15,088 research outputs found
Multi-component lattice-Boltzmann model with interparticle interaction
A previously proposed [X. Shan and H. Chen, Phys. Rev. E {\bf 47}, 1815,
(1993)] lattice Boltzmann model for simulating fluids with multiple components
and interparticle forces is described in detail. Macroscopic equations
governing the motion of each component are derived by using Chapman-Enskog
method. The mutual diffusivity in a binary mixture is calculated analytically
and confirmed by numerical simulation. The diffusivity is generally a function
of the concentrations of the two components but independent of the fluid
velocity so that the diffusion is Galilean invariant. The analytically
calculated shear kinematic viscosity of this model is also confirmed
numerically.Comment: 18 pages, compressed and uuencoded postscript fil
Effects of Residue Background Events in Direct Dark Matter Detection Experiments on the Determination of the WIMP Mass
In the earlier work on the development of a model-independent data analysis
method for determining the mass of Weakly Interacting Massive Particles (WIMPs)
by using measured recoil energies from direct Dark Matter detection experiments
directly, it was assumed that the analyzed data sets are background-free, i.e.,
all events are WIMP signals. In this article, as a more realistic study, we
take into account a fraction of possible residue background events, which pass
all discrimination criteria and then mix with other real WIMP-induced events in
our data sets. Our simulations show that, for the determination of the WIMP
mass, the maximal acceptable fraction of residue background events in the
analyzed data sets of O(50) total events is ~20%, for background windows of the
entire experimental possible energy ranges, or in low energy ranges; while, for
background windows in relatively higher energy ranges, this maximal acceptable
fraction of residue background events can not be larger than ~10%. For a WIMP
mass of 100 GeV with 20% background events in the windows of the entire
experimental possible energy ranges, the reconstructed WIMP mass and the
1-sigma statistical uncertainty are ~97 GeV^{+61%}_{-35%} (~94
GeV^{+55%}_{-33%} for background-free data sets).Comment: 27 pages, 22 eps figures; v2: revised version for publication,
references added and update
Reexamining the "finite-size" effects in isobaric yield ratios using a statistical abrasion-ablation model
The "finite-size" effects in the isobaric yield ratio (IYR), which are shown
in the standard grand-canonical and canonical statistical ensembles (SGC/CSE)
method, is claimed to prevent obtaining the actual values of physical
parameters. The conclusion of SGC/CSE maybe questionable for neutron-rich
nucleus induced reaction. To investigate whether the IYR has "finite-size"
effects, the IYR for the mirror nuclei [IYR(m)] are reexamined using a modified
statistical abrasion-ablation (SAA) model. It is found when the projectile is
not so neutron-rich, the IYR(m) depends on the isospin of projectile, but the
size dependence can not be excluded. In reactions induced by the very
neutron-rich projectiles, contrary results to those of the SGC/CSE models are
obtained, i.e., the dependence of the IYR(m) on the size and the isospin of the
projectile is weakened and disappears both in the SAA and the experimental
results.Comment: 5 pages and 4 figure
A Lattice Boltzmann method for simulations of liquid-vapor thermal flows
We present a novel lattice Boltzmann method that has a capability of
simulating thermodynamic multiphase flows. This approach is fully
thermodynamically consistent at the macroscopic level. Using this new method, a
liquid-vapor boiling process, including liquid-vapor formation and coalescence
together with a full coupling of temperature, is simulated for the first time.Comment: one gzipped tar file, 19 pages, 4 figure
Diffusion in a multi-component Lattice Boltzmann Equation model
Diffusion phenomena in a multiple component lattice Boltzmann Equation (LBE)
model are discussed in detail. The mass fluxes associated with different
mechanical driving forces are obtained using a Chapman-Enskog analysis. This
model is found to have correct diffusion behavior and the multiple diffusion
coefficients are obtained analytically. The analytical results are further
confirmed by numerical simulations in a few solvable limiting cases. The LBE
model is established as a useful computational tool for the simulation of mass
transfer in fluid systems with external forces.Comment: To appear in Aug 1 issue of PR
Families of Graphs With Chromatic Zeros Lying on Circles
We define an infinite set of families of graphs, which we call -wheels and
denote , that generalize the wheel () and biwheel ()
graphs. The chromatic polynomial for is calculated, and
remarkably simple properties of the chromatic zeros are found: (i) the real
zeros occur at for even and for odd;
and (ii) the complex zeros all lie, equally spaced, on the unit circle
in the complex plane. In the limit, the zeros
on this circle merge to form a boundary curve separating two regions where the
limiting function is analytic, viz., the exterior and
interior of the above circle. Connections with statistical mechanics are noted.Comment: 8 pages, Late
Frozen water waves over rough topographical bottoms
The propagation of surface water waves over rough topographical bottoms is
investigated by the multiple scattering theory. It is shown that the waves can
be localized spatially through the process of multiple scattering and wave
interference, a peculiar wave phenomenon which has been previously discussed
for frozen light in optical systems (S. John, Nature {\bf 390}, 661, (1997)).
We demonstrate that when frozen, the transmission of the waves falls off
exponentially, and a cooperative behavior appears, fully supporting previous
predictions. A phase diagram method is used to illustrate this distinct phase
states in the wave propagation.Comment: 4 pages and 5 figure
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