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Computational studies on magnetism and ferroelectricity

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Chinese Physics B 2022年第9期31卷 76-86页

作者： ke xu Junsheng Feng Hongjun Xiang Hubei key Laboratory of Low Dimensional Optoelectronic Materials and Devices School of Physics and Electronics EngineeringHubei University of Arts and ScienceXiangyang 441053China School of Physics and Material Engineering Hefei Normal UniversityHefei 230601China key Laboratory of Computational Physical Sciences(Ministry of Education) State Key Laboratory of Surface Physicsand Department of PhysicsFudan UniversityShanghai 200433China

Magnetics,ferroelectrics,and multiferroics have attracted great attentions because they are not only extremely im-portant for investigating fundamental physics,but also have important applications in information ***,recent computational studies on magnetism and ferroelectricity are *** first give a brief introduction to magnets,fer-roelectrics,and ***,theoretical models and corresponding computational methods for investigating these materials are *** particular,a new method for computing the linear magnetoelectric coupling tensor without applying an external field in the first principle calculations is proposed for the first *** functionalities of our home-made Property Analysis and Simulation Package for materials(PASP)and its applications in the field of magnetism and ferroelectricity are ***,we summarize this review and give a perspective on possible directions of future computational studies on magnetism and ferroelectricity.

关键词： magnets ferroelectrics multiferroics Monte Carlo simulation four-state method DFT calculation Property Analysis and Simulation Package for materials(PASP)software

A TVD discretization method for shallow water equations:Numerical simulations of tailing dam break

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International Journal of Modeling, Simulation, and Scientific Computing 2017年第3期8卷 338-359页

作者： Chen Luo ke xu Yunsheng Zhao College of Engineering China University of Geosciences Room 401 Structure Building388 Lumo Road Hongshan DistrictWuhan 430074P.R.China Safety Science and Technology Research Center University of Science and Technology Beijing Room 305 Main Building30 Wuluo Road Wuchang DistrictWuhan 430074P.R.China

In view of the disastrous consequences of tailings dam break and its unique evolutionary process in complex areas,this paper constructs two-dimensional shallow water equations,rheological equations and mathematical models of tailings sand flows on the basis of Navier–Stokes equations(N–S equations).It performs total variation diminishing(TVD)discretization on these equations,develops forward simulation programs in MATLAB2016 and conducts numerical analyses on three kinds of dam breaks(ideal dam break,asymmetric dam break and dam break with obstacles in the downstream area).The results show that TVD discretization is effective in capturing shock *** to the analysis on consequences of Huangmailing Tailings Dam break,the author obtains the maximum distance of tailings sand flow,the flow rate of tailings and the time that tailings reach destinations in the downstream area,thereby providing scientific basis for disaster analyses on similar tailings dam breaks and supplying technical support for emergency rescues after disasters.

关键词： Tailings reservoir dam-break sand flow model two-dimensional shallow water equation total variation diminishing discretization

Coordinated Scheduling of Two-Agent Production and Transportation Based on Non-Cooperative Game

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Intelligent Automation & Soft Computing 2023年第6期36卷 3279-3294页

作者： ke xu Peng Liu Hua Gong School of Management Shenyang University of TechnologyShenyang110870China School of Science Shenyang Ligong UniversityShenyang110159China

A two-agent production and transportation coordinated scheduling problem in a single-machine environment is suggested to compete for one machine from different downstream production links or various *** jobs of two agents compete for the processing position on a machine,and after the pro-cessed,they compete for the transport position on a transport vehicle to be trans-ported to two *** two agents have different objective *** objective function of the first agent is the sum of the makespan and the total trans-portation time,whereas the objective function of the second agent is the sum of the total completion time and the total transportation *** the competition between two agents for machine resources and transportation resources,a non-cooperative game model with agents as game players is *** job pro-cessing position and transportation position corresponding to the two agents are mapped as strategies,and the corresponding objective function is the utility *** solve the game model,an approximate Nash equilibrium solution algo-rithm based on an improved genetic algorithm(NE-IGA)is *** genetic operation based on processing sequence and transportation sequence,as well as the fitness function based on Nash equilibrium definition,are designed based on the features of the two-agent production and transportation coordination scheduling *** effectiveness of the proposed algorithm is demonstrated through numerical experiments of various *** compared to heuristic rules such as the Longest Processing Time first(LPT)and the Shortest Processing Time first(SPT),the objective function values of the two agents are reduced by 4.3%and 2.6% on average.

关键词： Coordinated scheduling two-agent production and transportation non-cooperative game genetic algorithm

Efficacy and safety of Usights UC100 illuminated microcatheter in microcatheter-assisted trabeculotomy

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International Journal of Ophthalmology(English edition) 2024年第2期17卷 272-277页

作者： Shuo Yu ke xu Chun Zhang Department of Ophthalmology Peking University Third HospitalBeijing 100191China Beijing key Laboratory of Restoration of Damaged Ocular Nerve Peking University Third HospitalBeijing 100191China

AIM:To evaluate the efficacy and safety of Usights UC100 illuminated microcatheter in microcatheter-assisted trabeculotomy(MAT).METHODS:Totally 10 eyes of 10 patients with primary open angle glaucoma(POAG)who underwent MAT facilitated by Usights UC100(5 eyes)or iTrack(5 eyes)were *** success of this surgery was defined as intraocular pressure(IOP)30%reduction,without oral glaucoma medications,or additional glaucoma ***:The mean pre-operative IOP was 25.38±10.22 mm Hg in the Usights UC100 group and 19.98±3.87 mm Hg in the iTrack *** was achieved in all eyes in both *** success rates for the Usights UC100 group and iTrack groups were in all and 4 eyes,*** microcatheters produced a statistically significant reduction in IOP,and eyes using Usights UC100 achieved a lower IOP than the iTrack group at 3mo followup(12.58±1.52 and 14.84±1.89 mm Hg,respectively),but no statistical significance was *** severe side effects were observed in either ***:MAT using Usights UC100 or iTrack both achieve significant pressure reduction in cases of POAG,and Usights UC100 is as safe as iTrack.

关键词： illuminated microcatheter microcatheterassisted trabeculotomy primary open angle glaucoma

Formal verification technique for grid service chain model and its application

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Science in China(Series F) 2007年第1期50卷 1-20页

作者： xu ke WANG Yuexuan WU Cheng Automation Department Tsinghua University Beijing 100084 China

Ensuring the correctness and reliability of large-scale resource sharing and complex job processing Is an Important task for grid applications. From a formal method perspective, a grid service chain model based on state PI calculus Is proposed In this work as the theoretical foundation for the service composition and collaboration in grid. Following the Idea of the Web Service Resource Framework （WSRF）, state PI calculus enables the life-cycle management of system states by associating the actions in the original PI calculus with system states. Moreover, model checking technique is exploltad for the design-time and run-time logical verification of grid service chain models. A grid application scenario of the dynamic analysis of material deformation structure is also provided to show the effectiveness of the proposed work.

关键词： grid grid service chain formal method model checking state Pi calculus

Research achievements on the new generation Internet architecture and protocols

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Science China(Information Sciences) 2013年第11期56卷 133-157页

作者： LIU Ying WU JianPing ZHANG Zhou xu ke Tsinghua National Laboratory for Information Science and Technology (TNList) Institute for Network Sciences and Cyberspace Tsinghua University Department of Computer Science and Technology Tsinghua University

Despite the great success achieved by the Internet,it has been facing increasingly severe technical challenges that include address exhaustion,low-level network security and trustworthiness,weak quality-ofservice control capability,limited bandwidth,and poor support toward *** this paper we summarize the principal challenges facing the current Internet,introduce the research status of the future Internet,analyze the principal design goals of the new generation Internet evaluation methods and models of the present Internet architecture,introduce the research achievements made under the new generation Internet architecture in detail,and propose our next-step research priorities and perspectives in the face of an increasing number of innovative Internet applications.

关键词： Internet technical challenges new generation Internet architecture evolvable architecture

Deposition of Ti-Si-N coatings in deep blind-hole with pulsed dc power

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中国有色金属学会会刊：英文版 2004年第z1期14卷 260-263页

作者： MA Da-yan MA Sheng-li xu ke-wei State key Laboratory for Mechanical Behavior of Materials Xi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of MaterialsXi''an Jiaotong University Xi''an 710049 China State Key Laboratory for Mechanical Behavior of MaterialsXi''an Jiaotong University Xi''an 710049 China

Multiphase nanocomposite Ti-Si-N coatings deposited by pulsed dc plasma enhanced chemical vapor deposition technique on the surface of HSS substrate, which were bolted with deep blind-hole to simulate the complexshaped surface of various tools, were investigated. The micrographs show that the surface morphologies of the coatings become coarser with an increasing depth of the bottom holes. And the silicon content increases in Ti-Si-N coatings, which are composed of nanocrystalline TiN, nano-sized amorphous Si3N4, and occasionally amorphous or nanocrysralline TiSi2. The thickness of the coatings decreases with the increasing depth of holes, which may result from the changes of the composition in the coatings. The microhardness of the coatings increases firstly with the increasing depth of holes, reaches a maximum value of about HV5 700 at 10mm depth, and then decreases at larger depth.

关键词： nanocomposite pulsed dc PCVD Ti-Si-N deep blind-hole

Type Synthesis of 1T2R Parallel Mechanisms Using Structure Coupling-Reducing Method

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Chinese Journal of Mechanical Engineering 2019年第5期32卷 70-79页

作者： Haitao Liu ke xu Huiping Shen Xianlei Shan Tingli Yang key Laboratory of Mechanism Theory and Equipment Design Ministry of EducationTianjin UniversityTianjin 300350China School of Mechanical Engineering Changzhou UniversityChangzhou 213164China

Direct kinematics with analytic solutions is critical to the real-time control of parallel ***,the type synthesis of a mechanism having explicit form of forward kinematics has become a topic of *** on this purpose,this paper deals with the type synthesis of 1T2R parallel mechanisms by investigating the topological structure coupling-reducing of the 3UPS&UP parallel *** the aid of the theory of mechanism topology,the analysis of the topological characteristics of the 3UPS&UP parallel mechanism is presented,which shows that there are highly coupled motions and constraints amongst the limbs of the *** methods for structure coupling-reducing of the 3UPS&UP parallel mechanism are proposed,resulting in eight new types of 1T2R parallel mechanisms with one or zero coupling *** obtained parallel mechanism is taken as an example to demonstrate that a mechanism with zero coupling degree has an explicit form for forward *** process of type synthesis is in the order of permutation and combination;therefore,there are no *** method is also appli cable to other configurations,and novel topological structures having simple forward kinematics can be obtained from an original mechanism via this method.

关键词： Type synthesis Structure coupling-reducing Coupling degree Parallel mechanism

Towards real-time ML-based DDoS detection via cost-efficient window-based feature extraction

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Science China(Information Sciences) 2023年第5期66卷 114-129页

作者： Haibin LI Yi ZHAO Wenbing YAO ke xu Qi LI Department of Computer Science and Technology Tsinghua University Beijing National Research Center for Information Science and Technology (BNRist) Institute for Network Sciences and Cyberspace Tsinghua University

Distributed denial of service(DDoS) detection is still an open and challenging problem. In particular, sophisticated attacks, e.g., attacks that disguise attack packets as benign traffic always appear, which can easily evade traditional signature-based methods. Due to the low requirements for computing resources compared to deep learning, many machine learning(ML)-based methods have been realistically deployed to address this issue. However, most existing ML-based DDo S detection methods are highly dependent on the features extracted from each flow, which incur remarkable detection delay and computation overhead. This article investigates the limitations of typical ML-based DDo S detection methods caused by the extraction of flow-level features. Moreover, we develop a cost-efficient window-based method that extracts features from a fixed number of packets periodically, instead of per flow, aiming to reduce the detection delay and computation overhead. The newly proposed window-based method has the advantages of well-controlled overhead and wide support of common routers due to its simplicity and high efficiency by design. Through extensive experiments on real datasets, we evaluate the performance of flow-based and window-based *** experimental results demonstrate that our proposed window-based method can significantly reduce the detection delay and computation overhead while ensuring detection accuracy.

关键词： DDoS attack machine learning feature extraction detection delay cost-efficiency