共查询到20条相似文献，搜索用时 46 毫秒
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《时间频率学报》编辑部 《时间频率学报》2008,31(2)
文后参考文献是为撰写或编辑论文和著作而引用的有关文献信息资源,是科技论文的重要组成部分.文后参考文献反映文中有关内容的科学依据和有关资料的出处,或提供文中提及而没有展开的内容的详尽文本.文后加注参考文献不仅有助于读者了解有关内容,而且是尊重他人研究成果的体现.此外,文后参考文献还是对期刊论文进行统计和分析的重要信息源之一. 相似文献
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动态Kerr黑洞的事件视界是旋转对称的,不是球对称的.它的位置、角速度和Hawking温度不仅依赖于时间,而且与极角有关. 相似文献
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近地卫星运动的坐标系附加摄动在拟平均根数法中的处理 总被引：1，自引：0，他引：1
在常用的历元地心天球坐标系中研究和处理近地卫星的轨道问题,就必须考虑由于地球赤道面摆动所引起的坐标系附加摄动,正因为如此,给实际工作带来一些麻烦.关于这一问题,曾提出了一种针对瞬根数和平根数之间的转换(仅与坐标系附加摄动的短周期项有关)的解决途径,但并未涉及采用分析法进行轨道外推的有关问题(这与坐标系附加摄动的长期和长周期项有关),这对处理近地卫星的轨道问题而言显然是不完整的.这里结合拟平均根数法进一步改进原提出的方法,较完善地解决这一坐标系附加摄动的计算问题.在此前提下,对于卫星定轨和预报及其相关工作,无论是采用数值法还是分析法,均可采用同一坐标系,即历元(目前是J2000.0)地心天球坐标系. 相似文献
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从Sloan数字巡天第2批释放的数据(SDSS DR2)中选择了395个在r波段亮于15等的面向晚型旋涡星系作为样本,研究了盘的颜色梯度与结构参数的关系.结果表明:盘的颜色梯度与盘的绝对星等(质量)无关;盘的颜色梯度与盘的尺度有关,越大的盘颜色梯度越陡;盘的颜色梯度与盘的颜色有关,越蓝的盘颜色梯度越陡;盘的颜色梯度与盘的表面亮度有关,越亮的盘颜色梯度越陡,并简单讨论了盘的颜色梯度与各结构参数的相关关系对晚型旋涡星系盘恒星形成历史的约束. 相似文献
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本文定义了一个完整的、全部由空间光线追迹组成的评价函数.这个函数一方面能够比较准确地表示光学系统性能的好坏;另一方面在这个函数中各象差间权重因子的选择比较清楚、简单,而且目标值全部是零,显著减少了由于这两类量的选择不当而引起的设计质量不佳.对这种评价函数应用勒万贝格(K.Levenberg)提出的阻尼最小二乘法可以求出它的极小值.本文同时讨论了阻尼最小二乘法和在应用阻尼最小二乘法中的一些有关问题.最后,列出了几个算例.原则上这里的评价函数和有关讨论,也可适用于其他一般的光学系统. 相似文献
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本刊编辑部 《中国天文和天体物理学报》1982,(3)
参加这次盛会的有各天文台、站、厂、馆,有关科研单位、大专院校、部队等40多个单位的代表147人.他们中间有为我国天文事业作出重要贡献的老一辈天文学家;有年富力强的中年科研骨干;有年轻的天文工作者;还有各单位及有关部门的党政领导干部和新闻出版部门的同志.陕西省省长于明涛同志,省科委科教部部长赵长河同志、当地驻军以及省科协、中国科学院西安分院等单位的领导同志参加了开幕式,给与会代表很大鼓舞. 会议期间,代表们欢聚一堂,庆祝中国天文学会成立六十周年,总结建会以来的经验 相似文献
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The paper considers wave coupling for an arbitrary direction of propagation on the basis of single fluid hydromagnetic equations appropriate for a rarefied plasma. The analysis is used to study the transfer of solar wind momenta into the magnetosphere. It is found that wave refraction is significant only during disturbed conditions for waves travelling with the wind. Enhanced reflection of waves might be important even under quiet conditions in the flanks of the magnetosphere. 相似文献
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Oldřich Semerák 《Astrophysics and Space Science》1997,250(2):235-243
In a classical-like language introduced in a previous paper, the fact that the ring singularity of the Kerr spacetime cannot be left/reached by timelike geodesic which is not bound to the equatorial plane is interpreted as a result of the interplay of the gravitational and – mainly – the centrifugal forces. 相似文献
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In this note some properties of the nonconvolved brightness profile close to the extreme solar limb are described. In particular, at 6 cm and 11 cm wavelength relatively strong, narrow spikes should occur, noticeably affected by inhomogeneities (for example spicules) in the solar atmosphere. 相似文献
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M.G. Morgan 《Planetary and Space Science》1980,28(4):359-361
Synoptic observations made on magnetic recording tape at Huancayo, Peru, at the magnetic dip equator, during the International Geophysical Year 1957–1958, were aurally reviewed at that time and no whistlers, hiss, or other emissions were heard. In view of the more recent observation of whistlers at geomagnetic latitudes as low as 12°, and in conjunction with a study of equatorial hiss observed in the topside ionosphere, these recordings have recently been reassessed by reducing them with modern real-time, digital spectrographic equipment. Although the observations were found to be of high quality, and to show the classical features of ground-wave and sky-wave propagation of sferics and VLF transmissions, again no evidence whatsoever of whistlers, hiss, or other emissions is found. Thus it is concluded that the whistlers observed at very low latitudes do not propagate subionospherically to the equator and it is confirmed that “hybrid” whistlers must be due to subionospheric propagation across the equator of the causative sferic rather than of the short whistler. 相似文献
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J. D. Landstreet 《Astronomy and Astrophysics Review》1992,4(1):35-77
Summary Magnetic fields have now been detected in stars in several parts of the Hertzsprung-Russell diagram. Roughly dipolar fields ranging in strength between 3× 102 and 3×104 G are found in many chemically peculiar A and B main sequence stars. Dipolar fields are also found in some 2–3% of white dwarfs, but with strengths between 1×106 and 5×108 G. In both these types of stars, the observed fields vary as the underlying star turns, but do not change in a secular manner. In solartype stars, structurally complex fields of a few kG are found with filling factors of the order of 0.1 to 0.8. Further indirect evidence of fields in cool main sequence stars is provided by detection of visible and ultraviolet line emission (chromospheric activity), x radiation (coronal matter), and giant starspots. In this review, we survey the observations of stellar magnetism in all these types of stars, as well as efforts to model the observed magnetic fields and associated photospheric peculiarities and activity.This article was processed by the author using the Springer-Verlag TEX AAR macro package 1991. 相似文献
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In the fall of 2005, a dedicated meteor observing campaign was carried out by the Panoramic Camera (Pancam) onboard the Mars Exploration Rover (MER) Spirit to determine the viability of using MER cameras as meteor detectors and to obtain the first experimental estimate of the meteoroid flux at Mars. Our observing targets included both the sporadic meteoroid background and two predicted martian meteor showers: one associated with 1P/Halley and a potential stream associated with 2001/R1 LONEOS. A total of 353 images covering 2.7 h of net exposure time were analyzed with no conclusive meteor detections. From these data, an upper limit to the background meteoroid flux at Mars is estimated to be for meteoroids with mass larger than 4 g. For comparison, the estimated flux to this mass limit at the Earth is [Grün, E., Zook, H.A., Fechtig, H., Giese, R.H., 1985. Icarus 62, 244-272]. This result is qualitatively consistent, within error bounds, with theoretical models predicting martian fluxes of ∼50% that at Earth for meteoroids of mass 10−3-101 g [Adolfsson, L.G., Gustafson, B.A.S., Murray, C.D., 1996. Icarus 119, 144-152]. The MER cameras, even using the most sensitive mode of operation, should expect to see on average only one coincident meteor on of order 40-150 h of total exposure time based on these same theoretical martian flux estimates. To more meaningfully constrain these flux models, a longer total integrated exposure time or more sensitive camera is needed. Our analysis also suggests that the event reported as the first martian meteor [Selsis, F., Lemmon, M.T., Vaubaillon, J., Bell, J.F., 2005. Nature 435, 581] is more likely a grazing cosmic ray impact, which we show to be a major source of confusion with potential meteors in all Pancam images. 相似文献