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Cubic Metric Reduction for Repetitive CAZAC Sequences in Frequency Domain

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China Communications 2021年第12期18卷 196-207页

作者： yajun zhao Juan Liu Saijin Xie Beijing Institute of Technology Beijing 100081China ZTE Corporation Beijing 100029China

To meet the requirements of Occupied Channel Bandwidth(OCB)of unlicensed spectrum,in NR-based Access to Unlicensed Spectrum(NR-U)of 5G New Radio(NR)system,the channels of PRACH and PUCCH have to employ some frequency domain sequence repetition *** repeti-tion schemes cause serious Cubic Metric(CM)prob-lems for these channels,although these two types of channels are composed of Constant Amplitude Zero Auto-correlation(CAZAC)*** the properties of CAZAC sequences,which are used for PRACH and PUCCH(refer to PUCCH format 0 and format 1)in 5G NR system,in this paper,we pro-pose some new schemes of CM reduction for these two channels taking into account the design princi-ples to ensure the sequence performance of the auto-correlation and *** the recom-mended CM reduction schemes are evaluated and the optimized parameters are further provided considering both CM performance and the complexity.

关键词： 5G OFDM cubic metric NR-U oc-cupied channel bandwidth CAZAC zadoff-chu se-quence

Potential key technologies for 6G mobile communications

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Science China(Information Sciences) 2020年第8期63卷 217-235页

作者： Yifei YUAN yajun zhao Baiqing ZONG Sergio PAROLARI China Mobile ZTE Corporation

The standard development of 5G wireless communication culminated between 2017 and 2019,followed by the worldwide deployment of 5G networks, which is expected to result in very high data rate for enhanced mobile broadband, support ultrareliable and low-latency services and accommodate massive number of connections. Research attention is shifting to future generation of wireless communications, for instance, beyond 5G or 6G. Unlike previous studies, which discussed the use cases, deployment scenarios,or new network architectures of 6G in depth, this paper focuses on a few potential technologies for 6G wireless communications, all of which represent certain fundamental breakthrough at the physical layer —technical hardcore of any new generation of wireless communications. Some of them, such as holographic radio, terahertz communication, large intelligent surface, and orbital angular momentum, are of revolutionary nature and many related studies are still at their scientific exploration stage. Several technical areas, such as advanced channel coding/modulation, visible light communication, and advanced duplex, while having been studied, may find more opportunities in 6 G.

关键词： 6G holographic radio terahertz large intelligent surface orbital angular momentum advanced channel coding modulation visible light communication

Reconfigurable intelligent surfaces for 6G:applications,challenges,and solutions

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Frontiers of Information Technology & Electronic Engineering 2023年第12期24卷 1669-1688页

作者： yajun zhao Beijing Institute of Technology Beijing100081China ZTE Corporation Beijing100029China

Scholars are expected to continue enhancing the depth and breadth of theoretical research on reconfigurable intelligent surface(RIS)to provide a higher theoretical limit for RIS engineering ***,significant advancements have been achieved through both academic research breakthroughs and the promotion of engineering applications and *** provide an overview of RIS engineering applications,focusing primarily on their typical features,classifications,and deployment ***,we systematically and comprehensively analyze the challenges faced by RIS and propose potential solutions including addressing the beamforming issues through cascade channel decoupling,tackling the effects and resolutions of regulatory constraints on RIS,exploring the network-controlled mode for RIS system architecture,examining integrated channel regulation and information modulation,and investigating the use of the true time delay(TTD)mechanism for *** addition,two key technical points,RIS-assisted non-orthogonal multiple access(NOMA)and RIS-based transmitter,are reviewed from the perspective of ***,we discuss future trends and challenges in this field.

关键词： 6G Reconfigurable intelligent surface(RIS) Cascade channel decoupling RIS regulatory constraint RIS system

Codebook Design and Beam Training for Extremely Large-Scale RIS:Far-Field or Near-Field?

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China Communications 2022年第6期19卷 193-204页

作者： Xiuhong Wei Linglong Dai yajun zhao Guanghui Yu Xiangyang Duan Beijing National Research Center for Information Science and Technology(BNRist)as well as the Department of Electronic Engineering Tsinghua UniversityBeijing 100084China ZTE Corporation Shenzhen 518038China

Reconfigurable intelligent surface(RIS)is more likely to develop into extremely large-scale RIS(XL-RIS)to efficiently boost the system capacity for future 6 G *** training is an effective way to acquire channel state information(CSI)for *** beam training schemes rely on the far-field ***,due to the large aperture of XL-RIS,the scatters are more likely to be in the near-field region of *** far-field codebook mismatches the near-field channel ***,the existing far-field beam training scheme will cause severe performance loss in the XL-RIS assisted nearfield *** solve this problem,we propose the efficient near-field beam training schemes by designing the near-field codebook to match the nearfield channel ***,we firstly design the near-field codebook by considering the near-field cascaded array steering vector of ***,the optimal codeword for XL-RIS is obtained by the exhausted training *** reduce the beam training overhead,we further design a hierarchical nearfield codebook and propose the corresponding hierarchical near-field beam training scheme,where different levels of sub-codebooks are searched in turn with reduced codebook *** results show the proposed near-field beam training schemes outperform the existing far-field beam training scheme.

关键词： extremely large-scale RIS near-field codebook design beam training

Multi-dimensional morphology of hydride diffusion layer and associated sequential twinning in commercial pure titanium

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Journal of Materials Science & Technology 2022年第8期103卷 105-112页

作者： Qian Wang Shun Xu yajun zhao Jean-Sébastien Lecomte Christophe Schuman Laboratoire d’Etude des Microstructures et de Mécanique des Matériaux(LEM3) Universitéde Lorraine CNRSArts et Métiers ParisTechMetz57073France Laboratory of Excellence on Design of Alloy Metals for low-mAss Structures(DAMAS) University of Lorraine57073France School of Iron and Steel Soochow UniversitySuzhou 215021China School of Materials Science and Engineering Dalian Jiaotong UniversityDalian 116021China

The dominant hydride precipitates have been well demonstrated to follow two types of orientation relationships(ORs)with Ti matrix:OR1 with{0001}//{001},//and OR2 with{0001}//{111},//.Within the grains with special orientations,the complicated interactions of different hydride variants inside Ti-hydride diffusion layer are characterized in this *** OR1 hydride layer,the orientations of{1010}plane parallel to the sample surface and a-axis parallel to the normal direction prefer multiple OR1 *** orientations favorable for OR2 hydride layer are:{1013}plane parallel to sample surface corresponding to the layer with one OR2 variant dominated and c-axis parallel to the surface normal with multiple OR2 variant layer ***,{1012}extension twins and{1122}contraction twins are activated to accommodate the OR2 hydride-induced surface expansion and local misfit *** stimulation of these two twins is also orientation-dependent:{1012}and{1122}twins are observed in the grains with c-axis parallel to and deviated from the surface normal,*** further variant selection for each twin mode is performed through shear accommodation of hydride-twin pairs.

关键词： Titanium Hydride Cross section Twin Variant selection

AIRIS:Artificial Intelligence Enhanced Signal Processing in Reconfigurable Intelligent Surface Communications

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China Communications 2021年第7期18卷 158-171页

作者： Shun Zhang Muye Li Mengnan Jian yajun zhao Feifei Gao State Key Laboratory of Integrated Services Networks Xidian UniversityXi’an 710071China Algorithm Department of Wireless Product R&D Institute ZTE CorporationBeijing 100029China Institute for Artificial Intelligence Tsinghua University(THUAI)State Key Lab of Intelligent Technologies and SystemsTsinghua UniversityBeijing National Research Center for Information Science and Technology(BNRist)Department of AutomationTsinghua University Beijing100084China

Reconfigurable intelligent surface(RIS)is an emerging meta-surface that can provide additional communications links through reflecting the signals,and has been recognized as a strong candidate of 6G mobile communications ***,it has been recently admitted that implementing artificial intelligence(AI)into RIS communications will extensively benefit the reconfiguration capacity and enhance the robustness to complicated transmission *** the conventional model-driven approaches,AI can also deal with the existing signal processing problems in a data-driven manner via digging the inherent characteristic from the real ***,AI is particularly suitable for the signal processing problems over RIS networks under unideal scenarios like modeling mismatching,insufficient resource,hardware impairment,as well as dynamical *** one of the earliest survey papers,we will introduce the merging of AI and RIS,called AIRIS,over various signal processing topics,including environmental sensing,channel acquisition,beamforming design,and resource scheduling,*** will also discuss the challenges of AIRIS and present some interesting future directions.

关键词： reconfigurable intelligent surface artifi-cial intelligence deep learning deep reinforcement learning signal processing

Iridic oxide nanoparticles grown in situ on BCN nanotubes as highly efficient dual electrocatalyst for rechargeable lithium-O2 batteries

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Journal of Energy Chemistry 2020年第10期29卷 291-298页

作者： Xufang Li yajun zhao Jing Zhang Chaoxiong Li Shan Wu Qiufan Shi Dawei Zhang Qingchun Yang School of Chemistry and Chemical Engineering Hefei University of TechnologyHefei 230009AnhuiChina Anhui Province Key Laboratory of Power Battery Tianneng Battery Group(Anhui Company)Jieshou 236500AnhuiChina School of Materials Science and Technology Hefei University of TechnologyHefei 230009AnhuiChina

Oxygen cathode catalysts can significantly address the issues faced by Li-O2 *** this research,a composite of IrO2 nanoparticles grown in situ on BCN nanotubes(IrO2@BCNNTs)has been synthesized by facile hydrothermal method,which is initially fabricated as cathode catalyst for Li-O2 *** results indicate that IrO2@BCNNTs nanocomposite has a better effect on improving the actual discharge capacity,voltage gap and cyclability of Li-O2 *** addition,it is also demonstrated that the Ir O2@BCNNTs composite exhibits bifunctional characteristics for both the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER)through rotating disk electrode(RDE)*** excellent performances of the synthesized catalyst may be attributed to the unique interconnected tubular structure and strong synergistic effect,which can provide more charged sites and defect sites and then facilitate reversible Li2 O2 formation and ***,it is promising for applying the rational design of the bifunctional catalyst to Li-O2 battery.

关键词： BCN nanotubes IrO2@BCNNTs composite Rechargeable Li-O2 batteries

Perovskite oxides La_(0.4)Sr_(0.6)Co_xMn_(1-x)O_3(x=0,0.2,0.4) as an effective electrocatalyst for lithium-air batteries

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Green Energy & Environment 2018年第1期3卷 78-85页

作者： yajun zhao Tao Liu Qiufan Shi Qingchun Yang Chunxiao Li Dawei Zhang Chaofeng Zhang School of Chemistry and Chemical Engineering Hefei University of Technology

Co-doped perovskite oxide La_(0.4)Sr_(0.6)Co_xMn_(1-x)O_3(x=0, 0.2, 0.4) composites are prepared by sol-gel method utilizing citric acid as chelating agent. These composites show good catalytic activities when tested as catalysts rechargeable lithium-air batteries. In particular, the La_(0.4)Sr_(0.6)Co_(0.4)Mn_(0.6)O_3 shows a lower potential gap. When these samples are tested as catalysts for Li-air batteries at a current density of100 mA g^(-1), the discharge capacities with different La_(0.4)Sr_(0.6)Co_xMn_(1-x)O_3(x=0,0.2, 0.4) catalysts are 5819, 6420, and 7227 mA h g^(-1),respectively. In addition, under a capacity limitation of 1000 mA h g^(-1), the cell using La_(0.4)Sr_(0.6)Co_(0.4)Mn_(0.6)O_3 as catalyst shows good cycling stability up to 46 cycles. The good electrochemical performance suggests that suitable doping of Co in Mn site of La_(0.4)Sr_(0.6)MnO_3 could be a promising route to improve the catalytic activity.

关键词： ORR OER Perovskite Lithium-air batteries

Composition optimization of inconel 718 via cluster formula and experimental verification

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Journal of Materials Science & Technology 2023年第9期140卷 249-259页

作者： Yancheng Li Mo Li Qing Wang yajun zhao Shuang Zhang Cunlei Zou Ying Li Lianchao Wang Chuang Dong Key Laboratory of Materials Modification by Laser Ion and Electron BeamsMinistry of EducationSchool of Materials Science and EngineeringDalian University of TechnologyDalian 116024China School of Materials Science and Engineering Dalian Jiaotong UniversityDalian 116028China Dongbei Special Steel Group Co. Ltd.Dalian 116105China

Superalloys feature multi-elements and complex elemental ranges,which makes the proper composition selection *** fact,more strict composition standards generally apply in practical *** objective of this paper is to understand and eventually to renew the composition standard via example of the most common grade Inconel *** have recently shown that t he alloy chemistry originates from a nearest-neighbor cluster[center-shell]plus a few next-neighbor glue atoms,or expressed in cluster for-mula[center-shell](glue atoms).By grouping the elements into Ni=(Ni,Co,Cu,Fe),Cr=(Cr,Mn,Si,Mo),and Nb=(Nb,Al,Ti),it is found that the reported alloys fall within a narrow composition zone Ni_(11.0-13.0)-Cr_(3.5-4.5)-Nb_(1) confined by cluster formulas of 16 and 18 *** composition zone is also expressed in terms of 288-atom supercluster formulas,Ni_(198-208)-Cr_(63-72)-Nb_(16-18),which leads to coordi-nated elemental variations in wt.%:69.0≤Ni+Co+Cu+Fe≤72.7;19.8≤Cr+Mn+1.7 Si+0.6 Mo≤22.8;8.7≤Nb+3.2 Al+1.9 Ti≤*** this composition zone,Ni_(206)-Cr_(65.5)-Nb_(16.5) is further pinpointed and validated by our own experiments to possess the optimal match of strength and plasticity both at room and at 923 K.

关键词： Inconel 718 superalloy Cluster-plus-glue-atom model Cluster formula Composition standard