• Tunnel and Underground Space
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• v.23 no.6
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• pp.521-537
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• 2013

While microseismicity induced by hydraulic stimulation carried out for EGS is useful means in estimating the range of permeability increase, it also affect surface structures and environments. In order to establish a mitigation plan for microseismicity triggered by hydraulic stimulation, we reviewed world-wide guidelines on the impact of ground vibration on the surface structure and human environment by blasting. Case studies from Europe and USA on the microseismicity by hydraulic stimulation are presented and suggestions are made for the guidelines on ground vibration by hydraulic stimulation for the ongoing Pohang EGS project.

• Tunnel and Underground Space
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• v.23 no.6
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• pp.506-520
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• 2013

While geothermal energy provides the only base-load power among renewable energy sources, its development has been carried out predominantly in volcanic area. EGS (Enhanced Geothermal System) is a ubiquitous technology that can allow the geothermal power generation virtually in any area. This manuscript introduces the current state-of-the-art of EGS development in the world and presents the hydraulic stimulation technology and associated microseismicity which are key technical component in EGS. Finally this paper suggests the key research areas required in Korea for further development of EGS.

• Tunnel and Underground Space
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• v.23 no.6
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• pp.572-580
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• 2013

In this case study, I examined the microseismic safety management system of Deep Heat Mining Basel (DHMB) as EGS Geothermal Project which was conducted in Basel, Switzerland. EGS Geothermal Power projects which require induced seismic event by stimulation for creation of EGS geothermal reservoir have to be controlled pressure and flow rate of stimulation by establishment of microseismic safety management system. Traffic light system and Communication response procedure of DHMB project to respond step by step corresponding microseismic event intensity through continuous monitoring during stimulation period have been managed and established in advance of stimulation. However, the project was discontinued because of an earthquake to occur larger than expected one due to post-injection seismicity occurring in the geothermal reservoir after completion of injection for stimulation. The result of post analysis, Real-time traffic light system was verified to need a establishment of new microseismic safe management system to be considered post-injection seismicity phenomenon.

• Tunnel and Underground Space
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• v.25 no.4
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• pp.320-331
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• 2015

This paper presents a case study of an enhanced geothermal system(EGS) demonstration project conducted in $Gro{\ss}$ $Sch{\ddot{o}}nebeck$, Northerm Germany, focusing on hydraulic stimulation. The project was conducted with doublet system in sandstone and volcanic formations at 4 - 4.4 km depth. Under normal faulting to strike-slip faulting stress regime, hydraulic stimulations were conducted at injection and production wells by massive waterfrac and gel-proppant fracturing. Injectivity index increased from $0.97m^3/(hr^*MPa)$ to $7.5m^3/(hr^*MPa)$ and productivity index increased from $2.4m^3/(hr^*MPa)$ to $10.1m^3/(hr^*MPa)$ by a series of hydraulic stimulations at both wells. After circulation tests through injection and production wells, however, productivity index decreased from $8.9m^3/(hr^*MPa)$ to $0.6m^3/(hr^*MPa)$ in two years. Slip tendency analysis for the stimulation in volcanic layer estimated the required pressure for shear slip and its preferred orientations and it showed reasonable match with actual stimulation results. Through the microseismicity observation for the stimulation of volcanic formation, only 80 seismic events with its moment magnitudes in -1.8<$M_W$<-1.0 were observed, which are unexpectedly low for EGS hydraulic stimulation.

• Tunnel and Underground Space
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• v.23 no.6
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• pp.493-505
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• 2013

This numerical study investigates seismicity and fault slip induced by fluid injection in deep geothermal reservoir with pre-existing fractures and fault. Particle Flow Code 2D is used with additionally implemented hydro-mechanical coupled fluid flow algorithm and acoustic emission moment tensor inversion algorithm. The output of the model includes spatio-temporal evolution of induced seismicity (hypocenter locations and magnitudes) and fault deformation (failure and slip) in relation to fluid pressure distribution. The model is applied to a case of fluid injection with constant rates changing in three steps using different fluid characters, i.e. the viscosity, and different injection locations. In fractured reservoir, spatio-temporal distribution of the induced seismicity differs significantly depending on the viscosity of the fracturing fluid. In a fractured reservoir, injection of low viscosity fluid results in larger volume of induced seismicity cloud as the fluid can migrate easily to the reservoir and cause large number and magnitude of induced seismicity in the post-shut-in period. In a faulted reservoir, fault deformation (co-seismic failure and aseismic slip) can occur by a small perturbation of fracturing fluid (<0.1 MPa) can be induced when the injection location is set close to the fault. The presented numerical model technique can practically be used in geothermal industry to predict the induced seismicity pattern and magnitude distribution resulting from hydraulic stimulation of geothermal reservoirs prior to actual injection operation.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.605-608
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• 2000

혼동 행렬 (confusion matrix)은 자극 또는 인식대상(데이터)에 대한 반응을 데이터화함으로써 인식대상(데이터)의 특성분석을 통하여 복잡한 시스템을 효율적으로 통제, 관리하기 위한 분석기법에 사용된다. 클러스터링은 인식 시스템을 위한 기법으로서 다양한 분야에서 널리 활용되고 있다. 본 연구에서는 혼동 행렬을 이용한 최적화 모델을 통하여 클러스터링(Clustering) 문제의 새로운 접근법을 제시한다. 최근 수리 계획 분야에서 클러스터링 분야에 대한 연구가 계속되고 있는데 그러한 수리 모델과 혼동 행렬을 접목하여 새로운 모델을 제시한다.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.2
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• pp.481-486
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• 2018

In this paper, we aimed to analysis EEG signals related to the relativity between musical stimuli and human brain activity for the arithmetical calculation and present the experimental results. We use two kinds of musical stimuli, one is a sedative tendency music and the other is a stimulative tendency music. The SMR wave and Mid-beta wave are analyzed because of the concentration. In our results, the sedative tendency music is not more interfere with human brain activity for the arithmetical calculations than the stimulative tendency music.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1327-1331
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• 2007

최근 전 세계적으로 기후 이상으로 인한 여러 가지 문제점들이 대두되고 있다. 특히 지구 온난화의 결과로 발생되는 하계 집중호우와 대형 태풍의 빈발은 막대한 인명과 재산의 손실이라는 결과를 초래하고 있다. 국내에서도 이러한 기후 변동의 여파로 2002년 태풍 루사, 2004년 태풍 매미, 2006년 강원도 지역의 집중호우 등이 발생하였으며, 이를 통해 제방붕괴 및 댐 저수지 붕괴라는 결과를 초래하였다. 국내에서 그 동안 발생한 피해를 들면 일산제 붕괴(1990년), 임진강유역 홍수(1996년), 연천댐붕괴(1996년), 장현 동막저수지 붕괴(2002년), 강원지역의 집중호우로 인한 범람 피해(2006년) 등을 들 수가 있다. 이러한 피해들은 그 규모가 기하급수적으로 증가하고 있으며, 피해 뿐 아니라 복구로 인한 경제적 손실 또한 막대하다. 그러므로 이러한 분야의 심층적인 연구가 필요할 것으로 판단된다. 위에서 언급한 바 있는 댐 붕괴나 하천의 범람에 관한 그 간의 연구는 수문학적인 방법을 통해 수행되어 왔다. 그러나 이러한 수문학적 방법은 하천에서의 흐름 특히 홍수시 발생할 수 있는 하천 부정류 흐름의 특성을 규명하기에는 미흡한 점이 있으며, 또한 광범위한 수리 수문학적 홍수추적 기법들을 특정한 문제에 대해 적용하는 기준은 명백하게 제시되어 있지 않다. 그러나 특정 사고과정과 일반적인 지침들은 홍수추적 기법의 선정에 대한 폭을 좁힐 수 있게 하여 최종적으로 적절한 기법의 선정을 가능케 하여 준다. 본 연구에서는 수리학적 홍수추적 기법들을 적용하여 하천에서의 흐름 양상을 규명하였으며, 각 추적기법들의 적용성을 파악하고 실제 적용시 수반되는 문제점들을 제시하였다. 또한 각 기법들의 문제점과 효용성을 검토하여 최적의 적용방안의 제시하였다.결과를 가시화하기 위해서 챠트 기능을 추가하였으며 매개변수를 자동으로 산정할 수 있도록 시스템을 구축하였다. HyGIS-RAS는 국내 하천유역에 대해서 기구축 되어있는 하천관리지리정보시스템(RIMGIS)자료를 직접 활용하도록 구성되어있고 자료를 활용하여 제내지와 제외지를 통합하여 TIN분석을 실시하여 범람 홍수해석에 활용할 수 있도록 하였다. 하천수리해석의 기능을 보강하기 위해 역산조도계수 산정모형, 상류-사류 천이류 구간에 대한 부등류 해석모형, 범람 홍수류에 대한 홍수위 산정모형, 하천수리계산시의 불확실도 해석모형 등의 새로운 기능을 추가하여 제시하였다. 모든 입출력자료는 프로젝트 단위별로 운영되어 data의 관리가 손쉽도록 하였으며 결과를 DB에 저장하여 다른 모형에서도 적용할 수 있도록 하였다. 그리고 HyGIS-HMS 및 HyGIS-RAS 모형에서 강우-유출-하도 수리해석-범람해석 등이 일괄되게 하나의 시스템 내에서 구현될 수 있도록 하였다. 따라서 HyGIS와 통합된 수리, 수문모형은 국내 하천 및 유역에 적합한 시스템으로서 향후 HydroInformatics 구현을 염두에 둔 특화된 국내 수자원 분야 소프트웨어의 개발에 기본 토대를 제공할 것으로 판단된다.았다. 또한 저자들의 임상병리학적 연구결과가 다른 문헌에서 보고된 소아 신증후군의 연구결과와 큰 차이를 보이지 않음을 알 수 있었다. 자극에 차이가 있지 않나 추측되며 이에 관한 추후 연구가 요망된다. 총대장통과시간의 단축은 결장 분절 모두에서 줄어들어 나타났으나 좌측결장 통과시간의 감소 및 이로 인한 이 부위의 통과시간 비율의 저하가 가장 주요하였다. 이러한 결과는 차가운 생수 섭취가 주로 결장 근위부를 자극하는 효과를 발휘하는 것이 아닌가 해석된다. 이와 같은 연구결과를 통해 생

• Tunnel and Underground Space
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• v.21 no.1
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• pp.11-19
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• 2011

Geothermal energy is believed to be an important source among the renewable energy sources to provide the base load electricity. Although there has been a drastic increase in the use of geothermal heat pump in Korea, there is no geothermal power plant in operation in Korea. Fortunately, the first EGS (Enhanced Geothermal System) Project in Korea has started in Dec 2010. This five year project is divided into two stages; two years for exploration and drilling of 3 km depth to confirm the minimum target temperature of 100 degrees, and another three years composed drilling 5 km doublet, hydraulic stimulation of geothermal reservoir with expected temperature of 180 degrees (40 kg/s) and construction of MW geothermal power plant in the surface. This EGS project would be a landmark effort that invited a consortium of industry, research institutes and university with expertises in the fields of geology, hydrogeology, geophysics, geomechanics and plant engineering.

• Journal of Soil and Groundwater Environment
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• v.25 no.4
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• pp.87-97
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• 2020

In this study, the applicability of the geostatistical evolution strategy as an inverse analysis method of estimating hydraulic properties of small-scale basin was tested. The geostatistical evolution strategy is a type of data assimilation method that can effectively estimate aquifer hydraulic conductivity by combining a global optimization model of the evolution strategy and a local optimization model of the ensemble Kalman filtering. In the applicability test, the geometry, hydraulic boundary conditions, and the distribution of groundwater monitoring wells of Hanlim-Eup were employed. On the other hand, a synthetic hydraulic conductivity distribution was generated and used as the reference property for ease of estimation quality assessment. In the estimations, two different cases were tested where, in Case I, both groundwater levels and hydraulic conductivity measurements were assumed to be available, and only the groundwater levels were available, in Case II. In both cases, the reference and estimated hydraulic conductivity fields were found to show reasonable similarity, even though the prior information for estimation was not accurate. The ability to estimate hydraulic conductivity without accurate prior information suggests that this method can be used effectively to estimate mathematical properties in real-world cases, many of which little prior information is available for the aquifer conditions.