O setor aeroportuário apresentou forte crescimento nos últimos anos, ressaltando as ineficiências na gestão de sua infraestrutura e de seus ativos, especialmente no Brasil. Assim, com a exaustão das técnicas tradicionais para a redução de custos, as empresas necessitam buscar melhorias apoiadas no uso de métodos mais complexos a fim de aumentar a produtividade de seus ativos. Desta forma, desponta a necessidade de modelos para a identificação da vida útil e análise da substituição econômica de ativos, uma vez que estas informações auxiliam na tomada de decisão e conduzem a melhores planos de manutenção, reduzindo as perdas do processo. Assim sendo, este trabalho tem por objetivo propor e aplicar uma sistemática para avaliação da substituição de ativos no setor aeroportuário, apoiado em modelos adequados às especificidades do setor através do estudo das suas variáveis. Para isto, são identificados os elementos que influenciam na vida útil dos ativos e, posteriormente, modelos de identificação de vida útil e substituição econômica de ativos são propostos e aplicados em um aeroporto brasileiro de grande porte. Pode-se concluir que a sistemática produziu resultados consistentes e que auxiliam a decisão de substituição de ativos de uma forma estruturada. / In the past years, an increase in aviation transport can be noticed and it highlights inefficiencies in asset management, especially in Brazil. Hence, the exhaustion of traditional techniques to cost reduction lead companies to seek improvements supported by more complex methods in order to increase productivity of their assets. Thus, it is crucial to develop models for useful life identification and economic replacement of assets, since these information assist the decision making process and lead to better maintenance plans, reducing wastage. As a result, the main objective of this work is develop and apply a systematic for evaluation of asset replacement in airports, supported by models that consider the specificities of the aviation sector and its particular variables. In this direction, elements that influence assets useful life are identified and, then, models for useful life identification and economic replacement of assets are developed and applied in an important Brazilian airport. It can be concluded that the systematic have produced consistent results and can assist in asset replacement decision in a structured form.

Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós-Graduação em Engenharia Oceânica, Escola de Engenharia, 2009. / Submitted by Lilian M. Silva (lilianmadeirasilva@hotmail.com) on 2013-04-20T20:31:09Z No. of bitstreams: 1 Estudo de viabilidade de empreendimento sob a ótica da vida útil O caso sobre a modernização do Porto Novo do Rio Grande – RS.pdf: 4308697 bytes, checksum: 19733200872e44b346c9b760ca0923d0 (MD5) / Approved for entry into archive by Bruna Vieira(bruninha_vieira@ibest.com.br) on 2013-06-04T16:55:51Z (GMT) No. of bitstreams: 1 Estudo de viabilidade de empreendimento sob a ótica da vida útil O caso sobre a modernização do Porto Novo do Rio Grande – RS.pdf: 4308697 bytes, checksum: 19733200872e44b346c9b760ca0923d0 (MD5) / Made available in DSpace on 2013-06-04T16:55:51Z (GMT). No. of bitstreams: 1 Estudo de viabilidade de empreendimento sob a ótica da vida útil O caso sobre a modernização do Porto Novo do Rio Grande – RS.pdf: 4308697 bytes, checksum: 19733200872e44b346c9b760ca0923d0 (MD5) Previous issue date: 2009 / A identificação do estado de conservação e manutenção, bem como, do obsoletismo funcional do cais do Porto Novo do Rio Grande, permitiu traçar diretrizes para a realização das obras de modernização desta estrutura. Em razãodo tipo de navios que atualmente navegam na costa brasileira, o projeto de modernização prevê a adequação dos berços de atracação e aprofundamento do calado, na linha próxima ao cais. O estudo da viabilidade para realizar tal empreendimento encontra-se alicerçado no potencial de funcionamento, ou seja, vida econômica e vida útil. Este trabalho apresenta relação entre a vida útil das estruturas de concreto, inseridas em ambientes marítimos, e os indicadores de viabilidade para este tempo de vida. São apresentadas as possibilidades de modernizar ou reabilitar cais com muro de gravidade, bem como, os fatores preponderantes na durabilidade de uma estrutura de concreto, como distância da água do mar, permitindo traçar estimativas quanto a vida útil destas estruturas. Estas estimativas estão baseadas, basicamente, no ambiente no qual estão inseridas e nas especificações de projeto como, cobrimento das armaduras e resistência característica do concreto. Foi observado um ganho considerável na vida útil da estrutura ao adotar-se a especificação do concreto com resistências características à compressão (fck) superiores. A partir desta premissa, o estudo dos indicadores de viabilidade foi baseado em duas possibilidades de horizontes: valor do investimento inicial com especificações do projeto utilizando fckigual a 35 MPa, com estimativa de vida útil de 56 anos e, alternativamente, o valor do custo do concreto com fck igual a 40 MPa agregado ao investimento, para o horizonte de 76 anos. Diante do panorama econômico e das séries históricas analisadas que compreendem o volume e tipo de cargas, número de embarcações que utilizam o cais e, das principais cargas movimentadas, foi identificado o volume anual e a mercadoria com maior movimentação, que corresponde a fertilizantes. A partir destas constatações, realizou-se o levantamento provável de despesas e receitas decorrentes da operação exclusiva no cais, compondo o fluxo de caixa do empreendimento, com cenário provável, pessimista e otimista. Os indicadores de viabilidade analisados foram: Valor Presente Líquido, Taxa Interna de Retorno, Índice de Lucratividade e Pay-back. As incertezas e riscos foram analisados através da geração analítica e numérica do VPL, fornecendo parâmetros para a tomada de decisão, com indicativo de viabilidade para a realização dasobras de recuperação e modernização do cais do Porto Novo do Rio Grande no horizonte de 76 anos. / The identification of the state of conservation andmaintenance as well as the functional obsoletism of the dock of Porto Novo do Rio Grande, allowed establish guidelines in order to perform the modernization work of this structure. Because of the type of vessels currently sailing along the Brazilian coast, the modernization project foresees the adequacy of the berthing cradles and deepening the draft in line next to the pier. The study of the feasibility to undertake such enterprise is based on the functioning potential, that is, economic and useful life. This paper presents relationship between the life of concrete structures, inserted in the marine environment, and indicators of viability for this time of life. The opportunities to upgrade or rehabilitate pier with gravity wall are presented as well as the predominant factors in the durability of a concretestructure, such as distance from the sea, allowing trace estimates of useful life of these structures. These estimates are based, basically, on the environment in which they are inserted and the project specifications, such as armor cover and the characteristic strength of concrete. It was observed a considerable gain in the lifetime of the structure by adopting the concrete specification with higher characteristic strength (fck). From this premise, the study of indicators of viability was based on two types of horizons: value of initial investment with the project specifications using fckequal to 35 MPa, estimated useful life of 56 years and, alternatively, the cost value of the concrete with fck equal to 40 MPa aggregated to the investment, for the horizon of 76 years. Considering the economic outlook and the analyzed historical seriesthat comprises the volume and type of loads, number of vessels using the wharf and the main cargo handled, the annual volume and the goods with more movement were identified, whichis fertilizer. From these findings, a survey of likely income and expenditure arising from the exclusive operation on the pier was undertaken, comprising the cash flow of the enterprise, with probable, pessimistic and optimistic scenario. The analyzed indicators of feasibility were: Net Present Value, Internal Rate of Return, Profitability Index and Pay-back. The uncertainties and risks were analyzed through the analytical and numerical generation of NPV, providing parameters for the decision, with an indication of viability to perform the works of rehabilitation and upgrading of Porto Novo Rio Grande's pier on the horizon of 76 years.

This thesis focuses on obtaining better estimates of remaining life for on-condition (OC) parts in aircraft engines. Aircraft engine components are commonly classified into three categories, life-limited parts (LLP), OC-parts and consumables. Engine maintenance typi-cally accounts for 10% to 20% of aircraft-related operating cost. Current methods to esti-mate remaining life for OC parts have been found insufficient and this thesis aims to devel-op a method that obtains better life estimates of OC part. Improved life estimates are es-sential to facilitate more reliable maintenance plans and lower maintenance costs. In the thesis, OC parts that need a better life estimates are identified and suitable prognosis methodologies for estimating the remaining life are presented. Three papers are appended to the thesis. The first paper lays out the main principles of air-craft engine maintenance and identifies the potential for improving maintenance planning by improving the remaining life estimation for the OC parts. The paper concludes that re-search is needed to find better estimates so that the right amount of maintenance is per-formed at each maintenance occasion. The second paper describes the aircraft and its engine from a system of system perspective. The aim of the paper is to show that no system is stronger than its weakest part and that there is a potential to increase the availability and readiness of the complete system, the aircraft engine, by introducing better life estimates for OC parts. Furthermore, a review of all engine parts, no matter if they are life-limited or on-condition, which needs to be incor-porated in a replacement model for maintenance optimization, is given. The paper con-cludes that the reliability of the complete aircraft engine would be increased if better life estimates are presented also for the OC parts. The third paper includes an evolved analysis of the subject and the analysis moves deeper in to a subsystem/module of the engine, the low pressure turbine. The specific subsys-tem/module is further analyzed to show the potential of increased reliability for the subsys-tem/module and the complete system, the aircraft engine, if better life estimates for the OC parts are obtained. Methods on how to estimate remaining life is discussed in this paper. It is stated that life estimates can be based on visual inspections, available testing methods (e.g. non destructive testing ) or new techniques that may be need to be developed based on remaining useful life estimations. To estimate the remaining life for the OC parts well es-tablished prognostic techniques such as physic-based, data-driven, symbolic, hybrid, or context awareness approaches that combine contextual/situation information awareness will be considered.

No description available.

No description available.

Ces dernières années ont vu apparaître sur le marché les premiers transistors de puissance de type MOSFET en carbure de silicium. Ce type de composant est particulièrement adapté à la réalisation d’équipement électrique à haut rendement et capable de fonctionner à haute température. Néanmoins, la question de la fiabilité doit être posée avant de pouvoir envisager la mise en œuvre de ces composants dans des applications aéronautiques ou spatiales. Les mécanismes de défaillance liés à l’oxyde de grille ont pendant longtemps retardé la mise sur le marché des transistors à grille isolée en carbure de silicium. Cette étude s’attache donc à estimer la durée de vie des MOSFET SiC de 1ére génération. Dans un premier temps, le mécanisme connu sous le nom de Time Dependent Dielectric Breakdown(TDDB) a été étudié au travers de résultats expérimentaux issus de la bibliographie. Notre analyse nous a permis de justifier de l’emploi d’une loi de Weibull pour modéliser la distribution des temps à défaillance issue de ces tests. Les résultats nous ont également permis de confirmer l’amélioration significative de la fiabilité de ces structures vis-à-vis de ce mécanisme. Dans un second temps, l’impact du mécanisme d’instabilité de la tension de seuil sur la fiabilité a été quantifié au travers de tests de vieillissement de type HTGB. Les données de dégradation ainsi collectées ont été modélisées à l’aide d’un processus gamma non-homogène, qui nous a permis de prendre en compte la variabilité entre les composants testés dans des conditions identiques et de proposer des facteurs d’accélération en tension et en température pour ce mécanisme. Enfin, ces travaux ont permis d’ouvrir la voie à la mise en œuvre d’outils de pronostic de la durée de vie résiduelle pour les équipements électriques. / Recent years have seen SiC MOSFET reach the industrial market. This type of device is particularly adapted to the design of power electronics equipment with high efficiency and high reliability capable to operate in high ambient temperature. Nevertheless the question of the SiC MOSFET reliability has to be addressed prior to considering the implementation of such devices in an aeronautic application. The failure mechanisms linked to the gate oxide of the SiC MOSFET have for a long time prevented the introduction of the device. In this manuscript we propose to study the reliability of the first generation of SiC MOSFET. First, the mechanism known as the Time–Dependent Dielectric Breakdown is studied through experimental results extracted from literature. Our study shows the successful application of a Weibull law to model the time-to-failure distribution extracted from the accelerated tests. The results show also a significant improvement of the SiC MOSFET structure with respect to this phenomenon. In a second step, the impact of the threshold voltage instability is quantified through accelerated tests known as High Temperature Gate Bias. The collected degradation data are modeled using a non-homogeneous Gamma process. This approach allows taking into account the variability between devices tested under the same conditions. Acceleration factors have been proposed with respect to temperature and gate voltage. Eventually the study delivers a primary estimation of the remaining useful lifetime of the SiC MOSFET in a typical aeronautic application.

O principal objetivo desta pesquisa é determinar o custo operacional e o ponto de renovação da frota de tratores agrícolas de pneus de uma empresa agropecuária, utilizando-se os dados dos dispêndios do uso de 39 tratores, entre os anos de 1983 e 1998. Aplicou-se o método do custo anualizado equivalente (CAE), pelo qual é possível determinar-se a idade de substituição dos tratores, a partir do custo operacional e do fluxo de caixa de cada trator. A análise dos resultados obtidos permitiu concluir que dentre os custos operacionais as despesas com reparos e manutenção são as mais elevadas o que pode ser atribuído às altas horas de trabalho acumuladas, tornando antieconômica a utilização da máquina na empresa. Os valores calculados através do custo anualizado equivalente (CAE), apresentaram resultados maiores que os calculados pelo custo operacional. A diferença fundamental entre os dois métodos de cálculo está no CAE que considera uma remuneração ao capital utilizando a taxa de desconto do fluxo de caixa. O método do custo anualizado equivalente, mostrou-se eficiente na análise da vida econômica de tratores e na determinação do ponto de substituição de frotas, pois permite a substituição da máquina antes que ocorram as despesas mais altas com a mesma. Caso contrário, a perda de capital provocada pela diminuição do valor presente do valor residual, calculado pelo CAE, pode inviabilizar o uso econômico da máquina. Verificou-se com a aplicação do CAE que a idade de substituição de uma máquina depende do valor de inicial, das despesas anuais com o trator, de valor de revenda em cada ano e da taxa de desconto. Especificamente para esta empresa verificou-se que a idade economicamente ótima de troca situou-se entre quatro e cinco anos de vida útil do trator. / The main objective of the present study was to determine the operational cost and the fleet renewal point of agricultural tractors of tires for an agricultural company, which provided data on expenditures for the use of 39 tractors, from 1983 to 1998. The computation took in account the yearly cost equivalent method (CAE), which allowed to determine the tractor substitution age , starting from the operational cost and from the cash flow of each tractor. The analysis results analysis showed that the greater item in the operational costs is the expenses with repairs and maintenance which can be attributed to the greater accumulated working hours, so far it may make not profitable the use of the machine in the company. The CAE method values showed bigger values than the operational cost method values (OC). The fundamental difference among them is that CAE considers a remuneration to the capital using the cash flow discount tax. Also , the CAE method was more efficient in the analysis of the tractor economical life and in the determination of the fleet substitution point, so it allowed the substitution of the machine before higher expenses might occur. Otherwise, the capital loss provoked by the decrease of the present value of the residual value, computed by CAE, would make unfeasible the economical use of the machine. Also ,the present study showed that the age of substitution of a machine depends on the initial value, on the annual expenses with the tractor, on the value of resale in every year and on the discount tax. Specifically for this company, it was verified that the economical age to change a vehicle is between four or five years of useful life of the tractor.

O principal objetivo desta pesquisa é determinar o custo operacional e o ponto de renovação da frota de tratores agrícolas de pneus de uma empresa agropecuária, utilizando-se os dados dos dispêndios do uso de 39 tratores, entre os anos de 1983 e 1998. Aplicou-se o método do custo anualizado equivalente (CAE), pelo qual é possível determinar-se a idade de substituição dos tratores, a partir do custo operacional e do fluxo de caixa de cada trator. A análise dos resultados obtidos permitiu concluir que dentre os custos operacionais as despesas com reparos e manutenção são as mais elevadas o que pode ser atribuído às altas horas de trabalho acumuladas, tornando antieconômica a utilização da máquina na empresa. Os valores calculados através do custo anualizado equivalente (CAE), apresentaram resultados maiores que os calculados pelo custo operacional. A diferença fundamental entre os dois métodos de cálculo está no CAE que considera uma remuneração ao capital utilizando a taxa de desconto do fluxo de caixa. O método do custo anualizado equivalente, mostrou-se eficiente na análise da vida econômica de tratores e na determinação do ponto de substituição de frotas, pois permite a substituição da máquina antes que ocorram as despesas mais altas com a mesma. Caso contrário, a perda de capital provocada pela diminuição do valor presente do valor residual, calculado pelo CAE, pode inviabilizar o uso econômico da máquina. Verificou-se com a aplicação do CAE que a idade de substituição de uma máquina depende do valor de inicial, das despesas anuais com o trator, de valor de revenda em cada ano e da taxa de desconto. Especificamente para esta empresa verificou-se que a idade economicamente ótima de troca situou-se entre quatro e cinco anos de vida útil do trator. / The main objective of the present study was to determine the operational cost and the fleet renewal point of agricultural tractors of tires for an agricultural company, which provided data on expenditures for the use of 39 tractors, from 1983 to 1998. The computation took in account the yearly cost equivalent method (CAE), which allowed to determine the tractor substitution age , starting from the operational cost and from the cash flow of each tractor. The analysis results analysis showed that the greater item in the operational costs is the expenses with repairs and maintenance which can be attributed to the greater accumulated working hours, so far it may make not profitable the use of the machine in the company. The CAE method values showed bigger values than the operational cost method values (OC). The fundamental difference among them is that CAE considers a remuneration to the capital using the cash flow discount tax. Also , the CAE method was more efficient in the analysis of the tractor economical life and in the determination of the fleet substitution point, so it allowed the substitution of the machine before higher expenses might occur. Otherwise, the capital loss provoked by the decrease of the present value of the residual value, computed by CAE, would make unfeasible the economical use of the machine. Also ,the present study showed that the age of substitution of a machine depends on the initial value, on the annual expenses with the tractor, on the value of resale in every year and on the discount tax. Specifically for this company, it was verified that the economical age to change a vehicle is between four or five years of useful life of the tractor.

O objetivo principal deste trabalho é a análise e possível otimização de um projeto de válvulas de esfera. É apresentado um estudo para determinação do torque de acionamento de válvulas de esfera industriais, bem como um estudo de vida útil das válvulas. Os estudos foram realizados utilizando projeto de experimentos e permitiram a construção de modelos de previsão de torque e de previsão de vida útil. A previsão de torque é fundamental para possibilitar a otimização do projeto das válvulas, na fase de desenvolvimento do produto. O uso dos modelos permitiu a determinação do ajuste ótimo, levando em conta pressão, temperatura, esmagamento das sedes, torque de aperto na porca da haste e torque de acionamento desejado. Já os estudos de vida útil são importantes para informar à empresa o número de ciclos até o vazamento. Os resultados do estudo, realizado através de ensaios acelerados, permitiram a construção de modelos de confiabilidade associada ao número de ciclos de operação, permitindo assim a avaliação e possível melhoria do projeto das válvulas. / The main objective of this dissertation is the analysis and optimization of a ball valve project. A study for determining the operational torque of industrial ball valves as well as a life study of valves are presented. The studies were performed using design of experiments and allowed the construction of torque and life prevision models. The prevision of torque is fundamental to enable project optimization on the phase of product development. Results allowed the definition of an optimal setting regarding pressure, temperature, seats tightening, stem nut tightening torque and the desired operational torque. Further, the life studies are helpful to inform the company the number of cycles until leakage. Results, obtained through accelerated tests, allowed the construction of reliability models associated to the number of operational cycles, conducting to valve design evaluation and optimization.

In the year of 2000 the European Commission adopted a communication called EU Financial Reporting Strategy: the Way Forward. The communication intended to make all listed companies within the EU arrange their financial statements in accordance with International Accounting Standards by 2005 at the latest. When the amendments of IFRS 3 was introduced in March 2004 it meant that companies from that moment on, when acquiring another company, have to allocate the part of the purchase price assignable to customer contracts and the related customer relationships as an intangible asset. IFRS 3 does not give any guidance whatsoever on how to accomplish the above described allocation and estimate a true and fair value of customer contracts and relationships. Let alone any direction regarding the establishment of the remaining useful life of the customer relationships and contracts, which constitutes the foundation of the fair valuation but also a true and fair view regarding amortizations. The purpose of this thesis is to examine how the establishments regarding remaining useful life of customer relationships and contracts have been done. Furthermore, the purpose of this thesis is to explain the decision process and motives that results in why management choose to apply the specific remaining useful life of customer relationships and contracts they do. This study has been carried out with a qualitative approach involving two listed group companies within three different industries, hence, six companies are involved in this thesis. Semi-structured telephone interviews have been made with the companies and the annual reports have been examined. In order to explain the actions behind the valuation and establishment process, the positive accounting theory has been used. None of the six companies taking part in this study have applied an outspoken method for the establishment of the remaining useful life of the customer relationships and contracts and only half of the companies have identified different customer groups. A relation can be identified between using an external consultant and applying different remaining lives for different customer groups. All companies amortize the customer relationships and contracts on a straight-line basis. This can be explained by the positive accounting theory to some extent. All companies applied straight-line amortization even though some of them actually admit that a declining balance would provide a fairer view. Furthermore, long amortization plans are used in some companies in order to decrease the amortization costs and hence increase the net income. Positive accounting has been applied in order to shift reported earnings. / Under år 2000 beslutade den Europeiska kommissionen om att anta ett förslag som hette EU Financial Reporting Strategy: the Way Forward. Antagandet av förslaget innebar att alla noterade bolag inom EU skulle presentera sin redovisning och sina årsredovisningar i linje med bestämmelserna i IAS – International Accounting Standards senast år 2005. När lagändringarna i IFRS 3 introducerades i mars 2004 innebar det att noterade bolag vid företagsförvärv fortsättningsvis skulle allokera den del av köpeskillingen som är hänförlig till kundkontrakt och relaterade kundrelationer som immateriell tillgång i balansräkningen. IFRS 3 ger ingen vägledning överhuvudtaget med avseende på hur bolagen ska genomföra den ovan beskrivna allokeringen och uppskatta ett rättvist värde på kundkontrakt och kundrelationer. Inte heller finns det någon anvisning angående fastställandet av livslängd på kundkontrakt och kundrelationer som i sin tur ligger till grund för en rättvis värdering och en rättvis avskrivningsplan. Syftet med den här uppsatsen är att undersöka hur fastställandet av livslängden på kundrelationer och kundkontrakt har utförts. Syftet är även att förklara beslutsprocessen och de bakomliggande motiven till varför företagsledningen väljer att använda den livslängd på kundrelationer och kundkontrakt de faktiskt gör. Studien har genomförts med en kvalitativ ansats som har involverat två noterade koncernbolag inom tre olika branscher, totalt har alltså sex bolag medverkat i uppsatsen. Semistrukturerade telefonintervjuer har gjorts med de involverade bolagen och även deras årsredovisningar har undersökts. För att kunna förklara handlandet angående värderingsprocessen och livslängdsprocessen har den positiva redovisningsteorin använts. Inget av de sex bolagen som medverkat i studien har använt sig av någon etablerad metod för att fastställa den återstående livslängden av kundrelationerna och kundkontrakten, och endast hälften av företagen har identifierat olika grupper av kunder. Ett samband har identifierats mellan att använda sig av en extern konsult vid fastställandet och att använda sig av olika återstående livslängder för olika kundgrupper. Alla sex företagen använder sig av linjär avskrivning på kundkontrakten och kundrelationerna. Detta kan till en viss gräns förklaras med positiv redovisningsteori. Alla företagen har använt sig av linjär avskrivning även om vissa av företagen till och med medger att degressiv avskrivning skulle ge en mer rättvis bild. Dessutom har långa avskrivningstider använts i en del av företagen för att sänka avskrivningskostnaderna som i sin tur ökar resultatet. Positiv redovisningsteori har alltså använts för att flytta vinster till innevarande år.