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什么叫摩擦力界?影响摩擦力界的因素是什么?

答案

参考答案:

在牵伸区域中,须条受到压力和张力,纤维在牵伸运动时受到摩擦力作用的空间称为摩擦力界。

其影响因素:

(1)罗拉压力:压力增加时,钳口内的纤维被更有力的握持,由于胶辊的变形以及须条本身的变形,须条在上、下罗拉接触的边缘点外移,摩擦力界的长度扩展,摩擦力界分布的峰值也增大。

(2)罗拉直径:直径增大时,同样的压力分配在较大的面积上,所以摩擦力界的分布曲线的峰值减小,但分布的长度扩大。

(3)须条定量:须条定量增加时,一般紧压后须条的厚度与宽度均有所增加,此时摩擦力界分布曲线的长度扩展,但因须条单位面积上的压力减小,使摩擦力界的峰值降低。

阅读理解

阅读理解。

     It came as something of a surprise when Diana, Princess of Wales, made a trip to Angola in 1997, to

support the Red Cross campaign for a total ban on all anti-personnel landmines. Within hours of arriving in

Angola, television screens around the world were filled with images of her comforting victims injured in

explosions caused by landmines. "I knew the statistics," she said."But putting a face to those figures brought

the reality home to me; like when I met Sandra, a 13- year-old girl who had lost her leg, and people like her."

     The Princess concluded with a simple message:"We must stop landmines". And she used every opportunity

during her visit to repeat this message.

     But, back in London, her views were not shared by some members of the British government, which

refused to support a ban on these weapons. Angry politicians launched an attack on the Princess in the press.

They described her as"very ill-informed" and a"loose cannon". (乱放炮的人)

     The Princess responded by brushing aside the criticisms:"This is a distraction (干扰) we do not need. All

I'm trying to do is help."

     Opposition parties, the media and the public immediately voiced their support for the Princess. To make

matters worse for the government, it soon emerged that the Princess's trip had been approved by the Foreign

Office, and that she was in fact very well-informed about both the situation in Angola and the British

government's policy regarding landmines. The result was a severe embarrassment for the government.

     To try and limit the damage, the Foreign Secretary, Malcolm Rifkidnd, claimed that the Princess's views

on landmines were not very different from government policy, and that it was "working towards" a

worldwide ban. The Defence Secretary, Michael Portillo, claimed the matter was "a misinterpretation or

misunderstanding."

     For the Princess, the trip to this war-torn country was an excellent opportunity to use her popularity to

show the world how much destruction and suffering landmines can cause. She said that the experience had

also given her the chance to get closer to people and their problems.

1. Princess Diana paid a visit to Angola in 1997 _______.

A. to clarify the British governments stand on landmines

B. to establish her image as a friend of landmine victims 1

C. to investigate the sufferings of landmine victims there

D. to voice her support for a total ban of landmines

2. Some members of the British government criticized Diana because _______.

A. she had not consulted the government before the visit

B. she was ill-informed of the governments policy

C. they were actually opposed to banning landmines

D. they believed that she had misinterpreted the situation in Angola

3. How did Diana respond to the criticisms?

A. She paid no attention to them

B. She made more appearances on TV.

C. She met the 13-year-old girl as planned

D. She rose to argue with her opponents

4. What did Princess Diana think of her visit to Angola?

A. It had caused embarrassment to the British government.

B. It had greatly promoted her popularity.

C. It had brought her closer to the ordinary people.

D. It had affected her relations with the British government.

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