qt实现计时器功能，用到qt的信号与槽机制，能够根据全局变量的变化控制计时器的开始和结束！-Qt realize timer function, use qt signals and slots mechanism, according to the change of global variable control the beginning and end of the timer!

from their own experiences. Usually there is no centralized control system dictating how individual particle will behave. It is the local interactions between particles that lead to the emergence of global behavior