光散射法测试粒径的一种优化反演组合算法

在目前常用的激光粒度仪反演算方法的优点和缺点基础上,为了实现各种方法的稳定性与准确性的统一,提出一种基于退火演化算法和遗传算法组合的随机反演方法,该方法具有更强的全局收敛性,也具有对粒径分布形状不敏感、抗噪声能力强等优点。该算法能对具有单峰及双峰分布形式的颗粒尺寸进行精确求解,并获得合理的颗粒粒径分布结果。     

激光衍射粒径测量中的Chin-Shifrin反演算法

建立了以线阵CCD作为探测组件的激光衍射粒径测量系统用于颗粒群直径分布的测量.在数值计算的基础上,分析了传统Chin-Shifrin积分变换粒径分布反演算法存在的两个问题:小粒径反演结果的发散和多假峰现象,并结合理论分析给出了这两种现象的物理图像.提出了修正积分变换公式以解决小粒径反演结果发散的间题并针对Chin-Sh...     

基于面阵CCD的散射式激光粒度测量方法研究

研究了基于CCD传感的激光粒度测量方法和优化。在系统设计和实验参数优化基础上,设计了CCD传感器的光环尺寸,并基于Mie散射理论,建立了理论计算模型,计算了待测颗粒的理论光能分布。对标称粒径为10.9μm和57.9μm的聚苯乙烯乳胶标准颗粒进行实验,获得颗粒散射光能分布图像,提出了一种新的光环中心确定方法,并由编写的图像处理程序分析散射光能分布。颗粒粒径的反演结果与标称尺寸比较表明,用此测量方法得到的颗粒散射光能分布与其理论分布较一致,稳定性与重复性较好。     

On the estimation of particle number

Two methods are proposed for estimating the number of separated particles within a solid structure per unit volume of structure, N_v. Apart from being arranged with independence of any size parameter, no special assumptions upon the size, shape and orientation of the particles are made. The first method is based on the identity N_V = (N_A)_u ? μ_u^?1, where (N_A)_u is the mean number of particle sections per unit area of a plane probe T_u which is uniform random within the structure and perpendicular to a given direction u, whereas μ_u is the mean particle caliper length along u. The second method uses N_V = A_A?V^?1, where A_A is the mean areal fraction of the particles per unit area of section, whereas v is the mean particle volume. The estimation of (N_A)_u, μ_u, and v requires the examination of parallel serial sections above and below T_u. Particle model reconstructions are not needed, however. Previous approaches to the problem are discussed.     

激光粒度测量的综合反演及参数选择

本论文提出了一种应用于激光粒度测量的无模式综合反演算法,即,二阶段迭法算法。该算法综合采用了改进共轭梯度法和松弛迭代法各自的优点,使用了共轭梯度法作为第一步预迭代,利用其快速收敛性和解的平滑性得到第二步迭代的初始解,而后,采用了改进的松弛迭代法对第一步的初始解进行改进。使用该方法能使解在稳定性和准确性方面得到了一定程度的改进。对算法进行了分块操作,并对所有模块如共轭迭代法,正则化法,松弛迭代法进行分析,指出模块的可行性与必要性,同时进行参数的最优化选择。     

Tissue shrinkage and unbiased stereological estimation of particle number and size*

This paper is a review of the stereological problems related to the unbiased estimation of particle number and size when tissue deformation is present. The deformation may occur during the histological processing of the tissue. It is especially noted that the widely used optical disector may be biased by dimensional changes in the z‐axis, i.e. the direction perpendicular to the section plane. This is often the case when frozen sections or vibratome sections are used for the stereological measurements. The present paper introduces new estimators to be used in optical fractionator and optical disector designs; the first is, as usual, the simplest and most robust. Finally, it is stated that when tissue deformation only occurs in the z‐direction, unbiased estimation of particle size with several estimators is possible.     

On the laser calibration of charged particle detectors

Problems coupled with laser reference systems of gas charged particle detectors (drift, time-projection, and streamer chambers) are considered: the physical principles of formation of laser tracks, the methods used to create thin laser beams, the characteristics of ultraviolet nitrogen lasers, etc. Examples of existing and currently being designed laser systems intended for spatial and energy calibration of the detectors are presented.     

Investigation of low-angle laser light scattering patterns using the modified Twomey iterative method for particle sizing

We first applied the Twomey iteration method to the low-angle laser light scattering (LALLS) method. The Twomey method is known by the simple iteration algorithm for Fredholm integral equation. However, the algorithm is not applied to the LALLS result itself because the kernel function pattern is not stable. We solved the unstable kernel issue by modifying the Twomey algorithm to fit the LALLS data in this study. The performance of inversion was studied by computer simulation and experimental results from detectors containing 24 elements from angle 0.0005 to 2.5 rad. The computer simulation was carried out for particles of mean sizes from 0.1 to 1000 μm with mono-dispersion and log-normal distributions. A conventional algorithm is also carried out to compare the performance of the Twomey method. The noise effect of the inverse problem was tested by computer simulation. Experimental results were measured with standard polystyrene latex from 0.081 to 1007 μm. All the tests were performed under conditions in which the light from a linearly polarized laser at 633 nm was scattered by a diluted aqueous suspension. The modified Twomey (MT) method and conventional method show good reproduction results for particles with log-normal distributions. However, narrow distribution particles indicate that the MT method shows excellent reproduction results when compared with the conventional method.     

光全散射法颗粒粒径分布测量的改进研究

提出并实验了一种新的光纤型样品池,用于光全散射法测量颗粒粒径及其分布,该样品池的突出特点是消除了池壁散射影响以及容易实现稳定的多波长测试。在颗粒折射率处理方面,引入了洛伦兹色散关系和多波长处理方法,提高了理论的严密性、合理性和实用性。选用公称粒径分别为1.00μm和2.06μm的聚苯乙烯乳胶球标准颗粒做了验证比对实验。结果表明光纤型样品池工作稳定,数据处理显示均值偏差和重复性都小于5%,且优于常规折射率估值方法,体现了改善效果和实用价值。     

激光衍射粒度测量中的旋滤波方法

激光衍射法测量颗粒粒径过程中,面阵CCD接收到的待测颗粒的衍射图样总是不可避免受到噪声污染,直接影响粒度的反演精度。通过对测试原理及衍射图样的深入分析,提出了采用曲线窗口旋滤波对衍射图样进行预处理的方法,并进行了粒子群粒度反演的数值模拟实验。经过旋滤波处理后的单峰粒子和双峰粒子的粒度分布误差从直接粒度反演的42．36％、46．099／6和39．06％、35．7％分别减小到5．3％、6．17％和6．48％、7．33％,实验结果证明了采用曲线窗口旋滤波方法,粒度分布误差明显降低。     

马尔文激光粒度仪在测定铬系催化剂粒度分布中的应用

介绍了用马尔文激光粒度仪湿法测定铬系催化剂样品粒度分布的方法。催化剂样品均匀分散在蒸馏水中并以一定流速通过激光束，衍射光由检测器收集，并将信号转换为粒度分布。讨论了应用中的经验。该方法容易建立，精密度高，非常适合在生产过程中应用。     

Optical scintillating fibres for particle detectors

The characteristics of plastic optical fibres (scintillating or not) are of interest for particle detection. Scintillating fibres added fine grain sampling to the time resolution and amplitude level measurements of classical scintillators. They can be used for hodoscopes, calorimeters and time of flight. Wire chambers' time resolution could be improved by the use of shifter fibres. Light guides and signal transmission could be made with non-doped fibres.The results of a feasibility study of such fibres at the Departement de Physique des Particules Elémentaires de Saclay will be presented.     

如何判断和选择激光粒度分析仪

以往的粒度分析方法通常采用筛分或沉降法。常用的沉降法存在着检测速度慢 (尤其对小粒子 )、重复性差、对非球型粒子误差大、不适用于混合物料 (即粒子比重必须一致才能较准确 )、动态范围窄等缺点。随着激光衍射法的发明 ,粒度测量完全克服了沉降法所带来的弊端 ,大大减轻了劳动强度及加快了样品检测速度 (从半小时缩短到了 1分钟 )。激光衍射法测量粒度大小基于以下事实 :即小粒子对激光的散射角大 ,大粒子对激光的散射角小。通过散射角的大小测量即可换算出粒子大小。其依据的光学理论为米氏理论和弗朗霍夫理论。其中弗朗霍夫理论为大颗…     

基于嵌入式系统的激光粒度仪电路设计

激光粒度仪是一种应用广泛的颗粒测量仪器.文中提出采用DSP和ARM嵌入式系统的设计方案,取代传统激光粒度仪所采用的数据采集卡,PC机,意在实现激光粒度仪的小型化,低成本.阐述了粒度仪数据采集系统的硬件组成,工作原理,电路的设计.设计提高了粒度仪的抗干扰能力和测量精度.     

动态光散射颗粒分布软测量

考虑传统动态光散射颗粒粒度分布测量用的反演算法复杂、精度不够、抗噪能力差,本文基于大数据思想,提出了一种动态光散射颗粒分布软测量方法。该方法通过调节颗粒粒度分布形状参数获得大量自相关函数及其对应颗粒分布的数据;使用这些数据对子学习机进行训练。最后,针对训练数据维数较高的特点对传统Bagging算法进行改进,并利用改进的Bagging集成算法集成子学习机以提高软测量模型的精度及泛化能力。通过模拟单峰数据和对300nm标准粒径进行软测量开展了验证实验。结果表明,该方法能够较好地测量出不同动态光散射颗粒分布的峰值及分布宽度,模拟单峰数据测量峰值精度可达1nm,300nm和503nm,标准粒径测量精度分别可达3nm和4nm,优于一般的反演算法。该软测量方法为动态光散射颗粒分布测量开辟了新的途径。     

利用离心沉降法测定氮化硅粉末粒度分布

采用BT-1500型离心沉降式粒度分布仪测定氮化硅粉末粒径大小及粒度分布,考察了样品浓度、分散介质和分散剂等因素对测试结果的影响。结果证实了离心沉降法在氮化硅粉体粒度测量上的可行性和准确性,有助于氮化硅材料的工艺制订及性能评价分析。     

基于电感式传感器的金属颗粒材质识别及粒径估计

传统的电感式颗粒传感器输出的是电感或电压幅值的脉冲信号,本质为标量信号。可通过脉冲信号的正负性区分金属颗粒是磁性或非磁性,且只能在已知颗粒材质的情况下估计颗粒的粒径。但在含有多种金属颗粒的油液中,基于标量信号的颗粒识别方法将失效。为此,本文采用了一种双锁相放大电路,将颗粒产生的复数域信号转化为一对直流信号。提出一种基于模糊隶属度函数的信号处理方法,实现了在噪音干扰下多种颗粒的材质识别和粒径估计。本文搭建了三线圈传感器实验系统。利用五种金属颗粒构建了隶属度函数,并进行系统标定。最后选取两种颗粒对标定后的系统进行了验证。结果表明系统对颗粒材质的识别准确,粒径估计误差小于2%。     

基于四象限探测的激光粒度仪自动对中技术

针对激光粒度仪手动对中自动化程度低、不易调整等问题,提出了基于四象限对中单元的新型50通道光电探测器的自动对中方法。该方法根据光束是否处于四象限探测器的感光范围,将自动对中过程分为粗对中和精对中两部分。当光束不在四象限探测器的感光范围内时,可根据探测器的特定结构进行粗对中;当光束处于四象限探测器感光范围内时,根据四象限探测器产生的光电流强弱判断探测器的运动方向进行精对中。在粗对中过渡到精对中后采取变步长方式,通过比较对中精度和对中所需时间确定算法的最佳截止条件。完成了激光粒度仪自动对中系统硬件和软件的设计,实验验证了对中系统的可靠性与准确性。结果表明,最终的对中分辨率高于5μm。使用该技术对标准颗粒样品进行了测量实验,结果证实自动对中后的测量数据符合国家激光粒度仪校准规范的要求。     

A new method of imaging particle tracks in solid state nuclear track detectors

Solid state nuclear track detectors are used to determine the concentration of α particles in the environment. The standard method for assessing exposed detectors involves 2D image analysis. However 3D imaging has the potential to provide additional information relating to angle as well as to differentiate clustered hit sequences and possibly energy of α particles but this could be time consuming. Here we describe a new method for rapid high-resolution 3D imaging of solid state nuclear track detectors. A 'LEXT' OLS3100 confocal laser scanning microscope (Olympus Corporation, Tokyo, Japan) was used in confocal mode to successfully obtain 3D image data on four CR-39 plastic detectors. Three-dimensional visualization and image analysis enabled characterization of track features. This method may provide a means of rapid and detailed 3D analysis of solid state nuclear track detectors.     

循环流化床颗粒团多参数的光散射测量方法

针对循环流化床床内颗粒团动态参数和行为特性的测量问题,提出了基于光散射原理的颗粒团运动速度、高度与浓度等多参数同时在线测量方法,利用该方法对二维冷态循环流化床试验台开展颗粒团参数测量,获得了颗粒经测量区造成的光强衰减信号,通过对上下测量单元光强信号进行互相关分析可获得颗粒团运动速度参数;对信号进行低通滤波,根据低频信号极值点时间差及运动速度测量结果,得到颗粒团高度参数;同时根据光强衰减程度计算颗粒团的浓度参数。由此实现了基于光散射原理的循环流化床床内颗粒团运动速度、高度与浓度多参数同时在线测量,测量结果显示,在典型工况下,提升管中心区域颗粒团运动速度较为稳定,平均速度为3.81 m/s,近壁面区域颗粒团运动速度有较大波动且出现负值,平均速度为0.65 m/s;中心区域颗粒浓度较近壁面区域小;中心区域颗粒团高度主要分布在20～40 mm区间,近壁面区域颗粒团高度主要分布在30～60 mm区间。这为循环流化床内颗粒团的形成、结构及其运动研究提供了一种有效的测量手段。