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Continuum description for the characteristic resistance sensed by a cylinder colliding against granular medium

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science China(Ph.s.cs,Mechanics & Astronomy) 2013年第8期56卷 1428-1436页

作者： PANG Yong liu Caishan state Key Laboratory for Turbulence and Complex systems College of EngineeringPeking University

In th.s.paper, we experimentally and theoretically study the resistance force that develops when a cylinder with a flat face colliding against dry quartzite sand. Observations from experimental data clearly show that the acceleration curves are characterized by a double-peak structure. The first agitated peak can be attributed to a shock process where sand responds elastically, and the valley bottom in the double-peak structure is related to a limited plastic load when a fully plastic region is formed in the sand, while the second agitated peak corresponds to a the occurrence of the maximum of viscous force in a homogeneous developed bulk flow. We use slip line theory (sL) developed in plastic mechanics to capture the value at the valley bottom, adopt the double shearing theory (Ds), together with a Local Rheological Constitutive Law (LRCL) suggested in th.s.paper, to capture the drag force generated in a homogeneous bulk flow. Good agreements in the comparisons between numerical and experimental results support the characteristic resistance by the cylinder to predict granular states.

关键词： granular material penetrating dynamics rheological property

An Inverse Problem of Identifying the Radiative Coefficient in a Degenerate Parabolic Equation

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Chinese Annals of Mathematics,series B 2014年第3期35卷 355-382页

作者： Zuicha DENG liu YANG Department of Mathematics Lanzhou Jiaotong University school of Mathematics and statistics Lanzhou University

The authors investigate an inverse problem of determining the radiative coefficient in a degenerate parabolic equation from the final overspecified data. Being different from other inverse coefficient problems in which the principle coefficients are assumed to be strictly positive definite, the mathematical model discussed in th.s.paper belongs to the second order parabolic equations with non-negative characteristic form, namely, there exists a degeneracy on the lateral boundaries of the domain. Based on the optimal control framework, the problem is transformed into an optimization problem and the existence of the minimizer is established. After the necessary conditions which must be satisfied by the minimizer are deduced, the uniqueness and stability of the minimizer are proved. By minor modification of the cost functional and some a priori regularity conditions imposed on the forward operator, the convergence of the minimizer for the noisy input data is obtained in th.s.paper. The results can be extended to more general degenerate parabolic equations.

关键词： Inverse problem Degenerate parabolic equation Optimal control Exis-tence Uniqueness stability Convergence

Recent Advances in soft Biological Tissue Manipulating Technologies

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Chinese Journal of Mechanical Engineering 2022年第3期35卷 3-36页

作者： Zhihua liu Zhirong Liao Dong Wang Chengyong Wang Chengli song haonan Li Yao liu Guangdong University of Technology GuangzhouChina Guangdong Provincial Key Laboratory of Minimally Invasive surgical Instruments and Manufacturing Technology Guangdong University of TechnologyGuangzhouChina Faculty of Engineering University of NottinghamNottinghamUK Faculty of Engineering University of ExeterExeterUK school of Medical Instrument and Food Engineering University of Shanghai for Science and TechnologyShanghaiChina shanxi Key Laboratory of Advanced Manufacturing Technology North University of ChinaTaiyuanChina

Biological soft tissues manipulation,including conventional(mechanical)and nonconventional(laser,waterjet and ultrasonic)processes,is critically required in most surgical ***,the soft tissues,with their nature of anisotropic and viscoelastic mechanical properties,and high biological and heat sensitivities,are difficult to ***,the mechanical and thermal induced damage on the surface and surrounding tissue during the surgery can impair the proliferative ph.s. of ***,understanding the manipulation mechanism and the resulted surface damage is of importance to the *** recent years,more and more scholars carried out research.s.on soft biological tissue cutting in order to improve the cutting performance of surgical instruments and reduce the surgery induced tissue ***,there is a lack of compressive review that focused on the recent advances in soft biological tissue manipulating ***,th.s.review paper attempts to provide an informative literature survey of the state-of-the-art of soft tissue manipulation processes in *** is achieved by exploring and recollecting the different soft tissue manipulation techniques currently used,including mechanical,laser,waterjet and ultrasonic cutting and advanced anastomosis and reconstruction processes,with highlighting their governing removal mechanisms as well as the surface and subsurface damages.

关键词： soft biological tissue surgical processing Tissue cutting Tissue welding

Rational design of Fes_(2)microspheres as high-performance catalyst for electrooxidation of hydrazine

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Journal of Materials science & Technology 2022年第15期110卷 161-166页

作者： Jie sun Chuangwei liu Wenhan Kong Jie liu Liangyu Ma song Li Yuanhong Xu Institute of Biomedical Engineering College of Life SciencesCollege of Materials Science and EngineeringQingdao UniversityQingdao 266071China Department of Energy Conversion and storage Technical University of Denmark2800 Kgs.LyngbyDenmark Key Lab for Anisotropy and Texture of Materials School of Materials Science and Engineering Northeastern UniversityShenyang 110819China

Inspired by the relatively recognized performance of transition metal sulfides in the oxidation of hydrazine,the catalytic properties of Fes_(2) and Fe_(3)s_(4) are compared via the density functional theory *** to the different coordination numbers of iron-sulfur,the free energies of the dehydrogenation steps on Fes_(2) are far less than th.s. on Fe_(3)s_(4),which led to the much better catalytic performance of Fes_(2).Accordingly,Fes_(2) microspheres are rationally proposed as a more efficient electrocatalyst for hydrazine oxidation,which is then prepared by a facile one-step hydrothermal *** Fes_(2)microspheres show great activity for hydrazine oxidation with an onset oxidation potential of 0.22 V *** hydrogen electrode,and a peak current density of 16 m A cm^(-2).Meanwhile,stability and high faradaic efficiency(3.5e-/N_(2)h_(4))is obtained for hydrazine oxidation to N_(2).

关键词： Rational design hydrazine electrooxidation Fes_(2)microspheres Electrochemistry

On the Countable Tightness of Product spaces

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Acta Mathematica sinica,English.s.ries 2005年第4期21卷 929-936页

作者： Chuan liu shou LIN Department of Mathematics Ohio University Zanesville Campus Zanesville OH43701 USA Department of Mathematics Ningde Teachers' College Ningde 352100 P. R. China

In th.s.paper, we discuss the countable tightness of products of spaces which are quotient simages of locally separable metric spaces, or k-spaces with a star-countable k-network. The main result is that the following conditions are equivalent：（1） b = ω1; （2） t（sω×sω1）〉 ω; （3） For any pair （X, Y）, which are k-spaces with a point-countable k-network consisting of cosmic subspaces, t（X×Y）≤ω if and only if one of X, Y is first countable or both X, Y are locally cosmic spaces. Many results on the k-space property of products of spaces with certain k-networks could be deduced from the above theorem.

关键词： Countable tightness k-spaces Cosmic spaces Product spaces k-networks Point-countablecollections star-countable collections

A new method for deriving analytical solutions of partial differential equations-Algebraically explicit analytical solutions of two-buoyancy natural convection in porous media

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science China(Ph.s.cs,Mechanics & Astronomy) 2008年第11期51卷 1733-1744页

作者： CAI RuiXian liu QiBin Institute of Engineering Thermoph.s.cs Chinese Academy of SciencesBeijing 100190China

Analytical solutions of governing equations of various phenomena have their irre-placeable theoretical meanings. In addition, they can also be the benchmark solu-tions to verify the outcomes and codes of numerical solutions, and even to develop various numerical methods such as their differencing schemes and grid generation skills as well. A hybrid method of separating variables for simultaneous partial differential equation sets is presented. It is proposed that different methods of separating variables for different independent variables in the simultaneous equa-tion set may be used to improve the solution derivation procedure, for example, using the ordinary separating method for some variables and using extraordinary methods of separating variables, such as the separating variables with addition promoted by the first author, for some other variables. In order to prove the ability of the above-mentioned hybrid method, a lot of analytical exact solutions of two-buoyancy convection in porous media are successfully derived with.s.ch a method. The ph.s.cal features of th.s. solutions are given.

关键词： analytical solution hybrid method of separating variables two-buoyancy natural convection porous me-dium

Density-functional-theory formulation of classical and quantum hooke's law

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science China(Technological sciences) 2014年第4期57卷 692-698页

作者： hU hao liu Feng Department of Materials science and Engineering University of Utah

A fundamental property of solid materials is their stress state. stress state of a solid or thin film material h.s.profound effects on its thermodynamic stability and ph.s.cal and chemical properties. The classical mechanical stress （σ^M） originates from lat- tice strain （e）, following hooke＇s law： σ^M=Cε, where C is elastic constant matrix. Recently, a new concept of quantum electronic stress （o-QE） is introduced to elucidate the extrinsic electronic effects on the stress state of solids and thin films, which follows a quantum analog of classical hooke＇s law： ~QE=E（An）, where E is the deformation potential of electronic states and An is the variation of electron density. here, we present mathematical derivation of both the classical and quantum hooke＇s law from density functional theory. We further discuss the ph.s.cal origin of quantum electronic stress, arising purely from electronic excitation and perturbation in the absence of lattice strain （g=0）, and its relation to the degeneracy pressure of electrons in solid and their interaction with the lattice.

关键词： stress in the solid quantum electronic stress quantum hooke's law density functional theory

The growth of B cell receptor microcluster is a universal response of B cells encountering antigens with different motion features

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Protein & Cell 2012年第7期3卷 545-558页

作者： Zhengpeng Wan Wanli liu school of Life sciences Tsinghua UniversityBeijing 100084China

B lymphocyte cell senses and acquires foreign anti-gens through clonal distributed B cell receptors(BCRs)expressed on the surface of plasma *** presentation formats of antigens are quite *** on their Brownian diffusion mobility,there are three forms:free mobile soluble antigens,lateral mobile membrane bound antigens,and fixed immobile ***,using high resolution high.s.eed live cell imaging approach.s.we provide evidence that BCR microclusters are formed on the surface of B cells shortly after B cell’s encountering of antigens with each format of motion *** high.s.eed live cell imaging,we determine that th.s. BCR microclusters show dynamic growth feature and by doing so function as the basic platforms for B cells to acquire the *** propose that the formation and dynamic growth of BCR microcluster is a universal mechanism for B cell to response to antigens with diverse motion features.

关键词： BCR microcluster TIRFM live cell imaging fixed immobile antigen lateral mobile antigen free mobile antigen

Recent Progress of Magnetically Actuated DNA Micro/Nanorobots

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Cyborg and Bionic systems 2022年第1期2022卷 43-54页

作者： Fengyu liu Xiaoming liu Qiang huang Tatsuo Arai Key Labraoryof Bmetic Robts and sym Minsry of EduationState KeyLaboratoryofInteligent Controlandcisnof Complex SystemBejing Advanced Innovation Center for Intlligent Robots and Systems and School of Mechatron ical Engineering Bejing Institute of TechnologyBeijing 100081China Center for Neuroscience and Biomedical Enginring The University of Eletro-CommunicationsTokyo 182-8585 Japan

In the past few decades,the field of DNA origami based micro/nanotechnology h.s.developed dramatically and spawned attention increasingly,as its high integrality,rigid structure,and excellent resistance ability to enzyme *** two-dimensional and three-dimensional DNA nanostructures coordinated with optical,chemical,or magnetic triggers have been designed and assembled,extensively used as versatile templates for molecular robots,nanosensors,and intracellular drug *** magnetic field h.s.been widely regarded as an ideal driving and operating system for micro/nanomaterials,as it does not require high intensity lasers like light control,nor does it need to change the chemical composition similar to chemical ***,we review the recent achievements in the induction and actuation of DNA origami-based nanodevices that respond to magnetic *** magnetic actuation-based DNA nanodevices were regularly combined with magnetic beads or gold nanopartides and applied to generate single stranded scaffolds,assemble various DNA nanostructures,and purify specific DNA ***,they also produced artificial magnetism or moved regularly driven by *** fields to explain deeper scientific issues.

关键词： resistance magnetic versatile