Nd3+-doped silica glass and fiber prepared by modified sol-gel method

Large-size Al³⁺/Nd³⁺co-doped silica glass with 5000 ppm Nd³⁺and 50,000 ppm Al³⁺doping concentrations was prepared by the modified sol-gel method combined with high-temperature melting and molding technology. Electron probe microanalyzer tests indicated that high doping homogeneity was achieved with this sample preparation method. The spectral properties of the Nd³⁺ions were evaluated. Nd³⁺-doped silica fiber(NDF) with a core-to-cl...     

过零双门限协作频谱感知算法

应用过零双门限协作频谱感知算法估计无线电频谱的占用状态,研究了认知用户个数、计算所用的采样点数、不同信噪比及判决系数对检测概率的影响,并与传统双门限能量检测、差分双门限能量检测算法的检测性能进行了对比研究,发现在信噪比为-5 dB,判决系数为0. 05,虚警概率小于等于0. 8时,过零双门限检测方法单认知用户检测性能明显优于其他2种检测方法;当信噪比均为-5 dB,参与协作感知的认知用户个数小于6时,过零双门限协作检测算法性能明显优于其他2种算法;在虚警概率恒定的情况下,增加计算所用的采样点数或增大判决系数能够明显提高检测概率;在虚警概率恒定情况下,算法检测概率随着信噪比增大而增大,当信噪比为-7 dB时,检测概率趋近于1;在相同的检测条件下,过零双门限协作检测算法的虚警概率要明显低于差分双门限检测的虚警概率。结果表明:过零双门限协作频谱感知算法可以降低系统的虚警概率,有效解决噪声不确定性问题,进一步提高系统感知性能。     

基于卷积神经网络的胶囊内镜息肉与溃疡辅助诊断

针对目前胶囊内镜(WCE)自动检测方法需要对每种病灶设计对应的识别算法以及识别准确率不高的问题,设计一种基于卷积神经网络的息肉与溃疡辅助诊断算法。与传统检测算法相比,卷积神经网络可自动学习病灶图像特征,实现更强泛化能力,更高准确率和效率。该方法针对具体WCE图像,首先评价图像R、G、B通道携带信息的特征;其次,分析全局直方图均衡化、伽玛变换和拉普拉斯变换对提升图像对比度的效果,选择其中表现最佳者与信息最丰富的2个颜色通道组合成3通道输入到卷积网络中训练和识别。测试表明,本算法识别准确率96.8%,比传统的经典图像检测方法高出至少16.73%,检测速度达到68.6图/s,能够推广应用到医疗辅助诊断领域。     

国产25/400μm掺镱双包层光纤实现2.2kW窄线宽单模激光输出

基于自主研制的均匀掺杂低热光系数25/400μm掺镱双包层光纤,开展了全光纤高功率窄线宽光纤激光放大实验。激光系统实现了中心波长为1060.3 nm、线宽为25 GHz、最高功率为2.2 kW的单模激光输出,其斜率效率达78%,光束质量因子M~2≈1.2,其功率是目前报道的基于国产25/400μm掺镱双包层光纤窄线宽放大器单模激光输出的最高功率。     

Effect of power scale of 974 and 633 nm lasers on the induced loss at 633 nm of Yb~(3+)/Al~(3+) co-doped silica fiber

Induced loss at 633 nm is tested in Yb~(3+)∕Al~(3+)co-doped silica fiber by a core pumped with a 974 nm laser and probed with a 633 nm laser. The fiber is prepared by the modified chemical vapor deposition method combined with solution doping. Different power scales of pump light and probe light are used in the tests. It is found that there is a dynamic equilibrium between photobleaching induced by 633 nm probe light and photodarkening(PD)induced by 974 nm pump light. For the first time to our knowledge, the effect of 633 nm probe laser power on an induced loss test of Yb~(3+)∕Al~(3+)co-doped silica fiber is studied quantitatively. It suggests that as long as the633 nm probe light power is less than 0.2 m W, the induced loss is mainly contributed by the PD effect of pumping light, and the deviation of induced loss is less than 5%.     

基于X射线的耐张线夹钢芯与铝管压接尺寸对导线承拉力综合影响的研究

X射线对电力金具进行无损检测具有检测方便、快捷、准确等特点。导线承拉能力主要取决于两端耐张线夹及接续管的钢芯压接尺寸与铝管压接尺寸。通过同时改变耐张线夹钢芯压接尺寸与铝管压接尺寸对导线进行压接。利用X射线数字成像技术检测耐张线夹钢芯及铝管的实际压接尺寸。通过设置多组实验来确定能满足规程规定的导线拉力值的临界点。选择曲线函数模拟钢芯压接尺寸、铝管压接尺寸-导线拉力的曲线图,得到导线压接时尺寸要求。对导线压接及质量检测具有重要意义。     

一种能够精确定位的光栅变画灯箱控制系统设计

本文详细介绍了以PHILIPS公司P89V51RC2FA单片机为控制器的光栅变画灯箱控制系统,分析了系统硬件结构及工作原理。系统采用步进电机驱动,利用美国Allegro公司的高灵敏度线性霍尔传感器UGN3503U作为距离感测元件,实现精确定位。该系统具有定位精确、速度快、成本低等优点。     

聚丙烯类树脂抗静电防老化多功能白色母粒的研制

本文通过单因素实验确定制备抗静电防老化的聚丙烯（PP）多功能白色母粒的优化配方.结果表明：载体树脂为60 kg,色素为12 kg,抗静电剂为10 kg,抗氧剂为10 kg,分散剂为6 kg,增容剂为2 kg是制备100 kg的多功能白色母粒的最佳配比.用该功能母粒制备的聚丙烯板材的表面电阻系数为0.6×10^9,氙灯老化500 h后色牢度为5级.     

线形芳酰胺聚合物的力学性能模拟

利用分子间氢键驱动分子自组装作用实现分子水平上的负泊松比这一思路,设计了一种具有类似倒插蜂窝状结构的线形芳酰胺聚合物。利用Materials Studio软件对所构建的线形芳酰胺聚合物分子模型进行了计算机模拟,通过分子力学和力学性质模块的计算得到了线形芳酰胺聚合物的一些力学参数,模拟结果表明,这种线形芳酰胺聚合物在氢键驱动的自组装作用下呈现类倒插蜂窝结构排列,该系列聚合物均具有负泊松比。     

2-um emission performance of Tm^3＋-Ho^3＋ co-doped tellurite glasses

The emission properties of 2-um region fluorescence of Tm^3＋-Ho^3＋ co-doped tellurite glasses are investigated. Introducing F- ions to the composition of tellurite glasses plays a positive effect on the 2-#m emission. A maximum intensity of 2-um emission is achieved when 1.5-mol% Tm2O3 and 1-mol% Ho203 concentration are doped in the glasses. The emission cross section and gain coefficient of the ^5I8-^5I7 transition of Ho^3＋ are calculated. The emission cross section has a maximum of 1.29×10-20 cm^2 at 2048 nm wavelength. The results indicate that Tm＆3＋-Ho^3＋ co-doped tellurite glasses are suitable for 2-um application.