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strain Gradient Finite Element Formulation of Flexoelectricity in Ferroelectric Material Based on Phase-Field Method

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Acta Mechanica solida sinica 2024年第4期37卷 570-579页

作者： shuai Wang Hengchang su Min yi Li-Hua shao National Key Laboratory of strength and structural Integrity Institute of Solid MechanicsSchool of Aeronautic Science and EngineeringBeihang UniversityBeijing100191People’s Republic of China state Key Laboratory of Mechanics and Control for Aerospace structures and Institute for Frontier science and Key Laboratory for Intelligent Nano Materials and Devices of Ministry of Education and College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing210016People’s Republic of China

Flexoelectricity is a two-way coupling effect between the strain gradient and electric field that exists in all dielectrics,regardless of point group ***,the high-order derivatives of displacements involved in the strain gradient pose challenges in solving electromechanical coupling problems incorporating the flexoelectric *** this study,we formulate a phase-field model for ferroelectric materials considering the flexoelectric effect.A four-node quadrilateral element with 20 degrees of freedom is constructed without introducing high-order shape *** microstructure evolution of domains is described by an independent order parameter,namely the spontaneous polarization governed by the time-dependent Ginzburg–Landau *** model is developed based on a thermodynamic framework,in which a set of microforces is introduced to construct the constitutive relation and evolution *** the flexoelectric part of electric enthalpy,the strain gradient is determined by interpolating the mechanical strain at the node via the values of Gaussian integration points in the isoparametric *** model is shown to be capable of reproducing the classic analytical solution of dielectric materials incorporating the flexoelectric *** model is verified by duplicating some typical phenomena in flexoelectricity in cylindrical tubes and truncated pyramids.A comparison is made between the polarization distribution in dielectrics and *** model can reproduce the solution to the boundary value problem of the cylindrical flexoelectric tube,and demonstrate domain twisting at domain walls in ferroelectrics considering the flexoelectric effect.

关键词： Flexoelectricity Phase-field method Ferroelectrics Domain configuration

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Epileptic brain network mechanisms and neuroimaging techniques for the brain network

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Neural Regeneration Research 2024年第12期19卷 2637-2648页

作者： yi Guo zhonghua Lin zhen Fan Xin Tian Department of Neurology Sichuan Provincial People’s HospitalUniversity of Electronic Science and Technology of ChinaChengduSichuan ProvinceChina sichuan Provincial Center for Mental Health Sichuan Provincial People’s HospitalUniversity of Electronic Science and Technology of ChinaChengduSichuan ProvinceChina Department of Geriatrics Sichuan Provincial People’s HospitalUniversity of Electronic Science and Technology of ChinaChengduSichuan ProvinceChina Department of Neurology Chongqing Key Laboratory of NeurologyThe First Affiliated Hospital of Chongqing Medical UniversityChongqingChina

Epilepsy can be defined as a dysfunction of the brain network,and each type of epilepsy involves different brain-network changes that are implicated diffe rently in the control and propagation of interictal or ictal *** more detailed information on brain network alterations can help us to further understand the mechanisms of epilepsy and pave the way for brain network-based precise therapeutic approaches in clinical *** increasing number of advanced neuroimaging techniques and electrophysiological techniques such as diffusion tensor imaging-based fiber tra ctography,diffusion kurtosis imaging-based fiber tractography,fiber ball imagingbased tra ctography,electroencephalography,functional magnetic resonance imaging,magnetoencephalography,positron emission tomography,molecular imaging,and functional ultrasound imaging have been extensively used to delineate epileptic *** this review,we summarize the relevant neuroimaging and neuroelectrophysiological techniques for assessing structural and functional brain networks in patients with epilepsy,and extensively analyze the imaging mechanisms,advantages,limitations,and clinical application ranges of each technique.A greater focus on emerging advanced technologies,new data analysis software,a combination of multiple techniques,and the construction of personalized virtual epilepsy models can provide a theoretical basis to better understand the brain network mechanisms of epilepsy and make surgical decisions.

关键词： electrophysiological techniques epilepsy functional brain network functional magnetic resonance imaging functional near-infrared spectroscopy machine leaning molecular imaging neuroimaging techniques structural brain network virtual epileptic models

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The flow behavior of droplet adsorption on a liquid-liquid interface accompanied by cross-linking reaction and phase separation in a microchannel

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Chinese Journal of Chemical Engineering 2024年第2期66卷 60-70页

作者： Haozhe yi Taotao Fu Chunying zhu Youguang Ma state Key Laboratory of Chemical Engineering School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China

The adsorption process of droplets on the liquid-liquid interface and phase separation process can regulate the spatial distribution of the fluid system,which are crucial for chemical ***,the cross-linking reaction,which is widely used in the field of polymers,can change the physical properties of the fluids and affect the flow behavior accordingly.A configuration of microchannels is designed to conveniently generate uniform droplets in one phase of the parallel *** flow behavior of the adsorption process of sodium alginate droplets on the liquid-liquid interface is investigated,and the subsequent process of phase separation is *** the process of droplet adsorption,the crosslinking reaction occurs synchronously,which makes the droplet viscosity and the elasticity modules of the droplet surface increase,thus affecting the dynamics of the adsorption process and the equilibrium shape of the *** variation of the adsorption length with time is divided into three stages,which all conform to power law *** exponents of the second and third stages deviate from the results of the Tanner's *** flow pattern maps of droplet adsorption and phase separation are drawn,and the operating ranges of complete adsorption and complete separation are *** study provides a theoretical basis for further studying the flow behavior of droplets with cross-linking reaction in a microchannel.

关键词： Microfluidics Droplet Dynamics Crosslink Adsorption separation

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Rainbow Pancyclicity in a Collection of Graphs Under the Dirac-type Condition

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Acta Mathematicae Applicatae sinica 2024年第2期40卷 269-274页

作者： Lu-yi LI Ping LI Xue-liang LI Center for Combinatorics and LPMC Nankai UniversityTianjin 300071China school of Mathematics and statistics Shaanxi Normal UniversityXi’an 710062China

Let G={Gi:i∈[n]} be a collection of not necessarily distinct n-vertex graphs with the same vertex set V,where G can be seen as an edge-colored(multi)graph and each Gi is the set of edges with color i.A graph F on V is called rainbow if any two edges of F come from different Gis’.We say that G is rainbow pancyclic if there is a rainbow cycle Cℓof lengthℓin G for each integerℓ2[3,n].In 2020,Joos and Kim proved a rainbow version of Dirac’s theorem:Ifδ(Gi)≥2/n for each i∈[n],then there is a rainbow Hamiltonian cycle in *** this paper,under the same condition,we show that G is rainbow pancyclic except that n is even and G consists of n copies of Kn/2,n/*** result supports the famous meta-conjecture posed by Bondy.

关键词： rainbow Hamiltonian cycle rainbow pancyclic meta-conjecture

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An environmentally sensitive zinc-selective two-photon NIR fluorescent turn-on probe and zinc sensing in stroke

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Journal of Pharmaceutical Analysis 2024年第4期14卷 578-584页

作者： Junfeng Wang Qibing Liu yingbo Li yi Pang Department of Chemistry The University of AkronAkronOH 44325USA Gordon Center for Medical Imaging Department of RadiologyMassachusetts General HospitalHarvard Medical SchoolBostonMA 02114USA Department of Pharmacy The First Affiliated Hospital of Hainan Medical UniversityHaikou570100China Engineering Research Center of Tropical Medicine Ministry of EducationHainan Medical UniversityHaikou571199China state Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical SciencesPeking UniversityBeijing100191China Maurice Morton Institute of Polymer science The University of AkronAkronOH 44325USA

A two-photon near infrared(NIR)fluorescence turn-on sensor with high selectivity and sensitivity for zn^(2+)detection has been *** sensor exhibits a large stokes'shift(-300 nm)and can be excited from 900 to 1000 nm,with an emission wavelength of-785 nm,making it ideal for imaging in biological *** sensor's high selectivity for zn^(2+)over other structurally similar cations,such as Cd^(2+),makes it a promising tool for monitoring zinc ion levels in biological *** the high concentration of zinc in thrombi,this sensor could provide a useful tool for in vivo thrombus imaging.

关键词： Near-infrared Molecular imaging Thrombus stroke

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Hyperspectral remote sensing identification of marine oil emulsions based on the fusion of spatial and spectral features

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Acta Oceanologica sinica 2024年第3期43卷 139-154页

作者： Xinyue Huang yi Ma zongchen Jiang Junfang Yang school of Geography and Marine science Nanjing UniversityNanjing 210023China First Institute of Oceanography Ministry of Natural ResourcesQingdao 266061China Marine Telemetry Technology Innovation Center Ministry of Natural ResourcesQingdao 266061China Harbin Institute of Technology Harbin 150001China China University of Petroleum(East China) Qingdao 266061China

Marine oil spill emulsions are difficult to recover,and the damage to the environment is not easy to *** use of remote sensing to accurately identify oil spill emulsions is highly important for the protection of marine ***,the spectrum of oil emulsions changes due to different water *** remote sensing and deep learning can use spectral and spatial information to identify different types of oil ***,hyperspectral data can also cause information redundancy,reducing classification accuracy and efficiency,and even overfitting in machine learning *** address these problems,an oil emulsion deep-learning identification model with spatial-spectral feature fusion is established,and feature bands that can distinguish between crude oil,seawater,water-in-oil emulsion(WO),and oil-in-water emulsion(OW)are filtered based on a standard deviation threshold–mutual information *** oil spill airborne hyperspectral data,we conducted identification experiments on oil emulsions in different background waters and under different spatial and temporal conditions,analyzed the transferability of the model,and explored the effects of feature band selection and spectral resolution on the identification of oil *** results show the following.(1)The standard deviation–mutual information feature selection method is able to effectively extract feature bands that can distinguish between WO,OW,oil slick,and *** number of bands was reduced from 224 to 134 after feature selection on the Airborne Visible Infrared Imaging spectrometer(AVIRIs)data and from 126 to 100 on the s185 data.(2)With feature selection,the overall accuracy and Kappa of the identification results for the training area are 91.80%and 0.86,respectively,improved by 2.62%and 0.04,and the overall accuracy and Kappa of the identification results for the migration area are 86.53%and 0.80,respectively,improved by 3.45%and 0.05.(3)The oil emulsion id

关键词： oil emulsions identification hyperspectral remote sensing feature selection convolutional neural network(CNN) spatial-temporal transferability

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Effects of multiple shapes for steady flow with transformer oil+Fe_(3)O_(4)+TiO_(2) between two stretchable rotating disks

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Applied Mathematics and Mechanics(English Edition) 2024年第2期45卷 373-388页

作者： M.RAHMAN M.TURKyiLMAzOGLU z.MUsHTAQ Department of Mathematics Mirpur University of Science and TechnologyMirpur 10250Pakistan Department of Mathematics Hacettepe UniversityBeytepeAnkara 06532Turkiye

In this study,we examine the effects of various shapes of nanoparticles in a steady flow of hybrid nanofluids between two stretchable rotating *** steady flow of hybrid nanofluids with transformer oil as the base fluid and Fe_(3)O_(4)+TiO_(2)as the hybrid nanofluid is *** shapes of Fe_(3)O_(4)+TiO_(2)hybrid nanofluids,including sphere,brick,blade,cylinder,and platelet,are *** shape exists in the same volume of a *** leading equations(partial differential equations(PDEs))are transformed to the nonlinear ordinary differential equations(ODEs)with the help of similarity *** system of equations takes the form of ODEs depending on the boundary conditions,whose solutions are computed numerically by the bvp4c MATLAB *** outputs are compared with the previous findings,and an intriguing pattern is discovered,such that the tangential velocity is increased for the rotation parameter,while it is decreased by the stretching values because of the lower *** the reaction rate parameter,the concentration boundary layer becomes shorter,and the activation energy component increases the rate at which mass transfers come to the higher disk but have the opposite effect on the bottom *** ranges of various parameters taken into account are Pr=6.2,Re=2,M=1.0,φ_(1)=φ_(2)=0.03,K=0.5,s=-0.1,Br=0.3,sc=2.0,α_(1)=0.2,γ=0.1,E_(n)=2.0,and q=1.0,and the rotation factor K is within the range of 0 to 1.

关键词： transformer oil Brinkman number skin friction coefficient double rotating disk Nusselt number sherwood number

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Total-factor energy efficiency of ten major global energy-consuming countries

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Journal of Environmental sciences 2024年第3期137卷 41-52页

作者： Xuan Wang Yonglong Lu Chunci Chen Xiaojie yi Haotian Cui state Key Laboratory of Urban and Regional Ecology Research Centre for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China state Key Laboratory of Marine Environmental science and Key Laboratory of the Ministry of Education for Coastal Wetland Ecosystems College of the Environment and EcologyXiamen UniversityFujian 361102China University of Chinese Academy of sciences Beijing 100049China

Improving energy efficiency is regarded as a key path to tackling global warming and achieving the sustainable Development Goals(sDGs).In 2020,the energy consumption of the world's ten major energy-consuming countries accounted for 66.8%of the global *** paper applied data envelopment analysis(DEA)to calculate these ten major energyconsuming countries'total-factor energy efficiency(TFEE)at national and sectoral levels from 2001-2020,and explored the infuencing factors of total-factor energy efficiency with the Tobit regression *** results showed significant difference in the ten countries'energy *** United states and Germany topped the list for total-factor energy efficiency,while China and India were at the ***,the energy efficiency of the industrial subsector has increased significantly over the past two decades,while that of the other subsectors has been relatively *** industrial structure upgrading,per capita GDP,energy consumption structure,and foreign direct investment had significant impacts on energy efficiency with national *** consumption structure and GDP per capita were determinative factors of energy efficiency.

关键词： Total-factor energy efficiency sBM-UN model Major energy-consuming country Carbon emission reduction

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Vibration Control of the Rail Grinding Vehicle with Abrasive Belt Based on structural Optimization and Lightweight Design

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Chinese Journal of Mechanical Engineering 2024年第3期37卷 311-337页

作者： Wengang Fan shuai zhang zhiwei Wu yi Liu Jiangnan Yu school of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Key Laboratory of Vehicle Advanced Manufacturing Measuring and Control TechnologyMinistry of EducationBeijing 100044China China Railway Materials Operation and Maintenance Technology Co. LtdBeijing 100036China

As a new grinding and maintenance technology,rail belt grinding shows significant advantages in many applications The dynamic characteristics of the rail belt grinding vehicle largely determines its grinding performance and service *** order to explore the vibration control method of the rail grinding vehicle with abrasive belt,the vibration response changes in structural optimization and lightweight design are respectively analyzed through transient response and random vibration simulations in this ***,the transient response simulation analysis of the rail grinding vehicle with abrasive belt is carried out under operating conditions and non-operating ***,the vibration control of the grinding vehicle is implemented by setting vibration isolation elements,optimizing the structure,and increasing ***,in order to further explore the dynamic characteristics of the rail grinding vehicle,the random vibration simulation analysis of the grinding vehicle is carried out under the condition of the horizontal irregularity of the American AAR6 ***,by replacing the Q235 steel frame material with 7075 aluminum alloy and LA43M magnesium alloy,both vibration control and lightweight design can be achieved *** results of transient dynamic response analysis show that the acceleration of most positions in the two working conditions exceeds the standard value in GB/T 17426-1998 *** optimizing the structure of the grinding vehicle in three ways,the average vibration acceleration of the whole car is reduced by about 55.1%from 15.6 m/s^(2) to 7.0 m/s^(2).The results of random vibration analysis show that the grinding vehicle with Q235 steel frame does not meet the safety conditions of 3σ.By changing frame material,the maximum vibration stress of the vehicle can be reduced from 240.7 MPa to 160.0 MPa and the weight of the grinding vehicle is reduced by about 21.7%from 1500 kg to 1175 *** modal analysis results indic

关键词： Vibration control Dynamic characteristics structural optimization Lightweight design Modal analysis

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self-propelled Leidenfrost droplets on femtosecond-laser-induced surface with periodic hydrophobicity gradient

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International Journal of Extreme Manufacturing 2024年第2期6卷 502-509页

作者： Bohong Li Lan Jiang Xiaowei Li zhipeng Wang Peng yi Laser Micro/Nano Fabrication Laboratory School of Mechanical EngineeringBeijing Institute of TechnologyBeijingPeople’s Republic of China Beijing Institute of Technology Chongqing Innovation Center ChongqingPeople’s Republic of China Yangtze Delta Region Academy of Beijing Institute of Technology JiaxingPeople’s Republic of China

The controllable transfer of droplets on the surface of objects has a wide application prospect in the fields of microfluidic devices,fog collection and so *** Leidenfrost effect can be utilized to significantly reduce motion ***,the use of 3D structures limits the widespread application of self-propulsion based on Leidenfrost droplets in microelectromechanical *** manipulate Leidenfrost droplets,it is necessary to create 2D or quasi-2D *** this study,femtosecond laser is applied to fabricate a surface with periodic hydrophobicity gradient(sPHG),enabling directional self-propulsion of Leidenfrost *** field analysis within the Leidenfrost droplets reveals that the vapor layer between the droplets and the hot surface can be modulated by the sPHG,resulting in directional propulsion of the inner *** viscous force between the gas and liquid then drives the droplet to move.

关键词： self-propelled Leidenfrost droplets periodic hydrophobicity gradient femtosecond laser fabrication

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