• Korean journal of food and cookery science
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• v.31 no.4
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• pp.505-509
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• 2015

Light emitting diodes (LED) are able to selectively control the wavelength of light, enabling them to enhance photosynthesis by increasing specific wavelengths. The objectives of this study were to determine the effects of LED light exposure with various wavelengths (630 nm: 550 nm: 450 nm=8:1:1) on plant growth and bio-active compound concentrations in cherry tomato and red cabbage. With cherry tomatoes, LED decreased the number of fruits compared to fluorescent light (FL) but resulted in a significantly higher value in the total weight of the fruits and in sugar content. However, lycopene contents were not significantly different between the groups. With red cabbages, the weight and length were both significantly higher in the LED group than in the FL group. Furthermore, the anthocyanin contents in the red cabbage LED group were two times higher than those of the FL group. These results suggested that exposure to LED light with a high ratio of red wavelength can increase the anthocyanins contents in red cabbages but not the lycopene content in cherry tomatoes. Further studies will be needed to determine which LED wavelength can enhance lycopene content in cherry tomatoes.

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.356-363
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• 2014

This work was conducted to investigate the field growth and yield of the sweetpotato (Ipomoea batatas) slips grown under different light emitting diodes (LEDs). Sweet potato cuttings of 3 cultivars ('Matnami', 'Shinhwangmi', and 'Yeonhwangmi') were cultivated under fluorescent lamp (FL) and several LEDs (PPF $150{\pm}5{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$ at 20cm distance) in deep flow culture system for 20 days. The plants were acclimatized under sunlight for 10 days, and then cuttings (30cm length) were planted with $75{\times}25cm$ planting density on June 10th, covered with black vinyl film during growth period. Length and diameter of vine, number of root were excellent in the red plus blue (7:3) LED than the other treatments. At 30 days after planting, the survival rate in red plus blue (7:3) LED was significantly higher than that in FL and red LED, and it was not different among cultivars. Vine length, vine diameter, and number of node were not significant among LED light qualities and cultivars. After 120 days in the field cultivation, vine length, vine diameter, number of node, number of branch, and fresh weight of shoot were not significant among LED light qualities, but those except the number of branch showed significant differences among cultivars. Yield characteristics among LED light colors were not significant, but weight of storage root per plant, mean weight of storage root, and yield showed significant differences among cultivars. The yield per 10a in 'Matnami', and 'Yeonhwangmi' was significantly higher than that in 'Shinhwangmi'.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.96-101
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• 2019

This study was conducted to investigate the effects of the light quality of a Light Emitting Diode (LED) on the phosphate uptake of Prasinophytes Tetraselmis suecica and Tetraselmis tetrathele. These species were exposed to a blue LED (max = 450 nm), a yellow LED (max = 590 nm), a red LED (max = 630 nm) and a fluorescent lamp (control) at $100{\mu}mol\;m^{-2}\;s^{-1}$. The maximum uptake rates (${\rho}_{max}$) of T. suecica and T. tetrathele under the red LED were $6.35pmol\;cell^{-1}\;hr^{-1}$ and $9.85pmol\;cell^{-1}\;hr^{-1}$, respectively. The half saturation constants (Ks) of two species were $9.43{\mu}M$ and $21.2{\mu}M$, respectively. The phosphate affinity of the two species under the red LED was higher than that of other wavelengths. Thus, the optimum light source to ensure economically effective and productive growth in a Tetraselmis culture system (Photo-Bioreactor) would be red LEDs because of the high growth rate shown, regardless of relatively low nutrient conditions.

• Korean Journal of Plant Resources
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• v.21 no.4
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• pp.304-309
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• 2008

All the seeds of rape (Brassica napus) sprout vegetables were germinated within three days after seeding irrelevant to the light colors. The total fresh weight of rape sprout vegetables at 6 days after seeding have been increased when grown under green and white color lights by 0.339g/10plants and 0.339g/10plants compared with the control. The total flavonoid contents in rape sprouts were increased under red and blue lights by 72.5 and 70.9mg${\cdot}L^{-1}$. Those DPPH radical scavenging activities at 2,000mg${\cdot}L^{-1}$ were increased by 90.0 and 90.3% which were sprouted and grown under blue and white lights. Nitrite radical scavenging activity of sprouts were most decreased compared with the control when grown under the red light by 57.4mg${\cdot}L^{-1}$. And mushroom tyrosinase inhibition activity of rape sprouts was extremely increased under the green light by 22.5mg${\cdot}L^{-1}$.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.167-171
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• 2014

While the development of a portable plate panel display, thinning, high color reproduction, high brightness studies have been actively performed. LED, OLED is used as a light source. The research on quantum dot is much accomplished by the material of light source. Such quantum dot is the next generation semiconductor nano fluorescent substance because quantum dot has the high color reproduction and flexible display characteristic. In this study, we presented to method of using the quantum dot for implementation of the plate panel display. Quantum Dot (CdSe/ZnS), having a 100um thickness, is spread in PET barrier film. A Blue LED having a wavelength of 455nm as a light source irradiating light to the optical characteristic of the devices produced and evaluated. Also we presented the possibility for application with the color change film of the LCD.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.299-299
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• 2014

기존의 고출력 광원들이 환경문제 등으로 외국에서 규제대상으로 지정되고 있는 가운데고체 상태의 광원인 Light-emitting diode (LED)는 기존의 광원에 비해 에너지 절감효과 크기 때문에 인해 널리 사용되고 있는 추세이다. 대부분의 백색 LED의 경우 청색 LED에 황색 형광체를 사용하는 것이 일반적이다. 그러나 이의 경우 빛의 흡수와 재방출 과정에서 생기는 에너지 변환손실의 문제가 불가피하다. 또한, 두 종류의 색을 섞어서 나타나는 낮은 연색성의 문제가 있고 사용할 수 있는 형광체의 종류와 조합도 일본 등 해외에 출원된 특허권으로 연구개발에 어려움이 있다. 이를 해결하기 위해 본 연구에서는 형광체를 사용하지 않는 단일 백색 LED를 개발을 위하여 극성과 반극성을 조합한 구조를 연구하였다. Photo-lithography를 이용하여 다양한 크기와 구조의 홀 패턴을 얻을 수 있었으며, metal organic chemical vapor deposition을 이용하여 다양한 형태의 피라미드 구조를 성장할 수 있었다. 패턴의 홀 크기와 홀 사이의 간격을 조절하면서 성장을 진행 하였고, 그 결과 pyramid와 truncated pyramid 모양의 GaN 구조를 성장할 수 있었다. [그림 1] Pyramid 구조의 반극성 면과 truncated pyramid 구조의 극성 면사이의 성장속도 차이 때문에 양자우물의 두께가 달라짐을 확인하였다. 이로 인해 양자구속효과가 달라져 다른 파장의 발광을 기대할 수 있었다. 뿐만 아니라 In의 확산거리가 Ga보다 길어서 홀사이 간격을 달리하면 In조성비가 달라지는 효과가 있음을 확인하였고 다양한 홀 사이 간격으로부터 각기 다른 파장의 발광을 얻을 수 있었다. 파장을 조금 더 상세하게 분석하기 위하여 Photoluminescence과 Cathodoluminescence을 사용하였다. 이로써 여러 파장을 발광하는 패턴을 섞어 넓은 영역의 발광 스펙트럼을 만들었다. 특히 패턴을 섞는 방법도 홀과 에피 구조를 섞는 방법, 크기가 다른 홀 패턴을 배열하는 방법등 다양히 하며 가장 좋을 패턴을 연구하였다. 그리하여 최적의 패턴과 구조, 성장조건을 찾아 백색의 CIE 좌표값을 얻을 수 있었다.

• Journal of the Korean Ceramic Society
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• v.43 no.5 s.288
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• pp.304-308
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• 2006

We have synthesized a $Eu^{2+}-activated\;Sr_3MgSi_2O_8$ blue phosphor and $(Sr,Ba)_2SiO_4$ yellow phosphor and prepared white LEDs by combining these phosphors with a InGaN UV LED chip. Three distinct emission bands from the InGaN-based LED and the two phosphors are clearly observed at 405 nm, 460 nm and at around 560 nm, respectively. The 405 nm emission band is due to a radiative recombination from a InGaN active layer. This blue emission was used as an optical transition of the $Sr_3MgSi_2O_8:Eu$ blue phosphor and $(Sr,Ba)_2SiO_4:Eu$ yellow phosphor. The 460 nm and 560 nm emission band is ascribed to a radiative recombination of $Eu^{2+}$ impurity ions in the $Sr_3MgSi_2O_8:Eu$ and $(Sr,Ba)_2SiO_4$ host matrix. As a consequence of a preparation of UV White LED lamp using the $Sr_3MgSi_2O_8:Eu$ blue phosphor and $(Sr,Ba)_2SiO_4:Eu$ yellow phosphor, the highest luminescence efficiency was obtained at the ration of epoxy/two phosphor (1/0.2361). At this time, the CIE chromaticity was CIE x = 0.3140, CIE y = 0.3201 and CCT (6500 K).

• Korean Journal of Materials Research
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• v.25 no.1
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• pp.1-8
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• 2015

This study suggested comprehensive structural characterization methods for the commercial blue light emitting diodes(LEDs). By using the Z-contrast intensity profile of Cs-corrected high-angle annular dark field scanning transmission electron microscope(HAADF-STEM) images from a commercial lateral GaN-based blue light emitting diode, we obtained important structural information on the epilayer structure of the LED, which would have been difficult to obtain by conventional analysis. This method was simple but very powerful to obtain structural and chemical information on epi-structures in a nanometer-scale resolution. One of the examples was that we could determine whether the barrier in the multi-quantum well(MQW) was GaN or InGaN. Plan-view TEM observations were performed from the commercial blue LED to characterize the threading dislocations(TDs) and the related V-pit defects. Each TD observed in the region with the total LED epilayer structure including the MQW showed V-pit defects for almost of TDs independent of the TD types: edge-, screw-, mixed TDs. The total TD density from the region with the total LED epilayer structure including the MQW was about $3.6{\times}10^8cm^{-2}$ with a relative ratio of Edge- : Screw- :Mixed-TD portion as 80%: 7%: 13%. However, in the mesa-etched region without the MQW total TD density was about $2.5{\times}10^8cm^{-2}$ with a relative ratio of Edge- : Screw- :Mixed-TD portion of 86%: 5%: 9 %. The higher TD density in the total LED epilayer structure implied new generation of TDs mostly from the MQW region.

• Journal of the Institute of Convergence Signal Processing
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• v.19 no.4
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• pp.167-173
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• 2018

We propose an air purification system that utilizes aerial plant parts and root zone of indoor plants where light is insufficient and air circulation is bad. In order to maximize the air purification effect of the plant, the aerial plant parts illuminates mixed light combining blue and green LED and CRI(Color Rendering Index) LEDs close to natural light, respectively. And the root zone was forcibly circulated by the fan to use the soil as a filter. The indoor air purification system combined with the light source and the fan removed most polluted air in the shortest. In the case of mixed light and CRI LEDs of indoor air purification system, fine dust decreased by 14%, 14.2%, and TVOC(Total volatile organic compounds) decreased by 7.5% and 9.4%, respectively. In the experiment in which the fan was operated for 15 minutes, the TVOC decreased to 97.8%. The photosynthesis of the plant and the use of soil as a filter were able to purify polluted air in a short time. And the fan's temporary operation gave the similar effect of continuous operation.

• Journal of Bio-Environment Control
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• v.25 no.3
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• pp.139-145
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• 2016

The objective of this study was to compare the growth and light use efficiency of red leaf lettuce grown under three types of combined light-emitting diodes (LEDs) and fluorescent lamps (FL) in a closed-type plant production system. The eighteen days-old lettuce seedlings of red leaf lettuce (Lactuca sativa L., 'Jeokchima') were transplanted to the close-type plant production system equipped with three types of combined LEDs with red (R, 655 nm), blue (B, 456 nm), green (G, 515 nm), and white (W, 456 nm + 558 nm) (R:B=8:2, R:W:B=8:1:1, R:G:B=8:1:1) and FL. The seedlings were grown under normal growth conditions ($20^{\circ}C$, $181{\pm}4{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, 12 h photoperiod) for four weeks. Lettuce plants grown under FL had significantly higher leaf shape index than those under all LED treatments. Although growth of shoots and roots was not show any significant difference among LED treatments, all of the LED treatments induced about 34% higher shoot fresh weight than that of the FL. On the other hands, the total power consumption of FL was 145 kW for 4 weeks, while the mean value of LED treatments was 54 kW, which was about 3 times lower value than that of the FL. The light use efficiency based on dry matter in LED treatments was about 34 mg/W and this was about 3.5 times higher energy saving value than the FL. In conclusion, this study showed that irradiation of optimal combined LEDs in closed-type plant production systems can improve the lettuce growth as well as maximize in light use efficiency through energy saving than the FL.