1 中国人民公安大学刑事科学技术学院, 北京 100038
2 北京石油化工学院化学工程学院, 北京 102617
为实现水彩笔油墨的准确分类,采用红外光谱法对3种品牌15个系列的60个水彩笔油墨样品进行了检验。经过平滑、校正等预处理后,利用均方根误差得到最佳小波变换压缩次数,以达到降低运算复杂度的目的。通过H?lder指数提取出30个样本特征波数,并将其作为输入变量导入人工神经网络的输入层。分配训练集、验证集和测试集对模型进行训练,最终得到该模型的分类正确率为83.3%。最后绘制了受试者工作特征(ROC)曲线,发现第2类样本的分类正确率高于其他两类样本,实现了对水彩笔油墨种类的模式识别。
红外光谱分析法 水彩笔油墨 人工神经网络 H?lder指数; 模式识别 受试者工作特征(ROC)曲线 激光与光电子学进展
2020, 57(15): 153005
1 中国科学院上海高等研究院, 上海 201210
2 上海科技大学物质科学与技术学院, 上海 201210
3 中国科学院大学, 北京 100049
4 天津大学精密仪器与光电子工程学院太赫兹研究中心, 天津 300072
将冷原子、超快和强激光技术结合,本课题组最近成功研发了一种新型磁光阱反冲离子动量谱仪(MOTRIMS)装置。介绍了MOTRIMS工作原理,使用吸收成像法和光电离法对靶的密度、温度和速度进行分析标定,得到三维MOT靶的温度为(130±30) μK,速度为(0.1±0.1) m/s,密度约为10 9 atom/cm 3,二维MOT和molasses靶的密度分别约为10 7 atom/cm 3和10 8 atom/cm 3。对比热蒸气靶,在离子飞行方向上冷原子靶的动量分辨率提高了约14倍,飞行时间谱的质量分辨率高达3000。利用800 nm飞秒激光探测Rb +的三维动量分布,在低激光强度10 11 W/cm 2下观测到明显的阈上电离现象,表明铷原子有很大的阈上电离截面。MOTRIMS具有高分辨离子动量分布全空间成像能力,是研究金属原子强场量子微观动力学的新工具。
原子与分子物理学 磁光阱反冲离子动量谱仪 离子高分辨动量分布 铷原子激光冷却 强场电离
Kaixuan Zhang 1,3Yizhu Zhang 1,2,5,*Xincheng Wang 4Tian-Min Yan 1,6,*Y. H. Jiang 1,3,4,7,*
Author Affiliations
Abstract
1 Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
2 Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Key Laboratory of Opto-electronics Information and Technical Science, Ministry of Education, Tianjin University, Tianjin 300072, China
3 University of Chinese Academy of Sciences, Beijing 100049, China
4 ShanghaiTech University, Shanghai 201210, China
5 e-mail: zhangyz@sari.ac.cn
6 e-mail: yantm@sari.ac.cn
7 e-mail: jiangyh@sari.ac.cn
The origin of terahertz (THz) generation in a gas-phase medium is still in controversy, although the THz sources have been applied across many disciplines. Herein, the THz generation in a dual-color field is investigated experimentally by precisely controlling the relative phase and polarization of dual-color lasers, where the accompanying third-harmonic generation is employed for in situ determination of the relative phase up to sub-wavelength accuracy. Joint studies with the strong approximation (SFA) theory reveal that the continuum-continuum (CC) transition within an escaped electron wave packet in the single atom gives birth to THz emission, without the necessity of considering the plasma effect. Meanwhile, we develop the analytic form from SFA-based CC description, which is able to reproduce and decompose the classical photocurrent model from the viewpoint of microscopic quantum theory, establishing the quantum-classical correspondence and bringing a novel insight into the mechanism of THz generation. Present studies leave open the possibility for probing the ultrafast dynamics of continuum electrons and a new dimension for the study of THz-related science and methodology.
Photonics Research
2020, 8(6): 06000760
