• Clean Technology
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• v.15 no.2
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• pp.122-129
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• 2009

The effect of calcination temperature or hydrothermal treatment of commercial Fe-beta zeolites in the range of $450{\sim}900^{\circ}C$ were examined in the direct decomposition of $N_2O$. Fe-beta zeolites used were characterized using XRD, $N_2$ sorption, $^{27}Al$ MAS NMR and XPS. Although the surface area and micropore volume of Fe-beta zeolite after calcination at $900^{\circ}C$ and hydrothermal treatment at $750^{\circ}C$ decreased ca. 30%, a larger decrease in the surface area and micropore volume by hydrothermal treatment was observed than by calcination treatment alone. However, the Al sites in frameworks of zeolite were conserved in stable tetrahedral form resulting from low degree of dealumination which was related to the adjacent Fe ions on the Al sites. This could likely be correlated with the conservation of high surface area and micropore volume of Fe-beta zeolites. The increase in the calcination or hydrothermal treatment temperature caused the increase of decomposition temperature of $N_2O$ and the severe deactivation was observed after hydrothermal treatment than calcination treatment.

• Textile Coloration and Finishing
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• v.21 no.3
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• pp.19-25
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• 2009

Polymerization of tetraethoxysilane on a glass substrate was investigated by remote microwave plasma using argon with portions of nitrous oxide as carrier gas. Transparent layer like a thickness of 0.5 ${\mu}m$ 3 ${\mu}m$ were obtained, differing in chemical composition, depending on plasma power and treatment time as well as on ageing time. In general the milder the treatment and the shorter the ageing was, the higher was the content of organic structural elements in the layer. We have identified that the chemical structure of our samples composed of mainly Si O and Si C groups containing aliphatics, carbonyl groups. These results were obtained by X ray photon spectroscopy, Fourier transformed infrared spectroscopy, and scanning electron microscope combined with Energy dispersive X ray spectroscopy.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.4
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• pp.937-945
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• 1996

Nitrous oxide has acquired widespread use as a tool for management of anxious and comprehensive pediatric dental patients. Clinical impressions have suggested that inhalation sedation with $N_2O/O_2$ reinforces the effect of other sedatives. Fifteen uncooperative children, mean age of 37months, who were regarded as fail in the first treatment using chloral hydrate-hydroxyzine orally, midazolam orally or intranasally, were sedated with the same sedatives in conjunction with $N_2O/O_2$. All the children were restrained in a pediwrap and were monitored with pulse oximeter for their heart rate and oxygen saturation. Degree of sleep, crying and movement were evaluated. The clinical results indicated that a satisfactory level of sedation was achieved in approximately two thirds of the cases (about 66 %) under those sedation manner. Complications were rare and those of treatments were successfully completed without difficulty.

• Journal of Yeungnam Medical Science
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• v.15 no.1
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• pp.97-113
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• 1998

The sympathoadrenal system plays an important role in homeostasis in widely varing external environments. Conflicting findings, however, have been reported on its response to hypoxia. We investigated the effect of hypoxia on the sympathoadrenal system in dogs under halothane anesthesia by measuring levels of circulating catecholamines in response to graded hypoxia. Ten healthy mongreal dogs were mechanically ventilated with different hypoxic gas mixtures. Graded hypoxia and reoxygenation were induced by progressively decreasing the oxygen fraction in the inhalation gas mixture from 21%(control) to 15%, 10% and 5% at every 5 minutes, and then reoxygenated with 60% oxygen. Mean arterial pressure, central venous pressure and mean pulmonary arterial pressure were measured directly using pressure transducers. Cardiac output was measured by the thermodilutional method. For analysis of blood gas, saturation and content, arterial and mixed venous blood were sampled via the femoral and pulmonary artery at the end of each hypoxic condition. The concentration of plasma catecholamines was determined by radioenzymatic assay. According to the exposure of graded hypoxia, not only did arterial and mixed venous oxygen tension decreased markedly at 10% and 5% oxygen, but also arterial and mixed venous oxygen saturation decreased significantly. An increased trend of the oxygen extraction ratio was seen during graded hypoxia. Cardiac output, mean arterial pressure and systemic vascular resistance were unchanged or increased slightly. Pulmonary arterial pressure(PAP) and pulmonary vascular resistance(PVR) were increased by 55%, 76% in 10% oxygen and by 82%, 95% in 5% oxygen, respectively(p<0.01). The concentrations of plasma norepinephrine, epinephrine and dopamine increased by 75%, 29%, 24% in 15% oxygen and by 382%, 350%, 49% in 5% oxygen. These data suggest that the sympathetic nervous system was activated to maintain homeostasis by modifying blood flow distribution to improve oxygen delivery to tissues by hypoxia, but hemodynamic changes might be blunted by high concentration of nitrous oxide except PAP and PVR. It would be suggested that hemodynamic changes might not be sensitive index during hypoxia induced by high concentration of nitrous oxide exposure.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.434-435
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• 2012

Plasma enhanced chemical vapor deposition (PECVD) silicon dioxide thin films have many applications in semiconductor manufacturing such as inter-level dielectric and gate dielectric metal oxide semiconductor field effect transistors (MOSFETs). Fundamental chemical reaction for the formation of SiO2 includes SiH4 and O2, but mixture of SiH4 and N2O is preferable because of lower hydrogen concentration in the deposited film [1]. It is also known that binding energy of N-N is higher than that of N-O, so the particle generation by molecular reaction can be reduced by reducing reactive nitrogen during the deposition process. However, nitrous oxide (N2O) gives rise to nitric oxide (NO) on reaction with oxygen atoms, which in turn reacts with ozone. NO became a greenhouse gas which is naturally occurred regulating of stratospheric ozone. In fact, it takes global warming effect about 300 times higher than carbon dioxide (CO2). Industries regard that N2O is inevitable for their device fabrication; however, it is worthwhile to develop a marginable nitrous oxide free process for university lab classes considering educational and environmental purpose. In this paper, we developed environmental friendly and material cost efficient SiO2 deposition process by substituting N2O with O2 targeting university hands-on laboratory course. Experiment was performed by two level statistical design of experiment (DOE) with three process parameters including RF power, susceptor temperature, and oxygen gas flow. Responses of interests to optimize the process were deposition rate, film uniformity, surface roughness, and electrical dielectric property. We observed some power like particle formation on wafer in some experiment, and we postulate that the thermal and electrical energy to dissociate gas molecule was relatively lower than other runs. However, we were able to find a marginable process region with less than 3% uniformity requirement in our process optimization goal. Surface roughness measured by atomic force microscopy (AFM) presented some evidence of the agglomeration of silane related particles, and the result was still satisfactory for the purpose of this research. This newly developed SiO2 deposition process is currently under verification with repeated experimental run on 4 inches wafer, and it will be adopted to Semiconductor Material and Process course offered in the Department of Electronic Engineering at Myongji University from spring semester in 2012.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.653-657
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• 2009

Nitrous oxide is a typical greenhouse gas which is produced from various organic or fossil fuel combustion processes as well as chemicals producing plants. $N_2O$ has a global worming potential of 310 times that of $CO_2$ on per molecule basis, and also acts as an ozone depleting material in the stratosphere. However, its removal is not easy for its chemical stability characteristics. Most SCR processes with several effective reducing agents generally require the operation temperature higher than $450^{\circ}C$, and the catalytic conversion becomes decreased significantly when NOx is present in the stream. Present experiments have been performed to obtain basic design data of actual application concerning the effects of $SO_2$ and $NH_3$ on the interim and long term activities of $N_2O$ reduction with CO over the mixed metal oxide (MMO) catalyst derived from a hydrotalcite-like compound precursor. The MMO catalysts used in the experiments, have shown prominent activities displaying full conversions of $N_2O$ near $200^{\circ}C$ when CO is introduced. The presence of $SO_2$ is considered to show no critical behavior as can be met in the $NH_3$ SCR DeNOx systems and the effect of $NH_3$ is considered to play as mere an impurity to share the active sites of the catalysts.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.2
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• pp.188-193
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• 2015

It has been generally recognized that $N_2O$(Nitrous Oxide) emission from marine diesel engines has a close correlation with $SO_2$(Sulfur Dioxide) emission, and diversity of fuel elements using ships affects characteristics of the $N_2O$ emission. According to recent reports, in case of existence of an enough large NO(Nitric Oxide) generated as fuel combustion, effect of the $SO_2$ emission in exhaust gas on the $N_2O$ formation is more vast than effect of the NO. Therefore, $N_2O$ formation due to the $SO_2$ element operates on a important factor in EGR(Exhaust Gas Recirculation) systems for NOx reduction. An aim of this experimental study is to investigate that intake gas of the diesel engine with increasing of $SO_2$ flow rate affects $N_2O$ emission in exhaust gas. A test engine using this experiment was a 4-stroke direct injection diesel engine with maximum output of 12 kW at 2600rpm, and operating condition was set up at a 75% load. A standard $SO_2$ gas with 0.499%($m^3/m^3$) was used for changing of $SO_2$ concentration in intake gas. In conclusion, the diesel fuel included out sulfur elements did mot emit the $SO_2$ emission, and the $SO_2$ emission in exhaust gas according as increment of the $SO_2$ standard gas had almost the same ratio compared with $SO_2$ rate in mixture inlet gas. Furthermore, the $N_2O$ element in exhaust gas was formed as $SO_2$ mixture in intake gas because increment of $SO_2$ flow rate in intake gas increased $N_2O$ emission. Hence, diesel fuels included sulfur compounds were combined into $SO_2$ in combustion, and $N_2O$ in exhaust gas should be generated to react with NO and $SO_2$ which exist in a combustion chamber.

• Journal of ILASS-Korea
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• v.25 no.3
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• pp.132-138
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• 2020

N₂O is hazardous atmosphere pollution matter which can damage the ozone layer and cause green house effect. There are many other nitrogen oxide emission control but N₂O has no its particular method. Preventing further environmental pollution and global warming, it is essential to control N₂O emission from industrial machines. In this study, the thermal decomposition experiment of N₂O gas mixture is conducted by using cylindrical reactor to figure out N₂O reduction and NO formation. And CHEMKIN calculation is conducted to figure out reaction rate and mechanism. Residence time of the N₂O gas in the reactor is set as experimental variable to imitate real SNCR system. As a result, most of the nitrogen components are converted into N2. Reaction rate of the N₂O gas decreases with N₂O emitted concentration. At 800℃ and 900℃, N₂O reduction variance and NO concentration are increased with residence time and temperature. However, at 1000℃, N₂O reduction variance and NO concentration are deceased in 40s due to forward reaction rate diminished and reverse reaction rate appeared.

• Environmental Engineering Research
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• v.20 no.1
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• pp.51-57
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• 2015

As expected, the expression of denitrifying genes in a Typha wetland (relatively stagnant compared to other ponds), showing higher nitrogen removal efficiency in summer, was affected by temperature. The abundance and gene transcripts of nitrate reductase (narG), nitrite reductase (nirS), nitric oxide reductase (norB), and nitrous oxide reductase (nosZ) genes in seasonal sediment samples taken from the Acorus and Typha ponds of free surface flow constructed wetlands were investigated using quantitative polymerase chain reaction (Q-PCR) and quantitative reverse transcription PCR (Q-RT-PCR). Denitrifying gene copy numbers ($10^5-10^8$ genes $g^{-1}$ sediment) were found to be higher than transcript numbers-($10^3-10^7$ transcripts $g^{-1}$ sediment) of the Acorus and Typha ponds, in both seasons. Transcript numbers of the four functional genes were significantly higher for Typha sediments, in the warm than in the cold season, potentially indicating greater bacterial activity, during the relatively warm season than the cold season. In contrast, copy numbers and expression of denitrifying genes of Acorus did not provide a strong correlation between the different seasons.

• Transactions on Electrical and Electronic Materials
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• v.13 no.4
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• pp.192-195
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• 2012

We reported diborane ($B_2H_6$) doped wide bandgap hydrogenated amorphous silicon oxide (p-type a-SiOx:H) films prepared by using silane ($SiH_4$) hydrogen ($H_2$) and nitrous oxide ($N_2O$) in a radio frequency (RF) plasma enhanced chemical vapor deposition (PECVD) system. We improved the $E_{opt}$ and conductivity of p-type a-SiOx:H films with various $N_2O$ and $B_2H_6$ ratios and applied those films in regards to the a-Si thin film solar cells. For the single layer p-type a-SiOx:H films, we achieved an optical band gap energy ($E_{opt}$) of 1.91 and 1.99 eV, electrical conductivity of approximately $10^{-7}$ S/cm and activation energy ($E_a$) of 0.57 to 0.52 eV with various $N_2O$ and $B_2H_6$ ratios. We applied those films for the a-Si thin film solar cell and the current-voltage characteristics are as given as: $V_{oc}$ = 853 and 842 mV, $J_{sc}$ = 13.87 and 15.13 $mA/cm^2$. FF = 0.645 and 0.656 and ${\eta}$ = 7.54 and 8.36% with $B_2H_6$ ratios of 0.5 and 1% respectively.