백반증이 동반된 선천성 거대 멜라닌세포성 모반 2예

오석훈,이무형 대한피부과학회 2003 大韓皮膚科學會誌 Vol.41 No.6

Congenital giant melanocytic nevi (CGMN) are lesions of more than 20 ㎝ in diameter, often in the distribution of a garment. Depigmented zones may appear around several types of acquired lesions such as dermal, junctional, and compourd nevi, Spitz nevus, blue nevus, and malignant melanoma. The depigmentation may occur within the lesion, around it, or at a distant site. In contrast, congenital nevi rarely develop depigmentation. Vitiligo-like leukoderma distant from the nevus has developed in only three cases with a CGMN. We report two cases of CGMN with vitiligo which is located away from primary CGMN lesion. (Korean J Dermatol 2003;41(6) : 805~808)

RMR 평가를 위한 지구물리 탐사자료와 시추공 자료의 지구통계학적 복합해석

오석훈,정호준,변영봉 한국암반공학회 2004 한국암반공학회 학술대회 및 세미나 자료집 Vol.- No.-

MRI 전류밀도 영상을 이용한 딥브레인 자극 평가기술

오석훈,정영진 한국전자파학회 2023 전자파기술 Vol.34 No.3

3차원 전기비저항 모델링을 통한 제체의 안정성 분석 연구

오석훈 한국지구과학회 2008 한국지구과학회지 Vol.29 No.6

Recently, the electrical DC survey has frequently been performed to assess the safety of embankment. This study showed that the damaged section of embankment could be appropriately detected by the survey only when the three dimensional effect was correctly considered. The shape of the three dimensional embankment was numerically implemented, and a proper modeling was performed to confirm the effect by analyzing the apparent and inverted true resistivity. Then, the field work was carried out. The three dimensional interpretation distinguished the erroneous weak zones from the geometrical artifact, and the embankment was ensured as safe both by the additional survey performed in rainy season and the partial excavation for direct observation. 최근 제체 등의 수자원시설물에 대한 안정성 검토를 위해 전기비저항 탐사가 많이 수행되고 있다. 본 연구에서는 전기비저항 조사를 통해 제체의 안정성을 검토하고자할 때, 제체의 3차원 형상에 의한 효과를 정확히 분석하여야만 손상 구간을 파악할 수 있음을 제시하고자 한다. 이의 검토를 위해 3차원 전기비저항 모델링을 통해 3차원 형태의 제체 모양을 수치모델로 구현하고, 제체 내부의 상태에 따른 겉보기 비저항과 역산 결과를 분석하였다. 또한 실제 3차원 곡면 형태를 가진 제체에서 전기비저항 탐사를 수행하여 그 결과를 분석하였다. 그 결과, 단순히 2차원으로 해석하였을 때 이상대로 추정되었던 구간이, 실제로는 3차원 곡면에 의한 기하학적 효과였음이 밝혀졌으며, 3개월 뒤에 수행된 우기의 추가 조사와 추후 일부 굴착을 통하여 제체의 내부가 안전한 상태임을 확인하였다.

웨이블릿 기반 셈블런스를 이용한 지구물리 자료의 필터링과 응용

오석훈,서백수,임은상 한국지구과학회 2009 韓國地球科學會誌 Vol.30 No.6

Wavelet transform has been widely used in terms that it may overcome the shortcoming of conventional Fourier transform. Fourier transform has its difficulty to explain how the transformed domain, frequency, is related with time. Traditional semblance technique in Fourier transform was devised to compare two time series on the basis of their phase as a function of frequency. But this method is known not to work well for the non-stationary signal. In this study, we present two applications of the wavelet-based semblance method to geophysical data. Firstly, we show filtered geomagnetic signal remained with components of high correlation to each observatory. Secondly, highly correlated residual signal of gravity and magnetic survey data, which are also filtered by this semblance method, is present. 웨이블릿 변환은 기존 푸리에 변환이 갖는 주파수 변환 결과의 시간 영역에 대한 모호성을 극복할 수 있는 변환 기법으로 널리 이용되어 왔다. 기존의 푸리에 변환에 의한 셈블란스는 두 개의 시계열 자료의 위상을 주파수 영역에서 비교할 수 있도록 하는 방법이다. 이 방법은 비정상상태의 신호에 대해서는 잘 작동하지 않는 것으로 알려져 있다. 본 연구에서는 자연계의 신호가 대부분 비정상상태임을 고려하여 웨이블릿 기반으로 개발된 셈블란스 기법을 지구물리자 료에 적용하였다. 첫 번째 사례는 지구자기장 자료처리로서, 원격으로 위치한 관측소의 자료끼리 서로 비교하여 상관성 이 높은 신호만 남도록 필터링한 결과를 제시한다. 두 번째 사례는 중력과 자력탐사를 복합적으로 분석할 수 있는 방 안으로서, 두 자료간 공간적 상관성이 높은 신호만을 추출하는 필터링 결과를 제시한다.

개방형 자기공명영상장치에서 보호자의 전자파 노출 분석

오석훈,홍선의,최형도 한국자기학회 2022 한국자기학회 학술연구발표회 논문개요집 Vol.32 No.2

Bayesian Inversion for Cavity Investigation

오석훈,서백수 한국자원공학회 2010 Geosystem engineering Vol.13 No.3

Geophysical investigation and Bayesian inversion have been performed to investigate the cavity structure. The targeted cavity is a lava cave in Cheju Island, Korea and the geometry of the cavity is already known. For the cavity detection, we have used the both dipole-dipole array resistivity and gravity method. Although the two methods generally have different objectives, common characteristics may be appeared in the cavity structure. That is, the resistivity value is high but the gravity one is low in the presence of the cavity. We choose the dipole-dipole array resistivity data as prior information for the Bayesian inversion of gravity data. We applied the indicator variogram modeling to transform the result of resistivity inversion to density information, as higher resistivity block has lower density one. This assumption is valid in Cheju Island where most of the rocks are composed of basalt. Generally, cavity investigation by single geophysical exploration is difficult to get effective result. However, this coupled interpretation proposes a new way to provide remarkable improvement and stability when compared to the result of single method.

Geomagnetic variation and its relation to microearthquakes in the seismically inactive Korean Peninsula

오석훈 한국지질과학협의회 2012 Geosciences Journal Vol.16 No.1

Some microearthquakes that occur in the Korean Peninsula show significant geomagnetic variation when subjected to a specialized principal component analysis, wavelet-based semblance filtering and eigenvalue analysis. In this study, the principal component analysis was used to reconstruct and predict the geomagnetic field based on the past observed magnetic fields, and the reconstructed field was compared with the field observed during the earthquake event. The wavelet-based filtering showed improved results in delineating the earthquake event’s geomagnetic variations from their background field. Finally, the change in the tendency of the eigenvalues was detected by the analysis of three components of the geomagnetic fields during the earthquake event. The basement rock of the Korean Peninsula is known to have a highly resistive electrical structure that makes it possible for small-magnitude earthquakes to generate exaggerated geomagnetic variations. This is the first study reporting the relation between these earthquake events and the geomagnetic variations observed in the Korean Peninsula.

지난 3년 동안(2009-2011) 한반도 지역에서 발생한 지진의 지자기 변동성 분석

오석훈,지윤수 한국지구과학회 2014 韓國地球科學會誌 Vol.35 No.6

Recent three years of geomagnetic data were analyzed using a method of Principal Component Analysis (PCA)and Wavelet Based Semblance Analysis to investigate any geomagnetic variation caused by earthquakes. This methodpredicts the geomagnetic variation using the PCA analysis of geomagnetic data, then compares the predicted geomagneticfield with the observation of finding any significant residual. Although it is well known that geomagnetic variation isrelated with earthquake, most analyses have been limited to some specific cases reflecting the correlation. In this study,we analyze seventeen cases of earthquakes that occurred in and around the Korean peninsula from 2009 to 2011 and thatshow the precursory and co-seismic relation between the earthquakes and geomagnetic variations. 최근 3년간 지진과 연관된 지자기 변동성을 파악하기 위해 주성분 분석 및 웨이블릿 기반 셈블런스에 기반한분석 기술을 적용하였다. 이 기술은 지자기 관측 자료의 주성분을 이용하여 지자기 예측을 수행하고, 지진이 발생한 전후로 예측한 지자기장과 실제 관측된 지자기장 사이에 유의미한 변화량이 있는지 분석한다. 일반적으로 지자기자료가지진에 의한 변동성을 잘 반영하는 것으로 알려져 있지만, 특정 지진에 대한 분석을 통해 상관성을 증명한 것이 대부분이다. 본 연구에서는 2009년부터 2011년까지 한반도 및 주변에서 발생한 총 17차례의 지진에 대해 다양한 지자기 변동성을 분석하여 지진 전조 및 지진 동반 신호를 성공적으로 발견할 수 있음을 확인하였다.

물리탐사 자료를 이용한 암반등급의 지구통계학적 역산

오석훈 한국자원공학회 2008 한국자원공학회지 Vol.45 No.6

Geostatistical inverse approach using geophysical data was applied to indirectly make the RMR classification at points apart from boreholes. The geostatistical approach was usually used to find optimized estimation which supports two or more different physical properties at unsampled points. However, in this study, an approach to solve inverse problem was proposed. The primary variable, RMR values obtained at known boreholes, is geostatistically simulated with many realization at pre-defined grid point according to the variogram model. The simulated values are sequentially compared with the physical property resulted from geophysical survey at an arbitrary grid point, and the most similar one is chosen. This process means that the spatial distribution of primary variable, RMR, is conformed well to the original pattern of the borehole observation, and ensure to fit the geophysical survey result to reflect the correlation between different physical properties.