• Journal of Digital Convergence
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• v.19 no.11
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• pp.341-349
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• 2021

We studies to verify results similar to those of previous experiments, and their potential as a lighting device through optical characteristics experiments and resonance and optical characteristics simulations of array devices. The photonic quantum ring (PQR) device having a mesa diameter of 40 ㎛ and an internal hole diameter of 3 ㎛ was fabricated. Through the near-field observation of the fabricated device, it was found that the PQR device operates even at ㎂, and also that the mesa and hole devices are driven independently of each other. As a result of measuring the wavelength spectrum of the device according to the location, the coupling phenomenon due to mesa and holes was confirmed.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.5
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• pp.91-101
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• 2009

This study's purpose is to revive pre-construction situation earlier than construction of media facade using light-emitting diode, and analyze the strong and weak points of simulation image making process and technology, including lots of expressing methods. Exterior building decoration that was originated from Super Graphic led to the LED construction with a trend of increased night activities of these days. Initial Super Graphic was just in the level of deciding what to do with simple CAD drawings, but today's media facade construction is not so simple as the previous ones. This is because of the problems that should think about balances between neighboring environment and buildings, including high construction costs. According to survey results, media facade construction simulation's various expressing methods, its processes of analysis, and its strong & weak points will suggest standards for its size of construction and simulation purpose, including recommending suggestions that can respond rapidly by clients' diverse demands.

• Journal of Periodontal and Implant Science
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• v.53 no.2
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• pp.110-119
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• 2023

Purpose: This study aimed to investigate the proper wavelengths for safe levels of light-emitting diode (LED) irradiation with bactericidal and photobiomodulation effects in vitro. Methods: Cell viability tests of fibroblasts and osteoblasts after LED irradiation at 470, 525, 590, 630, and 850 nm were performed using the thiazolyl blue tetrazolium bromide assay. The bactericidal effect of 470-nm LED irradiation was analyzed with Streptococcus gordonii, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, and Tannerella forsythia. Levels of nitric oxide, a proinflammatory mediator, were measured to identify the anti-inflammatory effect of LED irradiation on lipopolysaccharide-stimulated inflammation in RAW 264.7 macrophages. Results: LED irradiation at wavelengths of 470, 525, 590, 630, and 850 nm showed no cytotoxic effect on fibroblasts and osteoblasts. LED irradiation at 630 and 850 nm led to fibroblast proliferation compared to no LED irradiation. LED irradiation at 470 nm resulted in bactericidal effects on S. gordonii, A. actinomycetemcomitans, F. nucleatum, P. gingivalis, and T. forsythia. Lipopolysaccharide (LPS)-induced RAW 264.7 inflammation was reduced by irradiation with 525-nm LED before LPS treatment and irradiation with 630-nm LED after LPS treatment; however, the effects were limited. Conclusions: LED irradiation at 470 nm showed bactericidal effects, while LED irradiation at 525 and 630 nm showed preventive and treatment effects on LPS-induced RAW 264.7 inflammation. The application of LED irradiation has potential as an adjuvant in periodontal therapy, although further investigations should be performed in vivo.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.323-325
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• 2022

In this paper, after administration of Chlorin e6 to kill cervical cancer cells, PDT (photodynamic therapy) using laser or LED was studied for Ce6 concentration and apoptosis by administration time. After photostimulation was applied to cervical cancer cells, qualitative and quantitative evaluation through imaging and quantitative evaluation using CCK-8 were performed. As a result of the experiment, as the concentration of Ce6 increased, a large amount of cells were killed, and it was confirmed that the Ce6+PDT test group killed more. When comparing the LED and the laser, the laser was able to kill cells only at a local location, and the LED showed the result that it was possible to kill the cells in a wide range. In addition, when irradiating a local location, such as a laser, when measuring the cell viability, it is judged to be accurate to image processing the location.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.112-117
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• 2024

The Internet of Things (IoT) device is a key component for Industry 4.0, which is the network in homes, factories, buildings, and infrastructures to monitor and control the systems. To demonstrate the IoT network, batteries are widely utilized as power sources, and the batteries inevitably require repeated replacement due to their limited capacity. Magneto-mechano-electric (MME) generators are one of the candidate to develop self-powered IoT systems since MME generators can harvest electricity from stray alternating current (AC) magnetic fields arising from electric power cables. Herein, we report a magneto-mechano-triboelectric generator enabled by a ferromagnetic-ferroelectric composite. In the triboelectric nylon matrix, a ferromagnetic carbonyl iron powder (CIP) was introduced to induce magnetic force near the AC magnetic field for MME harvesting. Additionally, a ferroelectric ceramic powder was also added to the MME composite material to enhance the charge-trapping capability during triboelectric harvesting. The final ferromagnetic-ferroelectric composite-based MME triboelectric harvester can generate an open-circuit voltage and a short-circuit current of 110 V and 8 μA, respectively, which were enough to turn on a light emitting diode (LED) and charge a capacitor. These results verify the feasibility of the MME triboelectric generator for not only harvesting electricity from an AC magnetic field but also for various self-powered IoT applications.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.84-84
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• 2022

백리향(Thymus quinquecostatus)은 꿀풀과의 낙엽반관목으로 국내에서 자생하는 허브 식물 중 하나이다. 백리향은 특유의 좋은 향기 및 항산화, 항염증, 항균, 미백 등의 효능을 가지는 각종 폴리페놀 성분을 함유하고 있어 의약품이나 기능성 식품, 화장품의 천연 소재 원료로 활용되고 있다. 국내에서 백리향은 재배 환경에 맞추어 주로 고산지대의 노지에서 재배되고 있다. 노지 재배는 지역, 시기, 기후 등의 외부환경에 영향을 받아서 백리향의 유효성분, 품질 및 생산성을 안정적으로 유지하기 어렵다는 한계를 가지고 있다. 따라서 본 연구에서는 스마트팜 시스템을 활용하여 백리향의 유효 성분 등을 안정적으로 얻기 위한 생장조건을 탐색하기 위해 4종의 Light Emitting Diode(LED) 광원과 4종의 토양 조성에 따라서 백리향의 생육조건을 수행하였다. LED는 white, purple, RGB1, RGB2를 사용하였으며, 토양은 상토:펄라이트 비율(상토, 5:1, 3:1, 1:1)로 조성하여 백리향 묘목을 이식한 뒤 생장과 개화시기를 분석하였다. 재배환경은 백리향 재배지의 기상 데이터를 참고하여 동일하게 설정하였으며, 총 8주 동안 생육상태를 관찰하였다. 연구 결과 백리향 재배 4주차에 일부 개체에서 봉오리가 올라오며 개화를 시작하였으며, 8주차에는 대부분의 조건에서 개화를 관찰할 수 있었다. 백리향의 지상부 면적을 비교한 결과 가장 우수한 생장을 보이는 조건은 토양은 3(상토):1(펄라이트) 비율로 분석되었다. 따라서 이번 연구 결과를 바탕으로 백리향 재배에 스마트팜 농업 기술을 활용한다면 기존 노지 재배 한계를 보완하여 안정적이고 지속적인 백리향을 생산할 수 있을것으로 기대된다.

• Journal of the Korean Institute of Gas
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• v.27 no.4
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• pp.1-11
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• 2023

The size of the OLED material market is expected to grow from $1.1 billion in 2019 to $2.3 billion in 2023, with an average annual sustainable growth of more than 19%. Among the facilities mainly used by OLED material manufacturers, accidents such as fire, explosion, and leakage frequently occur when using filtration equipment, so it is necessary to improve the risk when using filtration equipment. In this study, it was divided into four main processes, namely, assembly and disassembly process, filtration process, wet cake recovery process, and washing process in order to derive the risks associated with the use of filtration equipment. Hazard factors were derived by conducting accident case investigations, preliminary interviews, and surveys. For the analysis of questionnaire results, statistical analysis such as frequency analysis and Pearson chi-square test analysis was performed using SPSS 21, and risk improvement measures were suggested using the analyzed results. It is expected that this study will serve as a basis for dealing with safety and risk factors that may occur as the size of the OLED market expands.

• ETRI Journal
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• v.46 no.2
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• pp.347-359
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• 2024

A simultaneous transfer and bonding (SITRAB) process using areal laser irradiation is introduced for high-yield and cost-effective production of mini- or micro-light-emitting diode (LED) display panels. SITRAB materials are special epoxy-based solvent-free pastes. Three types of pot life are studied to obtain a convenient SITRAB process: Room temperature pot life (RPL), stage pot life (SPL), and laser pot life (LPL). In this study, the RPL was found to be 1.2 times the starting viscosity at 25℃, and the SPL was defined as the time the solder can be wetted by the SITRAB paste at given stage temperatures of 80℃, 90℃, and 100℃. The LPL, on the other hand, was referred to as the number of areal laser irradiations for the tiling process for red, green, and blue LEDs at the given stage temperatures. The process windows of SPL and LPL were identified based on their critical time and conversion requirements for good solder wetting. The measured RPL and SPL at the stage temperature of 80℃ were 6 days and 8 h, respectively, and the LPL was more than six at these stage temperatures.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.386-386
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• 2012

For white light emitting diode (LED) applications, it has been reported that Y3Al5O12:Ce3+ (YAG:Ce) in nano-sized phosphor performs better than it does in micro-sized particles. This is because nano-sized YAG:Ce can reduce internal light scattering when coated onto a blue LED surface. Recently, there have been many reports on the synthesis of nano-sized YAG particles using bottom-up method, such as co-precipitation method, sol-gel process, hydrothermal method, solvothermal method, and glycothermal method. However, there has been no report using top-down method. Top-down method has advantages than bottom-up method, such as large scale production and easy control of doping concentration and particle size. Therefore, in this study, nano-sized YAG:Ce phosphors were synthesized by a high energy beads milling process with varying beads size, milling time and milling steps. The beads milling process was performed by Laboratory Mill MINICER with ZrO2 beads. The phase identity and morphology of nano-sized YAG:Ce were characterized by X-ray powder diffraction (XRD) and field-emission scanning electron microscopy (FESEM), respectively. By controlling beads size, milling time and milling steps, we synthesized a size-tunable and uniform nano-sized YAG:Ce phosphors which average diameters were 100, 85 and 40 nm, respectively. After milling, there was no impurity and all of the peaks were in good agreement with YAG (JCPDS No. 33-0040). Luminescence and quantum efficiency (QE) of nano-sized YAG:Ce phosphors were measured by fluorescence spectrometer and QE measuring instrument, respectively. The synthesized YAG:Ce absorbed light efficiently in the visible region of 400-500 nm, and showed single broadband emission peaked at 550 nm with 50% of QE. As a result, by considering above results, high energy beads milling process could be a facile and reproducible synthesis method for nano-sized YAG:Ce phosphors.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.2
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• pp.189-198
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• 2009

As a part of an effort to minimize the polymerization shrinkage which is considered to be a major cause of failed bonds to tooth, newly designed 'Double LED system' was tested in the present study. Analyses were performed on the pattern of micro-leakage and the changes of strain which have occurred during the polymerization process. The results can be summarized as follows: 1. In the strain change, dramatic increase was observed with initiation of polymerization which was followed by subsequent gradual decrease with elapse of time in both the single LED system and double LED system. 2. The single LED system were shown to develop and maintain the maximum stress more than double LED system(p<0.05). 3. Less micro-leakage was found in the double LED system than in the single LED system(p<0.05). From the above-mentioned results, the double LED system can be a very useful tool in a sense of reducing polymerization shrinkage when compared to the single LED system. However, practical problems such as size of curing unit and its application method with its light intensity should be solved before its clinical application.