• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.185-188
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• 2004

A diode structure of field emission lamps based upon carbon-nanotube is studied. The single-walled carbon nanotubes(SWNTs) were produced by arc discharge method. We made the 1-inch diode type flat lamp using CNTs. We applied anode voltage gradually to refine the field emission behavior of emitter in dynamic vacuum system to study the emission current. the brightness and efficiency, etc. The field emission properties was estimated by varying gaps between the cathode and anode, contents of the glass frit. The good luminous efficiency is showed in the gap $900{\mu}m$, $1200{\mu}m$ and contents of the proper glass frit. For the upper conditions, the luminous efficiencies were respectively 23.30, 11.12 1m/W.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.193-197
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• 2012

Oxygen plasma has been treated on the surface of indium-tin-oxide (ITO) to improve the efficiency of the organic light-emitting diodes (OLEDs) device. The plasma treatment was expected to inject the holes effectively due to the control of an ITO work-function and the reduction of surface roughness. To optimize the treatment condition, a surface resistance and morphology of the ITO surface were investigated. The effect on the electrical properties of the OLEDs was evaluated as a function of oxygen plasma powers (0, 200, 250, 300, and 450 W). The electrical properties of the devices were measured in a device structure of ITO/TPD/Alq3/BCP/LiF/Al. It was found the plasma treatment of the ITO surface affects on the efficiency of the device. The efficiency of the device was optimized at the plasma power of 250 W and decreased at higher power than 250 W. The maximum values of luminance, luminous power efficiency, and external quantum efficiency of the plasma treated devices increase by 1.4 times, 1.4 times, and 1.2 times, respectively, compared to those of the non-treated ones.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.100-103
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• 2003

고휘도 LED(light emitting diode) 빨강(R), 녹색(G), 파랑(B), 호박색(A), 백색(W) 등의 중요한 광학특성인 광속(luminous flux), 효율(luminous efficacy), 피크 파장(peak wavelength), 가중치 평균 파장(weighted average wavelength), 반치폭 (full width at ha1f maximum), 색도좌표(chromaticity coordinate), 주 파장(dominant wavelength), 자극순도 (excitation purity) 와 휘도순도(colorimetric purity)에 대해서 비교검토하였다. 시험결과로 제시된 LED의 기본적인 특성 데이터는 추후, 새로운 조명용 LED 램프나 등기구(luminaire)를 개발 및 특성연구에 많은 도움을 줄 것으로 사료된다.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.415-419
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• 2010

A phosphor-conversion white light source is demonstrated using an InGaN-based blue laser diode (LD) and a yellow-emitting phosphor excited by the blue LD. The photometric and colorimetric properties of this blue-LD-based white light source are characterized. When injection current of the LD is 100 mA, luminous flux and luminous efficiency of the white light are found to be over 5 lm and 10 lm/W, respectively. When injection current is >90 mA, luminance is estimated to be larger than 10 Mcd/$cm^2$. In addition, color characteristics of the white light such as chromaticity coordinates, a correlated color temperature, and a color rendering index are found to be quite stable as current and temperature of the LD varies. The demonstrated LD-based white light source is expected to be used in high-brightness illumination applications with good color stability.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.49.3-50
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• 2017

Metallicity is one of the most important properties in understanding galaxy evolution. However, measuring metallicity is limited to low redshift (z<3.5) due to the faintness of the metallicity indicators in normal galaxies. For high redshift universe, active galactic nuclei (AGN) can be used to constrain the host galaxy metallicity. Previous studies investigated AGN metallicity using emission line flux ratios (i.e., NV/CIV and FeII/MgII), finding no evolution up to z~6. Those results might be due to selection effect since previous studies are based on very luminous AGNs. The observed luminosity-metallicity relation of AGNs (e.g., Nagao et al. 2006) suggests that luminous AGNs may be already matured at the observed epoch. Considering the luminosity-metallicty relation, we focused on low luminosity AGNs to find young AGNs (i.e., low metallicity). Through the Gemini/GNIRS observation in 2012A and 2015A (K-GMT GN-2015A-Q-203 PI: Shin, J.), we obtained the Gemini/GNIRS data for 7 high redshift AGNs (3.0

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.583-585
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• 2002

The effects of phosphor properties such as the granular sizes and shape on the crosssectional shape of phosphor layer and plasma discharge characteristics for improving the luminance and luminous efficiency in ac PDP have been investigated. As the granular size decreases, the thickness of vertical side of barrier rib in blue cell decreases, and wheras the thickness of bottom side increases due to increased dispersibility. In addition, the phosphor with round granular shape showing good dispersibility shows better voltage margin and higher luminous efficiency due to their improved discharge volume and packing density.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.465-466
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• 2007

In electrode-less lamp, The key point in creating an efficient light source based on RF discharge is to minimize the RF power loss in the RF coupler which for Anderson's type of RF lamp is due to losses in the ferrite core. This loss depends on the particular ferrite material, its size, geometry, frequency in this kind of inductive lamp shows that the correct choice of discharge current has a crucial effect on the core loss. In this study, we measured Ferrite temperature in normal state, then analyzed electrical and optical characteristics according to ferrite shape. We were able to know that was ferrite of the antenna had relate closely with temperature and luminous of the lamp. Also we appraised temperature and electrical, optical properties during turn on the lamp.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.60.1-60.1
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• 2020

We present optical variability of nearby luminous active galactic nucleus (AGN). We use the multi-epoch data of 46 AGNs obtained from 2015 to 2019 through SNU AGN Monitoring Project (SAMP), which was carried out for the reverberation mapping of luminous AGNs. We estimated variability amplitudes and time scales using the various types of analytic function, such as structure function and damped random work. We present the comparisons between physical properties of AGNs and optical variability in order to unveil the origin of the variability of AGNs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.2
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• pp.80-83
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• 2016

In the present paper, garnet structured $Y_3Al_5O_{12}:Ce^{3+}$ (YAG : Ce) ceramic phosphor plate (CPP) for high power laser diode (LD) was prepared and optical properties were analyzed. We synthesized monodispersed spherical nano-sized YAG : Ce particles by liquid phase method, fabricated phosphor ceramic plate with the addition of $Al_2O_3$. $75{\mu}m$ and $100{\mu}m$ thick YAG : Ce CPPs were compared in terms of the factors of conversion efficacy, thermal quenching, luminance and correlated color temperature (CCT). In conclusion, conversion efficacy decreased by 25 % in both samples and $100{\mu}m$ thick sample provides better optical properties of thermal quenching, maximum light conversion efficacy and maximum luminance value.

• Korean Journal of Optics and Photonics
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• v.24 no.2
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• pp.64-70
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• 2013

In this paper, two white light emitting diodes(LEDs) were manufactured by using two kinds of yellow phosphor, YAG:Ce and $(Sr,Ba)_2SiO_4:Eu$, and their spectroscopic properties were compared and analyzed. We found that the asymmetric double sigmoidal function can be applied to both white LEDs to obtain the center wavelength, the half width, and the skewness parameters. According to this analysis, the half width of the emitting spectrum of silicate phosphor was smaller than that of YAG phosphor, indicating smaller color rendering index. However, the silicate phosphor exhibited better color stability depending on the driving current than the YAG phosphor. The current dependence of the luminous efficacy of both white LEDs was investigated, which showed that efficacy decreased monotonically with current. The efficacy of the silicate-based white LED was lower than that of the YAG-based LED by about 10~12 lm/W.