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艺术学界 2018年第2期 77-78页

作者：徐燕江苏省书法家协会中国标准草书学社

Analytic Smoothing Effect of the Time Variable for the Spatially Homogeneous Landau Equation

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Journal of Partial Differential Equations 2024年第1期37卷 88-103页

作者： xu Chaojiang XU Yan School of Mathematics and Key Laboratory of Mathematical MIIT Nanjing University of Aeronautics and AstronauticsNanjing 210016China.

In this work,we study the Cauchy problem of the spatially homogeneous Landau equation with hard potentials in a close-to-equilibrium framework.We prove that the solution to the Cauchy problem enjoys the analytic regularizing effect of the time variable with an L^(2)initial datum for positive time.So that the smoothing effect of the Cauchy problem for the spatially homogeneous Landau equation with hard potentials is exactly same as heat equation.

关键词： Spatially homogeneous Landau equation analytic smoothing effect hard potentials.

A calibration and compensation method for an industrial robot with high accuracy harmonic reducers

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Science China(Technological Sciences) 2024年第3期67卷 725-739页

作者： ZHAO Yiyang LIU xun CAO JiaBin LIU JinYu XU Yan yan WeiXin School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai 200240China College of Computer and Control Engineering Northeast Forestry UniversityHarbin 150040China

Industrial serial robots need high stiffness to keep absolute pose accuracy and meet the requirements in practical applications. However, the weak stiffness feature of robot joints and the payloads affected on robot end-effector, which will also increase the pose error of robot. Especially, the existing calibration methods often consider under no-payload condition without discussing the payload state. In this paper, we report a new industrial serial robot composed by a new harmonic reducer: Model-Y, based on high accuracy and high stiffness, and a kinematic parameter calibration algorithm which is based on a harmonic reducer forcedeformation model. To decrease the accuracy effects of payload, an iterative calibration method for kinematic parameters with payload situation was proposed. Simulation and experiments are conducted to verify the effectiveness of the proposed calibration method using the self-developed industrial serial robot. The results show a remarkably improved accuracy in absolute position and orientation with the robot's payload range. The position mean error has 70% decreased to 0.1 mm and the orientation mean error diminished to less than 0.01° after calibration with compensation. Additionally, online linear and circular tests are carried out to evaluate the position error of the robot during large-scale spatial and low-speed continuous movement. The accuracy is consistent with the previous calibration results, indicating the effectiveness and advantages of the proposed strategy in this article.

关键词： industrial serial robot Model-Y harmonic calibration stiffness model online compensation

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基于绿色经济理念下建筑经济可持续发展研究

经济研究导刊 2020年第16期 156-157页

作者：许艳山东建筑大学济南250101

如今,绿色经济理念逐渐成为我国各行业的指导思想。基于此,分析绿色经济理念下的建筑经济可持续发展的内涵外延,以及我国目前的建筑经济发展状况,继而提出发展绿色建筑经济的具体途径,以期更好地服务于可持续发展战略。新时代背景下,绿... 详细信息

如今,绿色经济理念逐渐成为我国各行业的指导思想。基于此,分析绿色经济理念下的建筑经济可持续发展的内涵外延,以及我国目前的建筑经济发展状况,继而提出发展绿色建筑经济的具体途径,以期更好地服务于可持续发展战略。新时代背景下,绿色发展成为了人们的共识,而城市经济发展结构转型升级是实现绿色发展的主要方式。基于此,围绕绿色经济理念下建筑经济可持续发展研究。

关键词：绿色经济理念建筑经济可持续发展

Generation of typical operation curves for hydrogen storage applied to the wind power fluctuation smoothing mode

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Global Energy Interconnection 2022年第4期5卷 353-361页

作者： yanhui xu Yijia xu yan Huang North China Electric Power University Beijing 102206P.R.China Energy Development Research Institute China Southern Power GridGuangzhou 510623P.R.China

In this paper,a typical-operation-curve generation method of a hydrogen energy storage system operating under the mode of stabilizing wind power fluctuations is proposed.This method is used to optimize the power and capacity configuration of the energy storage system.The time series curves of the charging and discharging powers of the hydrogen energy storage are obtained by EMD decomposition,and the curves are classified according to the similarities and differences of the characteristic parameters in different time periods.After the classification,typical charging and discharging power values of each type of curve at each moment are obtained by a cloud model,and then,typical operation curves of each type are obtained by integration.On this basis,the power and capacity of the energy storage system are optimized with the objective of economic optimization through the MATLAB CPLEX toolbox.Combined with the measured data of a wind farm with an installed capacity of 400 MW in Northeast China,the validity and rationality of the typical operation curve generation method proposed in this paper are verified.

关键词： Wind farm Hydrogen energy storage system Cluster analysis Typical operation curves Capacity configuration

SEMI-IMPLICIT SPECTRAL DEFERRED CORRECTION METHODS BASED ON SECOND-ORDER TIME INTEGRATION SCHEMES FOR NONLINEAR PDES

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Journal of Computational Mathematics 2024年第1期42卷 111-133页

作者： Ruihan Guo yan xu School of Mathematics and Statistics Zhengzhou UniversityZhengzhou 450001China School of Mathematical Sciences University of Science and Technology of ChinaHefei 230026China

In[20],a semi-implicit spectral deferred correction(SDC)method was proposed,which is efficient for highly nonlinear partial differential equations(PDEs).The semi-implicit SDC method in[20]is based on first-order time integration methods,which are corrected iteratively,with the order of accuracy increased by one for each additional iteration.In this paper,we will develop a class of semi-implicit SDC methods,which are based on second-order time integration methods and the order of accuracy are increased by two for each additional iteration.For spatial discretization,we employ the local discontinuous Galerkin(LDG)method to arrive at fully-discrete schemes,which are high-order accurate in both space and time.Numerical experiments are presented to demonstrate the accuracy,efficiency and robustness of the proposed semi-implicit SDC methods for solving complex nonlinear PDEs.

关键词： Spectral deferred correction method Nonlinear PDEs Local discontinuous Galerkin method Second-order scheme

Determining the moment of inertia of triaxial Mars with updated global gravity models

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地球与行星物理:英文版 2023年第6期7卷 615-619页

作者： ChangYi xu yan Jiang Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100029China

The principal moments of inertia(PMIs)with the principal axes are usually taken as the dynamic figure parameters of Mars;they can be deduced from satellite-observed degree-two gravitational potentials in recent global gravity models and from the dynamic ellipticities resulting from precession observations.These PMIs are natural and significant for the geodetic,geophysical,and geodynamic problems of Mars,which are functions of internal density distributions.In this study,a closed and concise formula for determining the PMIs of the entire planet and its core was developed based on the second invariants of gravity and a multipole expansion.We deduced the polar oblateness J^(2)and the equatorial ellipticity J_(22)of Mars to be 1.9566×10^(−3)and 6.3106×10^(−5),respectively.The preferred principal moments of inertia of Mars are A=2.66589×1036 kg·m^(2),B=2.66775×10^(36)kg·m^(2),and C=2.68125×10^(36)kg·m^(2).These values indicate that Mar is slightly triaxial.The equatorial principal moment of inertia of the Martian core is 1.46008×10^(35)kg·m^(2),accounting for~5.47%of the planet’s PMI;this result is critical for investigating the density and size of the core of Mars,and the planet’s free core nutation.

关键词： Mars principal moment of inertia dynamic ellipticity Chandler wobble core density and size

Design of Robust Var Reserve Contract for Enhancing Reactive Power Ancillary Service Market Efficiency

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 767-771页

作者： Yunyang Zou yan xu School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore 639798Singapore

In a deregulated Var market, market power issue is more serious than in an energy market since reactive power cannot be transmitted over long distances. This letter designs a multi-timescale Var market framework, where market power that may arise in the hourly-ahead Var support service market due to system configuration deficiency and market structure flaws can be eliminated by day-ahead contract-based Var reserve service market. Settlement of day-ahead Var reserve contract is formulated as a two-stage robust optimization (TSRO) model considering worst case of uncertainty realization and potential market power that may arise in hourly-ahead market. TSRO with integer recourses is then solved by a new column and constraint generation algorithm. Results show a robust Var reserve contract can fully eliminate market power, and prevent suppliers from manipulating market prices.

关键词： Market efficiency market power reactive power ancillary service two-stage robust optimization Var reserve

Malware Evasion Attacks Against IoT and Other Devices: An Empirical Study

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Tsinghua Science and Technology 2024年第1期29卷 127-142页

作者： yan xu Deqiang Li Qianmu Li Shouhuai xu School of Computer Science and Engineering Nanjing University of Science and TechnologyNanjing 210094China School of Computer Science Nanjing University of Posts and TelecommunicationsNanjing 210023China Department of Computer Science University of Colorado Colorado SpringsColorado SpringsCO 80918USA

The Internet of Things(loT)has grown rapidly due to artificial intelligence driven edge computing.While enabling many new functions,edge computing devices expand the vulnerability surface and have become the target of malware attacks.Moreover,attackers have used advanced techniques to evade defenses by transforming their malware into functionality-preserving variants.We systematically analyze such evasion attacks and conduct a large-scale empirical study in this paper to evaluate their impact on security.More specifically,we focus on two forms of evasion attacks:obfuscation and adversarial attacks.To the best of our knowledge,this paper is the first to investigate and contrast the two families of evasion attacks systematically.We apply 10 obfuscation attacks and 9 adversarial attacks to 2870 malware examples.The obtained findings are as follows.(1)Commercial Off-The-Shelf(COTS)malware detectors are vulnerable to evasion attacks.(2)Adversarial attacks affect COTS malware detectors slightly more effectively than obfuscated malware examples.(3)Code similarity detection approaches can be affected by obfuscated examples and are barely affected by adversarial attacks.(4)These attacks can preserve the functionality of original malware examples.

关键词： Android malware obfuscation adversarial examples

Cross-domain data cloud storage auditing scheme based on certificateless cryptography

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The Journal of China Universities of Posts and Telecommunications 2021年第6期28卷 36-47页

作者： XU Yan Li Zheng Ding Long xu Rui School of Computer Science and Technology Anhui UniversityHefei 230039China Anhui Engineering Laboratory of IoT Security Technologies Anhui UniversityHefei 230039China School of Computer University of Geosciences(Wuhan)Wuhan 430078China

With the development of Internet of things(IoT), more and more intelligent terminal devices outsource data to cloud servers(CSs). However, the CS is not fully trusted, and the heterogeneity among different domains makes it difficult for third-party auditor(TPA) to conduct an efficient integrity auditing of outsourced data. Therefore, the cross-domain data cloud storage auditing scheme based on certificateless cryptography is proposed, which can effectively avoid the big burden of certificate management or key escrow problems in identity-based cryptography. At the same time, TPA can effectively audit the integrity of outsourced data in different domains. Formal security proof and analysis show that the cloud storage auditing scheme satisfies the security and privacy requirements. Performance analysis demonstrates that the efficiency is acceptable.

关键词： cloud storage auditing certificateless cryptography cross-domain Internet of things(IoT)