Vanishing Viscosity Limits and Boundary Layers for Circularly Symmetric 2D Flows

We continue the work of Lopes Filho, Mazzucato and Nussenzveig Lopes [LMN], on the vanishing viscosity limit of circularly symmetric viscous flow in a disk with rotating boundary, shown there to converge to the inviscid limit in $L^2$-norm as long as the prescribed angular velocity $\alpha(t)$ of the boundary has bounded total variation. Here we establish convergence in stronger $L^2$ and $L^p$-Sobolev spaces, allow for more singular angular velocities $\alpha$, and address the issue of analyzing the behavior of the boundary layer. This includes an analysis of concentration of vorticity in the vanishing viscosity limit. We also consider such flows on an annulus, whose two boundary components rotate independently. [LMN] Lopes Filho, M. C., Mazzucato, A. L. and Nussenzveig Lopes, H. J., Vanishing viscosity limit for incompressible flow inside a rotating circle, preprint 2006

Fractal analysis of weld defect patterns obtained by radiographic tests

This paper presents a fractal analysis of radiographic patterns obtained from specimens with three types of inserted welding defects: lack of fusion, lack of penetration, and porosity. The study focused on patterns of carbon steel beads from radiographs of the International Institute of Welding (IIW). The radiographs were scanned using a greyscale with 256 levels, and the fractal features of the surfaces constructed from the radiographic images were characterized by means of Hurst, detrended-fluctuation, and minimal-cover analyses. A Karhunen-Loeve transformation was then used to classify the curves obtained from the fractal analyses of the various images, and a study of the classification errors was performed. The obtained results indicate that fractal analyses can be an effective additional tool for pattern recognition of weld defects in radiographic tests.Comment: 7 pages, 2 figures. To appear AIP Conference Proceedings - QNDE 200

Nambu monopoles interacting with lattice defects in two-dimensional artificial square spin ice

The interactions between an excitation (similar to a pair of Nambu monopoles) and a lattice defect are studied in an artificial two-dimensional square spin ice. This is done by considering a square array of islands containing only one island different from all others. This difference is incorporated in the magnetic moment (spin) of the "imperfect" island and several cases are studied, including the special situation in which this distinct spin is zero (vacancy). We have shown that the two extreme points of a malformed island behave like two opposite magnetic charges. Then, the effective interaction between a pair of Nambu monopoles with the deformed island is a problem involving four magnetic charges (two pairs of opposite poles) and a string. We also sketch the configuration of the field lines of these four charges to confirm this picture. The influence of the string on this interaction decays rapidly with the string distance from the defect.Comment: 7 pages, 13 figure

CNA 8170: linhagem de arroz adaptada para o ecossistema terra firme do Estado do Pará.

Cópia de trabalho editado em CD-ROM

Sobre o valor relevante das demonstrações financeiras separadas

A promulgação do Regulamento n.º 1606/2002 obrigou a que as entidades com títulos admitidos à cotação em Bolsa, na União Europeia, preparassem as suas demonstrações financeiras consolidadas de acordo com as International Financial Reporting Standards (IFRS) endossadas, mas concede a cada Estado Membro (EM) a escolha sobre o normativo a utilizar na preparação das demonstrações financeiras separadas. Dada a diversidade pelo facto de os Estados Membros poderem obrigar, permitir, ou proibir a aplicação das IFRS na preparação das demonstrações financeiras separadas das entidades que consolidam, este estudo tem como objetivo perceber se as DF separadas são relevantes, e se essa relevância é condicionada pela proibição ou obrigação do uso das IFRS na sua preparação. Este estudo inclui informação de entidades com títulos admitidos à cotação em bolsa em 17 países da EU nos quais a utilização das IFRS é exigida numas jurisdições e proibida em outras. Os resultados sugerem que as demonstrações financeiras separadas são relevantes para explicar o valor de mercado de uma entidade, e que a proibição do uso das IFRS na preparação dessas DF separadas mitiga o valor relevante do seu capital próprio e dos resultados líquidos, ainda que apenas no caso do capital próprio essa atenuação seja estatisticamente significativa.info:eu-repo/semantics/publishedVersio

Disorder Induced Localized States in Graphene

We consider the electronic structure near vacancies in the half-filled honeycomb lattice. It is shown that vacancies induce the formation of localized states. When particle-hole symmetry is broken, localized states become resonances close to the Fermi level. We also study the problem of a finite density of vacancies, obtaining the electronic density of states, and discussing the issue of electronic localization in these systems. Our results also have relevance for the problem of disorder in d-wave superconductors.Comment: Replaced with published version. 4 pages, 4 figures. Fig. 1 was revise