• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.561-568
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• 2002

Purpose of this research is estimating polymerization depth of different source of light. XL 3000 for halo-gen light, Apollo 95E for plasma arc light and Easy cure for LED light source were used in this study. Different shade (B1 & A3) resin composites (Esthet-X, Dentsply, U.S.A.) were used to measure depth of cure. 1, 2, and 3 mm thick samples were light cured for three seconds, six seconds or 10 seconds with Apollo 95E and they were light cured with XL-3000 and Easy cure for 10 seconds, 20 seconds, or 40 seconds. Vicker's hardness test carried out after store samples for 24 hours in distilled water. Results were as following. 1. Curing time increases from al1 source of lights, oui$.$ing depth increased(p<0.05). 2. Depth (that except 1mm group and 2mm group which lighten to halogen source of light) deepens in all groups, Vickers hardness decreased(p<0.05). 3. Vicker's hardness of A3 shade composite was lower in all depths more than B1 shade composites in group that do polymerization for 10 seconds and 20 seconds using halogen source of light(p<0.05), but group that do polymerization lot 40 seconds did not show difference(p>0.05). 4. Groups that do polymerization using Plasma arc and LED source of light did not show Vicker's hardness difference according to color at surface and 1mm depth(p>0.05), but showed difference according to color at 2mm and 3mm depth(p<0.05). The results showed that Apollo 95E need more polymerization times than manufacturer's recommendation (3 seconds), and Easy cure need polymerization time of XL-3000 at least.

• Proceedings of the Optical Society of Korea Conference
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• 2004.07a
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• pp.232-233
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• 2004

LED 광원의 특성인 높은 색재현성, 친환경성, 저소비전력 등을 디스플레이 광원으로 그 활용도가 높이 평가되고 있다. 최근 비약적인 광효율 증가를 보이고 있는 고출력 LED 광원을 대화면의 LCD TV 용 BLU 와 Projection TV의 조명계에 적용하기 위하여 기술개발에 필요한 주요 요소들을 살펴본다.

• 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 the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.1
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• pp.35-43
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• 2008

Aviation obstacle lights including controller for the safe night aviation service have applied to high voltage transmission line of which height is from $60{\sim}180 m$, Fresnel lens made by Augustine Fresnel have been applied to light houses, These Fresnel lens were applied to aviation obstacle lights and have been universally used, It was reported that Fresnel lens for aviation obstacle light was used in the first place in Korea in 1987, LEDs have recently been applied to aviation obstacle lights, So, the optimum physical design is essential to the design of aviation obstacle light. In this study, optical and three dimensional modeling of LED module and globe lens were performed, And thermal analysis due to LED thermal source and service thermal condition in high voltage transmission line was performed and was analyzed comparing with experiments, The optimum design process of medium intensity LED aviation obstacle lights was constructed with three dimensional modeling, thermal analysis, and thermal experimental technique.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.8
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• pp.167-171
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• 2014

While the development of a portable plate panel display, thinning, high color reproduction, high brightness studies have been actively performed. LED, OLED is used as a light source. The research on quantum dot is much accomplished by the material of light source. Such quantum dot is the next generation semiconductor nano fluorescent substance because quantum dot has the high color reproduction and flexible display characteristic. In this study, we presented to method of using the quantum dot for implementation of the plate panel display. Quantum Dot (CdSe/ZnS), having a 100um thickness, is spread in PET barrier film. A Blue LED having a wavelength of 455nm as a light source irradiating light to the optical characteristic of the devices produced and evaluated. Also we presented the possibility for application with the color change film of the LCD.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.358-365
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• 2011

Recently, the LED(Light Emitting Diode) replacing incandescent light bulbs and fluorescent light has great attentions as a most promising candidate for the next generation lighting source due to its environment-friendly characteristics, long life and excellent efficiency. Moreover, since it is a semiconductor device which can convert the electric energy to visible light at a very high speed, it can also used as a communication device. Therefore, the VLC(Visible Light Communication) using the LED can perform the near field communication and lighting function at the same time without additional expenses. However, since the switching device of the conventional LED driver for VLC is operated in the linear region, there exist several drawbacks such as a poor power conversion efficiency and serious heat generation. On the other hand, since the proposed driver is operated in the on/off switching region, it features a higher efficiency and more improved heat generation. To verify the validity of the proposed LED driver, experimental results from a prototype of 20W rated LED driver applied to 3MHz bps broadcasting audio system are given.

• Journal of Plant Biotechnology
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• v.41 no.2
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• pp.94-99
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• 2014

This study was conducted to elucidate the effect of light sources and explant types on in vitro shoot multiplication and rooting of a rare and endangered plant Abeliophyllum distichum. Both apical buds and axillary buds were used as explants under 4 different light sources, cool white florescent light (F), 100% blue light-emitting diode (LED) (B), 50% blue and 50% red LED mixture (BR), and 100% red LED (R). Clear difference was observed in terms of shoot proliferation by light sources types but not by position-dependent explant types. Multiple shoot induction rates were enhanced under both B and BR light sources. Spontaneous rooting was induced in shoot induction medium under B light source. Both the rates of rooting and numbers of roots per explant were higher in apical bud explants compared to axillary bud explants. Interestingly R light source stimulated shoot elongation but inhibited root development. Therefore, our results suggest that the use of apical bud explants under B or BR light sources is suitable for in vitro micropropagation of a rare and endangered plant species, Abeliophyllum distichum.

• Korean Journal of Optics and Photonics
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• v.35 no.5
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• pp.235-240
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• 2024

Since the coronavirus pandemic, research and application of space sterilization effects using UV light sources have been rapidly increasing. In this paper, the space-sterilization effect of UV LED light sources that can be built into indoor environmental systems or lighting devices is quantitatively analyzed through an illumination optical approach. Through this, it is possible to establish a foundation for optimizing the sterilization effect in indoor spaces in the 275±5 nm wavelength range, which is known to have excellent space-sterilization power.

• Science of Emotion and Sensibility
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• v.17 no.2
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• pp.55-62
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• 2014

In this study, a questionnaire was developed to assess error search and correction tasks, and an analysis was performed on the accuracy of the tasks and the time required for their completion in order to identify the effects of LED light source illumination on visual performance according to changes in a predicted mean vote(PMV) thermal environment. In addition, a subjective evaluation was performed by conducting a survey on the level of visual fatigue experienced during the tasks. In the experiment, four types of PMV thermal environments were established according to PMV values in the temperature range of $(17{\pm}1-29{\pm}1)^{\circ}C$ and the humidity range of $(50{\pm}5-60{\pm}5)%$, and the LED light source illumination was divided into three types: 400lx, 700lx, and 1000lx. The experimental results confirmed that the accuracy of the error search(LED p value=0.058, PMV*LED p value=0.083) and correction tasks and the time required(LED p value=0.004, PMV p value=0.000) for their completion were affected by changes in both the PMV thermal environment and the LED light source illumination, whereas a significant difference in visual fatigue was observed only in the PMV thermal environment(p value=0.003).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11B
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• pp.1394-1402
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• 2011

This paper describes solar light collecting system which employs parabolic reflector and Fresnel lens and its industrial application. We have introduced second-stage optical system so that it makes optical fiber overcome its numerical aperture limitation and also it makes focused light become collimated, which results in decreased light energy density. As result of these, light collecting efficiency become maximized and the system does not require separate cooling apparatus any more. The developed solar lighting system together with artificial light source like LED has been applied to plant factory as a hybrid lighting source. This makes us save electric energy for artificial lighting during day time. The intensity of LED light in the hybrid lighting system is controlled automatically according to ambient-light-sensor installed in the system so that the light intensity for a plant always keeps the same level no matter how the sun light changes. For a plant factory whose size is 330 square meters, when solar lighting system is applied, 28,080KWh electric energy can be saved per month.2 times.