Theoretical analysis and numerical simulation are conducted to investigate basic properties of two-dimensional disordered disk system under quasi-static isotropic compression. Some basic concepts such as average reduced overlap, reduced pressure are introduced. Via micromechanics analysis, we deduce functional relation between reduced pressure and statistical quantities of disk system. Based on numerical simulation, variations of physical quantities such as excess average contact number, average reduced overlap, reduced pressure with excess volume fraction are studied. An approximate formula of reduced pressure is presented. These simulation results show that mechanical responses of compression are different as disk system is far from or near critical jammed state.

Numerical simulation is conducted to investigate two-dimensional frictionless disks under isotropic compression.Results with different simulation conditions are contrasted.It shows that monodisperse system is easier to crystallize.Its critical packing fraction φ_C and critical mean contact number Z_C are larger than bidisperse system.On J point,relations of packing fraction increment Δφ to mean contact number increment ΔZ and average overlap δ are almost irrelevant to simulation conditions.Relation of pressure P and packing fraction increment Δφ is only determined by interaction form.These relationships can be fitted very well by power functions.

Discrete element method is used to study probability distribution of tangential forces in granular system with composition disorder.Primary tangential force and secondary tangential force are distinguished and their statistics are analyzed separately.As the rate of defects increases,tangential force distribution transforms from approximate normal distribution to a distribution with two peaks.Finally it becomes a distribution with one peak.Whereas secondary tangential force distribution is always exponential.It shows that force distribution of composition disorder with great defect rate and structural disorder are similar.

A deconvolution method for electron energy loss spectrum of diatomic molecules is proposed.Fitted energy positions are locked on accurate spectroscopic data.Calculated Franck-Condon factors are adjusted by a quadratic function.Precision requirement for Franck-Condon factors is reduced.Undermined parameters in deconvolution procedure are reduced dramatically.Precision of fitted results is improved. Optimized algorithm in fitting procedure avoids a lot of integral calculations.The program is used to deconvolve electron energy loss spectrum of H_2.Vibrationally resolved optical oscillator strengths are determined.The results agree well with previous experimental and theoretical studies.

Metropolis-Monte Carlo simulation is made to investigate autocorrelation of conformation energy and tangent vectors of minicircles(less than 500 base pairs) with flexible hinges.Direct conformation information and topology of minicircle containing flexible hinges are demonstrated.It provides powerful support for the existence of flexible hinge.

A model of planar disc pile is applied to complicated granular matters.We analyze force transfer in the disc pile.Numerical simulation shows that the pressure on the cylinder bottom saturates with increasing height of granules.The rule of the planar disc pile is extended to three-dimensional granules and the relation between the height Z of granules and the average pressure p on cylinder bottom is obtained.

A fractal model of coarse surface of SiC by using structure function is presented.Three parameters rms roughness Δ,fractal dimension D,and correlative length L are used to describe the covariance function of surface height.The method calculating these parameters is also given.With the present model,one can calculate the coarse dispersion of SiC/SiO₂ fractal interface to channel electrons.

Fast evaluation of frequency domain free surface Green Function with sufficient accuracy is the key of frequency domain approach for solving hydrodynamic problems.In this paper,the fast caculation of free surface Green Function and its derivatives (frequency domain,infinite depth) is investigated and discussed.This approach is shown to be applicable and efficient.