• Journal of the Korean earth science society
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• v.40 no.3
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• pp.259-271
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• 2019

A statistical downscaling method was adopted in order to establish the high-resolution wave prediction system in the East Sea coastal area. This system used forecast data from the Global Wave Watch (GWW) model, and the East Sea and Busan Coastal Wave Watch (CWW) model operated by the Korea Meteorological Administration (KMA). We used the CWW forecast data until three days and the GWW forecast data from three to seven days to implement the statistical downscaling method (inverse distance weight interpolation and conditional merge). The two-dimensional and station wave heights as well as sea surface wind speed from the high-resolution coastal prediction system were verified with statistical analysis, using an initial analysis field and oceanic observation with buoys carried out by the KMA and the Korea Hydrographic and Oceanographic Agency (KHOA). Similar to the predictive performance of the GWW and the CWW data, the system has a high predictive performance at the initial stages that decreased gradually with forecast time. As a result, during the entire prediction period, the correlation coefficient and root mean square error of the predicted wave heights improved from 0.46 and 0.34 m to 0.6 and 0.28 m before and after applying the statistical downscaling method.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.1
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• pp.93-100
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• 2019

The objective of this study was to analyze the color distribution of the maxillary primary central incisors and the relationship between the color of each tooth region by dividing tooth into incisal, middle and cervical region using a spectrophotometer. The subjects were 105 sound maxillary primary central incisors from 3 to 6 years old children. Color measurements were performed by one dentist using same protocol. CIE $L^*$, $a^*$, $b^*$, $C^*$, $h^*$ data and the best matched shades with coverage error were obtained for each region and whole labial surface. There was a significant difference in CIE $L^*$, $a^*$, $b^*$ according to regions and the difference in color between each region was more than the clinical acceptance. By correlating the relationship between the color of each region with $L^*$, $a^*$, $b^*$ values, it is possible to extrapolate the color of other region with one color or to be used as data for making restorative materials and prostheses that are more aesthetically pleasing for primary teeth.

• Clean Technology
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• v.27 no.2
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• pp.182-189
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• 2021

The adsorption of disperse yellow 3 (DY 3) on granular activated carbon (GAC) was investigated for isothermal adsorption and kinetic and thermodynamic parameters by experimenting with initial concentration, contact time, temperature, and pH of the dye as adsorption parameters. In the pH change experiment, the adsorption percent of DY 3 on activated carbon was highest in the acidic region, pH 3 due to electrostatic attraction between the surface of the activated carbon with positive charge and the anion (OH^-) of DY 3. The adsorption equilibrium data of DY 3 fit the Langmuir isothermal adsorption equation best, and it was found that activated carbon can effectively remove DY 3 from the calculated separation factor (R_L). The heat of adsorption-related constant (B) from the Temkin equation did not exceed 20 J mol^-1, indicating that it is a physical adsorption process. The pseudo second order kinetic model fits well within 10.72% of the error percent in the kinetic experiments. The plots for Weber and Morris intraparticle diffusion model were divided into two straight lines. The intraparticle diffusion rate was slow because the slope of the stage 2 (intraparticle diffusion) was smaller than that of stage 1 (boundary layer diffusion). Therefore, it was confirmed that the intraparticle diffusion was rate controlling step. The free energy change of the DY 3 adsorption by activated carbon showed negative values at 298 ~ 318 K. As the temperature increased, the spontaneity increased. The enthalpy change of the adsorption reaction of DY 3 by activated carbon was 0.65 kJ mol^-1, which was an endothermic reaction, and the entropy change was 2.14 J mol^-1 K^-1.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.164-170
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• 2001

The crystal structures of fully dehydrated Ni2+- and Tl+ -exchanged zeolite X (Ni17Tl58-X, and Ni12Tl68-X; X=Si100Al92O384) have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at $21(1)^{\circ}C$ (a=24.380(4) $\AA$, 24.660(4) $\AA$, respectively). Their structures have been refined to the final error indices R1=0.037 and R2=0.043 with 485 reflections, and R1=0.039 and R2=0.040 with 306 reflections, respectively, for which I >36(I). In Ni17Tl58-X, 17 Ni2+ ions per unit cell were found at only two sites: 15 at site I at the center of the hexagonal prism (Ni-O=2.203(9) $\AA)$ and the remaining 2 at site II near single six-oxygen rings in the supercage (Ni-O=2.16(3) $\AA).$ Fifty-eight Tl+ ions were found at five crystallographic sites: 28 at site II (Tl-O=2.626(8) $\AA)$, 2 at site I' in the sodalite cavity near the hexagonal prism (Tl-O=2.85(1) $\AA)$, another 2 at site II' in the sodalite cavity (Tl-O=2.77(1) $\AA).$ The remaining 26 were found at two nonequivalent Ⅲ' sites with occupancies of 23 and 3. In Ni12Tl68-X, 12 Ni2+ ions per unit cell were found at two sites: 10 at site I (Ni-O=2.37(2) $\AA)$ and the remaining 2 at site II (Ni-O=2.13(2) $\AA).$ Sixty-eight Tl+ ions were found at five crystallographic sites: 28 at site II (Tl-O=2.63(1) $\AA)$, 12 at site I' (Tl-O=2.62(1) $\AA)$, 2 at site II' (Tl-O=3.01(2) $\AA)$, and the remaining 26 at two III' sites with occupancies of 23 and 3. It appears that Ni 2+ ions prefer to occupy site I and II, in that order. The large Tl+ ions occupy the remaining sites, I', II, II' and two different III' sites. In both crystals, only the Ni2+ ions at site II were reduced and migrated to the external surface of zeolite X when these crystals were treated with hydrogen gas.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.320-325
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• 2021

In this study, an optimization for the production of water emulsion was designed by adding an extract of wheat sprout, which is known to contain a large amount of antioxidants. The central composite design of reaction surface analysis method (CCD-RSM) was used for the optimization process. The amount of emulsifier, emulsification time, and added amount of wheat sprout extract were selected as independent variables based on our preliminary experiments. The mean droplet size (MDS), viscosity, and emulsion stability index (ESI) were set as the responses to evaluate the stability of the emulsion. For each independent variable, the P-value and coefficient of determination were evaluated to verify the reliability of the experiments. From the result of CCD-RSM, optimum conditions for the emulsification were determined as 23.6 min, 7.7 wt.%, and 3.9 wt.% for the emulsification time, amount of emulsifier, and amount of sprout, respectively. From the optimized condition obtained, MDS, viscosity, and ESI after 7 days from reaction were estimated as 252.3 nm, 616.7 cP, and 88.7%, respectively. The overall satisfaction was 0.9137, which supported the validity of the experiments, and the error rate was measured at 0.5% or less by advancing the experiments. Therefore, an optimized process for producing an emulsion by adding the malt extract was designed by the CCD-RSM.

• Journal of Korea Water Resources Association
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• v.54 no.1
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• pp.27-38
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• 2021

Recently, many studies have been conducted to use the radar rainfall in hydrology. However, in the case of weather radar, the beam is blocked due to the limitation of the observation such as mountain effect, which causes underestimation of the radar rainfall. In this study, the radar rainfall was estimated using the Hybrid Sacn Reflectivity (HSR) technique for hydrological use of weather radar and the runoff analysis was performed using the GRM model which is a distributed rainfall-runoff model. As a result of performing the radar rainfall correction and runoff simulation for 5 rainfall events, the accuracy of the dual-polarization radar rainfall using the HSR technique (Q_H_KDP) was the highest with an error within 15% of the ground rainfall. In addition, the result of runoff simulation using Q_H_KDP also showed an accuracy of R2 of 0.9 or more, NRMSE of 1.5 or less and NSE of 0.5 or more. From this study, we examined the application of the dual-polarization radar and this results can be useful for studies related to the hydrological application of dual-polarization radar rainfall in the future.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.373-383
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• 2020

In this study we established an operational storm-surge system for the northwestern pacific ocean, based on the NEMO (Nucleus for European Modeling of the Ocean). The system consists of the tide and the surge models. For more accurate storm surge prediction, it can be completed not only by applying more precise depth data, but also by optimal parameterization at the boundaries of the atmosphere and ocean. To this end, we conducted several sensitivity experiments related to the application of available bathymetry data, ocean bottom friction coefficient, and wind stress and air pressure on the ocean surface during August~September 2018 and the case of typhoon SOULIK. The results of comparison and verification are presented here, and they are compared with POM (Princeton Ocean Model) based Regional Tide Surge forecasting Model (RTSM). The results showed that the RTSM_NEMO model had a 29% and 20% decrease in Bias and RMSE respectively compared to the RTSM_POM model, and that the RTSM_NEMO model had a lower overall error than the RTSM_POM model for the case of typhoon SOULIK.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.4
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• pp.139-147
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• 2021

In this study, waves were defined using the water surface elevation data observed from the HeMOSU-1 and 2 marine meteorological observation towers installed on the west coast of Korea, and correlation analysis was performed between wave parameters. The wave height and wave period were determined using the wave-train analysis method and the wave spectrum analysis method, and the relationship between the wave parameters was calculated and compared with the previous study. In the relation between representative wave heights, most of the correlation coefficients between waves showed a difference of less than 0.1% in error rate compared to the previous study, and the maximum wave height showed a difference of up to 29%. In addition, as a result of the correlation analysis between the wave periods, the peak period was estimated to be abnormally large at rates of 2.5% and 1.3% in HeMOSU-1&2, respectively, due to the effect of the bimodal spectrum that occurs when the spectral energy density is small.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.675-686
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• 2021

This study investigated the ground displacement occurring in a slope below a waste-rock dumping site and estimated the likelihood of a disaster due to a landslide. To start with, photogrammetry was conducted by unmanned aerial vehicles (UAVs) to investigate the size and extent of the ground displacement. From April 2019 to July 2020, the average error rate of the five UAV surveys was 0.011-0.034 m, and an elevation change of 2.97 m occurred due to the movement of the soil layer. Only some areas of the slope showedelevation change, and this was believed to be due to thegroundwater generated during rainfall rather than the effect of the waste-rock load at the top. Sensitivity analysis for LS-RAPID simulation was performed, and the simulation results were compared and analyzed by applying a digital elevation model (DEM) and a digital surface model (DSM)as terrain data with 10 m, 5 m, and 4 m grids. When data with high spatial resolution were used, the extent of the sedimentation of landslide material tended to be excessively expanded in the DEM. In contrast, in the result of applying a DSM, which reflects the topography in detail, the diffusion range was not significantly affected even when the spatial resolution was changed, and the sedimentation behavior according to the river shape could be accurately expressed. As a result, it was concluded that applying a DSM rather than a DEM does not significantly expand the sedimentation range, and results that reflect the site situation well can be obtained.

• Journal of Korea Water Resources Association
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• v.55 no.9
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• pp.679-686
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• 2022

As the occurrences of flash floods have increased due to climate change, faster and more accurate precipitation observation using X-band radar has become important. Therefore, the Ministry of Environment installed two dual-pol X-band radars at Samcheok and Uljin. The radar data used in this study were obtained from two different elevation angles and composed to reduce the shielding effect. To obtain quantitative rainfall, quality control (QC), K_DP retrieval, and Hybrid Surface Rainfall (HSR) methods were sequentially applied. To improve the accuracy of the quantitative precipitation estimation (QPE) of the X-band radar, we retrieved parameters for the relationship between rainfall rate and specific differential phase, which is commonly called the R-K_DP relationship; hence, an empirical approach was developed using multiple rain gauges for those two radars. The newly suggested relationship, R = 27.4K^0.81_DP, slightly increased the correlation coefficient by 1% more than the relationship suggested by the previous study. The root mean square error significantly decreased from 3.88 mm/hr to 3.68 mm/hr, and the bias of the estimated precipitation also decreased from -1.72 mm/hr to -0.92 mm/hr for overall cases, showing the improvement of the new method.