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Abstract

The main work of this paper focuses on the simulation of binary alloy solidification using the phase field model and adaptive octree grids. Ni-Cu binary alloy is used as an example in this paper to do research on the numerical simulation of isothermal solidification of binary alloy. Firstly, the WBM model, numerical issues and adaptive octree grids have been explained. Secondary, the numerical simulation results of three dimensional morphology of the equiaxed grain and concentration variations are given, taking the efficiency advantage of the adaptive octree grids. The microsegregation of binary alloy has been analysed emphatically. Then, numerical simulation results of the influence of thermo-physical parameters on the growth of the equiaxed grain are also given. At last, a simulation experiment of large scale and long-time has been carried out. It is found that increases of initial temperature and initial concentration will make grain grow along certain directions and adaptive octree grids can effectively be used in simulations of microstructure.
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Abstract

In order to compare the pathogenicity of different Tembusu virus (TMUV) strains from geese, ducks and chickens, 56 5-day-old Cherry Valley ducklings which were divided into 7 groups and infected intramuscularly with 7ยด105 PFU/ml per duck of six challenge virus stocks. The clinical signs, weight gain, mortality, macroscopic and microscopic lesions, virus loads in sera of 1, 3, 5, 7, 11 and 14 dpi and serum antibody titers were examined. The results showed that these viruses could make the young ducks sick, but the clinical signs differed with the different species-original strains. All the experimental groups lose markedly in weight gain compared to the control, but there were no obvious distinctions in weight gains, as well as macroscopic and microscopic lesions of dead ducks between the infected groups. However, the groups of waterfowl-derived strains (from geese and ducks) showed more serious clinical signs and higher relative expressions of virus loads in sera than those from chicken-derived. The mortality of waterfowl groups was 37.5%, and the greatest mortality of chicken groups was 12.5%. The serum antibodies of the geese-species group JS804 appeared earlier and were higher in the titers than others. Taken toghter, the pathogenicity of waterfowl-derived TMUV was more serious than chicken-derived TMUV and JS804 could be chosen as one TMUV vaccine strain to protect from the infection.
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