• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.73-82
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• 2012

The main and side reactions of the three selective catalytic reduction (SCR) reactions with ammonia over a vanadium-based catalyst have been investigated using synthetic gas mixtures in the temperature range of $170{\sim}590^{\circ}C$. The three SCR reactions are standard SCR with pure NO, fast SCR with an equimolar mixture of NO and $NO_2$, and $NO_2$ SCR with pure $NO_2$. Vanadium based catalyst has no significant activity in NO oxidation to $NO_2$, while it has high activity for $NO_2$ decomposition at high temperatures. The selective catalytic oxidation of ammonia and the formation of nitrous oxide compete with the SCR reactions at the high temperatures. Water strongly inhibits the selective catalytic oxidation of ammonia and the formation of nitrous oxide, thus increasing the selectivity of the SCR reactions. However, the presence of water inhibits the SCR activity, most pronounced at low temperatures. In this study, the experimental results are analyzed by means of a dynamic one-dimensional isothermal heterogeneous plug-flow reactor (PFR) model according to the Eley-Rideal mechanism.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.6
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• pp.598-603
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• 2014

The level of nitrous oxide ($N_2O$), a long-lived greenhouse gas, in atmosphere has increased mainly due to anthropogenic sources, especially application of nitrogen fertilizers. Quantifying $N_2O$ emission in the agricultural field is essential to develop National inventories of greenhouse gases (GHGs) emission. The objective of this study was to develop emission factor to estimate direct $N_2O$ emission from agricultural field by measuring $N_2O$ emissions in the red pepper cultivating field from 2010 to 2012. Emission factor of $N_2O$ calculated from accumulated $N_2O$ emission, nitrogen fertilization rate, and background $N_2O$ emission was $0.0086{\pm}0.00043kg$ $N_2O-N\;kg^{-1}$ N resulted from three year experiment of the research sites. More extensive studies need to be conducted to develop $N_2O$ emission factors for other upland crops in the various regions of Korea because $N_2O$ emission is influenced by many factors including climate characteristics, soil properties, and agricultural practices.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.547-555
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• 2009

The objectives of this research were focused on the effects of various operating parameters on nitrous oxide emission such as C/N ratio, ammonia concentration and HRT in the hybrid and suspension reactors. With the decreasing of C/N ratios, $N_2O$ emission rates in the both processes were increased because organic carbon source for denitrification was depleted. In case of biofilm reactor operated using medium, $N_2O$ release from the nitrification was not affected by the variation of ammonia concentration. But in the suspension reactor, $N_2O$ production from the nitrification was rapidly increased with the increase of ammonia. Nitrite accumulation caused by undesirable nitrification conditions could be a important reason for the increase in the $N_2O$ production from the aerobic reactor. And rapid increase in $N_2O$ production was reflected by the decrease of HRT, similar to the results observed in the results of ammonia loading changes. So it could be said that it is very important to put in consideration both its optimum conditions for wastewater treatment efficiency and suitable conditions for $N_2O$ diminish, simultaneously, in order to development an eco-friendly and advanced wastewater treatment, especially in BNR process.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.233-236
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• 2009

In this study, the characteristic of the hybrid rocket motor with $LN_2O$(Liquid Nitrous oxide) was investigated experimentally. HDPE(High Density PolyEthlene) was used as fuel with different sized single port. When used $LN_2O$, combustion efficiency is lower than using $GN_2O$(Gas Nitrous oxide), because of completeness of vaporization of droplet and mixing. And regression rate was changed by different oxidizer phase. This behavior was considered that flame temperature and combustion of solid fuel front/end surface.

• Korean Chemical Engineering Research
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• v.43 no.4
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• pp.467-473
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• 2005

Liquid phase nitrous oxide ($N_2O$) contains air, carbon monoxide, water, carbon dioxide and NOx as main impurities. It is known to be very dangerous to obtain a very pure $N_2O$ product by using solidification at low temperature. In this study a new method to obtain a high purity of $N_2O$ product based on a continuous distillation process was introduced. For the modeling of the continuous distillation process to obtain a product having a purity over 99.999％ of $N_2O$ stream, Intalox wire gauze packing- No. SCH-80S gauze packing column was used. Peng-Robinson equation of state was used for the modeling of the continuous distillation process and refrigeration system. Computational results performed in this work showed a good agreement with Aspen Plus simulation results.

• Applied Chemistry for Engineering
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• v.5 no.1
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• pp.139-148
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• 1994

The partial oxidation of methane with nitrous oxide on silica-supported metal-oxygen cluster compounds, known as heteropoly acids, has been studied. The effects of several variables such as reaction temperature, partial pressure of reactants, residence time, loading of the catalysts, and pretreatment temperature, on the conversion and product distribution were observed. The kinetics also has been studied. The conversion and yield of formaledehyde show maximum values at a loading of 20 wt%. The apparent reaction order of methane conversion is ca. 1.0 with respect to $CH_4$ and ca. 0.4 with respect to $N_2O$. In addition, the apparent activation energy is 30.78 kcal/mole. The addition of small quantities methane whereas water introduced to the reactant decreased the activity of catalyst under present study.

• Journal of Dental Anesthesia and Pain Medicine
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• v.15 no.4
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• pp.213-220
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• 2015

Background: Pediatric dentists face challenges when young patients require a mesiodens extraction. General anesthesia may be a burden to the child as well as the parent due to dental fears and costs. The aim of this study was to evaluate oral and intravenous sedation in the outpatient setting as a safe and effective means of managing patients who require a mesiodens extraction. Methods: Records were reviewed retrospectively to find patients who underwent a mesiodens removal procedure from January 2013 to September 2014 in the Department of Pediatric Dentistry at Ajou University Hospital (Suwon, Gyeonggi-do, Republic of Korea). A total of 81 patients (62 male and 19 female) between 4 and 11 years of age (mean [${\pm}SD$] $81.6{\pm}14.1$ months) were studied, with a mean weight of $22.9{\pm}3.3kg$ (16 kg to 30 kg). Vital signs, sedation drug dosage, and sedation time were studied. Results: Mean doses of $63.7{\pm}2.5mg/kg$ chloral hydrate and $1.36{\pm}0.22mg/kg$ hydroxyzine were used for oral sedation. Nitrous oxide/oxygen was administrated for $40.0{\pm}2.1$ min. The mean dose of midazolam administered intravenously was $0.14{\pm}0.06mg/kg$ ($2.38{\pm}0.97$ times). In all cases, the mesiodens was removed successfully. Conclusions: Intravenous sedation combined with oral sedation and nitrous oxide/oxygen inhalation can be an alternative to general anesthesia when administrated and monitored properly.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.3
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• pp.163-169
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• 2015

The level of nitrous oxide ($N_2O$), a long-lived greenhouse gas, in atmosphere has increased mainly due to anthropogenic sources, especially application of nitrogen fertilizers. Quantifying $N_2O$ emission in the agricultural field is essential to develop national inventories of greenhouse gases (GHGs) emission. The objective of this study was to develop an emission factor to estimate the direct $N_2O$ emission from an agricultural field cultivated with the Chinese cabbage during autumn season in 2010-2012. Emission factor of $N_2O$ calculated over three years experiment using accumulated $N_2O$ emission, nitrogen fertilization rate, and background $N_2O$ emission was $0.0058{\pm}0.00254kg\;N_2O-N\;kg^{-1}\;N$. More extensive studies need to be conducted to develop $N_2O$ emission factors for other upland crops in the various regions of Korea because $N_2O$ emission is influenced by many factors including climate characteristics, soil properties, and agricultural practices as well as crop species.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.4
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• pp.589-594
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• 1999

There are some problems in inhalation sedation of non-cooperative pediatric patients. Usually the pediatric patients reject the nasal hood and there's no cooperation for administration of nitrous oxide gas. In mouth breathing patient, other technics of sedation such as intravenous or oral sedation or general anesthesia were recommended. Common causes of mouth breathing are common cold, allergic rhinitis, sinus problem, anatomical disorder, and habitual mouth-breathing. However in some patient not indicated the general anesthesia and high failure rate in oral and intravenous sedation. Administration of $N_2O-O_2$ with suction catheter was applied in full mouth breathing patient. Clinically effective sedation were occurred during procedure about 45 to 55 minutes. There's no any side effects by $N_2O-O_2$ inhalation sedation. The patients awoke at the end of the procedure and received 100% oxygen for 2-3 minutes. There's still some problems in use of the suction catheter such as air pollution of operation theater and elevate arterial carbon dioxide tension.

• Journal of The Korean Dental Society of Anesthesiology
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• v.4 no.2 s.7
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• pp.90-95
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• 2004

Background: Sevoflurane, a rotatively new inhalational anesthetic. has non-pungent odor and is less reluctant to pediatric patients. The purpose of this study is to examine the feasibility of sevoflurane in inhalational sedation instead of the nitrous oxide for short and simple dental treatments in pediatric patients. Patients and Methods: Fifteen healthy children, whose dental treatment was abandoned due to their little or no cooperation, were selected with their caregivers' written permission. Deep sedation was induced and maintained with oxygen and 1-5% sevoflufane via specially designed nasal mask. Blood pressure, heart rate, oxygen saturation, and electrocardiogram were monitored at 3-nin interval. A dental anesthesiologist, who was independent of dental treatments, was wholly responsible for the sedation procedure. Post-sedation complications and operator's and caregiver's acceptability of this type of inhalational sedation were also investigated. Results: The systolic and diastolic blood pressure, heart rate, and oxygen saturation was significantly depressed during the deep sedation using sevoflurane (P < 0.05). No severe post-sedation complications were found, however, bradycardia was reported in 3 patients. Almost all the operators and caregivers answered that they would adapt this sedation procedure again if possible. Conclusion: In this study, inhalational deep sedation using sevoflurane for dental treatments was found to be very useful. Furthermore, the application of sevoflurane to conscious sedation for pediatric and adult dental patients should be added.