• Journal of Applied Reliability
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• v.15 no.4
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• pp.270-275
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• 2015

Purpose : UHMWPE (Ultra-high-molecular-weight-polyethylene) is one of the most widely used material in knife protection clothes because of high strength, elasticity, and light weight. The purpose of this study is to develop the accelerated life test method and predict the lifetime for the knife protection fabric composed by UHMWPE. Methods : In this study, degradation characteristics of UHMWPE fibers and knife protection fabric for cut resistance were evaluated under the hydrolysis and photo-degradation conditions. It was found out that the degradation rate of retained tensile strength was more significant in the photo-degradation than hydrolysis. Therefore, the failure time was determined as the time that the retained tensile strength in photo-degradation is less than 50%. Considering an acceleration factor for irradiance and exposure time, the lifetime was predicted from the calculated failure time. Results : As a result of the accelerated life test, the $B_{10}$ lifetime of knife protection fabric composed by UHMWPE fibers is estimated as 2.8 years for a 90% statistical confidence level. Conclusion: Since the lifetime is predicted by the view-point of radiant exposure in this study, there is a possibility that the estimated lifetime may differ from the actual lifetime. However, it is considered as an useful methodology to estimate the long-term lifetime of knife protection fabrics.

• Environmental Engineering Research
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• v.25 no.4
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• pp.447-461
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• 2020

In recent years, stimuli-responsive materials have garnered interest due to their ability to change properties when exposed to external stimuli, making it useful for various applications including gas separation. Light is a very attractive trigger for responsive materials due to its speedy and non-invasive nature as well as the potential to reduce energy costs significantly. Even though light is deemed as an appealing stimulus for the development of stimuli-responsive materials, this avenue has yet to be extensively researched, as evidenced by the fewer works done on the photo-responsive membranes. Of these, there are even less research done on photo-responsive materials for the purpose of gas separation, thus, we have collected the examples that answer both these criteria in this review. This review covers the utilisation of photo-responsive materials specifically for gas separation purposes. Photo-chromic units, their integration into gas separation systems, mechanism and research that have been done on the topic so far are discussed.

• Journal of Radiation Protection and Research
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• v.26 no.3
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• pp.333-335
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• 2001

The 2 GeV electron linac, the injector of the Pohang Light Source, was used as a photo-neutron source for radiation shielding research. The operational beam parameters are the nominal electron intensity of $0.5\;{\sim}5\;nC/sec$, the repetition rate of 10 Hz, and the beam pulse length of 1.0 nsec. One electron beam line was modified in order to install the target systems for producing pulsed photo-neutrons. The neutron spectrum and intensity were investigated by the time-of-flight technique. The reliable maximum energy of the measured neutrons was about 500 MeV. The number of neutrons above 20 MeV produced by one 1 GeV electron in a thick Pb target was about $6.45{\times}10^{-4}/sr$ at 90 degrees to the beam axis. The status of the photo-neutron source and the application research are presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.177-180
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• 2000

We studied the degradation of EVA for the protection of solar cell by UV-rays irradiation. We investigated the reduction of electrical efficiency, photo transmmitance and degradation of EVA by UV-rays irradiation. We utilized the UV irradiation equiped with fluorescent 313nm UV lamp and radiated for 400 hours. For the chemial analysis, we used the UV-vis spectrometer, XPS and examined the degradation mechanism by UV irradiation. It is found that the discolored phenomena, the decrease of photo transmmitance and oxidation reaction is occured by UV irradiation on the EVA sample for the protection of solar cell.

• Journal of Marine Bioscience and Biotechnology
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• v.10 no.2
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• pp.83-90
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• 2018

Ultraviolet (UV) radiation causes inflammation and matrix metalloproteinase (MMP) over-expression and extra cellular matrix depletion, leading to skin photo-aging such as wrinkle formation, dryness, and sagging. In this study, we demonstrated that pretreatment with the hexane extract of microalgae protects UVB mediated cell damages. The results of clinical study showed that Microalgal Oil treated group reduced wrinkle and improve elasticity. All these results suggest Microalgal Oil may be useful as new photo-aging cosmetics for protection against UV induced activity.

• Journal of Radiation Protection and Research
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• v.43 no.4
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• pp.131-136
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• 2018

Background: We investigated the current characteristics of a thin-film Ag electrode on a chemical vapor deposition (CVD) diamond. The CVD diamond is widely recognized as a radiation detection material because of its high tolerance against high radiation, stable response to various dose rates, and good sensitivity. Additionally, thin-film Ag has been widely used as an electrode with high electrical conductivity. Materials and Methods: Considering these properties, the thin-film Ag electrode was deposited onto CVD diamonds with varied deposition thicknesses (${\fallingdotseq}50/98/152/257nm$); subsequently, the surface thickness, surface roughness, leakage current, and photo-current were characterized. Results and Discussion: The leakage current was found to be very low, and the photo-current output signal was observed as stable for a deposited film thickness of 98 nm; at this thickness, a uniform and constant surface roughness of the deposited thin-film Ag electrode were obtained. Conclusion: We found that a CVD diamond radiation detector with a thin-film Ag electrode deposition thickness close to 100 nm exhibited minimal leakage current and yielded a highly stable output signal.

• Molecular & Cellular Toxicology
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• v.4 no.2
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• pp.150-156
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• 2008

The photoprotective effects of minerals from Korean indigenous ores, consisting mainly of sericite, on UVA-irradiated human dermal fibroblast (HDF) were examined. Zymographic analysis showed that the treatment of the minerals significantly reduced the UVA-enhanced MMP-1 activity and mRNA level. The minerals also showed strong inhibitory effect on MMP-2 activity and mRNA expression. Moreover, the minerals were better than polyphenol in reducing MMP-1 and MMP-2 expressions. Notably, the minerals significantly enhanced collagen biosynthesis in the HDF. Inhibition of the elastase activity and protection against the oxidatively damaged HDF cell were also found in the presence of the minerals. Taken together, the ore minerals may be used as the potent photo-protective and anti-skin-aging ingredients which can prevent skin cell damage by UVA.

• Journal of Radiation Protection and Research
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• v.41 no.2
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• pp.141-147
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• 2016

Background: A project for building a neutron time-of-flight (nTOF) facility is progressing. We expect that the construction will start in early 2016. Before that, a detailed simulation based on the current architectural drawings was performed to optimize the performance of our facility. Materials and Methods: Currently, several parts had been modified or changed from the original design to reflect requirements such as the layout of the electron beam line, shape of the vacuum chamber producing a neutron beam, and the underground layout of the nTOF facility. Detailed analysis for these modifications has been done with MCNP simulation. Results and Discussion: An overview of our photo-neutron source and KAERI nTOF facility were introduced. The numerical simulations for heat deposition, source term, and radiation shielding of KAERI nTOF facility were performed and the results are discussed. Conclusion: We are expecting that the construction of the KAERI nTOF facility will start in early 2016, and these results will be used as basic data.

• Journal of Radiation Protection and Research
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• v.19 no.1
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• pp.37-50
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• 1994

The experimental evaluation of exposure conversion formula using the relationship between optical photo-density, exposure dose and the quality of radiation characteristics of radiation energy to X-ray and ${\gamma}-rays$. The film badge dosimeter is analysed by exposure conversion formula which evaluate image fading characteristics for development time and directional characteristics for incident beam angle. In conclusion, exposure conversion formula evaluated of this study is satisfied with quality decision criterion of the film badge dosimeter.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.267.2-267.2
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• 2016

Semiconductor photo-catalysis offers the potential for complete removal of toxic chemicals through its effective and broad potential applications. Various new compounds and materials for chemical catalysts were synthesized in the past few decades. As one of the most important II-VI group semiconductors, zinc sulfide (ZnS) with a wide direct band gap of 3.8 eV has been extensively investigated and used as a catalyst in photochemistry, environmental protection and in optoelectronic devices. In this work, the ZnS films and nanostructures have been successfully prepared by wet chemical method. We show that the agglomerates with four successive scales are always observed in the case of the homogeneous precipitation of zinc sulfide. Hydrodynamics plays a crucial role to determine the size of the largest agglomerates; however, other factors should be invoked to interpret the complete structure. In addition, studies of the photocatalytic properties by exposure to UV light irradiation demonstrated that ZnS nanocrystals (NCs) are good photo-catalysts as a result of the rapid generation of electron-hole pairs by photo-excitation and the highly negative reduction potentials of excited electrons. A combination of their unique features of high surface-to volume ratios, carrier dynamics and rich photo-catalytic suggests that these ZnS NCs will find many interesting applications in semiconductor photo-catalysis, solar cells, environmental remediation, and nano-devices.