In the system,the life distribution of these two units is assumed to be exponential distribution,the repair distribution is assumed to be phase type distribution,and it is "as good as new" after the failed units repair.

Phase-Type distributions have gained widespread attention in the area of stochastic modeling,two primary reasons being their denseness and algorithmic tractability.

The second stage service is single server with pH-distribution.

Under the hypothesis that the time between rounds fired follows a PH-distribution,it deduces the PH expressions and characteristics of the time till killing a target and the duel duration in two situations,not considering the factor of finding the target and considering that.

Customers arrive according to a semi-Markov arrival process and the service times of individual customers have PH-distributions.

The main work is to research high resolution light scanning two-dimension pH image sensor based on EIS structure,and use this sensor measuring system to measure the two-dimension distribution of pH value of the solution.