火炮射击声信号AR模型特征研究

针对现代炮兵战场上的目标识别问题,阐述了火炮射击声信号数据—发射波、弹道波和爆炸波的特征,介绍了火炮射击声信号AR模型谱估计的方法和步骤,利用MATLAB信号处理工具箱具体实现了三种不同类型火炮发射波的AR模型谱估计,并对一批样本成功进行了分类识别实验,探讨了火炮射击声信号AR模型特征在现代战场火炮目标识别中的意义和应用价值。     

雷电回击地面水平电场的解析求解

假定大地为良导电平面 ,基于DU模型计算了雷电回击地面电磁场 ,并探讨了地面水平电场的求解。对于雷电回击水平电场的两种近似求解方法———大地表面阻抗法和斜波法 ,进行了解析推导 ,并从数学上证明了两种方法在远区场的等价法。     

水面舰船减阻节能球鼻艏理论及模型试验研究

基于线性兴波理论,对水面舰船加装减阻节能球鼻艏进行理论和试验研究,发现水面舰船加装减阻节能球鼻艏可获得较好的减阻效果。根据理论优化结果选取多个理论模型进行船模阻力及波形试验。试验结果表明,球鼻艏在特定的中高航速下可以使兴波阻力最多减少37%,总阻力最多减少15%。     

未来光电精确寻的制导技术发展前景预测

精确自寻的制导系统是精确制导武器中最重要的组成部分。精确寻的制导系统的性能直接影响武器的作战性能、应用范围和成本。分析了未来高技术战争对精确制导武器发展的要求,探索了21世纪光电精确寻的制导技术的发展趋势,分析了新的精确制导体制应具备的发展特点,并对未来的发展提出了建议和意见。     

Numerical simulation of the blast wave of a multilayer composite charge

The numerical simulation of a blast wave of a multilayer composite charge is investigated. A calculation model of the near-field explosion and far-field propagation of the shock wave of a composite charge is established using the AUTODYN finite element program. Results of the near-field and far-field calculations of the shock wave respectively converge at cell sizes of 0.25–0.5 cm and 1–3 cm. The Euler––flux-corrected transport solver is found to be suitable for the far-field calculation after mapping. A numerical simulation is conducted to study the formation, propagation, and interaction of the shock wave of the composite charge for different initiation modes. It is found that the initiation mode obviously affects the shock-wave waveform and pressure distribution of the composite charge. Additionally, it is found that the area of the overpressure distribution is greatest for internal and external simultaneous initiation, and the peak pressure of the shock wave exponentially decays, fitting the calculation formula of the peak overpressure attenuation under different initiation modes, which is obtained and verified by experiment. The difference between numerical and experimental results is less than 10%, and the peak overpressure of both internal and external initiation is 56.12% higher than that of central single-point initiation.     

Experimental research on the instability propagation characteristics of liquid kerosene rotating detonation wave

In order to study the instability propagation characteristics of the liquid kerosene rotating detonation wave (RDW), a series of experimental tests were carried out on the rotating detonation combustor (RDC) with air-heater. The fuel and oxidizer are room-temperature liquid kerosene and preheated oxygen-enriched air, respectively. The experimental tests keep the equivalence ratio of 0.81 and the oxygen mass fraction of 35% unchanged, and the total mass flow rate is maintained at about 1000 g/s, changing the total temperature of the oxygen-enriched air from 620 K to 860 K. Three different types of instability were observed in the experiments: temporal and spatial instability, mode transition and re-initiation. The interaction between RDW and supply plenum may be the main reason for the fluctuations of detonation wave velocity and pressure peaks with time. Moreover, the inconsistent mixing of fuel and oxidizer at different circumferential positions is related to RDW oscillate spatially. The phenomenon of single-double-single wave transition is analyzed. During the transition, the initial RDW weakens until disappears, and the compression wave strengthens until it becomes a new RDW and propagates steadily. The increased deflagration between the detonation products and the fresh gas layer caused by excessively high temperature is one of the reasons for the RDC quenching and re-initiation.     

磁流体动力学控制二维扩压器流场数值模拟研究

对常规扩压器进行了简介并作机理分析.用小磁雷诺数假设下基于Favre质量平均的全Navier-Stokes方程来求解外加电磁场的超声速扩压器流场.与常规扩压器比较可以发现,选用适当的外加电磁场组合可以使流动在更短的距离内实现减速扩压,并将部分动能转化为电能.研究表明:仅添加一定外磁场时,第一道激波位置、第二道激波位置、激波串长度分别为无外加电磁场情况的62.19%,77.74%和50.18%.     

激波对超声速流中横向射流的影响

为了揭示激波对超声速流中横向射流的影响,在超声速流中利用长9mm、坡度为23°的斜坡产生激波。组合利用高速摄影仪和纹影仪拍摄激波入射在气体和液体射流的不同位置,以及相同位置不同喷注压降时的流场纹影和阴影图像。结果表明,激波对气体和液体横向射流的影响基本相同,都表现为入射激波增强了湍流度,扩大了燃料空间发展区域,增强了与主流的混合,激波入射在射流的前部比射流的后部影响大。     

非良导体热导率测定实验的教学研究

通过总结对非良导体热导率测定实验的教学探讨 ,为物理实验教学研究提供一种可供借鉴的思路和方法。     

Effect of bending temperatures on the microstructure and springback of a TRIP steel sheet

Transformation-induced plasticity (TRIP) steel possesses high strength and formability, enabling the use of a thinner gauge material and allowing for the fabrication of complex shapes. In this research, we measured the effect of bending temperatures on the microstructure and air-bending springback angle of TRIP steel at temperatures from 25 to 600 °C. Real-time in situ X-ray diffraction and scanning electron microscopy were used for pre- and postbending analysis. As the prebending temperature increased from 25 °C to 600 °C, the retained austenite (RA) volume fraction decreased, and the RA transformed to bainite at temperatures above 400 °C. The springback angle was positively correlated with the prebending RA volume fraction, with the smallest springback angle achieved at 400 °C. Additionally, the springback angle was positively correlated with the bending angle, because the RA transformation ratio contributed to increased strain hardening. Further microstructure analysis revealed that the RA became elongated in the tension direction as the bending temperatures increased.