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Nano surface engineering and remanufacture engineering

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中国有色金属学会会刊：英文版 2004年第z1期14卷 1-5页

作者： xu bin-shi National Key Laboratory for Remanufacturing Academy of Armored Force Engineering Beijing 100072 China

Nano surface engineering and remanufacture engineering are introduced, and the relationship between them is set forth. It points out the superiority of nano surface engineering to the traditional one, and reveals the advantages of remanufacture engineering. Taking some nano surface techniques as samples, such as nano-materials brush electroplating, nano-materials thermal spraying and nano-materials self-repairing antifriction additive technology, it shows the applications of nano surface engineering technology to remanufacturing mechanical parts.

关键词： nano surface engineering nano composite coatings remanufacture engineering

Two performance enhanced control of flexible-link manipulator with system uncertainty and disturbances

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Science China(Information Sciences) 2017年第5期60卷 25-35页

作者： bin xu Yuan YUAN School of Automation Northwestern Polytechnical University School of Automation Science and Electrical Engineering Beihang University

Precision control of flexible-link manipulator for space operation is challenging due to the dynamics coupling and system uncertainty. In this paper, to deal with system uncertainty and time-varying disturbance,two performance enhanced controller designs, named Composite Learning Control and Disturbance Observer Based Control are presented respectively. To overcome the nonminimum phase, using output redefinition, the dynamics is transformed to two subsystems: internal system and input-output system. For the internal dynamics,the PD(proportion differentiation) control is used with pole assignment. For the input-output subsystem,considering the unknown dynamics, the composite learning control is designed using neural modeling error while in case of disturbance, the disturbance observer based design is proposed. The stability analysis of the closed-loop system is presented via Lyapunov approach. Simulation of 2-degrees of freedom(DOF) flexible-link manipulator is conducted and the results show that the proposed methods can enhance the tracking performance.

关键词： flexible-link manipulator composite learning control disturbance observer output redefinition system uncertainty

An overview on flight dynamics and control approaches for hypersonic vehicles

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Science China(Information Sciences) 2015年第7期58卷 7-27页

作者： xu bin SHI ZhongKe School of Automation Northwestern Polytechnical University National Key Laboratory of Aerospace Flight Dynamics Northwestern Polytechnical University

With the capability of high speed flying, a more reliable and cost efficient way to access space is provided by hypersonic flight vehicles. Controller design, as key technology to make hypersonic flight feasible and efficient, has numerous challenges stemming from large flight envelope with extreme range of operation conditions, strong interactions between elastic airframe, the propulsion system and the structural *** paper briefly presents several commonly studied hypersonic flight dynamics such as winged-cone model,truth model, curve-fitted model, control oriented model and re-entry motion. In view of different schemes such as linearizing at the trim state, input-output linearization, characteristic modeling, and back-stepping, the recent research on hypersonic flight control is reviewed and the comparison is presented. To show the challenges for hypersonic flight control, some specific characteristics of hypersonic flight are discussed and the potential future research is addressed with dealing with actuator dynamics, aerodynamic/reaction-jet control, flexible effects,non-minimum phase problem and dynamics interaction.

关键词： hypersonic flight vehicle linearizing at the trim state input-output linearization back-stepping non-minimum phase

CFD Simulation of Local and Global Mixing Time in an Agitated Tank

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Chinese Journal of Mechanical Engineering 2017年第1期30卷 118-126页

作者： LI Liangchao xu bin Key Laboratory of Testing Technology for Manufacturing Process of Ministry of Education Southwest University of Science and TechnologyMianyang 621010China

The Issue of mixing efficiency in agitated tanks has drawn serious concern in many industrial processes. The turbulence model is very critical to predicting mixing process in agitated tanks. On the basis of computational fluid dynamics（CFD） software package Fluent 6.2, the mixing characteristics in a tank agitated by dual six-blade-Rushton-turbines（6-DT） are predicted using the detached eddy simulation（DES） method. A sliding mesh（SM） approach is adopted to solve the rotation of the impeller. The simulated flow patterns and liquid velocities in the agitated tank are verified by experimental data in the literature. The simulation results indicate that the DES method can obtain more flow details than Reynolds-averaged Navier-Stokes（RANS） model. Local and global mixing time in the agitated tank is predicted by solving a tracer concentration scalar transport equation. The simulated results show that feeding points have great influence on mixing process and mixing time. Mixing efficiency is the highest for the feeding point at location of midway of the two impellers. Two methods are used to determine global mixing time and get close result. Dimensionless global mixing time remains unchanged with increasing of impeller speed. Parallel, merging and diverging flow pattern form in the agitated tank, respectively, by changing the impeller spacing and clearance of lower impeller from the bottom of the tank. The global mixing time is the shortest for the merging flow, followed by diverging flow, and the longest for parallel flow. The research presents helpful references for design, optimization and scale-up of agitated tanks with multi-impeller.

关键词： agitated tank mixing time computational fluid dynamics(CFD) detached eddy simulation(DES) numerical simulation

Numericals for total variation-based reconstruction of motion blurred images

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Applied Mathematics(A Journal of Chinese Universities) 2010年第3期25卷 367-373页

作者： xu Qiu-bin Department of Mathematics Nanjing Audit University Nanjing 211815 China

In this paper image with horizontal motion blur, vertical motion blur and angled motion blur are considered. We construct several difference schemes to the highly nonlinear term △↓.（△↓u/√｜△↓｜^2＋β） of the total variation-based image motion deblurring problem. The large nonlinear system is linearized by fixed point iteration method. An algebraic multigrid method with Krylov subspace acceleration is used to solve the corresponding linear equations as in [7]. The algorithms can restore the image very well. We give some numerical experiments to demonstrate that our difference schemes are efficient and robust.

关键词： Motion blur difference scheme fixed point method algebraic multigrid method.

On Rational Functions with More than Three Branch Points

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Algebra Colloquium 2020年第2期27卷 231-246页

作者： Jijian Song bin xu Center for Applied Mathematics Tianjin UniversityTianjin 300350China Wu Wen-Tsun Key Laboratory of Mathematics USTCChinese Academy of Sciences School of Mathematical SciencesUniversity of Science and Technology of China Hefei 230026China

Let d be a positive integer and八be a collection of partitions of d of the form(a1,...,ap),(b1,...,bq),(m1+1,1,...,1),...,(m1+1,1,...,1),where(m1,...,ml)is a partition of p+g-2>*** prove that there exists a rational f... 详细信息

关键词： branch data realizability problem Belyi function Riemann's existence theorem

Isolation of the cuspidal spectrum:The function field case

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Science China Mathematics 2022年第7期65卷 1331-1342页

作者： Li Cai bin xu Yau Mathematical Sciences Center Tsinghua UniversityBeijing 100084China School of Mathematics Sichuan UniversityChengdu 610064China

Isolating cuspidal automorphic representations from the whole automorphic spectrum is a basic problem in the trace formula *** example,matrix coefficients of supercuspidal representations can be used as test functions for ***,they kill a large class of interesting cuspidal automorphic *** the case of number fields,multipliers of the Schwartz algebra are used in the recent work(see Beuzart-Plessis et al.(2021))to isolate all the cuspidal *** particular,they are suitable for the comparison of orbital *** multipliers are then applied to the proof of the Gan-Gross-Prasad conjecture for unitary groups(see Beuzart-Plessis et al.(2021,2022)).In this article,we prove the similar result on isolating the cuspidal spectrum in Beuzart-Plessis et al.(2021)for the function field case.

关键词： cuspidal spectrum Hecke algebra trace formula automorphic representation

Evasion guidance algorithms for air-breathing hypersonic vehicles in three-player pursuit-evasion games

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Chinese Journal of Aeronautics 2020年第12期33卷 3423-3436页

作者： Tian YAN Yuanli CAI bin xu School of Electronic and Information Engineering Xi'an Jiaotong UniversityXi'an 710049China School of Automation Northwestern Polytechnical UniversityXi'an 710072China

In practical combat scenario,the cooperative intercept strategies are often carefully designed,and it is challenging for the hypersonic vehicles to achieve successful *** on the analysis,it can be found that if several Successive Pursuers come from the Same Direction(SPSD)and flight with a proper spacing,the evasion difficulty may increase *** address this problem,we focus on the evasion guidance strategy design for the Air-breathing Hypersonic Vehicles(AHVs)under the SPSD combat *** order to avoid the induced influence on the scramjet,altitude and speed of the vehicle,the lateral maneuver and evasion are *** guarantee the remnant maneuver ability,the concept of specified miss distance is introduced and utilized to generate the guidance command for the *** the framework of constrained optimal control,the analytical expression of the evasion command is derived,and the constraints of the overload can be ensured to be never *** fact,by analyzing the spacing of the pursers,it can be classified whether the cooperative pursuit is *** the coordination-unformed multiple pursers,the evasion can be achieved lightly by the proposed *** the coordination is formed,the proposed method will generate a large reverse direction maneuver,and the successful evasion can be maintained as a *** performance of the proposed algorithms is tested in numerical simulations.

关键词： Differential game theory Game theory Hypersonic vehicles Optimal control Pursuit-evasion strategy

Hyperspectral Image Classification Based on A Multi-Scale Weighted Kernel Network

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Chinese Journal of Electronics 2022年第5期31卷 832-843页

作者： SUN Le xu bin LU Zhenyu School of Computer Science Nanjing University of Information Science and Technology Engineering Research Center of Digital Forensics Ministry of Education Nanjing University of Information Science and Technology School of Artificial Intelligence Nanjing University of Information Science and Technology

Recently, many deep learning models have shown excellent performance in hyperspectral image(HSI) classification. Among them, networks with multiple convolution kernels of different sizes have been proved to achieve richer receptive fields and extract more representative features than those with a single convolution kernel. However, in most networks, different-sized convolution kernels are usually used directly on multibranch structures, and the image features extracted from them are fused directly and simply. In this paper, to fully and adaptively explore the multiscale information in both spectral and spatial domains of HSI, a novel multi-scale weighted kernel network(MSWKNet) based on an adaptive receptive field is proposed. First, the original HSI cubic patches are transformed to the input features by combining the principal component analysis and one-dimensional spectral convolution. Then, a three-branch network with different convolution kernels is designed to convolve the input features, and adaptively adjust the size of the receptive field through the attention mechanism of each branch. Finally, the features extracted from each branch are fused together for the task of *** on three well-known hyperspectral data sets show that MSWKNet outperforms many deep learning networks in HSI classification.

关键词： multibranch structures image features convolution kernels multiple convolution kernels adaptive receptive field image classification feature extraction HSI classification single convolution kernel convolutional neural nets hyperspectral image classification representative features hyperspectral imaging geophysical image processing deep learning (artificial intelligence) multiscale weighted kernel network deep learning networks hyperspectral data sets three-branch network HSI cubic patches principal component analysis 1D spectral convolution different-sized convolution kernels