408,435 research outputs found

    Visualizing and Interacting with Concept Hierarchies

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    Concept Hierarchies and Formal Concept Analysis are theoretically well grounded and largely experimented methods. They rely on line diagrams called Galois lattices for visualizing and analysing object-attribute sets. Galois lattices are visually seducing and conceptually rich for experts. However they present important drawbacks due to their concept oriented overall structure: analysing what they show is difficult for non experts, navigation is cumbersome, interaction is poor, and scalability is a deep bottleneck for visual interpretation even for experts. In this paper we introduce semantic probes as a means to overcome many of these problems and extend usability and application possibilities of traditional FCA visualization methods. Semantic probes are visual user centred objects which extract and organize reduced Galois sub-hierarchies. They are simpler, clearer, and they provide a better navigation support through a rich set of interaction possibilities. Since probe driven sub-hierarchies are limited to users focus, scalability is under control and interpretation is facilitated. After some successful experiments, several applications are being developed with the remaining problem of finding a compromise between simplicity and conceptual expressivity

    Study of a laminar falling film flowing over a wavy wall column: Part II. Experimental validation of hydrodynamic model

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    The interface position of a film flowing over a wavy wall column is experimentally studied by an optical method composed of a charge coupled device (CCD) video camera. The results are compared with theoretical calculations and show a good agreement between results for both the film thickness and the vortex position. However, there exist some discrepancies because the interface is travelled by waves not accounted for in the mathematical model as it is supposed to be flat. Some characteristics of the waves are experimentally noted. Furthermore, the in¯uence of the viscosity on the film thickness is established as well

    Gamow Shell-Model Description of Weakly Bound and Unbound Nuclear States

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    Recently, the shell model in the complex k-plane (the so-called Gamow Shell Model) has been formulated using a complex Berggren ensemble representing bound single-particle states, single-particle resonances, and non-resonant continuum states. In this framework, we shall discuss binding energies and energy spectra of neutron-rich helium and lithium isotopes. The single-particle basis used is that of the Hartree-Fock potential generated self-consistently by the finite-range residual interaction.Comment: 13 pages, 2 figures, presented by N. Michel at the XXVII Symposium On Nuclear Physics, Taxco, Guerrero, Mexico, January 5-8 200

    Modelling of the coupling hydrodynamic transfer for a gas-liquid countercurrent flow on a wavy surface

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    This paper concerns laminar countercurrent gas–liquid flow over a wavy wall column, in the case of a falling liquid film. The modelling concerns the coupling of hydrodynamic and heat and mass transfer for an absorption as an example of application. The falling liquid film interacts, through the free interface, with the gas phase. The wavy surface generates particular hydrodynamic conditions with the presence of a vortex in both phases. The consequence of these vortices is an increase of transfers compared to the smooth wall

    Enhancement of absorption efficiency for a laminar film flow by hydrodynamic conditions generated by a new type of column wall

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    Anumerical model is developed to quantify the effects of hydrodynamics on heat and mass transfer during an absorption, for a laminar film flowing over awavywall column. First of all, the modelling is written for a singlewave of thewall shape. Then, an experimental set up, composed of aCCDvideo camera, validates this model. Finally, the model is extended to an entire column. The results include a comparison with the simulation of a smooth column having the same geometrical and operating conditions. Thewavy column dissipates more heat through the wall (43%) due to the presence of a vortex in the furrows. This leads to an increase of the absorptionrate at the interface (10%). Moreover, the wavy column reaches equilibrium more rapidly in spite of a lower mean film temperature

    Study of a laminar falling film flowing over a wavy wall column: Part I. Numerical investigation of the flow pattern and the coupled heat and mass transfer

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    Flow pattern and heat and mass transfer characteristics for a film flowing over a vertical wavy column are numerically investigated in a laminar flow regime. In our approach, the heat and mass transfer coefficients are avoided in order to include hydrodynamics directly in the heat and mass transfer rates. As a consequence the numerical model is decomposed into two steps. Firstly, the flow pattern for a film with a free interface is developed. Secondly, heat and mass transfer are investigated with the incorporation of velocity fields. The heat and mass transfer coefficients increase in laminar flow

    The formation of young B/PS bulges in edge-on barred galaxies

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    We report about the fact that the stellar population that is born in the gas inflowing towards the central regions can be vertically unstable leading to a B/PS feature remarkably bluer that the surrounding bulge. Using new chemodynamical simulations we show that this young population does not remain as flat as the gaseous nuclear disc and buckles out of the plane to form a new boxy bulge. We show that such a young B/PS bulge can be detected in colour maps.Comment: 2 pages, 5 figures, to appear in IAU Symposium 245, Formation and Evolution of Galaxy Bulges, M. Bureau, E. Athanassoula, and B. Barbuy (eds.), Oxford, 16-20 July 200
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