Fabrication of Long-Period Fibre Gratings Using 800 nm Femtosecond Laser Pulses

Long-period fibre gratings inside standard single-mode optical communication fibres are successfully fabricated with infrared femtosecond laser pulses. The refractive index perturbations are well confined within the fibre core by choosing the proper laser focusing parameters and translation speed of the fibre during the direct laser writing process. With the self-focusing effect considered and at a constant average irradiation dose of 1.62 × 10^3 J/（cm^2μm）, the threshold intensity for fabricating long-period gratings with infrared femtosecond laser pulses is determined to be 5.13 × 10^13 W/cm2.     

离散大系统关于部分变元的关联稳定性

一、问题的提出在文献[1]中,曾提出了关于部分变元的稳定性问题.1957年,首先引进函数 V(t,x_1,…,x_n)关于变元 x_1,…,x_m(m≤n)为定号函数等概念,并给出了系统关于部分变元稳定性和渐近稳定性的定理.随后,许多学者从事这方面的研究工作.实际上这是与这个问题本身具有很重要的实用性分不开的.意义下的稳定性是针对系统的所有状态变量而言的.但实际上很多稳定性问题并不要求(或不可能要求)用同样的方式处理所有的状态变量.到目前为止,虽然关于全变元稳定性的许多结果已平行地推广到部分变元稳定性问题上来,但是从具体问题出发,来解决     

多气隙电阻板室抗辐照性能研究

给出了为RHIC-STAR飞行时间探测器设计的多气隙电阻板室(MRPC)的辐照实验结果. 实验采用100mCi⁶⁰Co γ源, 采用不同的剂量率对MRPC进行辐照. 一个室在大剂量率2.87×10^－2Gy/h下辐照了24h后, 其性能如噪声计数率, 暗电流等均大大退化. 另一个室在相对低剂量率5.31×10^－4Gy/h下辐照了530h, 其性能没有见到任何变坏. 实验的目的是为了了解这种探测器在几年的运行中经过大剂量的辐照后的性能变化情况.     

High-Dimensional Nonlinear Envelope Equations and Nonlinear Localized Excitations in Photonic Crystals

We investigate the nonlinear localized structures of optical pulses propagating in a one-dimensional photonic crystal with a quadratic nonlinearity. Using a method of multiple scales we show that the nonlinear evolution of a wave packet, formed by the superposition of short-wavelength excitations, and long-wavelength mean fields, generated by the self-interaction of the wave packet, are governed by a set of coupled high-dimenslonal nonlinear envelope equations, which can be reduced to Davey-Stewartson equations and thus support dromionlike high-dimensional nonlinear excitations in the system.     

微脉冲电子枪的初步实验研究

给出了微脉冲电子枪的模拟计算及其初步实验结果. 该电子枪采用铜铝镁合金作为冷阴极材料, 在以磁控管作为微波功率源的出束实验中得到了100mA/cm²的电流密度.实验结果与次级电子倍增解析计算和SEEG程序的模拟计算结果基本符合, 初步验证了微脉冲电子枪的基本原理, 为今后实验中得到更大的电流密度打下了基础.     

Effect of Incident Intensity on Films Growth in Pulsed Laser Deposition

Incident intensity, defined by the amount of particles deposited per pulse, is an important parameter in the film growth process of pulsed laser deposition （PLD）. Different from previous models, we investigate the irreversible and reversible growth processes by using a kinetic Monte Carlo method and find that island density and film morphology strongly depend on pulse intensity. At higher pulse intensities, lots of adatoms instantaneously diffuse on the substrate surface, and then nucleation easily occurs between the moving adatoms resulting in more smaller-size islands. In contrast, at the lower pulse intensities, nucleation event occurs preferentially between the single adatom and existing islands rather than forming new islands, and therefore the average island size becomes larger in this case. Additionally, our results show that substrate temperature plays an important role in film growth. In particular, it can determine the films shape and weaken the effect of pulse intensity on film growth at the lower temperatures by controlling the mobility rate of atoms. Our results can match the related theoretical and experimental results.     

Banach空间无界域上二阶脉冲积分微分方程的解

在比较宽松的条件下，研究了Banach空间中二阶脉冲积分微分方程在正半实轴上具有无穷个脉冲点的初值问题的解的存在性。利用递归法、Tonelii序列和局部凸拓扑，建立了新的存在性定理，对郭大钧的结果做了本质改进。     

脉冲磁场处理对碳纳米管掺杂MgB2线材临界电流密度的影响

对碳纳米管(CNT)掺杂MgB₂超导体磁场处理后的行为进行了研究. 结果表明，CNT掺杂MgB₂超导体经5T脉冲磁场处理后临界电流密度J_c(H)在低磁场下提高了2—3倍，高场下提高一个数量级以上，扫描电镜结果显示CNT沿着处理磁场方向规则排列并且成为MgB₂基体的形核中心和高效的磁通钉扎中心. 关键词： 2')" href="#">MgB₂ 碳纳米管 脉冲磁场处理     

欧美国家制成激光加速器

目前，世界上已有3个实验组独立成功地利用激光场的尾波加速单能电子束。当一束强的激光脉冲进入气体或等离子体时。激光的电场可以加速运动的电子，直到相对静止的离子通过库仑场把电子拉回为止。等离子体波沿着激光脉冲的尾场运动。在合适的条件下，电子能够被等离子体波带着走；而以前。被加速的电子的能量是分散的。但是，只要加速过程在合适的时间停止。正在加速的电子可以超过等离子体波，而且所有的电子都达到相同的能量。由法国科研中心（GNRS）的维克多·莫片（Victor Malka）领导的小组和由英国伦敦皇家学院的斯多达·孟格利斯（StuartMangles）领导的小组已精确地调整其激光器和等离子体的参数，分别产生了能量约为170MeV和70MeV的准直电子束。     

s波超导体绝缘层dx2-y2波超导体结的直流Josephson电流

在s波超导体绝缘层dx2-y2波超导体结(sId)中,考虑到结界面粗糙散射,运用BogoliubovdeGennes(BdG)方程和FurusakiTsukada(FT)电流公式,计算超导结中的准粒子传输系数和直流Josephson电流.结果表明:sId超导结的直流Josephson电流随温度以及结两侧的相位差变化的关系曲线强烈地依赖于d波超导体的晶轴方位;结界面的粗糙散射对Josephson电流有抑制作用 关键词： s/I/d超导结 dx2-y2波超导体 直流Josephson电流