While snow has brought smiles to the faces of children who have dusted off their sleds for the new season,for others, this cold snap just days before the Christmas break, has brought frustration.

VOA: standard.2009.12.21

You break the seal between them and feel the thing get cold, for example, right.

如果你买了制冷或加热包,你打开它们之间的封条。

麻省理工公开课 - 热力学与动力学课程节选

You break the seal between them and feel the thing get cold, for example, right.

如果你买了制冷或加热包,你打开它们之间的封条。

麻省理工公开课 - 热力学与动力学课程节选