• Journal of the Computational Structural Engineering Institute of Korea
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• 제34권5호
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• pp.319-325
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• 2021

The 2011 East Japan Earthquake caused accidents at a number of nuclear power plants in Fukushima, highlighting the need for a study on the seismic safety of multiple NPP (Nuclear Power Plant) units. In the case of nuclear power plants built on a site that shows a similar seismic response, there is at least a correlation between the seismic damage of structures, systems, and components (SSCs) of nuclear power plants. In this study, a probabilistic seismic safety assessment was performed for the loss of essential power events of twin units. To derive an appropriate seismic damage correlation coefficient, a probabilistic seismic response analysis was performed. Using the external event mensuration system program, we analyzed the seismic fragility and seismic risk by composing a failure tree of multiple loss of essential power events. Additionally, a comparative analysis was performed considering the seismic damage correlation between SSCs as completely independent and completely dependent.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1571-1584
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• 2023

In this study, a numerical analysis was performed as part of an international joint research project to reproduce a real cable tray fire that occurred in the heater bay area of the turbine building of a nuclear power plant. A sensitivity analysis was performed on various input parameters to derive results consistent with the sprinkler activation time obtained from the fire event analysis. For all sensitive parameters, the normalized sprinkler activation time correlated well with the power function of the normalized sprinkler height. A correlation equation was developed to identify the sprinkler activation time at any location when determining the slope or fire growth rate under the conditions assuming a linear or t-squared heat release rate (HRR) time curve. Various cable fire growth assumptions were used to determine which assumption was better to provide the prediction coincident with the information given from the fire event analysis in terms of the sprinkler activation time and total energy generated from cables damaged by fire. In the comprehensive analysis of all the sensitive parameters, the standard deviation of the input parameters increased as the sprinkler height decreased. Within the range of the sensitivity parameter values given in this study, when considering all sprinkler heights, the standard deviation of the cable model change was the largest and that of the overhang position change was the smallest.

• Journal of the Earthquake Engineering Society of Korea
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• 제23권2호
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• pp.101-108
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• 2019

The seismic safety of nuclear power plants has always been emphasized by the effects of accidents. In general, the seismic safety evaluation of nuclear power plants carries out a seismic probabilistic safety assessment. The current probabilistic safety assessment assumes that damage to the structure, system, and components (SSCs) occurs independently to each other or perfect dependently to each other. In case of earthquake events, the failure event occurs with the correlation due to the correlation between the seismic response of the SSCs and the seismic performance of the SSCs. In this study, the EEMS (External Event Mensuration System) code is developed which can perform the seismic probabilistic safety assessment considering correlation. The developed code is verified by comparing with the multiplier n, which is for calculating the joint probability of failure, which is proposed by Mankamo. It is analyzed the changes in seismic fragility curves and seismic risks with correlation. As a result, it was confirmed that the seismic fragility curves and seismic risk change according to the failure correlation coefficient. This means that it is important to select an appropriate failure correlation coefficient in order to perform a seismic probabilistic safety assessment. And also, it was confirmed that carrying out the seismic probabilistic safety assessment in consideration of the seismic correlation provides more realistic results, rather than providing conservative or non-conservative results comparing with that damage to the SSCs occurs independently.

• Journal of the Korean Institute of Landscape Architecture
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• 제31권2호
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• pp.28-35
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• 2003

This study was conducted to identify the characteristics of social carrying capacity at mega-events, especially the 2000 Kwangju Biennale in Korea. In particular, this paper has proposed some management policies for mega events taking into account the relations between social carrying capacity, satisfaction and crowding. The research method was to look into the general characteristics and distributive forms of the location, and then to confirm the possibility of sampling the factors involved in satisfaction degree; last, A factor analysis for causal analysis of perceived crowding was performed. The study needed correlation analysis in order to compare expected crowding and perceived crowding, and performed regression to examine the causality of perceived crowding and satisfaction. The research results were as follows: the correlation of expected crowding, perceived crowding, and the total satisfaction was very low or meaningless. The relation between satisfaction and elements for factor analysis such as convenient facilities and value experience showed partial meaningfulness. The factors of convenient facilities, entrance fee, parking lot use, toilet convenience, and exhibit room use had meaningful results; on the other hand, the factors of value experience showed a meaningful result in the guide service of an event place. In conclusion when those holding an event make a basic project, they should consider management measures for convenience of facilities, proper education for guide service, and systematic guidance. Also, as a method for perceived crowding lower than expected crowding, the study has proposed that it is possible to lower expected crowding by providing appropriate information on the number of tourists expected on the weekends and weekdays. Future research should control variables such as personal characteristics, seasons proper for vacation and holidays, and carefully consider their investigation and design. Moreover, it is necessary to study variables involved in expected crowding of more various space-intensive sightseeing places (mesa-events).

• KSCE Journal of Civil and Environmental Engineering Research
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• 제31권3B호
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• pp.265-276
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• 2011

Precipitation data and groundwater level data were collected for Korean peninsular and Jeju island. The relationship between precipitation and groundwater level and the correlation between the moving average of precipitation and goundwater level were analyzed. Critical infiltration, which is the spatially averaged maximum daily infiltration depth over interested region, is considered when the precipitation data was modified for moving average process and correlation between the moving average of modified precipitation and groundwater level. High correlation regions, which have greater than 0.6 correlation coefficients, were selected after the analysis with ciritical infiltration. Twenty-six regions were selected for high correlation regions. If we divide the regions by administrative district, there are nine regions for Gyungsang-Do, five regions for Chunchung-Do, four regions for Gyunggi-Do and Gangwon-Do, three regions for Jolla-Do, and one region for Jeju island. The groundwater level data for high correlation regions shows obvious response after precipitation event and there are few cases with abrupt change in groundwater level without precipitation-related event.

• Earthquakes and Structures
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• 제11권6호
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• pp.1143-1164
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• 2016

Time Delay of Arrival (TDOA) estimation methods based on correlation function analysis play an important role in the micro-seismic event monitoring. It makes full use of the similarity in the recorded signals that are from the same source. However, those methods are subjected to the noise effect, particularly when the global similarity of the signals is low. This paper proposes a new approach for micro-seismic monitoring based on cross wavelet transform. The cross wavelet transform is utilized to analyse the measured signals under micro-seismic events, and the cross wavelet power spectrum is used to measure the similarity of two signals in a multi-scale dimension and subsequently identify TDOA. The offset time instant associated with the maximum cross wavelet transform spectrum power is identified as TDOA, and then the location of micro-seismic event can be identified. Individual and statistical identification tests are performed with measurement data from an in-field mine. Experimental studies demonstrate that the proposed approach significantly improves the robustness and accuracy of micro-seismic source locating in mines compared to several existing methods, such as the cross-correlation, multi-correlation, STA/LTA and Kurtosis methods.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.967-973
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• 2021

In 2011, an earthquake and subsequent tsunami hit the Fukushima Daiichi Nuclear Power Plant, causing simultaneous accidents in several reactors. This accident shows us that if there are several reactors on site, the seismic risk to multiple units is important to consider, in addition to that to single units in isolation. When a seismic event occurs, a seismic-failure correlation exists between the nuclear power plant's structures, systems, and components (SSCs) due to their seismic-response and seismic-capacity correlations. Therefore, it is necessary to evaluate the multi-unit seismic risk by considering the SSCs' seismic-failure-correlation effect. In this study, a methodology is proposed to obtain the seismic-response-correlation coefficient between SSCs to calculate the risk to multi-unit facilities. This coefficient is calculated from a probabilistic multi-unit seismic-response analysis. The seismic-response and seismic-failure-correlation coefficients of the emergency diesel generators installed within the units are successfully derived via the proposed method. In addition, the distribution of the seismic-response-correlation coefficient was observed as a function of the distance between SSCs of various dynamic characteristics. It is demonstrated that the proposed methodology can reasonably derive the seismic-response-correlation coefficient between SSCs, which is the input data for multi-unit seismic probabilistic safety assessment.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제16권12호
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• pp.8791-8799
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• 2015

In this paper, One-way car-sharing System represents the verification system consider events in revenue effects. Revenue which the time and distance represented the graph, compare one-way vehicle relocate car-sharing system which proven in existing international papers with one-way vehicle relocate car-sharing system consider the event currently in the Korea. Especially, The maximum profit according to the distance and time were assessed through multiple linear regression analysis, and there are probable maximum loss allow for the maximum loss. The company suggested using the event as a discount coupon to customers through various marketing strategies, and then focused on increasing customer demand. So, Correlation analysis to determine the maximum revenue of the actual travel distance and time were carried out through Non-linear Regression.

• Convergence Security Journal
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• 제6권4호
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• pp.67-73
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• 2006

The method which research a standardization from real time cyber threat is finding the suspicious indication above the attack against cyber space include internet worm, virus and hacking using analysis the event of each security system through correlation with the critical point, and draft a general standardization plan through statistical analysis of this evaluation result. It means that becomes the basis which constructs the effective cyber attack response system. Especially at the time of security accident occurrence, It overcomes the problem of existing security system through a definition of the event of security system and traffic volume and a concretize of database input method, and propose the standardization plan which is the cornerstone real time response and early warning system. a general standardization plan of this paper summarizes that put out of threat index, threat rating through adding this index and the package of early warning process, output a basis of cyber threat index calculation.

• Journal of the Ergonomics Society of Korea
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• 제31권6호
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• pp.785-791
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• 2012

Objective: The aim of this study was to investigate the correlation between 3D visual fatigue and physiological measures by canonical correlation analysis enabling to categorical correlation. Background: Few studies have been conducted to investigate the physiological mechanism underlying the visual fatigue caused by processing 3D information which may make the cognitive mechanism overloaded. However, even the previous studies lack validation in terms of the correlation between physiological variables and the visual fatigue. Method: 9 Female and 6 male subjects with a mean age of $22.53{\pm}2.55$ voluntarily participated in this experiment. All participants were asked to report how they felt about their health sate at after viewing 3D. In addition, Low & Hybrid measurement test(Event Related Potential, Steady-state Visual Evoked Potential) and for evaluating cognitive fatigue before and after viewing 3D were performed. The physiological signal were measured with subjective fatigue evaluation before and after in watching the 3D content. For this study suggesting categorical correlation, all measures were categorized into three sets such as included Visual Fatigue set(response time, subjective evaluation), Autonomic Nervous System set(PPG frequency, PPG amplitude, HF/LF ratio), Central Nervous System set(ERP amplitude P4, O1, O2, ERP latency P4, O1, O2, SSVEP S/N ratio P4, O1, O2). Then the correlation of three variables sets, canonical correlation analysis was conducted. Results: The results showed a significant correlation between visual fatigue and physiological measures. However, different variables of visual fatigue were highly correlated to respective HF/LF ratio and to ERP latency(O2). Conclusion: Response time was highly correlated to ERP latency(O2) while the subjective evaluation was to HF/LF ratio. Application: This study may provide the most significant variables for the quantitative evaluation of visual fatigue using HF/LF ratio and ERP latency based human performance and subjective fatigue.