脉冲多普勒雷达特征提取技术分析

为了准确快速地对脉冲多普勒雷达进行识别,选择3个具有代表性的参数:相参性、脉内调制特性及脉冲重复频率进行提取,并讨论了各参数提取的几类理论研究和比较成功的应用方法,分析了脉冲多普勒雷达识别技术中存在的难点及发展方向.     

高效液相色谱仪色谱采集和控制卡

本文介绍了一种ＰＣ总线色谱采集和控制卡的设计和工作原理,带有此卡的ＰＣ机可实现与岛津高效液相色谱仪配套的专用色谱数据处理装置Ｃ－Ｒ３Ａ的功能,并可以和该色谱仪组成一完整系统,协同工作。     

基于飞机油箱模型形状特征的油量测量

在分析飞机数字式油量测量过程中目前广泛使用的切片法油量测量原理的基础上,针对现有的定步长切片法无法得到准确、可靠的燃油质量特性数据库的缺陷,结合对飞机油箱模型形状特征的分析,提出了基于飞机油箱模型形状特征的油量测量切片步长选择方法.此方法包括切片步长整体和局部选择两个过程,整体选择以实现相邻两切片平面所夹油箱模型体积近似相等为目的来确定切片步长,以体现油箱模型截面整体变化规律;局部选择以设计切片平面与截面突变平面重合或尽可能接近的方式,突出油箱截面的局部变化特征.实验结果表明:该切片步长选择方法较定步长方法能够建立更为合理、可靠的燃油质量特性数据库,从而提高了油量测量精度.     

A comparison of ionosonde measured foF2 and IRI-2016 predictions over China

A comparison of the ionospheric F-region critical frequency (foF2) between ionosonde measurements and IRI-2016 predictions is studied over China during the period from January 2008 to October 2016. Four stations are selected, and the latitude coverage starts at 49.4°N and ends at 23.2°N with a sequential latitude interval of about 10°, the corresponding geomagnetic latitudes are from 39.5°N to 13.2°N. The results show that the variability of the observed foF2 versus latitudes, seasons, local time and levels of solar activity could be well reproduced by IRI-2016. However, the daily lowest value of foF2 from the IRI-2016 prediction occurs earlier than that from the ionosonde. Around the sunrise, the IRI-2016 prediction shows a very sharp rise and grows much faster than the observed foF2 in every month. The foF2 difference between the two options (URSI and CCIR) in IRI-2016 increases as the F10.7 index decreases. During 2008–2009, the annual average deviations of URSI and CCIR range from ?5% to ?10% and from 5% to ?5%, respectively. Generally, the CCIR performs better than URSI during postsunset under low solar activity or in Equatorial Ionization Anomaly (EIA) region over China, while it shows no large difference in performance with URSI in other locations or for other time.     

信息战及其对机载计算机发展的影响

机载计算机系统是飞机航空电子系统的核心部件，它在信息战环境下的作战能力，直接决定了飞机在信息战中的生存能力和任务成功率。本文介绍了信息战的概念及特点，信息战对机载计算机系统的主要攻击形式，提出了机载计算机系统在现代信息战环境下必须加以考虑的几项关键技术。     

Simulation of underexpanded supersonic jet flows with chemical reactions

To achieve a detailed understanding of underexpanded supersonic jet structures influenced by afterburning and other flow conditions, the underexpanded turbulent supersonic jet with and without combustions are investigated by computational fluid dynamics(CFD) method.A program based on a total variation diminishing(TVD) methodology capable of predicting complex shocks is created to solve the axisymmetric expanded Navier–Stokes equations containing transport equations of species. The finite-rate ratio model is employed to handle species sources in chemical reactions. CFD solutions indicate that the structure of underexpanded jet is typically influenced by the pressure ratio and afterburning. The shock reflection distance and maximum value of Mach number in the first shock cell increase with pressure ratio. Chemical reactions for the rocket exhaust mostly exist in the mixing layer of supersonic jet flows. This tends to reduce the intensity of shocks existing in the jet, responding to the variation of thermal parameters.     

陕西高职教育教学质量监控评价体系调查报告

本系统地分析了高职高专教育教学质量监控评价体系的现状、成就、存在的问题和对策，对拟建立的体系提出了建议和模型。     

高温合金车削力的试验研究

根据高温合金的切削性能,确定刀具结构、刀具角度、刀具材料和切削用量。通过多次实验建立高温合金切削力经验公式,并与切45~#钢的经验公式对比,证明商温合金的切削力比切45~#钢大43％左右。     

基于PLC的过程控制无扰切换

在分析PLC的PID功能指令算法的基础上,提出了一种无扰切换的设计方法.在基于PLC的过程控制中,直接利用PLC实现手动操作和自动操作,并保证了手动自动之间的无扰动切换.以该方法设计的控制系统结构简单,不需要专用操作器,可靠性高,成本低.     

用模型喷管模拟研究发动机组外向辐射传热

根据热辐射理论，分析空间发动机外向辐射会传热的基本特点，得出在地面用模型喷管－电热喷管缩比件模拟这一传热现象的必要条件为两者几何相似，壁面热流密度q以及表面黑度ε相等。可行性分析为地面模拟试验提供了科学的依据，其结论可用来指导试验。