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Spinodal surface instability of soft elastic thin films

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Acta Mechanica Sinica 2008年第3期24卷 289-296页

作者： Shi Qing Huang Xi qiao feng Department of Engineering Mechanics Tsinghua University Beijing 100084 China

When the thicknesses of thin films reduce to microns or even nanometers, surface energy and surface interaction often play a significant role in their deformation behavior and surface morphology. The spinodal surface instability induced by the van der Waals force in a soft elastic thin film perfectly bonded to a rigid substrate is investigated theoretically using the bifurcation theory of elastic structures. The analytical solution is derived for the critical condition of spinodal surface morphology instability by accounting for the competition of the van der Waals interaction energy, elastic strain energy and surface energy. Detailed examinations on the effect of surface energy, thickness and elastic properties of the film show that the characteristic wavelength of the deformation bifurcation mode depends on the film thickness via an exponential relation, with the power index in the range from 0.749 to 1.0. The theoretical solution has a good agreement with relevant experiment results.

关键词： Thin film Surface instability Surface energy van der Waals force

Preface to the Special Issue in Celebration of Professor Shouwen Yu’s 85th Birthday

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Acta Mechanica Solida Sinica 2024年第3期37卷 361-362页

作者： Xi-qiao feng Qunyang Li Department of Engineering Mechanics Tsinghua UniversityBeijing100084China

Shouwen Yu,Emeritus Professor of Applied Mechanics at Tsinghua University,was born on May 4,1939 in Xianyou County,Fujian Province,*** pursued his undergraduate studies from 1955 to 1958 in the Department of Civil Str... 详细信息

关键词： Fujian Preface pursue

Two-dimensional model of vesicle adhesion on curved substrates

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Acta Mechanica Sinica 2006年第6期22卷 529-535页

作者： Wendong Shi Xi qiao feng Huajian Gao Department of Engineering Mechanics Tsinghua University Beijing 100084 China Division of Engineering Brown University 182 Hope Street Providence RI 02912 USA

We develop a two dimensional model of a vesicle adhered on a curved substrate via long-range molecular interactions while subjected to a detachment force. The relationship between the force and displacement of the vesicle is investigated as a function of the substrate shape. It is shown that both the force- displacement relationship and the maximum force at pull-off are significantly dependent on the substrate shape. The results suggest that probes with different tip shapes may be designed for cell manipulation. For example, we demonstrate that a vesicle can be pulled off a fiat surface using a probe with a curved tip.

关键词： Biomechanics Cell adhesion-Vesicle Adhesive contact Cell manipulation

About the special topic of mechanics and biomimetics of biomaterials and animal locomotion

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Acta Mechanica Sinica 2010年第1期26卷 3-4页

作者： Xi qiao feng Mao Sun Institute of Biomechanics and Medical Engineering Department of Engineering Mechanics Tsinghua University 100084 Institute of Fluid Mechanics Beihang University 100083 Beijing China

Scientists have increasingly been turning their attentions to searching for inspirations from the splendid living world in order to solve various challenging problems of technologically importance. Rapid advances in observation techniques and computational ability will make it a reality to understand, at different time and space scales, the functions,

关键词： locomotion challenging swimming reality searching striking running flying advances kinematics

Controllable Nanostructural Transitions in Grafted Nanoparticle-Block Copolymer Composites

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Nano Research 2010年第5期3卷 356-362页

作者： Guang-Kui Xu Xi-qiao feng Shou-Wen Yu Institute of Biomechanics and Medical Engineering Department of Engineering MechanicsTsinghua UniversityBeijing 100084China

We report a theoretical investigation of self-assembled nanostructures of polymer-grafted nanoparticles in a block copolymer and explore underlying physical mechanisms by employing the self-consistent field method. By varying the particle concentration or the chain length and density of the grafted polymer, one can not only create various ordered morphologies (e.g., lamellar or hexagonally packed patterns) but also control the positions of nanoparticles either at the copolymer interfaces or in the center of one-block domains. The nanostructural transitions we here report are mainly attributed to the competition between entropy and enthalpy.

关键词： Block copolymer nanocomposite pattern formation self-assembly self-consistent field theory

Monogamy and polygamy relations of multiqubit entanglement based on unified entropy

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Chinese Physics B 2020年第2期29卷 129-136页

作者： Zhi-Xiang Jin Cong-feng qiao School of Physics University of Chinese Academy of SciencesBeijing 100049China CAS Center for Excellence in Particle Physics Beijing 100049China

Monogamy relation is one of the essential properties of quantum entanglement,which characterizes the distribution of entanglement in a multipartite *** virtual of the unified-(q,s) entropy,we obtain some novel monogamy and polygamy inequalities in general class of entanglement *** the multiqubit system,a class of tighter monogamy relations are established in term of the a-th power of unified-(q,s) entanglement for a> *** also obtain a class of tighter polygamy relations in the β-th(0≤β≤1) power of unified-(q,s) entanglement of *** these results to specific quantum correlations,e.g.,entanglement of formation,Renyi-q entanglement of assistance,and Tsallisq entanglement of assistance,we obtain the corresponding monogamy and polygamy *** examples are presented for ***,the complementary monogamy and polygamy relations are investigated for theα-th(0≤α≤1) and β-th(β≥1) powers of unified entropy,respectively,and the corresponding monogamy and polygamy inequalities are obtained.

关键词： quantum monogamy quantum polygamy unified entropy

A dynamic cellular vertex model of growing epithelial tissues

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Acta Mechanica Sinica 2017年第2期33卷 250-259页

作者： Shao-Zhen Lin Bo Li Xi-qiao feng Institute of Biomechanics and Medical Engineering AMLDepartment of Engineering MechanicsTsinghua UniversityBeijing 100084China

Intercellular interactions play a significant role in a wide range of biological functions and processes at both the cellular and tissue scales, for example, embryogenesis, organogenesis, and cancer invasion. In this paper, a dynamic cellular vertex model is presented to study the morphomechanics of a growing epithelial monolayer. The regulating role of stresses in soft tissue growth is revealed. It is found that the cells originating from the same parent cell in the monolayer can orchestrate into clustering patterns as the tissue grows. Collective cell migration exhibits a feature of spatial correlation across multiple cells. Dynamic intercellular interactions can engender a variety of distinct tissue behaviors in a social context. Uniform cell proliferation may render high and heterogeneous residual compressive stresses, while stress-regulated proliferation can effectively release the stresses, reducing the stress heterogeneity in the tissue. The results highlight the critical role of mechanical factors in the growth and morphogenesis of epithelial tissues and help understand the development and invasion of epithelial tumors.

关键词： Soft tissue Cellular vertex model Cell Morphogenesis

Tuning frictional properties of molecularly thin erucamide films through controlled self-assembling

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Acta Mechanica Sinica 2021年第7期37卷 1041-1049,I0001页

作者： Youyu Di Shuai Zhang Xi-qiao feng Qunyang Li Applied Mechanics Laboratory Department of Engineering MechanicsTsinghua UniversityBeijing 100084China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

Self-assembled films(SAFs)have been proposed to be a promising candidate for molecularly thin ***,the frictional performance of SAFs is sensitively dependent on their molecular structures that are susceptible to external *** erucamide,a fatty amide widely used as a macroscale slip additive,as an example,we demonstrate that SAFs can be readily formed on various substrates,including silicon oxide,sapphire,copper,and *** high-resolution topography and friction measurements,two types of erucamide SAFs are *** first type is atomically flat and exhibits clear atomic stick–slip friction behavior and ultra-low frictional dissipation;while the second type has a stripe-like nanoscale pattern and shows much higher(8 times higher)frictional *** sharp contrast between these two types of SAFs is attributed to their distinct molecular structures originating from different interactions between erucamide molecules and *** further demonstrate that,by proper surface functionalization,we can actively and reliably control the molecular structures of SAFs through guided self-assembling,achieving rational friction tuning with patterning capability.

关键词： Friction Lubrication Erucamide Two-dimensional organic film Self-assembly

On the Historical Multi-modal Narration of the Literary Media of the Romance of the Three Kingdoms

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学术界 2014年第11期 256-260页

作者： feng qiao’e School of Language and Literature Zhejiang University of Science and Technology

The research upon mode and media has already expanded to the fields of social semiotics,education,medical science,linguistics and communication arts and sciences and so on. Based on the mode of"being divided into three kingdoms"of the historical narration,the narrative media of the tripartite confrontation of the political groups and the analysis perspective of character symbols of the R omance of the T hree Kingdoms,this paper attempts to make clear and comment on the media,symbol,mode and classification of the multi-mode theoretical frame of the C hinese historical novels and further explores the internal operating mechanism and analysis method of the multi-media events through multi-modal analysis.

关键词： historical literature mode multi-media event character symbol