共查询到20条相似文献，搜索用时 858 毫秒
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日长年际变化,ElNino／南方涛动和大气准两年振荡的小波分析 总被引：4，自引：0，他引：4
本文采用1964-1993年期间日长变化序列、海平面气压和纬向风速资料，通过小波变换等技术研究分析日长年际变化与ElNino／南方涛动、大气准两年振荡之间的关系．结果表明，日长年际变化与ElNino／南方涛动存在着相似的谱结构，而且ElNino／南方涛动叠加上大气准两年振荡后，与日长变化序列的小波变换时频谱更趋于一致．本文研究结果证实，ElNino／南方涛动和大气准两年振荡的贡献基本能够解释地球自转的年际变化． 相似文献
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华盛顿海军天文台天顶筒纬度观测残差与厄尼诺,南方涛动现象的相关性 总被引：1，自引：0，他引：1
厄尼诺、南方涛动是地球大气、海洋系统年际变化中最为显著的一种地球动力学运动。现在通常采用Ｔａｈｉｔｉ（１４８°Ｗ，１８°Ｓ）和Ｄａｒｗｉｎ（１３１°Ｅ，１２°Ｓ）两地海平面气压之差这一定量指标来刻划这一种大气、海洋系统的运动，简称为南方涛动指数ＳＯＩ。本文分析华盛顿海军天文台天顶筒１９３２－１９９１年间纬度观测的残差，证实它与ＳＯＩ在年际变化的频段内显著相关：最大相关系数达到０．６－０．７以上，但纬度残差的变化要滞后ＳＯＩ约２年时间。这很可能是一个证据，说明陆地部分的铬垂线变化与大气、海洋系统的大规模运动有关联。 相似文献
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在本文中，我们讨论了由中子星和黑洞构成的密近双星系统的引力效应，首先，我们清楚地解释了引力辐射存在引起的轨道圆化，并估算了圆化的时间尺度，求解了围绕史瓦西黑洞作圆轨道运动的矢量进动方程，得到了一个精确解，由进动周期和中心黑洞的质量的关系，我们得到了估算中子星伴随的黑洞质量的方法，随后我们讨论了以中子星脉冲信号随自旋进动变化来寻找黑洞的方法。 相似文献
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关于1949—1976年的地极运动 总被引：1，自引：0，他引：1
《天文学报》1979,(1)
利用国内外四十一个台站的纬度观测资料,分别就地极的长期和周期分量进行研究。建立了以1968.0年平北极为原点的地极坐标系统,用极原点三字的汉语拼音缩写JYD(1968.0)表示。并给出了1949.0—1976.9年的地极坐标。 相似文献
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本文讨论了地极周年运动多年变化与大气环流多年振动的关系,得到以下主要结果:(1)周年极运动多年变化与大气环流多年振动有关,(2)在太阳活动11年的偶周期内,周年极运动振幅和位相基本呈现单周期变化;而在奇周期内,似乎出现双周期变化现象;(3)太阳活动可能是引起周年极运动多年变化的扰动因子. 相似文献
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本文主要利用武昌时辰站1975—1980年六年纬度观测资料,分析了Z项对地极坐标的影响,提出今后计算地极坐标时,应尽量采用靠近观测年份的Z项表达式。并对相应于t_(23)及t_(12)时间求得的地极坐标进行了比较,认为今后在处理长期资料时,采用中间内插(即t_(12))计算地极坐标较为适宜。 相似文献
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1984年开始，天计算中采用FK5基本星表和新天常数，这些变动直接影响了经典光学仪器观测确定的地极坐标。本论述基本星表和天常数变动后，对1953－1961年期间中国地极坐标系统的影响，结果表明星表系统差对地极坐标最大影响约0.″02，章动系列变动的最大影响约为0.″02，光行差常数变动的最大影响为0.″1。 相似文献
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廖德春 《中国科学院上海天文台年刊》1997,27(18):34-40
利用依巴谷暂定星表（H37）为统一参考架解算出的地极坐标序列的POLE95序列，分析了地极价值的长期变化、Markowitz变化和其它低频变化。从两个序列得到地极移动长期漂移速度的平均值为3.86mas/yr，方向为西经82°.7；对Markowitz波动的分析表明，其周期约为25－30年，周期和振幅的变化程度分别为10％和40％。 相似文献
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Laura Schaefer 《Icarus》2004,169(1):216-241
We modified the MAGMA chemical equilibrium code developed by Fegley and Cameron (1987, Earth Planet. Sci. Lett. 82, 207-222) and used it to model vaporization of high temperature silicate lavas on Io. The MAGMA code computes chemical equilibria in a melt, between melt and its equilibrium vapor, and in the gas phase. The good agreement of MAGMA code results with experimental data and with other computer codes is demonstrated. The temperature-dependent pressure and composition of vapor in equilibrium with lava is calculated from 1700 to 2400 K for 109 different silicate lavas in the ONaKFeSiMgCaAlTi system. Results for five lavas (tholeiitic basalt, alkali basalt, Barberton komatiite, dunite, and a molten type B1 Ca, Al-rich inclusion) are discussed in detail. The effects of continuous fractional vaporization on chemistry of these lavas and their equilibrium vapor are presented. The predicted abundances (relative to Na) of K, Fe, Si, Al, Ca, and Ti in the vapor equilibrated with lavas at 1900 K are lower than published upper limits for Io's atmosphere (which do not include Mg). We predict evaporative loss of alkalis, Fe, and Si during volcanic eruptions. Sodium is more volatile than K, and the Na/K ratio in the gas is decreased by fractional vaporization. This process can match Io's atmospheric Na/K ratio of 10±3 reported by Brown (2001, Icarus 151, 190-195). Silicon monoxide is an abundant species in the vapor above lavas. Spectroscopic searches are recommended for SiO at IR and mm wavelengths. Reactions of metallic vapors with S- and Cl-bearing volcanic gases may form other unusual gases including MgCl2, MgS, MgCl, FeCl2, FeS, FeCl, and SiS. 相似文献
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《中国天文和天体物理学报》2014,(9)
正Research in Astronomy and Astrophysics publishes original research papers and reviews 011 all liranchcs of astronoiriy and astrophysics.Reviews arc by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length 相似文献
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《中国天文和天体物理学报》2014,(10)
正Research in Astronomy and Astrophysics publishes original research papers and reviews on all branches of astronomy and astrophysics.Reviews are by invitation only.Important new results that require rapid publication can be submitted as a Letter(Letters must be restricted in length to 6 printed pages).Authors who submit a paper are expected to be able to certify that the paper is original work, 相似文献
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Laura Schaefer 《Icarus》2005,173(2):454-468
We use chemical equilibrium calculations to model the speciation of alkalis and halogens in volcanic gases emitted on Io. The calculations cover wide temperature (500-2000 K) and pressure (10−6 to 10+1 bars) ranges, which overlap the nominal conditions at Pele (T=1760 K, P=0.01 bars). About 230 compounds of 11 elements (O, S, Li, Na, K, Rb, Cs, F, Cl, Br, I) are considered. The elemental abundances for O, S, Na, K, and Cl are based upon observations. CI chondritic elemental abundances relative to sulfur are used for the other alkalis and halogens (as yet unobserved on Io). We predict the major alkali species in Pele-like volcanic gases and the percentage distribution of each alkali are LiCl (73%), LiF (27%); NaCl (81%), Na (16%), NaF (3%); KCl (91%), K (5%), KF (4%); RbCl (93%), Rb (4%), RbF (3%); CsCl (92%), CsF (6%), Cs (2%). Likewise the major halogen species and the percentage distribution of each halogen are NaF (88%), KF (10%), LiF (2%); NaCl (89%), KCl (11%); NaBr (89%), KBr (10%), Br (1%); NaI (61%), I (30%), KI (9%). We predict the major halogen condensates and their condensation temperatures at P=0.01 bar are NaF (1115 K), LiF (970 K); NaCl (1050 K), KCl (950 K); KBr (750 K), RbBr (730 K), CsBr (645 K); and solid I2 (200 K). We also model disequilibrium chemistry of the alkalis and halogens in the volcanic plume. Based on this work and our prior modeling for Na, K, and Cl in a volcanic plume, we predict the major loss processes for the alkali halide gases are photolysis and/or condensation onto grains. Their estimated photochemical lifetimes range from a few minutes for alkali iodides to a few hours for alkali fluorides. Condensation is apparently the only loss process for elemental iodine. On the basis of elemental abundances and photochemical lifetimes, we recommend searching for gaseous KCl, NaF, LiF, LiCl, RbF, RbCl, CsF, and CsCl around volcanic vents during eruptions. Based on abundance considerations and observations of brown dwarfs we also recommend a search of Io's extended atmosphere and the Io plasma torus for neutral and ionized Li, Cs, Rb, and F. 相似文献
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Li Xin-nan Zhang Hai-ying Cui Xiang-qun Jiang Zi-bo Zheng Yi Liu Xing-tao Ni Hou-kun 《Chinese Astronomy and Astrophysics》2012
A special stressed annular polishing technique is proposed to mill the off-axis aspheric sub-mirrors of a large segmented mirror with an annular polishing machine. Based on the basic principle of stressed annular polishing technique, a set of special stressing mechanisms are designed to convert milling the aspheric surfaces of sub-mirrors with different off-axis distances into milling the spherical surfaces with identical radii of curvature, so that they can be pol- ished simultaneously on a continuous polishing machine. It took about contin- uous 40 hours to polish a scaled-down mirror of the planning Chinese Future Giant Telescope (CFGT) using this technique. This mirror has the 330 mm di- ameter, 3.6 m off-axis distance, and the 21.6 m radius of curvature, and its max- imum asphericity is 16 micron. The experiment shows that this method has a high effciency, suits batch manufacturing, especially the batch manufacturing of aspheric sub-mirrors of the segmented primary mirror of an extremely large aperture telescope. 相似文献
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In this paper, we investigate the dynamics of Born–Infeld (B–I) phantom model in the ω–ω′ plane, which is defined by the equation of state parameter for the dark energy and its derivative with respect to N (the logarithm of the scale factor a). We find the scalar field equation of motion in ω–ω′ plane, and show mathematically the property of attractor solutions which correspond to ω
φ
∼−1, Ω
φ
=1, which avoid the “Big rip” problem and meets the current observations well.
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In astronomical observations at optical wavelengths, a fast image tracking system can be adopted to reduce the effects of the atmospheric seeing and telescopic tracking error, and therefore improve the observing efficiency. Aiming at the need of astronomical observations, totally 5 kinds of algorithms in two categories were selected to make a comparative study on their accuracies and stabilities under different noise conditions by both numerical experiment and laboratory test. The results indicate that the normalized cross-correlation method and barycenter method have not only a higher accuracy but also a better reliability against interferences, they will be applied to the high-resolution spectrograph of the Xinglong 2.16 m telescope and the scienti?c instruments of the SONG (Stellar Observations Network Group) project, respectively. 相似文献