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CHARACTERISTIC EQUATIONS AND CLOSED-FORM SOLUTIONS FOR FREE VIBRATIONS OF RECTANGULAR MINDLIN PLATES

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Acta Mechanica Solida Sinica 2009年第2期22卷 125-136页

作者： yufeng Xing Bo Liu The Solid Mechanics Research Center Beijing University of Aeronautics and Astronautic Beijing 100083 China

The direct separation of variables is used to obtain the closed-form solutions for the free vibrations of rectangular Mindlin plates. Three different characteristic equations are derived by using three different methods. It is found that the deflection can be expressed by means of the four characteristic roots and the two rotations should be expressed by all the six characteristic roots,which is the particularity of Mindlin plate theory. And the closed-form solutions,which satisfy two of the three governing equations and all boundary conditions and are accurate for rectangular plates with moderate thickness,are derived for any combinations of simply supported and clamped edges. The free edges can also be dealt with if the other pair of opposite edges is simply supported. The present results agree well with results published previously by other methods for different aspect ratios and relative thickness.

关键词： Mindlin plate free vibration closed-form solution separation of variables

Electro-lubrication in Janus transition metal dichalcogenide bilayers

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Friction 2022年第11期10卷 1851-1858页

作者： Hao LI yufeng GUO Wanlin GUO State Key Laboratory of Mechanics and Control of Mechanical Structures MOE Key Laboratory for Intelligent Nano Materials and DevicesCollege of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China

Lubrication induced by a vertical electric field or bias voltage is typically not applicable to twodimensional(2D)van der Waals(vdW)*** performing extensive first-principles calculations,we reveal that the interlayer friction and shear resistance of Janus transition metal dichalcogenide(TMD)MoXY(X/Y=S,Se,or Te,and X≠Y)bilayers under a constant normal force mode can be reduced by applying vertical electric *** maximum interlayer sliding energy barriers between AA and AB stacking of bilayers MoSTe,MoSeTe,and MoSSe decrease as the positive electric field increases because of the more significant counteracting effect from the electric field energy and the more significant enhancement in interlayer charge transfer in AA ***,the presence of negative electric fields decreases the interlayer friction of bilayer MoSTe,because the electronegativity difference between Te and S atoms reduces the interfacial atom charge differences between AA and AB *** results reveal an electro-lubrication mechanism for the heterogeneous interfaces of 2D Janus TMDs.

关键词： Janus transition metal dichalcogenide(TMD) electro-lubrication electric field tuning first-principles calculations

General Mean-Field BDSDEs with Continuous and Stochastic Linear Growth Coefficients

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Journal of Systems Science & Complexity 2024年第5期37卷 1887-1906页

作者： WANG Jinghan SHI yufeng ZHAO Nana Institute for Financial Studies Shandong UniversityJinan 250100China Zhiyuan School of Liberal Arts Beijing Institute of Petrochemical TechnologyBeijing 102617China

In this paper,the authors study a class of general mean-field BDSDEs whose coefficients satisfy some stochastic ***,the authors prove the existence and uniqueness theorem of solution under stochastic Lipschitz condition and obtain the related comparison ***,the authors further relax the conditions and deduce the existence theorem of solutions under stochastic linear growth and continuous conditions,and the authors also prove the associated comparison ***,an asset pricing problem is discussed,which demonstrates the application of the general meanfield BDSDEs in finance.

关键词： Backward doubly stochastic differential equations comparison theorem mean-field stochastic conditions Wasserstein metric

Resources development and tourism environmental carrying capacity of ecotourism industry in Pingdingshan City, China

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Ecological Processes 2019年第1期8卷 87-92页

作者： yufeng Zhao Lei Jiao Henan University of Urban Construction Longxiang AvenuePingdingshan City 467000Henan ProvinceChina

Background:Pingdingshan City has unique and rich ecotourism *** realize the sustainable development of ecotourism industry in Pingdingshan and simultaneously achieve economic development and environmental protection in the development of ecotourism resources,literature analysis and field investigation methods were used to deeply explore the advantages and problems of Pingdingshan in the process of resources development in this ***,the indicator system of environmental carrying capacity of Pingdingshan was established and environmental carrying capacity was calculated to understand the local tourism environmental carrying ***:The development of ecotourism resources in Pingdingshan has advantages of natural conditions,convenient transportation,and sound infrastructure,but there were also problems,such as insufficient resources protection and unscientific management *** calculation,it was found that the environmental carrying capacity of ecotourism in Pingdingshan was ***:This study reveals the development of the tourism industry in Pingdingshan and provides a basis for the future development of Pingdingshan tourism resources,which is beneficial to the sustainable development of the local ecotourism industry.

关键词： Ecotourism resources Environmental carrying capacity Sustainable development Resource-based city

Linear quadratic stochastic integral games and related topics

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Science China Mathematics 2015年第11期58卷 2405-2420页

作者： WANG TianXiao SHI yufeng School of Mathematics Sichuan University School of Statistics Shandong University of Finance and Economics Institute for Financial Studies and School of Mathematics Shandong University

This paper studies linear quadratic games problem for stochastic Volterra integral equations(SVIEs in short) where necessary and sufficient conditions for the existence of saddle points are derived in two different *** a consequence,the open problems raised by Chen and Yong(2007) are *** characterize the saddle points more clearly,coupled forward-backward stochastic Volterra integral equations and stochastic Fredholm-Volterra integral equations are *** with deterministic game problems,some new terms arising from the procedure of deriving the later equations reflect well the essential nature of stochastic ***,our representations and arguments are even new in the classical SDEs case.

关键词： stochastic integral games backward stochastic Volterra integral equations stochastic Fredholm-Volterra integral equations saddle points linear quadratic optimal control problems

A Note on Restricted Representations of the Witt Superalgebras

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Chinese Annals of Mathematics,Series B 2013年第6期34卷 921-926页

作者： yufeng YAO Bin SHU Department of Mathematics Shanghai Maritime University Department of Mathematics East China Normal University

Let F be an algebraically closed field of prime characteristic p>3,and W(n)the Witt superalgebra over F,which is the Lie superalgebra of superderivations of the Grassmann algebra in n *** dimensions of simple atypical modules in the restricted supermodule category for W(n)are precisely calculated in this paper,and thereby the dimensions of all simple modules can be precisely ***,the restricted supermodule category for W(n)is proved to have one block.

关键词： Restricted Lie superalgebra Witt superalgebra Restricted representation Atypical weight

Ultralow friction of ion-containing water nanodroplets

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Nano Research 2023年第1期16卷 1792-1797页

作者： Jie Tan yufeng Guo Wanlin Guo State Key Laboratory of Mechanics and Control of Mechanical Structures MOE Key Laboratory for Intelligent Nano Materials and DevicesCollege of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China

We reveal the ultralow friction or superlubricity of water nanodroplets containing cations and anions on graphene substrates at high ion concentration by molecular dynamics *** the ion concentration is higher than 7 wt.%and the nanodroplet diameter is larger than 10 nm,the friction coefficients of water nanodroplets are lower than 10−2,and can decrease to the order of 10−3 with increasing the ion concentration *** a certain ion concentration,the optimal nanodroplet diameter of 17–20 nm exists at which the friction coefficient is the *** ultralow friction behaviors of water nanodroplets containing cations and anions are mainly attributed to the opposite variation trends between the interfacial adhesion energy and surface energy of water nanodroplet with ion concentration,and the interfacial hydrophobicity sustained by high ion *** results unveil the essential role of ions in achieving the superlubricity of water nanodroplets.

关键词： water nanodroplet ion ultralow friction molecular dynamics

EXACT SOLUTIONS FOR FREE IN-PLANE VIBRATIONS OF RECTANGULAR PLATES

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Acta Mechanica Solida Sinica 2011年第6期24卷 556-567页

作者： Bo Liu yufeng Xing The Solid Mechanics Research Center Beijing University of Aeronautics and Astronautics Beijing 100191 China

All possible exact solutions are successfully obtained in terms of 10 sets of distinct eigensolutions for the free in-plane vibration of isotropic rectangular plates. The plates have simply supported condition at two opposite edges and any combination of classical boundary conditions at the other two edges. The exact solutions are validated through both mathematical proof and comparisons with the solutions of differential quadrature method. Some unusual phenomena are revealed in free in-plane vibrations of rectangular plates due to one of the eigenvalues being zero. This work constitutes an improved version of very recent corresponding work by the same authors lint. J. Mech. Sci., 2009, 51： 246-255]. Both the solution forms and solving procedures in the previous work are substantially simplified. Some new results are also given, which are useful for validation purpose in future.

关键词： rectangular plate in-pane free vibration frequency mode shape exact solution

Giant magnetoresistance:history,development and beyond

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Science China(Physics,Mechanics & Astronomy) 2013年第1期56卷 2-14页

作者： TIAN yufeng YAN ShiShen School of Physics Shandong University

With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical *** addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.

关键词： giant magnetoresistance spintronics ferromagnetic semiconductors spin dependent scattering tunnelling magnetore-sistance