The oxygen mass transfer coefficient increases at the beginning and then decreases with the augment of carrier content, and increases with the augment of air flow rate and liquid flow rate.

氧传质系数则随着载体含量的增加先增后减，随着气流量和液流量的增大而增大。

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Oxygen, though, is only the beginning, according to Paul Spudis, a planetary scientist at Johns Hopkins University who was a member of the president's vision commission (yes, there really was one).

ECONOMIST: Spaceflight