Response regimes of narrow-band stochastic excited linear oscillator coupled to nonlinear energy sink

This paper draws attention to the issue of the vibration absorption of nonlinear mechanical system coupled to nonlinear energy sink(NES) under the impact of the narrow band stochastic excitation. Firstly, based on the complex-averaging method and frequency detuning methodology,response regimes of oscillators have been researched under the linear impact of coupling a nonlinear attachment with less relativistic mass and an external sinusoidal forcing, of which results turn out that the quasi-periodicity response regime of system which occurs when the external excitation amplitude exceeds the critical values will be the precondition of the targeted energy transfer.Secondly, basing on the path integration method, vibration suppression of NES has been researched when it is affected by a main oscillator with a narrow band stochastic force in the form of trigonometric functions, of which results show that response regimes are affected by the amplitude of stochastic excitation and the disturbance strength. Finally, all these conclusions have been approved by the numerical verification and coincided with the theoretical analysis; meanwhile, after the comparing analysis with the optimal linear absorber, it turns out that the NES which is affected by the narrow band stochastic force could also suppress the vibration of system with a better effect.     

几何和流动参数对上翘后体阻力系数的影响

利用N-S方程对9个上翘后体模型进行了气动力计算,主要研究后体几何参数和流动参数对上翘后体阻力系数的影响.研究结果表明, 后体的压差阻力系数分别随上翘角、收缩比的增加及迎角的减小而明显增加;后体摩擦阻力系数分别随后体的长细比的增加和雷诺数的减小而增加;后体越扁平,其压差阻力系数越大;在跨音速时,波阻系数也与上翘角有关,上翘角增加会导致波阻系数进一步加大.     

Chang'E-1 Lunar Mission:An Overview and Primary Science Results

Chang'E-1 is the first lunar mission in China, which was successfully launched on Oct. 24th, 2007. It was guided to crash on the Moon on March 1, 2009, at 52.36oE, 1.50oS, in the north of Mare Fecunditatis. The total mission lasted 495 days, exceeding the designed life-span about four months. 1.37 Terabytes raw data was received from Chang'E-1. It was then processed into 4 Terabytes science data at different levels. A series of science results have been achieved by analyzing and applicating these data, especially "global image of the Moon of China's first lunar exploration mission'. Four scientific goals of Chang'E-1 have been achieved. It provides abundant materials for the research of lunar sciences and cosmochemistry. Meanwhile these results will serve for China's future lunar missions.      

基于可复用面向对象的航空发动机典型故障管理系统

基于C/S架构,采用UML建模和可复用面向对象技术,开发了航空发动机典型故障信息管理系统。该系统以结构化和网络化的形式保存典型故障模式的基本信息、详细分析信息和相应的故障信息,并提供了方便的查询和输出的功能,具有可用性、灵活性和易扩展性的特征。     

某型飞机进气道对发动机性能和台架点的影响

对某双转子涡喷发动机装与不装飞机进气道进行了台架对比实验，测量了发动机的状态参数和进口压力场。根据实验结果，分析了飞机进气道引起发动机的进气畸变和对发动机台架性能及台架点的影响，并讨论了造成变化的原因。实验结果对于正确使用该类型双转子涡喷发动机具有重要的现实意义。     

含能材料及相关物的低温焓松驰研究──(Ⅰ)由DSC获得粘弹系数

用差示扫描量热仪（ＤＳＣ）技术研究了某些含能材料及相关物的低温焓松弛过程及时温等效,通过玻璃化转变温度与升温速率的关系,导出了ＷＬＦ方程粘弹系数的计算式,并计算了１０个体系的粘弹系数,实验结果表明,用ＤＳＣ技术可以测定焓松驰和ＷＬＦ方程的系数。     

1Cr18Ni10Ti不锈钢疲劳性能研究

采用真空感应加电渣重熔冶炼技术生产的1Cr18Ni10Ti不锈钢，其冶金质量和全面性能较以前相比均有很大提高。通过对1Cr18Ni10Ti棒材样品疲劳断口的研究分析表明，材料的疲劳性能与冶金质量、内部组织结构、试件表面完整性有关。改变热处理制度能显著提高材料的疲劳寿命，在其他条件相同的情况下，样品的表面完整性对疲劳寿命有很大影响。在试验过程中发现，疲劳裂纹源多为机加工留在表面的刀痕、划痕。     

军机适航“安全性分析与评估”条款浅析及其工程实施途径探究

在当今的军机研制过程中,军方借鉴民机的适航管理方式力推适航性审查,以确保飞机的安全性水平.如何贯彻适航要求、如何将适航与安全性设计深度融合成为飞机研制单位亟待解决的问题.本文从飞机总体设计单位的角度,探究适航与安全的关系,对比适航工作与安全性工作的异同,并结合工程实际,对军用飞机研制过程中如何将适航与安全性管理、设计和评估工作有机结合、高效开展的方式方法提出了建议.有效避免了适航工作和安全性设计工作的不协调甚至相互矛盾情况的出现,可供军机承研单位参考.     

Application of hybrid regularization method for tomographic reconstruction of midlatitude ionospheric electron density

Reconstructing ionospheric electron density (IED) is an ill-posed inverse problem, with classical Tikhonov regularization tending to smooth IED structures. By contrast, total variation (TV) regularization effectively resists noise and preserves discontinuities of the IED. In this paper, we regularize the inverse problem by incorporating both Tikhonov and TV regularization. A specific formulation of the proposed method, called hybrid regularization, is introduced and investigated. The method is then tested using simulated data for the actual positions of the GPS satellites and ground receivers, and also applied to the analysis of real observation data under quiescent and disturbed ionospheric conditions. Experiments demonstrate the effectiveness, and illustrate the validity and reliability of the proposed method.     

Initial virtual flight test for a dynamically similar aircraft model with control augmentation system

To satisfy the validation requirements of flight control law for advanced aircraft,a wind tunnel based virtual flight testing has been implemented in a low speed wind tunnel.A 3-degree-offreedom gimbal,ventrally installed in the model,was used in conjunction with an actively controlled dynamically similar model of aircraft,which was equipped with the inertial measurement unit,attitude and heading reference system,embedded computer and servo-actuators.The model,which could be rotated around its center of gravity freely by the aerodynamic moments,together with the flow field,operator and real time control system made up the closed-loop testing circuit.The model is statically unstable in longitudinal direction,and it can fly stably in wind tunnel with the function of control augmentation of the flight control laws.The experimental results indicate that the model responds well to the operator's instructions.The response of the model in the tests shows reasonable agreement with the simulation results.The difference of response of angle of attack is less than 0.5°.The effect of stability augmentation and attitude control law was validated in the test,meanwhile the feasibility of virtual flight test technique treated as preliminary evaluation tool for advanced flight vehicle configuration research was also verified.