• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.7
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• pp.394-399
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• 2016

The silicon dioxide ($SiO_2$) was deposited using various gas as oxygen and nitrous oxide ($N_2O$) in nowadays. In order to improve electrical characteristics and the interface state density ($D_{it}$) in low temperature, It was deposited with carbon dioxide ($CO_2$) and silane ($SiH_4$) gas by inductively coupled plasma chemical vapor deposition (ICP-CVD). Each $D_{it}$ of $SiO_2$ using $CO_2$ and $N_2O$ gas was $1.30{\times}10^{10}cm^{-2}{\cdot}eV^{-1}$ and $3.31{\times}10^{10}cm^{-2}{\cdot}eV^{-1}$. It showed $SiO_2$ using $CO_2$ gas was about 2.55 times better than $N_2O$ gas. After 10 years when the thin film was applied to metal/insulator/semiconductor(MIS)-nonvolatile memory(NVM), MIS NVM using $SiO_2$($CO_2$) on tunneling layer had window memory of 2.16 V with 60% retention at bias voltage from +16 V to -19 V. However, MIS NVM applied $SiO_2$($N_2O$) to tunneling layer had 2.48 V with 61% retention at bias voltage from +20 V to -24 V. The results show $SiO_2$ using $CO_2$ decrease the $D_{it}$ and it improves the operating voltage.

• Journal of Environmental Science International
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• v.31 no.2
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• pp.195-213
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• 2022

This research summarizes the generating factors of greenhouse gas (carbon dioxide, methane, nitrous oxide) in hydropower dams and related domestic/foreign researches. Microorganisms and eutrophication are the main factors in greenhouse gases in hydropower dam reservoirs. The greenhouse gas emission from the hydropower dam is affected by meteorological factors and dam operation periods, and greenhouse gases are also emitted from the outlets. The fluxes of greenhouse gas emission from the hydropower dams were -926~180,806 mg CO₂ m^-2d^-1, -0.19~3800 mg CH₄ m^-2d^-1, and 0.01~16.1 mg N₂O m^-2d^-1. In South Korea, the study on the greenhouse gas emission from Korean hydropower dams has been rarely, and therefore it is inquired. This research suggested the methods on the greenhouse gas emission from Korean hydropower dams and flux calculation.

• Microbiology and Biotechnology Letters
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• v.48 no.1
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• pp.72-78
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• 2020

The dynamics of nitrogen compounds and RNA-based functional genes were characterized in the nitrification-denitrification coupling process. For the removal of residual ammonium, intermittent aeration was introduced in the denitrification reactor. N₂O production was not observed in both reactors. In both reactors, the nitrifying genes (achaeal-amoA, bacterial-amoA and hor) and denitrifying genes (narG, nirK, norB and nosZ) had a copy number of 3.92 × 10²-7.25 × 10⁵ and 2.85 × 10²-3.06 × 10⁴ per ng of DNA, respectively. These results suggest that denitrification and nitrification reactions occur in both the nitrification and denitrification reactors, respectively. Therefore, the coupling process is a promising one for the conversion of ammonium to nitrogen without generating N₂O.

• Korean Journal of Agricultural Science
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• v.48 no.3
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• pp.589-596
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• 2021

Nitrogen applied to soil is highly prone to leaching and volatilization leading to gaseous emissions of nitrous oxide (N₂O) and ammonia (NH₃) which are of great environmental concern. Usage of biochar to reduce the discharge of nitrogen to the environment has attracted much interest in the recent past. Biochar is produced by pyrolyzing various biomasses under oxygen-limited conditions. Biochar is a carbonized material with high adsorptive powers for not only plant nutrients but also heavy metals. The objective of this study was to investigate the adsorption characteristics of NH₄-N onto biochar made from pine needles. The biochar was produced at various pyrolysis temperatures including 300, 400 and 500℃ and holding times of 30 and 120 minutes. The Langmuir isotherm was used to evaluate the adsorption test results. The chemical properties of the biochar varied with the pyrolysis conditions. In particular, the pH, EC and total carbon content increased with the increasing pyrolysis conditions. The rate of adsorption of NH₄-N by the biochar decreased with the increasing pyrolysis conditions. Of these conditions, biochar that was pyrolyzed at 300℃ for 30 minutes showed the highest adsorption rate of approximately 0.071 mg·g^-1. Thus, the use of biochar pyrolyzed at low temperatures with a short holding time can most efficiently reduce ammonia emissions from agricultural land.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.4-4
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• 2017

Atmospheric carbon dioxide enrichment ($eCO_2$) often increases soil nitrous oxide ($N_2O$) emissions, but the underlying mechanisms are not fully understood. Emerging evidence suggests that $eCO_2$ alters plant N preference in favor of ammonium ($NH_4{^+}-N$) over nitrate ($NO_3{^-}-N$). Yet, whether and how this attributes to the enhancement of $N_2O$ emissions has not been investigated. We examined the effects of $eCO_2$ on soil $N_2O$ emissions in the presence of two N forms ($NH_4{^+}-N$ or $NO_3{^-}-N$), using wheat (Triticum aestivum L.) as a model plant. Our results showed that N forms dominated $eCO_2$ effects on plant and microbial N utilization, and thus soil $N_2O$ emissions. Elevated $CO_2$ significantly increased the rate and the sum of $N_2O$ emissions by three to four folds when $NO_3{^-}-N$, but not $NH_4{^+}-N$, was supplied. Enhanced $N_2O$ emission was related to the reduced plant $NO_3{^-}-N$ uptake in wheat. We propose a new conceptual model in which $eCO_2$-inhibition of plant $NO_3{^-}-N$ uptake and/or $CO_2$-enhancement of soil labile C enhances the N and/or C availability for denitrifiers and increases the intensity and/or the duration of $N_2O$ emissions. Together, these findings suggest that to enhance plant N use efficiency and reduce $N_2O$ emission, crop breeding and management need to consider altered plant preference of N sources under future $CO_2$ scenarios.

• Korean Chemical Engineering Research
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• v.40 no.6
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• pp.746-751
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• 2002

Fluidized bed combustion is a coal combustion technology that can reduce both SOx and NOx emission; SOx is removed by limestone that is fed into the combustion chamber and the NOx is reduced by low temperature combustion in a fluidized bed combustor and air stepping, but $N_2O$ generation is quite high. $N_2O$ is not only a greenhouse gas but also an agent of ozone destruction in the stratosphere. The calcium oxide(CaO) is known to be a catalyst of $N_2O$ decomposition. This study of $N_2O$ decomposition reaction in fixed bed reactor packed over CaO bed has been conducted. Effects of parameters such as concentration of inlet $N_2O$ gas, reaction temperature, CaO bed height and effect of $CO_2$, NO, $O_2$ gas on the decomposition reaction have been investigated. As a result of the experiment, it has been shown that $N_2O$ decomposition reaction increased with the increasing fixed bed temperature. While conversion of the reaction was decreased with increasing $CO_2$ concentration. Also, under the present of NO, the conversion of $N_2O$ decomposition is decreased. From the result of kinetic study gained the heterogeneous reaction rate on $N_2O$ decomposition. In the case of $N_2O$ decomposition over CaO, heterogeneous reaction rate is. $\frac{d[N_2O]}{dt}=\frac{3.86{\times}10^9{\exp}(-15841/R)K_{N_2O}[N_2O]}{(1+K_{N_2O}[N_2O]+K_{CO_2}[CO_2])}$. In this study, it is found that the calcium oxide is a good catalyst of $N_2O$ decomposition.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.6
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• pp.11-18
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• 2014

The combustion flowfield at the near-injector region of a 50 N scale $N_2O/C_2H_5OH$ thruster was visualized using shadowgraph technique. The explosive ignition was occurred at the design spray condition, and the expanding combustion gas quenched the flame immediately. Approximately after 83 ms from the initial ignition, the propellant spray was re-ignited, and the flame was stabilized after 23 ms elapsed. In the increased oxidizer flow rate condition, the transient pressure at the moment of ignition was smoother than explosive ignition, and the blow down phenomenon was not appeared in the same operating sequence. In addition, the flame was stabilized within 17 ms, and it is caused by improved propellants mixing before ignition.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.1
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• pp.49-56
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• 1993

The net flux of global green house gases such as carbon dioxide($CO_2$), methane($CH_4$), and nitrous oxide($N_2O$) emitted from the rotation of paddy-upland soil during growing sesaon under different cropping system was determined. The results obtained were summarized as follows : 1. The net flux of $CO_2$ during the growing season was the highest from continuous cultivation of rice but the lowest from rotation cultivation of rice-soybean. Under the different cropping system the highst emission was from soil of continuous cultivation of rice, but the lowest from converted system. 2. The net emission of methane was the highest from the sold of continuous cultivation of rice, but the flux was remarkably decreased by differing the cropping system. 3. $N_2O$ was emitted greatly from the every two year rotation of potato-chinese cabbage and the next rank was from continuous cultivation of rice, but was decreased notably from rotation cultivation of rice-soybean and potato-chinese cabbage under rotation of paddy-upland cropping system. 4. The ratio of oxygen and carbon dioxide in the soil air was much different with glowing season, the ratio was varied with 4~10 percents for oxygen and 1~22 percents for carbon dioxide. The ratio of carbon dioxide was dozens or hundreds times to that of air, and the variation was very high also. 5. The emission of global green house gases such as carbon dioxide, methane and nitrous oxide was affected by the moisture, temperature and nutrients of soils and the growth period of crops.

• Journal of Climate Change Research
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• v.9 no.1
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• pp.59-67
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• 2018

In this study, the $N_2O$, emitted from combustion facility, were analyzed by using simulated gas and field samples to find out how long samples can be stored in Tedlar bag. According to the results of the experiment using simulated gases (1 ppm, 5 ppm, 10 ppm) in Tedlar bag, After 144hr, $N_2O$ concentration of simulated gases changed that 1 ppm is 5.3%, 5 ppm is 12.8%, and 10ppm is 10.5%. The higher initial concentration of simulated gas was, the larger rate of $N_2O$ concentration was changed. In case of high concentration samples, it need to be careful when it was analyzed after 144 hr. Stability evaluation in Tedlar bag was carried out through field samples such as combustion facility of bituminous coal, B-C oil and LNG. The concentration rate of field samples, which is under 1 ppm of average initial concentration, was evaluated using statistical method. As a result, $N_2O$ concentrations were changed to field samples in the bag even when 96 hr had passed. And after sampling, it is necessary that sample analysis should be quickly as soon as possible.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.153-160
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• 2021

Nitrous oxide is a global warming substance and is known as the main cause of the destruction of the ozone layer because its global warming effect is 310 times stronger than carbon dioxide, and it takes 120 years to decompose. Therefore, in this study, we investigated the characteristics of NOx emission from N2O reduction by thermal decomposition of N2O. Bunsen premixed flames were adopted as a heat source to form a high-temperature flow field, and the experimental variables were nozzle exit velocity, co-axial velocity, and N2O dilution rate. NO production rates increased with increasing N2O dilution rates, regardless of nozzle exit velocities and co-axial flow rates. For N2O, large quantities were emitted from a stable premixed flame with suppressed combustion instability (Kelvin Helmholtz instability) because the thermal decomposition time is not sufficient with the relatively short residence time of N2O near the flame surface. Thus, to improve the reduction efficiency of N2O, it is considered effective to increase the residence time of N2O by selecting the nozzle exit velocities, where K-H instability is generated and formed a flow structure of toroidal vortex near the flame surface.