Transport Reversal in a Thermal Ratchet
  Transport of a Brownian particle moving in a periodic potential is investigated in the presence of symmetric unbiased external force. The viscous medium is alternately in contact with the two heat reservoirs. We present the analytical expression of the net current at quasi-steady state limit. It is found that the competition of the asymmetric parameter of potential with the temperature difference leads to the phenomena like current reversal. The competition between the two driving factors is a necessary but not a sufficient condition for current reversals. 
Bao-quan Ai, Liqiu Wang, Lianggang Liu