The recently proposed digital reconfigurable metasurfaces make it possible to manipulate electromagnetic (EM) waves flexibly. However, most existing reconfigurable metasurfaces can only exhibit a relatively single performance in the spatial domain. Here, we propose a general frequency- and spatial-domain reconfigurable metasurface (FSRM) that can manipulate the EM waves and realize reconfigurable functions in multifrequency bands. In the frequency domain, FSRM can convert different linearly polarized (LP) incident waves into left- and right-hand circularly polarized reflected waves, in which PIN diodes are used to switch the polarization conversions in different frequency bands. When the polarization direction of the incident LP wave is 45° from the +x-axis, the FSRM modulates the incident waves as a 1-bit programmable metasurface in the spatial domain. Two-dimensional beam scanning, vortex beams with orbital angular momentums, and specific beams with desired transmission directions are demonstrated via real-time adjustment of the digital coding state. To validate the modulation methodology, an FSRM prototype is fabricated and measured, which could respond to different functions for different polarization incidences. The measured results agree well with the theoretical analyses. The proposed FSRM will provide new opportunities for smart material designs.

Based on the 3D unsteady incompressible Navier-Stokes equation and the turbulent model ofk-εtwo equations, the processes of electric multiple units CRH380B passing by sound barriers installed on viaducts at the speed of 350 km/h were numerically simulated by finite volume method. The aerodynamic impulse pressure on sound barriers was analyzed. The distribution of impulse pressure on perforated sound barriers was compared with that on those with no holes. Effects of the shape, the size, the density, and tilt angle of the holes on deloading properties of perforated sound barriers were investigated. The numerical results show that the deloading properties of perforated sound barriers with circular holes are similar to those with square holes. The holistic distribution of impulse pressure on perforated sound barriers is similar to those with no holes. The density increases in two different directions has almost the same influence on the deloading properties. Deloading properties of perforated sound barriers become worse when tilt angle of holes increases.