• 한국정보전자통신기술학회논문지
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• 제16권6호
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• pp.406-412
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• 2023

본 논문에서는 주변광으로 인한 잡음이 적외선을 사용한 반사형 PPG 측정 장치에 미치는 영향을 고찰하였다. 주변광으로 인한 잡음은 일반적인 상황과 특수한 상황으로 나누어 고찰하였으며, 일반적인 상황은 시간과 주변 광원의 변화로 인한 잡음을 무작위로 관찰하였고, 특수한 상황은 할로겐램프를 사용하여 측정 장치와 광원과의 거리에 따른 잡음 변화를 관찰하였다. 실험은 각각의 상황에 따라 PPG 신호를 실시간으로 측정하고 데이터를 획득하였으며, 측정된 데이터는 시간 영역과 주파수 영역에서 분석하였다. 먼저 일반적인 상황 실험을 통해 주변광의 밝기에 따라 잡음이 커짐을 육안으로 확인하였고, 주파수 분석을 통해 백색잡음, 전력선 잡음, 회로 내부 잡음이 발생함을 확인하였다. 또한 할로겐램프를 사용하여 주변광과의 거리 변화에 따른 잡음의 변화를 실험하고 SNR을 계산하였다, 실험 결과, 278.3W/m²의 복사조도를 갖는 50cm 거리에서는 3.2dB의 SNR을 나타내었고 그 이하의 SNR에서는 정상적인 측정이 어려움을 확인하였으며, 27.7W/m²의 복사조도를 갖는 2m의 거리에서 18.2dB 값을 나타내었고 그 이상 값에서 필터를 통해 정상적인 PPG 측정이 가능함을 확인하였다.

• 대한의용생체공학회:의공학회지
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• 제35권5호
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• pp.125-131
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• 2014

The purpose of this study is to verify the utility of reflected photoplethysmography sensor using two green light emitting diodes that influenced by ambient light. Recently it has been studied that green light emitting diode is suitable for light source of reflected photoplethysmography sensor at low temperature and high temperature. Another study showed that, green light is better for monitoring heart rate during motion than led light. However, it has a bad characteristic about ambient light noise. To verify the utility of reflected photoplethysmography sensor using green light emitting diode, this study measures the photoplethysmography signal that is distorted by ambient light and will propose a solution. This study has two parts of research method. One is measurement system that composed sensor and board. The sensor is made up PE-foam and Non-woven fabric for flexible sensor. The photoplethysmography signal is measured by measurement board that composed high-pass filter, low-pass filter and amplifier. Ambient light source is light bulb and white light emitting diode that has three steps brightness. Photoplethysmography signal is measured with lead II electrocardiography signal at the same time and it is measured at the finger and radial artery for 1 minute, 1000 Hz sampling rate. The lead II electrocardiography signal is a standard signal for heart rate and photoplethysmography signal that measured at the finger is a standard signal for waveform. The test is repeated 3 times using three sensor. The data is processed by MATLAB to verify the utility by comparing the correlation coefficient score and heart rate. The photoplethysmography sensor using two green light emitting diodes is shown better utility than using one green light emitting diode and red light emitting diode at the ambient light. The waveform and heart rate that measured by two green light emitting diodes are more identical than others. The amount of electricity used is less than red light emitting diode and error peak detectability factor is the lowest.

• 한국통신학회논문지
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• 제40권10호
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• pp.2062-2064
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• 2015

본 논문에서는 LED 패널의 신호를 받아 모바일 단말기에 장착된 이미지 센서를 통하여 임의의 위치에 있는 모바일 단말기의 위치를 추정하는 실내 측위 알고리즘을 제안하였다. 측위 성능평가를 위하여 실내에 존재하는 잡음 환경을 고려하였고, 제안한 알고리즘은 잡음환경에 무관하게 높은 측위 성능을 보임을 입증하였다.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.459-465
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• 2014

Visible light communications (VLC) using the intensity modulation of light-emitting diodes (LEDs) provides a new communication medium to overcome the shortage of radio spectrum, and allows reuse of LED lighting infrastructures. Orthogonal frequency-division multiplexing (OFDM) was introduced to VLC for its merits in mitigating the fading effects resulting from delay spread, and in avoiding low-frequency ambient interference. Noise and clipping are two major factors that degrade the performance of OFDM in VLC. A larger signal easily overcomes noise, but experiences impairment by clipping. Therefore, degradation due to clipping has a trade-off relationship with that due to noise, depending on the signal amplitude of OFDM. In this paper, the optimal signal amplitude in the trade-off is obtained by simulation when the dimming and LED intensity are given. The former indicates a user's requirement for lighting, and the latter represents the channel quality. The required LED intensity-to-noise ratio, as the channel quality that guarantees dimming as well as an adequate bit-error rate (BER), is also discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.411-414
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• 2000

Optical Triangulation Probes (OTPs) are widely used for their simple structure. high resolution, and long operating range. However, errors originating from speckle, inclination of the object, source power fluctuation, ambient light, and noise of the detector limit their usability. In this paper, we propose new design criteria for an error-reduced OTP. The light source module for the system consists of an incoherent light source and a multimode optical fiber for eliminating speckle and shaping a Gaussian beam Intensity profile. A diffuse-reflective white copy paper, which is attached to the object, makes the light intensity distribution on the change-coupled device(CCD). Since the peak positions of the intensity distribution are not related to the various error sources, a sub-pixel resolution signal processing algorithm that can detect the peak position makes it possible to construct an error-reduced OTP system

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.10-13
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• 2009

We have developed variety of LCD technologies for the out-door display, which improve out-door readability as well as reliability from external impacts. This improvement was made possible by new approach on LCD cell optical design and modification of LCD surface, which allows surrounding light to be transmitted to enhance the visibility and at the same time filtering out light, which are considered to be source of noise in terms of visibility. This technology enables users to maintain high display performance in both in-door & out-door environments moreover alternatively choosing in-door/out-door.

• 한국ITS학회 논문지
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• 제18권1호
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• pp.83-90
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• 2019

LED조명의 강점을 토대로 LED조명이 보급되고 있으며, 다양한 정부정책이 시행되고 있다. 조명을 활용한 무선통신 기술인 VLC 연구가 활발히 이루어지고 있으며, 많은 연구를 통해서 고속 데이터 전송기와 같은 일반적인 LED 광원을 사용할 수 있다는 것이 증명되었다. 그러나 여전히 주요 문제 중 하나로 라디오 방송의 잡음과 유사한 빛의 간섭문제가 있다. 이에 본 논문에서는 스펙트럼 분리형 VLC 채널을 위한 광 필터를 사용하여 주변 조명의 간섭을 제거하기 위한 모델을 제안하였다. 제안한 모델의 검증을 위하여 다양한 고휘도 RGB LED 모듈을 활용하여 비교분석을 진행하였으며, 추가로 실생활에 적용되어 활용 중인 고휘도 LED 조명을 활용한 실험을 통한 적용성을 검증하였다.

• 한국통신학회논문지
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• 제40권3호
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• pp.595-601
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• 2015

These days, research related to Intelligent Transportation System (ITS) technology is being widely considered. ITS is inevitable for future transportation systems to reduce accidents, congestion, and offer a smooth flow of traffic. The use of Visible Light Communication (VLC) in ITS systems has been considered widely because of its EMC/EMI free and LED infrastructure reusable properties. Among the VLC schemes, this study analyzed the performance of the Color Shift Keying (CSK) scheme under a Vehicle-to-Infrastructure (V2I) downlink scenario to verify the capability of CSK as a communication tool for ITS. By modeling daylight noise using the modified Blackbody radiation model, this study examined the performance of V2I VLC under daytime conditions. The relationship between BER, the communication distance, and the amount of ambient-light noises under the pre-described V2I scenario were determined by simulations.

• 디자인학연구
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• 제16권3호
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• pp.381-390
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• 2003

이 논문은 산후관리시설의 현 실태와 시설을 이용한 사용자들의 만족도를 비교 조사하여 산후관리시설의 효율성과 만족도를 높이기 위한 기초 자료를 제공하는 것을 목적으로 연구된 것이다. 상세한 연구를 위해 산후관리시설 중 산모실로 연구 대상을 한정 하였다. 이 논문을 위한 기초 자료는 240명의 산모를 대상으로 한 설문조사와 산후관리시설에 대한 관찰 조사를 병행하여 수집하였다. 설문조사는 2003년 3월 8일부터 2003년 3월 29일에 걸쳐 실시되었고 이 자료는 SPSS-WIN을 이용하여 빈도분석 하였다. 논문의 주요 결론은 다음과 같다. 첫째, 사용자의 만족도를 결정하는 부분에 있어 산모실의 소음, 통풍, 자연채광 같은 환경요소가 대단히 중요함을 알 수 있었다. 둘째, 산모실 면적, 창문의 유무, 개인 화장실 및 샤워실 등의 기능적인 요소들도 산모들의 이용 만족도에 중요한 요소가 됨을 발견 하였다.

• 전기학회논문지P
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• 제57권4호
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• pp.404-407
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• 2008

Because of directly receiving the thing in which a microwave is reflected and comparing the frequency, the microwave sensor with doppler effect completely overcomes the problem of the passive infrared sensor. The microwave sensor with doppler effect well operates about a temperature, the dust, and the peripheral noise because of being dull in the most of ambient conditions. The system developed in this research is the electricity saving detection sensor which it senses the real time action of a man as the microwave sensor and automatically turns on the electric lamp and turns off, minimizes the electrical energy consumption. Since the microwave sensor is not influenced in the light, the dust, and the natural element like the ambient temperature, the effectiveness is considered to be superior to the passive infrared sensor being used currently. There was the energy reduction effect more than about 60% in the performed example which established this system. When this was compared with the construction cost, the cost of establishing payback period was about 1-1.5 year. The microwave sensor with doppler effect developed from this research result is convinced in the future to do enough for the electric energy saving.