Learning a foreign language in the context of formal education often imposes on students the management of difficult tasks. This demands an adoption of adequate coping behaviour (achievement vs. avoidance). Easy tasks reduce learning opportunities, while too difficult ones lead to escape-motivated problem behavior. For the purpose of the present research it is proposed that the level of FL task difficulty is related to coping behaviour. The empirical results demonstrate that students who perceive FL tasks as difficult apply more avoidance strategies. Apart from that, students with higher and lower levels of task difficulty use similar amounts of achievement strategies. It follows that the implementation of achievement coping is independent from the level of task difficulty.

A robust Kalman filter improved with IGG (Institute of Geodesy and Geophysics) scheme is proposed and used to resist the harmful effect of gross error from GPS observation in PPP/INS (precise point positioning/inertial navigation system) tightly coupled positioning. A new robust filter factor is constructed as a three-section function to increase the computational efficiency based on the IGG principle. The results of simulation analysis show that the robust Kalman filter with IGG scheme is able to reduce the filter iteration number and increase efficiency. The effectiveness of new robust filter is demonstrated by a real experiment. The results support our conclusion that the improved robust Kalman filter with IGG scheme used in PPP/INS tightly coupled positioning is able to remove the ill effect of gross error in GPS pseudorange observation. It clearly illustrates that the improved robust Kalman filter is very effective, and all simulated gross errors added to GPS pseudorange observation are successfully detected and modified.