Search Results (9,137)

The rapid expansion of wireless communication in urban environments requires antenna systems that balance high electromagnetic performance with stringent aesthetic and security constraints. This review examines recent advances in concealed antenna technologies integrated into building structures, with a focus on performance variation, material-induced attenuation, and emerging concealment strategies. Techniques such as transparent conductors on glass, structural embedding within walls, and camouflage-based designs are shown to significantly influence resonance behavior, radiation efficiency, and pattern characteristics compared to free-space operation. Despite these challenges, optimized solutions including transparent conductive oxide arrays, wideband embedded antenna geometries, and metasurface-enhanced window structures can partially recover performance while maintaining optical transparency above 70%. Material loading effects are found to induce resonant frequency shifts of approximately 10–44%, depending on dielectric properties and environmental conditions. Transparent antenna arrays achieve gains ranging from 0.34 to 13.2 dBi, while signal-transmissive wall systems demonstrate transmission improvements of up to 22 dB relative to untreated building materials. These technologies enable a wide range of applications, including 5G and beyond-5G cellular networks across sub-6 GHz and millimeter-wave bands, as well as Internet of Things systems and smart city infrastructure. However, key challenges remain, including the need for comprehensive characterization of building material electromagnetic properties, optimization of multilayer structural environments, and the development of standardized design and evaluation methodologies. This review provides a unified framework for understanding the tradeoffs associated with antenna concealment and identifies critical research directions for the development of building-integrated wireless systems in next-generation communication networks. Full article

This study addresses the premature failure of electric motor bearings caused by inverter-induced parasitic currents. We propose a novel segmented end shield design utilizing 24 carbon fiber-reinforced polymer (CFRP) lamellae to provide both structural support and galvanic isolation. The “main working” of the design relies on a segmented architecture where the lamellae are adhesively bonded between a central bearing housing and an outer mounting flange, creating a high-impedance path that interrupts circulating currents. Experimental validation focused on both mechanical stability and dielectric performance. Results indicate that the assembly maintains rotor positional integrity under nominal loads while providing an insulation resistance > 1 GΩ at 1 kV and a structural capacitance of 2.47 nF. These parameters effectively mitigate low-frequency circulating currents. Data analysis, derived from the mean values of repeated test cycles, confirms that the composite architecture serves as a viable, mechanically robust alternative to conventional metallic end shields. Full article

Sea ice classification is of fundamental importance for polar monitoring and global climate research. Global Navigation Satellite System Reflectometry (GNSS-R) has emerged as a frontier technology in polar remote sensing due to its high spatiotemporal resolution and cost-effectiveness. Based on BeiDou System Reflectometry (BDS-R) data acquired from the Fengyun-3E (FY-3E) satellite, this study introduces a classification approach that integrates multi-dimensional sea ice information. A comprehensive feature set was constructed by integrating the Spectral Entropy (SE) of the Normalized Integrated Delay Waveform (NIDW) First-order Differential Curve to characterize the oscillatory complexity of the trailing edge power decay process as a scattering dynamic property, the Root Mean Square height (RMS) to characterize the attenuation magnitude of scattering intensity arising from surface roughness and related factors as a scattering intensity attenuation property, and salinity (S) and L-band brightness temperature (TB) data from SMOS to describe dielectric and radiative properties. These novel features are combined with traditional GNSS-R features. After selecting the optimal feature set via an ablation study, the features were used to train a Random Forest (RF) classifier for sea ice classification. Validated against Ocean and Sea Ice Satellite Application Facility (OSI SAF) sea ice type products, the proposed method yielded an overall accuracy of 93.86% and a Kappa coefficient of 0.8061. The integration of multi-dimensional features notably improved the identification of Multi-Year Ice (MYI), achieving a Recall of 85.11% and an F1-score of 84.43%. These results indicate that the proposed multi-dimensional feature set provides an effective solution for GNSS-R-based sea ice classification. Full article

The increasing integration of nonlinear loads in modern power systems has made harmonic pollution a critical challenge to the operational safety of power cables. This study develops a frequency-dependent high-voltage cable system model using the ATP-EMTP (Alternative Transients Program-Electro Magnetic Transient Program) electromagnetic transient simulation platform, systematically investigating the amplification mechanisms and propagation characteristics of grounding currents under multi-type harmonic disturbances. A frequency-dependent parameter correction model is established by integrating the conductor skin effect and the dielectric relaxation properties of the insulation layers. This model incorporates the multi-structure combination among conductors, insulation, and metallic screen. It effectively overcomes the limitations of conventional lumped-parameter models in higher frequency harmonic analysis. Key findings are as follows: (1) The combined influence of harmonic frequency and amplitude leads to a grounding current amplification of up to 445 times (at 1950 Hz with 30% distortion level). Notably, current-source excitation produces significantly greater amplification than voltage-source excitation. (2) The distributed capacitance of long-distance cables (>8 km) exacerbates resonance risks within specific frequency bands (750–1250 Hz), resulting in a maximum harmonic amplification factor of 34.73 (observed for the 17th harmonic in a 15 km cable). (3) The contribution of voltage-source harmonics diminishes to less than 5% of the total current at high frequencies (≥1250 Hz), indicating a pattern of current-dominated harmonic superposition. Full article

This study uses a bismuth ferrite (BiFeO₃) and MXene (Ti₃C₂Tx) to design a surface plasmon resonance (SPR) biosensor for the sensitivity enhancement at a 633 nm wavelength. Here, MXene serves as a biorecognition element (BRE) layer to ensure stable and reliable biomolecule adsorption. The MXene is a family of two-dimensional (2D) materials with metallic-like conductivity, a large surface area that can attach biomolecules, and improve biocompatibility. The addition of a conductive 2D MXene layer and a high-index BiFeO₃ dielectric layer greatly improves light–matter interaction and evanescent field penetration at the sensing interface. Strong plasmonic coupling is indicated by the reflectance analysis, which shows a distinct and consistent shift in the resonance angle as analyte RI increases. This study examined the sensitivity at optimized Ag and BiFeO₃ layer thickness. At an Ag of 39 nm and BiFeO₃ of 3 nm thickness, the maximal sensitivity of 340.68°/RIU with a remarkable figure of merit (FoM) of 47.38/RIU is obtained. The overall detection accuracy (DA) and FoM are significantly improved by the large sensitivity enhancement, despite a slight increase in full width at half maximum (FWHM). Furthermore, the penetration depth (PD) of 198.50 nm (at RI:1.330) and 199.52 nm (at RI:1.335) is attained with the proposed structure. Due to its high sensitivity, reusability, and reproducibility, the SPR biosensor has the potential to be used in biochemical, environmental, and medical detection. Full article

Oil-contaminated wastewater generated in oil-producing regions requires effective treatment methods capable of degrading persistent petroleum hydrocarbons and reducing the overall organic load. This study investigated plasma–ozone treatment of model oil-contaminated water representative of Kumkol-associated wastewater, with emphasis on reactive oxygen species formation and pollutant degradation. Experiments were carried out in a dielectric barrier discharge plasma reactor operating at 8–15 kV, 10–30 kHz, and 100–300 W. The plasma process generated ozone in the range of 3–18 mg/L and hydrogen peroxide in the range of 4–25 mg/L. For model wastewater containing 100–500 mg/L petroleum hydrocarbons, plasma–ozone treatment for 30 min achieved 70–90% hydrocarbon degradation. At the same time, COD decreased from 180–600 to 60–180 mg O₂/L, while TOC decreased from 60–250 to 20–90 mg/L. These results indicate that plasma–ozone treatment provides effective oxidation of petroleum hydrocarbons together with simultaneous reduction in key water quality indicators, demonstrating its potential for the treatment of oil-contaminated wastewater. Full article

Printed biosensors have attracted increasing attention as platforms for rapid, low-cost, and portable diagnostics because they can be fabricated on flexible or rigid substrates using scalable printing techniques. Their performance is strongly influenced by both the printing process and the materials employed, since factors such as ink rheology, particle dispersion, interfacial behavior, and post-processing conditions directly affect device architecture, sensing performance, and manufacturing reliability. This review summarizes recent advances in printed biosensors from the combined perspectives of printing technologies and functional materials. Commonly employed printing techniques, including inkjet, screen, aerosol jet, and roll-to-roll gravure printing, are discussed with emphasis on their processing characteristics and material requirements. The review also examines key material platforms used in printed biosensors, including carbon-based nanomaterials, metal oxides, metal nanoparticles, conductive polymers, dielectric materials, and hybrid composites, highlighting their roles in electrical conductivity, catalytic activity, biomolecule immobilization, mechanical flexibility, and overall analytical performance. Finally, current challenges and emerging research directions are outlined with respect to ink stability, post-processing strategies, sensor reliability, manufacturability, and practical translation. Overall, this review emphasizes that the development of high-performance printed biosensors depends on the synergistic integration of rational material design with optimized printing strategies. Full article

In optical sensing, electromagnetically induced transparency (EIT) and bound states in the continuum (BIC) substantially enhance light–matter interactions by leveraging high-Q resonances. This study theoretically demonstrates dual-resonance phenomena—namely, a quasi-symmetry-protected BIC (SP-BIC) and a quasi-BIC-induced EIT-like (QBIC-EIT) resonance—using a dielectric metasurface composed of pyramid-shaped lithium niobate nanoarrays operating in the near-infrared. The QBIC-EIT transmission window originates from the interference between surface lattice modes and toroidal dipole modes, triggered by symmetry breaking of the BIC state. Due to the absence of C_4v rotational symmetry in the pyramidal unit cells, the metasurface exhibits pronounced polarization-dependent responses: Under x-polarized incidence, a single quasi-SP-BIC resonance appears; under y-polarization, dual quasi-SP-BIC resonances along with a distinct QBIC-EIT resonance are observed. Both the high-Q quasi-SP-BIC resonance and the EIT-like window show strong sensitivity to changes in the ambient refractive index (RI). Specifically, the EIT-like window achieves a sensitivity of 404.9 nm/RIU, while the quasi-SP-BIC resonance delivers an exceptional sensitivity of 887.7 nm/RIU, confirming the metasurface’s performance as a high-sensitivity RI sensor. These findings establish a multi-band detection platform for advanced RI sensing and contribute to the development of high-performance metasurface-based optical sensors. Full article

This study investigates the development of sustainable composite materials using recycled low-density polyethylene (rLDPE) and high-density polyethylene (rHDPE) in an 80/20 mass ratio, incorporating kraft lignin as a bio-derived additive and polyethylene-graft-maleic anhydride (PE-g-MA) as a compatibilizer. Reactive melt mixing was employed to produce composites with varying lignin loadings (1, 3, 5, and 10 wt%). The structural, thermal, and mechanical properties and segmental dynamics of the materials were thoroughly examined using differential scanning calorimetry (DSC), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS), tensile testing, scanning electron microscopy (SEM), and dielectric relaxation spectroscopy (DRS). The incorporation of lignin exhibited minimal disruption to the polymeric thermal transitions, while it boosted thermal stability, as confirmed by the TGA curves. According to the segmental dynamics findings, the glass transition temperature of the polymeric blend (−35 °C) was increased systematically with the addition of lignin by ~1–20 K. Tensile tests showed that the 1 wt% additive ratio demonstrated the optimal balance of strength and ductility. Morphological observations supported these findings, revealing uniform dispersion at low additive ratio and increased agglomeration at higher ratios. Based on its superior performance, the composite containing 1 wt% lignin was successfully extruded into filament suitable for 3D-printing. This study highlights the synergy of bio-based additives and recycled polymers in engineering high-performance materials, promoting circular economy principles and reduced environmental footprint through upcycling post-consumer waste into functional, valuable products. Full article

For cable compound manufacturers, accurate formulation fine-tuning is essential to ensure safety, long-term durability, and compliance with international standards for dielectric strength, volume resistivity, and environmental and thermal ageing. This work presents an experimental study demonstrating how minor additives can critically affect the performance of complex flame-retardant elastomeric formulations. The investigation focuses on the role of small amounts of zinc oxide (ZnO) in commercial cable compounds based on a crosslinked elastomeric matrix composed of ethylene–propylene monomer (EPM), ethylene–propylene–diene monomer (EPDM), and thermoplastic polyolefin elastomer (POE). The formulations contain aluminium trihydroxide (ATH) as the major filler, together with several minor additives. Among these, a phenolic antioxidant (AN01) acting as a metal deactivator is also present. The addition of ZnO in low amounts (2–5 phr) allowed the compounds to maintain a volume resistivity ≥ 10¹² Ω·cm in water at 100 °C. To elucidate the role of ZnO, a systematic set of formulations was prepared by varying the type and content of selected additives. The compounds were prepared by melt mixing in an internal mixer (Banbury type), followed by peroxide crosslinking via compression molding. Electrical characterization results indicate that ZnO interacts with the phenolic additive through surface adsorption, forming a coated particle with significantly reduced electrical conductivity. Optimal electrical performance was achieved when the ZnO-to-additive ratio corresponded to the minimum amount required for complete surface complexation. Full article

Detecting changes in the permittivities of materials has important applications in electronic information, materials science, biomedicine, and many other fields. However, existing detection methods are limited by factors such as sample thickness and resonance intensity, making it difficult to achieve sensitive dielectric constant detection at desired frequency bands. This paper proposes a method for detecting the dielectric constant changes in samples based on destructive interference of spoof surface plasmon polaritons (SSPPs) in a dual-path transmission structure, which forms a characteristic absorption peak at the SSPPs’ cutoff frequency. Specifically, by utilizing the dependence of the SSPPs’ phase on the periodic unit, a constant π phase difference is formed at the cutoff frequency through the periodic unit number difference between the two paths, resulting in a cutoff frequency absorption peak. When the sample is coated on the SSPPs’ dual-path structure, the boundary conditions are altered, leading to a cutoff frequency shift, thereby enabling dielectric constant detection at the specified frequency. Simulation results show that, with proper structural design, the normalized characteristic frequency shift reaches 10.8%/${\epsilon }_S$ and further demonstrates dramatic robustness against initial phase difference, sample thickness and sample loss. In summary, this work provides a novel high-precision and high-robustness method for detecting dielectric constant changes in samples at specified frequencies. Full article

The synthesis and phase behavior of two liquid crystalline racemates containing four aromatic rings, differing in the number of methylene groups, were reported. These materials form smectic phases, as was confirmed by dielectric spectroscopy. The mesomorphic properties of the studied racemates were compared with those of the appropriate (S) enantiomers previously synthesized. Since these materials are racemic mixtures, they were subjected to chiral separation by high-performance liquid chromatography. This research was conducted on two chiral columns based on polysaccharides. We identified optimal conditions that enable the baseline separation of these racemates, which can be scaled up for preparative purposes. Then, there is no need for repeated synthesis of chiral equivalents. Full article

Aerogels represent an extraordinary class of materials characterized by remarkable properties, including an exceptionally high porosity (approximately 99.8%), minimal weight, extraordinarily low density, low thermal conductivity, a diminished dielectric constant, and a reduced refractive index. These attributes arise from their extensive micro-meter-sized pores. In recent years, there has been a notable surge of interest in carbon or carbon nanotube (CNT) based aerogels due to their compelling potential across various applications, encompassing sensors, energy systems, and catalysis, among others. In the context of our ongoing investigation, we have successfully synthesized lightweight aerogels by incorporating copper and carbon nanotubes (Cu-CNT) through electrospinning. Intriguingly, these aerogels exhibit an electrical conductivity of approximately 0.5 × 103 S/cm, positioning them within the realm of semiconductors. Concurrently, their density measures approximately 1.669 g/c.c (similar to CNTs), underscoring their notably low mass. These semi-conductive aerogels, uniquely characterized by their lightweight nature and expansive surface area (approximately 442 m²/g), manifest considerable potential across a spectrum of applications. This includes catalytic processes, energy storage mechanisms, bio-sensing technologies, thermoelectric systems, and the burgeoning domains of micro and wearable electronics. The distinctive combination of properties within these aerogels augments their suitability for these diverse applications, offering the prospect of innovative and impactful advancements in various scientific and technological arenas. Full article

In this work, the design and experimental validation of passive UHF RFID tag antennas are presented with the objective of evaluating the impact of chip placement and miniaturization approaches on tag performance. Four initial antenna layouts were developed by varying the position of the RFID integrated circuit within a coupling loop. The results show that chip placement directly affects the coupling-loop efficiency, the antenna–chip matching condition, and the practical tolerance of the structure to fabrication-related variations. Simulations and measurements identified Antenna 1 as the best-performing reference configuration, exhibiting the most favorable impedance behavior around 866 MHz and a measured power sensitivity of $-16.3$ dBm. Based on this reference design, a miniaturized version (Antenna 5) was obtained by integrating meander lines and capacitive end-loading, reducing the physical size while maintaining resonance at 866 MHz. Both structures were fabricated and evaluated using a Voyantic Tagformance measurement system, with read-range measurements performed under free-space conditions and in proximity to dielectric and conductive materials. The results demonstrate a maximum read range of $8.6$ m for Antenna 1 in free space, while Antenna 5 preserved a read range of $6.3$ m. In the presence of copper, Antenna 1 maintained a read range of 3 m, whereas Antenna 5 achieved approximately $0.5$ m, highlighting the trade-off between miniaturization and robustness under conductive loading. Full article

Ceramics are widely evaluated for their extreme hardness, high-temperature stability, and corrosion resistance, which enable applications in harsh service environments. However, these same properties, high melting points, brittleness, and low thermal shock resistance, make conventional manufacturing of complex ceramic components difficult and expensive. Traditional processes often require costly diamond tooling or energy-intensive sintering and tend to produce only simple geometries, with significant waste material and risk of defects. Additive manufacturing (AM) has recently emerged as a promising route to fabricate intricate, near-net-shape ceramic parts without these drawbacks. By building components layer by layer, AM reduces the need for extensive machining and enables the fabrication of geometrically complex, near-net-shape ceramic structures with reduced material waste, although challenges such as porosity, interlayer defects, and cracking during post-processing remain. Nonetheless, ceramic AM technologies lag behind their metal and polymer counterparts, and significant challenges remain in achieving fully dense parts with reliable mechanical properties. This review provides an in-depth overview of the state of the art in ceramics and ceramic composite additive manufacturing. We detail the most widely used AM processes (stereolithography, binder jetting, material extrusion, powder bed fusion, inkjet printing, and direct energy deposition) and typical feedstock formulations for each technique. We examine the resulting mechanical properties (strength, toughness, hardness, wear resistance) and functional properties (thermal stability, dielectric behavior, biocompatibility) of additively manufactured ceramics, and discuss their current and potential engineering applications in the aerospace, defense, automotive, biomedical, and energy sectors. Persistent challenges, including porosity, shrinkage and cracking during sintering, achieving uniform microstructures, high process costs, and scalability issues, are analyzed, and we highlight promising future directions such as multi-material grading, integration of machine learning for process optimization, and sustainable manufacturing approaches. Despite significant progress, challenges remain in achieving fully dense structures, improving process reliability, and scaling ceramic AM for industrial applications, highlighting the need for further research in process optimization, material design, and multi-material integration. Full article