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As the profit margins of 3G mobile network operators gradually decline, and market competition becomes increasingly intensive, they must develop rich and diverse varieties of brand new application services to attract new subscribers and retain old ones. Understanding the customer's purchasing behavior is a key issue in this process. The operator must(More)
As more and more documents become available on the internet, finding documents that fit users' needs from databases containing millions of documents is becoming increasingly important. Since a scientific document is a structured text, it has some useful features that can be used to improve retrieval performance. In this work, we investigate three such(More)