Induced Magnetic Field Research Articles

Iterative removal of sources to model the turbulent electromotive force

ABSTRACT We describe a novel method to compute the components of dynamo tensors from direct magnetohydrodynamic (MHD) simulations. Our method relies upon an extension and generalization of the standard Högbom CLEAN algorithm widely used in radio astronomy to systematically remove the impact of the strongest beams on to the corresponding image. This generalization, called the Iterative Removal of Sources (IROS) method, has been adopted here to model the turbulent electromotive force (EMF) in terms of the mean magnetic fields and currents. Analogous to the CLEAN algorithm, IROS treats the time series of the mean magnetic field and current as beams that convolve with the dynamo coefficients which are treated as (clean) images to produce the EMF time series (the dirty image). We apply this method to MHD simulations of galactic dynamos, to which we have previously employed other methods of computing dynamo coefficients such as the test-field method, the regression method, as well as local and non-local versions of the singular value decomposition (SVD) method. We show that our new method reliably recovers the dynamo coefficients from the MHD simulations. It also allows priors on the dynamo coefficients to be incorporated easily during the inversion, unlike in earlier methods. Moreover, using synthetic data, we demonstrate that it may serve as a viable post-processing tool in determining the dynamo coefficients, even when the power of additive noise to the EMF is twice as much the actual EMF.

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.

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.

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.

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.

Numerical heat featuring in radiative convective ternary nanofluid under induced magnetic field and heat generating source

The study of nanoliquid characteristics and their heat performance have attracted the interest of engineers. These engineered fluids have high thermal conductivity due to which such liquids are reliable for different engineering applications including heating/cooling of buildings, thermal and mechanical engineering, etc. Therefore, the current research design provides a new ternary nanoliquid model for the heat transport process under induced magnetic field effects, mixed convection, heating source and thermal radiations. The modeling has been done by implementing the ternary fluid characteristics and supportive transformations and then for results simulation; bvp4c is coded successfully. It is scrutinized that a higher inductive magnetic field (0.1–0.4) and nanoparticles amount (0.01–0.07) are better to resist the movement while the wedge parameter ([Formula: see text] promotes it. By promoting the heating source, Eckert and [Formula: see text], the heat transfer process is observed rapidly while the mixed convective number [Formula: see text] controls it. Further, the particular used ternary nanoliquid is examined and found to be good for cooling purposes.

МАТЕМАТИЧНА МОДЕЛЬ МАГНІТОЕЛЕКТРИЧНОЇ МАШИНИ

A mathematical model is proposed for the calculation of electromagnetic parameters of magnetoelectric machines using an analytical method. Permanent magnets are abstracted as equivalent solenoids with constant current represented as current loops. The model differs from known models by the presence of double linear current loops in the stator for the analysis of magnetoelectric machines with a two-layer winding. Additionally, the proposed model considers linear current loops of equivalent solenoids instead of point current loops for a more accurate calculation. The current loops of the stator and rotor are defined at the boundaries of the air gap of the electric machine, i.e., on the smooth slotless surfaces of the magnetic cores. The current loops are expressed for the first time as a product of three variables: current strength, linear current density coefficient, and spatial distribution coefficient. The inductance of stator slots and the resistance of the winding are taken into account using known analytical expressions from classical electric machine theory. The rotor rotation frequency is presented as a function of time. For magnetoelectric machines of specified dimensions and a given variable rotor rotation frequency, the distribution of magnetic field induction, vector magnetic potential, currents, winding spatial distribution coefficients, and electric field intensity of permanent magnets are calculated using the mathematical model. References 7, table 1, figures 4.

Modeling convective transport in a reactive fluid near a vertical pervious plate influenced by intense magnetic forces, induced magnetic field, Hall current and thermo-diffusion

Exploring convective transport in conducting fluids under potent magnetic influences yields essential insights into numerous natural and designed systems. Such insights aid researchers and engineers in making enlightened progressions in their domains. This paper delves into the convective motion in a reactive fluid moving past a vertically perforated plate, governed by intense magnetic forces, the induced magnetic field (IMF) and Hall current. The model integrates factors like thermal radiation and thermo-diffusion (Soret effect). Formative equations for this model, which encapsulate the effects of distinct physical phenomena, are solved analytically. Graphical representations illuminate the influence of vital flow parameters on velocity, temperature, concentration fields, shear stresses and the rates of heat and mass transfer. From the graphs, it’s evident that Hall currents hinder the primary flow but enhance the secondary flow. A rise in radiation and suction parameters leads to a temperature drop. A heightened Soret number appears to magnify concentration distribution throughout the boundary layer. Intensifying suction at the plate diminishes the boundary layer’s thickness, which in turn elevates the heat and mass transfer rate. This physical model finds extensive applicability across sectors, encompassing metallurgy, magnetic fusion, plasma physics, materials fabrication, geothermal phenomena, geochemistry and ionospheric activities.

Static Magnetic Field Reduces the Anticancer Effect of Hinokitiol on Melanoma Malignant Cells-Gene Expression and Redox Homeostasis Studies.

Melanoma malignant is characterized by a high mortality rate, accounting for as much as 65% of deaths caused by skin cancer. A potential strategy in cancer treatment may be the use of natural compounds, which include hinokitiol (β-Thujaplicin), a phenolic component of essential oils extracted from cypress trees. Many studies confirm that a high-induction SMF (static magnetic field) has anticancer effects and can be used as a non-invasive anticancer therapy in combination with or without drugs. The aim of this experiment was to evaluate the effect of a static magnetic field on melanoma cell cultures (C32 and COLO 829) treated with hinokitiol. Melanoma cells were exposed to a static magnetic field of moderate induction and hinokitiol. The research included determining the activity of the antioxidant enzymes (SOD, GPx, and CAT) and MDA concentration as well as the gene expression profile. Hinokitiol disturbs the redox homeostasis of C32 and COLO 829 melanoma malignant cells. Moreover, a static magnetic field has a protective effect on melanoma malignant cells and abolishes the anticancer effect of hinokitiol.

Ion activity in quasi-neutral current sheets and discharge plasma in crossed electric and magnetic fields

As part of a brief review, a classification is made and information is provided about four experimentally discovered plasma effects, where unexpected behavior of the ionic component appeared and for which there is no unambiguous interpretation. 1. Ions with the highest energies for a quasi-neutral current sheet were recorded at the O-point (island) with the direction of their movement opposite to the electric field at the X-point. 2. In a self-sustaining discharge in crossed electric and magnetic fields (E×B discharge), a large number of ions (not the tails of the distribution function) with energies significantly exceeding the energies equivalent to the discharge voltage are generated. This occurs in a certain range of pressures of the plasma-forming gas and magnetic fields. 3. The discovered region of effective ionization — the “anode layer”, with increasing pressure, moves abruptly from one plasma region to another, which is accompanied by a jump in the ion density up to 16 times. An increase in the magnetic field induction causes, on the contrary, the “anode layer” to jump in the opposite direction with the ion density decreasing 3–4 times. 4. Ion distribution functions in the E×B discharge contain isomagnetic density jumps with a relative amplitude from ~30 to 80 % of the total current at the released energy. Taking into account the “anomalous” behavior of ions in the plasma of quasi-neutral current sheets and discharges in crossed electric and magnetic fields will provide further insight into the processes in space plasma, the physics of coronal heating, and the formation of the solar wind.

Ионная активность в квазинейтральных токовых слоях и плазме разрядов в скрещенных электрическом и магнитном полях

As part of a brief review, a classification is made and information is provided about four experimentally discovered plasma effects, where unexpected behavior of the ionic component appeared and for which there is no unambiguous interpretation. 1. Ions with the highest energies for a quasi-neutral current sheet were recorded at the O-point (island) with the direction of their movement opposite to the electric field at the X-point. 2. In a self-sustaining discharge in crossed electric and magnetic fields (E×B discharge), a large number of ions (not the tails of the distribution function) with energies significantly exceeding the energies equivalent to the discharge voltage are generated. This occurs in a certain range of pressures of the plasma-forming gas and magnetic fields. 3. The discovered region of effective ionization — the “anode layer”, with increasing pressure, moves abruptly from one plasma region to another, which is accompanied by a jump in the ion density up to 16 times. An increase in the magnetic field induction causes, on the contrary, the “anode layer” to jump in the opposite direction with the ion density decreasing 3–4 times. 4. Ion distribution functions in the E×B discharge contain isomagnetic density jumps with a relative amplitude from ~30 to 80 % of the total current at the released energy. Taking into account the “anomalous” behavior of ions in the plasma of quasi-neutral current sheets and discharges in crossed electric and magnetic fields will provide further insight into the processes in space plasma, the physics of coronal heating, and the formation of the solar wind.

Enhancing electric vehicle charging performance through series-series topology resonance-coupled wireless power transfer.

The current electric vehicles (EVs) market is experiencing significant expansion, underscoring the need to address challenges associated with the limited driving range of EVs. A primary focus in this context is the improvement of the wireless charging process. To contribute to this research area, this study introduces a circular spiral coil design that incorporates transceiver coils. First, an in-depth analysis is conducted using Ansys Maxwell software to assess the effectiveness of the proposed solution through the magnetic field distribution, inductance properties, and mutual inductance between receiver and transmitter coils. In the next step, a direct shielding technique is applied, integrating a ferrite core bar to reduce power leakage and enhance power transmission efficiency. The ferrite magnetic shielding guides magnetic field lines, resulting in a significant reduction in flux leakage and improved power transmission. Lastly, a magnetic resonance series (SS) compensation wireless system is developed to achieve high coupling efficiency and superior performance. The system's effectiveness is evaluated through co-simulation using Ansys Simplorer software. The results confirm the effectiveness of the proposed solution, showing its ability to transmit 3.6 kilowatts with a success rate approaching 99%. This contribution significantly advances the development of wireless charging systems for electric vehicles, addressing concerns and promoting global adoption.

Exploring the contraction actuation of magnetically functionalized electrospun tubes

Recently, magnetically functionalized polymer tubes (MFPTs) have been fabricated through a multistep electrospinning process. These innovative MFPTs can serve as ducts suitable for microfluidic components and biomedical devices. Considering these applications, it is crucial to investigate the effectiveness of inducing oscillating contractions at low frequencies. For this purpose, we designed an experimental setup to study the cross-sectional contraction of these smart tubes when subjected to a magnetic field produced by the oscillation of a small permanent magnet. A magnetoelastic wave resonator placed near the MFPT section detects the induced contraction, enabling the calculation of both its magnitude and response times. The results demonstrate that oscillating contractions, resulting in a maximum reduction of duct radius by approximately 43%, can be achieved with an oscillating magnetic induction field of amplitude around 10 mT, at a low frequency not exceeding 1/2 Hz. These findings highlight the potential of such innovative MFPTs, particularly in the fields of surgery and endoscopy.

Modeling the Temperature Dependence of Shubnikov-De Haas Oscillations in Light-Induced Nanostructured Semiconductors

In this work, the influence of light on the temperature dependence of transverse magnetoresistance oscillations is studied. A generalized mathematical expression that calculates the temperature and light dependence of the quasi-Fermi levels of small-scale p-type semiconductor structures in a quantizing magnetic field is derived. New analytical expressions have been found to represent the temperature dependence of transverse differential magnetoresistance oscillations in dark and light situations, taking into account the effect of light on the oscillations of the Fermi energy of small-scale semiconductor structures. A mathematical model has been developed that determines the light dependence of the second-order derivative of the transverse magnetoresistance oscillations of p‑type semiconductors with quantum wells by magnetic field induction. A new theory is proposed, which explains the reasons for the significant shift of the differential magnetoresistance oscillations along the vertical axis measured in the experiment for dark and light conditions.

Electromagnetic forming of AA1060 sheet based on mixed forces generated by a three-coil dual-power system

The electromagnetic force used in electromagnetic forming is mainly divided into attraction and repulsion. Dual-coil attractive electromagnetic forming can be used in the field of sheet pit repair. However, the magnetic field and eddy current generated by the two coils compete with each other, and the energy utilization rate is low. Therefore, a compensation coil is introduced, and an electromagnetic forming scheme of a three-coil dual-power sheet based on mixed force is proposed and verified by simulation. It is found that the three-coil mixed force can effectively improve the competition between the magnetic field and eddy current. The loading of the mixing force is not a simple superposition of attraction and repulsion, but the mutual promotion of the two. The forming displacement of the three-coil mixed force forming scheme is 582% higher than that of the dual-coil attraction forming scheme, and 89% higher than that of the attract first and then repel forming scheme. The forming effect of the three-coil mixing force is related to the number of turns of the compensation coil. The research results can improve the energy utilization rate of electromagnetic forming and provide a new idea for the loading scheme of electromagnetic forming force field.

Stellar Cycle and Evolution of Polar Spots in an M+WD Binary

Stellar activity cycles reveal continuous relaxation and induction of magnetic fields. The activity cycle is typically traced through the observation of cyclic variations in total brightness or Ca H&K emission flux of stars, as well as cyclic variations in the orbital periods of binary systems. In this work, we report the identification of a semidetached binary system (TIC 16320250) consisting of a white dwarf (0.67 M ⊙) and an active M dwarf (0.56 M ⊙). The long-term multiband optical light curves spanning twenty years revealed three repeated patterns, suggestive of a possible activity cycle of about 10 years of the M dwarf. Light-curve fitting indicates the repeated variation is caused by the evolution, particularly the motion, of polar spots. The significant Ca H&K, Hα, ultra-violet, and X-ray emissions imply that the M dwarf is one of the most magnetically active stars. We propose that in the era of large time-domain photometric sky surveys (e.g., ASAS-SN, Zwicky Transient Facility, LSST, Sitian), long-term light-curve modeling can be a valuable tool for tracing and revealing stellar activity cycle, especially for stars in binary systems.

Design of differential probe with harmonic magnetic field and its data process method

To identify the condition of steel pipelines beyond the line of sight during operation, this study presents a design methodology for a differential probe, along with a harmonic magnetic field excitation technique and its corresponding data processing methodology. The coaxial arrangement of the excitation coils in a planar configuration generates a potent induced magnetic field, ensuring a sufficient standoff distance. Under the influence of harmonic excitation, the magnetic permeability of the pipeline surface decreases, resulting in an increased detection depth. Periodic alterations in the magnetic permeability of the pipeline surface enhance the amplitude of defects. Adjusting the position of the induction coil minimizes interference from the excitation magnetic field, thereby obtaining a pure induced magnetic field. Differential processing is applied to the two induction coils to counteract interference from the background magnetic field. Finally, the effectiveness and reliability of this probe are validated through three experiments: pipeline positioning, weld seam inspection, and damage detection.

Granular Aluminum Kinetic Inductance Nonlinearity

Granular Aluminum is a superconductor known for more than eighty years, which recently found its ap-plication in qubits, microwave detectors and compact resonators, due to its high kinetic inductance, critical magnetic field and critical current. Here we report on the nonlinear dependence of granular Aluminum inductance on current, which hints towards parametric amplification of the microwave signal in granular Aluminum films. The phase shift of the microwave signal reached 4 rad at a frequency of 7 GHz, which makes it possible to estimate the nonlinearity of the system as \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta \\phi {\ ext{/}}\\phi = 1.4{\\kern 1pt} \\% $$\\end{document} and the potential gain of the order of 17 dB.

Variation of magnetic properties with current in ferrimagnetic semiconductor Mn3Si2Te6

Orbital currents play a fundamental role in a wide range of transport phenomena. Recently, the discovery of a novel chiral orbital current state in the ferrimagnetic nodal-line semiconductor Mn3Si2Te6 has attracted significant interest, supported by anomalous I–V characteristics and time-dependent bistable switching. However, the direct experimental verifications, combining electrical transport and magnetic measurement, that detect the variation of the magnetic properties vs the current are still rare. Here, we investigate the transport properties of Mn3Si2Te6 and track the current-induced dynamics of the magnetic moment. Reflective magnetic circular dichroism reveals that significant alterations in Mn3Si2Te6 magnetoresistance in response to an electric field are necessarily coupled with a magnetic phase transition, establishing a rare correlation. Our findings indicate the predominance of magnetic chiral orbital currents in the colossal angular magnetoresistance effect, offering a unique platform for advanced studies in orbital magnetism.