The dosage of admixture in should be trial tested to see if all indexes of the mixture can meet the requirement.

配比中掺加剂的用量，应先试配，检验配合液的各项性能指标是否符合要求。

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Prior efforts had been a mixture of trial and error and hard work mixed with a basic understanding of the mechanics of flight.

ENGADGET: The Highs and Lows of Human-Powered Flight Alt