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Publicações

Publicações por CEGI

2011

Factory templates: A decision support framework for manufacturing processes management

Autores
Azevedo, A; Almeida, A; Caldas, A;

Publicação
Proceedings of the 6th Iberian Conference on Information Systems and Technologies, CISTI 2011

Abstract
In order to develop the new industrial paradigm, it is necessary to explore a framework supported by planning and operational tools. Indeed, it becomes clear that more and more the next factories need to be increasingly more flexible, agile and knowledge-based in order to be able to adapt in real time to the continuously changing market demands, technology options and regulations, as well as accelerate the design process and optimise production. Therefore, in this paper a framework capable of supporting the factory planning will be presented based on predefined templates and product requirements. Furthermore, the Factory Templates will allow for process deployment, control and evaluation in real-time. © 2011 AISTI.

2010

A hybrid GRASP/VND algorithm for two- and three-dimensional bin packing

Autores
Parreno, F; Alvarez Valdes, R; Oliveira, JF; Tamarit, JM;

Publicação
ANNALS OF OPERATIONS RESEARCH

Abstract
The three-dimensional bin packing problem consists of packing a set of boxes into the minimum number of bins. In this paper we propose a new GRASP algorithm for solving three-dimensional bin packing problems which can also be directly applied to the two-dimensional case. The constructive phase is based on a maximal-space heuristic developed for the container loading problem. In the improvement phase, several new moves are designed and combined in a VND structure. The resulting hybrid GRASP/VND algorithm is simple and quite fast and the extensive computational results on test instances from the literature show that the quality of the solutions is equal to or better than that obtained by the best existing heuristic procedures.

2010

Neighborhood structures for the container loading problem: a VNS implementation

Autores
Parreno, F; Alvarez Valdes, R; Oliveira, JF; Tamarit, JM;

Publicação
JOURNAL OF HEURISTICS

Abstract
This paper presents a Variable Neighborhood Search (VNS) algorithm for the container loading problem. The algorithm combines a constructive procedure based on the concept of maximal-space, with five new movements defined directly on the physical layout of the packed boxes, which involve insertion and deletion strategies. The new algorithm is tested on the complete set of Bischoff and Ratcliff problems, ranging from weakly to strongly heterogeneous instances, and outperforms all the reported algorithms which have used those test instances.

2010

Multiple machine continuous setup lotsizing with sequence-dependent setups

Autores
Almada Lobo, B; Klabjan, D; Carravilla, MA; Oliveira, JF;

Publicação
COMPUTATIONAL OPTIMIZATION AND APPLICATIONS

Abstract
We address the short-term production planning and scheduling problem coming from the glass container industry. A furnace melts the glass that is distributed to a set of parallel molding machines. Both furnace and machine idleness are not allowed. The resulting multi-machine multi-item continuous setup lotsizing problem with a common resource has sequence-dependent setup times and costs. Production losses are penalized in the objective function since we deal with a capital intensive industry. We present two mixed integer programming formulations for this problem, which are reduced to a network flow type problem. The two formulations are improved by adding valid inequalities that lead to good lower bounds. We rely on a Lagrangian decomposition based heuristic for generating good feasible solutions. We report computational experiments for randomly generated instances and for real-life data on the aforementioned problem, as well as on a discrete lotsizing and scheduling version.

2010

Comments on: Routing problems with loading constraints

Autores
Oliveira, JF;

Publicação
TOP

Abstract

2010

Heuristics and exact methods for number partitioning

Autores
Pedroso, JP; Kubo, M;

Publicação
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
Number partitioning is a classical NP-hard combinatorial optimization problem, whose solution is challenging for both exact and approximative methods. This work presents a new algorithm for number partitioning, based on ideas drawn from tree search, breadth first search, and beam search. A new set of benchmark instances for this problem is also proposed. The behavior of the new method on this and other testbeds is analyzed and compared to other well known heuristics and exact algorithms.

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