To investigate entropy generation caused by a grooved structure on flow, we used Fluent software and large eddy simulation (LES) technology to analyze entropy generation in flow over a plate with a grooved structure. It showed that a grooved structure was able to reduce entropy generation in the flow. At 30 m·s^-1(Re≈20 000), total entropy generation in near-wall region decreased by approximately 25%. And at 40 m·s^-1(Re≈27 000), it decreased by approximately 19%. However, the grooved structure did not have a sustained effect on subsequent flow. As distance from the wall in the normal direction increased, the effect decreased gradually. Entropy production at the top of the trench is much greater. And entropy production caused by turbulence is dominant. It provides a theoretical basis for optimizing drag reduction of trench structures.

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.

Monte Carlo method is used to study light extinction of smoke screen with clustered agglomerates consisting of spherical primary particles in a cluster-cluster aggregation(CCA) model.Extinction factor and absorption factor of randomly oriented smoke screen with clustered agglomerates are calculated with discrete dipole approximation(DDA).It shows that exinction properties are determined by radius and number of primitive particles besides refractive index and extinction properties can be decreased by aggregation.At a given primitive particle number,maximum extinction is obtained with optimum radius of primitive particles.

The finite element method is combined with the natural boundary element method to study the weak solvability and Galerkin approximations of a class of semilinear exterior boundary value problems.Theoretical analysis is mainly based on the variational formulation with constraints.The error estimate of the finite element solution and the asymptotic rate of convergence O(hⁿ) are obtained.Finally,a numerical example is devoted to illustrate this new method.

In this paper we present a new method-local accumulated deviation method for evaluating the fractal dimension of curves or one-dimensional(1D) surfaces. Our method is tested on various types of curves for Weierstrass-Mandelbrot fractal function and fractal Brownian motion with known fractal dimension. The results are good agreement with the theoritical values. Finally, using Monte-Carlo method, we simulated the randam rough(1D) surfaces with Gauss spectrum, and the new method is applied to data from simulating surfaces.