• Korean Journal of Materials Research
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• v.32 no.11
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• pp.449-457
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• 2022

Halide perovskites are emerging materials for next-generation display applications, thanks to their narrow emission linewidth and band gap tunability, capable of covering the entire range of visible light. Despite their short period of research, perovskite light emitting diodes (PeLEDs) have shown rapid progress in device external quantum efficiency (EQE) in the near-infrared (NIR), red, and green emission wavelengths, and the record EQE has exceeded over 20 %. However there has been limited progress with blue emission compared to the red and green counterparts. In this review, the current status and challenges of blue PeLEDs are introduced, and strategies to produce spectrally stable blue PeLEDs are discussed. The strategies include 1) a mixed halide system in the form of 3-dimensional (3D) perovskites, 2) colloidal perovskite nanocrystals and 3) low dimensional perovskites, known as quasi-2D perovskites. In the mixed halide system, previous reports based on the compositional engineering of 3D perovskites to reduce spectral instability (i.e., halide segregation) will be discussed. Since spectral instability issue originate from the mixed halide composition in perovskites, the two other strategies are based on enlarging the band gap with a single halide composition. Finally, the prospects for each strategy are discussed, for further improvement in spectrally stable blue PeLEDs.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.327-334
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• 2024

In this paper, we developed a system with a near-infrared LED light source with a wavelength of 950nm to acquire palm vein images and a white LED light source to acquire palm creases based on Raspberry Pi. In addition, we implemented a unique pattern-extractable image processing technology that can prevent counterfeiting and enhance security of mixed creases and palmprints through image pre-processing (Gray scaling, Histogram Equalization, Blurring, Thresholding, Thinning) for the acquired vein and palm images, and secured a source technology that can be used in a security-enhanced system.

• Journal of The Korean Astronomical Society
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• v.36 no.spc1
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• pp.49-54
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• 2003

We introduce the two-dimensional spectral observations of solar flares using the Solar Tower Tele-scope of Nanjing University, China. In particular, we introduce three typical events and the methods used to analyze the data. (1) The flare of November 11, 1998, which is a limb flare. We derive the temperature and density within the flaring loop using non-LTE calculations. The results show that the loop top may be hotter and denser than other parts of the loop, which may be a result of magnetic reconnect ion above the loop. (2) The flare of March 10, 2001, which is a white-light flare that shows an emission enhancement at the near infrared continuum. We propose a model of non-thermal electron beam heating plus backwarming to interpret the observations. (3) The flare of September 29, 2002, which shows unusual line asymmetries at one flare kernel. The line asymmetries are caused by an upward moving plasma that is accelerated and heated during the flare development.

• Textile Coloration and Finishing
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• v.4 no.1
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• pp.21-25
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• 1992

The charge-transfer(CT) complexes derived from various donors and acceptors were evaluated as coloring matter. Dyes absorbing light in the region from the visible to the near-infrared wavelengths were synthesized. In order to determine the molar ratio of the donor to the acceptor in the CT complex in the solution, the continuous variational method was applied to each system. A 1:1 correspondence between the donor and the acceptor molecules in the CT complex in the solution is established. Color development properties in paper were examined. The longer the exposure time at constant temperature, the deeper the strength of color in paper. The strength of color at high temperature was decreased, because sublimed CT dyes in paper were migrated out side of paper.

• Journal of the Ergonomics Society of Korea
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• v.16 no.3
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• pp.71-75
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• 1997

This paper presents the development of videobased 3-dimensional tracking system. Measurement of human motion is important in the application of ertonomics. The system uses advanced direct video measurement technology. Passive retro-reflecting markers are attached to a subject and movements of markers are observed by two CCD cameras. Infrared light emitted near the CCD cameras is reflected by the markers and is detected by the cameras. The images are captured by Samsung MVB302 board and the centers of markers are calculated by DSP program. The positions of markers are transferred from MVB02 board to the computer through AT bus. The computer then tracks the position of each marker and saves the data. This system has dynamic accuracy with 0.7% average error and 4.2% maximum error, and the sampling rate to 6 .approx. 10 Hz, and this system can analyse the trajectory and speed of the marker. The results of this study can be used for operator's motion analysis, task analysis, and hand movement characteristic analysis.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.399-401
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• 2009

Transparent conductive metal oxide films of $In_{2-x}Ti_xO_3$ (ITiO) and $In_{2-x}Sn_xO_3$ (ITO) were deposited by RF magnetron sputtering at substrate temperature of $300^{\circ}C$ and at high rate (${\sim}10$nm/min). Electrical and optical properties of the films were investigated as well as film structure and morphology, as it is compared with the commercial F:$SnO_2$ (FTO) glass. Near infrared ray transmittance of ITiO is the highest for wavelengths over 1000nm, which can increase dye sensitized compared to ITiO and FTO. Dye-sensitized solar cells (DSCs) were fabricated using the ITiO, ITO and FTO. Photoconversion efficiency (${\eta}$) of DSC using ITiO is 5.5%, whereas 5.0% is obtained from DSC with ITO. both at 100 mW/$cm^2$ light intensity.

• Proceedings of the ESK Conference
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• 1996.10a
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• pp.160-165
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• 1996

This paper presents the development of video-based 3-dimensional tracking system. Measurement of human motion is important in the application of ergonomics. The system uses advanced direct video measurement technology. Passive retro-reflecting markers are attached to a subject and movements of markers are observed by two CCD cameras. Infrared light emitted near the CCD cameras is reflected by the markers and is detected by the cameras. The image ae captured by Samsung MVBO2 board and the center of markers is calculated by DSP program. The position of markers are transferred from MVB02 board to the computer through AT bus. The computer then tracks the position of each marker and saves the data. This system has dynamic accuracy with 1% error and the sampling rate to 6-10 Hz, and can analyse the trajectory and speed of the marker. The results of this study can be used for operators motion analysis, task analysis, and hand movement characteristic analysis.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.63.1-63.1
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• 2017

We present the preliminary results obtained from the search of variable stars in the fields of open clusters located in the direction of the Galactic disk. The current study is based on J, H and Ks photometric data obtained in the near-infrared (NIR) VVV Survey. A first classification of the newly found variable stars is performed based on their light curves, periods and amplitudes. We also show the (Ks, J-Ks) color-magnitud decontaminated diagrams of the selected open clusters and examine the location of the variable stars in these diagrams. Available proper motion data are also used to analyze the possible membership of the discovered variable stars to the corresponding clusters, as well as to redetermine with more accuracy the parameters of the poorly studied clusters.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.126-128
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• 2008

본 연구에서는 포도송이를 절개하지 않고 광학적인 방법으로 당도를 측정하였다. 광원으로는 $615{\sim}635nm$ 파장 대역의 LED를 사용하였다. 포도의 당도는 안토시아닌의 분포량에 의해 결정되는데 적포도의 경우 적색이 강할수록 안토시아닌이 많이 분포되어있다. 측정 결과 적색을 많이 띠는 적포도의 경우 광 강도가 낮은 것을 확인하였다. 또한 광학적인 방법으로 측정된 광 강도와 당도계로 얻어진 당도를 비교 분석하였다. 그 결과 포도송이의 당도에 따른 상대적 광 강도를 확인하였다.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.149.1-149.1
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• 2011

보현산 천문대의 근적외선 카메라시스템인 KASINICS(KASI Near Infrared Camera System)를 사용하여 다주기 변광성 BL Cam을 관측하였다. BL Cam(${\alpha}=03^h47^m19^s$, ${\delta}=+63^{\circ}22'7"$[J2000.0], V=13.10, ${\Delta}V$=0.33mag)은 광학적 쌍성으로 SX Pheoenics 변광성 중 하나이며 0.03 - 0.08day의 짧은 주기를 갖는 다주기 변광성으로 알려져 있다. 대상 천체의 적외선 관측을 위하여 한국천문연구원에서 개발한 지상 망원경용 근적외선 카메라 시스템 KASINICS를 사용해 J, H, Ks filter로 시계열 관측을 하였다. 대상 천체의 가시광 파장대에서의 관측 자료와 적외선 파장대에서의 관측 자료를 비교 분석함으로써 천체의 외곽층에서 발생하는 상호작용에 대해 알아볼 수 있다.