O regime de meta para a inflação foi adotado por um amplo conjunto de países nos últimos anos. Evidentemente, a definição da meta de inflação a ser perseguida é parte essencial do regime. O presente trabalho pretende contribuir para o debate sobre a meta ótima para o Brasil. O trabalho está dividido em três ensaios que, por caminhos diversos, buscam estimar quantitativamente os custos e benefícios de diferentes metas de inflação para a economia brasileira. O foco é sobre os efeitos de longo prazo de diferentes metas, uma vez que esses são mais relevantes do que os possíveis custos de ajustamento para uma eventual nova meta de inflação. O primeiro artigo aborda a questão sobre a meta de inflação ótima para o Brasil por meio da perda de bem estar medida pela demanda de moeda, um canal clássico considerado pela literatura. O segundo avalia a relação entre o nível e a incerteza sobre a inflação futura, utilizando para tanto modelos para a estimação da variância condicional da inflação, as expectativas de inflação relatadas por analistas econômicos e medidas de inflação implícita em preços de ativos. O terceiro artigo apresenta um enfoque mais teórico e estrutural, apresentando um modelo no qual existe um trade-off para a meta de inflação e calibrando esse modelo para obter estimativas da meta ótima para a economia brasileira. O modelo considera, de um lado, a perda de bem estar causada pela inflação através da demanda de moeda e, de outro, o benefício pela redução da perda de eficiência econômica ocasionada pela rigidez dos salários nominais. Concluímos que a análise exposta no presente trabalho sugere que, tendo em vista a redução da incerteza macroeconômica na economia brasileira nos últimos anos, haveria motivos também para uma redução gradual da meta de inflação. Contudo, também aponta que não se deve buscar metas muito baixas, uma vez que o benefício adicional em se reduzir a meta de inflação é relativamente pequeno quando já se está em um nível de inflação baixo. / Inflation targeting regimes have been adopted by a large number of countries in recent years. Obviously, the definition of the actual inflation target to be pursued is an essential part of this regime. This work aims to make a contribution to the debate about the optimal target for Brazil. The three essays follow different paths in an attempt to estimate the quantitative costs and benefits of the different inflation targets for the Brazilian economy. The focus is on the long-term effects of the different targets as these are more important than the possible costs during the transition towards the new inflation target. The first article discusses the optimal inflation target based on the welfare loss measured by the money demand function, a classic channel highlighted in the literature. The second assesses the relation between the level and uncertainty of future inflation. We investigate this issue with the use of econometric models to estimate the conditional variance of inflation, of inflation expectations reported by professional economic analysts and of break-even inflation rates. The third article presents a more theoretical and structural focus. We present a model in which there is a trade-off for the inflation target and this model is calibrated to obtain estimates of the optimal target for the Brazilian economy. On one hand, the model considers the welfare loss caused by inflation through money demand and, on the other, the benefit from the reduced frequency of periods in which a downward nominal wage restriction binds. Our conclusion is that the analysis presented suggests that, considering the lower macroeconomic uncertainty observed in Brazil in the recent years, there would be reasons for a gradual reduction in the inflation target. However, it also suggests that very low targets should not be set as the additional benefit in reducing the inflation target is relatively small once the inflation target has already been set at a low level.

Apesar do esforço despendido pelas comunidades acadêmica e industrial (artigos, patentes e protótipos de laboratório), as Máquinas de Cinemática Paralela - MCPs - ainda apresentam uma participação inexpressiva no mercado de máquinasferramentas e robôs. Uma das razões para este fato são os seus baixos índices de acurácia e repetibilidade, em comparação aos das máquinas de usinagem convencionais. Este trabalho apresenta a avaliação dos mapeamentos de flexibilidade e da 1ª freqüência natural sobre o posicionamento da peça de trabalho e direções preferenciais de usinagem, dentro do espaço de trabalho disponível de uma máquina-ferramenta de cinemática paralela. Atualmente esta análise tem sido realizada em máquinas de cinemática paralela utilizando-se do princípio dos trabalhos virtuais ou parcialmente envolvendo este método e o método dos elementos finitos com a superposição linear dos resultados de ambos. Este trabalho apresenta análise de flexibilidade, utilizando apenas o método dos elementos finitos, aplicada a uma arquitetura paralela do tipo 2PRS+2PUS, com 4 graus de liberdade (duas translações - Y e Z - e duas rotações - \'teta\'x e \'teta\'YG), denominada Tetraglide. Em todas as análises feitas o grau de liberdade \'teta\'YG foi mantido constante, \'teta\'YG = 0°. Desta forma todas as análises ocorreram sobre o plano YZ. A partir dessa análise de flexibilidade são avaliadas as cargas axiais nas barras, que unem os atuadores à plataforma móvel ao longo do espaço de trabalho, determinando-se onde ocorre flambagem. Após isto, ainda com o método dos elementos finitos, obtém-se a 1ª freqüência natural ao longo de cada espaço de trabalho com orientação constante, uma vez que o conhecimento desta freqüência é fator importante na avaliação do comportamento estrutural dinâmico de máquinas-ferramentas. Após estas análises, analisam-se parâmetros estruturais em análises de sensibilidade visando maximizar a menor 1ª freqüência natural observada em cada espaço de trabalho com orientação constante. / In spite of the effort spent by the academic and industrial communities (goods, patents and laboratory prototypes), the Parallel Kinematics Machines - PKMs - they still present an inexpressive participation in the market of machine-tools and robots. One of the reasons for this fact is their low indexes of accuracy and precision, in comparison with the machines of conventional milling. This work presents the evaluation of the compliance mapping (kinetostatic analysis) and natural frequency about the positioning of the work piece and milling preferential directions, inside the available workspace of a parallel kinematics machine tool. At present this analysis has been accomplished in parallel kinematics machine using the virtual work principle or partially involving this method and the finite element method, with the overlap of the results of both. This work presents a compliance analysis just using the finite element method in parallel kinematics machine of type 2PRS+2PUS with 4 degrees of freedom (two moves - Y and Z - and two rotations - \'teta\'x e \'teta\'YG), denominated Tetraglide. In all of the done analyses the degree of freedom \'teta\'YG was maintained constant, \'teta\'YG = 0°. This way all of the analyses occurred on the plan YZ. Starting from the compliance analysis the axial loads are evaluated in the bars, which connect the actuators to the movable platform along the workspace, determining where the buckling occurs. After this, with the finite element method, 1st natural frequency is obtained along each constant-orientation workspace, once the knowledge of this frequency is important factor in the evaluation of the dynamic structural behavior of machine-tools. After these analyses, structural parameters are analyzed in sensibility analyses seeking to maximize to smallest 1st natural frequency observed in each constant-orientation workspace.

No presente trabalho consideramos homeomorfismos do círculo sem pontos periódicos e com o mesmo número finito de pontos críticos todos de tipo non-flat. Provamos que se existe uma conjugação topológica entre dois destes mapas que leva ponto crítico em ponto crítico, sem necessidade de preservar criticalidades, então dita conjugação é uma transformação quase-simétrica com distorção quase-simétrica local uniformemente limitada. Estes resultados são válidos para qualquer número de rotação irracional e são independentes da natureza das criticalidades dos pontos críticos, de modo que nossos resultados são válidos para toda criticalidade real. / In this work we consider circle homeomorphisms without periodic points and with finite number of critical points all of them being non-flat. We prove that if there exists a topological conjugacy between two of those maps which sends critical point into critical point, which not necessarily preserve criticalities, then this conjugacy is a quasi-symmetric map with quasi-symmetric distortion universally bounded. All these results are valid for any irrational rotation number and are independent of the nature of the criticalities, therefore our results are valid for all real criticalities.

La théorie de la rigidité permet de prédire les comportements de nombreuses propriétés de verres, que ce soit avec la composition, la température ou la pression, tout en réduisant la structure de ceux-ci à un simple critère mécanique : flexible, isostatique ou rigide sur-contraint. Des travaux récents ont mis en évidence l'utilité d'une telle analyse, tant de manière expérimentale que théorique. Dans cette thèse, nous appliquons une méthode d'établissement de contraintes à partir de simulations par dynamique moléculaire, afin d'explorer la rigidité dans différentes conditions de température, pression ou composition pour des verres ayant des potentiels d'application. Cet algorithme de dénombrement de contraintes, radiales ou angulaires, nous a permis de définir des zones de compositions particulières dans les verres d'oxydes, avec une compréhension différente de la structure et des contraintes entourant les ions dans la silice. Par la suite, nous avons aussi pu montrer des effets topologiques faibles des gaz nobles dans la silice, et relier les anomalies dynamiques observées dans la silice sous pression à des conditions de rigidité du réseau. / Rigidity theory allows to predict the behavior of many properties of glasses with respect to composition, while considering the underlying network as simple mechanical trusses that can be flexible, isostatic or stressed-rigid. Some recent works showed how useful such an analysis can be, either theoretically or experimentally. In the thesis we will use a method to analyse topological constraints from molecular dynamics simulations in order to establish the rigidity of silica systems of interest under various conditions of composition, pressure and temperature. Applying this constraints counting algorithm to radial and angular constraints in soda-lime systems allowed us to establish composition intervals of isostatic properties while giving a novel comprehension of the constraints and the structure surrounding the ions. We later highlight the faint influence of noble gases atoms upon silica when melted in the bulk. That study also allowed us to link dynamical anomalies of silica under pressure to rigidity changes of the network.

The purpose of this study was to examine the effects of segregation on the flexibility of individuals in the Negro and Anglo-American ethnic groups and to investigate the relationship between variations in flexibility and sociometric choices within the peer group.

Cold-formed steel purlin systems are widely used in modem building construction, for supporting the roof and floor structures. The rotational behaviour of beam-to-beam bolted connections, which are used between the sections, significantly affects the performance of purlin systems and is hard to predict. The behaviour models currently available for the connections only offer linear or multilinear predictions with low levels of accuracy. The aim of the research presented in this thesis is to develop and propose a nonlinear, more accurate behaviour model for the sleeved modified Z bolted connections, by means of experimental and numerical analysis. Finite element models are presented for the single-bolt, single-lap connection, sleeved modified Z connections in the simply supported arrangement, and a six-span purlin system. Based on the numerical results that have been validated by the experiments, a nonlinear behaviour model is proposed for the sleeved modified Z connections. In the model, the behaviour of the connections is divided into four stages, based on the dominant mechanism that provides the resistance to the rotation. Different formulas are used in different stages to determine the behaviour of the connection, boundary conditions, and magnitudes of bolt forces. The new model reflects well the true behaviour of the connections, and provides a good understanding of what happens inside the connections. The model reveals the failure pattern of the connections and enables optimization in the design of purl in systems, for improving efficiency in material usage.

Une variété riemannienne est dite rigide lorsque la longueur des géodésiques périodiques (cas des variétés fermées) ou des géodésiques diffusées (cas des variétés ouvertes) permet de reconstruire globalement la géométrie de la variété. Cette notion trouve naturellement son origine dans des dispositifs d’imagerie numérique tels que la tomographie par rayons X. Grâce une approche résolument analytique initiée par Guillarmou et fondée sur de l’analyse microlocale (plus particulièrement sur certaines techniques récentes dues à Faure-Sjostrand et Dyatlov-Zworski permettant une étude analytique fine des flots Anosov), nous montrons que le spectre marqué des longueurs, c’est-à-dire la donnée des longueurs des géodésiques périodiques marquées par l’homotopie, d’une variété fermée Anosov ou Anosov à pointes hyperboliques détermine localement la métrique de la variété. Dans le cas d’une variété ouverte avec ensemble capté hyperbolique, nous montrons que la distance marquée au bord, c’est-à-dire la donnée de la longueur des géodésiques diffusées marquées par l’homotopie, détermine localement la métrique. Enfin, dans le cas d’une surface asymptotiquement hyperbolique, nous montrons qu’une notion de distance renormalisée entre paire de points au bord à l’infini permet de reconstruire globalement la géométrie de la surface. / A Riemannian manifold is said to be rigid if the length of periodic geodesics (in the case of a closed manifold) or scattered geodesics (in the case of an open manifold) allows to recover the full geometry of the manifold. This notion naturally arises in imaging devices such as X-ray tomography. Thanks to a analytic framework introduced by Guillarmou and based on microlocal analysis (and more precisely on the analytic study of hyperbolic flows of Faure-Sjostrand and Dyatlov-Zworski), we show that the marked length spectrum, that is the lengths of the periodic geodesics marked by homotopy, of a closed Anosov manifold or of an Anosov manifold with hyperbolic cusps locally determines its metric. In the case of an open manifold with hyperbolic trapped set, we show that the length of the scattered geodesics marked by homotopy locally determines the metric. Eventually, in the case of an asymptotically hyperbolic surface, we show that a suitable notion of renormalized distance between pair of points on the boundary at infinity allows to globally reconstruct the geometry of the surface.

In this thesis we study qualitative as well as quantitative stability aspects of isometric and conformal maps from S^(n-1) to R^n, when n is greater or equal to 2 or 3 respectively. Starting from the classical theorem of Liouville, according to which the isometry group of S^(n-1) is the group of its rigid motions and the conformal group of S^(n-1) is the one of its Möbius transformations, we obtain stability results for these classes of mappings among maps from S^(n-1) to R^n in terms of appropriately defined deficits. Unlike classical geometric rigidity results for maps defined on domains of R^n and mapping into R^n, not only an isometric\ conformal deficit is necessary in this more flexible setting, but also a deficit measuring how much the maps in consideration distort S^(n-1) in a generalized sense. The introduction of the latter is motivated by the classical Euclidean isoperimetric inequality.

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Martin Lhota Formula Student Front Chassis Part Design DW, IAE, 2011, 75 pp, 62 pics The aim of the thesis is to suggest a suitable configuration of Formula Student Car’s front part of a frame according to current rules of SAE organization in the Formula Student competition. In this proposal low weight, manufacturability and sufficient torsion rigidity were preferred, whereas previously suggested solutions were reflected. At first there is presented a list of important SAE rules for the construction of front part followed by a short recherché of development of the constructional solution of frames and frames suitable for Formula Students car. Secondly there is described process during frame construction design and its computational model for the analysis which simulates torsion with the support of MKP system. Gained results and some parameters of the frame are compared with similar version of the frame construction which was suggested and made for the first Formula Student Car of our University. Moreover, there is also presented summary of suggested frame and also recommendation with possible alternatives for the next development.