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        검색결과 1,963

        259.
        2024.07 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Full spectrum fitting is a powerful tool for estimating the stellar populations of galaxies, but the fitting results are often significantly influenced by internal dust attenuation. For understanding howthe choice of the internal dust correction method affects the detailed stellar populations estimated from the full spectrum fitting, we analyze the Sydney-Australian Astronomical Observatory Multiobject Integral field spectrograph (SAMI) galaxy survey data using the Penalized PiXel-Fitting (PPXF) package. Three choices are compared: (Choice-1) using the PPXF reddening option, (Choice-2) using the multiplicative Legendre polynomial, and (Choice-3) using none of them (no dust correction). In any case, the total mean stellar populations show reasonable mass-age and mass-metallicity relations (MTR and MZR), although the correlations appear to be strongest for Choice-1 (MTR) and Choice-2 (MZR). Whenwe compare the age-divided mean stellar populations, theMZRof young (<109.5 yr ≈ 3.2 Gyr) stellar components in Choice-2 is consistent with the gas-phase MZR, whereas those in the other two choices hardly are. On the other hand, the MTR of old (≥109.5 yr) stellar components in Choice-1 seems to be more reasonable than that in Choice-2, because the old stellar components in low-mass galaxies tend to be relatively younger than those in massive galaxies. Based on the results, we provide empirical guidelines for choosing the optimal options for dust correction.
        4,000원
        260.
        2024.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this study, four different samples of Se60Ge40-xBix chalcogenides glasses were synthesized by heating the melt for 18 h in vacuum Pyrex ampoules (under a 10-4 Torre vacuum), each with a different concentration (x = 0, 10, 15, and 20) of high purity starting materials. The results of direct current (DC) electrical conductivity measurements against a 1,000/T plot for all chalcogenide samples revealed two linear areas at medium and high temperatures, each with a different slope and with different activation energies (E1 and E2). In other words, these samples contain two electrical conduction mechanisms: a localized conduction at middle temperatures and extended conduction at high temperatures. The results showed the local and extended state parameters changed due to the effective partial substitution of germanium by bismuth. The density of extended states N(Eext) and localized states N(Eloc) as a function of bismuth concentration was used to gauge this effect. While the density of the localized states decreased from 1.6 × 1014 to 4.2 × 1012 (ev-1 cm-3) as the bismuth concentration increased from 0 to 15, the density of the extended states generally increased from 3.552 × 1021 to 5.86 × 1021 (ev-1 cm-3), indicating a reduction in the mullet’s randomness. This makes these alloys more widely useful in electronic applications due to the decrease in the cost of manufacturing.
        4,000원