• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.8-15
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• 2018

Films with special properties (e.g., water-repellent films, optical films, anti-reflection films, and flexible films) are referred to as functional films. Recently, there has been interest in fine patterning methods for film fabrication. In particular there have been many studies that use a UV nanoimprint process involving a UV curing method. In this paper, a polymer film was fabricated by the UV nanoimprint process with a micro-pattern, and its durability was evaluated by a wear test and a nano-indentation test. The film mechanical properties (such as coefficient of friction, hardness, and modulus of elasticity) were measured. Moreover, the choice of PUA type resin used in the UV nanoimprint process was confirmed to impact the durability of the thin film. Despite making the polymer film samples using the same method and PUA type resin, different coefficient of friction, hardness, and modulus of elasticity values were obtained. PUA 4 resin had the most favorable coefficient of friction, hardness, and modulus of elasticity. This material is predicted to produce a high durability functional film.

• Journal of Adhesion and Interface
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• v.4 no.1
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• pp.9-17
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• 2003

The UV hard coating materials are attracting more and more attention to modern industry, in terms of the development of low or non solvent coating materials which will contribute to economizing both materials and energy and to reducing pollution. This study was performed in order to invent UV curable coating materials containing colloidal silica which have actual industrial applications. As results of experiments, the oligomers type and the concentration of colloidal silica acrylate oligomer (SAOC) have an influence on various especially, The properties of UV hardening cooling, such as chemical, abrasion resistance and weatherability, were greatly enhanced, the impact properties of coated polycarbonate substrate were improved compared with the noncoated that. The UV cured films containing 30 wt% SAOC obtained showed the best properties.

• Journal of Environmental Health Sciences
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• v.50 no.3
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• pp.201-211
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• 2024

Background: Organic ultraviolet (UV) filters are widely used in sunscreen products and have been identified as an emerging contaminant. Organic UV filters co-exist with multiple components, but their mixture toxicity remains largely unknown. Objectives: We investigated the toxicity of single and binary mixtures of commonly used UV-filters using the human adrenocarcinoma (H295R) cell line. Methods: After exposure to non-cytotoxic concentrations of avobenzone (AVO), homosalate (HS), octisalate (OS), octinoxate (OMC), and octocrylene (OC), the levels of testosterone (T) and 17β-estradiol (E2) were measured. The median effective concentration (EC₅₀) values for the E2 of the individual substances were used to determine the mixture effect of four binary combinations: OMC+AVB, OMC+HS, OMC+OS, and OMC+OC. The synergistic, additive, and antagonistic effects of the mixture were determined by calculating toxic units (TU). To examine the mechanism of mixture toxicity, eight genes involved in steroidogenesis were analyzed using the real-time polymerase chain reaction. Results: The significant increase in E2 in H295R cells exposed to AVO, HS, OS, OMC, and OC suggest an estrogenic effect of the tested UV-filters. A significant decrease in T was observed in cells exposed to HS and OS. EC₅₀ values for E2 increase were 105 nM for AVO, 110 nM for HS, 120 nM for OS, 55 nM for OMC, and 80 nM for OC. Both binary mixtures consisting of OMC+HS and OMC+OS have synergistic effects. Conclusions: Our results showed that five types of UV-filter substances increase E2 in H295R cells. We examined the mixture toxicity in terms of increased estrogenicity and confirmed that E2 significantly increased when OMC was mixed with a salicylate-based UV-filters. These findings highlight the importance of determining the impact of UV filter mixtures.

• Journal of the Korean Chemical Society
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• v.38 no.2
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• pp.169-173
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• 1994

The previously reported cytotoxic metabolites, against the KB cell line, xestoquinone, halenaquinol sulfate and $halenaquinol^{5,6}$ were isolated from the unidentified sponge collected in October 1992, Manado Bay, Sulawesi in Indonesia. Their structure were elucidated by $^1H-,\;^{13}C$-NMR, $^1H-,\;^{13}C$(1 bond) Heteronuclear Multiple Quantum Coherence Spectroscopy$(HMQC)^1$, $^1H-,\;^{13}C$C(2 and 3 bond) Heteronuclear multiple Bond Correlation Spectroscopy$(HMBC)^2$, Electron Impact Mass Spectroscopy(EI ms), Ultraviolet Spectroscopy(UV), and Infrared Spectroscopy(IR)

• Textile Coloration and Finishing
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• v.29 no.1
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• pp.37-44
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• 2017

An issue of major concern in the utilization of laminated composites based epoxy resin is associated with the occurrence of delaminations or interlaminar cracks, which may be related to manufacturing defects or are induced in service by low-velocity impacts. A strong interfacial filament/brittle epoxy resin bonding can, however, be combined with the high fracture toughness of weak interfacial bonding, when the filaments are arranged to have alternate sections of shear stress. To improve this drawback of the epoxy resin, UV-thermal dual curable resin were developed. This paper presents UV-thermal dual curable resin which were prepared using epoxy acrylate oligomer, photoinitiators, a thermal-curing agent and thermoset epoxy resin. The UV curing behaviors and characteristics of UV-thermal dual curable epoxy resin were investigated using Photo-DSC, DMA and FTIR-ATR spectroscopy. The mechanical properties of UV-thermal dual curable epoxy resin impregnated CF prepreg by UV curable resin content were measured with Tensile, Flextural, ILSS and Sharpy impact test. The obtained results showed that UV curable resin content improves the epoxy toughness.

• Journal of Microbiology and Biotechnology
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• v.33 no.1
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• pp.106-113
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• 2023

The supply of microbiological risk-free water is essential to keep food safety and public hygiene. And removal, inactivation, and destruction of microorganisms in drinking water are key for ensuring safety in the food industry. Ultraviolet-C (UV-C) irradiation is an attractive method for efficient disinfection of water without generating toxicity and adversely affecting human health. In this study, the disinfection efficiencies of UV-C irradiation on Shigella flexneri (Gram negative) and Listeria monocytogenes (Gram positive) at various concentrations in drinking water were evaluated using a water purifier. Their morphological and physiological characteristics after UV-C irradiation were observed using fluorescence microscopy and flow cytometry combined with live/dead staining. UV-C irradiation (254 nm wavelength, irradiation dose: 40 mJ/cm²) at a water flow velocity of 3.4 L/min showed disinfection ability on both bacteria up to 10⁸ CFU/4 L. And flow cytometric analysis showed different physiological shift between S. flexneri and L. monocytogenes after UV-C irradiation, but no significant shift of morphology in both bacteria. In addition, each bacterium revealed different characteristics with time-course observation after UV-C irradiation: L. monocytogenes dramatically changed its physiological feature and seemed to reach maximum damage at 4 h and then recovered, whereas S. flexneri seemed to gradually die over time. This study revealed that UV-C irradiation of water purifiers is effective in disinfecting microbial contaminants in drinking water and provides basic information on bacterial features/responses after UV-C irradiation.

• Journal of Bio-Environment Control
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• v.33 no.1
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• pp.45-54
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• 2024

A proper level of UV-A light treatment in terms of intensity, spectrum, and exposure duration is known to have a positive impact on plant growth, photosynthesis, and the biosynthesis of secondary metabolites. However, there are few studies investigating the physiological responses of spinach (Spinacia oleracea L.) to UV radiation. Hence, this study aimed to assess the effects of short-term UV-A radiation on the growth and bioactive compounds of spinach. Spinach seedlings were cultivated in a vertical farm module under the following environmental conditions: photosynthetic photon flux density 200 µmol·m^-2·s^-1, white LED, 12 h on/off, 20℃ air temperature, 70% relative humidity, and 500 µmol·mol^-1 CO₂ concentration. After 5 weeks of sowing, the seedlings were subjected to continuous UV-A (peak wavelength; 385 nm) irradiation at two different energy levels: 20 W·m^-2 and 40 W·m^-2 for 7 days. As a result, the UV-A_20W treatment increased the shoot fresh and dry weights of spinach. However, there were no significant differences observed in photosynthetic parameters between the UV-A treatments and the control. The maximum quantum efficiency of photosystem II (Fv/Fm) consistently decreased across all UV-A treatments for 7 days in UV-A treatments. Additionally, the total phenolic content and antioxidant capacity increased in the UV-A_20W treatment at 7 days of treatment as well as the total flavonoid content significantly increased at 5 and 7 days of treatment. These findings suggest that supplemental UV-A LED radiation can enhance the growth and quality of spinach cultivated in closed type plant production systems such as vertical farms.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.130-136
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• 2017

The present work is for an evaluation of tension behavior and surface deterioration of FRP Hybrid Bar due to UV exposure and freezing/thawing(F/T) actions. For the work, FRP Hybrid Bar is subjected to UV exposure test, then F/T test is performed successively to 180 cycles. In FRP Hybrid Bar, no significant surface deterioration is evaluated after UV exposure. Tension hardening performance, a unique engineering advantage of FRP Hybrid Bar, is still maintained after F/T test. The performance in FRP Hybrid Bar exposed to UV is still effective. FRP Hybrid Bar exposed to UV have almost similar tension behavior of FRP Hybrid Bar without UV exposure. Although F/T cycles increase to 180, steel rebar, FRP Hybrid Bar, and FRP Hybrid Bar exposed to UV show no significant changes in tension behavior. In the work, UV exposure and F/T actions are evaluated to have little negative effect on surface deterioration and tensile performance in FRP Hybrid Bar, however spalling of silica coating due to impact should be considered since it affects bonding strength to outer concrete.

• Smart Structures and Systems
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• v.22 no.2
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• pp.161-166
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• 2018

In the last decade, there has been an exponential increase of scientific interest in smart additive manufacturing (AM) technology. Among the different AM techniques, one of the most commonly applied processes is digital light processing (DLP). DLP uses a digital projector screen to flash an ultraviolet light which cures photopolymer resins. The resin is cured to form a solid to produce parts with precise high dimensional accuracy. During the curing process, there are several process parameters that need to be optimized. Among these, the exposure time affects the quality of the 3D printed specimen such as mechanical strength and dimensional accuracy. This study examines optimal exposure times and their impact on printed part. It was found that there is optimal exposure time for printed part to have appropriate mechanical strength and accurate dimensions. The gel fraction and TGA test results confirmed that the improvement of mechanical properties with the increasing UV exposure time was due to the increase of crosslinked network formation with UV exposure time in acrylic resins. In addition, gel fraction and thermogravimetric analysis were employed to microscopically investigate how this process parameter impacts mechanical performance.

• Journal of Korean Society on Water Environment
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• v.35 no.6
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• pp.459-469
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• 2019

The ozonation of sulfamethoxazole (SMX) was performed at 20℃ using a pilot scale countercurrent bubble column reactor. Ozonation systems were combined with UV irradiation and TiO₂ addition. As the oxidation reaction proceeded in each treatment system, the pH of the sample decreased and in the O₃/UV/TiO₂ system, the pH change was the largest from 4.54 to 2.02. Under these experimental conditions, the scavenger impact of carbonate is negligible. The highest COD and TOC removal rate was observed in the O₃/UV/TiO₂ system due to the UV irradiation and the photocatalytic effect of TiO₂. Also, the highest mineralization ratio(ε) value is 0.2 in the O₃/UV/TiO₂ system, which means theoxidation capacity of the systems. The highest SMX degradation rate constants calculated by COD and TOC values (COD and TOC) were 2.15 × 10^-4 sec^-1 and 1.00 × 10^-4 sec^-1 in the O₃/UV/TiO₂ system, respectively. The activation energy (E_a) of ozone treatment follows the Arrhenius law. It was calculated based on _COD and _TOC. Each activation energy decreased in order of single O₃> O₃/TiO₂> O₃/UV > O₃/UV/TiO₂ system. The result showed that ΔH^≠ is more effective than ΔS^≠ in each SMX ozontaionsystem, that is characteristic of the common oxidation reaction.