光学干涉技术定量显示双马赫反射的密度场

本文介绍了对激波管流动采用两次曝光全息干涉、M-Z 干涉和差分干涉三种技术所获得的双马赫反射二维密度场的定量测量结果,并与数值计算结果作了比较,两者十分吻合。     

球头钝锥高超声速动稳定性的实验研究

本文叙述在脉冲型高超声速风洞中，用模型自由飞方法测定８°球头钝锥的高超声速静、动稳定特性。采用同步高速摄影方法记录了２０ｍｓ准定常试验时间中模型的角运动并用参数微分法进行气动参数辨识。实验结果表明对质心位置Ｘｃｇ≤０．６０的模型在Ｍ∞＝７．８和Ｍ∞＝９．９两种条件下皆是静、动稳定的，稳定性随质心的后移而下降，在实验范围内马赫数对稳定性没有明显影响，同时模型的底部是否封闭也没有明显影响。     

多外载联合作用下圆板的非线性弯曲

分析了多外载联合作用下圆板的轴对称非线性弯曲问题。分析从极坐标系下圆板弯曲的Ｖｏｎ－Ｋａｒｍａｎ方程出发，运用微分求积方法（ＤＱ法）导出了控制方程的ＤＱ形式；边缘径向位移和边缘力矩由两个统一的方程来表示，通过改变方程中的约束刚度和边缘载荷系数，实现了对任意边界条件的模拟；对最终得到的非线性方程组，用Ｎｅｗｔｏｎ－Ｒａｐｈｓｏｎ方法进行了迭代求解。文中给出了圆板受横向均布力、板心横向集中力、边缘均布径向力、边缘均布弯矩等四种载荷两两联合作用下的计算结果曲线，讨论了不同联合载荷对回板非线性弯曲的影响。与文献结果比较表明，该方法能满足各种边界条件，具有较高的求解精度。     

基于基因算法与博弈论的气动高升力优化(英文)

讨论了基于基因算法与博弈论的组合优化算法在高升力气动优化问题中的应用。引入基因算法与博弈论相结合的分布式组合算法 ,可以将复杂的优化问题分解为几个简单的局部优化问题。文中论述了组合优化算法的构造方法 ,并应用于高升力多段翼型气动优化。与传统基因算法的数值计算结果进行了比较 ,表明本文构造的方法具有高效收敛性及强的鲁棒性 ,可广泛应用于先进气动设计问题。     

Numerical integration of stochastic differential equations: A parallel cosmic ray modulation implementation on Africa’s fastest computer

Three-dimensional studies of the transport and modulation of cosmic ray particles in turbulent astrospheres require large-scale simulations using specialized scientific codes. Essentially, a multi-dimensional Fokker-Planck type equation (a parabolic diffusion equation) must be integrated numerically. One such approach is to convert the relevant transport equation into a set of stochastic differential equations (SDEs), with the latter much easier to handle numerically. Due to the growing demand for high performance computing resources, research into the application of effective and suitable numerical algorithms to solve such equations is needed. We present a case study of the performance of a custom-written FORTRAN SDE numerical solver on the CHPC (Centre for High Performance Computing) Lengau cluster in South Africa for a realistic test problem with different set-ups. It is shown that SDE codes can scale very well on large parallel computing platforms. Finally, we consider an extremely computationally expensive application of the SDE approach to cosmic ray modulation, studying the behaviour of galactic cosmic ray proton latitude gradients and relative amplitudes in a physics-first manner. This is done using a modulation code that employs diffusion coefficients derived from first principles, which in turn are functions of turbulence quantities in reasonable agreement with spacecraft observations and modelled using a two-component turbulence transport model (TTM). We show that this approach leads to reduced latitude gradients qualitatively in line with spacecraft observations of the same, without making ad hoc assumptions as to anisotropic perpendicular diffusion coefficients as are often made in many cosmic ray modulation studies.     

基于近似动态规划的目标追踪控制算法

在目标跟踪问题中,针对飞行器控制算法难以适应目标大机动飞行甚至与我方博弈等难度较大任务的问题,提出了基于近似动态规划的目标追踪控制算法。该算法通过使用博弈策略对我方无人机进行训练形成经验,将双方位置等状态作为已知量,滚转方向作为控制量,利用两物体的相对位置得出其特征,并形成近似值函数;最终利用rollout算法进行最优跟踪决策求解,实现对跟踪目标甚至是博弈目标的灵活有效精确跟踪。仿真结果验证了近似动态规划用于控制算法的有效性。      

一种新型高效能双差动音圈电机设计与实现

针对高支撑刚度、大推力输出的需求,提出了一种双音圈差动结构、轴向支撑的新型音圈作动方法,实现了在紧凑结构空间内磁能的最大化利用,提高了音圈电机的效能。首先进行了结构设计,利用两块环状永磁建立了内外圈两个工作磁隙,每个工作磁隙采用一组差动音圈。然后进行了磁场设计,进行了有限元模型分析,以磁场均匀性和磁场强度为目标进行了结构参数的优化。最后,加工制造出样机,进行了实际的输出力特性测试、频率特性测试,测试结果表明：该差动音圈电机具有较高的推力,在运动范围内,推力平稳,效能满足设计预期     

基于Nash均衡与进化计算的协调航迹规划

在对策论框架下研究多无人飞行器的协调航迹规划问题,提出了一种基于Nash平衡和进化计算的航迹规划算法.协调航迹规划是一个多目标合作优化问题,也是一个非合作对策问题.飞行器编队的分布结构提供了一种隐性偏好信息,有助于找到飞行器编队的最优协调航迹和最优飞行代价分配.本文算法使用特定的航迹个体表示方法和进化算子,按照层次方法处理各种航迹约束.不同飞行器间的协同和竞争关系定义在航迹评价函数里.仿真结果验证了基于博弈论航迹规划算法的可行性和优越性.     

Solar Wind Sources and Their Variations Over the Solar Cycle

In this paper I will briefly summarize the present status of our knowledge on the four different sorts of solar wind, their sources and their short- and long-term variations. First: the fast solar wind in high-speed streams that emerges from coronal hole regions. Second: the slow solar wind emerging from the non-active Sun near the global heliospheric current sheet above helmet streamers and underlying active regions. Third: the slow solar wind filling most of the heliosphere during high solar activity, emerging above active regions in a highly turbulent state, and fourth: the plasma expelled from the Sun during coronal mass ejections. The coronal sources of these different flows vary dramatically with the solar activity cycle.     

基于PIDNN控制的飞行模拟器人感系统

针对飞行模拟器人感系统的高度非线性和易受干扰性,提出一种基于PIDNN(Proportional Integral Differential Neural Network)的控制方案.首先对飞行模拟器人感系统的模型进行分析研究,对它所受到的外界干扰作理论分析,整理出系统的数学模型,再利用PIDNN控制器优良的在线训练、学习和调整功能对该模型进行仿真控制.与传统PID(Proportional Integral Differential)控制器相比,PIDNN结构简单、自适应性强、收敛速度快、不会陷入局部极小.仿真结果表明:PIDNN控制系统响应速度快、稳态精度高、 具有良好的动静态特性和鲁棒性,满足实时控制的要求.