Induced Magnetic Field Research Articles

Miniaturization and Cross-Polarization Reduction of Quarter-Wave Microstrip Antennas Based on Magnetic Currents Reconstruction

In this work, a simple method is proposed to simultaneously reduce the size and cross-polarization level (XPL) of quarter-wave microstrip antennas by reconstructing the magnetic currents along the radiation edges. A design example of five shorted elements is given with a comparison of the quarter-wave microstrip antennas at 1.88 GHz. Measured results show an over 64% size reduction and 17-dB cross-polarization suppression enhancement for the proposed scheme as compared with the conventional one. Moreover, the proposed scheme exhibits good broadside radiation patterns with a gain of 5.4 dBi and the half-power beamwidths of about 104° in the E-plane and 84° in the H-plane.

Hybrid carbon molecular sieve membranes having ordered Fe3O4@ZIF-8-derived microporous structure for gas separation

Carbon molecular sieve (CMS) membranes have great promise in CO2 capture. However, tortuous transport passageways restrict the enhancement in the permeability due to the presence of disordered porous structure and dead-end pore. Herein, the growth of ZIF-8 layer on the surface of Fe3O4 formed magnetic core-shell Fe3O4@ZIF-8 particles, which were fixed into 6FDA/ODA:DABA polyimides under magnetic field-induction to fabricate a precursor membrane with vertically oriented chain-like particles. It was then pyrolyzed to form hybrid carbon molecular sieve (HCMS) membranes with ordered microporous structure under high temperature conditions. The cross-section scanning electron microscopy images and N2 adsorption for resultant HCMS membranes indicate that Fe3O4@ZIF-8-derived carbons frameworks were vertically oriented to form the ordered microporous structure, which also had good compatibility with carbon matrix stemmed from 6FDA/ODA:DABA polyimides. The as-prepared HCMS membranes embedded with 5 wt% Fe3O4@ZIF-8 manifested a highest gas separation performance (permeability of 5130 Barrer; CO2/N2 selectivity of 29; CO2/CH4 selectivity of 48), outperforming the pristine CMS membranes, which were near and beyond 2019 CO2/N2 and CO2/CH4 upper bounds, separately. These good separation performances resulted from vertical chain-like microporous particles, which provided fast transport channels to accelerate CO2 diffusion rate. In addition, we supposed that Fe3O4 prevent ZIF-8 frameworks from destruction during the pyrolysis and promote the size screening capability. More importantly, this membrane exhibited excellent aging resistance over 30 days aging testing compared to pristine CMS membranes. Therefore, it affords a feasible way for carbon capture from flue gas and natural gas.

Short Circuiting Transfer, Formation, and Microstructure of Ti-6Al-4V Alloy by External Longitudinal Magnetic Field Hybrid Metal Inert Gas Welding Additive Manufacturing.

In this work, the external longitudinal magnetic field hybrid metal inert gas welding (M-MIG) additive manufacturing method is employed to produce the Ti-6Al-4V alloy part. The effect of process parameters on the droplet transfer formation and microstructure of the part was studied by a high-speed camera, optical microscope, and electron backscattered diffraction. The results showed that a typical short-circuiting transfer was obtained with the wire feeding speed of 2 m/min-4 m/min. An external longitudinal magnetic field had an obvious effect on the arc shape. The uniform formation of the deposition layer was obtained with the wire feeding speed of 4 m/min. The width of M-MIG deposition layer was greater than that of the MIG, and the width of M-MIG deposition layer was increased with the increase of the magnetic excitation current. The microstructure of the deposition layer was mainly comprised of acicular martensite α' and massive martensite αm. In addition, the β grain size in the M-MIG was less than that of the MIG. The average microhardness of the MIG deposition layer was 281.6 HV, which was less than that of M-MIG.

Communication System Based on Magnetic Coils for Underwater Vehicles

In this work, a wireless communication system based on magnetic coils for underwater vehicles is presented. Firstly, the mathematical model of magnetic field induction using magnetic coils is discussed. Then, a description of the proposed communication system is presented, including the main components of the transmitter and receiver module. The experimental results show that due to the properties of the magnetic field, the proposed communication system can work properly in different environments such as air or water with the same efficiency. Underwater tests were carried out in different water circumstances: varying the temperature in a range from 10 °C to 35 °C, varying concentrations of clay in a range from 0% to 10%, and varying the salinity concentration in a range from 1000 ppm ( parts per million) to 35,000 ppm. It was observed that these conditions do not affect the information transfer. Finally, the advantages of using the proposed system compared to existing submarine communication systems are discussed.

Rotatory power reversal induced by magnetic current in bi-isotropic media

Bi-isotropic media constitute a proper scenario for scrutinizing optical effects stemming from magnetoelectric parameters. Chiral magnetic current is a macroscopic effect arising from the chiral magnetic effect that enriches the phenomenology of a classical dielectric medium. This work examines optical aspects of bi-isotropic media in the presence of magnetic conductivity. The full isotropic scenario manifests circular birefringence described by a dispersive rotatory power that changes sign at a given frequency. For a bi-isotropic medium with antisymmetric magnetic conductivity, an intricate dispersive rotatory power is attained, supplied with sign reversal as well. This scenario also indicates a handedness reversion of the medium, an unusual property in dielectrics, which may work as a signature of bi-isotropic media supporting chiral magnetic current.

Magnetic Forces by Permanent Magnets to Manipulate Magnetoresponsive Particles in Drug-Targeting Applications.

This study presents preliminary computational and experimental findings on two alternative permanent magnet configurations helpful for magnetic drug administration in vivo. A numerical simulation and a direct experimental measurement of the magnetic induction on the magnet system's surface were used to map the magnetic field. In addition, the ferrite-type (grade Y35) and permanent neodymium magnets (grade N52) to produce powerful magnetic forces were also examined analytically and quantitatively. Ansys-Maxwell software and Finite Element Method Magnetism (FEMM) version 4.2 were used for all numerical computations in the current investigation. For both magnets, the generated magnetic fields were comparatively studied for targeting Fe particles having a diameter of 6 μm. The following findings were drawn from the present investigation: (i) the particle deposition on the vessel wall is greatly influenced by the intensity of the magnetic field, the magnet type, the magnet size, and the magnetic characteristics of the micro-sized magnetic particles (MSMPs); (ii) ferrite-type magnets might be employed to deliver magnetoresponsive particles to a target location, even if they are less powerful than neodymium magnets; and (iii) the results from the Computational Fluid Dynamics( CFD) models agree well with the measured magnetic field induction, magnetic field strength, and their fluctuation with the distance from the magnet surface.

Experimental Setup for Measurement of AC Loss in HTS under Rotating Magnetic Field

High-temperature superconducting materials have shown great potential for the design of large-scale industry applications. However, they are complicated under AC conditions, resulting in penalties such as power loss or AC loss. This loss has to be considered in order to design reliable and efficient superconducting devices. Furthermore, when superconductors are used in rotating machines, they may be exposed to rotating magnetic fields, which is critical for the design of such machines. Existing AC loss measuring techniques are limited to measuring under one-dimensional AC magnetic fields or transport currents. Therefore, it is essential to develop and investigate robust experimental techniques to investigate the loss mechanism in HTS machines. In this paper, a new and novel experimental technique has been presented to measure AC loss in rotating magnetic field conditions. The loss under rotating magnetic fields is measured and compared by numerical modeling methods, and the results show a strong correlation with the numerical modeling and show the effectiveness of the experimental setup.

Unveiling confinement in pure gauge SU(3): flux tubes, fields, and magnetic currents

A characteristic signature of quark confinement is the concentration of the chromoelectric field between a static quark–antiquark pair in a flux tube. However, the structure of this flux tube, and hence of the confining force, has not been completely understood. Here we perform new lattice measurements of field distributions on smeared Monte Carlo ensembles in SU(3) gauge theory. On the basis of these simulations we demonstrate that the confining force can be understood using the analogy with the basic principles of electromagnetism as elucidated by Maxwell. We derive a chromomagnetic Lorentz force density coupling the chromoelectric field to chromomagnetic currents and integrate this force density over the flux tube interior to obtain a Maxwell-like force that squeezes the flux tube in the transverse direction. We show that the strength of this transverse confining force is equal to the value of the string tension calculated numerically from the chromoelectric field on the midplane between the quarks, verifying the consistency of these two complementary pictures of confinement.

Computational analysis and heat transfer on MHD transient‐free convection flow in a vertical microporous channel in the existence of Hall and ion slip current

AbstractThis investigation presents an analysis of the transient magnetohydrodynamic flow of Newtonian viscous fluid in a vertical microporous channel with the inclusion of ion slip‐Hall current as well as an induced magnetic field (IMF) effects. Owing to the nature of the flow equations which are difficult to obtain an analytical result, a numerical scheme (PDEPE) based on finite difference approximation is adopted in solving the governing dimensional partial differential equation. The active influence of different flow parameters on velocity and IMF along the main flow and induced flow directions are visualized. Furthermore, variations of shear stress and induced current density are also presented in tabular form for active nondimensional flow quantities and later on analyzed. To establish the validity of the results obtained in this computation, values for velocity and IMF in this analysis were correlated with the steady‐state existing benchmark when the values of nondimensional time are considered large. Significant results from the analysis show that at the transient time and in the simultaneous occurrence of suction/injection at the microchannel walls, higher values of ion slip current have no considerable influence on flow formation along the primary flow direction, whereas an oscillatory phenomenon is observed along the secondary flow direction. It is also significant to note that at a transient time, magnetic induction could be improved or controlled by choosing favorable values of the suction/injection parameter.

Suppression Effect on the Domain Wall Tilting in Synthetic Antiferromagnetic Racetrack Driven by the Spin–Orbit Torque

The perpendicularly magnetized synthetic antiferromagnet is an ideal candidate for racetrack memory due to the low stray field, allowing the closely packed domain wall (DW) and high recording density. Herein, the dynamics of DW motion driven by the magnetic field and current are investigated in the synthetic antiferromagnetic (SAF) Ta/Pt/Co/Pt/Ru/Pt/Co/Ta structures with different thicknesses of the top magnetic (TM) Co layers. The results illustrate that the direction of the DW motion will be reversed when the field pulse is below a critical field for the sample with a negligible remanence ratio. As for the current‐driven DW motion case, a significant enhancement of the DW velocity, as well as a strong suppression effect on the tilting of DW's plane due to the strong interlayer exchange coupling for the SAF structure, is found. The fast DW velocity and small tilting angle in SAF are valuable for spintronic racetrack memories.

Magnetic induction processes in hot Jupiters, application to KELT-9b

Abstract The small semimajor axes of hot Jupiters lead to high atmospheric temperatures of up to several thousand Kelvin. Under these conditions, thermally ionized metals provide a rich source of charged particles and thus build up a sizeable electrical conductivity. Subsequent electromagnetic effects, such as the induction of electric currents, Ohmic heating, magnetic drag, or the weakening of zonal winds have thus far been considered mainly in the framework of a linear, steady-state model of induction. For hot Jupiters with an equilibrium temperature Teq > 1500 K, the induction of atmospheric magnetic fields is a runaway process that can only be stopped by non-linear feedback. For example, the back-reaction of the magnetic field on to the flow via the Lorentz force or the occurrence of magnetic instabilities. Moreover, we discuss the possibility of self-excited atmospheric dynamos. Our results suggest that the induced atmospheric magnetic fields and electric currents become independent of the electrical conductivity and the internal field, but instead are limited by the planetary rotation rate and wind speed. As an explicit example, we characterize the induction process for the hottest exoplanet, KELT-9b, by calculating the electrical conductivity along atmospheric P–T profiles for the dayside and nightside. Despite the temperature varying between 3000 and 4500 K, the resulting electrical conductivity attains an elevated value of roughly 1 S m−1 throughout the atmosphere. The induced magnetic fields are predominately horizontal and might reach up to a saturation field strength of 400 mT, exceeding the internal field by two orders of magnitude.

Complex ophthalmic neurostimulation in the rehabilitation of patients with glaucomatous optic neuropathy

Glaucomatous optic neuropathy differs significantly from other known ophthalmic neuropathies due to the gradual but steady progression, irreversible course, and resistance to treatment. Despite the fact that in recent decades, retinoprotective therapy and various physiotherapeutic factors have been widely used in the treatment of ophthalmic diseases and, in particular, this pathology [1–17], it has not been possible to reduce the incidence rate so far. In this regard, there is an urgent need for further development of comprehensive rehabilitation programs to prevent the progression of the disease. Material and research methods. The study included 78 patients (102 eyes): the main group included 58 eyes with stage 1 primary open-angle glaucoma (POAG1) of 42 patients aged 56±3.1 years (16 men, 26 women), who underwent a course of complex ophthalmic neurostimulation including transcranial magnetic stimulation with a magnetic field induction of 43 mT and a pulsating frequency of 100 Hz, endonasal electrophoresis with Semax, heliox inhalation of a heated mixture of He+O2 (21), and acupuncture. There were 10 procedures of each in a combined schedule. The comparison group included 36 patients (44 eyes) with POAG1 (14 men, 22 women) aged 53±3.2 years, who underwent a course of complex ophthalmic neurostimulation including transcranial magnetic stimulation with a magnetic field induction of 43 mT and a pulsating frequency of 100 Hz, and endonasal electrophoresis with Semax. The control group included 47 eyes of 38 patients aged 50±3.9 years (18 men, 23 women), who did not undergo physiotherapy. Results. The most pronounced results in POAG1 were obtained under the influence of an extended complex of ophthalmic neurostimulation including transcranial magnetic stimulation, endonasal electrophoresis with Semax, heliox therapy, and acupuncture, which was confirmed by a significant decrease in the number of relative scotomas, a decrease in electrical perceptual threshold, an increase in P50 amplitude in PERG, and an increase in the GCC layer that persisted up to 48 weeks in most cases. Somewhat less significant results were obtained in the comparison group, with the greatest therapeutic effect for most of the studied parameters observed in terms of up to 24 weeks, while in patients who received a vitamin therapy complex, there was noted only a positive trend, the duration of which was no more than 12 weeks, followed by deterioration. Conclusion: More pronounced therapeutic results obtained in the main group are explained by the formation of the trophostimulating effect of magneto-electrotherapy, the neuroprotective effect of the drug, as well as the pronounced neurotrophic effects of heliox therapy and acupuncture.

The influence of the size of details on the frontal resistance forces during magnetic abrasive finishing

The magnetic abrasive finishing process (MAF) is an effective method of finishing details. It is especially beneficial of processing important parts with complex shape, such as cutting tools, gas turbine blades, medical products, etc. MAF allows to affect the quality of the treated surface, surface hardness, microgeometry of cutting edges (for a cutting tool), removal of residual stresses in the material of the details. The relative newness of the method and, hence, little awareness of the processes and phenomena that occur during MAF limit the wide use of the method in production. Insufficient awareness of the nature of MAF, especially regarding the forces that arise during the interaction of the processed part and the environment of the magnetic abrasive tool (MAT). Available researches provide only basic information that is not sufficient for a comprehensive study of MAF. This is especially true for the effect of size of the detail on features of the implementation of the process. Conducting research on the processing of parts of various sizes and determining the forces and phenomena accompanying the MAF. To perform the aim, a device with a dynamometric sensor that allows to measure the frontal resistance was used. Ferromagnetic and paramagnetic material cylindrical details with different diameters (8, 12 and 16 mm) were used. Polymam-M and Polymam-T (grain size 400/315 μm, 200/100 μm) powders were used. The speed of movement varied in range 1 - 3 m/s, induction of magnetic field: 0.20 - 0.24 T. It was established that for the specified processing conditions, the influence of the magnitude of the magnetic field induction prevails over the influence of the speed of movement of details. The effect of the size of the parts on the specifics of the MAO is shown, the nature of processing by individual structural formations of the MAO and the difference between them is determined. The question of fluctuations in the magnitude of the resistance force at MAO and the influence of movement speed on them is considered. The influence of technological parameters on the frontal resistance force during processing of parts of different diameters and materials with different magnetic properties has been determined, and further directions for research have been determined.

Simplified Closed-Form Optimized Trajectories Control for a Dual Active Bridge Converter With ZVS Implementation Over Whole Domain

A dual active bridge converter is widely used in electric vehicle charging systems and other fields for its excellent features. Despite the diversity of relevant studies on the triple-phase-shift (TPS) modulation, the existing investigations fail in the zero-voltage-switching (ZVS) implementation over the whole voltage and load domains, especially in the transition process between different modes. To address the current state of research, the magnetic current is introduced to bridge the ZVS gap between different modes in this article. A simpler method of the acceptable maximal magnetic inductance design in view of the current stress and the transformer's turns ratio is presented. Afterward, the evaluation method of system efficiency over the full voltage range is raised. Most critically, the simplified optimal control trajectories considering the impact of the magnetic current are proposed for the first time for the TPS modulation, eliminating the nonmonotonicity and leapfrogging of the control variables. Compared with the existing works, the method proposed in this article accomplishes ZVS over the whole domain, thereby reducing potential electromagnetic interference and enhancing the efficiency. Eventually, the proposed method is verified by a 1.0-kW prototype.

Magnetic Poles: A Missing Manual

This work provides a missing manual needed to understand permanent magnets (also known as “hard” magnets), the only source of magnetic induction field B (units of teslas), often called the magnetic field, that students are familiar with when they confront magnetic force acting on moving charges. Students see this magnetic force in two forms:

A Compact Wideband Filtering Antenna on Slots-Loaded Square Patch Radiator Under Triple Resonant Modes

In this article, a compact microstrip patch antenna (MPA) with enhanced bandwidth and filtering response is proposed and implemented solely by loading pairs of slots on the conventional square patch radiator. Initially, the dominant mode TM10 of the square patch radiator is theoretically investigated, revealing its broadside radiation pattern and its current flows in the consistent direction. After that, based on the regularities of field distribution, two pairs of slots are etched in the square patch so as to generate two extra modes without destroying both resonant and radiating properties of TM10 mode. By virtue of these two excited modes, two extra resonances are produced in proximity to its dominant one, so as to widen the bandwidth under triple resonant modes. Meanwhile, owing to the inverse equivalent magnetic currents (EMCs) along the radiation edges of the patch and the out-of-phase electric fields at the two sides of each slot under these two excited modes, radiation cancellation toward broadside direction and efficiency reduction occur simultaneously. Hence, radiation nulls are achieved in all direction, and particularly, the radiation null toward broadside direction is deeper than others. After our intensive investigation is done on the entire slots-loaded patch radiator, a wideband filtering MPA with three in-band resonances and two out-of-band radiation nulls has been finally constructed. For demonstration, a prototype antenna at a center frequency of 3.5 GHz is designed, fabricated, and measured. The measured results are found in good accordance with the simulated ones, demonstrating an impedance bandwidth of 9.14% with stable broadside realized gains as well as two radiation nulls at 3.12 and 3.83 GHz, respectively, in addition to its low profile of 0.029 free-space wavelength. Notably, the presented antenna has occupied the almost same area as the conventional square MPA, maintaining its good size compactness.

POSSIBILITIES FOR CORRECTING COGNITIVE DEFICITS IN STROKE IN PEOPLE WHO HAVE HAD COVID-19

Relevance. Mnestic functions in patients after stroke and coronavirus infection are not restored completely. Nowadays, the search for ways to overcome in such patients is actual.
 Objective: to find out the possibility of cognitive deficiency’ overcoming in persons after stroke who have suffered from COVID-19 by Phenibut pharmacocorrection and magnetic therapy.
 Materials and methods. 46 patients aged 40-60 years who had COVID-19 in anamnesis and ischemic stroke in the post-covid period were divided into 3 groups at the stage of comprehensive rehabilitation. In the 1st group (n=15) - the control group - no nootropic drugs and physiotherapeutic procedures were not asdministered; in group 2 (n=15), magnet stimulation procedures were performed for 20 days (frequency of basic impulses 180-195 Hz, frequency of a group of impulses 12,5-29 Hz, average induction of magnetic fields within 100 μT); group 3 (n=16) took Phenibut (β-Phenyl-GABA) one tablet (250 mg) 3 times a day for three months.
 The study of cognitive functions was carried out with the help of a short mental state scale - MMSE, a set of tests for the study of frontal dysfunction - FAB, a test for memorizing of 10 words according to the A.R. Luria’s method and clock drawing testing All groups were tested twice: at the beginning of the study and after three months.
 The obtained data were processed statistically; an ordinal logistic regression model was applied, in particular logistic regression with a cumulative relationship.
 The results. In group 2 the result of the subtest "Voluntary attention" improved (3,8±0,3 points vs. 3,1±0,2 in the control) and the FAB test (15, 2±1,2 points vs. 11,3±0,4 in control).
 In group 3, the cognitive functions in the MMSE (26,1±0,8 points vs. 21,2±0,6 in the control) and FAB (16,3±0,6 points vs. 11,3±0,4) tests probably improved. The results of the subtests "Discretionary attention" (3,8±0,1 points vs. 3,1±0,1) and "Memory" (2,6±0,2 points vs. 2,0±0,1) improved. In the test for 10 words memorizing, the difference in indicators, compared to the control, was in each subsequent presentation: 1,0±0,05; 1,1±0,09; 1,7±0,10 words, in delayed presentation 1,75±0,05 (in all cases p<0.05).
 Conclusions. The use of Phenibut and magnetic therapy in patients who have suffered a stroke after COVID-19 leads to regression of cognitive deficiency and depressive symptoms. The effect of Phenibut turned out to be better - the odds ratio, compared to the control, was 13,1.

Velocity-selective excitation: Principles and applications.

Velocity-selective (VS) excitation is a relatively new type of excitation that can be useful for generating image contrast based on spin's motion. This review aims to explain the principles of VS excitation and their utilization for clinical applications. We first review the generalized excitation k-space formalism, which reveals a Fourier relationship between sequence parameters and excitation profiles for spins with arbitrary spatial location, off-resonance, and velocity. Based on the k-space framework, we analyze practical VS excitation pulse sequences that yield sinusoidal or sinc-shaped velocity profiles. Then we demonstrate how these two types of VS excitation can be used as magnetization preparation for clinical applications, including saturation- or inversion-based arterial spin labeling and black- or bright-blood angiography. We also discuss practical considerations and issues for each application, including the determination of design parameters and the effects of MR system errors, such as magnetic field offsets and eddy currents.

Electromagnetic modeling and experimental study of can-effect on a canned switched reluctance machine

This paper proposes a novel electromagnetic modelling method, with experimental study of the magnetic can-shield effect, based on a novel canned switched reluctance machine. Such model considers the characteristic electromagnetic coupling relation between magnetic flux and eddy current on cans, with harmonic analysis by analytical calculation in vector form. The model is structured with multiple concentrated layers in cylindrical coordinate and the main modeling process includes domain solution of the magnetic field, and an energy vector deduction for loss and energy. Comparative measurement with an indirect method demonstrates the electromagnetic features by the use of cans and meanwhile verifies the analytical model.

Reflected impedanceometry: a contact-free technique for measuring induced magnetic hysteresis and eddy current heating

Reflected Impedanceometry is a new technique that can remotely measure the power absorbed during radiofrequency induction heating. It measures the total system impedance from the phase difference between current and voltage in the electromagnetic field work coil and uses the characteristic impedance of the work coil circuit to infer the heating power transferred into a susceptor bed. Induction heating of susceptor materials within alternating magnetic fields occurs by magnetic hysteresis, eddy currents, Néel relaxation or Brownian relaxation. It shows potential for replacing fossil fuels with renewable electricity in carbon-intensive industrial applications but requires advances in measurement techniques. Previously developed methods for measuring heating power, such as pick-up coils, are limited to applications involving magnetic materials. Results presented here show that reflected impedanceometry accurately measures heating power for both magnetic hysteresis and eddy currents, fulfilling the requirement for measuring induction heating power.