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김동준,정종문,김정현,황하청,정재윤,조윤희,임현교,구제환,최은하,조광섭,Jin, D.J.,Jeong, J.M.,Kim, J.H.,Hwang, H.C.,Chung, J.Y.,Cho, Y.H.,Lim, H.K.,Koo, J.H.,Choi, E.H.,Cho, G.S. 한국진공학회 2010 Applied Science and Convergence Technology Vol.19 No.1
관경이 수 mm인 세관 램프 내부에서 플라즈마의 확산을 조사하기 위하여 이극성(ambipolar) 확산방정식을 해하였다. 반경 방향의 확산에 의한 유리관 벽에서의 플라즈마 소멸 특성시간은 $\tau_r\;=\;(r_0/2.4)^2/D_a$로 주어진다. 반경 $r_0{\sim}1\;mm$이고 이극성 확산계수 $D_a{\sim}0.01\;m^2/s$ 이면, $\tau_r{\sim}17\;{\mu}s$이다. 이는 램프의 교류전원 구동에서 플라즈마를 유지하기 위한 구동 최소 주파수 ~30 kHz에 해당한다. 고전압이 인가되는 전극부에 발생한 고밀도의 플라즈마가 양광주로 확산되는 특성시간은 $\tau_z{\sim}0.1\;s$이다. 고밀도 플라즈마 경계에서의 시간에 대한 확산속도는 $t{\sim}10^{-6}\;s$일 때 $u_D{\sim}10^2\;m/s$이고, $t{\sim}10^{-3}\;s$이면 그 속도는 $u_D{\sim}1\;m/s$로 느려진다. 따라서 램프 길이 ~1 m에 대하여 전극부에서 생성된 고밀도 플라즈마가 양광주 전체로 확산되는 시간은 수 초가 걸린다. The ambipolar diffusion equation has been solved in a fine-tube lamp of a few mm in diameter. In the diffusion of radial direction, the plasma diffuses and vanishes away at the glass wall by recombination with the characteristic time of plasma loss is given by $\tau_r\;=\;(r_0/2.4)^2/D_a$. With the radius $r_0{\sim}1\;mm$ and the ambipolar diffusion coefficient $D_a{\sim}0.01\;m^2/s$, the vanishing time is calculated $\tau_r{\sim}10\;{\mu}s$ which corresponds to the least value of frequency 30 kHz for the sustaining the plasma in the operation of high voltage AC-power. In the diffusion of longitudinal z-direction, a high density plasma generated at the area of a high voltage electrode, diffuses into the positive column with the characteristic time $\tau_z{\sim}0.1\;s$. The plasma diffusion velocity at the boundary of high density plasma is $u_D{\sim}10^2\;m/s$ at the time $t{\sim}10^{-6}$ s and the diffusion velocity becomes slow as $u_D{\sim}1\;m/s$ at $t{\sim}10^{-3}\;s$. Therefore, for the long lamp of 1 m, it takes about several seconds for the high density plasma at the area of electrode to diffuse through the whole positive column space.
용융 열처리한 PMMA/Alumina 복합체의 기계 특성
김동준 ( D. J. Kim ),류수착 ( S. C. Ryu ) 한국열처리공학회 2018 熱處理工學會誌 Vol.31 No.3
The PMMA composited material mixed with alumina studied to find the optimal condition, the ade-quate ratio of mixing, for the associated mechanical properties such as anti-corrosive, weatherproof perfor-mance. The 80% of hardness and 52% of scratch coefficient improved according to increasing ratio of alumina, which is mostly 3 times higher than that of pure PMMA, on other hand 16% of tensile strength and 35% of flex-ural strength has lost while alumina was adding in. The most proper ratio, having the best availability in substan-tial production, of composite between pure PMMA and alumina is determined as 93 wt. % vs 7 wt. %. Results of related five properties had estimated by using of a pentagram. (Received April 25, 2018; Revised May 3, 2018; Accepted May 10, 2018)
김동준(D.C.KIM),김태형(T.H.KIM),김종원(J.W.KIM),김정훈(J.H.KIM),이강묵(K.M.LEE) 한국자동차공학회 1998 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1998 No.11_2
Today's metal-forming industry is looking for fast, effective and reliable techniques for product designs. If required final products are not known, trial and error techniques are often utilized for manufacturing products. However, these techniques are not adequate for current increasingly competitive markets, where rapid product developments are needed for staying in business. For this reason, lots of leading metal-forming industries are taking advantage of the Computer Aided Engineering(CAE) for their product and process designs. Through the CAE application in product developments, thousands of hours required for trial and error can be eliminated for metal-forming industries depending on empirical rules and intuition of engineers. The CAE plays an important role in reducing cost and development time of a product and achieving high quality products in a competitive market. However, lots of domestic metal-forming industries are not concerned about the application of CAE for their products, even if the CAE for metal-forming simulation is very popular in the U.S. and Europe at the present time. In this paper, an attempt is made to highlight the importance and application of CAE in forging and casting processes by means of specific examples that have been successfully performed at Samsung Electro-Mechanics Co.<br/>
증례 : 아메바성대장염에 유발된 다발성 관절염의 1 치험례
김동준 ( D. J. Kim ),조승환 ( S. H. Cho ),김홍수 ( H. S. Kim ),서주영 ( C. Y. Suh ) 대한내과학회 1968 대한내과학회지 Vol.11 No.4
1. A case of polyarthritis secondary to amebic colitis is reported, and this is considered to be a first case in Korea. 2. The diagnosis of amebic colitis was established by the isolation of the ameba from the stool and the subsequent rapid response of the
전력계통 과도안정도 해석을 위한 DFAG 모델링 연구(Ⅱ)
김동준(D.J. Kim),문영환(Y.H. Moon),이종주(J.J. Lee),서상수(S.S. Seo),김석주(S.J. Kim) 대한전기학회 2012 대한전기학회 학술대회 논문집 Vol.2012 No.5
This paper describes the modeling of DFAG (Doubly-Fed Asynchronous Generator) controllers such as electric and turbine controllers for the transient stability studies. The DFAG electric control model controls both the reactive power and electric power of DFAG. The DFAG turbine control model including wind power aerodynamic modeling controls the mechanical power by changing the pitch angle. The suggested DFAG controller models are tested against 6-machine and 23-bus system.