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罗先武 《中国空间科学技术》1997,17(3):15-20
参照欧空局的软件工程规范,研制了为星上数据管理任务服务的实时多任务操作系统RT86,它的硬件环境是两个互为冷配份的主控单元,通过1553B串行数据总线与多个远置单元联接,完成星上遥测、遥控及星上多项数据库管理任务。文章介绍了其设计要点,做到了系统设计思路简单清晰,程序易于修改维护,可靠性高,它为星上应用软件开发提供了通用设计平台。 相似文献
243.
针对行星齿轮系在工作过程中出现的局部缺陷,将引起齿轮啮合异常,并导致冲击异常,其特征频率就会发生变化。现用ADAMS与ANSYS建立行星齿轮系的刚柔耦合模型,通过快速傅里叶变换(FFT)得到其啮合力的频域曲线,并分析无缺陷行星齿轮系的特征频率、行星轮齿局部缺陷的特征频率、太阳轮齿局部缺陷的特征频率。仿真结果与理论值吻合,说明了所建虚拟样机模型可靠,得到无缺陷行星齿轮系的特征频率是265.34Hz,行星轮齿局部缺陷的特征频率是17.67Hz,太阳轮齿局部缺陷的特征频率是36.13Hz,可用于识别行星齿轮系的行星轮或太阳轮局部缺陷。对行星齿轮系振动特性、可靠性的研究具有一定的指导意义。 相似文献
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Herbert I. M. Lichtenegger Helmut Lammer Yuri N. Kulikov Shahin Kazeminejad Gregorio H. Molina-Cuberos Rafael Rodrigo Bobby Kazeminejad Gottfried Kirchengast 《Space Science Reviews》2006,126(1-4):469-501
The heating of the upper atmospheres and the formation of the ionospheres on Venus and Mars are mainly controlled by the solar
X-ray and extreme ultraviolet (EUV) radiation (λ = 0.1–102.7 nm and can be characterized by the 10.7 cm solar radio flux).
Previous estimations of the average Martian dayside exospheric temperature inferred from topside plasma scale heights, UV
airglow and Lyman-α dayglow observations of up to ∼500 K imply a stronger dependence on solar activity than that found on
Venus by the Pioneer Venus Orbiter (PVO) and Magellan spacecraft. However, this dependence appears to be inconsistent with
exospheric temperatures (<250 K) inferred from aerobraking maneuvers of recent spacecraft like Mars Pathfinder, Mars Global
Surveyor and Mars Odyssey during different solar activity periods and at different orbital locations of the planet. In a similar
way, early Lyman-α dayglow and UV airglow observations by Venera 4, Mariner 5 and 10, and Venera 9–12 at Venus also suggested
much higher exospheric temperatures of up to 1000 K as compared with the average dayside exospheric temperature of about 270
K inferred from neutral gas mass spectrometry data obtained by PVO. In order to compare Venus and Mars, we estimated the dayside
exobase temperature of Venus by using electron density profiles obtained from the PVO radio science experiment during the
solar cycle and found the Venusian temperature to vary between 250–300 K, being in reasonable agreement with the exospheric
temperatures inferred from Magellan aerobraking data and PVO mass spectrometer measurements. The same method has been applied
to Mars by studying the solar cycle variation of the ionospheric peak plasma density observed by Mars Global Surveyor during
both solar minimum and maximum conditions, yielding a temperature range between 190–220 K. This result clearly indicates that
the average Martian dayside temperature at the exobase does not exceed a value of about 240 K during high solar activity conditions
and that the response of the upper atmosphere temperature on Mars to solar activity near the ionization maximum is essentially
the same as on Venus. The reason for this discrepancy between exospheric temperature determinations from topside plasma scale
heights and electron distributions near the ionospheric maximum seems to lie in the fact that thermal and photochemical equilibrium
applies only at altitudes below 170 km, whereas topside scale heights are derived for much higher altitudes where they are
modified by transport processes and where local thermodynamic equilibrium (LTE) conditions are violated. Moreover, from simulating
the energy density distribution of photochemically produced moderately energetic H, C and O atoms, as well as CO molecules,
we argue that exospheric temperatures inferred from Lyman-α dayglow and UV airglow observations result in too high values,
because these particles, as well as energetic neutral atoms, transformed from solar wind protons into hydrogen atoms via charge
exchange, may contribute to the observed planetary hot neutral gas coronae. Because the low exospheric temperatures inferred
from neutral gas mass spectrometer and aerobraking data, as well as from CO+
2 UV doublet emissions near 180–260 nm obtained from the Mars Express SPICAM UV spectrograph suggest rather low heating efficiencies,
some hitherto unidentified additional IR-cooling mechanism in the thermospheres of both Venus and Mars is likely to exist.
An erratum to this article can be found at 相似文献
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247.
陈肖南 《沈阳航空工业学院学报》2003,20(3):56-57,23
建立人工神经网络BP算法,利用计算运行方式的变化改进传统的电力输电线系统的保护措施,可以实时跟踪故障点并同步实施控制。利用人工神经网络技术的快速性、自适应性和容错性,在一个周期内准确地定位区内、区外故障点,实现对输电线的速断保护。 相似文献
248.
王健%金周庚%刘哲军 《宇航材料工艺》2001,31(1):49-57
以复合材料为对象,以宽频带传感器及线阵列方式对各类模式试样采集了波形及信号参数,比较波形、信号参数、频谱及小波谱的特征,筛选出六类1300个样本,采用多分辨小波变换提取了5个特征向量,实现了特征空间的降维处理,采用B—P型反向传播神经网络构成了智能化模式分类器,研究了网络模型的学习效果和对与复合材料主要损伤机制有关的六类声发射信号的识别能力。试验结果表明,神经网络对六类信号的平均正确识别率达到90.4%。最佳识别率为97.2%。该方法成功用于90°、0°光滑和0°缺口三种试样的破坏过程分析,获得了满意的效果。 相似文献
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