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1.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(11):2551-2558
The whistler-mode chorus waves are one of the most important plasma waves in the Earth’s magnetosphere. Generally, the amplitude of whistler-mode chorus waves prefers to strengthen when the energetic fluxes of anisotropic electrons increase outside the plasmapause. This characteristic is commonly associated with the geomagnetic storms or substorms. However, the relationship between the solar wind dynamic pressure (Psw) and the long-time variation of chorus waves during the quiet period of the geomagnetic activity still needs more detailed investigations. In this paper, based on MMS observations, we present a chorus event just observed in the inner side of magnetopause without obvious geomagnetic storms or substroms. Interestingly, during this time interval, some Psw fluctuations were recorded. Both the amplitudes and frequencies of chorus waves changed as a response to the variation in Psw. It proved that the enhancement of Psw increases the energetic electrons fluxes, which provides free energies for the chorus amplification. Furthermore, the wave growth rates calculated using linear theory increases and the central frequency of the chorus waves shifts to a higher frequency when the Psw enhancement is greater, which are also consistent well with the observations. The results provide a direct evidence that the Psw play an important role in the long-time variation of whistler-mode chorus waves inside the magnetopause. 相似文献
2.
本给出了系统安全性评价的AHP方法,叙述了该方法的基本步骤,并以沈阳某集团公司热处理弹簧厂评价的实例说明了该方法的有效性。 相似文献
3.
本文提出了故障检测与分离的广义一致性算子法的一般形式。得出了两个故障可分离的充要条件和多个故障可分离的充要条件。最后给出了检测和分离故障的过程。 相似文献
4.
耿征 《南京航空航天大学学报》1988,(2)
本文利用特征结构配置法所揭示的线性多变量反馈控制系统闭环特征值和特征向量的配置自由度,求解具有二次型性能指标的控制系统设计问题,使得闭环系统在具有任意给定的希望特征值集合条件下,性能指标达到极小。文中建立了最优二次型性能指标与闭环特征结构的关系,提出了逐个优化特征向量的算法,这一算法概念直观并具有较高的运算效率,可以推广到一般的特征结构优化问题。 相似文献
5.
The short- and long-term effects of spacecraft explosions, as a function of the end-of-life re-orbit altitude above the geostationary orbit (GEO), were analyzed in terms of their additional contribution to the debris flux in the GEO ring. The simulated debris clouds were propagated for 72yrs, taking into account all the relevant orbital perturbations.The results obtained show that 6–7 additional explosions in GEO would be sufficient, in the long term, to double the current collision risk with sizable objects in GEO. Unfortunately, even if spacecraft were to re-orbit between 300 and 500km above GEO, this would not significantly improve the situation. In fact, an altitude increase of at least 2000km would have to be adopted to reduce by one order of magnitude the long-term risk of collision among geostationary satellites and explosion fragments. The optimal debris mitigation strategy should be a compromise between the reliability and effectiveness of spacecraft end-of-life passivation, the re-orbit altitude and the acceptable debris background in the GEO ring. However, for as long as the re-orbit altitudes currently used are less than 500km above GEO, new spacecraft explosions must be avoided in order to preserve the geostationary environment over the long term. 相似文献
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本文给出了解决运输问题为中心的一类特殊的线性规划问题的新的、简便的算法。网络最大流与最小割集的矩阵算法,不仅能解决许多这类问题,而且能使最小费用流、分配问题和运输问题容易通过计算机来实现。 相似文献
9.
A. Aran B. Sanahuja D. Lario 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,36(12):2333-2338
We present a preliminary version of a potential tool for real time proton flux prediction which provides proton flux profiles and cumulative fluence profiles at 0.5 and 2 MeV of solar energetic particle events, from their onset up to the arrival of the interplanetary shock at the spacecraft position (located at 1 or 0.4 AU). Based on the proton transportation model by Lario et al. [Lario, D., Sanahuja, B., Heras, A.M. Energetic particle events: efficiency of interplanetary shocks as 50 keV E < 100 MeV proton accelerators. Astrophys. J. 509, 415–434, 1998] and the magnetohydrodynamic shock propagation model of Wu et al. [Wu, S.T., Dryer, M., Han, S.M. Non-planar MHD model for solar flare-generated disturbances in the Heliospheric equatorial plane. Sol. Phys. 84, 395–418, 1983], we have generated a database containing “synthetic” profiles of the proton fluxes and cumulative fluences of 384 solar energetic particle events. We are currently validating the applicability of this code for space weather forecasting by comparing the resulting “synthetic” flux profiles with those of several real events. 相似文献
10.
针对Lagrange插值法无法处理连续野值的问题,提出了一种基于改进支持向量回归(Support Vector Regression, SVR)的导航传感器自适应野值检测方法。该方法结合了支持向量回归利用小样本数据就能够准确建模和3σ准则计算简易的优点,利用支持向量回归在线建立舰船的运动模型对测量值进行实时预测,并利用3σ准则自适应地计算阈值,然后通过比较阈值与预测残差来判别测量值是否为野值点。该方法可以自动地学习舰船的运动趋势,建立舰船的真实运动模型,而且不受连续野值点的影响,能够在没有其他传感器辅助的条件下完成野值检测。海试实测数据表明,提出的方法对离散和连续的野值点均具有较好的检测效果,同时可以更好地估计传感器的真实测量值。 相似文献