48 research outputs found
Transport in ratchet-type systems
Diffusion motion of overdamped Brownian particles in a spatially periodic
asymmetrical potential and driven by a zero-mean time-periodic
external force and zero-mean Gaussian white noise is considered. The
influence of asymmetry of the spatial potential, amplitude of the driving
force and intensity of the noise on an average translocation velocity of
particles is analyzed. The adiabatic approximation for calculation o f a
stationary particle current is used and verified by comparison with results
obtained from computer simulations of the process considered
Barrier crossing and transport activated by kangaroo fluctuations
We study barrier crossing of Brownian particles in a bistable symmetric
potential and transport of Brownian particles in spatially periodic structures,
driven by both kangaroo fluctuations and thermal equilibrium noise
of zero mean values. We consider exponentially and algebraically correlated
kangaroo fluctuations. Starting with the full Newton-Langevin equation for
the Brownian particle and by introducing scaling as well as dimensionless
variables, we show that the equation is very well approximated by overdamped
dynamics in which inertial effects can be neglected. We analyze
properties of selected macroscopic characteristics of the system such as the
mean first passage time (MFPT) of particles from one minimum of the
bistable potential to the other and mean stationary velocity of particles
moving in a spatially periodic potential. In dependence upon statistics of
kangaroo fluctuations and temperature of the system, macroscopic characteristics
exhibit distinctive non-monotonic behavior. Accordingly, there
exist optimal statistics of fluctuations optimizing macroscopic characteristics
Simulations of localized dissipative structures in excitable media by an ensemble of Brownian walkers
The effective method of simulation of stochastic excitable media by
en ensemble of Brownian particles is presented. The system studied is a
variant of Rinzel-Keller model with global inhibition. The formation, time
evolution, and statistical properties of localized structures — spots — are
investigated
Control of transport characteristics in two coupled Josephson junctions
We report on a theoretical study of transport properties of two coupled Josephson junctions and compare two scenarios for controlling the currentvoltage characteristics when the system is driven by an external biased DC
current and unbiased AC current consisting of one harmonic. In the first scenario, only one junction is subjected to both DC and AC currents. In the second scenario the signal is split — one junction is subjected to the
DC current while the other is subjected to the AC current. We study DC voltages across both junctions and find diversity of anomalous transport regimes for the first and second driving scenarios