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조관식 인제대학교 1990 仁濟論叢 Vol.6 No.1
The threshold and the growth rate of parametric decay of laser are investigated via the throe-fluid theory of the plasma consisting of electrons, positive and negative ions. Landau dampings of electrostatic waves are taken into consideration phenomenologically. The threshold is raised, and the decay process is enhanced near the threshold, while unaffected well above the threshold, by negative ions.
음이온이 포함된 다이온 플라즈마의 충돌없는 삼유체 모형에서의 파동들
조관식 인제대학교 1987 仁濟論叢 Vol.3 No.2
In the collisionless three-fluid model of the multi-ion plasma composed of electrons, positive ions, and negative ions, analytical solutions of the dispersion relation are obtained using the perturbation method. Effects of the relative population ratios between negative ions and electrons on the propagations of the various waves are investigated. Thus seven solutions are shown to be peculiar to the presence of negative ions, as compared with the other multi-ion plasmas without negative ions. In particular, the usual ion acoustic wave ω=kvs is obtained even though ions and electrons have nearly the same temperatures, when the electron pupulation ratio is much less than one. Furthermore the plasma oscillation ω2= ωe2+ ω+2+ ω_2 incorporating all the three species is obtained when the electron population ratio is comparable to electron to ion mass ratio.
조관식 인제대학교 1995 仁濟論叢 Vol.11 No.2
Filamentation of an electromagnetic wave in a plasma with negative ions is treated theoretically through the collisionless three-fluid model. The threshold intensity required by the instability is raised and the growth rate above the threshold is lowered, by negative ions. After all, the filamentation instability may be said to be weakened by the presence of negative ions. However, if the pump intensity is high enough to change the plasma property, the instability growth rate may be enhanced by negative ions. The less the particle mass of negative ions relative to that of positive ions, the more prominent the enhancement.
Cho, Guan-Sik 인제대학교 1999 仁濟論叢 Vol.14 No.3
음이온이 포함된 플라즈마에서, 임계밀도 부근에서 일어나는 센 광파의 이온음파분열과 진동이류불안정에 대한 분산관계식들을 유도하였다. 이 식들에는 음이온에 의하여 광파가 비동조되어 버림으로써 위의 두 현상들을 안정화 시켜버리는 효과가 들어 있다. In a fluid plasma with negative ions, quasineutrality relations, coupled wave equations, and dispersion relations are derived for parametric instabilities of an intense light wave arising at critical density layers (the ion acoustic decay and the oscillating two stream instabilities). Negative ion quantities are carefully treated to isolate detuning effects at final results.
졸겔법으로 제작된 Al-doped ZnO 박막의 Aluminum Chloride 농도에 따른 구조적 및 광학적 특성
조관식 ( Guan Sik Cho ),김민수 ( Min Su Kim ),임광국 ( Kwang Gug Yim ),이재용 ( Jae Yong Lee ),임재영 ( Jae Young Leem ) 대한금속재료학회(구 대한금속학회) 2012 대한금속·재료학회지 Vol.50 No.11
Al-doped ZnO (AZO) thin films were grown on quartz substrates by the sol-gel method. The effects of the Al mole fraction on the structural and optical properties of the AZO thin films were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-VIS spectroscopy. The particle size of the AZO thin films decreased with an increase in Al concentrations. The optical parameters, the optical band gap, absorption coefficient, refractive index, dispersion parameter, and optical conductivity, were studied in order to investigate the effects of Al concentration on the optical properties of AZO thin films. The dispersion energy, single-oscillator energy, average oscillator wavelength, average oscillator strength, and refractive index at an infinite wavelength of the AZO thin films were affected by the Al incorporation. The optical conductivity of the AZO thin films also increased with increasing photon energy.
R-plane Sapphire 기판에 수열합성법으로 제작된 ZnO 나노구조체의 성장 및 특성
조관식 ( Guan Sik Cho ),김민수 ( Min Su Kim ),임재영 ( Jae Young Leem ) 대한금속재료학회 ( 구 대한금속학회 ) 2012 대한금속·재료학회지 Vol.50 No.8
ZnO nanostructures were grown on R-plane sapphire substrates with seed layers annealed at different temperatures ranging from 600 to 800℃. The properties of the ZnO nanostructures were investigated by scanning electron microscopy, high-resolution X-ray diffraction, UV-visible spectrophotometer, and photoluminescence. For the as-prepared seed layers, ZnO nanorods and ZnO nanosheets were observed. However, only ZnO nanorods were grown when the annealing temperature was above 700℃. The crystal qualities of the ZnO nanostructures were enhanced when the seed layers were annealed at 700℃. In addition, the full width at half maximum (FWHM) of near-band-edge emission (NBE) peak was decreased from 139 to 129meV by increasing the annealing temperature to 700℃. However, the FWHM was slightly increased again by a further increase in the annealing temperature. Optical transmittance in the UV region was almost zero, while that in the visible region was gradually increased as the annealing temperature increased to 700℃. The optical band gap of the ZnO nanostructures was increased as the annealing temperature increased to 700℃. It is found that the optical properties as well as the structural properties of the rod-shaped ZnO nanostructures grown on R-plane sapphire substrates by hydrothermal method are improved when the seed layers are annealed at 700℃.
음이온이 포함된 플라즈마에서 레이저광의 매개변수적 불안정
조관식 인제대학교 1993 仁濟論叢 Vol.9 No.2
This study is on the effect of negative ions on nonrelativistic parametric instabilities of an intense light in a plasma ; e.g., parametric decay instability (PDI), oscillating-two-stream instability(OTSI), stimulated Brillouin backscattering (SBBS), and stimulated Raman backscattering(SRBS). Results are presented through simple functions of the density of negative ions. The main conclusion depends on whether plasma waves damp 1) by collision between species of particles or 2) by resonant particles. Thus in the first case the above instabilities can be said to be usually enhanced, except for SBBS and SRBS with pump well exceeding the threshold which are weakened, by negative ions. On the contrary in the second case of damping, they are weakened by negative ions exce0pt for PDI and OTSI well over the threshold which are enhanced.
조관식 인제대학교 1991 仁濟論叢 Vol.7 No.1
In the three-fluid model of the plasma consisting of electrons, positive ions, and negative ions, the threshold and the growth rate of oscillating- two - stream instability are considered analytically, incorporating a phenomenological damping term(collisional or Landau). Negative ions play the role of lowering the instability threshold, and thus enhancing the instability growth rate near the threshold, when the electron plasma wave is damped mainly by collision. On the contrary, the threshold is raised and the growth rate is lowered by negative ions, when the electron plasma wave is damped mainly by resonant particles. However, once the pump intensity far exceeds the threshold, the growth rate is not significantly influenced by negative ions.
Selective Epitaxial Growth of SiGe Layers with High Aspect Ratio Mask of Dielectric Films
CHOI, A-Ram,CHOI, Sang-Sik,PARK, Byung-Guan,SUH, Dongwoo,KIM, Gyungock,KIM, Jin-Tae,CHOI, Jin-Soo,CHO, Deok-Ho,HAN, Tae-Hyun,SHIM, Kyu-Hwan The Institute of Electronics, Information and Comm 2008 IEICE transactions on electronics Vol. No.
<P>This paper presents the selective epitaxial growth (SEG) properties of reduced pressure chemical vapor deposition (RPCVD) at low temperatures (LT) of 675-725°C with high aspect ratio mask of dielectric films. The SEG process could be explained in conjunction with the loading effect, the mask pattern shape/size, and the process parameters of RPCVD. The growth rates showed a large non-uniformity up to 40% depending upon the pattern size of the dielectric mask films, but as the SEG film becomes thicker, the growth rate difference converged on -15% between the narrow 2-μm and the wide 100-μm patterns. The evolution of SEG was controlled dominantly by the surface migration control at the initial stage, and converted to the surface topology control. The design of pattern size and distribution with dummy patterns must be useful to accomplish the reliable and uniform LT-SEG.</P>