Nonlinearly induced steady-state photon–phonon entanglement of a dissipative coupled system is studied in the bistable regime. Quantum dynamical characteristics are analysed by solving the mean-field and fluctuation ...Nonlinearly induced steady-state photon–phonon entanglement of a dissipative coupled system is studied in the bistable regime. Quantum dynamical characteristics are analysed by solving the mean-field and fluctuation equations of the system. It is shown that dissipative coupling can induce bistable behaviour for the effective dissipation of the system.Under suitable parameters, one of the steady states significantly reduces the dissipative effect of the system. Consequently,a larger steady-state entanglement can be achieved compared to linear dynamics. Furthermore, the experimental feasibility of the parameters is analysed. Our results provide a new perspective for the implementation of steady-state optomechanical entanglement.展开更多
By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,t...By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.展开更多
Electron–hole(e–h)recombination is a fundamental process that governs energy dissipation and device efficiency in semiconductors.In two-dimensional(2D)materials,the formation of tightly bound excitons makes exciton-...Electron–hole(e–h)recombination is a fundamental process that governs energy dissipation and device efficiency in semiconductors.In two-dimensional(2D)materials,the formation of tightly bound excitons makes exciton-mediated e–h recombination the dominant decay pathway.In this work,nonradiative e–h recombination within excitons in monolayer MoS2 is investigated using first-principles simulations that combine nonadiabatic molecular dynamics with𝐺𝑊and real-time Bethe–Salpeter equation(BSE)propagation.A two-step process is identified:rapid intervalley redistribution induced by exchange interaction,followed by slower phonon-assisted recombination facilitated by exciton binding.By selectively removing the screened Coulomb and exchange terms from the BSE Hamiltonian,their respective contributions are disentangled—exchange interaction is found to increase the number of accessible recombination pathways,while binding reduces the excitation energy and enhances nonradiative decay.A reduction in recombination lifetime by over an order of magnitude is observed due to the excitonic many-body effects.These findings provide microscopic insights for understanding and tuning exciton lifetimes in 2D transition-metal dichalcogenides.展开更多
The preparation of carbon-based electromagnetic wave(EMW)absorbers possessing thin matching thickness,wide absorption bandwidth,strong absorption intensity,and low filling ratio remains a huge challenge.Metal-organic ...The preparation of carbon-based electromagnetic wave(EMW)absorbers possessing thin matching thickness,wide absorption bandwidth,strong absorption intensity,and low filling ratio remains a huge challenge.Metal-organic frameworks(MOFs)are ideal self-sacrificing templates for the construction of carbon-based EMW absorbers.In this work,bimetallic FeMn-MOF-derived MnFe_(2)O_(4)/C/graphene composites were fabricated via a two-step route of solvothermal reaction and the following pyrolysis treatment.The results re-veal the evolution of the microscopic morphology of carbon skeletons from loofah-like to octahedral and then to polyhedron and pomegran-ate after the adjustment of the Fe^(3+)to Mn^(2+)molar ratio.Furthermore,at the Fe^(3+)to Mn^(2+)molar ratio of 2:1,the obtained MnFe_(2)O_(4)/C/graphene composite exhibited the highest EMW absorption capacity.Specifically,a minimum reflection loss of-72.7 dB and a max-imum effective absorption bandwidth of 5.1 GHz were achieved at a low filling ratio of 10wt%.In addition,the possible EMW absorp-tion mechanism of MnFe_(2)O_(4)/C/graphene composites was proposed.Therefore,the results of this work will contribute to the construction of broadband and efficient carbon-based EMW absorbers derived from MOFs.展开更多
To examine the effect of bedding angle upon burst proneness in terms of energy,phyllites with seven various bedding angles are selected for conventional uniaxial compression and single-cyclic loading eunloading uniaxi...To examine the effect of bedding angle upon burst proneness in terms of energy,phyllites with seven various bedding angles are selected for conventional uniaxial compression and single-cyclic loading eunloading uniaxial compression tests.The ejection and failure during compression process of phyllites are monitored in real-time by high-speed camera system.The results demonstrate that the phyllites with different bedding angles all consistently follow the linear energy storage and dissipation(LESD)law during compression.The ultimate energy storage of phyllites with varying bedding angles can be calculated precisely via using the LESD law.Based on this,four kinds of energy-based rockburst indices are applied to quantitatively assess the burst proneness for phyllites.Combined with the recorded images of high-speed camera system,ejection distance,and mass of rock fragments and powder,the burst proneness for phyllites with various bedding angles is qualitatively evaluated adopting the far-field ejection mass ratio.Next,burst proneness of anisotropic phyllites is assessed quantitatively and qualitatively.It is found that phyllites with bedding angles of 0°,15°,and 90°have a high burst proneness,and that with bedding angle of 30°has a medium burst proneness,whereas the ones with bedding angles of 45°,60°,and 75°have a low burst proneness.Finally,the published experimental data of shale and sandstone specimens with different bedding angles are extracted,and it is preliminarily verified that the bedding angle does not change the LESD law of rocks.展开更多
The combination of advanced photoelectric detectors has rendered single-band camouflage materials ineffective,necessitating the development of infrared multispectral camouflage.However,the design and fabrication of ex...The combination of advanced photoelectric detectors has rendered single-band camouflage materials ineffective,necessitating the development of infrared multispectral camouflage.However,the design and fabrication of existing works remain complex as they usually require the integration of multiscale structures.Here,we introduce phase modulation into the infrared camouflage metasurfaces with metal-dielectric-metal configuration,enabling them to achieve camouflage across more bands.Based on this strategy,a simple but effective single-layer cascaded metasurface is demonstrated for the first time to achieve low reflection at multi-wavelength lasers,low infrared radiation in atmospheric windows,and broadband thermal management.As a proof-of-concept,a 4-inch sample with a minimum linewidth of 1.8μm is fabricated using photolithography.The excellent infrared multispectral camouflage performance is verified in experiments,showing low reflectance in 0.9–1.6μm,low infrared emissivity in mid-wavelength infrared(MWIR)and long-wavelength infrared(LWIR)bands,and high absorptance at the wavelength of 10.6μm.Meanwhile,broadband high emissivity in 5–8μm can provide high-performance radiative heat dissipation.When the input power is 1.57 W·cm^(-2),the surface/radiation temperature of the metasurface decreases by 5.3℃/18.7℃ compared to the reference.The proposed metasurface may trigger further innovation in the design and application of compact multispectral optical devices.展开更多
Traditionally reduced graphene oxide(RGO)-based electromagnetic wave(EMW)absorbing materials have poor absorption effectiveness due to impedance mismatch caused by skin effect.The introduction of structural defects an...Traditionally reduced graphene oxide(RGO)-based electromagnetic wave(EMW)absorbing materials have poor absorption effectiveness due to impedance mismatch caused by skin effect.The introduction of structural defects and the design of heterogeneous interfaces play a crucial role in enhancing the polarization effect of EMW absorbers.In this study,nitrogen-doped reduced graphene oxide/zinc ferrite@nitrogen-doped carbon(NRGO/ZnFe_(2)O_(4)@NC)ternary composite with rich heterogeneous interfaces is constructed by combining solvothermal reaction,in-situ polymerization,annealing treatment with subsequent hydrothermal reaction.The research results have shown that the obtained NRGO/ZnFe_(2)O_(4)@NC ternary composite exhibits a unique core-shell structure and excellent EMW absorption performance.At a thickness of 2.61 mm,the maximum effective absorption bandwidth can reach 7.2 GHz,spanning the entire Ku-band and a portion of the X-band,and the minimum reflection loss is-61.1 dB,which is superior to most reported RGO-based EMW absorbers.The excellent EMW absorbing ability is mainly ascribed to the optimized impedance matching and the enhanced polarization loss caused by the abundant heterogeneous interfaces and structural defects derived from heteroatomic nitrogen doping.Furthermore,the radar cross section in the far field is simulated by a computer simulation technique.This study provides a novel way to prepare core-shell magnetic carbon composites as highly efficient and broadband EMW absorbers.展开更多
Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may ...Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.展开更多
With the urgent need to resolve complex behaviors in nonlinear evolution equations,this study makes a contribution by establishing the local existence of solutions for Cauchy problems associated with equations of mixe...With the urgent need to resolve complex behaviors in nonlinear evolution equations,this study makes a contribution by establishing the local existence of solutions for Cauchy problems associated with equations of mixed types.Our primary contribution is the establishment of solution existence,illuminating the dynamics of these complex equations.To tackle this challenging problem,we construct an approximate solution sequence and apply the contraction mapping principle to rigorously prove local solution existence.Our results significantly advance the understanding of nonlinear evolution equations of mixed types.Furthermore,they provide a versatile,powerful approach for tackling analogous challenges across physics,engineering,and applied mathematics,making this work a valuable reference for researchers in these fields.展开更多
Filler-reinforced polymer composites demonstrate pervasive applications due to their strengthened performances,multi-degree tunability,and ease of manufacturing.In thermal management field,polymer composites reinforce...Filler-reinforced polymer composites demonstrate pervasive applications due to their strengthened performances,multi-degree tunability,and ease of manufacturing.In thermal management field,polymer composites reinforced with thermally conductive fillers are widely adopted as thermal interface materials(TIMs).However,the three dimensional(3D)-stacked heterogenous integration of electronic devices has posed the problem that high-density heat sources are spatially distributed in the package.This situation puts forward new requirements for TIMs,where efficient heat dissipation channels must be established according to the specific distribution of discrete heat sources.To address this challenge,a 3D printing-assisted streamline orientation(3D-PSO)method was proposed to fabricate composite thermal materials with 3D programmable microstructures and orientations of fillers,which combines the shape-design capability of 3D printing and oriented control ability of fluid.The mechanism of fluid-based filler orientation control along streamlines was revealed by mechanical analysis of fillers in matrix.Thanks to the designed heat dissipation channels,composites showed better thermal and mechanical properties in comparison to random composites.Specifically,the thermal conductivity of 3D mesh-shape polydimethylsiloxane/liquid metal(PDMS/LM)composite was5.8 times that of random PDMS/LM composite under filler loading of 34.8 vol%.The thermal conductivity enhancement efficiency of 3D mesh-shape PDMS/carbon fibers composite reached101.05%under filler loading of 5.2 vol%.In the heat dissipation application of 3D-stacked chips,the highest chip temperature with 3D-PSO composite was 42.14℃lower than that with random composites.This is mainly attributed to the locally aggregated and oriented fillers'microstructure in fluid channels,which contributes to thermal percolation phenomena.The3D-PSO method exhibits excellent programmable design capabilities to adopt versatile distributions of heat sources,paving a new way to solve the complicated heat dissipation issue in 3D-stacked chips integration application.展开更多
This paper presents a nonlinear micropolar nonclassical continuum theory (MPNCCT) for finite deformation, finite strain deformation physics of thermosviscoelastic solid medium with memory (polymeric micropolar solids)...This paper presents a nonlinear micropolar nonclassical continuum theory (MPNCCT) for finite deformation, finite strain deformation physics of thermosviscoelastic solid medium with memory (polymeric micropolar solids) based on classical rotations cΘand their rates. Contravariant second Piola-Kirchhoff stress and moment tensors, in conjunction with finite deformation measures derived by the authors in recent paper, are utilized in deriving the conservation and balance laws and the constitutive theories based on conjugate pairs in entropy inequality and the representation theorem. This nonlinear MPNCCT for TVES with rheology: 1) incorporates nonlinear ordered rate dissipation mechanism based on Green’s strain rates up to order n;2) also incorporates an additional ordered rate dissipation mechanism due to microconstituents, the viscosity of the medium and the rates of the symmetric part of the rotation gradient (of cΘ) tensor up to order n, referred to as micropolar dissipation or micropolar viscous dissipation mechanism;3) incorporates the primary mechanism of memory or rheology due to long chain molecules of the polymer and the viscosity of the medium by using the contravaraint second Piola-Kirchhoff stress tensor and its rates up to order m, resulting in a relaxation spectrum;4) incorporates second mechanism of memory or rheology due to nonclassical physics, interaction of microconstituents with the viscous medium and long chain molecules by considering rates of the contravariant second Piola-Kirchhoff moment tensor up to order m, resulting in relaxation of second Piola-Kirchhoff moment tensor. This results in another relaxation spectrum for the second Piola-Kirchhoff moment tensor due to microconstituents, referred to as micropolar relaxation spectrum consisting of micropolar relaxation time constants of the material. This nonlinear MPNCCT for TVES with memory is thermodynamically and mathematically consistent, and the mathematical model consisting of conservation and balance laws and the constitutive theories has closure and naturally reduces to linear MPNCCT based on infinitesimal deformation assumption. BMM is the essential balance law for all MPNCCT and is used in the present work as well. In the absence of this balance law, a valid thermodynamically and mathematically consistent nonlinear MPNCCT is not possible. The nonlinear MPNCCT based on rotations (cΘ+αΘ) and αΘ(ignoring cΘ) is not considered due to the fact that even the linear MPNCCT based on these rotations is invalid and is thermodynamically and mathematically inconsistent MPNCCT.展开更多
The application of mass timber elements in different structures has gained publicity over the last few years,pri-marily due to climate change adaptation policies and net zero carbon targets.Timber is a renewable const...The application of mass timber elements in different structures has gained publicity over the last few years,pri-marily due to climate change adaptation policies and net zero carbon targets.Timber is a renewable construction material that can outperform other building materials regarding environmental impact.However,when used in seismically active regions,its application has been limited due to the uncertainties on their seismic behaviour in respect with different design standards and limited ductility in conventional connections.Conventional timber connections typically suffer from stiffness and strength degradation under cyclic loads.Their repairability is also low due to permanent damage in the fasteners and the associated crushing in the wood fibres.The use of friction connections can be an efficient way to mitigate these issues.They offer many advantages as they are economical and yet provide a high level of reliable and continuous energy dissipation.In recent years,a new generation of friction connections has been developed that can provide self-centring behaviour(i.e.,the ability of the structure to return to its original position at the end of an earthquake).However,how these connections perform compared to a mass timber system with conventional timber connections is still unknown.Several studies in the literature have suggested that these connections can enhance the performance of mass timber structures.However,the seismic performance of such systems specifically in terms of base shear,response drifts and response accelerations-has not been thoroughly investigated.This paper examines various design aspects of conventional friction connections and self-centring friction connections,providing insights into their differences concerning key seismic performance indicators.It compares the seismic performance of mass timber buildings equipped with both solutions,highlighting their advantages and limitations and drawing conclusions based on the results.The key findings are that friction connections can provides a superior seismic performance for timber structures.However,that may need to be combined with a parallel system avoid residual displacements.展开更多
Lycium barb arum,known as wolfberry or goji berry,is consumed by humans as a medicine and a food homology product.Conventionally grown wolfberry is often treated extensively with pesticides,which could pose a hazard t...Lycium barb arum,known as wolfberry or goji berry,is consumed by humans as a medicine and a food homology product.Conventionally grown wolfberry is often treated extensively with pesticides,which could pose a hazard to humans.Here,the degradation dynamics of dinotefuran and its 2 metabolites(1-methyl-3-(tetrahydro-3-furylmethyl)urea(UF)and 1-methyl-3-(tetrahydro-3-furylmethyl)guanidine(DN)),during wolfberry cultivation and processing was investigated.The half-life(T_(1/2))of dinotefuran was 11.36 and 9.76 days,respectively,under the recommended dosage and double the recommended dosage.During the oven and sun drying processes,processing factors(PFs)of dinotefuran were 1.07-1.34,implying the enrichment of pesticide residues.Decoction process made the removal rate of dinotefuran reach 87.48%,which is higher than that of the brewing process(14.7%),while dinotefuran remained in the wine with high ethanol content in the alcohol soaking process.The hazard quotient(HQ)of dinotefuran,as determined via dietary risk assessment combined with PFs,was<1,indicating an acceptable risk for human consumption.Bioaccessibility of dinotefuran in the three digestive stages were intestinal(18.20%-88.08%)>gastric(5.45%-86.72%)>oral(23.18%)via in vitro simulated digestive system.These findings provide scientific evidence for reasonable application and risk assessment of dinotefuran residues in wolfberry.展开更多
Viscoelastic nanofluid flow has drawn substantial interest due to its industrial uses,including research and testing of medical devices,lubrication and tribology,drug delivery systems,and environmental remediation.Thi...Viscoelastic nanofluid flow has drawn substantial interest due to its industrial uses,including research and testing of medical devices,lubrication and tribology,drug delivery systems,and environmental remediation.This work studies nanofluid flow over a viscoelastic boundary layer,focusing on mass and heat transmission.An analysis is performed on the flow traversing a porous sheet undergoing nonlinear stretching.It assesses the consequences of viscous dissipation and thermal radiation.The scientific nanofluid framework laid out by Buongiorno has been exploited.The partial differential equations illustrating the phenomena can be transfigured into ordinary differential equations by utilizing appropriate similarity transformations.The simplified equations are unmasked using the Homotopy Analysis Method(HAM),a semi-analytical approach designed to solve nonlinear ordinary and partial differential equations commonly encountered in numerous scientific and engineering disciplines.Calculations are executed to ascertain the numerical solutions related to temperature,concentration,and velocity fields,accompanied by the skin friction coefficient,local Nusselt number,and local Sherwood number.Visualizations of the results are accompanied by pertinent explanations grounded in scientific principles.The temperature distribution and corresponding thermal layer have been enhanced due to radiative and viscous dissipation characteristics.Additionally,it has been noted that a delay in fluid movement results from an improvement in the porous medium parameter and magnetic field values.A falling trend in the Nusselt number is observed as the Eckert and thermophoresis parameters increase.The current numerical results have been effectively validated against previous difficulties.展开更多
High temperature and high stress are critical challenges facing enhanced geothermal systems(EGS).This study investigates the physical and mechanical behavior and acoustic emission(AE)characteristics of granite subject...High temperature and high stress are critical challenges facing enhanced geothermal systems(EGS).This study investigates the physical and mechanical behavior and acoustic emission(AE)characteristics of granite subjected to heating–water cooling treatments at temperatures ranging from 25℃ to 400℃.Changes in physical properties,including volume expansion,mass loss,and P-wave velocity,were examined to quantify the extent of thermal damage.Results show that visible surface cracking occurs on granite samples treated above 300℃,with P-wave velocity being the most sensitive indicator of thermal damage.Uniaxial and triaxial compression tests were conducted to explore the effects of temperature and confining pressure on granite’s strength,deformation,failure modes,energy evolution,and brittleness.While peak strength remains largely unaffected by temperature,failure modes transition from axial splitting to shear as confining pressure increases.Thermal damage reduces the rock’s energy storage capacity and increases energy dissipation during loading.The brittleness index decreases with temperature and confining pressure,though granite still exhibits pronounced brittle behavior within the studied range.Distinct differences were observed in the AE temporal characteristics and energy evolution of granite samples under uniaxial and triaxial compression conditions.As the specimen approaches failure,the abrupt increase in AE hit rate occurs earlier than the corresponding rise in AE energy.The global b-value of the granite samples increased with treatment temperature,and the global b-value in triaxial compression tests was higher than that in uniaxial compression tests.The evolution of timedependent b-value also varied with increasing confining pressure.These findings,particularly the AE temporal characteristics and distinct b-value evolution under confinement of thermally damaged granite,provide important implications for microseismic-based stability assessment and early warning in thermally damaged rock masses.展开更多
The problems of tailings storage and high-stress conditions in deep mining have emerged as critical factors that limit the security,efficiency,and sustainability of such mines.This study explores the potential to util...The problems of tailings storage and high-stress conditions in deep mining have emerged as critical factors that limit the security,efficiency,and sustainability of such mines.This study explores the potential to utilize tungsten tailings to create cementitious backfill(CTB)materials and investigates the macroscopic strength features and microscopic damage evolution mechanisms of different-sized CTBs with varying dosages of hydroxypropyl methyl cellulose(HPMC).Specimens with bottom diameters of 50,75,and 100 mm are combined with HPMC dosages of 0,0.15wt%,0.25wt%,and 0.35wt%.A diameter/height ratio of 1:2 is maintained for all CTB specimens.The experimental results show that as the HPMC dosage is increased from 0 to 0.35wt%,the uniaxial compressive strength(UCS)of the CTBs decreases significantly in a linear manner.The 75 mm×150 mm CTB specimen exhibits relatively high plasticity and toughness,with good plastic deformation and energy absorption capabilities,indicating significant size effects.HPMC introduces connected bubbles during the CTB pouring process,but it exhibits anti-segregation and anti-bleeding characteristics,thus reducing tailing settling.The hydration reaction of the CTB doped with HPMC is more uniform,and the Ca/Si atomic ratio dispersion at different sites is smaller.The three CTB sizes all exhibit combined tensile and shear failure,with the 75 mm×150 mm specimen exhibiting macroscopic tensile cracks and relatively few shear cracks.At the micro-scale,excessive ettringite and hydrated calcium silicate are interwoven and fuse,and the tungsten tailings are tightly wrapped.These results provide valuable data and notional insights for optimizing the fluidity of the backfill,and elucidate the strength and damage evolution of solidified materials during filling and extraction.This study contributes to the advancement of green,economical,safe,and sustainable mining practices.展开更多
In this study,a coupled loading method combining three-dimensional static loading with graded cyclic impacts was developed to simulate the stress environment of the surrounding rock under impact ground pressure caused...In this study,a coupled loading method combining three-dimensional static loading with graded cyclic impacts was developed to simulate the stress environment of the surrounding rock under impact ground pressure caused by cyclic disturbances.The mechanical behavior and energy dissipation of coal under this loading method were studied using a split Hopkinson pressure bar(SHPB).The results showed that the pre-applied cyclic low-pressure impacts deteriorated the coal sample's resistance to external loads.Under both cyclic low-pressure impacts and single high-pressure impacts,the dynamic peak stress and secant modulus decreased with increasing impact cycles,exhibiting dynamic fatigue characteristics.The dynamic secant modulus of the sample decreased by 4.14%-6.67%after each impact.The dissipated energy for coal fragmentation samples increased with the number of impacts,averaging 28%under cyclic low-pressure impacts and 29%under single high-pressure impacts.The efficiency of dissipated energy for coal fragmentation initially increased and then decreased as the wave impedance ratio between the coal sample and the bar increased,reaching a maximum of 43.3%when the ratio was 0.06.Based on the defined damage variable,the damage to coal samples from high-pressure impacts was found to be 12 times greater than that under low-pressure conditions.The degree of coal fragmentation was positively correlated with the maximum damage increment.With increasing maximum damage increment,the failure mode of the coal sample evolved from tensile failure to tensile-compressive-shear composite failure.展开更多
Traditional impact protection structures(IPSs)dissipate impact energy according to the plastic dissipation mechanism,which is only effective for single impacts due to the irreversible deformation of structures.To achi...Traditional impact protection structures(IPSs)dissipate impact energy according to the plastic dissipation mechanism,which is only effective for single impacts due to the irreversible deformation of structures.To achieve multi-impact protection,this paper proposes a novel chiral periodic structure with the deformation self-recovery function and the high energy conversion efficiency based on the flexoelectric mechanism.A theoretical model is formulated on the electromechanical responses of a flexoelectric beam under rotational boundaries.The equivalent stiffness and damping characteristics are subsequently derived to construct the electromechanical responses of the structure under constant velocity and mass impacts.Discussions are addressed for the influence of the structural scale effect and resistance on the electromechanical responses.The results show that the energy conversion efficiency increases by 2 to 3 orders of magnitude,reaching as high as 85.3%,which can match well with those of structures reported in the literature based on the plastic energy dissipating mechanism.展开更多
After excavation,some of the surrounding rock mass is in a state of triaxial extension,exhibiting tensile or shear fracture modes.To study the energy mechanism of tensile fracture turning to shear fracture,a series of...After excavation,some of the surrounding rock mass is in a state of triaxial extension,exhibiting tensile or shear fracture modes.To study the energy mechanism of tensile fracture turning to shear fracture,a series of triaxial extension tests were conducted on sandstone under confining pressures of 10,30,50 and 70 MPa.Elastic energy and dissipated energy were separated by single unloading,the input energy u_(t),elastic energy u_(e),and dissipated energy u_(d)at different unloading stress levels were calculated by the integrating stress−strain curves.The results show that tensile cracks dominate fracture under lower confining pressure(10 MPa),and shear cracks play an increasingly important role in fracture as confining pressure increases(30,50 and 70 MPa).Based on the phenomenon that u_(e)and u_(d)increase linearly with increasing u_(t),a possible energy distribution mechanism of fracture mode transition under triaxial extension was proposed.In addition,it was found that peak energy storage capacity is more sensitive to confining pressure compared to elastic energy conversion capacity.展开更多
This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain...This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain responses,deformation,energy dissipation and fracture morphology are all impacted by the loading rate.A pronounced influence of the loading rate on rock deformation is found,with slower loading rate eliciting enhanced strain development,alongside augmented energy absorption and dissipation.In addition,it is revealed that the loading rate and cyclic loading amplitude jointly influence the phase shift distribution,with accelerated rates leading to a narrower phase shift duration.It is suggested that lower loading rate leads to more significant energy dissipation.Finally,the tensile or shear failure modes were intrinsically linked to loading strategy,with cyclic loading predominantly instigating shear damage,as manifest in the increased presence of pulverized grain particles.This work would give new insights into the fortification of mining structures and the optimization of mining methodologies.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 12074206)the Natural Science Foundation of Zhejiang Province of China (Grant No.LY22A040005)supported by the National Natural Science Foundation of China (Grant No. 22103043)。
文摘Nonlinearly induced steady-state photon–phonon entanglement of a dissipative coupled system is studied in the bistable regime. Quantum dynamical characteristics are analysed by solving the mean-field and fluctuation equations of the system. It is shown that dissipative coupling can induce bistable behaviour for the effective dissipation of the system.Under suitable parameters, one of the steady states significantly reduces the dissipative effect of the system. Consequently,a larger steady-state entanglement can be achieved compared to linear dynamics. Furthermore, the experimental feasibility of the parameters is analysed. Our results provide a new perspective for the implementation of steady-state optomechanical entanglement.
基金financially supported by the Science and Technology Innovation Program of Hunan Province(2024RC3003)the Central South University Innovation-Driven Research Programme(2023CXQD012)the Initiative for Sustainable Energy for its financial support。
文摘By combining the merits of radiative cooling(RC)and evaporation cooling(EC),radiative coupled evaporative cooling(REC)has attracted considerable attention for sub-ambient cooling purposes.However,for outdoor devices,the interior heating power would increase the working temperature and fire risk,which would suppress their above-ambient heat dissipation capabilities and passive water cycle properties.In this work,we introduced a REC design based on an all-in-one photonic hydrogel for above-ambient heat dissipation and flame retardancy.Unlike conventional design RC film for heat dissipation with limited cooling power and fire risk,REC hydrogel can greatly improve the heat dissipation performance in the daytime with a high workload,indicating a 12.0℃lower temperature than the RC film under the same conditions in the outdoor experiment.In the nighttime with a low workload,RC-assisted adsorption can improve atmospheric water harvesting to ensure EC in the daytime.In addition,our REC hydrogel significantly enhanced flame retardancy by absorbing heat without a corresponding temperature rise,thus mitigating fire risks.Thus,our design shows a promising solution for the thermal management of outdoor devices,delivering outstanding performance in both heat dissipation and flame retardancy.
基金supported by the National Key Research and Development Program of China (Grant Nos.2024YFA1409800 for J.Z.and2024YFA1408603 for Q.Z.)the National Natural Science Foundation of China (Grant Nos.12125408,12334004for J.Z.,and 12174363 for Q.Z.)+1 种基金the Innovation Program for Quantum Science and Technology (Grant No.2021ZD0303306 for J.Z.)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0450101 for J.Z.)。
文摘Electron–hole(e–h)recombination is a fundamental process that governs energy dissipation and device efficiency in semiconductors.In two-dimensional(2D)materials,the formation of tightly bound excitons makes exciton-mediated e–h recombination the dominant decay pathway.In this work,nonradiative e–h recombination within excitons in monolayer MoS2 is investigated using first-principles simulations that combine nonadiabatic molecular dynamics with𝐺𝑊and real-time Bethe–Salpeter equation(BSE)propagation.A two-step process is identified:rapid intervalley redistribution induced by exchange interaction,followed by slower phonon-assisted recombination facilitated by exciton binding.By selectively removing the screened Coulomb and exchange terms from the BSE Hamiltonian,their respective contributions are disentangled—exchange interaction is found to increase the number of accessible recombination pathways,while binding reduces the excitation energy and enhances nonradiative decay.A reduction in recombination lifetime by over an order of magnitude is observed due to the excitonic many-body effects.These findings provide microscopic insights for understanding and tuning exciton lifetimes in 2D transition-metal dichalcogenides.
基金supported by the Natural Science Research Project of the Anhui Educational Committee,China(No.2022AH050827)the Open Research Fund Program of Anhui Province Key Laboratory of Specialty Polymers,Anhui University of Science and Technology,China(No.AHKLSP23-12)the Joint National-Local Engineering Research Center for Safe and Precise Coal Mining Fund,China(No.EC2022020)。
文摘The preparation of carbon-based electromagnetic wave(EMW)absorbers possessing thin matching thickness,wide absorption bandwidth,strong absorption intensity,and low filling ratio remains a huge challenge.Metal-organic frameworks(MOFs)are ideal self-sacrificing templates for the construction of carbon-based EMW absorbers.In this work,bimetallic FeMn-MOF-derived MnFe_(2)O_(4)/C/graphene composites were fabricated via a two-step route of solvothermal reaction and the following pyrolysis treatment.The results re-veal the evolution of the microscopic morphology of carbon skeletons from loofah-like to octahedral and then to polyhedron and pomegran-ate after the adjustment of the Fe^(3+)to Mn^(2+)molar ratio.Furthermore,at the Fe^(3+)to Mn^(2+)molar ratio of 2:1,the obtained MnFe_(2)O_(4)/C/graphene composite exhibited the highest EMW absorption capacity.Specifically,a minimum reflection loss of-72.7 dB and a max-imum effective absorption bandwidth of 5.1 GHz were achieved at a low filling ratio of 10wt%.In addition,the possible EMW absorp-tion mechanism of MnFe_(2)O_(4)/C/graphene composites was proposed.Therefore,the results of this work will contribute to the construction of broadband and efficient carbon-based EMW absorbers derived from MOFs.
基金supported by the National Natural Science Foundation of China(Grant No.42077244).
文摘To examine the effect of bedding angle upon burst proneness in terms of energy,phyllites with seven various bedding angles are selected for conventional uniaxial compression and single-cyclic loading eunloading uniaxial compression tests.The ejection and failure during compression process of phyllites are monitored in real-time by high-speed camera system.The results demonstrate that the phyllites with different bedding angles all consistently follow the linear energy storage and dissipation(LESD)law during compression.The ultimate energy storage of phyllites with varying bedding angles can be calculated precisely via using the LESD law.Based on this,four kinds of energy-based rockburst indices are applied to quantitatively assess the burst proneness for phyllites.Combined with the recorded images of high-speed camera system,ejection distance,and mass of rock fragments and powder,the burst proneness for phyllites with various bedding angles is qualitatively evaluated adopting the far-field ejection mass ratio.Next,burst proneness of anisotropic phyllites is assessed quantitatively and qualitatively.It is found that phyllites with bedding angles of 0°,15°,and 90°have a high burst proneness,and that with bedding angle of 30°has a medium burst proneness,whereas the ones with bedding angles of 45°,60°,and 75°have a low burst proneness.Finally,the published experimental data of shale and sandstone specimens with different bedding angles are extracted,and it is preliminarily verified that the bedding angle does not change the LESD law of rocks.
基金financial supports from the National Natural Science Foundation of China(Grant Nos.51925503&52105575)the Fundamental Research Funds for the Central Universities(Grant No.QTZX23063)+2 种基金the Aeronautical Science Foundation of China(Grant No.2022Z073081001)the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20232028)the Open Research Funds of State Key Laboratory of Intelligent Manufacturing Equipment and Technology(Grant No.IMETKF2024008).
文摘The combination of advanced photoelectric detectors has rendered single-band camouflage materials ineffective,necessitating the development of infrared multispectral camouflage.However,the design and fabrication of existing works remain complex as they usually require the integration of multiscale structures.Here,we introduce phase modulation into the infrared camouflage metasurfaces with metal-dielectric-metal configuration,enabling them to achieve camouflage across more bands.Based on this strategy,a simple but effective single-layer cascaded metasurface is demonstrated for the first time to achieve low reflection at multi-wavelength lasers,low infrared radiation in atmospheric windows,and broadband thermal management.As a proof-of-concept,a 4-inch sample with a minimum linewidth of 1.8μm is fabricated using photolithography.The excellent infrared multispectral camouflage performance is verified in experiments,showing low reflectance in 0.9–1.6μm,low infrared emissivity in mid-wavelength infrared(MWIR)and long-wavelength infrared(LWIR)bands,and high absorptance at the wavelength of 10.6μm.Meanwhile,broadband high emissivity in 5–8μm can provide high-performance radiative heat dissipation.When the input power is 1.57 W·cm^(-2),the surface/radiation temperature of the metasurface decreases by 5.3℃/18.7℃ compared to the reference.The proposed metasurface may trigger further innovation in the design and application of compact multispectral optical devices.
基金supported by the Open Research Fund Program of Engineering Technology Research Center of Coal Resources Comprehensive Utilization,Anhui Province,Anhui University of Science and Technology(Grant No.MTYJZX202301)the Anhui Provincial Natural Science Foundation(Grant No.2008085J27).
文摘Traditionally reduced graphene oxide(RGO)-based electromagnetic wave(EMW)absorbing materials have poor absorption effectiveness due to impedance mismatch caused by skin effect.The introduction of structural defects and the design of heterogeneous interfaces play a crucial role in enhancing the polarization effect of EMW absorbers.In this study,nitrogen-doped reduced graphene oxide/zinc ferrite@nitrogen-doped carbon(NRGO/ZnFe_(2)O_(4)@NC)ternary composite with rich heterogeneous interfaces is constructed by combining solvothermal reaction,in-situ polymerization,annealing treatment with subsequent hydrothermal reaction.The research results have shown that the obtained NRGO/ZnFe_(2)O_(4)@NC ternary composite exhibits a unique core-shell structure and excellent EMW absorption performance.At a thickness of 2.61 mm,the maximum effective absorption bandwidth can reach 7.2 GHz,spanning the entire Ku-band and a portion of the X-band,and the minimum reflection loss is-61.1 dB,which is superior to most reported RGO-based EMW absorbers.The excellent EMW absorbing ability is mainly ascribed to the optimized impedance matching and the enhanced polarization loss caused by the abundant heterogeneous interfaces and structural defects derived from heteroatomic nitrogen doping.Furthermore,the radar cross section in the far field is simulated by a computer simulation technique.This study provides a novel way to prepare core-shell magnetic carbon composites as highly efficient and broadband EMW absorbers.
基金Project(2024JJ2073)supported by the Science Fund for Distinguished Young Scholars of Hunan Province,ChinaProjects(2023YFC3807205,2019YFC1904704)+4 种基金supported by the National Key R&D Program of ChinaProject(52178443)supported by the National Natural Science Foundation of ChinaProject(2024ZZTS0109)supported by Fundamental Research Funds for the Central Universities of Central South University,China。
文摘Permeable roads generally exhibit inferior mechanical properties and shorter service life than traditional dense-graded/impermeable roads.Furthermore,the incorporation of recycled aggregates in their construction may exacerbate these limitations.To address these issues,this study introduced a novel cement-stabilized permeable recycled aggregate material.A total of 162 beam specimens prepared with nine different levels of cement-aggregate ratio were tested to evaluate their permeability,bending load,and bending fatigue life.The experimental results indicate that increasing the content of recycled aggregates led to a reduction in both permeability and bending load.Additionally,the inclusion of recycled aggregates diminished the energy dissipation capacity of the specimens.These findings were used to establish a robust relationship between the initial damage in cement-stabilized permeable recycled aggregate material specimens and their fatigue life,and to propose a predictive model for their fatigue performance.Further,a method for assessing fatigue damage based on the evolution of fatigue-induced strain and energy dissipation was developed.The findings of this study provide valuable insights into the mechanical behavior and fatigue performance of cement-stabilized permeable recycled aggregate materials,offering guidance for the design of low-carbon-emission,permeable,and durable roadways incorporating recycled aggregates.
基金Supported by the National Natural Science Foundation of China(12201368,62376252)Key Project of Natural Science Foundation of Zhejiang Province(LZ22F030003)Zhejiang Province Leading Geese Plan(2024C02G1123882,2024C01SA100795).
文摘With the urgent need to resolve complex behaviors in nonlinear evolution equations,this study makes a contribution by establishing the local existence of solutions for Cauchy problems associated with equations of mixed types.Our primary contribution is the establishment of solution existence,illuminating the dynamics of these complex equations.To tackle this challenging problem,we construct an approximate solution sequence and apply the contraction mapping principle to rigorously prove local solution existence.Our results significantly advance the understanding of nonlinear evolution equations of mixed types.Furthermore,they provide a versatile,powerful approach for tackling analogous challenges across physics,engineering,and applied mathematics,making this work a valuable reference for researchers in these fields.
基金supported by the National Natural Science Foundation of China(Grant No.52106089)the National Key R&D Project from Ministry of Science and Technology of China(Grant No.2022YFA1203100)。
文摘Filler-reinforced polymer composites demonstrate pervasive applications due to their strengthened performances,multi-degree tunability,and ease of manufacturing.In thermal management field,polymer composites reinforced with thermally conductive fillers are widely adopted as thermal interface materials(TIMs).However,the three dimensional(3D)-stacked heterogenous integration of electronic devices has posed the problem that high-density heat sources are spatially distributed in the package.This situation puts forward new requirements for TIMs,where efficient heat dissipation channels must be established according to the specific distribution of discrete heat sources.To address this challenge,a 3D printing-assisted streamline orientation(3D-PSO)method was proposed to fabricate composite thermal materials with 3D programmable microstructures and orientations of fillers,which combines the shape-design capability of 3D printing and oriented control ability of fluid.The mechanism of fluid-based filler orientation control along streamlines was revealed by mechanical analysis of fillers in matrix.Thanks to the designed heat dissipation channels,composites showed better thermal and mechanical properties in comparison to random composites.Specifically,the thermal conductivity of 3D mesh-shape polydimethylsiloxane/liquid metal(PDMS/LM)composite was5.8 times that of random PDMS/LM composite under filler loading of 34.8 vol%.The thermal conductivity enhancement efficiency of 3D mesh-shape PDMS/carbon fibers composite reached101.05%under filler loading of 5.2 vol%.In the heat dissipation application of 3D-stacked chips,the highest chip temperature with 3D-PSO composite was 42.14℃lower than that with random composites.This is mainly attributed to the locally aggregated and oriented fillers'microstructure in fluid channels,which contributes to thermal percolation phenomena.The3D-PSO method exhibits excellent programmable design capabilities to adopt versatile distributions of heat sources,paving a new way to solve the complicated heat dissipation issue in 3D-stacked chips integration application.
文摘This paper presents a nonlinear micropolar nonclassical continuum theory (MPNCCT) for finite deformation, finite strain deformation physics of thermosviscoelastic solid medium with memory (polymeric micropolar solids) based on classical rotations cΘand their rates. Contravariant second Piola-Kirchhoff stress and moment tensors, in conjunction with finite deformation measures derived by the authors in recent paper, are utilized in deriving the conservation and balance laws and the constitutive theories based on conjugate pairs in entropy inequality and the representation theorem. This nonlinear MPNCCT for TVES with rheology: 1) incorporates nonlinear ordered rate dissipation mechanism based on Green’s strain rates up to order n;2) also incorporates an additional ordered rate dissipation mechanism due to microconstituents, the viscosity of the medium and the rates of the symmetric part of the rotation gradient (of cΘ) tensor up to order n, referred to as micropolar dissipation or micropolar viscous dissipation mechanism;3) incorporates the primary mechanism of memory or rheology due to long chain molecules of the polymer and the viscosity of the medium by using the contravaraint second Piola-Kirchhoff stress tensor and its rates up to order m, resulting in a relaxation spectrum;4) incorporates second mechanism of memory or rheology due to nonclassical physics, interaction of microconstituents with the viscous medium and long chain molecules by considering rates of the contravariant second Piola-Kirchhoff moment tensor up to order m, resulting in relaxation of second Piola-Kirchhoff moment tensor. This results in another relaxation spectrum for the second Piola-Kirchhoff moment tensor due to microconstituents, referred to as micropolar relaxation spectrum consisting of micropolar relaxation time constants of the material. This nonlinear MPNCCT for TVES with memory is thermodynamically and mathematically consistent, and the mathematical model consisting of conservation and balance laws and the constitutive theories has closure and naturally reduces to linear MPNCCT based on infinitesimal deformation assumption. BMM is the essential balance law for all MPNCCT and is used in the present work as well. In the absence of this balance law, a valid thermodynamically and mathematically consistent nonlinear MPNCCT is not possible. The nonlinear MPNCCT based on rotations (cΘ+αΘ) and αΘ(ignoring cΘ) is not considered due to the fact that even the linear MPNCCT based on these rotations is invalid and is thermodynamically and mathematically inconsistent MPNCCT.
文摘The application of mass timber elements in different structures has gained publicity over the last few years,pri-marily due to climate change adaptation policies and net zero carbon targets.Timber is a renewable construction material that can outperform other building materials regarding environmental impact.However,when used in seismically active regions,its application has been limited due to the uncertainties on their seismic behaviour in respect with different design standards and limited ductility in conventional connections.Conventional timber connections typically suffer from stiffness and strength degradation under cyclic loads.Their repairability is also low due to permanent damage in the fasteners and the associated crushing in the wood fibres.The use of friction connections can be an efficient way to mitigate these issues.They offer many advantages as they are economical and yet provide a high level of reliable and continuous energy dissipation.In recent years,a new generation of friction connections has been developed that can provide self-centring behaviour(i.e.,the ability of the structure to return to its original position at the end of an earthquake).However,how these connections perform compared to a mass timber system with conventional timber connections is still unknown.Several studies in the literature have suggested that these connections can enhance the performance of mass timber structures.However,the seismic performance of such systems specifically in terms of base shear,response drifts and response accelerations-has not been thoroughly investigated.This paper examines various design aspects of conventional friction connections and self-centring friction connections,providing insights into their differences concerning key seismic performance indicators.It compares the seismic performance of mass timber buildings equipped with both solutions,highlighting their advantages and limitations and drawing conclusions based on the results.The key findings are that friction connections can provides a superior seismic performance for timber structures.However,that may need to be combined with a parallel system avoid residual displacements.
基金supported by the China Agriculture Research System of MOF and MARA(CARS-21)the Central Public-interest Scientific Institution Basal Research Fund(Y2022QC12)the National Natural Science Foundation of China(32272443)。
文摘Lycium barb arum,known as wolfberry or goji berry,is consumed by humans as a medicine and a food homology product.Conventionally grown wolfberry is often treated extensively with pesticides,which could pose a hazard to humans.Here,the degradation dynamics of dinotefuran and its 2 metabolites(1-methyl-3-(tetrahydro-3-furylmethyl)urea(UF)and 1-methyl-3-(tetrahydro-3-furylmethyl)guanidine(DN)),during wolfberry cultivation and processing was investigated.The half-life(T_(1/2))of dinotefuran was 11.36 and 9.76 days,respectively,under the recommended dosage and double the recommended dosage.During the oven and sun drying processes,processing factors(PFs)of dinotefuran were 1.07-1.34,implying the enrichment of pesticide residues.Decoction process made the removal rate of dinotefuran reach 87.48%,which is higher than that of the brewing process(14.7%),while dinotefuran remained in the wine with high ethanol content in the alcohol soaking process.The hazard quotient(HQ)of dinotefuran,as determined via dietary risk assessment combined with PFs,was<1,indicating an acceptable risk for human consumption.Bioaccessibility of dinotefuran in the three digestive stages were intestinal(18.20%-88.08%)>gastric(5.45%-86.72%)>oral(23.18%)via in vitro simulated digestive system.These findings provide scientific evidence for reasonable application and risk assessment of dinotefuran residues in wolfberry.
文摘Viscoelastic nanofluid flow has drawn substantial interest due to its industrial uses,including research and testing of medical devices,lubrication and tribology,drug delivery systems,and environmental remediation.This work studies nanofluid flow over a viscoelastic boundary layer,focusing on mass and heat transmission.An analysis is performed on the flow traversing a porous sheet undergoing nonlinear stretching.It assesses the consequences of viscous dissipation and thermal radiation.The scientific nanofluid framework laid out by Buongiorno has been exploited.The partial differential equations illustrating the phenomena can be transfigured into ordinary differential equations by utilizing appropriate similarity transformations.The simplified equations are unmasked using the Homotopy Analysis Method(HAM),a semi-analytical approach designed to solve nonlinear ordinary and partial differential equations commonly encountered in numerous scientific and engineering disciplines.Calculations are executed to ascertain the numerical solutions related to temperature,concentration,and velocity fields,accompanied by the skin friction coefficient,local Nusselt number,and local Sherwood number.Visualizations of the results are accompanied by pertinent explanations grounded in scientific principles.The temperature distribution and corresponding thermal layer have been enhanced due to radiative and viscous dissipation characteristics.Additionally,it has been noted that a delay in fluid movement results from an improvement in the porous medium parameter and magnetic field values.A falling trend in the Nusselt number is observed as the Eckert and thermophoresis parameters increase.The current numerical results have been effectively validated against previous difficulties.
基金supported by the CHN Energy Investment Group,grant numbers GJNY-23-86 and GJNY-23-92.
文摘High temperature and high stress are critical challenges facing enhanced geothermal systems(EGS).This study investigates the physical and mechanical behavior and acoustic emission(AE)characteristics of granite subjected to heating–water cooling treatments at temperatures ranging from 25℃ to 400℃.Changes in physical properties,including volume expansion,mass loss,and P-wave velocity,were examined to quantify the extent of thermal damage.Results show that visible surface cracking occurs on granite samples treated above 300℃,with P-wave velocity being the most sensitive indicator of thermal damage.Uniaxial and triaxial compression tests were conducted to explore the effects of temperature and confining pressure on granite’s strength,deformation,failure modes,energy evolution,and brittleness.While peak strength remains largely unaffected by temperature,failure modes transition from axial splitting to shear as confining pressure increases.Thermal damage reduces the rock’s energy storage capacity and increases energy dissipation during loading.The brittleness index decreases with temperature and confining pressure,though granite still exhibits pronounced brittle behavior within the studied range.Distinct differences were observed in the AE temporal characteristics and energy evolution of granite samples under uniaxial and triaxial compression conditions.As the specimen approaches failure,the abrupt increase in AE hit rate occurs earlier than the corresponding rise in AE energy.The global b-value of the granite samples increased with treatment temperature,and the global b-value in triaxial compression tests was higher than that in uniaxial compression tests.The evolution of timedependent b-value also varied with increasing confining pressure.These findings,particularly the AE temporal characteristics and distinct b-value evolution under confinement of thermally damaged granite,provide important implications for microseismic-based stability assessment and early warning in thermally damaged rock masses.
基金National Key Research and Development Program of China(No.2022YFC2905004).
文摘The problems of tailings storage and high-stress conditions in deep mining have emerged as critical factors that limit the security,efficiency,and sustainability of such mines.This study explores the potential to utilize tungsten tailings to create cementitious backfill(CTB)materials and investigates the macroscopic strength features and microscopic damage evolution mechanisms of different-sized CTBs with varying dosages of hydroxypropyl methyl cellulose(HPMC).Specimens with bottom diameters of 50,75,and 100 mm are combined with HPMC dosages of 0,0.15wt%,0.25wt%,and 0.35wt%.A diameter/height ratio of 1:2 is maintained for all CTB specimens.The experimental results show that as the HPMC dosage is increased from 0 to 0.35wt%,the uniaxial compressive strength(UCS)of the CTBs decreases significantly in a linear manner.The 75 mm×150 mm CTB specimen exhibits relatively high plasticity and toughness,with good plastic deformation and energy absorption capabilities,indicating significant size effects.HPMC introduces connected bubbles during the CTB pouring process,but it exhibits anti-segregation and anti-bleeding characteristics,thus reducing tailing settling.The hydration reaction of the CTB doped with HPMC is more uniform,and the Ca/Si atomic ratio dispersion at different sites is smaller.The three CTB sizes all exhibit combined tensile and shear failure,with the 75 mm×150 mm specimen exhibiting macroscopic tensile cracks and relatively few shear cracks.At the micro-scale,excessive ettringite and hydrated calcium silicate are interwoven and fuse,and the tungsten tailings are tightly wrapped.These results provide valuable data and notional insights for optimizing the fluidity of the backfill,and elucidate the strength and damage evolution of solidified materials during filling and extraction.This study contributes to the advancement of green,economical,safe,and sustainable mining practices.
基金supported by the Youth Fund of the CCTEG Coal Mining Research Institute(Grant No.KCYJY-2023-QN-01)the National Natural Science Foundation of China(Grant No.52174080)the Science Foundation of Tiandi Technology Co.,Ltd.(Grant No.2022-2-TD-ZD016).
文摘In this study,a coupled loading method combining three-dimensional static loading with graded cyclic impacts was developed to simulate the stress environment of the surrounding rock under impact ground pressure caused by cyclic disturbances.The mechanical behavior and energy dissipation of coal under this loading method were studied using a split Hopkinson pressure bar(SHPB).The results showed that the pre-applied cyclic low-pressure impacts deteriorated the coal sample's resistance to external loads.Under both cyclic low-pressure impacts and single high-pressure impacts,the dynamic peak stress and secant modulus decreased with increasing impact cycles,exhibiting dynamic fatigue characteristics.The dynamic secant modulus of the sample decreased by 4.14%-6.67%after each impact.The dissipated energy for coal fragmentation samples increased with the number of impacts,averaging 28%under cyclic low-pressure impacts and 29%under single high-pressure impacts.The efficiency of dissipated energy for coal fragmentation initially increased and then decreased as the wave impedance ratio between the coal sample and the bar increased,reaching a maximum of 43.3%when the ratio was 0.06.Based on the defined damage variable,the damage to coal samples from high-pressure impacts was found to be 12 times greater than that under low-pressure conditions.The degree of coal fragmentation was positively correlated with the maximum damage increment.With increasing maximum damage increment,the failure mode of the coal sample evolved from tensile failure to tensile-compressive-shear composite failure.
基金Project supported by the National Natural Science Foundation of China(No.12272138)。
文摘Traditional impact protection structures(IPSs)dissipate impact energy according to the plastic dissipation mechanism,which is only effective for single impacts due to the irreversible deformation of structures.To achieve multi-impact protection,this paper proposes a novel chiral periodic structure with the deformation self-recovery function and the high energy conversion efficiency based on the flexoelectric mechanism.A theoretical model is formulated on the electromechanical responses of a flexoelectric beam under rotational boundaries.The equivalent stiffness and damping characteristics are subsequently derived to construct the electromechanical responses of the structure under constant velocity and mass impacts.Discussions are addressed for the influence of the structural scale effect and resistance on the electromechanical responses.The results show that the energy conversion efficiency increases by 2 to 3 orders of magnitude,reaching as high as 85.3%,which can match well with those of structures reported in the literature based on the plastic energy dissipating mechanism.
基金Project(52074352)supported by the National Natural Science Foundation of ChinaProject(2023JJ30680)supported by the National Science and Technology Major Project of China。
文摘After excavation,some of the surrounding rock mass is in a state of triaxial extension,exhibiting tensile or shear fracture modes.To study the energy mechanism of tensile fracture turning to shear fracture,a series of triaxial extension tests were conducted on sandstone under confining pressures of 10,30,50 and 70 MPa.Elastic energy and dissipated energy were separated by single unloading,the input energy u_(t),elastic energy u_(e),and dissipated energy u_(d)at different unloading stress levels were calculated by the integrating stress−strain curves.The results show that tensile cracks dominate fracture under lower confining pressure(10 MPa),and shear cracks play an increasingly important role in fracture as confining pressure increases(30,50 and 70 MPa).Based on the phenomenon that u_(e)and u_(d)increase linearly with increasing u_(t),a possible energy distribution mechanism of fracture mode transition under triaxial extension was proposed.In addition,it was found that peak energy storage capacity is more sensitive to confining pressure compared to elastic energy conversion capacity.
基金Project(52174069) supported by the National Natural Science Foundation of ChinaProject(8202033) supported by the Beijing Natural Science Foundation,ChinaProject(KCF2203) supported by the Henan Key Laboratory for Green and Efficient Mining&Comprehensive Utilization of Mineral Resources (Henan Polytechnic University),China。
文摘This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths.Testing results show that the fatigue lifetime,stress−strain responses,deformation,energy dissipation and fracture morphology are all impacted by the loading rate.A pronounced influence of the loading rate on rock deformation is found,with slower loading rate eliciting enhanced strain development,alongside augmented energy absorption and dissipation.In addition,it is revealed that the loading rate and cyclic loading amplitude jointly influence the phase shift distribution,with accelerated rates leading to a narrower phase shift duration.It is suggested that lower loading rate leads to more significant energy dissipation.Finally,the tensile or shear failure modes were intrinsically linked to loading strategy,with cyclic loading predominantly instigating shear damage,as manifest in the increased presence of pulverized grain particles.This work would give new insights into the fortification of mining structures and the optimization of mining methodologies.
