The dynamics of entanglement and the phenomenon of entanglement sudden death (ESD) [1] are discussed in bipartite systems, measured by Wootters Concurrence. Our calculation shows that ESD appears whenever the system is open or closed and is dependent on the initial condition. The relation of the evolution of entanglement and energy transfer between the system and its surroundings is also studied.

The relation between the geometric phase and quantum phase transition has been discussed in the Lipkin-Meshkov-Glick model. Our calculation shows the ability of geometric phase of the ground state to mark quantum phase transition in this model. The possibility of the geometric phase or its derivatives as the universal order parameter of characterizing quantum phase transitions has been also discussed.

C-C composite is a kind of typical difficult-to-machine materials due to its high hardness, high strength, and obvious anisotropy features. But, water-based or oil-based coolant cannot be used during its machining process. As a result, the machining defects, including burrs, orifice ripping, and interlayer delamination, are always unavoidable. In this article, taking the liquid nitrogen as coolant, C-C composite cryogenic drilling is researched experimentally. Taking the way of LN2 external spray cooling, a series of cryogenic drilling experiments were designed. Comparing with dry drilling, the thrust force was reduced, the machining defects were significantly inhibited, and a better roundness of holes was achieved in cryogenic drilling. It indicates that cryogenic condition has a positive effect on improving the C-C composite drilling quality.

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