• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.3
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• pp.359-364
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• 2011

The study uses department of the sensitivity and fuzzy reasoning, one of artificial intelligence algorithms, so that develop LED lighting system based on fuzzy reasoning for systematical control of the LED color temperature. In the area of sensitivity engineering, by considering the relation between color and emotion expressed as an adjective word, the corresponding sensitivity word can be determined, By taking into consideration the relation between the brain wave measured from the human brain and the color temperature, the preferred lesson subject can be determined. From the decision of the sensitivity word and the lesson subject, we adjust the color temperature of RGB (Red, Green, Blue) LED. In addition, by using the information of the latitude and the longitude from GPS(Global Positioning System), we can calculate the on-line moving altitude of sun. By using the sensor information of both temperature and humidity, we can calculate the discomfort index. By considering the altitude of sun as well as the value of the discomfort index, the illumination of W(white) LED and the color temperature of RGB LED can be determined. The (LED) sensitivity lighting control system is bulit up by considering the sensitivity word, the lesson subject, the altitude of sun, and the discomfort index The developed sensitivity lighting control system leads to more suitable atmosphere and also the enhancement of the efficiency of lesson subjects as well as business affairs.

• Korean Journal of Materials Research
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• v.27 no.6
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• pp.312-317
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• 2017

In the construction of a white LED, the region of the red emission is a very important factor. Red light emitting materials play an important role in improving the color rendering index of commercial lighting. These materials also increase the color gamut of display products. Therefore, the development of novel phosphors with red emission and the study of color tuning are actively underway to improve product quality. In the present study, heuristic algorithms were used to search for phosphors capable of increasing the color rendering index and color gamut. Using a heuristic algorithm, the phosphors that were identified were $SrGe_4O_9:Mn^{4+}$ and $BaGe_4O_9:Mn^{4+}$. Emission spectra study confirmed that these phosphors emit light in the deep red wavelength region, which can fulfill the requirement for the improvement in color rendering index and color gamut for a white LED.

• Journal of the Semiconductor & Display Technology
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• v.16 no.4
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• pp.11-15
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• 2017

Red phosphors, $Sr_2Si_5N_8:Eu^{2+}$, were synthesized as a single-phase crystal structure by optimizing carbon and $Eu^{2+}$ contents in a carbothermal reduction nitridation method. With increasing $Eu^{2+}$ contents, the photoluminescence spectra were red-shifted from 600 nm peak for 1 mol% for to 700 nm for 7 mol%. It was suggested that this red shift is attributed to the energy transfer from one low-energy sited $Eu^{2+}$ (1) to other high-energy sited $Eu^{2+}$ (2). Finally, the best red sample (620 nm emission peak and 80 nm half width for 3 mole% of $Eu^{2+}$) was packaged on a Blue LED together with two additional green and yellow phosphors, the fabricated White LED showed a high color-rendering index of 90 and white color coordinates of x= 0.321 and y = 0.305.

• Science of Emotion and Sensibility
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• v.17 no.3
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• pp.29-38
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• 2014

The purpose of this study was to verify human physiological responses to emotional lighting system using LED (light emitting diode) flat lighting. Subjects were ten males in their twenties without medical history to eyes. Colors of LED lighting are red, orange, yellow, green, blue, purple and colorless (white). They were stimulated by LED lighting for 5 minutes. We measured body temperature, heart rate variability (HRV) and electroencephalogram (EEG) before and after color stimulus. In case of EEG analysis, relative power ${\alpha}$ wave ratio decreased in the groups of colorless, red and orange color light. Also, sympathetic nerve was more activated than parasympathetic nerve and the body temperature was increased in the groups of colorless, red, orange, yellow color light. On the other hand, relative power ${\alpha}$ wave ratio increased and parasympathetic nerve was more activated than sympathetic nerve and the body temperature was decreased in the groups of green, blue and purple color light. The results imply that the LED color lighting system in the realistic experiment environment. In the future, studies with compounded both colors and modes according to situation or auditory as nature sound or olfactory as aroma will be required.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.293-300
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• 2015

Purpose: To evaluate blue light hazards of LED lightings in an optical store with blue light radiance used as the quantitative indicators of photobiological hazard. Methods: The spectral radiance of each LED lightings was measured, and blue-light radiance and the corresponding maximum exposure time were calculated. Then each LED lighting was classified according to the risk group from IEC 62471 standard. Results: The yellow LED lightings used in showcases and white LED lightings used on ceilings and logo were classified into risk group RG0. But the white LED lightings used on showcases were classified into risk group RG1. The blue light radiances of white LED lightings used in showcases are dozens of times larger than that of fluorescent lamp. Conclusions: Using the value of the blue light radiance could quantitatively express the blue light hazard to various lightings. It was confirmed that white LED lightings for the showcases had high blue light hazards because of their high luminance and color temperature. Therefore, when replacing lightings in optical shop it is necessary to select the appropriate brightness and color temperature for eye health in the long term.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.20-26
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• 2004

In this paper, luminaire optical efficiency and luminous intensity according to array of HB(high brightness) white LED(light emitting diode) and globe types of luminaire were simulated by computer and made a comparative analysis. LEDs were arranged by square of 7ea X 7ea. LED space has been divided into 8.2mm, 10mm and 15mm that mean distances between luminous centers of LEDs, and luminaire globes were classified into 30mm and 50mm 묘묘 from luminous center of LEDs. Also the simulations were made with / without globe, globe types were specified by convex and embossing types of which sizes are 8.2mm and 5.0mm, So total 27 classes of simulation were performed. This paper is to help luminire development using LED light source called digital lighting of 21th century, by studying luminire effciency and luminous intensity of different types of globes.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.376-383
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• 2013

The design of the LEDs lighting in general household illumination was proposed and compared with the fluorescent lighting in this study. Using the LED as a light source would promote energy saving lighting for household illumination purposes. We used the LightTools and DIALux software to design and simulate different standards of illuminance, different correlated color temperatures and different color rendering indices for household environments. The power consumption and efficiency of traditional illuminated light sources and an LED light source with the same standard of illuminance for lighting the household environment were analyzed and compared with each other. Finally, our results show the advantages of using white-light LEDs for lighting and household illumination.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.286.1-286.1
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• 2013

Nowadays, the glare towards the light-emitting diode (LED) lighting source has much attention due to its eco-friendly nature, reduced energy consumption, and low CO2 emission. LEDs can show versatile colors by changing the composition ratio of semiconductors. Phosphors re-emit light by absorbing light from LED, which is the key factor for emission. The endeavor to make replica of natural white light is increasing day by day. Industrially, blue LED chip crowned with a yellow phosphor coated lens gives low quality white light. Newly, many researchers are introducing modern approaches, adding red phosphor to the yellow phosphor to increase the quality of white light. Here, we synthesized structurally and chemically stable europium doped oxyapatite Ca8Gd2(PO4)6O2 nano-crystalline structures by a hydrothermal method. The ultrafine structures were formed due to the effect of ethylenediaminetetraacetic acid, which is confirmed by the transmission electron microscope images. The structural properties were analyzed using the X-ray diffraction patterns.

• Journal of Biosystems Engineering
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• v.38 no.4
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• pp.279-286
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• 2013

Purpose: This study was conducted to analyze the utilization efficiencies of electric energy and photosynthetically active radiation of lettuce grown under red LED, blue LED and fluorescent lamps with different photoperiods. Methods: Red LED with peak wavelength of 660 nm and blue LED with peak wavelength of 450 nm were used to analyze the effect of three levels of photoperiod (12/12 h, 16/8 h, 20/4 h) of LED illumination on light utilization efficiency of lettuce grown hydroponically in a closed plant production system (CPPS). Cool-white fluorescent lamps (FL) were used as the control. Photosynthetic photon flux, air temperature and relative humidity in CPPS were maintained at 230 ${\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, $22/18^{\circ}C$ (light/darkness), and 70%, respectively. Electric conductivity and pH were controlled at 1.5-1.8 $dS{\cdot}m^{-1}$ and 5.5-6.0, respectively. The light utilization efficiency based on the chemical energy converted by photosynthesis, the accumulated electric energy consumed by artificial lighting sources, and the accumulated photosynthetically active radiation illuminated from artificial lighting sources were calculated. Results: As compared to the control, we found that the accumulated electric energy consumption decreased by 75.6% for red LED and by 70.7% for blue LED. The accumulated photosynthetically active radiation illuminated from red LED and blue LED decreased by 43.8% and 33.5%, respectively, compared with the control. The electric energy utilization efficiency (EEUE) of lettuce at growth stage 2 was 1.29-2.06% for red LED, 0.76-1.53% for blue LED, and 0.25-0.41% for FL. The photosynthetically active radiation utilization efficiency (PARUE) of lettuce was 6.25-9.95% for red LED, 3.75-7.49% for blue LED, and 2.77-4.62% for FL. EEUE and PARUE significantly increased with the increasing light period. Conclusions: From these results, illumination time of 16-20 h in a day was proposed to improve the light utilization efficiency of lettuce grown in a plant factory.

• Journal of Bio-Environment Control
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• v.31 no.1
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• pp.14-21
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• 2022

Uniform scions and rootstocks should be produced to ensure grafting success. Light quality is an important environmental factor that regulates seedling growth. The effects of warm- and cool-white light emitting diode (LED) ratios on seedling growth were investigated. Scions and rootstocks of cucumber, tomato, and watermelon were grown in a closed transplant production system using LED as the sole lighting source. The LED treatments were W1C0 (only warm-white), W1C1 (warm-white: cool-white = 1:1), W3C1 (warm-white: cool-white = 3:1), and W5C2 (warm-white: cool-white = 5:2). The seedlings grown in W1C1 had the shortest hypocotyls, and the seedlings grown in W1C0 had the longest hypocotyls among the three tested vegetables. The hypocotyls of watermelon scions, watermelon rootstocks, and tomato rootstocks were shortest in W1C1, followed by those in W3C1, W5C2, and W1C0, but there was no significant difference between W3C1 and W5C2, which remained the same as the ratio of cool-white LEDs increased. In addition, tomato scions had the first and second longest hypocotyls in W1C0 and W3C1, respectively, and the shortest hypocotyls in W5C2 and W1C1, along with W5C2 and W1C1, although the difference was not significant. The stem diameter was highest in W1C0 except for tomato seedlings and rootstocks of watermelon. The shoot fresh weight of scions and rootstocks of cucumber and watermelon and the root fresh weight of cucumber scions were lowest in W1C1. These results indicated that different ratios of LED lighting sources had a strong effect on the hypocotyl elongation of seedlings.