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DEM investigation of angle of repose for super-ellipsoidal particles

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Particuology 2020年第3期18卷 53-66页

作者： Hao Chen Shiwei Zhao Xiaowen Zhou State Key Laboratory of Subtropical Building Science South China University of TechnologyGuangzhou 510641China

We explore the effect of particle shape on the angle of repose (AoR) in granular packing using a three-dimensional discrete element method.Non-spherical particles were modeled using super-ellipsoids characterized by aspect ratio and blockiness.The relationship between AoR and particle shape was examined,followed by a series of analyses on the origin of AoR from a microscopic perspective.Results show that,with blockiness deviating from unity,AoR has an approximate "M" shape that exhibits a strong to weak trend with aspect ratio,matching results of previous reports.Another finding suggests a parabolic relationship between normalized AoR and normalized coordination number,AoR increases with anisotropy related more with the anisotropy of particle orientation than with the anisotropy of contact normal.Particle shape is more likely to affect AoR by affecting the tangential force than the normal contact force.An analysis based on traction indicates that dips in stress associated with the tangential force (compared with the normal force) and non-spherical particles (compared with spheres) are more significant.For various particle shapes,AoR is positively correlated with friction mobilization but is negatively correlated with friction mobilization for various coefficient of friction.

关键词： Discrete element Angle of repose Non-spherical particles Granular fabric Packing

Dispersion stabilization of antimony-doped tin oxide(ATO)nanoparticles used for energy-efficient glass coating

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Particuology 2014年第6期12卷 49-53页

作者： Ning Li Qinglin Meng Nan Zhang State Key Laboratory of Subtropical Building Science Building Environment Energy Laboratory(BEEL)South China University of Technology

Nano-antimony-doped tin oxide（ATO） was synthesized using the sol-gel method.A colloidal dispersion of ATO nanoparticles in distilled water was achieved using a milling process in which different dispersants were studied.In this paper,different factors that affect the stability of ATO nanoparticles were discussed,such as zeta potential,dispersant,and pH value.Sodium polyphosphate was a suitable dispersant for stabilizing ATO nanoparticles in distilled water.A stable dispersion of ATO nanoparticles in distilled water was prepared.The stable dispersion of ATO nanoparticles was used to prepare nano-thermal insulation glass paint to block near-infrared rays of sunlight.

关键词： Nano-ATO dispersion Zeta potential Stabilization Energy-efficient glass coating

Experimental study on the shear behavior of the interface between cushion materials and the concrete raft

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Earthquake Engineering and Engineering Vibration 2018年第1期17卷 165-178页

作者： Li Yaokun Han Xiaolei Khaled Galal Ji Jing State Key Laboratory of Subtropical Building Science South China University of Technology Department of building Civil and Environmental EngineeringConcordia University

Cushion is a layer of granular materials between the raft and the ground. The shear behavior of the interface between the cushion and the raft may influence the seismic performance of the superstructure. In order to quantify such influences, horizontal shear tests on the interfaces between different cushion materials and concrete raft under monotonic and cyclic loading were carried out. The vertical pressure P_v, material type and cushion thickness h_c were taken as variables. Conclusions include： 1） under monotonic loading, P_v is the most significant factor; the shear resistance P_（hmax） increases as P_v increases, but the normalized factor of resistance μ_n has an opposite tendency; 2） for the materials used in this study, μ_n varies from 0.40 to 0.70, the interface friction angle δ_s varies from 20° to 35°, while u_（max） varies from 3 mm to 15 mm; 3） under cyclic loading, the interface behavior can be abstracted as a ＂three-segment＂ back-bone curve, the main parameters include μ_n, the displacement u_1 and stiffness K_1 of the elastic stage, the displacement u_2 and stiffness K_2 of the plastic stage; 4） by observation and statistical analysis, the significance of different factors, together with values of K_1, K_2 and μ_n have been obtained.

关键词： cushion/raft interface shear behavior monotonic test cyclic test ＂three-segment＂ back-bone curve

Flood cascading on critical infrastructure with climate change:A spatial analysis of the extreme weather event in Xinxiang,China

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Advances in Climate Change Research 2023年第3期14卷 458-468页

作者： Xiao-Ling QIN Shi-Fu WANG Meng MENGa Department of Urban Planning School of ArchitectureSouth China University of TechnologyGuangzhou510640China State Key Laboratory of Subtropical Building Science Guangzhou510640China

Floods caused by extreme weather events and climate change have increased in occurrence and severity all over the world,resulting in devastation and disruption of activities.Researchers and policy practitioners have increasingly paid attention to the role of critical infrastructure(CI)in disaster risk reduction,flood resilience and climate change adaptation in terms of its backbone functions in maintaining societal services in hazard attacks.The analysed city in this study,Xinxiang(Henan province,China),was affected by an extreme flood event that occurred on 17–23 July 2021,which caused great socio-economic losses.However,few studies have focused on medium-sized cities and the flood cascading effects on CI during this event.Therefore,this study explores the damages caused by this flooding event with links to CI,such as health services,energy supply stations,shelters and transport facilities(HEST infrastructure).To achieve this,the study first combines RGB(red,green blue)composition and supervised classification for flood detection to monitor and map flood inundation areas.Second,it manages a multiscenario simulation and evaluates the cascading effects on HEST infrastructure.Diverse open-source data are employed,including Sentinel-1 synthetic aperture radar(SAR)data and Landsat-8 OIL data,point-of-interest(POI)and OpenStreetMap(OSM)data.The study reveals that this extreme flood event has profoundly affected croplands and villagers.Due to the revisiting period of Sentinel-1 SAR data,four scenarios are simulated to portray the retreated but‘omitted’floodwater:Scenario 0 is the flood inundation area on 27 July,and Scenarios 1,2 and 3 are built based on this information with a buffer of 50,100 and 150 m outwards,respectively.In the four scenarios,as the inundation areas expand,the affected HEST infrastructure becomes more clustered at the centre of the core study area,indicating that those located in the urban centre are more susceptible to flooding.Furthermore,the affected transport facilities assemble in the north a

关键词： Flood cascading effects Critical infrastructure Extreme rainstorm event Flood scenarios

Numerical Modeling on Seismic Performance of Castellated Composite Beam⁃Reinforced Concrete Column Connection

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Journal of Harbin Institute of Technology(New Series) 2021年第2期28卷 62-73页

作者： Hongwei Ma Junjie Wang Yang Wang State Key Laboratory of Subtropical Building Science South China University of TechnologyGuangzhou 510640China

The hybrid structure consisting of castellated composite beam and compound spiral hoop reinforced concrete column take full advantages of steel and concrete material.To popularize the structural form in real conditions,a beam⁃through⁃type beam⁃column connection is proposed.Two 1/2⁃scaled connection specimens were tested and three⁃dimensional finite element models of the beam⁃column connection were set up.The longitudinal reinforcements,concrete beam,and column were simulated by link and solid elements,respectively.The influences of the parameters such as expansion ratio,location of web opening,and original height of steel beam were studied.The results show that connections possessed high initial rigidity.The expansion ratio of steel beam showed more important influence on the connection’s ultimate bearing capacity.For the connection models with steel beam expansion ratio of 1.4,the maximum increment of the ultimate bearing capacity of the connection could reach 28%.In order to prevent the local buckling failure of steel beam from occurring near web opening,the expansion ratio of steel beam should not be greater than 1.3.

关键词： castellated composite beam beam⁃column connection finite element analysis expansion ratio

The salt-activated CBF1/CBF2/CBF3-GALS1 module fine-tunes galactan-induced salt hypersensitivity in Arabidopsis

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Journal of Integrative Plant Biology 2023年第8期65卷 1904-1917页

作者： Jingwei Yan Ya Liu Jiawen Yan Zhihui Liu Heqiang Lou Jiasheng Wu state key laboratory of subtropical Silviculture Zhejiang A&F UniversityHangzhou 311300China

Plant growth and development are significantly hampered in saline environments,limiting agricultural productivity.Thus,it is crucial to unravel the mechanism underlying plant responses to salt stress.β-1,4-Galactan(galactan),which forms the side chains of pectic rhamnogalacturonan I,enhances plant sensitivity to high-salt stress.Galactan is synthesized by GALACTAN SYNTHASE1(GALS1).We previously showed that Na Cl relieves the direct suppression of GALS1 transcription by the transcription factors BPC1 and BPC2 to induce the excess accumulation of galactan in Arabidopsis(Arabidopsis thaliana).However,how plants adapt to this unfavorable environment remains unclear.Here,we determined that the transcription factors CBF1,CBF2,and CBF3 directly interact with the GALS1 promoter and repress its expression,leading to reduced galactan accumulation and enhanced salt tolerance.Salt stress enhances the binding of CBF1/CBF2/CBF3 to the GALS1 promoter by inducing CBF1/CBF2/CBF3 transcription and accumulation.Genetic analysis suggested that CBF1/CBF2/CBF3 function upstream of GALS1 to modulate salt-induced galactan biosynthesis and the salt response.CBF1/CBF2/CBF3 and BPC1/BPC2 function in parallel to regulate GALS1 expression,thereby modulating the salt response.Our results reveal a mechanism in which salt-activated CBF1/CBF2/CBF3 inhibit BPC1/BPC2-regulated GALS1 expression to alleviate galactan-induced salt hypersensitivity,providing an activation/deactivation fine-tune mechanism for dynamic regulation of GALS1 expression under salt stress in Arabidopsis.

关键词： Arabidopsis thaliana BPC1/BPC2 CBF1/CBF2/CBF3 β-1,4-galactan GALS1 salt stress

A novel robust design method for improving stability of optimized structures

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Acta Mechanica Sinica 2015年第1期31卷 104-111页

作者： Ming-Jie Cao Hai-Tao Ma Peng Wei State Key Laboratory of Subtropical Building Science Department of Civil Engineering South China University of Technology state key laboratory of Structural Analysis of Industrial Equipment Dalian University of Technology

It is known that structural optimization may lead to designs of structures having low stability and sometimes even kinematically unstable designs. This paper presents a robust design method for improving the stability of opti mized structures. A new approach is proposed, in which cer tain perturbation loads are introduced and the corresponding compliance is added to the objective function as a penaliza tion. The stability of the optimized structures can thus be improved substantially by considering structural responses to the original and the introduced loads. Numerical exam ples show the simplicity and effectiveness of the proposed method.

关键词： Structural optimization Robust design Penal-ization Perturbation loads

A modified model for concurrent topology optimization of structures and materials

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Acta Mechanica Sinica 2015年第6期31卷 890-898页

作者： Xingjun Gao Haitao Ma State Key Laboratory of Subtropical Building Science Department of Civil Engineering South China University of Technology state key laboratory of Structural Analysis of Industrial Equipment Dalian University of Technology

This paper presents a study on the concur- rent topology optimization of a structure and its material microstructure. A modified optimization model is proposed by introducing microstructure orientation angles as a new type of design variable. The new model is based on the assumptions that a structure is made of a material with the same microstructure, and the material may have a different orientation within the design domain of the structure. The homogenization theory is applied to link the material and structure scales. An additional post-processing technique is developed for modifying the obtained design to avoid local optima caused by the use of orientation angle variables. Numerical examples are presented to illustrate the viabil- ity and effectiveness of the proposed model. It is found that significant improvement in structural performance can be achieved by optimizing the orientation of microstructures in concurrent topology optimization of structures and materials.

关键词： Concurrent topology optimization · Materialswith microstructure · Microstructure orientation angle ·Orientation adjustment strategy

3D Dynamic Response of Layered Unsaturated Soils to Harmonic Loads

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Journal of Donghua University(English Edition) 2010年第3期27卷 407-411页

作者：徐明江魏德敏 State Key Laboratory of Subtropical Building Science South China University of Technology Guangzhou Institute of building science

Considering compression of solid grain and pore fluids,viscous-coupling interactions and inertial force of fluids,dynamic governing equations for unsaturated soils are established by adopting an exact constitutive formula of saturation.These equations are highly versatile and completely compatible with Biot's wave equations for the special case of fully saturated soils.The governing equations in Cartesian coordinates are firstly transformed into a group of state differential equations by introducing the state vector.Then the transfer matrix for layered media are derived by means of a double Fourier transform.Using the transfer matrix followed by boundary and continuity conditions between strata,solutions of steady-state dynamic response for multi-layered unsaturated soils are obtained.Numerical examples show that the echoes generated by boundary and stratum interfaces make the displacement amplitude of the ground surface fluctuate with distance;the relative position of soft and hard strata has a significant influence on displacement.

关键词：不饱和的土壤动态反应挥动方程两倍 Fourier 变换转移矩阵