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761.
762.
在研究了单极化条件下高分辨率距离像的目标识别后,给出一种利用目标全极化信息的投票识别方法。实验结果表明,该方法具有较高的识别率。 相似文献
763.
本文提出了VOR地面信标模仿仪对频率合成器的要求,介绍了集成锁相环芯片MC145152的工作特性,验证了基于MC145152的PLL频率合成器在VOR地面信标模仿仪中的设计与实现的有效性。 相似文献
764.
Tao Li C.-Y. She Scott E. Palo Qian Wu Han-Li Liu Murry L. Salby 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(9):1463-1471
The Colorado State University sodium lidar, located in Fort Collins, CO (41N, 105W), is capable of both daytime and nighttime operations and has conducted a number of continuous multiple-day observational campaigns over the past few years. Three such campaigns, lasting between 80 and 90 h, were conducted during August 2002–2004 when mesospheric winds and temperature observations were collected simultaneously. These data were processed to extract the vertical structure and temporal evolution of the quasi-two-day wave, which was found to be significant in the power spectra. The quasi-two-day wave in temperature, zonal wind and meridional wind was analyzed for each year, indicating that the wave activity in 2003 was weaker than the other two years. Concurrent TIMED/SABER (2002–2004) and TIMED/TIDI observations (2004) in August were also processed. The SABER temperature shows a quasi-two-day wave with a dominant westward propagating zonal wavenumber four (s = −4) component in 2002 and 2004 but not in 2003. Analysis of the TIDI winds in August 2004 also indicates significant quasi-two-day wave activity, with the zonal wavenumber three and four components of comparable strength. The results of this coordinated ground-based lidar and TIMED satellite observations during August are presented. The possible influence of quasi-biennial oscillation on the inter-annual variability of the quasi-two-day wave is investigated. 相似文献
765.
航天控制系统潜在分析技术应用研究 总被引:7,自引:0,他引:7
潜在分析技术是提高控制系统安全性与可靠性的一项重要的分析工具,它对查询运载火箭或导弹控制系统潜在问题与设计缺陷,保证系统安全性与可靠性具有非常重要的意义. 通过对国外潜在分析技术进行比较研究和对国内航天控制系统潜在分析技术的现状进行分析,得出重要结论:在航天领域应开发适合中国国情的人工智能计算机潜在分析技术,以保证火箭或导弹的安全性和可靠性. 相似文献
766.
L. Qian S.C. Solomon R.G. Roble B.R. Bowman F.A. Marcos 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
Recent measurements by the Solar EUV (Extreme Ultra Violet) Experiment (SEE) aboard the Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics satellite (TIMED) provide solar EUV spectral irradiance with adequate spectral and temporal resolution, and thus the opportunity to use solar measurements directly in upper atmospheric general circulation models. Thermospheric neutral density is simulated with the NCAR Thermosphere–Ionosphere–Electrodynamic General Circulation Model (TIEGCM) using TIMED/SEE measurements and using the EUVAC solar proxy model. Neutral density is also calculated using the NRLMSISE-00 empirical model. These modeled densities are then compared to density measurements derived from satellite drag data. It is found that using measured solar irradiance in the general circulation model can improve density calculations compared to using the solar proxy model. It is also found that the general circulation model can improve upon the empirical model in simulating geomagnetic storm effects and the solar cycle variation of neutral density. 相似文献
767.
768.
利用影像技术对帕金森病(Parkinsondisease,PD)大鼠模型的脑形态与功能信息进行了系统研究。利用磁共振(Magneticresonance imaging。MRI)及磁共振血管成像(Magneticresonanceangiography,MRA)获取PD大鼠脑部形态影像资料,利用质子磁共振波谱(1H—magneticreso—nancespectroscopy,1H—MRS)及CT灌注(CTperfusion,CTP)成像获取波谱及血流变化等功能影像学资料。研究结果表明PD大鼠在形态上影像无特征性异常,在功能影像学纹状体存在局部脑血流降低和波谱变化。 相似文献
769.
X. Zhang Z. Zeren M. Parrot R. Battiston J. Qian X. Shen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
ULF/ELF electric field perturbations in the ionosphere have been widely observed by the satellites. In this paper, we develop a method of Logarithm Electric Field Intensity (LEFI) to automatically distinguish this kind of disturbances based on the spectrum intensity and its damping exponent with frequency in electromagnetic signals. This method is applied to DEMETER data processing around Chile earthquakes with magnitude larger than 6.0. It is found that 2/3 earthquakes have shown obvious ULF/ELF electric field perturbations in this region. The temporal and spatial distributions of electron density and temperature were compared with that of electric field, which proved the existence of irregularities above epicentral area. Finally, the coupling mechanism of earthquake-ionosphere is discussed based on multi-parameter analysis. 相似文献
770.
现有的检测前跟踪算法对高分辨雷达隐身目标模型适应性不强,从而容易导致跟踪发散。针对该问题,把粒子滤波与检测前跟踪算法相结合应用于扩展隐身目标的检测跟踪,提出了一种隐身目标扩展模型检测前跟踪方法。首先,采用扩展模型对目标的扩展属性进行假设检验,从而判断目标是否为扩展目标;然后,把目标扩展长度引入状态向量,进行基于扩展模型的隐身目标检测前跟踪(Track-before-detect,TBD),克服粒子滤波易发散的不足,实现对目标空间长度的估计。仿真结果表明,该算法能够准确判断目标的扩展属性并进行有效的检测跟踪。 相似文献