Based on the saltation, creeping and stability models, a two-dimensional numerical model is established to study the development process of aeolian ripples.

通过简单的跃移模型、蠕移模型和稳定模型对风成沙纹的形成过程进行了二维数值模拟研究。

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The two-dimension CAD and its software of low layer are being used to draw is very popular, but the three-dimensional CAD system of independent development is still immature in domestic.

国内在将二维CAD及其软件用于低层次的绘图很普及，但自主开发的三维CAD系统还未成熟。

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To research on it and contribute to its development, this paper brings forward a business model analysis framework which is applicable to handset two-dimensional code business.

手机二维码业务作为一种新兴业务具有广阔的应用前景，本文为分析其商业模式，提出了适用于手机二维码业务的商业模式分析框架。

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