共查询到20条相似文献,搜索用时 93 毫秒
1.
2.
3.
文中提出了用流场的一次曝光像的强度谱作为模板提取杨氏条纹,以获取尖锐的自相关分布的方法,并给出了该方法用于激光散斑测速和粒子像测速技术的计算机模拟结果以及粒子像测速的应用例子。 相似文献
4.
本文提出了产生自成像局域空心光束(self-imaged bottle beams)的一种光学元件------液体轴棱锥.从衍射理论结合几何光学对经过轴棱锥后的光场进行了分析, 得出注入液体折射率小于轴棱锥材料折射率时可产生自成像局域空心光束.并通过软件MathCAD模拟, 得到一个完整周期光束的变换过程和局域空心光束的演变过程.研究发现液体轴棱锥产生的自成像局域 空心光束具有周期及相干长度可调的特点.分析了如何利用自成像局域空心光束对粒子进行俘获, 讨论了用自成像局域空心光束进行多层面粒子俘获的优势. 相似文献
5.
6.
7.
运用PIC程序研究了强流离子束中粒子的横向运动,发现了不加控制时束晕粒子并非一直处于晕区和施加非线性控制后粒子的横向运动被限制在一定的范围内形成环状,以及均方根半径的变化近似成为周期运动等性质.根据观察到的均方根半径及其变化率的规律性,提出了一种新的自适应控制器.用该控制器不仅能在很短的时间内完全控制住束晕,而且不需要对增益因子进行精确计算,也能在系统参数改变的情况下取得较好的控制效果.
关键词:
束晕_混沌
粒子跟踪
数值模拟
自适应控制 相似文献
8.
介绍了折反式大视场强焦比平场CCD照相机的设计思想和方法,给出了详细的结构参数和像斑弥散直径。照相机焦比0.9,对角视场22.2°,使用波长范围390~900nm,以660nm为分界波长分为红蓝两区照相机,各用一块1024×2048CCD接收器。照相机像质优良,结构全新。 相似文献
9.
10.
11.
This paper discusses the suitability of PIV for measuring simultaneously the velocity field of every phase and the size and concentration field of the disperse phases in multiphase flows. Velocity and disperse phase information are both inferred either directly from the Young’s fringe pattern (far field diffraction function) or from its 2-D Fourier transform (autocorrelation function). In the first case, the velocity is inferred from the orientation and spacing of the fringes while the disperse phase size is inferred from the size of the diffraction halo that modulates the fringes. In the second case, the velocity and particle shape are related to the position and shape of the strongest autocorrelation peaks, respectively. Particle sizes are used to discriminate between phases on the velocity measurements. The technique has been demonstrated on a high speed air-particle flow, where the potential for determining air velocities and particle size and velocities are shown. 相似文献
12.
N. Nagamatsu K. Nakagawa T. Asakura K. Morishita 《Optical and Quantum Electronics》1983,15(6):507-512
The autocorrelation function of polychromatic speckle patterns produced near the image plane of a double diffraction imaging system is experimentally studied. The condition under which the polychromatic speckle field obeys Gaussian statistics is further investigated as a function of the numberN of scattering cells, using the average contrast of the speckle intensity fluctuations. The profile of the autocorrelation function is next investigated as a function ofN and the defocused distance from the image plane. It is found that the average contrast and autocorrelation function of the polychromatic speckle intensity fluctuations converge less rapidly with an increase inN than those of the monochromatic ones. 相似文献
13.
14.
This paper describes a novel automated high-speed optical autocorrelation system for particle image velocimetry (PIV) analysis. In this system, a bistable ferroelectric optically addressed spatial light modulator (BOASLM) is used for real time optical autocorrelation. Input data from a PIV transparency is scanned into the system by utilising two scanning mirrors and the output autocorrelation signals are detected with a two-dimensional scanning tracking system implemented by two acousto-optic modulators. This data extraction system is equivalent to a random access camera, which is used to track the autocorrelation signals from region to region in order to retrieve velocity data at the full frame rate of the BOASLM. The factors that influence the processing capacity of the optical system are discussed in detail and a critical comparison is made with digital analysis systems. A working prototype of an optical PIV analysis system is described and the measurement of 1296 velocity vectors from a PIV transparency in approximately five seconds is demonstrated. 相似文献
15.
鉴于CCD相机在强光照射时会产生光晕,CCD敏感面像素之间互相影响,进而导致成像模糊不清,提出一种克服光晕现象的像质增强算法.利用HTPS(高温聚硅)液晶具有可实时控制各像素光透过率的特性,使液晶和主CCD由光纤光锥进行像素一对一耦合.用Cyclone II芯片作为图像处理单元,测光CCD采集图像信息,控制液晶改善图像质量.实验结果表明,该系统能够精确控制HTPS液晶上每个像素的透过率,使CCD相机能在强光下正常成像,其灰度分辨能力提高了1倍,从而提高了图像的清晰度. 相似文献
16.
The structure of foams and filled polymers can be analyzed by means of MRI. It is also possible to observe the deformation behavior of the structure of foams and filled polymers in situ. A displacement experiment (rigid body) was performed in the magnet and observed by MRI. The NMR images are analyzed by image processing. Average distances between particles are estimated by the use of the autocorrelation function and the spectrum of the autocorrelation function. The spectrum shows the spatial frequency of the distances. The displacement field was calculated by the cross-correlation function. Information about particle distances and micromechanical deformation can be obtained by NMR imaging methods by combining autocorrelation and cross-correlation. 相似文献
17.
X光针孔成像是惯性约束聚变(ICF)研究中重要的诊断方法,对其点扩散函数的计算可用于图像重建和系统空间分辨的判断。对菲涅耳衍射公式进行了化简,分析了X光能点、针孔尺寸及放大倍率对针孔点扩散函数的影响。实验在保证成像能获得足够高信噪比的条件下,通过模拟获得在最佳空间分辨时所要的针孔大小、放大倍率和X光能点等参数。在流体力学不稳定性的静态样品定标实验中,通过模拟获得了针孔的调制传递函数(MTF),结合实验测量的结果反推获得分幅相机本身的MTF值。同时采用测刀边函数的方法获得了分幅相机本身的刀边函数,进而得到相机在各空间频率下的MTF值。两种方法得到的分幅相机MTF值一致,验证了通过菲涅耳衍射模拟X光针孔成像的可行性。 相似文献
18.
The evaluation of flow records obtained by particle image velocimetry (PIV) employs the interrogation of certain regions in the flow image. Basic relations are derived for the case that the velocity is not constant within the region of interrogation. The influence of a distribution of velocities on the Young's fringe system and its Fourier transform, the autocorrelation of the flow record, are discussed. The considerations show that there is an easy access to statistical parameters of the flow by carrying out large-field interrogation. The autocorrelation function will reproduce the probability density function of the velocity, and there is no need for a large number of time-consuming small-area interrogations. Furthermore, the effects of velocity variations in ordinary fringe analysis are discussed. Examples are given from synthetic PIV records and measurements in a wind tunnel. 相似文献
19.
20.
Low-energy electron diffraction intensity profiles are Fourier inverted. The optical transform is more suitable for LEED than the usual cosine transform and yields a quantity related to the autocorrelation function. Transforms of individual LEED profiles taken at different diffraction geometry are not the same, but transforms of averaged, kinematic data give expected autocorrelation functions. 相似文献