• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2902-2909
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• 2011

Regional torrential rains in summer this year due to abnormal climate changes compared to last year, have been frequent. Since Typhoon Rusa and Typhoon Maemi resulted in major damage to railroad facilities in 2002 and 2003 consecutively, problems with abnormal climate changes became a global problem including railroad and floods and droughts around the globe, heavy snow and winter warming have been repeated until now. Serious problem of radiation leakage in Fukushima nuclear power plant by the Tsunami due to 9.0-scale earthquake, this year in March, in northeastern Japan happened, and has given an impact on the life of Japanese citizens and industries and has also influenced on Korean. This shows how important to secure and to protect major national facilities including railroad structures to natural disasters such as earthquake. Therefore, we will briefly discuss about technologies for securing and protecting railroad structures to earthquakes, floods and other natural disasters.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.3
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• pp.311-318
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• 2011

On March 11, 2011, an 9.0-magnitude earthquake occurred near the northeastem coast Japanese. It was the largest earthquake that hit Japan since the beginning of modern seismometry. The earthquake occurred 179km east of the Sendai, Miyagi Prefecture, leaving about 27,000 of people confirmed dead, injured or missing due to the earthquake and tsunami. In this study, crustal Deformation in Mizusawa, Tsukuba and Usuda station were calculated based on GPS data in IGS station of Japan. The observation data were processed by precise point positioning and relative-positioning method using on-line GPS data processing services and a high precision scientific GPS/GLONASS data processing software. The coseismic displacements in IGS stations before and after the earthquake were analyzed using kinematic precise point positioning method, and the crustal deformation of the areas before and after the earthquake were precisely calculated using the relative-positioning method. The results of the study calculated precise coordination that the RMSE is maximum ${\pm}0.003m$, respectively and showed that Mizusawa station moved 2.6m southeast by the earthquake.

• 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 the Earthquake Engineering Society of Korea
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• v.7 no.1
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• pp.41-55
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• 2003

A dynamically-interfaced multi-grid finite difference model for simulation of tsunamis in the East Sea(Choi et al.) was established and further applied to produce detailed feature of coastal inundations along the whole eastern coast of Korea. The computational domain is composed of several sub-regions with different grid sizes connected in parallel of inclined directions with 16 innermost nested models. The innermost sub-region represents the coastal alignment reasonably well and has a grid size of about 30 meters. Numerical simulations have been performed in the framework of shallow-water equations(linear, as well as nonlinear) over the plane or spherical coordinate system, depending on the dimensions of the sub-region. Results of simulations show the general agreements with the observed data of run-up height for both tsunamis. The evolution of the distribution function of tsunami heights is studied numerically and it is shown that it tends to the log-normal curve for long distance from the source.

• Journal of the Korean Society of Safety
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• v.34 no.5
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• pp.159-166
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• 2019

The seismic PSA is to probabilistically estimate the potential damage that a large earthquake will cause to a nuclear power plant. It integrates the probabilistic seismic hazard analysis, seismic fragility analysis, and system analysis and is utilized to identify seismic vulnerability and improve seismic capacity of nuclear power plants. Recently, the seismic risk of domestic multi-unit nuclear power plant sites has been evaluated after the Great East Japan Earthquake and Gyeongju Earthquake in Korea. However, while the currently available methods for system analysis can derive basic required results of seismic PSA, they do not provide the detailed results required for the efficient improvement of seismic capacity. Therefore, for in-depth seismic risk evaluation, improved system analysis method for seismic PSA has become necessary. This study develops a system analysis method that is not only suitable for multi-unit seismic PSA but also provides risk information for the seismic capacity improvements. It will also contribute to the enhancement of the safety of nuclear power plants by identifying the seismic vulnerability using the detailed results of seismic PSA. In addition, this system analysis method can be applied to other external event PSAs, such as fire PSA and tsunami PSA, which require similar analysis.

• Journal of Conservation Science
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• v.35 no.1
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• pp.51-60
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• 2019

This paper provides quantitative data that describes the evolution of the air quality in the Whale and Sea Museum, located in the Iwate prefecture, collected after the 2011 Great East Japan Earthquake and tsunami. The museum was damaged significantly by the disaster, and restoration works continued for over six years. The air quality in the temporary storage facility and museum was monitored during the rehabilitation process. Evaluation of air quality is carried out by gas chromatography- mass spectrometry, ion chromatography and high-performance liquid chromatography. The results showed that the characteristics of the chemical components differed depending on the measurement locations inside the building. The museum atmosphere tended to be alkaline as the airtightness increased because of the maintenance works at the entrance. It was also determined that it was necessary to study the intake/exhaust routes and to clean them according to the contamination degree. In Japan, there are recommended museum air quality standards for acetic acid, formic acid, alkali, and aldehydes. The results indicated that these standards should not be used as a reference for damaged museums. Furthermore, at the temporary storage facilities for to store the collections during the rehabilitation of the museum, solvents such as ethyl benzene, toluene, and xylene are initially abundant, although they can be reduced by ventilation, while other components such as 2E1H was confirmed in this case are likely to remain.

• Journal of the Korean Geophysical Society
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• v.10 no.1
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• pp.1-12
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• 2007

A method to quickly estimate broadband moment magnitudes (Mwp) to warn regional and teleseismic tsunamigenic earthquakes is tested for application of the method to the different seismic observation environment. In this study, the Mwp is calculated by integrating far-field P-wave or pP-wave of vertical component of displacement seismograms in time domain from earthquakes, having magnitude greater than 5.0 and occurred in and around the Korean peninsula from 2000 to 2006. We carefully set up the size of the time window for the computations to exclude S wave phases and other phases following after the P wave phase. The P wave velocities and the densities from the averaged Korean crustal model are used in the computations. Instrumental correction was performed to remove dependency on the seismograph. The Mwp after the instrumental correction is about 0.1 greater than the Mwp before the correction. The comparison of our results to the those of foreign agencies such as JMA and Havard CMT catalogues shows a higher degree of similarity. Thus our results provide an effective tool to estimate the earthquake size, as well as to issue the necessary information to a tsunami warning system when the effective earthquake occurs around the peninsula.

• Journal of Advanced Navigation Technology
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• v.22 no.2
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• pp.49-56
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• 2018

As the energy generated by earthquake, tsunami, etc. propagates through the air and disturbs the electron density in the ionosphere, the perturbation can be detected by analyzing the ionospheric delay in satellite signal. The electron density in the ionosphere is affected by various factors such as solar activity, latitude, season, and local time. To distinguish from the anomaly, therefore, it is required to inspect the normal trend of the ionosphere. Also, as the perturbation magnitude diminishes by distance it is necessary to develop an appropriate algorithm to detect long-distance disturbances. In this paper, normal condition ionosphere trend is analyzed via IONEX data. We selected monitoring value that has no tendency and developed an algorithm to effectively detect the long-distance ionospheric disturbances by using the lasting characteristics of the disturbances. In the end, we concluded the $2^{nd}$ derivative of ionospheric delay would be proper monitoring value, and the false alarm with the developed algorithm turned out to be 1.4e-6 level. It was applied to 2011 Tohoku earthquake case and the ionospheric disturbance was successfully detected.

• Earthquakes and Structures
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• v.20 no.3
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• pp.353-364
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• 2021

Natural hazards like earthquakes, high winds, and tsunami are a threat all the time for multi-story structures. The environmental forces cannot be clogged but the structures can be prevented from these natural hazards by using protective systems. The structural control can be achieved by using protective systems like the passive, active, semi-active, and hybrid protective systems; but the semi-active protective system has gained importance because of its adaptability to the active systems and reliability of the passive systems. Therefore, a semi-active protective system for the earthquake forces has been adopted in this work. Magneto-Rheological (MR) damper is used in the structure as a semi-active protective system; which is connected to the current driver and proposed controller. The Proportional Integral Derivative (PID) controller and reliable PID controller are two proposed controllers, which will actuate the MR damper and the desired force is generated to mitigate the vibration of the structural response subjected to the earthquake. PID controller and reliable PID controller are designed and tuned using Ziegler-Nichols tuning technique along with the MR damper simulated in Simulink toolbox and MATLAB to obtain the reduced vibration in a three-story benchmark structure. The earthquake is considered to be uncertain; where the proposed control algorithm works well during the presence of earthquake; this paper considers robustness to provide satisfactory resilience against this uncertainty. In this work, two different earthquakes are considered like El-Centro and Northridge earthquakes for simulation with different controllers. In this paper performances of the structure with and without two controllers are compared and results are discussed.

• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.129-134
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• 2016

Standard design of APR+(advanced power reactor plus) was certified at 2014 by Korea regulatory body. Based on the experience gained from OPR1000 and APR1400, the APR1400 was being developed as a 1,500MWe class reactor using Korean technologies for design code, reactor coolant pump, and man-machine interface system. APR+ has been basically designed to have the seismic design basis of safe shutdown earthquake (SSE) 0.3g, a 4-train safety concept based on N+2 design philosophy, and a passive auxiliary feedwater system (PAFS). Also, safety issues on the Fukushima-type accidents have been extensively reviewed and applied to enhance APR+ safety. APR+ provides higher reliability and safety against tsunami and earthquake. The purpose of this paper is to implement probabilistic safety assessment considering these design features and to analyze sensitivity of core damage frequency for large loss of coolant accident of APR+.