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The dependence of emission direction of fast electrons on the laser intensity has been investigated. The experimental results show that, at nonrelativistic laser intensities, the emission of fast electrons is mainly in the polarization plane. With the increase of the laser intensity, fast electrons emit towards the laser propagation direction from laser polarization direction. At relativistic laser intensities, fast electrons move away from the laser polarization plane, closely to the reflection direction of the incident laser beam. 相似文献
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在多通道超导量子干涉器件(SQUID)磁探测系统中,磁场电压转换系数(∂ B/∂ V)是系统的一个重要参数由于SQUID器件和读出电路之间不可避免地存在差异性因此对传感器系统进行系统标定(每个通道的单独标定)显得十分重要本文采用(PCB) 板印制圆形线圈对36通道心磁系统进行标定,并与传统的亥姆霍兹方形线圈产生均匀场的标定方法进行比较结果显示PCB圆形线圈的标定结果 在1.46–1.73 pT·mV-1 之间,亥姆霍兹方形线圈标定的结果大都在1.56–1.64 pT·mV-1之间,结果基本一致.
关键词:
超导量子干涉器件
磁探测
磁场-电压转换系数
系统标定 相似文献
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Superconducting quantum interference devices with different damped junctions operated in directly coupled current- and voltage-bias modes 下载免费PDF全文
We investigate niobium thin film superconducting quantum interference devices (SQUIDs) with different Steward- McCumber parameters βc operated in both current- and voltage-bias modes. We experimentally prove that there is no difference between the two bias modes with respect to the SQUID intrinsic noise and the noise contribution from the preamplifier. Furthermore, the relationships of the SQUID dynamic parameters, (Rd)current bias ≈ (Rd)voltage bias and (σV/σФ)current bias ≈ [σi/σФ)Rd]voltage bias, are always satisfied. For a strongly damped SQUID withβc ≈ 0.25, addi- tional positive feedback (APF) and noise cancellation (NC) were employed to enhance σV/σФ, the former showing a degradation in the linear flux range but otherwise the same with NC. For a weakly damped SQUID with βc ≈ 3, it is di- rectly connected to the preamplifier without APF or NC, and a low SQUID system noise of about 4μФ0/x/Hz is measured, which is close to its intrinsic noise. 相似文献
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A dual-washer superconducting quantum interference device(SQUID) with a loop inductance of 350 pH and two onwasher integrated input coils is designed according to conventional niobium technology. In order to obtain a large SQUID flux-to-voltage transfer coefficient, the junction shunt resistance is selected to be 33 ?. A vertical SQUID gradiometer module with a baseline of 100 mm is constructed by utilizing such a SQUID and a first-order niobium wire-wound antenna.The sensitivity of this module reaches about 0.2 fT/(cm·Hz1/2) in the white noise range using a direct readout scheme, i.e.,the SQUID is directly connected to an operational amplifier, in a magnetically shielded room. Some magnetocardiography(MCG) measurements with a sufficiently high signal-to-noise ratio(SNR) are demonstrated. 相似文献
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非线性振动一种稳定的模糊控制方法研究 总被引:2,自引:0,他引:2
由于非线性振动系统的非线性本质,在于传统控制理论的线性控制器用于非线性振动控制效果不佳。本文针对非线性振动系统提出了一种模糊自适应滑模控制方案。 相似文献
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粘弹复合结构特征问题的迭代算法 总被引:12,自引:1,他引:12
本文研究由弹性材料和粘弹性材料构成复合结构的动力学问题。引入耗散位移概述,将复合材料的动力学方程变换为状态方程,进一步研究了状态方程特征解的性质。为了求复合结构的模态参数,定义了复合结构的保守粘性结构的概念,提出了计算复合结构特值问题的一个实用算法。最后讨论了复合结构的动力响应。 相似文献
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SQUID gradiometer techniques are widely used in noise cancellation for biomagnetic measurements.An appropriate gradiometer baseline is very important for the biomagnetic detection with high performance.By placing several magnetometers at different heights along the vertical direction,we could simultaneously obtain the synthetic gradiometers with different baselines.By using the traditional signal-to-noise ratio(SNR) as a performance index,we successfully obtain an optimal baseline for the magnetocardiography(MCG) measurement in a magnetically shielded room(MSR).Finally,we obtain an optimal baseline of 7 cm and use it for the practical MCG measurement in our MSR.The SNR about 38 dB is obtained in the recorded MCG signal. 相似文献
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本文首先讨论工程振动信号频谱再分析技术,针对所存在问题,提出模糊式识别再分析方法,以滚动轴承振动成因研究中的谱分析为例,具体介绍了频谱的峰值频率分布模式,模糊子集及隶属函数的确定,以及综合评判的识别过程,最后给出一具体计算结果。 相似文献