Liquefaction Studies on Guaratuba Bay Erosion

The paper presents the studies conducted to explain the erosion process which occurred at the Guaratuba bay coast located in the South of Brazil [Tavares, 1989]. The subsoil in the area is composed mainly of be clean sand. The erosion occurred as a result of the liquefaction of the sandy subsoil and is described in the text. Several buildings, including the City Hall, and some streets near the affected area were sunk into the subsoil. The phenomenon took place on the 23rd of September of 1968. In the years of 1998, 1999 to March, 2000, new studies were performed to evaluate the strength potential of the sand. The implications of the findings as far as the seismic aspects of the liquefaction phenomenon is concerned is discussed in the text

The Welfare Cost of Macroeconomic Uncertainty in the Post-War Period

Lucas (1987) has shown the surprising result that the welfare cost of business cycles is quite small. Using standard assumptions on preferences and a fully-fledged econometric model we computed the welfare costs of macroeconomic uncertainty for the post-WWII era using the multivariate Beveridge-Nelson decomposition for trends and cycles, which considers not only business-cycle uncertainty but also uncertainty from the stochastic trend in consumption. The post-WWII period is relatively quiet, with the welfare costs of uncertainty being about 0.9% of per-capita consumption. Although changing the decomposition method changed substantially initial results, the welfare cost of uncertainty is qualitatively small in the post-WWII era - about $175.00 a year per-capita in the U.S. We also computed the marginal welfare cost of macroeconomic uncertainty using this same technique. It is about twice as large as the welfare cost -$350.00 a year per-capita.welfare costs of business cycles, Beveridge-Nelson decomposition

On the Welfare Costs of Business-Cycle Fluctuations and Economic-Growth Variation in the 20th Century

Lucas (1987) has shown a surprising result in business-cycle research: the welfare cost ofbusiness cycles are very small. Our paper has several original contributions. First, in computingwelfare costs, we propose a novel setup that separates the effects of uncertainty stemming frombusiness-cycle fluctuations and economic-growth variation. Second, we extend the sample from which to compute the moments of consumption: the whole of the literature chose primarily to work with post-WWII data. For this period, actual consumption is already a result of counter-cyclical policies, and is potentially smoother than what it otherwise have been in their absence. So, we employ also pre-WWII data. Third, we take an econometric approach and compute explicitly the asymptotic standard deviation of welfare costs using the Delta Method. Estimates of welfare costs show major differences for the pre-WWII and the post-WWII era. They can reach up to 15 times for reasonable parameter values -β=0.985, and ∅=5. For example, in the pre-WWII period (1901-1941), welfare cost estimates are 0.31% of consumption if we consider only permanent shocks and 0.61% of consumption if we consider only transitory shocks. In comparison, the post-WWII era is much quieter: welfare costs of economic growth are 0.11% and welfare costs of business cycles are 0.037% - the latter being very close to the estimate in Lucas (0.040%). Estimates of marginal welfare costs are roughly twice the size of the total welfare costs. For the pre-WWII era, marginal welfare costs of economic-growth and business- cycle fluctuations are respectively 0.63% and 1.17% of per-capita consumption. The same figures for the post-WWII era are, respectively, 0.21% and 0.07% of per-capita consumption.

Divisor resistivo para ensaios de frente de onda em isoladores

Orientador: Rene RobertDissertação (mestrado) - Universidade Federal do Parana, Setor de Ciencias ExatasInclui apendicesResumo: Este trabalho tem por objetivo desenvolver um divisor de tensão resistivo adequado para medir ondas de impulso atmosféricas cortadas na frente obtidas em ensaios de perfuração com ondas de impulso com frente íngreme em isoladores de suspensão. Ele aborda os métodos de projeto de divisores, levando em conta principalmente o efeito Skin, a distribuição de tensão ao longo da coluna e a solicitação térmica dos impulsos medidos pelo divisor. A meta foi alcançar parâmetros de resposta a degrau adequados para medir as ondas acima referidas. No que se refere ao efeito Skin, foi desenvolvida a solução a partir das equações de Maxwell para o vetor densidade de corrente para um impulso de corrente do tipo função degrau e a solução comparada com o valor medido experimentalmente. A distribuição de tensão ao longo da coluna foi calculada através do método dos elementos finitos utilizando o programa "ANSYSc 5.0", possibilitando assim o calculo da intensidade do campo elétrico, da distribuição de tensões e eficácia de elementos toroidais utilizados. O dimensionamento térmico foi determinado analiticamente levando-se em conta os tipos de solicitação a serem exigidos do divisor. Os resultados obtidos em relação ao efeito Skin coincidem com os resultados teóricos. Os dados obtidos do calculo das solicitações térmicas mostram que e possível utilizar o divisor sem problemas de aquecimento do material resistivo para o ensaio de perfuração. A resposta a degrau medida no divisor construído foi calculada através de um programa onde os dados digitais são filtrados de ruídos sobrepostos e tratados numericamente e os resultados foram adequados ao requerido pela literatura especializada, no que concerne a exatidão das medidas de parâmetros a degrau. As soluções utilizadas para confeccionar os elementos resistivos foram o Cloreto de Sódio e Ortofosfato de Sódio, onde este ultimo apresentou melhores resultados devido a sua propriedade não corrosiva. Com este divisor e possível medir tensões impulsivas obtidas nos ensaios de perfuração com uma exatidão melhor que 5%.Abstract: The main goal of this work is to develop a voltage divider suitable for measurements of atmospheric voltage impulse obtained in steep front voltage test on suspension insulators. It deals with methods of dividers design, taking into account the Skin effect, voltage distribution along the high voltage column of the divider and the heat generated by the impulses measured by the divider. By proper design it is possible to obtain certain values of the parameters of step response to measure correctly the impulses above referred to. As far as the Skin effect is concerned, it was found a solution to the vector current density to an applied current step function from the general Maxwell equations, this theoretical function was later compared with the practical one. The voltage distribution along the column was calculated by the finite element method using the software "ANSYS© 5.0". The thermic dimensioning was determined analytically considering the heat generated by the impulses applied to the divider. The results concerning the Skin effect agrees well with the measured ones. The data from the thermic stress calculation anticipates that the heating of resistive material for steep front voltage test will be very little. The divider's step response parameters were calculated by a software where the digital data was smoothed and numerically processed, obtaining results suitable with those required by the specialized literature, as far as accuracy on measurements of step response parameters is concerned. The resistive solutions used in the divider were made of Sodium Chloride and Sodium Orthophosphate, where the latter presented better results for it poses no problems concerning corrosion. With this divider is possible to measure steep front voltages waves with an accuracy better than 5%

Conceito de civilisação brasileira

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