• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.4
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• pp.132-138
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• 2023

Doped and undoped-BiVO₄ samples with different elements (Li, Mg) and amounts were synthesized with a hydrothermal method. The synthesized samples were characterized using various techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis diffusion reflectance spectroscopy (UV-Vis DRS), and photoluminescence (PL) spectroscopy. Photocatalytic activity of the samples was evaluated by measuring the degradation of methyl blue (MB) under visible light irradiation. The results indicated that the incorporation of Mg and Li into BiVO₄ caused lattice distortion, the presence of surface hydroxyl groups, a narrower band gap, and a reduced recombination ratio of photo-induced electron-hole pairs. Notably, the photocatalytic activity of Mg5%-Li5% co-doped BiVO₄ sample exhibited a significant improvement compared to that of undoped BiVO₄ sample.

• Journal of the Korean Ceramic Society
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• v.49 no.2
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• pp.135-141
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• 2012

To improve the visible-light induced photocatalytic application performances of $TiO_2$, in this study, the $NiS_2$ modied $TiO_2$ composites were prepared by two methods: hydrothermal method and sol-gel method. The composites were denoted as hs-$NiS_2$/$TiO_2$, and sg-$NiS_2$/$TiO_2$ and characterized by XRD, UV-vis absorbance spectra, SEM, TEM, EDX, and BET analysis. The photocatalytic activities under visible light were investigated by the degradation of methyl orange (MO). The photodegradation rate of methyl orange under visible light with $NiS_2$/$TiO_2$ composites was markedly higher than that of pure $TiO_2$, and the effect of hs-$NiS_2$/$TiO_2$ composites was better than that of sg-$NiS_2$/$TiO_2$. The results indicate that the hydrothermal process could partly inhibit the agglomeration of $NiS_2$/$TiO_2$. Thus, the dispersion of nanoparticles was improved, and that the promoting effect of $NiS_2$ could extend the light absorption spectrum toward the visible region.

• Korean Journal of Plant Resources
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• v.32 no.6
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• pp.633-643
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• 2019

Long-term ultraviolet (UV) exposure accelerates the phenomenon of skin photo-aging by activating collagenase and elastase. In this study, we aimed to investigate the effects of a combination of grapefruit and rosemary extracts (cG&Re) on UVB-irradiated damage in HaCaT cells and dorsal mouse skin. In HaCaT cells, cG&Re recovered UVB-reduced cell viability and inhibited protein expression of mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated kinases (p-Erk), c-Jun N-terminal kinases (p-JNK), and a class of MAPKs (p-P38). Also, cG&Re suppressed UVB-induced collagen and elastin degradation by decreasing matrix metalloproteinases (MMPs) and nuclear factor kappa light chain enhancer of activated B cells (NF-κB) expression, which is a transcription factor. Similar results were observed in dorsal mouse skin. Taken together, our data indicate that cG&Re prevent UVB-induced skin photo-aging due to collagen/elastin degradation via activation of MAPKs, MMPs, and the NF-κB signaling pathway in vitro and in vivo.

• Applied Chemistry for Engineering
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• v.24 no.2
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• pp.138-143
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• 2013

This paper studied the possibility to predict a mechanical property variation from changes in created carbonyl bands by irradiating the surface of high-density polyethylene with short-wavelength ultraviolet radiation of 254 nm to induce a fast chemical degradation. The meaning of this study lies in checking whether a mechanical property change with the same chemical property as the induced optical deterioration is caused by using a UVC lamp with high photon energy instead of optical deterioration via xenon arc light source and outdoor exposure test via natural sunlight requiring a long time. The mechanical strength of high-density polyethylene checked by a tensile test and a creep destruction test showed a similar tendency with CI changes. In particular, the yield strength and elongation had a close relationship with the exposure time to ultraviolet radiation. Accordingly, this paper presented a method to grasp the mechanical property change outdoors requiring a long time more fast through the relationship between the mechanical property change and the carbonyl index using a UVC lamp causing the fast surface degradation.

• Environmental Engineering Research
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• v.11 no.2
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• pp.84-90
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• 2006

UV-catalytic oxidation technique was applied for the treatment of bio-refractory character of the leachate, which is generally present in the form of adsorbable organic halogens (AOX). Destruction of AOX was likely to be governed by pH adjustment, quantitative measurement of oxidants, and the selection of oxidation model type. Peroxide induced degradation ($UV/H_2O_2$) facilitated the chemical oxidation of organic halides in acidic medium, however, the system showed least AOX removal efficiency than the other two systems. Increased dosage of hydrogen peroxide (from 0.5 time to 1.0 time concentration) even did not contribute to a significant increase in the removal rate of AOX. In ozone induced degradation system ($UV/O_3$), alkaline medium (pH 10) favored the removal of AOX and the removal rate was found 11% higher than the rate at pH 3. Since efficiency of the $UV/O_3$ increases with the increase of pH, therefore, more OH-radicals were available for the destruction of organic halides. UV-light with the combination of both ozone and hydrogen peroxide ($UV/H_2O_2$ 0.5 time/$O_3$ 25 mg/min) showed the highest removal rate of AOX and the removal efficiency was found 26% higher than the removal efficiency of $UV/O_3$. The system $UV/H2O_2/O_3$ got the economic preference over the other two systems since lower dose of hydrogen peroxide and relatively shorter reaction time were found enough to get the highest AOX removal rate.

• BMB Reports
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• v.33 no.3
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• pp.256-262
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• 2000

In this study the disassembly process of chlorophyII (ChI)protein complexes of a stay-green mutant (ore10 of Arabidopsis thaliana) was investigated during the dark incubation of detached leaves. During this dark-induced senescence (DIS), the Chi loss was delayed in the mutant, while the photochemical efficiency of photosystem II (PSII) or Fv/Fm was accelerated when compared with the wild type (WT) leaves. This indicates that the decrease in Fv/Fm is a separate process and not causally-linked to the degradation of Chi during DIS of Arabidopsis leaves. In the native green gel electrophoresis of the Chi-protein complexes, which was combined with an additional twodimensional SDS-PAGE analysis, the delayed senescence of this mutant was characterized by the appearance of an aggregate at 1 d or 2 d, as well as very stable light harvesting complex II (LHCII) trimers until 5 d after the start of DIS. The polypeptide composition of the aggregates varied during the whole DIS at 5 d. Dl protein appeared to be missing in the aggregates. This result supports the idea of a faster depletion of functional PSH in the mutants compared with WT, as suggested by the earlier reduction of Fv/Fm and the stable Chl a/b ratio in the mutants. At 5 d, the WT leaves also often showed aggregates, but the polypeptide composition was different from those of ore10. The results presented suggest that the formation of aggregates, or stable LHCII trimers in the stay-green mutants, is a way to structurally protect Chi-protein complexes from serious proteolytic degradation. Detailed disassembly processes of Chi-protein complexes in WT and ore10 mutants are discussed.

• The Korean Journal of Food And Nutrition
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• v.12 no.1
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• pp.85-90
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• 1999

The characcteristics of anthocyanin pigments from crab apple (Malus prunifolia Wild. Borkh. "red fruit") by ethanol extract were investigated at various condition of light temperature sugar, organic acid me-tal ion and pH. The pigments were stable(over the 60%) on the light irradiation throughout 20 days sto-rage period at room temperature and in the pesenc of Al-foil red blue green and yellow cover were rage period at room temperature and in the pesence of Al-foil red blue green and yellow cover were very stable. The pigments also showed high thermal stbility(over the 67% at 115$^{\circ}C$ 10min) at pH2.5 respectively. The pigments with added organic acid greatly increased thickness of red color. The pig-ments with added metal ions at pH 2.5 such as Na+ K+, Mg2+ Ca2+ and Mn2+ were stable throughout 20 days storage period at $25^{\circ}C$. But Cu2+ addition showed the rapidly degradation of the pigments and Al3+ addition induced the color conversion from red to redish violet. The thickness of the red color of anthocyanin pigments increased increased as the pH decreased. These results indicated that crab apple antho-cyanin pigments might be potental source of natural food colorant. colorant.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.12.1-12.1
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• 2011

최근 p-type 결정질 실리콘 태양전지의 광열화현상(light induced degradation)에 대한 관심이 높아지면서, 이를 해결하기 위한 많은 연구들이 수행되고 있다. 본 연구에서는 LID 현상을 원천적으로 제거 할수 있는 n-type 기판을 이용하여, 상업적으로 양산화 가능한 공정을 도입하고, 시뮬레이션을 통하여 고효율화 방안을 제시하고자 한다. 이를 위해 일반적인 p-type 결정질 실리콘 태양전지 제작 공정을 사용하여 알루미늄이 도핑된 후면 에미터 구조의 n-type 결정질 실리콘 태양전지를 제작하였으며, PC1D 시뮬레이션을 통해서 n+/n/p+구조의 n-type 결정질 실리콘 태양전지의 에너지 변환 효율 향상을 위한 방안을 제시하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.413-418
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• 2006

Highly stable thin-film transistor (TFT) pixel employing both low temperature polycrystalline silicon (LTPS) and amorphous silicon (a-Si) for active matrix organic light emitting diode (AMOLED) is discussed. ELA (excimer laser annealing) LTPS-TFT pixel should compensate $I_{OLED}$ variation caused by the non-uniformity of LTPS-TFT due to the fluctuation of excimer laser energy and amorphous silicon TFT pixel is desired to suppress the decrease of $I_{OLED}$ induced by the degradation of a-Si TFT. We discuss various compensation schemes of both LTPS and a-Si TFT employing the voltage and the current programming.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.485.2-485.2
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• 2014

Cz-Si 태양전지가 빛에 노출 되거나 소수 캐리어를 주입하는 경우 시간이 경과함에 따라서 전환 효율이 점점 감소하는 문제가 발생하는데 일반적으로 광열화(Light Induced Degradation) 현상이라고 명명한다. 이러한 현상은 준안정상태로 존재하는 결함들에 의해서 발생되는 것으로 연구되고 있으며 대표적인 결함으로 Cz-Si 물질 내부에 존재하는 B-O 결합이 있다. 광열화가 발생하는 명확한 기전은 아직 연구중에 있지만, 최근의 몇몇 연구결과들이 B농도와 O농도 사이의 상호관계에 대하여 밝혀냈다. 본 연구에서는 실시간으로 LID 현상을 관측하였으며, 초기상태와 비교하여 LID 이후에 열화 되는 특성들을 살펴보았다.