M. S. Kadyan

Profit analysis of a 2-out-of-2 redundant system with single standby and degradation of the units after repair

The purpose of this paper is to carry out the profit analysis of a three unit redundant system in which two units work in parallel and one unit is kept as spare in cold standby. Each unit has direct complete failure from normal mode. There is a single repairman (called server) who visits the system immediately to do repair, inspection and replacement of the units. The unit does not work as new after repair and so called a degraded unit. The degraded unit at its further failure undergoes for inspection to see the feasibility of its repair. If the repair is not feasible, it is replaced immediately by new unit. The system is considered in up-state if any two of original and/or degraded units are operative. The time to failure, repair and inspection of the units are taken as arbitrary with different probability density functions. By adopting semi-Markov process and regenerative point technique, the results for some measures of system effectiveness are obtained in steady state.

Reliability modeling of a single-unit system with arbitrary distributions subject to different weather conditions

The main concentration of the present study is on the evaluation of some important reliability measures of a single-unit system considering arbitrary distributions for the random variables associated with failure and repair times, time to change of weather conditions, inspection time and arrival time of the server. The system operates under two weather conditions-normal and abnormal. The unit fails completely via partial failure. There is a single server who takes some time to arrive at the system. Server inspects the unit at its complete failure to see the feasibility of its repair while repair of the unit at partial failure is done without inspection. The unit works as new after repair at partial failure whereas unit is assumed as degraded after repair at complete failure. Inspection of the degraded unit is also conducted at its failure to examine the feasibility of repair. The degraded unit is replaced by new one if inspection reveals that its repair is not feasible to the system. Some measures of system effectiveness are obtained using semi-Markov and regenerative point technique. Giving particular values to various parameters and costs, the numerical results for mean time to system failure, availability and profit function are obtained considering exponential and Rayleigh distributions for all random variables.

Profit Analysis of a System of Non-identical Units with Degradation and Replacement

This paper presents the profit analysis of a system of two nonidentical units in which one unit is original which is initially operative and the other is duplicate kept in cold standby. The units may fail completely directly from normal mode. There is a single server who visits the system immediately when required. The original unit undergoes for repair upon failure while only replacement of the duplicate unit is made by similar new one. The original unit does not work as new after repair and so called degraded unit. The system is considered in up-state if any one of new/duplicate/degraded unit is operative. The server inspects the degraded unit at its failure to see the feasibility of repair. The failure time of the units are exponentially distributed whereas the distributions of inspection time, replacement time of the duplicate unit and repair time of the original/duplicate/degraded unit are taken as arbitrary with different probability density functions. Some reliability characteristics of the system model are evaluated using semi-Markov process and regenerative point technique. The numerical results for a particular case are also obtained to depict the behavior of Mean Time to System Failure (MTSF), availability and profit function graphically.

Stochastic Modeling of a Single-Unit Repairable System with Preventive Maintenance under Warranty

In this paper a stochastic model for a single unit repairable system with Preventive Maintenance (PM) under warranty is analyzed in details by using supplementary variable technique.The cost of repair during warranty is born by the manufacturers, but warranty does not apply to product failure due to user-induced damage such as cracked screen or cracked casing, accident, misuse, physical damage, damage due to liquid and unauthorized modifications etc. within warranty period. Unit goes under PM during warranty and works as new after PM. There is a single server who always remains with the system. The time to failure of the system follows negative exponential distribution while PM and repair time distributions are taken as arbitrary. The expressions for some economic measures such as reliability, mean time to system failure (MTSF) and availability have been derived.A particular case is considered to highlight the behaviour of reliability and profit function.

Effect of Annealing Selection Operators in Genetic Algorithms on Benchmark Test Functions

The strategies to find optimal solutions can be broadly categorized into two: exploration and exploitation, but it has been shown in the literature that none can be claimed better than others in all the problems or all stages of the problems. In evolutionary approaches such as genetic algorithm, different operators used are inclined either towards exploration or exploitation but problems demand the operators having the blend of both. In this paper an annealed selection operator has been proposed, the behavior of which is controlled by the current generation i.e. in early cycle of evolution it is more like exploration and gradually it shifts towards exploitation. The experiments have been conducted using five different benchmark functions and implementation is carried out using MATLAB. Results show the improvement over existing selection operators.