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Publicações

2013

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

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

Publicação
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

Me4DCAP V0.1

Autores
Malta, Mariana Curado; Baptista, Ana Alice;

Publicação

Abstract
This report is framed in a research in progress project that has as goal the development of a method for the development of Dublin Core Application Pro les (Me4DCAP). The development of the rst version of Me4DCAP has been published. This paper describes in detail Me4DCAP V0.1, showing the sources used to justify its design. Me4DCAP was based in a Design Science Research methodological approach. It has as starting point the Singapore framework for Dublin Core Application Pro les (DCAP) and the Rational Uni ed Process; and integrates also knowledge from: (i) software development processes and techniques, focusing on the early stages of the processes that deal with data modeling; and from (ii) the practices of the metadata community concerning DCAP development. Me4DCAP establishes the way through the DCAP development. It establishes when activities must take place, how they interconnect, and which deliverables they will bring about; it also suggests which techniques should be used to build these deliverables.

2013

Robust and Fast Algorithm for Artificial Landmark Detection in an Industrial Environment

Autores
Pinto, M; Santos, F; Moreira, AP; Corves, BJ; Silva, R;

Publicação
Journal of Automation and Control Engineering - JOACE

Abstract

2013

Speeding-up poker game abstraction computation: Average rank strength

Autores
Teofilo, LF; Reis, LP; Cardoso, HL;

Publicação
AAAI Workshop - Technical Report

Abstract
Some of the most successful Poker agents that participate in the Annual Computer Poker Competition (ACPC) use an almost zero regret strategy: a strategy that approximates a Nash Equilibrium. However, it is still unfeasible to efficiently compute a Nash Equilibrium without some sort of information set abstraction due to the size of Poker's search tree. One popular technique for abstracting Poker information sets is to group hands with similar Expected Hand Strength (E[HS]) and thus play them in the same way. For large Poker variants, algorithms like CFR might need to calculate E[HS] billions of times, when the game abstraction is so large that it cannot be pre-computed, implying that E[HS] must be determined online. This way, improving the efficiency of this method would certainly reduce the computation time needed by CFR for these cases. In this paper we describe Average Rank Strength; a technique based on a pre-computed lookup table that speeds up E[HS] computation. Ours results demonstrate speed improvements of about three orders of magnitude and negligible results difference, when compared to the original E[HS]. Copyright

2013

Process performance assessment in collaborative manufacturing environments: A role oriented approach

Autores
Almeida, A; Ferreira, F; Azevedo, A; Caldas,;

Publicação
Lecture Notes in Mechanical Engineering

Abstract
Due to the increasing globalization process and the current economic situation, the power has shifted from the producer to the costumer, forcing companies to become more aware of the market needs. In order to become more customer-oriented, companies have been enhancing their management capabilities by shifting from a functional oriented approach to a process centered strategy, where core inter-firms processes can be seamlessly monitored and controlled. Since it is not possible to manage a system if its performance cannot be measured continuously during its entire life cycle, it is necessary to explore flexible and agile performance measurement and management systems as they are important tools capable of supporting the achievement of the strategic goals on the operational side. In the recent years several research projects have developed techniques and tools that support the collaboration. However they are restricted to the business level. In order to achieve the goals with the best performance, innovative and appropriate process monitoring and control mechanisms are needed. Consequently, this research provides an innovative solution that facilitates not only the gathering of operational and strategic information but also the assessment of collaborative manufacturing processes behavior following a fuzzy approach. © Springer International Publishing Switzerland 2013.

2013

Efficient Support for Mode-Directed Tabling in the YapTab Tabling System

Autores
Santos, J; Rocha, R;

Publicação
CoRR

Abstract

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