• Korean Journal of Medicinal Crop Science
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• v.17 no.1
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• pp.39-45
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• 2009

The effects of red, blue, and far-red light by illumination of light emitting diodes (LEDs) on growth, morphogenesis and eleutheroside contents of in vitro plantlets of Eleutherococcus senticosus were examined. As a control, plantlets were grown under a broad spectrum white fluorescent lamp (16/8 h illumination). The length of plantlets grown under the red/blue LEDs was taller than those under fluorescent lamps. Leaf area, root length and fresh weight of plantlets were highest under blue light compared to other kinds of light sources. Chlorophyll contents in plantlets grown under fluorescent lamps were higher than those in plantlets grown under LED illumination. Production of eleuthroside B and E in plantlets was highest under blue LED. However, production of eleuthroside E1 was highest under fluorescent lamps. These results suggest that plant growth and eleuthroside accumulation can be controlled by wave length of light under LED illumination system.

• Horticultural Science & Technology
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• v.30 no.6
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• pp.664-672
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• 2012

As an artificial light source, light-emitting diode (LED) with a short wavelength range can be used in closed-type plant production systems. Among various wavelength ranges in visible light, individual light spectra induce distinguishing influences on plant growth and development. In this study, we determined the effects of monochromatic LEDs on leaf shape index, growth and the accumulation of phytochemicals in a red leaf lettuce (Lactuca sativa L. 'Sunmang') and a green leaf lettuce (Lactuca sativa L. 'Grand rapid TBR'). Lettuce seedlings grown under normal growing conditions ($20^{\circ}C$, fluorescent lamp + high pressure sodium lamp, $130{\pm}5{\mu}mmol{\cdot}m^{-2}{\cdot}s^{-1}$, 12 hours photoperiod) for 18 days were transferred into incubators at $20^{\circ}C$ equipped with various monochromatic LEDs (blue LED, 456 nm; green LED, 518 nm; red LED, 654 nm; white LED, 456 nm + 558 nm) under the same light intensity and photoperiod ($130{\pm}7{\mu}mmol{\cdot}m^{-2}{\cdot}s^{-1}$, 12 hours photoperiod). Leaf length, leaf width, leaf area, fresh and dry weights of shoots and roots, shoot/root ratio, SPAD value, total phenolic concentration, antioxidant capacity, and the expression of a key gene involved in the biosynthesis of phenolic compounds, phenylalanine ammonia-lyase (PAL), were measured at 9 and 23 days after transplanting. The leaf shape indexes of both lettuce cultivars subjected to blue or white LEDs were similar with those of control during whole growth stage. However, red and green LEDs induced significantly higher leaf shape index than the other treatments. The green LED had a negative impact on the lettuce growth. Most of growth characteristics such as fresh and dry weights of shoots and leaf area were the highest in both cultivars subjected to red LED treatment. In case of red leaf lettuce plants, shoot fresh weight under red LED was 3.8 times higher than that under green LED at 23 days after transplanting. In contrast, the accumulation of chlorophyll, phenolics including antioxidants in lettuce plants showed an opposite trend compared with growth. SPAD value, total phenolic concentration, and antioxidant capacity of lettuce grown under blue LED were significantly higher than those under other LED treatments. In addition, PAL gene was remarkably activated by blue LED at 9 days after transplanting. Thus, this study suggested that the light quality using LEDs is a crucial factor for morphology, growth, and phytochemicals of two lettuce cultivars.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.66-66
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• 2018

Light fermentation has been conducted under different light conditions such as normal dark light, white light, and light emitting diodes (LEDs) various color (blue, green, red, white on blueberry powder with fermenting bacteria Bacillus subtilis (B2). The bacteria B2 was isolated and identified by 16S rRNA sequencing method. RYRP biologically converted to secondary metabolites through light fermentation in the presence of Bacillus subtilis, the bacteria actively involved in bioconversion process. LEDs fermentation to enhance the production of phenolic content while comparing to normal dark and white light. Among the different color LEDs, blue LEDs mediated fermentation showed higher amount of total phenolic and flavonoid content. Then blue LEDs mediated fermented compound were characterized by FTIR and GC-MS, subsequently the compound was analyzed antioxidant activity tests and the antioxidant activity exhibited higher. This is the first study to demonstrate that B. subtilis-LEDs mediated fermentation is useful for facilitating phenolic compound production and enhancing antioxidant activity, which may have greater application fermentation fields.

• Journal of Environmental Science International
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• v.21 no.6
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• pp.757-761
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• 2012

The purpose of this study was to determine optimum conditions for the cultivation of Tetraselmis suecica (T. suecica) under illumination of four different types of LEDs (i.e., blue, red, white, and mixed). Initial cell concentration was $4{\times}10^4$ cells/mL and temperature of reactor was maintained between 21-$24^{\circ}C$. Specific growth rates were 0.72 $day^{-1}$(white), 0.58 $day^{-1}$(red), 0.49 $day^{-1}$(mixed), and 0.49 $day^{-1}$(blue). Thus, white LEDs was used for the cultivation of T. suecica. Tests with white LEDs under different light intensity, which was conducted to determine optimum light intensity of white LEDs, showed that 9,000 lux of illumination resulted in fastest cell growth and greatest cell concentrations. To avoid shadow effects by dense cell populations, aeration was performed. Cell concentration increased 3.8 times when aeration was used.

• Korean Journal of Food Science and Technology
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• v.46 no.4
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• pp.526-529
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• 2014

A recently developed Chinese cabbage cultivar, Shinhong Ssam, was cultured under different light conditions at a plant factory to evaluate effects of light on the production of functional compounds. The effects of the following combinations of red (R), blue (B), and white (W) LED light were compared to that of fluorescent light: R+B, R+W, and R+B+W. Under R+B light, the Chinese cabbage failed to grow well. In contrast, under R+W, R+B+W, and fluorescent light conditions, cabbages had similar growth rates. Cyanidin, the only anthocyanidin detected, accumulated in cabbages under LED conditions to levels more than 2-fold of that in cabbages grown under fluorescent light. Phenolic acid and flavonol levels varied subtly, whereas caffeic acid was found to be between 70- and 160-fold greater in LED-illuminated cabbages than in those exposed to fluorescent light. The amounts of free amino acids and sugars that affect the taste of vegetables were greater in the cabbages exposed to LED light than in those grown under fluorescent light conditions. In conclusion, R+W LED light produced Shinhong Ssam with greater nutritional value than those grown under R+B+W LED and fluorescent lights.

• Horticultural Science & Technology
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• v.34 no.1
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• pp.55-66
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• 2016

This study was carried out to investigate the effect of artificial light sources with different light qualities on the growth and flowering characteristics of a herbaceous long-day plant, Petunia ${\times}$ hybrida Hort. Seedlings of petunia cultivar 'Madness Rose' were potted, acclimated for one week, and grown in a phytotron equipped with tube- and bulb-type fluorescent lamps (FL tube and bulb), tube-type white light-emitting diodes (LED tube), halogen lamps (HL), metal halide lamps (MH), and high pressure sodium lamps (HPS) for 10 weeks. The temperature, photoperiod, and photosynthetic photon flux density (PPFD) in the phytotron were $22{\pm}2^{\circ}C$, 16 h, and $25{\pm}2{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, respectively. Light sources combined with HL promoted stem elongation, and plant height and internode length decreased with increasing red to far-red (R:FR) ratio. FL tube + LED tube, HPS, and FL tube promoted branching, whereas plants grown under light sources combined with HL did not have any branches. Days to flowering (from longest to shortest) occurred as follows: FL tube + HL > FL tube + HL > MH > HPS = FL tube + FL bulb > FL tube + LED tube > LED tube > FL tube, indicating that reducing the R:FR ratio of the light sources promoted flowering. Only 20% of plants grown under an FL tube flowered, whereas under all other treatments, 100% of plants flowered. At 10 weeks after treatment, plants grown under HPS and MH had (cumulatively) 12 open flowers, and those grown under FL tube + FL bulb, LED tube, FL tube + LED tube, and HPS treatment had approximately seven flower buds. These results suggest that light sources with low R:FR ratios promote flowering and stem elongation in petunia, but they reduce its ornamental value due to overgrowth and poor branching.

• Journal of Korean Society of Forest Science
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• v.95 no.6
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• pp.716-722
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• 2006

Various light sources including LEDs (Light emitting diodes) affecting on shoot growth was examined using in vitro shoots of E. pellita. Generally, it appeared that ventilation treatment was the most important factor affecting on normal shoot growth, irrespective of irradiation sources. Ventilation resulted in better performance of the cultures under 100% blue LED radiation. These include better shoot growth, more number of leaves, more number of internodes, more number of axillary buds, and heavier dry matters. The highest total chlorophyll content was obtained under both cool-white fluorescent lamps and R5B5 (50% red LED + 50% blue LED). The value was $24.5{\mu}g/g$ and $20.1{\mu}g/g$, respectively. In addition, ventilation resulted in higher carotenoid content in all irradiation sources except 100% red LED radiation. In conclusion, shoot growth of E. pellita could be reached maximum by ventilation under R5B5 (50% red LED + 50% blue LED).

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.3-6
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• 2008

The purpose of this study is to investigate the luminous environment of fluorescent lamp and LED lamp in a office space for various color temperature by subject response test. For this, three different color temperatures were tested for the same illuminance level. Based on such test results for various color temperatures of fluorescent lamp and white LEDs, this study is to analyze the preferences of color temperature and light source, and perceptional brightness of each light source and color temperature. Then, this study is to derive the guidelines for the performance of color temperature which are suitable on the purpose and the mood of a office space.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.2
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• pp.10-18
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• 2011

In order to develop highly-integrated RGBY(Red, Green, Blue, Yellow) LED light, a high thermal radiation ceramic package was manufactured, and the encapsulation process was applied with a vacuum printing encapsulation system(VPES). After the completion of vacuum printing, the shape of the encapsulation layer could be controlled by heat treatment during the curing process, and the optical power became highly increased as the encapsulation layer approached a dome shape. The optical characteristics involved in a Correlated Color Temperature(CCT), a Color Rendering Index (CRI), and the efficiency of RGBY LED light were able to be identified by the experimental designing method. Regarding the characteristics of the white light of RGBY LED light, which were measured on the basis of the aforementioned optical characteristics, CRI posted 88, CCT recorded 5,720[$^{\circ}K$], and efficiency exhibited 52[lm/W]. The chip temperature of RGBY LEDs was below 55[$^{\circ}C$] when the consumption power of LED chips was 0.1[W] for the red, 0.3[W] for the green, 0.08[W] for the blue, and 0.24[W] for the yellow. Also, the thermal resistance of the highly-integrated RGBY LED light measured by T3Ster was 2.3[K/W].

• Clean Technology
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• v.20 no.2
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• pp.97-102
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• 2014

Currently various studies are underway for dispensing high-viscosity phosphor. These studies have reported limitations and challenges in the dispensing process. The discharged amount of phosphor was approximately the same each time which is important for the implementation of high-efficiency white LED technology. This paper present high-viscosity phosphor dispensing process for white LED implementation by using electrostatic printing technology. The voltage controlled DOD (Drop-On-Demand) discharge experiment was studied to determine angle of drop meniscus at nozzle and dot diameter. With increase in Discharge voltage, the discharge angle of meniscus increased while dot diameter decreased. Therefore it can be concluded that we can control the discharge rate by controling the discharge angle of meniscus.