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【单选题】
有四种CNC 系统或者数控机床,根据MTBF 指标,他们中可靠性最好的是( )。A.
MTBF=1000h
B.
MTBF=2500h
C.
MTBF=5000h
D.
MTBF=70000h
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举一反三
【单选题】(单选)有一外径为18mm的无缝钢管,管内通冷冻盐水,为减少冷量损失,在管外包一层导热系数λ=0.18W/(m·°C)的石棉,保温层外壁与空气对流给热系数α=10W/(m2·°C),比较石棉厚为5mm和8mm时的冷量损失:
A.
5mm时损失较大
B.
8mm时损失较大
C.
一样大
D.
不好说
【单选题】（单选）有一外径为18mm的无缝钢管，管内通冷冻盐水，为减少冷量损失，在管外包一层热导率λ=0.18W/(m·℃)的石棉，保温层外壁与空气对流给热系数α=10W/(m2·℃),比较石棉厚为5mm和8mm时的冷量损失（）*
A.
5mm 时损失较大
B.
8mm 时损失较大
C.
一样大
D.
不好说
【单选题】有一外径为18mm的无缝钢管,管内通冷冻盐水,为减少冷量损失,在管外包一层热导率λ=0.18W/(m·°C)的石棉,保温层外壁与空气对流给热系数α=10W/(m2·°C),比较石棉厚为5mm和8mm时的冷量损失()*
A.
5mm时热损失较大
B.
8mm时热损失较大
C.
一样大
D.
不好说
【单选题】We found that the plane_____ when we got to the airport.
A.
already took off
B.
had already taken off
C.
was already taking off
D.
was already taken off
【单选题】We missed the beginning of the football match. When we got to the stadium, the match ______.
A.
would start
B.
has started
C.
had started
D.
was starting
【单选题】有一外径为 18mm 的无缝钢管,管内通冷冻盐水,为减少冷量损失,在管外包一层热导率 λ =0.18W/(m · °C ) 的石棉,保温层外壁与空气对流给热系数 α =10W/(m2 · °C ), 比较石棉厚为 5mm 和 8mm 时的冷量损失( )
A.
没关系
B.
反比
C.
正比
D.
不确定
【单选题】有一外径为18mm的无缝钢管,管内通冷冻盐水,为减少冷量损失,在管外包一层导热系数 λ =0.18W/(m · °C )的石棉,保温层外壁与空气对流给热系数 α =10W/(m2 · °C ),比较石棉厚为5mm和8mm时的冷量损失()
A.
5mm时损失较大
B.
8mm时损失较大
C.
一样大
D.
不好说
【单选题】What a pity! When we got to the cinema，the movie The Assembly ，so we saw only the end of it．
A.
had just finished
B.
was finishing
C.
would finish
D.
just finished
【简答题】在“体检中心”页面,可以很醒目的看到目前店铺急需处理的()()()和待跟进申诉等。
【单选题】What a pity! When we got to the cinema, the movie Let the Bullets Fly ______, so we saw only the end of it
A.
was finishing
B.
would be finishing
C.
just finished
D.
had just finished
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