利用多普勒原理测量微机电系统中微结构的动态特性

介绍了将显微扫描激光多普勒测振仪与基础激振法相结合的微结构动态特性的非接触无损测量方法、扫描激光多普勒测振仪的工作原理、设计的基础激振器及其驱动信号.并给出典型微结构--微悬臂梁的测量结果.测量结果与理论计算及有限元仿真结果相符,验证了该方法的有效性.     

故障星分布对星座PDOP可用性影响的建模及评价

 导航星座定位精度衰减因子（PDOP）可用性是卫星导航系统顶层设计的重要指标。研究了不同故障星分布状况对全球导航星座PDOP可用性的影响。首先,从概率角度并采用组合方法建立了全球导航星座PDOP可用性指标的统计评价模型。进而对给定数量的故障星分布在单个或多个轨道面内的不同状况下,典型的Walker δ构型导航星座的PDOP可用性如何变化进行了仿真计算和比较分析。仿真结果表明,故障星分布状况和轨道平面数对星座PDOP可用性有较显著影响,适当地减少轨道平面数对于改善星座的PDOP可用性是有利的。提出的评价模型物理意义明确,避免了主观性和局限性,且可以保证较高的指标评价效率。     

RS码的时域编码频域译码技术

通过对于RS码的时域编码／频域译码的算法进行分析,找到了它们的不同之处及转换方法,得出了时域编码／频域译码的混合编译码方法,提高了运算速度和纠错能力。     

旋翼气动提前操纵角研究

为了保证某型直升机操纵系统设计的顺利进行,本文基于国内外相关资料对气动提前操纵角进行了深入的研究,得出该角度主要取决于桨叶挥舞基阶固有频率ωβ1.而ωβ1与挥舞铰外伸量e、桨叶根部弹性约束Kβ和挥舞调节系数Kp密切相关.通过分析e,Kβ和Kp对气动提前操纵角△ψ的影响,推导出计算该角度的具体公式.采用该公式对几个型号进行计算,经校核与验证后,表明本文提供的计算方法可行,能满足工程精度,可应用于工程研究,从而为布置助力器提供理论依据.     

基于超磁致伸缩材料的FBG电流传感器温度特性研究

针对基于超磁致伸缩材料的FBG电流传感器,分析了温度对传感头各个部分和整个传感头的影响,通过试验研究了FBG、Fe—Ga超磁致伸缩棒以及传感头三个部分的温度特性。结果表明,FBG的温度特性为线性,Fe—Ga超磁致伸缩棒以及传感头的温度特性整体为非线性,Fe—Ga超磁致伸缩棒的温度响应大于FBG的温度响应,传感头的温度特性主要取决于Fe—Ga超磁致伸缩棒的温度特性。在26℃到60℃范围内,根据传感头的温度特性,可采取分段补偿的方法消除温度影响,将温度特性分为线性区和非线性区两个范围,分别得到了传感头温度特性拟合方程。     

航天器地面模拟设备发展综述

本文回顾了高超音速地面模拟设备发展过程,这里既包括模拟理论方面的问题,也包括设备设计与建造方面的问题。目前,各国都在积极改进现有地面模拟设备或设计新型设备,以推进航天技术的发展。     

非牛顿特性对重载点接触热弹流润滑的影响

采用近似完全数值解法对HKD-1型航空润滑油进行了重载点接触热弹流分析,将两种不同流变模型下的计算结果进行比较,并进行了试验验证.结果表明:重载情况下,润滑油的非牛顿特性较显著,非牛顿特性对于弹流润滑中润滑油的温度、剪应力和拖动力影响较大,对压力分布影响较小.采用牛顿模型计算误差非常大,采用Evans-Johnson模型计算精度较高.滑滚比增加,油膜温升增加显著,压力变化不大,只是二次压力峰的峰值有所减小.      

非失速二维振荡叶栅非定常流动数值模拟研究

进一步完善了非定常雷诺平均N-S方程求解程序,借助快速网格生成方法,对周期性俯仰运动下NACA0012叶栅的非失速绕流问题进行了数值模拟研究,并分析了振荡叶栅的迟滞效应以及俯仰运动各个参数对迟滞效应的影响.数值模拟结果与实验结果对比表明,本文发展的数值模拟方法是可靠的;结果还表明,随着振幅,折合频率的增加迟滞效应增强,平均攻角对迟滞效应无影响;保持无量纲参数--振幅和折合频率的乘积--恒定时,迟滞效应相同.     

The Genesis Solar Wind Concentrator Target: Mass Fractionation Characterised by Neon Isotopes

The concentrator on Genesis provided samples of increased fluences of solar wind ions for precise determination of the oxygen isotopic composition. The concentration process caused mass fractionation as a function of the radial target position. This fractionation was measured using Ne released by UV laser ablation and compared with modelled Ne data, obtained from ion-trajectory simulations. Measured data show that the concentrator performed as expected and indicate a radially symmetric concentration process. Measured concentration factors are up to ∼30 at the target centre. The total range of isotopic fractionation along the target radius is 3.8%/amu, with monotonically decreasing ²⁰Ne/²²Ne towards the centre, which differs from model predictions. We discuss potential reasons and propose future attempts to overcome these disagreements.     

Fe/O Ratios in Interplanetary Shock Accelerated Particles

It is widely accepted that diffusive shock acceleration is an important process in the heliosphere, in particular in producing the energetic particles associated with interplanetary shocks driven by coronal mass ejections. In its simplest formulation shock acceleration is expected to accelerate ions with higher mass to charge ratios less efficiently than those with lower mass to charge. Thus it is anticipated that the Fe/O ratio in shock-accelerated ion populations will decrease with increasing energy above some energy. We examine the circumstances of five interplanetary shocks that have been reported to have associated populations in which Fe/O increases with increasing energy. In each event, the situation is complex, with particle contributions from other sources in addition to the shock. Furthermore, we show that the Fe/O ratio in shock-accelerated ions can decrease even when the shock is traveling through an Fe-rich ambient ion population. Thus, although shock acceleration of an Fe-rich suprathermal population has been proposed to explain large Fe-rich solar particle events, we find no support for this proposal in these observations.