Attenuation Of Magnetic Field Research Articles

Biocompatible polyethersulfone membrane modified by hydrophilic polymer decorated magnetic nanoparticles gilded by facile external magnetic field

AbstractPolymer‐based membranes such as polyethersulfone are widely used for hemodialysis and bio‐related applications; however, this type of membrane still fails to satisfy optimum performance in terms of clearance, safety, and bio‐adaptability. Herein, a polymer brush of polyvinylpyrrolidone is decorated on the surface of magnetic nanoparticles by using reversible addition‐fragmentation chain transfer polymerization (RAFT), and under the guidance of an external magnetic field, the prepared magnetic nanoparticles with the polymer brush system are blended with a polyethersulfone membrane during a liquid‐liquid phase inversion process. The prepared membranes with different loads of the pure magnetic nanoparticle and polyvinylpyrrolidone@magnetic nanoparticle polymer brushes are prepared, compared with the pristine membrane, the modified membrane shows a high flux value at 349 L m−2 h−1 and 99.9% bovine serum albumin protein rejection. This membrane also demonstrated improved hydrophilicity and pore structure compared with the pristine membrane. Concerning the blood biocompatibility analysis, the modified membranes acquire prolonged time for clotting factors such as prothrombin time, activated partial thromboplastin time, and thrombin time while exhibiting less fibrinogen concertation at 0.4 g L−1. Furthermore, for the first time, an innovative method for fouling detection based on magnetic field attenuation due to protein accumulation on the membrane surface is reported; the method in this work could be a positive booster for the safe use of polymeric membranes in hemodialysis and bio‐based applications.

Biplane Enhancement Coil for Magnetic Induction Tomography of Cerebral Hemorrhage.

Magnetic Induction Tomography (MIT) is a non-invasive imaging technique used for dynamic monitoring and early screening of cerebral hemorrhage. Currently, there is a significant challenge in cerebral hemorrhage MIT due to weak detection signals, which seriously affects the accuracy of the detection results. To address this issue, a dual-plane enhanced coil was proposed by combining the target field method with consideration of the spatial magnetic field attenuation pattern within the imaging target region. Simulated detection models were constructed using the proposed coil and cylindrical coil as excitation coils, respectively, and simulation imaging tests were conducted using the detection results. The simulation results indicate that compared to the cylindrical coil, the proposed coil enhances the linearity of the magnetic field within the imaging target region by 60.43%. Additionally, it effectively enhances the detection voltage and phase values. The simulation results of hemorrhage detection show that the proposed coil improves the accuracy of hemorrhage detection by 18.26%. It provides more precise detection results, offering a more reliable solution for cerebral hemorrhage localization and detection.

Propagation Characteristics and Magnetic Field Distribution of Rotating Magnet-Based Mechanical Antenna in the Air-Seawater-Seabed Three-Layer Medium

Aiming at the application requirements of underwater cross-domain communication, based on the equivalent relationship between the rotating permanent magnet and the orthogonal time-varying current loop, this paper establishes an air-seawater-seabed three-layer medium model and analyzes the magnetic field distribution and propagation characteristics of the rotating permanent magnet-based mechanical antenna (RMBMA). Based on the electromagnetic field simulation software FEKO, the influence of vertical rotation and horizontal rotation of RMBMA on the radiation magnetic field is analyzed. The magnetic field distribution and magnetic field attenuation characteristics of RMBMA at different depths are obtained by simulation. The influence of RMBMA operating frequency and magnetic moment on the propagation characteristics is studied. The research shows that the horizontal rotation of the magnetic source is better than the vertical rotation in the long-distance underwater communication. When the magnetic source and the receiving point are close to the interface of the medium, the magnetic field strength and the propagation distance can be relatively increased. With appropriate frequency and magnetic moment, the magnetic field strength and communication distance can be further increased.

Магнитное поле многовитковой цилиндрической катушки с ферромагнитным сердечником в непосредственной близости от металлических конструкций в задаче поиска людей под завалами в шахтах

Some aspects of the low-frequency magnetic field propagation in heterogeneous medium in mines are discussed in the paper. The theoretical model for calculation of magnetic field distribution in case of the parallel axis of transmitting antenna and bulk metal is developed. Metal structures are rail tracks, magnetic antenna is multiturn cylindrical coil with ferromagnetic core. Magnetic field according to proposed models principle in several stages using the method of integral equations was numerical calculated. This method of calculation of magnetic field in considered inhomogeneous space is based. The calculations of magnetic field strength of the multiturn cylindrical coil with ferromagnetic core in nearby proximity and at various distances from bulk metal were carried out. The possibility of use of low-frequency magnetic field attenuation for people search under avalanches was proved.

Numerical Comparison of Active Shielding Techniques for Magnetic Fluid Hyperthermia Application

This study aims to eliminate magnetic field leakage at 100 kHz with active shielding in Magnetic Fluid Hyperthermia (MFH) system. First of all, the structural and operational features of the MFH system were analyzed. Then, the active regions of the coils were determined, graphical results were obtained and the designs were compared with each other. We first simulated the magnetic field distribution of a circular coil active shielding system by the commercial software tool COMSOL Multiphysics. Secondly, a single D-shape shielding was configured in the MFH system and the size and location of the shielding were examined. The magnetic field attenuation percentages of the methods in the x, y, z axes and the target region selected as the representative tumor region were compared. The simulation results show that the shielding ability of the double D-shape shielding type is better in the x and y axes than the other coil types (51.43% for the x-axis and 95.77% for the y-axis). The fact that the attenuation percentage of this shielding type in the target region is 0.0287% is a secondary advantage. It has been observed that the attenuation in the z-axis is higher in other shielding types, but the attenuation percentage in the target region also increases.

A 7-nm FinFET 1.2-TB/s/mm2 3D-Stacked SRAM Module With 0.7-pJ/b Inductive Coupling Interface Using Over-SRAM Coil and Manchester-Encoded Synchronous Transceiver

A 0.7-pJ/bit, 8.5-Gb/s/link inductive coupling interchip wireless communication interface for a 3D-stacked static-random access memory (SRAM) has been developed in a 7-nm FinFET process. A new physical placement method that allows coils to be placed over off-the-shelf SRAM macros with small magnetic field attenuation, together with the use of synchronous communication using Manchester encoding and a clocked comparator to enable the detection of small-swing signals, achieves a 26% reduction in SRAM die area compared to through-silicon via (TSV)-based stacking. Interchip communication at 0.7 pJ/bit, 8.5 Gb/s/link was confirmed using test chips. A 4-hi 3D-stacked SRAM module using the proposed interface achieves a 1.2-TB/s/mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{2}$</tex-math> </inline-formula> area efficiency, representing a two orders-of-magnitude improvement over the state-of-the-art 3D-stacked SRAM.

Magnetic Behavior of a Laser Deposited Fe–Ni–Mo Alloy

Magnetic shielding in spacecraft is a mission‐critical issue that must be addressed in a timely and effective manner. The high permeability of Fe–Ni–Mo alloys, makes them excellent candidates for magnetic shielding. This article explores a new and innovative approach, enabled by additive manufacturing (AM), to design, build, and test geometrically complex magnetic shields. A Fe–79.7Ni–4.1Mo alloy is additively manufactured using blown powder laser‐directed energy deposition (DED). AM build conditions are explored in the production of magnetic test rings and magnetic shield prototypes. Magnetic hysteresis test data are obtained, allowing for the determination of magnetic permeability, saturation, and coercivity. Detailed microstructural characterization is carried out. Three different prototype shield designs are printed and magnetic shield attenuation data is obtained. The magnetic field attenuation (shield effectiveness) obtained for the AM components is comparable to wrought equivalents. The values reported here for the magnetic permeability are the highest, and that for the magnetic coercivity the lowest, for any blown powder DED‐printed material currently known. The magnetic behavior is discussed with regard to grain size and orientation, as well as grain boundary effects, with all of these attributes contributing to the ultimate performance.

Modeling of catenary electromagnetic emission with electrified train passing through neutral section

Rail transit entering the airport facilitates people’s travel, but it also brings potential electromagnetic interference. In this paper, based on the transmission line model of the arc harmonic conduction current generated by the pantograph and the catenary with the highly insulated ballastless railway, the electromagnetic emission model of the traction network is proposed in the working frequency band of the nondirectional beacon when the train passes through the neutral section of the electric phase separation. And the simplification of the transmission line model is realized by deforming the transmission line equation. Then, the finite difference time domain algorithm is used to solve the distributed current on the transmission line. However, the terminal of the conventional finite difference time domain algorithm can only be a pure resistive load. Therefore, the backward difference and the Implicit Wendroff difference format are used to extend the finite difference time domain algorithm to a more general case. Combined with a real ballastless railway in China, the effectiveness and accuracy of the proposed method are verified. From the perspective of magnetic field attenuation, ballastless railway is easier to pass the electromagnetic environment assessment of the airport than ballasted railway.

Mechanism of Magnetic Flux Leakage Detection Method Based on the Slotted Ferromagnetic Lift-Off Layer.

Magnetic flux leakage (MFL) testing is widely used in non-destructive testing of ferromagnetic components. In view of the serious attenuation of the leakage magnetic field (LMF) caused by the transmission of LMF in the lift-off layer between the measuring point and the workpiece, this paper introduces an MFL detection method based on the slotted ferromagnetic lift-off layer (SFLL). The conventional non-ferromagnetic lift-off layer is changed to a ferromagnetic lift-off layer with a rectangular slot. The magnetic sensor is fixed above the slot and scans the workpiece together with the lift-off layer. First, the detection mechanism of the new method was studied by an equivalent LMF coil model. The permeability perturbation effect and the magnetization enhancement effect were analyzed in the new method. Based on the detection mechanism, the lift-off tolerance of the new method was investigated. Then, the LMF enhancement and lift-off tolerance of the new method in the steel plate detection model were studied. Finally, experiments were conducted to compare the new method with the conventional method. The simulation and experimental results show that the slotted ferromagnetic lift-off layer enhances the amplitude of the MFL signal and is tolerant to the lift-off value. This method provides a new idea for optimizing the design of the MFL sensor and improving the sensitivity of MFL detection at a large lift-off value.

Experimental Investigation on the Dynamic Propagation Characteristics of Low-Frequency Electromagnetic Waves in Cylindrical Time-Varying Enveloping Plasma Generated by a Shock Tube

A feasible solution for mitigating radio blackout has been proposed using the magnetic field component of low-frequency (LF) electromagnetic waves (referred to as the LF magnetic field) to transmit critical low-rate data because of the low attenuation of the LF magnetic field in the electrically small plasma. Previous works have modeled the hypersonic plasma flow field as spherical or cylindrical steady-state plasma, ignoring the time-varying properties of the plasma. This article presents the dynamic propagation of the LF magnetic field in a hypersonic plasma flow field generated by a shock tube, introducing a colored-Gaussian time-varying electron density model. Analytical expressions for the propagation characteristics of the LF magnetic field in cylindrical time-varying plasma are derived using an equivalent circuit. Meanwhile, a frequency-division-multiplex experimental method for a shock tube is presented to quantitatively measure the propagation characteristics of a multifrequency LF magnetic field. The experimental results are in good agreement with the theoretical results. As the fluctuation intensity of the electron density increases, the fluctuation intensities of the time-varying envelope and phase shift increase, and the power spectral density broadens. As the frequency of the LF magnetic field increases, the effects of the time-varying plasma on the propagation characteristics strengthen. These results are important to the design of LF communication systems and modulation algorithms in the scenario of shock-tube-generated plasma.

Magnetic-responsive tension rheology behavior for grease-based magnetorheological suspensions

The tensile rheology behavior of grease-based magnetorheological (MR) suspensions at the presence of magnetic field was investigated by a magnetic-responsive tensile rheology model and the experiment in this research. The prediction for magnetic-responsive tension model corrected by the magnetic field-dependent attenuation coefficients is in accord with the experimental data under different magnetic field activation. Comparing with the thicker initial thickness of suspensions, the thinner initial thickness of suspensions at the application of same magnetic field induced larger tensile strength due to the stronger magnetic interaction between dipoles and the higher anti-deformation ability for the magnetic structures. Furthermore, the higher pull velocity promoted the formation of robust magnetic structures and activated the larger tensile rheological capacity for the grease-based MR suspensions along the direction of the magnetic field. Besides, the magnetic-structure tensile strength of MR suspensions inducing by the tensile traction of aluminum-created substrate material with the weak magnetic conductivity was much less than the tensile traction of steel-created substrate material with the strong magnetic conductivity. This study proposed a hypothesis where the difference between the magnetic-field attenuation rate and the magnetic-structure destruction rate leaded to the disagreement between the mechanical rheology model and experimental data at traction of the high tensile speed.

Experimental Installation for Determination of Attenuation Coefficient of Permanent Magnetic Field by Protective Materials

The permanent magnetic field in addition to electromagnetic radiation has a significant effect on performance of devices. This is particularly true for highly sensitive precision measuring equipment, such as, for example, magnetometers or photomultiplier tubes. In this regard a new high-performance materials for protection against permanent fields and electromagnetic radiation need to be developed. The purpose of this paper is a development of a hardware and software complex for high-precision determination of permanent magnetic field attenuation coefficient and certification of protective materials.This paper describes an experimental installation for determining the attenuation coefficient of a permanent magnetic field using materials and coatings on standard package for electronic equipment. The installation ensures a uniform magnetic field flow in the measurement volume. The advantage of the measuring device is the ability to measure magnetic field in three coordinates due to the use of three pairs of Helmholtz coils and a three-dimensional Hall sensor. The software will enable to control of the magnetic field in all three directions, simulating the real operating conditions of devices that require protection from such influences. In addition, a movable positioning system makes it possible to compensate for the Earth's magnetic field, which increases the accuracy of estimating the attenuation coefficient by protective materials in weak magnetic field.An alternative use of the capabilities of the installation is to test the performance of the devices in a permanent magnetic field and evaluate the electromagnetic compatibility. Experimental results of the work includes determination of the magnetic field attenuation coefficient using standard photomultiplier tube package made of electrolytically deposited permalloy and the sheet of annealed permalloy. Thus, the effect of annealing and closed magnetic circuit on the degree of weakening of the magnetic field is shown. It has been demonstrated that annealing which causes a significant increase in the magnetic permeability promotes an effective attenuation of weak magnetic fields (up to 1 mT). In magnetic fields with an induction of 1 mT or more, effective attenuation is provided by a closed magnetic circuit.

Electromagnetic Field Shielding in Incubators

Purpose: Cell experiments are vitally dependent on CO2 incubators. The heating system of usual incubators result in undesirable induction of Electromagnetic (EM) fields on cells that result in decreased accuracy in bio-electromagnetic tests. EM shields can cause a considerable decrease in the stray fields and eliminate the undesirable induction.&#x0D; Materials and Methods: CST-2019 is used for simulations. five different shielding systems have been examined in this paper. We try to modify shape and material used for shielding to achieve better result. (Iron, Mu-Metal, steel).&#x0D; Results: We introduce a simple practical design, together with variations of previously reported ones, and numerical evaluation of their magnetic field attenuation.&#x0D; Conclusion: The targeted design decreases the field within the shield to about 0.03 times of the incident magnetic field, while having holes for air and CO2 exchange.

Strong anisotropy of the electron-phonon interaction in NbP probed by magnetoacoustic quantum oscillations

In this study, we report on the observation of de Haas-van Alphen-type quantum oscillations (QO) in the ultrasound velocity of NbP as well as `giant QO' in the ultrasound attenuation in pulsed magnetic fields. The difference of the QO amplitude for different acoustic modes reveals a strong anisotropy of the effective deformation potential, which we estimate to be as high as $9\,\mathrm{eV}$ for certain parts of the Fermi surface. Furthermore, the natural filtering of QO frequencies and the tracing of the individual Landau levels to the quantum limit allows for a more detailed investigation of the Fermi surface of NbP as was previously achieved by means of analyzing QO observed in magnetization or electrical resistivity.

Influence of Solar Wind Parameters on Equatorial Magnetic Observatories during Intense Geomagnetic Storms of the Year 2015

Coronal mass ejection (CME) and Corotating interaction region (CIR), a dynamic phenomenon associated with the sun, is widely acknowledged as the main causative factor for the occurrence of the geomagnetic storms. In the present investigation, we studied the influence of solar wind parameters and interplanetary magnetic field (IMFBz) on two severe geomagnetic storms (Dst=&lt;-200 nT) occurred during March and June 2015 using magnetic data recorded at four low latitude Indian magnetic observatories namely Jaipur (Rajasthan), Desalpar (Gujarat), Alibag (Maharastra) and Hyderabad (Telangana). Residual H-component of magnetic field distinctly distinguish the different phases of storms. Solar wind density and pressure are more influencive factors during main phase of the magnetic storm with observed high MS coherence (&gt;0.8) with the H-comp. Dynamic spectrum of H-component of magnetic field at low latitudes and solar wind parameters reveals a burst-like nature during the main phase of these storms. During Ionospheric Disturbance Dynamo (Ddyn) for March Storm, it is observed that American sector has downward movement in H-component of magnetic field and prominent attenuation of EEJ in African and Indian sectors. Similarly, for June storm, downward H-component movement is observed in both the American and African sectors and attenuation of EEJ at Indian sector.

Self-Shielded Uniform Magnetic Field Coil Design for Miniature Atomic Sensors Using a Particle Swarm Optimization Algorithm

In this paper, an optimization method that uses the derivatives and the target field information of the magnetic field simultaneously is proposed to suppress the coupling between the coil and the magnetic shielding in miniature atomic sensors. The coupling between the coil and the magnetic shielding varies with the material magnetic permeability, which causes the magnetic field to fluctuate with the temperature as the material permeability. The magnetic field fluctuations will cause the measurement errors and drifts of the sensors. The proposed method can effectively suppress the magnetization of the magnetic shielding caused by the coil magnetic field. A shielded coil outside the main coil is used to efficiently attenuate the magnetic field outside the main coil to suppress the coupling between the coil and the magnetic shielding. A coil system consisting of pairs of circular coils distributed on two coaxial cylinder surfaces is proposed in this paper. The Taylor expansion is used to ensure the uniformity of the internal magnetic field, while the target field information is used to ensure the attenuation of the external magnetic field. A particle swarm optimization (PSO) algorithm is used to optimize the parameters of the main and shielded coils. The theoretical calculations and the finite element analysis prove that the proposed approach is an effective design method for the self-shielded coils.

Beam modelling and hardware design of an imaging heavy ion beam probe for ASDEX Upgrade

The imaging heavy ion beam probe (i-HIBP) developed at the ASDEX Upgrade tokamak is a new diagnostic concept for investigations at the edge of high temperature plasmas. By means of a heavy alkali beam injector, a neutral primary beam of an energy of 70 keV is injected into the fusion plasma, where it is ionized generating a fan of secondary beams. These are deflected by the magnetic field of the tokamak and intersect a scintillator plate in the limiter shadow of the tokamak. The light pattern on the scintillator detected with a high speed camera contains radial information on the density, electrostatic potential and the magnetic field in the edge region of the plasma. For the design of the i-HIBP, a detailed beam model including the 3D tokamak magnetic field and beam attenuation effects for cesium and rubidium atoms is developed in order to find the optimum injection scheme within the limited space of the tokamak environment for maximum signal intensities. Based on the optimized injection, the arrangement of the injector outside the vacuum-vessel and the detailed design of the optical in-vessel system is determined.

Modeling and experimental study of low-frequency electromagnetic wave propagation in cylindrical enveloping plasma produced by a shock tube

A promising solution has been proposed to overcome blackout using the magnetic field component of low-frequency electromagnetic waves to transmit a small amount of critical data. The principle of the method is that the magnetic-field attenuation is less than the electric-field attenuation for low-frequency electromagnetic waves in electrically small plasma. This paper presents an experiment based on a shock tube to verify the theory. Analytical expressions of SE and SH suitable for a shock-tube cylindrical model are derived using an equivalent circuit, which is used to describe the different forms of attenuation of electric and magnetic fields. For comparison, numerical simulations are conducted with varying plasma parameters. In the experiment, low-frequency electromagnetic waves penetrate the plasma produced by the shock tube from the test section, and measurements are made by field-strength probes at the center of the plasma flow field. A difference between SH and SE is found in both the experiment and theoretical simulation, with |SH| being less than |SE| by 20–30 dB when the frequency of low-frequency electromagnetic waves is 10 MHz. The verification of this theory thus shows that the magnetic field component of the low-frequency electromagnetic waves may potentially be used to transmit a small amount of critical data or vocal communication, allowing continuous communication during a period of radio blackout.

Propagation loss and apparent conductivity models for through‐the‐earth communication in sedimentary soil

Much of the channel modelling found in the literature for through-the-earth communication is based on deterministic formulations that consider few homogeneous layers of soil. However, due to the great variation in the properties of the soil, especially of its electrical conductivity, it is very difficult to generalise channel characterisation with such models. Some empirical models are used to identify apparent conductivity at specific sites in order to determine the propagation loss at these sites at any time. However, the use of these models is limited to the few frequencies used in the reference measurements. This study aims to statistically characterise magnetic field attenuation in underground coal mines. The authors use the Monte Carlo method based on electromagnetic simulations, using the finite element method. The simulations allowed empirical modelling, resulting in optimal operating frequency, propagation loss and apparent electrical conductivity statistics, especially for transmissions at the optimal frequency of each channel.

Experimental Research on the Bitter-Like HTS Magnet Energized by an Inner Flux Pump

High-temperature superconducting (HTS) 2G conductors have been extensively applied in high magnetic field. This paper presents a novel excitation method of the Bitter-like HTS magnet for a stack of the RE-Ba-Cu-O (RE = rare earth) annular plates. The Bitter-like HTS magnet was energized by a flux pump composed of a copper solenoid coil and a pulsed triangular waveform current source. A single REBCO annular plate's critical current Ic was measured in 77 K (LN2 bath) in self-field, and the structure design of the whole flux pump, the transient process of the induced magnetic field, and the magnetic field attenuation of the Bitter-like HTS magnet under different excitation methods were described and tested in 77 K. Results show that the Bitter-like HTS magnet energized by a flux pump can realize closed-loop operation, and the flux pump with variation pulsed current values has an impact on the induced magnetic field attenuation in the Bitter-like HTS magnet. Furthermore, the flux pump making use of the inner excitation method has a faster excitation speed than the outer excitation method in our previous study.