飞机垂尾抖振响应的飞行试验研究

介绍了国内外垂尾抖振试飞的最新进展情况,并就抖振试飞中可以采用的试飞方法,从理论上进行了分析。飞行试验采用收敛转弯的试飞方法,通过在左、右垂尾上加装的振动加速度传感器,得到了不同马赫数下垂尾的抖振响应情况。在对数据进行均方根分析、时频分析和自功率谱密度分析等方法的基础上建立起抖振响应和迎角、频率的关系后发现：垂尾抖振响应主要集中在垂尾低阶模态频率上;垂尾的抖振响应随迎角、马赫数的增加而增加,其中受迎角的影响大于受马赫数的影响;且飞机在超过初始抖振迎角以后,随迎角的继续增加,垂尾翼尖后缘处的抖振响应显著大于垂尾翼尖前缘位置。     

Numerical Simulation of 2D Supersonic Magnetohydrodynamic Channel and Study on Hall Effect

In this research effort,numerical simulation of two-dimensional magnetohydrodynamic(MHD) channel is performed and Hall effect is studied.The computational model consists of the Navier-Stokes(N-S) equations coupled with electrical-magnetic source terms,Maxwell equations and the generalized Ohm’s law.Boundary conditions for the electrical potential equation considering Hall effect are derived.To start with,the MHD channel with single-pair electrodes is studied and flow of the electric current is in accordance with physical principle.Then the MHD channel with five-pair electrodes is numerically simulated.The results show that the electrical current concentrates on the downstream of the anode and the upstream of the cathode due to Hall effect,and the flow field becomes asymmetrical.At the current value of the magnetic interaction parameter,the electrical-magnetic force affects the flow remarkably,decreasing the outlet Mach number and increasing the outlet pressure;what’s more,the flow structure in the channel becomes extremely complex.Performances of MHD channels with continual electrodes and segmented electrodes are compared.The results show that performance of the MHD channel with segmented electrodes is better than that with continual electrodes with the increase of Hall parameter.     

全同光纤布拉格光栅单纤复用能力的研究(英文)

本文从理论上研究和分析了一种基于OTDR和TDM技术的新型光纤布拉格光栅复用方法的复用能力。这种方法可以在同一根光纤上复用成百个全同的低反射率布拉格光栅,从而使布拉格光栅传感器在航空航天健康监测领域得到更广泛的应用。分析表明,当布拉格光栅的反射率足够低时,系统的复用能力可以大大提高。因此,基于这种复用方法,可以实现廉价的大规模分布传感系统。在评价这种系统的复用能力时,我们第一次提出应该考虑光栅间多次反射光的干涉效应的影响。     

李文正飞机设计专家

您多年从事飞机设计工作,请您谈一谈随着技术的发展我国飞机设计水平取得了哪些突破以及与国外航空工业大国相比,我国在飞机设计上存在怎样的差距。     

航空型号项目风险预测的BP神经网络模型及应用

本研究克服了单纯采用专家风险因子测度方法主观性较强的缺点,以及单纯采用人工神经网络评估模型模糊性的缺点,结合两种方法的优点,利用基于BP神经网络算法的Microsoft Visual C++程序,在专家风险因子测度基础上,通过大量风险评估成功案例数据的训练,成功建立了航空型号项目风险预测模型.该模型可以较为精确、客观地...     

基于最大信噪比的带噪测控信号分离算法

在实际卫星测控信号侦察中,混合副载波信号分离比较困难,且耗时较长.为此,提出一种基于小波变换和最大信噪比的副载波盲分离算法.先利用小波阈值算法对混合带噪信号进行消噪处理,然后采用基于最大信噪比的盲分离算法对消噪后的信号实施分离,最后得到测控副载波信号的估计.MATALAB仿真结果表明,该算法计算复杂度低,耗时短,能够较...     

运用监控手段提高继电器质量

继电器是导弹地面测试发控设备的关键器件之一.本文首先叙述提高产品可靠性的通用方法.然后,重点介绍采用监控手段进行继电器质量控制的具体过程和取得的效果.     

Laminar dust flames in a reduced-gravity environment

The propagation of laminar dust flames in suspensions of iron in gaseous oxidizers was studied in a low-gravity environment onboard a parabolic flight aircraft. The reduction of buoyancy-induced convective flows and particle settling permitted the measurement of fundamental combustion parameters, such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. Experimentally measured flame speeds and quenching distances were found in good agreement with theoretical predictions of a simplified analytical model that assumes particles burning in a diffusive mode. However, the comparison of flame speeds in oxygen–argon and oxygen–helium iron suspensions indicates the possibility that fine micron-sized particles burn in the kinetic mode. Furthermore, when the particle spacing is large compared to the scale of the reaction zone, a theoretical analysis suggests the existence of a new so-called discrete flame propagation regime. Discrete flames are strongly dependent on particle density fluctuations and demonstrate directed percolation behavior near flame propagation limits. The experimental observation of discrete flames in particle suspensions will require low levels of gravity over extended periods available only on orbital platforms.     

蓝天下的庄严--梅里朝圣记

为了那摇不断的虔诚，为了那搅不散的梦境，为了那捂不热的冰峰，为了那撇不下的绿茵，每年冬季，各地藏胞如涓流汇为江河般源源涌入云南德钦县，因为那里有他们魂牵梦萦的梅里雪山，“梅里”藏语即“神奇”，该山与果洛的阿尼玛卿，那曲的念青唐古拉及阿里的万山之王冈仁波钦合称藏区四大神山，在藏族人心目中，梅里是座永远让人敬畏的灵性之山。     

关于圆轴含有弯弯组合的合成弯矩图形状的讨论

本文结合弯弯扭组合变形的例题，利用相关数学知识，证明了圆轴含有弯弯组合的合成弯矩图如果出现曲线，则该曲线必是(上)凹的。