For a single sphere , t matrix method is compared with mie theory in both equation expression and numerical results
In chapter 4 windowed function of data signal processing is introduced and applied to addition theorem , which succeeds in solving the difficult problem : it has a bad result when recursive t - matrix is applied to calculate the wave scattering of electrically large objects and multiple objects in the excitation of te wave
In the paper , the new electromagnetic scattering algorithms have been introduced - recursive aggregate t - matrix algorithm ( ratma ) and fast multipole algorithm ( fma ) . two kinds of methods are precise and efficient and have advantages over conventional method of moment in computational speed and requirement for storage space
Thirdly , the cluster - cluster aggregation model is used to study the possible structure of aggregated smokescreen particle . we also develop the mathematical radiation extinction model of aggregated particle based on t - matrix method . associated with monte carlo method , another computer program is designed to simulate the extinction cross section and scattering cross section of actually aggregated particle
In the first part , the basic knowledge of particle scattering in meteorology and physics was introduced . the particles to be discussed include aerosol particles , fog droplets and raindrops and the em wave band in the discussion is near - infrared . in the second part , the mie theory was briefly reviewed and was applied to investigate the scattering characteristics of spherical atmospheric particles , the result shows that in the visibility measurement meter using forward - scattering method , when the working wavelegth is between 0 . 8 m ~ 2 m , the scattering angle is between 25 ~ 40 , the distinguishability and the relative scattering intensity would be better than those under other conditions . in the third part , the superellipsoid was used to describe a wide range of shapes such as spheres . ellipsoids and cylinders . an improved t - matrix method which can be used to calculate arbitry shaped particle ' s scattering field was introduced , and the scattering characteristics of non - spherical atmospheric particles was investigated with this method
Another mode of the total t matrix is derivated from the integral equation . finally the calculation result of two dielectric cylinders pro ves the effectiveness of windowed function and the correctness of the expression of the total t - matrix . windowed function is also applied into fma , which can accelerate the computation speed of the fma
The ratma can calculate the electromagnetic scattering of multiple cylinders , and can be used in remote sensing . in chapter 2 simply derivation of the ratma is given by the addition theorem , and the general t matrix of single cylinder is deduced . the worked out examples show th e effectiveness of the ratma in the analysis of the scattering field of single cylinder or multiple cylinders
Secondly , the mathematical radiation extinction model of nonspherical particle is developed based on t - matrix method , and a computer program is designed to calculate the extinction cross section , scattering cross section , absorption cross section and scattering phase function of fixed or randomly oriented axially symmetric particle
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