The traditional education in teachers' colleges is in system a pre-education before working, and has no virtual relations with the post-work education.

传统的师范教育在体制上更大程度上是一种职前预备教育，与职后教育没有实质性的联系；

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A subset of the database defined by a single relation, or by combining fields from two or more relations (or other views) into a single "virtual" relation.

数据库的一个子集，它是通过定义一个关系或联合两个至多个关系(或其它视图)中的多个字段为一个“虚”关系而得到的。

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And then the governing equations of the block dynamic system are deduced on the basis of the virtual work principle, the deformation compatibility condition and the constitutive relations.

随后，基于虚功原理、变形协调条件和本构关系，推导了块体动力系统的控制方程组。

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Apps that include virtual currency tend to work better than paid models, said Christine Lee, who runs partner relations for app-marketing firm Tapjoy Inc.

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