基于LS-DYNA的气垫式起落系统落震性能仿真

缓冲性能是气垫式起落系统的一个重要功能,基于以某型地效飞行器为背景的气垫式起落系统方案设计,建立了气垫式起落系统落震仿真模型.利用有限元理论和LS-DYNA仿真平台对气垫式起落系统缓冲性能进行仿真分析.结果表明气垫式起落系统在落震过程中未出现反弹,气囊最大压缩位移为1.015 m,小于允许最大压缩位移1.502 m;整个落震过程出现的最大过载为2.87 g,小于允许最大过载3 g.验证了气垫式起落系统在落震过程中缓冲行程及缓冲性能满足要求.     

How cosmic rays were discovered and why they received this misnomer

As many great discoveries, the phenomenon of cosmic rays was discovered mainly accidentally, during investigations that sought to answer another question: what are sources of air ionization? This problem became interesting for science about 230 years ago in the end of the 18th century, when physics met with a problem of leakage of electrical charge from very good isolated bodies. We describe the history how step by step cosmic rays was discovered and why this phenomenon received misnomer, how in cosmic rays was discovered the first antiparticle – positron. These discoveries were recognized among greatest in the 20th Century and were awarded by Nobel Prize.     

基于模糊控制的空气悬架模型建立

空气悬架以其优良的减振性能，在汽车振动控制中得到越来越广泛的应用。本文以空气悬架为研究对象，构建了带附加空气室空气悬架系统的1／4车辆振动模型；分析了空气悬架刚度调节原理和控制特性，本文采用了不依赖于被控对象精确数学模型的模糊控制策略进行空气悬架控制器的设计。     

防空信息系统面临的赛博战威胁与对策研究

结合21世纪防空作战概念,解析了防空信息系统对抗中赛博战的含义,分析了赛博战对防空信息系统的影响,并提出一些反制对策。这对于防空信息系统对抗赛博战、防空信息系统安全的理解,具有一定的参考意义。     

数控慢走丝线切割机床锥度切割的方法

模具行业的迅速发展推动了电火花线切割技术的进步，数控慢走丝线切割机床以其自动化程度高、精度好、加工稳定、可靠的优点开辟了广阔的市场前景。本文主要介绍了FUNAC线切割机床锥度切割的方法，重点介绍了当锥度有误差时，应如何进行补偿。     

经济视角下的航空货运网络结构分析

随着经济的快速发展和信息流通的加快，航空货运在经济发展中的作用日益凸显。航空货运的发展依赖于货运网络的完善，体现出构建中国航空货运网络的重要性。以中国城市经济发展形态为切入点，以中国各城市间航段货邮运输量为样本数据，绘制出2004--2009年中国航空货运网络结构图，建立航空货运网络核心一边缘结构模型．并对其平均路径长度、网络集聚系数、度分布、边权分布和点权分布进行分析。结果表明：中国航空货运网络具有聚集效应，对经济发展具有一定的推动作用，并在此基础上呈现中国航空货运网络的进一步完善发展方向．     

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.     

微小型飞行器的神经网络动态逆控制方法

微小型飞行器(MAV)精确的数学模型很难得到,限制了单纯动态逆控制方法的使用,比例-积分-微分(PID)等传统的控制方法已不能满足要求。针对这一问题,研究了应用动态逆控制方法的新途径──神经网络动态逆。选取串接积分器的多层前向神经网络训练飞行控制系统的动态逆模型,并自适应补偿逆误差。用MATLAB的NNCTRL20工具箱并结合NNSYSID20工具箱建立了仿真系统。升降舵和方向舵联合控制转弯。用PID控制器、近似神经网络动态逆模块、在线神经网络补偿器构建了飞行控制系统。仿真结果表明,神经网络动态逆有较强的鲁棒性、稳定性和指令跟随能力,比PID更适合于微小型飞行器的姿态控制。     

飞行间隔安全评估研究

 首先概述了飞行间隔安全评估研究中常用的概念,然后从REICH模型、交叉航路模型、概率论模型、随机分析模型、EVENT模型和RASRAM模型6种常用碰撞风险模型的角度,分析了各个模型的优缺点和各自的适用范围,分析结果表明飞行间隔安全评估中的关键问题为：模型的限制、管制意图和安全评价,并在此基础上分析了飞行间隔安全评估未来的研究方向。