Characteristics of stable L-band SFS using dual-forward synchronous pumping technique

We investigate the characteristics of the dual-forward synchronously pumped L-band erbium-doped su- perfiuorescent fiber source （SFS）. The effects of pump ratio and fiber length arrangements on the output characteristics of the L-band SFS in terms of mean wavelength, spectral linewidth, and output power are analyzed. It is shown that the optimized pump ratio and fiber length arrangements provide broadening spectral linewidth and enhanced pumping efficiency, while the synchronous pump ensures stable mean wavelength operation. A new single-forward pumping scheme with a section of unpumped fiber is pro- posed to achieve a mean wavelength stable L-band SFS with a broadening linewidth of 50.4 nm and a pumping efficiency of 33.5%.     

Dual-wavelength Bi_2Se_3-based passively Q-switching Nd~(3+)-doped glass all-fiber laser

We demonstrate a dual-wavelength passively Q-switched Nd~(3+)-doped glass fiber laser using a few-layer topological insulator Bi_2Se_3 as a saturable absorber(SA) for the first time, to the best of our knowledge. The laser resonator is a simple and compact linear cavity using two fiber end-facet mirrors. The SA is fabricated by Bi_2Se_3/polyvinyl alcohol composite film. By inserting the SA into the laser cavity, a stable Q-switching operation is achieved with the shortest pulse width and maximum pulse repetition rate of 601 ns and 205.2 kHz,respectively. The maximum average output power and maximum pulse energy obtained are about 6.6 mW and 38.8 nJ, respectively.     

一种结合主动和被动方式的网络延迟测量方法

在利用被动测量设备检测到的用户包数量基础上，考虑相邻探测包的延迟变化关系，实现了一种结合主动和被动方式的网络延迟有效测量方法．这种测量方法不但具有与协议无关、对网络流量影响小、使用简单等特点，在网络拥塞甚至存在丢包的情况下，能减小误差，更准确地反映网络的实际状况．     

基于分块图像小波相对能量和熵的视频镜头边界检测算法

提出了对检测窗内图像帧进行分块并进行小波变换,计算尺度j上分块图像的低频、水平、垂直和对角信号的小波相对能量和小波熵的方法,给出了分块图像小波熵的计算公式.采用尺度j上分块图像低频信号小波熵作为特征向量检测视频镜头是否发生转换,即在检测窗内,帧间低频信号小波熵值只发生一次大突变（与设定的阈值相比）就是剪切转换,若发生多次比较大的变化就是渐变转换.采用检测窗内分块图像在尺度j上的垂直、水平和对角高频信号的小波熵作为另一特征量可以区分渐变镜头的类型：淡进/出(fade in/out)或扫换(wipe).采用大量的高清和标清码流进行实验并与基于概率的方法进行比较.结果证明：本文的视频镜头检测方法具有强的鲁棒性、能检测出镜头转换的类型：剪切、淡进/出和扫换,同时有较高的查准率和查全率.     

基于模糊数算术运算的信息系统安全性定量评估技术研究

对信息系统的安全性进行评估面临大量的不确定性因素，主要表现为信息安全的随机性和模糊性。为了处理安全性评估中的主观性和模糊性，基于三角形模糊数运算，本文提出了一个安全性定量评估的模糊模型，并结合应用系统进行了实例分析。