• Journal of Powder Materials
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• v.27 no.6
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• pp.490-497
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• 2020

The 3D printing process provides a higher degree of freedom when designing ceramic parts than the conventional press forming process. However, the generation and growth of the microcracks induced during heat treatment is thought to be due to the occurrence of local tensile stress caused by the thermal decomposition of the binder inside the green body. In this study, an alumina columnar specimen, which is a representative ceramic material, is fabricated using the digital light process (DLP) 3D printing method. DTG analysis is performed to investigate the cause of the occurrence of microcracks by analyzing the debinding process in which microcracks are mainly generated. HDDA of epoxy acrylates, which is the main binder, rapidly debinded in the range of 200 to 500℃, and microcracks are observed because of real-time microscopic image observation. For mitigating the rapid debinding process of HDDA, other types of acrylates PETA, PUA, and MMA are added, and the effect of these additives on the debinding rate is investigated. By analyzing the DTG in the 25 to 300℃ region, it is confirmed that the PETA monomer and the PUA monomer can suppress the rapid decomposition rate of HDDA in this temperature range.

• Journal of dental hygiene science
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• v.20 no.4
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• pp.213-220
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• 2020

Background: The leaves of Perilla frutescens, commonly called perilla and used for food in Korea, contain components with a variety of biological effects and potential therapeutic applications. The purpose of this study was to identify the components of 70% ethanol extracted Perilla frutescens (EEPF) and determine its inhibitory effects on oral microbial activity and production of nitric oxide (NO) and prostaglandin E2 (PGE2) in lipopolysaccharides (LPS)-stimulated Raw264.7 macrophages, consequently, to confirm the possibility of using EEPF as a functional component for improving the oral environment and preventing inflammation. Methods: One kg of P. frutescens leaves was extracted with 70% ethanol and dried at -70℃. EEPF was analyzed using high-performance liquid chromatography analysis, and antimicrobial activity against oral microorganisms was revealed using the disk diffusion test. Cell viability was elucidated using a methylthiazolydiphenyl-tetrazolium bromide assay, and the effect of EEPF on LPS-induced morphological variation was confirmed through microscopic observation. The effect of EEPF on LPS-induced production of pro-inflammatory mediators, NO and PGE2 was confirmed by the NO assay and PGE2 enzyme-linked immunosorbent assay. Results: The main component of EEPF was rosemarinic acid, and EEPF showed weak anti-bacterial and anti-fungal effects against microorganisms living in the oral cavity. EEPF did not show toxicity to Raw264.7 macrophages and had inhibitory effects on the morphological variations and production of pro-inflammatory mediators, NO and PGE2 in LPS-stimulated Raw264.7 macrophages. Conclusion: EEPF can be used as a functional material for improving the oral environment through the control of oral microorganisms and for modulating inflammation by inhibiting the production of inflammatory mediators.

• Journal of the Korean Society of Clothing and Textiles
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• v.45 no.3
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• pp.409-422
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• 2021

A doctor's coat worn by Seo Jae-pil (1864-1951)-National Registered Cultural Heritage No. 607-was conserved with wet cleaning to remove thick wrinkles and brown stains that had been present for a long time. This paper also applied microscopic observation and infrared spectrophotometric analysis to obtain scientific investigation data on the cotton fabric of this doctor's coat. Information about Seo Jae-pil's time as a doctor, the process of changing his English name, and C.D.Williams & Co., which produced the medical coat, revealed that this doctor's coat was worn by Seo Jae-pil between 1892 and 1898 or 1926 and 1939. Additionally, this paper proposes a pad for filling relics that can protect the shape of modern and contemporary clothing, such as Seo Jae-pil's doctor's coat, for display at a museum site. Specifically, this research provides detailed information on the manufacturing of filling pads that can prevent damage to modern and contemporary jackets and coats so that they can be used in the cultural heritage field by developing filling materials for three-dimensional costume artifacts.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.5
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• pp.504-508
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• 2022

Single crystal gallium oxide (Ga₂O₃) has been an emerging material for power semiconductor applications. However, the defect distribution of Ga₂O₃ substrates needs to be carefully characterized to improve crystal quality during crystal growth. We analyzed the type and the distribution of defects on commercial (-201) Ga₂O₃ substrates to get a basic standard prior to growing Ga₂O₃ crystals. Etch pit technique was employed to expose the type of defects on the Ga₂O₃ substrates. Synchrotron white beam X-ray topography was also utilized to observe the defect distribution by a nondestructive manner. We expect that the observation of defect distribution with three-dimensional geometry will also be useful for other crystal planes of Ga₂O₃ single crystals.

• Parasites, Hosts and Diseases
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• v.60 no.5
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• pp.361-365
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• 2022

We report a species of diplostomid fluke recovered from 3 carcasses of wild Korean raccoon dog, Nyctereutes procyonoides koreensis, in Korea. A total of 107 diplostomid flukes were recovered from the small intestines of Korean raccoon dogs, which were obtained from the Gangwon Wildlife Medical Rescue Center. Worms fixed with 10% neutral formalin were subjected to microscopic observation and those fixed in 70% ethanol were used for molecular genomic analysis. The worm was divided into 2 separate parts, forebody and hindbody, with a total length of 3,020-4,090 (3,855) ㎛ and a width of 1,210-1,770 (1,562) ㎛. The boat-shaped forebody has a pair of characteristic tentacular appendage, 2 suckers, holdfast organ, and vitelline follicles. The oval to cylindrical hindbody has reproductive organs. The ovary was round or elliptical and located in the anterior of the testes. Two large testes were slightly segmented and tandemly arranged, occupying almost half of hindbody. The short uterus contained a relatively small number of unembryonated eggs sized 130-140×85-96 ㎛. The partial sequence of 18S rRNA of this fluke was consistent with Alaria alata. Based on the morphological and molecular characteristics, the diplostomid flukes recovered from the small intestine of Korean raccoon dogs were identified as A. alata (Digenea: Diplostomidae).

• Medical Lasers
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• v.10 no.2
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• pp.96-105
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• 2021

Background and Objectives Skin aging is reportedly associated with regulation in collagen and elastin synthesis. This study investigated the potential of combining light-emitting diode (LED) treatments using a 630-nm and 850-nm LED with simultaneous microcurrent application. Materials and Methods The dorsal skin of female pigs was treated with a home-use device. We examined the treatment effects using photography, thermocamera, microscopic pathology, and histological examination to determine the mechanism of action, efficacy, and safety of the procedure. A histological observation was performed using hematoxylin and eosin, Masson's trichrome, Victoria blue, and immunohistochemical staining. We also used the Sircol soluble collagen and elastin assay kit to measure the amounts of collagen and elastin in the porcine back skin tissue after 2 and 6 weeks. Results Evaluation by visual inspection and devices showed no skin damage or heat-induced injury at the treatment site. Histological staining revealed that accurate treatment of the targeted dermis layer effectively enhanced collagen and elastin deposition. Collagen type I, a protein defined by immunohistochemical staining, was overexpressed in the early stages of weeks 2 and 6. Combined therapy findings showed the superior capability of the 630-nm and 850-nm LED procedures to induce collagen; in contrast, elastin induction was more pronounced after microcurrent treatments. Conclusion The home-use LED device, comprising a combination of 630-nm and 850-nm LEDs and microcurrent, is safe and can be used as an adjunctive treatment for self-administered facial rejuvenation.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.3
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• pp.122-129
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• 2021

This study focuses on the microstructural development of 99% magnesium alloy sheet manufactured using twin roll casting (TRC) process. Herein, a plate with a thickness of 5 mm was manufactured using the TRC process, homogenization heat treatment was performed at 400℃ for 2-32 h, and finally, the change in microstructure was evaluated via optical microscopy and textural analysis. The results suggest that the plate manufactured using the TRC process was not destroyed and was successfully rolled into a plate. Microscopic observation suggested that the dendritic cast structure was arranged along the rolling direction. And the central layer of the rolled plate, where was present in a liquid state at the beginning of rolling, solidified later during the TRC process to form central segregation. The initial cast structure and inhomogeneous structure of the plate were recrystallized by homogenization heat treatment for only 2 h, and it was confirmed that the segregated part of the central layer became homogeneous and recrystallization occurred. Grain growth occurred as the heat treatment time increased, and secondary recrystallization occurred, wherein only some grains were grown. The textural analysis, which was conducted via X-ray diffraction, confirmed that the relatively weak basal plane texture developed using the TRC process was formed into a random texture after heat treatment.

• Composites Research
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• v.35 no.6
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• pp.463-468
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• 2022

The high porosity of the infill pattern of carbon chopped fiber-reinforced Nylon composite structures fabricated by the fused filament fabrication (FFF) type 3D printers determines the mechanical performance of the printed structures. This study experimentally evaluated the mechanical performance of Onyx composite specimens fabricated with a rectangular infill structure under the hot-pressing condition to improve the mechanical properties by reducing the porosity of the infill pattern of the printed structure, and evaluated the best mechanical performance. The hot-pressing conditions (145℃, 4 MPa, 12 min) that induce the most appropriate mechanical properties were found. As a result of microscopic observation, it was confirmed that the infill porosity of the composite specimens subjected to post hot-pressing treatment was effectively reduced. In order to confirm the mechanical performance of the post-treated specimen, a tensile test and a three-point bending test were performed with a control specimen without post-treatment and a specimen printed with the same density and dimensions after post-treatment to evaluate the mechanical properties. As a result of comparison, it was confirmed that the mechanical properties were effectively improved when the post-treatment of hot-pressing was performed.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.45.2-46
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• 2021

The Hayabusa 2 mission target asteroid (162173) Ryugu is a near-Earth, carbonaceous (C-type) asteroid. Before the arrival, this asteroid is expected to be covered with mm- to cm- sized grains through the thermal infrared observations [1]. These grains are widely understood to be formed by past impacts with other celestial bodies and fractures induced by thermal fatigue [2]. However, the close-up images by the MASCOT lander showed lumpy boulders but no abundant fine grains [3]. Morota et al. suggested that there would be submillimeter particles on the top of these boulders but not resolved by Hayabusa 2's onboard instruments [4]. Hence, we conducted polarimetry of Ryugu to investigate microscopic grain sizes on its surface. Polarimetry is a powerful tool to estimate physical properties such as albedo and grain size. Especially, it is known that the maximum polarization degree (Pmax) and the geometric albedo (pV) show an empirical relationship depending on surface grain sizes [5]. We observed Ryugu from UT 2020 November 30 to December 10 at large phase angles (ranging from 78.5 to 89.7 degrees) to derive Pmax. We modified TRIPOL (Triple Range Imager and POLarimeter, [6]) to attach to the 1.8-m telescope at the Bohyunsan Optical Astronomy Observatory (BOAO). With this instrument, we observed the asteroid and determined linear polarization degrees at the Rc-band filter. We obtained sufficient data sets from 7 nights at this observatory to determine the Pmax value, and collaborated with other observatories in Japan (i.e., Hokkaido University, Higashi-Hiroshima, and Nishi-Harima) to acquire linear polarization degrees of the asteroid from total 24 nights observations with large phase angle coverage (From 28 to 104 degrees). The observational results have been published in Kuroda et al. (2021) [7]. We thus found the dominance of submillimeter particles on the surface of Ryugu from the comparison with other meteorite samples from the campaign observation. In this presentation, we report our activity to modify the TRIPOL for the 1.8-m telescope and the polarimetric performance. We also examine the rotational variability of the polarization degree using the TRIPOL data.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.191-191
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• 2022

Heterostyly continues to fascinate evolutionary biologists interested in heredity, evolution, breeding, and adaptive function. Polymorphism demonstrates how simply inherited developmental changes in the location of plant sexual associations can have important consequences for population pollination and mating biology. In contrast to homozygous self incompatibility, only a small number of mating phenotypes can be maintained in the population because insect pollinators have limitations in achieving multiple segregation sites for pollen deposition. Field studies of pollen tube growth have shown that reciprocal style-stamen polymorphisms function to increase the capacity of insect-mediated cross-pollination. The genetic pattern of style morphs is well established in various taxa, but despite recent advances, the identity, number, and structure of the genes controlling the heteromorphic syndrome have been poorly elucidated. The phenomenon of heterostyly in buckwheat has been controlled by gene complex concentrate to S-locus. Homomorphic autogamous buckwheat strains were established by the interspecific hybridization. Backcrossing of this line to the common buckwheat (pin) and selecting homostylar progenies made it possible to introduce the self-compatible gene into common buckwheat. In the result, we obtained the BC₉F₂ generation, and defined the strong linkage between flower type and self-incompatibility by microscopic observation of pollen tube growth. This finding suggests that self-incompatibility character is not controlled by one gene. Moreover, we defined the strong linkage between flower type and self-incompatibility. It strongly supports the S supergene theory. Therefore, we have plan to elucidate the heterostyly self-incompatibility by using molecular genetics, proteome analysis and apply to exploitation of buckwheat improvement. In near future, the expression of heterozygous syndromes in genus Fagopyrum with single isolated heterozygous species may provide clues to early stages of polymorphic assembly and shed light on evolutionary models of heterozygous strains.