existence proof

• 存在性证明

existence proof的用法和样例：

例句

1. By use of multigrid method, this paper proposes a preconditioned iteration method solving the boundary value problem of elliptic equations, the proof of convergence is given.
   摘要利用多重网格法的思想，构造出一种求解椭圆型方程边值问题的预处理迭代格式，并给出了收敛性证明。