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Behavior of Fe Powder During High-Energy Ball Milling Cooperated with Dielectric Barrier Discharge Plasma

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Acta Metallurgica Sinica(English Letters) 2013年第1期26卷 63-68页

作者： Leyang dai Marine Engineering Institute Jimei University

In this study, nanostructured Fe powders were synthesized following 10 hours of high-energy ball milling with a superimposed dielectric barrier discharge plasma （DBDP）. The mean size of the milled powder was approximately 100 nm with an average grain size of 16.2 nm. The influence of DBDP on the underlying grain refinement mechanisms during ball milling was investigated by scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD） and BET methods. Our results show that the Fe particles displayed an extraordinary plasticity during the early milling stages under the action of DBDP, and that the plastic deformation experienced by the Fe particles during this stage was more severe than that present in normal milling. A high concentration of spherical Fe particles, approximately 50-100 nm in diameter, was documented via TEM. We propose that these spherical particles were generated via high temperature disintegration as a result of DBDP electron bombardment during ball milling. Our results suggest that it may be possible to significantly refine metallic powders during milling via the superimposition of DBDP.

关键词： Dielectric barrier discharge plasma (DBDP) High-energy ball milling Nano-Fepowder Plastic deformation Elevated temperature disintegration

Synthesis of 2,5-diformylfuran from renewable carbohydrates and its applications: A review

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Green Energy & Environment 2021年第1期6卷 22-32页

作者： Jinhang dai College of Environment and Resources Chongqing Technology and Business UniversityChongqing400067China

The synthesis of fine chemicals and fuel candidates from renewable biomass-based feedstocks has attracted much attention due to declining fossil *** value-added furan derivatives,such as 5-hydroxymethylfurfural(HMF),2,5-diformyfuran(DFF)and 2,5-furandicarboxylic acid,have been successfully produced from *** these,DFF,the aerobic oxidation product of HMF,is a key chemical and can be used in organic synthesis and functional polymer *** this review,different catalytic systems for the synthesis of DFF from monosaccharide,disaccharide and polysaccharide were summarized,while reaction pathways and catalyst stability were also ***,the applications of DFF were introduced in ***,prospects of more effective methods to DFF production and application were discussed.

关键词： 2,5-Diformyfuran Oxidation HMF Carbohydrate Biomass

Beam dynamics design of an SP-FEL compact THz source

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Nuclear Science and Techniques 2010年第5期21卷 266-270页

作者： dai Dongdong dai Zhimin Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China Graduate School Chinese Academy of Sciences Beijing 100049 China

In recent years,people are looking for a new compact THz source with high emission power,one potential choice is to build small accelerator with Smith-Purcell *** main difficulty is how to obtain high quality electron *** this paper,the beam dynamics design of a compact THz source is *** electron beam is produced by an electron gun and compressed by permanent *** electron gun is similar to the Shanghai EBIT,but permanent magnets are used,instead of the superconducting magnets in Shanghai *** this design,we can reduce the size and cost of the whole ***/Pandira was employed to simulate and optimize the magnetic *** was used to simulate the beam trajectories from the electron gun to the *** 2 centimeters around the center of longitudinal magnetic field,the calculation showed that the beam satisfies to our design aim.

关键词：动力学设计太赫兹紧凑型 FEL SP 束流永久磁铁 EBIT

AN ITERATIVE HYBRIDIZED MIXED FINITE ELEMENT METHOD FOR ELLIPTIC INTERFACE PROBLEMS WITH STRONGLY DISCONTINUOUS COEFFICIENTS

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Journal of Computational Mathematics 2003年第3期21卷 257-276页

作者： dai-quYang JenniferZhao DepartmentofMathematics WayneStateUniversityDetroitMI48202USA DepartmentofMathematicsandStatistics UniversityofMichigan-DearbornDearbornMI48128USA

An iterative algorithm is proposed and analyzed based on a hybridized mixed finite element method for numerically solving two-phase generalized Stefan interface problems with strongly discontinuous solutions, conormal derivatives, and coefficients. This algorithm iteratively solves small problems for each single phase with good accuracy and exchange information at the interface to advance the iteration until convergence, following the idea of Schwarz Alternating Methods. Error estimates are derived to show that this algorithm always converges provided that relaxation parameters are suitably chosen. Numeric experiments with matching and non-matching grids at the interface from different phases are performed to show the accuracy of the method for capturing discontinuities in the solutions and coefficients. In contrast to standard numerical methods, the accuracy of our method does not seem to deteriorate as the coefficient discontinuity increases.

关键词： Mixed finite element method Interface problems Discontinuous solutions.

Adaptive ordering and filament polymerization of cell cytoskeleton by tunable nanoarrays

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Nano Research 2021年第3期14卷 620-627页

作者： Jing dai Yuan Yao School of Physical Science and Technology ShanghaiTech UniversityShanghai201210China

Matrix adaptation reconstructs the architecture of cell,and has important implication in proper biological ***,how the network of cytoskeleton filament undergoes reconstruction,reordering,and surface adaptation,requires a systematic ***,we show that surface sensing and adaptation occur correspondingly with related reorganization of cytoskeleton filaments(actin,tubulin,and vimentin).The microstructure of filament network is built by adaptive change of chemical polymerization on cytoskeleton *** transition of cellular morphology,from spheroidal architecture on nanoarray to extending structure with stress fibers on flat surface,involves spatial reorganization and polymerization modulation of *** dimension of filaments(diameter,orientation,and density)are changed accordingly to spatiotemporal distribution of cytoskeleton *** addition,our findings elucidate how cell can tune their architecture at nanoscale by matrix adaptation,and provide a novel information on interplay between cytoskeleton and pathophysiology.

关键词： adaptation cytoskeleton polymerization reordering

The Impact of Oil Shocks on Systemic Risk of the Commodity Markets

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Journal of Systems Science & Complexity 2024年第6期37卷 2697-2720页

作者： dai Zhifeng WU Tong College of Mathematics and Statistics Hunan Provincial Key Laboratory of Mathematical Modeling and Analysis in Engineering Changsha University of Science and Technology

This study examines the influence of oil shocks on systemic risk spillover among the commodity markets. Specifically, this paper uses the DCC-GARCH approach combined with the TVP-VAR model to calculate risk connectedness and the GARCH-MIDAS model to explore how oil shocks from different sources affect the risk spillover effects among the commodity markets. The results are the following: First, there are significant risk spillovers among the commodity markets with important time-varying characteristics and with sharp changes in times of crisis. The industrial metals, agriculture, precious metals, and light energy commodity markets are risk recipients, and the energy and livestock commodity markets are risk exporters. Second, oil price shocks, particularly oil aggregate demand shocks, prominently affect the total risk connectedness among the commodity markets. In particular, the impact on the net risk spillover effect of different commodity market differs.

关键词： Commodity markets connectedness GARCH-MIDAS model oil price shocks systemic risk

Structural transition dynamics of the formation of warm dense gold: From an atomic scale view

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Science China(Physics,Mechanics & Astronomy) 2020年第6期63卷 33-41页

作者： QiYu Zeng JiaYu dai Department of Physics National University of Defense TechnologyChangsha 410073China

With the highly optimized embedded-atom-method(EAM)potential and electron-phonon coupling factor obtained from experimental data,the dynamics of the formation of warm dense gold and the nuclear response of gold foils upon intense laser excitation were investigated using two-temperature molecular dynamics *** laser energy densities ranging from 0.18 to 1.17 MJ/kg,we provide a microscopic picture of the formation of warm dense gold.A threshold(0.19 MJ/kg)for the laser energy density was determined,identifying two different melting *** an energy density below 0.19 MJ/kg,the melting of the foil is controlled by the propagation of melt fronts from external surfaces,which results in heterogeneous melting on the time scale of hundreds of *** an energy density above 0.19 MJ/kg,homogeneous nucleation and growth of liquid regions inside the foil play the leading role,and homogeneous melting occurs with several *** with previous simulations and experimental measurements,the evaluated different threshold value indicates that the improvement in the electron heat capacity for the two-temperature model by including the kinetic information of electrons may predict better laser-matter interactions under such extreme non-equilibrium conditions.

关键词： molecular dynamics numerical methods solid-liquid transitions laser ablation of solids

Fair multigroup multicast precoding design based on traffic demands for multibeam satellite systems

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Chinese Journal of Aeronautics 2023年第10期36卷 366-374页

作者： Zhiqi dai Zhen XU School of Electronic and Information Engineering Beihang UniversityBeijing 100191China

Onboard resources are limited for multibeam satellite communication systems,while differences exist in traffic demands among *** conventional multigroup multicast precoding methods do not take traffic demands for users into consideration,it is difficult to flexibly adjust the offered throughput to users’*** with higher demand may obtain lower throughput while users with lower demand may be over-satisfied,which results in the requested-offered throughput mismatch and resource *** paper proposes a fair multigroup multicast precoding design based on traffic *** obtain the precoding design,the optimization problem aimed at maximizing the minimum throughput satisfaction ratio,which is defined as the ratio of the offered throughput to the traffic demand,is formulated,so as to provide fair service for all users while satisfying per-feed power constraints and traffic demand *** address this problem,an auxiliary variable is first introduced to equivalently simplify ***,the semidefinite relaxation and the bisection search strategies are adopted to further handle the ***,the optimal precoding vectors are obtained by employing eigenvalue decomposition or Gaussian *** results indicate the effectiveness of the proposed precoding algorithm and demonstrate that it can better adapt to the scenarios with different traffic demands.

关键词： Satellite communication systems Multigroup multicast precoding Traffic demand Throughput satisfaction ratio Fairness optimization

Reconfigurable Intelligent Surfaces for 6G:Nine Fundamental Issues and One Critical Problem

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Tsinghua Science and Technology 2023年第5期28卷 929-939页

作者： Zijian Zhang Linglong dai Department of Electronic Engineering Tsinghua Universityand also with Beijing National Research Center for Information Science and Technology(BNRist)Beijing 100084China

Thanks to the recent advances in metamaterials,Reconfigurable Intelligent Surface(RIS)has emergedas a promising technology for future 6G wireless *** from its high array gain,low cost,and low power consumption,RISs are expected to greatly enlarge signal coverage,improve system capacity,andincrease energy *** this article,we systematically overview the emerging RIS technology with the focuson its key basics,nine fundamental issues,and one critical ***,we first explain the RIS basics,including its working principles,hardware structures,and potential benefits for *** on thesebasics,nine fundamental issues of RISs,such as“What’s the differences between RISs and massive MIMO?”and“Is RIS really intelligent?”,are explicitly addressed to elaborate its technical features,distinguish it from existingtechnologies,and clarify some misunderstandings in the ***,one critical problem of RISs is revealedthat,due to the“multiplicative fading”effect,existing passive RISs can hardly achieve visible performance gains inmany communication scenarios with strong direct *** address this critical problem,a potential solution calledactive RISs is introduced,and its effectiveness is demonstrated by numerical simulations.

关键词： Reconfigurable Intelligent Surface(RIS) sixth generation mobile system(6G) wireless communications