• Title/Summary/Keyword: 선경(仙境)

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An improved crystal rotation method for simultaneous measurement of pretilt angle and thickness of a liquid crystal layer (액정셀의 선경사각과 액정층의 두께를 함께 재는 개선된 결정회전법)

  • Son, Gong-Sook;Park, Chan;Park, Hee-Gap;Kim, Jin-Seung;Rho, Bong-Gyu;Lee, Hyong-Jong;Kim, Jae-Ki
    • Korean Journal of Optics and Photonics
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    • v.7 no.3
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    • pp.213-218
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    • 1996

  • An improved crystal rotation method with increased accuracy and range is proposed and experimentally verified for simultaneous measurement of molecular tilt angle and thickness of LC (liquid crystal) layer of an LC cell. The improvement is brought about by direct determination of difference between phases instead of intensities of two components of orthogonal linear polarization of the light passing through an LC cell filled with uniformly oriented molecules. By comparing the experimental data with theoretical result the thickness and pretilt angle are determined more precisely. Further improvement is brought about by use of a liquid gate filled with an index matching liquid in which the LC cell is immersed. Because of the index matching liquid reflection of light at the surfaces of an LC cell almost completely disappears and the range of angle of refraction in the LC layer increases significantly, which gives rise to increased signal to noise ration as well as decreased statistical error. With this improvement precise measurement for either very thin (<10 ${\mu}{\textrm}{m}$) and/or higher pretilt angle($\geq$10$^{\circ}$) LC cells become possible.

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Hydrophobicity and Adhesion of SiO2/Polyurethane Nanocomposites Topcoat for Aircraft De-icing with Different Pre-curing Time (선경화 시간에 따른 항공기 De-icing용 나노실리카/폴리우레탄 복합재료 탑코트의 소수성 및 접착특성 평가)

  • Kim, Jong-Hyun;Shin, Pyeong-Su;Kwon, Dong-Jun;Park, Joung-Man
    • Composites Research
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    • v.33 no.6
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    • pp.365-370
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    • 2020

  • The icing formation at aircraft occur problems such as increasing weight of the body, fuel efficiency reduction, drag reduction, the error of sensor, and etc. The viscosity of polyurethane (PU) topcoat was measured at 60℃ in real time to set the pre-curing time. SiO2 nanoparticles were dispersed in ethanol using ultra-sonication method. The SiO2/ethanol solution was sprayed on PU topcoat that was not cured fully with different pre-curing conditions. Surface roughness of SiO2/PU nanocomposites were measured using surface roughness tester and the surface roughness data was visualized using 3D mapping. The adhesion property between SiO2 and PU topcoat was evaluated using adhesion pull-off test. The static contact angle was measured using distilled water to evaluate the hydrophobicity. Finally, the pre-curing time of PU topcoat was optimized to exhibit the hydrophobicity of SiO2/PU topcoat.

  • https://doi.org/10.7234/composres.2020.33.6.365 인용 PDF KSCI