平面微波光子晶体的表面波带隙

光子晶体在微波毫米波领域已经有了广泛的应用,适合于微波集成电路结构的光子晶体结构将具有很大的应用前景。在微带介质层上周期加载矩形金属贴片,可以获得平面微波光子晶体,并且在特定频段内禁止表面波传播。利用格林函数和矩量法对这种平面微波光子晶体结构进行了计算,通过求解特征方程,得到在这种微带结构中表面波的传播常数,并通过参数设计得到所需要的表面波带隙。这种结构对于微波集成电路和相控阵天线具有很大的应用价值。     

火炮模拟终端对目标毁伤定量计算研究

计算火炮毁伤半径及对目标毁伤程度是实兵对抗训练系统的重要研究内容之一,对实兵对抗训练中火力毁伤建模具有重要意义。根据实际项目应用情况,提出一种火炮对目标毁伤定量计算方法,该方法通过计算炮弹爆炸时产生的冲击波超压,进而计算火炮毁伤半径及对目标产生的毁伤程度,提高了模拟火力打击的可信度和科学性,能较准确地体现火炮模拟终端在实兵对抗训练中火力打击的作用,贴近实战。     

槽头式野战管线水击波速计算方法研究

按照弹性水击理论,管线内发生水力瞬变时,其水击波速取决于管子的弹性、流体的可压缩性和管子受约束的情况。对于给定的输送介质,焊接式固定输油管线的水击波速是一个常数。而槽头式野战管线采用连接器连接,胶圈密封,这种特殊的连接方式改变了管子整体的弹性摸量,从而使水击波速的常规计算方法不再适用。本文研究了野战管线连接器连接方式时水击波速的影响,实验研究了在受到约束时,橡胶的弹性模量随所受压力的变化而变化的规律,推导出野战管线水击波速平均计算方法,推导的公式表明:与焊接式固定管线不同,野战管线的水击波速随管线内压力的增大而增大。     

槽头式野战管线水击波速测量研究

液体管道的水击波速受流体压力、温度、分子结构、含气量及管线几何尺寸、管材等因素的影响,准确地确定管线的水击波速是一个相当困难的问题,通过实验测量水击波速是一个常用方法。管线水击波速的常用测量方法有波前法和周期法。综合运用波前法和周期法,设计了实验测量野战管线的水击波速,并将实验结果与笔者先前提出的水击波速计算公式的计算结果作了对比,验证了公式的有效性。     

空间通信中影响电波传播的因素分析

航天技术和网络通信技术的发展使卫星间、卫星与地面之间的组网越来越具有可行性和现实需要,为探索其组网方式,对该网的物理层特性进行系统研究,对空间链路中可能影响电波传播的各种因素进行了分析和总结,首先分析了自由空间、大气、电离层等一般因素,其次还分析了天线、空间环境、敌方攻击等特殊因素的影响,为确保航天通信的可靠性和网络管理的有效性提供了理论依据。     

Modeling of the whole process of shock wave overpressure of free-field air explosion

The waveform of the explosion shock wave under free-field air explosion is an extremely complex problem. It is generally considered that the waveform consists of overpressure peak, positive pressure zone and negative pressure zone. Most of current practice usually considers only the positive pressure. Many empirical relations are available to predict overpressure peak, the positive pressure action time and pressure decay law. However, there are few models that can predict the whole waveform. The whole process of explosion shock wave overpressure, which was expressed as the product of the three factor functions of peak, attenuation and oscillation, was proposed in the present work. According to the principle of explosion similarity, the scaled parameters were introduced and the empirical formula was absorbed to form a mathematical model of shock wave overpressure. Parametric numerical simulations of free-field air explosions were conducted. By experimental verification of the AUTODYN numerical method and comparing the analytical and simulated curves, the model is proved to be accurate to calculate the shock wave overpressure under free-field air explosion. In addition, through the model the shock wave overpressure at different time and distance can be displayed in three dimensions. The model makes the time needed for theoretical calculation much less than that for numerical simulation.     

A fast-running method for blast load prediction shielding by a protective barrier

This study presents a simplified blast load prediction method on structures behind a protective barrier. The proposed method is basically an empirical approach based on Kingery-Bulamsh (K-B) chart and finite element (FE) analysis results. To this end, this study divides the structure into three regions by three critical points. Blast loads at each critical point can be calculated based on K-B chart and an approximation according to FE analysis results. Finally, peak reflected overpressure and impulse distributed on the structure can be approximately estimated by linearly connecting blast loads at each critical point. In order to confirm a feasibility of the proposed method, a series of numerical simulations were carried out. The simulation results were compared with FE analysis results which are presented in the open literature. From such comparisons, it was found that the proposed method is applicable to predict blast loads on structures behind a protective barrier.     

Experimental study of transient pressure wave in the behind armor blunt trauma induced by different rifle bullets

Pressure wave plays an important role in the occurrence of behind armor blunt trauma (BABT), and ballistic gelatin is widely used as a surrogate of biological tissue in the research of BABT. Comparison of pressure wave in the gelatin behind armor for different rifle bullets is lacking. The aim of this study was to observe dynamic changes in pressure wave induced by ballistic blunt impact on the armored gelatin block and to compare the effects of bullet type on the parameters of the transient pressure wave. The gelatin blocks protected with National Institute of Justice (NIJ) class III bulletproof armor were shot by three types of rifle bullet with the same level of impact energy. The transient pressure signals at five locations were recorded with pressure sensors and three parameters (maximum pressure, maximum pressure impulse, and the duration of the first positive phase) were determined and discussed. The results indicated that the waveform and the twin peak of transient pressure wave were not related to the bullet type. However, the values of pressure wave’s parameters were significantly affected by bullet type. Additionally, the attenuation of pressure amplitude followed the similar law for the three ammunitions. These findings may be helpful to get some insight in the BABT and improve the structure design of bullet.     

浅海舰船地震波场仿真中的边界处理

为解决舰船地震波场数值仿真中的边界反射问题,结合浅海传播环境特征和舰船地震波激发机理,提出边界处理算法。采用交错网格有限差分法对一阶速度-应力方程进行数值离散;采用应力镜像法处理海水和空气的自由表面,采用分裂式完全匹配层法处理区域边界;将该模型应用于平行海底近场、远场以及倾斜海底的波场仿真算例中。仿真结果表明:加入边界处理后,自由表面的吸收和区域边界的反射有效减少,波场特征清晰,该算法符合浅海舰船地震波场数值仿真的边界处理要求。     

铝合金板材相对均匀性的声-超声评价研究

基于Ritec-SNAP系统建立了声-超声技术实验系统,阐述了该实验系统的原理及应力波因子的定义,分析了在声-超声技术评价过程中用声信号的幅频特性及应力波因子表征材料相对均匀性的可行性。利用建立起来的实验系统,对铝板的相对均匀性进行了声-超声评价的实验研究。实验结果表明,用应力波因子评价铝合金板材的相对均匀性具有可行性。