IMPROVED FORMULA FOR FATIGUE CRACK GROWTH RATEUNDER DIFFERENT STRESS RATIO

An improved formula for fatigue crack growth rate in mode I,mode III and mixed mode I-III under different stress ratio R was proposed,which was based on J-integral range ΔJ. In the formula,the test data under different R could be normalized by correction factor M,which changed the test ΔJ under different R to ΔJeq0under R = 0,and the relationship of M and R was obtained empirically. The proposed formula was validated with available experimental fatigue crack growth data in mode I,mode III and mixed mode I-III under different stress ratio from literatures. It transpires that these test data can be well described with the present formula

GPS-Simulated Trajectory Detection

Due to the prevalence of GPS-enabled devices and wireless communication technology, spatial trajectories have become the basis of many location based applications, e.g., Didi. However, trajectory data suffers low quality problems causing by sensor errors and artificial forgeries. Sensor errors are inevitable while forgeries are always constructed on bad purpose. For example, some Didi drivers use GPS simulators to generate forgery trajectories and make fake transactions. In this work we aim to distinguish whether a given trajectory is a GPS simulated trajectory. By formulating this task as the problem of traffic speed extracting and irregular measuring, we propose a simulated trajectory detection framework. In traffic speed extracting phase, we first divide time into time slots and then extract the regular speed of each road during each time slot. In irregular measuring phase, we propose three methods to measure the distance between the speed of the given trajectory and the real traffic speeds. For empirical study, we apply our solution to a real trajectory dataset and have found that the simulated trajectory detection framework can detect most forgery trajectories