Competition and cooperation between thermal noise and external driving force

We consider the transport of an overdamped Brownian particle moving in a ro cked flashing ratchet-like potential. Together with a zero-mean driving for ce and a thermal white noise, the direction and behavior of the movement of the particle can be controlled. The expression of current is obtained by m eans of the perturbation approximation for fast flashing cases. Both the av erage velocity and position of the particle are simulated by use of the Lan gevin approach. The current reversal and the stepping motion of the particl e are obtained and shown. (C) 2000 Elsevier Science B.V. All rights reserve d.