Constructed wetland systems are a low-cost, low-energy-consumption and effective technology for water pollution control used increasingly in recent years in China. In this paper, the land treatment systems in China are introduced, the constructed wetland systems in North China are detailed, and the integrated reed bed wetland-lagoon system, as an advanced constructed wetland system, is compared with other land treatment systems. Lastly, the authors elaborate their opinion on problem “wetlands occupy larger lands” and energetically advocate to develop this new land treatment technique in China.

In this research, a molecular dynamics (MD) model was adopted to investigate the essence of the effect of strain rate on the mechanical behavior of the Fe14.6Ni (at%) elastocaloric refrigeration alloy. The study showed that the mechanical behavior of the Fe14.6Ni (at%) alloy was dependent on the strain rate. Besides, the investigation of temperature demonstrated that the strain rate influenced mechanical behavior by changing the transient temperatures. Furthermore, it was found that the adiabatic temperature change (ΔT_adi) was high and up to 51 K, which was a 1.57 times improvement. Finally, the conclusion was drawn that the strain rate influenced the mechanical behavior by changing the transient total kinetic energy and the phase content evolution processes, which was the essence of the effect of strain rate on the mechanical behavior. This work has clarified the essence and enriched the theory of the effect of strain rate on the mechanical behavior of elastocaloric refrigeration alloys.

Successive and pulsing loading methods were employed to evaluate the elastocaloric effects (eCEs) performance of the Fe14.6Ni(at%) alloy at 293 K by molecular dynamics (MD) simulation. The study included investigation of the loading methods and the cyclic stability of eCEs performance. The study of the loading methods indicated that the pulse cyclic loading method, compared with the successive loop loading method, was the optimal option due to the steady evolution processes of the parameters. Finally, the research on cyclic stability demonstrated that the Fe14.6Ni(at%) alloy remained sensitive to the external stimulus even after 80,414 cycles. This work proposes a promising strategy for optimizing the eCEs performance of the Fe14.6Ni(at%) alloy and demonstrates its great industrial potential.

In this study, the mechanical alloying (AM) and powder metallurgy (PM) techniques were adopted to synthesize the Fe₇₅ N_i(25-x) Cu _x elastocaloric refrigeration alloys to research the effect of Cu contents on phase transition characteristics and microstructure of Fe₇₅N_i(25-x) Cu_x elastocaloric refrigeration alloys. The conclusion was drawn that, with increasing Cu content, the phase transition characteristics changed and presented different changing trends. It was found that the phase enthalpy change value was 43.34J/g when the Cu content was 7at%, which was about 1.26 times of Fe15Ni (wt%) alloy. In addition, the FeNiCu alloy was a single-phase alloy with a crystal space group structure of Im-3m when the Cu content was 7at%, and the FeNiCu alloy was a two-phase alloy with crystal space group structures of Im-3m and Fm-3m when the Cu content was more than 7at%. This study provided an experimental basis for the theoretical investigation of the phase transition mechanism of FeNiCu elastocaloric refrigeration alloys.