• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.240-240
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• 2004

본 논문에서는 광학 기기 전반에 사용되고 있는 비구면 렌즈(aspheric lens)의 모델링과 제작 및 검증에 관한 연구를 수행하였다. 비구면 렌즈는 볼록렌즈, 오목렌즈와 달리 비구면을 사용함으로써, 사물의 원근에 관계없이 하나의 초점에 상을 맺을 수 있다. 그러나 이에 대한 모델링 정보는 공개되지 야고 있다. 따라서 본 연구에서는 다음의 식을 오일러 법(Euler method)을 적용하여 비구면 렌즈의 기하학적 형상을 모델링하였다.(중략)

• 발명특허
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• v.35 no.6
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• pp.26-33
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• 2010

본 연구에서는, 방명창의력 증진을 위한 전문 블록(다모블록)개발을 시도하고, 대학생들의 사용성 평가를 통해 통계적 검증이 이루어졌다. 개발된 다모블록은 각 면을 오목과 블록구조로 형성하여, 4면을 자유롭게 결합하는 슬라이드 방식의 특허기술이 적용된다. 결론적으로 개발된 다모블록은 발명교구로 사용될 수 있음은 물론, 발명원리를 발견하고 학생들의 다양한 발명사고 능력개발에 유용한 블록으로 평가된다.

• Journal of computational fluids engineering
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• v.16 no.2
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• pp.11-16
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• 2011

Numerical analyses have been carried out to analyze the three-dimensional turbulent heat transfer by impingement jet on a concave surface with variation of geometric configurations. Three-dimensional Reynolds averaged Navier-stokes equations have been calculated using the shear stress transport turbulent model. The numerical results for heat transfer rate were validated in comparison with the experimental data. The distance between jet nozzles and angle of inclined jet nozzle were selected as the geometric variables. Area-averaged Nusselt numbers on concave surface are evaluated to find the characteristics of heat transfer with the two geometric variables. The heat transfer increases as the distance between jet nozzles increases, and the inclined impinging jets show much better heat transfer performance than the vertical impinging jet.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.1083-1094
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• 1995

An experimental study has been carried out for jet-impingement cooling on the semi-circular concave surface. Two different nozzles(round edged nozzle and rectangular edged nozzle) are utilized and heat transfer coefficients on the concave surface have been measured under a constant heat flux condition. The characteristics of heat transfer has been discussed in conjunction with measured jet flow. Velocity and turbulence intensity of free jets issuing from two different nozzles have been measured by Laser Doppler Anemometry and theromocouple measurements have been done for temperatures on the concave surface. The effects of the nozzle shape, the distance between the nozzle exit and the stagnation point of the surface and the nozzle exit velocity on heat transfer were studied.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.3074-3080
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• 2013

Amplification of wave height at concave corner was investigated by three dimensional hydraulic tests. A typical rubble mound structure was tested with two-layer Tetrapod and the slope of 1:1.5. The irregular waves with Bretschneider-Mitsuyasu spectrum were applied to the tests. The center angles of concave corner were 120 degree, 140 degree and 160 degree. According to the test results, the maximum wave height amplification ratio at concave corner was about 1.5 times of incident wave height among the all test conditions, and the W-shaped wave height distribution was shown.

• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.391-392
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• 2008

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.327-333
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• 2008

In general, a lens with large NA makes image quality better. There are many kinds of cheap concave mirrors with large aperture and NA. This paper presents a method that uses a large aperture projection imaging system to enhance the image used for 3D shape measurement. This method makes it possible to enhance reflection uniformity on the object surface and increases SNR (Signal to Noise Ratio). Using a large aperture lens, it is possible to obtain a brighter image, reducing the shading nature in the image boundary, and enhancing the reflection uniformity even on woven surfaces. Because of the exorbitant cost of a large aperture projection lens larger than 150 mm in diameter, a refractive lens was exchanged with a concave mirror resulting in the same optical effect. In experiment, changing NA $0.15{\sim}0.8$, image contrast was enhanced from 46 to 1.33. Incidentally, the effect of the concave mirror was tested successfully through the experiment.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.9
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• pp.2991-3006
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• 1996

An experimental study of jet flow and heat transfer has been carried out for the jet impingement cooling on a semi-circular concave surface. For the jet impingement on the concave surface, three different regions-free jet region, stagnation region, and wall jet flow region-exist, and the distributions of mean velocity and fluctuating velocity for each region have been measured by Laser Doppler Velocimeter. Of particular interests are the effects of jet Reynolds number, the distance between the nozzle exit and cooling surface apex, and the distance from the stagnation point in the circumferential direction. The resulting characteristics of heat transfer at the stagnation point and the variation of heat transfer along the circumferential direction including the existence of secondary peak have been explained in conjunction with measured impinge jet flow.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.1149-1154
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• 2008

The present study investigates the heat transfer characteristics on concave surface with array impinging jet and fin arrangement. The heat transfer coefficients was measured by TLC method. The Reynolds number based on jet hole diameter is 10,000 and hole diameter-to-plate distance ratio (H/d) is fixed at 2. The rectangular fins are installed in the curved channel and the width of fin varies from 1d to 3d. Without fins, the averaged heat transfer coefficients decreases as moves downstream region. While, the rectangular fins block the crossflow and higher heat transfer rates were observed compared to smooth channel.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1098-1103
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• 2004

In this study, the effect of channel flow in the concave surface on local heat transfer characteristics of array jets was investigated experimentally. A TLC method is employed to determine local heat transfer coefficients on the target plate and also flow visualization has been conducted to investigate the behavior of a row of impinging jets and array of impinging jets. Two different array patterns of impinging array jets devices are tested for Reynolds number(Re=10,000). In a row of impinging jets, secondary vortex is strongly maintained by main vortex at nozzle-to-plate distance of H/d=2. Therefore, the Nusselt number slowly decreased at the mid-way region between adjacent jets. In array jets, the local maximum Nusselt number region move further in the downstream direction due to the increase of channel flow velocity.