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        검색결과 15

        1.
        2024.01 KCI 등재 SCOPUS 구독 인증기관·개인회원 무료
        This study investigates the impact of magnetic turbulence on cosmic ray (CR) electrons through Fermi-II acceleration behind merger-driven shocks in the intracluster medium and examines how the ensuing synchrotron radio emission is influenced by the decay of magnetic energy through dissipation in the postshock region. We adopt simplified models for the momentum diffusion coefficient, specifically considering transit-time-damping resonance with fast-mode waves and gyroresonance with Alfvén waves. Utilizing analytic solutions derived from diffusive shock acceleration theory, at the shock location, we introduce a CR spectrum that is either shock-injected or shock-reaccelerated. We then track its temporal evolution along the Lagrangian fluid element in the time domain. The resulting CR spectra are mapped onto a spherical shell configuration to estimate the surface brightness profile of the model radio relics. Turbulent acceleration proves to be a significant factor in delaying the aging of postshock CR electrons, while decaying magnetic fields have marginal impacts due to the dominance of inverse Compton cooling over synchrotron cooling. However, the decay of magnetic fields substantially reduces synchrotron radiation. Consequently, the spatial distribution of the postshock magnetic fields affects the volume-integrated radio spectrum and its spectral index. We demonstrate that the Mach numbers estimated from the integrated spectral index tend to be higher than the actual shock Mach numbers, highlighting the necessity for accurate modeling of postshock magnetic turbulence in interpreting observations of radio relics.
        9.
        2016.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본고에서는 전기~송국리단계의 주거지, 토기, 석촉, 석도 등의 변화상을 검토하고 이들 변화가 의미하는 것이 무엇인지 고찰하였다. 그 결과 다음과 같은 결론을 얻을 수 있었다. 토기, 석촉, 주거지 등은 자체의 성능이 향상되기보다 도구 제작비용이 절감되는 방향으로 변하였고, 석도는 도구 자체의 효율성과 제작의 생산성이 모두 향상되는 방향으로 변하였다. 그리고 이러한 도구제작의 생산성 향상은 전체적인 생산력 향상과 밀접한 관련이 있으며 이렇게 높아진 생산력은 송국리문화가 복합사회로 발전할 수 있는 토대가 된다.
        5,200원
        10.
        2016.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The Sausage radio relic is the arc-like radio structure in the cluster CIZA J2242.8+5301, whose observed properties can be best understood by synchrotron emission from relativistic electrons accelerated at a merger-driven shock. However, there remain a few puzzles that cannot be explained by the shock acceleration model with only in-situ injection. In particular, the Mach number inferred from the observed radio spectral index, Mradio  4.6, while the Mach number estimated from X-ray observations, MX−ray  2.7. In an attempt to resolve such a discrepancy, here we consider the re-acceleration model in which a shock of Ms  3 sweeps through the intracluster gas with a pre-existing population of relativistic electrons. We find that observed brightness profiles at multi frequencies provide strong constraints on the spectral shape of pre-existing electrons. The models with a power-law momentum spectrum with the slope, s  4.1, and the cutoff Lorentz factor, e,c  3−5×104, can reproduce reasonably well the observed spatial profiles of radio fluxes and integrated radio spectrum of the Sausage relic. The possible origins of such relativistic electrons in the intracluster medium remain to be investigated further.
        4,200원
        11.
        2016.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The Toothbrush radio relic associated with the merging cluster 1RXS J060303.3 is presumed to be produced by relativistic electrons accelerated at merger-driven shocks. Since the shock Mach number inferred from the observed radio spectral index, Mradio  2:8, is larger than that estimated from X-ray observations, MX . 1:5, we consider the re-acceleration model in which a weak shock of Ms  1:2 - 1:5 sweeps through the intracluster plasma with a preshock population of relativistic electrons. We nd the models with a power-law momentum spectrum with the slope, s  4:6, and the cutoff Lorentz factor, e;c  7-8104 can reproduce reasonably well the observed pro les of radio uxes and integrated radio spectrum of the head portion of the Toothbrush relic. This study con rms the strong connection between the ubiquitous presence of fossil relativistic plasma originated from AGNs and the shock-acceleration model of radio relics in the intracluster medium.
        4,000원
        14.
        1995.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study aims at examinating the change of architectural technique in the residential district of Seoktanri(石灘里), and then extracting the restorable types from it. The constructive technique was advanced in the composition of walls and the use of footing. The arrangement of columns was developed to standing them in a row and three rows in the center of interior space. In the light of excavated relics and the position of furnace, the interior space is seperated into cooking-heating, working and storing space. By the difference of height and the slope, the floor is divided into two parts which are low and high. According to the arrangement of column-holes, the types of roofs to be restored are as follows; the gable roof without column-hole, the hipped roof with center-column-holes(中央柱孔) in a row and the gable roof with center-column-holes in three rows.
        4,600원
        15.
        2003.12 KCI 등재 서비스 종료(열람 제한)
        The purpose of this paper is to describe and classify various relics found in English and to account for linguistic motivations behind the existence of relics by looking at their linguistic contexts. Although there are previous studies of relics, most of them focused on either a single particular form or a mere taxonomy of some relics, even the latter being rare. No systematic studies have been done about the linguistic context retaining relics. The examination of phoneme, morpheme, meaning, word, construction, and word order relics shows that compounds, affixation, and idiomatic phrases tend to retain relics. It is argued that the formulaic property of those linguistic expressions motivates the occurrence of a relic, whereby the syntactic and semantic structures of the expressions become so opaque as to be unfeasible for a linguistic change.