We study effect of addition of graphene on mechanical properties (elastic modulus and Poisson's ratio) of hydroxyapatite composites. Firstly, generating algorithm of random distribution geometric model of graphene/hydroxyapatite composites was created and model's automatic generation program was developed. Then, finite element model of graphene/hydroxyapatite composite was established. Finite element analysis of uniaxial tensile tests of composite materials was carried out. Finally, mechanical properties of different mass fraction of graphene of composite were calculated. Validity of the algorithm is verified by experimental data. It shows that elastic modulus of composite increased 12% to 50% with addition of 0.25% to 1.25% (wt.) graphene. Mechanical properties of hydroxyapatite can be effectively improved by addition of graphene.

Lattice Boltzmann method is adopted to investigate mixed convection in an enclosure filled with porous medium.A heated cylinder (D/L=0.4) is located at center of the enclosure with high temperature.Inlet flow with low temperature is located at lower-left wall of the enclosure and exit is at upper-left wall.Other walls are assumed adiabatic.Influences of Richardson number Ri and Darcy number Da on average Nusselt number Nu around heated cylinder are investigated while Prandtl and Grashof numbers are kept at 0.71 and 1.4×10⁴, respectively.It indicates that Nu decreases with increasing Ri.Influence of Richardson number on Nu is significant as Darcy number is great.At 10^-5≤Da≤10^-2, Nu increases with increasing Darcy number as forced convection dominates flow (Ri≤0.1).As natural convection dominates flow (Ri=10), Nu is not sensitive to Darcy number.

Wind sand flows affect surface electric field and potential on insulators. We established a gas-solid flow model for insulator surrounded by sand and a sand-electricity coupling model made up of high voltage insulator based on finite volume method (FVM). Spatial distribution and deposition of sand on surface of insulator and electric field distribution along insulator under different wind sand flow are calculated. It shows that surface potential and electric field distortion are influenced obviously by wind speed and particle size. Distortion of electric potential increases with increase of wind speed and particle size, while distortion of electric field decreases with increase of wind speed and particle size. Different spatial distribution and deposition of sand make different distortion on potential and electric field along insulator.

A self-adaptive precise algorithm in the time domain is presented for convective heat transfer problems.By expanding variables at a discretized time interval,a time and space coupled problem is converted into a series of boundary value problems.Based on a finite element method,a recursive and self-adaptive computation is conducted without the requirement of additional assumption and iteration for non-linear analysis.A couple of examples with high accuracy are shown.