Any system capable of a free vibration without external force is a counter example, e. g. a wire in the piano.
任何一个无外力而能自由振动的系统就是一个反例，譬如钢琴中的一条钢丝。
Considered as the branch system of building structure foundation engineering and analyses according to given-force structure, i. e. the concept design.
作为房屋结构分体系的基础工程，按照予力结构进行分析，即是概念设计。
Considered as the branch system of building structure foundation engineering and analyses according to given-force structure, i. e. the concept design.
作为房屋结构分体系的基础工程，按照予力结构进行分析，即是概念设计。
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