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具有理想约束的质点系在某一位置处于平衡的必要和充分的条件是，对于任何虚位移，作用于质点系的各力所作的虚功总和为零。()
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刚结点只传递力矩，不传递力。()
根据核安全文化的定义，核安全文化工作分为()推进核安全文化建设以及提高()核安全文化素养。
在EADI上速度偏差刻度位于指示空速读数的右侧，有一个黄色的中间基准标线，在标线的上下两侧各有两个刻度点，当快慢指针靠近最上面刻度点表示：
Directions:Read the text below. Write an essay about 120 words, in which you should summarize the key points of the text and make comments on them. Try to use your own words.
It seems the nation’s younger citizens are finally favoring the beauty of the natural world over the cries of amateur singers.
The BBC has confirmed that the first three episodes of Planet earth Ⅱ have attracted more viewers in the 16 to 34 age group than The X Factor. The best ratings so far were for the second episode, which brought in 1.8 million young viewers compared to The X Factor’s 1.4 million.
The show’s narrator, Sir David Attenborough credited improvements in technology with the show’s increased success in its second season, which have brought animals close to the viewer and made their environments look real.
“You feel like the camera is with the animals.”said producer Mike Gunton. “It&39;s very active. For example, you see a monkey leaping through the forest. Normally you&39;ll stand back to film that. But here the monkey almost jumps over your shoulder. The camera is running with it. Visually, Planet Earth told you to look down on the Earth and see the scale of the planet. What Planet earth Ⅱ is doing is saying “Let’s get ourselves into the lives of the animals, and see it from their perspective.”
“The music of Hans Zimmer is also a big factor,”added Attenborough. “That pleases me enormously.” Besides technology and music, Attenborough said that viewers are “reconnecting with a planet whose beauty is spoiled and whose health is falling.” He believes that young people are learning that their future is linked to that of the environment.
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