• Korean Journal of Agricultural and Forest Meteorology
• /
• v.24 no.4
• /
• pp.285-294
• /
• 2022

In order to accurately calculate greenhouse gas emissions in the agricultural field, Korea has been developing national-specific emission factors through direct measurement of gas fluxes using the closed-chamber method. In the rice paddy, only national-specific emission factors for methane (CH₄) have been developed. It is thus necessary to develop those for nitrous oxide (N₂O) affected by the application of nitrogen fertilizer. However, since the concentration of N₂O emission from rice cultivation is very low, the QA/QC methods such as method detection and practical quantification limits are important. In this study, N₂O emission from a rice paddy was evaluated affected by the amount of nitrogen fertilizer, by taking into account both method detection and practical quantification limits for N₂O concentration. The N₂O emission from a rice paddy soils affected by the nitrogen fertilizer application was estimated in the following order. The method detection limit (MDL) of N₂O concentration was calculated at 95% confidence level based on the pooled standard deviation of concentration data sets using a standard gas with 98 nmol mol^-1 N₂O 10 times for 3 days. The practical quantification limit (PQL) of the N₂O concentration is estimated by multiplying 10 to the pooled standard deviation. For the N₂O flux data measured during the rice cultivation period in 2021, the MDL and PQL of N₂O concentration were 18 nmol mol^-1 and 87 nmol mol^-1, respectively. The measured values above the PQL were merely about 12% of the total data. The cumulative N₂O emission estimated based on the MDL and PQL was higher than the cumulative emission without nitrogen fertilizer application. This research would contribute to improving the reliability in quantification of the N₂O flux data for accurate estimates of greenhouse gas emissions and uncertainties.

• Journal of Yeungnam Medical Science
• /
• v.36 no.1
• /
• pp.50-53
• /
• 2019

Awareness during general anesthesia occurs in approximately 0.1-0.2% of cases; nevertheless, particular attention is required because it can lead to critical complications including insomnia, depression, anxiety, and post-traumatic stress disorder. To prevent these complications, bispectral index (BIS) and end-tidal anesthetic gas (ETAG) concentration monitoring are commonly used to examine patient consciousness during surgery. In the present case, an 80-year-old man was scheduled for total gastrectomy. Anesthesia was maintained using desflurane 4.0-5.0% vol, oxygen, and nitrous oxide. The authors simultaneously monitored BIS, which was maintained between 37 and 43, and ETAG, which was maintained between 0.9 and 1.2 minimum alveolar concentration (MAC). After the operation, however, the authors were surprised to learn that the patient complained of awareness during anesthesia. Although BIS and ETAG concentration monitoring are useful in preventing awareness during anesthesia, they cannot be completely trusted. Even though BIS was maintained at approximately 40 and ETAG at 0.7-1.3 MAC, awareness during anesthesia occurred.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.434-435
• /
• 2012

Plasma enhanced chemical vapor deposition (PECVD) silicon dioxide thin films have many applications in semiconductor manufacturing such as inter-level dielectric and gate dielectric metal oxide semiconductor field effect transistors (MOSFETs). Fundamental chemical reaction for the formation of SiO2 includes SiH4 and O2, but mixture of SiH4 and N2O is preferable because of lower hydrogen concentration in the deposited film [1]. It is also known that binding energy of N-N is higher than that of N-O, so the particle generation by molecular reaction can be reduced by reducing reactive nitrogen during the deposition process. However, nitrous oxide (N2O) gives rise to nitric oxide (NO) on reaction with oxygen atoms, which in turn reacts with ozone. NO became a greenhouse gas which is naturally occurred regulating of stratospheric ozone. In fact, it takes global warming effect about 300 times higher than carbon dioxide (CO2). Industries regard that N2O is inevitable for their device fabrication; however, it is worthwhile to develop a marginable nitrous oxide free process for university lab classes considering educational and environmental purpose. In this paper, we developed environmental friendly and material cost efficient SiO2 deposition process by substituting N2O with O2 targeting university hands-on laboratory course. Experiment was performed by two level statistical design of experiment (DOE) with three process parameters including RF power, susceptor temperature, and oxygen gas flow. Responses of interests to optimize the process were deposition rate, film uniformity, surface roughness, and electrical dielectric property. We observed some power like particle formation on wafer in some experiment, and we postulate that the thermal and electrical energy to dissociate gas molecule was relatively lower than other runs. However, we were able to find a marginable process region with less than 3% uniformity requirement in our process optimization goal. Surface roughness measured by atomic force microscopy (AFM) presented some evidence of the agglomeration of silane related particles, and the result was still satisfactory for the purpose of this research. This newly developed SiO2 deposition process is currently under verification with repeated experimental run on 4 inches wafer, and it will be adopted to Semiconductor Material and Process course offered in the Department of Electronic Engineering at Myongji University from spring semester in 2012.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.43 no.4
• /
• pp.435-442
• /
• 2016

The aim of this study was to analyze physiological changes, clinical and subjective symptoms by different $N_2O$ concentrations and administration method. This study surveyed 65 men and women ages 19 to 35 and all subjects were healthy volunteers, with no contraindication for use of $N_2O$ sedation. The $N_2O$ sedation was carried out in a way that increases by 10 percent to one-minute interval or increases at once the desired level. Each method was required to reach 30 or 50 percent $N_2O$ concentration. The way to gradually raise the $N_2O$ concentration can reduce the risk by decreasing the pulse reduction rate at the same $N_2O$ concentration. $SpO_2$ has no statistical significance according to $N_2O$ concentration and method of administration. Pulse rate reduced significantly when 50% $N_2O$ increase at once during sedation and 100% $O_2$ after 5 minutes. The way to gradually raise the $N_2O$ concentration is safe for reducing pulse rate.

• Journal of Advanced Marine Engineering and Technology
• /
• v.33 no.2
• /
• pp.267-271
• /
• 2009

The Marine Environment Protection Committee(MEPC) which is the IMO's specialized committee on marine pollution related matters deals with GHG related issues to discuss and compile possible approaches on technical, operational and market based measures to address GHG emissions from ships. The nitrous oxide($N_2O$) which remains generally in the atmosphere for around 114 years is one of the green house gases. The global warming potential of $N_2O$ is 310 times than $CO_2$ in the given period 100 years. It seems that the $N_2O$ formation is influenced by the nitrogen compound contained in the fuel which is named as "Fuel N" during the combustion process or the NOx, SOx and $H_2O$ through the emission gases before exhausted into the atmosphere. This paper has carried out an experimental study of the $N_2O$ concentration profiles by the change of $NH_3$ flows in the planner premixed combustion with using $C_3H_8$ and air.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.39 no.1
• /
• pp.11-16
• /
• 2012

Effect of supplementary intranasal midazolam on oral sedation of children The purpose of this study was to compare the cardiopulmonary parameters of two sedation regimens during dental treatment: (1) Oral chloral hydrate(CH) and hydroxyzine(HZ) with nitrous oxide-oxygen($N_2O/O_2$) inhalation(CH-HZ group); (2) Oral chloral hydrate(CH) and hydroxyzine(HZ) with nitrous oxide-oxygen($N_2O/O_2$) inhalation and supplementary intranasal(IN) midazolam administration(MIDA group). Among the patients of OO hospital who received dental treatment under sedation over the past 5 years, 44 patients were selected for each group of CH-HZ and MIDA according to their age, gender and weight. Following parameters that were recorded every 5 minutes were compared: 1) Heart rate(HR) 2) $O_2$ saturation 3) End tidal carbon dioxide concentration($EtCO_2$) 4) Respiratory rate(RR) 33 patients of Group MIDA who have complete data of 15 minutes before and after supplementary IN midazolam administration were selected. And measurements 15 minutes before and after midazolam administration in same patient were evaluated. The results were as follows: 1. Heart rate was significantly higher in MIDA group than in CH-HZ group, but it was within normal range. 2. Comparing HR, $O_2$ saturation, EtCO2, RR between before and after of supplementary IN midazolam administration in the same patient, the differences were not statistically significant.

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

• Korean Chemical Engineering Research
• /
• v.40 no.6
• /
• pp.746-751
• /
• 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 Marine Environment & Safety
• /
• v.21 no.2
• /
• pp.188-193
• /
• 2015

It has been generally recognized that $N_2O$(Nitrous Oxide) emission from marine diesel engines has a close correlation with $SO_2$(Sulfur Dioxide) emission, and diversity of fuel elements using ships affects characteristics of the $N_2O$ emission. According to recent reports, in case of existence of an enough large NO(Nitric Oxide) generated as fuel combustion, effect of the $SO_2$ emission in exhaust gas on the $N_2O$ formation is more vast than effect of the NO. Therefore, $N_2O$ formation due to the $SO_2$ element operates on a important factor in EGR(Exhaust Gas Recirculation) systems for NOx reduction. An aim of this experimental study is to investigate that intake gas of the diesel engine with increasing of $SO_2$ flow rate affects $N_2O$ emission in exhaust gas. A test engine using this experiment was a 4-stroke direct injection diesel engine with maximum output of 12 kW at 2600rpm, and operating condition was set up at a 75% load. A standard $SO_2$ gas with 0.499%($m^3/m^3$) was used for changing of $SO_2$ concentration in intake gas. In conclusion, the diesel fuel included out sulfur elements did mot emit the $SO_2$ emission, and the $SO_2$ emission in exhaust gas according as increment of the $SO_2$ standard gas had almost the same ratio compared with $SO_2$ rate in mixture inlet gas. Furthermore, the $N_2O$ element in exhaust gas was formed as $SO_2$ mixture in intake gas because increment of $SO_2$ flow rate in intake gas increased $N_2O$ emission. Hence, diesel fuels included sulfur compounds were combined into $SO_2$ in combustion, and $N_2O$ in exhaust gas should be generated to react with NO and $SO_2$ which exist in a combustion chamber.

• Korean Journal of Ecology and Environment
• /
• v.46 no.3
• /
• pp.409-418
• /
• 2013

Global warming due to climate change is a problem facing the entire world. Several factors, such as $CO_2O$ concentration, level of warming, soil temperature, precipitation, water content of soil and denitrification by denitrifying bacteria influence the emission of nitrous oxide ($N_2O$) from soil. In this study, we investigated nitrous oxide emissions from the soil of two wetlands, Jilmoineup in Mt. Odae and Moojechineup in Mt. Jungjok, according to temperature change. Soil collected in Jilmoineup in July showed increasing $N_2O$ emissions as temperature increases, but did not show any significant differences at $10^{\circ}C$ (p<0.05). Soil of $15^{\circ}C$ and $20^{\circ}C$ showed increasing pattern of $N_2O$ emissions until 24 h. After that, however, there was no difference in temperature. Overall, $N_2O$ emissions showed significant differences according to temperature (p<0.05). Soil collected from Moojechineup in July showed increasing $N_2O$ emissions according to temperature increase, but did not show any significant differences at $10^{\circ}C$ (p<0.05) as was the case for Jilmoineup soil. On the other hand, two wetland soils showed a slight increase of $N_2O$ emissions by additional nitrogen supply, but did not show any significant differences in the presence of nitrogen or between nitrogen sources. In conclusion, increasing temperature the wetland soil increased the emission of $N_2O$, which is a known greenhouse gas. In order to more clearly identify $N_2O$ emissions, various subsequent studies such as the influence and correlation of several factors are required.