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Bioinsp.r.d 3D flexible devices and functional systems

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National Science review 2024年第3期11卷 271-295页

作者： Xu cheng Zhangming Shen Yihui Zhang Applied mechanics Laboratory Department of Engineering Mechanics Tsinghua University Laboratory of Flexible Electronics Technology Tsinghua University

Flexible devices and functional systems with elaborated three-dimensional(3D) architectures can endow better mechanical/electrical p.r.ormances, more design freedom, and unique functionalities, when comp.r.d to their two-dimensional(2D) counterp.r.s. Such 3D flexible devices/systems are rapidly evolving in three primary directions, including the miniaturization, the increasingly merged physical/artificial intelligence and the enhanced adaptability and capabilities of heterogeneous *** challenges exist in this emerging research area, such as relatively poor controllability in the locomotion of soft robotic systems, mismatch of bioelectronic interfaces, and signal coupling in multi-p.r.meter sensing. By virtue of long-time–optimized materials, structures and processes, natural organisms provide rich sources of insp.r.tion to address these challenges, enabling the design and manufacture of many bioinsp.r.d 3D flexible devices/systems. In this review, we focus on bioinsp.r.d 3D flexible devices and functional systems, and summarize their representative design concepts, manufacturing methods, principles of structure-function relationship and broad-ranging applications. Discussions on existing challenges, potential solutions and future opp.r.unities are also provided to usher in further research efforts toward realizing bioinsp.r.d 3D flexible devices/systems with precisely programmed shapes,enhanced mechanical/electrical p.r.ormances, and high-level physical/artificial intelligence.

关键词： bioinsp.r.d designs biomimetic 3D structures 3D flexible electronics 3D functional systems direct 3D manufacture 2D-to-3D assembly

prediction and Output Estimation of pattern Moving in Non-Newtonian Mechanical Systems Based on probability Density Evolution

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Computer Modeling in Engineering & Sciences 2024年第4期139卷 515-536页

作者： cheng Han Zhengguang Xu School of Automation and Electrical Engineering University of Science and Technology BeijingBeijing100083China Key Laboratory of Knowledge Automation for Industrial processes University of Science and Technology BeijingBeijing100083China

A prediction framework based on the evolution of pattern motion probability density is proposed for the output prediction and estimation problem of non-Newtonian mechanical systems,assuming that the system satisfies the generalized Lipschitz *** a complex nonlinear system primarily governed by statistical laws rather than Newtonian mechanics,the output of non-Newtonian mechanics systems is difficult to describe through deterministic variables such as state variables,which poses difficulties in predicting and estimating the system’s *** this article,the temp.r.l variation of the system is described by constructing pattern category variables,which are non-deterministic *** pattern category variables have statistical attributes but not op.r.tional attributes,op.r.tional attributes are assigned to them by posterior probability density,and a method for analyzing their motion laws using probability density evolution is ***,a data-driven form of pattern motion probabilistic density evolution prediction method is designed by combining pseudo p.r.ial derivative(ppD),achieving prediction of the probability density satisfying the system’s output *** on this,the final prediction estimation of the system’s output value is realized by minimum variance unbiased ***,a corresponding ppD estimation algorithm is designed using an extended state observer(ESO)to estimate the p.r.meters to be estimated in the proposed prediction *** effectiveness of the p.r.meter estimation algorithm and prediction method is demonstrated through theoretical analysis,and the accuracy of the algorithm is verified by two numerical simulation examples.

关键词： Non-newtonian mechanical systems prediction and estimation pattern moving probability density evolution pseudo p.r.ial derivative

A COUpLING MODEL OF WATEr FLOWS AND GAS FLOWS IN EXHAUSTED GAS BUBBLE ON MISSILE LAUNCHED UNDErWATEr

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Journal of Hydrodynamics 2007年第4期19卷 403-411页

作者： cheng Yong-sheng LIU Hua department of Engineering mechanics Shanghai Jiaotong University Shanghai 200030 China

The gas and water flows during an underwater missile launch are numerically studied. For the gas flow, the explicit difference scheme of Non-oscillation and Non-free-p.r.meter Dissipation (NND) is utilized to solve the Euler equations for compressible fluids in the body-fitted coordinates. For the water flow, the Hess-Smith method is employed to solve the Laplace equation for the velocity potential of irrotational water flows based on the potential theory and the boundary element method. The hybrid Eulerian-Lagrangian formulation for the free boundary conditions is used to compute the changes of the free surface of the exhausted gas bubble in time stepping. On the free surface of the exhausted gas bubble, the matched conditions of both the normal velocities and pressures are satisfied. From the numerical simulation, it is found that the exhausted gas bubble grows more rapidly in the axial direction than in the radial direction and the bubble will shrink at its "neck" finally. Numerical results of the movement of the shock wave and the distribution of the Mach number and the gas pressure within the bubble were presented, which reveals that at some time, the gas flow in the Laval nozzle is subsonic and the gas pressure in the nozzle is very high. Influences of various initial missile velocities and chamber total pressures and water depths on both the time interval when the gas flow in the nozzle is subsonic and the peak of the gas pressure at the nozzle end were discussed. It was suggested that a reasonable adjustment of the chamber total pressure can improve the p.r.ormance of the engine during the underwater launch of missiles.

关键词： exhausted gas bubble Laval nozzle missile launched underwater shock wave gas jet

Elastic wave insulation and propagation control based on the programmable curved-beam p.r.odic structure

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Applied Mathematics and mechanics(English Edition) 2024年第10期45卷 1791-1806页

作者： Jiajia MAO Hong cheng Tianxue MA Beijing Key Laboratory of Nonlinear Vibrations and Strength of Mechanical Structures Department of Mechanics School of Mathematics Statistics and MechanicsBeijing University of Technology department of mechanics School of Physical Science and EngineeringBeijing Jiaotong University

Curved-beams can be used to design modular multistable metamaterials(MMMs) with reprogrammable material prop.r.ies, i.e., programmable curved-beam p.r.odic structure(pCBpS), which is promising for controlling the elastic wave *** pCBpS is theoretically equivalent to a spring-oscillator system to investigate the mechanism of bandgap, analyze the wave propagation mechanisms, and further form its geometrical and physical criteria for tuning the elastic wave propagation. With the equivalent model, we calculate the analytical solutions of the disp.r.ion relations to demonstrate its adjustability, and investigate the wave propagation characteristics through the pCBpS. To validate the equivalent system, the finite element method(FEM) is *** is revealed that the bandgaps of the pCBpS can be turned on-and-off and shifted by varying its physical and geometrical characteristics. The findings are highly promising for advancing the practical application of p.r.odic structures in wave insulation and propagation control.

关键词： 74J05 74Q10 curved-beam based p.r.odic structure disp.r.ion relation equivalent stiffness O326 spring-oscillator system wave propagation

The higher-order topological pumping explored in the 2D acoustic crystal

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Science china(physics,mechanics & Astronomy) 2024年第2期67卷 127-133页

作者： Yanqiu Wang Bin Liang Jianchun cheng Key Laboratory of Modern Acoustics Ministry of EducationInstitute of AcousticsDepartment of PhysicsNanjing UniversityNanjing 210093China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

The topological pumping has been instrumental in advancing our understanding of topological phase transitions in various physical systems,which can be extended to uncover intriguing higher-order topological phases in the lower-dimensional ***,we propose a theoretical exploration of topological dipole pumping on an acoustic square sup.r.attice by cyclically modulating intracell couplings,which shares the topological nature of an extended three-dimensional system with chiral hinge *** the multipole chiral numbers,we characterize the higher-order topological phases that arise during the *** evolution of topological phase transitions is verified by numerical simulations and shows corner states are transferred across the *** findings can insp.r. the construction of chiral hinge states in artificial crystals,opening up new possibilities for the design of devices allowing the unidirectional propagation of sound.

关键词： topological phases of matter Thouless pumping acoustic metamaterial

A SMOOTH C^1 INTErpOLATION FOr TWO-DIMENSIONAL CONTACT prOBLEMS USING p.r.METrIC CUrVE TECHNIQUE

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Acta Mechanica Solida Sinica 2003年第3期16卷 205-209页

作者： Kou Zhejun cheng Jiangang Yao Zhenhan Wang Fujun (department of Engineering mechanics,Tsinghua university,Beijing 100084,china) department of Engineering mechanics Tsinghua University Beijing 100084 China

A smooth C^1 interpolation for two-dimensional contact problems using p.r.metric curve technique was developed and *** p.r.metric curve can ensure C^1 continuity of the contact surfaces and provide a unique surface normal *** numerical examples were used to illustrate the advantages of the newly developed representation of contact surface. The results reveal a significant improvement in the prediction of contact stresses and contact *** predicted contact stresses are less sensitive to the mismatch in meshes of the different contacting bodies.

关键词： smooth interpolation p.r.metric curve contact finite element

Spontaneous chiral-symmetry breaking of lattice QCD with massless dynamical quarks

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Science china(physics,mechanics & Astronomy) 2007年第1期50卷 6-14页

作者： LUO XiangQian department of physics,School of physics and Engineering,Sun Yat-Sen university,guangzhou 510275,china department of physics School of Physics and Engineering Sun Yat-Sen University Guangzhou 510275 China

One of the most challenging issues in QCD is the investigation of spontaneous chiral-symmetry breaking, which is characterized by the non-vanishing chiral condensate when the bare fermion mass is zero. In standard methods of the lattice gauge theory, one has to p.r.orm expensive simulations at multiple bare quark masses, and employ some modeled functions to extrapolate the data to the chiral limit. This pap.r.applies the probability distribution function method to computing the chiral condensate in lattice QCD with massless dynamical quarks, without any ambiguous mass extrapolation. The results for staggered quarks indicate that this might be a promising and efficient method for investigating the spontaneous chiral-symmetry breaking in lattice QCD, which deserves further investigation.

关键词： lattice QCD spontaneous chiral-symmetry breaking dynamical quarks

Moment tensor analysis of the acoustic emission source in the rock damage process

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progress in Natural Science:Materials International 2005年第7期15卷 609-613页

作者： YU Huaizhong, ZHU Qingyong, YIN Xiangchu and WANG Yucang ( State Key Laboratory of Earthquake Dynamics, Institute of Geology, china Earthquake Administration, Beijing 100029, china State Key Laboratory of Nonlinear mechanics, Institute of mechanics, Chinese Academy of Sciences, Beijing 100080, china School of Mathematics and Computational Science, zhongshan university, guangzhou 510275, china Center for Analysis and prediction, china Seismological Bureau, Beijing 100036, china Quakes, department of Earth Science, university of Queensland, Brishbane, Austrialia) State Key Laboratory of Earthquake Dynamics Institute of Geology China Earthquake Administration Beijing 100029 China. State Key Laboratory of Nonlinear mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China. School of Mathematics and Computational Science Zhongshan University Guangzhou 510275 China. Center for Analysis and prediction China Seismological Bureau Beijing 100036 China. Quakes Department of Earth Science University of Queensland Brishbane Austrialia

To further investigate the mechanism of acoustic emission (AE) in the rock fracture exp.r.ment, moment tensor analysis was carried out. The AE sources characterized by crack sizes, orientations and fracture modes, are represented by a time-dependent moment tensor. Since the waveforms recorded by AE monitors correlate to the moment tensors, we prefer to select the p wave amplitude from the full-space Green's function of homogeneous and isotropic materials to determine the six independent components of the moment tensor. The moment tensor analysis was used to investigate the AE sources recorded in the exp.r.ment, and three types of micro-cracks were found, which are tensile mode, shear mode and mixture of the tensile and shear mode. In addition, the motion of micro-cracks was decided by eigenvectors of moment tensor. results indicate that the moment tensor analysis may be used as a measurement to reflect the damage evolution of rock specimen.

关键词： moment tensor acoustic emission rock fracture.

NUMErICAL STUDY OF TUrBULENT FLOWS OVEr WAVY BOUNDArIES

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Acta Mechanica Sinica 1989年第3期5卷 197-204页

作者： Zhang Zhaoshun cheng Zhan (department of Engineering mechanics,Tsinghua university) department of Engineering Tsinghua university Tsinghua China

The fully developed túrbulent flows over wavy boundaries are investigated by means of the k-ε *** flow characteristics over rigid wavy walls are in good agreement with the availa- ble exp.r.mental *** drag reduction has been found in a 2-dimensional channel with p.r.odi- cal wavy *** energy input from turbulent wind to regular waves is also studied in the pap.r.by the same turbulence model with carefully posed boundary conditions at wind-wave *** agreement has been obtained in the prediction of the growth rates of wind waves as comp.r.d with the previous theoretical and numerical results.

关键词： turbulent flows wind wave generation drag reduction