题目内容
Superconductor Ceramic (陶瓷)An underground revolution begins this winter. With the flip (轻击) of a switch, 30,000 homes in one part of Detroit will soon become the first in the country to receive electricity transmitted by ice-cold high-performance cables. Other American cities are expected to follow Detroit"s example in the years ahead, which could conserve enormous amounts of power.The new electrical cables at the Frisbie power station in Detroit are revolutionary because they are made of superconductors. A superconductor is a material that transmits electricity with little or no resistance. Resistance is the degree to which a substance resists electric current. All common electrical conductors have a certain amount of electrical resistance. They convert at least some of the electrical energy passing through them into waste heat. Superconductors don"t. No one understands how superconductivity works. It just does.Making superconductors isn"t easy. A superconductor material has to be cooled to an extremely low temperature to lose its resistance. The first superconductors, made more than 50 years ago, had to be cooled to-263 degrees Celsius before they lost their resistance. Newer superconducting materials lose their resistance at-143 degrees Celsius.The superconductors cable installed at the Frisbie station is made of a ceramic material that contains copper, oxygen, bismuth (铋), strontium (锶), and calcium (钙). A ceramic is a hard, strong compound made from clay or minerals. The superconducting ceramic has been fashioned into a tape that is wrapped lengthwise around a long tube filled with liquid nitrogen. Liquid nitrogen is super cold and lowers the temperature of the ceramic tape to the point where it conveys electricity with zero resistance.The United States loses an enormous amount of electricity each year to resistance. Because cooled superconductors have no resistance, they waste much less power, other cities are watching the Frisbie experiment in the hope that they might switch to superconducting cable and conserve power, too. What is the benefit of the revolution mentioned in the first paragraph
查看答案
搜索结果不匹配？点我反馈
更多问题
The CarCars are an important part of life in the United States. Without a car most people feel that they are poor. And even if a person is poor he doesn"t feel really poor when he has a car.Henry Ford was the man who first started making cars in large numbers. He probably didn"t know how much the car was going to affect American culture. The car made the United States a nation on wheels. And it helped make the United States what it is today.There are three main reasons why the ear becomes so popular in the United States. First of all, the country is a huge one and Americans like to move around in it. The car provides the most comfortable and cheapest form of transportation. With a car people can go anyplace without spending a lot of money.The second reason why cars are popular is the fact that the United States never really developed an efficient and inexpensive form of public transportation. Long-distance trains have never been as common in the country as they are in other parts of the world. Nowadays there is a good system of air-service provided by planes. But it is too expensive to be used frequently.The third reason is the most important one, though. The American spirit of independence is what really made cars popular. Americans don"t like to wait for a bus, or a train or even a plane. They don"t like to have to follow an exact schedule. A car gives them the freedom to schedule their own time. And this is the freedom that Americans want most to have.The gas shortage has caused a big problem for Americans. But the answer will not be a bigger system of public transportation. The real solution will have to be a new kind of car, one that does not use so much gas. "A nation on wheels" means that ______.
DennyHis nickname is Denny". He weighs 400 pounds; he is fearless and he never goes to sleep on the job. An ideal security guard For many situations he may be. And if he"s so good that you wish you had a dozen like him, just place your order. Denny is a robot guard.Denny can detect, within a 150-thor radius, the presence of anything or anybody that shouldn"t be there. Its swiveling (旋转) head contains microwave and infrared sensors that can detect people as well as smoke. In future editions the head will also contain sensors that can smell the weak smell of a human body.A high-resolution TV camera in Denny"s head is on at all time. When something unexpected comes into view, the TV transmitter switches on. Thus the human overseer (看管人) in the control center sees the sudden appearance of a picture on the monitor screen. At the same time the picture is automatically videotaped.Normal speed of the robot guards is about one mile an hour, and they can even talk: "you have been detected," warns the voice from the clever guard. Denny is designed to patrol corridors and other areas after lock-down hours (of course, he can work round the clock when necessary), not to move among people. If, say, a prisoner does get near the corridor where he should not be, it"ll immediately tell its base station by radio.Denny has understandable limitations. He can"t open doors or watch stairs, for example, or distinguish a friend from an enemy. Thus he will have to go about unarmed. And he won"t be able to replace human security guards where people move about freely. Denny is a robot guard, who ______.
The depiction of the lives of black people in the south is graphic.
Artificial SpeechBecause speech is the most convenient form of communication, in the future we want essentially natural conversations with computers. The primary point of contact will be a simple device that will act as our window into the world. It will have to be small enough to slip into our pocket, so there will be a screen but no keyboard: you will simply talk to it. The device will be permanently connected to the Internet and will keep relevant information up to you as it comes in. Such devices will evolve naturally in the next five to ten years.Just how quickly people will adapt to a voice-based Internet world is uncertain. Many believe that, initially at least, we will need similar conventions for the voice to those we use at present on screen: click, back, forward, and so on. But soon you will undoubtedly be able to interact by voice with all those IT-based services you currently connect with over the Internet by means of a keyboard. This will help the Internet serve the entire population.Changes like this will encompass (围绕，包围) the whole world. Because English is the language of science, it will probably remain the language in which the technology is most advanced, but most speech-recognition techniques are transferable to other languages provided (假如，若是) there is sufficient motivation to undertake the work.Of course, in any language there are still huge problems for us to solve. Carefully dictated, clear speech can now be understood by computers with only a 4～5 percent error rate, but even the most advanced technology still records 30～40 percent errors with spontaneous speech. Within ten years we will have computers that respond to goal-directed conversation, but for a computer to have a conversation that takes into account human social behaviors is probably 50 years off. We are not going to be chatting to the big screen in the living room just yet.In the past, insufficient speed and memory have held us back, but these days they are less of an issue. However, there are those in the IT community who believe that current techniques will eventually hit a brick wall. Personally, I believe that incremental (不断增长的) developments in performance are more likely. But it is true that by about 2040 or so, computer architectures will need to become highly parallel (并行的) if performance is to keep increasing. Perhaps that will inspire some radically new approaches to speech understanding that will replace the methods we are developing now. In the future, people will talk to a computer instead of typing and clicking.
微信支付 
支付宝支付