  Quantum radiative characteristics of slowly varying nonstationary Kerr-Newman
black holes are investigated by using the method of generalized tortoise
coordinate transformation. It is shown that the temperature and the shape of
the event horizon of this kind of black holes depend on the time and the angle.
Further, we reveal a relationship that is ignored before between thermal
radiation and non-thermal radiation, which is that the chemical potential in
thermal radiation spectrum is equal to the highest energy of the negative
energy state of particles in non-thermal radiation for slowly varying
nonstationary Kerr-Newman black holes. Also, we show that the deduced general
results can be degenerated to the known conclusion of stationary Kerr-Newman
black holes.
