Then, Bi-directional Evolutionary Structural Optimization (BESO) criteria and its arithmetic are given, combining ESO method with man-made material elements.

• 然后,结合基于人工材料的结构渐进优化(ESO)方法,构建了基于应变能的双方向结构渐进优化(BESO)方法的优化准则及算法。