• 지구물리와물리탐사
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• 제16권3호
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• pp.163-170
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• 2013

탄성파 탐사자료의 진폭변화를 분석하면 지층의 유체를 탐지하고 석유 가스 저류층의 정밀한 물성 도출이 가능하다. 본 연구는 동해 울릉분지의 심해 탄성파 탐사자료에 대하여 진폭변화를 분석하고 정리하였다. 중합단면에서 반사신호가 강하게 기록된 영역의 탄성파 공통깊이점-벌림 모음과 공통깊이점-반사각 모음을 관찰하여 진폭변화가 뚜렷한 영역을 선별하였다. 울릉분지의 중앙부 탄성파 탐사 반사각 모음의 주시 3200과 3300 ms 구간 탄성파 신호에 대한 종축절편과 진폭구배 속성을 계산하여 벌림에 따른 진폭 증가 및 감소를 확인하였다. 종축절편과 진폭구배를 곱한 속성과 합한 속성을 도출하여 울릉분지 퇴적층의 가스부존 가능 영역 상부와 하부 경계를 구분하였다. 가스로 포화된 퇴적층의 탄성파 진폭변화 특성을 보이는 영역은 탄성파주시 3 s 인근에서 간헐적으로 나타났다. 교차도표를 이용하여 울릉분지 탄성파자료의 진폭변화를 유형별로 확인할 수 있었다. 배경매질의 종축절편과 진폭구배는 함수 퇴적층의 일반적인 특징인 반비례관계를 보였고 가스함유 퇴적층의 진폭변화를 보이는 표본은 교차도표 단면상에서 1사분면과 3사분면에 위치하였다. 교차도표에서 선택된 표본들을 중합단면에서 추적한 결과 울릉분지 중앙부의 심해 퇴적지층 중 진폭변화 유형 3에 해당하는 영역이 수평연장 150 m 내로 분포함을 유추할 수 있었다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.157-162
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• 2007

Geophysical survey has been conducted on the continental margin off the South Shetland Islands aboard R/V Onnuri of KORDI in 1992/1993. About 800-line km of 96-channel reflection data have been acquired. On the seismic section, BSR with strong reflectivity and negative polarity has been found at 700 ms below the sea bottom. BSR is considered as the base of gas hydrates and AVO analysis was performed to study physical properties along BSR. True amplitude recovery and surface consistence amplitude were applied to seismic data and angle gathers were obtained. AVO gradient and AVO intercept are calculated on every CDP gather. Section of AVO intercept show strong reflectivity and negative polarity on BSRs and stronger continuity of BSR than stacked section. Cross plot of intercept-gradient indicates that the lower layer below BSR is filled with free gas.

• 자원환경지질
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• 제47권6호
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• pp.625-633
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• 2014

캐나다 아퀴스토어 프로젝트는 인근의 화력발전소에서 포집한 이산화탄소를 심부 약 3,500 m에 존재하는 염대수층에 저장하는 포집, 수송, 주입 및 저장의 전 과정을 포함하는 세계 최초의 통합 실증 프로젝트이다. 이산화탄소의 저장소로서의 염대수층은 기존의 한정적으로 분포된 석유가스 저류층과 비교했을 때 전 세계 어디서나 분포하므로 이에 대한 실증 연구는 이산화탄소 지중저장의 저변 확대에 큰 의미가 있다. 염대수층에 이산화탄소를 주입하고 추적하기 위해서는 지하의 물성을 파악하고 특성화해야 한다. 본 연구는 캐나다 아퀴스토어 이산화탄소 지중저장 현장의 탄성파 탐사자료로부터 석유가스 자원 탐사에 이용되는 진폭 변화 분석기술을 응용하여 지중저장 대상지층의 유체 포화 특성을 도출하였다. 시추공 검층자료에서 해석된 이산화탄소 저장층 구간의 상부 및 하부는 Winnipeg층 1,815 ms과 Deadwood 층 1,857 ms로 탄성파 자료와 대비하였다. 대상 구간의 탄성파 기록으로부터 입사각에 따른 진폭 크기변화를 확인한 결과 자료의 상관성은 45 %에서 81 % 범위였다. 종축절편과 진폭구배 속성을 교차출력한 결과는 반비례 관계를 보여 전형적인 함수 퇴적층에 해당하였다. 계산된 속성들에서 대수층의 기저를 공간적으로 도시하였고 이산화탄소 지중저장 구간의 포아송비 변화를 예측하였다.

• 한국인공지능학회지
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• 제12권2호
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• pp.17-23
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• 2024

Various methods have been developed to predict the flight path of an air-launched weapon to intercept a fast-moving target in the air. However, it is also getting more challenging to predict the optimal firing zone and provide it to a pilot in real-time during engagements for advanced weapons having new complicated guidance and thrust control. In this study, a method is proposed to develop an optimized weapon engagement zone by the SCG (Scaled Conjugate Gradient) algorithm to achieve both accurate and fast estimates and provide an optimized launch display to a pilot during combat engagement. SCG algorithm is fully automated, includes no critical user-dependent parameters, and avoids an exhaustive search used repeatedly to determine the appropriate stage and size of machine learning. Compared with real data, this study showed that the development of a machine learning-based weapon aiming algorithm can provide proper output for optimum weapon launch zones that can be used for operational fighters. This study also established a process to develop one of the critical aircraft-weapon integration software, which can be commonly used for aircraft integration of air-launched weapons.

• 지구물리
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• 제9권4호
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• pp.417-426
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• 2006

1993년 남극 하계 기간 동안 남쉐틀랜드 대륙주변부에서 한국해양연구원의 종합연구선 온누리호를 이용하여 탄성파 탐사를 실시하였으며 약 800 km의 탄성파자료를 획득하였다. 탄성파 자료에서 음의 반사계수를 보이며 상대적으로 강한 진폭을 갖는 BSR이 해저면 700 ms에서 발견되었으며 이는 가스수화물의 기저면으로 간주된다. BSR 경계면에서의 물성을 밝히기 위하여 AVO 분석을 수행하였다. 탄성파 자료에 대하여 실진폭 회수, surface consistence amplitude 보정, 입사각 변환 등을 수행하고, 각각의 CDP 자료에 대하여 AVO 절편 및 AVO 기울기를 구하였다. AVO 절편의 단면도는 BSR 경계면에서 극성이 음이고 강한 반사도를 보이며 중합단면도보다 BSR 경계면의 연속성이 뚜렷하였다. AVO 분석자료를 P-G 도면으로 표시한 결과, BSR이 뚜렷한 곳의 하부에는 가스로 채워졌음을 시사한다.

• Geomechanics and Engineering
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• 제17권4호
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• pp.343-354
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• 2019

The present study demonstrates the application of seismic petrophysics and amplitude versus angle (AVA) forward modeling to identify the reservoir fluids, discriminate their saturation levels and natural gas composition. Two case studies of the Lumshiwal Formation (mainly sandstone) of the Lower Cretaceous age have been studied from the Kohat Sub-basin and the Middle Indus Basin of Pakistan. The conventional angle-dependent reflection amplitudes such as P converted P ($R_{PP}$) and S ($R_{PS}$), S converted S ($R_{SS}$) and P ($R_{SP}$) and newly developed AVA attributes (${\Delta}R_{PP}$, ${\Delta}R_{PS}$, ${\Delta}R_{SS}$ and ${\Delta}R_{SP}$) are analyzed at different gas saturation levels in the reservoir rock. These attributes are generated by taking the differences between the water wet reflection coefficient and the reflection coefficient at unknown gas saturation. Intercept (A) and gradient (B) attributes are also computed and cross-plotted at different gas compositions and gas/water scenarios to define the AVO class of reservoir sands. The numerical simulation reveals that ${\Delta}R_{PP}$, ${\Delta}R_{PS}$, ${\Delta}R_{SS}$ and ${\Delta}R_{SP}$ are good indicators and able to distinguish low and high gas saturation with a high level of confidence as compared to conventional reflection amplitudes such as P-P, P-S, S-S and S-P. In A-B cross-plots, the gas lines move towards the fluid (wet) lines as the proportion of heavier gases increase in the Lumshiwal Sands. Because of the upper contacts with different sedimentary rocks (Shale/Limestone) in both wells, the same reservoir sand exhibits different response similar to AVO classes like class I and class IV. This study will help to analyze gas sands by using amplitude based attributes as direct gas indicators in further gas drilling wells in clastic successions.

• 상하수도학회지
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• 제22권2호
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• pp.245-250
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• 2008

Adsorption experiment was carried out to find the adsorption capacity and characteristics of heavy metals(Cd, Pb) onto soil and mixed soil with food compost. Result showed that mixed soil having higher organic content adsorbed more heavy metal than soil, indicating that food compost can be used effectively to prevent soil pollution. Linear adsorption isotherm which adopted to find the adsorption characteristics was used to calculate Retardation Factor(R). The value of Retardation Factor(R)s of Pb and Cd in mixed soil, found as 34.54, 24.42 respectively, are higher than those in soil which were found as 4.64, 3.67, respectively. The value of Retardation Factor(R) using Freundlich adsorption isotherm could be presented by the functions of concentration and showed similar result as the linear one. But Freundlich adsorption isotherm showed higher relationship than linear one and the retardation factor(R) from freundlich adsorption isotherm was thought as more effective method to assess adsorption capacity because it could reflect gradient and intercept of the isotherm.

• Geomechanics and Engineering
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• 제19권5호
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• pp.435-445
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• 2019

A series of element tests with different drainage conditions and strain rates were performed on compacted unsaturated non-plastic silt in unconfined conditions. Soil samples were compacted at water contents from dry to wet of optimum with the degree of saturation varying from 24 to 59.5% while maintaining the degree of compaction at 80%. The tests performed were shear infiltration tests in which specimens had constant net confining pressure, pore air pressure was kept drained and constant, just before the shear process pore water pressure was increased (and kept constant afterwards) to decrease matric suction and to start water infiltration. In constant water content tests, specimens had constant net confining pressure, pore air pressure was kept drained and constant whereas pore water pressure was kept undrained. As a result, the matric suction varied with increase in axial strain throughout the shearing process. In both cases, maximum shear strength was obtained for specimens prepared on dry side of optimum moisture content. Moreover, the gradient of stress path was not affected under different strain rates whereas the intercept of failure was changed due to the drainage conditions implied in this study.

• 한국농림기상학회지
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• 제7권3호
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• pp.227-234
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• 2005

From published data of mature forests worldwide, Raich and Nadelhoffer suggested that total belowground carbon allocation (TBCA) could be estimated from the difference between annual rates of soil respiration and aboveground litterfall. Here we analyze new measurements of IRGA-based soil respiration and litterfall of natural mature oak forests dominated by Quercus mongolica in Korea. Rates of in situ soil respiration and aboveground litter production are highly and positively correlated. Our results disagree with the Raich and Nadelhoffer model far world forests. A regression analysis of the data from Q. mongolica forests produced the following relationship: annual soil respiration : 141 + 2.08 ${\times}$ annual litterfall. The least squares regression line has a more gentle slope (2.08) than the slope (2.92) described by Raich and Nedelhoffer for mature forests worldwide. The regression slope of our study indicates that, on average, soil respiration is about two times the aboveground litterfall-C, which further implies that TBCA is similar with annual aboveground litterfall-C at natural Q. mongolica forests in Korea. The non-zero Y-intercept (141) of the regression indicates that TBCA may be greater than litterfall-C where litterfall rate are relativery low. Over a gradient of litterfall-C ranging from 200-370 g C $m^{-2}yr^{-l}$, TBCA increased from 350-530 g C $m^{-2}yr^{-l}$.

• Steel and Composite Structures
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• 제19권6호
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• pp.1549-1560
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• 2015

This paper presents the characterization of fatigue crack in the A283 Grade C steel using the MMM method by identifying the effects of magnetic flux leakage towards the crack growth rate, da/dN, and crack length. The previous and current research on the relation between MMM parameters and fatigue crack effect is still unclear and requires specific analysis to validate that. This method is considered to be a passive magnetic method among other Non-Destructive Testing (NDT) methods. The tension-tension fatigue test was conducted with a testing frequency of 10 Hz with 4 kN loaded, meanwhile the MMM response signals were captured using a MMM instrument. A correlation between the crack growth rate and magnetic flux leakage produces a sigmoid shape curve with a constant values which present the gradient, m value is in the ranges of 1.4357 to 4.0506, and the y-intercept, log C in the ranges of $4{\times}10^{-7}$ to 0.0303. Moreover, a linear relation was obtained between the crack length and magnetic flux leakage which present the R-Squared values is at 0.830 to 0.978. Therefore, MMM method has their own capability to investigate and characterize the fatigue crack effects as a main source of fracture mechanism for ferrous-based materials.