[pt] A perfuração de camadas espessas de sal para exploração do pré-sal brasileiro desafia a geomecânica no aprimoramento da modelagem computacional dessas rochas. Previsões acuradas podem evitar problemas operacionais na perfuração, desde a necessidade excessiva de repasses até a prisão da coluna de perfuração, ou mesmo a perda do poço. O comportamento mecânico das rochas salinas é diferente daquele geralmente descrito pela mecânica das rochas tradicional. A compreensão do fenômeno da fluência constitui um embasamento conceitual indispensável para simulações numéricas nessas rochas. Foram apresentadas metodologias para simulação do comportamento à fluência de rochas salinas adotando o programa comercial de elementos finitos ABAQUS. Três modelos constitutivos para fluência baseados em leis de potência foram testados em simulações de ensaios triaxiais de fluência, galeria de mineração e poços revestidos e não revestidos. Destaca-se o primeiro esforço no intuito de calibrar e validar o Modelo de Multi Mecanismo de Deformação para aplicação em halita brasileira. Além disso, é apresentada uma metodologia para análises probabilísticas de fechamento de poço e de plastificação de revestimento. O programa NESSUS foi adotado e métodos de confiabilidade de Valor Médio foram empregados. Um modelo transversal de poço revestido típico do cenário do pré-sal brasileiro é considerado. Para ambos os eventos e modelos constitutivos, resultados determinísticos estão associados à probabilidade de falha de 40 por cento. As variáveis de maior importância nas análises de fluência em rochas salinas são aquelas relacionadas ao estado de tensão, temperatura e a fluência secundária. Por fim, ressalta-se o excelente desempenho do Modelo de Multi Mecanismo de Deformação nas simulações numéricas realizadas nesta pesquisa. / [en] Drilling thick salt rock layers for Brazilian pre-salt exploitation challenges geomechanics in improving computational modeling of those rocks. Accurate predictions can avoid operational complications in the drilling job, ranging from the excessive necessity of new drillings to a stuck pipe or even the loss of the wellbore. Salt rock shows unique properties. The mechanical behavior of salt rock is different from that usually described in traditional rock mechanics. The understanding of the creep phenomenon constitutes an indispensable conceptual background for numerical simulation of salt rocks. Some methodologies are presented for the simulation of salt rock creep behavior using the commercial finite element code ABAQUS. Three power-law-based constitutive models for creep are tested on simulations of triaxial creep tests, a mining gallery and both cased and uncased wellbores. A first effort to calibrate and validate the Multi-mechanism Deformation Creep Model for application in the Brazilian halite should be highlighted. Moreover, a methodology for probabilistic analyses of wellbore closure and casing yielding is presented. The software NESSUS is adopted and the Mean Value reliability methods are employed. A transversal model of cased wellbore typical for a Brazilian pre-salt scenario is considered. For both events and constitutive models, deterministic results are associated to a probability of failure of 40 per cent. Variables with the highest importance in salt rock creep analyses are related to the stress state, temperature and steady-state creep. Finally, the excellent performance of the Multi-mechanism Deformation Creep Model in the numerical simulations carried out in this research is noteworthy.

Frequentemente é utilizada a abordagem determinística tanto em dimensionamentos quanto em análises do ciclo de vida de pavimentos rodoviários. A variabilidade inerente aos parâmetros pertinentes à implantação e ao desempenho de um pavimento é comumente desprezada, porém sua consideração pode ser contemplada com a utilização de uma abordagem probabilística, onde cada variável é caracterizada através de uma distribuição de probabilidade adequada. Uma análise econômica de um pavimento, seja asfáltico ou rígido, deve sempre abordar todos os custos pertinentes, desde a implantação. Os custos e benefícios tanto dos usuários quanto da administração rodoviária devem ser considerados. Um dos principais objetivos da avaliação econômica de pavimentos é o de apoiar a decisão quanto à seleção de alternativas de construção ou manutenção mais viáveis, quanto ao custo, e face de determinadas condições técnicas e econômicas. Este trabalho foca a utilização da abordagem probabilística no dimensionamento e em uma análise econômica de pavimentos rodoviários, tanto asfálticos quanto rígidos. São propostos procedimentos para a determinação da confiabilidade de uma estrutura de pavimento, asfáltico ou rígido, baseados nos métodos do DNIT e da AASHTO. Para análise do ciclo de vida são propostos modelos computacionais para a execução destas análises utilizando-se a equação de desempenho da AASHTO. Os custos dos usuários não foram contemplados nos modelos. O método Monte Carlo foi utilizado em todos os modelos. O risco de falha é determinado para o dimensionamento do pavimento. Os resultados contam ainda com uma distribuição dos custos totais ao longo de um período de projeto, possibilitando uma análise de risco. Os dados de saída (resultados) revelam- se como importantes balizadores para a tomada de decisão quanto à alocação de investimentos em alternativas de pavimentação, considerando os riscos inerentes às variabilidades das parcelas do processo consideradas neste trabalho. / A deterministic approach is often used for pavement design and life cycle cost analysis, which does not consider the inherent variability of some relevant parameters. The inherent variability of relevant parameters to the construction and performance of a pavement is often overlooked, but their consideration can be addressed with the use of a probabilistic approach, where each variable is characterized by a suitable probability distribution. An economic analysis of a pavement, either asphaltic or rigid, should always include an approach that considers all relevant construction costs, since its construction. The benefit-cost for both agency and road users should be considered. Improving the decision making process to choose among all construction and maintenance alternatives is one of the main pavement economic analysis goals. This thesis focuses on the use of probabilistic approach in the pavement design and in the Life Cycle Cost Analysis of road pavements, either asphalt or rigid. Procedures are proposed for determining the reliability of a structure of pavement, based on the methods of DNIT and AASHTO. For life cycle cost analysis, models are proposed for the implementation of these computational analyses using the performance equation of AASHTO. The user costs were not included in the models. The Monte Carlo method was used in all models. The reliability (and the risk of failure) is determined for pavements design. The results also come with a distribution of total costs over an analysis period, allowing a risk analysis. The output data (results) are revealed as important indicators for decision making process regarding the allocation of investments in alternative pavements solution, considering the inherent variability of the parcels of the process considered in this work.

The Black Rock volcanic cluster consists of 30 small volume monogenetic volcanoes. The volcanoes of this cluster have exhibited bimodal volcanism for > 9 Ma. The most recent eruption of Ice Springs volcano ~600 yrs. ago along with ongoing geothermal activity attests to the usefulness of a hazard assessment for this area. The likelihood of a future eruption in this area is estimated to be between a 0.16 and 24% chance over the next 1 Ka (95% confidence). The explosivity and nature of many of these eruptions is not well known. In particular, the physical volcanology of Tabernacle Hill suggests a complicated episodic eruption. Initial phreatomagmatic eruptions at Tabernacle Hill are reported to have begun no later than ~14 Ka. The initial eruptive phase produced a tuff cone approximately 150 m high and 1.5 km in diameter with distinct bedding layers. Recent mapping and sampling of Tabernacle Hill's lava and tuff cone deposits was aimed at better constraining the sequence of events, physical volcanology, and energy associated with this eruption. Blocks located on the rim of the tuff cone of were mapped and analyzed to yield preliminary minimum muzzle velocities of 60-70 m s-1. After the initial phreatomagmatic explosions, the eruption style transitioned to a more effusive phase that partially filled the tuff cone with a semi-steady state lava lake 200 m wide and 15 m deep. Eventually, the tuff cone was breached by the impinging lava resulting in large portions of the cone rafting on top of the lava flows away from the vent. Eruption onto the Lake Bonneville lake bed allowed the Tabernacle Hill lava flows to flow radially from the tuff cone and cover an area of 19.35 km², producing a very uniform high aspect ratio (100:1) flow field. Subsequent eruptive phases cycled several times between effusive and explosive, producing scoria cones and more lava flows, culminating in an almost complete drainage of the lava lake through large lava tubes and drain back.

In this thesis we study the standard probabilistic model for hashing with linear probing. The main purpose is to determine the asymptotic distribution for the maximum displacement. Depending on the ratio between the number of items and the number of cells, there are several cases to consider. Paper I solves the problem for the special case of almost full hash tables. That is, hash tables where every cell but one is occupied. Paper II completes the analysis by solving the problem for all remaining cases. That is, for every case where the number of items divided by the number of cells lies in the interval [0,1]. The last two papers treat quite different topics. Paper III studies the area covered by the supremum process of Brownian motion. One of the main theorems in Paper I is expressed in terms of the Laplace transform of this area. Paper IV provides a new sufficient condition for a collection of independent random variables to be negatively associated when conditioned on their total sum. The condition applies to a collection of independent Borel-distributed random variables, which made it possible to prove a Poisson approximation that where essential for the completion of Paper II.

Components are widely seen by software engineers as an important technology to address the "software crisis''. An important aspect of components in other areas of engineering is that system reliability can be estimated from the reliability of the components. We show how commonly proposed methods of reliability estimation and composition for software are inadequate because of differences between the models and the actual software systems, and we show where the assumptions from system reliability theory cause difficulty when applied to software. This thesis provides an approach to reliability that makes it possible, if not currently plausible, to compose component reliabilities so as to accurately and safely determine system reliability. Firstly, we extend previous work on input sub-domains, or partitions, such that our sub-domains can be sampled in a statistically sound way. We provide an algorithm to generate the most important partitions first, which is particularly important when there are an infinite number of input sub-domains. We combine analysis and testing to provide useful reliabilities for the various input sub-domains of a system, or component. This provides a methodology for calculating true reliability for a software system for any accurate statistical distribution of input values. Secondly, we present a calculus for probability density functions that permits accurately modeling the input distribution seen by each component in the system - a critically important issue in dealing with reliability of software components. Finally, we provide the system structuring calculus that allows a system designer to take components from component suppliers that have been built according to our rules and to determine the resulting system reliability. This can be done without access to the actual components. This work raises many issues, particularly about scalability of the proposed techniques and about the ability of the system designer to know the input profile to the level and kind of accuracy required. There are also large classes of components where the techniques are currently intractable, but we see this work as an important first step.

Computer Aided Engineering driven analysis is gaining grounds in automotive industry. Prediction of brake noise using CAE techniques has become populardue to its overall low cost as compared to physical testing. However, the presence of several uncertain parameters which affect brake noise and also the lack of basic understanding about brake noise, makes it difficult to make reliable decisions based on CAE analysis. Therefore, the confidence level in CAE techniques has to be increased to ensure reliability and robustness in the CAE solutions which support design work. One such way to achieve reliability in the CAE analysis isinvestigated in this thesis by incorporating the effects of different sources of uncertainty and variability in the analysis and estimating the probability of designfailure (probability of brake noise above a certain threshold). While incorporating the uncertainties in the CAE analysis ensures robustness, it is computationally intensive. This thesis work aims to gain an understanding about a brakenoise - creep groan, and to bring robustness into the CAE analysis along with reduction in computational time. A probabilistic analysis technique called hierarchical multi-fidelity statistical approachis explored in this thesis work, to estimate the probability of design failure or design robustness at a faster rate. It incorporates the stochasticity in the input parameters while running simulations. The method involves application of a hierarchy of approximations to the system response computed with variations in mesh resolution or variations in number of modes or changing solver time step,etc. And finally it uses the probability theory, to relate the information provided by approximate solutions to get the target failure estimation.Through this method, reliable data regarding the probability of design failure was approximated for every simulation and at a reduced computational time.Additionally, it provided information about critical parameters that influenced brake noise which was meritorious for design management. Estimation of probability of design failure by this method has been proved to be reliable in the case of brake noise according to the simulation results and the method can be considered robust. / Computer Aided Engineering (cae) driven analysis is gaining grounds in automotive industry. Brake noise is one such place where cae simulations are gaining more attention. The presence of several uncertain parameters which affect brake noises and also the lack of basic understanding about brake noise, makes it difficult to make reliable decisions based on cae deterministic analyses alone.Therefore, the confidence level in cae analyses has to be increased to ensure cae analysis robustness. One way to achieve this is by incorporating the effects of different sources of uncertainty and variability in the cae analysis and estimating the probability of design failure. Such a reliability measure (i.e. probability of noise event occurrence or exceedance of noise level than a threshold) can provide car manufacturers with an idea about the costs of warranty claims due to brake noise and can be used as a metric to evaluate different design solutions, before the final design goes to the production stage.  On one hand, using the high-fidelity models of brake/chassis system is generally computationally intensive, and thus, often only limited number of simula-tion runs are feasible for uncertainty analysis and design failure risk assessment. On the other hand, analyses on low-fidelity models, typically based on simplified assumptions during the development phase are fast but not always accu-rate. Striking for a good balance between efficiency and accuracy/robustness is an important task, when dealing with uncertainty/risk analysis of such complex dynamical systems To address these issues, a hierarchical multi-fidelity statistical approach has been adopted in this study, in order to estimate the probability of design failure. It employs a hierarchy of approximations to the system response computed with different fidelity by surrogate modelling, coarse spatial/temporal model mesh resolution variation, changing solver time step, etc., using probability theory, to relate information provided by approximate solu-tions to the target failure estimation. Using this approach opens up the possi-bility to use a low-fidelity models to accelerate the uncertainty quantification of complex brake/chassis systems, while granting unbiased estimation of system design failure risk/reliability. It also enables management of design changes, during fast iterations of the design process. This approach is used for studying one of the brake noise issue called creep groan, understand the root cause and providedesign proposals.

Frequentemente é utilizada a abordagem determinística tanto em dimensionamentos quanto em análises do ciclo de vida de pavimentos rodoviários. A variabilidade inerente aos parâmetros pertinentes à implantação e ao desempenho de um pavimento é comumente desprezada, porém sua consideração pode ser contemplada com a utilização de uma abordagem probabilística, onde cada variável é caracterizada através de uma distribuição de probabilidade adequada. Uma análise econômica de um pavimento, seja asfáltico ou rígido, deve sempre abordar todos os custos pertinentes, desde a implantação. Os custos e benefícios tanto dos usuários quanto da administração rodoviária devem ser considerados. Um dos principais objetivos da avaliação econômica de pavimentos é o de apoiar a decisão quanto à seleção de alternativas de construção ou manutenção mais viáveis, quanto ao custo, e face de determinadas condições técnicas e econômicas. Este trabalho foca a utilização da abordagem probabilística no dimensionamento e em uma análise econômica de pavimentos rodoviários, tanto asfálticos quanto rígidos. São propostos procedimentos para a determinação da confiabilidade de uma estrutura de pavimento, asfáltico ou rígido, baseados nos métodos do DNIT e da AASHTO. Para análise do ciclo de vida são propostos modelos computacionais para a execução destas análises utilizando-se a equação de desempenho da AASHTO. Os custos dos usuários não foram contemplados nos modelos. O método Monte Carlo foi utilizado em todos os modelos. O risco de falha é determinado para o dimensionamento do pavimento. Os resultados contam ainda com uma distribuição dos custos totais ao longo de um período de projeto, possibilitando uma análise de risco. Os dados de saída (resultados) revelam- se como importantes balizadores para a tomada de decisão quanto à alocação de investimentos em alternativas de pavimentação, considerando os riscos inerentes às variabilidades das parcelas do processo consideradas neste trabalho. / A deterministic approach is often used for pavement design and life cycle cost analysis, which does not consider the inherent variability of some relevant parameters. The inherent variability of relevant parameters to the construction and performance of a pavement is often overlooked, but their consideration can be addressed with the use of a probabilistic approach, where each variable is characterized by a suitable probability distribution. An economic analysis of a pavement, either asphaltic or rigid, should always include an approach that considers all relevant construction costs, since its construction. The benefit-cost for both agency and road users should be considered. Improving the decision making process to choose among all construction and maintenance alternatives is one of the main pavement economic analysis goals. This thesis focuses on the use of probabilistic approach in the pavement design and in the Life Cycle Cost Analysis of road pavements, either asphalt or rigid. Procedures are proposed for determining the reliability of a structure of pavement, based on the methods of DNIT and AASHTO. For life cycle cost analysis, models are proposed for the implementation of these computational analyses using the performance equation of AASHTO. The user costs were not included in the models. The Monte Carlo method was used in all models. The reliability (and the risk of failure) is determined for pavements design. The results also come with a distribution of total costs over an analysis period, allowing a risk analysis. The output data (results) are revealed as important indicators for decision making process regarding the allocation of investments in alternative pavements solution, considering the inherent variability of the parcels of the process considered in this work.

Behavior-Driven Development (BDD) is an emerging agile development approach where all stakeholders (including developers and customers) work together to write user stories in structured natural language to capture a software application's functionality in terms of re- quired "behaviors". Developers then manually write "glue" code so that these scenarios can be executed as software tests. This glue code represents individual steps within unit and acceptance test cases, and tools exist that automate the mapping from scenario descriptions to manually written code steps (typically using regular expressions). Instead of requiring programmers to write manual glue code, this thesis investigates a practical approach to con- vert natural language scenario descriptions into executable software tests fully automatically. To show feasibility, we developed a tool called Kirby that uses natural language processing techniques, code information extraction and probabilistic matching to automatically gener- ate executable software tests from structured English scenario descriptions. Kirby relieves the developer from the laborious work of writing code for the individual steps described in scenarios, so that both developers and customers can both focus on the scenarios as pure behavior descriptions (understandable to all, not just programmers). Results from assessing the performance and accuracy of this technique are presented. / Master of Science

Dams are vital infrastructure for society as they provide various services (e.g., flood prevention, storage of byproducts from mining operations, water storage for irrigation and hydropower generation) by the impoundment of liquids. However, the storage of considerable volumes of liquids introduces a risk of uncontrolled discharge, due to dam failure, which could result in catastrophic outcomes. Consequently, the safety must be ensured throughout a dam’s service life and thus regular assessments are required. For concrete dams, the current practices of stability assessment methods found in guidelines and regulatory rules require idealizations. This need for idealization is a weakness of current assessment methods as elucidated by the appended scientific articles. The essence of the results of the appended articles demonstrates that certain parameters and features of a dam, which are commonly neglected in current dam assessment, significantly influences the load capacity of a dam. Therefore, this study primarily deals with alternative assessment methods that can be used for dams. Therefore, as an outcome of an extensive literature review on probabilistic analysis and scale model testing, summarized in the chapters of the thesis, a framework for concrete dam assessment is proposed. Even though the methods can be individually employed to assess the stability and safety of a dam, an approach that integrates the strengths of each method is currently not available. The proposed framework is novel and combines scale model testing, finite element analysis, probabilistic analysis and is intended to resolve issues identified with current assessment methods. The framework integrates the strengths of each method provides a robust assessment strategy where cross-validation of the failure mode and capacity is achieved by utilizing both finite element analysis and scale model testing. Furthermore, in contrast to current dam assessment methods, it allows for large geometrical variations in the rock-concrete interface to be included in the analysis, which contributes significantly to the capacity of a concrete dam as elucidated by the appended articles. The work in this thesis presents the theoretical foundation of the framework. It is intended to be applied in a future case study to evaluate its performance on an existing buttress dam.

No description available.