• Journal of the Korean Wood Science and Technology
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• v.50 no.4
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• pp.283-298
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• 2022

Wood has always been used for various day-to-day applications such as interior or exterior construction materials, and household products. However, it can undergo photodegradation and discoloration by environmental factors including ultraviolet (UV) light, and thus has shortened its service life. Bleaching or delignification of wood surfaces is a suitable solution to stabilize wood against weathering by UV because these techniques can alter or remove the chromophores in lignin, which is a main factor of wood discoloration. To improve the color stability of wood surface according to the lifespan, surface delignification was conducted using peracetic acid (PAA) and hydrogen peroxide (HP) on the woods of Larix kaempferi and Quercus mongolica. After the PAA treatment, L^* increased considerably from 60-70 to 90-95. Furthermore, wood surface color did not change significantly after UV exposure. The color differences (𝜟E^*) between before and after PPA treatment of wood showed the 4.8-12.2 of L. kaempferi, and 1.7-3.7 of Q. mongolica, respectively. The lignin-related peaks in Fourier transform infrared spectroscopy (FT-IR) spectra disappeared with increased duration of PAA treatment. These results confirmed that the lignin component was partially or completely removed after the PAA treatment; the color differences (𝜟E^*) clearly showed that there was a reduction in redness (a^*) and yellowness (b^*), and an increase in lightness (L^*) owing to the removal of lignin. Based on these results, this study demonstrated that the partial removal of lignin from wood surfaces is a fundamental method for resolving photo-degradation.

• Biomedical Science Letters
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• v.17 no.1
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• pp.55-60
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• 2011

Skin is a physical barrier against diverse injury and damages. Exposure to ultraviolet (UV) radiation causes detrimental skin injuries such as inflammation and cell death. The value of natural pigments could be applied to many usages including cosmetics. This study was conducted to examine the protective effect of natural pigments extracted from mulberry, balsam pear, purple-colored sweet potato, pehmannia root, gardenia fruit, and black rice against UV-induced cell death in HaCaT cells, human keratinocyte cell lines. In the present study, the exposure of 50 mJ/$cm^2$ UV-B for 24 hr induced cell death in HaCaT cells, which was prevented by the pretreatment of extracts of mulberry, balsam pear, purple-colored sweet potato, rehmannia root, gardenia fruit, and black rice. In addition, the exposure of 50 mJ/$cm^2$ UV-B for 24 hr also increased lipid peroxide (LPO) formation, compared to control in HaCaT cells, which was prevented by the pretreatment of extracts of mulberry, balsam pear, purple-colored sweet potato, rehmannia root, gardenia fruit, and black rice. In conclusion, the extracts of mulberry, balsam pear, purple-colored sweet potato, rehmannia root, gardenia fruit, and black rice prevented the UV-B-induced cell apoptosis via the inhibition of oxidative stress in HaCaT cells.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.55.4-55
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• 2002

In the semiconductor fabrication, particle contamination is wide-spread and one of major causes to yield loss. Extensive testing has revealed that even careful handling of wafers during processing may cause photo-resist materials to flake off wafer edges. So, to remove the photo-resist at the outer 5mm of wafers, UV(Ultraviolet) rays are exposed. WEE (Wafer Edge Exposure) process station is the system that exposes the wafer edge as prespecified by controlling the positioning mechanism and maintaining the light intensity level In this work, WEE process station has been designed so as to significantly lower the amount of particle contamination which occurs even during the most r...

• Journal of the Korean Home Economics Association
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• v.45 no.10
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• pp.73-81
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• 2007

The purpose of this study was to increase the ultraviolet-light (UV)-cut ability of cellulose fabrics (cotton, ramie, and rayon) dyed with safflower yellow colorants. For this purpose, samples treated with UV-cut agent and tannic-acid were compared with the untreated samples after UV exposure in terms of K/S value, color changes(${\Delta}E$), SEM, and strength retention. The K/S value rapidly decreased after 28 days exposure, whereas the K/S value of the samples treated with both UV-cut agent and tannic-acid decreased to less than that of the untreated samples. In color changes, $L^*$ increased while $a^*$ and $b^*$ decreased, indicating less red and yellow character in color. This induced a change in the hue, value and chroma values. However the color change(${\Delta}E$) of the samples treated with both UV-cut agent and tannic-acid was less than that of the untreated samples. Scanning electron microscopy (SEM) pictures showed a severe degradation by exposure in all samples. Tensile strength rapidly decreased after 28 days for cotton and rayon, and after 21 days for ramie. However, the strength retention of the samples treated with UV-cut agent and tannic-acid was higher than that of the untreated samples.

• Safety and Health at Work
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• v.8 no.3
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• pp.237-245
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• 2017

Background: Solar furnaces are used worldwide to conduct experiments to demonstrate the feasibility of solar-chemical processes with the aid of concentrated sunlight, or to qualify high temperature-resistant components. In recent years, high-flux solar simulators (HFSSs) based on short-arc xenon lamps are more frequently used. The emitted spectrum is very similar to natural sunlight but with dangerous portions of ultraviolet light as well. Due to special benefits of solar simulators the increase of construction activity for HFSS can be observed worldwide. Hence, it is quite important to protect employees against serious injuries caused by ultraviolet radiation (UVR) in a range of 100 nm to 400 nm. Methods: The UV measurements were made at the German Aerospace Center (DLR), Cologne and Paul-Scherrer-Institute (PSI), Switzerland, during normal operations of the HFSS, with a high-precision UV-A/B radiometer using different experiment setups at different power levels. Thus, the measurement results represent UV emissions which are typical when operating a HFSS. Therefore, the biological effects on people exposed to UVR was investigated systematically to identify the existing hazard potential. Results: It should be noted that the permissible workplace exposure limits for UV emissions significantly exceeded after a few seconds. One critical value was strongly exceeded by a factor of 770. Conclusion: The prevention of emissions must first and foremost be carried out by structural measures. Furthermore, unambiguous protocols have to be defined and compliance must be monitored. For short-term activities in the hazard area, measures for the protection of eyes and skin must be taken.

• Korean Journal of Veterinary Service
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• v.36 no.3
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• pp.157-162
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• 2013

A good level of biosecurity practice is important for efficient porcine reproductive and respiratory syndrome (PRRS) control. In the current study, disinfecting ability of ozone against PRRS virus (PRRSV) was evaluated in comparison with ultraviolet (UV) and an organic acid-based disinfectant to assess the possible use of ozone for disinfecting farm vehicles, equipments, and materials to reduce the risk of new virus introduction. For in vitro evaluation, the levels of infectious virus and viral RNA were determined on the swabs collected from the floor surface of each room treated with either ozone, UV or the disinfectant up to 30 min after contamination with 100 mL of VR2332 ($10^5\;TCID_{50}/mL$). For in vivo evaluation, 3, 4-week old, PRRS-free pigs were housed into those rooms right after the last swab collection. Then the pigs in each room were injected intramuscularly with the corresponding swab samples collected at the last time point and pooled per each room. Although ozone, UV, and the disinfectant significantly reduced the levels of PRRSV RNA contamination, ozone was most effective in removing the viral RNA. In addition, the virus collected after at least 10 min exposure to ozone failed to replicate in pigs while the virus collected after treatment with UV and the disinfectant for 30 min still replicated in pigs. Based on the results, it was concluded that ozone is more effective in inactivating PRRSV as compared with UV and the organic acid-based disinfectant.

• International Journal of Oral Biology
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• v.45 no.4
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• pp.179-189
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• 2020

Green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) is a potent antioxidant with protective effects against neurotoxicity. However, it is currently unclear whether EGCG protects neuronal cells against radiation-induced damage. Therefore, the objective of this study was to investigate the effects of EGCG on ultraviolet (UV)-induced oxidative stress and apoptosis in PC12 cells. The effects of UV irradiation included apoptotic cell death, which was associated with DNA fragmentation, reactive oxygen species (ROS) production, enhanced caspase-3 and caspase-9 activity, and poly (ADP-ribose) polymerase cleavage. UV irradiation also increased the Bax/Bcl-2 ratio and mitochondrial pathway-associated cytochrome c expression. However, pretreatment with EGCG before UV exposure markedly decreased UV-induced DNA fragmentation and ROS production. Furthermore, the UV irradiation-induced increase in Bax/Bcl-2 ratio, cytochrome c upregulation, and caspase-3 and caspase-9 activation were each ameliorated by EGCG pretreatment. Additionally, EGCG suppressed UV-induced phosphorylation of p38 and rescued UV-downregulated phosphorylation of ERK. Taken together, these results suggest that EGCG prevents UV irradiation-induced apoptosis in PC12 cells by scavenging ROS and inhibiting the mitochondrial pathways known to play a crucial role in apoptosis. In addition, EGCG inhibits UV-induced apoptosis via JNK inactivation and ERK activation in PC12 cells. Thus, EGCG represents a potential neuroprotective agent that could be applied to prevent neuronal cell death induced by UV irradiation.

• Ceramist
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• v.22 no.4
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• pp.429-451
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• 2019

Quartz glass is a key material for making semiconductor process components because of its purity, low thermal expansion, high UV transmittance and relatively low cost. Domestic quartz glass has a market worth about 500 billion won in 2018, and the market power of Japanese materials is very high. Quartz glass for semiconductor process can be divided into general process and exposure. For general process, molten quartz glass is mainly used, but synthetic quartz glass with higher purity is preferred. Synthetic quartz glass is used as the photomask for the exposure process. Recently, as semiconductors started the sub-nm process, the transition from the transmission type using ArF ultraviolet (194 nm) to the reflection type using EUV ultraviolet (13.5 nm) began. Therefore, the characteristics required for the synthetic quartz glass substrates used so far are also rapidly changing. This article summarizes the current technical trends of quartz glass and recent technical issues. Lastly, the present situation and development possibility of quartz glass technology in Korea were diagnosed.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.10
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• pp.875-880
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• 2016

In this study, we proposed an effective and simple way to directly generate wrinkle patterns on a curved surface. A curved surface was prepared using a 3D printer and an UV (Ultraviolet)-lighting system was utilized to weakly polymerize the UV-curable thin resin layer coated on the surface, resulting in a gradient of material properties in the layer thickness. Subsequently, a thermal curing process was conducted to generate microscale wrinkles by compressive forces that were generated during complete curing. Wrinkle shapes from 5, 15, 25 sec of UV-light exposure were compared. With increasing UV-exposure, the line-width of wrinkles became thicker due to much higher strength of skin zone. The results indicated that the proposed fabrication process could be utilized for surface modification in diverse research fields.

• Journal of Conservation Science
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• v.32 no.4
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• pp.501-510
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• 2016

In this study, we investigated the degradation of adhesives when exposed to ultraviolet light irradiation using samples of lacquer (L), treated lacquer (TL), lacquer mixed with glue (LG), and urushiol mixed with glue (UG). Four types of film specimens were collected under the ultraviolet exposure time, and gloss test, tensile shear strength test, scanning electron microscope analysis, and infrared spectroscopic analysis were conducted for the specimens. LG and UG showed lowering rate of gloss is somewhat later than L. Also, it was observed that with increasing exposure time to ultraviolet irradiation, the surface of L began to show spherical pits and cracks when the polysaccharide layers started to be exposed, whereas the surfaces of LG and UG remained smooth. The Infrared spectra of L and TL showed that the intensity of the overall peak decreased with increasing ultraviolet irradiation time. There was no change in the peak intensity of LG, but for UG, the peaks at $3013cm^{-1}$, $1593cm^{-1}$ and so on disappeared and the overall intensity declined. The tensile shear strength of LG and UG was maintained or increased as compared to the initial test, whereas the tensile shear strength of L decreased sharply after 600 h. LG and UG exhibited fewer changes as a result of high temperature and humidity conditions, and they retained their strength under UV exposure. These results indicate that LG and UG are more durable than L when subjected to environmental change.