Conduction Plane Research Articles

Spherical image potentials for an N-charged particle system

The potential energy interaction between a system of N -charged particles and a spherical conducting surface is obtained by means of direct integration of the electrostatic energy density. Making use of the image charge method, we show that the full potential can be split into a sum of one-body central potentials and two-body contributions related to particle–particle and particle–sphere interactions. Analytical expressions are provided for all contributions. The spherical surface of radius R can be considered to correspond to a cavity inside a conductor or a metallic ball, with two different electric conditions, namely the grounded and isolated charged cases. By taking the limit R → ∞ of the spherical case, one recovers the image potential for an N -charged particle system interacting with a planar conductor. While the final results for the potential do not appear as unexpected, the provided analytical expressions should help in diverse physical applications modelled by a number of charged particles interacting close to a spherical surface.

Far-Field Estimation Method of Antennas Above Conductive Plane Using a Partially Spherical Near-Field

For evaluating the practical performance of land mobile communication antennas via near-field measurement, it is essential to measure the electromagnetic field, including the housing in which the antennas are mounted. When measuring a heavy housing, scattered waves from the supporting turntable for the antenna under test (AUT) disturb the electromagnetic field. A technique for eliminating the influence of scattered waves is required to evaluate the abnormal AUT radiation performance. This paper proposes a method for estimating the far-field when the antenna exists above an infinite conductive plane, using partially spherical near-field measurements that include the turntable. The proposed method estimates the far-field by combining the equivalent source reconstruction and the far-field estimation with the reflection coefficient method. In the proposed method, the equivalent source distribution surrounding an AUT is reconstructed from a partially spherical near-field to remove the effects of the turntable. Through numerical calculations and experiments, this paper shows that the proposed method can estimate the far-field pattern above an infinite conductive plane, with arbitrary electric constants from a partially spherical near-field. The far-field estimation error is less than -20 dB when the upper hemispherical near-field can be obtained.

Design optimization for microstrip antennas based on polymethyl methacrylate (PMMA) substrate and carbon nanotube (CNT) conductive material in sub-6 Ghz band

Abstract Background The rapid expansion of modern smart applications, demanding faster data transfer and extensive bandwidth, has prompted the development of new-generation networks like 5G and 6G. These networks encompass additional frequency bands such as sub-6 GHz, millimeter waves, and terahertz bands to meet the growing bandwidth requirements. However, despite the substantial bandwidth available in these bands, several challenges must be addressed to overcome unfavorable propagation characteristics. Moreover, numerous applications necessitate wireless devices with antennas that exhibit high flexibility and exceptional radiation responses, particularly when subjected to bending effects. This requirement highlights the importance of polymers-based antennas that can adapt to changing conditions while maintaining optimal performance. The present comprehensive study delves into the performance evaluation of rectangular and circular microstrip antennas utilizing PMMA (polymethyl methacrylate) polymer substrate with varying thicknesses. Results Notably, CNTs (Carbon Nanotubes) are employed as an alternative to traditional copper for the conductive part and ground plane. Both PMMA-based antennas, integrated with CNTs, exhibit a compact footprint of 27.8 × 47.8 × 1.5 mm3 for the circular antenna and 22.8 × 39.5 × 1.5 mm3 for the rectangular antenna. Impressively, the realized gain of both antennas surpasses 5 dBi, demonstrating robust performance in both flat and bending scenarios across different substrate thicknesses. Conclusions The rectangular antenna achieves a bandwidth of approximately 200 MHz, while the circular microstrip antenna showcase annotable bandwidth of 500 MHz. These exceptional outcomes position the two microstrip antennas as highly suitable for a diverse range of emerging applications within the sub-6 GHz band (the frequency range below 6 GHz in the radio spectrum). Thus, the combination of PMMA substrate, CNTs and the compact form factor of the antennas presents a compelling solution for meeting the demands of modern applications requiring efficient wireless communication with enhanced performance and bandwidth.

Scattering from a semi‐elliptical cavity with arbitrary orientation placed in a perfect electric conductor plane

AbstractA semi‐analytic solution for scattering from a semi‐elliptical cavity with arbitrary orientation placed in a perfect electric conductor plane is suggested. By imposing the boundary conditions at an elliptical border, three independent equations containing the Mathieu functions series are extracted. Finally, the solution of the problem is reduced to the solution of a simple system of linear equations by using Mathieu function addition theorem and the orthogonal properties of the angular Mathieu functions. Some examples are presented to demonstrate the reliability and the accuracy of the proposed solution.

Design and performance investigation of metamaterial-inspired dual band antenna for WBAN applications.

This paper presents the design and analysis of a metamaterial-based compact dual-band antenna for WBAN applications. The antenna is designed and fabricated on a 0.254 mm thick semi-flexible substrate, RT/Duroid® 5880, with a relative permittivity of 2.2 and a loss tangent of 0.0009. The total dimensions of the antenna are 0.26λo×0.19λo×0.002λo, where λo corresponds to the free space wavelength at 2.45 GHz. To enhance overall performance and isolate the antenna from adverse effects of the human body, it is backed by a 2×2 artificial magnetic conductor (AMC) plane. The total volume of the AMC integrated design is 0.55λo×0.55λo×0.002λo. The paper investigates the antenna's performance both with and without AMC integration, considering on- and off-body states, as well as various bending conditions in both E and H-planes. Results indicate that the AMC-integrated antenna gives improved measured gains of 6.61 dBi and 8.02 dBi, with bandwidths of 10.12% and 7.43% at 2.45 GHz and 5.80 GHz, respectively. Furthermore, the AMC integrated antenna reduces the specific absorption rate (SAR) to (>96%) and (>93%) at 2.45 GHz and 5.80 GHz, meeting FCC requirements for low SAR at both frequencies when placed in proximity to the human body. CST Microwave Studio (MWS) and Ansys High-Frequency Structure Simulation (HFSS), both full-wave simulation tools, are utilized to evaluate the antenna's performance and to characterize the AMC unit cell. The simulated and tested results are in mutual agreement. Due to its low profile, high gain, adequate bandwidth, low SAR values, and compact size, the AMC integrated antenna is considered suitable for WBAN applications.

Enhancing hydrogen evolution reaction activity through defects and strain engineering in monolayer MoS2.

Molybdenum disulfide (MoS2) has recently emerged as a promising electrocatalyst for the hydrogen evolution reaction (HER). However, the poor in-plane electrical conductivity and inert basal plane activity pose major challenges in realizing its practical application. Herein, we demonstrate a new approach to induce biaxial strain into CVD-grown MoS2 monolayers by draping it over an array of patterned gold nanopillar arrays (AuNAs) as an efficient strategy to enhance its HER activity. We vary the magnitude of applied strain by changing the inter-pillar spacing, and its effect on the HER activity is investigated. To capitalize on the synergistic effect of improved ΔG H via strain engineering and leverage basal plane activation by introduction of sulphur vacancies, we further exposed the strained MoS2 monolayers to oxygen plasma treatment to create S-vacancies. The strained MoS2 on AuNAs with optimal inter-pillar spacing is exposed to oxygen plasma treatment for different durations, and we study its electrocatalytic activity towards the HER using on-chip microcell devices. The strained and vacancy-rich monolayer MoS2 draped on AuNAs with a 0.5 μm inter-pillar spacing and exposed to plasma for 50 s (S0.5μmV50-MoS2) is shown to exhibit remarkable improvement in HER activity, with an overpotential of 53 mV in 0.5 M H2SO4. Thus, the synergistic creation of additional vacancy defects, along with strain-induced active sites, results in enhancement in HER performance of CVD-grown monolayer MoS2. The present study provides a highly promising route for engineering 2D electrocatalysts towards efficient hydrogen evolution.

High-Tg shape memory polyimide composites with “spot-plane” directional thermally conduction structure based on AlN nanoparticles and acidified graphene

In order to enhance the thermal conduction property and shorten response time of shape memory polyimide (SMPI), “spot-plane” directional thermally conductive acidified graphene/AlN/SMPI composites were prepared, in which AlN nanoparticles were used as “thermal conduction spots” and acidified graphene was used as two-dimensional “thermal conduction planes”. The SMPI composite doped with 6 wt% AlN and 0.8 wt% acidified graphene had good heat conducting properties (the in-plane thermal conductivity of 5.90 W m−1 K−1), excellent mechanical propertied (the tensile strength of 134.5 MPa, and Young’s modulus of 3.8 GPa), high shape memory transition temperature (at 419 ℃), and great thermal stability and shape memory properties. Compared with SMPI resin matrix, the response time of the acidified graphene/AlN/SMPI composite was shortened by 140 s, only 20 s, and it can be applied in flexible electronics, intelligent response structures and active deformation structures in high-temperature environment.

In-gap states and local structures around substitutional defects in La- or Nb-doped n-type SrTiO3

First-principles calculations with DFT+U method were conducted on the local structures and the in-gap electronic states of n-type SrTiO3, whose electron doping was realized by substitution of Sr by La or Ti by Nb. For both La-doped and Nb-doped SrTiO3, cubic structures were proved to be stable e3ven when tetragonal structures were assumed, as suggested also in a reported experimental study. In La-doped SrTiO3, O atoms neighboring the substitutional La were symmetrically attracted toward the dopants. Sharp electron band observed at the top of the bandgap, which gave n-type conductivity and resulted from the intersection of Fermi energy level at the conduction band bottom with La-doping, was composed of 3d orbitals in Ti. The La-doping transformed some of the p electrons in O into the d electrons in Ti in the sharp band, and these electrons at Fermi level were expected to act as n-type carriers. In Nb-doped SrTiO3, on the other hand, Ti atoms at the first, second and third nearest neighbors of the Nb, which were in the same Ti-O plane surrounding the dopants, were repelled away from the Nb dopants to be isotropic local expansion, while O atoms neighboring Nb were attracted toward the dopants in the expanded local structure. Sharp band of the in-gap states just below the Fermi energy of the Nb-doped SrTiO3 was not only of the 3d orbitals in the first nearest-neighbor Ti atoms, but also of those in the second and third nearest-neighbor Ti atoms of the dopants. The degree of Fermi level intrusion into conduction band and atomic rearrangements near Nb substitutions were milder than those of La substitutions. As replacement of Sr atoms by La not contained in Ti-O network does not disturb the electron transport within Ti-O conduction planes, Nb-doping in Ti site does not interrupt the n-type carrier transportation even though Nb atoms are in Ti-O network, because of the formation of conduction path which bypasses the unit cell containing the dopants.

Dark band artifact in transcranial MR-guided focused ultrasound: Mechanism and mitigation with passive crossed wire antennas

Current FDA-approved transcranial MR-guided focused ultrasound (tcMRgFUS) transducers cause a curved dark band in 3 T brain images that runs through midbrain targets of ablative treatments for essential tremor and other applications, and signal is reduced by at least 25% elsewhere in the brain. This limits the set of scans that can be performed to guide and assess the effects of treatment. An electromagnetic simulation study was performed to elucidate the mechanisms causing the dark band. Based on the results, a pair of passive antennas in a “propeller-beanie” configuration were designed to manipulate the reflected waves to avoid signal cancellation within the brain. The antennas were optimized and validated with in-vivo experiments and hydrophone measurements. The simulation study revealed that the dark band is caused by RF waves reflected from the transducer's ground plane, which cancel with incoming waves from the scanner's body coil. The passive antennas shifted the dark band out of the brain and increased transmit efficiency in the center of brain 2.3 times while improving field homogeneity by 50%. They also increased receive sensitivity and SNR in anatomic and temperature imaging. They caused no detectable distortion in hydrophone-measured focal pressure profiles. The conductive ground planes and coupling media used in tcMRgFUS and other piezoelectric FUS transducers interact with a 3 T scanner's RF fields to reduce transmit efficiency and SNR. For tcMRgFUS scenario, “propeller beanie” passive reflecting antennas alleviated these effects. This could make a broader set of imaging sequences available to guide tcMRgFUS treatment.

Miniaturized High Gain Broadband 16‐Element MIMO Array Using Planar Artificial Magnetic Conductor With Enhanced Isolation for WLAN/WiMAX Applications

AbstractA low‐profile 16‐element printed dipole antenna (PDA) array backed by a planar artificial magnetic conductor (AMC) is introduced for multiple‐input multiple‐output (MIMO) wireless communications. The proposed 16‐element MIMO array loaded by a 13 × 13 AMC reflector with various polarized directions exhibits a low‐profile wideband structure, which includes the broad measured bandwidths from 4.25 to 7.25 GHz with increased gains (>8 dBi) and high efficiency. The high isolation between the 16 elements with diverse polarizations is larger than 27 dB and reaches 67 dB over the operating band for MIMO systems. The suggested PDA with a microstrip V‐shaped dipole excited by a V‐shaped microstrip feedline is used to expand the broad simulated band spanning 5.34–6.70 GHz (S11 ≤ −10 dB). Moreover, the suggested 13 × 13 planar fractal AMC reflector is loaded into the PDA array to exhibit a reflection coefficient, S11, of less than −10 dB across the band of 4.26–6.90 GHz for wireless local area network and worldwide interoperability for microwave access applications. The proposed design with AMC compared to the design without AMC exhibits a size reduction of 50.3%, increased gain up to 8.2 dBi, and excellent impedance matching with unidirectional radiation patterns. The novel AMC unit cell is realized based on the planar patch with inserted slots to operate at 6.10 GHz with an AMC band spanning 5.15–7.10 GHz (32%).

Skin-Attachable and Stretchable Patch Antenna with Fractal Design for Remote On-Body Motion Sensing.

This article describes the implementation of a wireless human motion detection with interference resistance to untargeted deformations based on a stretchable patch antenna with fractal design. By rationally incorporating the Hilbert fractal pattern in the conductive patch and ground plane, the patch antenna shows a mechanical stretchability of ∼40% and a maximum gain of 2.95 dB at 2.5 GHz. Furthermore, the influence of the fractal order on the mechanical stretchability and radiation properties of the stretchable patch antenna is discussed. The resonant frequency of the stretchable fractal antenna demonstrates highly selective sensitivity to different deformations; i.e., it remains almost unchanged with bending deformations and is linearly dependent on the tensile strain. Remote detection of joint motions is experimentally verified by a wireless on-body strain sensor based on the fractal design-based stretchable microstrip antenna.

Investigation on magnetic shield thickness of remote field eddy current probes for inspection of ferromagnetic and non-ferromagnetic plates

Since Remote field eddy current (RFEC) detection technology is barely limited by the skin effect, it can realize the defect detection of large-thickness components. Whereas, the structure of the RFEC probe for the planar conductor is complicated, resulting in an oversized probe. This hinders the application and development of the RFEC testing technology. In this paper, finite element simulations and experimental verification are used to optimize the RFEC probe structure for flat conductors. The results have shown that the thickness of the magnetic shield is the dominant factor in achieving high performance of RFEC inspection of flat conductors. When inspecting both ferromagnetic and non-ferromagnetic flat conductors, cylindrical magnetic shields with appropriate thickness and appropriate excitation frequencies are preferred for improvement of RFEC testing.

Superconductivity and Fermi Surface Studies of β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-Crown-6

We report rf-penetration depth measurements of the quasi-2D organic superconductor β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-crown-6, which has the largest separation between consecutive conduction layers of any 2D organic metal with a single packing motif. Using a contactless tunnel diode oscillator measurement technique, we show the zero-field cooling dependence and field sweeps up to 28 T oriented at various angles with respect to the crystal conduction planes. When oriented parallel to the layers, the upper critical field, Hc2=7.6 T, which is the calculated paramagnetic limit for this material. No signs of inhomogeneous superconductivity are seen, despite previous predictions. When oriented perpendicular to the layers, Shubnikov–de Haas oscillations are seen as low as 6 T, and from these we calculate Fermi surface parameters such as the superconducting coherence length and Dingle temperature. One remarkable result from our data is the high anisotropy of Hc2 in the parallel and perpendicular directions, due to an abnormally low Hc2⊥=0.4 T. Such high anisotropy is rare in other organics and the origin of the smaller Hc2⊥ may be a consequence of a lower effective mass.

Morphodynamics of dendrite growth in alumina based all solid-state sodium metal batteries

Atomic scale imaging revealed that the deposition/stripping of Na from the β′′-Al2O3 solid electrolyte causes delamination cracks and the closure of the conduction planes.

Design of an octagonal-shaped curved sensor antenna for dielectric characterization of liquids

In this study, an octagonal microstrip antenna with a 3D-printed curved-shaped substrate was proposed as a microwave sensor for measuring the dielectric constants of liquids. During the development of the sensor, an octagonal radiating plane was placed on the curved structure by adding an empty semi-cylindrical structure to the planar substrate. The 30 × 30 × 1 mm3 substrate was designed using PLA material with a dielectric constant of 2.41, and the conductive planes were formed using copper tape. The sensor was analyzed using full-wave electromagnetic computation software, and the reflection coefficients were obtained through simulations. Using simulation-obtained reflection coefficient data, the multi-layer perceptron (MLP) was utilized to estimate the dielectric constant. Then, the sensor was manufactured using a 3D printer, and the reflection coefficient measurements of the antenna were performed by filling the curved structure with liquids of varying characteristics. The MLP, which has an APE of 0.20 % for training and 1.52 % for testing, made predictions with an APE of 0.172 % for the simulation of the five materials considered and 1.524 % for the measurement data. It has been observed that the variable dielectric constant results in differences in the resonant frequency and amplitude. The good agreement between simulation and measurement results demonstrates that the proposed sensor can be utilized effectively for measuring the dielectric constants of liquids.

Quantitative Prediction of Charge Mobilities and Theoretical Insight into the Regulation of Site-Specific Trifluoromethylethynyl Substitution to Electronic and Charge Transport Properties of 9,10-Anthraquinone.

Herein, we systematically studied the electronic and conducting properties of 9,10-anthraquinone (AQ) and its derivatives and discussed the substitute-site effects on their organic field-effect transistor (OFET) properties in detail. Our calculation results show the influence of different substitute sites on the ionization potential (IP), electronic affinity (EA), reorganization energy (λ), electronic couplings (V), and anisotropic mobility (μ) of semiconducting materials, which mainly originates from the variations of the frontier molecular orbital charge distributions, the steric hindrance, and the conjugate degree. Combining quantum-chemical calculations with charge transfer theory, we simulated the intermolecular hopping rate in the organic crystals of AQ derivatives and predicted the fluctuation range of three-dimensional (3D) anisotropic charge carrier mobility for the first time. Our calculation results well reproduced the experimental observations and provided evidence for the determination of the optimal OFET conduction plane and channel direction relative to the crystal axis.

Viability of circle and sphere theorems in potential theory and hydrodynamics via Maxwell's conjecture

AbstractIn A Treatise on Electricity and Magnetism, Maxwell determines the angles of intersection for which one may use Kelvin's inversion method to obtain the perturbed electric potential upon placing intersecting spherical conductors into a region with a known potential. There are numerous modern applications utilizing this geometric construction in potential theory and hydrodynamics, and generalized circle and sphere theorems play a foundational role in this area of mathematical physics. In his work, Maxwell gives an intuitive argument for obtaining the perturbed potential based on intersecting planar conductors and a spherical inversion, and in this paper we extend his ideas to a full proof using rotational transformations and reflections. In the process, we disprove results in [Proc Lond Math Soc., 1966:3(16)] and [Stud Appl Math., 2001:106(4); Z. Angew. Math. Mech., 2001:81(8)] on boundary value problems in hydrodynamics involving intersecting circles and spheres, and we detail the angles of intersection for which these theorems are viable. Moreover, our proof recovers a special case overlooked by Maxwell for which Kelvin's inversion method may be utilized to obtain full solutions.

Miniature 3-D-Dipole Antenna for UHF RFID Tag Mounted on Conductive Materials

A novel compact 3-D-dipole antenna for a radio frequency identification (RFID) tag is presented in this article. The proposed antenna enables the tag to be read when mounted on surfaces composed of electrically conductive materials. A close match between the input resistance and reactance of the antenna to the desired conjugate impedance of an Alien Higgs-4 chip ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8.2- j 148.5\,\,\Omega $ </tex-math></inline-formula> at 925 MHz) can be achieved by controlling the C-arm length and the width of the 3-D dipole. Experiments demonstrated that when an RFID tag antenna is attached to a conductive surface, a 0.2 mm gap between the antenna and the conductive plane enhances the antenna’s gain by increasing reflection from nearby surfaces (e.g., a metal object, a container of water, and a human wrist) within range of the antenna. Maximum read ranges are measured for the tag antenna fabricated with dimensions of 32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 25\times3.2$ </tex-math></inline-formula> mm3 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.10\,\,\lambda _{0} \times 0.08\,\,\lambda _{0} \,\,\times0.01\,\,\lambda _{0}$ </tex-math></inline-formula> ) and mounted on various materials and objects. In an outdoor environment, an effective isotropic radiated power (EIRP) transmitted by the RFID reader of 4.0 W achieves the maximum reading distances of 5.1, 3.3, and 3.9 m when the proposed tag antenna is placed on a metallic plate, a container of water, and a human wrist, respectively. The experiment and simulation results have a good agreement with each other.

A low‐profile sequential‐phase fed circularly polarized array antenna with an irregular ground

Grooving or subtracting a projection of the antenna on the ground is one of the effective methods to both improve the axial-ratio (AR) bandwidth and impedance bandwidth of a circularly polarized (CP) antenna. A bidirectional radiation, meanwhile, can be produced. Unfortunately, these methods will result in a decrease in the gain of the antenna due to a reduction of its ground size. To solve this issue, a conductive plane or a cavity is usually introduced at the antenna's bottom, but it will lead to a high profile and destroy the bidirectional radiation of the design. In this article, a CP array antenna based on a sequential-phase (SP) feeding network is taken as an example. Only the projection of the feeding network is preserved, while other conductors on the ground are subtracted. The simulated peak gain of this design is only 5.04 dBic. In order to obtain an ultra-wideband, a wide AR bandwidth, a moderate gain and a low profile of the antenna, a method of etching a circle of ground around the edge of the substrate is presented to expand the ground into a large irregular area. The measured results show that the proposed design can exhibit a 90.9% 10-dB impedance bandwidth, a 42.4% (5.2–8 GHz) 3-dB AR bandwidth, a 7.17 dBic peak gain, and a very low profile of 0.006λL. This method is very simple to implement and does not need to modify the original antenna structure. It may be applied to conveniently improve the performance of the bidirectional radiation CP antenna.

TM Scattering by a Shallow Elliptical-Shaped Cavity

In this letter, the problem of electromagnetic scattering by a shallow elliptical-shaped cavity in a perfect electric conductor plane is considered. We propose an efficient modal approach based on the region-matching technique that can calculate scattered fields without the use of the Mathieu functions. By enforcing boundary conditions at a semicircular auxiliary border, a system of linear equations is constructed. The results obtained by this method are compared with those provided by the method of moment. Finally, the effect of the shape of the cavity on the scattering signature is investigated.