羽毛

The variants were issued in limited numbers to special forces, helicopter crews, Air Force pilots, officers, radio operators, artillerymen, and troops other than front line riflemen.

这些改型只少量提供给特种部队，直升机机组，空军飞行员，士官，无线电操纵员，炮兵，以及其他部队，而不是前线士兵。

In the light of existent problems, the following suggestions are put forward: The erosion-resisting grouting material and small W/C ratio shall be applied, and the chemical grouts may be used if necessary.

针对存在的问题，提出了防渗灌浆材料应选用抗侵蚀性材料、采用小水灰比浆液、必要时用化学浆液等建议。