下载亿题库APP
联系电话:400-660-1360
请谨慎保管和记忆你的密码,以免泄露和丢失
请谨慎保管和记忆你的密码,以免泄露和丢失
英语是考研初试当中比较拉分的科目,历来令不少考生又爱又恨。许多考生的英语都有很大的进步空间,因此英语该如何学就成为了众多考生关心的重点。想要学好英语,实战经验很重要。下面,帮考网为大家带来考研初试英语科目的一些模拟试题,正在备考的小伙伴赶紧练起来吧。
Bryant Linares has one heck of a secret family recipe: how to make world-class diamonds. Seven years ago his father, Robert, produced a diamond in a high-pressure chamber of carbon gas and dropped it into an acid solution to clean it off. When he returned the next morning, he expected to find the usual yellow stone——a crude artificial diamond of some use to industry, perhaps, but not the stuff of dreams. At first there didn\'t seem to be any stone at all. Then he saw, at the bottom of the beaker, so clear it was almost invisible, a perfect quarter-carat crystal of pure carbon. “It was the eureka moment,” says Bryant. His father had managed what many scientists had given up on long ago: to manufacture a stone that wouldn\'t look out of place on an engagement ring.
Man-made diamonds are nothing new——industry started making them in the 1950s, and each year about 80 tons of low-quality synthetic diamonds are used in tools like drill bits and sanders. High-quality crystals, though, open up huge possibilities, jewelry being the least of them. Scientists are most excited about the prospect of making diamond microchips. As chips have shrunk over the years, engineers have struggled with ways of dissipating the heat they create. Because silicon, the main component of semiconductors, breaks down at about 200 degrees Fahrenheit, some experts believe a new material will be needed in a decade or so. Diamonds might fit the bill. They can withstand 1,000 degrees, and electrons move through them so easily that they would tend not to heat up in the first place. Engineers could cram a lot more circuits onto a diamond-based micro-chip——if they could perfect a way of making pure crystals cheaply.
The race is on. After working in secrecy for years refining their technique, the Linareses\' company, Apollo Diamond, now spits out 20 carats a week, both for jewelry and for diamond wafers that could be fashioned into microchips. Rivals have also been busy. Gemesis, a Sarasota, Fla., firm, has developed a “diamond growth chamber”——a press that squeezes out high-quality diamonds in much the same way that the early presses made rough ones. Gemesis is making blue diamonds——rare and sought-after gemstones.
Chipmakers are also getting into the act. The Japanese firm Nippon Telegraph and Telephone has already made prototype diamond semiconductors, and the Japanese government is actively promoting the technology. Most U.S. research is going on in universities and military labs, but Intel has recently taken an interest. Before the technology is ready for prime time, chipmakers will have to come up with a way to keep out impurities during manufacturing. And the attribute that makes diamonds so attractive——their hardness——also makes them difficult to manipulate.
The new diamonds are likely to show up first as tiny light-emitting diodes, or LEDs, in flat-screen displays and high-definition televisions. And then, of course, there\'s jewelry. Although synthetics still carry a stigma, even experts can\'t tell the difference. Natural-diamond merchants claim they aren\'t worried, but De Beers has made a device that can distinguish between the natural stones and the synthetics and is distributing it to jewelers. Will consumers care? We might find out next year when Gemesis is ready to market its blue diamonds in the United States.
注(1):本文选自Newsweek,10/25/2004, p60-61, 2p, 3c
注(2):本文习题命题模仿对象2002年真题Text 4
1. From the first paragraph, we learn that______________.
[A] All the diamonds are almost invisible.
[B] Many scientists had tried hard to make perfect crystals long time ago.
[C] His father expected to find a diamond used in industry.
[D] Diamond are produced with carbon gas.
2. Which of the following statements is not true according to the text?
[A] Diamond can withstand higher degree than silicon.
[B] The main component of semiconductors will be replaced in a few years.
[C] High-quality crystals have least usages, esp. in jewelry.
[D] Engineers could not find perfect ways of making pure crystal cheaply.
3. According to the passage, why can the companies increase and perfect their production
of diamond?
[A] They all work in secrecy.
[B] They have improved their techniques.
[C] They have developed their own diamond chambers.
[D] They have turned the rough diamond to high-quality one‘s.
4. Which of the following best defines the word “attribute”(Line 5, Paragraph 4)?
[A] quality
[B] contribution
[C] appearance
[D] value
5. The new diamond is Not first used in___________.
[A] LEDs
[B] flat-screen display
[C] high-definition televisions
[D] prototype diamond semiconductor
答案:B C B A D
以上就是帮考网为大家带来的全部内容,希望能给大家一些帮助。帮考网提醒:在最后阶段,调整自己的心态也是非常重要的,每年都有考生临考前放弃,所以小伙伴们要注意不要给自己太大的压力哦。另外,小伙伴们如果还有其他关于考研信息的疑问,也可以留言咨询哦。
以前年度的普通研究生入学考试成绩还能查询吗?:以前年度的普通研究生入学考试成绩还能查询吗?以前的考研成绩能查,成绩查询可以登录中国研究生招生信息网,根据自己报考研究生考试的报名号登陆,即可查询以前的考研成绩。
研究生入学考试要考哪几门?:研究生入学考试要考哪几门?(1)初试是每年1月份全国统考,考试科目分为政治(满分100)、外语(满分100)、专业课一(如数学)、专业课二。公共课包含政治、外语、数学,由全国统一命题。专业课由各学校自主命题。有些专业课统一命题进行联考。有的专业不考数学,考由学校命题的两门专业课。(2)复试分为面试和笔试,学校专业不同,科目形式设置会有不同。
普通研究生入学考试现场确认必须要本人到吗?:普通研究生入学考试现场确认必须要本人到吗?现场确认时,报考者要带着本人身份证、学位证、学历证等证件的原件和复印件,原件由现场老师验查,复印件直接提交给现场老师。如果现场确认时审核出材料不实,考生将被取消录取资格,确认无误后本人要签字,这也是不能找人代替的原因之一。
2020-06-06
2020-06-06
2020-06-06
2020-06-06
2020-06-06
微信扫码关注公众号
获取更多考试热门资料