• 한국수자원학회논문집
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• 제44권8호
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• pp.683-694
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• 2011

기후변화에 따른 지역적 영향인 기온 상승과 강수량 변화로 인한 수자원 변화 특성을 파악하기 위하여 기상청(KMA)으로부터 전국 59개 관측지점에 대해서 1973년부터 2009년까지 강수량 및 기온자료를 이용하여 산정한 강수효율자료와 국가수자원관리종합시스템(WAMIS)으로부터 1966년부터 2007년까지 PRMS 모의 유출량 자료를 수집, 분석하였다. 분석결과, 전반적으로 강수효율의 거동은 강수량의 변화 특성을 따르나 지역적으로 강수량이 증가함에도 불구하고 기온 상승에 따라 강수효율이 감소하는 거동을 보였으며, 이는 유출량의 변화 특성과 유사하였다. 또한 유출량의 평균대비 변화율은 강수량 변화보다 상당히 크게 나타나, 기후변화의 영향에 민감한 것으로 나타났다. 강수량이 증가하는 5월~9월을 제외한 전체 기간에 대하여 강수효율은 강수량보다 더 유의한 감소 경향을 나타내고 있어 해당기간의 가용 수자원량이 줄어들 것으로 판단되며, 이러한 특성은 봄, 가을 및 겨울철 수자원 관리에 반영되어야 할 것이다.

• 대기
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• 제27권1호
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• pp.105-118
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• 2017

This study assesses the performance of the Weather Research and Forecasting (WRF) model in reproducing regional climate over CORDEX-East Asia Phase 2 domain with different cumulus parameterization schemes [Kain-Fritch (KF), Betts-Miller-Janjic (BM), and Grell-Devenyi-Ensemble (GD)]. The model is integrated for 27 months from January 1979 to March 1981 and the initial and boundary conditions are derived from European Centre for Medium-Range Weather Forecast Interim Reanalysis (ERA-Interim). The WRF model reasonably reproduces the temperature and precipitation characteristics over East Asia, but the regional scale responses are very sensitive to cumulus parameterization schemes. In terms of mean bias, WRF model with BM scheme shows the best performance in terms of summer/winter mean precipitation as well as summer mean temperature throughout the North East Asia. In contrast, the seasonal mean precipitation is generally overestimated (underestimated) by KF (GD) scheme. In addition, the seasonal variation of the temperature and precipitation is well simulated by WRF model, but with an overestimation in summer precipitation derived from KF experiment and with an underestimation in wet season precipitation from BM and GD schemes. Also, the frequency distribution of daily precipitation derived from KF and BM experiments (GD experiment) is well reproduced, except for the overestimation (underestimation) in the intensity range above (less) then $2.5mm\;d^{-1}$. In the case of the amount of daily precipitation, all experiments tend to underestimate (overestimate) the amount of daily precipitation in the low-intensity range < $4mm\;d^{-1}$ (high-intensity range > $12mm\;d^{-1}$). This type of error is largest in the KF experiment.

• 대기
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• 제29권5호
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• pp.615-626
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• 2019

To find any effects of precipitation climate on the forecast verification methods, we processed the hourly records of precipitation over South Korea. We examined their relationship between the climate and the methods of verification. Precipitation is an intermittent process in South Korea, generally less than an hour or so. Percentile ratio of precipitation period against the entire period of the records is only 14% in the hourly amounts of precipitation. The value of the forecast verification indices heavily depends on the climate of rainfall. The direct comparison of the index values might force us to have a mistaken appraisal on the level of the forecast capability of a weather forecast center. The size of the samples for verification is not crucial as long as it is large enough to satisfy statistical stability. Our conclusion is still temporal rather than conclusive. We may need the amount of precipitation per minute for the confirmation of the present results.

• 대한원격탐사학회지
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• 제23권2호
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• pp.71-87
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• 2007

본 연구는 NASA/GSFC에서 제공하는 MODIS 구름 산출물 자료를 활용하여 국지적 현상으로 나타난 영동지역의 14개 대설 사례를 분석하였다. MODIS에 의해 특정시간에 관측된 영동지역의 구름은 운정 온도(CTT), 광학 두께(COT), 유효 입자 반경$(r_e)$, 입자상(CP)과 같이 구름 내 속성의 특징에 따라 A, B, C 형으로 분류하였다. 각각의 구름 형태에 대한 강수량과 구름의 속성 사이의 연관성 분석에서 COT는 A와 B형에서 상당히 높은 통계적으로 유의한 관계성을 보였으며, CTT는 A형에서만 높은 상관성을 보였다. 그렇지만, C형에서는 통계적으로 유의한 관계성이 구름의 특성물에 대해 나타나지 않았다. A형 구름은 작은 크기의 물방울과 함께 주로 낮은 층운형 구름으로 구성되어 있으며, 동해에서 종관적으로 유도된 하층 한기 이류 하에서 발생할 수 있다. B형 구름은 발달하는 적운형 구름과 관련되어 있으며, 이러한 구름은 동해상에서 발달하는 저기압 중심과 밀접하게 관련되어 있다. 그렇지만, C형 구름은 다층 구름들로써 영동대설과 직접적으로 관련된 하층 구름을 상층구름이 덮고 있어 위성 관측이 어렵다. 따라서 MODIS 구름 산출물은 영동대설의 경우에 다층 구름을 제외하고 위성 자료로부터 강수량 추정과 대설 기작을 이해하는데 도움이 될 수 있다고 결론지을 수 있다.

• 한국대기환경학회지
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• 제20권3호
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• pp.381-396
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• 2004

In order to understand the precipitation acidity and chemical composition of ion species in Iksan area as well as to know the difference of chemical characteristics in precipitation samples from the viewpoint of precipitation sampling method, precipitation samples were collected by wet-only automatic precipitation sampler and bulk manual precipitation sampler in Iksan, from March 2003 to August 2003. The mean pH of precipitation was 5.0. There was a little significant difference in the mean value of pH between automatic and manual sampler. However, pH values of some precipitation samples were lower in automatic sampler than in manual sampler, especially in case of precipitation samples with small rainfall for March 2003. The mean concentrations of each ions in precipitation were generally a little higher in precipitation samples collected by the manual sampler than in those collected by the automatic sampler because of accumulation of dry deposition on the surface of glass funnel installed at the manual sampler during the sampling period or no rainfall. Dominant species determining the acidity of precipitation, were N $H_4$$^{[-10]}$ and nss-C $a^{2+}$ for cations and nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ for anions. The mean concentration of N $H_4$$^{+}$ and nss-C $a^{2+}$ were 31 $\mu$eq/L and 9 $\mu$eq/L for the automatic sampler and 40 ueq/L and 16 ueq/L for the manual sampler, respectively. In addition, nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were 27 $\mu$eq/L and 13 $\mu$eq/L for the automatic sampler and 32 $\mu$eq/L and 17 $\mu$eq/L for the manual sampler, respectively. Although the concentrations of the acidifying ions of nss-S $O_4$$^{2-}$ and N $O_3$$^{[-10]}$ were about 3 times higher than those for foreign pristine sites, precipitation acidity were estimated to be natural due to the neutralization reaction of the alkaline species of N $H_4$$^{+}$ and nss-C $a^{2+}$ with its higher concentrations. Considering the ratios of nss-S $O_4$$^{2-}$/N $O_4$$^{[-10]}$ nss-S $O_4$$^{2-}$, it was found that ammonium sulphate was dominant in Iksan precipitation. The major non-sea salt ions were maximum concentrations for March, but decreased with increasing of precipitation amount.on amount.

• 대기
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• 제19권2호
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• pp.155-168
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• 2009

Characteristics of seasonal mean diurnal temperature range (DTR) and their causes over South Korea are investigated using the 60 stations data of Korea Meteorological Administration from 1976 to 2005. In general, the seasonal mean DTR is greatest during spring (in inland area) and least during summer (urban and coastal area). The spatial and seasonal variations of DTR are closely linked with the land surface conditions (especially vegetation activity and soil moisture) and atmospheric conditions (cloud amount, precipitation, local circulation). The seasonal mean DTR shows a decreasing trend at the major urban areas and at the north-eastern part of South Korea. Whereas, it shows an increasing trend at the central area of the southern part. Decreasing and increasing trends of DTR are more significant during summer and fall, and during spring and winter. The decrease (increase) of DTR is mainly caused by the stronger increase of daily minimum (maximum) temperature than daily maximum (minimum) temperature. The negative effects of precipitation and cloud amount on the DTR are greater during spring and at the inland area than during winter and at the coastal area. And the effect of daytime precipitation on the DTR is greater than that of nighttime precipitation.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.886-889
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• 2018

This article presented two-staged chemical precipitation for radioactive wastewater decontamination by using chemical agents. The total amount of radioactive wastewater was $35m^3$, and main radionuclides were Cs-137, Cs-134, and Co-60. Initial radioactivity concentration of the liquid waste was 2264, 17, and 9 Bq/L for Cs-137, Cs-134 and Co-60, respectively. Potassium ferrocyanide, nickel nitrate, and ferrum nitrate were selected as chemical agents at high pH levels 8-10 according to the laboratory jar tests. After the process, radioactivity was precipitated as sludge at the bottom of the tank and decontaminated clean liquid was evaluated depending on discharge limits. By this precipitation method decontamination factors were determined as 66.5, 8.6, and 9 for Cs-137, Cs-134, and Co-60, respectively. By using the potassium ferrocyanide, about 98% of the Cs-137 was removed at pH 9. At the bottom of the tank, radioactive sludge amount from both stages was totally $0.98m^3$. It was transferred by sludge pumps to cementation unit for solidification. By chemical processing, 97.2% of volume reduction was achieved. The potassium ferrocyanide in two-staged precipitation method could be used successfully in large-scale applications for removal of Cs-137, Cs-134, and Co-60.

• 한국인쇄학회지
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• 제16권2호
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• pp.11-22
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• 1998

For the purpose of preparation of monodispersed spherical zinc oxide fine particles, an experimental research on the preparation of zinc oxide particles from zinc salts solutions by high temperature precipitation reaction was performed. Zinc oxide particles were precipitated from all the precipitation solutions tested if the precipitation temperature was higher than 60$^{\circ}$. As the precipitation temperature Increased until 80$^{\circ}$, the average particle diameter of zinc oxide particles decreased and the narrower particle size distribution were obtained. Spherical zinc oxide fine particles with relatively narrow particle size distribution were precipitated from the ZnSO$_4$ solutions with NaOH as precipitant. Final pH of precipitation solution had an effect on the amount of zinc oxide precipitated, but had no effect on the their particle size or size distribution.

• 소성∙가공
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• 제6권2호
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• pp.102-109
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• 1997

The multistage deformation and stress relaxation were carried out to investigate the strain induced precipitation by torsion tests in the range of 1000~80$0^{\circ}C$, 0.05~5/sec for V-microalloyed steel. The starting temperature and time for the initiation of precipitation were determined by stress relaxation tests. The distribution of precipitates increased, as the strain rate increased and the mean size of precipitates was found to be about 10~30nm. The precipitation starting time$(P_s)$ decreased with increasing strain rate and the amount of pre-strain. The effect of deformation conditions on the no-recrystallization temperature$(T_nr)$ was also determined in the multistage deformation. $T_nr$ Tnr decreased with increasing the strain and strain rate. In the controlled rolling simulation, grain refinement and precipitation hardening effects could be achieved by the alternative large pass strain at the latter half pass stage under the condition of low temperature and high strain rate.

• 대기
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• 제21권3호
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• pp.257-271
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• 2011

The aim of this study is to examine weather modification by urbanization and human activities. The characteristics of the urban heat island (UHI) and precipitation in Seoul metropolitan area of Korea are investigated to demonstrate that cities can change or modify local and nearby weather and climate, and to confirm that cities can initiate convection, change the behavior of convective precipitation, and enhance downstream precipitation. The data used in this study are surface meteorological station data observed in Seoul and its nearby 5 cities for the period of 1960 to 2009, and 162 Automatic Weather System stations data observed in the Seoul metropolitan area from 1998 to 2009. Air temperature and precipitation amount tend to increase with time, and relative humidity decreases because of urbanization. Similar to previous studies for other cities, the average maximum UHI is weakest in summer and is strong in autumn and winter, and the maximum UHI intensity is more frequently observed in the nighttime than in the daytime, decreases with increasing wind speed, and is enhanced for clear skies. Relatively warm regions extend in the east-west direction and relatively cold regions are located near the northern and southern mountains inside Seoul. The satellite cities in the outskirts of Seoul have been rapidly built up in recent years, thus exhibiting increases in near-surface air temperature. The yearly precipitation amount during the last 50 years is increased with time but rainy days are decreased. The heavy rainfall events of more than $20mm\;hr^{-1}$ increases with time. The substantial changes observed in precipitation in Seoul seem to be linked with the accelerated increase in the urban sprawl in recent decades which in turn has induced an intensification of the UHI effect and enhanced downstream precipitation. We also found that the frequency of intense rain showers has increased in Seoul metropolitan area.