Browsing by Issue Date, starting with "2011-11"
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- Capacidade de diferentes medidas de adiposidade para discriminar o risco metabólico em adolescentesPublication . Moreira, Carla Marisa Maia; Santos, Rute; Vale, Susana; Santos, Paula; Abreu, Sandra; Marques, Ana; Soares-Miranda, Luisa; Mota, JorgeEste estudo tem como objectivo determinar o poder discriminante das diferentes medidas de adiposidade: índice de massa corporal (IMC), perímetro da cintura (PC) e rácio cintura-altura (RCA) na identificação do risco metabólico em adolescentes açorianos.
- Relação entre índice de massa corporal pré-gestacional e ganho ponderal na gravidezPublication . Santos, Paula Clara; Abreu, Sandra; Ferreira, Margarida; Alves, Odete; Moreira, Carla; Vale, Susana; Santos, Rute; Marques, Ana; Moreira, Pedro; Mota, JorgeNa gravidez ocorre um aumento do peso, sendo que um ganho ponderal adequado é protector da saúde materno/fetal. O aumento de peso excessivo pode levar ao desenvolvimento de diversas patologias, presentando relação com maior retenção de peso no pós-parto e risco de obesidade.
- Alteração no consumo de fruta e sopa durante a gravidez e a sua associação com o índice de massa corporal pré-gestacionalPublication . Abreu, Sandra; Santos, Paula Clara; Moreira, Carla; Vale, Susana; Santos, Rute; Soares-Miranda, Luísa; Mota, Jorge; Moreira, PedroEncontra-se descrito que durante a gravidez, em benefício da saúde do feto, a mulher altera alguns dos seus hábitos alimentares. O objectivo deste estudo foi determinar as alterações no consumo de fruta e sopa na gravidez de acordo com o IMC pré-gestacional.
- On the use of VISIR under different course implementationsPublication . Viegas, Maria C.; Marques, Maria A.; Costa-Lobo, Maria; Alves, Gustavo R.; Alberto, António; Dias, Custódio; Azevedo, Manuel; Alves, Mario; Guimarães, Pedro; Gustavsson, IngvarThis paper addresses different course integrations of VISIR. The didactic approaches are summarized and the analysis done provides explanations to some of the problems encountered, plus some guidelines for future implementations. A number of strengths and weaknesses are highlighted, leading to suggestions on how to enhance some strategic approaches to motivate teachers and students to the potential of using VISIR in teaching and learning processes. Proper references to previously published work also help to understand the research background and the lessons derived from a more intensive usage of VISIR.
- Pareto and Zipf laws for city size distributionPublication . Pinto, Carla; Lopes, A. M.; Tenreiro Machado, J. A.Pareto and Zipf distributions have been used in the modeling of distinct phenomena, namely in biology, demography, computer science, economics, amongst others. In this paper, it is presented a short review of applications of these distributions in city sizes.
- Visualization of Relations Between Financial Indices Using Multidimensional ScallingPublication . Tenreiro Machado, J. A.; Duarte, Gonçalo M.; Duarte, Fernando B.This paper applies Multidimensional scaling techniques for visualizing possible time-varying correlations between twenty five stock market values. The method is useful for observing stable or emerging clusters of stock markets with similar behavior. The graphs may also guide the construction of multivariate econometric models.
- Spreading Algorithm for Single-Objective ProblemsPublication . Pires, E. J. Solteiro; Mendes, Luís; Lopes, António M.; Oliveira, P. B. de Moura; Tenreiro Machado, J. A.This paper addresses the problem of finding several different solutions with the same optimum performance in single objective real-world engineering problems. In this paper a parallel robot design was proposed. Thereby, this paper presents a genetic algorithm to optimize uni-objective problems with an infinite number of optimal solutions. The algorithm uses the maximin concept and -dominance to promote diversity over the admissible space. The performance of the proposed algorithm is analyzed with three well-known test functions and one function obtained from practical realworld engineering optimization problems. A spreading analysis is performed showing that the solutions drawn by the algorithm are well dispersed.
- Some Notes About the Fermi-Pasta-Ulam ProblemPublication . Tenreiro Machado, J. A.During 1953, at Los Alamos, Fermi, Pasta and Ulam (FPU) developed computer simulations of a mechanical system composed of masses and springs [1]. We should also refer Mary Tsingou that helped in the programming of the computer Maniac. The idea formulated by Enrico Fermi was to simulate the one-dimensional analogue of atoms in a crystal by mean of a chain of particles linked by springs fixed at the extreme points. The springs were modeled by a term following a linear model (Hooke’s law) and a nonlinear term either quadratic (FPU -α), or cubic (FPU -β). These researchers found a dynamics considerably different from what linear systems would suggest. In fact, they thought that the system would exhibit “thermalization”, that is, a behavior in which the influence of the initial modes of vibration would fade, becoming all modes excited equally. Nevertheless, the simulations revealed a complex quasi-periodic dynamics. They thought that the energy introduced into the first frequency mode (k = 1) should drift to the other modes until the equipartition of energy would be reached. For the first instants of the simulation the higher modes (k = 2, 3,…) were successively excited, reaching almost an equipartition state, but after some time they verified that almost all energy was back to the first mode. Further simulations revealed the repetition of this phenomenon and that a kind of recurrence emerges, being recovered replicas of the initial state [2-4].
- Multidimensional Scaling Analysis of Robotic SignalsPublication . Lima, Miguel F. M.; Tenreiro Machado, J. A.This paper analyzes the signals captured during impacts and vibrations of a mechanical manipulator. To test the impacts, a flexible beam is clamped to the end-effector of a manipulator that is programmed in a way such that the rod moves against a rigid surface. Eighteen signals are captured and several metrics are calculated between them, such as the correlation, the mutual information and the entropy. A sensor classification scheme based on the multidimensional scaling technique is presented.
- Fractional Order Darwinian Particle Swarm OptimizationPublication . Couceiro, Micael S.; Ferreira, N. M. Fonseca; Tenreiro Machado, J. A.The Darwinian Particle Swarm Optimization (DPSO) is an evolutionary algorithm that extends the Particle Swarm Optimization (PSO) using natural selection, or survival-of-the-fittest, to enhance the ability to escape from local optima. This paper presents a method for controlling the convergence rate of the DPSO using fractional calculus (FC) concepts. The fractional order (FO) DPSO, denoted as FO-DPSO, is tested using several well-known functions and the relationship between the fractional order velocity and the convergence of the algorithm is observed.