<p>A computerized tomography scan enables the visualization of an object interior without opening it up. This technique is used in many fields e.g. in medical imaging, geology, and industry. To obtain information about an object, exterior measurements by means of X-rays are performed. Then, to reconstruct an image of the object’s interior, image-reconstructions methods are applied. The problem of reconstructing images from measurements of X-ray radiation belongs to the class of inverse problems. A class of important methods for inverse problems is Algebraic Reconstruction Techniques (ART). The performance of these methods depends on the choice of a relaxation parameter.</p> <p>In this thesis, we compare numerically various ART methods, namely Kaczmarz, symmetric Kaczmarz, randomized Kaczmarz and simultaneous ART. We perform an extensive numerical investigation of the behaviour of these methods, and in particular, study how they perform with respect to this relaxation parameter. We propose a simple heuristic for finding a good relaxation parameter for each of these methods. Comparisons of the new proposed strategy with a previously proposed one shows that our strategy has a slightly better performance in terms of relative error, relative residual and image discrepancy of the reconstructed image. Both strategies showed relatively close numerical results, but interestingly enough, for different values of this parameter.</p> / Master of Computer Science (MCS)

Nesse trabalho, apresentaremos o método econômico desenvolvido por Taguchi para monitoramento on line da qualidade para atributos. O propósito deste método é obter o intervalo de inspeção que minimiza o custo esperado por item produzido em um processo industrial. Em seguida, mostraremos o modelo alternativo proposto por Nayebpour e Woodall (1993) e a derivação dos estimadores de máxima verossimilhança e de Bayes desenvolvida por Borges, Esteves e Wechsler (2005). Finalmente, apresentaremos uma nova solução para o problema de determinação do intervalo de inspeção ótimo sob a perspectiva da Teoria de Decisão Bayesiana. A última solução será ilustrada com alguns exemplos. / In this work, we present Taguchi\'s economic on line quality monitoring method for attributes. The aim of this method is to obtain the inspection interval that minimizes the expected cost per item produced in an industrial process. After that, we will consider the alternative method proposed by Nayebpour e Woodall (1993) and the derivation of the maximum likelihood and Bayes estimators developed by Borges, Esteves e Wechsler (2005). Finally, we will propose a new solution to the problem of inspection interval determination through Bayesian Decision Theory. This last solution will be implemented and its performance will be illustrated with a few examples.

Nesse trabalho, apresentaremos o método econômico desenvolvido por Taguchi para monitoramento on line da qualidade para atributos. O propósito deste método é obter o intervalo de inspeção que minimiza o custo esperado por item produzido em um processo industrial. Em seguida, mostraremos o modelo alternativo proposto por Nayebpour e Woodall (1993) e a derivação dos estimadores de máxima verossimilhança e de Bayes desenvolvida por Borges, Esteves e Wechsler (2005). Finalmente, apresentaremos uma nova solução para o problema de determinação do intervalo de inspeção ótimo sob a perspectiva da Teoria de Decisão Bayesiana. A última solução será ilustrada com alguns exemplos. / In this work, we present Taguchi\'s economic on line quality monitoring method for attributes. The aim of this method is to obtain the inspection interval that minimizes the expected cost per item produced in an industrial process. After that, we will consider the alternative method proposed by Nayebpour e Woodall (1993) and the derivation of the maximum likelihood and Bayes estimators developed by Borges, Esteves e Wechsler (2005). Finally, we will propose a new solution to the problem of inspection interval determination through Bayesian Decision Theory. This last solution will be implemented and its performance will be illustrated with a few examples.

The Flux Jacobian matrices, the elements of which are the derivatives of the flux vectors with respect to the flow variables, are needed to be evaluated in implicit flow solutions and in analytical sensitivity analyzing methods. The main motivation behind this thesis study is to explore the accuracy of the numerically evaluated flux Jacobian matrices and the effects of the errors in those matrices on the convergence of the flow solver, on the accuracy of the sensitivities and on the performance of the design optimization cycle. To perform these objectives a flow solver, which uses exact Newton&rsquo / s method with direct sparse matrix solution technique, is developed for the Euler flow equations. Flux Jacobian is evaluated both numerically and analytically for different upwind flux discretization schemes with second order MUSCL face interpolation. Numerical flux Jacobian matrices that are derived with wide range of finite difference perturbation magnitudes were compared with analytically derived ones and the optimum perturbation magnitude, which minimizes the error in the numerical evaluation, is searched. The factors that impede the accuracy are analyzed and a simple formulation for optimum perturbation magnitude is derived. The sensitivity derivatives are evaluated by direct-differentiation method with discrete approach. The reuse of the LU factors of the flux Jacobian that are evaluated in the flow solution enabled efficient sensitivity analysis. The sensitivities calculated by the analytical Jacobian are compared with the ones that are calculated by numerically evaluated Jacobian matrices. Both internal and external flow problems with varying flow speeds, varying grid types and sizes are solved with different discretization schemes. In these problems, when the optimum perturbation magnitude is used for numerical Jacobian evaluation, the errors in Jacobian matrix and the sensitivities are minimized. Finally, the effect of the accuracy of the sensitivities on the design optimization cycle is analyzed for an inverse airfoil design performed with least squares minimization.

The topic of this master thesis is to compare benefits from the building society account with the mortgage loan. The whole comparison will be done according to the new legislative. The aim of this study is to find whether it is more profitable to invest into your property with the mortgage or the building society account. For this collation eight different companies are approached. Four of them are building societies and four are banks. The experts from those companies were given three examples with different height of LTV from different applicants with different purposes. Those experts also assessed which indicators applicants should consider. According to these recommendations clients have ordered indicators by their assumed importance. Finally offers were evaluated by TOPSIS method and ordered by its advantageousness.

Cluster analysis is one of the classification methods of multivariate statistical analysis. The task of this analysis is to classify the objects into clusters so that objects inside these clusters are as similar as possible. The aim of this study is to evaluate the success of the classification of objects using six hierarchical cluster analysis methods. To reflect the distance between the objects, are used squared Euclidean and Mahalanobis distances. The success methods are evaluated through the information, which cluster the object belongs to, and this information is already contained in the data files. This thesis pointed out that the Ward's method is one of the most successful hierarchical method in a classification of objects into clusters. This method has been more successful in sorting objects than the other hierarchical methods, both in the case of leaving the correlated variables in the data file as well as removing them. The results of this work show that the highest success of classification objects into clusters is when the data set is cleaned of correlated variables. If the data file is not cleaned, the methods reach better results when the distance between objects is measured by Euclidean metric.

The Master´s thesis deals with the engineering design of single-axle brakeless dump trailer for a tractor designed for transporting and dumping of particulate materials and firewood. The engineering design of the trailer is based on the proposed kinematic scheme and the basic calculations that are checked by FEM analysis in Ansys Workbench. The drawing documentation is done in AutoCAD.

Os eletrodos de metais nobres, considerados os melhores, implicam em altos custos para qualquer tipo de aplicação em larga escala. Com intuito de minimizar os custos e manter a eficiência, muitos estudos buscam materiais alternativos. O óxido de estanho apresenta-se como uma boa alternativa para material de eletrodo, principalmente por poder ser utilizado na forma de filme condutor transparente. Atualmente, é aplicado em sensores eletroquímicos para detecção de gases, painéis de cristal líquido e em células fotovoltaicas. Como se trata de um semicondutor, é comum o uso de dopantes para melhorar a condutividade elétrica do composto. Entre os diversos dopantes já estudados, o flúor apresenta resultados muito bons, sendo um dos mais utilizados hoje em dia. Entretanto, pouco se sabe sobre como esse aditivo influi sobre as características físico-químicas do óxido de estanho. A proposta do presente trabalho é estudar a influência do uso de haletos (F e Cl) como aditivos para o óxido de estanho. Inicialmente, foram preparados pós de SnO2 com diferentes concentrações de flúor ou cloro, através do método de precursores poliméricos. Esses pós foram caracterizados por difração de raios X, reflectância difusa de infravermelho e medidas de área superficial através de isoterma BET. Os resultados obtidos mostram que os aditivos concentram-se no contorno de grão. As amostras dopadas sofreram aumento de área superficial e mudança no espectro IV da superfície. Os padrões de difração de raios-X permaneceram inalterados, indicando que não houve formação de solução sólida ou qualquer outro tipo de alteração no retículo cristalino do Sn O2. Os pós também foram submetidos à análise térmica e estudos de mobilidade dinâmica eletroforética. Desses estudos foi possível concluir que a presença dos aditivos modifica a interface do óxido, influindo sobre sua acidez e hidrofobicidade. Além do estudo dos pós, também foi explorada a resposta eletroquímica do óxido dopado, na forma de filmes e pastilhas. As pastilhas foram preparadas através da sinterização dos pós. Os filmes foram preparados por dip coating utilizando vidro ou ouro como substrato. Devido à alta resistência elétrica das pastilhas e dos filmes suportados sobre vidro, não foi possível obter resposta eletroquímica satisfatória. Já os filmes suportados sobre ouro foram caracterizados eletroquimicamente usando eletrólito inerte, sonda eletroquímica (par redox Fe(CN)6-4 / Fe(CN6-3) e eletrólito simulando ambiente corrosivo. Os resultados obtidos mostram que os filmes são pouco homogêneos e que parte do substrato metálico ficou exposto. Os filmes dopados com flúor também foram caracterizados por espectroscopia de impedância eletroquímica. Um circuito equivalente foi ajustado às respostas obtidas. Parâmetros como resistência da transferência de carga e capacitância da dupla camada elétrica puderam ser calculados. / Alternative materiaIs for electrochemical applications are studied and developed due to the high cost of noble metaIs electrodes, still the best materiaIs for electrodes today. Tin oxide presents good results as an alternative electrode material. The material is capable to show both transparency and electrical conductivy when applied as a film. It is currently used as electrochemical sensors for gases detection, liquid crystal display\'s and photovoltaic cells. Being tin oxide a semiconductor, dopants are usually added in order to improve the conductivity. Among several already known additives, fiuorine is one of the most applied, providing very good results. However, there are few information about the fiuorine action over the phisycal-chemistry properties ofthe oxide. The present work focus on the infiuence of halide (F or Cl) doping over some tin oxide characteristics. At first, Sn O2 powders with different additive contents were prepared via a Pechini\'s method derived route. These powders were characterized by X-ray diffraction, diffuse refiectance infrared spectroscopy and BET isoterm suface area measurement. From the obtained results, it can be infered that the additives are mainly in the grain surface. The doped samples showed higher surface areas and differences in the IR spectra. The XRD pattern showed neither shifts nor new phases. Therefore, there were neither solid solution formation nor any kind of crystaline lattice changing. Moreover, thermal analysis and electrophoretic dynamic mobility measurements were performed and showed that the additive presence modifies the tin oxide acidity and hydrofobicity. Besides, the electrochemical behavior of films and syntered tin oxide were explored. Films were prepared through dip coating and supported on glass or gold substrates. Syntered tin oxide was prepared in pellet shape. Pellets and glass supported films showed high resistivity, which leads to poor electrochemical response. Only the gold supported fiims showed good response. These films were electrochemicaly characterized with an inert electrolyte, an electrochemical probe (Fe(CN6-4 / Fe(CN6-3 redox pair) and an corrosive electrolyte. Scaning electronic microscopy was performed too. According to the results, the films are not homogeneous and the metallic substrate was exposed. Electrochemical impedance spectroscopy studies were either performed with fiuorine-doped films. A proposed equivalent circuit was capable to fit the results. Charge transfer resistance and double layer capacity ofthe films could be calculated.

The aim of this study is to obtain optimal position and orientation of a trajectory frame with respect to the fixed frame of the manipulator. The work path which is given in the trajectory frame is also constrained in the workspace of the 3 &ndash / PRS parallel kinematic machine. In the analysis, forward and inverse kinematics solutions are derived as well as the inverse dynamics model using Lagrange&rsquo / s Method. Several algorithms governing the motion of the manipulator are developed. Moreover, optimization goals are defined and evaluated with the genetic algorithm.

I denna rapport presenteras ett tillvägagångssätt för att hitta och datera brytpunkter i tidsserier. En brytpunkt definieras av det datum då det skett en stor nivåförändring i tidsserien. Det presenteras även en strategi för att skatta effekten av daterade brytpunkter. Genom att analysera tidsserier över AFA Försäkrings ärendeinflöde visar det sig att brytpunkter i tidsserien sammanfaller med exogena händelser som kan ha orsakat dessa brytpunkter, till exempel villkors- eller lagförändringar inom försäkringsbranschen. Rapporten visar att det genom ett metodiskt angreppssätt går att skatta effekten av en exogen händelse. Dessa skattade effekter kan användas vid framtida prognoser då en liknande förändring förväntas inträffa. Dessutom skapas prognoser över ärendeinflödet två år framåt med olika tidsseriemodeller.