Two-pion interferometry for viscous hydrodynamic sources

The space-time evolution of the (1+1)-dimensional viscous hydrodynamics with an initial quark-gluon plasma (QGP) produced in ultrarelativistic heavy ion collisions is studied numerically. The particle-emitting sources undergo a crossover transition from the QGP to hadronic gas. We take into account a usual shear viscosity for the strongly coupled QGP as well as the bulk viscosity which increases significantly in the crossover region. The two-pion Hanbury-Brown-Twiss (HBT) interferometry for the viscous hydrodynamic sources is performed. The HBT analyses indicate that the viscosity effect on the two-pion HBT results is small if only the shear viscosity is taken into consideration in the calculations. The bulk viscosity leads to a larger transverse freeze-out configuration of the pion-emitting sources, and thus increases the transverse HBT radii. The results of the longitudinal HBT radius for the source with Bjorken longitudinal scaling are consistent with the experimental data.     

多点光子多普勒测速光纤阵列耦合系统设计北大核心CSCD

设计了一种基于鱼眼镜头的高效率光纤阵列耦合系统,并将其应用于多点光子多普勒测速仪,可以在爆轰物理、冲击波物理和强激光等众多领域中开展多点测速。为满足大范围的空间光进行聚焦,设计了一款视场角为120°的大视场高分辨率低畸变的鱼眼镜头,再将光纤端面整体抛光8°角度进行阵列排布后与鱼眼镜头耦合,通过采用高精度机械零件及定心装调进行准确定位,使光纤阵列的中心与鱼眼镜头焦面重合,实现鱼眼镜头与光纤阵列的精密机械耦合。最后对所涉及的光纤机械耦合型鱼眼镜头组件的回波损耗进行了实际测量和讨论,经过验证该组件的37根光纤束每根的回波损耗大于55dB,符合设计指标要求。     

基于气压鼓泡法研究石墨烯力学性能

通常假设二维材料为连续介质薄膜,然后采用连续介质薄膜的研究方法进行二维材料力学性能研究,其中气压鼓泡法是一种主要测试方法．但实验观测发现,悬空石墨烯并非处于气压鼓泡测试分析模型中假设的固支边界条件,而是处于一种粘附边界条件：靠近孔壁边界处,有小部分材料通过范德华吸引粘附在基底柱形孔的侧壁上,而且粘附部分可以在极小载荷作用下剥离．这导致石墨烯悬空部分的实际半径大于基底孔半径,即鼓泡实验中的石墨烯是一种松弛薄膜,而非通常认为的预拉伸薄膜．通过有限元数值模拟研究发现,可基于含有名义松弛应变的鼓泡分析模型获得处于粘附边界条件下的石墨烯弹性模量．