• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 춘계학술회의 초록집
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• pp.16-16
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• 2010

GaN-based light-emitting diodes (LEDs) are attracting great interest as candidates for next-generation solid-state lighting, because of their long lifetime, small size, high efficacy, and low energy consumption. However, for general illumination applications, the external quantum efficiency of LEDs, determined by the internal quantum efficiency (IQE) and the light extraction efficiency, must be further increased. The IQE is determined by crystal quality and epitaxial layer structure and high value of IQE more than 70% for blue LEDs have been already reported. However, there is much room for improvement of light extraction efficiency because most of the generated photons from active layer remain inside LEDs by total internal reflection at the interface of semiconductor with air due to the high refractive index difference between LEDs epilayer (for GaN, n=2.5) and air (n=1). The light confining in LEDs will be reabsorbed by the metal electrode or active layer, reducing the efficacy of LEDs. Here, we present the first demonstration of enhanced light extraction by forming a MgO nano-pyramids structure on the surface of vertical-LEDs. The MgO nano-pyramids structure was successfully fabricated at room temperature using conventional electron-beam evaporation without any additional process. The nano-sized pyramids of MgO are formed on the surface during growth due to anisotropic characteristics between (111) and (200) plane of MgO. The ZnO layer with quarter-wavelength in thickness is inserted between GaN and MgO layers to increase the critical angle for total internal reflection, because the refractive index of ZnO (n=1.94) could be matched between GaN (n=2.5) and MgO (n=1.73). The MgO nano-pyramids structure and ZnO refractive-index modulation layer enhanced the light extraction efficiency ofV-LEDs with by 49%, comparing with the V-LEDs with a flat n-GaN surface. The angular-dependent emission intensity shows the enhanced light extraction through the side walls of V-LEDs as well as through the top surface of the n-GaN, because of the increase in critical angle for total internal reflection as well as light scattering at the MgO nano-pyramids surface.

• Journal of Welding and Joining
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• 제22권6호
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• pp.43-49
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• 2004

In this study, a visual sensor system which can detect I-butt weld joint with height variation and includes a seam tracking algorithm was investigated. Three-dimensional position of an object can be acquired by using the method of distance measurement, i.e., an optical trigonometry which results from the spatial relations between the camera, the object and the structured light by a visible laser. Effects of laser intensity and iris number for the image quality as well as object material were investigated for the optical system design. For the image processing, a region of interest is defined from the whole image and a line image of laser is drew by using the gray level difference in the image. From the drew laser line, the weld joint can be recognized in searching the biggest point position calculated from the central difference method. Through a series of welding experiments, a good tracking performance was confirmed under GMA welding.

• 대한전자공학회논문지
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• 제25권6호
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• pp.694-699
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• 1988

Optical phase conjugate mechanism and edge enhancement by degenerate four wave mixing (DFWM) in photorefractive material are described, and image reconstruction is perfromed sucessfully in BaTiO3 single crystal. Also, the edge enhancement is carried out in the crystal by the same DFWM geometry. But the intensities of three incident beams are inverted. Good quality of edge enhancement is observed in real-time (processing time 10 sec) with low incident light intensity (5.38mW/cm\ulcorner.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권4호
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• pp.275-285
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• 2012

This paper presents a changes of luminescence property for converted white LEDs with the commercially available silicate phosphor. If silicate phosphor's quantity increase step by step. luminescence property will be changing. we analyze luminescence property for these change and carry out the high temperature aging test for 7,000 hours, the high temperature and humidity aging test for 7,000 hours for reliability. LED degradation not only results in reduced light output but also in color changes. so we monitor correlated color temperature (CCT), chromaticity coordinates(x, y) and spectrum intensity. Those results suggest that humidity factor more bad effect in color changes than temperature factor and Lighting quality is related with quantity of phosphor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1402-1403
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• 2011

Photovoltaic solar energy policy in the keynote of the world in the development of new technologies in terms of renewable energy sources has been a great interest. Solar energy is the energy density, low light intensity, temperature, and a lot of areas affected by the difference, the effective use difficult. For the installation of photovoltaic solar power systems to develop farmland or forest land resulting from deforestation has become such a problem. In this paper, a way to resolve these issues as part of the development of the reservoir water through the efficient use of land and water resources through the eco-friendly energy production, water quality improvement, the cooling effect of solar modules, solar water system has the advantage of was installed. Terrestrial solar systems installed under the same conditions and solar radiation, power, module temperature, ambient temperature and analyzed. Through this award to demonstrate the effectiveness of the solar system is.

• 방송공학회논문지
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• 제22권6호
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• pp.702-712
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• 2017

본 논문에서는 신호 구조에 가중치 맵으로써 Laplacian을 이용한 언샤프 마스킹과 평균 밝기에 가중치 맵으로써 영상의 평균 밝기를 이용한 감마 변환 알고리듬을 제안하고자 한다. 패치를 기반으로 한 기존의 가중치 맵은 신호 구조 및 평균 밝기 영역에서 영상 내 밝기 값이 한쪽으로 치우쳐 세부 정보가 손실되는 단점이 있다. 본 논문에서는 패치 단위의 언샤프 마스킹을 이용하여 세부정보를 향상시켰고, 전역적 및 지역적 영상의 평균 밝기 값을 이용하여 감마 변환된 값을 선형 결합한 기법을 제안한다. 제안하는 알고리듬은 영상 내 윤곽선과 같은 세부 정보를 보존시키고 빛의 밝기 조절을 통해 주관적 화질을 향상시켰다. 실험 결과를 통해 기존 알고리듬에 비해 제안한 알고리듬이 우수한 성능을 나타내는 것을 확인하였다.

• 한국잡초학회지
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• 제6권2호
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• pp.110-123
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• 1986

올챙고랭이의 종실(種實)과 월동주기부(越冬株基部)의 발아(출아)(發芽(出芽)) 습성(習性)을 파악(把握)하기 위하여 포장조건(圃場條件)과 생장상(生長床), 항온기(恒溫器)에서 petridish와 pot를 이용한 일련의 환경요인처리반응(環境要因處理反應)을 조사하였으나 환경요인(環境要因) 처리(處理)는 온도(溫度) 7처리(處理), 광유무(光有無) 및 광량(光量) 5처리(處理), 광엽조건(廣葉條件) 5처리, 광질(光質)(spectrum) 6처리(處理), 토양산도(土壤酸度) 7처리(處理), 주기부중량(株基部重量) 5종(種), 산소농도(酸素濃度) 5처리(處理), 수분조건(水分條件) 6처리(處理) 및 복토심(覆土深) 6 처리(處理)를 하였다. 결과를 요약(要約)하면 다음과 같다. 1. 온도조건(溫度條件) (1) 종실발아적온(種實發芽適溫)은 $25\sim35^{\circ}C$이었고 $20^{\circ}C$에서도 10% 전후(前後)의 발아(發芽)가 가능하였다. (2) 주기부(株基部)의 출아적온(出芽適溫)은 지속성(持續性) 위주로 볼 때 $20\sim25^{\circ}C$, 출아수(出芽數)주에서는 $20\sim30^{\circ}C$로 판단되었다. 2. 광량(光量)(유무(有無) 및 조도차(照度差) (1) 암조건(暗條件)에서의 종자발아(種子發芽) 10%에 비(比)하여 광조건(光條件)에서는 50%의 차이를 보였다. (2) 2~11 K Lux의 광도(光度)범위에서 광도(光度)가 높을수록 발아(發芽)는 향상되었으나 광도간(光度間) 유의차(有意差)는 인정되지 않았다. (3) 야외한냉사처리(野外寒冷絲處理)에 의한 주기부(株基部)의 차광반응(遮光反應)은 0~45%의 차광(遮光)보다 95% 차광(遮光)에서 출아율(出芽率)이 높았다. 3. 광질(光質)(spectrum) (1) petridish pot 시험방법간(試驗方法間)에 양적(量的) 차이(差異)는 있었으나 공통적(共通的)으로 투명(透明) 및 황색(黃色) film 투과광(透過光)하에서 종실발아(種實發芽)가 촉진(促進)되었다. (2) 주기부(株基部)의 출아(出芽)는 투명(透明) 및 청색(靑色) film 투과광((透過光)이 적색(赤色)이나 황색투과광(黃色透過光)보다 효과적(效果的)이었다. 4. 토양산도(土壤酸度) (1) 종실(種實) 및 월동주기부(越冬株基部) 모두 토양산도(土壤酸度) 5.53에서 가장 발생율(發生率)이 높았고 그 이상이나 그 이하 조건(條件)으로 될 수록 감소경향(減少傾向)이었다. 5. 주기부(株基部) 중량(重量) (1) 생체중(生體重) 1g 전후의 것은 거의 경수분화(莖數分化)가 안되었고, 2g이나 5g 정도의 것보다 3~4g 정도의 주기부(株基部)가 경수분화수(莖數分化數)나 분화속도(分化速度)에서 유의적(有意的)으로 효과적(效果的)이었다. 6.산소농도(酸素濃度) (1) 산소농도(酸素濃度) 0~5%에서 종자발아(種子發芽)는 90%로 가장 높고 빨랐으며 15~20%에서는 75%로 낮고 늦어지는 경향이었다. 7. 수분조건(水分條件) (1) 種實發芽는 1cm 수심(水深)에서 가장 촉진(促進)되었고 다음으로는 -5~10cm의 범위로서 비슷한 정도였으며 -10cm 수심(水深)(지하수위(地下水位) 10cm)에서는 발아(發芽)가 억제(抑制)되는 경향이었다. (2) 월동주기부(越冬株基部)는 종자(種子)보다 낮은 수심(水深) 및 깊은 지하수위(地下水位) 조건(條件)에서 출아(出芽)가 잘 되는 경향이었다. 8. 복토심(覆土深) (1) 종실발아(種實發芽)는 1~1.5cm 복토(覆土)에서 가장 양호하였고 5cm에서는 거의 불가능(不可能)하였다. (2) 주기부(株基部)의 출아(出芽)는 0.5~1.0cm 복토심(覆土深)에서 가장 양호하였고 3~5cm 복토심(覆土深)에서는 유의적(有意的)으로 감소(減少)하는 경향이었다.

• 한국정밀공학회지
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• 제22권7호
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• pp.27-37
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• 2005

Direct writing technology on the silicon wafer surface is used to reduce the size of the chip as the miniature trend in electronic circuit. In order to improve the productivity and efficiency, the real time quality estimation is very important in each semiconductor process. In laser marking, marking quality is determined by readability which is dependant on the contrast of surface, the line width, and the melting depth. Many researchers have tried to find theoretical and numerical estimation models fur groove geometry. However, these models are limited to be applied to the real system. In this study, the estimation system for the line width during the laser marking was proposed by process monitoring method. The light intensity emitted by plasma which is produced when irradiating the laser to the silicon wafer was measured using the optical sensor. Because the laser marking is too fast to measure with external sensor, we build up the coaxial monitoring system. Analysis for the correlation between the acquired signals and the line width according to the change of laser power was carried out. Also, we developed the models enabling the estimation of line width of the laser marking through the statistical regression models and may see that their estimating performances were excellent.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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• pp.361-377
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• 1998

The measurement of welding temperature of connector is usually performed with an infra red temperature gauge. However, the factors, which influence the temperature measurement, are rarely known. This research used the welding temperature measurement of the connector as an example, applying the experimental design, in two-phase experiments, to search the affecting factors. In phase-I experiment, we used a resolution III, seven-factor fractional factorial design with two levels for each factor. The result showed that none of the factor was significant in affecting the welding temperature when the type I error ${\alpha}$ was 0.05. Next, we did the phase-II factorial experiment with three factors and each factor had three levels. The experiment showed the experimental time was significant in affecting the temperature measurement when the type I error ${\alpha}$ was 0.05. Further Duncan's multiple range tests on the second experimental data showed that the later the experimental time, the weaker the light intensity could have on the temperature measurement and the average of the highest temperatures was lower. Moreover, the later the experimental time, the smaller was the variance of the temperature measurement and the difference between the averages of the highest and the lowest temperatures was also lower.

• 한국환경농학회지
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• 제32권3호
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• pp.193-200
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• 2013

형광등이나 LED와 같은 인공광을 사용하는 식물공장(인공광 식물공장)은 계절에 상관없이 광, 온도 및 습도 등을 인위적으로 제어하면서 작물을 안정적으로 연중 생산할 수 있는 시스템이다. 본 연구에서는 수경재배 방식을 채택하고 있는 인공광 식물공장 시스템 내에서 엽채재배용 배양액을 이용한 방풍나물의 수경재배 가능성과 혼합광질이 생장에 미치는 영향을 검토하였다. 방풍나물은 청색과 적색 LED를 1:1 및 1:3의 비율로 혼합한 혼합광 조건에서 90일간 수행하였다. 광원의 광강도는 $100{\mu}mol/m^2/s$로 설정한 후 30일 간격으로 지상부 잎을 3회 수확하여 생장량을 조사하였다. 재배기간 동안 형광등과 LED의 혼합광 조사는 방풍나물 지상부 생장에 유의한 영향을 미치는 것으로 나타났다. 재배개시 30일째 방풍나물 지상부 생체중 및 건물중은 형광등+청색+적색의 혼합광(청, 적색 혼합비율 1:3, FLBR13구)에 의한 영향을 받아, 대조구인 형광등 조사구(FL구)에 비해 각각 3.7배 및 2배 증가하였다. 또한 식물체당 전개엽수는 FLBR13구에서 형광등+청색+적색 혼합광(청, 적색 혼합비율 1:1) 조사구인 FLBR11구에 비해 유의하게 증가하였다. LED와 형광등을 혼합 조사한 처리구에서와 같이, 형광등을 혼합하지 않고 청색과 적색의 LED만을 혼합하여 조사한 처리구에서도 청색과 적색의 혼합비율이 1:1인 BR11구에 비해 적색광의 혼합비율을 3배 증가시킨 BR13구에서 방풍나물의 지상부 생장이 촉진되었다.