从爱因斯坦火车到洛伦兹变换

爱因斯坦火车是狭义相对论中展示同时性的相对性的经典模型, 爱因斯坦利用该模型证明了“ 同时性 的相对性” . 在狭义相对论中, 空间和时间并不相互独立, 而是一个统一的四维时空整体, 不同惯性参考系之间的时 空坐标变换关系式与洛伦兹变换在数学表达式上是一致的, 通过分析爱因斯坦火车模型中光在不同惯性参考系内 到达车壁的时间, 利用简单的数学变换更加容易地得到了洛伦兹变换, 从而验证了洛伦兹变换在狭义相对论的核 心地位     

Helium bubble formation and evolution in NiMo-Y2O3 alloy under He ion irradiation

We report helium ion irradiation experiments for a new type of dispersion-strengthened NiMo-Y₂O₃ alloy with three different irradiation doses and varying irradiation dose rates at 750 ℃ to evaluate its helium-induced damage behavior. Transmission electron microscopy was used to reveal the evolution of helium bubbles after irradiation. The experimental results show that with increasing ion dose, the number density of helium bubbles increases continuously. However, the mean size of helium bubbles first increases and then decreases, mainly due to the varied ion dose rates. The volume fractions of helium bubbles in the three investigated samples after irradiation are 0.15%, 0.32%, and 0.27%, which are lower than that of the Hastelloy N alloy (0.58%) after similar irradiation conditions. This indicates that the NiMo-Y₂O₃ alloy exhibits better helium-induced-swelling resistance than the Hastelloy N alloy, highlighting its potential applicability to MSRs, from the perspective of irradiation performance.