• Journal of Korean Society for Atmospheric Environment
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• 제26권3호
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• pp.330-338
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• 2010

In this study, removal characteristics of nitrogen oxides $(NO_x)$ from road transport by using peat as the packing media for biodegradation have been investigated in the long term. Physicochemical and biological treatment of peatmixed media eliminates any requirement to use chemical substances and also facilitates the biodegradable actions of microorganism. Safe biodegradation of pollutants, no need to apply additional microbes owing to their active growth, and no generation of secondary pollutants were found in this experiment. It was concluded that average removal efficiencies of nitric oxide (NO) and nitrogen dioxide $(NO_2)$ were 80% and 97% respectively with respect to the linear velocity 35~40 mm/s and 0.3 ppm ozone concentration in the long period operation. Inflow concentration of nitric oxide over 0.05 ppm was suitable when pretreated with ozone. Non-ozone stage was performed with linear velocity 20~100 mm/s and then the average removal efficiency of nitric oxide and nitrogen dioxide were 38% and 94% respectively. Other results showed that the apparent static pressure was raised with increases in applied water content and aerial velocity in mixed media during fan operation.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.159-159
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• 2015

A new approach for antimicrobial is based on the overproduction of reactive nitrogen species (RNS), especially; nitric oxide (NO) and peroxinitrite (ONOO-) are important factors to deactivate the bacteria. Recently, non-thermal atmospheric pressure plasma jet (APPJ) has been frequently used in the field of microbial sterilization through the generation of different kinds of RNS/ROS species. However, in previous study we showed APPJ has combine effects ROS/RNS on bacterial sterilization. It is not still clear whether this bacterial killing effect has been done through ROS or RNS. We need to further investigate separate effect of ROS and RNS on bacterial sterilization. Hence, in this work, we have enhanced NO production, especially; by applying a 1% of HNO3 vapour to the N2 based APPJ. In comparison with nitrogen plasma with inclusion of water vapour plasma, it has been shown that nitrogen plasma with inclusion of 1% of HNO3 vapour has higher efficiency in killing the E. coli through the high production of NO. We also investigate the enhancement of NO species both in atmosphere by emission spectrum and inside the solution by ultraviolet absorption spectroscopy. Moreover, qPCR analysis of oxidative stress mRNA shows higher gene expression. It is noted that 1% of HNO3 vapour plasma generates high amount of NO for killing bacteria.

• Applied Chemistry for Engineering
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• 제25권6호
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• pp.613-618
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• 2014

In this study, nitrogen doped graphene oxide (GO) was prepared using liquid phase ammonia treatment to improve its electrical properties. Also, the aminated GO was manufactured into a film format and the electromagnetic interference (EMI) shielding efficiency was measured to evaluate its electrical properties. The XPS result showed that the increase of liquid phase ammonia treatment concentration led to the increased nitrogen functional group on the GO surface. The measurement of EMI shielding efficiency reveals that EMI shielding efficiency of the liquid phase ammonia treated GO was better than that of non-treated GO. When GO was treated using the ammonia solution of 21% concentration, the EMI shielding efficiency increased by -5 dB at higher than 2950 MHz. These results were maybe due to the fact that nitrogen functional groups on GO help to improve the absorbance of electromagnetic waves via facile electron transfer.

• Tribology and Lubricants
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• 제17권6호
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• pp.459-466
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• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk on friction characteristics in various sliding conditions were investigated. AISI52100 steel ball was used for the substrate of coated ball specimens, which were prepared by depositing TiN coating with 1(m in coating thickness. AISI1045 steel was used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of two materials, the tests were performed both in air for forming oxide layer on the contact parts and in nitrogen environment to avoid oxidation. From the test results, the frictional characteristic between the two materials was predominated by iron oxide layer that formed on wear tract of counter-body and this layer caused friction transition and high friction. And the adhesive wear occurred from steel disk to TiN coated ball caused the formation of oxide layer on counter parts between the two materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제36권4호
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• pp.376-384
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• 2023

Nitrogen-doped graphene was synthesized by a hydrothermal method using graphene oxide (GO) as the raw material, urea as the reducing agent and nitrogen as the dopant. The morphology, structure, composition and electrochemical properties of the samples are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption analysis, electrical conductivity and electrochemical tests. The results show that urea can effectively reduce GO and achieve nitrogen doping under the hydrothermal conditions. By adjusting the mass ratio of raw materials to dopants, the graphene with different nitrogen doping contents can be obtained; the nitrogen content range is from 5.28~6.08% (atomic fraction percentage).When the ratio of dopant to urea is 1:30, the nitrogen doping content reaches a maximum of 6.08%.The supercapacitor performance test shows that the nitrogen content prepared by the ratio of 6.08% is the best at 0.1 A·g^-1. The specific capacitance is 95.2 F·g^-1.

• Korean Journal of Soil Science and Fertilizer
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• 제50권6호
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• pp.574-587
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• 2017

Excessive application of nitrogen (N) fertilizer to support switchgrass growth for bioenergy production may cause adverse environmental effects. The objective of this study was to determine optimum N application rate to increase biomass yield of switchgrass and to reduce adverse environmental effects related to N. Switchgrass was planted in May 2008 and biomass yield, N uses of switchgrass, nitrate ($NO_3$) leaching, and nitrous oxide ($N_2O$) emission were evaluated from 2010 through 2011. Total N removal significantly increased with N rate despite the fact that yield did not increased with above $56kg\;N\;ha^{-1}$ of N rate. Apparent nitrogen recoveries were 4.81 and 5.48% at 56 and $112kg\;N\;ha^{-1}$ of N rate, respectively. Nitrogen use efficiency decreased into half with increasing N rate from 56 to $112kg\;N\;ha^{-1}$. Nitrate leaching and $N_2O$ emission were related to N use of switchgrass. There was no significant difference of cumulative $NO_3$ leaching between 0 and $56kg\;N\;ha^{-1}$ but, it significantly increased at $112kg\;N\;ha^{-1}$. There was no significant difference of cumulative $N_2O$ emission among N rates in crest, but it significantly increased at $112kg\;N\;ha^{-1}$ in toe. Excessive N application rate (above $56kg\;N\;ha^{-1}$) beyond plant requirement could accelerate $NO_3$ leaching and $N_2O$ emission in switchgrass field. Overall, $56kg\;N\;ha^{-1}$ might be optimum N application rate in reducing economic waste on N fertilizer and adverse environmental impacts.

• Korean Journal of Microbiology
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• 제52권2호
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• pp.166-174
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• 2016

In order to find an efficient bacterial strain that can carry out nitrification and denitrification simultaneously, we isolated many heterotrophic nitrifying bacteria from wastewater treatment plant. One of isolates NS13 showed high removal rate of ammonium and was identified as Alcaligenes faecalis by analysis of its 16S rDNA sequence, carbon source utilization and fatty acids composition. This bacterium could remove over 99% of ammonium in a heterotrophic medium containing 140 mg/L of ammonium at pH 6-9, $25-37^{\circ}C$ and 0-4% of salt concentrations within 2 days. It showed even higher ammonium removal at higher initial ammonium concentration in the medium. A. faecalis NS13 could also reduce nitrate and nitrous oxide by nitrate reductase and nitrous oxide reductase, respectively, which was confirmed by detection of nitrate reductase gene, napA, and nitrous oxide reducase gene, nosZ, by PCR. One of metabolic intermediate of denitrification, $N_2O$ was detected from headspace of bacterial culture. Based on analysis of all nitrogen compounds in the bacterial culture, 42.8% of initial nitrogen seemed to be lost as nitrogen gas, and 46.4% of nitrogen was assimilated into bacterial biomass which can be removed as sludge in treatment processes. This bacterium was speculated to perform heterotrophic nitrification and aerobic denitrification simultaneously, and may be utilized for N removal in wastewater treatment processes.

• Korean Journal of Materials Research
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• 제23권9호
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• pp.477-482
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• 2013

We investigated the detection properties of nitrogen monoxide (NO) gas using transparent p-type $CuAlO_2$ thin film gas sensors. The $CuAlO_2$ film was fabricated on an indium tin oxide (ITO)/glass substrate by pulsed laser deposition (PLD), and then the transparent p-type $CuAlO_2$ active layer was formed by annealing. Structural and optical characterizations revealed that the transparent p-type $CuAlO_2$ layer with a thickness of around 200 nm had a non-crystalline structure, showing a quite flat surface and a high transparency above 65 % in the range of visible light. From the NO gas sensing measurements, it was found that the transparent p-type $CuAlO_2$ thin film gas sensors exhibited the maximum sensitivity to NO gas in dry air at an operating temperature of $180^{\circ}C$. We also found that these $CuAlO_2$ thin film gas sensors showed reversible and reliable electrical resistance-response to NO gas in the operating temperature range. These results indicate that the transparent p-type semiconductor $CuAlO_2$ thin films are very promising for application as sensing materials for gas sensors, in particular, various types of transparent p-n junction gas sensors. Also, these transparent p-type semiconductor $CuAlO_2$ thin films could be combined with an n-type oxide semiconductor to fabricate p-n heterojunction oxide semiconductor gas sensors.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제3권2호
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• pp.471-475
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• 1999

The metal plasma-etch damage immunity of nMOSFET with $N{_2}O$ gate oxide is found to be improved comparing to that with regular pure oxide of similar thickness. With increasing the antenna ratio (AR), the characteristics of nMOSFETs with $N{_2}O$ oxide shows tighter initial distribution and smaller degradation under constant field stress, which is explained by the effect of the nitrogen at the substrate $Si/SiO_2$ interface. Also, if $N{_2}O$ gate oxide is used, the maximum allowable size of metal AAR and PAR may be increased to the much larger values. These improvements of nMOSFETs with $N{_2}O$ gate oxide are attributed to the effect of the interface hardness improved by the nitrogen included at the substrate-Si/$N{_2}O$-oxide interface.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
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• pp.71-72
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• 1998

반도체 집적 공정의 발달로 차세대 소자용으로 30 A 이하의 극 박막 Si02 절연막이 요구되고 있으며, 현재 제품으로 50-70 A 두께의 절연막을 사용한 것이 발표되고 있다. 절연막의 두께가 앓아질수록 많은 문제가 발생할 수 있는데 그 예로 절연막의 breakdo때둥에 의한 신뢰성 특성의 악화, 절연막올 통한 direct tunneling leakage current, boron풍의 dopant 침투로 인한 소자 특성 ( (Threshold Voltage)의 불안, 전기적 stress하에서의 leakage current증가와 c charge-trap 및 피terface s쩌.te의 생성으로 인한 소자 특성의 변화 둥으로 요약 된다. 절연막의 특성올 개선하기 위해 여러 가지 새로운 공정들이 제안되었다. 그 예로, Nitrogen올 Si/Si02 계면에 doping하여 절연막의 특성을 개선하는 방법 으로 고온 열처 리 를 NH3, N20, NO 분위 기 에서 실시 하거 나, polysilicon 또는 s silicon 기판에 nitrogen올 이온 주입하여 열처리 하는 방법, 그리고 Plasma분 위기에서 Nitrogen 함유 Gas를 이용하여 nitrogen을 doping시키는 방법 둥이 연구되고 있다. 또한 Oxide cleaning 후 상온에서 성장되는 oxide를 최소화 하여 절연막의 특성올 개선하기 위하여 LOAD-LOCK을 이용하는 방법, C뼈피ng 공정의 개선올 통한 contamination 감소와 silicon surface roughness 감소 로 oxide 신뢰성올 개선하는 방법 둥이 있다. 구조적 인 측면 에 서 는 Polysilicon 의 g없n size 를 최 적 화하여 OxideIPolysilicon 의 계면 특성올 개선하는 연구와 Isolation및 Gate ETCH공정이 절연막의 특성에 미 치 는 영 향도 많이 연구되 고 있다 .. Plasma damage 가 Oxide 에 미 치 는 효과 를 제어하는 방법과 Deuterium열처리 퉁올 이용하여 Hot electron Stress하에서 의 MOS 소자의 Si/Si02 계면의 신뢰성을 개선하고 있다. 또한 극 박막 전연막의 신뢰성 특성올 통계적 분석올 통하여 사용 가능한 수명 올 예 측 하는 방법 과 Direct Tunneling Leakage current 를 고려 한 허 용 가농 한 동작 전 압 예측 및 Stress Induced Leakage Current 둥에 관해서 도 최 근 활발 한 연구가 진행되고 있다.