Um sistema reparável opera sob uma estratégia de manutenção que exige ações de recuperação preventiva em tempos pré-definidos e ações de reparo quando ocorre a perda de função do sistema. A manutenção preventiva (MP) é programada periodicamente e muitas vezes possui um intervalo de tempo fixo para ações. No entanto, as atividades de MP podem não restaurar o sistema para uma condição similar ao início de vida deste, mas para uma situação intermediária. Nesse caso, a MP é denominada de imperfeita. Além disso, ao longo da vida do sistema, são executados diferentes planos de manutenção com condições e atividades distintas que podem afetar a intensidade de falha de diferentes maneiras. Para modelar essas características da MP em um sistema reparável, propõe-se uma nova classe de modelo de fator de melhoria, denominado fator de melhoria variável que possibilita a modelagem da situação de manutenção perfeita. A formulação da função de verossimilhança foi desenvolvida para estimação dos parâmetros bem como desenvolvidos testes de verificação da qualidade de ajuste, intervalos de confiança para os parâmetros e otimização da periodicidade de realização da MP com base no enfoque dos novos modelos propostos. Os resultados foram aplicados em dados reais e verificou-se uma parametrização mais flexível a MP imperfeita e maior versatilidade nas análises de confiabilidade do sistema quando utilizado os novos modelos. / A repairable system operates under a maintenance strategy that calls for preventive repair actions at prescheduled times and the repair actions that restore system when failure occurs. The preventive maintenance (PM) is scheduled periodically and it often holds a fixed time interval for PM actions. However, PM activities are generally imperfect and cannot restore the system to as good as new condition but to an intermediate situation, which is called imperfect PM. In addition, throughout system life are implemented diverse maintenance policies with different activities and conditions that may affect the failure intensity in different ways. To model these PM characteristics, proposes a new model class of improvement factor called variable improvement factor that also enables modeling perfect maintenance situation. The likelihood function is developed for parameter estimation as well as goodness-of-fit tests and confidence intervals for the parameters are developed, and optimization of the PM intervals based on the proposed models is presented. The proposed model was applied to a data set and a more flexible parameterization for imperfect PM and greater versatility in the system reliability analysis were verified with the use of the new model.

L’augmentation de la puissance électrique des composants électroniques pose le problème de la dissipation de la chaleur générée. Les boîtiers électriques doivent permettre la dissipation de cette chaleur en conservant une isolation électrique. La solution retenue pour évacuer la chaleur par transfert thermique consiste en matériaux composites dont les renforts par leur structuration vont améliorer la conductivité thermique. Des composites à matrice polymère ont été choisis pour leur aptitude de mise en forme. La conductivité thermique et l’isolation électrique sont assurées par des charges céramiques. Les méthodes d’homogénéisation donnent des pistes d’amélioration du comportement de composites en fonction des propriétés de leurs constituants, de leur géométrie et de leur distribution. Elles fournissent ainsi une formulation optimisée de matériaux répondant à certaines caractéristiques issues de cahiers des charges émanant du partenaire industriel (Institut de Soudure). La conductivité thermique attendue des composites impose une forte fraction volumique de charges pour compenser le caractère isolant de la matrice polymère. Des méthodes d’homogénéisation ont été développées pour prédire la conductivité thermique effective pour de forts taux de charges (supérieur à 20%) et des contrastes élevés de conductivité thermique. La présence d’une interphase provenant d’incompatibilités fortes entre les composants doit également être modélisée / The increase of electronic components in the integrated circuits and the required electrical power set the question of the dissipation of the heat generated. The electrical box must favor the heat dissipation while maintaining electrical insulation. The solution chosen to transfer the heat is to develop composite materials whose reinforcements by their structure will improve the thermal conductivity. Polymer-based composite materials were chosen for their building ability. Thermal conductivity and electrical insulation are insured by ceramic reinforcements. The homogenization methods allow to improve the composites’ design according to the properties of their constituents, their geometry and their distribution. They thus provide an optimized formulation of materials satisfying the characteristics emanating from the industrial partner (‘Institut de Soudure’). The expected thermal conductivity of the composites imposes a high volume fraction of reinforcements to counterbalance the insulating polymer matrix. Homogenization methods have been developed to provide predictions of effective thermal conductivity for high (greater than 20%) reinforcement rates and high thermal conductivity contrasts. The presence of an interphase resulting from strong physico-chemical incompatibilities between the components must also be modeled

Cette thèse est composée de trois chapitres distincts.Dans le premier chapitre, je montre que les mesures de liquidités traditionnelles, telles que la profondeur du marché, ne sont pas toujours pertinentes pour mesurer le bien-être des investisseurs. Je construis un modèle de marché conduit par les ordres et montre qu'une offre de liquidité élevée peut correspondre à de mauvaises conditions d'éxécution pour les fournisseurs de liquidité et à un bien-être relativement faible.Dans le deuxième chapitre, je modélise la vitesse des ajustements de prix à l'arrivée de nouvelles dans les marchés conduits pas les ordres, lorsque les investisseurs ont une capacité d'attention limitée.En raison de leur attention limitée, les investisseurs suivent imparfaitement l'arrivée de nouvelles. Ainsi, les prix s'ajustent aux nouvelles après un certain délai. Ce délai diminue lorsque le niveau d'attention des investisseurs augmente.Le délai d'ajustement des prix diminue également lorsque la fréquence à laquelle les nouvelles arrivent, augmente. Le troisième chapitre présente un travail écrit en collaboration avec Thierry Foucault. Nous construisons un modèle pour expliquer en quoi le trading à haute fréquence peut générer des "mini flash crashes" (un brusque changement de prix suivi d'un retour très rapide au niveau antérieur). Notre théorie est basée sur l'idée qu'il existe une tension entre la vitesse à laquelle l'information peut être acquise et la précision de cette information. Lorsque les traders à haute fréquence mettent en oeuvre des stratégies impliquant des réactions rapides à des événements de marché, ils augmentent leur risque à réagir à du bruit et génèrent ainsi des "mini flash crashes". Néanmoins, ils augmentent l'efficience informationnelle du marché. / This dissertation is made of three distinct chapters. In the first chapter, I show that traditional liquidity measures, such as market depth, are not always relevant to measure investors' welfare. I build a limit order market model and show that a high level of liquidity supply can correspond to poor execution conditions for liquidity providers and to a relatively low welfare.In the second chapter, I model the speed of price adjustments to news arrival in limit order markets when investors have limited attention.Because of limited attention, investors imperfectly monitor news arrival. Consequently prices reflect news with delay. This delay shrinks when investors' attention capacity increases. The price adjustment delay also decreases when the frequency of new arrival increases. The third chapter presents a joint work with Thierry Foucault. We build a model to explain why high frequency trading can generate mini-flash crashes (a sudden sharp change in the price of a stock followed by a very quick rversal). Our theory is based on the idea that there is a trade-off between speed and precision in the acquisition of information. When high frequency traders implement strategies involving fast reaction to market events, they increase their risk to trade on noise and thus generate mini flash crashes. Nonetheless they increase market efficiency.

A considerable body of theoretical and empirical literature has evaluated the credit channel of monetary transmission. This paper sets up an open-economy model under floating exchange rates with imperfect international capital mobility based on the Bernanke and Blinder model (1988). Employing our model, we show that a change in money supply has different impacts on the economy in many cases compared to the previous literature. The exchange rate puzzle may occur and when the exchange rate puzzle appears, the Fleming proposition is violated. Besides, by means of a cointegration analysis, we empirically verify the particular case of the exchange rate puzzle with the monthly data from May 1984 to January 2005 in Taiwan. Therefore, our empirical evidences can be matched with our theoretical derivations successfully.

This research has developed several models and methodologies with the aim of improving the accuracy and applicability of reliability predictions for complex repairable systems. A repairable system is usually defined as one that will be repaired to recover its functions after each failure. Physical assets such as machines, buildings, vehicles are often repairable. Optimal maintenance strategies require the prediction of the reliability of complex repairable systems accurately. Numerous models and methods have been developed for predicting system reliability. After an extensive literature review, several limitations in the existing research and needs for future research have been identified. These include the follows: the need for an effective method to predict the reliability of an asset with multiple preventive maintenance intervals during its entire life span; the need for considering interactions among failures of components in a system; and the need for an effective method for predicting reliability with sparse or zero failure data. In this research, the Split System Approach (SSA), an Analytical Model for Interactive Failures (AMIF), the Extended SSA (ESSA) and the Proportional Covariate Model (PCM), were developed by the candidate to meet the needs identified previously, in an effective manner. These new methodologies/models are expected to rectify the identified limitations of current models and significantly improve the accuracy of the reliability prediction of existing models for repairable systems. The characteristics of the reliability of a system will alter after regular preventive maintenance. This alternation makes prediction of the reliability of complex repairable systems difficult, especially when the prediction covers a number of imperfect preventive maintenance actions over multiple intervals during the asset's lifetime. The SSA uses a new concept to address this issue effectively and splits a system into repaired and unrepaired parts virtually. SSA has been used to analyse system reliability at the component level and to address different states of a repairable system after single or multiple preventive maintenance activities over multiple intervals. The results obtained from this investigation demonstrate that SSA has an excellent ability to support the making of optimal asset preventive maintenance decisions over its whole life. It is noted that SSA, like most existing models, is based on the assumption that failures are independent of each other. This assumption is often unrealistic in industrial circumstances and may lead to unacceptable prediction errors. To ensure the accuracy of reliability prediction, interactive failures were considered. The concept of interactive failure presented in this thesis is a new variant of the definition of failure. The candidate has made several original contributions such as introducing and defining related concepts and terminologies, developing a model to analyse interactive failures quantitatively and revealing that interactive failure can be either stable or unstable. The research results effectively assist in avoiding unstable interactive relationship in machinery during its design phase. This research on interactive failures pioneers a new area of reliability prediction and enables the estimation of failure probabilities more precisely. ESSA was developed through an integration of SSA and AMIF. ESSA is the first effective method to address the reliability prediction of systems with interactive failures and with multiple preventive maintenance actions over multiple intervals. It enhances the capability of SSA and AMIF. PCM was developed to further enhance the capability of the above methodologies/models. It addresses the issue of reliability prediction using both failure data and condition data. The philosophy and procedure of PCM are different from existing models such as the Proportional Hazard Model (PHM). PCM has been used successfully to investigate the hazard of gearboxes and truck engines. The candidate demonstrated that PCM had several unique features: 1) it automatically tracks the changing characteristics of the hazard of a system using symptom indicators; 2) it estimates the hazard of a system using symptom indicators without historical failure data; 3) it reduces the influence of fluctuations in condition monitoring data on hazard estimation. These newly developed methodologies/models have been verified using simulations, industrial case studies and laboratory experiments. The research outcomes of this research are expected to enrich the body of knowledge in reliability prediction through effectively addressing some limitations of existing models and exploring the area of interactive failures.

Submitted by Murilo Resende Ferreira (muriloresende82@gmail.com) on 2014-10-28T15:22:42Z No. of bitstreams: 1 Tesedoutoradomuriloresende.PDF: 806113 bytes, checksum: e6d9cfcc660128de80d20f44f9c5213e (MD5) / Approved for entry into archive by BRUNA BARROS (bruna.barros@fgv.br) on 2014-11-10T11:34:49Z (GMT) No. of bitstreams: 1 Tesedoutoradomuriloresende.PDF: 806113 bytes, checksum: e6d9cfcc660128de80d20f44f9c5213e (MD5) / Approved for entry into archive by Marcia Bacha (marcia.bacha@fgv.br) on 2014-11-13T13:40:01Z (GMT) No. of bitstreams: 1 Tesedoutoradomuriloresende.PDF: 806113 bytes, checksum: e6d9cfcc660128de80d20f44f9c5213e (MD5) / Made available in DSpace on 2014-11-13T13:40:15Z (GMT). No. of bitstreams: 1 Tesedoutoradomuriloresende.PDF: 806113 bytes, checksum: e6d9cfcc660128de80d20f44f9c5213e (MD5) Previous issue date: 2014-06-27 / This thesis contains two chapters, each one dealing with banking theory and the history of financiai arrangements. In Chapter 1, we extend a Diamond and Dybvig economy with imperfect monitoring of early withdrawals and make a welfare comparison between all possible allocations, as proposed by Prescott and Weinberg(2003) [37]. This imperfect monitoring is introduced by establishing indirect communication( trough a mean of payment) between the agents and the machine that is an aggregate of the financiai and the productive sector. The extension consists in studying allocations where a fraction of the agents can exploit imperfect monitoring and defraud the contracted arrangement by consuming more in the early period trough multiple means of payment. With limited punishment in the period of late consumption, this new allocation is called a separating allocation in contrast with pooling allocations where the agent with the ability of fraud is blocked from it by a costly mean of payment or by receiving enough future consumption to make fraud unattractive. The welfare comparison in the chosen range of parameters show that separating allocations are optimal for poor economies and pooling allocations for intermediary and rich ones. We end with a possible historical context for this kind of model, which connects with the historical narrative in chapter 2. In Chapter 2 we explore the quantitative properties of an early warning system for financiai crises based on the boom and bust framework described in more detail in appendix 1. The main variables are: real growth in equity and housing prices, the yield spread between the 10-year government bond and the 3-month interbank rate and the growth in total banking system assets. These variables display a higher degree of correct signals for recent crises (1984-2008) than comparable early warning systerns. Taking into account an increasing base-line risk ( due to increasing rates of credit expansion , lower interest rates and the accumulation of distortions) also proves to be informative and to help signaling crises in countries that did not go trough a great boom in previous years. / Esta tese contém dois capítulos, cada um lidando com a teoria e a história dos bancos e arranjos financeiros. No capítulo 1, busca-se extender uma economia Diamond-Dybvig com monitoramento imperfeito dos saques antecipados e realizar uma comparação do bem estar social em cada uma das alocações possíveis, como proposto em Presscott and Weinberg(2003). Esse monitoramento imperfeito é implementado a partir da comunicação indireta ( através de um meio de pagamento) entre os agentes e a máquina de depósitos e saques que é um agregado do setor produtivo e financeiro. A extensão consiste em estudar alocações onde uma fração dos agentes pode explorar o monitoramento imperfeito e fraudar a alocação contratada ao consumirem mais cedo além do limite, usando múltiplos meios de pagamento. Com a punição limitada no período de consumo tardio, essa nova alocação pode ser chamada de uma alocação separadora em contraste com as alocações agregadoras onde o agente com habilidade de fraudar é bloqueado por um meio de pagamento imune a fraude, mas custoso, ou por receber consumo futuro suficiente para tornar a fraude desinteressante. A comparação de bem estar na gama de parâmetros escolhida mostra que as alocações separadoras são ótimas para as economias com menor dotação e as agregadoras para as de nível intermediário e as ricas. O capítulo termina com um possível contexto histórico para o modelo, o qual se conecta com a narrativa histórica encontrada no capítulo 2. No capítulo 2 são exploradas as propriedade quantitativas de um sistema de previsão antecedente para crises financeiras, com as váriaveis sendo escolhidas a partir de um arcabouço de ``boom and bust'' descrito mais detalhadamente no apêndice 1. As principais variáveis são: o crescimento real nos preços de imóveis e ações, o diferencial entre os juros dos títulos governamentais de 10 anos e a taxa de 3 meses no mercado inter-bancário e o crescimento nos ativos totais do setor bancário. Essas variáveis produzem uma taxa mais elevada de sinais corretos para as crises bancárias recentes (1984-2008) do que os sistemas de indicadores antecedentes comparáveis. Levar em conta um risco de base crescente ( devido à tendência de acumulação de distorções no sistema de preços relativos em expansões anteriores) também provê informação e eleva o número de sinais corretos em países que não passaram por uma expansão creditícia e nos preços de ativos tão vigorosa.

Submitted by JOAO BARROSO (joao.barroso@bcb.gov.br) on 2010-08-03T20:13:37Z No. of bitstreams: 1 TESE.pdf: 1045913 bytes, checksum: 1c6912b208fc1e79faee0ef3e07a6198 (MD5) / Approved for entry into archive by Andrea Virginio Machado(andrea.machado@fgv.br) on 2010-08-04T12:22:02Z (GMT) No. of bitstreams: 1 TESE.pdf: 1045913 bytes, checksum: 1c6912b208fc1e79faee0ef3e07a6198 (MD5) / Made available in DSpace on 2010-08-04T17:23:36Z (GMT). No. of bitstreams: 1 TESE.pdf: 1045913 bytes, checksum: 1c6912b208fc1e79faee0ef3e07a6198 (MD5) Previous issue date: 2010-02-05 / The thesis uses international price data to identify parameters of trade models with imperfect competition, therefore allowing inference on exchange rate behavior, gains from trade and variety of domestic goods. First, we investigate Brazilian exporters pricing behavior over the long-run following destination specific exchange rate shocks. We find evidence of incomplete exchange-rate pass-through in the long-run, which supports the market structure explanations over short-run sticky-price explanations. Second, we calculate import price indexes and the implied welfare gains from new varieties of imported goods, based on disaggregated estimates of elasticity of substitution parameters. Finally, we qualify standard results in the literature that point to a reduction in domestic varieties after trade liberalization; domestic varieties may expand if we introduce an additional margin in firms‟ technology, such as intermediate goods or high skilled labor. / Esta tese utiliza a informação contida em preços internacionais para identificar parâmetros de modelos de comércio sob competição imperfeita, desta forma permitindo inferência sobre o comportamento das exportações, sobre os ganhos de troca da abertura comercial e sobre a variedade de bens produzidos domesticamente. Em primeiro lugar, investigamos o repasse cambial, no longo prazo, para os preços praticados por exportadores brasileiros. O foco no longo prazo permite controlar os efeitos da rigidez de preço no curto prazo, de maneira que o repasse incompleto evidencie competição imperfeita com preços flexíveis. Em segundo lugar, calculamos os ganhos de troca de novas variedades de bens importados baseando-nos em estimativas para as elasticidades de substituição desagregadas. Finalmente, qualificamos a ênfase da literatura de comércio em ganhos de eficiência no lugar de ganhos de variedade, demonstrando que a variedade de bens produzidos domesticamente se amplia após aberturas comerciais desde que as firmas tenham uma margem de decisão em bens intermediários ou na qualificação da mão de obra.

Intra-industry trade occurs when goods from the same industry category are both exported and imported. Types of intra-industry trade are identified, and theoretical models of intraindustry trade under conditions of imperfect competition are examined. The results of thirtyseven empirical studies on the determinants of intra-industry trade are analysed. Methods of measuring intra-industry trade and marginal intra-industry trade are discussed, and various measurement problems are dealt with. The extent of intra-industry trade in South Africa in 1992 and 1997 is measured, using the Grubel-Lloyd and Michaely indices. The BrUlhart indices are applied to measure marginal intra-industry trade. South Africa has a relatively low and stable level of intra-industry trade in manufactured goods: the GrubelLloyd index for 1997 is calculated to be 37 per cent. / Economics and Management Sciences / M.Com. (Economics)

Le présent travail est une petite recherche sur l'apprentissage du français, et plus particulièrement sur l'alternance de l'imparfait et le passé composé parmi des suédophones. Le but du mémoire est de comprendre comment les apprenants appliquent la grammaire malgré la différence entre leur langue maternelle et la langue de l'apprentissage. L'étude part de la différence entre le français et le suédois. Le corpus se compose de dix récits au passé écrits par des étudiants des niveau trois et quatre du système scolaire suédois. Le titre de leur devoir était Un souvenir de mon enfance. Un exercice pris du manuel est aussi analysé. Le résultat montre que d'abord les suédophones apprennent à utiliser les verbes d'état à l'imparfait, puis les suédophones expérimentent avec l'aspect des verbes pour l’alternance entre l’imparfait et le passé composé En conclusion, l'alternance entre l'imparfait et le passé composé est un défi pour les suédophones, mais ce n'est pas un défi insurmontable. / The current piece of research is a study of how second language learners adapt to the distinction between imperfect and perfect in the narrative of past in the French language. The aim of the study is to find out how the learners adopt the grammar despite the difference between their native language and their learning language. The study describes the difference between Swedish and French. The corpus is defined, consisting of ten narratives by ten second language learners on the levels three and four in the Swedish school system. The title was Un souvenir de mon enfance. An exercise in the schoolbook is also analysed. The result shows that the students first learn how to use imperfect in sentences containing a state verb. Later the students attempt the aspect of the verb to practise the shift between the past tense and the perfect tense. In conclusion, the shift between perfect and imperfect is a challenge to the Swedish learner. However, it is not an unbridgeable gap.

Um sistema reparável opera sob uma estratégia de manutenção que exige ações de recuperação preventiva em tempos pré-definidos e ações de reparo quando ocorre a perda de função do sistema. A manutenção preventiva (MP) é programada periodicamente e muitas vezes possui um intervalo de tempo fixo para ações. No entanto, as atividades de MP podem não restaurar o sistema para uma condição similar ao início de vida deste, mas para uma situação intermediária. Nesse caso, a MP é denominada de imperfeita. Além disso, ao longo da vida do sistema, são executados diferentes planos de manutenção com condições e atividades distintas que podem afetar a intensidade de falha de diferentes maneiras. Para modelar essas características da MP em um sistema reparável, propõe-se uma nova classe de modelo de fator de melhoria, denominado fator de melhoria variável que possibilita a modelagem da situação de manutenção perfeita. A formulação da função de verossimilhança foi desenvolvida para estimação dos parâmetros bem como desenvolvidos testes de verificação da qualidade de ajuste, intervalos de confiança para os parâmetros e otimização da periodicidade de realização da MP com base no enfoque dos novos modelos propostos. Os resultados foram aplicados em dados reais e verificou-se uma parametrização mais flexível a MP imperfeita e maior versatilidade nas análises de confiabilidade do sistema quando utilizado os novos modelos. / A repairable system operates under a maintenance strategy that calls for preventive repair actions at prescheduled times and the repair actions that restore system when failure occurs. The preventive maintenance (PM) is scheduled periodically and it often holds a fixed time interval for PM actions. However, PM activities are generally imperfect and cannot restore the system to as good as new condition but to an intermediate situation, which is called imperfect PM. In addition, throughout system life are implemented diverse maintenance policies with different activities and conditions that may affect the failure intensity in different ways. To model these PM characteristics, proposes a new model class of improvement factor called variable improvement factor that also enables modeling perfect maintenance situation. The likelihood function is developed for parameter estimation as well as goodness-of-fit tests and confidence intervals for the parameters are developed, and optimization of the PM intervals based on the proposed models is presented. The proposed model was applied to a data set and a more flexible parameterization for imperfect PM and greater versatility in the system reliability analysis were verified with the use of the new model.