• Environmental Engineering Research
• /
• v.24 no.1
• /
• pp.107-116
• /
• 2019

Nitrogen removal, nitrous oxide ($N_2O$) emission and microbial community in sequencing batch and continuous-flow intermittent aeration processes were investigated. Two sequencing batch reactors (SBRs) and two continuous-flow multiple anoxic and aerobic reactors (CMRs) were operated under high dissolved oxygen (DO) (SBR-H and CMR-H) and low DO (SBR-L and CMR-L) concentrations, respectively. Nitrogen removal was enhanced under CMR and low DO conditions (CMR-L). The highest total inorganic nitrogen removal efficiency of 91.5% was achieved. Higher nitrifying and denitrifying activities in SBRs were observed. CMRs possessed higher $N_2O$ emission factors during nitrification in the presence of organics, with the highest $N_2O$ emission factor of 60.7% in CMR-L. SBR and low DO conditions promoted $N_2O$ emission during denitrification. CMR systems had higher microbial diversity. Candidatus Accumulibacter, Nitrosomonadaceae and putative denitrifiers ($N_2O$ reducers and producers) were responsible for $N_2O$ emission.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.3
• /
• pp.47-58
• /
• 2020

In this study, a thrust modulation through oxidizer mass flow rate control and internal ballistic analysis based on Whitmore and Chandlers' models was conducted on a blow-down hybrid rocket using nitrous oxide. The tank pressure prediction considering mass flow rate control of the self-pressuring oxidizer was conducted, and the results showed good agreements with experimental results. In order to verify the internal ballistic analysis, a ground combustion test using a 500 N class hybrid rocket was conducted, and it was confirmed that the experimental results and the analytical results were quite consistent in the chamber pressure and thrust, thereby, a modeling technique capable of predicting the thrust modulation performance is proposed.

• Korean Journal of Soil Science and Fertilizer
• /
• v.19 no.1
• /
• pp.76-82
• /
• 1986

A laboratory experiment was conducted to find out the denitrification rate upon the levels of nitrogen and source of organic matter in submerged sandy and sandy loam soil. The results obtained were sumarized as follows; 1. Evolution of nitrous oxide was increased at 1st and 10 days after incubation. And dinitrogen was increased at 1st and 30 days after incubation. Applications of green manure was enhanced the evolution of nitrous oxide ($N_2O$) and dinitrogen ($N_2$). 2. The cumulative denitrification rates at 50 days was high in Gyuam sandy loam soil (O-M: 1.52%) than that of Hamchang sandy soil (O-M: 3.81%). On the other hand, the cumulative emission of dinitrogen was high in Gyuam sandy loam soil while nitrous oxide was high in Hamchang sandy soil. The total mount of denitrification rate was high in order of green manure > rice straw > compost > control soil. 3. Increases of fertilizer nitrogen was enhanced the rate of emission of dinitrogen and nitrous oxide during the incubation time. 4. According to Michaelis-Menten kinetic equation, denitrification rates and reaction efficiency were remarkably increased by application of readily decomposable organic matter with in higher organic matter content of soil. 5. The negative relationship was observed between the evolution of dinitrogen and carbon ($CO_2+CH_4$) while the nitrous oxide with carbon was positive. 6. Under the this experiment conditions 1 mg of carbon was required for production of 4 mg N as $N_2O$ and 3 mg of N as $N_2$, respectively.

• Journal of the Korean Institute of Gas
• /
• v.13 no.6
• /
• pp.34-38
• /
• 2009

Nitrous oxide, which is used as an anesthetic gas, has been shown to be a chronic health hazard. It is necessary to monitor and control the nitrous oxide exposure of the operating theaters staff. In this study, N2O exposure level of the operating nurses is assessed with a GC-ECD. The nitrous oxide gas is collected on a molecular sieve 5A contained in a glass tube and desorbed for 12 hours at $100^{\circ}C$ in heating block. As a result of the test using GC-ECD, calibration curve's $R^2$ of $N_2O$ is 0.9992, LOD is $0.96{\mu}g$/injection, LOQ is $3.21{\mu}g$/injection, desorption efficiency is 94.78 4.50% in average and break through is within 10% compared with the concentration. The average concentration before operation is 5.12ppm and it is 42.3ppm during operation. There are a significant difference showing that the P value is lower than 0.05. Assessing exposure level to nitrous oxide based on nurses' working positions, the exposure levels do not show significant difference( P>0.005). And $N_2O$ in active sampling method is higher than passive sampling method(P<0.05).

• Journal of the korean academy of Pediatric Dentistry
• /
• v.47 no.1
• /
• pp.53-61
• /
• 2020

Midazolam is a short-acting benzodiazepine that is widely used in pediatric dental sedation. However, its clinical effectiveness as an intravenous sedative agent in children has not been widely documented. A retrospective study was conducted to evaluate the efficacy and safety of intravenous midazolam and nitrous oxide inhalation sedation in pediatric dental treatment. The subjects were 115 patients (118 cases) who received dental treatment under intravenous midazolam and nitrous oxide inhalation sedation. Demographic factors, general health status, sedation time, midazolam and nitrous oxide dosage, and success rate of sedation were evaluated from electronic medical records. Behavioral management was the main reason of choosing sedation. Mean duration of sedation was 56.7 minutes for surgical treatment, and 74.4 minutes for restorative treatment. The initial dosage of intravenous midazolam was 0.051 ± 0.019 mg/kg. In 34 cases (28.8%), additional midazolam of 0.036 ± 0.057 mg/kg was delivered during the treatment. The concentration of nitrous oxide was maintained between 40% and 50%. The success rate of sedation was 99% (n = 117). In 1 case, laryngospasm occurred and the patient was reversed with benzodiazepine antagonist, flumazenil. Intravenous midazolam sedation with nitrous oxide was shown to be clinically effective for the dental treatment in children, if administered by trained personnel and patients are carefully selected in accordance with guidelines.

• 대한치과마취과학회:학술대회논문집
• /
• 2001.11a
• /
• pp.52-57
• /
• 2001

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 1992.10a
• /
• pp.101-106
• /
• 1992

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.9
• /
• pp.1045-1050
• /
• 2014

$N_2O$(Nitrous Oxide) is known as the third major GHG(Green House Gas) following $CO_2$(Carbon Oxide) and $CH_4$(Methane). The GWP(Global Warming Potential) factor of $N_2O$ is 310 times as large as that of $CO_2$ because $N_2O$ in the atmosphere is very stable, and it becomes a source of secondary contamination after photo-degradation in the stratosphere. Investigation on the cause of the $N_2O$ formation have been continuously reported by several researchers on power sources with continuous combustion form, such as a boiler. However, in the diesel engine, research on $N_2O$ generation which has effected from fuel components has not been conducted. Therefore, in this research, author has investigated about $N_2O$ emission rates which was changed by nitrogen and sulfur concentration in fuel on the diesel engine. The test engine was a 4-stroke direct injection diesel engine with maximum output of 12 kW at 2600rpm, and operating condition of that was set up at a 75% load. Nitrogen and sulfur concentrations in fuel were raised by using six additives : nitrogen additives were Pyridine, Indole, Quinoline, Pyrrol and Propionitrile and sulfur additive was Di-tert-butyl-disulfide. In conclusion, diesel fuels containing nitrogen elements less than 0.5% did not affect $N_2O$ emissions in the all concentrations and kinds of the additive agent in the fuel. However, increasing of the sulfur additive in fuel increased $N_2O$ emission in exhaust gas.

• Korean Journal of Environmental Agriculture
• /
• v.13 no.3
• /
• pp.359-372
• /
• 1994

A simplified closed static chamber method was devised for measurement of methane flux from paddy fields. Compared to automatic methane measuring system(AMMS) this chamber method provides availability with moderate costs of setup and maintenance, while it also provides the time-effectiveness compared to other closed top-type chamber method. It accomodates 30 chambers within 2 hours sampling period with two persons. And it provide a rapid and accurate analysis of methane, 30-40 samples per hour. Modified method for $N_2O$ measurements provides a precise and accurate analysis of nitrous oxide without upgrading additional heating zones for gas sampling(switching) valves.

• Journal of Environmental Science International
• /
• v.20 no.6
• /
• pp.755-765
• /
• 2011

Nitrous oxide ($N_2O$) is one of six greenhouse gases listed up in the Kyoto Protocol, and it effects a strong global warming because of its much greater global warming potential (GWP), by 310 times over a 100-year time horizon, than $CO_2$. Although such $N_2O$ emissions from both natural and anthropogenic sources occur, the latter can be controlled using suitable abatement technologies, depending on them, to reduce $N_2O$ below acceptable or feasible levels. This paper has extensively reviewed the anthropogenic $N_2O$ emission sources and their related compositions, and the state-of-the-art non-catalytic and catalytic technologies of the emissions controls available currently to representative, large $N_2O$ emission sources, such as adipic acid production plants. Challengeable approaches to this source are discussed to promote establishment of advanced $N_2O$ emission control technologies.