• Asian Journal of Atmospheric Environment
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• v.10 no.1
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• pp.42-50
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• 2016

This study presents a performance evaluation of four different land surface models (LSM) available in Weather Forecast Research (WRF). The research site was located in Haean Basin in South Korea. The basin is very unique by its geomorphology and topography. For a better representation of the complex terrain in the mesoscale model were used a high resolution topography data with a spatial resolution of 30 meters. Additionally, land-use layer was corrected by ground mapping data-sets. The observation equipments used in the study were an ultrasonic anemometer with a gas analyzer, an automatic weather station and a tethered balloon sonde. The model simulation covers a four-day period during autumn. The result shows significant impact of LSM on meteorological simulation. The best agreement between observation and simulation was found in the case of WRF with Noah LSM (WRF-Noah). The WRF with Rapid Update Cycle LSM (WRF-RUC) has a very good agreement with temperature profiles due to successfully predicted fog which appeared during measurements and affected the radiation budget at the basin floor. The WRF with Pleim and Xiu LSM (WRF-PX) and WRF with Thermal Diffusion LSM (WRF-TD) performed insufficiently for simulation of heat fluxes. Both overestimated the sensible and underestimated the latent heat fluxes during the daytime.

• Journal of Environmental Science International
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• v.11 no.1
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• pp.25-32
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• 2002

In order to control of water quality in Jeju harbor, variation of physical oceanographic environments was estimated using material cycle model. It is composed of the three-dimensional hydrodynamic model for the simulation at water flow and material cycle model for the simulation of water quality. The three dimensional hydrodynamic model simulation of the circulation and mixing in Jeju Harbor has been conducted forced by Sanzi River Discharge, Tidal elevation, wind and Solar heat in case of August and November, 2000 and February and May, 2001, respectively. The results of numerical model and observation show that the model can produce realistic results of current in the harbor. The monthly variation of velocity pattern are not so much changed are found In Jeju Harbor. The residual current was forced by temperature, salinity, density, wind and tidal current. The residual current of August, 2000 are the strongest among four month. It can be explained that the density effect can be important role in residual current at Jeju Harbor. As the results of salinity distribution simulation, very low concentration of all levels were simulated in August, 2000. The flowrate of Sanzi river was investigated 77,760 ㎥ /d in August, 2000. Therefore, pollutant loadings from Sanzi river should be considered for water quality management in Jeiu harbor.

• Journal of Environmental Science International
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• v.20 no.10
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• pp.1347-1355
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• 2011

In Jeju island, runoff has frequently happened when the rainfall depth is over a threshold value. To simulated this characteristic rainfall-runoff model structure has to be modified. In this study, the TRSM (Threshold Runoff Simulation Method) was developed to overcome the limitations of SWAT in applying to the hydrologic characteristics of Jeju island. When the precipitation and soil water are less than threshold value, we revised the SWAT routine not to make surface/lateral or groundwater discharge. For Hancheon watershed, the threshold value was set as 80% of soil water through the analysis of rainfall-runoff relationship. Through the simulation of test watershed, it was proven that TRSM performed much better in simulating pulse type stream flow for the Hancheon watershed.

• Atmosphere
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• v.17 no.4
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• pp.349-364
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• 2007

The main purpose of this study is to examine the sensitivity of the WRF (Weather Research and Forecasting) in the wind field to the steepness of mountains in the case with a strong downslope wind occurred in the Yeongdong province. We conducted WRF simulations for February 13 2006. The initial and boundary data are from the NCEP/NCAR $1^{\circ}{\times}1^{\circ}$ GDAS. Arbitrary terrains of the mountains with a symmetric orography and an asymmetric one with steeper leeward slope, were introduced to examine the sensitivity of the shape of the mountains. The simulation with an asymmetric terrain results in stronger maximum surface wind by about $10ms^{-1}$ than with a symmetric terrain, especially in the narrow region from the peak to ~ 4 km away in the downstream. However, the maximum surface wind speed is weaker by $20ms^{-1}$ than with a symmetric terrain away from the narrow peak region. This indicates that the steeper slope leads to the intensification of downslope wind in the narrower region leeward. In addition, for the simulation with an asymmetric terrain, the strength of wave breaking is greater and the Lee wave is more dominant than for that with a symmetric terrain.

• KIEAE Journal
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• v.16 no.1
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• pp.73-79
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• 2016

This study aimed to investigate the flood prevention effect expected from the afforestation of a large area metal roof of an industrial complex located in an area prone to floods in the rainwater outflow reduction aspect through computer simulation based on soil, which is a key element of the system. In order to conduct a more realistic simulation, the properties of the surveyed soil were generated through substantive analysis, soil texture analysis, and saxton method. A comparative performance evaluation was conducted by using soil depth and ponding depth, which are key elements of the system, as variables. The study result showed that during the heavy rainfall period, the bottom ash artificial soil had 61% rainwater outflow reduction effect, which was 11% higher than the SWMM standard sand.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.213-220
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• 2010

This study presents a numerical simulation model of vertical ground heat exchangers, considering unsaturated hydro static ground conditions induced by the ground water table fluctuation. Heat transfer in ground and grout is modeled by a 3-D FEM transient conductive heat transfer model, where heat transfer between circulating fluid and heat exchanging pipe is treated as 1-D quasi steady state forced convective elements. To take into account the unsaturated ground condition, soil thermal conductivity and heat capacity which are dependent on the matric suction are applied to ground elements. Parametric studies considering various ground water table conditions are conducted to investigate the influence of unsaturated hydro static ground condition on the mean heat exchange rate of ground heat exchanger. Simulation results considering water table fluctuation show 60~100% of mean heat exchange rate for a saturated soil condition and 125~208% of that for a dry soil condition. Thus consideration of unsaturated soil condition is substantially recommended for more accurate design and performance evaluation for ground heat exchangers.

• International Journal of Concrete Structures and Materials
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• v.10 no.3
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• pp.297-306
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• 2016

This paper developed an analytical software, called Simulation of Concrete Structures (SCS), which is used for numerical analysis of shear-critical prestressed steel fiber concrete structures. Based on the previous research at the University of Houston (UH), SCS has been derived from an object-oriented software framework called Open System for Earthquake Engineering Simulation (OpenSees). OpenSees was originally developed at the University of California, Berkeley. New module has been created for steel fiber concrete under prestress based on the constitutive relationships of this material developed at UH. This new material module has been integrated with the existing material modules in OpenSees. SCS thus developed has been used for predicting the behavior of the prestressed steel fiber concrete I-beams and Box-beams tested earlier in this research. The analysis could well predict the entire behavior of the beams including the elastic stiffness, yield point, post-yield stiffness, and maximum load for both web shear and flexure shear failure modes.

• Journal of Environmental Science International
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• v.18 no.4
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• pp.375-388
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• 2009

Numerical simulation is essential to indicate the flow of the atmosphere in the region with a complicated topography which consists of many mountains in the inland while it is neighboring the seashore. Such complicated topography produces land and sea breeze as the mesoscale phenomenon of meteorology which results from the effect of the sea and inland. In the mesoscale simulation examines, the change of the temperature in relation to the one of the sea surface for the boundary condition and, in the inland, the interaction between the atmosphere and land surface reflecting the characteristic of the land surface. This research developed and simulated PNULSM to reflect both the SST and vegetation effect as a bottom boundary for detailed meteorological numerical simulation in coastal urban area. The result from four experiments performed according to this protocol revealed the change of temperature field and wind field depending on each effect. Therefore, the lower level of establishment of bottom boundary suitable for the characteristic of the region is necessary to figure out the atmospheric flow more precisely, and if the characteristic of the surface is improved to more realistic conditions, it will facilitate the simulation of regional environment.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.5
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• pp.59-69
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• 2016

This study aims to evaluate the Soil and Water Assessment Tool (SWAT) hourly hydrological modeling performance and compare it with daily SWAT modeling parameters. For the Byeolmicheon catchment ($1.17km^2$) located in the upstream of Gyeongancheon watershed and total 18 storm events measured during 3 years (2011-2013), the hourly SWAT was calibrated and validated using the Green and Ampt (G&A) infiltration equation. The determination coefficient ($R^2$) and Nash-Sutcliffe model efficiency (NSE) of hourly SWAT discharge were 0.81 and 0.73 respectively, and the most sensitive parameter was soil saturated hydraulic conductivity (SOL_K) and calibrated with the average value of 0.075 mm/hr. In addition, the hourly SWAT simulation by G&A was compared with the daily SWAT simulation by SCS-CN (Soil Conservation Service-Curve Number) method for the whole 3 years period. The houlrly G&A results showed $R^2$ and NSE of 0.71 and 0.50, and the daily SCS-CN results were 0.71 and 0.66, respectively. The SOL_K by daily SCS_CN method was calibrated at 75.5 mm/hr, 1,000 times greater than the hourly G&A method. The next sensitive parameters for the hourly simulation were lag time of lateral flow (LAT_TIME) and lag time of surface runoff (SURLAG).

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.793-796
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• 1996

This study proposes a new algorithm which performs a production simulation under various constraints and maintains computational efficiency. In order to consider the environmental and operational constraints, the proposed algorithm is based on optimization techniques formulated in LP form In the algorithm, "system characteristic constraints" reflect the system characteristics such as LDC shape, unit loading order and forced outage rate. By using the concept of Energy Invariance Property and two operational rules i.e. Compliance Rule for Emission Constraint, Compliance Rule for Limited Energy of Individual Unit, the number of system characteristic constraints is appreciably reduced. As a solution method of the optimization problem, the author uses Karmarkar's method which performs effectively in solving large scale LP problem. The efficiency of production simulation is meaningful when it is effectively used in power system planning. With the proposed production simulation algorithm, an optimal expansion planning model which can cope with operational constraints, environmental restriction, and various uncertainties is developed. This expansion planning model is applied to the long range planning schemes by WASP, and determines an optimal expansion scheme which considers the effect of supply interruption, load forecasting errors, multistates of unit operation, plural limited energy plants etc.