The stiffness of the back cover of computer was studied by means of experimental modal theory.

以显示器后壳为研究对象，利用试验模态分析理论，研究了后壳的刚度；

After surgery you may experience jaw muscle stiffness and limited opening of your mouth. This is normal and will improve in 5 to 10 days.

手术后您可能经历颚肌肉之僵硬及开口困难。这是正常的，且在5至10天内改善，请每天练习开口运动及热敷。

She complained of stiffness in her joints. Accordingly she was admitted to hospital for further tests.

她诉说自己的关节不灵活,于是被留院作进一步检查。