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Science China(Physics,mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 156-168页

作者： Yifeng Li Zhuoran Yang Ziming Yan Huibin Shi Zhanli Liu Kaijie Wang Department of engineering mechanics School of Aerospace Engineering Tsinghua University Beijing Tongren Eye Center Beijing Tongren Hospital Capital Medical University Beijing Ophthalmology & Visual Sciences Key Lab

Orthokeratology(OK) is widely used for effective myopia correction and control. However, the incomplete understanding of its biomechanical mechanisms makes OK lens fitting rely heavily on clinician judgment, complicating accurate predictions of treatment outcomes. In this paper, we performed clinical experiments and numerical analysis to study corneal deformation modes and long-term changes in central corneal thickness. Clinical experiments were conducted on 194 Chinese myopic patients under OK treatment for 3 months. Based on the experimental data, a patient-specific computational biomechanical model for OK was established and validated. Specifically, the anisotropic mechanical properties of the cornea were incorporated into the model to describe the significant difference between its shear modulus(29.5 kPa) and tensile modulus(768.4 kPa). Additionally, a viscohyperelastic material model with a prolonged corneal relaxation time of 5.6 h was developed to capture the long-term deformation response. The results show that corneal thickness reduction in OK is primarily due to out-of-plane shear deformation,influenced by the cornea's low shear resistance. Modeling the extended corneal relaxation time is crucial for predicting long-term biomechanical responses. The computational model effectively captures long-term changes in central corneal thickness, potentially improving OK lens fitting accuracy.

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Targets capture by distributed active swarms via bio-inspired reinforcement learning

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Science China(Physics,mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 210-221页

作者： Kun Xu Yue Li Jun Sun Shuyuan Du Xinpeng Di Yuguang Yang Bo Li Institute of Biomechanics and Medical engineering Applied Mechanics Laboratory Department of Engineering MechanicsTsinghua University Institute of Nuclear and New Energy Technology Tsinghua University Shanghai aerospace Control Technology Institute Shanghai Key Laboratory of aerospace Intelligent Control Technology college of Automation engineering Nanjing University of Aeronautics and Astronautics

Natural swarms arranged from cells to herds are usually decentralized but display intriguing collective intelligence in coordinating individuals across large scales to efficiently achieve their common goals. Learning from nature may provide new strategies for controlling collective dynamics of synthetic swarms to accomplish specific functions. Here, we present a bioinspired computational framework that steers distributed active swarms to collectively capture and merge targets via reinforcement learning. We exploit collective milling structures of natural herds to cage the targets, and adopt a switching control policy inspired by sperms' chiral dynamics to optimize the trajectories of individuals, through which the active swarms can selforganize to enclose single or multiple distant targets in a dynamical, adaptive and scalable manner. There exists a critical swarm size, beyond which the excessive competition between agents would generate large mechanical forces, leading to capture instability but enabling the transition from short-distance to long-distance merging capture of multiple targets. This work provides physical insights into distributed active swarms and could offer a multilevel, decentralized strategy toward controlling swarm robotics in wide applications such as bio-medical devices, machine immunity, and target clearance.

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Packing properties of binary mixtures in disordered sphere systems

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Particuology 2014年第5期12卷 155-166页

作者： Lingyi Meng Peng Lu Shuixiang Li Department of mechanics & aerospace engineering College of EngineeringPeking University

Mixtures of binary spheres are numerically simulated using a relaxation algorithm to investigate the effects of volume fraction and size ratio, A complete profile of the packing properties of binary spheres is given. The density curve with respect to the volume fraction has a triangular shape with a peak at 70% large spheres. The density of the mixture increases with the size ratio, but the growth becomes slow in the case of a large size disparity, The volume fraction and size ratio effects are reflected in the height and movement, respectively, of specific peaks in the radial distribution functions. The structure of the mixture is further analyzed in terms of contact types, and the mean coordination number is demonstrated to be primarily affected by ＂large-small＂ contacts. A novel method for estimating the average relative excluded volume for binary spheres by weighting the percentages of contact types is proposed and extended to polydisperse packings of certain size distributions. The method can be applied to explain the density trends of polydisperse mixtures in disordered sphere systems,

关键词： Disordered packing Binary spheres Volume fraction Size ratio

Analysis on high-temperature oxidation and growth stress of iron-based alloy using phase field method

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Applied Mathematics and mechanics(English Edition) 2011年第6期32卷 757-764页

作者：杨帆刘彬方岱宁 Department of engineering mechanics School of AerospaceTsinghua University Department of mechanics and aerospace engineering College of EngineeringPeking University

High-temperature oxidation is an important property to evaluate thermal protection materials. However, since oxidation is a complex process involving microstructure evolution, its quantitative analysis has always been a challenge. In this work, a phase field method （PFM） based on the thermodynamics theory is developed to simulate the oxidation behavior and oxidation induced growth stress. It involves microstructure evolution and solves the problem of quantitatively computational analysis for the oxidation behavior and growth stress. Employing this method, the diffusion process, oxidation performance, and stress evolution axe predicted for Fe-Cr-A1-Y alloys. The numerical results agree well with the experimental data. The linear relationship between the maximum growth stress and the environment oxygen concentration is found. PFM provides a powerful tool to investigate high-temperature oxidation in complex environments.

关键词： high-temperature oxidation phase field method growth stress

Amplitude control of limit cycle in a van der Pol Duffing system

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Chinese Physics B 2009年第11期18卷 4748-4753页

作者：欧阳克俭唐驾时梁翠香 college of Civil engineering Hunan University college of mechanics and aerospace Hunan University

This paper applies washout filter technology to amplitude control of limit cycles emerging from Hopf bifurcation of the van der Pol-Duffing system. The controlling parameters for the appearance of Hopf bifurcation are given by the Routh-Hurwitz criteria. Noticeably, numerical simulation indicates that the controllers control the amplitude of limit cycles not only of the weakly nonlinear van der Pol-Duffing system but also of the strongly nonlinear van der Pol-Duffing system. In particular, the emergence of Hopf bifurcation can be controlled by a suitable choice of controlling parameters. Gain-amplitude curves of controlled systems are also drawn.

关键词： bifurcation control limit cycle Hopf bifurcation van der Pol-Duffing system

Lattice Boltzmann simulation of flows in bifurcate channel at rotating inflow boundary conditions and resulted different outflow fluxes

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Acta Mechanica Sinica 2011年第4期27卷 510-518页

作者： Qing-Dong Cai Department of mechanics and aerospace engineering college of engineering Peking University 100871 Beijing

The Lattice Boltzmann method （LBM） is used to simulate the flow field in a bifurcate channel which is a simplified model of the draft tube of hydraulic turbine machine. According to the simulation results, some qualitative conclusions can be deduced. The reason of uneven flux in different branches of draft tube is given. Not only the vortex rope itself, but also the attenuation of the rotation strength is important in bringing on the uneven flux. The later leads to adverse pressure gradient, and changes the velocity profile. If the outlet contains more than one exit, the one that contains the vortex rope will lose flux because of this adverse pressure gradient. Several possible methods can be used to minimize the adverse pressure gradient domain in order to improve the efficiency of turbine machine.

关键词： Lattice Boltzmann method - Hydraulic turbinemachine Draft tube Vortex rope

EXACT ANALYSIS OF WAVE PROPAGATION IN AN INFINITE RECTANGULAR BEAM

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Applied Mathematics and mechanics(English Edition) 2004年第7期25卷 768-778页

作者：孙卫明杨光松李东旭 Institute of engineering mechanics Third Institute college of aerospace and Material engineering

The Fourier series method was extended for the exact analysis of wave propagation in an infinite rectangular ***,by solving the three-dimensional elastodynamic equations a general analytic solution was derived for wave motion within the *** then for the beam with stress-free boundaries,the propagation characteristics of elastic waves were *** accurate wave propagation model lays a solid foundation of simultaneous control of coupled waves in the beam.

关键词： infinite rectangular beam wave propagation exact analysis Fourier series traveling wave active control

Sphericities of non-spherical objects

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Particuology 2012年第1期10卷 97-104页

作者： Teng Li Shuixiang Li Jian Zhao Peng Lu Lingyi Meng Department of mechanics ＆aerospace engineering College of Engineering Peking University Beijing 100871 China

Sphericity, as one of the most important shape parameter for non-spherical objects, is extensively applied in evaluating the porosity or packing density of particles. In this paper, the sphericities of common non- spherical objects are deduced and investigated. Maximum sphericities and optimum shapes of these objects are presented as well. A decreasing order of sphericity from sphere （1.0） to regular tetrahedron （0.671） for objects with constant sphericity is given. Similar trends are found in most sphericity-aspect ratio relationships, which exhibit single Peak and the sphericity increases with the growth of aspect ratio before the peak point and decreases afterward. The peak loci of aspect ratio are all around 1.0 which makes the shape approaching to a sphere. The information in the paper could be useful as literature for general application.

关键词： SphericityAspect ratioNon-spherical particleOptimum shape

Group Invariant Solutions of the Two-Dimensional Elastodynamics Problem in the Polar Coordinate System

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Chinese Physics Letters 2012年第8期29卷 149-151页

作者： LI Hou-Guo HUANG Ke-Fu Department of mechanics and aerospace engineering College of EngineeringPeking UniversityBeijing 100871

Some group invariant solutions of the two-dimensional elastodynamics problem in linear homogeneous isotropic materials are considered using the group-theoretical *** the polar coordinate system,three group invariant solutions are constructed by the invariants of the Lie group,which are admitted by the governing equations for the two-dimensional elastodynamics *** graphical figures of the group invariant solutions are presented,and the physical meanings of the group invariant solutions are expounded in some cases.

关键词： method problem invariant

The solution of a wedge disclination dipole interacting with an annular inclusion and the force acting on the disclination dipole

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Chinese Physics B 2008年第12期17卷 4592-4598页

作者：宋豪鹏方棋洪刘又文 college of mechanics and aerospace Hunan University

The interaction between a wedge disclination dipole and an elastic annular inclusion is investigated. Utilizing the Muskhelishvili complex variable method, the explicit series form solutions of the complex potentials in the matrix and the inclusion region are derived. The image force acting on the disclination dipole centre is also calculated. The influence of the location of the disclination dipole and the thickness of the annular inclusion as well as the elastic dissimilarity of materials upon the equilibrium position of the disclination dipole is discussed in detail. The results show that a stable equilibrium point of the disclination dipole near the inclusion is found for certain combinations of material constant. Moreover, the force on the disclination dipole is strongly affected by the position of the disclination dipole and the thickness of annular inclusion. The repulsion force increases （or the attraction force reduces） with the increase of the thickness of the annular inclusion. An appropriate critical value of the thickness of the annular inclusion may be found to change the direction of the force on the disclination dipole. The present solutions include previous results as special eases.

关键词： wedge disclination dipole annular inclusion image force