已证实快门式Q开关必须采用两倍或四倍加速装置,腔内光束有一微小摆动.解释了产生多脉冲的机理.用计算机进行了典型情况下的计算.证明快门式Q开关的性能可以得到改进,方法是在有一定折射率的气体的封闭室内放置棱镜.
采用I类相位匹配或II类相位匹配，可在非线性晶体中有效地产生光学二次谐波。为了满足非临界匹配条件，通常采取温度调谐。温度调谐的优点是转换效率高，输入光束和输出光束共线传播,无光束分离,这就可用于三倍频或和频。表1列出了大部分常用的二次谐波产生晶体。氘化晶体具有更多的优点：吸收小(每厘米吸收0.6%),有较高的损伤阈值、不因受热而失调。
Photoacoustic microscopy (PAM) is recognized as a powerful tool for various microcirculation system studies. To improve the spatial resolution for the PAM images, the requirements of the system will always be increased correspondingly. Without additional
Filamentary structures can form within the beam of protons accelerated during the interaction of an intense laser pulse with an ultrathin foil target. Such behaviour is shown to be dependent upon the formation time of quasi-static magnetic field structure
In lung CT images, the edge of a tumor is frequently fuzzy because of the complex relationship between tumors and tissues, especially in cases that the tumor adheres to the chest and lung in the pathology area. This makes the tumor segmentation more diffi
针对相似度目标跟踪算法主要考虑目标的类内相似,而忽略不同目标的类间差异的问题,提出基于分类-验证模型的视觉跟踪算法。该算法通过增加目标的属性(类别)信息,利用相似度信息与类别信息构建损失函数,在高维空间学习目标的类内相似和类间差异;将目标模板与候选目标输入网络模型,分别通过分类与验证模块实现网络参数更新;利用训练网络提取目标模板与候选目标的深度嵌入特征,实现目标跟踪。在OTB50和UAV123数据库上进行实验,结果表明,该算法可以大幅提高跟踪效果,对相似目标具有较强的稳健性。
An automated flow-batch analyzer (FBA) based on spectrophotometry was developed for the determination of nitrite (NO2-) in environmental waters. The FBA consists of a homemade flow cell, light source, detector and a mini-syringe pump