Wide Frequency Range Research Articles

An open dataset for human SSVEPs in the frequency range of 1-60 Hz

A steady-state visual evoked potential (SSVEP)-based brain-computer interface (BCI) system relies on the photic driving response to effectively elicit characteristic electroencephalogram (EEG) signals. However, traditional visual stimuli mainly adopt high-contrast black-and-white flickering stimulations, which are easy to cause visual fatigue. This paper presents an SSVEP dataset acquired at a wide frequency range from 1 to 60 Hz with an interval of 1 Hz using flickering stimuli under two different modulation depths. This dataset contains 64-channel EEG data from 30 healthy subjects when they fixated on a single flickering stimulus. The stimulus was rendered on an LCD display with a refresh rate of 240 Hz. Initially, the dataset was rigorously validated through comprehensive data analysis to investigate SSVEP responses and user experiences. Subsequently, BCI performance was evaluated through offline simulations of frequency-coded and phase-coded BCI paradigms. This dataset provides comprehensive and high-quality data for studying and developing SSVEP-based BCI systems.

A hybrid constitutive model of high-damping viscoelastic materials used for vibration control of civil structures

The dynamic mechanical properties of high-damping viscoelastic (VE) materials exhibit significant frequency and temperature dependences in the glass transition zone. However, the current state of VE constitutive models face a challenge in balancing the accuracy, simplicity, and ease of structural dynamic analysis. In this study, a power-law and exponent-law hybrid model is proposed to model the frequency-dependent and temperature-dependent complex modulus of VE materials. The equivalence of hybrid model and existing VE constitutive models is presented. A total of 12 groups of experimental data are collected to validate the accuracy of hybrid model. An efficient numerical method for the hybrid model is proposed and then validated through a viscoelastically damped frame. Results show that the hybrid model is equivalent to two rheological models or fractional derivative models owning to the unshared model coefficients. The hybrid model is superior to the eight-parameter fractional derivative model in predicting the complex modulus over a wide equivalent frequency range. The proposed numerical method performs quite well in calculating seismic responses of proportional and non-proportional damped frames.

Microfluidic Metasurface with Constant Absorption Efficiency Throughout the Ku Band

AbstractMetasurfaces with designable electromagnetic parameters are ideal candidates for broadband and tunable microwave absorbers. Water‐based metasurface microwave absorbers have been demonstrated to exhibit ultra‐broadband and near‐unity absorption. However, a broadband microwave absorber with constant and designable efficiencies remains a challenge due to stringent impedance‐matching conditions over a large frequency region. In this work, a design paradigm of microfluidic metasurface absorbers is proposed to regulate absorption efficiency over a wide frequency range. As an example, microfluidic metasurface absorbers are demonstrated with constant absorption efficiency over the Ku band, which is designable from 61.8% to 99.9%. The broadband metasurface absorbers have the advantages of easy fabrication, low cost, and optical transparency, making them highly promising for applications in fields like electromagnetic shielding, active camouflage, electromagnetic pollution control, and wireless communications.

A Statistical Analysis of Wireless Body Area Network using Clustering Based Routing Protocols

Recently, research on wireless body-area sensor networks (WBASN) or wireless body area networks (WBANs) has gained great importance in medical applications, and now plays an important role in patient monitoring. Clustering is the most important task in wireless sensor networks (WSNs) by data aggregation through each cluster head (CH). The development of technology has seen comfort in the domestic and professional life of an individual. However, such survival was not able to meet medical emergencies during the pandemic COVID-19 and other health surveillance scenarios. As a result, it is important to design an energy-efficient routing system for WBAN. Existing routing algorithms focus more on energy efficiency than security. A Secure Optimal Path-Routing (SOPR) protocol is proposed to identify and discover routes in WBAN that are secure against black-hole attacks. In this paper the sensor's wireless capability has been tested with a simulator to detect and transmit signals across a wide range of frequencies and to ensure that data is transferred successfully. CARF reduces the maximum work done by relay nodes in case of overloaded nodes and thereby increases the energy distribution in the network. The proposed CARF design reduces packet loss and time delay, thereby increasing network lifetime compared to other fuzzy and heuristic methods used for routing in WSNs. The proposed algorithm maintains more than 75% of the residual energy in the network at a minimum initial energy level of 1 J to enable data syncing. A SAC-TA approach for data aggregation in WSNs is presented. False injection attacks are identified based on traffic analysis at the time of the route discovery process. One-time key generation algorithm is introduced to eliminate malicious nodes from the network. The presented paper proposes a congestion-free routing framework for data transmission from source to sink nodes in WSNs. Congestion-aware routing mechanisms modeled using fuzzy sets (CARF) include operations such as establishing non-localized nodes, by which more paths can be created for traffic distribution, and predicting an optimal congestion.

Multicentric evaluation of high and low power lasers on RIRS success using propensity score analysis

In this study, we aimed to evaluate the effect of HPL on different parameters by different centers and urologists. While doing this, we evaluated different parameters by comparing HPL(High Power laser) and LPL(Low-power laser). This is an observational, retrospective, comparative, multicentric study of prospectively organised database. A total of 217 patients who underwent RIRS for kidney stones smaller than 2 cm in three different centers were included in the study. The patients were divided into two groups; LPL used (Group1, n:121 patients) and HPL used (Group2, n:96). Propensity score matching was done in the data analysis part. After matching, a total of 192 patients, 96 patients in both groups, were evaluated. There was no difference between the groups regarding age, gender, stone side, and stone location. The stone-free rate on the first day was 80.3% in Group 1, it was 78.1% in Group 2 (p = 0.9). In the third month, it was 90.7% in Group 1 and 87.5% in Group 2 (p:0.7).Hospitalization duration was significantly higher in Group 1. (2.35 ± 2.27 days vs. 1.42 ± 1.10 days; p < 0.001).The operation duration was 88.70 ± 29.72 min in Group1 and 66.17 ± 41.02 min in Group2 (p < 0.001). The fluoroscopy time (FT) was 90.73 ± 4.79 s in Group 1 and 50.78 ± 5.64 s in Group 2 (p < 0.001). Complications according to Clavien Classification, were similar between the groups(p > 0.05). According to our study similar SFR and complication rates were found with HPL and LPL. In addition, patients who used HPL had lower operation time, hospital stay, and fluoroscopy time than the LPL group. Although high-power lasers are expensive in terms of cost, they affect many parameters and strengthen the hand of urologists thanks to the wide energy and frequency range they offer.

Wideband nonuniform metasurface antenna with stable gain

Abstract A novel wideband nonuniform metasurface antenna with stable gain is demonstrated. The nonuniform metasurface is composed of square patches and rings and is excited by a slot antenna. Based on characteristic mode analysis, two characteristic modes with same current direction are selected to achieve stable radiation performance in a wide frequency range. The wideband operation is achieved by assembling the resonant modes of the metasurface and slot antenna. The measured results show that the −10 dB impedance bandwidth of the proposed antenna is from 4.3 to 8.4 GHz (64.57%), and the 2 dB gain bandwidth is from 4.3 to 6.2 GHz (36.2%) with a peak gain value of 9.42 dBi. Moreover, broadside radiation performance is achieved.

Fully angularly resolved 3D microrheology with optical tweezers

Microrheology with optical tweezers (MOT) is an all-optical technique that allows the user to investigate a materials’ viscoelastic properties at microscopic scales, and is particularly useful for those materials that feature complex microstructures, such as biological samples. MOT is increasingly being employed alongside 3D imaging systems and particle tracking methods to generate maps showing not only how properties may vary between different points in a sample but also how at a single point the viscoelastic properties may vary with direction. However, due to the diffraction limited shape of focussed beams, optical traps are inherently anisotropic in 3D. This can result in a significant overestimation of the fluids’ viscosity in certain directions. As such, the rheological properties can only be accurately probed along directions parallel or perpendicular to the axis of trap beam propagation. In this work, a new analytical method is demonstrated to overcome this potential artefact. This is achieved by performing principal component analysis on 3D MOT data to characterise the trap, and then identify the frequency range over which trap anisotropy influences the data. This approach is initially applied to simulated data for a Newtonian fluid where the trap anisotropy induced maximum error in viscosity is reduced from ~ 150% to less than 6%. The effectiveness of the method is corroborated by experimental MOT measurements performed with water and gelatine solutions, thus confirming that the microrheology of a fluid can be extracted reliably across a wide frequency range and in any arbitrary direction. This work opens the door to fully spatially and angularly resolved 3D mapping of the rheological properties of soft materials over a broad frequency range.

Electrically Reconfigurable Metasurfaces for Frequency Selective Transmission via IPMC Kirigami

AbstractMetasurface with programmable configurations has attracted tremendous attention due to their exotic abilities to manipulate electromagnetic waves. Herein, an electrically reconfigurable metasurface for frequency selective transmission is developed based on ionic polymer–metal composite (IPMC) kirigami. First, low‐voltage driven IPMC actuators with stable actuation performance are realized, and then a thermomechanical equivalent model and a numerical electromagnetic analysis model are proposed for evaluating the deformation of the IPMC actuators and predicting the electromagnetic tunable properties of the IPMC kirigami metasurfaces, respectively. Subsequently, large‐area IPMC kirigami metasurfaces are proposed and produced by using programmable nanosecond laser micro‐processing technique that endows the uniformity of the kirigami units. Finally, the electromagnetic functionalities of these IPMC kirigami metasurfaces are researched and validated by experiments and numerical simulations. Both theoretical and experimental results demonstrate that the electromagnetic transmission frequency of the fabricated IPMC kirigami metasurface with 10 × 10 units can be tuned from 19.3 to 20.8 GHz by the application of a low voltage of 3 V. Compared with the existing reconfigurable metasurfaces, the proposed IPMC kirigami metasurface demonstrates clear advantages in its compact structure, lower driving‐voltage, low‐acoustic noise, and wide working frequency range.

Survey of Wideband Acoustic Immittance Use by Clinical Audiologists.

Wideband acoustic immittance (WAI) is a promising measure of middle-ear mechanics. In contrast to standard tympanometry, which is generally measured at a single stiffness-dominated low frequency, WAI detects mechanical effects on both the mass and stiffness properties of the middle ear across a wide range of frequencies, resulting in a more comprehensive assessment of middle-ear mechanics in healthy and pathological ears. Despite a plethora of research demonstrating the clinical utility of this measure, clinical adoption of WAI is still limited. This work explores audiologists' use and perceptions of WAI, with the goal of identifying the barriers to its clinical adoption. A survey on the perception and use of WAI by clinical audiologists in the United States was developed and administered using the Research Electronic Data Capture application. The survey was distributed broadly across the United States. Participation was voluntary and anonymous, and no compensation was provided. Findings from 132 survey respondents across 32 states were included in the analyses. Overall, findings suggest the largest barriers to clinical adoption of WAI are lack of access to equipment that measures WAI and lack of training and/or confidence in measuring or interpreting WAI. Several barriers to clinical adoption of WAI were identified. However, findings also provide optimism in that audiologists utilizing WAI find it more useful than standard tympanometry, and most audiologists who do not currently use WAI are open to implementing the measure in their clinical practice. We proposed steps to address the highest priority issues and increase the clinical viability of WAI.

A pulsed bipolar current-mode power supply with high power factor in a single stage for dielectric barrier discharge application

Purpose Dielectric barrier discharge (DBD) is widely used in the treatment of skin disease, surface modification of material and other fields of electronics. The purpose of this paper is to design a high-performance power supply with a compact structure for excimer lamps in electronics application. Design/methodology/approach To design a high-performance power supply with a compact structure remains a challenge for excimer lamps in electronics application, a current-source type power supply in a single stage with power factor correction (PFC) is proposed. It consists of an excitation voltage generation unit and a PFC unit. By planning the modes of the excitation voltage generation unit, a bipolar pulse excitation voltage with a high rising and falling rate is generated. And a high power factor (PF) on the AC side is achieved by the interaction of a non-controlled rectifier and two inductors. Findings The experimental results show that not only a high-frequency and high-voltage bipolar pulse excitation voltage with a high average rising and falling rate (7.51GV/s) is generated, but also a high PF (0.992) and a low total harmonic distortion (5.54%) is obtained. Besides, the soft-switching of all power switches is realized. Compared with the sinusoidal excitation power supply and the current-source power supply, the proposed power supply in this paper can take advantage of the potential of excimer lamps. Originality/value A new high-performance power supply with a compact structure for DBD type excimer lamps is proposed. The proposed power supply can work stably in a wide range of frequencies, and the smooth regulation of the discharge power of the excimer lamp can be achieved by changing the switching frequency. The ideal excitation can be generated, and the soft switching can be realized. These features make this power supply a key player in the outstanding performance of the DBD excimer lamps application.

Polarization of disk electrodes in high-conductivity electrolyte solutions.

We investigate the polarization of disk electrodes immersed in an electrolyte solution and subjected to a small external AC voltage over a wide range of frequencies. A mathematical model is developed based on the Debye-Falkenhagen approximation to the coupled Poisson-Nernst-Planck equations. Analytical techniques are used for predicting the spatial distribution of the electric potential and the complex impedance of the system. Scales for impedance and frequency are identified, which lead to a self-similar behavior for a range of frequencies. Experiments are conducted with gold electrodes of sizes in the range 100-350 μm immersed in a high-conductivity KCl solution over five orders of magnitude in frequency. A collapse of data on impedance magnitude and phase angle onto universal curves is observed with scalings motivated by the mathematical model. A direct comparison with the approximate analytical formula for impedance is made without any fitting parameters, and a good agreement is found for the range of frequencies where the analytical model is valid.

Effect of magnetic field on impedance characteristics in manganese sulfide Mn0.9S

Manganese sulfide with a lack of manganese cations in the lattice is being studied. Samples that are single-phase and have a cubic structure have been certified. The impedance components were measured over a wide range of frequencies and temperatures without a magnetic field and in a magnetic field. The real and imaginary parts of the impedance as a function of temperature are described in the Debye model. The relaxation time of current carriers is found from the impedance hodograph. The change in impedance components in a magnetic field is described in a model of an inhomogeneous electrical medium.

Fe-based amorphous powder cores with low core loss and improvement of permeability

Fe-based amorphous powder cores of Fe–Si–B–Cr–C magnetic powder and phenolic binder were fabricated, and the effects of annealing and compaction pressure on the soft magnetic properties and core loss were investigated. The formation of Fe–B and α-Fe (Si) phases was confirmed at the annealing temperature above 773 K. The density gradually increased from 5.3 to 5.5 g/cm3 as annealing temperature increased, resulting in the saturation magnetization 4πMs increased to 1.0 T at 773 K. The effect of compaction pressure was studied by using samples annealed at 723 K. Both the density and 4πMs enhanced with compaction pressure from 980 to 1960 MPa. The real part of permeability µ’ remained constant for the frequency up to 2 MHz. The initial value of µ’ increased from 25 to 38 with compaction pressure. Consequently, at Bm of 50 mT and frequency of 100 kHz, the considerably low core loss of 67 kW/m3 was obtained. The low core loss and moderately high permeability of Fe–Si–B–Cr–C amorphous powder core across a wide frequency range indicate its potential for application in high frequency electronic components.

Capacitive Bionic Magnetic Sensors Based on One-Step Biointerface Preparation.

Magnetic biomolecule-based bionic magnetic field sensors are anticipated to open up novel pathways for magnetic field detection. The detection range and accuracy of current bionic magnetic field sensors are limited, and little work is based on the capacitive response principle. We successfully developed a biochemical interface with an extralarge target-receptor size ratio, which can be manufactured in a single step for weak magnetic field detection across a wide frequency range, and we used electrochemical capacitance as a magnetic field change conduction strategy. The thickness-controllable nanoscale bovine serum albumin/graphene layer on an indium tin oxide working electrode combines with the one-step preparation method to immobilize the MagR/Cry4 complex. This capacitive bionic magnetic sensor can achieve the detection range of 0-120 mT. This biointerface design strategy obtains the further improvement of the performance of this bionic magnetic field sensor. Furthermore, the biointerface construction and optimization methodology in this proposal has potential applications in the design of other medical biosensors.

Some statistical properties of aeolian saltation

Aeolian sediment transport is a process that commonly occurs on celestial bodies with atmospheric layers and solid surfaces. At present, it is very difficult to predict the instantaneous mass flux accurately. For the purpose of statistical prediction, the near-surface saltating grain count and the wind velocity above the saltation layer are synchronously measured in two dune fields. The duration and intensity of the saltation event obey exponential distribution, whereas sand transportation via saltation events with a smaller probability for a longer duration is significant. It is found for the first time that the Hilbert marginal energy spectrum of mass flux density follows the “−1” power law in a wide frequency range. In addition, the timescales of the energy-containing mass flux density mode and the strong wind–sand interaction of fluctuations are determined.

Frequency-dependent physical parameters, the voltage-dependent profile of surface traps, and their lifetime of Au/(ZnCdS-GO:PVP)/n-Si structures by using the conductance method

In this study, frequency-dependent physical parameters, voltage-dependent of surface traps/states, and their lifetime of the Au/(ZnCdS-GO:PVP)/n-Si (MPS) type structures were investigated by using conductance measurements (Y = 1/Z = G + jωC) both in wide range frequency (3 kHz-3 MHz) and voltage (from − 4.00 V to 1.50 V). Firstly, basic physical parameters such as density of doping donor atoms (ND), diffusion potential (VD), Fermi-energy (EF), barrier height ΦB(C-V), depletion-layer thickness (WD), and maximum electric field (Em) were calculated from these measurements for each frequency. These values were found as 1.69 × 1016 cm−3, 0.444 eV, 0.193 eV, 0.606 eV, 1.31 × 10−5 cm, 7.66 × 104 V/cm for 10 kHz, and 1.42 × 1016 cm−3, 0.461 eV, 0.198 eV, 0.628 eV, 1.46 × 10−5 cm, 7.80 × 104 V/cm for 3 MHz, respectively. While ND decreases with increasing frequency, the other parameters increase. The density of surface states (Nss) and their lifetimes (τ) were also obtained from conductance techniques. While the Nss were changed between 2.78 × 1012 at 0.40 V and 2.61 × 1012 eV-1cm−2 at 1.3 V, and the Nss-V curve shows two distinctive peaks which correspond to 0.5 V (2.87 × 1012 eV−1cm−2) and 1.2 V (2.68 × 1012 eV−1cm−2), respectively. The values of τ were changed between 105 µs (at 0.4 V) and 15.3 µs (at 1.3 V) and decreased with increasing voltage as exponentially. These lower values of Nss were attributed to the used (ZnCdS-GO:PVP) interlayer.

Performance of a combined electrotrophic and electrogenic biofilm operated under long-term, continuous cycling.

Evaluate electrochemically active biofilms as high energy density rechargeable microbial batteries toward providing persistent power in applications where traditional battery technology is limiting (, remote monitoring applications). Here we demonstrated that an electrochemically active biofilm was able to store and release electrical charge for alternating charge/discharge cycles of up to 24h periodicity (50% duty cycle) with no significant decrease in average current density (0.16 ± 0.04 A/m2) for over 600days. However, operation at 24h periodicity for > 50days resulted in a sharp decrease in the current to nearly zero. This current crash was recoverable by decreasing the periodicity. Overall, the coulombic efficiency remained near unity within experimental error (102 ± 3%) for all of the tested cycling periods. Electrochemical characterization here suggests that electron transfer occurs through multiple routes, likely a mixture of direct and mediated mechanisms. These results indicate that bidirectional electrogenic/electrotrophic biofilms are capable of efficient charge storage/release over a wide range of cycling frequency and may eventually enable development of sustainable, high energy density rechargeable batteries.

Ultrawide-band Wearable Antenna with Uniplanar Compact Electromagnetic Band Gap

Ultrawide-band technology, commonly known as UWB, sends data over a wide frequency range for many applications. WBAN applications use wearable antennas because they have flexible materials and are suitable for telemedicine technology and have many advantages such as small size, lightweight, able to work at a wide enough frequency, easy fabrications, and affordable costs. In this research, the hexagonal patch ultrawide-band monopole planar wearable antenna was designed using Cordura Delinova 2000 textile material for the substrate and copper tape for the groundplane and patch. The Uniplanar Compact Electromagnetic Band Gap (UC-EBG) as a metamaterial was added to the design of the monopole planar antenna in this final project which aims to improve antenna parameters, increase efficiency, and reduce the effects of radiation on the body. From the measurement results on the antenna with the addition of the UC-EBG structure at the bottom of the patch, it produces a 6% fractional bandwidth increase and able to work in the frequency range of 3-10 GHz off-body conditions and 2-11 GHz on-body conditions. In the SAR test at 45 mm, it was found that the value decreased from previously 1.535 W/Kg to 1.31 W/Kg at a frequency of 3.5 GHz and previously from 1.421 to 1.267 W/Kg at a frequency of 5 GHz on a wrist phantom object which is a good value for SAR. The resulting increase in antenna gain after the addition of the UC-EBG structure. The radiation pattern on the antenna is bidirectional.

Light-induced nonlinear spin Hall current in single-layer WTe2

In this theoretical investigation, we analyze light-induced nonlinear spin Hall currents in a gated single-layer 1T ′ -WTe2, flowing transversely to the incident laser polarization direction. Our study encompasses the exploration of the second and third-order rectified spin Hall currents using an effective low-energy Hamiltonian and employing the Kubo’s formalism. We extend our analysis to a wide frequency range spanning both transparent and absorbing regimes, investigating the influence of light frequency below and above the optical band gap. Additionally, we investigate the influence of an out-of-plane gate potential on the system, disrupting inversion symmetry and effectively manipulating both the strength and sign of nonlinear spin Hall responses. We predict a pronounced third-order spin Hall current relative to its second-order counterpart. The predicted nonlinear spin currents show strong anisotropic dependence on the laser polarization angle. The outcomes of our study contribute to a generalized framework for nonlinear response theory within the spin channel will impact the development of emerging field of opto-spintronic.

Principle of signal-to-noise ratio direct measurement

The sensitivity of radio receivers and other systems used in all fields of practical applications of electronics is carried out at certain signal-to-noise ratio value. Examples of systems, for which this ratio is one of the important qualitative indicators, are given. The aim of the investigation is to solve the actual problem of signal-to-noise ratio measurement in a wide range of frequencies, simplify instruments and improve their technical and metrological parameters. A principle of signal-to-noise ratio measurement has been proposed, its theoretical foundation has been given. Precise relationship between the signal-to-noise ratio and the parameters of noise amplitude, phase and frequency modulation has been established, thus modulation meters can measure signal-to-noise ratio. There are three options for implementing the developed measurement principle. All of them use one existing industrial modulation meter and provide direct signal-to-noise ratio. For two options there are no restrictions on the origin and type of noise, it may be arbitrary. A pilot test of the measurement principle was conducted, and three implementation options were actually tested. Their discrepancies with the original data of the signal and noise generator lie within error limits of the instrumentation of the former. Mathematical modeling of the principle of signal-to-noise ratio measurement in Mathcad software package was also carried out. Recommendations on the use of the principle are given. The fundamental advantages of the developed principle consist of simple implementation by a single industrial instrument and solving the problem of metrological ensuring of signal-to-noise measuring instruments using the existing state verification plans. The main technical and metrological characteristics obtained by using the principle are determined by parameters of existing modulation meters and are proven to be high, the frequency range is till 26,5 GHz and the measurement error is as low as 8 %.