• Title, Summary, Keyword: Uniform light irradiation of LED

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Solar Tracking Performance using a Heliostat and Uniform Irradiation of LED Light for a Plant Factory (식물공장의 헬리오스탯을 이용한 태양광 추적성능 및 LED 균일광 조사)

  • Koo, Kyung-Wan;Kim, Tae-Jin;Kim, Youngshik;Ryu, Bong-Jo
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.12
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    • pp.1761-1767
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    • 2015
  • This paper deals with the solar tracking performance using a small heliostat, the light reduction rate of the sun light, and the performance of uniform irradiation of LED light for a plant factory. A high precision encoder is attached to the heliostat to improve tracking accuracy. As a result, our heliostat-based solar tracking systems track efficiently the movement of the sun light in experimental tests. The reduction rate of the sun light in the plant factory is then measured by using an illumination sensor. The average reduction rate is 4.29%, which represents lower light reduction rates. In uniform irradiation tests of LED light, sixteen points are measured, and overall deviations of irradiation were within eight percents.

Effect of LED light on the inactivation of Bacillus cereus for extending shelf-life of extruded rice cake and simulation of the patterns of LED irradiation by various arrays of LEDs (압출떡의 유통기한 연장을 위한 LED 조사의 Bacillus cereus 억제 효과 및 LED의 배열에 따른 빛의 조사 패턴 시뮬레이션)

  • Jung, Hwabin;Yuk, Hyun-Gyun;Yoon, Won Byong
    • Journal of Applied Biological Chemistry
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    • v.62 no.2
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    • pp.181-186
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    • 2019
  • The optimum design of LED device for irradiation of 460 nm blue light on extruded rice cake using simulation and the effect of the blue light on the inactivation of Bacillus cereus (B. cereus) group on the rice cake were investigated. The irradiated light intensity patterns on the surface area of the sample were simulated with three different LED arrays (centered, cross, and evenly spaced) and at various distances (22, 32, 42 mm) between the LED modules and the sample. In addition, the uniformity was calculated as Petri factor. The evenly spaced array resulted the most uniform light intensity pattern in the simulation, and the Petri factor of 32 and 42 mm of the distances showed higher than 0.9, which represents the ideal uniformity of LED device. The bacterial population of the rice cake decreased to less than the initial bacterial population during exposure to LED blue light, whereas the bacterial population of the control sample increased. The bacterial count of the rice cake after blue light irradiation for 24 h was 1.21 log CFU/g lower than the control sample. Petri factor increased with increase of the distance between the light source and sample, however, the reduction rate of B. cereus group decreased. Therefore, the design of LED device, that represented the Petri factor higher than 0.9 and inactivated the population of B. cereus group, with evenly spaced and 32 mm of distance between the light source and sample was suitable for extending shelf-life of rice cake.

Polymerization Shrinkage Distribution of a Dental Composite during Dental Restoration Observed by Digital Image Correlation Method (디지털 이미지 상관법을 이용한 치과용 복합레진의 수복 시 중합수축분포 관찰)

  • Park, Jung-Hoon;Choi, Nak-Sam
    • Composites Research
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    • v.30 no.6
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    • pp.393-398
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    • 2017
  • The shrinkage distribution of a dental composite (Clearfil AP-X, Kuraray, Japan) used for dental restoration was observed using a digital image correlation method. In order to analyze the shrinkage distribution formed during and after light irradiation, digital images were taken with different photographing conditions for each period. Optimal photographing conditions during LED irradiation were obtained through a preliminary experiment in which the exposure time was applied from 0.15 ms to 0.55 ms in 0.05 ms intervals. The DIC analysis results showed that the strain was non-uniform. For the initial 20 s of light irradiation the composite resin shrank to the level of 50~60% of the final curing shrinkage. Such large shrinkage amount of the composite resin lump affected the tensile stress concentration near the adhesive region between the composite resin and the substrate.