Research on Night Vision System Based on Range-Gated Imaging

A design of low-light-level night vision system is described, which can image objects selectively in the specific space. The system can selectively image some objects in specific distances, meanwhile ignore those shelters on the way of observation by combining an intensifying charge coupled device （ICCD） with a near infrared laser assisted in vision, whose operation wavelength matches with the photocathode of the image tube, and adopting the gated mode and adjustable time- delay. A semiconductor laser diode of 100 W in peak power is chosen for illumination. The laser and the image tube operate in 150 ns pulse width and 2 kHz repeat frequency. Some images of different objects at the different distances within 100 m can be obtained clearly, and even behind a grove by using a sampling circuit and a delay control device at 100 W in peak power of semiconductor laser diode, 150 ns in pulse width of laser and image tube, 2 kHz in repeat frequency.     

Application of Two-dimensional Viscous CE/SE Method in Calculation of Two-phase Detonation

The method of two-dimensional viscous space-time conservation element and solution element (CE/SE) can be used to calculate the gas-liquid two-phase interior flow field in pulse detonation engine (PDE). In this paper, the evolution of the detonation wave and the distribution of its physical parameters were analyzed. The numerical results show that the change of axial velocity of gas is the same as that of detonation pressure. The larger the liquid droplet radius is, the longer the time to get stable detonation wave is. The calculated results coincide with the experimented results better.     

Study on the Performance of PECVD Silicon Nitride Thin Films

Mechanical properties and corrosion resistance of Sia N4 films are studied by using different experi- ment parameters, such as plasma enhanced chemical vapor deposition （PECVD） RF power, ratio of reaction gas, reaction pressure and working temperature. The etching process of Sis N4 is studied by inductively coupled plasma （ICP） with a gas mixture of SF6 and 02. The influence of the technique parameters, such as ICP pow- er, DC bias, gas composition, total flow rate, on the etching selectivity of Si3 N4/EPG533 which is used as a mask layer and the etching rate of Si3N4 is studied, in order to get a better etching selectivity of Si3 N4/EPG533 with a faster etching rate of SigN4. The optimized process parameters of etching Si3N4 by ICP are obtained after a series of experiments and analysis. Under the conditions of total ICP power of 250 W, DC bias of 50W, total flow rate of 40 sccm and 02 composition of 30% , the etching selectivity of 2.05 can be reached when SisN4 etching rate is 336 nm/min.     

Experimental and numerical study of the fragmentation of expanding warhead casings by using different numerical codes and solution techniques

There has been increasing interest in numerical simulations of fragmentation of expanding warheads in 3D. Accordingly there is a pressure on developers of leading commercial codes, such as LS-DYNA, AUTODYN and IMPETUS Afea, to implement the reliable fracture models and the efficient solution techniques. The applicability of the Johnson-Cook strength and fracture model is evaluated by comparing the fracture behaviour of an expanding steel casing of a warhead with experiments. The numerical codes and different numerical solution techniques, such as Eulerian, Lagrangian, Smooth particle hydrodynamics （SPH）, and the corpuscular models recently implemented in IMPETUS Afea are compared. For the same solution techniques and material models we find that the codes give similar results. The SPH technique and the corpuscular technique are superior to the Eulerian technique and the Lagrangian technique （with erosion） when it is applied to materials that have fluid like behaviour such as the explosive and the tracer. The Eulerian technique gives much larger calculation time and both the Lagrangian and Eulerian techniques seem to give less agreement with our measurements. To more correctly simulate the fracture behaviours of the expanding steel casing, we applied that ductility decreases with strain rate. The phenomena may be explained by the realization of adiabatic shear bands. An implemented node splitting algorithm in IMPETUS Afea seems very promising.     

Research on Estimation of Time Delay Difference in Passive Locating for Impulse Signal

Analyzed the relation between time delay difference and time delay estimation errors, based on the principles of three-point locating, a reformed threshold method for time delay difference estimation of impulse signals, called as amendment estimation for short, is developed by introducing channel equalization technique to its conventional version, named as direct estimation in this paper, to improve the estimation stability. After inherent relationship between time delay and phase shift of signals is analyzed, an integer period error compensation method utilized the diversities of both contribution share and contribution mode of concerned estimates is proposed under the condition of high precision phase lag estimation. Finally, a cooperative multi-threshold estimation method composed of amendment and direct estimations to process impulse signals with three thresholds is established. In sea trials data tests of passive locating, this method improves the estimation precision of time delay difference efficiently. The experiments verify the theoretical predictions.     

Feasibility analysis of WDM links for radar applications

Active phased array antennas enhances the performance of modern radars by using multiple low power transmit/receive modules in place of a high power transmitter in conventional radars. Fully distributed phased array radars demand the distribution of various signals in radio frequency(RF) and digital domain for real time operation. This is normally achieved through complex and bulky coaxial distribution networks. In this work, we intend to tap the inherent advantages of fiber links with wavelength division multiplexed(WDM) technology and a feasibility study to adapt these links for radar applications is carried out. This is done by analysing various parameters like amplitude, delay, frequency and phase variation response of various radar waveforms over WDM links. This also includes performance evaluation of non-linear frequency modulation(NLFM) signals, known for better signal to noise ratio(SNR) to specific side lobe levels. NLFM waveforms are further analysed using pulse compression(PC) technique. Link evaluation is also carried out using a standard simulation environment and is then experimentally verified with other waveforms like RF continuous wave(CW), pulsed RF and digital signals. Synchronization signals are generated from this variable duty cycle digital signals during real time radar operation. During evaluation of digital signals, variable transient effects for different duty cycles are observed from an amplifier configuration. A suppression method is proposed to eliminate this transient effects. Further, the link delay response is investigated using different lengths of fiber spools. It can be inferred from the experimental results that WDM links are capable of handling various signals significant to radar applications.     

An Impulse Thruster for Radial Thrust Trajectory Correction

A prototype of impulse thruster for radial thrust trajectory correction munitions is designed. It adopts semiconductor bridge （SCB） as ignition element, Ti/KClO4 （TK） as ignition charge and ammonium perchlorate/aluminium （NA） or potassium picate/RDX （KR） as main charge. A thrust test device of impulse thruster is also designed. The output performance of the impulse thruster prototype is tested by the device. The tested results show that it can meet the safety requirements of 1A1W/5 min no-fire level and produce 0.2 - 0.6 N·s thrust impulse within 3ms of action time under certain test conditions; the corresponding ignition delay time is less than 0.5 ms.     

Experimental Study on Plasma Temperature of Semiconductor Bridge

The plasma temperature of the semiconductor bridge (SCB) was measured in real-time according to relative intensity ratio of dual lines of atomic emission spectrum.The plasma temperature under different discharge pulses and the influence of discharge pulse energy on it were studied.The results show that the plasma peak temperature rises gradually with the increase of initial discharging voltage and charging capacitance.For the capacitance of 22 μF,if the initial discharging voltage increases from 21 V to 63 V,the plasma peak temperature rises from 2 000 K to 6 200 K.For the discharging voltage of 39 V,the peak temperature rises from 2 200 K to 3 800 K when the capacitance increases from 6.8 μF to 100 μF.The change of pulse discharge has a very small effect on the plasma temperature at the late time discharge (LTD).In view of the change of plasma temperature with the pulse energy,the discharging voltage has a greater effect on the plasma temperature than the capacitance.The results provide some experimental basis for the further research on SCB ignition and detonation mechanisms.     

A Rapid Method for Compensating Output Error of Electromagnetic Tracker

Some methods which use an optical tracker （OT） as a standard reference of electromagnetic tracker （EMT） were proposed in order to compensate the output error of electromagnetic tracker. Usually, they use a magneto-optic tool to collect the outputs of OT and EMT simultaneously, and then compare the output of OT with that of EMT to compensate the error of EMT. Although the outputs of EMT and OT can be matched each other by using a time stamp which denotes when the acquirement command is sent, but the accuracy will decrease if the tool moves faster for the errors of the time stamp itself. A rapid method for compensating EMT output error is proposed. A particular scan mode of the magneto-optic tool is designed for collecting EMT and OT outputs, and a data registration method is proposed to match the outputs of EMT and OT. The simulated results show that the output error of EMT can be decreased efficiently and the accuracy of the compensation can be improved by about 15 % compared with that of the existing methods.     

Study on Inertial Response Performance of A Micro Electrical Switch for Fuze

The design, modeling, and simulation of a micro electlical switch for fuze are presented. It consists of spring mass system with zigzag slot in mass, latching and electlical cnnecfion mechanism and movement-lhnit mechanism. The switch keeps off-state until it is subjected to an acceleration when fuze is launched normally. The acceleration is simulated as half-shoe pulse with specific amplitude and duration. The dynamics model of the switch is studied. Based on zigzag slot in mass, the methods used for recogllizing acceleration load are estahhshed and analyzed according to the dynamics theory. Two typical half-shoe accelerations are loaded on the switch in simulation. The simulation resuhs are in accordance with those of tfieoretical analysis. The inertial response characteristics of the switch can ensure that the fuze power supply and circuit are connected safely and reliably.     

脉冲激光辐照CCD探测器仿真研究

通过实验验证了脉冲激光辐照CCD引起的饱和干扰,详细分析了峰值功率、脉冲宽度、重复频率等脉冲激光参数,通过构建仿真模型分析了单个参数对探测器饱和阈值的影响,仿真结果表明:脉宽越大,峰值功率越高,重复频率越大,越能使探测器达到饱和状态。     

Theoretical Studies of the Output Pulse with Variation of the Pumping Pulse for RF Excited CO2 Pulsed Waveguide Laser

The behavior of a RF-excited waveguide CO2 laser in the pulse regime is studied theoretically. The output pulse evolution is studied by applying three types of pulses namely the square, sine and the triangular ones as the excitation pulses. The frequency dependence behavior of the output pulse is also presented.     

一种小型脉冲激光器能量和重复频率测量电路

针对传统激光功率计无法实时检测的缺点,设计一种基于PIN光电二极管的小型激光脉冲能量和频率实时检测电路。在激光器输出窗口前端设置光学玻璃对激光输出进行透射和散射,利用PIN光电二极管探测激光散射信号并完成光电转换。微弱电信号经后续信号调理电路处理以外部中断方式触发单片机计时、计数,单片机同时采集调理电路的输出电压。系统最终实现了激光脉冲频率及能量的检测。测试结果表明:该系统的频率测量精度优于0.02%,能量测量精度优于1%,灵敏度优于0.8 V/mW,响应时间不大于3 ns。     

RDX激光点火特性数值分析

用数值模拟分析计算了黑索今(RDX)的激光点火过程。结果表明,RDX经加热、熔化、分解、蒸发,反应物进入气相后,随反应物的积累,温度和气相反应速率的增加,气相被点着。讨论了环境压力和激光功率密度对点火延迟时间和临界点火距离的影响,计算所得的点火延迟时间与文献报道的研究结果一致。     

基于现场可编程门阵列的脉冲激光引信高精度实时定距技术研究

采用电子计数法实现脉冲激光引信定距的本质是测量发射脉冲和目标反射回波脉冲的时间差。为实现脉冲激光引信的精确定距，在分析电子计数法时间测量的原理和误差因素基础上，给出了脉冲激光引信高精度实时定距的原理框图，用Ahera公司Cyclone系列的FPGA芯片实现了时间测量模块，其高速计数器的工作频率达到800MHz，满足脉冲激光引信的精度和实时性要求。在QuartusⅡ软件中进行了后仿真，得到了满意的结果。     

负压环境下铝镁贫氧推进剂激光点火及燃烧特性

为研究不同负压对铝镁贫氧推进剂的点火及燃烧特性的影响,在负压环境下(0.01,0.02,0.04,0.06,0.08,0.1 MPa)和不同热流下(1.26,1.86,2.23,2.79 W·mm~(-2))采用CO_2激光点火系统对铝镁贫氧推进剂进行点火实验,使用高速摄影仪记录点火燃烧过程,使用两个光电二极管同时监测激光和火焰信号得到其点火延迟时间,研究了负压对推进剂点火延迟时间、燃烧过程和燃速的影响。结果表明,压强影响推进剂热解气体的扩散,压强为0.08 MPa时,初焰为圆柱状,随着压强降低至0.02 MPa,初焰为圆球状;随着压强的降低,推进剂点火延迟时间增加,但随着热流密度的增大,压强对点火延迟时间的影响显著降低;压强对推进剂燃速影响较大,随着压强的降低,推进剂燃速降低,当压强从0.1 MPa降至0.01 MPa时,燃速降低47%;同时,在负压环境下,Vielle燃速公式更适用于表征铝镁贫氧推进剂的燃速特性。     

一种基于光纤延迟环的低PRF状态测速方法

介绍了PD雷达在低PRF状态下的测速模糊问题.将光纤技术应用于PD雷达,采用光纤延迟环进行脉冲复制,提出了一种可在低PRF状态下进行测速的方法,采用这种方法能够消除低PRF状态测速模糊,提高低PRF状态的测速范围.通过Matlab进行仿真,验证了方法的正确性.     

大功率窄脉冲半导体激光光源等效电路参数研究

针对大功率窄脉冲激光光源的激光器多管芯组合结构等效电路的参数提取困难的问题,提出了基于外特性测量法来提取激光器多管芯组合结构等效电路参数的简捷方法。其特点是：在不知道半导体激光器的材料及内部结构的情况下,通过对实物电路系统电参数的测量并利用Pspice仿真软件经多次参数拟合来获得半导体激光器等效电路参数。实验结果表明,利用该方法提取的半导体激光器等效电路参数与国外产品给出的等效电路参数相吻合。它为大功率窄脉冲半导体激光器驱动源的设计提供了依据,对多个管芯的组合方式、组合结构设计及装配工艺具有指导意义。在此基础上,设计并制作了半导体激光器板载结构的驱动源电路实验系统,其输出功率为180 W,光脉冲的上升时间为3.2 ns,脉冲的宽度为8.3 ns.     

RDX-CMDB推进剂激光点火特性

采用CO2激光点火的方法研究了双基推进剂SQ-2和RDX-CMDB推进剂在不同热流密度作用下的点火特性,探讨了RDX含量、Al粉和燃烧催化剂对RDX-CMDB推进剂点火性能的影响.实验结果表明,SQ-2和RDX-CMDB推进剂(含Al粉的配方除外)的点火延迟时间随热流密度增加而递减,且热流密度较高时,点火延迟时间变化趋...     

多波段激光检测光源模块设计

利用特定波长的激光信号模拟激光脉冲信息是评价激光装备接收性能的一种主要手段,为满足不同波长激光装备检测集成化的需求,设计了一种多波段激光检测光源模块。通过激光光源的选型,基于透反镜的共轴光路设计和光纤准直镜头的设计,实现了905、1064和1550 nm波长的多波段激光的共光轴匀化输出。为满足激光光源的窄脉冲驱动需求,选用超高速器件将脉冲上升沿转换成窄脉冲驱动信号,控制RC充放电电路进行功率放大,实现激光光源的窄脉冲发射。分别进行了光斑质量、波长、发射功率等参数的实验验证,结果表明多波段激光检测光源能够满足应用要求。