A Low-Complexity Precoding Scheme for Downlink Massive MU-MIMO Systems with Low-Resolution DACs

In this paper, we investigate the problem of downlink precoding for the narrowband massive multi-user multiple-input multiple-output (MU-MIMO) system with low-resolution digital-to-analog converters (DACs). We introduce a low-complexity precoding scheme based on the alternating direction method of multipliers (ADMM) framework in this work. An efficient gradient descent (GD) algorithm with adaptive step-size determination mechanism (ASGD) is proposed to alleviate the computational complexity bottleneck of the inherent matrix inversion. Numerical results demonstrate that the ASGD precoder achieves an attractive trade-off between the performance and computational complexity compared with other counterparts.

     

Face anti-spoofing based on multi-modal and multi-scale features fusion

Face anti-spoofing is used to assist face recognition system to judge whether the detected face is real face or fake face. In the traditional face anti-spoofing methods, features extracted by hand are used to describe the difference between living face and fraudulent face. But these handmade features do not apply to different variations in an unconstrained environment. The convolutional neural network (CNN) for face deceptions achieves considerable results. However, most existing neural network-based methods simply use neural networks to extract single-scale features from single-modal data, while ignoring multi-scale and multi-modal information. To address this problem, a novel face anti-spoofing method based on multi-modal and multi-scale features fusion ( MMFF) is proposed. Specifically, first residual network ( Resnet )-34 is adopted to extract features of different scales from each modality, then these features of different scales are fused by feature pyramid network (FPN), finally squeeze-and-excitation fusion ( SEF) module and self-attention network ( SAN) are combined to fuse features from different modalities for classification. Experiments on the CASIA-SURF dataset show that the new method based on MMFF achieves better performance compared with most existing methods.     

Adaptive Clustered Federated Learning for Heterogeneous Data in Edge Computing

Mobile Networks and Applications - Although federated learning has been widely used in collaborative training of machine learning models, its practical uses are still challenged by heterogeneous...     

Low-rank tensor completion via combined Tucker and Tensor Train for color image recovery

Applied Intelligence - In recent years, low-rank tensor completion has been widely used in color image recovery. Tensor Train (TT), as a balanced tensor rank minimization method, has achieved good...     

Transformation of monolayer MoS<Subscript>2</Subscript> into multiphasic MoTe<Subscript>2</Subscript>: Chalcogen atom-exchange synthesis route

Molybdenum ditelluride (MoTe2),which is an important transition-metal dichalcogenide,has attracted considerable interest owing to its unique properties,such as its small bandgap and large Seebeck coefficient.However,the batch production of monolayer MoTe2 has been rarely reported.In this study,we demonstrate the synthesis of large-domain (edge length exceeding 30 μm),monolayer MoTe2 from chemical vapor deposition-grown monolayer MoS2 using a chalcogen atom-exchange synthesis route.An in-depth investigation of the tellurization process reveals that the substitution of S atoms by Te is prevalently initiated at the edges and grain boundaries of the monolayer MoS2,which differs from the homogeneous selenization of MoS2 flakes with the formation of alloyed Mo-S-Se hybrids.Moreover,we detect a large compressive strain (approximately-10％) in the transformed MoTe2 lattice,which possibly drives the phase transition from 2H to 1T'at the reaction temperature of 500 ℃.This phase change is substantiated by experimental facts and first-principles calculations.This work introduces a novel route for the templated synthesis of two-dimensional layered materials through atom substitutional chemistry and provides a new pathway for engineering the strain and thus the intriguing physics and chemistry.     

Ultrathin 2D Zirconium Metal–Organic Framework Nanosheets: Preparation and Application in Photocatalysis

Synthesizing ultrathin 2D metal–organic framework nanosheets in high yields has received increasing research interest but remains a great challenge. In this work, ultrathin zirconium‐porphyrinic metal–organic framework (MOF) nanosheets with thickness down to ≈1.5 nm are synthesized through a pseudoassembly–disassembly strategy. Owing to the their unique properties originating from their ultrathin thickness and highly exposed active sites, the as‐prepared ultrathin nanosheets exhibit far superior photocatalysis performance compared to the corresponding bulk MOF. This work highlights new opportunities in designing ultrathin MOF nanosheets and paves the way to expand the potential applications of MOFs.     

Imparting Designer Biorecognition Functionality to Metal–Organic Frameworks by a DNA‐Mediated Surface Engineering Strategy

Surface functionality is an essential component for processing and application of metal–organic frameworks (MOFs). A simple and cost‐effective strategy for DNA‐mediated surface engineering of zirconium‐based nanoscale MOFs (NMOFs) is presented, capable of endowing them with specific molecular recognition properties and thus expanding their potential for applications in nanotechnology and biotechnology. It is shown that efficient immobilization of functional DNA on NMOFs can be achieved via surface coordination chemistry. With this strategy, it is demonstrated that such porphyrin‐based NMOFs can be modified with a DNA aptamer for targeting specific cancer cells. Furthermore, the DNA–NMOFs can facilitate the delivery of therapeutic DNA (e.g., CpG) into cells for efficient recognition of endosomal Toll‐like receptor 9 and subsequent enhanced immunostimulatory activity in vitro and in vivo. No apparent toxicity is observed with systemic delivery of the DNA–NMOFs in vivo. Overall, these results suggest that the strategy allows for surface functionalization of MOFs with different functional DNAs, extending the use of these materials to diverse applications in biosensor, bioimaging, and nanomedicine.     

Emergence of photoluminescence on bulk MoS<Subscript>2</Subscript> by laser thinning and gold particle decoration

We demonstrate a facile and effective approach to significantly improve the photoluminescence of bulk MoS₂ via laser thinning followed by gold particle decoration. Upon laser thinning of exfoliated bulk MoS₂, photoluminescence emerges from the laser-thinned region. After further treatment with an AuCl₃ solution, gold particles self-assemble on the laser-thinned region and thick edges, further increasing the fluorescence of bulk MoS₂ 28 times and the Raman response 3 times. Such fluorescence enhancement can be attributed to both surface plasmon resonance and p-type doping induced by gold particles. The combination of laser thinning and AuCl₃ treatment enables the functionalization of bulk MoS₂ for optoelectronic applications. It can also provide a viable strategy for mask-free and area-selective p-type doping on single MoS₂ flakes.

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