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        검색결과 533

        301.
        2003.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        LIST is the Lyman-α Imaging Solar Telescope, a project funded by the Korean government to fly on the second Korean Science and Technology research Satellite (STSat-2) due to launch in December 2005. The Principal Investigator is Dr. Minhwan Jang of Kyung-Hee University and of the Space Payload Research Center (SPARC), a consortium of Korean universities and institutions formed to develop scientific research projects in space. The purpose of the LIST project is to design, build, and operate an instrument on STSat-2 which will make images of the Sun from Earth orbit at the wavelength of the Hydrogen Lyman-a emission line at 121.6 nm. LIST has a simple design concept comprised of a small telescope to image the full disk of the Sun onto a CCD detector and a set of filters to isolate the 121.6 nm wavelength.
        4,000원
        302.
        2003.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In the present study, we have investigated morphology and evolution of small-scale Ha dynamic features on the quiet sun by analyzing video magnetograms and high resolution Ha images simultaneously taken for 5 hours at Big Bear Solar Observatory on April 18, 1997. From comparisons between time sequential longitudinal magnetograms and Hα images covering 150" × 150", several small-scale Hα dynamic features have been observed at a site of magnetic flux cancellation. A close relationship between such features and cancelling magnetic fluxes has been revealed temporarily and spatially. Our results support that material injection by chromospheric magnetic reconnect ion may be essential in supporting numerous small-scale Hα dynamical absorption features, being in line with recent observational studies showing that material injection by chromospheric magnetic reconnect ion is essential for the formation of solar filaments.
        4,000원
        304.
        2003.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Alpha-SiAlON ceramics having various compositions and modifying cations were investigated with respect to their phase stability, transformation kinetics. and resulting microstructures. Each composition was heat treated at 150 for 1h and measured the -SiAlON transformation. The phase-boundary composition in the single-phase -SiAlON region showed sluggish transformation from - to -SiAlON compared to the phase-center composition in the diagram. Using the different rare earth modifying cations, dependence of transformation kinetics on the phase stability in a fixed composition was also explained. By changing size of the stable u-phase region with exchanging cations, systematic change in transformation was observed. Transformation rate of -SiAlON at low temperature has an important role on controlling the final microstructure. Less transformation gives more chances to develop elongated grain in the microstructure.
        4,000원
        305.
        2002.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Almost half of primeval galaxies show P-Cygni type profiles in the Lyα emission line. The main underlying mechanism for the profile formation in these systems is thought to be the frequency re-distribution of the line photons in expanding scattering media surrounding the emission source. A Monte Carlo code is developed to investigate the Lyα line transfer in an optically thick and moving medium with a careful consideration of the scattering in the damping wings. Typical column densities and expansion velocities of neutral hydrogen investigated in this study are NH1 ~10 17-20 cm -2 and ΔV ~ 100 km s-1. We investigate the dependence of the emergent profiles on the kinematics and on the column density. Our numerical results are applied to show that the damped Lyα absorbers may possess an expanding H I supershell with bulk flow of ~ 200 km s-l and H I column density NH1 ~ 10 19 cm -2. We briefly discuss the observational implications.
        4,200원
        312.
        2002.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We carried out this experiment to observe electrochemical properties for LB films of phospholipid(Dilauroyl-L-α-Phosphayidylcholine) and 4-octyl-4'-(5-carboxypentamethylene-oxy)azobenzene mixture by the cyclic voltammetry. LB films of 8A5H and 8A5H-DLPC(1:1, 2:1) were deposited by using the Langmuir-Blodgett method on the ITO glass. We determined electrochemical measurement by using cyclic voltammetry with a three-electrode system, An Ag/AgCl reference elect rode, a platinum wire counter electrode and LB film-coated ITO working electrode measured in 0.1, 0.5, and 1.0 mol/L NaClO4 solution. A measuring range was reduced from initial potential to -1350 mV, continuously oxidized to 1650 mV and measured to the initial point. The scan rate were 50, 100, 150 and 200 mV/s. As a result, LB films of 8A5H 8A5H-DLPC appeared irreversible process caused by only the oxidation current from the cyclic voltammogram.
        4,000원
        313.
        2002.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Copolymerization of α-Methylstyrene(AMS) with Acrylonitrile(AN) was carried out with benzoylperoxide(BPO) as an initiator in toluene at 80℃ in a continuous stirred tank reactor. Reaction volume and residence time were 0.6 liters and 3 hours, respectively. The monomer reactivity ratios, rAMS and rAN determined by both the Kelen-Tüdös method and the Fineman-Ross method were rAMS=0.16(0.14), rAN=0.04(0.06). The cross-termination factor Φ of the copolymer over the entire AMS composition ranged from 0.75 to 0.92. The Φ factors of poly(AMS-co-AN) were increased with increasing AMS content. The simulated conversions and copolymerization rates were compared with the experimental results. It was observed that the average time to reach dynamic steady-state was three times the residence time.
        4,000원