And we can find the deep-seated reasons of Ling Shan's success by analyzing with the four-level model of cultural tourism products, which proves that the evaluation system is reasonable.
运用文化旅游产品的四层次评价模型对灵山文化旅游产品进行剖析可以发现其成功的深层次理由，同时也证明了模型的合理性。
A model of the photon avalanche in a four level coupled system is proposed.
提出了四能级耦合系统的光子雪崩上转换模型。
A data transformation interface was developed to get the four-level product model.
开发了数据转换接口，获得了四层次的产品模型。
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