液压支架用安全阀的功能时什么？

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问题问答题简答题

液压支架用安全阀的功能时什么？

答案

参考答案：

1、使立柱保持恒定工作阻力

2、当顶板压力超过支架工作阻力时，使立柱工作腔的液体释放，不仅保证恒定工作阻力，同时起过载保护作用；

3、液体压力未达到额定释放压力时，为常闭，起密封作用。

阅读理解

根据短文内容判断下列句子正误，正确的写“T ”，错误的写“F ”。

Nick is an American boy. His parents work in Chengdu. And he studies in a school in Chengdu. He

doesn't have brothers. This is his bedroom. Look! The baseball is on the table. And his computer game

is on the table, too. The books are on the sofa. His shoes are under his bed. Where's his pencil case? It's

in his backpack.

( )1. Nick is in China.

( )2. His computer game and baseball are on the table.

( )3. His books are in his backpack.

( )4. His backpack is in his pencil case.

( )5. His shoes are not under the bed.

问答题

读地球部分经纬网图，完成下列要求．

（1）请你在图中描画出0°经线．

（2）如果每条经线的间隔是15°，那么A点的经度是______，E点的经度是______．

（3）如果某飞机从B点一直向正北方向飞行，它能经过的地点应该是A、C、D三点中的______点

（4）你能判断A、C、D、E位于哪个半球吗？请你把相对应的字母填到下面的表格里．