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경량기포콘크리트의 밀도변화와 철판구조에 따른 열적특성에 관한 기초적 연구
최훈국,정은혜,서정필,강철,박선규,김진만 대한건축학회지회연합회 2006 대한건축학회지회연합회 학술발표대회논문집 Vol.2 No.1
The light weight foamed concrete has many advantages. Because there are many pores in the matrix of concrete at the viewpoint of the insulation and fire resistance. Therefore it has been used in applications requiring insulation. The insulation property of light weight foamed concrete varies according to density. Also, density is varies according to hardened matrix and pore rate. The purpose of the experiment is to know the thermal properties of light weight foamed concrete according to the change of density and the shape of iron plate, when heating the light weight foamed concrete. The results of this experiment are as follows. The higher density of concrete, the lower temperature of that. This tendency is not same as that of ordinary light weight foamed concrete. It seems that temperature decrease of concrete can be affected by vapor phenomenon of inner water of concrete when concrete is heated. The specimen of density 0.9 is showed lowest temperature. Also, the perforated specimen was efficient in preventing temperature increase.
CO<sub>2</sub> 레이저를 이용한 초정밀 광섬유 연마 레이저 기술
최훈국,손익부,노영철,정덕,이만섭,이서영,이형종,Choi, Hun-Kook,Sohn, Ik-Bu,Noh, Young-Chul,Jung, Deok,Lee, Man-Seop,Lee, Seo-Young,Lee, Hyung-Jong 한국레이저가공학회 2013 한국레이저가공학회지 Vol.16 No.2
In this paper, we controlled the edge angle of fiber by using $CO_2$ laser. In order to control the angle, tilting angle of fiber on stage and the number of scan repetition are adjusted, and laser power is fixed at 30 W in the experiment. In the polishing result, the edge angle of fiber can be changed from $4^{\circ}$ to $8^{\circ}$, as changing the tilting angle and the number of scan repetition. This $CO_2$ laser polishing can fabricate ball lenses with various curvatures and a sharp probe as well as the edge angled fiber.
최훈국,유동윤,손익부,노영철,김영식,김수용,김완춘,김진봉,Choi, Hun-Kook,Yoo, Dongyoon,Sohn, Ik-Bu,Noh, Young-Chul,Kim, Young-Sic,Kim, Su-yong,Kim, Wan-Chun,Kim, Jin-Bong 한국레이저가공학회 2015 한국레이저가공학회지 Vol.18 No.1
In this paper, micro trench structure is fabricated by femtosecond laser for inserting optical reflecting wavelength filter in planar waveguide. The width and depth of the trench is controlled by femtosecond laser machining condition. Also, large scale of single channel with 500um and 1000um on silica plate is fabricated by femtosecond laser, and roughness of the channel surface is polished by $CO_2$ laser for the insertion of the filter. Then, the characteristic of the planar waveguide inserted the filter is verified.
최훈국,정덕,손익부,노영철,이용탁,김진태,Md. Shamim Ahsan 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.10
This research demonstrates laser-assisted fabrication of high-efficiency diffraction gratings infused-silica glass samples. Initially, femtosecond laser pulses are used to engrave diffraction gratingson the glass surfaces. Then, these micro-patterned glass samples undergo CO2 laser polishingprocess. unpolished diffraction gratings encoded in the glass samples show an overall diffractionefficiency of 18.1%. diffraction gratings imprinted on the glass samples and then polished four timesby using a CO2 laser beam attain a diffraction efficiency of 32.7%. We also investigate the diffractionpatterns of the diffraction gratings encoded on fused-silica glass surfaces. The proposed CO2laser polishing technique shows great potential in patterning high-efficiency diffraction gratings onthe surfaces of various transparent materials.
CO2 Laser Assisted Fabrication of Micro-lensed Single-mode Optical Fiber
최훈국,손익부,유동윤,노영철,성재희,이성구,정태문,Md. Shamim Ahsan,김진태 한국광학회 2015 Current Optics and Photonics Vol.19 No.4
This paper reports the fabrication of various micro-lensed single-mode optical fibers through the useof an enhanced peak power CO2 laser beam. The end faces of the optical fibers are exposed to the CO2laser beam to form convex, concave, and conical shape optical fiber tips. Peak power of the CO2 laserbeam was varied from 0.8 W to 1.5 W depending on the shape of the optical fiber tip. We also discoverthe dependence of the angle of the optical fiber tip on the rotation angle and the number of CO2 laserirradiations. The angle shows an increasing trend with both these parameters. We achieve a wide rangeof lenticular fibers with end face angle varying from 4.47° to 8.13°. Furthermore, we investigate theemission pattern of light from the developed micro-lensed fibers. The proposed CO2 laser based opticalfiber reshaping technique shows great consistency, and thus is suitable for commercial applications
최훈국,손익부,노영철,이용택,김진태,Shamim Ahsan 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.1
We have fabricated double-layer diffraction gratings with a zigzag shape inside fused silica glass byusing a femtosecond laser, the intention of which is to overcome the hindrance of shortening grating’speriod. Our primary focus is to utilize double-layer gratings to achieve a diffraction pattern similarto that from a single-layer diffraction grating with the same period as the double-layer grating. Wefabricated two kinds of double-layer gratings, where the grating’s period was either 6 μm or 2 μmfor both layers. The first set of diffraction gratings was printed 70 μm inside the glass substrates. This layer was followed by the second layer grating engraved just below the first layer grating (Theshifted grating’s position was shifted to the right by 3 μm for the 6-μm-period grating and by 1 μmfor the 2-μm-period grating). By varying the layer gap, we have found the optimal position (layergap: 500 nm) to achieve a diffraction pattern similar to that of a single-layer diffraction gratingwith half the grating’s period of the double-layer gratings.