Coral reef limestone(CRL)constitutes a distinctive marine carbonate formation with complex mechanical properties.This study investigates the multiscale damage and fracture mechanisms of CRL through integrated experime...Coral reef limestone(CRL)constitutes a distinctive marine carbonate formation with complex mechanical properties.This study investigates the multiscale damage and fracture mechanisms of CRL through integrated experimental testing,digital core technology,and theoretical modelling.Two CRL types with contrasting mesostructures were characterized across three scales.Macroscopically,CRL-I and CRL-II exhibited mean compressive strengths of 8.46 and 5.17 MPa,respectively.Mesoscopically,CRL-I featured small-scale highly interconnected pores,whilst CRL-II developed larger stratified pores with diminished connectivity.Microscopically,both CRL matrices demonstrated remarkable similarity in mineral composition and mechanical properties.A novel voxel average-based digital core scaling methodology was developed to facilitate numerical simulation of cross-scale damage processes,revealing network-progressive failure in CRL-I versus directional-brittle failure in CRL-II.Furthermore,a damage statistical constitutive model based on digital core technology and mesoscopic homogenisation theory established quantitative relationships between microelement strength distribution and macroscopic mechanical behavior.These findings illuminate the fundamental mechanisms through which mesoscopic structure governs the macroscopic mechanical properties of CRL.展开更多
In the present paper,a hierarchical multi-scale method is developed for the nonlinear analysis of composite materials undergoing heterogeneity and damage.Starting from the homogenization theory,the energy equivalence ...In the present paper,a hierarchical multi-scale method is developed for the nonlinear analysis of composite materials undergoing heterogeneity and damage.Starting from the homogenization theory,the energy equivalence between scales is developed.Then accompanied with the energy based damage model,the multi-scale damage evolutions are resolved by homogenizing the energy scalar over the meso-cell.The macroscopic behaviors described by the multi-scale damage evolutions represent the mesoscopic heterogeneity and damage of the composites.A rather simple structure made from particle reinforced composite materials is developed as a numerical example.The agreement between the fullscale simulating results and the multi-scale simulating results demonstrates the capacity of the proposed model to simulate nonlinear behaviors of quasi-brittle composite materials within the multi-scale framework.展开更多
A multi-scale damage model of concrete is proposed based on the concept of energy equivalent strain for generic two-or three-dimensional applications.Continuum damage mechanics serves as the framework to describe the ...A multi-scale damage model of concrete is proposed based on the concept of energy equivalent strain for generic two-or three-dimensional applications.Continuum damage mechanics serves as the framework to describe the basic damage variables,namely the tensile and compressive damage.The homogenized Helmholtz free energy is introduced as the bridge to link the micro-cell and macroscopic material.The crack propagation in micro-cells is modeled,and the Helmholtz free energy in the cracked micro-structure is calculated and employed to extract the damage evolution functions in the macroscopic material.Based on the damage energy release rates and damage consistent condition,the energy equivalent strain is used to expand the uniaxial damage model to the multi-dimensional damage model.Agreements with existing experimental data that include uniaxial tensile and compressive tests,biaxial compression and biaxial peak stress envelop demonstrate the capacity of the multi-scale damage model in reproducing the typical nonlinear performances of concrete specimens.The simulation of precast laminated concrete slab further demonstrates its application to concrete structures.展开更多
Retinal ganglion cells are the bridging neurons between the eye and the central nervous system,transmitting visual signals to the brain.The injury and loss of retinal ganglion cells are the primary pathological change...Retinal ganglion cells are the bridging neurons between the eye and the central nervous system,transmitting visual signals to the brain.The injury and loss of retinal ganglion cells are the primary pathological changes in several retinal degenerative diseases,including glaucoma,ischemic optic neuropathy,diabetic neuropathy,and optic neuritis.In mammals,injured retinal ganglion cells lack regenerative capacity and undergo apoptotic cell death within a few days of injury.Additionally,these cells exhibit limited regenerative ability,ultimately contributing to vision impairment and potentially leading to blindness.Currently,the only effective clinical treatment for glaucoma is to prevent vision loss by lowering intraocular pressure through medications or surgery;however,this approach cannot halt the effect of retinal ganglion cell loss on visual function.This review comprehensively investigates the mechanisms underlying retinal ganglion cell degeneration in retinal degenerative diseases and further explores the current status and potential of cell replacement therapy for regenerating retinal ganglion cells.As our understanding of the complex processes involved in retinal ganglion cell degeneration deepens,we can explore new treatment strategies,such as cell transplantation,which may offer more effective ways to mitigate the effect of retinal degenerative diseases on vision.展开更多
The research of modern mechanics reveals that the damage and failure of structures should be considered on different scales. The present paper is dedicated to establishing the multi-scale damage theory for the nonline...The research of modern mechanics reveals that the damage and failure of structures should be considered on different scales. The present paper is dedicated to establishing the multi-scale damage theory for the nonlinear structural analysis. Starting from the asymptotic expansion based homogenization theory, the multi-scale energy integration is proposed to bridge the gap between the micro and macro scales. By recalling the Helmholtz free energy based damage definition, the damage variable is represented by the multi-scale energy integration. Hence the damage evolution could be numerically simulated on the basis of the unit cell analysis rather than the experimental data identification. Finally the framework of the multi-scale damage theory is established by transforming the multi-scale damage evolution into the conventional continuum damage mechanics. The agree- ment between the simulated results and the benchmark results indicates the validity and effectiveness of the proposed theory.展开更多
A multi-scale model is developed to link the continuum damage variable in macroscale to the number density of multiple pits and cracks in microscale for studying the corrosion fatigue of aluminum alloy from multi-scal...A multi-scale model is developed to link the continuum damage variable in macroscale to the number density of multiple pits and cracks in microscale for studying the corrosion fatigue of aluminum alloy from multi-scale viewpoint.The developed model is used to predict the coherent multi-scale corrosion fatigue process of aluminum alloy component in the 3.5 wt% NaC1water solution under constant stress amplitude at a nominal frequency of 5Hz, and the numerical prediction results are compared with the experimental results.It shows that the model is effective and can be used to study the corrosion fatigue mechanisms of alurninum alloy from both macro and microscale viewpoints.展开更多
In order to better understand the fatigue mechanisms of steel structures working under high temperature, a multi-scale fatigue damage model at high temperature is developed. In the developed model, the macroscopic fat...In order to better understand the fatigue mechanisms of steel structures working under high temperature, a multi-scale fatigue damage model at high temperature is developed. In the developed model, the macroscopic fatigue damage of metallic materials due to the collective behavior of micro-cracks is quantified by using the generalized self-consistent method. The influence of temperature on fatigue damage of steel structures is quantified by using the previous creep damage model. In addition, the fatigue damage at room temperature and creep damage is coupled in the multi-scale fatigue damage model. The validity of the developed multi-scale damage model is verified by comparing the predicted damage evolution curve with the experimental data. It shows that the developed model is effectiveness. Finally, the fatigue analysis on steel crane runway girders (CRGs) of industrial steel melt shop is performed based on the developed model.展开更多
We present an in-depth study of the failure phenomenon of solid expandable tubular (SET) due to large expansion ratio in open holes of deep and ultra-deep wells. By examining the post-expansion SET, lots of microcrack...We present an in-depth study of the failure phenomenon of solid expandable tubular (SET) due to large expansion ratio in open holes of deep and ultra-deep wells. By examining the post-expansion SET, lots of microcracks are found on the inner surface of SET. Their morphology and parameters such as length and depth are investigated by use of metallographic microscope and scanning electron microscope (SEM). In addition, the Voronoi cell technique is adopted to characterize the multi-phase material microstructure of the SET. By using the anisotropic elastoplastic material constitutive model and macro/microscopic multi-dimensional cross-scale coupled boundary conditions, a sophisticated and multi-scale finite element model (FEM) of the SET is built successfully to simulate the material microstructure damage for different expansion ratios. The microcrack initiation and growth is simulated, and the structural integrity of the SET is discussed. It is concluded that this multi-scale finite element modeling method could effectively predict the elastoplastic deformation and the microscopic damage initiation and evolution of the SET. It is of great significance as a theoretical analysis tool to optimize the selection of appropriate tubular materials and it could be also used to substantially reduce costly failures of expandable tubulars in the field. This numerical analysis is not only beneficial for understanding the damage process of tubular materials but also effectively guides the engineering application of the SET technology.展开更多
Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters accordi...Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters according to the monitoring data information in the structural health monitoring(SHM)system,so as to provide a scientific basis for structural damage identification and dynamic model modification.In view of this,this paper reviews methods for identifying structural modal parameters under environmental excitation and briefly describes how to identify structural damages based on the derived modal parameters.The paper primarily introduces data-driven modal parameter recognition methods(e.g.,time-domain,frequency-domain,and time-frequency-domain methods,etc.),briefly describes damage identification methods based on the variations of modal parameters(e.g.,natural frequency,modal shapes,and curvature modal shapes,etc.)and modal validation methods(e.g.,Stability Diagram and Modal Assurance Criterion,etc.).The current status of the application of artificial intelligence(AI)methods in the direction of modal parameter recognition and damage identification is further discussed.Based on the pre-vious analysis,the main development trends of structural modal parameter recognition and damage identification methods are given to provide scientific references for the optimized design and functional upgrading of SHM systems.展开更多
Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer ...Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer composite plate by explosive welding.The microscopic properties of each bonding interface were elucidated through field emission scanning electron microscope and electron backscattered diffraction(EBSD).A methodology combining finite element method-smoothed particle hydrodynamics(FEM-SPH)and molecular dynamics(MD)was proposed for the analysis of the forming and evolution characteristics of explosive welding interfaces at multi-scale.The results demonstrate that the bonding interface morphologies of TC4/Al 6063 and Al 6063/Al 7075 exhibit a flat and wavy configuration,without discernible defects or cracks.The phenomenon of grain refinement is observed in the vicinity of the two bonding interfaces.Furthermore,the degree of plastic deformation of TC4 and Al 7075 is more pronounced than that of Al 6063 in the intermediate layer.The interface morphology characteristics obtained by FEM-SPH simulation exhibit a high degree of similarity to the experimental results.MD simulations reveal that the diffusion of interfacial elements predominantly occurs during the unloading phase,and the simulated thickness of interfacial diffusion aligns well with experimental outcomes.The introduction of intermediate layer in the explosive welding process can effectively produce high-quality titanium/aluminum alloy composite plates.Furthermore,this approach offers a multi-scale simulation strategy for the study of explosive welding bonding interfaces.展开更多
Investigating the combined effects of mining damage and creep damage on slope stability is crucial,as it can comprehensively reveal the non-linear deformation characteristics of rock under their joint influence.This s...Investigating the combined effects of mining damage and creep damage on slope stability is crucial,as it can comprehensively reveal the non-linear deformation characteristics of rock under their joint influence.This study develops a fractional-order nonlinear creep constitutive model that incorporates the double damage effect and implements a non-linear creep subroutine for soft rock using the threedimensional finite difference method on the FLAC3D platform.Comparative analysis of the theoretical,numerical,and experimental results reveals that the fractional-order constitutive model,which incorporates the double damage effect,accurately reflects the distinct deformation stages of green mudstone during creep failure and effectively captures the non-linear deformation in the accelerated creep phase.The numerical results show a fitting accuracy exceeding 97%with the creep test curves,significantly outperforming the 61%accuracy of traditional creep models.展开更多
Improving the volumetric energy density of supercapacitors is essential for practical applications,which highly relies on the dense storage of ions in carbon-based electrodes.The functional units of carbon-based elect...Improving the volumetric energy density of supercapacitors is essential for practical applications,which highly relies on the dense storage of ions in carbon-based electrodes.The functional units of carbon-based electrode exhibit multi-scale structural characteristics including macroscopic electrode morphologies,mesoscopic microcrystals and pores,and microscopic defects and dopants in the carbon basal plane.Therefore,the ordered combination of multi-scale structures of carbon electrode is crucial for achieving dense energy storage and high volumetric performance by leveraging the functions of various scale structu re.Considering that previous reviews have focused more on the discussion of specific scale structu re of carbon electrodes,this review takes a multi-scale perspective in which recent progresses regarding the structureperformance relationship,underlying mechanism and directional design of carbon-based multi-scale structures including carbon morphology,pore structure,carbon basal plane micro-environment and electrode technology on dense energy storage and volumetric property of supercapacitors are systematically discussed.We analyzed in detail the effects of the morphology,pore,and micro-environment of carbon electrode materials on ion dense storage,summarized the specific effects of different scale structures on volumetric property and recent research progress,and proposed the mutual influence and trade-off relationship between various scale structures.In addition,the challenges and outlooks for improving the dense storage and volumetric performance of carbon-based supercapacitors are analyzed,which can provide feasible technical reference and guidance for the design and manufacture of dense carbon-based electrode materials.展开更多
Convolutional neural networks(CNNs)-based medical image segmentation technologies have been widely used in medical image segmentation because of their strong representation and generalization abilities.However,due to ...Convolutional neural networks(CNNs)-based medical image segmentation technologies have been widely used in medical image segmentation because of their strong representation and generalization abilities.However,due to the inability to effectively capture global information from images,CNNs can easily lead to loss of contours and textures in segmentation results.Notice that the transformer model can effectively capture the properties of long-range dependencies in the image,and furthermore,combining the CNN and the transformer can effectively extract local details and global contextual features of the image.Motivated by this,we propose a multi-branch and multi-scale attention network(M2ANet)for medical image segmentation,whose architecture consists of three components.Specifically,in the first component,we construct an adaptive multi-branch patch module for parallel extraction of image features to reduce information loss caused by downsampling.In the second component,we apply residual block to the well-known convolutional block attention module to enhance the network’s ability to recognize important features of images and alleviate the phenomenon of gradient vanishing.In the third component,we design a multi-scale feature fusion module,in which we adopt adaptive average pooling and position encoding to enhance contextual features,and then multi-head attention is introduced to further enrich feature representation.Finally,we validate the effectiveness and feasibility of the proposed M2ANet method through comparative experiments on four benchmark medical image segmentation datasets,particularly in the context of preserving contours and textures.展开更多
The Zika virus(ZIKV),a member of the Flaviviridae family,attracted worldwide attention for its connection to severe neurological effects,notably microcephaly in newborns,first reported during the 2015 epidemic in Braz...The Zika virus(ZIKV),a member of the Flaviviridae family,attracted worldwide attention for its connection to severe neurological effects,notably microcephaly in newborns,first reported during the 2015 epidemic in Brazil.Yet,its impact goes beyond fetal and neonatal abnormalities,also affecting the central nervous system(CNS)in both children and adults,leading to enduring cognitive and behavioral impairments.展开更多
Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some sho...Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some shortcomings because of the low permeability and tightness of shale,complex gas flow behavior of multi-scale gas transport regions and multiple gas transport mechanism superpositions,and complex and variable production regimes of shale gas wells.Recent research has demonstrated the existence of a multi-stage isotope fractionation phenomenon during shale gas production,with the fractionation characteristics of each stage associated with the pore structure,gas in place(GIP),adsorption/desorption,and gas production process.This study presents a new approach for estimating shale gas well production and evaluating the adsorbed/free gas ratio throughout production using isotope fractionation techniques.A reservoir-scale carbon isotope fractionation(CIF)model applicable to the production process of shale gas wells was developed for the first time in this research.In contrast to the traditional model,this model improves production prediction accuracy by simultaneously fitting the gas production rate and δ^(13)C_(1) data and provides a new evaluation method of the adsorbed/free gas ratio during shale gas production.The results indicate that the diffusion and adsorption/desorption properties of rock,bottom-hole flowing pressure(BHP)of gas well,and multi-scale gas transport regions of the reservoir all affect isotope fractionation,with the diffusion and adsorption/desorption parameters of rock having the greatest effect on isotope fractionation being D∗/D,PL,VL,α,and others in that order.We effectively tested the universality of the four-stage isotope fractionation feature and revealed a unique isotope fractionation mechanism caused by the superimposed coupling of multi-scale gas transport regions during shale gas well production.Finally,we applied the established CIF model to a shale gas well in the Sichuan Basin,China,and calculated the estimated ultimate recovery(EUR)of the well to be 3.33×10^(8) m^(3);the adsorbed gas ratio during shale gas production was 1.65%,10.03%,and 23.44%in the first,fifth,and tenth years,respectively.The findings are significant for understanding the isotope fractionation mechanism during natural gas transport in complex systems and for formulating and optimizing unconventional natural gas development strategies.展开更多
The DDR(DNA damage response)is an essential cellular mechanism that detects and repairs DNA lesions to maintain genomic stability.Dysregulation of DDR pathways is frequently observed in human tumors,leading to increas...The DDR(DNA damage response)is an essential cellular mechanism that detects and repairs DNA lesions to maintain genomic stability.Dysregulation of DDR pathways is frequently observed in human tumors,leading to increased genomic instability and promoting tumor progression.Consequently,targeting DDR mechanisms has emerged as a promising therapeutic strategy in oncology.This review provides an overview of the major DDR pathways,highlighting the roles of key proteins involved in various DDR processes.A detailed understanding of these molecular mechanisms has paved the way for the development of targeted antitumor agents,including inhibitors of PARP1,ATM,ATR,CHK1,CHK2,DNA-PK,and WEE1.Additionally,the significant challenges in the development of DDR inhibitors are examined,including tumor microenvironment heterogeneity,resistance mechanisms,issues with selectivity and toxicity,and the complexities associated with clinical trial design.Finally,future directions and emerging strategies to improve DDR-targeted therapies are discussed.These strategies include biomarker-driven precision medicine,novel combination therapies,advanced drug delivery systems,and the potential application of artificial intelligence to optimize treatment outcomes.展开更多
The penetration-deflagration coupling damage performance of rod-like reactive shaped charge pene-trator(RRSCP)impacting thick steel plates is investigated by theoretical analysis and experiments.A penetration-deflagra...The penetration-deflagration coupling damage performance of rod-like reactive shaped charge pene-trator(RRSCP)impacting thick steel plates is investigated by theoretical analysis and experiments.A penetration-deflagration coupling damage model is developed to predict the penetration depth and cratering diameter.Four type of aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with densities of 2.3,2.7,3.5,and 4.5 g·cm^(-3) are selected to conduct the penetration experiments.The comparison results show that model predictions are in good agreement with the experimental data.By comparing the penetration depth and cratering diameter in the inert penetration mode and the penetration-deflagration coupling mode,the influence mechanism that the penetration-induced chemical response is unfavorable to penetration but has an enhanced cratering effect is revealed.From the formation characteristics,penetration effect and penetration-induced chemical reaction be-haviors,the influence of reactive liner density on the penetration-deflagration performance is further analyzed.The results show that increasing the density of reactive liner significantly increases both the kinetic energy and length of the reactive penetrator,meanwhile effectively reduces the weakened effect of penetration-induced chemical response,resulting in an enhanced penetration capability.However,due to the decreased diameter and potential energy content of reactive penetrator,the cratering capa-bility is weakened significantly.展开更多
This study examines the slug-induced vibration(SIV)response and fatigue behavior of offshore risers subjected to internal slug flow.A structural model incorporating internal slug flow dynamics is developed using the A...This study examines the slug-induced vibration(SIV)response and fatigue behavior of offshore risers subjected to internal slug flow.A structural model incorporating internal slug flow dynamics is developed using the Absolute Nodal Coordinate Formulation(ANCF)and a spatial-temporal density variation equation to analyze how slug flow parameters affect the SIV response of risers.Structural displacement,stress,and fatigue responses are systematically evaluated to characterize the structural behavior under SIV conditions.Longer slugs induce more pronounced traveling wave characteristics,while shorter slugs facilitate a mixed traveling-standing wave mode.Moreover,higher slug frequencies lead to increased fatigue accumulation,especially over an extended touchdown zone,thereby compromising the structural integrity of the riser.The findings yield valuable insights into the dynamic interactions between slug flow and riser response.This research advances the understanding of SIV mechanisms and provides a theoretical foundation for fatigue assessment and structural optimization,contributing to the safe and efficient design of offshore risers in deepwater environments.展开更多
Combined pulsed laser(CPL),introduced in 1975 for target damage,integrates different lasers to achieve high peak power and pulse energy.However,despite decades of research,CPL remains unused for long-range target dama...Combined pulsed laser(CPL),introduced in 1975 for target damage,integrates different lasers to achieve high peak power and pulse energy.However,despite decades of research,CPL remains unused for long-range target damage due to the challenge of maintaining high peak power density over long distances.We note that a potential solution lies in leveraging the air filament generated by femtosecond laser,which can transmit peak power densities higher than 1014 W/cm^(2)under the power clamping effect.To address this,a concept of a femtosecond laser induced air filament-CW CPL for surface damage of ceramics was introduced.We found no surface changes in ceramic targets when irradiated with a CW laser alone.By way of contrast,the target can be penetrated in a very short time(20 ms)with the assistance of the femtosecond laser induced air filament.In this context,we employ high-speed shadow imaging,cross-timescale simulation models and macro-microscopic characterization,to elucidate the CPL damage mechanism.The optimal CPL,combining a 1 mJ femtosecond laser and a 500 W CW laser,yields a damage rate of 1.51×10^(7)μm^(3)/J,representing an improvement of approximately 175%compared to single femtosecond laser ablation and around 59%enhancement compared to coating-assisted CW laser ablation.Furthermore,the efficacy of the proposed femtosecond-CW CPL method is demonstrated in causing penetration damage of ceramic/metal composite material or direct damage of sapphire,showcasing its versatility in damaging applications.Consequently,the femtosecond-CW CPL ablation method presented in this paper holds great promise as a new type of damage method for transparent hard and brittle materials.展开更多
The loaded rock experiences multiple stages of deformation.It starts with the formation of microcracks at low stresses(crack initiation,CI)and then transitions into unstable crack propagation(crack damage,CD)near the ...The loaded rock experiences multiple stages of deformation.It starts with the formation of microcracks at low stresses(crack initiation,CI)and then transitions into unstable crack propagation(crack damage,CD)near the ultimate strength.In this study,both the acoustic emission method(AEM)and the ultrasonic testing method(UTM)were used to examine the characteristics of AE parameters(b-value,peak frequency,frequency-band energy ratio,and fractal dimension)and ultrasonic(ULT)properties(velocity,amplitude,energy attenuation,and scattering attenuation)of bedded shale at CI,CD,and ultimate strength.The comparison involved analyzing the strain-based method(SBM),AEM,and UTM to determine the thresholds for damage stress.A fuzzy comprehensive evaluation model(FCEM)was created to describe the damage thresholds and hazard assessment.The results indicate that the optimal AE and ULT parameters for identifying CI and CD stress are ringing count,ultrasonic amplitude,energy attenuation,and scattering attenuation of the S-wave.Besides,damage thresholds were detected earlier by AE monitoring,ranging from 3 MPa to 10 MPa.CI and CD identified by UTM occurred later than SBM and AEM,and were in the range of 12 MPa.The b-value,peak frequency,energy ratio in the low-frequency band(0e62.5 kHz),correlation dimension,and sandbox dimension showed low values at the peak stress,while the energy ratio in a moderate-frequency band(187.5e281.25 kHz)and amplitude showed high values.The successful application of FCEM to laboratory testing of shales has demonstrated its ability to quantitatively identify AE/ULT precursors of seismic hazards associated with rock failure.展开更多
基金National Key Research and Development Program of China (No.2021YFC3100800)the National Natural Science Foundation of China (Nos.42407235 and 42271026)+1 种基金the Project of Sanya Yazhou Bay Science and Technology City (No.SCKJ-JYRC-2023-54)supported by the Hefei advanced computing center
文摘Coral reef limestone(CRL)constitutes a distinctive marine carbonate formation with complex mechanical properties.This study investigates the multiscale damage and fracture mechanisms of CRL through integrated experimental testing,digital core technology,and theoretical modelling.Two CRL types with contrasting mesostructures were characterized across three scales.Macroscopically,CRL-I and CRL-II exhibited mean compressive strengths of 8.46 and 5.17 MPa,respectively.Mesoscopically,CRL-I featured small-scale highly interconnected pores,whilst CRL-II developed larger stratified pores with diminished connectivity.Microscopically,both CRL matrices demonstrated remarkable similarity in mineral composition and mechanical properties.A novel voxel average-based digital core scaling methodology was developed to facilitate numerical simulation of cross-scale damage processes,revealing network-progressive failure in CRL-I versus directional-brittle failure in CRL-II.Furthermore,a damage statistical constitutive model based on digital core technology and mesoscopic homogenisation theory established quantitative relationships between microelement strength distribution and macroscopic mechanical behavior.These findings illuminate the fundamental mechanisms through which mesoscopic structure governs the macroscopic mechanical properties of CRL.
基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20170680)the National Natural Science Foundation of China(Grant No.51708106)are gratefully appreciated.
文摘In the present paper,a hierarchical multi-scale method is developed for the nonlinear analysis of composite materials undergoing heterogeneity and damage.Starting from the homogenization theory,the energy equivalence between scales is developed.Then accompanied with the energy based damage model,the multi-scale damage evolutions are resolved by homogenizing the energy scalar over the meso-cell.The macroscopic behaviors described by the multi-scale damage evolutions represent the mesoscopic heterogeneity and damage of the composites.A rather simple structure made from particle reinforced composite materials is developed as a numerical example.The agreement between the fullscale simulating results and the multi-scale simulating results demonstrates the capacity of the proposed model to simulate nonlinear behaviors of quasi-brittle composite materials within the multi-scale framework.
基金National Science Foundation of China under Grant No.51808499Science Foundation of Zhejiang Province of China under the Grant No.LQ18E080009 and2018C03033-2 is gratefully acknowledged.
文摘A multi-scale damage model of concrete is proposed based on the concept of energy equivalent strain for generic two-or three-dimensional applications.Continuum damage mechanics serves as the framework to describe the basic damage variables,namely the tensile and compressive damage.The homogenized Helmholtz free energy is introduced as the bridge to link the micro-cell and macroscopic material.The crack propagation in micro-cells is modeled,and the Helmholtz free energy in the cracked micro-structure is calculated and employed to extract the damage evolution functions in the macroscopic material.Based on the damage energy release rates and damage consistent condition,the energy equivalent strain is used to expand the uniaxial damage model to the multi-dimensional damage model.Agreements with existing experimental data that include uniaxial tensile and compressive tests,biaxial compression and biaxial peak stress envelop demonstrate the capacity of the multi-scale damage model in reproducing the typical nonlinear performances of concrete specimens.The simulation of precast laminated concrete slab further demonstrates its application to concrete structures.
基金supported by the National Key Research and Development Program of China,No.2019YFA0111200the National Natural Science Foundation of China,Nos.U23A20436,82371047+3 种基金Key Research Project in Shanxi Province,No.202302130501008Shanxi Provincial Science Fund for Distinguished Young Scholars,No.202103021221008Key Research and Development Program in Shanxi Province,No.202204051001023Shanxi Medical University Doctor’s Startup Fund Project,No.SD22028(all to YG)。
文摘Retinal ganglion cells are the bridging neurons between the eye and the central nervous system,transmitting visual signals to the brain.The injury and loss of retinal ganglion cells are the primary pathological changes in several retinal degenerative diseases,including glaucoma,ischemic optic neuropathy,diabetic neuropathy,and optic neuritis.In mammals,injured retinal ganglion cells lack regenerative capacity and undergo apoptotic cell death within a few days of injury.Additionally,these cells exhibit limited regenerative ability,ultimately contributing to vision impairment and potentially leading to blindness.Currently,the only effective clinical treatment for glaucoma is to prevent vision loss by lowering intraocular pressure through medications or surgery;however,this approach cannot halt the effect of retinal ganglion cell loss on visual function.This review comprehensively investigates the mechanisms underlying retinal ganglion cell degeneration in retinal degenerative diseases and further explores the current status and potential of cell replacement therapy for regenerating retinal ganglion cells.As our understanding of the complex processes involved in retinal ganglion cell degeneration deepens,we can explore new treatment strategies,such as cell transplantation,which may offer more effective ways to mitigate the effect of retinal degenerative diseases on vision.
基金supported by the National Natural Science Foundation ofChina (Grant No. 90715033)
文摘The research of modern mechanics reveals that the damage and failure of structures should be considered on different scales. The present paper is dedicated to establishing the multi-scale damage theory for the nonlinear structural analysis. Starting from the asymptotic expansion based homogenization theory, the multi-scale energy integration is proposed to bridge the gap between the micro and macro scales. By recalling the Helmholtz free energy based damage definition, the damage variable is represented by the multi-scale energy integration. Hence the damage evolution could be numerically simulated on the basis of the unit cell analysis rather than the experimental data identification. Finally the framework of the multi-scale damage theory is established by transforming the multi-scale damage evolution into the conventional continuum damage mechanics. The agree- ment between the simulated results and the benchmark results indicates the validity and effectiveness of the proposed theory.
基金Fundamental Research Funds for the Central Universities,Natural Science Foundation of Jiangsu Province (BK20170655,BK20170677),and the National Program on Key Research Project (2016YFC0701301-02).
文摘A multi-scale model is developed to link the continuum damage variable in macroscale to the number density of multiple pits and cracks in microscale for studying the corrosion fatigue of aluminum alloy from multi-scale viewpoint.The developed model is used to predict the coherent multi-scale corrosion fatigue process of aluminum alloy component in the 3.5 wt% NaC1water solution under constant stress amplitude at a nominal frequency of 5Hz, and the numerical prediction results are compared with the experimental results.It shows that the model is effective and can be used to study the corrosion fatigue mechanisms of alurninum alloy from both macro and microscale viewpoints.
文摘In order to better understand the fatigue mechanisms of steel structures working under high temperature, a multi-scale fatigue damage model at high temperature is developed. In the developed model, the macroscopic fatigue damage of metallic materials due to the collective behavior of micro-cracks is quantified by using the generalized self-consistent method. The influence of temperature on fatigue damage of steel structures is quantified by using the previous creep damage model. In addition, the fatigue damage at room temperature and creep damage is coupled in the multi-scale fatigue damage model. The validity of the developed multi-scale damage model is verified by comparing the predicted damage evolution curve with the experimental data. It shows that the developed model is effectiveness. Finally, the fatigue analysis on steel crane runway girders (CRGs) of industrial steel melt shop is performed based on the developed model.
基金Project supported by the National Major Science & Technology Project of China (Grant No. 2016ZX05020-003).
文摘We present an in-depth study of the failure phenomenon of solid expandable tubular (SET) due to large expansion ratio in open holes of deep and ultra-deep wells. By examining the post-expansion SET, lots of microcracks are found on the inner surface of SET. Their morphology and parameters such as length and depth are investigated by use of metallographic microscope and scanning electron microscope (SEM). In addition, the Voronoi cell technique is adopted to characterize the multi-phase material microstructure of the SET. By using the anisotropic elastoplastic material constitutive model and macro/microscopic multi-dimensional cross-scale coupled boundary conditions, a sophisticated and multi-scale finite element model (FEM) of the SET is built successfully to simulate the material microstructure damage for different expansion ratios. The microcrack initiation and growth is simulated, and the structural integrity of the SET is discussed. It is concluded that this multi-scale finite element modeling method could effectively predict the elastoplastic deformation and the microscopic damage initiation and evolution of the SET. It is of great significance as a theoretical analysis tool to optimize the selection of appropriate tubular materials and it could be also used to substantially reduce costly failures of expandable tubulars in the field. This numerical analysis is not only beneficial for understanding the damage process of tubular materials but also effectively guides the engineering application of the SET technology.
基金supported by the Innovation Foundation of Provincial Education Department of Gansu(2024B-005)the Gansu Province National Science Foundation(22YF7GA182)the Fundamental Research Funds for the Central Universities(No.lzujbky2022-kb01)。
文摘Modal parameters can accurately characterize the structural dynamic properties and assess the physical state of the structure.Therefore,it is particularly significant to identify the structural modal parameters according to the monitoring data information in the structural health monitoring(SHM)system,so as to provide a scientific basis for structural damage identification and dynamic model modification.In view of this,this paper reviews methods for identifying structural modal parameters under environmental excitation and briefly describes how to identify structural damages based on the derived modal parameters.The paper primarily introduces data-driven modal parameter recognition methods(e.g.,time-domain,frequency-domain,and time-frequency-domain methods,etc.),briefly describes damage identification methods based on the variations of modal parameters(e.g.,natural frequency,modal shapes,and curvature modal shapes,etc.)and modal validation methods(e.g.,Stability Diagram and Modal Assurance Criterion,etc.).The current status of the application of artificial intelligence(AI)methods in the direction of modal parameter recognition and damage identification is further discussed.Based on the pre-vious analysis,the main development trends of structural modal parameter recognition and damage identification methods are given to provide scientific references for the optimized design and functional upgrading of SHM systems.
基金Opening Foundation of Key Laboratory of Explosive Energy Utilization and Control,Anhui Province(BP20240104)Graduate Innovation Program of China University of Mining and Technology(2024WLJCRCZL049)Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX24_2701)。
文摘Because of the challenge of compounding lightweight,high-strength Ti/Al alloys due to their considerable disparity in properties,Al 6063 as intermediate layer was proposed to fabricate TC4/Al 6063/Al 7075 three-layer composite plate by explosive welding.The microscopic properties of each bonding interface were elucidated through field emission scanning electron microscope and electron backscattered diffraction(EBSD).A methodology combining finite element method-smoothed particle hydrodynamics(FEM-SPH)and molecular dynamics(MD)was proposed for the analysis of the forming and evolution characteristics of explosive welding interfaces at multi-scale.The results demonstrate that the bonding interface morphologies of TC4/Al 6063 and Al 6063/Al 7075 exhibit a flat and wavy configuration,without discernible defects or cracks.The phenomenon of grain refinement is observed in the vicinity of the two bonding interfaces.Furthermore,the degree of plastic deformation of TC4 and Al 7075 is more pronounced than that of Al 6063 in the intermediate layer.The interface morphology characteristics obtained by FEM-SPH simulation exhibit a high degree of similarity to the experimental results.MD simulations reveal that the diffusion of interfacial elements predominantly occurs during the unloading phase,and the simulated thickness of interfacial diffusion aligns well with experimental outcomes.The introduction of intermediate layer in the explosive welding process can effectively produce high-quality titanium/aluminum alloy composite plates.Furthermore,this approach offers a multi-scale simulation strategy for the study of explosive welding bonding interfaces.
基金support from the National Natural Science Foundation of China(No.52308316)the Scientific Research Foundation of Weifang University(Grant No.2024BS42)+2 种基金China Postdoctoral Science Foundation(No.2022M721885)the Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province(No.ZJRMG-2022-01)supported by Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(NO.SKLGME023017).
文摘Investigating the combined effects of mining damage and creep damage on slope stability is crucial,as it can comprehensively reveal the non-linear deformation characteristics of rock under their joint influence.This study develops a fractional-order nonlinear creep constitutive model that incorporates the double damage effect and implements a non-linear creep subroutine for soft rock using the threedimensional finite difference method on the FLAC3D platform.Comparative analysis of the theoretical,numerical,and experimental results reveals that the fractional-order constitutive model,which incorporates the double damage effect,accurately reflects the distinct deformation stages of green mudstone during creep failure and effectively captures the non-linear deformation in the accelerated creep phase.The numerical results show a fitting accuracy exceeding 97%with the creep test curves,significantly outperforming the 61%accuracy of traditional creep models.
基金funded by the Joint Fund for Regional Innovation and Development of National Natural Science Foundation of China(U21A20143)the National Science Fund for Excellent Young Scholars(52322607)the Excellent Youth Foundation of Heilongjiang Scientific Committee(YQ2022E028)。
文摘Improving the volumetric energy density of supercapacitors is essential for practical applications,which highly relies on the dense storage of ions in carbon-based electrodes.The functional units of carbon-based electrode exhibit multi-scale structural characteristics including macroscopic electrode morphologies,mesoscopic microcrystals and pores,and microscopic defects and dopants in the carbon basal plane.Therefore,the ordered combination of multi-scale structures of carbon electrode is crucial for achieving dense energy storage and high volumetric performance by leveraging the functions of various scale structu re.Considering that previous reviews have focused more on the discussion of specific scale structu re of carbon electrodes,this review takes a multi-scale perspective in which recent progresses regarding the structureperformance relationship,underlying mechanism and directional design of carbon-based multi-scale structures including carbon morphology,pore structure,carbon basal plane micro-environment and electrode technology on dense energy storage and volumetric property of supercapacitors are systematically discussed.We analyzed in detail the effects of the morphology,pore,and micro-environment of carbon electrode materials on ion dense storage,summarized the specific effects of different scale structures on volumetric property and recent research progress,and proposed the mutual influence and trade-off relationship between various scale structures.In addition,the challenges and outlooks for improving the dense storage and volumetric performance of carbon-based supercapacitors are analyzed,which can provide feasible technical reference and guidance for the design and manufacture of dense carbon-based electrode materials.
基金supported by the Natural Science Foundation of the Anhui Higher Education Institutions of China(Grant Nos.2023AH040149 and 2024AH051915)the Anhui Provincial Natural Science Foundation(Grant No.2208085MF168)+1 种基金the Science and Technology Innovation Tackle Plan Project of Maanshan(Grant No.2024RGZN001)the Scientific Research Fund Project of Anhui Medical University(Grant No.2023xkj122).
文摘Convolutional neural networks(CNNs)-based medical image segmentation technologies have been widely used in medical image segmentation because of their strong representation and generalization abilities.However,due to the inability to effectively capture global information from images,CNNs can easily lead to loss of contours and textures in segmentation results.Notice that the transformer model can effectively capture the properties of long-range dependencies in the image,and furthermore,combining the CNN and the transformer can effectively extract local details and global contextual features of the image.Motivated by this,we propose a multi-branch and multi-scale attention network(M2ANet)for medical image segmentation,whose architecture consists of three components.Specifically,in the first component,we construct an adaptive multi-branch patch module for parallel extraction of image features to reduce information loss caused by downsampling.In the second component,we apply residual block to the well-known convolutional block attention module to enhance the network’s ability to recognize important features of images and alleviate the phenomenon of gradient vanishing.In the third component,we design a multi-scale feature fusion module,in which we adopt adaptive average pooling and position encoding to enhance contextual features,and then multi-head attention is introduced to further enrich feature representation.Finally,we validate the effectiveness and feasibility of the proposed M2ANet method through comparative experiments on four benchmark medical image segmentation datasets,particularly in the context of preserving contours and textures.
文摘The Zika virus(ZIKV),a member of the Flaviviridae family,attracted worldwide attention for its connection to severe neurological effects,notably microcephaly in newborns,first reported during the 2015 epidemic in Brazil.Yet,its impact goes beyond fetal and neonatal abnormalities,also affecting the central nervous system(CNS)in both children and adults,leading to enduring cognitive and behavioral impairments.
基金supported by the Natural Science Foundation of China(Grant No.42302170)National Postdoctoral Innovative Talent Support Program(Grant No.BX20220062)+3 种基金CNPC Innovation Found(Grant No.2022DQ02-0104)National Science Foundation of Heilongjiang Province of China(Grant No.YQ2023D001)Postdoctoral Science Foundation of Heilongjiang Province of China(Grant No.LBH-Z22091)the Natural Science Foundation of Shandong Province(Grant No.ZR2022YQ30).
文摘Prediction of production decline and evaluation of the adsorbed/free gas ratio are critical for determining the lifespan and production status of shale gas wells.Traditional production prediction methods have some shortcomings because of the low permeability and tightness of shale,complex gas flow behavior of multi-scale gas transport regions and multiple gas transport mechanism superpositions,and complex and variable production regimes of shale gas wells.Recent research has demonstrated the existence of a multi-stage isotope fractionation phenomenon during shale gas production,with the fractionation characteristics of each stage associated with the pore structure,gas in place(GIP),adsorption/desorption,and gas production process.This study presents a new approach for estimating shale gas well production and evaluating the adsorbed/free gas ratio throughout production using isotope fractionation techniques.A reservoir-scale carbon isotope fractionation(CIF)model applicable to the production process of shale gas wells was developed for the first time in this research.In contrast to the traditional model,this model improves production prediction accuracy by simultaneously fitting the gas production rate and δ^(13)C_(1) data and provides a new evaluation method of the adsorbed/free gas ratio during shale gas production.The results indicate that the diffusion and adsorption/desorption properties of rock,bottom-hole flowing pressure(BHP)of gas well,and multi-scale gas transport regions of the reservoir all affect isotope fractionation,with the diffusion and adsorption/desorption parameters of rock having the greatest effect on isotope fractionation being D∗/D,PL,VL,α,and others in that order.We effectively tested the universality of the four-stage isotope fractionation feature and revealed a unique isotope fractionation mechanism caused by the superimposed coupling of multi-scale gas transport regions during shale gas well production.Finally,we applied the established CIF model to a shale gas well in the Sichuan Basin,China,and calculated the estimated ultimate recovery(EUR)of the well to be 3.33×10^(8) m^(3);the adsorbed gas ratio during shale gas production was 1.65%,10.03%,and 23.44%in the first,fifth,and tenth years,respectively.The findings are significant for understanding the isotope fractionation mechanism during natural gas transport in complex systems and for formulating and optimizing unconventional natural gas development strategies.
文摘The DDR(DNA damage response)is an essential cellular mechanism that detects and repairs DNA lesions to maintain genomic stability.Dysregulation of DDR pathways is frequently observed in human tumors,leading to increased genomic instability and promoting tumor progression.Consequently,targeting DDR mechanisms has emerged as a promising therapeutic strategy in oncology.This review provides an overview of the major DDR pathways,highlighting the roles of key proteins involved in various DDR processes.A detailed understanding of these molecular mechanisms has paved the way for the development of targeted antitumor agents,including inhibitors of PARP1,ATM,ATR,CHK1,CHK2,DNA-PK,and WEE1.Additionally,the significant challenges in the development of DDR inhibitors are examined,including tumor microenvironment heterogeneity,resistance mechanisms,issues with selectivity and toxicity,and the complexities associated with clinical trial design.Finally,future directions and emerging strategies to improve DDR-targeted therapies are discussed.These strategies include biomarker-driven precision medicine,novel combination therapies,advanced drug delivery systems,and the potential application of artificial intelligence to optimize treatment outcomes.
基金supported by the National Natural Science Foundation of China(Grant No.12172052)the Foundation of State Key Laboratory of Explosion Science and Safety Protection(Grant No.QKKT24-02).
文摘The penetration-deflagration coupling damage performance of rod-like reactive shaped charge pene-trator(RRSCP)impacting thick steel plates is investigated by theoretical analysis and experiments.A penetration-deflagration coupling damage model is developed to predict the penetration depth and cratering diameter.Four type of aluminum-polytetrafluoroethylene-copper(Al-PTFE-Cu)reactive liners with densities of 2.3,2.7,3.5,and 4.5 g·cm^(-3) are selected to conduct the penetration experiments.The comparison results show that model predictions are in good agreement with the experimental data.By comparing the penetration depth and cratering diameter in the inert penetration mode and the penetration-deflagration coupling mode,the influence mechanism that the penetration-induced chemical response is unfavorable to penetration but has an enhanced cratering effect is revealed.From the formation characteristics,penetration effect and penetration-induced chemical reaction be-haviors,the influence of reactive liner density on the penetration-deflagration performance is further analyzed.The results show that increasing the density of reactive liner significantly increases both the kinetic energy and length of the reactive penetrator,meanwhile effectively reduces the weakened effect of penetration-induced chemical response,resulting in an enhanced penetration capability.However,due to the decreased diameter and potential energy content of reactive penetrator,the cratering capa-bility is weakened significantly.
基金financially supported by the National Natural Science Foundation of China(Grant No.52222111)the Science Foundation of China University of Petroleum,Beijing(Grant No.2462025SZBH002)。
文摘This study examines the slug-induced vibration(SIV)response and fatigue behavior of offshore risers subjected to internal slug flow.A structural model incorporating internal slug flow dynamics is developed using the Absolute Nodal Coordinate Formulation(ANCF)and a spatial-temporal density variation equation to analyze how slug flow parameters affect the SIV response of risers.Structural displacement,stress,and fatigue responses are systematically evaluated to characterize the structural behavior under SIV conditions.Longer slugs induce more pronounced traveling wave characteristics,while shorter slugs facilitate a mixed traveling-standing wave mode.Moreover,higher slug frequencies lead to increased fatigue accumulation,especially over an extended touchdown zone,thereby compromising the structural integrity of the riser.The findings yield valuable insights into the dynamic interactions between slug flow and riser response.This research advances the understanding of SIV mechanisms and provides a theoretical foundation for fatigue assessment and structural optimization,contributing to the safe and efficient design of offshore risers in deepwater environments.
基金supports from National Natural Science Foundation of China(Grant No.52105498)The science and technology innovation Program of Hunan Province(Grant No.2021RC3074)+2 种基金Advanced Laser Technology Laboratory of Anhui Province(AHL2022KF04)National Key R&D Program of China(Grant No.2023YFB14605500)Changsha Natural Science Foundation(kq2402089).
文摘Combined pulsed laser(CPL),introduced in 1975 for target damage,integrates different lasers to achieve high peak power and pulse energy.However,despite decades of research,CPL remains unused for long-range target damage due to the challenge of maintaining high peak power density over long distances.We note that a potential solution lies in leveraging the air filament generated by femtosecond laser,which can transmit peak power densities higher than 1014 W/cm^(2)under the power clamping effect.To address this,a concept of a femtosecond laser induced air filament-CW CPL for surface damage of ceramics was introduced.We found no surface changes in ceramic targets when irradiated with a CW laser alone.By way of contrast,the target can be penetrated in a very short time(20 ms)with the assistance of the femtosecond laser induced air filament.In this context,we employ high-speed shadow imaging,cross-timescale simulation models and macro-microscopic characterization,to elucidate the CPL damage mechanism.The optimal CPL,combining a 1 mJ femtosecond laser and a 500 W CW laser,yields a damage rate of 1.51×10^(7)μm^(3)/J,representing an improvement of approximately 175%compared to single femtosecond laser ablation and around 59%enhancement compared to coating-assisted CW laser ablation.Furthermore,the efficacy of the proposed femtosecond-CW CPL method is demonstrated in causing penetration damage of ceramic/metal composite material or direct damage of sapphire,showcasing its versatility in damaging applications.Consequently,the femtosecond-CW CPL ablation method presented in this paper holds great promise as a new type of damage method for transparent hard and brittle materials.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U20A20266 and 12302503)Scientific and technological research projects in Sichuan province(Grant No.2024NSFSC0973).
文摘The loaded rock experiences multiple stages of deformation.It starts with the formation of microcracks at low stresses(crack initiation,CI)and then transitions into unstable crack propagation(crack damage,CD)near the ultimate strength.In this study,both the acoustic emission method(AEM)and the ultrasonic testing method(UTM)were used to examine the characteristics of AE parameters(b-value,peak frequency,frequency-band energy ratio,and fractal dimension)and ultrasonic(ULT)properties(velocity,amplitude,energy attenuation,and scattering attenuation)of bedded shale at CI,CD,and ultimate strength.The comparison involved analyzing the strain-based method(SBM),AEM,and UTM to determine the thresholds for damage stress.A fuzzy comprehensive evaluation model(FCEM)was created to describe the damage thresholds and hazard assessment.The results indicate that the optimal AE and ULT parameters for identifying CI and CD stress are ringing count,ultrasonic amplitude,energy attenuation,and scattering attenuation of the S-wave.Besides,damage thresholds were detected earlier by AE monitoring,ranging from 3 MPa to 10 MPa.CI and CD identified by UTM occurred later than SBM and AEM,and were in the range of 12 MPa.The b-value,peak frequency,energy ratio in the low-frequency band(0e62.5 kHz),correlation dimension,and sandbox dimension showed low values at the peak stress,while the energy ratio in a moderate-frequency band(187.5e281.25 kHz)and amplitude showed high values.The successful application of FCEM to laboratory testing of shales has demonstrated its ability to quantitatively identify AE/ULT precursors of seismic hazards associated with rock failure.
