在普通车床上用两顶尖装夹长轴加工外圆时,若机床刚度较低,则工件易产生中凹的形状误差;若工件刚度较低,则工件产生( )的形状误差。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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