本文认为产业结构是一个经济系统，具有系统结构的特性。
As an economic system, industry structure has the properties of systemic structure.
圆周模型对于分析港口产业经济特性非常恰当。
Circle model is suitable for the analysis of economic characteristics of port industry.
邮政产业属于传统意义上的自然垄断产业，具有明显的网络特性。
The postal industry is a traditional natural monopoly industry with obvious network characteristics.
邮政产业属于传统意义上的自然垄断产业，具有明显的网络特性。
The postal industry is a traditional natural monopoly industry with obvious network characteristics.
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