预应力混凝土结构的混凝土强度等级不应低于(),当采用预应力钢较线、钢丝、热处理钢筋作为预应力钢筋时,混凝土强度等级不宜低于()。
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影响柔度大小的因素有()
A. 杆长
B. 约束
C. 材料
D. 截面
The ( )model is the basis for today’s computers.
A. Ron Newman
B. von Newman
C. Pascal
D. Charles Babbage
According to the von Neumann model, ( )stored in memory.
A. only data are
B. only programs are
C. data and programs are
D. none of the above