La conception d'une colonne d'extraction liquide-liquide repose sur le mécanisme de transfert d'énergie conduisant à une fragmentation de la phase légère en gouttelettes permettant le transfert de matière avec la phase lourde. Toutefois ce mécanisme présente de façon récurrente à chaque plateau une coalescence des gouttes suivie d'une fragmentation. Le processus étudié dans ce mémoire repose sur l'emploi d'une colonne pulsée instrumentée par des techniques optiques (analyse d'images et Anémométrie Doppler Laser) afin de disposer d'outils non intrusifs pour qualifier les processus de transfert et l'hydrodynamique de la colonne. Le modèle expérimental choisi consiste à étudier le transfert de matière de l'acide acétique de la phase dispersée (acétate d'éthyle - acide acétique) à la phase continue (eau). Le système d'analyse d'image a permis de mesurer in situ la distribution des gouttes de la phase légère selon leur taille (DSD) en fonction des paramètres physicochimiques et thermodynamiques. La tension de surface de chaque liquide vis-à-vis des plateaux perforés (PTFE) a été déterminée à partir des mesures d'angle de contact. Les transferts d'énergie et de matière caractérisés par le rapport surface/volume des gouttes sont corrélés avec les paramètres d'action afin d'interpréter le phénomène restrictif tels que le Hold-up et l'efficacité de séparation. Cependant, l'étude du travail d'adhésion entre la goutte et la surface des plateaux indique que les variations des propriétés interfaciales sont fonction de la concentration du soluté et doit être prises en compte dans la corrélation du diamètre moyen de Sauter. Nous avons utilisé des codes industriels Hysys/Aspen afin d'établir le rôle déterminant de la tension de surface sur les codes de calcul et la convergence des modèles. A partir de ces modèles nous avons déterminer l'efficacité de chaque plateau et de mettre en évidence le rôle du transfert d'énergie responsable du phénomène d'engorgement. Nous avons estimé la vitesse moyenne et le temps de séjour moyen sur chaque plateau par ADL en fonction de l'énergie transmise au plateau par pulsation mécanique et à partir de ces résultats nous avons simulé sous Comsol 3.4 l'écoulement hydrodynamique de la colonne type pulsée.

L'objectif de cette thèse est de contribuer à une meilleure compréhension des Partenariats Public-Privé (PPPs). Ces accords entre une autorité publique et un opérateur privé sont considérés comme une "troisième voie" entre fourniture publique et privatisation des services publics. Cependant, les résultats que les PPPs ont produits dans le monde à ce jour sont mitigés. La littérature théorique sur ce sujet a souligné que les PPPs, comme tout contrat de long terme, se caractérisent par une forte incertitude et sont donc sujets à des adaptations ex post non contractuelles. Cette caractéristique a deux conséquences préjudiciables sur l'efficacité des PPPs: premièrement, lorsque des investissements spécifiques sont impliqués, les renégociations peuvent laisser place à d'éventuels comportements opportunistes, de l'autorité publique et de l'opérateur privé. Deuxièmement, les renégociations génèrent des inefficacités dans la mesure où les hold-ups conduisent à des décisions ex ante tordues. Dans ce contexte, les contributions de ma thèse sont les suivantes: premièrement, je montre empiriquement, en analysant le comportement à enchérir des participants aux enchères de contrats de concessions routières à péage, que incertitude et renégociations opportunistes sont bien caractéristiques des PPPs, jusque-là supposées par la littérature. Deuxièmement, je montre théoriquement et empiriquement que ces problèmes peuvent être pris en compte lors de l'arbitrage entre rigidité et flexibilité contractuelle. Troisièmement, je montre théoriquement que les contrats qui ne font pas supporter le risque de demande à l'opérateur privé, afin de remédier aux problèmes d'incertitude et de renégociations, introduisent des incitations tordues pour les autorités publiques à être attentives ex post aux préférences des consommateurs.

Este estudo faz uma análise teórica e empírica dos processos de licitação e contratação de obras e reformas de prédios públicos em uma Universidade Pública Federal, utilizando a Teoria da Informação Assimétrica e dos Contratos. O período da pesquisa foi entre 2010 a 2013, na Universidade Federal do Rio Grande do Sul, sendo que foram analisados 127 processos licitatórios e contratos. As análises revelaram diversas ocorrências em licitações e nas contratações de obras e reformas. Na etapa licitatória, anterior à contratação (ex ante), a sessão para lances das licitações de obras e reformas, em alguns casos, estiveram desertas. Na contratação e execução de obras e reformas (ex post), foram constatados diversos pedidos de prorrogação de prazos e de reequilíbrio econômico financeiro, e na fiscalização das obras e reformas foram constatadas 31 ocorrências nos serviços finalizados pelas Empreiteiras. Os resultados também indicaram que, do total dos processos analisados no período de 2010 – 2013, cerca de 30% das obras e reformas ainda não foram finalizadas ou estão suspensas, o que demonstra deficiências na fiscalização e na gestão dos contratos. Além disso, o tempo médio entre a abertura do processo e a conclusão dos serviços gira em torno de três anos, sendo que grande parte deste tempo foi despendido com procedimentos internos da UFRGS. Tais fatos indicam problemas de seleção adversa e assimetria de informações, além do Hold up problem, em que o Principal é tomado como refém pelo Agente e do problema do Risco moral (Moral Hazard), em que o Agente passa a agir de modo não apropriado ou não aprovado pelo Principal, com a ocorrência dos custos de transação. / This study makes a theoretical and empirical analysis of the processes of bidding and contracting works and reforms of public buildings in a Federal Public University, using Asymmetric Information Theory and Contracts. The period analyzed was between 2010 and 2013, at the Federal University of Rio Grande do Sul, being that 127 bidding processes and contracts were analyzed. The analyses revealed several occurrences in tenders and hiring of work and restoration. In the bidding phase, prior to hiring (ex ante), the bidding session for work and renovations, in some cases, was deserted. There were several requests for deadline extension, and economic-financial adjustment in the work and restoration hiring and execution (ex post), while in the inspection of work and restoration it could be noticed 31 occurrences in services finalized by the contractors. The results also indicated that, of the total number of processes analyzed in the period 2010-2013, about 30% either have not been completed or are suspended, which shows deficiencies in the supervision and management of the contracts. In addition, the average time between the opening of the process and the conclusion of services is about three years, and much of this time was spent with internal procedures of UFRGS. These facts indicate problems of adverse selection and information asymmetry , in addition to the "Hold up problem", in which the Principal is taken hostage by the Agent besides the problem of Moral Hazard, when the Agent begins to act inappropriately or in a way which is disapproved by the Principal, together with the incidence of transaction costs.

Este estudo faz uma análise teórica e empírica dos processos de licitação e contratação de obras e reformas de prédios públicos em uma Universidade Pública Federal, utilizando a Teoria da Informação Assimétrica e dos Contratos. O período da pesquisa foi entre 2010 a 2013, na Universidade Federal do Rio Grande do Sul, sendo que foram analisados 127 processos licitatórios e contratos. As análises revelaram diversas ocorrências em licitações e nas contratações de obras e reformas. Na etapa licitatória, anterior à contratação (ex ante), a sessão para lances das licitações de obras e reformas, em alguns casos, estiveram desertas. Na contratação e execução de obras e reformas (ex post), foram constatados diversos pedidos de prorrogação de prazos e de reequilíbrio econômico financeiro, e na fiscalização das obras e reformas foram constatadas 31 ocorrências nos serviços finalizados pelas Empreiteiras. Os resultados também indicaram que, do total dos processos analisados no período de 2010 – 2013, cerca de 30% das obras e reformas ainda não foram finalizadas ou estão suspensas, o que demonstra deficiências na fiscalização e na gestão dos contratos. Além disso, o tempo médio entre a abertura do processo e a conclusão dos serviços gira em torno de três anos, sendo que grande parte deste tempo foi despendido com procedimentos internos da UFRGS. Tais fatos indicam problemas de seleção adversa e assimetria de informações, além do Hold up problem, em que o Principal é tomado como refém pelo Agente e do problema do Risco moral (Moral Hazard), em que o Agente passa a agir de modo não apropriado ou não aprovado pelo Principal, com a ocorrência dos custos de transação. / This study makes a theoretical and empirical analysis of the processes of bidding and contracting works and reforms of public buildings in a Federal Public University, using Asymmetric Information Theory and Contracts. The period analyzed was between 2010 and 2013, at the Federal University of Rio Grande do Sul, being that 127 bidding processes and contracts were analyzed. The analyses revealed several occurrences in tenders and hiring of work and restoration. In the bidding phase, prior to hiring (ex ante), the bidding session for work and renovations, in some cases, was deserted. There were several requests for deadline extension, and economic-financial adjustment in the work and restoration hiring and execution (ex post), while in the inspection of work and restoration it could be noticed 31 occurrences in services finalized by the contractors. The results also indicated that, of the total number of processes analyzed in the period 2010-2013, about 30% either have not been completed or are suspended, which shows deficiencies in the supervision and management of the contracts. In addition, the average time between the opening of the process and the conclusion of services is about three years, and much of this time was spent with internal procedures of UFRGS. These facts indicate problems of adverse selection and information asymmetry , in addition to the "Hold up problem", in which the Principal is taken hostage by the Agent besides the problem of Moral Hazard, when the Agent begins to act inappropriately or in a way which is disapproved by the Principal, together with the incidence of transaction costs.

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No. of bitstreams: 1 TeseGYR.pdf: 8156092 bytes, checksum: 727d9cd338ae7ed90fe24238b42228bd (MD5) Previous issue date: 2015-03-25 / Outra / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Pneumatic bioreactors are devices free of moving parts which have the purpose of converting raw materials in bio-products of commercial interest by the action of enzymes or cells. They are promising in the biochemical industry, ensuring good oxygen transfer and consuming less energy. Global performance parameters such as global gas hold up and the volumetric oxygen transfer coefficient are important criteria in the design and selection among different geometries of the mentioned devices. In the present work it was carried out modeling and simulation of pneumatic bioreactors based on Computational Fluid Dynamics (CFD) in order to estimate the global gas hold up and the volumetric oxygen transfer coefficient in three different geometries of pneumatic bioreactors: bubble column, concentric tube airlift and split tube airlift. The simulated results of each performance parameter were verified by comparison with the experimental values reported by Thomasi et al. (2010) and Mendes and Badino (2015) for the fluids distilled water, glycerol solution 10 cP and xanthan gum solution 0.2% w/v (weight/volume) in a wide range of specific air flow rate (0 to 5 min- 1). Application suite ANSYS® 14.5 was used for numerical simulations in CFD. Important parameters such as the bubble diameter played a great influence on results of the volumetric oxygen transfer coefficient. It can be observed by the experimental and simulated results that the concentric tube airlift bioreactor was the best alternative to the global gas hold up and the volumetric oxygen transfer coefficient (reaching 14% and 0.06 s-1 for distilled water, respectively). It was found that the results obtained via the CFD agreed with the majority trend of experimental data, capturing the most important hydrodynamic phenomena and mass transfer characteristics, showing that the modeling of different systems with different fluids fulfilled the main objective of obtaining reliable models design and performance of other geometries of pneumatic bioreactors. / Os biorreatores pneumáticos são equipamentos industriais isentos de partes móveis que têm a finalidade de converter matérias-primas em bioprodutos de interesse comercial pela ação de enzimas ou células. São promissores na indústria bioquímica, pois garantem boa transferência de oxigênio consumindo menos energia. Parâmetros globais de desempenho, como a retenção gasosa global e o coeficiente volumétrico de transferência de oxigênio são critérios importantes no projeto e seleção entre geometrias diferentes dos equipamentos mencionados. No presente trabalho foi realizada a modelagem e a simulação de biorreatores pneumáticos baseada na Fluidodinâmica Computacional (CFD - Computational Fluid Dynamics) de forma a estimar a retenção gasosa global e o coeficiente volumétrico de transferência de oxigênio em três geometrias distintas: coluna de bolhas, airlift de cilindros concêntricos e airlift split. Os resultados simulados de cada parâmetro de desempenho foram verificados comparando-se com os valores experimentais reportados nos trabalhos de Thomasi et al. (2010) e Mendes e Badino (2015) para os fluidos água destilada, solução de glicerol 10 cP e solução de goma xantana 0,2% m/v (massa/volume) e vazão de alimentação específica de ar numa ampla faixa (0 a 5 min-1). Foi empregada a suíte de aplicativos ANSYS® 14.5 para as simulações numéricas em CFD. Parâmetros importantes, como o diâmetro de bolha, exerceram grande influência nos resultados referentes ao coeficiente volumétrico de transferência de oxigênio. Destaca-se, pelos resultados experimentais e simulados, que o biorreator pneumático do tipo airlift de cilindros concêntricos apresentou-se como a melhor alternativa para a retenção gasosa global e para o coeficiente volumétrico de transferência de oxigênio (atingindo 14% e 0,06 s-1 para a água destilada, respectivamente). Verificou-se que os resultados obtidos via CFD concordaram com a tendência majoritária dos dados experimentais, capturando os fenômenos mais relevantes das características hidrodinâmicas e da transferência de massa, mostrando que a modelagem dos diferentes sistemas com diferentes fluidos atendeu ao principal objetivo de obter modelos confiáveis para o projeto e comparação de desempenho de outras geometrias de biorreatores pneumáticos. / CNPq: 478472/2011-0 / CNPq: 140466/2011-8

La théorie bancaire récente a bien mis en évidence l'avantage comparatif des banques dans l'octroi du crédit aux petites et moyennes entreprises. La dépendance des PME vis-à-vis du financement bancaire est caractérisée par une asymétrie d'information due à l'opacité des firmes. Afin d'échapper à la surveillance de la banque prêteuse, les entreprises se dirigent vers une multibancarisation comme étant d'une part un contrat d'assurance implicite contre le risque de rationnement et d'une autre part une stratégie de diversification des sources de financement. Cette stratégie élimine également le risque de capturation (Hold-up problem) provenant de l'avantage informationnel détenu par la banque prêteuse et assure des conditions de crédits plus favorables. Ce travail de recherche teste et analyse les effets de la relation durable et de la multibancarisation sur les conditions de crédits. Après une présentation des fondements théoriques nous testons, sur un échantillon de 150 PME libanaises, l'effet du financement relationnel multibancaire respectivement sur le coût du crédit, le rationnement du crédit et les garanties demandées. Nous testons de même l’effet de la consolidation bancaire sur la propension des PME à diversifier leurs relations bancaires. / The recent banking theory highlights the comparative advantage of banks in financing SME (Small and Medium-Sized Enterprises. The dependence of the SME from the banking financing is mainly due to their information opacity. To escape the permanent control of the banks, companies go to a multi-banking relationship as an implicit insurance contract against the availability risk but also as an efficient way to diversify sources of funding. This strategy also eliminates the risk of capturation (Holdup Problem) resulting from the informative advantage detained by banks and insures more favorable credit terms. This research tests and analyzes the effects of the long-lasting relation and the multi-banking relationships on credit terms. After a detailed presentation of the literature review when we developed the main theoretical concepts we tested our hypothesis on a sample of 150 Lebanese SME firms. Our empirical works was focused on the effect of the multi-banking financing respectively on the credit cost, on credit availability and on collaterals. We also tested the effect of banking Mergers and acquisitions on SME’s intention to diversify their banking relations.

This dissertation reports a series of studies on social influences in decision making with wide ranging marketing implications in areas such as gamification initiatives, participative pricing mechanisms, and charity fundraising strategies. The body of this work comprises of three indepth, stand-alone studies. The first study, "Contagion of the Competitive Spirit: The Influence of a Competition on Non-Competitors", investigates the influence of a competition on noncompetitors who do not participate in it but are aware of it. In a series of experimental studies, the study shows that the mere awareness of a competition can affect a non-competitor's performance in similar tasks. These experiments provide confirmatory and process evidence for this contagion effect, showing that it is driven by heightened social comparison motivation due to mere awareness of the competition. In addition, the study finds evidence that the reward level for the competitors could moderate the contagion effect on the non-competitors. The second study, "The Negative Effects of Precommitment on Reciprocal Behaviour: Evidence from a Series of Voluntary Payment Experiments", examines the effects of precommitment on reciprocal behaviour towards a forthcoming benefit. Through a series of experiments in several countries, the study shows that precommitment often weakens reciprocal behaviour. In two field experiments, a laboratory and an online experiment, the study finds consistent evidence that voluntary payment amounts decrease for individuals who are asked to precommit their payment. The results from a final online trust-game experiment support the posited mental-accounting mechanism for the effect. The third study, "Hold-Up Induced by Demand for Fairness: Theory and Experimental Evidence", explores the domain of hold-up and fairness concerns. While recent research suggests that fairness concerns could mitigate hold-up problems, this study proposes a starkly opposite possibility: that fairness concerns can also induce hold-up problems and thus significant inefficiencies. The study reports theoretical analysis and experimental evidence of hold-up in scenarios in which it will not occur if agents are purely self-interested, but could occur if they care about fairness at ex post negotiation.

TFT-LCD（薄膜電晶體液晶顯示器）是台灣全力發展的重點產業。TFT-LCD 產業特徵是專業分工產業，LCD產業價值鏈可分成上游材料廠商、中游面板廠商、下游應用廠商。主要的上游零件及材料包括玻璃基板(glass substrate)、彩色濾光片(color filter)、偏光板/膜(polarizer)、背光模組(backlight module)、驅動IC(Driver IC)、配向膜(alignment layer)。 LCD面板生產所需要的這些原材料占面板生產總成本的70％以上。對面板製造商來說，透過整合減少成本成為一個重要的議題。許多面板的關鍵零組件是設計導入(design in)的產品，對於面板設計，需要配合製造商的要求和規格。所以面板廠商和關鍵零組件廠商之間的快速溝通和反應是非常重要。 目前部分材料是從國外進口的，其中配向膜是日商擁有90%的市佔率。雖然LCD面板成本結構中的比重不高，但是液晶配向膜是決定液晶顯示器面板品質的關鍵材料。主要的配向膜廠商分別是日產化學和JSR。雙方都是日商的化學公司。JSR是2005年投入台灣市場，設立JSRmicro(台灣捷時雅邁科股份有限公司)，日產化學則是2010年才進入台灣市場。而且日產化學是液晶配向膜的先鋒者，10年前的市占率大約80%，但是今年降低到50%。日產化學進來台灣時，透過日系綜合商社來交易。而JSR在台灣則是透過台灣的中間商(華立通路商)來交易。 本研究以日系液晶顯示器關鍵材料配向膜廠商「台灣日產化學」為實例，進行專業訪談。探討台灣日產化學之中游面板廠商的產業鏈，並希望運用邱志聖(2010)之策略行銷4C架構分析，進行深入探討日產化學在台灣市場中，如何降低台灣LCD面板廠商的交易成本包含外顯單位效益成本、資訊搜尋成本、道德危機成本、專屬陷入成本，進而了解此公司的競爭優勢，繼而進行跟競爭對手的4C成本比較分析，提供個案公司建議。 本研究目的為了解： 1.日產化學跟客戶之間的4C關係 2.日產化學與通路商之間的關係 3.日產化學跟競爭對手(JSR)的作法比較 研究結果發現： 1.中間商的選擇、數量、提供的產品種類多寡，以及中間商提供的服務都會影響到日產化學對面板廠商的交易成本。 2.相同產業內供應商提供的產品種類多寡會影響到對面板廠商以及中間商的交易成本。 3.製造商之知名度的高低會影響到中間商的選擇權力。 / TFT-LCD (thin film transistor liquid crystal display) is one of the key industries in Taiwan. TFT-LCD industry is characterized as a specialization industry. The LCD industry value chain can be divided into upstream materials manufacturers, the midstream panel manufacturers, and downstream application vendors. Upstream material parts include glass substrate, color filter, polarizer film, backlight module, the driver IC, and alignment layer. These essential components needed in LCD panel production account for more than 70% of the total cost in panel production. Therefore an important issue for panel makers is to reduce costs through integration. As many of the key components of the panel is the “design in product”, which need to be designed according to manufacturer's requirements and specifications, rapid communication and response between panel manufacturers and key components manufacturers is very important. Some materials are imported from abroad; Japanese companies have 90% market share in the alignment film market. Although the proportion of the cost structure of the LCD panel is not high, but the alignment layer is the key material to determine the quality of liquid crystal display panel. Two main alignment film makers are Nissan Chemical and JSR. They both are Japanese chemical companies. JSR devotes into Taiwanese market in 2005, and established JSRmicro. Nissan Chemical started its business in Taiwan at 2010, by establishing Taiwan Nissan Chemical. Nissan Chemical is the pioneer in liquid crystal alignment film and once had approximately 80 percent of market share 10 years ago, but it has declined to 50% as of now. Nissan Chemical transact through Japanese Sogo Shosha in Taiwai. JSR transact through Taiwanese intermediaries (Wahlee distributor) in Taiwan. In this study, Japanese liquid crystal alignment layer manufacturer Taiwan Nissan Chemical were professionally interviewed, then explored between Taiwan Nissan Chemical and the panel manufacturers’ industry chain. This study will also apply strategic marketing 4C framework for analysis, then conduct an in-depth investigation on how Taiwan Nissan Chemical reduces transaction costs for Taiwan LCD panel manufacturers, illustrate the company's competitive advantage through the transaction costs analysis, including buyer utility cost, information searching cost, moral hazard cost, and asset specificity cost, and lastly compare with the competitor’s transaction cost. The purposes of this research are: 1. The 4C relationship between Nissan Chemical and the client 2. The relationship between Nissan chemical and the distributors 3. The 4C comparison between Nissan Chemical and the competitor (JSR) The results of study show that: 1. A choice of intermediaries, the number of intermediaries, the number of product that intermediaries offer, and the services intermediaries provide will affect the transaction costs of Nissan Chemical for panel makers. 2. The product range provided by the suppliers within the same industry would affect the transaction costs of panel makers and intermediaries, 3. The well-known level of the manufacturer will affect the power of choice for intermediaries.

Submitted by André Fava Pestana (afpestana@gmail.com) on 2014-12-23T22:09:45Z No. of bitstreams: 1 Tese_AFP_MPFE_VersãoFinal.pdf: 441121 bytes, checksum: d3fd4490be660a716f9368bbf366064e (MD5) / Rejected by Renata de Souza Nascimento (renata.souza@fgv.br), reason: Prezado André, Não deve constar números de página nas páginas de 1 á 8. Peço a gentileza de excluir estes números e postar novamente. Lembrando que o Sumário está correto, seu trabalho se inicia na página 9. À disposição para qualquer esclarecimento. Att. Renata Souza Cursos de Pós-Graduação (55 11) 3799-7764 SRA - Secretaria de Registros Acadêmicos on 2014-12-29T11:26:26Z (GMT) / Submitted by André Fava Pestana (afpestana@gmail.com) on 2014-12-29T13:32:24Z No. of bitstreams: 1 Tese_AFP_MPFE_VersãoFinal.pdf: 442163 bytes, checksum: c1d9e18d4959a2ad10458a4c85047465 (MD5) / Approved for entry into archive by Renata de Souza Nascimento (renata.souza@fgv.br) on 2014-12-29T13:37:54Z (GMT) No. of bitstreams: 1 Tese_AFP_MPFE_VersãoFinal.pdf: 442163 bytes, checksum: c1d9e18d4959a2ad10458a4c85047465 (MD5) / Made available in DSpace on 2015-01-05T11:30:06Z (GMT). No. of bitstreams: 1 Tese_AFP_MPFE_VersãoFinal.pdf: 442163 bytes, checksum: c1d9e18d4959a2ad10458a4c85047465 (MD5) Previous issue date: 2014-12-19 / Banks, as diligent agents, actively monitor their debtors in order to obtain a precise assessment of their financial position. This monitoring stance usually allows them to access non-public information regarding a firm and its business, and acquire hold up power in the credit granting activity. This hold up power is believed to allow banks to charge the firm higher interest rates than otherwise would be justified by the company’s credit risk profile through the economic cycle, mainly during recessions. The presence of hold up power is tested on this paper in businesses more or less dependent on bank credit. By comparing the evolution of bank spreads paid by Brazilian public companies with and without access to the corporate bond market and through the economic cycle comprising the 2009 crisis, some insight is gained on the impact of an economic downturn and of holding corporate bonds in reducing the bank’s hold up power and hence the spreads paid by the company. Data from 50 firms for the years 2007 to 2013 were organized in a panel and modeled using the Estimated Generalized Least Squares (EGLS) technique, as an alternative to the classic Least Squares (LS) technique. The dummies, i) access to corporate bond credit, ii) economic recession and iii) interaction of the 2 previous variables were created and tested after controlling for firm specific factors such as credit restriction, firm size, leverage, etc and statistical evidence was found supporting the intuition that having access to the bond market can reduce the bank spreads during recessions. / A concessão de crédito bancário demanda esforço do agente credor que se dedica de forma ativa na obtenção de informações relativas à firma, até então não disponíveis ao público. Dado o hold up power do banco detentor de informações não públicas, este deveria poder cobrar spreads mais altos do que seria justificado unicamente pelo risco de crédito do tomador ao longo dos ciclos econômicos, sendo tal dinâmica mais acentuada em cenários de crise. Testa-se aqui esta hipótese e para isso são comparadas as variações do spread bancário médio da dívida de empresas brasileiras com diferentes composições de endividamento, levando-se em conta sua dependência do crédito bancário. Foram criadas: i) uma variável dummy identificando o acesso ao crédito direto para que se pudesse avaliar o seu efeito nos spreads; ii) outra dummy identificando cenários de recessão que permite avaliar o impacto do ciclo econômico nos spreads e iii) dummy interação que viabilizou o estudo do efeito combinado das duas variáveis anteriores. Fatores de risco individuais da firma, tais como tamanho, nível de alavancagem e sua natureza em termos de restrição a crédito foram controlados na análise. Os dados foram organizados em painel com os quais foi montada regressão linear valendo-se da técnica Estimated Generalized Least Squares (EGLS), alternativa ao Least Squares (LS) clássico. Encontrou-se evidência estatística de que em cenários de recessão econômica o acesso ao mercado direto de crédito traz efeito benéfico sobre os spreads bancários pagos pelas firmas.

Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-10-05T19:18:20Z No. of bitstreams: 1 TeseCEMac.pdf: 12049463 bytes, checksum: acd65707762e60b912f35a2d267ad5b7 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T13:40:54Z (GMT) No. of bitstreams: 1 TeseCEMac.pdf: 12049463 bytes, checksum: acd65707762e60b912f35a2d267ad5b7 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-20T13:41:14Z (GMT) No. of bitstreams: 1 TeseCEMac.pdf: 12049463 bytes, checksum: acd65707762e60b912f35a2d267ad5b7 (MD5) / Made available in DSpace on 2016-10-20T13:41:32Z (GMT). No. of bitstreams: 1 TeseCEMac.pdf: 12049463 bytes, checksum: acd65707762e60b912f35a2d267ad5b7 (MD5) Previous issue date: 2016-04-26 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Due to the high capacity of oxygen transfer and versatility, pneumatic reactors have been constantly used in bioprocesses. However, aiming to expand the use of these bioreactors in the industry, as well as increase the understanding of the complex phenomena that occur in these devices, this thesis aimed to evaluate the hydrodynamic, oxygen transfer and shear conditions in three models of pneumatic reactors (bubble column, concentric-tube airlift and split-cylinder airlift) in the scales of 5 and 10 L, using as liquid phase four Newtonian fluids and eight non-Newtonian fluids, and five specific air flow rate (air of 1 to 5 vvm). Related to the hydrodynamic were studied the global gas hold-up (g), the gas hold-ups in the riser (R) and in the downcomer (D), liquid circulation time (tC), superficial liquid velocity in the riser (ULR) and in the downcomer (ULD), and the percentage energy losses in the riser (%ER+%EFR), in the downcomer (%ED+%EFD), and in the bottom (%EB) of airlift reactors. The values of g, R, D, ULR and ULD showed increasing behaviour with increase of air and decreasing behaviour with the kinematic liquid viscosity (L) and the rheologic properties (K e n), and observed the opposite for tC. The higher values of g, R, D and tC were obtained for concentric-tube airlift reactor (ACC) and scale of 10 L. With exception of ULR of Newtonian fluids, the others liquid velocity tests resulted in higher values for split-cylinder airlift reactors (ASC) and scale of 10 L. This result was attributed to the greater driving force (R-D) to liquid circulation obtained in the ASC reactors and the higher energy losses in the riser and in the downcomer observed in the ACC reactors. In the bottom of the airlift reactors, the higher values of %EB were obtained to the ASC reactor. To evaluate the mass transfer were studied, the average bubble diameter (Db), the volumetric oxygen transfer coefficient (kLa) and the terms that compose the kLa, the convective mass transfer coefficient (kL) and the specific interfacial area of mass transfer (aL). With the increase of air, L, K and n, the air bubbles were predominantly coalescent in water, presenting distorted shape, and non-coalescent with spherical/elliptical shape in the other solutions. It was observed a similar behavior between the kLa and aL parameters, which were directly proportional to the air and inversely proportional to the L, K and n. In water, the aL values were lower than glycerol solutions due to the higher Db values observed in this liquid. For the kL, it was observed a decreasing behaviour with the increase of the air in the most solutions. The magnitude of kL values was due mainly the oxygen difusivity in the liquid, and the higher values were observed to the water, following by the non-Newtonian solutions. In general, the higher values of the mass transfer parameters were obtained in the ACC reactor and in the scale of 10 L. The proposed method to the estimate the average shear rate velocity based on Kolmogorov’s theory of isotropic turbulence showed results consistent with the literature relative to the behavior and magnitude of this variable, as well as the results obtained by the analysis of the morphological changes of Streptomyces clavuligerus in two models of airlift reactors and two aeration conditions. Were proposed correlations to predict all evaluated parameters. Were obtained in all cases a good fit with the experimental data, with deviations between the calculated and experimental values below 20%. / Devido à alta capacidade de transferência de oxigênio e versatilidade, reatores pneumáticos têm sido constantemente utilizados em bioprocessos. Entretanto, visando ampliar a utilização destes reatores na indústria, assim como aumentar a compreensão dos fenômenos complexos que ocorrem nestes dispositivos, na presente tese teve-se como objetivo avaliar as condições hidrodinâmicas, de transferência de oxigênio e de cisalhamento em três modelos de reatores pneumáticos (coluna de bolhas, airlift de cilindros concêntricos e airlift split-cylinder) nas escalas de 5 e 10 L, utilizando como fase líquida quatro fluidos newtonianos e oito fluidos nãonewtonianos e cinco vazões específicas de ar (ar de 1 a 5vvm). Em termos hidrodinâmicos foram estudadas as retenções gasosas global (g), no riser (R) e no downcomer (D), tempo de circulação do líquido (tC), velocidade superficial do líquido no riser (ULR) e no downcomer (ULD) e as perdas percentuais de energia no riser, no downcomer e na base (%EB) de reatores airlift. Os valores de g, R, D, ULR e ULD apresentaram comportamento crescente com o aumento de ar e decrescente com a viscosidade cinemática do líquido (L) e propriedades reológicas (K e n), sendo observado o oposto para tC. Os maiores valores de g, R, D e tC foram obtidos em reator airlift de cilindros concêntricos (ACC) e escala de 10 L. Com exceção de ULR de fluidos newtonianos, os demais testes de velocidade do líquido resultaram em maiores valores nos reatores airlift split-cylinder (ASC) e escala de 10 L. Tal resultado foi atribuído a maior força motriz (R-D) para circulação do líquido obtida em ASC e às maiores perdas de energia no riser e no downcomer observadas em reatores ACC. Na base dos reatores, os maiores valores de %EB foram obtidos para reator ASC. Para avaliação da transferência de massa foram estudados o diâmetro da bolha (Db), o coeficiente volumétrico de transferência de oxigênio (kLa) e os termos que o compõe, coeficiente convectivo de transferência de massa (kL) e área interfacial específica de transferência de massa (aL). Bolhas de ar, com o aumento de ar, L, K e n foram predominantemente coalescentes em água, apresentando formato distorcido e nãocoalescentes com formato esférico/elíptico nas demais soluções. Observou-se um comportamento análogo entre kLa e aL, com relação direta à ar e inversa à L, K e n. Em água, os valores de aL foram inferiores às soluções de glicerol em virtude do maior Db observado neste líquido. Para kL, observou-se um comportamento decrescente com o aumento de ar na maioria das soluções. A magnitude dos valores de kL obedeceu principalmente a difusividade do oxigênio no líquido, sendo os maiores valores observados para água, seguido das soluções não-newtonianas. De maneira geral, os maiores valores dos parâmetros de transferência de massa foram obtidos em reator ACC de 10 L. O método proposto para estimativa da taxa de cisalhamento com base na teoria de turbulência isotrópica de Kolmogorov apresentou resultados condizentes com a literatura em termos de comportamento e magnitude desta variável, assim como com os resultados obtidos pela análise das alterações morfológicas de Streptomyces clavuligerus em dois modelos de reatores airlift e duas condições de aeração. Para todos os parâmetros avaliados foram propostas correlações para sua predição, sendo obtidos em todos os casos bons ajustes aos dados experimentais com desvios inferiores à 20%. Palavras-chave: reatores pneumáticos, retenção gasosa, kLa, diâmetro da bolha, velocidade