unsound kernel

例句：

1. 1. The foundation of the building is unsound, which makes it difficult to hold up.
   这座建筑的基础不牢固，很难支撑。
2. 2. The engine was found to be unsound after the inspection.
   在检查后发现这台发动机有缺陷。
3. 3. The design of the new product is unsound, which may affect its performance.
   新产品的设计不完善，可能会影响其性能。