• 한국통신학회논문지
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• 제36권12B호
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• pp.1595-1600
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• 2011

IM/DD 방식을 이용한 가시광 무선 통신의 성능 저하를 발생시키는 인공광과 태양광에 의한 잡음 레벨을 분석하였다. 통신 성능을 확인하기 위해 LED에 QPSK로 변조된 50ksymbol/sec의 신호를 2MHz의 부반송파에 전송하였으며 PD를 통해 수신된 신호의 EVM과 스펙트럼을 분석하였다. 또한 차광막을 이용하여 신호의 성능을 향상시켰으며 이를 통해 IM/DD방식으로 실외 가시광 통신이 가능함을 확인하였다.

• 한국정보통신학회논문지
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• 제16권11호
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• pp.2431-2436
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• 2012

본 논문에서는 LED(Light Emitting Diode)조명을 통해 통신을 접목하여 이용이 간편한 가시광통신 시스템을 구현 하고자 한다. LED 가시광 통신을 실현시키고자 송신부에는 1~12개의 LED 발광 소자와 수신부에는 가변 PD(Photo Diode)인 센서를 사용한다. LED가시광통신을 하고자 개발이 이루어진 송 수신부의 초기 거리 값은 0~1.5m 이상으로 하고, 전체 시스템 전송 속도는 수 천 kbps의 가변성을 가지는 가시광 미디어 전송 시스템을 이루었다. LED 모듈의 전체적인 효율 증대를 위해 렌즈 착용시와 미착용시 성능 실험을 하여 효율 측정을 하였으며, 구현된 연구의 성능 분석을 위한 기존 PC 모듈에 LED 및 PD를 구성하여 LED 개수, 전송속도에 따른 최대 송수신의 통신 거리를 실험하고 응용 방법과 가능성에 대해서 확인하고자 한다.

• 대한치과교정학회지
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• 제34권4호
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• pp.333-342
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• 2004

기존의 가시광선 중합기와 비교해서 plasma are light와 LED) 방식의 중합기를 이용해 브라켓을 치아표면에 접착한 후 탈락시키는 실험을 시행해 각각의 중합방식별로 전단결합강도와 접착파절양상을 비교함으로써 임상에서의 유용성을 평가하고자 하였다. 교정치료를 위해 발거한 상, 하악 소구치 60개를 윈통형의 레진블록에 매몰하여 시편을 제작하였다. 광중합형 접착레진인 Transbond XT를 이용하여 광중합 방식별로 조건(가시광선 중합기는 40초, LED방식의 중합기는 20춘, 그리고 plasma arc light 방식의 중합기는 3초)에 따라 브라켓을 접착한 후 만능물성실험기로 전단결합강도를 측정하고 브라켓 기저면을 광학현미경으로 관찰해 접착파절양상을 관찰하여 다음과 같은 결과를 얻었다. 1. 가시광선 중합방식과 LED 중합방식으로 중합시킨 군간에 전단결합강도의 유의성 있는 차이는 없지만 plasma arc Light방식으로 중합시킨 군은 앞의 두 군에 비해 유의성이 있게 작은 간을 나타내었다(p>0.05). 2. 가시광선 중합방식으로 중합한 군과 LED방식을 이용한 군에서는 파절양상이 거의 유사하게 나타났다. 두 군 모두 잔류접착제가 치아면에만 있는 경우가 제일 적은 비율을 도였으며 브라켓 기저면에 50% 이상의 집착제가 남아 있는 양상이 더 큰 비율을 보였다. 3. Plasma arc light 로 중합시킨 경우에는 접착제가 브라켓 기저면에 50% 이하로 남아있는 양상이 큰 비율로 나타났으며 잔류 접착제 전체가 치아면에 남아 있는 경우는 15%였다. 이상의 실험결과 plasma arc light를 이용한 중합 방식이 가시광선이나 LED 방식을 이용한 중합 방식에 비해 유의성 있게(p>0.05) 낮은 전단결합강도를 보였으나 세 방식 모두 인상적으로 사용하기에 충분한 전단결합강도를 보여 유용하게 사용할 수 있음을 알 수 있었다.

• 한국정보전자통신기술학회논문지
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• 제11권5호
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• pp.608-614
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• 2018

ICT기술 확산과 더불어 효율적인 정보 운용을 위해 다양한 프로토콜의 근거리 무선통신기술이 적용되고 있다. 하지만 근거리 무선통신의 제한사항으로 인하여 주파수 혼선 및 창고형 공장 등 주파수 환경이 좋지 않은 곳에서 통신이 원활하지 못하다. 이에 대한 대안이 필요한 시점에 LED 기술의 발달과 빠른 보급을 통한 인프라 확충으로 LED 기반 가시광 통신이 대안으로 주목되고 넒은 분야에 확산되고 있다. 또한 신재생에너지 활성화에 맞춰 태양광 패널 또한 빠른 보급으로 인프라가 확충되어 있다. 이러한 상황에서 PD를 활용한 가시광 통신은 PD의 수신각도 및 주변 환경의 빛으로 인해 LoS가 확보되고 주변의 빛에 영향이 적은 초근거리 환경에서 제한적으로 적용되어 왔다. 이를 해결하고자 현재 인프라가 확충되어 있는 LED 조명과 수신 면적이 넓은 태양광 패널을 이용하여 가시광 통신을 구현하였으며, 주변 환경 빛에서도 정확한 데이터를 복원을 위한 회로를 제안하였다. 본 연구결과를 통해 태양광 패널을 수신부로 하는 가시광 통신 연구의 기반 자료로 활용 되어 가시광 통신이 더욱 넓게 응용될 것으로 기대한다.

• Restorative Dentistry and Endodontics
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• 제17권2호
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• pp.307-330
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• 1992

The aim of this study was to investigate the physical properties of visible light curing Glass Ionomer cement for restorative esthetic filling. The control group was the autopolymerizing GC Fuji II Glass Ionomer cement (2.2: 1 P/L ratio) and the experimental groups were made by following procedure. To induce the polymerization by visible light, the powder of GC Fuji II GI cement and the liquid of Vitrabond for base & liner were mixed in an amalgam capsule with 2.5:1, 3.0:1, 3.5:1 P/L ratio (% wt/wt). After fabrication of specimens, compressive strength, fracture toughness ($K_{IC}$) Scanning Electron Microscope and X-ray Diffraction, water-leachable content, marginal leakage and surface roughness were studied. The results were as follows: 1. Only experimental No. 1 group (visible light curing) showed less compressive strength than control group 1 hour after curing. Strength was increased with aging in all groups, so the compressive strength of light curing groups was no less than that of autopolymerizing group after 3 weeks. 2. Experimental No.3 group (visible light curing) was inferior to No.2 group (visible light curing) in fracture resistance but light curing groups were more resistant to fracture than autopolymerizing group and showed ductile fracture pattern as compared with the brittle fracture pattern of autopolymerizing group. 3. From scanning electron microscopic image, various sized unreacted powder particles, surrounded by silica gel, were embedded in polysalt matrix. Light curing groups showed little crack and more dense unreacted particles than autopolymerizing group. 4. From X-ray diffraction analysis, GC Fuji II Glass Ionomer cement powder and all groups showed glassy appearance but light curing groups seemed to be more intensive in crystaline than autopolymerizing group. S. The most significant dissolution was shown in early setting period in all group. Light curing groups were dissolved less than autopolymerizing group. 6. Marginal leakage was not different significantly in case of cavity margin composed of same tooth structure (ex. only enamel margin, only dentin margin) but much more leakage was shown in dentin/cementum margin than enamel margin. In only case of only enamel margin, light curing groups were superior to autopolymerizing group. 7. All groups showed relatively smooth surface, which irregularity was less than $1{\mu}m$. Light curing groups were smoother than autopolymerizing group.

• 대한한의진단학회지
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• 제15권2호
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• pp.149-158
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• 2011

Objectives: The objective of this study is to compare the colour intensity of tongue body and that of tongue coat under the visible light and the ultraviolet light. Methods: We selected 7 subjects with completely or partially peeled tongue coat among the recruited 94 adults for the experiment. We took each tongue picture under the visible light and the ultraviolet light (315-400 nm) and then extracted sample images from the tongue body and tongue coat regions. Mean, median and mode of colour intensity from the sample images were calculated in 256 RGB system. Results: The green and the blue colour intensities of the tongue coats were significantly higher than those of the tongue bodies under the visible light. In all channels, the red, green and blue, the colour intensities of the tongue coats were significantly higher than those of the tongue bodies under the ultraviolet light. The colour differences between tongue coats and tongue bodies under the ultraviolet light were significantly higher than the colour differences under the visible light. Especially the colour difference under the ultraviolet light was highest in the green channel. Conclusions: We suggested that green colour image of the RGB system taken under the ultraviolet light could be used for more easy separating tongue coat region from tongue body.

• 미생물학회지
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• 제6권4호
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• pp.122-130
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• 1968

Action of various wavelengths of visible light on ultraviolet-radiation damage to haploid yeast cells, Saccharomyces cerevisiae 23971, was studied. The results were obtained on the basis of the survival and respiration rates by pre- and post-illuminations of various wavelengths before and after U.V.-irradiations on the yeast cells. Among the wavelengths tested, 635 $m{\mu}$, 429 $m{\mu}$ and white light which caused increase of respiration in pre-treatment alone, induced less resistance to the U. V.-damage than in the control, in both pre- and U.V.-treatment. On the contrary, such wavelengths as 574 $m{\mu}$and 530 $m{\mu}$, showing a weak effect on respiration in pre-treatment increased the susceptability to U.V.-radiation. Photoinactivation was generally obtained by both pre- and post- illuminations along with U.V.-treatment. At 635 $m{\mu}$ the PI rate was the lowest and also a low PI rate was shown at 429 $m{\mu}$. But 429 $m{\mu}$, in the post-treatment of the yeast cells pre-treated by the white light and the darkness respectively, showed the highest PI rate. In both pre- and post- treatment of 574, 530 and 473 $m{\mu}$,the PI rates were high to the same degree. Post-treatments of the wavelengths on U.V.-treated yeasts incubated rather under the white light than the darkness induced lower PI rate. It is assumed that there are great differences in action even of the same wavelength, depending upon the various combination of pre- and post-treatments, and that, moreover, the action of various wavelengths of visible light on U.V.-damage on the cells are concerned with the doses and dose rates of U.V. and visible lights. These observations led to an interpretation that each wavelength of visible light might exert distinctively different effects oil U. V.-damage, mainly causing the inhibition or stimulation of enzymes in the yeast cells.

• Bulletin of the Korean Chemical Society
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• 제32권5호
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• pp.1657-1661
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• 2011

In this study, CdSe-$TiO_2$ photocatalyst were synthesized by a facile solvothermal method and characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis and UV-vis diffuse reflectance spectrophotometer. The photocatalytic activity was investigated by degrading methylene blue (MB) in aqueous solution under irradiation of UV light as well as visible light. The absorbance of degraded MB solution was determined by UV-vis spectrophotometer. The results revealed that the CdSe-$TiO_2$ photocatalyst exhibited much higher photocatalytic activity than $TiO_2$ both under irradiation of UV light as well as visible light.

• 센서학회지
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• 제27권3호
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• pp.143-149
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• 2018

In this paper, we introduce an edge-spike modulation method for visible light communication (VLC). This method is effective in preventing LED flicker and 120 Hz noise interference in base-band VLC. In the VLC transmitter, edge-spikes are generated by passing the digital data through a simple RC-high pass filter (HPF). The LED modulation of the edge-spikes does not change the average power of the LED light; thus it prevents LED flicker. In the VLC receiver, the 120 Hz noise from other lighting lamps is easily eliminated by RC-HPF, while the edge-spike signal is detected normally. In our experiment, the message of an air-quality sensor was successfully transmitted using edge-spike modulation. This structure is useful in constructing, e.g., wireless gas monitoring sensor systems to warn and prevent harmful gas leakage accidents in buildings using LED light.

• 센서학회지
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• 제25권3호
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• pp.189-195
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• 2016

In this paper, we newly introduce a visible light communication (VLC) repeater using the LED array in an LED lamp. The LED array is used for a light source in the repeater, which radiates light both for illumination and data transmission. A VLC repeater is made by adding some electronic circuits to the LED array including a photodetector, a demodulator, and a modulator. The repeater is installed on the ceiling of a room like a conventional LED lamp, receives the VLC signal from an arbitrary transmitter, recovers data, and radiates the signal to wide area in the room. We used a carrier frequency of 100 kHz for the uplink from a transmitter to the repeater, and 500 kHz for the downlink from the repeater to a receiver. The repeater is useful for increasing the transmission path to wide area over the obstacles that may exist between VLC transmitters and receivers.