We experimentally obtain cylindrical vector beams（CVBs） in a passively mode-locked fiber laser based on nonlinear polarization rotation. A mode-selective coupler composed of both a single-mode fiber（SMF） and a two...We experimentally obtain cylindrical vector beams（CVBs） in a passively mode-locked fiber laser based on nonlinear polarization rotation. A mode-selective coupler composed of both a single-mode fiber（SMF） and a twomode fiber（TMF） is incorporated into the cavity to act as a mode converter from LP01 mode to LP11 mode with broad spectral bandwidth. CVBs in different mode-locked states including single-pulse, multi-pulse, and bound pulse are obtained, for the first time to our best knowledge. The ultrafast CVBs with different operation states have potential applications in many fields such as laser beam machining, nanoparticle manipulation, and so on.展开更多
The reaction path of the reaction NCO+H2→HNCO + H has been traced by Fukui’s theory and the ab initio method. On this basis, the dynamical properties along the reaction path, canonical variational theory (CVT) rate ...The reaction path of the reaction NCO+H2→HNCO + H has been traced by Fukui’s theory and the ab initio method. On this basis, the dynamical properties along the reaction path, canonical variational theory (CVT) rate constants and vibrational-mode-selected rate constants have been computed. The results show that the effect of the electron correlation energy on the activation barrier is large, and tiros the correction by MP4 method is effective; the results also show that the recrossing and tunneling effects exist, and thus the corrections by the variational transition state theory (VTST) and the small curvature (SC) approximation method are also effective. In the reaction, the coupling and energy transfer between mode 8(7) and reaction path are strong, so the rate is effectively enhanced while these modes, especially H2 stretching, are vibrationally excited.展开更多
传统的窃电检测方法大多直接在原始功率序列上构建模型,且没有同时考虑长时序列中的周期依赖关系以及周期之间的局部关联特征,限制了电力用户行为规律的深层挖掘。提出了一种综合采用时频模态融合和多尺度特征提取的高精度窃电检测模型...传统的窃电检测方法大多直接在原始功率序列上构建模型,且没有同时考虑长时序列中的周期依赖关系以及周期之间的局部关联特征,限制了电力用户行为规律的深层挖掘。提出了一种综合采用时频模态融合和多尺度特征提取的高精度窃电检测模型。采用经验模态分解方法,将原始信号分解为多个本征模态信号和一个残差信号,依据模糊熵值与皮尔逊相关系数找到同时包含局部信息与原始信号信息较多的模态,并将选择的模态信号与原信号进行拼接,这样既可以提升模型的维度,又能放大窃电用户与正常用户的局部差异;将拼接好的数据先输入卷积神经网络进行局部特征提取,并从提取到的特征输入多头自注意力机制神经网络模型中提取全局特征,从而实现多尺度特征提取,以增强模型提取特征的适应性。在公开数据集上的实验结果表明,所提模型的F1值达到了76.71%、召回率达到了87.99%、曲线下面积(area under the curve,AUC)值达到了93.11%,相比于现有方法均取得了明显提升。展开更多
对于小电流接地系统的单相接地故障选线,传统方法普遍采用基于一维信号的选线模型,存在选线准确率低、抗噪性弱等问题。为此提出一种改进的变分模态分解及Conv Ne Xt的小电流接地系统单相接地故障选线方法。首先引入蚁狮算法优化变分模...对于小电流接地系统的单相接地故障选线,传统方法普遍采用基于一维信号的选线模型,存在选线准确率低、抗噪性弱等问题。为此提出一种改进的变分模态分解及Conv Ne Xt的小电流接地系统单相接地故障选线方法。首先引入蚁狮算法优化变分模态分解算法,通过蚁狮算法自动寻优选取合适的分解次数和惩罚因子,计算分解得到的各分量的分布熵,将其中的噪声分量筛选去除,将其余有效分量进行线性重构得到降噪后的零序电流信号;其次,将经过降噪处理后的一维零序电流信号经格拉姆角场转换为二维图像,制备故障选线数据集;然后,引入预训练的ConvNeXt模型,根据该研究数据模型特征,在其已有权重基础上对模型参数进行对应微调,从而提高模型精度并形成最终的选线模型;最后引入绝对平均误差、均方根误差作为评价指标验证所提降噪算法有效性。分别在加入噪声与否的前提下,将所提模型与3种选线模型相比较。实验结果表明该模型的准确率最高、抗噪性方面更好,其中该研究算法准确率达到了99.82%并且在不同噪声条件下都能维持91%以上的准确率,高于其他选线模型,克服了传统故障选线方法准确率低、抗噪性差的问题。展开更多
基金supported by the National Science Foundation of Jiangsu Province(Nos.BK20161521 and BK20150858)the Nanjing University of Posts and Telecommunications(NUPTSF)(Nos.NY214059,NY214002,and NY215002)+2 种基金the Distinguished Professor Project of Jiangsu(No.RK002STP14001)the Six Talent Peaks Project in Jiangsu Province(No.2015-XCL-023)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Nos.SJCX17_0234 and KYCX17_0744)
文摘We experimentally obtain cylindrical vector beams（CVBs） in a passively mode-locked fiber laser based on nonlinear polarization rotation. A mode-selective coupler composed of both a single-mode fiber（SMF） and a twomode fiber（TMF） is incorporated into the cavity to act as a mode converter from LP01 mode to LP11 mode with broad spectral bandwidth. CVBs in different mode-locked states including single-pulse, multi-pulse, and bound pulse are obtained, for the first time to our best knowledge. The ultrafast CVBs with different operation states have potential applications in many fields such as laser beam machining, nanoparticle manipulation, and so on.
基金Project supported by the National Natural Science Foundation of China
文摘The reaction path of the reaction NCO+H2→HNCO + H has been traced by Fukui’s theory and the ab initio method. On this basis, the dynamical properties along the reaction path, canonical variational theory (CVT) rate constants and vibrational-mode-selected rate constants have been computed. The results show that the effect of the electron correlation energy on the activation barrier is large, and tiros the correction by MP4 method is effective; the results also show that the recrossing and tunneling effects exist, and thus the corrections by the variational transition state theory (VTST) and the small curvature (SC) approximation method are also effective. In the reaction, the coupling and energy transfer between mode 8(7) and reaction path are strong, so the rate is effectively enhanced while these modes, especially H2 stretching, are vibrationally excited.
文摘传统的窃电检测方法大多直接在原始功率序列上构建模型,且没有同时考虑长时序列中的周期依赖关系以及周期之间的局部关联特征,限制了电力用户行为规律的深层挖掘。提出了一种综合采用时频模态融合和多尺度特征提取的高精度窃电检测模型。采用经验模态分解方法,将原始信号分解为多个本征模态信号和一个残差信号,依据模糊熵值与皮尔逊相关系数找到同时包含局部信息与原始信号信息较多的模态,并将选择的模态信号与原信号进行拼接,这样既可以提升模型的维度,又能放大窃电用户与正常用户的局部差异;将拼接好的数据先输入卷积神经网络进行局部特征提取,并从提取到的特征输入多头自注意力机制神经网络模型中提取全局特征,从而实现多尺度特征提取,以增强模型提取特征的适应性。在公开数据集上的实验结果表明,所提模型的F1值达到了76.71%、召回率达到了87.99%、曲线下面积(area under the curve,AUC)值达到了93.11%,相比于现有方法均取得了明显提升。
文摘对于小电流接地系统的单相接地故障选线,传统方法普遍采用基于一维信号的选线模型,存在选线准确率低、抗噪性弱等问题。为此提出一种改进的变分模态分解及Conv Ne Xt的小电流接地系统单相接地故障选线方法。首先引入蚁狮算法优化变分模态分解算法,通过蚁狮算法自动寻优选取合适的分解次数和惩罚因子,计算分解得到的各分量的分布熵,将其中的噪声分量筛选去除,将其余有效分量进行线性重构得到降噪后的零序电流信号;其次,将经过降噪处理后的一维零序电流信号经格拉姆角场转换为二维图像,制备故障选线数据集;然后,引入预训练的ConvNeXt模型,根据该研究数据模型特征,在其已有权重基础上对模型参数进行对应微调,从而提高模型精度并形成最终的选线模型;最后引入绝对平均误差、均方根误差作为评价指标验证所提降噪算法有效性。分别在加入噪声与否的前提下,将所提模型与3种选线模型相比较。实验结果表明该模型的准确率最高、抗噪性方面更好,其中该研究算法准确率达到了99.82%并且在不同噪声条件下都能维持91%以上的准确率,高于其他选线模型,克服了传统故障选线方法准确率低、抗噪性差的问题。
