  This work presents a microscopic study of dissipation in fission dynamical
evolutions with the time-dependent Hartree-Fock+BCS method in terms of energy
dependence and pairing dependence. The friction coefficients and dissipation
energies are extracted by mapping the symmetric fission process of $^{258}$Fm
into a classical equation of motion. Density-constrained calculations are used
to obtain the dynamical potential. The obtained friction coefficients have a
strong dependence of deformations, and averagely match the coefficients adopted
in statistical models. The dissipation indeed increase with increasing initial
excitation energies or with decreasing pairings. It is also shown that
post-scission dissipations play a significant role. The demonstrated
characteristics of dissipations will be valuable for calibrations of various
fission models.
