• Nuclear Engineering and Technology
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• v.50 no.5
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• pp.627-638
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• 2018

This article describes an integrated Level 1-Level 2 probabilistic risk assessment (PRA) methodology to evaluate the radiological risk during postulated accident scenarios initiated during the decommissioning phase of a typical Mark I containment boiling water reactor. The fuel damage scenarios include those initiated while the reactor is permanently shut down, defueled, and the spent fuel is located into the spent fuel storage pool. This article focuses on the integrated Level 1-Level 2 PRA aspects of the analysis, from the beginning of the accident to the radiological release into the environment. The integrated Level 1-Level 2 decommissioning PRA uses event trees and fault trees that assess the accident progression until and after fuel damage. Detailed deterministic severe accident analyses are performed to support the fault tree/event tree development and to provide source term information for the various pieces of the Level 1-Level 2 model. Source terms information is collected from accidents occurring in both the reactor pressure vessel and the spent fuel pool, including simultaneous accidents. The Level 1-Level 2 PRA model evaluates the temporal and physical changes in plant conditions including consideration of major uncertainties. The goal of this article is to provide a methodology framework to perform a decommissioning Probabilistic Risk Assessment (PRA), and an application to a real case study is provided to show the use of the methodology. Results will be derived from the integrated Level 1-Level 2 decommissioning PSA event tree in terms of fuel damage frequency, large release frequency, and large early release frequency, including uncertainties.

• Korean Journal of Construction Engineering and Management
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• v.5 no.2 s.18
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• pp.136-143
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• 2004

This study presents a risk management methodology using fuzzy theory for early construction stage and is focused on risk identification and risk analysis. This study identifies various risk factors associated with activities clearly construction stage, then establishes the Risk Breakdown Structure(RBS) by classifying the risks into the three groups; Common risks, risks for Earth works, and risks for Foundation works. The risk analysis method presented in this study is based on the RBS that has two levels such as upper level and lower level. The risk exposure of lower level risk factors is assessed by fuzzy inference. The weight of risks is estimated by fuzzy measure. Then, the estimated risk exposures and weights are aggregated to assess the risk exposure of upper level risks by Choquet fuzzy integral. The risk exposure of upper level risks determine the priority of risk factors in view of risk management. This study performs case study to validate the proposed method. The result of case study shows that the methodology suggested in this thesis would be utilized well in evaluating risk exposure.

• Geomechanics and Engineering
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• v.28 no.6
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• pp.573-584
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• 2022

Water inrush may occur during seaside urban tunnel excavation. Various factors affect the water inrush, and the water inrush mechanism is complex. In this study, nine evaluation indices having potential effects on water inrush were analysed. Specifically, the geographic and geomorphic conditions, unfavourable geology, distance from the tunnel to sea, strength of the surrounding rock, groundwater level, tidal action, cyclical footage, grouting pressure, and grouting reinforced region were analysed. Furthermore, a two-step interval risk assessment method for water inrush management during seaside urban tunnel excavation was developed by a multi-index system and interval risk assessment comprised of an interval analytic hierarchy process, fuzzy comprehensive evaluation, and relative superiority analysis. The novel assessment method was applied to the Haicang Tunnel successfully. A preliminary interval risk assessment method for water inrush was performed based on engineering geological conditions. As a result, the risk level fell into a risk level IV, which represents a section with high risk. Subsequently, a secondary interval risk assessment method was performed based on engineering geological conditions and construction conditions. The risk level of water inrush is reduced to a risk level II. The results agreed with the current tunnel situation, which verified the reliability of this approach.

• Proceedings of the Korea Environmental Mutagen Society Conference
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• 2004.11a
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• pp.166-166
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• 2004

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.3244-3251
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• 2012

In the construction and operation of large marine structure, hazard risk analysis is one of important factors. Therefore, this paper investigates the hazard risk indexes and evaluates the risk level in the construction and operation of SFT on the basis of expert survey and Fuzzy analytic hierarchy process. Hazard risk is divided into natural hazard risk (earthquake, typhoon, tsunami, and ice collision) and human factor hazard risk (fire, explosion, traffic accident, ship or submarine collision). Also, the influence of hazard risk indexes on SFT was evaluated in tunnel tube, supporting system, ventilation tower, foundation, and connection part. As the hazard risk level of SFT is compared with those of bridge, underwater tunnel, and immersed tunnel, the intrinsic risk level of SFT was evaluated. Tsunami and earthquake had higher risk level in natural hazard risk, and the risk levels of fire and explosion were higher in human factor hazard risk. Hazard risk level of SFT was 1.4 times higher than immersed tunnel, and 3.2 times higher than bridge.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.2
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• pp.158-170
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• 2009

This paper considers how the optimal export level is influenced by export risk, the degree of risk-averseness for exporting firms, and those firms' cost structure. In addition, export insurance is incorporated into some simple theoretical model to analyze the optimal export level. This paper applies genetic algorithm simulation to show that the exporting firms'risk-averseness do not affect the optimal export decision while export risk and cost function characteristic have relatively more significant effects on the optimal export level. Finally, our findings suggest that the most influential factor for the optimal export levels seems to be the monopoly power of exporting firms.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.52-62
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• 2022

In the SORA methodology developed for the operational risk assessment of a specific category of operation of a UAS, the ground and the air risk levels are determined, and a SAIL indicating the level of assurance and integrity for the corresponding risk is assigned, and accordingly, the operational safety level for the proposed operation. Objectives should be demonstrated at an appropriate level of robustness. Because of the nature of the specific category of operation, people on the ground are the first risk subjects to be considered. The resulting ground risk class plays an important role in the allocation of SAIL. In this paper, the impact on SAIL and OSO according to the final risk level and the reduction of the level through the determination of the ground risk level and the application of mitigation measures among risk assessments for specific categories of UAV operation was investigated.

• The Korean Journal of Food & Health Convergence
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• v.7 no.1
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• pp.17-26
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• 2021

The purpose of this study was to develop strategies and policies for smoking prevention that are tailored to the characteristics of different groups of smokers. The structured survey was conducted with regular smokers. The results were as follows: It has been demonstrated that Risk Perception Attitude framework can be used as a major research framework to predict behavioral changes related to the prevention of smoking. The smokers were divided into four attitude groups based on perceived risks and self-efficacy: indifference, proactive, avoidance, and responsive. The smoker groups showed significant differences in information seeking, information avoidance, prevention behavior and addiction degree. Especially, the difference in prevention behavior depended on the self-efficacy when the perceived risk level was high. Information avoidance was the lowest when the perceived risk level was high and the self-efficacy was low. Information seeking was lowest when the perceived risk level was low. When the level of self-efficacy was high, if the perceived risk level was high, prevention behavior was actively performed. Therefore, the self-efficacy was related to preventive behavior, and the perceived low-risk played a role in hindering information seeking. Smoking prevention strategies are important to raise awareness of the risk of smoking and to improve the positive willingness of smokers to quit smoking through self-efficacy.

• Journal of Nutrition and Health
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• v.37 no.5
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• pp.385-393
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• 2004

This study examined the relations of educational level and life-style behaviors to the obesity. A total of 507 male adults aged 30 - 50 years completed the self-reported questionnaires. Educational level was used for measuring socioeconomic status. Activity at work, leisure-time activity and TV watching were measured for life-style behaviors related to physical activity, and some demographic and family history of disease as well. Subjects were categorized as obese when BMI was equal to or over 25kg/$m^2$, in which 19.7％ resulted obesity. Using multivariate logistic regression, the association between the measured factors and obesity was assessed. The odds ratios (OR) for risk of obesity did not differ with either age or monthly income. Subjects who completed high school (OR = 0.36; 95％ CI = 0.20 - 0.66) or university (OR = 0.34; 95％ CI = 0.16 - 0.71) had lower risk of obesity than those with education below middle school. Those with moderate activity level at work (OR = 0.41; 95％ CI = 0.24 - 0.72) showed lower risk of obesity than in inactive ones. The subjects watching TV more than 3.5 hr/day presented higher risk of obesity (OR = 2.46; 95％ CI = 1.28 - 4.74), compared with those watching TV less than 1.5 hr/day. The higher risk of obesity observed in high level of leisure time activity than in low one was considered due to that physical activity at work and leisure-time might counteract each other. Educational level and activity at work or leisure-time activity or TV watching were jointed and categorized, and then OR for obesity was estimated. The extent of obesity risk at a given level of each work activity or leisure-time activity or TV watching was different depending the educational level, which was significantly high when educational level was below middle school. Educational difference had no effect on activity level at work. However, higher educational attainment increased the leisure activity and reduced TV watching (p＜0.05), indicating that low education tended to contribute to more sedentary life-style. The findings of this study is concluded that low education was related to obesity in adult males, and its relation can partly be explained through acquiring inactive life-style behaviors. Individuals with low education might be more susceptible to the risk factors of obesity.

• Journal of Korean Society for Quality Management
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• v.41 no.3
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• pp.465-474
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• 2013

Purpose: To provide a variety of stable military supplies, risk should be avoided or removed. This paper aims to provide an objective method of risk assesment for risk matrix to evaluate risk level. Methods: According to previous results of risk assesment through risk matrix, some parameters and probability density functions, which include characteristics of military supplies, are selected and Risk matrix is modelled based on that. Results: Results show that a proposed method can evaluate objectively risk level through the stochastic modelling and provide well-balanced risk assessments by categorizing into 3 levels such as high, middle and low level risk. Conclusion: A current risk assessment method includes substantial subjectivity of risk assessment and as a problem about military supplies comes up, we can not show any appropriate evidences for decision of risk assessment. We propose an objective scheme employing stochastic modelling with parameters and probability density functions.