Chinese scientists applied a specially developed new technology to laser-ranging (激光测距) telescopes, which enabled them to identify space waste more effectively than previous techniques, according to a study published in the Journal of Laser Applications. “After improving the pointing accuracy of the telescope through a neural (神经的) network , space debris (碎片) with a cross sectional area of one square meter ( 10 square feet) and a distance of 1 ,500 kilometers (932 miles ) can be identified," Tianming Ma, an author of the study from the Chinese Academy of Surveying and Mapping, Beijing and Liaoning Technical University, Fuxin, said in a statement.
Debris can include non-functional spacecraft, abandoned launch vehicle stages, and other mission-related space waste. It is very dangerous for astronauts and spacecraft in orbit above the Earth as they travel very fast — up to 18,000 miles per hour. Worryingly, there are probably many millions of tiny debris pieces in low-Earth orbit, and tens of thousands larger than a softball, NASA said. Fortunately, there have been surprisingly few collisions.
Laser-ranging technology has previously been used to find space waste. However, these systems have their limitations when it comes to accurately identifying small, fast-moving pieces. In fact, previous laser-ranging methods have only been accurate to within about 0. 6miles.
In an attempt to overcome the inaccuracies in laser-ranging techniques, the Chinese team used so-called neural networks to improve the effectiveness of their telescope system. Neural networks are computing systems which are inspired by biological networks in the brain. They can learn to become better at tasks without being given a specific set of rules to follow. Ma and his team tested this method against more traditional techniques at the Beijing Fangshen laser range telescope station. According to the team, this is the first time that neural network has been used to significantly improve the pointing accuracy of a laser-ranging telescope. They say that the latest findings could have significant meaning for guiding spacecraft in orbit.
1. What are laser-ranging telescopes designed to do?| A．Set up a neural network in space. |
| B．Find out the precise position of space waste. |
| C．Help the telescopes work more accurately. |
| D．Confirm the amount and size of space waste. |
| A．Useless man-made objects in space. | B．Fast-travelling softballs. |
| C．Launch vehicle stages in low-Earth orbit. | D．Satellites moving too fast. |
| A．Rule followers. | B．Biological computing. |
| C．Machine learning. | D．Spacecraft guidance |
| A．New Technology Used to Find Space Waste |
| B．The First Telescope to Handle Space Debris |
| C．An Invention for Astronauts and Spacecraft |
| D．The Substitute for Laser-ranging Telescopes |
相似题推荐
【推荐1】Americans are worried about new technology. They are concerned that machines, including robots, will take over work now done by humans. These findings come from a new report by the Pew Research Center of Washington DC.
About 75 percent of Americans questioned by Pew said automation will increase income inequality between the rich and the middle class and the poor. And 64 percent of people expect automation to be so common in America that people will face difficulty finding things to do with their lives.
Some of the concerns about technology come from a distrust about whether machines will always make the right decision. Many Americans believe humans have better judgment in dealing with complex matters. One example is selecting a person for a job. Three quarters of Americans said they would not want to apply for a job that uses a computer program to choose the most qualified person.
Most Americans want the government to limit automation. For example, 87 percent support a requirement that all driverless vehicles have a human in the driver seat who can take control when needed. And 85 percent want to limit machines to mostly doing jobs that are dangerous or unhealthy for humans. And only 25 percent expect more jobs to come from automation, Pew said.
Mark Zuckerberg, the co-founder of Facebook, spoke last May to graduating seniors from Harvard University in Massachusetts. His talk centered on the uncertain future facing young people. “Our generation will have to deal with tens of millions of jobs replaced by automation like self-driving cars and trucks,” Zuckerberg told the graduates.
Zuckerberg said young people will have to find projects that will bring both jobs and direct benefits to the people of the world. He said in his speech that 300,000 people worked to put a man on the moon, and millions of people built, the Hoover Dam as well as other great projects over the last 100 years.
1. What do Americans think of technology?| A．Useful. |
| B．Effective |
| C．Dangerous. |
| D．Undependable. |
| A．Use machines to do dangerous and harmful jobs. |
| B．Increase job chances by introducing machines |
| C．Select a person for a job by computer. |
| D．Get rid of all driverless vehicles. |
| A．Refuse self-driving vehicles. |
| B．Create new job chances. |
| C．Consider large projects. |
| D．Fight against robots. |
| A．New Technology Creates More Jobs |
| B．New Technology Makes New Unfairness |
| C．Americans Worry Robots Will Take Jobs |
| D．Robots Make Work Easy to Do for Workers. |
【推荐2】Much of Puerto Rico is still without power after Hurricane Fiona struck the island on Sept. 19. The storm laid it in darkness and thousands of people in trouble, even some missing.
Yet some see signs of hope. Over the past five years, around 50,000 solar and battery power systems have been installed on homes in Puerto Rico, says Chris Rauscher, senior director of public policy at Sunrun, the biggest residential solar company in the United States. And almost all that equipment appears to have continued supplying electricity while the island’s central power system went dark, according to market participants and industry observers.
Climate change is making hurricanes wetter and more powerful, increasing the risks to electric reliability in places like Puerto Rico. That strengthens the case for more investment in home solar set-ups, Rauscher says.
“It’s showing that renewables paired with storage ... are really the fundamental building blocks of a clean recovery that we need to really focus on on the island and elsewhere,” he says.
John Berger, chief manager of Sunnova, another big solar company, agrees, calling Puerto Rico “a window into the future.” “The technology’s just physically and fundamentally better,” than the traditional power system, Berger says. “And that’s not going to change.”
But big challenges are still hanging over the island. Lots of reconstruction is still needed. And now on top of that, the hurricane season is not over yet. “The next storm after this — and it will come, I don’t know if it’s next week or next year or two years from now, but it will come — we’ll be in even better shape than we are right now,” Berger says.
1. What did the Hurricane Fiona result in?| A．The newly-built island’s central power system. | B．Power failure in much of Puerto Rico. |
| C．The loss of thousands of people. | D．Losing eyesight of some people. |
| A．To make the point convincing. | B．To give more choices for the islanders. |
| C．To state the status of Puerto Rico. | D．To make comparisons between the two companies. |
| A．The reconstruction work. | B．The coming hurricane. |
| C．The shortage of money. | D．The need for a safe shelter. |
| A．A Severe Hurricane | B．Natural Disasters Are Approaching |
| C．Renewable Energy Give Puerto Rico Light | D．A Newly-rebuilt Island |
【推荐3】This year marks exactly two centuries since the publication of “Frankenstein; or, The Modern Prometheus,” by Mary Shelley. Even before the invention of the electric light bulb, the author produced a remarkable work of speculative fiction that would foreshadow (预示) many ethical questions to be raised by technologies yet to come.
Today the rapid growth of artificial intelligence (Al) raises fundamental questions: “What is intelligence, identity, or consciousness? What makes humans humans?” What is being called artificial general intelligence, machines that would imitate the way humans think, continue to puzzle scientists. Yet humans remain fascinated by the idea of robots that would look, move and respond like humans, similar to those depicted on sci-fi TV series such as “Humans”. Just how people think is still far too complex to be understood, let alone reproduced, says David Eagleman, a Stanford University neuroscientist. “We are just in a situation where there are no good theories explaining what consciousness actually is and how you could ever build a machine to get there.”
But that doesn’t mean crucial ethical issues involving AI aren’t at hand. The coming use of autonomous vehicles, for example, poses thorny (棘手的) ethical questions. Human drivers sometimes must make split-second decisions. Their reactions may be a complex combination of instant reflexes, input from past driving experiences, and what their eyes and ears tell them in that moment. AI “vision” today is not nearly as sophisticated as that of humans. And to anticipate every imaginable driving situation is a difficult programming problem.
Whenever decisions are based on masses of data, “you quickly get into a lot of ethical questions,” notes Tan Kiat How, chief executive of a Singapore-based agency that is helping the government develop a voluntary code for the ethical use of Al. Along with Singapore, other governments and mega-corporations are beginning to establish their own guidelines. Britain is setting up a data ethics center India released its Al ethics strategy this spring.
On June 7 Google promised not to design or employ Al that would cause “overall harm,” or to develop Al-directed weapons or use AI for surveillance (监视) that would break international norms (规则). It also promised not to employ AI whose use would violate international laws or human rights.
While the statement is vague, it represents one starting point. So does the idea that decisions made by Al systems should be explainable, transparent, and fair.
To put it another way: How can we make sure that the thinking of intelligent machines reflects humanity’s highest values? Only then will they be useful servants and not Frankenstein’s out-of-control monster.
1. Mary Shelley’s novel Frankenstein is mentioned because it________.| A．fascinates AI scientists all over the world |
| B．has remained popular for as long as 200 years |
| C．involves some concerns raised by Al today |
| D．has sparked serious ethical controversies |
| A．helps explain artificial intelligence | B．can be misleading to robot making |
| C．inspires popular sci-fi TV series | D．is too limited for us to reproduce it |
| A．can hardly ever be found | B．is still beyond our capacity |
| C．causes little public concern | D．has aroused much curiosity |
| A．AI’s Future: In the Hands of Tech Giants |
| B．Frankenstein, the Novel Predicting the Age of AI |
| C．The Conscience of AI: Complex but Inevitable |
| D．AI Shall Be Killers Once Out of Control |
【推荐1】At this very moment you’re thirsty and hunting for something to drink. So you start walking towards the drinks machine at school. As you drink you hear your teacher say those frightening words: “Could I see you for a moment in the classroom, please?”
You can almost feel your blood pressure rise as you walk to your English class. She’s always picking on you. What can it be this time? You think of the test you did last Friday. Now your mind is racing, your heart is pounding, and your forehead is pouring with sweat. In situations like this you will often feel like running away but you may also feel like hitting someone on the nose.
Your teacher asks you to go into the class. “Here it comes,” you think. But what you hear is: “Well done. Your test was excellent.” You can hardly believe your ears.
Our fight or flight response is designed to protect us from tigers that would have once hidden in the woods around us, threatening(威胁) our survival. At times when our survival is threatened, there is no greater response to have on our side. When activated(刺激), the response causes stress hormones to pump through our body.
When we face very real dangers to our survival, it is invaluable. However, few of the “tigers” we face in our lives cause a serious physical threat to our existence. They cause us no end of stress, triggering(引发) the full activation of our fight or flight response. They tend to cause us to overreact to the situation in a counterproductive (事与愿违的) way. It is counterproductive to hit someone (the fight response) or run away (the flight response).
By recognizing the symptoms, we can begin to take steps to handle the stress overload. By learning to recognize the signals of fight or flight activation, we can avoid reacting excessively (过度地) to events and fears that are not life threatening. In doing so, we use this extra energy to help ourselves, borrowing the beneficial effects in order to change our emotional environment and deal productively with our fears, thoughts and potential dangers.
1. You feel nervous when walking to the classroom because ________.| A．you broke the school rules | B．you failed the test last Friday |
| C．your teacher spoke to you loudly | D．your teacher always blames you |
| A．The power of our fight or flight response. |
| B．How our fight or flight response works. |
| C．The benefits of our fight or flight response. |
| D．How we control our fight or flight response. |
| A．fierce tigers | B．real dangers |
| C．dangers we face | D．serious physical threats |
| A．get rid of unnecessary stress | B．face real dangers bravely |
| C．find hidden dangers | D．take threats seriously |
【推荐2】A good modern newspaper is an extraordinary piece of reading. It's great first for what it contains：the range of news from local crime to international politics, from sports to business，from fashion to science, and the range of comment and special feature(特写) as well，from editorial page to feature articles and interviews to criticism of books, art theatre and music.
A newspaper is even greater for the way one reads it：never completely, never straight through，but always by jumping from here to there, in and out, glancing at one piece，reading another article all the way through, reading just a few paragraphs of the text.
A good modern newspaper offers a variety(多样性) to attract many different readers, but far more than the reader is interested in. What brings this variety together in one place is its topicality(时事性), its immediate relation to what is happening in your world and your locality now. But immediacy and the speed of production that goes with it also mean that much of what appears in a newspaper has no more than transient(短暂的) value.
For all these reasons, no two people really read the same paper：what each person does is to put together, out of the pages of that day's paper, his own selection and order, his own newspaper. For all these reasons, reading newspapers efficiently, which means getting what you want from them without missing things you need and without wasting time，demands skill and self-awareness as you change and apply the techniques of reading.
1. A modern newspaper is great for all the following EXCEPT its________.| A．wide variety | B．similar style |
| C．speed in reporting news | D．popularity |
| A．people look through the news they are interested in |
| B．different people prefer different newspapers |
| C．people are rarely interested in the same kind of news |
| D．people have different views about what a good newspaper is |
| A．apply reading techniques skillfully | B．jump from one newspaper to another |
| C．appreciate the variety of a newspaper | D．usually read a newspaper selectively |
| A．How to read newspaper? | B．Where to find a good newspaper? |
| C．What is a good newspaper? | D．Newspaper. |
| A．advertise | B．introduce |
| C．argue | D．compare |
【推荐3】For generations, the standard way to learn how to ride a bicycle was with training wheels or a tricycle (三轮脚踏车).But in recent years, many parents have chosen to train their kids with balance bikes, pedalless (无踏板的) two-wheelers that enable children to develop the ability to control their movements well, which is not as easily acquired with an extra set of wheels. Given the benefits of balance bikes, why did it take so long for them to replace training wheels?
Leidy Klotz, an engineer at the University of Virginia, noticed that there are many similar phenomena in life, in which removing elements from existing models is uncommon. So he reached out to Gabrielle Adams, a social psychologist at the university, to try to figure out why this was the case. The two researchers thought that there might be a psychological explanation: when faced with a problem, people tend to select solutions that involve adding new elements rather than taking existing components away.
Adams, Klotz and their colleagues first carried out a set of observational studies without a control group. In one, they asked 91 participants to make a pattern symmetrical (对称的) by either adding or removing colored boxes. Only 18 people used subtraction(移除). In another, the team scanned through a collection of ideas for improvement submitted to an incoming university president and found that only 11% of 651 proposals involved removing an existing regulation, practice or program.
Next, the team conducted a series of eight experiments with over 1,500 individuals. In one experiment, people were asked to stabilize the roof of a Lego structure held up by a single block that rested atop a cube-shaped base. The reward for completing the task was $1. The researchers wrote that one group was offered a cue about potential subtractive solutions by being told, “Each piece that you add costs ten cents but removing pieces is free,” while another group was just told, “Each piece you add costs ten cents.” Almost two thirds of people in the cued group chose to remove the single block rather than adding new ones, compared with 41% of those who hadn’t received the cue.
The researchers also observed that when participants were asked to create a symmetrical pattern by adding or removing colored blocks, they tended to conduct removal more often if they were given practice trials than if they had just one chance to handle the problem. On the other hand, having to simultaneously (同时地) handle another task—like keeping track of numbers on a screen—made individuals less likely to remove elements to solve the same problem.
These findings suggest that “additive solutions tend to come to mind quickly and easily,” says Benjamin Converse, a social psychologist at the University of Virginia and a co-author of the study. “Subtractive solutions aren’t necessarily harder to consider, but they take more effort to find.”
1. What does the first paragraph intend to show?| A．A new effective way of learning to ride a bicycle. |
| B．The difficulty in changing the old way of learning. |
| C．People’s tendency to overlook subtractive solutions. |
| D．The confusion about how people learn to ride a bicycle. |
| A．They needed to be further verified later. |
| B．They confirmed the researchers’ assumption. |
| C．They proved addition is more helpful than subtraction. |
| D．They showed addition and subtraction work in the same way. |
| A．To discover why people tend to choose additive solutions. |
| B．To prove people prefer additive solutions to subtractive ones. |
| C．To figure out how people would cope with their issues in life. |
| D．To find out exactly what people think of subtractive solutions. |
| A．They are loaded with much work. |
| B．They are free to cope with the issue. |
| C．They are given constructive advice. |
| D．They are given more chances to try. |
【推荐1】Facebook lets friends connect. They can give each other updates, share photos and post comments. But that’s not all. Facebook might also stress users out.
In a new study, 88 volunteers how much time they spent on Facebook and the types of Facebook posts and comments that they made. In addition, they answered questions about their feelings and state of mind. They also offered saliva. Researchers tested it for cortisol. This chemical is a stress hormone. Levels of it vary throughout the day.
In this study, people with the most Facebook friends, more than 300, had somewhat higher cortisol levels. Additionally, the more Facebook friends that users had, the more likely they were to feel anxious. On the other hand, youths who gave lots of ''likes'' and supportive comments on Facebook had lower cortisol levels. ''The more social support you give to others, the lower your stress hormone levels will be, '' says Lupien.
''This research decidedly combines the social science approach and the medical science approach on an important question in our social-media age, '' says Wenhong Chen, a sociologist at the University of Texas at Austin. ''It's ready pleasantly new to see Lupien’s team study cortisol levels-along with questionnaire data. ''
One finding from Lupien's work surprised Chen. Teens who felt they got a lot of support from others also had higher cortisol levels. Usually, she says, those feelings should protect people from stress. ''There are many potential dangers of social media use among young people, '' Chen notes. So, she says, enjoy Facebook, but be aware of the risks.
Lupien suggests that teen Facebook users share information with and support their friends on the site. They shouldn’t just stay silent. ''if anyone is more stressed, it's the watchers, not the sharers, '' she says. Also, she recommends that people who use social media heavily should find time to take active walks, to run or to do other activities. Cortisol increases a person's energy. “The best way to reduce stress hormones is to use the energy, '' she says.
1. Paragraph 2 shows us the ________.| A．research proposes | B．research methods |
| C．research contents | D．research results |
| A．Share as many nine photos as possible. |
| B．Give more positive comments to others. |
| C．Listen to music frequently on social media. |
| D．Communicate less with others on Facebook. |
| A．Cautious. | B．Critical. |
| C．Doubtful. | D．Approving. |
| A．There are many dangers on social media. |
| B．Getting support from e-friends makes us healthier. |
| C．Sharers on Facebook live a happier life than watchers. |
| D．Doing physical exercise helps reduce the levels of cortisol. |
The site attracts 78 million visitors every month, and it is available in more than 270 different languages. It’s one of the most comprehensive (综合的) resources available, and it’s got much more information than an ordinary encyclopedia. The site is updated on a daily basis by thousands of people around the world. Anyone with an Internet connection can look through and edit the contents or add a new page at any time. And you don’t need any formal training.
Of course, there are some controls. Wikipedia has a team of more than 1,500 administrators who check for false information. And main targets for horrible comments (such as politicians) are forbidden to public editing. But with more than 16 million articles to keep an eye on, it isn’t easy. So, while Wikipedia benefits from being constantly updated with information from all over the world, it’s also open to “vandals”(故意捣乱者).
Some of the damage is easy to notice. Someone drew horns and a moustache on Microsoft chairman Bill Gates’ photo. But other things are harder to spot. The most common form of vandalism involves adding tiny items of false information into the biography of a famous person. Unbelievably, some of this misinformation has appeared in newspapers, withThe Daily Mail, The GuardianandThe Independentall having fallen victim to the tricks. For example, in an obituary (讣告) for British comedian Sir Norman Wisdom, one newspaper claimed that he co-wrote Dame Vera Lynn’s wartime song “There’ll be Bluebirds over the White Cliffs of Dover”. In fact, he did no such thing.
So if you’re going to use any information from Wikipedia, make sure you double-check it first.
1. What do we know about Wikipedia?
| A．It makes profits from its users. |
| B．It is run by the Hawaiian government. |
| C．It provides a huge amount of information. |
| D．It is the most popular website worldwide. |
| A．78 million people visit Wiki each day |
| B．To forbid wrong public editings is quite easy |
| C．Formal education is needed to do editing for Wifi |
| D．Some people change the information on Wiki just for fun |
| A．Wikipedia sometimes contains false information |
| B．some newspapers likeThe Guardianare irresponsible |
| C．Norman Wisdom is unpopular with some people |
| D．Wikipedia affects people’s lives greatly |
| A．To look through Wikipedia frequently. |
| B．To update Wikipedia on a daily basis. |
| C．To turn to other websites for valid information. |
| D．To be careful when using the information from Wikipedia. |
【推荐3】Since the early 1980s, sponsorship （赞助）has become a major part of sport. But how effective is it?
There were some big changes to football shirts in the early 1980s. Instead of shirts telling you the name of the team, they gave you the name of a company. At times, it wasn't clear if the team playing was Manchester United or Sharp Electronics. However, fans soon got used to the new look shirts until they changed again: first to Vodafone, then to American Insurance Company AIG, and then to American re-insurance company Aon. It's hard to keep track sometimes.
So, why has sports sponsorship become so popular? Both sides see clear advantages. Most large companies are keen to link their brand to a well-known sporting personality because they believe raising their image in this way will increase sales. And the large sums they offer to do so is a big incentive （激励）for the other side. There's a lot of money involved in sports sponsorship, and many predict that the sums will be rising over the coming years.
But problems can arise. For example, what happens if they sponsor an unsuccessful player or team? Will they look stupid at the end of the season if their team has lost? And what happens if they sponsor a team or player who gets into trouble? DeutscheTelekom was one of the major sponsors of the famous cyclist Lance Armstrong but found it in an awkward situation when he failed drugs tests. As a result of this scandal（丑闻），many companies have moved away from sponsoring cyclists. Instead many now choose to sponsor events rather than the people. Of course, it doesn't matter which team wins because the audiences will see lots of company ads and logos everywhere and the companies know that they will win.
But the really important question is, does sponsorship work? Will you buy their products after the game just because you've seen their ads and logos? There's clearly more research to be done.
1. What's one of the effects of sports sponsorship on the football fans?| A．They can buy cheaper football shirts. |
| B．They recognize the teams more easily. |
| C．They welcome the changes of sponsorship. |
| D．They are confused about the names on the shirts. |
| A．Sponsorship is often a win-win situation. |
| B．Many sports teams actually dislike sponsorship. |
| C．The money on sports sponsorship will decrease. |
| D．Sports sponsorship certainly promotes a company's sales. |
| A．To better spread their brands. |
| B．To cut the cost of sponsorship. |
| C．To attract more people's attention. |
| D．To avoid unexpected troubles of the players . |
【推荐1】Ultrasound（超声）is used widely in medical imaging, but in recent years scientists have started developing it for another use: stimulating nerves to treat disease. In two new studies in mice, researchers focused the sound waves on nerves in the spleen（脾）that communicate with the immune system, reducing symptoms. If the approach proves safe and effective in people, it could serve as a treatment for diseases such as arthritis（关节炎）.
In one study, led by scientists at the Feistein Institute and GE Research, mice receiving a few minutes of ultrasound treatment to the spleen nerve had a diminished symptoms to an injected（注射）poison. In another study, researchers at the University of Minnesota and their colleagues reduces symptoms of arthritis in mice by stimulating their spleen nerves for 20 minutes every day for a week. “Zeroing in on the spleen may provide a more precise approach than focusing on the vagus nerve（交感神经）, which connects with the immune system via a second nerve that stimulates the spleen.” says Hubert Lin, lead author of the latter study. “When we’re targeting the spleen we have less of an effect all over the body.”
“Little is known about how repeated ultrasound affects the spleen or whether it has other harmful effects,” says neuroscientist Denise Bellinger of Loma Linda University, who was not involved in either study. An ongoing clinical trial aims to assess the treatment’s safety in humans with arthritis. A bigger unknown is how ultrasound activates in general. Scientists are now exploring the use of ultrasound on other parts of the nervous system, including the brain. “We know how to control nerves with electricity, and we’ve been doing it for more than 100 years,” neuroscientist Kevin Tracey says, “But the idea of controlling nerve signals with ultrasound is a brand-new field.”
1. What do scientists expect of the new application of ultrasound?| A．It'll be applied in medical imaging |
| B．It'll be used to activate nerves to treat disease. |
| C．It’ll be applied in spleen transplantation. |
| D．It'll be employed to rebuild immune system. |
| A．Complicated. | B．Worsened. |
| C．Decreased. | D．Associated. |
| A．Side effect. | B．Time length. |
| C．The procedure. | D．The cost. |
| A．Assessing the treatment' s safety on humans. |
| B．Activating nerves in general with ultrasound. |
| C．Exploring the use of ultrasound on the brain. |
| D．Controlling nerve signals with ultrasound. |
【推荐2】Plastics remain one of the most - used materials for making many things. Things made of plastics can be very strong and last a long time. Plastics are also much lighter than metal and can easily be formed into different shapes. Plastics can take hundreds of years to break down on their own. And very few kinds are highly recyclable.
A team of researchers working at the US Department of Energy says it has created a kind of plastic that could lead to products that are 100 percent recyclable. It recently reported the discovery in a study in the journal Nature Chemistry.
The researchers say the new material is a plastic polymer (聚合体)called polydiketoenamine, or PDK. The team reports the material can be broken down in parts at the molecular (分子的)level. It can then be built up again to form plastics of different shapes, textures and colors. The researchers say this process can be repeated over and over again—without the plastic material losing any performance or quality.
"Most plastics were never made to be recycled, ” lead researcher Peter Christensen said in a statement. " But we have discovered a new way to assemble plastics that takes recycling into consideration from a molecular perspective. ”
Many plastics have different chemicals added to them to make them more useful and powerful. The problem is that these chemicals attach to the monomers (单体),which remain in plastics even after the material gets processed at a recycling plant. The research team reported that, with the newly discovered PDK material, the monomers could be recovered and separated from any chemical additives.
Next, the researchers plan to develop PDK plastics "with a wide range of thermal and mechanical properties. These plastics could be used for many kinds of cloth, as well as things such as 3D printed materials and foams. In addition, the team is trying to include plant - based materials in the process.
1. What is the first paragraph mainly about?| A．Plastics are never highly recyclable. |
| B．Plastics are widely used in our lives. |
| C．Plastics have both advantages and disadvantages. |
| D．Plastics take hundreds of years to be broken down. |
| A．The new material. | B．The research team. |
| C．The molecular level. | D．The producing process. |
| A．To make them easy to break down. |
| B．To make them easy to get processed. |
| C．To make it possible for them to be recycled. |
| D．To make them stronger and more widely used. |
| A．PDK plastics will be soon put to good use. |
| B．PDK plastics may have a promising prospect. |
| C．The researchers are busy developing PDK plastics. |
| D．Plant - based materials have been used in the new plastics. |
【推荐3】Triple Olympic and world sprint（短跑） champion Usain Bolt of Jamaica said on Monday he expects years of fast feats to ease doping doubts in athletics and has no plans to play American football.
Appearing on ESPN programs and in light-hearted races outside the television sport network's studios, Bolt said he feels he must prove himself to a skeptical sports world in the wake of past doping scandals（诽谤）.
"I have to prove myself to the world that you can run fast without it," Bolt said.
Bolt cited the speeds he and countryman Asafa Powell and American Tyson Gay have achieved without positive doping tests.
"We just （have to） continue to run fast," Bolt said．"In a couple of years everyone will continue to watch again and have less doubts."
Bolt won gold in the 100m, 200 and 4x100 relay in world record times at last year's Beijing Olympics and last month in Berlin set world records of 9.58 seconds in the 100 and 19.19 in the 200 and helped a relay title in a World Championships treble.
"I want to be a legend in the sport．For me it's all a focus on winning championships after championships," Bolt said.
"I don't consider myself a legend．When I defend my titles I will consider myself a legend."
Bolt's defending of World and Olympic gold should be the feature attraction of the 2011 IAAF World Championships in Daegu, South Korea, and the 2012 London Olympics.
1. Why does Usain Bolt say that he has no plans to play American football?| A．Because he wants to ease doping doubts in athletics. |
| B．Because he wants to show his fast feats. |
| C．Because he is doubted by some people. |
| D．Because he runs fastest in the world． |
| A．three times． | B．four times． |
| C．five times． | D．eight times． |
| A．Usain Bolt plans years of fast feats to ease doping doubts. |
| B．Usain Bolt is doubted for his athletics. |
| C．Usain Bolt set world records again in Berlin last month. |
| D．Usain Bolt wants to a legend in the sport. |
| A．on TV | B．on the Internet |
| C．in a book | D．in a newspaper. |
