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目前基本上所有天文仪器都是数字化的，几乎所有天文设备与计算机都有接口问题。我们在多套系统中采用计算机打印口来控制天文终端，认为这样做有不少好处。本文介绍了利用打印机接口天文仪器控制的技术，并给出两个例子。 相似文献
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概述了数字图像压缩技术在天文领域应用的必要性。针对天文观测的特点和研究的需要，经过研究，分析和比较，提出了天文图像压缩的可行方案。通过应用计算机编程及压缩实验给出相应的结果。 相似文献
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本文简要介绍了国内外众多天文组织徽标的现状与发展情况。这些天文徽标多数属于天文爱好者协会,也有少量属于天文机构。作者在其收藏的众多天文徽标藏品中精心挑选了32款供读者赏析。这些徽标不但非常美观,而且具有很强的代表性,也可供大学天文社团设计自己的徽标时参考。 相似文献
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钟鸣 《紫金山天文台台刊》1997,16(1):43-52
本文讨论软件工程中有关质量管理方面的概念和技术,以及在天文软件开发工作中的一些应用。特别讨论了天文软件工程的测试问题,给出了测试控制程序的结构,以及测试用例及其数据生成模式。 相似文献
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金属丰度是表征星系特征的重要参量,对于理解星系的形成与演化具有重要意义。随着观测设备的不断完善与发展,已经获得越来越多的星系(包括近邻星系、中等红移及高红移星系)金属丰度的观测资料。在光致电离模型方面也取得了很大进展．这些对于理解星系中金属及恒星成分的累积历史有非常重要的作用。有多种方法可以用来估计星系的金属丰度(主要是星际介质中气相的O丰度),介绍和评述了估计星系的O丰度的多种方法,包括电子温度的方法、R23方法以及其他一些“强线”比值的方法,并给出了相应的解析公式,同时介绍了电离星云的物理本质及由光致电离模型估计星系金属丰度的方法,还给出了估计星系的C和N元素丰度的方法。 相似文献
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Yehouda Enzel Rivka Amit Uri Dayan Onn Crouvi Ron Kahana Baruch Ziv David Sharon 《Global and Planetary Change》2008,60(3-4):165-192
Modern-day synoptic-scale eastern Mediterranean climatology provides a useful context to synthesize the diverse late Pleistocene (60–12 ka) paleohydrologic and paleoenvironmental indicators of past climatic conditions in the Levant and the deserts to its south and east. We first critically evaluate, extract, and summarize paleoenvironmental and paleohydrologic records. Then, we propose a framework of eastern Mediterranean atmospheric circulation features interacting with the morphology and location of the southeast Mediterranean coast. Together they strongly control the spatial distribution of rainfall and wind pattern. This cyclone–physiography interaction enforces the observed rainfall patterns by hampering rainfall generation south and southeast of the latitude of the north Sinai coast, currently at 31°15′.The proposed framework explains the much-increased rains in Lebanon and northern Israel and Jordan as deduced from pollen, rise and maintenance of Lake Lisan, and speleothem formation in areas currently arid and semiarid. The proposed framework also accounts for the southward and eastward transition into semiarid, arid, and hyperarid deserts as expressed in thick loess accumulation at the deserts' margins, dune migration from west to east in the Sinai and the western Negev, and the formation of hyperarid (< 80 mm yr− 1) gypsic–salic soils in the southern Negev and Sinai. Our climatic synthesis explains the hyperarid condition in the southern Negev, located only 200–250 km south of the much-increased rains in the north, probably reflecting a steeper rainfall gradient than the present-day gradient from the wetter Levant into its bordering southern and eastern deserts.At present, the rainiest winter seasons in Lebanon and northern and central Israel are associated with more frequent (+ 20%), deeper Cyprus Lows traversing the eastern Mediterranean at approximately the latitude of southern Turkey. Even these wettest years in northern Israel do not yield above average annual rainfall amounts in the hyperarid southern Negev. This region is mainly influenced by the Active Red Sea Troughs that produce only localized rains. The eastern Mediterranean Cyprus Lows also produce more dust storms and transport higher amounts of suspended dust to the loess area than any other atmospheric pattern. Concurrent rainfall and dust are essential to the late Pleistocene formation of the elongated thick loess zone along the desert northern margin. Even with existing dust storms, the lack of rain and very sparse vegetation account for the absence of late Pleistocene loess sequences from the southern Negev and the formation of hyperarid soils.When the north Sinai coast shifted 30–70 km northwest due to last glacial global sea level lowering, the newly exposed coastal areas supplied the sand and dust to these active eastern Mediterranean cyclones. This enforced the latitude of the northern boundary of the loess zone to be directly due east of the LGM shoreline. This shift of coast to the northwest inhibited rainfall in the southern Levant deserts and maintained their hyperaridity. Concurrently, frequent deep eastern Mediterranean Cyprus Lows were funneled along the northern Mediterranean increasing (probably doubling) the rains in central and northern Israel, Lebanon, southwestern Syria and northern Jordan. These storms and rains formed lakes, forests, and speleothems only a short distance north of the deserts in the southern Levant. 相似文献
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P. Kenneth Seidelmann B. A. Archinal M. F. A’hearn A. Conrad G. J. Consolmagno D. Hestroffer J. L. Hilton G. A. Krasinsky G. Neumann J. Oberst P. Stooke E. F. Tedesco D. J. Tholen P. C. Thomas I. P. Williams 《Celestial Mechanics and Dynamical Astronomy》2007,98(3):155-180
Every three years the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements revises tables giving the
directions of the poles of rotation and the prime meridians of the planets, satellites, minor planets, and comets. This report
introduces improved values for the pole and rotation rate of Pluto, Charon, and Phoebe, the pole of Jupiter, the sizes and
shapes of Saturn satellites and Charon, and the poles, rotation rates, and sizes of some minor planets and comets. A high
precision realization for the pole and rotation rate of the Moon is provided. The expression for the Sun’s rotation has been
changed to be consistent with the planets and to account for light travel time 相似文献
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时间频率量的特征及其对时频系统建设的影响 总被引：2，自引：1，他引：1
分析了物理量测量中时间频率量的特点，主要有：时间的流逝性；其基准是自然基准；时间和频率既密切相关又有区别；时间频率具有最高的测量精细度(分辨率)与准确度；其计量标准可通过电磁波发播；其测量精确度与测量时间有关。另外，从基准、守时、授时、时间频率设备的研制、生产和队伍建设等方面阐发了这些特点对时间频率系统建设的影响。 相似文献
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A pulsar has the very stable rotation and can be used as the time standard. The astrometric parameters and astrophysical parameters of many pulsars, such as the spatial position, proper motion, distance, rotation period and its derivative, etc., can be all accurately determined. Since the pulsar can provide the time signal and the coordinates of its spatial position simultaneously, the pulsar navigation system installed on a spacecraft enables the autonomous navigation of the spacecraft to be realized. Firstly, the position of the spacecraft is predicted based on the equation of orbit dynamics of the spacecraft and then the Kalman filtering is applied to calculating the estimation error of the spacecraft position through the difference between the pulse arrival time observed on the spacecraft and the predicted pulse arrival time, thereby modifying the position of the spacecraft. Finally, the effects of the initial error, measuring accuracy of the pulse arrival time and number of pulsars on the navigation accuracy are analyzed. 相似文献
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白矮星演化与宇宙纪年学 总被引：2，自引：0，他引：2
近几年白矮星研究在理论与观测方面都取得了很大进展，这推动了白矮星宇宙纪年学的应用和发展。白矮星宇宙纪年学，即利用白矮星的演化结果计算白矮星理论光度函数，并通过与现测光度函数的对比来确定天体年龄。简要描述了白矮星的基本性质，回顾了白矮星演化研究的历史和基本方法；介绍了白矮星宇宙纪年学研究的基本原理及其在银盘、球状星团、疏散星团以及银晕年龄确定方面的应用现状。白矮星宇宙纪年学是一个很新的研究领域，但它已经在确定天体年龄方面显示出很大的潜力。最后讨论了目前研究中存在的问题，并提出今后需要进一步研究的几项工作。 相似文献
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In June 2006 Venus Express crossed several times the outer boundary of Venus induced magnetosphere, its magnetosheath and its bow shock. During the same interval the Cluster spacecraft surveyed the dawn flank of the terrestrial magnetosphere, intersected the Earth's magnetopause and spent long time intervals in the magnetosheath. This configuration offers the opportunity to perform a joint investigation of the interface between Venus and Earth's outer plasma layers and the shocked solar wind. We discuss the kinetic structure of the magnetopause of both planets, its global characteristics and the effects on the interaction between the planetary plasma and the solar wind. A Vlasov equilibrium model is constructed for both planetary magnetopauses and provides good estimates of the magnetic field profile across the interface. The model is also in agreement with plasma data and evidence the role of planetary and solar wind ions on the spatial scale of the equilibrium magnetopause of the two planets. The main characteristics of the two magnetopauses are discussed and compared. 相似文献
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20世纪人类在探索宇宙奥秘的道路上取得了辉煌的成就 .其主要标志是恒星的内部结构与演化理论和宇宙大爆炸标准模型的建立。这一理论框架为宇宙中一切物质 ,包括基本粒子 ,原子 ,分子 ,行星 ,恒星 ,生命的产生和发展提供统一的科学图象 ,受到越来越丰富的观测的支持。然而在大爆炸宇宙模型和恒星演化理论之间存在一个人们了解甚少的领域 :就是由大量恒星组成而又作为宇宙基本单元的星系是如何形成和演化的 ?回答这一重要问题无疑是对 2 1世纪天文学的重大挑战。世界发达国家正在投巨资建造新一代巨型天文设备 ,如各个波段的地面的和空间的望远镜 ,把人类探测能力延伸到宇宙演化的早期。中国也己确定星系形成与演化作为我国天文学科发展的国家目标之一 ,在国家重大科学工程中安排大天区面积多目标光纤光谱天文望远镜———LAMOST以增加我国在这一重大领域的竞争力。“星系形成和演化”项目的目标 ,就是要在LAMOST建成之前 ,充分利用国内中小设备和国外大型设备资料 ,开展大样本统计 ,数值模拟和理论研究 ,提高我国在这一领域的开拓创新的能力 ,形成在国际上有竞争力的队伍 ,在若干优选的课题方向上先期做出有高显示度的成果 ,以期在LAMOST建成之后 ,我国在宇宙大尺度结构 ,星系形成与演化方面跻身国际先 相似文献
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In the light of the wide applications of a series of ephemerides developed by the Jet Propulsion Laboratory (JPL) of the National Aeronautics and Space Administration (NASA) of the USA to many aspects like the deep-space navigation and interplanetary exploration, it is necessary to make comparisons of their contents, applicable ranges, realizations and maintenances. In view of the fact that the explorations of the Venus and Mars are expected to carry out in China, their dynamical models and the adopted observational data are analysis by taking the DE405, DE421 and DE423 to be the examples. From the evaluations of the accuracies and performances of the above-mentioned ephemerides of different editions, their effects on the probes orbiting around the Venus or Mars are emphatically discussed, and a suggestion is given for their use that as far as the Venus missions are concerned, the use of the DE423 is recommend, and that the use of the DE421 or DE423 is recommended for the Mars Missions. 相似文献