转子振动和轴承振动有何区别？
参考答案：
转子的绝对振动等于转子的相对振动与轴承对基础振动的矢量和.
读某国工业化、城市化进程比较图，回答1~2题。
1、关于该国工业化、城市化进程特点的叙述，正确的是：
①城市化与工业化呈同步增长趋势、②阶段Ⅰ城市化进程速度比阶段Ⅱ快、③该国可能属发达国家、④阶段Ⅱ，工业化促进了城市化 [ ]
B、①②
C、③④
D、②④
2、阶段Ⅲ，该国新增就业机会主要来自：
①资金密集型产业、②技术密集型产业、③资源密集型产业、④现代服务业 [ ]
A、①③
Children are a relatively modem invention. Until a few hundred years ago they look like adult, wearing grown-up clothes and grown-up expressions, performing grown-up tasks. Children did not exist because the family as we know it had not evolved. Children today not only exist; they have taken over in no place more than in America, and at no time more than now. It is always Kids Country here. Our civilization is child-centered, child-obsessed. A kid’s body is our physical ideal. In Kids Country we do not permit middle-aged. Thirty is promoted over 50, but 30 knows that soon his time to be overtaken will come. We are the first society in which parents expect to learn from their children. Such a topsy-turvy situation has come to abort at least in part because, unlike the rest of the world, ours is an immigrant society, and for immigrants the only hope is in the kids. In the Old Country, that is, Europe, hope was in the father, and how much wealth he could accumulate and pass along to his children. In the growth pattern of America and its ever- expanding frontier, the young man was ever advised to GO WEST; the father was ever inheriting from his son. Kids Country may be the inevitable result. Kids Country is not at all bad. America is the greatest country in the world to grow up in because it is Kids Country. We not only wear kids clothes and eat kids food; we dream kids dreams and make them come tree. It was, after all, a boys’ game to go to the moon. If in the old days children did not exist, it seems equally true today that adults, as a class, have begun to disappear, condemning all of us to remain boys and girls forever, jogging and doing push-ups against eternity.
The sentence "Children are a relatively modem invention" underlined in Paragraph 1 means that children ______ .
A．were exactly the same as adults a few hundred years agoB．did not exist at that time because there were no families yetC．were not different from adults in physical appearanceD．were not different from adults
