Dobson semi-empirical model and dielectric complex permittivity are used to represent real and imaginary parts of soil dielectric constant. Soil surface is simulated with exponential distribution model and Monte Carlo method. Composite electromagnetic scattering from soil surface and partially buried multiple columns with rectangular cross-section is studied with finite difference time domain method. It shows that composite scattering coefficient oscillates with scattering angle. Root mean square of soil surface, soil moisture content, dielectric constant of target and incidence angle have great influence on composite scattering coefficient. Correlation length of soil surface, width, height, distance of target section, and dip angle have weak influence on composite scattering coefficient. Buried depth of target hardly has effect on composite scattering coefficient. Compared with other numerical methods, finite difference time domain method obtains higher accuracy, and reduces calculation time and amount of memory occupying as well. It can be used to calculate complex scattering from rough ground and sea surface with nearby arbitrary multiple targets.

Support vector machine and neural network theory and internal network training differences of them are studied.Root mean square height and correlation length of Gauss rough surface are inversed by support vector machine and neural network,respectively.Simulation results and inversing errors show that in the case of small numbers of rough surface sample inversion of support vector machine are better than that of neural network,while in the case of sufficient numbers of rough surface samples inversion accuracy of neural network increases and time of inversion by neural network is much less than that of support vector machine.

Electromagnetic wave transmission through 1D band-limited Weierstrass fractal rough surfaces of layered medium is investigated with a hybrid method based on method of moment (MoM) and Kirchhoff approximation (KA). The upper rough surface and the under rough surface are divided into MoM region and KA region, respectively. Transmission coefficient as a function of scattering angle of transmission wave is obtained. Influences of fractal dimension, height root mean square, permittivity of substrate medium, permittivity and mean layer thickness of intermediate medium, frequency of incident wave on transmission coefficient are discussed. It shows that transmission coefficient is affected by parameters of upper rough surface considerably.

Composite electromagnetic scattering of 1D band-limited Weierstrass fractal layered rough land surface and a conducting column with rectangular cross-section is studied with FDTD.Composite scattering coefficient with varying scattering angle is obtained based on bistatic scattering coefficient.Influence of root-mean-square of height fluctuation,dimension of fractal,parameters of the middle layer medium,lower medium and conducting column with rectangular cross-section on composite scattering coefficient is discussed.

With analysis on internal carrier transport mechanism in silicon carbide(SiC),an improved analytical model for dc current voltage and small signal parameters of 4H-SiC metal-semiconductor field effect transistor(MESFET) is proposed considering carrier velocity saturation and charge controlling.Incomplete dopant ionization and parasitic drain-source resistances are considered simultaneously.The simulated maximum transconductance is 48 mS·mm^-1 at a gate voltage of 0 V.Simulations and physical measurements show good agreement.The model is simple in calculation and distinct in physical mechanism.It is suitable for design and research of SiC devices and circuits.

Optical wave transmission through slightly rough surface of three layered medium is studied. Transmission coefficients with different polarization are derived using a small perturbation method. A Gaussian rough surface is used to describe rough surface of layered medium. Influence of permittivity of layered medium, mean layer thickness of intermediate medium, roughness surface parameters and incident wavelength on the transmission coefficient of HH polarization is diacussed.

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.