Batteries can power anything from small sensors to large systems. While scientists are finding ways to
make them smaller but even more powerful, problems can arise when these batteries are much larger and
heavier than the devices themselves. University of Missouri(MU) researchers are developing a nuclear energy
source that is smaller, lighter and more efficient.
"To provide enough power, we need certain methods with high energy density (密度)", said Jae Kwon,
assistant professor of electrical and computer engineering at MU. "The radioisotope (放射性同位素) battery
can provide power density that is much higher than chemical batteries."
Kwon and his research team have been working on building a small nuclear battery, presently the size and
thickness of a penny, intended to power various micro / nanoelectromechanreal systems (M/NEMS). Although
nuclear batteries can cause concerns, Kwon said they are safe.
"People hear the word "nuclear" and think of something very dangerous," he said, "However, nuclear power
sources have already been safely powering a variety of devices, such as pace-makers, space satellites and
underwater systems."
His new idea is not only in the battery"s size, but also in its semiconductor (半导体). Kwon"s battery uses
a liquid semiconductor rather than a solid semiconductor.
"The key part of using a radioactive battery is that when you harvest the energy, part of the radiation energy
can damage the lattice structure (晶体结构) of the solid semiconductor," Kwon said, "By using a liquid semicon
ductor, we believe we can minimize that problem."
Together with J. David Robertson, chemistry professor and associate director of the MU Research Reactor,
Kwon is working to build and test the battery. In the future, they hope to increase the battery"s power, shrink
its size and try with various other materials. Kwon said that battery could be thinner than the thickness of
human hair.
1. Why do airplanes take longer to fly west than east? It can take five hours to go west-east from New York (NY) to London but seven hours to travel east- west from London to NY. The reason for the difference is an atmospheric phenomenon known as the jet (喷射) stream. The jet stream is a very high altitude wind which always blows from the west to the east across the Atlantic. The planes moving at a constant air speed thus go faster in the west-east direction when they are moving with the wind than in the opposite direction. |
阅读理解。 |
This brief book is aimed at high school students, but speaks to anyone learning at any stage of life. Its formal, serious style closely matches its content, a school-masterly book on schooling. The author, W. H. Armstrong, starts with the basics: reading and writing. In his opinion, reading doesn"t just mean recognizing each word on the page; it means taking in the information, digesting it and incorporating it into oneself just as one digests a sandwich and makes it a part of himself. The goal is to bring the information back to life, not just to treat it as dead facts on paper from dead trees. Reading and writing cannot be completely separated from each other; in fact, the aim of reading is to express the information you have got from the text. I"ve seen it again and again: someone who can"t express an idea after reading a text is just as ineffective as someone who hasn"t read it at all. Only a third of the book remains after that discussion, which Armstrong devotes to specific tips for studying languages, math, science and history. He generally handles these topics thoroughly (透彻地) and equally, except for some weakness in the science and math sections and a bit too much passion (激情) regarding history. Well, he was a history teacher -if conveyed only a tenth of his passion to his students, that was a hundred times more than my history teachers ever got across. To my disappointment, in this part of the book he ignores the arts. As a matter of fact, they demand all the concentration and study that math and science do, though the study differs slightly in kind. Although it"s commonly believed that the arts can only be naturally acquired, actually, learning the arts is no more natural than learning French or mathematics. My other comment is that the text aged. The first edition apparently dates to the 1960s-none of the references (参考文献) seem newer than the late 1950s. As a result, the discussion misses the entire computer age. These are small points, though, and don"t affect the main discussion. I recommend it to any student and any teacher, including the self-taught student. |
1. According to Armstrong, the goal of reading is to _____. |
[ ] |
A. gain knowledge and expand one"s view B. understand the meaning between the lines C. express ideas based on what one has read D. get information and keep it alive in memory |
2. The author of the passage insists that learning the arts _____. |
[ ] |
A. requires great efforts B. demands real passion C. is less natural than learning maths D. is as natural as learning a language |
3. What is a shortcoming of Armstrong"s work according to the author? |
[ ] |
A. Some ideas are slightly contradictory. B. There is too much discussion on studying science. C. The style is too serious. D. It lacks new information. |
4. This passage can be classified as _____. |
[ ] |
A. an advertisement B. a book review C. a feature story D. a news report |