锥形罩锥角对射流形成和侵彻影响的数值模拟

采用Lagrange方法及多物质单元ALE法分别就锥形罩射流形成过程及对钢靶板的侵彻进行了理论推导与数值模拟。分析了锥形装药结构中药型罩锥角对所形成的聚能射流和侵彻参数的影响。结果显示锥形罩锥角大小对象能射流的形状、射流速度、射流质量、侵彻深度、宽度有着明显的影响。研究结果对聚能装药的理论研究具有一定的指导作用。     

基于LS-DYNA的串联聚能战斗部前级装药结构研究

设计了一种小长径比变锥角前级装药结构,利用LS-DYNA有限元分析软件,采用多物质ALE算法,分别对锥形和变锥角装药结构在中心和环形起爆方式下的射流形成过程进行了数值模拟。仿真结果表明,文中设计的变锥角装药结构在环形起爆方式下形成的射流直径大、杵体小、速度梯度小,更符合串联聚能战斗部前级装药的特性要求。     

不同锥角和楔角对锥形和线形聚能装药射流的影响

文中阐述了锥形和线形聚能装药各自射流形成的机理，运用有限元软件Lsdyna 2D，对锥形聚能装药和线形聚能装药的射流形成过程进行了模拟．比较说明了两种装药结构形成射流和杵体的不同。并且通过改变锥角和楔角来研究它们对射流的影响，结果显示锥形罩锥角和线形罩楔角对射流形状及速度有着重要的影响。     

壁厚变化率对小锥角聚能射流形成影响的数值模拟

基于油气井射孔弹的设计原理,应用LS-DYNA 有限元程序,采用ALE 方法对某特定结构小锥角聚能装药在不同壁厚变化率的情况下射流形成过程及侵彻双层靶板进行了数值模拟,计算结果表明:采用顶部薄、锥底厚的药型罩,射流速度梯度高,可形成高速细长射流;射流侵彻双层靶板孔径小,剩余速度大;小锥角聚能射流侵彻强度高,药型罩壁厚变化率选0.9%为最佳.     

不同上下罩高对复合药型罩射流形成影响的数值模拟

在两种双锥罩的基础上,设计4种变壁厚和等壁厚相结合的复合双锥药型罩。应用LS-DYNA3D有限元程序,采用ALE方法对复合药型罩的小锥角聚能装药,在5种不同上下罩高比例的情况下射流形成过程进行数值模拟。结果表明:采用罩壁外母线为直线、上锥罩为等壁厚和下锥罩为变壁厚相结合的复合药型罩,射流速度梯度高于两种双锥罩和其他3种复合药型罩,且当上下罩高比例为5/5时,射流头部速度达到最大,为7 174 m/s;4种复合药型罩在上下罩高比例为7/3时,均出现射流较短并且射流中段较早发生失稳断裂的情况。     

基于BP神经网络和遗传算法的环形药型罩优化

环形聚能装药相比传统的聚能装药具有侵彻口径大的优势,为了得到可以形成稳定的环形聚能射流的最优环形药型罩结构,提出了一种将数值模拟结果与BP神经网络相结合,并通过遗传算法对环形药型罩进行优化设计的方法。首先,利用正交试验法对环形药型罩进行方案设计,得到各因素对环形聚能射流稳定性的重要程度,其次利用LS-DYNA软件进行数值模拟得到最初的样本数据,然后通过MATLAB软件拟合出神经网络训练所需的样本数据,接着将环形药型罩结构参数作为BP神经网络的输入,射流头部速度、射流横向速度、射流长度分别作为输出进行训练,同时将测试值作为适应度,最后结合遗传算法选择最优的环形药型罩结构参数。研究结果表明:影响环形聚能射流成形的主要因素是药型罩口径和锥顶角,次要因素为药型罩罩顶厚、内罩偏移量和外罩偏移量; 当药型罩罩顶高为0.81 mm,药型罩口径为15.43 mm,罩顶角为61.89°,内罩偏移量为11.38%,外罩偏移量为14.36%时所形成的环形射流形态比正交实验所得环形聚能射流更好。     

双锥结合罩射流特性影响因素的模拟研究

为了消除杵堵,通过对聚能装药进行结构改变,设计出一种锥-锥结合药型罩,上锥罩为铜下锥罩为铝。改变上、下锥罩的长度比例和下锥罩锥角,分析组合药型罩形成射流的规律。研究表明:下锥罩锥角为100°时,随着双锥罩上、下罩长度比增大,射流的连续性好,头部射流速度减小,形成的射流愈稳定;上、下锥罩长度比为2∶1时,随着下锥角角度增大,射流的速度梯度变小,总体能量减小。     

聚能装药射流形成与破甲模拟计算研究

依据经典的射流形成和破甲理论,建立了聚能装药破甲深度工程计算模型,实现了聚能装药破甲的计算模拟.分别以等壁厚单锥罩和双锥罩装药结构为例,试算了破甲深度,并与实验结果进行了比较,表明该模型和计算程序有一定的准确性,能够方便、快速地计算破甲深度等射流形成和侵彻参数,为聚能装药结构设计和破甲计算提供工程应用工具.     

圆锥罩结构和起爆方式对聚能射流形成的影响

为了研究圆锥罩聚能射流形成的影响因素,通过Lagrangian显式动力学有限元方法对圆锥罩聚能射流的形成过程进行了数值计算。采用对称罚函数接触算法处理炸药和圆锥罩之间接触,采用网格自适应算法防止网格严重畸变造成的计算中断。根据数值计算的结果深入分析了圆锥罩厚度、圆锥罩锥角和起爆方式对聚能射流形状和速度的影响,得到了射流形状和速度的变化规律,为圆锥罩聚能射流的优化设计提供了参考依据。     

两种典型串联聚能射流的数值模拟

为了进一步提高金属射流量和破甲深度,设计了单锥和双锥药型罩相结合的两种不同结构的串联药型罩,且利用Truegrid和有限元软件LS-DYNA对两种聚能射流的形成及侵彻钢板的过程进行了数值模拟。结果表明:这两种结构均能很好的形成射流,能够有效提高射流对靶板的侵彻深度,且以双锥罩为前级的装药结构形成的射流比以单锥罩为前级的装药结构形成射流的速度要高,前者的穿孔孔径较后者要大,在相同条件下,前者对靶板的穿深较后者要深。     

Stability of the Third Generation Intensifier under Illumination

The stability under illumination of transmission-mode GaAs photocathode sealed in the third generation intensifier is investigated by use of spectral response testing instruments. The variations of spectral response with the illumination times under weak and intense illumination are compared. The variations of photoemission performance parameters are also characterized. The results show that during initial several weak illuminations photocathode behaves no evident decay and a maximum sensitivity is achieved, while under intense illumination the sensitivity of photocathode begin to decrease largely at the first illumination. The calculated performance parameters show that the variation of surface escape probability with illumination times is a direct cause of instability of photocathode. It is also found that under intense illumination peak wavelength is moved towards short-wave and peak response is decreased, which shows that the ability of long-wave response of photocathode is decreased.     

Passive Acoustic Radar for Detecting Supersonic Cruise Missile

A Passive Acoustic Radar is presented as a necessary complement to electromagnetic wave radar, which will be expected to be an effective means for detecting cruise missiles. Acoustic characteristics of supersonic flying projectiles with diverse shapes are expounded via experiment. It is pointed out that simulation experiment could be implemented using bullet or shell instead of cruise missile. Based on theoretical analysis and experiment, the ““acoustic fingerprint““ character of cruise missile is illustrated to identify it in a strong noise environment. After establishing a locating mathematical model, the technique of acoustic embattling is utilized to resolve a problem of confirming the time of early-warning, considering the fact that velocity of sound is much slower than that of light. Thereby, a whole system of passive acoustic radar for detecting supersonic cruise missile is formed.     

Design and Analysis of Test Schemes of Static Postponing Time on Shrapnels Used to Riot Control

The test scheme of static postponing time given in our actual national military test standard on shrapnels used to control riot is a nine-point test scheme on the combined action of three kinds of temperatures and three kinds of pressures,the consumed ammunitions are more excessive. Statistic analysis and tentative checkout about a lot of test data are done,feasibility gists are put forward for optimizing of the test design scheme. The optimizing design and data analysis of test scheme of the item are done by managing uniformity design theory, two scientific and reasonable six-point test schemes are confirmed. The feasibility and reliability of the optimizing design schemes put forward above are proved ulteriorly by test validating. The gained schemes not only have good design uniformity and little ammunition wastage and meet the test demand, but also have better forecast ability for the result data of other points using the mathematic models from the actual test points.     

Super-resolution Restoration of Remote-sensing Images

A novel image restoration scheme, which is super-resolution image restoration algorithm Poisson-maximum-afterword-probability based on Markvo constraint （MPMAP） combined with evaluating image detail parameter D, has been proposed. The advantage of super-resolution algorithm MPMAP incorporated with parameter D lies in the fact that superresolution algorithm MPMAP model is discrete, which is in accordance with remote-sensing imaging model, and the algorithm MPMAP is proved applicable to linear and non-linear imaging models with a unique solution when noise is not severe. According to simulation experiments for practical images, super-resolution algorithm MPMAP can retain image details better than most of traditional restoration methods; at the same time, the proposed parameter D can help to identify real point spread function （PSF） value of degradation process. Processing result of practical remote-sensing images by MPMAP combined with parameter D are given, it illustrates that MPMAP restoration scheme combined PSF estimation has a better restoration result than that of Photoshop processing, based on the same original images. It is proved that the proposed scheme is helpful to offset the lack of resolution of the original remote-sensing images and has its extensive application foreground.     

Design and Simulation of TF and TA Controller for Missile

A nonlinear terrain following(TF) and terrain avoidance(TA) controller is proposed for missile control systems. Based on classical TF algorithm (adaptive angle method), a new method for TF controller is proposed by using angle of attack. A method of obtaining terrain outline data from digital elevation map (DEM) for TF control is discussed in order to save store space. A TA algorithm is proposed by using bank-to-turn technique. The block control model, which is suitable for backstepping design, is given for nonlinear model of missile. Making full use of the characteristics of the system and combining block control principle and backstepping technique, a robust controller design method is proposed. Uncertainties in every sub-block are allowed, and can be canceled by using the idea of nonlinear damping. It is proved that the state tracking errors are converged to a neighborhood of the origin exponentially. Finally, nonlinear six-degree-of-freedom simulation results for the missile model are presented to demonstrate the effectiveness of the proposed control law.     

Design of Non-fragile Satisfactory Estimator for Linear Continuous Perturbed Stochastic Systems

The design problem of non-fragile estimator is addressed for a class of perturbed linear continuous systems. The perturbations occur on the plant and estimator parameters. The estimator designed should force the error system to achieve the desired decay rate and force the steady error variance less than the specified upper bound irrdevancy of the admissible plant perturbations and estimator perturbations. Consistency problem of the decay rate with the variance upper bound is first considered via linear matrix inequality （LMI） approach. The solution of the estimator parameter under specifications to be consistent is then discussed. The consistency condition of specifications and estimator parameter solution are transformed to feasible or minimum problems subject to a set of LMI respectively. The method is illustrated by a numerical example.     

An Improved Scene-based Nonuniformity Correction Algorithm for Infrared Focal Plane Arrays Using Neural Networks

The improved scene-based adaptive nonuniformity correction （NUC） algorithms using a neural network （NNT） approach for infrared image sequences are presented and analyzed. The retlna-like neural networks using steepest descent model was the first proposed infrared focal plane arrays （IRFPA） nonuniformity compensation method, which can perform parameter estimation of the sensors over time on a frame by frame basis. To increase the strength and the robustness of the NNT algorithm and to avoid the presence of ghosting artifacts, some optimization techniques, including momentum term, regularization factor and adaptive learning rate, were executed in the parameter learning process. In this paper, the local median filtering result of Xij （ n ） is proposed as an alternative value of desired network output of neuron Xij （ n ）, denoted as Tij （ n ）, which is the local spatial average of Xij （ n ） in traditional NNT methods. Noticeably, the NUC algorithm is inter-frame adaptive in nature and does not rely on any statistical assumptions on the scene data in the image sequence. Applications of this algorithm to the simulated video sequences and real infrared data taken with PV320 show that the correction results of image sequence are better than that of using original NNT approach, especially for the short-time image sequences （several hundred frames） subjected to the dense impulse noises with a number of dead or saturated pixels.     

Piecewise Filter of Infrared Image Based on Moment Theory

The disadvantages of IR images mostly include high noise, blurry edge and so on. The characteristics make the existent smoothing methods ineffective in preserving edge, To solve this problem, a piecewise moment filter （PMF） is put forward. By using moment and piecewise linear theory, the filter can preserve edge. Based on the statistical model of random noise, a related-coefficient method is presented to estimate the variance of noise. The edge region and model are then detected by the estimated variance. The expectation of first-order derivatives is used in getting the reliable offset of edge. At last, a fast moment filter of double-stair edge model is used to gain the piecewise smoothing results and reduce the calculation. The experimental result shows that the new method has a better capability than other methods in suppressing noise and preserving edge.     

Bistatic Sonar Localization Based on Best Linear Unbiased Estimation

A best linear unbiased estimation （BLUE） algorithm for bistatic sonar localization is proposed. The Cramer-Rao bound for bistatic Sonar and the geometrical dilution of precision （GDOP） in different conditions are given. The simulation results show that the location accuracy of BLUE algorithm is higher than the weighted least square method.     

Research on Gear-broken Fault Diagnosis in a Tank Gearbox

A fault diagnosis method of working position gear in a tank gearbox is put forward based on simulating the fault of working position gear in an actual tank, extracting the envelope of vibration signal by Hilbert transformation amplitude demodulation method, and zooming the low-frequency band to envelope signal.