| Obtaining the morphology characteristics of small particles by measuring their s volume scattering function(VSF)is an emerging nondestructive measurement measuring technique,especially in the fields of ocean monitoring,chemical industry and biology.However,the available commercially measuring instruments can only acquire the one dimensional VSF,hence the particle size analysis based on these instruments has limitations.Aiming at the requirement of particle size analysis in the ocean,this thesis focuses on the design and implementation of the three dimensional volume scattering function(3D VSF)measurement system of particle suspension and then tested in the marine in-situ experiments.By calculating and analyzing the three dimensional distribution of scattering lights from suspended submicron particles,this thesis developed a 3D VSF measurement system based on spatial mapping.This system can analyze the scattring distribution of water or particle suspension quickly through the photographed two dimensional scattering patterns.The 3D VSF of 11 kinds of standard particles with different diameters from 60 nm to 1?m have been measured by the prototype,the results showed high repeatability and can match the VSF calculated by Mie theory.This thesis also proposes a retrieval algorithm to retrieve the 3D VSF from 2D scattering patterns of particle suspension,and acquire the 1D VSF of any scattering planes.Then the the scattering distribution like intensity and polarization characteristics of submicron particles have been analyzed.The quantitative analysis show that when the incident polarization is fixed to vertical or horizontal,the prototype can measure the VSF curves of particles with a range of scattering angle ?(21°,160°)and azimuthal angle ?(1°,89°)during only one measurements.To improve the performance and application of 3D VSF measuring system,controlled experiments of different particle concentration and mixture of particles with different diameters have been designed.The controlled experiment of different concentration eliminated the effect of multiple scattering,and the experimental results of particle mixture confirmed that particles with different diameters can be distinguished through 3D VSF measurement.To calibrate the effect of aggregation,introducing the equivalent sphere which have a 126% diameter to origin sphere and the same volume of two sphere polymer,and calibrate the experimental curves through the compensation matrix from curves of equivalent sphere.Finally,the calibrated curves of particles with a dimeter less than 200 nm show a high degree of consensus to the theoretical ones,with an average relative error less than 15% on almost all the scattering planes and a correlation coefficient more than 0.990.Based on the experimental results,the laboratory device was optimized to a shipborne prototype.In the summer of 2016,the “Dongfanghong 2” marine scientific research vessel participated in the investigation of the Yellow Sea and Ocean Ocean Scientific Research,during the scientific research,the prototype acquired the 3D VSF of 80 layers of seawater and their filtered seawater from 25 sites.Differences between seawater from different sites and layers have been observed and investigated through the 3D VSF.The results confirmed that seawater near the coast and seabed will contain more particles,meanwhile most scattering lights are from the particles with a diameter larger than 0.7?m.The 3D VSF measuring device designed and developed in this thesis can acquire the VSF on plenty scattering planes with a wide angular range quickly and accuracy during only one measurements,its real-time and consistency are the main advantages,which makes the in-situ analysis of spatial and temporal distribution of marine plankton possible. |
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