Dynamic Magnetic Field Research Articles

Development of a magnetic rotator to enhance the hydrogen evolution reaction in a proton exchange membrane water electrolysis cell

In this study, a large-scale magnetic rotator for hydrogen production boosting was designed. The study addresses the challenge of selecting and designing mechanical components for a dynamic magnetic field (DMF) magnetic rotator in a green hydrogen electrolysis power plant, focusing on ensuring component reliability and efficiency under operational stresses. The aim is to determine suitable machine element materials (shaft, clutch, gears, etc.), allowable shear stress, and interconnection mechanisms through theoretical and practical evaluations. The method includes calculating the allowable shear stress for the spline based on carbon steel tensile strength, applying safety factors for material properties and load considerations, and determining shaft diameter using torque and shock load factors. Standard catalogs guide the selection of interconnections like clutches, gears, and bearings to ensure compatibility and performance. The results indicate that a 95 mm diameter S30C carbon steel shaft, with an allowable shear stress of 7.8 kg/mm2, meets the design requirements. The chosen spline dimensions and a 12.5 MW, 14-pole induction motor align with the system’s needs, ensuring reliable operation. The discussion highlights the critical balance between theoretical predictions and practical application in design optimization. It underscores the importance of incorporating safety factors and verifying component suitability to ensure robust performance of the magnetic rotator. This study provides a comprehensive approach to design optimization, integrating theoretical analysis with practical considerations to achieve optimal performance and reliability. The design output of this study can be used to boost the hydrogen evolution reaction in the SIEMENS Sylizer 300 electrolysis cell.

Correction of dynamic magnetic field errors at the rapid cycling synchrotron of China Spallation Neutron Source

At a Rapid Cycling Synchrotron (RCS), dynamic magnetic field errors, such as magnetic field tracking errors and dynamic fringe field effects, can cause time-dependent tune shift during beam acceleration. If the tune shift is significant enough to pass through resonance lines, it can lead to emittance growth and beam losses. Correcting time-dependent tune shift during acceleration is crucial for a RCS. Modulating the exciting current and magnetic field of quadrupole magnets at a RCS, which are powered by resonant circuits, is challenging during the ramping process. Correcting time-dependent tune shift at a RCS poses a significant technical challenge. We have proposed a method for correcting time-dependent tune shift at the rapid cycling synchrotron of China Spallation Neutron Source (CSNS), based on waveform compensation at the quadrupole magnets. This approach involves modulating the magnetic field variation process by injecting time harmonic exciting current into the quadrupole magnets. This method has been validated during the CSNS beam commissioning and has been applied at the RCS of CSNS to correct various dynamic magnetic field errors.

Non-uniform dynamic magnetic field compensation for a lightweight magnetically shielded room based on distributed differential coils

Abstract Due to the influence of material characteristics and engineering imperfections, the residual magnetic fields including static and dynamic field in a lightweight magnetically shielded room (MSR) present non-uniform distribution characteristic. To effectively reduce the residual static field, a non-uniform field compensation method based on distributed coils has been proposed. This method takes the L2-norm of the magnetic field at the target array points as the objective function, to optimize the compensation current in each of the designed distributed coils, achieving non-uniform field compensation. To further achieve compensation for non-uniform residual dynamic field, a closed-loop control system containing a voltage divider and multi-channel amplifiers is designed in this paper. Additionally, the coil constant of the distributed differential coils and the initial magnetic field distribution vector for dynamic compensation are redefined. In conjunction with a PI controller, dynamic compensation is achieved using a single optically pumped magnetometer (OPM) as the feedback component. The experimental results indicate that the average dynamic field decreased from 376.75 pT to 27.80 pT over the central volume of (300 mm)³ in MSR, achieving a near-zero magnetic environment. This method has universal applicability for compensating non-uniform residual field under different working conditions.

Systematic simulation of tumor cell invasion and migration in response to time-varying rotating magnetic field.

Cancer invasion and migration play a pivotal role in tumor malignancy, which is a major cause of most cancer deaths. Rotating magnetic field (RMF), one of the typical dynamic magnetic fields, can exert substantial mechanical influence on cells. However, studying the effects of RMF on cell is challenging due to its complex parameters, such as variation of magnetic field intensity and direction. Here, we developed a systematic simulation method to explore the influence of RMF on tumor invasion and migration, including a finite element method (FEM) model and a cell-based hybrid numerical model. Coupling with the data of magnetic field from FEM, the cell-based hybrid numerical model was established to simulate the tumor cell invasion and migration. This model employed partial differential equations (PDEs) and finite difference method to depict cellular activities and solve these equations in a discrete system. PDEs were used to depict cell activities, and finite difference method was used to solve the equations in discrete system. As a result, this study provides valuable insights into the potential applications of RMF in tumor treatment, and a series of in vitro experiments were performed to verify the simulation results, demonstrating the model's reliability and its capacity to predict experimental outcomes and identify pertinent factors. Furthermore, these findings shed new light on the mechanical and chemical interplay between cells and the ECM, offering new insights and providing a novel foundation for both experimental and theoretical advancements in tumor treatment by using RMF.

A new theoretical model for high-order harmonics of SH0 mode ultrasonic guided waves based on magnetostrictive mechanism

In recent years, it was found that magnetostrictive ultrasonic guided wave transducers experimentally excited nonlinear harmonic components under a certain combination of dynamic and static magnetic fields. However, a satisfactory model for the relevant excitation mechanisms is not available. In this study, a new magnetostrictive guided wave excitation model was established and the causes for harmonics generation were analyzed. In addition, the calculation results of the model were obtained under different magnetic field parameters. We firstly changed the calculation conditions of magnetostrictive strain in the model and then theoretically calculated the odd and even harmonics of SH0 mode ultrasonic guided waves for the first time. Furthermore, the accuracy of the model was experimentally verified. By changing the strength ratio of the dynamic magnetic field to the static magnetic field (HD/HS), the excitation amplitudes of odd and even harmonics could be regulated with a magnetostrictive sensor. As the ratio of HD/HS increased, the normalized amplitude of the second harmonic firstly increased and then decreased, whereas the normalized amplitude of the third harmonic showed an exponential growth with different curvatures. This study enriched the theory of magnetostrictive guided wave excitation and provided a theoretical basis for the applications of magnetostrictive sensors.

Eddy Current Mechanism Model for Dynamic Magnetic Field in Ferromagnetic Metal Structures

The degaussing process is crucial for ensuring magnetic protection in ships. It involves the application of oscillating and attenuating magnetic fields to eliminate residual magnetism in the ship’s structure. However, this process can lead to the generation of distorted magnetic fields within the ship’s cabin, posing a potential threat to electronic equipment performance. Therefore, it is essential to have a comprehensive understanding of the dynamic magnetic field response in ship structures to develop effective degaussing systems. To address this need, this paper proposes an eddy current model for analyzing the dynamic magnetic field response in ferromagnetic metal structures. This model focuses on the role of eddy currents in shaping the magnetic field response and provides valuable insights into the underlying mechanisms. Using the proposed eddy current model, the effects of key system parameters such as thickness, conductivity, and the length-scale of the ship structure can be analytically investigated. This analysis helps in understanding how these parameters influence the dynamic magnetic field response and aids in the design and optimization of degaussing systems. The effectiveness and applicability of the proposed eddy current model are demonstrated through comprehensive investigations involving two simulation cases of varying complexity. The model accurately predicts the changing trends of the dynamic magnetic field response, as confirmed through finite element simulations. This validation highlights the model’s ability to reproduce simulation results accurately and its potential as a powerful tool for analyzing and optimizing dynamic magnetic field responses. In summary, the proposed eddy current model represents a significant advancement in the field. It provides a valuable theoretical framework for understanding and analyzing the dynamic magnetic field response in ferromagnetic metal structures. By offering insights into the underlying mechanisms and the influence of key parameters, this research contributes to the development of improved degaussing systems and enhances the overall magnetic protection capabilities of ships.

Ultrafast Switching of Sliding Polarization and Dynamical Magnetic Field in van der Waals Bilayers Induced by Light.

Sliding ferroelectricity is a unique type of polarity recently observed in van der Waals bilayers with a suitable stacking. However, electric-field control of sliding ferroelectricity is hard and could induce large coercive electric fields and serious leakage currents that corrode the ferroelectricity and electronic properties, which are essential for modern two-dimensional electronics and optoelectronics. Here, we proposed laser-pulse deterministic control of sliding polarization in bilayer hexagonal boron nitride by first principles and molecular dynamics simulation with machine-learned force fields. The laser pulses excite shear modes that exhibit certain directional movements of lateral sliding between bilayers. The vibration of excited modes under laser pulses is predicted to overcome the energy barrier and achieve the switching of sliding polarization. Furthermore, it is found that three possible sliding transitions-between AB (BA) and BA (AB) stacking-can lead to the occurrence of dynamical magnetic fields along three different directions. Remarkably, the magnetic fields are generated by the simple linear motion of nonmagnetic species, without any need for more exotic (circular, spiral) pathways. Such predictions of deterministic control of sliding polarization and multistates of dynamical magnetic field thus expand the potential applications of sliding ferroelectricity in memory and electronic devices.

Micro magnetic field sensor based on bifunctional diodes

Multiple-quantum well (MQW) diodes can be used as bifunctional diodes due to the emission-detection spectral overlap. When integrated with magnetic fluids (MFs) that have tunable refractive index, they can be designed as micro magnetic field sensors. The sapphire substrate of the MQW diode chip that consists of an MQW transmitter and receiver that is directly exposed to the MF, and the external magnetic field strength is used to change the refractive index at the boundary between the sapphire and the MF, thus modulating the reflected light and realizing external magnetic field sensing. Verified by experimental measurements, the micromagnetic field sensor has a detection range of 0.001-0.05 T, a sensitivity of 127.3 µA/T, and a resolution of 4.5×10−5 T, with excellent stability and repeatability. Additionally, the sensor demonstrates good velocity resolution under dynamic magnetic fields and can detect the direction of magnetic field motion, providing significant application value.

Dynamic fringe field effect of the rapid ramping quadrupole magnets at a Rapid Cycling Synchrotron

For a DC quadrupole magnet, the normalized magnetic field distribution along the beam trajectory is mainly determined by the mechanical structure of the magnet and remains almost independent of the exciting current. However, the magnetic field measurement results of the Rapid Cycling Synchrotron (RCS) at the China Spallation Neutron Source (CSNS) show that the normalized magnetic field distribution along the beam trajectory varies during the exciting current ramping process for rapid ramping magnets. Consequently, for rapid ramping quadrupole magnets, there are significant differences between the dynamic and static magnetic field gradient distribution. And the changes in the distribution of the magnetic field gradient can cause time dependent tune-shifts during the exciting current ramping process. For RCS, the tune is crucial, and the shifts of tune may lead to the beam approaching the resonance line, thereby causing beam loss. The impact of the fringe field effect of the rapid ramping quadrupole magnets on beam dynamics at CSNS-RCS was detailly studied. A new method for correcting the time-dependent tune shifts caused by the dynamic field distribution, based on waveform compensation at the quadrupole magnets, has also been proposed for the RCS of CSNS. Related simulation and experiment have been conducted, and the simulation results and experimental results are consistent with theoretical study results.

Dynamic J-A model improved by waveform scale parameters and R-L type fractional derivatives

PurposeThe purpose of this study is to model the global dynamic hysteresis properties with an improved Jiles–Atherton (J-A) model through a unified set of parameters.Design/methodology/approachFirst, the waveform scaling parameters β, λk and λc are used to improve the calculation accuracy of hysteresis loops at low magnetic flux density. Second, the Riemann–Liouville (R-L) type fractional derivatives technique is applied to modified static inverse J-A model to compute the dynamic magnetic field considering the skin effect in wideband frequency magnetization conditions.FindingsThe proposed model is identified and verified by modeling the hysteresis loops whose maximum magnetic flux densities vary from 0.3 to 1.4 T up to 800 Hz using B30P105 electrical steel. Compared with the conventional J-A model, the global simulation ability of the proposed dynamic model is much improved.Originality/valueAccurate modeling of the hysteresis properties of electrical steels is essential for analyzing the loss behavior of electrical equipment in finite element analysis (FEA). Nevertheless, the existing inverse Jiles–Atherton (J-A) model can only guarantee the simulation accuracy with higher magnetic flux densities, which cannot guarantee the analysis requirements of considering both low magnetic flux density and high magnetic flux density in FEA. This paper modifies the dynamic J-A model by introducing waveform scaling parameters and the R-L fractional derivative to improve the hysteresis loops’ simulation accuracy from low to high magnetic flux densities with the same set of parameters in a wide frequency range.

Adhesion switchable transition on bio-inspired Janus surface for multi-directional droplet manipulation

Achieving precise and rapid droplets manipulation in versatile directions transport remains a considerable challenge, however adhesion switchable transitions deemed to be rather serviceable. Here, a double-sided microplate array (DMPA) with bio-inspired Janus surfaces, is proposed to fulfill adjustable adhesion through surface wettability switching and microplate dynamic deformation, thereby executing the droplet multi-dimensional manipulation in response to dynamic magnetic field. The triple-coupled bio-inspired Janus surfaces are newly designed with a convex hull and striped structure respectively, inspired by the respiratory ciliary motion and surface properties of lotus and rice leaves. Leveraging variation in superhydrophobicity and low adhesion of convex hull side on Janus surface, diverse droplet directional transports are achieved in plane, such as high-speed horizontal transport (120 mm/s and 500 µL), anti-gravitational climbing (inclined by 15°), and selective droplet orientation. The adhesion switchable transition of surface striped structure on other side is predominated by solid–liquid contact lines evolution resulting from microplate bending deformation, realizing droplet capture/release for long-distance multi-dimensional transport. Concurrently, a magnetic-responsive droplet switch is developed based on multi-directional droplet manipulation, demonstrating enormous potential for practical application.

Key factors governing the direction of SH0 mode guided waves generated by FeCo strip-based magnetostrictive sensor

Magnetostrictive sensors (MsS) are widely used to generate ultrasonic guided waves of SH0 mode for the purpose of detecting defects in plate-like structures. An MsS commonly employs a rectangular magnetostrictive strip and a sensor unit (including detection coil and magnet) to generate SH0 waves. However, the effect of coverage range of static magnetic field (Ls) and dynamic magnetic field (LD) on the SH0 wave generation direction has not been fully explored. So far, the cases of LS<<LD and LD>>LS are seldom discussed in the development of MsS for generating SH0 mode. In this study, the key factor governing the direction of SH0 mode generated by FeCo strip-based MsS was experimentally clarified. The transition phenomenon in the generation direction of SH0 wave was observed while the combination parameters crossing the control line of Ls≈LD. The phenomenon could be interpreted by the alterations in the operation mechanism of Wiedemann effect and reversed Wiedemann effect. As a result, the generation direction of SH0 mode could be tuned along the static magnetic field (Ls<<LD), the dynamic magnetic field (Ls>>LD) or the direction of both static and dynamic magnetic fields (Ls≈LD). The findings in this study is of benefit for guiding the design of MsS array with the tunable generation direction of SH0 mode.

Effect of the dipolar interaction on the dynamic hysteresis of properties of 2D-nanodisks: In-plane driving field case

The effect of the dipolar interaction strength on the dynamical hysteresis behavior of the nanodisk is investigated within the Heisenberg model and Monte Carlo simulation. The system is under the effect of the dynamical periodic sinusoidal magnetic field. It has been shown that dipolar interaction strength can induce dynamical phase transition and the transition from the fully dynamically ordered ground state to the weak dynamically ordered ground state. Besides, it has been shown that rising dipolar interaction raises the hysteresis loop area for higher temperatures and a linear relationship between the peak positions of the hysteresis loop area and the temperature locations of the peaks obtained.

Variational model-based reconstruction techniques for multi-patch data in Magnetic Particle Imaging

Magnetic Particle Imaging is an emerging imaging modality through which it is possible to detect tracers containing superparamagnetic nanoparticles. The exposure of the particles to dynamic magnetic fields generates a non-linear response that is used to locate the particles and produce an image of their distribution. The bounding box that can be covered by a single scan curve depends on the strength of the gradients of the magnetic fields applied, which is limited due to the risk of causing peripheral nerve stimulation (PNS) in the patients. To address this issue, multiple scans are performed. The scan data must be merged together to produce reconstructions of larger regions of interest. In this paper we propose a mathematical framework which can deal with rather general multi-patching scenarios including rigid transformations of the field of view (FoV), the specimen and of the scanner. We show the flexibility of this framework in a variety of different scanning scenarios. Moreover, we describe an iterative reconstruction algorithm that yields a reconstruction of the target distribution by minimizing a convex functional which includes positivity constraints and sparsity enforcing priors. We show its convergence to a minimizer and perform numerical experiments on simulated data.

Dynamic Magnetic Field Analysis and Delivery Strategy Optimization for Scanning Magnet in Proton Therapy System

In pencil beam scanning proton therapy, the regulation and stabilization of the scanning magnetic field between two spots should be completed as quickly as possible in order to reduce treatment time. Because of the eddy current effect, the dynamic magnetic field lags behind the excitation current. It is significant to analyze the dynamic field and reduce the field stability time to minimize the delivery time and improve the therapy efficiency. In this paper, dynamic magnetic field simulation is carried out with a full lamination model of the scanning magnet in the Huazhong University of Science and Technology Proton Therapy Facility. In addition, a single lamination model instead of a full lamination model is explored to reduce time cost and memory for lamination of no more than 1-mm thickness. The eddy current diffusion trend and the influence of lamination on the eddy current are investigated. Moreover, the effect of lamination thickness (ranging from 5 to 0.1 mm) and current ramp rate (ranging from 20 to 100 A/ms) on the magnetic field stability time is studied. In addition, the characteristic of magnetic stability time for various spot steps is analyzed. Considering two spot patterns with discrete or clustered spots, an optimized delivery strategy with various scanning dead times according to the step is presented. When the lamination is 1 mm, the scanning time can be reduced by 39.2% for a clustered pattern and 38.4% for a discrete pattern using a genetic algorithm based on the different scanning dead-time strategy instead of the fixed dead-time strategy. With a thinner 0.1-mm lamination, the scanning time can be reduced by 49.8% for the clustered pattern and 43.3% for the discrete pattern, compared to that of the 1-mm lamination.

Magnetically Controlled Strategies for Enhanced Tissue Vascularization

AbstractTissue vascularization plays a critical role in the regeneration and repair of damaged tissues. However, in certain instances of tissue injury, the pace and effectiveness of vascularization can be limited. Innovative strategies leveraging magnetic fields and magnetic nanoparticles (MNPs) are devised to enhance the efficacy of tissue vascularization. This review explores the potential of magnetic field‐assisted strategies in augmenting tissue vascularization and repair. Direct application of static or dynamic magnetic fields, alone or in combination with MNPs, offers a means to modulate cellular behaviors and gene expression, thereby promoting angiogenesis and tissue regeneration. Techniques such as cell labeling, gene delivery using MNPs, and magnetic targeting have shown promise in efficiently repairing various ischemic tissue injuries by enhancing tissue vascularization. These strategies have broad applications in bone and skin tissue regeneration, limb ischemia treatment, myocardial injury treatment, and diabetic wound therapy. By summarizing recent advancements in magnetically controlled strategies, this review aims to shed light on their future prospects in tissue regeneration and clinical treatment.

Ultra-fast in vivo directional dark-field x-ray imaging for visualising magnetic control of particles for airway gene delivery

Objective. Magnetic nanoparticles can be used as a targeted delivery vehicle for genetic therapies. Understanding how they can be manipulated within the complex environment of live airways is key to their application to cystic fibrosis and other respiratory diseases. Approach. Dark-field x-ray imaging provides sensitivity to scattering information, and allows the presence of structures smaller than the detector pixel size to be detected. In this study, ultra-fast directional dark-field synchrotron x-ray imaging was utlilised to understand how magnetic nanoparticles move within a live, anaesthetised, rat airway under the influence of static and moving magnetic fields. Main results. Magnetic nanoparticles emerging from an indwelling tracheal cannula were detectable during delivery, with dark-field imaging increasing the signal-to-noise ratio of this event by 3.5 times compared to the x-ray transmission signal. Particle movement as well as particle retention was evident. Dynamic magnetic fields could manipulate the magnetic particles in situ. Significance. This is the first evidence of the effectiveness of in vivo dark-field imaging operating at these spatial and temporal resolutions, used to detect magnetic nanoparticles. These findings provide the basis for further development toward the effective use of magnetic nanoparticles, and advance their potential as an effective delivery vehicle for genetic agents in the airways of live organisms.

Nanoarchitectonic Engineering of Thermal-Responsive Magnetic Nanorobot Collectives for Intracranial Aneurysm Therapy.

Stent-assisted coiling is a main treatment modality for intracranial aneurysms (IAs) in clinics, but critical challenges remain to be overcome, such as exogenous implant-induced stenosis and reliance on antiplatelet agents. Herein, an endovascular approach is reported for IA therapy without stent grafting or microcatheter shaping, enabled by active delivery of thrombin (Th) to target aneurysms using innovative phase-change material (PCM)-coated magnetite-thrombin (Fe3O4-Th@PCM) FTP nanorobots. The nanorobots are controlled by an integrated actuation system of dynamic torque-force hybrid magnetic fields. With robust intravascular navigation guided by real-time ultrasound imaging, nanorobotic collectives can effectively accumulate and retain in model aneurysms constructed in vivo, followed by controlled release of the encapsulated Th for rapid occlusion of the aneurysm upon melting the protective PCM (thermally responsive in a tunable manner) through focused magnetic hyperthermia. Complete and stable aneurysm embolization is confirmed by postoperative examination and 2-week postembolization follow-up using digital subtraction angiography (DSA), contrast-enhanced ultrasound (CEUS), and histological analysis. The safety of the embolization therapy is assessed through biocompatibility evaluation and histopathology assays. This strategy, seamlessly integrating secure drug packaging, agile magnetic actuation, and clinical interventional imaging, avoids possible exogenous implant rejection, circumvents cumbersome microcatheter shaping, and offers a promising option for IA therapy.

Spin-wave self-imaging: Experimental and numerical demonstration of caustic and Talbot-like diffraction patterns

Extending the scope of the self-imaging phenomenon, traditionally associated with linear optics, to the domain of magnonics, this study presents the experimental demonstration and numerical analysis of spin-wave (SW) self-imaging in an in-plane magnetized yttrium iron garnet film. We explore this phenomenon using a setup in which a plane SW passes through a diffraction grating, and the resulting interference pattern is detected using Brillouin light scattering. We have varied the frequencies of the source dynamic magnetic field to discern the influence of the anisotropic dispersion relation and the caustic effect on the analyzed phenomenon. We found that at low frequencies and diffraction fields, the caustics determine the interference pattern. However, at large distances from the grating, when the waves of high diffraction order and number of slits contribute to the interference pattern, the self-imaging phenomenon and Talbot-like patterns are formed. This methodological approach not only sheds light on the behavior of SW interference under different conditions but also enhances our understanding of the SW self-imaging process in both isotropic and anisotropic media.

FPGA-Based Magnetic Field Camera for Dynamic Magnetic Field Mapping

FPGA-Based Magnetic Field Camera for Dynamic Magnetic Field Mapping