发现在梯形近似下，它们是自洽并有内在联系的；但在更一般的非梯形近似的情况下，这种内在联系并未找到。
It is found that they are compatible and interrelated in the ladder approximation, whereas beyond this approximation the interrelation is not established.
梯形明渠临界水深的近似解法已有多种，渐趋成熟。
There have been several approximate solutions for critical depth of a channel with trapezoidal section, and some of them are satisfactory.
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