Учебное пособие Издание второе, переработанное и дополненное Москва Астрель act 2005
 Скачать 0.99 Mb.
|
|
CLASSWORK READING(20B) • Read the passages carefully and say why this discovery is of interest to physicists. A) THE TROPHIES THAT WILL BE HUNTED WITH THE NEW ACCELERATORS However much has been learned in the past 50 years, it would be misleading to suggest that the present understanding of elementary particles is even approaching finality or completion. The status ofthe field is tantalizing rather than satisfying1; there is no shortage of questions to be answered. A first order ... is tantalizing rather than satisfying — скорее заставляет испытывать танталовы муки, чем приносит удовлетворение of business for the new accelerators will be filling in the blanks in the catalogue of hadrons, particularly those that incorporate top and bottom quarks in their structure. It is also important to find out whether the list of quarks and leptons ends with the six of each that are now known or whether more will be found at higher energies. In a sense six quarks and six leptons are already too many; all ofthe ordinary matter in the universe could be constructed out ofjust four elementary particles: the electron, the electron neutrino and the up and down quarks. The existence of the other leptons and quarks, which appear only in high-energy-physics experiments, is a puzzle. Another puzzle is the failure of all attempts so far to detect a free quark. Various theoretical constructs have been offered, after the fact, to explain why quarks should be permanently confined to hadrons. The possibility remains, however, that a quark can be knocked loose from a hadron if enough energy is supplied. Future experimental programs are therefore certain to include quark searches. B) NEW STATE OF MATTER CREATED AT CERN At a special seminar on 10 February, spokespersons from the experiments on CERN's Heavy Ion programme presented compelling evidence for the existence of a new state of matter in which quarks instead of being bound up into more complex particles such as protons and neutrons are liberated to roam freely. Theory predicts that this state must have existed at about 10 microseconds after the Big Bang, before the formation of matter as we know it today, but until now it had not been confirmed experimentally. Our understanding of how the universe was created, which was previously unverified theory for any point in time before the formation of ordinary atomic nuclei, about three minutes after the Big Bang, has with these results now been experimentally tested back to a point only a few microseconds after the Big Bang. Professor Luciano Maiani, CERN Director General, said: "Thecombined data com'mgfrom the seven experiments on CERN's Heavy Ion programme have given a clear picture of a new state of matter. This result verifies an important prediction of the present theory offundemental forces between quarks. It is also an important step forward in the understanding of the early evolution of the universe. We now have evidence of a new stale of matter where quarks and gluons are not confined. There is still an entirely new territory to be explored concerning the physical properties of quark-gluon matter. The challenge now passes to the Relativistic Heavy Ion Collider at the Brookhaven National Laboratory and later to CERN's Large Hadron Collider. " The aim of CERN's Heavy Ion programme was to collide lead ions so as to create immensely high energy densities which would break down the forces which confined quarks inside more complex particles. A very high energy beam of lead ions (33 TeV) was accelerated in CERN's Super Proton Synchrotron (SPS) and crashed into targets inside the seven different experimental detectors. The collisions created temperatures over 100 000 times as hot as the centre of the sun, and energy densities twenty times that of ordinary nuclear matter, densities which have never before been reached in laboratory experiments. The collected data from the experiments gives compelling evidence that a new state of matter has been created. This state of matter found in heavy ion collisions at the SPS features many of the characteristics ofthe theoretically predicted quark-gluon plasma, the primordial soup in which quarks and gluons existed before they clumped together as the universe cooled down. The project is an excellent example of collaboration in physics research. Scientists from institutes in over twenty countries have participated in the experiments. The programme has also allowed a productive partnership to develop between high energy physicists and nuclear physicists. More importantly, this step forward has been made possible by the collaboration between the individual experiments. The picture of quark-gluon plasma resembles a jigsaw puzzle, with many pieces provided by the different experiments. The data from any one experiment is not enough to give the full picture but the combined results from all experiments agree and fit. Whereas all attempts to explain them using established particle interactions have failed, many of the observations are consistent with the predicted signatures of a quark-gluon plasma. The results from CERN present strong incentive forthe future planned experiments. While all ofthe pieces ofthe puzzle seem to fit with a quark-gluon plasma explanation, it is essential to study this newly produced matter at higher and lower temperature in order to fully characterize its properties and definitively confirm the quark gluon plasma interpretation. CERN Press Releases 2000 HOMEWORK • Translate into Russian.
5. Should the Universe be finite, its expansion would eventually stop and be replaced by a contraction. 2. Translate into English. Begin each sentence with should. Model: Если бы вы помогли мне, я был бы вам признателен. Should you help me, 1 would be thankful to you.
SUPPLEMENTARY READING TEXT 1 • The paper says that the 21 st century would be impossible without the computer. Do you think the same? What reasons does the author give in favour of his opinion? Read the passage below attentively and find all the facts in favour of the idea. THE COMPUTER REVOLUTION Without the computer space programs would be impossible and the 21st century would be impossible. The incredible technology we are building, the complexity and the knowledge we are amassing are all beyond the unaided mind and muscle of man. More than any other single invention, perhaps even more than wheel, the computer offers a promise so dazzling and a threat so awful that it will forever change the direction and meaning of our lives. Computers today arc running our factories, planning our cities, teaching our children, and forecasting the possible futures we maybe heir to. In the new age of exploration the computer is solving in milliseconds the problems a generation of mathematicians would need years to solve without its help. The small, fifty-ninc-pound computer, which takes up only one cubic foot of space in the vehicle will do all of the mathematics needed to solve one billion different space-manoeuvring, navigation, and re-entry problems. Moreover, it translates the answer into simple numbers and tells the astronaut the altitude to which he must bring the spacecraft before firing the thrustcrs, and indicates to him exactly how long they must be fired. TEXT 2 • Read the passage below as fast as you can and say a few words about the computer applications mentioned in the text. microfiche ['maikroufi(:)Jl n ииформ. микрофиша (карточка с несколькими кадрами микрофильма) descendant/; потомок thief |Bi:f] п пор COMPUTERS CONCERN YOU When Charles Babbage, a professor of mathematics at Cambridge University, invented the first calculating machine in 1812 he could hardly have imagined the situation we find ourselves in today. Nearly everything wc do in the modern world is helped, or even controlled, by computers, the complicated descendants of his simple machine. Computers are being used more and more extensively in the world today, forthe simple reason that they arc far more efficient than human beings. They have much better memories and can store huge amounts of information, and they can do calculations in a fraction of the time taken by a human mathematician. No man alive can do 500,000 sums in one second, but an advanced computer can. In fact, computers can do many of the things wc do, but faster and better. They can pay wages, reserve seats on planes, control machines in factories, work out tomorrow's weather, and even play chess, write poetry, or compose music. Let's look now at some ofthe ways in which computers concern people in their daily lives and work. Chief inspector Harston talks about ways in which computers can help the police fight crime. Members of the public often think of detective work as fast and exciting when most of it is slow and boring. For example, a detective on a stolen carcase may have to check through long lists of information, and in the time it takes him to do this the thief may well escape. With the new National Police Computer we are now able to find out details of car ownership and driving licences in a fraction of the time it takes by traditional methods. In police work speed is often essential, so computers are ideal for helping us catch criminals. Many people associate computers with the world of science and maths, but they are also a great help to scholars in other subjects, in history, literature and so on. It's now possible for a scholar to find a book or article he needs very quickly, which, when a million or more new books are published each year, is quite an advantage. There's a system, controlled by computer, of giving books a code number, reducing them in size by putting them on microfiche, and then storing 3,000 or more in a container no biggerthan a washing machine. You tell the computer which subject you're interested in and it produces any microfiche you need in seconds. It's rather like going to an expert who has read all the works on your subject and can remember where to find the correct information, which few human experts can! There are also systems being developed to translate articles from foreign magazines by computer, and to make up the many lists of information that are needed in a modem library. So computers can help us to deal with the knowledge explosion in many ways.
Even before a rocket is launched, it is flown from ten to a hundred times through space-computer-simulated space — on flights constructed of mathematical symbols, on trajectories built of information bits, encountering hazards that are numbers without menace. For one ofthe computer's greatest assets is its ability to simulate one or a million variants of the same theme. "What if?" is the question the computer can answer accurately, swiftly, and over and over again. From this variety of possibilities, a trip from the earth to the moon can be simulated as often as necessary, with every possible trajectory plotted and every mile of the journey through space marked with symbolic signposts that will provide assurance that, mathematically at least, man has travelled this way before. The computer can do far more than simulate the mechanics of space flight; it can furnish accurate models of life itself. In computer simulation, then, there may come the great breakthrough needed to convert the inexact social sciences — the studies of man as a social being — into exact science. For the sociologist the problem has always been the lack of an adequate yardstick by which to measure and count. The one absolutely essential tool of science is the measuring device. Anything that can be counted, measured, quantified, can be studied with scientific accuracy, Now it becomes possible to perform controlled experiments, in which every factor that goes in is known in advance and the answers that come out are then valid. With computer simulation you can have a series of problems in which you can figure out all the ramifications, all the permutations and combinations, and do it very quickly and know the different combinations that are at stake. So you can use it really as a means of controlled experiment. You can get a computer model of a city and play out all the different effects, so that if you decide, for example, to relocate traffic in one way you can trace out very quickly, on the model, the effects on industry locations, residential densities, and the like. And more important, when you have alternative plans ofthis kind you can then choose, and that is the fundamental aspect of all such notions of planning. It allows you to have a sense of wider choice, to see therefore the consequences of it and say, I prefer this scheme rather than another. TEXT 4 • Read the passage carefully. Choose the key word or sentence that best sums up the main idea of each paragraph. There are two types of computers, the analogue and the digital. Basically, today's analogue computer is a device for measuring such physical quantities as lengths and voltages and, through a mechanical linkage, exhibiting the measurement as a numerical value. However, the analogue computer is limited to special classes of problems and when most people say 'computer' today, they mean the digital computer, which is a marvel of precision and accuracy, for it works with specific units rather than approximations. The modern electronic digital computer counts with incredible speed using only two numbers - the one and zero of what mathematicians call the binary system. The counting ability of the computer is used to feed it information. But first the information is translated into a code. The information is then stored in a memory bank made of magnets. The direction in which electrical signals run through the magnets means one or zero, yes or no, off or on. Each magnet contains one piece ofinformation called a bit. A large computer system can store hundreds of millions of such information bits. But information by itselfis useless. The computer must be told what to do with it — to add, subtract, multiply, ordividc the coded pulses stored in its memory. Parts of that memory contain instructions, prepared by a human brain, that provide the computerwith the road to follow in orderto solve a problem. These instructions are called the program. What makes the computer different from an adding machine is that the computercan modify its instructions. If a problem cannot be solved by following one route, the computer can search its memory for another set of instructions until a solution is found. And it docs all this at superhuman speeds. The on-off switching of the computer's logic circuits has been clocked at a billionth ofa second. That is to one second what one second is to thirty years. But the computer cannot actually think. It performs all ofits functions by route. Once an answer is achieved, another program within the memory tells the computer how to display the solution, to type it out on paper, display it as pictures or words on a television screen, or perhaps even to speak the answer in words a man can hear. In every field ofhuman endeavourthe body of knowledge is being swollen to the bursting point by a flood of new facts, which by their existence help to generate still more facts until the mass ofinformation threatens to engulf us. But the problem can be controlled and reduced to usable proportions by the computer. AH that is required is a human mind at one end of the system with enough sense to say "Halt! I've learned just about all I want to know about wickets." This will become the touchstone to the computerized library ofthe 21st century, in which requests for information will be answered instantly and as fully as the user wants. • Translate the passage at sight. retrieve v отыскивать justify v подтверждать schedule v составлять график, таблицу setting n id. окружение rule of thumb практическое, эмпирическое правило ARTIFICIAL INTELLIGENCE Expert systems are a class of computer programs that can advise, analyse, design, diagnose, explain, explore, forecast, form concepts, identify, interpret, justify, learn, manage, monitor, plan, present, retrieve, schedule, test and tutor. They address problems normally thought to require human specialists for their solution. Some of these programs have achieved expert levels of performance on the problems for which they were designed. Expert systems are usually developed with the help of human experts who solve specific problems and reveal their thought processes as they proceed. If this process of protocol analysis is successful, the computer program based on this analysis will be able to solve the narrowly defined problems as well as an expert. Experts typically solve problems that are unstructured and ill-defined, usually in a setting that involves diagnosis or planning. They cope with the lack of structure by employing heuristics, which are the rules of thumb that people use to solve problems when a lack of time or understanding prevents an analysis of all the parameters involved. Likewise, expert systems employ programmed heuristics to solve problems. Experts engage in several different problem-solving activities: identify the problem, process data, generate questions, collect information, establish hypothesis space, group and differentiate, pursue and test hypotheses, explore and refine, ask general questions, and make decisions. As researchers of the domain point out, a robust expert system that can explain, justify, acquire new knowledge, adapt, break rules, determine relevance and behave as human experts do, will have to use a multitude of knowledge representations, that lie in a space whose dimensions include deep and surface (representations), qualitative/quantitative, approximate/exact, specific/general and descriptive/prescriptive representations. Expert systems, like human experts, can have both deep and surface representations of knowledge. Deep representations are causal models, categories abstractions and analogies. In such cases, we try to represent an understanding of structure and function. Surface representations are often empirical associations. With surface representations, all the system knows is that an empirical association exists; it is unable to explain why, beyond repeating the association. Systems that use knowledge represented in different forms have been termed multilevel systems. Work isjust beginning in building such multilevel systems, and they will be a major research topic for this decade. Work needs to be done in studying and representing in a general way the different problem-solving activities an expert does. When you build expert systems, you realize that power behind them is that they provide a regimen (управлеи ие) for experts to crystallize and codify their knowledge, and in the knowledge lies the power. |