Radiative Properties Inversion Of Dispersed Particles

Dispersed particles is close to our daily life,its radiative properties are widely used in various aspects,such as industrial production,national defense and so on.In this paper the radiative properties inversion of dispersed particles is studied.According to the characteristics of the inverse problem,the study focus on two aspects:one hand,computation of forward problem for the radiative transfer in the material;on the other hand,computing method of inverse problem.The main research work are as follows:On the aspect of the radiative transfer forward computation,the radiative properties of particles with different shapes were calculated by COMSOL.What's more,the Generalized Multiparticle Mie-solution(GMM)and cluster-cluster aggregation model(CCA)were used to calculate the radiative properties of aggregation particles.The result shows that the shape of particles has significant influence on scattering by the size parameter.Based on calculating the radiative properties of particles,the forward radiative transfer model of particle dispersion material was established for the inverse problem on the MATLAB platform,including the hemisphere transmission and hemisphere reflection model simulated by the Monte Carlo method and the collimated transmission model simulated by the BEER law.On the aspect of the computing method of radiative characteristic parameter inversion,based on the L-M gradient optimization method,the complex refractive index of the particle material was retrieved by the inversion programme combining with the particle scattering theory and the Kramers-Kronig(K-K)relation in the MATLAB environment.The non-measurement was extrapolated and the alternate permutation discrete interval was adopted to avoid the Cauchy principal value integral singularity in the K-K relation.Useing the COMSOL livelink with MATLAB module and GMM executable file,which combined the inversion algorithm,we retrieved different shapes and aggregations of fly-ash particles'complex refractive index.Different from fitting the transmission,the hemisphere transmission,reflection and collimated transmission combined method was used to inverse the dispersed particles' radiation characteristic parameter and particles' complex refractive index based on the BP neural network method.The influence of network parameters and measurement errors on the inversion results is analyzed.When the scattering asymmetry factor is close to 0,the measurement error has a great influence on the accuracy of the inversion accuracy of the scattering asymmetry factor,and it has little influence on the absorption coefficient and scattering coefficient.