• International Journal of Reliability and Applications
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• 제9권1호
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• pp.113-122
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• 2008

In this paper, we consider a periodic preventive maintenance policy in which each preventive maintenance reduces the hazard rate of amount proportional to the failure intensity, which increases since the system started to operate. And the effect of preventive maintenance at each preventive maintenance epoch is different. The expected cost rate per unit time for the proposed model is obtained. We discuss the optimal number N of the periodic preventive maintenance and the optimal period x, which minimize the expected cost rate per unit time and obtain the optimal preventive maintenance schedule for given cost structures of the model. A numerical example is given for the purpose of illustrating our results when the failure time distribution is Weibull distribution.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권2호
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• pp.104-113
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• 2018

Purpose: This paper proposes the non-periodic preventive maintenance policy based on the level of cumulative hazard intensity. We aim to construct a cost-effectiveness on the proposed model with relaxing the constraint on reliability. Methods: We use the level of cumulative hazard intensity as a condition variable, instead of reliability. Such a level of cumulative hazard intensity can derive the reliability which decreases as the frequency of preventive maintenance action increases. We also model the imperfect preventive maintenance action using the proportional age setback model. Conclusion: We provide a numerical example to illustrate the proposed model. We also analyze how the parameters of our model affect the optimal preventive maintenance policy. The results show that as long as high reliability is guaranteed, the inefficient preventive maintenance action is performed reducing the system operation time. Moreover, the optimal value of the proposed model is sensitive to changes in preventive maintenance cost and replacement cost.

• Journal of Preventive Medicine and Public Health
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• 제40권4호
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• pp.278-284
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• 2007

Despite extensive researches and pre-market clinical trials, only limited information on the adverse drug reactions (ADRs) of a drug can be collected at the time of market approval from regulatory agency. ADRs constitute a major public health problem. Post-marketing surveillance of drugs is important to detect signals for ADR. In Korea, one of the main methods for monitoring the safety of marketed drugs is spontaneous reporting system of suspected ADRs. Re-examination and re-evaluation system are in force for monitoring safety of new market approval drugs and currently under marketing drugs, respectively. Recently, regional pharmacovigilance centers were designated from Korean Food and Drug Administration for facilitating ADR surveillance. Over recent years, with the development of information technology, there has been an increased interest in establishing data mining system for detecting signals from Health Insurance Review Agency database. The purpose of this paper is to review the current status of Korean ADR surveillance system and suggest the possible solutions for developing active pharmacovigilance system in Korea.

• Journal of Preventive Medicine and Public Health
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• 제39권2호
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• pp.159-164
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• 2006

Objectives : This study was conducted to evaluate the effects of the personal stereo system on the hearing in adolescents. Methods : A total of 68 adolescents(age: 13-18 years) who visited the ENT Department at a University Hospital in Daegu were personally interviewed. The questionnaires were about general characteristics of the subjects, the time of personal stereo system use (year, hour) and place. Cumulative exposure to the personal stereo system was calculated by the product of the total years and the daily hours of their use. Pure tone audiometry was performed and the hearing threshold was measured at 500, 1000, 2000, 4000 and 8000 Hz. Results : The average time of using a personal stereo system a day was about 3 hours and 75% of the subjects used a personal stereo system for 2-5 years. The elevation of threshold was more prominent in the subjects who used personal stereo systems for 4 years and more compared with those subjects who used them for 3 years and under. The elevation of hearing threshold was also more prominent in the subjects who used personal stereo systems for 4 hours and more a day compared with those subjects who used personal stereo systems for 3 hours and under a day. The elevation of hearing threshold was more prominent in the subjects who used personal stereo systems for 13 hour. years and more compared to the subjects who used them 12 hour. years and under. Conclusions : These results suggest that the elevation of hearing threshold can happen to adolescents who used personal stereo systems for a long time. In order to prevent hearing loss, we need to teach adolescents appropriate usage of the personal stereo system and hearing tests should be included in the periodic school-based physical examination for the adolescents.

• Journal of the Korean Data and Information Science Society
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• 제17권2호
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• pp.367-377
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• 2006

This paper develops a periodic preventive maintenance(PM) policy following the expiration of warranty. Two types of warranty are considered: renewing warranty and non-renewing warranty. Also, we consider the situation where each PM cost is an increasing function of the PM effect. We determine the optimal number of PM's before replacing the system by a new one and the optimal length of period for the periodic PM following the expiration of warranty. Explicit solutions to determine the optimal periodic PM are presented for the Weibull distribution case.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.561-566
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• 2008

The EMU of maintenance technique or system is changing on a large scale. To subway operation beginning the breakdown was born and every that time after the fact repaired. But, recently before the breakdown of the subway occurs, repairs in advance with the preventive maintenance concept which was exchanged. However, the preventive maintenance is to readjust, cleaning, tighten and the oil the repetition by the worker simple experience. This study on introduces the EMU of maintenance method which applies a automatic inspection equipment from the study contributing which develops the preventive maintenance system.

• Journal of Preventive Medicine and Public Health
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• 제28권2호
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• pp.297-313
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• 1995

• Journal of Preventive Medicine and Public Health
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• 제28권2호
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• pp.314-324
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• 1995

• Journal of Preventive Medicine and Public Health
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• 제24권2호
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• pp.128-145
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• 1991

• Journal of Preventive Medicine and Public Health
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• 제56권2호
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• pp.200-202
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• 2023