2010-2019考研英语二新题型.pdf

2010 Copying Birds May Save Aircraft Fuel Both Boeing and Airbus have trumpeted the efficiency of their newest aircraft. The 787 and 350 respectively . Their clever designs and lightweight composites certainly make a difference . But a group of researchers at Stanford University , led by Ilan Kroo , has suggested that airlines could take a more naturalistic approach to cutting jet-fuel use and it would not require them to buy new aircraft. The answer, says Dr Kroo , lies with birds . Since 1914, scientists have known that birds flying in formation-a V-shape-expend less energy. The air flowing over a bird ’wingss curls upwards behind the wingtips . a phenomenon known as upwash. Other birds flying in the upwash experience reduced drag, and spend less energy propelling themselves . Peter Lissaman, an aeronautics expert who was formerly at Caltech and the University of Southern California ,has suggested that a formation of 25 birds might enjoy a range increase of 71%. When applied to aircraft, the principles are not substantially different . Dr Kroo and his team modeled what would happen if three passenger jets departing from Los Angeles, San Francisco and I as Vegas were to assemble over Utah, assume an inverted V-formation occasionally change places so all could have a turn in the most favourable positions , and proceed to London. They found that the aircraft consumed as much as 15% less fuel (coupled with a reduction in carbon-dioxide output). Nitrogen-oxide emissions during the cruising portions of the flight fell by around a quarter. There are , of course , knots to be worked out . One consideration is safety , or at least the perception of it . Would passengers feel comfortable travelling in companion? Dr Kroo points out that the aircra