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Journal of Materials Science & Technology 1995年第2期11卷 141-152页

作者： Mingshi SONG Sizhu wu and Xiuyun DU(Research institute of Polymeric Materials, {2. University of Chemical Technology, {2., 10002., China) beijing Univ of Chemical Technology Beijing China

An integral constitutive equation and a set of material functions for describing the strain history of polymer melts were formulated in terms of the Cauchy-Green and Finger tensors. A simple memory function and the dependence of ηo and τt on M3.4 were derived from the theory of non-linear viscoelasticity with constraints of entanglements for polymer melts and substituted into the Oldroye-Walters-Fredickson constitutive equation. An integral constitutive equation for polymer melts was consequently obtained. Some material functions of the constitutive equation related to certain 'test flow' are examined as follows : (1) simple steady shear flow; (2. steady elongation flow; (3) small-amplitude oscillatory shear flow; (4) stress growth upon the inception of steady shear elongation flow; (5) stress relaxation (modulus and compllance). These theoretical relations for simple steady shear flow were compared with experimental data from our laboratory and references for various polymer melts and concentrated solutions. A good agreement between the theory and experiment was achieved.

关键词： LDPE Material Function with Nagai Chain Constraints and Determination of Their Parameters from Flow Curves Rheological Behaviour for Polymer Melts and Concentrated SolutionsPart Flow GR

theoretical and experimental research on static stiffness,performance,and lift-off characteristics of multi-layer gas foil thrust bearings

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Friction 2024年第11期12卷 2458-2479页

作者： Yang HU Pengjing DING Fangling wu Xiaojing WANG Bo LIANG Yonggang MENG School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200072China Aviation Key Laboratory of Science and Technology on Aero Electromechanical System Integration Nanjing Engineering Institute of Aircraft SystemsNanjing 211106China State Key Laboratory of Tribology Tsinghua UniversityBeijing 100084China

In this study,a new comprehensive fully coupled elastic–hydrodynamic model is developed for a multi-layer gas foil thrust bearing(GFTB).The interaction effects among the top foil,back board,middle foil,and bottom foil,as well as the Coulomb friction effect,are *** stiffness and static characteristics obtained by the experimental and theoretical approaches are in good agreement,which verifies the accuracy of the *** contribution of each foil layer to the overall stiffness and the load-carrying mechanism are *** effects of the load,preload,and rotational speed on the static performance are investigated ***,start–stop tests are performed to achieve the lift-off speed,start-up torque,and shut-down torque under various operating conditions.

关键词： multi-layer gas foil thrust bearing(GFTB) load carrying mechanism static performance

OH regulator of highly dispersed Ru sites on host Pd nanocrystals for selective ethanol electro-oxidation

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Nano Research 2024年第5期17卷 3863-3871页

作者： Zhihe Xiao Yueguang Chen Renjie wu Yuwei He Chunfeng Shi Leyu Wang State Key Laboratory of Chemical Resource Engineering College of ChemistryBeijing University of Chemical TechnologyBeijing 100029China Research institute of Petroleum Processing SINOPECBeijing 100083China

The ethanol oxidation reaction(EOR)is crucial in direct alcohol fuel cells and chemical ***,the electro-oxidation of ethanol molecules to produce acetaldehyde and carbon monoxide can poison the active sites of nanocatalysts,resulting in reduced performance and posing challenges in achieving high activity and selectivity for ethanol *** this study,we employed a dynamic seed-mediated method to precisely modify highly dispersed Ru sites onto well-defined Pd *** oxyphilic Ru sites serve as"OH valves",regulating water dissociation,while the surrounding Pd atomic arrangements control electronic states for the oxidation dehydrogenation of carbonaceous ***,Ru0.040@Pd nanocubes(Ru:Pd=0.04 at.%),featuring(100)facets in Ru-Pd4 configurations,demonstrate an outstanding mass activity of 6.53 A·mgPd^(-1) in EOR under alkaline conditions,which is 6.05 times higher than that of the commercial Pd/C catalyst(1.08 A·mgPd-1).Through in-situ experiments and theoretical investigations,we elucidate that the hydrophilic Ru atoms significantly promote the dynamic evolution of H_(2.O dissociation into OHads species,while the electron redistribution from Ru to adjacent Pd concurrently adjusts the selective oxidation of C_(2. *** host-guest interaction accelerates the subsequent oxidation of carbonaceous intermediates(CH_(3)CO_(ads))to acetate,while preventing the formation of toxic*CHx and*CO species,which constitutes the rate-determining step.

关键词： OH regulator atomic sites ethanol electro-oxidation host-guest interaction

Carbon-based interface engineering and architecture design for high-performance lithium metal anodes

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Carbon Energy 2024年第1期6卷 207-235页

作者： Na Zhu Yuxiang Yang Yu Li Ying Bai Junfeng Rong Chuan wu SINOPEC Research institute of Petroleum Processing Co. Ltd.BeijingChina beijing Key Laboratory of Environmental Science and Engineering School of Materials Science and EngineeringBeijing Institute of TechnologyBeijingChina Yangtze Delta Region academy of beijing {2. of Technology JiaxingChina

Metallic lithium(Li)is considered the“Holy Grail”anode material for the nextgeneration of Li batteries with high energy density owing to the extraordinary theoretical specific capacity and the lowest negative electrochemical ***,owing to inhomogeneous Li-ion flux,Li anodes undergo uncontrollable Li deposition,leading to limited power output and practical *** materials and their composites with controllable structures and properties have received extensive attention to guide the homogeneous growth of Li to achieve high-performance Li *** this review,the correlation between the behavior of Li anode and the properties of carbon materials is ***,we review emerging strategies for rationally designing high-performance Li anodes with carbon materials,including interface engineering(stabilizing solid electrolyte interphase layer and other functionalized interfacial layer)and architecture design of host carbon(constructing three-dimension structure,preparing hollow structure,introducing lithiophilic sites,optimizing geometric effects,and compositing with Li).Based on the insights,some prospects on critical challenges and possible future research directions in this field are *** is anticipated that further innovative works on the fundamental chemistry and theoretical research of Li anodes are needed.

关键词： carbon materials dendrites hosts interfacial layers Li metal anodes

The ultrasonic transient field radiated by a normal shear wave probe

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chinese Journal of Acoustics 2008年第1期27卷 65-74页

作者： wu Di LI Mingxuan WANG Xiaomin CHENG Yue institute of Acoustics Chinese Academy of Sciences Beijing 100080

The ultrasonic transient field of horizontally polarized shear wave radiated by a 2.2.piezoelectric composite normal probe was analyzed. The analytic field solutions for two different surface force sources were deduced and the transient displacement field distribution on the central cross-section was plotted by numerical calculations. Direct wave and edge wave as well as head wave were observed distinctly in the plots. The experimental results of time domain waveform conformed with the theoretical predictions, which supported the theoretical and numerical results about the transient field of the transducer.

关键词： wave The ultrasonic transient field radiated by a normal shear wave probe

Practice and technical approach of GPS observation of mining-induced ground subsidence

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中国有色金属学会会刊：英文版 2005年第S1期15卷 65-68页

作者： GAO Jun-hai~(1,2. wu Li-xin~1 (1. China University of Mining and Technology beijing Campus, beijing 100083, China 2. Tangshan Branch, China Coal Research {2., Tangshan 063012. China) China Univ Min & Technol Beijing 100083 Peoples R China China Coal Res Inst Tangshan Branch Tangshan 063012 Peoples R China

The base vector between 2.poins and a high-precision geodetic height difference can be obtained by GPS. If the geodetic height of a point is known, the geodetic height of each observation point in a net can be obtained. When surveying the subsidence value in the mining-induced ground subsidence, the change of the height of monitoring point is needed. On the above theoretical basis, the problem involved in GPS observation of mining-induced ground subsidence and their counter measures were discussed, and an introduction was made that the subsidence value obtained in the monitoring mining-induced ground subsidence can use the change of height of geodetic as a alternative, the result of check on the accuracy and reliability of repetitions observations was analysed. Finally, the effect of errors on accuracy of GPS observation and their reduction measures were elaborated.

关键词： mining-induced ground subsidence GPS observation observation accuracy reliability

Experiment Study of LD Pumped Solid State of Dual-Frequency Laser

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chinese Journal of Lasers 2000年第2期9卷 97-102页

作者： LU Congcong WEI Guanghui ZHAO Changming wu Keying MA Yu (Department of Optical Engineering, beijing {2. of Technology, beijing 100081, China ) 北京理工大学北京

Dual-frequency laser resulting from fine detuning twisted-mode cavity is discussed in this paper. Two measurement systems, a Fabry-Perot etalon and a confocal spherical interferometer, are adopted. The former reflects directly the interferogram of multimode and single mode. The latter can judge accurately the mode spectrum of single frequency and dual-frequency laser. Moreover, the experimental results provide the relationship between frequency difference and the angle of the relative rotation of the two quarter-wave plates and agree well with the theoretical analyses. The range of difference frequency is from 50 MHz to 1 GHz.

关键词： dual-frequency laser twisted-mode cavity of fine detuning diode-pumped solid-state laser (DPSL)

Integrating theory with the nanoreactor concept to synthesize hollow carbon sphere-encapsulated PtNi alloys for enhanced H_(2. generation

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Carbon Energy 2024年第7期6卷 150-162页

作者： Yufeng wu Minwei Song Ziyi Zhao Guang-Hui Wang Changlong Wang Didier Astruc institute of Circular Economy Faculty of Materials and ManufacturingBeijing University of TechnologyBeijingChina Key Laboratory of Biofuels Qingdao Institute of Bioenergy and Bioprocess TechnologyChinese Academy of SciencesQingdaoChina ISM UMR CNRS N°5255Universitéde BordeauxTalence CedexFrance

The rational design of efficient bimetallic nanoparticle(NP)catalysts is challenging due to the lack of theoretical understanding of active components and insights into the mechanisms of a specific ***,we report the rational design of nanoreactors comprising hollow carbon sphere-confined PtNi bimetallic NPs(PtNi@HCS)as highly efficient catalysts for hydrogen generation via ammonia borane hydrolysis in *** both density functional theory calculations and molecular dynamics simulations,the effects of an active PtNi combination and the critical synergistic role of a hollow carbon shell on the molecule diffusion adsorption behaviors are *** isotope effects and theoretical calculations allow the clarification of the mechanism,with oxidative addition of an O-H bond of water to the catalyst surface being the rate-determining *** remarkable catalytic activity of the PtNi@HCS nanoreactor was also utilized for successful tandem catalytic hydrogenation reactions,using in situ-generated H_(2. from ammonia borane with high *** concerted design,theoretical calculations,and experimental work presented here shed light on the rational elaboration of efficient nanocatalysts and contribute to the establishment of a circular carbon economy using green hydrogen.

关键词： ammonia borane hydrogen nanoalloy nanoreactor solid catalyst

On characteristic modeling of a class of flight vehicles'attitude dynamics

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Science China(Technological sciences) 2010年第8期53卷 2074-2080页

作者： MENG Bin &wu HongXin National Laboratory of Space Intelligent Control,beijing {2. of Control Engineering,beijing 100190,China National Laboratory of Space Intelligent Control Beijing Institute of Control Engineering Beijing China

The characteristic modeling problem of flight vehicles'attitude dynamics is considered in this *** terms of the affine nonlinear system with triangle form of flight vehicles'attitude dynamics,a general method is presented to compress the dynamics into the characteristic model parameters,by introducing the time scale of nonlinear systems and a class of system states related compress *** parameter region and limit of the characteristic model are also *** the given parameter region it is seen that the bound of the characteristic model parameters is dependent on the sampling period,the modeling error,the system order and the system change *** modeling error of the established characteristic model can be arbitrarily small according to the control precision,showing the difference between the characteristic model and other model reduction methods,that is,no system information is lost using this *** the basis of this modeling approach,the characteristic model of the flexible satellite attitude is established,as well as the bound and limit of the parameters,which sets a theoretical foundation for characteristic model based control design of flight vehicles.

关键词： characteristic modeling modeling error time scale of nonlinear systems spacecraft attitude dynamics

Classification of high-ordered topological nodes towards Moiré flat bands in twisted bilayers

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Science China(physics,Mechanics & Astronomy) 2024年第9期67卷 133-147页

作者： Fan Cui Congcong Le Qiang Zhang Xianxin wu Jiangping Hu Ching-Kai Chiu beijing National Laboratory for Condensed Matter physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical sciences University of Chinese Academy of SciencesBeijing 100190China RIKEN Interdisciplinary theoretical and Mathematical sciences(iTHEMS) Wako 351-0198Japan CAS Key Laboratory of theoretical physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China Kavli institute of theoretical {2. University of Chinese Academy of SciencesBeijing 100190China New Cornerstone Science Laboratory Beijing 100190China

At magic twisted angles,Dirac cones in twisted bilayer graphene(TBG)can evolve into flat bands,serving as a critical playground for the study of strongly correlated *** chiral symmetry is introduced,rigorous mathematical proof confirms that the flat bands are locked at zero energy in the entire Moiré Brillouin zone(BZ).Yet,TBG is not the sole platform that exhibits this absolute band *** to this flatness phenomenon are topological nodes and their specific locations in the *** this study,considering twisted bilayer systems that preserve chiral symmetry,we classify various ordered topological nodes in base layers and all possible node locations across different ***,we constrain the node locations to rotational centers,such as Γ and M points,to ensure the interlayer coupling retains equal strength in all *** this classification as a foundation,we systematically identify the conditions under which Moiré flat bands ***,through the extension of holomorphic functions,we provide proof that flat bands are locked at zero energy,shedding light on the origin of the band ***,beyond Dirac cones,numerous twisted bilayer nodal platforms can host flat bands with a degeneracy number of more than two,such as four-fold,six-fold,and *** multiplicity of degeneracy in flat bands might unveil more complex and enriched correlation physics.

关键词： twisted bilayer systems high-ordered topological nodes Moriéflat bands high degeneracy