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This study examines the relationship between in ation and price dispersion during the hyperin ationary episode in Brazil. We look at micro data on price dynamics through the perspective of dispersion at the store level, building on the informational consequences of high price dispersion. Rather than focus on which theoretical framework best explains the relative price variability seen on the data, we focus on a top-down approach to the information embedded in prices: we analyze price setting behavior from the perspective of economic segments as whole and from the perspective of each seller taken individually. In the former case we seek to answer the following: do higher levels of in ation favor higher price dispersion? In the latter, we focus on the time-series properties of each of more than 150 real price trajectories in both high and low in ation periods. We provide further empirical evidence of the loss of information embedded in prices, be it deriving from greater overall dispersion or from a greater volatility in each seller\'s price trajectory relative to its peers\'. Our findings extend previous results, accounting for a higher level of in ation, a longer time span and a broader selection of items. / Este trabalho investiga a relação entre inflação e dispersão de preços durante a experiência de hiperinflação vivida no Brasil. Estudamos micro dados de preços sob a perspectiva da dispersão no nível do vendedor, buscando evidências das consequências informacionais de uma alta dispersão de preços. Ao invés de investigar qual arcabouço teórico melhor explica a variabilidade de preços relativos encontrada nos dados, focamos em uma abordagem sobre a informação incorporada nos preços que vai do geral para o particular: analisamos primeiramente a formação de preços de maneira agregada e depois sob o ponto de vista do vendedor individualmente. No primeiro caso queremos responder à seguinte pergunta: níveis maiores de inflação geram níveis maiores de dispersão de preços? No segundo caso, focamos nas características das séries temporais de mais de 150 trajetórias de preços reais tanto para o período de alta inflação quanto para o período pós-estabilização. Fornecemos evidências empíricas adicionais da diminuição do caráter informacional dos preços, resultante tanto de uma maior dispersão das distribuições de preços, quanto da maior volatilidade na trajetória individual dos preços, relativamente aos preços dos concorrentes. Nossos resultados estendem trabalhos anteriores uma vez que considera um ambiente de inflação mais alta e mais volátil, um horizonte de tempo maior e uma seleção mais ampla de produtos.

Um dos componentes mais importantes de um Reator Nuclear é o Combustível Nuclear. Atualmente, o mais avançado combustível comercial, cuja aplicabilidade nos reatores brasileiros vem sendo desenvolvida pelo IPEN desde 1985, é o siliceto de urânio U3Si2. Este é formado por placas combustíveis com núcleos de dispersão (onde o material físsil (U3Si2) é disperso homogeneamente em uma matriz de alumínio) revestidos por alumínio. Tal combustível é produzido no Brasil com tecnologia totalmente nacional, resultado do esforço realizado pelo grupo de fabricação de combustíveis nucleares (CCN Centro do Combustível Nuclear) do IPEN. Diante da necessidade do aumento da potência do reator IEA-R1 e da construção do Reator Multipropósito Brasileiro (RMB), para a produção de radioisótopos principalmente para fins na área da medicina , haverá significativo aumento na produção deste combustível nuclear no IPEN. Em face desta conjuntura, faz-se necessário o desenvolvimento de técnicas de qualificação mais modernas e automatizadas. Visando a este objetivo, neste trabalho foi desenvolvido um novo método computacional de medição de espessuras de núcleos e revestimentos de placas combustíveis, o qual é capaz de realizar tais medidas em tempo menor e com dados estatísticos mais significativos, quando comparado com o método atual de medição. / One of the most important components of a nuclear reactor is the Nuclear Fuel. Currently, the most advanced commercial fuel, whose applicability in Brazilian reactors has been developed by IPEN since 1985, is the silicide U3Si2. This is formed by fuel plates with nuclei dispersion (where the fissile material (U3Si2) is homogeneously dispersed in a matrix of aluminum) coated aluminum. This fuel is produced in Brazil with developed technology, the result of the efforts made by the group of manufacturing nuclear fuel (CCN - Center of Nuclear Fuel) of IPEN. Considering the necessity of increasing the power of the IEA- R1 and Brazilian Multipurpose Reactor Building (RMB), for the production of radioisotopes - mainly for the area of medicine - there will be significant increase in the production of nuclear fuel at IPEN. Given this situation, if necessary, make the development of more modern and automated classification techniques. Aiming at this goal, this work developed a new computational method for measuring thickness of core and cladding of fuel plates, which are able to perform such measurements in less time and with more meaningful statistical data when compared with the current method of measurement.

Data can be collected in the form of counts in many situations. In other words, the number of deaths from an accident, the number of days until a machine stops working or the number of annual visitors to a city may all be considered as interesting variables for study. This study is motivated by two facts; first, the vital role of the continuous Weibull distribution in survival analyses and failure time studies. Hence, the discrete Weibull (DW) is introduced analogously to the continuous Weibull distribution, (see, Nakagawa and Osaki (1975) and Kulasekera (1994)). Second, researchers usually focus on modeling count data, which take only non-negative integer values as a function of other variables. Therefore, the DW, introduced by Nakagawa and Osaki (1975), is considered to investigate the relationship between count data and a set of covariates. Particularly, this DW is generalised by allowing one of its parameters to be a function of covariates. Although the Poisson regression can be considered as the most common model for count data, it is constrained by its equi-dispersion (the assumption of equal mean and variance). Thus, the negative binomial (NB) regression has become the most widely used method for count data regression. However, even though the NB can be suitable for the over-dispersion cases, it cannot be considered as the best choice for modeling the under-dispersed data. Hence, it is required to have some models that deal with the problem of under-dispersion, such as the generalized Poisson regression model (Efron (1986) and Famoye (1993)) and COM-Poisson regression (Sellers and Shmueli (2010) and Sáez-Castillo and Conde-Sánchez (2013)). Generally, all of these models can be considered as modifications and developments of Poisson models. However, this thesis develops a model based on a simple distribution with no modification. Thus, if the data are not following the dispersion system of Poisson or NB, the true structure generating this data should be detected. Applying a model that has the ability to handle different dispersions would be of great interest. Thus, in this study, the DW regression model is introduced. Besides the exibility of the DW to model under- and over-dispersion, it is a good model for inhomogeneous and highly skewed data, such as those with excessive zero counts, which are more disperse than Poisson. Although these data can be fitted well using some developed models, namely, the zero-inated and hurdle models, the DW demonstrates a good fit and has less complexity than these modifed models. However, there could be some cases when a special model that separates the probability of zeros from that of the other positive counts must be applied. Then, to cope with the problem of too many observed zeros, two modifications of the DW regression are developed, namely, zero-inated discrete Weibull (ZIDW) and hurdle discrete Weibull (HDW) models. Furthermore, this thesis considers another type of data, where the response count variable is censored from the right, which is observed in many experiments. Applying the standard models for these types of data without considering the censoring may yield misleading results. Thus, the censored discrete Weibull (CDW) model is employed for this case. On the other hand, this thesis introduces the median discrete Weibull (MDW) regression model for investigating the effect of covariates on the count response through the median which are more appropriate for the skewed nature of count data. In other words, the likelihood of the DW model is re-parameterized to explain the effect of the predictors directly on the median. Thus, in comparison with the generalized linear models (GLMs), MDW and GLMs both investigate the relations to a set of covariates via certain location measurements; however, GLMs consider the means, which is not the best way to represent skewed data. These DW regression models are investigated through simulation studies to illustrate their performance. In addition, they are applied to some real data sets and compared with the related count models, mainly Poisson and NB models. Overall, the DW models provide a good fit to the count data as an alternative to the NB models in the over-dispersion case and are much better fitting than the Poisson models. Additionally, contrary to the NB model, the DW can be applied for the under-dispersion case.

Spectral rendering, or the synthesis of images by taking into account the wavelengths of light, allows effects otherwise impossible with other methods. One of these effects is dispersion, the phenomenon that creates a rainbow when white light shines through a prism. Spectral rendering has previously remained in the realm of off-line rendering (with a few exceptions) due to the extensive computation required to keep track of individual light wavelengths. Caustics, the focusing and de-focusing of light through a refractive medium, can be interpreted as a special case of dispersion where all the wavelengths travel together. This thesis extends Adaptive Caustic Mapping, a previously proposed caustics mapping algorithm, to handle spectral dispersion. Because ACM can display caustics in real-time, it is quite amenable to be extended to handle the more general case of dispersion. A method is presented that runs in screen-space and is fast enough to display plausible dispersion phenomena in real-time at interactive frame rates.

Made available in DSpace on 2017-07-25T19:31:04Z (GMT). No. of bitstreams: 1 Ariane Lentice de Paula.pdf: 1722376 bytes, checksum: c8624e6fac60c0feeda5de3290e79f6b (MD5) Previous issue date: 2017-03-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The water dispersible clay study contributes to monitoring possible improvements or deteriorations in soilstructure. This work aimed to evaluate water dispersible clay in Oxissols after a long time no tillage. The experiment was carried out at "Capão da Onça" School Farm, belonging to State University of Ponta Grossa-UEPG. A toposequence was identified in the area, and divided into three parts: upper third (UT), middle third (MT) Lower third (LT). In each toposequence, three systematic sampling was carried out, with a regular mesh of 5x4 m implantation, with 20 demarcated points, a meter distanced each other. The soil samples were collected with a metal cylinderin the superficial layer (0,00-0,05 m). The indicators of soil structural stability, readily dispersible clay (RDC), mechanically dispersed clay (MDC) and water dispersible clay (WDC) were determined. For RDC determination, the turbidimetry method was used. For MDC determination, the same procedure was followed for RDC, however, a longer sample shaking time was used. The WDC determination used the similar methodology for granulometric analysis determination, without chemical dispersant use. The RDC, MDC and WDC levels were correlated with physical and chemical soil attributes. The RDC showed correlation with clay, sand, P, K+, Ca2+ and Mg2+. MDC showed correlation with clay, sand, K+ and Mg2+, while WDC showed correlation only with Ca2+. The third toposequence components presented almost in RDC levels, and there was no difference between them. In these areas, when there is a brief increase in energy inputs, it was observed that the dispersion was approximately two or three times higher, when RDC and MDC levels are compared. However, MDC levels didn‟t differ in the proportions in the samples. When soil samples were subjected to high energy inputs, as in WDC case, the dispersion increased approximately fifteen times. These results suggest that, under field conditions, dispersion clay in these soil samples maybe primarily due to the effect external mechanical forces. It was concluded that these soils presented low clay dispersion. However, the dispersion can increase significantly if they are subjected to high energy inputs, for example the intense machine‟s traffic. / O estudo de argila dispersa em água contribui para o monitoramento de possíveis melhorias ou deteriorações na estrutura do solo. Este trabalho teve como objetivo avaliar argila dispersa em água em Latossolo após longo tempo de plantio direto. O experimento foi realizado na Fazenda Escola “Capão da Onça” pertencente a Universidade Estadual de Ponta Grossa-UEPG. Na área foi identificada uma topossequência quefoi dividida em três partes: Terço Superior (TS), Terço Médio (TM) e Terço Inferior (TI). Em cada terço realizou-se amostragem sistemática, com a implantação de uma malha regular de 5x4m, com 20 pontos demarcados, distanciados a cada metro. As amostras de solo foram coletadas na camada superficial (0,00–0,05 m), com auxílio de um cilindro metálico. Os indicadores de estabilidade estrutural do solo, argila prontamente dispersa em água (APDA), argila mecanicamente dispersa em água (AMDA) e argila dispersa em água (ADA) foram determinados. Para a determinação da APDA utilizou-se o método da turbidimetria. Para a determinação da AMDA seguiu-se o mesmo procedimento da APDA, com tempo maior para a agitação das amostras. A determinação da ADA utilizou a metodologia semelhante para a determinação da análise granulométrica, sem uso de dispersante químico.Os teores de APDA, AMDA e ADA foram correlacionados com atributos físicos e químicos do solo. A APDA apresentou correlação com a argila, areia, P, K+, Ca2+ e Mg2+. A AMDA apresentou correlação com argila, areia, K+ e Mg2+ enquanto que a ADA apresentou correlação apenas com o Ca2+. Os terços componentes da topossequência apresentaram teores quase nulos de APDA, não havendo diferença entre eles. Nestas áreas, quando se teve um breve aumento nas entradas de energia, observou-se que a dispersão foi aproximadamente duas a três vezes mais elevada, quando se compara os teores de APDA e AMDA. Contudo, os teores de AMDA não diferiram nas proporções amostradas. Quando se submeteu as amostras de solo a altas entradas de energias, como no caso da ADA, a dispersão aumentou aproximadamente quinze vezes. Estes resultados sugerem que, sob condições de campo, a dispersão de argila nestas amostras de solo, podem ser primeiramente advindas do efeito de forças mecânicas externas. Conclui-se que estes solos apresentam baixa dispersão de argila. No entanto, a dispersão pode aumentar significativamente se os mesmos forem submetidos a altas entradas de energias, a exemplo do intenso tráfego de máquinas.

In my first chapter, I provide a solution for how to model bargaining when there is on-the-job search and worker turnover depends on the wage. Bargaining is a standard feature in models without on-the-jobs search, but, due to endogeneity of the match surplus, a solution does not exist when worker turnover depends on the wage. My solution is based on wages being infrequently renegotiated. With renegotiation, the equilibrium wage distribution and the bargaining outcomes are both unique and the model nests earlier models in the literature as limit cases when wages are either continuously or never renegotiated. Furthermore, the rate of renegotiation has important implications for the nature of the equilibrium. A higher rate of renegotiation lowers the response of the match duration to a wage increase, which decreases a firm's willingness to accept a higher wage. This results in a lower share of the match surplus going to the worker. Moreover, a high rate of renegotiation also lowers the positive wage spillovers from a minimum wage increase, since these spillovers rely on firms' incentives to use higher wages to reduce turnover. In the standard job ladder model, search is modelled via an employment-specific Poisson rate. The size of the Poisson rate governs the size of the search friction. The Poisson rate can represent the frequency of applications by workers or the rate at which firms post suitable vacancies. In the second chapter, which is co-authored with Jake Bradley, we set up a model which has both of these aspects. Firms infrequently post vacancies and workers occasionally apply for these vacancies. The model nests the standard job ladder model and a version of the stock-flow model as special cases while remaining analytically tractable and easy to estimate empirically from standard panel data sets. The structurally estimated parameters are consistent with recent survey evidence of worker behavior. The model fits moments of the data that are inconsistent with the standard job ladder model and in the process reconciles the level of frictional wage dispersion in the data with replacement ratios used in the macro labor literature. In my third chapter, which is co-authored with Coen Teulings, we develop a simple method to measure the position in the job ladder in models with on-the-job search. The methodology uses two implications from models with on-the-job search: workers gradually select into better paying jobs until they get laid off at which time they start again to climb the job ladder. The measure relies on two sources of variation: (i) time-variation in job-finding rates and (ii) individual variation in the time since the last lay-off. We use the method to quantify the returns to on-the-job search and to establish the shape of the wage offer distribution by means of simple OLS regressions with wages as dependent variables. Moreover, we derive a simple prediction on the distribution of job durations. Applying the method to the NLSY 79, we find strong support for this class of models. We estimate the standard deviation of the wage offer distribution to be 12%. OJS accounts for 30% of the experience profile and 9% of the total wage dispersion.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Ellen Schwartz Tormey. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Mark V. Parish. / M.S.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE / Includes bibliographical references. / by Charles Hubert Smith. / Ph.D.