SL9彗星碎块穿入木星大气的深度

ＳＬ９慧星撞击木星类似于大气中陨落的流星现象，是替星与木星大气相互作用的过程．慧星碎块的质量取为１０（１２）、１０（１３）和１０（１４）ｋｇ，其密度分别为３．０、１．０、０．８、０．５和０．２ｇ／ｃｍ３．结果表明：这些慧星碎块能穿透木星大气的氨云层，在接近１ｂａｒ的地方爆炸，这与文［１］的模拟结果一致．     

Effects of rotation on the colours and line indices of stars 6. The reality of the blue straggler phenomenon

The effect of rotation on the observed colours of stars has been considered as a possible cause for the blue straggler phenomenon in clusters listed by Mermilliod (1982). It appears that this phenomenon is definitely not real in the case of the late B and early A spectral type blue stragglers that are intrinsic slow rotators. Among clusters containing the early B type blue stragglers it is found that the anomalous position of the stragglers in NGC 6633, NGC 6475 and NGC 2516 cannot be accounted for by rotation effects alone. on leave from Assumption College, Changanacherry, Kerala.     

The application of geodetic radio interferometric surveying to the monitoring of sea-level

Summary. Under project IRIS (International Radio Interferometric Surveying) geodesists are using Very Long Baseline Interferometry (VLBI) to monitor polar motion to 1-2 ms of arc and UT1 to 0.05-0.10 ms, and to develop a global geodynamic network to detect and study centimetre level displacements of reference points associated with large-scale phenomena such as tectonic plate motion and glacial rebound. Differential positioning techniques using the signals broadcast by the satellites of the Global Positioning System (GPS) are being used to study finer scale phenomena, such as localized subsidence, and economically to relate these specialized surveys to the geodynamic network. Including tide gauge stations in this system will make it possible to detect motions of specific gauges and correct or delete the measurements from those gauges when computing changes in sea-level. The National Oceanic and Atmospheric Administration (NOAA) has selected several tide gauges on the east and west coasts of the United States, and initial epoch GPS surveys to tie the gauges to VLBI observations have already begun. Other countries participating in project IRIS are planning similar activities. In addition to providing a globally based land reference datum for the tide gauge measurements, the IRIS polar motion and UT1 time series may contribute directly to monitoring and interpreting global sea level changes. Changes in the volume and distribution of ice masses result in long-term motions of the axis of rotation, and sea-level changes affect the length of day (lod). The IRIS time series will certainly have the resolution required to detect the expected polar motion and changes in lod, and a properly designed global VLBI/GPS network should allow the ice/sea-level effects to be separated from crustal dynamics effects.     

水库诱发地震的能源研究

根据力学原理证明水库蓄水使地球释放动能，能量释放地在库区或库区邻近。导出了计算此动能的公式。指出它是诱发水库地震的一个新因素     

GPS measurements (2003–2006) in the Sikhote Alin network,the Far East

This paper considers results of geodynamic studies using the GPS method in the territory of the Far East. GPS measurements using TRIMBLE-4700 geophones were launched along the Sikhote Alin profile in 2003. The technology of the GPS measurements and the problems of selecting the measurement sites and network configuration with reference to the region’s structure are discussed. The results of GPS measurements in 2003–2006 were used to study the fault system of the Far East continental margin. Different models of the Eurasia rotation (from the known NNR-NUVEL-1A to the recent ones) were analyzed. The solid-body rotation of Eurasia was predicted in the framework of the AR-IR-2006 model with a pole located at 51.045°N latitude, 255.842° longitude and rotating at a rate of 0.2423°/Ma. The parameters of the Amur plate rotation were preliminarily estimated (57.6° ± 0.5°N, 117.1 ± 0.5°E, and 0.083° ± 0.004°/m.y) using results on the Sikhote Alin and Transbaikalian network.     

近景摄影测量中大角度问题的探讨

应用摄影测量中的解析算法,研究倾斜摄影和交向摄影中大角度摄影情况下的解算方法对经典解析算法的影响,推导大角度摄影情况下从相对定向至绝对定向这一解析过程的算法,通过算例证明在大倾角摄影条件下利用该算法能够准确计算出地面点坐标以及反算出像片的外方位元素,从而验证本算法在大倾角近景摄影测量中的适用性。     

地球自转参数的RFFLS短期预报算法研究

地球自转参数(ERP)是实现地心天球坐标系(geocentric celestial reference system,GCRS)与国际地球坐标系(international terrestrial reference system,ITRS)相互转换的必要参数,是国际GNSS服务组织(IGS)和国际GNSS监测评估系统(iGMAS)分析中心的重要产品。本文针对最小二乘地球自转参数预测算法会造成数据饱和以及新旧数据在数据处理及预报中被同等对待等问题,将遗忘因子引入最小二乘预测算法,进而提高ERP预报精度。遗忘因子递推最小二乘算法能防止数据饱和,降低旧数据的影响,加强新数据的作用,降低在求解拟合参数时出现秩亏矩阵求逆的几率,提高预报精度。本文详细推导了遗忘因子递推最小二乘表达式,探究了最佳遗忘因子,并通过ERP试验将该方法和原最小二乘的试验结果及LS-AR模型的预报结果作对比,发现仅用遗忘因子最小二乘模型预测就可以达到与LS-AR组合模型预测相当的精度。     

Multi-Data Approach for remote sensing-based regional crop rotation mapping: A case study for the Rur catchment,Germany

Spatial land use information is one of the key input parameters for regional agro-ecosystem modeling. Furthermore, to assess the crop-specific management in a spatio-temporal context accurately, parcel-related crop rotation information is additionally needed. Such data is scarcely available for a regional scale, so that only modeled crop rotations can be incorporated instead. However, the spectrum of the occurring multiannual land use patterns on arable land remains unknown. Thus, this contribution focuses on the mapping of the actually practiced crop rotations in the Rur catchment, located in the western part of Germany. We addressed this by combining multitemporal multispectral remote sensing data, ancillary information and expert-knowledge on crop phenology in a GIS-based Multi-Data Approach (MDA). At first, a methodology for the enhanced differentiation of the major crop types on an annual basis was developed. Key aspects are (i) the usage of physical block data to separate arable land from other land use types, (ii) the classification of remote sensing scenes of specific time periods, which are most favorable for the differentiation of certain crop types, and (iii) the combination of the multitemporal classification results in a sequential analysis strategy. Annual crop maps of eight consecutive years (2008–2015) were combined to a crop sequence dataset to have a profound data basis for the mapping of crop rotations. In most years, the remote sensing data basis was highly fragmented. Nevertheless, our method enabled satisfying crop mapping results. As an example for the annual crop mapping workflow, the procedure and the result of 2015 are illustrated. For the generation of the crop sequence dataset, the eight annual crop maps were geometrically smoothened and integrated into a single vector data layer. The resulting dataset informs about the occurring crop sequence for individual areas on arable land, so that crop rotation schemes can be derived. The resulting dataset reveals that the spectrum of the practiced crop rotations is extremely heterogeneous and contains a large amount of crop sequences, which strongly diverge from model crop rotations. Consequently, the integration of remote sensing-based crop rotation data can considerably reduce uncertainties regarding the management in regional agro-ecosystem modeling. Finally, the developed methods and the results are discussed in detail.     

A note on Earth's rotation angular velocity in the general-relativity framework

 The value of the Earth's rotational angular velocity determined from observations is given in the GCRS (geocentric celestial reference system) defined by Resolution B1 of the 2000 IAU General Assembly. The same quantity derived from dynamical theories of the Earth's rotation, such as SMART97, is referred to the␣DGRSC (dynamically non-rotating ecliptical reference system). The relativistic theory of reference systems (RSs) enables unambiguous general-relativity relations between these quantities to be derived. Received: 9 November 2000 / Accepted: 9 July 2001     

A Hamiltonian approach to dissipative phenomena between the Earth's mantle and core, and effects on free nutations

The Hamiltonian formalism was recently applied by Getino (1995a,b) for the study of the rotation of a non-rigid earth with a heterogeneous and stratified liquid core. That earth model is generalized here by including the effect of the dissipation arising from the mantle-core interaction, using a model similar to that of Sasao, Okubo & Saito (1980), which includes both viscous and electromagnetic coupling. First, a solution for the free nutations is obtained following a classical approach, which in our opinion is more familiar to most of the readers than the Hamiltonian treatment. This solution provides a theoretical basis clear enough to study both the qualitative and quantitative effects of the dissipations considered in the hypotheses. The main qualitative features are, besides the delays, that the free core nutation (FCN) suffers an exponential damping, while the chandler wobble (CW) is not damped at first order, by the dissipation considered. The numerical values obtained for the complex compliances agree with the most recent experimental computations.
Next, the problem is studied under a Hamiltonian formalism, and a solution equivalent to the above is obtained. Besides its interest from a theoretical point of view, this formalism is necessary in order to apply canonical perturbation methods in order to obtain analytical nutation series.