• Journal of the Optical Society of Korea
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• 제16권3호
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• pp.203-209
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• 2012

Visible light communications (VLC) use modern solid-state light-emitting diodes (LEDs) to broadcast information. Emerging white-light LEDs allow the combination of lighting and optical wireless communication in one optical source. In this paper, a new LED lighting design using one-chip-type white LEDs is proposed for efficient illumination and optical wireless communications under the existence of several obstacles. Lighting and communication performance are analyzed to show the effectiveness of the proposed LED lighting. Specifically, the signal-to-noise ratio considering intersymbol interference and the bit-error rate of variable pulse position modulation (VPPM) with dimming control are considered.

• Fisheries and Aquatic Sciences
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• 제18권2호
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• pp.211-220
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• 2015

We investigated the differences in the expression of the neurohormones kisspeptin (Kiss) and gonadotropin-inhibitory hormone (GnIH) and cytochrome P450 aromatase (P450arom), gonadotropin hormones (GTHs), and sex steroids in the goldfish Carassius auratus exposed to light-emitting diodes (LEDs). The expression levels of Kiss1, Kiss2, G-protein-coupled receptor 54 (GPR54), GTHs, GnIH, and P450arom were compared between the control (white light) and LED-treated goldfish. Furthermore, we measured the plasma levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The levels of Kiss1 mRNA and protein; Kiss2, GPR54, and $GTH{\alpha}$ protein; GTH mRNA; and plasma FSH and LH in the hypothalamus and cultured hypothalamus cells were significantly higher in the green and purple LED treatment groups than in the other groups. These results suggested that red LEDs inhibit the sex maturation hormones, Kiss, GPR54, GTHs, and P450arom, and that GnIH plays a role in the negative regulation of reproductive function in goldfish.

• 한국수산과학회지
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• 제41권6호
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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.

• Environmental Engineering Research
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• 제19권3호
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• pp.293-298
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• 2014

An anaerobic photosynthetic treatment process utilizing purple non-sulfur photosynthetic bacteria (PNSB) was applied to the recovery of organic carbon from food processing wastewater. PNSB cells, by-product from the treatment, have high nutrition such as proteins and vitamins which are a good alternative for fish feed. Effects of light source on performance of anaerobic photosynthetic process were investigated in this study. Two bench-scale photo-bioreactors were lighted with infrared light emitting diodes (LEDs) and tungsten lamps covered with infrared transmitting filter, respectively, aiming to supply infrared light for photosynthetic bacteria growth. The photo-bioreactors were operated to treat noodle-processing wastewater for 323 days. Hydraulic retention time (HRT) was set as 6 days. Organic removals in the photo-bioreactor lighted with infrared LEDs (91%-95%) was found higher than those in photo-bioreactor with tungsten lamps with filter (79%-83%). Biomass production in a 150 L bench-scale photo-bioreactor was comparable to a 8 L small-scale photo-bioreactor in previous study, due to improvement of light supply efficiency. Application of infrared LEDs could achieve higher treatment performance with advantages in energy efficiency and wavelength specifity.

• 마이크로전자및패키징학회지
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• 제21권1호
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• pp.19-23
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• 2014

LED (Light Emitting Diode) 시장의 발전이 빠르게 이루어지고 있음에 따라 점차 고효율 LED의 필요성이 증가하고 있다. 이에 우리는 Hole Type의 Padless 신 구조 수직형 LED에서, 접촉 전극의 크기와 그 배치가 Chip의 가동 전압에 어떠한 영향을 미치는지 알아보았다. 이를 위하여 LED simulation을 통한 계산과 실제 Chip 제작을 통한 전기적 특성 평가를 하였다. 그 결과, Simulation 을 통하여 n전극의 크기가 커질수록 구동전압이 낮아짐을 확인하였고, N 전극의 형태가 확산됨에 따라서도 구동전압이 낮아짐을 확인하였다. 이러한 추세는 실제 제작한 LED Chip의 측정 결과와 비슷한 경향을 나타내었다.

• 한국해양바이오학회지
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• 제8권1호
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• pp.24-29
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• 2016

Microalgae are considered as superior biodiesel producers, because they could effectively produce high amount of lipid with fast growth rate. In this study, Chlorella vulgaris was exposed to various light wavelengths (${\lambda}_{max}$ 470 nm, ${\lambda}_{max}$ 525 nm, and ${\lambda}_{max}$ 660 nm) using light emitting diodes (LEDs) to examine effect of light quality on their growth and fatty acid production in 0.4-L bubble column photobioreactors. Fluorescent lamps were also used as polychromatic light sources (control). From the results, biomass productivity was varied by light wavelength from 0.05 g/L/day to 0.30 g/L/day. Maximum biomass productivity was obtained from red LED among tested ones. We also observed that contents of oleic acid and linolenic acid, which affect biodiesel properties, were significantly changed depending on supplied wavelength. These results indicated that production of algal biomass, and fatty acid content and productivity could be improved or controlled by supplying specific light wavelength.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.575-576
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• 2006

It was analyzed qualitatively the light extraction in GaN-on-sapphire LEDs based on a simple model. The light extraction efficiency in the LEDs is simulated numerically by using ray tracing method. In the present study, the extraction efficiency was simulated on three different types of LEDs, which a have a different pattered sapphire substrate. And, the role of the patterned sapphire substrate are analyzed and discussed. Based on the analysis, the improvements of extraction efficiency in the LED structures were discussed and these analyses are helpful in the design of high brightness GaN LEDs.

• 한국통신학회논문지
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• 제37C권9호
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• pp.784-790
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• 2012

본 논문에서는 가시광 통신(visible light communication: VLC) 상향 전송에서 전송거리 확대를 위한 전송방식을 제안하였다. 이를 위해 집광된 infrared(IR)-light emitting diode(LED)의 출력을 이용하여 조명에 위치한 광수신부에 전송하였다. 이러한 집광을 하는 경우 지향성이 너무 커서 IR-LED를 조명부 수신모듈에 정확히 향하지 않는다면 전송이 어렵게 되는 문제점이 있는데, 이를 해결하기 위해 여러 개의 IR-LED를 조금씩 다른 방향을 향하도록 배치하고, 수신부와 통신을 통해 이 중 최고의 전송성능을 보이는 IR-LED를 선택하는 방법을 제안하였다. 통신 성능을 주기적으로 감시하고, 성능이 저하되면 LED 재검색 과정을 통해 새롭게 최상의 성능을 보이는 LED로 통신을 교체하도록 한다.

• 한국전기전자재료학회논문지
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• 제34권1호
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• pp.44-49
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• 2021

Recently, infrared (IR) and near-infrared (NIR) light-emitting diodes (LEDs) were widely used for home medical applications owing to its low output power and wide exposed area for curing. For deep penetration of the light under the skin, multiple LEDs with wavelengths of 700~10,000 nm were located on a flexible printed circuit board. When multiple wavelengths of LEDs were soldered on a circuit board, the lifetime of LED module highly depends on LEDs with a short lifetime. The mean time to failure (MTTF) was able to calculate with the experimental results under high temperature and the Arrhenius model. The results of this study could help companies to approve the warranty of LED modules and its product.

• 한국지반환경공학회 논문집
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• 제13권10호
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• pp.63-68
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• 2012

본 연구는 해양미세조류의 일종인 Isochrysis galbana를 다양한 파장의 발광다이오드를 이용하여 배양한 후 최적 파장을 찾아내고, 최적파장을 광원으로 하여 회분식 실험에서의 대량 배양 조건을 찾기 위해 수행되었다. I. galbana 배양에 가장 효율적인 파장은 백색 LED였으며, 백색 LED의 광도에 따른 실험을 통해 3,000Lux의 광도가 본 미세조류의 성장에 최적임을 알 수 있었다. 형광등과의 비교 실험 시 같은 광도에서 백색 LED가 미세조류의 배양에 있어 10% 정도 높은 효율을 나타내었다. 배양이 진행되어 셀 농도가 증가하면서 발생하는 그림자 효과를 상쇄시키기 위해 공기 공급을 하였으며, 4가지 조건의 공기 공급 속도에서 모두 비슷한 성장특성을 보여주었다. 공기를 주입한 경우 주입하지 않은 경우보다 최대 3배 이상 균체 농도가 증가하였다.