检索结果-南通市图书馆

Physical layer security for massive access in cellular Internet of Things

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2020年第2期63卷 104-115页

作者： Qiao QI xiaoming chen Caijun ZHONG Zhaoyang ZHANG College of Information Science and Electronic Engineering Zhejiang University

The upcoming fifth generation(5G) cellular network is required to provide seamless access for a massive number of Internet of Things(IoT) devices over the limited radio spectrum. In the context of massive spectrum sharing among heterogeneous Io T devices, wireless security becomes a critical issue owing to the broadcast nature of wireless channels. According to the characteristics of the cellular IoT network,physical layer security(PHY-security) is a feasible and effective way of realizing secure massive access. This article reviews the security issues in the cellular IoT network with an emphasis on revealing the corresponding challenges and opportunities for the design of secure massive access. Furthermore, we provide a survey on PHY-security techniques to improve the secrecy performance. Especially, we propose a secure massive access framework for the cellular Io T network by exploiting the inherent co-channel interferences. Finally, we discuss several potential research directions to further enhance the security of massive IoT.

关键词： 5G and beyond PHY-security massive access cellular IoT

Low-cost intelligent reflecting surface aided Terahertz multiuser massive MIMO: design and analysis

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2021年第10期64卷 73-87页

作者： Guanghua YU xiaoming chen Xiaodan SHAO Caijun ZHONG College of Information Science and Electronic Engineering Zhejiang University

Terahertz(THz) multiuser massive multiple-input multiple-output(MIMO) has been envisioned as a promising technique to support massive connectivity in next-generation wireless networks. However,due to ultra-high frequency band, the path attenuation of THz channels is extremely severe, resulting in limited wireless coverage. In this paper, we propose an intelligent reflecting surface(IRS)-assisted THz multiuser massive MIMO technique to enhance coverage. First, we design an IRS-assisted THz communication framework with a low-cost sub-connected hybrid precoding architecture, including uplink data transmission and downlink data transmission. In particular, precoding errors due to the limitations of physical devices and environments are taken into consideration. Then, we derive the closed-form expressions for uplink and downlink spectral efficiencies, and reveal the impacts of system parameters. Finally, we conduct extensive simulations to verify the effectiveness of the proposed IRS-assisted THz multiuser massive MIMO technique.

关键词： THz communication IRS massive MIMO precoding error coverage enhancement

Recovery of scandium from silicate minerals by high-pressure leaching in sulfuric acid

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Rare Earths 2024年第7期42卷 1375-1384,I0007页

作者： Peng Yan xiaoming chen Likun Gao Bo Yang Faculty of Metallurgical and Energy Engineering Kunming University of Science and TechnologyKunming650093China Faculty of Land Resources Engineering Kunming University of Science and TechnologyKunming650093China School of Chemistry and Chemical Engineering Kunming UniversityKunming650214China

This study investigated the leaching of scandium from a Sc-bearing silicate *** Sc concentrate obtained by beneficiation pre-enrichment has 1.03×10^(−4) wt%Sc and 14.66 wt%*** main Sc-bearing minerals are limonite,chlorite,sericite,and hornblende,in the form of ***-pressure leaching(HPL)with sulfuric acid(98 wt%)and NaF was used to dispose this *** Sc leaching efficiency of 91.82%was obtained under the optimum conditions,which are pressure of 5.0×10^(5) Pa,A/O value of 1.1,L/S value of 1.8,NaF dosage of 2 wt%,at 130℃ for 6 *** X-ray diffraction(XRD)and scanning electron microscopy(SEM)results show that the residue is mainly quartz phase in the multihole *** with ordinary leaching for silicate,high-pressure leaching has significant advantages in saving acid and energy consumption.

关键词： Silicate minerals Scandium High-pressure Leaching Concentrated sulfuric acid Rare earths

维普期刊数据库

Tracking guided actions recognition for cows

在线全文

学校读者我要写书评

暂无评论

Quantitative Biology 2022年第4期10卷 351-365页

作者： Yun Liang xiaoming chen Guangzhou Key Laboratory of Intelligent Agriculture College of Mathematics and InformaticsSouth China Agricultural UniversityGuangzhou 510642China

Background:Cows actions are important factors of cows health and their *** monitoring the individual cows actions,we prevent cows diseases and realize modern precision cows ***,traditional cows actions monitoring is usually conducted through video recording or direct visual observation,which is time-consuming and laborious,and often lead to misjudgement due to the subjective consciousness or ***:This paper proposes a method of cows actions recognition based on tracked trajectories to automatically recognize and evaluate the actions of ***,we construct a dataset including 60 videos to describe the popular actions existing in the daily life of cows,providing the basic data for designing our actions recognition ***,eight famous trackers are used to track and obtain temporal and spatial information of ***,after studying and analysing the tracked trajectories of different actions about cows,a rigorous and effective constraint method is designed to realize actions recognition by ***:Many experiments demonstrate that our method of actions recognition performs favourably in detecting the actions of cows,and the proposed dataset basically satisfies the actions evaluation for ***:The proposed tracking guided actions recognition provides a feasible way to maintain and promote cows health and welfare.

关键词： public framework actions recognition visual tracking precision agriculture cows health

Localized Corrosion and Stress Corrosion Cracking Behavior of AA7003 in a 3.5 wt% NaCl Aqueous Solution

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2020年第5期35卷 986-995页

作者： QI Xing SUN Bin chen xiaoming SONG Renguo School o f Materials Science and Engineering Changzhou UniversityChangzhou 213164China Jiangsu Key Laboratory o f Materials Surface Science and Technology Changzhou UniversityChangzhou 213164China Jiangsu Collaborative Innovation Center o f Photovolatic Science and Engineering Changzhou UniversityChangzhou 213164China Key Laboratory o f Research on Hydraulic and Hydro-Power Equipment Surface Engineering Technology1 o f Zhejiang Province Hangzhou 310012China

The microstructure,localized corrosion (LC) and stress corrosion cracking (SCC) behavior of 7003 aluminum alloy (AA7003) under various aging treatments (peak aging (PA),double peak aging (DPA),regression and re-aging (RRA)) were investigated by means of transmission electron microscope (TEM),scanning electron microscopy (SEM),electrochemical impendence spectroscopy (EIS) and slow strain rate tensile *** results of TEM showed a discontinuous distribution of grain boundary precipitates of AA7003 under DPA and RRA treatments,which is beneficial for increasing the resistance of LC and ***,LC was found initiating firstly on intermetallics which caused the dissolution of surrounding matrix,then pitting holes were formed and developed into *** addition,the SCC process of AA7003 could be divided into two stages,i e,initial pre-cracking and breeding *** EIS analysis,cross-section morphologies and fracture surfaces of specimens indicated that DPA and RRA treatments significantly decreased the crack growth rate during breeding cracking stage,especially for RRA treatment.

关键词： 7003 aluminum alloy localized corrosion stress corrosion cracking

维普期刊数据库

Breaking the von Neumann bottleneck:architecture-level processing-in-memory technology

在线全文

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2021年第6期64卷 60-69页

作者： Xingqi ZOU Sheng XU xiaoming chen Liang YAN Yinhe HAN Institute of Computing Technology Chinese Academy of Sciences Zhejiang Lab Department of Computer Technology and Information Anhui Normal University University of Chinese Academy of Sciences

The "memory wall" problem or so-called von Neumann bottleneck limits the efficiency of conventional computer architectures, which move data from memory to CPU for computation; these architectures cannot meet the demands of the emerging memory-intensive applications. Processing-in-memory(PIM) has been proposed as a promising solution to break the von Neumann bottleneck by minimizing data movement between memory hierarchies. This study focuses on prior art of architecture level DRAM PIM technologies and their implementation. The key challenges and mainstream solutions of PIM are summarized and introduced. The relative limitations of PIM simulation are discussed, as well as four conventional PIM ***, research directions and perspectives are proposed for future development.

关键词： processing-in-memory(PIM) von Neumann bottleneck memory wall PIM simulator architecture-level PIM

A vector hybrid triboelectric sensor(HTS)for motion identification via machine learning

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2023年第7期16卷 10120-10130页

作者： Nannan Zhou Hongrui Ao xiaoming chen Shan Gao Hongyuan Jiang School of Mechatronics Engineering Harbin Institute of TechnologyHarbin 150001China School of Control Engineering Northeastern University at QinhuangdaoQinhuangdao 066004China

Rapidly responding and cost-effective sensors played a crucial role in industrial ***,the lack of versatile strategies for identifying and classifying operating states on various practical behaviors has limited the rapid development of monitoring *** study developed a vector hybrid triboelectric sensor(HTS)with surface nanocrystalline containing triboelectric vibration and rotation units(triboelectric vibration unit(TVU),triboelectric rotation unit(TRU))capable of detecting the vibrational and rotary states of the *** synchronous detection of two sensing signals can be achieved due to the hierarchical structure as the basic unit of the HTS,which contributed to reducing the volume and spatial distribution of the *** on the voltage/current/charge(U-I-Q)signal amplitudes and phase features generated by the TVU,the vibration frequency and orientation of the device can be identified by using a double-layer neural network(D-LNN),in which the accuracy reaches 96.5%and 95.5%***,by combining logistic regression,D-LNN,and linear regression,the accuracy of the TRU for rotary classification exceeds 93.5%in practical *** this study,the great potential application of the HTS combined with the machine learning methods was successfully explored and exhibited and it might speed up the development of industrial detection in the near future.

关键词： vector triboelectric sensor surface nanocrystalline hierarchical structure sensing properties state detection machine learning

Transformation of a metasurface on the substrate interface into the same metasurface in a homogenized substrate based on two kinds of modified Babinet's principles

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2023年第12期66卷 238-250页

作者： Xiaobo LIU Rui LU Anxue ZHANG Qiang chenG xiaoming chen School of Information and Communications Engineering Xi'an Jiaotong University School of Mathematics and Statistics Xi'an Jiaotong University State Key Laboratory of Millimeter Waves and School of Electrical Engineering Southeast University

Previously, the metasurface was usually manufactured on a dielectric substrate using the printed circuit boards(PCB) technology. However, due to the existence of the substrate interface, the electromagnetic radiation and coupling of the sub-wavelength metasurface becomes more complex for theoretical analysis. To this end, an indirect method is developed to transform the problem of a metasurface in a dielectric half-space into a simpler problem of the same metasurface in a homogenized dielectric space. Specifically, two different theoretical models of complementary metasurfaces in a dielectric half-space are first given. A specific yet unknown relative permittivity is included in one model to realize the above transformation. By comparing these two theoretical models in terms of the surface impedance matrix, the specific yet unknown relative permittivity is analytically derived as (εr,unk)1/2=(εr,1)1/2/2 +(εr,2)1/2/2. Finally, two arbitrary metasurfaces are given to verify the proposed theory for arbitrary incidence wave in dielectric half-space. The theory can greatly simplify the analysis and design of the metasurface in a dielectric halfspace, because only the metasurface in a homogenized dielectric space like vacuum needs to be theoretically solved after completing the above transformation.

关键词： dielectric half-space homogenized dielectric space metasurface relative permittivity surface impedance matrix substrate interface

Complete sequence and gene organization of the mitochondrial genome of Batocera lineolata Chevrolat(Coleoptera:Cerambycidae)

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2012年第27期57卷 3578-3585页

作者： WANG chengYe FENG Ying chen xiaoming Key Laboratory of Cultivating and Utilization of Resource Insects of State Forestry Administration Research Institute of Resource Insects Chinese Academy of ForestryKunming 650224China

Batocera lineolata Chevrolat,1852 is an important forest pest that is found mainly in China,Vietnam,India,and *** complete mitochondrial genome(mitogenome) sequence of *** was determined by long polymerase chain reaction(PCR) and conserved primer walking *** results showed that the entire mitogenome is 15418 bp long with 74.48% A+T *** positions and arrangement of the 37 genes encoded by the genome are identical to the mitogenomes of two other longhorn beetles for which the complete gene content and arrangement are publicly *** protein-coding genes start with the ATN codon that is a typical initiation codon in *** transfer RNAs(tRNAs) were predicted to form the standard clover-leaf structure,except for tRNA Ser(AGN),which lacks the dihydrouridine(DHU) *** most unusual feature that was found was the use of TCT as the tRNA Ser(AGN) anticodon instead of the GCT that is used in most other *** lack of tandem repeat motif in the 735 bp long A+T-rich region was another unusual feature of the *** *** short,highly conserved polythymidine stretch that was previously described in the Orthoptera and Diptera orders was also present in the A+T-rich region of the ***(order Coleoptera) *** sequence and annotation of the mitogenome of *** will provide further insights into the diversity and evolution of the Cerambycidae family of long-horned *** *** mitogenome sequence has been deposited in GenBank(http://***/Genbank/) under accession number JN986793.

关键词：线粒体基因组基因组序列天牛科鞘翅目基因组织云斑美国国立卫生研究院起始密码子

维普期刊数据库