• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.569-576
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• 2017

The electromagnetic valve of pneumatic doors of EMUs has a high failure rate due to air leakage because it supplies air on and off to operate the doors repeatedly. The electromagnetic valve is a very important safety component for which a very high reliability is required because failure makes it impossible to operate the passenger cars. However, domestic urban railway operators maintain electronic valves of the EMU door under a fixed cycle with a spare period according to the full overhaul cycle of the EMU. An improvement of the current maintenance cycle was suggested based on the reliability function and mission reliability. Using the statistical program MINITAB for the operational data of EMU line 6, we analyzed the characteristics of the fault distribution and derived the shape and scale parameters of the reliability function. If we limit the specific reliability probability to under a certain failure rate and calculate its statistical parameters, we can calculate the allowable inspection period with mission reliability. Through this study, we suggested a maintenance period based on RCM (reliability centered-maintenance) to improve the reliability of electromagnetic valves from 68% to 95%.

• Journal of Distribution Science
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• v.17 no.5
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• pp.5-17
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• 2019

Purpose - This study aims to exploratorily analyze relationship among pressure on business failure, social safety net perception, and entrepreneurial intention targeting potential business founders - pre-entrepreneurs and re-entrepreneurs. Research design, data, and methodology - Out of 450 collected surveys, 386 were used for analysis. Among these, 216 were from pre-entrepreneurs and 170 were from re-entrepreneurs. Frequency analysis, reliability and validity analysis, and regression analysis were performed. Results - In analysis of pre-entrepreneur and re-entrepreneur's pressure on business failure and social safety net perception, objective environment perception - a subfactor of social safety net perception - had statistically significant difference between the two potential entrepreneur groups. Conclusions - We categorized potential entrepreneurs into pre-entrepreneurs and re-entrepreneurs. Also, the current study suggests importance of social safety net to vitalize food service business startup by validifying its mediating effect between pressure on business failure and attitude towards restaurant business establishment. This research also established groundwork for future studies on ways to improve entrepreneurial intention or startup business sustainability by deducing social safety net perception difference between pre-entrepreneurs and re-entrepreneurs. This study was able to analyze relationship between those two groups in terms of entrepreneurial intention and startup business sustainability.

• Human Ecology Research
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• v.53 no.6
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• pp.655-665
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• 2015

This study classified respondents by food-lifestyle and investigated differences in diet-related attitudes and demographic variables among food-lifestyle groups. Diet-related attitudes consisted of variables such as interest in diet, trial number of diet, diet period, weight loss, diet motivation, verification of products approved by the Ministry of Food and Drug Safety, verification of manufacturer's reliability, examination of damage cases and side effects, and awareness of consumer protection law. This study administered a questionnaire survey to adults between the ages of 20 and 39 who lived in Daegu and Uijeongbu from November 17th to December 14th 2014. Data collected from 293 respondents were analyzed using descriptive statistics, factor analyses, cluster analysis, analysis of variance (ANOVA) and chi-square tests. Four clusters (passive eating habit group, active eating habit group, convenience oriented group, and taste and health oriented group) were developed according to four factors of food-lifestyle (health-conscious, popularity-seeking, taste-seeking, convenience-seeking). The results of the ANOVA and chi-square tests indicated significant differences in interest in diet, awareness of consumer protection law, verification of products approved by the Ministry of Food and Drug Safety, verification of manufacturer's reliability, examination of damage cases and side effects, gender, education levels and household monthly income levels among food-lifestyle groups.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.2
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• pp.34-39
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• 2014

Airworthiness authorities specify the technical standards of airworthiness that propose minimum requirement of the commercial transport category and apply the rules in the certification process to ensure the safety of the aircraft. The Federal Aviation Administration and other national airworthiness authorities define the fatal accident risk levels for the safety assessment of the aircraft system and establish standard procedures to apply both qualitative and quantitative analysis techniques. However, an accident or incident may occur by the combination of various factors, although the aircraft is designed in accordance with the strict standards and approval by the Airworthiness Authorities. There are some key factors, such as human error, unpredictable complex system failures, degradation of the components reliability, improper maintenance task and intervals. Risk can be reduced by reflecting aircraft operational experience with similar types of aircraft in the process of aircraft development and safety assessment. Result of the root cause analysis for the Airbus A300-600 incident in which the aircraft engine reverser was deployed in the air have been introduced to reflect the design of system and related components. Also, this paper suggests to create a big-database in order to provide a feed-back to the FAR Part 25 transport category design and safety assessment of the operational experience.

• Tunnel and Underground Space
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• v.31 no.5
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• pp.360-373
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• 2021

Many sources of uncertainty exist in geotechnical analysis ranging from the material parameters to the sampling and testing techniques. The conventional deterministic stability analysis of a plane failure in rock slope produce a safety factor but not a probability of failure or reliability index. In the conventional slope stability analysis by evaluating the ground uncertainty as an overall safety factor, it is difficult to evaluate the stability of the realistic rock slope in detail. This paper reviews some established probabilistic analysis techniques, such as the MCS, FOSM, PEM, Taylor Series as applied to plane failure of rock slopes in detail. While the Monte - Carlo methods leads to the most accurate calculation of the probability of safety, this method is too time consuming. Therefore, the simplified probability methods could be alternatives to the MCS. In this study, using these simple probability methods, the failure probability estimation of a plane failure in rock slope is presented.

• Journal of Web Engineering
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• v.19 no.2
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• pp.139-166
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• 2020

The functions, capabilities, and effects produced by the application services of cyber physical systems (CPS) are usually consumed by users performing their daily activities in a variety of environmental conditions. Thus, it is critical to ensure that those systems neither interfere with human activities nor harm the users involved. In this paper, we propose a framework for testing and verifying the safety and reliability of CPS services from the perspectives of CPS environments and users. The framework provides an environmentaware testing method by which the efficiency of testing CPS services can be improved by prioritizing CPS environments and by applying machinelearning techniques. The framework also includes a metric by which we can automate the test of the most effective services that deliver effects from physical devices to users. Additionally, the framework provides a computational model that assesses mental workloads to test whether a CPS service can cause cognitive depletion or contention problems for users. We conducted a series of experiments to show the effectiveness of the proposed approaches for ensuring the safety and reliability of CPS application services during the development and operation phases.

• Journal of the Korean Institute of Gas
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• v.15 no.6
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• pp.44-50
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• 2011

This study is to investigate the role of the private institution which has the essential resources to solve an urgent problem for the decreasing and prevention of the industrial accident and to suggest the reinforcing model of reliability, expertise, competency of private institution. And the result of this study will be judged to present a milestone to establish a role essentially for preventing industrial accident among government agencies, public institutions and private institutions. It will also help the vitalization of an industrial safety and health market and can be utilized for the revision of Industrial Safety and Health Law and a state affairs plan.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2008.09a
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• pp.148-151
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• 2008

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2008.09b
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• pp.148-151
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• 2008

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.34-44
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• 2012

Many kind of sensors in the dam produce a lot of data associated with the maintenance and safety of the dam. So it is important to measure the reliability of the sensor (or measured data). In this paper, the new method using modified coherence function is proposed to measure the reliability of the sensor remotely. To verify feasibility of proposed method in the field, proposed method was applied to data of piezometer and earth pressure cell. Through field applications, the potential of the proposed method was verified.