67,944 research outputs found

    Uniform Polynomial Equations Providing Higher-order Multi-dimensional Models in Lattice Boltzmann Theory

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    We present a set of polynomial equations that provides models of the lattice Boltzmann theory for any required level of accuracy and for any dimensional space in a general form. We explicitly derive two- and three-dimensional models applicable to describe thermal compressible flows of the level of the Navier-Stokes equations

    Fragility, Stokes-Einstein violation, and correlated local excitations in a coarse-grained model of an ionic liquid

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    Dynamics of a coarse-grained model for the room-temperature ionic liquid, 1-ethyl-3-methylimidazolium hexafluorophosphate, couched in the united-atom site representation are studied via molecular dynamics simulations. The dynamically heterogeneous behavior of the model resembles that of fragile supercooled liquids. At or close to room temperature, the model ionic liquid exhibits slow dynamics, characterized by nonexponential structural relaxation and subdiffusive behavior. The structural relaxation time, closely related to the viscosity, shows a super-Arrhenius behavior. Local excitations, defined as displacement of an ion exceeding a threshold distance, are found to be mainly responsible for structural relaxation in the alternating structure of cations and anions. As the temperature is lowered, excitations become progressively more correlated. This results in the decoupling of exchange and persistence times, reflecting a violation of the Stokes-Einstein relation.Comment: Published on the Phys. Chem. Chem. Phys. websit

    Dirac Coupled-channel Analyses of Polarized Proton Scatterings to the 2+^+ Gamma Vibrational Band in 24^{24}Mg and 26^{26}Mg

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    Dirac coupled channel calculations are performed phenomenologically for the high-lying excited states that belong to the 2+^+ gamma vibrational band at the 800-MeV polarized proton inelastic scatterings from the s-d shell nuclei, 24^{24}Mg and 26^{26}Mg. Optical potential model is used and scalar and time-like vector potentials are considered as direct potentials. First-order vibrational collective models are used to obtain the transition optical potentials in order to accommodate the high-lying excited vibrational collective states. The complicated Dirac coupled channel equations are solved phenomenologically to reproduce the differential cross section and analyzing power data by varying the optical potential and deformation parameters. It is found that the relativistic Dirac coupled channel calculation could describe the high-lying excited states of the 2+^+ gamma vibrational band at the 800-MeV polarized proton inelastic scatterings from s-d shell nuclei 24^{24}Mg and 26^{26}Mg reasonably well, showing better agreement with the experimental data compared to the results obtained from the nonrelativistic calculations. Calculated deformation parameters for the excited states are analyzed and compared with those of nonrelativistic calculations.Comment: 13pages, 6 figures. arXiv admin note: text overlap with arXiv:1501.00650, arXiv:1407.5441, arXiv:1511.0172
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