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Numerical simulation and scaling analysis of elasticity-induced lift force in a viscoelastic fluid between confining surfaces

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Journal of Hydrodynamics 2022年第4期34卷 756-766页

作者： xin zhao Chao Wei The State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China Science and Technology on Vehicle Transmission Laboratory Beijing Institute of TechnologyBeijing 100081China

How to accurately characterize the lift force on the particles near the solid surfaces is an ongoing challenge in fluid mechanics and microfluidic techniques, especially in a complex system with viscoelastic fluid or/and soft surface that is commonly encountered in a biological system. The motions of the particles in vicinity of a surface can be simplified to be a rigid cylinder surrounded by the viscoelastic fluid moving along a substrate which can be rigid or soft according to different cases. In such an inertial free system with a wide range of Weissenberg number (Wi < 5.00, representing the ratio of the elastic force to the viscous force), firstly we numerically evaluate the influence of the systematic parameters, including the polymer viscosity, the geometry and Wi, on the net normal force for a cylinder closely moving along a rigid substrate, and the elasticity-induced lift force in a scaled form. It is shown that a strong shear arises in the viscoelastic confinement between the moving cylinder and the rigid substrate, it leads to the asymmetry of the first normal stress distribution around the cylinder, and thus the lift force. Then, the influence of a soft substrate on the lift force is considered, and we find that the lift force induced by the viscoelastic fluid always dominates in magnitude over that induced by the soft substrate deformation. This work provides a reliable scaling that can be utilized to quantify the elasticity-induced lift force on the particles in a viscoelastic system, such as the micro- and nanofluidic systems in biological applications.

关键词： Viscoelastic fluid scaling expression computational fluid dynamics lift force

Zero Problems of the Bergman Kernel Function on the First Type of Cartan-Hartogs Domain

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Chinese Annals of Mathematics,Series B 2022年第2期43卷 265-280页

作者： xin zhao An WANG Information Institute Canvard CollegeBeijing Technology and Business UniversityBeijing100018China School of Mathematical Sciences Capital Normal UniversityBeijing 100048China

The authors give the condition that the Bergman kernel function on the first type of Cartan-Hartogs domain exists *** the Bergman kernel function of this type of domain has zeros,the zero set is composed of several pa... 详细信息

关键词： Cartan-Hartogs domain Zeros of Bergman kernel function Path connectivity

Soluble Two-dimensional Supramolecular Organic Frameworks(SOFs):An Emerging Class of 2D Supramolecular Polymers with Internal Longrange Orders

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Chinese Journal of Polymer Science 2019年第1期37卷 1-10页

作者： Shu-Yan Jiang xin zhao CAS Key Laboratory of Synthetic and Self-assembly Chemistry for Organic Functional Molecules Center for Excellence in Molecular Synthesis Shanghai Institute of Organic Chemistry Chinese Academy of Sciences

Two-dimensional(2D) materials have been demonstrated to exhibit unique properties originating from its 2D nature. In recent years, the construction of 2D materials has become a topic of great interest. This article summarizes the recent advance of 2D supramolecular organic frameworks(SOFs) which are homogeneously constructed in solution phase through self-assembly of rationally designed building blocks. These 2D SOFs are soluble and still maintain stable network structures in solutions, which exhibit uniqueness not only in structures but also in properties. In this concise review, the SOFs-related background is briefly introduced firstly, followed by outlining the research progress of soluble 2D SOFs from the perspective of monomer design, assembly, and structural *** article ends with a personal outlook on the future development of this new class of supramolecular polymers.

关键词： Supramolecular organic frameworks(SOFs) Self-assembly Two-dimensional Supramolecular polymers

Decentralized Resilient H_∞Load Frequency Control for Cyber-Physical Power Systems Under DoS Attacks

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IEEE/CAA Journal of Automatica Sinica 2021年第11期8卷 1737-1751页

作者： xin zhao Suli Zou Zhongjing Ma School of Automation Beijing Institute of TechnologyBeijing 100081China

This paper designs a decentralized resilient H_(∞)load frequency control(LFC)scheme for multi-area cyber-physical power systems(CPPSs).Under the network-based control framework,the sampled measurements are transmitted through the communication networks,which may be attacked by energylimited denial-of-service(DoS)attacks with a characterization of the maximum count of continuous data losses(resilience index).Each area is controlled in a decentralized mode,and the impacts on one area from other areas via their interconnections are regarded as the additional load disturbance of this ***,the closed-loop LFC system of each area under DoS attacks is modeled as an aperiodic sampled-data control system with external *** this modeling,a decentralized resilient H_(∞)scheme is presented to design the state-feedback controllers with guaranteed H∞performance and resilience index based on a novel transmission interval-dependent loop functional *** given the controllers,the proposed scheme can obtain a less conservative H_(∞)performance and resilience index that the LFC system can *** effectiveness of the proposed LFC scheme is evaluated on a one-area CPPS and two three-area CPPSs under DoS attacks.

关键词： Cyber-physical power systems(CPPSs) denial-of-service(DoS)attacks load frequency control(LFC) sampled-data control

Interpolation-based contour error estimation and componentbased contouring control for five-axis CNC machine tools

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Science China(Technological Sciences) 2018年第11期61卷 1666-1678页

作者： LI XiangFei zhao Huan zhao xin DING Han State key Laboratory of Digital Manufacturing Equipment and Technology Huazhong University of Science and Technology

High accuracy contour error estimation and direct contour error control are two major approaches to reduce the contour ***, two key factors make them complex for five-axis machine tools: the nonlinear kinematics and the coupling between the tool position and orientation. In this study, by finding the reference point nearest to the current actual position, and interpolating the point with two neighboring reference points and using the distance ratio, a new contour error estimation method for five-axis machine tools is proposed, which guarantees high accuracy while depending on only the reference points. By adding a weighted contour error on the tracking error in the workpiece coordinate system, and specifying a desired second-order error dynamics based on the error variable, an effective contouring control method is proposed, which can alleviate the problem: when the contour error components are introduced into the controller, the contour errors increase instead in some regions of the tracking trajectory. A series of experiments are performed on a tilting-rotary-table(TRT) type five-axis machine tool. The results reveal that the proposed estimation method has high accuracy, and compared with the case without contour error control, the proposed control approach can reduce the contour error along the whole trajectory.

关键词： five-axis contour error contouring control interpolation component-based

Integrated guidance and control design of the suicide UCAV for terminal attack

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Journal of Systems Engineering and Electronics 2017年第3期28卷 546-555页

作者： Huan Zhou Hui zhao Hanqiao Huang xin zhao Aeronautics and Astronautics Engineering College Air Force Engineering UniversityXi’an 710038China

A novel integrated guidance and control (IGC) design method is proposed to solve problems of low control accuracy for a suicide unmanned combat aerial vehicle (UCAV) in the terminal attack stage. First of all, the IGC system model of the UCAV is built based on the three-channel independent design idea, which reduces the difficulties of designing the controller. Then, IGC control laws are designed using the trajectory linearization control (TLC). A nonlinear disturbance observer (NDO) is introduced to the IGC controller to reject various uncertainties, such as the aerodynamic parameter perturbation and the measurement error interference. The stability of the closed-loop system is proven by using the Lyapunov theorem. The performance of the proposed IGC design method is verified in a terminal attack mission of the suicide UCAV. Finally, simulation results demonstrate the superiority and effectiveness in the aspects of guidance accuracy and system robustness.

关键词： integrated guidance and control (IGC) unmanned combat aerial vehicle (UCAV) trajectory linearization control (TLC) terminal attack nonlinear disturbance observer (NDO)

Absence of eigenvalues for quasiperiodic Schrodinger type operators

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Frontiers of Mathematics in China 2019年第3期14卷 645-659页

作者： Jiahao XU xin zhao Department of Mathematical Sciences Nanjing University Nanjing 210093 China

We obtain the matrix-valued Schrodinger-type operators [Hα,θ] with Lipschitz potentials having no eigenvalues on the set {E : L ( E )<δ)C,d(α,θ),where δ is an explicit function depending on the sampling function... 详细信息

关键词： Quasiperiodic Schrodinger type operators absence of eigenvalues singular continuous spectrum

A sub-grid scale model for Burgers turbulence based on the artificial neural network method

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Theoretical & Applied Mechanics Letters 2024年第3期14卷 162-165页

作者： xin zhao Kaiyi Yin Department of Mechanics Beijing Institute of TechnologyBeijing 100081China

The present study proposes a sub-grid scale model for the one-dimensional Burgers turbulence based on the neuralnetwork and deep learning *** filtered data of the direct numerical simulation is used to establish thetraining data set,the validation data set,and the test data *** artificial neural network(ANN)methodand Back Propagation method are employed to train parameters in the *** developed ANN is applied toconstruct the sub-grid scale model for the large eddy simulation of the Burgers turbulence in the *** proposed model well predicts the time correlation and the space correlation of the Burgers turbulence.

关键词： Artificial neural network Back propagation method Burgers turbulence Large eddy simulation Sub-grid scale model

Subspace choices for the Celis-Dennis-Tapia problem

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Science China Mathematics 2017年第9期60卷 1717-1732页

作者： zhao xin FAN JinYan School of Mathematical Sciences Shanghai Jiao Tong UniversityShanghai 200240China School of Mathematical Sciences and MOE-LSC Shanghai Jiao Tong UniversityShanghai 200240China

Grapiglia et al.(2013) proved subspace properties for the Celis-Dennis-Tapia(CDT) problem. If a subspace with lower dimension is appropriately chosen to satisfy subspace properties, then one can solve the CDT problem in that subspace so that the computational cost can be reduced. We show how to find subspaces that satisfy subspace properties for the CDT problem, by using the eigendecomposition of the Hessian matrix of the objection function. The dimensions of the subspaces are investigated. We also apply the subspace technologies to the trust region subproblem and the quadratic optimization with two quadratic constraints.

关键词： CDT problems subspace properties subspace choices