逆向涡流发生器减小涡轮叶尖泄漏流的数值研究

逆向涡流发生器可以有效减小涡轮叶尖泄漏流,提高叶片周向载荷.对影响逆向涡流器减小泄漏流的几个关键因素进行了数值研究,结果表明:入流和出流孔径比增大,涡流器流量增加,对叶尖泄漏流的减小效果越好,孔径比2∶1时比孔径比1∶1时涡流器流量增加了24%,叶尖泄漏流量降低了0.8%,叶片周向载荷提高了1%;与叶片前缘布置涡流器相比,在叶片中后部布置时涡流器流量增大,叶片周向载荷提高;涡流器布置越密,涡流器总流量增加,布置33个涡流器比布置9个涡流器叶尖泄漏流量降低了1.6%,叶片周向载荷提高了2.7%;出流角越小,叶尖泄漏流量越小,叶片周向载荷越大,出流角30°时泄漏流量比60°时降低了1.2%,叶片周向载荷提高了约2%.     

Monocular Vision-based Two-stage Iterative Algorithm for Relative Position and Attitude Estimation of Docking Spacecraft

Visual sensors are used to measure the relative state of the chaser spacecraft to the target spacecraft during close range rendezvous phases. This article proposes a two-stage iterative algorithm based on an inverse projection ray approach to address the relative position and attitude estimation by using feature points and monocular vision. It consists of two stages: absolute orientation and depth recovery. In the first stage, Umeyama's algorithm is used to fit the three-dimensional (3D) model set and estimate the 3D point set while in the second stage, the depths of the observed feature points are estimated. This procedure is repeated until the result converges. Moreover, the effectiveness and convergence of the proposed algorithm are verified through theoretical analysis and mathematical simulation.     

Space astronomy in China: 2008—2010

In 2008 to 2010, the main activities in Chinese space astronomy were focused on: fulfilling the long-term plan of Chinese space astronomy; initiating the long-term plan of Chinese space astronomy; undertaking some astronomical missions set by CNSA in ``Development Program of Space Science for 2006--2010'. This paper summarizes in brief all these activities.      

Auroral Electrojet Event Associated With Magnetospheric Substorms

The auroral electrojet index is an important index in monitoring and predicting substorms. A substorms usually includes auroral breakup, auroral electrojet event marked by AE increase, energetic particle injection at geosynchronous orbit, mid-low latitude Pi2, etc. However the question whether an auroral electrojet event corresponds to a substorm remains unanswered. Using the auroral electrojet index in 2004, we analyzed five auroral electrojet events and studied their relation with substorms. The results show that there are three kinds of auroral electrojet events: (1) simultaneous rapid increase of westward auroral electrojet and eastward auroral electrojet; (2) rapid increase of westward auroral electrojet and almost unchangeable eastward auroral electrojet; (3) rapid increase of eastward auroral electrojet and almost unchangeable westward auroral electrojet. Most of auroral electrojet events correspond to substorms. However a few auroral electrojet events are not accompanied by substorms. This situation most often occurs for the auroral electrojet event in which eastward auroral electrojet dominates.      

国外空间对抗装备技术的发展途径与趋势

空间已成为事关国家安全和利益的战略“制高点”。主要航天国家围绕控制“制高点”,采取不同策略发展空间对抗能力。国外已具备有限的空间对抗实战能力,但是空间对抗装备在世界范围内总体上仍处于技术发展阶段。空间对抗装备技术将在与导弹攻防对抗、网络攻防对抗技术的交叉与叠加中演进升级。预计2030年前后,国外将形成一个比较全面、完整和成熟的空间对抗装备体系。     

基于混沌序列加权抽样和排序变换的图像置乱

为增强网络中传输的数字图像信息的安全性,对一类典型的基于混沌排序图像置乱算法——Ye算法进行了研究,给出应用间隔抽样混沌序列置乱图像可以提高混沌排序置乱算法置乱度这一性质,并依据近似熵理论给出其提升的依据.为增加图像置乱算法的密钥空间,结合Shannon加权保密思想,设计了基于加权抽样混沌序列排序图像置乱算法.结果表明,该方法密钥空间大,置乱强度高,抗重构攻击.     

椭圆轨道非线性相对运动模型的周期解与应用

在长期的航天器编队飞行中传统的基于线性相对运动模型设计编队保持轨道的方法会引起较多的燃料消耗.首先采用摄动法解析地求得了考虑二阶非线性项时椭圆轨道相对运动模型的周期性条件和周期解;然后以此周期解为参考轨道设计了基于Lyapunov稳定的PD保持控制律.仿真结果表明:基于椭圆轨道非线性相对运动模型的周期解较基于椭圆轨道线性相对运动模型的周期解,精度明显提高;以前者为参考轨道的保持控制与以后者为参考轨道的保持控制相比,燃耗明显降低.     

通气位置对潜射航行体流体动力特性影响分析

基于均质平衡流理论,通过求解混合介质的RANS方程、SST湍流输运方程和各相之间的质量输运方程,开展了通气位置对潜射航行体流体动力特性影响的三维数值模拟研究,对比分析了不同通气位置条件下空泡形态特性、表面压力分布以及阻力变化特性.结果表明:当两个通气口间距增加到一定值后,在两个通气口之间区域空泡发生断裂,在断裂区域迎流面和背流面表面压力值升高,且在空泡断裂闭合位置出现压力峰值;在相同通气量条件下,随着通气口间距的增大,压差阻力系数和粘性阻力系数均呈减小趋势变化.     

S波段锁相环调频发射机设计

调频技术是遥测通信技术中的关键技术之一.介绍准两点注入式锁相调频发射机的基本工作原理以及相应的理论分析,随后提出电路的具体实现方案.测试结果表明,发射机调频工作时相位噪声在偏离中心频率10kHz处不低于-83.3dBc,杂散抑制超过70dBc.理论分析和实验表明,准两点注入式锁相调频发射机具有平坦的宽带调制特性,能够满...     

电磁铆接技术在大飞机制造中的应用初探

 电磁铆接是一种新型连接工艺,本文介绍了电磁铆接技术的特点及其发展。针对大飞机制造的技术需求,分析了电磁铆接技术在大飞机研制中的作用,重点介绍了电磁铆接技术在干涉配合铆接、复合材料结构铆接、干涉配合紧固件安装等方面的应用。实验研究表明电磁铆接形成的干涉量均匀,能够提高结构疲劳寿命,可以安装大干涉量干涉配合紧固件,对复合材料结构铆接可以减少安装损伤。分析了为满足大飞机研制的需要,中国下一阶段在电磁铆接技术方面要进行的工作。