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RISS 인기검색어
- 검색키워드
- 저자 : 권명희(M. H. Kwon) (검색결과 4 건)
- 무료
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치환형 Sr - Ba 육방 페라이트들의 자기적 성질에 수소환원이 미치는 효과에 관한 Mossbauer 분광학적 연구
박재윤(J. Y. Park),권명희(M. H. Kwon),이재광(J. G. Lee) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.1
Sr substituted materials for some barium in M-type barium ferrite powder and Co-Ti substituted Sr-Ba hexagonal ferrite powder were prepared by citrate sol-gel method and 2 MOE sol-gel method. These hexaferrite particles were reduced for 1hr in the hydrogen gas. The reduction temperatures were varied in the range of 250 ℃ to 500 ℃. X-ray diffraction patterns were measured using diffractometer with Cu Kα radiation. Mossbauer absorption spectra were measured with a constant acceleration spectrometer. We have focused on studying the origin of increasing Ms by Mossbauer spectroscopy. Ferrite particles which were sintered at 1050 ℃ were found to be typical magnetoplumbite structure and single phase. XRD patterns with varying the reduction temperatures in Sr_(0.5)Ba_(0.5)Fe_(10)O_(19) indicates ferrites particles become composite hexaferrites containing α-Fe at Tred. = 350 ℃. On the otherhand, it was found that Co²+ ions and Ti⁴+ ions in Sr_(0.7)Ba_(0.3)Fe_(10)CoTiO_(19) prevent from changing Fe³+ ions to α-Fe during the H₂ reduction. Comparing Mossbauer results with XRD results, we have determined most of α-Fe are reduced from 4fvi sites and 12k sites of Fe³+ ions. These α-Fe phase bring the induced anisotropy and increase saturation magnetization Ms.
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레이저빔 조사에 의한 Al 금속표면과 기체의 물리적 상호작용에 관한 연구
권명희(M. H. Kwon),박인호(I. H. Park),김남춘(N. C. Kim),서동만(D. M. Seu),최성을(S. E. Choi) 한국진공학회(ASCT) 1994 Applied Science and Convergence Technology Vol.3 No.3
본 연구에서는 Al 금속 표변에 CW CO₂ 레이저 범의 조사시 표면 온도의 증가에 따른 표면과 기체 분자의 계면사이에서 발생하는 다양한 물리적 현상을 측정하였다. 온도 증가에 따른 계면에서의 물리적 현상은 Al 표면에 힘의 변화를 초래하는데, 이 힘의 변화를 시간에 따라 정확하게 측정하고, 측정한 힘을 온도와 연계하여 분석하면 계면의 상호작용에 의한 물리적 현상을 설명할 수 있다. 즉 레이저와 표면의 상호작용은 레이저 강도에 따라 기체와 표면 사이의 에너지 및 선운동량의 전달, 표면 흡착 원자의 방출 및 표면 물질의 증발 등으로 구분되는데, 이러한 상호 작용시 수반되는 힘의 변화를 이용하여 Al 금속 표면에 대한 기체 종류별 Momentum Accommodation Coefficient (MAC)를 계산하였고, Al 표면에 흡착된 원자의 종류, 갯수 벚 결합 에너지를 구하였다. In this study, we have investigated various physical phenomena between gas molecules and Al surface which is experienced temperature increasing by irradiation of CW CO₂ laser beam. The surface has force change during the interactions with gas molecules at the interface. We can explain those physical interactions from the accurate measurement and analysis of those changed forces with surface temperature. Those interactions can be categorized in 3 different phenomena, energy and momentum transfer at the interface, desorption of adsorbed molecules and ablation of materials at the surface, depend on laser intensity. Using these force changes by the gas-surface interaction, we can calculate momentum accommodation coefficient of different gases and number and binding energy of adsorbed molecules at the Al surface.
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조이현(L. H. Cho),김인기(I. G. Kim),이재일(J. I. Lee),장영록(Y. R. Jang),박인호(I. H. Park),최성을(S. E. Choi),권명희(M. H. Kwon) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.3
The magnetism and electronic structure of Ru monolayer with square lattice is investigated using the FLAPW band method. The dependence of total energies on the lattice constant was calculated for three magnetic states, i.e., para-, ferro-, and antiferromagnetic ones. It was found that there is no energy difference between para- and antiferromagnetic states for all the lattice constant. The possibility of antiferromagnetism in square Ru monolayer is thus excluded. The ferromagnetic state is most stable for the lattice constants greater than 7.30 a.u. The energy minimum is found at the lattice constant of 6.53 a.u. where it is paramagnetic. It is calculated that the magnetic moment is 2.49 μ_B at 7.72 a.u., which is close to the lattice constant of Ag. The magnetic moment is almost saturated to be 2.57 μ_B at the lattice constant of 7.86 a.u.
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BSO 유도 루타치온 저감 흰쥐에서 1, 2, 4-trichlorobenzene의 급성독성에 관한 연구
안영수,권명희,이정섭,김정우,김대선,류홍일,강인구 한국환경독성학회 1996 환경독성보건학회지 Vol.11 No.1
1, 2, 4-Trichlorobenzene (1, 2, 4-TCB) is used as a dye carrier, as an intermediate in the synthesis of herbicides, as a flame retardant, and for other purpose. After a single oral administration of 1, 2, 4-TCB (200 mg/kg, 400 mg/kg) in rats, toxic effects were studied by means of serum biochemical and heatological analysis, and liver calcium concentration. Administration of 1, 2, 4-TCB resulted in dose-dependent liver and kidney damage as estimated by increased serum alanine aminotransferase (ALT) activities, liver calcium concentration and blood urea nitrogen (BUN). Pretreatment with DL-buthionine sulfoximine (BSO, 2 mmol/kg, i. p. ) considerably decreased liver glutathione concentration, which was accompanied by markedly elevated serum ALT activates. It is well-known that toxicity of halogenated benzene such as bromobenzene, 1, 4-dichlorobenzene is increased by pretreatment of henobarbital (PB), and protected by pretreatment of cytochrome P450 inhibitor including metyrapone (MP). However, there was no obvious alterations in toxicity of 1, 2, 4-TCB by pretreatment of phenobarbital or metyrapone. In comparison with control group, treatment groups exhibited significant changes in some parameters of hematological analysis but all hematological values remined within normal ranges.
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