一种脉冲强电流条件下导线电阻测量方法

在超强激光辐照电容线圈靶产生强磁场实验中,在约50 ps时,线圈电流达到20 kA以上。通过该实验结果与磁场产生理论模型对比,可得出该导线电阻值比常温直流电阻高出3个量级。对导线材料电阻率与趋肤效应的分析结果表明,该电阻值在量级上是合理的。获得超快脉冲强电流条件下的导线电阻值,有助于更深入理解线圈靶产生强磁场过程。     

浅谈平面振子的阻尼运动

从动力学方程出发并结合Mathcad数值计算,研究了平面振子的阻尼运动,并分析了阻尼系数对平面振子运动轨迹的影响.     

光学读出非制冷红外成像技术的光学灵敏度分析

不同于传统的非制冷红外成像技术,提出了基于微电子机械系统(MEMS)的新概念光学读出非制冷红外成像技术。它的光学读出系统基于空间刀口滤波原理,具有高灵敏度、高分辨率和高抗震性等优点,但同时也受到了反光板的弯曲变形、粗糙度等复杂因素的影响。在大量实验数据的基础上,利用夫琅禾费近场衍射理论,建立了复杂因素下光学灵敏度的理论分析模型,详细分析了刀口滤波位置、反光板的长度、曲率半径、粗糙度、LED光源的强度以及扩展宽度等对光学灵敏度的影响,并提出了通过极限操作使系统的光学灵敏度最大化的光学优化方法。     

A bit-level image encryption algorithm based on spatiotemporal chaotic system and self-adaptive

This paper proposes a bit-level image encryption algorithm based on spatiotemporal chaotic system which is self-adaptive. We use a bit-level encryption scheme to reduce the volume of data during encryption and decryption in order to reduce the execution time. We also use the adaptive encryption scheme to make the ciphered image dependent on the plain image to improve performance. Simulation results show that the performance and security of the proposed encryption algorithm can encrypt plaintext effectively and resist various typical attacks.     

过模结构表面波振荡器模式选择

过模结构能提高器件的功率容量和工作频率, 能使器件工作在低磁场状态, 越来越多的器件采用过模结构.但是过模结构允许多个模式同时存在, 这可能会引起模式竞争问题.本文通过理论分析和数值计算, 研究了过模结构模式选择问题.计算结果表明, 通过选择合适的结构参数和电参数, 使得器件工作在行波状态, 可以实现不同横向模式的选择.在此基础上, 通过选择合适的电子束和结构参数, 能实现不同纵向模式的选择.对计算结果进行了粒子模拟验证, 与理论分析符合较好, 达到了模式选择的目的. 关键词： 过模结构 模式选择 色散关系 表面波振荡器     

The physics of spin rectification and its application

A coherent nonlinear coupling between the charge and spin dynamics of electrons results in the rectification of microwaves,which is enhanced through resonant magnetization dynamics such as ferromagnetic resonance.This property,known as the spin rectification effect,enables the spin dynamics within a material to be electrically detected with a high sensitivity.Techniques utilizing this property have been widely used to study the magnetization dynamics of various ferromagnetic materials and structures in the past decade.Additionally,the coherent nature of spin rectification opens the door for spintronic devices to be used in phase-resolved microwave sensing techniques.In this work we review the physics of spin rectification and its applications in several interesting topics of magnetism and spintronics.     

WMS的玻璃药瓶内氧气含量检测及其标定方法改进

应用激光波长调制光谱(WMS)技术,建立了一种开放光路短光程检测玻璃药瓶内氧气含量的方法。选择氧气分子位于760.885(13 142.58 cm-1)的吸收谱线,通过多次调试优化了系统相关参数,给出了实时扣背景及实时谱线校正等数据处理的方法和步骤。采集七种不同氧气含量的玻璃药瓶样本,获取相应的二次谐波信号,分别建立二次谐波峰值、半高谱峰面积与浓度的线性回归方程进行定量预测。实验结果表明,其拟合系数分别为0.996 6和0.997 8,后者相比前者的标定方法提高了0.12%。采用完全交互验证的方法来评价两个模型的预测精度,其预测的均方根误差(RMSEP)分别是0.003 1和0.002 0,后者相比前者降低了37.69%。对浓度是4%的气体样品,比较不同时间的20次测量结果,标准差分别为0.002 2和0.001 6,后者相比前者降低了27.3%,同时其测量灵敏度分别为0.198%和0.097%,后者相比前者的灵敏度提高了约51%。证明了该系统及数据处理方法对玻璃药瓶内氧气含量检测是可行的,且利用半高谱峰面积更丰富的幅值信息来反演气体浓度可以降低波峰失真影响,检测精度更高,稳定性更好。     

布里渊动态光栅原理及其在光纤传感中的应用

自从2007年布里渊动态光栅被首次提出用于实现光存储以来,该技术得到了国际上的广泛关注和研究.布里渊动态光栅本质上是由相干声波场激发的折射率光栅,一般情况下两束抽运光(频率差等于光纤的布里渊频移)以相同的偏振态从光纤两端注入到光纤中,通过受激布里渊散射效应激发出相干声波场,即形成布里渊动态光栅.光纤布里渊动态光栅因具有全光产生、参数灵活可控的优点,已被广泛研究应用于光纤传感、光纤特性表征、光存储、全光信号处理、微波光子学和高精度光谱分析等.本文分析布里渊动态光栅产生和探测原理,重点探讨在高性能分布式光纤传感上的应用,这些应用包括高灵敏度温度和应变分布式传感、温度和应变同时解调、分布式横向压力传感、分布式静压力(气压或液压)传感、高空间分辨率分布式传感和高精度光谱分析.     

Optical studies of pulsed-laser fragmentation of biliary calculi

The fragmentation of gallstones and kidney stones using pulsed visible laser radiation has recently been demonstrated; however, the fragmentation mechanism is not well understood. The temporal and spectral characteristics of the bright flash of light accompanying fragmentation of gallstones were studied using 0.8 and 360-s-long, 690-nm-wavelength, dye-laser pulses. Time-resolved visible emission spectra show a broad continuum upon which line spectra are superimposed. The continuum emission is due to free-free and free-bound electron transitions indicative of a plasma and the line spectra are due to neutral and ionized calcium. Initiation of this plasma is fluence rather than intensity dependent. A model is proposed in which laser energy is coupled to the plasma, which then impulsively expands, generating intense acoustic transients which fracture the stone.