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Publications

Publications by CESE

2001

Monitoring an ocean outfall using an AUV

Authors
Ramos, P; Cruz, N; Matos, A; Neves, MV; Pereira, FL;

Publication
OCEANS 2001 MTS/IEEE: AN OCEAN ODYSSEY, VOLS 1-4, CONFERENCE PROCEEDINGS

Abstract
The wastewater plumes show to be very difficult to observed in detail. The several studies already conducted exhibit very complex and patchy structures both in vertical and horizontal sections. It is not clear if this plume patchiness is due to physical processes or measurement limitations. Rapid tow-yo sampling is expected to reduce the time variability during and between transects. The AUVs may be a useful instrument to map and detect wastewater plumes. This paper presents several prediction studies using time series files of actual in-situ measurements integrated in a near field model. The model predictions of the plume characteristics at the end of near field support the definition of the best sampling strategy for an AUV monitoring mission in a Portuguese west coast outfall.

2000

Cylinder packing by simulated annealing

Authors
Correia, MH; Oliveira, JF; Ferreira, JS;

Publication
Pesquisa Operacional - Pesqui. Oper.

Abstract

2000

TOPOS - A new constructive algorithm for nesting problems

Authors
Oliveira, JF; Gomes, AM; Ferreira, JS;

Publication
OR SPEKTRUM

Abstract
In this paper we present a new constructive algorithm for nesting problems. The layout is built by successively adding a new piece to a partial solution, i.e. to the set of pieces previously nested. Several criteria to choose the next piece Co place and its orientation are proposed and tested. Different objective functions are also proposed to evaluate and compare partial solutions. A total of 126 variants of the algorithm, generated by the complete set of combinations of criteria and objective functions, are computationally tested. The computational experiments are based on data sets published in the literature or provided by other authors. In some cases this new algorithm generates better solutions than the best known (published) solutions.

2000

Distributed planning and control systems for the virtual enterprise: organizational requirements and development life-cycle

Authors
Soares, AL; Azevedo, AL; de Sousa, JP;

Publication
JOURNAL OF INTELLIGENT MANUFACTURING

Abstract
This paper describes the requirements analysis and system specification of an Order Promise module to be used as part of a broader Decision Support System for production and operations planning of a Virtual Enterprise. This work is part of a broader project with a particular focus on the microelectronics industry which is a good example of Virtual Enterprise, and where a quick response to the customers needs and to unpredictable changes in production conditions is considered a major factor for success. First, the analysis and specification are presented within a development framework that involves the study of organizational issues of semiconductor enterprises. The use of ontological engineering for supporting the communication and shared understanding of the system concepts is explained and a virtual enterprise ontology is outlined. Following the clarification of the concept of virtual enterprise, the generic techno-organizational requirements for the information system are derived. Finally, a specification of the global planning module and a more detailed one regarding the order promise module is presented.

2000

Order planning for networked make-to-order enterprises - a case study

Authors
Azevedo, AL; Sousa, JP;

Publication
JOURNAL OF THE OPERATIONAL RESEARCH SOCIETY

Abstract
From the general trend towards global markers and a growing customer orientation, new concepts and forms of organisation are emerging, such as distributed or networked enterprises. One key requirement of these new paradigms is the availability of models and tools to support order negotiation with the optimisation of manufacturing routes and logistics and ensuring the co-ordination of all participating entities. We address the problem of planning an incoming customer order to be produced in a distributed (multi-site) and multi-stage production system, in particular, we have used as a case study the industry of semiconductors (in the business area of application specific integrated circuits). The problem is tackled in a hierarchical model, in two levels: there is a global network planning procedure, and a set of local capacity models associated to the different production units reflecting their particular features. An approach based on simulated annealing is presented, as well as a specially designed constructive heuristic, that takes into account many of the real world constraints and complexities. The general performance of the simulated annealing algorithm is assessed through some preliminary computational experiments. Finally, some concluding remarks and current directions of research are presented.

2000

A component-based approach to support order planning in a distributed manufacturing enterprise

Authors
Azevedo, AL; Sousa, JP;

Publication
JOURNAL OF MATERIALS PROCESSING TECHNOLOGY

Abstract
Traditional Production Planning and Control systems do not successfully deal with new organisational forms of manufacturing, like production "islands", product oriented or customer driven production. These current trends lead in practice to a strong decentralisation of production management tasks and to an "object oriented structuring" of the manufacturing process. Planning and operation in this global environment requires new skills and new approaches, namely, the co-ordination of global networks of manufacturing units and of large complex supply chains. In this paper, we present a decentralised information system designed to address the tasks of production planning that result from sales orders, originated in customers located anywhere in the world, and accomplished through a distributed manufacturing network. The system addresses the requirements of a make-to-order environment and is hopefully able to produce realistic satisfactory delivery dates. The information infrastructure designed and implemented using distributed object-oriented technology with a component based architecture has proven to be efficient and powerful, satisfying all the major tight requirements of information systems in an environment of distributed manufacturing.

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