Application of Light Reflectance-Transmittance Measurement Method to Reconstruct Geometrical Morphology of Particle Fractal Aggregates

Particles,including soot,aerosol and ash,usually exist as fractal aggregates.The radiative properties of the particle fractal aggregates have a great influence on studying the light or heat radiative transfer in the particle medium.In the present work,the performance of the single-layer inversion model and the double-layer inversion model in reconstructing the geometric structure of particle fractal aggregates is studied based on the light reflectancetransmittance measurement method.An improved artificial fish-swarm algorithm(IAFSA)is proposed to solve the inverse problem.The result reveals that the accuracy of double-layer inversion model is more satisfactory as it can provide more uncorrelated information than the single-layer inversion model.Moreover,the developed IAFSA show higher accuracy and better robustness than the original artificial fish swarm algorithm(AFSA)for avoiding local optimization problems effectively.As a whole,the present work supplies a useful kind of measurement technology for predicting geometrical morphology of particle fractal aggregates.

Fractal Dimension Analysis of the Fine Aggregate Gradation of Interlocking Skeleton Asphalt Mixture

By analyzing the fine aggregate gradation scales from standards,fine aggregate in the asphalt mixture is regarded as a whole research object and fractal dimensions X of the samples were obtained by linear regression and（AC-13）is 2.43-2.56,Sup-13 is 2.28-2.54,SMA-13 is 2.66-2.88 and SAC-13 is 2.54-2.73.In the dense gradation mixture,there are little different between fractal dimensions of coarse and fine aggregates but it makes sense for skeleton asphalt mixture.For a given coarse aggregate gradation and the same percentage of coarse aggregates,the compressive strengths and splitting strengths of the asphalt mixture are studied when the fractal dimensions are selected as 2.60,2.65 and 2.70,respectively.When asphalt-stone ratio is less than optimal asphalt-stone ratio,the higher compressive strength is,the bigger X can be gotten.When asphalt-stone ratio is larger than optimal asphalt-stone ratio,little difference of compressive strength can be observed under these three conditions.The largest splitting strength can be got when X is 2.65,and larger splitting strength can be observed with the ascending of the asphalt-stone ratio.

Kinetic Simulation of Fractal Aggregation on Liquid Surfaces

A modified fractal growth model based on the deposition, diffusion, and aggregation (DDA) with cluster rotation is presented to simulate two-dimensional fractal aggregation on liquid surfaces. The mobility (including diffusion, and rotation) of clusters is related to its mass, which is given by D-m = D-0s(-gamma D) and theta(m) = theta(0)s (-gamma theta,) respectively. We concentrate on revealing the details of the influence of deposition flux F, cluster diffusion factor gamma(D) and cluster rotation factor gamma(B) on the dynamics of fractal aggregation on liquid surfaces. It is shown that the morphologies of clusters and values of cluster density and fractal dimension depend dramatically on the deposition flux and migration factors of clusters.

Fractal Aggregation of Nonequilibrium Iodine

A large number of particles evaporated from liquid iodine deposited on the wall of a glass container. The deposits demonstrate three structural shapes:globule chain,network formation,and dendrite. The globule chain displays clearly self-similar feature,and can be characterized by fractal geometry. The fractal dimension of the globule chain patterns ranges from D=1.50 to 1.75.The in situ sublimat- ing process of an iodine fractal aggregate was observed.It revealed reversal of the random growth process under nonequilibrium condition.The analytical results show that the nucleation-aggregation (NA) model can explain the growth process of iodine fractal aggregate.

The Aggregation Kinetics of Colloidal Particles of Basic Yttrium Carbonate

The aggregation kinetics of basic yttrium carbonate pericles in aqueous solution havebeen studied using dynamic light-scattering techniques. In 1.00mol/l NaCl solution fast diffusionlimited aggregation behavior was observed with an increase in aggregate size over time describedby a power law. The aggregates are characterized by a fractal dimension D=1.82. Smoluchowskiand fractal theories were used to characterize the aggregation mechanism and to obtain theaggregation rate constant.