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对颈动脉多普勒血流信号实现了一种基于自回归滑动平均(ARMA)模型、并采用反向传输(BP)神经网络分析ARMA模型极点特征的系统,以达到诊断脑梗塞疾病的目的。首先对音频颈动脉多普勒血流信号分时间段建立ARMA模型,得出模型极点分布的特征参数,研究这些特征参数对脑梗塞疾病诊断的敏感性,然后对敏感的特征参数利用BP神经网络进行分类,对是否存在脑梗塞的血流状况进行判别。共使用474例颈动脉血流信号来建立合适的神经网络,使用52例信号进行测试,结果表明:系统训练和测试的正确率均大于94%,可以满足临床的要求。 相似文献
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We develop a pair of tapered-tip single fiber optical tweezers, and study its multi-trapping characteristic. The finite difference time domain method is employed to simulate the trapping force characteristic of this pair of single fiber optical tweezers, and the results show that the number of trapped particles depends on the refractive index and the size of the particles. The trapping force of this pair of tapered-tip single fiber optical tweezers is calibrated by the experimental method, and the experimental results are consistent with the theoretical calculation results. The multi-trapping capability realized by the tapered-tip single fiber optical tweezers will be practical and useful for applications in biomedical research fields. 相似文献
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A hybrid high quality factor (Q-factor) microwave photonic filter with a cascaded active filter and a passive filter is presented and experimentally demonstrated. The active infinite impulse response filter is realized by a recirculating delay line loop with a semiconductor optical amplifier, and a much narrower 3 dB bandwidth of response peaks can be achieved. A passive finite impulse response filter is realized by an unbalance Mach-Zehnder interferometer, and it is cascaded to select the desired filter frequencies and to suppress the intermediate peaks. Compared with the purely active filter scheme, the free spectrum range and the Q-factor of the hybrid structure can be doubled. Stable operation and a high Q-factor of 362 are experimentally demonstrated. 相似文献
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We propose and demonstrate single fiber dual-functionality optical tweezers based on a graded-index multimode fiber. By using the multi-angle fiber grinding and polishing technology, we fabricate the multimode fiber tip to be a special tapered shape, contributing to focus the outgoing beam with a large intensity gradient for the first functionality—three-dimensional contactless trapping of a microparticle. By adjusting the radial direction offset between the lead-in single mode fiber and the graded-index multimode fiber, we perform the second functionality—axial shift of the trapped microparticle with respect to the fiber tip without need of moving the fiber probe itself. It is convenient for practical applications. The theoretical and experimental results about the relationship between the radial offset and the equilibrium positions of the microparticle have the good consistency. Tailoring the trap and axial shift of the microparticle based on the graded-index multimode fiber provides convenient avenues for fiber optical tweezers applied in practical researches. 相似文献
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