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专题限时训练(三十七) [科普知识型阅读理解(一)]

(限时：25分钟)

(一)

Traffic lights are key tools for regulating traffic now.They are not, however, perfect. Drivers exchange the traffic jams that would happen at unmanaged crossings for a pattern of stop-go movement that can still be annoying, and which burns more fuel than a smooth passage would.

Creating such a smooth passage means adjusting a vehicle's speed so that it always arrives at the lights when they are green.That is theoretically possible, but practically hard.Roadside signs wired to traffic lights can help get the message across a couple hundred metres from a crossing, but such signs are expensive, and are not widespread.Margaret Martonosi and Emmanouil Koukoumidis at Princeton University, and Li-Shiuan Peh at the Massachusetts Institute of Technology, however, have an idea that could make the process cheaper and more effective.Instead of a hardwired network of signs, they propose to use mobile-phone applications.

For a driver to benefit, he must load the team's software, named SignalGuru, into his phone and then put it on a special thing attached to the inside of his car's windscreen, with the camera lens (镜头) pointing forward.SignalGuru is designed to detect traffic lights and track their status as red, yellow or green.It broadcasts this information to other phones in the area that are fitted with the same software, and—if there are enough of them, the phones thus each know the status of most of the lights around town.Using this information, SignalGuru is able to calculate the traffic-light schedule for the area and suggest the speed at which a driver should travel in order to avoid red lights.

Tests in Cambridge, Massachusetts, where five drivers were asked to follow the same route for three hours, and in Singapore, where eight drivers were asked to follow one of two routes for 30 minutes, revealed that SignalGuru was capable of predicting traffic-light activity with an accuracy of 98.2% and 96.3% respectively, in the two cities.This was particularly impressive because in Cambridge the lights shifted,

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roughly half-way through the test, from their unbusy schedule to their afternoon-traffic schedule, while in Singapore lights are adaptive, using detectors fixed under the road to determine how much traffic is present and thus when a signal should change.In neither case was SignalGuru fooled.

Fuel consumption fell, too—by about 20%.SignalGuru thus reduces both annoyance and fuel use, and makes going back and forth to work a slightly less horrible experience.

1．Roadside signs wired to traffic lights are not the best way to create a smooth passage because ________，

A．they are expensive and easily break B．they are too costly and not widely used C．they are complex and confusing to drivers

D．they are theoretically possible but practically useless 2．SignalGuru is an application used on ________. A．a camera B．a computer C．a mobile phone

D．a GPS system in one's car

3．With the information it collects and processes, SignalGuru is able to ________.

A．help drivers avoid traffic accidents B．allow drivers to adjust their speed C．change the traffic lights in advance D．send information to all cell phones

4．The tests in Cambridge and Singapore were impressive because SignalGuru ________.

A．proved to be unreliable B．operated at a high speed C．functioned rather stably D．understood drivers'schedules

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(二)

Have you ever wondered why stems(茎)grow upwards and roots downwards? Why plants always seem to turn towards the light and climbing plants run up rather than down? The answer is simple: auxin(生长素), a chemical substance that controls growth in plants.

Auxin gives away its secrets

Auxin is a plant hormone(激素). Darwin was already interested in it in the 19th century. Only in recent years, however, has the hormone started to give away its secrets, thanks to intensive molecular research. Auxin is produced in the young, growing parts of plants and then transported throughout the plant—to a low-lying stem for example. The stem needs to straighten out as soon as possible to be able to absorb the topside, resulting in the underside growing faster and the stem straightening out. For the same reason, plants in front of windows will always turn to the light. This active regulation of auxin transport allows plants to take ideal advantage of local and changing conditions.

A new means of transport for auxin

The transport of auxin through the plant plays a vital role. And, from all appearances, it is not a simple matter. The researchers identified an important new link and means of transport for auxin: PILS proteins (蛋白质). PILS proteins are vital for auxin-dependent plant growth and adjust the intracellular(细胞内的)storage of the hormone. It is exactly this compartmentalizing (分类) of auxin that seems functionally important for the various developmental processes.

Growing crops more efficiently: the right amount of auxin in the right place

Higher auxin levels at the right moment and in the right place result in better growth and greater harvest. Better adjustment of auxin levels would make plants grow more efficiently. The researchers hope to contribute to the development of more efficient growing processes by continuing to sort out auxin transport

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