1·His sudden entrance took everyone by surprise.
他的突然出场使所有人都感到意外。
—— 《牛津词典》
2·The sudden entrance of the icy air through the broken window changed the particles of water into snow.
窗户被打破以后，冷风突然涌进大厅，湿热的空气中的水汽于是就凝成了雪花。
3·The non-symmetric refracted flow is possible to correspond to the non-symmetric entrance condition of upstream cross before sudden expansion section, and also to the symmetric entrance condition.
这种非对称折冲流动可能与上游突扩前断面非对称入口条件相对应，也可能与上游突扩前断面对称入口条件相对应。