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

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.5
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• pp.46-52
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• 2009

In this study the predictions of NOx in methane-air lean premixed combustion in PSR were carried out with GRI 3.0 methane-air combustion mechanism and Zeldovich, nitrous oxide, prompt, and NNH NO formation mechanism by using CHEMKIN code. The results are compared to the JSR experimental data of Rutar for the validation of the model. This study concerns about the importance of the chemical pathways. The chemical pathway most likely to form the NO in methane-air lean-premixed combustion was investigated. The results obtained with the 4 different NO mechanisms for residence time(0.5-1.6ms) and pressure(3, 4.7, 6.5 atm) are compared and discussed.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.1
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• pp.20-24
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• 2012

Denitrification rate was determined for various freshwater wetland types in the Mississippi River Coastal delta plain. Site 1 and 4 were collected from forested-tupelo dominated wetland, and site 2 and 3 were from floating emergent marsh. The maximum $N_2O$ emission was $7.47mg\;N\;m^{-2}$ for site 1 at day 6 after the addition of nitrate, $6.96mg\;N\;m^{-2}$ for site 2 at day 4, $6.63mg\;N\;m^{-2}$ for site 3 at day 3, and $9.64mg\;N\;m^{-2}$ for site 4 at day 4. The denitrification rate was determined using the acetylene inhibition method $1.24mg\;N\;m^{-2}d^{-1}$ for site 1, $1.93mg\;N\;m^{-2}d^{-1}$ for site 2, $2.24mg\;N\;m^{-2}d^{-1}$ for site 3, and $2.78mg\;N\;m^{-2}d^{-1}$ for site 4. The maximum denitrification rate was in the order of site 4 > site 3 > site 2 > site 1.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.7
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• pp.1030-1035
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• 2008

Recently, the International Maritime Organization makes an effort for an effective solution against the emissions from shipping in the international maritime industry. The objective of the study was to quantify the exhaust emissions of marine heavy fuel oil in the combustion process of the spray flame. An experiment was performed to measure CO, $CO_2$, NOx, $SO_2$, ${N_2}O$, DS, SOF and the other components with the flame temperature. The sampling probe was directly set up in the flame fields at each position of 103, 324, 545, 766 and 987mm vertically apart from the fuel-injected nozzle in the burner furnace. From the results of the study, it was estimated that approximately 270ppm of oxides of nitrogen (NOx), $1000{\sim}1400ppm$ of sulfur dioxide ($SO_2$), 8ppm of nitrous oxide (${N_2}O$), $2.0{\sim}2.5g/m^3$ of particulate matter (PM) divided with dry soot (DS) and soluble organic fraction (SOF) and $60{\sim}80mg/m^3$ of sulfuric acid. With respect to further development of this work, the emission quantification could also be applied to assessing emission reduction from the international shipping.

• Journal of Microbiology and Biotechnology
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• v.23 no.5
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• pp.719-723
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• 2013

Nitrification in wastewater treatment emits a significant amount of nitrous oxide ($N_2O$), which is one of the major greenhouse gases. However, the actual mechanism or metabolic pathway is still largely unknown. Selective nitrification inhibitors were used to determine the nitrification steps responsible for $N_2O$ emission with activated sludge and enriched nitrifiers. Allylthiourea (86 ${\mu}M$) completely inhibited ammonia oxidation and $N_2O$ emission both in activated sludge and enriched nitrifiers. Sodium azide (24 ${\mu}M$) selectively inhibited nitrite oxidation and it led to more $N_2O$ emission than the control experiment both in activated sludge and enriched nitrifiers. The inhibition tests showed that $N_2O$ emission was mainly related to the activity of ammonia oxidizers in aerobic condition, and the inhibition of ammonia monooxygenase completely blocked $N_2O$ emission. On the other hand, $N_2O$ emission increased significantly as the nitrogen flux from nitrite to nitrate was blocked by the selective inhibition of nitrite oxidation.

• Journal of Microbiology and Biotechnology
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• v.16 no.5
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• pp.678-682
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• 2006

To remove nitrate from wastewater, a novel bioelectrochemical denitrification system is introduced. In this proposed system, biological reactions are coupled with reactions on the electrode, whereby the electrons are transferred to the bacterial enzymes via a mediator as an electron carrier. The denitrification reaction was achieved with permeabilized Ochrobactrum anthropi SY509 containing denitrifying enzymes, such as nitrate reductase, nitrite reductase, and nitrous oxide reductase, and methyl viologen was used as the mediator. The electron transfer from the electrode to the enzymes in the bacterial cells was confirmed using cyclic voltammetry. A high removal efficiency of nitrate was achieved when the bioelectrochemical system was used with the permeabilized cells. Furthermore, when the permeabilized cells were immobilized to a graphite felt electrode using a calcium alginate matrix containing graphite powder, a high removal efficiency was achieved (4.38 nmol/min mg cell) that was comparable to the result when using the free permeabilized cells.

• Asian Journal of Atmospheric Environment
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• v.9 no.4
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• pp.272-279
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• 2015

The information about the dispersion and scavenging of traffic-related pollutants at the locations near busy expressways is very helpful to highway planners for developing better plans to reduce exposures to air pollution for people living as well as children attending schools and child care centers near roadways. The objective of the current study was to give information in the dispersion and scavenging of vehicle-derived pollutants at the region near a busy urban expressway by a combination of two different model calculations. The modified Gaussian dispersion model and the Lagrange type below-cloud scavenging model were applied to evaluate $NO_x$ dispersion and DEP (Diesel exhaust particles) wet removal, respectively. The highest $NO_x$ was marked 53.17 ppb within 20-30 meters from the target urban expressway during the heaviest traffic hours (08:00AM-09:00AM) and it was 2.8 times higher than that of really measured at a nearby ambient measuring station. The calculated DEP concentration in size-resolved raindrops showed a continuous decreasing with increasing raindrop size. Especially, a noticeable decrease was found between 0.2 mm and 1.0 mm raindrop diameter.

• 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.

• Journal of Animal Environmental Science
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• v.20 no.4
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• pp.139-146
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• 2014

This research was conducted to examine the temporal methane ($CH_4$) and nitrous oxide ($N_2O$) emission trends in livestock agriculture from year 1990 to 2011 with Tier 1 national greenhouse gas (GHG) inventory reporting method, which was related to efforts of decreasing GHG emissions and to achievement of voluntary GHG mitigation target. Methane emissions from enteric fermentation were calculated with default $CH_4$ emission factors of IPCC. Methane and $N_2O$ emissions from manure treatment processes were calculated with Tier 1 and mixture of Tier 1 and Tier 2 including $N_2O$ emission factors of manure treatment systems and nitrogen excretion rate of livestock, respectively. According to 2013 National GHG Inventory Monitoring, Reporting, and Verification report, GHG emission fluctuations from enteric fermentation and manure treatment processes were similarto livestock head fluctuation. GHG emissions from enteric fermentation were mainly affected by beef cattle including Hanwoo, while manure treatment processes were affected by various livestock.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.1
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• pp.32-37
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• 2006

In this study, we have purified and characterized the membrane bound nitrate reductase obtained from the denitrifying bacteria, Ochrobactrum anthropi SY509, which was isolated from soil samples. O. anthropi SY509 can grow in minimal medium using nitrate as a nitrogen source. We achieved an overall purification rate of 15-fold from the protein extracted from the membrane fraction, with a recovery of approximately 12% of activity. The enzyme exhibited its highest level of activity at pH 5.5, and the activity was increased up to $70^{\circ}C$. Periplasmic and cytochromic proteins, including nitrite and nitrous oxide reductase, were excluded during centrifugation and were verified using enzyme essay. Reduced methyl viologen was determined to be the most efficient electron donor among a variety of anionic and cationic dyestuffs, which could be also used as an electron donor with dimethyl dithionite. The effects of purification and storage conditions on the stability of enzyme were also investigated. The activity of the membranebound nitrate reductase was stably maintained for over 2 weeks in solution. To maintain the stability of enzyme, the cell was disrupted using sonication at low temperatures, and enzyme was extracted by hot water without any surfactant. The purified enzyme was stored in solution with no salt to prevent any significant losses in activity levels.