Electronic structure and optical properties of GaN systems doped with transition metals (GaN:TM, TM=V, Cr, Mn, Fe, Co, Ni) are studied with first-principles calculations. Influences of transition metals on electronic structure and optical properties are discussed. It shows that doped materials are direct semiconductors with half-metal property except Fe-doped material. Transition metal impurity introduces defect levels in energy gap of GaN, which is contributed by 3d electron states of transition metals. For GaN:V, Cr, Mn, Co, absorption peaks appear near defect level in low energy region. These peaks can be attributed to transiton between 3d electrons and N-2p electrons.

With density functional theory(DFT) and elastic scattering Green's function method,electronic transport of alkanemonothiol molecular membranes were simulated theoretically.It shows that conductive ability of molecular membranes increased 2 to 3 orders of magnitude than that of a single molecule due to interaction between molecules.Conductive ability of a molecular junction increases with increasing external force.Increase of current is mainly due to increased probability of tunneling within and between chains in a molecular junction.The increased probability is caused by coupling enhancement between molecule and electrode and between molecules.

A hybrid method of physical optics and time domain integral equation(PO-TDIE) is presented to analyze antenna electromagnetic compatibility(EMC) on electrically large platform.General formulation and computational complexity are deduced in detail.Numerical results show that the computational cost is reduced obviously compared with classical marching-on in time(MOT) solver.The hybrid method could be effectively applied in EMC analysis.

Based on thermodynamics and energy conservation law, an elastic body physical model is established. A physical equation of infrared radiation temperature and radiant exitance is achieved. With finite element method(FEM) the model can be used to analyzing infrared radiant energy of a three-point bending beam of elastic-photo material subjected to external loading in room-temperature. It shows that results calculated are highly coincidence with those of experiments. The model and relative theories are rational in quantitative analysis. A quantitative method is shown to analyse and reveal mechanism of infrared radiation of solid materials by computer.

Kelvin-Helmholtz instability is carried out with local Steger-Warming flux splitting method and NND scheme for hydrodynamic equations. Linear growth rates agree well with linear stability analysis. The method provides clear interface deformation images.

To study scaling behavior of holes in surface and interface rough growth, simulated growth of holes in a Ballistic Deposition (BD) model is simulated and analysed. It shows that relation between number of holes and growth time exceeds linearity at initial stage and approachs to linearity. The rule is analyzed theoritieally.

Molecular dynamics simulations are carried out to study flow of Ar around a nanoscale (Pt(FCC (100))) circular cylinder at a low Reynolds number (Re=20) with standard Lennard-Janes potential. Appearance, periodic shedding and oscillation of vortices are shown with streamlines and velocity vectors. Periodic time is about 0.3 ns and Strouhal number is about 0.2. Length of time-average vortices is 1.4 times larger than diameter of the cylinder. Velocity distribution in characteristic regions and recirculation region are obtained.

A simplified off-lattice model of protein is studied with a PSO algorithm.Interaction between atoms is represented by a physical-based potential.The protein's RMSD value between computed and experimental structures is 6.12Å in optimizing the potential in global space. The protein total energy and radius of gyration at PSO steps and the relation between minimum energy and corresponding RMSD value are investigated.It shows basic characteristics of protein folding.

Molecular dynamics simulations are performed for a block copper with an orbicular hole in the center under minus static pressures. The distortions, characteristics of atoms and radial distribution functions are calculated. Under a small minus pressure, an elastic stretch distortion appears and as the pressure exceeds a certain value plastic deformation and local phase transformation are found. Under extreme minus pressure, the material fractures. As the minus pressure increases the material experiences complex procedures： from an uniform elastic stretch to a local fcc~hcp struture transformation, then from a defect generation to a defect accumutation and finally a fracture forms.

An improvement on the Discrete Ordinate Method (DOM)-‘divide and rule’is shown. The tiny dominated body is plotted into districts according to the projection relation between the interfaces in the radiative heat-transfering direction. The radiative intensity of the subsidiary dominated bodies is solved after an integral to the radiative heat-transfering equation in the radiative heat-transfering direction. In the new DOM, the average volume is regarded as the final radiative intensity of the nodes. Numerical simulation is performed on the process of radiative heat-transfer in a three-dimension rectangular furnace. Compared with the traditional DOM and the district method, numerical results indicate that the new DOM solves the fake scattering preferably, and ameliorates the precision of the calculation as well.

A confined turbulent jet diffusion flame is studied using the probability density function(PDF) approach together with the k-ε two-equation model. The effect of solid wall and pressure gradient on the velocity and scalar is mainly concerned with. Then two confined turbulent combustion fields with different dimensions are simulated, of which the fluid structure, flame structure and flame shape are studied. In the end, the result is analyzed and conclusions are made.

The current voltage characterization of a standard double barrier tunneling junctions (DBTJ) which forms room temperature single electron devices is computed by means of time-dependent Schrödinger equation.For Au nanoparticles self assembly systems at room temperature it is simulated by wave packet evolution method.It is found that the simulated results are in good agreement with the experimental ones.This numerical method is proved to be of importance for the experiment and realization of the nanostructure devices.

A similarity model describing the physics of slab target X-ray lasers is constituted from the ideal hydrodynamic equations. The parameters of the plasma(e.g., temperature, density, and scale length) are predicted, which are important for the experimental design of slab target X-ray lasers. The model provides a mathematic tool for quantitatively predicting and explaining experimental results.

The Generalized Difference Method (GDM) is studied to solve Biot partial differential equations. The GDM has some advantages on the computational simplicity, the accuracy, and preserving the mass conservation. The difference approximation to the Biot equations and corresponding boundary conditions are presented. A numerical example is given to check this method.

By virtue of a simplified model of gain region, the propagation and amplification of soft-x-ray within the plasma with linear electron density profile are studied in the geometrical optics approximation. A simple formulation evaluating the deflection and divergence angles and the maximum x-ray intensity are obtained. The results are in better agreement with experimetally measured data and numerically simulated results.

The best coupling structure of the reflective-type-semicircular-optical fiber probe has been studied by using the method of numerical simulation. Distributive curve of the intensity of the reflective light on the incident plane of the light is given by computer simulation to the different radii of optical fiber cores which are separately 3μm, 5μm, 10μm, 15μm. and the radius of the optical fibers are totally 20m. The results show that the best coupling radius of the reflective type semicircular optical fiber probe satisfies the formula. ρ_max=R-0.01004a³+0.37429a²-3.38095a+16.85714(μm).

A new integral equation method is proposed to identify a multi-component decay curve from the observed data.This method is based on an integral equation of the gross intensity.The numerical examples show that the new method is very effective.

A Godunov-Type difference method with high resolution on non-uniform rectangle mesh for 2-dimensional Unsteady Multi-material flow is described.A Simple method for representing interfaces is also introduced.Results of several numerical examples are presented and have displayed the efficiency of this method.

In this paper, a lagrangian arbitrary triangular mesh finite volume method for numerical simulating 2-dimensional high velocity impact problem is described. The elasticity and plasticity of material are considered. Some computational results of several impact examples are shown.

In this article, the attenuation of broad beam of γ-ray passing through a medium has been researched with Monte-Carlo method and it was pointed out that the beam obeys the exponential rule if an equivalent absorption coefficient is used. A new idea of design forγ-ray thicknessmeter was then advanced for weakening radiation intensity, increasing count, and improving measurement precision. An absorption experiment of broad beam of γ-ray with energy of 60 keV in aluminium has been done and the result agrees with Monte-Carlo calculation.

We consider the effect of the impinging of a plane wave on a surface of a stratified media at two different angles of incidence. The Goupillaud's equal-traveltime layer model and it's exact inverse formulas[1] are used, the time sequence of the video impedances can be computed.In order to compute the deepness distribution of the densities and velocities for the layered media, we propose in this paper "The contrast method of the layer-interfaces", by which, the computational experiments were made and the numerical results are satisfactory.

As a plane shock wave with shock mach number Mi propagates down a backward step of height H (fig 1) a part of the shock front turns to be curvilinear It reflects from the horizontal part behind step.This unsteady regular reflection eventually becomes Mach reflection.We present here the results of shock tube experiment (M_i ≤ 2.20) and numerical simulation of this phenomena, say the transition from regular reflection (RR) to Mach reflection (MR).The dependence of the position of transition L_k and critical angle of transition ω_Ck on strength of the impinging plane shock M_i and height of step H are analysed.Our experimental and numerical results are compared with the theoretical criLerion of transition of Iton & Itaya^[15].It should be mentioned that the numerical method of FLIC type with triangular mesh developed in^[13] is successful.