Nitrogen air lasing induced by multiple filaments array

Air lasing emission by launching intense ultrafast laser pulses in atmosphere has recently attracted increasing interest in the ultrafast laser science and atmospheric science fields, especially for remote sensing techniques. We demonstrated the fluorescence emissions at 337 nm, 357 nm and 391 nm induced by multiple filaments using four kinds of step phase plates. Our results have indicated that the fluorescence signal has been amplified as it propagates along the filament through amplified spontaneous emission (ASE), and the fluorescence intensity is also enhanced in the backward direction via multiple filaments. Furthermore, the gain coefficient through ASE is increased with the number of filaments.     

近红外光谱结合线性非负回归测定梗丝掺配比例

目的：建立成品烟丝中梗丝含量的近红外光谱快速测定方法。方法：以掺配不同比例梗丝（5%,8%,11%,14%）的成品烟丝为试验对象,分别采集纯梗丝、纯叶丝及掺配不同比例梗丝烟丝样品的近红外光谱信息,采用正交偏最小二乘判别分析（OPLS-DA）识别上述3类样品近红外光谱信息的整体差异性。利用方差光谱、变量重要性投影（VIP）特征光谱及全光谱分别建立了不同比例梗丝样品的线性非负性回归模型,并对预测模型的准确性和稳定性进行评价。结果：① OPLS-DA模式识别分析表明,3类样品的近红外光谱整体信息存在较大差异性。② 基于VIP值大于1,筛选出光谱波数范围为：4 000～4 165,4 582～4 609,4 612～5 264 cm^-1。方差较大的波长范围：4 000～6 100,6 900～7 500 cm^-1。③ 方差光谱筛选波长变量建立的预测模型准确性和稳定性均优于VIP算法和全波长变量。结论：近红外光谱结合线性非负回归系数回归法快速测定成品烟丝中梗丝含量的方法具有较好的稳定性和准确性。