Resonant Research Articles

Influence of flexoelectricity on coupled electromechanical response of 2D MXene/graphene-based hybrid piezocomposites.

This study investigates the influence of flexoelectricity on the coupled electromechanical behavior of MXene/graphene-based hybrid piezocomposite (MGHPC) plates. We developed an analytical model based on Navier's solution and Kirchhoff's plate theory, as well as an approximate model based on the Ritz method for validation purposes. A three-phase micromechanical modeling is developed for determining the effective properties of MGHPC composed of 2D MXene and graphene nano-reinforcements embedded in an epoxy matrix. These micromechanical models were implemented to predict the static and dynamic electromechanical response of MGHPC plates subject to various edge support and loading conditions. Both the analytical and approximate solutions provided unequivocal evidence of the profound impact of the flexoelectric effect on the bending and modal analysis of MGHPC nanoplates. The flexoelectric effect enhanced the stiffness of the nanoplate, irrespective of the support condition. This implies that MGHPC plates can be tailored for precise resonance frequencies and static deflection within nanoelectromechanical systems. This can be achieved by manipulating parameters such as boundary conditions and geometric attributes, including plate thickness/aspect ratio and graphene/MXene nano-reinforcements volume fractions.

MEMS fast steering mirror with a large optical aperture and high surface quality for free-space optical communication

This work presents a MEMS fast steering mirror fabricated by an 8-inch AlScN platform, with a large optical aperture of up to 10 mm and high surface quality (RMS < 20 nm, PV < 120 nm), intended for free-space optical communication. The device comprises a high reflective mirror plate, a pillar and four cantilever beams with AlScN thin films. This device is prepared by a wafer-level eutectic bonding process. A reinforcement structure is proposed to increase the resonant frequency and the resistance to deformation. The mechanical performance, including resonant frequency, step response, linearity, and long-term stability are characterized. The maximum tilting angle is 1.38 mrad at 68 V, the settling time is improved from 400 ms in the open-loop control mode to 0.5 ms with the double step algorithm. The relationship of the resonant frequency, surface figure, and the depth of reinforced ribs is studied through characterizing devices with different depths of reinforced ribs. The bonding quality and the mutual melting states of bonding layers interface are investigated.

Linear and Nonlinear Optical Properties of Symmetric and Asymmetric Double Triangular Quantum Dots Withinside the Presence of Magnetic Field

AbstractLinear and third‐order nonlinear optical absorption coefficients and relative refractive index changes in symmetric and asymmetric double triangular quantum dots are examined theoretically. The dependence of these optical properties on the magnetic field is examined. After calculating energies and wave functions within the effective mass and parabolic band approaches, analytical expressions of linear and nonlinear optical properties are obtained using the compact density matrix approach and iterative method. Numerical calculations are presented for typical GaAs/AlGaAs material. The results show that the magnetic field causes different effects on the and transitions. Moreover, the calculated results also reveal that the resonance frequency and nonlinear contribution are different in symmetric and asymmetric structures. As a result, it is concluded that the magnetic field plays a vital and important role in the electronic and optical properties of the system and can be used to tune the inter‐subband transitions and change the corresponding optical sensitivities.

An electromagnetic indirect-driving scanning mirror for wide-field coaxial LiDAR applications

This paper reports an electromagnetic indirect-driving scanning mirror with an enlarged mirror plate (17mm×17mm) supported by high-strength polymer hinges for wide-field coaxial LiDAR (Light Detection and Ranging) applications. An indirect-driving mechanism was developed to achieve large tilting angle through mechanical amplification, while maintaining a relatively high resonance frequency of the enlarged mirror plate. A prototype mirror was designed, fabricated, and tested. A Hall scan position sensor was integrated to monitor the pose of the mirror in real time. The testing results show a coupled resonance frequency of 54.9 Hz with an optical tilting angle of ±60°, corresponding to a field of view (FoV) of 120°. A wide-field coaxial LiDAR system was also built based on the indirect-driving scanning mirror, and 2D imaging was demonstrated.

Resolving the Role of Configurational Entropy in the Optimization of Mechanical, Thermal, and Microwave Dielectric Properties of SrLa(Al0.50-xGaxZn0.125Mg0.125Ti0.25)O4 Ceramics.

The demand for high-performance microwave dielectric ceramics has surged with the proliferation of fifth-generation (5G) communication networks. In this work, SrLa(Al0.50-xGaxZn0.125Mg0.125Ti0.25)O4 (x = 0-0.20) ceramics were designed by leveraging the unique properties of SrLaAlO4 ceramics and high-entropy engineering. The effects of configurational entropy (Sconf = 1.23R - 1.54R) on the mechanical, thermal, and microwave dielectric properties of SrLa(Al0.50-xGaxZn0.125Mg0.125Ti0.25)O4 ceramics were investigated. X-ray diffractometer and transmission electron microscope analyses confirmed that each composition belonged to the tetragonal structure with a space group of I4/mmm. Significant improvements in Vickers hardness were observed with increasing Sconf, reaching 8.05 GPa at Sconf = 1.54R compared to 5.64 GPa in SrLaAlO4 ceramics. Additionally, the increasing entropy showed great potential in reducing the thermal expansion coefficient (CTE) from 12.32 to 11.49 ppm/°C. The optimal quality factor (Q × f) of 98,000 GHz was achieved at Sconf = 1.37R, attributed to the optimization of intrinsic lattice energy and infrared-damped modes. The temperature coefficient of resonant frequency (τf) was successfully modified toward zero due to entropy-driven CTE and structural modifications. Excellent microwave dielectric properties with εr = 22.5, Q × f = 98,000 GHz, and τf = -2.0 ppm/°C were obtained at Sconf = 1.37R. This work highlights the potential of entropy-engineering in developing high-performance microwave dielectric ceramics, offering a promising pathway for the advancement of 5G communication components.

A novel performance prediction method for harmonic reducers based on the trend-enhanced Fisher’s discriminant ratio-Wiener process

Abstract Harmonic reducers, as core components of industrial robots, play a critical role in maintaining robot health. Performance degradation assessment (PDA) and remaining useful life (RUL) prediction are essential for ensuring the operational reliability of such robots. To address the multistage characteristics and stochastic uncertainties in the performance degradation of harmonic reducers, a performance prediction method based on Fisher’s discriminant ratio and Wiener process is proposed. Firstly, the health indicator (HI) construction is defined as an optimization problem based on Fisher’s discriminant ratio and trend monotonicity constraints. By leveraging the sum of the multiplication of frequency amplitudes and optimized weights, precise segmentation of the multistage degradation process over the entire lifecycle is achieved. Notably, the optimized weights can automatically identify the resonance frequency bands caused by damage. Subsequently, a nonlinear Wiener process model with a drift coefficient in the form of a power function is established. The probability density function (PDF) expression for RUL is derived based on the concept of first hit time (FHT). Additionally, a logarithmic likelihood function (Log-LF) for the unknown parameters in the degradation model is constructed. The experimental results indicate that the proposed method surpasses the other two Wiener process models in terms of root mean square error (RMSE), mean absolute percentage error (MAPE), and cumulative relative accuracy (CRA). This provides robust support for preventive maintenance decision-making for harmonic reducers.

Harmonic Vibration Analysis in a Simplified Model for Monitoring Transfemoral Implant Loosening.

A simplified axisymmetric model of a transfemoral osseointegration implant was used to investigate the influence of the contact condition at the bone-implant interface on the vibrational response. The experimental setup allowed the degree of implant tightness to be controlled using a circumferential compression device affixed to the bone. Diametrically placed sensors allowed torsional modes to be distinguished from flexural modes. The results showed that the structural resonant frequencies did not shift significantly with tightness levels. The first torsional mode of vibration was found to be particularly sensitive to interface loosening. Harmonics in the vibrational response became prominent when the amplitude of the applied torque increased beyond a critical level. The torque level at which the third harmonic begins to rise correlated with implant criticality, suggesting a potential strategy for early detection of implant loosening based on monitoring the amplitude of the third harmonic of the torsional mode.

Wideband circularly polarized dielectric resonator antenna with multi-functional metasurface assistance for low profile

ABSTRACT A low-profile broadband circularly polarized (CP) dielectric resonator antenna (DRA) is proposed, utilizing DR reutilization and metasurface (MS) techniques. Two resonant frequencies and an AR minimum are achieved simultaneously, by exciting a rectangular DR with an inclined corner-truncated coupling slot, for it generates nearly degenerated TE111 modes. For significant bandwidth enhancement and low profile, a new resonator is formed by reusing the DR and loading an MS above, which works in orthogonal TM modes. To increase the axial ratio bandwidth (ARBW) further without enlarging the antenna size， two parasitic patches are printed on two adjacent side walls of the DR. To verify the rationality and feasibility, the antenna is fabricated and measured. The fabricated prototype possesses the profile of 0.06λ 0 (λ 0 is the free-space wavelength at the center frequency). The measured impedance bandwidth (IBW) and ARBW are 36.05% (4.23 ~ 6.09 GHz) and 22.46% (4.9 ~ 6.14 GHz), respectively. The proposed antenna has both broadband characteristics and a low profile, making it easy to integrate into space-limited wireless communication systems with high data rates.

GAIT PATTERN INVESTIGATIONS OF BIONIC PIEZOELECTRIC ROBOT

The development of micro-robots based on bionic motion has garnered increasing attention with the advancement of bionic technology. These micro-robots can be employed in various tasks, such as military applications, disaster search and rescue, in vivo drug delivery, minimally invasive surgery, and tumor treatment. Robot joint motion is commonly achieved through actuators, which encompass motor, hydraulic, or pneumatic components that often carry excessive weight. To achieve the goal of miniaturizing robotic mechanisms, innovative actuators need to be developed. This study focuses on designing a four-limbed micro-robot that utilizes piezoelectric actuators. Automatic Dynamic Analysis of the Mechanical System is employed to investigate the kinematic aspects of the micro-robot’s motion, and finite element analysis is also used to obtain the resonant characteristics of the limbs actuated by piezoelectric bimorphs. The results indicate that the gait pattern of a piezoelectric robot changes according to the walking strategy and the robot dimension. The forward travel speed varies depending on the gait pattern, and adjustments in gait design can reduce the up/down oscillation and right/left offset. The robot’s travel speed increases with both trunk and limb length, although longer thigh and leg lengths might lead to greater offset and vertical oscillation. The resonant frequency and mode shapes change with the limb structure and affect the limb motion style. By adjusting the driving frequency of the bimorph actuators, the gait pattern can be manipulated. The information presented in this study contributes to a deeper understanding of micro-robot design.

A Novel Approach of the Viscoelasticity of Axially Functional Graded Bar and Application of Harmonic Vibration Analysis of an Isotropic Beam as Support

The use of smart materials and passive controllers in modern technologies has stimulated the study of vibration in elastic systems with viscoelastic damping. It is also possible to create components with precise material distribution coefficients and distinct properties, such as Functionally Graded Materials. This work investigates the resonant frequency characteristics of a beam supported at its ends by Axially Functionally Graded (AFG) viscoelastic bars using the finite element method. The set of equations governing motion is obtained by assuming Euler–Bernoulli beam theory for the beam and bar theory for the bars using Lagrange’s equations. The material properties of the functionally graded bar is assumed to vary through the length according to the power law distribution. The longitudinal loss factor values are used to define the internal damping coefficient, which is also dependent on the Young’s modulus value varying along the bar. The effects of the length-varying material properties and internal damping of the FG support bars on the force transmission TR and frequency parameters λ are examined in detail. No study has been found in the literature on the vibration of viscoelastic FG bar-supported beams subjected to a harmonic force at the centre point. It is shown that using bars formed with combinations of different materials considering material damping will be useful to keep the vibration level and force transmission at a certain value and control the frequency parameters.

Experimental investigation on the three-dimensional liquid sloshing behavior in an offshore circular cylindrical container

A series of experimental cases are conducted to explore the three-dimensional sloshing response in a cylindrical container under lateral excitation. When the forcing frequency is in the vicinity of the resonance frequency of the lowest asymmetric mode (1, 1), three different wave regimes are observed: planar, irregular and swirling. The results of the wave regimes at the second asymmetric mode (1, 2) exhibit a number of similarities to those at the mode (1, 1), such as the generation of irregular mode and swirling mode at the forcing frequency close to the resonance frequency of mode (1, 2). The present experiments also exhibit some spectacular phenomena that are unique to the resonant sloshing at the mode (1, 2). In particular, when the sloshing wave builds up sufficient energy, the energy will be transferred to adjacent natural modes, i.e., (3, 1) and (2, 2). As a consequence, the motion of the sloshing wave is dominated by three natural modes and exhibits very complicated wave patterns.

Shear horizontal wave propagation on a piezoelectric substrate with periodic gradient local resonant metasurfaces

In this paper, analytical solutions for shear horizontal (SH) waves propagating in a piezoelectric (PE) substrate with periodic gradient mass oscillators are obtained. Both wave-mode method and spectral method are used to obtain the dispersion equation of SH waves. The influences of mass-spring oscillators on dispersion curves and the wave mode shapes are discussed via numerical examples. It reveals that the numerical results obtained by wave-mode method and spectral method are well matched. In addition, the mass-spring oscillators have evident effects on the propagation characteristic of SH waves, and the effects are closely related with the frequency. Moreover, the widths of the local resonant and Bragg resonant bandgaps become evident wider when oscillator's natural resonance frequency is close to the Bragg scattering frequency. In particular, based on our proposed structure, we can design a sensor with advantages such as filtering and only sensitive to specific frequencies, amplify lossless signals and multi frequency sensitivity.

Magnetoelectrics for Implantable Bioelectronics: Progress to Date.

ConspectusThe coupling of magnetic and electric properties manifested in magnetoelectric (ME) materials has unlocked numerous possibilities for advancing technologies like energy harvesting, memory devices, and medical technologies. Due to this unique coupling, the magnetic properties of these materials can be tuned by an electric field; conversely, their electric polarization can be manipulated through a magnetic field.Over the past seven years, our lab work has focused on leveraging these materials to engineer implantable bioelectronics for various neuromodulation applications. One of the main challenges for bioelectronics is to design miniaturized solutions that can be delivered with minimally invasive procedures and yet can receive sufficient power to directly stimulate tissue or power electronics to perform functions like communication and sensing.Magnetoelectric coupling in ME materials is strongest when the driving field matches a mechanical resonant mode. However, miniaturized ME transducers typically have resonance frequencies >100 kHz, which is too high for direct neuromodulation as neurons only respond to low frequencies (typically <1 kHz). We discuss two approaches that have been proposed to overcome this frequency mismatch: operating off-resonance and rectification. The off-resonance approach is most common for magnetoelectric nanoparticles (MENPs) that typically have resonance frequencies in the gigahertz range. In vivo experiments on rat models have shown that MENPs could induce changes in neural activity upon excitation with <200 Hz magnetic fields. However, the neural response has latencies of several seconds due to the weak coupling in the off-resonance regime.To stimulate neural responses with millisecond precision, we developed methods to rectify the ME response so that we could drive the materials at their resonant frequency but still produce the slowly varying voltages needed for direct neural stimulation. The first version of the stimulator combined a ME transducer and analog electronics for rectification. To create even smaller solutions, we introduced the first magnetoelectric metamaterial (MNM) that exhibits self-rectification. Both designs have effectively induced neural modulation in rat models with less than 5 ms latency.Based on our experience with in vivo testing of the rectified ME stimulators, we found it challenging to deliver the precisely controlled therapy required for clinical applications, given the ME transducer's sensitivity to the external transmitter alignment. To overcome this challenge, we developed the ME-BIT (MagnetoElectric BioImplanT), a digitally programmable stimulator that receives wireless power and data through the ME link.We further expanded the utility of this technology to neuromodulation applications that require high stimulation thresholds by introducing the DOT (Digitally programmable Overbrain Therapeutic). The DOT has voltage compliance up to 14.5 V. We have demonstrated the efficacy of these designs through various in vivo studies for applications like peripheral nerve stimulation and epidural cortical stimulation.To further improve these systems to be adaptive and enable a network of coordinated devices, we developed a bidirectional communication system to transmit data to and from the implant. To enable even greater miniaturization, we developed a way to use the same ME transducer for wireless power and data communication by developing the first ME backscatter communication protocol.

Design of the Helmholtz resonators assembly for optimizing the broadband sound absorption of acoustic metasurface

The acoustic metasurface (AMS) can give a broadband sound absorption by a planar periodic array assembling small Helmholtz resonators tuned at different resonant frequencies, which work as unit cells which have equivalent small area to a fraction of the wavelength. The author has suggested that the broadband flat sound absorption is obtained by the AMS assembling the small Helmholtz resonators of more quantities at the lower resonant frequencies in the target frequency range. Their resonant frequencies are ordinary tuned by parameters of an airtight cavity with a multiple folded long neck reaching to the opening on the sound incident surface, which have a longer neck for a lower resonant frequency in this study. The formulation for the sound absorption coefficient of the AMS referring to the prior study shows the flat and nearly perfect sound absorption in one octave band with its center frequency of 125 Hz, 250 Hz and 500 Hz. Numerical case studies suggests that the area ratio of unit cells for the flat sound absorption of the AMS is formulated as a power function of frequency ratio to the center frequency and that its formulation will be identical for any center frequency.

Influence of randomly placed resonant aggregates on the attenuation properties of metaconcrete: A numerical study

Concrete is a key material for many structural components in engineering, but its acoustic performance remains under discussion. Hence, the potential of the so-called metaconcrete has gained attention in research, mainly due to its capability to control vibrations and sound transmission when resonant aggregates are embedded in the concrete. These resonant aggregates are designed to have resonant frequencies regarding frequency bands of interest, so the interaction with the incident sound waves is attenuated within those frequencies. While available research has focused on the characterization of metaconcrete with a periodic arrangement of resonant aggregates, there is a gap regarding how their random allocation affects the characterization of metaconcrete. This study focuses on the numerical analysis of metaconcrete and the influence of randomly placed resonant aggregates on its attenuation properties. The numerical approach concentrates on the aggregate's material composition, location and volume fraction within the concrete to identify configurations that exhibit great wave attenuation. The results have shown that the attenuation effect is substantially advantageous when using a multi-frequency configuration for aggregates within the metaconcrete. Additionally, the random embedding of resonant aggregates offers a practical solution for their application in concrete structures.

A piezoelectric acoustic black hole absorber for rail vibration reduction and energy harvesting: Semi-analytical model

Theoretically, vibration energy can be converted and harvested during the process of vibration reduction, thus enabling a self-powered supply for sensor nodes. However, little research was reported on rail absorbers that combine vibration reduction and energy harvesting. Accordingly, this study aims to design an absorber based on the acoustic black hole (ABH) effect, termed the P-ABH absorber, that can simultaneously achieve broadband vibration reduction and energy harvesting. Firstly, the P-ABH absorber was preliminarily designed, and the semi-analytical model of the track with the P-ABH absorber was established by the Rayleigh-Ritz method. Secondly, the semi-analytical model was verified by the 3D finite element method, and the vibration reduction and energy harvesting performance were initially evaluated. The dimensions of the ABH structure, along with the sizes of the piezoelectric patches, were then determined. Finally, the vibration reduction and energy harvesting performances of the P-ABH absorbers fully deployed between each fastener were evaluated. The results demonstrated that the P-ABH absorber exhibited a wider vibration reduction bandwidth than the uniform piezoelectric absorber and the piezoelectric patches, with an increase in energy harvesting power by 27.47 % and 115.26 %, respectively. The vibration reduction and energy harvesting performance were significantly affected by the number of piezoelectric patches but little affected by the thickness and total length. When the P-ABH absorbers were fully attached to the rail, the overall mean square velocities at the three resonant frequencies, which required emphatic control, were reduced by 36.77 %, 98.37 %, and 3.52 %, respectively. Meanwhile, the energy harvesting performance was excellent. The P-ABH absorber presents a promising solution for improving the sustainability and cost-effectiveness of track systems.

Experimental analysis of Local Defect Resonance in an aluminum plate

In the context of non-destructive evaluation and testing of structures, the use of Local Defect Resonance is promising for the detection of delamination-type defects in composites. In this context, an experimental analysis Local Defect Resonance is proposed. It is here carried out on a model system: a thin aluminum plate with a Flat Bottom Hole (FBH) defect consisting in a self-adhesive aluminum sheet (a shim) adhesively bonded over a circular through hole. First, the local defect resonance frequencies and mode shapes are analyzed assuming linear vibrations of the structure. Then, a nonlinear approach is used to compare two types of FBH defects, a first flawless one and a second one including a damaged area. For this purpose a high amplitude vibration around the resonance frequencies are used in order to generate high order harmonics. This enhancement is identified as associated with mainly quadratic nonlinearity.

Resonant frequencies of multi-layer building constructions: Estimation by measurement of acceleration amplitudes

The Austrian building regulation requirements for impact sound insulation are based on the weighted standardized impact sound pressure level as single-number specification. In recent years, it has become apparent that not only the single-number specification, but the extended frequency range and frequency characteristics of impact sound insulation of constructions can have noticeable influence on the perceived acoustic performance of a construction. Therefore, the Austrian Classification Standard ÖNORM B 8115-5: 2021-04 includes extended requirements on impact sound insulation. It provides two ways for verification of the sound insulation classes A to C. One way is the verification via the resonance frequency of multi-layer constructions. However, there exist as yet no standardized measurement methods for the estimation of the resonance frequency of multi-layer building constructions. In response, in course of this study a new measurement method for the estimation of the resonance frequencies of multi-layer constructions was developed. For this development acceleration measurements were carried out on both surfaces of particularly double-layer building constructions, that were excited with a rubber hammer. From these measurement results, in conjunction with an analytical model, it was possible to derive a measurement method for estimating the resonant frequency via the frequency characteristics of the acceleration amplitudes.

Wideband tympanometry in otitis Media

BackgroundOtitis media with effusion (OME) is one of the most frequent infectious diseases in children and is the most common cause of acquired hearing loss in childhood. Diagnosis of OME is mainly dependent on the single-frequency tympanometry. Wideband tympanometry (WBT) is an emerging technology that has been utilized to overcome the limitations of conventional tympanometric procedures. This study aimed to evaluate the diagnostic value of wideband acoustic absorbance in children suffering from otitis media.MethodsThis study included a control group of 50 children with 100 ears with bilateral normal peripheral hearing and bilateral normal middle ear function and a study group which included 100 children with 176 ears complaining of otitis media. Measures included subjects history, basic audiological evaluation and wideband tympanometry. Resonant frequency, tympanometric peak pressure and middle ear absorbance were measured from wideband tympanometry and compared in both groups.ResultsThere was a statistically significant reduction of resonsnce frequency in the study group in comparison to the control group. Also, there was a statistically significant reduction of tympanometric peak pressure in the study group in comparison to the control group. As regards the absorbance, there was a statistically significant reduction of absorbance in the study group in comparison to the control group at all tested frequencies (250Hz- 8000Hz). The best area under the receiver operating characteristic curve values for diagnosing OM were obtained at all tested frequencies. Data of this work showed that higher values were mainly at 250Hz, 500Hz and 1kHz (0.84, 0.88 and 0.93 respectively).ConclusionFindings of this study suggested that wide band tympanometry can be used efficiently in various degrees of OM.

Environmental noise reduction by sonic crystals barrier

In order to reduce unpleasant effects on human health in environment, recent research has moved towards low-frequency and broadband noise mitigation. However, traditional noise barriers have several common shortcomings: airflow blocking, inefficient noise reduction, visual obstruction. Inspired by the classic design of sonic crystals (SCs), the basic C-shaped unit is improved to replace the conventional vertical outdoor barriers with a compact size. This paper explores the acoustic performance of the shadowed-C-shaped SC both numerically and experimentally. The simulation results show that this novel design can achieve broader band gap in the range below 5000Hz, especially at the resonant frequencies, the transmission coefficients approach to zero. Experiments are carried out with a full-scale model to evaluate the practical application of SC as noise barriers. It is verified that there is a good performance of insertion loss in broadband which is basically consistent with the simulation results.