新GRE阅读全真题详解：乙醇汽油(文章).

　　新GRE考试非常人性的一点，对于考题出的很严格，经过多次锤炼之后，能考验出考生们的水平。考生们可以根据题库的题目复习新GRE考试，下面就将新GRE阅读理解真题进行解析，为考生们彻底分析在GRE阅读中出现的真题，帮助考生们复习。一下就是新GRE阅读全真题详解：

　　1. 乙醇汽油

　　Although, recent years have seen substantial reductions in noxious pollutants from individual motor vehicles, the number of such vehicles has been steadily increasing consequently, more than 100 cities in the United States still have levels of carbon monoxide, particulate matter, and ozone (generated by photochemical reactions with hydrocarbons from vehicle exhaust) that exceed legally established limits. There is a growing realization that the only fective way to achieve further reductions in vehicle emissions—short of a massive shift away from the private automobile—is to replace conventional diesel fuel and gasoline with cleaner-burning fuels such as compressed natural gas, liquied petroleum gas, ethanol, or methanol.

　　All of these alternatives are carbon-based fuels whose molecules are smaller and simpler than those of gasoline. These molecules burn more cleanly than gasoline, in part because they have fewer, if and, carbon-carbon bonds, and the hydrocarbons they do emit are less likely to generate ozone. The combustion of larger molecules, which have multiple carbon-carbon bonds, involves a more complex series of reactions. These reactions increase the probability of incomplete combustion and are more likely to release uncombusted and photochemically active hydrocarbon compounds into the atmosphere. On the other hand, alternative fuels do have drawbacks. Compressed natural gas would require that vehicles have a set of heavy fuel tanks—a serious liability in terms of performance and fuel ficiency—and liquied petroleum gas faces fundamental limits on supply.

　　Ethanol and methanol, on the other hand, have important advantages over other carbon-based alternative fuels: they have a higher energy content per volume and would require minimal changes in the existing network for distributing motor fuel. Ethanol is commonly used as a gasoline supplement, but it is currently about twice as expensive as methanol, the low cost of which is one of its attractive features. Methanol’s most attractive feature, however, is that it can reduce by about 90 percent the vehicle emissions that form ozone, the most serious urban air pollutant.

　　Like any alternative fuel, methanol has its critics. Yet much of the criticism is based on the use of “gasoline clone” vehicles that do not incorporate even the simplest design improvements that are made possible with the use of methanol. It is true, for example, that a given volume of methanol provides only about one-half of the energy that gasoline and diesel fuel do; other things being equal, the fuel tank would have to be somewhat larger and heavier. However, since methanol-fueled vehicles could be designed to be much more ficient than “gasoline clone” vehicles fueled with methanol, they would need comparatively less fuel. Vehicles in corporating only the simplest of the engine improvements that methanol makes feasible would still contribute to an immediate lessening of urban air pollution.

　　以上就是新GRE阅读全真题详解，希望考生们通过对GRE阅读理解真题的复习，对于考试就会有更大的把握。在这里澳际教育预祝考生们取得理想成绩，达成留学梦想，更多关于新GRE阅读方面的经验请关注澳际教育。