• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.76-81
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• 2019

In this study, the causes of human error were identified through the survey of the drivers of the three organizations: Seoul Metro, Seoul Metropolitan Rapid Transit Corporation, and Korail. It was started with the aim of finding and eliciting causes in various directions including human factors, job factors, and environmental factors. The Cronbach alpha value was 0.95 for the reliability significance of the stress-induced factors in the operational area. The significance probability for organisational factors was shown to be 0.82, and the significance of the sub-accident experience and the driving skill factors in operation was 0.81 In addition, the analysis results showed that stress-induced in the field of driving is higher than the human factors in the reliability analysis. The results of the analysis confirmed that the reliability of the organizational and operational stress-induced factors was higher than other causes. In order to reduce urban railroad accidents, this paper suggests a method for operating safe urban railroad through the minimization human errors.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.1
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• pp.86-93
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• 2015

Globally, wind power development is experiencing dramatic growth and wind power penetration levels are increasing. Wind generation is highly variable in time and space and it doesn't guarantee the system reliability and secure system operation. As wind power capacity becomes a significant portion of total generation capacity, the reliability assessment for wind power are therefore needed. At present, this operational reliability assessment is focusing on a generation adequacy perspective and does not consider transmission reliability issues. In this paper, we propose the critical transmission operating constraint prediction(CTOCP) system with high wind power penetration to enhance transmission reliability.

• IE interfaces
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• v.25 no.4
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• pp.382-392
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• 2012

Reactor protection system to keep nuclear safety and operational economy of plants requires high reliability. Such a high reliability of the system can be achieved through the redundant design of components. However, common cause failures of components reduce the benefits of redundant design. Thus, the common cause failure analysis, to accurately calculate the reliability of the reactor protection system, is carried out using alpha-factor model. Analysis results to 24 operating months are that 1) the system reliability satisfies the reliability goal of EPRI-URD and 2) the common cause failure contributes 90% of the system unreliability. The uncertainty analysis using alpha factor parameters of 0.05 and 0.95 quantile values shows significantly large difference in the system unreliability.

• Journal of Applied Reliability
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• v.10 no.1
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• pp.57-64
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• 2010

The HANARO nuclear research reactor had been operated successfully and smoothly up to the year 2008 since its first year of instability in year 1995 just after the completion of construction. But the reliability of the reactor has been degraded from the year 2009 due to new experimental facilities such as Feul Test Loop(FTL) and Cold Neutron Source(CNS) which were installed in the HANARO plant. It turned out that these new facilities contributed unexpected stoppage of the plant. This paper describes causes of stoppage and suggestions to improve the reliability of the plant.

• Journal of the Korean Society of Safety
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• v.25 no.2
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• pp.24-28
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• 2010

The nuclear power Plant onsite AC electrical power sources are required to supply power to the engineering safety facility buses if the offsite power source is lost. Typically, Diesel Generators are used as the onsite power source. The 125 VAC buses are part of the onsite Class 1E AC and DC electrical power distribution system. The DC power distribution system ensure the availability of DC electrical power for system required to shutdown the reactor and maintain it in a safety condition after an anticipated operational occurrence or a postulated Design Base Accident. Recently, onsite DC power supply system trip occurs the loss of system function. To obtain the performance such as reliability and availability, we analyzed the cause of battery charger trip and described the improvement of DC power supply system reliability. Finally, we provide reliability performance criteria of charger in order to ensure the probabilistic goals for the safety of the nuclear power plants.

• Journal of Applied Reliability
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• v.18 no.2
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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.

• Journal of Coastal Disaster Prevention
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• v.4 no.4
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• pp.189-196
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• 2017

Ocean Research Stations (ORSs) is the ocean platform type observation towers and measured oceanic, atmospheric and environmental data. These station located on the offshore area far from the coast, so they can produce the data without land effect. This study focused to improve the wave data quality of ORS station. The wave observations at ORSs are used by the C-band (5.8 GHz, 5.17 cm) MIROS Wave and Current Radar (MWR). MWR is convenient to maintenance and produce reliability wave data under bad weather conditions. MWR measured significant wave height, peak wave period, peak wave direction and 2D wave spectrum, so it's can provide wave information for researchers and engineers. In order to improve the reliability of MWR wave data, Datawell Waverider Buoy was installed near the one ORS (Socheoncho station) during 7 months and validate the wave data of MWR. This study found that the wave radar tend to be overestimate the low wave height under wind condition. Firstly, this study carried out the wave Quality Control (QC) using wind data, however the quality of wave data was limited. So, this study applied the four filters (Correlation Check, Direction Filter, Reduce White Noise and Phillips Check) of MWR operating software and find that the filters effectively improve the wave data quality. After applying 3 effective filters in combination, the RMSE of significant wave height decreased from 0.81m to 0.23m, by 0.58m and Correlation increased from 0.66 to 0.96, by 0.32, so the reliability of MWR significant wave height was significantly improved.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.6
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• pp.449-456
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• 2020

This study examines the relation between the quality of leader-member relationship and operational performance of processing enterprises employees in Vietnam, while job satisfaction and innovation are as a mediator variable. In depth interviews are first conducted with five managers and professional workers in five processing enterprises to determine the latent variables and build the structured questionnaire with observed variables. A quantitative survey with 438 employees and managers from 300 processing enterprises was carried out. The method of exploratory factor analysis (EFA), Cronbach's alpha analysis, and confirmatory factor analysis (CFA) was used to test the reliability, the convergent nature, and the consistency of the concepts. Structural equation modeling (SEM) is used to test the proposed model. The result shows that job satisfaction, innovation and operational performance have positive effects on the quality of leader-member relationship. The relationship between leaders and members had indirect impact on employee's operational performance via their job satisfaction and innovation, which illustrates a mediator role of job satisfaction and innovation for employees' performance. The findings of this study suggest that managers need to focus on developing relationship with employees to improve their satisfaction, innovation and performance.

• Proceedings of the KSRS Conference
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• 1999.11a
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• pp.19-24
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• 1999

This paper addresses a new project being carried out at Satellite Technology Research Center. The purpose of the project is to implement a system which receives, processes and stores 1m resolution satellite image transmitted at over 300Mbps down link data rates. In order to develop such a system, a system operational concept design and a requirements study were being carried out As a result of the operational concept design, system objectives, system context and system functions were defined. The system shall be operated according to the philosophy of maximum automation. rapid processing, reliability, integrity, cost effectiveness, and expandability. The system is divided into twelve independent processes and its behavior is modeled by operational scenario, which are combinations of independent processes. Process information and logs generated by the system shall be stored in databases and data received and generated be automatically archived and managed in a hierarchical storage device. The system shall have redundant components in order to be ready for recovering from sudden system failures. This paper will describe in detail the system operational concept design and the system requirements derived from the operational concept design.

• Journal of Korean Society for Quality Management
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• v.45 no.1
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• pp.1-10
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• 2017

Purpose: Most enterprises adopt six sigma acts to maximize the business performance with raising the executiveness for the project improvements in each parts. But there are little studies about six sigma actual operations in manufacturing whether the six sigma improvements that have injected a lot of budget, efforts, labours and time are run properly. Methods: This study select 31 interviewees who have MBB or BB from 5 large enterprises running six sigma over 10 years and 5 SMEs running six sigma over 5 years to understand and review the operational status of six sigma actions in manufacturing industry and to secure representativeness. This study identify the operational status of six sigma actions and key factors enhancing or impeding execution of six sigma projects through face-to-face interviews and online surveys by e-mail. Results: This study figured out the operational status of six sigma actions and key factors enhancing or impeding execution of six sigma projects. We used SPSS 16.0 for the reliability and the validity of survey data. Conclusion: There can be a lot of different factors that affect six sigma project improvements besides the key factors from this study. More study need to think of the organization characteristics and the basic conditions and to remedy the unreasonable points and defects rather than following foreign companies and enterprises.