The effects of the component gradient distribution at interface and the fiber gradient distribution on the strength of cement-based materials were studied. The results show that the flexural strength and compressive s...The effects of the component gradient distribution at interface and the fiber gradient distribution on the strength of cement-based materials were studied. The results show that the flexural strength and compressive strength of the mortar and concrete with interface component and fiber gradient distributions are obviously improved. The strengthes of the fiber gradient distributed mortar and concrete (FGDM/C) are higher than those of fiber homogeneously distributed mortar and concrete (FHDM/C). To obtain the same strength, therefore, a smaller fiber volume content in FGDM/C is needed than that in FHDM/C. The results also show that the component gradient distribution of the concrete can be obtained by means of multi-layer vibrating formation.展开更多
Gradient distributions of temperature and deformation(GDTD)are crucial for achieving dual-performance discs of titanium alloys which is required by the service environment of aeroengine.However,heating,cooling and def...Gradient distributions of temperature and deformation(GDTD)are crucial for achieving dual-performance discs of titanium alloys which is required by the service environment of aeroengine.However,heating,cooling and deforming sequence in the whole process of the titanium disc forming,which leads to difficulties for achieving GDTD due to a lot of parameters.To solve this problem,a whole-process model of the titanium disc forming for GDTD has been established.In the model,heating and cooling via heat radiation,conduction and convection,and deforming by local loading with mold chilling are all considered.Experiments on heating and cooling as well as deforming were carried out by using a furnace and the Gleeble-3500 machine.The experimental data are used to determine thermal parameters and constitutive relations of the IMI834 titanium alloy,and then to verify the reliability of the model.Then the model was used to simulate the evolution rules of temperature and deformation of the titanium disc.The results show that the heating surface,furnace temperature,billet profile and loading rate play the core role for the control of GDTD,and thus a set of parameters were determined.Therefore,this work provides a base for developing a new forming technology of the dual-performance titanium discs with the approach of local heating and local loading.展开更多
Based on the car front-wheel-hub forging forming process of numerical simulation, the temperature gradient expression of forging model cavity near the surface layer was got ten, which illustrates that the forging temp...Based on the car front-wheel-hub forging forming process of numerical simulation, the temperature gradient expression of forging model cavity near the surface layer was got ten, which illustrates that the forging temperature gradient is related to forging die materials thermal conductivity, specific heat and impact speed, and the correlation coefficient is 0.97. Under the different thermal conductivity, heat capacity and forging speed, the temperature gradient was compared with each other. The paper obtained the relevant laws, which illustrates the temperature gradient relates to these three parameters in a sequence of thermal conductivity 〉 impact speed〉 specific heat capacity. To reduce thermal stress in the near-surface layer of hot forging cavity, the material with greater thermal conductivity coefficient and specific heat capacity should be used.展开更多
The Industrial Internet of Things(IIoT)is increasingly vulnerable to sophisticated cyber threats,particularly zero-day attacks that exploit unknown vulnerabilities and evade traditional security measures.To address th...The Industrial Internet of Things(IIoT)is increasingly vulnerable to sophisticated cyber threats,particularly zero-day attacks that exploit unknown vulnerabilities and evade traditional security measures.To address this critical challenge,this paper proposes a dynamic defense framework named Zero-day-aware Stackelberg Game-based Multi-Agent Distributed Deep Deterministic Policy Gradient(ZSG-MAD3PG).The framework integrates Stackelberg game modeling with the Multi-Agent Distributed Deep Deterministic Policy Gradient(MAD3PG)algorithm and incorporates defensive deception(DD)strategies to achieve adaptive and efficient protection.While conventional methods typically incur considerable resource overhead and exhibit higher latency due to static or rigid defensive mechanisms,the proposed ZSG-MAD3PG framework mitigates these limitations through multi-stage game modeling and adaptive learning,enabling more efficient resource utilization and faster response times.The Stackelberg-based architecture allows defenders to dynamically optimize packet sampling strategies,while attackers adjust their tactics to reach rapid equilibrium.Furthermore,dynamic deception techniques reduce the time required for the concealment of attacks and the overall system burden.A lightweight behavioral fingerprinting detection mechanism further enhances real-time zero-day attack identification within industrial device clusters.ZSG-MAD3PG demonstrates higher true positive rates(TPR)and lower false alarm rates(FAR)compared to existing methods,while also achieving improved latency,resource efficiency,and stealth adaptability in IIoT zero-day defense scenarios.展开更多
This paper uses the Oseen transformation to solve the differential equations governing motion of the vertical linear gradient flow distribution close to a wall surface. The Navier-Stokes equations are used to consider...This paper uses the Oseen transformation to solve the differential equations governing motion of the vertical linear gradient flow distribution close to a wall surface. The Navier-Stokes equations are used to consider the inertia term along the flow direction. A novel contour integral method is used to solve the complex Airy function. The boundary conditions of linear gradient flow distribution for finite problems are determined. The vorticity function, the pressure function, and the turbulent velocity profiles are provided, and the stability of particle trajectories is studied. An Lx-function form of the third derivative circulation is used to to simplify the solution. Theoretical results are compared with the experimental measurements with satisfactory agreement.展开更多
The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to...The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to obtain cell struts with gradient distribution of Al 2 O 3 and ZrO 2 particles and high packing density.Aqueous Al 2 O 3-20vol.% ZrO 2 slurries with 20vol.% solid contents were prepared and the dispersion and rheological characteristics of the slurries were investigated.The settling velocity and mass segregation of Al 2 O 3 and ZrO 2 particles at different centrifugal accelerations were calculated and studied.The drying behavior,macrostructure,microstructure,compressive property and resistance to thermal shock of the sintered products were also investigated.The results show that the difference of settling velocity of Al 2 O 3 and ZrO 2 particles increases and mass segregation becomes acute with an increase in centrifugal acceleration.The cell struts prepared at a centrifugal acceleration of 1,690 g have high sintered density(99.0% TD) and continuous gradient distribution of Al 2 O 3 and ZrO 2 particles.When sintered at 1,550 o C for 2 h,the cell size of gradient Al 2 O 3-ZrO 2 foam is approximately uniform,about 1.1 mm.With the porosity of gradient Al 2 O 3-ZrO 2 ceramic foams increasing from 75.3% to 83.0%,the compressive strength decreases from 4.4 to 2.4 MPa,and the ceramic foams can resist 8-11 repeated thermal shock from 1,100 o C to room temperature.展开更多
How to distribute total sum of funds among different investment priorities？ It is not only a theoretical problem in Management Accounting, but also a realistic problem in the investment decision of an enterprise. In ...How to distribute total sum of funds among different investment priorities？ It is not only a theoretical problem in Management Accounting, but also a realistic problem in the investment decision of an enterprise. In this paper, the author queries the method of ＂use linear programming to find out optimum combination＂, which put forward in management accounting, and gives a convenient and reasonable method---effective gradient method.展开更多
In this study,the functional gradient materials(FGMs)were the first attempt to homogenise the electric field distribution in the cable accessory,where zinc oxide particles(ZnO_(k))were filled into ethylene propylene d...In this study,the functional gradient materials(FGMs)were the first attempt to homogenise the electric field distribution in the cable accessory,where zinc oxide particles(ZnO_(k))were filled into ethylene propylene diene monomer with the composi-tionally gradient distribution using laminating and hot-pressing methods.The constructed FGMs with significantly improved non-linear conductivity can avoid the electric field distortion in cable accessories.The results show that the configuration of compositionally gradient structured fillers can significantly improve the electrical conductivity of FGMs compared to the homogeneous distribution.Additionally,compositionally gradient structures of ZnOk fillers can also improve the thermal conductivity of FGM composites,which facilitates the heat dissipation of dielectric and reduces the probability of electrothermal coupling breakdown.The mechanical properties of the composites are deeply affected by the filler's content and configuration,both improved tear elongation and tensile strength can be achieved at an optimal content and gradient structure of ZnOk fillers.Finally,the simulation analysis results show that FGM composites can homogenise the electric field more efficiently in comparison with homogeneous composites.This work demonstrates that compositionally gradient structures can improve the utilisation of functional fillers and develop the FGM composites for high-voltage direct current cable accessory applications.展开更多
Multi-scale design in metal-support interaction allows for the comprehensive control of the electronic migration and magnetic respond behaviors,providing tuning frequency electromagnetic(EM)absorption.Herein,synergizi...Multi-scale design in metal-support interaction allows for the comprehensive control of the electronic migration and magnetic respond behaviors,providing tuning frequency electromagnetic(EM)absorption.Herein,synergizing confined reduction and Kirkendall diffusion were proposed to design the metal Nickel(e.g.signal atoms,clusters and nanoparticles)in the carbon matrix.In our work,residual carbon(RC)was used as substrate to load carbon-encapsulated Ni particles to build unique magnetic-dielectric RC-Ni@C composites.With tuning multi-scale magnetic and electric interaction,as-synthesized RC-Ni@C composite exhibited remarkable tuning frequency absorption feature,which the RC-Ni@C-2 sample hold the outstanding EM dissipation in the low-frequency C-band(4-8 GHz).To confirm the magnetic and electric interaction,visual evidence of electric field distribution was offered via the advanced integrated differential phase contrast(iDPC)technology.Combined with density functional theory(DFT)calculation and EM parameters analysis,related EM energy absorption mechanisms were discussed in this multi-scale heterostructures,including the dielectric polarization,conduction loss and magnetic dissipation.As results,special gradient magnetic particles regulating in carbon substrates provide new design idea to build low-frequency EM wave absorption.展开更多
In current federated learning frameworks,a central server randomly selects a small number of clients to train local models at the beginning of each global iteration.Since clients’local data are non-dependent and iden...In current federated learning frameworks,a central server randomly selects a small number of clients to train local models at the beginning of each global iteration.Since clients’local data are non-dependent and identically distributed,partial local models are not consistent with the global model.Existing studies employ model cleaning methods to find inconsistent local models.Model cleaning methods measure the cosine similarity between local models and the global model.The inconsistent local model is cleaned out and will not be aggregated for the next global model.However,model cleaning methods incur negative effects such as large computation overheads and limited updates.In this paper,we propose a data distribution optimization method,called federated distribution optimization(FedDO),aiming to overcome the shortcomings of model cleaning methods.FedDO calculates the gradient of the Jensen-Shannon divergence to decrease the discrepancy between selected clients’data distribution and the overall data distribution.We test our method on the multi-classification regression model,the multi-layer perceptron,and the convolutional neural network model on a handwritten digital image dataset.Compared with model cleaning methods,FedDO improves the training accuracy by 1.8%,2.6%,and 5.6%,respectively.展开更多
Wrinkles in flat graded elastic layers have been recently described as a timevarying Hamiltonian system by the energy method.Cylindrical core/shell structures can also undergo surface instabilities under the external ...Wrinkles in flat graded elastic layers have been recently described as a timevarying Hamiltonian system by the energy method.Cylindrical core/shell structures can also undergo surface instabilities under the external pressure.In this study,we show that by treating the radial direction as a pseudo-time variable,the graded core/shell system with radially decaying elastic properties can also be described within the symplectic framework.In combination with the shell buckling equation,the present paper addresses the surface wrinkling of graded core/shell structures subjected to the uniform external pressure by solving a series of ordinary differential equations with varying coefficients.Three representative gradient distributions are showcased,and the predicted critical pressure and critical wave number are verified by finite element simulations.The symplectic framework provides an efficient and accurate approach to understand the surface instability and morphological evolution in curved biological tissues and engineered structures.展开更多
The polystyrene-based polymer blends, partially miscible poly(bisphenol A carbonate)/polystyrene (PC/PS) and completely miscible poly(2,6-dimethylphenylene oxide)/polystyrene (PPO/PS), in nanorods with gradient compos...The polystyrene-based polymer blends, partially miscible poly(bisphenol A carbonate)/polystyrene (PC/PS) and completely miscible poly(2,6-dimethylphenylene oxide)/polystyrene (PPO/PS), in nanorods with gradient composition distribution were discussed. The polymer blend nanorods were prepared by infiltrating the polymer blends into nanopores of anodic aluminum oxide (AAO) templates via capillary action. Their morphology was investigated by micro-Fourier transform infrared spectroscopy (micro-FTIR) and nano-thermal analysis (nano-TA) with spatial resolution. The composition gradient of polymer blends in the nanopores is governed by the difference of viscosity and miscibility between the two polymers in the blends and the pore diameter. The capillary wetting of porous AAO templates by polymer blends offers a unique method to fabricate functional nanostructured materials with gradient composition distribution for the potential application to nanodevices.展开更多
The notorious growth of sodium dendrites and significant volume fluctuations have posed substantial challenges to the practical application of sodium metal anodes.In this work,an aerogel composed of MgF_(2) nanopartic...The notorious growth of sodium dendrites and significant volume fluctuations have posed substantial challenges to the practical application of sodium metal anodes.In this work,an aerogel composed of MgF_(2) nanoparticles(NPs)onto a three-dimensional(3D)printed reduced graphene oxide(rGO)(MgF_(2)/rGO)monolith was employed as a scaffold for sodium metal anodes.During the initial discharge process,the MgF_(2) NPs underwent an electrochemical in-situ conversion into NaF and sodiophilic Mg NPs,which act as the Na metal nucleation centers and contribute to the formation of a stable solid electrolyte interface(SEI)layer.Benefiting from these synergistic effects,the 3D printed MgF_(2)/rGO electrode exhibits a high Coulombic efficiency of 99.49% after 1200 cycles at 0.5 mA·cm^(-2) with 1 mAh·cm^(-2).It also shows a long cycle lifespan of 2500 h with a high capacity of 10 mAh·cm^(-2) at 5 mA·cm^(-2).Moreover,when assembled into a full cell with a Na@MgF_(2)/rGO anode and a Na3V2(PO4)3@C-rGO cathode,the cell delivers an extended cycle life of 3500 cycles at 1 C,preserving a reversible capacity of 86.98 mAh·g^(-1).This work paves the way for utilization of 3D printed metal-fluorides to enhance the electrochemical performance of the sodium metal anodes.展开更多
An innovative and accurate method for controlling the interfacial structure of Mg-alloy/steel direct lap joints using a hybrid laser-gas tungsten arc(GTA)flexible control heat source was proposed.The study investigate...An innovative and accurate method for controlling the interfacial structure of Mg-alloy/steel direct lap joints using a hybrid laser-gas tungsten arc(GTA)flexible control heat source was proposed.The study investigated the impact of spatial regulation of a flexible hybrid heat source on the thermal gradient distribution across the joint geometry and the resulting stress states in the joints,revealing the respective bonding and strengthening mechanisms.The findings indicate that the malposition alters the thermal gradient distribution within the joint,influencing the metallurgical bonding area,interfacial structure,fracture mode,and fracture path.Furthermore,the results showed that varying the laser pulse frequency affected the frequency of the laser-induced arc and the number of keyholes generated per unit length of the joint,which effectively altered the joint geometry and interfacial stress state,and could be used to enhance the load-bearing capacity of the joints.The joint's maximum load was measured to be 325.2 N/mm,which is approximately 88%of the Mg-alloy matrix and the highest reported strength for Mg alloy-steel dissimilar lap joints.A composite interfacial layer structure was achieved,consisting of Al_(11)(Mn,Fe)_(4)and a small amount of Mg_(2)Al_(3)intermetallic compounds(IMCs)at the weld front,along with Al_(11)(Mn,Fe)_(4)and Fe3Al IMCs in the weld middle.The key factors to achieving a high bonding strength of Mg-alloy/steel lap joints have been summarized.This study provides a technical and theoretical reference for the precise collaborative control of joint geometry,interfacial structure,and mechanical properties of dissimilar material lap joints.展开更多
We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is...We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is used for discretizations of distributed and boundary H^(1) shape gradient flows.Convergence analysis with a priori error estimates is provided under general and different regularity assumptions.We investigate the performances of shape gradient descent algorithms for energy dissipation minimization and obstacle flow.Numerical comparisons in 2D and 3D show that the distributed H1 shape gradient flow is more accurate than the popular boundary type.The corresponding distributed shape gradient algorithm is more effective.展开更多
Effective operation strategies in the solid oxide fuel cell(SOFC)can adjust the spatial distribution of temperature gradient favoring the long-term stability.To investigate the effects of different operating condition...Effective operation strategies in the solid oxide fuel cell(SOFC)can adjust the spatial distribution of temperature gradient favoring the long-term stability.To investigate the effects of different operating conditions on the thermal behavior inside SOFC,a three-dimensional model is developed in this study.The model is verified by comparing it with the experimental data.The heat generation rate and its variation under different operating conditions are analyzed.The combined effects of operating voltage and gas temperature are considered to be the key factor influencing the temperature gradient.Compared to the original case,the temperature of SOFC decreases by 21.4 K when the fuel velocity reaches 5 m/s.But the maximum temperature gradient increases by21.2%.Meanwhile,higher fuel velocities can eliminate about 32%of the area with higher temperature gradient.And when the oxidant velocity reaches 7.5 m/s,the peak temperature gradient effectively decreases by 16.59%.Simultaneous adjustment of the oxidant and fuel velocities can effectively reduce the peak temperature gradient and increase the safety zone.The effects of operation conditions on the temperature gradient of the cell are clarified in this study,which can be a reference for further research on the reliability of SOFCs.展开更多
The separator is of great significance to alleviate the shuttle effect and dendrite growth of lithium-sulfur batteries.However,most of the current commercial separators cannot meet these requirements well.In this work...The separator is of great significance to alleviate the shuttle effect and dendrite growth of lithium-sulfur batteries.However,most of the current commercial separators cannot meet these requirements well.In this work,a dense metal-organic-framework(MOF)modification layer is in-situ prepared by the assistant of polydopamine on the polypropylene separators.Due to the unique structure and synergistic effect of polydopamine(PDA)and zeolitic imidazolate framework-8(ZIF-8),the functional separator can not only trap the polysulfides effectively but also promote the transport of lithium ions.As a result,the battery assembled with the functional separator exhibits excellent cycle stability.The capacity remains 711 mAh·g^(−1)after 500 cycles at 2 C,and the capacity decay rate is as low as 0.013%per cycle.The symmetrical battery is cycled for 1,000 h at 2 mA·cm^(−2)(2 mAh·cm^(−2))with the plating/stripping overpotential of 20 mV.At the same time,the modification separator shows a higher lithium ion transference number(0.88),better thermal stability and electrolyte wettability than the unmodified separator.展开更多
Nonhomogeneous coatings (NCs) are new type of engineering structures that is not yet fully understood. One important aspect in the mechanical analysis of NCs is to determine the gradient distribution that creates the ...Nonhomogeneous coatings (NCs) are new type of engineering structures that is not yet fully understood. One important aspect in the mechanical analysis of NCs is to determine the gradient distribution that creates the maximum thermal stress relaxation. This paper employs numerical analysis using the finite element method and experimental analysis using moire interference to study the stress distribution in NCs. Attention focused on the edge effect stresses in the coating/substrate structures and their dependence on the different gradient distributions of this new kind of composite structure.展开更多
文摘The effects of the component gradient distribution at interface and the fiber gradient distribution on the strength of cement-based materials were studied. The results show that the flexural strength and compressive strength of the mortar and concrete with interface component and fiber gradient distributions are obviously improved. The strengthes of the fiber gradient distributed mortar and concrete (FGDM/C) are higher than those of fiber homogeneously distributed mortar and concrete (FHDM/C). To obtain the same strength, therefore, a smaller fiber volume content in FGDM/C is needed than that in FHDM/C. The results also show that the component gradient distribution of the concrete can be obtained by means of multi-layer vibrating formation.
基金the National Natural Science Foundation of China(No.51675433)the Natural Science Foundation for Distinguished Young Scholars of Shaanxi Province(No.2019JC-09)for financial supports given to this research。
文摘Gradient distributions of temperature and deformation(GDTD)are crucial for achieving dual-performance discs of titanium alloys which is required by the service environment of aeroengine.However,heating,cooling and deforming sequence in the whole process of the titanium disc forming,which leads to difficulties for achieving GDTD due to a lot of parameters.To solve this problem,a whole-process model of the titanium disc forming for GDTD has been established.In the model,heating and cooling via heat radiation,conduction and convection,and deforming by local loading with mold chilling are all considered.Experiments on heating and cooling as well as deforming were carried out by using a furnace and the Gleeble-3500 machine.The experimental data are used to determine thermal parameters and constitutive relations of the IMI834 titanium alloy,and then to verify the reliability of the model.Then the model was used to simulate the evolution rules of temperature and deformation of the titanium disc.The results show that the heating surface,furnace temperature,billet profile and loading rate play the core role for the control of GDTD,and thus a set of parameters were determined.Therefore,this work provides a base for developing a new forming technology of the dual-performance titanium discs with the approach of local heating and local loading.
基金Funded by the Fundamental Research Funds for the Central University (No.2010-II-025)the National Natural Science Foundation of China(No.50675165)
文摘Based on the car front-wheel-hub forging forming process of numerical simulation, the temperature gradient expression of forging model cavity near the surface layer was got ten, which illustrates that the forging temperature gradient is related to forging die materials thermal conductivity, specific heat and impact speed, and the correlation coefficient is 0.97. Under the different thermal conductivity, heat capacity and forging speed, the temperature gradient was compared with each other. The paper obtained the relevant laws, which illustrates the temperature gradient relates to these three parameters in a sequence of thermal conductivity 〉 impact speed〉 specific heat capacity. To reduce thermal stress in the near-surface layer of hot forging cavity, the material with greater thermal conductivity coefficient and specific heat capacity should be used.
基金funded in part by the Humanities and Social Sciences Planning Foundation of Ministry of Education of China under Grant No.24YJAZH123National Undergraduate Innovation and Entrepreneurship Training Program of China under Grant No.202510347069the Huzhou Science and Technology Planning Foundation under Grant No.2023GZ04.
文摘The Industrial Internet of Things(IIoT)is increasingly vulnerable to sophisticated cyber threats,particularly zero-day attacks that exploit unknown vulnerabilities and evade traditional security measures.To address this critical challenge,this paper proposes a dynamic defense framework named Zero-day-aware Stackelberg Game-based Multi-Agent Distributed Deep Deterministic Policy Gradient(ZSG-MAD3PG).The framework integrates Stackelberg game modeling with the Multi-Agent Distributed Deep Deterministic Policy Gradient(MAD3PG)algorithm and incorporates defensive deception(DD)strategies to achieve adaptive and efficient protection.While conventional methods typically incur considerable resource overhead and exhibit higher latency due to static or rigid defensive mechanisms,the proposed ZSG-MAD3PG framework mitigates these limitations through multi-stage game modeling and adaptive learning,enabling more efficient resource utilization and faster response times.The Stackelberg-based architecture allows defenders to dynamically optimize packet sampling strategies,while attackers adjust their tactics to reach rapid equilibrium.Furthermore,dynamic deception techniques reduce the time required for the concealment of attacks and the overall system burden.A lightweight behavioral fingerprinting detection mechanism further enhances real-time zero-day attack identification within industrial device clusters.ZSG-MAD3PG demonstrates higher true positive rates(TPR)and lower false alarm rates(FAR)compared to existing methods,while also achieving improved latency,resource efficiency,and stealth adaptability in IIoT zero-day defense scenarios.
基金Project supported by the National Natural Science foundation of China(No.51079095)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(No.51021004)
文摘This paper uses the Oseen transformation to solve the differential equations governing motion of the vertical linear gradient flow distribution close to a wall surface. The Navier-Stokes equations are used to consider the inertia term along the flow direction. A novel contour integral method is used to solve the complex Airy function. The boundary conditions of linear gradient flow distribution for finite problems are determined. The vorticity function, the pressure function, and the turbulent velocity profiles are provided, and the stability of particle trajectories is studied. An Lx-function form of the third derivative circulation is used to to simplify the solution. Theoretical results are compared with the experimental measurements with satisfactory agreement.
基金financially supported by the Natural Science Foundation of Liaoning Province(No.:201102090)the Doctoral Initiating Project of Liaoning Province Foundation for Natural Sciences,China(No.:20111068)+2 种基金the High School Development Plan for Distinguished Young Scholars of Liaoning Province Education Committee(No.:LJQ2012056)the National High-Tech Research and Development Program of China("863"Program,No.:2011AA060102)the International Science and Technology Cooperation Program of China,(No.:2011DFR50270)
文摘The aim of the present research is to provide a novel technique for preparing gradient Al 2 O 3-ZrO 2 ceramic foams.This technique used epispastic polystyrene spheres to array templates and centrifugal slip casting to obtain cell struts with gradient distribution of Al 2 O 3 and ZrO 2 particles and high packing density.Aqueous Al 2 O 3-20vol.% ZrO 2 slurries with 20vol.% solid contents were prepared and the dispersion and rheological characteristics of the slurries were investigated.The settling velocity and mass segregation of Al 2 O 3 and ZrO 2 particles at different centrifugal accelerations were calculated and studied.The drying behavior,macrostructure,microstructure,compressive property and resistance to thermal shock of the sintered products were also investigated.The results show that the difference of settling velocity of Al 2 O 3 and ZrO 2 particles increases and mass segregation becomes acute with an increase in centrifugal acceleration.The cell struts prepared at a centrifugal acceleration of 1,690 g have high sintered density(99.0% TD) and continuous gradient distribution of Al 2 O 3 and ZrO 2 particles.When sintered at 1,550 o C for 2 h,the cell size of gradient Al 2 O 3-ZrO 2 foam is approximately uniform,about 1.1 mm.With the porosity of gradient Al 2 O 3-ZrO 2 ceramic foams increasing from 75.3% to 83.0%,the compressive strength decreases from 4.4 to 2.4 MPa,and the ceramic foams can resist 8-11 repeated thermal shock from 1,100 o C to room temperature.
文摘How to distribute total sum of funds among different investment priorities？ It is not only a theoretical problem in Management Accounting, but also a realistic problem in the investment decision of an enterprise. In this paper, the author queries the method of ＂use linear programming to find out optimum combination＂, which put forward in management accounting, and gives a convenient and reasonable method---effective gradient method.
基金National Engineering Research Center of UHV Technology and Novel Electrical Equipment Basis,Grant/Award Number:NERCUHV-2023-KF-02。
文摘In this study,the functional gradient materials(FGMs)were the first attempt to homogenise the electric field distribution in the cable accessory,where zinc oxide particles(ZnO_(k))were filled into ethylene propylene diene monomer with the composi-tionally gradient distribution using laminating and hot-pressing methods.The constructed FGMs with significantly improved non-linear conductivity can avoid the electric field distortion in cable accessories.The results show that the configuration of compositionally gradient structured fillers can significantly improve the electrical conductivity of FGMs compared to the homogeneous distribution.Additionally,compositionally gradient structures of ZnOk fillers can also improve the thermal conductivity of FGM composites,which facilitates the heat dissipation of dielectric and reduces the probability of electrothermal coupling breakdown.The mechanical properties of the composites are deeply affected by the filler's content and configuration,both improved tear elongation and tensile strength can be achieved at an optimal content and gradient structure of ZnOk fillers.Finally,the simulation analysis results show that FGM composites can homogenise the electric field more efficiently in comparison with homogeneous composites.This work demonstrates that compositionally gradient structures can improve the utilisation of functional fillers and develop the FGM composites for high-voltage direct current cable accessory applications.
基金supported by the National Natural Science Foundation of China(No.52200139)the Open Research Fund Program of Anhui Provincial Institute of Modern Coal Processing Technology,Anhui University of Science and Technology(No.MTY202402).
文摘Multi-scale design in metal-support interaction allows for the comprehensive control of the electronic migration and magnetic respond behaviors,providing tuning frequency electromagnetic(EM)absorption.Herein,synergizing confined reduction and Kirkendall diffusion were proposed to design the metal Nickel(e.g.signal atoms,clusters and nanoparticles)in the carbon matrix.In our work,residual carbon(RC)was used as substrate to load carbon-encapsulated Ni particles to build unique magnetic-dielectric RC-Ni@C composites.With tuning multi-scale magnetic and electric interaction,as-synthesized RC-Ni@C composite exhibited remarkable tuning frequency absorption feature,which the RC-Ni@C-2 sample hold the outstanding EM dissipation in the low-frequency C-band(4-8 GHz).To confirm the magnetic and electric interaction,visual evidence of electric field distribution was offered via the advanced integrated differential phase contrast(iDPC)technology.Combined with density functional theory(DFT)calculation and EM parameters analysis,related EM energy absorption mechanisms were discussed in this multi-scale heterostructures,including the dielectric polarization,conduction loss and magnetic dissipation.As results,special gradient magnetic particles regulating in carbon substrates provide new design idea to build low-frequency EM wave absorption.
基金supported in part by the National Key R&D Program of China(No.2018YFB2101100)National Natural Science Foundation of China(Nos.62402519,61932001,and 61872376).
文摘In current federated learning frameworks,a central server randomly selects a small number of clients to train local models at the beginning of each global iteration.Since clients’local data are non-dependent and identically distributed,partial local models are not consistent with the global model.Existing studies employ model cleaning methods to find inconsistent local models.Model cleaning methods measure the cosine similarity between local models and the global model.The inconsistent local model is cleaned out and will not be aggregated for the next global model.However,model cleaning methods incur negative effects such as large computation overheads and limited updates.In this paper,we propose a data distribution optimization method,called federated distribution optimization(FedDO),aiming to overcome the shortcomings of model cleaning methods.FedDO calculates the gradient of the Jensen-Shannon divergence to decrease the discrepancy between selected clients’data distribution and the overall data distribution.We test our method on the multi-classification regression model,the multi-layer perceptron,and the convolutional neural network model on a handwritten digital image dataset.Compared with model cleaning methods,FedDO improves the training accuracy by 1.8%,2.6%,and 5.6%,respectively.
基金Project supported by the National Natural Science Foundation of China(No.11972259)。
文摘Wrinkles in flat graded elastic layers have been recently described as a timevarying Hamiltonian system by the energy method.Cylindrical core/shell structures can also undergo surface instabilities under the external pressure.In this study,we show that by treating the radial direction as a pseudo-time variable,the graded core/shell system with radially decaying elastic properties can also be described within the symplectic framework.In combination with the shell buckling equation,the present paper addresses the surface wrinkling of graded core/shell structures subjected to the uniform external pressure by solving a series of ordinary differential equations with varying coefficients.Three representative gradient distributions are showcased,and the predicted critical pressure and critical wave number are verified by finite element simulations.The symplectic framework provides an efficient and accurate approach to understand the surface instability and morphological evolution in curved biological tissues and engineered structures.
基金supported by a Grant-in-Aid for the Global COE Program "Science for Future Molecular Systems" from the Ministry of Education, Culture, Science, Sports and Technology of JapanZ.S. thanks the National Natural Science Foundation of China (50921062) for support
文摘The polystyrene-based polymer blends, partially miscible poly(bisphenol A carbonate)/polystyrene (PC/PS) and completely miscible poly(2,6-dimethylphenylene oxide)/polystyrene (PPO/PS), in nanorods with gradient composition distribution were discussed. The polymer blend nanorods were prepared by infiltrating the polymer blends into nanopores of anodic aluminum oxide (AAO) templates via capillary action. Their morphology was investigated by micro-Fourier transform infrared spectroscopy (micro-FTIR) and nano-thermal analysis (nano-TA) with spatial resolution. The composition gradient of polymer blends in the nanopores is governed by the difference of viscosity and miscibility between the two polymers in the blends and the pore diameter. The capillary wetting of porous AAO templates by polymer blends offers a unique method to fabricate functional nanostructured materials with gradient composition distribution for the potential application to nanodevices.
基金supported by the Natural Science Foundation of Henan Province(Nos.252300421283 and 242300421427)Tackling Key Scientific and Technological Problems of the Henan Province(No.242102220104)the Major Science and Technology Projects of Henan Province(No.231100230300).
文摘The notorious growth of sodium dendrites and significant volume fluctuations have posed substantial challenges to the practical application of sodium metal anodes.In this work,an aerogel composed of MgF_(2) nanoparticles(NPs)onto a three-dimensional(3D)printed reduced graphene oxide(rGO)(MgF_(2)/rGO)monolith was employed as a scaffold for sodium metal anodes.During the initial discharge process,the MgF_(2) NPs underwent an electrochemical in-situ conversion into NaF and sodiophilic Mg NPs,which act as the Na metal nucleation centers and contribute to the formation of a stable solid electrolyte interface(SEI)layer.Benefiting from these synergistic effects,the 3D printed MgF_(2)/rGO electrode exhibits a high Coulombic efficiency of 99.49% after 1200 cycles at 0.5 mA·cm^(-2) with 1 mAh·cm^(-2).It also shows a long cycle lifespan of 2500 h with a high capacity of 10 mAh·cm^(-2) at 5 mA·cm^(-2).Moreover,when assembled into a full cell with a Na@MgF_(2)/rGO anode and a Na3V2(PO4)3@C-rGO cathode,the cell delivers an extended cycle life of 3500 cycles at 1 C,preserving a reversible capacity of 86.98 mAh·g^(-1).This work paves the way for utilization of 3D printed metal-fluorides to enhance the electrochemical performance of the sodium metal anodes.
基金financially supported by the National Key Research and Development Program of China(No.2022YFB4600900)the National Natural Science Foundation of China(Nos.U1960111 and 52375309)the Liaoning ProvinceApplied Basic Research Program Project(Nos.2023JH2 and 101300157).
文摘An innovative and accurate method for controlling the interfacial structure of Mg-alloy/steel direct lap joints using a hybrid laser-gas tungsten arc(GTA)flexible control heat source was proposed.The study investigated the impact of spatial regulation of a flexible hybrid heat source on the thermal gradient distribution across the joint geometry and the resulting stress states in the joints,revealing the respective bonding and strengthening mechanisms.The findings indicate that the malposition alters the thermal gradient distribution within the joint,influencing the metallurgical bonding area,interfacial structure,fracture mode,and fracture path.Furthermore,the results showed that varying the laser pulse frequency affected the frequency of the laser-induced arc and the number of keyholes generated per unit length of the joint,which effectively altered the joint geometry and interfacial stress state,and could be used to enhance the load-bearing capacity of the joints.The joint's maximum load was measured to be 325.2 N/mm,which is approximately 88%of the Mg-alloy matrix and the highest reported strength for Mg alloy-steel dissimilar lap joints.A composite interfacial layer structure was achieved,consisting of Al_(11)(Mn,Fe)_(4)and a small amount of Mg_(2)Al_(3)intermetallic compounds(IMCs)at the weld front,along with Al_(11)(Mn,Fe)_(4)and Fe3Al IMCs in the weld middle.The key factors to achieving a high bonding strength of Mg-alloy/steel lap joints have been summarized.This study provides a technical and theoretical reference for the precise collaborative control of joint geometry,interfacial structure,and mechanical properties of dissimilar material lap joints.
基金This work was supported in part by the National Natural Science Foundation of China under grants(No.11571115 and No.12071149)Natural Science Foundation of Shanghai(No.19ZR1414100)Science and Technology Commission of Shanghai Municipality(No.18dz2271000).
文摘We consider optimal shape design in Stokes flow using H^(1) shape gradient flows based on the distributed Eulerian derivatives.MINI element is used for discretizations of Stokes equation and Galerkin finite element is used for discretizations of distributed and boundary H^(1) shape gradient flows.Convergence analysis with a priori error estimates is provided under general and different regularity assumptions.We investigate the performances of shape gradient descent algorithms for energy dissipation minimization and obstacle flow.Numerical comparisons in 2D and 3D show that the distributed H1 shape gradient flow is more accurate than the popular boundary type.The corresponding distributed shape gradient algorithm is more effective.
基金the supports provided by the Science and Technology Research Program of Henan Province,China(No.222102320230)the National Natural Science Foundation of China(No.51776190)。
文摘Effective operation strategies in the solid oxide fuel cell(SOFC)can adjust the spatial distribution of temperature gradient favoring the long-term stability.To investigate the effects of different operating conditions on the thermal behavior inside SOFC,a three-dimensional model is developed in this study.The model is verified by comparing it with the experimental data.The heat generation rate and its variation under different operating conditions are analyzed.The combined effects of operating voltage and gas temperature are considered to be the key factor influencing the temperature gradient.Compared to the original case,the temperature of SOFC decreases by 21.4 K when the fuel velocity reaches 5 m/s.But the maximum temperature gradient increases by21.2%.Meanwhile,higher fuel velocities can eliminate about 32%of the area with higher temperature gradient.And when the oxidant velocity reaches 7.5 m/s,the peak temperature gradient effectively decreases by 16.59%.Simultaneous adjustment of the oxidant and fuel velocities can effectively reduce the peak temperature gradient and increase the safety zone.The effects of operation conditions on the temperature gradient of the cell are clarified in this study,which can be a reference for further research on the reliability of SOFCs.
基金the Ministry of Science and Technology of the People’s Republic of China(No.2017YFE0127600)the National Natural Science Foundation of China(No.51702247)+3 种基金the Fundamental Research Funds for the Central Universities(No.WUT:2020III023,2020III050,2021IVA123,2021III009)Hainan Provincial Joint Project of Sanya Yazhou Bay Science and Technology City(No.520LH056)Sanya Science and Education Innovation Park of Wuhan University of Technology(No.2020KF0021)the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(WUT:2021-ZD-1).
文摘The separator is of great significance to alleviate the shuttle effect and dendrite growth of lithium-sulfur batteries.However,most of the current commercial separators cannot meet these requirements well.In this work,a dense metal-organic-framework(MOF)modification layer is in-situ prepared by the assistant of polydopamine on the polypropylene separators.Due to the unique structure and synergistic effect of polydopamine(PDA)and zeolitic imidazolate framework-8(ZIF-8),the functional separator can not only trap the polysulfides effectively but also promote the transport of lithium ions.As a result,the battery assembled with the functional separator exhibits excellent cycle stability.The capacity remains 711 mAh·g^(−1)after 500 cycles at 2 C,and the capacity decay rate is as low as 0.013%per cycle.The symmetrical battery is cycled for 1,000 h at 2 mA·cm^(−2)(2 mAh·cm^(−2))with the plating/stripping overpotential of 20 mV.At the same time,the modification separator shows a higher lithium ion transference number(0.88),better thermal stability and electrolyte wettability than the unmodified separator.
文摘Nonhomogeneous coatings (NCs) are new type of engineering structures that is not yet fully understood. One important aspect in the mechanical analysis of NCs is to determine the gradient distribution that creates the maximum thermal stress relaxation. This paper employs numerical analysis using the finite element method and experimental analysis using moire interference to study the stress distribution in NCs. Attention focused on the edge effect stresses in the coating/substrate structures and their dependence on the different gradient distributions of this new kind of composite structure.
