• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.76-76
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• 2011

Polymer-fullerene based bulk heterojunction (BHJ) solar cells can be fabricated in large area using low-cost roll-to-roll manufacturing methods. However, because of the low mobility of the BHJ materials, there is competition between the sweep-out of the photogenerated carriers by the built-in potential and recombination within the thin BHJ film [12-15]. Useful film thicknesses are limited by recombination. Thus, there is a need to increase the absorption by the BHJ film without increasing film thickness. Metal nanoparticles exhibit localized surface plasmon resonances (LSPR) which couple strongly to the incident light. In addition, relatively large metallic nanoparticles can reflect and scatter the light and thereby increase the optical path length within the BHJ film. Thus, the addition of metal nanoparticles into BHJ films offers the possibility of enhanced absorption and correspondingly enhanced photo-generation of mobile carriers. In this work, we have demonstrated several positive effects of shape controlled Au and Ag nanoparticles in organic P3HT/PC70BM, PCDTBT/PC70BM, Si-PCPDTBT/PC70BM BHJ-based PV devices. The use of an optimized concentration of Au and Ag nanomaterials in the BHJ film increases Jsc, FF, and the IPCE. These improvements result from a combination of enhanced light absorption caused by the light scattering of the nanomaterials in an active layer. Some of the metals induce the plasmon light concentration at specific wavelength. Moreover, improved charge transport results in low series resistance.

• Journal of Gifted/Talented Education
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• v.26 no.1
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• pp.101-122
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• 2016

The purpose of this study is to explore a possibility finding gifted underachievers who have high spatial ability, but low verbal ability in elementary science field. In Korea, because teachers used to refer students' academic achievement only when they recommend gifted students, underachievers used to be excluded. The participants are 5th-grade students in elementary school. In this research, developed teaching materials were given to students to find underachievers. Results of spatial ability test, verbal ability test, science academic achievement, non-verbal test, and interviews about light propagation concept were obtained. By analyzing results of this study, we found that spatial ability is the most important factors to understand light propagation. And there are some features to understand light propagation according to spatial ability. Lastly, this study shows the possibility of non-verbal test to find gifted underachievers with high spatial ability and low verbal ability.

• Korean Journal of Optics and Photonics
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• v.34 no.2
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• pp.45-52
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• 2023

In this study, we have investigated the effect of photobiomodulation (PBM) on corneal wound healing, using a low-power light-emitting diode (LED) at different wavelengths. We found that LEDs with wavelengths ranging from 623 to 940 nm had no significant cytotoxic effects on corneal epithelial cells. The effect of PBM on promoting cell migration was analyzed by scratch assay, and it was found that PBM at 623 nm significantly increased cell migration and promoted wound healing. Furthermore, the expression of genes related to cell migration and wound healing was analyzed, and it was found that PBM at 623 nm upregulated the expression of the genes FGF-1 and MMP2, which are known to promote cell proliferation and extracellular matrix degradation. These findings suggest that PBM with low-powered light at specific wavelengths, particularly 623 nm, could be utilized to treat corneal injury.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.56 no.6
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• pp.878-888
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• 2023

Growth responses of Chlorella vulgaris exposed to different light intensities and wavelengths of light-emitting diodes (LEDs) were investigated. C. vulgaris was cultured under red LED (650 nm), blue LED (450 nm), green LED (520 nm), and fluorescent lamps (three wavelengths, control). The maximum growth rates (µ_max) of C. vulgaris were highest under the blue LED, followed by the red LED, green LED, and fluorescent lamps. The low compensation photon flux density (I₀) and low half-saturation constants (K_s) were observed in C. vulgaris cultured under the red LED, indicating that high C. vulgaris growth is closely related to the low light intensity of the red LED suggesting that the red LED can be useful for the biomass production of C. vulgaris. Furthermore, it was observed that under the blue LED during the stationary phase, there was an increase in useful bioactive substances, such as proteins and lipids, which are beneficial for biomass production. In conclusion, the red LED is an economical light source that can enhance cell density, and the blue LED is effective in promoting valuable intracellular substances.

• Journal of Technologic Dentistry
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• v.42 no.2
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• pp.65-71
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• 2020

Purpose: To know the transmittance of light when wearing shading goggles and to protect eyes from blue light emitted from dental scanner when using CAD/CAM works or inducing polymerization reactions of dental resin with curing unit and infrared light occurred when melting Dental precious metal and non-precious metal alloys. Methods: By measuring and comparing the average transmittances of blue light, visible light and infrared ight by using UV-Vis Spectrophotometer analysis measuring instrument, I compared 3 GREEN Color Goggles worn when casting Dental precious metal and non-precious metal alloys, and compared each of YELLOW, ORANGE Color Goggles worn when using Dental CAD/CAM scanners and Light Curing(LED) the Dental resin. Results: In blue light range, YELLOW Color Goggles are more effective than ORANGE Color Goggles. In infrared light range, No.12 Goggles are more effective than No.10 and No.11 Goggles. Conclusion: When wearing blue light shading goggles to avoid harmful blue light occurred in using dental scanner and curing light, and when wearing infrared light shading goggles to avoid harmful infrared light during casting, to avoid the Side Effects like transmittance rate of blue light and infrared light goggles becomes too high to block appropriate amount of harmful light or too low that causing lower image clarity.

• Journal of Practical Agriculture & Fisheries Research
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• v.22 no.2
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• pp.123-133
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• 2020

Four LEDs (blue, green, red, and white light) were tested to identify the most attractive wave length to utilize as the forecasting tools for the B. tabaci in glass houses. Attractiveness was evaluated by the total number of the B. tabaci attached to a yellow sticky trap. In the condition of no host plant supplement, the attraction efficacy was ordered from high to low as blue light (107.3±2.5), white light (83.0±12.1), red light (58±21.8), and green light (39.7±8.1). In the supplement of the host plant, the attraction was observed in the order of blue light (52±17.4), red light (38.7±5.8), green light (12.7±1.5), and white light (11.7±5.0). In both experimental conditions, blue light showed the highest attraction. In terms of the host plant effect to LED attraction, it varied following as white light (85.9%), green light (68.1%), blue light (51.6%), and red light (33.3%). This result suggests that red light is the least affected by the host plant. In the evaluation of the relative control efficacy, it was determined following as red light (66.7%), blue light (48.5%), green light (31.9%) and white light (14.1%) (F_3,8 = 14.7, P = 0.001). Taken together, blue light had a very high initial attraction, and red light was revealed low attraction effect by the supplement of the host plant. In field demonstration experiments, a high attractive efficacy was not observed due to low-temperature conditions, but similar higher attractive efficacy was observed in blue and red lights compared to the control. The commercialization of LEDs using red and blue in the future is expected to provide important information regarding B. tabaci population density forecast in glass house.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.3
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• pp.129-136
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• 2020

In this paper, we propose a thermal imagery-based object detection algorithm for low-light level nighttime surveillance system. Many features selected by Haar-like feature selection algorithm and existing Adaboost algorithm are often vulnerable to noise and problems with similar or overlapping feature set for learning samples. It also removes noise from the feature set from the surveillance image of the low-light night environment, and implements it using the lightweight extended Haar feature and adaboost learning algorithm to enable fast and efficient real-time feature selection. Experiments use extended Haar feature points to recognize non-predictive objects with motion in nighttime low-light environments. The Adaboost learning algorithm with video frame 800*600 thermal image as input is implemented with CUDA 9.0 platform for simulation. As a result, the results of object detection confirmed that the success rate was about 90% or more, and the processing speed was about 30% faster than the computational results obtained through histogram equalization operations in general images.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.59-66
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• 2015

A new concept of an inorganic foaming process at low temperature was demonstrated for the production of inorganic thermal insulating materials with the properties of flexible light-weight, the advantages of organic-based thermal insulation material. The foaming process was proceeded by establishing a skeleton of the foam body by using inorganic fibrous sepiolite and aluminum silicate. A cavity was formed by the expansion of fibrous skeleton body, by the gas which was generated from foaming agent at low temperature. Then the multi-vesicular expanded perlite with low thermal conductivity was filled into the cavity in a skeleton of the foam body. Finally through these overall process, a new inorganic foamed body could be obtained at low temperature without the hot melting of inorganic materials. In order to achieve this object, various preparations such as fibrous sepiolite fibrillation process, heat treatment process of the fibrous slurry were needed, and the optimal compositional condition of slurry was required. The foam body produced showed the properties of flexible light-weight thermal insulation materials such as bulk density, yield strength, flexural strength, and high heat resistance.

• Horticultural Science & Technology
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• v.32 no.5
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• pp.584-589
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• 2014

Jeffersonia dubia is a spring-flowering perennial found in rich forests in Korea and Northern China and has potential as an ornamental or medicinal plant. However, illegal picking and land use change have decreased the number of populations and overall population size of this plant in its natural habitat. Although J. dubia has been reported to be a shade-preferring plant, no study has determined the optimum light intensity for its growth. The objectives of this work were to observe the effects of various shading levels on the physiological responses of J. dubia and to determine the proper shading level for cultivation. Treatments consisted of four shading levels (0%, 50%, 75%, and 95% shade) imposed using black mesh cloth. The number of leaves and dry weight increased with decreased shading. The shoot-to-root ratio increased with increased shading, mainly due to decreased root dry weight under shading. Plants showed low net $CO_2$ assimilation rates and $F_v/F_m$ values combined with low dry matter levels when grown under 0% shade (full sunlight). These results indicate that J. dubia plants experience excessive irradiance without shading, resulting in damage to the photosynthetic apparatus. By contrast, the net photosynthesis rate increased as the shading level increased. $F_v/F_m$, the potential efficiency of PSII, was 0.8 under 95% shade, indicating that J. dubia is well-adapted under heavy shading. However, the low dry matter of plants in the 95% shade treatment indicated that the low light intensity under 95% shade led to a decline in plant growth. Thus, moderate light (50% shading) is recommended for cultivating J. dubia without physiological defects.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.07a
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• pp.269-274
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• 2000