• 한국자동차공학회논문집
• /
• 제16권5호
• /
• pp.179-189
• /
• 2008

The performance of Lean NOx Trap (LNT) based on the catalysts of Pt/K/Ba/$\gamma-Al_2O_3$ with proprietary washcoat formulation is studied using a bench flow reactor system. To investigate the effect of temperature and gas hourly space velocity (GHSV) on the nitrogen oxides (NOx) trapping capacity as well as NOx breakthrough time and final ratio of $NO_2$ to NO of LNT, series of adsorption isotherms are carried out with simulated exhaust gases of the lean burn engines. Since typical operation of LNT requires periodic regeneration with a short rich excursion, where the stored or trapped NOx is released and subsequently reduced to $N_2$, the effect of the duration of lean and rich phase and type of reductants on the NOx conversion is investigated. NOx storage capacity and breakthrough time obtained from adsorption isotherms shows a volcano-type dependence on the temperature with a maximum NOx storage capacity occurring $350^{\circ}C$ and with a maximum breakthrough time occurring $400^{\circ}C$ at all GHSVs investigated in this study. Also, maximum ratio of $NO_2$ to NO is obtained at $400^{\circ}C$ with a GHSV of $75,000\;hr^{-1}$ Lean/rich cycle of 100 s lean and 5 s rich used with a concentration of 1.33% of $H_2$ and 4% of CO in the rich phase is found to be optimum at operating temperature of $350^{\circ}C$ and a GHSV of $50,000\;hr^{-1}$.

• KSBB Journal
• /
• 제5권1호
• /
• pp.25-35
• /
• 1990

In the Xanthan gum fermentation by Xanthomonas campestris there are problems of the large energy consumption by long fermentation time, the mass transfer of oxygen and nutrients by high viscous fermentation broth. In this study, the media optimization and the fed batch fermentation were carried out to decrease fermentation time and increase Xanthan gum yield. The $O_2$ uptake rate (OUR) and $CO_2$ evolution rate(CER) which were obtained from the analysis of fermentation exit gas using a gas chromatograph were investigated. As a result, the fermentation time decreased at optimal assimilable nitrogen concentration but increased at poor or rich assimilable nitrogen concentration, the Xanthan gum biosynthesis was stimulated under the limited condition of assimilable nitrogen source and the optimum fermentation medium was obtained as follow; Glucose=30g / l, Peptone=8.0g / l, $K_2HPO_4=2.0g/l$, $MgS0_47H_2O=10g/l$, Sodium acetate=20g/l, Sodium pyruvate=0.5g/1. As the agitation speed and nitrogen concentration increased, the $O_2$ uptake rate and $CO_2$ evolution rate increased. The OUR and CER were 37.3mmol $O_2/\;l$ hr and 20.2 mmol $CO_2/\;L$ hr at peptone 11g / l and agitation speed 990RPM, respectively. In fed batch fermentation, the final concentration of Xanthan gum was enhanced up to 29g / l.

• 연구논문집
• /
• 통권31호
• /
• pp.23-43
• /
• 2001

An experimental investigation on the reduction of nitrogen oxide emission from swirling, turbulent diffusion flames was conducted using multi air staged combustor, The combustor utilizes swirler to dampen fuel/air mixing, allowing an extended residence time for fuel pyrolysis and fuel-N conversion chemistry in an locally fuel-rich environment prior to burnout. This process also allow to reduce thermal NOx formation to lessen the temperature of reaction zone. The aerodynamic process therefore emulates the conventional staged combustion process, but without the need for the physically separate fuel-rich and -lean stages. Parametric studies on the ratios of each staged air and droplet size were carried out the feasibility of fuel/air mixing for low NOx combustion with diesel and pyridine mixed diesel fuel oil.

• 대한화학회지
• /
• 제66권3호
• /
• pp.185-193
• /
• 2022

본 연구에서는 tetrazine과 oxadiazole 등의 질소가 많이 함유되어 있는 헤테로 고리화합물을 가진 음이온과 NH₂OH, NH₂NH₂, CH₈N₆, C₂H₅N₅ 등의 양이온들과의 이온 결합을 통하여 생성된 에너지 염(energetic salts)에 대하여 열역학적 안정성, 밀도, 그리고 폭발 성능 등을 밀도 범함수 이론(dentisy functional theory, DFT)을 이용하여 계산하고 기존의 고성능 에너지 물질들과 비교하였다. 분자 구조 최적화 및 안정화 에너지는 B3LYP/cc-pVDZ 이론 수준에서 그리고 엔탈피 계산은 G2MP2 이론 수준에서 계산하였으며 폭발 성능은 Kamlet-Jacobs 방정식을 통하여 계산하였다. 결과적으로 크기가 작은 NH₃OH⁺(1)와 NH₂NH₃⁺(2) 양이온을 활용한 에너지 염은 폭발 성능 향상에 도움이 되며, 상대적으로 아미노기(-NH₂)가 많은 CH₉N₆⁺(3) 양이온은 안정성을 높이는데 효과적일 것으로 예측되었다.

• 한국표면공학회지
• /
• 제37권1호
• /
• pp.53-57
• /
• 2004

Austenitic stainless steel AISI 304 was nitrided in a low-pressure RF plasma using pure nitrogen. With a treatment of time of 4.0h at $400^{\circ}C$, the nitrogen-rich layer on the sample was $3\mu\textrm{m}$thick and had a hardness of approximately 4.4 times higher than that of untreated material. XRD data showed that as the process temperature rose from 350∼$450^{\circ}C$, the expanded austenite peaks became more prominent while the austenite peaks became weaker. Expanded austenite was transformed to ferrite and CrN at the treatment of$ 500^{\circ}C$. Langmuir probe measurements showed that electron density decreased above $450^{\circ}C$.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.663-664
• /
• 2006

Sintered Ti(C,N)-based cermets were treated with hot isostatic pressing (HIP) at different nitrogen pressures. The tribological properties of the treated cermets have been evaluated. The results show that a hard near-surface area rich in TiN formed after HIP treatment. The cermets treated at higher pressure had a relatively lower friction coefficient and specific wear rate. In all cases the microhardness of treated cermets is higher than that without HIP natridation. The wear mechanisms of cermets were hard particle flaking-off and ploughing. It was also found that the HIP natridation is well-suited for improving the tribological properties of cermets.

• Bulletin of the Korean Chemical Society
• /
• 제33권2호
• /
• pp.373-374
• /
• 2012

• E2M - 전기 전자와 첨단 소재
• /
• 제6권1호
• /
• pp.55-62
• /
• 1993

수소 관련된 species를 포함하지 않고 자기제한특성으로 초박막 성장을 용이하게 제어할 수 있는 N$_{2}$O 가스 분위기에서 실리콘의 산화는 질화된 산화막의 재산화공정 보다 훨씬 간단한 공정이다. N$_{2}$O산화로 형성된 Si-SiO$_{2}$ 계면에서 nitrogen-rich층은 산화막 구조를 강화할 뿐만 아니라 게이트 유전체의 질을 개선하고 산화율을 감소시키는 산화제의 확산 장벽으로 작용한다. 초박막 oxynitride 게이트 유전체가 종래의 열산화 방법으로 제작되었고 oxynitride막의 특성이 AES와 I-V 특성 측정의 결과를 분석하여 연구하였다.

• 천문학회보
• /
• 제42권2호
• /
• pp.43.2-43.2
• /
• 2017

We report our discovery of a significant population of CN-enhanced red clump stars in the classical bulge component of the Milky Way. Since CN-rich stars trace a population with enhanced Helium, Nitrogen, and Sodium originated in globular clusters (GCs), this is a direct evidence that proto-GCs were the major building blocks in the formation of the classical bulges and early-type galaxies in the hierarchical merging paradigm.

• 한국생물공학회:학술대회논문집
• /
• 한국생물공학회 2002년도 생물공학의 동향 (X)
• /
• pp.399-402
• /
• 2002

Industrial wastewater with high ammonium concentration was treated in batch biological systems which was a modified Ludzack- Ettinger process. Up to 78% conversion of $NH_4\;^+-N$ to $NO_x\;^--N$ was achieved in batch culture condition. Under anoxic condition with methanol as the carbon source, the denitrifiers decreased $NO_x\;^--N$ concentration from 608 mg/L to 5.6 mg/L in 22 d. As well as anoxic denitrification of $NO_x\;^-$ to $N_2$, dissimilatory nitrate reduction to ammonium also occurred under the condition as respiratory denitrification.