Directed motion induced by shifting ratchet

The motion of Brownian particles in a spatial asymmetric periodic potential is considered. In the absence of any external macroscopic driving force, w hen the potential transits stochastically between two configurations which are shifted by a distance relative to each other, directed motion can be in duced. The dependence of the average velocity on the transition rate, the s trength of thermal noise and the shift distance between the two configurati ons of potential are analyzed. The efficiency of the system is evaluated.