344,019 research outputs found

    Adsorption of hard spheres: structure and effective density according to the potential distribution theorem

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    We propose a new type of effective densities via the potential distribution theorem. These densities are for the sake of enabling the mapping of the free energy of a uniform fluid onto that of a nonuniform fluid. The potential distribution theorem gives the work required to insert a test particle into the bath molecules under the action of the external (wall) potential. This insertion work W_ins can be obtained from Monte Carlo (MC) simulation (e.g. from Widom's test particle technique) or from an analytical theory. The pseudo-densities are constructed thusly so that when their values are substituted into a uniform-fluid equation of state (e.g. the Carnahan-Starling equation for the hard-sphere chemical potentials), the MC nonuniform insertion work is reproduced. We characterize the pseudo-density behavior for the hard spheres/hard wall system at moderate to high densities (from \rho^*= 0.5745 to 0.9135). We adopt the MC data of Groot et al. for this purpose. The pseudo-densities show oscillatory behavior out of phase (opposite) to that of the singlet densities. We also construct a new closure-based density functional theory (the star-function based density functional theory) that can give accurate description of the MC density profiles and insertion works. A viable theory is established for several cases in hard sphere adsorption.Comment: 15 pages, 10 figure

    Coleonyx fasciatus

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    Number of Pages: 2Integrative BiologyGeological Science

    Coleonyx switaki

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    Number of Pages: 2Integrative BiologyGeological Science

    Large-N droplets in two dimensions

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    Using lattice effective field theory, we study the ground state binding energy of N distinct particles in two dimensions with equal mass interacting weakly via an attractive SU(N)-symmetric short range potential. We find that in the limit of zero range and large N, the ratio of binding energies B_{N}/B_{N-1} approaches the value 8.3(6).Comment: 18 pages, 6 figures, version to appear in Phys. Rev.

    Influence of quality control variables on failure of graphite/epoxy under extreme moisture conditions

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    Tension tests on graphite/epoxy composites were performed to determine the influence of various quality control variables on failure strength as a function of moisture and moderate temperatures. The extremely high and low moisture contents investigated were found to have less effect upon properties than did temperature or the quality control variables of specimen flaws and prepreg batch to batch variations. In particular, specimen flaws were found to drastically reduce the predicted strength of the composite, whereas specimens from different batches of prepreg displayed differences in strength as a function of temperature and extreme moisture exposure. The findings illustrate the need for careful specimen preparation, studies of flaw sensitivity, and careful quality control in any study of composite materials
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