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후드를 이용한 협소 터널 미기압파 감소 효과에 대한 수치적 연구
윤수환(Su-Hwan Yun),김병열(Byung-Yeol Kim),구요천(Yo-Cheon Ku),이동호(Dong-ho Lee),권혁빈(Hyeok-Bin Kwon),고태환(Tae-hwan Ko) 한국철도학회 2005 한국철도학회 학술발표대회논문집 Vol.- No.-
The train entry into a tunnel generates a strong compression wave in the tunnel The high amplitude of compression wave causes high pressure gradients that are responsible for both the aural discomfort of passengers and the impulsive acoustical wave called the mira-pressure wave. This paper provides a numerical study on effects of hood for micro-pressure wave reduction. An axisymmetric numerical solver, considering the crass-sectional area of Korean Tilting Train express, is used for a transient flow field in the tunnel Results show that the micro-pressure wave is able to be reduced by a hood. In this results, the maximum reduction of micro-pressure wave is shown at 2L(length), 1.35D(diameter) hood around 56% against the non-hood case.
홀로그램 암호화와 간섭 복호화를 이용한 디지털 워터마킹
김병열,도양희 제주대학교 공과대학 첨단기술연구소 2002 尖端技術硏究所論文集 Vol.13 No.2
A new optical watermarking system is proposed. The proposed system is applied for digital watermarking by using binary phase hologram and Mach-Zehnder interferometer. A mark image to be hidden is randomly phase-modulated image, and its Fourier-transformed hologram image is superposed on the original image. The information for authentication is extracted by using Mach-Zehnder interferometer. The availability of the proposed watermarking system is confirmed by computer simulation.
도양회,김병열 제주대학교 공과대학 첨단기술연구소 2003 尖端技術硏究所論文集 Vol.14 No.1
A new optical system is proposed for digital watermarking. The proposed system uses binary phase hologram and Mach-Zehnder interferometer. The mark image to be hidden is randomly phase-modulated image, and its Fourier-transformed hologram image is superposed on the original image. The mark image, the information for authentication, is extracted by using Mach-Zehnder interferometer. The availability of the proposed watermarking system is confirmed by computer simulation and optical experiment.