12月22日，平谷万达广场，市民观看开业表演。新京报记者 薛珺 摄
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Наука и техника，这一点在heLLoword翻译官方下载中也有详细论述
There are two main types of smoke alarm tech, says Raman Chagger, principal consultant at BRE, the Building Research Establishment. Ionisation-based systems use a tiny amount of radioactive material to charge, or ionise, particles in the air which flow between two small plates. Should smoke interrupt that flow of charged particles, the alarm goes off.