Tracking characteristics of tracer particles for PIV measurements in supersonic flows

The tracking characteristics of tracer particles for particle image velocimetry (PIV) mea-surements in supersonic flows were investigated. The experimental tests were conducted at Mach number 4 in Multi-Mach Wind Tunnel (MMWT) of Shanghai Jiao Tong University. The motion of tracer particles carried by the supersonic flow across shockwaves was theoretically modelled, and then their aerodynamic characteristics with compressibility and rarefaction effects were evalu-ated. According to the proposed selection criterion of tracer particles, the PIV measured results clearly identified that the shockwave amplitude is in good agreement with theory and Schlieren visu-alizations. For the tracer particles in nanoscales, their effective aerodynamic sizes in the diagnostic zone can be faithfully estimated to characterize the tracking capability and dispersity performance based on their relaxation motion across oblique shockwaves. On the other hand, the seeding system enabled the tracer particles well-controlled and repeatable dispersity against the storage and humidity.     

高空无人机载GPS/INS系统干扰效能及对策研究

GPS/INS系统在高空无人机完成作战任务过程中发挥着重要作用.在建立GPS干扰方程以及对INS导航误差分析的基础上,针对GPS天线特点,对GPS干扰机的兵力需求进行分析计算.通过仿真分析,给出了对抗高空无人机机载GPS/INS的对抗策略.     

基于CCSDS Proximity-1协议的动态变帧长策略研究

为提高邻近航天器之间的通信效率,研究了Proximity-1协议与传统链路层协议的最大区别——"通信互动"功能。对航天器之间通信过程中的动态变帧长策略进行了分析,给出了不同信道环境下的最佳帧长取值,并通过实时选择最佳帧长实现了动态变帧长策略方案。利用仿真手段验证了动态变帧长策略对通信效率的改善性能。仿真结果表明,吞吐量效率最多可提高80%,证明文章提出的动态变帧长策略能在很大程度上提高通信效率。     

河北预算定额软件的开发应用

本文介绍了采用计算机对施工图预算进行电算化的软件系统。本文从该系统的特点、主要组成和设计思想等方面进行了论述，作为适用的商业应用软件，为社会和教学提供了有力的服务手段。     

用弯剪法计算两向正交正放平板网架各杆内力

本文在节点法和截面法的基础上，将两者融为一体，为计算两向正交正放平板网架各杆内力，提供了一种新颖方法，称其为弯剪法，文中引用了实例，结果与其它方法完全一致，并符合实际，这就证实了本法的有效性和可靠性，有一定的参考价值。     

基于CIINS的航空企业数据库及其编码设计研究

本文是基于航空企业CIINS工程目标进行设计研究的。主要通过对企业需求及业务流程的分析讨论，给出数据库系统的设计方案，阐述了数据库系统的逻辑结构、物理结构、配置方案等，并对数据信息编码设计提出相应规则。     

近地空间航天员训练视景真实感渲染技术研究

载人航天任务中,地面模拟训练是培养提升航天员操作技能的重要手段。视景系统是航天飞行训练模拟的重要组成部分,高逼真度的仿真场景对提升航天员训练效果有重要的意义。针对空间视景仿真场景调度和渲染的特殊性,提出并设计实现视景仿真软件的总体架构。对影响空间场景真实感的地球纹理数据库的生成和调度技术、大气散射仿真技术、场景光照实时渲染等关键技术进行研究,融合各种方法,在视景仿真系统中基于GPU实现。试验验证表明,实现算法准确,模型设计合理,已经应用于航天员的训练中。     

末段突防高度对反舰导弹飞行安全的影响

末段突防击水概率是反舰导弹设计和使用人员必须解决的一个问题。文章综合考虑了击水概率影响因素,从掠海飞行导弹背景建模、反舰导弹高度控制系统和弹体纵向运动方程等方面人手,对给定海情下反舰导弹高度输出进行仿真研究,并利用统计试验的方法对击水概率进行计算。仿真结果证实了不同海情下飞行高度对击水概率的影响。     

Wire electrochemical machining with axial electrolyte flushing for titanium alloy

Titanium and its alloys have found very wide application in aerospace due to their excellent characteristics although their processing is still a challenge. Electrochemical machining is an important issue in the fabrication of titanium and titanium alloys. Wire electrochemical machining (WECM) is mainly used for workpiece cutting under the condition of different thickness plates. It has a great advantage over wire electro-discharge machining, which is the absence of heat-affected zone around the cutting area. Moreover, the wire electrode in WECM could be used repetitively because it is not worn out. Thus, much attention has been paid to WECM. The effective way of removing electrolysis products is of importance to WECM. In this paper, the axial electrolyte flushing is presented to WECM for removing electrolysis products and renewing electrolyte. The Taguchi experiment is conducted to optimize the machining parameters, such as wire feedrate, machining voltage, electrolyte concentration, etc. Experimental results show that WECM with axial electrolyte flushing is a promising issue in the fabrication of titanium alloy (TC1). The feasibility of multi-wire electrochemical machining is also demonstrated to improve the machining productivity of WECM.     

碳纤维-微晶复合材料反射镜光学加工实验

采用环抛方法对有预埋件和无预埋件的两块碳纤维-微晶复合材料反射镜进行光学加工,之后进行了稳定性实验研究,采用Zygo干涉仪实测了碳纤维-微晶复合材料反射镜面形.稳定实验后,有预埋件反射镜面形P-V值为3.013λ,RMS值为0.669λ;无预埋件反射镜面形P-V值为2.313λ,RMS值为0.276λ(λ=632.8 nm).实验结果证明,有预埋件的碳纤维-微晶复合材料反射镜结构优于无预埋件结构,为碳纤维-微晶复合材料反射镜的工程化提供参考.