横向振动方柱锁定区近尾迹结构

对雷诺数为150≤Re≤3600,振幅与柱宽比 A/h 为0.24和0.7条件下横向强迫振动单方柱的锁定现象、涡脱落过程和近尾迹特性,用流动显示和热线技术进行了研究,结果表明锁定区的范围随振幅比和雷诺数的增高而扩大,在大振幅比情况下,锁定区上、下临界折合速度值比小振幅比情况均有增高。流动显示结果清晰而系统地揭示了柱振动频率越过共振锁定点时,方柱上下两侧涡脱落规律发生的变化以及振幅的改变对近尾迹结构的影响。在低振幅比情况下,锁定区近尾迹结构基本为2S 型,在高振幅比情况下,由2S 型变为 P+S 型,这是非对称的尾迹结构,每一振动周期,从物体上脱落三个涡。在高频振动情况下,近尾迹由大尺度涡结构转化为小尺度涡结构。     

系统电磁兼容技术综述与展望

系统电磁兼容问题已成为飞行器等大型复杂系统全寿命周期中必须面对的客观问题。如果解决不当,不仅带来大量研制经费的浪费,同时还将导致系统从根本上丧失使用能力。系统电磁兼容问题不同于设备分系统电磁兼容问题,无论是在分析方法、设计方法、试验方法方面,均为系统工程问题。重点围绕航空飞行器研制中的电磁兼容问题,介绍一种全新的系统电磁兼容设计方法:飞机整机电磁兼容精确化协同优化设计方法。该方法有效实现了从飞机总体角度进行全机电磁兼容性设计和从飞机顶层高度提出全机电磁兼容量化指标要求。该技术不但可以实现全机电磁兼容问题在过程中得到管理和控制,并且实现了飞机全机电磁兼容设计的一次性成功,从电磁兼容角度保证了飞机的安全性。     

IP网络设备典型故障分析及其对策

针对IP网络设备在使用过程中产生的广播风暴、传输数据丢包、MP-group(Multilink-group,复用链路组)接口链路层运行PPP(Point to Point Protocol,点对点协议)异常等问题,结合华为S9300交换机设备、NE40E路由器设备的工作原理,对策略路由机理、STP(Spanning Tree Protocol生成树协议)、广播数据帧复制过程进行了研究和分析。并通过分析问题产生的机理,发现了目前网络数据配置存在的不足,提出了在核心层交换机上配置流过滤策略等应对措施和快速处理故障的方法,对系统进行了完善与改进,并优化了相关领域的应用,为维护人员在任务中迅速、合理地实施应急处置提供了参考。     

Design and performance test of spacecraft test and operation software

Main test processor (MTP) software is the key element of Electrical Ground Support Equipment (EGSE) for spacecraft test and operation used in the Chinese Academy of Space Technology (CAST) for years without innovation. With the increasing demand for a more efficient and agile MTP software, the new MTP software was developed. It adopts layered and plug-in based software architecture, whose core runtime server provides message queue management, share memory management and process management services and forms the framework for a configurable and open architecture system. To investigate the MTP software's performance, the test case of network response time, test sequence management capability and data-processing capability was introduced in detail. Test results show that the MTP software is common and has higher performance than the legacy one.     

基于ANSYS的推力球轴承仿真的不同网格划分的研究

在有限元软件ANSYS对推力球轴承的接触进行了仿真时,为了得到一种合适的网络划分方式,针对有限元模型采用了两种不同的网格划分,对比它们的计算结果,指出了采用ANSYS有限元软件在仿真球轴承接触时网格划分应注意的问题.     

OFDM系统采用自适应技术结合限幅降低PAPR的研究

针对OFDM系统峰均比PAPR（Peak—to-Average Power Ration）较大的问题，文章提出一种新的OFDM系统降低PAPR的方案，即自适应技术结合限幅Clipping。文章给出的计算机仿真结果表明，OFDM系统采用自适应技术结合Clipping进一步降低PAPR的同时又改善系统的BER性能，这就在降低PAPR和改善系统性能之间自动实现折衷。该方案实现起来简单且增加通信系统的智能化，故具有实用价值。     

Optimal combination of InSAR and GPS for measuring interseismic crustal deformation

High spatial resolution measurements of interseismic deformation along major faults are critical for understanding the earthquake cycle and for assessing earthquake hazard. We propose a new remove/filter/restore technique to optimally combine GPS and InSAR data to measure interseismic crustal deformation, considering the spacing of GPS stations in California and the characteristics of interseismic signal and noise using InSAR. To constrain the longer wavelengths (>40 km) we use GPS measurements, combined with a dislocation model, and for the shorter wavelength information we rely on InSAR measurements. Expanding the standard techniques, which use a planar ramp to remove long wavelength error, we use a Gaussian filter technique. Our method has the advantage of increasing the signal-to-noise ratio, controlling the variance of atmosphere error, and being isotropic. Our theoretical analysis indicates this technique can improve the signal-to-noise ratio by up to 20%. We test this method along three segments of the San Andreas Fault (Southern section near Salton Sea, Creeping section near Parkfield and Mojave/Big Bend section near Los Angeles), and find improvements of 26%, 11% and 8% in these areas, respectively. Our data shows a zone of uplift to the west of the Creeping section of the San Andreas Fault and an area of subsidence near the city of Lancaster. This work suggests that after only 5 years of data collection, ALOS interferograms will provide a major improvement in measuring details of interseismic deformation.     

Tool Life and Surface Integrity in High-speed Milling of Titanium Alloy TA15 with PCD/PCBN Tools

Titanium alloys are widely used in aeronautics that demand a good combination of high strength, good corrosion resistance and low mass. The mechanical properties lead to challenges in machining operations such as high process temperature as well as rapidly increasing tool wear. The conventional tool materials are not able to maintain their hardness and other mechanical properties at higher cutting temperatures encountered in high speed machining. In this work, the new material tools, which are polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) tools, are used in high-speed milling of Ti-6.5Al-2Zr-1Mo-1V (TA15) alloy. The performance and wear mechanism of the tools are investigated. Compared to PCBN tool, PCD tool has a much longer tool life, especially at higher cutting speeds. Analyses based on the SEM and EDX suggest that attrition, adhesion and diffusion are the main wear mechanisms of PCD and PCBN tools in high-speed milling of TA15. Oxidation wear is also observed at PCBN tool/workpiece interface. Roughness, defects, micro-hardness and microstructure of the machined surface are investigated. The recorded surface roughness values with PCD/PCBN tools are bellow 0.3 μm at initial and steady cutting stage. Micro-hardness analysis shows that the machined surface hardening depth with PCD and PCBN tools is small. There is no evidence of sub-surface defects with PCD and PCBN tools. It is concluded that for TA15 alloy, high-speed milling can be carried out with PCD/PCBN tools.     

无人作战飞机任务系统设计关键技术

介绍无人作战飞机的发展对现代空战的影响,元人作战飞机的作战使命、操控方式,重点描述无人作战飞机任务系统设计的关键技术,强调开展无人作战飞机任务系统研究的必要性。     

氨质子化团簇红外振动光谱研究

运用Gaussian03W计算程序,在B3LYP／6—31G（d）方法水平上得到了氨质子化团簇（NH3）nH^＋（n=1～8）的最稳定构型,并对其相应红外振动光谱进行了研究。通过对红外振动光谱中谱峰位置与振动模式之间的关系的分析,发现光谱中的最强峰均来自于NH4^＋核中N—H键的反对称伸缩振动（n=2除外）。