Search Results (484)

The plasma-catalytic conversion of CO₂ is a promising route toward sustainable fuel and chemical production under mild operating conditions. However, many aspects still need to be better understood to improve performance and better understand the catalyst-plasma synergies. Among them, one aspect concerns understanding whether photons emitted by plasma discharges could induce changes in the catalyst, thereby promoting interaction between plasma species and the catalyst. This question was addressed by investigating the CO₂ splitting reaction in a planar dielectric barrier discharge (pDBD) reactor using titania-based catalysts that simultaneously act as discharge electrodes. Four systems were examined feeding pure CO₂ at different flow rates and applied voltage: bare titanium gauze, anodically formed TiO₂ nanotubes (TiNT), TiNT decorated with Ag–Au nanoparticles (TiNTAgAu), and TiNT supporting Ag–Au nanoparticles coated with polyaniline (TiNTAgAu/PANI). The TiNTAgAu exhibited the highest CO₂ conversion (35% at 10 mL min⁻¹ and 5.45 kV) and the most intense optical emission, even in the absence of external light irradiation, suggesting that the improvement is primarily attributed to plasma–nanoparticle interactions and self-induced localized surface plasmon resonance (si-LSPR) rather than conventional photocatalytic pathways. SEM analyses indicated severe plasma-induced degradation of TiNT and TiNTAgAu surfaces, leading to performance decay over time. In contrast, the TiNTAgAu/PANI catalyst retained structural integrity, with the polymeric coating mitigating plasma etching while maintaining competitive efficiency. There is thus a complex behavior with catalytic performance governed by nanostructure stability, plasmonic enhancement, and the interfacial protection. The results demonstrate how integrating plasmonic nanoparticles and conductive polymers can enable the rational design of durable and efficient plasma-photocatalysts for CO₂ valorization and other plasma-assisted catalytic processes. Full article

Background/Objectives: Chronic pudendal neuralgia is a relatively rare condition in the general population, with an incidence of 1%. Although diagnosis of pudendal neuralgia is mainly clinical, Magnetic Resonance Imaging (MRI) is commonly performed to obtain further information. However, clear criteria and guidelines for MRI diagnosis and the clinical–radiological correlation are still not definite. Methods: We reviewed 81 patients with chronic pudendal neuralgia, studied by an MRI designed protocol for a pelvis and pelvic floor examination. A key element of the protocol was the use of a diffusion-weighted imaging (DWI) technique with echo planar imaging (EPI) sequence (b-values of 0, 100, and 600) for the neurographic evaluation of the nerve. Results: MRI examination revealed DWI abnormalities in 42/81 patients. Pudendal nerve abnormalities were unilateral in 33/42 patients and bilateral in 9/42. Moreover, in 23/42 patients, pathologies related to a high probability of neuropathy have been identified. Conclusions: This study highlights the role of pelvic MRI as a valuable imaging modality in the evaluation of patients with chronic pudendal neuralgia. In the study protocol we propose, an essential role is played by the DWI technique, which improves the visual definition of the pudendal nerve and related anatomical structures. By focusing on anatomical visualization and structured image interpretation, our work provides a practical imaging-oriented contribution to a field in which standardized MRI evaluation is still lacking. Full article

In this study, a hybrid sensor based on a defective square-truncated patch antenna (STPA) and a frequency-selective surface (FSS) was analyzed numerically and experimentally for different glucose–distilled water solutions. Here, an FSS was employed to enhance the sensitivity of the hybrid sensor. The sensing principle relies on monitoring variations in the loss tangent ($tan\delta$) and relative permittivity (${\epsilon }_r$) caused by different glucose concentrations applied to the sample under test (SUT). An open-ended coaxial probe was used to measure the complex permittivity of the solutions, which was then fitted to the Debye relaxation model. The simulated and experimental results of the novel sensor showed good agreement in a glucose concentration monitoring application. The sensor spanned the glucose range from 0 mg/dL to 5000 mg/dL, exhibiting a sensitivity of 55.44 kHz/mgdL⁻¹ and a figure of merit (FOM) of 6.23 × ${10}^{-4}$ (1/mgdL⁻¹) in the experiments and 53.60 kHz/mgdL⁻¹ and 1.71 × ${10}^{-4}$ (1/mgdL⁻¹) FOM in the simulations. When solutions with different concentrations were tested in the SUT, the resonance frequency of the antenna ($f_0$, in GHz) changed. To further characterize the sensor response, the relationship between the glucose concentration (C, in mg/dL) and $f_0$ was examined. A regression-based prediction model was constructed to map the measured scattering parameters to the glucose concentration, yielding a coefficient of determination ($R^2$) of 0.976. The high sensitivity, compact size, and compatibility with planar fabrication suggest that the proposed hybrid sensor has the potential to contribute to the development of non-invasive glucose-monitoring systems. Full article

High-density 380 V–12 V $LLC$ resonant converters typically employ planar transformers with integrated leakage inductance. To achieve Zero-Voltage Switching (ZVS), an air gap is introduced to adjust the magnetizing inductance ($L_m$). However, this gap alters the internal magnetic field (H) distribution. In Center-Tapped (CT) structures, this alteration leads to asymmetric leakage inductances between the positive and negative half-cycles, causing resonant frequency mismatch and performance degradation, particularly under light-load conditions. In this work, the asymmetrical leakage inductance effect in a CT transformer for a 380 V–12 V $LLC$ resonant converter is systematically investigated. A mathematical model is derived to quantify the leakage inductance distribution, revealing that the relative position between the air gap and the windings significantly affects the symmetry. Based on this modeling analysis, the centralized assembly method is identified as the optimal solution to ensure impedance symmetry. The accuracy of the proposed model and the effectiveness of this structure are validated through Finite Element Analysis (FEA) simulations and a hardware prototype of a 250-W, 600-kHz $LLC$ converter. Results demonstrate that this method eliminates the approximately 11% leakage inductance discrepancy (1.8 μH vs. 1.6 μH), ensuring stable operation across the full load range. Full article

Following the persistent evolution of terrestrial 5G wireless systems, a new field of underwater communication has emerged for various related applications like environmental monitoring, underwater mining, and marine research. However, establishing reliable high-speed underwater networks remains notoriously difficult due to the severe RF attenuation in conductive seawater, which strictly limits range coverage. In this article, we focus on a comprehensive review of different antenna types for future underwater communication and sensing systems, evaluating their performance and suitability for Autonomous Underwater Vehicles (AUVs). We critically examine and compare distinct antenna technologies, including Magnetic Induction (MI) coils, electrically short dipoles, wideband traveling wave antennas, printed planar antennas, and novel magnetoelectric (ME) resonators. Specifically, these antennas are compared in terms of physical footprint, operating frequency, bandwidth, and realized gain, revealing the trade-offs between miniaturization and radiation efficiency. Our analysis aims to identify the benefits and weaknesses of the different antenna types while emphasizing the necessity of innovative antenna designs to overcome the fundamental propagation limits of the underwater channel. Full article

Non-invasive glucose monitoring remains a significant challenge in diabetes management, with existing approaches often limited by poor accuracy, high cost, or patient discomfort. Microwave-based biosensors offer a promising label-free alternative by exploiting the dielectric contrast between glucose and water. This paper presents a compact, dual-band concentric square-shaped split-ring resonator (SRR-type) biosensor fabricated on a low-cost FR-4 substrate for aqueous glucose detection. The sensor leverages electric field confinement in inter-ring gaps to transduce glucose-induced permittivity changes into measurable shifts in resonance frequency and reflection coefficient. Experimental results demonstrate a linear, monotonic response across the clinical range up to 250 mg/dL, with a frequency-domain sensitivity of 1.964 MHz/(mg/dL) and amplitude-domain sensitivity of 0.0332 dB/(mg/dL), achieving high coefficients of determination (R² = 0.9956 and 0.9927, respectively). The design achieves a normalized size of 0.137 λ_g², combining high sensitivity and compact size within a scalable platform. Operating in the UWB-adjacent band (2.76–3.25 GHz), the proposed biosensor provides a practical, reproducible, and PCB-compatible solution for next-generation label-free glucose monitoring. Full article

Sensors to monitor the immune status of an individual play a crucial role in understanding the acquired immunity or signs of a latent infection. Such sensors can be an effective tool to manage infection and to design treatment options in vulnerable populations. We demonstrate here highly sensitive detection of acquired immunity to Cytomegalovirus CMV by detection of anti-CMV antibodies using plasmon-enhanced fluorescence (PEF). The PEF sensors leverage plasmonic enhancement from a high density of intense electromagnetic hotspots in self-assembly-derived gold nanopillar arrays. Comparing PEF assays with assays on a planar surface plasmon resonance sensor shows the PEF sensors to be sensitive to a small fraction of the antibodies on the surface. The detection scheme deploys peptide monolayers with specific affinity to anti-CMV antibodies to capture them onto the sensor surfaces. The results of the assay on the PEF sensor reveal high promise for sensors with miniaturized sensing footprints, ease of spatial multiplexing, high sensitivity, and quick response times. The developments are readily applicable to a range of other diagnostic contexts where peptide–protein interactions and self-assembly-derived PEF sensors can be leveraged. Full article

Accurate co-registration between on-scalp Optically Pumped Magnetometer (OPM)–Magnetoencephalography (MEG) sensors and anatomical Magnetic Resonance Imaging (MRI) remains a critical bottleneck restricting the spatial fidelity of source localization. Optical Scanning Image (OSI) methods can provide high spatial accuracy but depend on surface visibility and cannot directly determine the internal sensitive point of each OPM sensor. Coil-based magnetic dipole localization, in contrast, targets the sensor’s internal sensitive volume and is robust to occlusion, yet its accuracy is affected by coil fabrication imperfections and the validity of the dipole approximation. To integrate the complementary advantages of both approaches, we propose a hybrid co-registration framework that combines Rigid Coil Structures (RCS), magnetic dipole-based sensor localization, and optical orientation constraints. A complete multi-stage co-registration pipeline is established through a unified mathematical formulation, including MRI–OSI alignment, OSI–RCS transformation, and final RCS–sensor localization. Systematic simulations are conducted to evaluate the accuracy of the magnetic dipole approximation for both cylindrical helical coils and planar single-turn coils. The results quantify how wire diameter, coil radius, and turn number influence dipole model fidelity and offer practical guidelines for coil design. Experiments using 18 coils and 11 single-axis OPMs demonstrate positional accuracy of a few millimeters, and optical orientation priors suppress dipole-only orientation ambiguity in unstable channels. To improve the stability of sensor orientation estimation, optical scanning of surface markers is incorporated as a soft constraint, yielding substantial improvements for channels that exhibit unstable results under dipole-only optimization. Overall, the proposed hybrid framework demonstrates the feasibility of combining magnetic and optical information for robust OPM–MEG co-registration. Full article

The high-frequency and high-amplitude pyroshock environment during the use of spacecraft will cause damage to the equipment. To simulate this environment, a pyroshock environment simulator based on electromagnetic excitation is presented in this work. A multiphysics finite-element model with electromagnetic–force coupling is established to analyze field distributions during excitation and the acceleration response of a resonant plate under Lorentz loading. Parametric analyses examine coil structural parameters, coil current, and plate thickness and their effects on the SRS. It is suggested that the pyroshock environment excited by electromagnetic force has the characteristics of wide frequency band and high amplitude similar to the explosive-based pyrotechnical event, and compared with the single coil, the multi-coil combination can excite a higher peak acceleration without changing the SRS shape. At the same time, the structural parameters of the planar induction coil and the current in the coil only affect the SRS amplitude of the resonant plate, and the degree of influence of the parameters on the SRS peak amplitude is coil width > coil lift-off distance > coil thickness > coil turn-to-turn distance. Additionally, the experimental results are in good agreement with the simulated SRS, verifying the validity of the above-mentioned analysis. Full article

A compact, single-layer W-band microstrip antenna for forward-looking ADAS radar in the 77–79 GHz band is presented. The 16.5 × 22 mm² PCB element integrates a linear microstrip taper, two shorting vias, and a slot-loaded cavity to stabilize input reactance and broaden the in-band match. Full-wave simulations and launcher-based measurements using WR-12 TRL de-embedding and anechoic-chamber substitution confirm S₁₁ ≤ −10 dB across 77–79 GHz. At 77/79 GHz, the antenna achieves end-fire realized gains of ≈9.9/≈11.2 dBi. The main beam is end-fire (peak near θ ≈ 90°), with −3 dB beamwidths of ≈36° in the θ-cut at φ = 0 (pointing ≈ 61°/56°) and ≈11.6° in the φ-cut at θ = 90°. First sidelobes are about −2.3/−2.5 dB (θ-cut) and −3.1/−3.4 dB (φ-cut). Cross-polarization is ≥18 dB below co-polarization, and the simulated radiation efficiency reaches ≈85% at 77 GHz and ≈80% at 79 GHz. A controlled thermal sweep (25–105 °C) yields < 100 MHz resonance drift while maintaining ≥ 10 dB return loss. Due to its planar architecture and clean feed integration, compact module packaging in short- to medium-range automotive radars. Full article

This article introduces the design of a trowel-shaped planar antenna (TSPA) with high-performance features. Wideband Impedance bandwidth, high gain, excellent radiation efficiency, and stable radiation patterns are achieved by using a trowel-shaped radiator, a triangular tapered feed line, and a partial ground plane. The antenna exhibits broad impedance bandwidth from 15 GHz to 54 GHz, with an impressive fractional ratio of 113.05% at S₁₁ ≤ −10 dB. The proposed antenna has compact electrical dimensions of 1.05λ₀ × 0.775λ₀ × 0.0254λ₀, where the wavelength λ₀ is concerning the minimum edge of the 15 GHz frequency. The proposed antenna is fabricated on Rogers RT/Duroid RO5880 substrate, offering a cost-effective yet high-performance solution. Moreover, TSPA achieved a high gain of 9.67 dBi at 51.8 GHz and demonstrated an impressive radiation efficiency exceeding 92%. The proposed antenna’s strong intensity of current flow at multiple resonances is observed, contributing to strong far-field radiation patterns. The simulation and measurement results show excellent agreement, further validating the antenna’s high efficiency and reliability. The TSPA exhibits superior wideband performance compared to existing reported structures, making it highly suitable for next-generation 6G wireless communication systems. Full article

This study comparatively investigates the effects of vacuum sintering and traditional sintering on the structure and electrical properties of lead zirconate titanate (PZT) 5H (PZT-5H) piezoelectric ceramics. The density of the vacuum-sintered ceramics increases from 7.67 g/cm³ (for traditionally sintered ceramics) to 7.98 g/cm³. Importantly, the dielectric constant (ε_r), remnant polarization (P_r), planar electromechanical coupling coefficient (k_p), and piezoelectric coefficient (d₃₃) for the PZT-5H ceramics increase by 35%, 20%, 9%, and 12%, respectively, when vacuum sintering is employed instead of traditional sintering. Over a temperature range from room temperature to 180 °C, the d₃₃ variation measured by the resonant method is only about 4% for the vacuum-sintered PZT-5H ceramics. High-temperature impedance spectroscopy analysis reveals that vacuum sintering reduces the hole concentration in PZT-5H ceramics, leading to significant improvements in their dielectric and piezoelectric performance. This research demonstrates that vacuum sintering is a simple and effective method to enhance the density, dielectric, and piezoelectric properties of PZT-5H ceramics. Full article

Accurate, non-invasive glucose monitoring remains a major challenge in biomedical sensing. We present a high-sensitivity planar microwave biosensor that progresses from a 2-cell hexagonal array to an 8-cell hexagonal array, and finally to a 16-cell double-honeycomb (DHC-CSRR) architecture to enhance field confinement and resonance strength. Full-wave simulations using Debye-modeled glucose phantoms demonstrate that the optimized 16-cell array on a Rogers RO3210 substrate substantially increases the electric field intensity and transmission response |S₂₁| sensitivity compared with FR-4 and previous multi-CSRR designs. In vitro measurements using pharmacy-grade glucose solutions (5–25%) and saline mixtures with added glucose, delivered through an acrylic channel aligned to the sensing region, confirm the simulated trends. In vivo, vector network analyzer (VNA) tests were conducted on four human subjects (60–150 mg/dL), comparing single- and dual-finger placements. The FR-4 substrate (${\mathsf{\epsilon }}_{\mathrm{r}}$ = 4.4) provided higher frequency sensitivity (2.005 MHz/(mg/dL)), whereas the Rogers RO3210 substrate (${\mathsf{\epsilon }}_{\mathrm{r}}$ = 10.2) achieved greater amplitude sensitivity (9.35 × 10⁻² dB/(mg/dL)); dual-finger contact outperformed single-finger placement for both substrates. Repeated intra-day VNA measurements yielded narrow 95% confidence intervals on |S₂₁|, with an overall uncertainty of approximately ±0.5 dB across the tested glucose levels. Motivated by the larger |S₂₁| response on Rogers, we adopted amplitude resolution as the primary metric and built a compact prototype using the AD8302-EVALZ with a custom 3D-printed enclosure to enhance measurement precision. In a cohort of 31 participants, capillary blood glucose was obtained using a commercial glucometer, after which two fingers were placed on the sensing region; quadratic voltage-to-glucose calibration yielded R² = 0.980, root–mean–square error (RMSE) = 2.316 mg/dL, overall accuracy = 97.833%, and local sensitivity = 1.099 mg/dL per mV, with anthropometric variables (weight, height, age) showing no meaningful correlation. Clarke Error Grid Analysis placed 100% of paired measurements in Zone A, indicating clinically acceptable agreement with the reference meter. Benchmarking against commercial continuous glucose monitoring systems highlights substrate selection as a dominant lever for amplitude sensitivity and positions the proposed fully non-invasive, consumable-free architecture as a promising route toward portable RF-based glucose monitors, while underscoring the need for larger cohorts, implementation on flexible biocompatible substrates, and future regulatory pathways. Full article

In recent years, with the development of electronic products toward high frequency and high speed, Printed Circuit Board (PCB) routing technology has been continuously evolving to meet the requirements of complex signal transmission. Meanwhile, the increase in circuit frequency and device density has led to a sharp deterioration of simultaneous switching noise (SSN), which has escalated from a minor interference to a core bottleneck. SSN not only impairs signal integrity and increases bit error rate, but also interferes with circuit operation, causes device failure, and even leads to system collapse, becoming a “fatal obstacle” to the performance and reliability of high-frequency products. The SSN problem has become increasingly severe due to the rise in circuit operating frequency and device density, posing a key challenge in high-speed circuit design. To address the challenge of suppressing SSN at the PCB board level in high-speed digital circuits, this paper proposes a collaborative optimization scheme integrating simulation analysis and the Seagull Optimization Algorithm (SOA). In this study, a multi-physical field coupling model of SSN is established to reveal that SSN essentially arises from the electromagnetic interaction between the parasitic inductance of the power distribution network (PDN) and high-speed transient current. Based on the research on frequency-domain impedance analysis, time-domain response prediction, and decoupling capacitor suppression mechanism, the limitations of traditional capacitor placement in suppressing GHz-level high-frequency noise are overcome. This method enables precise power integrity (PI) design via simulation analysis frequency-domain parameter extraction and power–ground noise simulation quantify PDN impedance characteristics and the coprocessor switching current spectrum; resonance analysis locates key frequency points and establishes an SSN–planar resonance correlation model to guide decoupling design; finally, noise coupling analysis optimizes signal–power plane spacing, markedly reducing mutual inductance coupling. On this basis, the SOA is innovatively introduced to construct a multi-objective optimization model, with capacitor frequency, capacitance value, and package size as variables. A spiral search algorithm is used to balance noise-suppression performance and cost constraints. Simulation results show that this scheme can reduce the SSN amplitude by 37.5%, effectively suppressing the signal integrity degradation caused by SSN and providing a feasible solution for SSN suppression. Full article

Rapid and reliable detection of pesticide residues in vegetables is essential for food safety and sustainable agriculture. This work presents a four-port closed-loop ring resonator (CLRR) sensor for quantitative detection of carbamate residues in leafy vegetables. Operating through the S₃₁ transmission path, the sensor enhances electric-field coupling and sensing resolution in the high-field region. Four resonance modes were identified at 1.05, 2.10, 3.12, and 4.11 GHz, with the third mode (3.12 GHz) showing the most stable and linear response. Vegetable extracts of Chinese kale and Choy sum were prepared with carbamate concentrations of 0–8% (w/v). Increasing concentration caused a red-shift in resonance frequency corresponding to a reduction in dielectric constant. Regression analysis revealed a strong linear correlation between frequency shift and concentration (R² = 0.9855–0.9988). The CLRR achieved average normalized sensitivities of 6.39% and 6.54% per unit dielectric variation, outperforming most planar and metamaterial sensors. Fabricated on a single-layer FR-4 substrate, the sensor combines high sensitivity, low cost, and excellent repeatability, offering a practical, label-free, non-destructive tool for on-site monitoring of pesticide contamination in leafy vegetables. Full article