• Title/Summary/Keyword: dense morphology

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Property of Spin-sprayed ZnO Film on PC Substrate (스핀 스프레이법으로 PC 기판에 제작한 산화아연 박막의 특성)

  • Hoong, Jeongsoo;Matsushita, Nobuhiro;Katsumata, Ken-ichi;Park, Yongseo;Kim, Kyunghwan
    • Journal of the Semiconductor & Display Technology
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    • v.17 no.3
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    • pp.27-30
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    • 2018
  • In this study, ZnO film was deposited on polycarbonate substrate by spin-spray method at low substrate temperature of $85^{\circ}C$. Surface morphology of ZnO films was changed by adding citrate from rod to dense structure. As-deposited ZnO film indicated high transmittance above 80%. In case of the resistivity, as-deposited ZnO film had high resistivity due to the existence of organic substance in the film. However, organic substance was removed and resistivity was decreased to $3.9{\times}10^{-2}{\Omega}{\cdot}cm$, after UV irradiation.

Environmental Dependence of High-redshift Galaxies in CFHTLS W2 Field

  • Paek, Insu;Im, Myungshin;Kim, Jae-Woo
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.36.1-36.1
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    • 2018
  • Star formation activity of galaxies, along with color and morphology, show significant environmental dependence in local universe, where galaxies in dense environment tend to be more quiescent and redder. However, many studies show that such environmental dependence does not continue at higher redshifts beyond z~1. The question of how the environmental dependence of galactic properties have developed over time is crucial to understanding cosmic galactic evolution. By combining data from Canada-France-Hawaii Telescope Legacy Survey(CFHTLS), Infrared Medium-Deep Survey(IMS), and other surveys, the photometric redshifts of galaxies in CFHTLS W2 field were estimated by fitting spectral energy distribution. The distribution of galaxies was mapped in redshift bins of 0.05 interval from 0.6 to 1.4. For each redshift bin, the number density was mapped. The galaxies in high density regions were grouped into clusters using friend-of-friend method. The color of galaxies were analyzed to study the correlation with redshift as well as environmental difference between field galaxies and cluster member galaxies.

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Anti Corrosive Performance of Al and Zn Coatings Deposited by Plasma Arc Thermal Spray Process in Artificial Ocean Water (인공해양환경에서 플라즈마 아크 용사 공법이 적용된 Al 및 Zn 코팅의 부식 방지 성능 평가)

  • Adnin, Raihana Jannat;Lee, Han-Seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2020.11a
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    • pp.52-53
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    • 2020
  • The thermal spray coating process is being used to protect the metals and alloys from wear, abrasion, fatigue, tribology, and corrosion failure. Therefore, in the present study, Al and Zn was deposited by plasma arc thermal spray process onto the steel substrate and their performance was assessed. The bond adhesion result shows that Al coating has higher value attributed to compact, dense, and less porous compared to Zn coating which contain defects/pores and uneven morphology assessed by scanning electron microscopy (SEM). Electrochemical results show that the Al coating exhibited higher impedance value compared to Zn in artificial ocean water solution at prolonged exposure periods. However, both coatings show the increment in polarization resistance with exposure periods which reveal that porosity of coatings is filled by the corrosion products.

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Performance of Al-Zn Coating by Arc Thermal and Plasma arc Thermal Spray Processes in 3.5% NaCl Solution (3.5% NaCl에서 Arc Thermal and Plasma Arc Spray 공법이 적용된 Al- Zn 코팅 강재의 내 식 성능 평가에 관한 연구)

  • Jannat, Adnin Raihana;Lee, Han-Seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.11a
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    • pp.17-18
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    • 2021
  • In the present study, Al-Zn coating was deposited by Arc thermal (AT) and plasma arc thermal (PAT) spray processes, and their corrosion characteristics were studied in 3.5% NaCl through electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM) and mechanical tests. The bond adhesion result showed that plasma arc sprayed coating had a higher value attributed to compact, dense, and less porous coating compared to arc thermal spray coating which contains defects/pores and uneven morphology as revealed by scanning electron microscope analysis. Electrochemical results revealed that the plasma arc sprayed coating had a high polarization resistance at early stage of immersion, suggesting its excellent corrosion protection performance.

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First Record of Teloganopsis chinoi (Ephemeroptera: Ephemerellidae) Based on Larval Morphology and mtDNA in Korean Peninsula, with a Checklist of Korean Ephemerellidae

  • Sang Woo Jung;Jaeick Jo;Jeong Mi Hwang
    • Animal Systematics, Evolution and Diversity
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    • v.39 no.3
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    • pp.86-91
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    • 2023
  • The genus Teloganopsis Ulmer belonging to the family Ephemerellidae is only known from the species of T. punctisetae (Matsumura, 1931) in the Korean Peninsula. The members of the genus Teloganopsis are characterized by the following characteristics: head and abdominal tergites without any tubercles and complex setae; forefemur with a row of long and stout setae perpendicularly; maxilla covered with dense setae. A total of 17 species had been previously recorded in this family. Here, Teloganopsis chinoi (Gose, 1980), is newly recorded in Korea which was found under a large stone in Kyeongho river. Larval habitus, habitat, line-drawings of key characters of the species, a checklist with habitus photos of Korean Ephemerellidae, and a key to the larvae of Korean Teloganopsis are provided.

Geomorphological Characteristics and OSL Ages of the Moraeul dune in Daechoengdo Island, South Korea (대청도 모래울 사구의 지형 특성과 OSL 연대)

  • Choi, Kwang Hee
    • Journal of The Geomorphological Association of Korea
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    • v.27 no.4
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    • pp.1-11
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    • 2020
  • Coastal dunes play an important role in coastal defense. The Moraeul dune in Daecheongdo Island is representative in this regard. However, there is little knowledge, concerning the morphology, grain size, and formation timing of the dune. This study investigated the geomorphological characteristics of the Moraeul dune using topographic surveys, grain size analyses, and OSL dating. The dune was classified as 'single accreted foredune', which was developed under dense vegetation cover and efficient sand trapping. The dune consisted of fine to medium sand with 1.6Φ of mean grain size, and was covered with pine trees (> 100 years old). The samples from the upper part of the dune yielded quartz OSL ages ranging 0.5 ~ 0.7 ka. Therefore, it is likely that the dune developed at least before the Little Ice Age and became what it is today about one century ago.

A Study on Long-Term Cycling Performance by External Pressure Change for Pouch-Type Lithium Metal Batteries

  • Seong-Ju Sim;Bong-Soo Jin;Jun-Ho Park;Hyun-Soo Kim
    • Journal of Electrochemical Science and Technology
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    • v.15 no.2
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    • pp.314-320
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    • 2024
  • Lithium dendrite formation is one of the most significant problems with lithium metal batteries. The lithium dendrite reduces the lithium metal batteries' cycling life and safety. To apply consistent external pressure to a lithium metal pouch cell, we design a press jig in this study. External pressure creates dense lithium morphology by preventing lithium dendrite formation. After 300 cycles at 1 C, the cells with the external pressure perform far better than the cells without it, with a cycling retention of 97.8%. The formation of stable lithium metal is made possible by external pressure, which also enhances safety and cyclability.

Effect of pulse frequency and duty cycle on microstructure, residual stress and mechanical properties of ZrN coatings deposited by mid-frequency magnetron sputtering (펄스 주파수 및 듀티 사이클이 중간 주파수 마그네트론 스퍼터법으로 증착된 ZrN 코팅막의 미세구조, 잔류응력 및 기계적 특성에 미치는 영향)

  • Sung-Yong Chun
    • Journal of the Korean institute of surface engineering
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    • v.57 no.4
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    • pp.348-354
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    • 2024
  • Nanocrystalline zirconium nitride (ZrN) coatings were deposited by mid-frequency direct current sputtering (mfMS) with varying pulsed plasma parameters such as pulse frequency and duty cycle to understand the effect of pulsed plasma on the microstructure, residual stress and mechanical properties. The results show that, with the increasing pulse frequency and decreasing duty cycle, the coating morphology changed from a porous columnar to a dense structure, with finer grains. Mid-frequency magnetron sputtered ZrN coatings with pulse frequency of 30 kHz showed the highest both nanoindentation hardness of 16.3 GPa, and elastic modulus of 214.4 GPa. In addition, Effect of pulse frequency on a residual stress and average crystal grain sizes was also investigated.

In-vitro and In-vivo Biocompatibility Evaluation of Silica Based Bio-active Glass Prepared by Hydrothermal Method

  • Sarkar, Swapan Kumar;Nguyen, Phuong Thi;Lee, Byong-Taek
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.05a
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    • pp.53.1-53.1
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    • 2011
  • Bioactive glass powders were synthesized by hydrothermal chemical route by the use of ultrasonic energy irradiation. We used sodalime, calcium nitrate tetra hydrate and di ammonium hydrogen phosphate as the precursor material to synthesize $SiO_2$ rich bio-active glass materials. The $SiO_2$ content was varied in the precursor mixture to 60, 52 and 45 mole%. Dense compacts were obtained by microwave sintering at $1,100^{\circ}C$. Mechanical properties were characterized for the fabricated dense bioactive glasses and were found to be comparable with conventional CaO-$SiO_2$-$Na_2O$-$P_2O_5$ bioactive glass. Detailed biocompatibility evaluation of the glass composition was investigated by in-vitro culture of MG-63 cell and mesenchyme stem cell. Cell adhesion behavior was investigated for both of the cell by one cell morphology for 30, 60 and 90 minutes. Cell proliferation behavior was investigated by culturing both of the cells for 1, 3 and 7 days and was found to be excellent. Both SEM and confocal laser scanning microscopy were used for the investigation. Western blot analysis was performed to evaluate the bimolecular level interaction and extent and rate of specific protein expression. The ability to form biological apatite in physiological condition was observed with simulated body fluid (SBF). In-vivo bone formation behavior was investigated after implanting the materials inside rabbit femur for 1 and 3 month. The bone formation behavior was excellent in all the bioglass compositions, specially the composition with 60% $SiO_2$ content showed most promising trend.

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Effect of Surface Modification by Solvent Treatment on Morphology and Radionuclide Pick-up Efficiency of Polysulfone Film (폴리설폰 필름의 형상 및 방사성 오염물 채취에 있어 용매처리의 효과)

  • 한명진;이근우;서범경;박진호;남석태
    • Membrane Journal
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    • v.14 no.2
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    • pp.126-131
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    • 2004
  • The surface of dense polysulfane films was modified through solvent treatment. The modification process consisted of dipping a film for one second in dimethylformamide and then immersing it Into a nonsolvent bath. After being solidified, the original transparent film transformed into an opaque white one, which is due to the light scattering on pores newly developed on the surface. The surface roughness entailing the pore formation was more explicit on a film coagulated by water as nonsolvent than on a film coagulated by isopropanol. The surface-modified films show the better pick-up efficiency than a conventional filter paper on the detaching of radioactive contaminants on the contaminated area. The pick-up efficiency of the film prepared by the water immersion process was superior to that of the film prepared in the isopropanol bath, which was consistent with the surface roughness result. The surface-modified films kept the dense inner structure, playing a major role preventing a possible secondary contamination during the pick-up process.