Teacher attended could be divided into three groups: low grade in primary school (grade 1 ~ 3), high grade in primary school (grade 4 ~ 6) and middle school.

所有班级的当地教师来自三个等级，小学低年级(1 ~ 3年级)，小学高年级(4 ~ 6年级)以及中学。

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Mineral component and process mineralogy characteristic of middle and low grade phosphate deposit are important study objects for reasonable phosphate resource usage.

中低品位磷矿床的物质组成及工艺矿物学特征是合理利用磷矿资源重要的研究内容。

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The polyphenols antioxidants are extracted by solvent method from the middle and low-grade tea, and how to improve the purity of product and lower costs are also discussed.

研究了以中、低档茶叶为原料，采用溶剂法提取多酚类抗氧化物质的工艺技术。并在工艺上进行了一定的改进，提高了产品的纯度，降低了成本。

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