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Plasma science and Technology 2024年第8期26卷 104-111页

作者：王重马石朝毅张秀青卢文武张胜高先和许涛邵兴星黄连生 Hefei university Hefei 230000People’s Republic of China Institute of Plasma Physics Chinese Academy of SciencesHefei 230031People’s Republic of China

In the design realm of fusion power supplies,structural components play a pivotal role in ensuring the safety of fusion *** verify the reliability of the converter structure design at the Comprehensive Research Facility for Fusion Technology(CRAFT),meticulous analysis of the converter's dynamic impact is carefully performed based on the worst fault current(400k A),***,the thermal stress analysis based on the maximum allowable steadystate temperature is finished,and the equivalent thermal stress,thermal deformation,maximum shear stress of a single bridge arm and the whole converter are ***,a simple research method involving the current-sharing characteristics of a bridge arm with multithyristor parallel connection is proposed using a combination of simplorer with Q3D in *** results show that the current-sharing characteristics are ***,the structural design has been meticulously tailored to meet the established requirements.

关键词： electrodynamic analysis thermal stress current-sharing characteristics CRAFT

Multi-layer phenomena in petawatt laser-driven acceleration of heavy ions

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Plasma science and Technology 2024年第2期26卷 70-76页

作者：苏琬晴曹喜光马春旺王玉廷张国强 College of Physics Henan Normal UniversityXinxiang 453007People's Republic of China shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210People's Republic of China shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800People's Republic of China university of Chinese Academy of sciences Bejing 100049People's Republic of China Institute of Nuclear science and Technology Henan Academy of ScienceZhengzhou 450046People's Republic of China

Laser-accelerated high-flux-intensity heavy-ion beams are important for new types of accelerators.A particle-in-cell program(smilei) is employed to simulate the entire process of station of Extreme Light(sEL) 100 PW laser-accelerated heavy particles using different nanoscale short targets with a thickness of 100 nm Cr, Fe, Ag, Ta, Au, Pb, Th and u, as well as 200 nm thick Al and Ca. An obvious stratification is observed in the simulation. The layering phenomenon is a hybrid acceleration mechanism reflecting target normal sheath acceleration and radiation pressure acceleration, and this phenomenon is understood from the simulated energy spectrum,ionization and spatial electric field distribution. According to the stratification, it is suggested that high-quality heavy-ion beams could be expected for fusion reactions to synthesize superheavy nuclei. Two plasma clusters in the stratification are observed simultaneously, which suggest new techniques for plasma experiments as well as thinner metal targets in the precision machining process.

关键词： petawatt laser-plasma interaction laser-driven heavy-ion accelerator for synthesizing superheavy nuclei particle-in-cell multi-layer phenomena target fabrication

simulation of ion cyclotron wave heating in the EXL-50u spherical tokamak based on dispersion relations

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Plasma science and Technology 2024年第2期26卷 54-61页

作者：马好杰谢华生李博 school of Physics Beihang UniversityBeijing 100191People's Republic of China Hebei Key Laboratory of Compact Fusion Langfang 065001People's Republic of China ENN science and Technology Development Co.Ltd. Langfang 065001People's Republic of China

This study investigates the single-pass absorption(sPA) of ion cyclotron range of frequency(ICRF) heating in hydrogen plasma of the EXL-50u spherical tokamak,which is an upgraded EXL-50 device with a central solenoid and a stronger magnetic *** reliability of the kinetic dispersion equation is confirmed by the one-dimensional full-wave code,and the applicability of Porkolab's simplified theoretical sPA model is discussed based on the kinetic dispersion *** are conducted to investigate the heating effects of the fundamental and second harmonic *** results indicate that with the design parameters of the EXL-50u device,the sPA for second harmonic heating is 63%,while the sPA for fundamental heating is 13%.Additionally,the optimal injection frequencies are 23 MHz at 0.9 T and 31 MHz at 1.2 *** wave vector of the antenna parallel to the magnetic field,with a value of k_‖=7.5 m^(-1),falls within the optimal heating *** reveal that the ICRF heating system can play an important role in the ion heating of the EXL-50u.

关键词： ion cyclotron range of frequency single-pass absorption spherical tokamak

Age-of-Information-Aware Federated Learning

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Journal of Computer science & Technology 2024年第3期39卷 637-653页

作者：徐殷肖明军吴晨吴杰周津锐孙贺 student Member CCF 1.School of Computer Science and TechnologyUniversity of Science and Technology of ChinaHefei 230026China suzhou Institute for Advanced Research University of Science and Technology of ChinaSuzhou 215123China school of Data science University of Science and Technology of ChinaHefei 230026China Department of Computer and Information sciences Temple UniversityPhiladelphiaPA 19122U.S.A.

Federated learning(FL)is an emerging privacy-preserving distributed computing paradigm,enabling numerous clients to collaboratively train machine learning models without the necessity of transmitting clients’private datasets to the central *** most existing research where the local datasets of clients are assumed to be unchanged over time throughout the whole FL process,our study addresses such scenarios in this paper where clients’datasets need to be updated periodically,and the server can incentivize clients to employ as fresh as possible datasets for local model *** primary objective is to design a client selection strategy to minimize the loss of the global model for FL loss within a constrained *** this end,we introduce the concept of“Age of Information”(AoI)to quantitatively assess the freshness of local datasets and conduct a theoretical analysis of the convergence bound in our AoI-aware FL *** on the convergence bound,we further formulate our problem as a restless multi-armed bandit(RMAB)***,we relax the RMAB problem and apply the Lagrangian Dual approach to decouple it into multiple ***,we propose a Whittle’s Index Based Client selection(WICs)algorithm to determine the set of selected *** addition,comprehensive simulations su.s.antiate that the proposed algorithm can effectively reduce training loss and enhance the learning accuracy compared with some state-of-the-art methods.

关键词： federated learning Age of Information restless multi-armed bandit Whittle’s index

Dynamic propagation velocity of a positive streamer in a 3 m air gap under lightning impulse voltage

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Plasma science and Technology 2024年第4期26卷 114-121页

作者：李志伟雷挺苏宇姚修远杨冰雪刘德龙律方成丁玉剑 North China Electric Power university Beijing 102206People’s Republic of China China Electric Power Research Institute Beijing 100192People’s Republic of China

streamers represent an important stage in the initiation of gap discharge. In this work, we used an eight-frame intensified charge-coupled device camera to capture the streamer development process when a lightning impulse voltage of 95%–100% u50% was applied in a 3 m rod–plate gap and the streamer velocity was analyzed. Analysis of the observations shows that streamer velocity can be defined by three stages: rapid velocity decline(stage 1), rapid velocity rise(stage 2)and slow velocity decline(stage 3). The effects of electrode shape, applied voltage and gap breakdown or withstanding on streamer velocity were analyzed. The electrode with a larger radius of curvature will result in a higher initial velocity, and a higher voltage amplitude will cause the streamer to propagate faster at stage 3. Gap withstanding or breakdown has no obvious effect on streamer velocity. In addition, the experimental results are compared with previous results and the statistical characteristics of the primary streamer discharge are discussed.

关键词： lightning impulse 3 m air gap development process streamer velocity

Climatic implications in earlywood and latewood width indices of Chinese pine in north central China

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Journal of Forestry Research 2024年第3期35卷 143-153页

作者： Kaixuan Yang Junzhou Zhang Haowen Fan Yuan Yan College of Geographic sciences Qinghai Normal UniversityXining 810016People's Republic of China Key Laboratory of Tibetan Plateau Land surface Processes and Ecological Conservation(Ministry of Education) Xining 810016People's Republic of China Key Laboratory of Western China's Environmental systems(Ministry of Education) College of Earth and Environmental SciencesLanzhou UniversityLanzhou 730030People's Republic of China Gansu Liancheng Forest Ecosystem Field Observation and Research station Lanzhou UniversityLanzhou 730333People's Republic of China school of Geography and Information Engineering University of GeoscienceWuhan 430074People's Republic of China

Latewood width(LWW)indices of trees are considered a reliable proxy of summer precipitation in the Northern ***,the strong coupling and high correlation between earlywood width(EWW)and LWW indices often prevent registration of climate signals of the LWW *** this study,328-year-long earlywood width and latewood width chronologies were developed from Chinese pine at two sites in the Hasi Mountains,north central *** climate responses of these chronologies were analyzed and the LWW index used to derive sum-mer precipitation *** analyses showed that LWW was particularly influenced by earlywood growth and recorded stronger climate signals of the previous year as EWW,rather than those of the current year with infrequent summer climate ***,after removing the effect of earlywood growth using a simple regression model,the adjusted LWW chronology(LWW_(adj))showed a strong relationship with July precipitation in dry *** suggests that the LWW_(adj) chronology has the potential to be used to investigate long-term variability in summer precipitation in drought-limited regions.

关键词： Dendroclimatology Latewood width Climate response summer precipitation Earlywood effect

Deep convolutional Ritz method: parametric PDE surrogates without labeled data

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Applied Mathematics and Mechanics(English Edition) 2023年第7期44卷 1151-1174页

作者： J.N.FuHG A.KARMARKAR T.KADEETHuM H.YOON N.BOuKLAs sibley school of Mechanical and Aerospace Engineering Cornell UniversityNew York 14853U.S.A Geomechanics Department Sandia National LaboratoriesAlbuquerque 87123U.S.A.

The parametric surrogate models for partial differential equations(PDEs)are a necessary component for many applications in computational sciences,and the convolutional neural networks(CNNs)have proven to be an excellent tool to generate these surrogates when parametric fields are *** are commonly trained on labeled data based on one-to-one sets of parameter-input and PDE-output ***,residual-based deep convolutional physics-informed neural network(DCPINN)solvers for parametric PDEs have been proposed to build surrogates without the need for labeled *** allow for the generation of surrogates without an expensive *** this work,we present an alternative formulation termed deep convolutional Ritz method(DCRM)as a parametric PDE *** approach is based on the minimization of energy functionals,which lowers the order of the differential operators compared to residualbased *** on studies involving the Poisson equation with a spatially parameterized source term and boundary conditions,we find that CNNs trained on labeled data outperform DCPINNs in convergence speed and generalization *** surrogates generated from the DCRM,however,converge significantly faster than their DCPINN counterparts,and prove to generalize faster and better than the surrogates obtained from both CNNs trained on labeled data and *** hints that the DCRM could make PDE solution surrogates trained without labeled data possibly.

关键词： physics-informed constraint physics-informed neural network(PINN) deep energy network convolutional neural network(CNN)

Gyrokinetic simulation of magnetic-island-induced electric potential vortex mode

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Plasma science and Technology 2024年第1期26卷 34-41页

作者：王丰李继全曲洪鹏彭晓东 southwestern Institute of Physics Chengdu 610041People’s Republic of China

Ion temperature gradient(ITG)-driven turbulence with embedded static magnetic islands is simulated by utilizing a gyrokinetic theory-based global turbulence transport code(GKNET)in this *** from the traditional equilibrium circular magnetic-surface average(EMsA)method,an advanced algorithm that calculates the perturbed magnetic-surface average(PMsA)of the electric potential has been developed to precisely deal with the zonal flow component in a non-circular magnetic surface perturbed by magnetic *** show that the electric potential vortex structure inside islands induced by the magnetic islands is usually of odd parity when using the EMsA *** is found that the odd symmetry vortex can transfer into an even one after a steep zonal flow gradient,*** flow shear has been built in the vicinity of the magnetic islands by adopting the PMsA *** phase of the potential vortex in the poloidal cross section is coupled with the zonal flow *** an electric potential vortex mode may be of essential importance in wide topics,such as the turbulence spreading across magnetic islands,neoclassical tearing mode physics,and also the interaction dynamics between the micro-turbulence and MHD activities.

关键词： magnetic islands electric vortex ITG perturbed magnetic flux surface average

Reconfigurable(4, 6^(2)) and(4, 8^(2)) Archimedean plasma photonic crystals in dielectric barrier discharge

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Plasma science and Technology 2024年第6期26卷 70-78页

作者：李蕊王启晗刘富成高匡雅侯笑含贾萌萌李庆范伟丽 College of Physics science and Technology Hebei UniversityBaoding 071002People’s Republic of China Institute of Electrostatic Technology Hebei UniversityBaoding 071002People’s Republic of China

Archimedean photonic crystal has become a research area of great interest due to its various unique properties. Here, we experimentally demonstrate the realization of reconfigurable(4, 6^(2))and(4, 8^(2)) Archimedean plasma photonic crystals(APPCs) by use of dielectric barrier discharges in air. Dynamical control on both the macrostructures including the lattice symmetry and the crystal orientation, and the microstructures including the fine structures of scattering elements has been achieved. The formation mechanisms of APPCs are studied by time-resolved measurements together with numerical simulations. Large omnidirectional band gaps of APPCs have been obtained. The tunable topology of APPCs may offer new opportunities for fabricating multi-functional and highly-integrated microwave devices.

关键词： Archimedean lattice plasma photonic crystals dielectric barrier discharge

Gyro-Landau-fluid simulations of impurity effects on ion temperature gradient driven turbulence transport

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Plasma science and Technology 2024年第1期26卷 8-15页

作者：刘逸飞李继全 southwestern Institute of Physics Chengdu 610041People’s Republic of China

The effects of impurities on ion temperature gradient(ITG)driven turbulence transport in tokamak core plasmas are investigated numerically via global simulations of microturbulence with carbon impurities and adiabatic *** simulations use an extended fluid code(ExFC)based on a four-field gyro-Landau-fluid(GLF)*** multispecies form of the normalized GLF equations is presented,which guarantees the self-consistent evolution of both bulk ions and *** parametric profiles of the cyclone base case,well-benchmarked ExFC is employed to perform simulations focusing on different impurity density *** a fixed temperature profile,it is found that the turbulent heat diffusivity of bulk ions in a quasi-steady state is usually lower than that without impurities,which is contrary to the linear and quasilinear *** evolutions of the temperature gradient and heat diffusivity exhibit a fast relaxation process,indicating that the destabilization of the outwardly peaked impurity profile is a transient state ***,the impurity effects from different profiles can obviously influence the nonlinear critical temperature gradient,which is likely to be dominated by linear *** results suggest that the improvement in plasma confinement could be attributed to the impurities,most likely through adjusting both heat diffusivity and the critical temperature gradient.

关键词： gyro-Landau-fluid simulation impurity effects ion temperature gradient mode turbulence transport