http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : 황윤홰 (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
-
Sound Propagation in 5CB Liquid Crystals Homogeneously Confined in a Planar Cell
고재현,황윤홰,김종현 한국정보디스플레이학회 2009 Journal of information display Vol.10 No.2
The Brillouin spectrum of 4΄-n-pentyl-4-cyano-biphenyl (5CB) liquid crystals homogeneously confined in a planar liquid crystal (LC) cell was measured using a 6-pass tandem Fabry-Perot interferometer. By adopting a special right-angle scattering geometry, the sound velocity of 5CB was estimated from the Brillouin shift without knowing the refractive index. The sound velocity of the longitudinal wave propagating along the direction of the directors aligned parallel to the glass plates of the LC cell was 1784±7 m/s at 300 K. The attenuation coefficient was estimated to be approximately 1.9ⅹ10⁶m⁻¹, which is about twice as large as that of the longitudinal sound wave propagating along the direction perpendicular to the directors. The present method may be very useful in the evaluation of the elastic properties of the materials used in display devices, whose refractive indices are not known.
-
고재현,전병억,황윤홰,Do Han Kim,Seiji Kojima 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2
The acoustic properties of two potassium lithium niobate single crystals have been investigated by using Brillouin spectroscopy. The temperature dependence of the Brillouin shifts corresponding to two elastic constants, C11 and C33, was obtained over a wide temperature range including the phase transition temperature (Tc). Consistent with the uniaxial nature of the tetragonal tungsten- bronze structure and the Ising-type order parameter along the c-axis, only the C33 showed a large acoustic anomaly at Tc while C11 did not show a substantial change in both crystals. This result indicates that the longitudinal acoustic wave propagating along the polar direction couples strongly to the order parameter fluctuations, resulting in a significant softening of C33, as well as a substantial increase in the acoustic damping in the paraelectric phase. Changes in the acoustic properties above Tc have been partly ascribed to the electrostrictive coupling between the strain and the squared order parameter of polar nanoregions and fluctuation damping, which seem to be correlated with the diffuse nature of the ferroelectric phase transition observed in the present study. However, another microscopic origin seems to contribute to the softening of C33 at temperatures above Tc, which is unclear at present.
-
이광세,서정아,황윤홰,김형국,이철의,Kusuo Nishiyama 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2
Raman spectra of polycrystalline squaric acid (H2C4O4) were measured in the frequency shift region of 150 - 4000 cm-1 below and above the antiferroelectric phase transition (Tc = 373 K). No marked changes of internal vibrations of the H2C4O4 molecule in the crystal were observed up to 473 K, indicating that the symmetry of the H2C4O4 in the antiferroelectric phase persisted to the paraelectric phase. Raman spectra of polycrystalline squaric acid (H2C4O4) were measured in the frequency shift region of 150 - 4000 cm-1 below and above the antiferroelectric phase transition (Tc = 373 K). No marked changes of internal vibrations of the H2C4O4 molecule in the crystal were observed up to 473 K, indicating that the symmetry of the H2C4O4 in the antiferroelectric phase persisted to the paraelectric phase.
-
Diffuse Phase Transition of Potassium Lithium Niobate Single Crystals Probed by Brillouin Scattering
고재현,Do Han Kim,Seiji Kojima,Byeong-Eog Jun,황윤홰 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
A Brillouin light scattering study has been carried out on tungsten-bronze K5.80Li3.82Nb10.12O30 (KLN-1) single crystals, which exhibited diffuse ferroelectric phase transitions at Tc 700 K. Polarized central peaks (CPs) were observed in the paraelectric phase, indicating the existence of precursor polar clusters. The relaxation time, estimated from the width of the CP, showed a substantial increase at T Tc + 100 K, at which the polar clusters seemed to become more correlated and longer lived than at higher temperatures, similar to the case of the most typical uniaxial relaxor, (Sr0.61Ba0.39)5Nb10O30 (SBN-61). The temperature dependence of the relaxation time showed a different behavior from that of the typical order-disorder-type ferroelectrics, which has been ascribed to the intrinsic disorder of the unfilled tungsten-bronze structure and the resulting quenched random electric fields. A Brillouin light scattering study has been carried out on tungsten-bronze K5.80Li3.82Nb10.12O30 (KLN-1) single crystals, which exhibited diffuse ferroelectric phase transitions at Tc 700 K. Polarized central peaks (CPs) were observed in the paraelectric phase, indicating the existence of precursor polar clusters. The relaxation time, estimated from the width of the CP, showed a substantial increase at T Tc + 100 K, at which the polar clusters seemed to become more correlated and longer lived than at higher temperatures, similar to the case of the most typical uniaxial relaxor, (Sr0.61Ba0.39)5Nb10O30 (SBN-61). The temperature dependence of the relaxation time showed a different behavior from that of the typical order-disorder-type ferroelectrics, which has been ascribed to the intrinsic disorder of the unfilled tungsten-bronze structure and the resulting quenched random electric fields.
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
