Stochastic behaviour of a repairable system operating under fluctuating weather

A repairable system which operates under fluctuating weather conditions is considered. There are 3 types of weathers: normal, abnormal 1 and abnormal 2. Weather changes from normal to abnormal 1 and abnormal 2 at exponential rates. Failure time distribution of the system from normal weather is exponential whereas it is general from abnormal states. Repair time distributions are different and general. The model is analysed by the help of SMP technique and reliability parameters viz MTSF, steady-state availability, absorption probabilities etc. are obtained.     

Stochastic behaviour and profit analysis of a redundant system with slow switching device

This paper studies various economic measures of a two unit cold standby system subject to slow transfer switch. Each unit of the system can be in one of the three modes—normal, partial failure and total failure. Repair time distribution of the units are general while all other transition time distributions are negative exponential. Regenerative point technique in Markov-renewal process is applied to obtain the economic measures.     

Cost-benefit analysis of a system with intermittent repair and inspection under abnormal weather

This paper studies a repairable system with intermittent repair. Weather under which the system works changes randomly (in time) from normal to abnormal weather and vice-versa. By intermittent repair, we mean that the repair facility is not available instantaneously but takes random time to be available. The system operating under abnormal weather is sent for inspection randomly with Poisson process. Failure rates of the system and rates of change of weather are constant while repair times, inspection time and inter-inspection time are arbitrarily distributed. The system is analysed by using regenerative point technique to obtain various economic measures such as mean time to system failure, steady state availability, probability that the repairman is busy, expected number of visits by repairman and expected profit earned by the system.     

Stochastic behaviour of man-machine systems operating under different weather conditions

This paper presents two mathematical models to predict the performance of the man—machine systems under different weather conditions. The operator may be in good or poor physical condition which also affects the performance of the system. Failure rate of the system, rate of change of weather conditions as well as rate of change of physical conditions of the operator are assumed to be constant while the repair time distributions are general. Regenerative technique in MRP is applied to obtain several reliability characteristics of interest.     

Stochastic behaviour of man-machine systems operating under different weather conditions

This paper presents some comments on ‘Stochastic behaviour of man-machine systems operating under different weather condition’ [1]. In addition, reliability analysis of one of the models given in [2] is performed. State probability, human operator reliability, mean time to human error (MTTHE) and probability of human error plots are shown.     

Stochastic behaviour of a maintained system with protection system

This paper deals with the analysis of a single unit system backed by a protection system (.P.S.). Both are subject to failure with exponential failure time distribution. Repair time of working unit, fault detection and inspection time of protection system are assumed to follow general distribution. The system has been investigated in detail by the help of semi-Markov process and several parameters of interest are obtained.     

Operational behaviour and profit function for a bleaching and screening system in the paper industry

This paper discusses the bleaching and screening system (each having four subsystems) in the paper industry with three states: good, reduced and failed. The failure rate for each subsystem is constant while the repair rates are arbitrary. Mathematical formulation is carried out using the supplementary variable technique. The equations are solved using direct integration method. Expressions and graphs for steady state availability and mean time to system failure (MTSF) are given, depicting the effect of failure and repair rates. Profit analysis is also carried out.     

Cost analysis of a system with partial failure mode and abnormal weather conditions

This paper deals with the cost analysis of a system having three modes (normal, partial failure and total failure) in two weather conditions—normal and stormy. Failure rates of the system and rates of change of weather conditions are constant while the repair rates are general. The repair time distribution depends upon the starting state of the repair and it does not alter with the change in weather. The system is observed at suitable regenerative epochs in order to obtain reliability characteristics of interest to system designers and operations managers. Earlier results are verified as particular cases.     

Stochastic behaviour of a two-unit paralleled system

This paper deals with a two-unit paralleled system with a single repair facility. Most papers on this subject assumed that at least one of the life time and repair time distribution is exponential. However the above assumption is violated by this paper. Then the various state probabilities (densities) have derived by employing the method of supplementary variables. We obtain the stochastic behaviour from these probabilities; (1) the long-run availability, (2) the idleness probability for the repair crew, and (3) the expected number (per unit time in long run) of system failures. Also comparison between the constant failure rate and non-constant failure rate is shown by numerical example.     

Stochastic behaviour of a two-unit redundant system with switchover time

There is a two-unit standby redundant system. Standby is kept in cold state. Whenever one unit is operating and the other is in the waiting standby state, switching is initiated on the latter after a random time. If the operative unit fails before the time to initiate switching action on the waiting standby unit, the system fails and the failed unit immediately undergoes repair type 2 along with the switching. However, if the operative unit fails when the other unit is as standby (after switchover), the failed unit undergoes repair type 1 and the unit as standby takes over the operation. All the distributions are arbitrary except failure-time, which is exponential.The system is defined with the help of states which generate a pseudo semi-Markov process. Abundant use of results from the theory of SMP has been made to obtain a large number of parameters which measure reliability characteristics of the system viz. MTSF, steady-state availability, expected number of visits to a state, conditional transition probabilities, first passage time distributions, expected profit rate, etc. Numerical examples are included to illustrate the results.     

Stochastic behaviour of a standby redundant system with three modes

This paper discusses the stochastic behaviour of a two-unit cold standby redundant system in which each unit works in three different modes-normal, partial failure and total failure. Failure-time distributions of units are exponential, whereas repair-time distributions are arbitrary. Explicit expressions for the Laplace-Stieltjes transforms of the distribution function of the first passage time, mean time to system failure and steady state availability of the system are obtained. A few particular cases are discussed.     

Stochastic behaviour of a two-unit standby system with better utilization of units

This paper obtains various measures of reliability of a two-unit redundant system with three modes. Upon partial failure of an operative unit the cold standby starts operation only when it becomes active. A single service facility is available (1) for repairing a partially or totally failed unit and (2) to activate the cold standby unit whenever required. Failure time distributions are negative exponential while repair and activating time distributions are general.     

Stochastic behaviour of a three-state complex repairable system with three types of failures

This paper deals with the operational availability of a three-state complex repairable system consisting of n distinct units arranged in series. Single service facility is available for three types of failures of the complex system. A mathematical model for the complex system under severe restrictions has been developed for exponential failures and general repairs. Laplace transforms of various state probabilities have been evaluated and availability is then obtained by the inversion process. Few graphical illustrations are also given in the end so as to explain the practical utility of the model.     

Stochastic behaviour of a two-unit cold standby system with three modes and allowed down time

This paper discusses the stochastic behaviour of a two-unit cold standby redundant system under two very general sets of conditions: (i) each unit of the system having three different modes of working—normal, partial failure and total failure; (ii) breakdown of the system occurring when with both the units in total failure mode, the system is not regarded as failed (the system fails only when the breakdown does not terminate within the allowed down time). Failure-time distributions of units are exponential, whereas repair time distributions are arbitrary. Several reliability characteristics of interest to system designers as well as operations managers have been evaluated.     

Stochastic behaviour of a two-unit (dissimilar) hot standby system with three modes

A hot standby system composed of two non-identical units is analysed under the assumption that each unit works in three possible modes—normal, partial failure and total failure. For each unit the failure time distribution is negative exponential and the repair time distribution is arbitrary. Breakdown of the system occurs when both the units are in total failure mode. There is only one repair service and when both the units are in the same mode, priority is given to the first unit in the matter of operation as well as repair. Several reliability characteristics of interest to system designers and operations managers have been evaluated.     

Stochastic behaviour of a two-unit cold standby redundant system with administrative delay and two types of repairs

In this paper we consider a two-unit cold standby redundant system in which each unit works in three modes—normal, partial failure and total failure with two types of repairs (major and minor) after partial failure mode, with administrative delay to locate expert repair man for major repair. The administrative time distribution is assumed to be exponential, whereas the repair and failure time distributions are exponential and arbitrary. The technique of regenerative processes is applied to obtain various reliability characteristics of interest to system designers.     

Stochastic behaviour of a two-unit cold standby redundant electronic equipment under human failure

This paper presents a mathematical model to evaluate availability and M.T.T.F. of a two-unit cold standby system with three possible states of each unit; viz. good, partially failed and failed, incorporating the concept of human failure. The model has been developed for exponential failures and general repairs. Single service facility is available in each state during the operational stage of the electronic equipment. Laplace transforms of the various state probabilities have been obtained. Steady-state probabilities, steady-state availability and mean time to failure have been derived.     

浅析高校网络系统的信息安全与防范措施

随着计算机网络迅速发展和网络应用的广泛普及,网络安全问题日益突出.论文浅析了高校网络办公系统中威胁计算机网络安全的各种因素,并就几种主要的计算机网络安全防范措施进行了探讨.