• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.588-593
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• 2012

Compatibility of unsaturated polyester (UP) and low profile agent (LPA) of polystyrene (PS) have been investigated under various mixing conditions such as the ratio of UP and LPA, mixing time, mixing temperature, and input amount of 2nd UP. It was possible to obtain mixture with small particle size and low phase separation in condition of 35 g of LPA, 25 g of 1st UP input, 5 min of mixing time, 1700 rpm of mixing speed, and 45 g of 2nd UP input. It was found that compatibility of UP and LPA was very sensitive to mixing conditions. In addition, molded sample using sheet molding compound prepared by stable mixing condition appeared good properties such as low water adsorption, low shrinkage, and high gloss.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.2
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• pp.69-76
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• 2002

To study the behavior of $NH_4{^+}$ of CMS (condensed molasses solubles) in soil, a laboratory incubation experiment was conducted during a period of up to 21 days at $25^{\circ}C$. The $NH_4{^+}$ of CMS was labeled with $^{15}N$ and was applied to water-unsturated and water-saturated conditions. Soil pH was gradually decreased from 6.1 to 5.4 under unsaturated condition. However, soil pH was increased to 6.5 within 2 days under saturated condition and then was constant. The concentration of ammonium was decreased 3 times faster under unsaturated condition than under saturated condition. The concentration of nitrate was increased from 17.4 to $155.4mg\;kg^{-1}$ under unsaturated condition. But concentration of nitrate was kept with low(below $8.0mg\;kg^{-1}$) under saturated condition. During the incubation, 52.4% of $^{15}NH_4{^+}$ applied was existed in the form of $NO_3{^-}$ by nitrification under unsaturated condition. Most of applied nitrogen was immobilized within 4 days of incubation. On 21 days of the incubation the percentage of immobilized nitrogen derived from $^15NH_4{^+}$(NDFA) was 19.6% under unsaturated condition and 17.0% under saturated condition. The percentage of unaccounted N, which was lost by denitrification, was 28.4% under unsturated condition and 67.6% under saturated condition.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.1
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• pp.29-37
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• 2007

A conventional single compartment model cannot simulate reasonably the migration phenomenon of contaminants through unsaturated zone, due to the intrinsic unrealistic assumption of the compartment model that contaminants entering a compartment are immediately and uniformly mixed. Although, a multi-compartments model, in which even physically identical layer is divided into multiple compartments, may be used for explaining the retardation of contaminant mass flux along with increasing number of compartments, its numerical modeling is usually time-consuming and appropriate analytical solutions have not been reported yet. In order to improve the conventional compartment models on contaminant migration through unsaturated zone, a series of analytical solutions for multi-compartments model were derived and a generalized constraint under which the results from multi-compartments model can be simply approximated by single compartment model was proposed. The simplified approximation method was verified by a simple numerical analysis on the constraint under hypothetical conditions. It was also proved that the influent contaminant transfer rate from the bulk unsaturated zone can be generally represented into a time-dependent nominal transfer rate rather than a constant. In addition, the nominal transfer rate turned out to be very sensitive to the contaminant transfer rate between compartments in unsaturated zone, but to be almost insensitive to the transfer rate from contaminated zone. It is expected that the simplified approximation method developed in this study can be used for rapid and reasonable estimation of the migration phenomenon of contaminant through unsaturated zone, instead of time-consuming multi-compartments modeling.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.905-905
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• 2012

현재 도시유역의 홍수피해를 경감시키기 위한 방안으로 우수유출 저감시설에 대한 연구가 활발히 진행 중에 있다. 그러나 침투형 우수유출 저감시설의 경우 침투량 산정에 필요한 여러 인자 중 토성에 의해 저감 능력에 많은 차이를 보이고 있으며, 강우시 침투로 인한 토양내 함수비의 변화와 선행강우 조건 등에 의해 정량적인 분석이 어려워 활용도가 미흡한 실정이다. 따라서 본 연구에서는 2009년 국립방재연구원에서 시행한 침투실험 자료의 조건과 동일하게 투수계수 및 형상이 다른 두 종류의 투수성 보도블록 A, B와 토양내 선행강우의 유무에 대하여 표 1과 같이 검증 케이스로 구분하고, 4 가지의 강우강도로 모의 조건을 설정한 후 불포화 투수층의 침투해석을 실시하고 실험결과를 이용하여 모의결과에 대한 검증을 시행하였으며, 모의 결과의 검증을 뒷받침하기 위하여 통계적인 적합도를 나타내는 평균제곱오차(RMSE), 평균편차비율(PBIAS), 모형 효율성 계수(NSE), 지속성 모형효율성 계수(PME)을 산정해 보았다. 검증 결과 그림 1과 같이 투수성 보도블록 B의 형태가 투수성 보도블록 A의 형태보다 적합도가 높게 나타났고, 50mm/hr의 강우강도에서 변동성이 크게 나타났으나, 50mm/hr를 제외한 나머지 강우조건에서 양호한 적합도를 보였으며, 선행강우가 있는 조건이 선행강우가 없는 조건에 비해 높은 적합도를 나타내었다.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.89-98
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• 2008

In this study, the behaviour of an unsaturated soil was analyzed by performing $K_0$ consolidated triaxial tests. Unsaturated triaxial tests were performed with matric suctions for weathered soils and stress paths under consolidation and stress-strain relationships under shear were obtained. As a result, the $K_0$ value decreased as the matric suction increased. Besides, both isotropic and $K_0$ conditions had similar shear strength envelopes at the same matric suction. Especially, strength parameters could be obtained by stress variables used in the critical state theory more reasonably than by those of Mohr circles at failure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4D
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• pp.571-576
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• 2011

In general, conventional road pavements are designed under the assumption that the shear strength of geomaterials are under saturated state. In reality, however, most of the pavement geomaterials exists under the unsaturated state. To deal with this gap between saturated and unsaturated conditions, in this paper, unsaturated shear strength was estimated using the results from the triaxial compression test and soil-water characteristics curves. Then, yield loads were assessed using 2-Dimensional finite element method with the selected nonlinear elastic model and the Mohr-Coulomb yield criteria. In addition, various unsaturated condition and surface layer effects on the yield load of granular materials were identified. Therefore, the results demonstrated would provide a possibility to estimate bearing capacity of paved or unpaved roads using unsaturated soil mechanics.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.2
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• pp.119-131
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• 2020

A numerical model was developed using COMSOL Multiphysics to evaluate groundwater flow that causes radionuclide migration in the unsaturated zone of a near-surface disposal facility, which is considered as a domestic low and an intermediate-level radioactive waste disposal facility. Each scenario was modeled by constructing a two-dimensional domain that included the disposal vault, backfill, disposal cover, and unsaturated aquifer. A comparison of the continuous and intermittent rainfall conditions exhibited no significant difference in any of the factors considered except the wave pattern of water saturation. The input data, such as porosity and residual water content of the unsaturated aquifer, were observed to not have a significant effect on the groundwater flow. However, the hydraulic conductivity of the unsaturated aquifer was found to have a significant effect on the groundwater flow. Therefore, it is necessary to assess the hydraulic conductivity of an unsaturated aquifer to determine the extent of groundwater infiltration into the disposal vault.

• Journal of Aquaculture
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• v.2 no.1
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• pp.43-51
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• 1989

Fatty acid contents were measured in the cultures of the flagellate green algae Dunaliella tertiolecta Butcher under different conditions of light intensity, duration of light, and temperature. Duration of light and temperature, in particular, affected the growth rate of D. tertiolecta. The maximun cell number reached $2.32{\times}10^6$ cells/ml. The division rate per day was 1.97 in the exponential phase. The analysis of fatty acids obtained from various conditions showed that the lipid mainly contained C16, C18:3$\omega$3 fatty acids and there was no significant level of polyunsaturated fatty acids such as EPA and DHA. Polyene fatty acid increased with decreasing temperature and light intensity did not influence on fatty acid composition. The increasing duration of light enhanced the growth of D. tertiolecta, whereas polyene($\omega$3) slightly increased with decreasing the light period.

• Journal of the Korean Geotechnical Society
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• v.39 no.1
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• pp.15-25
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• 2023

Recent weather changes have led to an increase in heavy rainfall resulting in frequent large-scale slope failures. To minimize damage to life and property, a measurement system is used in slope failure warning systems. However, understanding the slope failure behavior is difficult as the measurement system only measures a specific point. Therefore, numerical analysis must be p erformed with the measurement system. The soil water characteristic curve (SWCC) drying curve and boundary conditions that consider evapotranspiration and precipitation have been applied to numerical analysis, but the hysteresis of SWCC affects the numerical analysis results. To address this, a new evapotranspiration calculation method is proposed and applied to boundary conditions, and the measurement data are compared with the results of the numerical analysis. This method takes into account the different infiltration behaviors on evapotranspiration according to the drying and wetting curves of the SWCC, and allows for a more rational prediction of water movement on unsaturated slopes.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.699-706
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• 1996

인자로 중대사고시 생성되는 흡습성(hygroscopic) 에어로졸의 거동을 해석적인 방법을 이용하여 분석하였다. 분석한 내용는 상대습도가 불포화, 포화, 과포화 조건에서 CsOH 에어로졸의 수증기 응축률, 입자성장에 따른 크기분포의 변화. 중력침전에 의한 전체 에어로졸량의 변화이다. 용질효과를 고려한 흡습성 에어로졸 모델을 사용한 경우 상대습도가 불포화 조건에서도 에어로졸 입자에 수증기 응축이 발생하며 입자의 크기가 평형반경에 달할 때까지 지속됨을 발견하였다. 이러한 입자 성장은 매우 빠른 입자크기분포 변화를 초래하여 중력침전에의한 급속한 에어로졸 감소를 초래하는 것으로 예측되었다. 따라서 현재 사용되고 있는 MELCOR 및 CONTAIN 코드는 흡습성 에어로졸에 대해서 용질효과를 고려한 모델을 사용하여야 할 것이다.