• 한국광학회:학술대회논문집
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• 한국광학회 2007년도 하계학술발표회 논문집
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• pp.275-276
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• 2007

체적형 홀로그래픽 메모리는 고용량의 저장밀도와 빠른 전송속도를 가지는 장점을 가지고있다. 더 높은 저장밀도를 얻기 위해 다양한 다중화 기법들이 연구되고 있다. 일정한 공간에 여러 개의 정보를 한꺼번에 저장할 수 있는 다중화 기법에는 각도에 따른 다중화, 기록 위치에 따른 다중화, 위상 변화에 따른 다중화를 비롯한 여러 가지 방법이 있다. 대부분의 다중화 기법들은 홀로그램을 저장할 때 순차적으로 기록하게 된다. 하지만 포토폴리머에 한번 정보가 저장되면 그 위에 다시 기록이 되지 않는다. 그래서 한번에 여러 개의 데이터를 저장하고 재생하는 시스템의 필요성이 요구된다. 본 논문에서는 이러한 점을 고려하여 빛의 편광성분을 이용해 다중화 하는 방법을 연구하였다.

• 대한기계학회논문집
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• 제18권10호
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• pp.2675-2685
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• 1994

A study has been conducted to provide the experimental information for the velocity and temperature profiles of steam-air mixutre and to investigate their roles on the film condensation with wavy interface. Saturated gas mixture of steam-air was made to flow through the nearly horizontal$(4.1^{\circ})$ square duct of 0.1m width and 1.56m length at atmospheric pressure, and was condensated on the bottom cold plate. The air mass fraction in the gas mixture was changed from zero(W =0, pure steam) to one(W =1, pure air), and the bulk velocity was varied from 2 to 4 m/s. Water film was injected concurrently to investigate the effect of wavy interface on the condensation. The velocity and temperature profiles were measured by LDA system and thermocouples along the three parameters ; air mass fraction, mixture velocity and film flow rate. The profiles moved toward the interface with increasing steam mass fraction, mixture velocity and film flow rate. The Prandtl and Schmidt numbers were near one in the present experimental range, however there was no complete similarity between the velocity and temperature profiles of gas mixture. And the heat transfer characteristics and interfacial structure were coupled with each other.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1962-1963
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• 2002

The hand-piece fiber optics is applied to medical appliances such as glaucoma theraphy to focus semiconductor laser on the affected parts efficiently. In this paper, we evaluate optical properties such as beam power and radius of a hand-piece probe by experiments and we also simulate the hand-piece optics by ray tracing method in order to study major parameters to optimize focalization ability. As results, we show experimental and simulation results of the hand-piece optics and also summarize several requirements that have to be considered in optimizing the hand-piece optics.

• Tribology and Lubricants
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• 제25권4호
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• pp.217-224
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• 2009

In this study, friction tests were carried out in order to investigate the friction behavior of textured surface in unlubricated state using ball-on-disk type apparatus. Test specimens were SUJ2 bearing steel ball and SM45C steel disk. Square arrays of circular micro-dimples were created on the surface of disk specimen by Nd:YAG Laser. Friction tests were performed for the disk specimen with various micro-dimple parameters and was also conducted for the variation of normal loads and relative velocities. The results showed that fiction coefficient of textured surface was lower than that of non-textured surface and the deeper depth of micro-dimple was, the lower friction coefficient obtained at the same diameter of micro-dimple in unlubricated state. Area density of micro-dimple had an effect on the friction coefficient. It was also found that friction coefficient generally decreased with the increase of normal load and relative velocity.

• 한국광학회지
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• 제11권3호
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• pp.202-205
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• 2000

Er과 Yb이 첨가된 인산염 유리를 KNO3 응용액에 담구는 1단계 이온교환 공정을 통하여 채널 도파로를 제조하고자 하였다. 이온교환시 반응기 내부에 산소를 흘려줌으로서 인산염 유리의 열학한 화학적 내구성에서 비롯되는 유리 도파로 표면의 손상을 억제할 수 있었다. 제조된 도파로의 $1.5{\mu}m$ 신호광에 대한 증폭특성을 평가한 경과, 이온교환 공정 최적화 작업을 거친 45nm도파로의 경우, 2개의 980nm LD를 사용하는 양방향 펌핑시 160mW 파워에서 7.5dB의 순이득을 얻을 수 있었다.

• 한국자동차공학회논문집
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• 제14권1호
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• pp.17-24
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• 2006

This study was performed to figure out spray behavior and fuel atomization characteristics of a piezo-driven injector and a solenoid-driven injector in the common-rail injection system under the same design parameters and test conditions. The process of spray injection was visualized by using the spray visualization system composed of a Nd:YAG laser and an ICCD camera. The atomization characteristics were investigated in terms of axial mean velocity, Sauter mean diameter(SMD) and droplet distributions obtained from a phase Doppler particle analyzer system. Compared with solenoid-driven injector, the piezo-driven injector has short injection delay and reaches quickly to the maximum injection value. Spray tip penetration shows some difference, however, spray angle of piezo-driven injector is wider than that of solenoid-driven injector. Sauter mean diameter of piezo-driven type injector is smaller than that of solenoid-driven type.

• 한국광학회지
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• 제6권4호
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• pp.352-358
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• 1995

$Tb^{3+}$이온이 첨가된 Hoya FR5 유리와 $Ce^{3+}$이론이 첨가된 Hoya FR4 유리의 Faraday 회전과 자기화를 4.2K-10K 저온 영역에서 자기장을 80kG까지 증가시키면서 온도 T와 자기장 H의 함수로 측정하였다. 사용파장은 아르곤 레이저의 514.5nm였다. H/T> $5kG.K^{-1}$ 이상에서 나타난 자기화 및 Faraday 회전의 포화현상을 상자성체 양자이론으로 해석할 수 있었다. 계산된 맺음변수들로부터 $Ce^{3+}$ 유리의 큰 Verdet 상수는 $4f\rightarrow5d$궤도 유효 전기쌍극자 전이효과에 기인되고 $Tb^{3+}$ 유리의 큰 Verdet 상수는 자기화에 기인됨을 알 수 있었다.

• 한국인터넷방송통신학회논문지
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• 제12권1호
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• pp.51-56
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• 2012

새롭게 발전시킨 등가 전송선로 해석법을 이용하여 원형 수직 캐비티 표면 광방출 레이저(VCSELs)의 공진특성을 연구되었다. VCSEL을 설계하기 위하여 필요한 광학변수들인 주기적인 Bragg 거울에서 나타나는 차단대역 특성과 반사율을 분석하였다. 또한, 설계된 VCSEL의 양자효율과 문턱 전류밀도를 평가하기 위하여 원형 모드 전송 선로 해석법의 횡방향 공진조건을 이용하였다. 이 해석법은 원형 VCSEL의 광학적 특성들을 분석하기 위한 수치해석 시간을 현저하게 줄여 주며, 명확한 설계개념을 제공한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1661-1665
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• 2004

Hard disk drives (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. Laser sheet and digital camera was used for 2-dimensional visualization of the unsteady flow between co-rotating disks in air with a cylindrical enclosure (or shroud). Geometric parameters are gap height (H) between disks, and gap distance (G) between disk tip and shroud. The lobe-structured boundary between inner region and outer region was detected by inserted particles, and the number of dominant vortices was determined clearly It is found from flow visualization that the number of vortex cells can be correlated with Reynolds number based on H which is defined as $Re_H={\Omega}RH/v$ ranging from $7.96{\times}10^2$ to $1.43{\times}10^4$, and decreases as the disk speed increases. The lobe pattern by vortex cells is changed to a circular pattern for the wide gap than narrow one.

• 제어로봇시스템학회논문지
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• 제21권7호
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• pp.602-608
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• 2015

This paper proposes an algorithm for precise detection of corner points on a coplanar checkerboard in order to perform stereo camera calibration using a single frame. Considering the conditions of automobile production lines where a stereo camera is attached to the windshield of a vehicle, this research focuses on a coplanar calibration methodology. To obtain the accurate values of the stereo camera parameters using the calibration methodology, precise localization of a large number of feature points on a calibration target image should be ensured. To realize this demand, the idea with respect to a checkerboard pattern design and the use of a Homography matrix are provided. The calibration result obtained by the proposed method is also verified by comparing the depth information from stereo matching and a laser scanner.