• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3427-3432
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• 2014

This study introduces a new method of combining Imaging Differential Optical Absorption Spectroscopy (Imaging-DOAS) data and plume dispersion formulas for power plant emissions to determine the three-dimensional structure of a dispersing pollution plume and the spatial distributions of trace gas volume mixing ratios (VMRs) under conditions of negligible water droplet and aerosol effects on radiative transfer within the plume. This novel remote-sensing method, applied to a power plant stack plume, was used to calculate the two-dimensional distributions of sulfur dioxide ($SO_2$) and nitrogen dioxide ($NO_2$) VMRs in stack emissions for the first time. High $SO_2$ VMRs were observed only near the emission source, whereas high $NO_2$ VMRs were observed at locations several hundreds of meters away from the initial emission. The results of this study demonstrate the capability of this new method as a tool for estimating plume dimensions and trace gas VMRs in power plant emissions.

• Journal of the Korean Data and Information Science Society
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• v.27 no.3
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• pp.803-814
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• 2016

Recent times have seen an exponential increase in the amount of spatial data, which is in many cases associated with temporal data. Recent advances in computer technology and computation of hierarchical Bayesian models have enabled to analyze complex spatio-temporal data. Our work aims at modeling data of daily average nitrogen dioxide (NO2) levels obtained from 25 air monitoring sites in Seoul between 2003 and 2010. We considered an independent Gaussian process model and an auto-regressive model and carried out estimation within a hierarchical Bayesian framework with Markov chain Monte Carlo techniques. A Gaussian predictive process approximation has shown the better prediction performance rather than a Hierarchical auto-regressive model for the illustrative NO2 concentration levels at any unmonitored location.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.117-121
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• 2006

Non-thermal plasma technology has many applications in various areas. One of the applications is regenerating diesel particulate filter (DPF). DPF is a widely applied device to control the particulate emission of diesel engines. But it needs periodic removal of clogged soot for the smooth running of engine. Conventional high-temperature removal processes easily leads to the breakage of DPF. Herein, low-temperature plasma formed in a dielectric barrier discharge (DBD) reactor was used to form active oxidants such as ozone and nitrogen dioxide. Experimentally, the effects of discharge power and frequency on the performance of DBD reactor were studied. Two oxidants, $O_3$ and $NO_2$, were synthesized and used for incinerating soot in the used DPF. Performances of the two oxidants on the reduction of soot were compared, and it was found that $NO_2$ is more effective than $O_3$ for getting rid of soot

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.11
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• pp.1043-1048
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• 1998

The decomposition performance of the Surface induced Plasma Chemical Processing(SPCP) for benzene, toluene, xylene and $NO_2$ were experimentally examined. Discharge exciting frequency range was 5kHz and 10kHz, and low frequency discharge requires high voltage to inject high electric power in gas and to decompose contaminants. The decomposition rate of dioxide nitrogen for 5kHz power in gas and to decompose contaminants. The decomposition rate of dioxide nitrogen for 5kHz power supply is only 85%, but it’s rate for 10kHz power supply is very high, more than 96% when peak voltage is 12kv. Aromatic hydrocarbon vapor of up to 1000ppm is almost throughly decomposed at the flow rate of 1000$\ell$/min or lower rate under the discharge with electric power of several hundred watts. High decomposition rate is shown in every case, that is, for SPCP reactor is necessary to obtain the decomposition rate of more than 80~98%. The decomposition rate of benzene, toluene and xylene were 90~98% and dioxide nitrogen was 45~96%.

• Journal of Environmental Science International
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• v.11 no.3
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• pp.247-255
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• 2002

Indoor and outdoor nitrogen dioxide (NO$_2$) concentrations were measured and compared with measurements of personal exposures of 95 persons in Seoul, Korea and 57 persons in Brisbane, Australia, respectively. Time activity diary was used to determine the impact on NO$_2$ exposure assessment and microenvironmental model to estimate the personal NO$_2$ exposure. Most people both Seoul and Brisbane spent their times more than 90% of indoor and more than 50% in home, respectively. Personal NO$_2$ exposures were significantly associated with indoor NO$_2$ levels with Pearson coefficient of 0.70 (p＜0.01) and outdoor NO$_2$ levels with Pearson coefficient of 0.66 (p＜0.01) in Seoul and of 0.51 (p＜0.01) and of 0.33 (p＜0.05) in Brisbane, respectively. Using microenvironmental model by time weighted average model, personal NO$_2$ exposures were estimated with NO$_2$ measurements in indoor home, indoor office and outdoor home. Estimated NO$_2$ measurements were significantly correlated with measured personal exposures (r = 0.69, p＜0.001) in Seoul and in Brisbane (r = 0.66, p＜0.001), respectively. Difference between measured and estimated NO$_2$ exposures by multiple regression analysis was explained that NO$_2$ levels in near workplace and other outdoors in Seoul (p = 0.023), and in transportation in Brisbane (p = 0.019) affected the personal NO$_2$ exposures.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.22 no.2
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• pp.128-133
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• 2012

People are exposed to air pollution from a range of indoor and outdoor sources. Concentration of nitrogen dioxide $(NO_2)$, which is hazardous to health, can be significant in both types of environment. This paper reports on the measurement and analysis of indoor and outdoor $NO_2$ concentrations and their comparison with measured personal exposure in house and workplace indoors with 28 office workers during winter and summer seasons. Time activity patterns were used to determine the effects of these factors on personal exposure. The residential indoor and office indoor times were $12.29{\pm}1.58,$ $7.86{\pm}1.97$ hours in winter and $11.04{\pm}2.18,$ $8.26{\pm}2.04$ hours in summer, respectively. Measured residential indoor, outdoor and office indoor, personal exposure $NO_2$ concentrations were $23.10{\pm}8.46$ ppb, $23.97{\pm}6.86$ ppb, $21.91{\pm}11.50$ ppb, $22.08{\pm}8.64$ ppb in winter, and $19.94{\pm}6.04$ ppb, $21.21{\pm}6.84{\pm}$ ppb, $22.55{\pm}9.54$ ppb, $27.45{\pm}8.96$ ppb in summer, respectively. Contributions of residential and office indoor $NO_2$ concentration on personal exposure were estimated by 57.98%, 35.62% in winter and 37.38%, 28.97% in summer, respectively.

• Journal of Environmental Health Sciences
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• v.34 no.2
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• pp.148-152
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• 2008

Coated filters were developed to replace the glass impinger methods that use reagent solutions. The purpose of this study was to simultaneously measure nitrogen dioxide ($NO_2$) and respirable suspended particles (RSP) by a filtration method with a cyclone connected to a pump. A first pre-filter for RSP and second filter for $NO_2$, which was soaked in a TEA (Triethanolamine) solution, were loaded into a filter cassette with a pump flow rate of 1.7 l/m. After sampling, the TEA soaked filter was removed from the cassette, placed in a large test tube (10 ml), mixed, and allowed time to develop. The absorbance (abs) of the diazo compound of the $NO_2$ and N-(1-Napthylethylenediamine dihydrochloride) in the color reagent was measured at 545 nm on a spectrophotometer. The collection efficiency(%) of $NO_2$ by each 3 filter soaked in TEA solution and used in the cyclone with a pump flow rate 1.7 l/m was $89{\pm}3%$ and the correlation coefficient between the true $NO_2$ concentration and that determined by the TEA soaked filters was 0.993(p<0.001).

• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.4
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• pp.165-170
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• 2011

The ambient concentrations of nitrogen dioxide ($NO_2$) at 65 forest areas were measured every month using passive diffusive samplers from 2002 to 2009 and were compared to those at urban areas in order to investigate the characteristics of temporal and spatial distributions of $NO_2$ from the forest and urban areas. The annually averaged concentrations of $NO_2$ gradually decreased for both areas. The average concentration of $NO_2$ in the forest areas was 8.0 ppb, which was lower than that in the urban areas (i.e., 19.4 ppb) and the ecological standard level of the European Union (i.e., 14.6 ppb). The monthly average of $NO_2$ concentration depicted seasonal variations particularly in the urban areas, showing higher concentration in winter and lower concentration in summer. Strong locality of $NO_2$ concentration distribution illustrates that the locations near the metropolitan areas (e.g., Gyeonggi and Chungnam provinces) had the highest concentration during the measurement period. A significant positive correlation between $NO_x$ emissions and $NO_2$ concentration was observed, suggesting that the magnitude and proximity to sources of atmospheric nitrogen oxides would be important controlling factors.

• Journal of Environmental Health Sciences
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• v.32 no.3
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• pp.207-214
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• 2006

This study was designed to assess the level of nitrogen dioxide from several microenvironments including inside the home, outdoors near the home, inside the school, outdoors near the school, and on the road for 42 primary schoolchildren during the month of December 2002 in Seoul, Korea. The average personal, indoor, outdoor $NO_2$ levels, and indoor/outdoor ratio were 45.08 ppb, 27.89 ppb, 30.96 ppb, and 0.89, respectively. The indoor $NO_2$ concentrations were significantly associated with the presence of a smoker with a gas stove. The estimated personal $NO_2$ exposure using time-weighted average equation of $34.64{\pm}5.29$ ppb was significantly lower than the measured personal exposure of $45.08{\pm}5.50$ ppb. Our results indicate that indoor $NO_2$ levels were associated with the presence of a smoker and a gas stove. Moreover, personal $NO_2$ exposure with a gas stove in the house was significantly higher than those without a gas stove.

• Journal of the Korean institute of surface engineering
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• v.54 no.5
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• pp.260-266
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• 2021

Synthesizing low-dimensional structures of oxide semiconductors is a promising approach to fabricate highly efficient gas sensors by means of possible enhancement in surface-to-volume ratios of their sensing materials. In this work, vertically aligned zinc oxide (ZnO) nanorods are successfully synthesized on a transparent glass substrate via seed-mediated hydrothermal synthesis method with the use of a ZnO nanoparticle seed layer, which is formed by thermally oxidizing a sputtered Zn metal film. Structural and optical characterization by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy reveals the successful preparation of the ZnO nanorods array of the single hexagonal wurtzite crystalline phase. From gas sensing measurements for the nitrogen dioxide (NO₂) gas, the vertically aligned ZnO nanorod array is observed to have a highly responsive sensitivity to NO₂ gas at relatively low concentrations and operating temperatures, especially showing a high maximum sensitivity to NO₂ at 250 ℃ and a low NO₂ detection limit of 5 ppm in dry air. These results along with a facile fabrication process demonstrate that the ZnO nanorods synthesized on a transparent glass substrate are very promising for low-cost and high-performance NO₂ gas sensors.