• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.90-101
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• 2004

The present trend of disposing treated sewage water by allowing it to infiltrate the soil brings a new dimension to environmental problems. It is therefore necessary to identify the chemicals likely to be present in treated sewage water. A soil column experiment was conducted to determine the behavior of chemical species in soil columns applied with secondary treated sewage water. To predict the behavior of chemical species, a multicomponent solute transport model that includes the biochemical redox process and cation exchange process was developed. The model computes changes in concentration over time caused by the processes of advection, dispersion, biochemical reactions and cation exchange reactions. The solute transport model was able to predict the behavior of the different chemical species. The model reproduced the sequential reduction reaction. To design the safe depth of plow layer where $NO_3^-$ is totally reduced, a numerical study of $NO_3^-$ leach was done and it was found out that the pore velocity and concentration of $CH_2O$ at the inject water was found to affect $NO_3^-$ reduction in the mobile pore water phase. It is revealed that the multicomponent solute transport model is useful to design the land treatment system for $NO_3^-$ removal from wastewater.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.195-198
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• 2002

Nitrogen pollution in urban and rural groundwater is a common problem and poses a major threat to drinking water supplies based on groundwater. In this work, the kinetics of nitrification-denitrification coupled reactions are modeled and new reaction modules for the RT3D code (Clement, 1997) describing the fate and transport nitrogen species, dissolved oxygen, dissolved organic carbon, and biomass are developed. The proposed nitrogen transformations and transport model showed very good match with results of a conceptual model. However, the model simulation results for the major reactive species should be tested for validation using experimental and field data.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.430-433
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• 2003

Nitrogen pollution in urban and rural groundwater is a common problem and poses a major threat to drinking water supplies based on groundwater. In this work, the kinetics of nitrification-denitrification coupled reactions are modeled and new reaction modules for the RT3D code describing the fate and transport of nitrogen species, dissolved oxygen, dissolved organic carbon, and biomass are developed and tested. The proposed nitrogen transformations and transport model showed very good match with the results of other public codes.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.158-159
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• 2006

The resistance-capacitance (RC) delay of signals through interconnection materials becomes a big hurdle for high speed operation of semiconductors which contain multilayer interconnection layers. In order to reduce the RC delay, low-k materials will be used for inter-metal dielectric (IMD) materials. We have developed self-consistent simulation tool that includes neutral-species transport model, based on the relaxation continuum (RCT) model. We present the parametric study of the modeling results of a two-frequency capacitively coupled plasma (2f-CCP) with $N_2/H_2$ gas mixture that is known as promising one for organic low-k materials etching. We include the neutral transport model as well as plasma one in the calculation. The plasma and neutrals are calculated self-consistently by iterating the simulation of both species till a spatiotemporal steady state profile could be obtained.

• Journal of Korean Society on Water Environment
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• v.28 no.1
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• pp.26-37
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• 2012

Multi-dimensional hydrodynamic and water quality models are widely used to simulate the physical and biogeochemical processes in the surface water systems such as reservoirs and estuaries. Most of the models have adopted the Eulerian grid modeling framework, mainly because it can reasonably simulate physical dynamics and chemical species concentrations throughout the entire model domain. Determining the optimum grid cell size is important when using the Eulerian grid-based three-dimensional water quality models because the characteristics of species are assumed uniform in each of the grid cells and chemical species are represented by concentration (mass per volume). The objective of this study was to examine the effect of grid-size of a three dimensional hydrodynamic and water quality model (EFDC) on hydrodynamics and mass transport in the Saemangeum Reservoir. Three grid resolutions, respectively representing coarse (CG), medium (MG), and fine (FG) grid cell sizes, were used for a sensitivity analysis. The simulation results of numerical tracer showed that the grid resolution affects on the flow path, mass transport, and mixing zone of upstream inflow, and results in a bias of temporal and spatial distribution of the tracer. With the CG, in particular, the model overestimates diffusion in the mixing zone, and fails to identify the gradient of concentrations between the inflow and the ambient water.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.12
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• pp.601-605
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• 2006

The resistance-capacitance (RC) delay of signals through interconnection materials becomes a big hurdle for high speed operation of semiconductors which contain multi-layer interconnections in smaller scales with higher integration density. Low-k materials are applied to the inter-metal dielectric (IMD) materials in order to overcome the RC delay. Relaxation continuum (RCT) model that includes neutral-species transport model have developed to model the etching process in a capacitively coupled plasma (CCP) device. We present the parametric study of the modeling results of a two-frequency capacitively coupled plasma (2f-CCP) with $N_2/H_2$ gas mixture that is known as promising one for organic low-k materials etching. For the etching of low-k materials by $N_2/H_2$ plasma, N and H atoms have a big influence on the materials. Moreover the distributions of excited neutral species influence the plasma density and profile. We include the neutral transport model as well as plasma one in the calculation. The plasma and neutrals are calculated self-consistently by iterating the simulation of both species till a spatio-temporal steady state profile could be obtained.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.318-322
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• 2004

Arsenic is a toxic and carcinogenic metalloid, whose sources in nature include mineral dissolution and volcanic eruption. Abandoned mines and hazardous waste disposal sites are another major source of arsenic contamination of soil and aquatic systems. To predict concentrations of the toxic inorganic arsenic in aqueous phase. the biogeochemical redox processes and transport behavior need to be studied together and be coupled in a reactive transport model. A new reaction module describing the fate and transport of inorganic arsenic species (As(II)), dissolved oxygen, nitrate, ferrous iron, sulfate, and dissolved organic carbon are developed and incorporated into the RT3D code.

• Journal of computational fluids engineering
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• v.18 no.2
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• pp.9-16
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• 2013

The heat transfer enhancement of heat sink with mist flow is studied numerically by solving the conservation equations for mass, momentum and energy in the continuous and dispersed phases. A Lagrangian method is used for tracing dispersed water droplets in the heat sink and an Eulerian species transport model for air and steam mixture. The continuous and dispersed phases are interacted with the drag and evaporation source terms. The computed results show that addition of evaporating mist droplets enhances the cooling performance of heat sink significantly.

• Computers and Concrete
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• v.13 no.2
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• pp.149-171
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• 2014

This study presents the mathematical model for predicting chloride penetration into saturated concrete under non-isothermal condition. The model considers not only diffusion mechanism but also migration process of chloride ions and other chemical species in concrete pore solution such as sodium, potassium, and hydroxyl ions. The coupled multi-ionic transport in concrete is described by the Nernst-Planck equation associated with electro-neutrality condition. The coupling parameter taken into account the effect of temperature on ion diffusion obtained from available test data is proposed and explicitly incorporated in the governing equations. The coupled transport equations are solved using the finite element method. The numerical results are validated with available experimental data and the comparison shows a good agreement.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.2
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• pp.128-133
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• 2000

Numerical analysis of the transport phenomena in an inductively coupled plasma reactor was conducted with two-dimensional axisymmetric model including the electromagnetic field model, electron and species density models. The spatial distribution of the charged species in the ion flux to the wafer have been calculated to examine the influence of the process conditions including antenna and reactor geometry. The antenna radius had a significant influence on the plasma state and axial ion flux distribution.