A pyramid provides a useful conceptual model for organizing scientific knowledge. 金字塔给科学知识的组织提供了一个有用的概念性模型。
Conceptional Model System of Urban Runoff in Chengdu is a group of concep-tional models on the basis of urban runoff pollution and its impact on the urban waters. 概念性模型是根据城市径流形成过程及对水体影响变化的物理机理建立的一套数学模型，模型及参数均有明确的物理意义。
