Resonance Research Articles

Coupling analysis between wave resonance in the moonpool and heave motion of the twin hulls with mooring effect

Fluid resonance in the moonpool formed by two identical rectangular hulls in water waves is investigated by employing the Computational Fluid Dynamics (CFD) package OpenFOAMⓇ. The influence of vertical stiffness on the behavior of moonpool resonance coupling with the heave motion response is presented. Numerical simulations show that the free surface oscillation in the moonpool exhibits a two-peak variation with the incident wave frequency, defined as the first and second peak frequencies. A local Keulegan–Carpenter (KC) number is introduced for describing the influence of fluid viscosity and flow rotation on the fluid resonance and heave motion resonance. At the first peak frequency, the free surface oscillation and heave motion response show an in-phase relationship, where increase in the vertical stiffness can increase the relative motion between them. This finally leads to an increase in the KC number, indicating the increased effect of energy dissipation with increase in the vertical stiffness. At the second peak frequency with an out-of-phase relationship between the free surface oscillation and heave motion response, the variation of the KC number is not sensitive to the vertical stiffness. Correspondingly, the influence of energy dissipation is not strongly dependent on the vertical stiffness.

Resonant Excitation of Kelvin Waves by Interactions of Subtropical Rossby Waves and the Zonal Mean Flow

Abstract Equatorial Kelvin waves can be affected by subtropical Rossby wave dynamics. Previous research has demonstrated the Kelvin wave growth in response to subtropical forcing and the resonant growth due to eddy momentum flux convergence. However, the relative importance of the wave–mean flow and wave–wave interactions for the Kelvin wave growth compared to the direct wave excitation by the external forcing has not been made clear. This study demonstrates the resonant Kelvin wave excitation by interactions of subtropical Rossby waves and the mean flow using a spherical shallow-water model. The use of Hough harmonics as basis functions makes Rossby and Kelvin waves prognostic variables of the model and allows the quantification of terms contributing to their tendencies in physical and wave spaces. The simulations show that Kelvin waves are resonantly excited by interactions of Rossby waves and the balanced zonal mean flow in the subtropics, provided the Rossby and Kelvin wave frequencies, which are modified by the mean flow, match. The resonance mechanism is substantiated by analytical expressions. The Kelvin wave tendencies are caused by velocity and depth tendencies: The velocity tendencies due to the meridional advection of the zonal mean velocity can be outweighed by the zonal advection of the Rossby wave velocity or by the depth tendencies due to Rossby wave divergence. Identifying the resonant excitation mechanism in data should contribute to the quantification of Kelvin wave variability originating in the subtropics. Significance Statement This study seeks to understand how Kelvin waves, which are eastward-propagating disturbances in the tropical atmosphere, are connected to Rossby wave dynamics in the subtropics. Using idealized simulations, the Kelvin wave excitation is explained as a resonance effect due to interactions of Rossby waves and the zonal mean flow. The mechanism contributes to the understanding of atmospheric wave interactions and extratropical effects on the tropics. Further work searching for evidence of the new mechanism in atmospheric data may shed a new light on subseasonal variability in the tropics, such as the Madden–Julian oscillation.

Temperature-dependent properties of wurtzite and rock salt ScxAl1-xN for applications in BAW resonators

Abstract Scandium aluminum nitride (AlxSc1-xN) is known for its tremendous enhancement of piezoelectric properties. This material can improve the energy efficiency of a wide range of applications, for example bulk acoustic wave (BAW) resonators. Such devices heat up during operation and are thus sensitive to temperature-dependent material properties. As a result, device characteristics change with temperature, causing undesirable shifts in achievable frequency and performance. These shifts are well known for AlN-based resonators, where the frequency shifts are compensated without increasing the bandwidth of the frequency filter. For the ternary alloy AlxSc1-xN, many temperature-dependent structural, mechanical and piezoelectric properties have not or have been insufficiently investigated. This review provides an overview of relevant temperature dependent properties of hexagonal wurtzite (x < 0.5) and cubic rock salt AlxSc1-xN (x > 0.5) crystals up to 2000 K. The properties studied are the thermal expansion coefficient (TEC) α, the elastic tensor C ij, the piezoelectric coefficient d 33, the piezoelectric stress coefficient e 33 and the permittivity ε33. Based on these material properties, the derived characteristics for BAW resonators are determined from 0 to 1400 K, which are the resonance frequency f R and the electromechanical coupling coefficient k t 2.

Simulation and experimental analysis of traveling wave resonance of flexible spiral bevel gear system

Considering the traveling wave resonance (TWR) phenomenon of the spiral bevel gear system in the aero engine accessory casing, the flexible spiral bevel gear model is established by three-dimensional (3D) shell element and beam element. The dynamic model of flexible bevel gear system considering the change of meshing teeth pairs in the operating process is established by component mode synthesis (CMS) method and rotational modal projection method. The proposed model is verified by finite element (FE) solid model and experiment test results. On this basis, the TWR phenomenon of the bevel gear system is studied in combination with dynamic response and vibration stress experimental test. The results show that the bevel gear system has 3 nodal diameter resonance speeds within the actual operating speed range, which are one 1st nodal diameter resonance of pinion and two 1st nodal diameter resonance of gear. When the bevel gear system operates at TWR state, the amplitude corresponding to fm ± m·fr (fm is meshing frequency, m is nodal diameter number, fr is shaft rotational frequency) is larger than that corresponding to fm in the Fast Fourier transform (FFT) spectrum of the of the gear foundation vibration stress, and the vibration stress cloud map of the gear foundation shows the corresponding nodal diameter vibration shape. The research results provide a theoretical basis for feature recognition and influence law evaluation of TWR of bevel gear system.

Proton-Coupled Electron Transfer between a Pendant Thiol and a Ferrous Dioxygen Adduct.

The mechanism of thiol oxidation by O2, as catalyzed by ferrous porphyrins, is investigated by trapping intermediates of the transformation at low temperatures and subsequently characterizing them using continuous wave and pulsed electron paramagnetic resonance and resonance Raman spectroscopy. A Fe(III)-O2•- species is initially formed in an iron porphyrin with a pendant thiol functional group, which undergoes proton-coupled electron transfer (PCET) (not HAT) to form an Fe(III)-OOH species. Following O-O bond homolysis, this forms a Fe(IV)═O species with concomitant oxidation of the thiol to an RSO3H group.

Suppression of Nonlinear Chorus Wave Growth by Active Control of Gyroresonant Interactions With Electron Hole Deformation

AbstractNonlinear gyroresonant acceleration is an essential mechanism for the formation of relativistic electrons in Earth's radiation belts, yet we still have only limited knowledge of how electron motion interacts nonlinearly with plasma waves. Here we demonstrate the compelling suppression of whistler‐mode chorus emissions as a resonant wave with energetic electrons by tuning an external transmitter signal in space plasmas. Through forcible modification of electron motions via phase trapping by the external waves, the nonlinear gyroresonant current is suppressed along with the electron hole deformation. Moreover, this can decrease the population of relativistic electrons due to the lack of coherent resonant waves seen by the phase‐organized electrons. Understanding such nonlinear wave suppression effects is crucial for a potential active control of Earth's plasma environment.

Graphene Decorated Shear Horizontal Surface Acoustic Wave Resonator as Humidity Sensor

Graphene Decorated Shear Horizontal Surface Acoustic Wave Resonator as Humidity Sensor

A spurious-free SAW filter employing a novel transducer structure on bulk LiNbO3 substrates

In order to cope with the ubiquitous wireless connections and the rapid transmission of data in communication systems, surface acoustic wave filters are required to have high performance. With a large electromechanical coupling coefficient (K2), conventional bulk 64°YX-LiNbO3 substrates are attractive for low-cost mass production of surface acoustic wave (SAW) resonators. However, the influence of the transverse modes restricts their practical application. In this work, a novel and simple tilted transducer is fabricated, and successfully achieved spurious-free passband SAW filters based on 64°YX-LN piezoelectric substrates. In this work, the transverse modes suppression method is theoretically studied and designed, and the effectiveness of the energy concentrated structure is verified. The optimal tilt IDT angle for eliminating the influence of transverse modes in Al/64 °YX-LN structure is about 6°. Subsequently, based on the above research, three types of tilted resonators were designed and fabricated, which not only verified the reliability of the aforementioned results but also enhanced the performance of the devices, compensating for the deficiency caused by the reduction of the Q factor due to the tilted structure. Finally, based on the double busbar tilted structure, a SAW filter was designed, which has a large 3 dB fractional bandwidth (FBW) and a spurious-free passband. The SAW filter designed in this work has low cost and excellent performance, and can be mass produced. In the field of low-cost RF devices, this work contributes to maintaining the competitive advantage of SAW technology.

Ultrasensitive liquid sensor based on an embedded microchannel bulk acoustic wave resonator

The high-frequency and high-quality factor characteristics of bulk acoustic wave (BAW) resonators have significantly advanced their application in sensing technologies. In this work, a fluidic sensor based on a BAW resonator structure is fabricated and investigated. Embedded microchannels are formed beneath the active area of the BAW device without the need for external processes. As liquid flows through the microchannel, pressure is exerted on the upper wall (piezoelectric film) of the microchannel, which causes a shift in the resonant frequency. Using density functional theory, we revealed the intrinsic mechanism by which piezoelectric film deformation influences BAW resonator performance. Theoretically, the upwardly convex piezoelectric film caused by liquid flow can increase the resonant frequency. The experimental results obtained with ethanol solutions of different concentrations reveal that the sensor, which operates at a high resonant frequency of 2.225 GHz, achieves a remarkable sensitivity of 5.1 MHz/% (221 ppm/%), with an ultrahigh linearity of 0.995. This study reveals the intrinsic mechanism of liquid sensing based on BAW resonators, highlights the potential of AlN/Al0.8Sc0.2N composite film BAW resonators in liquid sensing applications and offers insights for future research and development in this field.

Theoretical investigation of Rayleigh-type surface acoustic waves with high electromechanical coupling coefficient in c-axis-tilted ScAlN film/3C-SiC substrate structure

Surface acoustic wave (SAW) resonators are essential components of mobile communication technology. Advanced performance SAW resonators are needed to support beyond fifth-generation mobile communication technology, which aims to achieve unprecedentedly high data rates and low latency using wide frequency bands in the RF spectrum. This study theoretically investigates the propagation characteristics of a non-leaky Rayleigh-type SAW (RSAW) propagating in a c-axis-tilted ScAlN film/3C-SiC substrate structure. By appropriately selecting the c-axis tilt angle and the film thickness of the ScAlN film, a high electromechanical coupling coefficient (K2) value was obtained in the second-mode RSAW (Sezawa wave). The maximum K2 value for the Sezawa wave was 8.03%, with a phase velocity of 7456 m/s and a power flow angle of 0° under the structural conditions where the K2 value was maximized. These properties offer significant advantages for achieving wide frequency bands, high operating frequencies, and ease of design for SAW resonators. The structural conditions under which good propagation characteristics were obtained in the Sezawa waves were found to coincide with the conditions that maximize the electromechanical coupling coefficient of the quasi-longitudinal wave in the ScAlN film, and a significant increase in the shear vertical component of Sezawa wave particle displacement was observed. Additionally, ScAlN films with a 40% Sc concentration can be fabricated using sputtering and molecular beam epitaxy. Recent advancements have reported the production of high-quality 3C-SiC wafers and large 3C-SiC film/silicon wafers. Therefore, the c-axis-tilted ScAlN film/3C-SiC substrate structure shows great potential as a candidate for next-generation SAW resonators.

Recent Advances in Aluminum Nitride (AlN) Growth by Magnetron Sputtering Techniques and Its Applications

This review explores the processes involved in enhancing AlN film quality through various magnetron sputtering techniques, crucial for optimizing performance and expanding their application scope. It presents recent advancements in growing AlN thin films via magnetron sputtering, elucidating the mechanisms of AlN growth and navigating the complexities of thin-film fabrication. Emphasis is placed on different sputtering methods such as DC, RF, pulsed DC, and high-power impulse DC, highlighting how tailored sputtering conditions enhance film characteristics in each method. Additionally, the review discusses recent research findings showcasing the dynamic potential of these techniques. The practical applications of AlN thin films, including wave resonators, energy harvesting devices, and thermal management solutions, are outlined, demonstrating their relevance in addressing real-world engineering challenges.

A quarter wave infrasonic noise generator

The far-field prediction of infrasonic noise, e.g. from large emitters such as wind turbines, requires precise measurement of the sources. A method to determine the source power based on near-field holography techniques are currently under development in our group. However, tuning the method requires a calibrated infrasound source. In this work, we present the concept of a traceable loudspeaker driven infrasound source using the quarter wave resonator principle in a pipe. The power emitted by the source is measured in situ based on the two-port theory. The infrasonic frequencies can be tuned by adjusting the length of the resonator pipe. Results of the free-field measurements at multiple points at varying distances away from the source are presented. The results suggest that the infrasonic source can be used as a calibrated reference for method development and validation.

Formation and conversion of high-peak-power structured beams by an Nd:YVO4/Cr4+:YAG laser subject to tight-focusing off-axis pumping

A compact Nd:YVO4/Cr4+:YAG passively Q-switched laser in a near-hemispherical resonator is exploited to realize high-peak-power pulsed beams with high spatial degrees of freedom. Beneficial from the advantages of strong intracavity beam focusing as well as the point-like excitation condition for the proposed cavity design, various high-order structured pulses as coherent superpositions of multiple degenerate eigenmodes are stably generated under different off-axis pump schemes. Besides, by employing external-cavity astigmatic mode conversion (AMC), the oval-shaped and chessboard-like structured pulses under on-axis and 1D off-axis pumping are transformed into exotic modes with polygonal and figure-eight-shaped envelopes to further enrich the spatial complexity of the generated fields. With well-defined beam structures that are reconstructed using the analytical resonant wave functions of the resonator, the phase structures of AMC pulsed fields are numerically resolved to present a variety of singularity arrays. Experimental results reveal that the overall peak power of the on-axis and off-axis generated structured pulses respectively exceeds 600 W and 1 kW while maintaining good pulse train stability with peak-to-peak amplitude fluctuation to be less than 10% and 15%.

Performance analysis of shear horizontal one port surface acoustic wave (SAW) resonator for optimal liquid sensing based on finite element method

This paper presents the numerical study using finite element method for optimal liquid sensing performance of one port surface acoustic wave (SAW) resonator. Simulation shows that the extend of IDT-reflector gap can be optimized to contain most of the piezoelectric displacement. Various settings of liquid placement on the mentioned region yield distinct resonant frequency responses of the SAW sensor. For concentrated liquid with higher order of viscosity, magnitude of S-Parameter and phase of the propagating SAW can be applied to sense the liquid solutions. Based on the results, optimal liquid sensing performance of the device can be achieved when liquid droplet sized about 10 % of the aperture is placed in the middle position of the IDT-reflector gap conditioned at 1.5 λ. Using the formulated strategy, the one port SAW device distinguishes well 0 % to 100 % glycerine concentrations compared to limited detection range reported in the previous study. The finding includes equation of liquid turnover viscosity before shift in direction of the changes in S-Parameter measurement. The derived parameters can be set as reference to design the microfludic cell or lab-on-chip based on the one port SAW configuration for optimized liquid sensing performance.

Wave Resonance in the Narrow Gap between Two Boxes under Irregular Wave Actions

Wave Resonance in the Narrow Gap between Two Boxes under Irregular Wave Actions

Parametric resonance of gravitational waves in general scalar-tensor theories

Gravitational waves offer a potent mean to test the underlying theory of gravity. In general theories of gravity, such as scalar-tensor theories, one expects modifications in the friction term and the sound speed in the gravitational wave equation. In that case, rapid oscillations in such coefficients, e.g. due to an oscillating scalar field, may lead to narrow parametric resonances in the gravitational wave strain. We perform a general analysis of such possibility within DHOST theories. We use disformal transformations to find the theory space with larger resonances, within an effective field theory approach. We then apply our formalism to a non-minimally coupled ultra-light dark matter scalar field, assuming the presence of a primordial gravitational wave background, e.g., from inflation. We find that the resonant peaks in the spectral density may be detectable by forthcoming detectors such as LISA, Taiji, Einstein Telescope and Cosmic Explorer.

Gold as a Promising Electrode Material for LiNbO3-on-Insulator (LNOI) SH-SAW Resonators: An Experimental Study.

The need for wideband radio frequency front ends (RFFEs) with next-generation wireless protocols highlights the importance of electromechanical coupling [Formula: see text]. The hetero acoustic layered (HAL) surface acoustic wave (SAW) resonator with aluminum (Al) electrodes has shown superior performance compared to conventional SAW devices. Despite gold (Au) having excellent conductivity and stable properties, its high acoustic absorption and low phase velocity have made it less favorable for electrodes. This work demonstrates that high-performance shear horizontal (SH)-SAW resonators can be fabricated on the lithium niobate-on-insulator (LNOI) platform using a setup specifically designed for an Au electrodes. Experimental validation shows that the device achieves a high quality factor (Q) over 870, excellent [Formula: see text] up to 40%, and operates around 765 MHz. Unwanted transverse spurious modes are suppressed through adequate electrode design, and the temperature stability of LNOI SH-SAW with Au electrodes is discussed. This study highlights gold's potential as an electrode material for high [Formula: see text], clean spectrum, and wideband applications.

Acoustic scattering by smooth and rough elastic cylinders insonified by directional sonars: Bistatic experiments.

Bistatic laboratory measurements are presented for acoustic scattering from both smooth and rough elastic cylinders insonified by directional spherical waves. A scattering model, accounting for incident directional spherical waves while assuming negligible end effects, was derived in a previous article [Mursaline, Stanton, Lavery, and Fischell, J. Acoust. Soc. Am. 154, 307-322 (2023)] but only evaluated for monostatic scattering by smooth cylinders. The evaluation is extended here to bistatic geometries for both smooth and rough cylinders. The effect of axi-symmetric Gaussian roughness (axi-symmetric random variations in cylinder radius) on the cylinder on overall scattering levels and resonances is investigated. Particular emphasis is given to the influence of roughness on the excitation of axially propagating guided wave resonances associated with oblique incident angles. Bistatic laboratory observations presented herein further substantiate the effects on scattering due to the properties of the incident field from practical sonars, such as spherical spreading, as observed in the above-mentioned article. For smooth cylinders, axially propagating guided wave resonances are seen to become more prominent during bistatic in-plane scattering compared to bistatic orthogonal-plane scattering and previously published monostatic data. For rough cylinders, both overall scattering levels and resonances are found to be diminished compared to the smooth case.

Design and fabrication of lithium niobate asymmetrical mode resonators toward C-band and Ku-band

Abstract This work presents a laterally excited bulk wave resonator (XBAR) based on the suspended Z-cut lithium niobate thin film. In order to systematically analyze the influence of geometric structure on the performance of resonators, including electromechanical coupling coefficient (kt 2) and quality factor (Q), the pitch of inter-digital transducers and lateral reflective boundary width (D) were optimized via finite element analysis simulation. Besides, the XBARs with the broadband piston mode structure (BPM-XBAR) were further studied, and the transverse displacement was weakened after optimization, hence enhancing the Q value of the targeted mode. Consequently, the fabricated devices exhibited first order asymmetrical (A1) mode resonance at 5.87 GHz with kt 2 of 12.98% and Q of 218, a nearly 70% increase in Q value. The third order asymmetrical (A3) mode resonance occurred at 17.18 GHz with kt 2 of 7.91%. The above devices have the potential to construct large bandwidth and low loss filters toward the C-band and Ku-band.

Mechanically forced meniscus water waves in a square container with functionalized wetting conditions

Capillary–gravity surface waves, called meniscus waves, are excited at the air–water interface near the lateral boundary of a mechanically forced square container. Experiments are conducted in two working containers: one is overall hydrophilic at four boundaries and the other is functionalized to have a hydrophobic boundary. The static meniscus structures and instantaneous wave topography are reconstructed at high resolution from the side-view and top-view high-speed camera recordings. Wave resonances arise from the interaction of four inward-traveling waves, with the frequency-response characteristics indicating the effect of wetting conditions on the selection of standing wave patterns. The most-resonant modes are identified as a superposition of dominant modes and higher-order components. An analytical model of the rest-state meniscus and resonant-state wave surface decomposes the wave responses into two groups of resonances along two transverse directions linked by a frequency-dependent parameter γ. Theoretical selection of the dominant wave components and the second-order harmonics is in close agreement with the spatiotemporal surface-fitting experimental results. Additionally, the wetting boundary conditions can be functionalized to excite specific standing wave patterns, which could provide a novel approach to precise pattern control in bioprinting technology for tissue engineering applications.