• 자원환경지질
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• 제25권1호
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• pp.41-50
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• 1992

Mineral assemblages, mineral chemistries and stable isotope compositions of altered rocks of the Ogmae, Seongsan, Haenam and Gusi mines near the Haenam volcanic field in the southwestern part of the Korea peninsula were studied. Characteristic hydrothermal alteration zones in these deposits occurring in the Cretaceous volcanics and volcanogenic sediments, acidic tuff, and rhyolite, were outlined. Genetic environment with particular reference to the spatial and temporal relationships for these deposits were considered. The alteration zones defined by a mineral assemblage in the Ogmae and Seongsan deposits can be classified as alunite, pyrophyllite, kaolinite or dickite, quartz, illite or illite/smectite. Alunite was not developed in the Gusi and Haenam deposits. Boundaries between the adjacent zones are always gradational except for vein-type alunite. Alteration zones are superimposed upon each other in some localities. These deposits formed $71.8{\pm}2.8{\sim}76.6{\pm}2.9$ Ma ago, which is the almost same age of later volcanic rocks $79.4{\pm}1.7{\sim}82.8{\pm}1.2$ Ma, the Haenam Group, corresponding to Campanian. It indicates that hydrothermal alteration of these deposits appeared to be related to felsic volcanism in the area. Consideration of the stability between kaolinite, alunite, pyrite and pyrophyllite, and the geothermometry based on the mineral chemistry of illite and chlorite suggests that the maximum formation temperature for alunite and pyrophyllite can be estimated at about $250^{\circ}C$ and $240{\sim}290^{\circ}C$, respectively. It also suggests that these deposits were formed by acidic sulfate solution with high aqueous silica and potassium activity in a shallow depth environment. Compositional variation of alunite also suggests that the physico-chemical conditions fluctulated considerably during alteration processes, indicating shallow depth environment. The Haenam deposit was formed at a relatively greater depth than the others. The sulfur isotope composition of alunite and pyrite indicates that sulfur probably had a magmatic source, and the oxygen isotope composition for kaolinite indicates that the magmatic hydrothermal solution was diluted by circulating meteoric water.

• 한국지하수토양환경학회지:지하수토양환경
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• 제25권2_spc호
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• pp.16-27
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• 2020

Nitrate contamination has received much attention at local as well as regional scales. The domestic situation is not out of exception, and it has been reported to be very serious, particularly within agricultural areas as a result of excessive usage of nitrogen fertilizers. Meanwhile, nitrate can be naturally attenuated by denitrification in subsurface environments. The denitrification occurs through biotic (biological) and abiotic processes, and numerous previous studies preferentially focused the former. However, abiotic denitrification seems to be significant in specific environments. For this reason, this study reviewed the previous studies that focused on abiotic denitrification processes. Firstly, the current status of nitrate contamination in global and domestic scales is presented, and then the effect of geological media on denitrification is discussed while emphasizing the significance of abiotic processes. Finally, the implications of the literature review are presented, along with future research directions that warrant further investigations. The results of previous studies demonstrated that several geological agents could play a vital role in reducing nitrate. Iron-containing minerals such as pyrite, green rust, magnetite, and dissolved ferrous ion are known to be powerful electron donors triggering denitrification. In particular, it was proven that the rate of denitrification by green rust was comparative to that of biological denitrification. The results indicate that abiotic denitrification should be taken into account for more accurate evaluation of denitrification in subsurface environments.

• 기술사
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• 제44권1호
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• pp.44-47
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• 2011

Huge amount of energy produced by an underground nuclear test is released into the surrounding rock. Depending on the properties of the bed rock surrounding the detonation and overlaying it a variety of effects can occur. At some particular depth the increasing amount of material thrown upward is exactly balanced by the decreasing fraction escaping the crater, the crater volume reaches to a maximum. This depth is called the optimum depth of burial and varies somewhat with the geology of the site, being greater for less dense and structurally weaker material.

• Geomechanics and Engineering
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• 제15권5호
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• pp.1071-1080
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• 2018

The study of behavior and values of deformations in the geological medium makes the scientific basis of the methodology of synthesis of true values of parameters of its physico-mechanical and density properties taking into account the influence of geodynamic impacts. The segments of continuous variation of homogeneous elastic uniform deformations are determined under overall compression of the medium. The limits of these segments are defined according to the criteria of instability (on geometric form changes and on "internal" instability). Analytical formulae are obtained to calculate current and limiting (critical) values of deformations within the framework of various variants of small and large initial deformations of the non-classically linearized approach of non-linear elastodynamics. The distribution of deformation becomes non-uniform in the medium while the limiting values of deformations are achieved. The proposed analytical formulae are applicable only within homogeneous distribution of deformations. Numerical experiments are carried out for various elastic potentials. It is found that various forms of instability can precede phase transitions and destruction. The influence of these deformation phenomena should be removed while the physico-mechanical and density parameters of the deformed media are determined. In particular, it is necessary to use the formulae proposed in this paper for this purpose.

• 지질공학
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• 제19권1호
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• pp.1-8
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• 2009

지구물리 탐사는 대전대학교에 위치한 자연사면의 상부에서 2개 측선을 실시하였다. 전기비저항 탐사와 탄성파 굴절법 탐사는 천부에 퍼한 지층 경계, 풍화대 지역 및 지질 특성을 파악하기 위해 실시한 반면, AMT 탐사는 비교적 깊은 심도에 대한 정보를 얻기 위해 측선 2에서 병행하였다. 탐사 결과를 보면, 전기비저항 탐사와 탄성파 굴절법 탐사는 찾고자 하는 지질 특성에 관련하여 서로 일치하는 양상으로 나타났으며, AMT 탐사는 전반적인 기반암의 분포와 파쇄대에 대한 영상을 제시하였다. 그러므로 자연사면에서 복합 물리탐사의 적용은 지하 구조에 대해 상세한 정보를 제공하므로, 이를 통해 사면붕괴에 대해 보다 정확한 해석을 할 수 있다.

• 지질공학
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• 제20권3호
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• pp.271-279
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• 2010

광물의 용해현상과 밀접하게 관련된 암석의 시간의존성 변형과 파괴현상은 실내시험에서 비교적 용이하게 관찰된다. 본 연구에서는 고준위 방사성폐기물의 지하 처분장 건설시 완충제로 사용되어지는 벤토나이트에 많이 포함된 석영의 고 알칼리 환경 하에서의 용해 현상을 정량적으로 관찰하기 위해서 수산화 이온의 확산과 석영의 용해 문제를 균질화 해석법을 이용하여 평가하였다. 해석결과에 의하면 석영의 용해량은 주변 환경의 온도 및 층간수의 두께와 비례한다. 특히 고알칼리 환경 하에서는 층간수의 두께가 작아지면서 반응표면적이 커지게 되고 그 결과 용해 속도는 층간수의 두께가 작아질수록 커지는 결과를 나타내고 있다.

• Journal of Microbiology and Biotechnology
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• 제23권5호
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• pp.602-613
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• 2013

This paper aims at an investigation of the features of bacterial communities in surface sediments of the South China Sea (SCS). In particular, biogeographical distribution patterns and the phylogenetic diversity of bacteria found in sediments collected from a coral reef platform, a continental slope, and a deep-sea basin were determined. Bacterial diversity was measured by an observation of 16S rRNA genes, and 18 phylogenetic groups were identified in the bacterial clone library. Planctomycetes, Deltaproteobacteria, candidate division OP11, and Alphaproteobacteria made up the majority of the bacteria in the samples, with their mean bacterial clones being 16%, 15%, 12%, and 9%, respectively. By comparison, the bacterial communities found in the SCS surface sediments were significantly different from other previously observed deep-sea bacterial communities. This research also emphasizes the fact that geographical factors have an impact on the biogeographical distribution patterns of bacterial communities. For instance, canonical correspondence analyses illustrated that the percentage of sand weight and water depth are important factors affecting the bacterial community composition. Therefore, this study highlights the importance of adequately determining the relationship between geographical factors and the distribution of bacteria in the world's seas and oceans.

• Journal of Astronomy and Space Sciences
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• 제37권1호
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• pp.19-27
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• 2020

Pc1 pulsations are important to consider for the interpretation of wave-particle interactions in the Earth's magnetosphere. In fact, the wave properties of these pulsations change dynamically when they propagate from the source region in the space to the ground. A detailed study of the wave features can help understanding their time evolution mechanisms. In this study, we statistically analyzed Pc1 pulsations observed by a Bohyunsan (BOH) magneto-impedance (MI) sensor located in Korea (L = 1.3) for ~one solar cycle (November 2009-August 2018). In particular, we investigated the temporal occurrence ratio of Pc1 pulsations (considering seasonal, diurnal, and annual variations in the solar cycle), their wave properties (e.g., duration, peak frequency, and bandwidth), and their relationship with geomagnetic activities by considering the Kp and Dst indices in correspondence of the Pc1 pulsation events. We found that the Pc1 waves frequently occurred in March in the dawn (1-3 magnetic local time (MLT)) sector, during the declining phase of the solar cycle. They generally continued for 2-5 minutes, reaching a peak frequency of ~0.9 Hz. Finally, most of the pulsations have strong dependence on the geomagnetic storm and observed during the early recovery phase of the geomagnetic storm.

• 지질공학
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• 제4권2호
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• pp.207-218
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• 1994

가동 코일형으로 수진기의 고유정수를 free impedance와 step force법에 의해 결정할 수 있다. 전자의 방법으로는 수진기의 고유주파수($f_o$)와 감쇠정수($h_o$)와 motinal impedance로 부터 관성질량(m) 등을, 후자의 방법으로는 감도(G)를 결정하는 것이 바람직하다. 특히 후자의 방법에 의한 측정에서 측정 시스템을 자체의 고유한 장적기에 의한 잠음발생 문제를 보정해야 한다. 이들의 수진기 고유정수로부터 주파수 특성분석, 즉 위상특성과 진폭특성을 분석한 결과, 고유주파수를 경계로하여 수진기가 가속도계와 변위계로 작용함을 알 수 있다.

• 한국수산과학회지
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• 제37권4호
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• pp.312-322
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• 2004

Physical and geoacoustic properties of inner shelf sediment in the South and Southeastern Seas of Korea have been studied based on six piston core samples. The sediments are largely composed of homogeneous mud except the core from the southeasternmost part of the area. Both physical and geoacoustic properties and mean grain size are relatively uniform with sediment depth, suggesting little effect of sediment compaction and/or consolidation. Mean grain size appears to be the most Important variable to determine the physical and acoustic properties. In contrast, the attenuation shows more or less fluctuations. Correlations between physical properties and sediment texture show slight deviations from those of the compared data, caused by the difference of sedimentary processes, mineral composition, and the difference of measurement system. In particular, the velocity is lower (approximately 20-30 m/s) than that of the previous data measured in the same area. This is probably due to the difference in velocity measurement system (particularly, error by a length of sample). We propose new relationships for physical and geoacoustic characteristics of shelf sediment in the study area.