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71.
同步三轴卫星中的能源分系统是卫星各系统中重要的组成部分,能源系统中任何异常将严重影响卫星功能的发挥。预想能源系统中分流器异常,通过对南分流器异常的分析,提出两种应对策略,并在仿真计算的基础上进行可行性分析,得出一种切实可行的应对策略,为同步三轴卫星长期管理中异常处理提供了分流器异常的可行性预案。 相似文献
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A.P. Kropotkin V.I. Domrin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Dynamics of the magnetotail involves elementary processes of magnetic field merging (reconnection layer formation) occurring on medium spatial scales. Every such process features two different stages, a fast one and a subsequent slower one. The corresponding short time scale T1 is associated with disturbances propagating in the tail lobes. The longer time scale T2 is associated with plasma motions in the plasma sheet. A disturbance appearing in the magnetotail on the time scale T1 results in a loss of equilibrium in the plasma sheet. By means of theoretical argument and numerical simulation, it is shown that the relaxation process which follows on the time scale T2, produces extremely thin embedded current sheets, along with generation of fast plasma flows. The process provides an effective mechanism for transformation of magnetic energy accumulated in the magnetotail, into energy of plasma flows. The fast flows may drive turbulent motions on shorter spatial scales. In their turn, those motions can locally produce very thin current sheets; after that, nonlinear tearing process leads to generation of neutral lines, and reconnection. The latter produces new fast disturbances on the time scale T1 closing the feedback loop. 相似文献
74.
本文介绍民用飞机点火源防护的历史来源,提出接地故障保护的概念,分析接地故障中断继电器的基本工作原理及其在民用飞机上的应用。 相似文献
75.
Over the last 25 years, considerable scientific effort has been expended in the development of quantitative models of the dynamics of Earth's inner magnetosphere, particularly on studies of the injection of the storm-time ring current and of dynamic variations in the shape and size of the plasmasphere. Nearly all modeling studies of ring-current injection agree that time-varying magnetospheric convection can produce approximately the ion fluxes that are observed in the storm-time ring current, but the truth of that assumption has never been demonstrated conclusively. It is not clear that the actual variations of convection electric fields are strong enough to explain the observed flux increases in ~100 keV ions at the peak of the storm-time ring current. Observational comparisons are generally far from tight, primarily due to the paucity of ring-current measurements and to basic limitations of single-point observations. Also, most of the theoretical models combine state-of-the-art treatment of some aspects of the problem with highly simplified treatment of other aspects. Even the most sophisticated treatments of the sub-problems include substantial uncertainties, including the following: (i) There is still considerable theoretical and observational uncertainty about the dynamics of the large-scale electric fields in the inner magnetosphere; (ii) No one has ever calculated a force-balanced, time-dependent magnetic-field model consistent with injection of the storm-time ring current; (iii) The most obvious check on the overall realism of a ring-current injection model would be to compare its predicted Dst index against observations; however, theoretical calculations of that index usually employ the Dessler-Parker-Sckopke relation, which was derived from the assumption of a dipole magnetic field and cannot be applied reliably to conditions where the plasma pressure significantly distorts the field; (iv) Although loss rates by charge exchange and Coulomb scattering can be calculated with reasonable accuracy, it remains unclear whether wave-induced ion precipitation plays an important role in the decay of the ring current. However, considerable progress could be made in the next few years. Spacecraft that can provide images of large regions of the inner magnetosphere should eliminate much of the present ambiguity associated with single-point measurements. On the theoretical side, it will soon be possible to construct models that, for the first time, will solve a complete set of large-scale equations for the entire inner magnetosphere. The biggest uncertainty in the calculation of the size and shape of the plasmasphere lies in the dynamics and structure of the electric field. It is still not clear how important a role interchange instability plays in determining the shape of the plasmapause or in creating density fine structure. 相似文献
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介绍一种使用电流传感器的交流电流-直流电压(ACI/DCV)转换电路,具有与被测电路隔离、体积小、测量范围广、线性度好等特点。 相似文献
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A novel co-rotating electrochemical machining method is proposed for fabricating convex structures on the inner surface of a revolving part. The electrodes motion and material removal method of co-rotating electrochemical machining are different from traditional electrochemical machining. An equivalent kinematic model is established to analyze the novel electrodes motion,since the anode and cathode rotate in the same direction while the cathode simultaneously feeds along the line of centres. Acc... 相似文献
80.
在卫星导航系统动态定位中,采用基于瞬时多普勒观测量的最小二乘法确定速度,当载体高机动时,多普勒误差迅速增大,从而导致测速精度大幅度降低。针对该问题,提出一种同时实现动态模型自适应修正和观测模型自适应更新的Kalman滤波算法。算法采用滑动窗方式来建立实时更新的动态模型参数,使当前统计模型自适应地跟踪载体的动态特性。此外,算法提出观测模型的自适应更新方法,通过设置载体状态判决门限,高、中机动时仅进行受动态应力影响小的伪距更新,低机动下添加精度较高的伪距率更新。通过Sprient GSS8000模拟器产生的动态场景验证表明,相对于最小二乘法和常规Kalman滤波算法,提出的自适应Kalman滤波算法能够全面提高载体在多种运动状态下的测速精度。 相似文献