• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.52-55
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• 2009

A red phosphor, $(Sr,Ca)_2P_2O_7:Eu^{2+},Mn^{2+}$, for UV-LED was synthesized under a reducing atmosphere, and its luminescent properties were investigated. The phosphor absorbs ultraviolet light at around 400 nm and efficiently emits red light at approximately 610 nm through an energy transfer from $Eu^{2+}$ to $Mn^{2+}$. Using the varied input current test for the phosphor-loaded LED lamps, it was found that the luminescent efficiency of the phosphor decreased with increasing light flux. This might be due to an increased probability of excited-state absorption and the consequent non-radiative relaxation in $Mn^{2+}$ ions in the condition of high photon influx.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.651-654
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• 2009

Novel compounds with rod and disc mesogens were synthesized and characterized. The molecular structures were confirmed by FT-IR, $^1H$-NMR spectroscopy and elemental analysis. The optical properties of these molecules were investigated by UV-vis absorption spectroscopy and photo-luminescence spectroscopy. We found that they are a novel series of blue light-emitting molecules. The absorption spectra peaks of these compounds varied from 336 nm-341 nm, while the maximum emissions centered form 410 nm-450 nm in chloroform solution. However, unexpectedly we could not found their biaxiality and mesomorphic properties by POM, conoscopy and DSC method.

• Bulletin of the Korean Chemical Society
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• v.34 no.8
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• pp.2276-2280
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• 2013

The accurate prediction of vertical excitation energies is very important for the development of new materials in the dye and pigment industry. A time-dependent density functional theory (TD-DFT) approach coupled with 22 different exchange-correlation functionals was used for the prediction of vertical excitation energies in the halogenated copper phthalocyanine molecules in order to find the most appropriate functional and to determine the accuracy of the prediction of the absorption wavelength and observed spectral shifts. Among the tested functional, B3LYP functional provides much more accurate vertical excitation energies and UV-vis spectra. Our results clearly provide a benchmark calibration of the TD-DFT method for phthalocyanine based dyes and pigments used in industry.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.511-514
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• 2000

Photoreactive multilayer films were prepared using long-chin alkyl diesters of p-phenylenediacrylic acid(p-PDA). In spite of the absence of hydrophilic groups in these molecules, they formed stable monolayers on the water surface when mixed with arachidic acid. Surface showed the presence of a condecsed phase and these monolayer could be transferred onto a substrate with Y-type deposition. The UV spectra of mixed multilayer films showed of absorption peak compared with that in solution. The linear relationship between absorbanoe and the number of layers supports the successful formation of multilayer films.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.86-89
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• 2004

Recently polymer arresters are being used widely but we don't have appropriate long term characteristics test methods. Therefore we need to develop special test facility to evaluate long term reliability of polymer arresters. It's polymeric housing can be degraded by environmental stress and the interface between housing and inner module can be affected by moisture absorption. This moisture absorption can cause leakage current and tracking in the interface. We developed multi stress accelerated ageing test facility to simulate field conditions including UV, temperature, humidity, voltage, salt fog and rain. In addition, we carried out field exposure test at the outdoor test yard and characteristics analysis of field operated specimens to evaluate accelerating factor of this accelerated aging test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.77-81
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• 1992

$C_{22}$-Quinolium-TCNQ LB films were deposited on the glass substrates by Langmuir-Blodgett technique at room temperature. Transfer ratios and UV-visible absorption spectra were studied for X, Y and Z-Types. Absorption in Z-Type was higher than X and Y-Types, which indicates a better arrangement in this type. We have also investigated dc electrical conductivities and ac responses along the horizontal and vertical direction to the film surface. As a result, we are able to determine the capacitance of film and the measured horizontal conductivity was about $10^{-7}$~$10^{-8}$ S/cm.

• Bulletin of the Korean Chemical Society
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• v.13 no.1
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• pp.17-20
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• 1992

Photoionization processes of TMPD in $H_2O$ and $D_2O$ were studied, by measuring steady-state absorption, emission, fluorescence excitation spectra, and fluorescence lifetimes on picosecond time scale. The steady-state absorption spectra showed that there exists a cation-ion pair (Wurster's Blue) in $H_2O$ and in $D_2O$ in the electronic ground state. Temperature and excitation wavelength dependence were also studied and the results show that the photoionization reaction in water is an activated process and the fluorescence lifetime is independent of the vibrational excess energy in the uv excitation range of 283-310 nm.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.607-612
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• 1996

A series of new NLO-active poly(4-nitrophenylallylamine) derivatives was synthesized by the nucleophilic substitution reaction of several substituted 4-nitrohalobenzenes and poly(allylamine hydrochloride). All polymers obtained were amorphous and their glass transition temperatures (Tg) were observed around 148-160 ℃. For each of these polymers, their specific Tg values were dependent on characteristic electronic structures. UV-visible absorption spectra showed maximum absorption intensity at 355-393 nm for π-π* transition of alkylaminonitrophenyl groups. The χ(2)value of poly(4-nitrophenylallylamine), as determined by the second harmonic generation at 1064 nm, for a thin polymer film poled at an elevated temperature, was 1.4x10-8esu. The third-order NLO properties of poly(4-nitrophenylallylamine) derivatives were evaluated through measurement of degenerate four-wave mixing technique and χ(3) coefficient in the range of 2.7~3.2x10-12 esu at 602 nm was found with 400 fs laser pulses.

• Journal of Integrative Natural Science
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• v.2 no.4
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• pp.270-274
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• 2009

Organometallic polymers containing spirosilole unit have been interested, since spirosiloles has a unique optical and electronic properties. New functionalized spirosiloles (2,5-dibromo-3,4,6,7,8,9-hexaphenylspirosilole, DBHPSS) have been synthesized from the reduction of bis(1,1-phenylethynyl)-2,3,4,5-tetraphenylsilole with lithium naphthalenide for the possible applications in optics. DBHPSS has been characterized by $^1H$-NMR, fluorescence, and UV-vis absorption spectroscopy and elemental analysis. Bis(phenylethynyl)tetraphenylsilole displays an emission maxima at 490 nm with an excitation wavelength of 380 nm. However, DBHPSS displays an emission maxima at 550 nm with an excitation wavelength of 420 nm.

• Food Engineering Progress
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• v.13 no.4
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• pp.282-288
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• 2009

A dark brownish pigment from fruit body of Auricularia auricula was isolated and characterized in this report. The pigment was obtained with a yield of 0.61%(w/w) by alkaline extraction and subsequent purification steps. It showed the positive $FeCl_3$ test which was the indication of phenolic compounds. A synthetic melanin showed a similar spectrometric characteristics to the pigment extract regarding a characteristic UV absorption between 200-250 nm and infrared absorptions profiles in the finger print region including absorption peaks at 1701 and 1624 $cm^{-1}$. Its element analysis indicated that its atomic copmposition is close to that of DOPA melanin (eumelanin). With the result of its antioxidant activity in the TNBT (5-thio-2-nitrobenzoic acid) assay, we concluded that the dark brownish pigment from A. auricula is a melanin-like compound having a powerful antioxidative activity.