1·Even though the bottom one takes up the least amount of space in this optical illusion, it is the flattest circle and therefore has the largest diameter.
尽管下面的圈看起来占的地方最小，但是它是最平坦的，也就是它的直径是最大的。
2·And during the inversion, two constrained models, flattest and smoothest model, were incorporated into the sensitivity matrix calculated by theoretical formula.
在反演过程中，根据理论公式计算迭代过程中灵敏度矩阵，并采用平坦模型和光滑模型两种约束。