Made available in DSpace on 2014-12-17T14:58:17Z (GMT). No. of bitstreams: 1 FelipePMA_DISSERT.pdf: 3715487 bytes, checksum: 630bbbaabad6ec787270701f99c61fb0 (MD5) Previous issue date: 2012-04-18 / A critical problem in mature gas wells is the liquid loading. As the reservoir pressure decreases, gas superficial velocities decreases and the drag exerted on the liquid phase may become insufficient to bring all the liquid to the surface. Liquid starts to drain downward, flooding the well and increasing the backpressure which decreases the gas superficial velocity and so on. A popular method to remedy this problem is the Plunger Lift. This method consists of dropping the "plunger"to the bottom of the tubing well with the main production valve closed. When the plunger reaches the well bottom the production valve is opened and the plunger carry the liquid to the surface. However, models presented in literature for predicting the behavior in plunger lift are simplistic, in many cases static (not considering the transient effects). Therefore work presents the development and validation of a numerical algorithm to solve one-dimensional compressible in gas wells using the Finite Volume Method and PRIME techniques for treating coupling of pressure and velocity fields. The code will be then used to develop a dynamic model for the plunger lift which includes the transient compressible flow within the well / Um problema cr?tico em po?os maduros de g?s ? a carga l?quida. Quando a press?o do reservat?rio diminui, a velocidade superficial diminui e o arrasto exercido na fase l?quida pode se tornar insuficiente para trazer todo o l?quido para a superf?cie. O l?quido come?a a drenar para baixo, afogando o po?o e aumentando a contrapress?o, a qual diminui a velocidade superficial, e assim por diante. Um m?todo popular para remediar esse problema ? o plunger lift. Esse m?todo consiste em derrubar um plunger na fundo coluna de produ??o com a v?lvula principal fechada. Quando o plunger alcan?a o fundo do po?o a v?lvula de produ??o ? aberta e o plunger carrega o l?quido para a superf?cie. Atualmente, os modelos presentes na literatura para prever o comportamento do plunger s?o simplistas, em muitos casos est?ticos (n?o consideram efeitos transientes). Assim, esse trabalho apresenta e valida um algor?timo num?rico para resolver escoamentos em po?os de g?s usando o M?todo dos Volumes Finitos e a t?cnica PRIME para tratar o acoplamento da press?o e velocidade. Esse modelo ser? usado para desenvolver modelos din?micos para plunger lift que incluem efeitos transientes e compress?veis nos escoamentos em po?os

Veículos Submarinos Não Tripulados (UUVs Unmanned Underwater Vehicles) possuem muitas aplicações comerciais, militares e científicas devido ao seu elevado potencial e relação custo-desempenho considerável quando comparados a meios tradicionais utilizados para a obtenção de informações provenientes do meio subaquático. O desenvolvimento de uma plataforma de testes e amostragem confiável para estes veículos requer o projeto de um sistema completo além de exigir diversos e custosos experimentos realizados no mar para que as especificações possam ser devidamente validadas. Modelagem e simulação apresentam medidas de custo efetivo para o desenvolvimento de componentes preliminares do sistema (software e hardware), além de verificação e testes relacionados à execução de missões realizadas por veículos submarinos reduzindo, portanto, a ocorrência de potenciais falhas. Um ambiente de simulação preciso pode auxiliar engenheiros a encontrar erros ocultos contidos no software embarcado do UUV além de favorecer uma maior introspecção dentro da dinâmica e operação do veículo. Este trabalho descreve a implementação do algoritmo de controle de um UUV em ambiente MATLAB/SIMULINK, sua conversão automática para código compilável (em C++) e a verificação de seu funcionamento diretamente no computador embarcado por meio de simulações. Detalham-se os procedimentos necessários para permitir a conversão dos modelos em MATLAB para código C++, integração do software de controle com o sistema operacional de tempo real empregado no computador embarcado (VxWORKS) e a estratégia de simulação com Hardware In The Loop (HIL) desenvolvida - A principal contribuição deste trabalho é apresentar de forma racional uma estrutura de trabalho que facilite a implementação final do software de controle no computador embarcado a partir do modelo desenvolvido em um ambiente amigável para o projetista, como o SIMULINK. / Unmanned Underwater Vehicles (UUVs) have many commercial, military, and scientific applications because of their potential capabilities and significant costperformance improvements over traditional means of obtaining valuable underwater information The development of a reliable sampling and testing platform for these vehicles requires a thorough system design and many costly at-sea trials during which systems specifications can be validated. Modeling and simulation provide a cost-effective measure to carry out preliminary component, system (hardware and software), and mission testing and verification, thereby reducing the number of potential failures in at-sea trials. An accurate simulation environment can help engineers to find hidden errors in the UUV embedded software and gain insights into the UUV operation and dynamics. This work describes the implementation of a UUV\'s control algorithm using MATLAB/SIMULINK, its automatic conversion to an executable code (in C++) and the verification of its performance directly into the embedded computer using simulations. It is detailed the necessary procedure to allow the conversion of the models from MATLAB to C++ code, integration of the control software with the real time operating system used on the embedded computer (VxWORKS) and the developed strategy of Hardware in the loop Simulation (HILS). The Main contribution of this work is to present a rational framework to support the final implementation of the control software on the embedded computer, starting from the model developed on an environment friendly to the control engineers, like SIMULINK.

O problema do desenvolvimento do \"Software\" para a pilotagem automática de embarcações é tratado através da aplicação de conceitos de controle estocástico. O movimento da embarcação é descrito de forma aproximada através do modelo clássico das derivadas hidrodinâmicas. A partir do Princípio da Separação desenvolve-se um procedimento sequencial em que os problemas de estimação do estado e de controle são tratados concomitantemente com as identificação de efeitos não modelados da dinâmica adotada para o piloto automático. A estimação de estados realiza-se através do filtro estendido de Kalman, que opera sobre informações de posição e velocidade da embarcação. O controlador, de natureza sequencial, atua sobre a embarcação em tempo discreto, sendo o leme o único elemento de controle. O piloto automático proposto foi testado através de simulação digital e alguns resultados obtidos são apresentados e discutidos. / The software development problem for the ship automatic steering is considered through the application of stochastic control concepts. Ship motion is described in an approximate way by the classical hydrodynamic derivatives model. A sequential procedure based on the Separation Principle is developed, being state estimation and control problems handled simultaneously with the identification of unmodeled effects of automatic pilot ship dynamics. State estimates are provided by the extended Kalman filter by using ship position and velocity measurements. The rudder is the only control element for the sequential, discrete-time controller. Digital simulation is employed for testing of the proposed automatic pilot, and some results are presented and discussed.

Orientador: Edevar Luvizotto Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-07T09:53:33Z (GMT). No. of bitstreams: 1 ArandaSaldana_EdwinAntonio_M.pdf: 1687985 bytes, checksum: 0c5e968a32c41fdf3cc83eca866e6ea6 (MD5) Previous issue date: 2006 / Resumo: O presente trabalho apresenta as bases para a elaboração de um modelo hidráulico computacional baseado na filosofia de programação orientada por objetos (POO) para o tratamento de problemas de escoamento de fluidos em condutos forçados em regime permanente e transitório. Na modelação hidráulica foi empregado um modelo dinâmico inercial elástico com solução através do Método das Características (MOC). Os estudos de casos apresentados mostram o potencial da ferramenta proposta para a análise de escoamentos de instalações hidráulicas em condutos forçados / Abstract: The present work shows the basis for the elaboration of a computational hydraulic model based on the object oriented programming (POO) philosophy for the management of flow problems such as flow rate in pipe systems in steady and unsteady states. The hydraulic modeling is based on the inertial dynamic model with solved through the Method of Characteristics (MOC). The different cases of studies presented in this dissertation show the potential of this tool proposal for the analysis of pipe flow installations in hydraulic systems / Mestrado / Recursos Hidricos / Mestre em Engenharia Civil

A disponibilidade da água fornecida para a agricultura reduz-se por efeitos das mudanças dos ciclos hidrológicos e pelo crescimento populacional, portanto, põem-se em risco a sustentabilidade dos sistemas de irrigação comunitários. Em vista de isso, os usuários da irrigação estabelecem estratégias que permitam sobrelevar as novas realidades. Sem embargo, as políticas e a análise da gestão e manejo da irrigação são feitas a partir da hidrologia, a hidráulica, sociologia e economia de forma separada, em esse sentido, o propósito de este trabalho foi estudar as inter-relações sociais, ambientais, econômicas e culturais que ocorrem nos sistemas de irrigação comunitários e como o enfoque da gestão comunitária da água estabelecida na constituição e legislação do Equador no marco do Bom Viver, ajuda a sua sustentabilidade e a melhorar o uso da água na agricultura. O estudo foi realizado em 13 sistemas de irrigação comunitários da bacia do rio Pisque, localizada na serra norte do Equador. Foi usada a metodologia de dinâmica de sistemas a qual permite, avaliar sistemas complexos de forma qualitativa e quantitativa. A participação da organização comunitária foi importante e foram usadas ferramentas como: observações em campo, entrevistas, etnografia, grupos de diálogo e avaliações de vazões e volume da água utilizada na produção agrícola. Neste trabalho se encontrou que a irrigação comunitária é concebida como um sistema integral, composto pela natureza, comunidade e infraestrutura, na qual os usuários da irrigação conformam organizações com resiliência, sendo a tecnificacão da irrigação uma estratégia para reduzir as perdas da água e incrementar a produtividade agrícola. Os indicadores, eficiência técnica e produtividade económica da água foram avaliados, em três sistemas de produção, leite, produção de flores em ambientes protegidos e na agricultura diversificada familiar, sendo a produção de flores a mais eficiente. A tecnificacão dos sistemas de irrigação melhora a agricultura, mas também provoca mudanças nos comportamentos socioculturais, no meio ambiente e nas relações socioeconômicas no território comunitário. Portanto o modelo para a gestão e manejo sustentável dos sistemas da irrigação comunitários considera estas realidades locais e conforma-se por três subsistemas, natureza, uso do solo e a comunidade, onde em cada um destes interatuam variáveis exógenas e endógenas que intervêm na sustentabilidade dos sistemas de irrigação. Incorporar variáveis sociais inerentes à comunidade na estrutura do modelo permitiu identificar e compreender o comportamento das causalidades nas variáveis da natureza e da produtividade do uso da água e do solo, de maneira que as soluções aos problemas, sejam abordadas de forma integral tendo em conta os princípios da sustentabilidade e do Bom Viver, sendo os fundamentos do enfoque da gestão comunitária da água. / The availability of water supplied to agriculture is reduced by the effects of the changes in the hydrological cycle and population growth. This fact puts at risk the sustainability of the community irrigation systems. Therefore, irrigation users stablish strategies that allow overcome new realities. However, the policies, management and operation of irrigation are done considering the hydrology, hydraulics, sociology, and economics separately. In this sense, the purpose of this work was to study the social, environmental, economic, and cultural interrelationships that occur in the community irrigation systems. In addition, this research analyses the community\'s water management approach established in Ecuador`s Constitution of 2008 focusing in the Good Living framework, which conceptually tries to reach sustainability and improve the use of water in agriculture. The study was conducted in 13 community irrigation systems at the Pisque river basin, located in the highlands in Ecuador. The methodology consisted in the systems dynamics which allows to evaluate complex systems in a qualitative and quantitative way. The participation of the community was a key element and different tools were applied such as field observations, interviews, ethnography, focus groups, and assessments of water flow and volume used in agricultural production. This study shows that community irrigation is conceived as an integrated system composed by nature, the community, and infrastructure. Within this system, the irrigation users form resilient organizations and the modernization of irrigation is a strategy to reduce water losses and increase agricultural productivity. The indicators technical efficiency and economic productivity of water were evaluated in three production systems: milk, flower production in protected environments, and family\'s diversified agriculture. The results demonstrate that flower production is the most efficient. The technification of the irrigation systems improves agriculture but also causes changes in the socio-cultural behavior, the environment, and the socio-economic relationships within the community. Thus, the model for the operation and a sustainable management of the community irrigation systems considers these local realities, and it is formed by three subsystems: nature, land use and community. Each subsystem has exogenous and endogenous variables that intervene in the sustainability of the irrigation systems. Social variables inherent to community were incorporated in the model structure which allowed identifying and understanding the behavior of the causalities in nature and water and land productivity. Therefore, solutions to problems are addressed in an integral way considering the principles of sustainability and Good Living, as fundamentals of the community\'s water management approach.

De grandes variations physiologiques s’opèrent tout au long du développement de l’enfant et touchent toutes les étapes du devenir du médicament dans l’organisme. Ces changements physiologiques vont être à l’origine de l’importante variabilité interindividuelle des paramètres pharmacocinétiques chez l’enfant. Il est donc essentiel de connaître la pharmacocinétique des différentes molécules administrées ainsi que la variation des paramètres associés. Dans ce but, la pharmacocinétique de population semble être la méthode de choix. L’approche de population contrairement aux études pharmacocinétiques classiques peut se réaliser à partir de très peu de prélèvements sanguins par patient obtenus à des délais variables, ce qui représente un grand intérêt du point de vue éthique. La pharmacologie des antirétroviraux reste très peu connue chez l’enfant et très peu d’information est disponible sur l’efficacité des doses pédiatriques actuellement recommandées. Nous avons modélisé la pharmacocinétique de population de la lamivudine chez l’enfant et montré que les enfants les pluslégers donc les plus jeunes étaient potentiellement sous-exposés avec la dose recommandée et nous avons proposé une posologie plus adaptée. Nous avons également pu, pour la première fois, proposer des doses chez le nouveau-né car jusqu’alors les doses n’étaient basées que sur des hypothèses de maturation physiologique par rapport à l’adulte. Des doses pédiatriques pour le ténofovir ont pu être déterminées pour la première fois à partir de la modélisation de sa pharmacocinétique. La dernière étape de ma thèse a été consacrée à l’utilisation de l’approche de population dans un cadre pharmacocinétique et pharmacodynamique : un modèle reliant les concentrations de la lamivudine, de la didanosine et de l’efavirenz à l’efficacité virologique de cette trithérapie chez l’enfant nous a permis d’élaborer un score prédictif de l’échec de la thérapie très puissant et prometteur quant à son utilité dans la prise en charge thérapeutique des enfants infectés par le VIH. / Large physiological variations are observed throughout the development of children, these variations are involved in all steps of the fate of the drug. These physiological changes induce a high interindividual variability of pharmacokinetic parameters in children. Thus, it is important to study the pharmacokinetics of various compounds administered in children as well as the variation of associated parameters. For this purpose, population pharmacokinetics seems to be well adapted. The population approach unlike conventional pharmacokinetic studies can be performed with very few blood samples per patient obtained at different times, which presents a great interest in terms of ethics in children. The pharmacology of many antiretroviral drugs remains unknown in children and very few information is available on the effectiveness of currently recommended pediatric doses. A population pharmacokinetic model of lamivudine in children has been performed and we found that the youngest children were potentially underexposed with the recommended dose and an appropriate dosage has been proposed. For the first time, doses for newborns have been proposed as well; indeed the current lamivudine doses are based on physiological maturity assumptions derived from adults. Pediatric doses for tenofovir were proposed also for the first time thanks’ to population modeling. In the last part of this thesis we use the population approach to perform a pharmacokinetic and pharmacodynamic model linking the concentrations of lamivudine, didanosine and efavirenz to virologic efficacy in children. A composite score has been derived from the model and provided a high predictive performance to treatment failure. This score seems to be very useful in the therapeutic management of HIV-1 infected children.

Cette thèse s’inscrit dans le cadre du projet SCRIB (“dispositif Solaire de Climatisation Réversible Intégré au Bâti”) porté par la société Helioclim. Ce projet est financé par l’état français dans le cadre des « Investissements d’avenir » pilotés par l’ADEME (Agence de l’Environnement et de la Maîtrise de l’Energie). Le but de ce projet est de développer une solution de climatisation solaire réversible capable de répondre à l’ensemble des besoins thermiques des bâtiments industriels et tertiaires (climatisation, chauffage, production de froid industriel, eau chaude sanitaire). Le système est constitué d’une machine à absorption réversible, alimentée par un système de capteurs solaires innovants. Le cycle de la machine à absorption est en configuration GAX (Generator-Absorber heat eXchange – échange de chaleur entre le générateur et l’absorbeur).Ce travail de thèse s’est intéressé au développement d’un outil logiciel aidant à la conception et au contrôle d’une telle machine. Un modèle de connaissance prenant en compte les paramètres de fonctionnement et de dimensionnement a été ainsi mis en œuvre. L’originalité de ce travail repose sur les points suivants :- L’outil logiciel propose plusieurs modules qui permettent de simuler différentes configurations de machine à absorption (mono ou multi-étagée).- Les propriétés thermodynamiques des mélanges ont été modélisées à l’aide de modèles basés sur l’utilisation d’une équation d’état ou d’un modèle d’enthalpie libre d’excès. Ainsi, le couple fluide pourra être facilement changé.- Un modèle de « Flash Positif » permet de prédire l’état de chaque courant (liquide sous-refroidi, liquide-vapeur ou vapeur surchauffée) sans poser d’hypothèses a priori. Chaque courant est considéré multiconstituant.- Les bilans matière et d’énergie sont écrits pour les différents appareils (évaporateur, absorbeur, détenteur,…).- Le générateur est modélisé par un empilement d’étages théoriques. Les équations MESH (Mass balance, Equilibrium, Summation, Heat balance) ont été écrites pour chaque étage.- Les inerties thermiques et de matière sont prises en compte.Les résultats de simulation obtenus à l’aide de cet outil logiciel ont été comparés avec succès à une étude publiée qui concernait un cycle GAX fonctionnant avec le couple ammoniac/eau. A l’aide de cet outil, le régime permanent et le comportement dynamique du système soumis à une perturbation peuvent être simulés, ce qui peut constituer une aide importante dans le développement de la politique de contrôle du système. / This PhD thesis was carried on in the framework of the SCRIB project (“dispositif Solaire de Climatisation Réversible Intégré au Bâti”) led by the Helioclim company. This project is funded by the French government (“Investissements d’Avenir” operated by the French Agency for Energy and Environment, ADEME). The goal of this project is to develop a reversible solar cooling system which can respond to a set of thermal requirements in industrial and tertiary building sector (cooling system, heating system, industrial cooling system and domestic hot water). Thus an ammonia/water absorption chiller prototype, powered by innovative thermal solar concentrators, has been built. This absorption chiller has a GAX (Generator-Absorber heat eXchange) configuration.This PhD work focused on the development of a support tool for the conception and the control of such device. A software tool has been developed implementing knowledge-based model, which took into account the operating and design parameters of the absorption chiller. The key originalities of the proposed work are as follows:- The software has been designed in a modular way allowing the simulation of various absorption chiller configurations (single or multi-stage).- The thermodynamic properties of the mixture have been modeled by equation of state or excess Gibb’s energy model. The working fluids can then be changed easily.- A “Positive Flash” model allows the description of all the possible states (sub-cooled, super-heated, biphasic…) of the various streams which are all considered as multicomponent mixtures, without a priori assumptions.- The various devices (evaporator, absorber, valves, etc.) are modeled from balance equations (mass, energy). - The generator is modeled using the concept of theoretical plates. MESH equations (Mass balance, Equilibrium, Summation, Heat balance) have been written for each stage.- Both thermal and material inertia are considered.Simulation results obtained with this software have been successfully compared to an earlier published experimental study for a GAX configuration absorption chiller which used ammonia/water as working fluids. Thanks to this tool, the steady state and the transient behavior of the system submitted to a perturbation can be simulated, which can be helpful for the development of the control policy of the absorption chiller.

La compréhension de la coexistence des espèces végétales et leur l’assemblage dans les communautés naturelles reste un des objectifs fondamentaux de l’écologie, et c’est un enjeu majeur dans le contexte actuel des changements globaux. Ce travail de thèse a consisté à apporter des éléments de compréhension quant aux effets des facteurs abiotiques et biotiques pour l’assemblage des communautés d’arbres en milieu tempéré. Ces questions nécessitent d’être considérées sur le long terme, ce qui est particulièrement difficile en milieu forestier du fait de leurs dynamiques lentes. C’est pourquoi nous avons utilisé ici une approche originale basée sur un modèle mécaniste de dynamique forestière. Dans la filiation des études empiriques basées sur les traits fonctionnels en écologie des communautés, nous avons cherché à identifier les signatures fonctionnelles du filtre environnemental et de la compétition dans l’assemblage des communautés forestières, et ce le long d’un gradient de productivité en Europe centrale. Nos résultats montrent que le filtre environnemental est un déterminant majeur de la structure des communautés en restreignant la gamme de variation des traits, avec des effets plus marqués dans les milieux très contraignants et peu productifs. Par ailleurs, nos résultats montrent que la compétition pour la lumière mène à une convergence de la structure fonctionnelle des communautés, convergence d’autant plus forte que les milieux sont productifs. Dans le but d’approfondir la compréhension des mécanismes d’assemblages et de coexistence, nous avons montré qu’une augmentation de la variabilité climatique interannuelle n’aboutit pas systématiquement à une perte de diversité, et pourrait même favoriser la coexistence en modifiant le pouvoir compétitif relatif des espèces au cours du temps. Enfin, nous avons montré que les différences de valeurs de traits des espèces d’arbres pouvaient favoriser leur coexistence via des réponses différentielles des espèces à la variabilité climatique interannuelle et aux conditions de lumière. L’ensemble de ces résultats apporte de nouveaux éléments quant à la compréhension de la structuration des communautés forestières, et propose une vision intégrative des processus complexes d’assemblage et de coexistence au sein des communautés. / Understanding the coexistence of plant species and their assembly within natural communities remains one of the fundamental goals of ecology, and this major challenge appears even more crucial in the current context of global change. The aim of this work was to better understand how the abiotic and biotic factors determined tree communities’ assembly in temperate forests. These questions can only be considered on the long term, which is especially difficult for forest ecosystems because of their slow dynamics. Therefore we used an original approach based on a forest dynamic model. Following trait-based empirical studies in community ecology, we tried to identify the functional signatures of environmental filtering and competition in forest communities along a productivity gradient in Central Europe. Our results showed that environmental filtering is a major determinant of community structure as it reduced the trait range all along the gradient, with stronger effects in harsh sites with low productivity. Further looking for identifying underlying causal processes, we showed that competition for light led to a convergence of functional community structure, and that this convergence increased with site productivity. Furthermore, our results suggested that inter-annual climatic variability does not systematically result in biodiversity loss, and could even promote species coexistence through changes in the hierarchy of competitors over time. Finally, we showed that differences in trait values of tree species could promote coexistence through differential species responses to inter-annual climatic variability and to light conditions. These findings bring new insights regarding the understanding of tree communities’ structure, and they provide an integrative understanding of the complex processes driving community assembly and species coexistence in natural forests.

Com o avanço tecnológico e econômico, que facilitaram o processo de comunicação e aumento do poder de compra, transações com cartão de crédito tornaram-se o principal meio de pagamento no varejo nacional e internacional (Bolton e Hand , 2002). Neste aspecto, o aumento do número de transações com cartão de crédito é crucial para a geração de mais oportunidades para fraudadores produzirem novas formas de fraudes, o que resulta em grandes perdas para o sistema financeiro (Chan et al. , 1999). Os índices de fraudes têm mostrado que transações no comércio eletrônico (e-commerce) são mais arriscadas do que transações presencias em terminais, pois aquelas não fazem uso de processos seguros e eficientes de autenticação do portador do cartão, como utilização de senha eletrônica. Como os fraudadores se adaptam rapidamente às medidas de prevenção, os modelos estatísticos para detecção de fraudes precisam ser adaptáveis e flexíveis para evoluir ao longo do tempo de maneira dinâmica. Raftery et al. (2010) desenvolveram um método chamado Dynamic Model Averaging (DMA), ou Ponderação Dinâmica de Modelos, que implementa um processo de atualização contínuo ao longo do tempo. Nesta dissertação, desenvolvemos modelos DMA no espaço de transações eletrônicas oriundas do comércio eletrônico que incorporem as tendências e características de fraudes em cada período de análise. Também desenvolvemos modelos de regressão logística clássica com o objetivo de comparar as performances no processo de detecção de fraude. Os dados utilizados para tal são provenientes de uma empresa de meios de pagamentos eletrônico. O experimento desenvolvido mostra que os modelos DMA apresentaram resultados melhores que os modelos de regressão logística clássica quando analisamos a medida F e a área sob a curva ROC (AUC). A medida F para o modelo DMA ficou em 58% ao passo que o modelo de regressão logística clássica ficou em 29%. Já para a AUC, o modelo DMA alcançou 93% e o modelo de regressão logística clássica 84%. Considerando os resultados encontrados para os modelos DMA, podemos concluir que sua característica de atualização ao longo do tempo se mostra um grande diferencial em dados como os de fraude, que sofrem mudanças de comportamento a todo momento. Deste modo, sua aplicação se mostra adequada no processo de detecção de transações fraudulentas no ambiente de comércio eletrônico. / Regarding technological and economic development, which made communication process easier and increased purchasing power, credit card transactions have become the primary payment method in national and international retailers (Bolton e Hand , 2002). In this scenario, as the number of transactions by credit card grows, more opportunities are created for fraudsters to produce new ways of fraud, resulting in large losses for the financial system (Chan et al. , 1999). Fraud indexes have shown which e-commerce transactions are riskier than card present transactions, since those do not use secure and efficient processes to authenticate the cardholder, such as using personal identification number (PIN). Due to fraudsters adapt quickly to fraud prevention measures, statistical models for fraud detection need to be adaptable and flexible to change over time in a dynamic way. Raftery et al. (2010) developed a method called Dynamic Model Averaging (DMA), which implements a process of continuous updating over time. In this thesis, we develop DMA models within electronic transactions coming from ecommerce environment, which incorporate the trends and characteristics of fraud in each period of analysis. We have also developed classic logistic regression models in order to compare their performances in the fraud detection processes. The database used for the experiment was provided by a electronic payment service company. The experiment shows that DMA models present better results than classic logistic regression models in respect to the analysis of the area under the ROC curve (AUC) and F measure. The F measure for the DMA was 58% while the classic logistic regression model was 29%. For the AUC, the DMA model reached 93% and the classical model reached 84%. Considering the results for DMA models, we can conclude that its update over time characteristic makes a large difference when it comes to the analysis of fraud data, which undergo behavioral changes continuously. Thus, its application has proved to be appropriate for the detection process of fraudulent transactions in the e-commerce environment.

The categories of 'ethnicity' or 'Roma' could obscure the whole topic, as they may suggest an idea that the socially excluded are somehow special or unrecognizable. It is therefore very important to use these categories clearly and specifically. That is what I am trying to do in this thesis. The theoretical part is divided into three main parts: the dynamic model of practice, culturally sensitive social work and the chapter entitled Roma. In the first part, the dynamic model, I try to have a look at the practical implementation of social work as described by Karen Healy (from page 10 onwards). I also explore the areas that influence the interactions between the social worker and their client. The dynamic model is focused on professional goals, which are made up of four areas: the institutional context, the needs and expectations of the service users and the community, the professional foundation, and an emerging framework for practice that develops through critical reflection on professional experience. These four elements further interact within the framework of the professional goal. I have also included a subsection where I attempt to define social work and its relationship to social services (p. 19). In the next chapter, I describe the culturally sensitive social work (from p. 25) on which the...