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何为浇口比，吸动区？

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浇口比指的是浇注系统中直浇道，横浇道，内浇道的截面积之比（即S直：S横：S内：）横浇道内，在内浇道入口周围存在一个区域只要金属液进入该区就会自动流入内浇道，该区域称为吸动区。

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When you stop and think about your high school or college alma mater, were your experiences more positive or negative Do your feelings of (1) in that school have anything to do with whether or not your school was single-sex or coed (2) to send their children to single-sex schools, because they feel both (3) when they study in the company of students of the same sex. They (4) .
For years, only parents who could afford to send their children to private schools, or who had (5) , chose single-sex education for their children. Single-sex schooling was (6) for most American families. Today, however, along with (7) , public schools are experimenting with the idea of (8) .
Girls may be the ones who benefit most from single-sex schooling. Studies have shown that (9) in coed classrooms because teachers sometimes pay more attention to boys. Girls’ (10) toward their studies tends to disappear as they begin to feel less successful. They start to (11) outperform them in math and science. As boys (12) , girls start to lose it. Moreover, adolescence is (13) for girls. As they experience adolescent changes, some girls become depressed, develop an addiction, or suffer from (14) .
In the early 1990s, some influential people said that being in single-sex classes could (15) . Schools across the country began creating single-sex classrooms and schools. But many critics claim that (16) may actually be detrimental to a girl’s education because they (17) of sex differences.
The renewed interest in single-sex schooling (18) among Americans. Those who give it full endorsement believe girls need an all-female environment to take risks and find their own voices. Those who (19) of single-sex schooling wonder whether students’ lack of achievement warrants returning to an educational system that divides the sexes. They believe there is no (20) .
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聚合物的热性能包括几个方面？如何提高聚合物的热稳定性？
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