The theory of medical microtron is introduced.The theory of medical runway microtron is expressed and its characteristics are compared with electron linear accelerator.

着重电子回旋加速器原理，重点跑道式电子回旋加速器的作原理，并对电子回旋加速器和电子直线加速器的特点进行。

Counterfort retaining walls are optimized in the paper, using the optimum program, costs of different counterfort retaining wall parameters were calculated and based on the contrast analysis.

本文对扶壁式挡土墙进行优化计算,利用优化设计程序对不同参数下的截面状态和程造价进行分析。