In places, the water table is declining at a rate of a meter a year, necessitating the periodic deepening of wells and the use of ever-more-powerful pumps.
在一些地方，水位正以每年一米的速度下降，需要定期加深井并使用更强大的水泵。
2
And points out that the periodic maintenance is great helpful to reduce the failure rate of CT.
并指出CT的定期保养对减少故障率有很大的作用。
3
For example, as a preparer or user, knowing that a zero-coupon bond matures in 10 years, how do you use the implicit interest rate to compute the periodic interest expense?