共查询到20条相似文献,搜索用时 72 毫秒
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模拟仿真了谐振式光纤环腔的透射谱线以及鉴频曲线,得透射谱线最低谷值对应为调制谐振点,鉴频曲线的线性区为陀螺的工作范围区,线性区中点对应谐振点,可作为标度因数最大值.为了实现谐振点的高精度锁频和稳频,设计了谐振式光纤陀螺角速率测定方案,使用比例积分反馈电路实施锁频,利用正弦波扫描窄线宽激光器(线宽小于1kHz)的压电转化模块,使激光器谐振腔长发生变化,从而改变其输出频率,对谐振光纤环腔随外界环境变化同时进行跟踪和锁定.利用线宽法测试并计算出光纤环形谐振腔的品质因数值为107,对比分析了光纤环腔在谐振点和非谐振点锁定情况下的光电探测实时输出,并通过转动测试,得到两种情况下锁定后陀螺的连续转动效果.计算了光纤陀螺系统理论检测灵敏度,结果表明:谐振点锁定后转动效果对应的陀螺输出电平值为锁定非谐振点转速电平值的3倍,验证了谐振式光学陀螺谐振点锁频的重要性. 相似文献
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针对传统实验方法存在操作繁琐、谐振点附近电压变化缓慢等问题,提出了改进实验测量的方法,通过测量电容电感两端合电压与信号源输出电压的比值随频率变化曲线来测定谐振频率。与传统实验方法对比表明,该实验方法不仅能达到与传统实验方法相同的实验结果,而且能改进实验操作,并加深学生从不同角度对电路谐振特性的理解。为RLC串联电路谐振频率的测量提供了新的思路和切实可行的实验方案。 相似文献
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Ciobanu L Webb AG Pennington CH 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,170(2):187-256
Inadequate signal-to-noise ratio is a major factor limiting applications of magnetic resonance microscopy. The "Diffusion Enhancement of Signal and Resolution" (DESIRE) scheme promises potential sensitivity enhancements of between one and three orders of magnitude, but images using this mechanism have not been shown to date. Here, we report the first images obtained using the DESIRE method, and obtain excellent agreement between numerical simulations and experimental data with signal-to-noise enhancements of close to one order of magnitude. 相似文献
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The misunderstanding of the labeling for an “MR conditional” respiratory ventilator system resulted in the placement of this device, which had substantial ferromagnetic components, too close to a 3-T magnetic resonance (MR) system, causing a projectile incident. Magnetic resonance imaging health care professionals should be aware of the potentially dangerous consequences when such medical devices that have Food and Drug Administration-approved MR conditional labeling are brought into the MR system room. Recommendations to prevent future incidents are provided herein. 相似文献
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本文从耦合振动的角度出发,对超声加工系统中出现的“局部共振”现象进行了研究,通过对振动系统的分析用计算,指出“局部共振”流言是耦合振动的一种表现。 相似文献
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N. B. Brandt B. M. Bulychev Yu. A. Velikodnyi A. V. Zoteev E. A. Konstantinova A. V. Krechetov V. A. Kul’bachinskii V. G. Kytin V. P. Tarasov 《Moscow University Physics Bulletin》2009,64(2):172-176
The structure and electron properties of Na n C60 (n = 2, 3) sodium fullerides synthesized from simple compounds in toluene were studied. It was shown that Na2C60 fulleride forms a face-centered cubic lattice at temperatures above 300 K. As the temperature is lowered, the phase transition to a structure with a simple cubic lattice takes place. The temperature dependences of the properties of Na3C60 with a more complex structure exhibit features that are presumably due to sodium atom redistribution in the Na3C60 fulleride lattice and the formation of sodium ion clusters. 相似文献
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对超声复合振动系统中的“局部共振”现象,基于熟知的棒或管中声波产生和传播的理论,提出一种机理解释。 相似文献
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X-band EPR measurements were performed at room temperature on layered Cu(Hippurate)24H2O single crystals. Despite the dimeric molecular structure the EPR spectra are characteristic for individual Cu-complexes with square-pyramidal structure and g-factors: gx=2.045, gy=2.085 and gz=2.346. The anticipated zero-field splitting from dimers with S=1 is averaged out by interdimer exchange coupling within the layers. The dimers in adjacent layers are not exchange coupled as we determined from the two-component EPR spectra. Thus, the crystal is an ideal 2D magnetic system and shows a strong spin diffusion effect in the EPR line width. The spin diffusion contribution to the line width is described as P(3cos2Θ−1)2 with which is much higher compared to other 2D copper(II) crystals. The background line width is due to dipolar coupling and non-resolved hyperfine structure. Exchange coupling was determined from the exchange narrowing effect as of about 0.1 cm−1. 相似文献