• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1347-1353
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• 2015

We implemented a 10 Gb/s 4-channel vertical cavity surface emission lasers (VCSEL) driver array in a $0.13{\mu}m$ CMOS process technology. To enhance high current resolution, power dissipation, and chip space area, digital APC/AMC with time division sensing technology is primarily adopted. The measured -3 dB frequency bandwidth is 9.2 GHz; the small signal gain is 10.5 dB; the current resolution is 0.01 mA/step, suitable for the wavelength operation up to 10 Gb/s over a wide temperature range. The proposed APC and AMC demonstrate 5 to 20 mA of bias current control and 5 to 20 mA of modulation current control. The whole chip consumes 371 mW of low power under the maximum modulation and bias currents. The active chip size is $3.71{\times}1.3mm^2$.

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.309-317
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• 2002

A spectrofluorimetric method for the simultaneous determination of amino acids (tryptophan and tyrosine) based on the application of multivariate calibration method such as principal component regression and partial least squares (PLS) to luminescence measurements has been studied. Emission spectra of synthetic mixtures of two amino acids were obtained at excitation wavelength of 257 ㎚. The calibration model in PCR and PLS was obtained from the spectral data in the range of 280-500 ㎚ for each standard of a calibration set of 32 standards, each containing different amounts of two amino acids. The relative standard error of prediction ($RSEP_a$) was obtained to assess the model goodness in quantifying each analyte in a validation set. The overall relative standard error of prediction ($RSEP_m$) for the mixture obtained from the results of a validation set, formed by 6 independent mixtures was also used to validate the present method.

• Journal of the Korean Chemical Society
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• v.51 no.6
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• pp.513-519
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• 2007

A vesicle forming polymer, poly(sodium acrylamidoundecanoate) (PSAU) and a water-soluble distyrylbenzene- based fluorophore, TPADSB-C were synthesized and characterized by using UV-vis and photoluminescence (PL) spectroscopy. An inter-chain vesicle formation of PSAU was observed at ~0.01 g/L from N-phenyl naphthylamine fluorescence measurement with changing PSAU concentration in water. Above critical aggregation concentration of PSAU, optical properties of TPADSB-C were investigated to study the microenvironment modulation through dye incorporation in the polymeric vesicle. The emission of TPADSB-C in the presence of PSAU vesicles was blue-shifted and the PL quantum efficiency was increased to 90% due to the microenvironment (e.g. polarity) change in aqueous solution. This study shows that the polymeric vesicle containing molecular fluorophores has a great potential as an efficient, stable and biocompatible labeling tag in biological cell imaging.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.3
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• pp.106-111
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• 2018

Halide perovskite nanocrystals have become attractive for LED applications due to their high color purity and excellent luminescent properties. $CsPbX_3$ (X = I, Br, and Cl) nanocrystals were synthesized by hot-injection method and the emission wavelength was controlled by changing the composition of halide ion. Green- and red-emitting films were fabricated using a polymer binder. The outstanding optical properties of the synthesized nanocrystals and fabricated films were confirmed. The wLED designed by green- and red-emitting perovskite nanocrystal films on blue InGaN LED was characterized.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.9
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• pp.581-586
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• 2015

We studied optical and electrical properties of two-wavelength white tandem organic light-emitting diodes using red and blue materials. White fluorescent OLEDs were fabricated using Alq3 : Rubrene (3 vol.% 5 nm) / SH-1 : BD-2 (3 vol.% 25 nm) as emitting layer (EML). White single fluorescent OLED showed maximum current efficiency of 9.7 cd/A, and tandem fluorescent OLED showed 18.2 cd/A. Commission Internationale de l'Eclairage (CIE) coordinates of single and tandem fluorescent OLEDs was (0.385, 0.435), (0.442, 0.473) at $1,000cd/m^2$, respectively. White hybrid OLEDs were fabricated using SH-1 : BD-2 (3 vol.% 10 nm) / CBP : $Ir(mphmq)_2(acac)$ (2 vol.% 20 nm) as EML. White single hybrid OLED showed maximum current efficiency of 7.8 cd/A, and tandem hybrid OLED showed 26.4 cd/A. Maximum current efficiency of tandem hybrid OLED was more twice as high as single OLED. CIE coordinates of single hybrid OLED was (0.315, 0.333), and tandem hybrid OLED was (0.448, 0.363) at $1,000cd/m^2$. CIE coordinates in white tandem OLEDs compared to those for single OLEDs observed red shift. This work reveals that stacked white OLED showed current efficiency improvement and red shifted emission than single OLED.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.373-373
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• 2010

광촉매능을 갖는 $TiO_2$는 국내외적으로 많은 연구가 진행되고 있다. 빛의 조사로 발생하는 다양한 물리 화학적 촉매특성이 환경정화 뿐만 아니라 및 에너지 흡수차단 기능도 갖고 있어 최근 주목을 받고 있다. 응용분야로 초친수성 유리제품, 필터, 살균기능의 의료용 부품소재, 고효율 수소생산 및 태양전지 등에 활용성이 커서 친환경에너지 소재로 각광을 받고 있다. 본 연구에서는 초친수성 자동차의 사이드미러 개발을 위해 유리표면에 초친수성 $TiO_2$를 코팅하 고 그의 특성을 평가하였다. 특히, 이종밴드갭을 갖는 복합구조 $TiO_2/Cr_2O_3$/Cr 박막을 스퍼터링법으로 증착하여 중간층인 $Cr_2O_3$의 역할을 고찰하였다. 제조된 박막의 결정구조는 thin film형 X-선회절기(XRD)를 사용하여 분석하였으며, 박막의 표면 미세구조는 FE-SEM(Field Emission Scanning Electron Microscope)와 AFM(Atomic Force Microscope)으로, 화학구조는 XPS(X-ray Photoelectron Spectroscope)로 분석하였다. 친수성 평가는 실온 분위기에서 접촉각 측정기(Topcon-UVR2)를 사용하여 평가 하였으며 이때 조사되는 UV는 파장이 365nm이다. $Cr_2O_3$(비정질)/Cr박막위에 제조된 $TiO_2$ 박막은 균일한 anatase-$TiO_2$가 성장했으나, Cr, $Cr_2O_3$(결정질)박막위에 제조 된 $TiO_2$ 박막은 anatase상과 rulile상이 혼합된 형태로 성장하였다. $TiO_2$/Cr, $TiO_2/Cr_2O_3$(비정질)/Cr, $TiO_2/Cr_2O_3$(결정질)/Cr박막은 UV조사 1시간 만에 $10^{\circ}$ 이하의 초친수성을 나타내었다. 이종 밴드갭을 갖는 $TiO_2/Cr_2O_3$(비정질)/Cr박막은 40시간까지 친수성을 유지하는 결과를 나타냈다.

• Fire Science and Engineering
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• v.31 no.4
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• pp.20-25
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• 2017

In the present study, the temperature distribution of droplet diffusion flames was predicted from the measurements of radiative emissions of soot particles formed. In order to predict the temperature distributions, the radiative emissions from soot particles filtered at both 700 nm and 900 nm were measured using CCD cameras and local emission distributions within the flame deconvoluted with Abel transformation were plugged into a two color method. The experimental results obtained from the present study demonstrate that the two color method as tool for temperature measurements is feasible but can introduce approximately 2% maturement errors in a deconvolution process depending on intervals for the line of sight. The estimated error in temperature measurements was found to be within 18 K at 2000 K.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.25 no.3
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• pp.219-228
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• 1992

The steady state and decay characteristics of primary fluorescence of twelve clones of phytoplankton were investigated in vivo. At 380-435nm region, intense fluorescence emission spectra were obtained from the all phytoplankton, examined', The primary fluorescence of phytoplankton in different growth states was examined In order to find out fluorophores for the observed fluorescence, eight different pteridine derivatives in phosphate buffer solution were examined for their fluorescence characteristics and compared with those of phytoplankton. Fluorescence lifetimes $(\tau)$ and decay curves were compared with standard solution of candidate organic compounds. Decay kinetics of observed fluorescence were shown as hi- and tri-exponential decay curves with 430nm cut-off filter for phytoplankton. Comparison between fluorescence characteristics of bacteria and phytoplankton showed distinct differences for their steady state fluorecence spectra and decay kinetics.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.71-74
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• 2019

In this study, we fabricated two standard and inverted quantum dot light emitting diodes (QLEDs) using $TiO_2$ nanoparticles (NPs) with lower electron mobility than ZnO NPs as inorganic electron transport layer to suppress electron injection into the emitting layer. Current density was much higher for the inverted QLEDs than the standard ones. The inverted QLEDs were brighter, but showed low current efficiency due to the high current density. In addition, as the current density was higher, the driving voltage was higher, and the red shift was confirmed in the emission wavelength spectrum. The low current density in the standard structured devices showed that the possibility that $TiO_2$ NPs could suppress the electron injection in the QLEDs.

• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.22-27
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• 1990

The cavity-length detuning characteristics of the hybridly mode-locked dye laser have been studied with a collinear autocorrelator. In the optimum condition, the pulse width is 0.65 ps about three times as short as that of the synchronously mode-locked dye laser. As the cavity length is increased, the pulse width becomes broader than that at the optimum cavity length because of the effect of spontaneous emission. Also, the spectrum width becomes broad, therefore the time bandwidth product ($\Deltat\Deltav$) is increased. The peak power of autocorrelation is maximum at $\Deltat=5.0\umm$ longer than the optimum cavity length. On the other hand, as the cavity length is decreased, the pulse width becomes broader and the satellite pulses appear because of the gain recovery. Also the spectrum width becomes narrower than that at the optimum cavity length. In particular, at the mismatched cavity length the center of the lasing spectrum moves to shorter wavelengths. ngths.