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.     

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．