Realization of Stable Narrow Linewidth Dual-Wavelength Lasing in an Erbium-Doped Fibre Laser by Cleaving the Wavelength-Selective Filter Spectrum

We propose and demonstrate a new concept of stable narrow-line-width and close wavelength spacing dualwavelength lasing in an Er-doped fibre ring laser （EDFRL） by cleaving the spectrum with a wavelength-selective component in the EDFRL. A fibre loop mirror （FLM） combining with a polarization controller （PC） acts as the cleaver. The cleaver can produce a fine pectinate spectrum. By adjusting the PC, the fine pectinate spectrum can be so changeable that cleaving the spectrum of a fibre Bragg grating （FBG） into two parts. As a result, we obtain the dual-wavelength fibre lasering with a bandwidth of only 0.03nm and a wavelength spacing of only 0.07nm. Furthermore, the laser can also perform stable switchable single wavelength or stable different-bandwidth dual-wavelength by carefully adjusting the PC at room temperature.     

YAG对撞增强相位共轭腔的脉宽研究

报道了在YAG激光器上运行新型的对撞型受激布里渊散射相位共轭腔的实验情况,该腔具有较低的启动阈值,并能输出稳定的ns量级自调Q激光脉冲.本文给出了不同参量条件下的输出脉宽情况.     

两个完全图的乘积的树宽

本文确定了乘积图Km×Kn的树宽.我们的结果是若m和n都是偶数,且m≥n,或m是奇数而n是偶数,或m和n都是奇数且n≥m,则Km×Kn的树宽是TW(Km×Kn)=n(m+1)/2-1.这恰好是图Km×Kn的带宽.     

SIMULTANEOUS SAXS／WAXS／DSC STUDIES ON MICROSTRUCTURE OF CONVENTIONAL AND METALLOCENE-BASED ETHYLENE-BUTENE COPOLYMERS

The fractions of one metallocene-based (mPE) and one conventional (znPE) ethylene-butene copolymer eluted at 80-82℃ from temperature rising elution fractionation were selected for DSC and time-resolved small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) characterization. The DSC and WAXS results show that two crystal structures exist in both mPE and znPE: structure A with higher melting temperature and structure B with lower melting temperature. It was found that original znPE (s-znPE) contains more highly ordered structure A than original mPE (s-mPE) in spite of the higher comonomer content of znPE. Another structure C is also identified because of higher crystallinity measured by WAXS than by DSC and is attributed to the interfacial region. The SAXS data were analyzed with correlation function and two maxima were observed in s-mPE and s-znPE, in agreement with the conclusion of two crystal populations drawn from DSC and WAXS results. These two crystal populatiorts have close long periods in s-mPE, but very different long periods in s-znPE. In contrast, freshly crystallized mPE and znPE (f-mPE and f-znPE) contain only a single crystal population with a broader distribution of long period     

高效液相色谱-串联质谱法测定牛奶中3种糖肽类抗生素

提出了高效液相色谱-串联质谱法测定牛奶中万古霉素、去甲万古霉素和替考拉宁等3种糖肽类抗生素的含量。样品经乙腈-10%(体积分数)三氯乙酸(6+4)溶液提取,同时加入硫酸铵沉淀蛋白,以HLB固相萃取柱净化。以XBridge C18色谱柱为分离柱,以不同体积比的乙腈和乙酸(0.3+99.7)溶液的混合液为流动相进行梯度洗脱,采用电喷雾正离子源多反应监测模式检测。3种化合物的质量分数在5.00~500μg·kg-1范围内与其峰面积呈线性关系,方法的检出限(3S/N)在1.0~2.0μg·kg-1之间。在5.00,10.0,20.0μg·kg-1等3个浓度水平进行加标回收试验,回收率在70.0%~83.5%之间,测定值的相对标准偏差(n=6)在4.2%~11%之间。     

拓宽视角,让数学教学更自然——“直线与圆的位置关系”(第1课时)教学再认识

翻看数学史,不难发现：数学定理、数学思想、数学方法都是数学家们经历曲折、艰辛的研究结果;完美的数学符号、概念、法则是数学界长期自然、合理进化的结果．从再创造的角度出发,学生的思维和当初创建这些数学知识的数学家们的思维本质一致．     

HIAF-BRing快循环全储能脉冲电源高低压切换控制及其切换点平滑算法

应用于强流重离子加速器装置增强环（HIAF-BRing）的快循环全储能脉冲电源需要在极宽的输出电压范围内保持极高的控制精度,为此电源采用了高压功率单元和低压功率单元串联的拓扑方式,在低压段采用低压功率单元,电压升高之后切换到高压功率单元,通过高低压切换控制来实现电流全阶段的高精度输出。但是在样机实测中发现存在切换点的振荡问题,导致切换点处的输出电流绝对误差无法满足指标要求。本文提出了一种切换点平滑控制算法来平滑处理切换点占空比,给出了仿真结果,并且在HIAF-BRing快循环全储能脉冲电源样机上面实际验证了高低压切换控制方法及其切换点平滑控制算法的有效性。实验结果表明：100 A注入平台的输出电流绝对误差由±500 mA降至±50 mA, 100 A注入平台的切换点处输出电流绝对误差由±1.16 A降至±120 mA,100 A注入平台输出精度较低的问题得以解决。     

光纤激光宽温度范围运行研究进展

简要回顾了高功率掺镱光纤激光器的发展历程,指出宽温运行光纤激光器的需求与应用场景。综述已有关于光纤激光器在变温条件下的研究成果,在高功率光纤激光器的发展中,工作温度对光纤激光器造成的影响将进一步显现。介绍了利用现有光纤器件以及传统光纤激光器设计的宽温运行光纤激光器案例。通过系统设计和结构优化,本课题组已成功实现千瓦级的宽温运行光纤激光器,整机运行温度从常温拓展到-30℃。进一步的功率提升和温度范围拓展还需要对光纤激光器工作机理、光纤器件温度特性等方面进行深入研究。此外,展望了宽温运行光纤激光器的发展趋势,研究结果为高功率宽温运行光纤激光器的发展提供了参考。     

宽象限相依随机变量部分和的中偏差及其在保险中的应用

研究了控制变换尾分布的宽象限相依实值随机变量部分和的中偏差.相应于所得到的理论结果,进一步给出了在相依保险风险模型中的两个应用;一是在基于顾客到达过程的保险风险模型中,保险公司盈余的渐近估计;二是在复合更新风险模型中,有限时和无限时破产概率的一致渐近估计.