Earthquakes usually occur several days or tens of days after the F-content's return to the background value, and only few qua kes occur at the time of the maximum value of the F-content.
而地震常常发生在F -含量恢复背景值后数天或数十天，仅有个别地震发生在F -含量达最高值时。
2
The results showed when social background variables is added into the earning, education return becomes obviously lower.
在收入方程中引入社会背景变量后，明显地降低了个人教育收益率的估计值。
3
In the background of globalization, the float exchange rate system will return to the fixed one, in the form of currency unions.