White dwarfs with a surface electrical charge distribution: Equilibrium and stability

The equilibrium configuration and the radial stability of white dwarfs composed of charged perfect fluid are investigated. These cases are analyzed through the results obtained from the solution of the hydrostatic equilibrium equation. We regard that the fluid pressure and the fluid energy density follow the relation of a fully degenerate electron gas. For the electric charge distribution in the object, we consider that it is centralized only close to the white dwarfs' surfaces. We obtain larger and more massive white dwarfs when the total electric charge is increased. To appreciate the effects of the electric charge in the structure of the star, we found that it must be in the order of $10^{20}\,[{\rm C}]$ with which the electric field is about $10^{16}\,[{\rm V/cm}]$. For white dwarfs with electric fields close to the Schwinger limit, we obtain masses around $2\,M_{\odot}$. We also found that in a system constituted by charged static equilibrium configurations, the maximum mass point found on it marks the onset of the instability. This indicates that the necessary and sufficient conditions to recognize regions constituted by stable and unstable equilibrium configurations against small radial perturbations are respectively $dM/d\rho_c>0$ and $dM/d\rho_c<0$.Comment: This is a preprint. The original paper will be published in EPJ

CFD AND SWIMMING: PRACTICAL APPLICATIONS

In this presentation topics in swimming simulation from a computational fluid dynamics perspective are discussed. This perspective means emphasis on the fluid mechanics and computational fluid dynamics methodology applied in swimming research. This talk presents new information based on recent scientific research conducted at the Research Centre in Sports Sciences, Health Sciences and Human Development (CIDESD, Vila Real, Portugal). We concentrated on numerical simulation results, considering the scientific simulation point-of-view and especially the practical implications with swimmers and coaches. Computational Fluid Dynamics has been applied to swimming in order to understand its relationships with performance. The numerical techniques have been applied to the analysis of the propulsive forces generated by the propelling segments and to the analysis of the hydrodynamic drag forces resisting forward motion

Caracterização dos solos de áreas experimentais do Centro Nacional de Pesquisa de Caprinos e Ovinos Tropicais.

A caracterização dos solos das áreas experimentais do Centro Nacional de Pesquisa de Caprinos e Ovinos Tropicais (CNPCOT) foi considerada necessária como informação básica para os trabalhos experimentais em andamento ou a serem implantados. Os dados apresentados aqui constituem parte do estudo, perfazendo uma área de 477 ha da qual aproximadamente a metade já tem a caracterização completa. Isto e, dados de observações de campo, descrição morfológica dos perfis, delimitação dos solos e análises de laboratório. No restante da área foram feitas apenas as observações de campo, assinalando-se os locais para descrição morfológica dos solos. Foi feita também a delimitação preliminar dos solos. Esta parte da área estudada ainda necessita das descrições de perfis e análises de laboratório, e estes dados poderão modificar em alguns casos a classificação dos solos e os seus limites agora mapeados.bitstream/item/57245/1/BP-01.pd

Relationship of force metrics with swimming performance in age-group swimmers

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The Kumaraswamy-G Poisson Family of Distributions

For any baseline continuous G distribution, we propose a new generalized family called the Kumaraswamy-G Poisson (denoted with the prefix “Kw-GP”) with three extra positive parameters. Some special distributions in the new family such as the Kw-Weibull Poisson, Kw-gamma Poisson and Kw-beta Poisson distributions are introduced. We derive some mathematical properties of the new family including the ordinary moments, generating function and order statistics. The method of maximum likelihood is used to fit the distributions in the new family. We illustrate its potentiality by means of an application to a real data set