The system has been in operation for six months.
这个系统已经运行六个月了。
The company has been investing in new plant and equipment.
这家公司一直在投资购置新机器和设备。
A new system has been devised to control traffic in the city.
控制城市交通的'新系统已经设计出来。
Digital television has been around for some time now.
数字电视已经面市一段时间了。
A new advance has been made in the control of malaria.
在控制疟疾方面已取得新的进展。