今天给大家整理出的26重点资源是 👇
• 26英语-新题型英语真题汇总✔
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📚【英语二新题型汇总】2010——2024年📚
2010英语二【判断正误】
Directions:
Read the following text and decide whether each of the statements is true or false. Choose T if the statement is true or F if the statement is not true. Mark your answers on ANSWER SHEET 1。 (10 points)
Copying Birds May Save Aircraft Fuel
Both Boeing and Airbus have trumpeted the efficiency of their newest aircraft, the 787 and A350 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’s wings 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 Las 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 aircraft could be separated by several nautical miles, and would not be in the intimate groupings favoured by display teams like the Red Arrows. A passenger peering out of the window might not even see the other planes. Whether the separation distances involved would satisfy…
