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Heterogeneities of grain boundary contact for simulation of laboratoryscale mechanical behavior of granitic rocks

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第7期16卷 2629-2644页

作者： Xiongyu Hu Marte Gutierrez Zhiwei yan Key Laboratory of Transportation Tunnel Engineering Ministry of EducationSouthwest Jiaotong UniversityChengdu610031China University Transportation Center for Underground Transportation Infrastructure Colorado School of MinesGoldenUSA School of Civil Engineering Southwest Jiaotong UniversityChengdu610031China

From a practical point of view,grain structure heterogeneities are key parameters that control the rock response and still remains a challenge to incorporate in a quantitative *** of the less discussed topics in the context of the grain-based model(GBM)in the particle flow code(PFC)is the contact heterogeneities and the appropriate contact model to mimic the grain boundary ***,the smooth joint(SJ)model and linear parallel bond(LPB)model are used to simulate the grain boundary ***,the literature does not document the suitability of different models for specific *** challenge in implementing GBM in PFC is that only a single bonding parameter is used at the grain *** aim of this study is to investigate the responses of a laboratory-scale specimen with SJ and LPB models,considering grain boundary heterogeneous and homogeneous contact *** and biaxial compression tests are performed to calibrate the response of Creighton *** stressestrain curves,volumetric dilation,inter-crack(crack in the grain boundary),and intra-crack(crack within the grain)development,and failure patterns associated with different contact models are *** was found that both the SJ and LPB models can reproduce the pre-peak behavior observed for a granitic rock ***,the LPB model is unable to reproduce the post-peak *** to the large interlocking effect originating from the balls in contact and the ball size in the LPB model,local dilation is induced at the grain *** overestimates the volumetric dilation and residual shear *** LPB model tends to result in discontinuous inter-cracks and stress localization in the rock specimen,resulting in fine fragments at the rock surface during failure.

关键词： Grain boundary contact Smooth joint(SJ)model Linear parallel bond(LPB)model Contact heterogeneities Particle flow code(PFC) Granitic rock

BSEC Method for Unveiling Open Clusters and its Application to Gaia DR3:83 New Clusters

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Research in Astronomy and Astrophysics 2024年第5期24卷 169-184页

作者： Zhong-Mu Li Cai-yan Mao Institute of Astronomy and Information Dali UniversityDali 671003China

Open clusters(OCs) are common in the Milky Way, but most of them remain undiscovered. There are numerous techniques, including some machine-learning algorithms, available for the exploration of OCs. However, each method has its limitations and therefore, different approaches to discovering OCs hold significant values. We develop a comprehensive approach method to automatically explore the data space and identify potential OC candidates with relatively reliable membership determination. This approach combines the techniques of Hierarchical Density-Based Spatial Clustering of Applications with Noise, Gaussian mixture model, and a novel cluster member identification technique, color excess constraint. The new method exhibits efficiency in detecting OCs while ensuring precise determination of cluster memberships. Because the main feature of this technique is to add an extra constraint(EC) for the members of cluster candidates using the homogeneity of color excess,compared to typical blind search codes, it is called Blind Search-Extra Constraint(BSEC) method. It is successfully applied to the Gaia Data Release 3, and 83 new OCs are found, whose color–magnitude diagrams(CMDs) are fitted well to the isochrones. In addition, this study reports 621 new OC candidates with discernible main sequence or red giant branch. It is shown that BSEC technique can discard some false negatives of previous works, which takes about three percentage of known clusters. It shows that as an EC, the color excess(or twocolor) constraint is useful for removing fake cluster member stars from the clusters that are identified from the positions and proper motions of stars, and getting more precise CMDs, when differential reddening of member stars of a cluster is not large(e.g., ΔE(G_(BP)-G_(RP)) < 0.5 mag). It makes the CMDs of 15% clusters clearer(in particular for the region near turnoff) and therefore is helpful for CMD and stellar population studies. Our result suggests that the color excess con

关键词： Galaxy stellar content-(Galaxy:)open clusters and associations general-stars fundamental parameters

Dust particle surface potential in an argonhelium plasma using the(r,q)-distribution function

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Communications in Theoretical Physics 2024年第9期76卷 141-148页

作者： Bahaaudin M Raffah A A Abid Abdullah Khan amin Esmaeili Yas Al-Hadeethi M N S Qureshi Department of Physics Faculty of SciencesKing Abdulaziz UniversityJeddah 21589Saudi Arabia Lithography in Devices Fabrication and Development Research Group Deanship of Scientific ResearchKing Abdulaziz UniversityJeddah 21589Saudi Arabia Joint Laboratory of Plasma Application Technology Institute of Advanced TechnologyUniversity of Science and Technology of ChinaHefei230026China CAS Key Laboratory of Geospace Environment University of Science and Technology of ChinaHefei230026China Department of Physics Zhejiang Normal UniversityJinhua321005China Department of Physics Graduate School of ScienceTokyo Metropolitan UniversityMinami-Osawa 1-1Hachioji City192-0397Japan Department of Physics GC UniversityLahore 54000Pakistan

In this paper,the dust particle surface potential for argon-helium plasma is evaluated analytically and numerically in the context of negatively charged dust particles by employing a power-law(r,q)-distribution *** studies have reported the argon-helium plasma and conducted a brief theoretical and experimental *** deepen our understanding further,this study aims to analyze the argon-helium plasma comprehensively using the same pattern but with the(r,q)-distribution *** this purpose,the current balance equations are derived for electron,helium and argon ions,when these charge species attain the quasineutrality *** numerically examined the currents of plasma species for a broad range of effective distribution function parameters r and *** is revealed that the surface potential of dust particles is significantly affected by the parameters r and q,helium ion-to-electron temperature ratio,argon ion-to-electron temperature ratio,and helium ion to argon ion number density *** incorporating the multi-ion(argon-helium)species,the significance of low-temperature nonMaxwellian dusty(complex)plasma is briefly examined.

关键词： dusty plasma dust charge potential plasma physics helium argon plasma r q distribution function non-Maxwellian distribution

Carbon Emission Effects Driven by Evolution of Chinese Dietary Structure from 1987 to 2020

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Chinese Geographical Science 2024年第1期34卷 181-194页

作者： ZHU Yuanyuan ZHANG yan ZHU Xiaohua Key Laboratory of Geographic Process Analysis&Simulation Hubei Province Central China Normal UniversityWuhan430079China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing100101China

Exploring carbon emission effects based on the evolution of residents’ dietary structure to achieve the carbon neutrality goal and mitigate climate change is an important *** study took China as the research object(data excluding Hong Kong,Macao and Taiwan) and used the carbon emission coefficient method to quantitatively measure the food carbon emissions from 1987–2020,then analyzed the carbon emission effects under the evolution of dietary *** results showed that during the study period,the Chinese dietary structure gradually changed to a high-carbon consumption *** dietary structure of urban residents developed to a balanced one,while that of rural residents developed to a high-quality *** the study period,the per capita food carbon emissions and total food consumption of Chinese showed an increasing *** per capita food carbon emissions of residents in urban and rural showed an overall upward *** total food carbon emissions in urban increased significantly,while that in rural increased first and then *** influence of beef and mutton on carbon emissions is the highest in dietary *** with the balanced dietary pattern,the food carbon emissions of Chinese residents had not yet reached the peak,but were evolving to a high-carbon consumption pattern.

关键词： dietary structure structural evolution carbon emission effects carbon neutrality China

Bio-inspired surface manipulation of halloysite nanotubes for highperformance flame retardant polylactic acid nanocomposites

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Nano Research 2024年第3期17卷 1595-1606页

作者： Yaru Sun Bin Yu yan Liu Junbo yan Zixi Xu Bo Cheng Fenglei Huang Jun Wang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China State Key Laboratory of Fire Science University of Science and Technology of ChinaHefei 230026China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401120China National Engineering Research Center of Flame Retardant Materials Beijing Institute of TechnologyBeijing 100081China

High-performance flame-retardant polylactic acid(PLA)bio-composites based on biobased fillers to meet usage requirements represents a promising direction for creating a sustainable *** flame retardant PLA composites have been reported extensively,it still remains a huge challenge to develop mechanically *** flame retardant PLA composites due to plastication effect of organic flame retardants and poor compatibility of organic fillers with the matrix lead to the severe deterioration in mechanical *** this work,a bio-inspired surface manipulation strategy for halloysite nanotubes(HNTs)was proposed via a facile and green self-assembly *** structure and morphology of bio-inspired HNTs(b-HNTs)proved that biomass nanofillers(PA-NA-Fe)grew well both within the lumen and on the surface of *** growth of biomass on the inner and outer surfaces of HNTs was inspired from wooden towards enhancing the interface compatibility and imparting multi-properties to PLA *** mechanical properties(tensile,thermomechanical and anti-impact mechanical),great fire safety(heat release and smoke emission),thermostability and improved electromagnetic interference shielding effectiveness of this well-designed PLA nanocomposite were *** mechanisms of the enhanced performances of the PLA bio-composites by loading b-HNTs were *** work presents a facile and environmentally-friendly bio-inspired modification strategy for HNTs to fabricate high-performance,multi-functional polymer composites,which is also suitable for surface modification of many other nanomaterials,including nanofibers,nanotubes,nanowires,and nanosheets.

关键词： mechanical properties thermostability fire safety electromagnetic interference shielding biomass

Homoclinic Solutions for a Class of Perturbed Fractional Hamiltonian Systems with Subquadratic Conditions

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Acta Mathematica Sinica,English Series 2024年第5期40卷 1177-1196页

作者： Ying LUO Fei GUO yan LIU School of Mathematics Tianjin UniversityTianjin 300354P.R.China Tianjin Key Laboratory of Brain-Inspired Intelligence Technology Tianjin300354P.R.China

In this paper,we consider the following perturbed fractional Hamiltonian systems{tD_(∞)^(α)(_(-∞)D_(t)^(α)u(t))+L(t)u(t)=■_(u)W(t,u(t))+■(u)G(t,u(t)),t∈R,u∈H^(α)(R,R^(N)),whereα∈(1/2,1],L∈C(R,R^(N×N))is symmetric and not necessarily required to be positive definite,W∈C1(R×R^(N,R))is locally subquadratic and locally even near the origin,and perturbed term G∈C1(R×R^(N,R))maybe has no parity in *** the perturbed method improved by the authors,a sequence of nontrivial homo clinic solutions is obtained,which generalizes previous results.

关键词： Perturbed fractional Hamiltonian systems subquadratic condition perturbed method homoclinic solutions multiplicity

MIXED DISCONTINUOUS GALERKIN METHOD FOR QUASI-NEWTONIAN STOKES FLOWS

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Journal of Computational Mathematics 2024年第3期42卷 885-910页

作者： yanxia Qian Fei Wang Wenjing yan School of Mathematics and Statistics Xi'an Jiaotong UniversityXi'an 710049China School of Mathematics and Statistics&State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049China

In this paper,we introduce and analyze an augmented mixed discontinuous Galerkin(MDG)method for a class of quasi-Newtonian Stokes *** the mixed formulation,the unknowns are strain rate,stress and velocity,which are approximated by a discontinuous piecewise polynomial triplet ■for k≥***,the discontinuous piecewise polynomial function spaces for the field of strain rate and the stress field are designed to be *** addition,the pressure is easily recovered through simple *** the benefit of the analysis,we enrich the MDG scheme with the constitutive equation relating the stress and the strain rate,so that the well-posedness of the augmented formulation is obtained by a nonlinear functional *** k≥0,we get the optimal convergence order for the stress in broken ■(div)-norm and velocity in L^(2)-***,the error estimates of the strain rate and the stress in-norm,and the pressure in L^(2)-norm are optimal under certain ***,several numerical examples are given to show the performance of the augmented MDG method and verify the theoretical *** evidence is provided to show that the orders of convergence are sharp.

关键词： Quasi-Newtonian fows Mixed discontinuous Galerkin method Symmetric strain rate Symmetric stress Optimal convergence orders

Sobolev Mapping of the Bergman Projections on Generalized Hartogs Triangles

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Acta Mathematica Sinica,English Series 2024年第2期40卷 451-466页

作者： Hong yan LIU Zhen Han TU School of Mathematics and Statistics Wuhan UniversityWuhan 430072P.R.China

In this paper,we investigate Sobolev mapping properties of the Bergman *** domain we focus on is defined byΩm/n:={(z,w)∈C^(1+N):|w1|<|z|m1/n1<1,…|wN|<|z|/m_(N)/n_(N)<1},where m=(m1,…mN)∈(Z^(+))^(N),n=(n1,…nN)∈(Z^(+))N,N∈Z^(+).Sobolev irregularity of the Bergman projections on 2 is *** also prove some Sobolev regularity results of the Bergman projections onΩm/n for m=(1,…1).

关键词： Bergman projections generalized Hartogs triangles Sobolev spaces

Design,fabrication,and characterization of hierarchical mechanical metamaterials

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Frontiers of Mechanical Engineering 2024年第1期19卷 73-83页

作者： Jian SONG Junfei yan Bengang YI Automotive Engineering Research Institute BYD Auto Industry Co.Ltd.Shenzhen 518000China College of Civil and Transportation Engineering Shenzhen UniversityShenzhen 518060China

Natural mechanical materials,such as bamboo and bone,often exhibit superior specific mechanical properties due to their hierarchical porous *** the principle of hierarchy as inspiration can facilitate the development of hierarchical mechanical metamaterials(HMMs)across multiple length scales via 3D *** this work,we propose self-similar HMMs that combine octet-truss(OCT)architecture as the first and second orders,with cubic architecture as the third or more *** HMMs were fabricated using stereolithography 3D printing,with the length sizes ranging from approximately 200µm to the centimeter *** compressive stress–strain behaviors of HMMs exhibit a zigzag characteristic,and the toughness and energy absorption can be significantly enhanced by the hierarchical *** compressive moduli are comparable to that of natural materials,and the strengths are superior to that of most polymer/metal foams,alumina hollow/carbon lattices,and other natural ***,the flexural stress–strain curves exhibit a nonlinear behavior,which can be attributed to the hierarchical architecture and local damage *** relatively high mechanical properties can be attributed to the synergistic effect of the stretch-dominated OCT architecture and the bending-dominated cube ***,an ultralight HMM-integrated unmanned aerial vehicle(HMM-UAV)was successfully designed and *** HMM-UAV is~85%lighter than its bulk counterpart,remarkably extending the flight duration time(~53%).This work not only provides an effective design strategy for HMMs but also further expands the application benchmark of HMMs.

关键词： 3D printing mechanical metamaterials hierarchical architecture mechanical behavior unmanned aerial vehicle(UAV)