A REVIEW OF DU AN LA PURA

To submit a assert sort on the web for the Quick Box settlement, head to this page. Alternatively, you can down load a PDF declare variety to return by mail or e-mail for the settlement administrator.频率是单位时间内完成振动的次数，是描述振动物体往复运动频繁程度的量，为了纪念德国物理学家赫兹的贡献，