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排序方式: 共有53条查询结果,搜索用时 0 毫秒
1.
L. I. Matveenko 《Astronomy Letters》2001,27(11):686-690
The core (injector) and the jet (relativistic plasma outflow) of AGN objects are surrounded by an ionized medium, an H II region observed in emission lines. The synchrotron radiation from the core and the jet is observed through a thin screen that cocoons the structure under consideration. The screen transparency depends on wavelength and distance from the injector. We consider the objects 3C 345 and 1803+784 whose core emission at decimeter wavelengths is absorption by more than 25 dB. The visible bright compact component is the bright nearby portion of the jet that extends outside the dense part of the screen. We explore the possibility of measuring the screen transparency from absorption in Hα recombination lines with different quantum numbers at centimeter wavelengths. 相似文献
2.
顾及拓扑与尖角的分类矢量数据分组压缩算法 总被引:1,自引:1,他引:0
针对现有拆分重组法对存在复杂内环以及复杂相交岛屿多边形的分类矢量数据的压缩结果中包含裂缝、重叠及大量尖锐夹角的问题,提出了一种顾及拓扑一致性与尖角的分组压缩方法。依据分类矢量数据中多边形与多边形及其内环的相交关系对矢量矢量数据分组,以修正后拆分重组法结合直接分割法和间接分割法对分类矢量数据分组压缩,压缩结果中不存在裂缝与重叠现象,维护了分类矢量数据的拓扑一致性;通过取回尖角点前后被删除的点,解决了压缩结果中尖角过多的问题。以Landsat8遥感影像分类矢量数据实验验证了文章算法,并与直接分割法、间接分割法、拆分重组法进行了对比分析,验证了本文方法的有效性。 相似文献
3.
4.
K. R. Anantharamaiah 《Journal of Astrophysics and Astronomy》1986,7(3):131-139
Radio recombination lines are known to be observable at positions along the galactic ridge which are free of discrete continuum
sources. Based on the results of a recent survey of H272α lines it is shown that most of the observed galactic ridge recombination
lines can be explained as emission from outer low-density envelopes of normal Hn regions. The distribution of low-density
ionized gas and discrete HII regions as a function of the distance from the galactic centre is also derived. 相似文献
5.
V. K. Dubrovich 《Astronomy Letters》2007,33(10):645-648
Some problems of the two-photon decay of highly excited atomic hydrogen and helium levels are considered. The necessary accuracy of calculating the transition probabilities is shown to require abandoning the purely dipole approximation in the theory of atomic hydrogen radiation. The range of applicability of the perturbation theory to this process is discussed. We suggest a new mechanism of the Lyman photon redistribution due to very close locations of the 20P and 19P levels in the hydrogen and deuterium atoms, respectively (hydrogen-deuterium resonance). 相似文献
6.
N.I. Rovenskaya 《Astrophysics and Space Science》2004,293(3):355-362
The density matrix equations of highly excited carbon are analytically solved as functions of line number and temperature.
Allowing for the series of the impact approximation theory and quadrupole interaction potential, the line widths are found
with the theoretical error less than 0.06 in the range of temperatures T
e = 25 − 100 K. To determine the medium temperature and density by using the experimental values of line widths, the Doppler,
radiational and impact broadening are calculated for the lines with the principal quantum numbers n > 300.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
N.I. Rovenskaya 《Astrophysics and Space Science》2004,291(2):113-122
The intensities of carbon radio recombination lines (RRL’s) are definedallowing for the effect of dielectronic-like recombination. The rate ofdielectronic-like recombination is calculated as functions of line number,electron density and temperature accurate to 0.05. Following from the balanceequation solutions for populations, the RRL intensities are analytically foundby the method of successive approximations to an accuracy of 0.15. Theobservations of carbon RRL’s are analyzed toward Cassiopeia A. The averageelectron temperature, density, expanded CII region lengths and inaccuraciesare found with the experimental values of RRL widths and intensities. 相似文献
8.
利用气象海洋数据资料和卫星遥感图片,分析研究了2005年第16号热带气旋"韦森特"(VICENTE)的特征,从最先的初始扰动到自身环流的分裂发展重组过程,以至当时周围相对应的大气环流,发现该热带气旋活动过程具有很多特性。对其移动过程进行的综合分析表明,只要存在合适距离等一定有利的条件,弱的两个涡旋之间完全可以发生强的作用力,高空辐散场的抽气作用对气旋的发展有极好的作用,所得的结论可对今后的预报提供一些启示和参考。 相似文献
9.
J.L. McLain 《Planetary and Space Science》2009,57(13):1642-39
A study has been made using a variable temperature flowing afterglow Langmuir probe technique (VT-FALP) to determine the equilibrium temperature dependencies of the dissociative electron-ion recombination of the protonated cyanide ions (RCNH+, where R=H, CH3 and C2H5) and their symmetrical proton-bound dimers (RCNH+NCR). The power law temperature dependencies of the recombination coefficients, αe, over the temperature range 180 to 600 K for the protonated ions are αe(T)(cm3 s−1)=3.5±0.5×10−7 (300/T)1.38 for HCNH+, αe(T)=3.4±0.5×10−7 (300/T)1.03 for CH3CNH+, and αe(T)=4.6±0.7×10−7 (300/T)0.81 for CH3CH2CNH+. The equivalent values for the proton-bound dimers are αe(T)(cm3 s−1)=2.4±0.4×10−6(300/T)0.5 for (HCN)2H+ to αe(T)=2.8±0.4×10−6(300/T)0.5 for (CH3CN)2H+, and αe(T)=2.3±0.3×10−6(300/T)0.5 for (CH3CH2CN)2H+. The relevance of these data to molecular synthesis in the interstellar medium and the Titan ionosphere are discussed. 相似文献
10.