material and overmatch welds are introduced to determine crack growth resistance data from laboratory measurements of load-displacement records. This experimental characterization provides additional toughness data which serve to evaluate crack growth resistance properties of pipeline girth welds using SE(T) and SE(B) specimens with weld centerline cracks.

Subsea pipelines are subjected to wave and steady current loads which cause pipeline stability problems. Current knowledge and understanding on the pipeline on-bottom stability is based on the research programmes from the 1980’s such as the Pipeline Stability Design Project (PIPESTAB) and American Gas Association (AGA) in Joint Industry Project. These projects have mainly provided information regarding hydrodynamic loads on pipeline and soil resistance in isolation. In reality, the pipeline stability problem is much more complex involving hydrodynamic loadings, pipeline response, soil resistance, embedment and pipe-soil-fluid interaction. In this thesis Computational Fluid Dynamics (CFD) modelling is used to investigate and establish the interrelationship between fluid (hydrodynamics), pipe (subsea pipeline), and soil (seabed). The effect of soil types, soil resistance, soil porosity and soil unit weight on embedment was examined. The overall pipeline stability alongside pipeline diameter and weight and hydrodynamic effect on both soil (resulting in scouring) and pipeline was also investigated. The use of CFD provided a better understanding of the complex physical processes of fluid-pipe-soil interaction. The results show that the magnitude of passive resistance is on the average eight times that of lateral resistance. Thus passive resistance is of greater significance for subsea pipeline stability design hence the reason why Coulomb’s friction theory is considered as conservative for stability design analysis, as it ignores passive resistance and underestimates lateral resistance. Previous works (such as that carried out by Lyons and DNV) concluded that soil resistance should be determined by considering Coulomb’s friction based on lateral resistance and passive resistance due to pipeline embedment, but the significance of passive resistance in pipeline stability and its variation in sand and clay soils have not be established as shown in this thesis. The results for soil porosity show that increase in pipeline stability with increasing porosity is due to increased soil liquefaction which increases soil resistance. The pipe-soil interaction model by Wagner et al. established the effect of soil porosity on lateral soil resistance but did not attribute it to soil liquefaction. Results showed that the effect of pipeline diameter and weight vary with soil type; for sand, pipeline diameter showed a greater influence on embedment with a 110% increase in embedment (considering combined effect of diameter and weight) and a 65% decrease in embedment when normalised with diameter. While pipeline weight showed a greater influence on embedment in clay with a 410% increase. The work of Gao et al. did not completely establish the combined effect of pipeline diameter and weight and soil type on stability. Results also show that pipeline instability is due to a combination of pipeline displacement due to vortex shedding and scouring effect with increasing velocity. As scoring progresses, maximum embedment is reached at the point of highest velocity. The conclusion of this thesis is that designing for optimum subsea pipeline stability without adopting an overly conservative approach requires taking into consideration the following; combined effect of hydrodynamics of fluid flow on soil type and properties, and the pipeline, and the resultant scour effect leading to pipeline embedment. These results were validated against previous experimental and analytical work of Gao et al, Brennodden et al and Griffiths.

The VISTA Variables in the Vía Láctea survey is a multi-epoch, near-infrared (NIR) search for RR Lyrae stars, which trace the structure and evolutionary history of the Galactic Bulge. To measure accurate light-curves for these and other variable sources in the crowded fields of the Bulge, we have built a pipeline to perform difference imaging analysis (DIA) on VVV data. This is the first time DIA has been carried out with a large-scale NIR survey, which presents certain specific challenges such as the large pixel scales and high variable background. This thesis begins with an investigation into the wider problem of reference image selection for DIA. Through this study, we found that an alternative formulation of traditional DIA - Target Image Convolution - yields better results for VVV. This technique is employed in the core image subtraction engine for the VVV DIA pipeline. This work also details the pipelines for carrying out calibration, period-finding and Fourier modelling on the light-curves of DIA sources, as well as for obtaining their dereddened NIR magnitudes and colours. To validate the pipelines, the magnitude calibration is checked against another NIR survey (in the most challenging Galactic centre field) and analysis results are crosschecked against the OGLE-IV catalogue of RR Lyrae (in a low-extinction region of the Galactic bulge). Both studies are used to determine the efficacy of the existing pipeline and identify areas for improvement. DIA generally shows a significant improvement over existing aperture photometry. Using the NIR properties of VVV DIA counterparts to the OGLE-IV RR Lyrae, we demonstrate that it is possible to identify new variables with this pipeline, including RR Lyrae.

Buried pipelines are vulnerable to the threat of corrosion. Hence, they are normally coated with a protective coating to isolate the metal substrate from the surrounding environment with the addition of CP current being applied to the pipeline surface to halt any corrosion activity that might be taking place. With time, this barrier will deteriorate which could potentially lead to corrosion of the pipe. The External Corrosion Direct Assessment (ECDA) methodology was developed with the intention of upholding the structural integrity of pipelines. Above ground indirect inspection techniques such as the DCVG which is an essential part of an ECDA, is commonly used to determine coating defect locations and measure the defect's severity. This is followed by excavation of the identified location for further examination on the extent of pipeline damage. Any coating or corrosion defect found at this stage is repaired and remediated. The location of such excavations is determined by the measurements obtained from the DCVG examination in the form of %IR and subjective inputs from experts which bases their justification on the environment and the physical characteristics of the pipeline. Whilst this seems to be a straight forward process, the factors that comes into play which gave rise to the initial %IR is not fully understood. The lack of understanding with the additional subjective inputs from the assessors has led to unnecessary excavations being conducted which has put tremendous financial strain on pipeline operators. Additionally, the threat of undiscovered defects due to the erroneous nature of the current method has the potential to severely compromise the pipeline's safe continual operation. Accurately predicting the coating defect size (TCDA) and interpretation of the indication signal (%IR) from an ECDA is important for pipeline operators to promote safety while keeping operating cost at a minimum. Furthermore, with better estimates, the uncertainty from the DCVG indication is reduced and the decisions made on the locations of excavation is better informed. However, ensuring the accuracy of these estimates does not come without challenges. These challenges include (1) the need of proper methods for large data analysis from indirect assessment and (2) uncertainty about the probability distribution of quantities. Standard mean regression models e.g. the OLS, were used but fail to take the skewness of the distributions involved into account. The aim of this thesis is thus, to come up with statistical models to better predict TCDA and to interpret the %IR from the indirect assessment of an ECDA more precisely. The pipeline data used for the analyses is based on a recent ECDA project conducted by TWI Ltd. for the Middle Eastern Oil Company (MEOC). To address the challenges highlighted above, Quantile Regression (QR) was used to comprehensively characterise the underlying distribution of the dependent variable. This can be effective for example, when determining the different effect of contributing variables towards different sizes of TCDA (different quantiles). Another useful advantage is that the technique is robust to outliers due to its reliance on absolute errors. With the traditional mean regression, the effect of contributing variables towards other quantiles of the dependent variable is ignored. Furthermore, the OLS involves the squaring of errors which makes it less robust to outliers. Other forms of QR such as the Bayesian Quantile Regression (BQR) which has the advantage of supplementing future inspection projects with prior data and the Logistic Quantile Regression (LQR) which ensures the prediction of the dependent variable is within its specified bounds was applied to the MEOC dataset. The novelty of research lies in the approaches (methods) taken by the author in producing the models highlighted above. The summary of such novelty includes: * The use of non-linear Quantile Regression (QR) with interacting variables for TCDA prediction. * The application of a regularisation procedure (LASSO) for the generalisation of the TCDA prediction model.* The usage of the Bayesian Quantile Regression (BQR) technique to estimate the %IR and TCDA. * The use of Logistic Regression as a guideline towards the probability of excavation * And finally, the use of Logistic Quantile Regression (LQR) in ensuring the predicted values are within bounds for the prediction of the %IR and POPD. Novel findings from this thesis includes: * Some degree of relationship between the DCVG technique (%IR readings) and corrosion dimension. The results of the relationship between TCDA and POPD highlights a negative trend which further supports the idea that %IR has some relation to corrosion. * Based on the findings from Chapter 4, 5 and 6 suggests that corrosion activity rate is more prominent than the growth of TCDA at its median depth. It is therefore suggested that for this set of pipelines (those belonging to MEOC) repair of coating defects should be done before the coating defect has reached its median size. To the best of the Author's knowledge, the process of employing such approaches has never been applied before towards any ECDA data. The findings from this thesis also shed some light into the stochastic nature of the evolution of corrosion pits. This was not known before and is only made possible by the usage of the approaches highlighted above. The resulting models are also of novelty since no previous model has ever been developed based on the said methods. The contribution to knowledge from this research is therefore the greater understanding of relationship between variables stated above (TCDA, %IR and POPD). With this new knowledge, one has the potential to better prioritise location of excavation and better interpret DCVG indications. With the availability of ECDA data, it is also possible to predict the magnitude of corrosion activity by using the models developed in this thesis. Furthermore, the knowledge gained here has the potential to translate into cost saving measures for pipeline operators while ensuring safety is properly addressed.

Made available in DSpace on 2014-12-17T15:42:08Z (GMT). No. of bitstreams: 1 AlcidesOWN_TESE.pdf: 3644832 bytes, checksum: b30265cac81e679890142573e54a4e61 (MD5) Previous issue date: 2010-03-06 / Corrosion usually occurs in pipelines, so that it is necessary to develop new surface treatments to control it. Surfactants have played an outstanding role in this field due to its capacity of adsorbing on metal surfaces, resulting in interfaces with structures that protect the metal at low surfactant concentrations. The appearance of new surfactants is a contribution to the area, as they increase the possibility of corrosion control at specific conditions that a particular oil field presents. The aim of this work is to synthesize the surfactants sodium 12 hydroxyocadecenoate (SAR), sodium 9,10-epoxy-12 hydroxyocadecanoate (SEAR), and sodium 9,10:12,13-diepoxy-octadecanoate (SEAL) and apply them as corrosion inhibitors, studying their action in environments with different salinities and at different temperatures. The conditions used in this work were chosen in order to reproduce oil field reality. The study of the micellization of these surfactants in the liquid-gas interface was carried out using surface tensiometry. It was observed that cmc increased as salt concentration was increased, and temperature and pH were decreased, while cmc decreased with the addition of two epoxy groups in the molecule. Using the values of cmc and the Gibbs equation, the values of Gibbs free energy of adsorption, area per adsorbed molecule, and surface excess were calculated. The surface excess increases as salt concentration and temperature decreases, increasing as pH is increased. The area per adsorbed molecule and the free energy of adsorption decrease with salt concentration, temperature, and pH increase. SAXS results showed that the addition of epoxy group in surfactant structure results in a decrease in the repulsion between the micelles, favoring the formation of more oblong micellar structures, ensuring a better efficiency of metal coverage. The increase in salt and surfactant concentrations provides an increase in micellar diameter. It was shown that the increase in temperature does not influence micellar structure, indicating thermal stability that is advantageous for use as corrosion inhibitor. The results of inhibition efficiency for the surfactants SEAR and SEAL were considered the best ones. Above cmc, adsorption occurred by the migration of micelles from the bulk of the solution to the metal surface, while at concentrations below cmc film formation must be due to the adsorption of semi-micellar and monomeric structures, certainly due to the presence of the epoxy group, which allows side interactions of the molecule with the metal surface. The metal resistance to corrosion presented values of 90% of efficiency. The application of Langmuir and Frumkin isotherms showed that the later gives a better description of adsorption because the model takes into account side interactions from the adsorbing molecules. Wettability results showed that micelle formation on the solid surface occurs at concentrations in the magnitude of 10-3 M, which isthe value found in the cmc study. This value also justifies the maximum efficiencies obtained for the measurements of corrosion resistance at this concentration. The values of contact angle as a function of time suggest that adsorption increases with time, due to the formation of micellar structures on metal surface / O fen?meno da corros?o est? presente em oleodutos e por isso existe a necessidade de desenvolver novos materiais que controle tal fen?meno. Os tensoativos t?m se destacado para tal fim devido ao seu poder de adsorver-se em interfaces e formar estruturas que protejam o metal em baixas concentra??es. O surgimento de novos tensoativos ? uma contribui??o para o setor, pois aumentam as possibilidades de controlar a corros?o nas condi??es espec?ficas de cada campo. Este trabalho objetiva, principalmente, sintetizar e aplicar os tensoativos 12 hidroxioctadecenoato de s?dio (SAR), 9,10-ep?xi-12 idroxioctadecanoato de s?dio (SEAR) e 9,10:12,13-diep?xi-octadecanoato de s?dio (SEAL) como inibidores de corros?o, estudando-os em ambientes que apresentam, simultaneamente, salinidade, acidez e temperatura variadas. As condi??es estudadas s?o para reproduzir o m?ximo poss?vel ? realidade do campo. O estudo da miceliza??o destes tensoativos na interface l?quido-g?s foi realizado a partir de medidas de tens?o superficial. Observou-se que a eleva??o da concentra??o salina, abaixamento da temperatura e diminui??o do pH proporcionam aumento nos valores da cmc, com tamb?m os valores da cmc aumentam quando se adiciona um e dois grupos ep?xi na mol?cula, respectivamente. A partir da cmc, usando equa??o de Gibbs, foram encontrados valores para a energia livre de Gibbs de adsor??o, ?rea por mol?cula adsorvida e excesso superficial. O aumento dos valores de excesso superficial ? provocado pela diminui??o da concentra??o salina e temperatura, e aumenta com a eleva??o do pH. A ?rea por mol?cula adsorvida e a energia livre de adsor??o diminuem com aumento da salinidade e temperatura, e com o aumento do pH. Os resultados de SAXS mostraram que a adi??o do grupo ep?xi e o seu aumento na estrutura do tensoativo proporcionam diminui??o na intera??o de repuls?o entre as micelas, assim como favorecem a forma??o de estruturas micelares mais alongadas, garantindo maior efici?ncia na cobertura do metal. O aumento da concentra??o salina e da concentra??o do tensoativo proporciona aumento do di?metro da micela. O aumento da temperatura mostrou que n?o influencia a estrutura micelar, o que indica estabilidade t?rmica, sendo vantajoso para sua atua??o como inibidor de corros?o. Os resultados de efici?ncia para os tensoativos SEAR e SEAL foram os melhores. A cima da cmc a adsor??o se deve a migra??o da micela do seio da solu??o para a superf?cie do metal, enquanto em concentra??es abaixo da cmc a forma??o do filme se deve a adsor??o de estruturas semimicelares e monom?ricas, nas quais s?o caracter?sticas dos tensoativos que apresentam o grupo ep?xi, pois possibilita intera??o lateral da mol?cula com a superf?cie met?lica. A resist?ncia do metal ? corros?o apresentou valores de 90% de efici?ncia. A aplica??o das isotermas de Langmuir e Frumkin mostrou que esta ?ltima melhor valida o fen?meno da adsor??o, devido haver em sua express?o matem?tica o par?metro de intera??o lateral. Os resultados de molhabilidade mostraram que a forma??o da micela na superf?cie do s?lido se d? em concentra??es na ordem de 10-3 M, valor encontrado no estudo da cmc. Este valor justifica, tamb?m, os valores m?ximos de efici?ncia obtidos para as medidas de resist?ncia a corros?o a partir desta concentra??o. Os valores de ?ngulo de contato em fun??o do tempo sugerem que a adsor??o aumenta com o tempo, devido a forma??o de estruturas micelares na superf?cie do metal

La cristallisation des hydrates pendant la production de pétrole est une source de risques, surtout liés au bouchage des lignes de production dû à l’agglomération des hydrates. Pendant l'extraction de pétrole, l'huile et l'eau circulent dans le pipeline et forment une émulsion instable. La phase eau se combine avec les composants d'hydrocarbures légers et peut former des hydrates. La cristallisation des hydrates a été intensivement étudiée, principalement à faible fraction d’eau. Cependant, lorsque le champ de pétrole devient mature, la fraction d’eau augmente et peut devenir la phase dominante, un système peu étudié concernant à la formation d'hydrates. Plusieurs techniques peuvent être combinées pour éviter ou remédier la formation d'hydrates. Récemment, une nouvelle classe d'additifs a commencé à être étudiée : Inhibiteurs d'Hydrates à Bas Dosage (LDHI), divisés en Inhibiteurs Cinétiques (KHI-LDHI) et anti-agglomérants (AA-LDHI).Ce travail est une étude paramétrique de la formation d'hydrates à partir de l'émulsion, en variant la fraction d’eau, le débit, en absence et en présence d’AA-LDHI. Les expériences ont été réalisées sur la boucle d'écoulement Archimède, qui est en mesure de reproduire les conditions de la mer profonde. L'objectif de cette étude est d'améliorer la compréhension de la formation d'hydrate et de comprendre comment l'additif dispersant évite l'agglomération. Pour ce faire, un modèle comportemental de la cristallisation pour les systèmes sans et avec additif a été développé. Il a également été proposé une technique pour déterminer la phase continue du système et un mécanisme d'action pour l'anti-agglomérant a été suggéré. / Crystallization of hydrates during oil production is a major source of hazards, mainly related to flow lines plugging after hydrate agglomeration. During the petroleum extraction, oil and water circulate in the flow line, forming an unstable emulsion. The water phase in combination with light hydrocarbon components can form hydrates. The crystallization of hydrates has been extensively studied, mainly at low water content systems. However, as the oil field matures, the water fraction increases and can become the dominant phase, a system less known in what concerns hydrate formation. Actually, several techniques can be combined to avoid or remediate hydrate formation. Recently, a new class of additives called Low Dosage Hydrate Inhibitor (LDHI) started to be studied, they are classified as Kinetic Hydrate Inhibitors (KHI-LDHI) and Anti-Agglomerants (AA-LDHI).This work is a parametric study about hydrate formation from emulsion systems ranging from low to high water content, where different flow rates and the anti-agglomerant presence were investigated. The experiments were performed at the Archimède flow loop, which is able to reproduce deep sea conditions. The goal of this study is enhancing the knowledge in hydrate formation and comprehending how the dispersant additive acts to avoid agglomeration. For this matter, it was developed a crystallization topological model for the systems without and with additive. A technique to determine the system continuous phase and a mechanism of the anti-agglomerant action from the chord length measurements were also proposed.