According to the analysis of the turbulent intensity level around the high-speed train, the maximum turbulent intensity ranges from 0.2 to 0.5 which belongs to high turbulent flow. The flow field ...distribution law was studied and eight types of flow regions were proposed. They are high pressure with air stagnant region, pressure decreasing with air accelerating region, low pressure with high air flow velocity region I, turbulent region, steady flow region, low pressure with high air flow velocity region II, pressure increasing with air decelerating region and wake region. The analysis of the vortex structure around the train shows that the vortex is mainly induced by structures with complex mutation and large curvature change. The head and rear of train, the underbody structure, the carriage connection section and the wake region are the main vortex generating sources while the train body with even cross-section has rare vortexes. The wake structure development law studied lays foundation for the train drag reduction.
This paper describes a new method to design a laser mirror with high reflectivity, wide reflection bandwidth and high laser- induced damage threshold. The mirror is constructed by three materials of ...HfO/TiO2/SiO2 based on electric field and temperature field distribution characteristics of all-dielectric laser high reflector. TiO/SiO2 stacks act as the high reflector （HR） and broaden the reflection bandwidth, while HfO2/SiO2 stacks are used for increasing the laser resistance. The HfO/ TiO/SiO2 laser mirror with 34 layers is fabricated by a novel remote plasma sputtering deposition. The damage threshold of zero damage probability for the new mirror is up to 39.6 J/cm^2 （1064 nm, 12 ns）. The possible laser damage mechanism of the mirror is discussed.
The performance of broadband polarizing beam splitters（PBSs） is sensitive to the incident angle.By taking account of the spectrum of the laser source and using the needle optimization method,a large ...acceptance angle PBS for laser-based displays is designed.The average degrees of polarization in transmission and reflection can reach 0.989 and 0.980 for an acceptance angle of 13.6in air using two materials,while better results of 0.993 and 0.989 for an acceptance angle of 14.8？in air are attained when three common materials are used.Both designs consist of 40 layers.
