The numerical implementation of the displacement model of the hybrid-{T}refftz finite element formulation is presented. The geometry of the supporting element is not constrained a priori. Unbounded, non-convex and multiply connected elements can be used. The approximation basis is naturally hierarchical and very rich. It is constructed on polynomial solutions of the governing differential equation, and extended to include the particular terms known to model accurately important local effects, namely the singular stress patterns due to cracks or point loads. Numerical and semi-analytical methods are used to compute the finite element matrices and vectors, all of which present boundary integral expressions. Appropriate procedures to store, manipulate and solve symmetric highly sparse systems are used. The characteristics of the finite element solving system in terms of sparsity and conditioning are analysed, as well as its sensitivity to the effects of mesh distortion, incompressibility and rotation of the local reference systems. Benchmark tests are used also to illustrate the performance of the element in the estimation of displacements, stresses and stress intensity factors.

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Partners search and selection is an important activity in the life cycle of a Virtual Enterprise. Among other factors, the commitment of the potential partners to fulfil quality requirements is a major decision criterion during the selection phase. An approach to search suppliers in suppliers’ directories available on Internet is presented and the major negotiation steps leading to an adequate selection of partners are introduced. The quality-related information management functionalities required in a virtual enterprise support platform are also discussed.

Electronic procurement of partners is an important functionality during the life cycle of a virtual enterprise. A prototype implementation, featuring selection based on both internal or Internet-based suppliers’ directories, is discussed. The generation of call for tenders and support for management of received bids is introduced and directions for contract negotiation and decision support system are discussed.

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This work is focused on the correction of Infeasible Linear problems. Its motivation is not difficult to understand if one thinks on the complexity of model building in large real problems. The inconsistency can arise in the definition of the model due, for instance, to structural or data type errors. The identification of conflict sets of constraints is very useful but might not be enough to overcome the problem, since the implementation of a solution may require the definition of a new feasible model. We present a short review on known procedures for the diagnosis of these problems. The approach we propose is based on the correction of (potentially) all the parameters of the model restrictions. We present a pure algebraic methodology based on the Singular Value Decomposition of a matrix. This method is quite rigid in the changes of the matrix coefficients changes, so we give insights on a heuristic based approach in order to attain more flexibility.

The present paper describes the properties of a photochemical sensor based on amorphous silicon MIS (Metal-Insulator-Semiconductor) diodes. The structure of the sensors used in this work are based on glass/Cr/a-SiH(n +)/a-Si:H(i)SiOx/Pd, where the amorphous silicon layers have been deposited by conventional plasma r.f. techniques. The proposed photochemical sensors present a 2-3 orders of magnitude change in the saturation current and a decrease of up to 40% on the open circuit voltage when in the presence of 400 ppm of hydrogen. The overall performance of these sensors, associated with the low cost fabrication technology, suggests that, in the near future, it will be possible to use them in several industrial applications. © 1998 Elsevier Science Ltd. All rights reserved.

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Fuscoredoxin is a unique iron containing protein of yet unknown function originally discovered in the sulfate reducers of the genus Desulfovibrio. It contains two iron-sulfur clusters: a cubane [4Fe-4S] and a mixed oxo- and sulfide-bridged 4Fe cluster of unprecedented structure. The recent determination of the genomic sequence of Escherichia coli (E. coli) has revealed a homologue of fuscoredoxin in this facultative microbe. The presence of this gene in E. coli raises interesting questions regarding the function of fuscoredoxin and whether this gene represents a structural homologue of the better-characterized Desulfovibrio proteins. In order to explore the latter, an overexpression system for the E. coli fuscoredoxin gene was devised. The gene was cloned from genomic DNA by use of the polymerase chain reaction into the expression vector pT7-7 and overexpressed in E. coli BL21(DE3) cells. After two chromatographic steps a good yield of recombinant protein was obtained (approximately 4 mg of pure protein per liter of culture). The purified protein exhibits an optical spectrum characteristic of the homologue from D. desulfuricans, indicating that cofactor assembly was accomplished. Iron analysis indicated that the protein contains circa 8 iron atoms/molecule which were shown by EPR and Mossbauer spectroscopies to be present as two multinuclear clusters, albeit with slightly altered spectroscopic features. A comparison of the primary sequences of fuscoredoxins is presented and differences on cluster coordination modes are discussed on the light of the spectroscopic data. (C) 1999 Academic Press.

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The increasing demand in automation processes in finishing techniques also calls for automatic measurement and inspection methods. These methods ought to be installed as close as possible to the production process and they ought to measure the values needed in a safe and fast way, without disturbing the process itself. Simultaneously they should be free of wear and insensitive against mechanical perturbations. This approach can be reached by proper combination of the laser triangulation technique with an array of linear position sensitive detectors, able to supply information about the surface finishing of an object. This is the aim of this paper that envisages to present experimental results of the performances exhibited by such an array constituting 128 elements. The analogue information supplied by this array is processed by an analogue/digital converter, directly coupled to the array and whose information is computer processed, concerning the recognition of patterns and the processing of information collected over the object to be inspected. © 1999 Elsevier Science S.A. All rights reserved.

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We describe our experimentation with the design and implementation of specific environments, consisting of heterogeneous computational, visualization, and control components. We illustrate the approach with the design of a problem–solving environment supporting the execution of genetic algorithms. We describe a prototype supporting parallel execution, visualization, and steering. A life cycle for the development of applications based on genetic algorithms is proposed.

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