• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.235-236
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• 2008

A configuration of illumination for high-speed color document scanner has been proposed utilizing white light emitting diode and transparent plastic lightguide. The design of illumination system including lightguide for high optical efficiency and uniform image quality is performed based on a simulation using ray-tracing method. The device characteristics are also experimentally evaluated in terms of illumination distribution against longitudinal and transverse direction on document plane. Uniform illumination distribution about 85% of in longitudinal and transverse direction is realized by control of mechanical dimension and position of lightguide.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.119-126
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• 2017

Purpose: The aim of the present study was to compare clinical antiplaque and antigingivitis effect between Light Emitting Diode (LED) electronic toothbrush and electronic toothbrush without LED for gingivitis and mild periodontitis patients. Materials and Methods: 30 patients included in this study. 15 patients in experimental group used LED electronic tooth brush which has red and white LED within its head, and other 15 patients in control group used same product which specially modified that function without LED. Clinical parameters ($L{\ddot{o}}e-Silness$ gingival index (GI), Quigley-Hein plaque index (PI)) were measured at the baseline, 2 weeks and 4 weeks later. Wilcoxon signed rank test and Mann-Whitney test were used for statistical analysis. Results: Compare of GI change between experimental and control group with time, both groups showed that reduced GI, but lower GI values detected at 2 weeks and 4 weeks later in experimental group than control group. And lower PI values detected at 4 weeks later in experimental group than control group, but not statistically significant. Conclusion: Based on these results and within the limits of this study, the electronic toothbrush with LED could reducing gingivitis in a short period and infer that decreasing plaque accumulation in a long period.

• Journal of Environmental Science International
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• v.27 no.10
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• pp.821-829
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• 2018

This study was conducted to examine the influence of Light-Emitting Diode (LED) light quality in urban agricultural plant factories on the growth and development of Seolhyang strawberry daughter plants in order to improve the efficiency of daughter plant growth and urban agriculture. LED light quality by demonstrated that above-ground growth and development were greatest for daughter plant 2. Daughter plant 1 showed the next highest growth and development, followed by daughter plant 3. Among the different qualities of LED light, the stem was thickest and growth rate of leaves was highest for R + B III (LED quality: red 660 nm + blue 450 nm/photosynthetic photon flux density (PPFD): $241-243{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$) and lowest for R (red $660nm/115-117{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$). Plant height, leaf width, petiole length, and the leaf growth rate were highest for W (white fluorescent lamp/$241-243{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$) and lowest for R + B I (red 660nm+blue 450nm/$80-82{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$). For above-ground growth and development, as the plants surpassed the seedling age, mixed light (red + blue), rather than monochromatic light (red or blue), and higher PPFD values tended to increase development. Regarding the quality of the LED light, daughter plant 2 showed the highest chlorophyll content, followed by daughter plant 1, and daughter plant 3 showed the least chlorophyll content. When the wavelength was monochromatic, chlorophyll content increased, compared to that when PPFD values were increased. Mixed light vitality was highest in daughter plant 2, followed by 1, and 3, showed increased photosynthesis when PPFD values were high with mixed light, in contrast to the results observed for chlorophyll content.

• 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.

• Journal of the Korean Ceramic Society
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• v.54 no.3
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• pp.217-221
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• 2017

Improvement studies of existing phosphors are needed for use in light emitting diodes (LEDs). Among the phosphors discovered recently, the SLA ($SrLiAl_3N_4:Eu^{2+}$) is a phosphor that has a narrow width. It is now known as a good red phosphor that meets the industry's needs for warm white (color temperature ranging from 2700 to 4000 K) and high CRI (> 80). However, SLA phosphors are obtained from difficult synthetic methods. All commercially available phosphors should be derived from the general solid state synthesis method. The phosphors produced by difficult synthetic methods will inevitably fall out of price competitiveness and will be scrapped. This study succeeded in synthesizing SLA ($SrLiAl_3N_4:Eu^{2+}$) phosphors by using a general solid phase synthesis method based on the reaction energy obtained from DFT calculations. As a result, we found an optimal solid state synthesis method for SLA phosphors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.9
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• pp.708-713
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• 2010

In this research a ring light was developed so that a partial shadowless shooting for the patient's affected area at the medical treatment room and surgical operation room using high luminance light emitting diode (LED) for which attention is being paid as new lighting parts for medical purpose. LED which was applied to the development used high luminance three color LED for full color for which various color materialization and the adjustment of radiation intensity are possible and we can get white light in order to emphasize the delicate expression for generic tone of shooting object, strong highlight, simple shadow and three dimensional effect at the time of close-up shadowless shooting of the affected area. And at the time of design of ring light, the characteristics of LED and the loss of light at the time of penetrating light diffusion PC were considered so that intensity of illumination for over 150 lx can be obtained. The result of measurement of the intensity of illumination of the ring light that was developed revealed that maximum intensity of illumination of 225.7 lx was obtained, while smoke index was measured to be maximum 78 Ra in the case of Red(50%) Green(100%) and Blue LED(60%). We could confirm that response speed was also very fast as 1.72 ms.

• Environmental Engineering Research
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• v.23 no.2
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• pp.205-209
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• 2018

The spectral composition of light can affect the growth and biochemical composition of photosynthetic microalgae. This study examined the use of light filtering through a solution of soluble colored additives, a cost-effective method to alter the light spectrum, on the growth and lipid production of an oleaginous microalga, Nannochloropsis gaditana (N. gaditana). Cells were photoautotrophically cultivated under a white light emitting diode (LED) alone (control) or under a white LED that passed through a solution of red and yellow color additive (4:1 ratio) that blocked light below 600 nm. The specific growth rate was significantly greater under filtered light than white light ($0.2672d^{-1}$ vs. $0.1930d^{-1}$). Growth under filtered light also increased the fatty acid methyl ester (FAME) yield by 22.4% and FAME productivity by 80.0%, relative to the white light control. In addition, the content of saturated fatty acids was greater under filtered light, so the biodiesel products had better stability. These results show that passing white light through an inexpensive color filter can simultaneously enhance cellular growth and lipid productivity of N. gaditana. This approach of optimizing the light spectrum may be applicable to other species of microalgae.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.2
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• pp.83-90
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• 2009

White LEDs(Light Emitting Diode) offer advantageous properties such as high brightness, improved reliability, lower power consumption, and long lifetimes. An LED is an electronic device that converts an electrical signal into a tight signal and is used not only in Optical Communication Indoor wireless optical illuminating rooms, but also for wireless optical communication systems. Currently, studies about these white LEDs have been being progressed, and in this raper, we discuss the multiplex and the multiple access method of VLC(Visible Light Communication) systems using white LEDs. In proposed system, CDMA(Code Division Multiple Access) apples to VLC system to reduce interference of VLC system, and improve capacity. The superiority of OOK modulation is presented in analysis of results by comparing VLC-CDMA communication system using OOK(On-off keying) modulation and BPSK modulation in AWGN(Additive White Gaussian Noise) channel and Diffuse channel. And we investigate the significance of a solution of interference by multipath by comparing BER in multipath channel and AWGN channel. In the proposed system, we assume Directed LOS(Line Of Sight) and Diffuse Link, and suppose VLC-CDMA using OOC(Optical Orthogonal Code) as methods to increase efficiency of system by removing ISI(Inter Symbol Interference) caused by multiple access, optical spreading code, and also present an analysis of its performance.

• Journal of Animal Science and Technology
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• v.64 no.3
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• pp.432-442
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• 2022

The purpose of this study was to analyse the effects of light colour on rabbit reproductive performance and the expression of key follicular development genes. Rabbits (n = 1,068, 5 months old, 3.6-4.4 kg live body weight) were divided randomly into four groups, housed individually in wire mesh cages and exposed to red, green, blue, and white light-emitting diode (LED) light (control). The lighting schedule was 16 L : 8 D-15 d / 150 lx / 6:00 am-22:00 pm (3 d preartificial insemination to 12 d postartificial insemination). Red light and white light affected the conception rate and kindling rate and increased the total litter size at birth (p < 0.05). The effects of red light on litter size at weaning, litter weight at weaning, and individual weight at weaning increased compared with the green and blue groups. The effects of red light on live litter size at birth were increased compared with those in the blue group (p < 0.05). Compared to white light, green and blue light reduced the number of secondary follicles (p < 0.05). Compared to red light, green and blue light reduced the number of tertiary follicles (p < 0.05). Compared with white light, red LED light resulted in greater ovarian follicle stimulating hormone receptor and luteinizing hormone receptor mRNA expression (p < 0.05). Compared with green and blue LED light, red LED light resulted in greater B-cell lymphom-2 mRNA expression (p < 0.05). Compared with green LED light, red LED light inhibited FOXO1 mRNA expression in rabbit ovaries (p < 0.05). Red light can affect the reproductive performance of female rabbits and the expression of key genes for follicular development.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.6
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• pp.511-517
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• 2008

The radiation characteristics and economic efficiency of high - luminance light - emitting diodes (LEDs), a metal halide lamp, and a halogen lamp were studied to evaluate their potential as an energy-saving light source for fishing lamps. The wavelengths at which irradiance was maximum were 709, 613, 473, 501, 525, 465, 578, and 973 nm for red, orange, blue, peacock blue, green, and white LEDs, the metal halide lamp, and the halogen lamp, respectively. If the irradiance characteristics at 300-1,100 nm wavelengths are set as 100%, the irradiance rates at 381-780 nm were 99-78%, 82%, and 24% for the LEDs, metal halide lamp, and halogen lamp, respectively. The economic efficiency was superior in the order metal halide lamp, halogen lamp, peacock blue LED, and blue LED at 381-780 nm and metal halide lamp, peacock blue LED, blue LED, and halogen lamp at 480-520 nm. Based on the radiation characteristics and economic efficiency evaluated at 480-520 nm, the blue and peacock blue LED light sources can be used as energy-saving light sources for fishing lamps.