On The Structure Of The Chan-Paton Factors For D-Branes In Type II Orientifolds

We determine the structure of the Chan-Paton factors of the open strings ending on space filling D-branes in Type II orientifolds. Through the analysis, we obtain a rule concerning possible distribution of O-plane types. The result is applied to classify the topology of D-branes in terms of Fredholm operators and K-theory, deriving a proposal made earlier and extending it to more general cases. It is also applied to compactifications with N=1 supersymmetry in four-dimensions. We adapt and develop the language of category in this context, and use it to describe some decay channels.Comment: 137 page

Dynamical interpretation of the wavefunction of the universe

In this paper, we study the physical meaning of the wavefunction of the universe. With the continuity equation derived from the Wheeler-DeWitt (WDW) equation in the minisuperspace model, we show that the quantity $\rho(a)=|\psi(a)|^2$ for the universe is inversely proportional to the Hubble parameter of the universe. Thus, $\rho(a)$ represents the probability density of the universe staying in the state $a$ during its evolution, which we call the dynamical interpretation of the wavefunction of the universe. We demonstrate that the dynamical interpretation can predict the evolution laws of the universe in the classical limit as those given by the Friedmann equation. Furthermore, we show that the value of the operator ordering factor $p$ in the WDW equation can be determined to be $p=-2$

Numerical simulation of material flow in AA6082 during friction stir spot welding

Friction stir spot welding (FSSW) is a new solid state joining technology based on the linear friction stir welding which can be used to replace the conventional resistance spot welding as well as riveting. However, some key problems such as heat transfer and thermoplastic material flow have not yet been studied sufficiently and block the application of this advanced technology. This paper presents the coupled thermo-mechanical viscoplastic finite element formulation based on the character of FSSW. The model was calibrated by comparing temperature history between simulation results and experimental data and subsequently used to investigate the effective strain rate and material flow in joint. The temperature study showed that the simulation and experiment results coincided well with each other thus proofing the correctness of the model. The simulation results showed that the effective strain rate distribution were not uniform. The material close to the pin’s cylindrical surface had a higher effective strain rate than that of the other material. The materials in weld centre mainly experienced a compression process and the other material under the tool experienced both compression and shear process

Study on SiCp/6063Al composites laser welding process with Al75Cu20Ti5 foil interlayer

This experiment chooses 6063 aluminum matrix composites containing 55~75% SiC particle reinforcing phase as the parent metal and Al75Cu20Ti5 foil as the interlayer. The laser power, defocusing amounts and welding speed are discussed using three important parameters for the joint forming, microstructure and shear strength. The result shows that the weld width is mainly affected by laser power, and the weld penetration is almost determined by the defocusing amount. The welding speed has a certain influence on both weld width and weld penetration. When suitable laser heat input is adopted, superior weld appearance and satisfied shear strength could be obtained. The highest shear strength is 217MPa, with the laser power of 520W, the defocusing amounts of -1mm, and the welding speed of 1.5cm/s