共查询到20条相似文献,搜索用时 15 毫秒
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在宇宙太空,许多天体(包括人造天体)被赋予了人物名字。这些天体的命名,记载了人类探索宇宙的漫长历程中一个个的闪光点,也是对那些在科学上做出不朽贡献的‘巨人’的最好纪念。每当人们看到那个在太空中熠熠发光的天体时,就会想到与之同名的那个人的不凡一生,想到他们为了人类的科学事业所付出的辛劳汗水甚至宝贵的生命。这里的“太空明星”已经具有了双重含义,一方面是指真实的宇宙天体,另一方面也指那些将名字留在了太空的著名科学家。它们的风采会令你眼界大开,他们的人生会使你的心灵感动。自本期让我们一起走进‘太空明星风采录’栏目。 相似文献
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Yan-Xia Zhang Yong-Heng ZhaoNational Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2003,3(2):183-190
The sizes of astronomical surveys in different wavebands are increasing rapidly. Therefore, automatic classification of objects is becoming ever more important. We explore the performance of learning vector quantization (LVQ) in classifying multi-wavelength data. Our analysis concentrates on separating active sources from non-active ones. Different classes of X-ray emitters populate distinct regions of a multidimensional parameter space. In order to explore the distribution of various objects in a multidimensional parameter space, we positionally cross-correlate the data of quasars, BL Lacs, active galaxies, stars and normal galaxies in the optical, X-ray and infrared bands. We then apply LVQ to classify them with the obtained data. Our results show that LVQ is an effective method for separating AGNs from stars and normal galaxies with multi-wavelength data. 相似文献
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Xiao-Qiang Tang Jin-Song Wang Qi-Ming Wang Department of Precision Instruments Tsinghua University Beijing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2003,3(5):478-490
We propose a spatial three-degree-of-freedom (DOF) parallel mechanism combining two degrees of rotations and one degree of translation to support the active reflector units of a large spherical radio telescope. The kinematics, workspace and accuracy of the mechanism are analyzed. One-dimensional and two-dimensional fitting errors to the working region of active reflector are investigated. Dimensional parameters of the mechanism and active reflector unit are examined with respect to the requirement of fitting accuracy. The result of accuracy analysis shows the effectiveness and feasibility of the proposed mechanism, and gives a design rule to guarantee the highest working frequency required by large radio telescope. 相似文献
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