A weighted Bayesian inversion method is proposed for estimation of unimodal particle size distribution in multi-angle dynamic light scattering measurements. Particle size informiation distribution in autocorrelation function is used as base and adjustment parameters as exponent in the weight coefficient. Traditional Bayesian inversion method is recovered. Simulation and experimental data at different noise levels show that weighted Bayesian inversion method obtains inversion results with smaller distribution error. It weakens effectively influence of data noise and improves accuracy of particle size distribution.

Necessity for calculating boundary temporary field components in reduced finite-difference time-domain method(R-FDTD) is discussed.A periodic symmetric R-FDTD method is proposed.Temporary components in supplement calculation are given based on symmetry and periodic boundary conditions(PBC).Computational domain is reduced to 1/4 and lateral field components of a symmetry plane are obtained with symmetry relations.Compared with original FDTD,memory storage is reduced to 1/6 while ensuring accuracy. It is shown that the improved algorithm agrees with FDTD method by numerical simulation of EM impulse responses tO infinity wire mesh reinforcement and reinforced concrete layer.The improved algorithm has advantages in saving memory storage and calculation time.

A Brownian dynamic simulation of perikinetic flocculation of fine sediment with ionization is presented.Langevin equation is used as dynamical equation in tracking particles in a floc.Monte Carlo method is used in simulating random variation in particle movement.Sludge particles are supposed in uncharged and charged state in dispersion system.Electrostatic force on a particle in a simulation cell is considered as a sum of electrostatic force from other particles in the original cell.Particle initial place is decided by particle diameter and sludge density.Particle initial velocity is determined by Gauss random distribution.Effects of particle diameter and sludge density on flocculation and floc structure are discussed.On the other hand,effects of electrostatic force on flocculation are presented.The model proposed coincide well with practical situations.

With hypothesis that radiation is incoherent, based on Planek's definition of radiative entropy, radiative entropy transfer equation and local radiative entropy generation in semitransparent graded index medium are derived. A calculation method based on discrete-ordinates approach is used to solve radiative entropy transfer equation in semitransparent graded index medium. A one-dimensional slab system filled with semitransparent graded index medium is taken as an example to verify the radiative entropy transfer equation and the calculation method. Numerical results of dimensionless radiative entropy generation of the slab system agree well with entire thermodynamics analysis.

Charge transfer in He⁺-H^- collisions is investigated using two-center atomic orbital close-coupling(TC-AOCC) method.All bound states of He⁺ (nl) with n≤7,as well as 1s bound states and ns(n=2~6) quasi-continuum states of H^- are included in the AOCC basis.Energies of bound states calculated are in good agreement with NIST data and theoretical results.The total and state-selective cross sections are calculated within a range of energy from 4 to 400 keV.For low-energy collisions,dominant capturing channels are those with quantum numbers n=3-5.With increasing incident energies,transfer of charge to n=2 becomes the dominant reaction.Moreover,for low-energy collisions,cross sections for electrons capture to higher-l states are bigger than that to lower l states.For high-energy collisions,dominant channel is to l=1 states.Charge exchange spectrum due to electron captured to excited states is calculated.Importance of cascade effects is found.

The laminar flamelet model in combination with joint probability density function (PDF) transport equation of mixture fraction and turbulence frequency is used to simulate fluctuating behavior of radiative source term in turbulent jet diffusion flames of hydrogen.The frequency distributions of radiative source terms in the combustion zone are calculated. The results show that, for the given ensemble, about 95% samples of radiative source term locate within the region of ±3.0 standard deviation of the mean radiative source term. The profile of frequency distribution indicates having a single peak.

The asteroids are the most important small bodies in the solar system,and they mainly lies in the two locations-a main belt between the Mars's orbit and the Jupiter's and the near Earth space.The most feature of the orbits of Near Earth Asteroids (NEAs) is that the semi major axes of the orbits are nearly equal to that of the Earth or the perihelia distances are approximate to or even less than the mean distance between the Sun and the Earth,thus they could move into inside of the Earth's orbit,so that they might close approach or even colliside with the Earth (or other planets,such as the Venus,the Mars,etc.).The characteristic brings about some difficulties in the numerical research during their orbital evolution,which leads to the failure of the normalization technique in the general removal impact singularities of celestial mechanics methods and the Symplectic Algorithm which is successfully applied to the investigation in quality.By comparing the computation effects of several common numerical methods (including Symplectic Algorithm),and considering the nature of the movement of the small bodies,the corresponding treatments are provided here to improve the reliability of the computation.

The coupled heat transfer processes of radiation, conduction and convection in semitransparent planar slab are analyzed. An inverse method is presented for estimating the unknown boundary incident radiation heat flux in semitransparent planar slab with transparent boundaries from the knowledge of the radiation intensities exiting the boundaries. The effects of anisotropic scattering, absorption coefficient, scattering coefficient, fluid temperature outside the boundaries, convection heat transfer coefficients, conduction coefficient of semitransparent media and slab thickness on the accuracy of the inverse analysis are investigated. The results show that this method is praticable.

The discrete ordinate approximation method of three-dimensional radiative transfer equation in absorbing scattering medium is expounded. The selection of quadrature sets of in-scattering term are analysed. The causes about the formation of false scattering and ray effect and its influence on the accuracy of solutions are also analysed. By detailed comparison, it is shown that false scattering and ray effect exact not only in discrete-ordinates method, but also in zone method, discrete transfer method, etc., and the influence of false scattering and ray effect on solution accuracy of radiative transfer equation can be reduced by decreasing grid size and increasing the number of solid angle discretation. The process of radiative heat transfer in a three-dimension rectangular furnace is simulated using discrete ordinates method. By comparison with zone method and discrete transfer method, it is found that discrete ordinates method has a good accuracy, and recently is one of the best method to simulate the process of radiative heat transfer in furnace.

The numerical research about the orbital evolution of NEAs has been made by adopting the improved explicit Symplectic Algorithm. For the mechanic model, Post-Newtonian effect has also been taken into account, apart from considering the gravitational perturbations of major Planets, while for the algorithms the investigation focuses on the applicable prospect that the Symplectic Algorithm would be suitable for the study of the orbital evolution of the NEAs, especially for the effectiveness of the Symplectic Algorithm in the case that the NEAs close approach a major planet.

Discussion is given on the existance of conservative laws of symplectic difference scheme for the Hamilton System and the relationship between them and the stability of the symplectic difference-scheme. The results show there are not any linear variations in all conservative laws of Hamilton System for symplectic difference scheme. In general, when the symplectic differencescheme stable, the conservative laws are convergent.

The restricted three-body problem is a Hamiltonian dynamical model used usually in dynamics of the solar system. At present, Numerical methods are mainly adopted for some important problems. It is due to the fact that the mathematical tools or methods are poor. But, in order to understand the evolution of the solar system, it needs to dolong-term tracking computations. Hence the requirement for algorithms is very high, that is to say, the algorithms must maintain the global characteristics of the motions. The symplectic algorithms just satisfy the requirement. In this paper, an explicit symplectic difference scheme has been constructed for circular and elliptic restricted three——body problem in the rotative coordinate system by means of algorithm composition, respectively.Some computational examples have shown the scheme is effective.

Based on the property that the great majority of celestial motions in solar system can be described by the model of two-body problem with perturbations, we use the composition of algorithm to construct out a improved explicit symplectic algorithm with higher accuracy. Numerical results have shown that the algorithm have advantages in the computations of celestial orbits compared with usual symplectic algorithms.

The accuracy of orbital seminajor axis is improved by the energy relation so that the growth of the along-track error in traditional integrators can be controlled. This is called numerical stabilization. The change of step-size can be solved by the transformation of time variable: df=r^3/2ds.