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  3. Commuter trains are often stuffy and crowded, and they frequently fail to ru

Commuter trains are often stuffy and crowded, and they frequently fail to ru

游客2023-09-01  56
问题     Commuter trains are often stuffy and crowded, and they frequently fail to run on time. As if that were not bad enough, Tsuyoshi Hondou, a physicist at Tohoku University in Japan, published a paper in 2002 that gave commuters【C1】______  another mason to feel uncomfortable. Dr Hondou examined mobilephone usage in enclosed spaces such as railway carriages, buses and lifts, all of which are, in 【C2】______ , metal boxes. His model predicted that a large number of passengers crowded together, all blathering, sending text messages, or browsing the web on their phones, could produce levels of electromagnetic radiation that【C3】______  international safety standards. That is because the radio waves produced by each phone are reflected off the metal walls of the carriage, bus or lift. Enough radiation escapes to allow the phone to communicate with the network, but the rest bathes the inside of the carriage with bouncing microwaves.
    This sounds worrying. But maybe it isn’t after all. In a paper published recently in Applied Physics Letters, Jaime Ferret and Lucas Fernandez Seivane from the University of Oviedo in Spain along with colleagues from the Polytechnic University of Madrid and Telefonica Moviles, a Spanish mobile operator【C4】______ Dr Hondou’s findings. They conclude that the level of radiation is safe after all.
    The【C5】______ addition to the new research is the effect of the passengers themselves. While each phone produces radiation that bounces around the car, the passengers absorb some of it, which has the effect of reducing the overall intensity, just as the presence of an audience changes the acoustics of a concert hall,【C6】______  it less reverberant. Dr Hondou’s model, in short, was valid only in the case of a single passenger sitting in an empty carriage with an active mobile phone on every seat.
    While Dr Hondou acknowledged this in his original paper, he did not【C7】______ calculate the effect that leaving out the other passengers would have on the radiation level. As a result, say the authors of the new paper, he significantly overestimated the level of electromagnetic radiation. When one is sitting on a train, Dr Ferrer and his colleagues found, the most important sources of radiation are one’s own phone, and those of one’s 【C8】______ neighbours. The radiation from these sources far exceeds that from other phones or from waves bouncing around the carriage. And all these sources together produce a level of radiation within the bounds 【C9】______  by the ICNIRP, the international body that regulates such matters.
    People concerned about the effects of mobile phone radiation are unlikely to take much comfort from Dr Ferrer’s results. They worry that even small amounts of microwave radiation within the ICNIRP’s limits may have adverse health effects. The evidence so far is ambiguous, 【C10】______  and sparse. Indeed, Dr Ferret says he was surprised at how little research has been done in this area.
A) exceed                 I) recently
B) quite                  J) specifically
C) consistent             K) profit
D) inconsistent           L) defined
E) dispute                M) key
F) yet                    N) essence
G) represent              O) immediate
H) making [br] 【C5】
选项
答案 M
解析 此处需要一个形容词修饰名词，key意为“关键的”。
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