• 한국농공학회:학술대회논문집
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• 한국농공학회 2002년도 학술발표회 발표논문집
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• pp.297-300
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• 2002

Semi-two dimension numerical models were applied to study on the hydraulic and sedimentologic characteristics of upstream and downstream channel section in Dal stream. The feature of this paper is (1) to analyse the effects of bed changes by sediment transport formulas, (2) to analyse the effects of bed changes by stream tube. The simulation results of Meyer-peter and Muller formula for long-term bed changes are good when compared to the measured data.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 추계학술발표회
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• pp.282-284
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• 2003

Multi-phase extraction of LNAPLs not only floating on groundwater but also captured in soil pores was studied in a simulated soil system. The extraction rate of LNAPL under the MPE conditions was much higher than the rate under usual hydraulic gradient conditions. The WE might be especially useful for recovery of oils in fine-textured soils such as clay-dominant soils. The vacuum-enhanced transport of LNAPL in soils also depended on the properties of LNAPL such as viscosity and density as well as soil textures.

• Environmental Engineering Research
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• 제11권5호
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• pp.241-249
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• 2006

A mathematical model is described for the prediction of convective upward transport of an organic solvent driven by evaporation at the surface, which is known as the major transport mechanism in the in-situ photolysis of a soil contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD). A finite-element model was proposed to incorporate the effects of multiphase flow on the distribution of each fluid, gravity as a driving force, and the use of hysteretic models for more accurate description of k-S-p relations. Extensive numerical calculations were performed to study fluid flow through three types of soils under different water table conditions. Predictions of relative permeability-saturation-pressure (k-S-p) relations and fluids distribution for an illustrative soil indicate that hysteresis effects may be quite substantial. This result emphasizes the need to use hysteretic models in performing flow simulations including reversals of flow paths. Results of additional calculations accounting for hysteresis on the one-dimensional unsaturated soil columns show that gravity affects significantly on the flow of each fluid during gravity drainage, solvent injection, and evaporation, especially for highly permeable soils. The rate and duration of solvent injection also have a profound influence on the fluid saturation profile and the amount of evaporated solvent. Key factors influencing water drainage and solvent evaporation in soils also include hydraulic conductivity and water table configuration.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권1호
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• pp.65-75
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• 2015

An artificial recharge test aimed at investigating transport characteristics of the injected water plume in a fractured rock aquifer was conducted. The test used an injection well for injecting tap water whose temperature and electrical conductivity were different from the groundwater. Temporal and depth-wise variation of temperature and electrical conductivity was monitored in both the injection well and a nearby observation well. A highly permeable fracture zone acting as the major pathway of groundwater flow was distinctively revealed in the monitoring data. A finite element subsurface flow and transport simulator (FEFLOW) was used to investigate sensitivity of the transport process to associated aquifer parameters. Simulated results showed that aperture thickness of the fracture and the hydraulic gradient of groundwater highly affected spatio-temporal variation of temperature and electrical conductivity of the injected water plume. The study suggests that artificial recharge of colder water in a fractured rock aquifer could create a thermal plume persistent over a long period of time depending on hydro-thermal properties of the aquifer as well as the amount of injected water.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권2호
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• pp.41-46
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• 2015

The drag of the excess charge in an electrical double layer at the solid fluid interface due to water flow induces the streaming current, i.e., the streaming potential (SP). Here we introduce a sandbox experiment to study this hydroelectric coupling in case of a tracer test. An acrylic tank was filled up with homogeneous sand as a sand aquifer, and the upstream and downstream reservoirs were connected to the sand aquifer to control the hydraulic gradient. Under a steady-state water flow condition, a tracer test was performed in the sandbox with the help of peristaltic pump, and tracer samples were collected from the same interval of five screened wells in the sandbox. During the tracer test, SP signals resulting from the distribution of 20 nonpolarizable electrodes were measured at the top of the tank by a multichannel meter. The results showed that there were changes in the observed SP after injection of tracer, which indicated that the SP was likely to be related to the solute transport.

• Environmental Engineering Research
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• 제23권4호
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• pp.462-473
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• 2018

The uranium ore residues from the legacies of past uranium mining and milling activities that resulted from the less stringent environmental standards along with the uranium residues from the existing nuclear power plants continue to be a cause of concern as the final uranium residues are not made safe from radiological and general safety point of view. The deposition of uranium in ponds increases the risk of groundwater getting contaminated as these residues essentially leach through the upper unsaturated geological formation. In this context, a numerical model has been developed in order to forecast the $^{238}U$ and its progenies concentration in an unsaturated soil. The developed numerical model is implemented in a hypothetical uranium tailing pond consisting of sandy soil and silty soil types. The numerical results show that the $^{238}U$ and its progenies are migrating up to the depth of 90 m and 800 m after 10 y in silty and sandy soil, respectively. Essentially, silt may reduce the risk of contamination in the groundwater for longer time span and at the deeper depths. In general, a coupled effect of sorption and hydro-geological parameters (soil type, moisture context and hydraulic conductivity) decides the resultant uranium transport in subsurface environment.

• 방사성폐기물학회지
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• 제21권1호
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• pp.175-182
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• 2023

APro, a modularized process-based total system performance assessment framework, was developed at the Korea Atomic Energy Research Institute (KAERI) to simulate radionuclide transport considering coupled thermal-hydraulic-mechanical-chemical processes occurring in a geological disposal system. For reactive transport simulation considering geochemical reactions, COMSOL and PHREEQC are coupled with MATLAB in APro using an operator splitting scheme. Conventionally, coupling is performed within a MATLAB interface so that COMSOL stops the calculation to deliver the solution to PHREEQC and restarts to continue the simulation after receiving the solution from PHREEQC at every time step. This is inefficient when the solution is frequently interchanged because restarting the simulation in COMSOL requires an unnecessary setup process. To overcome this issue, a coupling scheme that calls PHREEQC inside COMSOL was developed. In this technique, PHREEQC is called through the "MATLAB function" feature, and PHREEQC results are updated using the COMSOL "Pointwise Constraint" feature. For the one-dimensional advection-reaction-dispersion problem, the proposed coupling technique was verified by comparison with the conventional coupling technique, and it improved the computation time for all test cases. Specifically, the more frequent the link between COMSOL and PHREEQC, the more pronounced was the performance improvement using the proposed technique.

• Ecology and Resilient Infrastructure
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• 제1권1호
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• pp.8-18
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• 2014

본 연구에서는 수공구조물 하류에서의 하천흐름 특성을 3차원 수치모형인 Delft3D 모형을 이용하여 분석하고, 하천흐름 특성을 분석한 결과를 기반으로 홍수시에 어류의 피난처를 예측하였다. 수공구조물은 통수단면적을 변화시키고 유속과 수심을 변화시켜서 어류활동에 영향을 준다. 대상유역인 구미보 직하류에서는 흐름의 중심이 되는 저수로가 좌안으로 집중되면서 우안에서 수심이 낮고, 유속이 느리게 나타나서 어류의 피난처 형성은 우안을 중심으로 발생하였다. 어류의 활동범위를 분석하기 위해 수직방향 유속을 비교한 결과, 30년 빈도와 50년 빈도 경우 우안에서 최대 0.0043 m/s, 0.0052 m/s로 나타났고, 80년 빈도와 100년 빈도는 좌안에서 최대 0.0046 m/s, 0.0039 m/s로 나타났다. 또한 유량이 증가함에 따라 수심이 깊어지고 난류에너지가 상승하여 어류의 피난처가 감소되었다. 30년 빈도 홍수량와 100년 빈도 홍수량에 대하여 어류의 피난처를 비교하면 우안에 형성되는 어류의 피난처 예상 면적이 61.5%에서 39.0%으로 감소하였다.

• 대한지하수환경학회지
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• 제4권1호
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• pp.54-59
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• 1997

하천 주변의 쓰레기 매립장 등과 같은 오염원은 하천수와 지하수의 오염을 야기시킨다. 하천 수위의 영향을 받는 하천구역에서 오염원의 이동과 대수층 특성과의 반응을 고찰하였다. 이를 위해 하천 수위의 변화에 따른 변동속도 성분을 지하수의 지배방정식에 대한 해석해를 이용하여 유도하였다. 변동 속도 성분을 고려하여 이송확산방정식에 대한 수치모형을 구성하였으며 구성된 수치 모형의 타당성을 위해 해석해와 비교한 결과 거의 일치하였다. 수치실험을 위한 자료는 난지도의 대수층 특성값을 이용하였다. 대수층 특성값에 대한 범위를 설정하고 이를 이용하여 하천 수위와 오염원의 이동에 대한 반응을 고찰한 결과, 저류계수를 제외한 수리전도도와 유효공극율은 오염원의 이동에 대한 반응이 미소하게 나타났다. 그리고 하천 수위의 변화에 민감한 반응을 나타낸 경우는 저류계수가 $10^{-2}$ 차수임을 알았다.

• 한국해양공학회지
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• 제22권6호
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• pp.88-94
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• 2008

The concentration of atmospheric carbon dioxide (CO2), which is one of the major greenhouse gases, continues to rise with the increase in fossil fuel consumption. In order to mitigate global warming the amount of CO2 discharge to the atmosphere must be reduced. Carbon dioxide capture and storage (CCS) technology is now regarded as one of the most promising options. To complete the carbon cycle in a CCS system, a huge amount of captured CO2 from major point sources such as power plantsshould be transported for storage into the marine or ground geological structures. Since 2005, we have developed technologies for marine geological storage of CO2,including possible storage site surveys and basic design of CO2 transport and storage process. In this paper, the design parameters which will be useful to construct on-shore and off-shore CO2 transport systems are deduced and analyzed. To carry out this parametric study, we suggested variations in thedesign parameters such as flow rate, diameter, temperature and pressure, based on a hypothetical scenario. We also studied the fluid flow behavior and thermal characteristics in a pipeline transport system.