Positive control. 基本例句 un.积极性管制；正调节；阳性控制🌏阳性对照；阳性对照品；阳性对照组 Lever& spring, also available for swing check valves, provides more positive control in closing the disc. Tension of the spring maybe adjusted to control the pressure against disc. 操纵杆和弹簧，也可在旋启式止回阀上配置，能够更加有效地关闭阀瓣，弹簧的拉力可以对阀瓣的压力进行调节。 jukuu