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Scientists studying the impact of climate change on the Arctic need to consider ways to reduce their own carbon footprints(碳排放量), says Ryan Brook, a researcher who regularly flies north to study the health of caribous(驯鹿).He calls on scientists to show leadership by examining and sharing ways to reduce the impact of working in polar regions. “The importance of the research is not at question here. It is important to our understanding of and adapting to climate change. But we need to think about better approaches,” says Brook. “This is an issue for all scientists, though polar researchers often travel particularly long distances using commercial air travel. We also rely extensively on small aircraft, icebreakers, and snowmobiles, all of which produce large amounts of carbon.” Brook studies the health of caribou herds in Nunavut and Northwest Territories. He works with northern wildlife managers. This work typically takes him north five or six times per year and when he calculated his own carbon footprint, he was not happy with the result. “My research footprints are about the same as the annual footprints of an average Toronto resident. Basically, I have two footprints — my own personal life, which is moderate, and my research footprint.” Climate scientists can rightly argue that Arctic research is a specialized field and the community of scientists who travel north is relatively small. Even if all scientists working in the north reduced their carbon emissions, it would not make a big impact on the global scale. For Brook, it’s the option that matters. There are ways researchers can reduce the amount of carbon they use. Some helicopters use less fuel than others. Solar and wind power are alternatives to gas-fired generators. And while carbon offsets(抵消) don’t reduce the amount of carbon emitted, they are an easy first step. “There aren’t necessarily any easy answers, but we need to start talking about it,” says Brook. “This is particularly important for the next generation of scientists being trained and I hope to see them become leaders in this issue.” 小题1:What did Brook find when he calculated his own carbon footprints? A.His carbon footprints are more than the annual footprints of a Toronto resident. B.His personal life footprints are more than the annual footprints of a Toronto resident. C.His research footprints are about the same as his personal life footprints. D.His personal life footprints are more than his research footprints. 小题2: Brook’s opinion is challenged by the statement that . A.arctic research is very important B.the Arctic is a special environment C.the footprints of Arctic scientists are small D.Brook’s situation is a common phenomenon 小题3:We can infer from the last paragraph that . A.we should take actions immediately instead of just talking B.it’s easy to start talking about the problem of carbon emissions C.it’s necessary now to pay attention to the problem of research footprints D.the next generation of scientists are more interested in research footprints 小题4:What’s the main idea of the text? A.The importance of arctic research is not at question. B.Climate change becomes worse because of arctic research. C.Brook suggests ways of reducing the use of carbon. D.Scientists must look at their own carbon footprints.
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参考答案:
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【判断题】根据焦点位置的不同,双曲线的标准方程有两种不同的表达形式。
A.
正确
B.
错误
【单选题】在曲柄滑块机构中,如果取滑块为机架,则形成( )机构
A.
导杆
B.
摇杆
C.
定块
【简答题】三相异步电动机拖动恒转矩负载从基频向下的变频调速时,为了保持磁通不变,应保持()的条件。
【单选题】拖动恒转矩负载的三相 异步 电动机,保持磁通不变,当f1=50Hz时,n=2900r/min,若降低频率到f1=40Hz时,电动机的转速为( )。
A.
2900r/min
B.
2500r/min
C.
2300r/min
D.
2400r/min
【简答题】拖动恒转矩负载的三相异步电动机保持 E1/f1 = 常数,当f1 = 50Hz,n = 2900 r/min ,若频率降低到f1 = 40Hz,则电动机的转速为多少 ?(r/min)
【单选题】若拖动恒转矩负载的三相异步电动机保持f 1 /E 1 =常数,当f 1 =50Hz时,n=2900r/min.若降低频率到f 1 =45Hz时,则电动机的转速为()。
A.
2900/min
B.
2320r/min
C.
2600r/min
D.
2400r/min
【简答题】三相异步电动机基频以上变频调速,保持U 1 =U N 不变时,电动机的最大转矩将如何变化?能否拖动恒转矩负载?为什么?
【单选题】若拖动恒转矩负载的三相异步电动机保持E1/f1=常数,当f1=50Hz,n=2900r/min时,若降频率到f1=40Hz,电动机转速则为______。
A.
2900r/min
B.
2320r/min
C.
2300r/min
D.
2400r/min
【单选题】若拖动恒转矩负载的三相异步电动机保持 常数 , 当 f 1 =50Hz 时 , n=2900r/min 。若降低频率到 f 1 =40Hz 时 , 则电动机转速为 ____ 。
A.
2900r/min
B.
2320r/min
C.
2300r/min
D.
2400r/min
【单选题】双曲线的标准方程有()个
A.
一个
B.
两个
C.
三个
D.
四个
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