• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.48 no.1
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• pp.40-50
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• 2012

This study aims to analyze the performance of a submersible fish cage which was designed for developing an economical cage system can be applied in korean aquaculture environment easily. To analyze the performance of the designed cage a model test was carried out. In the test, inclination changes of the upper frame and mooring tensions of model cage were measured during the submerging and surfacing motion in still water and wave condition (period: 2s, wave height: 0.1, 0.2, 0.3m). As a result, in the still water condition the model cage kept horizontal balance and inclination degree of the upper frame was about $1^{\circ}$. In the wave condition, the model cage showed bilateral symmetric up-and-down motion but the average inclination degree of the upper frame was about $0^{\circ}$. When the model cage reached at a depth of 1m, the up-and-down motion of the cage was decreased by 12% compared with that of at the surface (period 2s, height 0.3m). In the same wave condition, the maximum and average line tension under the bottom position were about 8% and 11% respectively compared with that of at surface.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.3
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• pp.19-29
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• 2014

This study was to evaluate the potential climate change impact on watershed hydrological components of evapotranspiration, surface runoff, lateral flow, return flow, and streamflow using Soil and Water Assessment Tool (SWAT). For Yongdam dam watershed (930 $km^2$), the SWAT model was calibrated for five years (2002-2006) and validated for three years (2004-2006) using daily streamflow data at three locations and daily soil moisture data at five locations. The Nash-Sutcliffe model efficiency (NSE) and coefficient of determination ($R^2$) were 0.43-0.67 and 0.48-0.70 for streamflow, and 0.16-0.65 and 0.27-0.76 for soil moisture, respectively. For future evaluation, the HadGEM3-RA climate data by Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios were adopted. The biased future data were corrected using 30 years (1982-2011, baseline period) of ground weather data. The HadGEM3-RA 2080s (2060-2099) temperature and precipitation showed increase of $+4.7^{\circ}C$ and +22.5 %, respectively based on the baseline data. The impacts of future climate change on the evapotranspiration, surface runoff, baseflow, and streamflow showed changes of +11.8 %, +36.8 %, +20.5 %, and +29.2 %, respectively. Overall, the future hydrologic results by RCP emission scenarios showed increase patterns due to the overall increase of future temperature and precipitation.

• Journal of the Korean Chemical Society
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• v.51 no.1
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• pp.21-30
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• 2007

A multiwavelength spectrophotometric titration method was applied to study protolytic constants of four water-soluble vitamins, folic acid(vitamin B9 or B0), thiamine(vitamin B1), riboflavin(vitamin B2) and pyridoxal (vitamin B6) in binary ethanol-water mixtures at 25oC and an ionic strength of 0.1M NaNO3. The protolytic equilibrium constants, spectral profiles, concentration diagrams and also the number of components has been calculated from the curve fitting of the pH-absorbance data with appropriate mass balance equations by an established factor analysis model. DATAN program was used for determination of acidity constant and SPECFIT program was used for calculation of standard deviations and partial correlation coefficients. A glass electrode calibration procedure based on the four parameter equation pH=α+SpcH+JH+[H+]+ JOH-Kw/[H+] based on the Gran,s plots was used to obtain pH-readings in the concentration scale (pcH). The effect of the solvent on the protolytic constants was discussed.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.5
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• pp.31-40
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• 2017

The aim of this study is to estimate net irrigation requirements for red pepper during growing period using soil moisture model. The soil moisture model based on water balance approach simulates soil moisture contents of 4 soil layers in crop root zone considering soil moisture extraction pattern. The LAMP (Land-Atmosphere Modeling Package) high resolution meteorological data provided from National Center for AgroMeteorology (NCAM) was used to simulate soil moisture as the input weather data. Study area for the LAMP data and soil moisture simulation covers $36.92^{\circ}{\sim}37.40^{\circ}$ in latitude and $127.36^{\circ}{\sim}127.94^{\circ}$ in longitude. Soil moisture was monitored using FDR (Frequency Domain Reflectometry) sensors and the data were used to validate the simulation model from May 24 to October 20 in 2016. The results showed spatially detailed soil moisture pattern under different weather conditions and soil texture. Net irrigation requirements were also different by location reflecting the spatially distributed weather condition. The average of the requirements was 470.7 mm and averages about soil texture were 466.8 mm, 482.4 mm, 456.0 mm, 481.7 mm, and 465.6 mm for clay loam, sandy loam, silty clay loam, clay, and sand respectively. This study showed spatial differences of soil moisture and the irrigation requirements of red pepper about spatially uneven weather condition and soil texture. From the results, it was demonstrated that high resolution meteorological data could provide an opportunity of spatially different crop water requirement estimation during the irrigation management.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.4
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• pp.21-35
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• 2016

This study is to evaluate the applicability of SWAT (Soil and Water Assessment Tool) model for multi-purpose dams and multi-function weirs operation in Namhan river basin ($12,577km^2$) of South Korea. The SWAT was calibrated (2005 ~ 2009) and validated (2010 ~ 2014) considering of 4 multi-purpose dams and 3 multi-function weirs using daily observed dam inflow and storage, evapotranspiration, soil moisture, and groundwater level data. Firstly, the dam inflow was calibrated by the five steps; (step 1) the physical rate between total runoff and evapotranspiration was controlled by ESCO, (step 2) the peak runoff was calibrated by CN, OV_N, and CH_N, (step 3) the baseflow was calibrated by GW_DELAY, (step 4) the recession curve of baseflow was calibrated by ALPHA_BF, (step 5) the flux between lateral flow and return flow was controlled by SOL_AWC and SOL_K, and (step 6) the flux between reevaporation and return flow was controlled by REVAPMN and GW_REVAP. Secondly, for the storage water level calibration, the SWAT emergency and principle spillway were applied for water level from design flood level to restricted water level for dam and from maximum to management water level for weir respectively. Finally, the parameters for evapotranspiration (ESCO), soil water (SOL_AWC) and groundwater level fluctuation (GWQMN, ALPHA_BF) were repeatedly adjusted by trial error method. For the dam inflow, the determination coefficient $R^2$ was above 0.80. The average Nash-Sutcliffe efficiency (NSE) was from 0.59 to 0.88 and the RMSE was from 3.3 mm/day to 8.6 mm/day respectively. For the water balance performance, the PBIAS was between 9.4 and 21.4 %. For the dam storage volume, the $R^2$ was above 0.63 and the PBIAS was between 6.3 and 13.5 % respectively. The average $R^2$ for evapotranspiration and soil moisture at CM (Cheongmicheon) site was 0.72 and 0.78, and the average $R^2$ for groundwater level was 0.59 and 0.60 at 2 YP (Yangpyeong) sites.

• Korean Journal of Environmental Agriculture
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• v.8 no.1
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• pp.30-36
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• 1989

To determine irrigated water temperature under the rice plant canopy, micrometeorological elements air temperature, relative humidity, water temperature, solar radiation, and the rice leaf area index the rice plant canopywere measured. Water temperature under the canopy was also estimated from these data. The results are as follows ; 1. Maximum and minimum temperatures of water in the paddy field were higher about $1-2^{\circ}C$ than those of air temperature. 2. Mean water temperature under the canopy became lower than mean air temperature when the leaf area indices were greater than 4, because of decreased light penetration rates 3. Penetration amounts of net radiation under the canopy can be estimated by an exponential equation 4. Estimated water temperatures under the canopy by a combination method model was adaptable in Suweon, a plain area, but its accuracy was lower in Jinbu, an alpine area.

• Journal of Korea Water Resources Association
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• v.42 no.1
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• pp.21-31
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• 2009

The characteristics, intensity and direction of groundwater.surface water interactions are controlled by groundwater head gradients, hydraulic conductivity and by the riverbed geometry. As a result of the spatial heterogeneity of these factors and the subsequent variability of the impact of these interaction processes, the water balance is also characterized by highly variable spatial patterns and temporal dynamics. However, spatially detailed studies concerning the spatio-temporal variability of the extent and intensity of surface-groundwater interactions have been limited to the investigation of cross-sections or small stream reaches. Thus, the extensive study on the watershed based interaction between surface water and groundwater is to be analyzed. In this study, the intensity and the spatial extent of interactions along the stream were found by using integrated SWAT-MODFLOW model. This integrated modeling approach was applied to Anyangcheon watershed in Korea. The effluent stream characteristics were found in the watershed, namely, baseflow was annually discharged except heavy rainy periods. The intensity and the spatial extent of surface-groundwater interactions in different sub-watersheds were found on a daily basis. The influential extent of surface-groundwater interaction become larger as the watershed elevations are lower.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.161-176
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• 2021

In this study, one of the distributed hydrologic models, VELAS, was used to analyze the variation of hydrologic elements based on water balance analysis to evaluate the groundwater recharge in more detail than the annual time scale for the past and future. The study area is located in Yanggok-ri, Seobu-myeon, Hongseong-gun, Chungnam-do, which is very vulnerable to drought. To implement the VELAS model, spatial characteristic data such as digital elevation model (DEM), vegetation, and slope were established, and GIS data were constructed through spatial interpolation on the daily air temperature, precipitation, average wind speed, and relative humidity of the Korea Meteorological Stations. The results of the analysis showed that annual precipitation was 799.1-1750.8 mm, average 1210.7 mm, groundwater recharge of 28.8-492.9 mm, and average 196.9 mm over the past 18 years from 2001 to 2018 in the study area. Annual groundwater recharge rate compared to annual precipitation was from 3.6 to 28.2% with a very large variation and average 14.9%. By the climate change RCP 8.5 scenario, the annual precipitation from 2019 to 2100 was 572.8-1996.5 mm (average 1078.4 mm) and groundwater recharge of 26.7-432.5 mm (average precipitation 16.2%). The annual groundwater recharge rates in the future were projected from 2.8% to 45.1%, 18.2% on average. The components that make up the water balance were well correlated with precipitation, especially in the annual data rather than the daily data. However, the amount of evapotranspiration seems to be more affected by other climatic factors such as temperature. Groundwater recharge in more detailed time scale rather than annual scale is expected to provide basic data that can be used for groundwater development and management if precipitation are severely varied by time, such as droughts or floods.

• Korean Journal of Agricultural Science
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• v.14 no.1
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• pp.68-80
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• 1987

This study was carried out to investigate the evapotranspiration and variations of soil moisture contents for soybeans. The relationship between actual evapotranspiration obtained by the water balance equation and estimated evapotranspiration obtained by the soil moisture model was analyzed. The results obtained were summarized as follows; 1. The total amount of actual evapotranspiration of soybeans during growing season was 405.7mm. The total amount of reference crop evapotranspiration of soybeans that was estimated by Pan evaporation and Hargreaves method were 547.8 mm and 586.8 mm, respectively. Crop coefficient during growing season were shown on Table 1. 2. Measured actual evapotranspiration of soybean during growing season was 405.7 mm and estimated actual evapotranspiration by pan evaporation and Hargreaves method were 424.7 mm, and 426.1mm, r3 respectively. 3. The variations of soil moisture content for soybeans were high at 10cm layer, as compared with those at 30cm and 50cm layers. Because discrepancy between the variations of soil moisture content predicted by model and observed by soil moisture meter was still great, it is required to study the consumptive types of soil moisture at each root depth.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.2
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• pp.61-72
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• 2008

Leaf area index (LAI) is a key biophysical variable influencing land surface processes such as photosynthesis, transpiration and energy balance, and is a required input to estimate evapotranspiration in various ecological and hydrological models. The development of more correct and useful LAIs estimation techniques is required by these importance, but LAIs had been assumed in most LAI research through simple relations with the normalized difference vegetation index (NDVI) because the field measurement is difficult on wide area. This paper is to evaluate the MODIS LAI Product's practical use by comparing with LAIs that is derived from NOAA AVHRR NDVIs and the 2 years (2003-2004) measured LAIs of Korea Forest Research Institute in Gyeongancheon watershed (561.12 $Km^2$). As a result, the MODIS LAIs of deciduous forests showed higher values about 14 % and 15~30 % than the measured LAIs and NOAA LAIs. In the year of 2003, the MODIS LAIs in coniferous forests were 5 % higher than the measured LAIs, and showed about 7 % differences comparing with the NOAA LAIs except April. These differences come from the insufficient field data measured in partial points of the target area, and the extracted reference data from MODIS LAIs include the limits of spatial resolution and the error of incorrect land cover classification. Thus, using the MODIS data by the proper correction with the measured data can be useful as an input data for ecological and hydrological models which offers the vegetation information and simulates the water balance of a given watershed.