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추정된 모수를 사용한 CCC-r 관리도에서 관리상태의 성능
김재연,김민지,이재헌,Kim, Jaeyeon,Kim, Minji,Lee, Jaeheon 한국통계학회 2018 응용통계연구 Vol.31 No.4
CCC-r 관리도는 고품질공정에서 공정불량률을 관리하는 경우 매우 효율적이라고 알려져 있다. 이 관리도를 사용할 때 관리상태의 공정모수는 일반적으로 알려져 있지 않기 때문에 제1국면의 표본을 추출하여 이를 추정해야 한다. 제2국면에서 관리도의 성능은 제1국면에서 추정한 모수와 관리한계에 영향을 받기 때문에, 추정 오차의 영향을 살펴보는 것은 중요하다. 이 논문에서는 일반적으로 많이 사용하는 평균런길이의 평균(average of average run length) 이외에 평균런길이의 표준편차(standard deviation of average run length)를 사용하여 CCC-r 관리도의 관리상태의 성능을 평가하였다. 그 결과 CCC-r 관리도에서 안정적인 관리상태의 성능을 유지하기 위해서는 이전에 권장하던 제1국면의 표본 크기보다 훨씬 더 큰 표본이 필요하다는 사실을 알 수 있었다. The CCC-r chart is more effective than traditional attribute control charts for monitoring high-quality processes. In-control process parameters are typically unknown and should be estimated when implementing a CCC-r chart. Phase II control chart performance can deteriorate due to the effect of the estimation error. In this paper, we used the standard deviation of average run length (ARL) as well as the average of ARL to quantify the between-practitioner variability in the CCC-r chart performance. The results indicate that the CCC-r chart requires larger Phase I data than previously recommended in the literature in order to have consistent chart in-control performance among practitioners.
전기화학분극법에 의한 리튬 이온 전지의 열적 기계적 손상 평가
김재연(Jaeyeon Kim),유기태(Kitae Yoo),왕택립(Zeli Wang),임미나(Mina Lim),조소연(Soyeon Cho),김동오(Dongo Kim),이명훈(Myounghun Lee),변재원(Jaiwon Byeon) 한국신뢰성학회 2019 신뢰성응용연구 Vol.19 No.1
Purpose: Health and safety of lithium ion batteries have become important issue due to increasing reports on explosion and firing accident during use. In this research, mechanical and thermal damages of a lithium ion battery were evaluated by applying alternative current electrochemical impedance spectroscopy. Methods: Nyquist plot was obtained for the isothermally exposed batteries to 85℃, 100℃ and 120℃ as well as mechanically twisted and bended lithium polymer batteries, respectively. Ohmic, SEI (secondary electrolytic interface), and charge transfer resistance were extracted and compared among them. Results: Nyquist plot of both thermally exposed and mechanically deformed batteries were observed to shift toward high resistance region. SEI resistance value increased with thermal exposure, which is attributed to the decomposition reaction of lithium salt over 60℃. For the mechanically deformed battery, Ohmic resistance increased, while little change in SEI resistance was observed. Conclusion: SEI resistance and Ohmic resistance value extracted from the Nyquist plot can be applied as a state-of-health monitoring indicator of the lithium ion batteries used under thermal exposure or mechanical deformation condition, respectively.
무인운전열차시스템 관제실 근무환경, 직무만족, 업무성과간의 관련성에 관한 실증 분석
김재연(Jaeyeon Kim) 한국인터넷전자상거래학회 2015 인터넷전자상거래연구 Vol.15 No.3
In this study, the relationships among the practice environment, the job satisfaction and the job performance of railway dispatchers in OCC(Operation Control Center) on unmanned train system are analyzed. An important result of this study is that the job satisfaction of railway dispatchers is affected negatively in recognition of their health status of dispatchers who works in shift pattern. Nevertheless the mitigation level of the event processing pressure in system failures and unusual situations is affected positively by the job satisfaction. By the results, some practical suggestions are proposed. First, the supervisor has to play a major role in controlling system in critical factors. Second, standard operation procedure for dispatchers has to be made by dispatching priorities. Third, the building layout of OCC has to be designed by applying dispatcher’s opinions.