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Featured researches published by Eiji Koyama.


Optical Data Storage '91 | 1991

Highly reliable 7-GB, 1.2- to 2.2-MB/s, 12-inch write-once optical disk

Hitoshi Watanabe; Eiji Koyama; T. Nunomura; Toshiaki Taii; Michio Miura; Akira Gotoh; Tetsuya Nishida; Shinkichi Horigome; Norio Ohta

In order to extend an application area of 12 inch write once optical disks, both a larger data capacity and higher data transfer rate are required, which in turn requires more advanced reliability and durability. This paper describers a double sided 7GB twelve inch diameter disk suitable for high data transfer (1.2-2.2 MB/s) application. A storage data capacity is increased by using both the pit- edge method and the Modified Constant Angular Velocity (MCAV) method. The corrosion resistant Te based ternary alloy recording layer has an excellent pit length characteristics and less thermal interference, which results in wide jitter margin in the pit edge detection. The high speed disk rotation gives the high data transfer rate. Acceleration tests prove a disk life longer than 45 years.


Optical Storage Technology and Applications | 1988

Optical Disc Substrate Using Photo-Curable Casting Resin

Ryouichi Sudou; Hiroaki Miwa; Tetsuo Tajima; Shinkichi Horigome; Norio Ohta; Eiji Koyama

The manufacture of high performance Φ 130 mm magneto-optical (MO) discs requires the substrates with low retardation, high heat resistance and low cost in the market. The molding methods for newly compounded photo-curable acrylic resin (PHC) were studied. Thus, the pre-grooved substrate using PHC resin has been developed for the MO disc, and is capable of fast molding by a simple machine. Carrier to noise ratio (C/N) characteristics and the reliability of the MO disc with the PHC substrate are almost equal to those of glass substrate.


Proceedings of the ASME/JSME Joint Fluids Engineering Conference | 2003

Measurement of Turbulent Mass Mixing Caused by a Particle Wake

Toru Koso; Eiji Koyama; Takayuki Mikamoto

When a particle moves in a fluid, the fluid is disturbed by the particle and the fluid mass is mixed. This phenomenon is commonly observed in particle-laden flows and dispersed bubble flows. This mass mixing can be composed of two mechanisms. One is the mass transfer by convective flows that are induced by the reaction of the particle drag and the other is the turbulent mass mixing in the turbulent wake of the particle. The effect of the former one can be evaluated using the previous studies on the particle drag. However, the effect of the turbulent mixing is little understood. The turbulent mixing caused by a particle wake is investigated by visualization and noninvasive concentration measurement using a photochromic dye. A sphere brass particle of 5mm in diameter is dropped in kerosene filled in a vertical pipe and the mixing of dye is visualized. The photochromic dye, which is activated by an ultraviolet light, keeps its color in a few minutes after the activation. A part of the fluid is activated without disturbances and is subjected to the mixing by the particle wake. The visualized dye patterns indicate the dye is mixed isotropically by large-scale vortex motions when the particle sheds the vortices. Furthermore, the photochromic concentration measuring (PCM) technique is developed to obtain the concentration of the mixed dye. This PCM technique is based on the Lambert-Beer’s law for light adsorption and provides the average dye concentration along the light path. The measured concentration distribution shows rather isotropic mixing in longitudinal direction. The turbulent diffusion coefficient (TDC) is calculated from the temporal changes in the measured concentration distributions. The evaluated TDC shows strong time-dependency, which is attributed to the change in scale and strength of wake vortices. The TDC is about 104 times larger than the molecular diffusion coefficient at its maximum. The effect of particle Reynolds number on the turbulent mixing is also investigated for the Reynolds number range from 263 to 3290. The observed mixing patterns show a drastic change at the critical Reynolds number on the vortex shedding from the particle. The Reynolds number dependency on the non-dimensional TDC and mixing time are discussed.Copyright


Archive | 2008

Optical adjusting member, and illumination device and liquid crystal display device including the same

Katsusuke Shimazaki; Yoichi Ogawa; Masataka Sato; Eiji Koyama


Archive | 1997

Magneto-optical recording medium and process for producing the same

Katsusuke Shimazaki; Satoru Ohnuki; Masatoshi Hashimoto; Yoshinori Shirai; Norio Ohta; Hideo Fujiwara; Masafumi Yoshihiro; Yukinori Yamada; Eiji Koyama; Hitoshi Furusho


Archive | 2003

Information recording media and information recording drive

Fumiyoshi Kirino; Nobuyuki Inaba; Hiroki Yamamoto; Takashi Naitou; Ken Takahashi; Eiji Koyama; Motoyasu Terao; Sumio Hosaka; Hiroki Kuramoto


Archive | 2005

Illumination device and manufacturing method of the same

Masaya Adachi; Hideo Honma; Eiji Koyama; Hajime Murakami; Toshishige Shibazaki; 栄二 小山; 秀男 本間; 村上 元; 利成 柴崎; 昌哉 足立


Archive | 2007

Lighting device and display apparatus

Yoichi Ogawa; Masataka Sato; Katsusuke Shimazaki; Eiji Koyama; Hiroyuki Tsukamoto; Toshihiro Yamanaka


Archive | 1999

Optically functional element and production method and application therefor

Hiroki Yamamoto; Takashi Naito; Ken Takahashi; Motoyasu Terao; Toshimichi Shintani; Fumiyoshi Kirino; Eiji Koyama; Sumio Hosaka; Sachiko Okuzaki; Takashi Namekawa; Tetsuo Nakazawa


Archive | 2002

Magnetic recording disk, method of the magnetic recording disk and magnetic recording apparatus

Fumiyoshi Kirino; Nobuyuki Inaba; Ken Takahashi; Takashi Naitou; Sumio Hosaka; Eiji Koyama; Motoyasu Terao; Hiroki Yamamoto; Hiroki Kuramoto

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