871 research outputs found

    Perception of Nuclear Energy and Coal in France and the Netherlands

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    This study focuses on the perception of large scale application of nuclear energy and coal in the Netherlands and France. The application of these energy-sources and the risks and benefits are judged differently by various group in society. In Europe, France has the highest density of nuclear power plants and the Netherlands has one of the lowest. In both countries scientists and social scientists completed a questionnaire assessing the perception of the large scale application of both energy sources. Furthermore, a number of variables relating to the socio cultural and political circumstances were measured. The results indicate that the French had a higher risk perception and a more negative attitude toward nuclear power than the Dutch. But they also assess the benefits of the use of nuclear power to be higher. Explanations for these differences are discussed

    Structure and Thermodynamics of the Mixed Alkali Alanates

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    The thermodynamics and structural properties of the hexahydride alanates (M2M'AlH6) with the elpasolite structure have been investigated. A series of mixed alkali alanates (Na2LiAlH6, K2LiAlH6 and K2NaAlH6) were synthesized and found to reversibly absorb and desorb hydrogen without the need for a catalyst. Pressure-composition isotherms were measured to investigate the thermodynamics of the absorption and desorption reactions with hydrogen. Isotherms for catalyzed (4 mol% TiCl3) and uncatalyzed Na2LiAlH6 exhibited an increase in kinetics, but no change in the bulk thermodynamics with the addition of a dopant. A structural analysis using synchrotron x-ray diffraction showed that these compounds favor the Fm-3m space group with the smaller ion (M') occupying an octahedral site. These results demonstrate that appropriate cation substitutions can be used to stabilize or destabilize the material and may provide an avenue to improving the unfavorable thermodynamics of a number of materials with promising gravimetric hydrogen densities.Comment: 6 pages, 7 figures,3 tables, submitted to PR

    Superconductivity with hard-core repulsion: BCS-Bose crossover and s-/d-wave competition

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    We consider fermions on a 2D lattice interacting repulsively on the same site and attractively on the nearest neighbor sites. The model is relevant, for instance, to study the competition between antiferromagnetism and superconductivity in a Kondo lattice. We first solve the two-body problem to show that in the dilute and strong coupling limit the s-wave Bose condensed state is always the ground state. We then consider the many-body problem and treat it at mean-field level by solving exactly the usual gap equation. This guarantees that the superconducting wave-function correctly vanishes when the two fermions (with antiparallel spin) sit on the same site. This fact has important consequences on the superconducting state that are somewhat unusual. In particular this implies a radial node-line for the gap function. When a next neighbor hopping t' is present we find that the s-wave state may develop nodes on the Fermi surface.Comment: 10 pages, 9 fig

    Phase Diagram of the 1D Anderson Lattice

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    We map out the phase diagram of the one--dimensional Anderson lattice by studying the ground state magnetization as a function of band--filling using the density matrix renormalization group technique. For strong coupling, we find that the quarter--filled system has an S=0 ground state with strong antiferromagnetic correlations. As additional electrons are put in, we find first a ferromagnetic phase, as reported by M\"{o}ller and W\"{o}lfle, and then a phase in which the ground state has total spin S=0S=0. Within this S=0S=0 phase, we find RKKY oscillations in the spin--spin correlation functions.Comment: REVTEX manuscript with 5 Postcript figures included in uu file. Submitted to Phys. Rev.

    An automatic critical care urine meter

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    Nowadays patients admitted to critical care units have most of their physiological parameters measured automatically by sophisticated commercial monitoring devices. More often than not, these devices supervise whether the values of the parameters they measure lie within a pre-established range, and issue warning of deviations from this range by triggering alarms. The automation of measuring and supervising tasks not only discharges the healthcare staff of a considerable workload but also avoids human errors in these repetitive and monotonous tasks. Arguably, the most relevant physiological parameter that is still measured and supervised manually by critical care unit staff is urine output (UO). In this paper we present a patent-pending device that provides continuous and accurate measurements of patient’s UO. The device uses capacitive sensors to take continuous measurements of the height of the column of liquid accumulated in two chambers that make up a plastic container. The first chamber, where the urine inputs, has a small volume. Once it has been filled it overflows into a second bigger chamber. The first chamber provides accurate UO measures of patients whose UO has to be closely supervised, while the second one avoids the need for frequent interventions by the nursing staff to empty the containe

    ISML: an interface specification meta-language

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    In this paper we present an abstract metaphor model situated within a model-based user interface framework. The inclusion of metaphors in graphical user interfaces is a well established, but mostly craft-based strategy to design. A substantial body of notations and tools can be found within the model-based user interface design literature, however an explicit treatment of metaphor and its mappings to other design views has yet to be addressed. We introduce the Interface Specification Meta-Language (ISML) framework and demonstrate its use in comparing the semantic and syntactic features of an interactive system. Challenges facing this research are outlined and further work proposed

    Superconductivity in the SU(N) Anderson Lattice at U=\infty

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    We present a mean-field study of superconductivity in a generalized N-channel cubic Anderson lattice at U=\infty taking into account the effect of a nearest-neighbor attraction J. The condition U=\infty is implemented within the slave-boson formalism considering the slave bosons to be condensed. We consider the ff-level occupancy ranging from the mixed valence regime to the Kondo limit and study the dependence of the critical temperature on the various model parameters for each of three possible Cooper pairing symmetries (extended s, d-wave and p-wave pairing) and find interesting crossovers. It is found that the d- and p- wave order parameters have, in general, very similar critical temperatures. The extended s-wave pairing seems to be relatively more stable for electronic densities per channel close to one and for large values of the superconducting interaction J.Comment: Seven Figures; one appendix. Accepted for publication in Phys. Rev.

    Soft and non-soft structural transitions in disordered nematic networks

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    Properties of disordered nematic elastomers and gels are theoretically investigated with emphasis on the roles of non-local elastic interactions and crosslinking conditions. Networks originally crosslinked in the isotropic phase lose their long-range orientational order by the action of quenched random stresses, which we incorporate into the affine-deformation model of nematic rubber elasticity. We present a detailed picture of mechanical quasi-Goldstone modes, which accounts for an almost completely soft polydomain-monodomain (P-M) transition under strain as well as a ``four-leaf clover'' pattern in depolarized light scattering intensity. Dynamical relaxation of the domain structure is studied using a simple model. The peak wavenumber of the structure factor obeys a power-law-type slow kinetics and goes to zero in true mechanical equilibrium. The effect of quenched disorder on director fluctuation in the monodomain state is analyzed. The random frozen contribution to the fluctuation amplitude dominates the thermal one, at long wavelengths and near the P-M transition threshold. We also study networks obtained by crosslinking polydomain nematic polymer melts. The memory of initial director configuration acts as correlated and strong quenched disorder, which renders the P-M transition non-soft. The spatial distribution of the elastic free energy is strongly dehomogenized by external strain, in contrast to the case of isotropically crosslinked networks.Comment: 19 pages, 15 EPS figure

    Index de qualité du cacao-une proposition

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    Les concepts de qualité ont fait d'énormes progrès à partir de la révolution industrielle, après la Deuxième Guerre Mondiale et, plus récemment, stimulés para la mondialisatioiL La définition de qualité pour les aliments a démontré des tendances contradictoires pendant les recherches, mais elle a progressé de l'adéquation des normes vers le service clients. Comme pour d'autres matériaux, il faut avancer vers l'adoption de méthodes plus exhaustives pou. l'évaluation des aliments, dont un ensemble représentatif des indicateurs. Un outil important pour l'évaluation du cacao est la création d'un indice de qualité, tenant compte des propriétés, procédés et caractéristiques parmi les conditionnements chimiques, physiques et biologiques du produit La croissance de la qualité du cacao peut avoir une influence positive dans le marché du produit, bénéficiant producteurs et consommateurs. L'objectif de notre proposition est l'élaboration d'un Index de qualité du Cacao (IQC), ayant comme base l'analyse des fèves de cacao forastero, avec les mêmes procédures et originaires de deux sites avec différents types de sols (Latosol Rouge-Jaune Distrofyque argisol - LV Ad) et Nitosol Ha plique Eutrophique - Nxe). En général, le Nxe présente les meilleures conditions édaphiqucs, surtout par rapport aux données de pH, saturation par bases, capacité d'échange cationique, et argile. L'IQC proposé a été élaboré d'après le modèle d'un indice de qualité, appliqué aux sols, mais avec des modifications pour son application à un aliment. L'obtention de cet IQC concerne les étapes suivantes: définition de l'objectif de l'évaluation; sélection des fonctions; attribution des indicateurs aux fonctions; définition des poids des fonctions et des indicateurs; définition du comportement des indicateurs; mise en place des limites critiques des indicateu.s; normalisation des valeurs; normalisation des valeurs entre 0 et 1,0; calcul du IQC. En ce cas particulier, nous avons adopté comme fonctions basiques les caractéristiques souhaitées par 1 'industrie, en ce qui concerne la saveur et la santé humaine. Les indicateurs analysés sont dismbués parmi les fonctions suivantes: matière grasse totale, acidité totale, phénols totaux, phénoliques, acides organiques, métaux lourds, aminoacides, caféine, théobromine, pH, sucres et éléments nutritifs. Les moyennes obtenues ont été comparées au moyen du test Tukey à 5% de signification. Les valeurs de IQC des sites 1 et 2 n'ont pas indiqué des différences mathématiques, mais d'après le classement qualitatif adopté, le site 2 (Nxe) a montré un «bon» CQI (0,703), supérieur à la valeur «régulier» (0,652) du site 1 (LVA). (Résumé d'auteur

    A coordination model for interactive components

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    Although presented with a variety of ‘flavours’, the notion of an interactor, as an abstract characterisation of an interactive com- ponent, is well-known in the area of formal modelling techniques for interactive systems. This paper replaces traditional, hierarchical, ‘tree-like’ composition of interactors in the specification of complex interactive sys- tems, by their exogenous coordination through general-purpose software connectors which assure the flow of data and the meet of synchronisation constraints. The paper’s technical contribution is twofold. First a modal logic is defined to express behavioural properties of both interactors and connectors. The logic is new in the sense that its modalities are indexed by fragments of sets of actions to cater for action co-occurrence. Then, this logic is used in the specification of both interactors and coordination layers which orchestrate their interconnection
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