  Evolution process could be calculated from the relativistic hydrodynamic
equation with certain estimated initial conditions about a single spherical
fireball here. So one could estimate a kind of initial condition qualitatively
with a possible energy density about $\epsilon_0\approx 1.9$ $GeV/fm^3$, based
on this process to fit the experimental data at thermal freeze-out. The
evolution from a cylindrical fireball will be discussed simply in a later
chapter.
