The impact of physical design characteristics on backend dielectric reliability was modeled. The impact of different interconnect geometries on backend low-k time dependent dielectric breakdown was reported and modeled. Physical design parameters that are crucial to backend dielectric reliability were identified. A methodology was proposed for determining chip reliability but combining the insights gathered by modeling the impact of physical design on backend dielectric breakdown. A methodology to model variation in device parameters and characteristics was proposed. New methods of electrical and physical parameter extraction were proposed. Models that consider systematic and random source of variation in electrical and physical parameters of CMOS devices were proposed, to aid in circuit design and timing analysis.

In alkalischen Lösungen führt die Reaktion von Hydroxylionen mit den Si-O-Si-Bindungen des Glasnetzwerks zur Bildung hydratisierter Oberflächen und gelöstem Silikat. Der Grad der Korrosion bzw. der Alterung der Glasfaser ist abhängig von der chemischen Zusammensetzung des Glases und Korrosionslösung sowie von Zeit und Temperatur. Die Untersuchung von Glasfasern verschiedener chemischer Zusammensetzung in NaOH- sowie Zementlösungen zeigte, dass die inhibierende Wirkung von Ca-Ionen zu einem veränderten Korrosionsmechanismus führt. Dies konnte anhand der mechanischen Eigenschaften der Glasfasern sowie rasterelektronenmikroskopischen Untersuchungen gezeigt werden. Während die Korrosion in NaOH-Lösung zu einer ausgeprägten Umwandlung der gesamten äußeren Glasfaserschicht in Reaktionsprodukte führte, zeigten Glasfasern in Zementlösung bei gleichem pH-Wert einen stark lokal begrenzten, punktförmigen Angriff. Daraus resultieren unterschiedliche mechanische Eigenschaften der Glasfasern in Abhängigkeit von der gewählten Korrosionslösung.

AR-Glas wird in Form von Multifilamentgarn zur Verstärkung in textilbewehrtem Beton eingesetzt. Während des Herstellungsprozesses wird auf die AR-Glasfilamente die Schlichte aufgebracht, deren chemische Zusammensetzung maßgeblich die Qualität der Filament-Matrix-Grenzschicht bestimmt, sowie die chemische Beständigkeit im alkalischen Milieu gewährleistet. Zur Beurteilung der chemischen Beständigkeit in alkalischer Umgebung werden beschleunigte Alterungsversuche in wässrigen, alkalischen Lösungen durchgeführt. Die Reaktion von Hydroxid-Ionen mit dem Si-O-Si-Gruppen des Glasnetzwerkes führt zur Ausbildung hydratisierter Oberflächen und gelösten Silikaten. Das Ausmaß der Glaskorrosion ist von der chemischen Zusammensetzung der Glasfaser, der Schlichte bzw. Beschichtung und der alkalischen Lösung sowie von Zeit und Temperatur abhängig. Die beschleunigte Alterung von verschiedenen AR-Glasfasern in NaOH-Lösung sowie Zementlösung zeigt, dass sich der Korrosionsmechanismus aufgrund der vorhandenen Calcium-Ionen unterscheidet. Die Filamentbruchspannung wird anhand der Weibull-Verteilungsfunktion analysiert. Das mechanische Verhalten hängt deutlich von der chemischen Zusammensetzung der Alterungslösung ab, was zu unterschiedlichen Parametern der Weibull-Verteilungsfunktion sowie vermengten Verteilungen führen kann. Die Alterung in NaOH-Lösung führt zur Ausbildung einer korrodierten Schicht an der Filamentoberfläche. In Ca-haltigen Zementlösungen kommt es dagegen zu einer lokal begrenzten Korrosion. Für die Beurteilung verschiedener Polymerbeschichtungen werden Betonverbunde bei unterschiedlichen Temperaturen und Umgebungsfeuchten gelagert, wodurch geeignete Alterungsbedingungen evaluiert werden und den Vergleich der chemischen Beständigkeit unterschiedlicher Beschichtungen ermöglichen. / Rovings made of AR-glass are used in textile reinforced concrete. During the manufacturing process the sizing is applied on the AR-glass filaments. The chemical constitution of the sizing determines the quality of the filament-matrix-interface but also the chemical durability of the glass filaments in alkaline environment. The durability is evaluated by accelerated ageing tests in aqueous, alkaline solutions. In alkaline solutions, the reaction of hydroxyl ions with Si-O-Si-groups of the glass network leads to the formation of hydrated surfaces and dissolved silicate. The rate of this corrosion depends on the chemical constitution of the fibre and the alkaline solution as well as on time and temperature. The investigation of the ageing of glass fibres with different chemical constitutions in NaOH and cement solutions shows that the corrosion mechanism changes due to the inhibiting effect of calcium ions. The strength distributions have been evaluated using a Weibull distribution function. The mechanical behaviour strongly depends on the chemistry of the solution and determines the parameters of the Weibull distribution function in terms of either single or mixed distributions. The corrosion in NaOH solution leads to a strong dissolution of the outer layer of the glass fibres, whereas during aging in cement solution at the same pH-value a limited, local attack was revealed. The evaluation of polymer coatings is realised by the ageing of concrete composites at different temperatures and humidities to deduce adequate ageing conditions for the comparison of different coatings.

Made available in DSpace on 2016-06-02T20:06:04Z (GMT). No. of bitstreams: 1 3451.pdf: 871063 bytes, checksum: 8af58118f0d60c000ca46f5d8bfda544 (MD5) Previous issue date: 2011-02-24 / In survival analysis, some studies are characterized by having a significant fraction of units that will never suffer the event of interest, even if accompanied by a long period of time. For the analysis of long-term data, we approach the standard mixture model by Berkson & Gage, where we assume the generalized modified Weibull distribution for the lifetime of individuals at risk. This model includes several classes of models as special cases, allowing its use to discriminate models. The standard mixture model implicitly assume that those individuals experiencing the event of interest possess homogeneous risk. Alternatively, we consider the standard mixture model with a frailty term in order to quantify the unobservable heterogeneity among individuals. This model is characterized by the inclusion of a unobservable random variable, which represents information that can not or have not been observed. We assume multiplicative frailty with a gamma distribution. For the lifetime of individuals at risk, we assume the Weibull distribution, obtaining the frailty Weibull standard mixture model. For both models, we realized simulation studies with the purpose of analyzing the frequentists properties of estimation procedures. Applications to real data set showed the applicability of the proposed models in which parameter estimates were determined using the approaches of maximum likelihood and Bayesian. / Em análise de sobrevivência determinados estudos caracterizam-se por apresentar uma fração significativa de unidades que nunca apresentarão o evento de interesse, mesmo se acompanhados por um longo período de tempo. Para a análise de dados com longa duração, abordamos o modelo de mistura padrão de Berkson & Gage supondo que os tempos de vida dos indivíduos em risco seguem distribuição Weibull modificada generalizada. Este modelo engloba diversas classes de modelos como casos particulares, propiciando o uso deste para discriminar modelos. O modelo abordado assume implicitamente que todos os indivíduos que falharam possuem risco homogêneo. Alternativamente, consideramos o modelo de mistura padrão com um termo de fragilidade com o objetivo de quantificar a heterogeneidade não observável entre os indivíduos. Este modelo é caracterizado pela inclusão de uma variável aleatória não observável, que representa as informações que não podem ou que não foram observadas. Assumimos que a fragilidade atua de forma multiplicativa com distribuição gama. Para os tempos de vida dos indivíduos em risco consideramos a distribuição Weibull, obtendo o modelo de mistura padrão Weibull com fragilidade. Para os dois modelos realizamos estudos de simulação com o objetivo de analisar as propriedades frequentistas dos processos de estimação. Aplicações a conjunto de dados reais mostraram a aplicabilidade dos modelos propostos, em que a estimação dos parâmetros foram determinadas através das abordagens de máxima verossimilhança e Bayesiana.

Recently wind resource assessment studies have become an important research tool to identify the possible wind farm locations.  In this thesis work technical analysis was carried out to determine the wind resource potential of two candidate sites in Eritrea with help of suitable software tools. The first site is located along the Red Sea cost which is well known for its wind resource potential, whereas the second site is located in the central highlands of Eritrea with significant wind resource potential. Detailed wind resource assessment, for one year hourly weather data including wind speed and wind direction, was performed for the two candidate sites using MS Excel and MATLAB. The measured wind data at Assab wind site showed that the mean wind speed and power density was 7.54 m/s and 402.57 W/m2 , whereas the mean wind speed and mean power density from Weibull distribution was 7.51 m/s and 423.71 W/m2 respectively at 80m height. Similarly, the measured mean wind speed and mean power density at Dekemahre wind site was obtained to be 5.498 m/s and 141.45 W/m2, whereas the mean wind speed and mean power density from Weibull distribution was 5.4859m/s and 141.057W/m2 respectively. Based on the analysis results Assab wind site classified as wind class-III and Dekemhare as wind class-I.  Wind farm modeling and Annual Energy Production (AEP) estimation was performed for E-82 & E-53 model turbines from Enercon Company with the help of MATLAB and Windpro software. The analysis revealed that Assab wind farm was an ideal site for wind energy production with capacity factor (CF) 53.4% and 55% for E-82 and E-53 turbines respectively. The gross and net AEP for turbine E-82 at Assab wind farm was 469.5 GWh and 446.025 GWh respectively with 95% park efficiency. Similarly, the analysis showed that the CF in Dekemhare site was very low with typical value 14.2% and 15.26% for E-82 and E-53 turbines respectively. The gross and net AEP of that site for model turbine E-53 was 53.5 GWh and 50.825 GWh respectively with 5% wake loss. Finally, a simplified economic analysis was carried out to determine the economic feasibility of possible wind power projects in both sites by assuming investment cost 1600 €/kW for E-82 turbine and 2000 €/kW for E-53 turbine. The total wind farm investment cost was found to be 215.85 and 107.93 Million Euro for E-82 and E-53 model turbines respectively. The levelized cost of energy at Assab and Dekemhare wind farm for E-82 model turbine was 0.0307 €/kWh and 0.5526 €/kWh respectively. The analysis result show that the levelized cost of energy in Dekemhare wind fasrm was much higher than that of Assab wind farm.

Made available in DSpace on 2015-03-03T15:28:32Z (GMT). No. of bitstreams: 1 FelipeHAM_DISSERT.pdf: 2307848 bytes, checksum: c94e3d62e5fe54424d6cbe1491c8d85d (MD5) Previous issue date: 2011-12-28 / Universidade Federal do Rio Grande do Norte / In survival analysis, the response is usually the time until the occurrence of an event of interest, called failure time. The main characteristic of survival data is the presence of censoring which is a partial observation of response. Associated with this information, some models occupy an important position by properly fit several practical situations, among which we can mention the Weibull model. Marshall-Olkin extended form distributions other a basic generalization that enables greater exibility in adjusting lifetime data. This paper presents a simulation study that compares the gradient test and the likelihood ratio test using the Marshall-Olkin extended form Weibull distribution. As a result, there is only a small advantage for the likelihood ratio test / Em an?lise de sobreviv?ncia, a vari?vel resposta e, geralmente, o tempo at? a ocorr?ncia de um evento de interesse, denominado tempo de falha, e a principal caracter?stica de dados de sobreviv?ncia e a presen?a de censura, que ? a observa??o parcial da resposta. Associados a essas informa??es, alguns modelos ocupam uma posi??o de destaque por sua comprovada adequa??o a v?rias situa??es pr?ticas, entre os quais ? poss?vel citar o modelo Weibull. Distribui??es na forma estendida de Marshall-Olkin oferecem uma generaliza??o de distribui??es b?sicas que permitem uma flexibilidade maior no ajuste de dados de tempo de vida. Este trabalho apresenta um estudo de simula??o que compara duas estat?sticas de teste, a da Raz?o de Verossimilhan?as e a Gradiente, utilizando a distribui??o Weibull em sua forma estendida de Marshall-Olkin. Como resultado, verifica-se apenas uma pequena vantagem para estat?stica da Raz?o de Verossimilhancas

In this work, we study the so-called combined models, generalized linear mixed models with extension to allow for overdispersion, in the context of genetics and breeding. Such flexible models accommodates cluster-induced correlation and overdispersion through two separate sets of random effects and contain as special cases the generalized linear mixed models (GLMM) on the one hand, and commonly known overdispersion models on the other. We use such models while obtaining heritability coefficients for non-Gaussian characters. Heritability is one of the many important concepts that are often quantified upon fitting a model to hierarchical data. It is often of importance in plant and animal breeding. Knowledge of this attribute is useful to quantify the magnitude of improvement in the population. For data where linear models can be used, this attribute is conveniently defined as a ratio of variance components. Matters are less simple for non-Gaussian outcomes. The focus is on time-to-event and count traits, where the Weibull-Gamma-Normal and Poisson-Gamma-Normal models are used. The resulting expressions are sufficiently simple and appealing, in particular in special cases, to be of practical value. The proposed methodologies are illustrated using data from animal and plant breeding. Furthermore, attention is given to the occurrence of negative estimates of variance components in the Poisson-Gamma-Normal model. The occurrence of negative variance components in linear mixed models (LMM) has received a certain amount of attention in the literature whereas almost no work has been done for GLMM. This phenomenon can be confusing at first sight because, by definition, variances themselves are non-negative quantities. However, this is a well understood phenomenon in the context of linear mixed modeling, where one will have to make a choice between a hierarchical and a marginal view. The variance components of the combined model for count outcomes are studied theoretically and the plant breeding study used as illustration underscores that this phenomenon can be common in applied research. We also call attention to the performance of different estimation methods, because not all available methods are capable of extending the parameter space of the variance components. Then, when there is a need for inference on such components and they are expected to be negative, the accuracy of the method is not the only characteristic to be considered. / Neste trabalho foram estudados os chamados modelos combinados, modelos lineares generalizados mistos com extensão para acomodar superdispersão, no contexto de genética e melhoramento. Esses modelos flexíveis acomodam correlação induzida por agrupamento e superdispersão por meio de dois conjuntos separados de efeitos aleatórios e contem como casos especiais os modelos lineares generalizados mistos (MLGM) e os modelos de superdispersão comumente conhecidos. Tais modelos são usados na obtenção do coeficiente de herdabilidade para caracteres não Gaussianos. Herdabilidade é um dos vários importantes conceitos que são frequentemente quantificados com o ajuste de um modelo a dados hierárquicos. Ela é usualmente importante no melhoramento vegetal e animal. Conhecer esse atributo é útil para quantificar a magnitude do ganho na população. Para dados em que modelos lineares podem ser usados, esse atributo é convenientemente definido como uma razão de componentes de variância. Os problemas são menos simples para respostas não Gaussianas. O foco aqui é em características do tipo tempo-até-evento e contagem, em que os modelosWeibull-Gama-Normal e Poisson-Gama-Normal são usados. As expressões resultantes são suficientemente simples e atrativas, em particular nos casos especiais, pelo valor prático. As metodologias propostas são ilustradas usando dados de melhoramento animal e vegetal. Além disso, a atenção é voltada à ocorrência de estimativas negativas de componentes de variância no modelo Poisson-Gama- Normal. A ocorrência de componentes de variância negativos em modelos lineares mistos (MLM) tem recebido certa atenção na literatura enquanto quase nenhum trabalho tem sido feito para MLGM. Esse fenômeno pode ser confuso a princípio porque, por definição, variâncias são quantidades não-negativas. Entretanto, este é um fenômeno bem compreendido no contexto de modelagem linear mista, em que a escolha deverá ser feita entre uma interpretação hierárquica ou marginal. Os componentes de variância do modelo combinado para respostas de contagem são estudados teoricamente e o estudo de melhoramento vegetal usado como ilustração confirma que esse fenômeno pode ser comum em pesquisas aplicadas. A atenção também é voltada ao desempenho de diferentes métodos de estimação, porque nem todos aqueles disponíveis são capazes de estender o espaço paramétrico dos componentes de variância. Então, quando há a necessidade de inferência de tais componentes e é esperado que eles sejam negativos, a acurácia do método de estimação não é a única característica a ser considerada.

Assumir suposições especiais sobre a função de risco tem sido a estratégia adotada por vários autores, com intuito de garantir modelos gerais e abrangentes, tanto para a análise de dados de sobrevivência quanto de conDabilidade. Neste estudo, modelos aplicados a dados da área de sobrevivência e conDabilidade são considerados. A Dnalidade deste estudo é propor modelos mais Pexíveis e/ou mais abrangentes de forma a generalizar modelos já existentes, bem como estudar suas propriedades e propor possíveis comparações entre os modelos via testes de hipóteses. Considera-se nesta tese, três classes de modelos baseados na função de risco (modelos de risco). A primeira classe apresenta-se como um caso particular do modelo de risco estendido (Louzada-Neto, 1999), formada por modelos que relacionam o parâmetro de escala a covariáveis, sendo que esse relacionamento pode ser considerado log-linear ou log-nãolinear. Considera-se um modelo particular onde a dependência do parâmetro de escala se dá de forma log-não-linear. Na segunda classe considera-se modelos que estão vinculados a dados de riscos competitivos, quando se tem ou não informação sobre qual tipo de risco foi responsável pela falha de um equipamento ou pelo óbito de um paciente. A terceira classe de modelos foi proposta, nesta tese, relacionando o contexto de modelos de longa duração. / Assuming special suppositions for the hazard function have been the strategy used for many authors in order to guarantee general and Pexible models for survival and reliability data. The present thesis considers two classes of hazard models, with the basic objective of proposing more Pexible models, studying their properties and proposing possible comparisons via hypothesis tests. We consider, three families of models where the struture was based in hazard function. The Drst class is a special case of the extented hazard model (Louzada, 1999). This class of models is composed by models with relationship between the scale parameter and the covariates could be log-linear or log-non-linear, we consider the log-non-linear. The second class is into the context of competing risk, where we do not known what kind of risk is responsable for the fail.or death. The third class, proposed in this work refers to a context of long term survivals. All the procedures were ilustrated in real datasets

No presente trabalho, e proposto um modelo de regressão utilizando a distribuição gama generalizada exponenciada (GGE) para dados censurados, esta nova distribuição e uma extensão da distribuição gama generalizada. A distribuição GGE (CORDEIRO et al., 2009) que tem quatro parâmetros pode modelar dados de sobrevivência quando a função de risco tem forma crescente, decrescente, forma de U e unimodal. Neste trabalho apresenta-se uma expansão natural da distribuição GGE para dados censurados, esta distribuição desperta o interesse pelo fato de representar uma família paramétrica que possui como casos particulares outras distribuições amplamente utilizadas na analise de dados de tempo de vida, como as distribuições gama generalizada (STACY, 1962), Weibull, Weibull exponenciada (MUDHOLKAR et al., 1995, 1996), exponencial exponenciada (GUPTA; KUNDU, 1999, 2001), Rayleigh generalizada (KUNDU; RAKAB, 2005), dentre outras, e mostra-se útil na discriminação entre alguns modelos probabilísticos alternativos. Considerando dados censurados, e abordado o método de máxima verossimilhança para estimar os parâmetros do modelo proposto. Outra proposta deste trabalho e introduzir um modelo de regressão log-gama generalizado exponenciado com efeito aleatório. Por fim, são apresentadas três aplicações para ilustrar a distribuição proposta. / In the present study, we propose a regression model using the exponentiated generalized gama (EGG) distribution for censored data, this new distribution is an extension of the generalized gama distribution. The EGG distribution (CORDEIRO et al., 2009) that has four parameters it can model survival data when the risk function is increasing, decreasing, form of U and unimodal-shaped. In this work comes to a natural expansion of the EGG distribution for censored data, is awake distribution the interest for the fact of representing a parametric family that has, as particular cases, other distributions which are broadly used in lifetime data analysis, as the generalized gama (STACY, 1962), Weibull, exponentiated Weibull (MUDHOLKAR et al., 1995, 1996), exponentiated exponential (GUPTA; KUNDU, 1999, 2001), generalized Rayleigh (KUNDU; RAKAB, 2005), among others, and it is shown useful in the discrimination among some models alternative probabilistics. Considering censored data, the maximum likelihood estimator is considered for the proposed model parameters. Another proposal of this work was to introduce a log-exponentiated generalized gamma regression model with random eect. Finally, three applications were presented to illustrate the proposed distribution.

Nous appliquons la théorie asymptotique des expériences statistiques à des problèmes liés aux valeurs extrêmes. Quatre modèles semi-paramétriques sont envisagés. Tout d'abord le modèle d'échantillonnage de fonction de répartition de type Pareto. L'index de Pareto est le paramètre d'intérêt tandis que la fonction à variation lente, qui intervient dans la décomposition de la fonction de survie, joue le rôle de nuisance. Nous considérons ensuite des observations i.i.d. de fonction de répartition de type Weibull. Le troisième modèle étudié est un modèle de régression. On considère des couples d'observations $(Y_i,X_i)$ indépendants, les v.a. $X_i$ sont i.i.d. de loi connue et on suppose que la fonction de répartition de la loi de $Y$ conditionnellement à $X$ est de type Pareto, avec une fonction à variation lente et un index $gamma$ qui dépendent de $X$. On fait l'hypothèse que la fonction $gamma$ a une forme quelconque mais connue, qui dépend d'un paramètre $\ / Doctorat en sciences, Orientation statistique / info:eu-repo/semantics/nonPublished