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
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
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
Stress accumulation is a key factor leading to sodium storage performance deterioration for NiSe_(2)-based anodes.Therefore,inhibiting the concentrated local stress during the sodiataion/desodiation process is crucial...Stress accumulation is a key factor leading to sodium storage performance deterioration for NiSe_(2)-based anodes.Therefore,inhibiting the concentrated local stress during the sodiataion/desodiation process is crucial for acquiring stable NiSe2-based materials for sodium-ion batteries(SIBs),Herein,a stress dissipation strategy driven by architecture engineering is proposed,which can achieve ultrafast and ultralong sodium storage properties.Different from the conventional sphere-like or rod-like architecture,the three-dimensional(3D)flower-like NiSe_(2)@C composite is delicately designed and assembled with onedimensional nanorods and carbon framework.More importantly,the fundamental mechanism of improved structure stability is unveiled by simulations and experimental results simultaneously.It demonstrates that this designed multidimensional flower-like architecture with dispersed nanorods can balance the structural mismatch,avoid concentrated local strain,and relax the internal stress,mainly induced by the unavoidable volume variation during the repeated conversion processes.Moreover,it can provide more Na^(+)-storage sites and multi-directional migration pathways,leading to a fast Na^(+)-migration channel with boosted reaction kinetic.As expected,it delivers superior rate performance(441 mA h g^(-1)at 5.0 A g^(-1))and long cycling stability(563 mA h g^(-1)at 1.0 A g^(-1)over 1000 cycles)for SIBs.This work provides useful insights for designing high-performance conversion-based anode materials for SIBs.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
The study of the mechanical property and damage state of coal materials under compression is a fundamental area of research in underground mining engineering.Drawing upon the compaction effect and linear energy dissip...The study of the mechanical property and damage state of coal materials under compression is a fundamental area of research in underground mining engineering.Drawing upon the compaction effect and linear energy dissipation(LED)law,a novel compressive damage constitutive model for brittle coal is proposed.Utilizing the energy-defined damage method for mate-rials,the LED law is innovatively introduced to accurately characterize the energy dissipation during the loading process,and a novel formula for characterizing the damage variable of brittle coal is proposed.On this basis,considering that the constitutive model based on the hypothesis of strain equivalence is incapable of accurately describing the compaction effect exhibited by coal material during the compression process,a correction coefficient is proposed and apply it in the novel damage constitutive model.The established conventional monotone loading and single-cyclic loading-unloading uniaxial compression damage constitutive models have been validated using experimental data from cylindrical and cuboid coal specimens.In addition,compared with the constitutive model obtained via the traditional energy calculation method based on the hypothesis that the unloading curve is a straight line,the constitutive model employing LED law can describe the stress-strain state of brittle coal more precisely.This approach introduces a new perspective and enhances the convenience for constructing the constitutive model based on energy theory.展开更多
Mangrove forest is always considered an effective barrier to protect habitats from high waves,especially tsunami.Therefore,the estimation of wave energy dissipation is required for disater warning.The aim of this stud...Mangrove forest is always considered an effective barrier to protect habitats from high waves,especially tsunami.Therefore,the estimation of wave energy dissipation is required for disater warning.The aim of this study is to calculate wave attenuation in mangrove areas by combining field survey method and mathematical modeling method.The application area is Cu Lao Dung mangrove forest,Soc Trang,Vietnam.From data measurements of hydrodynamics and mangrove characteristics,the wave attenuation coefficient r,the drag coefficient Cd were determined in mud area,mud-mangrove area and mangrove area.In addition,using WAPROMAN model,the attenuation of wave height is simulated in different cases such as without mangrove,with mangrove,breaking wave effect and wave trunk interaction effect.Both the results from the measured method and the model method show the role of mangroves in reducing wave energy.The results from modeling are smaller than the calculated results.However,both methods tend to be suitable.Such difference required more considerations not only on calculation formulas but also on modeling adjustment.The research clearly demonstrated the effectiveness of mangroves in coastal protection,with wave-trunk interaction becoming the dominant factor in energy dissipation deeper into the forest.For future,extending the study to different mangrove forests and longer time scales could provide a more comprehensive understanding of the role of mangroves in coastal protection across various geographical and temporal contexts.展开更多
Longitudinal seismic performance is a critical aspect to be considered during the tunnel design process,in addition to cross-sectional considerations.The present study proposed using a laminated shear energy dissipati...Longitudinal seismic performance is a critical aspect to be considered during the tunnel design process,in addition to cross-sectional considerations.The present study proposed using a laminated shear energy dissipation(LSED)structure to achieve effective longitudinal seismic design.The proposed structure consists of thin steel plates and alternately bonded layers of rubber,which can be installed around the periphery of the secondary lining.This configuration guarantees that the tunnels will exhibit optimal axial deformation capacity and robust rigid resistance to circumferential compression from the surrounding rock.To evaluate the impact of the LSED structure on the longitudinal seismic performance of the tunnel,a fine numerical model of the LSED structureetunnel liningesurrounding rock system was developed using finite element simulation.The evaluation criteria include maximum principal stress and strain energy.The seismic response of the tunnel with the LSED structure exhibited a notable reduction of over 40%in terms of seismic attenuation rate when subjected to the Trinidad seismic wave compared to the tunnel without the LSED structure.Furthermore,the aseismic mechanism of the proposed LSED structure is discussed,considering both internal factors such as the rubber shear modulus,steel plate dimensions,and number and location of structures,and external influencing factors such as seismic wave parameters and surrounding rock quality.Meanwhile,the effectiveness of the tunnel with the LSED structure has been quantitatively demonstrated in terms of seismic fragility curves.展开更多
The design principles for conventional reinforced concrete structures have gradually transitioned to seismic-resistant design since the 1970s.However,until recently,the implementation of strength capacity and ductilit...The design principles for conventional reinforced concrete structures have gradually transitioned to seismic-resistant design since the 1970s.However,until recently,the implementation of strength capacity and ductility design has not been rigorously enforced inmany developing countries that are prone to seismic risks.Numerous studies have evaluated the effectiveness of joint behavior based on both ductile and non-ductile designs under cyclic loading.Previous research has demonstrated that enhancing joint regions with Ultra-High Performance Steel Fiber Reinforced Concrete(UHPSFRC)significantly improves the seismic resistance of structural components.This paper presents a detailed analysis of the considerable improvements in energy dissipation capacity and stiffness degradation observed in both reinforced test samples compared to the control sample.Furthermore,assessing the effective performance of enhanced reinforced concrete joints is a critical parameter for evaluating the feasibility of this approach.The findings highlight the potential for UHPSFRC to enhance the resilience of concrete structures under seismic loads,providing a viable solution to improve the safety and durability of infrastructure in earthquake-prone regions.This study aims to inform future design methodologies and standards in seismic-resistant construction in developing nations,emphasizing the importance of adopting innovative materials to mitigate earthquake risks effectively.展开更多
As the integration of electronic components in high-performance servers increases,heat generation significantly impacts performance and raises failure rates.Therefore,heat dissipation has become a critical concern in ...As the integration of electronic components in high-performance servers increases,heat generation significantly impacts performance and raises failure rates.Therefore,heat dissipation has become a critical concern in electronic circuit design.This study uses numerical simulations to investigate the heat dissipation characteristics of electronic components in air-cooled servers.By adjusting airflow speed,heat sink configurations,and the arrangement of straight-fin heat sinks,we optimize heat dissipation performance and analyze the mechanisms at different airflow speeds.The results show that,at the same airflow speed,the temperature of the heat sink is lower than that of the electronic components,creating a temperature gradient that enhances heat transfer.Compared to a front-to-back arrangement of two straight-fin heat sinks,placing the heat sinks parallel to each other results in a lower maximum component temperature and better temperature uniformity.Heat sinks with fins significantly improve heat dissipation.The heat sink with semicylindrical fins on the rib surface provides the best cooling performance.Moreover,compared to natural convection,the maximum temperature of the electronic components decreases by 56.17%and 61%when the incoming flow velocity is 6 m/s with two parallel flat ribbed heat sinks and front-to-back arrangement,respectively.展开更多
The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and ce...The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and cement-sand ratio on the strength and energy consumption of backfill,whole tailings were used as aggregate to prepare slurry with mass concentration of 74%,and the slurry with cement-sand ratio of 1:4,1:6,1:8 and 1:12 was poured into backfill.Uniaxial compression tests were conducted on backfill body specimens that had been cured for 7 days,14 days,28 days,and 45 days.It aims at studying the compressive strength,damage,energy storage limit,energy dissipation,and crack propagation of the fill.The results show that when the cement-sand ratio is held constant,the strength of the backfill increases with curing age.Simultaneously,when the curing age is fixed,the strength is positively correlated with the cement-sand ratio.During uniaxial compression tests,it is observed that the pre-peak energy consumption,post-peak energy consumption,total energy consumption,and unit volume strain energy of the cemented backfill body exhibit exponential relationships with both curing age and cement-sand ratio.The energy storage limit of the backfill reflects its capacity to absorb energy prior to failure,while the relationship between damage and energy consumption provides an accurate depiction of its internal failure mechanisms at different stages.In the failure process of the cemented backfill body,primary cracks accompany secondary cracks,many microcracks initiate and propagate from the stress direction,and crack propagation consumes a significant amount of energy.This study on the strength,energy storage limit,and failure of the cemented backfill body can provide valuable insights for mine safety production.展开更多
Flexible microporous metal rubber(FMP-MR)is widely used in national defense applications,yet its mechanical behavior under high-speed impact conditions remains insufficiently explored.In this study,dynamic and static ...Flexible microporous metal rubber(FMP-MR)is widely used in national defense applications,yet its mechanical behavior under high-speed impact conditions remains insufficiently explored.In this study,dynamic and static experiments were conducted to systematically investigate the mechanical response of metal-wrapped microporous materials under impact loading that spanned 10~6 orders of magnitude.By combining a high-precision numerical model with a spatial contact point search algorithm,the spatio–temporal contact characteristics of the complex network structure in FMP-MR were systematically analyzed.Furthermore,the mapping mechanism from turn topology and mesoscopic friction behavior to macroscopic mechanical properties was comprehensively explored.The results showed that compared with quasi-static loading,FMP-MR under high-speed impact exhibited higher energy absorption efficiency due to high-strain-rate inertia effect.Therefore,the peak stress increased by 141%,and the maximum energy dissipation increased by 300%.Consequently,the theory of dynamic friction locking effect was innovatively proposed.The theory explains that the close synergistic effect of sliding friction and plastic dissipation promoted by the stable interturn-locked embedded structure is the essential reason for the excellent dynamic mechanical properties of FMP-MR under dynamic loading conditions.Briefly,based on the in-depth investigation of the mechanical response and energy dissipation mechanism of FMP-MR under impact loads,this study provides a solid theoretical basis for further expanding the application range of FMP-MR and optimizing its performance.展开更多
Motivated by the widespread applications of nanofluids,a nanofluid model is proposed which focuses on uniform magnetohydrodynamic(MHD)boundary layer flow over a non-linear stretching sheet,incorporating the Casson mod...Motivated by the widespread applications of nanofluids,a nanofluid model is proposed which focuses on uniform magnetohydrodynamic(MHD)boundary layer flow over a non-linear stretching sheet,incorporating the Casson model for blood-based nanofluid while accounting for viscous and Ohmic dissipation effects under the cases of Constant Surface Temperature(CST)and Prescribed Surface Temperature(PST).The study employs a two-phase model for the nanofluid,coupled with thermophoresis and Brownian motion,to analyze the effects of key fluid parameters such as thermophoresis,Brownian motion,slip velocity,Schmidt number,Eckert number,magnetic parameter,and non-linear stretching parameter on the velocity,concentration,and temperature profiles of the nanofluid.The proposed model is novel as it simultaneously considers the impact of thermophoresis and Brownian motion,along with Ohmic and viscous dissipation effects,in both CST and PST scenarios for blood-based Casson nanofluid.The numerical technique built into MATLAB’s bvp4c module is utilized to solve the governing system of coupled differential equations,revealing that the concentration of nanoparticles decreases with increasing thermophoresis and Brownian motion parameters while the temperature of the nanofluid increases.Additionally,a higher Eckert number is found to reduce the nanofluid temperature.A comparative analysis between CST and PST scenarios is also undertaken,which highlights the significant influence of these factors on the fluid’s characteristics.The findings have potential applications in biomedical processes to enhance fluid velocity and heat transfer rates,ultimately improving patient outcomes.展开更多
Design of multi-functional microwave absorption materials with strong dissipation ability is a practical approach to address the current issue of electromagnetic radiation pollution.Herein,based on the ex-change bias ...Design of multi-functional microwave absorption materials with strong dissipation ability is a practical approach to address the current issue of electromagnetic radiation pollution.Herein,based on the ex-change bias interaction between ferromagnetic and anti-ferromagnetic interfaces,a series of absorbers composed of the porous biochar loaded with ferromagnetic/anti-ferromagnetic NiCO_(2)O_(4)/CoO were suc-cessfully prepared via a fairly simple process of one-step calcination.By regulating the calcination tem-perature,the pore size and porosity of porous carbon,morphology of loaded NPs as well as the elec-tromagnetic response property and impedance matching characteristic in such composites can be mod-ulated.The porous biochar/NiCO_(2)O_(4)/CoO composite prepared under 350 ℃ possesses a remarkable elec-tromagnetic absorption reflection loss(RL)of-48.41 dB at 9.12 GHz with 2.5 mm thickness,and the effective absorption bandwidth(EAB)of 4.32 GHz with 2.2 mm thickness is located at X band,this is owing to the strong coupling effect of multiple dielectric polarizations,magnetic resonances,and eddy current consumption under matched impedance.In addition,the microwave absorbing patch prepared with this composite exhibits a well-hydrophobic property for self-cleaning function,and the large exten-sibility with substantial breaking strength endows its practical usage as a flexible absorber.展开更多
Many rock engineering projects show that the growth of tensile cracks is often an important cause of engineering disasters,and the mechanical behavior of rocks is essentially the transmission,storage,dissipation and r...Many rock engineering projects show that the growth of tensile cracks is often an important cause of engineering disasters,and the mechanical behavior of rocks is essentially the transmission,storage,dissipation and release of energy.To investigate the tensile behavior of rock from the perspective of energy,uniaxial tension tests(UTTs)and uniaxial compression tests(UCTs)were carried out on three typical rocks(granite,sandstone and marble).Different unloading points were set before the peak stress to separate elastic energy and dissipated energy.The input energy density ut,elastic energy density ue,and dissipated energy density ud at each unloading point were calculated by integrating stress-strain curves.The results show that there is a strong linear relationship between the three energy parameters and the square of the unloading stress in UCT,but this linear relationship is weaker in UTT.The ue and ud increase linearly with the increase in ut in UCT and UTT.Based on the phenomenon that ue and ud increase linearly with ut,the applicability of W_(et)^(p) index in UTT was proved and the relative energy storage capacity and absolute energy distribution characteristics of three rocks in UCT and UTT were evaluated.The tensile behavior of marble and sandstone in UTT can be divided into two stages vaguely according to the energy distribution,but granite is not the case.In addition,based on dissipated energy,the damage evolution of three types of rocks in UCT and UTT was discussed.This study provides some new insights for understanding the tensile behavior of rock.展开更多
Dilatancy is a fundamental volumetric growth behavior observed during loading and serves as a key index to comprehending the intricate nonlinear behavior and constitutive equation structure of rock.This study focuses ...Dilatancy is a fundamental volumetric growth behavior observed during loading and serves as a key index to comprehending the intricate nonlinear behavior and constitutive equation structure of rock.This study focuses on Jinping marble obtained from the Jinping Underground Laboratory in China at a depth of 2400 m.Various uniaxial and triaxial tests at different strain rates,along with constant confining pressure tests and reduced confining pressure tests under different confining pressures were conducted to analyze the mechanical response and dilatancy characteristics of the marble under four stress paths.Subsequently,a new empirical dilatancy coefficient is proposed based on the energy dissipation method.The results show that brittle failure characteristics of marble under uniaxial compression are more obvious with the strain rate increasing,and plastic failure characteristics of marble under triaxial compression are gradually strengthened.Furthermore,compared to the constant confining pressure,the volume expansion is relatively lower under unloading condition.The energy dissipation is closely linked to the process of dilatancy,with a rapid increase of dissipated energy coinciding with the beginning of dilatancy.A new empirical dilatancy coefficient is defined according to the change trend of energy dissipation rate curve,of which change trend is consistent with the actual dilatancy response in marble under different stress paths.The existing empirical and theoretical dilatancy models are analyzed,which shows that the empirical dilatancy coefficient based on the energy background is more universal.展开更多
The research of rolling mill vibration theory has always been a scientific problem in the field of rolling forming,which is very important to the quality of sheet metal and the stable operation of equipment.The essenc...The research of rolling mill vibration theory has always been a scientific problem in the field of rolling forming,which is very important to the quality of sheet metal and the stable operation of equipment.The essence of rolling mill vibration is the transfer of energy,which is generated from inside and outside.Based on particle damping technology,a dynamic vibration absorber(DVA)is proposed to control the vertical vibration of roll in the rolling process from the point of energy transfer and dissipation.A nonlinear vibration equation for the DVA-roller system is solved by the incremental harmonic balance method.Based on the obtained solutions,the effects of the basic parameters of the DVA on the properties of vibration transmission are investigated by using the power flow method,which provides theoretical guidance for the selection of the basic parameters of the DVA.Furthermore,the influence of the parameters of the particles on the overall dissipation of energy of the particle group is analyzed in a more systematic way,which provides a reference for the selection of the material and diameter and other parameters of the particles in the practical application of the DVA.The effect of particle parameters on roll amplitude inhibition is studied by experiments.The experimental results agree with the theoretical analysis,which proves the correctness of the theoretical analysis and the feasibility of the particle damping absorber.This research proposes a particle damping absorber to absorb and dissipate the energy transfer in rolling process,which provides a new idea for nonlinear dynamic analysis and stability control of rolling mills,and has important guiding significance for practical production.展开更多
This paper is devoted to understanding the stability of perturbations around the hydrostatic equilibrium of the Boussinesq system in order to gain insight into certain atmospheric and oceanographic phenomena.The Bouss...This paper is devoted to understanding the stability of perturbations around the hydrostatic equilibrium of the Boussinesq system in order to gain insight into certain atmospheric and oceanographic phenomena.The Boussinesq system focused on here is anisotropic,and involves only horizontal dissipation and thermal damping.In the 2D case R^(2),due to the lack of vertical dissipation,the stability and large-time behavior problems have remained open in a Sobolev setting.For the spatial domain T×R,this paper solves the stability problem and gives the precise large-time behavior of the perturbation.By decomposing the velocity u and temperatureθinto the horizontal average(ū,θ)and the corresponding oscillation(ū,θ),we can derive the global stability in H~2 and the exponential decay of(ū,θ)to zero in H^(1).Moreover,we also obtain that(ū_(2),θ)decays exponentially to zero in H^(1),and thatū_(1)decays exponentially toū_(1)(∞)in H^(1)as well;this reflects a strongly stratified phenomenon of buoyancy-driven fluids.In addition,we establish the global stability in H^(3)for the 3D case R^(3).展开更多
When a human lands from a high drop,there is a high risk of serious injury to the lower limbs.On the other hand,cats can withstand jumps and falls from heights without being fatally wounded,largely due to their impact...When a human lands from a high drop,there is a high risk of serious injury to the lower limbs.On the other hand,cats can withstand jumps and falls from heights without being fatally wounded,largely due to their impact-resistant paw pads.The aim of the present study was to investigate the biomechanism of impact resistance in cat paw pads,propose an optimal hierarchical Voronoi structure inspired by the paw pads,and apply the structure to bionic cushioning shoes to reduce the impact force of landing for humans.The microstructure of cat paw pads was observed via tissue section staining,and a simulation model was reconstructed based on CT to verify and optimize the structural cushioning capacity.The distribution pattern,wall thickness of compartments,thickness ratio of epidermis and dermis,and number of compartments in the model were changed and simulated to achieve an optimal composed structure.A bionic sole was 3D-printed,and its performance was evaluated via compression test and a jumping-landing experiment.The results show that cat paw pads are a spherical cap structure,divided from the outside to the inside into the epidermis,dermis,and compartments,each with different cushioning capacities.A finite element simulation of different cushioning structures was conducted in a cylinder with a diameter of 20 mm and a height of 10 mm,featuring a three-layer structure.The optimal configuration of the three layers should have a uniform distribution with 0.3–0.5 mm wall thickness,a 1:1–2 thickness ratio of epidermis and dermis,and 100–150 compartments.A bionic sole with an optimized structure can reduce the peak impact force and delay the peak arrival time.Its energy absorption rate is about 4 times that of standard sole.When jumping 80,100,and 120 cm,the normalized ground reaction force is also reduced by 8.7%,12.6%and 15.1%compared with standard shoes.This study provides theoretical and technical support for effective protection against human lower limb landing injuries.展开更多
Quantum resources such as entanglement and coherence are the holy grail for modern quantum technologies. Although the unwanted environmental effects tackle quantum information processing tasks, suprisingly these key q...Quantum resources such as entanglement and coherence are the holy grail for modern quantum technologies. Although the unwanted environmental effects tackle quantum information processing tasks, suprisingly these key quantum resources may be protected and even enhanced by the implementation of some special hybrid open quantum systems. Here, we aim to show how a dissipative atom-cavity-system can be accomplished to generate enhanced quantum resources.To do so, we consider a couple of dissipative cavities, where each one contains two effective two-level atoms interacting with a single-mode cavity field. In practical applications, a classical laser field may be applied to drive each atomic subsystem. After driving the system, a Bell-state measurement is performed on the output of the system to quantify the entanglement and coherence. The obtained results reveal that the remote entanglement and coherence between the atoms existing inside the two distant cavities are not only enhanced, but can be stabilized, even under the action of dissipation. In contrast, the local entanglement between two atoms inside each dissipative cavity attenuates due to the presence of unwanted environmental effects.Nevertheless, the local coherence may show the same behavior as the remote coherence.Besides, the system provides the steady state entanglement in various interaction regimes,particularly in the strong atom-cavity coupling and with relatively large detuning. More interestingly, our numerical analyses demonstrate that the system may show a memory effect due to the fact that the death and revival of the entanglement take place during the interaction. Our proposed model may find potential applications for the implementation of long distance quantum networks. In particular, it facilitates the distribution of quantum resources between the nodes of large-scale quantum networks for secure communication.展开更多
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.
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the financial support from the Guangxi Natural Science Foundation(grant no.2021GXNSFDA075012,2023GXNSFGA026002)National Natural Science Foundation of China(52104298,22075073,52362027,52462029)Fundamental Research Funds for the Central Universities(531107051077).
文摘Stress accumulation is a key factor leading to sodium storage performance deterioration for NiSe_(2)-based anodes.Therefore,inhibiting the concentrated local stress during the sodiataion/desodiation process is crucial for acquiring stable NiSe2-based materials for sodium-ion batteries(SIBs),Herein,a stress dissipation strategy driven by architecture engineering is proposed,which can achieve ultrafast and ultralong sodium storage properties.Different from the conventional sphere-like or rod-like architecture,the three-dimensional(3D)flower-like NiSe_(2)@C composite is delicately designed and assembled with onedimensional nanorods and carbon framework.More importantly,the fundamental mechanism of improved structure stability is unveiled by simulations and experimental results simultaneously.It demonstrates that this designed multidimensional flower-like architecture with dispersed nanorods can balance the structural mismatch,avoid concentrated local strain,and relax the internal stress,mainly induced by the unavoidable volume variation during the repeated conversion processes.Moreover,it can provide more Na^(+)-storage sites and multi-directional migration pathways,leading to a fast Na^(+)-migration channel with boosted reaction kinetic.As expected,it delivers superior rate performance(441 mA h g^(-1)at 5.0 A g^(-1))and long cycling stability(563 mA h g^(-1)at 1.0 A g^(-1)over 1000 cycles)for SIBs.This work provides useful insights for designing high-performance conversion-based anode materials for SIBs.
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 National Science Fund for Distinguished Young Scholars(52225403)the National Natural Science Foundation of China(42077244).
文摘The study of the mechanical property and damage state of coal materials under compression is a fundamental area of research in underground mining engineering.Drawing upon the compaction effect and linear energy dissipation(LED)law,a novel compressive damage constitutive model for brittle coal is proposed.Utilizing the energy-defined damage method for mate-rials,the LED law is innovatively introduced to accurately characterize the energy dissipation during the loading process,and a novel formula for characterizing the damage variable of brittle coal is proposed.On this basis,considering that the constitutive model based on the hypothesis of strain equivalence is incapable of accurately describing the compaction effect exhibited by coal material during the compression process,a correction coefficient is proposed and apply it in the novel damage constitutive model.The established conventional monotone loading and single-cyclic loading-unloading uniaxial compression damage constitutive models have been validated using experimental data from cylindrical and cuboid coal specimens.In addition,compared with the constitutive model obtained via the traditional energy calculation method based on the hypothesis that the unloading curve is a straight line,the constitutive model employing LED law can describe the stress-strain state of brittle coal more precisely.This approach introduces a new perspective and enhances the convenience for constructing the constitutive model based on energy theory.
基金funded by Vietnam National University Ho Chi Minh City(VNU-HCM)under grant number B2019-18-09.
文摘Mangrove forest is always considered an effective barrier to protect habitats from high waves,especially tsunami.Therefore,the estimation of wave energy dissipation is required for disater warning.The aim of this study is to calculate wave attenuation in mangrove areas by combining field survey method and mathematical modeling method.The application area is Cu Lao Dung mangrove forest,Soc Trang,Vietnam.From data measurements of hydrodynamics and mangrove characteristics,the wave attenuation coefficient r,the drag coefficient Cd were determined in mud area,mud-mangrove area and mangrove area.In addition,using WAPROMAN model,the attenuation of wave height is simulated in different cases such as without mangrove,with mangrove,breaking wave effect and wave trunk interaction effect.Both the results from the measured method and the model method show the role of mangroves in reducing wave energy.The results from modeling are smaller than the calculated results.However,both methods tend to be suitable.Such difference required more considerations not only on calculation formulas but also on modeling adjustment.The research clearly demonstrated the effectiveness of mangroves in coastal protection,with wave-trunk interaction becoming the dominant factor in energy dissipation deeper into the forest.For future,extending the study to different mangrove forests and longer time scales could provide a more comprehensive understanding of the role of mangroves in coastal protection across various geographical and temporal contexts.
基金supported by the National Natural Science Foundation of China(Grant No.52109132)the Shandong Provincial Natural Science Foundation(Grant No.ZR2020QE270).
文摘Longitudinal seismic performance is a critical aspect to be considered during the tunnel design process,in addition to cross-sectional considerations.The present study proposed using a laminated shear energy dissipation(LSED)structure to achieve effective longitudinal seismic design.The proposed structure consists of thin steel plates and alternately bonded layers of rubber,which can be installed around the periphery of the secondary lining.This configuration guarantees that the tunnels will exhibit optimal axial deformation capacity and robust rigid resistance to circumferential compression from the surrounding rock.To evaluate the impact of the LSED structure on the longitudinal seismic performance of the tunnel,a fine numerical model of the LSED structureetunnel liningesurrounding rock system was developed using finite element simulation.The evaluation criteria include maximum principal stress and strain energy.The seismic response of the tunnel with the LSED structure exhibited a notable reduction of over 40%in terms of seismic attenuation rate when subjected to the Trinidad seismic wave compared to the tunnel without the LSED structure.Furthermore,the aseismic mechanism of the proposed LSED structure is discussed,considering both internal factors such as the rubber shear modulus,steel plate dimensions,and number and location of structures,and external influencing factors such as seismic wave parameters and surrounding rock quality.Meanwhile,the effectiveness of the tunnel with the LSED structure has been quantitatively demonstrated in terms of seismic fragility curves.
文摘The design principles for conventional reinforced concrete structures have gradually transitioned to seismic-resistant design since the 1970s.However,until recently,the implementation of strength capacity and ductility design has not been rigorously enforced inmany developing countries that are prone to seismic risks.Numerous studies have evaluated the effectiveness of joint behavior based on both ductile and non-ductile designs under cyclic loading.Previous research has demonstrated that enhancing joint regions with Ultra-High Performance Steel Fiber Reinforced Concrete(UHPSFRC)significantly improves the seismic resistance of structural components.This paper presents a detailed analysis of the considerable improvements in energy dissipation capacity and stiffness degradation observed in both reinforced test samples compared to the control sample.Furthermore,assessing the effective performance of enhanced reinforced concrete joints is a critical parameter for evaluating the feasibility of this approach.The findings highlight the potential for UHPSFRC to enhance the resilience of concrete structures under seismic loads,providing a viable solution to improve the safety and durability of infrastructure in earthquake-prone regions.This study aims to inform future design methodologies and standards in seismic-resistant construction in developing nations,emphasizing the importance of adopting innovative materials to mitigate earthquake risks effectively.
基金supported by the key technology project of China Southern Power Grid Corporation(GZKJXM20240009).
文摘As the integration of electronic components in high-performance servers increases,heat generation significantly impacts performance and raises failure rates.Therefore,heat dissipation has become a critical concern in electronic circuit design.This study uses numerical simulations to investigate the heat dissipation characteristics of electronic components in air-cooled servers.By adjusting airflow speed,heat sink configurations,and the arrangement of straight-fin heat sinks,we optimize heat dissipation performance and analyze the mechanisms at different airflow speeds.The results show that,at the same airflow speed,the temperature of the heat sink is lower than that of the electronic components,creating a temperature gradient that enhances heat transfer.Compared to a front-to-back arrangement of two straight-fin heat sinks,placing the heat sinks parallel to each other results in a lower maximum component temperature and better temperature uniformity.Heat sinks with fins significantly improve heat dissipation.The heat sink with semicylindrical fins on the rib surface provides the best cooling performance.Moreover,compared to natural convection,the maximum temperature of the electronic components decreases by 56.17%and 61%when the incoming flow velocity is 6 m/s with two parallel flat ribbed heat sinks and front-to-back arrangement,respectively.
基金funded by the National Natural Science Foundation of China(52474131)the National Natural Science Foundation of China(42467022)+1 种基金the Yunnan Major Scientific and Technological Projects(Grant No.202202AG050014)the Yunnan Fundamental Research Projects(NO.202101BE070001-038,202201AT070146).
文摘The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and cement-sand ratio on the strength and energy consumption of backfill,whole tailings were used as aggregate to prepare slurry with mass concentration of 74%,and the slurry with cement-sand ratio of 1:4,1:6,1:8 and 1:12 was poured into backfill.Uniaxial compression tests were conducted on backfill body specimens that had been cured for 7 days,14 days,28 days,and 45 days.It aims at studying the compressive strength,damage,energy storage limit,energy dissipation,and crack propagation of the fill.The results show that when the cement-sand ratio is held constant,the strength of the backfill increases with curing age.Simultaneously,when the curing age is fixed,the strength is positively correlated with the cement-sand ratio.During uniaxial compression tests,it is observed that the pre-peak energy consumption,post-peak energy consumption,total energy consumption,and unit volume strain energy of the cemented backfill body exhibit exponential relationships with both curing age and cement-sand ratio.The energy storage limit of the backfill reflects its capacity to absorb energy prior to failure,while the relationship between damage and energy consumption provides an accurate depiction of its internal failure mechanisms at different stages.In the failure process of the cemented backfill body,primary cracks accompany secondary cracks,many microcracks initiate and propagate from the stress direction,and crack propagation consumes a significant amount of energy.This study on the strength,energy storage limit,and failure of the cemented backfill body can provide valuable insights for mine safety production.
基金National Natural Science Foundation of China-NSAF(Grant No.U2330202)the National Natural Science Foundation of China(Grant Nos.52175162 and 51805086)+1 种基金Fujian Provincial Technological Innovation Key Research and Industrialization Projects(Grant Nos.2023XQ005 and 2024XQ010)The National Independent Innovation Demonstration Platform Project of Fujian Province(2024QZFX07)。
文摘Flexible microporous metal rubber(FMP-MR)is widely used in national defense applications,yet its mechanical behavior under high-speed impact conditions remains insufficiently explored.In this study,dynamic and static experiments were conducted to systematically investigate the mechanical response of metal-wrapped microporous materials under impact loading that spanned 10~6 orders of magnitude.By combining a high-precision numerical model with a spatial contact point search algorithm,the spatio–temporal contact characteristics of the complex network structure in FMP-MR were systematically analyzed.Furthermore,the mapping mechanism from turn topology and mesoscopic friction behavior to macroscopic mechanical properties was comprehensively explored.The results showed that compared with quasi-static loading,FMP-MR under high-speed impact exhibited higher energy absorption efficiency due to high-strain-rate inertia effect.Therefore,the peak stress increased by 141%,and the maximum energy dissipation increased by 300%.Consequently,the theory of dynamic friction locking effect was innovatively proposed.The theory explains that the close synergistic effect of sliding friction and plastic dissipation promoted by the stable interturn-locked embedded structure is the essential reason for the excellent dynamic mechanical properties of FMP-MR under dynamic loading conditions.Briefly,based on the in-depth investigation of the mechanical response and energy dissipation mechanism of FMP-MR under impact loads,this study provides a solid theoretical basis for further expanding the application range of FMP-MR and optimizing its performance.
基金funded by Universiti Teknikal Malaysia Melaka and Ministry of Higher Education(MoHE)Malaysia,grant number FRGS/1/2024/FTKM/F00586.
文摘Motivated by the widespread applications of nanofluids,a nanofluid model is proposed which focuses on uniform magnetohydrodynamic(MHD)boundary layer flow over a non-linear stretching sheet,incorporating the Casson model for blood-based nanofluid while accounting for viscous and Ohmic dissipation effects under the cases of Constant Surface Temperature(CST)and Prescribed Surface Temperature(PST).The study employs a two-phase model for the nanofluid,coupled with thermophoresis and Brownian motion,to analyze the effects of key fluid parameters such as thermophoresis,Brownian motion,slip velocity,Schmidt number,Eckert number,magnetic parameter,and non-linear stretching parameter on the velocity,concentration,and temperature profiles of the nanofluid.The proposed model is novel as it simultaneously considers the impact of thermophoresis and Brownian motion,along with Ohmic and viscous dissipation effects,in both CST and PST scenarios for blood-based Casson nanofluid.The numerical technique built into MATLAB’s bvp4c module is utilized to solve the governing system of coupled differential equations,revealing that the concentration of nanoparticles decreases with increasing thermophoresis and Brownian motion parameters while the temperature of the nanofluid increases.Additionally,a higher Eckert number is found to reduce the nanofluid temperature.A comparative analysis between CST and PST scenarios is also undertaken,which highlights the significant influence of these factors on the fluid’s characteristics.The findings have potential applications in biomedical processes to enhance fluid velocity and heat transfer rates,ultimately improving patient outcomes.
基金Surface Project of Local Development in Science and Technology Guided by Central Government(No.2021ZYD0041)National Natural Science Foundation of China(Nos.52377026 and 52301192)+2 种基金Natural Science Foundation of Shandong Province(No.ZR2019YQ24)Shandong Taishan Scholars Young Expert Program(No.tsqn202103057)Qingchuang Talents Induction Program of Shandong Higher Education Institution(Research and Innovation Team of Structural-Functional Polymer Composites).
文摘Design of multi-functional microwave absorption materials with strong dissipation ability is a practical approach to address the current issue of electromagnetic radiation pollution.Herein,based on the ex-change bias interaction between ferromagnetic and anti-ferromagnetic interfaces,a series of absorbers composed of the porous biochar loaded with ferromagnetic/anti-ferromagnetic NiCO_(2)O_(4)/CoO were suc-cessfully prepared via a fairly simple process of one-step calcination.By regulating the calcination tem-perature,the pore size and porosity of porous carbon,morphology of loaded NPs as well as the elec-tromagnetic response property and impedance matching characteristic in such composites can be mod-ulated.The porous biochar/NiCO_(2)O_(4)/CoO composite prepared under 350 ℃ possesses a remarkable elec-tromagnetic absorption reflection loss(RL)of-48.41 dB at 9.12 GHz with 2.5 mm thickness,and the effective absorption bandwidth(EAB)of 4.32 GHz with 2.2 mm thickness is located at X band,this is owing to the strong coupling effect of multiple dielectric polarizations,magnetic resonances,and eddy current consumption under matched impedance.In addition,the microwave absorbing patch prepared with this composite exhibits a well-hydrophobic property for self-cleaning function,and the large exten-sibility with substantial breaking strength endows its practical usage as a flexible absorber.
基金supported by the National Natural Science Foundation of China(Grant No.52074352)the National Natural Science Foundation of Hunan Province of China(Grant No.2023JJ30680)the Fundamental Research Funds for the Central Universities of Central South University(Grant No.2024ZZTS0423).
文摘Many rock engineering projects show that the growth of tensile cracks is often an important cause of engineering disasters,and the mechanical behavior of rocks is essentially the transmission,storage,dissipation and release of energy.To investigate the tensile behavior of rock from the perspective of energy,uniaxial tension tests(UTTs)and uniaxial compression tests(UCTs)were carried out on three typical rocks(granite,sandstone and marble).Different unloading points were set before the peak stress to separate elastic energy and dissipated energy.The input energy density ut,elastic energy density ue,and dissipated energy density ud at each unloading point were calculated by integrating stress-strain curves.The results show that there is a strong linear relationship between the three energy parameters and the square of the unloading stress in UCT,but this linear relationship is weaker in UTT.The ue and ud increase linearly with the increase in ut in UCT and UTT.Based on the phenomenon that ue and ud increase linearly with ut,the applicability of W_(et)^(p) index in UTT was proved and the relative energy storage capacity and absolute energy distribution characteristics of three rocks in UCT and UTT were evaluated.The tensile behavior of marble and sandstone in UTT can be divided into two stages vaguely according to the energy distribution,but granite is not the case.In addition,based on dissipated energy,the damage evolution of three types of rocks in UCT and UTT was discussed.This study provides some new insights for understanding the tensile behavior of rock.
基金Project(2022NSFSC0279)supported by the General Project of Sichuan Natural Science Foundation,ChinaProject(Z17113)supported by the Key Scientific Research Fund of Xihua University,ChinaProject(SR21A04)supported by the Research Center for Social Development and Social Risk Control of Sichuan Province,Key Research Base of Philosophy and Social Sciences,Sichuan University,China。
文摘Dilatancy is a fundamental volumetric growth behavior observed during loading and serves as a key index to comprehending the intricate nonlinear behavior and constitutive equation structure of rock.This study focuses on Jinping marble obtained from the Jinping Underground Laboratory in China at a depth of 2400 m.Various uniaxial and triaxial tests at different strain rates,along with constant confining pressure tests and reduced confining pressure tests under different confining pressures were conducted to analyze the mechanical response and dilatancy characteristics of the marble under four stress paths.Subsequently,a new empirical dilatancy coefficient is proposed based on the energy dissipation method.The results show that brittle failure characteristics of marble under uniaxial compression are more obvious with the strain rate increasing,and plastic failure characteristics of marble under triaxial compression are gradually strengthened.Furthermore,compared to the constant confining pressure,the volume expansion is relatively lower under unloading condition.The energy dissipation is closely linked to the process of dilatancy,with a rapid increase of dissipated energy coinciding with the beginning of dilatancy.A new empirical dilatancy coefficient is defined according to the change trend of energy dissipation rate curve,of which change trend is consistent with the actual dilatancy response in marble under different stress paths.The existing empirical and theoretical dilatancy models are analyzed,which shows that the empirical dilatancy coefficient based on the energy background is more universal.
基金Supported by National Natural Science Foundation of China(Grant No.52205404)National Key Research and Development Project(Grant No.2018YFA0707300)+2 种基金Fundamental Research Program of Shanxi Province(Grant Nos.202203021212293,202203021221054)Xinjiang Intelligent Equipment Research Institute Directed Commissioned Research Projects(Grant No.XJYJY2024012)Open Research Fund from the Hai’an&Taiyuan University of Technology Advanced Manufacturing and Intelligent Equipment Industrial Research Institute(Grant No.2023HA-TYUTKFYF004).
文摘The research of rolling mill vibration theory has always been a scientific problem in the field of rolling forming,which is very important to the quality of sheet metal and the stable operation of equipment.The essence of rolling mill vibration is the transfer of energy,which is generated from inside and outside.Based on particle damping technology,a dynamic vibration absorber(DVA)is proposed to control the vertical vibration of roll in the rolling process from the point of energy transfer and dissipation.A nonlinear vibration equation for the DVA-roller system is solved by the incremental harmonic balance method.Based on the obtained solutions,the effects of the basic parameters of the DVA on the properties of vibration transmission are investigated by using the power flow method,which provides theoretical guidance for the selection of the basic parameters of the DVA.Furthermore,the influence of the parameters of the particles on the overall dissipation of energy of the particle group is analyzed in a more systematic way,which provides a reference for the selection of the material and diameter and other parameters of the particles in the practical application of the DVA.The effect of particle parameters on roll amplitude inhibition is studied by experiments.The experimental results agree with the theoretical analysis,which proves the correctness of the theoretical analysis and the feasibility of the particle damping absorber.This research proposes a particle damping absorber to absorb and dissipate the energy transfer in rolling process,which provides a new idea for nonlinear dynamic analysis and stability control of rolling mills,and has important guiding significance for practical production.
基金supported by National Natural Science Foundation of China(12071391,12231016)the Guangdong Basic and Applied Basic Research Foundation(2022A1515010860)。
文摘This paper is devoted to understanding the stability of perturbations around the hydrostatic equilibrium of the Boussinesq system in order to gain insight into certain atmospheric and oceanographic phenomena.The Boussinesq system focused on here is anisotropic,and involves only horizontal dissipation and thermal damping.In the 2D case R^(2),due to the lack of vertical dissipation,the stability and large-time behavior problems have remained open in a Sobolev setting.For the spatial domain T×R,this paper solves the stability problem and gives the precise large-time behavior of the perturbation.By decomposing the velocity u and temperatureθinto the horizontal average(ū,θ)and the corresponding oscillation(ū,θ),we can derive the global stability in H~2 and the exponential decay of(ū,θ)to zero in H^(1).Moreover,we also obtain that(ū_(2),θ)decays exponentially to zero in H^(1),and thatū_(1)decays exponentially toū_(1)(∞)in H^(1)as well;this reflects a strongly stratified phenomenon of buoyancy-driven fluids.In addition,we establish the global stability in H^(3)for the 3D case R^(3).
基金approved by the Science and Ethics Committee of the School of Biological Science and Medical Engineering at Beihang University(protocol code:BM201900125).
文摘When a human lands from a high drop,there is a high risk of serious injury to the lower limbs.On the other hand,cats can withstand jumps and falls from heights without being fatally wounded,largely due to their impact-resistant paw pads.The aim of the present study was to investigate the biomechanism of impact resistance in cat paw pads,propose an optimal hierarchical Voronoi structure inspired by the paw pads,and apply the structure to bionic cushioning shoes to reduce the impact force of landing for humans.The microstructure of cat paw pads was observed via tissue section staining,and a simulation model was reconstructed based on CT to verify and optimize the structural cushioning capacity.The distribution pattern,wall thickness of compartments,thickness ratio of epidermis and dermis,and number of compartments in the model were changed and simulated to achieve an optimal composed structure.A bionic sole was 3D-printed,and its performance was evaluated via compression test and a jumping-landing experiment.The results show that cat paw pads are a spherical cap structure,divided from the outside to the inside into the epidermis,dermis,and compartments,each with different cushioning capacities.A finite element simulation of different cushioning structures was conducted in a cylinder with a diameter of 20 mm and a height of 10 mm,featuring a three-layer structure.The optimal configuration of the three layers should have a uniform distribution with 0.3–0.5 mm wall thickness,a 1:1–2 thickness ratio of epidermis and dermis,and 100–150 compartments.A bionic sole with an optimized structure can reduce the peak impact force and delay the peak arrival time.Its energy absorption rate is about 4 times that of standard sole.When jumping 80,100,and 120 cm,the normalized ground reaction force is also reduced by 8.7%,12.6%and 15.1%compared with standard shoes.This study provides theoretical and technical support for effective protection against human lower limb landing injuries.
文摘Quantum resources such as entanglement and coherence are the holy grail for modern quantum technologies. Although the unwanted environmental effects tackle quantum information processing tasks, suprisingly these key quantum resources may be protected and even enhanced by the implementation of some special hybrid open quantum systems. Here, we aim to show how a dissipative atom-cavity-system can be accomplished to generate enhanced quantum resources.To do so, we consider a couple of dissipative cavities, where each one contains two effective two-level atoms interacting with a single-mode cavity field. In practical applications, a classical laser field may be applied to drive each atomic subsystem. After driving the system, a Bell-state measurement is performed on the output of the system to quantify the entanglement and coherence. The obtained results reveal that the remote entanglement and coherence between the atoms existing inside the two distant cavities are not only enhanced, but can be stabilized, even under the action of dissipation. In contrast, the local entanglement between two atoms inside each dissipative cavity attenuates due to the presence of unwanted environmental effects.Nevertheless, the local coherence may show the same behavior as the remote coherence.Besides, the system provides the steady state entanglement in various interaction regimes,particularly in the strong atom-cavity coupling and with relatively large detuning. More interestingly, our numerical analyses demonstrate that the system may show a memory effect due to the fact that the death and revival of the entanglement take place during the interaction. Our proposed model may find potential applications for the implementation of long distance quantum networks. In particular, it facilitates the distribution of quantum resources between the nodes of large-scale quantum networks for secure communication.
