Search Results (4,138)

An axial field hybrid excitation synchronous generator (AF-HESG) is proposed for an independent power supply system, and its electromagnetic performance is studied in this paper. The distinguishing feature of the proposed generator is the addition of static magnetic bridges at both ends to place the field windings and the use of a sloping surface to increase the additional air-gap cross-sectional area. The advantage of the structure is that it achieves brushless excitation and improves the flux-regulation range. The structure and magnetic circuit characteristics are introduced in detail. Theoretical analysis of the flux-regulation principle is conducted by studying the relationship between field magnetomotive force, rotor reluctance, and air-gap flux density. Quantitative calculation is performed using a magnetomotive force (MMF)-specific permeance model, and the influence of the main parameters on the air-gap flux density and flux-regulation range is analyzed. Subsequently, magnetic field, no-load, and load characteristics are investigated through three-dimensional finite element analysis. The loss distribution is analyzed, and the temperature of the generator under rated conditions is simulated. Finally, a 30 kW, 1500 r/min prototype is developed and tested. The test results show good flux-regulation capability and stable voltage output performance of the proposed generator. Full article

To effectively separate strong cultural noise in Magnetotelluric (MT) signals under strong interference conditions and restore the true forms of apparent resistivity and phase curves, this paper proposes an improved method for suppressing strong cultural noise based on Particle Swarm Optimization (PSO) and Variational Mode Decomposition (VMD). First, the effects of two initial parameters, the decomposition scale K and penalty factor α, on the performance of variational mode decomposition are studied. Subsequently, using the PSO algorithm, the optimal combination of influential parameters in the VMD is determined. This optimal parameter set is applied to decompose electromagnetic signals, and Intrinsic Mode Functions (IMFs) are selected for signal reconstruction based on correlation coefficients, resulting in denoised electromagnetic signals. The simulation results show that, compared to traditional algorithms such as Empirical Mode Decomposition (EMD), Intrinsic Time Decomposition (ITD), and VMD, the Normalized Cross-Correlation (NCC) and signal-to-noise ratio (SNR) of the PSO-optimized VMD method for suppressing strong cultural noise increased by 0.024, 0.035, 0.019, and 2.225, 2.446, 1.964, respectively. The processing of field data confirms that this method effectively suppresses strong cultural noise in strongly interfering environments, leading to significant improvements in the apparent resistivity and phase curve data, thereby enhancing the authenticity and reliability of underground electrical structure interpretations. Full article

Micromagnetic stimulation (μMS) is a promising branch of neurostimulation but without some of the drawbacks of electrical stimulation. Microcoil (μcoil)-based magnetic stimulation uses small micrometer-sized coils that generate a time-varying magnetic field, which, as per Faraday’s Laws of Electromagnetic Induction, induces an electric field on a conductive surface. This method of stimulation has the advantage of not requiring electrical contact with the tissue; however, these μcoils are not easy to operate. Large currents are required to generate the required magnetic field. These large currents are too large for standard test equipment to provide, and additional power amplifiers are needed. To aid in the testing and development of micromagnetic stimulation devices, we have created a compact single-unit test setup for driving these devices called the µCoil Driver. This unit is designed to drive small inductive loads up to ±8 V at 5 A and 10 kHz. Full article

In response to the difficulties and poor timeliness in detecting feeding metallic foreign objects during high-yield continuous crushing operations in coal mines, this paper proposes a new method for detecting metallic foreign objects, combining pulsed eddy current testing with the Truncated Region Eigenfunction Expansion (TREE) method. This method is suitable for the harsh working conditions in coal mine crushing stations, which include high dust, strong vibration, strong electromagnetic interference, and low temperatures in winter. A model of the eddy current field of feeding metallic foreign objects in the truncated region is established using a coaxial excitation and receiving coil with a Hall sensor. The full-cycle time-domain analytical solution for the induced voltage and magnetic induction intensity of the reflective field under practical square wave signals is obtained. Simulation and experimental results show that the effective time range, peak value, and time to peak of the received voltage and magnetic induction signals can be used to classify and identify the size, thickness, conductivity, and magnetic permeability of feeding metallic foreign objects. Experimental results meet the actual needs for removing feeding metallic foreign objects in coal mine sites. This provides core technical support for the establishment of a predictive fault diagnosis system for crushing equipment. Full article

Recently, there has been increasing interest in organic carbon (OC) certification of soil as an incentive for farmers to adopt sustainable agricultural practices. In this context, this pilot project combines geochemical and geophysical methods to map the distribution of OC contents in agricultural fields, allowing us to detect variations in time and space. Here we demonstrated a relationship between soil OC contents estimated in the laboratory and the apparent electrical conductivity (ECa) measured in the field. Specifically, geochemical elemental analyses were used to evaluate the OC content and relative isotopic signature in collected soil samples from a hazelnut orchard in the Emilia–Romagna region of Northeastern Italy, while the geophysical Electromagnetic Induction (EMI) method enabled the in situ mapping of the ECa distribution in the same soil field. According to the results, geochemical and geophysical data were found to be reciprocally related, as both the organic matter and soil moisture were mainly incorporated into the fine sediments (i.e., clay) of the soil. Therefore, such a relation was used to create a map of the OC content distribution in the investigated field, which could be used to monitor the soil C sequestration on small-scale farmland and eventually develop precision agricultural services. In the future, this method could be used by farmers and regional and/or national policymakers to periodically certify the farm’s soil conditions and verify the effectiveness of carbon sequestration. These measures would enable farmers to pursue Common Agricultural Policy (CAP) incentives for the reduction of CO₂ emissions. Full article

Interferometric radiometers operating at L-band, such as ESA’s SMOS mission, enable crucial Earth observations providing high-resolution measurements of soil moisture, ocean salinity, and other geophysical parameters. However, the increasing electromagnetic spectrum utilization has led to significant Radio Frequency Interference (RFI) challenges, particularly critical given the sensors’ fine temperature resolution requirements of less than 1 K. This work presents the hardware implementation of an advanced RFI detection and mitigation algorithm specifically designed for interferometric radiometers, targeting future L-band missions. The implementation processes 1-bit quantized signals at 57.69375 MHz from multiple receivers, employing time-frequency analysis and polarimetric detection techniques while optimizing Field Programmable Gate Array (FPGA) resource utilization. Novel optimization strategies include overclocked processing cores operating at 230.775 MHz, efficient resource sharing through operation serialization, and strategic memory management. The system achieves real-time processing capabilities while maintaining detection probabilities above 63% with false alarm rates below 1% for typical interference scenarios. Performance validation using synthetic datasets demonstrates robust operation across various RFI conditions, making this implementation suitable as part of the RFI detection and mitigation efforts for future interferometric radiometer missions beyond SMOS. Full article

This paper presents a modularized reconfigurable functional electromagnetic surface (MRFES) for broadband absorption and polarization conversion by using tightly coupled dipole antennas (TCDA) and back-loaded radio frequency (RF) circuits (BLRFC). A dual-polarized antenna array with tight coupling and wide angular scanning characteristics is designed. By loading different RF circuits on the back side of the antenna array’s ground plane, switchable broadband absorption and polarization conversion functions are achieved. The design adopts modularization to facilitate the replacement of back-loaded RF circuits for diverse electromagnetic (EM) control functions. The final design of the tightly coupled antenna array has a thickness of 13.437 mm and a size of 119.5 mm × 119.5 mm. It works in a bandwidth range of 4.14–13 GHz. Upon loading the absorption circuit board, a broadband absorbing electromagnetic (EM) surface is formed, achieving dual-polarization absorption within a bandwidth of 4.14–12.4 GHz. With the polarization conversion circuit board attached, polarization conversion effects are realized within a bandwidth of 4.4–12.9 GHz. Both simulations and experiments verify that the designed EM surface possesses modular reconfigurable functions for broadband absorption/polarization conversion. The proposed design scheme holds promising prospects for applications in active stealth, adaptive camouflage, intelligent communication and other fields. Full article

This paper outlines the specific provisions of Italian legislation regarding workers’ exposure to electromagnetic fields (EMFs) from 0 Hz to 300 GHz compared to the minimum health and safety requirements set in European Directive 2013/35/EU. In particular, the path to be followed to assess and manage occupational exposure to EMFs is outlined in relation to the distinction between ‘professional’ and ‘non-professional’ exposure of workers, as well as to the precautionary limits regarding exposures from power lines (50 Hz) and broadcast and telecommunication fixed systems (100 kHz–300 GHz) established by Italian regulations. The reasons underlying such an approach—mainly relying on the intent to reconcile scientific evidence with risk perception in public opinion—are analysed and discussed with the aim of increasing the knowledge of national regulatory provisions on occupational risk assessment, which may be more stringent than the requirements envisaged by international guidelines and community regulations. Full article

Wireless communication very often causes problems due to its quality. Problems with the network are very important when installing wireless networks inside buildings. The reason is the effects created during the propagation of electromagnetic waves inside rooms due to, among other factors, the construction of the walls and the building materials used. At the stage of network design, it is possible to use numerical methods, which allow for multivariate and fast analysis. This article presents a multivariate analysis of the impact of the variability in the electrical parameters of concrete and reinforced concrete on the propagation of electromagnetic waves and the value of the electric field intensity. The subject of the analysis was a wall composed of a homogeneous material (concrete) or non-homogeneous material (concrete with reinforcement). In the case of the homogeneous wall, the analysis was performed taking into account four electric permittivity values and a wide range of conductivity values. The analysis was performed at two frequencies used in wireless communication (2.4 GHz and 5 GHz). The analysis was performed using the time method based on Maxwell’s equations—the finite difference time domain method (FDTD). The results of the numerical analysis were compared with the results obtained from the presented analytical relationships. In the next step, four models and calculations were obtained for systems with a reinforced concrete wall, taking into account the variability in the spacing between the bars, the diameter of the reinforcement and the number of rows of reinforcement. The analysis of complex systems was performed at a frequency of 2.4 GHz. The aim of the presented analysis was to check how the change in the value of the electric permittivity of concrete affects the values of the field intensity and its effect on the analysis of systems composed of concrete with reinforcement. In the case of concrete, it was observed that, for conductivity above 0.9 S/m, regardless of the electric permittivity, all characteristics had a similar course. For low concrete loss, the greatest differences in the electric field intensity were observed at a frequency of 2.4 GHz rather than at 5 GHz. On the other hand, the analysis of systems with reinforced concrete showed, among other aspects, that models with two rows of bars and spacing of 0.15 m, regardless of the reinforcement diameter, were characterized by lower values of the electric field intensity compared to the variants with one row of bars. Full article

This paper focuses on presenting an intelligent model that can generate the desired geometry of a unit cell metasurface for a given resonant frequency at which we expect the metasurface structure to work. The model consists of the use of a multilayer perceptron and filters, which represent the output geometry of the unit cell as a 6 × 6 matrix stored in a binary state. The value 0 in the matrix denotes the dielectric substrate on which the geometry of the unit cell is built, and the value 1 denotes the blocks as the conducting parts of the unit cell metasurface. The proposed model was tested using simulation data from the Comsol Multiphysics environment. The test confirmed the effectiveness of the model, and it is possible to develop and apply it to larger and other datasets. Full article

Background: The rapid development of mobile communication has caused an increase in electromagnetic field (EMF) emissions in the environment. However, there is a lack of research on the impact of EMFs on microorganisms. Thus, the aim of the study was the determine the effect of exposure to 900 and 1800 MHz electromagnetic fields on the entomopathogenic fungi (EPFs) Beauveria bassiana, Cordyceps fumosorosea, and Metarhizium anisopliae. Methods: The entomopathogenic fungi developed under exposure to an EMF for seven days. After the termination of exposure, the linear colony growth, sporulation, gemination, and pathogenicity of the EPFs were investigated. Results: The effect of EMFs on B. bassiana, C. fumosorosea, and M. anisopliae depended on the EMF frequency and the tested fungus species. Exposure to the 900 MHz frequency stimulated the growth of the mycelium and the pathogenicity of the entomopathogenic fungi, whereas the 1800 MHz electromagnetic field inhibited sporulation and spore germination. Conclusions: The exposure to the 900 MHz frequency stimulated the development of the mycelium of all tested species and the pathogenicity of C. fumosorosea. The sporulation and germ tube length of the entomopathogenic fungi were stimulated by the 900 MHz frequency. The 1800 MHz electromagnetic field inhibited the sporulation and spore germination of B. bassiana. Full article

This paper reviews the field of cascaded metasurfaces, which are advanced optical devices formed by stacking or serially arranging multiple metasurface layers. These structures leverage near-field and far-field electromagnetic (EM) coupling mechanisms to enhance functionalities beyond single-layer metasurfaces. This review comprehensively discusses the physical principles, design methodologies, and applications of cascaded metasurfaces, focusing on both static and dynamic configurations. Near-field-coupled structures create new resonant modes through strong EM interactions, allowing for efficient control of light properties like phase, polarization, and wave propagation. Far-field coupling, achieved through greater interlayer spacing, enables traditional optical methods for design, expanding applications to aberration correction, spectrometers, and retroreflectors. Dynamic configurations include tunable devices that adjust their optical characteristics through mechanical motion, making them valuable for applications in beam steering, varifocal lenses, and holography. This paper concludes with insights into the potential of cascaded metasurfaces to create multifunctional, compact optical systems, setting the stage for future innovations in miniaturized and integrated optical devices. Full article

Simulating electromagnetic (EM) fields can obtain the EM responses of geoelectric models at different times and spaces, which helps to explain the dynamic process of EM wave propagation underground. EM forward modeling is regarded as the engine of inversion. Traditional numerical methods have certain limitations in simulating the EM responses from large-scale geoelectric models. In recent years, the emerging physics-informed neural networks (PINNs) have given new solutions for geophysical EM field simulations. This paper conducts a preliminary exploration using PINN to simulate geophysical frequency domain EM fields. The proposed PINN performs self-supervised training under physical constraints without any data. Once the training is completed, the responses of EM fields at any position in the geoelectric model can be inferred instantly. Compared with the finite-difference solution, the proposed PINN performs the task of geophysical frequency domain EM field simulations well. The proposed PINN is applicable for simulating the EM response of any one-dimensional geoelectric model under any polarization mode at any frequency and any spatial position. This work provides a new scenario for the application of artificial intelligence in geophysical EM exploration. Full article

The quantum electromagnetic (EM) field is formulated in the Weyl–Wigner representation (WW), which is equivalent to the standard Hilbert space one (HS). In principle, it is possible to interpret within WW all experiments involving the EM field interacting with macroscopic bodies, the latter treated classically. In the WW formalism, the essential difference between classical electrodynamics and the quantum theory of the EM field is just the assumption that there is a random EM field-filling space, i.e., the existence of a zero-point field with a Gaussian distribution for the field amplitudes. I analyze a typical optical test of a Bell inequality. The model admits an interpretation compatible with local realism, modulo a number of assumptions assumed plausible. Full article

This study investigates the influence of electromagnetic fields on the propulsion performance of laser plasma propulsion. Based on the principle of pulsed plasma thrusters, an electromagnetic field is utilized to accelerate laser plasma, achieving enhanced propulsion performance. This approach represents a novel method for the electromagnetic enhancement of laser propulsion performance. In this paper, pulsed plasma thrusters induced by laser ablation are employed. The generated plasma is subjected to the Lorentz force under the influence of an electromagnetic field to obtain higher speed, thus increasing impulse and specific impulse. An experimental platform for laser-ablation plasma electromagnetic acceleration was constructed to explore the enhancement effect of discharge characteristics and propulsion performance. The results demonstrate that increased laser energy has little effect on discharge characteristics, while the trend of propulsion performance parameters initially rises and then declines. After coupling the electromagnetic field, the propulsion performance is significantly enhanced, with stronger electromagnetic fields yielding more pronounced effects. Full article