【单选题】道路专题数据生产中,除采集空间数据和属性数据外,还应建立相应的元数据。下列数据项中,属于元数据的是( )
【单选题】钢筋混凝土允许带裂缝工作是因为 ( )
A.
实际结构很少出现裂缝, “ 允许带裂缝工作 ” 只是一个理论概念
D.
裂缝可作为破坏的先兆,有利于及时对结构进行加固处理
【多选题】煤中含硫量对电力生产有哪些危害?()
A.
煤中硫燃烧产生S0 2 是电厂排向大气的主要污染物,而空气中SO 2 是形成酸雨的主要来源
C.
煤中含硫量对锅炉受热面特别是空气预热器易造成腐蚀和堵灰
【单选题】In the calculation of stability, the critical pressure P cr of a column is obtained by using the Euler’s formula, and the column is intermediate column, then ___.
A.
the real critical pressure is equal to P cr
B.
the real critical pressure is greater than P cr and shall be safe
C.
the real critical pressure is greater than P cr and shall be unsafe
D.
the real critical pressure is less than P cr and shall be unsafe
【简答题】英译汉 critical pressure
【单选题】Pressure at critical point represent
A.
the highest one at which a pure material can exist in solid-liquid equilibrium
B.
the lowest one at which a pure material can exist in solid-liquid equilibrium
C.
the lowest one at which a pure material can exist in vapor-liquid equilibrium
D.
the highest one at which a pure material can exist in vapor-liquid equilibrium