The system life-time are determined by the damage accumulate additively, called to failure, exceeding random thresholds, the system fails. Failures occur according to a non-homogeneous Poisson process with mean-value function ∫ λ(x)ax, where λ(l) is failure rate. Thus, our overall aim is to obtain properties of the survival function of system from models for the stochastic mechanism leading to failure. In this paper, the basic composition Formular is used in deriving many of the results.

Abstract
 1. Introduction
 2. Formulation of Models
 3. Stochastic Comparisons between TN1 and TN2
 4. The Model
 5. Conclusion
 Bibliography

• 박태근(Dept. of Industrial and Systems Engineering, Jeonju Technical College)
• 최동순(Dept. of Industrial and Systems Engineering, Jeonju Technical College)