They have low friction and can be produced with high precision and in quiet running variants.
它们摩擦力低，可以制造出精确度高，满足安静运行要求的各种类型。
2
Experimental results show the change of friction factor is correlative with the difference of running temperature and installation temperature but not the force time.
经过数据整理得出了以下结论：摩擦系数的大小变化决定于运行温度和安装温度差，和“推动次数”无关。
3
The influence of train running speed, wheel-rail friction coefficient, vehicle load, track geometric irregularity, partly load, gauge and the shape of wheel tread on derailment was emphasized.