用全球定位系统对导弹进行实时跟踪

本文将介绍一套利用全球定位系统(GPS)对远程导弹进行实时跟踪的系统。全球定位系统全面投入工作后(八十年代后期),用它来跟踪导弹、飞机和地面车船正是其英雄用武之地。为了充分利用该系统,必须要有一种高经济效率的跟踪方案。在跟踪导弹这样一些非回收性试验体时,尤其要注意这一点。本文所介绍的这些技术就是跟踪非回收性试验导弹的一种经济实惠的方法。其基本方案是被试导弹接收多个GPS信号,将这些混合信号的频率变换到一个新的S波段频率上、然后再将混合的S波段信号发送到地面接收站。地面站接收经转发的GPS信号,并加以处理,得到该导弹的正常伪距和伪距离率测量值。用卡尔曼滤波器计算出位置和速度解。除了能独立工作之外,本文所介绍的系统还能与现有跟踪系统相结合,提高跟踪精度。     

抓好两头 带动全局 对我国民航机场建设的观察与思考

尽管我国民航机场建设近年来已取得长足进展,但仍处于发展的初级阶段。机场数量少,发展不平衡,投资体制落后等痼疾如果不能有效根除,机场建设难以走出“体弱多病”的困境     

晶体谐振器—振荡器测试设备及测试结果

一、引言美国陆军电子技术及器件实验室(ETDL)的频率控制与计时分部的主要任务是要提高晶体谐振器与振荡器工艺水平,以满足军队用户的要求。第二个任务是向计划管理人员、系统设计人员提供谘询并维持晶体谐振器与振荡器的军用技术指标(也就是MIL-C-3098和MIL-0-55310)。这些任务要求对晶体谐振器和振荡器的工艺水平有详细而实际的了解。本文的目的是概述本实验室的技术力量,介绍一些研究结果,并在需要时向国防部所属用户提供晶体振荡器的测试、选择、技术指标和研制方面的帮助。     

临近空间飞艇横向稳定性分析

临近空间飞艇由螺旋桨提供偏航控制力矩,空速大时操纵效率低,飞行试验中多次出现偏航通道发散,飞艇稳定性问题凸显。选用HALE-D和HiSentinel两种飞艇,通过CFD仿真方法,得到两种飞艇的静态气动参数,以强迫振荡方法获得其动导数,两种飞艇在计算角度内组合导数均为负值,模型处于阻尼状态;在此基础上,通过飞艇横向稳定性分析获得两种飞艇的稳定区间。结果表明,HALE-D飞艇的横向稳定区间大于HiSentinel飞艇,相同迎角(侧滑角)时,HALE-D飞艇的阻力较大,临近空间飞艇设计需综合考虑阻力、稳定裕度和操纵性之间的平衡。研究结果为临近空间飞艇横向稳定性分析提供了一种方法。     

连续驱动摩擦焊摩擦界面稳态扭矩微观分布的研究

根据金属压力加工和摩擦学的原理,结合连续驱动摩擦焊摩擦加热过程的特点,研究了连续驱动摩擦焊初始摩擦阶段稳态扭矩在摩擦界面分布的规律,探讨了过渡及稳定摩擦阶段稳态扭矩分布的特性.     

Microbially induced iron precipitation associated with a neutrophilic spring at Borra Caves, Vishakhapatnam, India

The present investigation uncovers various pieces of evidence for the possible biologically induced mineralization in iron mats associated with a pH-neutral spring in the Borra caves, Vishakhapatnam, India. Electron microscopy [scanning electron microscopy (SEM) and transmission electron microscopy (TEM)] demonstrated large numbers of (i) hollow tubes (diameter ～1?μm) resembling sheaths of the iron-oxidizing bacteria Leptothrix, (ii) thin (diameter <1?μm) solid fibers of uncertain origin, (iii) nanoscale subspherical to irregularly shaped particles encrusting tubes and fibers, and (iv) aggregates of broken and partially disintegrated sheaths, fibers, and particles embedded in extracellular polymeric substances (EPS) occasionally including microbial cells. X-ray microanalyses by energy dispersive spectroscopy (EDS) revealed that the mat accumulated largely Fe but also smaller amounts of Si and traces of P and Ca. Particles rich in Si and Al (possibly kaolinite) and Ca (carbonate) were also observed. High-resolution TEM/EDS of unstained ultrathin sections suggests that microbial sheaths were highly mineralized by amorphous to cryptocrystalline Fe-rich phases and less frequently by other fine-grained and fibrous authigenic claylike minerals. Total number of microorganisms in the iron mats was 5.8×10(5) cells, g sed(-1) (wet weight). Analysis of the 16S rRNA gene diversity revealed microorganisms assigned to eight different phyla [Proteobacteria (62%), Chloroflexi (8%), Bacteroidetes (7%), Planctomycetes (1%), Actinobacteria (5%), Acidobacteria (6%), Nitrospira (1%), Firmicutes (5%)]. Within the Proteobacteria, Betaproteobacteria was the predominant class, which accounted for 28% of the sequences. Within this class some obvious similarities between the obtained sequences and sequences from other cave systems could be seen, especially sequences affiliated with Leptothrix, Siderooxidans, Crenothrix, Comamonadaceae, Dechloromonas, and many uncultured Betaproteobacteria. Four (4%) of the sequences could not be assigned to phylum level but were affiliating with the candidate division TM7 (2%), candidate division OP11 (1%), and candidate division WWE3 (1%). The results allow us to infer a possible relationship of microbial sheaths, EPS, and the iron precipitates to microbial community diversity in the Borra cave springs. Understanding biogenic iron oxides in caves has important astrobiological applications as it provides a potential tool for the detection of extraterrestrial life.     

转发式GPS外测系统的接收站设备

在高级拦截器技术计划中利用GPS卫星导航系统来精确测定两种飞行器的弹道。在每个飞行器上安装一个弹道导弹GPS转发器(BMT)咸一个GPS遥测发射机(GTT)。接收站布在现有遥测站上,安装了所需的专门设备,负责接收、记录和处理来BMT和GTT的信号。     

电大尺寸散射体的RCS计算方法研究

为了更加有效的求解电大目标散射计算问题,在避免谐振区效应情况下获得复杂目标的隐身雷达散射截面(RCS)特性,引用混合场积分方程(CFIE),在快速算法的求解迭代过程中采用共轭梯度算法(CG)的收敛技术,能够稳定的求解电大尺寸的RCS。计算和分析了金属球双站RCS和金属立方体双站RCS,并和精确计算、相关参考文献进行了比较,证明了方法的正确性,计算结果稳定,在工程实际上有较大的应用价值。