• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.39-39
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• 2013

We present a study of correlations between the elemental abundances and galaxy morphologies of 91 blue compact galaxies (BCGs) at z=0.20-0.35 with Sloan Digital Sky Survey (SDSS) DR7 data. We classify the morphologies of the galaxies as either 'disturbed' or 'undisturbed', by visual inspection of the SDSS images, and using the Gini coefficient and M20. We derive oxygen and nitrogen abundances using the Te method. We find that a substantial fraction of BCGs with disturbed morphologies, indicative of merger remnants, show relatively high N/O and low O/H abundance ratios. The majority of the disturbed BCGs exhibit higher N/O values at a given O/H value compared to the morphologically undisturbed galaxies, implying more efficient nitrogen enrichment in disturbed BCGs. We detect Wolf-Rayet (WR) features in only a handful of the disturbed BCGs, which appears to contradict the idea that WR stars are responsible for high nitrogen abundance. Combining these results with Galaxy Evolution Explorer (GALEX) GR6 ultraviolet (UV) data, we find that the majority of the disturbed BCGs show systematically lower values of the $H{\alpha}$ to near-UV star formation rate ratio. The equivalent width of the $H{\beta}$ emission line is also systematically lower in the disturbed BCGs. Based on these results, we infer that disturbed BCGs have undergone star formation over relatively longer time scales, resulting in a more continuous enrichment of nitrogen. We suggest that this correlation between morphology and chemical abundances in BCGs is due to a difference in their recent star formation histories.

• Polymer(Korea)
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• v.37 no.6
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• pp.736-743
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• 2013

Novel carbazole based copolymers were synthesized by Suzuki coupling polymerization. (Diphenylene)vinylene and n-octyl was introduced to carbazole as pendants for reducing band gap and improving solubility, respectively. Thermal, photoluminescence and electro-luminescence of copolymers were studied for applying the emitting layer of polymer light emitting diode (PLED). Maximum UV-vis absorption and photoluminescence (PL) emission wavelength of copolymers showed 333~340 nm and 409~464 nm in solution state, respectively. The relative quantum yield using 9,10-diphenylanthracene as a reference was 25.8%. These copolymers exhibited high thermal stability ($T_d$ = $350^{\circ}C$) and good film forming ability. Good luminance was obtained at voltages lower than 8 V and the onset voltage was observed at 4.0 V.

• Textile Coloration and Finishing
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• v.25 no.2
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• pp.94-101
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• 2013

Poly(acrylonitrile) (PAN) nanofibers containing different amounts of titanium dioxide ($TiO_2$) have been prepared by electrospinning technique. Photocatalytic activity of these electrospun PAN/$TiO_2$ nanofibers and the effect of $TiO_2$ content on the photocatalytic efficiency of PAN/$TiO_2$ nanofibers have been evaluated by monitoring the photodecomposition of fluorescein dye, rhodamine B and methylene blue under UV irradiation with respect to irradiation time. Moreover, the effect of hydrogen peroxide ($H_2O_2$) on the photocatalytic behavior of PAN/$TiO_2$ nanofibers has also been investigated. The results showed that PAN/$TiO_2$ nanofibers are effective photocatalyst and their photocatalytic efficiency increases with the increase of $TiO_2$ content in the PAN/$TiO_2$ nanofibers. It is also observed that the presence of $H_2O_2$ significantly enhances the photocatalytic ability of PAN/$TiO_2$ nanofibers. The morphology and the photocatalytic behavior of the PAN/$TiO_2$ nanofibers containing different amounts of $TiO_2$ nanoparticles have been investigated by field-emission scanning electron microscopy (FE-SEM) and UV/Visible spectroscopy, respectively.

• Advances in nano research
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• v.7 no.1
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• pp.13-24
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• 2019

Well-crystalline $SnO_2$ nanoparticles of 4-5 nm size with different In contents were synthesized by hydrothermal process at relatively low temperature and characterized by transmission electron microscopy (TEM), microRaman spectroscopy and photoluminescence (PL) spectroscopy. Indium incorporation in $SnO_2$ lattice is seen to cause a lattice expansion, increasing the average size of the nanoparticles. The fundamental phonon vibration modes of $SnO_2$ lattice suffer a broadening, and surface modes associated to particle size shift gradually with the increase of In content. Incorporation of In drastically enhances the PL emission of $SnO_2$ nanoparticles associated to deep electronic defect levels. Although In incorporation reduces the band gap energy of $SnO_2$ crystallites only marginally, it affects drastically their dye degradation behaviors under UV illumination. While the UV degradation of methylene blue (MB) by undoped $SnO_2$ nanoparticles occurs through the production of intermediate byproducts such as azure A, azure B, and azure C, direct mineralization of MB takes place for In-doped $SnO_2$ nanoparticles.

• Publications of The Korean Astronomical Society
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• v.15 no.spc1
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• pp.147-151
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• 2000

Symbiotic stars, believed to be binary systems of a mass-losing giant and a white dwarf with an emission nebula, are known to exhibit very broad wings around Hex that extend to $\~10^3km\;s^{-1}$. The wing formation mechanism is not a settled matter and recently Lee (2000) proposed that Raman scattering of Ly$\beta$ by neutral hydrogen is responsible for the broad H$\alpha$ wings. In this model, it is predicted that. the Hex wings will be polarized depending on the geometric and kinematic distribution of the scatterers relative to the UV emission region. In this paper, we investigate the polarization of Hex wings in symbiotic stars. Noting that many symbiotic stars possess bipolar nebular morphology, we assume that the distribution of neutral scatterers follows the similar pattern with a receding velocity of several tens of km $s^{-1}$ that mimics the expansion of the neutral envelope of the nebula. It is found that the red wing is more strongly polarized than the blue and main part and that the polarization direction is along the equatorial plane. We obtain a typical degree of polarization $\~10$ percent, however, it varies depending on the detailed distribution of H I scatterers We conclude that spectropolarimetry will provide very important information on the origin of the Hex wings.

• Journal of the Korean Ceramic Society
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• v.44 no.1 s.296
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• pp.32-36
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• 2007

Zinc gallate $(ZnGa_2O_4)$ thin film phosphors have been formed on ITO glass substrates by a sol-gel spinning coating method. For the formation of the film phosphors, the starting materials of zinc acetate dihydrate, gallium nitrate hydrate and 2-methoxyethanol as a solution were used. The thin films deposited were firstly dried at $100^{\circ}C$ and fired at $500^{\circ}C\;or\;600^{\circ}C$ for 30 min and then, annealed $500^{\circ}C\;or\;600^{\circ}C$ at for 30 min under an annealing atmosphere of 3% $H_2/Ar$. The thin films deposited on ITO glass plates showed the (220), (222), (400), (422), (511), and (440) peaks of spinel structure as well as the (311) peak indicating a standard powder diffraction pattern. The surface morphologies of the thin film phosphors were observed with a firing and an annealing condition. The $ZnGa_2O_4$ film phosphors showed the blue emission spectra around 410 nm as well as the emission spectra in the UV region (360-380 nm).

• Advances in materials Research
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• v.3 no.4
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• pp.227-232
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• 2014

$Ce^{4+}$, $Eu^{3+}$, $Tb^{3+}$ co-doped $Ca_3Si_3O_8F_2$ phosphor was synthesized via solid state reaction method using $CaF_2$, $CaCO_3$ and $SiO_2$ as raw materials for the host and $Eu_2O_3$, $CeO_2$, and $Tb_4O_7$ as activators. The luminescent properties of the phosphor was analysed by spectrofluorophotometer at room temperature. The effect of excitation wavelengths on the luminescent properties of the phosphor i.e. under near-ultraviolet (nUV) and visible excitations was investigated. The emission peaks of $Ce^{4+}$, $Eu^{3+}$, $Tb^{3+}$ co-doped $Ca_3Si_3O_8F_2$ phosphor lays at 480(blue band), 550(green band) and 611nm (red band) under 380nm excitation wavelength, attributed to the $Ce^{4+}$ ion, $Tb^{3+}$ ion and $Eu^{3+}$ ions respectively. The results reveal that the phosphor emits white light upon nUV (380nm) / visible (465nm) illumination, and a red light upon 395nm / 535nm illumination. RE ions doped $Ca_3Si_3O_8F_2$ is a promising white light phosphor for LEDs. The emission colours can be seen using Commission international de l'eclairage (CIE) co-ordinates. A single host phosphor emitting different colours under different excitations indicates that it is a potential phosphor having applications in many fields.

• 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 Society Of Semiconductor Equipment Technology
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• 2007.06a
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• pp.188-192
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• 2007

High brightness and long persistent luminescence phosphor $CaAl_2O_4:Eu^{2+}$ was prepared with varying $Eu^{2+}$ concentration by solid state reaction technique. Synthesized materials were investigated by powder X-ray diffractometer (XRD), SEM, TEM, photoluminescence excitation and emission spectra. Broad band UV excited luminescence of the $CaAl_2O_4:Eu^{2+}$ was observed in the blue region (${\lambda}_{max}\;=\;440\;nm$) due to transitions from the $4f^65d^1$ to the $4f^7$ configuration of the $Eu^{2+}$ ion. The decay time of the persistence indicated that the persistent luminescence phosphor has bright phosphorescence and maintains a long duration. These materials have great potential for outdoor night time displays.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.533-536
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• 2008

The anthracene derivatives were synthesized by Suzuki coupling reaction. The thermal, optical and electronic properties of MNAn and BIPAn were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry(DSC), UV-vis absorption, photoluminescen ce spectroscopies, and cyclic voltammetry. The materials exhibit high thermal stability and high per formance in EL devices.