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。     

防空导弹平均速度分析

分析了防空导弹平均速度的计算方法。首先给出了水面舰艇编队防空作战中目指线和自卫线的计算模型,阐述了防空导弹平均速度在其中的重要影响,然后分析了防空导弹速度特性,在此基础上得出满足作战要求的计算方法,最后根据典型弹道参数对防空导弹平均速度进行了仿真计算。     

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。     

利用固定周数测时法测定目标速度

利用固定多普勒频率的周期进行测速是测速的方法之一 ,此法应用到雷达测速中 ,通过测出径向速度 ,检验数据的合理性 ,再利用合理的数据进行径向速度外推和非线性修正 ,求得目标的速度。     

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.     

尾流模拟火箭弹空中弹道对模拟尾流生成区域的影响

为了研究尾流模拟火箭弹的空中弹道特性对模拟尾流区域的影响,建立火箭弹质点外弹道模型、阻力板和发动机空间运动微分方程以及连接绳的受力模型,得到火箭弹无控飞行、空中转向、空中分离至爆索展开入水全过程的空间运动微分方程。对尾流模拟火箭弹全程弹道进行仿真分析,着重分析不同初始射击诸元对爆索空中弹道的影响,探究初始发射角、脉冲发动机的喷管数量、点火时间以及火箭弹空中分离时间对模拟尾流生成区域的影响。仿真结果表明：初始发射角为15°时火箭弹射程和最大射高相对比较合理;火箭弹空中转向角度依赖于脉冲发动机总冲量,与点火时刻无关;空中分离时刻对爆索入水发泡区域影响不太明显,在满足转向要求和发泡区域要求的情况下应该尽早完成空中转向和分离。     

Schedule design for liner services under vessel speed reduction incentive programs

Gas and particulate emissions from ship transportation have been increasing in recent years. In order to mitigate ship emissions near coastal areas, voluntary vessel speed reduction incentive programs (VSRIPs) were put in place by a number of ports. This paper studies a schedule design problem faced by liner shipping companies under VSRIPs. It proposes a mixed-integer nonlinear mathematical model for the minimization of the total cost, consisting of fuel cost, as well as operating cost, minus dockage refunds. The model balances three determinants, that is, the compliance of VSRIPs, the speed limit (the maximum physical speed of ships and the upper speed limit imposed by VSRIPs), and the limited number of ships. An enumerative algorithm and a piecewise-linear approximation algorithm are developed, based on some properties of the nonlinear model. The efficiency of the proposed algorithms is validated through extensive computational experiments.     

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。