  We present numerical simulation of bulk Lorentz factor of relativistic
electron positron jet driven by Compton rocket effect from accretion disk
radiation. The plasma is assumed to have a power-law energy distribution and is
continuously reheated to compensate for radiation losses. We include
Klein-Nishina (hereafter KN) corrections, and study the role of energy upper
cut-off, spectral index, and source compactness. We determine terminal bulk
Lorentz factor in the case of supermassive black holes relevant to AGN and
stellar black holes relevant to galactic microquasars. In the latter case,
effects of KN corrections are more important and induce terminal bulk Lorentz
factor smaller than in the former case. The result can explain the low bulk
Lorentz factors for galactic sources (GRS1915+105, GROJ1655-40) compared to
extragalactic ones. We also take into account the influence of the size of the
accretion disk; if the external radius is small enough, the bulk Lorentz factor
can be as high as 60, which is comparable to the values needed to explain
extragalactic gamma-ray bursts.
