Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T12:55:19Z No. of bitstreams: 0 / Made available in DSpace on 2016-06-22T12:55:19Z (GMT). No. of bitstreams: 0 / O objetivo do presente trabalho foi o de estabelecer uma nova característica ao programa de Monte Carlo ESQUEMA, destinado a simular todo o processo de detecção em um sistema de coincidência 4π(β,EC)-γ e possibilitou o conhecimento antecipado do comportamento da atividade aparente da fonte radioativa como função da eficiência do detector 4π. Esta metodologia foi aplicada anteriormente para os casos onde a eficiência é variada pela colocação de absorvedores sobre a fonte radioativa ou variando-se o nível de discriminação eletrônica, com a exclusão completa das contagens abaixo deste nível. No presente trabalho, esta metodologia foi modificada com a inclusão dos eventos não coincidentes abaixo do nível de discriminação eletrônica, adotado para a via beta. Desta forma, a curva de extrapolação passa a ter um comportamento rigorosamente linear e o valor extrapolado corresponde a atividade da fonte radioativa, esperando-se obter uma melhor acurácia no seu valor. Esta alteração é inovadora e particularmente apropriada para ser aplicada ao caso de medidas com o Sistema de Coincidências por Software (SCS), desenvolvido recentemente pelo LMN. O trabalho consiste na modificação de um programa desenvolvido no LMN, denominado ESQUEMA, que leva em conta as características gerais de um esquema de desintegração complexo, incluindo-se os diversos tipos de transição, além das características experimentais do sistema de medidas por coincidência 4π(β,EC)-γ. Estas modificações permitem a obtenção das curvas de extrapolação, aplicando-se o método proposto de Discriminação com Reposição. O software MCNP5 é usado para simular o transporte de radiação. A simulação de Monte Carlo é comparada com valores experimentais para o radionuclídeo padronizados no LMN, o 111In . / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Orientador: Katia Lucchesi Cavalca Dedini / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-25T11:01:37Z (GMT). No. of bitstreams: 1 Machado_TiagoHenrique_D.pdf: 3995652 bytes, checksum: f00b87b92c83f91394b947dc2de4ccee (MD5) Previous issue date: 2014 / Resumo: Este trabalho tem como objetivo identificar os parâmetros de um modelo de desgaste em mancais hidrodinâmicos, um dos problemas típicos e inerentes ao funcionamento repetido de máquinas rotativas, o qual pode ser acentuado em partidas e paradas ou durante a passagem pela velocidade crítica do rotor. Desta forma, é proposto um modelo matemático capaz de representar este desgaste em termos de alguns de seus principais parâmetros, que para este trabalho são: profundidade máxima e posição angular. O cálculo da distribuição de pressão e, consequentemente, das forças hidrodinâmicas geradas pelo filme de óleo, é feito através do método dos volumes finitos, adaptado para situações onde o filme de óleo é descontínuo. Na modelagem do sistema rotor-mancais, o modelo do rotor é representado pelo método clássico dos elementos finitos e os mancais são aproximados por coeficientes dinâmicos de rigidez e amortecimento, a fim de representar tais efeitos inerentes ao filme de óleo. A identificação dos parâmetros característicos escolhidos para representar o desgaste é feita a partir da resposta dinâmica, em coordenadas direcionais, do sistema rotor-mancais no domínio da frequência. Esta identificação é realizada através de um método de busca que visa minimizar uma função objetivo, a qual, por sua vez, compara a resposta obtida numericamente com a resposta experimental proveniente de uma bancada de testes instrumentada. Através da comparação com os dados experimentais provenientes desta bancada, os resultados apresentados mostram que o modelo de desgaste desenvolvido neste trabalho é capaz de representar, de forma satisfatória, o comportamento de um mancal desgastado, assim como a resposta do sistema rotativo na presença desse tipo de falha. Com relação ao processo de identificação, o método de busca empregado mostra-se suficientemente robusto para identificar os parâmetros do desgaste real nas diferentes configurações empregadas nos mancais montados na bancada de testes / Abstract: The present work aims to identify the wear parameters of hydrodynamic bearings, one of the typical and inherent problems due to repeated use of rotating machineries, which can be accentuated in starts and stops or during the passage through the critical speed of the rotor. Thereby, a mathematical model capable of representing the wear in terms of its main parameters is proposed, which in the present work are the maximum depth and the angular position. The pressure distribution calculation and, consequently, the hydrodynamic forces generated by the oil film are numerically obtained by the finite volume method, adapted for situations where the oil film is discontinuous. In the rotor-bearing system modeling, the rotor model is represented by classic finite element method and the bearings are approximated by dynamic coefficients of stiffness and damping, in order to represent such inherent oil film effects. The identification of the parameters chosen to represent the wear is taken from the dynamic response, in directional coordinates, of the rotor-bearing system in the frequency domain. This identification is accomplished through a search method that aims to minimize an objective function which, in turn, compares the numerical response with the experimental response taken from an instrumented test rig. The results show that the wear model developed in this work is able to satisfactorily represent the behavior of a worn bearing, as well as the response of the rotating system in the presence of this type of failure. With respect to the identification process, the search method proves to be robust enough to identify the real wear parameters into the different configurations employed in the bearings mounted on the test rig / Doutorado / Mecanica dos Sólidos e Projeto Mecanico / Doutor em Engenharia Mecânica

Large, ever more complex, technological systems surround us and provide products and services that both construct and define much of what we consider as modern society. Our societal bargain is the trade-off between the benefits of our technologies and our constant vigilance over the safe workings and the occasional failures of these often hazardous sociotechnical systems during their operating life. Failure of a system's infrastructure, whether a complex subsystem or a single component, can cause planes to crash, oil rigs to burn, or the release of radioactivity from a nuclear power plant. To prevent catastrophes, much depends not only on skilled and safe operations, but upon the effective maintenance of these systems. Using the commercial nuclear power industry, of the United States, as a case study, this dissertation examines how nuclear power plant maintenance functions to ensure the plants are reliable and can safely operate for, potentially, eighty years; the current, government regulation defined limit, of their functional life. This study explores the history of U.S. nuclear maintenance regulatory policy from its early Cold War political precursors, the effect of the 1979 Three Mile Island reactor melt-down accident, through its long development, and finally its implementation by nuclear power licensees as formal maintenance programs. By investigating the maintenance of nuclear power plants this research also intends to expand the conceptual framework of large- technological-system (LTS) theory, in general, by adding a recognizable, and practically achievable, end-of-life (EOL) phase to the heuristic structure. The dissertation argues that maintenance is a knowledge producing technology that not only keeps a sociotechnical system operating through comprehension, but can be a surveillance instrument to make system end-of-life legible; that is both visible and understandable. With a discernible and legible view of system end-of-life, operators, policy makers, and the public can make more informed decisions concerning a system's safety and its continued usefulness in society. / Doctor of Philosophy / Large, ever more complicated, technical systems surround us and provide products and services that define much of what we consider as modern society. Our societal bargain is the trade-off between the benefits of our technologies and our constant vigilance over the safe workings and the occasional failures of these often hazardous systems during their operating life. Failure of a system's infrastructure, whether a complex subsystem or a single component, can cause planes to crash, oil rigs to burn, or the release of radioactivity from a nuclear power plant. To prevent catastrophes, much depends not only on skilled and safe operations, but upon the effective maintenance of these systems. Using the commercial nuclear power industry, of the United States, as a case study, this dissertation examines how nuclear power plant maintenance functions to ensure the plants are reliable and can safely operate for, potentially, eighty years; the current, government regulation defined limit, of their functional life. This study explores the history of U.S. nuclear maintenance regulatory policy from its early Cold War political precursors, the effect of the 1979 Three Mile Island reactor melt-down accident, through its long development, and finally its implementation by nuclear power licensees as formal maintenance programs. By investigating the maintenance of nuclear power plants this research also intends to develop a method to determine when a nuclear power plant, or other large technological system, is approaching or has reached the end of its reliable and safe operational life. The dissertation presents maintenance as a technology of knowledge that not only keeps a system operating through understanding of its components, but can be a general surveillance instrument to make system end-of- life legible. With a discernible and understandable view of end-of-life, operators, policy makers, and the public can make more informed decisions concerning a system's safety and its continued usefulness to society.

Sistemų gedimo modeliavimas paprastai vykdomas taikant taip vadinamus gedimų medžius. Sistemos gedimo tikimybės ir gedimo atsiradimo priežasčių vertinimas dažniausiai atliekamas sudarant minimalių kirtimų aibę (MCS) ir pagal ją įvertinant gedimo tikimybę. Pastaruosius dvidešimt metų tiksliam gedimo tikimybės vertinimui yra taikoma dvejetainė sprendimų diagrama (BDD). Tačiau BDD sudarymo ir taikymo metodika vis dar yra tobulinama. Iki šiol Lietuvoje sistemos gedimo tikimybės vertinimui BDD dar nebuvo taikyta. Pristatant atliktą darbą aprašomi pagrindiniai MCS ir BDD sudarymo metodai bei jų taikymo ypatybės. Taip pat pateikiamas Kauno hidroelektrinės užtvankos vartų valdymo sistemos gedimo modelis ir gedimo tikimybės vertinimas. Šiuo tikslu buvo taikomi skirtingi MCS ir BDD sudarymo metodai bei atitinkamos programinės priemonės. Atlikus bandomuosius skaičiavimus taip pat pateikiamas gautų rezultatų palyginimas. Darbe apibūdinami pagrindiniai MCS ir BDD taikymo privalumai ir trūkumai bei pristatoma naujai sukurta programinė priemonė „DemoITE“. Taikant išanalizuotus algoritmus bei sukurtą programinę priemonę „DemoITE“ buvo ištirtos ir nustatytos sistemos gedimo priežastys bei tiksliai įvertinta sistemos gedimo tikimybė. Be to, pasiūlyta bazinių įvykių rangavimo principas, įgalinantis gauti mažiausią BDD struktūrą. / Modelling of system failure usually is performed applying so-called fault trees. Assessment of system failure probability and failure occurrence causes usually is performed developing a minimal cut-set (MCS) and according to it evaluating probability of system failure. The last twenty years a binary decision diagram (BDD) has been applied for the exact evaluation of system failure. However, a methodology of creation and application of BDD is still under development. Till now in Lithuania for the assessment of system failure probability BDD has not been applied yet. Presenting a performed work the main methods of development of MCS and BDD as well as features of their application is described. Also, the model and assessment of failure of Kaunas hydropower dam gates’ control system is presented. For this task the different methods of development of MCS and BDD as well as corresponding software was applied. Having performed the testing calculations a comparison of results is presented too. In the work the main advantages and disadvantages of MCS and BDD application are described and newly created software “DemoITE” is introduced. The developed algorithms and universal software “DemoITE” is used for visualization of failure causes and for exact estimation of the investigated system failure probability. Also, it is proposed the order of basic events on purpose to design the least BDD.

<p>I ulykkessammenheng går to av de vanligste undersøkelsesmetodene ut på henholdsvis å kartlegge det juridiske ansvaret for ulykken og å klarlegge årsaksforholdene. I media får vi stort sett bare høre om førstnevnte i form av oppslag om at ulykken skyldes menneskelig svikt. Årsaksforholdene tar gjerne lengre tid å kartlegge og har heller ikke elementer av helt eller syndebukk i seg, og er således mindre interessante å skrive om. I forebyggende sammenheng er det likevel gjerne her det er mest å hente. I erkjennelsen av at mennesket er og blir feilbarlig, bør man nettopp gripe tak i disse bakenforliggende årsakene, gjerne kalt latente feil, som også kan medvirke til å avverge at et tilløp får lov å utvikle seg til en ulykke. I denne oppgaven blir det gjort rede for bakenforliggende årsaker til en alvorlig samferdselsulykke på Vestlandet i 1999, nemlig hurtigbåten MS Sleipners forlis. Det blir også vist hvordan ulykken kunne vært unngått, eller i det minste at skadeomfanget kunne vært vesentlig redusert, dersom det hadde vært større fokus på å avdekke slike latente forhold. For å få offentligheten til å forstå viktigheten av slik årsakskartlegging, og ikke minst at ansvarlige instanser følger opp funnene i ettertid, er det viktig at media griper fatt i problemstillingen og setter den på dagsorden.</p> / <p>Two of the most common forms of investigations after accidents are the search for the judicial aspects of guilt on the one hand and the investigation to find the causes of the accident on the other hand. Media mainly tell us the result of the first one, namely that “the cause of the accident was human error”. Usually it takes more time to establish an understanding of the underlying causes. This investigation does not point out a hero, neither a scapegoat. Therefore the real causes are less interesting to the media. Still, when it comes to accident prevention, this is where one should make an effort. By recognizing the fact that humans are eligible to fail, it is here one should try to take preventive measures. By recognizing these latent conditions one may succeed to avoid potentially dangerous situations from developing to serious accidents. In this paper the underlying causes related to a serious accident that struck public transportation in Western Norway will be presented. The accident is the shipwreck of the high speed craft MS Sleipner in 1999. It will also be shown how this accident could have been prevented, or at least how the extent of the damage could have been substantially reduced, if only latent conditions had been paid a little more attention to. To make the general public understand the importance of uncovering such latent conditions, not to say make sure that they who are responsible take action to remove these conditions, it is vital that the media put these questions on the agenda.</p>

Systems can become misconfigured for a variety of reasons such as operator errors or buggy patches. When a misconfiguration is discovered, usually the first order of business is to restore availability, often by undoing the misconfiguration. To simplify this task, we propose Ocasta to automatically determine which files contain configuration state. Ocasta uses a novel {\em similarity} metric to measures how similar a file's versions are to each other, and a set of filters to eliminate non-persistent files from consideration. These two mechanisms enable Ocasta to identify all 72 configuration files out of 2363 versioned files from 6 common applications in two user traces, while mistaking only 33 non-configuration files as configuration files. Ocasta allows a versioning file system to eliminate roughly 66\% of non-configuration file versions from its logs, thus reducing the number of file versions that a user must manually examine to recover from a misconfiguration.

Systems can become misconfigured for a variety of reasons such as operator errors or buggy patches. When a misconfiguration is discovered, usually the first order of business is to restore availability, often by undoing the misconfiguration. To simplify this task, we propose Ocasta to automatically determine which files contain configuration state. Ocasta uses a novel {\em similarity} metric to measures how similar a file's versions are to each other, and a set of filters to eliminate non-persistent files from consideration. These two mechanisms enable Ocasta to identify all 72 configuration files out of 2363 versioned files from 6 common applications in two user traces, while mistaking only 33 non-configuration files as configuration files. Ocasta allows a versioning file system to eliminate roughly 66\% of non-configuration file versions from its logs, thus reducing the number of file versions that a user must manually examine to recover from a misconfiguration.

The successful elimination of the Y2K vulnerability from the information technology (IT) systems of a large, complex critical sector organization provided a model to study how organizations contend with problems affecting the security of electronically stored and transmitted information, and how context influences their solutions. This dissertation proposed that the institutionalized environments of sub-unit business areas influenced compliance solutions during the Year 2000 Program process at Delta Air Lines, Inc. The investigation applied rival organization theories. A comparative case study method was employed to explain the Y2K compliance solutions of four business areas as embedded sub-cases. Data for the study were the Delta Year 2000 Program archive, and personal interviews with individuals related to the Delta Year 2000 Program. Data analysis revealed characteristics of both the institutional and the rational-contingency models. Case results showed that: * A positive relationship among entities in the sectoral environment benefited the air transportation field in addressing the Y2K problem. In this cooperative setting, addressing common issues in one place helped a vast network of related organizations. Recognizing that all were stakeholders made it work. * Business area decisions were influenced by the institutionalized environments of their respective fields. * The Year 2000 Program team lacked awareness that the Y2K bug was an information security issue. * In the process of eliminating the Y2K bug from the Delta systems, new vulnerabilities were introduced. While tradeoffs are always required among security, functionality, and efficiency within the IT structures and systems of the present time, this negative effect might have been anticipated; but it was not. * The success of this complex, short-term project at Delta underscored the importance of leadership, understanding of IT, vision, motivation, IT skills, understanding of assets, and appropriate strategy. The Delta case study contributes to the fields of information security and organization studies. Results have implications for policymaking and for future research in the field of information security.

I ulykkessammenheng går to av de vanligste undersøkelsesmetodene ut på henholdsvis å kartlegge det juridiske ansvaret for ulykken og å klarlegge årsaksforholdene. I media får vi stort sett bare høre om førstnevnte i form av oppslag om at ulykken skyldes menneskelig svikt. Årsaksforholdene tar gjerne lengre tid å kartlegge og har heller ikke elementer av helt eller syndebukk i seg, og er således mindre interessante å skrive om. I forebyggende sammenheng er det likevel gjerne her det er mest å hente. I erkjennelsen av at mennesket er og blir feilbarlig, bør man nettopp gripe tak i disse bakenforliggende årsakene, gjerne kalt latente feil, som også kan medvirke til å avverge at et tilløp får lov å utvikle seg til en ulykke. I denne oppgaven blir det gjort rede for bakenforliggende årsaker til en alvorlig samferdselsulykke på Vestlandet i 1999, nemlig hurtigbåten MS Sleipners forlis. Det blir også vist hvordan ulykken kunne vært unngått, eller i det minste at skadeomfanget kunne vært vesentlig redusert, dersom det hadde vært større fokus på å avdekke slike latente forhold. For å få offentligheten til å forstå viktigheten av slik årsakskartlegging, og ikke minst at ansvarlige instanser følger opp funnene i ettertid, er det viktig at media griper fatt i problemstillingen og setter den på dagsorden. / Two of the most common forms of investigations after accidents are the search for the judicial aspects of guilt on the one hand and the investigation to find the causes of the accident on the other hand. Media mainly tell us the result of the first one, namely that “the cause of the accident was human error”. Usually it takes more time to establish an understanding of the underlying causes. This investigation does not point out a hero, neither a scapegoat. Therefore the real causes are less interesting to the media. Still, when it comes to accident prevention, this is where one should make an effort. By recognizing the fact that humans are eligible to fail, it is here one should try to take preventive measures. By recognizing these latent conditions one may succeed to avoid potentially dangerous situations from developing to serious accidents. In this paper the underlying causes related to a serious accident that struck public transportation in Western Norway will be presented. The accident is the shipwreck of the high speed craft MS Sleipner in 1999. It will also be shown how this accident could have been prevented, or at least how the extent of the damage could have been substantially reduced, if only latent conditions had been paid a little more attention to. To make the general public understand the importance of uncovering such latent conditions, not to say make sure that they who are responsible take action to remove these conditions, it is vital that the media put these questions on the agenda.

Orientadores: Flávio Vasconcelos da Silva, Luís Cláudio Oliveira Lopes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-24T13:32:43Z (GMT). No. of bitstreams: 1 Costa_ThiagoVazda_D.pdf: 18980163 bytes, checksum: 01508b929c51cbd2ad88d0be37d75084 (MD5) Previous issue date: 2014 / Resumo: A consideração sistemática relacionada ao tratamento de falhas na estrutura de controle é essencial para se atingir as metas de um processo ao mesmo tempo seguro e produtivo. Nesse sentido, este trabalho propõe o estudo e a implementação de técnicas baseadas no controle reconfigurável com aplicações em processos químicos. Essa técnica está relacionada à etapa que lida com a falha no sistema em malha fechada, por meio de sua reconfiguração, evitando a evolução dos seus efeitos na estrutura de controle. Nesse estudo, a atenção é voltada ao rastreamento do comportamento nominal do sistema considerando as técnicas baseadas nos atuadores virtuais. O método considera o desvio da planta em relação ao seu comportamento nominal na presença de falhas em seus atuadores. Deste modo, se o distanciamento em relação ao comportamento nominal pode ser estabilizado por meio das redundâncias físicas e analíticas presentes no processo, o comportamento da planta sujeita à falha também pode ser estabilizado. Neste sentido, uma consideração sobre esse desvio no futuro é proposta, permitindo que técnicas baseadas no controle ótimo e preditivo sejam utilizadas. São consideradas especificamente falhas que comprometam o desempenho do processo quando existe a perda total ou parcial de suas variáveis de entrada. Com os componentes comprometidos devidamente localizados, a redistribuição dos sinais de controle da planta é encaminhada para que a estabilidade e desempenho do processo sejam assegurados. A concepção do atuador virtual com horizonte móvel possibilita o uso de técnicas de otimização, permitindo que as informações referentes às características físicas das redundâncias do processo sejam incluídas, evitando a saturação dos componentes utilizados durante o tratamento da falha. A validação da técnica proposta é avaliada experimentalmente em um processo de neutralização, no qual ferramentas de injeção de falhas são capazes de simular os efeitos de falha dos atuadores no processo real. As estratégias estudadas foram implementadas em um software em código aberto e foram testadas experimentalmente a partir do uso de comunicação OPC (Object Linking and Embedding for Process Control). Cenários com diferentes falhas afetando os atuadores do processo foram concebidos e avaliados. Em todos os estudos, observou-se a capacidade da ferramenta em efetuar a reconfiguração do sistema em malha fechada para mitigar os efeitos indesejáveis da falha. Com base nos resultados, conclui-se que a utilização das técnicas em cenários industriais é viável e pode garantir a operação estável do processo mesmo quando surjam falhas em seus componentes, consideradas as condições de controlabilidade e estabilizabilidade do sistema / Abstract: A systematic approach to fault handling in control loops is important to achieve safe and productive process goals. Therefore, the present work proposes the study and implementation of reconfigurable control methods with applications in chemical processes. This technique is related to the fault handling stage in the closed loop system by means of reconfiguration, preventing the progression of fault effects in the control structure. In this study, particular focus is given to virtual actuator based techniques for tracking nominal system behavior. The method considers the deviation of the plant in relation to its nominal behavior when there are faults in its actuators. Therefore, if the nonconformity from the nominal response can be stabilized using the process physical and analytical redundancies, the faulty plant behavior can also be stabilized. Hence, it is proposed the use of the deviation from the nominal system response in the future, enabling the use of optimal and predictive control techniques. Faults affecting process performance due to total or partial loss of input variables are particularly considered. Once the faulty components are located, input signal redistribution is determined in order to ensure process performance and stability. The moving horizon virtual actuator proposal provides the use of optimization techniques allowing information about physical characteristics of the process redundancies to be included, avoiding component saturation during the fault handling approach. The validation of the technique is performed experimentally in a neutralization process, in which fault injection tools are able to simulate the effects of actuators faults in the real process. The studied strategies were implemented using open-source software and tested experimentally by means of an OPC (Object Linking and Embedding for Process Control) communication. Several fault scenarios considering actuator faults were planned and fulfilled for evaluation. The experimental tests showed that the proposed framework is capable of performing closed loop system reconfiguration to mitigate undesirable fault effects. Based on the results, it is concluded that using such a technique in industrial scenarios is feasible and can guarantee stable process operation even when there are faults in its components, considering system controllability and stabilizability conditions / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química