• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2245-2250
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• 2014

A new accepter unit, 6,7-difluoro-2,3-dihexylquinoxaline, was prepared and utilized for the synthesis of the conjugated polymers containing electron donor-acceptor pair for OPVs. New series of copolymers with dioctyloxybenzodithiophene as the electron rich unit and 6,7-difluoro-2,3-dihexylquinoxaline as the electron deficient unit are synthesized. The solid films of poly[2,6-(4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-alt-5,8-(6,7-difluoro-2,3-dihexylquinoxaline)] (PBQxF) and poly[2,6-(4,8-bis(2-ethylhexyloxy) benzo[1,2-b:4,5-b']dithiophene)-alt-5,8-(6,7-difluoro-2,3-dihexyl-5,8-di(thiophen-2-yl) quinoxaline)] (PBDTQxF) show absorption bands with maximum peaks at about 599 and 551 nm and the absorption onsets at 692 and 713 nm, corresponding to band gaps of 1.79 and 1.74 eV, respectively. The devices comprising PBQxF with $PC_{71}BM$ (1:2) showed open-circuit voltage ($V_{OC}$) of 0.64 V, short-circuit current density ($J_{SC}$) of $1.58mA/cm^2$, and fill factor (FF) of 0.39, giving power conversion efficiency (PCE) of 0.39%. To obtain absorption in the longer wavelength region, thiophene units without any alkyl group are incorporated as one of the monomers in PBDTQxF, which may result in low solubility of the polymers to lead lower efficiency.

• Fisheries and Aquatic Sciences
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• v.3 no.3_4
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• pp.195-199
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• 2000

Tyrosinase inhibitory activities of 14 kinds of seaweed, Ecklonia stolonifera, Ecklonia cava, Undaria pinnatiflda, Laminaria japonica, Sargassum fulvellum, Sargassum miyabei, Sargassum thunbergii, Porphyra yezoensis, Gracilaria verrucosa, Carpopeltis affinis, Pachymeniopsis elliptica, Gelidium amansii, Codium fragile and Ulva pertusa were determined using commercially available mushroom tyrosinase in an in vitro assay system. The $1\%$ (w/v) methanol extract from E. stolonifera showed the highest tyrosinase inhibitory activity of $79.0\%$, electron donating activity of $79.0\%$ and total phenol content of 3.75 mg/100g. Ethyl acetate-methanol-water (7 : 2 : 0.2, v/v) fraction $(0.5\%,\;w/v)$ isolated from the methanol extract showed tyrosinase inhibitory activity of $75.9 \%$, electron donating activity of $88.1 \%$ and total phenol content of 4.38 mg/100g. Tyrosinase inhibitory activity was closely associated with total phenol content (R = 0.99) and electron donating activity (R=0.99). Maximum absorption wavelength of the fraction was 218nm and that of phenolic compounds showed about a range from 210 to 220nm. The inhibition mode of the fraction was noncompetitive inhibition.

• Journal of The Korean Astronomical Society
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• v.50 no.5
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• pp.139-149
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• 2017

The Korea Astronomy and Space Science Institute plans to develop a coronagraph in collaboration with National Aeronautics and Space Administration (NASA) and to install it on the International Space Station (ISS). The coronagraph is an externally occulted one-stage coronagraph with a field of view from 3 to 15 solar radii. The observation wavelength is approximately 400 nm, where strong Fraunhofer absorption lines from the photosphere experience thermal broadening and Doppler shift through scattering by coronal electrons. Photometric filter observations around this band enable the estimation of 2D electron temperature and electron velocity distribution in the corona. Together with a high time cadence (<12 min) of corona images used to determine the geometric and kinematic parameters of coronal mass ejections, the coronagraph will yield the spatial distribution of electron density by measuring the polarized brightness. For the purpose of technical demonstration, we intend to observe the total solar eclipse in August 2017 with the filter system and to perform a stratospheric balloon experiment in 2019 with the engineering model of the coronagraph. The coronagraph is planned to be installed on the ISS in 2021 for addressing a number of questions (e.g., coronal heating and solar wind acceleration) that are both fundamental and practically important in the physics of the solar corona and of the heliosphere.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.117-120
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• 1998

In this study, $Al_2O_3/MgO$ bilayer was prepared with Electron-beam evaporation and the properties of the film was investigated in order to improve the property of MgO film, which is used for the protection layer in PDP(P1asma Display Panel). The thickness of $Al_2O_3/MgO$ bilayer was optimized by the Matrix Theory for the fabrication of antireflection structure for 5350A wavelength. The secondary electron emission yields of as-deposited film and annealed film were measured and compared, the bilayer was considered for the applicability as PDP. XRD showed the strong (200) primary peak of MgO. The intensity of (200) peak in the film annealed at 300C was decreased. As the result of SEM analysis for MgO films and Alz03 films, it is considered that the morphology of the films were improved of roughness and it were condensed by annealing.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.171-177
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• 2007

We prepared $TiO_2$ thin films by electron-beam evaporation at various oxygen pressures, and investigated their optical and structural properties as a function of the annealing temperature. The physical properties of the $TiO_2$ thin films depend upon the injection oxygen content. With the increased injection of oxygen, the phase transformation temperature and the transmittance of $TiO_2$ thin films in the range of visible wavelength were increased. For low injection of oxygen, the absorption edges of $TiO_2$ thin films were more red-shifted when annealed at temperatures from $700^{\circ}C$ to $1100^{\circ}C$.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.201-213
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• 1995

By the use of computer simulation including collisional mixing kinetic processes of the B- and C-state in the upper laser level the output characteristics of electron-beam pumped XeF$(C\rightarrowA$ excimer laser are analyzed. We compared the results between experiments and simulations for the $XeF^*(C)$ formation that correlated the number of densities of the $XeF^*(B)$. We obtained good agreement$(28.5 mJ\pm5%)$ with comparisons between experiment and simulation and confirmed the optimal gas mixing ratio of $Xe/F_2/Ar=5.26/0.49/94.28%$ at atmospheric pressure laser medium under the condition of 70 ns [FWHM] electron-beam (800 kV, 21 kA). Also through the simulation we have investigated that the $XeF^*(C)$ formation channel, the $XeF^*(C)$ relaxation channel, and the absorption channel of bluegreen wavelength region as a function of F2 halogen donor and Xe partial pressure. ssure.

• Transactions on Electrical and Electronic Materials
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• v.4 no.6
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• pp.9-12
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• 2003

The electrical properties of stabilized amorphous selenium typical of the material used in direct conversion x-ray imaging devices are reported. Carrier mobility was measured using time-of-flight (TOF) measurements to investigate the transport properties of holes and electrons in stabilized a-Se film. A laser beam with pulse duration of 5 ns and wavelength of 350nm was illuminated on the surface of a-Se with thickness of 400 $\mu\textrm{m}$. The photo induced signals of a-Se film as a function of time were measured. The measured transit times of hole and electron were about 8.73${\mu}\textrm{s}$ and 229.17${\mu}\textrm{s}$, respectively. The hole and electron drift mobilities decreases with increase of electric field up to 4V/$\mu\textrm{m}$. Above 4V/$\mu\textrm{m}$, the measured drift mobilities exhibited no observable dependence with respect to electric field. The experimental results showed that the hole and electron drifting mobility were 0.04584 $\textrm{cm}^2$ V$\^$-1/s$\^$-1/ sand 0.00174 $\textrm{cm}^2$V$\^$-1/s$\^$-1/ at 10 V/$\mu\textrm{m}$.

• Journal of the Optical Society of Korea
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• v.17 no.6
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• pp.548-558
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• 2013

In this work, laser induced breakdown spectroscopy (LIBS) is used to investigate soil samples collected from different desert areas of Riyadh city in Saudi Arabia. Both qualitative analysis and plasma parameters are studied via the observed LIBS spectra. These experiments have been done using a Spectrolaser-7000 system with 50 mJ fundamental wavelength of Nd:YAG laser and detection delay time of 1 microsecond. Many spectral lines are highly resolved for many elements like Al, Fe, Mg, Si, Mn, Na, Ca and K. The electron temperatures Te and electron densities Ne, for the constituent of generated LIBS plasma, are determined for all the collected samples. It is found that both Te and Ne vary from one desert area to other. This variation is due to the change of the elemental concentration in different desert areas that affects the sample's matrices. Time dependent measurements have also been performed on the soil samples. While the signal-to-base ratio (SBR) reached its optimal value at 1 microsecond, the plasma parameters Ne and Te reach values of $4{\times}10^{17}cm^{-3}$ and 9235 K, respectively, at 2.5 microsecond. The later indicate that the plasma cooling processes are slow in comparison to the previously observed results for metallic samples. The observed results show also that in the future it is possible to enhance the exploitation of LIBS in the remote on-line environmental monitoring application, by following up only the values of Ne and Te for one element of the soil desert sample using an optical fiber probe.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.2
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• pp.74-78
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• 2019

$Zn_2SnO_4$ thin films were deposited on quartzs substrates by using radio-frequency magnetron sputtering system. Thermal treatments at various temperatures were performed to evaluate the effect of annealing temperatures on the properties of $Zn_2SnO_4$ thin films. Surface morphologies were examined by using field emission-scanning electron microscopy and showed that sizes of grains were slightly increased and grain boundaries were clear with increasing annealing temperatures. The deposited $Zn_2SnO_4$ thin films on quartzs substrates were amorphous structures and no distinguishable crystallographic changes were observed with variations of annealing temperatures. The optical transmittance was improved with increasing annealing temperatures and was over 90% in the wavelength region between 350 and 1100 nm at the annealing temperature of $600^{\circ}C$. The optical energy bandgaps, which derived from the absorbance of $Zn_2SnO_4$ thin films, were increased from 3.34 eV to 3.43 eV at the annealing temperatures of $450^{\circ}C$ and $600^{\circ}C$, respectively. As the annealing temperature was increased, the electron concentrations were decreased. The electron mobility was decreased and resistivity was increased with increasing annealing temperatures with exception of $450^{\circ}C$. These results indicate that heat treatments at higher annealing temperatures improve the optical and electrical properties of rf-sputtered $Zn_2SnO_4$ thin films.

• Fibers and Polymers
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• v.2 no.3
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• pp.159-163
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• 2001

Five yellow disperse dyes were synthesized and their dyeing, fastness and photodegradation behaviors were investigated. It was found that dyes derived from phenylindole and N-alkylaminobenzene showed dye uptake directly proportional to the dye concentration, but the build-up of dyes derived from carbazole and pyridone were not good. The wavelength at maximum absorption. molar extinction coefficient. and the tendency to the photodegradation were strongly dependent on the electron donating ability of the coupling component. The dye, whose coupling component was phenylindole, possessed the excellent dyeing properties and the high degree of lightfastness. UVA had an effect on the inhibition of the photodegradation especially for the easily photodegradabte dyes.