We studied adsorption characteristics of oil-water system on calcite and dolomite surface with molecular dynamic simulation. To study wettability of calcite/dolomite surfaces, we analyzed equilibrium conformation, relative concentration, radial distribution function and adsorption energy of calcite/dolomite-oil/water system. Then, we proposed a two-step adsorption mechanism. It shows that dolomite-oil/water system is more easily to achieve thermodynamic stability and is more stable; A water film is formed on calcite and dolomite surfaces, which is a double-layer structure; There are interactions among oil molecules, water molecules and the crystal surface; Attraction of dolomite surface to oil and water molecules is stronger than calcite. Finally, we divided the adsorption process into two steps:Water molecules adsorbed on crystal surfaces form a tightly adsorbed layer under van der Waals forces, electrostatic forces and O(CaCO₃,CaMg(CO₃)₂)-H(H₂O) hydrogen bonds. In addition, the remaining water molecules move to the crystal surface form a diffusion layer under the influence of O(H₂O)-H(H₂O) hydrogen bonds. It reveals wettability formation and alteration mechanisms on calcite and dolomite surface, which paves a foundation of further enhance oil reovery.

We adopt lattice Boltzmann method to investigate double diffusive natural convection around a heated cylinder in an enclosure with Soret and Dufour effects. The inner heated cylinder is located at center of a square enclosure and four surrounding walls are assumed with low temperature and concentration. In the model, distributions of velocity, temperature and concentration are solved with three independent LBGK equations which are combined into a coupled equation through Boussinesq approximation. Influences of Soret number and Dufour number on double diffusive natural convection are analyzed. Streamlines, isotherms, isoconcentrations, average Nusselt and Sherwood numbers around heated cylinder in enclosure are presented. It shows that Soret and Dufour effects have significant influence on double diffusive natural convection.

A characteristic finite element method (FEM) is proposed for nonlinear fractional convection-diffusion equations. With the characteristic technique and fractional FEM framework, a fully discrete characteristic finite element scheme is constructed. It is utilized to simulate physical systems and studied in contrast with conventional schemes. It is demonstrated that the method captures exact solutions of governing equations well. The method enjoys good stability and high accuracy even if convection dominates diffusion essentially.

Smoothed particle hydrodynamics (SPH) is tested for simulating flow driven by high speed underwater body (FDUB).Developing history of supercavity induced by a body is predicated by SPH.Shape of developed supercavity derived by SPH is compared with result given by principle of independence of cavity sections expansion of Logvinovich.Ghost particle method and Dummy particle method,that remedy boundary deficiency of SPH,are combined to implement wall conditions.

Structures,stabilities,and magnetic properties of Pt_n(n=1-9) are calculated with generalized gradient approximation functional BPW91 and three-parameter hybrid density functional B3LYP in density functional theory.The methods give same stable structures and same lowest-energy structures but different stable order of sub-stable structures.Average coordination numbers and average bond lengths in two methods have similar patterns.They increase with cluster size,and have a great increase at n=2-3 and a small increase at n=4-9.Analysis of energies by two methods show that there are greater values at n=2,5,8,which illustrate that corresponding clusters have high stabilities.Study of Pt clusters indicates that average magnetic moment oscillates with cluster size.It has a gradually decrease trend.It shows that two methods can describe structures,stabilities and magnetism of clusters.

With numerical solution of density matrix motion equations of an open V-type three-level atomic system with spontaneously generated coherence,we analyze transient evolution of gain of lasing without inversion(LWI).It is shown that relative phase(Ф) between probe and driving fields has a significant effect on transient evolution of gain regardless of incoherent pump;Greater transient and steady gains can be obtained by selecting φ;As incoherent pump is absent,longer time is needed to get the greatest transient gain and steady gain.Oscillation amplitude in the evolution process is greater,and gain is also greater;Changing atomic exit rate r₀(ratio of atomic injection rates S) leads to detail of gain transient evolution.In certain range of r₀(S),transient and steady gains increase with S(r₀).

A radial symmetrical model of radon transport in vicinity of an underground tunnel is developed with continuum mechanics theory.Distribution of radon concentration in the vicinity of tunnel is analyzed under the assumption that only diffusion and permeation are considered.Analytic solutions are obtained.A rock mass range affecting the radon concentration in the tunnel is defined as effective transport distance.Effective transport distance as functions of effective porosity and velocity are given.Expressions of radon exhalation rate on tunnel wall are shown.

Magnetic field molding is a key technique in obtaining hish-performance permanent magnetic materials from strontium ferrite,Based on a mathematical model,we focus on effect of domain center and material geometrical center's relative position on magnetic properties of strontium ferrite.It shows that the external magnetic field atcts on magnetic domain center more obviously as the center shifts downward;as the sample is flat and the external magnetic field vertically acts on the sample absolutely.the effect is the greatest,and strontium ferrite in shape anisotropy can be obtained.

A new RDF program with wide adaptability and good reliability is suggested. It can be used both to prepare experimental radial distribution qunction (RDF) from wide angle X-ray scattering (WAXS) and to calculate theoretical RDF from model structure. In addition, it can also determine structure parameters from RDF.