检索结果-南通市图书馆

Revealing and predicting the long-term biomechanical response of orthokeratology by developing a patient-specific computational model

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

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.

关键词： orthokeratology computational biomechanical model long-term viscoelasticity myopia correction

Mechanical Properties and Deformation Mechanisms of Metallic Glasses Under Hydrostatic Pressure

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2023年第3期36卷 390-404页

作者： Haiming Lu Yao Tang Fanheng Jiang Panpan Wan Haofei Zhou center for x-mechanics Department of Engineering MechanicsZhejiang UniversityHangzhou 310027China

Metallic glasses(MGs)are promising structural materials with high strength,large elastic strain limit and enhanced wear *** the way to tune the mechanical performance of MGs,numerous efforts have been devoted to investigating the effect of hydrostatic pressure(σh)on the mechanical properties and deformation mechanisms of *** application of sufficiently large magnitudes ofσh to MGs has been considered a feasible way to improve strength and delocalize plastic deformation in *** this paper,we review recent studies on pressure-dependent thermodynamic properties,mechanical strength and hardness,as well as elevated ductility of MGs due to the pressure-induced change of deformation and failure *** of intriguing mechanical behaviors of MGs,and the corresponding theoretical modeling and atomistic understanding of plastic deformation in MGs under pure hydrostatic pressure and more general stress states are *** findings not only deepen the understanding of pressure-dependent mechanical behaviors of MGs,but also point out the potential of tuning mechanical behaviors of MGs through stress engineering.

关键词： Metallic glass Hydrostatic pressure Mechanical property Deformation mechanism Microstructure

A chemo-mechanical model for fully-coupled lithiation reaction and stress generation in viscoplastic lithiated silicon

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2019年第8期62卷 1365-1374页

作者： BUREBI Yi Ming JIA Zheng QU Shaoxing Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Center for X-MechanicsDepartment of Engineering MechanicsZhejiang University

Development of stresses in silicon(Si) anodes of lithium-ion batteries is strongly affected by its mechanical properties. Recent experiments reveal that the mechanical behavior of lithiated silicon is viscoplastic, thereby indicating that lithiation-induced mechanical stresses are dependent on the lithiation reaction rate. Experimental evidence also accumulates that the rate of lithiation reaction is conversely affected by the magnitude of mechanical stresses. These experimental observations demonstrate that lithiation reaction and stress generation in silicon anodes are fully coupled. In this work, we formulate a chemo-mechanical model considering the two-way coupling between lithiation reaction and viscoplastic deformation in silicon nanoparticle *** on the model, the position of the lithiation interface, the interface velocity, and the lithiation-induced stresses can be solved simultaneously via numerical methods. The predicted interface velocity is in line with experimental measurements reported in the literature. We demonstrate that the lithiation-induced stress field depends on the lithiation reaction through two parameters:the migration velocity and the position of the lithiation interface. We identify a stress-mitigation mechanism in viscoplastic silicon anodes: the stress-regulated lithiation reaction at the interface serves as a "brake" to reduce the interface velocity and mitigate the lithiation-induced stresses, protecting the Si nanoparticle anode from being subjected to excessive mechanical stresses.

关键词： lithium-ion battery lithiation-induced stress stress-regulated lithiation viscoplasticity

A compact design of four-degree-of-freedom transmission electron microscope holder for quasi-four-dimensional characterization

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2020年第7期63卷 1272-1279页

作者： ZHANG YiZhi BU YeQiang FANG xiaoYang WANG HongTao center for x-mechanics Zhejiang UniversityHangzhou 310027China Institute of Applied mechanics Zhejiang UniversityHangzhou 310027China

Electron tomography(ET) has been demonstrated to be a powerful tool in addressing challenging problems, such as understanding 3 D interactions among various microstructures. Advancing ET to broader applications requires novel instrumentation design to break the bottlenecks both in theory and in practice. In this work, we built a compact four-degree-of-freedom(threedirectional positionings plus self-rotation) nano-manipulator dedicated to ET applications, which is called x-Nano transmission electron microscope(TEM) holder. All the movements of the four degrees of freedom are precisely driven by built-in piezoelectric actuators, minimizing the artefacts due to vibration and drifting of the TEM stage. Full 360° rotation is realized with an accuracy of 0.05° in the whole range, which solves the missing wedge problem. Meanwhile, the specimen can move to the rotation axis with an integrated 3D nano-manipulator, greatly reducing the effort in tracking sample locations during ***, in-situ stimulation function can be seamlessly integrated into the x-Nano TEM holder so that dynamic information can be uncovered. We expect that more delicate researches, such as those about 3D microstructural evolution, can be carried out extensively by means of this holder in the near future.

关键词： electron tomography in-situ transmission electron microscopy nano manipulation

x-mechanics——An endless frontier

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,mechanics & Astronomy) 2019年第1期62卷 1-8页

作者： Wei Yang HongTao Wang TieFeng Li Shaoxing Qu center for x-mechanics Zhejiang University Institute of Applied mechanics Zhejiang University Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University

In contrast to the conventional wisdom that mechanics is a relatively mature subject, the new manifestation of mechanics in an extended or crossed form is unfolding. mechanics is now powering all subjects, from physical sciences, life sciences to social sciences. We name this new phase for the development of mechanics x-mechanics. The present article outlines the contents of x-mechanics from four aspects: cross media, cross scales, cross compliances, and cross cyber/physical spaces. x-mechanics constitutes an endless frontier of science and technology.

关键词： x-mechanics soft matters multi-scales multi-physics adaptive

Lithiation-enhanced charge transfer and sliding strength at the silicon-graphene interface:A first-principles study

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Solida Sinica 2017年第3期30卷 254-262页

作者： Cheng Chang xiaoyan Li Zhiping xu Huajian Gao Applied mechanics Laboratory Department of Engineering Mechanics Center for Nano and Micro MechanicsCenter for Advanced Mechanics and Materials Tsinghua University School of Engineering Brown University

The application of silicon as ultrahigh capacity electrodes in lithiumion batteries has been limited by a number of mechanical degradation mechanisms including fracture, delamination and plastic ratcheting, as a result of its large volumetric change during lithiation and delithiation. Graphene coating is one feasible technique to mitigate the mechanical degradation of Si anode and improve its conductivity. In this paper, first-principles calculations are performed to study the atomic structure, charge transfer and sliding strength of the interface between lithiated silicon and graphene. Our results show that Li atoms segre- gate at the （lithiated） Si-graphene interface preferentially, donating electrons to graphene and enhancing the interfacial sliding resistance. Moreover, the interfacial cohesion and sliding strength can be further enhanced by introducing single-vacancy defects into graphene. These findings provide insights that can guide the design of stable and efficient anodes of silicon/graphene hybrids for energy storage applications.

关键词： Lithium-ion batteries Silicon anode Graphene coating Interracial sliding strength First-principles calculations

Molecular Mechanism of the Early Stage of Amyloidogenic Hexapeptides(NFGAIL) Aggregation

在线全文

学校读者我要写书评

暂无评论

Communications in Theoretical Physics 2013年第10期60卷 515-520页

作者：施碧云周波蔡卓伟修鹏杨再兴 Bio-x Lab Department of Physics Zhejiang University Department of Engineering mechanics and Soft Matter Research Center Zhejiang University

Peptides/proteins aggregation can give rise to pathological conditions of many human *** partially ordered oligomers formed in the early stage of aggregation,rather than mature fibrils,are thought to be the main toxicity agent for the living ***,understanding the pathway and the underlying physical mechanism in the early stage of aggregation is very important for prevention and treatment of these protein functional *** we use all-atom molecular dynamics simulations to study the aggregation of four NFGAIL hexapeptides(NFGAIL peptide is a core segment of human islet amyloid polypeptide and exhibits similar aggregation kinetics as the full-length polypeptide).We observe that the peptide monomers in water mainly adopt non-structural coil configurations;the four peptides which are randomly placed in water aggregate spontaneously to partially ordered oligomer(β-sheets)through dimerization or trimerization,with the dimerization *** parallel and anti-parallelβ-sheets are *** hydrophobic interactions drive the initial peptides associations,and the subsequent conformational fluctuations promote the formation of more hydrogen bonds between the dangling hydrogen sites in the main chains of peptides.

关键词： peptides aggregation dimerization and trimerization hydrophobic interactions molecular dy-namics simulations

Research progress on advanced rail materials for electromagnetic railgun technology

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2021年第2期17卷 429-439页

作者： Hong-bin xie Hui-ya Yang Jian Yu Ming-yu Gao Jian-dong Shou You-tong Fang Jia-bin Liu Hong-tao Wang School of Materials Science and Engineering Zhejiang UniversityHangzhou310027China center for x-mechanics Faculty of EngineeringZhejiang UniversityHangzhou310027China

Electromagnetic railgun attracts more and more attention due to its advantage in speed,cost,and *** is found that the rail should withstand huge mechanical and thermal shocks during the launching *** forms of rail failure are accompanied by gouge,grooving,transition,and arc ablation,*** service life of the rail has become a bottleneck restricting the development of electromagnetic railgun technology.A series of researches are carried out to solve rail failure,including analysing the failure mechanism and using various advanced rail *** paper provides a comprehensive review of rail materials,including material composition,preparation,microstructure,and *** begin from a short background of the requirement of the rail *** a detailed investigation of rail materials is described,and the performances of those materials are ***,further development prospect of rail material is discussed.

关键词： Strength Conductivity Electromagnetic railgun Copper alloys Rai

Design and analysis of an untethered micro flapping robot which can glide on the water

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2022年第8期65卷 1749-1759页

作者： CHEN YanHong LIU YiDe LIU TaiShan LI Hua QU Shaoxing YANG Wei State Key Laboratory of Fluid Power&Mechatronic System Key Laboratory of Soft Machines and Smart Devices of Zhejiang ProvincesCenter for X-MechanicsDepartment of Engineering MechanicsZhejiang UniversityHangzhou 310027China

Flapping-wing flying insects possess various advantages,such as high agility and *** design and manufacture of insect-scale flapping-wing micro aerial vehicle(FWMAV)have attracted increasing attention in recent *** to the limitations of size and weight,the FWMAV with an onboard battery which can fully mimic insect flight has not been *** this work,we design and fabricate a highly integrated flapping-wing microrobot named *** Robomoth consists of a carbon chassis,customized power and control devices,and two piezoelectric ceramic actuators symmetrically distributed in the thorax and controlled *** weighs 2.487 g,spans 5.9 cm in length,possesses 9 cm of wingspan,and carries a 0.355 g rechargeable lithium *** demonstrate the mobility of the Robomoth through untethered gliding and making turns on the water surface.A simplified dynamic model of the flapping system is proposed to explain the relationship between the driving frequency and the flapping *** Robomoth is one new untethered bioinspired flapping-wing robot that can perform stable water surface motion,which holds potential applications such as search and rescue on the *** robot can also provide insight for designing insect-scale flying vehicles.

关键词： micro/nanorobots biologically inspired robots flapping-wing flying piezoelectric ceramic actuator