Background:Human skin is affected by ultraviolet rays on a daily basis,and excessive ultraviolet radiation(UVR)can lead to sunburn erythema,tanning,photoaging,and skin tumors.The combination of Astragali Radix(AR)and ...Background:Human skin is affected by ultraviolet rays on a daily basis,and excessive ultraviolet radiation(UVR)can lead to sunburn erythema,tanning,photoaging,and skin tumors.The combination of Astragali Radix(AR)and Anemarrhenae Rhizoma(AAR)is a common pairing in traditional Chinese medicine(TCM).According to earlier studies,they possess properties capable of alleviating the adverse impacts of UVR on the skin.However,the specific actions and underlying mechanisms require further investigation.The study aims to analyze the efficacy of AR-AAR in preventing UVR-induced skin damage and to clarify the associated molecular mechanisms.Methods:Potential signaling pathways by which AR and AAR may protect against UVR-induced skin damage were identified with network pharmacology,molecular docking techniques and molecular dynamics(MD)simulation.Except the normal group,the back skin of SD rats was exposed to 1.1 mW/cm^(2) UVA combined with 0.1 mW/cm^(2) UVB daily,and the UVR skin damage model was established.Morphological features of skin tissues of different groups were discovered through Hematoxylin and Eosin(HE)staining,Masson staining,Weigert staining.ELISA was utilized to measure the levels of reactive oxygen species(ROS),Interleukin 6(IL-6),Interleukin 1β(IL-1β)and Tumor necrosis factos-α(TNF-α)in skin tissues.RT-PCR and Western blot were employed to quantify the mRNA and protein contents of PI3K,AKT,and MMP-9.Results:Network pharmacology analysis predicts that AR-AAR may improve skin damage induced by UVR through the PI3K/AKT signaling pathway.Histological staining shows that AR-AAR can significantly reduce inflammatory infiltration and fibrosis in damaged skin.Treatment with AR-AAR(2:1)significantly reduced the expression levels of IL-1β,IL-6,TNF-αand ROS in UVR-damaged rat skin.After treatment with AR-AAR(2:1),not only did the relative mRNA expression levels of PI3K and AKT and the protein expression levels of PI3K,AKT,P-PI3K,and P-AKT increase,but the mRNA and protein expression levels of MMP-9 decreased.Conclusion:The study indicate that the AR-AAR combination and its active components may mitigate UVR skin damage by modulating the PI3K/AKT signaling pathway.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
Deep hole pre-cracking blasting(DHPB)technology is the preferred means of preventing and controlling rockburst induced by hard-thick rock layers in coal mines.When DHPB is applied to hard-thick rock layers,the insuffi...Deep hole pre-cracking blasting(DHPB)technology is the preferred means of preventing and controlling rockburst induced by hard-thick rock layers in coal mines.When DHPB is applied to hard-thick rock layers,the insufficient knowledge about the crack extension scale under different rock properties and blasting parameters may result in undesirable pressure relief.Therefore,LS-DYNA was adopted to analyse the crack extension characteristics under the combined effect of rock tensile strength,explosive density,blasthole spacing,and decoupled coefficient.The Holmquist–Johnson–Cook model(HJC),verified by the results of blasting experiment and numerical simulation in literature,was used to characterise coal-bearing rocks.Numerical analysis was conducted to study the blasting crack extension and fractal damage for rock tensile strength,explosive densities,blasthole spacing,and decoupled coefficients.The results show that the tensile strength of rock is the key factor for blasting design.The fractal damage caused by blasting increases when the tensile strength of rock decreases.For rocks with lower tensile strength,more blasting energy is consumed by the increasing damage area in the crushed zone.Higher explosive density can promote the development of blasting cracks and increase fractal damage,but the increasing range of the crushed zone also wastes a large amount of energy.As the blasthole spacing increases,the fractal damage decreases,and the crack extension scale in the fractured zone first increases and then decreases,and eventually remains almost unchanged.An optimum interval exists for the decoupled coefficient,and the full utilization of explosive energy within the interval leads to penetrating blast cracks and smaller crushed zones.Based on the simulation results,the optimal blasting parameters for coarse sandstone were validated in the field practice.Monitoring data show that the optimized blasting significantly reduces the risk of rockburst.展开更多
In order to study the mechanical properties of damaged reinforced concrete(RC)beams reinforced with ultra-high-performance concrete(UHPC),a four-point bending test was conducted to systematically investigate the influ...In order to study the mechanical properties of damaged reinforced concrete(RC)beams reinforced with ultra-high-performance concrete(UHPC),a four-point bending test was conducted to systematically investigate the influence of factors such as the number of reinforcement surfaces and the degree of damage.The results indicate that single-sided repaired beams have certain advantages in crack resistance performance,but are more disadvantageous in ultimate bearing capacity,with obvious debonding phenomenon before the end of loading.Compared with single-sided reinforcement,the cracking load of the three-sided reinforced beam increased by an average of 1.85 times,the ultimate bearing capacity increased by an average of 177.5%,and a good UHPC-RC combination effect could be formed,which could work synergistically until the end of loading.The degree of pre damage has a significant impact on the crack resistance performance of reinforced beams,while its impact on the ultimate bearing capacity is relatively limited.When the pre splitting width of the RC beam increases from 0.2 mm to 0.4 mm,the ultimate bearing capacity decreases by 28.33%.展开更多
Ensuring the structural integrity of piping systems is crucial in industrial operations to prevent catastrophic failures and minimize shutdown time.This study investigates a transportation-damaged pipe exposed to high...Ensuring the structural integrity of piping systems is crucial in industrial operations to prevent catastrophic failures and minimize shutdown time.This study investigates a transportation-damaged pipe exposed to high-temperature conditions and cyclic loading,representing a realistic challenge in plant operation.The objective was to evaluate the service life and integrity assessment parameters of the damaged pipe,subjected to 22,000 operational cycles under two daily charge and discharge conditions.The flaw size in the damaged pipe was determined based on a failure assessment procedure,ensuring a conservative and reliable input.The damage was characterized as a long axial surface crack with a depth of a=2 mm and half-length c=50 mm(c/a=25),a geometry not well covered by existing Stress Intensity Factor solutions.To address this limitation,a modified magnification factor(M*)was introduced and tested for the present damage case(c/a=25)and for additional crack geometries(c/a=28–70),which showed improved agreement with Finite Element Analysis(FEA)than Newman’s original formulation.Stress Intensity Factor and Plastic Limit Pressure,essential parameters for structural integrity assessment,were computed numerically using FEA and validated against analytical predictions.Fatigue crack growth was evaluated using the Paris law with crack propagation simulated numerically by Ansys’s S.M.A.R.T.The Failure Assessment Diagram(FAD)was used to assess service life,incorporating constant working pressure and fracture toughness while considering evolving crack size during propagation.Results showed that analytical predictions with the modified magnification factor matched FEA within 5%,while the original Newman formulation overestimated results.The analytical service life solution predicted approximately 8500 fewer cycles than the numerical,remaining conservative but efficient.These findings are based on the present case of a long axial surface crack with high aspect ratios(c/a=25–70,depending on crack depth),and while the modified magnification factor may also improve predictions for other geometries,this requires structured validation in future studies.展开更多
This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mini...This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mining technology associated with SIETCS differ significantly from those of generally inclined coal seams,resulting in notable variations in roadway stress distributions.On SIETCS have predominantly examined the impact of rock layers flanking coal seams on rock bursts,with limited emphasis on SIETCS roadways.This study employs comprehensive methods,integrating numerical simulations,theoretical analyses,and field detections to investigate the stress distribution of SIETCS and the mechanisms of rock burst-induced vertical damage,subsequently validated in situ.The vertical stress in SIETCS is minimal,while horizontal stress is concentrated,leading to the formation of layered crack structures(LCS)that distribute above and below the roadways.Additionally,elastic energy significantly concentrates within the LCS.Axial dynamic compressive stress and vertical dynamic tensile stress along the LCS diminish its stability,readily triggering failure.During the LCS failure process,the stored energy is released,converting into kinetic energy required for coal body ejection after reaching the minimum energy for failure and dissipative energy,ultimately leading to rock burst-induced vertical damage in roadways.On-site detection and analysis within SIETCS,along with historical rock burst data,confirm the existence of LCS and its role in inducing vertical rock burst damage.This research establishes essential foundations for preventing rock bursts within SIETCS.展开更多
A thermal-mechanical-damage coupled finite elements model was established to investigate temperature changes, edge cracks and rolling force during roiling of magnesium alloy sheet. A cuneal sheet was also adopted to s...A thermal-mechanical-damage coupled finite elements model was established to investigate temperature changes, edge cracks and rolling force during roiling of magnesium alloy sheet. A cuneal sheet was also adopted to study the influence of reduction on temperature, damage and rolling force. The results show that with increasing the reduction, the rolling force increases, and the temperature of the Mg sheet decreases. Edge cracks occur when the reduction is above 51.6%, with the damage value of above 0.49. The plastic-damage in Mg sheet rolling is a result of hole development, shearing deformation and accumulative plastic strain.展开更多
By introducing a fatigue blunting factor, the cyclic elasto-plastic Hutchinson-Rice-Rosengren （HRR） field near the crack tip under the cyclic loading is modified. And, an average damage per loading-cycle in the cycl...By introducing a fatigue blunting factor, the cyclic elasto-plastic Hutchinson-Rice-Rosengren （HRR） field near the crack tip under the cyclic loading is modified. And, an average damage per loading-cycle in the cyclic plastic deformation region is defined due to Manson-Coffin law. Then, according to the linear damage accumulation theory-Miner law, a new model for predicting the fatigue crack growth （FCG） of the opening mode crack based on the low cycle fatigue （LCF） damage is set up. The step length of crack propagation is assumed to be the size of cyclic plastic zone. It is clear that every parameter of the new model has clearly physical meaning which does not need any human debugging. Based on the LCF test data, the FCG predictions given by the new model are consistent with the FCG test results of Cr2Ni2MoV and X12CrMoWVNbN 10-1-1. What＇s more, referring to the relative researches, the good predictability of the new model is also proved on six kinds of materials.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
In this paper,the cyclic constitutive equations were proposed to describe the constitutive behavior of cyclic loading and unloading.Firstly,a coupled damage variable was derived,which contains two parts,i.e.,the compa...In this paper,the cyclic constitutive equations were proposed to describe the constitutive behavior of cyclic loading and unloading.Firstly,a coupled damage variable was derived,which contains two parts,i.e.,the compaction-induced damage and the cracking-induced damage.The compaction-induced damage variable was derived from a nonlinear stress–strain relation of the initial compaction stage,and the cracking-induced damage variable was established based on the statistical damage theory.Secondly,based on the total damage variable,a damage constitutive equation was proposed to describe the constitutive relation of rock under the monotonic uniaxial compression conditions,whereafter,the application of this model is extended to cyclic loading and unloading conditions.To validate the proposed monotonic and cyclic constitutive equations,a series of mechanical tests for marble specimens were carried out,which contained the monotonic uniaxial compression(MUC)experiment,cyclic uniaxial compression experiments under the variable amplitude(CUC-VA)and constant amplitude(CUC-CA)conditions.The results show that the proposed total damage variable comprehensively reflects the damage evolution characteristic,i.e.,the damage variable firstly decreases,then increases no matter under the conditions of MUC,CUC-VA or CUC-CA.Then a reasonable consistency is observed between the experimental and theoretical curves.The proposed cyclic constitutive equations can simulate the whole cyclic loading and unloading behaviors,such as the initial compaction,the strain hardening and the strain softening.Furthermore,the shapes of the theoretical curves are controlled by the modified coefficient,compaction sensitivity coefficient and two Weibull distributed parameters.展开更多
The finite element formulation for analyzing static damage near a conducting crack in a thin piezoelectric plate is established from the virtual work principle of piezoelectricity.The damage fields under various mecha...The finite element formulation for analyzing static damage near a conducting crack in a thin piezoelectric plate is established from the virtual work principle of piezoelectricity.The damage fields under various mechanical and electrical loads are calculated carefully by using an effective iterative procedure.The numerical results show that all the damage fields around a crack tip are fan-shaped and the electric field applied has great influence on the mechanical damage, which is related to the piezoelectric properties.展开更多
Based on the theory of damage mechanics, a method for fatigue crack initiation life prediction of notched components is proposed in this paper. The damage evolution equation of notched specimen under tensioncompressio...Based on the theory of damage mechanics, a method for fatigue crack initiation life prediction of notched components is proposed in this paper. The damage evolution equation of notched specimen under tensioncompression loading is obtained in term of closed-form solution. The crack initiation life of notched specimen is estimated by the proposed method even when material and stress concentration factor are different. It has been verified that the result calculated by the proposed method agrees with the experimental result. The proposed method is concise, effective and feasible to practical application.展开更多
Crack damage factor expressed by Normalized Cockcroft & Latham (N C&L) criterion was used for estimating the crack damage accumulation during multiple passes equal-channel angular pressing (ECAP) of 6061Al rod...Crack damage factor expressed by Normalized Cockcroft & Latham (N C&L) criterion was used for estimating the crack damage accumulation during multiple passes equal-channel angular pressing (ECAP) of 6061Al rod. First the simulation of crack damage factor was carried out by a software DEFORM-3D, and then the ECAP experiments of 6061 rod were performed. The damage places were found locating at the upper and bottom surface of the rod after ECAP. It has also been demonstrated that the ECAP routes including route A, Bc and C have strong effects on the strain distribution and the strain accumulation from both the experiment and the simulation.展开更多
Based on the damage constitutive model for concrete, the Weibull distribution function was used to characterize the random distribution of the mechanical properties of materials by finely subdividing concrete slab ele...Based on the damage constitutive model for concrete, the Weibull distribution function was used to characterize the random distribution of the mechanical properties of materials by finely subdividing concrete slab elements, and a concrete random mesoscopic damage model was established. The seismic response of a 100-m high concrete face rockfill dam(CFRD), subjected to ground motion with different intensities, was simulated with the three-dimensional finite element method(FEM), with emphasis on exploration of damage and the cracking process of concrete slabs during earthquakes as well as analysis of dynamic damage and cracking characteristics during strong earthquakes. The calculated results show that the number of damaged and cracking elements on concrete slabs grows with the duration of earthquakes. With increasing earthquake intensity, the damaged zone and cracking zone on concrete slabs grow wider. During a 7.0-magnitude earthquake, the stress level of concrete slabs is low for the CFRD, and there is almost no damage or slight damage to the slabs. While during a 9.0-magnitude strong earthquake, the percentages of damaged elements and macrocracking elements continuously ascend with the duration of the earthquake, peaking at approximately 26% and 5% at the end of the earthquake, respectively. The concrete random mesoscopic damage model can depict the entire process of sprouting, growing, connecting, and expanding of cracks on a concrete slab during earthquakes.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
In order to further study the damage and failure mechanism for rock similar materials,this study investigated the mechanical properties and failure characteristics,law of damage space development,and damage evolution ...In order to further study the damage and failure mechanism for rock similar materials,this study investigated the mechanical properties and failure characteristics,law of damage space development,and damage evolution characteristics for rock similar materials with pre-existing cracks of varying length under uniaxial compression load.The equipment used in this study is the self-developed YYW-Ⅱ strain controlled unconfined compression apparatus and the PCIE-8 acoustic emission monitoring system.Results show that,as the length of pre-existing crack increases:(1) the peak and residual strength reduces,and the peak axial strain and the strain during the initial compression phase increases;(2) the major failure mode is changed from shear failure to tensile failure along a vertical plane that passes the middle of the pre-existing crack;(3) The damage increases during the stable and accelerated development stage,and the effect of the pre-existing cracks is more during the accelerated development stage than the stable development stage.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 this paper,a simplified brittle damage model is proposed according to the Mazars-Lemaitre damage model for concrete.A closed-form solution for a mode Ⅲ crack is obtained based on the simplified model under small s...In this paper,a simplified brittle damage model is proposed according to the Mazars-Lemaitre damage model for concrete.A closed-form solution for a mode Ⅲ crack is obtained based on the simplified model under small scale damage conditions,which allows for discontinuities of displacement-gradient and tangential stress on the damage boundary.It is pointed out that the discontinuities of field variables near the tip region exist for the brittle damaged material induced by the softening effect of the material.展开更多
The effects of inclusions in powder superalloy FGH96 on low-cycle fatigue life were studied, and a low-cycle crack initiation life prediction model based on the theory of damage mechanics was proposed. The damage char...The effects of inclusions in powder superalloy FGH96 on low-cycle fatigue life were studied, and a low-cycle crack initiation life prediction model based on the theory of damage mechanics was proposed. The damage characterization parameter was proposed after the construction of damage evolution equations. Fatigue tests of the powder superalloy specimens with and without inclusion were conducted at 530 and 600 ℃, and the model verification was carried out for specimens with elliptical, semi-elliptical, polygon and strip-shaped surface/subsurface inclusion. The stress analysis was performed by finite element simulation and the predicted life was calculated. The results showed a satisfying agreement between predicted and experimental life.展开更多
In the present paper, a micromechanically based damage model for microcrack-weakened solids is developed. The concept of the domain of microcrack growth (DMG) is defined and used to describe the damage state and the a...In the present paper, a micromechanically based damage model for microcrack-weakened solids is developed. The concept of the domain of microcrack growth (DMG) is defined and used to describe the damage state and the anisotropic properties of brittle materials. After choosing an appropriate fracture criterion of microcrack, we obtain the analytical expression of DMG under a monotonically in- creasing proportional plane stress. Under a complex loading path, the evolution equation of DMG and the overall effective compliance tensor of damaged materials are given.展开更多
基金supported by the Shaanxi Qinchuang Yuan“scientist+engineer”team construction(No.2023KXJ-080)Shaanxi Chiral Drug Engineering Technology Research Center(Department of Science and Technology of Shaanxi Province.No.[2011]-251).
文摘Background:Human skin is affected by ultraviolet rays on a daily basis,and excessive ultraviolet radiation(UVR)can lead to sunburn erythema,tanning,photoaging,and skin tumors.The combination of Astragali Radix(AR)and Anemarrhenae Rhizoma(AAR)is a common pairing in traditional Chinese medicine(TCM).According to earlier studies,they possess properties capable of alleviating the adverse impacts of UVR on the skin.However,the specific actions and underlying mechanisms require further investigation.The study aims to analyze the efficacy of AR-AAR in preventing UVR-induced skin damage and to clarify the associated molecular mechanisms.Methods:Potential signaling pathways by which AR and AAR may protect against UVR-induced skin damage were identified with network pharmacology,molecular docking techniques and molecular dynamics(MD)simulation.Except the normal group,the back skin of SD rats was exposed to 1.1 mW/cm^(2) UVA combined with 0.1 mW/cm^(2) UVB daily,and the UVR skin damage model was established.Morphological features of skin tissues of different groups were discovered through Hematoxylin and Eosin(HE)staining,Masson staining,Weigert staining.ELISA was utilized to measure the levels of reactive oxygen species(ROS),Interleukin 6(IL-6),Interleukin 1β(IL-1β)and Tumor necrosis factos-α(TNF-α)in skin tissues.RT-PCR and Western blot were employed to quantify the mRNA and protein contents of PI3K,AKT,and MMP-9.Results:Network pharmacology analysis predicts that AR-AAR may improve skin damage induced by UVR through the PI3K/AKT signaling pathway.Histological staining shows that AR-AAR can significantly reduce inflammatory infiltration and fibrosis in damaged skin.Treatment with AR-AAR(2:1)significantly reduced the expression levels of IL-1β,IL-6,TNF-αand ROS in UVR-damaged rat skin.After treatment with AR-AAR(2:1),not only did the relative mRNA expression levels of PI3K and AKT and the protein expression levels of PI3K,AKT,P-PI3K,and P-AKT increase,but the mRNA and protein expression levels of MMP-9 decreased.Conclusion:The study indicate that the AR-AAR combination and its active components may mitigate UVR skin damage by modulating the PI3K/AKT signaling pathway.
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funded by the projects:National Natural Science Foundation of China(52274098,U21A20110)National key research and development program(2022YFC3004603)+1 种基金Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX23_2798)Graduate Innovation Program of China University of Mining and Technology(2023WLKXJ036).
文摘Deep hole pre-cracking blasting(DHPB)technology is the preferred means of preventing and controlling rockburst induced by hard-thick rock layers in coal mines.When DHPB is applied to hard-thick rock layers,the insufficient knowledge about the crack extension scale under different rock properties and blasting parameters may result in undesirable pressure relief.Therefore,LS-DYNA was adopted to analyse the crack extension characteristics under the combined effect of rock tensile strength,explosive density,blasthole spacing,and decoupled coefficient.The Holmquist–Johnson–Cook model(HJC),verified by the results of blasting experiment and numerical simulation in literature,was used to characterise coal-bearing rocks.Numerical analysis was conducted to study the blasting crack extension and fractal damage for rock tensile strength,explosive densities,blasthole spacing,and decoupled coefficients.The results show that the tensile strength of rock is the key factor for blasting design.The fractal damage caused by blasting increases when the tensile strength of rock decreases.For rocks with lower tensile strength,more blasting energy is consumed by the increasing damage area in the crushed zone.Higher explosive density can promote the development of blasting cracks and increase fractal damage,but the increasing range of the crushed zone also wastes a large amount of energy.As the blasthole spacing increases,the fractal damage decreases,and the crack extension scale in the fractured zone first increases and then decreases,and eventually remains almost unchanged.An optimum interval exists for the decoupled coefficient,and the full utilization of explosive energy within the interval leads to penetrating blast cracks and smaller crushed zones.Based on the simulation results,the optimal blasting parameters for coarse sandstone were validated in the field practice.Monitoring data show that the optimized blasting significantly reduces the risk of rockburst.
文摘In order to study the mechanical properties of damaged reinforced concrete(RC)beams reinforced with ultra-high-performance concrete(UHPC),a four-point bending test was conducted to systematically investigate the influence of factors such as the number of reinforcement surfaces and the degree of damage.The results indicate that single-sided repaired beams have certain advantages in crack resistance performance,but are more disadvantageous in ultimate bearing capacity,with obvious debonding phenomenon before the end of loading.Compared with single-sided reinforcement,the cracking load of the three-sided reinforced beam increased by an average of 1.85 times,the ultimate bearing capacity increased by an average of 177.5%,and a good UHPC-RC combination effect could be formed,which could work synergistically until the end of loading.The degree of pre damage has a significant impact on the crack resistance performance of reinforced beams,while its impact on the ultimate bearing capacity is relatively limited.When the pre splitting width of the RC beam increases from 0.2 mm to 0.4 mm,the ultimate bearing capacity decreases by 28.33%.
文摘Ensuring the structural integrity of piping systems is crucial in industrial operations to prevent catastrophic failures and minimize shutdown time.This study investigates a transportation-damaged pipe exposed to high-temperature conditions and cyclic loading,representing a realistic challenge in plant operation.The objective was to evaluate the service life and integrity assessment parameters of the damaged pipe,subjected to 22,000 operational cycles under two daily charge and discharge conditions.The flaw size in the damaged pipe was determined based on a failure assessment procedure,ensuring a conservative and reliable input.The damage was characterized as a long axial surface crack with a depth of a=2 mm and half-length c=50 mm(c/a=25),a geometry not well covered by existing Stress Intensity Factor solutions.To address this limitation,a modified magnification factor(M*)was introduced and tested for the present damage case(c/a=25)and for additional crack geometries(c/a=28–70),which showed improved agreement with Finite Element Analysis(FEA)than Newman’s original formulation.Stress Intensity Factor and Plastic Limit Pressure,essential parameters for structural integrity assessment,were computed numerically using FEA and validated against analytical predictions.Fatigue crack growth was evaluated using the Paris law with crack propagation simulated numerically by Ansys’s S.M.A.R.T.The Failure Assessment Diagram(FAD)was used to assess service life,incorporating constant working pressure and fracture toughness while considering evolving crack size during propagation.Results showed that analytical predictions with the modified magnification factor matched FEA within 5%,while the original Newman formulation overestimated results.The analytical service life solution predicted approximately 8500 fewer cycles than the numerical,remaining conservative but efficient.These findings are based on the present case of a long axial surface crack with high aspect ratios(c/a=25–70,depending on crack depth),and while the modified magnification factor may also improve predictions for other geometries,this requires structured validation in future studies.
基金support of the National Natural Science Foundation of China(52374180,52327804).
文摘This study focuses on steeply inclined and extremely thick coal seams(SIETCS)characterized by immense thickness,a steep inclination of coal seams(87°),and high horizontal stress.The geological conditions and mining technology associated with SIETCS differ significantly from those of generally inclined coal seams,resulting in notable variations in roadway stress distributions.On SIETCS have predominantly examined the impact of rock layers flanking coal seams on rock bursts,with limited emphasis on SIETCS roadways.This study employs comprehensive methods,integrating numerical simulations,theoretical analyses,and field detections to investigate the stress distribution of SIETCS and the mechanisms of rock burst-induced vertical damage,subsequently validated in situ.The vertical stress in SIETCS is minimal,while horizontal stress is concentrated,leading to the formation of layered crack structures(LCS)that distribute above and below the roadways.Additionally,elastic energy significantly concentrates within the LCS.Axial dynamic compressive stress and vertical dynamic tensile stress along the LCS diminish its stability,readily triggering failure.During the LCS failure process,the stored energy is released,converting into kinetic energy required for coal body ejection after reaching the minimum energy for failure and dissipative energy,ultimately leading to rock burst-induced vertical damage in roadways.On-site detection and analysis within SIETCS,along with historical rock burst data,confirm the existence of LCS and its role in inducing vertical rock burst damage.This research establishes essential foundations for preventing rock bursts within SIETCS.
基金Project (2007CB613700) supported by the National Basic Research Program of China Project (2007BAG06B04) supported by the National Sci & Tech Support Program, China+1 种基金 Project (CSTC, 2009AB4008) supported by Chongqing Sci & Tech Program, China Project (50725413) supported by the National Natural Science Foundation of China
文摘A thermal-mechanical-damage coupled finite elements model was established to investigate temperature changes, edge cracks and rolling force during roiling of magnesium alloy sheet. A cuneal sheet was also adopted to study the influence of reduction on temperature, damage and rolling force. The results show that with increasing the reduction, the rolling force increases, and the temperature of the Mg sheet decreases. Edge cracks occur when the reduction is above 51.6%, with the damage value of above 0.49. The plastic-damage in Mg sheet rolling is a result of hole development, shearing deformation and accumulative plastic strain.
基金co-supported by National Natural Science Foundation of China (No. 11072205)College Students' National Innovation Foundation of China (No. 101061323)
文摘By introducing a fatigue blunting factor, the cyclic elasto-plastic Hutchinson-Rice-Rosengren （HRR） field near the crack tip under the cyclic loading is modified. And, an average damage per loading-cycle in the cyclic plastic deformation region is defined due to Manson-Coffin law. Then, according to the linear damage accumulation theory-Miner law, a new model for predicting the fatigue crack growth （FCG） of the opening mode crack based on the low cycle fatigue （LCF） damage is set up. The step length of crack propagation is assumed to be the size of cyclic plastic zone. It is clear that every parameter of the new model has clearly physical meaning which does not need any human debugging. Based on the LCF test data, the FCG predictions given by the new model are consistent with the FCG test results of Cr2Ni2MoV and X12CrMoWVNbN 10-1-1. What＇s more, referring to the relative researches, the good predictability of the new model is also proved on six kinds of materials.
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This study was financially supported by the National Natural Science Foundation of China(Nos.51978292,42077254 and 51874144).
文摘In this paper,the cyclic constitutive equations were proposed to describe the constitutive behavior of cyclic loading and unloading.Firstly,a coupled damage variable was derived,which contains two parts,i.e.,the compaction-induced damage and the cracking-induced damage.The compaction-induced damage variable was derived from a nonlinear stress–strain relation of the initial compaction stage,and the cracking-induced damage variable was established based on the statistical damage theory.Secondly,based on the total damage variable,a damage constitutive equation was proposed to describe the constitutive relation of rock under the monotonic uniaxial compression conditions,whereafter,the application of this model is extended to cyclic loading and unloading conditions.To validate the proposed monotonic and cyclic constitutive equations,a series of mechanical tests for marble specimens were carried out,which contained the monotonic uniaxial compression(MUC)experiment,cyclic uniaxial compression experiments under the variable amplitude(CUC-VA)and constant amplitude(CUC-CA)conditions.The results show that the proposed total damage variable comprehensively reflects the damage evolution characteristic,i.e.,the damage variable firstly decreases,then increases no matter under the conditions of MUC,CUC-VA or CUC-CA.Then a reasonable consistency is observed between the experimental and theoretical curves.The proposed cyclic constitutive equations can simulate the whole cyclic loading and unloading behaviors,such as the initial compaction,the strain hardening and the strain softening.Furthermore,the shapes of the theoretical curves are controlled by the modified coefficient,compaction sensitivity coefficient and two Weibull distributed parameters.
基金Project supported by the National Natural Science Foundation of China (No.10172036)the Education Ministry Scientific Research Foundation for Returned Overseas Chinese Scholars.
文摘The finite element formulation for analyzing static damage near a conducting crack in a thin piezoelectric plate is established from the virtual work principle of piezoelectricity.The damage fields under various mechanical and electrical loads are calculated carefully by using an effective iterative procedure.The numerical results show that all the damage fields around a crack tip are fan-shaped and the electric field applied has great influence on the mechanical damage, which is related to the piezoelectric properties.
基金the National Natural Science Foundation of China(Nos.51605212 and 51665028)the Natural Science Foundation of Gansu Province(No.17JR5RA122)
文摘Based on the theory of damage mechanics, a method for fatigue crack initiation life prediction of notched components is proposed in this paper. The damage evolution equation of notched specimen under tensioncompression loading is obtained in term of closed-form solution. The crack initiation life of notched specimen is estimated by the proposed method even when material and stress concentration factor are different. It has been verified that the result calculated by the proposed method agrees with the experimental result. The proposed method is concise, effective and feasible to practical application.
文摘Crack damage factor expressed by Normalized Cockcroft & Latham (N C&L) criterion was used for estimating the crack damage accumulation during multiple passes equal-channel angular pressing (ECAP) of 6061Al rod. First the simulation of crack damage factor was carried out by a software DEFORM-3D, and then the ECAP experiments of 6061 rod were performed. The damage places were found locating at the upper and bottom surface of the rod after ECAP. It has also been demonstrated that the ECAP routes including route A, Bc and C have strong effects on the strain distribution and the strain accumulation from both the experiment and the simulation.
基金supported by the Key Laboratory of Failure Mechanism and Safety Control Techniques of Earth-rock Dams of the Ministry of Water Resources(Grant No.YK914019)the CRSRI Open Research Program(Grant No.CKWV2016376/KY)the National Natural Science Foundation of China(Grant No.51009055)
文摘Based on the damage constitutive model for concrete, the Weibull distribution function was used to characterize the random distribution of the mechanical properties of materials by finely subdividing concrete slab elements, and a concrete random mesoscopic damage model was established. The seismic response of a 100-m high concrete face rockfill dam(CFRD), subjected to ground motion with different intensities, was simulated with the three-dimensional finite element method(FEM), with emphasis on exploration of damage and the cracking process of concrete slabs during earthquakes as well as analysis of dynamic damage and cracking characteristics during strong earthquakes. The calculated results show that the number of damaged and cracking elements on concrete slabs grows with the duration of earthquakes. With increasing earthquake intensity, the damaged zone and cracking zone on concrete slabs grow wider. During a 7.0-magnitude earthquake, the stress level of concrete slabs is low for the CFRD, and there is almost no damage or slight damage to the slabs. While during a 9.0-magnitude strong earthquake, the percentages of damaged elements and macrocracking elements continuously ascend with the duration of the earthquake, peaking at approximately 26% and 5% at the end of the earthquake, respectively. The concrete random mesoscopic damage model can depict the entire process of sprouting, growing, connecting, and expanding of cracks on a concrete slab during earthquakes.
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.
基金This paper is an extended version of a published conference paper Li et al.(2017)this paper gets its funding from Project(51734007)+1 种基金supported by National Natural Science Foundation of ChinaWe would also like to acknowledge the editor-in-chief,editors and the anonymous reviewers for their valuable comments,which have greatly improved this paper.
文摘In order to further study the damage and failure mechanism for rock similar materials,this study investigated the mechanical properties and failure characteristics,law of damage space development,and damage evolution characteristics for rock similar materials with pre-existing cracks of varying length under uniaxial compression load.The equipment used in this study is the self-developed YYW-Ⅱ strain controlled unconfined compression apparatus and the PCIE-8 acoustic emission monitoring system.Results show that,as the length of pre-existing crack increases:(1) the peak and residual strength reduces,and the peak axial strain and the strain during the initial compression phase increases;(2) the major failure mode is changed from shear failure to tensile failure along a vertical plane that passes the middle of the pre-existing crack;(3) The damage increases during the stable and accelerated development stage,and the effect of the pre-existing cracks is more during the accelerated development stage than the stable development stage.
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.
基金The preoject supported by the National Natural Science Foundation of China.
文摘In this paper,a simplified brittle damage model is proposed according to the Mazars-Lemaitre damage model for concrete.A closed-form solution for a mode Ⅲ crack is obtained based on the simplified model under small scale damage conditions,which allows for discontinuities of displacement-gradient and tangential stress on the damage boundary.It is pointed out that the discontinuities of field variables near the tip region exist for the brittle damaged material induced by the softening effect of the material.
基金sponsored by AECC Beijing Institute of Aeronautical Materialsfunded by National High-tech R&D Program of China (863 Program) (No. 2015AA034401)。
文摘The effects of inclusions in powder superalloy FGH96 on low-cycle fatigue life were studied, and a low-cycle crack initiation life prediction model based on the theory of damage mechanics was proposed. The damage characterization parameter was proposed after the construction of damage evolution equations. Fatigue tests of the powder superalloy specimens with and without inclusion were conducted at 530 and 600 ℃, and the model verification was carried out for specimens with elliptical, semi-elliptical, polygon and strip-shaped surface/subsurface inclusion. The stress analysis was performed by finite element simulation and the predicted life was calculated. The results showed a satisfying agreement between predicted and experimental life.
基金The project supported by National Natural Science Foundation of China
文摘In the present paper, a micromechanically based damage model for microcrack-weakened solids is developed. The concept of the domain of microcrack growth (DMG) is defined and used to describe the damage state and the anisotropic properties of brittle materials. After choosing an appropriate fracture criterion of microcrack, we obtain the analytical expression of DMG under a monotonically in- creasing proportional plane stress. Under a complex loading path, the evolution equation of DMG and the overall effective compliance tensor of damaged materials are given.
