半膜的

The relationship between population and economic development plays as a key to regional sustainable development, which explains the reason why it attracts great attention from geography, economy as well as demology.

人口和经济发展的关系是地区可持续发展的关键问题，因此长期以来倍受地理学家、经济学家和人口学家的关注。

Experiments have been made to investigate the performance of pump operating under conditions of air-water, solid-water and air-water-solid, also considered influence of adding frother when entrained air.

通过大量的试验，进行了气液、固液、气液固等各工况下泵性能的研究，并考虑了通气时加入起泡剂的影响。