With wide-pulse neutron injection the fission chain fluctuates statistically.A calculation approach is presented, in which numerical solutions of the statistical distribution W_n equations are disassembled and then synthesized.It makes the computation suitable for generalized conditions (with arbitrary time distribution,zero time (t₀) injection probability distribution P(t₀) and number probability distribution S(n) etc.).The equivalent conditions in practical physical models are discussed and expanded from single-medium to multi-medium.In addition, the average computing formulae for required parameters in solving W_n equations are given as well.

The problem about a projectile with high veiocity impacting on a target is an important subject in penetration mechanics, It is also an important question in Studying dynamic response of materials.In this paper,the calculations of cylindric steel projectiles impacting on Aluminum targets have been performed using the dual lagrange APHEMP code and the results are compared with the experiments the dynamic picture of the impacting processes is preliminarily Studied.