Characteristics Of Electromagnetic Field Research Articles

Mathematical Assessment of Pollution Factors from Eddy Currents in the Durrës Seaport

Eddy currents, a significant phenomenon in electromagnetic fields, were first distinguished from general electric currents by Foucault. These currents, influenced by the magnetic field vector (H), magnetic flux density (B), and electric field (E), are present in various environments, including homogeneous and non-homogeneous areas, linear and non-linear environments, and open boundary problems. In marine environments, these currents, referred to as planetary currents, contribute to electrical pollution, impacting maritime infrastructure, machinery, and ecosystems. This study aims to assess the impact of eddy currents in the Durrës Seaport, Albania, focusing on how meteorological factors such as temperature, atmospheric pressure, and humidity influence pollution levels. Using the TES-92 Electro-smog meter and the PCE-THB 40 Thermo-hygrometer and barometer, we measured electromagnetic field characteristics and meteorological parameters. Our results highlight the significant impact of stray currents on marine environments, emphasizing the need for effective measures to minimize their effects and improve the quality and selection of materials and equipment in port facilities. This study provides valuable insights into the environmental and infrastructural challenges posed by electromagnetic pollution and proposes recommendations for mitigating these impacts.

Analysis of Electromagnetic Field Characteristics of Wave Glider

A wave glider is an ocean observation platform that utilizes wave energy to drive and solar energy to power. Its metal structure will generate related electromagnetic fields due to corrosion and underwater motion. In the detection of weak electromagnetic field signals underwater, its own electromagnetic field characteristics will have an impact on signal detection. To study the applicability of electric field sensors and magnetic field sensors on wave glider platforms, the structural characteristics of the wave glider were analyzed, and the installation positions of electric field sensors and magnetic field sensors were designed based on the different motion states of the water surface mother body and underwater towing body. The measured electromagnetic field data of the wave glider platform were measured, and the measured data were analyzed. It was determined that the interference electric field energy under typical working conditions of the wave glider was mainly concentrated within 1 Hz, which decreased with increasing frequency, and the magnitude was mV/m. The magnitude of the interference magnetic field is several tens of nT, indicating that the electromagnetic field interference is significant during the working state of the wave glider. Installing an electric field sensor directly at the bottom of the wave glider will cause significant noise interference, while installing the magnetic field sensor directly at the bottom of the tractor will affect the servo and the shaking-induced magnetic field. Moreover, wave gliders should not use electric field signals below 1 Hz as signal sources, but they can utilize axial frequency electromagnetic fields to detect weak electromagnetic signals underwater.

A Study on the Electromagnetic Field Characteristics of Two-Inverter System of Three-Phase Motor Assuming a Failure

A Study on the Electromagnetic Field Characteristics of Two-Inverter System of Three-Phase Motor Assuming a Failure

Математическая модель для проектирования линейных асинхронных электродвигателей и ее программная реализация

Mathematical models are the main tool for the layout design of linear asynchronous electric motors. Existing design models of linear asynchronous electric motors assume that the device is powered from a source of multiphase symmetrical positive sequence current, which excludes from consideration the asymmetry of the inductor phase currents and the associated reduction in traction force. This approach is not flexible enough, since the operation of linear asynchronous electric motors in a wide range of movement speeds assumes a functional relationship between the current asymmetry coefficient and the movement speed. The study developed a mathematical model for design purposes that implements the functional relationship between the current asymmetry coefficient and the speed of movement. The mathematical model represents 13 linear equations linking geometric dimensions, current loads, electromagnetic field characteristics and mechanical forces with the speed of the secondary element of the electric motor. The current load of an electric motor has a variable degree of ellipticity depending on the speed of movement. An algorithmic study of the mathematical model was carried out and corresponding software modeling tools were developed. The proposed program algorithm, containing two subroutines, is implemented using the Maple symbolic computing software package. In order to expand the range of users, the software model is additionally implemented in C++. In this case, the functional dependence of the asymmetry coefficient of the exciting current wave on the speed of movement is implemented in the form of an iterative procedure for the case of connecting the winding of the linear asynchronous electric motors inductor to a source of symmetrical three-phase voltage according to the “triangle” circuit. Using the example of a three-phase linear asynchronous electric motors, the electromagnetic and mechanical characteristics of the electric motor were simulated. It was stated that the influence of current asymmetry on the mechanical characteristics of the linear asynchronous electric motors is small and is expressed in the region of high speeds. This makes it possible, in design tasks for the layout of an electric motor, to use models that involve powering the linear asynchronous electric motors from a symmetrical current source or to introduce a fixed asymmetry coefficient into them.

Research on electromagnetic field characteristics of rotating-magnet based mechanical antenna through the earth

Conventional low-frequency electromagnetic wave (LFEM) transmitting antennas are enormous in size, which limits the application of LFEM in underground space. Rotating-magnet Based Mechanical Antennas can realize the miniaturization of low-frequency antennas, which is expected to bring new possibilities for underground electromagnetic detection or ground penetration communication. Firstly, this paper establishes a synthetic field method for solving the electromagnetic field of a rotating permanent magnet in the air-earth cross-domain case. The method equates the magnet as an orthogonal superposition of vertical and horizontal dipole sources, and the phase difference between vertical and horizontal dipole sources is 𝜋/2. Based on the half-space theory of multilayer planar media, the quasi-analytical solution of the electromagnetic field of the magnetic dipole in the case of air-earth trans dimensionality can be found by superposition. Secondly, based on the finite element numerical model, the trans-earth propagation characteristics of the electromagnetic field excited by the rotating permanent magnet across the air-earth dual domain are studied. At the same time, the radiation characteristics in the rotating plane of the permanent magnet are also studied. Again, this paper systematically investigates the influence of parameters such as earth conductivity, emission frequency, and propagation distance on the electromagnetic field propagation. Finally, the principle prototype is developed and experiments are carried out. The results show that the finite element numerical model established in this paper is correct, the experimental results are consistent with the theoretical values, and a field strength signal of 0.9 nT can be received at 20 m. The research work in this paper lays the foundation for the future use of mechanical antennas for electromagnetic detection and ground penetration communication.

One-dimensional parallel forward modeling for geophysical electromagnetic fields excited by sagging overhead transmission lines

Geophysicists often regard the 50/60 Hz electromagnetic (EM) waves and their harmonics, excited by overhead transmission lines, as noise that interferes with geophysical prospecting. However, some researchers view them as effective signals for geophysical exploration. Forward modeling can be used to study the characteristics of EM fields generated by overhead transmission lines. It can help in either eliminating or utilizing power-frequency EM fields. Nevertheless, current research on the forward modeling of EM fields excited by transmission lines neglects the sagging shape and direction of the actual transmission lines, simplifying them into infinitely long straight lines. In this research, we develop a one-dimensional forward modeling algorithm specifically designed for overhead transmission lines, which can accurately calculate the EM fields excited by realistic overhead transmission lines considering the three-phase system, design parameters, sag, and orientation of the transmission lines. To construct an accurate transmission line model, we represent the sagging shape of a single transmission line within a span by a catenary equation. We then derive analytical expressions for the EM fields excited by sagging overhead transmission lines. During forward modeling, an appropriate number of Gauss points must be selected to balance accuracy and speed. The optimal number of Gauss points is determined based on the distance between the observation point and the transmission line source, as well as the type of fields being calculated. OpenMP parallelization is used to improve computational speed. The forward modeling results reveal significant differences between the forward responses of a single infinitely long straight line and realistic transmission lines. This highlights the importance of fully incorporating the three-phase system, design parameters, and geometric shapes of transmission lines in the forward modeling process. Moreover, the inversion test demonstrates the potential utility of EM fields radiated by transmission lines for geophysical exploration.

Electromagnetic–thermal field coupling in tissue ablation: The EAES design and optimization

The coupling control of multi-physics fields has become a focal issue in the engineering domain, especially for achieving a more precise simulation and prediction of physical phenomena. This approach plays a crucial role in enhancing design efficiency and optimizing material selection. Focusing primarily on the controllability between microwave and temperature fields, the Emission Area Extension Structure (EAES) is a novel structure in response to the demand for high circularity in microwave ablation. Finite element analysis was employed to examine the distribution characteristics of electromagnetic and temperature fields in liver tissue under varying power and time conditions. Comparative analyses were conducted to evaluate the impact and performance of the EAES vs traditional structures in ablation. Incorporating the EAES into conventional ablation needles allows for a more concentrated distribution of the electromagnetic field without altering the needle diameter. In the simulation of tissue ablation, the circularity of ablation increased by 10%, while water-cooling efficiency increased by 11%. The introduction of EAES, while maintaining its minimally invasive characteristics, effectively enhanced the controllability of conformal ablation. Furthermore, a mathematical model was developed to serve as a theoretical basis for selecting optimal preoperative parameters, incorporating conditions such as ablation time, power, range, and circularity. Overall, by conducting a multi-physics field coupling analysis on microwave ablation needles and proposing the EAES solution, this study aims to enhance the predictability, controllability, and safety of conformal ablation.

Study of electromagnetic field characteristics at errors of focusing phase distributions

Study of electromagnetic field characteristics at errors of focusing phase distributions

Study on the Three-component Response Characteristics of Ground-airborne Electromagnetic Field

At any point in space, an electromagnetic field consists of three components: Hx, Hy, and Hz. The ground airborne electromagnetic method (GAEM) does not usually retrieve the Hx and Hy components of the electromagnetic field, less data may result in less accurate goaf interpretations. In this study, we numerically simulate the characteristics of the frequency-domain ground-airborne electromagnetic signal sources, quantify the induction signal distribution laws in the x-, y-, and z- directions, and identify the various factors that influence ground-airborne electromagnetic signals. The results of this study provide theoretical support for the future development of a three-component receiver for ground airborne electromagnetic field surveys. Furthermore, this data also provides information that will prove valuable in the design of field work construction.

The role of the modulated intrinsic electromagnetic field characteristics inside the carbon nanopores on molecular hydrogen densification

While the anomalous phenomenon of H2 densification in sub-1 nm carbon nanopores have attracted the attention of many researchers, there have been few in-depth studies on the fundamentals. Recently, we discovered that significant intrinsic electromagnetic fields (IEMFs) inside carbon nanopores with diameters below 1 nm are modulated with the difference in morphology, and it seems to be linked to the anomalous phenomenon. As a follow-up study, we find that the IEMFs inside carbon nanopores can be modulated by tuning pore diameter or atomic composition. Moreover, it is suggested that these modulations are highly correlated to the degree of molecular hydrogen densification. Particularly, given the widely accepted fact that the H2 densification is possible in only sub-1 nm nanopore, it is notable that the nanopores larger than 1 nm may play a substantial role in H2 densification by controlling atomic composition. This paper carefully suggests that this concept can be applied to the field of hydrogen storage materials so that the development of H2 storage materials with high performance may be achievable.

Electromagnetic Compatibility Time Domain Response Characteristics of EEDs

The theory and algorithm of electric initiation are applied to the study of time-domain response of electromagnetic compatibility of electro-explosive devices(EEDs). based on the antenna theory and transmission line theory, the mathematical model of electromagnetic wave time domain response of different signal characteristics of EEDs was established, and the time domain response characteristics of electromagnetic field of typical EEDs were calculated and analyzed. The time domain characteristics of response of EEDs in electromagnetic field were tested and studied based on the characterization method of electromagnetic induction energy of transducer. The experimental results are consistent with the calculated results.

Analysis of Induction Heater System Considering Electromagnetic Field and Thermal Characteristics of Motor Rotor Bearing

Analysis of Induction Heater System Considering Electromagnetic Field and Thermal Characteristics of Motor Rotor Bearing

Design and Study of the Key Characteristics of a New DC Vacuum Interrupter With a High Peak and Low Residual Magnetic Field

With the rapid development of multiterminal high-voltage direct current (HVdc) transmission systems, the research and development of high-speed and stable high-voltage dc circuit breakers have received attention. Among them, mechanical dc circuit breakers based on manual zero-crossing dc breaking technology have been applied in practical projects, owing to their small size, low on-state loss, and low price. However, this method adds a high-frequency current, which deteriorates the magnetic field between the poles of the interrupter when the arc is broken. Therefore, the development of HVdc circuit breakers that maintain high peak magnetic fields and low residual magnetic fields at high frequencies has become the key to the development of multiterminal HVdc transmission. To solve this problem, this article proposes a new interrupter for a vacuum dc circuit breaker based on artificial zero-crossing technology and studies its key characteristics, such as temperature rise, electromagnetic field, and arc column plasma distribution characteristics. The results reveal that the new interrupter proposed in this article has a low-temperature rise, uniformly distributed electric field, high peak value and low remanence of the longitudinal magnetic field, and uniformly distributed plasma in the arc column, and exhibits arc diffusion. Its ability to cope with high-frequency current is significantly higher than that of the traditional cup-shaped axial magnetic field (AMF) contact system interrupter, which is conducive to the high-speed and stable breaking of the interrupter.

ELF-EM fields in the multi-layer spherical ‘Earth-ionosphere’ model based on WKB

Abstract With a high signal-to-noise ratio and a great depth of exploration, the wireless electromagnetic method (WEM) has wide applications in the exploration of deep mineral resources and oil and gas reservoirs. Extremely low-frequency electromagnetic (ELF) waves emitted from a horizontal antenna are used to achieve synchronous acquisition for different receivers of multi-coverage information in a global region. However, previous research based on a planar model ignored the curvature of the Earth. This work focuses on the electromagnetic fields (EM fields) in the model of a spherical ‘Earth ionosphere’ to extend the coverage of WEM. By transferring the EM fields from a vertical electric dipole (VED) as well as a vertical magnetic dipole (VMD) in the multi-layered medium of the Earth, we obtain the formulae for the EM fields emitted by a horizontal electric dipole (HED) by using a reciprocity theorem. The correctness of the proposed method is verified by comparing it with the approximate analytical formula and previous work. Based on the above results, we have studied the propagation and frequency characteristics of electromagnetic fields in a spherical waveguide consisting of the ionosphere and earth. The results show that the electromagnetic fields under the spherical model produce interference effects that are different from those of the planar model. The electromagnetic response of the layered Earth was then discussed, and its potential as an electromagnetic technique for exploring the deep Earth was demonstrated.

Passive radiative cooling design with novel selectively grating structure under direct sunlight

Daytime radiators spontaneously transfer excess heat to the external space and become an attractive choice for radiative cooling technology with the advantages of no energy consumption and no pollutant generation. A grating selective structure with high reflectivity in the solar band and high absorptivity in the 8–13 µm band was proposed for daytime radiative cooling in this paper. The structural parameters and constituent materials of the structure were optimally solved using the RCWA-PSO algorithm to maximize its net cooling power. It was shown that the grating selective structure composed of SiO2, AlON, and MgAl2O4 with a solar band absorptivity of 4.9% can achieve a net cooling power of 72.42 W/m2 under intense solar radiation, while achieving a net cooling power of 121.47 W/m2 at night. Its cooling performance is better than that of more than 80% of flat panel radiators. Additionally, the electromagnetic field characteristics study revealed that SiO2 is easier to excite the magnetic polaritons (MPs) resonance mechanism than AlON and MgAl2O4, but the coupled resonance effects of MPs and Surface Plasmon Polaritons (SPPs) are easily excited inside MgAl2O4. Thus, SiO2 and MgAl2O4 may be the preferred materials for radiators.

Characteristics of electromagnetic vector field generated from rock fracturing

Rock fracturing is often accompanied by electromagnetic phenomenon. As a vector field, in addition to the intensity that is widely concerned, the generated electromagnetic field also has obvious directionality. To this end, a set of electromagnetic antennas capable of simultaneous three-axis measurement is used to monitor the electromagnetic vector field generated from rock fracturing based on Brazilian tests. The signal amplitude on each axis can represent the magnitude of actual magnetic flux density component on the three axes. The intensity and directional characteristics of electromagnetic signals received at different positions are studied using vector synthesis. The directionality of electromagnetic radiation measured using a three-axis electromagnetic antenna shows that the direction of the magnetic flux intensity generated by rock fracturing tends to be parallel to the crack surface, and the measured signal intensity is greater in a direction closer to the crack surface.

An ultra-narrow-band optical filter based on zero refractive index metamaterial

Owing to the photonic band gap effect and defect state effect, photonic metamaterials have received much attention in the design of narrow bandpass filters, which are the key devices of optical communication equipment such as wavelength division multiplexing devices. In this work, based on zero-index metamaterial (ZIM), a compact filter with both high peak transmission coefficient and ultra-narrow bandwidth is proposed. The photonic metamaterial with conical dispersion and Dirac-like point is achieved by optimizing the structure and material component parameters of dielectric rods with square lattice in air. It is demonstrated that a triply degenerate state can be realized at the Dirac-like point, which relates this metamaterial to a zero-index medium with effective permittivity and permeability equal to zero simultaneously. Electromagnetic (EM) wave can propagate without any phase delay at this frequency, and strong dispersion occurs in the adjacent frequency cone, leading to dramatic changes in optical properties. We introduce a ZIM into photonic metamaterial defect filter to compress the bandwidth to the realization of ultra-narrow bandpass filter. The ZIM is embedded into the resonant cavity of line defect filter, which is also composed of dielectric rods with square lattice in air. In order to increase the sensitivity of the phase change with frequency, the Dirac-like frequency is adjusted to match the resonant frequency of the filter. We study the transmission spectrum of the structure through the COMSOL Multiphysics simulation software, and find that the peak width at half-maximum of the filter decreases as the thickness of ZIM increases, and the peak transmittance is still high when bandwidth is greatly compressed. The zero phase delay inside the slab can be observed. Through field distribution analysis, the zero-phase delay and strong coupling characteristics of electromagnetic field are observed at peak frequency. The comparison with conventional photonic metamaterials filter is discussed. We believe that this work is helpful in investigating the realization of ultra-narrow bandpass filters.

An Out-of-Phase Wireless Power Transfer System for Implantable Medical Devices to Reduce Human Exposure to Electromagnetic Field and Increase Power Transfer Efficiency.

For the wireless power transfer (WPT) system in implantable medical devices (IMDs), human tissue is positioned between the transmitting and receiving coils which are different from general WPT systems. Because this space is where the strongest electromagnetic field (EMF) occurs, it is essential to reduce the EMF at the interspace to reduce human exposure to the EMF. In this paper, an out-of-phase coupled WPT system for IMDs is proposed to reduce human exposure to EMF. Considering the EMF exposure and power transfer efficiency (PTE) of the proposed system, a design procedure for determining the phase difference of each capacitor is analyzed and presented. Based on the equivalent circuit model analysis of the proposed system, the EMF and PTE characteristics of the WPT system depending on the design variables are comprehensively analyzed. The proposed system is compared with conventional systems through simulation and measurements. It is verified that the proposed system can reduce the EMF by 41.05% and increase the PTE by 9.62% compared to the conventional system. In addition, through simulation, human exposure to EMFs is assessed considering the exposure environment and electrical properties of human tissues. As a result, the current density, induced electric field, and specific absorption rate were reduced by 44.10%, 38.90%, and 63.82%, respectively.

Исследование эффективности формирования сфокусированного излучения при погрешностях определения параметров сред

The variations of characteristics of focusing electromagnetic field are described in the paper. The variations are occurred when medium parameters are defined with some errors. Errors in determination of attenuation coefficient and phase coefficient are discussed. Modeling the distribution of electromagnetic intensity was carried out with software MathCad. As parameters of the focused field, the size of the focused area and the level of local maxima adjacent to the focused area were considered. The paper shows that errors in media parameters slightly reduce the efficiency of focused field formation, but the focus principle itself is not questioned. The errors of phase coefficient are most influential and reduce electromagnetic field concentration near focusing point.

Propagation characteristics of electromagnetic field penetrated into laminated CFRPs using eddy current testing with pancake coil

Propagation characteristics of electromagnetic field (EMF) is crucial to identify and position the potential defects when using eddy current testing (ECT) method for conductive medium. Therefore, in this work, the EMF propagation characteristics in carbon fiber reinforced polymer (CFRP) composites are thoroughly investigated by using finite element (FE) method. Considering the layered structure, stacking sequence, and interlaminar interface, we utilize a contact impedance interior boundary condition to model CFRP laminates, and then discuss the calculation accuracy and mesh refinement. The numerically solved results are compared to the theoretically calculated ones, and clearly point out the significant discrepancy between the true skin depth and the standard one. The findings reveal that the electrical anisotropy is one of the important factors in affecting the EMF propagation. The strong anisotropy results in more power loss and a frequency-independent decay rate than the ones in the weak and isotropic cases, which is proved by introducing Poynting theorem. Additionally, the other critical factor affecting the EMF attenuation is the lay-up stacking sequence of CFRPs, which is quite different from that of the isotropic mterials. Besides, the driving coil geomerty is another factor in affecting the EMF propagation characteristics from the point of the incident field.