Because of no natural ventilation, semi - closed tunnel was most seriously polluted.

半密闭坑道未形成自然通风, 所以真菌数最高.

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Impeller has open, semi - closed and closed three.

叶轮有开式 、 半闭式和闭式三种.

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The Datong Basin is a semi - closed fault basin developed in an arid dry desert environment.

山西大同盆地属干冷荒漠景观条件的半封闭型断陷盆地.

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