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本文针对声发射技术中的三维定位问题提出一种新的简易实验方案.通过传感器接收的时差信息和空间坐标实现三维立体结构中的声发射源定位,操作和计算简单,降低了实验成本.该实验方法不仅可以直观地实现三维声发射源定位过程,还可以实现声速的测量.本设计加深了学生对物理问题的理解,提高了学生对声发射技术和声源定位技术的兴趣,适合普及. 相似文献
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在对冲击激励声发射应力波在铝合金板上的传播机理进行分析的基础上,利用ABAQUS软件构建了钢球冲击铝合金板几何模型,仿真分析了冲击应力波传播过程.理论分析了冲击应力波与FBG传感器的作用机理,基于边缘滤波原理构建了声发射传感系统,采集冲击激励声发射应力波,建立了声发射区域定位模型,提出了基于扩散映射与支持向量机(SVM)的声发射区域定位方法并进行了实验验证.在300 mm×300 mm×2 mm的铝合金板上对36个测试区域进行了多次声发射区域定位实验,实验结果表明,扩散映射结合SVM的定位结果较优,区域定位精度为30 mm×30 mm,定位正确率为97.5%,耗时0.781 s.研究结果为声发射区域定位检测提供了一种有效方法. 相似文献
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A. K. Mohapatra S. Chaudhuri S. Roy C. S. Unnikrishnan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):287-298
We report the results from a series of experiments in which
ferromagnetic thin films were used as atom mirrors for laser-cooled
rubidium atoms released from a magneto-optical trap. The thin films were
made of cobalt and lanthanum calcium manganite (LCMO) with thicknesses
between 20 and 300 nm. The magnetic domains in these thin films have
a periodic structure where the spatial period is of the order of the
thickness of the film, and the field decays exponentially above the film
over a length scale comparable to the domain size. Thus, the neutral
atoms reflect off these films from distances comparable to the thickness
of the film, resulting in modification of the reflectivity due to the
competition between the repulsive magnetic force and the attractive
short-range forces such as van der Waals and Casimir forces. The
smoothness of the atom mirror is also modified due to the proximity of
the magnetic domains. The reflectivity is sensitive to the domain
structure and size, which can be modified in LCMO by applying a modest
external magnetic field. In this paper, we discuss the evaluation of the
thin films as magnetic mirrors for atom optics, and the measurement of
the van der Waals force with an accuracy of about 15%, using cobalt
thin films. We also discuss some preliminary results on the
temperature-dependent reflectivity for atoms near the ferromagnetic
transition at 250 K in the LCMO film, and on the domain dynamics and
relaxation. 相似文献