皮皮学,免费搜题
登录
logo - 刷刷题
搜题
【简答题】
After the violent earthquake that shook Los Angeles in 1994, earthquake scientists had good news to report: The damage and death toll (死亡人数) could have been much worse. More than 60 people died in this earthquake. By comparison, as earthquake of similar intensity that shook America in 1988 claimed 25,000 victims. Injuries and deaths were relatively less in Los Angeles because the quake occurred at 4:31 a.m. on a holiday, when traffic was light on the city’s highways. In addition, changes made to the construction codes in Los Angeles during the last 20 years have strengthened the city’s buildings and highways, making them more resistant to quakes. Despite the good new, civil engineers aren’t resting on their successes. Pinned to their drawing boards are blueprints (蓝图) for improved quake-resistant buildings. The new designs should offer even greater security to cities where earthquakes often take place. In the past, making structures quake-resistant meant firm yet flexible materials, such as steel and wood, that bend without breaking. Later, people tried to lift a building off its foundation, and insert rubber and steel between the building and its foundation to reduce the impact of ground vibrations. The most recent designs give buildings brains as well as concrete and steel supports. Called smart buildings, the structures respond like living organisms to an earthquake’s vibrations. When the ground shakes and the building tips forward, the computer would force the building to shift in the opposite direction. The new smart structures could be very expensive to build. However, they would save many lives and would be less likely to be damaged during earthquakes. 21. One reason why the loss of lives in the Los Angeles earthquake was comparatively low is that ________. A) new computers had been installed in the buildings B) it occurred in the residential areas rather than on the highways C) large numbers of Los Angeles residents had gone for a holiday D) improvements had been made in the construction of buildings and highways 22. The function of the computer mentioned in the passage is to ________. A) counterbalance an earthquake’s action on the building B) predict the coming of an earthquake with accuracy C) help strengthen the foundation of the building D) measure the impact of an earthquake’s vibrations 23. The smart buildings discussed in the passage ________. A) would cause serious financial problems B) would be worthwhile though costly C) would increase the complexity of architectural design D) can reduce the ground vibrations caused by earthquakes 24. It can be inferred from the passage that in minimizing the damage caused by earthquakes attention should be focused on ________. A) the increasing use of rubber and steel in capital construction B) the development of flexible building materials C) the reduction of the impact of ground vibrations D) early forecasts of earthquakes 25. The author’s main purpose in writing the passage is to ________. A) compare the consequences of the earthquakes that occurred in the U.S. B) encourage civil engineers to make more extensive use of computers C) outline the history of the development of quake-resistant building materials D) report new developments in constructing quake-resistant buildings Passage Four Questions 26 to 30 are based on the following passage. Even plants can run a fever, especially when they’re under attack by insects or disease. But unlike humans, plants can have their temperature taken from 3,000 feet away-straight up. A decade ago, adapting the infrared (红外线) scanning technology developed for military purposes and other satellites, physicist Stephen Paley came up with a quick way to take the temperature of crops to determine which ones are under stress. The goal was to let farmers precisely target pesticide (杀虫剂) spraying rather than rain poison on a whole field, which invariably includes plants that don’t have pest (害虫) problems. Even better, Paley’s Remote Scanning Services Company could detect crop problems before they became visible to the eye. Mounted on a plane flown at 3,000 feet at night, an infrared scanner measured the heat emitted by crops. The data were transformed into a color-coded map showing where plants were running “fevers”. Farmers could then spot-spray, using 50 to 70 percent less pesticide than they otherwise would. The bad news is that Paley’s company closed down in 1984, after only three years. Farmers resisted the new technology and long-term backers were hard to find. But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to get back into operation. Agriculture experts have no doubt the technology works. “This technique can be used on 75 percent of agricultural land in the United States,” says George Oerther of Texas A&M. Ray Jackson, who recently retired from the Department of Agriculture, thinks remote infrared crop scanning could be adopted by the end of the decade. But only if Paley finds the financial backing which he failed to obtain 10 years ago. 26. Plants will emit an increased amount of heat when they are ________. A) sprayed with pesticides B) facing an infrared scanner C) in poor physical condition D) exposed to excessive sun rays 27. In order to apply pesticide spraying precisely, we can use infrared scanning to ________. A) estimate the damage to the crops B) draw a color-coded map C) measure the size of the affected area D) locate the problem area 28. Farmers can save a considerable amount of pesticide by ________. A) resorting to spot-spraying B) consulting infrared scanning experts C) transforming poisoned rain D) detecting crop problems at an early date 29. The application of infrared scanning technology to agriculture met with some difficulties due to ________. A) the lack of official support B) its high cost C) the lack of financial support D) its failure to help increase production 30. Infrared scanning technology may be brought back into operation because of ________. A) the desire of farmers to improve the quality of their produce B) growing concern about the excessive use of pesticides on crops C) the forceful promotion by the Department of Agriculture D) full support from agricultural experts
手机使用
分享
复制链接
新浪微博
分享QQ
微信扫一扫
微信内点击右上角“…”即可分享
反馈
参考答案:
举一反三
【简答题】已知单位负反馈系统的开环传递函数为 ,当输入信号为单位阶跃信号时系统的稳态误差 。
【简答题】若要对某一图层中的所有不透明区域用前景色进行填充,选中图层调板上的“保留透明区域”选项后, 按Alt+Delete键进行填充。
【简答题】已知单位负反馈系统的开环传递函数为 求当 时,以 a 为参变量的根轨迹。
【单选题】已知单位负反馈系统的开环传递函数为【图片】,当输入信号是【图片】时,系统的稳态误差是( )。
A.
20
B.
10
C.
D.
0
E.
2
F.
40
【简答题】已知单位负反馈系统开环传递函数为 ,当 r(t) 为 1(t) 时,求系统的稳态误差 e ss。
【简答题】已知单位负反馈系统的开环传递函数为 求当 时,以 为参变量的根轨迹。
【单选题】扫黑除恶专项斗争把专项治理和系统治理、( )、依法治理、源头治理结合起来。
A.
综合治理
B.
综合整理
C.
科学治理
【判断题】. 若要对某一图层中的所有不透明区域用前景色进行填充,选中图层调板上的“保留透明区域”选项后, 按Alt+Delcte键进行填充
A.
正确
B.
错误
【简答题】已知单位负反馈系统的开环脉冲传递函数为 当采样周期T=1s时,闭环系统的输入信号为 ,试求系统的稳态误差。
【多选题】已知某单位负反馈系统的开环传递函数为 ,则下面说法正确的是
A.
该系统开环传递函数的 Nyquist 图是以( 0.5,0) 为圆心、 0.5 为半径的圆
B.
该系统开环传递函数的 Bode 图渐近线幅频图当 ω > 1/K 时, | L (i ω )|>1
C.
系统是结构稳定的
D.
该系统开环传递函数的 Bode 图幅相频图在 90° 到 0 ° 之间
相关题目:
参考解析:
知识点:
题目纠错 0
发布
创建自己的小题库 - 刷刷题