电磁声(EMA)检测技术的研究、开发与工程化

本文概述了近年来EMA技术的研究、开发与工程化的进展情况。从中可以看出：EMA检测技术已进入了工程应用阶段。特别是在冶金工业中,它的应用已趋成熟。在机械制造、能源和铁道运输工业中,也开始进入了工程应用阶段。但其基础性研究工作,尚待努力加强。     

涂层厚度与粘接质量的电磁声谐振无损检测

为了解决电磁超声(EMAT)涂层质量检测中接收信号信噪比较低的问题,将电磁声谐振技术(EMAR)应用于涂层质量检测,有效提高了超声接收信号的信噪比。在EMAR仿真中,通过变步长离散仿真得出了谐振与非谐振状态下的时域波形和频谱图,验证了利用电磁声谐振进行涂层质量检测的可行性。以电磁超声谐振驻波作为检测信号,实验中谐振信号的幅值为未谐振反射回波的2.52倍,信噪比由26 dB(反射回波)提高到34 dB(谐振信号)。利用EMAR信号的谐振频率差进行涂层厚度检测,对0.2~0.8 mm的试件的检测误差在5%以内且涂层厚度越大,谐振频率越多,谐振频率差越小,检测精度越高;通过功率谱密度函数(PSD)表征不同粘接程度的试件,不同试件的PSD比值为61.17:4.15:1,区分度相对于峰峰值比值提升明显。     

薄板声谐振子扰动的声学特征检测研究

为进行快速ＮＤＴ,研究了薄板声谐振子扰动和声学特征变化的关系,用有限元方法分析在睡无缺陷薄板的振动频率和振型。利用数字信号处理技术,实验研究了样品中缺陷对声学特征的影响。实现和理论分析结果一致性很好。研究结果有助于正确利用样品声学特征进行无损检测。     

无人机系统强电磁环境效应检测技术

对电子系统强电磁环境实验效应检测技术研究现状进行了系统的研究分析,提出通过对内部电路节点电压信号实时监测实现无人机电子系统强电磁环境效应检测判断的方法。设计了以阻抗变换和电光转换电路为核心的光纤输出型电压探头,实现1 M高输入阻抗、DC 450 MHz带宽、数百m传输距离等技术要求。在无人机系统强电磁脉冲环境实验中利用所设计的电压探头实现了无人机舵机、飞控、链路等电路节点工作电压信号波形的远程监测,获取了无人机电路节点耦合的电压脉冲波形。     

无人机系统强电磁环境效应检测技术

对电子系统强电磁环境实验效应检测技术研究现状进行了系统的研究分析,提出通过对内部电路节点电压信号实时监测实现无人机电子系统强电磁环境效应检测判断的方法。设计了以阻抗变换和电光转换电路为核心的光纤输出型电压探头,实现1 M高输入阻抗、DC 450 MHz带宽、数百m传输距离等技术要求。在无人机系统强电磁脉冲环境实验中利用所设计的电压探头实现了无人机舵机、飞控、链路等电路节点工作电压信号波形的远程监测,获取了无人机电路节点耦合的电压脉冲波形。     

电磁声实验平台的研制与实验研究

研制了一个多功能的电磁声实验平台,在此实验平台,进行了     

电磁防护技术发展综述与展望

针对复杂电磁对抗环境中电子信息装备面临的强电磁环境威胁以及防护加固需求,对强电磁防护技术的发展现状进行了综述,并提出了强电磁系统级综合防护的发展展望。强电磁防护是为了保证电子信息装备在强电磁环境中免受损伤或损毁的技术手段,从电磁波的耦合途径分析了当前电磁防护的重点和难点,然后分别以限幅器技术、频率滤波技术、能量选择防护技术三个方面对前门防护技术的发展现状进行了分析总结,最后从新型屏蔽材料和防护器件两个方面对新型电磁防护技术进行了展望,并从前后门一体防护、场路一体防护、多域联合防护三个角度对系统级电磁防护进行了总结,为电子信息装备在复杂电磁环境下的电磁防护加固设计提供了支撑。     

’94北京检测技术交流会在京召开

由北京机械工程学会无损检测分会、中国声学学会检测声学分会、中国机械工程学会无损检测分会超声专业委员会和促进无损检测器材发展工作委员会联合主办,北京NDT技术交流中心承办的“’94北京检测技术交流会”于1994年10月8日一10日在北京国际会议中心隆重召开．这是无损检测学会与声学检测学会第一次在北京联合召开的全国性大规模学术交流会,也是第一次由从事无损检测与声学检测两个方面的科技工作者联合参加的检测技术交流会．出席大会的代表近200人．大会共收到论文110篇．特邀大会报告6篇：中科院院士应崇福先生的“激光超声研究与…     

利用光差分技术检测激光激发声表面波定征薄膜材料

利用激光激发声表面波及改进的光差分检测技术,研究沉积在基片表面的薄膜样品的特性和参量。根据实验获得的声色散曲线和基片已知参数,结合层状媒质中声表面波传播理论,拟合得到薄膜材料的弹性模量、密度和厚度等物理量。结合扫描电子显微镜和X光衍射结果分析,并与文献值比较,表明所采用的技术是定征薄膜材料的弹性模量和力学参量的有效方法。     

“基桩声测与动测技术”书评

吴庆曾高级工程师编著的\"基桩声测与动测技术\",由中国电力出版社2008年底出版。全书共18章,包括五个部分内容:1.绪论;2.声学原理、换能器、超声检测仪器、跨孔检测桩身缺陷原理、声波层析成像(CT)在桩基工程中应用等;3.单孔声波测井、介绍管波勘探对桩位围岩岩溶与软弱结构面的探测原理和方法;4.介绍声波反射波法(低应变反射波法)检测基桩完整性、反射波频域分析、信号分析与处理、反射波     

Nonlinear gravito-electromagnetism

There is a non-linear and covariant electromagnetic analogy for gravity, in which the full Bianchi identities are Maxwell-type equations for the free gravitational field, encoded in the Weyl tensor. This tensor gravito-electromagnetism is based on a covariant generalization of spatial vector algebra and calculus to spatial tensor fields, and includes all non-linear effects from the gravitational field and matter sources. The non-linear vacuum Bianchi equations are invariant under spatial duality rotation of the gravito-electric and gravito-magnetic tensor fields. The super-energy density and super-Poynting vector of the gravitational field are natural duality invariants, and satisfy a super-energy conservation equation.     

Can Special Relativity Be Derived from Galilean Mechanics Alone?

Special relativity is based on the apparent contradiction between two postulates, namely, Galilean vs. c-invariance. We show that anomalies ensue by holding the former postulate alone. In order for Galilean invariance to be consistent, it must hold not only for bodies’ motions, but also for the signals and forces they exchange. If the latter ones do not obey the Galilean version of the Velocities Addition Law, invariance is violated. If, however, they do, causal anomalies, information loss and conservation laws’ violations are bound to occur. These anomalies are largely remedied by introducing waves and fields that disobey Galilean invariance. Therefore, from these inconsistencies within classical mechanics, electromagnetism could be predicted before experiment proved its existence. Special relativity, it might be argued, would then follow naturally, either as a resolution of the resulting conflict or as an extrapolation of the path between the theories. We conclude with a review of earlier attempts to base SR on a single postulate, and point out the originality of the present work.     

电磁场中二能级原子的量子相干性

求解了经典电磁场中二能级原子系统的密度矩阵演化方程,得到了系统状态的相干特性x     

Piezoelectric transducer vibrations in a one-dimensional approximation

Summary The theory of piezoelectric transducer vibrations, which may be treated as onedimensional, is developed in detail for thin discs vibrating in a pure thickness extensional mode. An effort has been made to obtain relations of general validity, which include losses, and which are in a simple explicit form convenient for practical calculations. The behaviour of transducers is discussed with special attention to their characteristics at the two fundamental frequencies, the so-called parallel and series resonances. Several peculiarities occur when transducers are coupled to media with considerably different acoustic impedances. These peculiarities are discussed and illustrated by numerical results for quartz and PZT 4 piezoelectric discs radiating into water, air and liquid hydrogen. The application of the theory to different types of vibrations is briefly illustrated for thin bars vibrating longitudinally. Short discussions are included on compound transducer systems, and on the properties of thin discs as receivers.     

北京七色光儿童艺术剧院的声学设计

北京七色光儿童艺术剧院是一个以演出儿童话剧为主,同时还可以进行歌舞、音乐等其他文艺形式的演出的多功能剧场,该剧院形式活泼,音质良好。本文从音质和噪声控制的几个方面对其声学设计进行了介绍。     

Acoustics and new learning environment – A case study

This study presents the results of an acoustic performance evaluation of classrooms and their corridors on a test area of the Finnish Oulu Normal School. The project, “Spaces for learning and creation of new knowledge”, was organised by Rym Ltd and was a re-design pilot study where spatial analysis of some new schools and new forms of future school design have been made.     

用扫描隧道显微镜研究肿瘤细胞膜表面的纳米结构

用扫描隧道显微镜技术研究肿瘤细胞膜的超分子结构以及外加纵向电磁场对其超分子结构的作用.结果表明,在扫描隧道显微镜照片中,肿瘤细胞膜表面纳米结构的图象由环形波纹构成.在外加纵向电磁场的作用下,肿瘤细胞膜的表面环形波纹结构消失,出现了一些损伤的痕迹.这可能是在电磁场作用下肿瘤细胞膜表面带电离子的运动受洛仑兹力以及感应电流的综合影响所致.