Magnetic Field Simulation Research Articles

Modeling and experimental evaluation of vibration reduction of hydraulic-driven joint with a MRF damper

In order to reduce the impact force of the legged hydraulic-robot when it is driving on the ground, a new method based on magnetorheological technology is proposed for damping control of hydraulic mechanical legs in this paper. Firstly, the structure of hydraulic-driven leg with magnetorheological fluid (MRF) damper is designed, and the magnetic field simulation analysis of MRF damper is carried out to verify the rationality of magnetic circuit. Then the effects of different damping ratios on the dynamic performance of valve-controlled cylinder system are analyzed by theoretical modeling. Further, the co-simulation modeling of MRF damper and valve-controlled cylinder is established based on AMESIM to analyze the vibration reduction effect under impact force. Finally, the experiments of the hydraulic system designed in this paper are carried out under step load and triangular-wave load to obtain the system output displacement and pressure under two kinds of loads. Compared with the results without MRF damper, it is found that the new method can reduce the increase of pressure impact by 82% and almost eliminate the pressure fluctuation in the high pressure chamber of hydraulic cylinder.

Microplastic Collection With Ultra-High Magnetic Field Magnet by Magnetic Separation

In recent years, the increase of microplastics (MPs) in ocean have been recognized as one of ocean pollution listed in Sustainable Development Goals (SDGs). Since MPs absorb harmful chemicals while floating in ocean, small fish which eats the absorbed MPs may fall into bad digestion and poor health condition. To solve the ocean pollution problem, a good MP collection method must be proposed with a high processing speed and a high MP collection ability. While, recently, the performances of 2nd generation high-temperature superconducting (HTS) magnets which can generate a field higher than 15 T have been improved. It is expected that MP collection performances are enhanced with such high field superconducting magnets. In this paper, we propose a conceptual design for MP collector from seawater using superconducting magnets. To evaluate the performances of the device, we developed a fluid simulation coupled with magnetic field simulation. The simulation results indicate that MPs can effectively be collected with a high magnetic field with a high processing speed.

The three-point eccentric magnetorheological polishing technology for hard brittle alumina ceramics

Abstract. This work presents the design of a pressurised three-point eccentric magnetorheological polishing (MRP) device, for alumina ceramics' hard and brittle characteristics, and a carrier disc magnetic field generator and a single closed-loop uniform magnetic field generator for a more uniform and increased magnetic field distribution. When compared with the traditional gap type, this device considerably enhances polishing efficiency. This apparatus has also been used to explore the mechanism of MRP. Static magnetic field simulations were conducted, and the fundamentals of the three-point eccentric magnetorheological process were addressed. Alumina ceramics were polished with a three-point eccentric wheel MRP equipment. Polishing tests were conducted to explore the effects of rotational speed, working pressure, abrasive type, abrasive particle size and polishing duration on polishing properties, and optimised polishing parameters were established. The surface roughness (Ra) of the samples was dramatically reduced from 500 to 22.41 nm using the three-point eccentric MRP device. The pit markings on the alumina ceramics' surface vanished after polishing. Therefore, the approach has considerable polishing potential for hard and brittle materials that can be nanofabricated with minimal surface sub-damage.

Effects of combined coils on the uniformity of RF ion source

The radio frequency (RF) ion source is significant in the industry because of its advantages of easy control and maintenance, low gas consumption, high energy and high-density plasma generation abilities. Unfortunately, the problem of high-density plasma uniformity limits its applications. RF coils, as the most important part of the ion source, play a critical role on plasma density and distribution. In this paper, we performed simulations of the combined coils magnetic field and plasma with power distribution and conducted process experiments with the RF ion source to obtain its etching uniformity by the characterization of a step profiler. The results show that the application of the same direction and a suitable coil current is beneficial to extend the uniformity range. The uniformity is improved by applying reversed coil currents. The results of process experiments are consistent with the simulation conclusions. This paper provides informative suggestions for the optimization of coil structures in the RF ion source.

Enhancing Wire-Rope Damage Signals Based on a Radial Magnetic Concentrator Bridge Circuit.

Hall-effect sensors are used for the non-destructive testing of wire ropes owing to their low power consumption and high operation frequency. The high-speed operation of wire ropes causes vibration inclination at different frequencies, which makes it difficult to detect the ropes. Considering that the radial signal in the magnetic flux leakage (MFL) detection method can respond to damages to the maximum extent possible, this study proposes a radial magnetic concentrator suitable for the non-destructive testing of wire ropes based on theoretical analysis and transient magnetic field simulations. The concentrator improves the radial magnetic circuit, polymerizes the leakage of the magnetic field in the detection device, and the leakage of the magnetic field of the defect converges at the sensor position of the circumferential array to improve the signal-to-noise ratio of the Hall-effect sensor. In addition, the MFL field is homogenized through the structure of the magnetic concentrator when the wire rope is tilted, which weakens the influence of the vibration tilt of the wire rope on the test results. Finally, the experiments show that the amplitude of the wire-rope damage signal is effectively improved by using the proposed radial magnetic concentration technology, hence being convenient for defect analyses.

Construction of Co@C nanocapsules by one-step carbon reduction of single-crystal Co3O4 nanoparticles: Ultra-wideband microwave absorber verified via coaxial and arch methods

It is highly demanding and challenging to construct the nano-scale microwave absorber with wide-frequency responding feature. Herein, a series of Co@C nanocapsules (NCs) are fabricated via one-step carbon reduction of Co3O4 nanoparticles (NPs) of only 20 nm obtained by the nitrate pyrolysis method. The electromagnetic parameters of the samples can be effectively regulated by flexibly adjusting the carbon shell thickness. Surprisingly, all samples exhibit ultra-wide microwave absorption (MA) performance investigated by the coaxial method. For the Co@C NCs with a carbon shell of 25 nm, especially, the effective absorption bandwidth (EAB) for reflection loss (RL) below −10 dB reaches a record high of 15.2 GHz (2.8–18 GHz), which completely covers the whole C-, X-, and Ku-bands. More excitingly, the absorption bandwidth for RL ≤ −20 dB is up to 7.1 GHz at only 2.0 mm thickness. Such outstanding MA properties are attributed to nano-size effect, synergistic effects of strong dielectric/magnetic loss, and superior impedance matching characteristics. Notably, the polarization and magnetic coupling behaviors are clarified with the aid of electric field and magnetic field simulations using High-Frequency Structure Simulator (HFSS). The plate coating sample is further prepared and measured by the arch method, which also displays an ultrawide MA bandwidth. This work provides a new design strategy toward the facile synthesis of ultra-broadband microwave absorbers.

Updated bounds on axion-like particles from X-ray observations

ABSTRACT In this work, we revisit five different point sources within or behind galaxy clusters to constrain the coupling constant between axion-like particles (ALPs) and photons. We use three distinct machine learning (ML) techniques and compare our results with a standard χ2 analysis. For the first time, we apply approximate Bayesian computation to search for ALPs and find consistently good performance across ML classifiers. Further, we apply more realistic 3D magnetic field simulations of galaxy clusters and compare our results with previously used 1D simulations. We find constraints on the ALP-photon coupling at the level of state-of-the-art bounds with $g_{a\gamma \gamma } \lesssim 0.6 \times 10^{-12} \, \rm{GeV}^{-1}$, hence improving on previous constraints obtained from the same observations.

Sealing Behavior Research on the Radial Ferrofluid Seal Structure with Oblique Teeth

Considering various unstable factors when the large-diameter spindle operates at a high speed, such as eccentricity, centrifugal force, etc., the ordinary ferrofluid seal structures will show poor sealing performance. This paper proposes an axial-radial bidirectional ferrofluid seal structure with radial oblique teeth to improve the sealing performance. The pressure resistance of the radial ferrofluid seal structure in the magnetic circuit is theoretically analyzed. The magnetic flux distribution characteristic in the gap of the oblique teeth is studied by magnetic field simulation. According to the analysis results of the magnetic induction intensity, to obtain the larger theoretical pressure resistance, the optimal angle of oblique teeth is 77.87°, 64.28° and 62.81° under the radial seal structure with different gaps of 0.1 mm, 0.15 mm and 0.2 mm, respectively. In addition, simulation analysis is carried out to obtain the fluid pressure and velocity distribution of the radial ferrofluid seal structure with different oblique teeth angles. When the oblique teeth angle is small, the pressure drops and gas flow speeds in the ferrofluid area are all lower, and the pressure resistance is higher.

Influence of measurement field on the magnetic domains for zero-field cooling exchange bias effect in Ni50Mn37Ga13 alloy

The exchange bias effect obtained after zero field cooling (ZEB) not only saves energy but also makes the device easier to control and reduces the size of the device. In this work, the ZEB effect under different measurement fields is obtained in Ni50Mn37Ga13 alloy, further, combining the macroscopic magnetic test and phase field simulation, the microscopic magnetic states under different measurement fields are studied. Through phase field simulation, it is revealed that the density of the ferromagnetic (FM)/antiferromagnetic (AFM) interface first expands and then shrinks with the increase of measurement field, which thus explains the optimum ZEB at an intermediate measurement field. This work reveals the important role of the FM/AFM interface in the ZEB effect.

Metal Object Detection by Monitoring Fifth-Order Harmonic Current of IPT System With Dual Frequency Tuning

A key challenge for safe operation of inductive power transfer (IPT) systems is to detect the presence of metal objects (MOs), particularly when a power receiver (Rx) is misaligned from a power transmitter (Tx) during online charging. This letter proposes a metal object detection (MOD) method by monitoring the fifth-order harmonic current of a dual-frequency IPT system driven by a voltage-fed inverter with square-wave output. While power transfer is maintained by tuning at the fundamental frequency, the Tx circuit is tuned simultaneously at the fifth-order frequency to ease the detection of the fifth-order harmonic current for MOD. The Rx circuit is also fully tuned at the fifth-order frequency, but the fifth order current is completely blocked. With the proposed dual-frequency tuning configuration, the presence of MO causes a significant drop in the fifth-order harmonic current at the Tx side, whereas the Rx behaves as an open circuit with no effect on power transfer. Circuit and magnetic field simulation results show the fifth-order harmonic current presents a unique response to the existence of MO, which is in good agreement with practical measurements. Experimental results demonstrate that at a constant 10 W power output, both nonferrous and ferrous MOs within the Tx charging area can be 100% detected, even when the Rx is misaligned by 50% of the Tx coil radius.

Long-term general relativistic magnetohydrodynamics simulations of magnetic field in isolated neutron stars

ABSTRACT Strong magnetic fields play an important role in powering the emission of neutron stars. Nevertheless, a full understanding of the interior configuration of the field remains elusive. In this work, we present general relativistic magnetohydrodynamics (MHD) simulations of the magnetic field evolution in neutron stars lasting ${\sim } {880}\,$ms (∼6.5 Alfvén crossing periods) and up to resolutions of $0.1155\,$km using Athena++. We explore two different initial conditions, one with purely poloidal magnetic field and the other with a dominant toroidal component, and study the poloidal and toroidal field energies, the growth times of the various instability-driven oscillation modes, and turbulence. We find that the purely poloidal setup generates a toroidal field, which later decays exponentially reaching $1{{\ \rm per\ cent}}$ of the total magnetic energy, showing no evidence of reaching equilibrium. The initially stronger toroidal field setup, on the other hand, loses up to 20 per cent of toroidal energy and maintains this state till the end of our simulation. We also explore the hypothesis, drawn from previous MHD simulations, that turbulence plays an important role in the quasi-equilibrium state. An analysis of the spectra in our higher resolution setups reveals, however, that in most cases we are not observing turbulence at small scales, but rather a noisy velocity field inside the star. We also observe that the majority of the magnetic energy gets dissipated as heat increasing the internal energy of the star, while a small fraction gets radiated away as electromagnetic radiation.

Lattice-based Monte Carlo simulation of the effects of nutrient concentration and magnetic field exposure on yeast colony growth and morphology.

Yeasts exist in communities that expand over space and time to form complex structures and patterns. We developed a lattice-based framework to perform spatial-temporal Monte Carlo simulations of budding yeast colonies exposed to different nutrient and magnetic field conditions. The budding patterns of haploid and diploid yeast cells were incorporated into the framework, as well as the filamentous growth that occurs in yeast colonies under nutrient limiting conditions. Simulation of the framework predicted that magnetic fields decrease colony growth rate, solidity, and roundness. Magnetic field simulations further predicted that colony elongation and boundary fluctuations increase in a nutrient- and ploidy-dependent manner. These in-silico predictions are an important step towards understanding the effects of the physico-chemical environment on microbial colonies and for informing bioelectromagnetic experiments on yeast colony biofilms and fungal pathogens.

Plasma and electrical characteristics depending on an antenna position in an inductively coupled plasma with a passive resonant antenna

We investigated the plasma and electrical characteristics depending on the antenna position in an inductively coupled plasma with a passive resonant antenna. When the powered antenna and passive resonant antenna are installed near the top plate and in the middle of the cylindrical reactor (setup A), respectively, the ion density at the resonance is about 2.4 times to 9 times higher than that at non-resonance. This is explained by the reduction in power loss in the powered antenna (including the matching circuits) and the increase in power absorbed by the plasma discharge. However, when the powered antenna and passive resonant antenna are interchanged (setup B), the ion density at the resonance is not significantly different from that at the non-resonance. When RF power is changed from 50 to 200 W, the ion density at the resonance of setup B is 1.6 times to 5.4 times higher than at the non-resonance of setup A. To analyse this difference, the profile of the z-axis ion density is measured and the electric and magnetic field simulations are investigated. The results are discussed along with the electron kinetics effect and the coupling loss between the antenna and the metal plate.

Evaluation of Lithium-Ion Battery Pack Capacity Consistency Using One-Dimensional Magnetic Field Scanning

The capacity inconsistency among commercial lithium-ion battery packs is an important factor affecting their service life. However, there is still a lack of detection methods to accurately test the capacity consistency of lithium-ion battery packs at cell level. To solve this problem, a non-destructive testing method for capacity consistency of lithium-ion battery pack based on 1-D magnetic field scanning is proposed in this article. First, a magnetic field simulation model and measurement setup of lithium-ion battery are developed to study the principle of detection technology. On such basis, a capacity consistency evaluation method of lithium-ion battery packs is proposed using magnetic field feature extraction and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> -nearest neighbors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> -NNs), and the effectiveness of the method is verified by experimental testing. Finally, measuring factors affecting magnetic field distribution features and practicality of the method are discussed using multi-cells’ magnetic field simulation models. The results show that the proposed method can accurately diagnose the capacity consistency of the tested battery pack, which provides a basis for battery pack performance testing and maintenance.

Nonlinear systems of parabolic IBVP: A stable super-supraconvergent fully discrete piecewise linear FEM

The main purpose of this paper is the design of discretizations for second order nonlinear parabolic initial boundary value problems which are stable and present second order of convergence with respect to H1-discrete norms. The convergence results are established assuming that the solutions are in H3. The stability analysis of numerical methods around a numerical solution requires the uniform boundness of such solution. Although such bounds are usually taken as an assumption, in this paper these will be deduced as a corollary of suitable error estimates. As the methods can be simultaneously seen as piecewise linear finite element methods and finite difference methods, the convergence results can be seen simultaneously as superconvergence results and supraconvergence results. Numerical results illustrating the sharpness of the smoothness assumptions and an application to simulation of the solar magnetic field in the umbra (the central zone of a sunspot) are also included.

Comparative study of the tribology of amorphous carbon films via magnetron sputtering depending on the different magnetic field

The magnetic field configuration of magnetron sputtering has an important influence on films' properties. Here, two kinds of magnetic field configurations, Sm2Co17(outer)/Sm2Co17(inner) and Sm2Co17(outer)/Ferrite(inner), were used to deposit amorphous carbon (a-C) films. Tribo-meter, Nano-indentation, Raman spectroscopy, XPS, high resolution transmission electron microscopy as well as OPERA-2D for magnetic field simulation were employed to study the influence of the magnetic field configuration on the mechanical and tribological properties of a-C films. Our results show that higher coefficients of geometrical unbalance induced a higher deposition rate and a higher hardness of a-C films. However, the friction coefficient shows an inverse trend, and the wear life is short, which can be ascribed to saturation effects via adsorption of H, O, and OH and corrosion wear, which would accelerate the wear rate. Our work will booster interesting to study the magnetic field configurations influence on a-C films properties via magnetron sputtering.

A Comparison of Sparse and Non-sparse Techniques for Electric-Field Inversion from Normal-Component Magnetograms

An important element of 3D data-driven simulations of solar magnetic fields is the determination of the horizontal electric field at the solar photosphere. This electric field is used to drive the 3D simulations and inject energy and helicity into the solar corona. One outstanding problem is the localisation of the horizontal electric field such that it is consistent with Ohm’s law. Yeates (Astrophys. J.836(1), 131, 2017) put forward a new “sparse” technique for computing the horizontal electric field from normal-component magnetograms that minimises the number of non-zero values. This aims to produce a better representation of Ohm’s law compared to previously used “non-sparse” techniques. To test this new approach we apply it to active region (AR) 10977, along with the previously developed non-sparse technique of Mackay, Green, and van Ballegooijen (Astrophys. J.729(2), 97, 2011). A detailed comparison of the two techniques with coronal observations is used to determine which is the most successful. Results show that the non-sparse technique of Mackay, Green, and van Ballegooijen (2011) produces the best representation for the formation and structure of the sigmoid above AR 10977. In contrast, the Yeates (2017) approach injects strong horizontal fields between spatially separated, evolving magnetic polarities. This injection produces highly twisted unphysical field lines with significantly higher magnetic energy and helicity. It is also demonstrated that the Yeates (2017) approach produces significantly different results that can be inconsistent with the observations depending on whether the horizontal electric field is solved directly or indirectly through the magnetic vector potential. In contrast, the Mackay, Green, and van Ballegooijen (2011) method produces consistent results using either approach. The sparse technique of Yeates (2017) has significant pitfalls when applied to spatially resolved solar data, where future studies need to investigate why these problems arise.

Experimental and theoretical investigation on magnetic fluid seal in capillary tube

The application of magnetic fluid (MF) in microfluidics such as micropump and microvalve has been a hot topic recent years. Furthermore, the researches and the applications of MF seal are relatively mature and systematic. However, the seal capacity, which significantly influences the performance of micropump and microvalve, has not been studied specifically and overly. This paper focuses on the theoretical and experimental study about the seal capacity of MF seal in capillary tube. Furthermore, the influence of the clearance between the heads of steel poles, the inner diameter of the capillary tube, and the length of MF plug is investigated numerically and experimentally. In the simulation work, the conventional calculation model of magnetic pressure is applied to the occasion under the presence of low magnetic field and the simulation of magnetic field in the capillary tube is also conducted. Subsequently, the experiments are conducted and compared with our theoretical simulation results. In order to improve the prediction of the theory, the influence of viscosity is considered and the optimized theoretical results are compared with conventional theoretical results, which revealed that the viscosity cannot be ignored in the study of MF seal in capillary tube.

Magnetic field simulations using explicit time integration with higher order schemes

PurposeA transient magneto-quasistatic vector potential formulation involving nonlinear material is spatially discretized using the finite element method of first and second polynomial order. By applying a generalized Schur complement the resulting system of differential algebraic equations is reformulated into a system of ordinary differential equations (ODE). The ODE system is integrated in time by using explicit time integration schemes. The purpose of this paper is to investigate explicit time integration for eddy current problems with respect to the performance of the first-order explicit Euler scheme and the Runge-Kutta-Chebyshev (RKC) method of higher order.Design/methodology/approachThe ODE system is integrated in time using the explicit Euler scheme, which is conditionally stable by a maximum time step size. To overcome this limit, an explicit multistage RKC time integration method of higher order is used to enlarge the maximum stable time step size. Both time integration methods are compared regarding the overall computational effort.FindingsThe numerical simulations show that a finer spatial discretization forces smaller time step sizes. In comparison to the explicit Euler time integration scheme, the multistage RKC method provides larger stable time step sizes to diminish the overall computation time.Originality/valueThe explicit time integration of the Schur complement vector potential formulation of eddy current problems is accelerated by a multistage RKC method.

The Mie representation for Mercury\u2019s magnetospheric currents

Poloidal–toroidal magnetic field decomposition is a useful application of the Mie representation and the decomposition method enables us to determine the current density observationally and unambiguously in the local region of magnetic field measurement. The application and the limits of the decomposition method are tested against the Mercury magnetic field simulation in view of BepiColombo’s arrival at Mercury in 2025. The simulated magnetic field data are evaluated along the planned Mercury Planetary Orbiter (MPO) trajectories and the current system that is crossed by the spacecraft is extracted from the magnetic field measurements. Afterwards, the resulting currents are classified in terms of the established current system in the vicinity of Mercury.Graphical