• Geophysics and Geophysical Exploration
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• v.13 no.2
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• pp.144-152
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• 2010

To study the thickness variation of volcanic rocks of Jeju Island, microtremor data were recorded at eight and four sites using short-period and broadband seismometers, respectively, for 30 ~ 60 minutes with a 100 Hz sampling rate. During the daytime, these records show increased cultural noise at frequencies above 1.8 Hz. Natural noise occurs in the frequency range of 0.4 to 0.8 Hz in both daytime and nighttime data. Predominant frequencies determined by the H/V spectral-ratio method are in the range of 0.2 ~ 0.7 Hz. These frequencies decrease gradually as the central part of the Mt. Halla is approached. This may indicate that the basement is warped downward beneath the center of the island, which is consistent with previous gravimetric and magnetic models. Assuming an average shear-wave velocity of 1,800 m/s for the overburden basalts, the depths to basement are estimated to be between 640 and 2,140 m.

• Economic and Environmental Geology
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• v.49 no.3
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• pp.225-242
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• 2016

Rock physics serves as a useful tool for seismic reservoir characterization and monitoring by providing quantitative relationships between rock properties and seismic data. Rock physics models can predict effective moduli for reservoirs with different mineral components and pore fluids from well-log data. The distribution of reservoirs and fluids for the entire seismic volume can also be estimated from rock physics models. The first part of this report discusses the Voigt, Reuss, and Hashin-Shtrikman bounds for effective elastic moduli and the Gassmann fluid substitution. The second part reviews various contact models for moderate- to high-porosity sands. In the third part, constant-cement model, known to work well for the sand that gradually loses porosity with deteriorating sorting, was applied to the well-log data from an oil field in the North Sea. Lastly, the rock physics template constructed from the constant-cement model and the results from the prestack inversion of 2D seismic data were combined to predict the lithology and fluid types for the sand reservoir of this oil field.

• Economic and Environmental Geology
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• v.24 no.4
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• pp.409-419
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• 1991

A gravity survey was conducted in the western Marquette district, Michigan, to delineate the subsurface structure and the relationship of the Proterozoic Marquette Range Supergroup rocks (Precambrian X) and Archean basement (Precambrian W) where the Republic, Michigan River, and Marquette troughs join. In order to accomplish these purposes, three hundred and forty gravity stations were established in the area of $380km^2$. Positive anomalies are associated with the Precambria X, metasedimentary sequence which has a higer density with respect to the Precambrian W, basement rocks. The dominant positive gravity anomalies follow the axes of the three troughs which are filled with Precambrian X rocks. Subsurface structure was modelled by using the Talwani method. Gravity model studies indicate that the Marquette trough is asymetrically shaped and steeply dipping at the north edge except in the eastern part of the study area. The interpretive results obtained from two dimensional model studies suggest that the basement structure of the study area is relatively flat, and that the troughs were formed contemporaneously.

• 한국해양학회지
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• v.26 no.2
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• pp.117-132
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• 1991

Marine total magnetic intensity over the southern part of the Ulleung Basin and geomagnetic data measured at a land base station are analyzed. Fourteen days observation of geomagnetic field at a fixed on-land base station showed how the geomagnetic field around the study area behaves. geomagnetic data at the base station can also be used as correction data for a diurnal variation. Magnetic anomalies in the study area do not reflect an effect of sea bottom topography but mainly subsurface basement. The southern part of the Ulleung Basin can be devided into two zones according to a different anomaly pattern; along the coastal shelves the isolated anomalies with a short wave and a strong amplitude are dominant, and toward the open sea the anomalies become much more subdued. The high anomaly zone adjoined to land is interpreted to be caused by granitic intrusives or volcanic rocks, and the weak anomaly zone to the outer sea to be arisen from an existence of deep basement. A spectrum analysis is applied to estimate magnetic basement depths from three anomaly profiles with a long period and a weak amplitude toward the outer sea. The calculated depths are 7.0km, 5.0km, and 2.6km respectively from outer profile. The basement might be correlated with the mixed layer of tuff, basalt, and sediment, which had been defined as L-2 layer in the Yamato basin and the Japan Basin.

• Proceedings of the Korea Contents Association Conference
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• 2014.11a
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• pp.227-228
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• 2014

방사선치료의 발전으로 3차원치료보다 진보된 호흡연동방사선치료가 시행되어지고 있다. 호흡의 규칙성과 환자의 위치 재현성이 중요한 치료적응 인자이며, 호흡연동 방사선치료의 효율을 높일 수 있는 지표이다. 국가암통계상 고령의 암환자가 증가하며, 수술, 화학요법을 병행하는 암 치료법이 널리 이용이 되고 있다. 고식적인 치료를 요하는 고령의 복부 암 환자분들에 호흡연동 방사선치료법을 사용하는데 에는 호흡의 불규칙성과 체위의 재현성의 문제점으로 인한 치료 효율의 저하를 가져온다. 본 연구에서는 호흡에 의한 종양 움직임이 있는 방사선 치료에서 내부표적체적 기반의 치료계획과 호흡연동 기법을 적용한 치료계획과의 선량비교 분석하였다. 2가지 치료법 모두 정상조직 보호선량에 부합한 것으로 나타났으며 치료체적은 처방선량의 95%이상 포함된 선량분포로 적합하였다. ITV 설정을 통한 3D Plan은 고식적 치료을 목적으로 하는 고령의 환자, 체위 및 호흡의 불안정성 환자에게 처방선량의 95% 이상의 4D Plan의 치료법 보다 짧은 시간에 치료함으로써 치료효율을 높일 수 있을 거라 사료된다. 다만 정상조직보호선량(NTCP)에 부합하는지에 대한 평가가 전제되어야 한다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.11a
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• pp.257-267
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• 2006

암은 한국에서 전체 사망률의 가장 많은 원인 중의 하나이며 이 중 간세포 암은 암에 의한 사망원인 중 성별에 관계없이 위암 다음으로 사망률이 높다. 특히 $40{\sim}60$세까지 중장년 기에서의 간암 발생률은 세계에서 가장 높은 발병률을 보이고 있으며 OECD 국가 중에서 간암 사망률로 최고 수치를 기록하고 있다. 본 논문에서는 조영증강 CT 영상에서 간암을 자동으로 추축하는 방법을 제안하여 전문의를 보조할 수 있는 보조 전문가 시스템으로서의 유용성을 확인하고자 한다. 흉부로부터 5mm 간격으로 약 $40{\sim}50$장 정도 촬영한 조영 증강 CT 영상으로부터 늑골의 정보를 이용하여 장기들의 정보만으로 구성된 내부 영역과 늑골 및 피하지방층, 그리고 배경으로 구성된 외부 영역을 구분한다. 간 영역의 정보가 포함된 내부 영역에서 명암도와 명암의 분포도, 간의 형태 및 위치 정보, 그리고 각 슬라이드를 기준으로 이전 CT 영상과 다음 CT 영상의 정보를 이용하여 간 영역을 추출한다. 간암은 추출된 간 영역에 형태기반 보간법을 적용하여 CT 촬영시 생기는 슬라이드 사이의 5mm 공간정보를 복원한 후, 각 슬라이드를 기준으로 이전 CT 영상과 다음 CT 영상의 정보와 간암이 가지는 명암도 및 형태학적 특정 정보를 이용하여 추출한다. 제안된 간 영역 및 간암 추출 방법을 전문의가 판별한 것과 비교 분석한 결과, 전문의를 보조 할 수 있는 보조 전문가 시스템으로서 효율적임을 확인할 수 있었다.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.253-256
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• 2008

지하 토사 조건 및 지질 구조는 지진 시 지반 운동의 증폭에 관련된 부지 효과에 매우 큰 영향을 미친다. 본 연구에서는 국내 홍성 지역을 대상으로 시추 조사와 현장 탄성파 시험을 포함한 현장 조사 및 지표 부근지질 정보를 획득하기 위한 부지 답사를 통해 부지 효과를 확인하였다. 홍성 지역은 1978년 계기 지진이 발생한 지역으로서 기반암 상부에 최대 약 50 m 두께의 풍화대 지층이 분포한다. 연구 대상 지역의 공간 지층 구조를 효율적으로 확인하기 위하여 지리정보시스템(GIS) 기법 기반의 지반 정보 시스템(GTIS)의 구축하였으며, 홍성 지역은 분지는 얕고 넓은 형상임을 확인하였다. 홍성 지역의 부지 지진 응답을 평가하기 위하여 대표 단면에 대한 2차원 유한 요소 해석을 수행하였다. 도출된 지진 응답으로부터 지반 운동이 기반암 상부 토사층을 통해 전단파가 전파되면서 증폭되고 분지 형상에 따른 전단파의 상호 작용으로 생성된 표면파로 인해 분지 경계 부근 진동 지속 시간이 증가됨을 확인하였다. 뿐만 아니라, 분지 내의 선정된 토사 부지들에 대해서 추가적인 1차원 유한 요소 지진 응답 해석을 수행하였으며, 본 연구 대상 분지가 매우 얕고 넓음에 따라 분지 경계 부근을 제외하고는 분지 내 대부분의 위치에서 2차원 지진 응답과 유사한 결과를 보였다.

• The Journal of the Korea Contents Association
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• v.9 no.4
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• pp.19-26
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• 2009

The microwave exposure device for microwave breast cancer detection consists of RF transceiver and several antennas. The microwave information of object acquired from the microwave exposure device can be calculated permittivity and conductivity by using the inverse scattered analysis. In this paper, we have developed the software for detecting breast cancers based on microwave tomography, by which users not only can check out the existence of breast cancers through the permittivity and conductivity information analysis of the object's internal, but also can analysis easily information for distribution of breast cancers. The developed software provides the function for visualizing the captured permittivity and conductivity information as 2D or 3D color images on which users can easily detect the existence of breast cancers. For more detailed analysis of tomography images, the proposed software also has provided the functions for displaying their cutting profiles as well as position and size information of special area in them.

• The Journal of the Petrological Society of Korea
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• v.13 no.3
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• pp.142-151
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• 2004

The metamorphic rocks of Yongin-Anseong area in Gyeonggi massif are composed of high-grade gneisses and schists which are considered as Precambrian basement, and Jurassic granite which intruded the metamorphic rocks. In this paper, we discuss the geochemical characteristics of metamorphic rocks and granites in this area based on REE and Nd isotope geochemistry. And we also discuss the petrogenetic relationship between metamorphic rocks and granites in this area. Most of Nd model ages (T$\_$DM/$\^$Nd/) from the metamorphic rocks range ca. 2.6Ga～2.9Ga which are correspond to the main crustal formation stage in Gyeonggi massif by Lee et. al. (2003). And Nd model ages show that the source material of quartzofeldspathic gneiss is slightly older than that of biotite banded gneiss. In chondrite-normalized rare earth element pattern, the range of (La/Yb)$\_$N/ value from biotite banded gneiss is 37～136, which shows sharp gradient and suggests that biotite banded gneiss was originated from a strongly fractionated source material. However, that of amphibolite is 4.65～6.64, which shows nearly flattened pattern. Particularly, the chondrite normalized REE patterns from the high-grade metamorphic rocks show the REE geochemisoy of original source material before metamorphism. In addition, the values of (La/Yb)$\_$N/ and Nd model ages of granite are 32～40 and 1.69Ga～2.08Ga, respectively, which suggest that the source material of granite is different from that of Precambrian basement such as biotite banded gneiss and quartzofeldspthic gneiss in the area.

• Journal of the Speleological Society of Korea
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• no.72
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• pp.19-30
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• 2006

The purpose of this study is to clarified the geology and geomorphic characteristics of the Hantan River Basin. In this area, some kind of landforms are developed such as pre-land forms, lava plateau, and present landforms etc. Some river terraces are peculiar features in the area. Some conclusions are as follows : The vicinity of the Hantan River is lava plateau formed from the volcanic activity. Some steptoes are located in the lava plateau. Baekeuiri formation means the river bed boulder beneath the lava formation. The development of drainage patterns are unstable and the bifurcation ratio, the ratio of mean length of the river are lower than the other rivers. The relative height of the terraces is about $5{\sim}25m$ and the terraces are alluvial terraces. In the Jiktang Fall area, bedrock is granite and basalt plateau covered the bedrock. In that point, the old erosion surface is relatively steeper than the horizontal-basalt plateau. Vertical columnar joints are developed and weathering materials creep on the valley wall. The cross section of the landform of the Kosukjung vicinities are somewhat different from the landforms of Jiktang Fall. The bedrock near the Kosukjung is granite that is the same with the Jiktang Fall. But the cross section shows a asymmetrical curve from each side.