Department of Mathematics

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Author: search.filters.author.Kulshrestha, RakheeSubject: search.filters.subject.Machine repair

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    Reliability Analysis of Redundant Repairable System with Degraded Failure
    (MERC, 2004) Kulshrestha, Rakhee
    This investigation deals with the transient analysis of the machine repair system consisting of M-operating units operating under the care of single repairman. To improve the system reliability/availability, Y warm standby and S cold standby units are provided to replace the failed units. In case when all spares are being used, the failure of units occurs in degraded fashion. In such situation there is a facility of one additional repairman to speed up the repair. The lifetime and repair time of units are exponentially distributed. We use matrix method to solve the governing Chapman-Kolmogorov equations. Expressions for the system reliability, availability, mean time to system failure, etc. are established in terms of transient probability. Computational scheme is discussed to facilitate the numerical results. Sensitivity analysis is also carried out to depict the effect of various parameters on the system reliability.
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    Bilevel control of degraded machining system with warm standbys, setup and vacation
    (Elsevier, 2004-12) Kulshrestha, Rakhee
    In this paper, we study (N, L) switch-over policy for machine repair model with warm standbys and two repairmen. The repairman (R1) turns on for repair only when N-failed units are accumulated and starts repair after a set up time which is assumed to be exponentially distributed. As soon as the system becomes empty, the repairman (R1) leaves for a vacation and returns back when he finds the number of failed units in the system greater than or equal to a threshold value N. Second repairman (R2) turns on when there are L(>N) failed units in the system and goes for a vacation if there are less than L failed units. The life time and repair time of failed units are assumed to be exponentially distributed. The steady state queue size distribution is obtained by using recursive method. Expressions for the average number of failed units in the queue and the average waiting time are established.