Demand can exist in different forms and derived demand is one of them.
需求可以有不同的存在形式以及他们其中之一所衍生的其他需求。
The equation of air demand was derived from the theory of oxygen transfer in aeration.
根据曝气过程中氧转移的有关理论，推导出需气量的表达式；
The equation of air demand was derived from the theory of oxygen transfer in aeration.
根据曝气过程中氧转移的有关理论，推导出需气量的表达式；
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