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651.
G.Y.Smolkov 《空间科学学报》2005,25(5):345-350
Presented are the ideas and proposals in regards to the pooling of by RAS, SB, ISTP, and CSSAR,CAS toward coordinated usage of existing ground-based and orbiting helio-geophysical observatories, single large installations as well as creating, forecasting services and new observing facilities, in the interests of achieving a profitable activity of the China-Russia Joint Research Center on Space Weather (JRCSW). 相似文献
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654.
微细电火花线切割加工工艺研究 总被引:3,自引:0,他引:3
通过对微细电火花线切割加工极间放电状态的分析,提出了微细电火花线切割加工伺服进给系统的特点,并总结了微细电火花线切割加工的工艺规律,为实现生产领域的高精度、高效率加工提供了可靠的工艺保障。 相似文献
655.
Detection of random signals via spectrum matching 总被引:1,自引:0,他引:1
Using a priori knowledge of the signal power spectral density (PSD), a spectrum matching approach which effectively utilizes the available signal spectral shape is developed for random signal detection. Two spectrum matching detector (SMD) structures, which are implemented by correlogram and periodogram, respectively, are examined. Theoretical calculation of their false alarm rates is derived and confirmed by simulations. It is also demonstrated that the proposed detectors outperform the standard periodogram, Bartlett method, and energy detector under constant false alarm rate (CFAR) condition for two different random signals. 相似文献
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657.
X.Y. Xu W.J. Liu M.L. Zhong X.L.Li S. Yang R. Z. Ba 《航空制造技术》2004,(Z1):73-78
对激光合成颗粒增强金属间化合物基复合材料进行了研究,包括Ni3Al/WC、NiAl/TiC、Ti3Al/TiC和MoSi2/SiC,用扫描电镜、能谱仪和X射线衍射仪对材料成分和组织特征进行了分析,提出并讨论了影响激光合成金属间化合物基复合材料的关键问题.激光合成具有多种强韧化方法协同、提高金属间化合物强度和塑性的特点,有利于金属间化合物性能的综合改善. 相似文献
658.
N. Cornilleau-Wehrlin P. Chauveau S. Louis A. Meyer J. M. Nappa S. Perraut L. Rezeau P. Robert A. Roux C. De Villedary Y. De Conchy L. Friel C. C. Harvey D. Hubert C. Lacombe R. Manning F. Wouters F. Lefeuvre M. Parrot J. L. Pinçon B. Poirier W. Kofman Ph. Louarn 《Space Science Reviews》1997,79(1-2):107-136
The Spatio-Temporal Analysis of Field Fluctuations (STAFF) experiment is one of five experiments which together comprise the Wave Experiment Consortium (WEC). STAFF consists of a three-axis search coil magnetometer to measure magnetic fluctuations at frequencies up to 4 kHz, and a spectrum analyser to calculate in near-real time aboard the spacecraft, the complete auto- and cross-spectral matrices using the three magnetic and two electric components of the electromagnetic field. The magnetic waveform at frequencies below either 10 Hz or 180 Hz is also transmitted. The sensitivity of the search coil is adapted to the phenomena theo be studied: the values 3 × 10-3 nT Hz-1/2 and 3 × 10-5 nT Hz-1/2 are achieved respectively at 1 Hz and 100 Hz. The dynamic range of the STAFF instruments is about 96 dB in both waveform and spectral power, so as to allow the study of waves near plasma boundaries. Scientific objectives of the STAFF investigations, particularly those requiring four point measurements, are discussed. Methods by which the wave data will be characterised are described with emphasis on those specific to four-point measurements, including the use of the Field Energy Distribution function. 相似文献
659.
Kleczek J. van Gent R. H. Rutten Robert J. de Munck J. C. Slottje C. Severne G. Pecker Jean-Claude Postma H. Grishchuk L. P. Niewenhuijzen H. Schuiling R. D. van Beek H. F. Reijnen G. C. M. Heidmann Jean Lemaire J. Bleeker Johan Icke V. Neéman Y. Feast M. W. de Graaff W. 《Space Science Reviews》1986,43(3-4):383-396
Space Science Reviews - 相似文献
660.
Modeling and a Correlation Algorithm for Spaceborne SAR Signals 总被引:3,自引:0,他引:3
A mathematical model of a spaceborne synthetic aperture radar (SAR) response is presented. The associated SAR system performance, in terms of the resolution capability, is also discussed. The analysis of spaceborne SAR target response indicates that the SAR correlation problem is a two-dimensional one with a linear shift-variant response function. A new digital processing algorithm is proposed here in order to realize an economical digital SAR correlation system. The proposed algorithm treats the two-dimensional correlation by a combination of frequency domain fast correlation in the azimuth dimension and a time-domain convolver type of operation in the range dimension. Finally, digitally correlated SEASAT satellite SAR imagery is used in an exemplary sense to validate the SAR response model and the new digital processing technique developed. 相似文献