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Publications

1996

Integration of manufacturing applications: Overcoming heterogeneity to preserve investment

Authors
Carvalho, A; Tovar, E; Oliveira, J; Alves, M; Sousa, M; Portugal, P;

Publication
BALANCED AUTOMATION SYSTEMS II: IMPLEMENTATION CHALLENGES FOR ANTHROPOCENTRIC MANUFACTURING

Abstract
The work presented in this paper consisted on the integration of several areas within a factory by using different communication standards. The described implementation satisfies several types of requirements, which include not only the functional requirements, but also the preservation of previous investments. The fulfilment of the latter imposed the use of heterogeneous technologies, both in terms of vendors and generations. This resulted in additional difficulties for the integration that were overcome. The use of OSI based technologies, such as those developed in the scope of CCE-CNMA, contributed to the success of this work.

1996

Semantics of non-terminating rewrite systems using minimal coverings

Authors
Barros, J; Goguen, J;

Publication
COMPUTER SCIENCE LOGIC

Abstract
We propose a new semantics for rewrite systems based on interpreting rewrite rules as inequations between terms in an ordered algebra. In particular, we show that the algebra of normal forms in a terminating system is a uniquely minimal covering of the term algebra. In the non-terminating case, the existence of this minimal covering is established in the completion of an ordered algebra formed by rewriting sequences. We thus generalize the properties of normal forms for non-terminating systems to this minimal covering. These include the existence of normal forms for arbitrary rewrite systems, and their uniqueness far confluent systems, in which case the algebra of normal forms is isomorphic to the canonical quotient algebra associated with the rules when seen as equations. This extends the benefits of algebraic semantics to systems with non-deterministic and non-terminating computations. We first study properties of abstract orders, and then instantiate these to term rewriting systems.

1996

Evaluation of i(DD)/V-OUT cross-correlation for mixed current/voltage testing of analogue and mixed-signal circuits

Authors
daSilva, JM; Matos, JS;

Publication
EUROPEAN DESIGN & TEST CONFERENCE 1996 - ED&TC 96, PROCEEDINGS

Abstract
The use of cross-correlation between power supply current and output voltage dynamic responses is presented as a methodology for improved mixed current/voltage testing of analogue and mixed-signal circuits. Results obtained from simulations are presented which show that better fault coverage and a simplification of test circuitry can be obtained, when compared with the results obtained from the direct observation of the individual signals. These advantages are important factors to develop viable new design for testability and built-in self test techniques.

1996

Factory automation using OSI technologies: Processes automation in a transformers manufacturing plant

Authors
Tovar, E; Oliveira, J; Alves, M; Azevedo, R; Carvalho, A; Sousa, M; Portugal, P; Carvalho, J;

Publication
FLEXIBLE AUTOMATION AND INTELLIGENT MANUFACTURING 1996

Abstract
This paper presents the work carried out in order to improve one of the areas of a factory plant, integrating it within the factory using different communication standards. The implementation described satisfies a set of data flow requirements and claims to be an example of different vendors and technologies integration. Distribution transformers have always been dried within ovens heated for the effect This drying process has several drawbacks: a low efficiency, dependence on the transformer volume and requiring a long time to complete. The new approach, presented in this paper, eliminates all those constraints.

1996

Andorra-I Compilation

Authors
Costa, VS; Warren, DHD; Yang, R;

Publication
New Generation Comput.

Abstract
Andorra-I is an experimental parallel Prolog system which transparently exploits both dependent and-parallelism and or-parallelism. One of the main components of Andorra-I is its preprocessor. In order to obtain efficient execution of programs in Andorra-I, the preprocessor includes a compiler for Andorra-I. The compiler includes a determinacy analyser and a clause compiler, and generates code for a specialised abstract machine. In this paper we discuss the main issues in the Andorra-I compiler, presenting its abstract instruction set and describing the algorithms used in its implementation.

1996

Assortment problems with cutting policies

Authors
Borges, PC; Ferreira, JS;

Publication
Control and Cybernetics

Abstract
Assortment selection problems with cutting policies play an important role in several industries but, possibly due to their combinatorial characteristics, they did not receive as much attention as cutting stock problems did, though the two problems are closely related. In this paper we graph several examples of cost functions of one and two-dimensional problems which reveal that many local optima with cost close to optimum exist. Several implementations of known meta-heuristics are tested with a real problem. Two different neighbourhood structures are considered and the different performance of the implemented heuristics is briefly discussed.

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