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Wyszukujesz frazę "Cho, H.-S." wg kryterium: Autor

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    Wyświetlanie 1-7 z 7
    Tytuł:
    Improvement of Microwave Absorbance of Polymer Composites of W-Type Hexaferrite Powders by Attachment of Frequency Selective Surface
    Autorzy:
    Cho, H.-S.
    Kim, S.-S.
    Powiązania:
    https://bibliotekanauki.pl/articles/352824.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    frequency selective surface
    microwave absorbers
    hexaferrite powders
    polymer composites
    Opis:
    This work investigates the effect of a frequency selective surface (FSS) composed of a regular array of square loop elements on the absorption properties of grounded ferrite composites. Polymer matrix composites of CoZnW hexaferrite powders having small magnetic loss were used as the substrate material. Computational tools were used to model the interaction between electromagnetic waves and materials and determine the reflection coefficient. Reflection loss and bandwidth were greatly improved by attaching an FSS with controlled electrical resistance (R) onto the grounded ferrite composites. For the FSS with R = 800 Ω, the minimum reflection loss decreased to –25 dB at 10 GHz and the bandwidth was broadened to 7.5-12.5 GHz with respect to –10 dB reflection loss.
    Źródło:
    Archives of Metallurgy and Materials; 2017, 62, 2B; 1325-1328
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fabrication of Porous Silica Fibers by Electrospinning for Sound Absorbing Materials
    Autorzy:
    Cho, Y.-S.
    Lee, H. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/353561.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    electrospinning
    porous silica fiber
    thermal insulator
    sound absorption
    Opis:
    Macroporous silica fibers having spherical cavities were fabricated by electrospinning using the spinning solution prepared from the mixed dispersion of tetraethylorthosilicate (TEOS) and polystyrene nanospheres as precursor and sacrificial templates, respectively, by injection through metallic nozzle. By applying electric field, the electro-spun fibers obtained by evaporation-driven self-assembly were collected on flat substrate or rotating drum, followed by the removal of the templates by calcination. The sound absorption coefficient of the porous fibers was measured by impedance tube, and the measured value was larger than 0.9 at high frequency region of incident waves. The surface of the resulting fibers was modified using fluorine-containing silane coupling agent to produce superhydrophobic fibrous materials to prevent the infiltration of humidity.
    Źródło:
    Archives of Metallurgy and Materials; 2018, 63, 3; 1497-1502
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect Of Carbon Nanotubes On The Properties Of Spark Plasma Sintered ZrO2/CNT Composites
    Wpływ nanorurek węglowych na właściwości spiekanych metodą sps kompozytów ZrO2/CNT
    Autorzy:
    Shim, D. H.
    Jung, S. S.
    Kim, H. S.
    Cho, H.
    Kim, J. K.
    Kim, T. G.
    Yoon, S. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/351266.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    CNT
    ZrO2
    composite
    SPS
    kompozyty
    Opis:
    Zirconia matrix ZrO2/CNT composite materials reinforced with multiwall carbon nanotubes were fabricated using a spark plasma sintering technique. The effects of the amount of CNTs addition, sintering temperature and sintering pressure on the properties of the resulting ZrO2/CNT composites were examined. 0 to 9 vol. % CNTs were dispersed in zirconia powder, and the resulting mixture was sintered. The electrical conductivity, hardness, flexural strength, and density were measured to characterize the composites. The friction and wear properties of the composites were also tested. The flexural strength and friction coefficient of the composites were improved with up to 6 vol.% of CNT addition and the flexural strength showed a close relationship with the relative density of the composite. The electrical conductivity increased with increasing proportion of the CNTs, but the efficiency was reduced at more than 6 vol.% CNTs.
    Źródło:
    Archives of Metallurgy and Materials; 2015, 60, 2B; 1315-1318
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Fabrication and Characterization of CoCrFeNiMn High Entropy Alloy Powder Processed by Gas Atomization
    Autorzy:
    Park, T. G.
    Lee, S. H.
    Lee, B.
    Cho, H. M.
    Choi, W. J.
    Kim, B. S.
    Shin, K. S.
    Kim, T.-S.
    Powiązania:
    https://bibliotekanauki.pl/articles/353649.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    high entropy alloy
    gas atomization
    spark plasma sintering
    CoCrFeNiMn
    Opis:
    In this study, precisely controlled large scale gas atomization process was applied to produce spherical and uniform shaped high entropy alloy powder. The gas atomization process was carried out to fabricate CoCrFeNiMn alloy, which was studied for high ductility and mechanical properties at low temperatures. It was confirmed that the mass scale, single phase, equiatomic, and high purity spherical high entropy alloy powder was produced by gas atomization process. The powder was sintered by spark plasma sintering process with various sintering conditions, and mechanical properties were characterized. Through this research, we have developed a mass production process of high quality and spherical high entropy alloy powder, and it is expected to expand applications of this high entropy alloy into fields such as powder injection molding and 3D printing for complex shaped components.
    Źródło:
    Archives of Metallurgy and Materials; 2018, 63, 2; 1055-1059
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Multistep Heat-Treatment Effects on Electrospun Nd-Fe-B-O Nanofibers
    Autorzy:
    Jeon, E. J.
    Eom, N. S. A.
    Lee, J.
    Lee, B.
    Cho, H. M.
    On, J. S.
    Choa, Y.-H
    Kim, B. S.
    Powiązania:
    https://bibliotekanauki.pl/articles/354311.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Nd-Fe-B
    nanofibers
    electrospinning
    heat treatment
    Opis:
    Neodymium-Iron-Boron (Nd-Fe-B) magnets are considered to have the highest energy density, and their applications include electric motors, generators, hard disc drives, and MRI. It is well known that a fiber structure with a high aspect ratio and the large specific surface area has the potential to overcome the limitations, such as inhomogeneous structures and the difficulty in alignment of easy axis, associated with such magnets obtained by conventional methods. I n this work, a suitable heat-treatment procedure based on single-step and multistep treatments to synthesize sound electrospun Nd-Fe-B-O nanofibers of Φ572 nm was investigated. The single-step heat-treated (directly heat-treated at 800°C for 2 h in air) samples disintegrated along with the residual organic compounds, whereas the multistep heat-treated (sequential three-step heat-treated including three steps;: dehydration (250°C for 30 min in an inert atmosphere), debinding (650°C for 30 min in air), and calcination (800°C for 1 h in air)) fibers maintained sound fibrous morphology without any organic impurities. They could maintain such fibrous morphologies during the dehydration and debinding steps because of the relatively low internal pressures of water vapor and polymer, respectively. In addition, the NdFeO3 alloying phase was dominant in the multistep heat-treated fibers due to the removal of barriers to mass transfer in the interparticles.
    Źródło:
    Archives of Metallurgy and Materials; 2018, 63, 3; 1433-1437
    1733-3490
    Pojawia się w:
    Archives of Metallurgy and Materials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of InAs Coverage on Transition of Size Distribution and Optical Properties of InAs Quantum Dots
    Autorzy:
    Kim, G.
    Jeon, S.
    Cho, M.
    Choi, H.
    Kim, D.
    Kim, M.
    Kwon, Y.
    Choe, J.
    Kim, J.
    Leem, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1535820.pdf
    Data publikacji:
    2010-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    81.15.Hi
    68.37.Ps
    78.55.Cr
    78.67.Hc
    Opis:
    The influence of InAs coverage on the formation of self-assembled quantum dots grown by molecular-beam epitaxy was investigated by atomic force microscopy and photoluminescence measurements. As the InAs coverage increased from 2.0 to 3.0 monolayers, the quantum dot density decreased from 1.1 × $10^{11}$ to 1.36 × $10^{10} cm^{-2}$. This result could be attributed to the coalescence of neighboring small InAs quantum dots resulting in the formation of much larger InAs quantum dots with lower quantum dot density. Atomic force microscopy results revealed that as the InAs quantum dot coverage increased, the transition of size distribution of InAs quantum dots from single-modal to multimodal occurred. The temperature-dependent photoluminescence spectra showed that the photoluminescence spectra red shifted and the photoluminescence peak intensity decreased as the InAs coverage increased. The thermal activation energy was strongly dependent on the InAs coverage, and for InAs quantum dots with 3.0 ML thick InAs coverage, this energy was estimated to be 147 meV.
    Źródło:
    Acta Physica Polonica A; 2010, 118, 4; 673-676
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optical Properties of Multi-Stacked InAs Quantum Dots Embedded in GaAs/InGaAs Strained Layer and its Annealing Behaviors
    Autorzy:
    Kim, D.
    Kim, G.
    Jeon, S.
    Cho, M.
    Choi, H.
    Kim, M.
    Lee, D.
    Kim, J.
    Eom, G.
    Leem, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1537752.pdf
    Data publikacji:
    2010-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    78.67.Hc
    78.55.Cr
    81.05.Ea
    Opis:
    Multi-stacked InAs QDs embedded in ten periods of GaAs/$In_{0.1}Ga_{0.9}As$ strained layers were grown by MBE and their optical properties were investigated by using PL spectroscopy. For the QDs embedded in ten periods of GaAs/$In_{0.1}Ga_{0.9}As$ strained layers, the PL intensity is enhanced about 4.7 times and a narrower FWHM of 26 meV is observed compared to those of the conventional multi-stacked QDs. The PL spectra of the InAs QDs show blue-shifts of about 50 meV with increasing annealing temperature up to 850°C. At annealing temperature of 600°C, the FWHM of the PL peak is reduced to 16 meV and PL intensity is enhanced compared to those of the as-grown sample, which indicates improvement of size uniformity and crystal quality of the QDs.
    Źródło:
    Acta Physica Polonica A; 2010, 117, 6; 941-944
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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