• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.959-961
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• 2001

Nanosized CeO$_2$Powders were prepared under high temperature and pressure conditions by precipitation from metal nitrates with aqueous potassium hydroxide. Spherical shape of CeO$_2$powder was obtained at 175$^{\circ}C$ for 6h. TEM and X-ray diffraction patterns showed that the synthesized particle was crystalline. The average size and size distribution of the synthesized particles were below 30 nm and narrow, respectively. In addition, the effects of synthesis parameters under hydrothermal process are discussed.

• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.677-683
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• 1990

Melt-textured growth of the YBa2Cu3O7-x phase from a supercooled melt created locally aligned, barshaped grains of the orthorhombic 1-2-3 phase. Based on all the observed phenomena, the gross mechanism of the melt-textrued growth of YBa2Cu3O7-x on the (100) plane of MgO was delineated by three basic patterns of reactions. These are : (ⅰ) formation of the aligned 1-2-3 phase and the Y-rich 2-1-1 phase at the bulk region away from the (100) plane of MgO ; (ⅱ) formation of the Cu-richprecipitates at the interfacial region by the selective interface-induced precipitation of the liquid phase ; (ⅲ) condensation reaction of the entrapped Cu-rich vapor with Mg atoms during the initial stage of rapid cooling from 130$0^{\circ}C$ to 98$0^{\circ}C$.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.357-357
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• 2012

우리나라는 기후변화로 추정되는 폭우, 폭설 등과 같은 기존의 강우의 패턴과는 다른 현상들이 잦아지고 있다. 최근 발생하는 기상이변은 예측 할 수 없고 단시간에 많은 양의 강우로 인하여 큰 피해가 발생하며 수공구조물에도 많은 영향을 미친다. 또한 장 단기 수자원계획과 수공구조물의 설계를 위하여 확률강우량의 산정은 매우 중요한 과정 중의 하나이다. 즉, 과거의 여러 수문 사상에 대한 통계적인 분석을 통해서 수공구조물들의 설계빈도를 결정하는 우리나라의 현실에서 사용된 수문 사상의 자료기간에 따라 확률 값은 큰 차이를 보일 수 있기 때문에 관측 자료 기간을 달리하여 빈도 해석한 결과를 비교함으로서 우리나라의 확률강우량의 변화 특성을 파악 할 수 있으며 미래 강우 형태를 파악하는데 기여 할 수 있다. 본 논문에서는 우리나라 기상청 강우자료를 사용하여 기초 통계량의 변화와 강우 발생의 패턴을 분석하고자 한다.

• Journal of the Korean earth science society
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• v.40 no.5
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• pp.476-486
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• 2019

This study examines the controlling role of synoptic disturbances on $PM_{10}$ spring variability in the Korean Peninsula by using empirical orthogonal function (EOF) and back trajectory analyses. Three leading EOF modes are identified, and a lead-lag analysis suggests that $PM_{10}$ variabilities be closely related to the synoptic weather systems. The first EOF shows the spatially homogeneous distribution of $PM_{10}$, which is influenced by travelling anticyclonic disturbance with negative precipitation and descending motion. The second and third modes exhibit the dipole structures of $PM_{10}$, being associated with propagating cyclones. Furthermore, the back-trajectory analysis suggests that the transport of pollutants by anomalous winds associated with synoptic disturbances also contribute to the altered $PM_{10}$ concentration. Hence, a substantial synoptic control should be considered in order to fully understand the $PM_{10}$ spatiotemporal variability.

• Journal of Industrial Technology
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• v.25 no.B
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• pp.37-46
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• 2005

From 2000 to 2004, the research was carried out at Naerin-cheon and Inbook-cheon, the upper streams of Soyang Lake, to study the relationship between precipitation and eutrophication-causing water pollutants, BOD, T-N and T-P. During the five years, the amount of flowing water was measured, and the water quantity was examined under different precipitation levels. From the observation, outflow patterns of the water pollutants and changes in the water quality factors at the time of rainfall were clarified. In addition, estimation of the unit load was made for each stream; for Naerin-cheon at the time of rainfall, we estimated BOD to be $1,112kg/km^2/year$, T-N to be $2,077kg/km^2/year$, and T-P to be $223kg/km^2/year$; for Inbook-cheon at the time of rainfall, we estimated BOD to be $1,229kg/km^2/year$, T-N to be $1,565kg/km^2/year$, and T-P to be $255kg/km^2/year$. For the time of no rainfall different estimation was made; for Naerin-cheon, we estimated BOD to be $2,403g/km^2/day$, T-N to be $5,004g/km^2/day$, and T-P to be $53g/km^2/day$; and for Inbook-cheon, we estimated BOD to be $1,550g/km^2/day$, T-N to be $2,283g/km^2/day$, and T-P to be $42g/km^2/day$.

• Journal of Korea Water Resources Association
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• v.45 no.11
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• pp.1081-1091
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• 2012

SWAT model is applied to simulate rainfall-runoff and pollutant loadings in the Nakdong River basin as the condition for extreme droughts and floods. The year 1994 and 2002 are chosen as the drought and flood year, respectively, through the analysis of past rainfall data for 30 years. The simulation results show decreases in both runoff and pollutant loadings for the drought year but increases for the flood year. However, the pollutant loadings on some upper sub-basins increase for drought year due to highly-regulated dam discharge and soil moisture change. Collectively, extreme droughts and floods have negative impacts on water quality, showing elevated SS loadings during wet season and concentrated T-P concentrations during low flow season. The extent of these impacts is highly influenced by antecedent dry days and precipitation patterns.

• 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.

• The Korean Journal of Applied Statistics
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• v.18 no.2
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• pp.281-296
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• 2005

This article summarizes our research on estimation of area-specific and time-adjusted rainfall rates during 2004KEOP (Korea enhanced observation period: June 1, $2004{\sim}$ August 31, 2004). The rainfall rate is defined as the proportion of rainfall days per week and areas are consisting of Haenam, Yeosu, Janghung, Heuksando, Gwangju, Mokpo, Jindo, and Wando. Our objectives are to analyze periodicity in area-specific precipitation and the meteorological measures and investigate the relationships between the geographic pattern of the rainfall rates and the corresponding pattern in potential explanatory covariates such as temperature, wind, wind direction, pressure, and humidity. A generalized linear model is introduced to implement the objectives and the patterns are estimated by considering a set of rainfall rates produced using samples from the posterior distribution of the population rainfall rates.

• Journal of Environmental Science International
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• v.25 no.4
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• pp.459-472
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• 2016

We assessed the distribution of benthic macroinvertebrate at four surveying sites in Upo Wetland, a Ramsar site and the largest wetland in Korea, from February 2006 to November 2013. A long-term ecological monitoring was done monthly by using quantitative sampling method with dip net for analyzing the community change and correlation between the biodiversity and the environmental factors because environmental factors have a decisive effect on the community structure of the benthic macroinvertebrates. Total samples from the Upo Wetland area were classified into 3 phyla, 6 classes, 17 orders, 68 families, 176 species, and 25,720 individuals. Among the 176 species, 62 of the species had not been previously reported in this area. Asellus sp., Diplonychus esakii, and Gyraulus chinensis were the most common species in Upo Wetland. The change patterns of annual species diversity and species richness were calculated by using the average number of monthly occurring species and individuals. Diversity index increased from March to May and decreased after that showing lower diversity indices in July and August. It increased again in September and in October. Richness index showed similar tendency and fell around February and July, followed by a rising tendency around May and October. Correlation and regression analyses were performed with the change of biodiversity and each environmental factor. We found that water temperature have very significant positive correlation with species diversity in spring, and have significant indices in autumn and winter. On the other hand, precipitation showed a significantly negative correlation value in summer and autumn suggesting it has an effect on the community structure of benthic macroinvertebrates.

• Ecology and Resilient Infrastructure
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• v.5 no.3
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• pp.134-144
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• 2018

In this study, the historical drought in East Asia was analyzed with the Community Land Model (CLM) and CLM-Variable infiltration capacity (CLM-VIC). The observation dataset, Climate Research Unit (CRU), were also applied to check and estimate the historical drought for 1951 - 2010. The annual precipitation, temperature and evapotranspiration by CRU, CLM and CLM-VIC were investigated before estimating the meteorological drought index, which is the Standardized precipitation evapotranspiration index (SPEI). Three variables by observation and simulations have generally similar spatial pattern in East Asia even though there are some mere differences depending on the local area. These similar patterns are also founded in the results of SPEI by CRU, CLM and CLM-VIC. However, the similarity of SPEI becomes weaker as the drought severity goes severer from D1 to D4.