对水轮机调速器两组整定参数进行自动切换时,一般用____的辅助节点控制。
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对于开度或功率指令信号而言,还可以通过改变信号的____而减小开度或功率指令信号的实现时间。
水轮机调节系统是指以____作为控制器,以____作为控制对象构成的____控制系统。
1. Fads are common in the United States because ________.A. Americans are foolish and vainB. Americans can afford to follow fadsC. Americans want to see changes in their livesD. Americans are easily influenced by people from other countries2. The difference between a fad and a trend is that ________.A. a fad lasts longerB. a fad is more importantC. a trend lasts longerD. a trend will never change3.The elderly woman in the TV advertisement became popular, and this example shows that ________.A. Americans like old people as well as young peopleB. Americans sometimes like to follow the lives of ordinary peopleC. Americans enjoy following the lives of famous peopleD. Americans pay a lot of attention to people with special abilities4. The desire for money cannot explain fads in ________.A. languageB. fashionC. furnitureD. food5. According to the text, fads are common in any country that ________.A. has a long historyB. is in the WestC. is famous for its fashion designD. is developed
下列哪种说法是不正确的
A. 子代数和原代数是同种的代数系统。
B. 最大和最小子代数称为V 的平凡子代数。
C. 对于任何代数系统 V ,其子代数不一定都存在。
D. 最大的子代数就是V 本身.