2. 外语
  3. Few human records survive for long, the 16 000-year-old Paleolithic cave paintings at Lascaux, France, being one exception. Now

Few human records survive for long, the 16 000-year-old Paleolithic cave paintings at Lascaux, France, being one exception. Now

admin2013-09-24  72
问题     Few human records survive for long, the 16 000-year-old Paleolithic cave paintings at Lascaux, France, being one exception. Now researchers led by Alex Zettl of the University of California, have devised a method that will, they reckon, let people store information electronically for a billion years.
    Dr. Zettl and his colleagues constructed their memory cell by taking a particle of iron just a few billionths of a meter or nanometers(纳米)across and placing it inside a hollow carbon nanotube. They attached electrodes(电极)to either end of the tube. By applying a current, they were able to shuttle the particle back and forth. This provides a mechanism to create the "1" and "0" required for digital representation: if the particle is at one end it counts as a "1", and at the other end it is a "0".
    The next challenge was to read this electronic information. The researchers found that when electrons flowed through the tube, they scattered when they came close to the particle. The particle’s position thus altered the nanotube’s electrical resistance on a local scale. Although they were unable to discover exactly how this happens, they were able to use the effect to read the stored information.
    What makes the technique so durable is that the particle’s repeated movement does not damage the walls of the tube. That is not only because the lining of the tube is so hard； it is also because friction is almost negligible when working at such small scales.
    Theoretical studies suggest that the system should retain information for a long time. To switch spontaneously from a "1" to a "0" would entail(使必要)the particle moving some 200 nanometers along the tube using thermal energy. At room temperature, the odds(几率)of that happening are once in a billion years. In tests, the stored digital information was found to be remarkably stable. Yet the distance between the ends of the tube remains small enough to allow for speedy reading and writing of the memory cell when it is in use. The next challenge will be to create an electronic memory that has millions of cells instead of just one. But if Dr. Zettl succeeds in commercializing this technology, digital decay itself could become a thing of the past.
Why does not the particle’s movement damage the tube?
选项 A、The tube is tested before being used.
B、The friction can be neglected in the process.
C、It moves slowly to avoid friction.
D、The whole process can be monitored.
答案B
解析 事实细节题。定位句表明，粒子的运动不会损坏纳米管的原因有两个：一是纳米管内壁十分坚固，二是小范围内的运动摩擦可以忽略不计。B)“该过程中的摩擦可以忽略不计”符合文意，故为本题正确答案。
转载请注明原文地址:https://kaotiyun.com/show/dRc7777K
0

大学英语四级

相关试题推荐
随机试题
最新回复(0)