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A novel fractal-statistical scaling model of rocks considering strain rate

Journal of Rock Mechanics and Geotechnical Engineering 2023年第11期15卷 2831-2841页

作者： Changtai Zhou Heping Xie Zhihe Wang Tao Zhou Jianbo Zhu Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization Institute of Deep Earth Sciences and Green EnergyCollege of Civil and Transportation EngineeringShenzhen UniversityShenzhen518060China Shenzhen Key Laboratory of Deep Underground Engineering Sciences and Green Energy Shenzhen UniversityShenzhen518060China

The scaling-dependent behaviors of rocks are significant to the stability and safe operation of the structures built in or on rock masses for practical ***,many size effect models are employed to connect laboratory measurements at small scales and engineering applications at large ***,limited works consider the strain rate *** this study,an fractal-statistical scaling model incorporating strain rate is proposed based on a weakest-link approach,fractal theory and dynamic fracture *** proposed scaling model consists of 8 model parameters with physical meaning,***-dependent parameter,intrinsic material parameter,dynamic strain rate,quasi-static strain rate,quasi-static fracture toughness,micro-crack size,micro-crack intensity and fractal dimension,enabling the proposed scaling model to model the scaling behaviors under different external *** predictions are consistent with experimental data on red sandstone,proving the reliability and effectiveness of the proposed scaling ***,the scaling behaviors of rocks under dynamic loading conditions can be captured by the proposed fractal-statistical scaling *** sensitivity analysis indicates that the nominal strength difference becomes more obvious with a higher strain rate,larger fractal dimension,smaller micro-crack size or lower micro-crack ***,the proposed scaling model has the potential to capture the scaling behaviors considering the thermal effect,weathering effect,anisotropic characteristic etc.,as the proposed scaling model incorporated model parameters with physical *** findings of this study are of fundamental importance to understand the scaling behaviors of rock under dynamic loading condition,and thus would facilitate the appropriate design of rock engineering.

关键词： size effect Strain rate Uniaxial compressive strength(UCS) Dynamic fracture mechanics

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Molecular dynamics study on the dependence of thermal conductivity on size and strain in GaN nanofilms

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Chinese Physics B 2023年第6期32卷 454-458页

作者：唐莹刘俊坤于子皓孙李刚朱林利 College of Optics and Electronics Technology China Jiliang UniversityHangzhou 310018China Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province School of Aeronautics and AstronauticsZhejiang UniversityHangzhou 310027China School of Science Harbin Institute of TechnologyShenzhen 518055China

The thermal conductivity of GaN nanofilm is simulated by using the molecular dynamics(MD)method to explore the influence of the nanofilm thickness and the pre-strain field under different *** is demonstrated that the thermal conductivity of GaN nanofilm increases with the increase of nanofilm thickness,while decreases with the increase of ***,the thermal conductivity of strained GaN nanofilms is weakened with increasing the tensile *** film thickness and environment temperature can affect the strain effect on the thermal conductivity of GaN *** addition,the analysis of phonon properties of GaN nanofilm shows that the phonon dispersion and density of states of GaN nanofilms can be significantly modified by the film thickness and *** results in this work can provide the theoretical supports for regulating the thermal properties of GaN nanofilm through tailoring the geometric size and strain engineering.

关键词： molecular dynamics simulation GaN nanofilm thermal conductivity phonon properties size effect strain effect

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effects of model size and particle size on the response of sea-ice samples created with a hexagonal-close-packing pattern in discrete-element method simulations

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Particuology 2018年第1期16卷 106-113页

作者： Shaocheng Di Yanzhuo Xue Xiaolong Bai Qing wang College of Shipbuilding Engineering Harbin Engineering University Harbin 150001 China

We investigated the effects of model size and particle size on the simulated macroscopic mechanical properties, uniaxial compressive strength, Young＇s modulus, and flexural strength of sea-ice samples, using the discrete-element method （DEM） with a bonded-particle model. Many different samples with a hexagonal-close-packing pattern and a unique particle size were considered, and several ratios of particle size to sample dimension （D/L） were studied for each sample. The macroscopic mechanical properties simulated by the DEM decrease monotonously with an increase in D/L. For different samples with different particle sizes, the macroscopic mechanical properties will be identical when D/L is constant. The quanti- tative relationships between macroscopic mechanical properties and ratio of particle size to sample size are important aspects in engineering applications of the DEM method. The results provide guidance on the choice of a particle size in the DEM simulation for numerical samples with a hexagonal-close-packing pattern.

关键词： Discrete-element method Bonded-particle model Sample size Particle size size effect

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Stability and regeneration of metal catalytic sites with different sizes in Fenton-like system

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中国化学快报:英文版 2023年第8期34卷 142-146页

作者： Yanan Shang Yujiao Kan Xing Xu School of Safety and Environmental Engineering Shandong University of Science and TechnologyQingdao 266590China School of Environmental Science and Engineering Shandong UniversityQingdao 266237China

Metal-based catalysts with different site sizes(e.g.,metal nanoparticles(NPs)and single atom catalysts(SACs))demonstrated outstanding catalytic activities in versatile Fenton-like ***,the surface/structural instability is a critical issue,which will result in rapid passivation in Fenton-like reaction and fail in long-term *** catalytic stability of the catalysts with different metal sizes considering versatile peroxides(H_(2)O_(2),peroxymonosulfate(PMS),and peroxodisulfate(PDS))should be *** addition,strategies for catalyst regeneration and recyclability improvement are also important to realize the metal-based catalysts for practical *** this review,catalytic stability of catalysts with different metal sizes in the backgrounds of versatile peroxides and water matrixes in Fenton-like reactions were first *** of metal catalytic sites with different methods were also ***,major challenges and development of methods concerning the stability and regeneration of metal catalytic sites with different sizes were discussed to understand the future researches of metal catalytic sites in Fenton-like reactions.

关键词： size effect Metal nanoparticles catalysts Single atom catalysts Fenton-like

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An insight into aggregation kinetics of polystyrene nanoplastics interaction with metal cations

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Chinese Chemical Letters 2022年第12期33卷 5213-5217页

作者： Yucheng Zhang Xiaotong Su Nora FYTam Xiaolan Lao Meiling Zhong Qihang Wu Huifang Lei Zihui Chen Zhang Li Jie Fu Key Laboratory for Water Quality and Conservation of the Pearl Stream Delta Ministry of EducationSchool of Environmental Science and EngineeringGuangzhou UniversityGuangzhou 510006China State Key Laboratory of Marine Pollution and Department of Chemistry City University of Hong KongHong KongChina School of Science and Technology Open University of Hong KongHong KongChina School of Environmental Science and Engineering Huazhong University of Science and TechnologyWuhan 430074China

Once inevitably released into the aquatic environment,polystyrene nanoplastics(PS-NPs)will present complicated environmental behaviors,of which the aggregation is a key process determining their environmental fate and *** this study,the aggregation kinetics of different sizes(30 nm and 100 nm)of PS-NPs with metal cations(Na^(+),K^(+),Ca^(2+),Mg^(2+)and Pb^(2+))at different solution pH(3,6 and 8)were *** results showed that the aggregation of PS-NPs increased with cation *** Pb^(2+)as an example,the adsorption behavior of cations onto PS-NPs was determined by transmission electron microscopy(TEM)and energy dispersive X-ray(EDX)spectroscopy,which demonstrated Pb^(2+)could be adhered onto the surface of PS-NPs with the effect of charge *** critical coagulation concentrations(CCC)of smaller PS-NPs were higher than that of larger PS-NPs for monovalent cations,whereas a different pattern is observed for divalent *** was suggested that there were other factors that DLVO theory does not consider affect the stability of NPs with different particle *** addition,it should be noted that PS-NPs had the capacity of adsorbing large amounts of heavy metal cations and carried them transport to a long distance,and the corresponding ecological risks need to further elucidate.

关键词： Polystyrene nanoplastics Lead cation Aggregation kinetics Critical coagulation concentration size effect

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The metastable constituent effects on size-dependent deformation behavior of nanolaminated micropillars: Cu/FeCoCrNi vs Cu/CuZr

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Journal of Materials Science & Technology 2021年第9期68卷 16-29页

作者： Yufang Zhao Jinyu Zhang YaQiang Wang Shenghua Wu Xiaoqing Liang Kai Wu Gang Liu Jun Sun State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong UniversityXi'an710049China

Metastable high entropy alloys(HEAs) and amorphous metallic glasses(MGs), with the chemical disordered character, are intensively studied due to their excellent performance. Here, we introduce Cu to separately constrain these two metastable materials and comparatively investigate their deformation behaviors and mechanical properties of Cu/HEA Fe Co Cr Ni and Cu/MG Cu Zr nanolaminated micropillars in terms of intrinsic layer thickness h and extrinsic pillar diameter D. The metastable HEA layers, as the hard phase in Cu/HEA micropillars, are stable and dominate the deformation, while transformation(crystallization) occurs in MG which plays a minor role in deformation of Cu/MG micropillars. The h-controlled deformation mode transits from the D-independent homogenous-like deformation at large h to the Ddependent shear banding at small h in both Cu/HEA and Cu/MG micropillars. Although both Cu/HEA and Cu/MG micropillars exhibit a maximum strain hardening capability controlled by h, the former manifests much lower hardening capability compared with the latter. The intrinsic size h and extrinsic size D have a strong coupling effect on the strength of Cu/HEA and Cu/MG micropillars. The strength of strength of Cu/HEA micropillars exhibits the D-dependent transition from "smaller is stronger" to "smaller is weaker"with increasing h. By contrast, the strength of Cu/MG micropillars exhibits the transition from bulk-like D-independent behavior at large h to small volume D-dependent behavior(smaller is stronger) at small h.

关键词： High-entropy alloys Metallic glasses Nanolaminated micropillars size effect

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size-dependent thermoelasticity of a finite bi-layered nanoscale plate based on nonlocal dual-phase-lag heat conduction and Eringen's nonlocal elasticity

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Applied Mathematics and Mechanics(English Edition) 2021年第1期42卷 1-16页

作者： Zhangna XUE Gongqi CAO Jianlin LIU College of Pipeline and Civil Engineering China University of Petroleum(East China)Qingdao 266580Shandong ProvinceChina

The size effects on heat conduction and elastic deformation are becoming significant along with the miniaturization of the device and wide application of ultrafast *** this work,to better describe the transient responses of nanostructures,a size-dependent thermoelastic model is established based on nonlocal dual-phase-lag(N-DPL)heat conduction and Eringen's nonlocal elasticity,which is applied to the one-dimensional analysis of a finite bi-layered nanoscale plate under a sudden thermal *** the numerical part,a semi-analytical solution is obtained by using the Laplace transform method,upon which the effects of size-dependent characteristic lengths and material properties of each layer on the transient responses are discussed *** results show that the introduction of the elastic nonlocal parameter of Medium 1 reduces the displacement and compressive stress,while the thermal nonlocal parameter of Medium 1 increases the deformation and compressive *** findings may be beneficial to the design of nano-sized and multi-layered devices.

关键词： thermoelasticity size effect multi-layered nanostructure

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Growing actin networks regulated by obstacle size and shape

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Acta Mechanica Sinica 2017年第2期33卷 222-233页

作者： Bo Gong Ji Lin Jin Qian Department of Engineering Mechanics Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province Zhejiang University Hangzhou 310027 China

Growing actin networks provide the driving force for the motility of cells and intracellular pathogens. Based on the molecular-level processes of actin polymerization, branching, capping, and depolymerization, we have developed a modeling framework to simulate the stochastic and cooperative behaviors of growing actin networks in propelling obstacles, with an emphasis on the size and shape effects on work capacity and filament orientation in the growing process. Our results show that the characteristic size of obstacles changes the protrusion power per unit length, without influencing the orientation distribution of actin filaments in growing networks. In contrast, the geometry of obstacles has a profound effect on filament patterning, which influences the orientation of filaments differently when the drag coefficient of environment is small, intermediate, or large. We also discuss the role of various parameters, such as the aspect ratio of obstacles, branching rate, and capping rate, in affecting the protrusion power of network growth.

关键词： Actin network Growth dynamics Monte Carlo simulation size effect Shape effect

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The size-dependent elastohydrodynamic lubrication contact of a coated half-plane with non-Newtonian fluid

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Applied Mathematics and Mechanics(English Edition) 2021年第7期42卷 915-930页

作者： Jie SU Hongxia SONG Liaoliang KE S.M.AIZIKOVICH School of Mechanical Engineering Tianjin UniversityTianjin 300350China School of Mathematical Science Inner Mongolia UniversityHohhot 010021China Laboratory of Functionally Graded and Composite Materials Research and Education Center"Materials"Don State Technical UniversityRostov-on-Don 344000Russia

Based on the couple-stress theory,the elastohydrodynamic lubrication(EHL)contact is analyzed with a consideration of the size *** lubricant between the contact surface of a homogeneous coated half-plane and a rigid punch is supposed to be the non-Newtonian *** density and viscosity of the lubricant are dependent on fluid *** of film thickness,in-plane stress,and fluid pressure are calculated by solving the nonlinear fluid-solid coupled equations with an iterative *** effects of the punch radius,size parameter,coating thickness,slide/roll ratio,entraining velocity,resultant normal load,and stiffness ratio on lubricant film thickness,in-plane stress,and fluid pressure are *** results demonstrate that fluid pressure and film thickness are obviously dependent on the size parameter,stiffness ratio,and coating thickness.

关键词： elastohydrodynamic lubrication(EHL) non-Newtonian fluid size effect couple-stress theory coating

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size and temperature effects on band gaps in periodic fluid-filled micropipes

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Applied Mathematics and Mechanics(English Edition) 2021年第9期42卷 1219-1232页

作者： Jun HONG Zhuangzhuang HE Gongye ZHANG Changwen MI Jiangsu Key Laboratory of Engineering Mechanics School of Civil EngineeringSoutheast UniversityNanjing 210096China

A new model is proposed for determining the band gaps of flexural wave propagation in periodic fluid-filled micropipes with circular and square thin-wall cross-sectional shapes, which incorporates temperature, microstructure, and surface energy effects. The band gaps depend on the thin-wall cross-sectional shape, the microstructure and surface elastic material constants, the pipe wall thickness, the unit cell length, the volume fraction, the fluid velocity in the pipe, the temperature change,and the thermal expansion coefficient. A systematic parametric study is conducted to quantitatively illustrate these factors. The numerical results show that the band gap frequencies of the current non-classical model with both circular and square thin-wall cross-sectional shapes are always higher than those of the classical model. In addition,the band gap size and frequency decrease with the increase of the unit cell length according to all the cases. Moreover, the large band gaps can be obtained by tailoring these factors.

关键词： band gap couple stress surface energy size effect conveying fluid thermal load

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