Notes on two identities of derangements;

In this paper,the probabilistic interpretations of Bernoulli number and the number of derangements are given,and their recurrence relation formulae are obtained by using the probabilistic method.

A staged software reliability growth model was presented,where the reliability growth planning methods with immediate correction and delayed correction combined was considered,weighted average of effectiveness factors was employed,and the fault removal efficiency function was introduced.

New idea of fault-removing-RDB by multi-agent;