As more and more mobile applications are developed, mobile app testing and quality assurance have become very important. Due to the diversity of mobile devices and platforms, compatibility testing for mobile apps has been identified as one urgent and challenging issue. There are two major reasons contributing to this issue. They are: a) the large number of mobile devices with diverse features and platforms which are upgraded frequently; b) a higher cost and complexity in mobile app compatibility testing. This paper proposes one optimized compatibility testing strategy using a statistical approach to reduce test costs, and improve engineer's operation efficiency. The paper provides a solution to generate an optimized compatibility test sequence for mobile apps using the K-Means statistical algorithm. A compatibility testing service has been proposed for mobile apps. Moreover, two case study results are reported to demonstrate its potential application and effectiveness.
Based on the differential principle of thread transmission, an analytical model considering helical directions between screw and roller threads in planetary roller screw mechanism (PRSM) is presented in this work. The model is critical for the design of PRSM with a smaller lead and a bigger pitch to realize a higher transmission accuracy. The kinematic principle of planetary transmission is employed to analyze the PRSM with different screw thread and roller thread directions. In order to investigate the differences with different screw thread and roller thread directions, the numerical model is developed by using the software Adams to validate the analytical solutions calculated by the presented model. The results indicate, when the helical direction of screw thread is identical with the direction of roller thread, that the lead of PRSM is unaffected regardless of whether sliding between screw and rollers occurs or not. Only when the direction of screw thread is reverse to the direction of roller thread, the design of PRSM with a smaller lead can be realized under a bigger pitch. The presented models and numerical simulation method can be used to research the transmission accuracy of PRSM.
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