光学锁相环的研究进展

光学锁相环（OPLL）根据其锁定的两束激光间是否存在频差可分为零差光学锁相环和外差光学锁相环。主要介绍了外差光学锁相环的研究进展,它是一种通过鉴频鉴相方式使激光间的频率差保持相对稳定的偏频锁定方法。相较于其他激光偏频锁定方法,光学锁相环具有结构简单、伺服频率带宽大、频率偏置范围宽、锁定准确度高等优势,在原子相干、冷原子系统、相干功率合成以及外差干涉测量等领域都得到了越来越广泛的应用。首先介绍了激光偏频锁定的主要方法及光学锁相环的特点;其次介绍了光学锁相环的基本模型,分析了光学锁相环的误差反馈过程,并按照光学锁相环实现方法的不同详细介绍了其采用的关键技术和研究进展,对近年来光学锁相环在不同领域的应用进展做了简要介绍;最后对该方法的发展路线进行了总结和展望。     

量子电压标定的噪声温度计系统设计

针对传统噪声温度计2个噪声源的功率和阻抗不能同时匹配的问题,为实现热力学温度自动化准确测量,以量子电压任意波形合成技术为基础,合成频率、幅度已知的赝噪声源作为参考端信号,并以高精度数字分析仪PXI—5922为数据采集平台,完成量子电压标定的噪声温度计系统设计。初步实验结果表明:此系统运行良好,可以实现水三相点热力学温度的准确测量。     

Block adaptive kernel principal component analysis for nonlinear process monitoring

On‐line modeling of multivariate nonlinear system based on multivariate statistical methods has been studied extensively due to its industrial requirements. In order to further improve the modeling efficiency, a fast Block Adaptive Kernel Principal Component Analysis algorithm is proposed. Comparing with the existing work, the proposed algorithm (1) does not rely on iterative computation in the calculating process, (2) combines the up‐ and downdating operations to become a single one (3) and describes the adaptation of the Gram matrix as a series of rank‐1 modification. In addition, (4) the updation of the eigenvalues and eigenvectors is of and high‐precision. The computational complexity analysis and the numerical study show that the derived strategy possesses better ability to model the time‐varying nonlinear variable interrelationships in process monitoring. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4334–4345, 2016     

Orientation of the fiber suspending in the flow through a tube containing a sphere

Fiber suspensions flow through a tube containing a sphere in the dilute and concentrated regimes is simulated numerically with the Lattice Boltzmann Method (LBM). The numerical results of fiber orientation distribution based on a statistical scheme are obtained and agree qualitatively with the experimental ones for the flow through a parallel plate channel containing a cylinder. The results show that the sphere in the tube results in a change in the fiber orientation distribution downstream of the sphere along the flow and transverse directions. The influences of the sphere on the fiber orientation distribution are more significant for the concentrated suspensions than for the dilute one. The effect of the initial fiber orientations on the fiber orientation distribution is significant upstream of the sphere but small downstream of the sphere.     

Extrusion of AlSBA-15 molecular sieves: An industrial point of view

AlSBA-15 in the powder form with different n_Si/n_Al ratios (45, 136 and 215) were synthesized by hydrothermal technique. The powdered materials were made into cylindrical extrudates with the addition of bentonite as a binder. The AlSBA-15 materials were characterized by XRD, N₂ adsorption, AAS and thermogravimetric analysis. The orderly growth of AlSBA-15 is evidenced by its XRD. The surface area of the powder catalyst is around 950 m²/g and that of extrudate is close to 600 m²/g. Vapor phase alkylation of phenol with tert-butanol was carried out over the extrudates of AlSBA-15 as a model reaction. The activity of AlSBA-15 extrudates follows the order: AlSBA-15 Si/Al = 45 > AlSBA-15 Si/Al = 136 > AlSBA-15 Si/Al = 215. The reaction products were found to be 2-TBP, 4-TBP and 2,4-DTBP. The selectivity to para tertiary butylation is higher than other reactions.     

多边法位姿测量系统中跟踪方式对测量精度的影响研究

为了精确测量大尺寸位姿,建立了一种由7台激光跟踪干涉仪组成的大尺寸位姿测量装置。根据测量各反射镜的激光跟踪干涉仪数量的不同,采用322和331两种跟踪方式对位姿测量精度的影响进行仿真实验,从而发现被测点位置与基站构成平面的距离相关,由坐标解算公式推导被测点坐标值与测量基站之间的相对位置与测量误差间的误差模型,通过分析x、y、z 方向上误差对距离变化的敏感程度,发现z方向距离变化引起的误差最为敏感。当被测点与测量基站的距离由1300.8mm减小到0mm时,测量误差由2.2μm增大到2626.1μm。实际姿态测量结果表明:当采用一种跟踪方式时可以避免被测点与测站点平面过近,有利于提高系统测量精度,所提出的误差模型可为多边法位姿测量系统的优化布局提供一种量化的理论分析方法。     

基于光学锁相环的高稳定度激光稳频方法研究

报道了一种基于光学锁相环的高稳定度激光稳频方法,用于提高可调谐外腔半导体激光器(TECDL)的频率稳定度和准确度。自行研制的光学锁相环电路采用数字鉴相与差分运算相结合的方式获得高灵敏度的鉴频鉴相误差信号,并通过高速模拟PID实现整个系统的闭环锁定。利用该光学锁相环系统进行了TECDL偏频锁定至光学频率梳(OFC)的实验,实验结果表明环路锁定后拍频频率波动在±0.3Hz范围内,偏置频率为50MHz时,光学锁相环系统在1s和1000s积分时间的相对阿伦方差分别为1.5×10^-9和8.5×10^-13。系统锁定后,拍频线宽由500kHz压缩至2kHz。该研究表明采用基于光学锁相环的激光稳频方法可以实现亚Hz级的激光频差控制,通过将TECDL偏频锁定至高稳定度的参考激光源可显著提高其频率稳定度,使其能够满足超精密测量、冷原子/离子干涉测量等领域对激光频率稳定度和准确度的要求。     

基于小波变换的故障电弧断路器设计

故障电弧是引起电气火灾的主要原因之一,故障电弧断电保护作为一项较新的电路保护技术,能较好地防止因故障电弧而引发的火灾.通过分析故障电弧特征信号,提出了一种故障电弧检测方法,设计了故障电弧断路器的硬件和软件.利用电流互感器采集电流信号,经滤波处理后送入MCU,利用Daubechies 4阶小波变换对检测到的电流信号进行处理分析,判断有无故障电弧产生并做出相应处理.经试验分析,表明该设计是有效的,该故障电弧断路器同时具有漏电保护功能,具有识别率高、误动作率低等特点,可最大限度地保护供电系统、用电设备和人员的安全.     

脉冲方波驱动强化热电制冷的瞬态特性

采用有限差分法对脉冲电压驱动下的瞬态热电效应及其动态特性过程进行了理论分析,探索了非稳态工况下帕尔帖效应、焦耳热效应与傅里叶导热效应之间的耦合关系及其关键制约因素对制冷性能的影响规律,进而探讨了脉冲驱动强化热电制冷性能的作用机理。分析结果得到,在合理电压域值内采用主动控制方法,对热电模块周期性施加数倍于稳态工况理想电压的脉冲突变电压,有益于充分利用帕尔贴制冷效应而推迟出现以焦耳热和傅里叶热耗散形式为主的内部热积聚对热电模块冷端引起的负效应,并能瞬态实现冷端面的制冷强化作用和最大程度实现输入电能的有效转换。该结论不仅为进一步提出脉冲驱动模式的优化控制策略提供了理论依据,也为瞬态热电制冷效应的应用开辟了一条新思路。     

基于小波变换的故障电弧检测方法研究

描述了故障电弧的危害、定义及检测方法分类。提出了一种基于Daubechies 4阶小波变换的故障电弧检测方法。通过试验分析证明,其具有计算简单、实时性强等特点,能有效检测线路中是否有故障电弧产生。