• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.201-203
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• 2001

Safety is emphasized in nuclear power plant system for its characteristic. One of the most important systems to guarantee the safety of nuclear power plant is the PPS(Power protection system). The measurement control system includes PPS, which is similar to the human nervous system, is very important factor not only for the safety but also for the operation. Therefore, developing a technology to level up the performance of measurement system and reliability of the plant will bring cost-effective and safe generation of nuclear power. In this study, I researched composition of digitized PPS and algorithm for cyclic inspection.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.137-146
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• 2006

This is the second of a two-part paper which describes comparison of reliability design methods by application to Donghae Harbor Breakwaters. In this paper, Part 2, we deal with sliding of caissons. The failure modes of a vertical breakwater, which consists of a caisson mounted on a rubble mound, include the sliding and overturning of the caisson and the failure of the rubble mound or subsoil, among which most frequently occurs the sliding of the caisson. The traditional deterministic design method for sliding failure of a caisson uses the concept of a safety factor that the resistance should be greater than the load by a certain factor (e.g. 1.2). However, the safety of a structure cannot be quantitatively evaluated by the concept of a safety factor. On the other hand, the reliability design method, for which active research is being performed recently, enables one to quantitatively evaluate the safety of a structure by calculating the probability of failure of the structure. The reliability design method is classified into three categories depending on the level of probabilistic concepts being employed, i.e., Level 1, 2, and 3. In this study, we apply the reliability design methods to the sliding of the caisson of the breakwaters of Donghae Harbor, which was constructed by traditional deterministic design methods to be damaged in 1987. Analyses are made for the breakwaters before the damage and after reinforcement. The probability of failure before the damage is much higher than the allowable value, indicating that the breakwater was under-designed. The probability of failure after reinforcement, however, is close to the allowable value, indicating that the breakwater is no longer in danger. On the other hand, the results of the different reliability design methods are in fairly good agreement, confirming that there is not much difference among different methods.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.195-202
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• 2008

Underestimation of the capacity can have serious economic consequences, as deficient bridges must be posted, repaired or replaced. Accurate prediction of bridge behavior may allow for more bridges to remain in service with or without minor repairs. The presented research is focused on the reliability evaluation of the actual load carrying capacity of existing bridges based on the field testing. Reliability analysis is performed on 17 previously tested bridges. Bridges are first evaluated based on the code specified values and design resistance. However, after the field testing program, it is possible to apply the experimental results into the bridge reliability evaluation procedures. The girder distribution factors obtained from the tests are also applied in the reliability calculation. The results indicate that the reliability indices of selected bridges can be significantly increased due to the reduction of uncertainties without sacrificing the safety of structures, by including the result of field measurement data into calculation.

• Korean Journal of Community Nutrition
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• v.20 no.6
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• pp.399-410
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• 2015

Objectives: This study aims to identify self-resilience factors that drive right dietary and food safety practices in middle school students. Methods: Data was collected from 438 middle school students in Daegu using a self-administered questionnaire in December, 2013. The questionnaire consisted of 81 items with the following categories: general information, self-resilience, right dietary and food safety practices. Statistical analyses to determine frequency, average, ANOVA, factor analysis, reliability analysis, and regression analysis were performed using SPSS 21. Results: The results of factor analysis indicated that self-resilience was classified into challenge, adaptability, patience and achievement needs, and right dietary practices were sub-grouped into family meals, experience of dietary life, eco-friendly, balanced food, economy and bad food control, and food safety practices consisted of management of bacteria, hand washing and eating off a plate, safety food and food purchasing. The score of right dietary and food safety practices showed significant differences by sex, grade, and school achievement (p < 0.05). The economy factor of right dietary practices was significantly affected by the management of bacteria (p < 0.001), hand washing and eating off a plate (p < 0.001), safety food (p < 0.01), food purchasing of food safety practices (p < 0.05). The challenge factor of self-resilience significantly affected family meals, experience of dietary life, balanced food, economy, bad food control, management of bacteria, hand washing and eating off a plate, and safety food (p < 0.05). The adaptability factor of self-resilience was associated with factors such as eco-friendly, balanced food, economy, bad food control, management of bacteria, hand washing and eating off a plate, and food purchasing (p < 0.05). Conclusions: This study suggests that dietary education programs for middle school students could incorporate food safety practices, and self-resilience such as challenge, adaptability, patience and achievement needs to be effective.

• Physical Therapy Rehabilitation Science
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• v.11 no.4
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• pp.414-420
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• 2022

Objective: In this study, the test-retest reliability and validity were presented to evaluate the usability of isokinetic rehabilitation equipment for the knee joint. Design: Cross-sectional design, reliability & validity study. Methods: Thirty healthy adults participated in the study. A CSMI dynamometer was used as a standardized measuring device to present the validity of the equipment. It was measured based on the dominant leg. The average peak torque value was selected as the measurement variable. After the measurement, a questionnaire was conducted on safety, satisfaction, and performance through the usability evaluation questionnaire. Results: The knee joint isokinetic rehabilitation equipment showed high reliability with Intraclass Correlations Coefficients (ICC) =0.883~0.956. In order to check the validity of the equipment, the 95% confidence interval of the mean difference limit was confirmed by the Bland & Altman plot. As a result, all three angular velocities showed a smaller confidence interval in the flexion than in extension. There were less than 10 plots that were not included in 2 Standard Deviation (SD) between all measurements. As a result of the usability evaluation questionnaire, the average of the safety domain(4.9±0.4), satisfaction domain(4.1±0.8), performance domain(4.3±0.8). Conclusions: If the product is improved by supplementing the items identified in the usability evaluation process, it is judged that it can be used as a useful device in various knee joint rehabilitation fields.

• Korean Journal of Construction Engineering and Management
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• v.10 no.1
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• pp.114-125
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• 2009

In this study, a design value analysis technique that considered stochastic LCC and stochastic performance evaluation was proposed, and by introducing the concept of reliability analysis, a decision making that secured reliability was supported. The results of this study, which was carried out according to the above objectives and methods, are summarized as follows: 1) The design value analysis procedures and value state function, improved in order to carry out a reliable analysis when evaluating alternate proposals that were extracted after the function definition was complete, were formalized, and in order to secure consistency and efficiency for value evaluation procedures, an evaluation index scheme was proposed; 2) Database collection and analysis were done for a bridge's LCC analysis. As for the collection scope of data, literature of previous research done on a bridge's LCC analysis was used as the basis for analysis, and for securing reliability regarding analysis results and dealing with uncertainty of collected data, the MCS technique was applied; 3) Weights and evaluation ranks for performance evaluation of each of the alternate proposals, as well as LCC analysis model, analysis period, discount rate, user expense, safety inspection and safety diagnosis expense conditions for LCC analysis were proposed. Lastly, a feasibility study was done and conclusion was made about "OO grand bridge and connecting road construction work execution design" project centered on value analysis execution case.

• Safety and Health at Work
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• v.9 no.1
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• pp.42-52
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• 2018

Background: Maintenance operations on-board ships are highly demanding. Maintenance operations are intensive activities requiring high man-machine interactions in challenging and evolving conditions. The evolving conditions are weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress. For example, extreme weather condition affects seafarers' performance, increasing the chances of error, and, consequently, can cause injuries or fatalities to personnel. An effective human error probability model is required to better manage maintenance on-board ships. The developed model would assist in developing and maintaining effective risk management protocols. Thus, the objective of this study is to develop a human error probability model considering various internal and external factors affecting seafarers' performance. Methods: The human error probability model is developed using probability theory applied to Bayesian network. The model is tested using the data received through the developed questionnaire survey of >200 experienced seafarers with >5 years of experience. The model developed in this study is used to find out the reliability of human performance on particular maintenance activities. Results: The developed methodology is tested on the maintenance of marine engine's cooling water pump for engine department and anchor windlass for deck department. In the considered case studies, human error probabilities are estimated in various scenarios and the results are compared between the scenarios and the different seafarer categories. The results of the case studies for both departments are also compared. Conclusion: The developed model is effective in assessing human error probabilities. These probabilities would get dynamically updated as and when new information is available on changes in either internal (i.e., training, experience, and fatigue) or external (i.e., environmental and operational conditions such as weather conditions, workplace temperature, ship motion, noise and vibration, and workload and stress) factors.

• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.14-19
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• 2015

The purpose of this paper is to study the correlation application that electrical fire causes occurs for overcurrent and leakage current signals in the indoor wiring. In the order to purpose, the causes data of overcurrent, or leakage current of electrical fire are drawn out referring to past studies, consulting with experts and experimental data. The correlation application was then applied with fuzzy logic of intelligent technique. To check the reliability and performance of the correlation application, modified center of area(CoA) was adopted to calculate the possibility that electrical fire occurs, whose value was then compared to the results. The chance of electrical fire calculated is higher when two causes of fire are put into the CoA of the correlation application of this paper than that of when each cause is separately put into the CoA. The correlation application developed in this study enables better analysis on possible electrical fire due to overcurrent, or leakage current and provides managers with the possibility of electrical fire so that they can better manage at a time of overcurrent, or leakage current.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1163-1168
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• 2013

The maximum allowable value of loop impedance($Z_s$) to secure the operation of overcurrent protective devices and the safety for indirect contact is a very important in TN-C-S system. The loop impedance is divided into inner loop impedance which consumer can adjust and external loop impedance($Z_e$) which only electric operator can adjust. Thus, an external loop impedance which limits to less than a certain value is a very important factor for human body protection against electric shock in TN-C-S system. The concept of loop impedance($Z_s$) is recently introduced to the domestic, the study about external loop impedance is yet insufficient. However, the study about the reference impedance as specified by the IEC 60725 standard to improve the quality and reliability of the power supply is being made. In this paper, reference value of external loop impedance($Z_e$) to meet domestic environment will be proposed by the nationwide measurement and statistical analysis.

• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.108-114
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• 2019

Unattended Train operation(UTO) requires higher safety target than other systems, since all train operations are automatic. The system provider to deliver without accident or failure, and the operator to transport passengers without accident by putting all trains supplied, including them, into service. Safety rates without such failures can be represented as indicators of RAMS, among which availability is continuously controllable to achieve the target, with a clear target. Availability is often required by the licensee from the initial stage of the project to demonstrate that the request for proposal (RFP) is usually specified and to maintain separate availability targets at the operational stage. In particular, unlike unmanned operation light rail in complex systems, simple formulas are often presented to facilitate verification at each stage. This paper presents this method of usability calculation in an integrated manner at all levels and analyzes the existing usability values to ensure reliability of the availability formula for integrated use in unmanned light rail systems.