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Characteristics of Tremolite Asbestos from Abandoned Asbestos Mines in Boryeong Area, Chungnam (충남 보령지역의 폐석면 광산에서 산출하는 투각섬석 석면의 특성)

  • Yoon, Keun-Taek;Hwang, Jin-Yeon;Oh, Ji-Ho;Lee, Hyo-Min
    • Journal of the Mineralogical Society of Korea
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    • v.23 no.1
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    • pp.73-84
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    • 2010
  • We studied the geological occurrence, associated minerals, mineralogical properties and formation process of tremolites from two abandoned asbestos mines, Jungang (Sinsuk) and Daebosuksan, located in Boryoung area, Chungnam. Morphologically different tremolites such as long fibrous, needle-like, bladed and prismatic forms coexisted. Fibrous tremolite, known for its high toxieity to human health, was systematically analyzed by polarized light microscopy and scanning electron microscopy. The average length of tremolite fibers was 31.2 ${\mu}m$ although the maximum length of some asbestos was 210.0 ${\mu}m$. The average width and aspect ratio were 1.6 ${\mu}m$ and 19.9, respectively. Tremolite showed inclined extinction in the range of 6.1~20.2$^{\cric}$. X-ray diffraction patterns were slightly different between fibrous (asbestiform) and prismatic (non-asbestiform) tremolites. EPMA analysis of tremolites in the study area indicated extremely high Mg content with very low Fe content, close to the composition of tremolite in end-member in the tremolite-actinolite solid solution series. The formational conditions of asbestiform and non-asbestiform tremolite appear to be different. Asbestiform tremolite was estimated to have been formed in later stage.

Kr Atoms and Their Chlustering in Zeolite A

  • Im, U Taek;Jang, Jang Hwan;Jeong, Gi Jin;Heo, Nam Ho
    • Bulletin of the Korean Chemical Society
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    • v.22 no.9
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    • pp.1023-1029
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    • 2001
  • The positions of Kr atoms encapsulated in the molecular-dimensioned cavities of fully dehydrated zeolite A of unit-cell composition Cs3Na8HSi12Al12O48 (Cs3-A) have been determined. Cs3-A was exposed to 1025 atm of krypton gas at 400 $^{\circ}C$ for four days, followed by cooling at pressure to encapsulate Kr atoms. The resulting crystal structure of Cs3-A(6Kr) (a = $12.247(2)\AA$, R1 = 0.078, and R2 = 0.085) has been determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m at $21(1)^{\circ}C$ and 1 atm. In the crystal structure of Cs3-A(6Kr), six Kr atoms per unit cell are distributed over three crystallographically distinct positions: each unit cell contains one Kr atom at Kr(1) on a threefold axis in the sodalite unit, three at Kr(2) opposite four-rings in the large cavity, and two at Kr(3) on threefold axes in the large cavity. Relatively strong interactions of Kr atoms at Kr(1) and Kr(3) with Na+ ions of six-rings are observed: Na-Kr(1) = 3.6(1) $\AA$ and Na-Kr(3) = $3.08(5)\AA.$ In each sodalite unit, one Kr atom at Kr(1) was displaced $0.74\AA$ from the center of the sodalite unit toward a Na+ ion, where it can be polarized by the electrostatic field of the zeolite, avoiding the center of the sodalite unit which by symmetry has no electrostatic field. In each large cavity, five Kr atoms were found, forming a trigonal-bipyramid arrangement with three Kr(2) atoms at equatorial positions and two Kr(3) atoms at axial positions. With various reasonable distances and angles, the existence of Kr5 cluster was proposed (Kr(2)-Kr(3) = $4.78(6)\AA$ and Kr(2)-Kr(2) = $5.94(7)\AA$, Kr(2)-Kr(3)-Kr(2) = 76.9(3), Kr(3)-Kr(2)-Kr(3) = 88(1), and Kr(2)-Kr(2)-Kr(2) = $60^{\circ}).$ These arrangements of the encapsulated Kr atoms in the large cavity are stabilized by alternating dipoles induced on Kr(2) by four-ring oxygens and Kr(3) by six-ring Na+ ions, respectively.

A Study on 8 × 4 Dual-Polarized Array Antenna for X-Band Using LTCC-Based ME Dipole Antenna Structure (LTCC 기반 ME Dipole 안테나 구조를 활용한 X-Band 용 8 × 4 이중편파 배열안테나에 관한 연구)

  • Jung, Jae-Woong;Seo, Deokjin;Ryu, Jong-In
    • Journal of the Microelectronics and Packaging Society
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    • v.28 no.3
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    • pp.25-32
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    • 2021
  • In this paper, the Magneto-Electric(ME) dipole array antenna with dual-polarization in the X-Band is proposed and it is implemented and measured. The proposed array antenna is composed of 32 single ME dipole antenna and a Teflon PCB. 1 × 1 ME dipole antenna is implemented dual-polarization by radiating vertical polarization and horizontal polarization from two pairs of radiators. 2-port feeding structures are realized by lamination process using LTCC. And, each port independently feeds the radiator through a Γ-shaped feeding strip with isolation between ports. The Teflon PCB used in the antenna array has a 4-layer structure, and 2-port is fed through the top and bottom layers. The λg/4 transformer is applied to the transmission line of the Teflon PCB for impedance matching of the arrayed antenna and the Teflon PCB, and the optimal parameters are obtained through simulation. The measured maximum antenna gains of port 1 was 18.2 dBi, Cross-pol was 1.0 dBi. And the measured maximum antenna gains of port 1 was 18.1 dBi, Cross-pol was 3.2 dBi.

Synthesis and Characterization of Polymers with Azobenzene and Hexamethylene Groups in Main Chain (주사슬에 아조벤젠기와 헥사메틸렌기를 갖는 고분자의 합성 및 특성)

  • Gu, Su-Jin;Lee, Eung-Jae;Bang, Moon-Soo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.4
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    • pp.86-92
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    • 2019
  • Polymers with various compositions of azobenzene and hexamethylene groups in the main chain were synthesized by a Schotten-Baumann reaction and their properties were investigated. The chemical structures and physical properties of the synthesized polymers were investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, and x-ray diffraction. The polymers showed an inherent viscosity of 1.28-1.36 dl/g and were relatively insoluble in most organic solvents. The melt transition temperature increased rapidly with increasing number of azobenzene groups in the polymer. When the azobenzene monomer content was more than 50 mol%, no melting transition occurred below the decomposition temperature. Among the polymers with a melt transition temperature, the MP-A3C7 and MP-A5C5 polymers were liquid crystalline materials and exhibited a nematic phase with weak liquid crystallinity over a wide liquid crystal temperature range. This difference in the properties of the synthesized polymers is likely due to the changes in intermolecular forces resulting from the linearity and polarity of the trans-form of azobenzene.

Polarimetry of solar system small bodies using the Seoul National University 61cm telescope and TRIPOL

  • Jin, Sunho;Ishiguro, Masateru;Kwon, Yuna Grace;Geem, Jooyeon;Bach, Yoonsoo P.;Seo, Jinguk;Sasago, Hiroshi;Sato, Shuji
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.64.2-64.2
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    • 2019
  • It is known that lights scattered by comets and asteroids are partially polarized. From polarimetric observations of those objects, we can investigate physical properties, such as albedos, sizes of cometary dust particles and regolith of asteroids. Since the polarization degrees of those objects highly depend on their phase angles (Sun-object-observer's angles), long-term monitoring observations are required. Moreover, comets show unforeseeable activations (i.e., outbursts) which need follow-up observations to understand the mechanism. In order to realize such monitoring and transient observations, we installed the Triple-Range Imager and POLarimeter (TRIPOL) on the 61cm telescope of Seoul National University (Hereafter, SNU) Gwanak campus. With this combination, we can obtain g', r', i' bands photopolarimetric images simultaneously with $8.0^{\prime}{\times}8.0^{\prime}$ field of view and pixel resolution of 0.94" pixel-1. Here, we make a presentation regarding the photometric and polarimetric performances of TRIPOL on the SNU 61cm telescope. In addition, we introduce initial polarimetric results of asteroid and comets with the instruments. First, we determine the limiting magnitudes (defined as magnitudes for S/N=5) of $15.17{\pm}0.06$ (g'-band), $15.68{\pm}0.01$ (r'-band), $16.24{\pm}0.03$ (I'-band), respectively, with total 240-seconds exposure (four 60-seconds exposure images, each was taken at different rotation angle for the half-wave plate). Second, we found that the instrumental polarization is negligibly small, ($-0.32{\pm}0.04%$ in the g', $-0.36{\pm}0.05%$ in the r' and $-0.21{\pm}0.04%$ in the i'-bands), while the polarization efficiencies are large enough to maximize the performance (i.e., $97.52{\pm}0.03%$ in the g', $98.83{\pm}0.02%$ in the r' and $99.15{\pm}0.02%$ in the i'-bands). With the instruments, we made observations of three Jupiter-family comets, 21P/Giacobini-Zinner, 38P/Stephan-Oterma, and 46P/Wirtanen and plan to observe one near-Earth asteroid, (433) Eros, on a trial basis. Especially for comets, we discriminate signals from dust and gas to eliminate gas contamination, which are known to change observed degree of linear polarization, using multi-band images. We confirm that the phase angle dependency of these comets are consistent with previous observations, probably because polarimetric property of Jupiter-family comets are broadly homogeneous unlike asteroids. We will also describe future observation plans using TRIPOL and SNU 61cm telescope.

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Automatic Classification and Vocabulary Analysis of Political Bias in News Articles by Using Subword Tokenization (부분 단어 토큰화 기법을 이용한 뉴스 기사 정치적 편향성 자동 분류 및 어휘 분석)

  • Cho, Dan Bi;Lee, Hyun Young;Jung, Won Sup;Kang, Seung Shik
    • KIPS Transactions on Software and Data Engineering
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    • v.10 no.1
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    • pp.1-8
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    • 2021
  • In the political field of news articles, there are polarized and biased characteristics such as conservative and liberal, which is called political bias. We constructed keyword-based dataset to classify bias of news articles. Most embedding researches represent a sentence with sequence of morphemes. In our work, we expect that the number of unknown tokens will be reduced if the sentences are constituted by subwords that are segmented by the language model. We propose a document embedding model with subword tokenization and apply this model to SVM and feedforward neural network structure to classify the political bias. As a result of comparing the performance of the document embedding model with morphological analysis, the document embedding model with subwords showed the highest accuracy at 78.22%. It was confirmed that the number of unknown tokens was reduced by subword tokenization. Using the best performance embedding model in our bias classification task, we extract the keywords based on politicians. The bias of keywords was verified by the average similarity with the vector of politicians from each political tendency.

Skin Barrier Function Enhancement Effect about Ceramide Liquid Crystal Emulsion: Similar Ratio of Skin Lipid Composition (피부 지질 조성 모사 Ceramide 액정 에멀젼의 피부 장벽 강화 효과 확인에 관한 연구)

  • Han, Ji Hye;Lee, Ju Yeon;Lee, Kwan Hyoung;Kim, Hee Sun;Park, Chang Yeol;Maeng, Ji Hye;So, Ji Min;Nam, Gae Won;Kim, Sang Chul
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.47 no.1
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    • pp.49-56
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    • 2021
  • In this study, a liquid crystal emulsion with a composition ratio similar to the skin lipid composition was manufactured using ceramide, glycolipids, cholesterol, and fatty acids, and a polarized microscope was used to identify liquid crystal particles in the formulation, and a cryso-SEM was used to confirm the formation of a multilayer structure. The above samples were stored at room temperature for one month and the liquid crystal structure was continuously maintained through microscopic observation. In addition, a cream composition containing liquid crystal emulsion was manufactured, and the efficiency of ceramide skin penetration was confirmed using three-dimensional artificial skin. Clinical trials were conducted using the cream composition and the results of clinical trials on skin barrier improvement were confirmed by measuring skin moisture retention (skin hydration) and transepidermal water loss (T EWL) of subjects compared to general emulsion.

A Study on the Liquid Crystal Formed in PLO Gel Containing Ceramide NP (Ceramide NP 를 함유한 PLO Gel 에서 형성되는 액정에 관한 연구)

  • Heo, Min Geun;Yoon, Kyung-Sup
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.47 no.1
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    • pp.85-92
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    • 2021
  • The stratum corneum is formed from keratinocytes and intercellular lipids, with ceramide as the main component of intercellular lipids. Ceramides are one of the important components of the intercellular lipids to form a lamellar structure, but they are insoluble and therefore are not suitable for direct application to the skin. Thus, it was intended to apply ceramide to the formulation of pluronic lecithin organogel (PLO gel), which received constant attention among drug delivery systems. A suitable oil for formulation was selected and a PLO gel containing ceramide was manufactured. Liquid crystal formation and variation were observed using polarized microscopes, and viscoelastic analysis was performed to find out the viscoelastic behavior of the PLO gel. Small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) analysis were performed to confirm the structures in the formulation. Results showed that the size and stability of the liquid crystal differed depending on the content ratio of ceramide and lecithin in the PLO gel containing ceramide. Furthermore, viscoelastic analysis showed the stability of the formulation, and SAXS/WAXS analysis confirmed that the PLO gel without ceramide had hexagonal structure of the quadrilateral system array, and the PLO gel with ceramide had the lamellar structure of the quadrilateral system array.

Geophysical Logging of Frequency-domain Induced Polarization for Mineral Exploration (광물탐사를 위한 진동수영역 유도분극 물리검층)

  • Shin, Seungwook
    • Geophysics and Geophysical Exploration
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    • v.24 no.3
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    • pp.73-77
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    • 2021
  • Induced polarization (IP) is useful for mineral exploration and hydrogeological studies by visualizing the electrochemical reactions at the interface between polarized minerals and groundwater. Frequency-domain IP (FDIP) is not actively applied to field surveys because it takes longer to acquire data, despite its higher data quality than conventional time-domain IP. However, data quality is more important in current mineral exploration as the targets gradually shift to deep or low-grade ore bodies. In addition, the measurement time reduced by automated instrumentation increases the potential for FDIP field applications. Therefore, we demonstrate that FDIP can detect mineral exploration targets by performing geophysical logging in the boreholes of a skarn deposit, in South Korea. Alternating current (AC) resistivity, percent frequency effect (PFE) and metal factor (MF) were calculated from impedance values obtained at two different frequencies. Skarn zones containing magnetite or pyrite showed relatively low AC resistivity, high PFE, and high MF compared to other zones. Therefore, FDIP surveys are considered to be useful for mineral exploration.

Evaluating the Effectiveness of an Artificial Intelligence Model for Classification of Basic Volcanic Rocks Based on Polarized Microscope Image (편광현미경 이미지 기반 염기성 화산암 분류를 위한 인공지능 모델의 효용성 평가)

  • Sim, Ho;Jung, Wonwoo;Hong, Seongsik;Seo, Jaewon;Park, Changyun;Song, Yungoo
    • Economic and Environmental Geology
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    • v.55 no.3
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    • pp.309-316
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    • 2022
  • In order to minimize the human and time consumption required for rock classification, research on rock classification using artificial intelligence (AI) has recently developed. In this study, basic volcanic rocks were subdivided by using polarizing microscope thin section images. A convolutional neural network (CNN) model based on Tensorflow and Keras libraries was self-producted for rock classification. A total of 720 images of olivine basalt, basaltic andesite, olivine tholeiite, trachytic olivine basalt reference specimens were mounted with open nicol, cross nicol, and adding gypsum plates, and trained at the training : test = 7 : 3 ratio. As a result of machine learning, the classification accuracy was over 80-90%. When we confirmed the classification accuracy of each AI model, it is expected that the rock classification method of this model will not be much different from the rock classification process of a geologist. Furthermore, if not only this model but also models that subdivide more diverse rock types are produced and integrated, the AI model that satisfies both the speed of data classification and the accessibility of non-experts can be developed, thereby providing a new framework for basic petrology research.