煤矿井下常用的雷管种类和使用范围？
参考答案：
煤矿井下常用的雷管有三种，一是瞬发电雷管，煤矿许用的瞬发电雷管适用于各级矿井及有煤与瓦斯突出危险的采掘工作面；二是秒延期电雷管，适用于地面延期爆破和井下无瓦斯岩石工作面全断面一次爆破。瓦斯矿井无瓦斯、煤尘爆炸危险的煤层爆破也可使用，但要距瓦斯煤、岩层10米以外，严禁用于有瓦斯、煤尘爆炸危险的工作面；三是毫秒延期电雷管，它适用于露天和井下毫秒爆破作业。但在有瓦斯、煤尘爆炸危险的工作面不准使用。
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| For a few years, I have been wearing a ring on my right hand. It's not always the 1 ring, but it's always a ring that has 2 on it so that when I look at it, I'm 3 or reminded of something important . I have made a 4 of buying rings like this whenever I see one in a store. Sometimes I give them away as 5 to someone like Jennie. I first met Jennie in the 6 waiting room and we had talked several times. One night I sat down beside her and 7 how her son was going because I knew that he was in very 8 condition. She told me that she didn't know what to do any more because it seemed none of the 9 from the doctors was good. They weren't at all sure her son was going to 10 the accident that had hurt him so badly. With 11 in her eyes she said, "They're taking away my 12 ." I knew then that it was 13 just a coincidence (巧合) that I was wearing the ring that I had on that day. As she 14 to talk, I 15 slipped the ring off my finger and placed it in Jennie's hand. I told her to wear it to remember that God loved her and He would be with her 16 all of this. 17 Jennie looked down at the ring, she got excited and then held it tightly, 18 the word written on the ring was "HOPE". The last day I was at the hospital, I saw Jennie in the distance as I got on the lift. She 19 and held up the hand with the ring on it as she called out to me saying, "Look, I 20 have Hope!" | ||||
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