Breaking the core-envelope symmetry in p-mode pulsating stars

It has been shown that there is a potential ambiguity in the asteroseismic determination of the location of internal structures in a pulsating star. We show how, in the case of high-order non-radial acoustic modes, it is possible to remove this ambiguity by considering modes of different degree. To support our conclusions we have investigated the seismic signatures of sharp density variations in the structure of quasi-homogeneous models.Comment: 3 pages, 3 figures, accepted for publication in Astronomy and Astrophysic

Representation of Nelson Algebras by Rough Sets Determined by Quasiorders

In this paper, we show that every quasiorder $R$ induces a Nelson algebra $\mathbb{RS}$ such that the underlying rough set lattice $RS$ is algebraic. We note that $\mathbb{RS}$ is a three-valued {\L}ukasiewicz algebra if and only if $R$ is an equivalence. Our main result says that if $\mathbb{A}$ is a Nelson algebra defined on an algebraic lattice, then there exists a set $U$ and a quasiorder $R$ on $U$ such that $\mathbb{A} \cong \mathbb{RS}$.Comment: 16 page

(Unmet)needs: A challenging concept and a complex social construction

This paper is based on an investigation entitled "Unmet Needs in Portugal - Tradition and emerging trends". Among other objectives, the study in question sought to develop an operative notion of needs, interpreting them as generated by the non-achievement of individual aspirations / expectations, through mismatch between opportunities and capabilities, in a dynamic process between the social context of action and the individual. Of the six case studies conducted within the scope of the research, we extracted the analysis of how two of those groups (adults in transition to retirement and adults in training transition) face the complex relationship that involves the satisfaction of their needs. We chose the first group because it allows us to analyse how these (older) adults live an important period of transition and the consequent recomposition of their needs that this stage of life (the transition to retirement) entails. In the case of adults in training transition, we use the testimonies of this group as an aid to understand how learning processes (at least, formal ones) interfere with the questioning, perception and achievement of the unmet needs. Therefore, a better understanding of the possible centrality of education in contributing to the satisfaction of needs, and its impact on well-being.info:eu-repo/semantics/publishedVersio

Porto Oscillation Code (POSC)

The Porto Oscillation Code (POSC) has been developed in 1995 and improved over the years, with the main goal of calculating linear adiabatic oscillations for models of solar-type stars. It has also been used to estimate the frequencies and eigenfunctions of stars from the pre-main sequence up to the sub-giant phase, having a mass between 0.8 and 4 solar masses. The code solves the linearised perturbation equations of adiabatic pulsations for an equilibrium model using a second order numerical integration method. The possibility of using Richardson extrapolation is implemented. Several options for the surface boundary condition can be used. In this work we briefly review the key ingredients of the calculations, namely the equations, the numerical scheme and the output.Comment: Accepted for publication in Astrophysics and Space Science

The dynamics of corporate credit risk: an intensity-based econometric analysis

Lucas, A. [Promotor

Parameter Driven Multi-state Duration Models: Simulated vs Approximate Maximum Likelihood Estimation

Likelihood based inference for multi-state latent factor intensity models is hindered by the fact that exact closed-form expressions for the implied data density are not available. This is a common and well-known problem for most parameter driven dynamic econometric models. This paper reviews, adapts and compares three different approaches for solving this problem. For evaluating the likelihood, two of the methods rely on Monte Carlo integration with importance sampling techniques. The third method, in contrast, is based on fully deterministic numerical procedures. A Monte Carlo study is conducted to illustrate the use of each method, and assess its corresponding finite sample performance