• Journal of Korean Society of Transportation
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• v.27 no.2
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• pp.95-105
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• 2009

Traffic accidents on highways are likely to happen when there is an imbalance in the complex relationships among key elements such as road geometries, driver related factors, and mechanical performances. The Demand-Effort Model (DEM), which evaluates highway safety, can be explained by the imbalance, which occurs when the level of demand of the driver's attention to the road environment exceeds that of the response from the driver. This study suggests a new model that improves the reliability of the current DEM through the reinterpretation on the physiological signals with the help of the Neural Network Model (NNM). The data were collected from 149 subjects, who drove a test vehicle on the Yongdong, Honam, and Seohaean Expressways in Korea. Three important results could be drawn from the recursive tests as follows; (1) Only 5 out of 10 parameters on the physiological signals which are currently used were proven to be meaningful through the Normality Test, Cluster Analysis, and Mann-Whitney Analysis. (2) The revised DEM, which internally uses the NNM, showed more reliable results than existing DEM. Group 1, which is based on the new DEM showed 80.0% of accuracy in measuring the level of driver's efforts, however, that of Group 2 based on the current DEM was 74.3%. (3) Field tests on the Honam Expressway showed lower 'type II error' with the new DEM (40.5%) than the old DEM (58.8%). The DEM is designed as a quick and easy way to determine highway safety prior to the minute road safety audit (RSA) by a professional audit team. Then a new DEM, which is based on the NNM, needs to be considered since it showed higher reliability and lower error.

• Fire Science and Engineering
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• v.30 no.4
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• pp.103-110
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• 2016

While the demand for the gas system fire extinguishers increases every year, there are insufficient safety measures for assessing the extinguishing performance, such as system safety and reliability in the preparation of increasing demand, which has emerged as a social problem. One of the most critical causes of accidents occurring with the gas extinguishing system is pressure leakage from the extinguishing agent storage container. This is considered to be one of the critical factors on which the success of fire suppression depends. In this study, its safety measure was studied, Because it was deemed urgently necessary. The newly developed pressure leakage monitoring system is a system monitoring storage condition, pressure, leakage and discharge of the storage container related to agent concentration, which is one of the critical factors for fire suppression. This was developed to be applicable to the $CO_2$ and HFC-23 systems. Therefore, for structural safety analysis, the safety performance was verified by the fluid structure coupling analysis of the safety problems that may occur when the pressure leakage monitoring system is applied to the gas fire extinguisher. For analysis programs, the FloEFD program from Mentor Graphics was used for computational fluid dynamics analysis and ABAQUS from Dassault Systems was used for structural analysis. From the result of numerical analysis, the structure of $CO_2$ did not develop plastic deformation and its safety was verified. However, plastic deformation and deviation issue occurred with the HFC-23 monitoring system and therefore verified the structural safety of pressure leakage monitoring system by data obtained from redesigning and adjusting the condition of numerical interpretation three times.

• Steel and Composite Structures
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• v.42 no.5
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• pp.633-647
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• 2022

This paper presents the results from reliability analyses of the current Eurocode 4 (EN 1994-1-1) and AISC 360-16 design models for predicting the resistance of headed stud shear connectors within profiled steel sheeting, when the ribs are oriented transverse to the supporting beam. For comparison purposes, the performance of the alternative "Luxembourg" and "Stuttgart" model were also considered. From an initial database of 611 push-out tests, 269 cases were included in the study, which ensured that the results were valid over a wide range of geometrical and material properties. It was found that the current EN 1994-1-1 design rules deliver a corrected partial safety factor γ_M^* of around 2.0, which is significantly higher than the target value 1.25. Moreover, 179 tests fell within the domain of the concrete-related failure design equation. Notwithstanding this, the EN 1994-1-1 equations provide satisfactory results for re-entrant profiled sheeting. The AISC 360-16 design equation for steel failure covers 263 of the tests in the database and delivers 𝛾_M^*≈2.0. Conversely, whilst the alternative "Stuttgart" model provides an improvement over the current codes, only a corrected partial safety factor of 𝛾_M^*=1.47 is achieved. Finally, the alternative "Luxembourg" design model was found to deliver the required target value, with a corrected partial safety factor 𝛾_M^* between 1.21 and 1.28. Given the fact that the Luxembourg design model is the only model that achieved the target values required by EN 1990, it is recommended as a potential candidate for inclusion within the second generation of Eurocodes.

• Journal of the Korean Society of Safety
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• v.25 no.3
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• pp.118-122
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• 2010

In order to provide the necessary operation flexibility during the Nuclear power operation, the extension of existing allowed outage time(AOT) is needed. The extension of AOT affects the Nuclear power plant safety. The validity of changed technical specification requirements should be proved by the safety assessments. In this paper, we evaluated the extension of emergency diesel generator AOT for a single inoperable emergency diesel generator(EDG) from 3days to 7days, 10days and 14days. Finally, the AOT extension contributes the NPP performances through decreasing the unexpected plant trips, reinforcing maintenance and avoiding risks due to unnecessary operation mode changes when the NPP is under the surveillance tests or maintenance.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.80-85
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• 2010

The study of the safety perceptions between two groups, trained and untrained student pilots were compared as pre-studies of that how the safety perceptions of the flight instructors affect that of the student pilots. As a results, the factors of the communication and the safety procedures shows higher values on the one-year trained group than the other because the trained students get used to the safety procedures which are necessary to the practical training. In reliability for the flight instructor, the factors of two groups show the high tendency without regard to groups. Despite of the lack of the specific research, the result implies that the student pilots are influenced by the safety perceptions of the flight instructors. In addition, the factors of the accident report were investigated as that the trained group has lower mean, however the factors of the receiving penalties of the trained group were higher than the other. These results imply that the trained group feels concern for the penalties and the punishments by reporting the accidents in spite of amounts of the training.

• Journal of the Korean Society of Safety
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• v.28 no.5
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• pp.5-9
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• 2013

Recently, eco-friendly sources of energy by fuel cells that use hydrogen as an energy source has emerged as the next generation of energy to solve the problem of environmental issues and exhaustion of energy. A solid oxide fuel cell(SOFC) classified based on the type of ion transfer mediator electrolyte has actively being researched. However, the reliability according to the thermal cycle is low during the operation of the fuel cell, and deformation problem comes from the difference in thermal expansion coefficient between the electrode material, the components made of ceramic material is also brittle, which means disadvantages in terms of the strength. Therefore, in this study, considering the states of the manufacturing and operating of SOFC single cells, the stress analyses in the each of the interfacial layer between the anode, electrolyte and the cathode were performed to get the basic data for reliability assessment of SOFC. The obtained results show that von Mises stress according to the thickness direction on operating state occurred maximum stress value in the electrolyte layer. And also the stresses inside the active area on a distance of 1 ${\mu}m$ from the electrode interface were estimated. Futhermore the evaluation was done for the variation of the stress according to the stage of the operation divided into three stages of manufacturing, stack, and operating.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.121-128
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• 2005

This study focuses on evaluating the reliability index of a deck of RC slab having chloride contamination and studying the relation of grades of rebar corrosion and the reliability index of a bridge deck For this purpose, first, the failure probability related to flexural strength was calculated using a model for deterioration, which contains the application of deicing salts that usually causes significant long-term deterioration and reduction in the structural safety for strength of structure. And also, according to the depth of covering, the chloride contents depending on time due to depths of RC slab deck, the appearance time for initial corrosion of rebar and the occurrence time for split of covering were investigated using a MCS method.

• Geomechanics and Engineering
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• v.22 no.3
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• pp.207-217
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• 2020

Slope reliability analysis and risk assessment for spatially variable soils under rainfall infiltration are important subjects but they have not been well addressed. This lack of study may in part be due to the multiple and diverse evaluation indexes and the low computational efficiency of Monte-Carlo simulations. To remedy this, this paper proposes a highly efficient computational method for investigating random field problems for slopes. First, the probability density evolution method (PDEM) is introduced. This method has high computational efficiency and does not need the tens of thousands of numerical simulation samples required by other methods. Second, the influence of rainfall on slope reliability is investigated, where the reliability is calculated from based on the safety factor curves during the rainfall. Finally, the uncertainty of the sliding mass for the slope random field problem is analyzed. Slope failure consequences are considered to be directly correlated with the sliding mass. Calculations showed that the mass that slides is smaller than the potential sliding mass (shallow surface sliding in rainfall). Sliding mass-based risk assessment is both needed and feasible for engineered slope design. The efficient PDEM is recommended for problems requiring lengthy calculations such as random field problems coupled with rainfall infiltration.

• Journal of the Korean Geotechnical Society
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• v.29 no.9
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• pp.71-80
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• 2013

This work studies the reliability analysis of a slope that considers multiple failure modes. The analysis consists of two parts. First, significant failure modes that contribute most to system reliability are determined. The so-called barrier method proposed by Der Kiureghian and Dakessian to identify significant failure modes successively is employed. Second, the failure probability for the slope is estimated on the basis of the identified significant failure modes and corresponding design points. For reliability problems entailing multiple design points, failure probability can be estimated by the multi-point first-order reliability method (FORM), Ditlevsen's bounds method, and Monte Carlo simulation. In this paper, a comparative study between these methods has been made through example problems. Analysis results showed that while a soil slope may have a large number of potential slip surfaces, its system failure probability is usually governed by a few significant slip surfaces. Therefore, the most important step in the system reliability analysis for a soil slope is to identify all the significant failure modes in an efficient way.

• Journal of the Korean Institute of Gas
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• v.7 no.2 s.19
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• pp.42-47
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• 2003

To prevent major accident from toxic gas release, explosion, or fire in chemical processes, it needs dynamic control of human error with mechanical failure. Although most of major accidents occur with a coupling of human error and mechanical failure, numbers of researches have studied human error and mechanical reliability independently, but no where cross each other, to reduce the risk in the process. This work focuses on the coincidence of human error and mechanical failure for management of human error, and on some important performance shaping factors to propose a method for improving safety effectively of the process industries.