Magnetic Induction Research Articles

Numerical Analysis of the Influence of a Magnetic Field on the Group Dynamics of Iron-Doped Carbon Nanotori

Columnar phases consisting of a group of carbon toroidal molecules (C120, C192, C252, C288) are studied numerically. Each nanotorus was previously doped with an iron atom. This made it possible to use an external magnetic field as a tool for influencing both an individual molecule and a linear fragment of the columnar phase. A high-precision scheme for calculating the dynamics of large molecules with a rigid frame structure is proposed to solve the problem. The group dynamics of nanotori clusters under the influence of an external magnetic field has been studied using classical molecular dynamics methods. The influence of the molecular cluster size, temperature, magnetic moment of the molecule, and magnetic field direction on the collective behavior of iron-doped toroidal molecules with different contents of carbon atoms is analyzed. Molecular dynamics calculations showed that systems of nanotori doped with a single iron atom retain a columnar structure both in the absence and in the presence of an external magnetic field. The columnar fragment behaves as a stable linear association of molecules even at sufficiently high values of magnetic induction, performing a coordinated collective orbital rotation around a common center of mass on a nanosecond time scale.

A smart structural optimization method of magnetorheological damper for ultra-precision machine tool

To address the problem of multi-source vibration in ultra-precision machine tools, a vibration reduction stand was designed by replacing passive damping components with magnetorheological dampers (MRDs). In this work, the structural parameters of MRDs were optimized using an improved pelican optimization algorithm (IPOA) to realize the maximum capability in reducing vibration. Firstly, the working principle of MRDs was explained, and the mathematical models of MRDs were established. Then, an IPOA based on singer chaotic mapping, nonlinear inertia weight factor, and Cauchy mutation strategy was proposed to enhance the global search capability and convergence efficiency of the algorithm. Subsequently, the IPOA was applied to optimize key structural parameters of MRDs, including output damping force, controllable damping range, response time, and power consumption. Finally, COMSOL Multiphysics software was used to verify the effectiveness of the proposed algorithm by comparing the magnetic induction intensity distribution of MRDs before and after optimization, as well as the variation of the four performance indexes under the different applied currents. After being optimized using the proposed IPOA, the MRDs can deliver a larger maximum damping force and a wider damping controllable range, with less power consumption and quick response, which could meet the requirement for vibration suppression of ultra-precision machine tools.

Phase-field modeling of fracture for ferromagnetic materials through Maxwell’s equation

Electro-active materials are classified as electrostrictive and piezoelectric materials. They deform under the action of an external electric field. Piezoelectric material, as a special class of active materials, can produce an internal electric field when subjected to mechanical stress or strain. In return, there is the converse piezoelectric response, which expresses the induction of the mechanical deformation in the material when it is subjected to the application of the electric field. This work presents a variational-based computational modeling approach for failure prediction of ferromagnetic materials. In order to solve this problem, a coupling between magnetostriction and mechanics is modeled, then the fracture mechanism in ferromagnetic materials is investigated. Furthermore, the failure mechanics of ferromagnetic materials under the magnetostrictive effects is studied based on a variational phase-field model of fracture. Phase-field fracture is numerically challenging since the energy functional may admit several local minima, imposing the global irreversibility of the fracture field and dependency of regularization parameters related discretization size. Here, the failure behavior of a magnetoelastic solid body is formulated based on the Helmholtz free energy function, in which the strain tensor, the magnetic induction vector, and the crack phase-field are introduced as state variables. This coupled formulation leads to a continuity equation for the magnetic vector potential through well-known Maxwell’s equations. Hence, the energetic crack driving force is governed by the coupled magneto-mechanical effects under the magneto-static state. Several numerical results substantiate our developments.

The effect of a rotating magnetic field on the antioxidant system in healthy volunteers - preliminary study.

Oxidative stress is characterized by an excessive concentration of reactive oxygen species (ROS) resulting from a disturbance in the balance between ROS production and their removal by antioxidant systems (SOD, CAT, GPx). Prolonged and intense oxidative stress can cause various forms of damage to cells, which markers are total antioxidant capacity (TAC), reactive oxygen species modulator (ROMO1), and malondialdehyde (MDA). It has been demonstrated that magnetic fields can positively affect human health, for example, by reducing oxidative stress. Determination of the effect of a rotating magnetic field (RMF) on the activity/concentration of selected oxidative stress markers. A group of 30 healthy volunteers (15 women and 15 men) (mean age 24.8 ± 5.1) in the study classified into the following groups: internal control group (CG);1h 25Hz (samples placed in the field for one hour at 25Hz); 3h 25Hz (samples placed in the field for 3h at 25Hz), the 1h 50Hz group ( placed in RMF for an hour at 50Hz), and a group of 3h 50Hz (samples placed in the field for 3h at 50Hz). Serum samples were collected in K2EDTA tubes.. The magnetic induction value obtained for RMF is 37.06 mT and 42.64 mT.Activity/concentration of selected oxidative stress markers was analyzed by ELISA. The influence of an RMF on the activity/concentration of SOD, MDA, TAC, and ROMO1 was demonstrated (p < 0.001; p = 0.0013; p < 0.001; p = 0.003). The RFM can reduce oxidative stress, as evidenced by higher SOD and CAT activities in the CG than in samples placed in the RFM. Prolonged exposure to the RFM at 50Hz increased the TAC level, indicating an intensification of oxidative stress in these samples. The optimal conditions for staying in the RFM (reducing oxidative stress) are 1h 50Hz for SOD and MDA; 3h 25Hz for CAT and TAC. In the case of ROMO1, it is stated that 1h 25Hz are the optimal conditions for no increased production of ROS.

Impact of magnetic induction on the flow of self-rewetting power-law fluid over a disk surface: Onset of Marangoni convection

In the present investigation, the onset of Marangoni convection in the flow of self-rewetting fluid over a stretching disk has been discussed. The self-rewetting fluid is considered to be electrically conducting and the flow problem is discussed under the influence of an induced magnetic field. The fluid flow is mainly induced due to two different mechanisms: (i) onset of Marangoni convection due to presence of temperature gradient along the liquid-gas interface and (ii) induction of magnetic field due to presence of an external magnetic field, which modifies the original field. The governing partial differential equations are written, following Navier-stokes equations and Prandtl boundary layer equation. With the use of similarity transformations, the governing equations are turned into a system of ordinary differential equations. Nonlinear systems of ordinary differential equations are solved by the bvp4c technique. The reciprocal of the magnetic Prandtl number diminishes the induced magnetic profile.

Periodic magnetically oriented gradient structures with flower-like surface for enhancing microwave absorption efficiency

In order to overcome the inherent trade-off between magnetic absorber's effective absorption, filling concentration, and thickness while achieving real-time control over the effective absorption bandwidth (EAB) below −10 dB, periodic magnetically oriented gradient structures featuring flower-like surfaces that can be reconfigured using magnetic induction technology. The arch test results demonstrated that even with particle filling concentration of only 30 wt%, reflection loss (RL) of the magnetically oriented periodic gradient structures achieved −37.5 dB, and EAB could be extended to 6.5 GHz, outperforming samples 60 wt%–0 mT. Especially for samples 50 wt%–100 mT, which EAB with four distinct peaks in its EAB reaching 10.5 GHz. This was due to magnetically-oriented macro–micro structure that facilitated to reduce hyperosmotic threshold of conductive loss network of absorbing material. Meanwhile, the gradient structure with flower-like surface was conducive to absorption peaks, impedance matching patterns and electromagnetic wave scattering. The reconfigurable structure was also found to have remarkably stability, maintaining its nearly uniform electromagnetic loss capability even after 3 months. This study is scientifically important for establishing the regulatory mechanism of orientation distribution structure on EAB and absorption resonance peaks, as well as providing an experimental and theoretical foundation for exploring low detectable and electromagnetic protection devices.

On the Uniqueness of the Solution to the Inverse Problem of Determining the Diffusion Coefficient of the Magnetic Field Necessary for Constructing Analytical Models of the Magnetic Field of Mercury

This paper considers the problem of the uniqueness of the solution to the coefficient inverse problem for the system of equations of magneto-hydrodynamics, the solution to which allows more accurately describing the processes of generating the magnetic field of planets with a magneto-hydrodynamic dynamo. The conditions under which it is possible to determine three components of the magnetic induction vector and the magnetic field diffusion coefficient are determined.

Magnetic induction heating-assisted synthesis of biodiesel using an alumina/iron oxide nanocatalyst

While generating biodiesel from vegetable oils presents various advantages over fossil fuels, ongoing actions aim to improve the efficiency of this production process. Emphasis is placed on optimizing experimental conditions, including the catalyst selection, reaction media and the energy source for heating and mixing, thereby revealing existing research gaps in biodiesel production. In this sense, we have designed a magnetic nanocatalyst based on iron oxide nanoparticles (IONPs) of 18 nm in diameter incorporated within an alumina matrix of around 500 nm infused with potassium hydroxide that provides the catalyst's mesoporosity and basicity. Magnetization analyses confirmed the superparamagnetic behaviour of the nanocatalyst at room temperature and a saturation magnetisation high enough to ease magnetic recovery for reuse. Additionally, magnetic nanoparticles can serve as nanoheaters when subjected to an alternating magnetic field. The heating efficiency of the isolated IONPs was assessed under various frequency and field conditions, yielding specific absorption rate values of up to 80 W/g. Such heating capacity has allowed the synthesis of fatty acid methyl ester (FAMEs), which constitute the biodiesel at 65 °C under optimal field conditions (100 kHz and 48 kA/m) and ideal reaction parameters: 5 % catalyst, methanol/oil ratio 12:1 and 6 h of reaction, with a conversion of up to 98.6 % determined through NMR characterization of the FAMEs and a 95.6 % yield. FAMEs presence was confirmed by optimizing a swift and efficient FTIR method and their purity by TLC. Overall, the designed nanocatalyst presented for FAME synthesis, which incorporates magnetic separability and effective heating capabilities, holds great promise for cost reduction and process efficiency.

On-line minimum loss control strategy of IPMSM in torque-controlled application

This study proposes an on-line minimum loss (ML) control strategy that considers the iron and copper losses of an interior permanent magnet synchronous motor in torque-controlled applications. The proposed ML control strategy utilizes a constrained optimization problem to satisfy torque reference tracking and loss minimization. An equivalent iron loss resistance circuit is adopted for the loss minimization. To solve the optimization problem, the Lagrange multiplier method is applied through a numerical analysis algorithm. The resulting solution provides the optimal current reference for every sampling instant. The Lagrange multiplier method needs parameters such as magnetic flux linkages, dynamic inductances, and iron loss resistance. Fundamental magnetic flux linkages are estimated using a flux observer, and the dynamic inductances are estimated with high-frequency voltage signal injection. The proposed iron loss resistance estimator estimates the equivalent iron resistance without any preliminary experiments. DC input power is measured using a current sensor for the accurate on-line estimation of iron loss resistance. To analyze the effectiveness of ML control compared with conventional maximum torque per ampere control, finite element analysis is used. The feasibility of the proposed ML control strategy is verified through simulation and experiments.

Functional magnetic resonance imaging of the brain in patients with insomnia: a prospective study

INTRODUCTION: Insomnia is one of the most common sleep disorders, the interest of scientists in the occurrence and pathophysiology of insomnia is growing every year. In particular, the brain connectome and its changes in sleep disorders are being actively studied based on the data of resting state functional magnetic resonance imaging.OBJECTIVE: The study is to assess changes in brain connectomes in patients with chronic insomnia using functional magnetic resonance imaging.MATERIALS AND METHODS: 53 people took part in the study, of which 34 patients who applied for a somnologist’s appointment at the Almazov National Research Medical Center of the Ministry of Health of the Russian Federation were diagnosed with chronic insomnia, confirmed by polysomnography. All participants of the study had an MRI of the brain on tomographs with a magnetic field induction force of 3.0 Tl at two time points.Statistics: Statistical analysis of MRI data was performed using MathLab 2018a, CONN v1.7. Descriptive statistics, the Kolmogorov-Smirnov criterion were used to process the materials, depending on the characteristics of the data, the MannWhitney U-criterion and Pearson Chi-squared were used to analyze demographic data.RESULTS: The study, neuroimaging markers of insomnia were identified and changes in the functional networks of the brain were described in patients with insomnia and a group of healthy volunteers at different time points.DISCUSSION: The obtained functional data demonstrate ambiguous results. Both an increase and a decrease in the functional connectivity of the medial prefrontal cortex with the structures of the visual analyzer, an increase in functional connections with the temporal pole, in particular with the hippocampus, is determined, which indicates changes in the consolidation of visually encoded information. The relative limitation in this study can be considered the heterogeneity of the age composition of the group.CONCLUSSION: Resting state functional MRI of the brain is a key neuroimaging method in determining the functional connections of the brain in patients with sleep disorders, which allows us to establish a impairment of functional interaction between brain structures involved in the processes of falling asleep and maintaining sleep.

The influence mechanism of Halbach array magnetic field control on discharge channels in EDM

The use of magnetic field to actively control Electrical Discharge Machining(EDM) can effectively improve the problems of low material removal rate and poor surface quality, but due to the limitation of materials, the magnetic induction intensity of permanent magnets after magnetization is not high, and the magnetic induction lines of permanent magnets are too concentrated and difficult to control. In order to overcome the above shortcomings, this study applied the Halbach array magnetic field to the field of EDM for the first time, established a model of the trajectory of the charged particle beam in the discharge channel, analyzed the influence of the Halbach array magnetic field on the discharge channel, and clarified the improvement mechanism of the Halbacch array magnetic field in EDM. In addition, several sets of experiments were carried out by controlling the distance between the workpiece and the working surface of the Halbach array permanent magnets. The experimental results show that when the distance between the workpiece and the working surface of the Halbach array permanent magnet is less than 10mm, the material erosion rate of the workpiece increases significantly, and the electrode loss rate and surface roughness decrease significantly. When the workpiece is 0mm away from the working surface, the material removal rate is increased by 18.18%, from 0.4513mm3/min to 0.5333mm3/min, the tool wear ratio is reduced by 46.87%, from 0.2587 to 0.13745 mm3/min, and the surface roughness is reduced by 39.56%, from 4.186 μm to 2.53 μm.

A central vein sign in the magnetic resonance diagnosing of multiple sclerosis

Background. Multiple sclerosis (MS) is a chronic autoimmune demyelinating disease, which is characterized by the inevitable disability of patients in the long term, which determines the relevance of this problem. Currently, active improvements are being made in the methods of diagnosing multiple sclerosis, which include the use of the central vein sign in magnetic resonance imaging (MRI) as a neuroimaging biomarker of MS with high sensitivity and specificity.Aim of study. Determination of the possibility of assessing the central vein sign (CVS) according to MRI data as a potential diagnostic biomarker of MS.Object and methods. An open single-center prospective study of brain MR data was conducted in 55 patients with a verified diagnosis of MS (EDSS 1.0-6.5) aged 19 to 72 years. MR-images were obtained on a tomograph with a magnetic field induction force of 3.0 T. Patients underwent MRI of the brain according to the standard protocol: T2-VI, FLAIR, T1-VI (before and after administration of contrast agent), SWI. A comprehensive statistical analysis and evaluation of the obtained MRI data was performed using the Statistica 12 program.Result. During the evaluation of MR-tomograms, all patients with a verified diagnosis in the foci of MS were found to have CVS. In 14.5 % of patients, CVS was detected in 10-30 % of foci, in 61.8 % of patients in 30-60 %, in 23.6 % of patients, from 60 to 95 % was detected. Accordingly, 52.7 % of patients overcame the threshold value of 45 % required for the differential diagnosis of MS from other conditions.Conclusion. The use of CVS in MRI helps to solve the problem of differential diagnosis of MS from other demyelinating diseases when using its threshold criterion – the percentage of foci containing central veins.

Special texture evolution behavior of strip-cast non-oriented electrical steel combined with in-situ experiment and CPFEM

The impact of shear deformation on texture evolution in strip-cast Fe-1.5%Si non-oriented electrical steel was studied combined with in-suit experiments and crystal plasticity finite element method (CPFEM). Throughout the deformation process, the texture evolution predominantly follows a traditional route: transitioning from {211}<036> and {411}<148> to {111}<112> orientation. In certain regions with specific stress conditions, orientation evolution shifts from {310}<236> to {411}<148>, {100}<021>, and finally to {100}<001> orientation. Crystal plasticity finite element (CPFE) simulation results show that the rotation of {310}<236> through {411}<148> to {100}<021> orientation, {211}<236> and {112}<110> orientations transition to {111} and {110} orientations, respectively, which is consistent with the experimental observations. Recrystallization texture mainly includes favorable λ and near-λ (<100>∥ND, normal direction) textures, with detrimental γ (<111>∥ND) texture essentially diminishing. In-situ heating experiments revealed {411}<148> as the primary recrystallization orientation, the mechanism involves both oriented nucleation and growth. In the edge region lacking stress constraints, the Schmid factor (SF) reaches up to 0.48, the (21-3)[111] slip system is preferentially activated, with shear bands appearing earlier in the same region. Indicating that when slip mechanism alone are inadequate for sustaining plastic deformation, the shear deformation becomes the favored mode of activation. {411}<148> orientation can serve as a transitional orientation for transitioning to {100} orientation, and further as an advantageous transitional orientation during the nucleation and growth of recrystallization. Due to the texture improvement, superior magnetic properties were achieved, with the average magnetic induction (B50) and iron loss (P1.5/50) being 1.77 T and 4.25 W/kg, respectively.

Magnetic Micro and Nano Sensors for Continuous Health Monitoring

Magnetic micro and nano sensors can be used in a broad variety of applications, e.g., for navigation, automotives, smartphones and also for health monitoring. Based on physical effects such as the well-known magnetic induction, the Hall effect, tunnel magnetoresistance and giant magnetoresistance, they can be used to measure positions, flow, pressure and other physical properties. In biomedicine and healthcare, these miniaturized sensors can be either integrated into garments and other wearables, be directed through the body by passive capsules or active micro-robots or be implanted, which usually necessitates bio-functionalization and avoiding cell-toxic materials. This review describes the physical effects that can be applied in these sensors and discusses the most recent micro and nano sensors developed for healthcare applications.

Magnetic Induction Heating-Driven Flow Chemistry Enabling Uniform and Continuous Growth of Metal–Organic Frameworks in Confined Microchannels of Wood

Magnetic Induction Heating-Driven Flow Chemistry Enabling Uniform and Continuous Growth of Metal–Organic Frameworks in Confined Microchannels of Wood

The method for noninvasive investigation of the boundaries of homogeneous magnetizable inclusions inside a biological object

Currently, in modern medicine and related areas of medical technology, the problem of noninvasive investigation of the internal structure of a biological object with the aim of detecting and subsequently visualizing hidden metallic foreign inclusions in the body is becoming increasingly important. Determining the spatial position and identifying the boundaries of such inclusions in the body can be a rather time-consuming process, as solving this problem is mainly done through noninvasive methods of introscopy, which require very careful application. Thus, a method for noninvasive investigation of hidden differently oriented homogeneous inclusions that allow for magnetization by an externally periodically time-varying magnetic field inside a biological object, is proposed in the study. This is achieved by representing the investigated volume as a set of parallel sections and measuring the distribution of the vector function of magnetic field induction in each of them using a working element in the form of spatially oriented contours based on a pair of inductance coils with an equal number of turns and opposing winding inclusion. This allows for non-invasive tomographic scanning of a biological object aimed at detecting the refraction effect of the altered vector field of magnetic field induction, followed by the reconstruction of inclusions based on projection data. The reconstruction is carried out using the back-projection method with prior spatial filtering in the original area through convolution of projection data with a convolution function.

Influence of design and annealing parameters on measurements of AC properties of NiFe-SiO2 multilayer structures

In this article, due to the exceptionally interesting electrical and magnetic properties of nanocomposites, which include ferromagnetic materials in a dielectric matrix, multilayer NiFe-SiO2 nanocomposites were obtained. The entire sequence of technological processes using magnetron sputtering equipment in the presence of argon was presented, the aim of which was to create structures with different numbers and thicknesses of layers, as well as in two measurement configurations. Measurements of AC electrical properties were carried out in a variable temperature range, i.e. from room temperature to 373 K, using the 4-point method. The obtained measurement results were compared in terms of design parameters, such as thickness and number of layers, as well as technological parameters, such as heating duration. Structural analysis was performed using scanning electron microscopy (SEM) to investigate the effect of oxidation on the multilayer structures and to confirm the granular structure of the nanocomposite. Additionally, the chemical composition of the obtained multilayers was examined using Energy-dispersive X-ray spectroscopy (EDX). Resistive parameters were tested in the range of magnetic field induction from 0 T to 0.3 T. Based on the conductivity relationships, it was proven that a hopping mechanism of current conduction occurs in the tested samples. Using the frequency dependencies of the phase shift angle, it is possible to adjust the equivalent RC electronic circuit, thereby determining the potential application of the tested materials.

A novel adjustable magnetorheological fluid gradient material of low frequency vibration isolation: a theoretical and experimental study

In this paper, a novel adjustable magnetorheological fluid (MRF) gradient material for low-frequency control is proposed, and the vibration isolation performance of this gradient material is investigated theoretically and experimentally. The gradient material has an excellent ability to control the sound waves and vibrations. However, the currently prepared gradient material does not have the parameter adjustability. At the same time, the MRF can change its material parameters according to the external magnetic field. After applying the traveling magnetic field (TMF) to the MRF with continuously varying and adjustable magnetic induction strength, its material parameters will also be continuously varying and adjustable to constitute an adjustable gradient material. In order to investigate the vibration transfer characteristics of this adjustable gradient material, this paper establishes a micro-mechanical model of MRF and theoretically investigates and numerically calculates the mechanical impedance and vibration transfer characteristics of the adjustable gradient material through the machine-electric analogy theory. At the same time, experimental research was conducted by building an experimental platform to conduct experiments. The results show that the novel adjustable gradient material composed of a TMF and MRF has a good vibration suppression effect in the low-frequency range (10 ∼ 60 Hz) with the vibration level difference of up to 30 dB or more, which has a broad application prospect in the field of vibration control.

Organic package substrate embedded coupled magnetic core inductors using lithographic via technology for power supply in package

In this work, a cost-effective organic package substrate embedded coupled magnetic core inductor technology is proposed and demonstrated for power supply in package applications. Based on a novel lithographic via process, it involves a solid copper pillar electroplating step for creating a groove and integration of the vertical interconnects of the inductor. The primary and secondary windings of the coupled inductor are interleaved on the rectangular magnetic composite core which is accommodated within the groove. The coupled inductor combines solid vertical interconnecting with low loss magnetic composite core, therefore bringing together tight process tolerances and superior current capability. Experimental results show that the 2.9-mm2 coupled inductor achieves a high inductance to resistance ratio of 0.28 nH/mΩ, and a coupling factor of 0.57. In addition, the proposed inductor achieves an ultra-high saturation current of 16.52 A that is the highest reported value for a high-frequency integrated magnetic core inductor to the best of our knowledge. The performance of the coupled inductor has been calculated for a standard 1.8 to 1 V interleaved converter. Notably, it demonstrated a remarkable efficiency exceeding 95% across a wide range of phase currents between 0.11 and 2.32 A.

ANALYSIS OF THE CHARACTERISTICS AND CAPABILITIES OF MODERN VIBRATION AND STRAIN GAUGES OF MODERN MEASURING EQUIPMENT

The article analyses the characteristics and capabilities of modern vibration and strain gauges, as well as the existing requirements for vibration measurement devices for wheeled armoured vehicles. The main physical parameters for assessing the strength and vibration characteristics of wheeled armoured vehicles to be measured are determined. Modern accelerometers for measuring vibration have better universal characteristics compared to other types of sensors, as well as a wide frequency and dynamic linearity range. The use of piezoelectric, strain gauge, magnetic induction and laser measuring equipment will allow to obtain physical values of vibration parameters and the stress-strain state of wheeled armoured vehicles and, using data acquisition systems and software, to analyse deviations of limit values in the design and components of the vehicle.&#x0D; Improvement of the methodological apparatus for experimental studies of strength and vibration characteristics during testing of wheeled armoured vehicles will improve the quality and simplify the measurement process, which in turn will significantly reduce the time for testing prototypes and ensure timely delivery of weapons and military equipment (components) to the Armed Forces of Ukraine. The use of modern vibration and strain gauges to assess the strength and vibration characteristics of structures and their components will simplify and automate the measurement process, minimising possible errors during testing of armoured vehicles. The results of the work can be used for a rational and justified selection of vibration and strain gauges for testing wheeled armoured vehicles.