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Granular collapse in fluids:Dynamics and flow regime identification

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Particuology 2024年第9期92卷 30-41页

作者： Hu tang Bisong lin Dengming Wang Department of Mechanics and Engineering Science School of Civil Engineering and MechanicsKey Laboratory of Mechanics on Disaster and Environment in Western China of Ministry of EducationLanzhou UniversityLanzhou730000China

The collapse of granular material in fluids is a prevalent phenomenon in both natural and industrial processes,displaying a notable sensitivity to initial configuration of the *** study is specifically oriented towards falling process of collapsing material under various fluid conditions,employing the computational fluid dynamics-discrete element method(CFD-DEM)to primarily investigate the dynamics and scaling laws of deposit morphology of collapsed *** a comprehensive analysis of particle sedimentation in fluids,we introduce a refined inertial characteristic time for granular collapse within the inertial ***,we propose modifications to conventional fluid-particle density ratio and Reynolds number,aiming to enhance the accuracy of depicting collapse dynamics and identifying flow regimes across diverse column heights and fluid ***,we construct a phase diagram of flow regimes using modified dimensionless numbers,emphasizing the role of column height in transition between viscous and inertial *** parameters demonstrate enhanced relevance in governing the collapse of immersed granular columns,thereby contributing to a more nuanced understanding of fluid-particle interations in dense granular flows under different regimes.

关键词： Immersed granular material Collapse Dynamic Flow regime Computational fluid dynamics-discrete element method

Improved catalytic performance of CO_(2) electrochemical reduction reaction towards ethanol on chlorine-modified Cu-based electrocatalyst

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Nano Research 2024年第5期17卷 3761-3768页

作者： Yifan Liu Hehua tang Yitian Zhou Bo-lin lin School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China

Effective electrochemical conversion of CO_(2) to value-added liquid multi-carbon products driven by renewable energy is a promising approach to alleviate excessive CO_(2) emission and achieve large-scale renewable energy ***,the selectivity and catalytic activity towards liquid multi-carbon products of CO_(2) electroreduction reaction are still unsatisfactory due to the sluggish C-C coupling process and the formation of complex oxygen-containing ***,designing and fabricating highly effective electrocatalysts is crucial for practical applications in this ***,we developed Cl-modified Cu catalyst(Cu-Cl)for efficient electrochemical reduction of CO_(2) to *** optimal Faradaic efficiency and partial current density of ethanol on the Cu-Cl sample reached 26.2%and 343.2 mA·cm^(-2) at-0.74 V(*** hydrogen electrode(RHE)),which were 1.66 and 1.76 times higher than those of the catalyst without Cl decoration,outperforming those in most previously reported *** functional theory(DFT)calculations revealed that the Cl-modified Cu surface suppressed the parasitic hydrogen evolution reaction(HER)and reduced the energy barrier for the C-C coupling process,making the formation of key intermediates favorable for ethanol ***,the decoration of Cl on the Cu surface facilitated ethanol formation.

关键词： CO_(2)electrochemical reduction halogen chlorine Cu-based catalysts ethanol multi-carbon products

A Numerical Calculation Algorithm of the Inclination Function Based on the Representation of SO(3) Group

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Acta Mathematicae Applicatae Sinica 2024年第1期40卷 137-148页

作者： Yu-xiao Wei Wen-lin tang Department of Geophysics School of Geology Engineering and GeomaticsChang’An UniversityXi’an710064China Key Laboratory of Electronics and Information Technology for Space Systems National Space Science CenterChinese Academy of SciencesBeijing100190China

In the determination of the Earth gravity field in satellite geodesy, the inclination functions represent the projection of data observed along the orbital plane of a satellite orbit into the sphere in the terrestial reference frame. The inclination functions in this work is studied from a group theoretical perspective. The inclination functions are proved to generate a representation of the SO(3) group. An orthogonal relation of the inclination functions is derived and some recurrence relations for the inclination functions are given, based on which an algorithm to calculate the inclination functions is proposed.

关键词： SO(3)group inclination function satellite geodesy representation of SO(3)

Flexible and Robust Functionalized Boron Nitride/Poly(p‑Phenylene Benzobisoxazole)Nanocomposite Paper with High Thermal Conductivity and Outstanding Electrical Insulation

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Nano-Micro Letters 2024年第2期16卷 423-437页

作者： lin tang Kunpeng Ruan Xi Liu Yusheng tang Yali Zhang Junwei Gu Chongqing Key Laboratory of Green Synthesis and Applications College of ChemistryChongqing Normal UniversityChongqing 401331People’s Republic of China Shaanxi Key Laboratory of Macromolecular Science and Technology School of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi’an 710072People’s Republic of China

With the rapid development of 5G information technology,thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming *** this work,“high-temperature solid-phase&diazonium salt decomposition”method is carried out to prepare benzidine-functionalized boron nitride(m-BN).Subsequently,m-BN/poly(pphenylene benzobisoxazole)nanofiber(PNF)nanocomposite paper with nacremimetic layered structures is prepared via sol–gel film transformation *** obtained m-BN/PNF nanocomposite paper with 50 wt%m-BN presents excellent thermal conductivity,incredible electrical insulation,outstanding mechanical properties and thermal stability,due to the construction of extensive hydrogen bonds andπ–πinteractions between m-BN and PNF,and stable nacre-mimetic layered ***λ∥andλ_(⊥)are 9.68 and 0.84 W m^(-1)K^(-1),and the volume resistivity and breakdown strength are as high as 2.3×10^(15)Ωcm and 324.2 kV mm^(-1),***,it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640°C,showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment.

关键词： Poly(p-phenylene-2,6-benzobisoxazole)nanofiber Boron nitride Thermal conductivity Electrical insulation

Water–solid contact electrification and catalysis adjusted by surface functional groups

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Nano Research 2024年第4期17卷 3344-3351页

作者： Yusen Su Andy Berbille Zhong lin Wang Wei tang CAS Center for Excellence in Nanoscience Beijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijing100083China School of Nanoscience and Technology University of Chinese Academy of SciencesBeijing100049China Georgia Institute of Technology AtlantaGA 30332-0245USA

Chemical functional groups on solid surfaces greatly influence contact electrification(CE)at water–solid *** studies of their effects mainly swapped materials or bonded related molecules to a substrate,introducing other factors of *** work aims at unambiguously demonstrating the role of functional groups in water-polymer *** study the contribution of functional groups,by using ion coupled plasma etching to modify a high-density polyethylene(HDPE)film,a polymer with a naturally quasi-null charge transfer ***(HDPE–F)and hydroxyl(HDPE–OH)functional groups are generated and endowed HDPE with charge withdrawing ***–F withdraws 2.5–2.7 times more charges than HDPE–***,the surface charges accumulated generate electrostatic forces,altering the droplets *** phenomenon provides another approach to study CE,helping to evaluate the contribution of electrons to solid–liquid ***,employing HDPE–F to perform contact-electro-catalysis shows its activity is 2.4 times higher than that of commercial fluorinated films.

关键词： contact-electro-catalysis charge transfer solid–liquid interfaces contact electrification

Positive definiteness of real quadratic forms resulting from the variable-step L1-type approximations of convolution operators

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Science China Mathematics 2024年第2期67卷 237-252页

作者： Hong-lin Liao Tao tang Tao Zhou School of Mathematics Nanjing University of Aeronautics and AstronauticsNanjing 211106China Division of Science and Technology BNU-HKBU United International CollegeZhuhai 519087China SUSTech International Center for Mathematics Shenzhen 518055China NCMIS&LSEC Institute of Computational Mathematics and Scientific/Engineering ComputingAcademy of Mathematics and Systems ScienceChinese Academy of SciencesBeijing 100190China

The positive definiteness of real quadratic forms with convolution structures plays an important rolein stability analysis for time-stepping schemes for nonlocal operators. In this work, we present a novel analysistool to handle discrete convolution kernels resulting from variable-step approximations for convolution *** precisely, for a class of discrete convolution kernels relevant to variable-step L1-type time discretizations, weshow that the associated quadratic form is positive definite under some easy-to-check algebraic conditions. Ourproof is based on an elementary constructing strategy by using the properties of discrete orthogonal convolutionkernels and discrete complementary convolution kernels. To our knowledge, this is the first general result onsimple algebraic conditions for the positive definiteness of variable-step discrete convolution kernels. Using theunified theory, we obtain the stability for some simple nonuniform time-stepping schemes straightforwardly.

关键词： discrete convolution kernels positive definiteness variable time-stepping orthogonal convolution kernels complementary convolution kernels

Field Study of HPTRM Combined with Vegetation and Anchor to Protect Newly Excavated Expansive Soil Slope

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Journal of Earth Science 2024年第4期35卷 1277-1288页

作者： Yingzi Xu Xuhang Liao linqiang tang lin Li College of Civil&Architectural Engineering Guangxi UniversityNanning530004China Guangxi Key Laboratory of Disaster Prevention and Engineering Safety Nanning530004China Guangxi Transport Vocational and Technical College Nanning530004China Department of Civil&Architectural Engineering Tennessee State UniversityTennessee37209NashvilleUSA

Anchor reinforced vegetation system(ARVS)comprises high performance turf reinforcement mats(HPTRM),vegetation and *** is a new attempt to apply the system in expansive soil slope *** goal of this paper was to evaluate the effectiveness of ARVS in protecting newly excavated expansive soil *** field tests on the bare slope,grassed slope and ARVS protective slope were carried out,including natural and artificial *** the test,the soil water content,soil deformation,and anchor axial force were monitored,and then the slope protection mechanism of ARVS was *** was found that ARVS can effectively protect expansive soil slopes compared with bare slopes and grassed *** vegetation and HPTRM form a reinforced turf,and the anchors fix it to the slope surface,thus restraining the expansion *** axial force on the anchor of ARVS includes frictional resistance and tensile force transmitted by HPTRM,which is maximum at the early stage of *** neutral point of the anchor of ARVS moves deeper under atmospheric action,but the vegetation and HPTRM on the slope surface can limit this movement.

关键词： expansive soil slope anchor reinforced vegetation system high performance turf reinforcement mats field test slope protection

Recent Advances in Mechanistic Understanding of Metal-Free Carbon Thermocatalysis and Electrocatalysis with Model Molecules

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Nano-Micro Letters 2024年第7期16卷 74-97页

作者： Wei Guo linhui Yu ling tang Yan Wan Yangming lin CAS Key Laboratory of Design and Assembly of Functional Nanostructures Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002People’s Republic of China Xiamen Key Laboratory of Rare Earth Photoelectric Functional Materials Xiamen Institute of Rare Earth MaterialsHaixi InstituteChinese Academy of SciencesXiamen 361021People’s Republic of China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of SciencesFuzhou 350002People’s Republic of China Institute of Urban Environment Chinese Academy of SciencesXiamen 361021People’s Republic of China

Metal-free carbon,as the most representative heterogeneous metal-free catalysts,have received considerable interests in electro-and thermo-catalytic reac-tions due to their impressive performance and *** the past decade,well-designed carbon catalysts with tunable structures and heteroatom groups coupled with various characterization techniques have proposed numerous reaction ***,active sites,key intermediate species,precise structure-activity relationships and dynamic evolution processes of carbon catalysts are still rife with controversies due to the monotony and limitation of used experimental *** this Review,we sum-marize the extensive efforts on model catalysts since the 2000s,particularly in the past decade,to overcome the influences of material and structure limitations in metal-free carbon *** both nanomolecule model and bulk model,the real contribution of each alien species,defect and edge configuration to a series of fundamentally important reactions,such as thermocatalytic reactions,electrocatalytic reactions,were systematically *** with in situ techniques,isotope labeling and size control,the detailed reaction mechanisms,the precise 2D structure-activity relationships and the rate-determining steps were revealed at a molecular ***,the outlook of model carbon catalysis has also been proposed in this work.

关键词： Metal-free carbon catalysts Model catalyst Electrocatalysis Active site Reaction mechanisms

CFD-DEM simulation of fluorination reaction in fluidized beds with local grid and time refinement method

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Particuology 2024年第1期84卷 145-157页

作者： Mofan Qiu lin Jiang Rongzhen Liu Yaping tang Malin Liu Institute of Nuclear and New Energy Technology Collaborative Innovation Center of Advanced Nuclear Energy TechnologyTsinghua UniversityBeijing100084China

The gas-solid reaction process with wide particle size distribution is extensively used in the chemical engineering field,especially the particle reacts with the gas gradually,such as fluorination reactions in fluidized *** the computational fluid dynamics-discrete element method(CFD-DEM)is used for the coupling simulation of multiphase and polydisperse particle reaction system,the grid size directly affects the accuracy of flow field information and simulation of chemical ***,particle calculation time step will directly affect the efficiency of coupling *** this work,a local grid and time step refinement method is proposed to simulate multiphase and polydisperse particle fluid-ization reaction *** this method,the refined DEM grids are automatically generated in the computational domain around the fine particles,and the detailed fluid phase information is obtained with the interpolation *** the two-phase coupling process,particles are divided into different groups based on physical properties,each group has its own independent time *** multistage conical-cylindrical spouted bed is proposed for the fluorination reaction process;the operating gas ve-locity range of the polydisperse particle system is extended by the new design while the particle size distribution changes with the gas-solid reaction *** is demonstrated that the local grid and time step refinement method can improve the accuracy and efficiency of the traditional CFD-DEM method in the reaction process simulation,which describes a polydisperse particle system with wide particle size *** at improving the simulation accuracy and efficiency,this paper will be helpful for simulating the particle reaction process in the gas-solid fluidized bed and beneficial for the development of the CFD-DEM method.

关键词： CFD-DEM Polydisperse particle Two-phase flow Fluidized bed