Three-dimensional path planning for unmanned aerial vehicle based on interfered fluid dynamical system

This paper proposes a method for planning the three-dimensional path for low-flying unmanned aerial vehicle(UAV) in complex terrain based on interfered fluid dynamical system(IFDS) and the theory of obstacle avoidance by the flowing stream. With no requirement of solutions to fluid equations under complex boundary conditions, the proposed method is suitable for situations with complex terrain and different shapes of obstacles. Firstly, by transforming the mountains, radar and anti-aircraft fire in complex terrain into cylindrical, conical, spherical, parallelepiped obstacles and their combinations, the 3D low-flying path planning problem is turned into solving streamlines for obstacle avoidance by fluid flow. Secondly, on the basis of a unified mathematical expression of typical obstacle shapes including sphere, cylinder, cone and parallelepiped, the modulation matrix for interfered fluid dynamical system is constructed and 3D streamlines around a single obstacle are obtained. Solutions to streamlines with multiple obstacles are then derived using weighted average of the velocity field. Thirdly, extra control force method and virtual obstacle method are proposed to deal with the stagnation point and the case of obstacles’ overlapping respectively. Finally, taking path length and flight height as sub-goals, genetic algorithm(GA) is used to obtain optimal 3D path under the maneuverability constraints of the UAV. Simulation results show that the environmental modeling is simple and the path is smooth and suitable for UAV. Theoretical proof is also presented to show that the proposed method has no effect on the characteristics of fluid avoiding obstacles.     

马克思论资本主义股份制--《资本论》思想研究之二

资本主义股份制是资本主义生产方式范围内的一种消极扬弃,马克思在<资本论>中对此做了深刻的阐述.马克思强调,资本主义股份制的产生带来私人资本向社会资本转化及私人企业向社会企业转化的社会进步;具有扩大生产规模聚集能力的资本主义股份制是资本主义生产方式向联合的生产方式转化的过渡形式.     

Hall MHD reconnection with an initial guide field By0

An uniform out-of-plane magnetic field component B_y0 is added to the equilibrium Harris sheet with plasma β = 0.5 and L_c = 0.5d_i (where L_c is the half-width of the equilibrium current layer and d_i is the ion inertial length). Driven by the continuous boundary inflows, the magnetic reconnections with the guide field B_y0/B₀ ranging from 0 to 4.0 are investigated using a 2.5D Hall magnetohydro-dynamic (MHD) code developed from a multi-step implicit scheme. The features of the reconnection field are substantially altered in the presence of the guide field. The openness of the magnetic separatrix angle is slightly reduced and the anti-symmetric quadrupolar structure of B_y field and the symmetric distribution of plasma pressure P are replaced by an asymmetric B_y four-wing structure and an asymmetric P plot as a non-zero B_y0 is added. The decoupling of electrons and ions also occurs near the X line in the case with a finite B_y0, but the effect of initial B_y0 on the electron flow is greater than that on the ion flow. The reconnection rates at the X-line drops from 0.151 to 0.06, namely, ∂A/∂t is reduced by a factor of 2.5 as B_y0/B₀ increases from 0 to 4.0. The reduction of reconnection rate might be related to the reducing openness of reconnection layer with the increasing B_y0.     

荫罩孔径透过率自动测量系统的设计与实现

介绍一种双处理机三轴方式的全自动荫罩孔径透过率自动测量装置 ,给出了系统的设计方案与实现方法。     

国外航天元器件发展现状与思考

以航天元器件供应与采购问题为中心,分析国外航天元器件发展现状和国外宇航机构在航天元器件发展方面的主要做法与成功经验,并在借鉴吸收的基础上,结合我国的实际,对我国航天元器件的发展提出建议.     

基于神经网络的翼盒结构响应重构方法应用

翼盒结构复杂，航行中承载条件恶劣，利用有限测点信息重构其它位置响应对于实时健康监测具有很强的现实意义。通过误差反向传播神经网络训练得到响应之间的非线性关系，建立基于神经网络的响应重构方法，开展有限元分析对其进行数值仿真验证，并将该方法应用于实测随机激励环境下翼盒典型承力结构的响应重构及损伤定位与判断分析。结果表明：采用该方法重构出的预测响应功率谱密度的均方根相对误差不超过1.90 dB，主要频点误差小于10%；判断出翼盒关键测点e 的损伤或故障发生在所截取片段数据3 s 后，其故障特征频率为240 Hz 左右，该方法应用于响应重构预示及健康监测分析具有可行性。     

Novel DSC-IPM for Compact Converters at Elevated Temperatures

A novel two-side cooling for integrated power modules (IPMs) for improved compactness and capability for elevated temperature operations is presented. This approach applies and improves off-the-shelf products of IPM without significantly changing original packaging and fabrication process. It can reduce a device's p-n junction-temperature rise by 20% at an equivalent load, thus increasing operating ambient temperatures, which is desirable for aircraft applications. The size and volume associated with a conventional cooling mechanism can be reduced, achieving improved compactness and power density.     

30CrMnSiA钢管外圆磁力研磨工艺的研究

采用化学粘结Ｆｅ＋ＳｉＣ磁性料对３０ＣｒＭｎＳｉＡ钢管外圆进行磁力研磨试验，研究了磨料成分、粒度以及研磨时间与研磨后表面粗糙度的关系，试验所得到的研磨表面粗糙度达到了Ｒａ０．０５μｍ。     

ISO10012标准宣贯中的几个问题

简述了现行企业计量管理工作在宣贯ＩＳＯ１００１２标准中，遇到的主要问题及处理方法 。     

Incremental maneuver estimation model for target tracking

An incremental model for maneuver detection and estimation for use in target tracking with the Kalman filter is described. The approach is similar to the multiple Kalman filter bank, but with a memory for the maneuver status for the track under consideration. The advantage of this approach is that the target acceleration can be more accurately estimated. The maneuver-detection model has shown good maneuver-following capability. Moreover, it needs only a finite number of Kalman filters to handle all possible maneuver values and it responds quickly as maneuver occurs. When there is an abrupt maneuver change the model can still track the targets in short time