Effect of primary aberrations on transverse displacement of laser speckle patterns

The effect of primary aberrations on the transverse displacement of laser speckle patterns in the real image plane due to transverse displacement of an object is studied in the approximation of Fourier optics. Primary aberrations cause: (i) a complementary displacement of the speckle pattern; and (ii) its decorrelation. The main features of complementary displacements are as follows: (a) the overall complementary displacement is the sum of complementary displacements caused by each one of the primary aberrations; (b) the complementary displacement caused by the spherical aberration is uniform in the image plane; (c) spherical aberration and curvature of field cause complementary displacements that are parallel to the object's displacement; (d) the complementary displacement caused by distortion is always zero on the optical axis; (e) the complementary displacement caused by distortion is free of decorrelation; (f) complementary displacements are non-proportional to the object's displacement; and (g) complementary displacements depend on the position of the illuminating source with the exception of the complementary displacement caused by distortion.     

局地零平面位移对非均匀地表有效空气动力学参数的影响

利用最新提出的非均匀地表有效空气动力学参数联合计算方案, 研究了三种非均匀地表情况下局地零平面位移对有效粗糙度和有效零 平面位移影响的统计特征.结果表明, 局地零平面位移对有效粗糙度有增幅作用, 随着局地零平面位移的增加, 有效粗糙度也相应增大, 但局地零平面位移对有效粗糙度的增幅作用随地表粗糙变率增加而略有减小; 有效零平面位移随局地零平面位移的增加而增加, 但总小于线性加权平均值, 且随着地表粗糙变率的增大, 有效零平面位移却有所减小. 关键词： 非均匀地表 局地零平面位移 有效粗糙度 有效零平面位移     

多孔介质中含溶解反应的互溶驱替过程格子Boltzmann研究

采用格子Boltzmann方法研究了孔隙尺度下多孔介质内含流固溶解反应的互溶驱替过程,重点研究了被驱替流体与驱替流体黏性差异较大的情况下,溶解反应引起的多孔介质内部结构变化对驱替过程的影响;定量分析了不同达姆科勒数及佩克莱数下多孔介质孔隙率和驱替过程驱替效率随时间的演变.研究结果表明:达姆科勒数较大时,溶解反应的发生会在多孔介质内部生成虫洞,导致一部分被驱替流体不能被波及,驱替流体沿虫洞离开多孔介质,造成驱替效率的减少.在此基础上,随着达姆科勒数的增大,孔隙率变化越大,生成的虫洞越宽,最终驱替效率变大,但仍小于无溶解反应时的驱替效率;随着佩克莱数的增大,指进增长速度越快,孔隙率变化越小,驱替效率越小.     

双目立体视觉技术在结构试验中的应用

传统的动态位移测量方法属于接触式测量,常用应变式位移计直接测量结构变形,其测量精度往往取决于位移计安装情况,且测量的电信号容易受到试验环境的影响。随着光学测量技术的不断发展,基于双目立体视觉和数字图像处理技术的光学测量方法已开始应用于位移测量。为了解决传统动态位移测量的精度问题和环境对信号的干扰问题,将双目立体视觉技术应用到三层钢框架结构的振动台试验中,对结构在地震作用下的位移进行测量。研究结果表明:从位移时程和位移偏差率两方面同传统测量方法进行对比分析,光学测量方法减少了2.0 s~3.5 s的相对滞后时间,增强数据可靠性;位移偏差率最大为7.03%,最小为0.02%,均在测量误差允许范围之内,验证了光学测量位移方法在结构抗震试验中的可行性及优越性。     

The influence of lattice vibrations on the2 S−2 P transition of impurity centers with cubic symmetry

The incommensurate phase of NaNO₂ is known to contain a transverse displacement modulation in addition to the modulated ferroelectric ordering, but the phase and sign of the displacement was left undetermined by the X-ray structural analysis. We discuss the phase, sign and magnitude of the displacement modulation from several points of view and build up a more detailed picture of its origin than previously. Rigorous group theoretical arguments fix the phase as zero, in contrast to the assumption of some workers, and indicate other possible aspects of the structure. The sign of the displacement is found to be positive due to the dominance of electrostatic forces and O–O repulsion over O–Na repulsion. The magnitude of the displacement seen in molecular dynamics simulations and estimated from simple atom packing agree reasonably with the X-ray value. The results confirm the displacement modulation as the essential ingredient responsible for the existence of the incommensurate phase.     

High-precision technique for in-situ testing of the PZT scanner based on fringe analysis

A technique based on fringe analysis is presented for the in-situ testing of the PZT scanner, including the end rotation analysis and displacement measurement. With the interferograms acquired in the Twyman-Green interferometer, the testing can be carried out in real time. The end rotation of the PZT scanner and its spatial displacement deviation are analyzed by processing the fringe rotation and interval changes; displacement of the PZT scanner is determined by fringe shift according to the algorithm of template-matching, from which the relation between the driving voltage and displacement is measured to calibrate the nonlinearity of the PZT scanner. It is shown by computer simulation and experiments that the proposed technique for in-situ testing of the PZT scanner takes a short time, and achieves precise displacement measurement as well as the end rotation angle and displacement deviation measurement. The proposed method has high efficiency and precision, and is of great practicality for in-situ calibration of the PZT scanner.     

Optical measurements of the self-demodulated displacement and its interpretation in terms of radiation pressure

Using a sensitive optical interferometer, the low frequency displacement nonlinearly generated by an ultrasonic tone burst propagating in a liquid is studied. Close to the source, the low frequency displacement contains a quasi-static component, which is affected by diffraction effects farther from the transducer. The experimental setup provides quantitative results, which allow the determination of the nonlinearity parameter of the liquid with a good accuracy. Such measurements are carried out in water and ethanol. Finally, the pressure associated with the low frequency displacement is discussed. Introducing the temporal mean value of the displacement, as already done in lossless solids, the noncumulative part of this second order pressure is associated with the static part of the low frequency displacement. This interpretation leads to extend the definition of the Rayleigh radiation pressure usually introduced for a continuous plane wave radiated in a confined fluid.     

Relationship between Timing Jitter and Prism Separation in Mode-locked Solid State Lasers

The function expression of the group delay dispersion (GDD) depending on the prism separation and the normal displacement is derived, and that the GDD is proportional to the prism separation and near to a linear function of the normal displacement in the case of small normal displacement are found. Then we discuss the timing jitter caused by the amplified spontaneous emission (ASE) which depends on the prism separation and the normal displacement. We find that the timing jitter is near to a linear function of the prism separation and can be regrded as a linear function of the normal displacement in the case of small normal displacement. Based on the theoretic work, we suggest an experimental setup to measure the relationship between the timing jitter and the prism separation or the normal displacement.     

ICF中可调法布里-珀罗滤波器间距稳定度研究

 在神光Ⅱ第9路ICF高功率激光装置中，采用可调法布里-珀罗(F-P)滤波器对幅度调制效应进行补偿，根据补偿装置的技术要求，提出一种应用nm量级精度的电容式位移传感器对可调F-P滤波器间距稳定度进行监控的系统，详细论述了监控系统的结构与工作原理。给出了电容式位移传感器的驱动电路及数据处理与控制软件的设计方案，并对电容式位移传感器的精度进行了标定。实验结果表明，该位移监控系统能够使可调F-P滤波器的间距稳定度保持在15 nm/h以内，使幅度调制效应的调制深度优于4%。     

A new laser displacement sensor based on triangulation for gauge real-time measurement

A new laser displacement sensor has been designed, constructed, and used in a train running at a speed of 64 km/h. The laser displacement sensor is insensitive to ambient light and to temperature. The parameters of the laser displacement sensor are as follows: the measurement range is 20 mm, and the laser displacement sensor resolution is 0.3 mm. All the results show that this new displacement sensor meets the requirement for real-time gauge measurement.     

Relationship between Timing Jitter and Prism Separation in Mode-locked Solid State Lasers

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Exploration of Displacement Reaction/Sorption Strategies in Spectrometric Analysis

Abstract

Displacement reactions are very popular in nature, ranging from texbook knowledge of the Zn-CuSO₄ system to modern functional nucleic acid–involved metal ion displacement. Though synthetic chemistry harvests a lot from displacement reactions, analytical chemistry benefits greatly from various displacement reaction strategies, such as sensitivity improvement. In particular, the use of indicator displacement assay for new sensor development is of great interest worldwide. In this review, we summarize the advances in utilization of displacement reactions for improved spectrometric analysis. The main contents include displacement-based preconcentration schemes for trace metal analysis by analytical atomic spectrometry, indicator displacement assays focusing on the use of advanced nanomaterials, and displacement immunoassays using spectrometric measurements, with 117 references.     

用亥姆霍兹定理讨论电位移

从亥姆霍兹定理出发,阐明了电位移与场源之间的内在联系,指出电位移不仅与自由电荷分布有关,而且还与电介质、极化电荷及边界条件有关;着重分析了电位移仅与自由电荷分布有关的条件。     

Angular Dependence of Lateral and Levitation Forces in Asymmetric Small Magnet/Superconducting Systems

The dipole-dipole interaction model is used to calculate the angular dependence of lateral and levitation forces on a small permanent magnet and a cylindrical superconductor in the Meissner state lying laterally off the symmetric axis of the cylinder. Under the assumption that the lateral displacement of the magnet is small compared with the physical dimensions of the system, we obtain analytical expressions for the lateral and levitation forces as functions of geometrical parameters of the superconductor as well as the height, the lateral displacement and the orientation of magnetic moment of the magnet. The effect of thickness and radius of the superconductor on the levitation force is similar to that for a symmetric magnet/superconducting cylinder system, but within the range of lateral displacement. The splitting in the levitation force increases with the increasing angle of orientation of the magnetic moment of the magnet. For a given lateral displacement of the magnet, the lateral force vanishes when the magnetic moment is perpendicular to the surface of the superconductor and has a maximum value when the moment is parallel to the surface. For a given orientation of the magnetic moment, the lateral force has a linear relationship with the lateral displacement. The stability of the magnet above the superconducting cylinder is discussed in detail.     

Connection Structures of Topological Singularity in Micromechanics from a Viewpoint of Generalized Finsler Space

Geometric structures of Cosserat or micropolar continuum are discussed based on geometric objects in a non-Riemannian space. A microrotation is described in a microscopic level than a macroscopic displacement level. In this case, a microscopic rotation can be expressed as a nonlocal internal variable attached to each point in a generalized Finsler space. Such non-local hierarchy is geometrically realized by using a second-order vector bundle viewpoint. Then, two kinds of torsion tensor in the second-order vector bundle are obtained. One is characterized by the macroscopic displacement. The other is characterized by the microscopic rotation. These torsion tensors are equivalent to nonintegrability conditions for multivalued macroscopic displacement and microscopic rotation. Especially, a path dependency of the displacement and the microscopic rotation is represented by a non-vanishing condition of torsion tensors. Moreover, the concept of non-locality of the Finsler geometry implies that the approach of higher-order geometry is applicable to a finite deformation in nonlinear mechanics. The singularity given by the multivalued function is also described as a boundary value problem. An application of the generalized Finsler geometry to a gradient theory is also discussed.     

Simultaneous quantitative evaluation of in-plane and out-of-plane deformation by use of a carrier method of large image-shearing shearography

A carrier method for separating out-of-plane displacement from in-plane components based on large imageshearing shearography is presented. A reference surface is fixed on the side of a test object. They are illuminated by two expanded symmetric illuminations respectively. The carrier is introduced by rotating the reference surface to modulate the displacement of an object. By using Fourier transform to demodulate the modulated fringe pattern, two phase maps, which include out-of-plane and in-plane displacements, can be obtained. Then the out-of-plane displacement can be easily separated from in-plane displacement by subtraction and addition of the two unwrapped phase distributions. The principle of the method is presented and proved by a typical three-point-bending experiment. Experimental results show that the method enjoys high visibility of carrier fringes. The system does not need a special beam as a reference light and has simple optical setup.     

Effects of draining cochlear fluids on stapes displacement in human middle-ear models.

Displacement-frequency characteristics of the stapes footplate were measured in five human temporal bones before and after draining the vestibule. Measurements were made in the 0.125-8 kHz range at 80 dB input sound pressure level, using a laser Doppler vibrometer. A circuit model was also used to predict stapes displacement. The temporal bone studies show a slight decrease in stapes footplate displacement at low frequency, and little change above 1 kHz. The displacement change is not as great as that found by other investigators or predicted by the model. There is little difference in stapes motion in temporal bones when the inner ear is intact or drained.     

散斑位移量与照明激光束特性关系的实验研究

激光照射到粗糙物体的表面会形成激光散斑，散斑随物体的运动而运动，特别是物体在自身平面内运动时散斑的同步运动比较显著，因此可以用这一现象测物体的微小位移，散斑运动规律与照明光束的特性有关，本文通过实验研究了不同光束照明下散斑位移的规律，验证了散斑位移理论，并指出散斑位移测量中应注意的问题。     

用Zernike多项式实现光机分析的技术方法

由于光学软件不能直接利用有限元分析的结果，而Zernike多项式的各项与光学像差有对应关系，因此常用Zernike多项式作为光机接口。针对目前常用轴向位移作为拟合量描述拟合面形的不足，给出了几种常用的表面位移校正方法并说明了其优缺点。用具体实例比较各校正位移，并对其进行Zernike多项式拟合，从拟合系数的差异可以看出,曲率比较大的表面必须采用校正位移进行拟合。最后指出：在不知道初始表面方程的情况下，轴向和法向校正位移均采用从初始表面出发的方法，如果已知初始表面方程，则轴向校正位移采用从变形表面出发的方法，法向校正位移仍采用从初始表面点出发进行计算。     

Analytical study of a potential model of tsunami with a simple source of piston type. 1. Exact solution. Creation of tsunami

A linear hydrodynamic problem concerning the generation of gravitational waves on the free surface of a liquid by a source (defined as an initial instant vertical displacement of the bottom of the basin) is studied, where the displacement is defined by a rather simple axially symmetric function of the horizontal coordinates. A solution to the problem is obtained in the form of single integrals and is regarded as a distribution (a ??generalized function??) with respect to time. These integrals are evaluated numerically and asymptotically. In this part of the paper, using the results of numerical evaluation carried out for each source (having a given characteristic radius in a wide range of values), we find the initial instantaneous displacement of the fluid, determine the parameters of the leading crest of the created surface wave, and estimate the minimal radius which a source must have to be referred to tsunami generators.