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Publications

Publications by LIAAD

2013

A new Branch and Bound method for a discrete truss topology design problem

Authors
Cerveira, A; Agra, A; Bastos, F; Gromicho, J;

Publication
COMPUTATIONAL OPTIMIZATION AND APPLICATIONS

Abstract
Our paper considers a classic problem in the field of Truss Topology Design, the goal of which is to determine the stiffest truss, under a given load, with a bound on the total volume and discrete requirements in the cross-sectional areas of the bars. To solve this problem we propose a new two-stage Branch and Bound algorithm. In the first stage we perform a Branch and Bound algorithm on the nodes of the structure. This is based on the following dichotomy study: either a node is in the final structure or not. In the second stage, a Branch and Bound on the bar areas is conducted. The existence or otherwise of a node in this structure is ensured by adding constraints on the cross-sectional areas of its incident bars. In practice, for reasons of stability, free bars linked at free nodes should be avoided. Therefore, if a node exists in the structure, then there must be at least two incident bars on it, unless it is a supported node. Thus, a new constraint is added, which lower bounds the sum of the cross-sectional areas of bars incident to the node. Otherwise, if a free node does not belong to the final structure, then all the bar area variables corresponding to bars incident to this node may be set to zero. These constraints are added during the first stage and lead to a tight model. We report the computational experiments conducted to test the effectiveness of this two-stage approach, enhanced by the rule to prevent free bars, as compared to a classical Branch and Bound algorithm, where branching is only performed on the bar areas.

2013

Online social networks: Recommendation diffusion and co-consumption influence

Authors
Torres, A; Martins, FV;

Publication
Handbook of Research on Enterprise 2.0: Technological, Social, and Organizational Dimensions

Abstract
The chapter is conceptual, based on analysis and synthesis of social network theory and e-consumer literature. Despite a broad spectrum of disciplines that investigate social networks and the interest of marketing practitioners in the consequences of social networks, there are still areas open for research into networked-consumer behavior in marketing. Based on previous theoretical and empirical research, this study examines and discusses the influence of social network structure and ties in matched dyads, recommendation diffusion, social contagion and co-consumption influence, and individual motivations to spread market information. The chapter proposes a theory of matched dyadic ties in close networks of connections as a proxy for information about the potential market that is difficult and expensive for businesses to measure or access directly. © 2014, IGI Global.

2013

Measuring internet commerce experience and valuing nettworked customers: A structural modeling approach

Authors
Ana Isabel Perdigão Lopes Pereira Torres;

Publication

Abstract

2013

Classifying heart sounds: Approaches to the PASCAL challenge

Authors
Gomes, EF; Bentley, PJ; Coimbra, M; Pereira, E; Deng, Y;

Publication
HEALTHINF 2013 - Proceedings of the International Conference on Health Informatics

Abstract
In this paper we describe a methodology for heart sound classification and results obtained at PASCAL Classifying Heart Sounds Challenge. The results of competing methodologies are shown. The approach has two steps: segmentation and classification of heart sounds. We also describe the data collection procedure.

2013

The lottery Blotto game

Authors
Osorio, A;

Publication
ECONOMICS LETTERS

Abstract
In this paper we relax the Colonel Blotto game assumption that for a given battle the player who allocates the higher measure of resources wins that battle. We assume that for a given battle, the Colonel who allocates the higher measure of resources is more likely to win. We have a simpler model for which we are able to compute all Nash equilibria in pure strategies for any valuations profile that players might have, something that is not possible for the original Blotto game.

2013

Sporadic and reversible chromothripsis in chronic lymphocytic leukemia revealed by longitudinal genomic analysis

Authors
Bassaganyas, L; Beà, S; Escaramís, G; Tornador, C; Salaverria, I; Zapata, L; Drechsel, O; Ferreira, PG; Rodriguez Santiago, B; Tubio, JMC; Navarro, A; Martín García, D; López, C; Martínez Trillos, A; López Guillermo, A; Gut, M; Ossowski, S; López Otín, C; Campo, E; Estivill, X;

Publication
Leukemia

Abstract

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