Less Is More
It sounds all wrongdrilling 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 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 damaged it is almost as dense. Julian Vincent at Bathe University and his team were convinced the woods internal structure could explain the differences.
Many trees have tubular vessels that run the trunk and carry water to the leaves. In oak they are large, and arranged in narrow bands, but in hickory they are smaller, and more evenly distributed. The researchers this layout might distribute a blows energy 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 vessels, and found that withstood a harder knock. when there were more than about 30 holes per square centimetre did the woods performance drop off.
A uniform substance doesnt cope well with knocks because only a small proportion of the material is actually . All the energy from the blow goes towards breaking the material in one or two places, but often the pieces left are pristine .
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 the wood breaks, and it can then absorb more , more safely.
The researchers believe the principle could be applied to any material- example, to manufacture lighter and more protective packaging. It could be used in car bumpers, crash barriers and armour for military vehicles, says Ulrike Wegst, the Max Plank Institute for Mental Research in Stuttgart. But she emphasizes that you to design the substance with the direction of force in mind. The direction of loading is crucial, she says.
1 A in B since C for D at
2 A or B although C and D despite
3 A down B over C up D into
4 A knew B concluded C saw D thought
5 A no B per C each D every
6 A it B the idea C they D spruce
7 A If B Just C Only D Rarely
8 A effected B beaten C slapped D affected
9 A behind B beyond C for D in
10 A which B there C that D where
11 A water B air C energy D safety
12 A among B in C as D for
13 A also B besides C else D yet
14 A over B at C around D on
15 A have B must C should D had
【参考答案】
1. C 2. B 3. C 4. D 5. A
6. A 7. C 8. D 9. A 10. D
11. C 12. D 13. A 14. B 15. A
浅论英文报刊阅读与学生阅读能力的提高
论网络交流工具与体验式英语写作教学
初中英语教育向高中英语教育过渡问题的研...
名师谈初中生中考英语写作教学
利用多媒体提高农村学生写作能力
如何教授创意性写作?
运用英语报刊指导小学高年级阅读
阅读Teens英文报刊,培养英语阅读能力
教学生写散文——10步轻松搞定
概念图在初中英语阅读教学中的运用
丰富词汇教学手段 提升学习效果
精心设计任务 有效实施交际法
英语报刊阅读教学模式初探
关于高效率英语课堂教学的思考——以一堂...
新课标理念下英语教师的科学人文精神
开学第一堂课:点睛之作(下)
初中英语报刊阅读辅助教学初探
书面表达复习的“一二三四五”法
如何运用任务进行中学英语写作教学
有效开展写作教学 提高学生写作能力
商务英语写作教学中的教师反馈
外研社2010年暑期“外语教学中的行动研究...
基于“输入”与“输出”理论的报刊教学设...
浅谈二十一世纪报刊阅读
巧用“替代法” 提升作文语言质量
如何让赏识教育在中职英语教学中发挥作用...
模仿与朗读课的实施和效果— 济南外国语学...
麦格劳-希尔在线英语写作自动评分系统介绍...
基于元认知的英语写作教学
在动态课堂中历练应变能力
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |