• 한국유기농업학회지
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• 제19권spc호
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• pp.161-164
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• 2011

Nitrogen fixation by legumes can be valuable sources for organic farming. This study was to investigate the effect of different legume mixtures on nitrogen fixation and transfer to grasses on spring paddy field. Three different mixtures were used (rye+hairy vetch, Italian ryegrass+crimson clover, oat+pea) in a randomized complete block design with three replications and sowed in pots with different sowing rate (5:5 rye:hairy vetch,7:3=Italian:crimson, 6:4=oat:pea) on early March. $(^{15}NH_4)SO_4$ solution at. 99.8 atom%$^{15}N$ was applied to the each pot at the rate of 2kg N $ha^{-1}$ on $16^{th}$ April. Forage were harvested at ground level in heading stage and separated into legume and grass. Total N content and $^{15}N$ value were determined using a continuous flow stable isotope ratio mass spectrometry. DM yield of rye+vetch, Italian+crimson and oat+pea were 6,607, 3,213 and 4,312kg/ha, respectively. Proportion of N from fixation was 0.73(rye+vetch), 0.42(Italian+crimson) and 0.93(oat+pea). The percentages of N transfer from legume to grass were from 61% to 24% in different method by treatments and -35% to 21% in isotope dilution method.

• 한국초전도ㆍ저온공학회논문지
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• 제17권3호
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• pp.9-12
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• 2015

NbN thin films were deposited on thermally oxidized Si substrate at room temperature by using reactive magnetron sputtering in an $Ar-N_2$ gas mixture. Total sputtering gas pressure was fixed while varying $N_2$ flow rate from 1.4 sccm to 2.9 sccm. X-ray diffraction pattern analysis revealed dominant NbN(200) orientation in the low $N_2$ flow rate but emerging of (111) orientation with diminishing (200) orientation at higher flow rate. The dependences of the superconducting properties on the $N_2$ gas flow rate were investigated. All the NbN thin films showed a small negative temperature coefficient of resistance with resistivity ratio between 300 K and 20 K in the range from 0.98 to 0.89 as the $N_2$ flow rate is increased. Transition temperature showed non-monotonic dependence on $N_2$ flow rate reaching as high as 11.12 K determined by the mid-point temperature of the transition with transition width of 0.3 K. On the other hand, the upper critical field showed roughly linear increase with $N_2$ flow rate up to 2.7 sccm. The highest upper critical field extrapolated to 0 K was 17.4 T with corresponding coherence length of 4.3 nm. Our results are discussed with the granular nature of NbN thin films.

• 해양환경안전학회지
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• 제23권5호
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• pp.541-548
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• 2017

본 연구에서는 해양플랜트설비 건조 현장에서 사용되고 있는 기존 고온 오일 플러싱 장비에 대한 성능개선을 위해 기존의 플러싱 장치에 사용되던 오일에 질소가스를 혼합한 고온 오일 플러싱 시스템에 대하여 국제표준화기구 코드(ISO code)를 기준으로 이론적 연구를 수행하였다. 연구를 위해 오일-질소가스 혼합유체 플러싱 시스템 공정을 설계 후 청정성능에 영향을 주는 혼합유체의 혼합비율, 온도, 레이놀즈수 및 액상분율 등에 대한 공정모사 결과도 분석하였다. 그 결과 관 직경과 가스상의 체적분률이 일정한 상태에서 혼합유체의 체적유량이 증가될수록 수평 유압배관 입출구의 액상분율 차이 ${\Delta}{\alpha}_L$ 값은 증가하게 되고 배관길이 방향의 위치에 따라 오일과 질소가스 기포 사이의 상분포가 달라짐을 확인했다. 이러한 상분포의 변화는 오일-질소가스 혼합유체 플러싱 시스템의 청정성능에도 커다란 영향을 줄 것으로 예상된다.

• 한국진공학회지
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• 제11권1호
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• pp.22-27
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• 2002

Reactive sputtering 방법으로 증착된 tungsten nitride ($(WN_x)$) 박막에 대해 $N_2$ 유량비 변화에 따르는 구조, 화학결합, 그리고 비저항 값의 변화를 조사하였다. $(WN_x)$ 박막 증착시 $N_2$ 유량비를 20%, 40%, 60%로 늘려감에 따라 그 구조는 각각 bcc $\beta$-W상, 비정질상, 그리고 fcc W$_2$N상으로 변화하였으며, 비정질상이 형성되었을 때 박막 표면이 가장 평탄하였다. $(WN_x)$ 박막이 공기 중에 노출된 경우, 모든 시료 표면에서 $WO_3$ 산화물이 형성되었으며, $N_2$유량비가 증가할수록 $(WN_x)$ 박막내 N의 조성비가 증가하였고, W $4f_{7/2}$ peak가 높은 binding energy 쪽으로 이동하였다. 하지만 시료표면을 $Ar^+$ 이온으로 etching한 후에는 WNx 박막 표면이 비정질화되기 때문에 N의 조성비가 변화함에도 불구하고 $W4f_{7/2}$ / peak가 거의 변화하지 않았다. 박막의 비저항 값은 $N_2$ 유량비가 증가함에 따라 증가하였다.

• 한국자동차공학회논문집
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• 제2권3호
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• pp.113-122
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• 1994

This paper describes the effects of combustion parameters on the characteristics of combustion products in swirling flow furnace. The concentration of combustion products and temperature distribution of flow field in the furnace have been investigated by numerical method. The fuel was injected into the furnace and the swirling device was constructed with three kinds of vane swirler at inlet port of furnace. The results of this study showed that the effect of combustion parameters on the concentration characteristics of carbon monoxide and nitrogen monoxide of combustion products. It was found that the pollutant formation wad dependent on the equivalence ratio and swirl intensity level.

• 한국물환경학회지
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• 제27권4호
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• pp.461-466
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• 2011

The feasibility of utilizing food waste leachate as an external carbon source was tested to enhance biological nutrient removal from an industrial wastewater with an average flow rate of $164,800m^3/d$ and a low carbon/nitrogen ratio of 2.8. A considerable improvement in the removal of nitrogen and phosphorus was observed when a certain amount of the leachate, ranging from 70 to $142m^3/d$, was supplemented to the biological industrial wastewater treatment process. The addition of the leachate led to an increase in the BOD/N ratio (4.5) and the removal efficiency of nutritents from 29.7% to 71.7% for nitrogen and from 34.8% to 65.6% for phosphorus. However, an excessive dose of the leachate that significantly exceeded $120m^3/d$ caused serious operational problems, like oil-layer formation in the grit chamber and scum layer in the primary clarifier. Thus, an supplement of food waste leachate at a dose acceptable to an existing facilities can be a practical and effective means to enhance the nutrient removal from industrial wastewater and to dispose of the food waste leachate.

• 한국전기전자재료학회논문지
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• 제26권6호
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• pp.446-450
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• 2013

Growth mechanism of GS-MBE(Gas source-Molecular Beam Epitaxy) has been investigated. We observed that the growth rate of GaN films is changing from 520 nm/h to 440 nm/h by the variation of V/III ratio under nitrogen-rich growth condition. It was explained that the amount of hydrogen on the growth front varies by the ammonia flow, and gallium hydrides are generated on the surface by a reaction of hydrogen and gallium, resultantly the amount of gallium supplying is changing along with the $NH_3$ flow. Reflection high energy electron diffraction (RHEED) observation was used to confirm the N-rich condition. The crystal quality of GaN was estimated by photoluminescence (PL) and X-ray diffraction (XRD).

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.14-15
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• 2006

In this study, a new laval type nozzle was designed and manufactured. Using this nozzle tin powder was produced in close coupled system by using nitrogen gas at different operating conditions. The results showed that the increasing the gas pressure up to 1.47 MPa reduced the mean powder size down to 11.39 microns with a gas/melt mass flow rate ratio of 2.0. Powders are spherical in shape and have smooth surfaces.

• 한국추진공학회지
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• 제19권2호
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• pp.1-8
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• 2015

이중펄스 로켓 추진기관은 하나의 펄스분리장치에 의해 분리된 2개의 추진제 그레인을 가진 변형된 고체 추진기관이다. 이러한 추진기관의 주요 성능은 펄스분리장치 홀 면적대 노즐 목 면적비의 변화에 영향을 받는다. 본 연구에서는 펄스분리장치 홀 면적대 노즐 목 면적비 변화에 따른 내부유동특성을 고찰하기 위해 유동해석을 수행하였다. 유동해석에 사용된 기체로는 hot gas로 HTPB/AP계 복합추진제 연소가스와 cold gas로 질소가스롤 사용하였다. 이중펄스 로켓 추진기관의 내부유동해석 결과는 공압실험 결과와 비교 분석을 통해 검증하였다. 본 논문에서는 상용 CFD(Computational Fluid Dynamics) 코드인 ANSYS FLUENT V14.5를 이용하여 유동을 모사하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2101-2104
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• 2003

Experimental investigations are performed for the rarefied gas flows in a disk-type drag pump (DTDP). The pump considered in this paper consists of grooved spiral channel on rotors and planar stators. The flow-metre method is adopted to calculate the pumping speed. Compression ratio and pumping speeds for the nitrogen gas are measured under the inlet pressure range of $0.001{\sim}4$ Torr. The maximum of compression ratio was about 3300 for three-stage DTDP, 1000 for two-stage and 100 for single-stage DTDP at zero throughput. The number of stage influences the pumping speed of DPDT