The governing equation of moving boundary problem is heat conductive equation. Its definite solution domain varies with time. Highly precision numerical algorithms on space-time domain were presented to solve 1+1 dimensional moving boundary problems. An initial moving boundary was given to form an irregular physical domain, and a regular region (a rectangular in Cartesian coordinate system) was chosen to cover the irregular physical domain. The heat equation was numerically computed with a barycentric interpolation collocation method (BICM) on space-time regular region with fixed and moving boundary conditions and initial condition to obtain numerical data in regular region. The data on moving boundary of physical domain were computed with barycentric interpolation. Then, the governing equation of moving boundary was solved with BICM to recover a new moving boundary. Repeat the process, numerical data of temperature and final moving boundary position were given. Numerical examples illustrate effectiveness and accuracy of the method.

Cluster dynamics (CD) is a fast method for simulating long-term defect evolution in materials under irradiation. However, CD models based on mean-field rate theory do not account for spatial correlations between defects/clusters in cascades. Object kinetic Monte Carlo (OKMC) models take intrinsically account of defect spatial correlations, but they are limited by time scale and irradiation dose. A CD model with spatial correlation effect, termed as CD-SC, is developed based on a simple constant-time annealing method to determine CD source term by coupling Monte Carlo (IM3D) and OKMC (MMonCa) models. It shows that, results by CD-SC match those by full OKMC well. It is helpful for accuracy improvement of sequential multi-scale models of long-term radiation damage under typical irradiation conditions.

B3LYP/6-311++g(d,p) method is adopted to optimize ground state structure of CH₃Br molecule. Bond length, energy gap and dissociation potential energy surface of CH₃Br molecule in external electric field (0-0.05 a.u.) are studied. It shows that direction and magnitude of applied electric field is of great significance to molecular structure and potential energy surface. With negative electric field (C-Br bond direction) increases from 0 to 0.05 a.u., bond length of C-Br bond decreases first and then increases. Bond length of C-H bond increases gradually. Molecular energy gap E_G decreases gradually. Vibrational frequency of C-Br bond increases while IR vibration frequency decreases. It is found that potential energy of methyl bromide molecule decreases and dissociation barrier decreases, which indicating that CH₃Br molecule is easy to be excited and dissociated in external electric field.

Effect of biofilm structure on bioreaction as well as flow and mass transfer are investigated with lattice Boltzmann method (LBM) on meso-scale. Porous construction of biofilm is regenerated by Quartet Structure Generation Set (QSGS) method, and LB method is coupled with multi-block model to obtain detail information and save computational cost. It indicates that properly increasing porosity benefits mass transportation between main region and biofilm, and hence improve substrate consumption efficiency under condition of stable biofilm structure. At given porosity of biofilm, changing growth construction of biofilm can also promote mass transfer between inner and outer of biofilm, leading to higher substrate consumption efficiency.

As a high-temperature phase of Pu, δ-Pu doped with little Ga can stay to room temperature. Crystal structure and electronic structure of systems with different contents of Ga are calculated with density functional theory (DFT) method. Calculations mainly include lattice constant, density, formation energy, density of states(DOS), electron density and Mulliken population. It shows that within studied doping scope, lattice constant of systems decrease and density of systems increase with increase of content of Ga, while stability of system with 6.25% content of Ga is superior to that with 3.125% and 12.5% content of Ga. Ga-doping enhanced locality and strengthens bonding ability of electrons, which, to some degree, reveals electronic mechanism of Ga stabilizing δ-Pu. Character of Pu-Ga bond is metallic state, and interaction is mainly contributed by Pu 7s, 6p, 6d and Ga 4s, 4p orbital electrons. While interaction is relatively weak, doped systems maintain fine mechanical properties and machining performance. Contribution of Ga to stability of δ-Pu lies mainly in its improvement on bonding performance of Pu, instead of its immediate bonding effect with Pu.

Density functional theory on level of B3LYP at 6-311++G(d,p) was used to calculate CCl₃F geometrical parameters, dipole moments, charge distribution and total energies of ground state of CCl₃F molecule under external electric fields(F=-0.025~0.025 a.u.). It shows that with decreasing of C-Cl band distance, charge distribution of Cl increases. Molecular geometric parameter and total energy are strongly dependent on increasing field intensity. IR vibrationt spectrum of CCl₃F molecule shows observable blue shift as electric field increased to F=-0.02 a.u.

Modeling of high-altitude electromagnetic pulse (HEMP) consists of one self-consistent process. Current density produced by Compton effects of gamma rays not only is the source in Maxwell's equation to produce electromagetic pulse, but also is influenced by electric fields. In this paper, analytical relation of Compton current and local electric field was deduced with reasonable hypotheses in one dimension model. It shows that self-consistent process is equivalent to an effective conductivity and can be combined with original non-self-consistent model. Analytical relation between Compton current and electric filed was verified using particle in cell and finite-difference time-domain methods. Finally, an example of HEMP environments calculated by this means was shown.

Importance of accurate calculation of average reaction rate in thermonuclear reactions is introduced. Two types of nuclear involved in thermonuclear reactions are assumed in thermal equilibrium state under same temperature. With comparison between analytical expressions of average reaction rate and average rate of thermonuclear reaction using MC method directly, correctness of MC method is obtained. Finally, MC method is extended to calculation of average thermonuclear reaction rate in several typical distributions.

With given total toroidal current and central current density of plasma, temperature, density and magnetic field profiles of tokamak plasma with different elongation and triangularity are obtained numerically with Grad-Shafranov equation. Electron cyclotron wave ray trajectories and current drive in configurations are investigated with Fokker-Planck equation incorporated into a ray tracing code. It shows that as electron cyclotron wave of X-mode are launched from top, rays propagate toward low-field side with increasing elongation. As electron cyclotron wave are launched from mid-plane and low-field-side, high quotient power deposition is obtained with greater elongation, and driven current profile is close to central plasma with increase of triangularity. Current drive profile moves toward central plasma and peak current density increases with decreasing poloidal or toroidal injection angle.

We analyze non-physical solutions in laser ray tracing simulation.With a system of nonlinear equations,a new algorithm for intersection is presented.A special preconditioner is used to improve numerical stability.The algorithm is suitable for any intersectant condition.Numerical experiments show that the algorithm has better precision and adaptability.Simulation in LARED code shows good performance.

We introduce an ignition hohlraum 2D-simulation design method with 2D code.A design sequence,in which X-rays drive tempetature is tuned before P² asymmetry,is put forward.Details in designing laser power is studied.It indicates that control of P² asymmetry during trough pulse limits the maximum of filling gas density and expansion of capsule ablator can be restrained by longer drive pulse.An ignition hohlraum 2D-simulation design is given.

Geometries of Mg_xAl_yN (x,y=1-5) clusters are studied by using hybrid density functional theory (B3LYP) with 6-311+G^* basis sets. For lowest-energy structures of Mg_xAl_yN clusters, stabilities and electronic properties are investigated. It shows that planar structures are dominant structures of Mg_xAl_yN (x+y≤4) clusters. The lowest-lying Mg_xAl_yN clusters mostly derived from ground-state structures of Al_nN or Mg_x-1Al_y+1N clusters. Mg_xAl_yN clusters are stable with respect to fragmentation into atoms or smaller clusters. Compared with neighboring clusters, MgAl₃N and Mg₃Al₃N clusters own higher stability. For all Mg_xAl_yN clusters studied, we found co-existence of covalent, ionic, and metallic bonding characteristics. Furthermore, ionization potential and electron affinity exhibit weak oscillations as increasing cluster size. Ro general pattern is observed.

We give a convergence analysis on splitting iterative (SI) algorithm of multi-group radiation diffusion equations. Spectral radii of iterative matrix is shown. Numerical computation and analysis on spectral radii formulae reveal a relation between convergence rate and radiation coefficients. Numerical results confirm theoretical results, and give applicable conditions of the algorithm.

Heating of magnetized plasmas by low-frequency Alfvén waves propagating along background magnetic field is studied with test particle simulation.It shows that ions in perpendicular and parallel directions of the background magnetic field are heated significantly.In a stage of non-resonance heating,perpendicular heating is more significant than parallel heating,and anisotropic temperature comes into being.In a stage of stochastic heating,perpendicular and parallel temperatures of ions finally reach saturation and convergence.In heating process,the maximum kinetic temperature of ions is dependent on the ratio of magnetic field energy density and plasma density,which has no relevance with Alfvön-wave frequency and amplitude.Ions are significantly accelerated in parallel direction.and attained a bulk speed that is roughly equal to phase velocity of Alfvén waves.

Foam microscopic seepage experiments show that foam present two seepage states: Flowing foam and trapped foam.Foam plugging experiment show that foam plugging ability has accumulating effect.Plugging pressure gradient near core inlet is less than that of downstream of the core when foam flooding reaches steady state.A multi-component mathematical model characterizing foam flooding is established based on bubble population balance theory and foam properties.The model is solved numerically with fully implicit method.Validity of the model is verified with foam plugging experiment.Meanwhile,foam microscopic seepage characteristic parameters such as foam texture,pressure and aqueous phase saturation in foam flooding are studied.

We consider a many-particle model which concludes interaction of molecular BEC,and gave a semi-analytical method to calculate conversion efficiency of Fermion atom pairs convert to Boson molecules.The method used mainly independent crossing approximation.With mean-field theory we get an equation for conversione efficiency.Calculating results are supported by numerical simulation and experiment of ⁶Li by Hulet group in 2003.

In this article,long range part of electrostatic interaction is accelerated using GPUs in NIVIDIA CUDA programming environment.Particle Mesh Ewald algorithm is adopted and split into 5 procedures:parameters designation,discretization of point charges into grids,Fourier transformation of grids,potential of electrostatic interaction,and force calculation of electrostatic interaction.The codes are tested by seven biomolecular systems with different sizes.Roughly 7-fold speedup over one core of mainstream CPUs is obtained.The codes can be integrated into molecular dynamic simulation software packages that already exst or used as part of GPU codes developed in the future to further speedup traditional MD simulations.

A series of exact solutions are constructed for two-dimensional radiative transfer and radiative diffusion problems with outer source.These solutions exhibt physical characteristics with simple expressions.Moreover,transport solutions degenerate directly into solutions of corresponding diffusion equations.Test results of the diffusion model with LARED-R are presented and analyzed.

Strong-coupled multigroup radiative transfer in optically thick regions are analyzed.A simple conner balance method in 2D is presented.A grey transport acceleration scheme is generalized to accelerate source iteration convergence of differenced multigroup transport equations.

We provide a radiant energy probing method based on single contour integration,including annulus probing and uniform probing.It probes the radiant field of an anisotropy light source and is used as an efficient visualization method.

Construction of difference schemes for parabolic equations on distorted meshes with large aspect ratio is discussed.The limitation of 9-point scheme is provided.An assistant mesh difference method is proposed for distorted meshes with large aspect ratio to improve precision and efficiency.Based on the conservation law,applying appropriate rezone methods for meshes we modify the 9-point method to reduce computation error due to poor regularity of the meshes and low precision due to the approximation to vertices values by an average of neighboring cell values.The nonlinear system obtained is a different system from the 9-point scheme.Its solution approximates to the solution with the original meshes.The designed scheme is implemented easily and adapts well to distorted meshes.Numerical experiments show good precision and stability.

An LU-SGS(Lower-Upper Symmetric Gauss-Seidel) scheme and improvement for three-dimensional unstructured grid Euler computation are presented.Grid reordering for efficient implementation of the improved LU-SGS and the original LU-SGS is proposed.In order to test the feasibility and efficiency of the improved LU-SGS algorithm,two numerical examples of transonic inviscid flow around an ONERA M6 wing and an LANN supercritical wing are presented.It shows that the numerical results agree well with the experimental data.Moreover,the efficiency of the improved LU-SGS scheme is two times higher than that of the original LU-SGS scheme and seven times higher than that of the explicit Four-Stage-Runge-Kutta scheme.

In terms of the combination of patched grid and domain decomposition techniques, the N S equation of the complex flow around a wing body combination with deflection of control surface (aileron) is solved. In the computation Van Leer's scheme is employed to discretize the inviscid flux terms and the viscous flux terms are discretized by adopting central difference scheme. An internal coupling condition satisfying the conservation of flux is used on the interface of neighboring regions. Numerical results show that the present method is effective one for solving the flow around a wing body combination with control surface deflection.

A new concept of pulse tube refrigerator using gap regenerator as its regenerator is suggested.The physical model of this pulse tube refrigerator is established.The influences of frequency,gap width,opening of orifice and double inlet valves on the refrigerator performance have been analyzed by numerical calculation based on the finite difference method.It shows that in the pulse tube refrigerator with a gap regenerator, the optimum frequency,optimum openings of orifice and double inlet valves are less than those of the pulse tube refrigerator with screen-matrix regenerator.

Recently Wu Z N and Zou H proposed an overlapping grid method.The suitability of applying the method to parallel computation of steady and unsteady compressible inviscid flows with three-point block-tridiagonal implicit schemes was addressed in the paper [1],and an easily usable interface treatment was constructed and analyzed for both steady and unsteady problems.This method is here applied to the computation of N-S equations.In both steady and unsteady cases a good absolute parallel efficiency has been still demonstrated for bidimensional subsonic and transonic flow computations.

An interactive method of block grid generation is studied, including the issues of interactive input, graphics view, grid quality check, visual random control of grid solving process, etc. An interactive generation system-BIGG is developed by the above techniques. The numerical results of grid generation and flow solution indicate that the interactive technique presented is feasible and effective, the system-BIGG improves the generation efficiency and grid quality.

An internal coupling condition which can guarantee the conservation of flux on the irregular patched grids for the domain decomposition method is given. The Euler equations are solved by using the finite Volume method combined with van Leer's flux vector splitting. The TVD character and second order accuracy are realized by adopting a new limiter function. Numerical examples are presented as well.

Based on the MT(Multipole Theory),a new method is presented for calculating the electrical conductance of cables with complicated cross-section.By analyzing two examples, it is proven that the calculating accuracy of the MT is much better than that of the BEM(Boundary Element Method).

Based on the theoretical study of spatial coherence of laboratory x-ray lasers, a principle setup is proposed for x-ray laser holography, and corresponding theoretical simulation is performed for the recording and reconstruction of the lenseless Fourier transform hologram.

A new class of limiter functions is co nstructed which can guarantee the TVD property while maintain the smoothness of the Van.Albada's limiter.When coo rperated with the Flux vector splitting scheme, it gives a stable result for the 3-D viscous flow around a blunt body.