电磁超声水平剪切导波的缺陷检测研究进展

超声导波检测技术是新型的无损检测方法之一。水平剪切(SH)导波是超声导波的一种。在板和管结构的检测中，SH导波检测技术占据着越来越重要的位置。电磁声传感器(EMAT)常被用于SH导波的激励或接收。SH-EMAT具有适应性强、效率高的特点，基于SH-EMAT检测技术的应用场景越来越多。以近十几年的相关文献为基础，介绍了SH-EMAT设计以及SH导波缺陷检测技术的研究现状和进展，提供了SH导波检测在不同应用背景下的传感器选择，总结了不同频率SH导波的检测能力，分析了不同SH导波检测技术的优缺点。同时还对电磁超声水平剪切导波检测的未来研究趋势进行了展望，为相关研究人员提供了研究方向和思路。     

超声波气体流量测量系统的实现

超声波气体流量计因为其具有许多优点,在工业上获得越来越广泛的应用。超声波气体流量测量需应用一种新的流量测量技术,因为超声气体流量计工作在噪声较强的场合,且信号微弱。超声波气体流量计信号不能用传统的方法检测,在此,数字平均技术及相关技术得到应用,数字平均技术可使信号得到加强,相关技术可使渡越时间测量更精确,流量测量精度可达±2%。     

超声信号的非线性行为及应用

超声波检测技术广泛地应用于材料与设备的无损检测中.而表征材料与设备性能和缺陷信息的超声回波信号由于与传输介质、缺陷相互作用,再加上各信道中不同种类的噪声介入,变得非常复杂.充分理解和认识超声信号中的非线性行为,对材料和缺陷检测与评估有重要意义.本文以海底管道检测为背景,以缺陷的脉冲超声回波信号为研究对象,通过替代数据法和统计特征量方法,从时域的角度检验了超声信号中的非线性行为特性.通过大量的试验数据分析表明,超声信号中存在明显的非线性行为,而且这种非线性不是由测量过程中测量函数引起,而是由系统本身产生的,即由超声波与目标体相互作用而产生.论文还就超声信号中蕴涵的非线性特征的应用和前景进行了分析和展望.为更深入地认识和利用这些超声信号提供了一种手段.     

多层复合材料超声检测的数值模拟

介绍了超声反射法的基本原理及其特点,并利用有限元方法对超声检测过程进行了数值模拟。通过对接收信号的分析,可以看出超声波检测复合材料检测精度较高,检测效果较明显,可以准确地识别出是否存在缺陷以及判断出缺陷的位置。     

超声电机及其在机器人驱动中的应用

声波电机(Ultrasonic Motor,简称USM)是一种近二十年来发展起来的一种利用超声波振动能作为驱动源的新原理电机.以行波型超声电机为例,介绍超声电机原理结构、特点及其驱动控制技术,并以超声电机驱动的二轴机械臂控制系统为例子介绍超声电机在机器人控制、执行中的应用.     

High-resolution ultrasonic spectroscopy for analysis of industrial emulsions and suspensions

This article describes the application of high-resolution ultrasonic spectroscopy (HR-US) for the analysis of industrial emulsions and suspensions. The benefits of HR-US are discussed, including the ability to perform a direct analysis of emulsions and suspensions, which would otherwise be impossible, require significantly more effort in the laboratory, or produce erroneous results. The HR-US 102 spectrometer is also introduced. Manufacture of this laboratory-scale instrument is now possible due to recent technological advances in HR-US. The article outlines the principles of the HR-US technique and illustrates the application of the HR-US 102 spectrometer for analysis of absorption of ligands on the surface of particles, thermal stability, and effects of thermal history on microstructure of emulsions, crystallization, and particle sizing in diluted and concentrated emulsions.     

基于经验模式分解的骨密度参数检测

轴向定量超声法诊断骨质疏松症成本低、辐射小、检测能力强,已成为一种检测骨密度的简便、有效方法.根据超声在长骨中轴向传播特性,定量超声在长骨中的传播速度可以表征人体的骨质状况.本系统通过自行研发的数据采集模块采集超声信号,然后通过改进的信号处理方法滤去噪声,提取出超声在长骨中的传播速度,成功实现并优化了骨密度参数检测方法...     

Input/output lot sizing in single stage batch production systems under constant demand

This paper develops an integrated input/output lot sizing model under deterministic conditions for a single product manufactured within a batch production environment. Our analysis incorporates the effects of work-in-process inventories resulting from multiple input items that are converted to output at finite rates in a single stage process and encompasses, simultaneously, the lot sizing decisions for the end product, as well as the externally procured input items. The resulting model represents a nonlinear mixed integer optimization problem, for which an efficient heuristic solution technique is suggested.     

一种动态检测土粒度核子分析仪的研究

研制了一种动态检测土粒度核子分析仪.该分析仪的检测原理是将被测土颗粒放在样桶中经搅拌充分分散,并加入分散剂,然后利用137Cs发射γ射线在样桶一定深度处水平照射样桶,该处悬浮液的密度逐渐减小,分析仪检测出悬浮液密度p与时间t的关系,根据Stokes原理和土工试验方法标准(GB/T50123-1999),微型计算机系统分...     

巨电致伸缩共聚物P(VDF-TrFE)超声传感器的研制

设计制作了以电子辐照的共聚物P(VDF-TrFE)为工作单元的巨电致伸缩超声传感器,通过去耦合电路的保护,测试了不同偏置电压下近场和远场的响应频率和带宽,分析了诱导压电常数随外电场的变化,合理的解释了正负偏压下的波形翻转现象.这样就把电子辐照P(VDF-TrFE)共聚物材料的应用频率范围提高到超声领域,为进一步研制相关巨电致伸缩超声传感器提供了参考.     

Acoustophoresis of hollow and core-shell particles in two-dimensional resonance modes

Motivated by the applications of ultrasonic particle manipulation in a biotechnological context, a study on acoustophoresis of hollow and core-shell particles is presented with analytical derivations, numerical simulations and confirming experiments. For a long-wavelength calculation of the acoustic radiation forces, the Gor’kov potential of hollow, air-filled particles and particles with solid or fluid core and shell is derived. The validity as well as the applicable range of the long-wavelength calculation is evaluated with numerical simulations in Comsol Multiphysics^®. The results are experimentally verified in the acoustic field of an intrinsically two-dimensional fluid resonance mode, which allows for a more complex analysis than the common one-dimensional ultrasonic standing waves or their superposition to two-dimensional fields. Experiments were conducted with hollow glass particles (13.9 μm diameter) in a microfluidic chamber of 1.2 mm × 1.2 mm × 0.2 mm on a silicon-based device with piezoelectric excitation around 870 kHz. The described resonance mode is of additional interest for particle trapping and medium exchange on certain particle types, and it reveals a novel approach for particle characterization or separation.     

基于神经网络的超声导波管道缺陷识别

在役石油管道的腐蚀是造成石油管线运输故障的重要原因,适时检测在役管道是否被腐蚀至关重要。研究了超声导波进行长距离在役管道检测技术,并利用人工神经网络进行管道缺陷的智能识别,通过超声导波设备进行了管道缺陷检测实验,从原始检测数据的信号处理结果中提取出了样本特征值,并建立和训练了一种用于实现管道缺陷识别的BP神经网络。实验表明:使用该网络可进行超声导波管道缺陷的自动识别。     

基于超声导波的骨损伤检测技术

对骨损伤尤其是轻微骨裂的现场检测往往依赖于经验,缺乏可靠的现场测试技术。针对这一问题,对基于超声导波的骨损伤现场诊断应用技术进行了基础研究。分析了管状结构中的导波传播特性,根据骨损伤对导波传播影响,研究采用导波能量衰减曲线检测和定位骨损伤的发生情况;在仿生骨结构试件上进行了实验验证,对比健康和损伤骨结构中的导波传播能量衰减情况,可以较清晰地观察到骨损伤的发生和大致位置。实验结果表明,超声导波技术可以应用于骨损伤现场快速诊断中,具有较好的实用性。     

巨电致伸缩共聚物P(VDF2TrFE) 超声传感器的研制

设计制作了以电子辐照的共聚物P(VDF2TrFE) 为工作单元的巨电致伸缩超声传感器,通过去耦合电路的保 护,测试了不同偏置电压下近场和远场的响应频率和带宽,分析了诱导压电常数随外电场的变化,合理的解释了正 负偏压下的波形翻转现象。这样就把电子辐照P(VDF2TrFE) 共聚物材料的应用频率范围提高到超声领域,为进一 步研制相关巨电致伸缩超声传感器提供了参考。     

A model for transient ultrasonic field in solid generated by a transducer in immersion

A model has been developed which can be used to calculate the particle velocity waveforms at arbitrary positions in a solid immersed in a fluid when irradiated by a transmitting transducer, launching a short pulse of a longitudinal wave into the fluid. Mode-converted longitudinal and shear waves are generated at the interface between the solid and the fluid. Calculations performed agree well with the results of experimental measurements using a specially constructed miniature piezoelectric receiving probe. The model constructed has been used to explain the radiation of a transmitting transducer into an immersed solid and it can be used for the optimal design of a transducer and ultrasonic NDT device in immersion mode, that has been widely used for ultrasonic imaging and automatic inspection.     

一种面向分布式深度学习系统的资源及批尺寸协同配置方法

如何在受限时间内满足深度学习模型的训练精度需求并最小化资源成本是分布式深度学习系统面临的一大挑战.资源和批尺寸超参数配置是优化模型训练精度及资源成本的主要方法.既有工作分别从计算效率和训练精度的角度,对资源及批尺寸超参数进行独立配置.然而,两类配置对于模型训练精度及资源成本的影响具有复杂的依赖关系,既有独立配置方法难以...     

统计分析法及其在精度仿真中的应用研究

计算机化的统计分析方法在飞行器的研制和定型过程中有着重要的作用。本文论述了三种统计分析方法：蒙特卡洛法、统计协方差法和伴随系统（反演）法，并探讨了它们在命中精度数字仿真的应用研究。     

机器人视觉伺服系统的标定

机器人视觉伺服系统是机器人领域一项重要的研究方向,它的研究对于开发手眼协调的机器人在工业生产、航空航天等方面的应用有着重要的意义。本文针对机器人视觉伺服系统的特点,对典型的标定算法进行了分类和比较,最后对标定方法进行了总结。     

Evaluating low-cost spectrometer designs for utility in reflectance and transmittance applications

Recent advances in low-cost microprocessors and sensors have allowed for the development of low-cost spectrometers for public experimentation and education outreach. In the context of the present paper and other recent research, low-cost spectrometers are important remote sensing instruments for numerous applications in citizen science and education. We built five spectrometer designs then tested them for absorption using concentrations of fluids and reflectance using colour swatches and minerals found on Mars as well as other materials possessing a high near infra-red (NIR) reflectance. These results were then compared with a laboratory grade spectrometer. We found that while all spectrometers produced meaningful results during the fluid concentration tests, there were considerable differences in accuracies between home-made instruments during the reflectance testing. Two spectrometer designs were identified that produced useful results for a range of low-cost scientific applications.     

分离谱法在超声信号处理中的应用

在超声无损检测中，由于某些特殊材料(如离心铸造的不锈钢、碳纤维复合材料等)组织结构比较复杂，所得到的超声回波信号会受到较强的结构噪声干扰，信噪比较低，严重影响了缺陷信号的识别。结合相关课题讨论了分离谱法在消除结构噪声方面的应用，实验结果表明，该方法可以得到良好的滤波效果。