第三是在机泵皮带传动时，皮带的紧边应在下，以提高传动效率。

The third is in the Pump transmission belt, the belt should bear in the next-to enhance the transmission efficiency.

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这种声音也叫作“紧喉音”，发音时拉长特定音节，这样就会让喉咙深处发出颤音，产生一种像棍子一边移动一边敲击栏杆的哒哒声。

Also known as creaky voice, it involves elongating certain syllables so that they vibrate at the back of the throat, creating a tapping sound like a stick running along a railing.

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先给出这些问题的提法，然后使用列紧性原理和极值原理证明了上述二阶椭圆型方程边值解的存在性和唯一性。

Fristly the boundary value problems for the equations is formulated, and then by using the compactness principle, the existence of solutions for the above problems is proved.

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