带内双频电磁辐射对频率步进连续波雷达的虚警干扰规律

为掌握带内双频电磁辐射对雷达的虚警干扰规律,以频率步进连续波雷达为研究对象,基于理论分析与效应试验,研究了虚警目标的电平变化规律、波形特征以及出现位置规律。结果表明:受试雷达在带内双频电磁辐射作用下,不考虑互调干扰时,至多产生两个位置随机的“山丘型”虚警目标,两者距离差与双频干扰频差有关。双频干扰中两分量互相压制,即当任一干扰分量强度恒定时,随着另一个分量的增强,前者形成的虚警目标电平缓慢下降,最终降速基本恒定,而后者形成虚警目标电平逐渐升高,直至电平恒定;若双频干扰信号两分量同比例增强,则两个虚警目标电平均在初期近似线性上升,而后增速逐渐降低至零。     

基于步进频率正交信号的星载MIMO-GMTI雷达空时频处理研究

多发多收(MIMO)体制雷达综合采用多通道、多频技术,为解决星载GMTI面临的探测慢速运动目标和消除盲速估计等问题提供了有效途径。MIMO雷达工作的基础是有效的波形设计。因此,在分析正交波形性能的基础上,结合GMTI应用需求,建立了星载MIMO雷达步进频率正交信号的基本参数确定准则,研究了步进频率MIMO雷达空时频联合自适应处理的基本原理,通过仿真验证了MIMO雷达在杂波抑制和GMTI性能上的优势。     

气动式振动台气锤产生激励信号的机理及其性能研究

建立了阶梯式活塞气锤的力学模型,揭示了该类气锤产生碰撞信号的机理,针对两种不同型号的气锤,结合大量工程实验仿真生成了不同气压作用下两种气锤产生的激励信号,以激励信号的低频能量为气锤的性能指标,进一步评价了两种气锤的性能优劣.研究结果表明:大气锤的性能明显优于小气锤的性能.     

基于步进加速寿命试验的制导弹药储存寿命评估

介绍步进应力加速寿命试验原理,通过对制导弹药自动导引头贮存状态和失效机理的分析,确定了加速寿命试验应力和应力水平．假设产品寿命服从威布尔分布,应用极大似然估计和Bayes的方法处理数据,建立制导弹药可靠储存寿命预测模型,并计算得到自动导引头在正常应力水平下的可靠储存寿命．     

CFRP筋混凝土柱骨架曲线数值模拟

为研究CFRP筋混凝土柱在低周反复荷载作用下的骨架曲线,基于已有的3根CFRP筋混凝土柱的滞回曲线,采用混凝土损伤塑性本构模型和碳纤维筋本构模型,运用有限元分析软件ABAQUS对其试验过程进行数值模拟,并将模拟所得骨架曲线与试验结果进行对比。结果表明:通过数值模拟得到的骨架曲线与试验结果吻合较好,数值模拟趋势与试验得到的趋势一致,从而对该有限元模型的适用性进行了验证。     

全CFRP筋混凝土柱低周反复荷载试验研究

考虑轴压比、剪跨比和配箍形式的影响,对6根全CFRP筋混凝土柱进行低周反复荷载试验,通过分析滞回曲线、骨架曲线、位移延性系数和耗能能力等特征,研究CFRP筋混凝土柱的抗震性能。试验结果表明:CFRP筋混凝土柱具有较强承载能力和变形能力;轴压比和剪跨比是影响试件抗震性能的主要因素,轴压比越小,试件的变形和耗能能力越强,刚度退化越平缓,剪跨比越大,试件的变形能力越强;通用屈服弯矩法计算得到的延性系数能够较好反映CFRP筋混凝土柱的延性,轴压比越小、剪跨比越大,试件的延性越好;新型螺旋式矩形箍筋在试件延性及耗能方面表现良好,可以应用于工程实际。     

支座弹性对压杆临界荷载的影响

在考虑支座弹性的情况下 ,研究了几种常见的压杆结构 ,推导出了计算临界荷载的方程式 ,给出了以稳定系数表示的临界压力的简明表达式及稳定系数列表。由于考虑了支座弹性 ,使本文提出的方法更具有一般意义和工程价值。     

Experimental investigation on dynamic response and damage models of circular RC columns subjected to underwater explosions

Reinforced concrete (RC) columns are widely used as supporting structures for high-piled wharfs. The study of damage model of a RC column due to underwater explosion is a critical issue to assess the wharf’s antiknock security. In this study, the dynamic response and damage model of circular RC columns subjected to underwater explosions were investigated by means of scaled-down experiment models. Experiments were carried out in a 10.0 m diameter tank with the water depth of 2.25 m, under different explosive quantities (0.025 kg–1.6 kg), stand-off distances (0.0 m–7.0 m), and detonation depths (0.25 m–2.0 m). The shock wave load and dynamic response of experiment models were measured by configuring sensors of pressure, acceleration, strain, and displacement. Then, the load distribution characteristics, time history of test data, and damage models related to present conditions were obtained and discussed. Three damage models, including bending failure, bending-shear failure and punching failure, were identified. In addition, the experience model of shock wave loads on the surface of a RC column was proposed for engineering application.     

混沌随机频率步进信号分析与处理

混沌具有类随机性、对初值敏感、易于产生和控制,频率步进信号易于工程实现和处理,结合二者的优势,提出一种基于混沌序列的随机频率步进雷达信号。介绍了信号产生模型,从理论上推导、分析了该信号的模糊函数和互相关函数性能,给出了信号直接相关和先排序存储、后匹配滤波两种回波处理方法。应用四种典型混沌进行数值仿真,并和已有的线性频率步进信号、高斯和均匀随机频率步进信号进行对比分析。结果表明,混沌随机频率步进信号具有较优良的性能,是一种有潜力的雷达信号。     

The campaign of the lost footsteps: the pacification of Burma, 1885-95

ABSTRACT

What Rudyard Kipling called the ‘campaign of lost footsteps’ was the longest campaign fought by the Victorian army. The conquest of Upper Burma, an area of 140,000 sq. miles with a population of four million, took only three weeks in November 1885 and was accomplished with minimum cost. However, the removal and deportation of the Burmese King and dismantling of all traditional authority dismantled led to growing resistance to British rule leading to an increasingly difficult guerrilla war. Though the Burmese guerrillas were characterised by the British as mere bandits or dacoits, many were former soldiers along with Buddhist monks. The extremely difficult nature of campaigning in the terrain and climate of Burma was not sufficiently appreciated by the War Office, who viewed the conflict as a ‘subaltern’s war’ and ‘police’ work. Intended regime change was also not accompanied by any consideration of the likely implications. Prolonged insurgency necessitated deploying a force far larger than originally intended; though order was finally secured by 1895, the campaign proved destructive of Burmese society while British recruitment of hill tribes into the police and armed forces sowed the seeds for future divisions.