• Journal of the Korean institute of surface engineering
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• v.55 no.6
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• pp.353-362
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• 2022

Recently, transmittance of photomasks for ultra-violet (UV) region is getting more important, as the light source wavelength of an exposure process is shortened due to the demand for technologies about high integration and miniaturization of devices. Meanwhile, such problems can occur as damages or the reduction of yield of photomask as electrostatic damage (ESD) occurs in the weak parts due to the accumulation of static electricity and the electric charge on chromium metal layers which are light shielding layers, caused by the repeated contacts and the peeling off between the photomask and the substrate during the exposure process. Accordingly, there have been studies to improve transmittance and antistatic performance through various functional coatings on the photomask surface. In the present study, we manufactured antireflection films of Nb₂O₅, | SiO₂ structure and antistatic films of ITO designed on 100 × 100 × 3 mmt sodalime glass by DC magnetron sputtering system so that photomask can maintain high transmittance at I-line (365 nm). ITO thin film deposited using In/Sn (10 wt.%) on sodalime glass was optimized to be 10 nm-thick, 3.0 × 103 𝛺/☐ sheet resistance, and about 80% transmittance, which was relatively low transmittance because of the absorption properties of ITO thin film. High average transmittance of 91.45% was obtained from a double side antireflection and antistatic thin films structure of Nb₂O₅ 64 nm | SiO₂ 41 nm | sodalime glass | ITO 10 nm | Nb₂O₅ 64 nm | SiO₂ 41 nm.

• Korean Journal of Optics and Photonics
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• v.33 no.2
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• pp.59-66
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• 2022

A free-form Mueller matrix ellipsometer (MME) based on independent control of the azimuthal angle of each polarizing element is introduced. The azimuthal angles of the polarizer and the matching compensator which generate the optimum Stokes vectors of an incident beam are investigated for the polarization state generator, where the spectral responses of the retardation angle and transmittance ratio of a nonideal compensator are taken into account. Similarly, the azimuthal angles of the analyzer and the corresponding compensator are investigated for the polarization-state detector, to unambiguously determine the Stokes vector of the outcoming beam from the sample, and explicit expressions for the Stokes elements are derived. Since the suggested technique enables one to utilize a nonideal quarter-wave plate as the compensator for an MME, it will contribute to the construction and application of a Mueller matrix spectroscopic ellipsometer (MMSE) operating over a wide spectral range from deep ultra-violet to near infrared.

• Journal of Veterinary Science
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• v.23 no.4
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• pp.62.1-62.10
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• 2022

Background: The corneal and limbal morphology relevant to corneal epithelial maintenance in ten different species was examined using histological methods. Objectives: The presence of a Bowman's layer, limbal epithelial cell, and superficial stromal morphology was examined in the following species to evaluate the differences in corneal thickness and epithelium: Java sparrows, frogs, macaws, spoonbills, red pandas, penguins, horses, Dobermans, orangutans, and humans. Methods: Corneal sections (4 ㎛) were obtained from ten ocular globes from three different animal classes: Aves, Amphibia, and Mammalia. All sections were stained with hematoxylin and eosin and periodic acid-Schiff reaction. After microscopy, all stained slides were photographed and analyzed. Results: Significant morphological differences in the corneal and limbal epithelia and their underlying stroma between species were observed. The number of corneal epithelial cell layers and the overall corneal epithelial thickness varied significantly among the species. The presence of a Bowman's layer was only observed in primates (orangutans and humans). Presumed supranuclear melanin caps were noted in four species (orangutans, macaws, red pandas, and horses) in the limbal basal epithelial layer (putative site of corneal epithelial stem cells). The melanin granules covered the apex of the cell nucleus. Conclusions: Supranuclear melanin capping has been described as a process within the epidermis to reduce the concentration of ultraviolet-induced DNA photoproducts. Similarly, there may be a relationship between limbal stem cell melanin capping as a protective mechanism against ultra-violet radiation.

• Analytical Science and Technology
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• v.34 no.4
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• pp.160-171
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• 2021

Synthetic azo dyes are used extensively in herbal medicines to render the medicines more visually attractive to consumers. This study developed and validated a rapid high-performance liquid chromatography (HPLC) method to determine whether synthetic colorants such as Tartrazine, Auramine O, Metanil yellow, Sunset yellow, and Orange II are used extensively in Typha orientalis. To increase the recovery of the synthetic dyes, this method employed containing 50 mM ammonium acetate in 70 % methanol at first extraction and 100 mM HCl in 70 % methanol at second extraction. Five synthetic pigments in Typha orientalis were separated by gradient elution with a mobile phase consisting of acetonitrile and 50 mM ammonium acetate in distilled water at ultra-violet (UV) detection 428 nm or 500 nm. Additionally, this study established the liquid chromatography tandem mass spectrometry (LC-MS/MS) method to confirm positive samples suspected by HPLC results. The HPLC-UV method had good linearity, indicating r²> 0.999. The recoveries of the samples spiked with three different concentration ranged from 73.8~91.5 %, and relative standard deviation values indicated 0.2~5.2 %. The established LC-MS/MS could successfully identify the synthetic pigments in herbal medicine samples. The study demonstrates that Typha orientalis adulterated by yellowish synthetic dyes can be successfully distinguished when using the HPLC-UV method.

• Applied Chemistry for Engineering
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• v.34 no.1
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• pp.94-97
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• 2023

2,7-bis(3',6'-diphenyl-[1,1':2',1"-terphenyl]-4'-yl)-9,9'-spirobi[fluorene] (BTPSF) and 2,7-bis(1,4-diphenyltriphenylen-2-yl)-9,9'-spirobi[fluorene] (BDTSF) were successfully synthesized as novel blue-emission materials for organic light-emitting diodes (OLEDs) based on the spirobifluorene (SBF) moiety. BTPSF and BDTSF were obtained in high purity via a Diels-Alder reaction, without the use of a catalyst. Photoluminescence spectra of the synthesized materials showed maximum emitting wave-lengths of approximately 381 and 407 nm in solution and 395 and 434 nm in the film state, for BTPSF and BDTSF, respectively, indicating ultra-violet and deep blue emission colors. BDTSF was applied as an emissive layer (EML) in non-doped devices and achieved a current efficiency of 0.61 cd/A and an external quantum efficiency (EQE) of 0.46%.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.60.2-60.2
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• 2021

In this study, we determinate the differential emission measure(DEM) of solar corona using three SDO/AIA EUV channel images and three AI-generated ones. To generate the AI-generated images, we apply a deep learning model based on multi-layer perceptrons by assuming that all pixels in solar EUV images are independent of one another. For the input data, we use three SDO/AIA EUV channels (171, 193, and 211). For the target data, we use other three SDO/AIA EUV channels (94, 131, and 335). We train the model using 358 pairs of SDO/AIA EUV images at every 00:00 UT in 2011. We use SDO/AIA pixels within 1.2 solar radii to consider not only the solar disk but also above the limb. We apply our model to several brightening patches and loops in SDO/AIA images for the determination of DEMs. Our main results from this study are as follows. First, our model successfully generates three solar EUV channel images using the other three channel images. Second, the noises in the AI-generated EUV channel images are greatly reduced compared to the original target ones. Third, the estimated DEMs using three SDO/AIA images and three AI-generated ones are similar to those using three SDO/AIA images and three stacked (50 frames) ones. These results imply that our deep learning model is able to analyze temperature response functions of SDO/AIA channel images, showing a sufficient possibility that AI-generated data can be used for multi-wavelength studies of various scientific fields. SDO: Solar Dynamics Observatory AIA: Atmospheric Imaging Assembly EUV: Extreme Ultra Violet DEM: Diffrential Emission Measure

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2D
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• pp.209-216
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• 2009

This study was conducted to develop a thin paving technique using polymer epoxy resin materials which is considered as a durable pavement materials. The mechanical performance characteristics of the polymer epoxy resin materials were also evaluated to confirm the validity as a pavement materials. To estimate the performance properties of the materials, bending tests and bonding tests were performed using freeze-thaw and ultra-violet rays to accelerate the aging of materials. In addition, HYUNStay, a commercial structural analysis program for cable-stayed bridges, was used to compare the effect of paving materials between the polymer epoxy resin materials and the conventional ones on the reduction of cable tension and on the stability of the main tower. According to the test results, it is noted that the thin paving technique using polymer epoxy resin materials can improve the performance and durability of pavement compared to the conventional one.

• Advances in nano research
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• v.15 no.1
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• pp.35-48
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• 2023

Nanoparticles are known for their outstanding properties such as particle size, surface area, optical and electrical properties. These properties have significantly boasted their applications in various surface phenomena. In this work, calcium oxide nanoparticles were synthesized from periwinkle shells as an approach towards waste management through resource recovery. The sol gel method was used for the synthesis. The nanoparticles were characterized using X-Ray diffractometer (XRD), Fourier Transformed Infra-Red Spectrophotometer (FTIR), Brunauer Emmett Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultra violet visible spectrophotometer (UV-visible). While DLS and SEM underestimate the particle diameter, the BET analysis reveals surface area of 138.998 m²/g, pore volume = 0.167 m³/g and pore diameter of 2.47 nm. The nanoparticles were also employed as an adsorbent for the purification of dye (methyl orange) contaminated water. The adsorbent showed excellent removal efficiency (up to 97 %) for the dye through the mechanism of physical adsorption. The adsorption of the dye fitted the Langmuir and Temkin models. Analysis of FTIR spectrum after adsorption complemented with computational chemistry modelling to reveal the imine nitrogen group as the site for the adsorption of the dye unto the nanomaterials. The synthesized nanomaterials have an average particle size of 24 nm, showed a unique XRD peak and is thermally and mechanically stable within the investigated temperature range (30 to 70 ℃).

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.68-73
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• 2024

In this study, the praseodymium-doped yttrium phosphate (YPO₄:Pr³⁺) powder, which is well known for its high luminescent efficiency, and long life in the UV range, was synthesized with various content ratios of Pr₆O₁₁ and calcination temperature. Crystal structure and luminescent properties of various phosphor powders based on different concentrations and calcination conditions were characterized by XRD (X-Ray Diffraction) and PL (photoluminescence) spectrometers. From the XRD analysis, the structure of YPO₄:Pr³⁺ which is calcinated at 1,200℃ was stable tetragonal phase and crystal size was calculated about 25 nm by Scherrer equation. PL emission of YPO₄:Pr³⁺ with a different content ratio of Pr₆O₁₁ by excitation λ_exc=250 nm shows that 0.75 mol% phosphor powder has maximum PL intensity and PL decreases with the increase of the ratio of Pr₆O₁₁ up to 1.25 mol% which is caused by changes of crystallinity of phosphor powders. With increasing dopant ratio, photo-luminescence Emission decreases due to Concentration quenching, which is commonly observed in phosphors. Currently, 0.75 mol% is considered the optimal doping concentration. A hybrid ultraviolet-emitting device incorporating YPO₄:Pr³⁺ fluorescent material with plasma discharge was fabricated to enhance UV germicidal effects while minimizing ozone generation. UV emission from the plasma discharge device was shown at about 200 nm and 350 nm which caused additional emission of the regions of 250 nm, 315 nm, and 370 nm from the YPO₄:Pr³⁺ phosphor.

• Korean Journal of Food Science and Technology
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• v.4 no.3
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• pp.206-212
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• 1972

Oxidative changes in the rice lipids under accelerated condition were studied by measuring the changes in weight gain, total carbonyl compound, malonaldehyde, and fatty acid composition. Rice lipids were prepared by extraction with either n-hexane or ethanol from polished rice grain and purified by Folch's method. The lipid preparations were either incubated in dark at $40^{\circ}C$ or irradiated with ultra-violet light for a period of 55 days. Weight gain by oxygen absorbed sharply increased within 3 days in the rice lipids under UV light irradiation. However, with the rice lipids at $40^{\circ}C$ incubation a moderate increase in weight was observed only after 45 days storage. Their induction periods were one day (hexane extracted, under UV light), 2 days (ethanol extracted, under UV light), 30 days (hexane extracted, at $40^{\circ}C$), and 40 days (ethanol extracted, at $40^{\circ}C$) respectively. Oxidative rancid odor appeared at the end of the induction period. Total carbonyl compound and malonaldehyde markedly increased within 7 days, and decreased in the rice lipids under ultra violet light irradiation, while at $40^{\circ}C$ incubation they were continued to increase slowly through out the storage. The hexane extracted lipid were less stable than ethanol extracted lipid on the basis of oxygen absorption, malonaldehyde and other carbonyl compound formation. With the hexane extracted lipid during 55 days incubation at $40^{\circ}C$, the contents of linoleic and linolenic acids decreased, while the oleic, stearic, and palmitic acids increased.