• Environmental Engineering Research
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• v.23 no.3
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• pp.339-344
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• 2018

The Cu loading of a cubic $Ce_{0.8}Zr_{0.2}O_2$-supported Cu catalyst was optimized for a single-stage water gas shift (WGS) reaction. The catalyst was prepared by a co-precipitation method, and the WGS reaction was performed at a gas hourly space velocity of $150,494h^{-1}$. The results revealed that an 80 wt% $Cu-Ce_{0.8}Zr_{0.2}O_2$ catalyst exhibits excellent catalytic performance and 100% $CO_2$ selectivity ($X_{CO}=27%$ at $240^{\circ}C$ for 100 h). The high activity of 80 wt% $Cu-Ce_{0.8}Zr_{0.2}O_2$ catalyst is attributed to the presence of abundant surface Cu atoms and the low activation energy of the resultant process.

• Particle and aerosol research
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• v.7 no.2
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• pp.59-68
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• 2011

The objective of the study was to investigate the main factors that contribute the variation of $PM_{10}$ concentration of Seoul and to quantify their effects using generalized additive model (GAM). The analysis was performed with 3 year air pollution data (2004~2006) measured at 27 urban sites and 7 roadside sites in Seoul, a background site in Gangwha and a rural site in Pocheon. The diurnal variation of urban $PM_{10}$ concentrations of Seoul showed a typical bimodal pattern with the same peak times as that of roadside, and the maximum difference of $PM_{10}$ level between urban and roadside was about $14{\mu}g/m^{3}$ at 10 in the morning. The wind direction was found to be a major factor that affects $PM_{10}$ level in all investigated areas. The overall $PM_{10}$ level was reduced when air came from east, but background $PM_{10}$ level in Gangwha was rather higher than the urban $PM_{10}$ level in Seoul, indicating that the $PM_{10}$ level in Gangwha is considerably influenced by that in Seoul metropolitan area. When hourly variations of $PM_{10}$ were analyzed using GAM, wind direction and speed explained about 34% of the variance in the model where the variables were added as a 2-dimensional smoothing function. In addition, other variables, such as diurnal variation, difference of concentrations between roadside and urban area, precipitation, month, and the regression slope of a plot of carbon monooxide versus $PM_{10}$, were found to be major explanatory variables, explaining about 64% of total variance of hourly variations of $PM_{10}$ in Seoul.

• Journal of Korea Water Resources Association
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• v.51 no.5
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• pp.451-459
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• 2018

We calculated the optimal exponent values based on the hourly rainfall data observed in South Korea by treating the exponent value as a variable without fixing it as a square in the inverse distance method. For this purpose, rainfall observation stations providing the data are classified into four groups which are located at the Han river upstream, downstream, the Geum river upstream, and the Nakdong river midstream area. A total of 52 cases were analyzed for seven stations in each group. The optimal exponent value of distance was calculated in a case including one base station and four surrounding stations in a group. We applied the golden section search method to calculating this optimum values using rainfall data for 10 years (2004~2013) and verified the optimum values for the last three years (2014~2016). We compared and analyzed two results of the conventional inverse distance method and the inverse distance method in this study. The optimal values of distance exponent obtained in this study were 3.280, 1.839, 2.181, and 2.005 respectively, in the four groups, and totally mean value was 2.326. It is shown the proposed inverse distance method applying the optimal exponent is superior to the conventional inverse distance method.

• Journal of the Korean Data and Information Science Society
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• v.27 no.5
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• pp.1119-1131
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• 2016

The Neyman-Scott Rectangular Pulses Model (NSRPM) is mainly used to construct hourly rainfall series. This model uses a modest number of parameters to represent the rainfall processes and underlying physical phenomena, such as the arrival of storms or rain cells. In NSRPM, the method of moments has often been used because it is difficult to know the distribution of rainfall intensity. Recently, approximated likelihood function for NSRPM has been introduced. In this paper, we propose a hierarchical model for applying a spatial structure to the NSRPM parameters using the approximated likelihood function. The proposed method is applied to summer hourly precipitation data observed at 59 weather stations (Korea Meteorological Administration) from 1973 to 2011.

• Atmosphere
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• v.15 no.1
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• pp.47-57
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• 2005

Extending the success of the Tropical Rainfall Measuring Mission (TRMM), the spaceborne measurement of precipitation by Global Precipitation Measurement (GPM) is initiated. The GPM consists of a core satellite which will have a dual-frequency precipitation radar (DPR) and a constellation of small satellites equipped with microwave radiometers. The GPM is inherently a global program. Responding to the GPM plan, many other nations are much interested in participating in the GPM team or simply utilizing GPM products aiming at the development of meteorological technology. Korea can fully function its role if Korea is selected as a CAL/VAL site for the GPM because Korea maintains a well-established dense rain gauge network (AWS), precipitation radars, and the Haenam super site for surface observation. In this feasibility study, the necessities of the GPM project in the context of academical and social backgrounds and associated international and domestic activities are investigated. And GPM-related core technologies and application areas are defined. As a result, it is found that GPM will represent a great opportunity for us because of its ability to provide not only much enhanced three-hourly global rain products but also very useful tools for the enhancement of weather forecasting capabilities, management of water resources, development and implementation of monitoring techniques for severe weather phenomena, agricultural managements and climate application. Furthermore, rain retrieval and CAL/VAL technologies obtained during the involvement in the international GPM project will serve as basic knowledges to run our own geostationary satellite program.

• Journal of Korea Water Resources Association
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• v.44 no.9
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• pp.721-730
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• 2011

The objective of this study is to assess the availability of streamflow simulation using Radar-AWS Rain rate (RAR) data which is produced by KMA on real-time. Chuncheon dam upstream basin is selected as study area and total area is 4859.73 $km^2$. Mean Areal Precipitation (MAP) using AWS and RAR are calculated on 5 subbasin. The correlationship of hourly MAPs between AWS and RAR is weak on ungauged subbasins but that is relatively high on gauged ones. We evaluated the simulated discharge using the MAPs derived from two data types during flood season from 2006 to 2009. The simulated discharges using AWS on Chuncheon dam (gauged basin) are well fitted with measured ones. In some cases, however, discharges using AWS on Hwacheon dam and Pyeonghwa dam with some ungauged subbasins are overestimated on the other hand, ones using RAR in the same case are well fitted with measured ones. The hourly RAR data is useful for the real-time river forecast on the ungauged basin in view of the results.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.213-216
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• 2009

WGS(Water Gas Shift)반응은 일산화탄소(CO)를 이산화탄소($CO_2$)로 전환하는 반응으로 일체형 수소생산시스템의 실현을 위한 고순도 수소생산에 있어서 중요한 단계이다. WGS 반응은 열역학적 평형을 고려하여 고온전이반응(HTS: High Temperature Shift)과 저온전이반응(LTS: Low Temperature Shift) 두 단계 반응으로 진행된다. 두 단계 공정의 통합을 위해 낮은 온도에서 높은 활성을 갖는 WGS 반응용 촉매 개발이 필요하다. 최근 낮은 온도에서 높은 활성을 갖는 귀금속 촉매에 다양한 담체를 적용시킨 연구가 활발히 진행되고 있다. 선행 연구 결과, Ce-$ZrO_2$ 구조는 Ce/Zr 비에 따라 다양한 특성 변화를 관찰하였다. 따라서 낮은 온도에서 높은 활성을 갖는 WGS 반응용 촉매 제조를 위해 환원성 담체인 $CeZrO_2$에 Pt 을 담지시켜 성능을 평가하였다. 제조된 모든 담체는 공침법(Co-precipitation)으로 제조 하였으며 $500^{\circ}C$에서 6시간 소성하였다. 제조된 담체에 백금(Pt)을 함침법(Incipient Wetness Impregnate)으로 담지시켰다. 특성분석은 BET를 이용하여 표면적을 측정하였다. 촉매 반응 실험조건은 $200^{\circ}C{\sim}400^{\circ}C$ 온도범위에서 기체공간속도(GHSV: Gas Hourly Space Velocity) 45,000 ml/$h{\cdot}g-cat$ 으로 혼합가스($H_2$:60%, $N_2$:20%,$CH_4$:1%,CO:9%,$CO_2$:10%)를 흘려 반응 후 배출되는 가스를 Micro-Gas Chromatography 를 이용하여 측정하였다.

• Journal of Korea Water Resources Association
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• v.50 no.12
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• pp.849-862
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• 2017

The increased frequency of meteorological disasters has been observed due to increased extreme events such as heavy rainfalls and flash floods. Numerous studies using high-resolution weather radar rainfall data have been carried out on the hydrological effects. In this study, a conditional merging technique is employed, which makes use of geostatistical methods to extract the optimal information from the observed data. In this context, three different techniques such as kriging, inverse distance weighting and spline interpolation methods are applied to conditionally merge radar and ground rainfall data. The results show that the estimated rainfall not only reproduce the spatial pattern of sub-hourly rainfall with a relatively small error, but also provide reliable temporal estimates of radar rainfall. The proposed modeling framework provides feasibility of using conditionally merged rainfall estimation at high spatio-temporal resolution in ungauged areas.

• Journal of Korea Water Resources Association
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• v.48 no.5
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• pp.357-365
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• 2015

Both exponents of distance and elevation into distance-and-elevation ratio method for estimating missing rainfall data are expressed as squares together but in this study the two exponents are differently separated and analyzed. We used 326 hourly rainfall events of precipitation data during 10 years of 2004 to 2013 observed at a base station of Pyeongchang and the five neighboring index stations-Bangrim, Suju, Cheongoksan, Jinbu, Yeongwol1-in Han River basin for a case study. As a result, exponent values of distance and elevation appropriate for a topography of the site appear as 3.7 and 0.57 respectively. The exponents of distance and elevation difference need to be applied according to topographical characteristics of site where estimating missing data or interpolation are required.

• Journal of Environmental Science International
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• v.16 no.10
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• pp.1157-1167
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• 2007

In an effort to interpret the characteristics of fine particle concentrations in Busan, time variations of hourly monitored concentrations $PM_{10}$ (Particulate Matter with aerodynamic Diameter ${\le}10\;{\mu}m$) in Busan are analyzed for the period from 2000 to 2005. The characteristics of aerosol second generation formation process is also interpreted qualitatively, by using the statistical analysis of the meteorological variables including temperature, wind speed, and relative humidity. The result shows some significant annual, seasonal, weekly and diurnal variations of $PM_{10}$ concentrations. In particular, seasonal(i.e., spring) variations are governed by frequency of yellow sand events even for the non-yellow sand cases where yellow-sand days are eliminated in our analysis. However, in seasonal variation, summer season predominate lower $PM_{10}$ concentrations due to the frequent precipitation, and weekly and diurnal variations are both found to be reflecting the emission rate from traffic amount. Correlation coefficients between $PM_{10}$ concentration and meterological variables for non-yellow sand days show overall negative correlation with visibility, wind speed, cloud amounts, and relative humidity. However for non-precipitation days, during non-yellow sand period positive correlation are found clearly with relative humidity, suggesting the importance of secondary aerosol formation in Busan that can be achieved by both homogeneous aerosol formation and heterogeneous transformations resulting from hygroscopic aerosol characteristics.