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The word conservation has a thrifty meaning. To conserve is to save and protect, to leave what we ourselves enjoy in such good condition that others may also share the enjoyment. Our forefathers had no idea that human population would increase faster than the supplies of raw materials; most of them, even until very recently, had the foolish idea that the treasures were "limitless" and "inexhaustible". Most of the citizens of earlier generations knew little or nothing about the complicated and delicate system that runs all through nature, which means that, as in a living body, an unhealthy condition of one part will sooner or later be harmful to all the others. Fifty years ago nature study was not part of the school work; scientific forestry was a new idea; timber was still cheap because it could be brought in any quantity from distant woodlands; soil destruction and river floods were not national problems; nobody had yet studied long-term climatic cycles in relation to proper land use; even the word "conservation" had nothing of the meaning that it has for us today. For the sake of ourselves and those who will come after us, we must now set about repairing the mistakes of our forefathers. Conservation should, therefore, be made a part of everyone's daily life. To know about the water table in the ground is just as important to us as a knowledge of the basic arithmetic formulas. We need to know why all watersheds need the protection of plant life and why the running current of streams and rivers must be made to yield their full benefit to the soil before they finally escape to the sea. We need to be taught the duty of planting trees as well as of cutting them. We need to know the importance of big, mature trees, because living space for most of man's fellow creatures on this planet is figured not only in square measure of surface but also in cubic volume above the earth. In brief, it should be our goal to restore as much of the original beauty of nature as we can.
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【单选题】二OO八年某建筑工地焊工黄某焊接时发现电焊机一次接线柱处冒烟而且闻到电线的焦糊味,于是就找来电工杨某进行维修,电工杨某发现是一次线接线螺丝松动,就用扳手将松动的螺丝拧紧后交给焊工黄某继续使用。焊工黄某当手触碰到电焊机时,大叫一声倒下,送医院抢救无效死亡。经查焊机一次接线端子电木板烧穿,螺丝碰到焊机外壳上导致电焊机外壳带电,焊工黄某触电死亡。一般要求焊机金属外壳接地(接零)的螺栓不得小于多少()。
A.
M5
B.
M6
C.
M8
D.
M10
【单选题】古希腊悲剧的基本主题是________。
A.
.人与自然的冲突
B.
人与命运的冲突
C.
.人与人的冲突
D.
.人与社会的冲突
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A.
串联校正
B.
反馈校正(并联校正)
C.
前馈校正
D.
滞后 校正
【多选题】校正装置加入系统中的位置不同,所起的校正作用不同,根据校正装置与系统不可变部分的连接方式,可分为( )基本的校正方法。
A.
串联校正
B.
反馈校正
C.
复合校正
D.
前馈校正
【多选题】基本校正方式有
A.
串联校正。
B.
局部反馈校正。
C.
前馈校正。
D.
混合/复合校正。
【单选题】右面漫画的哲学寓意是( )
A.
只要耐心
B.
人生发展不能“等靠要”
C.
自觉能动性是人区别于动物的根本特点
D.
思想意识是人脑对客观事物的反映
【多选题】根据校正装置和系统不可变部分的连接方式,通常可分成三种基本的校正方式: ; ; 。
A.
串联校正
B.
滞后 校正
C.
反馈校正(并联校正)
D.
前馈校正
【多选题】校正装置加入系统中的位置不同,所起的校正作用也不相同,根据校正装置与系统不可变部分的连接方式,可分为( )基本的校正方式。
A.
串联校正
B.
反馈校正
C.
复合校正
D.
前馈校正
【简答题】控制系统的基本的校正方式有____校正、____校正、____校正和____校正。
【简答题】根据校正装置和系统不可变部分的连接方式,通常可分成三种基本的校正方式:
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