• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.78-84
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• 2013

This study was conducted in order to evaluate the removal process for long-term contamination sources including chlorinated hydrocarbons (TCE and PCE) and explosive compounds (TNT, RDX, and HMX) in underground water using a pulsed-UV system. Crystallized cells containing the contaminants were placed 10, 20, and 40 cm away from a lamp that emits pulsed-UV rays in order to examine how the removal efficiency is influenced by the distance between the source of the light and the compounds. Chlorinated hydrocarbons were completely removed in 30 minutes with a distance of 10 cm, while PCE was completely removed even with a distance of 20 cm. In the case of explosive compounds, removal efficiencies slightly varied depending on the compounds. The majority of the compounds were perfectly removed with a contact time of 10 minutes. In particular, for RDX, the results showed that complete removal was obtained within one minute, regardless of the distance from the UV source. The amount of light energy is in inverse proportion to the distance, and thus the energy reaching the compounds severely diminishes as the distance increases. Therefore, the removal efficiency decreased with increasing distance in the system.

• Journal of Soil and Groundwater Environment
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• v.17 no.6
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• pp.43-51
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• 2012

Rreactivity of persulfate (PS) for oxidation of TCE under various conditions such as heat, $Fe^{2+}$, and UV was investigated. It was found that degradation rate of TCE increased with increasing temperature from 15 to $35^{\circ}C$. At pH 7.0, the rate constants (k) at 15, 25, 30, and $35^{\circ}C$ were 0.07, 0.30, 0.74, and $1.30h^{-1}$, respectively. For activation by $Fe^{2+}$, removal efficiency of TCE increased with increasing $Fe^{2+}$ concentration from 1.9 mM to 11 mM. The maximum removal efficiency of TCE was approximately 85% when pH of the solution dropped from 7.0 to 2.5. Degradation of TCE by UV-activated PS was the most effective, showing that the degradation rate of TCE increased with inreasing PS dosage; the rate constants (k) at 0.5, 2.5, and 10 mM were 34.2, 40.5, and $55.9h^{-1}$, respectively. Our results suggest that PS activation by UV/PS process could be the most effective in activation processes tested for TCE degradation. For oxidation process by PS, however, pH should be observed and adjusted to neutral conditions (i.e., 5.8-8.5) if necessary.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.645-654
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• 1994

Photocatalytic oxidation conditions of reactant recirculation flow rate 275 mL/min, aeration rate 2 LPM and $UV+TiO_2+H_2O_2$(500 mg/L) proved to be appropriate for water including organic materials treatment. With increasing turbidity and suspended solids concentration, at turbidity 10 NTU-suspended solids concentration 29 mg/L the phenol degradation efficiency increased, which in turn decreased at turbidity 50 NTU-suspended solids concentration 170 mg/L, however no significant differences were observed, demonstrating similar results with those obtained at zero turbidity and suspended solids concentration. The degradation efficiency of phenol decreased with increasing influent phenol concentrations. The $UV+TiO_2+H_2O_2$ photocatalytic advanced oxidation process conducted is considered to be possibly applied to the drinking water treatment, and the post-treatment process of biological wastewater treatment.

• Journal of Electrical Engineering and Technology
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• v.2 no.4
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• pp.518-524
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• 2007

This paper describes several improved characterizations of the EPIC CCD, which now has modified electrode and channel structures. From a 3-D numerical simulation of the device, its channel doping and potential distributions are then observed for the optimization of the charge transfer. A wavelength-dependence on the device structure is observed in terms of the reflectivity of the incident radiation. The optical properties of ultra-low energy levels, when using an open-electrode structure, are then considered to improve their quantum efficiency.

• Environmental Engineering Research
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• v.13 no.4
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• pp.197-202
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• 2008

This study evaluated the photocatalytic oxidation of BPA using the RPOD reactor under various conditions. This study found that the RPOD was effective for BPA degradation. It could reduce 1 mg/L of BPA by half within 5 min under the optimum conditions. According to the study results, $TiO_2$ coating was important for the BPA oxidation. As the coating thickness increased, the removal efficiency improved. The light source, the light intensity and the drum rotating speed were important for the oxidation. The UV light was more effective for the BPA degradation than the visible light. The removal efficiency improved with increasing intensity. As the drum speed increased, the removal efficiency improved. The maximum speed was 240 rpm in this study. Addition of air and nitrogen was not beneficial for the BPA degradation in this study probably due to enough oxygen in the water.

• Macromolecular Research
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• v.9 no.3
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• pp.171-178
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• 2001

We report the diffraction behavior of the functionalized sol-gel film composed of two different silanes. One silane (SGDR1) contains disperse red 1 (DR1) that is composed of an azobenzene unit. The other silane (SGCHC) bears a chalcone derivative that is photocrosslinkable under UV irradiation. Two-beam coupling method was employed for fabricating the diffraction gratings. The dynamics of formation and erasure of the gratings was studied in term of the variation of the diffraction efficiency. The decaying behavior of the polarization efficiency was also observed after turning off the two pump beams. For complete erasure of the diffraction gratings, we irradiated the linearly polarized single beam. During two-beam coupling, we irradiated UV light on the film surface. The effects of the photocrosslink between the double bonds in chalcone units on the value and dynamic properties of diffraction efficiency are mainly studied in this work.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.316-316
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• 2010

Six metal-free organic dyes having thiophene (1), benzene-thiophene (2), thiophene-benzene (3), thiophene-pyridine(4), thiophene-thiophene (5), and pyridine (6) linkers between 9,9-dimethylfluorenyl terminal group and $\alpha$-cyanoacrylic acid anchor were synthesized. Among them, organic dye 5 showed the longest ${\lambda}}max$ value (424 nm) in UV-Vis absorption spectrum, better incident monochromatic photon-to-current conversion efficiency (IPCE), highest short circuit photocurrent density (JSC, 9.33 mA2/cm2), and highest overall conversion efficiency ($\eta$, 3.91%).

• Environmental Engineering Research
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• v.24 no.3
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• pp.389-396
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• 2019

The electrical energy consumption (EEC) in removal of NO by a $UV/H_2O_2$ oxidation process was introduced and related to removal efficiency of this gas. The absorption-reaction of NO was conducted in a bubble column reactor in the presence of $SO_2$. The variation in NO removal efficiency was investigated for various process parameters including NO and $SO_2$ inlet concentrations, initial concentration of $H_2O_2$ solution and gas flow rate. EEC values were obtained in these different conditions. The removal efficiency was increased from about 22% to 54.7% when $H_2O_2$ concentration increased from 0.1 to 1.5 M, while EEC decreased by about 70%. However, further increase in $H_2O_2$ concentration, from 1.5 to 2, had no significant effect on NO absorption and EEC. An increase in NO inlet concentration, from 200 to 500 ppm, decreased its removal efficiency by about 10%. However, EEC increased from $2.9{\times}10^{-2}$ to $3.9{\times}10^{-2}kWh/m^3$. Results also revealed that the presence of $SO_2$ had negative effect on NO removal percentage and EEC values. Some experiments were conducted to investigate the effect of $H_2O_2$ solution pH. The changing of pH of oxidation-absorption medium in the ranges between 3 to 10, had positive and negative effects on removal efficiency depending on pH value.

• Journal of the Korea Society of Computer and Information
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• v.26 no.2
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• pp.119-124
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• 2021

In this study, we propose an antibacterial efficiency according to the direction of UV irradiation. In the experiment, we measured the effective irradiation angle of UVC using S.aureus, a Gram-positive bacterium, and the variation of the antibacterial region according to the distance according to the direction of ultraviolet irradiation. Also, as a method to increase the antibacterial efficiency during horizontal irradiation of ultraviolet rays, we tested reflecting leaking UVC. As a result, the angle of ultraviolet irradiation was measured smaller than the product description, and in the case of the antibacterial area according to the direction of ultraviolet irradiation, the distance from the sample was increased during vertical irradiation, and the antibacterial area was increased as the distance from the sample was closer during horizontal irradiation. In addition, it was confirmed that antibacterial efficiency can be increased by reflecting leaking UVC during horizontal irradiation of UVC.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.269-272
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• 2002

UV curing technology becomes important in various sectors of applications due to the high efficiency, environmental protection, and saving of energy. The effect of different proportion of vinylester (VE) and unsaturated polyester (UP) for VE/UP blend system was investigated in context of mechanical properties. The compositions of VE/UP blend were varied within 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0 by weight percent. 1 wt% 1-hydroxy-cyclohexyl-phenyl-ketone was used as photoinitiator. The used intensity of UV light was in the range of $40~70 mW/\textrm{cm}^2$. The flexural strength of vinylester was not sensitive to the intensity of UV light. But the unsaturated polyester was very sensitive to the intensity of UV light. The flexural strength of vinylester was always superior to that of unsaturated polyester. The addition of the vinylester increased the flexural strength of blend system.