基于相控阵雷达自适应波束形成的抗干扰技术

基于相控阵雷达自适应多波束,研究了相控阵雷达抗干扰的新方法,该方法把自适应波束调零控制技术、副瓣对消技术和极化选择抗干扰技术综合应用于相控阵接收多波束形成中,使相控阵雷达具有良好的抗干扰性能。     

隐身涂料的研究及发展现状

综述了隐身涂料的分类、研究及发展现状,包括可见光隐身涂料,红外隐身涂料,激光隐身涂料、雷迭隐身涂料,声呐隐身涂料和多功能隐身涂料等。     

太赫兹粗糙金属目标镜面雷达散射截面预估方法

在太赫兹频段,研究金属目标表面粗糙度对雷达散射截面(Radar Cross Section,RCS)的调制作用,对粗糙金属目标的RCS缩比测量具有重要意义.通过研究太赫兹粗糙金属目标镜面RCS随粗糙度的变化规律,结合相干、非相干散射理论,在基尔霍夫近似法的基础上,提出一种特定参数区间粗糙金属目标镜面RCS的预估方法,并...     

挠性航天器变幅值输入成形姿态机动策略

针对变参数挠性航天器的姿态机动问题,在变幅值零振动成形器的基础上,提出了鲁棒性较强的变幅值零振动和零微分成形器设计方法,设计了鲁棒姿态机动策略.该机动策略的控制目标是,将航天器机动到期望状态的同时,消除挠性结构的残余振动.以含转动挠性太阳翼的航天器进行三轴姿态机动为例,进行数值仿真.仿真结果表明,该机动策略对挠性结构频...     

多站纯方位定位系统的可观测性条件

对多运动站纯方位目标定位系统的可观测性问题进行了研究.通过运动等效,将多运动站纯方位定位系统等效成一个特殊的单运动站定位问题.利用拟线性估计方程,导出了系统不完全可观测的一些条件,分析中还发现了系统不完全可观测的新情形.     

星载双基地SAR系统模糊性

针对星载双基地SAR由双基地几何关系引入的新问题,提出了计算其模糊比的新方法和近似分解方法。利用此方法通过仿真计算对星载双基地SAR模糊性变化规律做了进一步研究。结果表明,因接收天线的面积限制,与其伴随飞行的大卫星SAR相比,模糊性问题更为严重,但变化规律基本一致。比较而言,由于小卫星天线尺寸在高度上更接近大卫星天线,在距离模糊比上相对大卫星SAR抬高得不多,而在方位模糊比上抬高较大。     

质量功能展开与多约束条件下的概念设计

针对产品在设计时需要大量的资源,研究了资源的投入影响顾客满意度的问题.提出了质量功能展开与多约束条件相结合进行概念设计的方法.利用质量功能展开的基本原理,通过引进设计属性的实际可达水平和计划可达水平,给出了设计资源约束条件下的优化模型.最后以火控雷达的概念设计为例,以研制费用和研制进度为约束条件建立模型,计算说明此模型是有效的.     

基于学习矢量量化(LVQ)神经网络的雷达体制识别

由于现代战争中雷达体制的多样化、复杂化及其综合应用使得雷达体制识别中要处理大量复杂的高维数据,学习矢量量化(LVQ)神经网络不仅能处理有监督分类,而且相对于其他神经网络能以较小的计算量处理大量输入数据,所以采用LVQ对雷达体制进行识别,同时针对LVQ学习速率的变化可能引起学习算法不稳定,采用修正的学习速率算法.在简要介绍雷达体制和LVQ的基础上构造了LVQ神经网络对雷达体制进行分类.通过与径向基神经网络(RBFN)识别算法的仿真对比,证实了方法的有效性.     

Electronic warfare in the optical band: Main features,examples and selected measurement data

The paper presents the possibilities of, and methods for, acquiring, analysing and processing optical signals in order to recognise, identify and counteract threats on the contemporary battleground. The main ways electronic warfare is waged in the optical band of the electromagnetic wave spectrum have been formulated, including the acquisition of optical emitter signatures, as well as ultraviolet (UV) and thermal (IR) signatures. The physical parameters and values describing the emission of laser radiation are discussed, including their importance in terms of creating optical signatures. Moreover, it has been shown that in the transformation of optical signals into signatures, only their spectral and temporal parameters can be applied. This was confirmed in experimental part of the paper, which includes our own measurements of spectral and temporal emission characteristics for three types of binocular laser rangefinders. It has been further shown that through simple registration and quick analysis involving comparison of emission time parameters in the case of UV signatures in “solar-blind” band, various events can be identified quickly and faultlessly. The same is true for IR signatures, where the amplitudes of the recorded signal for several wavelengths are compared. This was confirmed experimentally for UV signatures by registering and then analyzing signals from several events during military exercises at a training ground, namely Rocket Propelled Grenade (RPG) launches and explosions after hitting targets, trinitrotoluene (TNT) explosions, firing armour-piercing, fin-stabilised, discarding sabots (APFSDS) or high explosive (HE) projectiles. The final section describes a proposed model database of emitters, created as a result of analysing and transforming the recorded signals into optical signatures.     

Investigation on the process parameters of TIG-welded aluminum alloy through mechanical and microstructural characterization

Multi-pass TIG welding was conducted on plates (15×300×180 mm3) of aluminum alloy Al-5083 that usually serves as the component material in structural applications such as cryogenics and chemical processing industries. Porosity formation and solidification cracking are the most common defects when TIG welding Al-5083 alloy, which is sensitive to the welding heat input. In the experiment, the heat input was varied from 0.89 kJ/mm to 5 kJ/mm designed by the combination of welding torch travel speed and welding current. Tensile, micro-Vicker hardness and Charpy impact tests were executed to witness the impetus response of heat input on the mechanical properties of the joints. Radiographic inspection was performed to assess the joint's quality and welding defects. The results show that all the specimens displayed inferior mechanical properties as compared to the base alloy. It was established that porosity was progressively abridged by the increase of heat input. The results also clinched that the use of me-dium heat input (1-2 kJ/mm) offered the best mechanical properties by eradicating welding defects, in which only about 18.26% of strength was lost. The yield strength of all the welded specimens remained unaffected indicated no influence of heat input. Partially melted zone (PMZ) width also affected by heat input, which became widened with the increase of heat input. The grain size of PMZ was found to be coarser than the respective grain size in the fusion zone. Charpy impact testing revealed that the absorbed energy by low heat input specimen (welded at high speed) was greater than that of high heat input (welded at low speed) because of low porosity and the formation of equiaxed grains which induce better impact toughness. Cryogenic (-196 C) impact testing was also performed and the results corroborate that impact properties under the cryogenic environment revealed no appreciable change after welding at designated heat input. Finally, Macro and micro fractured surfaces of tensile and impact specimens were analyzed using Stereo and Scanning Electron Microscopy (SEM), which have supported the experimental findings.