共用题干 Less Is MoreIt sounds all wrong—drilling holes in a piece of wood to make it more resistant to knocks. But it works because the energy from the blow gets distributed throughout the wood rather than fo-cusing on one weak spot. The discovery should lead to more effective and lighter packaging mate-rials.Carpenters have known______(51)centuries that some woods are tougher than others. Hickory,for example,was turned into axe handles and cartwheel spokes because it can absorb shocks without breaking. White oak,for example,is much more easily damaued,________(52)it is almost as dense.Julian Vincent at Bathe University and his team were convinced the wood's internal structure could explain the differences.Many trees have tubular vessels that run_______(53)the trunk and carry water to the leav- es .In oak they are large,and arranged in narrow bands,but in hickory they are smaller,and more evenly distributed.The researchers________(54)this layout might distribute a blow's en-ergy throughout the wood, soaking up a bigger hit.To test the idea,they drilled holes 0.65 millimetres across into a block of spruce,a wood with_______(55)vessels,and found that_______(56)withstood a harder knock_______(57)when there were more than about 30 holes per square centimeter did the wood's performance drop off.A uniform substance doesn't cope well with knocks because only a small proportion of the material is actually______( 58).All the energy from the blow goes towards breaking the material in one or two places , but often the pieces left _________( 59 ) are pristine(未经破坏的).But instead of the energy being concentrated in one place,the holes provide many weak spots that all absorb energy as they break,says Vincent.“You are controlling the places______(60) the wood breaks,and it can then absorb more______(61),more safely.”The researchers believe the principle could be applied to any material—_________(62)example,to manufacture lighter and more protective packaging.It could_______(63)be used in car bumpers,crash barriers and armor for military vehicles,says Ulrike Wegst,_______(64) the Max Plank Institute for Mental Research in Stuttgart. But she emphasizes that you'd ________(65)to design the substance with the direction of force in mind.“The direction of loading is crucial,”she says. 51._________
A.for B.since C.in D.at正确答案A
