2014英语四级听力练习慢速4.3(1)_大学英语听力

2014英语四级听力练习慢速4.3(1)

　　With advances in materials, advances in design and analysis capability and the need for higher efficiency, you end up with you are driving yourself toward very lightweight designs.

　　Project scientist Richard Wahls says one of those designs is the long, truss-supported wing.

　　That allows you to stiffen the wing, keep the wing thin, grow the span to reduce, to reduce drag.

　　If someone decides to build such an aircraft, he or she will be able to use the results of NASA tests.

　　Researchers are also testing a new way of manufacturing composite materials. Instead of placing the fibers in straight lines, the material is instead placed around the points of heavy load, explains materials research engineer Karen Taminger. She also says new structural designs will help manufacturers to reduce the weight of airplanes and make them more energy efficient.

　　Fay Collier supervises NASAs Environmentally Responsible Aviation project. He says researchers also want to reduce the pollution that comes out of airplane engines.

　　We want to take advantage of alternative fuels and the emergence of alternative fuels, and we want to design advanced combustors to minimize the output of what I call oxides of nitrogen.

　　American scientists wanted to learn about the smoke of an airplane that burned a mixture of petroleum, an oil-based product, and an alternative-based fuel. To do this, they flew a second plane right behind the first one. Equipment on the second plane measured the percentage of pollutants contained in different fuel mixtures.