36,543 research outputs found
Galilean invariance of lattice Boltzmann models
It is well-known that the original lattice Boltzmann (LB) equation deviates
from the Navier-Stokes equations due to an unphysical velocity dependent
viscosity. This unphysical dependency violates the Galilean invariance and
limits the validation domain of the LB method to near incompressible flows. As
previously shown, recovery of correct transport phenomena in kinetic equations
depends on the higher hydrodynamic moments. In this Letter, we give specific
criteria for recovery of various transport coefficients. The Galilean
invariance of a general class of LB models is demonstrated via numerical
experiments
Relative Entropy: Free Energy Associated with Equilibrium Fluctuations and Nonequilibrium Deviations
Using a one-dimensional macromolecule in aqueous solution as an illustration,
we demonstrate that the relative entropy from information theory, , has a natural role in the energetics of equilibrium and
nonequilibrium conformational fluctuations of the single molecule. It is
identified as the free energy difference associated with a fluctuating density
in equilibrium, and is associated with the distribution deviate from the
equilibrium in nonequilibrium relaxation. This result can be generalized to any
other isothermal macromolecular systems using the mathematical theories of
large deviations and Markov processes, and at the same time provides the
well-known mathematical results with an interesting physical interpretations.Comment: 5 page
r-Process Nucleosynthesis in Shocked Surface Layers of O-Ne-Mg Cores
We demonstrate that rapid expansion of the shocked surface layers of an
O-Ne-Mg core following its collapse can result in r-process nucleosynthesis. As
the supernova shock accelerates through these layers, it makes them expand so
rapidly that free nucleons remain in disequilibrium with alpha-particles
throughout most of the expansion. This allows heavy r-process isotopes
including the actinides to form in spite of the very low initial neutron excess
of the matter. We estimate that yields of heavy r-process nuclei from this site
may be sufficient to explain the Galactic inventory of these isotopes.Comment: 11 pages, 1 figure, to appear in the Astrophysical Journal Letter
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Dynamic Behavior of Precast Concrete Beam-Column Sub-Assemblages with High Performance Connections Subjected to Sudden Column Removal Scenario
Unbonded posttensioned precast concrete (UPPC) structure has shown its excellent aseismic performance in laboratory tests and earthquake investigation. However, the progressive collapse behavior of UPPC subjected to column removal scenario is still unclear. To fill this knowledge gap, two 1/2 scaled UPPC beam-column sub-assemblages were tested under a penultimate column removal scenario. The dynamic test results indicated that UPPC sub-assemblages have desirable load redistribution capacity to mitigate progressive collapse. The failure modes of the sub-assemblages observed in dynamic test were quite similar to that in static counterparts
SS Ari: a shallow-contact close binary system
Two CCD epochs of light minimum and a complete R light curve of SS Ari are
presented. The light curve obtained in 2007 was analyzed with the 2003 version
of the W-D code. It is shown that SS Ari is a shallow contact binary system
with a mass ratio and a degree of contact factor f=9.4(\pm0.8%). A
period investigation based on all available data shows that there may exist two
distinct solutions about the assumed third body. One, assuming eccentric orbit
of the third body and constant orbital period of the eclipsing pair results in
a massive third body with and P_3=87.00.278M_{\odot}$. Both of the cases
suggest the presence of an unseen third component in the system.Comment: 28 pages, 9 figures and 5 table
Formation of helical states in wormlike polymer chains
We propose a potential for wormlike polymer chains which can be used to model
the low-temperature conformational structures. We successfully reproduced helix
ground states up to 6.5 helical loops, using the multicanonical Monte Carlo
simulation method. We demonstrate that the coil-helix transition involves four
distinct phases: coil(gaslike), collapsed globular(liquidlike), and two helical
phases I and II (both solidlike). The helix I phase is characterized by a
helical structure with dangling loose ends, and the helix II phase corresponds
to a near perfect helix ordering in the entire crystallized chain.Comment: 5 pages, 2 figures, Submitted to PR
COMPUTER SIMULATION OF "SPLASH CONTROL IN COMPETITIVE DIVING
The purpose of the study was to examine the relationship between the hand pattern and the water splash height during a diver's entry using a computer simulation method. A physical and mathematical model of the impact of a wedged solid object with an ideal fluid was developed. The motion equation (interaction function of solid and fluid) of the solid was established with satisfaction of control functions and initial boundary conditions of the fluid. A finite element method was used to simulate the impact process, with the wedge angle changed from 4" to 80- during the impact. The results suggested that the fluid splash height is inversely proportional to the wedge angle. The "splash control" technique derived from the simulation was also applied in training professional divers and positive results were obtained
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