• Journal of Korean Society for Atmospheric Environment
• /
• v.18 no.3
• /
• pp.247-252
• /
• 2002

In this technical information, the TSP measurement data at Gosan between 1992 and 1999 are presented and analyzed. The average ratio of N $O_3$$^{[-10]}$ /nss-S $O_4$$^{2-}$ is highest in March. The annual average ratio concentration of N $O_3$$^{[-10]}$ increased and it was found that the annual average ratio of N $O_3$$^{[-10]}$ /nss-S $O_4$$^{2-}$ increased during the period, probably due to the change of emission characteristics of China.

• Korean Chemical Engineering Research
• /
• v.47 no.1
• /
• pp.96-104
• /
• 2009

In order to lower a reaction temperature with high conversions for simultaneous catalytic reduction of NO and $N_2O$ over Pd-Rh supported mixed metal oxide honeycomb catalysts, $H_2$ or CO was utilized as a reductant. When using the reductants, the effects of reaction conditions were examined in NO and $N_2O$ conversions, where reaction temperatures, concentrations of the reductants and oxygen and the concentration ratio of $N_2O$ to NO were varied. In using $H_2$ reductant, larger than 50% of NO and $N_2O$ conversions was observed at the temperatures below $200^{\circ}C$ in absence of $O_2$. In using CO reductant, NO and $N_2O$ conversions increased from the temperatures higher than $200^{\circ}C$ and $300^{\circ}C$, respectively. However, in use of both reductants, NO and $N_2O$ conversions decreased with increasing oxygen concentration. As a result, $H_2$ reductant could reduce simultaneously NO and $N_2O$ at relatively lower reaction temperature than CO. Also, NO and $N_2O$ conversions were less influenced by using $H_2$ reductant than CO one. Concentration ratio between NO and $N_2O$ did not affect their conversions regardless the type of reductants. Pretreatment of the catalyst in $H_2$ was more effective in simultaneous reduction of NO and $N_2O$ at low reaction temperature than that in $O_2$.

• Clean Technology
• /
• v.20 no.4
• /
• pp.390-397
• /
• 2014

This study was performed to investigate the effects of fluidizing media on $N_2O$ production in fluidized bed incineration of sewage sludge. The fluidized media were prepared in a form of 2 mm bead by mixing zeolite powders in our lab. Sand having 0.4 mm of the mean size showed 0.44 m/s of minimum fluidization velocity ($U_{mf}$), while the prepared zeolite media 0.5 m/s. When the ratio of fluidizing media height to the inside diameter of the incinerator (bed aspect ratio) increased from 1.4 to 3.1, it was found that $U_{mf}$ of the zeolite media was varied from 0.5 m/s to 0.7 m/s. Under the operation conditions in 1.79 of excess air ratio, $909^{\circ}C$ of bed temperature and ca. 1.65 m/s of superficial velocity, as the weight of fluidizing meadia was increased, $O_2$ concentration in the flue gas was slightly decreased, and $CO_2$ increased. Above 6 kg of fluidizing media weight (1.98 of bed aspect ratio), it was observed that $N_2O$ concentration was significantly reduced, which might result from the decomposition of $N_2O$ on the zeolite media rather than transformation of $N_2O$ to NOx. On the other hand, in a variation of the zeolite media mixing ratio to sand and bed temperature at a constant total bed height, significant difference was exhibited in $N_2O$ emission concentration according to the temperature. Considering the operation temperature in the incineration, the effective calcination temperature of the zeolite media was suggested to be around $900^{\circ}C$.

• Transactions on Electrical and Electronic Materials
• /
• v.9 no.1
• /
• pp.12-15
• /
• 2008

Hafnium oxynitride films have been deposited onto a silicon substrate by means of radio frequency (RF) reactive sputtering using a hafnium dioxide $(HfO_2)$ target with a variety of nitrogen! argon $(N_2/Ar)$ gas flow ratios. Auger electron spectroscopy (AES)results confirm that $N_2$ was successfully incorporated into the HfON films. An increase in the $N_2/Ar$ gas flow ratio resulted in metal oxynitride formation. The films prepared with a $N_2/Ar$ flow ratio of 20/20 sccm show (222), (530), and (611) directions of $HfO_2N_2$, and the (-111), (311) directions of $HfO_2$. From X-ray reflectometry measurements, it can be concluded that with $N_2$ incorporated into the HfON films, the film density increases. The density increases from 9.8 to $10.1g/cm^3$. XRR also reveals that the surface roughness is related to the $N_2/Ar$ flow ratio.

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.06a
• /
• pp.105.1-105.1
• /
• 2010

Korea Electric Power Research Institute (KEPRI) has developed a compact coal-gasification system to accumulate our experiment skills. The combustion furnace for residual oil was modified as a small size coal gasifier. Recently, coal feeding system was also upgraded to control coal feed rate more accurately. Our research group has conducted several experiments to find out the effect of $O_2$/coal ratio on the cold gas efficiency. Furthermore, the effect of $N_2$/coal ratio on the transport characteristics was also studied. According to the calculation of heat and mass balance, the cold gas efficiency was estimated to the maximum at $O_2$/coal ratio of around 0.73. But small size gasifier such as ours required higher value of $O_2$/coal ratio than that of the theoretical estimation. On the optimal $N_2$/coal ratio, we noticed that the coal feed rate was intimately related with the transporting gas pressure and the pipe diameter.

• Electrical & Electronic Materials
• /
• v.9 no.1
• /
• pp.9-17
• /
• 1996

Plasma enhanced chemical vapor deposition (PECVD) allows low temperature processing and so it is widely used, but it causes instability of devices due to serious amount of impurities within the film. In this paper, electrical and chemical characteristics of the PECVD oxynitride film formed by different N$_{2}$O to N$_{2}$O+NH$_{3}$ gas ratio is studied. It has been found that hydrogen concentration of PECVD oxynitride film was decreased from 4.25*10$^{22}$ [cm$^{-2}$ ] to 1.18*10$^{21}$ [cm$^{-2}$ ] according to the increase of N$_{2}$O gas. It was also found that PECVD oxynitride films have low trap density in the oxide and interface in comparison with PECVD nitroxide films, and has higher refractive index and capacitance than oxide films. In particular, oxynitride film formed in gas ratio of N$_{2}$O/(N$_{2}$O+NH$_{3}$)= 0.88 shows increased capacitance and decreased leakage current due to small portion of hydrogen in oxide and the accumulation of nitrogen about 4[atm.%] at the interface.

• Clean Technology
• /
• v.17 no.2
• /
• pp.134-141
• /
• 2011

The effects of the compounds and concentrations of nitrogenous electron acceptor, the ratio of electron donor/electron acceptor (C/N), and the complexity of electron donor on the emission of $N_2O$ during wastewater denitrification were quantitatively investigated in this study. The higher ${NO_3}^-$ and ${NO_2}^-$ concentrations, the more $N_2O$ emission was observed. ${NO_2}^-$ has strong effect on $N_2O$ emission as it emitted morc $N_2O$ than ${NO_3}^-$, 50 mg/L of ${NO_2}^-$-N gave the highest conversion (9.3%) and yield (9.8%) of $N_2O$ while ${NO_3}^-$-N (50 mg/L) gave 5.6% conversion and 11.0% yield. Lower C/N ratio decreases nitrogen removal efficiency, but it increases the conversion of $N_2O$ because of the incomplete denitrification by the limited organic carbon. When real domestic wastewater is used as the electron donor of the denitrification, $N_2O$ emission is reduced to 1/10 of the emission when single carbon (acetate) is used. It is thought that multiple carbon source utilizes many denitrification pathways and it seems to be helpful for the reduction of $N_2O$ emission.

• Journal of the Korean Chemical Society
• /
• v.18 no.4
• /
• pp.267-271
• /
• 1974

The tetradentate schiff base, N,N'-bis(salicylaldehyde)-ethylene diimine has been reacted with a series of Mo(IV), Mo(V), Mo(IV), and Mo(III) oxidation states to form new Complexes; $[MoO_2(C_{16}H_{14}O_2N_2)], (MoO(C_{16}H_{14}O_2N_2)]_2O, (Mo(SCN)(C_{16}H_{14}O_2N_2)]_2O, and (Mo(H_2O)(C_{16}H_{14}O_2N_2)]_2O.$ These complexes have hexa coordinated configurations and the mole ratio of these ions to the ligand was 1:1. These complexes have been identified by visible spectra, infrared specra, T.G.A., D.T.A., and elemental analysis.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.29 no.6
• /
• pp.49-57
• /
• 2015

This paper presents the discharge characteristics and economic feasibility of a Dry $Air/O_2$ and a $N_2/O_2$ mixture gas in order to review $SF_6$ alternative. From AC discharge experiment in an quasi-uniform field, it was found that the optimal $N_2/O_2$ mixing ratio which breakdown voltage and surface flashover voltage were the highest was 70/30 and that the pressure dependence on the breakdown voltage was higher than that of the surface flashover voltage in the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas. The mixing ratio (70/30) and the tendency of the pressure dependence were described in detail based on physical factors (impact ionization coefficient, electron attachment coefficient, secondary electron emission coefficient) involved in discharge mechanism and a electron source, respectively. In addition, the performance insulation and the economic feasibility of the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas were discussed so that Dry $Air/O_2$ mixture gaswas more suitable than $N_2/O_2$ mixture gas to the $SF_6$ alternative.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.11
• /
• pp.1029-1034
• /
• 2003

The Bi$_2$Sr$_2$Ca$_{n}$Cu$_{n+1}$ O$_{x}$, superconducting thin films arc fabricated by using the sputtering and evaporation method. Because we confirmed the sticking ratio of Bi element in the Bi$_2$Sr$_2$Ca$_{n}$Cu$_{n+1}$ O$_{x}$ superconducting thin film fabricated by using the sputtering method was much lower than the expected value, to get the enough number of the flakes of Bi, faraday cup was used to evaporate Bi clement. As a result of the fabrication, Bi 2201 and Bi 2212 single phases could be made by the optima of deposition condition. And we confirmed the sticking coefficient of Bi element was clearly related to the temperature change of the substrate and the generation of Bi22l2 phase