• 한국정보전자통신기술학회논문지
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• 제4권3호
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• pp.153-157
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• 2011

본 논문에서는 고휘도, 신뢰성, 저 전력 소비, 긴 수명의 장점을 가진 조명으로 사용되는 LED를 이용한 실내 조명제어 가시광통신 시스템을 구현하기 위한 연구를 수행하였으며, 현재 가속화 되고 있는 유비쿼터스 등의 다양한 응용분야의 적용 가능성을 확인하고자 한다. 이러한 시스템을 구현하기 위해 컴퓨터 프로그래밍 언어를 사용하여 Date 신호를 전송하는 가시광 통신 송 수신기를 설계하여 통신 성능 실험을 하였다. 이번 연구 결과 원활한 Date의 송 수신이 이루어지는 실내 조명제어 가시광통신 구현이 가능함을 확인하였다.

• Membrane and Water Treatment
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• 제10권3호
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• pp.223-229
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• 2019

Titania modified by 2-ethylimidazole (2-EI) (denoted as $2-EI-TiO_2$) demonstrated visible light photocatalytic activity for the degradation of organic compounds. $2-EI-TiO_2$ was a bright brown powder that exhibited similar crystallinity and morphology with the control $TiO_2$. A diffuse reflectance spectrum indicated that $2-EI-TiO_2$ absorbs visible light of all wavelengths. X-ray photoelectron spectroscopy (XPS) confirmed the cationic state of nitrogen species (e.g. Ti-O-N) on the surface of $2-EI-TiO_2$. Visible light-illuminated $2-EI-TiO_2$ degraded $10{\mu}M$ 4-chlorophenol (4-CP) by approximately 85% in 4 h. The photochemical activity of $2-EI-TiO_2$ was selective in targeting the organic compound. The repeated use of $2-EI-TiO_2$ decreased the photocatalytic activity for the 4-CP degradation. Experiments using radical scavengers and oxidant probes revealed that the oxidation by photogenerated holes is responsible for the degradation of organic compounds by illuminated $2-EI-TiO_2$ and the role of $^{\bullet}OH$ is negligible.

• 한국재료학회지
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• 제30권12호
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• pp.641-649
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• 2020

A facile microwave assisted solvothermal process is designed for fabricating SnS nanoparticles decorated on graphene nanosheet, which used as visible light driven photocatalyst. Some typical characterization techniques such as XRD, FT-IR, SEM with EDX analysis, and TEM and BET analysis are used to analyse the physical characteristics of as-prepared samples. Spherical SnS nanoparticles are uniformly dispersed on the surface of graphene nanosheet due to ammonia, which can prevent the aggregation of graphene oxide. Meanwhile, microwave radiation provides fast energy that promotes the formation of spherical SnS nanoparticles within a short time. The visible light photocatalytic activity of as-prepared SnS-GR nanocomposites is analysed through photodegradation efficiency of methylene blue with high concentration. According to the higher photocatalytic property, the as-prepared SnS-GR nanocomposites can be expected to be an efficient visible light driven photocatalyst. After five cycles for decolorization, the rate decreases from 87 % to 78 % (about 9 %). It is obvious that the photocatalytic activity of SnS-GR nanocomposite has good repeatability.

• 한국전자통신학회논문지
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• 제14권4호
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• pp.715-722
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• 2019

본 논문은 가시광 통신을 이용한 사용자 인식 시스템의 구현 방법과 시스템 동작 결과를 소개하고 있다. 가시광 통신을 이용한 사용자 인식 시스템은 안드로이드 시스템 기반의 송신부와 오픈소스 컨트롤러 기반의 수신부로 나뉘어져 있다. 송신부 모듈에서는 사용자의 개인 인식 정보 데이터를 코드로 변환하고 이를 안드로이드 기반의 스마트폰 카메라 인터페이스를 사용하여 가시광으로 변환하여 수신부로 전송한다. 수신부에서는 포토다이오드 모듈을 통해 가시광을 수신하고 이를 전기신호로 변환한다. 수신 데이터에 대한 프로세싱 모듈역할은 오픈소스 컨트롤러가 맡게 되며, 본 시스템에서는 AVR 마이크로 컨트롤러 기반의 아두이노를 사용하였다. 버스트모드(burst mode) 방식의 통신이 가능하도록 0111의 비트 패턴을 스타트비트로 설정하고 이를 인식하도록 하였다. 실험 결과, 제안하는 시스템은 가시광을 매개로 맨체스터 데이터 인코딩 (Manchester data encoding)방식의 데이터 송신과 수신이 가능함을 확인하였다.

• 센서학회지
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• 제29권4호
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• pp.243-248
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• 2020

In this study, we applied transition-frequency modulation to prevent the flickering of light-emitting diodes (LEDs) in visible light communication (VLC). In the VLC transmitter, rectangular waveforms with transition frequencies of four and two in each bit time were used for the high and low bits, respectively, in the non-return-to-zero data. In the VLC receiver, an RC-high-pass filter (HPF) was used to eliminate the interference of the 120 Hz noise light from the adjacent lighting lamps, and an SR-latch circuit was used to recover the transmitted signal using spikes from the output of the RC-HPF. This configuration is useful for constructing VLC systems that are flicker-free and resistant to adjacent noise light interference.

• 한국통신학회논문지
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• 제37A권10호
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• pp.834-840
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• 2012

The use of ranging sensors on automobiles is becoming common with the desire of traffic safety by providing drivers the information of the relative distance between the vehicles. In this paper, the LED visible light ranging system different from the conventional ranging systems using the RF signal is investigated. For such a system, we propose a novel ranging algorithm which combines the time-of-flight (TOF) with the CDMA technology. Via the CDMA technology, the TOF ranging system can accurately distinguish the desired ranging signal from the visible light interferences of the neighbor vehicles. In addition, the proposed system can also overcome the light noise from other luminaries, i.e. sun-light, traffic-light, and so on. The simulation results show that the CDMA-based LED ranging system has a significant improvement for the ranging accuracy compared with the case without employing the CDMA.

• 한국안광학회지
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• 제18권3호
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• pp.297-304
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• 2013

목적: 광원에 따른 청광차단렌즈의 청광차단율과 청광비율을 조사하고, 이를 활용한 청광차단렌즈의 처방에 대하여 고찰하였다. 방법: 광원에 따른 청광차단렌즈의 청광차단율과 청광비율의 조사를 위해 UV-VIS 분광광도계를, 청광차단렌즈와 관련된 처방을 평가하는 기준으로 태양광에 대한 청광비율을 이용하였다. 결과: 렌즈의 청광차단율과 청광비율은 광원에 따라 다르게 나타났다. 모든 BLU 광원의 청광비율은 태양광($D_{65}$ 광원)의 청광비율보다 큰 것으로 확인되었다. 태양광의 청광비율과 렌즈 투과광의 청광비율을 통해 각 광원에 적합한 청광차단렌즈들을 선별할 수 있었다. 결론: 청광차단렌즈 처방에 있어서 렌즈의 청광차단율과 청광비율이 광원에 의존하므로 사용자의 광원에 대한 문진이 선행되어야 한다. 태양광의 청광비율에 기준한 렌즈 투과광의 청광비율은 청광차단렌즈의 처방과 관련된 하나의 평가 방법으로 유용하게 활용될 수 있다.

• 센서학회지
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• 제23권5호
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• pp.349-355
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• 2014

In this paper, we developed a new method to transmit multiple visible light channels in time division mode using the AC power line frequency in order to prevent the crosstalk between adjacent optical signals. Synchronizing pulses are generated from the 220 V power line, and one pulse period is subdivided into several time slots for visible light channels. Each channel transmits data in a predefined time slot without interfering adjacent channels. In experiments, synchronizing pulses with a repetition rate of 240 Hz were generated from the 60 Hz power line, and three VLC channels with a bit rate of 9.6 kbps transmitted data independently using the time slots between synchronizing pulses. This configuration is very useful in constructing time division VLC networks for multiple sensors.

• Rapid Communication in Photoscience
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• 제4권3호
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• pp.73-75
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• 2015

Cr(VI) reduction was successfully achieved in the presence of cationic micelles (CMs) under visible light illumination. Micelle formation of cationic surfactants seems to be critical in Cr(VI) reduction. Cr(VI) was reduced very fast above the critical micelle concentration (cmc) of CTAB solutions, but was not reduced at all either below or around the cmc of CTAB. The reduction rate of Cr(VI) was enhanced in the absence of dissolved oxygen, supporting that the removal of Cr(VI) should be achieved via a reductive pathway. When CTAB was substituted by Brij 35 or SDS, the reduction of Cr(VI) was negligible. This indicates that the electrostatic interaction between Cr(VI) and headgroups of surfactants is important in the visible light-induced Cr(VI) reduction in micellar solutions.

• 한국대기환경학회지
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• 제26권6호
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• pp.649-656
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• 2010

Boron-doped $TiO_2$ photocatalysts were synthesized by a modified sol-gel method and their photocatalytic activities were performed and compared with those of pure synthetic and commercial $TiO_2$ catalysts under UV or visible light conditions. Pure $TiO_2$ itself exhibited very negligible photocatalytic performance under visible light conditions in the aspects of toluene decomposition reactions, although significant decomposition potential was observed as expected with UV light conditions. However, boron doping over $TiO_2$ significantly improved photocatalytic activity particularly under visible conditions, where over 95% degradation of toluene was achieved with 1wt% $B-TiO_2$ within 2 hrs. All the decomposition reactions seemed to follow pseudo first-order kinetics. The effects of boron-doping and its characteristics are further discussed through the kinetic studies and comparison of results.