Corrections to the luni-solar precession derived from a compilation catalogue of extragalactic radio sources     

H. G. Walter 《Celestial Mechanics and Dynamical Astronomy》1992,53(1):71-80

Observation catalogues of extragalactic radio sources obtained by Very long Baseline Interferometry during the last decade agree in the mean to a few milliarcseconds (mas). Within this range the position differences show constant, linear and periodic offsets. To reduce the influence of individual catalogue properties the construction of a compilation catalogue seems to be the appropriate procedure. In some detail the compilation method is described providing simultaneous adjustment of source positions and catalogue corrections. The compilation catalogue consists of 40 objects having positional errors of 0.2 mas in right ascension (RA) and 0.3 mas in declination (Dec). Comparing this catalogue with the IERS Celestial Reference Frame compiled by means of other precepts yields weighted root-mean-square differences of 0.7 mas in RA and 1.3 mas in Dec. Finally, the terms of general precession in RA and Dec are included in the adjustment process giving estimates of the correction to the luni-solar precession between –1 and –3 mas/yr, the latter figure applying when some early data are added.  相似文献   

导电性对地面核磁共振信号的影响研究   总被引：3，自引：0，他引：3  

孙淑琴  林君  张世雄 《物探化探计算技术》2005,27(2):127-130

与其它勘探方法相比,核磁共振(NuclearMagneticResonance,缩写NMR)的方法是直接勘探地下水中NMR信号的唯一有效方法,该信号的初始振幅决定了含水层深度及自由水的含量。但在实际工作中,大地导电性对含水地层中的NMR信号有直接影响,使得同样脉冲矩条件下,勘探深度有变化。为了评价大地(岩石)导电性对勘探深度的影响,建立了一个地面找水模型,对NMR信号进行数值模拟。仿真结果表明,NMR信号的振幅可以评价含水地层的结构,但大地导电性的增强将导致勘探深度的降低。  相似文献   

Glaciation-induced variations in the Earth's precession frequency, obliquity and insolation over the last 2.6 Ma     

J. X. Mitrovica  A. M. Forte  R. Pan 《Geophysical Journal International》1997,128(2):270-284

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Considerations concerning the non-rigid Earth nutation theory     

F. Arias  Ch. Bizouard  P. Bretagnon  A. Brzezinski  B. Buffett  N. Capitaine  P. Defraigne  O. de Viron  M. Feissel  H. Fliegel  A. Forte  D. Gambis  J. Getino  R. Gross  T. Herring  H. Kinoshita  S. Klioner  P.M. Mathews  D. Mccarthy  X. Moisson  S. Petrov  R.M. Ponte  F. Roosbeek  D. Salstein  H. Schuh  K. Seidelmann  M. Soffel  J. Souchay  J. Vondrak  J.M. Wahr  P. Wallace  R. Weber  J. Williams  Y. Yatskiv  V. Zharov  S.Y. Zhu 《Celestial Mechanics and Dynamical Astronomy》1998,72(4):245-309

This paper presents the reflections of the Working Group of which the tasks were to examine the non-rigid Earth nutation theory. To this aim, six different levels have been identified: Level 1 concerns the input model (giving profiles of the Earth's density and theological properties) for the calculation of the Earth's transfer function of Level 2; Level 2 concerns the integration inside the Earth in order to obtain the Earth's transfer function for the nutations at different frequencies; Level 3 concerns the rigid Earth nutations; Level 4 examines the convolution (products in the frequency domain) between the Earth's nutation transfer function obtained in Level 2, and the rigid Earth nutation (obtained in Level 3). This is for an Earth without ocean and atmosphere; Level 5 concerns the effects of the atmosphere and the oceans on the precession, obliquity rate, and nutations; Level 6 concerns the comparison with the VLBI observations, of the theoretical results obtained in Level 4, corrected for the effects obtained in Level 5.Each level is discussed at the state of the art of the developments.  相似文献   

On the use of analytical theories in the calculation of precession-nutation     

P. Bretagnon 《Celestial Mechanics and Dynamical Astronomy》1996,65(1-2):95-106

We present the use of the analytical solutions of the planets and of the Moon's motion in the determination of the quantities which relate the barycentric and the geocentric coordinate systems and of the expressions of precession-nutation. The computation of the precession and nutation quantities are built with the analytical theories of the motion of the Moon, the Sun and the planets of the Bureau des longitudes. We take into account the influence of the Moon, the Sun and all the planets on the potential of the Earth limited to C _j,0 for j from 2 to 5, C _2,2, S _2,2, C _3, S _3, , for from 1 to 3 and C _4,1, S _4,1. We determine the 3 Euler angles , , and 2 calculating the components of the torque of the external forces with respect to the geocenrer in the case of the rigid Earth. The equations are solved by iterations and so are taken into account the nutations-on-the-nutations effects. We have determined the analytical variations of the angles and w fixing the equator with respect to the ecliptic J2000. We find, in w, a secular term of –26.5026 mas per century. The analytical solution of the precession-nutation has been compared to a numerical integration over the time span 1900–2050. The differences do not exceed 16 µas for and 12 µas for .  相似文献   

57～48万年前东亚夏季风的神农架石笋记录   总被引：2，自引：0，他引：2  

童凯  汪永进  程海  姜修洋 《海洋地质与第四纪地质》2007,27(4):111-116

应用MC-ICP-MS和MAT-253质谱技术,实测神农架山宝洞一支长达1.2 m石笋(SB32)的3个230Th年龄和236个氧同位素数据。在年龄误差范围内,运用天文轨道调谐方法重建了570~480 kaBP时段百年至千年际分辨率东亚夏季风降水记录。该记录跨越4个完整的岁差旋回,在岁差周期上石笋δ18O平均振幅达4‰。研究时段内东亚夏季风轨道尺度变化仍然受太阳辐射的控制。石笋记录的深海氧同位素阶段MIS14/13转换过程与末次冰消期具有类似特征。一系列千年尺度事件叠加在岁差周期夏季风变化趋势上,表明千年尺度气候变化是地球气候系统内部自我维持的固有频率,可能属于海-陆-气相互作用的结果。  相似文献   

质子激发X射线荧光分析及其在海洋科学中的应用     

邢娜  黄奕普 《台湾海峡》2007,26(3):443-452

质子激发X射线荧光分析是一种多元素微量分析技术,具有高灵敏度、高空间分辨率和非破坏性等特点,近年来在地球科学诸多领域得到大量应用.本文简介了质子激发X荧光分析技术的基本原理、实验装置及特点,与其他地质学方法进行了比较,并着重介绍该技术在海洋科学领域的应用进展.  相似文献   

核旋仪野外比测记录和数据通讯系统研究     

张振国 《地震地磁观测与研究》1995,16(4):61-67

本系统包括用ＰＣ－１５００Ａ－ＣＡＳ进行核旋仪野外比测（Ｆ、Ｚ）记录程序（简写ＢＣＪＬ）及记录数据的通讯传送程序（简写ＢＣＴＸ－１）和（ＩＢＭ－ＰＣ）微机通讯接收程序（简写ＢＣＴＸ－２）共３个程序。该３个程序采用ＢＡＳＩＣ语言编写。ＢＣＪＬ程序是在１９９２年的核旋仪野外经测（Ｆ、Ｚ）记录程序的基础上，做了进一步的修改。本程序增加了主、副桩组均值限差大于３ｎＴ达４０种情况的超限判断，解决了计算结果数  相似文献   

North-south asymmetry in response of geomagnetic activity to different solar events     

G. K. Rangarajan 《Journal of Earth System Science》1987,96(2):195-202

Study of the response of geomagnetic activity to five different kinds of solar events reveals that an average north-south asymmetry of about 15% exists which diminishes with enhanced geomagnetic activity. The response of the geomagnetic field is quite significant only when high speed solar wind stream in association with sector boundary of interplanetary magnetic field (IMF) or solar proton streams near sector boundary sweeps past the earth. When the frequency of occurrence of indices of geomagnetic activity is considered, the index zero shows a marked difference in its response characteristics for the southern hemisphere. This appears to be a real feature and not attributable to any artefact of the index or its derivation.  相似文献   

科学技术界要关注高新能源的发展态势          下载免费PDF全文

刘广志 《探矿工程》2004,31(1):7-10

为适应广大科技工作者了解国外新能源的发展态势，从而关注我国新能源发展前景，集中编辑了有关生物质能、生物柴油、太阳能、风能、地热、氢能等多种新能源的国内外发展态势，分析了各自的开发利用潜力和前景,以供大家借鉴，有利于开展某些项目的研发。相信不久的将来，我国新能源事业，能尽快走上“快车道”、“高速路”。  相似文献