Search Results (260)

Since around the year 2000, following the introduction of electric vehicles (EVs) to the market, some people have expressed concerns about the level of magnetic flux density (MFD) inside vehicles. In 2013, we reported the results of MFD measurements for electric vehicles (EVs), hybrid electric vehicles (HEVs), and internal combustion engine vehicles (ICEVs). However, those 2013 measurements were conducted using a chassis dynamometer, and no measurements were taken during actual driving. In recent years, with the rapid global spread of EVs and plug-in hybrid electric vehicles (PHEVs), the international standard IEC 62764-1:2022, which defines methods for measuring magnetic fields (MF) in vehicles, has been issued. In response, and for the first time, we conducted new MF measurements on current Japanese vehicle models in accordance with the international standard IEC 62764-1:2022, identifying the MFD levels and their sources at various positions within EVs, PHEVs, and ICEVs. The measured MFD values in all vehicle types were below the reference levels recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for public exposure. Furthermore, we performed comparative measurements with the MF data obtained in 2013 and confirmed that the MF levels remained similar. These findings are expected to provide valuable insights for risk communication with the public regarding electromagnetic fields, particularly for those concerned about MF exposure inside electrified vehicles. Full article

Alzheimer’s disease (AD) is a leading cause of dementia, characterized by progressive cognitive and language impairments that significantly impact communication and quality of life. Neuromodulation techniques, including repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), and deep brain stimulation (DBS), have emerged as promising interventions. This study employs bibliometric analysis to evaluate global research trends in neuromodulation treatments for AD-related language impairments. A total of 88 publications from the Web of Science Core Collection (2006–2024) were analyzed using bibliometric methods. Key indicators such as publication trends, citation patterns, collaboration networks, and research themes were examined to map the intellectual landscape of this field. The analysis identified 580 authors across 65 journals, with an average of 34.82 citations per article. Nearly half of the publications were produced after 2021, indicating rapid recent growth. The findings highlight a predominant focus on non-invasive neuromodulation methods, particularly rTMS and tDCS, within neurosciences and neurology. While research activity is increasing, significant challenges persist, including ethical concerns, operational constraints, and the translational gap between research and clinical applications. This study provides insights into the current research landscape and future directions for neuromodulation in AD-related language impairments. The results emphasize the need for novel neuromodulation techniques and interdisciplinary collaboration to enhance therapeutic efficacy and clinical integration. Full article

In order to break through the difficulties with a very-low-frequency (VLF) miniaturized antenna with small power capacity and low radiation efficiency, this paper proposes a high-radiation-field-strength magnetic loop antenna based on a nanocrystalline alloy magnetic core. A high-permeability nanocrystalline toroidal core (μ_r = 50,000, B_s = 1.2 T) is used to optimize the thickness-to-diameter ratio (t = 0.08) and increase the effective permeability to 11,000. The Leeds wires, characterized by their substantial carrying capacity, are manufactured through a toroidal winding process. This method results in a 68% reduction in leakage compared to traditional radial winding techniques and enhances magnetic induction strength by a factor of 1.5. Additionally, this approach effectively minimizes losses, thereby facilitating support for kilowatt-level power inputs. A cascaded LC resonant network (resonant capacitance 2.3 μF) and ferrite balun transformer (power capacity 3.37 kW) realize a 20-times amplification of the input current. A series connection of a high-voltage isolation capacitor blocks DC bias noise, guaranteeing the stable transmission of 1200 W power, which is 6 times higher than the power capacity of traditional ring antenna. At 7.8 kHz frequency, the magnetic field strength at 120 m reaches 47.32 dBμA/m, and, if 0.16 pT is used as the threshold, the communication distance can reach 1446 m, which is significantly better than the traditional solution. This design marks the first instance of achieving kilowatt-class VLF effective radiation in a compact 51 cm-diameter magnetic loop antenna, offering a highly efficient solution for applications such as mine communication and geological exploration. Full article

The risk of developing symptomatic knee osteoarthritis (KOA) during a lifetime, i.e., pain, aching, or stiffness in a joint associated with radiographic KOA, was estimated in 2008 to be around 40% in men and 47% in women. The clinical and scientific communities lack an efficient diagnostic method to effectively monitor, evaluate, and predict the evolution of KOA before and during the therapeutic protocol. In this review, we summarize the main methods that are used or seem promising for the diagnosis of osteoarthritis, with a specific focus on non- or low-invasive methods. As standard diagnostic tools, arthroscopy, magnetic resonance imaging (MRI), and X-ray radiography provide spatial and direct visualization of the joint. However, discrepancies between findings and patient feelings often occur, indicating a lack of correlation between current imaging methods and clinical symptoms. Alternative strategies are in development, including the analysis of biochemical markers or acoustic emission recordings. These methods have undergone deep development and propose, with non- or minimally invasive procedures, to obtain data on tissue condition. However, they present some drawbacks, such as possible interference or the lack of direct visualization of the tissue. Other original methods show strong potential in the field of KOA monitoring, such as electrical bioimpedance or near-infrared spectrometry. These methods could permit us to obtain cheap, portable, and non-invasive data on joint tissue health, while they still need strong implementation to be validated. Also, the use of Artificial Intelligence (AI) in the diagnosis seems essential to effectively develop and validate predictive models for KOA evolution, provided that a large and robust database is available. This would offer a powerful tool for researchers and clinicians to improve therapeutic strategies while permitting an anticipated adaptation of the clinical protocols, moving toward reliable and personalized medicine. Full article

Background: The increasing use of technologies operating between 10 and 200 kHz, such as RFID, wireless power transfer systems, and induction cooktops, raises concerns about electromagnetic interference (EMI) with cardiac implantable electronic devices (CIEDs). The mechanisms of interaction within this frequency range have been only partially addressed by both the scientific and regulatory communities. Methods: A physical twin of a pacemaker/implantable defibrillator (PM/ICD) was developed to experimentally assess voltages induced at the input stage by low-to-mid-frequency magnetic fields. The setup simulates the two sensing modalities programmable in PMs/ICDs and allows for the analysis of different implant configurations, lead geometries, and positions within a human body phantom. Results: Characterization of the physical twin demonstrated its capability to reliably measure induced voltages in the range of 5 mV to 1.5 V. Its application enabled the identification of factors beyond the implant’s induction area that contribute to the induced voltage, such as the electrode-tissue interface and body-induced currents. Conclusions: This physical twin represents a valuable tool for experimentally validating the mechanisms of EMI in CIEDs, providing insights beyond current standards. The data obtained can serve as a reference for the validation of numerical models and patient-specific digital twins. Moreover, it offers valuable information to guide future updates and revisions of international electromagnetic compatibility standards for CIEDs. Full article

To address the challenges of small aperture size, limited scanning angles, and high fabrication costs in existing scanning micromirrors, this paper proposes a large-aperture biaxial electromagnetically driven scanning micromirror. The scanning micromirror utilizes a stainless-steel mirror structure and an actuation structure composed of arc-shaped permanent magnets (NdFeB 52), iron cores, and copper coils. By optimizing the magnet layout and coil design, it achieves large optical scanning angles in biaxial non-resonant scanning mode. Experimental results demonstrate that the optical scanning angles reach 61.4° (x-axis) under a DC driving current of ±18.1 mA and 61.1° (y-axis) under a DC driving current of ±25.2 mA with an effective mirror aperture of 9.54 mm × 10 mm. The resonant frequencies are 89 Hz (x-axis) and 63 Hz (y-axis). Experimental results verify the feasibility of biaxial independent control in non-resonant scanning mode. The design is fabricated using a low-cost computer numerical control (CNC) milling process and exhibits application potential in fields such as LiDAR, projection display, and optical communication, providing a novel approach for performance optimization of large-aperture scanning micromirrors. Full article

This communication introduces a novel antenna miniaturization approach by strategically loading ferrites in distinct near-field regions. By identifying electric (E)- and magnetic (H)-field dominant zones in the antenna near-field, region-specific ferrites are strategically selected: high permittivity (ε_r) materials for E-field zones and high permeability (µ_r) materials for H-field zones. This strategy maximizes miniaturization while minimizing losses and the increase in antenna weight resulting from ferrite loading. To validate this method, a bent inverted-F antenna was designed and measured. The experimental results demonstrate that loading ferrites in E-field regions reduces the operating frequency from 2555–2620 MHz to 2230–2293 MHz with 68% efficiency, 20% higher than traditional full-coverage loading. Equivalent circuit analysis further reveals that selective loading increases capacitance/inductance for miniaturization while suppressing losses. This work establishes a new paradigm for a functional-material-based antenna design and offers a new research route for the fabrication of functional materials, aligning with 5G/6G demands for compact, integrated, low-loss systems. Full article

Liquid crystals based on dispersions of two-dimensional (2D) materials have recently been developed for light modulation, exhibiting superior performances compared to conventional organic liquid crystals in a variety of prototypical applications, including coloration, solar-blind communications and blue-light fluoresce. Among the diverse family of 2D liquid crystals, vermiculite-based liquid crystals stand out with advantages in low cost, ease of mass production and environmental sustainability, owing to the high natural abundance of the material. Here, we demonstrated magnetic-field tunable optics with 2D vermiculite dispersions prepared through a facile ‘exchange and redispersion’ method. By exploiting the intrinsic ion-exchange capability of clay minerals, we observed a significantly enhanced magneto-birefringence of the vermiculite dispersion upon replacing the native cations with magnetic ions, manifesting in a doubled Cotton–Mouton coefficient, representing the highest value among previous reports. Magnetization measurements reveal that there is a remarkable magnetic anisotropy in Fe ion-exchanged vermiculite samples in contrast to the isotropic magnetism of pristine vermiculite, which accounts for the observed enhancement of magneto-birefringence. Our findings demonstrate that ion exchange can serve as a simple and effective strategy to modulate the physical and chemical properties of 2D materials’ dispersions, thereby opening avenues for broader and more diverse applications. Full article

In order to meet the demand for high-frequency current sensors in 5G communication and new energy fields, there is an urgent need to develop high-performance nickel-zinc ferrite-based co-fired ceramic magnetic cores. In this study, a nickel-zinc ferrite core based on low temperature co-fired ceramic (LTCC) technology was developed. The regulation mechanism of BaCo_0.06Bi_0.94O₃ doping on the low-temperature sintering characteristics of NiZn ferrites was systematically investigated. The results show that the introduction of BaCo_0.06Bi_0.94O₃ reduces the sintering temperature to 900 °C and significantly improves the density and grain uniformity of ceramics. When the doping amount is 0.75 wt%, the sample exhibits the lowest coercivity of 35.61 Oe and the following optimal soft magnetic properties: initial permeability of 73.74 (at a frequency of 1 MHz) and quality factor of 19.64 (at a frequency of 1 MHz). The highest saturation magnetization reaches 66.07 emu/g at 1 wt% doping. The results show that BaCo_0.06Bi_0.94O₃ doping can regulate the grain boundary liquid phase distribution and modulate the magnetocrystalline anisotropy, which provides an experimental basis and optimization strategy for the application of LTCC technology in high-frequency current sensors. Full article

Solar flares, caused by magnetic field reconnection in the sun’s atmosphere, are intense bursts of electromagnetic radiation that can disrupt the Earth’s space environment, affecting communication systems, GPSs, and satellites. Traditional physics-based methods for solar flare forecasting have utilized the statistical relationships between solar activity indicators, such as sunspots and magnetic field properties, employing techniques like Poisson distributions and discriminant analysis to estimate probabilities and identify critical parameters. While these methods provide valuable insights, limitations in predictive accuracy have driven the integration of deep learning approaches. With the accumulation of solar observation data and the development of data-driven algorithms, deep learning methods have been widely used to build solar flare prediction models. Most research has focused on designing or selecting the right deep network for the task. However, the influence of the magnetic field height on deep-learning-based prediction models has not been studied. This paper investigates how different magnetic field heights affect solar flare prediction performance. Active regions were observed using HMI magnetograms from 2010 to 2019. The magnetic field heights were stratified to create a database of active regions, and deep neural networks like AlexNet, ResNet-18, and SqueezeNet were used to evaluate prediction performance. The results show that predictions at around 7200 km above the photosphere outperform other heights, aligning with physical method analysis. At this altitude, the average AUC of the predictions from the three models reaches 0.788. Full article

This paper proposes a tri-band wide-angle polarization-insensitive absorber operating in the C-band and Ku-band, based on the design concept of metal–dielectric–metal. The absorber achieves absorption efficiencies of 99.05%, 99.3%, and 97.9% at 4.23 GHz, 7.403 GHz, and 14.813 GHz, respectively. The first two absorption frequencies are in the C-band, while the third absorption frequency is in the Ku-band, both of which are commonly used in satellite communication. The designed absorber consists of three differently sized regular hexagonal rings. To analyze the interaction mechanism between the electromagnetic wave and the absorber, we applied the theory of impedance matching and equivalent media to analyze the metamaterial properties of the absorber. In addition, the equivalent circuit model of the absorber has been analyzed. We then determined the existence of coupled electromagnetic resonances between the top and bottom surfaces by analyzing the distribution of the electric field, magnetic field, and surface currents on the absorber. By varying the polarization angle and incident angle of the incoming wave, we found that the absorber exhibits polarization insensitivity and wide-angle absorption characteristics. The TE and TM waves maintain more than 90% absorption efficiency up to incident angles of 50° and 60°, respectively. The absorber’s thickness is 1.07 mm, which is 0.0154 times the wavelength corresponding to the lowest resonant frequency ${(\lambda }_0)$, and the edge length of the subunit’s regular hexagon is 7.5 mm (0.108${\lambda }_0$), making the absorber sub-wavelength in scale while maintaining its compactness. The proposed absorber operates in the C-band and Ku-band, and can be applied in the field of satellite communications, achieving functions such as electromagnetic shielding and stealth. Full article

Magnetic Resonance (MR) technology is extensively used in academic and industrial research laboratories and represents one of the most significant methodologies in clinical radiology. Although MR does not use ionizing radiation, it cannot be considered risk-free due to the strong static magnetic fields and time-varying electromagnetic fields employed in the technology. To mitigate risks for MR operators, the European Community and ICNIRP have established safety limits based on the existing literature, primarily related to diagnostic MR. However, the literature on occupational exposure in non-clinical nuclear magnetic resonance (NMR) spectroscopy is limited. Due to their specificity, non-medical NMR environments present unique challenges from the point of view of operator exposure. NMR spectrometers are characterized by extremely high static magnetic fields, reaching up to 28 T in commercial systems; moreover, routine activities performed near the magnet, where field gradients are highest, increase operator exposure. Such environments are not typically perceived as hazardous and are frequented by various types of personnel, often without specific training. This study aims to highlight the critical issues in managing a preclinical MR laboratory equipped with a high-field NMR spectrometer, discussing operator safety challenges and presenting risk assessment data. Full article

MXene is widely used in the fields of microwave absorption and electromagnetic shielding to balance electromagnetic pollution with the development of communication technologies and human health, due to its excellent surface functional groups and tunable electronic properties. Although pure multilayered MXene has an excellent accordion-like structure, the weak dielectric loss and lack of magnetic loss result in poor microwave absorption performance. Here, we propose a strategy for the catalytic growth of CNTs by the electrophoretic deposition of adsorbed metal ions, leading to the successful preparation of Ni-MWCNTs/Ti₃C₂T_x composites with a “layer-by-layer” structure, achieved through in situ regulated growth of CNTs. By introducing dielectric–magnetic synergy to improve the impedance matching conditions, and by regulating the diameter of the CNTs to alter the electromagnetic parameters of Ni-MWCNTs/Ti₃C₂T_x, the 2-Ni-MWCNTs/Ti₃C₂T_x composite achieves the best reflection loss (RL) value of −44.08 dB and an effective absorption bandwidth of 1.52 GHz at only 2.49 mm thickness. This unique layered structure and the regulation strategy provide new opportunities for the development of few-layered MXene composites. Full article

The purpose of this study is to provide a comprehensive resource for the selection of data representations for machine learning-oriented models and components in solar flare prediction tasks. Major solar flares occurring in the solar corona and heliosphere can bring potential destructive consequences, posing significant risks to astronauts, space stations, electronics, communication systems, and numerous technological infrastructures. For this reason, the accurate detection of major flares is essential for mitigating these hazards and ensuring the safety of our technology-dependent society. In response, leveraging machine learning techniques for predicting solar flares has emerged as a significant application within the realm of data science, relying on sensor data collected from solar active region photospheric magnetic fields by space- and ground-based observatories. In this research, three distinct solar flare prediction strategies utilizing the photospheric magnetic field parameter-based multivariate time series dataset are evaluated, with a focus on data representation techniques. Specifically, we examine vector-based, time series-based, and graph-based approaches to identify the most effective data representation for capturing key characteristics of the dataset. The vector-based approach condenses multivariate time series into a compressed vector form, the time series representation leverages temporal patterns, and the graph-based method models interdependencies between magnetic field parameters. The results demonstrate that the vector representation approach exhibits exceptional robustness in predicting solar flares, consistently yielding strong and reliable classification outcomes by effectively encapsulating the intricate relationships within photospheric magnetic field data when coupled with appropriate downstream machine learning classifiers. Full article

The literature reports on radiofrequency (RF) transmit (Tx) elements tailored for ultrahigh-field (UHF) magnetic resonance imaging (MRI) showed confounded reproducibility due to variations in simulation tools, modeling assumptions, and meshing techniques. This study proposes a standardized methodology to improve reproducibility and consistency across research sites (testers) and simulation tools (testing conditions). The methodology includes detailed simulation workflow and performance metrics for RF Tx elements. The impact of the used mesh setting is assessed. Following the methodology, a reproducibility study was conducted using CST Microwave Studio Suite, HFSS, and Sim4Life. The methodology and simulations were ultimately validated through 7 T MRI phantom experiments. The reproducibility study showed consistent performance with less than 6% standard deviation for B₁⁺ fields and 12% for peak SAR averaged over 10 g tissue (pSAR_10g). The SAR efficiency metric (|B₁⁺|/√pSAR_10g) was particularly robust (<5%). The simulated and experimental |B₁⁺| maps showed good qualitative agreement. This study demonstrates the feasibility of a standardized methodology for achieving reproducible RF Tx element electromagnetic field simulations. By following the FAIR principles including making the framework publicly available, we promote transparency and collaboration within the MRI community, supporting the advancement of technological innovation and improving patient safety in UHF-MRI. Full article