根据下面材料请回答 51～65 题
Less Is More
It 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 focusing on one weak spot.The discovery should lead to more effective and lighter packaging materials.
Carpenters have known________ (1)centuries that some woods are tougher than others.Hickory(山核桃木),for example,was turned into axe handles and cartwheel spokes(轮辐)because it can absorb shocks without breakin9.White oak,for example,is much more easily damaged,________ (2)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(管的)vessels that run________ (3)the trunk and carry water to the leaves.In oak they are large,and arranged in narrow bands,but.Il hickory they are smaller, and more evenly distributed.The researchers________ (4)this layout might distribute a blow's energy throughout the wood,soaking up a bigger hit.To test time idea,they drilled holes 0.65 millimeters across into a block of spruce(云杉),a wood with________ (5)vessels,and found that________ (6)withstood a harder knock.________ (7) 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________ (8).All the energy from the blow goes towards breaking the material in one or two places,but often the pieces left________ (9)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________ (10)the wood breaks,and it can then absorb more________ (11),more safely.'
The researchers believe the principle could be applied to any material________ (12)example,to manufacture lighter and more protective packaging.It could ________ (13)be used in car bumpers,crash barriers and armour for military vehicles,
says Ulrike Wegst________ (14) the Max Plank Institute for Mental Research in Stuttgart.But she emphasizes that you________ (15)to design the substance with the direction of force in mind.'The direction of loading is crucial,'she says.
第 51 题
A．in
B．since
C．for
D．at