Acoustic dipole radiation model for magnetoacoustic tomography with magnetic induction

An acoustic dipole radiation model for magnetoacoustic tomography with magnetic induction （MAT-MI） is pro- posed, based on the analyses of one-dimensional tissue vibration, three-dimensional acoustic dipole radiation and acoustic waveform detection with a planar piston transducer. The collected waveforms provide information about the conductiv- ity boundaries in various vibration intensities and phases due to the acoustic dipole radiation pattern. Combined with the simplified back projection algorithm, the conductivity configuration of the measured layer in terms of shape and size can be reconstructed with obvious border stripes. The numerical simulation is performed for a two-layer cylindrical phantom model and it is also verified by the experimental results of MAT-MI for a tissue-like sample phantom. The proposed model suggests a potential application of conductivity differentiation and provides a universal basis for the further study of conductivity reconstruction for MAT-MI.

Reception pattern influence on magnetoacoustic tomography with magnetic induction

Based on the acoustic radiation theory of a dipole source, the influence of the transducer reception pattern is studied for magnetoacoustic tomography with magnetic induction（MAT-MI）. Numerical studies are conducted to simulate acoustic pressures, waveforms, and reconstructed images with unidirectional, omnidirectional, and strong directional transducers.With the analyses of equivalent and projection sources, the influences of the model dimension and the layer effect are qualitatively analyzed to evaluate the performance of MAT-MI. Three-dimensional simulation studies show that the strong directional transducer with a large radius can reduce the influences of equivalent sources, projection sources, and the layer effect effectively, resulting in enhanced pressure and improved image contrast, which is beneficial for boundary pressure extraction in conductivity reconstruction. The reconstructed conductivity contrast images present the conductivity boundaries as stripes with different contrasts and polarities, representing the values and directions of the conductivity changes of the scanned layer. The favorable results provide solid evidence for transducer selection and suggest potential practical applications of MAT-MI in biomedical imaging.

Simulation research on effect of magnetic nanoparticles on physical process of magneto–acoustic tomography with magnetic induction

Magneto–acoustic tomography with magnetic induction（MAT-MI） is a multiphysics coupled imaging technique that is combined with electrical impedance tomography and ultrasound imaging. In order to study the influence of adding magnetic nanoparticles as a contrast agent for MAT-MI on its physical process, firstly, we analyze and compare the electromagnetic and acoustical properties of MAT-MI theoretically before and after adding magnetic nanoparticles, and then construct a two-dimensional（2 D） planar model. Under the guidance of space-time separation theory, we determine the reasonable simulation conditions and solve the electromagnetic field and sound field physical processes in the two modes by using the finite element method. The magnetic flux density, sound pressure distribution, and related one-dimensional（1 D）, 2 D, and three-dimensional（3 D） images are obtained. Finally, we make a qualitative and quantitative analysis based on the theoretical and simulation results. The research results show that the peak time of the time item separated from the sound source has a corresponding relationship with the peak time of the sound pressure signal. At this moment, MAMPTMI produces larger sound pressure signals, and the sound pressure distribution of the MAMPT-MI is more uniform, which facilitates the detection and completion of sound source reconstruction. The research results may lay the foundation for the MAT-MI of magnetically responsive nanoparticle in subsequent experiments and even clinical applications.

Boundary normal pressure-based electrical conductivity reconstruction for magneto–acoustic tomography with magnetic induction

As a kind of multi-physics imaging approach integrating the advantages of electrical impedance tomography and ul- trasound imaging with the improved spatial resolution and image contrast, magneto-acoustic tomography with magnetic induction （MAT-MI） is demonstrated to have the capability of electrical impedance contrast imaging for biological tissues with conductivity differences. By being detected with a strong directional transducer, abrupt pressure change is proved to be generated by the gradient of the induced Lorentz force along the force direction at conductivity boundary. A simplified boundary normal pressure （BNP）-based conductivity reconstruction algorithm is proposed and the formula for conductivity distribution inside the object with the clear physical meaning of pressure derivative, is derived. Numerical simulations of acoustic pressure and conductivity reconstruction are conducted based on a 2-layer eccentric cylindrical phantom model using Hilbert transform. The reconstructed two-dimensional conductivity images accord well with the model, thus success- fully making up the deficiency of only imaging conductivity boundary in traditional MAT-MI. The proposed method is also demonstrated to have a spatial resolution of one wavelength. This study provides a new method of reconstructing accurate electrical conductivity and suggests the potential applications of MAT-MI in imaging biological tissues with conductivity difference.

Spin-polarized pairing induced by the magnetic field in the Bernal bilayer graphene

Recent experimental findings have demonstrated the occurrence of superconductivity in Bernal bilayer graphene when induced by a magnetic field.In this study,we conduct a theoretical investigation of the potential pairing symmetry within this superconducting system.By developing a theoretical model,we primarily calculate the free energy of the system with p+ip-wave parallel spin pairing,p+ip-wave anti-parallel spin pairing and d+i d-wave pairing symmetry.Our results confirm that the magnetic field is indeed essential for generating the superconductivity.We discover that the p+ip-wave parallel spin pairing leads to a lower free energy for the system.The numerical calculations of the energy band structure,zero-energy spectral function and density of states for each of the three pairing symmetries under consideration show a strong consistency with the free energy results.

Preliminary Study on Magnetic Induction Intensity Induced by Plasma During Hypervelocity Impact

An experimental system has been built to produce and measure the magnetic field in the backward ejected matter during hypervelocity impact. The designs of measurement system and coil, the choice of associated equipment, and the system calibration are also described in detail. The measurement of magnetic induction intensity for different given coil positions and azimuth angles are performed with two-stage light-gas gun. On condition that impact velocities are approximately equal and incidence angles are 45°, 60° and 90° respectively, the relationship between average magnetic induction intensity and impact angle at different time spans is obtained. Experimental results show that the average magnetic induction intensity with incidence angle of 90° is larger than those with incidence angles of 45°and 60°.

Rapid preparation of carbon-supported ruthenium nanoparticles by magnetic induction heating for efficient hydrogen evolution reaction in both acidic and alkalinemedia

Ruthenium has been hailed as a competitive alternative for platinum toward hydrogen evolution reaction(HER),a critical process in electrochemical water splitting.In this study,we successfully prepare metallic Ru nanoparticles supported on carbon paper by utilizing a novel magnetic induction heating(MIH)method.The samples are obtained within seconds,featuring a Cl-enriched surface that is unattainable via conventional thermal annealing.The best sample within the series shows a remarkable HER activity in both acidic and alkaline media with an overpotential of only-23 and-12 mV to reach the current density of 10 mA/cm^(2),highly comparable to that of the Pt/C benchmark.Theoretical studies based on density functional theory show that the excellent electrocatalytic activity is accounted by the surface metal-Cl species that facilitate charge transfer and downshift the d-band center.Results from this study highlight the unique advantages of MIH in rapid sample preparation,where residual anion ligands play a critical role in manipulating the electronic properties of the metal surfaces and the eventual electrocatalytic activity.

Controlled synthesis of magnetic carbon nanoparticles via glycerol/ferrocene co-pyrolysis with magnetic induction

We performed a controlled synthesis of magnetic carbon nanoparticles （M-CNPs） via co-pyrolysis of glycerol and ferrocene with magnetic induction. The morphology of the synthesized M-CNPs was confirmed by transmission electron microscopy, and thermogravimetric analysis was used to analyze the carbon and Fe contents. M-CNPs that responded to magnetic stimulation were also examined with an AC-magnetic susceptibility analyzer. Our investigations on the influence of synthesis temperature in the range 700-1000℃ suggested that for an initial glycerol to ferrocene weight ratio of 3：1 and a temperature of 800 ℃ gave the highest yield of M-CNPs. Comparing the synthesis with and without magnetic induction, the controlled synthesis under the influence of magnetic induction shows promise as a method for producing high quality M-CNPs in high yields.

Magnetic Field Induction and Time Intervals of the Electron Transitions Approached in a Classical and Quantum-Mechanical Way

The motion of electron wave packets of a metal is examined classically in the presence of the magnetic field with the aim to calculate the time intervals between two states lying on the same Fermi surface. A lower limiting value of the transition time equal to about 10–18 sec is estimated as an average for the case when the states are lying on the Fermi surface having a spherical shape. Simultaneously, an upper limit for the electron circular frequency in a metal has been also derived. A formal reference of the classical transition time to the time interval entering the energy-time uncertainty relations known in quantum mechanics is obtained.

A novel transient rotor current control scheme of a doubly-fed induction generator equipped with superconducting magnetic energy storage for voltage and frequency support

A novel transient rotor current control scheme is proposed in this paper for a doubly-fed induction generator（DFIG）equipped with a superconducting magnetic energy storage（SMES） device to enhance its transient voltage and frequency support capacity during grid faults. The SMES connected to the DC-link capacitor of the DFIG is controlled to regulate the transient dc-link voltage so that the whole capacity of the grid side converter（GSC） is dedicated to injecting reactive power to the grid for the transient voltage support. However, the rotor-side converter（RSC） has different control tasks for different periods of the grid fault. Firstly, for Period I, the RSC injects the demagnetizing current to ensure the controllability of the rotor voltage. Then, since the dc stator flux degenerates rapidly in Period II, the required demagnetizing current is low in Period II and the RSC uses the spare capacity to additionally generate the reactive（priority） and active current so that the transient voltage capability is corroborated and the DFIG also positively responds to the system frequency dynamic at the earliest time. Finally, a small amount of demagnetizing current is provided after the fault clearance. Most of the RSC capacity is used to inject the active current to further support the frequency recovery of the system. Simulations are carried out on a simple power system with a wind farm. Comparisons with other commonly used control methods are performed to validate the proposed control method.

MEASUREMENT AND ANALYSIS OF MAGNETIC FIELDS OF ELECTROMAGNETIC CASTING ALUMINUM ALLOYS

Results of magnetic field investigation in a Kaiser type caster show that magnetic induction decays rapidly on moving inward from the outer surface and is almost doubled near corner.In the presence of screenings magnetic field strength is attenuated near periphery,but it isn't influenced within the interior.The resultant electromagnetic pressure balances with static head of liquid column,i.e,the upper magnetic induction is smaller than the lower's.However»the maximum pressure moves downward about 1 cm from half height of inductor.

Study on eliminating noises in short-period data of geomagnetic intensity by using nu-merical multichannel predictive filtering

The effectiveness of eliminating the noises in short-period data of geomagnetic intensity recorded in a little seismo-geomagnetic array by using numerical multichannel predictive filtering has been studied. The result shows that this technique is effective to fit external magnetic disturbance to inner electromagnetic induced difference field and reduce the noise level of difference data successfully. The filter quality factor Q of two examples in this work are 0. 86 and 0.68 respectively. The spectral analysis shows that during geomagnetic-calm days the fourfold-frequency harmonics of S q in difference data are main components. The length of the optimum filter depends on not only the frequency of predicable energy in difference data but also maybe the phase difference between input and expected output data. It is difficult to obtain the filter fitting both the data during magnetic-disturbed days and calm days. The result shows that the conductivity in Yanqing-Huailai basin west to Beijing may be much non-uniform.

Pattern transition and regulation in a subthalamopallidal network under electromagnetic effect

Although the significant roles of magnetic induction and electromagnetic radiation in the neural system have been widely studied,their influence on Parkinson’s disease(PD)has yet to be well explored.By virtue of the magnetic flux variable,this paper studies the transition of firing patterns induced by magnetic induction and the regulation effect of external magnetic radiation on the firing activities of the subthalamopallidal network in basal ganglia.We find:(i)The network reproduces five typical waveforms corresponding to the severity of symptoms:weak cluster,episodic,continuous cluster,episodic,and continuous wave.(ii)Magnetic induction is a double-edged sword for the treatment of PD.Although the increase of magnetic coefficient may lead the physiological firing activity to transfer to pathological firing activity,it also can regulate the pathological intensity firing activity with excessiveβ-band power transferring to the physiological firing pattern with weakβ-band power.(iii)External magnetic radiation could inhibit continuous tremulous firing andβ-band power of subthalamic nucleus(STN),which means the severity of symptoms weakened.Especially,the bi-parameter plane of the regulation region shows that a short pulse period of magnetic radiation and a medium level of pulse percentage can well regulate pathological oscillation.This work helps to understand the firing activity of the subthalamopallidal network under electromagnetic effect.It may also provide insights into the mechanisms behind the electromagnetic therapy of PD-related firing activity.

Effect of Cutting Techniques on the Structure and Magnetic Properties of a High-grade Non-oriented Electrical Steel

The high grade non-oriented electrical steel sheets containing 3.0%Si were manufacturing processed using different cutting techniques, then they were stress relief annealed（SRA）, the profiles and textures of the cutting edges were compared before and after annealing, and the magnetic properties of these specimens were tested and compared. The experimental results show that the iron loss of the specimen by water jet cutting is the lowest, but the magnetic induction under the low magnetic field is the highest, the iron loss of the specimen by laser cutting is the highest, but the magnetic induction under the low magnetic field is the lowest. It is necessary to adopt suitable production conditions and minimize the deterioration involved, and the magnetic property can be recovered by SRA effectively.

Quantum of the Magnetic Flux Characteristic forExperiments Performed on the Integer and Fractional Quantum Hall Effects

Experimentally the plateaus characteristic for the integer quantum Hall effect is obtained in vicinity of specific values of the magnetic induction. The paper demonstrates that the ratios of these induction values to carrier concentration in the planar crystalline samples approach systematically the quanta of the magnetic flux important for the behavior of superconductors. Moreover, the same quanta can be deduced from the Landau levels theory and their application in the magnetoresistance theory gives results being in accordance with experiments. The quanta of the magnetic flux similar to those for the integer quantum Hall effect can be obtained also for the fractional quantum Hall effect. This holds on condition the experimental ratio of the magnetic flux to carrier concentration is multiplied by the filling factor of the Landau level.

Influential Factors on Electromagnetic Properties of Selected 3D Reticulated Ceramics

3D reticulated ceramics (3DRCs) with the composition containing SrFe12O19-SiC-TiO2 were prepared by a replication process with polyurethane sponges as the template in ceramic slurry. The electrical conductivity, dielectric and magnetic parameters of 3D reticulated ceramics (3DRCs) were measured with changes in cell size of the sponges, contents in the slurry and sintering temperature in this paper. Discussions about the influential factors of those parameters were focused on their electrical conductivity. The experimental results indicated that the electrical conductivity of 3DRCs raised with the increase of cell size, SiC/SrO 6Fe2O3 with weight ratio and sintering temperature. X-ray diffractions and SEM were used to investigate the relationship between electrical conductivity and sintering temperature. Deoxidizing reactions of SrO 6Fe2O3 caused the increasing electrical conductivity. The real part of permittivity (ε') and imaginary part of permeability (μ') raised with the increase of electrical conductivity (σ). The imaginary part of permittivity (ε') has a maximum at 10o S/cm with the increase of a, and the real part of permeability (μ') changes slightly with the increase of a. When a is at the range of 10-4 S/cm to 10o S/cm (a semi conductive state), both the imagine part of permittivity and permeability raises with increasing a, therefore, the 3DRCs present their high electromagnetic loss properties.

Magnetic transition of ferromagnetic material at high pressure using a novel system

A system for the investigation of the magnetic properties of materials under high pressure is fabricated based on diamond anvil cell （DAC） technology. The system is designed with an improved coil arranged around the diamond of a non-magnetic DAC. Using this system, the magnetic transition of ferromagnetic （Fe） sample under increasing pressure can be observed. We successfully obtain the evolution of magnetic properties as a function of applied pressure reaching 26.9 GPa in the Fe sample. A magnetic transition is observed at approximately 13 GPa, which is consistent with the theoretical prediction.

Performance Study of a Self-Excitation Dual Stator Winding Induction Generator for Renewable Distributed Generation Systems

Renewable power generation is a suitable technology used to deliver energy locally to customers especially in remote regions. Wind energy based on induction generator situates in a foreground position in the total energy produced using renewable sources. In the last few decades, a new self- excitation generator was based on multi-stator induction strongly emerges. This article presents a systematic modelling, a detailed analysis and the performance analysis of self-excitation dual stator winding induction generator (SE-DSWIG). The modelling of the SE-DSWIG was done with taking in account the common mutual leakage inductance between stators and the magnetizing inductance, which played a principal role in the stabilization of the output voltage in the steady state. The generator feeds the end user emulated by an inductive-resistive load. In order to simulate the weather conditions’ variation, a step change of the prime mover speed was applied on the SE-DSWIG. A passive series and shunt compensator was used to mitigate the voltage sag and swell appeared in the power system due to wind variation and the lack of reactive power consumed by the inductive load.

Proper Understanding of the Natures of Electrons, Protons, and Modifying Redundancies in Electro-Magnetism

When considering electromagnetism, the unit of the Ammeter’s measurement should be limited to its proper unit in “Watt/Volt” which is, according to physical principles, the division quotient of the measured electrical power by its electrical potential. However, the Ammeter’s reading has also a traditional definition as the rate of flow of electric charges whose unit is “Ampere”. According to recent studies that define the electric charge as energy possessing an electric potential, such traditional definition is wrong as the Ammeter’s reading should, then, has the unit “Watt”. Such duality of the Ammeter’s reading is due to the wrong definition of electric charges as electrons and insertion of the “Ampere”, as a wrong unit of the flow of electric charges. This duality represents a “redundancy” in electromagnetism as the proper Ammeter’s reading, in Watt/Volt, is a unit of entropy of the flowing energy charges. Such redundancy led to further redundancies in the field of electromagnetism. In this article, it is followed the impacts of inserting the “Ampere” as illogic unit and it is derived the proper modifications of the results of replacing the “Ampere” by its logical substitute “Watt/Volt”. Such modifications lead to a robust definition of the electron as an elementary particle which has an elementary charge of energy 1.602 × 10-19 Joules and has a negative electric potential of 1 Volt and to a proper definition of the protons as elementary particles which are charged by a similar charge of electron, but it has a positive potential of 1 Volt. Additionally, the electron-volt is properly defined as an elementary charge whose energy is 1.602 × 10-19 Joules and whose potential is ±1 Volt. Such modifications also lead to improve the understanding of magnetic induction and modifying the equations that characterize the performance of electric machines. The truth of such innovative understandings is verified analytically and experimentally in this article.

An Attempt to Analyze a Human Nervous System Algorithm for Sensing Earthquake Precursors

We statistically validate the 2011-2022 earthquake prediction records of Ada, the sixth finalist of the 2nd China AETA in 2021, who made 147 earthquake predictions (including 60% of magnitude 5.5 earthquakes) with a prediction accuracy higher than 70% and a confidence level of 95% over a 12-year period. Since the reliable earthquake precursor signals described by Ada and the characteristics of Alfvén waves match quite well, this paper proposes a hypothesis on how earthquakes are triggered based on the Alfvén (Q G) torsional wave model of Gillette et al. When the plume of the upper mantle column intrudes into the magma and lithosphere of the soft flow layer during the exchange of hot and cold molten material masses deep inside the Earth’s interior during ascent and descent, it is possible to form body and surface plasma sheets under certain conditions to form Alfven nonlinear isolated waves, and Alfven waves often perturb the geomagnetic field, releasing huge heat and kinetic energy thus triggering earthquakes. To explain the complex phenomenon of how Ada senses Alvfen waves and how to locate epicenters, we venture to speculate that special magnetosensory cells in a few human bodies can sense earthquake precursors and attempt to hypothesize an algorithm that analyzes how the human biological nervous system encodes and decodes earthquake precursors and explains how human magnetosensory cells can solve complex problems such as predicting earthquake magnitude and locating epicenters.