The nonlinear traveling wave vibration of rotating ferromagnetic functionally graded(FG)cylindrical shells under multi-physics fields is investigated.Grounded in the Kirchhoff-Love thin shell theory,the geometric nonl...The nonlinear traveling wave vibration of rotating ferromagnetic functionally graded(FG)cylindrical shells under multi-physics fields is investigated.Grounded in the Kirchhoff-Love thin shell theory,the geometric nonlinearity is incorporated into the model,and the constitutive equations are derived.The physical parameters of functionally graded materials(FGMs),which exhibit continuous variation across the thickness gradient,are of particular interest.The nonlinear magneto-thermoelastic governing equations are derived in accord with Hamilton's principle.The nonlinear partial differential equations are discretized with the Galerkin method,and the analytical expression of traveling wave frequencies is derived with an approximate method.The accuracy of the proposed method is validated through the comparison with the results from the literature and numerical solutions.Finally,the visualization analyses are conducted to examine the effects of key parameters on the traveling wave frequencies.The results show that the factors including the power-law index,temperature,magnetic field intensity,and rotating speed have the coupling effects with respect to the nonlinear vibration behavior.展开更多
This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite elem...This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite element model of GMM smart component in electric, magnetic, and mechanical fields by step computation to optimize the design of GMM smart com-ponent. The proposed model is implemented by using COMSOL multi-physics V3.2a. The effects of the smart component on the deformation and the system resonance frequencies are studied. The results calculated by the model are in excellent agreement (relative errors are below 10%) with the experimental values.展开更多
This study presents preliminary results of tidal-induced magnetic field signals extracted from 9 months of data collected by the Macao Science Satellite-1(MSS-1) from November 2023 to July 2024. Tidal signals were iso...This study presents preliminary results of tidal-induced magnetic field signals extracted from 9 months of data collected by the Macao Science Satellite-1(MSS-1) from November 2023 to July 2024. Tidal signals were isolated using sequential modeling techniques by subtracting non-tidal field model predictions from observed magnetic data. The extracted MSS-1 results show strong agreement with those from the Swarm and CryoSat satellites. MSS-1 effectively captures key large-scale tidal-induced magnetic anomalies, mainly due to its unique 41-degree low-inclination orbit, which provides wide coverage of local times. This finding underscores the strong potential of MSS-1 to recover high-resolution global tidal magnetic field models as more MSS-1 data become available.展开更多
With the continuous upgrading of traditional manufacturing industries and the rapid rise of emerging technology fields,the performance requirements for the permanent magnet synchronous motors(PMSMs)have become higher ...With the continuous upgrading of traditional manufacturing industries and the rapid rise of emerging technology fields,the performance requirements for the permanent magnet synchronous motors(PMSMs)have become higher and higher.The importance of fast and accurate electromagnetic thermal coupling analysis of such motors becomes more and more prominent.In view of this,the surfacemounted PMSM(SPMSM)equipped with unequally thick magnetic poles is taken as the main object and its electromagnetic thermal coupling analytical model(ETc AM)is investigated.First,the electromagnetic analytical model(EAM)is studied based on the modified subdomain method.It realizes the fast calculation of key electromagnetic characteristics.Subsequently,the 3D thermal analytical model(TAM)is developed by combining the EAM,the lumped parameter thermal network method(LPTNM),and the partial differential equation of heat flux.It realizes the fast calculation of key thermal characteristics in 3D space.Further,the information transfer channel between EAM and TAM is built with reference to the intrinsic connection between electromagnetic field and temperature field.Thereby,the novel ETcAM is proposed to realize the fast and accurate prediction of electromagnetic and temperature fields.Besides,ETcAM has a lot to commend it.One is that it well accounts for the complex structure,saturation,and heat exchange behavior.Second,it saves a lot of computer resources.It offers boundless possibilities for initial design,scheme evaluation,and optimization of motors.Finally,the validity,accuracy,and practicality of this study are verified by simulation and experiment.展开更多
Reducing coke use is an effective measure to reduce carbon emission and energy consumption in the blast furnace(BF)ironmaking.Essentially,BF is a high-temperature moving bed reactor,where complex physical transformati...Reducing coke use is an effective measure to reduce carbon emission and energy consumption in the blast furnace(BF)ironmaking.Essentially,BF is a high-temperature moving bed reactor,where complex physical transformations coupled with complicated reactions occur.This makes it challenging to investigate the factors determining BF performance with the conventional method.A multi-physical field coupling mathematical model of BF was thus developed to describe its mass and heat transfer as well as its intrinsic reactions.Then,the proposed model was validated with the production data.Under coupling conditions,influences of dominating reactions on BF performance(temperature distribution,gas distribution,iron formation reaction,and direct reduction degree)were revealed.The results indicated that coke combustion,indirect reduction,and direct reduction of iron ore mainly took place nearby the shaft tuyere,cohesive zone,and dripping zone,respectively.Besides,the rate of coke solution loss reaction was increased with the rising coke porosity in the cohesive zone.Considering the effect of coke porosity on the efficiency and stability of BF,the coke porosity of 0.42 was regarded as a reasonable value.展开更多
Aircraft disturbs the adjacent atmospheric environment in flight,forming spatial distribution features of atmospheric density that differ from the natural background,which may potentially be utilized as tracer charact...Aircraft disturbs the adjacent atmospheric environment in flight,forming spatial distribution features of atmospheric density that differ from the natural background,which may potentially be utilized as tracer characteristics to introduce new technologies for indirectly sensing the presence of aircraft.In this paper,the concept of a long-range aircraft detection based on the atmospheric disturbance density field is proposed,and the detection mode of tomographic imaging of the scattering light of an atmospheric disturbance flow field is designed.By modeling the spatial distribution of the disturbance density field,the scattered echo signal images of active light towards the disturbance field at long distance are simulated.On this basis,the characteristics of the disturbance optical signal at the optimal detection resolution are analyzed.The results show that the atmospheric disturbance flow field of the supersonic aircraft presents circular in the light-scattering echo images.The disturbance signal can be further highlighted by differential processing of the adjacent scattering images.As the distance behind the aircraft increases,the diffusion range of the disturbance signal increases,and the signal intensity and contrast with the background decrease.Under the ground-based observation conditions of the aircraft at a height of 10000 m,a Mach number of1.6,and a detection distance of 100 km,the contrast between the disturbance signal and the back-ground was 30 d B at a distance of one time from the rear of the fuselage,and the diffusion diameter of the disturbance signal was 50 m.At a distance eight times the length of the aircraft,the contrast decreased to 10 dB,and the diameter increased to 290 m.The contrast was reduced to 3 dB at a distance nine times the length of the aircraft,and the diameter was diffused to 310 m.These results indicate the possibility of long-range aircraft detection based on the characteristics of the atmospheric density field.展开更多
Laser powder bed fusion(LPBF)has revolutionized modern manufacturing by enabling high design freedom,rapid prototyping,and tailored mechanical properties.However,optimizing process parameters remains challenging due t...Laser powder bed fusion(LPBF)has revolutionized modern manufacturing by enabling high design freedom,rapid prototyping,and tailored mechanical properties.However,optimizing process parameters remains challenging due to the trial-and-error approaches required to capture subtle parameter-microstructure relationships.This study employed a multi-physics computational framework to investigate the melting and solidification dynamics of magnesium alloy.By integrating the discrete element method for powder bed generation,finite volume method with volume of fluid for melt pool behavior,and phase-field method for microstructural evolution,the critical physical phenomena,including powder melting,molten pool flow,and directional solidification were simulated.The effects of laser power and scanning speed on temperature distribution,melt pool geometry,and dendritic morphology were systematically analyzed.It was revealed that increasing laser power expanded melt pool dimensions and promoted columnar dendritic growth,while high scanning speeds reduced melt pool stability and refined dendritic structures.Furthermore,Marangoni convection and thermal gradients governed solute redistribution,with excessive energy input risking defects such as porosity and elemental evaporation.These insights establish quantitative correlations between process parameters,thermal history,and microstructural characteristics,providing a validated roadmap for LPBF-processed magnesium alloy with tailored performance.展开更多
Seepage refers to the flow of water through porous materials.This phenomenon has a crucial role in dam,slope,excavation,tunnel,and well design.Performing seepage analysis usually is a challenging task,as one must cope...Seepage refers to the flow of water through porous materials.This phenomenon has a crucial role in dam,slope,excavation,tunnel,and well design.Performing seepage analysis usually is a challenging task,as one must cope with the uncertainty associated with the parameters such as the hydraulic conductivity in the horizontal and vertical directions that drive this phenomenon.However,at the same time,the data on horizontal and vertical hydraulic conductivities are typically scarce in spatial resolution.In this context,so-called non-traditional approaches for uncertainty quantification(such as intervals and fuzzy variables)offer an interesting alternative to classical probabilistic methods,since they have been shown to be quite effective when limited information on the governing parameters of a phenomenon is available.Therefore,the main contribution of this study is the development of a framework for conducting seepage analysis in saturated soils,where uncertainty associated with hydraulic conductivity is characterized using fuzzy fields.This method to characterize uncertainty extends interval fields towards the domain of fuzzy numbers.In fact,it is illustrated that fuzzy fields are an effective tool for capturing uncertainties with a spatial component,since they allow one to account for available physical measurements.A case study in confined saturated soil shows that with the proposed framework,it is possible to quantify the uncertainty associated with seepage flow,exit gradient,and uplift force effectively.展开更多
Earthquakes are caused directly by the motion of the stress field,therefore,observing the stress field is significant.Experiments on the relationships among wave velocity,stress factors,and faults show that the wave v...Earthquakes are caused directly by the motion of the stress field,therefore,observing the stress field is significant.Experiments on the relationships among wave velocity,stress factors,and faults show that the wave velocity of rock media under stable stress fields corresponds one-to-one with stress factors.Therefore,the wave velocity gradient can indicate the direction of stress vector,and the gradient divergence can indicate the strength of the stress field.To verify the results,considering the limitations of wave velocity measurement in solid crustal media,two quantities,namely the apparent wave velocity and Poisson ratios relating to wave velocity,were used to refl ect the stress field state.The seismic data of the Tangshan and Luzhou regions were studied separately.The calculated apparent wave velocity and Poisson ratios were interpolated to achieve regional data gridding.The gradients and the gradient divergences of the apparent wave velocity and Poisson ratio fields in the two regions were analyzed,and it was found that their spatial distribution in the same region was the same.They are believed to refl ect the vertical projection of the stress direction vector and strength on the surface in the stress field,consistent with the experimental results.Whether it can eff ectively refl ect the stress field requires further analysis of the specific situation of the local medium and the movement mode of the stress field.展开更多
After the fabrication of magnetic resonance superconducting magnets,the magnetic field inhomogeneity needs to be accurately measured for subsequent shimming.However,conventional measurement methods are susceptible to ...After the fabrication of magnetic resonance superconducting magnets,the magnetic field inhomogeneity needs to be accurately measured for subsequent shimming.However,conventional measurement methods are susceptible to magnetic fields,have poor compatibility,and are difficult to adapt to various types of magnets.This paper proposes a new field measuring system based on a three-axis movable platform.The system utilizes non-magnetic materials and an innovative hand-wheel lifting design that can be adapted to various aperture magnets,thus obviating the necessity for electrically driven equipment and addressing safety concerns in strong magnetic fields.In addition,the measurement system offers high accuracy up to 1 mm and a wide measurable range.The fields of 3 T and 7 T magnets were mapped using the designed system with diameter of spherical volume(DSV)of 160 mm and 130 mm,respectively.Experimental results demonstrate that the magnetic field measurement system has strong compatibility and can accurately map the magnetic field at arbitrary positions,which is critical for shimming studies.展开更多
As the plasma current power in tokamak devices increases,a significant number of stray magnetic fields are generated around the equipment.These stray magnetic fields can disrupt the operation of electronic power devic...As the plasma current power in tokamak devices increases,a significant number of stray magnetic fields are generated around the equipment.These stray magnetic fields can disrupt the operation of electronic power devices,particularly transformers in switched-mode power supplies.Testing flyback converters with transformers under strong background magnetic fields highlights electromagnetic compatibility(EMC)issues for such switched-mode power supplies.This study utilizes finite element analysis software to simulate the electromagnetic environment of switched-mode power supply transformers and investigates the impact of variations in different magnetic field parameters on the performance of switched-mode power supplies under strong stray magnetic fields.The findings indicate that EMC issues are associated with transformer core saturation and can be alleviated through appropriate configurations of the core size,air gap,fillet radius,and installation direction.This study offers novel solutions for addressing EMC issues in high magnetic field environments.展开更多
Nitrate(NO_(3)^(-))accumulation and transport processes in the thick vadose zone affect the evolution of the groundwater NO_(3)^(-)content in intensive agricultural regions.Agricultural land-use change(ALUC),typically...Nitrate(NO_(3)^(-))accumulation and transport processes in the thick vadose zone affect the evolution of the groundwater NO_(3)^(-)content in intensive agricultural regions.Agricultural land-use change(ALUC),typically accompanied by substantial alterations in nitrogen fertilizer application and irrigation practices,is an important influencing factor.This study evaluated the changes in NO_(3)^(-)accumulation and transport in the deep vadose zone(DVZ,below the root zone),and the groundwater NO_(3)^(-)content associated with ALUC from grain to vegetable fields in the North China Plain(NCP).The ALUC from grain to vegetable resulted in nitrate–nitrogen(NO_(3)^(-)-N)accumulation in DVZ increased by 235.5 kg ha^(-1)m^(-1)(163.2%)in the piedmont plain and 224.9 kg ha^(-1)m^(-1)(102.7%)in the central plain,respectively.This change accelerated downward transport velocity in the DVZ(from 0.81±0.47 to 0.89±0.55 m yr^(-1)in the piedmont plain,and from 0.24±0.12 to 0.92±0.12 m yr^(-1)in the central plain)and increased NO_(3)^(-)leaching fluxes.High transport velocity and leaching fluxes resulted in chemical N-fertilizer entering the aquifer in several areas in the piedmont plain.The impact of the agricultural activity intensity changes,accompanied by the ALUC,on groundwater quantity and quality should be considered in similar regions.展开更多
Development of robust electrocatalyst for oxygen reduction reaction(ORR)in a seawater electrolyte is the key to realize seawater electrolyte-based zinc-air batteries(SZABs).Herein,constructing a local electric field c...Development of robust electrocatalyst for oxygen reduction reaction(ORR)in a seawater electrolyte is the key to realize seawater electrolyte-based zinc-air batteries(SZABs).Herein,constructing a local electric field coupled with chloride ions(Cl-)fixation strategy in dual single-atom catalysts(DSACs)was proposed,and the resultant catalyst delivered considerable ORR performance in a seawater electrolyte,with a high half-wave potential(E_(1/2))of 0.868 V and a good maximum power density(Pmax)of 182 mW·cm^(−2)in the assembled SZABs,much higher than those of the Pt/C catalyst(E_(1/2):0.846 V;Pmax:150 mW·cm^(−2)).The in-situ characterization and theoretical calculations revealed that the Fe sites have a higher Cl^(−)adsorption affinity than the Co sites,and preferentially adsorbs Cl^(−)in a seawater electrolyte during the ORR process,and thus constructs a low-concentration Cl^(−)local microenvironment through the common-ion exclusion effect,which prevents Cl^(−)adsorption and corrosion in the Co active centers,achieving impressive catalytic stability.In addition,the directional charge movement between Fe and Co atomic pairs establishes a local electric field,optimizing the adsorption energy of Co sites for oxygen-containing intermediates,and further improving the ORR activity.展开更多
A recent study demonstrated that solid-state photochemically induced dynamic nuclear polarization(photo-CIDNP)can achieve significant 1H NMR hyperpolarization at high magnetic fields(9.4 T and 21.1 T).This was accompl...A recent study demonstrated that solid-state photochemically induced dynamic nuclear polarization(photo-CIDNP)can achieve significant 1H NMR hyperpolarization at high magnetic fields(9.4 T and 21.1 T).This was accomplished using a specially designed donor-chromophore-acceptor(D-C-A)molecule,which exhibits an excited state electron-electron interaction that is finely tuned to match the proton Larmor frequency under high-field conditions[1].展开更多
Spiral waves,as a typical self-organized structure with chiral characteristics,are widely found in excitable media such as cardiac tissues,chemical reactions,and neural networks.Based on the Fitz Hugh–Nagumo model,we...Spiral waves,as a typical self-organized structure with chiral characteristics,are widely found in excitable media such as cardiac tissues,chemical reactions,and neural networks.Based on the Fitz Hugh–Nagumo model,we investigated the mechanisms underlying the effects of direct current electric fields(DCEF),alternating current electric fields(ACEF),and polarized electric fields(PEF)on the interaction and annihilation processes of counter-rotating spiral waves.We found that in a direct current electric field,the drift direction of the spiral wave is determined jointly by its chirality and the electric field direction,which allows selective attraction or repulsion.In an alternating current electric field,the annihilation behavior of spiral waves can be influenced by the phase and intensity of the electric field,where a specific range of parameters induces resonance drift and eventual annihilation.On the other hand,the polarized electric field exhibits a more complex modulation capability on spiral waves:the trajectory and annihilation efficiency of spiral waves can be regulated by both the intensity and phase of the polarized electric field.These results reveal the potential feasibility of regulating multichiral spiral waves through multiple electric fields,providing theoretical insight for the control of spiral waves in relevant systems.展开更多
Direct numerical simulations have been conducted to investigate the evolution process of liquid metal laminar to turbulent flow in a rectangular duct under the influence of a non-uniform magnetic field.The Reynolds nu...Direct numerical simulations have been conducted to investigate the evolution process of liquid metal laminar to turbulent flow in a rectangular duct under the influence of a non-uniform magnetic field.The Reynolds number is Re=6299,and the inlet Hartmann number is Ha=2900,with the magnetic field strength decreasing along the flow direction.The results indicate that the dynamic reversal of the three-dimensional(3D)Lorentz force direction near the inflection point of the magnetic field dominates the flow reconstruction,driving the wall jet acceleration and forming an M-type velocity distribution.Moreover,the high-speed shear layer of the jet triggers Kelvin-Helmholtz instability,resulting in the generation of secondary vortex structures near the parallel layer in the non-uniform magnetic field region.In the cross-section perpendicular to the flow direction,the secondary flow gradually evolves into a four-vortex structure,while the velocity fluctuations and turbulent kinetic energy reach the peak.Based on the characteristics of the vortex rotation direction near the shear layer,the intrinsic mechanism behind the unique bimodal distribution of the root-mean-square of velocity fluctuations in the parallel layers is revealed.Furthermore,by comparing the evolution of turbulence under different magnetic field gradients,it is revealed that the distributions of shear stress,Reynolds stress,and turbulent kinetic energy exhibit significant parameter dependence.The strong 3D magnetohydrodynamic effects at the magnetic field gradientγ=0.6 have an immediate impact on the pressure distribution.The transverse Lorentz force LFz further promotes the fluid to accumulate at the wall,leading to a significant increase in the pressure drop and transverse pressure difference in the flow.展开更多
The strong crustal magnetic fields significantly alter the structure of the Martian space environment,including all plasma boundaries.The stretches of mini-magnetospheres formed by crustal fields from the location of ...The strong crustal magnetic fields significantly alter the structure of the Martian space environment,including all plasma boundaries.The stretches of mini-magnetospheres formed by crustal fields from the location of the Martian bow shocks were first found from the Mars Atmosphere and Volatile EvolutioN(MAVEN)observations.The present study aims to test whether this effect is also present in the shocks observed by Mars Express(MEX).We find that the bow shocks above the crustal field regions are enlarged,resulting in a north−south asymmetry and a longitude dependence in the shock size.The longitude dependence is more pronounced for near-subsolar shocks,and more dispersed for near-terminator shocks.The enlarged shocks are also observed to have shifted tailward from the longitudes of the strongest crustal fields.Due to a dawnside bias in MEX shock crossings,the enlarged shocks generally display a westward shift from the strongest crustal field region.These results confirm that stretches of the mini-magnetosphere are also present in the MEX shock observations.展开更多
In this paper we present certain bilinear estimates for commutators on Besov spaces with variable smoothness and integrability,and under no vanishing assumptions on the divergence of vector fields.Such commutator esti...In this paper we present certain bilinear estimates for commutators on Besov spaces with variable smoothness and integrability,and under no vanishing assumptions on the divergence of vector fields.Such commutator estimates are motivated by the study of well-posedness results for some models in incompressible fuid mechanics.展开更多
Batteries play a critical role in electric vehicles and distributed energy generation.With the growing demand for energy storage solutions,new battery materials and systems are continually being developed.In this proc...Batteries play a critical role in electric vehicles and distributed energy generation.With the growing demand for energy storage solutions,new battery materials and systems are continually being developed.In this process,molecular dynamics(MD)simulations can reveal the microscopic mechanisms of battery processes,thereby boosting the design of batteries.Compared to other MD simulation techniques,the machine learning force field(MLFF)holds the advantages of first-principles accuracy along with large spatial and temporal scale,offering opportunities to uncover new mechanisms in battery systems.This review presents a detailed overview of the fundamental principles and model types of MLFFs,as well as their applications in simulating the structure,transport properties,and chemical reaction properties of bulk battery materials and interfaces.Notably,we emphasize the long-range interaction corrections and constant-potential methods in the model design of MLFFs.Finally,we discuss the challenges and prospects of applying MLFF models in the research of batteries.展开更多
The extreme removal of SiO2 and MnO inclusions in 304 stainless steel in supergravity fields was investigated using an inhouse high-temperature supergravity equipment.The influences of the gravity coefficient and sepa...The extreme removal of SiO2 and MnO inclusions in 304 stainless steel in supergravity fields was investigated using an inhouse high-temperature supergravity equipment.The influences of the gravity coefficient and separation time on the removal efficiency of the inclusions were studied.After supergravity treatment,the inclusions migrated to the top of the sample and formed large aggregates.Meanwhile,the lower part of the sample was purified considerably and appeared significantly cleaner than the raw material.At the gravity coefficient of 500 and separation time of 600 s,the total oxygen content at the bottom of the sample(position E)decreased from 240 to 28 ppm.This corresponded to a total oxygen removal rate of 88.33%.The volume fraction and number density of inclusions exhibited a gradient distribution along the supergravity direction,with values of 8.5%and 106 mm^(-2) at the top of the sample(position A)and 0.06%and 22 mm^(-2) at its bottom.展开更多
基金supported by the National Natural Science Foundation of China(No.12172321)。
文摘The nonlinear traveling wave vibration of rotating ferromagnetic functionally graded(FG)cylindrical shells under multi-physics fields is investigated.Grounded in the Kirchhoff-Love thin shell theory,the geometric nonlinearity is incorporated into the model,and the constitutive equations are derived.The physical parameters of functionally graded materials(FGMs),which exhibit continuous variation across the thickness gradient,are of particular interest.The nonlinear magneto-thermoelastic governing equations are derived in accord with Hamilton's principle.The nonlinear partial differential equations are discretized with the Galerkin method,and the analytical expression of traveling wave frequencies is derived with an approximate method.The accuracy of the proposed method is validated through the comparison with the results from the literature and numerical solutions.Finally,the visualization analyses are conducted to examine the effects of key parameters on the traveling wave frequencies.The results show that the factors including the power-law index,temperature,magnetic field intensity,and rotating speed have the coupling effects with respect to the nonlinear vibration behavior.
基金supported by the National Natural Science Foundation of China (No. 50575205)the Hi-Tech Research and Development (863) Program of China (Nos. 2006AA04Z233 and 2007AA04Z101)+1 种基金the Doctoral Foundation of Ministry of Education of China (No. 20070335204)the Zhejiang Provincial Natural Science Foundation of China (No. Z1080537)
文摘This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material (GMM) in the component. We propose the finite element model of GMM smart component in electric, magnetic, and mechanical fields by step computation to optimize the design of GMM smart com-ponent. The proposed model is implemented by using COMSOL multi-physics V3.2a. The effects of the smart component on the deformation and the system resonance frequencies are studied. The results calculated by the model are in excellent agreement (relative errors are below 10%) with the experimental values.
基金financially supported by the National Natural Science Foundation of China(42250102,42250101)the Macao Foundation and Macao Science and Technology Development Fund(0001/2019/A1)the Pre-research Project on Civil Aerospace Technologies funded by China National Space Administration(D020303)。
文摘This study presents preliminary results of tidal-induced magnetic field signals extracted from 9 months of data collected by the Macao Science Satellite-1(MSS-1) from November 2023 to July 2024. Tidal signals were isolated using sequential modeling techniques by subtracting non-tidal field model predictions from observed magnetic data. The extracted MSS-1 results show strong agreement with those from the Swarm and CryoSat satellites. MSS-1 effectively captures key large-scale tidal-induced magnetic anomalies, mainly due to its unique 41-degree low-inclination orbit, which provides wide coverage of local times. This finding underscores the strong potential of MSS-1 to recover high-resolution global tidal magnetic field models as more MSS-1 data become available.
基金supported by the Project of National Natural Science Foundation of China under Grant 52077122。
文摘With the continuous upgrading of traditional manufacturing industries and the rapid rise of emerging technology fields,the performance requirements for the permanent magnet synchronous motors(PMSMs)have become higher and higher.The importance of fast and accurate electromagnetic thermal coupling analysis of such motors becomes more and more prominent.In view of this,the surfacemounted PMSM(SPMSM)equipped with unequally thick magnetic poles is taken as the main object and its electromagnetic thermal coupling analytical model(ETc AM)is investigated.First,the electromagnetic analytical model(EAM)is studied based on the modified subdomain method.It realizes the fast calculation of key electromagnetic characteristics.Subsequently,the 3D thermal analytical model(TAM)is developed by combining the EAM,the lumped parameter thermal network method(LPTNM),and the partial differential equation of heat flux.It realizes the fast calculation of key thermal characteristics in 3D space.Further,the information transfer channel between EAM and TAM is built with reference to the intrinsic connection between electromagnetic field and temperature field.Thereby,the novel ETcAM is proposed to realize the fast and accurate prediction of electromagnetic and temperature fields.Besides,ETcAM has a lot to commend it.One is that it well accounts for the complex structure,saturation,and heat exchange behavior.Second,it saves a lot of computer resources.It offers boundless possibilities for initial design,scheme evaluation,and optimization of motors.Finally,the validity,accuracy,and practicality of this study are verified by simulation and experiment.
基金supported by the National Natural Science Foundation of China(Grant Nos.22278001 and 21776002)the Natural Science Foundation of Anhui Provincial Education Department(No.KJ2021A0407)+1 种基金the Natural Science Foundation of Anhui Province(Grant No.2008085QB87)Anhui Provincial Postdoctoral Science Foundation(No.2021B538).
文摘Reducing coke use is an effective measure to reduce carbon emission and energy consumption in the blast furnace(BF)ironmaking.Essentially,BF is a high-temperature moving bed reactor,where complex physical transformations coupled with complicated reactions occur.This makes it challenging to investigate the factors determining BF performance with the conventional method.A multi-physical field coupling mathematical model of BF was thus developed to describe its mass and heat transfer as well as its intrinsic reactions.Then,the proposed model was validated with the production data.Under coupling conditions,influences of dominating reactions on BF performance(temperature distribution,gas distribution,iron formation reaction,and direct reduction degree)were revealed.The results indicated that coke combustion,indirect reduction,and direct reduction of iron ore mainly took place nearby the shaft tuyere,cohesive zone,and dripping zone,respectively.Besides,the rate of coke solution loss reaction was increased with the rising coke porosity in the cohesive zone.Considering the effect of coke porosity on the efficiency and stability of BF,the coke porosity of 0.42 was regarded as a reasonable value.
文摘Aircraft disturbs the adjacent atmospheric environment in flight,forming spatial distribution features of atmospheric density that differ from the natural background,which may potentially be utilized as tracer characteristics to introduce new technologies for indirectly sensing the presence of aircraft.In this paper,the concept of a long-range aircraft detection based on the atmospheric disturbance density field is proposed,and the detection mode of tomographic imaging of the scattering light of an atmospheric disturbance flow field is designed.By modeling the spatial distribution of the disturbance density field,the scattered echo signal images of active light towards the disturbance field at long distance are simulated.On this basis,the characteristics of the disturbance optical signal at the optimal detection resolution are analyzed.The results show that the atmospheric disturbance flow field of the supersonic aircraft presents circular in the light-scattering echo images.The disturbance signal can be further highlighted by differential processing of the adjacent scattering images.As the distance behind the aircraft increases,the diffusion range of the disturbance signal increases,and the signal intensity and contrast with the background decrease.Under the ground-based observation conditions of the aircraft at a height of 10000 m,a Mach number of1.6,and a detection distance of 100 km,the contrast between the disturbance signal and the back-ground was 30 d B at a distance of one time from the rear of the fuselage,and the diffusion diameter of the disturbance signal was 50 m.At a distance eight times the length of the aircraft,the contrast decreased to 10 dB,and the diameter increased to 290 m.The contrast was reduced to 3 dB at a distance nine times the length of the aircraft,and the diameter was diffused to 310 m.These results indicate the possibility of long-range aircraft detection based on the characteristics of the atmospheric density field.
基金supported by the Ministry of Science and Technology of the People’s Republic of China(2025YFE0110100)Xjenza Malta through SINOMALTA-2024-11(Science and Technology Cooperation)+8 种基金National Natural Science Foundation of China(52165043)Jiang Xi Provincial Natural Science Foundation of China(20224ACB214008,20232BAB214007)Jiangxi Provincial Cultivation Program for Academic and Technical Leaders of Major Subjects(20225BCJ23008)Excellent Research and Innovation Team in Anhui Province(2024AH010031)The University Synergy Innovation Program of Anhui Province(GXXT-2023-025,GXXT-2023-026)Anhui Province Science and Technology Innovation Tackle Plan Project of Anhui Province(202423i08050011)Anhui Provincial Natural Science Foundation of China(2308085ME171)The Project for Cultivating Academic(or Disciplinary)Leaders of Anhui University(DTR2024044)Talent research start-up fund project(2024tlxyrc056).
文摘Laser powder bed fusion(LPBF)has revolutionized modern manufacturing by enabling high design freedom,rapid prototyping,and tailored mechanical properties.However,optimizing process parameters remains challenging due to the trial-and-error approaches required to capture subtle parameter-microstructure relationships.This study employed a multi-physics computational framework to investigate the melting and solidification dynamics of magnesium alloy.By integrating the discrete element method for powder bed generation,finite volume method with volume of fluid for melt pool behavior,and phase-field method for microstructural evolution,the critical physical phenomena,including powder melting,molten pool flow,and directional solidification were simulated.The effects of laser power and scanning speed on temperature distribution,melt pool geometry,and dendritic morphology were systematically analyzed.It was revealed that increasing laser power expanded melt pool dimensions and promoted columnar dendritic growth,while high scanning speeds reduced melt pool stability and refined dendritic structures.Furthermore,Marangoni convection and thermal gradients governed solute redistribution,with excessive energy input risking defects such as porosity and elemental evaporation.These insights establish quantitative correlations between process parameters,thermal history,and microstructural characteristics,providing a validated roadmap for LPBF-processed magnesium alloy with tailored performance.
文摘Seepage refers to the flow of water through porous materials.This phenomenon has a crucial role in dam,slope,excavation,tunnel,and well design.Performing seepage analysis usually is a challenging task,as one must cope with the uncertainty associated with the parameters such as the hydraulic conductivity in the horizontal and vertical directions that drive this phenomenon.However,at the same time,the data on horizontal and vertical hydraulic conductivities are typically scarce in spatial resolution.In this context,so-called non-traditional approaches for uncertainty quantification(such as intervals and fuzzy variables)offer an interesting alternative to classical probabilistic methods,since they have been shown to be quite effective when limited information on the governing parameters of a phenomenon is available.Therefore,the main contribution of this study is the development of a framework for conducting seepage analysis in saturated soils,where uncertainty associated with hydraulic conductivity is characterized using fuzzy fields.This method to characterize uncertainty extends interval fields towards the domain of fuzzy numbers.In fact,it is illustrated that fuzzy fields are an effective tool for capturing uncertainties with a spatial component,since they allow one to account for available physical measurements.A case study in confined saturated soil shows that with the proposed framework,it is possible to quantify the uncertainty associated with seepage flow,exit gradient,and uplift force effectively.
文摘Earthquakes are caused directly by the motion of the stress field,therefore,observing the stress field is significant.Experiments on the relationships among wave velocity,stress factors,and faults show that the wave velocity of rock media under stable stress fields corresponds one-to-one with stress factors.Therefore,the wave velocity gradient can indicate the direction of stress vector,and the gradient divergence can indicate the strength of the stress field.To verify the results,considering the limitations of wave velocity measurement in solid crustal media,two quantities,namely the apparent wave velocity and Poisson ratios relating to wave velocity,were used to refl ect the stress field state.The seismic data of the Tangshan and Luzhou regions were studied separately.The calculated apparent wave velocity and Poisson ratios were interpolated to achieve regional data gridding.The gradients and the gradient divergences of the apparent wave velocity and Poisson ratio fields in the two regions were analyzed,and it was found that their spatial distribution in the same region was the same.They are believed to refl ect the vertical projection of the stress direction vector and strength on the surface in the stress field,consistent with the experimental results.Whether it can eff ectively refl ect the stress field requires further analysis of the specific situation of the local medium and the movement mode of the stress field.
基金supported by the National Science Foundation of China(Grant No.52293423 and Grant No.52277031).
文摘After the fabrication of magnetic resonance superconducting magnets,the magnetic field inhomogeneity needs to be accurately measured for subsequent shimming.However,conventional measurement methods are susceptible to magnetic fields,have poor compatibility,and are difficult to adapt to various types of magnets.This paper proposes a new field measuring system based on a three-axis movable platform.The system utilizes non-magnetic materials and an innovative hand-wheel lifting design that can be adapted to various aperture magnets,thus obviating the necessity for electrically driven equipment and addressing safety concerns in strong magnetic fields.In addition,the measurement system offers high accuracy up to 1 mm and a wide measurable range.The fields of 3 T and 7 T magnets were mapped using the designed system with diameter of spherical volume(DSV)of 160 mm and 130 mm,respectively.Experimental results demonstrate that the magnetic field measurement system has strong compatibility and can accurately map the magnetic field at arbitrary positions,which is critical for shimming studies.
基金supported by the Natural Science Foundation of Anhui Province(No.228085ME142)the Comprehensive Research Facility for the Fusion Technology Program of China(No.20180000527301001228)the Open Fund of the Magnetic Confinement Fusion Laboratory of Anhui Province(No.2024AMF04003)。
文摘As the plasma current power in tokamak devices increases,a significant number of stray magnetic fields are generated around the equipment.These stray magnetic fields can disrupt the operation of electronic power devices,particularly transformers in switched-mode power supplies.Testing flyback converters with transformers under strong background magnetic fields highlights electromagnetic compatibility(EMC)issues for such switched-mode power supplies.This study utilizes finite element analysis software to simulate the electromagnetic environment of switched-mode power supply transformers and investigates the impact of variations in different magnetic field parameters on the performance of switched-mode power supplies under strong stray magnetic fields.The findings indicate that EMC issues are associated with transformer core saturation and can be alleviated through appropriate configurations of the core size,air gap,fillet radius,and installation direction.This study offers novel solutions for addressing EMC issues in high magnetic field environments.
基金National Natural Science Foundation of China,No.41930865Project for Innovative Capacity Improvement in Hebei Province,No.225A4201D。
文摘Nitrate(NO_(3)^(-))accumulation and transport processes in the thick vadose zone affect the evolution of the groundwater NO_(3)^(-)content in intensive agricultural regions.Agricultural land-use change(ALUC),typically accompanied by substantial alterations in nitrogen fertilizer application and irrigation practices,is an important influencing factor.This study evaluated the changes in NO_(3)^(-)accumulation and transport in the deep vadose zone(DVZ,below the root zone),and the groundwater NO_(3)^(-)content associated with ALUC from grain to vegetable fields in the North China Plain(NCP).The ALUC from grain to vegetable resulted in nitrate–nitrogen(NO_(3)^(-)-N)accumulation in DVZ increased by 235.5 kg ha^(-1)m^(-1)(163.2%)in the piedmont plain and 224.9 kg ha^(-1)m^(-1)(102.7%)in the central plain,respectively.This change accelerated downward transport velocity in the DVZ(from 0.81±0.47 to 0.89±0.55 m yr^(-1)in the piedmont plain,and from 0.24±0.12 to 0.92±0.12 m yr^(-1)in the central plain)and increased NO_(3)^(-)leaching fluxes.High transport velocity and leaching fluxes resulted in chemical N-fertilizer entering the aquifer in several areas in the piedmont plain.The impact of the agricultural activity intensity changes,accompanied by the ALUC,on groundwater quantity and quality should be considered in similar regions.
基金supported by the National Natural Science Foundation of China(52164028,52274297)the Start-up Research Foundation of Hainan University(KYQD(ZR)20008,KYQD(ZR)21125,KYQD(ZR)23169))+1 种基金Collaborative Innovation Center of Marine Science and Technology of Hainan University(XTCX2022HYC14)Innovative Research Project for Postgraduate Students in Hainan Province(Qhyb2024-95).
文摘Development of robust electrocatalyst for oxygen reduction reaction(ORR)in a seawater electrolyte is the key to realize seawater electrolyte-based zinc-air batteries(SZABs).Herein,constructing a local electric field coupled with chloride ions(Cl-)fixation strategy in dual single-atom catalysts(DSACs)was proposed,and the resultant catalyst delivered considerable ORR performance in a seawater electrolyte,with a high half-wave potential(E_(1/2))of 0.868 V and a good maximum power density(Pmax)of 182 mW·cm^(−2)in the assembled SZABs,much higher than those of the Pt/C catalyst(E_(1/2):0.846 V;Pmax:150 mW·cm^(−2)).The in-situ characterization and theoretical calculations revealed that the Fe sites have a higher Cl^(−)adsorption affinity than the Co sites,and preferentially adsorbs Cl^(−)in a seawater electrolyte during the ORR process,and thus constructs a low-concentration Cl^(−)local microenvironment through the common-ion exclusion effect,which prevents Cl^(−)adsorption and corrosion in the Co active centers,achieving impressive catalytic stability.In addition,the directional charge movement between Fe and Co atomic pairs establishes a local electric field,optimizing the adsorption energy of Co sites for oxygen-containing intermediates,and further improving the ORR activity.
基金financially supported by the National Natural Science Foundation of China(Grant No.22325405,22402187 and 22432005).
文摘A recent study demonstrated that solid-state photochemically induced dynamic nuclear polarization(photo-CIDNP)can achieve significant 1H NMR hyperpolarization at high magnetic fields(9.4 T and 21.1 T).This was accomplished using a specially designed donor-chromophore-acceptor(D-C-A)molecule,which exhibits an excited state electron-electron interaction that is finely tuned to match the proton Larmor frequency under high-field conditions[1].
基金supported by the National Natural Science Foundation of China(Grant No.12175080)by Self-Determined Research Funds of Central China Normal University from the Colleges’Basic Research and Operation of MOE(Grant No.CCNU25JC012)。
文摘Spiral waves,as a typical self-organized structure with chiral characteristics,are widely found in excitable media such as cardiac tissues,chemical reactions,and neural networks.Based on the Fitz Hugh–Nagumo model,we investigated the mechanisms underlying the effects of direct current electric fields(DCEF),alternating current electric fields(ACEF),and polarized electric fields(PEF)on the interaction and annihilation processes of counter-rotating spiral waves.We found that in a direct current electric field,the drift direction of the spiral wave is determined jointly by its chirality and the electric field direction,which allows selective attraction or repulsion.In an alternating current electric field,the annihilation behavior of spiral waves can be influenced by the phase and intensity of the electric field,where a specific range of parameters induces resonance drift and eventual annihilation.On the other hand,the polarized electric field exhibits a more complex modulation capability on spiral waves:the trajectory and annihilation efficiency of spiral waves can be regulated by both the intensity and phase of the polarized electric field.These results reveal the potential feasibility of regulating multichiral spiral waves through multiple electric fields,providing theoretical insight for the control of spiral waves in relevant systems.
基金supported by the Chinese Academy of Sciences Project for Young Scientists in Basic Research(Grant No.YSBR-087)and the National Key R&D Program of China(Grant No.2022YFA1204100)。
文摘Direct numerical simulations have been conducted to investigate the evolution process of liquid metal laminar to turbulent flow in a rectangular duct under the influence of a non-uniform magnetic field.The Reynolds number is Re=6299,and the inlet Hartmann number is Ha=2900,with the magnetic field strength decreasing along the flow direction.The results indicate that the dynamic reversal of the three-dimensional(3D)Lorentz force direction near the inflection point of the magnetic field dominates the flow reconstruction,driving the wall jet acceleration and forming an M-type velocity distribution.Moreover,the high-speed shear layer of the jet triggers Kelvin-Helmholtz instability,resulting in the generation of secondary vortex structures near the parallel layer in the non-uniform magnetic field region.In the cross-section perpendicular to the flow direction,the secondary flow gradually evolves into a four-vortex structure,while the velocity fluctuations and turbulent kinetic energy reach the peak.Based on the characteristics of the vortex rotation direction near the shear layer,the intrinsic mechanism behind the unique bimodal distribution of the root-mean-square of velocity fluctuations in the parallel layers is revealed.Furthermore,by comparing the evolution of turbulence under different magnetic field gradients,it is revealed that the distributions of shear stress,Reynolds stress,and turbulent kinetic energy exhibit significant parameter dependence.The strong 3D magnetohydrodynamic effects at the magnetic field gradientγ=0.6 have an immediate impact on the pressure distribution.The transverse Lorentz force LFz further promotes the fluid to accumulate at the wall,leading to a significant increase in the pressure drop and transverse pressure difference in the flow.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFF0503204)the National Natural Science Foundation of China(Grant No.42388101)+3 种基金Youth Innovation Promotion Association CAS(2020065)Young Elite Scientist Sponsorship Program by CAST(YESS20200152)the Key Research Program of the Institute of Geology&Geophysics,CAS(IGGCAS-202102)the Key Research Program of Chinese Academy of Sciences(Grant ZDB-SSW-TLC00103).
文摘The strong crustal magnetic fields significantly alter the structure of the Martian space environment,including all plasma boundaries.The stretches of mini-magnetospheres formed by crustal fields from the location of the Martian bow shocks were first found from the Mars Atmosphere and Volatile EvolutioN(MAVEN)observations.The present study aims to test whether this effect is also present in the shocks observed by Mars Express(MEX).We find that the bow shocks above the crustal field regions are enlarged,resulting in a north−south asymmetry and a longitude dependence in the shock size.The longitude dependence is more pronounced for near-subsolar shocks,and more dispersed for near-terminator shocks.The enlarged shocks are also observed to have shifted tailward from the longitudes of the strongest crustal fields.Due to a dawnside bias in MEX shock crossings,the enlarged shocks generally display a westward shift from the strongest crustal field region.These results confirm that stretches of the mini-magnetosphere are also present in the MEX shock observations.
文摘In this paper we present certain bilinear estimates for commutators on Besov spaces with variable smoothness and integrability,and under no vanishing assumptions on the divergence of vector fields.Such commutator estimates are motivated by the study of well-posedness results for some models in incompressible fuid mechanics.
基金funding support from the National Natural Science Foundation of China(92472109,T2325012)the Program for HUST Academic Frontier Youth Team+1 种基金support from the Fundamental Research Funds for the Central Universities(HUST,5003120083)supported by the Postdoctoral Fellowship Program of CPSF(GZC20240532)。
文摘Batteries play a critical role in electric vehicles and distributed energy generation.With the growing demand for energy storage solutions,new battery materials and systems are continually being developed.In this process,molecular dynamics(MD)simulations can reveal the microscopic mechanisms of battery processes,thereby boosting the design of batteries.Compared to other MD simulation techniques,the machine learning force field(MLFF)holds the advantages of first-principles accuracy along with large spatial and temporal scale,offering opportunities to uncover new mechanisms in battery systems.This review presents a detailed overview of the fundamental principles and model types of MLFFs,as well as their applications in simulating the structure,transport properties,and chemical reaction properties of bulk battery materials and interfaces.Notably,we emphasize the long-range interaction corrections and constant-potential methods in the model design of MLFFs.Finally,we discuss the challenges and prospects of applying MLFF models in the research of batteries.
基金supported by the National Natural Science Foundation of China(No.52174275).
文摘The extreme removal of SiO2 and MnO inclusions in 304 stainless steel in supergravity fields was investigated using an inhouse high-temperature supergravity equipment.The influences of the gravity coefficient and separation time on the removal efficiency of the inclusions were studied.After supergravity treatment,the inclusions migrated to the top of the sample and formed large aggregates.Meanwhile,the lower part of the sample was purified considerably and appeared significantly cleaner than the raw material.At the gravity coefficient of 500 and separation time of 600 s,the total oxygen content at the bottom of the sample(position E)decreased from 240 to 28 ppm.This corresponded to a total oxygen removal rate of 88.33%.The volume fraction and number density of inclusions exhibited a gradient distribution along the supergravity direction,with values of 8.5%and 106 mm^(-2) at the top of the sample(position A)and 0.06%and 22 mm^(-2) at its bottom.
