• Structural Engineering and Mechanics
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• 제3권5호
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• pp.429-443
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• 1995

The deformational response of plastic board drains installed to accelerate consolidation of soft soils, is examined as a problem of downdrag. The drain is modelled as a beam-column in which the axial load increases nonlinearly with depth. The soil response is represented by the Winkler medium whose coefficient of subgrade modulus increases linearly with depth. The governing equations for the drain-soil system are derived and solved as an eigenvalue problem. The critical buckling loads and the shape of the drain are obtained as functions of the normalized subgrade modulus of the soil at the top, the parameters signifying the variation of axial load along the length of the drain and the increase of subgrade modulus with depth. The derived deformed shapes of the drain are consistent with the observed ones.

• Archives of Pharmacal Research
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• 제8권2호
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• pp.67-75
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• 1985

To find emylase inhibitors produced by microorganisms from soil, a strain which had a strong inhibitory activity against bacteria .alpha.-amylase was isolated from the soil smaple collected in Seoul. The morphological and physiological characteristics of this strain on several media and its utilization of carbon sources showed that it was one of Streptomyces specties according to the international Streptomyces Project method. The amylase inhibitor of this strain was purified by means of acetone precipitation, adsorption on Amberlite XAD-2, and column chromatography on Amberlite CG-50 and SP-Sephadex C-25. The inhibitor was stable at the pH range of 1-10 and at 100.deg.C for half an hour, and had inhibitory activities against other amylases such as salivary .alpha.-amylase, pancreatic .alpha.-amylase, fungal .alpha.-amylase and glucoamylase. The kinetic studies of the inhibitor showed that its inhibitory effect on starch hydrolysis by .alpha.-amylase was non-competitive.

• 한국지하수토양환경학회지:지하수토양환경
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• 제17권4호
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• pp.73-80
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• 2012

The objectives of this research were to study the applicability and limitations of permeable reactive barrier (PRB) for the removal of tetrachloroethylene (PCE) from the groundwater. PRB column tests were conducted using reactive material with Moringa Oleifera Mass - Bentonite (Mom-Bentonite). Most of the PCE in the groundwater was degraded and/or captured (sorpted) in the zone containing activated material (MOM-Bentonite). The removal rate of PCE from the groundwater was 90% and 75% after 30 days and 180 days, respectively. The effect of micro-organisms on the long-term permeability and reactivity of the barrier is not well understood. MOM-Bentonite PRB system in this research has the potential to be developed into an environmentally and economically acceptable technology for the in situ remediation of PCE-contaminated groundwater.

• 한국환경농학회지
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• 제17권4호
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• pp.362-367
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• 1998

사양토, 양토, 식양토의 3가지의 토양을 2' column에 충진한 후 인공 산성비( pH 2.0, 4.0, 6.0) 1200㎜를 처리하여 산성비의 토양내 침투수량에 따른 토양 중 무기양분의 이동 양상과 토양내에서의 환경변화에 대한 시험 결과, 산성비의 토양침투에 따른 토양의 pH 변화는 산성비의 pH가 4.0가 6.0에서는 별 차이가 없었으나 pH2.0에서는 토심별로 큰 차이를 보였으며, pH감소는 사양토> 양토> 식양토 순위였다. 산성비의 토양침투에 따른 토양의 토심별 치환성과 수용성 염기의 용탈양은 Ca> Mg> K 순위였으며, 산성비의 pH2.0에서 가장 많은 양이 이동하였다. 이들 염기들의 평균이동거리를 pH2.0의 산성비 처리에서는 사양토, 양토, 식양토 공히 Mg> Ca> K의 순위였으나, 산성비의 pH4.0인 경우 사양토와 식양토는 Mg> K> Ca, 양토의 경우는 K> Mg> Ca의 순위였다. 인산의 경우 평균 이동거리는 다른 성분에 비하여 매우 짧았으며 산성비의 산도가 증가할수록 증가하였고, 일반 강우 조건에서는 거의 이동하지 않았다.

• Structural Engineering and Mechanics
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• 제49권1호
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• pp.95-110
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• 2014

The study deals with physical modeling of space frame-pile foundation and soil system using finite element models. The superstructure frame is analyzed using complete three-dimensional finite element method where the component of the frame such as slab, beam and columns are descretized using 20 node isoparametric continuum elements. Initially, the frame is analyzed assuming the fixed column bases. Later the pile foundation is worked out separately wherein the simplified models of finite elements such as beam and plate element are used for pile and pile cap, respectively. The non-linear behaviour of soil mass is incorporated by idealizing the soil as non-linear springs using p-y curve along the lines similar to that by Georgiadis et al. (1992). For analysis of pile foundation, the non-linearity of soil via p-y curve approach is incorporated using the incremental approach. The interaction analysis is conducted for the parametric study. The non-linearity of soil is further incorporated using iterative approach, i.e., secant modulus approach, in the interaction analysis. The effect the various parameters of the pile foundation such as spacing in a group and configuration of the pile group is evaluated on the response of superstructure owing to non-linearity of the soil. The response included the displacement at the top of the frame and bending moment in columns. The non-linearity of soil increases the top displacement in the range of 7.8%-16.7%. However, its effect is found very marginal on the absolute maximum moment in columns. The hogging moment decreases by 0.005% while sagging moment increases by 0.02%.

• 한국지하수토양환경학회지:지하수토양환경
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• 제7권2호
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• pp.13-22
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• 2002

본 연구에서는 토양에 오염된 디이젤 성분을 제거하기 위한 토양세척 기술 중에서 적절한 계면활성제를 사용하여 토양입자에 결합되어 있는 유해 유기물질의 표면장력을 약화시켜 제거하는 기술을 이용하기 위해 생분해성이 우수하고 2차 오염문제가 없는 생물계면활성제를 생산하였다. Peudomonas aeruginosa ATCC 9027를 이용하여 생산된 생물계면활성제인 rhamnolipid와 기존에 사용되고 있는 화학계면활성제와의 디이젤 세척효능을 비교분석하였다. 회분식, 연속식 세척실험 결과 디이젤 오염토양 초기농도 5,000ppm에서 계면활성제 1%, 세척시간 24시간 경과 후 본 연구에서 생산된 rhamnolipid의 세척효율이 모두 약 95%로 사용된 계면활성제 중에서 가장 우수한 세척효율을 보였다. 화학계면활성제들은 대부분 50∼80% 미만의 세척효율을 나타내었으며, HLB값이 8에서 15사이에서의 화학계면활성제의 경우 75%이상의 분해효율을 나타내었다. 그러나, HLB값이 8이하이거나 15이상에서는 60%이하의 낮은 디이젤 분해효율을 나타내었다.

• 한국토양환경학회지
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• 제2권3호
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• pp.59-67
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• 1997

다층토양구조에서 유기물과 토양의 깊이가 토양수 이동에 미치는 영향을 조사하기 위하여 풍건한 유기퇴비를 토양에 0, 2, 4, 6%로 처리한 단층과 다층 토양구조를 가진 토양칼럼을 이용하여 포화수리전도도를 측정하였다. 한편 측정된 수리전도도는 현장에서 실제 측정없이 적용하기 위하여 Jury가 제시한 효율적 수리전도도공식을 이용하여 환산한 후 이 수치를 실제값과 비교하여 보았다. 단층과 다층 토양구조의 수리전도도는 토양에 가해진 유기물 함량이 증가함에 따라 수리전도도는 급격히 감소하였으나 다층구조의 경우 토양칼럼의 길이가 길어짐에 따라 길이가 증가된 만큼의 점진적으로 수리전도도가 증가되는 것이 조사되었다. 그러므로 다층구조의 토양에서 실제의 수리전도도값을 얻기 위해서는 Jury 의 효율적 수리전도도공식의 변형이 필요하다.

• 분석과학
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• 제16권1호
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• pp.48-58
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• 2003

본 이화학적 특성이 다른 토양 중 PCBs 분석에 대해 연구하기 위해, 세 종류의 우리나라 토양을 선정하여 용매별 (톨루엔, 아세톤:헥산, 디클로로메탄) 추출효율을 조사하였다. 또한, 실리카겔, 플로리실 및 알루미나 정제 컬럼을 이용한 용출패턴 특성을 조사하였으며, 현재 이용되고 있는 미국, 일본 및 우리나라 PCBs 시험방법을 우리나라 토양에 적용하여 분석결과를 비교하였다. 토양 중 62종의 PCBs 용매별 추출효율은, 톨루엔의 경우 토양 A, 토양 B 및 토양 C에 대하여 평균회수율은 각각 77.94%, 53.65% 및 44.52%로 나타났다. 아세톤:헥산 (1:1)의 경우에는 토양에 따라 각각 58.59%, 80.32% 및 60.35%로 나타났으며, 디클로로메탄의 경우에는 각각 54.20%, 68.27% 및 56.36%로 나타났다. PCBs 분석을 위한 정제컬럼별 용출효율은, 실리카겔의 경우 1Cl에서 10Cl의 평균회수율이 89.67% (1Cl)~44.85% (8Cl)로 나타났으며, 플로리실의 경우 1Cl에서 10Cl의 평균 회수율은 67.00% (8Cl)~98.26% (10Cl)로 나타났다. 또한, 알루미나의 경우 알루미나 I은 1Cl에서 10Cl의 평균 회수율은 63.01% (9Cl)~88.17% (1Cl)로 나타났으며, 알루미나 II는 1Cl에서 10Cl의 평균 회수율은 61.40% (7Cl)~80.78% (1Cl)로 나타났다. 미국, 일본 및 본 연구의 시험방법을 비교한 결과, 토양 A에 대한 62종의 PCBs의 평균회수율은 각각 37.15%, 45.92% 및 44.46%로 나타났으나, 시험방법에 따라 개별 피이크의 회수율은 비교적 큰 차이를 보이고 있다.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 창립총회 및 춘계학술발표회
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• pp.101-107
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• 2000

Column tests using KCl and Benzene as tracers were conducted for four different cases: 1) no hydrogen peroxide and no microorganism; 2) hydrogen peroxide only; 3) microorganism only; 4) hydrogen and microorganism to investigate the sorption and degradation characteristics of Benzene. The observed BTCs of KCl and Benzene in all cases showed that the arrival times of the peaks of both tracers coincided well but the peak concentration of Benzene was much lower than that of KCl. This result reveals that a predominant process affecting the transport of Benzene in a sandy soil is an irreversible sorption and/or degradation rather than retardation. Decay of Benzene through sorption and degradation increased with the addition of hydrogen peroxide and/or microorganism. Dissolved oxygen decreased with the increase of Benzene in all cases indicating that Benzene was degraded by dissolved oxygen. For BTCs with the addition of microorganisms (case 3 and case 4), microorganism showed much lower concentrations compared to the initial levels and an increasing tendency with time although concentrations of Benzene returned to zero, indicating a possible retardation of microorganism due to reversible and irreversible sorption to the particle surfaces.

• 한국환경보건학회:학술대회논문집
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• 한국환경보건학회 2002년도 춘계 국제 학술대회
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• pp.9-12
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• 2002

Diffusive transport of volatile organic compounds(VOCs) and their degradation by bacteria in unsaturated soils are couple by poorly understood mass transfer kinetics at the gas/water interface. Determination of the fate of VOCs in unsaturated soil is necessary to evaluate the feasibility of natural attenuation as a VOC remediation strategy. The objective of this study was to develop a mechanistically based mathematical model that would consider the interdependence of VOC transport, microbial activity, and sorptive interaction in a moist, unsaturated soil. Because the focus of the model was on description of natural attenuation, the advective VOC transport that is induced in engineered remediation processes such as vapor extraction was not considered. The utility of the model was assessed through its ability to describe experimental observations form diffusion experiments using toluene as a representative VOC in well-defined soil columns that contained a toluene degrading bacterium, Pseudomonas Putida, as the sole active microbial species. The coefficient for gas-liquid mass-transfer, K$\sub$LA/, was found to be a key parameter controlling the ability of bacteria to degrade VOCs. This finding indicates that soil size and geometry are likely to be important parameters in assessing the possible success of natural attenuation of VOCs in contaminated unsaturated soils.