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A multiscale model is developed for simulating the microstructure evolution during solidification processes of Ti-6Al-4V alloy in vertical centrifugal casting, which combines the 3D finite difference method (FDM) at the macroscale with a 2D cellular automaton (CA) model at the microscale. The macro model is used to simulate the fluid flow, mass, heat and species transfer throughout the casting under centrifugal conditions. The micro model is used to predict the nucleation and growth of microstructures for the vertical central plane. A semi-coupled scheme between the 3D macroscopic and 2D microscopic calculations is adopted. Based on the CA cell, a modified method for simulating the shrinkage cavity is given. With the proposed model, numerical simulations are performed to investigate the influences of mould rotation speed, superheat, and mould material on microstructure formation. Calculated results reveal that the equiaxed zone is found to expand with increasing the mould rotation speed, as well as decreasing melt superheat and heat diffusivity of mould. The role of rotation speed is much greater than that of superheat and mould material in centrifugal casting. The underlying mechanisms responsible for those physical phenomena are discussed.

We have investigated the phase transition, the structural and the thermodynamic properties of AlAs in three crystallographic structures, i.e. B3 （zinc blende）, B1 （rocksalt）, and B8 （nickel arsenide）, at high pressures by using the full-potential linearized muffin-tin orbital scheme in the framework of density functional theory. By taking the common tangent to the energy-volume curves of B3-B8 and B3-B1 structures, we obtain a pressure of about 5.44 GPa for the transition from B3 to B8 and forecast a transition pressure of about 6.46 GPa for the transition from B3 to B1. We have also investigated the structural properties of B8 under high pressures, the results show that c/a ratio keeps nearly constant （～0.2% fluctuation） when V/V0≈0.7—1.05; c/a ratio increases linearly with the value of V/V0 decreasing when V/V0≈0.4—0.7. The relation between relative volume V/V0 and pressure P is obtained by fitting equation of state （EOS）, and the EOS of B8 accords well with measurements. Finally according to quasi-harmonic Debye model the dependences of bulk module B on pressure P and heat capacity CV on temperature T under different pressures are successfully obtained.

A dynamic architecture description must provide a dynamic behavior specification of software system. Based on the high-order multi-type π calculus theory, a dynamic architecture description language D-ADL is proposed. In D-ADL, components, connectors, and architecture are modeled as the 'Abstraction' type of high-order π calculus; system behavior is modeled as the 'Process'; and the interaction point between component and connector is modeled as the 'Channel'. D-ADL separates the dynamic behavior expressed in an explicit way from the computation behavior, which is helpful to edit and understand the changing logic in system. The result of the dynamic behavior can be beforehand deduced because this behavior is formalized as the high-order 'Process'. On the basis of D-ADL specification, rules about applying the theory of behavior equivalence and behavior simulation in π calculus to online evolution and architecture refinement are proposed. How D-ADL can be used is illustrated