网格错误诊断

请问各位大侠，下面的 诊断是啥意思？请大侠不吝赐教
Mesh-Based Errors Summary
-------------------------
ERROR
Some elements in mesh "2d_mesh(1)" have missing nodal thicknesses in their element
associated data
ERROR
Some elements in mesh "2d_mesh(2)" have missing nodal thicknesses in their element
associated data.