In this paper, a novel low-profile, dual-polarized reflect-transmit-array antenna is proposed to independently control the forward and backward beams. A single-layer polarization-dependent element is designed with $0.1~\lambda _{0}$ -thickness at 10 GHz, which comprises only two layers of metal patches printed on a dielectric substrate and two metallized vias. Through changing the polarization direction of the incident wave, the operating mode of the proposed array can be easily shifted among reflection mode, reflection-transmission mode, as well as transmission mode. To verify the design concept, a circular reflect-transmit-array ( $D =250$ mm) is designed, fabricated, and measured. The measured results indicate a 1 dB bandwidth of 17% (9.8-11.5 GHz) in reflection mode and a measured peak gain of 24.2 dB at 10.5 GHz. Moreover, a 1 dB bandwidth of 6% (9.7-10.3 GHz) can be achieved in transmission mode, and the measured peak gain is 24.6 dB at 10 GHz. The results prove that the proposed design is promising for bidirectional wireless communication applications.

A particular phenomenon was found in packed beds with dielectric barrier discharge (DBD): The temperature of the gaseous phase is significantly higher than that of the pellet phase. This is completely different from the conventional packed bed where the phases have essentially the same temperature. A simplified model was developed to estimate this phenomenon in the packed bed with DBD under natural convection. The power consumption mechanism was investigated. The mechanisms for the electrical energy of inlet plasma transformed into heat energy in the two phases, gaseous and pellets of the packed bed reactor, are different. The energy transformation in the gaseous phase includes electron absorption as well as ion absorption. The energy absorbed by electrons, including ohmic heating and stochastic heating, maintains plasma condition. The energy absorbed by ions transfers to other heavy particles with frequent collisions in plasma sheath and, finally, raises the macro temperature of the gas. The energy consumption in pellet phase is dielectric polarization loss and depends on packed bed geometry and DBD. These mechanisms of energy consumption are introduced into the packed bed heat transfer model to develop the simplified model. Some experiments are performed and the results agree well with the numerical simulation of this model.

This letter develops a novel synthesis method for the circular aperture orbital angular momentum (OAM) antennas. The method, derived from the continuous aperture, effectively reduces the sidelobe levels (SLLs) of OAM waves and can achieve precise adjustments. Moreover, a discretization method is proposed, thus extending the applicability of the synthesis method to discrete arrays. Compared to the traditional direct sampling method, the proposed method can reduce the performance degradation of antennas in terms of SLL caused by discretizing continuous aperture distributions, especially for high-order OAM waves. Using the proposed approaches, a complex amplitude transmission metasurface is designed to generate a 2nd-order OAM wave with the desired SLLs of -25 dB. Experimental results show that the SLLs of the E-plane and H-plane are -22.87 dB and -23.02 dB, respectively. The effectiveness of the approaches for controlling SLL is demonstrated by theoretical analyses, simulations, and experiments.

The promotion of CO oxidization and inhibition of NO formation by gaseous iron species were analyzed using the Sandia SENKIN program. It is shown that the relative ratio of CO oxidization dramatically varies with combustion time at early burning stage in the presence of iron species, and all peak values are greater than 2.4. The relative ratio of CO oxidization decreases with the increase of air stoichiometric ratio and CO concentration in off-gas. The circulation reactions of Fe−FeO/FeO₂−Fe achieve the catalytic effect on CO oxidization. Gaseous iron species can greatly inhibit NO formation, NO reduction ratio can reach above 70% at T = 2073 and 2273 K, and gaseous iron species can effectively inhibit NO formation when combustion temperature is not higher than 2273 K during the off-gas combustion. There are O₂ competitive reactions between thermal NO formation and Fe oxidization, and high chemical activity of iron species inhibits thermal-NO formation.

In this letter, an ultrathin polarization-converting transmissive Huygens element is proposed achieving nearly 100% transmission efficiency for circularly polarized (CP) incident waves. The element consists of a single-layer dielectric substrate with a thickness of only 0.03λ0 and asymmetric S-shaped patches located on both sides. By utilizing surface currents flowing in the reverse direction of the upper and lower patches to form a magnetic dipole, while generating an electric dipole in the orthogonal direction, the electromagnetic response satisfies the Huygens resonance requirement, which makes the transmitarray extremely high efficient for transmission. The independent regulation of CP beam and 360° phase coverage can be flexibly achieved by adjusting rotation angle of the element. The designed element is experimentally integrated to form a metalens antenna to generate directional beam with high gain and low sidelobes. The measured results show that the achieved peak gain of 24.4 dBi at 9.8 GHz with the peak aperture efficiency of 51.3%, which well demonstrated the advantages of low profile, high efficiency, and easy integration of the designed transmitarray structure. Above all, the proposed metalens antenna exhibits superiority for further being applied in device-to-device satellite communications.