In this chapter, we discuss the optimal preventive maintenance policies for the system that fails... more In this chapter, we discuss the optimal preventive maintenance policies for the system that fails when the cumulated amount of damage by shocks exceeds a stochastic failure level, assuming a continuous distribution and a discrete one, respectively. We apply the expected costs per unit time in the steady state as criteria of optimality and seek the optimal policies minimizing these expected costs. We show that there exists a unique optimal policy under certain conditions, respectively. Furthermore, we refer to the modified models where the shock does not always give the damage to the system.
Abstract. During the last three decades, a few attentions have been paid for investigating the co... more Abstract. During the last three decades, a few attentions have been paid for investigating the cost distribution for the optimal maintenance problems. In this article, we derive the moment of the discounted cost distribution over an infinite time horizon for the basic age replacement problem. With first two moments of the discounted cost distribution, we approximate the underlying distribution function by three theoretical distributions. Through a Monte Carlo simulation, we conclude that the log-normal distribution is the best fitted one to approximate the discounted cost distribution.
International Journal of Reliability, Quality and Safety Engineering, 1997
This paper presents a new stochastic model for determining the optimal release time for a compute... more This paper presents a new stochastic model for determining the optimal release time for a computer software in testing phase, taking account of the debugging time lag. In the earlier works, most of software release models were considered, but it was assumed that an error detected can be removed instantaneously. In other words, none discussed quantitatively the effect of the software maintenance action in the optimal software release time. Main purpose of this work is to relate the optimal software release policy with the arrival-service process on the software operation phase by users. We use the Non-Homogeneous Poisson Process (NHPP) type of software reliability growth models as the software error detection phenomena and obtain the optimal software release policies minimizing the expected total software costs. As a result, the usage circumstance of a software in operation phase gives a monotone effect to the software release planning.
International Journal of Reliability, Quality and Safety Engineering, 2004
In this paper, we consider a cost model with periodic rejuvenation and derive the optimal softwar... more In this paper, we consider a cost model with periodic rejuvenation and derive the optimal software rejuvenation policy which minimizes the expected total discounted cost over an infinite time horizon, based on the familiar net present value approach. Further, since the failure time distribution can not be easily estimated from a few data samples in practice, we develop a statistically non-parametric algorithm to estimate the optimal periodic rejuvenation policy, provided that the complete sample data of failure times is given. Numerical examples based on the Monte Carlo simulation are illustrated to show asymptotic property of the proposed estimator.
Journal of Quality in Maintenance Engineering, 1998
This paper deals with economic manufacturing quantity (EMQ) models with stochastic machine breakd... more This paper deals with economic manufacturing quantity (EMQ) models with stochastic machine breakdown and repairs. Under two minimal repair policies to maintain a production machine, the expected cost functions per unit time in the steady state, incurred in the manufacturing operation, are formulated and the optimal policies which minimize them are calculated. As a special case, we consider the case where the machine breakdown time follows the homogeneous Poisson process and calculate the optimal EMQ policies numerically. Also, an approximation method is used to represent the expected cost.
In this chapter, we discuss the optimal preventive maintenance policies for the system that fails... more In this chapter, we discuss the optimal preventive maintenance policies for the system that fails when the cumulated amount of damage by shocks exceeds a stochastic failure level, assuming a continuous distribution and a discrete one, respectively. We apply the expected costs per unit time in the steady state as criteria of optimality and seek the optimal policies minimizing these expected costs. We show that there exists a unique optimal policy under certain conditions, respectively. Furthermore, we refer to the modified models where the shock does not always give the damage to the system.
Abstract. During the last three decades, a few attentions have been paid for investigating the co... more Abstract. During the last three decades, a few attentions have been paid for investigating the cost distribution for the optimal maintenance problems. In this article, we derive the moment of the discounted cost distribution over an infinite time horizon for the basic age replacement problem. With first two moments of the discounted cost distribution, we approximate the underlying distribution function by three theoretical distributions. Through a Monte Carlo simulation, we conclude that the log-normal distribution is the best fitted one to approximate the discounted cost distribution.
International Journal of Reliability, Quality and Safety Engineering, 1997
This paper presents a new stochastic model for determining the optimal release time for a compute... more This paper presents a new stochastic model for determining the optimal release time for a computer software in testing phase, taking account of the debugging time lag. In the earlier works, most of software release models were considered, but it was assumed that an error detected can be removed instantaneously. In other words, none discussed quantitatively the effect of the software maintenance action in the optimal software release time. Main purpose of this work is to relate the optimal software release policy with the arrival-service process on the software operation phase by users. We use the Non-Homogeneous Poisson Process (NHPP) type of software reliability growth models as the software error detection phenomena and obtain the optimal software release policies minimizing the expected total software costs. As a result, the usage circumstance of a software in operation phase gives a monotone effect to the software release planning.
International Journal of Reliability, Quality and Safety Engineering, 2004
In this paper, we consider a cost model with periodic rejuvenation and derive the optimal softwar... more In this paper, we consider a cost model with periodic rejuvenation and derive the optimal software rejuvenation policy which minimizes the expected total discounted cost over an infinite time horizon, based on the familiar net present value approach. Further, since the failure time distribution can not be easily estimated from a few data samples in practice, we develop a statistically non-parametric algorithm to estimate the optimal periodic rejuvenation policy, provided that the complete sample data of failure times is given. Numerical examples based on the Monte Carlo simulation are illustrated to show asymptotic property of the proposed estimator.
Journal of Quality in Maintenance Engineering, 1998
This paper deals with economic manufacturing quantity (EMQ) models with stochastic machine breakd... more This paper deals with economic manufacturing quantity (EMQ) models with stochastic machine breakdown and repairs. Under two minimal repair policies to maintain a production machine, the expected cost functions per unit time in the steady state, incurred in the manufacturing operation, are formulated and the optimal policies which minimize them are calculated. As a special case, we consider the case where the machine breakdown time follows the homogeneous Poisson process and calculate the optimal EMQ policies numerically. Also, an approximation method is used to represent the expected cost.
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Papers by Naoto Kaio