Research On Polarization And Scattering Identification Theory And Practical Application Of Suspended Particles

The polarization information in the light scattering process of the suspension system particle is sensitive to the inherent properties of the scatterer such as the shape,structure,refractive index,and particle size of the scatterer.Therefore,particle recognition technology based on polarized light scattering has many applications in the fields of atmospheric monitoring,marine biological monitoring,and biological cell detection.The scientific problem that this thesis pays attention to is the arbitrary orientation of the scattering process and the extraction of the characterization index under the on-line suspension system of complex morphology particles,and the combination of theoretical simulation prediction results and measured signal analysis.The main work of the thesis is divided into simulation and experiment.In the simulation,the work of the thesis includes the establishment of a new simulation method for the polarization scattering modality model,and the results of the polarization index analysis based on the morphological characteristics of the particulate matter extracted by the theoretical calculation tool.The main contribution of this part of the thesis lies in the establishment of a NMDDA calculation method based on DDA algorithm,and its speed performance is far superior to the existing DDSCAT.A variety of complex morphological particles,arbitrary particle orientation,full-space distribution output of polarization index and scattering matrix are implemented.In the simulation of complex morphological particles,the thesis demonstrates the average scattering matrix of various morphologies at a specific scattering angle,and analyzes the influence of the scatterer's properties on these matrix elements,and discusses the polarization indices that reasonably characterize the scatterers' morphological characteristics,demonstrates the importance of fractal particle modeling.At the same time,the thesis work carried out experimental verification and field measurement.The data used in this thesis was collected by our research group on source emission pollutants from the Chinese Academy of Environmental Sciences in Beijing from the winter of 2017 to the spring of 2018.They include three different combustion-generated particles,which are the combustion products of corn stover,hay,and coal.The thesis focuses on the analysis of the two key polarization indices in the previous research work.It not only verifies the ability to distinguish three types of source pollutants based on polarization scattering on-line measurement,but also demonstrates the simulation ability of NMDDA algorithm on the modeling of different source particles for the first time.