positive displacement

基本解释

Twin-screw pump as a positive displacement pump, pump room exhaust inhalation chamber should be strictly separated.
雙螺杆泵作爲一種容積式泵，泵內吸入室應與排出室嚴密地隔開。
Refrigerating systems and heat pumps - Safety and environmental requirements - Positive displacement refrigerant compressors.
制冷設備和熱泵。安全和環境要求。容積式制冷劑壓縮機。
Double screw pump as a positive displacement pump, the pump suction chamber should be closely separated and discharge chamber inside.
雙螺杆泵作爲一種容積式泵，泵內吸入室應與排出室嚴密地隔開。

So now that means if this is where the center of positive excess charge lies and on top of it is the center there is no displacement of the charge so there is no net dipole.
所以現在我們說,如果正電荷中心,就位於,那麽還是在這裡負電荷中心也在這裡,所以沒有空間偶極。
麻省理工公開課 - 固態化學導論課程節選