孤立波的存在性及轨道稳定性

给出一个具有物理意义的系统,研究该系统是否有孤立波,并研究在什么情况下,该孤立波是轨道稳定的.     

高超音速飞行器“黑障”解决方法

简述了"黑障"问题产生的原理、等离子鞘的流场分布及其对通信的影响;重点讨论了4种解决黑障的方法,从原理、具体实现等几个方面对其进行了阐述,并分析了这几种方法的优缺点。对其他的几种方法进行了简单的介绍。     

组网电子对抗中应对远程威胁的对抗优选决策

在组网电子对抗作战背景下,简单分析作战中远程威胁目标,讨论了威胁决策因子及其优属度获取办法,在此基础上,提出了经过对抗方案总体设计、最优方案选择的决策方法,建立了应对远程威胁目标的决策模型。最后,通过合理假定作战场景进行实例分析,验证了该方法是科学合理的。     

水下声源引起的水表面横向微波的理论研究

利用水下声信号在水表面引起的水表面横向微波振幅很小的条件,将普遍的流体力学方程线性化,推导出在水下点声源的激励下,水表面产生的二维横向微波色散关系以及波的传播形式。结果表明,二维水表面的横向微波具有和一维情况类似的结果,即具有波长短、传播速度小的特点,因而可以对入射到表面的激光束进行调制,为水下声信号检测奠定了理论基础。     

多径条件下米波OFDM-MIMO雷达波束性能及特性分析

针对米波正交频分多路复用-多输入多输出(Orthogonal Frequency Division Multiplexing-Multiple Input Multiple Output, OFDM-MIMO)雷达波束形成问题,建立了米波条件下频分复用MIMO雷达阵列信号模型,理论导出了该体制下多径特性定量分析的理论框架、直达波和多径回波模型及其联合发射-接收双程方向图增益闭合表达式。提出了利用米波OFDM-MIMO雷达阵列双程方向图具有距离-角度二维分辨能力抑制多径算法。所提方法能够有效抑制阵列法线方向多径回波,同时有效抑制输出信干噪比周期性损失,且随频偏带宽的增大抑制能力进一步提升。     

Influence of a liquid-filled compartment structure on the incoming shaped charge jet stability

Liquid-filled compartment structure consists of a bulk steel plate with matrix blind holes which are filled with liquid and a steel front plate to seal up the liquid with rings and bolts.The liquid-filled compart-ment structure can resist the shaped charge warhead effectively.This paper presents experimental and theoretical investigations of the penetration ability of the residual shaped charge jet emerging from the liquid-filled compartment structure after the penetration process at different impact angles.On the basis of shock wave propagation theory,the influence of the liquid-filled compartment structure on jet sta-bility is analysed.The interferences of the liquid backflow caused by a reflected shock wave and a back plate on jet stability under different impact angles are also examined.In addition,the range of the disturbed velocity segments of the jet at different impact angles and the penetration ability of the re-sidual jet are obtained.A theoretical model is validated against the experimental penetration depths.     

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.     

Fracture mechanism of a cylindrical shell cut by circumferential detonation collision

The failure mechanism of a cylindrical shell cut into fragments by circumferential detonation collision was experimentally and numerically investigated. A self-designed detonation wave regulator was used to control the detonation and cut the shell. It was found that the self-designed regulator controlled the fragment shape. The macrostructure and micro-characteristics of fragments revealed that shear fracture was a prior mechanism, the shell fractured not only at the position of detonation collision, but the crack also penetrated the shell at the first contact position of the Chapmen-Jouguet (C-J) wave. The effects of groove number and outer layer thickness on the fracture behavior were tested by simulations. When the thickness of the outer layer was 5–18 mm, it has little effect on fragmentation of the shell, and shells all fractured at similar positions. The increase of the groove number reduced the fracture possibility of the first contact position of the C-J wave. When the groove number reached 7 with a 10 mm outer layer (1/4 model), the fracture only occurred at the position of detonation collision and the fragment width rebounded.     

Numerical investigation on free air blast loads generated from center-initiated cylindrical charges with varied aspect ratio in arbitrary orientation

In current guidelines, the free air blast loads (overpressure and impulse) are determined by spherical charges, although most of ordnance devices are more nearly cylindrical than spherical in geometry. This may result in a great underestimation of blast loads in the near field and lead to an unsafe design. However, there is still a lack of systematic quantitative analysis of the blast loads generated from cylindrical charges. In this study, a numerical model is developed by using the hydrocode AUTODYN to investigate the influences of aspect ratio and orientation on the free air blast loads generated from center-initiated cylindrical charges. This is done by examining the pressure contours, the peak overpressures and impulses for various aspect ratios ranged from 1 to 8 and arbitrary orientation monitored along every azimuth angle with an interval of 5°. To characterize the distribution patterns of blast loads, three regions, i.e., the axial region, the vertex region and the radial region are identified, and the propagation of blast waves in each region is analyzed in detail. The complexity of blast loads of cylindrical charges is found to result from the bridge wave and its interaction with primary waves. Several empirical formulas are presented based on curve-fitting the numerical data, including the orientation where the maximum peak overpressure emerges, the critical scaled distance beyond which the charge shape effect could be neglected and blast loads with varied aspect ratio in arbitrary orientation, all of which are useful for blast-resistant design.     

航空轮胎用橡胶弹性体Mullins效应动态加载方法

航空轮胎用橡胶弹性体在服役过程中遭受严苛的动态循环工况。为了研究弹性体在此工况下的力学响应特征和损伤机理,提出基于应力波作用的Mullins效应动态加载实验方法。根据应力波传导与作用特征,采用Hopkinson压杆加载思路,设计和配置了各单元尺寸参数,进而搭建可用于橡胶弹性体材料动态循环加载的实验系统,并开展了航空轮胎用丁苯橡胶的动态循环加载试验。基于试验信号分析发现：加载系统实现了弹性体材料Mullins效应动态应变递增的试验加载。最后开展加载测试参数的影响因素分析,结果表明通过优化系统各单元可实现Mullins效应的动态加、卸载参数的控制。