空间太阳电池板银互连片原子氧效应模拟试验

空间太阳电池板可作为空间飞行器的动力源,但由于原子氧在空间太阳电池板银互连片上的腐蚀作用,可能影响空间太阳电池板的有效寿命.因此,在北航流体所设计的原子氧效应地面模拟试验设备中,对空间太阳电池板的银互连片进行了抗原子氧效应地面模拟试验研究.获得了银箔和不同防护镀层材料在原子氧环境中的不同剥蚀结果,这为进行银互连片表面的原子氧防护提供了必要的应用和设计依据.     

原子氧对航天器表面材料作用的数值模拟

对低地球轨道环境对航天器表面材料的影响和航天器表面材料的低地球轨道环境寿命评定方法进行了介绍,并对低地球轨道环境和地面试验环境下,有无保护涂层的聚酰亚胺所受冲蚀作用进行了成功的数值模拟,获得了具有工程应用价值的数值计算结果.该项工作对太空航天器的设计具有重要的指导意义.      

基于BP神经网络的复合材料性能预测

针对复合材料性能表征十分复杂、困难的情况,利用人工神经网络的BP算法,建立了复合材料性能预测模型。模型由3层神经元组成,分别为输入层、隐含层和输出层。以碳/陶瓷复合材料性能与成分的关系为研究对象,选取了38组实验数据作为学习样本,模型总误差为0.18,用建立的网络预测未知,并给出预报曲线。和试验值相比较表明,所建立的网络能反映碳/陶瓷复合材料组分与其材料性能之间的关系,为实验设计提供了新的思路,节省了时间和劳力。     

Nighttime thermospheric meridional neutral winds inferred from ionospheric h′F and hpF2 data

Nighttime thermospheric meridional winds aligned to the magnetic meridian have been inferred using h′F and hpF2 ionosonde data taken from two equatorial stations, Manaus (2.9°S, 60.0°W, dip latitude 6.0°N) and Palmas (10.17°S, 48.2°W, dip latitude 6.2°S), and one low-latitude station, Sao Jose dos Campos (23.21°S, 45.86°W, dip latitude 17.26°S), during geomagnetic quiet days of August and September, 2002. Using an extension of the ionospheric servo model and a simple formulation of the diffusive vertical drift velocity, the magnetic meridional component of the thermospheric neutral winds is inferred, respectively, at the peak (hpF2) and at the base (h′F) heights of the F region over Sao Jose dos Campos. An approach has been included in the models to derive the effects of the electrodynamic drift over Sao Jose dos Campos from the time derivative of hpF2 and h′F observed at the equatorial stations. The magnetic meridional winds inferred from the two methods, for the months of August and September, are compared with winds calculated using the HWM-90 model and with measurements from Fabry–Perot technique. The results show varying agreements and disagreements. Meridional winds calculated from hpF2 ionospheric data (servo model) may produce errors of about 59 m/s, whereas the method calculated from the F-region base height (h′F) ionospheric data gives errors of about 69 m/s during the occurrence of equatorial spread-F.     

Mars Express/ASPERA-3/NPI and IMAGE/LENA observations of energetic neutral atoms in Earth and Mars orbit

The low energy neutral atom imagers on Mars Express and IMAGE have revealed that the neutral atom populations in interplanetary space come from a variety of sources and challenge our current understanding of heliospheric physics. For example, both in cruise phase and at Mars, the neutral particle instrument NPD on Mars Express observed “unexplained neutral beams” unrelated to Mars which appear to be either of heliospheric or solar wind origin. Likewise, the NPI instrument on Mars Express has revealed streams of neutral atoms with different properties than those observed by NPD. Independently, IMAGE/LENA has reported neutral atom observations that may be interpreted as a “secondary stream” having different characteristics and flowing from a higher ecliptic longitude than the nominal upstream direction. Both sets of observations do not appear to fit in easily with the neutral atom environment from 1.0 to 1.57 AU as it is currently understood. In this paper, we examine some highly suggestive similarities in the IMAGE/LENA and Mars Express/ASPERA-3/NPI data to try to determine potential origins for the observed signal.     

Cosmic ray anisotropies in the outer heliosphere

The observation of the directional distribution of energetic and cosmic ray particles has been done with the Voyager spacecraft over a long period. Since 2002, when the first flux enhancements of charged particles associated with the approach of Voyager 1 to the solar wind termination shock were observed, these anisotropy measurements have become of special interest. They play an important role to understand the magnetic field and shock structure and the basics of the modulation of cosmic ray and anomalous particles at and beyond the termination shock. They also serve as motivation to study the spatial behavior of galactic and anomalous cosmic ray anisotropies with numerical modulation models in order to illustrate how the radial anisotropy, at different energies, change from upstream to downstream of the termination shock. Observations made by Voyager 1 indicate that the termination shock is a complicated region than previously thought, hence the effects of the latitude dependence of the termination shock’s compression ratio and injection efficiency on the radial anisotropies of galactic and anomalous protons will be illustrated. We find that the magnitude and direction of the radial anisotropy strongly depends on the position in the heliosphere and the energy of particles. The effect of the TS on the radial anisotropy is to abruptly increase its value in the heliosheath especially in the A > 0 cycle for galactic protons and in both polarity cycles for anomalous protons. Furthermore, the global effect of the latitude dependence of the shock’s compression ratio is to increase the radial anisotropy for galactic protons throughout the heliosphere, while when combined with the latitude dependence of the injection efficiency this increase depends on modulation factors for anomalous protons and can even alter the direction of the radial anisotropy.     

用于铷原子磁光阱的超高真空系统设计

上抛式冷原子干涉重力仪,以Rb原子作为操控介质,使其在二维磁光阱中被冷却,在三维磁光阱中装载并在干涉区内实现探测。根据重力仪对真空系统的特殊要求,对真空系统的结构和参数进行设计,完成真空泵、真空腔室结构及光学玻片等关键部件的选型及设计,设计出结构紧凑实用的超高真空系统。在后期磁光阱的装配中,提出了相应的关键工艺技术,实现了超高真空系统的组装搭建。通过差分管的设计,二维磁光阱的真空度控制在10-6Pa,三维磁光阱的极限真空度达到10-8Pa。     

带筋整体壁板预应力喷丸成形数值模拟及变形预测

带筋整体壁板特别是高筋整体壁板具有优异的结构效率、减重效益和密封效果,在航空航天等领域备受青睐。预应力喷丸成形是大中型、长寿命、高性能复杂带筋整体壁板的一种不可多得的有效成形手段。数值模拟是促进带筋整体壁板预应力喷丸成形技术研究、进步与应用的一种极具潜力的途径。针对带筋整体壁板预应力喷丸成形数值模拟,建立了基于响应面函数的多弹丸撞击有限元模型、基于应变中性层内移的反弯曲应力场法模拟模型、预应力喷丸成形RBF神经网络预测模型,实现了喷丸成形应力场法数值模拟、预应力喷丸成形较高精度数值模拟与变形预测,为带筋整体壁板预应力喷丸成形技术研究和实际应用提供了一种更为便捷、高效、经济的途径。     

波音757右IDG电源输出中线接地点故障分析

以实际维修工作中遇到的波音757右整体驱动发电机（IDG）电源输出中线接地点故障为例．对该故障的现象、特点和难点进行分析和判断,找到了故障的原因,并提出了排故方案和维修建议。     

冷镱原子光钟的研究进展

光学原子钟是一类基于原子或离子中光频跃迁的新型原子钟,近年来已成为研究热点并获得了重大进展,其性能已优于最好的铯基准微波钟,可满足更高精度定位、导航与授时应用的需求。阐述了冷镱原子光钟的基本工作原理及构成,分析了系统不确定度和稳定度等性能指标,给出了目前世界范围内的发展现状,介绍了华东师范大学的研究进展,其中一台光钟的系统不确定度评估为1.7×10~(-16),稳定度为2.9×10~(-15)/τ~(1/2),在5000s平均后稳定度优于4×10~(-17)。最后简要对冷镱原子光钟的应用前景进行了展望。