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Nb$_2$O$_{5}$ 첨가가 Mn-Zn Ferrites의 전자기적 특성에 미치는 효과
서정주,신명승,한영호,Suh, Jung-Ju,Shin, Myung-Seung,Han, Young-Ho 한국재료학회 1995 한국재료학회지 Vol.5 No.8
저손실 망간징크 페라이트에서 CaO-SiO$_2$첨가는 입계에 높은 전기저항층을 형성시켜 와류에 의한 손실을 감소시키는 것으로 알려져 있다. 본 실험에서는 Nb$_2$O$_{5}$ 를 제 3의 첨가제로 사용하여 저손실 망간징크 페라이트에서의 전자기적 물성변화를 관찰하였다. Nb$_2$O$_{5}$ 300ppm 이상 첨가시 부분적인 과대입자 성장이 관찰되었으며, 200ppm 첨가시 CaO-SiO$_2$만 첨가한 시편에 비하여 밀도가 증가하였다. Nb$_2$O$_{5}$ 첨가시에는 100ppm 이하의 SiO$_2$첨가에서 우수한 전력손실 특성이 나타났으며, 고온 소결시 Nb$_2$O$_{5}$-CaO를 첨가한 시편에서 낮은 전력손실을 나타내었다. It is well known that the addition of CaO-SiO$_2$to Mn-Zn ferrites forms an insulating grain bounary layer with high electrical resistivity. This study investigated the effect of Nb$_2$O$_{5}$ on the electromagnetic properties of high frequency low loss Mn-Zn ferrites. The addition of 300ppm Nb$_2$O$_{5}$ developed an exaggerated grain growth while the addition of CaO-SiO$_2$addition with 200ppm Nb$_2$O$_{5}$ more effectively increased the density than that without Nb$_2$O$_{5}$. The addition of Nb$_2$O$_{5}$ showed the lower power loss below 100 ppm SiO$_2$and the Nb$_2$O$_{5}$-CaO addition lowered the power loss at higher sintering temperature.
분사율 형상에 따른 디젤기관의 연소해석에 관한 시뮬레이션
왕우경,서정주 여수대학교 2002 論文集 Vol.17 No.-
Diesel combustion is fundamentally controlled by the mixing process of fuel with air in the combustion chamber. The injection rate shape has an important role in controlling the turbulent mixing and combustion process. Because it is difficult to change the injection rate shape freely by a experimental apparatus, its effects have not been investigated yet. Therefore, Influences of the injection rate shapes on the spray behavior, combustion characteristics and engine performance were simulated based on a two-zone thermodynamic model. It was shown that the shape with a high injection rate in the first stage of the injection period improved the air entrainment and heat release. Also, the shape with a high injection rate in the middle of the injection period improved the engine performance.
디젤기관의 경유-메탄올 혼합유 사용에 관한 실험적 조사
왕우경,서정주 여수대학교 2001 論文集 Vol.16 No.-
The combustion and performance of diesel engines fueled with alcohol-diesel oil have been investigated because of its potential for low NOx and particulates emissions. One of the problems encountered in the use of alcohol-diesel oil blended fuel is the phase separation between two fuels. In this study, diesel oil and methanol were mixed compulsorily in preventing phase separation with installing agitators and a fuel oil boost pump on fuel oil line of test engine. The effects of diesel oil-methanol blended fuel on combustion characteristics and engine performance were investigated under various loads and blending ratio. The results showed that the engine performance and combustion characteristics were influenced by methanol blending ratio and variation of load. Especially, the result of 30% methanol blended fuel was different from those of other test fuels.