单元刚度矩阵反映了该单元杆端位移与杆端力之间的关系,均具有对称性。
参考答案:对
I’ll never forget such an attractive city ___ I spent many happy hours there with my classmates last summer holidays.
A.that
B.where
C.in which
D.because
某同学画的表示磁场B、电流I和安培力F的相互关系如图所示,其中正确的是 [ ]
A.
B.
C.
D.