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Publications

Publications by CESE

2013

An approach for integrated design of flexible production systems

Authors
Marques, AF; Alves, AC; Sousa, JP;

Publication
FORTY SIXTH CIRP CONFERENCE ON MANUFACTURING SYSTEMS 2013

Abstract
The paper presents a holistic methodological approach for designing flexible production systems, integrating the management of the production resources, operations planning, internal logistics and quality. The proposed methodology relies on lean principles and encompasses a series of stages and tools that may be used to design and to assess the robustness of the production system for tackling small series and frequent changes in the productive processes due to customized production. This approach has been applied to the redesign of the production system of a Portuguese machinery manufacturing industrial company. Results show that it effectively led to a new flexible production system and a new industrial layout capable of responding to diverse future scenarios of products demand. (C) 2013 The Authors. Published by Elsevier B.V.

2013

The airport business in a competitive environment

Authors
Jimenez, E; Claro, J; de Sousa, JP;

Publication
EUROPEAN JOURNAL OF TRANSPORT AND INFRASTRUCTURE RESEARCH

Abstract
The liberalisation of the European air transport market has introduced new dynamics in the airport industry. In recent decades, airports evolved from infrastructure providers in a monopolistic context, to commercially orientated enterprises in a competitive environment. Current studies of airport strategic management lack a comprehensive perspective that enables airport operators to best identify the opportunities created by such dynamics. This paper analyses an airport as a multi-service firm that interacts with a network of stakeholders - the airport business network - to deliver several service packages to different groups of customers. An integrated conceptual framework was developed to aid academics and practitioners in the appraisal and design of competitive strategies for airports. Such framework covers a clear gap in existing literature, partly due to the fact that current perspectives on airport management fail to address the complexity of the industry in the present competitive environment.

2013

Combining optimization and simulation tools for short-term planning of forest operations

Authors
Marques, AF; de Sousa, JP; Ronnqvist, M; Jafe, R;

Publication
Scandinavian Journal of Forest Research

Abstract
The use of optimization techniques is well established in forest short-term planning and decision-making. Yet, existing techniques may pose some limitations for tackling with stochastic factors impacting in the execution of forest operations, such as delays, equipment breakdowns and other unexpected events. This paper explores the potential of using optimization techniques in combination with discrete-event simulation (DES) models for planning harvesting and logistics operations acknowledging uncertainty. DES models may be useful for assessing the performance and identifying bottlenecks associated with the execution of the deterministic plans retrieved with optimization techniques, when such stochastic events occur. This paper further presents an approach for the combination of a heuristic and a DES model developed in SIMIO. This approach was used to solve the raw material reception problem (RMRP) at a Portuguese pulp mill. This paper concludes with the analysis of the performance of deterministic schedules for the wood trucks considering uncertainty in their arrival at the mill. © 2013 © 2013 Taylor & Francis.

2013

Circle covering using medial axis

Authors
Rocha, P; Rodrigues, R; Toledo, FMB; Gomes, AM;

Publication
IFAC Proceedings Volumes (IFAC-PapersOnline)

Abstract
A good representation of a simple polygon, with a desired degree of approximation and complexity, is critical in many applications. This paper presents a method to achieve a complete Circle Covering Representation of a simple polygon, through a topological skeleton, the Medial Axis. The aim is to produce an efficient circle representation of irregular pieces, while considering the approximation error and the resulting complexity, i.e. the number of circles. This will help to address limitations of current approaches to some problems, such as Irregular Placement problems, which will, in turn, provide a positive economic and environmental impact where similar problems arise. © 2013 IFAC.

2013

Irregular packing problems: Industrial applications and new directions using computational geometry

Authors
Gomes, AM;

Publication
IFAC Proceedings Volumes (IFAC-PapersOnline)

Abstract
Cutting and Packing problems are hard Combinatorial Optimization problems that naturally arise in all industries and services where raw-materials or space must be divided into smaller non-overlapping items, so that waste is minimized. All the Cutting and Packing problems have in common the existence of a geometric sub-problem, originated by the natural item non-overlapping constraints. An important class of Cutting and Packing problems are the Irregular Packing problems that occur when raw materials have to be cut into items with irregular shapes. Irregular Packing problems, also known as Nesting problems, naturally arises in the garment, footwear, tools manufacturing and shipbuilding industries, among others. Each industrial application has its owns particular issues mainly related to the raw material's specific characteristics. Several challenges remain open in the Irregular Packing problems field. Some are due to the combinatorial nature of these problems. Others are of geometric nature, due to the non-convex and non-regular geometry of the items involved. Moreover these geometric challenges do not allow the combinatorial ones being properly tackled. This paper is mainly focused on presenting and discussing efficient tools and representations to tackle the geometric layer of nesting algorithms that capture the needs of the real-world applications of Irregular Packing problems. © 2013 IFAC.

2013

Preface to the Special Issue on Contributions to Applied Combinatorial Optimization

Authors
Viana, A; Miguel Gomes, AM; Costa, T;

Publication
INTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH

Abstract

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