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NarratorNow listen to a part of a talk in a United Science class.
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案例分析题Set 3The Evolution of the PhotofitSecurity technology: A new type of computerised photofit system takes a novel evolutionary approach to generating images of suspects. If you have ever tried to describe someone’s face in detail, you will understand why the "photofit" composite images used by the police look so dodgy. In recent years, computerised "E-Fit" systems have helped improve the accuracy of these images by allowing witnesses to choose from a wider range of facial features. But researchers at the University of Stirling in Scotland found that, despite these improvements, people still have a hard time constructing recognisable faces--especially if there is a delay of moreThe problem is that people tend to recoguise faces as whole entities, rather than as separate features. So picking from a range of eyes, noses and mouths is not necessarily the most suitable approach, says Charlie Frowd, a psychologist at the University of Stifling. Next year, however, British police are expected to begin trials of a new computerised system, called EvoFIT, developed by Dr. Frowd and his colleague Peter Hancock. It uses an evolutionary approach, known as a genetic algorithm, to "evolve" faces rather than piece them together."The process is entirely non-verbal and takes a fraction of the normal time," claims Dr. Frowd. A witness is shown an array of 60 different faces with random features. Having studied them closely, the witness is asked to choose the six images that most closely resemble the person they are trying to describe. These six are then used to generate another set of 60, by switching featurees between some of the images and by making random changes to others. The witness is then asked to repeat the task, whereupon a new batch of faces is generated, and so on. In evolutionary terms, this process is known as "genetic crossover and mutation", and is a powerful way to search a large number of possibilities for a particular solution. By allowing the user to steer the selection process, the program is able to generate a good likeness for the original face after just a few cycles.In one of its early versions, EvoFIT was used by police in Northampton shire who were trying to catch a violent attacker. The attacker was never caught, but the senior investigating officer, Superintendent Paul Spick, says the witness involved found the new software much quicker and easier to use than traditional E-Fit systems. It was also more accurate: the final image caused the witness visible distress when displayed. A further important advantage of EvoFIT over traditional composites is that an image can be generated even if the witness can only provide a sketchy verbal description.The researchers have since made a number of further improvements to their system and are now in the process of commercializing it in partnership with ABM, a British firm which supplies police forces with photofit, one of the leading computerized composite systems. The images are more realistic, and the system can generate three-quarter angle views of the face, which are easier to distinguish than direct frontal views, says Dr. Frowd.His team has also found that by combining the images generated by different witnesses, or even from a single witness, it is possible to get an even better likeness.This could be particularly useful when multiple witnesses come forward and the police are unsure which of the images they produce is the most accurate.In the latest version, witnesses are given a selection of face shapes to choose from before facial features are added. This makes it less likely that the correct facial features will be rejected simply because they are on the wrong-shaped face.These modifications appear to make all the difference. In recent experiments, Dr. Frowd and Dr. Hancock compared EvoFIT with the computerized systems currently in use by asking volunteers to construct an image of a face two days after seeing it, and then showing the resulting image to people who were familiar with the person depicted. With traditional composites, the person was correctly identified about 4% of the time; the figure rose to 25% with EvoFIT images.Next year ABM will perform inhouse evaluations of the system and will then team up with police forces for further trials. Although things look promising so far, two things in particular need further testing, says Leslie Bowie, ABM’s director of research. Do the EvoFIT images distract witnesses or contaminate their memories of the face they are trying to recall And while EvoFIT has performed well in the calm conditions of the laboratory, how will it cope with real-life witnesses, who are often traumatized by their experiences If it can address these two questions, EvoFIT could be the next step in the evolution of the photofit. The word contaminate in paragraph 8 could best be replaced by().
案例分析题Set 5President Hoover’s Politics During the Great DepressionAt first everything seemed fine and dandy. America was enjoying one of the biggest economic surges in the nation’s history. However, even though America benefited from the economic boom of the so called "Roaring Twenties", the imbalance between the rich and the poor combined with the production of more and more goods and rising personal debt caused one of the biggest recessions in history. On Black Tuesday, October 29, 1929, the stock market crashed, triggering the Great Depression, which was the worst economic collapse in the history of the modem, industrial world. It spread from the United States and rippled out to the rest of the world, with banks failing and businesses going bust for over a span of a decade, leaving more than a quarter of the working force in America without jobs.President Herbert Hoover, underestimating the seriousness of the crisis, called it "a passing incident in our national lives," and assured Americans that it would be over within two months. Hoover did not think that the federal government should offer relief to the poverty-stricken population because he firmly believed in individualism. Focusing on economic programs to help finance businesses and banks, Hoover met with resistance from business executives who preferred to lay off workers. Blamed by many for the Great Depression, Hoover was widely ridiculed.Hoover’s economy was put to the test with the onset of the Great Depression in 1929. It was his vocal stance on non-intervention that led to Democratic criticism that Hoover was a "sitting duck" president; on the other hand, his more pro-free market opponents also denied he was a laissez-faire president and condemned him for being an interventionist. Hoover tried to restore confidence with a series of speeches but his weak speaking style hampered these efforts. The biggest problem was that his predictions of an upturn just around the comer never materialized. His promises were not delivered and he lost a lot of the public’s confidence.Together, the government and businesses actually spent more in the first half of 1930 than the previous year; yet frightened consumers cut back their expenditures by ten percent. A severe drought ravaged the agricultural heartland beginning in the summer of 1930, while foreign banks declared bankruptcy, draining U.S. wealth and destroying world trade. The combination of these factors caused a downward spiral: as earning fell, domestic banks collapsed, and mortgages were called in. Hoover’s hold-the- line policy in wages lasted little more than a year. Unemployment soared from five million in 1930 to over eleven million in 1931, causing this sharp recession to become the Great Depression.In 1930, Hoover reluctantly signed the Smoot-Hawley Tariff Act, which raised tariffs on over 20,000 dutiable items. The Tariff, combined with the 1932 Revenue Act, which hiked taxes and fees across the board, is often blamed for deepening the economic depression, and is considered by some to be Hoover’s biggest political mistakes. Moreover, the Federal Reserve System’s tightening of the money supply is also regarded by most modem economists as a mistaken tactic, under the circumstances.In order to cover the expenses of these government programs, Hoover agreed to one of the largest tax increases in American history.The Revenue Act of 1932 raised taxes on the highest incomes from 25% to 63%, while the estate tax was doubled, and corporate taxes were raised by almost 15%.Also, a "check tax" was included that placed a 2-cent tax on all bank checks. During the 1932 elections, Hoover’s opponents blasted the Republican incumbent for spending and taxing too much, increasing national debt, raising tariffs, and blocking trade, as well as placing millions on the dole of the government.Roosevelt attacked Hoover for "reckless and extravagant" spending, and of leading "the greatest spending administration in peacetime in all of history."Unemployment rose to 24.9% by the end of Hoover’s presidency in 1933, a year that is considered to be the depth of the Great Depression. The word incumbent in the passage is closest in meaning to().
NarratorRead the "Announcement from the president". You will have 45 seconds to read it. Begin reading now.NarratorNow listen to two students as they discuss the announcement.
案例分析题Set 4Importance of VitaminsVitamins, which come in many different types all of which are quite diverse in chemical configuration and function, can be any of several organic substances that are separated into water-soluble and fat-soluble groups. Originally defined as organic compounds obtainable in a normal diet and capable of maintaining life and promoting growth, vitamins are differrent from carbohydrates, fats, and proteins in function, as well as in the quantities in which organisms require them. So critical are vitamins to a body’s essential strength and health that if they are absent from the diet or not properly absorbed by an organism, a specific deficiency disease may develop.The term vitamin originated from "vitamine," a word first used in the early 19th century to designate a group of compounds considered vital for life (though the term "accessory food factor" sometimes is used interchangeably to refer to these substances). Like other nutrients, vitamin consumption is imperative to keep our bodies functioning properly, and if there is a lack of vitamin consumption, the body will fail to react in a way that’s considered healthy. Lack of vitamin A will result in various disorders that most commonly involve the eye and the tissues around it. One of the earliest symptoms of vitamin A deficiency is nyctalopia, the medical term for night blindness, which causes a visual failure to adapt quickly from light to darkness and an inability to see in the dark. This aspect of vision is normally dependent on rhodopsin, a protein found in the eye that maintains itself only in the presence of vitamin A; in the lack of vitamin A, rhodopsin will malfunction.These earlier symptoms are quite harmless but the side effects can become increasingly serious if not treated early on. If the deficiency is severe and persists, especially in malnourished infants and children, a condition known as xerophthalmia--when the eyes are sensitive to light, the secretion of lubricating tears is stopped, and the eyelids become swollen and develop pus -- may develop. Furthermore, the mucous surfaces of the eye may become eroded, allowing infection to set in, thus leading to ulceration and other destructive changes of the cornea and other structures of the eye, resulting eventually in blindness.Early signs of vitamin A deficiency may also be reflected in changes in the membranes of the mouth, throat, and respiratory and genito-urinary passages where the lining membranes become malnourished and dry and lose their cilia, the tiny hairlike projections that normally help in clearing away foreign particles.The natural immune system is weakened and if insufficient intake of vitamin A is prolonged, the skin may become dry and rough.Vitamin A deficiency may also result in defective bone and teeth formation and in poor general growth.However, an excessive intake of vitamin A can also cause severe damages to the body causing a symptom called "hypervitaminosis A", which happens when a person takes in more than 150 milligrams of vitamin A over a long period of time; the vitamins are stored in the liver and can reach dangerous level because the A vitamins are not employed to make the bodies stronger, but rather, stored as toxic material. Excessive amounts of vitamin A can cause nausea, dryness of skin, blurred vision, drowsiness, and bone pain.Vitamin A can be found in all animal livers, in milk products, and in many yellow and green leafy vegetables which contain carotenes, chemically related substances that are converted to vitamin A in the body. There are various other vitamins that the human body needs in order to survive; the excessive intake of vitamin A, or the lack of intake of other vitamins, causes detriment to the human body--at all times, moderation is key. According to the paragraph 6, which of the following is true of carotene().
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