In this work, a broadband and broad-angle polarization-independent random coding metasurface structure is proposed for radar cross section (RCS) reduction. An efficient genetic algorithm is utilized to obtain the optimal layout of the unit cells of the metasurface to get a uniform backscattering under normal incidence. Excellent agreement between the simulation and experimental results show that the proposed metasurface structure can significantly reduce the radar cross section more than 10 dB from 17 GHz to 42 GHz when the angle of incident waves varies from 10° to 50°. The proposed coding metasurface provides an efficient scheme to reduce the scattering of the electromagnetic waves.

Activated carbon was synthesized by a simple one-step calcination of deoxygenated agar in a hot KOH aqueous solution, in which KOH plays both deoxidant and activation agent. The deoxygenation course omits high temperature carbonization in the conventional technology and leads to molecular level activation of agar in subsequent one-step calcination. The one-step activated carbon has superior specific surface area of 1672 m 2 g −1 and total pore volume of 0.81 cm 3 g −1 . It also shows a maximum specific capacitance of 226 F g −1 in the KOH electrolyte, which is 1.4 times as high as that for the activated carbon by the conventional two-step method. This study provides potentially economical and effective means for the production of commercial activated carbon with high porosity for supercapacitors.

Cellulose (8%) can be dissolved in tetrabutylammonium acetate (TBAA) with dimethyl sulfoxide (DMSO) and crown ether (18-crown-6) within 5 min at 40 C without any pretreatment.

In this work, a metasurface acting as a linear polarization rotator, that can efficiently convert linearly polarized electromagnetic waves to cross polarized waves within an ultra wide frequency band and with a broad incident angle, is proposed. Based on the electric and magnetic resonant features of the unit cell, composed by a double-head arrow, a cut-wire, and two short V-shaped wire structures, three resonances, which lead to the bandwidth expansion of cross-polarization reflections, are generated. The simulation results show that an average polarization conversion ratio of 90% from 17.3 GHz to 42.2 GHz can be achieved. Furthermore, the designed metasurface exhibits polarization insensitivity within a broad incident angle, from 0 to 50. The experiments conducted on the fabricated metasurface are in good agreement with the simulations. The proposed metasurface can find potential applications in reflector antennas, imaging systems, and remote sensors operating at microwave frequencies. Published by AIP Publishing.

We provide further theoretical insights and experimental verification of the modal-dispersion-induced effective surface-plasmon polaritons (ESPPs) by engineering the transverse-electric (TE) modes in conventional rectangular waveguides. The complete field distributions, dispersion relations, and asymptotic frequency of the ESPPs are derived analytically. Wave-port excitations and smooth bridges are designed for the mode conversion between propagating modes in rectangular waveguides and the ESPPs. Analytical calculations and numerical simulations are performed for TE 10 -and TE 20 -mode-induced ESPPs, showing excellent agreement. Moreover, we design a double-layered substrate-integrated waveguide showing that ESPPs are supported at the interface between the two layers with different dielectric constants. This work opens up an avenue for low-frequency designer surface plasmons and may find potential applications in the design of compact filters, resonators, and sensors of ESPPs in the microwave and terahertz frequencies.