问题 问答题 简答题

等离子弧焊的带电粒子流在运动过程中受到哪几种“压缩效应”的作用?详细解释这几种“压缩效应”。

答案

参考答案:

(1)机械压缩效应:是使经高频振荡使气体产生电离形成的电弧通过喷嘴细孔道,弧柱被强迫压缩。

(2)热压缩效应:是水冷喷嘴以及通入一定压力的冷气(氩气、氮气)使电弧外层冷却,迫使带电粒子流(离子和电子)向弧柱中心收缩。

(3)磁压缩效应:是无数根平行导线(带电粒子在弧柱中的运动)所产生的自身磁场,使这些导线相互吸引,电弧被进一步压缩。

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I was 9 years old when I found out my father was ill. It was 1994, but I can remember my mother's words as if it were yesterday: “Kerrel, I don't want you to take food from your father, because he has AIDS. Be very careful when you are around him.”

AIDS wasn't something we talked about in my country when I was growing up. From then on, I knew that this would be a family secret. My parents were not together anymore, and my dad lived alone. For a while, he could take care of himself. But when I was 12, his condition worsened. My father's other children lived far away, so it fell to me to look after him.

We couldn't afford all the necessary medication for him, and because Dad was unable to work, I had no money for school supplies and often couldn't even buy food for dinner. I would sit in class feeling completely lost, the teacher's words muffled as I tried to figure out how I was going to manage.

I did not share my burden (负担) with anyone. I had seen how people reacted to AIDS. Kids laughed at classmates who had parents with the disease. And even adults could be cruel. When my father was moved to the hospital, the nurses would leave his food on the bedside table even though he was too weak to feed himself.

I had known that he was going to die, but after so many years of keeping his condition a secret, I was completely unprepared when he reached his final days. Sad and hopeless, I called a woman at the nonprofit National AIDS Support. That day, she kept me on the phone for hours. I was so lucky to find someone who cared. she saved my life.

I was 15 when my father died. He took his secret away with him, having never spoken about AIDS to anyone, even me. He didn't want to call attention to AIDS. I do.

60. What does Kerrel tell us about her father?

A. He had stayed in the hospital since he fell ill.

B. He depended on the nurses in his final days.

C. He worked hard to pay for his medication.

D. He told no one about his disease.

61. What can we learn from the underlined sentence?

A. Kerrel couldn't understand her teacher.             

B. Kerrel had special difficulty in hearing.

C. Kerrel was too troubled to focus on the lesson.

D. Kerrel was too tired to hear her teacher's words.

62. Why did Kerrel keep her father's disease a secret?

A. She was afraid of being looked down upon.             B. She thought it was shameful to have AIDS.

C. She found no one willing to listen to her.          D. She wanted to obey her mother.

63. Why did Kerrel write the passage?

A. To tell people about the sufferings of her father.

B. To show how little people knew about AIDS.

C. To draw people's attention to AIDS.                 

D. To remember her father.