有许多设计采用了两圈短而粗的、反向对转的采用复合材料制作的叶片。
A number of designs use two rings of stubby, counter-rotating blades made from composite materials.
生物学家们长久以来认为这些短而粗的附肢是一种进化过程中的适应。
Biologists have long assumed that these stumpy appendages are an evolutionary adaptation.
通常这种等级的木材是从短原木和短而粗的圆木块上锯下的，以保证其具有完美的径切四分瓣。
Often this grade of wood is hand-split from bolts or blocks that are taken from rounds straight from the tree to ensure perfect quarter orientation.
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