再入飞行器的气动噪声响应分析和试验验证

利用再入飞行器气动噪声的试验结果和MSC／NASTRAN软件首次完成了再入飞行器复杂结构气动噪声的响应分析与试验验证，从而将随机响应分析的单个激励下的结构随机响应分析推进到多个面激励下的复杂结构随机响应分析与试验验证。     

再入体气动参数辨识

采用极大似然辨识方法对再入体的气动力和气动力矩系数及小不对称量进行辨识，用辨识的气动参数重构再入体的飞行弹道，用以验证气动参数辨识的准度。     

再入飞行器基于气动力热约束的飞行轨迹控制优化研究

@@@@为了计算再入飞行器的可压流场特性,采用计算流体力学（CFD）方法获得不同工况下飞行器流场的气动特性。通过对多个工况点下流场热力学状态的分析与对比,给出高超声速飞行器再入飞行过程中的气动加热率与气动特性的数值分布,并依据这些数据对再入飞行器进行飞行轨迹的一体化优化设计与总体飞行仿真。     

飞船再入速度和再入角对气动加热率峰值的影响

主要分析了载人飞船再入大气层时主要参数对气动加热率的影响.首先,建立了飞船再入飞行的数学模型,基于再入轨迹的最优化,广泛地研究了大范围的再入速度RV (7 ~10.8 km/s)和再入角RA在不同组合下对加热率的影响,以及在指定加热率峰值的情况下,不同的再入速度对应的极限再入角.经过大量数值仿真和分析得出了相关特性图和再入走廊.     

VTVL高超声速航天飞行器优化气动布局研究

针对垂直起飞、垂直降落飞行器－一种先进的、能重复使用航天飞行器的选型和气动经布局，研究分析了飞行器外形尺寸参数高超声速再入气动性能的影响，给出了优化气动布局，并通过实验验证了布局的正确性，结构实验和理论分析给出了飞行器高超声速气动特性参数。     

考虑弹头滚转姿态变化影响的防热层厚度优化

基于气动热/结构温度响应耦合计算方法,研究了弹头固定攻角再入条件下锥身典型子午面结构温度响应特性,以及滚转姿态变化时刻对各子午面结构温度响应的影响,建立了考虑弹头滚转姿态变化影响的防热层厚度优化方法,并基于该方法开展了弹头防热层厚度优化。最后,研究了滚转姿态变化次数对优化效果的影响。结果表明：在再入弹道前段进行滚转姿态变化可使外壁面气动加热量更为合理,有效降低弹体锥身壳体内壁面温升。当迎、背风面壳体内壁面最大温升约束为25 K时,与无滚转姿态变化状态下相比,滚转姿态变化设计可使防热层厚度减小0.725 mm,减小幅度为5.4%。通过与滚转姿态变化时刻的联合设计可有效降低锥身防热层厚度。与单次滚转姿态变化时相比,两次滚转姿态变化时防热层厚度减小量仅增大1.9%,增加滚转姿态变化次数对优化效果影响较小。     

高温多层碳再入飞行器防热层温度测量

当高性能的再入飞行器以大约每秒6公里的速发进入地球大气层时,气动加热作用会在防热层的外表面产生大约1至3KW/cm~2的传热速率。这种异乎寻常的加热作用使表面温度达到3000K。在执行这些再入飞行器的飞行试验计划的过程中,为了评价再入飞行器的性能和防热层设计的合理性以及气动加热环境,需要防热层的温度数据。在最近的飞行试验中,测量了碳碳防热层内部的温度。该碳碳防热层的结构形式是:将     

尾缘控制措施对开式空腔噪声抑制效果研究

利用基于Menter SST k-ω湍流模型的改进延迟分离涡模拟方法,对开式空腔气动声学特性进行了数值模拟研究,在腔体尾缘采用后壁开孔板加耗能腔的方法进行流动控制。分别研究了在亚声速和超声速来流条件下,所选取的控制措施对气动噪声的抑制效果;利用数值纹影方法等流场分析技术对开式空腔气动噪声的控制机理进行了分析。研究结果表明：亚声速来流条件下,耗能腔尺寸的选择对噪声抑制效果存在较大影响,若耗能腔尺寸过小,不但无法有效抑制腔体内气动噪声反而会使噪声水平大幅升高,最高升幅达12 dB;耗能腔尺寸增加后,腔体内噪声得到抑制,噪声降低幅度随着耗能腔尺寸的增加而增大。超声速来流条件下,所选用的控制措施可以有效地抑制腔体内气动噪声水平,开式空腔内自持振荡循环被终止,各阶模态频率的纯音噪声消失,噪声最高降幅达到23 dB.     

可重复使用低温贮箱热防护系统热传导分析

建立了可重复使用低温贮箱热防护系统的瞬态热传输理论模型，给出了数值计算方法。分析了地面和飞行再入两个阶段热防护系统中的温度分布。在地面阶段，考虑了风速、太阳辐射、地球反射辐射以及空气辐射等对温度分布的作用；在再入返回阶段，主要考虑了气动加热和贮箱外表面辐射对温度分布的作用。本文方法可用于热防护系统的结构优化设计。     

航天飞机轨道器实验(上)

美国国家空间运输系统的定期使用又一次给气动热力学工作者以研究气动热现象的机会，而这种现象只有飞行器在高超音速度飞行条件下进入才会产生。从７０年代中期开始，航天飞机轨道器试验计划将轨道器作为一种再入飞行器进行试验（作为正常任务的附属任务）。由轨道器求试验得出的数据表明，对于升力体再入飞行器，至今的基准超音飞行结果数据是不能用的。这些数据目前正用来验证现代方法（试验方法和计算方法）的整个过程，以模拟或     

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.