• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.269-272
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• 2009

Catalytic decomposition of nitrous oxide was investigated experimentally. Two noble metal catalyst (Pt, Ir) were chosen to decompose nitrous oxide. Each catalyst was tested with different chamber pressure and preheating temperature. Ir decomposed $N_2O$ at lower temperature ($230^{\circ}C$) and suitable for $N_2O$ decomposition. In addition, the minimum required preheating temperature decreased as the chamber pressure increased. However, deactivation of Ir catalyst was observed during the experiments.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.4
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• pp.398-404
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• 2007

In this paper, thermal characteristics of a nitrous oxide ($N_2O$) catalytic reactor with packed-bed geometry are theoretically and numerically investigated. Several researchers experimentally presented that catalytic decomposition of $N_2O$ in a packed bed generates about 82kJ/mole in the exothermic reaction. Based on the results they have studied the catalytic decomposition of $N_2O$ in a packed bed to use it not only as a mono-propellant thrust for small satellites but also as an igniter system for hybrid rockets. So we aim to identify important parameters existing in an $N_2O$ packed-bed geometry, and to clarify its critical effect on thermal characteristics of the catalytic igniter using a porous medium approach.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.139-141
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• 2017

By modulating the flow rate of $N_2O$ into a HR motor assembly, a control valve of a hybrid rocket engine plays a role to increase or decrease the thrust. In this study, the control valve has been designed to meet the requirements which are response speed(${\leq}$ about 1 second) and torque(${\geq}$ about $36N{\cdot}m$). Then, when analog signal 0~10V is applied, the situation where the valve is opened and closed has to be realized. To do this, the data values have to be entered into the actuator. Finally, the performance evaluation of the control valve has been performed to validate this product.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.144-147
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• 2017

A hybrid rocket engine capable of thrust throttling and underwater-working was developed for the underwater high-speed vehicle propulsion system. The hybrid rocket engine was designed and made by two types of ground test motor and underwater working motors. An engine performance was verified by the ground tests with the ground test motor and in the case of underwater motors the ground tests and underwater tests were performed. For the underwater operation a two-stage ignition system was adopted and a rupture disc was installed at the end of nozzle for a water-tight just before an ignition. Successful ignition and propulsion were confirmed in the underwater test with the final selected double rupture disc.

• Journal of Power System Engineering
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• v.18 no.6
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• pp.106-112
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• 2014

The diesel engine, which has high compression ratio than other heat engines, has been using as the main power source of marine transport. Especially, since marine diesel engines offer better specific fuel consumption (SFC), it is environment-friendly compared to those used in other industries. However, attentio should be focused on emissions such as nitrous oxide ($N_2O$) which is generated from combustion of low-grade fuels. Because $N_2O$ in the atmosphere is very stable, the global warming potential (GWP) of $N_2O$ is 310 times as large as that of $CO_2$, and it becomes a source of secondary contamination after photo-degradation in the stratosphere. It has been hitherto noted on the $N_2O$ exhaust characteristics from stationary power plants and land transportations, but reports on $N_2O$ emission from the marine diesel engine are very limited. In this experimental study, a author investigated $N_2O$ emission characteristics by using changed diesel fuel components of nitrogen and sulfur concentration, assessed on the factors which affect $N_2O$ generation in combustion. The experimental results showed that $N_2O$ emission exhibited increasement with increasing of sulfur concentration in fuel. However, all kinds of nitrogen component additives used in experiment could not change $N_2O$ emission.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.251-254
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• 2008

Ground firing test facility and test field for firing test of hybrid rocket engine were constructed. Ground firing test facility were composed of hybrid rocket engine, thrust stand, oxidizer storage/supply system, control system and data acquisition system. Firing tests of thrust 50 kgf class were conducted. Stable performance data was obtained and operational reliability of ground firing test facility were found.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.3
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• pp.112-118
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• 2019

The development of an underwater rocket propulsion system was described in this paper. Throttle able liquid propellant and hybrid rocket propulsion systems were selected for underwater propulsion. A subscale liquid rocket combustion chamber and it's portable stand were developed and their applicability was examined. 1.5-ton.f and 1.8-ton.f hybrid rockets were developed for underwater applications. The test results indicated that the 18-ton.f hybrid rocket fully complies to the performance and underwater cruise stability requirements; thus, its development was concluded to be successfully complete.

• Korean Journal of Environmental Agriculture
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• v.42 no.4
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• pp.418-426
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• 2023

This study focused on nitrous oxide, a major greenhouse gas produced in agricultural settings through bacterial nitrogen oxidation in aerobic soil. Nitrogen fertilizer in farmland is identified as a primary source of nitrous oxide. The importance of reducing excess nitrogen in soil to mitigate nitrous oxide production is well-known. The study investigated the use of liquefied pig manure as an alternative to urea fertilizer in conventional agriculture. Results showed a more than two-fold reduction in nitrous oxide emissions in pepper cultivation areas with liquefied pig manure compared to that with urea fertilizer. The population of Nitrosospira, a nitrous oxide-producing bacterium, decreased by over 10% with liquefied pig manure. Additionally, nirK and nosZ, which are related to the denitrification process, significantly increased in the urea fertilizer group, whereas levels in the liquefied pig manure group resembled those with no nitrogen treatment. In conclusion, the experiment confirmed that liquefied pig manure can serve as an eco-friendly nitrogen fertilizer, significantly reducing nitrous oxide production, a major contributor to the atmospheric greenhouse effect.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1195-1206
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• 2011

This study was conducted to apply LCA (Life cycle assessment) methodology to lettuce (Lactuca sativa L.) production systems in Namyang-ju as a case study. Five lettuce growing farms with three different farming systems (two farms with organic farming system, one farm with a system without agricultural chemicals and two farms with conventional farming system) were selected at Namyangju city of Gyeonggi-province in Korea. The input data for LCA were collected by interviewing with the farmers. The system boundary was set at a cropping season without heating and cooling system for reducing uncertainties in data collection and calculation. Sensitivity analysis was carried out to find out the effect of type and amount of fertilizer and energy use on GHG (Greenhouse Gas) emission. The results of establishing GTG (Gate-to-Gate) inventory revealed that the quantity of fertilizer and energy input had the largest value in producing 1 kg lettuce, the amount of pesticide input the smallest. The amount of electricity input was the largest in all farms except farm 1 which purchased seedlings from outside. The quantity of direct field emission of $CO_2$, $CH_4$ and $N_2O$ from farm 1 to farm 5 were 6.79E-03 (farm 1), 8.10E-03 (farm 2), 1.82E-02 (farm 3), 7.51E-02 (farm 4) and 1.61E-02 (farm 5) kg $kg^{-1}$ lettuce, respectively. According to the result of LCI analysis focused on GHG, it was observed that $CO_2$ emission was 2.92E-01 (farm 1), 3.76E-01 (farm 2), 4.11E-01 (farm 3), 9.40E-01 (farm 4) and $5.37E-01kg\;CO_2\;kg^{-1}\;lettuce$ (farm 5), respectively. Carbon dioxide contribute to the most GHG emission. Carbon dioxide was mainly emitted in the process of energy production, which occupied 67~91% of $CO_2$ emission from every production process from 5 farms. Due to higher proportion of $CO_2$ emission from production of compound fertilizer in conventional crop system, conventional crop system had lower proportion of $CO_2$ emission from energy production than organic crop system did. With increasing inorganic fertilizer input, the process of lettuce cultivation covered higher proportion in $N_2O$ emission. Therefore, farms 1 and 2 covered 87% of total $N_2O$ emission; and farm 3 covered 64%. The carbon footprints from farm 1 to farm 5 were 3.40E-01 (farm 1), 4.31E-01 (farm 2), 5.32E-01 (farm 3), 1.08E+00 (farm 4) and 6.14E-01 (farm 5) kg $CO_2$-eq. $kg^{-1}$ lettuce, respectively. Results of sensitivity analysis revealed the soybean meal was the most sensitive among 4 types of fertilizer. The value of compound fertilizer was the least sensitive among every fertilizer imput. Electricity showed the largest sensitivity on $CO_2$ emission. However, the value of $N_2O$ variation was almost zero.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.1
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• pp.52-61
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• 1998

Nitrification and denitrification are important processes in the landfill site as they are deeply related with degradation and stabilization of refuse. Also nitrous oxide ($N_2O$) which is released from both nitrification and denitrification is known as greenhouse gas (GHG). The purpose of this study was to clarify the process by which $N_2O$ produced using $^{15}N$ isotope. Nitrate which was labeled to 10.08% with $^{15}KNO_3$ was used and $N_2O$ was analyzed with GC mass. Results was that even also when $O_2$ of bulk was 15%, $N_2O$ was released from denitrification. And as concentrations of $O_2$ increase, sum of $N_2O$ was released from denitrification. And as concentrations of $O_2$ increase, sum of $N_2O$ and $N_2$ was decreased and ratios of $N_2O$ in the reduced gases were increased. FISH technics also adaped to confirm whether which of nitrifiers existed in the substrates. When NEU was used of which the target was ammonia oxidizing bacteria, nitrifier was not detected at all. So it was confirmed that during the reaction denitrification was dominant process. Total bacteria distributions which were detected by EUB probe explained that as $O_2$ increase the number of bacteria also increase, but between the 10-15% of $O_2$ there was no any differences.