• Title, Summary, Keyword: Imperfect Maintenance

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A Value-based Real Time Pricing Under Imperfect Information on Consumer Behavior

  • Kim, Balho H.;Park, Jong-Bae
    • Journal of Energy Engineering
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    • v.8 no.4
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    • pp.505-511
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    • 1999
  • One of the major challenges confronting a multiservice electric utility is the establishment of the right prices, for its services. The key objectives of particular pricing schemes are reasonableness of company earnings. Economic efficiency, the responsiveness of supply and of the allocation of sources to the desires of consumers, and maintenance of some degree of competition. This paper proposes a value-based pricing mechanism amenable to the current deregulation situation in electricity market allowing service differentiation. The proposed pricing mechanism can be implemented ina nodal auction model, and can also be applied to direct load control.

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Bayesian Method on Sequential Preventive Maintenance Problem

  • Kim Hee-Soo;Kwon Young-Sub;Park Dong-Ho
    • Communications for Statistical Applications and Methods
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    • v.13 no.1
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    • pp.191-204
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    • 2006
  • This paper develops a Bayesian method to derive the optimal sequential preventive maintenance(PM) policy by determining the PM schedules which minimize the mean cost rate. Such PM schedules are derived based on a general sequential imperfect PM model proposed by Lin, Zuo and Yam(2000) and may have unequal length of PM intervals. To apply the Bayesian approach in this problem, we assume that the failure times follow a Weibull distribution and consider some appropriate prior distributions for the scale and shape parameters of the Weibull model. The solution is proved to be finite and unique under some mild conditions. Numerical examples for the proposed optimal sequential PM policy are presented for illustrative purposes.

The Software Reliability Growth Models for Software Life-Cycle Based on NHPP

  • Nam, Kyung-H.;Kim, Do-Hoon
    • The Korean Journal of Applied Statistics
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    • v.23 no.3
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    • pp.573-584
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    • 2010
  • This paper considers the differences in the software execution environments in the testing phase and the operational phase to determine the optimal release time and warranty period of software systems. We formulate equations for the total expected software cost until the end of the software life cycle based on the NHPP. In addition, we derive the optimal release time that minimizes the total expected software cost for an imperfect debugging software reliability model. Finally, we analyze the sensitivity of the optimal testing and maintenance design related to variation of the cost model parameters based on the fault data observed in the actual testing process, and discuss the quantitative properties of the proposed model.

Bayesian Method for Sequential Preventive Maintenance Policy

  • Kim Hee Soo;Kwon Young Sub;Park Dong Ho
    • Proceedings of the Korean Reliability Society Conference
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    • pp.131-137
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    • 2005
  • In this paper, we propose a Bayesian approach to determine the adaptive preventive maintenance(PM) policy for a general sequential imperfect PM model proposed by Lin, Zuo and Yam(2000) that PM not only reduces the effective age of the system but also changes the hazard rate function. Assuming that the failure times follow Weibull distribution, we adopt a Bayesian approach to update unknown parameters and determine the Bayesian optimal sequential PM policies. Finally, numerical examples of the optimal adaptive PM policy are presented for illustrative purposes.

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Determining an Optimal Production Time for EPQ Model with Preventive Maintenance and Defective Rate (생산설비의 유지보수서비스와 제품의 불량률을 고려한 최적 생산주기 연구)

  • Kim, Migyoung;Park, Minjae
    • Journal of the Korean Society for Quality Management
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    • v.47 no.1
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    • pp.87-96
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    • 2019
  • Purpose: The purpose of this paper is to determine an optimal production time for economic production quantity model with preventive maintenance and random defective rate as the function of a machinery deteriorates. Methods: If a machinery shifts from "in-control" state to "out-of-control" state, a proportion of defective items being produced increases. It is assumed that time to state shift is a random variable and follows an arbitrary distribution. The elapsed time until process shift decreases stochastically as a production cycle repeats and quasi-renewal process is used to implement for production facilities to deteriorate. Results: When the exponential parameter for exponential distribution increases, the optimal production time increases. When Weibull distribution is considered, the optimal production time is closely affected by the shape parameter of Weibull distribution. Conclusion: A mathematical model is suggested to find optimal production time and optimal number of production cycles and numerical examples are implemented to validate the patterns for changes of optimal times under different parameters assumptions. The real application is implemented using the proposed approach.

Establishment of Sensor-based Safety Management Network for Main Infrastructures (센서기반 국가 주요 기반시설물 안전관리 네트워크 구축)

  • Lee, Jung-Seok;Kim, Yong-Soo;Ahn, Sang-Ro
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.171-174
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    • 2007
  • During last 30 years, Korea economy has grown so fast and many leading-edge technologies ware introduced from the advanced countries. but this fast growth inevitably produced imperfect completion of infrastructures and caused man-made catastrophes like Sungsu Bridge and Sampoong Department Store. After the incidents, Korea Government and National Assembly established "The Special Law for Safety Maintenance of Infrastructures". According to this law, most of infrastructures must be inspected periodically. During last 10 years after the establishment of the law, many infrastructures were improved and the quality of construction was upgraded. However, important and weak-to-disaster infrastructures need to be watched continuously. Many monitoring technologies were developed and tested in the field. In this paper, the new research project "Establishment of Testbed of Safety Management Network for Main Infrastructures", funded by government, was introduced.

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Studies on the Effects of Herbal Medicine in the pregnancy to the Fatus ( I ) - A study on the Herbal Medicines during pregnancy written in Dongeibogam(東醫寶鑑) - (한약(韓藥)이 임신중(妊娠中) 태아(胎兒)에 미치는 영향(影響) ( I ) - 동의보감중(東醫寶鑑中) 임신병(妊娠病) 치료(治療)에 사용(使用)된 처방(處方) 및 약물(藥物)에 관(關)한 연구(硏究) -)

  • Lee, Jae-Sung;Jang, Jun-Bock;Song, Byoung-Key
    • The Journal of Korean Medicine
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    • v.19 no.2
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    • pp.17-35
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    • 1998
  • Medication used during pregnancy may affect the growth of fetus and maintenance of pregnancy so that it may cause fetal deformity or abortion. Before 1940 it was recognized that only genetic factor could affect the incidence of fetal deformity and the teratogen was protected by placenta barrier. But since the report that Thalidomide caused phocomelia was announced in l962 and 1962, it was acknowledged that the placenta barrier was imperfect. In oriental medical care, there were so many prescription used during pregnancy for nausea, threatened abortion, recurrent spontaneous abortion and it was acknowledged that those medication did not harm both maternity and fetus. Most of them are composed of the material that was not classified as prohibition during pregnancy. But we thought that it should be demonstrated through objective methods that these materials do not affect the incidence of fetal deformity or abortion and have the effect of preventing abortion and maintenance of pregnancy. As the first step of that study we researched 78 prescription and each materials, their kinds and using frequency, used for illness and symptoms during pregnancy written in Dongeuibokam(東醫寶鑑) so that we got to know the tendency about what materials are used for each illness and symptoms.

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Surface aging and hydrophobicity recovery of silicone rubber by salt fog method (Salt fog 시험법에 의한 실리콘 고무의 표면 열화 및 발수성 회복 특성)

  • 김정호;서광석;문중섭;송우창;이재형;박용관;양계준;유영식
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.7
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    • pp.636-641
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    • 2000
  • The purpose of this study is assessing the characteristics of surface aging and recovery of hydrophobicity for silicone rubber which takes a great interest as outdoor insulation recently subjected to the combined stressed of salt fog and AC power. The methods for assessing are contact angle ATR-FRIR, AFM and XRD. In addition salt fog method is adopted as the artificial contamination experiment and AC power is applied 24 hour on and 24 hour off repeatedly for 5 cycles. The results suggest that degraded surface was more rough than virgin but was restored water repellency through the off cycle. It was due to not only the formation of fractal surface but also maintenance of hydrophobic surface by diffusion of low molecular oil. Although surface recovers initial hydropohbicity there are possibilities of decreasing electrical performance due to irreversable changes such as depolymerization of surface and loss of filler particles. This fact is confirmed by surface conductivity measurement showing that the degradation is significant and the recovery of hydrophobicity is imperfect as the energized cycle increases.

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Improvement of Regulations for Establishing Spatial Information Data Base of Railway Facilities (철도시설 공간정보DB 구축을 위한 법제도 개선방안)

  • Chung, Sung Bong;Choi, Ji Ho;Won, Jongun;Kim, Dongsun
    • Journal of The Korean Society of Civil Engineers
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    • v.37 no.1
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    • pp.187-193
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    • 2017
  • Government has established and operated GIS Data Base in such fields as land-use, road, and underground facilities since 1995. Based on these circumstances, the importance of spatial information industry began to emerge and accordingly MLIT (Ministry of Land, Infrastructure and Transport) established "National Spatial Information Policy Master Plan" and "National Spatial Information Policy Action Plan". However, compared to other fields of transportation, the spatial information data base for railway facilities are not established and provided systematically. As shown in 'Korea National Spatial Data Infrastructure System', only 'transportation information' as an related information and 'transportation' field as an administrative information are included in the system. Detailed information for railway and its facilities are not included in the system. The reason why detailed information for railway facilities are not included in the system is that regulations for establishing and utilizing the spatial information of railway and its facilities are imperfect. In this study, trend of establishing spatial information and regulations related to railway and its facilities are reviewed. Through this review, improvement items such as complementing existent laws and establishing organization for managing spatial information data of railway are deduced and suggested. Based on this research 'Korea National Spatial Data Infrastructure System' could set a legal fundament and both integrated maintenance and operation of railway facilities could be possible.