• 대한예방의학회:학술대회논문집
• /
• 1998.10b
• /
• pp.70-71
• /
• 1998

• 대한예방의학회:학술대회논문집
• /
• 1998.10b
• /
• pp.272-274
• /
• 1998

• IE interfaces
• /
• v.25 no.1
• /
• pp.127-133
• /
• 2012

This paper considers the preventive maintenance scheduling problem of the cluster tool which is one of the most important manufacturing equipments in the next-generation semiconductor production environment. We define a random process that expresses the successive amount of chemicals accumulating inside the tool. Based on the renewal theory, we find the expected value and probability distribution of the time that the amount of accumulated chemicals exceeds a predetermined level. For a given probability that the accumulated chemicals exceeds the predetermined level we present a method to obtain the number of chamber operations to perform the preventive maintenance of that chamber. In addition, a method to get the preventive maintenance schedule for the whole cluster tool is presented. A numerical example is provided to illustrate our method.

• 대한예방의학회:학술대회논문집
• /
• 2002.10a
• /
• pp.352-353
• /
• 2002

• 대한예방의학회:학술대회논문집
• /
• 2000.10a
• /
• pp.159-160
• /
• 2000

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.41 no.2
• /
• pp.24-31
• /
• 2018

As a system complexity increases and technology innovation progresses rapidly, leasing the equipment is considered as an important issue in many engineering areas. In practice, many engineering fields lease the equipment because it is an economical way to lease the equipment rather than to own the equipment. In addition, as the maintenance actions for the equipment are costly and need a specialist, the lessor is responsible for the maintenance actions in most leased contract. Hence, the lessor should establish the optimal maintenance strategy to minimize the maintenance cost. This paper proposes two periodic preventive maintenance policies for the leased equipment. The preventive maintenance action of policy 1 is performed with a periodic interval, in which their intervals are the same until the end of lease period. The other policy is to determine the periodic preventive maintenance interval minimizing total maintenance cost during the lease period. In addition, this paper presents two decision-making models to determine the preventive maintenance strategy for leased equipment based on the lessor's preference between the maintenance cost and the reliability at the end of lease period. The structural properties of the proposed decision-making model are investigated and algorithms to search the optimal maintenance policy that are satisfied by the lessor are provided. A numerical example is provided to illustrate the proposed model. The results show that a maintenance policy minimizing the maintenance cost is selected as a reasonable decision as the lease term becomes shorter. Moreover, the frequent preventive maintenance actions are performed when the minimal repair cost is higher than the preventive maintenance cost, resulting in higher maintenance cost.

• Nuclear Engineering and Technology
• /
• v.56 no.10
• /
• pp.4327-4334
• /
• 2024

Preventive Maintenance(PM) for safety component during power operation at nuclear power plants, On-Line Maintenance(OLM) refers to intentionally entering the Limited Condition of Operation(LCO) specified in the Technical Specification(TS) for safety-related systems and components in order to perform preventive maintenance within the Allowed Outage Time (AOT). This study assessed the feasibility of conducting OLM at the domestic APR1400 nuclear power plant. It focused on preventive maintenance duration and risk perspectives. A total of 78 FEGs were developed for 4450 facilities, considering system functions and preventive maintenance scope during output operation for eight safety-related systems. Additionally, maintenance items included in FEGs were selected, designated as targets for OLM, and their maintenance durations were evaluated and compared with AOT for each maintenance item. As a result, the Auxiliary Feedwater and Essential Chilled Water systems were identified as systems allowing OLM. Furthermore, utilizing the Risk Monitoring System (RIMS), the increased risk value due to the unavailability of target equipment during preventive maintenance was analyzed to determine whether it falls within the acceptable range. Regarding the temporary risk increase caused by OLM, it was observed that in all systems, it falls within Zone III according to NUMARC93-01 standards, allowing for normal equipment arrangement for OLM. However, according to the risk increase standards rate in domestic nuclear power plants, when maintaining the A-train in four systems including Component Cooling Water, they are all evaluated as 'Orange,' indicating that measures for risk mitigation are necessary for OLM to be feasible. When considering extending AOT up to 1.6 times the maintenance time, the risk increase falls within Zone III according to permissible change in risk standards, indicating that AOT extension might be feasible based solely on risk changes. To apply OLM within the permissible risk management scope in domestic nuclear power plants, regulatory policies need to allow voluntary LCO entry for preventive maintenance, necessitating clear determination by regulatory agencies using risk-informed policies. While OLM seems viable concerning maintenance duration and quantitative risk aspects, for inducing regulatory policy changes, comprehensive OLM guidelines are necessary, including risk management strategies.

• Korea Journal of Hospital Management
• /
• v.7 no.3
• /
• pp.84-101
• /
• 2002

This study estimated the influence of 'the separation of prescribing and dispensing roles' (SPD) policy, which implemented in July 2000, on the community pharmacies in Korea, by using data on the revenues and expenditures in the previous researches. We first assumed the rate of drug price differential was 20% with four different models which was based on various data of studies carried out in the similar period. Later, we applied different rates for the sensitivity analysis. According to the results, all community pharmacies made the net profit of 118.9 billion won (0.552 million won monthly per one pharmacy) after the SPD policy. The ratio of net profit to net sales dropped by 7.41%p from 22.19% to 14.78%. Additional sensitivity analysis indicated there were wide range of differences about whether net profit or net gain, and that extent which either existed.

• Journal of Korean society of Dental Hygiene
• /
• v.16 no.2
• /
• pp.215-224
• /
• 2016

Objectives: The purpose of the study was to investigate the related factors of performance of radiation safety management in dental hygienists. Methods: A self-reported questionnaire was completed by 183 dental hygienists using dental radiography in 110 dental clinics in G area by convenience sampling methods. The questionnaire consisted of general characteristics of the subjects, radiation-related characteristics, and performance and management of radiation safety. Results: Performance score of radiation safety management was $35.71{\pm}12.49$ in dental hygienists. The performance score of radiation safety management were associated with sex, numbers of dental hygienists, the average numbers of admitted patients per day, the total clinical experience, existence of manual for radiation safety management and perceived need for education of radiation safety management. Conclusions: The performance score was relatively low. The performance score was associated with radiation safety manual and safety equipment. The preparation of radiation protective environment and equipment will improve the performance of radiation safety management in dental hygienists.

• 대한예방의학회:학술대회논문집
• /
• 2001.10a
• /
• pp.250-251
• /
• 2001