经颅多普勒检查脑供血866例的临床分析

目的用EMS-9经颅多普勒检查脑供血,统计分析脑供血不足或脑供血增加在男性和女性人群中的各年龄段的发病率.方法用EMS-9经颅多普勒检查脑供血情况.结果临床检查脑血供共866例,有脑供血不足426例,脑血管痉挛供血增高403例,女性发病率高于男性,大约是男性的6.3倍,脑供血部分增高部分降低37例.男女年龄相近.结论经颅多普勒检查脑供血情况有较高的可靠性     

多光束激光外差高精度测量玻璃厚度的方法

利用基于激光外差测量技术和激光多普勒技术的非接触式多光束激光外差测量方法,得到了光电探测器输出电流的谐波表达式.讨论了该测量方法用于玻璃厚度超精密测量的可行性及理论依据,并利用Matlab软件对不同情况进行了仿真实验.结果表明：该方法在不同入射角时测量平板玻璃厚度最大的误差为0.3%,明显比其他测量方法精度高. 关键词： 外差探测 多光束激光外差 激光多普勒技术 非接触式测量     

Numerical investigation of multi-beam laser heterodyne measurement with ultra-precision for linear expansion coefficient of metal based on oscillating mirror modulation

This paper proposes a novel method of multi-beam laser heterodyne measurement for metal linear expansion coefficient. Based on the Doppler effect and heterodyne technology, the information is loaded of length variation to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain many values of length variation caused by temperature variation after the multi-beam laser heterodyne signal demodulation simultaneously. Processing these values by weighted-average, it can obtain length variation accurately, and eventually obtain the value of linear expansion coefficient of metal by the calculation. This novel method is used to simulate measurement for linear expansion coefficient of metal rod under different temperatures by MATLAB, the obtained result shows that the relative measurement error of this method is just 0.4%.