  A simplified frequency-integrated radiative transfer equation is solved to
study Compton scatterings in the corona of the disk by using numerical
iterating method. We find that the vertical thickness of the corona cannot be
used as the typical length to measure the optical depth of the corona. A
semi-analytical approach is proposed to calculate the energy dissipations in
the corona of the disk. We demonstrate that our approach can reproduce the
numerical solutions to an accuracy of <2 %.
