动态真空校准装置的设计

动态真空校准装置由供气系统、抽气系统、校准系统、烘烤系统、测控及分析系统五部分组成。利用快开超高真空插板阀与限流元件组合的方法,在20ms至1s的时间范围内实现标准压力105Pa至100Pa范围的瞬态阶跃变化。采用稀薄流下DSMC法与连续流下Navier-Stokes方程相结合的模型,确定快速膨胀过程中标准压力时间常数。动态真空校准装置预计达到的技术指标为校准范围10-1Pa～105Pa,合成标准不确定度小于15%。     

原子钟频率稳定度测试中的噪声处理

原子钟的测量噪声会被引入到频率稳定度评估过程,尤其是对中短期频率稳定度的影响更大。重叠Allan方差可以克服调频闪变噪声和调频随机游走噪声随时间变化出现的非平稳问题,但由于受到测量噪声的影响,评估结果仍会出现误差。为此,本文通过对原子钟的数学模型和噪声特性进行分析,提出了原子钟频率稳定度评估的加窗平滑噪声处理方法,通过对时差观测序列合理的加窗设计和平滑处理,抑制测量噪声对评估结果的影响。实验结果表明,利用铷钟观测序列的100点平滑可以有效地提高短期频率稳定度结果（100~1 000）s的可信度。     

红外动态目标模拟器光学系统的设计

设计了一种用于红外导引头性能测试的红外动态目标模拟器,利用数字微镜阵列(DMD)对黑体红外辐射进行反射调制,并由光学准直系统实现红外场景生成系统与红外导引头的光学耦合。用光学设计软件（ZEMAX）对准直光学系统进行了设计和优化,准直光学系统成像质量良好,接近衍射极限,点列图直径小于艾里斑直径,畸变小于0.1%。结果表明该系统环境适应性强,能很好地用于红外导引头动态图像的校准。     

小转矩电动式负载模拟器的设计

设计了适用于小转矩范围的电动式负载模拟器,并分析了其结构和动态性能. 介绍了电动式负载模拟器的结构和工作原理,建立了电动式负载模拟器的数学模型,并对系统稳定性进行了理论分析和仿真研究.在系统中引入多重反馈和前馈,再辅以控制方法进行电机控制,收到了良好的效果.仿真数据表明,所设计的电动式负载模拟器在小转矩范围内能够达到电液负载模拟器的控制性能指标.      

A comprehensive numerical model investigating the thermal-dynamic performance of scientific balloon

The increase of balloon applications makes it necessary for a comprehensive understanding of the thermal and dynamic performance of scientific balloons. This paper proposed a novel numerical model to investigate the thermal and dynamic characteristics of scientific balloon in both ascending and floating conditions. The novel model consists of a dynamic model and thermal model, the dynamic model was solved numerically by a computer program developed with Matlab/Simulink to calculate the velocity and trajectory, the thermal model was solved by the Fluent program to find out the balloon film temperature distribution and inner Helium gas velocity and temperature field. These models were verified by comparing the numerical results with experimental data. Then the thermal and dynamic behavior of a scientific balloon in a real environment were simulated and discussed in details.     

Stability of relative equilibria of the full spacecraft dynamics around an asteroid with orbit–attitude coupling

The full dynamics of spacecraft around an asteroid, in which the spacecraft is considered as a rigid body and the gravitational orbit–attitude coupling is taken into account, is of great value and interest in the precise theories of the motion. The spectral stability of the classical relative equilibria of the full spacecraft dynamics around an asteroid is studied with the method of geometric mechanics. The stability conditions are given explicitly based on the characteristic equation of the linear system matrix. It is found that the linearized system decouples into two entirely independent subsystems, which correspond to the motions within and outside the equatorial plane of the asteroid respectively. The system parameters are divided into three groups that describe the traditional stationary orbit stability, the significance of the orbit–attitude coupling and the mass distribution of the spacecraft respectively. The spectral stability of the relative equilibria is investigated numerically with respect to the three groups of system parameters. The relations between the full spacecraft dynamics and the traditional spacecraft dynamics, as well as the effect of the orbit–attitude coupling, are assessed. We find that when the orbit–attitude coupling is strong, the mass distribution of the spacecraft dominates the stability of the relative equilibria; whereas when the orbit–attitude coupling is weak, both the mass distribution and the traditional stationary orbit stability have significant effects on the stability. We also give a criterion to determine whether the orbit–attitude coupling needs to be considered.     

改善高频宽压控晶振频率温度稳定性方法

高频宽压控晶体振荡器广泛应用于各种接收机和应答机中,工作温度范围通常为-40℃～+85℃。对于该类晶振,极易出现频率温度稳定性相对于其内部石英谐振器明显恶化的现象。对此,从理论上分析了引起恶化的原因,并提出通过合理控制振荡电路的压控范围和石英谐振器的激励功率,可以改善高频宽压控晶振的温频特性。最后,研制并测试了4只102.3MHz压控晶振,结果优于指标要求,充分验证了方法的有效性。     

超声速粘性剪切流空间稳定性对称紧致差分数值分析

用一类高精度对称紧致差分格式数值离散一阶改型三维可压粘性扰动方程,对导出的非线性离散特征值问题采用二阶修正Ｎｅｗｔｏｎ－Ｒａｐｈｓｏｎ边值迭代局部解法,实现了超声速剪切流的线性空间稳定性分析。基于对流Ｍ数、Ｒｅ数、速度比、密度比等参数研究,讨论了压缩性效应、粘性效应、超声速扰动快／慢模态等,结果显示超声速粘性剪切流的弱不稳定性同多种影响因素密切相关。