Permittivity Values Research Articles

Determination of significant factors for sugarcane fiber extraction as potential dielectric composite material

This study aims to determine the significant factors involved in the extraction of sugarcane fiber as a potential dielectric composite material. The factors include sugarcane waste weight (0.5 and 2.5 g), ratio of sugarcane waste to distilled water (1:15 and 1:20), boiling time (30 and 50 min), and cutting length (5 and 10 cm). The factors were analyzed using the Design-Expert software through a two-level factorial analysis to determine the significant factor. The extracted fiber was analyzed for cellulose content using a Kurschner-Hanack method, and the permittivity value was determined through an Agilent vector network analyzer (VNA). The results show that the ratio of sugarcane waste to distilled water and boiling time were the two most significant factors contributing to the cellulose content and permittivity value of the extracted fiber. The best conditions for sugarcane extraction were obtained at 2.5 g sugarcane waste, 1:20 ratio of sugarcane waste to distilled water, 50 min boiling time, and cutting length of 10 cm, resulting in 47.25% cellulose and 3.12 permittivity value. The findings of this study suggest that sugarcane waste could be a potent material for dielectric composite with a suitable application as a microwave absorber.

Room temperature superparaelectric state in 20BaTiO3-60V2O5-20Bi2O3 glass for capacitive energy storage applications

Materials with high dielectric constant exhibit excellent charge storage capacity, making them favorable solutions for next-generation dielectric capacitors. The glass system with the composition of 20BaTiO3-60V2O5-20Bi2O3 was prepared by conventional melt quenching technique. The glassy nature of the sample was confirmed by using DSC and XRD measurement while the existence of nano polar cluster inside the glass matrix was confirmed using HRTEM. The real permittivity (ε\\) value shows two peaks in which the dielectric constant gradually increases up to a maximum value (εm) with the increase in temperature, and then it smoothly decreases, suggesting two phase transitions around 180 and 280 ◦ C. The measurements of the P–E hysteresis loop illustrated energy storage density of 124 mJ/cm3 and energy storage efficiency about 84% at room temperature. The glass sample shows superparaelectric behavior confirmed by the dielectric and P-E loop measurements. For high-energy storage applications, dipolar glasses have more outstanding potential than conventional ceramic dielectrics. Eventually, the glass matrix maintains high breakdown strength and can effectively stabilize nanocluster phases. So, we consider the present glass sample to be a good candidate for capacitive energy storage applications.

Study on the Electric Field Distribution Characteristics of 66 kV Dry-Type Transformer Based on Functional Graded Material (FGM) Treatment

Functional graded materials (FGMs) have been successfully applied for improving the insulation performance of insulators, yet there is currently no relevant literature on their application in dry-type transformers. Therefore, it is meaningful to study the feasibility of using FGMs to improve the insulation performance of dry-type transformers through research on electric field distribution. This paper sets FGMs in the dry-type transformer spacer only or both the spacer and winding end to change the relative permittivity values in the corresponding areas. By comparing the electric field distribution characteristics on the inner and outer surfaces of the high-voltage coil and the lower surface of the spacer of the dry-type transformer under each control method with the case without setting FGMs, the study found that when FGMs were only set on the spacer, the control methods set in this paper could not improve the electric field distribution of the transformer. When FGMs are employed at the spacers and end windings, two modulation strategies can mitigate the electric field intensity on the outer surface of the high-voltage windings. Specifically, a continuous increase in relative permittivity can reduce the electric field intensity by 34.02%, while an initial decrease followed by an increase can result in a reduction of 13.58%. This paper provides theoretical guidance for insulation design of transformers with high voltage levels of 66 kV and above, especially as transformers with high voltage levels face greater challenges in regulating surface electric fields.

Determination of Significant Factors and Optimum Condition for Pineapple Leaf Fiber Extraction as Potential Dielectric Material

The aim in this study was to evaluate the most significant factor affecting the extraction of pineapple leaf fibers and to optimize the extraction conditions. The selected four factors of pineapple leaf powder mass, pineapple leaves to distilled water ratio, pulping time, and heating option were analyzed through two-level factorial analysis via Design-Expert software. The optimum conditions were determined using central composite design (CCD) of response surface methodology (RSM). The extracted fibers were analyzed through the Kurschner-Hanack method for cellulose content and were used to produce dielectric materials. The permittivity value of the developed dielectric material was measured through an Agilent vector network analyzer (VNA). The best condition was obtained with a heated sample at 3 g pineapple leaf powder mass, 1:10 PL: DW, and 49.24 min pulping time, which produced 59.25% cellulose content and 2.89 permittivity value. The optimum condition was achieved at 50 min of pulping time and 1000 mL water with 46.84% cellulose content and 2.97 permittivity value. Therefore, based the obtained permittivity value, pineapple leaves could be further explored as potential dielectric materials.

Carbon dots induced homeotropic alignment in a negative dielectric nematic liquid crystal material

Abstract Recently, doping guest materials such as quantum dots (QDs) into liquid crystals (LCs) has been of great interest since their addition substantially enhances the properties of LC and opens new avenues for scientific advancement. Here, we report the induction of homeotropic alignment in cells without alignment layers of the negative dielectric nematic liquid crystal, N-(4-Methoxybenzylidene)-4-butylaniline (MBBA) by doping with carbon dots (CDs ∼2.8 ± 0.72 nm). The CDs-MBBA composites (CDs concentration: 0.002, 0.01, 0.03, 0.1 and 0.3 wt%) were investigated using optical polarising microscopy, electro-optical and dielectric techniques. Polarizing optical micrographs and voltage dependent optical transmission revealed the induced homeotropic alignment for all the composites under investigation. Interestingly, the least concentrated sample, 0.002 wt% exhibited partial homeotropic alignment. However, due to light leakage, the optical transmission value below threshold voltage was relatively higher than the rest of the composites. MBBA is a negative dielectric material, hence the application of a voltage across the cell was able to switch the alignment from a dark to a bright state for all composites. However, above a certain voltage (>threshold voltage), the bright state produced some instabilities. The value of dielectric permittivity was observed to decrease with increasing concentration, confirming the effect of CDs in producing homeotropic alignment in MBBA. Measurements as a function of temperature were conducted to examine the thermal stability of the induced alignment. The alignment was found to be stable throughout the nematic phase of MBBA. The induction of such alignment without conventional alignment (i.e., rubbing of polyimides) technique can be helpful in addressing the evolving display demands by making liquid crystal displays (LCDs) and other display devices cost effective.

Dielectric Hybrid Optimization Model Based on Crack Damage in Semi-Rigid Base Course

To accurately predict the relative permittivity of cement-stabilized base materials, a study on the dielectric mixing model for cracked base materials was conducted. Based on the electromagnetic mixing theory of multiphase composites, a comprehensive dielectric mixing model of cement-stabilized base materials was derived. The volume ratios and relative permittivity values of the specimen constituents in different cracking states of the cement-stabilized base were determined using industrial CT and a Percometer relative permittivity meter, with comprehensive consideration given to the effects of different initial porosities and crack widths on the dielectric properties. Based on the volumetric and dielectric properties of the base material specimens in both intact and cracked states, as well as the error analysis between the predicted and measured values of the relative permittivity constant, the u-optimal solution of the dielectric mixing model for cement-stabilized base material was determined to be 1. Consequently, an optimization dielectric mixing model for semi-rigid base course materials in a cracked state was developed. The optimization model proposed is suitable for predicting the dielectric properties of cement-stabilized base material with crack widths generally greater than 3 mm during the service life of semi-rigid base course in engineering practice.

Modeling and simulation of the structural, and optoelectronic properties of aluminum trihydride (β-[formula omitted]) for hydrogen storage

Hydrogen is a promising clean energy source, but its storage poses challenges. In this research, we conducted an in-depth study of the structural and optoelectronic properties of the β-AlH3 phase as a potential material for hydrogen storage. Using the density functional theory (DFT)-based Wien2k code, we optimized the structure of β-AlH3. Hydrogen storage properties show that β-AlH3 contains 10.1% hydrogen by weight, which is a significant amount. Electronic properties reveal that this material is a semiconductor with a wide indirect bandgap of 5.947 eV, obtained by the generalized gradient approximation with modified Becke-Johnson correction (GGA-mBJ). The optical response of β-AlH3 to photons with energies from 0 to 10 eV is also examined for a better understanding of this material. β-AlH3 exhibits a static dielectric permittivity value ε1(ω) of 2.1, indicative of its semiconducting nature. The optical conductivity σ1(ω) shows peaks at 7.25 eV and 8.5 eV, while the absorption coefficient α(ω) increases significantly above the band gap of 5.947 eV, with peaks at 7.2 eV and 9 eV. The refractive index n(ω) and extinction coefficient κ(ω) both display notable features at 7.2 eV and 9 eV, reflecting substantial electronic transitions and optical resonances.This research is crucial to understanding how this material can meet the technological demands of hydrogen storage. The results provide valuable insights into the potential of β-AlH₃ within the future energy landscape, highlighting both advances and challenges in this promising field.

Evaluating the effect of A- and B-site cobalt doping on the structural, morphological, dielectric, and non-ohmic properties of CaCu3Ti4O12 ceramics prepared by the hydrothermal method

CaCu3Ti4O12 (CCTO), CaCu3-xCoxTi4O12 (CCCxTO) and CaCu3Ti4-xCoxO12 (CCTCxO) ceramics with x = 0.1 were synthesized by the hydrothermal process at 200 °C for 24 h. The influence of cobalt substitution on the copper and titanium sites in CaCu3Ti4O12 on the structural, morphological, and physical properties was investigated. It was shown through the analysis of X-ray diffractograms of CCTO, CCCxTO, and CCTCxO compounds that they crystallized in a pure perovskite structure without the presence of secondary phases. The refinement of the spectra using the Rietveld method showed an efficient formation of the crystalline phase of the cubic structure (Im3¯), which remains unchanged, with an increase in the unit cell due to the substitution of Co2+/Co3+ in the Cu2+ and Ti4+ sites of the CCTO ceramic. Raman spectroscopy was used as a complementary characterization method to XRD in order to detect vibrational bands and highlight any changes in the crystal lattice. SEM results showed that cobalt insertion increased the average grain size. The dielectric properties were studied by complex impedance spectroscopy in a frequency range from 1 kHz to 1 MHz at different temperatures, where the insertion of cobalt in the Cu2+ and Ti4+ sites has a significant effect on the permittivity value (εr) and dielectric losses (tanδ). The non-ohmic characteristics showed that the change in grain size due to cobalt incorporation is beneficial to improving the breakdown strength (Eb) and nonlinear coefficient (α), which can be attributed to the grain boundary properties of the Internal Barrier Layer Capacitor (IBLC) model and the behavior of the Schottky barrier.

Tunable negative permittivity behavior and excellent electromagnetic shielding performance of pyrolytic carbon‐glass fiber felt/epoxy resin metacomposites

AbstractEffective and accurate adjustment of negative permittivity behavior is worthy of further investigation. Herein, pyrolytic carbon‐glass fiber felt/epoxy resin (PyC‐GFF/ER) metacomposites with tunable negative permittivity were prepared using an impregnation‐calcination method. The permittivity, electrical conductivity, and electromagnetic shielding performance of the polymer metacomposites were investigated. Due to the inherent three‐dimensional structural network of GFF, the PyC adhering to the surface of glass fiber easily formed a conductive network in the composites. As the PyC content increased in the ER composites, the conductivity mechanism changed from hopping conduction to metal‐like conduction. The ER composites with high PyC contents showed negative permittivity behavior and the epsilon‐near‐zero response owing to the low frequency plasma state of free electrons in the PyC‐conduction network. By controlling the PyC content, the negative permittivity behavior of ER composites could be effectively tuned. With the increase in PyC content, the values of negative permittivity increased, and the epsilon‐near‐zero frequency shifted to a higher frequency. Moreover, the ER composites with high PyC contents showed excellent electromagnetic shielding properties (29.4 dB) at X‐band. This work not only provided a feasible method to realize the tunable negative permittivity of polymer metacomposites, but also promoted its application in the microwave field.Highlights The pyrolytic carbon‐glass fiber felt/epoxy resin composites were fabricated. The negative permittivity was first reported in the PyC‐GFF/ER composites. Tunable negative permittivity could be well explained by Drude model. The polymer composites had excellent electromagnetic shielding property.

Tunable negative permittivity behavior in alumina ceramic composites with different carbon fillers

Carbon/ceramic composites with negative permittivity have motivated a considerable concern due to their special properties and various applications. Herein, series of alumina ceramic composites consisting of different carbon fillers were prepared by the hot-pressed sintering, and the carbon fillers included carbon sphere (CS), carbon black (CB), carbon fibre (CF), carbon nanofibre (CNF) and graphene nanosheet (GN). The impact of various carbon fillers on the electrical performance of composites were investigated comparatively. It was found that CF ceramic had hopping conduction, capacitive character and positive permittivity, and micron-sized CFs were embedded in isolation within the ceramic composite. The other ceramics with carbon nanofillers demonstrated metallic-type conductance, inductive character and negative permittivity. The carbon nanofillers evenly dispersed and easily formed carbon network that improve the flow of free electrons in the composites, and the negative permittivity behavior imputed to the low frequency plasmonic state of abundant free electrons in the carbon networks. Furthermore, the magnitude of negative permittivity was in connection with the type of carbon nanofiller. The one- or two-dimensional carbon nanofillers were more easily connected to each other to form a denser carbon network, and thus the CNF and GN ceramics had the larger absolute values of negative permittivity, which was in accord with Drude model.

Significantly Improved dielectric performance and Vickers-Hardness in High-Entropy TiO2-based Ceramics

Remarkable dielectric properties and enhanced hardness were achieved in high-entropy TiO2-based ceramics in this work by incorporating multiple pairs of donor-acceptor (D-A) cations (D = Nb5+, A = In3+, Al3+, Fe3+, Ga3+, La3+). The introduction of high-entropy engineering may facilitate the creation of favorable and stable microstructural features as lattice distorted and localized defect cluster, thereby enhancing the dielectric performance, thermal stability and mechanic properties. The composition of [Nb0.5(In0.2Al0.2Fe0.2Ga0.2La0.2)0.5]0.01Ti0.99O2 exhibits remarkably colossal permittivity (εr) value of approximately 18488 and low dielectric loss (tanδ) value of around 0.014 at 1 kHz. Furthermore, the thermal stability of the dielectric permittivity for [Nb0.5(In0.2Al0.2Fe0.2Ga0.2La0.2)0.5]0.01Ti0.99O2 ceramic meets the X9D standard, and the dielectric loss stays below ∼ 0.05 in the temperature range from -55 to 150 °C. Besides, the Vickers-hardness of [Nb0.5(In0.2Al0.2Fe0.2Ga0.2La0.2)0.5]0.01Ti0.99O2 gets increased by over 37% as compared to that of (Nb5+, In3+) co-doped ceramic (INTO). We presented in this work the influence of high-entropy on the dielectric and mechanic properties of TiO2-based ceramics, offering valuable insight into future development of colossal dielectric ceramics.

Characterizing heterogeneities in the subsurface with an ultra-wideband GPR: Application to WISDOM, the GPR of the Rosalind Franklin ExoMars mission

Ultra-wideband Ground Penetrating Radars (GPR) are sensitive to a large range of scatterer sizes. Considering fractal heterogeneities in the subsurface, we propose a method to retrieve their typical size L. The determination of L with this method does not require a priori knowledge of the statistical distribution of permittivity values in the investigated subsurface. The method relies on the analysis of the backscattered signal by frequency/wavelength sub-bands. It is adapted to WISDOM, the GPR onboard the rover of the Rosalind Franklin ExoMars mission (ESA), but can be applied to any ultra-wideband GPR. Based on numerical simulations, a maximum in volume backscattering is reached at the wavelength (in the subsurface) . We demonstrate that this maximum, and therefore L, can be identified even in presence of moderate electrical losses, compatible with conditions expected on the Moon or Mars. Assuming an average permittivity of 5, WISDOM (0.5-3 GHz) data products could be used to estimate L as long as it is in the range 0.9-4.2 cm The retrieval method for L is validated on experimental WISDOM data acquired in a controlled environment.

Large improvement in RF magnetic fields and imaging SNR with whole-head high-permittivity slurry helmet for human-brain MRI applications at 7 T.

To optimize the design and demonstrate the integration of a helmet-shaped container filled with a high-permittivity material (HPM) slurry with RF head coil arrays to improveRF coil sensitivity and SNR for human-brain proton MRI. RF reception magneticfields ( ) of a 32-channel receive-only coil array with various geometries and permittivity values of HPM slurry helmet are calculated with electromagnetic simulation at 7 T. A 16-channel transmit-only coil array, a 32-channel receive-only coil array, and a 2-piece HPM slurry helmet were constructed and assembled. RF transmission magnetic field ( ), , and MRI SNR maps from the entire human brain were measured and compared. Simulations showed that averaged improvement with the HPM slurry helmet increased from 57% to 87% as the relative permittivity (εr) of HPM slurry increased from 110 to 210. In vivo experiments showed that the average improvement over the human brain was 14.5% with the two-piece HPM slurry (εr ≈ 170) helmet, and the average and SNR were improved 63% and 34%, respectively, because the MRI noise level was increased by the lossy HPM. The RF coil sensitivity and MRI SNR were largely improved with the two-piece HPM slurry helmet demonstrated by both electromagnetic simulations and in vivo human head experiments at 7 T. The findings demonstrate that incorporating an easily producible HPM slurry helmet into the RF coil array significantly enhances human-brain MRI SNRhomogeneity and quality at ultrahigh field. Greater SNR improvement is anticipated using the less lossy HPM and optimal design.

Synthesis and Characterizations of Structural, Dielectric and Optical Properties of CCTO– PT Composite

In this study, we have synthesized the (1-x) CaCu3Ti4O12 – (x) PbTiO3 (CCTO-PT) composites with x = 0.00, 0.50 and 1.00 by using the solid-state method. We have then studied the structural, optical and dielectric properties of these composites. The X-ray diffraction diffractogram (XRD) showed that the ceramics at x = 0.00 and 1.00 (CCTO and PT) crystalize in a pure cubic and tetragonal phase respectively. Likewise, for CCTO-PT composite, we observed a coexistence of tetragonal and cubic phase in CCTO-PT composite composites. The scanning electron microscopy (SEM) micrographs showed homogeneous microstructure samples and consist of different grain shape. The large spherical grain structure is attributed to CCTO ceramic while the smaller grain form can be ascribed to the PT ceramic. The dielectric measurements results revealed an increase in dielectric permittivity value for CCTO-PT composite compared with pure CCTO and PT. The optical band gaps of the CCTO and PT are 2.50 and 3.00 eV, and increased to 3.50 eV for the CCTO/PT composite.

Susceptibility to Translational Landslides in Ecuador Caused by Changes in Electrical Permittivity of Andepts Soils Using Software-Defined Radar for Detection

Landslides are widespread and global geological disasters, affecting millions of people and causing numerous deaths each year. Despite technological advances, it is still difficult to accurately prevent landslides. Due to its geography and climatic conditions, Ecuador has been significantly affected by landslides, and the city of Penipe remains one of the most affected. For this reason, a low-cost SDRadar system was designed to detect translational landslide risk levels by measuring the electrical permittivity of Andepts subtype soils. Controlled laboratory tests were performed with soil samples to relate permittivity values to landslide risk levels, and subsequently field tests were carried out in Penipe to determine the efficiency of the methodology. The results showed that moderate humidity is important for soil compaction, regardless of the degree of sloping. However, with permittivity values lower than 1.5 or higher than 20, the risk of landslides is very high on slopes greater than 45°. These results were compared with records of the serious landslides that occurred in June 2024 in Ecuador, in which rainfall intensity values similar to those obtained in this study were recorded, suggesting that this system can prevent future disasters.

Interpretation of dielectric spectroscopy measurements of ferroelectric nematic liquid crystals

The magnitude of the relative permittivity of the ferroelectric nematic phase (NF) has been the subject of lively scientific discussion since the phase was recently discovered. Dielectric spectroscopy measurements (DSMs) give a huge value of relative permittivity, which depends on the cell thickness, but this is argued to result from a misinterpretation of the DSM results. We have conducted DSM using a set of cells differing in thickness of the NF layer, type of electrodes, and presence/absence of nanoscale-thick surface polymer layers. To model the DSM results, cells are presented by an equivalent electric circuit that includes a capacitor due to the NF layer with frequency dependent complex relative permittivity, capacitors due to surface layers, and a resistor describing the limited conductivity of electrodes. DSM results for different cells with the same liquid crystal in the NF phase are semiquantitatively reproduced by the same set of physical parameters if a huge relative permittivity of the NF, which is even orders of magnitude larger than the measured apparent values, is assumed. We show that the capacitance of surface layers should also be considered in cells with no polymer alignment layer on the electrodes. Published by the American Physical Society 2024

Properties of Sn-Doped PBZT Ferroelectric Ceramics Sintered by Hot-Pressing Method.

This work investigated the structure, microstructure, and ferroelectric and dielectric behavior of (Pb0.97Ba0.03)(Zr0.98Ti0.02)1-xSnxO3 (PBZT_xSn) solid solution with variable tin content in the range x = 0.00-0.08. Synthesis was carried out using the powder calcination method, and sintering was carried out using the hot-pressing method. For all the PBZT_xSn samples at room temperature, X-ray diffractograms confirmed the presence of an orthorhombic (OR) crystal structure with space group Pnnm, and the microstructure is characterized by densely packed and properly shaped grains with an average size of 1.36 µm to 1.73 µm. At room temperature, PBZT_xSn materials have low permittivity values ε' ranging from 265 to 275, whereas, at the ferroelectric-paraelectric phase transition temperature (RE-C), the permittivity is high (from 8923 to 12,141). The increase in the tin dopant in PBZT_xSn lowers permittivity and dielectric loss and changes the scope of occurrence of phase transitions. The occurring dispersion of the dielectric constant and dielectric loss at low frequencies, related to the Maxwell-Wagner behavior, decreases with increasing tin content in the composition of PBZT_xSn. Temperature studies of the dielectric and ferroelectric properties revealed anomalies related to the phase transitions occurring in the PBZT_xSn material. With increasing temperature in PBZT_xSn, phase transitions occur from orthorhombic (OR) to rhombohedral (RE) and cubic (C). The cooling cycle shifts the temperatures of the phase transitions towards lower temperatures. The test results were confirmed by XRD Rietveld analysis at different temperatures. The beneficial dielectric and ferroelectric properties suggest that the PBZT_xSn materials are suitable for micromechatronic applications as pulse capacitors or actuator elements.

MR electrical properties mapping using vision transformers and canny edge detectors.

We developed a 3D vision transformer-based neural network to reconstruct electrical properties (EP) from magnetic resonance measurements. Our network uses the magnitude of the transmit magnetic field of a birdcage coil, the associated transceive phase, and a Canny edge mask that identifies the object boundaries as inputs to compute the EP maps. We trained our network on a dataset of 10 000 synthetic tissue-mimicking phantoms and fine-tuned it on a dataset of 11 000 realistic head models. We assessed performance in-distribution simulated data and out-of-distribution head models, with and without synthetic lesions. We further evaluated our network in experiments for an inhomogeneous phantom and a volunteer. The conductivity and permittivity maps had an average peak normalized absolute error (PNAE) of 1.3% and 1.7% for the synthetic phantoms, respectively. For the realistic heads, the average PNAE for the conductivity and permittivity was 1.8% and 2.7%, respectively. The location of synthetic lesions was accurately identified, with reconstructed conductivity and permittivity values within 15% and 25% of the ground-truth, respectively. The conductivity and permittivity for the phantom experiment yielded 2.7% and 2.1% average PNAEs with respect to probe-measured values, respectively. The in vivo EP reconstruction truthfully preserved the subject's anatomy with average values over the entire head similar to the expected literature values. We introduced a new learning-based approach for reconstructing EP from MR measurements obtained with a birdcage coil, marking an important step towards the development of clinically-usable in vivo EP reconstruction protocols.

Interfacial capacitance in lithium disilicate glass: Experimental factors and charge carrier density

AbstractThe formation of an electric double‐layer (EDL) is an important phenomenon for many research areas, including energy storage technology. Although EDL is well‐known in electrochemistry, most of the studies involve the characterization of liquid electrolyte/electrode interfaces, and only a limited number of studies in solid‐solid contacts, such as solid electrolyte/electrode interface are available. This paper employed electrochemical impedance spectroscopy (EIS) to systematically investigate the influence of experimental factors in the interfacial capacitance arising from the electrode polarization in a lithium disilicate glass/gold electrode interface. It analyzed the influence of a.c. input voltage amplitude, samples' roughness (mechanical and chemomechanical polishing) and thickness, range of applied frequency and temperature, and the number of impedance cycles. In short, it was found that an input voltage range of 15–60 mV is indicated to minimize potential electrochemical processes during electrode polarization, where the data is reproducible from the second measurement cycle onward. Smoother surfaces closely approximated ideal electrode spike behavior, with surface treatment exhibiting influence on interfacial capacitance values. Moreover, as expected, we observed an increase in relative permittivity values with increasing thickness, accompanied by decreased capacitance values. Finally, by employing optimal experimental conditions and analyzing the inflection frequency () of the versus log() curve, we determined that the ratio between effective charge carriers () and the total number of charge carriers () falls within the range of 5–12% between 130°C and 280°C.

Classification with electromagnetic waves

AbstractThe integration of neural networks and machine learning techniques has ushered in a revolution in various fields, including electromagnetic inversion, geophysical exploration, and microwave imaging. While these techniques have significantly improved image reconstruction and the resolution of complex inverse scattering problems, this paper explores a different question: Can near‐field electromagnetic waves be harnessed for object classification? To answer this question, we first create a dataset based on the MNIST dataset, where we transform the grayscale pixel values into relative electrical permittivity values to form scatterers and calculate the electromagnetic waves scattered from these objects using a 2D electromagnetic finite‐difference frequency‐domain solver. Then, we train various machine learning models with this dataset to classify the objects. When we compare the classification accuracy and efficiency of these models, we observe that the neural networks outperform others, achieving a 90% classification accuracy solely from the data without a need for projecting the input data into a latent space. The impacts of the training dataset size, the number of antennas, and the location of antennas on the accuracy and time spent during training are also investigated. These results demonstrate the potential for classifying objects with near‐field electromagnetic waves in a simple setup and lay the groundwork for further research in this exciting direction.