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It is a pleasure to be here today to commemorate the first Earth Day with you by looking through this 'Window on the American Environment'. While I have not yet viewed the television series, from the accompanying book I can see that it is a very ambitious effort. The producers have interviewed a large number of environmental leaders in the United States, from early founders back in the 1970s through those involved in the contemporary movement. // I am sure you will hear many different opinions, because the diversity of the American environmental movement is part of its strength. The ability of individuals and non-governmental organizations to express their opinions and make their voices heard in the press and in the electoral process is the root of the movement and why it flourishes today. I vividly remember going outdoors with my elementary school class on Earth Day 1970 to examine our environment by looking at what grew in the pond behind our school. The motto of that first Earth Day was 'think globally, act locally', and our young teacher wanted us to better understand what was right around us. // Nowadays teachers have access to all sorts of wonderful educational materials to help students study the environment and learn about concepts like biodiversity, climate change and protection of the ozone layer that were still foreign to us in 1970. But we knew then about toxic chemicals, deforestation, water pollution—the subject of our pond study—and land use issues, and we were learning to understand how much of an impact these could make on our futures. // Earth Day 1970 was a novel idea proposed by individuals—not a government—that grew on its own, so that in that very first year, over 20 million Americans participated. We said, 'think globally', but Americans were not yet thinking as much beyond their borders as we do today. Equally it would have been unimaginable in 1970 that China would air a 22-part television series on the United States. It would be another two years before the images of President Nixon's famous trip to China would be broadcast on our television screens in the United States and we started to have the opportunity to learn about each other. // Today the United States and China have a great deal to celebrate together for Earth Day. We are working together in areas from water conservation to the protection of endangered species to the development of new, cleaner sources of energy. We have an active program to work with Beijing to support its goal of a Green Olympics in 2008. Together we are researching climate change and exploring the possibilities for using hydrogen and fusion as energy sources. The United States government, through agencies like the Environmental Protection Agency, the Department of Energy, the Fish and Wildlife Service, the National Parks Service and dozens more has an active program of cooperation with its Chinese counterparts. //
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【简答题】当半径为r的圆,圆心角所对的圆弧长是 ,那么角 的弧度数的绝对值是 (1) ; 2.规定:正角的弧度为 (2); 负角的弧度为 (3) ; 零角的弧度为 (4).
【单选题】进行等级保护定义的最后一个环节是:
A.
信息系统的安全保护等级由业务信息安全保护等级和系统服务安全保护等级的较低者决定
B.
信息系统的安全保护等级由业务信息安全保护等级和系统服务安全保护等级的较高者决定
C.
信息系统的安全保护等级由业务信息安全保护等级决定
D.
信息系统的安全保护等级由系统服务安全保护等级决定
【单选题】已知一圆弧的弧长等于它所在圆的内接正三角形的边长,则这段弧所对的圆心角的弧度数是(   )
A.
B.
C.
D.
2
【单选题】正角的弧度数是什么数?
A.
正数
B.
负数
C.
【简答题】直动尖顶从动件盘形凸轮机构的压力角是指(__);直动滚子从动件盘形凸轮机构的压力角是指(__);而直动平底从动件盘形凸轮机构的压力角等于(__)。
【单选题】直动平底从动件盘形凸轮机构的压力角 。
A.
恒等于0
B.
等于常数
C.
随凸轮转角变化
【简答题】直动尖顶从动件盘形凸轮机构的压力角是指();直动滚子从动件盘形凸轮机构的压力角是指();而直动平底从动件盘形凸轮机构的压力角等于常数。
【判断题】负角的弧度数是正数 ( )
A.
正确
B.
错误
【判断题】利用matlab roblocks 模块在simulink进行仿真,当输入角度为[0 pi/2 -pi/2 0 0 0]时,此时相对于世界坐标系下的雅可比矩阵为:【图片】
A.
正确
B.
错误
【简答题】狭义上的信息安全等级保护定义是什么?
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