准规则生物组织超声背散射信号的仿真

超声背散射信号能提供反映组织微结构的有用信息.本文在原有的生物组织超声背散射信号仿真模型基础上,将影响平均散射元间距(MSS)估计的组织特性具体为4个主要参数,为检测各种平均散射元间距估计方法的性能提供了方便.文中用AR倒谱方法对仿真信号4个参数的合理性进行反向测试,实验结果表明,仿真信号的4个参数能表示影响平均散射元间距估计性能的组织特性.通过仿真信号与人体脾组织的背散射信号以及相关文献中组织信号的比较,证明仿真信号与具有准周期性的生物组织背散射信号基本类似.     

高速轨道超声成像伤损检测及其参数学习方法

针对高速轨道伤损检测问题,提出一种基于0°、37°、70°超声探头探伤的检测方法.该方法基于B型图像显示分析了各伤损的颜色、面积、倾斜角度、长度、质心坐标等特征,并根据其伤损特征的内在逻辑关系设计了检测算法.此外,由于超声成像过程受多种不确定因素的影响,同类伤损的图像特征常出现较大差异而影响检测准确率,为了提高算法检测...     

背散射电子成像技术在氧化铈陶瓷低温烧结研究中的应用

本文成功将背散射电子成像技术应用于观察少量助烧结剂在氧化铈基陶瓷材料中的显微结构与分布形态.结合X射线衍射和能谱分析结果发现,Co基助烧结剂主要以晶格掺杂和晶界第二相的形式存在.当Co掺杂量小于其在氧化铈基陶瓷中的固溶极限时,主要以晶格掺杂的形式存在;当Co掺杂量大于其固溶极限时,多余的Co将以富集相的形式聚集在晶粒晶界上.     

高能X-射线数字平板成像系统中的射线背散射问题探讨

通过实例介绍了高能X-射线数字平板成像系统受射线背散射的影响,并给出解决的办法,供参考。     

基于二阶多项式模型的焊缝缺陷几何量定征技术

为了解决超声TOFD成像难以精确测量缺陷位置及其尺寸的问题,提出了一种基于二阶多项式模型的焊缝缺陷几何量精确定征技术。在分析焊缝缺陷超声TOFD成像特性的基础上建立超声TOFD检测图像的参数化模型,并采用模型与实测数据之间的代数距离作为优化目标函数,将非线性的参数估计转换为线性的矩阵求解问题,在精确获取焊缝缺陷的尺寸及其位置等几何量信息的同时还能够大幅度地提高缺陷几何信息参数的估计效率。仿真与实验结果显示误差均在5%以内,表明了该定征方法的可行性和有效性。     

超声CT成像方法及应用

超声CT(超声层析成像)是指根据物体周围的散射波反演物体内部结构图像的技术。由于超声波具有无电离辐射、对人体无害、设备价格便宜等优点,这一技术广泛应用于生物医学工程、无损检测、地球物理、模式识别等领域。本文介绍了超声CT的基本概念、特点、成像方法及国内外的研究应用现状。     

超声弹性成像对乳腺癌预后因素的预测价值及二者的关系

目的探讨超声弹性成像定性及定量弹性参数与乳腺癌各预后因素之间的联系,及其在评价乳腺癌预后因素中的应用价值。方法回顾性分析479例经手术病理证实为乳腺癌的超声弹性定性、定量参数及病理相关数据并进行相关性分析、差异性分析及预测性能分析和比较。结果肿块大小与VTIQ所得超声定量参数有显著相关性及组间差异性(P<0.05);腋窝淋巴结转移与VTI评分及VTIQ所得SWVMAX、SWVMEAN、SWVratio1及SWVratio2均有显著相关性及组间差异性(P<0.05);将模型2与单独应用定性或定量参数相比,预测效能具有显著差异。结论超声弹性成像定性、定量参数与乳腺癌预后因素之间存在相关性,将定性及定量弹性参数结合能提高乳腺癌预后情况评估的准确性。     

全数字化超声成像系统

本文简要介绍现代全数字化超声成像系统的性能特点和基本工作原理。     

基于超声背散射信号递归分析的金属材料微缺陷识别

为了能有效识别金属材料超声检测信号中的微小缺陷回波,使用递归分析方法对检测信号进行分析。通过对超声波背散射信号进行建模,说明其组成要素。在超声检测信号中,缺陷回波信号会对系统的递归特性产生影响。使用递归分析对含0.8mm平底孔人工模拟缺陷的直径为120mm低碳钢棒材试块实验采集的背散射信号和无缺陷背散射信号进行了研究。截取试块检测信号中的背散射信号部分,通过合理的参数选择对其进行递归分析并绘制递归图。通过与实验采集的无缺陷信号的递归图进行对比,发现缺陷信号会在递归图中产生明显的白色交叉条纹带。使用递归定量分析进一步研究了含缺陷背散射信号的递归特征量,结果表明捕获时间(TT)、确定率(DET)与递归熵(ENTR)这三项特征量对缺陷信号比较敏感,在缺陷位置处均会出现明显的峰值。     

聚合物微结构热辅助超声波压印成形

提出了基于硅模具的热辅助超声波压印成形方法,用于高效率、高精度地复制热塑性聚合物微结构。该方法利用作用于聚合物基片与模具间的超声波振动,快速升高界面温度,以达到聚合物的成形温度。为了降低破坏模具的风险,将模具预热到低于玻璃点转化温度(Tg)以下35℃至50℃之后再施加超声波进行成形。最后,通过正交实验研究了超声振幅、超声波压力、超声波时间、热辅助温度以及聚合物基片厚度对压印结果的影响,揭示了超声波压印工艺的成形机理。实验结果表明,热辅助温度对压印影响最大,其次为超声波振幅,而超声波压力是影响复制均匀性的最重要的参数;薄的聚合物基片在同样的超声波参数和模具结构下更容易成形。通过优化参数,对聚甲基丙烯酸甲酯(PMMA)基片的深度复制精度达到了99%,复制周期小于50s。研究表明,热辅助超声波压印成形效率高,是一种具有批量制造潜力的聚合物微结构成形方法。     

Progressive steps in the development of electron backscatter diffraction and orientation imaging microscopy

Ten years ago electron backscatter diffraction (EBSD) became available to a wider group active in materials research. This paper highlights some of the more significant developments in camera technology and software developments that have arisen since then. The use of slow‐scan charge couple device cameras for phase identification and rapid determination of orientation image micrographs is reviewed. The current limiting spatial resolution of the technique is shown to be less than 10 nm. A procedure for improving lattice spacing measurement by utilizing the full resolution of the camera is described with experimental measurements on silicon and nickel showing relative errors of plus/minus 3%. An investigation of partially recrystallized aluminium shows how the recrystallized fraction can be extracted with confidence but that the mapping of substructure in the highly deformed regions is questionable. Phase identification is described for complex cases in which the phase data tabulated in standard databases do not correspond to what is observed in the EBSD patterns. Phase mapping in a complex mineral in which chemical data and EBSD data are collected simultaneously is shown to be improved by recording both the chemical and the EBSD data into computer memory and proceeding with the phase discrimination and orientation measurement in off‐line analysis.     

Microstructural and microtextural characterization of oxide scale on steel using electron backscatter diffraction

High‐temperature oxidation of steel has been extensively studied. The microstructure of iron oxides is, however, not well understood because of the difficulty in imaging it using conventional methods, such as optical or electron microscopy. A knowledge of the oxide microstructure and texture is critical in understanding how the oxide film behaves during high‐temperature deformation of steels and more importantly how it can be removed following processing. Recently, electron back‐scatter diffraction (EBSD) has proved to be a powerful technique for distinguishing the different phases in scales. This technique gives valuable information both on the microstructure and on the orientation relationships between the steel and the scale layers. In the current study EBSD has been used to investigate the microstructure and microtexture of iron oxide layers grown on interstitial free steel at different times and temperatures. Heat treatments have been carried out under normal oxidation conditions in order to relate the results to real steel manufacturing in industry. The composition, morphologies, microstructure and microtexture of selected conditions have been studied using EBSD.     

门选通技术抑制后向散射分析与实验

分析了大气条件下光学主动成像中的后向散射过程,得出最近后向散射距离是影响后向散射效应的主要因素。通过对最近后向散射距离的分析,得出大视场条件下门选通技术是抑制后向散射的有效方法。利用半导体激光器研制成的主动照明光源在晴朗大气条件下进行主动成像的实验。实验表明门选通成像较普通主动成像有效提高了成像质量,验证了理论分析的正确性和门选通技术的有效性。     

矩阵换能器超声三维成像方法研究*

针对常规超声检测难以直观地显示被检对象缺陷的形状及走向等问题,开展矩阵换能器超声三维成像方法研究。超声三维成像技术具有直观显示被测对象内部缺陷三维特征的优点,基于矩阵换能器的超声三维成像方法具有扫查速度快、分辨率高等优点,是当前超声三维成像技术的研究热点。本文介绍了矩阵换能器体扫查原理及其控制方法;提出了矩阵换能器体扫查时三维体数据采集方法和数据融合算法;基于矩阵换能器和相控阵板卡系统对铝标样等试样进行了体扫查检测实验,采用等值面和体绘制两种算法对缺陷进行三维成像,并对单一缺陷进行了定量分析,定量精度较高。研究结果表明,矩阵换能器超声三维成像方法能够表征缺陷的三维形貌特征,在无需移动换能器的情况下便可实现缺陷三维检测,是超声三维检测的有效方法。     

Machinability of ultrasonic vibration-assisted micro-grinding in biological bone using nanolubricant

Bone grinding is an essential and vital procedure in most surgical operations. Currently, the insufficient cooling capacity of dry grinding, poor visibility of drip irrigation surgery area, and large grinding force leading to high grinding temperature are the technical bottlenecks of micro-grinding. A new micro-grinding process called ultrasonic vibration-assisted nanoparticle jet mist cooling (U-NJMC) is innovatively proposed to solve the technical problem. It combines the advantages of ultrasonic vibration (UV) and nanoparticle jet mist cooling (NJMC). Notwithstanding, the combined effect of multi parameter collaborative of U-NJMC on cooling has not been investigated. The grinding force, friction coefficient, specific grinding energy, and grinding temperature under dry, drip irrigation, UV, minimum quantity lubrication (MQL), NJMC, and U-NJMC micro-grinding were compared and analyzed. Results showed that the minimum normal grinding force and tangential grinding force of U-NJMC micro-grinding were 1.39 and 0.32 N, which were 75.1% and 82.9% less than those in dry grinding, respectively. The minimum friction coefficient and specific grinding energy were achieved using U-NJMC. Compared with dry, drip, UV, MQL, and NJMC grinding, the friction coefficient of U-NJMC was decreased by 31.3%, 17.0%, 19.0%, 9.8%, and 12.5%, respectively, and the specific grinding energy was decreased by 83.0%, 72.7%, 77.8%, 52.3%, and 64.7%, respectively. Compared with UV or NJMC alone, the grinding temperature of U-NJMC was decreased by 33.5% and 10.0%, respectively. These results showed that U-NJMC provides a novel approach for clinical surgical micro-grinding of biological bone.     

超声检测并联机器人位姿分析研究

针对多自由度超声检测机器人检测曲面工件时位姿调整困难问题,通过分析超声检测并联机器人的运动学模型,提出了超声背散射检测与并联机器人一体化技术。以实现超声检测探头姿态的特殊控制要求为目标,对检测并联机器人建立了数学模型,提出了一种位姿控制计算方法,并利用Matlab对位姿控制进行了仿真分析,为计算机控制检测探头进行曲面检测提供准确的控制参数。通过超声C扫查实验,对比了超声图像中噪声所占的面积比例和图像轮廓清晰度。实验结果表明,超声检测并联机器人在提高超声探头的位姿控制精度后,能够降低噪声,提高信噪比。     

缺陷散射对相控阵超声全聚焦成像的影响研究

相控阵超声全聚焦成像充分利用了检测信号,具有成像精度高、可进行缺陷识别等特点,是未来最具应用前景的相控阵成像算法之一。然而,目前相控阵超声全聚焦成像仍不能实现缺陷的高分辨率成像,无法对缺陷进行准确的定性、定量分析。为此,采用有限元仿真相控阵传感器的全阵列采集(FMC)过程,在全矩阵数据的基础上设计全聚焦成像程序,对圆孔和裂纹两种典型缺陷进行TFM成像,研究典型缺陷的TFM成像规律,从缺陷散射的角度分析影响相控阵超声全聚焦成像的因素。结果表明,实际检测中相控阵超声传感器只能接收到缺陷的部分散射信息,而相控阵超声在缺陷处的散射场分布与缺陷的类型、尺寸、角度及入射波类型、入射角度等因素有关,因此能否接收到缺陷散射的主要能量是影响全聚焦成像精度的关键。     

Quantitative analysis of martensite and bainite microstructures using electron backscatter diffraction

In the present work, ultra‐high‐strength steels with multiphase microstructures containing martensite and bainite were prepared by controlling the cooling rate. A new approach was proposed for quantitatively statistical phase analysis using electron backscatter diffraction (EBSD) based on the band contrast which correlates to the quality and intensity of the diffraction patterns. This approach takes advantage of the inherently greater lattice imperfections of martensite, such as dislocations and low‐angle grain boundaries, relative to that of bainite. These can reduce the intensity and quality of the EBSD patterns of martensite, which decrease the band contrast. Thus, combined with morphological observations, Gaussian two‐peak fitting was employed to analyze the band contrast profile and confirm the ranges of band contrast for the two phases. The volume fractions of bainite and martensite in different samples were determined successfully. In addition, the results show that increased cooling rates improve the proportion of martensite and the ratio of martensite to bainite. Microsc. Res. Tech. 79:814–819, 2016. © 2016 Wiley Periodicals, Inc.