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Potential energy is the energy, chemical or physical, stored within an object, atom or molecule（分子）. Think about a car at the top of a roller-coaster （过山车）, pausing just before it slopes into the next turn. A log resting in a fireplace just before it is about to be lit is a treasure house of potential energy. As the log burns, the connections between carbon atoms that make up the wood are being broken down, and the potential energy stored within those connections is being released as heat and light. As a comet approaches a planet or star, it slows, momentarily affected by the larger body’s gravity. The potential energy builds up and then reaches a breaking point as the comet accelerates around the larger body, and is shot out to the other side.
Sports show countless examples every day of potential energy being transformed into kinetic energy. Kinetic energy is the energy of movement. When an archer（弓箭手）draws and holds her arrow, her bow is filled with stored potential energy. When she releases the bowstring, all the potential energy is quickly transformed into kinetic energy, which is transferred to the arrow that takes flight.
The transformation of stored potential energy into kinetic energy can also be made use of to power homes, factories and entire cities. The most notable example is the Hoover Dam. The Hoover Dam is an arch-gravity dam by design. This design name is the first clue as to how exactly the dam makes use of energy. Located in the Black Canyon of the Colorado River, the Hoover Dam formed, and now holds back Lake Mead — the largest reservoir in the United States.
Gravity acts as a force upon Lake Mead. Held at bay by the Hoover Dam, the waters of Lake Mead and the Colorado River gain greater potential energy with each passing moment. The Arizona and Nevada spillways（溢洪道）are two means by which the waters of Lake Mead can escape the dam. As the lake water falls over the walls into a spillway, potential energy is instantly transformed into kinetic energy. The channels through which the water normally escapes every day are the four intake towers. These towers allow the water flow through passageways to the powerhouse and hydroelectric generators. When the water reaches the intake towers and is allowed to flow down through the passageways, all the stored potential energy created by the force of gravity acting upon the water is transformed into kinetic energy, just as when water flows over the wall into a spillway. By taking advantage of the transformed potential energy of Lake Mead, the Hoover Dam provides power to California, Nevada and Arizona.
Moments like these happen all across the physical world, whether on the molecular or universe level.
Main points | Supporting details |
What is potential energy? | Potential energy is the energy existing either in the chemical or physical 1., which is stored in an object. When a car is sloping into the next turn from the top of a roller-coaster, it is building up potential energy. When a log is burning, the connections between carbon atoms are being broken down, 2. potential energy as light and heat. When a comet approaches a planet or star, the potential energy 3. to a breaking point and then the comet is shot out to the other side. |
How is potential energy transformed into kinetic energy? | Potential energy can be transformed into kinetic energy, which is the energy4. by movement. When the bowstring is released by an archer, the potential energy stored in the full bow is quickly transferred to the arrow, thus transformed into kinetic energy which sets the arrow 5. far away. Hoover Dam is the most notable example of energy transformation. Hoover Dam is 6. in the Black Canyon of the Colorado River, holding back Lake Mead. The waters of Lake Mead escape the Dam, falling over the walls into Arizona and Nevada spillways, leading to the 7. transformation from potential energy into kinetic energy. The 8. of potential energy is from the force of gravity acting upon the water |
What 9. is the energy transformation made of? | Homes, factories and cities are efficiently 10. thanks to the powerhouses and hydroelectric generators taking advantage of the transformed potential energy. |
In November 2016, two influential art curators（艺术策展人）threw a memorable party in Shanghai. The hosts — Linyao Kiki Liu, and Klaus Biesenbach, — picked an unusual place for the great event: a repaired underground bomb shelter. That night it was filled mostly with an oversea crowd that had flown in to celebrate the art event. Shanghai seemed determined to present itself as a new centre of the art world.
Chinese contemporary art was actually born in Beijing. In 1979, soon after the country began rolling out economic reforms, a small group of artists held an unofficial exhibition, which lasted just two days but the seed for China’s grass roots arts movement was sown. By the early 2000s the 798 arts district in the north-east of the city was becoming a vital destination for international dealers and curators. Now Shanghai is competing with Beijing to become China’s cultural capital.
Shanghai’s initial embrace of art was restricted. Beginning in the early 2000s, a few local galleries supported a scattering of artists. There were no more than a handful of museums. The prospect of hosting Expo 2010 helped motivate Shanghai’s local government to encourage property developers to launch an ambitious urban-regeneration programme that would reframe the city as a cultural hub. At the heart of this renewal was West Bund, a 9.4km belt of Shanghai riverside, whose old industrial buildings and former airport were to be repurposed under the declaration “Culture First, Industry Oriented”.
In 2014 two landmark contemporary-art museums opened there — the Long Museum and Yuz Museum. The same year also saw the introduction of Le Freeport West Bund, a warehouse built to help the tax-free import, export and storage of artworks, a prime example of the city’s market-friendliness.
The inflow of collectors triggered by the series of events presented an important opportunity for galleries to hold exhibitions, unveil new spaces and host parties. Much of the activity took place in the newest art facilities — West Bund and the Power Station of Art.
All the glamour, though, cannot mask the concern felt by some artists and gallerists in Shanghai. Does projecting the city as such a high-end, outward-looking hub risk endangering some of other important corners of the city? Rapid gentrification（中产阶级化）is already forcing many small businesses, like the family-run noodle joints and the bicycle-repair shops, to close down. And indeed, the art party, Shelter, is due to close after the Culture Bureau refused to renew its lease（租约）.
This upgrading of the city is already affecting the arts sector. Rising rents — a direct outcome of urban redevelopment—have made the production of art in Shanghai difficult, forcing artists to the city’s fringes, and beyond. It risks crushing the kind of grass roots, artist-led initiatives on which so much of China’s contemporary art was founded. The shift also affects galleries. Three of the city’s most important names — MadeIn Gallery, Aike Dellarco and ShanghART — have relocated this year from Shanghai’s original art hub, M50, to West Bund. Their departure will mean fewer visitors to M50’s remaining lower-tier, entry-level galleries for whom a move to West Bund is out of the question. If M50 struggles, that may affect new artists seeking representation in the city.
The cultural transformation of Shanghai has been astonishing. But it risks threatening the kind of complex and sustainable engagement that a lively arts sector needs. If local government can encourage affordable spaces for young artists and help promote a climate where artists and art professionals can prosper, then this most dynamic of cities might truly have it all.
1.“Linyao Kiki Liu, and Klaus Biesenbach” are mentioned at the beginning of the passage to show that _____.
A.Shanghai has been racing to become China’s cultural capital.
B.Shanghai encourages property developers to build museums.
C.Shanghai is appealing to more celebrities（名人）to go sight-seeing.
D.Shanghai has beaten Beijing in holding art exhibitions.
2.The underlined phrase “roll out” in Paragraph 2 has the closest meaning to the one in _____.
A.“We’ll give her some VIP treatment and roll out the red carpet”.
B.“He let a couple of golden apples roll out from under the basket”.
C.“Then it was time to roll out of bed and line up for breakfast”.
D.“We have rolled out an improvement initiative across our organization”.
3.According to the author’s introduction, we can learn that _____.
A.the 798 arts district in Shanghai has already attracted many international dealers.
B.Shanghai has adopted preferential tax policies in West Bund to inspire cultural industry.
C.the prospect of contemporary art in Shanghai is greatly determined by Expo 2010.
D.more art enthusiasts will go and appreciate high quality art exhibitions in M50.
4.The upgrading of Shanghai may have negative effects on the following corners EXCEPT _____.
A.local galleries B.new artists
C.Culture Bureau D.bicycle-repair shops
5.What is the author’s attitude towards contemporary art in Shanghai?
A.Critical. B.Optimistic.
C.Subjective. D.Indifferent.
6.In which section of a magazine might the article appear?
A.Global business. B.Finance and economics.
C.Books and arts. D.The world this week.
Dec 21st 2018
On December 19th Gatwick airport, Britain’s second-biggest, was forced to close due to several sightings of drones（无人机）flying near its runways. The airport only reopened on the morning of December 21st. ① .
The potential for an incident of this scale has been recognized for some years now. The falling price of small drones in recent years has resulted in the number flying dangerously near aircraft to rise sharply. ② .
This is a threat that the authorities have to take seriously. Recent research suggests that small unmanned aerial vehicles (UAVs) can be much more damaging than birds — a surprisingly common cause of aircraft crashes — at the same impact speed, even if they are a similar weight. The researchers found that the drones’ rigid and dense materials—such as metal, plastic and lithium batteries—can put aero planes at much greater risk than a bird carcass（动物尸体）. If a drone were to hit an aircraft’s fan blades when it is operating at its highest speed, the blades could break and power to the engine could be lost.
③ . But it also underlined the potential for destruction that drones afford. The British police do not think that terrorism was the motivation behind the latest incident at Gatwick. According to the Daily Telegraph, a British newspaper, environmental activists are suspected of being behind the attack, which has happened before.
As attention turns to what can be done to prevent a repeat, two solutions stand out. The first is regulation. Regulators in America and Britain already ban drones from flying too close to airports. America has introduced a compulsory registration scheme for drones and Britain plans to follow suit.
But as the chaos at Gatwick shows, even serious punishments will not stop those intending to cause harm deliberately. ④ . Technology is the second, and more important, answer to the threat. In the US the FAA has experimented with a system. Drones can have pre-programmed software that keeps them away from prohibited areas, an approach known as “geofencing”. British engineers have come up with a system that catches drones with a net and then softly lands them with a parachute. Dutch police have even attempted to train eagles to catch drones in the sky and return them to their trainers as if they were song birds. The closure at Gatwick will give ideas such as these a mighty push forward.
1.Compared to birds, drones have become a more serious threat to airplane crash in that _____.
A.drones are much heavier than birds in general
B.drones usually fly even faster than birds
C.drones will attack airplanes on purpose
D.drones are made of rigid and dense materials
2.The sentence “The extended closure of Gatwick was a justified response to this threat.” should be put in _____.
A.① B.②
C.③ D.④
3.It can be inferred from the article that _____.
A.The decreasing size of drones recently has led to frequent accidents of this kind.
B.Among the solutions, technology is considered to be a more reliable one.
C.The FAA has adopted a “geofencing” system with the help of trained eagles.
D.The British police think environmentalists conducted the latest incident at Gatwick.
4.What can be a suitable title for the article?
A.Drones or birds, which is more harmful?
B.How to stop unmanned aerial vehicles?
C.Several drones close Gatwick airport.
D.Drones have become a pressing issue.
Scientists say they have used the gene-editing tool CRISPR to repair a person’s eyesight for the first time. The CRISPR tool makes it possible to change DNA to add needed genes or take some away if they lead to problems.
A patient recently had the procedure done for an inherited form of blindness. The operation took place at Oregon Health and Science University in Portland. “We literally have the potential to treat people who are essentially blind and make them see,” said Charles Albright. He is chief scientific officer at Editas Medicine in Cambridge, Massachusetts. Editas is one of the companies developing the treatment. Albright added, “We think it could open up a whole new set of medicines to go in and change your DNA.”
The people taking part in the study have a genetic condition that keeps the body from making a protein needed to turn light into signals to the brain, which leads to sight.
Scientists have found it difficult to treat the condition with usual gene therapy. So, they are aiming to edit or remove the mutation（突变）by making two cuts on either side of it. The hope is that the ends of DNA will reconnect and make the gene work as it should. Through a tube the width of a human hair, doctors put three drops of fluid containing the gene editing machinery just under the retina（视网膜）, which is the lining at the back of the eye that contains the light-sensing cells. Doctors believe they need to fix one-tenth to one-third of the cells to repair vision. In animal tests, scientists were able to correct half of the cells with the treatment, Albright said.
Some independent experts were hopeful about the new study. Dr. Kiran Musunuru is a gene-editing expert at the University of Pennsylvania. He said the treatment seems likely to work, based on tests in mice and monkeys. The gene editing tool stays in the eye and does not travel to other parts of the body. So, “If something goes wrong, the chance of harm is very small.” Musunuru said. “It makes for a good first step for doing gene editing in the body.”
1.Who can most possibly benefit from this new treatment?
A.Patients who are essentially color-blinded.
B.Patients who turn blind due to accidents or diseases.
C.Patients who are born with no ability to see.
D.Patients who lose their vision at a young age.
2.Which is Paragraph 4 mainly about?
A.The result of the treatment.
B.The theory of the treatment.
C.The difficulty of the treatment.
D.The disadvantage of traditional treatment.
3.What is likely to be discussed after the last paragraph?
A.The function of the gene-editing tool.
B.The limitation of the gene-editing tool.
C.The effect of the treatment on animals.
D.The research of the treatment on humans.
Downloading files is one of the primary uses of the Internet. You can find virtually anything online, and chances are that you've been downloading files ever since you started using your computer. Your Operating System will attempt to put all of your downloads in one central location, but eventually you may have downloaded files all over your computer. Knowing how to quickly find your downloaded files can save you a lot of time and headache.
● Check your Downloads folder（文件夹）. Windows includes a Downloads folder that acts as the default (默认的) download location for most programs for every user. There are a couple of ways you may be able to find your Downloads folder:
Click the Start menu and then click your user name. You should see a Downloads folder in the window that opens.
Open Windows Explorer ⊞ Win+E. Your Downloads folder may be listed in the left frame under "Favorites" or "Computer/This PC".
Press ⊞ Win+R and type shell: downloads. Press ↵ Enter to open the Downloads folder.
● Check other locations. If you download with a lot of programs, chances are that your downloads have become a bit spread out. Other popular places for your downloads to appear are your Desktop and your Documents/My Documents folder.
If you have a secondary drive that acts as a file storage, check to see if you've created a download folder on it as well.
● Search for the file. If you know the name of the file you downloaded, you can search for it to quickly open it. Press ⊞ Win and start typing the name of the file. You should see it appear in the search results.
● Open your downloaded files. You shouldn't have much difficulty opening most files that you download online, but you may run across a few file types that can give you problems. See the guides below for details on opening these troublesome files.
Playing MKV video files
……
1.This passage aims to instruct Internet users _____.
A.how to download files from the Internet
B.how to search for files on the Internet
C.how to find files downloaded from the Internet
D.how to open the folders on the Internet
2.If you can’t find the file at the default download location in your computer, you might try to _____.
A.press ⊞ Win+R B.click My Documents
C.extract an RAR file D.open the Downloads folder.
One afternoon many years ago, I parked my car by the street, waiting to_______ my mother from work.
As I looked outside the car window to my right, there was a small park where I saw a little boy, around two years old, running freely on the grass as his mother _______ from a short distance. The boy had a big smile on his face as if he had just been _______ from some sort of prison. The boy would then fall to the grass, get up, and without hesitation or without looking back at his mother, run as fast as he could, again, still with a smile on his face, _______ nothing had happened.
Actually, with kids, when they fall down, they don’t think of their falling down as failure; _______, they treat it as a learning experience. They _______ try and try again until they succeed. While I was _______ by the boy’s persistence, I was equally touched by the manner in which he ran. With each _______, he looked so confident and so natural. No _______ of fear, nervousness, or of being discouraged — as if he didn’t give a care about the world around him.
His only aim was to run freely and to do it as effectively as he could. He was just being a child — being just himself completely in the moment. He was not looking for approval or was not worrying about ________ someone was watching or not. He wasn’t ________ about being judged. He didn’t seem to be ________ by the fact that maybe someone would see him fall and that it would be ________ if he did fall. No, all that ________ to him was to accomplish the task or activity at hand to the best of his ability — to run and to feel the experience of running fully and freely. I learned a lot from that ________ and experience, and have successfully brought that lesson with me in my many pursuits in life.
________, I’ve always believed that in each of us is a little child with absolute courage, a child that has the ability to run freely without a care for anything external（外在的）. I believe that courageous part of us — that courageous child ________ us all, will always be with us ________ we live. We only need to allow it to emerge more fully. We only need to once again ________ that child within us — and give that child permission to run freely, just like that boy in the ________.
1.A.pick out B.look for C.pick up D.look after
2.A.smiled B.watched C.waved D.shouted
3.A.set on B.set down C.set free D.set up
4.A.as if B.even if C.only if D.if only
5.A.meanwhile B.moreover C.though D.rather
6.A.will B.must C.should D.might
7.A.disappointed B.discouraged C.touched D.treasured
8.A.attempt B.failure C.adventure D.mistake
9.A.signals B.signs C.marks D.symbols
10.A.why B.how C.while D.whether
11.A.concerned B.serious C.curious D.upset
12.A.accused B.bothered C.interrupted D.impressed
13.A.appealing B.surprising C.embarrassing D.exciting
14.A.happened B.attracted C.worked D.mattered
15.A.observation B.exposure C.evolution D.procedure
16.A.Until then B.During that C.Since then D.After that
17.A.for B.within C.beyond D.by
18.A.as well as B.as soon as C.as far as D.as long as
19.A.conclude with B.compare with C.connect with D.compromise with
20.A.car B.open C.wild D.park
