长期热老化下一种PBX的拉伸性能和蠕变性能（英文）

利用单轴拉伸试验和数小时下的拉伸蠕变试验评定了在长期热老化下作用下某PBX的力学性能。试验用的哑铃型样品分别在45,55,65℃和75℃下贮存了36个月。拉伸试验在45℃下进行,贮存了6个月和36个月的样品的拉伸蠕变试验也在45℃下进行。结果显示,与原始样品相比,45℃下,样品的拉伸强度和拉伸模量在长期热老化后没有明显变化,但是除75℃下的老化样品,其余样品的蠕变断裂时间均大大延长。通过扫描电镜观察并结合粘结剂的接触角分析,提出,在55℃以下,该PBX的力学失效是由热流变机制控制的,而高于55℃时,炸药晶体和粘结剂界面之间的热应力失配起到了关键作用。同时也表明,低于75℃下的长期贮存有助于改善PBX的蠕变性能,延长其蠕变断裂时间。     

热老化对TATB基高聚物粘结炸药力学性能的影响

对某TATB基高聚粘结炸药(PBX)进行了55～75℃加速老化试验,并对老化前后的样品进行了不同温度下压缩性能、拉伸性能和弯曲蠕变实验,用扫描电子显微镜对老化前后炸药高温拉伸断口形貌进行了观察。结果表明:长期高温贮存后,TATB基高聚物粘结炸药晶体与粘合剂仍具有良好的粘合界面,其模量、破坏强度、破坏应变和稳态蠕变速率等力学性能指标均未发生明显的变化。     

F2314氟树脂在老化过程中的结晶度变化及其对力学性能的影响研究

对F2314氟树脂及以F2314为粘结剂的高聚物粘结炸药(PBX)进行了老化试验,老化前后检测了F2314的结晶度、贮存模量、损耗因子及以F2314为粘结剂的PBX的力学性能.结果表明F2314氟树脂在老化后结晶度升高,进而导致F2314在老化后贮存模量升高,损耗因子降低,以F2314为粘结剂的PBX在老化后其压缩强度和压缩模量也略有升高;但以F2314为粘结剂的PBX在老化后其拉伸强度和拉伸模量呈现下降的趋势,这也有可能是由于F2314结晶后其粘结性能变差导致界面作用减弱引起的.     

TATB基PBX及其改性配方的蠕变性能

为探讨粘结剂组成对TATB基高聚物粘结炸药(PBX)蠕变性能的影响,用电子万能试验机和动态力学分析仪分别研究了TATB基PBX及其改性配方的拉伸、压缩和三点弯曲蠕变行为。结果表明,加入高玻璃化转变温度和高力学强度的增强剂苯乙烯共聚物可改善TATB基PBX的抗蠕变性能。改性配方的蠕变应变降低,蠕变破坏时间延长。由50 ℃/3 MPa下拉伸蠕变、70 ℃/10 MPa下压缩蠕变以及70 ℃/6 MPa下三点弯曲蠕变试验所得原配方的破坏时间分别为14,12.7,12 min,而同样条件下,改性配方未发生蠕变破坏。根据时温等效原理,获得TATB基PBX及其改性配方在参考温度60 ℃下的蠕变柔量主曲线。与原配方相比,TATB基PBX改性配方的蠕变柔量主曲线向下偏移,抗蠕变性能提高。     

TATB基高聚物粘结炸药高温力学性能

为分析TATB基高聚物粘结炸药(PBX)在高温状态下的性能变化,对该高聚物粘结炸药在不同温度下的压缩性能、拉伸性能、蠕变性能及泊松比进行了测试,并采用扫描电子显微镜对其高温蠕变断面形貌进行了观察。结果表明,该高聚物粘结炸药的压缩强度、拉伸强度、抗蠕变持久应力及持久时间均随温度升高而降低,其泊松比随温度升高无明显变化; 在高温70 ℃、拉伸应力为3 MPa下,该PBX拉伸蠕变破坏模式主要为炸药颗粒与粘结剂脱粘,而在相同拉伸应力、温度为50 ℃和60 ℃下,其拉伸蠕变破坏模式还表现为炸药颗粒断裂。     

高聚物粘结炸药老化模型比较分析

概述并分析了Arrhenius、时间温度叠加原理和神经网络三种高聚物粘结炸药(PBX)老化模型的建立方法,利用上述方法对HMX基PBX在45～75℃下老化后的质量变化数据建模并预测寿命.上述三种方法预测该炸药在20℃下质量损失0.1％的贮存寿命分别为390 a、490 a和15.2 a.三种方法预测该炸药在50℃和60...     

热老化及辐照对TATB基PBX热膨胀性能的影响

为了掌握TATB基高聚物粘结炸药(PBX)件受热及辐照环境影响后的尺寸稳定性情况,研究了该PBX经高温老化、γ及中子辐照实验后的热膨胀性能。结果表明,经高温55℃、65℃和75℃老化60 d后,该TATB基PBX热膨胀系数出现了下降,且热老化温度越高,热膨胀系数越小,但经一定条件下的γ及中子辐照环境试验后,其热膨胀性能却无明显变化。     

时间-温度-应力等效原理在TATB基PBX拉伸蠕变中的适用性分析

为验证时间-温度-应力原理在TATB基PBX拉伸蠕变中的适用性,实现长期拉伸蠕变变形评估计算,开展了某TATB基PBX恒应力不同温度的常规拉伸蠕变实验和恒温度梯级拉伸蠕变实验,采用陈氏法对梯级加载蠕变曲线进行分解处理,得到恒温度不同应力的拉伸蠕变曲线,基于非线性粘弹性材料的时间-温度-应力等效原理,采用二分法计算程序对各蠕变柔量曲线进行了平移汇集,获得了参考温度和应力（30 ℃、3.0 MPa）下的温度应力耦合蠕变柔量主曲线和考虑温度和应力的Williams-Landel-Ferry方程参数。结果表明在所分析的温度范围（30~50 ℃）和应力范围内（1.0~5.5 MPa）,TATB基PBX的拉伸蠕变行为较好地符合时间-温度-应力等效原理描述,可以利用该原理通过高温度高应力的PBX短期拉伸蠕变实验预测其低温低应力的长期拉伸蠕变变形。     

高温及机械应力对PBX力学行为的影响规律及机理分析

为了获得高温和机械应力对高聚物粘接炸药(PBX)力学行为的影响规律,基于材料试验机的结果获得了以HMX为基的PBX-1及以TATB为基的PBX-2在不同高温和机械应力作用下的力学响应规律,用动态热机械分析仪(DMA)和扫描电子显微镜(SEM)分析了它们的力学性能的变化机理。结果表明,在25~90℃高温-力耦合加载下,两种PBX的拉伸、压缩强度随温度升高而降低,但破坏应变在一些温度点产生突变,PBX-1的应变突变温度点约为65℃,PBX-2分别约为35、55℃和75℃;PBX-1的高温-力顺序加载响应规律包含两个温度段,25~150℃为第一阶段,该范围的高温作用下材料压缩强度和破坏应变几乎不会变化,150~200℃为第二阶段,破坏应变随温度升高而增大,压缩强度先减小后增大,在180℃最低。高温-力耦合作用下,粘结剂相态变化和粘弹特性改变是影响PBX高温软化和力学性能劣化的主要原因,其软化-流动-粘流化将引起PBX的变形行为特别是拉伸及压缩破坏应变的突变,同时导致PBX破坏模式由脆断向脱粘失效转变,PBX的突变温度与粘结剂的物态转变温度相对应。对于高温-力顺序加载,粘结剂弹性回复和炸药晶体无损伤是PBX-1在25~150℃力学性能不变的主要原因,炸药晶体在180℃附近会发生高温破碎,导致PBX-1的压缩强度在180℃附近达到最低值。     

拉剪复合试验测试炸药晶体/粘结剂界面力学特性

为了研究高聚物粘结炸药(PBX)中炸药晶体/粘结剂界面的力学特性,设计了一种可实现0°、15°、30°、45°、60°、75°及90°共7个角度拉伸的拉剪复合加载夹具,实现了PBX界面单轴拉伸、纯剪切及拉剪复合作用的多状态加载。制备了用于拉剪复合试验的模拟界面,开展了拉剪复合试验测试炸药晶体/粘结剂界面力学特性的方法研究。结果表明,PBX界面的剪切破坏载荷为0.980 MPa,大于拉伸破坏载荷0.759 MPa,随着加载角度的增加,拉应力不断降低,剪应力不断增加,而复合应力随加载角度的增加线性增大。提出了一种椭圆模型用于描述PBX界面的强度相关性规律:σ~2/a~2+τ~2/b~2=1,该模型可以较好地描述PBX中炸药晶体/粘结剂界面的拉剪强度特性。     

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.     

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 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.     

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.