• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 학술대회 논문집 전문대학교육위원
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• pp.64-66
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• 2002

This study is to develop electromagnetic plasma reactors for indoor air purification, Removal effect of nitrogen oxide using magnetic field are investigated. And AC or DC high voltage is applied for corona discharge, flow rates are 150${\sim}$1500${\ell}$/min and NO initial concentration is about 10 ppm. In the results, NOx removal rate by AC power is about 10 % higher than that by DC power under the experimental condition of 700 ${\ell}$/min, 5 magnets. When magnet is applied to the reactor, NOx removal rate increased.

• Asian-Australasian Journal of Animal Sciences
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• 제18권3호
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• pp.326-331
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• 2005

A rumen simulated continuous culture (RSCC) system was used to study the influence of supplementation of the three different types of protein sources such as urea, casein and soy protein on rumen microbial synthesis in terms of rumen microbial synchronization. The urea treatment showed the highest pH value. Ammonia nitrogen concentration was rapidly increased after feeding and not significantly different in the urea treatment (13.53 mg/100 ml). Protozoa numbers were not significantly different for soy protein and casein treatment compared to urea treatments during incubation. The average concentration of total VFA (mMol) was not detected with significant difference among treatments, but iso-butyrate production showed the highest for soy protein treatment among treatments (p<0.001). The lowest concentration in total iso-acids (iso-butyrate and iso-valerate) production was observed in urea treatment. The soy protein treatment showed no significantly change in acetate/propionate. The amounts of dry matter (DM) out flow showed no significant difference among treatments. Organic matter (OM) flow was the highest for urea treatments and the lowest for casein treatment (p<0.03). The nitrogen flow for casein treatment was not significantly different from other treatments. The efficiency of microbial protein synthesis in terms of microbial nitrogen (MN) synthesis (g MN/kg ADOM) digested in the rumen was highest for casein treatment (58.53 g MN/kg ADOM) compared to soy protein and urea (p<0.05). This result suggests that rumen ammonia releasing rate may influence on microbial protein synthesis in the rumen.

• 대한환경공학회지
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• 제27권3호
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• pp.262-272
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• 2005

본 연구는 하구호 수질개선을 위한 유입하천정화 시설의 기초설계 자료를 마련하기 위한 일환으로 시작되었다. 조사대상 하천은 삽교호 유입 국가하천으로 도시관통 하천(곡교)과 농경지 관통하천(무한, 삽교)이었다. 3년 동안의 장기적인 수질관측결과 시기적으로 큰 변화를 나타내었다. 도시지역이나 농경지를 관통하는 하천에서 유량이 증가할수록 질소농도는 뚜렷이 감소하였다. 인 농도는 도시하천의 경우에는 질소와 마찬가지의 변화특성을 나타내었으나 반면에 농경지 유역하천의 경우에는 유량이 영향이 상대적으로 적었지만 유량이 크게 증가할 경우 오히려 크게 증가하였다. 그 이유는 강우에 따른 유량증가시 도시지역이나 농경지를 흐르는 하천수의 부유물질 농도는 크게 증가하지만 유출되는 부유물질의 화학적 특성이 전혀 다르기 때문으로 판단된다. 용존성 질소(dissolved-TN)는 대상하천에서 총질소의 약 $40{\sim}60%$를 차지하였으며 총인의 경우는 약 35% 가량이 용존성 인(dissolved-TP) 상태로 존재하였다. 하구호인 삽교호의 3개 유입하천에 대한 대표수질은 건기와 우기로 구분하여 결정하는 것이 타당하며, 대표수질 항목으로는 측정오차가 적고 유량변동에 따른 수질변화 특성을 가장 잘 표현하고 있는 TDS와 SS를 이용하는 것이 바람직할 것으로 사료된다. TDS는 건기의 총질소 농도 증가를 반영하며, SS는 우기의 총인 농도 증가를 설명하는데 효과적이다. 본 논문에서 제시된 누적확률그래프는 하천정화시설의 설계목적으로 다른 유역의 하천수질을 비교 평가하는데 유용하게 사용될 수 있을 것으로 사료된다.

• 한국안전학회지
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• 제14권1호
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• pp.73-77
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• 1999

In this study, $SO_2$ and $NO_2$ reduction have been investigated by using coil type plasma reactor. The experiments have been carried out changing discharge power, gas flow rate frequency and electrode style to obtain the decomposition rate. Decomposition rates of $SO_2$ and $NO_2$ were obtained 20~98% at gas flow rate 100ml/min~1,000ml/min and discharge power 5~25w respectively. The energy efficiency is very good at the high frequency power. The decomposition rate of $SO_2$ for 5kHz power supply is only 90%, but for 10kHz power supply is very high, more than 98% for 15w. The decomposition rate is increasing according to the residence time or the power consumption of the discharge. About 15W discharge power for 17$cm^2$ reactor is necessary to obtain the decomposition rate of $SO_2$ and $NO_2$ of more than 85% or 98%. From these experiments, the consumption power of the decomposition rate of 98% in 300ppm $NO_2$ gas in nitrogen gas proved to be 18W and 300ppm $SO_2$ gas to be 15w.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제34회 춘계학술대회논문집
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• pp.264-267
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• 2010

This research focuses on the development of numerical code to deal with compressible two phase flow around three dimensional objects combined with cavitation model suggested by Weishyy et al. with k-e turbulent model. The cryogenic cavitation is carried out by considering the thermodynamic effect on physical properties of cryogenic fluids in physical point of view and implementing the temperature sensitivity in the energy equation of the government equations in numerical point of view, respectively. The formulation has been extensively validated for both liquid nitrogen and liquid hydrogen by simulating the experiments of Hord on hydrofoils. Then, simulations of cavitating turbopump inducers at their design flow rate are presented. Results over a broad range of Nss numbers extending from single-phase flow conditions through the critical head break down point are discussed. In particular, thermal depression effects arising from cavitation in cryogenic fluids are identified and their impact on the suction performance of the inducer quantified.

• 설비공학논문집
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• 제18권1호
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• pp.81-86
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• 2006

High temperature superconducting (HTS) power cable requires forced sub-cooled LN2 flow cooling. Liquid nitrogen is circulated by a pump and cooled back by cooling system. Typical operating temperature range is expected to be between 65 K and 77 K. The HTS power cable needs sufficient cooling to overcome its low temperature heat load. For successful cooling, the hydraulic characteristics of the HTS power cable must be well investigated to design the cables. Especially, the pressure drop in the cable is an important design parameter, because the pressure drop decides the length of the cable, size of the coolant circulation pump and circulation pressure, etc. This paper describes measurement and investigation of the pressure drop of the cooling system. In order to reduce the total pressure drop of the cooling system, the flow rate of liquid nitrogen must be controlled by rotational speed of the circulation pump.

• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.64-68
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• 2016

High Temperature Superconductor power cable systems are being developed actively to solve the problem of increasing power demand. With increases in the unit length of the High Temperature Superconductor power cable, it is necessary to develop highly efficient and reliable cryogenic pumps to transport the coolant over long distances. Generally, to obtain a high degree of efficiency, the cryogenic pump requires a high pressure rise with a low flow rate, and a partial emission type pump is appropriate considering its low specific speed, which is different from the conventional centrifugal type, full emission type. This paper describes the design of a partial emission pump to circulate subcooled liquid nitrogen. It consists of an impeller, a circular case and a diffuser. The conventional pump and the partial emission pump have different features in the impeller and the discharge flow passage. The partial emission pump uses an impeller with straight radial blades. The emission of working fluid does not occur continuously from all of the impeller channels, and the diffuser allows the flow only from a part of the impeller channels. As the area of the diffuser increases gradually, it converts the dynamic pressure into static pressure while minimizing the loss of total pressure. We used the known numerical method for the optimum design process and made a CFD analysis to verify the theoretical performance.

• 소성∙가공
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• 제20권4호
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• pp.296-302
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• 2011

The objective of this paper is to determine the effect of process parameters on the behavior of a 18Cr-10Mn-$0.44N_2$ nitrogen steel sample deformed by hot rolling. Compression tests were carried out at high temperatures to determine the flow stresses needed for a finite element(FE) analysis. The strain rate, ranging from 0.1 to $1.0s^{-1}$, significantly affected the flow stress at temperatures higher than $1,000^{\circ}C$. Non-isothermal rolling simulations and laboratory rolling tests were performed with plate specimens 14.5mm thick, 135mm wide and 226mm long. A rolling reduction of 15% per pass leading to a cumulative rolling reduction of 60% was determined as optimal. The extension ratio of 176.5% in the length direction was about 30.4 times greater than the extension ratio of 5.8% in the width direction. Isotropic properties for tensile strength, microstructure and grain size were measured after mock-up hot rolling tests. The results from the mockup tests were found to be in good agreement with those of the simulations.

• 한국자기학회지
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• 제18권1호
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• pp.14-18
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• 2008

본 연구에서는 Bi:YIG($Bi_{0.5}Y_{2.5}Fe_5O_{12}$) 막을 에어로졸 성막법을 이용하여 제작함에 있어서, 에어로졸을 구성하는 수송가스의 유량이 막의 자기적 특성과 광학적인 특성에 대하여 분석하였다. 직경 $100{\sim}500$ nm 의 Bi:YIG 분말을 질소 가스를 수송가스로 사용하여 성막을 실시하였고, 이 때, 수송가스의 유량은 0.5 l/min${\sim}10$ l/min 사이에서 변화시켰다. 수송가스의 유량이 증가할수록 Bi:YIG 막의 보자력은 51 Oe에서 37 Oe까지 지수함수적으로 감소하였다. 이것은 충돌에너지가 증가함에 따라 막내부 혹은 막표면의 결함이 감소하였기 때문이라고 고찰되었다. 포화자화는 유량이 증가할수록 감소하였는데, 이는 충돌에너지가 강해짐에 따라 결정이 왜곡되는 힘을 받았기 때문이라고 고찰되었다.

• 한국전기전자재료학회논문지
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• 제15권7호
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• pp.640-648
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• 2002

This study is to develop electromagnetic-catalyst application plasma reactors for indoor air purification. Nitrogen Oxide(NOx) removal characteristics are measured in the electromagnetic catalyst application plasma reactors with various parameters and the effect of catalyst or/and magnetic field are investigated on the NOx removal. And AC or DC high voltage is applied for corona discharge, flow rates are 150~1500 $\ell/min$ and NO initial concentration is about 10 ppm. $Mn0_2$ and $TiO_2$ catalysts to increase NOx removal rate are used. In the results, NOx removal rate by AC power is about 10 % higher than that by DC power under the experimental condition of 700 $\ell/min$, 5 magnets, $MnO_2$ and $Ti)_2$ catalysts. When magnet is applied to the reactor, NOx removal rate increased. Also, the reactor with $MnO_2$ and $Ti)_2$ catalyst and magnet have the best removal rate.