Comparison of reliability characteristics of two semi-Markov repairable systems under degradation and abnormal environment

摘要: This article launches two stochastic models of a single-unit system with the notion degradation and abnormal environment. In both models, becomes degraded after repair while preventive maintenance original or unit is perfect. There single server in models; second model no effect environment considered he only performs activity whereas first does all these activities also. The remains still working under such as mild/harsh, maximum/minimum level demand, etc. Some important reliability characteristics, transition probabilities, mean sojourn time, availability, time to failure busy period are derived via semi-Markov processes regenerative point technique. mathematical expressions numerical results for differences between characteristics have been also provided three cases: (1) when random variables Weibull distribution; (2) exponential distribution particular case shape parameter equal one; (3) Rayleigh two.