【判断题】
数字信号是不连续的，在时间和幅度上都是离散的电信号。
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相关试题
【判断题】
运算放大器是一种高放大倍数的直接耦合放大器。
【判断题】
只有当稳压电路两端的电压小于稳压管击穿电压时，才有稳压作用。
【判断题】
逆变器是将直流变换成频率和幅度均可调的直流。
【判断题】
集成运算放大器在信号运算方面可完成比例.求和.积分.微分.乘法.除法等运算。
【判断题】
在逻辑运算中，能把所有可能条件组合并将其结果一一对应列出的表格称为数值表。
【判断题】
可关断可控硅可用于数字电路，组成单稳态.双稳态.环形计数等电路。
【判断题】
凝汽式发电厂既供给用户电能，又供给热能，因此总效率较高。
【判断题】
按负荷发生的时间不同，电力负荷可分为高峰负荷.低俗负荷和平均负荷。
【判断题】
电压变动幅度是指实际电压偏离额定值的大小。
【判断题】
.提高电力网的电压水平，可以有效降低电力网的功率损耗。
【判断题】
电力线路和热力线路连接起来构成的整体。
【判断题】
计算短路电流的目的是为了选择有足够机械稳定性和热稳定性的设备。
【判断题】
最大运行方式是系统在该方式下运行，具有最大的短路阻抗。
【判断题】
最小运行方式是系统在该方式下运行，发生短路后产生的短路电流最小。
【判断题】
接地装置的接地电阻可采用电压电流表法进行测量。
【判断题】
在中性点绝缘的系统中，可以采用保护接零。
【判断题】
发电厂和变电所的电气主接线).备用容量.运行方式以及各种保护的能力有关。
【判断题】
电力系统动态稳定的条件是转子在加速期间储存的动能等于过剩转矩对系统所做的功。
【判断题】
偏差不得超过土0．5 Hz；不足3*106kW的系统其允许偏差不得超过±0．2 Hz。
【判断题】
周期小于该点距离保护某段的整定时间时，则该段距离保护不会误动作。
【判断题】
电能在各级电网中输送时的损耗量占供电量的百分比称为线路损耗。
【判断题】
热稳定的要求，同时还应考虑运行中的电晕。
【判断题】
系统发生振荡时，应先使频率尽可能相等，再采取提高发电机励磁和提高系统电压的措施。
【判断题】
通过提高功率因数确定补偿容量的方法简单明确，为国内外所通用。
【判断题】
电阻中电能的损耗不应超过10W(指电网在额定电压时)。
【判断题】
并联电容器可用来产生无功，减少线路的无功输送，减少电压损失。
【判断题】
过剩时便欠励磁运行。由此可知，改变调相机励磁电流的大小，就可调节无功功率。
【判断题】
在调相机的励磁回路中不装设熔断器，可以避免因熔断器熔断而使励磁回路开路。
【判断题】
在一般的情况下，变压器总是将高压绕组放在里面靠近铁芯处，将低压绕组放在外面。
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___ the huge financial benefits, biological companies have been rushing to set up laboratories and new research projects.
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Unfortunately, ___ lack of funds, the studies he began just two months ago, had to be ended early.
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As a person who loves peace, he is committed ___ realizing peace between countries.
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___ that the patient smokes 50 cigarettes a day, it would be reasonable to assume there is some lung damage.
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___ all obstacles and failures, the scientist continued doing his experiments day and night.
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I’m willing to ___ that a larger car would have cost more, but I still think we should have bought one.
A. withdraw
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Manufacturing (制造) companies spend millions of pounds on advertisements, trying to ___ customers that their products are better than those of other companies.
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He is not the right person for the project: he is not very technically minded and ___, he does not have the sense of responsibility.
A. instead
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Death rates declined in many places, partly because of the ___ in hunger.
A. decrease
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In deciding whether or not a situation is safe, pilots must be taught to assume that the worst will happen, and then to ___ whether there is a risk or not.
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【单选题】
Measures have been taken to ensure that no student will have to ___ of college for economic reasons.
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You shouldn’t ___ – let your children make their own decisions.
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This is a huge and difficult project and if you take it up, you ___ many difficulties.
A. like to encounter
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The ability to live for a long time without water is characteristic ___ the camel.
A. of
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C. about
D. in
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Rising sales is a good ___ that this product is well received in the market.
A. response
B. convention
C. indication
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When tourists travel abroad, they are sometimes ___ by the local people because the tourists don’t know the real value of products.
A. turned in
B. given chase
C. wrapped up
D. ripped off
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The professor’s lecture ___ the capacity of his young audience. They all looked puzzled at him.
A. pointed out
B. went beyond
C. contributed to
D. kept off
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We must ___ on the amount of time we use on this project.
A. cut both ways
B. cut in line
C. cut off
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We have to be very patient with this experiment. It will take time for some effects to ___ clearly.
A. build up
B. break up
C. clear up
D. show up
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Perhaps there is a(n) ___ of truth in both theories, but few of us would ever have the opportunity to find out.
A. lump
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C. section
D. element
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Be careful when you get along with her because she is known for her short ___.
A. temper
B. emotion
C. mood
D. feeling
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It seems that wearing less formal clothing to school and work is becoming a(n) ___.
A. trend
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C. goal
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You cannot correct children’s bad behavior simply with a (n) ___ or two on the hand or face.
A. slap
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Our investigations (调查) ___ something very surprising – many of the employees are underpaid and work overtime all the time.
A. reveal
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C. rip
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She was James’s faithful assistant, in whom he could have ___ confidence.
A. essential
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If you visit this website, you can ___ the categories to find information about all the universities in that area.
A. observe
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Making New Year’s resolutions (计划) is a custom that still ___ in this country.
A. prevails
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The military officers were more ___ about their own victory and therefore more willing to predict their enemy’s defeat.
A. appropriate
B. ignorant
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___ is no doubt that overwork and much worry caused his illness.
A. It
B. There
C. Here
D. This
