Frequency Range Research Articles

A Novel FSS Loaded Circular Slot Monopole Antenna for Microwave Breast Imaging Application

Breast cancer continues to be a major contributor to women's global mortality rates, emphasizing the need to explore alternative and supplementary early-stage detection techniques. This study delves into a circular slot monopole ultra-wideband (UWB) antenna equipped with a frequency-selective surface (CSMA-FSS) for early detection microwave imaging applications. To expand the impedance bandwidth of the traditional circular monopole antenna, a circular slit is introduced on a monopole structure. Additionally, a 10 × 10 unit cell FSS structure is integrated into the antenna as a far-field reflecting plane to enhance gain characteristics. The antenna, crafted with dimensions of 50 × 50 × 1.6 mm³ and a 1.6 mm thick FR4 substrate, operates across the ultra-wideband frequency spectrum, spanning from 3.1 GHz to 12 GHz, while consistently maintaining a reflection coefficient (S 11) value of – 10 dB or lower. Notably, the antenna showcases a gain of over 5 dBi across the entire 3.1 GHz to 12 GHz frequency range. The suggested antenna is ideal for microwave imaging applications due to its broad impedance bandwidth, impressive gain, and excellent directivity. Furthermore, it maintains a relatively uniform group delay, with a deviation of ±0.5 ns throughout the UWB band. In the time domain characteristics, the antenna exhibits excellent pulse handling capabilities and strong signal correlation, featuring an S 21 value of less than – 25 dB. The characteristics, observed in both the time and frequency domains, suggest that the proposed antenna holds significant potential for substantially enhancing breast cancer imaging system.

Research on abnormal vibration of high-speed train based on wheel-rail coupling modal analysis

During dynamic line testing of a high-speed train, it was observed that the vehicle exhibited significant abnormal vertical vibrations under specific track conditions. The frequency of this vibration varies with the train speed and exhibits harmonics through analysis. As the speed approaches 400 km/h, the peak frequency is close to 44 Hz, corresponding to the system structure's natural frequency. A finite element model of the wheel-rail coupling was established for modal analysis, which revealed that the coupling between the bogie and the track will form a bogie P2 force resonance mode, which closely matches the frequency range of the abnormal vibrations. A dynamic model of vehicle-track rigid-flexible coupling was established, to simulate vibration reproduction and the bogie P2 force resonance mode variation law. Additionally, irregularities of specific wavelengths on the track can excite this mode, leading to a significant increase in amplitude. Some sections of the track line have slab warping, with a wavelength of approximately 2.45m. The frequency range of excitation formed when the vehicle speed approaches 400 km/h is close to that of the bogie P2 resonance mode. As a result, coupling resonance occurs between the vehicle and track systems, ultimately causing abnormal vibrations.

Changes in hearing function and intracochlear morphology after electrode array insertion in minipigs

Background In temporal bone specimens from long-term cochlear implant users, foreign body response within the cochlea has been demonstrated. However, how hearing changes after implantation and fibrosis progresses within the cochlea is unknown. Objectives To investigate the short-term dynamic changes in hearing and cochlear histopathology in minipigs after electrode array insertion. Material and Methods Twelve minipigs were selected for electrode array insertion (EAI) and the Control. Hearing tests were performed preoperatively and on 0, 7, 14, and 28 day(s) postoperatively, and cochlear histopathology was performed after the hearing tests on 7, 14, and 28 days after surgery. Results Electrode array insertion had a significant effect for the frequency range tested (1 kHz–20kHz). Exudation was evident one week after electrode array insertion; at four weeks postoperatively, a fibrous sheath formed around the electrode. At each time point, the endolymphatic hydrops was found; no significant changes in the morphology and packing density of the spiral ganglion neurons were observed. Conclusions and Significance The effect of electrode array insertion on hearing and intracochlear fibrosis was significant. The process of fibrosis and endolymphatic hydrops seemed to not correlate with the degree of hearing loss, nor did it affect spiral ganglion neuron integrity in the 4-week postoperative period.

Development of a novel, concentric micro-ECoG array enabling simultaneous detection of a single location by multiple electrode sizes.

Detection of the epileptogenic zone is critical, especially for patients with
drug-resistant epilepsy. Accurately mapping cortical regions exhibiting high activity during
spontaneous seizure events while detecting neural activity up to 500 Hz can assist clinicians'
surgical decisions and improve patient outcomes. We designed, fabricated,
and tested a novel hybrid, multi-scale micro-electrocorticography (micro-ECoG) array with
a unique embedded configuration. This array was compared to a commercially available
microelectrode array (Neuronexus) for recording neural activity in rodent sensory cortex
elicited by somatosensory evoked potentials and pilocarpine-induced seizures. Main results
Evoked potentials and spatial maps recorded by the multi-scale array ("micros", "mesos", and
"macros" refering to the relative electrode sizes, 40 micron, 1 mm, and 4 mm respectively)
were comparable to the Neuronexus array. The SSEPs recorded with the micros had higher
peak amplitudes and greater signal power than those recorded by the larger mesos and macro.
Seizure onset events and high-frequency oscillations (∼450 Hz) were detected on the multi-
scale, similar to the commercially available array. The micros had greater SNR than the mesos
and macro over the 5-1000 Hz frequency range during seizure monitoring. During cortical
stimulation experimentation, the mesos successfully elicited motor effects. 
Previous studies have compared macro- and microelectrodes for localizing seizure activity in
adjacent regions. The multi-scale design validated here is the first to simultaneously measure
macro- and microelectrode signals from the same overlapping cortical area. This enables direct
comparison of microelectrode recordings to the macroelectrode recordings used in standard
neurosurgical practice. Previous studies have also shown that cortical regions generating
high-frequency oscillations are at an increased risk for becoming epileptogenic zones. More
accurate mapping of these micro seizures may improve surgical outcomes for epilepsy patients.

Study of a cubic cavity resonator for gravitational waves detection in the microwave frequency range

Study of a cubic cavity resonator for gravitational waves detection in the microwave frequency range

Sonoluminescence: Photon production in time-dependent analog systems

Sonoluminescence is a well-known laboratory phenomenon where an oscillating gas bubble in the appropriate environment periodically emits a flash of light in the visible frequency range. In this work, we study the system in the framework of analog gravity. We model the oscillating bubble in terms of analog geometry and propose a nonminimal coupling prescription of the electromagnetic field with the geometry. The geometry behaves as an analogous oscillating time-dependent background in which repeated flux of photons are produced in a wide frequency range through parametric resonance from quantum vacuum. Due to our numerical limitation, we could reach the frequency up to ∼105 m−1. However, we numerically fit the spectrum in a polynomial form including the observed frequency range around ∼107 m−1. Our current analysis seems to suggest that parametric resonance in analog background may play a fundamental role in explaining such phenomena in the quantum field theory framework. Published by the American Physical Society 2024

A bifunctional metamaterial with broadband properties of absorption and linear-to-linear polarization conversion

This paper proposes, measures, and investigates a bifunctional metamaterial capable of achieving absorption and reflective linear-to-linear polarization conversion simultaneously, which both exhibit the characteristics of broadband. The unit cell consists of a metal pattern with resistors, a dielectric plate, an air layer, and a metal backplate. The simulation results demonstrate that the designed metamaterial acquires over 90% absorption in the microwave band of 6.5–9.3 GHz. Within the frequency range of 12.7 GHz–17.2 GHz, the polarization conversion rate exceeds 90%, effectively converting y-polarized incident waves into x-polarized reflected waves. The experimental results align with the simulation data. The surface current and electric field distributions are utilized to analyze the absorption and polarization conversion phenomena. This bifunctional metamaterial exhibits potential application in radar imaging, enhancing data transmission rates, and wireless communication.

Dual-functional pentamode metamaterial with water-like and topological transmission properties

In this paper, a water-like pentamode metamaterial (PM) with a single metallic material is designed and the topological edge-state transmission properties of elastic waves in the PM are thoroughly investigated. Numerical results indicate that by introducing structural perturbation into PM, the Dirac point degeneracy at K-point can be opened and topological band inversion can be generated. Topological edge states are also obtained by organizing PM structural units, which are robust to defects such as bending and cavities. In addition, it also has the mimics water in acoustic properties over a wide frequency range, i.e. it exhibits transparency when surrounded by water. Therefore, it will have both good transmission efficiency and acoustic stealth performance when used as an underwater waveguide. The dual-functional PM proposed in this study provides theoretical guidance for designing underwater stealth acoustic waveguides.

Wearable flexible Kapton-graphene electromagnetic sensors

This research is dedicated to the development of a new technology for a quick diagnosis of virial virus, using electromagnetic technology facilitated by either a Rectangular Patch Resonator (RPR) or a Wearable Flexible Sensor (WFS) designed for non-invasive viral disease detection, including Nano-virus, and macro-virus. These devices is tailored for a precise and non-invasive detection of a wide array of viruses. To enhance diagnostic precision, an electromagnetic sensor was meticulously explored and simulated, to be capable of detecting and identifying even the most minuscule viruses. Employing numerical modeling with a focus on the 10 GHz to 20 GHz frequency range. We hold a strong sense of optimism regarding this sensor's potential for non-invasive virus detection. Extensive simulations conducted throughout this study have underscored the WFS's selectivity across all viruses, boasting an exceptional limit of detection and sensitivity. Moreover, the WFS exhibited the capability to distinguish between varying infection percentages, each corresponding to a distinct reflection pattern.

Study on mode properties of GaAs based hybrid plasmonic terahertz waveguide

Abstract The Terahertz (THz) field is emerging with the goal of addressing the critical challenges associated with achieving high data rates and rapid communication. In this study, a hybrid plasmonic THz waveguide has been designed and analyzed operating in 2.5-3.5 THz frequency range. The waveguide is constructed using GaAs (Gallium Arsenide) as the high refractive index core, surrounded by AlAs (Aluminium Arsenide), Ag (Silver) and placed on an HDPE (high-density polyethylene) substrate. Graphene is strategically positioned between HDPE layer to enhance light confinement. The mode properties of the designed waveguide that have been simulated using multiphysics simulations of finite element method shows unique characteristics. The observations of the simulated results at 2.5 to 3.5 THz, shows the effective refractive index of 3.79, effective mode area of 1.88 mm2, birefringence of 0.2, dispersion of 0.10 ps/THz/cm, mode field diameter of 15.8 mm, beat length of 123 mm, confinement loss 1.79 x 10-9 mm-1 has been obtained. These features make the proposed waveguide suitable for applications in photonic integrated circuits for THz communications.

Enhancing motor impedance measurements: broadening the spectrum from low to high frequencies

Three-phase induction motors serve as critical parts in various industrial applications, lauded for their high energy efficiency and notable power density. Obtaining their broadband impedance information is paramount for analyzing conducted emissions, evaluating overvoltage ringing, and assessing motor health status. Nonetheless, conventional methods for motor impedance measurements typically rely on Kelvin clip leads or extension cables, which are effective only in a relatively low-frequency region (i.e. below 1 MHz). This paper presents an improved approach to extend the measurable spectrum from low to high frequencies, up to 120 MHz. The proposed method develops a series of fixture adapters to enable seamless interconnection between the terminals of an induction motor and the coaxial ports of an impedance analyzer. The parasitics introduced by these adapters are identified using boundary-element analysis, and their impacts are minimized based on the de-embedding concept. Experimental results affirm the accuracy and effectiveness of the proposed method for four types of motor impedances (i.e. single-phase, phase-to-ground, common-mode, and differential-mode) across a broad frequency range from 100 Hz to 120 MHz. Moreover, the inaccuracy of motor impedance measurements at high frequencies (i.e. above 1 MHz) using conventional methods, including Kelvin clip leads and extension cables, is also demonstrated.

Experimental investigation of the polarity-switching process with different bipolar ionic liquid thruster operating frequencies

The bipolar ionic liquid thruster employs ionic liquid as a propellant to discharge positively and negatively charged high-energy particles under an alternating current (AC) power source, effectively suppressing electrochemical reaction and ensuring charge neutrality. Determining an optimal AC supply power source frequency is critical for sustained stable thruster operation. This study focuses on the emission characteristics of the ionic liquid thruster under varied AC conditions. The AC power supply was set within the frequency range of 0.5–64 Hz, with eight specific frequency conditions selected for experimentation. The experimental results indicate that the thruster operates steadily within a voltage range of ±1470 to ±1920 V, with corresponding positive polarity current ranging from 0.41 to 4.91 μA and negative polarity current ranging from −0.49 to −4.10 μA. During voltage polarity switching, an emission delay occurs, manifested as a prominent peak signal caused by circuit capacitance characteristics and a minor peak signal resulting from liquid droplets. Extended emission test was conducted at 16 Hz, demonstrating approximately 1 h and 50 min of consistent emission before intermittent discharge. These findings underscore the favorable impact of AC conditions within the 8–16 Hz range on the self-neutralization capability of the ionic liquid thruster.

Viscous Mechano‐Electric Response of Ferroelectric Nematic Liquid

AbstractDirect viscous mechano‐electric response is demonstrated for a room‐temperature ferroelectric nematic liquid, which combines large spontaneous electric polarization with 3D fluidity. The mechano‐electric transduction is observed in the frequency range 1 −200 Hz via a simple demonstrator device. The liquid is placed into a deformable container with electrodes and the electric current induced by both periodic and irregular actuation of the container is examined. The experiments reveal a rich interplay of several distinct viscous mechano‐electric phenomena, where both shape deformations and material flow cause changes in the electric polarization structure of a ferroelectric nematic liquid. The results show that the mechano‐electric features of the material promise a considerable applicative perspective spanning from sensitive tactile sensors to energy harvesting devices.

Effect of Bentonite on the Electrical Properties of a Polylactide-Based Nanocomposite

In this paper, a novel polylactide-based nanocomposite with the addition of bentonite as a filler, Fusabond, and glycerine as a compatibilizer and plasticizer, were prepared and investigated. Four samples with different contents of bentonite (1, 5, 10, and 15 wt.%), as well as three samples without fillers, were prepared with an easily scalable method: melt blending. The electrical properties of all prepared samples were investigated with broadband dielectric spectroscopy in the frequency range between 0.1 Hz and 1 MHz. Measurements were conducted at nine temperatures between 293.15 and 333.15 K (20 to 60 ∘C) with steps of 5 K. It was found that the increase in the content of bentonite in polylactide has a significant effect on the electrical properties of the prepared nanocomposites.

Hadamard Error-Correcting Codes and Their Application in Digital Watermarking

In communication technologies such as digital watermarking, wireless sensor networks (WSNs), and visual light communication (VLC), error-correcting codes are crucial. The Enhanced Hadamard Error-Correcting Code (EHC), which is based on 2D Hadamard Basis Images, is a novel error correction technique that is presented in this study. This technique is used to evaluate the effectiveness of the video watermarking scheme. Even with highly sophisticated embedding techniques, watermarks usually fail to resist such comprehensive attacks because of the extraordinarily high compression rate of approximately 1:200 that is frequently employed in video dissemination. It can only be used in conjunction with a sufficient error-correcting coding method. This study compares the efficacy of the well-known Reed–Solomon Code with this novel technique, the Enhanced Hadamard Error-Correcting Code (EHC), in maintaining watermarks in embedded videos. The main idea behind this newly created multidimensional Enhanced Hadamard Error-Correcting Code is to use a 1D Hadamard decoding approach on the 2D base pictures after they have been transformed into a collection of one-dimensional rows. Following that, the image is rebuilt, allowing for a more effective 2D decoding procedure. Using this technique, it is possible to exceed the theoretical error-correcting capacity threshold of ⌊dmin−12⌋ bits, where dmin is the Hamming distance. It may be possible to achieve better results by converting the 2D EHC into a 3D format. The new Enhanced Hadamard Code is used in a video watermarking coding scheme to show its viability and efficacy. The original video is broken down using a multi-level interframe wavelet transform during the video watermarking embedding process. Low-pass filtering is applied to the video stream in order to extract a certain frequency range. The watermark is subsequently incorporated using this filtered section. Either the Reed–Solomon Correcting Code or the Enhanced Hadamard Code is used to protect the watermarks. The experimental results show that EHC far outperforms the RS Code and is very resilient against severe MPEG compression.

Giant magneto-photoluminescence at ultralow field in organic microcrystal arrays for on-chip optical magnetometer

Optical detection of magnetic field is appealing for integrated photonics; however, the light-matter interaction is usually weak at low field. Here we observe that the photoluminescence (PL) decreases by > 40% at 10 mT in rubrene microcrystals (RMCs) prepared by a capillary-bridge assembly method. The giant magneto-PL (MPL) relies on the singlet-triplet conversion involving triplet-triplet pairs, through the processes of singlet fission (SF) and triplet fusion (TF) during radiative decay. Importantly, the size of RMCs is critical for maximizing MPL as it influences on the photophysical processes of spin state conversion. The SF/TF process is quantified by measuring the prompt/delayed PL with time-resolved spectroscopies, which shows that the geminate SF/TF associated with triplet-triplet pairs are responsible for the giant MPL. Furthermore, the RMC-based magnetometer is constructed on an optical chip, which takes advantages of remarkable low-field sensitivity over a broad range of frequencies, representing a prototype of emerging opto-spintronic molecular devices.

Design and Simulation of High-Power Planar Čerenkov Oscillators with Two-Dimensional Distributed Feedback in the Subterahertz Frequency Range

Design and Simulation of High-Power Planar Čerenkov Oscillators with Two-Dimensional Distributed Feedback in the Subterahertz Frequency Range

Large-scale engineered meta-barriers for attenuation of seismic surface waves

This study evaluates the performance of large-scale meta-barriers in attenuating seismic surface waves and transportation-induced vibrations in the most disastrous frequency range of 0–30 Hz. By developing analytical and three-dimensional numerical models, it evaluates the properties of the proposed meta-barrier and presents their effects on the attenuation range. Moreover, it discusses a simplified mass-spring-mass model of the meta-barrier, demonstrating that the attenuation range of a unit cell can be approximated using this model. The proposed design consists of three-dimensional two-layers (3D-2C) unit cells arranged periodically with different configurations to be placed between the wave source and structure. Specifically, the meta-barriers can be arranged gradually (periodic spacing along the length), widening the attenuation range to block nearly 85% of the most devastating waves using typically arranged stacked unit cells and triangular-like arrangement (double wedge). The results show that a typical stacked unit cells reflect the incoming waves towards the source, while using the double wedge design, the surface wave can be converted to bulk wave, thereby reducing the risk to the surroundings. Moreover, the study validates the attenuation range using three-dimensional time history analysis subjected to an artificial wavelet (Ormsby wavelet) and three actual seismic records (1975 Oroville, 1984 Bishop, and 2001 Anza time histories).

Simulation‐Guided Design of Gradient Multilayer Microwave Absorber with Tailored Absorption Performance

AbstractFlexible microwave absorber (MAR), vital in advanced applications such as wearable electronics and precision devices, are highly valued for their lightweight, exceptional electromagnetic waves (EWs), and ease of fabrication. However, optimizing the electromagnetic parameters of microwave absorption materials (MAMs) to enhance absorption ability and expand effective absorption broadband (EAB, reflection loss (RL) <−10 dB) is a considerable challenge. Herein, a permittivity‐attenuation evaluation diagram (PAED) is constructed using parameter scanning based on the Materials Genome Initiative to determine the ideal electromagnetic parameters and thickness, optimize absorption efficiency, and obtain highly efficient absorbers. Guided by the PAED, a multilayer MAR consisting of a “matching‐absorption‐reflection layer” and a dielectric loss gradient aligned with the direction of EWs propagation is developed. This design significantly enhances the EWs penetration and ensures effective absorption, attributed to the well‐matched impedance and attenuation characteristics. As anticipated, the microwave absorption of the absorber (density = 0.063 g cm−3) is optimized, with an RL of −34 dB at d = 4 mm and an EAB covering the entire X‐band (8.2–12.4 GHz). This study presents a novel approach for establishing a material database for MAMs and developing high‐performance absorbers characterized by thinness, lightness, broad operational frequency range, and robust absorption capacity.

Bio-based composite active film/coating from deccan hemp seed protein, taro starch and leaf extract: Characterizations and application in grapes

This study aimed to create a novel, cost-effective, and environmentally friendly food packaging film or coating using agricultural waste materials such as deccan hemp seeds and leaves. The process involved blending deccan hemp seed protein and leaf extract at an optimal ratio through a casting technique. Additionally, starch isolated from taro root was added into the protein-based film to enhance its structural, barrier, and mechanical properties. The introduction of bioactive compounds, like deccan hemp leaf extract, led increase in antioxidant activity and enriching the film with beneficial phenolic compounds.The combination of leaf extract and starch with the protein film resulted in a homogeneous, dense, and smooth film matrix, as evidenced by scanning microscopy images. FTIR spectroscopy confirmed interlinkage among the various constituents in the film. Rheological analysis of the film-forming solution showed its shear-thinning behavior, with the storage modulus exceeding the loss modulus in the angular frequency range of 0.1 rad/s to 100 rad/s, indicating the film's elastic nature. Furthermore, the physical and optical attributes of the films were enhanced through the addition of starch and leaf extract.In a practical application, the film-forming solution was applied to grapes, leading to improved quality and extended shelf life for grapes stored under ambient conditions for ten days. Overall, this study's findings suggest that the use of deccan hemp seed protein-based packaging film holds promise as an emerging solution for enhancing the shelf life of vegetables and fruits, offering a sustainable and effective alternative for food packaging.