This paper investigates the bifurcations of the periodic solutions in the piecewise linear systems. Firstly the equation about amplitude-frequency response is deduced by the averaging method. Then the bifurcation classification is conducted by applying the singularity theory. The effects of the two parameters, the mass and the excitation amplitude, are discussed. The balance position will be changed when the quality changed, So the system is divided into two kinds of state. The results show that the parameter plane is divided into thirteen regions where bifurcation types are different. At last, discussing the amplitude- frequency response of different regions. this paper provides some theoretical guidance for system of considering load variation, and it is significant to help research the change in amplitude-frequency characteristic of piecewise linear system.

This study explored the applications of a vertical electrokinetic system (V-EK), which consists of multilayer electrodes positioned in shallow soil to form an 'electric sieve' to mitigate and prevent soil salinization caused by salts rising from saline groundwater in coastal areas. The experiments were conducted in column reactors in the laboratory. Compared to the control column, the level of ions in the surface soil was significantly reduced after the V-EK treatment, particularly for the column with voltages at 10 V and 20 V. At a voltage of 20 V, Na + was detected at a range of 0.06-0.08 mg g À1 in the surface soil; this is a >99% reduction compared to the controls. Similar efficacy was observed for Cl À in the V-EK column. The concentrations of Cl À were detected with a range of 0.01-0.02 mg g À1 and 0.02-0.06 mg g À1 at the surface soil with a voltage of 20 V and 10 V, respectively, compared to the Cl À concentrations at 0.84-2.70 mg g À1 in the control. After the application of the vertical 'electric sieve', the total salt content of surface soil could be controlled at a low value (<0.25‰) at voltages of 10 V and 20 V, compared to that in the control column (4.86‰). Finally, rising of salts from the artificial saline groundwater was effectively mitigated under voltages of 10 V and 20 V. Results from this work have demonstrated that the 'electric sieve' can effectively mitigate and prevent salts from rising in shallow groundwater to surface soil and reduce soil salinity.