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micromechanical adaptation as a treatment for spinal cord injury

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Neural Regeneration Research 2019年第11期14卷 1909-1911页

作者： Veronica estrada Hans werner Müller Molecular Neurobiology Laboratory Department of Neurology Heinrich-Heine-University Medical Center Düsseldorf

Spinal cord injury: Thus far injury of the spinal cord is incurable and, in the majority of cases, a devastating and life-changing event. The worldwide incidence rate of spinal cord injury (SCI) ranges from 250,000 to 900,000 (***, 2013;Kumar et al., 2018) new cases per year. SCI outcome includes the damage of axons, demyelination of axons, loss of signal transduction, and consequential long-lasting motor and sensory deficits. Additionally, the non-use of muscles can lead to atrophy and joint contractures, thereby further reducing the possibility of recovery. Depending on the spinal level and the severity of the injury, the extent of the damage can vary and spontaneous recovery is possible to varying degrees.

关键词： micromechanical adaptation spinal cord injury spinal cord injury(SCI)

Effect of heat treatment on the microstructure and micromechanical properties of the rapidly solidified Mg61.7Zn34Gd4.3 alloy containing icosahedral phase

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International Journal of Minerals,Metallurgy and Materials 2019年第7期26卷 869-877页

作者： Wen-bo Luo Zhi-yong Xue Wei-min Mao School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Institute for Advanced Materials North China Electric Power University Beijing 102206 China School of Energy Power and Mechanical Engineering North China Electric Power University Beijing 102206 China

In this paper, the microstructure evolution of the rapidly solidified (RS) Mg61.7Zn34Gd4.3 (at%, atomic ratio) alloy at high temperatures was investigated. The hardness and elastic modulus of the main precipitated phases were also analyzed and compared with those of the α-Mg matrix on the basis of nanoindentation tests. The results show that the RS alloy consists of either a petal-like icosahedral quasicrystal (IQC) phase (~20 μm) and block-shaped H1 phase (~15 μm) or IQC particles with an average grain size of ~107 nm as well as a small proportion of amorphous phase, which mainly depends on the holding time at the liquid temperature and the thickness of the ribbons. The IQC phase gradually transforms at 400?C to a short-rod-shaped μ-phase (Mg28.6Zn63.8Gd7.7) with a hexagonal structure. The hardness of the IQC phase is higher than that of H1 phase, and both phases exhibit a higher hardness than the α-Mg matrix and the μ-phase. The elasticity of the H1 phase is superior to that of the α-Mg matrix. The IQC phase possesses a higher elastic modulus than H1 phase. The easily formed H1 phase exhibits the poorest plastic deformation capacity among these phases but a higher elastic modulus than the α-Mg matrix.

关键词： magnesium alloy icosahedral phase rapidly solidification nanoindentation micromechanical properties

A micromechanical model based on hypersingular integro-differential equations for analyzing micro-crazed interfaces between dissimilar elastic materials

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Applied Mathematics and Mechanics(English Edition) 2020年第2期41卷 193-206页

作者： X.WANG W.T.ANG H.FAN School of Mechanical and Aerospace Engineering Nanyang Technological University50 Nanyang AvenueSingapore 639798Singapore

The current work models a weak(soft) interface between two elastic materials as containing a periodic array of micro-crazes. The boundary conditions on the interfacial micro-crazes are formulated in terms of a system of hypersingular integro-differential equations with unknown functions given by the displacement jumps across opposite faces of the micro-crazes. Once the displacement jumps are obtained by approximately solving the integro-differential equations, the effective stiffness of the micro-crazed interface can be readily computed. The effective stiffness is an important quantity needed for expressing the interfacial conditions in the spring-like macro-model of soft interfaces. Specific case studies are conducted to gain physical insights into how the effective stiffness of the interface may be influenced by the details of the interfacial micro-crazes.

关键词： micromechanical modeling micro-crazed interface effective stiffness coefficient hypersingular integro-differential equation

Optimization of micromechanical Cleavage Technique of Natural Graphite by Chemical Treatment

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Graphene 2014年第1期3卷 1-5页

作者： Luis Torres Luis Gomez Armas Antonio Carlos Seabra Centro de Ciências Naturais e Humanas Universidade Federal do ABC Sao Paulo Brazil Grupo de óptica Micro e Nanofabricao de Dispositivos (GOMNDI) Universidade Federal do Pampa Rio Grande do Sul Brazil Laboratório de Sistemas Integráveis do Departamento de Engenharia de Sistemas Eletronicos da Escola Politécnica da USP (LSI-PSI/EPUSP) Sao Paulo Brazil

In this work,we report a method to improve the efficiency of the micromechanical cleavage technique to obtain few-layers graphene samples, from natural graphite flakes, which were previously submitted to two chemical treatment times with H2SO4(17 and 25 hours). After the chemical treatment times, Raman spectroscopy reveals a hydrogenation of the few-layer graphene samples, which were obtained from the treated graphite flakes. To analyze the hydrogenation of the samples, the G and 2D bands of the Raman spectra of the treated and un-treated samples were analyzed and compared, as well as the I(2D)/I(G) ratio, revealing a p-doping on the treated samples when compared with the untreated samples. Our studies could be of great importance to obtain larger and greater amount of few-layer graphene samples.

关键词： Graphene micromechanical Cleavage Raman Spectroscopy Chemical Treatment

Wireless actuation of micromechanical resonators

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Microsystems & Nanoengineering 2016年第1期2卷 129-134页

作者： Farrukh Mateen Carsten Maedler Shyamsunder Erramilli Pritiraj Mohanty Department of Mechanical and Aerospace Engineering Boston University110 Cummington StreetBostonMA 02215USA Department of Physics Boston University590 Commonwealth AvenueBostonMA 02215USA

The wireless transfer of power is of fundamental and technical interest,with applications ranging from the remote operation of consumer electronics and implanted biomedical devices and sensors to the actuation of devices for which hard-wired power sources are neither desirable nor *** particular,biomedical devices that are implanted in the body or brain require small-footprint power receiving elements for wireless charging,which can be accomplished by micromechanical ***,for fundamental experiments,the ultralow-power wireless operation of micromechanical resonators in the microwave range can enable the performance of low-temperature studies of mechanical systems in the quantum regime,where the heat carried by the electrical wires in standard actuation techniques is detrimental to maintaining the resonator in a quantum *** we demonstrate the successful actuation of micron-sized silicon-based piezoelectric resonators with resonance frequencies ranging from 36 to 120 MHz at power levels of nanowatts and distances of~3 feet,including comprehensive polarization,distance and power dependence *** unprecedented demonstration of the wireless actuation of micromechanical resonators via electric-field coupling down to nanowatt levels may enable a multitude of applications that require the wireless control of sensors and actuators based on micromechanical resonators,which was inaccessible until now.

关键词： biomedical implant MEMS micromechanical nanomechanical wireless actuation wireless power transfer

Analysis of the structures and characteristics for an InP-based micromechanical tunable filter

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Analysis of the structures and characteristics for an InP-ba...

Modeling the Interaction between Vacancies and Grain Boundaries during Ductile Fracture

Photonics Asia 2004;Optoelectronics,Microelectronics,and Nanotech

作者： Bin Chen,Zhen Zhou*,Yongqing Huang*,Xiaomin Ren*(Beijing University of Posts & Telecommunications,P.O.Box 66,Beijing,100876,China)

In this letter,a InP-based micromechanical tuneable filter by electrostatic actuation is *** simulation of the DBR reflectance spectra and the F-P cavity transimission spectra,the filte

关键词： micromechanical Tunable filter Cantilever

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Computer Modeling in Engineering & Sciences 2024年第8期140卷 2019-2034页

作者： Mingjian Li Ping Yang Pengyang Zhao Department of Engineering Mechanics School of Naval ArchitectureOcean and Civil EngineeringShanghai Jiao Tong UniversityShanghai200240China

The experimental results in previous studies have indicated that during the ductile fracture of pure metals,vacancies aggregate and form voids at grain ***,the physical mechanism underlying this phenomenon remains not fully *** study derives the equilibrium distribution of vacancies analytically by following thermodynamics and the micromechanics of crystal *** derivation suggests that vacancies cluster in regions under hydrostatic compression to minimize the elastic strain ***,a finite element model is developed for examining more general scenarios of interaction between vacancies and grain *** model is first verified and validated through comparison with some available analytical solutions,demonstrating consistency between finite element simulation results and analytical solutions within a specified numerical accuracy.A systematic numerical study is then conducted to investigate the mechanism that might govern the micromechanical interaction between grain boundaries and the profuse vacancies typically generated during plastic *** simulation results indicate that the reduction in total elastic strain energy can indeed drive vacancies toward grain boundaries,potentially facilitating void nucleation in ductile fracture.

关键词： Ductile fracture vacancy grain boundary micromechanical finite element method

Computational modeling of fracture in concrete: A review

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Frontiers of Structural and Civil Engineering 2020年第3期14卷 586-598页

作者： Luthfi Muhammad MAULUDIN Chahmi OUCIF Institute of Structural Mechanics Bauhaus Universitat WeimarWeimar 99423Germany Teknik Sipil Politeknik Negeri BandungGegerkalong Hilir Ds.CiwarugaBandung 40012Indonesia

This paper presents a review of fracture modeling of *** complex material,such as concrete,has been widely used in construction industries and become trending issue in the last *** on comprehensive literature review,there are two main approaches considered to-date of concrete fracture modeling,such as macroscopic and micromechanical *** purpose of this review is to provide insight comparison from different techniques in modeling of fracture in concrete which are *** the first section,an overview of fracture modeling in general is *** different approaches both of macroscopic and micromechanical models will be *** heterogeneity of concrete material is major concern in micromechanical-based concrete modeling,one section will discuss this ***,the summary from all of reviewed techniques will be pointed out before the future perspective is given.

关键词： concrete fracture macroscopic micromechanical heterogeneity

Measuring fracture toughness of human dental enamel at small scale using notched microcantilever beams

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Biosurface and Biotribology 2021年第4期7卷 228-232页

作者： Kangjie Chu Cancan Zhao Fuzeng Ren Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhenChina

Dental enamel is the most mineralised hard tissue with a complex hierarchically organised anisotropic structure and it protects human teeth from mechanical damage during the dental *** to the sample size constraints,the available data for quantitative evaluation of the fracture toughness of human enamel is very ***,on the basis of microstructural characterisation,the fracture toughness of human dental enamel at small scale with respect to orientation was measured using notched microcantilever beams fabricated by focussed ion *** fracture toughness of human enamel with perpendicular orientation was measured to be 1.244±0.12 MPa·m^(1/2),80%tougher than that of in-plane parallel orientation(0.698±0.18 MPa·m^(1/2)).The present results are expected to provide deep insights into cusp fractures and the synthesis of enamel-like restorative materials.

关键词： hydroxyapatite micromechanical properties texture tooth enamel