The pistons are graphite-coated to reduce friction.活塞上涂了一层石墨以减小摩擦力。Some pistons have seating rings of metal or leather.有些活塞上有金属或皮革的密封环.A pump uses valves and pistons.泵使用阀和活塞....
Somewhere close at hand a train rattled by.一辆火车从我的身边轰隆隆地开过。The steam pipes rattled suddenly, and Franklin uttered a shriek and jumped with fright...蒸汽管突然发出咯咯的响声，富兰克林尖叫一声，吓得跳了起来。The bus from Odense rattled into a dusty vi...
A courtesy shuttle bus operates between the hotel and the town.有免费班车往返于酒店和市区。The train operates the 2,400-mile round trip once a week.这趟火车每周一次往返行驶2,400英里。The tourist office operates a useful room-finding service.这家旅游办事处提...