• 한국세라믹학회지
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• 제56권1호
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• pp.98-103
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• 2019

Optical filters to control light wavelength of displays or cameras are fabricated by multi-layer stacking process of low and high index thin films. The process of multi-layer stacking of thin films has received much attention as an optimal process for effective manufacturing in the optical filter industry. However, multi-layer processing has disadvantages of complicated thin film process, and difficulty of precise control of film morphology and material selection, all of which are critical for transmittance and coloring effect on filters. In this study, the composite $TiO_2$, which can be used to control of UV absorption, coated on nano hollow silica sol, was synthesized as a coating material for optical filters. Furthermore, systematic analysis of the process parameters during the chemical reaction, and of the structural properties of the coating solutions was performed using SEM, TEM, XRD and photo spectrometry. From the structural analysis, we found that the 85 nm nano hollow silica with 2.5 nm $TiO_2$ shell formation was successfully synthesized at proper pH control and titanium butoxide content. Photo luminescence characteristics, excited by UV irradiation, show that stable absorption of 350 nm-light, correlated with a 3.54 eV band gap, existed for the $TiO_2$ shell-nano hollow silica reacted with 8.8 mole titanium butoxide solution. Transmittance observed on substrate of the $TiO_2$ shell-nano hollow silica showed effective absorption of 200-300 nm UV light without deterioration of visible light transparency.

• 수산해양기술연구
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• 제31권3호
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• pp.213-219
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• 1995

색광에 대한 감성돔, Acanthopagrus schlegelii [Bleeker]의 행동을 조사하기 위하여, 2가지씩의 서로 다른 색광을 조합하여 수조의 양단에서 동시에 광자극을 가했을 때의 반응을 주간과 야간으로 구분 조사한 결과는 다음과 같다. 1. 수조내에서의 감성돔의 구간별 분포곡선은 중앙구간보다 양단구간에 많이 모여서 대체로 U자형이 되었으며, 주야간의 차이도 다소 있었다. 2. 양색광쪽에서의 평균 분포차는 7.18%(0.35~19.55%)였고, 주간(8.20%) 보다 야간(6.15%)에 더 적었다. 3. 감성돔이 잘 모이는 색광은 주간에는 청색, 황색, 적색, 백색의 순이며, 야간에는 청색, 적색, 황색, 백색의 순으로 나타났다. 4. 조명시간의 경과에 따른 집어율의 변화는 일정한 증감추세를 보이지 않고 계속 불안정하게 변동했다. 5. 두 가지 색광에 대한 집어율의 차는 비교적 뚜렷하지 않았으나, 주간보다 야간에 그 차가 심했다.

• 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.

• 한국정보전자통신기술학회논문지
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• 제16권6호
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• pp.413-419
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• 2023

LED는 조명뿐만 아니라 휴대폰, 자동차, 디스플레이 등과 같은 다양한 분야에 널리 사용되고 있으며, LED 조명과 통신이 융합된 가시광 통신(VLC)이 크게 주목을 받고 있다. 본 논문에서는 일반적인 차량에서 사용되고 있는 적색, 황색 LED를 이용하여 차량 간(V2V) 데이터를 전송할 수 있는 차량 간 가시광 통신시스템을 직접 구현하고 실험하였다. 전위 차량에서 수집된 데이터와 속도 데이터인 서로 다른 데이터들을 차량의 후미등인 적색, 황색 LED를 이용해 NRZ-OOK로 변조하여 가시광으로 각각 전송했으며, 광 검출기(PD)는 가시광 신호를 수신하여 데이터를 복원한다. 형광등과 자연광의 간섭 광의 영향을 감소시키기 위해, 간섭제거를 위한 PD를 설치하였으며, 편광필터와 차동증폭기를 이용한 간섭제거기를 사용하였다. 제안된 가시광 통신시스템이 이상적인 경우, 실내 그리고 실외환경에서 성능을 분석하였다. 실외환경에서 약 30[cm]거리를 유지하고 4800[bps] 전송속도를 갖는 차량 간 데이터전송에서 적색 LED는 약 13.63[dB], 황색 LED는 약 11.90[dB]의 성능 향상을 얻을 수 있음을 알 수 있었다.

• Journal of Biosystems Engineering
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• 제37권4호
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• pp.265-270
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• 2012

Purpose: An analytic method to design excitation and emission filters of a multispectral fluorescence imaging system is proposed and was demonstrated in an application to poultry fecal inspection Methods: A mathematical model of a multispectral imaging system is proposed and its system parameters, such as excitation and emission filters, were optimally determined by linear discriminant analysis (LDA). An alternating scheme was proposed for numerical implementation. Fluorescence characteristics of organic materials and feces of poultry carcasses are analyzed by LDA to design the optimal excitation and emission filters for poultry fecal inspection. Results: The most appropriate excitation filter was UV-A (about 360 nm) and blue light source (about 460 nm) and band-pass filter was 660-670 nm. The classification accuracy and false positive are 98.4% and 2.5%, respectively. Conclusions: The proposed method is applicable to other agricultural products which are distinguishable by their spectral properties.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권6호
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• pp.2483-2503
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• 2016

Traffic congestion is a severe problem in many modern cities around the world. Real-time and accurate traffic congestion identification can provide the advanced traffic management systems with a reliable basis to take measurements. The most used data sources for traffic congestion are loop detector, GPS data, and video surveillance. Video based traffic monitoring systems have gained much attention due to their enormous advantages, such as low cost, flexibility to redesign the system and providing a rich information source for human understanding. In general, most existing video based systems for monitoring road traffic rely on stationary cameras and multiple vehicle tracking method. However, most commonly used multiple vehicle tracking methods are lack of effective track initiation schemes. Based on the motion of the vehicle usually obeys constant velocity model, a novel vehicle recognition method is proposed. The state of recognized vehicle is sent to the GM-PHD filter as birth target. In this way, we relieve the insensitive of GM-PHD filter for new entering vehicle. Combining with the advanced vehicle detection and data association techniques, this multiple vehicle tracking method is used to identify traffic congestion. It can be implemented in real-time with high accuracy and robustness. The advantages of our proposed method are validated on four real traffic data.

• 천문학회지
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• 제30권1호
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• pp.83-94
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• 1997

We have identified the candidates for the primordial galaxies in the process of formation in the Hubble Deep Field (hereafter HDF). In order to select these objects we have removed objects brighter than 29-th magnitude in the HDF images and smoothed the maps with the Gaussian filters with the FWHM of 0.8' and 4' to obtain the difference maps. This has enabled us to find. very faint diffuse structures close to the sky level. Peaks are identified in the difference map for each of three HDF chips with three filters (F450W, F606W, and F814W). They have the apparent AB magnitudes typically between 29 and 31. The objects identified in different wavelengths filters have a strong cross-correlations. The correlation lengths are about 0.8'. This means that an object found in one filter can be also found as a peak within 0.8' separation in another filter, thus telling the reality of the identified objects. This angular scale is also the size of the primordial galaxies which have strong color fluctuations on their surfaces. Their large-scale distribution quite resembles that of nearby galaxies, supporting the idea that these objects are ancestors of the present bright galaxies forming at statistically high density regions. Inspections on individual objects show that these primordial galaxy candidates have tiny multiple glares embedded in diffuse backgrounds. Their radial light distributions are quite different from that of nearby bright galaxies. We may be now looking at the epoch of galaxy formation.

• IEIE Transactions on Smart Processing and Computing
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• 제1권1호
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• pp.8-16
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• 2012

An image obtained from a low light environment results in a low-exposure problem caused by non-ideal camera settings, i.e. aperture size and shutter speed. Of particular note, the multiple color-filter aperture (MCA) system inherently suffers from low-exposure problems and performance degradation in its image classification and registration processes due to its finite size of the apertures. In this context, this paper presents a novel method for the color enhancement of low-exposure images and its application to color shift model-based MCA system for image refocusing. Although various histogram equalization (HE) approaches have been proposed, they tend to distort the color information of the processed image due to the range limits of the histogram. The proposed color enhancement algorithm enhances the global brightness by analyzing the basic cause of the low-exposure phenomenon, and then compensates for the contrast degradation artifacts by using an adaptive histogram specification. We also apply the proposed algorithm to the preprocessing step of the refocusing technique in the MCA system to enhance the color image. The experimental results confirm that the proposed method can enhance the contrast of any low-exposure color image acquired by a conventional camera, and is suitable for commercial low-cost, high-quality imaging devices, such as consumer-grade camcorders, real-time 3D reconstruction systems, digital, and computational cameras.

• 전기학회논문지P
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• 제65권4호
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• pp.285-291
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• 2016

A light-emitting diode (LED) has been increasingly applied to various industrial fields and general lightings because of its high efficiency, low power consumption, environment-friendly characteristic and long lifetime. To drive the LED lighting, a power converter with the constant output current is needed. Among many power converters, the flyback converter is chosen by many converter designers due to high power density, structural simplicity, and miniaturization. In this converter, an electrolytic capacitor is generally chosen for the stabilization of the DC voltage because of having the large capacitance and the low price. However, the disadvantages are the short expected life time and 120Hz ripple currents on the converter output node. In this paper, a single-stage dimmable PFC DCM flyback converter without the electrolytic capacitor is proposed to prolong the lifetime of the LED driver. For the long lifetime of the converter, the polyester film capacitor with the small capacitance is substituted for the electrolytic capacitor on the output node and an LC resonant filter is added to damp 120Hz ripple current. The proposed converter is verified through the simulation and the experimental works.

• Journal of the Optical Society of Korea
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• 제18권6호
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• pp.766-771
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• 2014

Single-ring all-pass filters with various coupling ratios are designed, fabricated, and characterized to assess the validity of the split-step time-domain modeling approach, which is considered for direct simulation of time-domain characteristics, such as optical delay, of various ring resonator devices. When the coupling ratio of the single-ring all-pass filter is 0.4 and 0.8, the delay time is measured to be about 145 and 42 ps respectively, which is comparable to the time-domain modeling results of 151 and 47 ps respectively. The measurements for two- and three-ring all-pass filters are also found to agree quite well with the simulation results. With these results it is confirmed that the split-step time-domain model could be efficiently incorporated into an optical-communication simulation module for ring resonator delay components in an all-optical packet switching system.