直流电动机调压调速是恒转速调速,弱磁调速是恒功率调速。

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问题:

直流电动机调压调速是恒转速调速,弱磁调速是恒功率调速。

考点:电力机车电工考试高级机车电工高级机车电工题库
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如图,倾角为θ的斜面固定。有n个质量都为m的相同的小木块(可视为质点)放置在斜面上。相邻两小木块间距离都为l,最下端的木块距底端也是l,小木块与斜面间的动摩擦因数都为μ。在开始时刻,第一个小木块从斜面顶端以初速度v0沿斜面下滑,其余所有木块都静止,由于第一个木块的下滑将依次引起一系列的碰撞。设每次碰撞的时间极短,在每次碰撞后,发生碰撞的木块都粘在一起运动,直到最后第n个木块到达底端时,速度刚好为零。己知重力加速度为g。求:

(1)第一次碰撞后小木块l的速度大小v;

(2)从第一个小木块开始运动到第一次碰撞后系统损失的机械能△E;

(3)发生一系列碰撞后,直到最后第n个木块到达底端,在整个过程中,由于碰撞所损失的总机械能△E

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It happened to a very young pastor (牧师).His church was very old and what's worse, a storm knocked a hole in the wall of the church.
One day the pastor1_____an auction(拍卖)and bid a beautiful tablecloth for six dollars. Hecarried the cloth back to the church and put it up on the wall. It completely hid the 2_____!
Just before noon of Christmas Eve, the pastor noticed a woman standing in the cold at the bus stop. “The 3 _____won’t be here for 40 minutes!” he called, and he invited her into the church to get 4_____ .She told him that she had come from the city to be interviewed for ajob as governess to the children of one wealthy family in town but she had been turned down.
The woman saw the tablecloth and rose suddenly. The pastor smiled and started to tell her about the storm 5_____, but she didn’tseem to 6_____“It is mine!” she said. “My husband had the cloth made 7_____ for mc !
She explained that she and her husband decided to go separately in the War II. They planned that he would 8_____ her. But she never saw him again. Later she heard that he had died. The pastor tried to 9_____ her, advising her to take the cloth with her. She 10_____ . Then she went away.
On Christmas Eve, after the service in church, one middle-aged man—the local clock-and-watch repairman—looked rather 11_____.‘‘It is strange,”he said in his soft accent.
Many years ago, my wife and I owned such a cloth.
The pastor suddenly became very 12_____ . He told him about the woman who had been in church 13_____ in the day.Together the two got in touch with the 14_____ who had interviewed her. And this man and his wife -who had been separated through so many saddened 15_____were reunited.
小题1:
A.hadB. attendedC. heldD. took
小题2:
A.wallB. churchC. holeD. table
小题3:
A.bossB. companyC. trainD. bus
小题4:
A.warmB. readyC. coolD. calm
小题5:
A.damageB. storyC. factD. truth
小题6:
A.workB. believeC. listenD. understand
小题7:
A.carefullyB. attentivelyC. finallyD. especially
小题8:
A.joinB. writeC. bringD. leave
小题9:
A.amuseB. comfortC. pleaseD. help
小题10:
A.criedB. acceptedC. refusedD. continued
小题11:
A.puzz ledB. delightedC. determinedD. disappionted
小题12:
A.sadB. shockedC. hopefulD. excited
小题13:
A.laterB. earlierC. warmerD. colder
小题14:
A.womanB. managerC. husbandD. family
小题15:
A.weeksB. countriesC. ChristmasesD. centuries
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奇脉

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竹制缏条及类似产品

题型:判断题

《东北地区振兴规划》指出,大力发展专业化工业设计,建立以( )为核心的国家数字电影制作和国产动漫产品生产基地。

A.长春、哈尔滨
B.长春、沈阳
C.哈尔滨、大连
D.长春、大连

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