Spectral characteristics of laser-plasma instabilities with a broadband laser

Recent experimental progresses regarding broadband laser-plasma instabilities(LPIs)show that a 0.6%laser bandwidth can reduce backscatters of the stimulated Brillouin scattering(SBS)and the stimulated Raman scattering(SRS)at normal incidence[Phys.Rev.Lett.132035102(2024)].In this paper,we present a further discussion of the spectral distributions of the scatters developed by broadband LPIs,in addition to a brief validation of the effectiveness of bandwidth on LPIs mitigation at oblique incidence.SBS backscatter has a small redshift in the broadband case contrary to the blueshift with narrowband laser,which may be explained by the self-cross beam energy transfer between the various frequency components within the bandwidth.SRS backscatter spectrum presents a peak at a longer wavelength in the broadband case compared to the short one in the narrowband case,which is possibly attributed to the mitigation effect of bandwidth on filaments at underdense plasmas.The three-halves harmonic emission(3ω/2)has a one-peak spectral distribution under the broadband condition,which is different from the two-peak distribution under the narrowband condition,and may be related to the spectral mixing of different frequency components within the bandwidth if the main sources of the two are both two-plasmon decays.

基于动态约简的铁路牵引供电系统故障诊断研究

对铁路牵引供电系统中的复杂信息进行采集并构建决策表,基于动态约简方法建立故障诊断数学模型,降低了已有诊断方法中对专家主观判断的依赖性,提高了故障诊断结果的可靠性。后对津山线牵引供电系统的故障情况进行了分析。

铁道牵引供电系统故障诊断的约简模型与应用

针对铁道牵引供电系统故障诊断中的复杂信息,构建关系数据表,基于近似约简方法建立故障诊断模型,以快速地对可能发生的故障进行预测、判断和处理,从而有效地保障铁道运输安全,提高运输效率。首先,从牵引变电所的变配电设备和接触网供电系统处共收集34路信号,作为数据挖掘的输入量;其次,利用近似约简算法构建铁道牵引供电系统故障诊断模型,从数据离散化,近似约简、故障预测方面进行了详细介绍;最后,通过实例说明了这种方法的有效性,从而对正确预测设备性能和故障状态起到积极的指导作用。

一种基于内容的新闻推荐系统实例

互联网的飞速发展产生了”信息过载”问题，新闻数量的爆炸性增长使得读者受到“信息迷航”问题的困扰。为解决这一问题新闻推荐系统应运而生。文章针对该系统的关键部分即新闻特征值提取和用户画像做了深入的研究。采用了TFIOF进行新闻分词及特征值提取，将新闻用空间向量模型表示并利用PuLearning来解决用户画像时负反馈数据难以得到的问题。最后以实例证明了该方法的可行性。