• Journal of Korean Society for Atmospheric Environment
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• 제21권E3호
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• pp.75-85
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• 2005

A mathematical sensitivity analysis of the flow-through dynamic flux chamber technique, which has been utilized usually for various trace gas flux measurement from soil and water surface, was performed in an effort to provide physical and mathematical understandings of parameters essential for the NO flux calculation. The mass balance equation including chemical reactions was analytically solved for the soil NO flux under the steady state condition. The equilibrium concentration inside the chamber, $C_{eq}$, was found to be determined mainly by the balance between the soil flux and dilution of the gas concentration inside the chamber by introducing the ambient air. Surface deposition NO occurs inside the chamber when the $C_{eq}$ is greater than the ambient NO concentration ($C_{0}$) introducing to the chamber; NO emission from the soil occurs when the $C_{eq}$ is less than the ambient NO concentration. A sensitivity analysis of the significance of the chemical reactions of NO with the reactive species (i.e. $HO_{2},/CH_{3}O_{2},/O_{3}$) on the NO flux from soils was performed. The result of the analysis suggests that the NO flux calculated in the absence of chemical reactions and wall loss could be in error ranges from 40 to $85\%$ to the total flux.

• 한국대기환경학회지
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• 제13권6호
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• pp.451-461
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• 1997

The soil NO flux measurements in Korea were made from 17 May 1997 to 16 June 1997 on grass land at Kunsan National University in southwestern Korea by using flow-through chamber technique. The experiment was conducted in an effort to determine the role of natural emissions of NO on rural atmospheric photochemistry, and to understand the soil NO emission mechanism with respect to soil parameters. Soil NO fluxes were measured every minutes and averaged in every 15 minutes as well as soil temperature. Soil samples were analyzed for $NO_3^-, NH_4^+$, and moisture in soil. Soil nitrate was not detected in most times, and total N-containing was limited in site soils. There was a optimum range of soil moisture and temperature for soil NO flux. The overall average of soil NO emission rates were found to be 1.30 $\pm 0.92 ngNm^{-2}s^{-1}$ (n=1219), and ranged from 0.01 ngNm^{-2}s^{-1}$ to 5.62 ngNm^{-2}s^{-1}$. Diurnal variation of soil NO emission was typical, which was in higher level during daytime, and was in lower level over the night. NO flux showed a strong soil temperature dependence $(r^2=0.78)$, but not with soil moisture and soil N-containing during this experimental period; NO fluxes increased exponentially as soil temperature increased. In order to assure the relevant relationship between soil NO flux and the soil parameters, long-term soil flux measurement on different types of land use should be planned and conducted continuously.

• 한국대기환경학회지
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• 제30권6호
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• pp.531-537
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• 2014

Terrestrial vegetation has been known as a main source of biogenic volatile organic compounds (BVOCs). Isoprene and monoterpene among the BVOCs are most abundant species emitted by forests, and have a significant impact on atmospheric chemistry. Abundancy of these species could lead to an increase or decrease in the production of natural tropospheric ozone in forests, depending on the nitric oxide (NO) concentration. Soil is the most significant source of natural NO. Understanding of NO emission from forest soil could be critical in evaluation of air quality in the forest area. Flux-gradient similarity theory (FGST) was applied for practical use to estimate forest soil NO emission at Mt. Taewha where is available micro-meteorological data near surface monitoring from flux tower. NO fluxes calculated by FGST were compared to flux results by flow-through dynamic chamber (FDC) measurement. Surface NO emission trends were shown between two different techniques, however their magnitudes were found to be different. NO emissions measured from FDC technique were relatively higher than those from theoretical results. Daily mean NO emissions resulted from FGST during Aug. 13, 14 and 15 were $0.28{\pm}8.45$, $2.17{\pm}15.55$, and $-3.18{\pm}13.65{\mu}gm^{-2}hr^{-1}$, respectively, while results from FDC were $2.26{\pm}1.44$, $5.11{\pm}3.85$, and $2.23{\pm}6.45{\mu}gm^{-2}hr^{-1}$. Trends of daily means were shown in similar pattern, which NO emissions were increasing during late afternoon ($r^2$=0.04). These emission trends could be because soil temperature and moisture influence importantly soil microbiology.

• 마이크로전자및패키징학회지
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• 제28권2호
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• pp.45-50
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• 2021

Flip chip 제품의 난이도 증가에 따라 solder wetting 및 신뢰성 관점에서 강점을 갖는 flux 소재에 대한 관심이 높아지고 있다. 지용성 flux의 경우 별도의 세정 공정이 없기 때문에 공정 효율화 측면에서 유리하나, 리플로우 공정이후 반응을 마친 잔여물이 잔존하게 되는 경우 Cu migration 및 delamination을 발생시킬 수 있다. 본 연구에서는 저잔사 flux 구현을 위해 신규 resin에 적합한 solvent 및 activator를 변경 하였으며, package 환경에서 non-wet 및 신뢰성 개선 유무를 확인하였다. 저장 안정성 평가를 통해 신규 소재에 대한 안정성을 확보하였으며, boiling point가 상이한 solvent와 activator 2종 적용 및 activator 함량 증대를 통해 non-wet 미 발생 flux 소재를 확보하였다. 해당 소재에 대한 신뢰성 검증 이후 평면 분석 결과 flux residue 기인성 delamination 현상은 발견되지 않았으며, 이를 통해 저잔사 flux에 대한 최종 조성을 확보하였다.

• 한국대기환경학회지
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• 제17권2호
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• pp.203-212
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• 2001

During the growing season from June to August, 2000, the soil NO and $N_2$O fluxes were measured to elucidate characteristics of soil nitrogen emissions from different types of intensively managed agricultural soils at outskirts of Kunsan City, located in the western inland of Korea, Flux measurements were made using a closed chamber technique at two different agricultural fields; one was made from upland field, and the other from rice paddy field. The flux data from upland field were collected for both the green onion and soybean field. Concentrations of NO and $N_2$O inside a flux chamber ar 15 minute sampling interval were measured to determine their soil emissions. Either polyethylene syringes of teflon air bags were used for gas samples of $N_2$O and NO. The analysis of NO and $N_2$O was made using a chemiluminesence NO analyzer and GC-ECD, respectively no later than few hours after sample collection at laboratory. The gas fluxes were varied more than one standard deviation around their means. Relatively high soil gas emissions occurred in the aftermoon for both NO and $N_2$O. A sub-peak for $N_2$O emission was observed in the morning period, but not in the case of NO. NO emissions from rice paddy field were much less than those from upland site. It seems that water layer over the rice paddy field prevents gases from escaping from the soil surface covered with were during the irrigation and acts as a sink of these gases. The NO fluxes resulted from these field experiments were compared to those from grass soil and they were found to be much higher. Diurnal and daily variations of NO and $N_2$O emission were discussed and correlated with the effects of nitrogen fertilizer application on the increase of the level of soil nitrogen availability.

• 한국농림기상학회지
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• 제9권3호
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• pp.170-178
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• 2007

지난 수 세기 동안 온실기체와 기타 화학적으로 중요한 미량기체들이 급격하게 증가하였다. 이러한 주요기체가 기후 변화에 미치는 영향을 이해하기 위해서는 각 기체들의 흡원과 발원을 규명하고, 생물권과 대기권 사이에서 발생하는 생물 기원 기체 플럭스들을 특성화하며, 주요 기체를 조절하는 프로세스들을 이해해야 한다. 본 논문에서는 야외 실험을 위한 실용적 방법인 enclosure 기반의 관측법을 소개한다. 특히, 토양표면에서 방출되는 일산화질소 플럭스에 대한 enclosure내에서의 질량수지 방정식과 flow-through dynamic 플럭스 챔버 기법의 민감도를 제시하고 flow-through dynamic 플럭스 챔버 방법의 물리적인 시스템과 이론을 소개한다. 또한 챔버 벽에서 발생하는 일산화질소의 손실을 고려하므로써 새로운 플럭스 계산식을 소개하였고 그 계산식의 불확실성을 논의하였다.

• 멤브레인
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• 제24권5호
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• pp.400-408
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• 2014

유도용액으로 비료를 사용하는 정삼투식 해수담수화에서 유도용액의 성능을 평가하였다. 일반적으로 많이 사용되는 비료 중에서 삼투압, 용해도 및 pH 등을 고려하여 $NH_4NO_3$, $NH_4H_2PO_4$, $(NH_4)_2HPO_4$, KCl, $KNO_3$ 및 $KHCO_3$를 유도용액 후보군으로 선정하였다. 수투과선속, 질소와 인의 역용질선속 및 비역용질선속을 측정하여 유도용액의 성능을 평가하였다. KCl은 본 연구에서 선정된 유도용액 중에서 가장 높은 수투과선속을 나타낸 반면에 $(NH_4)_2HPO_4$는 가장 낮은 수투과선속을 나타내었다. $NH_4H_2PO_4$가 가장 낮은 역용질선속 및 비역용질선속을 보였으며, $(NH_4)_2HPO_4$ < $KNO_3$ < $NH_4NO_3$의 순서로 역용질선속 및 비역용질선속이 증가하였다. $NH_4H_2PO_4$는 비록 다른 유도물질에 비해 수투과선속이 낮으나 비료의 주요 성분인 질소와 인을 모두 포함하고 있을 뿐만 아니라 질소와 인의 역용질선속 및 비역용질선속이 다른 유도물질에 비해 매우 낮으므로 FDFO (fertilizer drawn forward osmosis)에서 효과적으로 사용될 수 있을 것으로 판단된다.

• 자원환경지질
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• 제53권1호
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• pp.99-110
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• 2020

국외에서는 DNAPL오염부지 정화처리 과정에서 오염된 저투수성 매체를 주요 관리대상으로 고려하며, 저투수성 매체로부터 역확산하는 오염물질과 대수층 오염 지속성에 관한 연구가 활발히 진행되어 왔다. 그러나 국내 지하수 분야에서는 관련 연구가 미비한 실정이기 때문에, 본 논문은 저투수성 매체에서 오염물질의 정확산 및 역확산 현상을 소개하고 대표적인 연구사례를 통해 그 중요성을 제안하고자 한다. 본 논문에서는 저투수성 매체의 경계조건에 따른 6개의 정확산 및 역확산 시나리오와 각각의 시나리오에 사용된 해석해를 제시하였다. FI (forward diffusion into infinite domain)와 BI (back diffusion from infinite domain) 시나리오는 저투수성 매체의 깊이를 무한하게 가정한 경우, 정확산과 역확산 시나리오를 나타내며 과거 대다수의 저투수성 매체와 관련된 연구에서 사용되었다. 최근 연구에서는 저투수성 매체의 깊이를 유한하게 고려하고 있으며, 본 연구에서 사용한 유한 경계에서 정확산 시나리오는 FFN(forward diffusion into finite domain with no flux boundary), 역확산 시나리오는 BFN (back diffusion from finite domain with no flux boundary)이다. 또한 저투수성 매체 하부 경계를 통한 오염물질의 이동이 가능할 때 정확산 시나리오는 FFF (forward diffusion into finite domain with flux boundary), 역확산 시나리오는 BFF (back diffusion from finite domain with flux boundary)에 해당한다. 본 논문에서 제시한 시나리오와 해석해를 사용한 모델링은 저투수성 매체의 깊이 또는 오염 노출 기간 등의 현장 특성에 맞는 오염처리 공법을 선정하는데 기여할 수 있다. 또한 모델링 결과는 대수층의 정화 이후에도 역확산으로 발생하는 오염의 지속기간, 오염 정도 등의 정보를 제공함으로써 보다 효율적인 오염 정화처리에 기여할 것으로 사료된다.

• Water Engineering Research
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• 제1권2호
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• pp.119-127
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• 2000

In the process of crossflow microfiltration, a deposit of cake layer tends to form on the membrane, which usually controls the performance of filtration. It is found, however, that there exist a condition under which no deposit of cake layer is made. This condition is called the sub-critical flux condition, and the critical flux here means a flux below which a decline of flux with time due to the deposit of cake layer does not occur. In order to study the characteristics of the critical flux, a numerical model is developed to predict the critical flux condition, and is verified with experimental results. For development of the model, the concept of effective particle diameter is introduced to find a representative size of various particles in relation to diffusive properties of particles. The model is found to be in good match with the experimental results. The findings from the use of the model include that the critical flux condition is determined by the effective particle diameter and the ratio of initial permeate flux to crossflow velocity.

• Journal of Korean Society for Atmospheric Environment
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• 제11권E호
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• pp.31-43
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• 1995

Natural emissions of NOx from soils were measured at an agricultural corn field during 3 weeks of growing season in summer (from May to June) 1995. This experiment was conducted in an effort to characterize the role of soil NOx on tropospheric ozone formation in rural atmosphere, and understand the natural NOx emission mechanism with respect to soil parameters. NO fluxes were ranged from 3.1 ng Nm$^{-2}s^{-1}$ to 259.0 ng Nm$^{-2}s^{-1}$, and average NO flux during experimental period was found to be 47.6 $\pm$ 50.6 ng Nm$^{-2}s^{-1}$ with 732 number of data. Diurnal variation of NO flux was shown clearly with daytime maximum and nighttime minimum. NO fluxes were correlated with soil temperature. Exponential soil temperature dependency of NO fluxes was found with 0.0160$^{circ}C^{-1} of k and r^2=0.508$, which agrees well to the value estimated at corn fields in eastern United States. The significant increases of NO fluxes from agricultural soil were detected after applying N fertilizers to soil. THe mechanisms attributed to this are enhanced biological nitrification and denitrification. In the view of rural ozone formation, the roles of natural NO emissions are very essential, especially in NOx - limited region such as southern United States.