Electromagnetic Field Variations Research Articles

Experimental study on sheet grinding based on magnetic abrasive tool driven by variable electromagnetic fields

Experimental study on sheet grinding based on magnetic abrasive tool driven by variable electromagnetic fields

On the photon emission by a variable electromagnetic field

On the photon emission by a variable electromagnetic field

Effect of Electromagnetic Power on the Microstructure and Properties of 2219 Aluminum Alloy in Electromagnetic Continuous Casting Technology

Electromagnetic continuous casting technology serves as a significant means for enhancing the casting performance of 2219 aluminum alloy. Investigating the influence of electromagnetic field variations on the solidification process is crucial for studying the microstructure and mechanical properties of electromagnetic cast billets. Through experimental research, variations in the microstructure and mechanical properties were examined for ordinary direct chill casting, as well as three different electromagnetic power casting ingots. The COMSOL software (COMSOL Multiphysics 6.0) was utilized to simulate the temperature and flow field, enabling an explanation of the resulting performance changes. The results showed the effect on electromagnetic continuous casting technology by the electromagnetic field generated by the Lorentz force and melt stirring, improving the melt flow and temperature distribution so that the melt center and the edge of the melt forcible convection were enhanced, thus realizing the tissue refinement, mechanical properties, and Cu element segregation of the improvement. With an increase in electromagnetic power, the distribution of the temperature field was more homogeneous, the segregation phenomenon was more alleviated, and the improvement in mechanical properties was more significant. The optimal microstructure and mechanical properties were achieved at a power of 20.0 kW, with a 74.7% improvement in grain refinement in the center and a tensile strength increase of 30.8%. Additionally, significant improvements were observed in segregation phenomena.

Дослідження впливу змінного електромагнітного поля на трибологічні властивості моторних олив

A set of studies was conducted on the influence of mechanical, thermal and electromagnetic factors under the action of the variable electromagnetic field of the oil pumping device on the properties of M-6В3 motor oils; M-10Г; M-10Г2. The research was carried out on a special stand, which allows to simulate the operating conditions of the oil injection device on the car engine during the start-up period. The evaluation of the efficiency of the oil pumping device was determined by the volume and effective coefficients of the useful action. In the process of research, oils (fresh and used) that were exposed to an alternating electromagnetic field and oils that were not exposed to the corresponding influence were compared according to the main physicochemical properties: kinematic viscosity at temperatures of 373, 323, 293, 273 and 258 K; solidification temperature of oil, K; viscosity index; ash content, %; the content of refractory mechanical impurities, %; iron content, %. The results were obtained on the effect of an alternating electromagnetic field on the viscosity-temperature parameters of fresh M-6В3 oils; M-10Г; M-10Г2. In the temperature range of 293...323 K, a decrease in the viscosity of the studied oils was observed. An increase in temperature eliminates the difference between processed and unprocessed oils. The effect of the duration of the alternating electromagnetic field on the viscosity index of the studied oils at a temperature of 258 K was studied. The optimal duration of olive processing was determined, which is 9...12 minutes, depending on its organic basis and the presence of additives in it. The characteristics of changes in the viscosity-temperature characteristics of the studied oils after certain periods of time after the action of a variable electromagnetic field on them were analyzed. It has been confirmed that these characteristics of processed oils are approaching the similar characteristics of untreated oils over time, except for M-6В3 oil, which stably retains the acquired properties even after a long time of its processing. With the use of a special installation that simulates the work of tribo-coupling "cam-pusher", the influence of an alternating electromagnetic field on the anti-wear and anti-seize properties of the studied oils was investigated. A 1.2-1.5 times reduction in the amount of wear of both the working surfaces of the pushers and the cams was noted, in the absence of varnish deposits on them.

Near-Field Observation of the Photonic Spin Hall Effect.

The photonic spin Hall effect, referring to the spatial separation of photons with opposite spins due to spin-orbit interactions, has enabled potential for various spin-sensitive applications and devices. Here, using scattering-type near-field scanning optical microscopy, we observe spin-orbit interactions introduced by a subwavelength semiring antenna integrated in a plasmonic circuit. Clear evidence of unidirectional excitation of surface plasmon polaritons is obtained by direct comparison of the amplitude- and phase-resolved near-field maps of the plasmonic nanocircuit under excitation with photons of opposite spin states coupled to a plasmonic nanoantenna. We present details of the antenna design and experimental methods to investigate the spatial variation of complex electromagnetic fields in a spin-sensitive plasmonic circuit. The reported findings offer valuable insights into the generation, characterization, and application of the photonic spin Hall effect in photonic integrated circuits for future and emerging spin-selective nanophotonic systems.

Hygienic regulation of electromagnetic fields in the Russian Federation: history and current state

The article presents in detail the history of the creation of hygienic normative documents regulating the industrial and non-industrial effects of electromagnetic fields in the Russian Federation. Systematic scientific research in the field of biological action and hygienic regulation of radio frequency electromagnetic fields in our country began at the Research Institute of Occupational Hygiene and Occupational Diseases, Academy of Medical Sciences of the USSR, where in 1952 specialists created the first laboratory of electromagnetic waves of radio frequencies in the country. In the future, a number of scientific institutions of hygienic, biomedical and physico-technical profile joined these studies. Scientists have scientifically substantiated the methodology of rationing hygienic factors. Over the past period, scientists have developed about 30 documents, including the maximum permissible level of electromagnetic fields. Currently, in the Russian Federation, the main current document establishing the maximum permissible level of permanent and variable electromagnetic fields in the workplace and for the public is SanPiN 1.2.3685-21 "Hygienic standards and requirements for ensuring the safety and(or) harmlessness of environmental factors for humans". The analysis made it possible to evaluate its advantages and identify disadvantages, as well as to outline promising areas of scientific research to improve existing and develop new maximum permissible levels of electromagnetic fields created by modern sources.
 Ethics. This study did not require the conclusion of the Ethics Committee.

Successive Energy Conversion at a Stepwise Dipolarization Front

Dipolarization fronts (DFs), ion-scale magnetic structures characterized by sharp enhancement of northward magnetic field developed within plasma jets, have been suggested to play a crucial role in the energy transfer chain in the terrestrial magnetotail. Here we present the first observation of successive energy conversion driven by multiple current layers at a stepwise DF, using high-cadence measurements from NASA’s Magnetospheric Multiscale mission. The multiple current layers are adjacent and cause gradual variations of particles and electromagnetic fields, leading to an intense, successive increase of energy conversion rates at the DF in the satellite frame, with electromagnetic field energy being transformed into particle energy. The energy conversion is contributed by both ion and electron currents. The motional electric field drives the energy conversion, while the wave electric field fed by lower hybrid drift instability modulates the energy partition. These results provide new insights into understanding energy transfer in the terrestrial magnetotail.

Relating GPR system parameters to regulatory emissions limits

AbstractGround penetrating radar (GPR) is regulated regarding emission limits for ultra‐wideband in a number of jurisdictions. The definitions of these regulations employ concepts and terminology that are more suited to traditional narrow band radio transmitters. Further, the emissions limits were based on limited quantitative factual information and have resulted in stringent limitations on GPR technology advancement. Factual theoretical and experimental information on the emissions from actual GPR devices is not generally available, and the relationship with regulatory requirements is poorly understood by users. This information gap must be filled if a compelling argument for less stringent emissions levels is to be mounted in the future. Moreover, the current regulations have the potential to trigger further review of emission limits in the future which could be detrimental to the use of GPR. In this paper, we present the basic steps entailed in translating impulse time‐domain GPR instrument behaviour into ‘regulatory’ parameters. To achieve this, we also employ three‐dimensional finite‐difference time‐domain numerical modelling to simulate the transient electromagnetic field variation around dipole antennas placed on the surface of a half‐space or at a height over it to illustrate the dependency on sensor height and ground permittivity. The ultimate goal is to establish the foundation for more sensible rule making, if and when, the regulatory standards come under scrutiny for revision and further user understanding.

Magnetotelluric Power Line Noise Removal Using Temporally Varying Sinusoidal Subtraction of the Grid Utility Frequency

The magnetotelluric method relies on variations of natural electromagnetic fields, which in the vicinity of human settlements are persistently distorted by anthropogenic electromagnetic noise. A large source of noise to the magnetotelluric response is caused by the harmonic oscillations of the power network utility frequency centered on 50/60 Hz along with the associated higher harmonics. Removing this type of noise is essential for high frequency magnetotelluric measurements used for shallow surveys. There are a large number of approaches for how to treat power line noise in magnetotelluric signals, however, commonly used methods do not take into account time variations/instabilities of the utility frequency. That is not serious problem in vicinity of well balanced grid networks, but can cause issues in regions with larger utility frequency variations. Under such conditions, commonly used methods loose more of the natural signal, which is undesirable especially in case of very noisy datasets. Hence, we adopted approach for removing of power line noise with respect to time variations of the utility frequency and applied it to magnetotelluric signals to preserve more of natural signal. The method is based on modelling of the grid network harmonic oscillations by the optimum utility frequency and its integer multiples. The resulting sum of sinusoidal signals is subsequently subtracted from recorded data and only particular noise frequencies are removed from the original signal with high precision, while frequency ranges around power line harmonics are cleaned.

Electromagnetic Field Variation of ELF Near-Region Excited by HED in a Homogeneous Half-Space Model

Great attention has been paid to the propagation of electromagnetic (EM) waves across the sea surface due to its important applications. Most of the previous research, however, focuses on the half-space model illustrating the deep sea environment. In this paper, EM field distribution in the extremely low frequency (ELF) near-region under horizontal electric dipole (HED) excitation in homogeneous half-space seawater is analyzed based on the general expression of the Sommerfeld integral using the quasistatic approximation method. The focus is on deriving complete and effective solutions in air and seawater regions under the cylindrical coordinates for the EM near-field, which is generated by an HED in a shallow sea. The resulting formulas can be given by a few summands in closed form as the well-known Fourier–Bessel integrals. The analytical approximate expression of ELF Sommerfeld EM field integral excited by the HED in the homogeneous half-space seawater is deduced under the condition that the propagation distance ρ satisfies kρ << 1. To this end, the EM field distribution in the range close to the HED antenna in seawater is simulated, the results have shown that the minimum attenuation value of the vertical electric component Ez is about 15 dB, and that of the radical magnetic components Hφ is about 30 dB, and these values are found to be of greatest potential for the near-field region propagation among the electric and magnetic components. Finally, the correctness of the proposed method is verified by comparison with Pan’s approximation method and Margetis’s exact expression approximation method, which demonstrated the correctness of the proposed method.

Research of the Influence of the Combined Electromagnetic Field on Biogas Output

The purpose of research is determining the conditions of stimulating effect of the combined influence of constant and variable electromagnetic fields on the substrate and microorganisms in the bioreactor. This goal is achieved by solving the following tasks: development of mathematical model, conducting numerical simulation to determine the distribution of magnetic field in active zones of the stator-bioreactor system; conducting experimental researches during the fermentation of pig’s manure with litter from wheat straw in the mesophilic mode of fermentation. One category of bioreactors (control samples) was not exposed to influence of magnetic field, for the other, periodically were made treatment simultaneously with a low-frequency electromagnetic field and constant magnetic field synchronously with the process of mixing the substrate. The most significant results are: an experimental proof of effectiveness of the proposed method of intensification of the biogas output and increasing its quality, high accuracy of mathematical model of distribution the magnetic field in active zones of the stator-bioreactor system; assessment of the levels of consumption of nutrients by microorganisms from the substrate under the influence of the combined magnetic field and without influence of the magnetic field. The significance of obtained results lies in the fact that the proposed approach to intensification of the biogas output provides increase of the level production, the quality of biogas, and cumulative rate of methane output per unit of organic mass in the reactor.

A Kinematically Constrained Kalman Filter for Sensor Fusion in a Wearable Origami Robot

AbstractSensing for wearable robots is an ongoing challenge, especially given the recent trend of soft and compliant robots. Recently, a wearable origami exoshell has been designed to sense the user’s torso motion and provide mobility assistance. The materials of the exoshell contribute to a lightweight design with compliant joints, which are ideal characteristics for a wearable device. Common sensors are not ideal for the exoshell as they compromise these design characteristics. Rotary encoders are often rigid metal devices that add considerable weight and compromise the flexibility of the joints. Inertial measurement unit sensors are affected by environments with variable electromagnetic fields and therefore not ideal for wearable applications. Hall effect sensors and gyroscopes are utilized as alternative compatible sensors, which introduce their own set of challenges: noisy measurements and drift due to sensor bias. To mitigate this, we designed the Kinematically Constrained Kalman filter for sensor fusion of gyroscopes and Hall effect sensors, with the goal of estimating the human’s torso and robot joint angles. We augmented the states to consider bias related to the torso angle in order to compensate for drift. The forward kinematics of the robot is incorporated into the Kalman filter as state constraints to address the unobservability of the torso angle and its related bias. The proposed algorithm improved the estimation performance of the torso angle and its bias, compared to the individual sensors and the standard Kalman filter, as demonstrated through bench tests and experiments with a human user.

Improvement of Operational Parameters for Precision Rolling Bearings by Cleaning Working Surfaces from Micro Pollution of Various Nature

In manufacturing high-precision rolling bearings for aviation and urban machinery, the key tasks are to reduce the cost of production of such products, increase their efficiency and resource, and ensure their reuse after performing appropriate repair work. The results of many years of research show that these tasks can be successfully solved by cleaning the working surfaces of the parts of such precision tribonodes by non-contact pulse methods, particularly by using variable electromagnetic fields. The article describes the process of deep cleaning the working surfaces of parts of various high-precision ball bearings (from overall to miniature). During this cleaning, ferromagnetic and other impurities in the form of micro-, sub-micro- and nanoparticles were removed on a developed stand that can be used on an industrial scale. Further studies of cleaned bearings showed improved operational parameters such as reduced noise and vibration and the degree of magnetization. To achieve the specified results, appropriate cleaning methods were developed and tested.

Variable electromagnetic fields in physiotherapy of diseases of the musculoskeletal system

Increasing evidence suggests that the exogenous electromagnetic field may be involved in many biological processes of great importance for therapeutic interventions.
 It is known that variable electromagnetic fields are a non-invasive, safe and effective therapeutic tool without obvious side effects. Numerous studies have shown that variable electromagnetic fields can become an independent or additional method of treating diseases of the musculoskeletal system. However, several questions remain unresolved. Prior to their widespread clinical application, further research is needed based on well-designed, high-quality studies to standardize treatment parameters and develop an optimal protocol for healthcare decision making.
 In this review, we aimed to provide up-to-date data on the mechanism of action, clinical application, and controversy regarding variable electromagnetic fields in the physiotherapy of musculoskeletal disorders.

Responsive materials architected in space and time.

Rationally designed architected materials have attained previously untapped territories in materials property space. The properties and behaviours of architected materials need not be stagnant after fabrication; they can be encoded with a temporal degree of freedom such that they evolve over time. In this Review, we describe the variety of materials architected in both space and time, and their responses to various stimuli, including mechanical actuation, changes in temperature and chemical environment, and variations in electromagnetic fields. We highlight the additive manufacturing methods that can precisely prescribe complex geometries and local inhomogeneities to make such responsiveness possible. We discuss the emergent physics phenomena observed in architected materials that are analogous to those in classical materials, such as the formation and behaviour of defects, phase transformations and topologically protected properties. Finally, we offer a perspective on the future of architected materials that have a degree of intelligence through mechanical logic and artificial neural networks.

Fluid-Kinetic Variations in the Storm-Time Inner Magnetosphere.

Storm‐time broadband electromagnetic field variations along the interface between the dipolar field of the Earth's inner‐magnetosphere and the stretched fields of the plasma‐sheet are decomposed as a superposition of fluid‐kinetic modes. Using model eigen‐vectors operating on the full set of Van Allen Probes fields measurements it is shown how these variations are composed of a broad spectrum of dispersive Alfvén waves with significant spectral energy densities in the fast and slow modes over scales extending into the kinetic range. These modes occupy volumes in k‐space that define the field variations observed at each spacecraft frame frequency (fsc). They are in aggregate not necessarily planar and often comprise filamentary structures with no distinct propagation direction in the perpendicular plane. Within these volumes the characteristic parallel phase speeds of the fast and Alfvénic modes coincide over a broad range of fsc suggestive of coupling/conversion between modes.

The effect of microwave electric field on sulfur vacancies formation over the edge sites of Co/Ni-promoted and unpromoted MoS2 catalysts through DFT investigations

The elementary reactions for the formations of sulfur vacancies over various edges of Mo-based active phases were systematically investigated and compared under the action with/without microwave electric field via DFT calculations. The results reveal that the H2 dissociation is extremely difficult over the M−edge of pure MoS2 clusters. The partial doping of Co/Ni can significantly reduce the difficulty, while the difficulty over the S-edge is obviously lower than that of the M−edge. Compared with CoMoS-I, H2 dissociation becomes more favorable over the S-edge of NiMoS. The atomic H migration is unlikely to occur over the edge of MoS2, however, it becomes spontaneous after being dopped by Co/Ni along specific paths. The effect of electric field direction differs on each step of the vacancy formation over various edges. Either EX+ (the field applied along the direction of the x-axis) or EX- field would highly benefit H2 dissociation, H migration and H2S desorption on both M−edge and sulfur edge, thus it presents great significance that microwave, the existence of variable electromagnetic field is conducive to the formation of sulfur vacancies. The findings would shed more light on understanding the promotion mechanism of Co/Ni doping and microwaves on the HDS process.

Coherence Resonance Behavior of FitzHugh‐Nagumo Neurons Induced by Electromagnetic Field Driven by Phase Noise

Noise exists widely in the nervous system, and plays a crucial role in the nervous system information processing. Noise can not only enhance but also weaken the ability of the nervous system to process information. Neurons are in a complex and variable electromagnetic field. Electromagnetic induction plays an important role in regulating the changes of neuronal membrane potential. Therefore, this paper simulates the electromagnetic field environment of the nervous system with a memristor and analyses the rich coherence resonance behavior of FitzHugh‐Nagumo (FHN) neuron system under the drive of phase noise. By taking the amplitude, period and noise intensity of phase noise as the main parameters and the parameters of memristor as auxiliary parameters, the two‐parameter changes are made from the angle of the amplitude and period of phase noise, the amplitude and intensity of phase noise, and the noise intensity and period of phase noise, respectively. The dynamic behaviors of coherent resonance of FHN neuron system are analyzed from the amplitude and period, amplitude and intensity as well as intensity and period of phase noise, respectively. When the amplitude and period of the phase noise and the intensity and period of the phase noise are used as independent variables for the two‐parameter analysis, the FHN neuron system shows rich dynamic behaviors such as coherence mono‐resonance, coherence bi‐resonance and coherence multi‐resonance. Especially when the amplitude and period of phase noise change as two‐parameter, the system presents a coherence resonance of discharge pattern with period‐adding cluster discharge at the valley. When the amplitude and intensity of phase noise are taken as independent variables for two‐parameter analysis, FHN neuronal system presents single or dual coherence resonance at any value of noise intensity with the change of phase noise amplitude. The simulated results show that the FHN neuron system demonstrates rich coherence resonance behaviors under the drive of phase noise when the effect of electromagnetic induction in the nervous system is simulated by memristor.

Modeling of Electromagnetic, Thermal, and Mechanical Processes in Magnetic Media with Regard for the Moment Factors

We study specific features of the construction of thermomechanical models for ferromagnetic (ferritic) solids with regard for the moment force factors caused by the interaction with electromagnetic fields. In particular, we obtain the input relations of these models in the presence of external fields in the form of a combination of constant magnetic fields with variable electromagnetic fields. These relations can be used for the analysis of specific practically important problems of the thermomechanical behavior of solids under the conditions of ferromagnetic resonance, induction heating in the course of magnetization, and propagation of magnetostatic waves in these solids.

Towards probing Earth\u2019s upper mantle with daily magnetic field variations: exploring a physics-based parametrization of the source

The electromagnetic (EM) field variations capable of probing the electrical conductivity of the upper mantle and mantle transition zone have a period range between a few hours and 1 day. At these periods, the dominant source of the EM signals is the ionospheric current system, which has a complex spatial and temporal structure. A concept of global-to-local (G2L) transfer functions can handle spatially complex source by relating global source expansion coefficients with locally measured magnetic (or/and electric) fields. When estimating the G2L transfer functions, the source is commonly expanded into spherical harmonics (SH). In this paper, we explore an alternative parametrization of the source based on a principal component analysis (PCA) of the Fourier transformed output from the physics-based Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM). Specifically, we investigate whether magnetic fields computed in the realistic three-dimensional conductivity model of Earth excited by the PCA-based source agree better with observatory data than those computed in the same model but induced by the SH-based source. Using PCA to capture the source current compared to SH parametrization, we find that agreement with the observatory data is better during magnetically disturbed times and at shorter periods. Vice versa, it is poorer during magnetically quiet times and at longer periods.