A 2-D mathematical model is developed in order to simulate a parametric electromagnetic instability oscillation process of a liquid metal droplet under the action of low frequency magnetic field. The Arbitrary Lagrang...A 2-D mathematical model is developed in order to simulate a parametric electromagnetic instability oscillation process of a liquid metal droplet under the action of low frequency magnetic field. The Arbitrary Lagrangian-Eulerian （ALE） method and weak form constraint boundary condition are introduced in this model for implementation of the surface tension and electromagnetic force on liquid droplet free surface. The results of the numerical calculations indicate the appearance of various regimes of oscillation. It is found that according to the magnetic field frequency various types of oscillation modes may be found. The oscillation is originated from an instability phenomenon. The stability diagram of liquid metal droplet in the parameter space of magnetic frequency and magnetic flux density is determined numerically. The diagram is very similar to that found in the so-called parametric instability.展开更多
The results of the study of the effect of partial substitution of Fe by Mn in the La Fe_(11.2-x)Mn_(x)Co_(0.7)Si_(1.1)system on magnetization,specific heat,magnetostriction and magnetocaloric effect are presented.Dire...The results of the study of the effect of partial substitution of Fe by Mn in the La Fe_(11.2-x)Mn_(x)Co_(0.7)Si_(1.1)system on magnetization,specific heat,magnetostriction and magnetocaloric effect are presented.Direct measurements of the adiabatic temperature change(ΔT_(ad))were carried out in alternating magnetic fields(AMF)using the magnetic field modulation method.Partial substitution of Fe atoms by Mn atoms leads to a shift in the Curie temperature(T_(C))towards lower temperatures without a noticeable deterioration in magnetic properties.A correlation was found between the structural component of the magnetocaloric effect and the stability of the frequency of theΔT_(ad)in the AMFs—an increase in the manganese concentration leads to a decrease in magnetostriction and to a lower dependence ofΔT_(ad)on the frequency of the magnetic field.Estimates of the specific cooling power Q_(C)as a function of the frequency of the AMF showed that the highest value of Q_(C)at f=20 Hz in a magnetic field of 12k Oe is 26.3 W g^(-1)and is observed for the composition with x=0.1.This value is higher than that of Gd,for which,under the same conditions,Q_(C)=21.6 W g^(-1).All the samples studied show stability of the value ofΔT_(ad)without any sign of deterioration of the effect up to 60,000cycles of switching on/off of the magnetic field of 12 k Oe.The discovered frequency and cyclic stability ofΔT_(ad)of the studied samples increase their prospects for application in magnetic cooling technology.展开更多
An alternating magnetic field(AMF)was introduced into the narrow gap laser-arc hybrid welding process for 2205 duplex stainless steel thick plates.The corrosion performance of the welded joints was evaluated through e...An alternating magnetic field(AMF)was introduced into the narrow gap laser-arc hybrid welding process for 2205 duplex stainless steel thick plates.The corrosion performance of the welded joints was evaluated through electrochemical studies.The results revealed that joints welded with the application of AMF had a lower corrosion current density compared to those welded without an external AMF.Additionally,these joints showed higher pitting potential and polarization resistance.Microscopic electrochemical analysis indicated that joints subjected to AMF exhibited minimal cathodic current in simulated seawater,with only slight fluctuations in the anodic current peak.Overall,the corrosion levels on the joint surfaces were relatively low.After 4 h of immersion in the corrosive medium,the average impedance of joints exposed to AMF increased by 60.7%compared to those not influenced by a magnetic field.These findings suggest that applying AMF during the narrow gap laser-arc hybrid welding process can significantly improve the corrosion resistance of duplex stainless steel welded joints,reducing their susceptibility to stress corrosion in seawater-like environments.展开更多
The use of an alternative magnetic field during vacuum arc remelting(VAR)can have significant effects on the primary carbide and mechanical properties of M50-bearing steel.The solidification structure and the primary ...The use of an alternative magnetic field during vacuum arc remelting(VAR)can have significant effects on the primary carbide and mechanical properties of M50-bearing steel.The solidification structure and the primary carbide morphology of the VAR ingot were analyzed by optical microscopy and scanning electron microscopy.Characterization and analysis of the growth direction of primary carbides were conducted using high-resolution rapid electron backscatter diffraction.Solute elements segregation was analyzed using an electron probe microanalyzer.FLUENT was utilized to conduct numerical simulations to validate the experimental findings and elucidate the underlying mechanism.Compared to traditional VAR,magnetic-controlled VAR generates a horizontal circulation,which makes a shallower and flatter molten pool and a more even temperature distribution.In the time dimension,the local solidification time is shortened,and the concentration of solute elements will be alleviated.In the spatial dimension,the secondary dendrite arm spacing decreases,alleviating the degree of inter-dendritic segregation.Consequently,the possibility of forming a segregation diminishes.Both aspects promote the even distribution of solute atoms,resulting in less segregation and hindering the development of primary carbide.This leads to the refinement of primary carbide size and its uniform distribution.The magnetic-controlled vacuum arc melting not only refines the dendritic structure in the M50 ingot,causing it to expand more axially along the ingot,but also refines primary carbides and improves tensile and wear-resistant mechanical properties.展开更多
The effects of alternating magnetic field on the corrosion morphologies, corrosion rate, and corrosion products of copper in 3.5% NaCl solution, sea water, and magnetized sea water were investigated using electrochemi...The effects of alternating magnetic field on the corrosion morphologies, corrosion rate, and corrosion products of copper in 3.5% NaCl solution, sea water, and magnetized sea water were investigated using electrochemical test, scanning electron microscopy/energy dispersive analysis system of X-ray （SEM/EDAX）, and X-ray diffraction （XRD）. The results show that the corrosion rate of copper in magnetized sea water is minimal. Moreover, the surface of the specimen in magnetized sea water is uniform and compact as compared with those in 3.5% NaCl solution and sea water. The corrosion products of copper in magnetized sea water are mainly Cu2O and CuCl2. However, the corrosion products in sea water are CuCl, Cu2Cl（OH）3, and FeCl3-6H2O. The electrochemical corrosion mechanisms of copper in the three media were also discussed.展开更多
Herein, a hot tearing measured system with external excitation coil and a differential thermal analysis system with applied magnetic field were used to study the effects of low-frequency alternating magnetic field on ...Herein, a hot tearing measured system with external excitation coil and a differential thermal analysis system with applied magnetic field were used to study the effects of low-frequency alternating magnetic field on the solidification behavior and hot tearing susceptibility(HTS) of the AXJ530 alloy under different magnetic field parameters. The hot tearing volume of the castings was measured via paraffin infiltration method. The microstructure of the hot tearing zone of the casting was observed using optical microscopy and scanning electron microscopy, and the phase composition was analyzed using X-ray diffraction and energy depressive spectroscopy. The experimental results show that the solidification interval of AXJ530 alloy was shortened and the dendrite coherency temperature of the alloy decreased with the increase in frequency of alternating magnetic field. Under appropriate magnetic field parameters, the electromagnetic force could enhance the convection in the melt to promote the flow of the residual liquid phase, refine the microstructure, and optimize the feeding channel in the late solidification stage, which reduced the HTS of the alloy. However, when the magnetic field frequency was increased to 15 Hz, the induced current generated excessive Joule heat to the melt. At this time, the thermal action of the magnetic field coarsened the microstructure of the alloy, resulting in an increase in HTS of the alloy.展开更多
Magnetotactic bacteria(MTB)intact cells have been applied in magnetic hyperthermia therapy of tumor,showing great efficiency in heating for tumor cell inhibition.However,the detailed magnetic hyperthermia properties a...Magnetotactic bacteria(MTB)intact cells have been applied in magnetic hyperthermia therapy of tumor,showing great efficiency in heating for tumor cell inhibition.However,the detailed magnetic hyperthermia properties and optimum heat production conditions of MTB cells are still poorly understood due to lack of standard measuring equipment.The specific absorption rate(SAR)of MTB cells is often measured by home-made equipment at a limited frequency and magnetic field amplitude.In this study,we have used a commercial standard system to implement a comprehensive study of the hyperthermic response of Magnetospirillum gryphiswaldense MSR-1 strain under 7 frequencies of 144-764 kHz,and 8 field amplitudes between 10 and 45 kA/m.The measurement results prove that the SAR of MTB cells increases with magnetic field frequency and amplitude within a certain range.In combination with the magnetic measurements,it is determined that the magnetic hyperthermia mechanism of MTB mainly follows the principle of hysteresis loss,and the heat efficiency of MTB cells in alternating magnetic field are mainly aff ected by three parameters of hysteresis loop,saturation magnetisation,saturation remanent magnetisation,and coercivity.Thus when we culture MTB in LA-2 medium containing sodium nitrate as source of nitrogen,the SAR of MTB LA-2 cells with magnetosomes arranged in chains can be as high as 4925.6 W/g(in this work,all SARs are calculated with iron mass)under 764 kHz and 30 kA/m,which is 7.5 times than current commercial magnetic particles within similar size range.展开更多
A magnetic abrasive finishing process using an alternating magnetic field is proposed for the finishing of complex surfaces.In an alternating field,the periodic changes in current will cause the magnetic cluster used ...A magnetic abrasive finishing process using an alternating magnetic field is proposed for the finishing of complex surfaces.In an alternating field,the periodic changes in current will cause the magnetic cluster used as a magnetic brush to fluctuate,which will not only continuously replace the abrasive particles in contact with the workpiece,but also periodically adjust the shape of the magnetic cluster to better fit the surface of the workpiece.In this paper,the influence of a combination of alternating and static magnetic fields on the magnetic field in the finishing area is analyzed.The feasibility of this process for finishing micro-grooves is investigated.Simulations and experimental measurements show that the combination of alternating and static magnetic fields can retain the advantages of the alternating field while increasing the magnetic flux density in the finishing area.The experimental results show that the process is feasible for finishing micro-grooves,with an excellent deburring effect on the groove edges.展开更多
A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic...A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision frequency.An equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision frequency.The applicable range of the LF method on a given plasma scale is analyzed.The upper diagnostic limit for the ratio of the electron density(unit:m^(-3))to collision frequency(unit:Hz)exceeds 1×10^(11),enabling an electron density to exceed 1×10^(20)m^(-3)and a collision frequency to be less than 1 GHz.In this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also assessed.Diagnosis experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF method.By comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF method.The ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma stabilization.The LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the model.Finally,the causes of diagnostic discrepancy between the two methods are analyzed.The proposed method provides a new avenue for diagnosing high-density enveloping plasma.展开更多
In order to reasonably control the free surface oscillations,by using GalnSn low-melting alloy,the fluctuation and distortion behaviour of metal free surface is investigated under AC magnetic field.By simultaneously s...In order to reasonably control the free surface oscillations,by using GalnSn low-melting alloy,the fluctuation and distortion behaviour of metal free surface is investigated under AC magnetic field.By simultaneously superposing DC magnetic field,the damping effect of DC magnetic field on free surface fluctuation is also investigated.In the cylindrical pool,the azimuthal and radial oscillation mode can be found simultaneously due to AC magnetic field. Moreover,the free surface is more stable in square pool than that in the cylindrical pool.Increase coil AC current,the free surface fluctuation is aggravated.A series of surface waves can be observed on free surface with compound magnetic field.Reasonable DC magnetic field can effectively damp the oscillations on the free surface in cylindrical pool.However. the DC magnetic field cannot effectively damp the surface oscillations in square pool.The DC magnetic field has no significant damping effect on the oscillations induced by the lower frequency magnetic force.展开更多
We consider the radiation from the beam electrons traveling in a strong uniform axial magnetic field and an axial alternating electric field of wavelength Aw generated by a voltage-supplied pill-box cavity. The beam e...We consider the radiation from the beam electrons traveling in a strong uniform axial magnetic field and an axial alternating electric field of wavelength Aw generated by a voltage-supplied pill-box cavity. The beam electrons emit genuine laser radiation that propagates only in the axial direction through free-electron two- quantum Stark radiation. We find that laser radiation takes place only at the expense of the axial kinetic energy when Aw 〈〈 c/（ωc/γ）, where ωc/γ is the relativistic electron--cyclotron frequency. We formulate the laser power based on quantum-wiggler electrodynamics, and envision a laser of length lore with estimated power 0.1 GW/（kA） in the 10-4 cm wavelength range.展开更多
Plant stress caused by exposure to magnetic fields （MF） induces modifications at molecular level, particularly in DNA synthesis, structure, and function. The objective of this study was to determine the effect of va...Plant stress caused by exposure to magnetic fields （MF） induces modifications at molecular level, particularly in DNA synthesis, structure, and function. The objective of this study was to determine the effect of various doses of non-ionizing radiation of magnetic field on date palm （Phoenix dactylifera L.） based on DNA content. Date palm seedlings （cv. Khalas） established for 2 weeks on filter paper were subjected to static magnetic field and alternating magnetic field. Static magnetic fields （SMF） were applied at 10, 50 and 100 mT for 30, 60, 120, 180, 240 and 360 min; while alternating magnetic field applied by magnetic resonance imaging （MRI） at 1500 mT for 1, 5, 10 and 15 min. The seedlings were grown in potting soil following exposure for 4 weeks after which DNA was extracted from leaves and its content was determined. Generally, the exposure to magnetic field caused reduction in the content of DNA. The lowest exposure time tested, 30 rain, was sufficient to induce reduction in DNA content. This was true even at the lowest intensity, 10 mT. This dosage caused the DNA content to decrease from 49 ~tg/g to 45 pg/g. Further, increase of the exposure duration to 60 min caused significant reduction in the DNA content, 36 μg/g. At intensities higher than 10 mT, DNA content decreased significantly even at the shortest exposure of 30 min. At 50 and 100 mT, significant decrease in DNA content was also noticed in response to 30 min exposure; whereas the level of DNA increased after 1 min of MRI exposure to 52 ~g/g, then decreased after 5 min to 46 ~g/g. However, longer durations caused no further decrease in the DNA content. These observations indicate that magnetic fields interact with DNA processes, probably by inhibiting synthesis or stimulating degradation of DNA. This response merits further exploration as a mutational agent for date palm genetic manipulation.展开更多
As the complexity of scientific satellite missions increases,the requirements for their magnetic fields,magnetic field fluctuations,and even magnetic field gradients and variations become increasingly stringent.Additi...As the complexity of scientific satellite missions increases,the requirements for their magnetic fields,magnetic field fluctuations,and even magnetic field gradients and variations become increasingly stringent.Additionally,there is a growing need to address the alternating magnetic fields produced by the spacecraft itself.This paper introduces a novel modeling method for spacecraft magnetic dipoles using an integrated self-attention mechanism and a transformer combined with Kolmogorov-Arnold Networks.The self-attention mechanism captures correlations among globally sparse data,establishing dependencies b.etween sparse magnetometer readings.Concurrently,the Kolmogorov-Arnold Network,proficient in modeling implicit numerical relationships between data features,enhances the ability to learn subtle patterns.Comparative experiments validate the capability of the proposed method to precisely model magnetic dipoles,achieving maximum Root Mean Square Errors of 24.06 mA·m^(2)and 0.32 cm for size and location modeling,respectively.The spacecraft magnetic model established using this method accurately computes magnetic fields and alternating magnetic fields at designated surfaces or points.This approach facilitates the rapid and precise construction of individual and complete spacecraft magnetic models,enabling the verification of magnetic specifications from the spacecraft design phase.展开更多
Research progress and frontiers of magnetic-mediated hyperthermia （MMH） are presented, along with clinical trials in Germany, the US, Japan, and China. Special attention is focused on MMH mediated by magnetic nanopa...Research progress and frontiers of magnetic-mediated hyperthermia （MMH） are presented, along with clinical trials in Germany, the US, Japan, and China. Special attention is focused on MMH mediated by magnetic nanoparticles, and multifunctional magnetic devices for cancer multimodality treatment are also introduced.展开更多
To investigate the effect of alternating magnetic field on austenite transformation process in the case of rapid heating,the austenite kinetics model of AISI 1045 steel was built for spot continual induction hardening...To investigate the effect of alternating magnetic field on austenite transformation process in the case of rapid heating,the austenite kinetics model of AISI 1045 steel was built for spot continual induction hardening(SCIH)process.The results shows that the effect of alternating magnetic field on austenite transformation fraction reaches the maximum(about 3%)when heating rate is the lowest.Relatively low magnetic flux density still has a certain effect on the austenite transformation process during the SCIH process.Concave surface structure can reduce the influence scope of alternating magnetic field on surface in all cases and the minimum influence scope appears when the feed path of inductor is longitudinal.Convex surface structure can minimize the influence scope of alternating magnetic field in depth when the feed path of inductor is longitudinal.The austenite distribution of transitional region on surface for horizontal movement is more uniform than that for longitudinal movement.The austenite distribution of transitional region in depth for longitudinal movement is more uniform than that for horizontal movement.The simulated results are consistent with the experimental results and the austenite transformation kinetics model developed for SCIH process is valid.展开更多
The use of low electrically conducting liquids is more and more widespread.This is the case for molten glass,salt or slag processing,ionic liquids used in biotechnology,batteries in energy storage and metallurgy.The p...The use of low electrically conducting liquids is more and more widespread.This is the case for molten glass,salt or slag processing,ionic liquids used in biotechnology,batteries in energy storage and metallurgy.The present paper deals with the design of a new electromagnetic induction device that can heat and stir low electricallyconducting liquids.It consists of a resistance-capacity-inductance circuit coupled with a low-conducting liquid load.The device is supplied by a unique electric power source delivering a single-phase high frequency electric current.The main working principle of the circuit is based on a double oscillating circuit inductor connected to the solid-state transistor generator.This technique,which yields a set of coupled oscillating circuits,consists of coupling a forced phase and an induced phase,neglecting the influence of the electric parameters of the loading part(i.e.,the low-conductivity liquid).It is shown that such an inductor is capable to provide a two-phase AC traveling magnetic field at high frequency.To better understand the working principle,the present work improves a previous existing simplified theory by taking into account a complex electrical equivalent diagram due to the different mutual couplings between the two inductors and the two corresponding induced current sets.A more detailed theoretical model is provided,and the key and sensitive elements are elaborated.Based on this theory,equipment is designed to provide a stirring effect on sodium chloride-salted water at 40 S/m.It is shown that such a device fed by several hundred kiloHertz electric currents is able to mimic a linear motor.A set of optimized operating parameters are proposed to guide the experiment.A pure electromagnetic numerical model is presented.Numerical modelling of the load is performed in order to assess the efficiency of the stirrer with a salt water load.Such a device can generate a significant liquid motion with both controlled flow patterns and adjustable amplitude.Based on the magnetohydrodynamic theory,numerical modeling of the salt water flow generated by the stirrer confirms its feasibility.展开更多
All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravit...All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravity. In order to ＂push＂ the molten metal into the weld, a new kind of U-frame excitation model, which could produce electromagnetic force to balance the gravity of the molten pool, was designed. The related parameters of the excitation model were simulated by Maxwell 3D, and the relationships between the parameters and the magnetic induction intensity were analyzed. Finally, the electromagnetic force in the molten pool was calculated, and the appropriate parameters of the U-frame excitation model were determined. The results of the simulation verify the feasibility of the all-position welding excitation model.展开更多
The influence of an alternative magnetic field on the growth of the diffusionlayer in Al-Zn diffusion couple was studied. The thickness of the diffusion layer was examined. Theresults show that the alternative magneti...The influence of an alternative magnetic field on the growth of the diffusionlayer in Al-Zn diffusion couple was studied. The thickness of the diffusion layer was examined. Theresults show that the alternative magnetic field increases the thickness of the diffusion layer andthe effect increases with the intensity and frequency of the alternative magnetic field increasing. The growth of the diffusion layer obeys the parabolic rate law and the growth rateincreases with the application of the alternative magnetic field. This growth rate change ismanifested through a change in the frequency factor k_0 and not through a change in the activationenergy Q. The frequency factor k_0 for the diffusion layer growth with the alternative magneticfield is 5.03 cm^2/s and the one without the magnetic field is 3.84 cm^2/s.展开更多
The influence of an alternative magnetic field on the diffusion of Al and Mg in AI-Mg diffusion couple is studied. The diffusion zone is composed of two intermediate phases, namelyβ and γ phase. Thickness of each in...The influence of an alternative magnetic field on the diffusion of Al and Mg in AI-Mg diffusion couple is studied. The diffusion zone is composed of two intermediate phases, namelyβ and γ phase. Thickness of each intermediate phase is examined. The results show that the alternative magnetic field increases the thicknesses of βand γ phase zone and the layer growth ofβ and γphase obeys the parabolic rate law. The growth rate of the β and γ phase are increased with the application of the alternative magnetic field. This change is manifested through a change in the frequency factor k0 and not through a change in the activation energy Q. The frequency factor k0 for intermediate phase growth with an alternative magnetic field is 39.95 cm2/s for 7 phase and 2.84×10-4 cm2/s for β phase compared with those without the magnetic field is 22.4 cm2/s for 7 phase and 1.53×10-4 cm2/s for β phase.展开更多
Our purpose in this study was to present a method for estimating the specific loss power (SLP) in magnetic hyperthermia in the presence of an external static magnetic field (SMF) and to investigate the SLP values esti...Our purpose in this study was to present a method for estimating the specific loss power (SLP) in magnetic hyperthermia in the presence of an external static magnetic field (SMF) and to investigate the SLP values estimated by this method under various diameters (D) of magnetic nanoparticles (MNPs) and amplitudes (H<sub>0</sub>) and frequencies (f) of an alternating magnetic field (AMF). In our method, the SLP was calculated by solving the magnetization relaxation equation of Shliomis numerically, in which the magnetic field strength at time t (H(t)) was assumed to be given by , with H<sub>s</sub> being the strength of the SMF. We also investigated the SLP values in the case when the SMF with a field-free point (FFP) generated by two solenoid coils was used. The SLP value in the quasi steady state (SLP<sub>qss</sub>) decreased with increasing H<sub>s</sub>. The plot of the SLP<sub>qss</sub> values against the position from the FFP became narrow as the gradient strength of the SMF (G<sub>s</sub>) increased. Conversely, it became broad as G<sub>s</sub> decreased. These results suggest that the temperature rise and the area of local heating in magnetic hyperthermia can be controlled by varying the H<sub>s</sub> and G<sub>s</sub> values, respectively. In conclusion, our method will be useful for estimating the SLP in the presence of both the AMF and SMF and for designing an effective local heating system for magnetic hyperthermia in order to reduce the risk of overheating surrounding healthy tissues.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51274137,10872123)supported by the China Scholarship Council and Région Rhne-Alpes (France) for supporting Lei's visiting in Grenoble
文摘A 2-D mathematical model is developed in order to simulate a parametric electromagnetic instability oscillation process of a liquid metal droplet under the action of low frequency magnetic field. The Arbitrary Lagrangian-Eulerian （ALE） method and weak form constraint boundary condition are introduced in this model for implementation of the surface tension and electromagnetic force on liquid droplet free surface. The results of the numerical calculations indicate the appearance of various regimes of oscillation. It is found that according to the magnetic field frequency various types of oscillation modes may be found. The oscillation is originated from an instability phenomenon. The stability diagram of liquid metal droplet in the parameter space of magnetic frequency and magnetic flux density is determined numerically. The diagram is very similar to that found in the so-called parametric instability.
基金financially supported by Russian Science Foundation(No.24-43-00156,https://rscf.ru/en/project/24-43-00156/)the National Natural Science Foundation of China(No.52171169)the State Key Laboratory for Advanced Metals and Materials(No.2023-ZD01)。
文摘The results of the study of the effect of partial substitution of Fe by Mn in the La Fe_(11.2-x)Mn_(x)Co_(0.7)Si_(1.1)system on magnetization,specific heat,magnetostriction and magnetocaloric effect are presented.Direct measurements of the adiabatic temperature change(ΔT_(ad))were carried out in alternating magnetic fields(AMF)using the magnetic field modulation method.Partial substitution of Fe atoms by Mn atoms leads to a shift in the Curie temperature(T_(C))towards lower temperatures without a noticeable deterioration in magnetic properties.A correlation was found between the structural component of the magnetocaloric effect and the stability of the frequency of theΔT_(ad)in the AMFs—an increase in the manganese concentration leads to a decrease in magnetostriction and to a lower dependence ofΔT_(ad)on the frequency of the magnetic field.Estimates of the specific cooling power Q_(C)as a function of the frequency of the AMF showed that the highest value of Q_(C)at f=20 Hz in a magnetic field of 12k Oe is 26.3 W g^(-1)and is observed for the composition with x=0.1.This value is higher than that of Gd,for which,under the same conditions,Q_(C)=21.6 W g^(-1).All the samples studied show stability of the value ofΔT_(ad)without any sign of deterioration of the effect up to 60,000cycles of switching on/off of the magnetic field of 12 k Oe.The discovered frequency and cyclic stability ofΔT_(ad)of the studied samples increase their prospects for application in magnetic cooling technology.
基金supported by the National Natural Science Foundation of China(No.52265054)the Inner Mongolia Autonomous Region Natural Science Foundation Project(No.2022ZD03)+3 种基金the Inner Mongolia Autonomous Region Science and Technology Plan Project(No.2020GG0313)the Inner Mongolia Autonomous Region Natural Science Foundation Doctoral Fund Project,(No.2021BS05016)the Construction project of integrated research and development platform for key technologies in the development and processing of new nonferrous metal materials(No.RZ2300001971)the Basic Research Business Fee Project for Autonomous Region Directly Affiliated Universities(Nos.JY20220199 and JY20220028).
文摘An alternating magnetic field(AMF)was introduced into the narrow gap laser-arc hybrid welding process for 2205 duplex stainless steel thick plates.The corrosion performance of the welded joints was evaluated through electrochemical studies.The results revealed that joints welded with the application of AMF had a lower corrosion current density compared to those welded without an external AMF.Additionally,these joints showed higher pitting potential and polarization resistance.Microscopic electrochemical analysis indicated that joints subjected to AMF exhibited minimal cathodic current in simulated seawater,with only slight fluctuations in the anodic current peak.Overall,the corrosion levels on the joint surfaces were relatively low.After 4 h of immersion in the corrosive medium,the average impedance of joints exposed to AMF increased by 60.7%compared to those not influenced by a magnetic field.These findings suggest that applying AMF during the narrow gap laser-arc hybrid welding process can significantly improve the corrosion resistance of duplex stainless steel welded joints,reducing their susceptibility to stress corrosion in seawater-like environments.
基金supported by the National Natural Science Foundation of China(Grant numbers 52204347,52274385,52004156,51904184,and 52204392)the National Key Research and Development Program of China(Grant number 2022YFC2904900)+1 种基金the Science and Technology Commission of Shanghai Municipality(13JC14025000,15520711000)the Shi Changxu Innovation Center for Advanced Materials(SCXKFJJ202204).
文摘The use of an alternative magnetic field during vacuum arc remelting(VAR)can have significant effects on the primary carbide and mechanical properties of M50-bearing steel.The solidification structure and the primary carbide morphology of the VAR ingot were analyzed by optical microscopy and scanning electron microscopy.Characterization and analysis of the growth direction of primary carbides were conducted using high-resolution rapid electron backscatter diffraction.Solute elements segregation was analyzed using an electron probe microanalyzer.FLUENT was utilized to conduct numerical simulations to validate the experimental findings and elucidate the underlying mechanism.Compared to traditional VAR,magnetic-controlled VAR generates a horizontal circulation,which makes a shallower and flatter molten pool and a more even temperature distribution.In the time dimension,the local solidification time is shortened,and the concentration of solute elements will be alleviated.In the spatial dimension,the secondary dendrite arm spacing decreases,alleviating the degree of inter-dendritic segregation.Consequently,the possibility of forming a segregation diminishes.Both aspects promote the even distribution of solute atoms,resulting in less segregation and hindering the development of primary carbide.This leads to the refinement of primary carbide size and its uniform distribution.The magnetic-controlled vacuum arc melting not only refines the dendritic structure in the M50 ingot,causing it to expand more axially along the ingot,but also refines primary carbides and improves tensile and wear-resistant mechanical properties.
文摘The effects of alternating magnetic field on the corrosion morphologies, corrosion rate, and corrosion products of copper in 3.5% NaCl solution, sea water, and magnetized sea water were investigated using electrochemical test, scanning electron microscopy/energy dispersive analysis system of X-ray （SEM/EDAX）, and X-ray diffraction （XRD）. The results show that the corrosion rate of copper in magnetized sea water is minimal. Moreover, the surface of the specimen in magnetized sea water is uniform and compact as compared with those in 3.5% NaCl solution and sea water. The corrosion products of copper in magnetized sea water are mainly Cu2O and CuCl2. However, the corrosion products in sea water are CuCl, Cu2Cl（OH）3, and FeCl3-6H2O. The electrochemical corrosion mechanisms of copper in the three media were also discussed.
基金the LiaoNing Revitalization Talents Program(No.XLYC1807021)the Innovation Talent Program in Sciences and Technologies for Young and Middle-aged Scientists of Shenyang(No.RC180111)the Doctoral Scientific Research Foundation of Liaoning Province(No.51504153)。
文摘Herein, a hot tearing measured system with external excitation coil and a differential thermal analysis system with applied magnetic field were used to study the effects of low-frequency alternating magnetic field on the solidification behavior and hot tearing susceptibility(HTS) of the AXJ530 alloy under different magnetic field parameters. The hot tearing volume of the castings was measured via paraffin infiltration method. The microstructure of the hot tearing zone of the casting was observed using optical microscopy and scanning electron microscopy, and the phase composition was analyzed using X-ray diffraction and energy depressive spectroscopy. The experimental results show that the solidification interval of AXJ530 alloy was shortened and the dendrite coherency temperature of the alloy decreased with the increase in frequency of alternating magnetic field. Under appropriate magnetic field parameters, the electromagnetic force could enhance the convection in the melt to promote the flow of the residual liquid phase, refine the microstructure, and optimize the feeding channel in the late solidification stage, which reduced the HTS of the alloy. However, when the magnetic field frequency was increased to 15 Hz, the induced current generated excessive Joule heat to the melt. At this time, the thermal action of the magnetic field coarsened the microstructure of the alloy, resulting in an increase in HTS of the alloy.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB41010403)the National Natural Science Foundation of China(Nos.41804070,41774076,41621004)+2 种基金the Key Program of Chinese Academy of Sciences(No.QYZDJ-SSWDQC024)the Key Research Program of the Institute of Geology and Geophysics,CAS(No.IGGCAS-201903)the PetroChina Innovation Foundation(No.2020D-5007-0105)。
文摘Magnetotactic bacteria(MTB)intact cells have been applied in magnetic hyperthermia therapy of tumor,showing great efficiency in heating for tumor cell inhibition.However,the detailed magnetic hyperthermia properties and optimum heat production conditions of MTB cells are still poorly understood due to lack of standard measuring equipment.The specific absorption rate(SAR)of MTB cells is often measured by home-made equipment at a limited frequency and magnetic field amplitude.In this study,we have used a commercial standard system to implement a comprehensive study of the hyperthermic response of Magnetospirillum gryphiswaldense MSR-1 strain under 7 frequencies of 144-764 kHz,and 8 field amplitudes between 10 and 45 kA/m.The measurement results prove that the SAR of MTB cells increases with magnetic field frequency and amplitude within a certain range.In combination with the magnetic measurements,it is determined that the magnetic hyperthermia mechanism of MTB mainly follows the principle of hysteresis loss,and the heat efficiency of MTB cells in alternating magnetic field are mainly aff ected by three parameters of hysteresis loop,saturation magnetisation,saturation remanent magnetisation,and coercivity.Thus when we culture MTB in LA-2 medium containing sodium nitrate as source of nitrogen,the SAR of MTB LA-2 cells with magnetosomes arranged in chains can be as high as 4925.6 W/g(in this work,all SARs are calculated with iron mass)under 764 kHz and 30 kA/m,which is 7.5 times than current commercial magnetic particles within similar size range.
文摘A magnetic abrasive finishing process using an alternating magnetic field is proposed for the finishing of complex surfaces.In an alternating field,the periodic changes in current will cause the magnetic cluster used as a magnetic brush to fluctuate,which will not only continuously replace the abrasive particles in contact with the workpiece,but also periodically adjust the shape of the magnetic cluster to better fit the surface of the workpiece.In this paper,the influence of a combination of alternating and static magnetic fields on the magnetic field in the finishing area is analyzed.The feasibility of this process for finishing micro-grooves is investigated.Simulations and experimental measurements show that the combination of alternating and static magnetic fields can retain the advantages of the alternating field while increasing the magnetic flux density in the finishing area.The experimental results show that the process is feasible for finishing micro-grooves,with an excellent deburring effect on the groove edges.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52107162 and 12202479)the Science and Technology Projects of Shaanxi Province,China(Grant Nos.2022CGBX-12 and 2022KXJ-57)the Science and Technology Projects of Xi’an City,China(Grant Nos.23KGDW0023-2022 and 23GXFW0011)。
文摘A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision frequency.An equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision frequency.The applicable range of the LF method on a given plasma scale is analyzed.The upper diagnostic limit for the ratio of the electron density(unit:m^(-3))to collision frequency(unit:Hz)exceeds 1×10^(11),enabling an electron density to exceed 1×10^(20)m^(-3)and a collision frequency to be less than 1 GHz.In this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also assessed.Diagnosis experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF method.By comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF method.The ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma stabilization.The LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the model.Finally,the causes of diagnostic discrepancy between the two methods are analyzed.The proposed method provides a new avenue for diagnosing high-density enveloping plasma.
基金Item Sponsored by National Natural Science Foundation of China[No.50834010 and 50834009]Natural Science Foundation of Liaoning Province[20102074]the Fundamental Research Funds for the Central Universities of China[N100409005]
文摘In order to reasonably control the free surface oscillations,by using GalnSn low-melting alloy,the fluctuation and distortion behaviour of metal free surface is investigated under AC magnetic field.By simultaneously superposing DC magnetic field,the damping effect of DC magnetic field on free surface fluctuation is also investigated.In the cylindrical pool,the azimuthal and radial oscillation mode can be found simultaneously due to AC magnetic field. Moreover,the free surface is more stable in square pool than that in the cylindrical pool.Increase coil AC current,the free surface fluctuation is aggravated.A series of surface waves can be observed on free surface with compound magnetic field.Reasonable DC magnetic field can effectively damp the oscillations on the free surface in cylindrical pool.However. the DC magnetic field cannot effectively damp the surface oscillations in square pool.The DC magnetic field has no significant damping effect on the oscillations induced by the lower frequency magnetic force.
文摘We consider the radiation from the beam electrons traveling in a strong uniform axial magnetic field and an axial alternating electric field of wavelength Aw generated by a voltage-supplied pill-box cavity. The beam electrons emit genuine laser radiation that propagates only in the axial direction through free-electron two- quantum Stark radiation. We find that laser radiation takes place only at the expense of the axial kinetic energy when Aw 〈〈 c/（ωc/γ）, where ωc/γ is the relativistic electron--cyclotron frequency. We formulate the laser power based on quantum-wiggler electrodynamics, and envision a laser of length lore with estimated power 0.1 GW/（kA） in the 10-4 cm wavelength range.
文摘Plant stress caused by exposure to magnetic fields （MF） induces modifications at molecular level, particularly in DNA synthesis, structure, and function. The objective of this study was to determine the effect of various doses of non-ionizing radiation of magnetic field on date palm （Phoenix dactylifera L.） based on DNA content. Date palm seedlings （cv. Khalas） established for 2 weeks on filter paper were subjected to static magnetic field and alternating magnetic field. Static magnetic fields （SMF） were applied at 10, 50 and 100 mT for 30, 60, 120, 180, 240 and 360 min; while alternating magnetic field applied by magnetic resonance imaging （MRI） at 1500 mT for 1, 5, 10 and 15 min. The seedlings were grown in potting soil following exposure for 4 weeks after which DNA was extracted from leaves and its content was determined. Generally, the exposure to magnetic field caused reduction in the content of DNA. The lowest exposure time tested, 30 rain, was sufficient to induce reduction in DNA content. This was true even at the lowest intensity, 10 mT. This dosage caused the DNA content to decrease from 49 ~tg/g to 45 pg/g. Further, increase of the exposure duration to 60 min caused significant reduction in the DNA content, 36 μg/g. At intensities higher than 10 mT, DNA content decreased significantly even at the shortest exposure of 30 min. At 50 and 100 mT, significant decrease in DNA content was also noticed in response to 30 min exposure; whereas the level of DNA increased after 1 min of MRI exposure to 52 ~g/g, then decreased after 5 min to 46 ~g/g. However, longer durations caused no further decrease in the DNA content. These observations indicate that magnetic fields interact with DNA processes, probably by inhibiting synthesis or stimulating degradation of DNA. This response merits further exploration as a mutational agent for date palm genetic manipulation.
基金supported by the National Key Research and Development Program of China(2020YFC2200901)。
文摘As the complexity of scientific satellite missions increases,the requirements for their magnetic fields,magnetic field fluctuations,and even magnetic field gradients and variations become increasingly stringent.Additionally,there is a growing need to address the alternating magnetic fields produced by the spacecraft itself.This paper introduces a novel modeling method for spacecraft magnetic dipoles using an integrated self-attention mechanism and a transformer combined with Kolmogorov-Arnold Networks.The self-attention mechanism captures correlations among globally sparse data,establishing dependencies b.etween sparse magnetometer readings.Concurrently,the Kolmogorov-Arnold Network,proficient in modeling implicit numerical relationships between data features,enhances the ability to learn subtle patterns.Comparative experiments validate the capability of the proposed method to precisely model magnetic dipoles,achieving maximum Root Mean Square Errors of 24.06 mA·m^(2)and 0.32 cm for size and location modeling,respectively.The spacecraft magnetic model established using this method accurately computes magnetic fields and alternating magnetic fields at designated surfaces or points.This approach facilitates the rapid and precise construction of individual and complete spacecraft magnetic models,enabling the verification of magnetic specifications from the spacecraft design phase.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.81172182,81172120,and 81041040)the 7th Singapore–China Cooperative Research Project Call between Agency of Science,Technology and Research(A*STAR)+1 种基金Singapore and the Ministry of Science and Technology(MOST),China(Grant No.20113010006)the National Key Technology Support Program(Grant No.2012857818)
文摘Research progress and frontiers of magnetic-mediated hyperthermia （MMH） are presented, along with clinical trials in Germany, the US, Japan, and China. Special attention is focused on MMH mediated by magnetic nanoparticles, and multifunctional magnetic devices for cancer multimodality treatment are also introduced.
基金Projects(51905390,51575415)supported by the National Natural Science Foundation of China。
文摘To investigate the effect of alternating magnetic field on austenite transformation process in the case of rapid heating,the austenite kinetics model of AISI 1045 steel was built for spot continual induction hardening(SCIH)process.The results shows that the effect of alternating magnetic field on austenite transformation fraction reaches the maximum(about 3%)when heating rate is the lowest.Relatively low magnetic flux density still has a certain effect on the austenite transformation process during the SCIH process.Concave surface structure can reduce the influence scope of alternating magnetic field on surface in all cases and the minimum influence scope appears when the feed path of inductor is longitudinal.Convex surface structure can minimize the influence scope of alternating magnetic field in depth when the feed path of inductor is longitudinal.The austenite distribution of transitional region on surface for horizontal movement is more uniform than that for longitudinal movement.The austenite distribution of transitional region in depth for longitudinal movement is more uniform than that for horizontal movement.The simulated results are consistent with the experimental results and the austenite transformation kinetics model developed for SCIH process is valid.
基金This study was supported by the Instrument and Equipment Development Project of the Chinese Academy of Sciences(YJKYYQ20200053)the“Double First-Class”Construction Fund(111800XX62)the Mechanical Engineering Discipline Construction Fund(111800M000).
文摘The use of low electrically conducting liquids is more and more widespread.This is the case for molten glass,salt or slag processing,ionic liquids used in biotechnology,batteries in energy storage and metallurgy.The present paper deals with the design of a new electromagnetic induction device that can heat and stir low electricallyconducting liquids.It consists of a resistance-capacity-inductance circuit coupled with a low-conducting liquid load.The device is supplied by a unique electric power source delivering a single-phase high frequency electric current.The main working principle of the circuit is based on a double oscillating circuit inductor connected to the solid-state transistor generator.This technique,which yields a set of coupled oscillating circuits,consists of coupling a forced phase and an induced phase,neglecting the influence of the electric parameters of the loading part(i.e.,the low-conductivity liquid).It is shown that such an inductor is capable to provide a two-phase AC traveling magnetic field at high frequency.To better understand the working principle,the present work improves a previous existing simplified theory by taking into account a complex electrical equivalent diagram due to the different mutual couplings between the two inductors and the two corresponding induced current sets.A more detailed theoretical model is provided,and the key and sensitive elements are elaborated.Based on this theory,equipment is designed to provide a stirring effect on sodium chloride-salted water at 40 S/m.It is shown that such a device fed by several hundred kiloHertz electric currents is able to mimic a linear motor.A set of optimized operating parameters are proposed to guide the experiment.A pure electromagnetic numerical model is presented.Numerical modelling of the load is performed in order to assess the efficiency of the stirrer with a salt water load.Such a device can generate a significant liquid motion with both controlled flow patterns and adjustable amplitude.Based on the magnetohydrodynamic theory,numerical modeling of the salt water flow generated by the stirrer confirms its feasibility.
基金This work was supported by the National Natural Science Foundation of China （No. 51075299）.
文摘All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravity. In order to ＂push＂ the molten metal into the weld, a new kind of U-frame excitation model, which could produce electromagnetic force to balance the gravity of the molten pool, was designed. The related parameters of the excitation model were simulated by Maxwell 3D, and the relationships between the parameters and the magnetic induction intensity were analyzed. Finally, the electromagnetic force in the molten pool was calculated, and the appropriate parameters of the U-frame excitation model were determined. The results of the simulation verify the feasibility of the all-position welding excitation model.
基金This work was financially supported by the National 863 Foundation of China (No. 2001AA332030)the National Key Basic Research Program (973) (No. G1999064905)
文摘The influence of an alternative magnetic field on the growth of the diffusionlayer in Al-Zn diffusion couple was studied. The thickness of the diffusion layer was examined. Theresults show that the alternative magnetic field increases the thickness of the diffusion layer andthe effect increases with the intensity and frequency of the alternative magnetic field increasing. The growth of the diffusion layer obeys the parabolic rate law and the growth rateincreases with the application of the alternative magnetic field. This growth rate change ismanifested through a change in the frequency factor k_0 and not through a change in the activationenergy Q. The frequency factor k_0 for the diffusion layer growth with the alternative magneticfield is 5.03 cm^2/s and the one without the magnetic field is 3.84 cm^2/s.
文摘The influence of an alternative magnetic field on the diffusion of Al and Mg in AI-Mg diffusion couple is studied. The diffusion zone is composed of two intermediate phases, namelyβ and γ phase. Thickness of each intermediate phase is examined. The results show that the alternative magnetic field increases the thicknesses of βand γ phase zone and the layer growth ofβ and γphase obeys the parabolic rate law. The growth rate of the β and γ phase are increased with the application of the alternative magnetic field. This change is manifested through a change in the frequency factor k0 and not through a change in the activation energy Q. The frequency factor k0 for intermediate phase growth with an alternative magnetic field is 39.95 cm2/s for 7 phase and 2.84×10-4 cm2/s for β phase compared with those without the magnetic field is 22.4 cm2/s for 7 phase and 1.53×10-4 cm2/s for β phase.
文摘Our purpose in this study was to present a method for estimating the specific loss power (SLP) in magnetic hyperthermia in the presence of an external static magnetic field (SMF) and to investigate the SLP values estimated by this method under various diameters (D) of magnetic nanoparticles (MNPs) and amplitudes (H<sub>0</sub>) and frequencies (f) of an alternating magnetic field (AMF). In our method, the SLP was calculated by solving the magnetization relaxation equation of Shliomis numerically, in which the magnetic field strength at time t (H(t)) was assumed to be given by , with H<sub>s</sub> being the strength of the SMF. We also investigated the SLP values in the case when the SMF with a field-free point (FFP) generated by two solenoid coils was used. The SLP value in the quasi steady state (SLP<sub>qss</sub>) decreased with increasing H<sub>s</sub>. The plot of the SLP<sub>qss</sub> values against the position from the FFP became narrow as the gradient strength of the SMF (G<sub>s</sub>) increased. Conversely, it became broad as G<sub>s</sub> decreased. These results suggest that the temperature rise and the area of local heating in magnetic hyperthermia can be controlled by varying the H<sub>s</sub> and G<sub>s</sub> values, respectively. In conclusion, our method will be useful for estimating the SLP in the presence of both the AMF and SMF and for designing an effective local heating system for magnetic hyperthermia in order to reduce the risk of overheating surrounding healthy tissues.
