一种X频段双圆极化器的设计

介绍了一种X频段双圆极化器的设计。设计实例采用方波导和圆波导两种形式,具有结构紧凑、功率容量大、极化轴比小、频带宽和适于星载使用等特点。仿真结果表明：设计出的双圆极化器,隔离度大于29dB,电压驻波比小于1.2,轴比小于0.5dB。该极化器的设计方法可应用于星载X频段双圆极化数传天线的设计。     

遥感图像去雾算法研究

针对现有的去雾算法对彩色图像处理后会出现色彩畸变的问题,提出了基于Retinex算法和色度比的去雾算法,该算法在用Retinex算法进行图像恢复的过程中引入了原图像的色彩信息,改善了处理后的图像的色彩。     

FM接收机中频滤波器的设计

介绍了一种基于双极技术的中心频率、带宽、增益可控的Gm-C型多相滤波器。分析了滤波器的基本原理,推导出其电路结构形式,并对其中关键的Gm单元进行了优化设计,实现了一个六级带通滤波器。该滤波器应用于低功耗FM低中频接收机中频滤波器的设计,镜像抑制比高达66 dB,总功耗仅为3.75 mW。     

中等后掠机翼平面参数设计与实验研究

采用Euler数值计算方法,对60多种中等后掠角及展弦比的切尖菱形机翼、双三角机翼纵向气动力特性进行了计算、分析和比较,从中筛选出16种切尖菱形机翼、14种双三角机翼进行了全机高速风洞实验研究,给出了机翼的展弦比、前缘后掠角、根梢比(后缘前掠角)及几何扭转变化对全机升力、阻力及俯仰力矩的影响曲线和数据分析,在此基础上提出了用于定量估算两类机翼纵向气动力特性的关系式及修正因子。本文研究结果为建立战斗机机翼气动力设计数据库及飞机气动布局设计提供了实用的数据和设计参考。     

A deformation model of flexible,HAMR objects for accurate propagation under perturbations and the self-shadowing effects

A new type of space debris in near geosynchronous orbit (GEO) was recently discovered and later identified as exhibiting unique characteristics associated with high area-to-mass ratio (HAMR) objects, such as high rotation rates and high reflection properties. Observations have shown that this debris type is very sensitive to environmental disturbances, particularly solar radiation pressure, due to the fact that its motion depends on the actual effective area, orientation of that effective area, reflection properties and the area-to-mass ratio of the object is not stable over time. Previous investigations have modelled this type of debris as rigid bodies (constant area-to-mass ratios) or discrete deformed body; however, these simplifications will lead to inaccurate long term orbital predictions. This paper proposes a simple yet reliable model of a thin, deformable membrane based on multibody dynamics. The membrane is modelled as a series of flat plates, connected through joints, representing the flexibility of the membrane itself. The mass of the membrane, albeit low, is taken into account through lump masses at the joints. The attitude and orbital motion of this flexible membrane model is then propagated near GEO to predict its orbital evolution under the perturbations of solar radiation pressure, Earth’s gravity field (J₂), third body gravitational fields (the Sun and Moon) and self-shadowing. These results are then compared to those obtained for two rigid body models (cannonball and flat rigid plate). In addition, Monte Carlo simulations of the flexible model by varying initial attitude and deformation angle (different shape) are investigated and compared with the two rigid models (cannonball and flat rigid plate) over a period of 100?days. The numerical results demonstrate that cannonball and rigid flat plate are not appropriate to capture the true dynamical evolution of these objects, at the cost of increased computational time.     

基于飞行参数的双发飞机发动机疲劳损伤差异分析

为给飞机发动机单机寿命监控提供依据,对两个用户的同型飞机发动机进行疲劳寿命分析。应用雨流计数法统计分析两个用户飞行参数,获得发动机使用载荷谱。应用线性累积损伤理论计算出关键件的疲劳损伤,将其与标准循环疲劳损伤比较,得到发动机飞行换算率。将同侧发动机的飞行换算率、同一飞机左右发的飞行换算率以及两个用户之间的发动机飞行换算率进行比较。计算表明:同一用户同侧发动机飞行换算率之间和两个用户之间的飞行换算率差异较大,同一飞机左右发飞行换算率之间存在一定差异,部分飞机左右发相差较大;两个用户总体的发动机飞行换算率和各个用户内部的发动机飞行换算率均服从对数正态分布;发动机在实际使用中的高低压转子飞行换算率均服从对数正态分布。     

孔壁通透率对平面附壁射流的影响

本文研究了不同壁面通透率对平面附壁射流动态特性的影响。实验结果表明孔壁减弱、甚至消除了流场中的低频摆动现象。随着孔壁通透率的增加,射流时均附壁点向下游逐渐移动,射流和壁面之间的回流区长度逐渐增大,而射流内侧剪切层内的涡旋与壁面之间的相互作用减小,壁面压强脉动强度变小,附壁射流的动态特性逐渐向自由射流转化。当孔壁通透率为40％左右时,射流与二维平面自由射流类似。距离射流出口不同位置上的壁面脉动压强之间的互谱表明,当孔壁通透率增大以后,射流内侧剪切层中的旋涡向下游传播距离变得更长,传播速度加快,这说明低孔壁通透率情况下的附壁射流中存在的低频摆动现象阻碍了剪切层高频旋涡向下游的发展。     

某型发动机喷口收放故障分析与排除

针对某型发动机在地面试车时发动机进入最大状态后放喷口的一次意外故障,结合喷口调节系统的原理和调节过程,分析可能的故障原因,并采取相应的排故措施进行验证,最终排除了故障。     

基于CFD/CSD的大展弦比机翼气动弹性研究

考虑气动力非定常效应和惯性载荷作用对机翼气动弹性行为的影响,采用基于Euler方程和有限元的CFD/CSD耦合方法分析了大展弦比机翼的气动弹性时域响应,实现静、动气动弹性一体化计算.计算结果显示在相同马赫数下,机翼静变形随着飞行动压增大而增大;但是随着飞行高度的增加,机翼在进入稳态之前振荡越剧烈,响应超调越大,升力损失...     

机匣内间断形深孔机械加工研究

通过优化方案自主设计了一套用于深孔加工的刀具方案,用于某发动机主机匣内部关键件凸轮轴的安装孔的加工,为系列化研制该类机型积累了加工经验.