In this paper, we first proposed a novel hybrid loop array (HLA) for low leakage electromagnetic field (EMF) level and high efficiency in a wireless high power transfer system. The proposed HLA ...effectively enhances the system efficiency and shields leakage EMF in a wireless power transfer (WPT) system using kHz range resonant frequency. The key originality of the proposed HLA is the combination of two types of loop coil; shielding loop coil (SLC) and amplifying loop coil (ALC). SLCs reduce leakage EMF, and ALCs significantly enhance the magnetic field from a Tx coil. The simulation and experiment results show that the proposed solution successfully overcomes the limitations of the existing solutions. Analytical modeling and design procedure are introduced and discussed. In addition, the experimental verification of the simulation result is included. We first designed and modeled an HLA considering the coupling effect of neighboring loop coils to evaluate its efficiency and leakage EMF. With the proposed HLA, we demonstrated a 9.36% improvement in the efficiency and 3 dBm reduction in the leakage EMF near the WPT system.
As the fifth-generation (5G) mobile communication is utilizing millimeter-wave (mmWave) frequency bands, electromagnetic field (EMF) exposure emitted from a 5G mmWave mobile handset should be ...evaluated and compliant with the relevant EMF exposure limits in terms of peak spatial-average incident power density (PD). In this work, a fast PD assessment method for a 5G mmWave mobile handset using the equivalent current (EQC) method is proposed. The EQC method utilizes the intermediate-field (IF) data collected by a spherical measurement system to reconstruct the EQCs over a reconstruction surface and then computes the PD in close proximity of the mobile handset with acceptable accuracy. The performance of the proposed method is evaluated using a mmWave mobile handset mock-up equipped with four quasi-Yagi antennas. The assessed PD results are compared with those computed using full-wave simulations and also those measured with a planar near-field (NF) scanning system. In addition, three influencing factors related to the accuracy of the EQC method, namely, the angular resolution, the phase error, and the handset position in the IF measurements, are also analyzed. The proposed method is a good candidate for fast PD assessment of EMF exposure compliance testing in the mmWave frequency range.
The effects of an oscillation electromagnetic field (EMF) generated by low frequency pulse current on the grain refinement and phase formation in direct-chill (DC) casting of AZ31B magnesium alloy ...have been investigated experimentally. The macrostructure evolution was quantitatively examined in terms of the grain size and its distribution, and fine equiaxed grains can be obtained. Given the Lorentz force and velocity variations, temperature distribution and heat extraction process during DC in different electromagnetic conditions, the grain refinement mechanism and the phase composition and formation of AZ31B magnesium alloy were discussed in detail. The grain sizes decrease from 549 ∼ 1094 μm (without EMF) to 402 ∼ 486 μm at the frequency of 15 Hz, and columnar grain region decreases significantly. Forced convection induced by EMF can strengthen the heat extraction along the diametrical direction of billet, weaken the contact heat transfer between melt and mold wall. For the formation of Mn-containing phases, eutectic transformations are dominant in DC casting process of AZ31B magnesium alloy, and the area fraction of eutectic Al8Mn5 phase decreases from center to edge of billet, and its distribution is more homogeneous in the presence of EMF.
A Note on Fractional Curl Operator Stefanski, Tomasz P.; Czachor, Marek
IEEE antennas and wireless propagation letters,
10/2023, Letnik:
22, Številka:
10
Journal Article
In this letter, we demonstrate that the fractional curl operator, widely used in electromagnetics since 1998, is essentially a rotation operation of components of the complex Riemann-Silberstein ...vector representing the electromagnetic field. It occurs that after the wave decomposition into circular polarisations, the standard duality rotation with the angle depending on the fractional order is applied to the left-handed basis vector whilst the right-handed basis vector stems from the complex conjugation of the left-handed counterpart. Therefore, the fractional curl operator describes another representation of rotations of the electromagnetic field decomposed into circular polarisations. Finally, we demonstrate that this operator can describe a single-qubit phase-shift gate in quantum computing.
•Electromagnetic field could reduce the dilution rate of laser cladding coating.•Electromagnetic field made the amount of Cr borides increase.•Electromagnetic field made Cr content increase while Fe ...content decrease in Cr borides.•Electromagnetic field reduced the range of columnar dendrite crystals at the bottom of the coating.
Ni-Cr-B-Si coatings were prepared on the surface of pure iron using an electromagnetic field assisted laser cladding technique. The effect of electromagnetic field on the cross-sectional morphology, the microstructure and the element distribution was investigated. The results showed that the dilution rate of coatings reduced and the grain size of Cr borides was refined under the electromagnetic field. The volume fraction of Cr borides in the coatings increased and the distribution morphology of phases is related to grain boundary wettability. The length of columnar dendrite crystals at the bottom of the coatings decreased with the increase of the electromagnetic force.
A high-intensity pulsed electromagnetic field (HI-PEMF) is a non-invasive and non-contact delivery method and may, as such, have an advantage over gene electrotransfer mediated by conventional ...electroporation using contact electrodes. Due to the limited number of in vitro studies in the field of gene electrotransfection by HI-PEMF, we designed experiments to investigate and demonstrate the feasibility of such a technique for the non-viral delivery of genetic material into cells in vitro. We first showed that HI-PEMF causes DNA adsorption to the membrane, a generally accepted prerequisite step for successful gene electrotransfection. We also showed that HI-PEMF can induce gene electrotransfection as the application of HI-PEMF increased the percentage of GFP-positive cells for two different combinations of pDNA size and concentration. Furthermore, by measuring the uptake of larger molecules, i.e., fluorescently labelled dextrans of three different sizes, we showed endocytosis to be a possible mechanism for introducing large molecules into cells by HI-PEMF.
This article describes the detailed design and development of a 300 kW permanent magnet (PM) synchronous motor for electric aircraft propulsion, taking into consideration manufacturability, balancing ...ease, and cost of high-volume production with motor performance. The motor consists of a slotless stator structure with custom litz wire and an outer rotor with a Halbach PM array. The design of the proposed motor is based on multi-physics performance including electromagnetic field, thermal and mechanical analysis. For ease of manufacturing and economies of scale, the detailed design is refined by altering the PM segment number, PM shape and litz wire construction. The impacts of changing these parameters are evaluated in detail using analytical and finite element methods. The simulation results are compared with experimental results in terms of torque production, back electromotive force, and current level.
The controlled source extremely low frequency (CSELF) method bears the potential for deep resource exploitation utilizing the skywave. The “Skywave” denotes the electromagnetic wave propagating ...through the waveguide formed by the Earth and ionosphere. It has a considerable penetration depth into the lithosphere due to its low-frequency band. Previous research on extremely low-frequency electromagnetic fields with the coupled lithosphere, atmosphere, and planar ionosphere models ignored the effect of the Earth’s curvature. Thus, we aimed to present the exact formulas for horizontal electric dipoles (HED) in a spherical “Earth-ionosphere” model. These new formulas consider the Earth’s curvature as a multilayer medium rather than a homogeneous underground. We introduce three techniques: function combination pairs, addition and subtraction terms, and Padé approximants, to handle slow convergence in numerical calculation. In the spherical waveguide, electromagnetic fields are mutually interfered with and produce oscillations, which is different from the planar model. The influence of Earth’s curvature cannot be neglected with the increase in source–receiver distance, though it is negligible within 3000 km. Furthermore, it is worth noting that apparent resistivity ρθφ enters the waveguide area earlier than ρφθ. This method can be used as Green’s function to simulate the electromagnetic field of actual antennas and 3-D models.
Thermal processing has been widely employed in the food industry for food safety assurance. However, thermal processing may cause some undesirable changes or form by-products that negatively affect ...the nutritional value, flavor, color and texture of the final product. With increasing awareness of food and health, consumers prefer more naturally and minimally processed foods. Therefore, investigation of nonthermal processing technologies is important and necessary not only for its minimal impact on food but also for its extension of product shelf-life by inhibiting or inactivating microorganisms.
This review presents a general perspective of nonthermal inactivation technologies based on electromagnetic fields, including pulsed electric fields, high voltage arc discharge, pulsed light, ionizing radiation, microwave and cold plasma. The inactivation mechanisms, characteristics and research progress, as well as the limitations of these technologies, are also discussed.
Compared to thermal treatments, nonthermal inactivation technologies have shown significant advantages with great potential. Hybrid technologies based on these methods should play a significant role in enhancing inactivation efficiency. In addition, combination of these methods with thermal treatment can lower the treatment temperature and achieve high reductions of microorganisms in foods. Despite various degrees of success in these technologies, their widespread applications in the food industry are yet to flourish. Further studies are still needed to understand these processes to provide a platform by which their limitations can be overcome.
•Non-thermal inactivation technologies shows growing interest and necessity.•Perspectives of non-thermal treatments in electromagnetic fields are presented.•Hybrid technologies can efficiently enhance inactivation efficacy and efficiency.•Various non-thermal processing treatments are compared and evaluated.
Unlike the role of mesenchymal stem cells (MSCs) in regenerative medicine, their application in cell therapy can be complicated by factors such as a reduction in the proliferation potential, ...senescent tendency of MSCs to expand, and an age-dependent decline in their number and functions. It was shown that there is an association between exposure to electromagnetic fields (EMFs) and response to stress, cell proliferation, aging, and cell death. Furthermore, the zinc ion, as an essential trace element, was reported to be involved in the regulation of the growth and cell proliferation. In this report, ratadipose tissue-derived mesenchymal stem cells (rADSCs) were randomly divided into four groups—group I (control without any ZnSO
4
and EMF); group II (ZnSO
4
treatment without EMF exposed); group III (EMF exposed without ZnSO
4
); and group ІV (EMF exposed with ZnSO
4
)—to evaluate whether 0.14 μg/ml Zinc sulfate (ZnSO
4
) could affect cell proliferation of rADSCs under extremely low frequency-electromagnetic field (ELF-EMF). The methyl thiazoltetrazolium (MTT) method was used to determine the cell proliferation of rADSCs following exposure to ELF-EMF in the presence of ZnSO
4
. The immunocytochemistry method as well as flow-cytometry was used to identify the cell surface markers. Next, oil red O, alizarin red, toluidine blue, and cresyl violet staining was done to evaluate the adipogenic, osteogenic, chondrogenic, and neurogenic differentiation of rADSCs as the pluripotent capacity of rADSCs, respectively. The results showed that an exposure to ELF-EMF caused a decrease in the proliferation of rADSCs. However, the ZnSO
4
supplementation significantly increased the cell proliferation of ELF-EMF-exposed rADSCs. In addition, in the presence of 0.14 μg/ml ZnSO
4
, rADSCs appeared to be growing faster than the control group and ZnSO
4
significantly decreased the doubling time of ELF-EMF-exposed rADSCs. It seems that ZnSO
4
would be a good element to induce the cell proliferation of ELF-EMF-exposed rADSCs.
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