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- 저자 : 김고은(Goeun Kim) (검색결과 39 건)
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이중 정합법을 이용한 볼록비구면 반사경의 형상 오차 측정
김고은,이윤우,양호순,Kim, Goeun,Lee, Yun-Woo,Yang, Ho-Soon 한국광학회 2021 한국광학회지 Vol.32 No.6
A reflecting telescope consists of a concave primary mirror and a convex secondary mirror. The primary mirror is easy to measure, because it converges the beam from an interferometer, while the secondary mirror diverges the beam and so is not easy to measure, even though it is smaller than the primary mirror. In addition, the Korsch-type telescope uses the central area of the secondary mirror, so that the entire area of the secondary mirror needs to be measured, which the classical Hindle test cannot do. In this paper, we propose a double-stitching method that combines two separate area measurements: the annular area, measured using the Hindle stitching method, and the central area, measured using a spherical wave from the interferometer. We test the surface error of a convex asphere that is 202 mm in diameter, with 499 mm for its radius of curvature and -4.613 for its conic constant. The surface error is calculated to be 19.5±1.3 nm rms, which is only 0.7 nm rms different from the commercial stitching interferometer, ASI. Also, the two results show a similar 45° astigmatism aberration. Therefore, our proposed method is found to be valuable for testing the whole area of a convex asphere.
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열적으로 안정한 리그닌 공중합물과 PP의 용융 블렌드 제조 및 물성
김고은(Goeun Kim),박인경(In-Kyung Park),김성훈(Sung-Hoon Kim),김영준(Youngjun Kim),서희원(Hee-Won Seo),윤주호(Ju-Ho Yun),김수현(Soo-Hyun Kim),김동관(Dong-Kwan Kim),남재도(Jae-Do Nam) 한국고분자학회 2016 폴리머 Vol.40 No.2
Lignin-based polycaprolactone (LigPCL) copolymer was synthesized by both the ring opening reaction of ε-caprolactone with the hydroxyl groups in the lignin and the concomitant polymerization of ε-caprolactone. FTIR spectra showed C=O (1755 cm<SUP>-1</SUP>) and C-O (1202 cm<SUP>-1</SUP>) peaks confirming that the esterification reaction took place successfully between lignin and ε-caprolactone. T₂, at which the weight loss of 2% occurs, of pristine lignin and LigPCL were measured as 63 and 211 °C, respectively, and so the synthesized LigPCL had superior thermal stability to the lignin. PP/Lig- PCL blends were prepared at various contents of LigPCL up to 30 wt% by a melt extrusion process. In proportion to the content of the LigPCL, tensile strengths, flexural strengths, and tensile modulus of PP/LigPCL blends greatly decreased, but elongations at break of those greatly increased. To improve the compatibility between PP and LigPCL, maleic anhydride-grafted polypropylene (PP-g-MA) was added. SEM images for the fracture surfaces of the blends showed that the PP-g-MA was effective in reducing the domain size of dispersed phase. Thus, T₂, tensile strength, tensile modulus, and elongation at break of a 70/30 blend of PP/LigPCL were enhanced by 6 °C, 17%, 31%, and 79%, respectively, by the addition of PP-g-MA. This work clearly demonstrates that thermoplastic LigPCL could be desirably synthesized and applied for value added and eco-friendly products through common melt processes used for polymer blend or composites manufacturing.
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