1,306 research outputs found
Tunable diffusion of magnetic particles in a quasi-one-dimensional channel
The diffusion of a system of ferromagnetic dipoles confined in a
quasi-one-dimensional parabolic trap is studied using Brownian dynamics
simulations. We show that the dynamics of the system is tunable by an in-plane
external homogeneous magnetic field. For a strong applied magnetic field, we
find that the mobility of the system, the exponent of diffusion and the
crossover time among different diffusion regimes can be tuned by the
orientation of the magnetic field. For weak magnetic fields, the exponent of
diffusion in the subdiffusive regime is independent of the orientation of the
external field.Comment: 9 pages, 13 figures, to appear in Phys. Rev. E (2013
Invasion Percolation Between two Sites
We investigate the process of invasion percolation between two sites
(injection and extraction sites) separated by a distance r in two-dimensional
lattices of size L. Our results for the non-trapping invasion percolation model
indicate that the statistics of the mass of invaded clusters is significantly
dependent on the local occupation probability (pressure) Pe at the extraction
site. For Pe=0, we show that the mass distribution of invaded clusters P(M)
follows a power-law P(M) ~ M^{-\alpha} for intermediate values of the mass M,
with an exponent \alpha=1.39. When the local pressure is set to Pe=Pc, where Pc
corresponds to the site percolation threshold of the lattice topology, the
distribution P(M) still displays a scaling region, but with an exponent
\alpha=1.02. This last behavior is consistent with previous results for the
cluster statistics in standard percolation. In spite of these discrepancies,
the results of our simulations indicate that the fractal dimension of the
invaded cluster does not depends significantly on the local pressure Pe and it
is consistent with the fractal dimension values reported for standard invasion
percolation. Finally, we perform extensive numerical simulations to determine
the effect of the lattice borders on the statistics of the invaded clusters and
also to characterize the self-organized critical behavior of the invasion
percolation process.Comment: 7 pages, 11 figures, submited for PR
Transition from single-file to two-dimensional diffusion of interacting particles in a quasi-one-dimensional channel
Diffusive properties of a monodisperse system of interacting particles
confined to a \textit{quasi}-one-dimensional (Q1D) channel are studied using
molecular dynamics (MD) simulations. We calculate numerically the mean-squared
displacement (MSD) and investigate the influence of the width of the channel
(or the strength of the confinement potential) on diffusion in finite-size
channels of different shapes (i.e., straight and circular). The transition from
single-file diffusion (SFD) to the two-dimensional diffusion regime is
investigated. This transition (regarding the calculation of the scaling
exponent () of the MSD ) as a
function of the width of the channel, is shown to change depending on the
channel's confinement profile. In particular the transition can be either
smooth (i.e., for a parabolic confinement potential) or rather sharp/stepwise
(i.e., for a hard-wall potential), as distinct from infinite channels where
this transition is abrupt. This result can be explained by qualitatively
different distributions of the particle density for the different confinement
potentials.Comment: 13 pages, 11 figure
Ação de biofertilizantes na cultivar brs aroeira em relação ao ataque de curuquerê-do-algodoeiro e pragas espontâneas.
Hygienization performances of innovative sludge treatment solutions to assure safe land spreading
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