• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.214-218
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• 2003

We studied the nematic liquid crystal (NLC) aligning capabilities by the UV alignment method on a diamond like carbon (DLC) thin film surface A good LC alignment by UV exposure on the DLC thin film surface at 200${\AA}$ of layer thickness was achieved. Also, a good LC alignment by the UV alignment method on the DLC thin film surface was observed at annealing temperature of 180$^{\circ}C$. However, the alignment defect of the NLC was observed above annealing temperature of 200$^{\circ}C$. Consequently, the good thermal stability of LC alignment by the UV alignment method o the DLC thin film surface can be achieved.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.8
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• pp.598-604
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• 1999

This paper describes the research to minimize the film stress and maximize the aspect ratio of photoresist structure, especially about SU-8 for electroplating mold. UV LIGA process using SU-8 allows fabricating high aspect ratio polymer structures. However, it is hard to get fine patterns in the high aspect ratio structures because of high internal stress and difficulty of removing SU-8. The purpose of this paper is to setup the process condition for the obtainment of both low film stress and high aspect ratio and to find design rules that make the pattern be less dependent on stress problem. Firstly, the process of heat treatment and exposure of SU-8 are proposed. These two conditions control the amount of cross-linkage in polymer structure, which is the most important parameter of both pattern generation and remaining stress. Heat treatment is dealed with soft bake and post-exposure-bake. Temperature and time duration of each step are varied with heat treatment condition. Some test patterns are fabricated to evaluate the proposed process. Nickel electroplating is performed with the mold fabricated through the proposed process to confirm the SU-8 as a good electroplating mold.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.601-602
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• 2012

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.1
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• pp.75-81
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• 2015

Purpose: The present study was conducted to investigate whether the changes in structure and activity of antioxidative enzymes, superoxide dismutase(SOD) and catalase(CAT) present in the eyes appeared when they were repeatedly exposed to UV-A, and reveal the correlation of these changes. Methods: Each enzyme solution was prepared from the standardized SOD and CAT, and repeatedly exposed to UV-A of 365 min under the condition of 30 minutes, 1 hour and 2 hours a day over 1, 2, 3, 4 and 5 days. Structural denaturation of SOD and CAT induced by repeat UV-A irradiation was confirmed by the electrophoretic analysis, and their enzyme activity was determined by the colorimetric assay using the proper assay kit. Results: SOD exposed repeatedly to UV-A showed the polymerization pattern through the electrophoretic analysis when it was repeatedly exposed under the condition of at least 1 hour a day however, the change of its activity was found to be less than 12%. On the other hand, CAT repeatedly exposed to UV-A showed reduced size of the electrophoretic band which indicated a structure denaturation and its activity was significantly decreased. In the case of that the repeat exposure time was longer, CAT activity was completely lost even though some enzyme band was shown in the electrphoretic analysis. Conclusions: From these results, it was revealed that the degree and pattern in structural denaturation of antioxidative enzymes differently appeared according to the type of enzyme, and the degree of structural denaturation was not always consistent with the reduction in enzyme activity.

• Journal of the Korean Ceramic Society
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• v.45 no.6
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• pp.345-349
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• 2008

$TiO_2$ coating ceramic tile for self-cleaning purpose was prepared by the precipitant dropping method using $TiCl_4$ as a precursor. $TiO_2$ film was formed on the ceramic tile by spray-coating technique and heat-treated at $500^{\circ}C$ for 1 h. The size and crystalline structure of $TiO_2$ particles were 15.3 nm and anatase phase. The outdoor exposure tests were conducted and the effects of outdoor exposure test conditions, such as exhaust concentration of contamination materials (test places), the UV light intensity (irradiation direction) and coating amounts of $TiO_2$ on the self-cleaning properties were investigated by the brightness measurements. As a results, self-cleaning property of $TiO_2$ coating tile was affected by the coating amount of $TiO_2$ however, not affected by the UV light intensity included in sun's ray (irradiation direction). $TiO_2$ coating ceramic tile can be utilized for exterior finishing materials because of self-cleaning property of $TiO_2$ coating tile.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.90-95
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• 2009

This study investigates the oxidative degradation of N-nitrosodimethylamine (NDMA), a probable human carcinogen, by advanced oxidation process (i.e., UV process). The experiments were performed with various pH, initial concentration, UV intensity, and addition of $H_2O_2$ or $TiO_2$ on UV process. The results showed that the direct UV photolysis was the most effective treatment method. The lower pH, intial concentration and higher intensity of UV stimulated higher NDMA removal. However, addition of oxidant ($H_2O_2$, $TiO_2$) slows down photochemical treatment of NDMA since the oxidant can filter out the UV light and block it to reach the NDMA molecules. Dimethylamine (DMA) and nitrite were found to be a major byproduct from NDMA oxidation. To evaluate the chronic toxicity effects of UV-treated NDMA on the growth of microalgae, "Skeletonema costatum", was studied as long term experiments. Results demonstrated that after the 13 days exposure the chronic toxicity was decreased about 15% with application of UV process on NDMA degradation.

• KSBB Journal
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• v.25 no.1
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• pp.33-40
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• 2010

Conventional disinfectants and disinfection method are expensive, hazardous and often require long periods of exposure. Recently, there is growing interest in complex disinfection process as a disinfection technique in medical instruments such as endoscope, hand piece bur to improve the disinfection efficiency and conveniency. The aim of this study was to evaluate the performance of a new complex process for the purpose of disinfection of Escherichia coli in water. Three single process (electrolysis, UV and ultrasonic process) was combined dual and triple disinfection process. The order of disinfection performance for E. coli in dual process lie in: Electrolysis + UV > Electrolysis + Ultrasonic > UV + Ultrasonic process. Disinfection efficiency of E. coli and degradation of N, N-Dimethyl-4-nitrosoaniline (RNO, indicating material of OH radical formation) of dual process was higher than that of the triple process (Electrolysis + UV + Ultrasonic process). In electrolysis + UV process, disinfection tendency was well agreed with RNO degradation tendency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.62-65
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• 2001

The effects of accelerated UV radiation on EPDM used for a polymeric insulator were investigated by contact angle, surface voltage decay after corona charging, SEM-EDX, ATR-FTIR and XPS. EPDM occurs as loss of hydrophobicity by UV treatment, which followed by surface cracking and chalking. The surface voltage decay on UV-treated EPDM show that the shorter decay time corresponded to the treated samples with a longer UV exposure time. The surface oxygen and aluminum content were found to increase and carbon decrease, as is observed in EDX analysis. The ATR-FTIR and XPS indicated that C-C and C-H groups decreased and the highly oxidized carbon bonds such as C-O, C=O and O-C=O increase with time. Also, the effects of surface charges on hydrophobicity based on our results is discussed.

• Korean Journal of Optics and Photonics
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• v.11 no.1
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• pp.33-36
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• 2000

KrF excimer laser, which is useful for fabrication of fiber gratings, was irradiated on the PLC-type WDM directional coupler and the transmission wavelength shift was observed as a function of UV exposure time. The effective refractive index change of rectangular silica waveguide was calculated from the wavelength shift measurement and the coupled mode theory. heory.

• Journal of the Korean Graphic Arts Communication Society
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• v.18 no.2
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• pp.13-27
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• 2000

The UV curing industry is one of the most wide application fields in the coating and printing inks industry. Applications extend to general coating for paper, board, wood tapes, compact discs and holograms, ink, photoresists for imaging processes and adhesives for welding and sealing in circuit boards. The UV-curing resins have advantages of quick set, space saving, clean environment and efficient use of energy. The purpose of this study has been to control of morphology structures consist of UV-curing resins and alkyd resins. Therefore, we are investigated with regard to rheology properties on the exposure to UV-curing, structures and mechanical properties for curing films.