30 research outputs found
Diffusion with a broad class of stochastic diffusion coefficients
In many physical or biological systems, diffusion can be described by
Brownian motions with stochastic diffusion coefficients (DCs). Recently,
specific models of the motions have been proposed for anomalous diffusion. In
the present study, we investigate properties of the diffusion with a broad
class of stochastic DCs using the Fokker-Planck formalism. We show that for a
finite time, the propagator is non-Gaussian and heavy-tailed. This means that
when the mean square displacements are the same, for a finite time, some of the
diffusing particles with stochastic DCs diffuse farther than the particles with
deterministic DCs or exhibiting a fractional Brownian motion.Comment: 4 page
Generic transport coefficients of a confined electrolyte solution
Physical parameters characterising electrokinetic transport in a confined
electrolyte solution are reconstructed from the generic transport coefficients
obtained within the classical non-equilibrium statistical thermodynamic
framework. The electro-osmotic flow, the diffusio-osmotic flow, the osmotic
current, as well as the pressure-driven Poiseuille-type flow, the electric
conduction, and the ion diffusion, are described by this set of transport
coefficients. The reconstruction is demonstrated for an aqueous NaCl solution
between two parallel charged surfaces with a nanoscale gap, by using the
molecular dynamic (MD) simulations. A Green-Kubo approach is employed to
evaluate the transport coefficients in the linear-response regime, and the
fluxes induced by the pressure, electric, and chemical potential fields are
compared with the results of non-equilibrium MD simulations. Using this
numerical scheme, the influence of the salt concentration on the transport
coefficients is investigated. Anomalous reversal of diffusio-osmotic current,
as well as that of electro-osmotic flow, is observed at high surface charge
densities and high added-salt concentrations.Comment: 6 pages with 6 figure
Coarse-grained model for spring friction study of micron-scale iron by smoothed particle hydrodynamics
The paper constructs a coarse-grained model to investigate dry sliding
friction of the body-centered-cubic Fe micron-scale system by smoothed particle
hydrodynamics simulations and examines influences of the spring force on the
characters of friction. The N_atom = 864 \times 10^12 atoms Fe system is
coarse-grained into the two different simple-cubic particle systems, one of
432000 and the other of 16000 particles. From the detection of stick-slip
motion, friction coefficient, dependence of friction coefficient on isotropy or
anisotropy of the spring force and externally applied normal load, we find that
the coarse-grained model is a reasonable modeling process for study of friction
of the Fe system and the anisotropic behavior presents better friction of the
system than the isotropic one