• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.50.2-50.2
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• 2009

사파이어는 질화물계 광전자소자 제작 시 박막 성장 기판으로 주로 사용되어 최근 그 중요성이 부각되고 있다. 특히 미세 패턴이 형성된 사파이어 기판을 이용하여 질화물계 발광다이오드 소자를 제작하면 빛의 난반사가 증가하여 광추출효율에 큰 개선이 나타난다. 또한 사파이어는 화학적 안정성이 뛰어나고, 높은 강도를 지녀 나노임프린트 등 여러 가지 패터닝 공정에서 패턴 형성 몰드로도 응용될 수 있다. 그러나 이와 같은 사파이어의 화학적 안정성으로 인하여 sub-micron 크기의 미세 패턴을 형성하기 힘들며, 현재 사파이어의 패턴은 micron 크기로 제한되어 사용되고 있다. 본 연구에서는 나노임프린트 리소그라피(NIL)를 사용하여 사파이어 웨이퍼의 c-plane위에 sub-micron 크기의 hole 패턴 및 pillar 패턴을 형성하였다. 우선 Hole 패턴을 형성하기 위해 사파이어 기판 위에 금속 hard mask 패턴을 UV 임프린트 공정과 etch 공정을 통해 형성하였다. 그리고 이 금속 패턴을 mask로 사파이어를 ICP 식각을 하여 hole 패턴을 형성하였다. 또한 Pillar 패턴을 형성하기 위해 lift-off 공정을 이용하여 금속 마스크 패턴을 형성하였고 이를 ICP 식각을 통해 사파이어 기판 위에 pillar 패턴을 형성하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.83-89
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• 2018

The thermal characteristics of concrete specimens were analyzed using cement paste specimens with artificial cracks. In order to understand the temperature characteristics of the specimen depending on the crack depth, the specimen was heated and the minimum temperatures of the specimens at which cracks appear were investigated according to the crack depth. It was confirmed that the surface temperature distribution of the specimen varies depending on whether the specimen is cracked or not, because of the single and multiple reflections of the incident energy. Furthermore, as the temperature distribution of the specimen reaches a steady state, the temperature data tends to decrease with the crack depth. Through the observation of the normalized temperatures, it was found that the temperature of the specimens obtained from this experiment reached a steady state after 10 minutes. At this time, the standard deviation of the normalized temperature is around 0.01 or less, and the temperature decreases linearly with increasing crack depth. This result is considered to be closely related to the area where multiple reflections occur in the cracked region. If the correlation between the crack region and the incident energy is analyzed for various specimens, it can be applied to the diffuse reflection of the light.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.1
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• pp.21-28
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• 2004

We have demonstrated a low speed weigh-in motion system using FBG sensors and performed field test at a trial road. Technique, called identical chirped grating interrogation, have used for a demodulation relying on the mismatching of two identical broadband chirped gratings. We compensated the fluctuation of LED power and the temperature of sensor and used a lock-in amplifier to reduce effect of noise. We could design a bending plate that the measurement results are independent of position of weight. The FBG sensors weigh-in motion system showed linearity and reproducibility.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.250-251
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• 2000

모드록킹된 광섬유 레이저 자이로스코프(ML-FLaG)$^{(1)}$ 는 일반 거울과 Sagnac 루프 거울로 이루어진 공진기 안에 이득 매질이 포함된 광섬유 레이저의 형태를 가진다. Sagnac 루프 거울을 서로 반대 방향으로 진행하는 두 빛 사이의 위상차를 변조시키면 루프 거울의 반사율이 변조되는데, 여기서 위상 변조 주파수를 공진기의 종모드 간격과 일치시키면 공진기 왕복 주기에 두 개의 펄스가 들어가는 모드록킹된 펄스열을 얻을 수 있다. 이 두 펄스 사이의 시간 간격은 회전율에 따라서 변하기 때문에, 두 펄스 사이의 시간 간격 변화를 측정하면 회전 각속도를 알아낼 수 있다. (중략)

• Korean Journal of Optics and Photonics
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• v.30 no.4
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• pp.142-145
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• 2019

Normally, a corner cube retroreflector (CCRR) sheet is used as a retroreflective mirror array (RRMA) in a volumetric display. Each CCRR unit reflects light in the retroreflective direction, which is parallel to the incident light, and it makes a blurred image, as it shifts the position of light within its dimensions. Adopting a "curved planar wall" and "parabolic focusing" (x-axis), a hybrid-t(transverse direction)-RRMA is proposed, to improve the image quality and brightness. The improvement of image contrast is achieved by tuning a "linear v-shaped groove" structure to a "parabolic v-shaped groove". Also, the system has been simplified and the brightness enhanced 4 times by removing the half mirror.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.73-76
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• 2010

The issue of inspection and characterization of microstructures has emerged as a major consideration in design, fabrication, and detection of MEMS devices. However, the conventional measurement techniques, including scanning electron microscopy (SEM) imaging, atomic force microscopy (AFM) scanning, and mechanical surface profiler, require often destructive process or may be difficult to measure with a wafer scale. In this paper, we characterize the surface profiles of microstructures using an optical scanner based on a DVD pick-up module. Scanning images of the microstructures are successfully generated using the intensity of reflected light from different depths of the surface profiles, based on the focus error signal (FES) from photodiodes. It is shown that the proposed optical scanner can be used as an alternative measurement system with high performance and low cost, compared to conventional measurement techniques.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.329-334
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• 2007

Various cooling techniques have been applied to the gas turbine blade in order to reduce heat load to the blade. On the blade surface, film cooling method is used and the accurate information of film cooling effectiveness should be evaluated in order to predict the exact temperature distribution in the blade. In this study, pressure sensitive paint (PSP) was used to measure the film cooling effectiveness on a flat plate. Results showed that PSP technique successfully evaluated the distribution of film cooling effectiveness. Three blowing ratios of 0.5, 1, and 2 were tested and the film cooling effectiveness near holes decreased as the blowing ratio increased, however, increased far downstream from the holes.

• Journal of Veterinary Clinics
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• v.32 no.2
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• pp.209-211
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• 2015

A 5-year-old Siamese cat was presented at the Veterinary Medical Teaching Hospital in Seoul National University with visual impairment. The cat was blind and its pupillary light reflexes were sluggish OU. While there were no remarkable findings in the anterior segment, generalized tapetal hyperreflectivity and retinal vascular attenuation were observed in the posterior segment of both eyes. Any historical significance and clinical symptoms suggestive of infection or inflammation were absent. All of the above findings strongly indicated a diagnosis of hereditary retinal degeneration in the cat. This clinical case report demonstrates the possibility of the presence of feline hereditary retinal degeneration in Korea. Awareness of the condition should be raised to prevent the spread of hereditary retinopathy in the Korean cat population.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.85-85
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• 2021

CDOM(Colored or Chromophoric Dissolved Organic Matter)은 바다, 호수 및 강에서 담수, 오수, 퇴적물 등으로부터 공급된 유기물질의 일종으로 가시광선에서 빛을 흡수하는 성질을 가지며, 2016년부터 환경부에서 선정한 하천, 호수 등 방류수의 수질오염 표준인 TOC(Total Organic Carbon)를 간접 추정할 수 있는 매개변수가 될 수 있다. 따라서, 본 연구에서는 백제보 상류 23 km 구간을 대상으로 2개년(2016~2017) 중 7일의 초분광영상 자료를 활용하여 내륙지역의 CDOM에 대한 적정 반사도 밴드값(R_rs)과 CDOM을 추정하는 알고리즘을 개발하고자 한다. CDOM은 흡수계수(α_CDOM)를 통해 간접 추정되며, 흡수계수의 기준 파장값(λ)은 연구별로 350 nm, 375 nm, 400 nm, 412 nm 및 440 nm 등 다르게 나타난다. 초분광영상은 AsaFENIX 초분광 센서에서 관측된 380~970 nm까지 4 nm 간격, 127개 대역의 분광해상도와 2 m의 공간해상도를 가진 영상을 활용하였으며, 자료의 연속성을 위해 smoothing 기법을 활용하여 가공하였다. 추정 알고리즘은 Random forest를 활용하였으며, 70%의 trainning과 30%의 test로 구분하여 적용하였다. 산출된 CDOM은 결정계수(R²), Nash-Sutcliffe efficiency(NSE)를 이용하여 실측 CDOM과 비교하였다. 흡수계수별 CDOM의 산정 결과 α_CDOM(350 nm)의 trainning, test에서 각각 R²가 0.71, 0.74, NSE가 0.25, 0.49로 가장 높았으며, 적정 반사도 밴드값은 R_rs(466), R_rs(493), R_rs(548), R_rs(641)를 사용하였을 때 trainning, test에서 각각 R²가 0.93, 0.90, NSE가 0.85, 0.69로 가장 높게 나타났다.

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.233-241
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• 2011

Currently, solar module is using the two methods such as a glass-filled method or a super-straight method. The common point of these methods is to use glass structure on the front of solar module. However, the reflectance of the solar module is high depending on the height of the incident sunlight due to the flat surface of the module front glass. Purposed to solve these problems, AG (anti-glare) structures were formed on the glass surface. Next is fabrication methods of AG structure. First, uneven structure made by micro blaster equipment was dipped in Hydro-fluidic acid (HF) acid. HF acid process was carried out to remove particles and to make high transmittance. The reflectance and transmittance of the anti-glare glass was compared to those of the bare glass. The reflectance of anti-glare glass decreased approximately 1% compared with bare glass. The transmittance of anti-glare glass was similar to bare glass. According to the sample angle, the difference of the reflectance between bare glass and the anti-glare glass was about 19%. Isc and efficiency value of anti-glare glass on bare solar cell appeared about 3.01 mA and 0.228% difference compared with bare glass. Anti-glare glass on textured solar cell appeared about 9.46 mA and 0.741% difference compared with bare glass. As a result, the role of anti-glare in the substrate is to reduces the loss of sunlight reflected from the surface. In this study, therefore, AG structure on the solar cell was used to improve the efficiency of solar cell.