Sonine approximation for collisional moments of granular gases of inelastic rough spheres

We consider a dilute granular gas of hard spheres colliding inelastically with coefficients of normal and tangential restitution $\alpha$ and $\beta$, respectively. The basic quantities characterizing the distribution function $f(\mathbf{v},\bm{\omega})$ of linear ($\mathbf{v}$) and angular ($\bm{\omega}$) velocities are the second-degree moments defining the translational ($T^\text{tr}$) and rotational ($T^\text{rot}$) temperatures. The deviation of $f$ from the Maxwellian distribution parameterized by $T^\text{tr}$ and $T^\text{rot}$ can be measured by the cumulants associated with the fourth-degree velocity moments. The main objective of this paper is the evaluation of the collisional rates of change of these second- and fourth-degree moments by means of a Sonine approximation. The results are subsequently applied to the computation of the temperature ratio $T^\text{rot}/T^\text{tr}$ and the cumulants of two paradigmatic states: the homogeneous cooling state and the homogeneous steady state driven by a white-noise stochastic thermostat. It is found in both cases that the Maxwellian approximation for the temperature ratio does not deviate much from the Sonine prediction. On the other hand, non-Maxwellian properties measured by the cumulants cannot be ignored, especially in the homogeneous cooling state for medium and small roughness. In that state, moreover, the cumulant directly related to the translational velocity differs in the quasi-smooth limit $\beta\to -1$ from that of pure smooth spheres ($\beta=-1$). This singular behavior is directly related to the unsteady character of the homogeneous cooling state and thus it is absent in the stochastic thermostat case.Comment: 14 pages, 8 figures; v2: some parts rewritten, new references added; published in a special topic decicated to Carlo Cercignan

The Effect of social security, demography and technology on retirement

This article investigates the causes in the reduction of labor force participation ofthe old. We argue that the changes in social security policy, in technology and indemography may account for most of the changes in retirement over the second partof the last century in the U.S. economy. We develop a dynamic general equilibriummodel with endogenous retirement that embeds social security legislation. The modelis able to match very closely the increase in the retirement rate of males aged 65 andolder. It also quanti es the isolated impact on retirement and on the solvency of thesocial security system of the di¤erent factors. The model suggests that technologicaland demographic changes had a strong in uence on retirement, so that it would haveincreased signi cantly even if the social security rules had not changed. However, asthe latter became much more generous in the past, changes in social security policycan account not only for a sizeable part of the expansion of retirement, but also for themost of the observed increase in the social security expenses as a share of GDP.

Réflexions autour des dispositifs didactiques implémentés à l’attention des personnes vivant avec le diabète : de quels modèles d’apprentissage parle-t-on ?

Il s'agit d'une revue de la littérature de 40 ans d'éducation thérapeutique dans le cadre du diabète. Cette revue cherche à voir les tendances qui ressortent des dispositifs pédagogiques implémentés à l'attention des patients diabétiques. Ces tendances suggèrent une vision réductrice du processus d'apprentissage du sujet patient-apprenant

The Effect of Social Security, Demography and Technology on Retirement

This article investigates the causes in the reduction of labor force participation ofthe old. We argue that the changes in social security policy, in technology and indemography may account for most of the changes in retirement over the second partof the last century in the U.S. economy. We develop a dynamic general equilibriummodel with endogenous retirement that embeds social security legislation. The modelis able to match very closely the increase in the retirement rate of males aged 65 andolder. It also quanti es the isolated impact on retirement and on the solvency of thesocial security system of the di¤erent factors. The model suggests that technologicaland demographic changes had a strong in uence on retirement, so that it would haveincreased signi cantly even if the social security rules had not changed. However, asthe latter became much more generous in the past, changes in social security policycan account not only for a sizeable part of the expansion of retirement, but also for themost of the observed increase in the social security expenses as a share of GDP.

Are Price Limits on Futures Markets That Cool? Evidence from the Brazilian Mercantile and Futures Exchange

This paper investigates the impact of price limits on the Brazilian futures markets using high frequency data. The aim is to identify whether there is a cool-off or a magnet effect. For that purpose, we examine a tick-by-tick data set that includes all contracts on the S�o Paulo stock index futures traded on the Brazilian Mercantile and Futures Exchange from January 1997 to December 1999. The results indicate that the conditional mean features a floor cool-off effect, whereas the conditional variance significantly increases as the price approaches the upper limit. We then build a trading strategy that accounts for the cool-off effect in the conditional mean so as to demonstrate that the latter has not only statistical, but also economic significance. The in-sample Sharpe ratio indeed is way superior to the buy-and-hold benchmarks we consider, whereas out-of-sample results evince similar performances.Cool-off effect, Futures markets, Magnet effect, Price limits, Transactions data

Banda comunitária da UFCSPA: um espaço de aprendizagem informal

Anais do 35º Seminário de Extensão Universitária da Região Sul - Área temática: CulturaA Banda Comunitária é um projeto de extensão da UFCSPA. Iniciado em 2013, busca estreitar laços entre a comunidade acadêmica e a comunidade em geral através da música instrumental. Vem se constituindo como um espaço de metodologia de aprendizagem informal, caracterizada pela ênfase na criatividade e autonomia. Realizou ao final de 2016 seu primeiro concerto independente, em que foram evidenciados para grande público não somente os resultados sonoros de sua trajetória, mas também a importância do projeto para a comunidad

Estudos Econômicos das Causas da Criminalidade no Brasil: Evidências e Controvérsias

O objetivo deste estudo é reunir e discutir os estudos econômicos da criminalidade realizados no Brasil. Apresentam-se as principais dificuldades, evidências e controvérsias encontradas nas pesquisas empíricas, além de algumas das principais bases de dados criminais disponíveis. A geral indisponibilidade de dados, a alta taxa de sub-registro nos dados oficiais e a causalidade inversa entre as variáveis de desterrense e as taxas de crimes são algumas das principais dificuldades inerentes à investigação econômica do crime. A maior controvérsia entre os estudos é o efeito da segurança pública sobre as taxas de crimes. As principais evidências são que a desigualdade de renda e os retornos do crime parecem ser fatores de incremento da criminalidade. Além disso, há efeitos espaciais afetando a criminalidade. Por fim, é um fato estilizado" na literatura que a criminalidade está sujeita aos efeitos de inércia.Economia do Crime, Criminalidade, Violência