汶川地震的天文背景

比较系统地分析了汶川地震发生时的天体位置、月亮白赤交角、太阳活动与地球自转等天文因素的影响,结果表明,无论从地震的孕育还是从发生来看这些天文因素的影响都是不可忽视的,是值得进一步深入研究的.     

地球自转变化与中国大陆地震活动关系的初步分析

本文利用天文观测的日长变化时间序列和我国地震资料，统计分析了地球自转十年尺度变化、年限变化和季节性变化与中国大陆地震活动间的相关性。结果表明，中国大陆地震活动与地球自转变化在时间尺度上存在着一定的全局性联系，地球自转变化引起的附加应力可能对中国大陆地震活动起一定的触发作用，中国大陆地震活动与地球自转变化在空间尺度上存在着一定的地区性联系，以东西向的天山地震带与日长变化的相关性最为显著，南北向的中轴地震带和东西向的燕山地震带次之，而北北东向的山西地震带跟日长变化则没有确定的对应关系。分析结果表明，天文观测的地球自转资料可以为我国大陆地震预测提供一种参考依据。     

天文潮汐与地震

从三个方面综述了天文潮汐与地震关纱的研究，内容包括，日、月、地球的相对位置与地震，天文潮汐的周期，相位与地震，天文潮汐应力与地震，日、月、地球的相对位置与地震和天文潮汐周期与地城的研究均属于从体积力的角度考虑问题，主要是从宏观角度揭示地震发生时的日月位置分布有何规律性，揭示地震发生时间丛集在潮汐周期变化过程中的相位或时段以及地城牟潮汐周期，天文潮汐应力与震的研究从引潮力在地震内部地震源处产生的潮汐应力角度出发，着重研究不同类型性质的发震断层与潮汐应力触发的关系，从物理意义上讲，该研究较深 次地切入了问题的实质，分析了采用某些方法和样本研究结果不一致性的原因，并提出了进一步研究的方向。     

地球自转极移近120天准周期变化的小波分析及其大气激发机制

本文利用小波变换这一新的频谱分析方法研究了地球自转极移近１２０天准周期变化的时频特征，证实了在极移序列中存在显著的近１２０天准周期振荡，得到了极移准周期变化的周期与振幅随时间变化的规律．以地球自转动力学为基础，在时域内分析了大气变化对自转极移季节内变化的激发．表明大气激发在本文所研究的频段内是极移短周期变化的主要激发源。并发现在极移近１２０天准周期振荡平静时期，发生ＥＬＮｉｎｏ事件，同时日长变化近１２０天准周期变化增强．     

SLR资料解算地球自转短周期变化的协方差分析

采用统计定轨理论中的协方差分析方法讨论了卫星激光测距资料解乍地球自转的短周期变化（sub-daily）可达到的内符和外符精度,建立协方差分析的Givens-Gentlemen正交变换算法,并将精密定轨和参数解算理论中的多级复弧法推广到协方差分析中,同时考察不解算地球自转的短周期变化时,其误差对精密定轨和解算地球自转参数的影响。     

地震引起地球自转速率变化的分析

由地震引起地球内部质量重新分布将影响地球惯量矩的变化，从而引起地球自转速率的变化，即日长的变化。一般说，大地震产生大的附加位移场。它对地球自转特性有较强的影响。本文采用Ｈａｒｖａｒｄ目录中１９７７－１９９４年间的地震有关参数，和根据地震激发地球自转的变化理论及Ｄａｈｌｅｎ和Ｌａｍ－ｂｅｃｋ推出有关公式计算了地震引起地球轴向惯量矩的变化。结果表明：由单个地震引起的日长变化要比观测值小几个量级，它的累积效应表现出长期的变化即日长减小，就是地震活动加速地球自转。地震使地球自转能量随时间稳定地增加。并表明，虽地震活动影响日长，但它不是十年尺度变化的主要原因，它可能是地球自转非潮汐加速机制之一     

RS CVn型双星的自转测量和研究(Ⅱ)

我们用美国McDonald天文台2.1米反光镜Coude Reticon观测,对31个RS CVn型双星系统的37颗子星的自转进行了测量。并结合以前测得的38颗子星的数据,对RS CVn型星是否同步作了统计分析,结果表明,绝大多数都显示出同步自转性质;但无论是短周期、正常周期还是长周期组的,都有少数与同步自转不一致的例子。这与过去认为短周期和正常周期的呈同步自转,而长周期的呈非同步自转的结论不一致。     

国内天文地球动力学中的潮汐研究

简要说明了天文地球动力学范畴内所研究的潮汐现象，包括由日月引潮力引起的固体潮、海洋潮、大气潮和由于地球自转轴的极移引起的极潮，以及这些潮汐对地球自转和地球自转的测量产生的效应。重点阐述中国天文学界在这一领域里的研究成果。这些研究涉及潮汐影响地球自转的机制，也就是各种潮汐效应与极移、自转速率变化和章动的关系，包括构建这类关系的理论模型，分析潮汐对它们的影响，利用中国古代丰富的天象记录计算地球自转的长期减慢，计算弹性或滞弹地球的洛夫数，依据某一地球模型计算潮汐效应或章动序列等等。研究也涉及在测量地球自转参数的不同技术中各种潮汐效应对测量结果产生的影响及其改正，并涉及与潮汐有关的观测方法的优化和数据处理过程的改进。最后介绍了中国学者所发现的脉冲星的周期和周期变率测量中的潮汐效应，尽管它们的量级甚微，但不容忽视。     

固体潮对测定地球自转的影响及改正(摘要)

一、基本原理经典天文测定地球自转是以垂线为依据的。垂线在南北方向的变化影响纬度测定,东西方向的变化影响地球自转速率的测定、固体潮使地球发生周期性形变,因而测站的垂线方向也有周期性变化,即在测定地球自转中有固体潮影响。在地面观测站P点,由日月引力产生的引潮位可表示为:     

天文因素对自然灾害的影响

本文综述太阳活动、太阳系天体的行为与自然灾害的关系,阐明天文因素对自然灾害的诱导、触发或调制作用是明显的。指出利用太阳活动和地球自转资料不仅可以预测某些灾害发生的趋势,而且通过监测其变化也可能预测某些灾害的发生。同时指出,行星和月球的运动及其变化对自然灾害的影响仍需继续研究。     

A thermodynamic model of high temperature lava vaporization on Io

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 ONaKFeSiMgCaAlTi 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.     

Instructions for authors

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,     

Research in Astronomy and Astrophysics CONTENTS

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Alkali and halogen chemistry in volcanic gases on Io

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.     

Born–Infeld type phantom model in the ω–ω′ plane

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.      

A Comparison of Several Image Locating Algorithms in Astronomical Instruments

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.     

Shear and vorticity in a combined Einstein-Cartan-Brans-Dicke inflationary lambda-Universe

A combined BCDE (Brans-Dicke and Einstein-Cartan) theory with lambda-term is developed through Raychaudhuri’s equation, for inflationary scenario. It involves a variable cosmological constant, which decreases with time, jointly with energy density, cosmic pressure, shear, vorticity, and Hubble’s parameter, while the scale factor, total spin and scalar field increase exponentially. The post-inflationary fluid resembles a perfect one, though total spin grows, but the angular speed does not (Astrophys. Space Sci. 312: 275, 2007d).      

Study on the Stressed Mirror Polishing with a Continuous Polishing Machine for Large Aperture Off-axis Aspheric Mirrors

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.