[外语类试卷]大学英语六级模拟试卷306及答案与解析.doc
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1、大学英语六级模拟试卷 306及答案与解析 一、 Part I Writing (30 minutes) 1 Directions: For this part, you are allowed 30 minutes to write a composition on the topic Changes in Peoples Ways of Communication. You should write at least 150 words following the outline given below in Chinese:1. 以下图为依据描述 1975年和 1995年人们交流通讯方式的
2、变化情况 2. 说明引起变化的各种原因 3. 预测未来的情况二、 Part II Reading Comprehension (Skimming and Scanning) (15 minutes) Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-4, mark: Y (for YES) if the statement agrees with th
3、e information given in the passage; N (for NO) if the statement contradicts the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 The Hydrogen Economy It seems that every day there is a new announcement in the news about automobiles powered by fue
4、l cells. The promises are great, since fuel cells have the potential to very quickly double the efficiency of cars while significantly reducing air pollution. At the same time, there have been news stories for decades about the problems associated with petroleum. Everything from oil spills to ozone
5、(臭氧 ) alerts to global warming gets blamed on our dependence on fossil fuels. These two forces are leading the worm toward what is broadly known as the hydrogen economy. If the predictions are true, over the next several decades we will all begin to see an amazing shift away from the fossil fuel eco
6、nomy we have today toward a much cleaner hydrogen future. Problems with the Fossil Fuel Economy While fossil fuels have played an important role in getting society to the point it is at today, there are four big problems that fossil fuels create. Air pollution When cars burn gasoline, the internal c
7、ombustion engine also produces carbon monoxide, a poisonous gas Nitrogen oxides (氮氧化物 ), the main source of urban smog unburned hydrocarbons, the main source of urban ozone. Environmental pollution The process of transporting and storing oil has a big impact on the environment whenever something goe
8、s wrong. An oil spill, pipeline explosion or well fire can create a huge mess. Global warming The carbon dioxide coming out of every cars tailpipe is a greenhouse gas that is slowly raising the temperature of the planet. The ultimate effects are unknown, but it is a strong possibility that, eventual
9、ly, there will be dramatic climate changes that affect everyone on the planet. Dependence The United States, and most other countries, cannot produce enough oil to meet demand, so they import it from oil-rich countries. That creates an economic dependence. When Middle East oil producers decide to ra
10、ise the price of oil, the rest of the world has little choice but to pay the higher price. Advantages of the Hydrogen Economy The hydrogen economy promises to eliminate all of the problems that the fossil fuel economy creates. Therefore, the advantages of the hydrogen economy include. The eliminatio
11、n of pollution caused by fossil fuels When hydrogen is used in a fuel cell to create power, it is a completely clean technology. The only byproduct is water. There are also no environmental dangers like oil spills to worry about with hydrogen. The elimination of greenhouse gases If the hydrogen come
12、s from the electrolysis of water, then hydrogen adds no greenhouse gases to the environment. There is a perfect cycle-electrolysis produces hydrogen from water, and the hydrogen recombines with oxygen to create water and power in a fuel cell. The elimination of economic dependence The elimination of
13、 oil means no dependence on the Middle East and its oil reserves. Distributed production-Hydrogen can be produced anywhere that you have electricity and water. People can even, produce it in their homes with relatively simple technology. The problems with the fossil fuel economy are so great, and th
14、e environmental advantages of the hydrogen economy are so significant, that the push toward the hydrogen economy is very strong. Technological Hurdles(障碍 ) The big question with the hydrogen economy is, “Where does the hydrogen come from?“ After that comes the question of transporting, distributing
15、and storing hydrogen. Hydrogen tends to be large and tricky in its natural gaseous form. Once both of these questions are answered in an economical way, the hydrogen economy will be in place. Where does the hydrogen come from? There are two possible sources for the hydrogen: electrolysis (电解 ) of wa
16、ter Using electricity, it is easy to split water molecules to create pure hydrogen and oxygen. One big advantage of this process is that you can do it anywhere. For example, you could have a box in your garage producing hydrogen from tap water, and you could fuel your car with that hydrogen. Reformi
17、ng fossil fuels Oil and natural gas contain hydrocarbons-molecules consisting of hydrogen and carbon. Using a device called a fuel processor or a reformer, you can split the hydrogen off the carbon in a hydrocarbon relatively easily and then use the hydrogen. You discard the leftover carbon to the a
18、tmosphere as carbon dioxide. The second option is, of course, slightly perverse(不正当的 ). You are using fossil fuel as the source of hydrogen for the hydrogen economy. This approach reduces air pollution, but it doesnt solve either the greenhouse gas problem or the dependence problem. However, it may
19、be a good temporary step to take during the transition to the hydrogen economy. The interesting thing about the first option is that it is the core of the real hydrogen economy. To have a pure hydrogen economy, the hydrogen must be derived from renewable sources rather than fossil fuels so that we s
20、top releasing carbon into the atmosphere. Having enough electricity to separate hydrogen from water, and generating electricity without using fossil fuels, it will he the biggest change that we see in creating the hydrogen economy. Where will the electricity for the electrolysis of water come from?
21、Currently, about 68 percent of the electricity produced in the United States comes from coal or natural gas. All of that generating capacity will have to be replaced by renewable sources in the hydrogen economy. How Do You Store and Transport the Hydrogen? Hydrogen is a large gas of its kind, and it
22、 is not nearly as easy to work with as gasoline. Compressing the gas requires energy, and compressed hydrogen contains far less energy than the same volume of gasoline. However, solutions to the hydrogen storage problem are surfacing. For example, hydrogen can be stored in a solid form in a chemical
23、 called sodium borohydride (硼氢 ). Once the storage problem is solved and standardized, then a network of hydrogen stations and the transportation infrastructure will have to develop around it. The main barrier to this might be the technological sorting-out process. Stations will not develop quickly
24、until there is a storage technology that clearly dominates the marketplace. For instance, if all hydrogen powered ears from all manufacturers used sodium borohydride, then a station network could develop quickly. That sort of standardization is unlikely to happen rapidly, if history is any guide. Pr
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