To consider the effects of the interactions and interplay among microstructures, gradient-dependent models of second- and fourth-order are included in the widely used phenomenological Johnson-Cook model where the effe...To consider the effects of the interactions and interplay among microstructures, gradient-dependent models of second- and fourth-order are included in the widely used phenomenological Johnson-Cook model where the effects of strain-hardening, strain rate sensitivity, and thermal-softening are successfully described. The various parameters for 1006 steel, 4340 steel and S-7 tool steel are assigned. The distributions and evolutions of the local plastic shear strain and deformation in adiabatic shear band （ASB） are predicted. The calculated results of the second- and fourth- order gradient plasticity models are compared. S-7 tool steel possesses the steepest profile of local plastic shear strain in ASB, whereas 1006 steel has the least profile. The peak local plastic shear strain in ASB for S-7 tool steel is slightly higher than that for 4340 steel and is higher than that for 1006 steel. The extent of the nonlinear distribution of the local plastic shear deformation in ASB is more apparent for the S-7 tool steel, whereas it is the least apparent for 1006 steel. In fourth-order gradient plasticity model, the profile of the local plastic shear strain in the middle of ASB has a pronounced plateau whose width decreases with increasing average plastic shear strain, leading to a shrink of the portion of linear distribution of the profile of the local plastic shear deformation. When compared with the sec- ond-order gradient plasticity model, the fourth-order gradient plasticity model shows a lower peak local plastic shear strain in ASB and a higher magnitude of plastic shear deformation at the top or base of ASB, which is due to wider ASB. The present numerical results of the second- and fourth-order gradient plasticity models are consistent with the previous numerical and experimental results at least qualitatively.展开更多
In this paper,we consider the fourth-order parabolic equation with p(x)Laplacian and variable exponent source ut+∆^(2)u−div(|■u|^(p(x)−2■u))=|u|^(q(x))−1u.By applying potential well method,we obtain global existence...In this paper,we consider the fourth-order parabolic equation with p(x)Laplacian and variable exponent source ut+∆^(2)u−div(|■u|^(p(x)−2■u))=|u|^(q(x))−1u.By applying potential well method,we obtain global existence,asymptotic behavior and blow-up of solutions with initial energy J(u_(0))≤d.Moreover,we estimate the upper bound of the blow-up time for J(u_(0))≤0.展开更多
The paper considers the initial value problem of inhomogeneous fourth-order Schr¨odinger equation with potential in energy space H^(2)(R^(d)).The global well-posedness is obtained in dimensions d≥5 resorting to ...The paper considers the initial value problem of inhomogeneous fourth-order Schr¨odinger equation with potential in energy space H^(2)(R^(d)).The global well-posedness is obtained in dimensions d≥5 resorting to contractive mapping principle,Strichartz estimates,Caffarelli-Kohn-Nirenberg-type inequality and the continuity method.展开更多
We investigate the alpha helical protein structure characterized by fourth-order interspine coupling,focusing on a three-coupled fourth-order nonlinear Schr??dinger system.We introduce a generalized Darboux transforma...We investigate the alpha helical protein structure characterized by fourth-order interspine coupling,focusing on a three-coupled fourth-order nonlinear Schr??dinger system.We introduce a generalized Darboux transformation,departing from the classical Darboux transformation.Based on this,we construct the two-and three-degenerate soliton solutions and four-degenerate asymptotic soliton solutions.Based on the asymptotic analysis,we find that the amplitudes of interacting solitons are retained upon the interactions.Elastic interactions between two degenerate solitons exhibiting four curve-type asymptotic solitons are depicted.When the lattice parameterβchanges,the velocities of the two degenerate solitons also change.Elastic interaction among three degenerate solitons comprising four curve-type asymptotic solitons and two line-type solitons is presented.Interaction among one soliton and two degenerate solitons with different velocities is shown.Elastic interaction among four degenerate solitons comprising eight curve-type asymptotic solitons is also presented.Interaction among two two-degenerate solitons with two spectral parameters is shown.The relative distance between two asymptotic solitons exhibits logarithmic growth with|t|,where t represents the retarded time.Acceleration of soliton separation decays exponentially with relative distance,and eventually approaches zero.Phase shifts depend on t.展开更多
In this work, an efficient spectral method is proposed to solve the fourth-order eigenvalue problem in cylinder domain. Firstly, the key point of this method is to decompose the original model into a kind of decoupled...In this work, an efficient spectral method is proposed to solve the fourth-order eigenvalue problem in cylinder domain. Firstly, the key point of this method is to decompose the original model into a kind of decoupled two-dimensional eigenvalue problem by cylindrical coordinate transformation and Fourier series expansion, and deduce the crucial essential pole conditions. Secondly, we define a kind of weighted Sobolev spaces, and establish a suitable variational formula and its discrete form for each two-dimensional eigenvalue problem. Furthermore, we derive the equivalent operator formulas and obtain some prior error estimates of spectral theory of compact operators. More importantly, we further obtained error estimates for approximating eigenvalues and eigenfunctions by using two newly constructed projection operators. Finally,some numerical experiments are performed to validate our theoretical results and algorithm.展开更多
A gradient structure was introduced into a metal laminated target plate,and the anti-penetration simulation of the gradient structure was compared with that of a uniform-layer-thickness target plate by finite element ...A gradient structure was introduced into a metal laminated target plate,and the anti-penetration simulation of the gradient structure was compared with that of a uniform-layer-thickness target plate by finite element simulation.The analysis was verified by an impact experiment.Results show that the high-level thickness and appropriate percentage of Ti alloy at the upper side of the gradient structure provide greater impact resistance against the bullet,which increases the warhead breakage and enhances the anti-penetration performance.In addition,during the impact process,the stress is transmitted and reflected in the form of waves in each layer of the target plate,and the interaction between the compression and tension waves causes non-synergistic deformation of the target plate and leads to delamination.The gradient target plate takes penetration resistance a step further through the higher energy absorption rate and more consumption of the bullet kinetic energy.This research provides a theoretical basis for the application of gradient structures in metallic laminated armor.展开更多
Recycling spent lithium-ion(Li+)batteries is critical for achieving environmental conservation and the strategic recovery of essential resources.Compared with conventional methods for recovering cathode materials,whic...Recycling spent lithium-ion(Li+)batteries is critical for achieving environmental conservation and the strategic recovery of essential resources.Compared with conventional methods for recovering cathode materials,which are energy-intensive and prone to secondary pollution,the direct regeneration approach has emerged as a rapid and highly efficient method,gaining widespread attention in recent years.However,this approach faces major challenges,including degraded electrochemical performances and limited economic value.This study,therefore,proposes a high-value direct regeneration strategy to convert degraded spent LiFePO_(4)(S-LFP)into a gradient manganese(Mn)-doped regenerated LiFe_(0.7)Mn_(0.3)PO_(4)/C(R-LFMP)composite.This method leverages the inherent microcracks and Li vacancies present in S-LFP,likely acting as diffusion channels for the Mn^(2+)/Li^(+)ions.Through a two-step mechanochemical ball-milling and carbothermal reduction process,this approach achieves simultaneous Li replenishment and surface-localised Mn gradient doping with enhanced structural control.Notably,the R-LFMP exhibits an exceptional electrochemical performance.At 0.1 C,it delivers a discharge capacity of 161.4 mA h g^(−1)and an energy density of 563.5 Wh kg^(−1)(representing a 60.5%improvement over S-LFP).Additionally,it maintains 83%capacity retention after 900 cycles at 0.5C,a considerable enhancement compared to commercial LFMP(62%).Furthermore,the regenerated cathode material generates a net profit of$7.102 kg^(−1),surpassing the profitability of conventional recycling methods by 90%.Overall,this study introduces a transformative and sustainable LFP regeneration technology,achieving breakthroughs in electrochemical restoration and high-value recycling,while paving the way for the closed-loop utilisation of LFP-based energy storage systems.展开更多
Optical phase-gradient metasurfaces have garnered significant attention for enabling flexible light manipulation,with applications across diverse domains.In this work,we will demonstrate that the metasurfaces with pha...Optical phase-gradient metasurfaces have garnered significant attention for enabling flexible light manipulation,with applications across diverse domains.In this work,we will demonstrate that the metasurfaces with phase gradient modulation can be used to achieve illusion optics,featuring the advantages of simple geometric structure and feasible implementation compared with the well-known transformation optics method.The underlying mechanism is the anomalous diffraction law caused by the phase gradient,which provides a theoretical basis for freely manipulating the propagation path of light.By considering a specific example,we will demonstrate that the phase gradient can transform spatial coordinates in real space into illusion space,thereby converting a plane in real space into a curved surface structure in illusion space to achieve the illusion effect.This approach provides a viable alternative to transformation optics for designing illusion devices.展开更多
Electrocatalytic CO_(2) reduction(CO_(2) RR)toward multi-carbon compounds is a challenging but meaningful route for carbon cycling.Copper-based catalysts are the most promising candidate for C_(2+)generation due to th...Electrocatalytic CO_(2) reduction(CO_(2) RR)toward multi-carbon compounds is a challenging but meaningful route for carbon cycling.Copper-based catalysts are the most promising candidate for C_(2+)generation due to their unique C–C coupling activity,yet the in situ reduction from Cu^(+) to Cu^(0) under cathodic potentials causes the catalyst deactivation.Herein,we develop a transient thermal shock strategy to embed Cu^(+) species into CeO_(2) lattices,constructing a CuO_(x)/CuCeO_(x)catalyst with a radial gradient Cu^(+) -Ov-Ce^(3+)/Ce^(4+)structure.Depth-profiling X-ray photoelectron spectroscopy(XPS)and density functional theory(DFT)calculations reveal that mismatched metal/oxygen diffusion kinetics drive continuous electron transfer from surface Cu^(+) to bulk Ce^(3+)/Ce^(4+)via oxygen vacancies(Ov),forming a dynamic“self-sacrificial”structure to preserve surface Cu^(+) states.In CO_(2)-saturated 0.1 M KHCO_(3),the optimized CuO_(x)/CuCeO_(x)-10 achieves a high C_(2) Faradaic efficiency(FE)of 85.8%at-1.4 V vs.RHE.In situ attenuated total reflection surface-enhanced infrared adsorption spectroscopy(ATR-SEIRAS)identifies the key intermediates of C_(2) are*OCCO and*OCCOH,while DFT reveals a drastic reduction of C–C coupling barrier from 0.842 to0.274 eV.This work demonstrates kinetically tailored metal-support interactions,enabling oxidationstate control for pathway-selective catalysis.展开更多
The paleo-geothermal gradient is a crucial parameter for converting the thermal history to the exhumation history.However,the precise estimation of this parameter has been a challenge.This paper presents a simple two-...The paleo-geothermal gradient is a crucial parameter for converting the thermal history to the exhumation history.However,the precise estimation of this parameter has been a challenge.This paper presents a simple two-step method to model the paleo-geothermal gradient using low-temperature thermochronology.(1)It uses the Monte Carlo approach to generate thermal histories in a vertical section randomly and calculates the entire thermal history within the goodnessof-fit thresholds based on different paleo-geothermal gradients.(2)It selects the optimum paleogeothermal gradient by comparing the entire thermal history within different goodness-of-fit thresholds.We validated the method with apatite(U-Th)/He and fission track data collected from two drill cores in the Haiyuan-Liupanshan region.The result revealed that the best-fit paleo-geothermal gradient was~42℃/km during the Early Cretaceous–Miocene and has decreased rapidly to 20℃/km since~10 Ma.The crust thickening in the study area may explain the rapid reduction in the paleogeothermal gradient since~10 Ma.Our results are consistent with earlier studies in the region,suggesting that our simple and more intuitive approach provides an alternative method for paleogeothermal gradient modeling.展开更多
Transformer models face significant computational challenges in private inference(PI).Existing optimization methods often rely on isolated techniques,neglecting joint structural and operational improvements.We propose...Transformer models face significant computational challenges in private inference(PI).Existing optimization methods often rely on isolated techniques,neglecting joint structural and operational improvements.We propose IG-3D,a unified framework that integrates structured compression and operator approximation through accurate importance assessment.Our approach first evaluates attention head importance using Integrated Gradients(IG),offering greater stability and theoretical soundness than gradient-based methods.We then apply a threedimensional optimization:(1)structurally pruning redundant attention heads;(2)replacing Softmax with adaptive polynomial approximation to avoid exponential computations;(3)implementing layer-wise GELU substitution to accommodate different layer characteristics.A joint thresholdmechanism coordinates compression across dimensions under accuracy constraints.Experimental results on the GLUE benchmark show that our method achieves an average 2.9×speedup in inference latency and a 50%reduction in communication cost,while controlling the accuracy loss within 2.3%,demonstrating significant synergistic effects and a superior accuracy-efficiency trade-off compared to single-technique optimization strategies.展开更多
Dear Editor,Mountain systems have long been refuges for many species,often viewed as"islands"that promote speciation due to geographic isolation(Rahbek et al.,2019).Their high environmental heterogeneity fos...Dear Editor,Mountain systems have long been refuges for many species,often viewed as"islands"that promote speciation due to geographic isolation(Rahbek et al.,2019).Their high environmental heterogeneity fosters centers of endemism,and they harbor over 85%of global species diversity(Zhao et al.,2022).Consequently,mountains are key systems for exploring biodiversity patterns along elevational gradients,where species richness often follows four recognized models:monotonic decrease,unimodal pattern(forward and backward peak patterns),and low plateau followed by a decrease along the elevational gradient(McCain et al.,2010).展开更多
Suffusion refers to the loss of fineparticles within the soil matrix without any associated volume change,induced by hydrodynamic forces.This study investigated the suffusion of sand-clay mixtures through one-dimensio...Suffusion refers to the loss of fineparticles within the soil matrix without any associated volume change,induced by hydrodynamic forces.This study investigated the suffusion of sand-clay mixtures through one-dimensional soil column experiments under a stepwise increase in hydraulic gradient(i),aiming to evaluate the critical hydraulic gradient(icrit)as a function of the size ratio between sand and clay,clay type,and ionic concentration.It was found that icrit was less than 0.1 for all sand-clay mixtures examined in this study.In addition,the lower peak concentrations of filtrated clay observed in sand-illite mixtures,compared to those of sand-kaolinite mixtures at the same level of i,suggest that illite particles are more susceptible to suffusion.Overall,the observed breakthrough curves,mass fraction of filtrated clay,volume of outflow,and total injection time presented in this study highlight the importance of considering clay type,sand-to-clay size ratio,and ionic concentration when assessing the suffusion behavior of clay-containing soils under a stepwise increase in hydraulic gradient.展开更多
In this study,an architecture featuring a gradient conductive network structure and three-dimensional dual-continuous network structure is constructed in a carbon nanotubes/cellulose-boron nitride/poly(vinyl alcohol)(...In this study,an architecture featuring a gradient conductive network structure and three-dimensional dual-continuous network structure is constructed in a carbon nanotubes/cellulose-boron nitride/poly(vinyl alcohol)(CNT/cellulose-BN/PVA)composite.Using cellulose aerogel as a template,CNT were incorporated into the cellulose template by vertically impregnating the CNT suspension.Following the impregnation of BN/PVA and high-pressure compression,three-dimensional dual-continuous network structure was successfully constructed in the CNT/cellulose-BN/PVA composite.The comprehensive performance of the composite,including electromagnetic interference(EMI)shielding and Joule heating performance,was investigated.The results indicate that the total EMI shielding effectiveness(SE)for the CNT/cellulose-BN/PVA composite reveals similar values for electromagnetic waves incident from different directions,but totally different shielding mechanisms.For the CNT/cellulose-BN/PVA composite with three impregnation cycles of CNT,the EMI SE values exceeded 39 dB for electromagnetic waves incident from both the high-and low-CNT-content sides.93%of the microwaves were reflected when electromagnetic waves were incident from the high-CNT-content side,while the reflection coefficient decreased to 0.44 for the transverse direction.In addition,the construction of the dual-continuous network structure enabled the composite to exhibit both excellent electrical conductivity and good thermal conductivity simultaneously,endowing the material with good Joule heating performance.CNT/cellulose-BN/PVA composite films have significant potential for application as EMI shielding materials in extremely cold weather.展开更多
Anammox bacteria in constructed wetlands(CWs)play pivotal role in sustainable nitrogen transformation,yet existing studies lack comprehensive analysis of environmental gradients and microbial interactions,both key fac...Anammox bacteria in constructed wetlands(CWs)play pivotal role in sustainable nitrogen transformation,yet existing studies lack comprehensive analysis of environmental gradients and microbial interactions,both key factors in anammox bacteria enrichment.This study investigated the mechanisms driving anammox bacteria enrichment in lab-scale simulated CWs treating high-nitrogen wastewater,focusing on bacterial community re-sponses across wetland layers with various strategies,including continuous up-flow influent,nitrogen loading increase,effluent recirculation,intermittent influent,and anammox bacteria inoculation.Results showed that total relative and absolute abundances of anammox bacteria ranged from 0.77%to 12.50%and from 0.13 to 6.46×10^(7) copies/g,respectively.Dissolved oxygen and pH had significant positive correlations with the absolute abundance of anammox bacteria,while organic matter and nitrate negatively impacted their relative abundance.Permutational multivariate analysis of variance indicated that spatial heterogeneity explained more variation in anammox bacteria abundance(43.44%)compared to operational strategies(8.58%).In terms of microbial interactions,60 dominant species exhibited potential correlations with anammox bacteria,comprising 170 interactions(105 positive and 65 negative),which suggested that anammox bacteria generally foster cooperative relationships with dominant bacteria.Notably,significant interspecies interactions were observed between Candidatus Kuenenia(dominant anammox bacteria in CWs)and species within the genera Chitinivibrio-nia and Anaerolineaceae,suggesting that microbial interactions primarily manifest as indirect facilitative effects rather than direct mutualistic relationships.Given that the Normalized Stochasticity Ratio in CWs were<50%,this study inferred that environmental gradients have greater influence on anammox bacteria than microbial interactions.展开更多
The osteochondral(OC)interface exhibits a mineral gradient,varying in thickness by several hundred micrometers across different species.Disruptions in this interface damage OC tissues,leading to osteoarthritis.The nat...The osteochondral(OC)interface exhibits a mineral gradient,varying in thickness by several hundred micrometers across different species.Disruptions in this interface damage OC tissues,leading to osteoarthritis.The natural architecture and composition of native OC interfaces can be replicated using biomaterial scaffolds via regenerative engineering approaches.A novel one-step bioextrusion process was employed to fabricate a unitary synthetic graft(USG),which mimics the native OC interface’s mineral concentration gradient.This novel USG is composed of an agarose-based cartilage layer and a bone layer,consisting of agarose enriched with 20%(200 g/L)hydroxyapatite.The USG features a gradient interface with mineral concentrations transitioning from 0%to 20%(mass fraction),mimicking the transition between the cartilage and bone.Thermogravimetric analysis revealed that the gradient transition lengths of the graft and native OC tissue harvested from bovine knees were similar((647±21)vs.(633±124)μm).The linear viscoelastic properties of the grafts,which were evaluated using strain sweep and frequency sweep tests with oscillatory shear,indicated a dominant storage modulus over loss modulus similar to that of native OC tissues.The compressive and stress relaxation behaviors of the USGs demonstrated that the graft maintained structural integrity under mechanical stress.Viability assays performed after bioextrusion showed that chondrocytes and human fetal osteoblast cells successfully integrated and survived within their designated regions of the graft.The novel USGs exhibit properties similar to native OC tissue and are promising candidates for regenerating OC defects and restoring knee joint functionality.展开更多
The S38C railway axle undergoes induction hardening,resulting in a gradient-distributed microstructure and mechanical properties.The accurate identification of gradient-distributed plastic parameters for the S38C axle...The S38C railway axle undergoes induction hardening,resulting in a gradient-distributed microstructure and mechanical properties.The accurate identification of gradient-distributed plastic parameters for the S38C axle remains a challenging task.To tackle this challenge,the present study proposes a novel approach for identifying the gradient-distributed plastic parameters for the S38C axle by integrating nano-indentation techniques with the machine learning method.Firstly,nano-indentation tests are conducted along the radial direction of the S38C axle to obtain the gradient-distributed load-displacement curves,nano-hardness,and elastic modulus.Subsequently,the dimensionless analysis is performed to obtain the representative stress,strain,and yield stress from load-displacement curves.These parameters are then incorporated into the machine learning method as physical information to identify the gradient-distributed plastic parameters of the S38C axle.The results indicate that the proposed method based on the physics-informed neural network and multi-fidelity neural network successfully identifies the gradient-distributed plastic parameters of the S38C axles and demonstrates superior prediction accuracy and generalization compared with the purely data-driven machine learning method.展开更多
Gradient refractive index(GRIN)metalenses are increasingly valued in high-frequency communication due to their exceptional radiation performance.Ceramics with high dielectric constants and low dielectric losses are id...Gradient refractive index(GRIN)metalenses are increasingly valued in high-frequency communication due to their exceptional radiation performance.Ceramics with high dielectric constants and low dielectric losses are ideal candidates for GRIN metalenses.Digital light processing(DLP)3D printing provides a feasible and efficient approach for manufacturing ceramic GRIN metalenses.However,the scattering of ultraviolet(UV)light by ceramic particles in the slurry reduces the printing accuracy of DLP technology,making it difficult to achieve the intricate structural features required for GRIN metalenses in high-frequency communication.In this work,we propose an approach to improve printing accuracy by optimizing the ceramic slurry composition and implementing a dimensional compensation design strategy.Utilizing geometric optics and the S-parameter inversion method,we design a GRIN metalens consisting of two distinct types of subwavelength unit cells(Y-shaped and circular hole geometries)with a minimum feature size of 160μm.Through a refined slurry formulation and precise design parameter compensation,high-fidelity ceramic GRIN metalenses are successfully fabricated.The fabricated metalens exhibits a maximum gain enhancement of 18.4 dBi and a deflection angle of±30°over a bandwidth of 37.84% in the W-band(75-110 GHz).The highly directional far-field beam radiation and efficient beam steering capabilities highlight the potential of ceramic GRIN metalenses for applications in satellite communications,radar systems,and other high-frequency technologies.展开更多
The migration mechanisms of ore-forming fluids have long been a focus in the field of ore deposit studies.Calcite is ubiquitously present in various types of rocks in the lithosphere,and the underlying mechanisms of i...The migration mechanisms of ore-forming fluids have long been a focus in the field of ore deposit studies.Calcite is ubiquitously present in various types of rocks in the lithosphere,and the underlying mechanisms of its influence on fluid migration are of crucial importance.While previous studies have revealed that salinity changes can modulate fluid migration,the underlying mechanisms remain poorly understood.We employ molecular dynamics simulations to elucidate how salinity variations in ore-forming fluids modulate the adsorption onto calcite nanopore walls,thereby revealing the microscopic mechanisms governing ore fluid transport through calcite nano-fractures.The results show that the adsorption energy Eint of the solution on the calcite surface increased from -14,948.84±182.48 kcal/mol to -12,144.08±118.2 kcal/mol as salinity increased,which is conducive to the long-range transport of the fluid in the calcite nanopore.展开更多
To investigate the evolution of grain orientation and slip modes in magnesium alloys with multiple texture components,an AZ31 gradient-structured magnesium alloy sheet was fabricated using hard plate rolling(HPR).The ...To investigate the evolution of grain orientation and slip modes in magnesium alloys with multiple texture components,an AZ31 gradient-structured magnesium alloy sheet was fabricated using hard plate rolling(HPR).The changes in texture and slip modes under different reductions were examined.The results demonstrate that the AZ31 magnesium alloy sheets display a self-epitaxial gradient structure,with the best mechanical properties observed at rolling temperature of 673 K and reduction of 50%.Significant changes in texture type and strength are observed along the normal direction(ND)of the sheet.The coarse-grain region exhibits a bimodal texture aligned with the rolling direction.These texture variations enhance the stress distribution at the fine grain-coarse grain interface,influencing the grain orientation and the activation of different slip modes,thus improving the mechanical properties of gradient-structured magnesium alloy sheets.This approach offers a new strategy for the fabrication of high-performance magnesium alloy sheets.展开更多
基金Item Sponsored by Educational Department of Liaoning Province of China (2004F052)
文摘To consider the effects of the interactions and interplay among microstructures, gradient-dependent models of second- and fourth-order are included in the widely used phenomenological Johnson-Cook model where the effects of strain-hardening, strain rate sensitivity, and thermal-softening are successfully described. The various parameters for 1006 steel, 4340 steel and S-7 tool steel are assigned. The distributions and evolutions of the local plastic shear strain and deformation in adiabatic shear band （ASB） are predicted. The calculated results of the second- and fourth- order gradient plasticity models are compared. S-7 tool steel possesses the steepest profile of local plastic shear strain in ASB, whereas 1006 steel has the least profile. The peak local plastic shear strain in ASB for S-7 tool steel is slightly higher than that for 4340 steel and is higher than that for 1006 steel. The extent of the nonlinear distribution of the local plastic shear deformation in ASB is more apparent for the S-7 tool steel, whereas it is the least apparent for 1006 steel. In fourth-order gradient plasticity model, the profile of the local plastic shear strain in the middle of ASB has a pronounced plateau whose width decreases with increasing average plastic shear strain, leading to a shrink of the portion of linear distribution of the profile of the local plastic shear deformation. When compared with the sec- ond-order gradient plasticity model, the fourth-order gradient plasticity model shows a lower peak local plastic shear strain in ASB and a higher magnitude of plastic shear deformation at the top or base of ASB, which is due to wider ASB. The present numerical results of the second- and fourth-order gradient plasticity models are consistent with the previous numerical and experimental results at least qualitatively.
基金Supported by NSFC(No.12101482)the Natural Science Foundation of Shaanxi Province,China(No.2018JQ1052)。
文摘In this paper,we consider the fourth-order parabolic equation with p(x)Laplacian and variable exponent source ut+∆^(2)u−div(|■u|^(p(x)−2■u))=|u|^(q(x))−1u.By applying potential well method,we obtain global existence,asymptotic behavior and blow-up of solutions with initial energy J(u_(0))≤d.Moreover,we estimate the upper bound of the blow-up time for J(u_(0))≤0.
基金Supported by National Natural Science Foundation of China(Grant No.11601122).
文摘The paper considers the initial value problem of inhomogeneous fourth-order Schr¨odinger equation with potential in energy space H^(2)(R^(d)).The global well-posedness is obtained in dimensions d≥5 resorting to contractive mapping principle,Strichartz estimates,Caffarelli-Kohn-Nirenberg-type inequality and the continuity method.
基金supported by the Natural Science Foundation of Shandong Province(Grant No.ZR2025QC30)。
文摘We investigate the alpha helical protein structure characterized by fourth-order interspine coupling,focusing on a three-coupled fourth-order nonlinear Schr??dinger system.We introduce a generalized Darboux transformation,departing from the classical Darboux transformation.Based on this,we construct the two-and three-degenerate soliton solutions and four-degenerate asymptotic soliton solutions.Based on the asymptotic analysis,we find that the amplitudes of interacting solitons are retained upon the interactions.Elastic interactions between two degenerate solitons exhibiting four curve-type asymptotic solitons are depicted.When the lattice parameterβchanges,the velocities of the two degenerate solitons also change.Elastic interaction among three degenerate solitons comprising four curve-type asymptotic solitons and two line-type solitons is presented.Interaction among one soliton and two degenerate solitons with different velocities is shown.Elastic interaction among four degenerate solitons comprising eight curve-type asymptotic solitons is also presented.Interaction among two two-degenerate solitons with two spectral parameters is shown.The relative distance between two asymptotic solitons exhibits logarithmic growth with|t|,where t represents the retarded time.Acceleration of soliton separation decays exponentially with relative distance,and eventually approaches zero.Phase shifts depend on t.
基金Supported by the National Natural Science Foundation of China(Grant No.12261017)the Scientific Research Foundation of Guizhou University of Finance and Economics(Grant No.2022ZCZX077)。
文摘In this work, an efficient spectral method is proposed to solve the fourth-order eigenvalue problem in cylinder domain. Firstly, the key point of this method is to decompose the original model into a kind of decoupled two-dimensional eigenvalue problem by cylindrical coordinate transformation and Fourier series expansion, and deduce the crucial essential pole conditions. Secondly, we define a kind of weighted Sobolev spaces, and establish a suitable variational formula and its discrete form for each two-dimensional eigenvalue problem. Furthermore, we derive the equivalent operator formulas and obtain some prior error estimates of spectral theory of compact operators. More importantly, we further obtained error estimates for approximating eigenvalues and eigenfunctions by using two newly constructed projection operators. Finally,some numerical experiments are performed to validate our theoretical results and algorithm.
基金National Defense Basic Scientific Research Program of China(JCKY2020408B002,WDZC2022-12)Key Research and Development Program of Shanxi Province(202102050201011,202202050201014)Fundamental Research Program of Shanxi Province(20210302124178,20210302123061,202103021224183)。
文摘A gradient structure was introduced into a metal laminated target plate,and the anti-penetration simulation of the gradient structure was compared with that of a uniform-layer-thickness target plate by finite element simulation.The analysis was verified by an impact experiment.Results show that the high-level thickness and appropriate percentage of Ti alloy at the upper side of the gradient structure provide greater impact resistance against the bullet,which increases the warhead breakage and enhances the anti-penetration performance.In addition,during the impact process,the stress is transmitted and reflected in the form of waves in each layer of the target plate,and the interaction between the compression and tension waves causes non-synergistic deformation of the target plate and leads to delamination.The gradient target plate takes penetration resistance a step further through the higher energy absorption rate and more consumption of the bullet kinetic energy.This research provides a theoretical basis for the application of gradient structures in metallic laminated armor.
基金supported by the National Key Research and Development Program of China(2023YFB3809300).
文摘Recycling spent lithium-ion(Li+)batteries is critical for achieving environmental conservation and the strategic recovery of essential resources.Compared with conventional methods for recovering cathode materials,which are energy-intensive and prone to secondary pollution,the direct regeneration approach has emerged as a rapid and highly efficient method,gaining widespread attention in recent years.However,this approach faces major challenges,including degraded electrochemical performances and limited economic value.This study,therefore,proposes a high-value direct regeneration strategy to convert degraded spent LiFePO_(4)(S-LFP)into a gradient manganese(Mn)-doped regenerated LiFe_(0.7)Mn_(0.3)PO_(4)/C(R-LFMP)composite.This method leverages the inherent microcracks and Li vacancies present in S-LFP,likely acting as diffusion channels for the Mn^(2+)/Li^(+)ions.Through a two-step mechanochemical ball-milling and carbothermal reduction process,this approach achieves simultaneous Li replenishment and surface-localised Mn gradient doping with enhanced structural control.Notably,the R-LFMP exhibits an exceptional electrochemical performance.At 0.1 C,it delivers a discharge capacity of 161.4 mA h g^(−1)and an energy density of 563.5 Wh kg^(−1)(representing a 60.5%improvement over S-LFP).Additionally,it maintains 83%capacity retention after 900 cycles at 0.5C,a considerable enhancement compared to commercial LFMP(62%).Furthermore,the regenerated cathode material generates a net profit of$7.102 kg^(−1),surpassing the profitability of conventional recycling methods by 90%.Overall,this study introduces a transformative and sustainable LFP regeneration technology,achieving breakthroughs in electrochemical restoration and high-value recycling,while paving the way for the closed-loop utilisation of LFP-based energy storage systems.
基金supported by the National Natural Science Foundation of China (Grant Nos.12274313 and 62375234)the Gusu Leading Talent Plan for Scientific and Technological Innovation and Entrepreneurship (Grant No.ZXL2024400)。
文摘Optical phase-gradient metasurfaces have garnered significant attention for enabling flexible light manipulation,with applications across diverse domains.In this work,we will demonstrate that the metasurfaces with phase gradient modulation can be used to achieve illusion optics,featuring the advantages of simple geometric structure and feasible implementation compared with the well-known transformation optics method.The underlying mechanism is the anomalous diffraction law caused by the phase gradient,which provides a theoretical basis for freely manipulating the propagation path of light.By considering a specific example,we will demonstrate that the phase gradient can transform spatial coordinates in real space into illusion space,thereby converting a plane in real space into a curved surface structure in illusion space to achieve the illusion effect.This approach provides a viable alternative to transformation optics for designing illusion devices.
基金financially supported by the National Natural Science Foundation of China(22378428,22138013)the National Key Research and Development Program of China(2023YFB4104500,2023YFB4104503)+1 种基金the Key Research and Development Program of Shandong Province(2024ZLGX08)the Science and Technology Innovation Project of the Shandong Energy Group Co.,Ltd.(SNKJ2023A03)。
文摘Electrocatalytic CO_(2) reduction(CO_(2) RR)toward multi-carbon compounds is a challenging but meaningful route for carbon cycling.Copper-based catalysts are the most promising candidate for C_(2+)generation due to their unique C–C coupling activity,yet the in situ reduction from Cu^(+) to Cu^(0) under cathodic potentials causes the catalyst deactivation.Herein,we develop a transient thermal shock strategy to embed Cu^(+) species into CeO_(2) lattices,constructing a CuO_(x)/CuCeO_(x)catalyst with a radial gradient Cu^(+) -Ov-Ce^(3+)/Ce^(4+)structure.Depth-profiling X-ray photoelectron spectroscopy(XPS)and density functional theory(DFT)calculations reveal that mismatched metal/oxygen diffusion kinetics drive continuous electron transfer from surface Cu^(+) to bulk Ce^(3+)/Ce^(4+)via oxygen vacancies(Ov),forming a dynamic“self-sacrificial”structure to preserve surface Cu^(+) states.In CO_(2)-saturated 0.1 M KHCO_(3),the optimized CuO_(x)/CuCeO_(x)-10 achieves a high C_(2) Faradaic efficiency(FE)of 85.8%at-1.4 V vs.RHE.In situ attenuated total reflection surface-enhanced infrared adsorption spectroscopy(ATR-SEIRAS)identifies the key intermediates of C_(2) are*OCCO and*OCCOH,while DFT reveals a drastic reduction of C–C coupling barrier from 0.842 to0.274 eV.This work demonstrates kinetically tailored metal-support interactions,enabling oxidationstate control for pathway-selective catalysis.
基金supported by the National Natural Science Foundation of China(Nos.42072229,42030301,41102131,41972049,41972302 and 41977231)the Guangdong Basic and Applied Basic Research Foundation(No.2025A1515010724)+3 种基金the Guangdong Natural Science Foundation(No.2021A1515011658)the Science and Technology Program of Guangzhou(No.202002030184)the Special Fund for Basic Scientific Research of Central Colleges,Chang'an University(No.300102260502)the Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project(No.2024ZD1001003)。
文摘The paleo-geothermal gradient is a crucial parameter for converting the thermal history to the exhumation history.However,the precise estimation of this parameter has been a challenge.This paper presents a simple two-step method to model the paleo-geothermal gradient using low-temperature thermochronology.(1)It uses the Monte Carlo approach to generate thermal histories in a vertical section randomly and calculates the entire thermal history within the goodnessof-fit thresholds based on different paleo-geothermal gradients.(2)It selects the optimum paleogeothermal gradient by comparing the entire thermal history within different goodness-of-fit thresholds.We validated the method with apatite(U-Th)/He and fission track data collected from two drill cores in the Haiyuan-Liupanshan region.The result revealed that the best-fit paleo-geothermal gradient was~42℃/km during the Early Cretaceous–Miocene and has decreased rapidly to 20℃/km since~10 Ma.The crust thickening in the study area may explain the rapid reduction in the paleogeothermal gradient since~10 Ma.Our results are consistent with earlier studies in the region,suggesting that our simple and more intuitive approach provides an alternative method for paleogeothermal gradient modeling.
文摘Transformer models face significant computational challenges in private inference(PI).Existing optimization methods often rely on isolated techniques,neglecting joint structural and operational improvements.We propose IG-3D,a unified framework that integrates structured compression and operator approximation through accurate importance assessment.Our approach first evaluates attention head importance using Integrated Gradients(IG),offering greater stability and theoretical soundness than gradient-based methods.We then apply a threedimensional optimization:(1)structurally pruning redundant attention heads;(2)replacing Softmax with adaptive polynomial approximation to avoid exponential computations;(3)implementing layer-wise GELU substitution to accommodate different layer characteristics.A joint thresholdmechanism coordinates compression across dimensions under accuracy constraints.Experimental results on the GLUE benchmark show that our method achieves an average 2.9×speedup in inference latency and a 50%reduction in communication cost,while controlling the accuracy loss within 2.3%,demonstrating significant synergistic effects and a superior accuracy-efficiency trade-off compared to single-technique optimization strategies.
基金supported by grants from the National Natural Science Foundation of China(Grant No.32360333)the Guizhou Provincial Science and Technology Projects(Grant Nos.ZK[2022]540 and[2023]099)+1 种基金the Survey of Amphibian and Reptile Resources in Leigongshan National Nature Reserve and Literature Publishing Services(P5226002023000019)the Guizhou Provincial Science and Technology Innovation Talent Team Construction Project 2024[Qian Ke He Talent CXTD(2025)053].
文摘Dear Editor,Mountain systems have long been refuges for many species,often viewed as"islands"that promote speciation due to geographic isolation(Rahbek et al.,2019).Their high environmental heterogeneity fosters centers of endemism,and they harbor over 85%of global species diversity(Zhao et al.,2022).Consequently,mountains are key systems for exploring biodiversity patterns along elevational gradients,where species richness often follows four recognized models:monotonic decrease,unimodal pattern(forward and backward peak patterns),and low plateau followed by a decrease along the elevational gradient(McCain et al.,2010).
基金supported by the National Research Foundation of Korea(NRF)grants(Grant Nos.RS-2020-NR049594 and RS-2022-NR071877)the Korea Agency for Infrastructure Technology Advancement under the Ministry of Land,Infrastructure and Transport(Grant No.RS-2024-00410248).
文摘Suffusion refers to the loss of fineparticles within the soil matrix without any associated volume change,induced by hydrodynamic forces.This study investigated the suffusion of sand-clay mixtures through one-dimensional soil column experiments under a stepwise increase in hydraulic gradient(i),aiming to evaluate the critical hydraulic gradient(icrit)as a function of the size ratio between sand and clay,clay type,and ionic concentration.It was found that icrit was less than 0.1 for all sand-clay mixtures examined in this study.In addition,the lower peak concentrations of filtrated clay observed in sand-illite mixtures,compared to those of sand-kaolinite mixtures at the same level of i,suggest that illite particles are more susceptible to suffusion.Overall,the observed breakthrough curves,mass fraction of filtrated clay,volume of outflow,and total injection time presented in this study highlight the importance of considering clay type,sand-to-clay size ratio,and ionic concentration when assessing the suffusion behavior of clay-containing soils under a stepwise increase in hydraulic gradient.
基金financially supported by the National Natural Science Foundation of China(No.52103127)the Opening Project of the State Key Laboratory of Polymer Materials Engineering(Sichuan University)(No.sklpme2022-4-10)Shaanxi Provincial Science and Technology Department(No.2025GH-YBXM-042).
文摘In this study,an architecture featuring a gradient conductive network structure and three-dimensional dual-continuous network structure is constructed in a carbon nanotubes/cellulose-boron nitride/poly(vinyl alcohol)(CNT/cellulose-BN/PVA)composite.Using cellulose aerogel as a template,CNT were incorporated into the cellulose template by vertically impregnating the CNT suspension.Following the impregnation of BN/PVA and high-pressure compression,three-dimensional dual-continuous network structure was successfully constructed in the CNT/cellulose-BN/PVA composite.The comprehensive performance of the composite,including electromagnetic interference(EMI)shielding and Joule heating performance,was investigated.The results indicate that the total EMI shielding effectiveness(SE)for the CNT/cellulose-BN/PVA composite reveals similar values for electromagnetic waves incident from different directions,but totally different shielding mechanisms.For the CNT/cellulose-BN/PVA composite with three impregnation cycles of CNT,the EMI SE values exceeded 39 dB for electromagnetic waves incident from both the high-and low-CNT-content sides.93%of the microwaves were reflected when electromagnetic waves were incident from the high-CNT-content side,while the reflection coefficient decreased to 0.44 for the transverse direction.In addition,the construction of the dual-continuous network structure enabled the composite to exhibit both excellent electrical conductivity and good thermal conductivity simultaneously,endowing the material with good Joule heating performance.CNT/cellulose-BN/PVA composite films have significant potential for application as EMI shielding materials in extremely cold weather.
基金supported by Natural Science Foundation of Xiamen,China(No.3502Z20227232)the STS Project of Fujian-CAS(No.2023T3018)Bureau of International Cooperation,Chinese Academy of Sciences(No.322GJHZ2022035MI).
文摘Anammox bacteria in constructed wetlands(CWs)play pivotal role in sustainable nitrogen transformation,yet existing studies lack comprehensive analysis of environmental gradients and microbial interactions,both key factors in anammox bacteria enrichment.This study investigated the mechanisms driving anammox bacteria enrichment in lab-scale simulated CWs treating high-nitrogen wastewater,focusing on bacterial community re-sponses across wetland layers with various strategies,including continuous up-flow influent,nitrogen loading increase,effluent recirculation,intermittent influent,and anammox bacteria inoculation.Results showed that total relative and absolute abundances of anammox bacteria ranged from 0.77%to 12.50%and from 0.13 to 6.46×10^(7) copies/g,respectively.Dissolved oxygen and pH had significant positive correlations with the absolute abundance of anammox bacteria,while organic matter and nitrate negatively impacted their relative abundance.Permutational multivariate analysis of variance indicated that spatial heterogeneity explained more variation in anammox bacteria abundance(43.44%)compared to operational strategies(8.58%).In terms of microbial interactions,60 dominant species exhibited potential correlations with anammox bacteria,comprising 170 interactions(105 positive and 65 negative),which suggested that anammox bacteria generally foster cooperative relationships with dominant bacteria.Notably,significant interspecies interactions were observed between Candidatus Kuenenia(dominant anammox bacteria in CWs)and species within the genera Chitinivibrio-nia and Anaerolineaceae,suggesting that microbial interactions primarily manifest as indirect facilitative effects rather than direct mutualistic relationships.Given that the Normalized Stochasticity Ratio in CWs were<50%,this study inferred that environmental gradients have greater influence on anammox bacteria than microbial interactions.
基金supported by the School of Engineering and Digital Sciences of Nazarbayev University,Astana,Kazakhstan(to CE)。
文摘The osteochondral(OC)interface exhibits a mineral gradient,varying in thickness by several hundred micrometers across different species.Disruptions in this interface damage OC tissues,leading to osteoarthritis.The natural architecture and composition of native OC interfaces can be replicated using biomaterial scaffolds via regenerative engineering approaches.A novel one-step bioextrusion process was employed to fabricate a unitary synthetic graft(USG),which mimics the native OC interface’s mineral concentration gradient.This novel USG is composed of an agarose-based cartilage layer and a bone layer,consisting of agarose enriched with 20%(200 g/L)hydroxyapatite.The USG features a gradient interface with mineral concentrations transitioning from 0%to 20%(mass fraction),mimicking the transition between the cartilage and bone.Thermogravimetric analysis revealed that the gradient transition lengths of the graft and native OC tissue harvested from bovine knees were similar((647±21)vs.(633±124)μm).The linear viscoelastic properties of the grafts,which were evaluated using strain sweep and frequency sweep tests with oscillatory shear,indicated a dominant storage modulus over loss modulus similar to that of native OC tissues.The compressive and stress relaxation behaviors of the USGs demonstrated that the graft maintained structural integrity under mechanical stress.Viability assays performed after bioextrusion showed that chondrocytes and human fetal osteoblast cells successfully integrated and survived within their designated regions of the graft.The novel USGs exhibit properties similar to native OC tissue and are promising candidates for regenerating OC defects and restoring knee joint functionality.
基金supported by the National Key Research and Development Plan(Grant No.2022YFB3401901)the National Natural Science Foundation of China(Grant Nos.12192210,12192214,12072295,and 12222209)+1 种基金Independent Project of State Key Laboratory of Rail Transit Vehicle System(Grant No.2023TPL-T03)Fundamental Research Funds for the Central Universities(Grant No.2682023CG004).
文摘The S38C railway axle undergoes induction hardening,resulting in a gradient-distributed microstructure and mechanical properties.The accurate identification of gradient-distributed plastic parameters for the S38C axle remains a challenging task.To tackle this challenge,the present study proposes a novel approach for identifying the gradient-distributed plastic parameters for the S38C axle by integrating nano-indentation techniques with the machine learning method.Firstly,nano-indentation tests are conducted along the radial direction of the S38C axle to obtain the gradient-distributed load-displacement curves,nano-hardness,and elastic modulus.Subsequently,the dimensionless analysis is performed to obtain the representative stress,strain,and yield stress from load-displacement curves.These parameters are then incorporated into the machine learning method as physical information to identify the gradient-distributed plastic parameters of the S38C axle.The results indicate that the proposed method based on the physics-informed neural network and multi-fidelity neural network successfully identifies the gradient-distributed plastic parameters of the S38C axles and demonstrates superior prediction accuracy and generalization compared with the purely data-driven machine learning method.
基金financial support by the National Key Research and Development Program of China(No.2023YFB4605400)the National Natural Science Foundation of China(No.12472152)the Department of Science and Technology of Guangdong Province(No.2019QN01Z438)。
文摘Gradient refractive index(GRIN)metalenses are increasingly valued in high-frequency communication due to their exceptional radiation performance.Ceramics with high dielectric constants and low dielectric losses are ideal candidates for GRIN metalenses.Digital light processing(DLP)3D printing provides a feasible and efficient approach for manufacturing ceramic GRIN metalenses.However,the scattering of ultraviolet(UV)light by ceramic particles in the slurry reduces the printing accuracy of DLP technology,making it difficult to achieve the intricate structural features required for GRIN metalenses in high-frequency communication.In this work,we propose an approach to improve printing accuracy by optimizing the ceramic slurry composition and implementing a dimensional compensation design strategy.Utilizing geometric optics and the S-parameter inversion method,we design a GRIN metalens consisting of two distinct types of subwavelength unit cells(Y-shaped and circular hole geometries)with a minimum feature size of 160μm.Through a refined slurry formulation and precise design parameter compensation,high-fidelity ceramic GRIN metalenses are successfully fabricated.The fabricated metalens exhibits a maximum gain enhancement of 18.4 dBi and a deflection angle of±30°over a bandwidth of 37.84% in the W-band(75-110 GHz).The highly directional far-field beam radiation and efficient beam steering capabilities highlight the potential of ceramic GRIN metalenses for applications in satellite communications,radar systems,and other high-frequency technologies.
基金financed jointly by the National Major Science and Technology Special Project on Deep Earth Exploration(2024ZD1001701-5)the National Natural Science Foundation of China(42472127,42172086)+2 种基金the Yunnan Major Project of Basic Research(202401BN070001-002)Yunnan Mineral Resources Prediction and Evaluation Engineering Research Center(2011)Innovation Team Program of Kunming University of Science and Technology,Yunnan Province。
文摘The migration mechanisms of ore-forming fluids have long been a focus in the field of ore deposit studies.Calcite is ubiquitously present in various types of rocks in the lithosphere,and the underlying mechanisms of its influence on fluid migration are of crucial importance.While previous studies have revealed that salinity changes can modulate fluid migration,the underlying mechanisms remain poorly understood.We employ molecular dynamics simulations to elucidate how salinity variations in ore-forming fluids modulate the adsorption onto calcite nanopore walls,thereby revealing the microscopic mechanisms governing ore fluid transport through calcite nano-fractures.The results show that the adsorption energy Eint of the solution on the calcite surface increased from -14,948.84±182.48 kcal/mol to -12,144.08±118.2 kcal/mol as salinity increased,which is conducive to the long-range transport of the fluid in the calcite nanopore.
基金supported by the Natural Science Foundation of Heilongjiang Province,China(No.JQ2022E004)。
文摘To investigate the evolution of grain orientation and slip modes in magnesium alloys with multiple texture components,an AZ31 gradient-structured magnesium alloy sheet was fabricated using hard plate rolling(HPR).The changes in texture and slip modes under different reductions were examined.The results demonstrate that the AZ31 magnesium alloy sheets display a self-epitaxial gradient structure,with the best mechanical properties observed at rolling temperature of 673 K and reduction of 50%.Significant changes in texture type and strength are observed along the normal direction(ND)of the sheet.The coarse-grain region exhibits a bimodal texture aligned with the rolling direction.These texture variations enhance the stress distribution at the fine grain-coarse grain interface,influencing the grain orientation and the activation of different slip modes,thus improving the mechanical properties of gradient-structured magnesium alloy sheets.This approach offers a new strategy for the fabrication of high-performance magnesium alloy sheets.
