1·Katla seems to erupt on a semi-regular basis, with typical periods between eruptions of between 30 and 80 years.
卡特拉似乎是半规律地喷发的，典型的周期是每次爆发之间相隔30到80年。
2·That said, Katla does seem to erupt on a semi-regular basis, with typical periods between eruptions of between 30 and 80 years.
那就是说，卡特拉正是在一个半正规的基础上喷发的，典型的周期是每次爆发之间相隔30到80年。
3·His team interviewed historians and speech writers, studied periods of crisis, and listened to past inaugural orations.
他的团队访问了历史学家和演讲作家，研究危机周期，聆听历任的演说集。
4·It may be one of many aspects of the climate that flop around, seemingly at random, over periods of years to decades.
这可能是数年至数十年的周期以来气候骤然变向的诸多方面之一，而且看似毫无章法。
5·Typically, the number of active service class periods in a system should not exceed 30.
通常，系统中的活动服务分类周期的数量不应该超过30。