【简答题】What’s the main idea of this paragraph? America has been hailed as “the land of the free and the home of the brave”, ever since that frightful night Francis Scott Key penned the words to The Star-Span...
【简答题】在图示的铰链四杆机构中,已知:l AB =15mm,l BC =45mm,l CD =35mm, l AD =30mm,AD为机架。 (1)试判断该机构是否存在曲柄。 (2)当AB为原动件时,试用图解法求出该机构的极位夹角θ(不必作文字说明, 但必须保留作图线),并计算其从动件CD的行程速度变化系数K。 注: 下图为示意图,自己按一定比例绘图。 (3)在l BC 、l CD 、和l AD 不变的情...