Theoretical Study of the Effect of Multi-Diameter Distribution on the Mie Scattering Characteristics of Milk Fat

To correct the light scattering property parameters of milk fat for improving the detection accuracy,the Mie-theory was used to establish a predictive model for light scattering properties of milk fat globule with multi-diameter distributions, by means of Monte Carlo approach to simulate actual multi-diameter size distribution of milk fat globule in milk fat solution. Scattering coefficient and absorption coefficient of multidiameter distribution milk fat particles were calculated by simulating the particles size distribution in milk fat solution. And the light scattering properties of multi-diameter distribution was compared with that of volume mean diameter,Sauter mean diameter and numerical mean diameter in milk fat solution. Theoretical simulation results indicate that the scattering coefficient and absorption coefficient of milk fat particles are determined by the particle size distribution in milk fat solution. There is a distinct difference in scattering characteristics between the milk fat particles with multi-diameter distribution and that with mean diameters. Compared to that with multi-diameter distribution,the scattering coefficient of the milk fat particles with mean diameter has a maximum mean deviation of 9042 m-1. The particle size distribution is not completely determined by the mean diameters. The dependence of the light scattering properties on the particle size distribution should be considered into the model and simulation. Therefore,it is found that the particle size distribution in milk fat solution is an essential and critical factor to significantly improve the detection accuracy of milk fat content.

Multiple scattering and modeling of laser in fog

When a laser is transmitted in fog, and the water droplets will scatter and absorb the laser, which affects the intensity of the laser transmission and the accuracy of radar detection. Therefore, it is of great significance to study the laser transmission in the fog. At present, the main method of calculating the scattering and attenuation characteristics of fog is based on the radiation transmission theory, which is realized by a large number of numerical calculations or physical simulation methods, which takes time and cannot meet the requirements for obtaining the fast and accurate results. Therefore, in this paper established are a new laser forward attenuation model and backward attenuation model in low visibility fog. It is found that in low visibility environments, the results calculated by the Monte Carlo method are more accurate than those from most of the existing forward attenuation models. For the cases of 0.86-μm, 1.06-μm, 1.315-μm, 10.6-μm typical lasers incident on different fogs with different visibilities, a backscatter model is established, the error between the fitting result and the calculation result is analyzed, the backward attenuation fitting parameters of the new model are tested, and a more accurate fitting result is obtained.

Super scattering phenomenon in active spherical nanoparticles

Localized surface electromagnetic resonances in spherical nanoparticles with gain are investigated by using the Mie theory. Due to the coupling between the gain and resonances, super scattering phenomenon is raised and the total scattering efficiency is increased by over six orders of magnitude. The dual frequency resonance induced by the electric dipole term of the particle is observed. The distributions of electromagnetic field and the Poynting vector around nanoparticles are provided for better understanding different multipole resonances. Finally, the scattering properties of active spherical nanoparticles are investigated when the sizes of nanoparticles are beyond the quasi-static limit. It is noticed that more highorder multipole resonances can be excited with the increase of the radius. Besides, all resonances dominated by multipole magnetic terms can only appear in dielectric materials.

A SIMPLE METHOD FOR PREDICTION OF THE REDUCED SCATTERING COEFFICIENT IN TISSUE-SIMULATING PHANTOMS

This paper proposes a method for predicting the reduced scattering coefficients of tissuesimulating phantoms or the desired amount of scatters for producing phantoms according to Mie scattering theory without measurements with other instruments.The concentration of the scatters TiO2 particles is determined according to Mie theory calculation and added to transparent host epoxy resin to produce phantoms with different reduced scattering coefficients.Black India Ink is added to alter the absorption coefficients of the phantoms.The reduced scattering coefficients of phantoms are measured with single integrating sphere system.The results show that the measurements are in direct proportion to the concentration of TiO2 and have identical with Mie theory calculation at multiple wavelengths.The method proposed can accurately determine the concentration of scatters in the phantoms to ensure the phantoms are qualified with desired reduced scattering coefficients at specified wavelength.This investigation should be possible to manufacture the phantom simply in reasonably accurate for evaluation of biomedical optical imaging systems.

Accuracy of radar-based precipitation measurement: An analysis of the influence of multiple scattering and non-spherical particle shape

Two assumptions are typically made when radar echo signals from precipitation are analyzed to determine the micro-physical parameters of raindrops:(1) the raindrops are assumed to be spherical;(2) multiple scattering effects are ignored. Radar cross sections(RCS) are usually calculated using Rayleigh's scattering equation with the simple addition method in the radar meteorological equation.We investigate the extent to which consideration of the effects of multiple scattering and of the non-spherical shapes within actual raindrop swarms would result in RCS values significantly different from those obtained by conventional analytical methods. First, we establish spherical and non-spherical raindrop models, with Gamma, JD, JT, and MP size distributions, respectively. We then use XFDTD software to calculate the radar cross sections of the above raindrop models at the S, C, X and Ku radar bands. Our XFDTD results are then compared to RCS values calculated by the Rayleigh approximation with simple addition methods. We find that:(1) RCS values calculated using multiple scattering XFDTD software differ significantly from those calculated by the simple addition method at the same band for the same model. In particular, for the spherical raindrop models, the relative differences in RCS values between the methods range from a maximum of 89.649% to a minimum of 43.701%; for the non-spherical raindrop models, the relative differences range from a maximum of 85.868% to a minimum of 11.875%.(2) Our multiple scattering XFDTD results, compared to those obtained from the Rayleigh formula,again differ at all four size distributions, by relative errors of 169.522%, 37.176%, 216.455%, and 63.428%, respectively. When nonspherical effects are considered, differences in RCS values between our XFDTD calculations and Rayleigh calculations are smaller; at the above four size distributions the relative errors are 0.213%, 0.171%, 7.683%, and 44.514%, respectively. RCS values computed by considering multiple scattering and non-spherical particle shapes are larger than Rayleigh RCS results, at all of the above four size distributions; the relative errors between the two methods are 220.673%, 129.320%, 387.240%, and 186.613%, respectively. After changing the arrangement of particles at four size distributions in the case of multiple scattering effect and non-spherical effect, the RCS values of Arrangement 2 are smaller than those of Arrangement 1; the relative errors for Arrangement 2, compared to Rayleigh, are 60.558%, 76.263%, 85.941%,64.852%, respectively. We have demonstrated that multiple scattering, non-spherical particle shapes, and the arrangement within particle swarms all affect the calculation of RCS values. The largest influence appears to be that of the multiple scattering effect.Consideration of particle shapes appears to have the least influence on computed RCS values. We conclude that multiple scattering effects must be considered in practical meteorological detection.

Electromagnetic scattering of charged particles in a strong wind-blown sand electric field

Some field experimental results have shown that the moving sands or dust aerosols in nature are usually electrified,and those charged particles also produce a strong electric field in air, which is named as wind-blown sand electric field.Some scholars have pointed out that the net charge on the particle significantly enhances its electromagnetic(EM) extinction properties, but up to now, there is no conclusive research on the effect of the environmental electric field. Based on the extended Mie theory, the effect of the electric field in a sandstorm on the EM attenuation properties of the charged larger dust particle is studied. The numerical results indicate that the environmental electric field also has a great influence on the particle's optical properties, and the stronger the electric field, the bigger the effect. In addition, the charged angle, the charge density, and the particle radius all have a specific impact on the charged particle's optical properties.

A NEW ALGORITHM FOR ELECTROMAGNETIC SCATTERING OF MULTILAYERED SPHERE

More stable and accurate recursive formulas and a computing procedure for scat-tering coefficient calculation of a multilayered sphere are proposed, This procedure involves threelogarithmic derivatives of Ricatti-Bessel function ψ_n~＇(z)/ ψ_n(z), X_n~＇(z)/X_n(z),ξ_n~＇(z)/ ξ_n(z), as wellas the ratioψ_n(z)/X_n(z). The asymptotic behavior, stability, and accuracy of the procedureand scattering coefficients a_n and b_n are discussed for various complex refractive indices. Thisprocedure can be applied to large and small inhomogeneous spherical particles.

A UNIFIED APPROACH FOR DEALING WITH THE EM SCATTERING FROM SYMMETRIC AND ANTI-SYMMETRIC STRUCTURES

It is of both the theoretical and practical importance to reduce the storage andCPU time of moment methods by utilizing the geometrical and physical features of the scatterer.An unified approach based on the group theory is presented to deal with the EM scattering fromsymmetric and anti-symmetric structures.

FUNDAMENTAL RESEARCH ON RADIOFREQUENCY ABLATION OF RAT BRAIN TISSUE BASED ON NEAR-INFRARED SPECTROSCOPY AND MIE THEORY

Near-infrared spectroscopy(NIRS)technology and Mie theory are utilized for fundamental research on radiofrequency ablation of biological tissue.Firstly,NIRS is utilized to monitor rats undergoing radiofrequency ablation surgery in real time so as to explore the relationship between reduced scattering coefficient(μ_(s)')and the degree of thermally induced tissue coagulation.Then,Mie theory is utilized to analyze the morphological structure change of biological tissue so as to explore the basic mechanism of the change of optical parameters caused by thermally induced tissue coagulation.Results show that there is a close relationship between μ_(s)' and the degree of thermally induced tissue coagulation;the degree of thermal coagulation can be obtained by the value of μ_(s)';when biological tissue thermally coagulates,the average equivalent scattering particle decreases,the particle density increases,and the anisotropy factor decreases.

Numerical calculation of multiple scattering with the layer model

The optical measurement technique based on Mie scattering has been applied to various areas, in which single scattering at low particle concentration is assumed. Nevertheless, since multiple scattering is usually unavoidable in online measurements, we present in this work a multiple scattering calculation method, in which a layer model is employed. The three-dimensional particle system is divided into a pile of layers the number of which is automatically determined, depending on the obscuration of the particle system. The calculation is found to be fast, reasonable and reliable.

Enhanced optical absorption in semiconductor nano- particles enabled by nearfield dielectric scattering

The optical absorption of semiconducting AgBr nanocubes is significantly increased by up to 5 times in the measured spectral range when they are bonded to the surface of dielectric SiO2 nanospheres through electrostatic interaction. The absorption enhancement factor depends on the wavelength and the size of the SiO2 nanoparticles （NPs）. Finite-difference time-domain calculations provide the nearfield intensity mapping of a heterostructure that is composed of a AgBr nanocube in close contact with a SiO2 nanosphere. The electric-field distributions indicate the field enhancement near the SiO2/AgBr interface due to light scattering and absorption enhancement in the AgBr nanocube, implying that the enhanced scattering nearfield increases the absorption cross section of the AgBr nanocube. The absorption cross-section spectra calculated using Mie theory agree with the experimental observations. This discovery sheds light on the utilization of dielectric spherical particles to increase the absorption in semiconductor NPs, thus improving the light-harvesting efficiency for solar-energy conversion.

基于Mie散射理论的微球体颗粒半径分析

为高效、经济、准确地对微球体颗粒的半径进行测量,基于Mie散射理论设计了一种测量装置。本文应用Mie散射理论对微球体颗粒光散射的性质进行了理论分析与数值计算,得出了散射光分布与入射光波长、微球体颗粒半径以及微球体相对折射率之间的关系。结果表明:入射光波长越小,散射光能量越集中分布在散射角较小的范围内;相对折射率的变化对散射光分布的影响不大;不同半径颗粒的散射光强的分布差异较大,因此通过测量散射光的分布可以确定微球体颗粒的半径,从理论上证明了该设计方案的可行性。结合理论分析与计算结果设计了一种用于测量微球体颗粒半径的装置,该装置具有结构简单、成本低、效率高等优点,可以用于实际测量,具有一定的实用性。

海水中矿物质颗粒吸收和散射特性Mie理论分析

利用Mie理论模型对不同粒径分布和复折射率的矿物质颗粒吸收和散射特性进行了模拟计算。颗粒的衰减和散射效率随着参数ρ的增大呈现出振幅依次减小的一系列有规则的振荡变化,而吸收效率则随着ρ的增加而增大;随着颗粒吸收性的增强,散射效率和吸收效率随着ρ的增大最终都将趋近极限值1。对于矿物质颗粒群,颗粒群的粒度分布变化对散射和后向散射特性影响很大,小粒径粒子对散射和后向散射的贡献比较大;折射率实部以及虚部变化对散射特性均有影响,颗粒的吸收性越强,则散射会相应地减弱;粒度分布以及折射率虚部对吸收系数也存在较大的影响,但是折射率实部对吸收系数的影响不大。

Light scattering and surface plasmons on small spherical particles

Light scattering by small particles has a long and interesting history in physics.Nonetheless,it continues to surprise with new insights and applications.This includes new discoveries,such as novel plasmonic effects,as well as exciting theoretical and experimental developments such as optical trapping,anomalous light scattering,optical tweezers,nanospasers,and novel aspects and realizations of Fano resonances.These have led to important new applications,including several ones in the biomedical area and in sensing techniques at the single-molecule level.There are additionally many potential future applications in optical devices and solar energy technologies.Here we review the fundamental aspects of light scattering by small spherical particles,emphasizing the phenomenological treatments and new developments in this field.

基于Mie理论的连铸二冷水雾粒子消光特性研究

基于Mie散射理论,建立了连铸二冷区水雾粒子的消光模型,分析了水雾粒子的散射特性,计算了水雾粒子在各粒径和各辐射波长下的消光特性.结果表明,水雾粒子为具有非灰性、参与性特点的弥散系.在模拟工况下,水雾散射角介于0°～2.5°,为强烈前向散射.消光作用随粒径增大而增强,粒径分布是影响水雾消光特性的直接因素.

球形粒子Mie散射参量的Matlab改进算法

本文主要讲述了Mie散射物理参量的一种改进数值算法,在抛弃了Mie散射物理参量的经典算法——连分式算法和后向递推算法之后,在现有利用Matlab计算散射参量的基础上,充分利用了Matlab内置命令集和函数集,得出了任意折射率且尺度参数在10-4~104的球形粒子散射参量的准确计算结果。收敛数度比改进后向递推快,相应的程序简单易读且执行时间大为缩短,比现有经典算法所用的递推关系较少,因此在很大程度上避免了递推过程中误差的积累,保证了计算结果的可靠性。

用简化Mie理论及K—K关系求微粒复折射率的透射法

用简化的Mie散射理论及Kramers-Kronig关系式,从单频透射比光谱反演微粒的复折射率。用较大粒径的碳黑微粒作了模拟计算,结果表明本方法计算比较简单,比现有方法提高了精度,扩大了波长及粒径范围。最后利用红外分光光度计测出的透射比光谱确定了煤粒的复折射率。

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。

基于Mie散射的卷云光学特性

基于中纬度卷云冰晶双峰、热带卷云冰晶三峰分布模型,利用Mie散射理论计算了1～13μm范围内中纬度及热带卷云的消光系数、散射系数、吸收系数。计算结果表明,由不同形状冰晶构成的热带卷云的相应光学参数比中纬度卷云的光学参数大些,但11支子弹玫瑰形状的相应参数要小一些;两种卷云在2.8～3.1μm,9.8～13μm范围内都存在两个基本相同的透射通带;在计算中纬度卷云的光学参数时,可以只考虑中空六棱柱与实心六棱柱中的一种,但计算热带卷云的光学参数时,实心六棱柱与空心六棱柱需要同时考虑。

基于Mie理论的四种典型水云的光散射计算

在Mie理论的基础上,利用修正伽马函数来描述水云的粒子尺度分布,计算了一类层云、二类层云、一类层积云和二类层积云这四种典型水云的消光系数、单次散射反照率、不对称因子和散射相函数。结果表明,粒子的消光系数、单次散射反照率和非对称因子随着入射波长的增加有较大的起伏,后两者随着波长的增加其变化趋势基本一致;消光系数主要受云中液态水含量的影响;对于单次散射反照率来说,在可见光波段,反照率非常接近于1;在短波段,粒子的非对称因子变化较小,并且随着波长的增加,非对称因子会逐渐增大;Mie相函数随着散射角的增加呈现出先减小后增大的趋势,但相函数随着波长的增加,并没有呈现出简单的线性关系。