某涡喷发动机前轴承弹性支承试验模态分析

用脉冲激励法对某发动机前轴承弹性支承进行了试验模态分析,并介绍了试验模态 方法和设备,所得模态分析结果表明,相干函数值均大于０．９,弹性支承的固有频率,振型符合发动机结构设计要求。     

Dynamic response analysis under atmospheric disturbances for helicopters based on elastic blades

A flight dynamics model based on elastic blades for helicopters is developed. Modal shape analysis is used to describe the rotating elastic blades for the purpose of reducing the elastic degrees of freedom for blades. The analytical result is employed to predict the rotor forces and moments. The equilibrium equation of the flight dynamics model is then constructed for the elastic motion for blades and the rigid motion for other parts. The nonlinear equation is further simplified, and the gradient descent algorithm is adopted to implement the trim simulation. The trim analysis shows that the effect of blade elasticity on the accuracy of rotor forces and moments is apparent at high speed, and the proposed method presents good accuracy for trim performance. The time-domain response is realized by a combination of the Newmark method and the adaptive Runge-Kutta method. The helicopter control responses of collective pitch show that the response accuracy of the model at a yaw-and-pitch attitude is improved. Finally, the influence of blade elasticity on the helicopter dynamic response in low-altitude wind shear is investigated. An increase in blade elastic-ity reduces the oscillation amplitude of the yaw angle and the vertical speed by more than 70%. Compared with a rigid blade, an elastic blade reduces the vibration frequency of the angular veloc-ity and results in a fast return of the helicopter to its stable flight.     

A new skeleton based flying bird detection method for low-altitude air traffic management

In low-altitude air traffic management, non-cooperation targets are the greatest threat to security of low-flying aircraft. Among various aviation fatalities, flying bird is the main factor with the highest risk and directs economic losses amounted to nearly 10 billion US dollars each year. Therefore, Flying Bird Detection (FBD) has attracted considerable attention in low-altitude air traffic management. In this paper, we propose a skeleton based FBD method via describing bird motion information with a set of key poses. To overcome the variability of birds, the skeleton feature is selected as a relatively fixed and common characteristic for the pose appearance of flying bird. Based on the geometric topology among some key parts of bird body, a set of key poses can be described by some extracted skeleton features, which are used to represent the bird motion information. Aimed at robustly handling with the pose variations, multiple pose-specific classifiers are individually trained to learn the representative poses of the flying bird. At the detection stage, the flying bird skeleton features are combined with extracted key-pose sets to perform the flying bird classification task from each image. Afterwards, the key-frame pose-change set and the consistency of the classification results from sequent images are employed to validate the final detection results. Experiments on flying bird datasets demonstrate the effectiveness and efficiency of the proposed method.     

可实时重构的国际C站卫星模拟器

我国自行研制的国际标准C频段统一测控系统,配置了功能齐全的卫星模拟器,但其一星一模拟器的方式已不能适应当前多星管理和未来星座管理的需要。本文旨在探讨利用现有的微波宽带器件技术和软件无线电技术,用一套硬件系统,根据需要实时重构成所需卫星的模拟器,达到多星共用一套模拟器,实现小型化、实时性的目的。     

让老师快乐地走进课堂

中职学生自我约束、自我学习能力差,中职教师面临教好书与管好学生的双重压力。通过体制与机制的完善,鼓励教师欣然地面对挑战,教师才会发现教书的乐趣,才会激发求知的欲望,才会参与教学的改革,才会产生对学校强烈的归属感、自豪感和使命感。提升了教师的积极性,老师才会快乐地走进课堂。     

防空导弹弹性振动抑制

基于防空导弹的数学模型,根据弹体弹性振动的特性,对抑制其振动的方法和稳定回路设计进行了研究。通过确定频带宽度稳定刚性弹体的姿态运动,采用陷波补偿相位稳定和增益稳定抑制弹性振动以稳定弹性弹体。给出了稳定回路的设计,并比较了不同方法的特点。     

非平稳大气紊流对弹性飞行器的影响

提出了采用复模态分析方法研究非平稳大气紊流对弹性飞行器的影响，首先给出了非平稳随机大气紊流模型，然后提出了弹性飞行器对非平稳随机大气紊流激励的复模态分析方法，该方法把复杂的随机动力响应计算问题转化为复代数运算问题，为研究飞行器对随机大气紊流的响应开辟了新的途径，最后以某型－空导弹为例，计算其对非平稳随机大气紊流的响应，从而说明非平稳随机大气紊流对弹性飞行器的影响。     

柔性关节空间机械臂的自适应滑模控制

探究一类时滞柔性关节空间机械臂鲁棒自适应滑模控制问题。针对该种空间机械臂具有强非线性特点，同时考虑系统的未建模动态与扰动以及时滞影响，提出一种新的鲁棒自适应滑模控制器。基于Lyapunov-Krasovskii泛函和线性矩阵不等式等凸优化方法，给出滑动模态的鲁棒渐近稳定条件，并证明系统状态在有限时间内到达滑模面。最后，三组仿真校验表明了所设计的控制器可行。     

现金流量在企业经营管理中的作用

现金流量是企业在一定时期内现金及其等价物的流入量和流出量的总称。它揭示了企业各种经济资源产生的收入和发生的费用情况；揭示了企业当前偿债能力和支付能力；揭示了企业投资和理财活动的经营成果。因此，通过探讨现金流量在企业经营管理中的客观存在及其重要作用，从而达到防范风降，提升企业价值，促进企业健康发展的目的。     

法宇航卫星制造中心管理方式剖析

在介绍了法车宇航部空间防卫部及其卫星制造中心的机械设置，各部门的职责范围的基础上，重点剖析了卫星研制系统的管理特点和经验。分析认为，法国卫星研制系统的管理方法和经验值得我们学习、借鉴。