It's disbennifit to become protected film if change the velocity of flow frequently.

频变水流速不利于在冷却器材料表面形成保护膜，而保护膜对于防腐蚀是至关重要。

Filter bed should be exposurd as less as possible because alternation of exposure and immersion is disbennifit to the penetrability of filter bed.

据水质资料分析了水源水质安全保障。

Our country practices tail system,and takes direct mode of inherit.It is very disbennifit to protect debtee because there is not efficiency supervision to haeres.So it is necessary to restrict haeres.

我国实行限定制度,又采取是直接方式,在缺乏对人有效监督情况下,对债权人保护极为不利,有必要对人予以限制。