  The revised Landau hydrodynamic model is used to discuss the pseudorapidity
distributions of the produced charged particles in Au+Au and Cu+Cu collisions
at energies of sqrt(s_NN)= 19.6 and 22.4 GeV correspondingly on the BNL
Relativistic Heavy Ion Collider. It is found that the revised Landau
hydrodynamic model alone can give a good description to the experimental
measurements. This is different from that in the same collisions but at the
maximum energy of sqrt(s_NN)= 200 GeV. Where, in addition to the revised Landau
hydrodynamic model, the effects of leading particles have to be taken into
account in order to explain the experimental observations. It can be attributed
to the different degrees of transparency of participants in different incident
energies.
