• Nuclear Engineering and Technology
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• 제54권6호
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• pp.2077-2083
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• 2022

In the unlikely event of core disruptive accident in sodium cooled fast reactors, the reactor containment building would be bottled up with sodium and fission product aerosols. The behavior of these aerosols is crucial to estimate the in-containment source term as a part of nuclear reactor safety analysis. In this work, the evolution of sodium aerosol characteristics (mass concentration and size) is simulated using HAARM-S code. The code is based on the method of moments to solve the integro-differential equation. The code is updated to FORTRAN-77 and run in Microsoft FORTRAN PowerStation 4.0 (on Desktop). The sodium aerosol characteristics simulated by HAARM-S code are compared with the measured values at Aerosol Test Facility. The maximum deviation between measured and simulated mass concentrations is 30% at initial period (up to 60 min) and around 50% in the later period. In addition, the influence of humidity on aerosol size growth for two different aerosol mass concentrations is studied. The measured and simulated growth factors of aerosol size (ratio of saturated size to initial size) are found to be matched at reasonable extent. Since sodium is highly reactive with atmospheric constituents, the aerosol growth factor depends on the hygroscopic growth, chemical transformation and density variations besides coagulation. Further, there is a scope for the improvement of the code to estimate the aerosol dynamics in confined environment.

• 한국결정성장학회지
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• 제27권2호
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• pp.70-74
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• 2017

건식 진동밀과 습식 볼밀로 출발원료를 혼합/분쇄하여 나트륨이온전지용 양극활물질인 $Na_{2/3}(Ni_{1/3}Mn_{2/3})O_2$를 합성하여 특성을 비교하였다. 건식 진동밀로 혼합/분쇄한 분말은 습식 볼밀한 분말보다 더 미세한 $1{\mu}m$ 이하의 입자였으며, $875{\sim}900^{\circ}C$에서 열처리 하였을 때 단일상을 얻을 수 있었다. 또한 전지 특성도 건식 진동밀을 사용한 분말이 습식 공정으로 합성한 분말보다 방전용량이 크고 방전 전위도 높게 나왔다.

• 한국대기환경학회지
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• 제24권4호
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• pp.470-482
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• 2008

Seasonal variations of chemical composition and optical properties of aerosols at Seoul and Gosan were investigated using the ground-based aerosol measurements and an optical model calculation. The mass fraction of elemental carbon was $8{\sim}17%$, but its contribution on light absorption was high up to $29{\sim}48%$ in Seoul. In Gosan, the contribution of water soluble aerosols on aerosol extinction was $83{\sim}94%$ due to the high mass fraction of these particles in the range of $56{\sim}88%$. Model calculation showed that the water holding capacity of aerosols was larger in Gosan than in Seoul because of higher relative humidity and temperature along with abundant water soluble aerosols. Difference between measured and calculated aerosol optical depths was the highest in summer. This was because aerosol optical depth calculated from ground-based measurements could not consider aerosol loadings at high altitude in spite of high column-integrated aerosol loadings observed by Sun photometer. Although hygroscopic growth was expected to be dominant in summer, the mass concentration of water soluble aerosols was too low to permit this growth.

• 농업과학연구
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• 제26권1호
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• pp.71-76
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• 1999

젖소 유방염 병원균에 대한 느릅나무 뿌리껍질(유백피(楡白皮))의 항균활성을 검토하기 위하여 용매분획별로 시험한 결과 일반적으로 chloroform 분획이 가장 효과적이었고 butanol 및 물분획의 활성은 낮았다. 유방염균을 Fleish extract broth에서 액체 배양할 경우에 chloroform 분획을 첨가하면 생육이 억제되었으며 특히 Staphylococcus aureus 및 Streptococcus sp. No. 12는 초기생육이 현저하게 저해되는 경향을 나타내었다. Hoechst 제약의 표준방법에 의한 MIC 시험에서도 유사한 결과를 얻었다. 또한 건조한 느릅나무의 뿌리껍질 100 g을 물로 추출하여 겉보기 점도 77.5 cP, 최대흡수 파장 440nm의 황갈색 수용성 점질물 4.500ml를 회수할수 있었다. 이를 정제 건조한 무게는 32~35 g이었으며, 탄수화물 함량이 $61.0{\pm}1.0%$, 단백질 $8.0{\pm}0.2%$로서 다당이 주성분이었다. 이상의 실험결과를 통해 유백피의 용매 추출분획물은 항균활성을 나타내는 성분으로, 그리고 수용성 점질물은 흡수성과 점성이 높은 다당류로서 염증 부위에 수렴작용을 나타내는 성분으로 결론지을 수 있었다

• 대기
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• 제17권4호
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• pp.407-420
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• 2007

Optical characteristics of aerosols in Seoul are investigated from the measurements of sky radiance by Skyradiometer at Yonsei University from December 2005 to November 2006. Aerosol optical depth (AOD) shows a maximum in June due to weak ventilation and particle growth by aging process and hygroscopic effect. Single scattering albedo (SSA) and Angstrom Exponent (AE) show the lowest value in spring due to the Asian dust. It is clear that coarse mode is dominant in spring and fine mode is dominant in summer from the volume size distribution measured in this study. The explanations on the changes of aerosol loadings are provided through the correlation between AOD and AE, while the pattern of wavelength dependency related to particle size is shown through the correlation between SSA and AE. Backward trajectory analysis by HYSPLIT provides information about origin of aerosol, which allows us to classify the case according to the source region and the path distance. Although the direction of backward trajectory traces back mostly to west, coarse mode particle is dominant in the case of long pathway and fine mode particle is dominant in the case of short pathway. This discrepancy is caused by the regional difference of emitted particles.

• 한국대기환경학회지
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• 제21권6호
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• pp.631-637
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• 2005

A UV-MFRSR instrument was used to measure the global and diffuse irradiances in 7 narrowband channels in the UV range 299.4, 304.4, 310.9, 317.3. 324.5, 331.3 and 367.4 nm at Gwangju ($35^{circ}\;13'N\;126^{circ}\;50'E$), Korea. Spectral UV-AOD was retrieved using the Langley plot method for data collected from April 2002 to July 2004. Temporal variation of AOD at 367.4 nm ($AOD_{367nm}$) showed a maximum in June ($0.95\pm0.43$) and a minimum in February ($0.31\pm0.14$). Clear seasonal variation of $AOD_{367nm}$ was observed with average values of $0.68\pm0.29,\;0.82\pm0.41,\;0.48\pm0.22\;and\;0.42\pm0.21$ in spring, summer, fall and winter, respectively, Average Angstrom exponent for the entire monitoring period was $2.03\pm0.75$ in the UV-A ($324.5\∼367.4$ nm) range. Seasonal variation of the Angstrom exponent showed a maximum in spring and a minimum in summer. The lowest Angstrom exponent in summer might be due to hygroscopic growth of particles under conditions of high relative humidity. UV-AOD changes under different atmospheric conditions were also analyzed. Uncertainty in retrieving spectral UV-AOD was also estimated to range between $\pm0.218\;at\;304.4\;nm\;and\;\pm0.135\;at\;367.4\;nm$. Major causes of uncertainty were total column ozone retrieval and extraterrestrial irradiance retrieval at shorter and longer wavelengths, respectively.

• 한국대기환경학회지
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• 제25권4호
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• pp.325-338
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• 2009

National parks provide recreation, health, and science to human being. The provision of beautiful landscape view of the national park improves an economic and social phase of a nation. However, visibility impairment frequently occurred in the national park area of Gyeongju. The purpose of this study is to investigate the physical and the chemical characteristics of visibility reduction observed at the national park area of Gyeongju. Optical, chemical, meteorological characteristics and scenic monitoring were performed at the visibility monitoring station of Gyeongju University located at the Seoak section of Gyeongju national park from April 28 to May 9, 2008. Light extinction, light scattering, and light absorption coefficients were continuously measured using a transmissometer, a nephelometer, and an aethalometer, respectively. In order to investigate the impact of aerosol chemistry on visibility impairment, size-resolved aerosols were collected at intervals of 2-hour (from 8 A.M. to 6 P.M.) and 14-hour (from 6 P.M. to 8 A.M.) interval each sampling day. The average light extinction coefficient and the average visual range were measured to be $270{\pm}135\;Mm^{-1}$ and $14.5{\pm}6.3\;km$ during the intensive monitoring period, respectively. It was revealed that sulfate particle was the largest contributor to the light extinction under hazy condition. Organic mass accounted for about 26% of the average light extinction. The mass extinction efficiencies for $PM_{1.0}$, $PM_{2.5}$, and $PM_{10}$ were estimated to be 9.0, 4.7, and $2.7\;m^2\;g^{-1}$ under the consideration of water growth function of hygroscopic aerosols, respectively.

• 대기
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• 제18권4호
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• pp.459-474
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• 2008

Aerosol scattering coefficients for three different wavelengths ($\lambda$=450,550,700 nm) are measured almost continuously by a nephelometer in Seoul for a period of 13 months (February 2007-February 2008), which includes two weeks break in August 2007 for measurements at Daegwallyeong and YoungJongdo. The mean of the daily average scattering coefficients at $\lambda$=550 nm is $194.1{\pm}144.2Mm^{-1}$ and the minimum and maximum are $14.3Mm^{-1}$ and $998.1Mm^{-1}$, respectively. The scattering coefficient shows a general increasing trend with atmospheric relative humidity (RH). When the data are classified according to weather conditions, the days with no major weather events show the smallest scattering coefficient and also the lowest RH. Surprisingly haze/fog days show the largest scattering coefficient and Asian dust days comes in second. Although the variation is large within a season, winter shows the largest and autumn shows the smallest scattering coefficient. The average ${\AA}ngstr{\ddot{o}}m$ exponent is $1.40{\pm}0.32$ for the entire Seoul measurement. As expected, Asian dust days show the smallest ${\AA}ngstr{\ddot{o}}m$ exponent and haze/fog days are the next, suggesting more efficient hygroscopic growth of aerosols for this weather condition. Aerosol scattering coefficient seems to show better correspondence with CCN concentration rather than total aerosol concentration, which may indicate that CCN active aerosols are also good scattering aerosols.

• 대한원격탐사학회지
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• 제34권3호
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• pp.451-463
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• 2018

본 연구는 서울지역에서 2015년 1월부터 12월까지 정지궤도 천리안 위성(Communication Ocean and Meteorological Satellite, COMS) 해양 탑재체(Geostationary Ocean Color Imager, GOCI)의 에어로졸광학두께(Aerosol Optical Depth, AOD)로부터 지상 초미세먼지(Particulate Matter; $PM_{2.5}$) 농도를 추정하기 위한 계절별 경험/통계모델을 개발했다. 행성경계층고도(Planetary Boundary Layer Height, PBLH) 그리고 에어로졸 수직 비율(Vertical Ratio of Aerosol, VRA)을 사용한 두 가지 수직보정방법과 흡습성장계수(Hygroscopic growth factor, f(RH))로부터의 습도보정방법이 각각의 경험적 모델에 적용된 결과 AOD에 대한 수직 보정과 $PM_{2.5}$에 대한 지표 습도보정이 모델 성능 향상에 중요한 역할을 했다. AOD-$PM_{2.5}$ 사이에 관련이 있다고 알려진 기상인자들(온도, 풍속, 시정)을 추가적으로 사용하여 다중 선형 회귀모델을 구성한 결과 경험모델에 비해 $R^2$값이 최대 0.25 증가했다. 본 연구에선 AOD-$PM_{2.5}$ 모델의 계절별, 월별, 시간별 특성을 분석하고 계절별로 구분하여 모델을 구성한 결과 고농도 사례에서 과소평가 되던 경향이 개선됨을 알 수 있고 관측된 $PM_{2.5}$와 추정된 $PM_{2.5}$의 월 및 시간변동성은 서로 경향성이 일치했다. 따라서 정지궤도 위성 AOD를 이용하여 지상 $PM_{2.5}$ 농도를 추정한 본 연구의 결과는 향후 발사 예정인 GK-2A와 GK-2B에 적용 가능할 것으로 기대된다.

• 보존과학회지
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• 제21권
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• pp.59-72
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• 2007

석조문화재의 손상된 표면층에 형성된 수용성 염과 세균과의 상관관계를 알아보고자 하였다. 먼저 몇 기의 석조문화재 표면의 훼손된 층에서 시료를 채취하여 수용성 염을 분석하였고, 검출된 수용성 염($Na_2SO_4$, $CaSO_4$ $2H_2O$, NaCl)을 배지에 첨가하여 시료로부터 미생물을 분리하였다. 예비실험을 통하여 분리된 100여종의 세균중에서 15종만을 선별하여 특성을 파악하였는데, 15종모두 그람양성균이었으며 한 종을 제외하고는 간균이었다. 이들은 배지에 첨가된 11가지 수용성 염 중 염이 첨가되지 않은 배지뿐만 아니라 $CaCO_3$, $CaSO_4$ $2H_2O$, $Ca(OH)_2$가 첨가된 배지에서 모두 생장이 가능한 것으로 확인되었으며, 균 B16, B56, B61은 칼슘이 첨가된 배지에서 점액을 생성하는 것으로 확인되었다. 실험에 사용된 수용성 염 중에서 $CaCl_2$ $2H_2O$는 가장 높은 흡습성을 나타내었으나, 세균의 생장에 도움을 주는 것 같지 않았으며, 암모늄 이온이 첨가된 배지에서도 대부분의 세균의 생장이 저해를 받았다.