• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2000년도 추계학술대회
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• pp.335-342
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• 2000

Preventive maintenance(PM) is an action taken on a repairable system while it is still operating, which needs to be carried out in order to keep the system at the desired level of successful operation. The PM improves the reliability of the system by predicting the possible failures and thereby preventing such failures from its occurrence. In this paper, we develop the optimal preventive maintenance policies based on the aperiodic PM model. We investigate an aperiodic preventive maintenance policy and propose several optimal PM policies which minimize the expected cost over an infinite time span. Park, Jung and Yum(2000) determine the optimal period and the optimal number of PMs based on Canfield's(1986) periodic model. Our techniques to derive the optimal preventive maintenance policies based on our aperiodic PM model is similar to those in Park, Jung and Yum(2000), which can be considered as the special case of our results.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권2호
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• pp.167-176
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• 2011

This paper introduces models for preventive maintenance policies and considers periodic preventive maintenance policy with minimal repair when the failure of system occurs. It is assumed that minimal repairs do not change the failure rate of the system. The failure rate under prevention maintenance received an effect by a previously prevention maintenance and the slope of failure rate increases the model where it considered. Also the start point of failure rate under prevention maintenance considers the degradation of system and that it increases quotient, it assumed. Per unit time it bought an expectation cost from under this prevention maintenance policy. We obtain the optimal periodic time and the number for the periodic preventive maintenance by using Nakagawa's Algorithm, which minimizes the expected cost per unit time.

• Smart Structures and Systems
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• 제15권3호
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• pp.609-625
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• 2015

Management of infrastructure stock is essential in sustainability of society, and its analysis and optimization are studied in the light of control system modeling in this paper. At the first part of the paper, cost of stock management is analyzed based on macroscopic statistics on infrastructure stock and economical growth. Stock management burden relative to economy is observed to become larger at low economic growth periods in developed economies. Then, control system modeling of stock management is introduced and by augmenting maintenance actions as control input, dynamic behavior of stock is simulated and compared with existing time history statistics. Assuming steady state conditions, applicability of the model to cross sectional data is also demonstrated. The proposed model is enhanced so that both preventive and corrective maintenance can be included as system inputs, i.e., feedforward and feedback control inputs. Optimal management strategy to achieve specified deteriorated stock level with minimal cost, expressed in terms of preventive and corrective maintenance actions, is derived based on estimated parameter values for corrosion of steel bridges. Relative cost effectiveness of preventive maintenance is shown when target deteriorated stock level is lower.

• Journal of Preventive Medicine and Public Health
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• 제33권3호
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• pp.373-382
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• 2000

Objectives : The most frequently cited health related slogan in North Korea is that socialistic medicine is preventive medicine. It implies that North Korea puts preventive medicine at the operational center of its national health care system. This study aimed at examining and comparing preventive medicine practices in North Korea with those of South Korea. Methods : Efforts have been made to obtain a textbook for analysis its contents. Many people have iassisted in the study by joining the interview. Some of these people are as follows : a former professor of PyongYang Medical School, NK physicians living in South Korea, WHO staffs, diplomatic officials, etc. The major items of analysis consisted of industrial medicine and hygiene, nutrition, school health, epidemiology, health statistics and heath policy & management. Results : Public health philosophy is finely noted and well integrated in the operation of the North Korean national health care system, particularly in the area of industrial medicine and hygiene. Preventive medicine with a strong health surveillance system spanning a number of broad social organizations is a major tool to improve the health of the people in North Korea. The emphasis on preventive medicine has a close relationship with the 'Juche Philosophy' and the shortage of pharmaceuticals and medical equipment. To cope with the shortage problem, North Korean health workers are encouraged to grow medicinal herbs. We have found that they put little effort into teaching newly emerging diseases, such as AIDS, VDT syndrome, hazards of EMF, and agricultural chemical poisonings. Of the subjects of the preventive medicine text, 78.9% coincide with those of South Korean industrial health manuals and 34.2% with South Korean epidemiology texts. However, an absolute difference was found to exist between the health policies and management systems. Conclusion : In North Korea, the concept of preventive medicine functions as the basic philosophic strategy of the national health care system. It differs greatly from the South Korean system in both practice and educational content. Its contribution to society is simply incomparable to that of South Korea. More communication and further study is called for in order to improve the preventive medicine practices in the future.

• 대한예방의학회:학술대회논문집
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• 대한예방의학회 2001년도 제53차 추계 학술대회 연제집
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• pp.462-463
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• 2001

• 대한예방의학회:학술대회논문집
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• 대한예방의학회 1996년도 제48차 추계 학술대회 연제집
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• pp.303-304
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• 1996

• 품질경영학회지
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• 제25권3호
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• pp.86-95
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• 1997

This paper considers a repairable system, which is maintained preventively at periodic times and is minimally repaired at each failure. Most preventive maintenance policies for such repairable systems assume that the cost of minimal repair is constant regardless of its age at failure. However, it is more practical to consider the situations where the cost of minimal repair is dependent not only on its age at failue, but also on the number of preventive maintenance carried out prior to its failure. We consider the preventive maintenance carried out prior to its failure. We consider the preventive maintenance policy with age-dependent minimal repair cost. The optimal policies which minimize the expected cost rate over an infinite time span are discussed. We obtain the optimal period and number of preventive maintenance prior to replacement of the system.

• 전기학회논문지
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• 제57권8호
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• pp.1305-1310
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• 2008

Traditional maintenance planning is based on a constant maintenance interval for equipment life. In order to consider economic aspect for time based preventive maintenance, preventive maintenance is desirable to be scheduled by RCM(Reliability-Centered Maintenance) evaluation. The main objective of RCM is to reduce the maintenance cost, by focusing on the most important functions of the system and avoiding or removing maintenance actions that are not strictly necessary. So, Markov state model is utilized considering stochastic state in RCM. In this paper, a Markov state model which can be used for scheduling and optimization of maintenance is presented. The deterioration process of system condition is modeled by the stepwise Markov model in detail. Also, because the system is not continuously monitored, the inspection is considered. In case study, simulation results about RCM will be shown using the real historical data of combustion turbine generating unit in Korean power systems.

• Journal of Information Processing Systems
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• 제16권3호
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• pp.648-662
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• 2020

Bluetooth low energy (BLE) beacon is an actively push-to-broadcast electronic signal and can be used for object identification. This paper uses such beacon-based identification and Internet of Things (IoT) technologies for the elder health management service system to simplify the user interfaces and steps for preventive elder care. In the proposed system, an elder's family member, caregiver, or medical worker can conveniently and quickly record daily health management information. Besides, through the statistics and analysis of the data on the back end of the system, it is helpful for the elderly to refer to the data of daily care management and future management trends. Similarly, it is also an essential reference data for system maintenance and the new preventive health care services development.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권2호
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• pp.184-191
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• 2018

Purpose: The purpose of this study is to propose a method to calculate the optimal preventive maintenance cycle of radar used in the aviation weapon system of ROKAF. Methods: A hybrid model is used to estimate the optimal preventive maintenance cycle in a system that can perform condition based predictive maintenance (CBPM) through continuous diagnosis. The failure data of the radars operating in the military were used to calculate the reliability. Results: According to the research results, the reliability threshold of the radar began to decrease after 5 flights, and decreased rapidly after 12 flights. Since the second check, costs have continued to decline. Conclusion: A method is proposed to determine the cycle of optimal preventive maintenance of radar within operational budget through modeling results between reliability limit and cost for radar. The results can be used to determine the optimal preventive maintenance cycle and frequency of various avionics equipment.