• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.5
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• pp.182-187
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• 2005

The FT-IR absorption spectrum by the lattice vibrations of ruby and garnet obtained from FT-IR shows quite different characteristics. By the UV-VIS spectroscopy it was found that the ruby has two transmission bands in red and blue region, while garnet has only one transmission band in red region. The color filter to distinguish ruby from garnet was developed and named HWANG JI HO filter. Through the HWANG JI HO filter, ruby was shown in blue color and garnet was shown in dark red color because of the only the blue region transmittance of the filter. Other red stones, such as spinel, tourmaline were shown in dark red color like as garnet. The ruby could be recognized easily from the red stone.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.407-415
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• 2009

The change of the nitrogen-related centers and the color change of electron beam irradiated type Ia natural diamonds were studied. The irradiation of diamond with high-energy electron beam creates lattice defects which are neutral single vacancy $V^0$. It increased with increasing electron dose density. The B aggregation seems to produce vacancies more easily than the A aggregation, because diamonds with more B aggregation have more platelets, which are sufficient breakable size by electron beam. Greenish blue color of irradiated diamond is changed to darker with increasing electron dose density. GR1 centers with a zero-phonon line at 741 nm and phonon sidebands make transmit visible light at 530 nm and it moves to 500 nm with higher intensity of GR1 centers.

• Journal of Applied Biological Chemistry
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• v.62 no.2
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• pp.181-186
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• 2019

The optimum design of LED device for irradiation of 460 nm blue light on extruded rice cake using simulation and the effect of the blue light on the inactivation of Bacillus cereus (B. cereus) group on the rice cake were investigated. The irradiated light intensity patterns on the surface area of the sample were simulated with three different LED arrays (centered, cross, and evenly spaced) and at various distances (22, 32, 42 mm) between the LED modules and the sample. In addition, the uniformity was calculated as Petri factor. The evenly spaced array resulted the most uniform light intensity pattern in the simulation, and the Petri factor of 32 and 42 mm of the distances showed higher than 0.9, which represents the ideal uniformity of LED device. The bacterial population of the rice cake decreased to less than the initial bacterial population during exposure to LED blue light, whereas the bacterial population of the control sample increased. The bacterial count of the rice cake after blue light irradiation for 24 h was 1.21 log CFU/g lower than the control sample. Petri factor increased with increase of the distance between the light source and sample, however, the reduction rate of B. cereus group decreased. Therefore, the design of LED device, that represented the Petri factor higher than 0.9 and inactivated the population of B. cereus group, with evenly spaced and 32 mm of distance between the light source and sample was suitable for extending shelf-life of rice cake.

• Journal of the Korean Ceramic Society
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• v.36 no.3
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• pp.319-324
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• 1999

기존의 고상 반응법에 의해 합성된 YNbO4 : Bi 형광체의 발광특성을 개선하기 위하여 B2O3 융체 첨가법으로 형광체를 합성하고, 빛발광(PL) 및 저전압 음극선발광(CL)을 측정하였다. PL 및 CL 모두 415~440 nm 영역에서 강한 청색 발광 스펙트럼을 나타냈으며, 고상 반응의 경우와 마찬가지로 Y/Nb 비율이 화학 양론상의 1:1인 경우보다 결함구조를 인위적으로 조절한 51/49나 54/46에서 최대의 발광강도를 보였다. 한편, 고상 반응에서는 125$0^{\circ}C$에서 4시간 열처리하는 것이 최대의 발광효과를 나타냈으나, B2O3융제를 첨가하고 110$0^{\circ}C$에서 열처리한 시료가 결정성이 좋고 입자의 크기 및 형태가 균일하여 PL뿐만 아니라 CL에서도 우수한 발광특성을 보였다. B2O3융제를 첨가하는 방법으로 열처리 온도를 낮추고 입자크기와 형태를 조절하여 형광체의 휘도를 개선할 수 있었다.

• Electrical & Electronic Materials
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• v.17 no.5
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• pp.21-29
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• 2004

현재 LED에 대한 관심과 투자, 수요는 날이 갈수록 증가되고 있다. 이러한 가장 큰 이유는 현재의 광원보다 에너지 절감효과가 뛰어나고 수명이 우수하기 때문이다. 최근 질화물계 반도체를 기반으로 한 청색 및 백색 LED가 상용화되고 그 효율이 증대됨에 따라 그 응용시장이 크게 확대 되면서 본격적인 LED 응용 시대가 도래하고 있다. 현대와 같이 에너지 절감이 절실한 시기에 LED의 가장 큰 강점은 에너지 소비량이 기존 백열전구의 단 10분의 1에 불과하다는 점이다. 청색, 백색 LED의 제작초기에는 휘도나 효율 면에 있어서 백열전구나 형광등에 비해 많은 문제가 있었으나 현재의 기술은 이러한 문제점을 크게 보완시켜 상용화가 가능하게 하였다. 또한 본격적인 대량 생산 체제가 갖추어지면 백열 전구나 형광등에 비해 훨씬 높은 원가 절감 효과를 가져 올 것이 확실하며, 이러한 효과는 현재의 많은 기업체나 연구소의 관심도, 수요 현황으로 볼 때 2007년 경에는 확연히 나타날 것으로 판단된다.(중략)

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.37.1-37.1
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• 2011

1990년 나카무라 연구팀에서 청색이 개발된 이래로 LED는 눈부시게 발전해 왔으며, 청색 LED로 인하여 조명용 백색 LED가 급격히 발전하고 있다. 현재까지 개발되고 있는 조명용 백색 LED는 통상적으로 c축 방향의 사파이어 기판위에 GaN film을 성장하여 제작하지만 원천적으로 생기는 자발분극과 압전분극 영향 때문에 양자우물에서의 밴드를 기울게 만들고 이것은 캐리어 재결합율을 감소시켜 그 결과 양자 효율을 낮춘다. 이러한 근본적인 문제를 해결하기 방안은 사파이어 기판에서 c-plane이외의 결정면에서 무분극(혹은 반극성) GaN LED를 성장하여 양자효율을 극대화하여 고효율 LED를 구현할 수 있음. 본 연구에서는 Carbonization mask를 이용하여 r-plane sapphire기판상에 a-plane GaN의 ELOG성장 방법에 대하여 연구하였다. Carbonization mask를 이용하면 기존에 사용되던 SiOx 나 SiNx 막을 사용하지 않고 mask를 만들 수 있다는 장점을 가지고 있으며, 이러한 mask를 이용하여 r-plane sapphire위에 ELOG법을 이용한 a-plane GaN을 성장할 수 있음을 실험을 통해 보이려 한다. ELOG 성장이 이루어 지는지 확인을 위하여 SEM을 통하여 ELOG가 되는 과정을 분석하였으며, 표면의 거칠기를 알아보기 위하여 AFM측정을 시행하였다. 실험 결과 약 20 um 두께로 성장되면서 merge가 되는 것을 확인 하였다.

• Journal of Bio-Environment Control
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• v.21 no.3
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• pp.220-227
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• 2012

This study was conducted to analyze the seeding quality of paprika and the growth and early yield after transplanting of paprika nursed under artificial light and natural light. In this study, blue LED, red LED, and white fluorescent lamps (FL) were used as artificial lighting sources. Photoperiod, average photosynthetic photon flux, air temperature, and relative humidity in a closed transplants production system (CTPS) were maintained at 16/8 h, $204{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, 26/$20^{\circ}C$, and 70%, respectively. Leaf length, leaf width, leaf area, top fresh weight and dry weight of paprika seedlings, and chlorophyll content in paprika leaves nursed under LED and fluorescent lamps for 21 days after experiment were significantly affected by light treatments. As compared with the control (white FL), leaf area of paprika grown under blue LED, red LED, and natural light was decreased by 63%, 63%, and 28%, respectively. Top dry weight of paprika grown under blue LED, red LED, and natural light was 64%, 50%, and 22%, respectively, compared with the control. Number of leaves on 18 days after transplanting showed with red LED, blue LED, and natural light by 86%, 84%, and 48%, respectively, compared with the control. On 114 days after transplanting, paprika nursed under blue LED and red LED had relatively short plant height. This result might be caused that the elongation of its internodes was suppressed by the illumination of sole blue or red light. Average number of fruits per plant harvested during 4 weeks after first harvest was 3.5 with red LED, 3.3 with blue LED, 1.0 with natural light, and 2.2 with control, respectively. Early yield of paprika nursed under red LED, blue LED, natural light, and control were 453 g/plant, 403 g/plant, 101 g/plant, and 273 g/plant, respectively. Larger fruit of 136 g was harvested with red LED treatment. Even though the early yield of paprika was greatly increased with artificial lighting, but total yield was almost similar as the harvest period after transplanting in greenhouses was lengthened. From the above results, we could understand that paprika nursed under white FL, blue LED, and red LED showed good growth after transplanting and was early harvested by a week as compared to the natural light. Therefore, the white FL, blue LED, and red LED as the artificial lighting sources in CTPS could be strategically used to enhance the seedling quality, to shorten the harvest time, and to increase the yield of paprika.

• Horticultural Science & Technology
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• v.32 no.3
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• pp.330-339
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• 2014

Growth and anthocyanins of lettuce (Lactuca sativa L., 'Mid-season') grown under LED lamps with blue light in the range of 430-470 nm or with red light in the range of 630-670 nm were analyzed in this study. Cool-white fluorescent light was used a s the control. P hotosynthetic photon flux, p hotoperiod, air temperature, relative humidity, and $CO_2$ concentration in a closed plant production system were $201{\pm}2\;{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, 16/8 hours (day/night), $22/18^{\circ}C$, 70%, and $400{\mu}mol{\cdot}mol^{-1}$, respectively. At 21 days after light quality treatment, growth characteristics and anthocyanins content of lettuce as affected by the peak wavelength of blue or red LED were significantly different. Among peak wavelengths treated in this stusy, R1 treatment (peak wavelength 634 nm) and R6 treatment (peak wavelength 659 nm) were effective for increasing leaf width, leaf area, shoot fresh weight, and photosynthetic rate of lettuce. B5 treatment (peak wavelength 450 nm) and B4 treatment (peak wavelength 446 nm) increased the anthocyanins concentration and chlorophyll content in lettuce leaves, respectively. Anthocyanins in lettuce leaves increased linearly with decreasing hue value of leaf color and with increasing SPAD value of lettuce leaves. From these results, it was concluded that the red LED with peak wavelengths of 634 nm and 659 nm and the blue LED with peak wavelengths of 450 nm can be used as potential light spectra for increasing the yield and anthocyanins accumulation of leafy vegetable.

• Journal of the Korea Convergence Society
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• v.12 no.7
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• pp.125-131
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• 2021

Blue light with strong energy is required for light-curing resin treatment, which is being used more frequently in dentistry. To reduce the risk of exposure to scattered light, we tried to use colored lenses. The tips for light curing machine and a commercially available yellow-type blue-light blocking lens and a yellow lens colored with yellow dye, which are expected to be effective in blocking blue light, were placed in a UV-Vis spectrometer device, and transmission and blocking of blue light were tested respectively. As a result, the average blue light blocking rate of the light curing machine tips was 99.49%, and the C lens with the highest color density among commercially available lenses showed a high blue light blocking rate of 99.54%. In the case of lenses tinted with yellow, the yellow tinted C lens with the highest tint concentration showed 87.57% of blue light blocking rate. It is judged that the side effects related to the eyes caused by blue light can be reduced if a yellow-type commercially available or colored lens is worn along with a light curing machine tip during resin treatment.

• Journal of Bio-Environment Control
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• v.17 no.2
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• pp.150-156
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• 2008

The influences of night break by costly artificial light sources were investigated on the photo-morphogenesis and growth of leafy perilla (Perilla ocymoides L.). The irradiation of red, blue, and three-colored light for night break significantly increased the stem length and stem diameter compared to dark. Three-colored light gave the highest fresh and dry weight of stem, followed by red and blue light. Floral induction was suppressed up to 100 days after the night break, by red and three-colored light, but the plants grown under the dark or treated with blue light showed 85% and 31% flowering rate, respectively. The time needed for floral induction after night break was 60 days in dark and 80 days in blue light. The number of leaf, leaf area, and fresh weight per plant were the highest in red and three-colored light night break, followed by blue light and dark. The photosynthetic rate observed 80 days after night break was the highest in red light, followed by blue and three-colored light. A low light compensation point of $20\;{\mu}mol\;m^{-2}{\cdot}s^{-1}$ was observed in three-colored light, while red and blue light tended to show higher measurements.