• Journal of Environmental Health Sciences
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• v.7 no.2
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• pp.89-95
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• 1981

A Continuous monitoring of Air Pollution in city of Seoul was carried out from January 1 to December 31 of 1979 at two selected sites, Kwanghwamun observatory and Kwanag observatory. The measured data were averaged on monthly basis. The maximun value of oxidant pollution was observed in July, and the minimum in February. It is the purpose of this study to determine the effect of hydrocarbon, nitrogenoxide, wind velocity and ambient temprature on the observed values of oxidant pollution for the above two months. The results of the study may be summarized as follows. 1) The oxidant concentration in February was higher than in July by about 2 times in both downtown area and the suburbia. The concentration in downtown area was $25.75\pm 4.75ppb$, and that in suburbia was $29.83\pm 5.16ppb$. As for the oxidant concentration in July, it was observed that the suburban area ($26.464\pm 7.59ppb$) had about 2.8 times higher value than the downtown area ($9.284\pm 1.55ppb$). 2) The peak oxidant concentration of suburban area during the daytime is occured from noon to 5:00 P.M.. These patterns are similar to the classical patterns, but the peak Oxidant Concentration of downtown area in February was occured at 9:00A.M. 3) The overall level of nitrogen oxide pollution was much higher in downtown area than in suburban area. Two peaks of nitrogen oxide concentration occured at 10 A.M. and 12 midnight in downtown area. This observation agrees with the report that the air pollution is higher in the area where the pollution sources are concentrated. 4) The multiple correlation analysis for the oxidant and the other variables measured in February in downtown area showed close correlation with nitrogen oxide and ambient temprature. The multiple correlation coefficient of oxidant with nitrogen oxide was 0.872, and that with nitrogen oxide and temperature simultaneously was 0.903. The multiple correlation equation used for this study may be expressed as follows:

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.7
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• pp.576-582
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• 2002

Nonvolatile semiconductor memory devices with reoxidized nitrided oxide(RONO) gate dielectrics were fabricated, and nitrogen distribution and bonding species which contribute to memory characteristics were analyzed. Also, memory characteristics of devices depending on the anneal temperatures were investigated. The devices were fabricated by retrograde twin well CMOS processes with $0.35\mu m$ design rule. The processes could be simple by in-situ process in growing dielectric. The nitrogen distribution and bonding states of gate dielectrics were investigated by Dynamic Secondary Ion Mass Spectrometry(D-SIMS), Time-of-Flight Secondary Ion Mass Spectrometry(ToF-SIMS), and X-ray Photoelectron Spectroscopy(XPS). As the nitridation temperature increased, nitrogen concentration increased linearly, and more time was required to form the same reoxidized layer thickness. ToF-SIMS results showed that SiON species were detected at the initial oxide interface which had formed after NO annealing and $Si_2NO$ species within the reoxidized layer formed after reoxidation. As the anneal temperatures increased, the device showed worse retention and degradation properties. It could be said that nitrogen concentration near initial interface is limited to a certain quantity, so the excess nitrogen is redistributed within reoxidized layer and contribute to electron trap generation.

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

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.17-20
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• 2001

Nonvolatile semiconductor memory devices with reoxidized nitrided oxide(RONO) gate dielectrics were fabricated, and nitrogen distribution and bonding species which contribute to memory characteristics were analyzed. Also, memory characteristics of devices depending on the anneal temperatures were investigated. The devices were fabricated by retrograde twin well CMOS processes with $0.35{\mu}m$ Nonvolatile semiconductor memory devices with reoxidized nitrided oxide(RONO) gate dielectric were fabricated, and nitrogen distribution and bonding species which contributing memory characteristics were analyzed. Also, memory characteristics of devices according to anneal temperatures were investigated. The devices were fabricated by $0.35{\mu}m$ retrograde twin well CMOS processes. The processes could be simple by in-situ process of nitridation anneal and reoxidation. The nitrogen distribution and bonding state of gate dielectric were investigated by Dynamic Secondary Ion Mass Spectrometry(D-SIMS), Time-of-Flight Secondary Ion Mass Spectrometry(ToF-SIMS), and X-ray Photoelectron Spectroscopy(XPS). Nitrogen concentrations are proportional to nitridation anneal temperatures and the more time was required to form the same reoxidized layer thickness. ToF-SIMS results show that SiON species are detected at the initial oxide interface and $Si_{2}NO$ species near the new $Si-SiO_{2}$ interface that formed after reoxidation. As the anneal temperatures increased, the device showed worse retention and degradation properties. These could be said that nitrogen concentration near initial interface is limited to a certain quantity, so excess nitrogen are redistributed near the $Si-SiO_{2}$ interface and contributed to electron trap generation.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.9
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• pp.407-411
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• 2003

The purpose of this paper is to study the removal of nitrogen oxide(NOx) using a wire-plate type plasma reactor with magnet attached for indoor air purification. In order to produce a more effective reactor, we conducted magnetic field simulations. The results of the magnetic field simulations show that NOx can be removed more effectively. The results from the magnetic field simulation show that when 7 magnets were applied to the reactor, the magnetic flux density was at its highest amount than when using 0, 3, or 5 magnets. From the data obtained by the simulation results a plasma reactor was made and thus, several experiments were conducted. The best removal efficiency was obtained with 14 W AC power to the reactor with 5 magnets.

• Journal of Power System Engineering
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• v.19 no.4
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• pp.82-88
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• 2015

The purpose of this study is to investigate the effect of the impinging plate on combustion process in Diesel engine. Especially, the variation of exhaust emission and engine performance by the change of fuel injection timing and fuel injection pressure between the trial engine with impinging plate and the prototype engine were examined. The nitrogen oxide concentration of the trial engine decreased more than 50% compared to the prototype engine, however, smoke concentration of the trial engine indicated higher degree than the prototype engine. The smoke concentration, fuel consumption rate and exhaust gas temperature decreased as the fuel injection timing become faster, whereas the nitrogen oxide concentration decreased as the fuel injection timing is retarded. The nitrogen oxide concentration, fuel consumption rate and exhaust gas temperature decreased as the fuel injection pressure become lower. But smoke concentration decreased as the fuel injection pressure become higher.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.11
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• pp.1119-1123
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• 2006

The flame image processing and analysis system has been investigated for the optimal pulverized coal firing of thermal power plant, especially for lower nitrogen oxide generation and more safe operation. We aimed at gaining the relationship between burner flame image information and emissions of nitrogen oxide and unburned carbon in furnace utilizing the flame image processing methods, by which we quantitatively determine the condition of combustion on the individual humors. Its feasibility test was undertaken with a pilot furnace for coal firing, through which the system was observed to be effective for the monitoring of the combustion condition of pulverized coal firing boilers.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.1
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• pp.92-98
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• 2008

The flame image observation and analysis has been investigated for combustion monitoring and management of the pulverized coal firing for thermal power plant, especially for lower nitrogen oxide generation and safer operation. We aimed at obtaining the relationship between burner flame image information and emissions of nitrogen oxide and unburned carbon in furnace utilizing the flame image processing methods, by which we quantitatively determine the conditions of combustion on the individual homers. Its feasibility test was undertaken with Samchonpo thermal power plant #4 unit which has 24 burners, through which the system was observed to be effective for evaluating the combustion conditions and continuous monitoring to prevent future loss of ignition.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.3
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• pp.6-13
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• 2000

Ultra-thin gate oxide was grown on nitrogen implanted silicon substrates. For nitrogen implantation, the energy was fixed at 25keV, but the dose was split into 5.0$\times$10$^{13}$ /c $m^{2}$ and 1.0$\times$10$^{14}$ /c $m^{2}$. The grown gate oxide thickness were 2nm, 3nm and 4nm. The oxidation time to grow 3nm was increased by 20% and 50% for the implanted wafers of 5.0$\times$10$^{13}$ /c $m^{2}$ and 1.0$\times$10$^{14}$ /c $m^{2}$ doses, respectively, when it was compared with control wafers which were not implanted by nitrogen. The value of charge-to-breakdown ( $Q_{BD}$ ) is decreased with increasing nitrogen doses. If an annealing process( $N_{2}$, 85$0^{\circ}C$, 60min.) is peformed after nitrogen implantation, $Q_{BD}$ is increased. It is indicated that nitrogen implantation damage affect gate oxide reliability and the damage can be removed by post-implantation annealing process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.5
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• pp.224-230
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• 2001

The characteristics of $NO/N_2O$ annealed reoxidized nitrided oxide being studied as super thin gate oxide and gate dielectric layers of Non-Volatile Semiconductor Memory (NVSM) were investigated by Dynamic Secondary Ion Mass Spectrometry (D-SIMS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), and Auger Electron Spectroscopy (AES). The specimen was annealed by $NO/N_2O$ after initial oxide process and then rcoxidized for nitrogen redistribution in nitrided oxide. Out-diffusion of incorporated nitrogen during the wet oxidation in reoxidation process took place more strongly than that of the dry oxidation. It seems to indicate that hydrogen plays a role in breaking the Si N bonds. As reoxidation proceeds, incorporated nitrogen of $NO/N_2O$ annealed nitrided oxide is obsen-ed to diffuse toward the surface and substrate at the same time. ToF-SIMS results show that SiON species are detected at the initialoxide interface, and Si,NO species near the new $Si_2NO$ interface that formed after reoxidation. These SiON and $Si_2NO$ species most likely to relate to the origin of the state of memory charge traps in reoxidized nitrided oxide, because nitrogen dangling bonds of SiON and silicon dangling bonds of $Si_2NO$ are contained defects associated with memory effect.