• Journal of Powder Materials
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• v.20 no.5
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• pp.371-375
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• 2013

ZnO nanoparticles in the size range from 5 to 15 nm were prepared by zinc-lithium-acetate system. The morphologies and structures of ZnO were characterized by TEM, XRD and FT-IR spectra. UV-visible results shows that the absorption of ZnO nanoparticles is blue shifted with decrease in particles size. Furthermore, photoluminescence spectra of the ZnO nanoparticles were also investigated. The ZnO nanoparticles have strong visible-emission intensity and their intensities depend upon size of ZnO nanoparticles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.277-280
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• 1997

It is important to investigate the molecular arrangement and the orientational distribution in the study of LB films. Polarized UV/visible absorption spectra make it possible to reveal the molecular arrangement and the orientational distribution. It is clarified that the PAAS LB films have specific directions in the molecular arrangement and the orientational distribution, which art different in intensity corresponding to the surface pressure. Unpolarized UV/visible absorption spectra reveal that the surface pressure is proportional to the finn thickness and is related to the molecular orientation. Current-Voltage(I-V) measurements provide that the current decreases as the surface pressure increases and there are certain phenomena called switching phenomena. Switching effort indicates that the current flows in high conductivity during on-state and suddenly decreases into low conductivity during off-state.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.139-140
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• 2010

This paper presents an indoor prototype for wireless digital signal transmission using Visible Light Communications (VLC) in which high power Light Emitting Diode (LED) is used. Using low cost and off-the-shelf components, the transmitter module is constructed using an AVR Atmega128 microcontroller and commercial white beam LEDs. Modulating the light intensity of the LED enables digital signals to be transmitted across the optical link. The receiver module employs a high speed PIN photodetector for optical signal detection and a recovery circuit for optical-electro signal conversion. By sending digitalized data via VLC technology, many applications can be realized in the areas of consumer advertising, traffic safety information and disaster control.

• Speech Sciences
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• v.14 no.1
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• pp.137-147
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• 2007

The purpose of this study was to examine the syllable structures of ten Korean numeric sounds produced by ten students. Each sound was normalized by its maximum intensity value and divided into onset, vowel, and coda sections after finding abrupt or visible changes in energy values or cumulative values of lower spectral energy at each pulse point using four Praat scripts. Then, segmental durations and cumulative intensity values of each syllable were obtained to find a statistical summary of the syllable structure. Intensity values at 100 proportional time points were also collected to compare the ten sounds. Results showed as follows: Firstly, there was not much deviation from the grand average duration and intensity for the majority of the sounds except the two diphthongal sounds on which their boundary points varied among the speakers. Secondly, the onset point for the CV or CVC category sounds and the boundary between the vowel and the nasal or lateral sound were easy to identify, which may be automatically traced later. Thirdly, there seems some tradeoff among the sections maintaining the same total duration per each syllable. Further studies on syllables with various onsets or codas would be desirable to make a general statement on the Korean syllable structure.

• Journal of Sensor Science and Technology
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• v.15 no.4
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• pp.284-290
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• 2006

This study uses neon, xenon, and helium gas mixture microdischarge to determine the effects of priming particles on the neon emission characteristics in an alternate current plasma display panel (AC PDP). The infrared (823 nm) and neon emission (585 nm) intensities are measured and compared in the blue cells in the case of new discharge with priming particles or conventional discharge without priming particles, respectively. It is found that the priming particles can produce a plasma discharge effectively even under the weak electric field condition, thereby resulting in reducing the neon emission intensity remarkably without sacrificing the IR emission intensity. As a result, it is found that the Ne emission intensity is reduced by about 46.4 % but the blue visible emission intensity is increased by about 15.2 % when compared with the conventional discharge without priming particles.

• Korean Journal of Radiology
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• v.21 no.4
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• pp.462-470
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• 2020

Objective: To demonstrate that human visual illusion can contribute to sub-endocardial dark rim artifact in contrast-enhanced myocardial perfusion magnetic resonance images. Materials and Methods: Numerical phantoms were generated to simulate the first-passage of contrast agent in the heart, and rendered in conventional gray scale as well as in color scale with reduced luminance variation. Cardiac perfusion images were acquired from two healthy volunteers, and were displayed by the same gray and color scales used in the numerical study. Before and after k-space windowing, the left ventricle (LV)-myocardium boarders were analyzed visually and quantitatively through intensity profiles perpendicular the boarders. Results: k-space windowing yielded monotonically decreasing signal intensity near the LV-myocardium boarder in the phantom images, as confirmed by negative finite difference values near the board ranging -1.07 to -0.14. However, the dark band still appears, which is perceived by visual illusion. Dark rim is perceived in the in-vivo images after k-space windowing that removed the quantitative signal dip, suggesting that the perceived dark rim is a visual illusion. The perceived dark rim is stronger at peak LV enhancement than the peak myocardial enhancement, due to the larger intensity difference between LV and myocardium. In both numerical phantom and in-vivo images, the illusory dark band is not visible in the color map due to reduced luminance variation. Conclusion: Visual illusion is another potential cause of dark rim artifact in contrast-enhanced myocardial perfusion MRI as demonstrated by illusory rim perceived in the absence of quantitative intensity undershoot.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.480-483
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• 2018

In this paper, we study the interference canceling and image sensing processing technology of multiple light sources for high speed transmission in CMOS sensor based visible light communication system. To improve transmission capacity in optical camera communications via image sensors, different data must be transmitted simultaneously from each LED. However, multiple LED light source environments for high-speed transmission can cause interference between adjacent LEDs. In this case, since the visible light communication system generally uses intensity modulation, when a plurality of LEDs transmit data at the same time, it is difficult to accurately detect the respective LEDs due to the light scattering interference of the adjacent LEDs. In order to solve this problem, the ON / OFF state of many LEDs of the light source is accurately recognized by using a dual CMOS sensor, and the spectral estimation technique and the pixel image signal processing technique of each LED are proposed. This technique can accurately recognize multiple LED pixels and improve the total average bit error rate and throughput of a MISO-VLC system.

• Environmental Engineering Research
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• v.13 no.4
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• pp.197-202
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• 2008

This study evaluated the photocatalytic oxidation of BPA using the RPOD reactor under various conditions. This study found that the RPOD was effective for BPA degradation. It could reduce 1 mg/L of BPA by half within 5 min under the optimum conditions. According to the study results, $TiO_2$ coating was important for the BPA oxidation. As the coating thickness increased, the removal efficiency improved. The light source, the light intensity and the drum rotating speed were important for the oxidation. The UV light was more effective for the BPA degradation than the visible light. The removal efficiency improved with increasing intensity. As the drum speed increased, the removal efficiency improved. The maximum speed was 240 rpm in this study. Addition of air and nitrogen was not beneficial for the BPA degradation in this study probably due to enough oxygen in the water.

• Bulletin of the Korean Chemical Society
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• v.25 no.8
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• pp.1202-1206
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• 2004

Novel naphthyl-containing biphenyl analogues were prepared by Suzki reaction for the chemiluminescent blue fluorophores. UV-Vis absorption, photoluminescence, chemiluminescence and CIE chromaticities were measured. The fluorophores displayed blue photoluminescence in solution with a maximum intensity around 378-415 nm. Sodium salicylate-catalyzed reaction of them with bis(2 carbopentyloxy-3,5,6-trichlorophenyl)-oxalate with hydrogen peroxide provided a strong chemiluminescent red light emission with wavelengths of 398-427 nm; these were similar to the photoluminescent spectra. The chemiluminescent intensity decayed exponentially and the glow of chemiluminescence, which was visible with naked eyes, was maintained for more than 4 h.

• Journal of Information Display
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• v.12 no.1
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• pp.29-35
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• 2011

In this study, plasma display panels with three different cell volumes were prepared by changing the spaces between the vertical barrier ribs into two and three times the reference structure. The discharge gap and area of the segmented ITO electrode were the same for the three cases, and Ne.20%Xe gas was used. The luminance and luminance efficiency were measured using applied voltage variations. The time evolution and intensity distribution of the infrared, which are related to the vacuum ultraviolet, were observed via intensified, charged, coupled device, and the visible-light intensity profiles were observed using PR-900 to analyze the discharge phenomena in the discharge cell.