Earticle

본 논문은 차량 사이의 텍스트 메시지 교환을 위한 단거리 광 카메라 통신시스템 시연결과를 제시한다. 텍스트 메시 지 전송을 위한 송신기로 저전력 적외선 LED 배열을 사용한다. 송신기의 배열형 LED는 송신 문자에 따라 패턴이 변화하고, 수신기에서 해당 LED배열의 패턴이 영상으로 수신된다. 수신기로 시중의 상보성 금속산화물반도체 (CMOS)로 구성된 이미지 센서에 기반한 USB 웹 카메라를 사용한다. USB 웹 카메라를 송신기의 LED패턴을 수 신하고 수신된 영상은 PC에서 처리되어 원본 텍스트 메시지를 복원하게 된다. 디코딩 과정은 Python에서 OpenCV를 활용하여 구현된다. 실험 결과에 따르면, 제안된 광카메라통신시스템은 5미터 거리에서 초당 10개의 문자 전송률로 동작할 경우, 1.6%의 프레임 에러율로 데이터를 복원할 수 있다.

This paper presents a demonstration of an short-range optical camera communication(OCC) system for vehicle-to-vehicle(V2V) text message exchange. The transmitter uses an array of low-power infrared(IR) light-emitting diodes(LEDs) to transmit text messages. The lighting patterns in the transmitter LED array vary with different characters, which are detected as different images at the receiver. The receiver is a commercial complementary metal oxide semiconductor(CMOS)-based USB web camera. The USB web camera receives the pattern of the transmitter LEDs and the received images are processed in PC to recover original text messages. The decoding process is implemented using OpenCV with Python. According to the experiment results, the data can be retrieved with 1.6 % frame error rate in a range up to 5 m at a data rate of 10 characters per second.

We aim to elucidate suitable color of light during development of fruit body in Pleurotus eryngii. The four color of LED(Light Emitting Diode), blue LED(475nm), green LED(525nm), yellowed LED(590nm), and red LED(660nm), were irradiated for formation of fruit body after mycelia growth. First, as effect of color of LED at all growth stage, the morphological properties of fruit body in fluorescent lamp and blue LED irradiation were showed thicker and longer pileus than those in other color LED irradiation. The commercial yields in blue and green LED treatment were similar to control(Fluorescent lamp). Second, as effect of color of LED by light irradiation time, we could obtain the highest commercial yields at the green LED continuous radiation, 1/1 and 1/2(lighting/lighting-out, hours). And we could obtain the highest number of available stipes and biological efficiency at the 1/1(lighting/lighting-out, hours). The ergosterol was the highest under the green LED continuous radiation.

Environmental movements to return captured wildlife to nature are accelerating globally. From dolphins to killer whales, many species of marine organisms receive training to adjust to life in the wild. Different techniques can be utilized in behavioral training process including exposure to light sources (light training). Using classical training to teach Rasbora (Rasbora daniconius) to associate green light and food, other colors were tested to observe the optimum wavelength for behavioral training. Colored LED lights of blue, red, and white with short, long, and mixed wavelengths respectively were tested after complete training with green light which lasted ten days. The group of Rasbora was successfully trained to show feeding behavior when conditioned stimulus of green light was presented even in the absence of food. When introduced light of red and white, Rasbora showed feeding behavior almost identical to that of green light exposure. However, blue light elicited no clear feeding behavior in the group. As Rasbora have preference over light with long and mixed wavelengths such as red and white light, it can be inferred that red and white light is more effective in behavioral training. Blue light of short wavelength was found to be ineffective for detection of stimulus.The results demonstrated that the potential programs for returning wildlife back to nature can achieve success based on the understanding visual perceptions of marine animals such as those of rasbora.

From the time of the industrial revolution, fossil fuel has been the main source of energy, acting as a stimulant for many modernized industries. Despite the positive changes fossil fuel has brought to the mankind, it has produced carbon emission, facilitating the rising temperature of Earth resulting in global warming. Limited supply of fossil fuel has also hastened the search for alternative sources of energy. Biofuel from microalgae is recently gaining attention for its environmental friendliness, for example CO2 fixation during cultivation and high lipid content. Two strains of microalgae are used, Botryococcus braunii and Nannochloropsis oceanica, for their high potential as biofuel sources. Different colored settings of LED light, Green, Red, White, Blue, Red: Blue = 5:1, Red: Blue 3:1, Red: Blue = 1:1 were controlled to investigate the effects of mixture of colors on growth and lipid content of microalgae. Spectrophotometry and fluorescence spectrophotometry were used to measure the growth and lipid content of each microalgae strain. The experiment was conducted over the period of eight days, with measurements done on day 0,2,4,6, and 8. The optimum color of light differed slightly between strains, with B. braunii Red: Blue = 5:1 and N. oceanica red. The mixture of red and blue LED light had the better growth and lipid content than the single colored lights, red and blue mixed light with 18% more lipid content than white light in Botryococcus braunii. The ultimate light conditions for the cultivation of microalgae vary among species, but the best outcomes can be expected from using a mixture of red and blue lights. To find the optimum light ratio for each microalgae strain, further research and experiments using various ratio mixtures of red and blue lights are essential.

This study was conducted to evaluate the effect of light spectrum using red (660㎚), blue (460㎚), red and blue mixed (Red : Blue = 6 : 4) LED (light-emitting diode), and fluorescent lamp on antioxidant activities and functional components of dandelion (Taraxacum officinale). Total polyphenol contents in dandelion irradiated with the red and blue mixed or the red LED were 121.77㎎/100 g or 115.36㎎/100 g, respectively, which were greater than those in dandelion treated with blue LED and fluorescent lamp. Asparagine showed the highest content among amino acids in leaves and roots regardless of treatments. Total amino acid was the highest when illuminated with the red LED. DPPH (1,1-diphenyl-2-picrylhydrazyl)radical-scavenging activity and SOD (super oxide dismutase) activity of ethanol extracts were increased under all of the LED treatments compared with fluorescent lamp, and the antioxidant activities were increased by the red and the mixed LED illumination. The results indicate that application of the red and the mixed LED illumination promote antioxidant activity and increase functional components during cultivation of dandelion.

The attractions of Lycoriella ingenua to different LED light sources were investigated in the mushroom cultivations which were located in Yongin of Gyeonggi-do province and Buyeo of Chungcheongnam-do Province. The LED light sources which were used in the investigations were white, green, red, blue and orange. Numbers of Lycoriella ingenua to LED lights in Yongin and Buyeo were 132.9 and 3,272.5 to white LED source, 120.3 and 3,109.5 to green LED source, 105.5 and 1,910.1 to red LED source, 88.3 and 2,708.3 to blue LED source and 46.7 and 2,465.5 to orange LED source, respectively. The numbers of Lycoriella ingenua to LED light sources were 2.7~3.5 times higher than the ones of untreated.

The antimicrobial properties of Light-Emitting Diode (LED) are an area of increasing interest. The aim of this study was to evaluate the bactericidal effects of blue (peak at 456 nm), green (peak at 518 nm), red (peak at 654 nm) and blue-green combined (blue 456 nm : green 558 nm = 69:31) LED irradiation to pathogenic bacteria. For this, LED equipment providing power density of 10 mW/cm2 was installed and plates were exposed to 0.9 or 3.0 mW/cm² to irradiate bacteria with 3.2 to 259.2 J/cm² of energy density. As a result, blue and combined LED have shown bactericidal effects on Escherichia coli KCTC 1467 and Listeria monocytogenes ATCC 19115 after irradiation of 3.0 mW/cm² for 2 and 4 hr, respectively. Staphylococcus aureus KCTC 1916 was inhibited at 518 nm green LED irradiation. However, red LED irradiation showed no inhibitory effect to the other tested strains. Light technology that utilizes the bactericidal properties of blue (at 456 nm) and blue-green(blue 456 nm : green 558 nm = 69:31) combined LED may have potential applications in the food industry sector.

In this study, we investigated the effects of sodium hypochlorite (NaOCl) and red or blue light-emitting diode (LED) light on embryo swelling and germination of Oreorchis patens (Lindl.) Lindl. A method for determining the swelling and protocorm formation in O. patens seeds through in vitro examination of immature seeds was established. NaOCl treatment of immature seeds was found to significantly enhance the extent of embryo swelling and protocorm formation in immature zygote embryos compared to those in the untreated controls. Additionally, the effects of white fluorescent light, and red and blue LED lights on embryo swelling and protocorm formation in in vitro cultured seeds were examined and compared to the conditions with or without NaOCl treatment. The most suitable light for embryo swelling and protocorm formation was the red LED light.

The purpose of this study was to clarify the effect of light emitting diode (LED) irradiation on healing of impaired wound and alteration of mast cells in experimental diabetic rats. Twenty-four male Sprague-Dawley rats were divided into four groups: excision (Ex), excision-LED irradiation (Ex-LED), diabetes + excision (DM) and diabetes + excision + LED irradiation (DM-LED). Diabetes was induced in rats by streptozotocin (STZ) injection (70 mg/kg, single dose) and 6 mm punch excision wounds were created on the back after shaving hair. The LED-irradiated rats were treated to a daily dose of $5\;J/cm^2$ LED (630 nm) light for 11 days after surgery, and were killed at day 1, 3, 7 and 11. The lesion and adjacent skin tissues were excised, fixed with 10% buffered formalin and embedded with paraffin. For evaluation of wound healing, hematoxylin-eosin (HE) and Masson trichrome staining were performed. Mast cells (MCs) were stained with toluidine blue (pH 0.5) and quantified using a computerized image analysis system. The proliferation activity of keratinocyte in skin tissues was analyzed on sections immunostained with proliferative cell nuclear antigen (PCNA). The results showed that wound healing rate, collagen density and neo-epidermis length, number of PCNA-positive cells, fibroblasts and mast cells were significantly higher in the LED-irradiated rats than in the DM and Ex rats throughout the periods of experiment. Exceptionally, the number of MCs was significantly lower at day 11 compared with day 7 after surgery in the all groups. These findings suggest that the LED irradiation may promote the tissue repair process by accelerating keratinocyte and fibroblast proliferation and collagen production in normal rats as well as in diabetic rats, and MCs may play an important role at an early stage of skin wound healing in normal and diabetic rats.

본 논문에서는 ISE-TCAD를 이용하여 GaN 기반의 LED특성을 분석하였다. LED는 GaN 버퍼층을 기반으로 GaN 장벽과 InGaN 양자우물로 구성된 활성 영역, AlGaN EBL(Electron Blocking Layer)과 AlGaN HBL(Hole Blocking Layer)로 이루어져 있다. Auger 재결합률, 양자 우물의 폭과 수, EBL의 Al 몰분율의 변화에 따른 LED의 출력 전력 특성을 분석하고 효율 개선을 위한 몇 가지 기준을 제시하였다.

In this paper, the GaN-based LED characteristics are analyzed using ISE-TCAD. The LED consists of GaN barriers, active region of InGaN quantum well, AlGaN EBL(Electron Blocking Layer) and AlGaN HBL(Hole Blocking Layer) on GaN buffer layer. The output power characteristics of LED considering Auger recombination rate, thickness of quantum well and number of quantum wells are analyzed and some criteria for the design of LED are proposed.

Uniform spreading of injection current in light-emitting diodes (LEDs) is one of the crucial requirements for better device performances. It is reported that non-uniform current spreading leads to low output power, high current crowding, heating, and reliability degradation of the LED device. This paper reports on the effects of different surface and electrode geometries in the LEDs. To increase the output power of LEDs and reduce the series resistance, a rectangular-type LED (RT-LED) with a centered island cathode has been fabricated and investigated by comparison with a conventional LED (CV-LED). The performances of RT-LEDs were prominently enhanced via uniform current spreading and low current crowding. Performances in terms of increased output power and lower forward voltage of simulated RT-LEDs are much superior to those of CV-LEDs. Based on these results, we investigated the correlation between device geometries and optical characteristics through the fabricated CV and RT-LEDs. The measured output power and forward voltage of the RT-LEDs at 100 mA are 64.7% higher and 8% smaller compared with those of the CV-LEDs.

우리나라 수위관측소에 설치되어 있는 수위표는 야간 시인성 부족으로 야간이나 우천시 수위관측을 수행하는데 있어 많은 어려움이 있다. 특히 유량측정 전후 수위관측이 반드시 필요하지만 야간일 경우 눈으로 확인하는 것이 쉽지 않다. 야간 수위관측시 시인성을 높이기 위해 일부 관측소에서 야광도료를 이용하거나 빛의 반사효과를 높인 수위표를 설치하는 등의 노력을 하고 있으나 그 효과는 크지 않다. 이에 본 연구에서는 야간 수위관측시 수위 식별이 어려운 문제를 해결하기 위해 첨단 소자인 LED(Light Emitting Diode)를 이용한 수위표를 개발하고 동시에 전류식 수위센서를 이용하여 자동 수위측정이 가능한 수위표를 개발하였다. 이는 기존의 눈으로 확인하는 수위표와 로거에 저장되는 수위측정장치를 하나로 통합한 것이며 주야간을 가리지 않는 탁월한 시인성과 정확한 수위측정 및 수위자료의 저장이 특징이다. LED는 최근 각광받고 있는 첨단 소자로서 각종 전광판 등에 다양하게 활용되고 있으며 전력을 크게 소비하지 않는 것이 특징이다. 또한 전기장치를 수중에 설치하는 것이므로 방수를 위해 실리콘을 이용하여 완벽 방수구조를 갖추었으며 홍수시 하천 유하물에 의한 파손을 방지하기 위해 내구성을 갖춘 구조로 설계 제작하였다. LED를 이용한 수위표는 야간이나 홍수시 수위관측을 수행할 때 많은 장점이 있을 것으로 판단되며 저전력 구조로 상용전원을 이용할 수 없는 위치에서 태양열 전지판을 이용한 배터리 기반 시스템으로 구성할 수 있으므로 측정의 정확도, 활용도 측면뿐만 아니라 설치의 편리성 문제도 큰 장점을 가질 것으로 판단된다.

The efficiency of light-emitting diode (LED) devices is a significant factor that reflects the capability of these devices to convert electrical power into optical power. In this study, a method for estimating the efficiency of LED devices is proposed. An efficiency model and a heat power model are established as convenient tools for LED performance evaluation. Such models can aid in the design of LED drivers and in the reliability evaluation of LED devices. The proposed estimation method for the efficiency and heat power of LED devices is verified by experimentally testing two types of commercial LED devices.

Among the environmental conditions employed in micropropagation, light quality plays an important role in growth, specially morphogenesis and photosynthesis. The effect of radiation quality (350-740 nm) on the development and growth of zygotic embryos and in vitro plantlets of open-pollinated chestnut (Castanea crenata S. et Z.) were studied. Two types of explants were exposed for 4 weeks to cool white (W, as control), monochromatic red (R, peak emission 650 nm), monochromatic blue (B, peak emission 440 nm), red+blue (R+B, 1:1), or red+far-red (R+Fr, 1:1, far-red peak emission 720 nm) radiation from a light-emitting-diode (LED) system. While the zygotic embryos showed positive photoblastic behavior, their germination was inhibited by blue radiation. Hypocotyl elongation and root development were promoted by red radiation. The emergence of primary leaf and its expansion were faster under blue than under red radiation. In the plantlets, red and red+far-red radiation significantly increased the formation and growth of the root, whereas blue light reduced rooting. Therefore, radiation quality appears to influence some steps in the development of zygotic embryos and plantlets in the chestnut.

The marine microalgae Chaetoceros calcitrans was cultured under a fluorescent lamp (CON) and light-emitting diodes (LEDs) of various wavelengths (blue, LB; red, LR; green, LG; white, LW); changes in growth, fucoxanthin, chlorophyll-a, amino acid and fatty acid profiles were investigated. LR-exposed cultures exhibited the highest specific growth rate (SGR) (0.34), whereas LG-exposed cultures showed the lowest SGR (0.26). After cultivation for 10 days, the maximum dry cell weight (g/L) of LR-exposed cultures was significantly higher than that of those exposed to other light conditions (LR${\geq_-}$CON>LB${\geq_-}$LW${\geq_-}$LG). Eicosapentaenoic acid (EPA) levels were significantly higher in CON-exposed cultures compared to those exposed to LW (P<0.05), with no marked difference compared to those exposed to LB, LR and LG (P>0.05). The fucoxanthin content was highest in LB-exposed cultures ($6.3{\mu}g/mL$), whereas LW showed the lowest ($3.6{\mu}g/mL$; P<0.05). Chlorophyll-a content was highest in cultures exposed to LB compared to other light sources. These results suggest consistent differences in growth and biochemical composition after exposure to light of different wavelengths.

The marine microalgae Nannochloropsis sp. was cultured under a metal halide lamp (MH) or light-emitting diodes (LEDs) of various wavelengths (blue, LB; red, LR; yellow, LY; green, LG; white, LW); changes in growth, total carotenoid, chlorophyll a, amino acid and fatty acid profiles were investigated. LB-exposed cultures exhibited the highest specific growth rate (SGR) (0.32), whereas LY-exposed cultures showed the lowest SGR (0.18). After cultivation for 9 days, the maximum dry cell weight (g/L) of LB-exposed cultures was significantly higher than that of those exposed to other light conditions (LB>MH>LW$${\geq_-}LG{\geq_-}$$LR>LY). The essential amino acid (EAA, %) contents of cultures exposed to LG, LB, LR and MH were higher than those exposed to LY and LW (P<0.05). Eicosapentaenoic acid and n-3 highly unsaturated fatty acid levels were significantly higher in MH-exposed cultures compared to those exposed to LY (P<0.05), with no marked difference compared to those exposed to LB, LG, LR and LW (P>0.05). The total carotenoid content was highest in LR-exposed cultures (18.0 mg/L), whereas MH showed the lowest (11.8 mg/L; P<0.05). Chlorophyll a content was highest in cultures exposed to LR compared to other light sources. These results suggest consistent differences in growth and biochemical composition after exposure to light of different wavelengths.

본 연구는 최근 친수공간 확대로 수중보의 경관조명 수요가 급격히 늘어나고 있으나 현재 사용하는 수중보 조명등의 안전성과 연출효과가 떨어지는 등 문제점이 발생되므로 수중보 조명등을 개선하기 위해 안전성, 에너지 절감, 연출에 대한 유연성에 주관점을 두고 실태조사를 통한 문제점을 도출 분석하여 수중보조명등을 LED몰드 수중등으로 개발하였다. 본 연구의 결과물을 실용화함으로써 수중보 조명은 댐, 분수, 수영장 등 수변공간에 다양하게 확대 적용 가능할 것으로 사료된다.

Recently, the demand of landscape lighting for underwater dam is rapidly increased by expansion of hydrophilic space. But it occurred the problems such as weakness of safety and display effect of underwater dam lighting lamp currently in use. Therefore, for solving these problems and improving underwater dam lighting lamp, this paper is focused on safety, energy saving, display flexibility of underwater dam lighting lamp and analyzed the related deriving problems by research on the actual condition. As a result, it presents a developed LED mold type underwater light instead of underwater dam lighting lamp. By the results of this research, it is considered that practical use of underwater dam lighting is very useful in waterside space for dams, water fountain, swimming pool, and etc. Moreover, it can be extended/applied in various ways.

This paper shows a derating design approach for LED reliability improvement. The LED is widely used in display devices or circuits. The main failure of interest is defined as 100% reduction of the light output intensity of LED resulting from corrosion due to stresses, i.e. temperature and humidity. The lifetime is varied according to the stress levels under where the LED operates so that correlation of the lifetime to these stress levels over time is modeled through accelerated life testings. A derating design approach to accomplish a required reliability level of LED is proposed to determine adequate the stress levels. In the approach, $B_{10}$ life, Failure rate, Sensitivity Analysis of LED are used as a reliability metric.

본 연구에서는 배추김치(RK)와 백김치(WK) 시료를 이용하여 72시간의 저장 기간 동안, Blue-LED 조사 효과를 확인하였다. BLED 처리에 의해 RK에서의 유산균 증식이 유의적으로 증가하였으나(p<0.05), 곰팡이 및 효모의 생육도에서는 대조구와 차이를 나타내지 않았다. 색도의 경우, BLED 처리 시 대부분 명도가 조금 높아지는 경향을 보였으며, BLED 조사에 의해 색의 변화가 일정기간 지연되는 효과를 확인할 수 있었다. BLED 처리에 의해 WK는 저장기간 동안 pH 감소가 유의적으로 지연되는 것을 관찰할 수 있었다(p<0.05). ABTS법에 의해 측정된 산화방지 활성에서는 두 종류의 김치시료액 모두 BLED처리구에서 유의적으로 높은 활성을 보였다(p<0.05). 두 김치에서 우점종으로 분리된 W. cibaria RK1와 W. cibaria WK1 유산균은 BLED에 민감하게 작용하여 모두 생육이 저해되었고, 표준 균주인 Leu. mesenteroides는 BLED 조사에 의한 생육도의 변화가 나타나지 않았다. 현재까지 BLED 조사를 이용한 유해 균주 억제 연구가 주로 이루어진 반면, 현 연구에서는 BLED조사에 의한 김치 발효상의 특성 변화와 발효미생물들의 생육도를 확인함으로써 발효 식품의 숙성 시기에 따라 적절한 LED 광원을 이용한 발효 미생물들의 생육 조절과 식품의 기능적 향상 가능성을 제시하였다.

Kimchi is a widely consumed traditional Korean food, and its probiotic properties have received great attention. In this study, changes in the quality characteristics of fermentation broths obtained from two types of Chinese cabbage kimchi (red with red pepper and white without red pepper) were assessed after the administration of blue light emitting diode (BLED) irradiation at 4℃; characteristics assessed included acidity, chromaticity, antioxidant activity, and growth modulation of isolated microorganisms. The pH of the white kimchi (WK) broth decreased with time; the decrease was delayed significantly under BLED irradiation (p<0.05). BLED irradiation decreased the L (lightness) and b (yellowness) values and increased a (redness) in WK, whereas the a and b values of the red kimchi (RK) broth increased with BLED irradiation. Growth stimulation of lactic acid bacteria by BLED irradiation was observed in both WK and RK. The numbers of yeast and mold were also increased in RK (p<0.05), but not in WK. There was no change observed in the scavenging activities against ABTS (2,2'-azido-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals in both kimchi broths after BLED treatment. The results of this study indicated that BLED irradiation could modulate the fermentation process and the quality characteristics of kimchi during storage.