Dose coefficients for external photon radiation are widely used for assessment of radiation dose to public and workers due to ground surface contamination and air immersion of radionuclides released in nuclear accidents. Dose coefficients based on Chinese reference voxel phantom were presented. Photons that incident into the cylinder, which is slightly larger than phantom, is simulated using Geant4, including distributions of angle, height and energy of photons; Secondly, photons are sampled on surface of cylinder around Chinese Reference Male/Female Voxel Phantom with MCNPX 2.4.k from the above source, dose coefficients of 20 initial gamma ray energies, from 15keV to 10 MeV, are calculated. Thirdly, dose coefficients of 68 important nuclides are evaluated by combining of decay data from ICRP 107 and photon coefficients using cubic-spline fitting. GB/T 17982-2000 shows an overestimation for ground contamination while an underestimation of high Z nuclides for air immersion compared to our results.

Smoothed particle hydrodynamics(SPH) method is applied to simulate transient viscoelastic flows.The method for viscoelastic flows is verified by comparing numerical solution with analytical solution of an Oldroyd-B fluid in a start-up Couette flow.An Oldroyd-B fluid in a lid-driven cavity is simulated by the method.In addition,a new treatment of solid wall boundaries is presented to prevent particles penetrating solid walls and improve numerical accuracy.It shows that SPH method is valid and stable in simulation of viscoelastic flows.

With the Dirac delta function discrete ordinate method,a one-speed time-dependent transport equation with anisotropy scatterings is studied in a slab.The scattering function is assumed a combination of linearly anisotropic and strongly forward-backward scattering.The angular flux is split into a delta function and a low order function.The source term is obtained by integrating the delta function and quadrature the low order function.Numerical results for criticality eigenvalues are obtained and tabulated with different scattering parameters including extreme regions.

Relationships between the choice of the positive and negative frequency expression of optical waves, adoption of Fourier transformation form and form of nonlinear Schrödinger equation are discussed. The generally accepted form of nonlinear Schrödinger equation is the result of choosing the negative frequency expression. In accord with the negative frequency expression, the form of Fourier transformation cannot be chosen at will. When the nonlinear Schrödinger equation is solved using numerical methods based on Fourier transformation, the form of fast Fourier transformation must be paid attention in the programming languages used. In most programming languages, the adopted forms of fast Fourier transformation and inverse transformation are opposite to the forms adopted in nonlinear optics. It is also pointed out that some related numerical errors existed in some references.