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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.

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

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 EngineeringChangsha University of Science and TechnologyChangsha 410114China

This study examines the influence of oil shocks on systemic risk spillover among the commodity ***,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 *** 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 *** industrial metals,agriculture,precious metals,and light energy commodity markets are risk recipients,and the energy and livestock commodity markets are risk ***,oil price shocks,particularly oil aggregate demand shocks,prominently affect the total risk connectedness among the commodity *** 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

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

Adaptive Output Regulation of a Class of Nonlinear Output Feedback Systems With Unknown High Frequency Gain

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IEEE/CAA Journal of Automatica Sinica 2020年第2期7卷 568-574页

作者： Yuan Jiang Jiyang dai Key Laboratory of Nondestructive Testing(Nanchang Hangkong University) Ministry of EducationNanchang 330063 School of Information Engineering Nanchang Hangkong UniversityNanchang 330063China

This paper presents an output feedback design approach based on the adaptive control scheme developed for nonlinearly parameterized systems,to achieve global output regulation for a class of nonlinear systems in output feedback *** solve the output regulation problem without the knowledge of the sign and the value of the high frequency gain a *** is not necessary to have both the limiting assumptions that the exogenous signal co and the unknown parameter ju belong to a prior known compact set and the high frequency gain has a determinate lower and upper *** effectiveness of the proposed algorithm is shown with the help of an example.

关键词： Adaptive control backstepping high frequency gain output regulation

Human-like Manipulation Planning for Articulated Manipulator

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Journal of Bionic Engineering 2012年第4期9卷 434-445页

作者： Yahui Gan Xianzhong dai School of Automation Southeast UniversityNanjing 210096P.R.China Key Lab of Measurement and Control of Complex Systems of Engineering Ministry of EducationNanjing 210096P.R.China

A new method based on human-likeness assessment and optimization concept to solve the problem of human-like ma- nipulation planning for articulated robot is proposed in this paper. This method intrinsically formulates the problem as a con- strained optimization problem in robot configuration space. The robot configuration space is divided into different subregions by human likeness assessment. A widely used strategy, Rapid Upper Limb Assessment （RULA） in applied ergonomics, is adopted here to evaluate the human likeness of robot configuration. A task compatibility measurement of the robot velocity transmission ratio along a specified direction is used as the target function for the optimization problem. Simple illustrative examples of this method applied to a two Degree of Freedom （DOF） planar robot that resembles the upper limb of a human are presented. Further applications to a humanoid industrial robot SDA10D are also presented. The reasonable planning results for these applications assert the effectiveness of our method.

关键词： manipulation planning human likeness rapid upper limb assessment applied ergonomics task compatibilitymeasurement velocity transmission ratio

Near-field wideband beam training for ELAA with uniform circular array

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Science China(Information Sciences) 2024年第6期67卷 370-383页

作者： Yuhao CHEN Linglong dai Department of Electronic Engineering Tsinghua UniversityBeijing National Research Center for Information Science and Technology (BNRist)

Extremely large-scale antenna array(ELAA) at millimeter wave(mmWave) and Terahertz(THz)band has been considered a key technology for combating high attenuation in high-frequency bands in future6G communications. Uniform circular arrays(UCAs) have attracted much attention because of their ability to provide flat beamforming gain at all angles. To realize efficient beamforming, beam training is widely used to acquire channel state information. However, with a large antenna number, the beam training overhead in ELAA systems becomes overwhelming. Moreover, with a large bandwidth, the beam defocus effect severely degrades beam training accuracy. To address these issues, this paper proposes a frequency-dependent focusing(FDF)-based beam training scheme to realize effective beam training in near-field wideband ELAA systems with UCA. Specifically, we first analyze the FDF property of UCA, where signals at different subcarriers can simultaneously focus on different distances. Then, by exploiting the FDF property to search different distances using different subcarriers simultaneously, we design a hierarchical codebook and propose an FDFbased beam training scheme. To reveal the effectiveness of the proposed scheme, we compare its necessary beam training overhead with that of existing schemes. Finally, the simulation results demonstrate that the proposed scheme can achieve accurate beam training in near-field wideband UCA systems with a low beam training overhead.

关键词： extremely large-scale antenna array (ELAA) uniform circular array (UCA) near-field wideband beam training

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

Inspection interval optimization for aircraft composite structures with dent and delamination damage

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Journal of Systems Engineering and Electronics 2021年第1期32卷 252-260页

作者： CAI Jing dai Dingqiang College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China

The optimization of inspection intervals for composite structures has been proposed,but only one damage type,dent damage,has been addressed so *** present study focuses on the two main damage types of dent and delamination,and a model for optimizing the inspection interval of composite structures is proposed to minimize the total maintenance cost on the premise that the probability of structure failure will not exceed the acceptable *** order to analyze the damage characteristics and the residual strength of the composite structure,the frequency,energy,size,and depth of the damage are studied,and the situation of missing detection during the inspection is *** structural residual strength and total maintenance cost are quantified corresponding to different inspection *** proposed optimization method relieves the constraints in previous simulation methods,and is more consistent with the actual ***,the outer wing of aircraft is taken as an example,and with the historical cases and experimental data,the optimization method is *** optimal inspection interval is shorter than the actually implemented inspection interval,and the corresponding maintenance cost is reduced by 23.3%.The result shows the feasibility and effectiveness of the proposed optimization method.

关键词： civil aircraft composite structure accidental impact damage failure probability inspection interval