阐述了国内外螺旋类零件的螺纹在车床上加工时存在的问题，并介绍了正确的判断方法及加工方法。
The problems that exist during machining screw with lathe both abroad and at home are presented, the method for judging and machining screw are introduced.
星系主要分为三类：螺旋星系、椭圆星系和不规则星系。
Galaxies are classified into three main types: spiral galaxies, elliptical galaxies, and irregular galaxies.
方形螺旋天线结构简单、频带范围宽，是一类性能优良的天线，但在变成定向辐射后其带宽会大大减小。
The square spiral antennas have many outstanding merits such that its structure is simple and its bandwidth is wide.
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