2003
Autores
Fontes, DBMM; Hadjiconstantinou, E; Christofides, N;
Publicação
NETWORKS
Abstract
In this paper, we describe a heuristic algorithm based on local search for the Single-Source Uncapacitated (SSU) concave Minimum-Cost Network Flow Problem (MCNFP). We present a new technique for creating different and informed initial solutions to restart the local search, thereby improving the quality of the resulting feasible solutions (upper bounds). Computational results on different classes of test problems indicate the effectiveness of the proposed method in generating basic feasible solutions for the SSU concave MCNFP very near to a global optimum. A maximum upper bound percentage error of 0.07% is reported for all problem instances for which an optimal solution has been found by a branch-and-bound method. (C) 2003 Wiley Periodicals, Inc.
2003
Autores
Ferreira, F; Pinto, AA;
Publicação
ERGODIC THEORY AND DYNAMICAL SYSTEMS
Abstract
For diffeomorphisms on surfaces with basic sets, we show the following type of rigidity result: if a topological conjugacy between them is differentiable at a point in the basic set then the conjugacy has a smooth extension to the surface. These results generalize the similar ones of D. Sullivan, E. de Faria and ours for one-dimensional expanding dynamics.
2003
Autores
Figueiredo, A; Gomes, P;
Publicação
COMMUNICATIONS IN STATISTICS-SIMULATION AND COMPUTATION
Abstract
In multivariate data with n individuals described by p variables it is usual to assume that the variables are fixed and the individuals are randomly selected; in the present study we assume that the individuals are fixed and the previously normalised variables are randomly selected from a population of variables. When we want to associate to the sample of variables a distribution, like the Bingham distribution, it is important to use beforehand a test of uniformity. In this article, we compare the power of Bingham and Gine tests of uniformity for some dimensions of the sphere, vs. a Bingham population or a mixture of Bingham populations.
2003
Autores
Barros, R; Oliveira, B; Moreira, P;
Publicação
International Journal of Consumer Studies
Abstract
In order to assess the influence of social desirability in a food frequency questionnaire (FFQ), 483 Portuguese university students (133 women and 350 men) were recruited to a two-part self-administered questionnaire: the first part included the Marlowe–Crowne Social Desirability Scale (M-CSDS), physical activity data and self-reported height and weight; the second part, a validated semiquantitative FFQ. All subjects completed the first part of the questionnaire but only 40.2% returned the FFQ fairly completed (no statistically significant differences were found between the two groups, for any of the variables studied). Statistical analysis included reliability and test–retest of M-CSDS, correlation and general linear model (GLM). The Cronbach's alpha of M-CSDS was 0.64 and a test–retest correlation of 0.80 was obtained in a subsample of 35 subjects who completed the scale twice. We found a significantly positive correlation between social desirability and vitamin E for women; when adjusted for physical activity, body mass index and energy, social desirability was positively correlated with vitamin E, magnesium and fibre for women; and vitamin C, magnesium and fibre, for men. In GLM, social desirability produced a significant upward bias in dietary fibre, sugars, ß-carotene, vitamins C, E, magnesium, potassium and iodine, for women; and in dietary fibre, pufa n-3, folate, vitamins C, E, magnesium, manganese and potassium, for men. In GLM, and for both genders, social desirability produced a significant upward bias in vegetable consumption. Moreover, social desirability produced for women a significant downward bias in white bread, onion and beer, and for men in biscuits. © 2017 Wiley.
2002
Autores
Jorge, A; Pocas, J; Azevedo, P;
Publicação
DISCOVERY SCIENCE, PROCEEDINGS
Abstract
Association rule engines typically output a very large set of rules. Despite the fact that association rules are regarded as highly comprehensible and useful for data mining and decision support in fields such as marketing, retail, demographics, among others, lengthy outputs may discourage users from using the technique. In this paper we propose a post-processing methodology and tool for browsing/visualizing large sets of association rules. The method is based on a set of operators that transform sets of rules into sets of rules, allowing focusing on interesting regions of the rule space. Each set of rules can be then seen with different graphical representations. The tool is web-based and uses SVG. Association rules are given in PMML.
2002
Autores
Jorge, A; Moyle, S; Voss, A;
Publicação
COLLABORATIVE BUSINESS ECOSYSTEMS AND VIRTUAL ENTERPRISES
Abstract
The basic principles of a methodology for remote collaborative data mining are proposed. Starting from CRISP-DM, a general data mining process designed to carry out data mining projects; it is described how the principles of knowledge sharing and ease of communication can be embedded in the data mining process, The aim is to allow the execution of data mining projects, with the participation of multiple experts working from distant locations. All the participants in such a project can profit from the knowledge produced by others and share their knowledge online with the other participants. The produced knowledge (for example data transformations, working hypothesis, models, results of experiments) is also stored for future inspection and use, in pursuit of organizational learning. A prototypical implementation (RAMSYS) of the remote collaborative methodology is described with examples.
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