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        검색결과 10

        5.
        2002.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We have mapped 1 deg2 region toward a high latitude cloud MBM 40 in the J = 1 - 0 transition of 12CO and 13CO, using the 3 mm SIS receiver on the 14 m telescope at Taeduk Radio Astronomy Observatory. We used a high resolution autocorrelator to resolve extremely narrow CO linewidths of the molecular gas. Though the linewidth of the molecular gas is very narrow (FWHP < 1 km s-1), it is found that there is an evident velocity difference between the middle upper part and the lower part of the cloud. Their spectra for both of 12CO and 13CO show blue wings, and the position-velocity map shows clear velocity difference of 0.4 km s-1 between two parts. The mean velocity of the cloud is 3.1 km s-1. It is also found that the linewidths at the blueshifted region are broader than those of the rest of the cloud. We confirmed that the visual extinction is less than 3 magnitude, and the molecular gas is translucent. We discussed three mass estimates, and took a mass of 17 solar masses from CO integrated intensity using a conversion factor 2.3 × 10 20 cm -2 (K km s-1)-1. Spatial coincidence and close morphological similarity is found between the CO emission and dust far-infrared (FIR) emission. The ratio between the 100 f.Lm intensity and CO integrated intensity of MBM 40 is 0.7 (MJy/sr)/(K km s-1), which is larger than those of dark clouds, but much smaller than those of GMCs. The low ratio found for MBM 40 probably results from the absence of internal heating sources, or significant nearby external heating sources.
        4,000원
        6.
        2000.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We have investigated the properties of the high-latitude cloud MBM 7 using the 3 mm transitions of CO, CS, HCN, HCO+,C3H2,N2H+, and SiO. The molecular component of MBM 7 shows a very clumpy structure with a size of ≤0.5 pc, elongated along the northwest-southeast direction, perpendicularly to an extended HI component, which could be resulted from shock formation. We have derived physical properties for two molecular cores in the central region. Their sizes are 0.1-0.3 pc and masses 1-2 M⊙ having an average volume density ~2×10 3 cm-3 at the peak of molecular emission. We have tested the stability of the cores using the full version of the virial theorem and found that the cores are stabilized with ambient medium, and they are expected not to be dissipated easily without external perturbations. Therefore MBM 7 does not seem to be a site for new star formation. The molecular abundances in the densest core appear to be much less (by about one order of magnitude) than the 'general' dark cloud values. If the depletions of heavy elements are not significant in the HLCs compared with those in typical dark clouds, our results may suggest different chemical evolutionary stages or different chemical environments of the HLCs compared with dense dark clouds in the Galactic plane.
        4,000원
        9.
        1994.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We observed the molecular transitions of 12CO(1−0) 12CO(1−0) , 13CO(1−0) 13CO(1−0) , C18O(1−0) C18O(1−0) , CS(2-1), HCO+(1−0) HCO+(1−0) , and HCN(1-0) toward the high-latitude mole cular cloud MBM12. We derived total H2 H2 column densities for the two velocity components using the optically thin C18O C18O transition. Molecular abundances have been derived for the observed species at the core of this cloud, which appear to be less than an order of magnitude in fractional abundances relative to H2 H2 , compared to typical cold dark clouds.
        4,300원
        10.
        2014.05 KCI 등재 서비스 종료(열람 제한)
        본 연구는 교량의 상시계측자료인 고유진동수 및 고유모드를 기준으로 계측기반모델을 구성하고, 구조해석을 수행하여 교량 공용상태에서 사장케이블 장력평가를 수행하였다. 케이블 설치 위치에 따라 하중유형별 케이블 장력이 다르다는 것을 알 수 있다. 고정하중과 활하중에 의한 케이블 계측장력은 케이블 설치위치에 따라 차이가 크지 않으나 설계하중을 적용한 해석결과보다 큰 값을 나타낸다. 계측기반모델에 대한 케이블장력분포는, 설계모델에 대한 장력보다 크지만, 계측장력과 유사한 분포를 나타낸다. 그러므로 장기거동을 고려하여 사장교 케이블설계는 계측기반모델의 해석결과를 반영할 필요가 있다. 이를 위하여 많은 계측자료를 이용한 장기거동 분석연구가 요구된다.