Magnetic Field Simulation Research Articles

The automatic identification and tracking of coronal flux ropes

Context. Constructing the relevant magnetic field lines from active region modelling data is crucial to understanding the underlying instability mechanisms that trigger the corresponding eruptions. Aims. We present a magnetic flux rope (FR) extraction tool for solar coronal magnetic field modelling data that builds upon a recent methodology. The newly developed method is then compared against its previous iteration. Furthermore, we apply the scheme to magnetic field simulations of active regions AR12473 (similar to our previous study) and AR11176. We compare the method to its predecessor and study the 3D movement of the newly extracted FRs up to heights of 200 and 300 Mm, respectively. Methods.The extraction method is based on the twist parameter Tw and a variety of mathematical morphology (MM) algorithms, including the opening transform and the morphological gradient. We highlight the differences between the methods by investigating the circularity of the FRs in the plane we extract from. The simulations for the active regions are carried out with a time-dependent data-driven magnetofrictional model (TMFM). We investigate the FR trajectories by tracking their apex throughout the full simulation time span. Results. Comparing the newly developed method to the previous extraction scheme, we demonstrate that this upgrade provides the user with more tools and less a priori assumptions about the FR shape, which in turn leads to a more accurate set of field lines. Despite some differences, both the newly extracted FR of AR12473 and the FR derived with the old iteration of the method show a similar general appearance, confirming that the two methods indeed extract the same structure. The methods differ the most in their emergence and formation stages, where the newly extracted FR deviates significantly from a perfectly circular cross-section (which was the basic assumption of the initial method). The propagation analysis yields that the erupting FR from AR12473 indeed shows stronger dynamics than the AR11176 FR and a significant deflection during its ascent through the domain. The modelling results are also verified with observations: AR12473 is dynamic and eruptive, while AR11176 only features an eruption outside of our simulation time window. Conclusions. We implemented a FR extraction method, incorporating mathematical morphology algorithms for 3D solar magnetic field simulations of active region FRs. This scheme was applied to AR12473 and AR11176. We find that the clearly eruptive FR of AR12473 experiences significant deflection during its rise. The AR11176 FR appears more stable, though there is still a notable deflection. This confirms that at these low coronal heights, FRs undergo significant changes in the direction of their propagation even for less dynamic cases.

The Novel Mathematical Model and Methodology for Computer Simulation of Magnetic Field in a Nonlinear Medium

The Novel Mathematical Model and Methodology for Computer Simulation of Magnetic Field in a Nonlinear Medium

Impact of Electromagnetic Stirring Roller Arrangement Pattern on Magnetic Field Simulation and Solidification Structure of PW800 Steel in the Second Cooling Zone.

Strand electromagnetic stirring (S-EMS), a technique applied in the secondary cooling zone, enhances the solidification structure of casting slabs. This study examines how the arrangement pattern of electromagnetic stirring rollers-face-to-face, side-to-side or up-down misalignment produces this enhancement. It uses simulations to analyze the electromagnetic field distribution in these configurations. The findings demonstrate that: (1) The magnetic flux density distribution in the casting slab is related to the arrangement pattern of the electromagnetic stirring rollers. (2) The face-to-face arrangement produces the largest and most concentrated electromagnetic force compared to the other two arrangement patterns. (3) S-EMS can effectively improve the equiaxed grain ratio of casting slabs. Before and after EMS is turned on, casting slabs' average equiaxed grain ratio goes up from 8% to 33%.

Advancing Solar Magnetic Field Extrapolations through Multiheight Magnetic Field Measurements

Nonlinear force-free extrapolations are a common approach to estimate the 3D topology of coronal magnetic fields based on photospheric vector magnetograms. The force-free assumption is a valid approximation at coronal heights, but for the dense plasma conditions in the lower atmosphere, this assumption is not satisfied. In this study, we utilize multiheight magnetic field measurements in combination with physics-informed neural networks to advance solar magnetic field extrapolations. We include a flexible height-mapping, which allows us to account for the different formation heights of the observed magnetic field measurements. The comparison to analytical and simulated magnetic fields demonstrates that including chromospheric magnetic field measurements leads to a significant improvement of our magnetic field extrapolations. We also apply our method to chromospheric line-of-sight magnetograms from the Vector Spectromagnetograph (VSM) on the Synoptic Optical Long-term Investigations of the Sun (SOLIS) observatory, in combination with photospheric vector magnetograms from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The comparison to observations in extreme-ultraviolet wavelengths shows that the additional chromospheric information leads to a better agreement with the observed coronal structures. In addition, our method intrinsically provides an estimate of the corrugation of the observed magnetograms. With this new approach, we make efficient use of multiheight magnetic field measurements and advance the realism of coronal magnetic field simulations.

Computational simulation of transcranial magnetic stimulation-induced electric fields in the dorsolateral prefrontal cortex of heavy cannabis using individuals

We aimed to investigate the influence of demographic and clinical modulators on the strength of transcranial magnetic stimulation (TMS)-induced electric fields (EFs) in the left dorsolateral prefrontal cortex (lDLPFC) in heavy cannabis using individuals. Structural T1-weighted magnetic resonance imaging scans of 20 heavy cannabis using individuals and 22 non-cannabis users (the controls) in the age range of 18–25 were retrieved. Computational simulations of TMS-induced EFs in the lDLPFC were performed. No significant difference in the strength of TMS-induced EFs was observed between heavy cannabis using individuals and the controls. A negative correlation between the scalp-to-cortex distance demonstrated and the strength of the induced EFs. The severity of cannabis use related problems did not correlate with the induced EFs in the lDLPFC of heavy cannabis using individuals. However, the severity of alcohol use related problems was negatively correlated with the induced EF in the lDLPFC localized by the 5-cm method in the whole sample. Early adulthood seems related to an increase in the induced EFs in the lDLPFC. In conclusion, the dominant factor influencing TMS-induced EFs was the scalp-to-cortex distance. In early adulthood, the interaction between age and comorbid substance use may influence with the magnitude of TMS-induced EFs, thereby complicating the treatment effect of TMS in young people with substance use disorders.

Research on identification method of transformer winding material based on vibration characteristic

At present, there are shoddy transformers in the market, of which the windings are replaced by aluminum and copper clad aluminum. The commissioning of these transformers may cause poor power supply performance and excessive winding heating. The existing detection methods of windings are complex, time-consuming to operate and destructive. Therefore, a winding material identification method based on vibration characteristics is proposed. Firstly, the vibration accelerations of transformer cores and windings with different winding materials are theoretically derived. Furthermore, through the coupling simulation of magnetic field and structure field of distribution transformers, the calculated vibration characteristics of copper, aluminum, and copper clad aluminum are verified. Finally, by comparing the time domain, the frequency domain and time-frequency domain of acceleration signals, preliminary identification of winding materials is conducted, which lays a theoretical foundation for establishing a precise identification model for winding materials in the future. This work provides guarantee for the safe operation of the distribution network.

Magnetic Field Simulation and Correlated Low-Frequency Noise Subtraction for an in-Orbit Demonstrator of Magnetic Measurements

Magnetic Field Simulation and Correlated Low-Frequency Noise Subtraction for an in-Orbit Demonstrator of Magnetic Measurements

Magnetic field simulations and measurements on the mini-ICAL detector

The ICAL (Iron Calorimeter) is a 51 kton magnetized detector proposed by the INO collaboration. It is designed to detect muons with energies in the 1–20 GeV range. A magnetic field of ∼ 1.5 T in the ICAL detector will be generated by passing a DC current through suitable copper coils. This will enable it to distinguish between μ- and μ+ that will be generated from the interaction of atmospheric νμ and νμ with iron. This will help in resolving the open question of mass ordering in the neutrino sector. Apart from charge identification, the magnetic field will be used to reconstruct the muon momentum (direction and magnitude). Therefore it is important to know the magnetic field in the detector as accurately as possible. We present here an (indirect) measurement of the magnetic field in the 85 ton prototype mini-ICAL detector working in Madurai, Tamil Nadu, for different coil currents. A detailed 3-D finite element simulation was done for the mini-ICAL geometry using Infolytica MagNet software and the magnetic field was computed for different coil currents. This paper presents, for the first time, a comparison of the magnetic field measured in the air gaps with the simulated magnetic field, to validate the simulation using real time data. Using the simulations the magnetic field inside the iron is estimated.

A Fast Calculation Method Based on Full-Boundary Magnetic Field Simulation for Calculating AC Loss in Bi-2223 HTS coils of Double-Stator HTS Machine

A Fast Calculation Method Based on Full-Boundary Magnetic Field Simulation for Calculating AC Loss in Bi-2223 HTS coils of Double-Stator HTS Machine

Research on temperature rise calculation and hot spot temperature inversion method for oil immersed transformer based on magnetic - thermal - fluid

The hot spot temperature of oil-immersed transformer winding is an important factor affecting the aging of material insulation. In this paper, a magnetic field simulation model is established based on the electrical and structural parameters of the oil-immersed transformer, and the loss distribution characteristics of each wall of the transformer core, winding and fuel tank are accurately calculated by using the finite element simulation software. The simulation model of transformer fluid- thermal field is established, the simulation results of transformer thermal field are obtained, and the temperature distribution of oil-immersed transformer core and winding and the flow velocity around it are obtained. According to the simulation results of thermal field, the characteristic temperature measuring points with strong correlation between tank wall and winding temperature were determined. The inversion models of tank wall and winding hot spot temperature were established by using the support vector regression and BP neural network algorithm respectively by central composite design method. The results show that the correlation coefficient of support vector regression algorithm in predicting winding hot spot temperature reaches 0.98, and the relative error between the model predicted value and the real value is less than 8%, which is more accurate than BP neural network. The above research provides the theoretical basis and technical support for real-time monitoring of oil-immersed transformer winding hot spot temperature.

Magnetism-enhanced biomaterial Mg guide wire by MAP process for development of catheter insertion

The surface topography of implant tools has indicated an interfacial contact in degradation still being discovered; however, the glossy texture of a tiny magnesium wire is important for absorbable medical devices. This paper investigated the alterations of surface quality by a magnetic abrasive polishing method using a rotational magnetic field-assisted system with input parameters of revolution, abrasive media, magnetic pole, flux density, vibration, and amplitude that could noticeably enhance asperities along a sample. Furthermore, the blood flow simulation is used to analyze flow within blood vessels while maintaining the surface roughness conditions of the guide wire. The results are compared and discussed. Magnetic field simulation is employed to investigate the magnetic field strength in the polishing zone. Scanning Electron Microscopy (SEM) provides visual aids for recognizing the differences between pre-and post-workpieces of magnesium wire. The experimental results reveal that a wire diameter of 0.50 mm predominantly achieves surface morphology from the initial roughness of 0.22 μm to 0.05 μm. The results corroborate that the distribution of blood in the circulatory system was relatively stable. Hence, this study establishes a crucial benchmark for the precision polishing of ultra-thin magnesium wires, which is vital for their use as high-precision biodegradable medical devices.

A metamaterial isolator with tunable low frequency stop-band based on magnetorheological elastomer and magnet spring

This paper proposed and prototyped a metamaterial isolator with periodic structure based on magnetorheological elastomer (MRE) and magnet spring. With acoustic metamaterial structure, the proposed metamaterial isolator can generate a stop-band, which means the vibration over specific frequency can’t be transferred and will be isolated effectively. Then, with the control of MRE stiffness, the cut-off frequency of the stop-band is tunable, which makes the isolator potential to be adapted to different working situations. The negative stiffness generated by the magnet spring can help to lower the start frequency of the stop-band and enhance the bearing capacity of the metamaterial isolator in vertical direction in the meantime. To verify the feasibility of the proposed device, the magnetic field simulation was first conducted and discussed, and the negative stiffness property of the magnet spring was numerically measured and demonstrated. Then, the mass-spring model of the metamaterial isolator was established in order to theoretically analyze the influence of MRE and the magnet spring on the vibration attenuation efficiency. A vibration platform was finally set up and the evaluation experiments were conducted to validate the theoretical analysis. In this paper, the structure design, theoretical modelling and experimental results of the metamaterial isolator are comprehensively discussed, which demonstrate that the prototype structure can work well as expected. The design of the metamaterial isolator with negative stiffness magnet spring can also enlighten more studies on lowering the bandgap frequency of the acoustic metamaterial without sacrificing large structure stiffness.

Design and Structure Optimization of Arresting Gear Based on Magnetorheological Damper

The UAV cluster combat puts forward higher requirements for short-distance arresting gears for multitype aircraft. Based on magnetorheological technology, an arresting gear was designed, and the structural parameters of the MR damper were optimized. An iterative optimization method of structural parameters via a genetic algorithm combined with parametric modeling and magnetic field simulation was proposed. The optimization method was applied to optimize the structure of both a single-coil and double-coil damper. The performance of the optimized arresting gear was studied. The results show that, under the same zero field damping upper limit, the variation range of the damping force of the double coil increases by 10.2% compared with that of the single coil. Comparing the peak overload of UAV before and after the optimization, when the UAV mass increases from 4000 kg to 10,000 kg, the reduction in the peak acceleration is increased from 19.8% to 25.4%. Compared with traditional hydraulic arresting gear, the new arresting gear has good adaptability to UAVs with various qualities and has higher arresting efficiency. This arresting gear has a certain advanced nature.

Magnetic field simulations of the GOLEM tokamak via the NICE code

In this paper, the direct and inverse equilibrium computation mode of the NICE code is put into operation for the case of the GOLEM tokamak. This enables, for the first time, simulations of GOLEM's magnetic field. The computation mode put into operation simulates the magnetohydrodynamic equilibrium of a tokamak plasma based on a given plasma position or given currents in poloidal magnetic field coils. In order to set up NICE, a virtual model of GOLEM is introduced that includes axially symmetrical approximations of GOLEM's iron core and primary transformer coils. The results of NICE simulations are compared with experimental measurements, and it is shown that NICE simulations produce plasma equilibrium configurations typical for GOLEM. Nevertheless, a more detailed validation of GOLEM's virtual model and of the results of NICE simulations is to be performed in the future.

Surface polishing of CoCrMo alloy by magnetorheological polishing

Improving the surface quality of biomedical alloys is of great practical significance to the evolution of orthopaedic implant surgery. In the polishing stage, traditional polishing methods are prone to problems, such as substandard surface roughness values and poor surface morphology, which severely affect the service life of materials. The surface quality of the CoCrMo alloy treated with magnetorheological polishing was studied. First, a polishing tool was designed based on magnetic field simulations of different magnetic pole arrangements and flow field simulations of the shear behaviour of the magnetorheological polishing cluster. Second, to improve the surface quality, an equally spaced pseudo-random path was planned, and the polishing effect for this path was verified using simulations and experiments. Moreover, the effect of different process parameters, i.e., the machining gap, polishing tool rotation speed, and abrasive particle size, on the polishing forces and the surface roughness values was studied. Finally, the wettability of the modified surface of the CoCrMo alloy after polishing was tested. The results confirm the ability of magnetorheological polishing to improve the surface quality of CoCrMo alloys, which has a certain guiding significance for the development of advanced biomedical implants.

A magnetorheological vibration absorber with bidirectional tunability for pipelines

A magnetorheological elastomer (MRE) is employed as a tunable stiffness element in a dynamic vibration absorber (DVA) due to its remarkable magnetic tunability. However, the natural frequency of the MRE-based DVA can only be tuned towards high frequency under magnetic fields, which fails to solve, or even exacerbates, the low-frequency pipeline vibration. To tackle this issue, an innovative DVA (H-DVA) with bidirectional magnetic tunability is proposed in this paper. The hard magnetic MRE filled by NdFeB particles is selected as the core tunable stiffness element in H-DVA. Besides, the discretization distribution design scheme for the mass oscillators is adopted to improve the flexibility of H-DVA. Then, the magnetic field simulation and resonance frequency shifting test of H-DVA under different magnetic fields are completed to validate the bidirectional magnetic tunability. Lastly, the vibration absorption effect is verified in a self-established experimental pipeline system. The experiment results demonstrate that the resonance frequency of the proposed H-DVA exhibites a maximum frequency shift of approximately −2.7 Hz under reversed magnetic field. Compared to H-DVA working in zero field state, the acceleration magnitude of the pipeline vibration is further reduced by 8.8% when applying −1.5 A to the H-DVA under 55 Hz excitation. Similarly, the acceleration magnitude is further reduced by 22.2% when applying 2 A to the H-DVA under 85 Hz excitation. Thus, these findings confirm that the H-DVA proposed in this paper not only achieves the bidirectional magnetic tunability, but also improves the vibration absorption effect for pipeline vibration.

Magnetic field model of radially magnetized cylindrical permanent magnets in a self-biased magnetic pendulum array

Self-Biased Magnetic Pendulum Array (SBMPA) is an efficient and portable transmitter in ultralow frequency (ULF). The resonance frequency of SBMPA is affected by the magnetic field of the radially magnetized cylindrical permanent magnets. In order to calculate the resonance frequency, the magnetic field model of a single radially magnetized cylindrical permanent magnet is derived based on the concept of magnetic charge. Then, the influence of the demagnetizing field and external magnetic field on the magnetization of permanent magnets is analyzed, and the magnetic field model of SBMPA is established. The results of the magnetic field model are verified through simulation. The average deviation of magnetic field intensity is determined as 0.021%; thus, the magnetic field model and simulation have consistent results. Finally, the influence of the size and distance of permanent magnets on the resonance frequency is analyzed, which could provide theoretical guidance for the dynamic analysis of SBMPA.

Synthesis of FeNi@kaolin soft magnetic composites with adjustable magnetic properties under different DC bias fields

Constructing the high-quality insulating layer and verifying the effects of DC bias field on magnetic properties is crucial in optimizing magnetic components based on soft magnetic composites. In this paper, a novel APTES-involved insulation technique has been developed to successfully coat kaolin on FeNi particles. Additionally, magnetic properties can be effectively regulated by changing the dosage of kaolin. The results show that anti-magnetization capacity and resistivity are improved by increasing kaolin content. Loss separation model and magnetic field simulation were used to investigate how the coating layer and DC bias field influence core loss for FeNi@kaolin SMCs. It can be found that structural demagnetizing field and eddy current were believed to be the main determinants of core loss variation in ideal sinusoidal waves, while the degree of magnetization state away from saturation plays a leading role in core loss under larger DC bias fields. Therefore, FeNi SMCs insulated with 1 wt% and 7 wt% kaolin exhibit the lowest core loss at DC bias field of 0 Oe and above 100 Oe, respectively. This work not only provides an effective insulating technique, but also supplies deeper insights into optimizing SMC-based magnetic components under larger DC bias fields.

Analysis of rotor fatigue characteristics of permanent magnet synchronous motor spindle in eccentric state

In this paper, the distribution of the air gap magnetic field in the motorized spindle is obtained through theoretical derivation, which is verified by comparing with the finite element simulation results. Based on the original calculation of air gap magnetic field, the rotor eccentricity theory is added, and the distribution of air gap magnetic field after rotor eccentricity is obtained. The correctness of the calculation theory of eccentric air gap magnetic field is verified by the finite element simulation results. Through the electromagnetic force calculation and finite element simulation of asymmetric magnetic field in eccentric state, the influence law of unbalanced electromagnetic force on the fatigue life of motorized spindle rotor is summarized.

C2DD—An omnidirectional receiver based on single‐coil transmitter

AbstractIn this paper, the omnidirectional receiver (Rx) of wireless power transfer (WPT) system is proposed, making any transmitter (Tx) into omnidirectional Tx. The omnidirectional Rx is composed of the quadrature double‐D (DD) coils and circular coil in series (C2DD). The C2DD Rx can utilize the toroidal magnetic field (TMF) and the linear magnetic field (LMF). The paper presents the circuit diagram model of WPT system. Based on the analysis of circuit model, the smooth mutual inductance of system is responsible for stable transmission performance during C2DD Rx movement. The result of numerical calculation and magnetic field simulation verifies the omnidirectional capability of the C2DD Rx with circular Tx as an example. Experiment shows that the C2DD Rx receives power in any direction. The C2DD Rx can receive maximum transmission power of 7.1 W with maximum transmission efficiency of 59%.