La présente thèse s’intéresse à la conception et la caractérisation des procédés microstructurés mettant en œuvre des réseaux de microcanaux de différentes dimensions. L’analyse de tels réseaux multi-échelles, représentatifs d’une parallélisastion de microsystèmes élémentaires, a essentiellement servi à identifier les principaux paramètres géométriques et physiques contrôlant les performances de ces réseaux complexes. On a cherché à quantifier l’influence des paramètres géométriques comme le rapport de résistances hydrodynamiques internes, le nombre de canaux et d’échelles opérant ainsi que leur répartition sur le réseau, sur des critères hydrodynamiques comme la maldistribution du fluide et la perte de charge résistive. Il est révélé qu’en fonction des contraintes imposées, un arrangement optimal des canaux sur un nombre pair d’échelles permet de réduire considérablement la maldistribution interne des flux et les pertes de charge résultantes. L’analyse thermique associée à l’analyse hydrodynamique a montré que les performances thermiques des réseaux sont fortement liées à leurs structurations géométriques internes. En présence de réactions catalytiques consécutives, ces mêmes réseaux enregistrent des déviations du rendement du produit désiré. Ces déviations peuvent être levées par une structuration appropriée du réseau catalytique multi-canal. La même architecture de ces réseaux peut être adaptée pour permettre le déroulement des opérations de mélange et/ou des réactions multi-phasiques. Ainsi, pour ces réseaux complexes, où un nombre élevé de variables imbriquées est considéré, des lignes directrices sont ressorties pour aider à leur conception et dimensionnement / This PhD thesis focuses on the design and the characterization of microstructured processes including microchannel networks of various dimensions. The analysis of such multi-scale networks, representative of elementary microsystems parallelization, is mainly used to identify the main geometrical and physical parameters controlling the network performances. Influence of geometrical parameters, such as the internal hydrodynamic resistances ratio, the number of channels and scales and their arrangement in the network, on hydrodynamic criteria like fluid maldistribution and pressure drop is investigated. It is shown that according to some specific constraints, an optimal arrangement of the channels on an even number of scales, allows to reduce significantly the internal flow maldistribution and the consequential pressure losses. The thermal analysis coupled with the hydrodynamic analysis illustrates that the thermal performances of microchannel networks are strongly affected by their internal geometrical arrangement. Nevertheless, the various mixture points located in the network compensate the fluid maldistribution resulting from a non appropriate geometrical arrangement. When consecutive catalytic reactions are performed inside these networks, deviations of the desired product rate can be recorded. These deviations can be reduced by an optimal catalytic network arrangement. The same architecture of these networks is also adapted to allow multi-phase mixing and /or reactions. Thus, using these complex networks, where several variables are considered, guidelines are derived in order to improve their design and their dimensionless

<div>The evaporation of a liquid drop containing particles resting on a substrate have diverse industrial applications including inkjet printing, spray coating, fabrication of functional nanomaterials, disease diagnosis, among others. In addition to these wide ranging practical applications, the sessile drop evaporation can be observed in everyday life with dew drops, coffee spills, and the dry patterns of other beverages.</div><div><br></div><div>The self-assembly of particles during drop evaporation is a process that is affected by various factors, such as contact line (CL) behaviors, microfluidic flows, short-range interactions of particle-interface and particle-particle. Each of these factors are complicated enough to study, let alone the total effects on the process. The primary goal of this work is to investigate the influence of microfluidic flows and the particle-interface interaction, viz. the evaporation process was subject to a pinned CL and the particle-particle interaction was neglected under dilute particle concentration. </div><div>To accomplish this goal, the Galerkin/Finite Element Method (G/FEM) is used to solve for the flow, the temperature and the particle concentration profiles. </div><div><br></div><div><br></div><div>The complexity of the problems comes from various surface phenomena, one of which is the surface tension. The surface tension brings capillary force in the normal direction and capillary flow toward the CL, which results in the well-known coffee-ring effect. Moreover, the surface tension changes with temperature, surfactant concentration, etc. resulting in Marangoni stresses in the tangential direction. The Marangoni stress on the surface leads to circulations of flow inside the drop and the circulation can be either clockwise or counterclockwise depending on the direction of the stress. </div><div><br></div><div>When the Marangoni stress is merely caused by temperature change, the circulation direction changes not only in time but also in space. At late stage of evaporation, i.e. with a small contact angle (CA), multi-circulation flow profiles emerge. This flow profiles are featured with stagnation points and transition points. The stagnation points can be further categorized into capillary-induced stagnation points and Marangoni-induced stagnation points. By introducing the concept of capillary-induced stagnation points, the simulations reached agreement with experiments in terms of the radial location of the observed stagnation points.</div><div><br></div><div><br></div><div>The multi-circulation flow profiles implied regional segregation inside the drop. When a large circulation is observed in most part of the drop and a small circulation exists near the CL, particle concentrations are relatively uniform in each individual region but differs significantly across the two regions. Transition points are used to characterize the location of the regional segregation, which can be adjusted by Marangoni stress.</div><div><br></div><div><br></div><div>Marangoni circulations in different directions revealed distinct influences on particle distribution and deposition. First, while both directions facilitate even distribution of particles, a clockwise circulation strengthens CL accumulation for a small Marangoni stress. Second, a counterclockwise circulation with a small Marangoni stress impedes the deposition rate of particles, while a clockwise circulation facilities the deposition no matter how small the Marangoni stress is. This results is under a condition of a strong adsorption between particles and substrates. </div><div><br></div><div>The analysis and understanding of the above results are crucial to elucidating and controlling the final deposition patterns of particles. Thus, the focus of this research is to understand the combined effect of Marangoni stress and capillary flow on particle deposition during sessile drop evaporation.</div><div><br></div>

[pt] Estudos recentes mostram que a injeção de emulsões óleo-água pode levar a uma melhor varredura do reservatório e reduzir consideravelmente a saturação residual de óleo em processos de recuperação avançada. Estes efeitos estão diretamente ligados ao comportamento do escoamento de gotas de óleos suspensas em água através das gargantas de poros. Desta forma, a otimização do processo de injeção e da formulação da emulsão com o objetivo de aumentar o volume de óleo recuperado requer por um melhor entendimento do escoamento na escala de poros. Este trabalho apresenta um estudo do escoamento de gotas de óleos suspensa em água através de micro canais de seção reta constante e através de uma garganta, que são usados como modelos do espaço poroso. O campo de velocidade da fase contínua e a velocidade da gota de óleo foi determinado através da técnica de velocimetria por imagem de partículas em escala micrométrica (Micro-PIV) para diferentes tamanhos de gotas e geometria do capilar e garganta. Os resultados obtidos mostram a variação do padrão do escoamento devido a presença da gotas de óleo e fornecem importantes informações de como gotas de óleo mudam a mobilidade do fluido injetado quando o mesmo escoa através de poros com gargantas menores do que tamanho das gotas. / [en] Recent studies show that oil-water emulsion injection may lead to a better reservoir sweep and reduce residual oil saturation in enhanced oil recovery processes. These effects are directly linked to the flow behavior of oil drops suspended in water through the pore throats of a porous material. Therefore, the optimization of the injection process and of the emulsion properties with the goal to increase the volume of oil displaced requires a better understanding of the emulsion flow in the pore scale. This work presents an analysis of the flow of oil drops suspended in water through micro channels with constant cross-section area and with a throat, that are used as a model for the pore scale. The velocity field of the continuous phase and the drop velocity are obtained using the micro particle image velocimetry techniques (Micro-PIV) for different drop sizes and micro channel geometries. The results show the changes in the flow pattern due to the presence of oil drops and yield important information on how oil drops reduce the mobility of the injected liquid when it flows through pore throats smaller than the drop size.

[pt] Na indústria do petróleo, durante a produção de um campo, é muito utilizada a injeção da água do mar para manutenção da pressão do reservatório. Com a injeção, há o aumento da fração de água no fluido produzido formando assim uma emulsão com uma determinada distribuição do tamanho de gotas. No sistema de produção, esta mistura sofre variações de pressão e temperatura que impactam na distribuição do tamanho de gotas da emulsão. As mudanças mais significativas nestes parâmetros ocorrem nos chokes instalados na chegada à planta de processo. O conhecimento desta distribuição é importante, pois influencia diretamente no dimensionamento dos separadores que serão instalados na plataforma, no caso offshore. O parâmetro considerado como o que melhor descrevia o processo de quebra de gotas era a potência dissipada no orifício. Nos experimentos desenvolvidos para avaliar a quebra de gotas nos chokes, foi observado que este termo possuía algumas limitações e um novo ajuste foi proposto para atender aos valores medidos. Nos testes foram utilizados dois tipos de óleos e diferentes orifícios que geraram os dados necessários para elaborar uma nova abordagem, onde a queda de pressão medida apresentou a melhor relação com os diâmetros das gotas após o orifício. Posteriormente, o efeito da viscosidade foi adicionado para que houvesse uma relação válida para ambos os óleos utilizados, tornando assim o modelo de quebra mais abrangente. / [en] In the oil industry, during an oilfield development, the sea water injection is largely used to maintain the reservoir pressure. As a result of this injection, there is the increase of the water fraction in the produced fluid, forming an emulsion with a determined droplet size distribution. In the production system, this mixture flows under different conditions of pressure and temperature that impact the emulsion droplet size distribution. The most meaningful changes of these conditions occur in the chokes that are installed at the process plant arrival. The knowledge of the droplet size distribution is important, because it impacts the sizing of the separators that will be installed at the platform, in an offshore scenario. The parameter that was considered as the most appropriate to describe the droplet break-up process was the energy dissipation rate. During the experiments performed to evaluate the droplet break-up in the chokes, it was observed that this parameter had some limitations and a new adjustment was proposed to fit with the measured values. In the tests, two oils with different viscosities were used while varying orifices characteristics to obtain the needed data to elaborate a new approach. Thus, it was found that the measured pressure drop through the restriction presented the best relation with the droplets diameters measured downstream the orifice. After this, the effect of the oil viscosity was also added to the model so to create a correlation valid for both tested oils. In this way, the break-up model proposed would be more complete and useful for different conditions.

The purpose of this mixed methodological study was to discover the possible causes of persistence for African-American high school girls attending a 4-year program in Mississippi. Currently there is a precise focus on African-American high school girls and the detrimental outcomes that follow as a consequence of behavioral referrals within schools. Unfortunately, the narrative of African-American high schools girls centers on discipline as a leading concern in their academic performances. This study sought to determine whether student perception of completing a 4-year high school program plays a significant role for African-American girls. Support systems of teachers towards high school African-American girls were assessed in consideration for the educational professionals and their influence to the academic advancement of students. Lastly, the social influences of social media were investigated as a contemporary factor for African- American girls considering completing a 4-year program. The consideration of organizational structures that are not conducive to the advancement of high school graduation is the primary discussion for educational leaders to evaluate.

Adaptive designs can improve the efficiency of drug development, but further research is needed before some are more widely implemented. One such design is a treatment-selection design, which begins with k treatment arms, but only a subset is carried forward after an interim analysis. The final analysis of the selected arm(s) is then performed using the data from both stages of the study. One issue with this design is ensuring the Type I error rate is controlled, but there have been a number of proposals that largely address this. A second drawback that has not yet been fully addressed is that the maximum likelihood estimate of the selected arm at the final analysis is often biased upward due to the selection method. Unbiased estimators already exist for this design, but methods with an acceptable balance between bias and mean squared error (MSE) are lacking. In this dissertation, two estimation approaches are proposed. The first is a parametric bootstrap resampling method in which the level of bias adjustment applied is driven by a comparison of the observed results to those expected when all arms have equal true means. The second approach is an empirical Bayes estimator that implements a novel limited translation function. These methods are compared to previously proposed approaches with respect to bias and MSE for studies that have either a normal or binomial endpoint. Both proposed methods are shown to exhibit reduced bias with reasonable MSE in some simulated scenarios, but the resampling method consistently shows similar, or improved, performance compared to previous approaches across the examined scenarios. The utility of this resampling method is further demonstrated by showing that it can be implemented when the arm with the second largest mean is selected for stage 2. It is also shown that the resampling method can be extended to when more than one arm is selected in stage 1, when there is a futility analysis, or when the study has a time-to-event endpoint. Recommendations on confidence intervals are also provided. The results demonstrate that the parametric bootstrap resampling method is a viable estimation approach for treatment-selection designs.

Le couplage entre processus physico-chimiques et le transfert de matière ou de chaleur peuvent donner lieu à des structures spatio-temporelles induites par des flux convectifs. Ces flux peuvent résulter de gradients de densité ou de tension superficielle et sont l'expression de la conversion d'énergie chimique en énergie mécanique. Quand la tension superficielle est à l'origine de ces mouvements, les effets correspondants sont connus sous le nom d'effet Marangoni. Ils jouent un rôle dans de nombreuses applications comme les procédés industriels d'extraction en amplifiant notablement la vitesse des processus de transfert. Les systèmes réels, trop complexes, doit être simplifiés par le développement de systèmes modèles afin d'établir au niveau fondamental la théorie sous-jacente à de telles dynamiques. Une succession de régimes dynamiques est observée lors de la dissolution d'une goutte de dichlorométhane (DCM) déposée sur une solution aqueuse de tensioactif (bromure de céthytriméthylammonium, CTAB). La succession remarquable de formes et de mouvements induits est déterminée par la concentration du tensioactif qui joue le rôle de paramètre de contrôle. A faible concentration en CTAB, un mouvement de translation ou des pulsations. Aux concentrations plus élevées, la goutte entre en rotation ou forme des structures polygonales. Bien que chimiquement simple, le système est complexe et implique plusieurs processus physico-chimiques : évaporation, solubilisation, transfert de tensioactifs, adsorption aux interfaces et agrégation. Les effets thermiques et de transport qui en résultent sont à l'origine des variations locales de tension interfaciale donnant lieu aux effets Marangoni. Nous nous sommes concentrés sur le comportement de la goutte quand la concentration en tensioactif conduit au régime de pulsation. Nous avons tout d'abord analysé le comportement de la goutte pendant la période d'induction qui précède le régime instable. L'analyse de la forme de la goutte corrélée à des mesures d'Imagerie par Vélocimétrie de Particules (PIV), ont montré que les flux créés par la dissolution du DCM limitent dans un premier temps l'adsorption du CTAB à l'interface eau/huile. L'instabilité ne démarre que lorsque la dissolution est réduite et que l'adsorption devient effective. La phase d'induction apparait comme une transition lente entre un coefficient d'étalement négatif (goutte ayant la forme d'une lentille) vers un coefficient d'étalement positif qui entraine l'expansion du film et les pulsations suivantes. Ces pulsations sont accompagnées par l'éjection de gouttelettes qui se forment à partir d'un bourrelet apparaissant au bord du film pendant la phase d'expansion. La rupture de ce bourrelet ressemble au phénomène connu sous le nom d'instabilité de Rayleigh-Plateau (RP). Cependant, la longueur d'onde caractéristique de formation des gouttelettes est deux fois plus faible que celle attendue dans le cas d'une instabilité de RP classique. L'origine de cet écart réside dans la modulation du bourrelet avant sa rupture. Cette modulation est en fait déterminée par des ondulations apparaissant à la surface du film et formant des rides en direction radiale. Ces rides pourraient être attribuées à un effet Marangoni thermique connu sous le nom d'instabilité de Bénard-Marangoni. Elles jouent également un rôle important dans la formation de la structure de démouillage hautement organisée décrite dans le dernier chapitre. L'ajout de CTAB dans la phase organique (goutte) donne lieu à des oscillations plus rapides qui, après une phase d'expansion de grande amplitude et l'éjection d'une couronne parfaite de gouttelettes, résultent lors de la phase de démouillage en une structure dont la forme rappelle une fleur. Une interprétation qualitative permettant d'identifier les principaux processus à l'œuvre et basée sur des mesures indépendantes de tension interfaciale apporte une explication des pulsations observées et de l'auto-organisation induite. / Far-from-equilibrium systems exhibit a wide variety of spatial and temporal patterns known as dissipative structures. The interplay between physico-chemical processes and mass or heat transfer can give rise to spatio-temporal structures induced by convective flows. These flows may result from density or surface tension gradients. They are the expression of the conversion from chemical into mechanical energy. When surface tension is the driving force, the corresponding effects are known as Marangoni effects. They are at play in numerous applications as extraction processes, oil recovery, and chemical reactors at all scales and noticeably modify transfer rates. The complexity of real systems deserves the development of model systems, essentials to settle, on a fundamental level, the theory governing the related dynamics. A succession of dynamical regimes is observed during the dissolution of a dichloromethane drop deposited on aqueous solutions of a cationic surfactant (cetyltrimethylammonium bromide, CTAB). The remarkable range of shapes and motion patterns that emerges is related to the surfactant concentration, which is used as a control parameter. For low surfactant concentrations, we observe translational motion and pulsations of the drop. At intermediate concentrations the drop transforms and starts to rotate. At higher concentrations polygonal shapes are observed. Although chemically simple and of easy implementation, the system is relatively complex and involves several processes: evaporation, solubilization, surfactant mass transfer, interfacial adsorption and self-aggregation. Thermal and transport effects induced are at the origin of local variations of interfacial tension leading to the Marangoni flows. In this thesis, we focused on the behavior of the dichloromethane drop when the aqueous surfactant concentration (0.5 mM) leads to the pulsating regime. At this concentration, we have first analyzed the behavior of the drop during the induction period that precedes the instable regime. Drop shape analysis, correlated to Particle Image Velocimetry (PIV) measurements, showed that dissolution flows initially hinder adsorption of CTAB at the water/oil interface. The instability is only triggered when dissolution is reduced and water/oil adsorption becomes effective. The induction period appears as a slow transition from an initial negative spreading coefficient (a lens shape drop) towards a positive spreading coefficient that triggers film expansion and following pulsations. These pulsations are accompanied by the ejection of smaller droplets which are formed from a toroidal rim that is created during the expanding phase of the drop. The break-up of this toroidal rim, resembles to what is known as the Rayleigh-Plateau (RP) instability. Nevertheless, the observed characteristic wavelength is a factor of 2 too small in respect to the classical RP instability. We have found the origin of this discrepancy in the fact that modulations that appear on the rim before it transforms into droplets are settled by deformations arising at the surface of the expanding film. They appear as wrinkles that form in the film and may be related to thermal Marangoni effects known as Benard-Marangoni instability. These wrinkles play an important part in the highly organized dewetting structure described in the last chapter of the thesis. The addition of CTAB also in the organic (drop) phase leads to faster pulsations which, after a very high amplitude expanding stage and the ejection of a perfect crown of droplets, result during the film receding stage in the formation of a pattern which symmetry is reminiscent of a flower. A qualitative interpretation aimed at identifying the main processes at play and based on independent surface tension data gives a consistent explanation of the observed pulsations and related self-organized patterns.

"Swirling multiphase flows are found in a wide range of industrial processes. Such flows are used for separation of flows containing phases of different densities and for devices such as the spinning tensiometer. These flows are challenging to predict computationally, due to the presence of a phase boundary and the large pressure gradient generated by the swirl. In the present work the applicability of the front tracking method to swirling multi-phase flows is demonstrated by studying the evolution of a bubble in spinning tensiometer. Previous studies show that the evolution of a bubble in the spinning drop tensiometer can be used to measure the interfacial tension and other rheological properties. The front tracking method is applied to the spinning tensiometer problem to study several cases and verify the convergence of the solutions. The results are validated with other computational methods, theoretical models and experimental results. The length scales obtained from the front tracking method are in agreement with the corresponding values from experiments and other computational studies. The shape of the end of the elongated bubble obtained from the simulations is found to be similar to that suggested by a theoretical expression from previous studies. The simulations predict that the relaxation of bubble radius is exponential with time, at a rate that is found to be slightly greater than that predicted by the theoretical model."

Submitted by Maicon Juliano Schmidt (maicons) on 2015-06-16T19:50:48Z No. of bitstreams: 1 Debora Skibinski Assumpção_.pdf: 703153 bytes, checksum: 05da14511a3fc89c057d8f67e2455465 (MD5) / Made available in DSpace on 2015-06-16T19:50:48Z (GMT). No. of bitstreams: 1 Debora Skibinski Assumpção_.pdf: 703153 bytes, checksum: 05da14511a3fc89c057d8f67e2455465 (MD5) Previous issue date: 2015-02-19 / Nenhuma / O presente estudo objetiva analisar como foram tratadas, no âmbito societário e fiscal, as reorganizações societárias conhecidas por drop down. Bastante comuns nos Estados Unidos, essas operações se caracterizam pelo aumento de capital que uma empresa produz em outra, ao transferir bens, direitos e/ou obrigações em troca de participação societária com controle acionário. Ademais, se assemelha à cisão em alguns aspectos, mas sem a redução do capital social ou a extinção da empresa cindida, o que induz alguns teóricos nacionais a denominarem como cisão branca. A essência do drop down - e consequentemente, a estratégia utilizada pelas empresas que optam por esse modelo de reestruturação societária - focaliza no core business, ou seja, concentra-se na atividade principal. A metodologia de pesquisa adotada para a construção desta dissertação, portanto, se estruturou em bases documentais, na qual constassem temas ligados à reestruturação ou à reorganização societária por intermédio da combinação de negócios que envolvessem as operações de drop down. Assim, o estudo pôde contribuir para a divulgação de novas formas de reorganizações societárias e sinalizar ao profissional contábil as formas de registros da operação e, posteriormente, auxiliar na divulgação das demonstrações contábeis. Os resultados obtidos revelaram que, mesmo não sendo muito conhecida no país, a operação de drop down vem ocorrendo como meio de reestruturação societária em empresas brasileiras. Também por meio da análise dos resultados, concluiu-se que, para as Companhias investigadas e/ou avaliadas pelos órgãos estaduais e do mercado de valores, a operação não foi objeto de questionamento por parte deles, haja vista que tão somente mensuraram como foram tratadas contábil e fiscalmente nas organizações selecionadas. Nas análises das empresas que não evidenciaram processos de avaliação pelos órgãos estaduais e pelo mercado de valores, identificou-se o foco no core business - a saber, a concentração de esforços nas atividades principais e a associação das empresas com as atividades afins. Igualmente, se observou se elas atentaram para as devidas contabilizações previstas nos pronunciamentos contábeis e nos registros contábeis da operação pretendida. / This study aims to analyze how corporate reorganizations known as drop down were treated in the corporate and fiscal scope. Quite common in the United States, these operations are characterized by the capital increase a company produces in another one, transferring assets, rights and/or obligations in exchange for share participation with share control. Moreover, in some aspects resembles a divestiture but without the reduction of equity capital or the termination of the divided company, which induces some national theorists call it white divestiture. The essence of drop down - and consequently the strategy used by companies that choose this corporate restructuring model - focuses on the core business, ie, focuses on the main business. The methodology adopted for the construction of this work, therefore, was built in document databases in which see covered in topics related to restructuring or reorganization through the business combination involving the drop down operations. Thus, the study could contribute to the spread of new forms of corporate restructuring and indicate to accounting professionals ways to record operations and, subsequently, assist in the disclosure of financial statements. The results revealed that, although not very known in the country, the drop-down operation has taken place as a means of corporate restructuring in Brazilian companies. Also by analyzing the results, it was concluded that, for companies investigated and/or evaluated by state agencies and the stock market, the operation was not a subject of questioning from them, given that only measured as they have been dealt accounting and fiscally in selected organizations. In the analyzes of companies which had no assessment procedures by state agencies and securities market, it was identified the focus on core business - namely, the concentration of efforts on core activities and the association of companies with similar activities. Likewise, it was observed if they attempted to the appropriate accountings provided in financial statements and accounting records of the intended operation.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2015-10-19T11:33:49Z No. of bitstreams: 1 CLEONICE SILVEIRA ROCHA_.pdf: 1131254 bytes, checksum: 5799f290f1a360368fd42b4ccf9b8388 (MD5) / Made available in DSpace on 2015-10-19T11:33:49Z (GMT). No. of bitstreams: 1 CLEONICE SILVEIRA ROCHA_.pdf: 1131254 bytes, checksum: 5799f290f1a360368fd42b4ccf9b8388 (MD5) Previous issue date: 2015-03-29 / Nenhuma / A educação superior no país está em um momento de expansão, caracterizada pelo aumento do número de instituições, de matrículas, bem como de criação de novos cursos. Para ampliar o acesso à educação superior para jovens oriundos da rede pública do ensino médio, o governo brasileiro criou o Programa Universidade para Todos (ProUni). Nos cursos de licenciatura, objeto de estudo desta tese, verifica-se o abandono dos estudantes, até mesmo para os que recebiam a bolsa através deste programa. O tema desta investigação é a evasão dos alunos prounistas nos cursos de licenciatura em uma instituição de educação superior privada. O objetivo geral consiste em identificar e analisar as causas/os motivos que levam os alunos prounistas dos cursos de licenciatura a se evadirem. A pesquisa é de cunho qualitativo utilizando, no seu caminho metodológico de coleta de dados, entrevistas e análise documental, em que os dados receberam um tratamento de análise de conteúdo. A pesquisa de campo envolveu os alunos bolsistas evadidos, coordenadores dos cursos e a gerente das licenciaturas e documentos institucionais. Tendo como período de corte os semestres 2013/1, 2013/2 e 2014/1, 2014/2, o total de participantes foram 18 sujeitos, sendo 8 alunos evadidos, 9 coordenadores de curso e um gerente. Como resultado, foi possível identificar que as causas/os motivos que levam os alunos ao abandono de seus cursos relacionam-se principalmente, com questões econômico-financeiras, dificuldades de aprendizagem, dificuldade de conciliar os estudos com o emprego e a família bem como se relacionam com a questão da valorização docente. Os alunos evadidos manifestaram interesse em retornar os seus estudos no curso de licenciatura. Fica evidenciado que a evasão nas licenciaturas relaciona-se com diferentes fatores. O estudo se torna relevante na medida em que realiza a escuta com alunos evadidos, sente suas realidades, percebe os seus sentimentos, as suas angústias, contribuindo para a pesquisa e também indicando ações de prevenção e redução da evasão. A escuta dos coordenadores dos diferentes cursos de licenciatura da Universidade também foi relevante para que a instituição pudesse discutir a temática da evasão com os seus coordenadores. Com certeza, a pesquisa oportunizará a realização de novas ações de prevenção à evasão. / Higher education has been expanding in the country characterized by an increased number of institutions, registration rates, as well as the creation of new academic courses. To provide further access to higher education, the Brazilian government created the program named University for All (ProUni), aimed at young people from state high schools. Concerning teacher training programs, which is the object of this dissertation, the dropping out level is high including those who received the ProUni scholarship. The theme of this research is the dropping out of ProUni students in teacher training courses in a private university in the South of Brazil. Our general objective is to identify and analyze the causes/reasons ProUni students from these undergraduate courses drop out. We present the context of the current scenario of higher education and the theoretical background about dropping out. We discuss public policies concepts about dropping out in the educational area. It is a qualitative research which utilizing methods such as interviews and documental analysis. Also, we used content analysis for the data collected. The participants of the field research were the students who dropped out, course coordinators, the teacher training course’s manager, and institutional documentation. The cohort period was the first and second semester of 2013 and 2014, the total of participants were 18, eight dropping out students, eight course coordinators and a manager. As a result, we found that the causes that led students to abandon their courses are related mainly to economic and financial reasons, learning difficulties, the difficulty of managing studies, work, and family and finally undervalue of education. These students who dropped out expressed interest in returning to the university and their courses. It is clear that dropping out in such courses is related different factors. The present study becomes relevant as it listens to these dropped-out students, feels their realities, realizes their feelings and anguish, contributing to researches on the field and indicating preventive and reductive options to dropping out. Listening to the coordinators of those different teacher training programs was also relevant so that the institution could discuss the topic of dropping out with them. Surely this research is going to make possible other preventive actions to dropping out.