THE BASIC PRINCIPLES OF RELEASE - TOPIC

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，人们把频率的单位命名为赫兹，简称“赫”。The company just released an updated version past week, And it will be used in over fifty undergraduate and graduate lecture rooms this comi