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排序方式: 共有1393条查询结果,搜索用时 250 毫秒
101.
Benot Noyelles 《中国天文和天体物理学报》2007,7(2):317-324
We describe and analyze observations of mutual events of Galilean satellites made at the Yunnan Observatory in February 2003 from CCD imaging for the first time in China. Astrometric positions were deduced from these photometric observations by modelling the relative motion and the photometry of the involved satellites during each event. 相似文献
102.
Jian-Yin Nie Shuang-Nan Zhang Department of Physics Center for Astrophysics Tsinghua University Beijing Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(2):199-208
We apply a Cross-Correlation (CC) method developed previously for detecting gamma-ray point sources to the WMAP first year data by using the Point-Spread Function of WMAP and obtain a full sky CC coefficient map. We find that the CC method is a pow- erful tool to examine the WMAP foreground residuals which can be further cleaned accord- ingly. Evident foreground signals are found in the WMAP foreground cleaned maps and the Tegmark cleaned map. In this process 101 point sources are detected, and 26 of them are new sources additional to the originally listed WMAP 208 sources. We estimate the ?ux of these new sources and verify them by another method. As a result, a revised mask file based on the WMAP first year data is produced by including these new sources. 相似文献
103.
A New Feature Vector Using Selected Line Spectra for Pulsar Signal Bispectrum Characteristic Analysis and Recognition 总被引:1,自引:0,他引:1
Zhen-Hua Xie Lu-Ping XU Guang-Ren Ni Yan Wang 《中国天文和天体物理学报》2007,7(4):565-571
Average pulse profiles of pulsar signals are analyzed using the bispectrum tech-nique. The result shows that there are nonlinear phase couplings between the two frequency axes of the bispectrum charts, which indicate nonlinear factors in the generation and prop-agation of pulsar signals. Bispectra can be used as feature vectors of pulsar signals because of their being translation invariant. A one-dimension selected line spectrum algorithm for ex-tracting pulsar signal characteristic is proposed. Compared with selected bispectra, the pro-posed selected line spectra have the maximum interclass separability measurements from the point of view of the whole one-dimension feature vector. Recognition experiments on several pulsar signals received at several frequency bands are carried out. The result shows that the selected line spectrum algorithm is suitable for extracting pulsar signal characteristics and has a good classification performance. 相似文献
104.
K. Karami R. Mohebi 《中国天文和天体物理学报》2007,7(4):558-564
We introduce a new method to derive the orbital parameters of spectroscopic bi-nary stars by nonlinear least squares of (o-c). Using the measured radial velocity data of the four double lined spectroscopic binary systems, AI Phe, GM Dra, HD 93917 and V502 Oph, we derived both the orbital and combined spectroscopic elements of these systems. Our numerical results are in good agreement with the those obtained using the method of Lehmann-Filhe's. 相似文献
105.
Zhi-Jian Luo Cheng-Gang Shu 《中国天文和天体物理学报》2007,7(4):590-594
According to the new preheating mechanism of galaxy formation suggested by Mo et al., we construct a simple model of formation of disk galaxies within the current paradigm of galaxy formation. It incorporates preheating, gas cooling, bulge formation and star for-mation. The predicted stellar and HI mass functions of galaxies are discussed and compared with the observations. It is found that our model can roughly match both the observed galaxy luminosity function and the observed HI-mass function. 相似文献
106.
Jun-Fang Zhu Xin Wu Da-Zhu Ma 《中国天文和天体物理学报》2007,7(4):601-610
Newtonian core-shell systems, as limiting cases of relativistic core-shell models under the two conditions of weak field and slow motion, could account for massive circumstellar dust shells and rings around certain types of star remnants. Because this kind of systems have Hamiltonians that can be split into a main part and a small perturbing part, a good choice of the numerical tool is the pseudo 8th order symplectic integrator of Laskar & Robutel, and, to match the symplectic calculations, a good choice of chaos indicator is the fast Lyapunov indicator (FLI) with two nearby trajectories proposed by Wu, Huang & Zhang. Numerical results show that the FLI is very powerful when describing not only the transition from regular motion to chaos but also the global structure of the phase space of the system. 相似文献
107.
Tao Hu Qiu-He Peng Hong-Shi Zong 《中国天文和天体物理学报》2007,7(4):579-589
We present disk thicknesses, some other parameters and their statistics of 108 non-edge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson's equation for a disturbance of matter density in three-dimensional spiral galaxies. From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point (the forbidden region with radius r 0 to the galactic center) of the spiral arm, and finally the thickness. 相似文献
108.
针对利用光谱混合分解提取不透水面特征通常受到端元类型和数量的限制,同时植被变化会影响估计精度的问题,该文提出 了一种综合季相和植被变化信息的不透水面提取框架.基于混合像元部分分解算法——混合调谐匹配滤波(MTMF),设计了多季相组合MTMF(SCMTMF)特征和多季相叠加MTMF(SSMTMF)两种策略,构造了不透水面的多季相MTMF特征,将不透水特征与多季相植被指数结合利用支持向量机实现对不透水面的精确分类.结果表明,利用多季相特征得到的不透水面提取效果相较于单季相有较明显的改善,该文所提出的策略有利于提高不透水面的估计精度. 相似文献
109.
全球雷电活动在地球-电离层空腔中产生的极低频(ELF)信号干涉叠加,在一系列固定频率上产生舒曼共振(SR)。利用2012年5月以色列Mitzpe-Roman(MR)站ELF水平磁场资料,采用频谱变换、时间平均、分析了实测SR日变化信号的时域和频域特征。同时基于全球ELF传播模式,利用OTD/LIS雷电卫星资料模拟了5~30 Hz磁场功率谱日变化情况。结果表明:时域背景信号幅值的均值和偏差满足正态分布的期望和标准差;水平磁场前三阶SR谐振频率非常稳定,月平均下的谐振频率日变化相对8、14、20 Hz理论值的偏移量分别不超过0.3 Hz、0.55 Hz和0.6 Hz。东南亚和美洲地区雷电活动主要响应于南北磁场分量第一阶SR的07—09时和19—22时时段内。而东西磁场分量前三阶SR在12—15时时段内都对非洲地区雷电活动有指示作用。磁场功率谱日变化模拟结果与实测基本一致,表明利用单站正交磁天线的不同阶SR信号能够指示全球不同"热斑"区域的雷电活动。 相似文献
110.
Binil Aryal 《中国天文和天体物理学报》2011,11(3)
We present an analysis of the winding sense(S and Z-shapes) of 1 621 field galaxies that have radial velocity between 3 000 km s-1 and 5 000 km s-1.The preferred alignments of S-and Z-shaped galaxies are studied using chi-square,autocorrelation and Fourier series tests.We classify all the galaxies into 32 subsamples and notice a good agreement between the position angle(PA) distribution of the S-and Zshaped galaxies.The homogeneous distribution of the S-and Z-shaped galaxies is more noticeable for the late-... 相似文献