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Repetitively pulsed gas discharges:memory effect and discharge mode transition

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High Voltage 2020年第5期5卷 569-582页

作者： Zheng Zhao jiangtao li School of Electrical Engineering Xi'an Jiaotong UniversityXi'anPeople's Republic of China

Repetitively pulsed gas volume and dielectric surface discharges have gained growing attention because of peculiar and exciting physics phenomena,high efficiency,high reactivity,and potential to obtain conventionally unachievable plasma ***,incomplete understanding of fundamental mechanisms renders the repetitively pulsed discharge far less predictable and controllable,where the inherent memory effect and the discharge mode transition are universal *** this topical review,the authors will explore the macroscopic characteristics of the gas gap breakdown and the surface flashover,state-of-the-art mechanisms and dominant agents of discharge memory effects,operation regimes and transitions of the discharge mode,and how waveform parameters affect the pulsed discharge *** and potential approaches for further understanding the memory effect and the discharge mode transition in the repetitively pulsed discharge are discussed.

关键词： properties. transition incomplete

Synthesis of Polycrystalline Nd∶YAG Nanopowders Used for Sintering Transparent Ceramics via Gel Combustion

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Journal of Rare Earths 2006年第z1期24卷 193-196页

作者： li Xianxue Hu Zhanggui li jiangtao Beijing Center for Crystal Research and Development Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100080 China Graduate School of Chinese Academy of Sciences Beijing 100039 China Beijing Center for Crystal Research and Development Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100080 China Functional Ceramic Research Group Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing 100080 China

Polycrystalline nano-sized neodymium doped yttrium aluminum garnet (Nd∶Y3Al5O12, Nd∶YAG) powders were synthesized via a gel combustion method using nitrates and citric acid as starting materials. The evolution of phase composition and micro-structure of the powders were characterized by X-ray powder diffraction, thermogravimetry/differential thermal analysis and scanning electron microscopy. Well-crystallized Nd∶YAG nano-sized powders could be obtained at 950 ℃ for 2 h. The resultant powders are well dispersed, have a relatively narrow size distribution with an average particle size of approximately 50 nm, and show excellent sinterability. These powders can be densified to 99.2% of the theoretical density by HP sintering at 1700 ℃ for 3 h under 20 MPa nitrogen pressure.

关键词： Nd∶YAG gel combustion sintering

Highly thermal-conductive graphite flake/Cu composites prepared by sintering intermittently electroplated core-shell powders

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Journal of Materials Science & Technology 2021年第2期61卷 93-99页

作者： Hong Sun Nan Deng Jianqiang li Gang He jiangtao li National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology CAS Key Laboratory of Green Process and Engineering.Institute of Process EngineeringChinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China School of Materials Science and Engineering University of Science and Technology BeijingBeijing100083China Technical Institute of Physics and Chemistry Chinese Academy of SciencesBeijing100190China

Graphite flake/Cu composite has attracted tremendous attention as a promising heat sinks materials owing to its easy machinability and superior thermal properties. However, its preparation process still faces several technological limitations including complex, time-consuming and costly synthetic approaches. In this work, a facile and scalable intermittently electroplated method is applied to prepare Cu-coated graphite flake composite powders, which are subsequently sintered into dense composite bulks. The results show that the graphite flake is successfully coated with a uniform and compact Cu shell,which effectively inhibits the segregation accumulation of graphite flakes and contributes to homogeneous distribution of graphite in the sintered graphite flake/Cu composites. The as-sintered composites exhibit an excellent thermal conductivity of 710 W·m-1·K-1and an outstanding bending strength of 93 MPa. Such performance, together with the simple, efficient powder-preparation process, suggests that the present strategy may open up opportunities for the development of thermal management materials.

关键词： Graphite flake Electroplating Powder processing Thermal properties

LED Adaptive Deployment Optimization in Indoor VLC Networks

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China Communications 2021年第6期18卷 201-213页

作者： jiangtao li Xu Bao Wence Zhang School of Computer Science and Communication Engineering Jiangsu UniversityZhenjiang 212013China

Driven by the continuous penetration of high data rate services and applications,a large amount of unregulated visible light spectrum is used for communication to fully meet the needs of 6th generation(6G)mobile *** light communication(VLC)faces many challenges as a solution that complements existing radio frequency(RF)*** paper studies the optimal configuration of LEDs in indoor environments under the constraints of illumination and quality of experience(QoE).Based on the Voronoi tessellation(VT)and centroidal Voronoi tessellation(CVT)theory,combined with the Lloyd’s algorithm,we propose two approaches for optimizing LED deployments to meet the illumination and QoE requirements of all *** on(i)the minimization of the number of LEDs to be installed in order to meet illumination and average QoE constraints,and(ii)the maximization of the average QoE of users to be served with a fixed number of *** Carlo simulations are carried out for different user distribution compared with hexagonal,square and VT *** simulation results illustrate that under the same conditions,the proposed deployment approach can provide less LEDs and achieve better QoE performance.

关键词： visible light communication lightemitting diodes centroidal Voronoi tessellation quality of experience optimal deployment

Current Status and Development Tendency of Wearable Cardiac Health Monitoring

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Chinese Journal of Electrical Engineering 2023年第1期9卷 71-92页

作者： Yifeng Wang Zheng Zhao jiangtao li School of Electrical Engineering Xi’an Jiaotong UniversityXi’an 710049China

Wearable cardiac monitoring devices can provide uninterrupted monitoring of cardiac activities over a long period of *** have developed rapidly in recent years in terms of convenience,comfort,and *** by the development of sensor and materials technology,big data and artificial intelligence,wearable cardiac monitoring can become a crucial basis for novel medical models in the ***,the basic concepts and representative devices of wearable cardiac monitoring are first ***,its core technologies and the latest representative research progress in physiology signal sensing,signal quality enhancement,and signal reliability are systematically ***,an insight and outlook on the future development trends and challenges of wearable cardiac monitoring are discussed.

关键词： Wearable cardiac monitoring electrocardiogram seismocardiography photoplethysmogram cardiovascular disease

Theoretical and Numerical Approximation Methods for Predicting Bending Characteristics of Bimodulus Sandwich Structures

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Acta Mechanica Solida Sinica 2023年第3期36卷 443-456页

作者： Zhenzhou Ye Xiaobin li Zhiting Xu jiangtao li Wei Shen Wei Chen Key Laboratory of High Performance Ship Technology(Wuhan University of Technology) Ministry of EducationWuhan 430063China School of Naval Architecture Ocean Energy Power EngineeringWuhan University of TechnologyWuhan 430063China Marine Design&Research Institute of China Shanghai 200011China

Sandwich materials are widely used in marine structures because of their excellent comprehensive ***,the solution of bimodulus is ***,the theoretical and numerical approximation methods for the analysis of load-bearing characteristics of bimodulus sandwich structures are put forward comprehensively in this *** on the superposition principle,a theoretical method for calculating the neutral surface position of bimodulus sandwich plate is derived,and the corresponding bending control equation is *** proposed theoretical approximation method can fully consider the sawtooth deformation between the plate and the core,as well as the sawtooth deformation inside the core at the tension–compression ***,a finite element model is established for complex sandwich structures to analyze the influence of *** examples show that the theoretical approximation model proposed in this paper has higher calculation accuracy.

关键词： Sandwich composite Bimodulus Superposition characteristics Layerwise deformation theory

Spatial Correlation in Typical Binary Polycondensation Systems: An Essential Extension of the Kirkwood-Buff Theory

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Chemical Research in Chinese Universities 2023年第6期39卷 985-991页

作者： GU Fang li jiangtao HONG Xiaozhong WANG Haijun College of Chemistry and Materials Science Hebei UniversityBaoding 071002P.R.China College of Physical Science and Technology Hebei UniversityBaoding 071002P.R.China Chemical Biology Key Laboratory of Hebei Province Hebei UniversityBaoding 071002P.R.China Key Laboratory of Medicinal Chemistry and Molecular Diagnosis Ministry of EducationHebei UniversityBaoding 071002P.R.China

We present the isothermal susceptibility(XT)for the typical binary polycondensation system of Af-Bg type,and relate XT to the weight-average degree of polymerization in terms of the Kirkwood-Buff(KB)*** investigation is based on a new expression of XT for mixtures,which is still expressed by the KB integrals(KBIs)but endowed with an explicit physical *** polymerization systems,it is proposed that the KBIs can be further decomposed according to whether there exists a bond between particles when conversions(extents of reaction)of functional groups are incorporated into the *** this way,XT is directly decomposed into its relevant components as *** is especially useful to reveal the relationship between local structures and average properties of various polymerization *** a consequence,the effect of polymerization on XT is greatly simplified in comparison with the free energy ***,we have provided a very simple method to carry out some thermodynamic properties of polymerization systems.

关键词： Isothermal compressibility Polycondensation Kirkwood-Buff theory Radial distribution function Spatial correlation

Streamer‐to‐precursor transition in N_(2)-SF_(6)mixtures under positive repetitive submicrosecond pulses

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High Voltage 2022年第2期7卷 382-389页

作者： Zheng Zhao Zhifeng Dai Anbang Sun jiangtao li School of Electrical Engineering Xi'an Jiaotong UniversityXi'anChina

The evolution of discharge dynamics in N_(2)-SF_(6)mixtures under long‐term repetitive submicrosecond pulses is investigated based on pulse‐sequence resolved electrical and optical *** effects of gas pressure,pulse repetition frequency(PRF),and SF6 concentration on discharge evolutions are *** number of applied pulses before breakdown is shown to non‐linearly decrease with increasing PRF for all included gas pressures and SF6 concentrations.A higher SF6 concentration is favourable for increasing relative insulation capability under repetitive *** complexities of discharge evolutions under repetitive pulses are reported for the first time for the discharge mechanism transition when a strong electronegative gas is introduced.A pulse‐to‐pulse progressive streamer(first discharge)‐to‐precursor(before breakdown)transition is observed in an N_(2)-SF_(6)mixture under positive repetitive pulses and is less dependent on gas pressure than traditional *** formation of a precursor section is jointly supported by electrical and optical *** discharge mechanism transition and the detour phenomenon under repetitive pulses are discussed based on the effects of space charges on the spatial distribution of the electric field strength.

关键词： breakdown transition second

Microstructure and properties of porous Si_(3)N_(4)ceramics by gelcasting-self-propagating high-temperature synthesis(SHS)

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Journal of Advanced Ceramics 2022年第1期11卷 172-183页

作者： Shile CHEN liang WANG Gang HE jiangtao li Chang-An WANG State Key Laboratory of New Ceramics and Fine Processing School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China CAS Key Laboratory of Cryogenics Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China

Porous silicon nitride ceramics have attracted a considerable attention due to their excellent overall performance,but poor porosity homogeneity and structural shrinkage induced by prolonged high temperature sintering limit its further ***,as a three-in-one solution for the above issues,for the first time we develop a novel approach that integrates the merits of gelcasting-SHS(self-propagating high-temperature synthesis)to prepare porous Si_(3)N_(4)ceramics to simultaneously achieve high porosity,high strength,high toughness,and low thermal conductivity across a wide temperature *** regulating the solid content,porous Si_(3)N_(4)ceramics with homogeneous pore structure are obtained,where the pore size falls inbetween 1.61 and 4.41 pm,and the elongated grains are interlaced and interlocked to form micron-sized coherent interconnected *** the same time,porous Si_(3)N_(4)ceramics with porosity of 67.83%to 78.03%are obtained,where the compressive strength reaches 11.79 to 47.75 MPa and fracture toughness reaches 1.20 to 6.71 MPa-m1/2.

关键词： porous Si_(3)N_(4)ceramics gelcasting self-propagating high-temperature synthesis(SHS) porosity