不同状态下AZ31镁合金板材V形弯曲性能研究

采用具有不同弯曲半径的V形槽弯曲模具对不同状态、不同厚度的AZ31镁合金板材进行系列弯曲试验,测算AZ31镁合金弯曲回弹量,分析板厚和相对弯曲半径对回弹的影响。研究表明:在凸模弯曲半径r不变时,板带厚度越大,回弹角越小;在板厚一定时,相对弯曲半径r/t越大,回弹角越大;厚度较小板带的回弹角变化幅度受弯曲半径的影响比厚度较大板带的更大;热处理态板材的弯曲成形性能优于冷轧态板材。     

介质覆层对圆柱共形微带天线性能的影响研究

研究了圆柱共形微带天线加载介质层对天线性能的影响。首先采用互易定理分析了加载介质层后圆柱共形微带天线辐射特性，然后运用有限元法计算了天线的方向图．与文献结果进行了比较，验证了程序的有效性。最后。对不同介质覆层厚度和不同覆盖层介电常数下天线的散射参数和辐射方向图进行了仿真。结果表明，圆柱共形微带天线加载介质层后，天线的谐振频率产生了漂移而且阻抗带宽明显降低，介质层厚度对天线阻抗带宽的影响较大，而介电常数的影响相对较小。     

EBG结构在柱面共形微带天线中的应用

利用光学Bragg反射条件,设计了两种曲面电磁带隙结构,观察了其带隙特性,并首次把他们应用到柱面共形微带贴片天线中.仿真结果显示,利用EBG结构后,微带天线的高次谐波得到了很好地抑制.     

近炸引信中的开槽共形定向微带天线

针对近炸引信中贴片微带天线带宽窄及定向辐射性能差等问题,提出了与弹体共形的具有侧向辐射、宽频带的微带天线。该微带天线采用倒方形贴片,在贴片上进行开方形槽,并在槽中加入圆形寄生贴片对天线性能进行优化。仿真与实物测试的结果表明：开槽的共形定向微带天线具有良好的宽带特性,在中心频率7.7 GHz附近方向图具有良好的侧向辐射性能,指标优良且尺寸小,满足近炸引信所需。     

管材弯曲过程中的弹塑性变形分析

在管材弯曲变形的基本假设和简单应力状态下的线性强化材料模型的基础上，对管材弯曲进行了变形分析。分析结果表明：弯管横截面上垂直于弯曲平面方向的对称轴两侧存在很小的弹性区，对弯曲卸载后的回弹产生一定影响；弯曲切向应力主要随相对弯曲半径减小、屈服强度和塑性模量增大而增大；在较小相对弯曲半径范围内，弯曲切向应力有急剧上升的倾向；根据弯曲切向应力小于材料拉伸极限的关系，推导出最小相对弯曲半径的计算公式，理论计算值略小于实际试验值，修正并完善后，可应用于生产。     

共形环状毫米波微带天线研究

与弹体共形天线的复杂结构使天线性能的准确分析十分困难,共形时域有限差分法是分析复杂结构天线的有效方法之一。在介绍共形时域有限差分法基本原理的基础上,分析了毫米波圆锥共形环状微带天线,制作并测试了35GHz的环状微带天线,实测数据与仿真结果吻合。     

弯管横截面畸变的试验与分析

在管材弯曲成形系列研究中,针对弯管壁厚变薄及横截面形状变形现象,展开了试验及有限元模拟分析。在平面应力和三向应力状态假设下,分别推导出弯管壁厚减薄率和横截面短轴变化率相互关系的近似计算公式。通过弯曲试验对公式计算值进行了比较和验证,结果表明,平面应力假设条件下的公式计算值相对准确。相对弯曲半径较大时,弯管外侧管壁材料的径向变形较小,外侧管壁变薄是导致弯管横截面畸变得主要原因。公式计算值与试验结果仍存在一定偏差,通过大量试验进一步修正后,可应用于实际生产。     

可调谐谐振频率的矩形微带天线改进模型

为提高矩形微带天线谐振频率的计算精度，提出了平均有效介电常数的概念，推出了具有和不具有空气隙的矩形微带天线谐振频率的改进公式，并给出了具有空气隙矩形微带天线的谐振频率随空气隙高度的变化曲线，阐述了仿真结果与实验值吻合得较好。     

刀—屑摩擦对斜角切削切屑流动特性影响的仿真研究

采用显式有限元程序,对不同刀—屑摩擦系数时的斜角切削过程进行三维仿真实验,研究切屑在前刀面上的流动特性,刀—屑摩擦对切屑流动方向和螺旋卷曲半径的影响规律和作用机理。结果表明,斜角切削时,切屑从切削刃处以倾斜方向流出,然后沿前刀面产生侧向弯曲,因此切屑流出速度方向与刀刃法向的夹角逐渐增大;当切屑与前刀面分离后,形成螺旋卷屑排出。刀—屑间摩擦力的分布情况是引起切屑在前刀面上产生侧向弯曲的主要原因。随着刀—屑摩擦系数的增大,切屑在前刀面上侧向弯曲曲率减小,而切屑螺旋卷曲半径增大。而且,刀具前角越小,刀—屑摩擦对切屑流动特性的影响越大。     

微带共形天线阵在遥测系统中的设计应用

论述了微带共形天线阵的设计方法,分析了设计中存在的微带天线保护涂层设计与微带天线宽带化等关键技术,仿真设计与实际测试结果表明设计满足系统要求。     

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.