• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.5
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• pp.29-36
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• 2002

In the maintenance and retrofit planning of a bridge system, the optimal strategy for inspection and repair are suggested by minimizing the expected total life-cycle cost, which includes the initial cost, the costs of inspection, repair, and failure. Degradation of seismic performance is modeled by using a damage function. And failure probability is computed according to the degree of damage detection by random vibration theory and the event tree analysis. As an example to illustrate the proposed approach, a 10-span continuous bridge structure is used. The numerical results show that the optimum number of the inspection and the repair are increased, as the seismic intensity is increased and the soil condition of a site becomes more flexible.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.107-114
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• 2019

In this paper, the P-wave multiple detection system for the fast and accurate earthquake early warning nearby the epicenter was developed. The developed systems were installed in five selected public buildings for the validation. During the monitoring, a magnitude 2.3 earthquake occurred in Pohang on 26 September 2019. P-wave initial detection algorithms were operated in three out of four systems installed in Pohang area and recorded as seismic events. At the nearest station, 5.5 km from the epicenter, P-wave signal was detected 1.2 seconds after the earthquake, and S-wave was reached 1.02 seconds after the P-wave reached, providing some alarm time. The maximum accelerations recorded in three different stations were 6.28 gal, 6.1 gal, and 5.3 gal, respectively. The alarm algorithm did not work, due to the high threshold of the maximum ground acceleration (25.1 gal) to operate it. If continuous monitoring and analysis are to be carried out in the future, the developed system could use a highly effective earthquake warning system suitable for the domestic situation.

• Journal of the Korean Institute of Gas
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• v.3 no.2 s.7
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• pp.17-23
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• 1999

The wire and/or wireless data communication system for anti-disaster system of natural gas governor station was developed. In oder to prevent accidents of governor station, the operator was replaced by RTU(Remote Terminal Unit) which gather and transmit safety situation of governor station. The database and MMI(Man Machine Interface) were also developed to analyze the situation of governor station. The data communication between server and RTU was designed to switch automatically from wire to wireless communication and vice versa when one of them failed communication. We also have developed the patrol car management system which was applied GPS(Global Position System)/GIS(Geometric Information System), and the earthquake detection/transmission system which was adopted three dimension acceleration sensor. When a earthquake may occur, the earthquake detection/transmission system monitors data such as PGA(Peak Ground Acceleration), Sl(Spectrum Intensity) and orders the emergency shutoff valve close immediately.

• Journal of Korean Society for Geospatial Information Science
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• v.7 no.1 s.13
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• pp.11-20
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• 1999

To establish the basis of GPS network for the perception of diastrophism, we slected 7 stations(baseline $100{\sim}300km$) all around south Korea considering the earthquake and the satellites all-in-view. As a result of periodical measurement, the change of relative positions between selected stations in Korea was very small. We could know that the baseline between Korea and Japan are decreasing by a few centimeters, as one of the results of analysing baseline vector changes by continuous measuring IGS stations and Korea(KAMC) station.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1235-1240
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• 2019

It is well known that the ground water level changes rapidly before and after the earthquake, and the variation of ground water level prediction is used to predict the earthquake. In this paper, we predict the ground water level in Miryang City using ANFIS algorithm for earthquake prediction. For this purpose, this paper used precipitation and temperature acquired from National Weather Service and data of underground water level from Rural Groundwater Observation Network of Korea Rural Community Corporation which is installed in Miryang city, Gyeongsangnam-do. We measure the prediction accuracy using RMSE and MAPE calculation methods. As a result of the prediction, the periodic pattern was predicted by natural factors, but the change value of ground water level was changed by other variables such as artificial factors that was not detected. To solve this problem, it is necessary to digitize the ground water level by numerically quantifying artificial variables, and to measure the precipitation and pressure according to the exact location of the observation ball measuring the ground water level.

• Journal of Korea Multimedia Society
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• v.15 no.7
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• pp.910-919
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• 2012

We have observed huge success in social network services like Facebook and Twitter, and many researchers have done their analysis on these services. As massive data observed by users is produced on Twitter, many researchers have been conducting research to detect an event on Twitter. Some of them developed a system to detect the earthquakes or to find the local festivals. However, they did not consider the credibility of location information on Twitter although their systems were using the location information. In this paper, we analyze the credibility of the profile location and the correlation between the spatial attributes on Twitter as the preliminary research of the event detection system on Twitter. We analyzed 0.5 million Twitter users in Korea and 2.8 million users around the world. 49.73% of the users in Korea and 90.64% of the users in the world posted tweets in their profile locations. This paper will be helpful to understand the credibility of the spatial attributes on Twitter when the researchers develop an application using them.

• The Journal of Engineering Geology
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• v.28 no.2
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• pp.217-246
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• 2018

During the selection and characterization of target formations in the Small-scale Offshore $CO_2$ Storage Demonstration Project in the Pohang Basin, we have carefully investigated the possibility of induced earthquakes and leakage of $CO_2$ during the injection, and have designed the storage processes to minimize these effects. However, people in Pohang city have a great concern on $CO_2$-injection-intrigued seismicity, since they have greatly suffered from the 5.4 magnitude earthquake on Nov. 15, 2017. The research team of the project performed an extensive self-investigation on the safety issues, especially on the possible $CO_2$ leakage from the target formation and induced earthquakes. The target formation is 10 km apart from the epicenter of the Pohang earthquake and the depth is also quite shallow, only 750 to 800 m from the sea bottom. The project performed a pilot injection in the target formation from Jan. 12 to Mar. 12, 2017, which implies that there are no direct correlation of the Pohang earthquake on Nov. 15, 2017. In addition, the $CO_2$ injection of the storage project does not fracture rock formations, instead, the supercritical $CO_2$ fluid replaces formation water in the pore space gradually. The self-investigation results show that there is almost no chance for the injection to induce significant earthquakes unless injection lasts for a very long time to build a very high pore pressure, which can be easily monitored. The amount of injected $CO_2$ in the project was around 100 metric-tonne that is irrelevant to the Pohang earthquake. The investigation result on long-term safety also shows that the induced earthquakes or the reactivation of existing faults can be prevented successfully when the injection pressure is controlled not to demage cap-rock formation nor exceed Coulomb stresses of existing faults. The project has been performing extensive studies on critical stress for fracturing neighboring formations, reactivation stress of existing faults, well-completion processes to minimize possible leakage, transport/leakage monitoring of injected $CO_2$, and operation procedures for ensuring the storage safety. These extensive studies showed that there will be little chance in $CO_2$ leakage that affects human life. In conclusion, the Small-scale Offshore $CO_2$ Storage Demonstration Project in the Pohang Basin would not cause any induced earthquakes nor signifiant $CO_2$ leakage that people can sense. The research team will give every effort to secure the safety of the storage site.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.353-361
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• 2013

To analyze the distribution of earthquake-induced strain data in rock masses, statistical analysis was performed on four-directional strain data obtained from a ground movement monitoring system installed in Korea. Strain data related to the 2011 Tohoku-oki earthquake and two aftershocks of >M7.0 in 2011 were used in x-MR control chart analysis, a type of univariate statistical analysis that can detect an abnormal distribution. The analysis revealed different dispersion times for each measurement orientation. In a more comprehensive analysis, the strain data were re-evaluated using multivariate statistical analysis (MSA) considering correlations among the various data from the different measurement orientations. $T_2$ and Q-statistics, based on principal component analysis, were used to analyze the time-series strain data in real-time. The procedures were performed with 99.9%, 99.0%, and 95.0% control limits. It is possible to use the MSA data to successfully detect an abnormal distribution caused by earthquakes because the dispersion time using the 99.9% control limit is concurrent with or earlier than that from the x-MR analysis. In addition, the dispersion using the 99.0% and 95.0% control limits detected an abnormal distribution in advance. This finding indicates the potential use of MSA for recognizing abnormal distributions of strain data.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.223-224
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• 2008

건축물 내에서 가스사용량, 가스압력 및 밸브상태 등을 점검 할 수 있는 안전기능을 갖춘 유비쿼터스 기반 지능형 가스미터를 개발하고, 이를 유선 RS-485와 무선 ZigBee(2.4GHz) 통신모듈을 탑재한 시스템 및 망을 구성하여 원격지에서 양방향으로 유비쿼터스 통신방식을 이용하여 원격검침, 가스누출검지, 지진감지에 의한 내부밸브 차단 및 개방과 위험통보등의 기능을 수행할 수 있게 하였다. 개발시제품과 데이터를 바탕으로 시스템운용 통신 토폴로지, 구현방법, 실험결과를 소개하고, 이 시스템의 보급을 통하여 가스사고 예방에 힘쓰고자 한다.

• Proceedings of the Korea Contents Association Conference
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• 2017.05a
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• pp.383-384
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• 2017

재난 재해 조기 예 경보시스템은 산불, 홍수, 지진, 화재, 붕괴, 가스 누출 등 다양한 재난 재해가 발생할 확률이 있거나 발생하였을 경우 다양한 매체를 이용하여 신속하게 이와 관련된 정보를 전파하는 시스템을 의미한다. 재난 재해 조기 예 경보시스템은 기후 변화와 현대 사회의 발전의 고도화로 각종 다양한 재난 재해의 발생이 매년 급증하고 있어 이에 대해 국민의 생명과 재산을 보호하기 위해 필요성이 날로 증가하고 있으며, 이와 관련된 재난통신, 단말기, 시스템의 시장규모는 지속적으로 빠르게 성장하고 있다. 최근 들어 IoT를 이용한 다양한 센서 디바이스를 활용하여 재난 재해 상황, 기상상황, 전염병 상황정보 등을 광범위하게 감지하고 분석함으로써 미래 적용 가능성이 상당히 높게 나타나고 있다.