问题 问答题 简答题

怎样降低频闪效应?

答案

参考答案:

降低频闪效应的方法有:

1、采用高频电子整流器(AC-DC-AC),但价格不菲;

2、调节灯管垂直高低,就想普通显像管电视机一样选个适当距离

3、不在一根火线上并联N个灯,采用三相分接,尽量三相平衡,如:双管日光灯灯管接在不同的相序。

4、采用三基色节能灯。

5、安装一些白炽灯等混合照明,也能降低频闪效应对人的影响

单项选择题
阅读理解

B

SYDNEY: As they sat sharing sweets beside a swimming pool in 1999. Shane Gould and Jessicah Schipper were simply getting along well, chatting about sport, life and anything else that came up.

Yet in Sydney next month, they will meet again by the pool, and for a short time the friends will race against each other in the 50 – meter butterfly in the Australian championships at Homebu Bay.

Gould, now a 47 – year – old mother of four, has announced she will be making a return to elite competition (顶级赛事) to swim the one event, having set a qualifying (合格的)time of 30. 32 seconds in winning gold at last year’s United States Masters championships. Her comeback comes 32 years after she won three golds at the Munich Olympics.

Schipper, now a 17 – year – old girl from Brisbane with a bright future of going to Athens for her first Olympics, yesterday recalled (回忆) her time with Gould five years ago.

“I was at a national youth camp on the Gold Coast and Shane had come along to talk to us and watch us train.” Schipper explained. “It seemed as if we had long been good friends. I don’t know why. We just started talking and it went from there.”

“She had a lot to share with all of us at that camp. She old us stories about what it was like at big meets like Olympics and what it was like to be on an Australian team. It was really interesting.”

Next time, things will be more serious: “I will still be swimming in the 50 m butterfly at the nationals, so there is a chance that I could actually be competing against Shane Gould.” said Schipper, who burst onto the scene at last year’s national championships with second places in the 100 m and 200 butterfly.

46.What is the passage mainly about?

A.Stories happening in swimming competitions.

B.Two women swimmers winning Olympic golds.

C.Lessons learned from international swimming championships.

D.Friendship and competition between two swimmers.

47.Gould and Schipper are going to____________.

A.talk about sport and life          B.go back to elite competition

C.set a qualifying time and win gold  D.take part in the same sports event

48.Gould won her three Olympic golds when she was____________.

A.15     B.17     C.22     D.30

49.The underlined word “it” in the fifth paragraph probably refers to         .

A.the Olympics          B.the youth camp

C.the friendship          D.the Australian team

50.What Schipper said showed that she___________.

A.was no longer Gould’s friend         B.had learned a lot from Gould

C.was not interested in Gould’s stories      D.would not like to compete against Gould