• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1182-1182
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• 2001

In this study, the newly constructed optical measurement system, which was mainly composed of a parametric tunable laser and a near infrared photoelectric multiplier, was introduced to clarify the optical characteristics of wood as discontinuous body with anisotropic cellular structure from the viewpoint of the time-of-flight near infrared spectroscopy (TOF-NIRS). The combined effects of the cellular structure of wood sample, the wavelength of the laser beam λ, and the detection position of transmitted light on the time resolved profiles were investigated in detail. The variation of the attenuance of peak maxima At, the time delay of peak maxima Δt and the variation of full width at half maximum Δw were strongly dependent on the feature of cellular structure of a sample and the wavelength of the laser beam. The substantial optical path length became about 30 to 35 times as long as sample thickness except the absorption band of water. Δt ${\times}$ Δw representing the light scattering condition increased exponentially with the sample thickness or the distance between the irradiation point and the end of sample. Around the λ=900-950 nm, there may be considerable light scattering in the lumen of tracheid, which is multiple specular reflection and easy to propagate along the length of wood fiber. Such tendency was remarkable for soft wood with the aggregate of thin layers of cell walls. When we apply TOF-NIRS to the cellular structural materials like wood, it is very important to give attention to the difference in the light scattering within cell wall and the multiple specular-like reflections between cell walls. We tried to express the characteristics of the time resolved profile on the basis of the optical parameters for light propagation determined by the previous studies, which were absorption coefficient K and scattering coefficient S from Kubelka-Munk theory and n from nth power cosine model of radiant intensity. The wavelength dependency of the product of K/S and n, which expressed the light-absorbing and -scattering condition and the degree of anisotropy, respectively, was similar to that of the time delay of peak maxima Δt. The variation of the time resolved profile is governed by the combination of these parameters. So, we can easily find the set of parameters for light propagation synthetically from Δt.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.89.2-89.2
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• 2010

The dye-sensitized solar cell (DSSC) is a device for the conversion of visible light into electricity, based on the sensitization of wide bandgap semiconductors. The performance of the cell mainly depends on a dye used as sensitizer. The absorption spectrum of the dye and the anchorage of the dye to the surface of $TiO_2$ are important parameters determining the efficiency of the cell. Generally, transition metal coordination compounds(ruthenium polypyridyl complexes) are used as the effective sensitizers, due to their intense charge-transfer absorption in the whole visible range and highly efficient metal-to ligand charge transfer. However, ruthenium polypyridyl complexes contain a heavy metal, which is undesirable from point of view of the environmental aspects. Moreover, the process to synthesize the complexes is complicated and costly. Alternatively, organic dyes can be used for the same purpose with an acceptable efficiency. The advantages of organic dyes include their availability and low cost. We designed and synthesized a series of organic sensitizers containing long wavelength absorption-chromophores for the dye sensitized solar cell. The DSSC composed of Blue-chromophores for the sensitization absorbed long wavelength region which is different also applied into the dye-cocktail (mixing) system. The photovoltaic property of DSSCs organic long wavelength absorption-chromophores were measured and evaluated by comparison with that of individual chromophores.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.7
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• pp.1249-1255
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• 2008

1530nm band has been studied as pump wavelength for long-wavelength-band erbium-doped fiber amplifier (L-band EDFA). The pump source is built using a tunable light source and cascaded conventional-band (C-band) EDFA. The L-band EDFA uses a forward pumping scheme. Within the 1530nm band, 1545nm pump demonstrates 0.45dB/mW gain coefficient, which is twice better than that of conventional 1480nm pumped EDFA. The noise figure of 1530nm pump is at worst 6.36dB, which is 0.75dB higher than that of 1480nm pumped EDFA. Such high gain coefficient indicates that the L-band EDFA consumes low power.

• Korean Journal of Food Science and Technology
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• v.47 no.6
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• pp.785-788
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• 2015

In this study, the effect of light irradiation on tyrosinase activity during storage in a low temperature incubator was investigated, with the goal of identifying the appropriate wavelength and intensity of light for inhibiting tyrosinase activity. Fluorescent light and blue light emitting diode (LED) irradiation were found to inhibit tyrosinase activity. In particular, tyrosinase activity was significantly inhibited under high intensity blue LED irradiation, suggesting that the activity of tyrosinase present in vegetables or fruits might be inhibited by LED irradiation. Therefore, blue LED irradiation during food storage and the distribution stage would be useful for ensuring good quality of food, owing to the inhibition of the enzymatic browning reaction.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.22 no.2
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• pp.16-21
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• 1986

Optical properties of sea water were studied in the entrance of Tokyo Bay, Japan. based on the data obtained from seven oceanographic stations in June. 1985. The observation of surface irradiance and underwater irradiance of sea water for eight kind of wavelength (378, 422, 481, 513, 570, 621, 653. 677nm) of sun light was conducted using the underwater irradiameter (Isigawa # SR-8). The mean att;enuation coefficient of the sea water was appeared to be 0.245 (0.042-0.776) and the attenuation co~fficient of the sea water for wavelength appeared such as 0.227 for 378 nm, 0.186 for 422 nm. O. 175 for 481 nm. O. 176 for 513 nm. O. 185 for 570 nm, 0.337 for 621 nm. O. 321 for 653 nm, O. 348 for 677 nm. The transparency was 7.0 m (5.5-9 m). water color was 10 (8.0-13.0) in the study area and the sun altitude was 60.95$^{\circ}$ (43.610-75.500). The relationship between attenuation coefficient (K) and transparency (D) was K = 2.63/ D (1.28/ D- 4. 87/D). The rate of light penetration for eight kind of wave Ie nth (378, 422. 481. 513. 570, 621, 653, 677 nm) were computed with reference to the surface light intensity respectively. The mean rate of light penetration in proportion to depths were 68.63% (46.02-86.07%) in 1 m layer, 18.40% (2.07 -48.48%) in 5m layer, 4.82% (0.042-22.30%) in 10m layer and 1.35% (0.01I-7.42%) in 20m layer. The rate of light penetration at the transparency layer with reference to the surface light intensity was shown as 10.39% (0.77-27.46%).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.4
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• pp.413-420
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• 2017

The increase in the number of mud shrimps Upogebia major is a concern because of their negative effects on shellfish aquaculture, including Manila clam Venerupis philippinatum along the west coast of Korea. This study developed a behavioral analysis system for aquatic animals using a set of monochromatic light-emitting diode (LED) modules covering the visible light range at similar intervals. Movements of mud shrimp were monitored using a tracking system under illumination with infra-red light and an LED of 660 nm wavelength without provoking stimulation. The minimum light intensity needed to induce a photoresponse by the mud shrimp was $10{\mu}mole/m^2/s$ under the conditions tested. Of the six kinds of LED illuminations tested, the most sensitive response was obtained with illumination with the 505 nm LED, followed in order by LEDs with peak wavelengths of $525nm{\fallingdotseq}465nm$ > $405nm{\fallingdotseq}590nm$ > 660 nm. These findings should help to identify LED sources that efficiently induce movement of the mud shrimp and also for monitoring movement without stimulating.

• 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 Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1514-1519
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• 2009

We fabricated the GaNLED emitting 400 nm wavelength and improved the optical extraction efficiency by making surface patterns on n-GaN layer and ITO layer above p-GaN. In addition, the light reflection metal under the n and p pad is made and the light reflection metal is installed on the backside of the chip. The light extraction efficiency is increased by 20 % with texturing n-GaN layer and 18% with texturing ITO layer at 20 mA. Compared to planar-surface LED, the light extraction efficiency for surface texturing both n-GaN and ITO is increased by 32% at 20mA.

• Physical Therapy Rehabilitation Science
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• v.3 no.1
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• pp.20-26
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• 2014

Objective: The low level lasers currently in the market vary in wavelength, dosage, and frequency. These devices are used with much different clinical pathology. Most notably, some studies claim that wounds heal faster with low level laser therapy due to the fact that bacteria commonly found in wounds are killed by laser light. Systemic and meta-analysis studies found the difficulty of comparison of numerous research studies because of differences in the intensities and frequencies of low level laser treatment (LLLT). The purpose of this study was to determine the effectiveness of LLLT on controlling bacterial growth. Design: Cross-sectional study. Methods: Variables included LLLT dosage and wavelength on 3 bacteria commonly seen in wounds, strains of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were used on commercially available 5.0-cm agar plates. Blue, green, and red, ultraviolet (UV) and infrared laser light sources were adjusted to either low or high intensity settings. Five Petri dishes at a time were placed directly beneath laser light sources with the exception of UV which was placed six inches below the suspended light and infrared which was placed directly on top of the Petri dish lid. Each group of five Petri dishes was irradiated for 15 minutes. Results: The results showed no effect of any of 9 different LLLT intensities or colors on bacteria growth compared to sham light. Conclusions: At least for claims of bacterial growth inhibition with LLLT, no support for this claim can be found here.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.333-338
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• 2021

This study determined the characteristics of LED illumination and photosynthetically active radiation flux density (PPFD) for LED lighting design in an indoor plant factory. This was done based on the light wavelength and PPFD intensity required for plant growth. It has been found that the wavelength and intensity are decreased according to the measuring distance, and green light has an important role in illumination characteristics, while blue light has an important role in the PPFD characteristics. Considering only the photosynthetic properties of plants, the effective order of photosynthesis was blue>red>white>green. When the measurement distance was 30 [cm], it was found that reduction levels of 60 [cm], 90 [cm], and 120 [cm] decreased to about 36 [%], 18 [%], and 10 [%], respectively. As a result of the characteristics of mixed light (red:blue=2:1, 3:1, 4:1) and the measurement distance, when the measured value at 30 [cm] is 100%, the measured value at 120 [cm] is 10-11 [%]. From the obtained results, an optimal structure was proposed for maximizing the light efficiency of an indoor greenhouse for future research.