Resonant Research Articles

Measurement of Pt consumption from Pt electrodes during water electrolysis using the quartz crystal microbalance (QCM) method: Effect of the water electrolysis method and the concentration of chloride ions in the aqueous solution

The consumption of the Pt electrocatalyst, which occurs when aqueous solution with neutral pH is electrolyzed with a Pt electrode to produce hydrogen or oxygen, was measured from the change in resonance frequency using the QCM method. First, it was found that the Pt consumption from the electrode during water electrolysis while applying a steady positive potential was very small, but it was almost proportional to the time the current was applied. Second, when electrolysis was performed by polarity reversal electrolysis of the anode and cathode periodically during electrolysis, the amount of Pt consumed increased in proportion to the number of polarity reversal was exchanged. The Pt consumption obtained by the QCM method was in close agreement with the value obtained by EDX method, proving the validity of the measurement method. The QCM measurement method was also proven to be a reliable method of measurement.

Dual-Polarized Microstrip Antenna With Single-Dimension-Constraint Resonant Frequency

Dual-Polarized Microstrip Antenna With Single-Dimension-Constraint Resonant Frequency

Cross-sectional analysis of timber boards using convolutional long short-term memory neural networks

This paper proposes a one-dimensional convolutional long short-term memory (1D-CNN-LSTM) model for estimating the pith position and average ring width in Norway spruce timber boards. The model predicts these cross-sectional parameters by processing sequences of light-intensity signals derived from optical scans of the board’s four surfaces. The dataset used for training the model consists of synthetic boards sawn from simulated 3D logs. The model was evaluated on a dataset consisting of 552 end cross-sections from actual Norway spruce boards. Comparisons between the automatic and manual pith and ring width estimations demonstrated a very good accuracy. The computational speed of the model was more than twice as fast as the quickest method available in the literature. A large set of boards was then used to determine the advantages of incorporating the automatically determined average ring width in formulating indicating properties for machine strength grading. This evaluation revealed that the average ring width could, in certain situations, compensate for unknown variables such as density or resonance frequency in predicting the tensile and bending strength of Norway spruce boards.

Chain-arranged Ni1-xCox micro/nano particles prepared via a magnetic field-assisted reduction for enhanced electromagnetic wave absorption

Transition metal magnetic alloys have garnered extensive interests in electromagnetic wave absorption due to the remarkable magnetic loss capacity and unique magnetism-frequency characteristics. Herein, we report a novel magnetic absorbent of Ni1-xCox micro chains that synthesized through a magnetic field-assisted reduction method. The precipitated Ni1-xCox particles could be connected and aligned during the magnetic reduction process. Due to the modified electronic structure of the Co active site by Ni, the particle size in the Ni1-xCox micro chains noticeably increases with increased x. Meanwhile, the complex dielectric constants exhibit a decreasing trend, which contributes to the improved impedance matching and higher resonance frequencies. The connected Ni1-xCox micro/nano particles not only benefit to the conductive loss, but also strengthened the polarization loss on the contacted interfaces among the particles. As a result, significantly enhanced electromagnetic wave absorption performance was obtained with the minimum reflection loss of −21.0 dB and the effective absorption bandwidth of 3.92 GHz at a thickness of only 1.35 mm. Overall, this work has demonstrated the strategy of designing aligned bimetallic absorbent, possessing great potentials in improving their microwave absorption properties.

Defect detection using spatial spectral entropy for noncontact acoustic inspection method

Inspection of concrete structures is important for maintaining social infrastructure such as tunnels and viaducts. Therefore, noncontact acoustic inspection method using acoustic irradiation induced vibration and a scanning laser Doppler vibrometer (SLDV) has been devised. Since this method uses flexural resonance, it can be said to be an alternative method for a hammering test. Using our method, internal defects of concrete can be detected up to a depth of about 10 cm from the surface of concrete, even at a distance of about 30 m. However, in a closed space such as an underground cavity, the signal-to-noise (S/N) ratio decreases due to reverberation from the surroundings, making it difficult to detect defects compared to open spaces such as viaducts. This problem can be solved by using spatial spectral entropy (SSE), which extends the concept of spectral entropy to the two-dimensional space of the measurement plane. In other words, by SSE analysis, the resonance frequency of both the defect and the SLDV can be detected and separated because of the difference in the spatial distribution characteristics of the vibration velocity spectrum for each the frequency. Therefore, it is possible to detect a defective part even in a place where the S/N ratio is not sufficient.

A hybrid summation and multiplication displacement amplification mechanism for piezoelectric actuators

Abstract This paper reports a novel amplified piezoelectric actuator featuring compliant displacement amplification mechanism of hybrid summation and multiplication. The hybrid amplification mechanism uses the concept of nesting a pair of Scott-Russell linkages into a toggle linkage to realize the hybrid amplification functions of summation and multiplication. Also, compliant amplification mechanisms with double output ports are designed, enhancing the flexibility of designs and applications. The hybrid displacement amplification principle is mathematically explained in detail. It is demonstrated based on finite element simulations that the displacement amplification ratio, output stiffness and resonance frequency of the proposed hybrid amplification mechanism of summation and multiplication outperform those of the classic rhombus-type and bridge-type compliant mechanisms. The experimental testing results of a prototype show that the amplified piezoelectric actuator is capable of providing 315 μm strokes with the displacement amplification ratio of 16.2. The fundamental resonance frequency with piezoelectric stacks mounted is 1218 Hz. Comparison to typical designs in literature shows well comprehensive performances of statics and dynamics, verifying the advantages of such a hybrid amplification mechanism of summation and multiplication.

Evaluating the Efficacy of Lead-Free Piezoelectric Materials in Microcantilever Based Vibration Energy Harvesters

Abstract The piezoelectric materials have been extensively utilized in various applications, such as sensors, actuators, and energy harvesters. This study evaluates the performance of six lead-free piezoelectric materials- aluminium nitride (AlN), barium titanate (BaTiO3), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), polyvinylidene fluoride (PVDF), and zinc oxide (ZnO) in MEMS-based piezoelectric vibration energy harvesters (PVEHs) using cantilever configurations. Finite element analysis via COMSOL Multiphysics was employed to assess the deflection, voltage, and power outputs of these materials at their resonance frequencies, both with and without proof masses. The results indicate that BaTiO3 and PVDF cantilevers exhibited the highest voltage outputs, reaching 207.14 mV and 202.07 mV, respectively, with AlN also showing comparable performance at 184.72 mV. ZnO-based cantilevers demonstrated the highest power output of 1.35 nW without proof masses and 190.5 nW with proof masses, indicating its potential for high-power applications. The addition of proof masses generally reduced resonant frequencies but enhanced power outputs, like for ZnO. This comprehensive analysis underscores the critical impact of material selection and structural modifications on the efficiency of PVEHs, with BaTiO3, PVDF, and ZnO emerging as the most promising candidates for optimizing energy harvesting devices. This research lays a foundation for further advancements in piezoelectric MEMS technology, aiming for more efficient energy harvesting solutions.

Flexible Hair‐Like Piezoelectric Acoustic Particle Velocity Sensor with Enhanced Sensitivity for Speaker Recognition

AbstractFlexible resonant acoustic sensors exhibit enhanced sensitivity near their resonant frequencies and have attracted increasing interest as essential components for next‐generation human‐machine speech interactions. However, membrane‐based resonant acoustic sensors are bulky owing to the inherently high bending stiffness of the sensing membrane. Inspired by the tiny hair‐based sensitive acoustic receptors of spiders, this study reports a hair‐like piezoelectric resonant acoustic particle velocity sensor (HP‐APVS) that enables highly sensitive sound sensing with a significantly reduced size. The HP‐APVS device is essentially a polyimide cantilever array fabricated using Nb0.02‐Pb(Zr0.6Ti0.4)O3 (PZT) on polyimide and self‐bending processes. The experimental results demonstrate that the HP‐APVS shows a linear response to acoustic particle velocity instead of acoustic pressure, with enhanced sensitivity in the resonance mode. Additionally, the proposed HP‐APVS exhibits an outstanding speaker recognition rate of 95.3% with an error rate reduction of 75% compared with that of a reference commercial microphone, indicating many potential applications in the realms of biometric authentication, voice user interfaces, and other intelligent acoustic electronics.

Frequency selective metasurface based radio frequency glucose sensor with a periodic array of meta cells

Nowadays, the operating principle of most of the experimental electromagnetic glucose sensors is based on the effect of an anomalous dispersion caused by a direct contact between an object under test and a two-dimensional metasurface. Due to the repeated uses, the metasurface will be subjected to a chemical attack over time. To avoid this problem, this work proposes a novel glucose sensor that is equipped with an interfacial dielectric layer of 0.254 mm thickness to separate the object under test and the metasurface. The results of our analysis suggest that, if the interfacial dielectric layer is sufficiently thin, there will be no shortage of sensitivity in the proposed sensor. Consistent with our theoretical prediction, the proposed sensor was found to resonate at 9–10 GHz, with its resonant frequency responding to the glucose concentration in a dose dependent manner. The correlation the resonant frequency shift and the glucose concentration was found to be highly linear over the clinical diabetic range with a sensitivity of 4 MHz/(mg dL−1). However, we could not obtain the same or similar sensitivity when the interfacial layer was substituted with a similar dielectric layer of 1 mm thick. Overall, the presence of the interfacial dielectric layer has not negatively impaired the sensing sensitivity of the glucose sensor if and only if its thickness was sufficiently small. This implication of this work can be advantageously used to tailor the future invivo glucose methodology or other health-care electronic devices.

The impact of exogenous ketone body suppletion on energy and pH balance in skeletal muscle during exercise in chronic heart failure patients: a prospective randomized double-blind cross-over study

Abstract Background Heart Failure (HF) is characterized by impediments in exercise capacity. Disruptions in the energy metabolism of skeletal muscle contribute to this condition. Pre-clinical and clinical evidence showed that reductions in carbohydrate and FA metabolism in HF may be partially overcome by a compensatory increase in ketone body oxidation and suggest that suppletion of ketone bodies (KB) may improve energy metabolism in HF. Purpose We tested the effect of exogenous KB suppletion on energy and pH balance during cycling exercise using 31P Magnetic Resonance (MR) Spectroscopy of the exercising quadriceps muscle in patients with HF. Methods In a randomized, double-blind, placebo-controlled cross-over study, 14 stable HF patients with reduced ejection fraction and diminished exercise capacity underwent maximal exercise testing in a MR scanner fitted with a cycling ergometer after KB or placebo treatment. Phosphocreatine (PCr) and inorganic phosphate (Pi) resonance amplitudes and frequencies were measured continuously in the quadriceps muscle during rest, exercise and recovery using in-vivo 31P MR spectroscopy (Figure 1). Results Patients had a median age of 66 [53 – 75] years, were 14% female, had a median LVEF of 37% [27 – 40] and circulating NT-pro BNP levels of 411 [182 – 946] pg/mL. Peak oxygen uptake (VO2) was 18.2 [15.2 – 20.3] ml/kg/min, which is 68% [62 – 78%] of predicted. After treatment, exercise performance in terms of cycling duration and workload were comparable between treatment arms (Figure 2). Quadriceps acidification during exercise was larger after KB suppletion compared to placebo (ΔpH: -0.2 [-0.3 - -0.1] vs -0.1 [-0.3 - -0.1] respectively; p=0.041) while quadriceps energy depletion during exercise was not altered by treatment (ΔPi/PCr 0.77 [0.55 – 2.51] vs 0.66 [0.46 – 0.81] respectively; p=0.087). Post-exercise mitochondrial oxidative function was similar between treatment arms (KB: PCr resynthesis rate 48 sec [25 – 59] versus placebo: 42 sec [36 – 63]; p=0.767). Conclusions Ketone body suppletion increased acidification and did not improve energy balance in skeletal muscle during exercise or mitochondrial function during recovery in patients with chronic HF. These results question the value of ketone bodies as treatment to boost muscular energy metabolism during exercise in HF.31P MRS Spectrum during exercise in HFExercise and energy parameters

Evaluating stiffness of gastric wall using laser resonance frequency analysis for gastric cancer.

Tumor stiffness is drawing attention as a novel axis that is orthogonal to existing parameters such as pathological examination. We developed a new diagnostic method that focuses on differences in stiffness between tumor and normal tissue. This study comprised a clinical application of laser resonance frequency analysis (L-RFA) for diagnosing gastric cancer. L-RFA allows for precise and contactless evaluation of tissue stiffness. We used a laser to create vibrations on a sample's surface that were then measured using a vibrometer. The data were averaged and analyzed to enhance accuracy. In the agarose phantom experiments, a clear linear correlation was observed between the Young's modulus of the phantoms (0.34-0.71 MPa) and the summation of normalized vibration peaks (Score) in the 1950-4050 Hz range (R2 = 0.93145). Higher Young's moduli also resulted in lower vibration peaks at the excitation frequency, signal-to-noise (S/N) ratios, and harmonic peaks. We also conducted L-RFA measurements on gastric cancer specimens from two patients who underwent robot-assisted distal gastrectomy. Our results revealed significant waveform differences between tumor and normal regions, similar to the findings in agarose phantoms, with tumor regions exhibiting lower vibration peaks at the excitation frequency, S/N ratios, and harmonic peaks. Statistical analysis confirmed significant differences in the score between normal and tumor regions (p = 0.00354). L-RFA was able to assess tumor stiffness and holds great promise as a noninvasive diagnostic tool for gastric cancer.

Second order triple band waveguide band-pass filter with adjustable centre frequency and 3-dB bandwidth

ABSTRACT This paper presents, a novel and simple resonator structure based second order triple band waveguide band-pass filter with adjustable centre frequency and 3-dB bandwidth. The planar insert consists of a circular shape etched part in which three stubs is placed. Three asymmetrical stub length and width are used to control three resonant frequency and 3-dB bandwidth independently. The insert is placed into the transverse plane of the WR-90 waveguide. To achieve second order band-pass filter response two symmetrical resonators is placed at an optimised distance of 8.99 mm. Simulation and optimisation analysis of the proposed filter is carried-out using CST Studio Suite (v23). To validate the 3D model, planar insert and WR-90 waveguide are fabricated individually and inserted manually. The measured results shows triple band bandpass filter characteristics having centre frequencies f 01 = 8.44 GHz, f 02 = 9.98 GHz and f 03 = 11.51 GHz with 3-dB bandwidth of 0.78, 0.12 and 0.3 GHz. The insertion loss of the measured filter is 0.35, 0.8 and 0.55 dB. The in band return loss of the proposed filter are better than 12 dB.

High quality and sensitivity phononic crystal channel drop filter to detect ethyl lactate in mixtures of ethyl lactate and 2-butoxy ethanol

This paper introduces a new sensing approach utilizing a solid-solid phononic crystal (PnC) channel drop filter structure for the detection of varying molar fractions of Ethyl lactate within a mixture of Ethyl lactate and 2-butoxy ethanol. The sensor features a two-dimensional PnC constructed from poly methyl methacrylate as the background material, incorporating a regular arrangement of circular Tungsten columns. The design integrates a bus waveguide linked to two interconnected ring resonators, which are coupled to a drop waveguide. Each ring resonator is equipped with three strategically positioned pillars near the coupling region, allowing for the accommodation of varying concentrations of Ethyl lactate. The sensor’s performance is significantly influenced by the ring resonators and the integrated pillars. It identifies specific resonance frequencies that shift in response to changes in Ethyl lactate concentrations within the resonators. The transmission resonance frequency exhibits valuable sensitivity to these concentration variations, reflecting the unique sound velocities and mass densities associated with each level of Ethyl lactate. The effectiveness of the proposed sensor is validated through coupled mode theory, demonstrating a close match with the device’s observed behavior. The measured frequency range spans from 1.972 MHz to 1.979 MHz with a step size of 1 Hz. Notably, the sensor displays considerable characteristics, including an average quality factor of 90,613, an average sensitivity of 3816 Hz, an average figure of merit of 172, an average signal-to-noise ratio of 137, an average resolution of 22 Hz, an average damping ratio of 0.56 × 10− 5, and an average limit of detection of 34 × 10− 5. These results underscore the potential of the channel drop filter for the accurate detection of Ethyl lactate concentrations with high quality factor and sensitivity. The sensor can effectively identify variations in Ethyl lactate levels, which are prevalent in various applications, including pharmaceuticals and food additives.

Analysis of active impedance characteristics and harmonic deterioration of multiple grid connected inverters considering nonlinear factors

AbstractThe harmonic problems caused by non‐linear factors of the grid connected inverter (GCI) system are more complicated, including both non‐characteristic harmonics emitted by the dead‐time and the changes in harmonic impedance characteristics. Harmonics interact with the changing impedance, and even cause harmonic amplification and resonance. The harmonic deterioration of the multiple GCIs system is serious. To analyse the mechanism and way of harmonic deterioration in grid‐connected system caused by nonlinear factors, the active impedance models of single inverter and multiple GCIs system including dead‐time effect and digital control delay are established first. In view of this, the influence mechanism of non‐linear factors on system stability is explored. The improved modal analysis method is used to traverse the network series parallel resonance caused by nonlinear factors. The results show that both the dead‐time effect and digital control delay reduce phase margin of the system, resulting in the resonant frequency shift and the resonant peak increase. When the harmonic excitation source interacts with the complex network under the influence of nonlinear factors, it will lead to further deterioration of harmonics. Finally, based on the MATLAB and RT‐LAB hardware‐in‐the‐loop simulation platforms, a multiple GCIs system model is built to verify the correctness of the established active impedance model and harmonic deterioration analysis.

The electromagnetic field of a circular parallel plate capacitor excited by an AC current and AC voltage supply

Abstract This study investigates the electromagnetic field (EMF) distribution of an ideal circular parallel plate capacitor excited by a time-harmonic power source. Considering the lead wire and capacitor as a charged whole, we formulate the boundary value problems of the Helmholtz equation for the EMF in the lead wire space and capacitor space, respectively. First, we solve for the EMF generated by the total current in the lead wire space of an AC current. Following this, we solve for the EMF boundary value problem of a capacitor filled with linear, uniform, isotropic, and non-magnetic lossy dielectric under an AC current excitation, using the continuity of the total current as a basis. Second, the EMF distributions in the capacitor space and the lead wire space under an AC voltage excitation are provided, following the principles of the generalized Helmholtz theorem. Third, the EMF distribution is discussed when the electromagnetic ``standing-wave phenomenon" occurs in the ideal dielectric capacitor, and identify the ``resonance phenomenon" and the ``current-stopping phenomenon" of the capacitor's EMF when excited by an AC current and AC voltage, respectively. We also present the corresponding ``resonance frequency" and ``current-stopping frequency". Finally, we explore the quasi-stable solution of the capacitor's EMF under low-frequency condition and the static solutions of the electric and magnetic fields under DC excitation and static voltage excitation. Our findings suggest that the existing formula for the capacitor's EMF approximates our analytical solution under quasi-stable condition.

All-microwave Lamb shift engineering for a fixed frequency multi-level superconducting qubit

It is known that the electromagnetic vacuum is responsible for the Lamb shift, which is a crucial phenomenon in quantum electrodynamics (QED). In circuit QED, the readout or bus resonators that are dispersively coupled can result in a significant Lamb shift of the qubit. However, previous approaches or proposals for controlling the Lamb shift in circuit QED demand overheads in circuit designs or non-perturbative renormalization of the system’s eigenbases, which can impose formidable limitations. In this work, we propose and demonstrate an all-microwave method for controlling the Lamb shift of fixed-frequency transmons. We employ the drive-induced longitudinal coupling between the transmon and resonator. By simply using an off-resonant monochromatic drive near the resonator frequency, we can control the net Lamb shift up to ±30 MHz and engineer it to zero with the drive-induced longitudinal coupling without facing the aforementioned challenges. Our work establishes an efficient way of engineering the fundamental effects of the electromagnetic vacuum and provides greater flexibility in non-parametric frequency controls of multilevel systems.

Wireless Powered Surface Acoustic Wave Platform for Achieving Integrated Functions of Fogging/Icing Protection and Monitoring.

In this study, we introduced an integrated approach using piezoelectric thin film-based surface acoustic wave (SAW) and wireless power transfer (WPT) technologies, designed for both passive monitoring and active defogging/icing functions. We systematically investigated the resonant frequency shifts of ZnO/glass SAW devices, establishing their correlations with variations in humidity and temperature under cold conditions. Acoustic waves generated through the ZnO/glass SAW device were used for defogging and deicing functions with effects of RF powers and acousto-heating thoroughly evaluated. More significantly, the WPT system was successfully applied for achieving defogging and deicing functions, with its performance comparable to that of conventional wired SAW systems. Our findings demonstrated that the WPT SAW system significantly minimizes localized acousto-heating effects, although the time taken for both defogging and deicing was slightly longer than the wired system. This work represents a significant advancement in developing multifunctional, optically compatible, and wireless-integrated solutions for SAW based ice protection.

Specificity of manifestation of nonlinearities for angular oscillations of the reservoir with liquid.

Theproblemabouttransient modes of motion of acylindricalreservoirwiththeliquidwithafreesurfaceon a pendulum suspension under short-time moment pulse applies to reservoir walls is under consideration. The problem is considered in nonlinear combined statement. It was ascertained that manifestation of internal mechanisms of nonlinear interaction between normal modes of oscillations of a liquid differs considerably from the case of harmonic moment disturbance on the resonant frequency. For advanced studying the nature of these differences we study problems about harmonic disturbance of oscillations for the system under the moment with a frequency, which is not resonant and immediately resonant disturbance.

Antenna RCS Minimization Using Load Tuning

Abstract This paper synthesizes antenna RCS using load tuning, beginning with the derivation of the theoretical load impedance to achieve minimum RCS (MRCS) based on antenna radiation and conjugate-matched scattering parameters. This condition is utilized to obtain feasible MRCS zones and minimize backward RCS (BRCS) for the dipole and microstrip patch antennas. The dipole antenna exhibits a full feasible MRCS zone with a BRCS reduction of 77 dB at the resonant frequency, a 63% relative −10dB reduction bandwidth, and a full plane of reduction angles compared to the conjugate-matched condition. However, mismatching of MRCS loading significantly affects the dipole received power. Conversely, the microstrip patch antenna has a feasible MRCS zone that excludes forward directions and demonstrates a negligible mismatching level with a BRCS reduction of 35.5 dB at the resonant frequency, a 0.67% relative reduction bandwidth, a 50° reduction in H-plane, and a 20° reduction in E-plane compared to the conjugate-matched condition. Tuning the load reactance between conjugate-matched and MRCS loadings results in a trade-off between BRCS reduction and the received power. The calculated MRCS load for specific incident direction is applicable for nearby incidence directions, demonstrating applicability with misalignment. The findings validate the efficiency of using load-tuning method with the derived condition to minimize RCS within specific incident angles.

Experimental determination of damping coefficient of a support with elastic ring under harmonic loading

The article describes the possibility of determining the damping coefficient of a support with an elastic ring based on dry friction forces using a special test bench. The forced excitation force is set by the oscillations of a compact speaker installed on top of the oscillating mass through a U-shaped crossbar. The object of the study is a damper with an elastic ring, that is a thin-walled ring with evenly distributed bulges inside and outside, arranged in a checkerboard pattern. The damping coefficient is estimated using a device for simulating a rotor support, an acceleration sensor, an exciter speaker, a controller and a processing station. The amount of damping is estimated according to the width of the peak at the resonant frequency. A comparison is given of the magnitude of the damping coefficient obtained from the analysis of the resonance peak and from the decay rate during the impact experiment.