1. The wells should be upright and not collapse in a period of time. 能源井的制作要求垂直度好，能在较长时间内不坍塌；
2. They have difficulty changing tasks or working on one project for a long period of time. 在改变任务或者长期为一个项目工作的时候，他们会觉得非常困难。
3. The period of time during which a user of a terminal can communicate with an interactive system, usually, the elapsed time between logon and logoff. 一个终端用户与交互系统进行通信的时间（间隔），通常是指从注册（进入系统）到注销（退出系统）之间所经过的时间。
