The ant colony optimization(ACO) algorithm based on the probability density function is applied for the retrieval of spherical particle size distribution(PSD). The spectral extinction data based on the Mie theory and the Lambert–Beer Law served as input for estimating five commonly use monomodal PSDs, i.e., Rosin–Rammer distribution, normal distribution, logarithmic normal distribution, modified beta distribution, and Johnson's SBdistribution. The retrieval results show that the ACO algorithm has high feasibility and reliability, thus providing a new method for the retrieval of PSD.
Based on the experimental infrared spectral transmittances,an inverse model has been developed to determine the optical constants of the aerosol particles (SiO2 and Al2O3).Combined with the Mie theory and Kramers-Kronig (K-K) relations,the complex refractive indices of the SiO2 and Al2O3 particles are retrieved.The effects of the measurement errors on the inverse results are also investigated.With the optical constants inversed from the experiment,the discrete ordinate method (DOM) is used to calculate the infrared transmission characteristics of the aerosol particle cloud.Considering the multi-scattering and self-emission of the particles,the equivalent transmittance ratio (ETR) is suggested to evaluate the infrared transmission characteristics of the aerosol particles.Particular attention is given to analyze the effects of the volume fraction and diameters on infrared transmission characteristics.When the volume fraction is larger than 0.001,the particle diameter has little effect on the infrared transmission characteristics.For the uniform monodisperse particles in the detection waveband range of 3-5 μm and 8-12 μm,there exists a critical diameter where the ETR reaches the minimum value.In addition,the ETR of 3-5 μm is smaller than that of 8-12 μm with the same volume fraction and particle diameter.
