Search

In order to realize the vibration reduction and sound insulation within the recognizable frequency of human ear within 20000 Hz, this paper proposes a new type of multi-functional acoustic metamaterial, namely the snowflake-like convex horn ligament structure (SCHLS). Combined with the finite element analysis method and Bloch's theorem, the energy band curve of the SCHLS is calculated, and the sound insulation performance and band gap simulation results are verified through the frequency response function of the finite size structure. The band gap is optimized by introducing elastic-material-wrapped resonators and adjusting the resonator distribution and size. At the same time, the innovative use of equal frequency curve, vibration mode and group velocity to explain the wave propagation mechanism in depth. Applying large deformations to the novel structures to explore the tuning properties of the structures. The results show that the SCHLS has the characteristics of multi-frequency noise reduction, the optimized structure has better multi-band elastic wave attenuation performance, and the active frequency modulation of the structure can further improve its practicability. This research provides a new research idea for realizing multi-frequency noise reduction, analysis of wave propagation energy and active frequency modulation. [Display omitted] • Bloch's theorem is used to explain the multi-frequency band gap of the structure. • Comparison of band gap and transmission curve of hexagonal and new structures. • Introducing resonators and adjusting the configuration to optimize band gap. • Using modal, iso-frequency curve and group velocity to analyze the noise reduction. • Investigating the tunability of the band gap under dynamic strain. [ABSTRACT FROM AUTHOR]

Constructed wetland is an efficient and convenient wastewater treatment technology that has been widely used in China and elsewhere. However, seasonal frozen soil is easily formed in the cold regions of northern China. The local wetlands are in the frozen soil layer, causing the pollutants from wastewater not to be removed well. Therefore, a new constructed wetland structure that uses shallow geothermal energy to keep the wetland not frozen in the winter is proposed in this paper. The results of the experiment show that the average removal rates of total nitrogen, ammonium ion, and total phosphorus in the multistage constructed wetland system are 54.8%, 44.5%, and 77.7%, respectively. This performance is substantially better than that of conventional wetlands in winter. The proposed wetland structure can be applied to conventional wetlands and avoid the conventional wetlands being idle during cold seasons, which is conducive to the popularization of constructed wetlands (CWs) in cold regions. Unlabelled Image • A new subsurface flow constructed wetland using shallow geothermal energy is proposed. • The proposed wetland system can keep not frozen in winter. • The new wetland structure showed good performance especially on removal of TN and NH 4 +-N by using shallow geothermal energy in winter. • The performance of the proposed wetland is substantially better than that of conventional wetlands in winter. • Using shallow geothermal energy for wetland insulation is more suitable for applying in cold regions of northern China than those of existing methods. [ABSTRACT FROM AUTHOR]