经典Mie散射的数值计算方法改进

介绍一种改进的Mie散射数值计算方法,对Mie散射系数中不同的参量选用合适的递推关系进行计算,数值计算结果表明该方法具有快速、稳定、不受颗粒粒径和折射率范围影响的优点.     

双层球形颗粒的光散射计算

在光散射颗粒测量技术中,Mie散射理论的计算非常重要。本文中讨论了双层球形颗粒光散射的计算方法,对计算过程中不同函数参量选用了合适的递推计算方法,改进的计算方法克服了以前算法在实际运算中遇到的误差。计算了若干物理量,如消光系数、散射系数、吸收系数以及CPU运算速度。计算结果表明,选用的方法简单、迅速、稳定且误差小。     

双层球形颗粒的光散射计算

在光散射颗粒测量技术中．Mie散射理论的计算非常重要。本文中讨论了双层球形颗粒光散射的计算方法．对计算过程中不同函数参量选用了合适的递推计算方法．改进的计算方法克服了以前算法在实际运算中遇到的误差计算了若干物理量．如消光系数、散射系数、吸收系数以及CPU运算速度,计算结果表明．选用的方法简单、迅速、稳定且误差小。     

颗粒层状结构对散射特性及激光粒度测量的影响

根据Aden-Kerker理论,对双层颗粒前向散射特性进行了研究。在此基础上,分别用衍射理论、Mie理论和Aden-Kerker理论计算了散射系数矩阵并采用非独立模式算法进行反演。数值计算结果表明,双层颗粒的散射光强由颗粒折射率和内外径决定,在实际的激光前向散射粒度测量中,如果沿用Fraunhofer衍射理论或Mie理论计算系数矩阵,在测量双层颗粒时,反演结果会有一定的误差。相比于Mie理论,衍射理论的反演误差更大。     

纳米及微米磁性颗粒在长波长下的光散射特性分析

根据Mie散射理论,分析计算了纳米级、微米级磁性颗粒的光散射特性。针对目前在导航、遥控及雷达等行业广泛应用的纳米、微米磁性颗粒,在Mie散射系数中引入磁导率变量,对比分析了磁性与非磁性颗粒、吸收性与非吸收性颗粒的散射特性规律。数值计算结果表明,磁导率的变化对具有吸收性磁性颗粒的散射特性造成影响,随着磁导率的增大,颗粒的散射光强及吸收性能将逐渐增大,同时磁导率增大对颗粒散射特性的影响将会受到复折射率实部的制约。     

高浓度超细颗粒系后向散射研究

为了研究高浓度状态下颗粒系后向散射规律 ,基于Beer-Lambert定律、Mie散射理论及复散射的相关理论建立了消光 -散射衰减模型 ,并针对具体算例进行了数值计算 ,给出计算结果。     

基于Mie散射理论的微球体颗粒数值模拟计算和实验研究

应用Mie散射理论,在散射角0～π范围内,模拟微球体颗粒的散射光强度与粒径大小的变化关系,分析了相对折射率的大小对散射光强度的影响;在实验装置条件下,分别模拟了散射光强度与粒径大小的变化关系及2um、5um、10um三种粒子的散射光强度与波长的变化关系。实验验证了数值模拟与实验结果基本一致,也证明实验中粒子散射遵从Mie散射理论模型。     

光散射粒度测量中Mie理论两种改进的数值计算方法

本提出了两种Ｍｉｅ散射程序算法：改进连分式方法和修正倒推法。改进连分式方法对Ｌｅｎｔｚ提出的连分式数值计算方法进行了改进,ｉｅ程序的计算范围大大拓宽;颗粒当量直径达到１０＾５,折射率虚部绝对值达到１０＾５。解决了以往一些算法不稳定的现象。     

火灾烟雾颗粒的光学散射特性研究

从理论和实验两个方面研究了几种常见的燃烧烟雾在不同波长激光下的散射特性。从Mie散射理论出发，比较几种Mie散射算法的优缺点，采用一种改进的连分式算法对火灾烟雾颗粒的散射光强分布进行计算，得出不同粒径大小和波长下光强分布图。结合理论计算，设计一套实验装置，测量并计算在不同角度下3种烟雾颗粒和面粉气溶胶散射光的相对光强比，实验测量值与理论计算值吻合较好。研究结果表明不同种类烟雾散射光相对光强比互不相同，火灾烟雾与非烟雾气溶胶差距较大，从而表明散射光相对光强比是区分不同烟雾特定的物性参数，为火灾烟雾探测技术发     

球形粒子对平面偏振光散射的数值计算与分析

论文在Mie理论基础上,给出了球形粒子对平面偏振光的散射强度和散射系数公式,利用连分式递推算法进行了编程计算,重点对1.06μm激光的模拟结果进行了分析.从得到的散射图像可以看出,散射强度角分布与散射粒子尺度有密切关系,随着粒子尺度的逐渐增大,散射光强主要集中到前、后向散射方向,集中的角度越来越窄,模拟结果明显出现了散射强度最弱的极值角,且该极值角随粒径的增大而增大,最后逼近90°方向.散射强度角分布与波长有关,当它们在同一数量级时达到最大值,与散射粒子折射率无关.该递推算法因为每一步计算都是独立的,与前后项的准确性没有关系,不存在不稳定、发散等情况,能够计算粒径参数范围从10-4开始,对上限不受任何限制.     

Modeling light scattering from Diesel soot particles

The Mie model is widely used to analyze light scattering from particulate aerosols. The Diesel particle scatterometer, for example, determines the size and optical properties of Diesel exhaust particles that are characterized by the measurement of three angle-dependent elements of the Mueller scattering matrix. These elements are then fitted by Mie calculations with a Levenburg-Marquardt optimization program. This approach has achieved good fits for most experimental data. However, in many cases, the predicted complex index of refraction was smaller than that for solid carbon. To understand this result and explain the experimental data, we present an assessment of the Mie model by use of a light-scattering model based on the coupled-dipole approximation. The results indicate that the Mie calculation can be used to determine the largest dimension of irregularly shaped particles at sizes characteristic of Diesel soot and, for particles of known refractive index, tables can be constructed to determine the average porosity of the particles from the predicted index of refraction.     

Measurement of scattering properties of individual particles with a scanning flow cytometer

A hydrofocusing head with an optical cuvette has been developed for the flow cytometer to generate complete scatter patterns of single particles at scattering angles ranging from 10° to 120°. The scatter signal has been measured as a function of the angle (a flying indicatrix) by the use of particle motion within a scanning system of the flow cytometer by the use of a single photomultiplier. Scattering data measured with the flow cytometer have been compared with those calculated from Mie theory for latex particles. A calculation algorithm has been used to estimate the size and the refractive index of spherical particles from the scattering data measured.     

Limited possibility for quantifying mean particle size by logarithmic light-scattering spectroscopy

Recent studies have shown that the slope of logarithmic scattering spectroscopy of a turbid medium is related to the sizes of the scattering particles within the turbid medium. Mie theory can be used to generate a logarithmic plot of the reduced-scattering coefficient versus wavelength. According to Nilsson et al. [Appl. Opt. 37, 1256 (1998)], the slope value of a linear fit of the logarithmic scattering spectroscopy between 600 and 1050 nm can be used for direct determination of particle size. We performed similar calculations using the Rayleigh-Gans approximation and obtained an analogous overall shape with additional sinusoidal features. Our calculations indicate a possible relationship between the slope and the particle size when the size is used to calculate the slope, namely, in the forward calculation. However, because of the sinusoidal pattern, the inverse calculation to obtain the particle size from the slope may be applied only for particles with a radius of <0.13 microm in combination with 650-1050-nm light. Caution should be exercised when inverse calculation is performed to determine the scattering particle sizes in the range of radii >0.13 microm, with the slope of logarithmic scattering spectroscopy within 650-1050 nm.     

Mie理论在静态光散射粒度测量的应用下限研究

测量下限是光散射颗粒测试技术的关键问题。本文通过理论分析、比较归一化散射光强的分布图和构造方差函数F(d)对颗粒散射光的光强分布进行了定性和定量的讨论,对Mie散射向Rayleigh散射趋近的情况进行了分析,讨论了散射光光强大小的分布,分析了测量不同粒径的颗粒的可行性,最终得到在入射光源是波长为0.6328μm的He-Ne激光器的情况下,当粒径d取200nm以上时,不同粒径颗粒的M ie散射光强分布有较大差别,适合用静态光散射的方法来判断颗粒粒径。     

Mie scattering computation of spherical particles with very large size parameters using an improved program with variable speed and accuracy

The electromagnetic radiation scattering patterns were computed using an improved C program to study variations in the patterns with changes in the size distribution, size parameters and refractive index of small particles in a volume element. The particle size distributions considered were gamma, normal and lognormal. The program is stable for computation of the theoretical values of the non-zero elements of the scattering matrix, efficiency factors, single scattering albedo, radiation pressure and asymmetry parameter for particles ranging from very small to very large size parameters. One of the significant features of the program is that it incorporates two methods for the determination of the optimal number of terms required for the computation of Mie series with the added benefit of having the option of either going for computational speed or accuracy. After a comparison of the C program with other reported benchmark results, it has been found that the program is very accurate and reliable for electromagnetic scattering computations.     

Accuracy estimation of multiangle light scattering detectors utilized for polydisperse particle characterization with field-flow fractionation techniques: a simulation study

The coupling of field-flow fractionation (FFF) and multiangle light scattering (MAIS) detectors is complementary in that the MALS system allows particle characterization when a narrow dispersity particle population is present in the detector. The fractionation process provides this narrow dispersity. Utilizing discrete particle simulations of FFF and optical calculations based on both the Mie theory of particle scattering and Rayleigh-Gans-Debye (RGD) scattering theory, the extent of polydispersity that can be tolerated for accurate particle quantitation is explored. It is found that flow, electrical, and sedimentation FFF provide adequate separation for accurate particle quantitation by MALS. The Mie theory is more accurate than the RGD theory, which is known to deviate at higher particle size. Low error in the measurement of mean diameters is found when only the particle diameter is of interest. It is shown that the reconstruction of the particle size distribution from time slice data is distorted due to errors in concentration, which result from finite polydispersity and other effects. A number of procedures are evaluated in restoring the size distribution to higher accuracy. None of these procedures is deemed of general purpose and none of these is reliable. The best results are obtained when fractionation is conducted under the minimal possible outlet polydispersity and when steric effects are minimized. In addition, best results are had for inherently narrow dispersity colloidal materials.