Search Results (419)

This work presents an experimental study of the electromagnetic behavior of water and its interaction with gasoline in the frequency range of 1.9 to 2.6 GHz, corresponding to the UHF band. This interval lies within the dielectric relaxation region of water, where significant absorption and reflection phenomena occur. The results show qualitative differences in the electromagnetic responses of water, gasoline, and their mixtures, particularly in the stability of amplitudes and phase variability. The mixtures exhibit an intermediate behavior between the pure liquids, highlighting the direct influence of the dielectric properties of the medium on the reflected signal. Furthermore, it was identified that the band between 2400 and 2550 MHz presents a more predictable amplitude response, making it a promising frequency range for the non-invasive detection of gasoline as a contaminant in aquatic environments. Full article

We developed a model to predict the quality of fresh goji berries during storage by analyzing the correlations of their dielectric properties. The variations in these properties with storage temperature, time, and frequency were systematically characterized to inform the model. Leveraging these relationships, we developed a model to predict quality. The analysis integrated measurements of dielectric properties with assessments of texture and key physicochemical indicators. Results indicate that dielectric parameters exhibit significant frequency dependence. Complex impedance (Z), capacitance (Cp), and resistance (Rp) all decreased sharply with increasing frequency, with the most pronounced change observed in Cp. Conductance, G, and reactance, X, increased with frequency, reaching maximum increases of 360.86% and 87.79%, respectively. Under the specific test frequency of 163,280 Hz, a strong polynomial relationship was observed between the dielectric parameters and storage time, with all fitted models yielding ${\mathit{R}}_{adj}^2$ values above 0.94. The quality factor Q (a dimensionless number for the energy efficiency of a resonant circuit or medium) showed a near-perfect correlation with brittleness, while reactance, X, was correlated with springiness and cohesiveness, with correlation coefficients approaching 0.999 under the optimal test frequency. The constructed ANN model demonstrated high prediction accuracy for hardness, brittleness, elasticity, cohesiveness, chewiness, and soluble solids content (R² > 0.97, MSE < 5%) but performed poorly in predicting adhesiveness, stickiness, and rebound elasticity (R² < 0.9). The constructed LSSVM model showed good prediction performance for some indicators (hardness, springiness, cohesiveness, and SSC) (R² > 0.94), but its prediction accuracy was low for brittleness and chewiness (R² < 0.9). Overall, its performance and generalization ability were inferior to the ANN model. This study shows that ANN models based on dielectric properties establish a technical foundation for the non-destructive, automated monitoring of goji berry storage quality, thereby providing a critical tool for dynamic quality tracking and value assessment within integrated warehouse management systems. Full article

Broadband absorption of electromagnetic energy plays an important role in energy harvesting and stealth. Here, we present and demonstrate an absorber with a wide bandwidth of 2.1 μm in mid-infrared. The trapezoidal metamaterial consists of alternating silicon carbide and dielectric films. We have numerically demonstrated that an ultrahigh absorption energy efficiency higher than 97.7% can be calculated from 10.6 μm to 12.7 μm. The proposed absorber has high absorption efficiency at a wide-angle range. The simulation results are consistent with the theoretical calculation based on effective medium theory. The theoretical model simplifies the multilayer structure into an effectively homogeneous metamaterial with hyperbolic dispersion. In addition, the distributions of magnetic field depict that different wavelengths can be trapped at structures with various widths. The mechanism of this phenomenon is attributed to the slowlight modes. Furthermore, a dual-sized absorber is designed to achieve high efficiency and broadband absorption, which is easy to manufacture. Our study has potential applications in the areas of energy harvesting materials, thermal emitters and photovoltaic devices in the mid-infrared. Full article

Ground-penetrating radar surveys on structures have a wide range of applications, and they are very useful in solving engineering problems: from detecting reinforcement, studying concrete characteristics, unfilled joints, analyzing brick elements, detecting water content in building bodies, and evaluating structural deformation. They generally pursued small investigation areas with measurements made in direct contact with target structures and for small depths. Detecting deep piles presents specific challenges, and surveys conducted from the ground level may be unsuccessful. To reach great depths, medium-low frequencies must be used, but this choice results in lower resolution. Furthermore, the pile signals may be masked when they are located beneath massive reinforced foundations, which act as an electromagnetic shield. Finally, GPR equipment looks for differences in the dielectric of the material, and the signals recorded by the GPR will be very weak when the differences in the physical properties of the investigated media are modest. From these weak signals, it is difficult to identify information on the differences in the subsurface media. In this paper, we are illustrating an exploration on plinth foundations, supported by drilled piles, submerged in soil, extensive, deep and uninformed. Pulse GPR prospecting was performed in common-offset and single-fold, bistatic configuration, exploiting the exposed faces of an excavation around the foundation. In addition, three velocity tests were conducted, including two in common mid-point and one in zero-offset transillumination, in order to explore the range of variation in relative dielectric permittivity in the investigated media. Thanks to the innovative survey on the excavation faces, it is possible to perform profiles perpendicular to the strike direction of the interface. The electromagnetic backscattering analysis approach allowed us to extract the weighted average frequency attribute section. In it, anomalies emerge in the presence of drilled piles with four piles with an estimated diameter of 80 cm. Full article

Polymer gel-based triboelectric nanogenerators (TENGs) have emerged as versatile platforms for self-powered sensing due to their inherent softness, stretchability, and tunable conductivity. This review comprehensively explores the roles of polymer gels in TENG architecture, including their function as triboelectric layers, electrodes, and conductive matrices. We analyze four operational modes—vertical contact-separation, lateral-sliding, single-electrode, and freestanding configurations—alongside key performance metrics. Recent studies have reported output voltages of up to 545 V, short-circuit currents of 48.7 μA, and power densities exceeding 120 mW/m², demonstrating the high efficiency of gel-based TENGs. Gel materials are classified by network structure (single-, double-, and multi-network), matrix composition (hydrogels, aerogels, and ionic gels), and dielectric medium. Strategies to enhance conductivity using ionic salts, conductive polymers, and nanomaterials are discussed in relation to triboelectric output and sensing sensitivity. Morphological features such as surface roughness, porosity, and micro/nano-patterning are examined for their impact on charge generation. Application-focused sections detail the integration of gel-based TENGs in health monitoring (e.g., sweat, glucose, respiratory, and tremor sensing), environmental sensing (e.g., humidity, fire, marine, and gas detection), and tactile interfaces (e.g., e-skin and wearable electronics). Finally, we address current challenges, including mechanical durability, dehydration, and system integration, and outline future directions involving self-healing gels, hybrid architectures, and AI-assisted sensing. This review expands the subject area by synthesizing recent advances and offering a strategic roadmap for developing intelligent, sustainable, and multifunctional TENG-based sensing technologies. Full article

The Cherenkov effect, whereby a charged particle emits light when traveling faster than the phase velocity of light in a dielectric medium, is widely employed in particle identification techniques. However, Cherenkov light yield is relatively low, typically amounting to only 100–200 visible photons per centimeter of path length in materials like water, plastic, or glass. In this study, we investigate the optical response of FB118, a wavelength-shifting (WLS) plastic developed by Glass to Power, under exposure to ionizing particles. Our measurements confirm the absence of residual scintillation in FB118, allowing for a clean separation of Cherenkov signals. Moreover, the intrinsic WLS properties of the material enable a significant enhancement of light detection in the visible range. These features make FB118 a promising candidate for use in compact Cherenkov detectors, particularly in astroparticle physics experiments where space and power constraints demand efficient, compact solutions. Full article

This paper reviews the historical progression of arc-quenching media and examines the unique properties of supercritical carbon dioxide (scCO₂), including its transport characteristics, electrical breakdown resilience, and structural behavior. Through analysis of ionization mechanisms, mean free path, and heat dissipation, scCO₂ emerges as a viable insulating and arc-quenching medium, offering competitive performance and reduced environmental impact. Projected performance metrics for arcing time and dielectric strength show scCO₂’s competitive edge. The limitations of alternative supercritical fluids and the potential benefits of scCO₂ mixtures are discussed. In addition, the paper highlights the development of the first 72 kV scCO₂ AC circuit breaker, marking a significant step toward sustainable high-voltage applications. This work positions scCO₂ as a viable, environmentally friendly alternative to SF₆, with promising implications for future power systems. Full article

The development of dielectric capacitors with high energy-storage density and ultrafast discharge capability is essential for next-generation pulsed power systems. In this work, (Pb, La, Ho, Zr, Ti)O₃ (PLZTH) ceramics were fabricated via medium-temperature sintering (950–1100 °C) combined with Ho³⁺ doping to systematically tailor their energy-storage properties. This processing strategy not only mitigates Pb volatilization but also enhances compatibility with base-metal electrodes such as Ni and Cu. In addition, Ho³⁺ ions exhibit amphoteric doping behavior, which contributes to the enhancement of relaxor characteristics and grain refinement. H4 ceramic delivers an outstanding recoverable energy-storage density (W_rec) of 0.91 J/cm³ and a high energy efficiency (η) of 87% under 216 kV/cm, along with a power density (P_D) of 28.8 MW/cm³ and an ultrafast discharge time (t_0.9) of only 4.97 ns at 180 kV/cm. This study not only proposes a viable route toward high-performance medium-temperature-sintered PLZT ceramics but also elucidates the effective mechanism of Ho³⁺ amphoteric doping in modulating the relaxor state and properties of perovskite-based ceramics. Full article

Molecular geometry, infrared (IR) vibrational frequencies, and ultraviolet–visible (UV-Vis) electronic absorption spectra of the trivalent iron tris(acetylacetonate) complex, Fe(III)(acac)₃, were computed using hybrid meta-generalized gradient approximation (meta-GGA) density functional theory (DFT). Calculations employed the Jorge double-$\zeta$ valence plus polarization basis sets (standard DZP and relativistic DZP + DKH). Solvent effects were modeled using the SMD continuum solvation framework with acetonitrile as the dielectric medium. This charge-neutral complex exhibits predominantly ionic metal–ligand bonding character, which simplifies the computational treatment. Despite extensive DFT applications to coordination compounds, systematic benchmarks for this bidentate ligand system remain limited. The computed harmonic frequencies ($\nu$) and electronic excitation energies (${\lambda }_{\max }$) demonstrate excellent agreement with available experimental measurements. These results enable comparative analysis of IR and UV-Vis spectral features, both with and without all-electron scalar relativistic effects with the second-order Douglas–Kroll–Hess approach. Full article

This paper discusses the design, manufacturing, and experimental characterization of a Ka-band fully dielectric reflectarray realized using Zetamix $\epsilon$ 7.5 ceramic material and additive manufacturing. Properly tuning the infill during the manufacturing process, it is possible to control the permittivity of the material, which can therefore be considered, to all intents and purposes, an additional degree of freedom for optimizing the unit cell and consequently the reflectarray performance. The optimal values of ${\epsilon }_r$ are determined through numerical analysis of the unit cell and experimental characterization of bricks manufactured with different printing parameters. Then, the unit cell is used to design a medium-sized reflectarray with an aperture of 207.4${\lambda }_0^2$ and a thickness of 0.44${\lambda }_0$, at the design frequency $f_0=30$ GHz. The full-wave simulations of the designed RA and experimental measurements of a prototype confirm the excellent performance of the antenna, which exhibits a broadband flat response from 28 to 31 GHz and an aperture efficiency exceeding 50%. Full article

BaTiO₃ (BT) is an essential material for many applications due to its dielectric, ferroelectric, and piezoelectric properties; nevertheless, it has been reported to possess a “critical size” in the nanoscale below which its outstanding properties are lost and the paraelectric cubic phase is stabilized at room temperature instead of the tetragonal phase. This value depends on multiple factors, mostly resulting from the synthesis route and conditions. Especially, internal stresses are known to promote the loss of tetragonality. Stresses are commonly present in water-containing synthesis routes because of the incorporation of hydroxyl groups into the oxygen sublattice of BaTiO₃. On the other hand, the use of an organic solvent instead of water as a reaction medium overcomes the mentioned problem. This work presents a one-pot water-free solvothermal treatment of a Ti(O-iPr)₄-Ba(OH)₂·8H₂O sol in methanol in the presence of small amounts of oleic acid, which allows the synthesis of spherical crystalline BT nanoparticles (from ~12 nm to ~30 nm in diameter) at temperatures as low as 100 °C with a cubic/tetragonal crystal structure confirmed by powder XRD, but predominantly tetragonal according to the Raman spectra. The retention of the tetragonal crystal structure is attributed to the lack of lattice hydroxyls (confirmed by FTIR spectroscopy) resulting from the use of an organic solvent (methanol) as reaction medium. To the best of the author’s knowledge, this synthesis approach is the first report of tetragonal BT nanoparticles synthesized in methanol without the addition of extra water and without the need for a post-synthetic calcination step. Full article

In the process of machining an aluminum matrix silicon carbide (SiCp/Al) composite material using wire electric discharge machining (WEDM), the thermal conductivity and dielectric properties of working fluid, such as discharge medium and cool carrier, directly determine the material removal rate (MRR) and surface roughness (R_a). In this paper, graphene-working fluid is innovatively used as working medium to optimize the discharge process due to its high thermal conductivity and field emission characteristics. The single-factor experiments show that graphene can increase the MRR by 11.16% and decrease the R_a by 29.96% compared with traditional working fluids. In order to analyze the multi-parameter coupling effect, an L16 (4⁴) orthogonal test is further designed, and the effects of the pulse width (T_on), duty cycle (DC), power tube number (PT), and wire speed (WS) on the MRR and R_a are determined using a signal-to-noise analysis. Based on a gray relational grade analysis, a multi-objective optimization model was established, and the priority of the MRR and R_a was determined using an AHP, and finally the optimal parameter combination (T_on = 22 μs, DC = 1:4, PT = 3, WS = 2) was obtained. Full article

Semiconductor device fabrication is conducted through highly precise manufacturing processes. An essential component of the semiconductor package is the lead frame on which the silicon dies are assembled. Impurities such as oxides or organic matter on the surfaces have an impact on the process yield. Plasma cleaning is a vital process in semiconductor manufacturing, employed to enhance production yield through precise and efficient surface preparation essential for device fabrication. This paper explores the various facets of plasma cleaning, with a particular emphasis on its application in the cleaning of lead frames used in semiconductor packaging. To provide comprehensive context, this paper also reviews the critical role of plasma in advanced and emerging packaging technologies. This study investigates the fundamental physics governing plasma generation, the design of plasma systems, and the composition of the plasma medium. A central focus of this work is the comparative analysis of different plasma systems in terms of their effectiveness in removing organic contaminants and oxide residues from substrate surfaces. By utilizing reactive species generated within the plasma—such as oxygen radicals, hydrogen ions, and other chemically active constituents—these systems enable a non-contact, damage-free cleaning method that offers significant advantages over conventional wet chemical processes. Additionally, the role of non-reactive species, such as argon, in sputtering processes for surface preparation is examined. Sputtering is the ejection of individual atoms from a target surface due to momentum transfer from an energetic particle (usually an ion). Sputtering is therefore a physical process driven by momentum transfer. Energetic ions, such as argon (Ar⁺), are accelerated from the plasma to bombard a target surface. Upon impact, these ions transfer sufficient kinetic energy to atoms within the material’s lattice to overcome their surface binding energy, resulting in their physical ejection. This paper also provides a comparative assessment of various plasma sources, including direct current, dielectric barrier discharge, radio frequency, and microwave-based systems, evaluating their suitability and efficiency for lead frame cleaning applications. Furthermore, it addresses critical parameters affecting plasma cleaning performance, such as gas chemistry, power input, pressure regulation, and substrate handling techniques. The ultimate aim of this paper is to provide a concise yet comprehensive resource that equips technical personnel with the essential knowledge required to make informed decisions regarding plasma cleaning technologies and their implementation in semiconductor manufacturing. This paper provides various tables which provide the reader with comparative assessments of the various plasma sources and gases used. Scoring mechanisms are also introduced and utilized in this paper. The scores achieved by both the sources and the plasma gases are then summarized in this paper’s conclusions. Full article

Vegetable oil is regarded as a medium that can replace kerosene in electrical discharge machining (EDM) hole processing due to its renewability and environmental friendliness. Meanwhile, numerical simulation serves as an effective means to study the behavior of the gap flow field during EDM processing. Based on this, this study explored the influence of hole size and different vegetable oil dielectrics (sunflower seed oil, canola oil, and soybean oil) on the movement of electro-corrosion residues in the processing gap. The simulation results demonstrate that the viscosity of the oil affects the escape rate of the particles. In holes of 1 mm and 4 mm of size, the escape rate of canola oil at any time period is superior to that of sunflower seed oil and soybean oil. In a 1 mm hole, its average escape rate reached 19.683%, which was 0.24% and 0.19% higher than that of sunflower seed oil and soybean oil, respectively. Subsequently, experiments were conducted in combination with the simulation results to explore the influence of current, pulse width, and pulse interval on hole processing. This further confirmed the application potential of vegetable oil in electrical discharge micro-hole processing and provided theoretical support and experimental basis for optimizing the green manufacturing process. Full article

Accurate diagnosis of the insulation condition of stator windings in pumped storage generator-motor units is crucial for ensuring the safe and stable operation of power systems. Time domain dielectric response testing is an effective method for rapidly diagnosing the insulation condition of capacitive devices, such as those in pumped storage generator-motors. To precisely identify the conductivity and relaxation process parameters of the insulating medium and accurately diagnose the insulation condition of the stator windings, this paper proposes a method for identifying the insulation dielectric response parameters of stator windings based on sparsity-enhanced dynamic mode decomposition of the depolarization current. First, the measured depolarization current time series is processed through dynamic mode decomposition (DMD). An iterative reweighted L1 (IRL1)-based method is proposed to formulate a reconstruction error minimization problem, which is solved using the ADMM algorithm. Based on the computed modal amplitudes, the dominant modes—representing the main insulation relaxation characteristics—are separated from spurious modes caused by noise. The parameters of the extended Debye model (EDM) are then calculated from the dominant modes, enabling precise identification of the relaxation characteristic parameters. Finally, the accuracy and feasibility of the proposed method are verified through a combination of simulation experiments and laboratory tests. Full article