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Gradient heterostructure is one of fundamental interfaces and provides an effective platform to achieve gradually changed properties in mechanics, optics, and electronics. Among different types of heterostructures, the gradient one may provide multiple resistive states and immobilized conductive filaments, offering great prospect for fabricating memristors with both high neuromorphic computation capability and repeatability. Here, we invent a memristor based on a homologous gradient heterostructure (HGHS), comprising a conductive transition metal dichalcogenide and an insulating homologous metal oxide. Memristor made of Ta–TaSxOy–TaS2 HGHS exhibits continuous potentiation/depression behavior and repeatable forward/backward scanning in the read‐voltage range, which are dominated by multiple resistive states and immobilized conductive filaments in HGHS, respectively. Moreover, the continuous potentiation/depression behavior makes the memristor serve as a synapse, featuring broad‐frequency response (10−1–105 Hz, covering 106 frequency range) and multiple‐mode learning (enhanced, depressed, and random‐level modes) based on its natural and motivated forgetting behaviors. Such HGHS‐based memristor also shows good uniformity for 5 × 7 device arrays. Our work paves a way to achieve high‐performance integrated memristors for future artificial neuromorphic computation. We invent a memristor based on a homologous gradient heterostructure (HGHS), comprising a conductive transition metal dichalcogenide and an insulating homologous metal oxide. Memristor made of Ta–TaSxOy–TaS2 HGHS exhibits continuous potentiation/depression behavior and repeatable forward/backward scanning in the read‐voltage range, which are dominated by multiple resistive states and immobilized conductive filaments in HGHS, respectively.

Objective: This study investigates solutions to the challenges of limited RF energy harvesting by designing a hybridized voltage multiplier system aimed at optimizing output across a wide frequency range. Theoretical Framework: The research centers on the principles and comparative efficiencies of the Cockcroft-Walton and Dickson voltage multipliers, known for their applications in RF energy harvesting. These multipliers’ performance was analyzed theoretically to guide a hybrid design that could adaptively respond to input frequency variations. Method: Voltage multipliers were designed and simulated in Multisim, with further analysis in MATLAB. Both the Cockcroft-Walton and Dickson voltage multipliers were subjected to a constant input of 1V across frequencies from 50 Hz to 5 GHz to assess their respective efficiencies. Subsequently, a hybrid voltage multiplier system was developed, combining an 8-stage Cockcroft-Walton and an 8-stage Dickson multiplier. A fast Fourier transform (FFT) frequency-selective algorithm, implemented in MATLAB, dynamically directed input voltages to the optimal multiplier based on frequency. Results and Discussion: Results showed that the Dickson multiplier excelled in the lower frequency range (50 Hz to 1 MHz), achieving a maximum output of 14.763V at 5 kHz and 10 kHz. In contrast, the Cockcroft-Walton multiplier was more effective in the higher frequency range (1 MHz to 5 GHz), reaching a peak output of 6.671V at 5 GHz. The hybrid system demonstrated efficient, frequency-dependent voltage multiplication and aligned well with anticipated performance metrics, suggesting an improvement in RF energy harvesting across the tested frequency range. Research Implications: This work contributes to the field of RF energy harvesting by introducing a frequency-adaptive system that enhances voltage output through targeted frequency routing. The results underscore the potential for hybrid designs to overcome limitations associated with individual voltage multipliers, presenting a versatile approach to harvesting RF energy effectively across broad frequency spectra. Originality/Value: By implementing a hybrid approach with a frequency-selective algorithm, this study offers an innovative solution for frequency-dependent RF energy harvesting. The findings provide a foundation for future research into adaptable energy harvesting systems that optimize voltage output across diverse frequencies, with practical implications for RF-powered devices and wireless energy transfer applications.

Usually, in situ electrical polarization measurements (in geophysical prospection referred to as induced polarization or spectral induced polarization (SIP)) are carried out at frequencies below 1 kHz. These techniques have mainly been used for mining exploration, followed by a larger panel of environmental applications. However, in this ultra low and extremely low-frequency domain, the duration of each individual measurement is long, i.e., typically several tens of minutes for a single full SIP spectrum down to the mHz range. This restriction makes it unrealistic to implement high-density measurement mapping campaigns over large areas, which would otherwise be possible at higher frequencies. In the intermediate frequency range [3 kHz–3 MHz], laboratory studies of soil and rock samples have shown that they can be strongly polarized notably in the presence of clays, and this property has been confirmed by several in situ mapping experiments using electromagnetic induction in the time and frequency domains (FDEM and TDEM), as well as by an electrostatic method (often named capacitive-coupled resistivity or CCR). The present paper recalls these results in an effort to promote polarization measurements at intermediate frequencies and to emphasize the importance of measuring this phenomenon.

A frequency-selective surface (FSS) is able to transmit or reflect incoming electromagnetic waves, and these properties of FSS can be utilized in printed antennas to improve the performance of these antennas. Sub-6 GHz frequency bands are used in fifth-generation (5G) systems for various applications. This paper presents the design and analysis of a wideband band-pass spatial filter using a double square loop frequency-selective surface (DSLFSS) for the sub-6 GHz 5G frequency range 1 (FR1). The proposed spatial filter consists of DSLFSS elements and can be placed on the patch radiator to increase the radiation characteristics in n77, n78, and n79 bands of the sub-6 GHz 5G spectrum. The effect of varying the width of the loops, angle of incidence. and polarization on the transmission coefficient in the frequency band of operation is analyzed. The design is synthesized using the closed form mathematical expressions for finding the physical dimensions of the spatial filter. Design trade-offs are reported based on the proposed mathematical formulation and simulations. The designed DSLFSS structure is fabricated and measured. The design results are authenticated by comparing results from the Ansys HFSS v20 Electronic Desktop Circuit Editor and measurement setup. In addition, the extension of the results from a unit cell is taken to the 2 × 2 array and 10 × 10 array, which shows nearly the same performance, hence confirming the stability of the DSLFSS structure. The proposed DSLFSS-based spatial filter has the potential for use in the design and development of patch radiators with improved radiation characteristics.

Vibration energy harvesting systems via an X-structure coupled with piezoelectric patches of special arrangements are investigated in this study. Two piezoelectric harvesters are specially installed on the X-shaped structure to explore potential benefits that the X-shaped structure could provide, and each piezoelectric pad has two layers composed of a polyvinyl chloride base patch and a micro-fibre composite patch. The theoretical analysis and experiment results indicate that the energy harvesting performance of the proposed novel arrangements of the piezoelectric harvesters can be enhanced especially in low-frequency range (below 10 Hz), compared with conventional cantilevered piezoelectric harvesters. More and higher energy harvesting peaks can be created and the effective harvesting frequency band can be obviously enlarged by expanding it to low-frequency range with the proposed methods. The X-structure-based generators can enable piezoelectric materials to harvest power from low-frequency vibration sources due to its advantages in designable equivalent nonlinear stiffness, which can be easily tuned by adjusting the key structural parameters. The design and results would provide an innovative solution and insight for smart piezoelectric materials to improve the energy harvesting efficiency in the low-frequency range including small-scale ocean wave power harvesting, human motion power and animal kinetic power harvesting, etc.

Purpose. Reducing the dispersion of radar reflections from local objects, with multi-frequency sensing, to solve the problem of orientation by radar reflections from objects. Methodology. Reflections from local objects in the entire frequency range of the radar station (RS) at the same radio engineering position were measured by three independent radars of the same type on different days and at different antenna elevations. The deviation of the radar stations in the position did not exceed 500 meters. Coordinates (azimuth, range) of reflections of several separate local objects were allocated for each radar. The average values of reflections from local objects and their dispersion in the frequency range were calculated. Using various algorithms, individual frequencies were sampled and the reflected signals were averaged at these frequencies. The decrease in the dispersion of the reflected signal from the number of frequencies at which reflections were measured and from the algorithm for selecting these frequencies was investigated. Findings. Averaging the values of reflections from local objects for several frequencies leads to a decrease in dispersion and, as a result, to a more accurate correspondence of the reflected signal level to the geometric size of the local object. The variance decreases most rapidly for a small number of frequencies selected for averaging when selecting frequencies located in an interval of at least 1% relative to each other. Originality. To solve the problem of orientation based on radar reflections from local objects, it is necessary to identify the landmarks selected on a digital terrain model. Due to the fact that local objects (hills) are a collection of many reflectors falling into the allowed volume of the radar, with different levels of reflections and random phases, there may not be radar reflection from a local object at a certain frequency, or it may be very small. In order to unambiguously identify all landmarks, measurements must be carried out at several frequencies. The work has established how many frequencies measurements should be performed at and on what principle these frequencies should be selected. Practical value. The advent of digital terrain models made it possible to solve the problem of terrain orientation by comparing radar reflections from local objects with reflection models based on digital terrain maps. Radar reflection models use mathematical expectations of reflection values, unlike real reflections, which have random deviations in signal levels depending on the operating frequency. Reducing the variance of these deviations increases the accuracy of identifying characteristic local objects (landmarks) used to orient the radar in the absence of data from satellite navigation systems.

The purpose of this study is to model the characteristics (scattering matrix element | S 11 | and 2D and 3D radiation patterns (RPs)) of phased-array antennas (PAAs) composed of graphene-based nanoribbon elements with different numbers of emitters ( N = 16, 64, and 256) and analyze their controllability under variable chemical potential (application of an external electric field) in the terahertz and far-IR frequency ranges using the CST Studio Suite 2021 software package. The characteristics (scattering matrix and 2D and 3D RPs) of a graphene antenna and a PAA composed of graphene nanoribbon elements with a different number of emitters ( N = 16, 64, and 256) and the controllability of the PAA depending on the chemical potential (µ c  = 0.3, 0.7, and 1 eV) in the frequency range f = 6–40 THz are simulated using the CST Studio Suite 2021 software. As follows from the electrodynamic simulation results, a change in the graphene chemical potential leads to changes in the PAA characteristics (half-power main lobe width , its amplitude, side-lobe level, direction of the RP main lobe, and operating frequencies). Phased-array antennas composed of rectangular graphene nanoribbon elements can be electrically controlled with frequency scanning by changing chemical potential µ c (by applying an external electric field) in the terahertz, far-IR, and mid-IR frequency ranges.

Speech production gives rise to distinct auditory and somatosensory feedback signals which are dynamically integrated to enable online monitoring and error correction, though it remains unclear how the sensorimotor system supports the integration of these multimodal signals. Capitalizing on the parity of sensorimotor processes supporting perception and production, the current study employed the McGurk paradigm to induce multimodal sensory congruence/incongruence. EEG data from a cohort of 39 typical speakers were decomposed with independent component analysis to identify bilateral mu rhythms; indices of sensorimotor activity. Subsequent time-frequency analyses revealed bilateral patterns of event related desynchronization (ERD) across alpha and beta frequency ranges over the time course of perceptual events. Right mu activity was characterized by reduced ERD during all cases of audiovisual incongruence, while left mu activity was attenuated and protracted in McGurk trials eliciting sensory fusion. Results were interpreted to suggest distinct hemispheric contributions, with right hemisphere mu activity supporting a coarse incongruence detection process and left hemisphere mu activity reflecting a more granular level of analysis including phonological identification and incongruence resolution. Findings are also considered in regard to incongruence detection and resolution processes during production.

The edge-fed monopole 5G antenna described in this article is intended for sub-6 GHz applications, with a specific focus on the n77 (3.7 GHz), n78 (3.5 GHz), and n79 (4.5 GHz) frequency bands. A novel methodology is employed to develop the antenna, which consists of binary operations on three patches (Patch1, Patch2, and Patch3), with their dimensions optimized for 3.5 GHz, 3.7 GHz, and 4.5 GHz, respectively. In order to generate an initial U-stub, Patch2 is subtracted from Patch1 followed by Patch3. Through the utilization of a coupling limb, Patch3 and the U-stub establish mutual current coupling. To remove extra bandwidth and maintain a gain more than 5 dBi, the antenna is parasitically loaded with a split-ring resonator (SRR) in a partial ground plane. The resultant antenna functions within the frequency range of 3.13 GHz to 5.06 GHz, exhibiting a maximum gain of 5.71 dBi and a maximum efficiency of 99.55%. By reducing its dimensions by 12.676% in comparison to a traditional rectangular patch antenna operating at 3.5 GHz (0.416λ 0  × 0.423λ 0  × 0.0186λ 0 ), the overall dimensions are as follows: 0.416λ 0  × 0.369λ 0  × 0.0186λ 0 . It is worth noting that λ0 is computed at 3.5 GHz. The RLC equivalent circuit is validated using ADS software, and antenna prototype measurements accord with simulated outcomes generated by HFSS and CST software.

In this study, a new approach is proposed for seismic design of latticed dome structures using natural frequencies. In order to obtain the critical natural frequencies, the structural behavior of two types of latticed domes, including a shallow double-layer dome and a single-layer Diamatic dome, under earthquake excitation is investigated. For this purpose, response history analysis is utilized considering the multi-component excitations. Also, the effects of two different mass definitions for the structure are studied. After conducting a suitable structural design based on nodal displacement and member stress criteria, the frequency content of each accelerogram obtained by Fourier amplitude spectrum is compared to range of the first ten natural frequencies of the designed structure. Results indicate the distribution of natural frequencies with respect to the frequency contents of earthquake accelerograms, and thereby revealing a critical frequency range for which a structure should be designed in such a way that its natural frequencies do not belong to that critical frequency range. This critical frequency range is appropriately far from the dominant frequency range of the selected earthquake accelerograms. The proposed approach can be applied for design of dome structures under earthquake excitations, which uses the natural frequency constraints (instead of displacement and stress constraints) to estimate a suitable design within less computational time.