• 인터넷정보학회논문지
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• 제9권5호
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• pp.117-130
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• 2008

본 논문은 LBG 알고리즘을 이용하여 다양한 조명에 노출된 의상들의 색상 유사성을 안정적으로 판단하는 방법을 제안한다. 색상 유사성 판별을 위하여 기존에 대표적으로 사용되어왔던 히스토그램 인터섹션이나 누적 히스토그램 방법은 조명 변화에 민감하게 반응하여, 동일한 의상 색상이라 할지라도 서로 다른 조명환경에서는 서로 상이한 색상 판별 결과를 나타낸다. 본 논문에서는 조명에 의한 영향을 줄이고 색상 자체의 분포 특성을 분석하기 위하여 조명조건의 변화에도 일관된 특성을 유지하는 색조와 채도 컬러 성분에 대한 분포 특성을 분석한다. 색조와 채도에 의해 정의되는 2차원 공간에서 각 의상 영상에 대한 색상 분포를 분석하기 위하여 LBG 알고리즘에 의한 비모수적 클러스터링 기법을 적용하고, 클러스터링 결과 얻어진 두 영상의 클러스터 사이의 평균 유클리디안 거리 값을 계산하여 이를 색상 유사성을 판단하는 유사 값으로 정의한다. 제안 기법의 안정성을 입증하기 위하여 서로 다른 조명 환경에서 촬영된 12벌의 의상에 대하여 기존 히스토그램 분석 기법을 기반으로 한 색상 유사성 판별 결과와 제안 기법의 적용 결과를 비교하였다. 실험 결과 제안기법은 동일한 의상 쌍과 상이한 의상 쌍에 대하여 구분을 지을 수 있는 객관적 기준 정의가 용이하였고, 기준에 따른 의상의 동일성 판별 실험에서 91.6%의 판별 성공률을 얻었다.

• 한국산학기술학회논문지
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• 제19권7호
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• pp.36-41
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• 2018

미광증폭장비는 밤과 같이 어두운 환경에서 주로 가시광선 대역의 약한 빛을 증폭시켜 육안으로 관측할 수 있을 정도의 밝기로 만들어주는 장비이다. 이러한 방식은 어느 정도의 약한 빛이 존재하는 환경에서는 그 증폭 효과를 제대로 발휘하여 선명한 영상을 얻을 수 있지만, 달빛조차 존재하지 않는 극 저조도 환경에서는 기본적으로 증폭시킬 빛이 부족하여 출력 영상에 많은 노이즈로 인하여 화면의 선명도가 저하된다. 본 연구에서는 이러한 극 저조도 환경에서 발생하는 미광증폭 장비의 출력 노이즈를 다중 필터와 이방성 확산을 이용하여 화질을 개선하는 방법을 제안하였다. 실험을 위하여 극 저조도 조건에 맞는 환경을 구성한 상태에서 미광증폭장비의 출력 영상을 촬영한 후, 화질 개선을 위한 신호처리를 하였다. 신호처리를 위한 필터의 구성은 영상에 나타나는 주된 노이즈인 점 노이즈 제거와 가우시안 노이즈의 효과적인 제거를 위하여 메디안 필터, 위너 필터를 적용시킨 후 이방성 확산을 이용하였다. 실험 결과 화질이 개선됨을 육안으로 확인할 수 있었고, 정량 지표인 PSNR 및 SSIM으로 비교하여 측정한 방법에서도 모두 개선된 값을 보여주었다.

• 한국전기전자재료학회논문지
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• 제36권2호
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• pp.143-150
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• 2023

Underwater wireless communication is a challenging issue for realizing the smart aqua-farm and various marine activities for exploring the ocean and environmental monitoring. In comparison to acoustic and radio frequency technologies, the visible light communication is the most promising method to transmit data with a higher speed in complex underwater environments. To send data at a speedier rate, high-performance photodetectors are essentially required to receive blue and/or cyan-blue light that are transmitted from the light sources in a light-fidelity (Li-Fi) system. Here, we fabricated high-performance organic phototransistors (OPTs) based on P-type donor polymer (PTO2) and N-type acceptor small molecule (IT-4F) blend semiconductors. Bulk-heterojunction (BHJ) PTO2:IT-4F photo-active layer has a broad absorption spectrum in the range of 450~550 nm wavelength. Solution-processed OPTs showed a high photo-responsivity >1,000 mA/W, a large photo-sensitivity >10³, a fast response time, and reproducible light-On/Off switching characteristics even under a weak incident light. BHJ organic semiconductors absorbed photons and generated excitons, and efficiently dissociated to electron and hole carriers at the donor-acceptor interface. Printed and flexible OPTs can be widely used as Li-Fi receivers and image sensors for underwater communication and underwater internet of things (UIoTs).

• 한국인터넷방송통신학회논문지
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• 제13권3호
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• pp.1-7
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• 2013

다양한 간섭환경에서 MIMO 기반 가시광 무선 통신 시스템의 성능 분석을 위해서 LED 패널을 고정하고, PD를 가진 단말기를 움직여 모의실험을 수행하으며 MIMO 기술을 기반으로 하여 외부광에 의한 간섭이 통신 채널 품질 변화에 미치는 영향을 분석하였다. 또한 채널에서의 전송시간 지연에 의한 왜곡은 등화기를 사용하여 보상해 주어야 하며, 특히 데이터 전송 속도가 고속이 될수록 등화기의 사용이 절대적으로 필요하게 된다. 따라서 본 논문에서는 VLC 시스템의 변조방식에 따라 채널 등화를 이용한 BER성능을 분석하였다.

• 한국실내디자인학회논문집
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• 제20권6호
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• pp.282-290
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• 2011

The public festival has a positive function to produce more pleasure and better life to urban residents on viewpoint of culture marketing. A research of relation between urban festival's media light environmental and personality type of audiences would give a design guide line on selection of festival media contents. The scope of study festival bounds three urban fesitvals from two thousand eight to two thousand ten. The personaliy indicator is used by self-mootioring scale called NEO-PI-R that Synyder, psychologist established in 1987. This indicator divides into five classes - N: Neutroticism, E: Extaversoon, O: Openness, A: Agreeableness, C: Conscientiousness. As a result, Anaysis of urban festival's media light environments considering five personality type of audiences are described, N type prefers the change a lot and low stability. E type prefers three dimensional video and dynamic production with passionate pressure. O type prefers radiates objects to promote the imaginative creatures with speculation. A type prefers contemplation arts with one way direction. C type prefers orderly art layout with accomplishing intention. The statistics datas anaynize ten factors to describe the urban complicated fesitival guide line clearly.

• 천문학회지
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• 제38권2호
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• pp.149-151
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• 2005

We have studied the environmental effect on optical-NIR color gradients of 273 nearby elliptical galaxies. Color gradient is a good tool to study the evolutionary history of elliptical galaxies, since the steepness of the color gradient reflects merging history of early types. When an elliptical galaxy goes through many merging events, the color gradient can be get less steep or reversed due to mixing of stars. One simple way to measure color gradient is to compare half-light radii in different bands. We have compared the optical and near infrared half-light radii of 273 early-type galaxies from Pahre (1999). Not surprisingly, we find that $r_e(V)s$ (half-light radii measured in V-band) are in general larger than $r_e(K)s$ (half-light radii measured in K-band). However, when divided into different environments, we find that elliptical galaxies in the denser environment have gentler color gradients than those in the less dense environment. Our finding suggests that elliptical galaxies in the dense environment have undergone many merging events and the mixing of stars through the merging have created the gentle color gradients.

• 한국재료학회지
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• 제27권5호
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• pp.255-262
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• 2017

Reactive oxygen species (ROS) can be produced by interactions between sunlight and light-absorbing substances in natural water environments and can completely destroy various organic pollutants in waste water. In this study, we used graphene oxide modified $Ag_2Se$ nanoparticles to enhance photochemically generated oxygen (PGO) species activity. Surface area and pore volumes of the $Ag_2Se-graphene$ ($Ag_2Se-G$) samples showed catastrophic decrease due to deposition of $Ag_2Se$. The generation of reactive oxygen species was detected through the oxidation reaction of DPCI to DPCO. The photocurrent density and the PGO effect increase in the case of the use of modified graphene. The PGO effect of the graphene modified with $Ag_2Se$ composites increased significantly due to a synergetic effect between graphene and the $Ag_2Se$ nanoparticles. The photocatalytic activity of sample was evaluated by measuring the degradation of organic pollutants such as methylene blue (MB) and industrial dyes such as Texbrite BA-L (TBA) under visible light.

• 대한공간정보학회지
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• 제24권2호
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• pp.25-35
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• 2016

Since a sophisticated location determination technology (LDT) is necessary for accurate positioning in urban area environments, numerous studies related to the LDT using the RFID (Radio Frequency IDentification) technology have been implemented for real-time positioning and data transferring. However, there are still lots of unsolved questions especially regarding what to use as base stations and what are corresponding results under the intrinsic complexity of alignment and configuration of components used for the RFID positioning. This study proposes the street light fixtures as base stations where the RFID receivers will be embedded for the mobile tracking scheme. As street light fixtures are usually installed at a certain distance interval, they can be used as base stations for the RFID receiver installation. Using the principle of the single row triangle network, the RFID receiver organization is determined based on the experiments such as recognition distance measurement and tag position accuracy estimation at inside and outside of the single row triangle network. The results verify that the mobile tracking scheme which uses RFID-embedded street light fixtures, suggested and configured in this study, is effective for the real-time outdoor positioning.

• 대한금속재료학회지
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• 제50권9호
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• pp.619-627
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• 2012

One of the barriers limiting wide applications of magnesium alloys to various industries is their poor corrosion resistance. The corrosion properties of AZ91 magnesium alloy, which is the most popular magnesium casting alloy, are affected by microstructural and environmental factors. The corrosion properties of AZ91 magnesium alloy are affected by the corrosion properties of ${\alpha}-Mg$ and ${\beta}$ phases, the volume fraction and distribution of ${\beta}$ phase and area ratio of ${\alpha}-Mg/{\beta}$ phases. The corrosion properties of AZ91 magnesium alloy under various environments also change according to the passivity of films and types of corrosion products formed on its surface. The corrosion resistance of the magnesium alloys can be improved by microstructural control through the addition of alloying elements and optimization of the production process.

• Current Optics and Photonics
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• 제7권2호
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• pp.136-146
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• 2023

Based on calculations using the macroscopic Maxwell's equations with mesoscopic boundary conditions, light absorption by a layered metal-insulator-metal (MIM) metamaterial system embedded in three different environments is investigated. Increasing the top metal thickness shifts the broad absorption band to lower dielectric-constant regions and longer wavelengths, for either TM or TE waves. Boosting the dielectric-layer thickness redshifts the broadband absorption to regions of larger dielectric constant. In air, for the dielectric-constant range of 0.86-3.40, the absorption of the system exceeds 98% across 680-1,033 nm. In seawater with optimized dielectric constant, ≥94% light absorption over 400-1,200 nm can be achieved; particularly in the wavelength range of 480-960 nm and dielectric-constant range of 0.82-3.50, the absorption is greater than 98%. In an environment with even higher refractive index (1.74), ≥98% light absorption over 400-1,200 nm can be achieved, giving better performance. The influence of angle of incidence on light absorption of the MIM system is also analyzed, and the angle tolerance for ≥90% broadband absorption of a TM wave is up to 40° in an environment with large refractive index. While the incident-angle dependence of the absorption of a TE wave is nearly the same for different circumstances, the situation is different for a TM wave.