First-principles calculations are used to study alloy effects on configurations, stability and water adsorption of PtRu_n-1(n=2-14) and H₂O-PtRu_n-1 (n=2-14) systems. It shows that substitution energy of a Pt atom to a Ru atom is low which manifests that Pt is easy to form alloy with Ru clusters. Compared with pure Ru_n cluster, alloy effects enhance adsorption energy of H₂O molecule on PtRu_n cluster, and H₂O molecule is not easy to release in molecular form from PtRu_n cluster. Considering van de Waals force, adsorption energy of water on PtRu₇ increased and dissociation barrier decreased, making it possible to split water on PtRu₇. In conclusion, PtRu_n is suitable to be catalyst for spliting water and producing hydrogen.

With three-dimensional(3D) filtering in Monte Carlo rough dose distributions with less particle history and short simulation time convergence is accelerated.We improve 3D Gaussian and Savitzky-Golay filters considering features of Monte Carlo dose distribution. Parallel and cascade mixture methods with 3D Gaussian and Savitzky-Golay filters are compared.A method simplifying mixture filter structure using equivalent convolution kernel is put forward.It shows that the improved Gaussian and Savitzky-Golay filters enhance denoising.The mixture filter reduces local errors of filtering results.Two types of mixture filters reduce noise in Monte Carlo dose distributions.Filtering of cascade mixture filter is slightly better than that of parallel mixture filter.