6G New Multiple Access Technology

As a basic technology at physical layer of mobile communications,non-orthogonal multiple access has been attracting wide attention across the academia and the industry.During the standardization of the fifth-generation(5G)of mobile communications,3GPP conducted preliminary study on non-orthogonal multiple access without reaching the consensus to standardize the technology.

Surface Cu^(+) modified ZnIn_(2)S_(4) for promoted visible-light photocatalytic hydrogen evolution

Surface modification by metal ion has been considered a promising strategy to enhance the photocatalytic activity by extending optical response and improving charge separation and transportation.Here,univalent copper species were modified on ZnIn_(2)S_(4)photocatalyst via an in-situ photodeposition method,exhibiting a much higher H2evolution rate of 41.10±3.43 mmol g^(-1)h^(-1)and an impressive apparent quantum efficiency(AQE)of 20.81%at 420±15 nm.Our characterizations indicate that the surface modification by copper species can broaden light utilization as well as promote charge separation and transportation.Besides,the density functional theory(DFT)results further exhibit that the energy levels(LUMO and HOMO)for copper-surface modified ZnIn_(2)S_(4)present spatial separation,locating on the Zn-S and In-S layers,respectively,which can suppress the recombination of electron and hole and thus achieves higher photocatalytic H2evolution efficiency.

Simultaneously transmitting and reflecting(STAR)RISs for 6G:fundamentals,recent advances,and future directions

Simultaneously transmitting and reflecting reconfigurable intelligent surfaces(STAR-RISs)have been attracting significant attention in both academia and industry for their advantages of achieving 360°coverage and enhanced degrees-of-freedom.This article first identifies the fundamentals of STAR-RIS,by discussing the hardware models,channel models,and signal models.Then,three representative categorizing approaches for STAR-RISs are introduced from the phase-shift,directional,and energy consumption perspectives.Furthermore,the beamforming design of STAR-RISs is investigated for both independent and coupled phase-shift cases.As a recent advance,a general optimization framework,which has high compatibility and provable optimality regardless of the application scenarios,is proposed.As a further advance,several promising applications are discussed to demonstrate the potential benefits of applying STAR-RISs in sixth-generation wireless communication.Lastly,a few future directions and research opportunities are highlighted.

Reconfigurable intelligent surfaces for wireless communications:Overview of hardware designs,channel models,and estimation techniques

The demanding objectives for the future sixth generation(6G)of wireless communication networks have spurred recent research efforts on novel materials and radio-frequency front-end architectures for wireless connectivity,as well as revolutionary communication and computing paradigms.Among the pioneering candidate technologies for 6G belong the reconfigurable intelligent surfaces(RISs),which are artificial planar structures with integrated electronic circuits that can be programmed to manipulate the incoming electromagnetic field in a wide variety of functionalities.Incorporating RISs in wireless networks have been recently advocated as a revolutionary means to transform any wireless signal propagation environment to a dynamically programmable one,intended for various networking objectives,such as coverage extension and capacity boosting,spatiotemporal focusing with benefits in energy efficiency and secrecy,and low electromagnetic field exposure.Motivated by the recent increasing interests in the field of RISs and the consequent pioneering concept of the RIS-enabled smart wireless environments,in this paper,we overview and taxonomize the latest advances in RIS hardware architectures as well as the most recent developments in the modeling of RIS unit elements and RIS-empowered wireless signal propagation.We also present a thorough overview of the channel estimation approaches for RIS-empowered communications systems,which constitute a prerequisite step for the optimized incorporation of RISs in future wireless networks.Finally,we discuss the relevance of the RIS technology in the latest wireless communication standards,and highlight the current and future standardization activities for the RIS technology and the consequent RIS-empowered wireless networking approaches.

Hydrophobic 1-octadecanethiol functionalized copper catalyst promotes robust high-current CO_(2) gas-diffusion electrolysis

The electrocatalytic reduction of CO_(2) presents a promising strategy in addressing environmental and energy crisis.Significant progress has been achieved via CO_(2) gas diffusion electrolysis,to react at high selectivity and high rate.However,the gas diffusion layer(GDL)of the gas diffusion electrode(GDE)still suffers from low tolerance and limited active sites.Here,the hydrophobic 1-octadecanethiol molecular was functionalized over the Cu catalyst layer of the GDE,which simultaneously stabilizes the GDL and exposes abundant active solid-liquid-gas three-phase interfaces.The resultant GDE exhibits multi-carbon(C_(2+))product selectivity over faradaic efficiency(FE)of 70.0%in the range of 100 to 800 mA·cm^(-2),with the peak FE^(c2+)of 85.2%at 800 mA·cm^(-2).Notably,the strengthened GDE could continuously drive high-current electrolysis for more than 100 h without flooding.This work opens a new way to improve CO_(2) gas diffusion electrolysis via surface molecular engineering.

Installation of high-valence tungsten in MIL-125(Ti) for boosted photocatalytic hydrogen evolution

Metal-organic frameworks(MOFs) possess the features of highly porosity-tunable and electronic-tunable structures,. Taking advantages of these merits, we successfully installed high-valence W6+ions onto the Ti-oxo clusters of MIL-125(Ti)(W-MIL-125). The installed W^(6+) ions which form a W–O–Ti structure trigger the metal-to-cluster charge transfer(MCCT), together with an enhanced light absorption.Structural and spectroscopic characterizations reveal that the MCCT process optimizes the charge transfer process and efficiently separates the photogenerated electron-hole spatially.The as-obtained sample of 3.45 W-MIL-125 with optimized electronic structure demonstrates an enhanced photocatalytic hydrogen evolution performance of 1110.7 ± 63.7 μmol g^(-1)h^(-1) under light irradiation, which is 4.0 times that of the pristine MIL-125(Ti). This work will open up a new avenue for local structural modification of MOFs to boost photocatalytic performance.