Monte Carlo method is used to study light extinction of smoke screen with clustered agglomerates consisting of spherical primary particles in a cluster-cluster aggregation(CCA) model.Extinction factor and absorption factor of randomly oriented smoke screen with clustered agglomerates are calculated with discrete dipole approximation(DDA).It shows that exinction properties are determined by radius and number of primitive particles besides refractive index and extinction properties can be decreased by aggregation.At a given primitive particle number,maximum extinction is obtained with optimum radius of primitive particles.

In this paper we present a new method-local accumulated deviation method for evaluating the fractal dimension of curves or one-dimensional(1D) surfaces. Our method is tested on various types of curves for Weierstrass-Mandelbrot fractal function and fractal Brownian motion with known fractal dimension. The results are good agreement with the theoritical values. Finally, using Monte-Carlo method, we simulated the randam rough(1D) surfaces with Gauss spectrum, and the new method is applied to data from simulating surfaces.