• Macromolecular Research
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• v.17 no.4
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• pp.271-275
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• 2009

This paper describes the out-of-plane order of a liquid crystalline(LC) methacrylate copolymer(3) comprised of a methacrylate(1) with a 4-styrylpyridine moiety as the photo-cyclodimerizable group and a benzoate moiety as the mesogenic group in the side chain, and another methacrylate(2) with a 4-(4-methoxyphenyl)benzoate moiety as the mesogenic group. The composition of 1 and 2 units in 3 was estimated to have a molar ratio of 54.2:45.8 by $^{1}H$ NMR spectroscopy. The X-ray diffraction study revealed that the copolymer forms a partial bilayer smectic structure. The copolymer gave rise to a high out-of-plane order parameter of about 0.74 in a wide LC temperature range of $110{\sim}160^{\circ}C$ after linearly polarized, UV light irradiation and subsequent annealing. Moreover, the external reflection IR analysis indicated that excess UV-light irradiation makes the out-of-plane LC structure of the copolymer appear in a higher and wider temperature range.

• Korean Journal of Microbiology
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• v.30 no.6
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• pp.483-487
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• 1992

Among a few number of UV-resistant isolated form various environmental sources (10), we made a comparative physio-chemoanalytical study on one of spherical bacteria isolated from air dust, presumably Deinococcus sp. (CM strain 29) with an UV resistant bacterium, Deinococcus radiophilus ATCC 27603 as the reference strain. Our isolate of UV resistant coccus, Deinococcus sp. CM 29 and D. radiophilus ATCC 27603 showed more than 75% matching coefficient in metabolic activity of various substrates. The most predominant cellular fatty acid of both strains was palmitoleic acid (C 16 :1, cis 9), but the detail fatty acid profiles were slightly dissimilar to each other. Cell-bound arange pigment seemed to be an identical chemicals on spectrophotometric analysis. L-ornithine was detected as cell-wall amino acid in both strains. Galactose was detected as cell-wall sugar in D. radiophilus ATCC 27603, whereas glucose in Deinococcus sp. CM 29. G-C molar ratio of both strains was comparable, 63-65%.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.213-213
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• 2011

Gold catalysts supported on TiO2 have shown a unique catalytic behavior on CO oxidation, depending on surface effects. Particle size has an influence on the surface activity. To make monodisperse Au nanoparticles, organic capping ligands, such as alkylthiols, were used by a "greener" synthesis method [1,2] and Au nanoparticles were deposited on TiO2. However, organic capping ligands must be removed for high catalytic activities by the Au nanoparticles without changing the Au size [3]. We used UV ozone treatment to decompose thiol ligands. The samples have been characterized by X-ray photoelectron spectroscopy to examine the surface modification by UV ozone treatment. We show the size distribution of the gold nanoparticles by light scattering analysis and transmission electron microscopy. Au/TiO2 have been prepared using the wetness impregnation method. The catalytic performance of CO oxidation over Au supported on TiO2 under oxidizing reaction conditions (40 Torr CO and 100 Torr O2) were tested. The results show that the catalytic activity depends on particle size and the time of UV ozone exposure, which suggests the role of sulfur bonding in determining the catalytic activity of Au/TiO2 catalysts.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2613-2619
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• 2020

This work investigated the gamma-ray shielding performance, and the physical and mechanical properties of poly (methyl methacrylate) (PMMA) composites embedded with 0-44.0 wt% bismuth trioxide (Bi₂O₃) fabricated by the fast ultraviolet (UV) curing method. The results showed that the addition of Bi₂O₃ had significantly improved the gamma shielding ability of PMMA composites. Mass attenuation coefficient and half-value layer were examined using five gamma sources (Cs-137, Ba-133, Cd-109, Co-57, and Co-60). The high loading of Bi₂O₃ in the PMMA samples improved the micro-hardness to nearly seven times that of the pure PMMA. With these enhancements, it was demonstrated that PMMA/Bi₂O₃ composites are promising gamma shielding materials. Furthermore, the fast UV curing exerts its great potential in significantly shortening the production cycle of shielding material to enable rapid manufacturing.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.95-99
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• 2011

$CaTi_{1-x}Fe_xO_3(0{\leq}x{\leq}0.4)$ solid solution photocatalysts were synthesized by iron doping during the conventional solid state reaction at $1100^{\circ}C$ for 5 h and characterized by ultraviolet-visible (UV-vis) absorption spectroscopy, X-ray diffraction, morphological analysis. We found that $CaTi_{1-x}Fe_xO_3$ samples not only absorb UV but also the visible light photons. This is because the Fe substitution at Ti-site in $CaTi_{1-x}Fe_xO_3$ lattice induces the band transition from Fe3d to the Fe3d + Ti3d hybrid orbital. The photocatalytic activity of Fe doped $CaTiO_3$ samples for hydrogen production under UV light irradiation decreased with the increase in the Fe concentration. There exists an optimized concentration of iron in $CaTiO_3$, which yields a maximum photocatalytic activity under visible light ($\lambda\geq420nm$) photons.

• Elastomers and Composites
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• v.57 no.4
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• pp.181-187
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• 2022

CdSe-Mn nanocomposites were synthesized using a microwave method with sodium sulfite (Na₂SO₃), selenium (Se), cadmium sulfate octahydrate (3CdSO₄·8H₂O), ammonia solution (NH₃·H₂O), and manganese (II) sulfate monohydrate (MnSO₄·H₂O). We obtained CdSe-Mn-C₆₀ nanocomposites by calcining CdSe-Mn nanocomposites and fullerene (C₆₀) in an electric furnace at 700 ℃ for 2 h. X-ray diffraction, Raman spectroscopy, and scanning electron microscopy were used to characterize the crystal structures, lattice vibrations, and surface morphologies of the products, respectively. The photocatalytic activities of the CdSe-Mn-C₆₀ nanocomposites were investigated based on the photocatalytic degradations of organic dyes such as BG, MB, MO, and RhB under ultraviolet (UV) irradiation at 254 nm. UV-visible spectrophotometry was used to confirm the degradation process.

• Journal of Korean Society on Water Environment
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• v.26 no.6
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• pp.1034-1039
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• 2010

Variation of formation potential of THM (THMFP) by chlorination of humic acid and characteristics of water quality with ${\gamma}$-ray irradiation were investigated, which were divided into two categories by the order of ${\gamma}$-ray irradiation and chlorination in water treatment process. The group A consisted of the ${\gamma}$-ray irradiation followed by chlorination process of humic acid, and the group B consisted of the chlorination followed by ${\gamma}$-ray irradiation process. The pH, ORP, $UV_{254}$, and DOC decreased rapidly with an increase in ${\gamma}$-ray irradiation of 3 kGy. while conductivity was little changed. Maximum degradation ratio of chloroform in THMs of group A was 82%, while that in group B was 69%. No brominated THMs were detected at high irradiation (>3 kGy). We found that group A water treatment process was more effective in lowering the THMFP than that of group B.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.707-712
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• 2010

Nitrogen-doped $TiO_2$ particles have been successfully prepared using titanium tetraisopropoxide as the Ti source and urea as the nitrogen source. As-prepared nitrogen-doped $TiO_2$ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller method (BET) and ultraviolet-visible light (UV-vis) absorption spectra techniques. Photocatalytic degradation of Methylene Blue (MB) has been carried out in both solar light (UV-vis) and the visible region (${\lambda}=420nm$). Nitrogen-doped $TiO_2$ exhibits higher activity than the commercial $TiO_2$ photocalyst, particularly under visible-light irradiation because bandgap of nitrogen-doped $TiO_2$ becomes remarkably decreased.

• KIEE International Transactions on Electrophysics and Applications
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• v.12C no.4
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• pp.214-219
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• 2002

The influence of ultraviolet (UV) irradiation and corona on the surface degradation of high temperature vulcanized (HTV) silicone rubber used for outdoor insulation through measuring surface voltage decay after corona charging, surface resistivity, contact angle and X-ray photoelectron spectroscopy (XPS) analysis was studied. The surface resistivity calculated by the surface voltage decay was compared with a value directly obtained from the three electrode method having the guard ring electrode. A good agreement between the two methods for surface resistivity was obtained. UV treated specimens showed the slower decrease of surface voltage decay, while the corona exposed specimens showed a dramatically faster decrease. Although both artificial treatments cause the same oxidative products, which was confirmed with XPS, we could distinguish the difference between the reactions of the two treatments by monitoring the surface voltage decay on corona-charged specimen. In addition, we could derive the specific surface states of the silicone rubber treated by accelerated artificial aging factors and the degradation process.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.109-112
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• 2003

In this paper, we investigated the phosphor degradation characteristics on the ultra violet ray (UV) irradiation as well as ion bombardment. We propose a novel experiment method which is related with phosphor degradation causes. The phosphor deterioration experiments were made on the UV irradiation as well as ion bombardment. To carry out the experiment and compare the results, we made up the specific experimental setup. The results show that the deterioration by ion damage is more rigorous than that by vacuum ultra violet (VUV) on the phosphor efficiency.