金属材料小缺陷超声反射信号建模及识别

为了能从含噪声金属材料超声检测信号中有效识别出微小缺陷回波,建立了金属材料超声反射信号模型并提出了基于相关系数的微小缺陷回波识别方法。对含微小缺陷金属材料超声脉冲反射信号的成分进行分析,建立了基于散射声场与高斯回波理论的优化超声回波模型。设计了超声缺陷回波位置识别方法。该方法对超声脉冲反射信号去噪后,取探头发射脉冲信号为参考信号;然后与去噪后的信号逐段求解相关系数;最后对该相关系数序列进行阈值化处理,获得缺陷回波在超声回波信号中的位置。将利用上述优化超声回波模型生成的超声反射信号及其频谱与实验获得的金属材料超声反射信号及其频谱进行了对比,结果表明:两者的时频域特征具有一致性。当将阈值设定为相关系数序列最大值的60%时,能够有效从超声背散射信号中识别出金属材料微小缺陷回波。     

微环厚度对垂直入射超声脉冲反射波影响分析

研究微环厚度对垂直入射超声脉冲反射回波影响对水泥声阻抗类测井仪器的固井质量评价方法具有一定的指导意义。基于超声脉冲反射测井原理,采用有限元分析方法数值模拟了水泥环材料一定,中心频率为250、350kHz及450kHz的声源,微环厚度从0~0.6mm范围内变化时的第I界面水泥声阻抗;数值模拟了声源中心频率一定,水泥环分别为低、中、高3种不同声阻抗材料时,不同微环厚度随第I界面水泥声阻抗的变化关系。数值研究结果表明,随着声源的中心频率增加,微环对固井质量评价产生影响时的临界微环厚度减小;对于特定频率的声源,随着水泥环声阻抗的升高,微环对固井质量评价产生影响的临界微环厚度增加。采用多功能超声成像测井仪在标准微环厚度的刻度井中进行了水泥声阻抗的测量,实测结果表明,微环厚度随水泥声阻抗的变化规律与数值模拟的结果相吻合。     

主动超声引信回声干扰与对策

介绍了主动超声引信在水下装备中的应用和特点，分析了主动超声引信的4种主要的回声干扰形式，针对不同的干扰形式提出相应的抗主动超声回声干扰的软件算法和硬件处理对策。     

Observing proton motion on the nanoscale in polymeric electrolyte membranes with quasielastic neutron scattering

The mechanism of proton conductivity in high temperature polymer electrolyte fuel cells (HT-PEFCs) has been investigated with macroscopic conductivity measurements and on a microscopic scale with quasielastic neutron scattering techniques. Polybenzimidazole membranes, which are used in HT-PEFCs, are doped with phosphoric acid (PA) to achieve the desired proton conductivity. Neutron spin echo experiments showed that the polymer matrix is very rigid incoherent scattering experiments, but incoherent scattering revealed rather fast diffusion processes, compatible with macroscopic conductivity measurements. The measured diffusion is faster than anticipated from the conductivity of a phosphoric acid doped PBI membrane, but slower than that expected for pure phosphoric acid. Over larger distances the fractal polymer membrane network slows down the locally fast diffusion to the macroscopic values. With elastic fixed window scans on a backscattering spectrometer an activation energy of 7.6 kJ/mol is obtained at typical conditions in an HT-PEFC.     

Heuristic dynamic programming using echo state network as online trainable adaptive critic

The present paper proposes an implementation of a relatively new recurrent neural network architecture—the echo state network (ESN)–within the frame of heuristic dynamic programming. The ESN is trained online to estimate the utility function and to adapt the control policy of an embodied agent. With the advantage of an easy training algorithm, the ESN architecture offers a simple way to calculate the derivatives required for adapting the controller. Experimental results are provided to validate the proposed learning approach. Copyright © 2012 John Wiley & Sons, Ltd.     

基于经验模板匹配算法的无线电引信探控模型

针对目前无线电近炸引信仿真中有限元分析法计算周期较长且无法直接给出引信终端信号的不足,以物理光学法、绕射理论为理论基础,结合交会条件解析引信探测状况,以平面、尖劈、孔径、台阶等单元散射模型为模版进行快速匹配,得到引信终点弹道段探测与控制功能工程化快速计算模型。通过试验数据的对比表明:在计算效率得到保证的同时,计算结果与实测数据具有较好的一致性。     

浅谈GPS结合回声测深仪在水下地形测量中的应用

本文介绍了GPS-RTK结合回声测深仪进行水下地形测量的原理,结合工程实践,分析了该方法在工程实践应用中的作业方法和注意事项,并与传统测量进行了比较,总结了GPS结合回声测深仪在水下地形测量中的优点。     

目标航迹的快速起始

为解决近程搜索跟踪系统对空中目标的快速锁定,分析了目标回波的特点,通过对目标回波进行的预处理,包括点迹的稳健凝集、副瓣和辅助质心的消除,提高了数据质量,减少了后续处理的工作量,为航迹快速起始奠定了基础。给出了目标航迹快速起始的2种方法:两点起始和三点起始航迹。建立的模型和采用的方法在多个工程项目中进行了应用,达到了快速起始的目的。     

对抗型长短期记忆网络的雷达回波外推算法

目的 雷达回波外推是进行短临降水预测的一种重要方法,相较于传统的数值天气预报方法能够实现更快、更准确的预测。基于卷积长短期记忆网络（convolutional long short-term memory network,ConvLSTM）的回波外推算法的效果优于其他的深度学习外推算法,但是忽略了普通卷积运算在面对局部变化特征时的局限性,并且在外推过程中将损失函数简单定义为均方误差（mean squared error,MSE）,忽略了外推图像与原始图像的分布相似性,容易导致信息丢失。为解决以上不足,提出了一种基于对抗型光流长短期记忆网络（deep convolutional generative adversarial flow based long short-term memory network,DCF-LSTM）的回波外推算法。方法 首先,采用光流追踪局部特征的方式改进ConvLSTM,突破了一般卷积核面对局部变化特征的限制。然后,以光流长短期记忆网络（flow based long short-term memory network, FLSTM）作为基本模块构建外推模型。最后,引入对抗网络,与外推模型组成端到端的博弈系统DCF-LSTM,两者交替训练实现外推图像分布向原图像分布的拟合。结果 在4种不同的反射率强度下进行了消融研究,并与3种主流的气象业务算法进行了对比。实验结果表明,DCF-LSTM在所有评价指标中表现最优,尤其在反射率为35 dBZ的条件下。结论 由实验结果可知,引入光流法能够使模型具有更好的抗畸变性,引入深度卷积生成对抗网络（deep convolutional generative adversarial network,DCGAN）判别模块能进一步增加结果的准确性。本文提出的DCF-LSTM回波外推算法相比于其他算法,雷达外推准确率获得了进一步提升。     

Comparison of NDT techniques on a post-tensioned beam before its autopsy

Following the complete demolition of a prestressed concrete bridge in southern France, a suspected weak post-tensioned beam was retained for non-destructive testing (NDT). Ground penetrating radar, Ferroscan^® (covermeter), gamma-ray radiography and impact-echo methods have all been tested and their results then discussed after the autopsy of the beam by means of hydro-demolition.

This paper describes the extent to which NDT surveys are able to respond to the needs of structural engineers, through the use of complementary NDT approaches. The introduction of a second technique should provide a more pertinent response while eliminating certain ambiguities either by improving measurement reliability or by focusing on questionable zones to obtain more precise local measurements.

Afterwards, the problems still not adequately resolved by these techniques are pinpointed. This step concludes with the set of needs heretofore unmet by such techniques.