• 대한원격탐사학회지
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• 제19권3호
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• pp.217-221
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• 2003

The Measurement of Pollution in the Troposphere (MOPITT) instrument is an eight-channel gas correlation radiometer that launched on the Earth Observing System (EOS) Terra spacecraft in 1999. Its main objectives are to measure carbon monoxide (CO) and methane (CH4) concentrations in the troposphere. This study analyzes tropospheric carbon monoxide distributions using MOPITT data and compare with ozone distributions in Northeast Asia. In general, seasonal CO variations are characterized by a peak in spring and decrease in summer. Also, this study revealed that the seasonal cycles of CO are maximum in spring and minimum in summer with average concentrations ranging from 118ppbv to 170ppbv. The monthly average of CO shows a similar profile to those of O3. This fact clearly indicates that the high concentration of CO in spring is caused by two possible causes: the photochemical CO production in the troposphere, or the transport of the CO in the northeast Asia. The CO and $O_3$ seasonal cycles in the Northeast Asia are influenced extensively by the seasonal exchange of the different types of air mass due to the Asian monsoon. The continental air masses contain high concentrations of $O_3$ and CO due to higher continental background concentrations and sometimes due to the contribution of regional pollution. In summer the transport pattern is reversed. The Pacific marine air masses prevail over Korea, so that the marine air masses bring low concentrations of CO and $O_3$, which tend to give the apparent minimum in summer.

• 한국환경보건학회지
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• 제45권5호
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• pp.474-486
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• 2019

Objectives: This study was performed to investigate the emission characteristics of aldehydes emitted by the printing industry and to evaluate their impact on adjacent residential areas. Methods: Aldehydes and THC were measured from the front of the control device in the printing and coating process. Aldehydes and ketones were measured by workplace area, residential area, and background area to evaluate their impact. Results: The concentrations of formaldehyde (<0.047 ppm) and acetaldehyde (<0.068 ppm) in the printing and coating process were relatively low, and the methyl ethyl ketone used as the primary solvent was the main carbonyl compound in the printing process. The daily mean concentrations of formaldehyde and acetaldehyde were not significantly different by workplace area, residential area, or background area. However, the concentration of methyl ethyl ketone was high in the order of workplace area, residential area, and background area. Conclusions: The concentrations of formaldehyde and acetaldehyde in the adjacent residential areas are considered to be more influenced by secondary sources of photochemical reactions than by primary sources. Methyl ethyl ketone is considered to be highly influenced by the primary source, which is printing facilities.

• 한국철도학회논문집
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• 제18권6호
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• pp.558-566
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• 2015

본 연구에서는 일반 앵커와 확공지압형 앵커 시스템에 대하여 전과정평가(LCA)를 수행하고 환경영향 특성을 분석하였다. 또한, 평가결과를 비교 분석하여 개발된 확공지압형 앵커 시스템의 환경저감 개선효과를 확인하였다. 환경영향범주별 기여도 분석결과, 두 앵커 시스템 모두 지구온난화가 대부분을 차지하는 것으로 나타났다. 개발된 확공지압형 앵커 시스템의 환경저감효과를 확인하기 위해 환경영향범주에 대한 정규화 결과, 모든 항목에서 확공지압형 앵커 시스템의 환경성이 개선된 것으로 나타났으며, 광화학 산화물 생성분야가 77%로 가장 크게 개선되었다. 최근 지구온난화와 관련하여 전세계적으로 관심이 고조되고 있는 온실가스 배출량은 약 44% 감소한 것으로 나타났다. 이러한 정량적인 환경영향평가 결과는 향후 토목분야 영구앵커 공법에 대한 환경영향평가시 기초자료로 활용할 수 있을 것으로 판단된다.

• 한국환경보건학회지
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• 제44권6호
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• pp.539-547
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• 2018

Objectives: Ozone ($O_3$) advisories are issued by provincial/prefectural and city governments in Korea and Japan when oxidant concentrations exceed the criteria of the related country. Advisories issued only after exposure to high $O_3$ concentrations cannot be considered ideal measures. Forecasts of $O_3$ would be more beneficial to citizens' health and daily life than real-time advisories. The present study was undertaken to present a simplified forecasting model that can predict surface $O_3$ concentrations for the afternoon of the day of the forecast. Methods: For the construction of a simple and practical model, a multivariate regression model was applied. The monitored data on gases and climate variables from Japan's air quality networks that were recorded over nearly one year starting from April 2016 were applied as the subject for our model. Results: A well-known inverse correlation between $NO_2$ and $O_3$ was confirmed by the monitored data for Iksan, Korea and Fukuoka, Japan. Typical time fluctuations for $O_3$ and $NO_x$ were also found. Our model suggests that insolation is the most influential factor in determining the concentration of $O_3$. $CH_4$ also plays a major role in our model. It was possible to visually check for the fit of a theoretical distribution to the observed data by examining the probability-probability (P-P) scatter plot. The goodness of fit of the model in this study was also successfully validated through a comparison (r=0.8, p<0.05) of the measured and predicted $O_3$ concentrations. Conclusions: The advantage of our model is that it is capable of immediate forecasting of surface $O_3$ for the afternoon of the day from the routinely measured values of the precursor and meteorological parameters. Although a comparison to other approaches for $O_3$ forecasting was not carried out, the model suggested in this study would be very helpful for the citizens of Korea and Japan, especially during the $O_3$ season from May to June.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2019년도 추계학술대회
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• pp.57-57
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• 2019

실내 수준에서 조사되는 광량조건에 따른 자생 상록활엽 2종의 생육과 광화학반응을 조사하였다. 식물재료는 3년생 사철나무(Euonymus japonicus Thunb.) 및 2년생 돈나무[Pittosporum tobira (Thunb.) W. T. Aiton] 실생묘로 유리온실에서 재배하면서 실험에 사용하였다. 실내 광량은 10, 50, 100 및 200 PPFD(${\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$)로 달리하여 8주간 재배하였으며, 광주기(12/12 h), 온도($25{\pm}1^{\circ}C$), 습도($55{\pm}3%$) 및 관수(1회/3일)조건은 고정되었다. 생육특성 및 광화학반응의 요인들이 측정되었으며, 동일기간 동안 유리온실에서 재배된 식물을 대조구로 사용하였다. 실험의 결과, 사철나무는 100, 200 PPFD의 광량에서 대조구에 비해 초장, 줄기직경, 엽수 및 엽장의 생육반응이 우수하였으며, 엽록소함량은 100 PPFD 이상의 광량에서 감소하였다. 또한 100 PPFD 이상의 광량에서 스트레스지수(Fm/Fo), 최대양자수율(Fv/Fm) 및 전자전달효율(ETo/RC)이 감소하였으며, 이는 대조구와도 유사한 경향이었다. 돈나무는 모든 광량조건에서 줄기직경과 엽폭을 제외하고 대조구와 관계없이 생육반응이 일정하였다. 그러나 스트레스지수와 최대양자수율은 10 PPFD 처리구에서 가장 낮게 조사되었고, 비광학적 에너지의 손실(DIo/RC)은 2.53으로 가장 높았다.

• 한국재료학회지
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• 제31권1호
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• pp.16-22
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• 2021

In this study, quantum dot-sensitized solar cells (QDSSC) using CdSe/ZnS quantum dots (QD) of various sizes with green, yellow, and red colors are developed. Quantum dots, depending their different sizes, have advantages of absorbing light of various wavelengths. This absorption of light of various wavelengths increases the photocurrent production of solar cells. The absorption and emission peaks and excellent photochemical properties of the synthesized quantum dots are confirmed through UV-visible and photoluminescence (PL) analysis. In TEM analysis, the average sizes of individual green, yellow, and red quantum dots are shown to be 5 nm, 6 nm, and 8 nm. The J-V curves of QDSSC for one type of QD show a current density of 1.7 mA/㎠ and an open-circuit voltage of 0.49 V, while QDSSC using three type of QDs shows improved electrical characteristics of 5.52 mA/㎠ and 0.52 V. As a result, the photoelectric conversion efficiency of QDSSC using one type of QD is as low as 0.53 %, but QDSSC using three type of QDs has a measured efficiency of 1.4 %.

• 대기
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• 제31권1호
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• pp.29-43
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• 2021

In this study, two-step statistical approach including Principal Component Analysis (PCA) and Multiple Linear Regression (MLR) was employed, and main meteorological factors explaining the high-PM2.5 episodes were identified in two regions: Seoul and Busan. We first performed PCA to isolate the Principal Component (PC) that is linear combination of the meteorological variables observed at two levels: surface and 850 hPa level. The employed variables at surface are: temperature (T2m), wind speed, sea level pressure, south-north and west-east wind component and those at 850 hPa upper level variables are: south-north (v850) and west-east (u850) wind component and vertical stability. Secondly we carried out MLR analysis and verified the relationships between PM2.5 daily mean concentration and meteorological PCs. Our two-step statistical approach revealed that in Seoul, dominant factors for influencing the high PM2.5 days are mainly composed of upper wind characteristics in winter including positive u850 and negative v850, indicating that continental (or Siberian) anticyclone had a strong influence. In Busan, however, the dominant factors in explanaining in high PM2.5 concentrations were associated with high T2m and negative u850 in summer. This is suggesting that marine anticyclone had a considerable effect on Busan's high PM2.5 with high temperature which is relevant to the vigorous photochemical secondary generation. Our results of both differences and similarities between two regions derived from only statistical approaches imply the high-PM2.5 episodes in Korea show their own unique characteristics and seasonality which are mostly explainable by two layer (surface and upper) mesoscale meteorological variables.

• Bulletin of the Korean Chemical Society
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• 제12권2호
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• pp.163-169
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• 1991

The photochemical and photophysical properties of N-(2-haloarylmethyl)pyridinium, N-(arylmethyl)-2-halopyridinium, N-(2-haloarylmethyl)-2-halopyridinium salts and N-(2-halobenzyl)-isoquinolinium salt are studied. The pyridinium salts photocyclize to afford isoindolium salts, while the isoquinolium salts do not. In the photocyclization of N-(2-chlorobenzyl)-2-chloropyridinium salts, pyrido[2,1-a]-4-chloroisoindolium salt is formed by the cleavage of chlorine of pyridinium ring. This indicates that the excited moiety is not the phenyl ring, but the pyridinium ring. The triplet states of the pyridinium salts are believed to be largely involved in the photocyclization, since oxygen retards most of the reaction. Some assistance of a ${\pi}$-complex between the excited chlorine moiety of the salt and phenyl plane of the same molecule is required to explain the reactivity of the salts. N-(Benzyl)-2-chloropyridinium salt is two times more reactive than N-(2-chlorobenzyl)pyridinium salt. N-(Benzyl)-2-chloropyridinium salt can form ${\pi}-complex$ effectively because of the electron-rich phenyl group. The ${\pi}$-complex affords an intermediate, phenyl radical by cleaving the chlorine atom. The photocyclized product, isoindolium salt is obtained by losing the hydrogen atom from the phenyl radical. The reactive pyridinium salts 1a, 2a and 3a have a low fluorescence quantum yield (${\Phi}F$ < 0.01) and a higher triplet energy (ET > 68 kcal/mole) than the unreactive quinolinium salt. The unreactivity of isoquinolinium salt can be understood in relation to its high fluorescence quantum yield and its low triplet energy $(E_T = 61 kcal/mole).$.

• 한국환경과학회지
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• 제30권7호
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• pp.547-555
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• 2021

To compare the vitality among cool-season turfgrasses under summer weather conditions and to obtain information to improve the management of turfgrasses in golf courses and sports fields., the chlorophyll fluorescence of three cool-season turfgrasses commonly planted on golf courses in the Jeju area was measured. The turfgrasses were perennial ryegrass (Lolium perenne L.), Kentucky bluegrass (Poa pratensis L.), and creeping bentgrass (Agrostis palustris Huds.). In perennial ryegrass and Kentucky bluegrass, the chlorophyll index was low in early summer and high in late summer. In creeping bentgrass, it remained low throughout the study. Fo tended to be low in the early summer and high in late summer in the three turfgrasses. However, the difference in F_o between late summer and early summer was markedly higher in perennial ryegrass than in Kentucky bluegrass or creeping bentgrass. F_m tended to be low in early summer and high in late summer, without obvious differences among the three turfgrasses. F_v/F_m, a measure of photochemical efficiency, was also low in early summer and high in late summer in the three turfgrasses. However, F_v/F_m in late summer was mostly higher in Kentucky bluegrass and creeping bentgrass than in perennial ryegrass, indicating that the former are more resistant to the high temperature and humidity of late summer. Furthermore, Kentucky bluegrass had a high chlorophyll index in late summer and would be most resistant to the harsh conditions of late summer.

• 한국기계가공학회지
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• 제21권2호
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• pp.1-10
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• 2022

Exhaust gases emitted from internal combustion engines contain nitrogen oxides (NOx) and sulfur oxides (SOx), which are major air pollutants causing acid rain, respiratory diseases, and photochemical smog. As a countermeasure, scrubber systems are being studied extensively. In this study, the pressure drop characteristics were analyzed by changing the exhaust gas inflow velocity using a scrubber for a 700 kW engine as a model. In addition, the fluid flow inside the scrubber and the behavioral characteristics of the droplets were studied using CFD, and the design compatibility of the cleaning device was verified. Flow analysis was performed using inertial and viscous resistances by applying porous media to the complex shape of the scrubber. The speed of the exhaust passing through the outlet nozzle from the inlet was determined through the droplet behavior analysis by spraying, and the flow characteristics for the pressure drop were studied. In addition, it was confirmed through computational analysis whether there was a stagnation section in the exhaust gas flow in the scrubber or the sprayed droplets were in good contact with the exhaust gas.