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【单选题】
设已知图a所示铰链四杆机构的尺寸和件1以等角速度ω1逆时针转动,其速度多边形和加速度多边形分别如图b和c所示(图中未标出个方向)。试指出下列正确的表达( )。A.
图b和图c是根据同一构件2上的B、C两点之间的速度和加速度的矢量方程进行图解所得;
B.
由速度及加速度多边形的特性可知:构件2上的E点的绝对速度是图b上由b点指向e点的矢量,而其绝对加速度也是在图c上由b'点引出而指向e'的矢量
C.
图b可判断滑块2的角速度ω2的方向为逆时针方向;图b中矢量cb代表了vCB,而图c中矢量c’b’则代表了aCB
D.
建立其运动矢量方程的基本原理是理论力学中的速度合成和加速度合成的原理,即
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【简答题】To trade _____ the people of all countries _____ the basis of equality and mutual benefit is our established policy.
【简答题】When entering a new culture, the problems people face are______.
【单选题】What basic problem are we told most trade unions face?
A.
They are equal in size of influence.
B.
They are less powerful than ever before.
C.
They don't have enough members.
D.
They are not organized efficiently.
【单选题】According to the passage, people should ______ .
A.
arrange a face-to-face meeting for their child and his/her friends on the net
B.
never give out the personal information like home address in a public message
C.
treat personal computers as electronic babysitters of their child
D.
be indifferent to any offers that even don't involve them sending credit-card information
【简答题】心理健康的规定不是一成不变的，它可以随着社会及个体的变化不断调整。心理平衡表现为没有欲望和观念的冲突，没有紧张、焦虑、畏缩等不良情绪反应。心理健康就是人通过不断的心理活动，把由于种种原因造成的心理失衡调适为心理平衡的状态。 这段文字意在表明( )。 A．心理活动和心理健康都是动态的 B.只要心理不平衡肯定心理不健康 C．心理平衡是心理健康的重要表现标志 D．心理健康的标准是相对的
【单选题】For two people who are planning to trade, it is impossible to
A.
have a comparative advantage in both goods.
B.
have an absolute advantage in both goods.
C.
specialize in the production of one good.
D.
trade so that both people will be better off.
【简答题】何谓高钾血症？试述高血钾对心脏的影响。
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