To improve resolution of a low-light image intensifier,simulation of electronic transport in a micro-channel plate(MCP) is made.Field distribution is obtained by calculating electron optics with numerical method.Distribution of photoelectron on fluorescent screen is determined by tracing electron trajectory in MCP.Influence of MCP tilt angle,channel diameter,voltage on electronic transport and resolution of image intensifier are studied.It shows that MCP has good electronic transport characteristics,image intensifier has good modulation transfer function(MTF) and high resolution at a title angle of 14°,channel diameter of 5.0 μm,a voltage of 900 V.

A boundary element method (BEM) based on multiple reciprocity method(MRM) is employed to solve eigenvalue and eigenfrequency of a two-dimensional linear acoustic cavity.By direct searching of the zero-points of determination of a matrix,we determine eigenfrequency of the system.An effective estimation for the first wave-number was suggested based on the principle of wave propagation.Estimation efficiency of several models is calculated.We evaluated fundamental solution's order and found that more than seven reciprocity are needed.Numerical results agree well with analysis and other literature.Estimation for the first wave-number is effective and correct.

We summarize conservative remapping algorithms based on ENO (essentially non-oscillatory) interpolation. Three numerical techniques in computational fluid dynamics are discussed:overlapping mesh method, adaptive refinement mesh method and moving mesh method. Physical quantities transfer between meshes. Conservativeness is important, especially in computing shock and contact discontinuity. We propose a remapping algorithm based on ENO which is conservative and accurate in transferring physical quantities between meshes and give numerical examples. It shows that the algorithm has ability of resolving conservative problems with above mesh techniques in computational fluid dynamics.

A model for an open four-level atomic system driven by two fields is presented. Density matrix equations of motion are obtained by electric dipole and rotating wave approximations. Physical mechanism of lasing without inversion (LWI) is discussed. Effects of detuning on gain without inversion and population difference are studied. Dispersion equals to zero as two driving and probe fields are resonant. As one driving field (probe field) is resonant, the gain and the population difference versus detuning of driving field (probe field)show even symmetry, and the dispersion shows central symmetry. As two or three of driving and probe fields are off-resonance, the symmetries disappear. LWI gain is obtained when the dispersion equals to zero. When beth driving and probe fields are off-resonance, the gain, the dispersion and the population difference change greatly. High dispersion without absorption is obtained by adjusting suitable parameters of the system.

A finite volume scheme is developed for Lagrangian equations in hydrodynamics.With ENO(essentially non-oscillatory) interpolating polynomials on structure grids,a high accurate finite volume scheme is constructed by modifying a first order finite volume scheme on rectangular meshes.Numerical experiments are made with an adaptive moving mesh and arbitrary Lagrangian-Eulerian method.It shows effectiveness of the method.

Natural radiative lifetimes of 6snd ³S₁(n=11~25) and 6snd ³D₁(n=12~24) Rydberg series of neutral mercury are calculated by means of multichannel quantum defect theory (MQDT). The lifetime of 6sns ³S₁ series can be approximated by τ=0.814v^2.835(ns) and that of the 6snd ³D₁ series by τ=0.302v^2.926(ns), where v is an effective quantum number.

In the research of simulation for problems with large distortion in fluid dynamics, it is often required to re-construct the computational meshes. The technique transferring physical quantities between the two computatioal meshes is called as rezoning (remapping). Based on ENO interpolation idea, in this paper, a new kind of conservative ENO rezoning (remapping) algorithm is developed to structure and unstructured computational meshes. Finally, the numerical results show that the algorithm appears to be effective.

An expert system is developed for the automatic determination of zoom lens layout. Its features include the calculation of Gaussian parameters for different zoom mechanisms, and the selection and optimization of each lens group in a zoom system.