问题
单项选择题
提高机床动刚度的有效措施是（）。
A.增大摩擦
B.增大切削用量
C.增大阻尼
D.减小阻尼
答案
参考答案：C
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提高机床动刚度的有效措施是（）。
A.增大摩擦
B.增大切削用量
C.增大阻尼
D.减小阻尼
参考答案：C
| 根据短文内容选择适当的单词，并用其正确形式填空，每个词限用一次。 | |
in Egypt, the 1. _ favorite game was throwing stones.But a badly thrown stone could 2. _ a child. Looking for something less 3. _ to throw, the people in Egypt 4. _ the first balls. At first, they used tree 5._____to make balls. They used vines ( 藤) to keep the leaves together. Later they began to use pieces of animal skin to make balls and 6. _ them with some light things. These balls were much 7. _ than the old one. Before long they invented a lot of ball games, and 8. _ had its own rules. They began to play these ball games according to the rules. They thought that ball playing was one of the best 9. _ to teach the young men to be brave and 10. _ . |