• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제14권1호
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• pp.37-41
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• 1978

Optical properties were studied in the costal waters of the southern part of Korea based on twenty oceanographic stations from 1 st to 9 th February, 1977. Submarine daylight intensity was measured by using an underwater luxmeter (Toshiba No.9). Daylight intensity in the upper 30m depth layer was measured at 1 m depth interval. The absorption coefficient of the sea water in the area ranged from 0.101 to 2.539 (mean 0.578). The Secchi-disc depth in the area ranged from 0.8 to 13 meters (mean 5.33 meters). The relationship between absorption coefficient (K) and transparency (D) was k= 1. 704/ D. The mean water color in the area was 5. 75 (3-9) in Forel scales. The rates of light penetration for daylight at 1m layer in the area ranged from 13.18 to 82. 05% and the mean was 59.56%, while the rate at 5m layer ranged from 0.007 to 46.1% and the mean was 18.47%.

• Journal of Korea Multimedia Society
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• 제10권12호
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• pp.1585-1590
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• 2007

This paper introduces adaptive PRML (Partial Response Maximum Likelihood) architecture with PR (a,b,c,d,e) channel type for the improved readability of high-density optical discs with capacity greater than 30GB. The proposed PRML architecture consists of an adaptive equalizer, a Viterbi detector and a channel identifier. Detailed description for each component is included. The architecture is implemented in chip and also confirmed its performance on the test board mounting the chip. Test results show that the proposed 5-tap PRML architecture is well operated, and less than $2{\times}10^{-4}$ of BER (Bit Error Rate) is achieved with radial and tangential tilt margin of ${\pm}0.6^{\circ}$ on self-made 30GB BD at 1x speed.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제14권7호
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• pp.1687-1692
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• 2010

In this paper, we research the method for write quality improvement by temperature characteristic of Laser diode for optical recording. Differential Resistance of Blu-ray laser diode is changed by temperature. We analyze the effect of the change of the differential resistance in low temperature and propose the method for the write quality improvement.

• Journal of KSNVE
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• 제9권5호
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• pp.984-990
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• 1999

This paper presents the geometrical methodology to decouple the vibration modes of an elastically supported single rigid body in three-dimensional space. It is shown that the vibration modes can be decoupled by placing the center of elasticity at suitable locations and thereby yielding the plane(s) of symmetry for the given stiffness matrix. The developed methodology has been applied to the actuator supported by the 4-wire suspensions in optical discs, which has one plane of symmetry. For this numerical example, the axes of vibrations have been computed and illustrated with the natural frequencies. The forced response at the objective lens is represented and its geometrical interpretation has been explained as the mutual moment between the axis of vibration and the applied wrench times the line coordinates of the axis of vibration.

• Proceedings of the Optical Society of Korea Conference
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• 한국광학회 2000년도 하계학술발표회
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• pp.82-83
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• 2000

굴절율이 외부보다 큰 실린더 (cylinder)나 스피어 (sphere)는 경계면에서의 전반사에 의해 손실이 매우 적은 high-Q 공진기가 될 수 있음이 잘 알려져 있다. 크기가 수 십 $mu extrm{m}$ 되는 실린더나 스피어에서의 공명모드는 편광(TM, TE), 모드 수 (mode number) n, 모드 순서 (mode order) l에 의해 정의되고 WGM (whispering gallery mode)라고도 불리워진다$^{(1)}$ . 모드 수n 이 클수록 모드 순서 l이 작을수록 공명모드의 Q 값은 큰 경향을 가진다. 액체 방울이나 액체 제트와 같이 열적 섭동에 민감한 마이크로 공진기 (micro-cavity)의 경우 Q값이 $10^{7}$ 정도로 제약되나, 실리카 마이크로 스피어 (micro-sphere)와 같은 고체 구에서 측정된 Q값은 약 $101^{10}$ 정도로 손실이 매우 적은 공진기가 될 수 있다$^{(2)}$ . 이와 같은 마이크로 공진기 특성을 이용하여 다양한 형태의 마이크로 공진기 레이저 대한 연구가 진행되어 왔다. 색소가 첨가된 고체구, 액체 방울, 액체 제트 등에서 기본적인 실험이 이루어졌고 반도체마이크로 스피어 구조에서 WGM 레이저$^{(3)}$ , polymer disc laser$^{(4)}$ , 광양자테 (photonic quantum ring)$^{(5)}$ 특성 연구 등이 실용가능성을 목표로 진행되고 있다. (중략)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.792-798
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• 2012

This study shows the vibration characteristics of an actuator with six wire-suspensions, used in optical pickups of optical disc drives (ODDs). In this paper, the vibration characteristics of this beam structure is induced mathematically. To obtain vibration modes of focusing direction, the vibration analysis is achieved in lateral and longitudinal directions of the structure. The accuracy of induced vibration characteristics is proved by comparing mode frequencies with a finite element analysis. Finally, it is shown that mode shapes can be modified by changing design parameters in mathematical expressions.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제22권11호
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• pp.1128-1136
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• 2012

This paper analyzes the vibration characteristics of an optical pickup actuator, which has six wire-suspensions and is used in optical disc drives(ODDs). The vibration characteristics of the actuator is mathematically described by analyzing its beam configuration and motion condition confined to lateral and longitudinal directions of the beams. The accuracy of the vibration characteristics is proved by comparing mode frequencies with a finite element analysis. Finally, it is shown that mode frequencies and shapes can be modified by changing design parameters in mathematical expressions.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.12-13
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• 2005

Near field recording (NFR) technology with SIL has been thought as the most promising generation optical storage device. A gap distance between the SIL and the disc should be controlled to be 20${\~}$40nm. We observed gap error signal in our NFR test-bed using a blue LD (405nm). The digital gap servo filter and control algorithm were developed to maintain a constant air gap by adopting a conventional actuator.

• Journal of Plant Biology
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• 제17권4호
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• pp.143-156
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• 1974

The purpose of this experiment was to study one side of germination physiology based on that protein profiles and protease relating to protein metabolism, that peroxidase, catalase, $\alpha$-amylase, $\beta$-amylase, and malate dehydrogenase involved in the carbohydrate metabolism of seed germination. All these experiments were divided into the two groups with and without acetone treatment, and were carried out. The protein bands of each germinating stage between the groups treated with and without acetone showed certain basic pattern in polyacrylamide gel disc electrophoresis. However, there was a little difference in the number of protein band, optical density, and migration velocity between two groups. The isozyme bands of peroxidase, and catalase between two groups in polyacrylamide gel disc electrophoresis did not show the numeral difference, but the optical density of certain germinating stage treated with acetone was higher than the group untreated with it and it showed their enzyme activity. The $\alpha$-amylase and $\beta$-amylase activities which involved in starch metabolism of seed germination were higher in the treated group than the other. On one hand, the protease activity of hydrolase occurred in the seeds for germination was also higher, more or less in the treated group than in the other. The isozyme band pattern of malate dehydrogenase in TCA cycle of energy metabolism pathway was very different between two groups growing for 72 hours with and without acetone treatment in cellulose acetate electrophoresis. It indicated that two isozyme bands of malate dehydrogenase was high. Consequently these experimental results mentioned above indicated that acetone treatment before sowing had an effect on dissolving certain complexed lipid substance involved in the seed coats, the activity of carbohydrate hydrolase increased with water absorption which was most comfortable in its germination, dissolved glycerin and fatty acid became certain energy source, and they stimulated the acceleration of respiration metabolism.

• Journal of Mechanical Science and Technology
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• 제17권11호
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• pp.1793-1800
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• 2003

The present study addresses an experimental investigation of the near field flow structures of supersonic, dual, coaxial, free, jet, which is discharged from the coaxial annular nozzle. The secondary stream is made from the annular nozzle of a design Mach number of 1.0 and the primary inner stream from a convergent-divergent nozzle. The objective of the present study is to investigate the interactions between the secondary stream and inner supersonic jets. The resulting flow fields are quantified by pitot impact and static pressure measurements and are visualized by using a shadowgraph optical method. The pressure ratios of the primary jet are varied to obtain over-expanded flows and moderately under-expanded flows at the exit of the coaxial nozzle. The pressure ratio of the secondary annular stream is varied between 1.0 and 4.0. The results show that the secondary annular stream significantly changes the Mach disc diameter and location, and the impact pressure distributions. The effects of the secondary annular stream on the primary supersonic jet flow are strongly dependent on whether the primary jet is under-expanded or over-expanded at the exit of the coaxial nozzle.