Resonant Vibration Modes Research Articles

Control of myotube orientation using ultrasonication

This study investigated a technique for controlling the orientation of C2C12-derived myotube cells using ultrasonication for future clinical applications of cultured skeletal muscle tissues. An ultrasonicating cell culture dish, comprising a plastic-bottomed culture dish and a circular glass plate (diameter, 35 mm; thickness, 1.1 mm) attached to an annular piezoelectric ultrasonic transducer (inner diameter, 10 mm; outer diameter, 20 mm; thickness, 1 mm), was constructed. A concentric resonant vibrational mode at 89 kHz was generated on the bottom of the dish, and the orientations of myotube cells were quantitatively evaluated using two-dimensional Fourier transform analysis of phase contrast microscopy images captured over a 14 × 10 mm2 area at the center of the dish. Unsonicated myotube cells grew in random directions, but ultrasonication aligned them circumferentially in the culture dish. The timing of treatment was important, with ultrasonication for 48 h before differentiation having a greater impact on myotube orientation than ultrasonication after differentiation. A larger ultrasonic vibration, with an amplitude of over 20 Vpp, resulted in significantly smaller angles of deviation in the circumferential direction than the control. Ultrasonication enhanced the expression of differentiation-related genes and the formation of aligned myotubes, suggesting that it promotes differentiation of C2C12 cells into myotubes.

Focus control of a concave–convex ultrasonic gel lens in the radial direction

Optical image stabilization (OIS) systems maintain the three-dimensional focal position of a lens through mechanical actuation systems. This paper examines an optical lens for OIS that utilizes ultrasound vibration to alter the focal position, not only in the depth direction but also in the radial direction. The lens has a simple structure with no mechanical moving parts and consists of an ultrasound transducer divided into four pieces, a glass disk, and a transparent viscoelastic gel film that functions as a lens. The acoustic radiation force generated by the resonant flexural vibration of the glass disk can alter the surface profile of the gel film, allowing for a variable-focus function. The concave and convex lenses can be interchanged using two resonant vibration modes: the standing-wave mode, in which the vibration loop appears at the center, and the traveling-wave mode, in which the vibration node appears at the center. The positions of ultrasound vibrations on the lens can be controlled in a two-dimensional plane by adjusting the driving amplitudes of each channel, thereby achieving focus control in the radial direction. The focusing characteristics of the lens are evaluated through ray-tracing simulation.

Phonon-Induced Spectral Line Broadening in Dye-Doped Glass in Terms of Resonant Vibrational Modes: Tetra-tert-Butylterrylene in Polyisobutylene

Phonon-Induced Spectral Line Broadening in Dye-Doped Glass in Terms of Resonant Vibrational Modes: Tetra-tert-Butylterrylene in Polyisobutylene

Ultrasonic liquid crystal tunable light diffuser

Conventional light diffusers have periodic surface profiles, periodic refractive index distributions, or light scattering layers containing colloids. In all such structures the optical directivity of the light diffuser is cannot typically be controlled. Here we propose an electrically tunable light diffuser based on the application of ultrasound to a nematic liquid crystal (LC) material. The ultrasonic LC diffuser consists of an LC layer sandwiched by two glass discs and an ultrasonic transducer. The electrodes of the transducer are divided in a circumferential direction so that a resonant non-coaxial flexural vibration mode can be generated on the diffuser by controlling the electrical input signals. A continuous reversed-phase sinusoidal electric signal to the transducer generates the non-coaxial resonant flexural vibration mode on the glass disc, inducing an acoustic radiation force acting on the boundary between the LC layer and glass discs. This effect changes the molecular orientation of the LC and the transmitted light distribution. The diffusion angle of the transmitted light depends on the input voltage amplitude, and the diffusion angle was maximized at 16.0 V. The vibrational distribution and the diffusion directivity could be rotated by adjusting the input voltages to different electrodes, meaning that an ultrasonic LC diffuser with a thin structure and no moving mechanical parts provided a tunable light-diffusing functionality with rotatable directivity.

Visualization of Chladni Patterns at Low-Frequency Resonant and Non-Resonant Flexural Modes of Vibration

In this study, Chladni patterns corresponding to resonant and non-resonant vibration modes are visualized on square plates made in steel and aluminum alloys in the low frequency domain of 10–210 Hz. Using a laser sensor, the plate displacement at its central excitation point is measured, and from the obtained frequency response, the resonant and anti-resonant vibration modes are identified. Using the quality-factor method, the damping ratio corresponding to the 1st resonant peak is evaluated. Over a wide range of excitation frequencies, transitions of Chladni figures between resonant patterns via non-resonant patterns could be observed. Such Chladni figures, of the simplest geometrical configuration, can be used to achieve a certain desired movement path of the particles on the vibrating plate by controlling the excitation frequency.

Метод чисельного визначення динамічних характеристик лопаті повітряного гвинта з композиційного матеріалу

The subject matter of this article is the dynamic characteristics of a composite propeller blade. Determination of the modes and frequencies of natural vibrations is necessary to predict the dangerous resonance modes of aircraft engines and to identify the most stressed local zones of the blade surface. The goal of this study is to develop a verified method for determining the dynamic characteristics of composite rotor parts of aircraft engines based on the known properties of the structural components of the composite material. A general mathematical statement of the problem of elasticity theory for the analysis of the dynamic characteristics of composite structures is described. A complete system of equations that describes the mechanical state of the body within the framework of the continuum mechanics approach was developed. Geometric modeling of the propeller blades was performed. Modeling and numerical investigation of the natural frequencies and mode shapes of the propeller blade were performed using the finite element method using the ANSYS software package. Based on the results of numerical research of the stressed and deformed state of the propeller blade, the first five natural vibration frequencies and the distribution of the local stress field were determined. The most stressed local zones on the blade surface were determined for each form of natural vibration. The propeller blade model was verified using an experimental study of the first five forms and frequencies of natural blade vibrations. The eigenfrequencies of the blade vibration were experimentally determined using the method of free (natural) vibrations. The resonance method was used to experimentally determine the resonant frequencies and vibration modes of the blade. The distribution of the blade deformation field was investigated using the strain gauge method. The highest error in the verification of numerical and experimental research is 4.11% for the fourth vibration frequency. Conclusions. The scientific novelty of the results obtained is that the effective elastic properties of the composite material for calculations should be determined using the procedure of numerical homogenisation of composite materials of different reinforcement structures by the properties of the matrix and fibers. The method does not require experimental determination of the effective elastic constants for the layers of blade components of different weave architecture patterns.

Quantum phase synchronization via exciton-vibrational energy dissipation sustains long-lived coherence in photosynthetic antennas

The lifetime of electronic coherences found in photosynthetic antennas is known to be too short to match the energy transfer time, rendering the coherent energy transfer mechanism inactive. Exciton-vibrational coherence time in excitonic dimers which consist of two chromophores coupled by excitation transfer interaction, can however be much longer. Uncovering the mechanism for sustained coherences in a noisy biological environment is challenging, requiring the use of simpler model systems as proxies. Here, via two-dimensional electronic spectroscopy experiments, we present compelling evidence for longer exciton-vibrational coherence time in the allophycocyanin trimer, containing excitonic dimers, compared to isolated pigments. This is attributed to the quantum phase synchronization of the resonant vibrational collective modes of the dimer, where the anti-symmetric modes, coupled to excitonic states with fast dephasing, are dissipated. The decoupled symmetric counterparts are subject to slower energy dissipation. The resonant modes have a predicted nearly 50% reduction in the vibrational amplitudes, and almost zero amplitude in the corresponding dynamical Stokes shift spectrum compared to the isolated pigments. Our findings provide insights into the mechanisms for protecting coherences against the noisy environment.

Frequency characteristics of an ultrasonic varifocal liquid crystal lens.

Compound lens systems with mechanical actuators are used to focus objects at near to far distances. The focal length of ultrasound varifocal liquid crystal (LC) lenses can be controlled by modulating the refractive index spatial distribution of the medium through the acoustic radiation force, resulting in thin and fast-response varifocal lenses. The frequency characteristics of such a lens are evaluated in this paper, and several axisymmetric resonant vibration modes over 20kHz are observed. The effective lens aperture decreased with the wavelength of the resonant flexural vibration generated on the lens, meaning that this parameter can be controlled with the driving frequency.

Multidomain modeling of acoustical transducers and arrays using electrical network theory

Modeling of piezoceramic acoustic transducers involves the transformation of energy in the electrical, mechanical, acoustical radiation domains. By using generalized coordinates and Lagrangian mechanics, in which principle of least action is applied in each domain, the electrical, piezoelectric, mechanical and sound radiation problems can be solved separately and then combined in a multi-contour equivalent electro-mechanical circuit with each mechanical vibrational resonant modes representing separate degrees of freedom in the coupled electrical circuit. This energy approach involves the calculation of the potential and kinetic energies of each practical mode of vibration, which can be determined analytically, experimentally, or by finite-element-analysis. This is an alternative to the use of Newtonian mechanics which requires an accurate description of the real boundary conditions in the device and is common in many FEA modeling approaches. The availability of software (e.g., Matlab, Python, LTSpice, etc.) to model electrical circuits (networks in the case of multi-resonant devices) makes for a powerful and efficient modeling approach. The historical emergence of this approach stems from adapting the Rayleigh-Ritz method for mechanical and electrical domains with the advent of piezoelectric and magnetostrictive bodies. Several example of piezoceramic transducers are presented.

Physical insight into optical spectroscopy of chiral covalent organic pillars as molecular nanotubes

In this paper, we theoretically investigate chiral covalent organic pillars synthesized by connecting rim-desymmetrized macrocycle, stimulated by recent experimental synthesis [Nat. Synth. 2023, 2, 395–402]. Transition densities reveal physical mechanism of spectral intensity in one-photon absorption (OPA) and two-photon absorption (TPA), and solvent effect strongly influence the spectral profile and intensity in TPA, but little influence the spectrum in OPA. The intra-unit and inter-unit charge transfer are visualized in five phenylenediamine linkers. The chirality of covalent organic pillars is revealed by electronic circular dichroism (ECD) spectroscopy, and interpreted by the visualized transition electric and magnetic dipole moments. Molecular vibrational information is demonstrated by normal and resonance Raman spectra and vibrational modes. The visualization of static and dynamic (hyper) polarization can reveal the physical mechanisms of polarization dependent normal and resonance Raman scattering. Our results provide deeper understanding on the physical mechanism of chiral covalent organic pillars as molecular nanotubes.

Dynamics modeling and stress response solution for liquid-filled pipe system considering both fluid velocity and pressure fluctuations

Dynamics modeling and stress response solution of the liquid-filled pipe system (LFPS) are necessary to predict the reliability of the pipe. However, the existing methods still need further research to solve the stress response of pipe system, and the influence of fluid velocity and pressure (FVAP) fluctuations on the vibration response is not considered. Based on this, a dynamics modeling method named FEM-TMM is proposed to solve the natural characteristics and stress response of the LFPS based on the combination of the finite element method (FEM) and transfer matrix method (TMM), which can consider the fluctuations of FVAP. The incompatible solid (Solid-NC) and virtual beam (VBeam) elements are constructed to establish the finite element models of the solid and fluid domains respectively, and the coupling elements are introduced to couple the solid and fluid domains. TMM is used to solve the FVAP fluctuations of the LFPS under external excitation, and the steady-state resonant frequency and vibration mode are obtained based on the iteration method. The virtual force iteration and stress smoothing methods are adopted to solve the stress response of the LFPS, then the dynamics modeling method FEM-TMM is obtained, and the rationality of the modeling method is verified by experiments. Finally, the analysis results show that the influence of velocity fluctuation on resonance frequency and stress response can be ignored. The critical pressures of resonant frequencies are less than or equal to those of resonant frequencies without considering pressure fluctuation. There are multiple stress barriers and valleys in the different-order stress responses of the LFPS, and the pressure fluctuation will change the distribution laws and maximum peak values of the stress barriers.

An assessment method of rail corrugation based on wheel–rail vertical force and its application for rail grinding

In practice, the assessment and treatment of rail corrugation are quantitatively based on the corrugation depth. Wheel–rail vertical forces (WRVF), as a direct reflection of wheel–rail interaction, can give expression to the corrugation depth and thus serve as a key parameter for assessing the corrugation. In this paper, we propose an evaluation method for rail corrugation based on the WRVF. First, a 3D wheel–rail dynamic finite element (FE) model was developed with typical parameters of CRTS II slab track and CRH3 vehicle for high-speed railways in China. The accuracy of the model was then validated with the measured WRVF data in the field. Second, using the validated model, the time–frequency domain distribution of WRVF (vehicle speed: 300 km/h) was obtained with consideration of the corrugation wavelength in the range of 40–180 mm. The non-linear least squares method and rational equation were used to fit the function between the large value of WRVF and the corrugation depth value under the conditions of different corrugation wavelengths. Next, effects of the Pinned–Pinned resonance frequency and vibration mode on the fitted parameters were analysed, by which an indicator for corrugation treatment (grinding) was proposed. Finally, the indicator was applied in the monitoring of rail corrugation for high-speed railway lines in the field. The results show that the misjudgement rate of rail grinding decisions (using the proposed indicator) is low with the accuracy at 92.5%. The proposed method can provide a basis for the rail corrugation evaluation and grinding decisions-making.

A thin acoustic touchless sensor using flexural vibration

This paper investigates a thin sensor used to detect the position of an object in front of an ultrasonic transducer using changes in the radiation impedance. The sensor consists of a rectangular plate and a piezoelectric transducer, and the configuration is determined based on the results of a finite element analysis simulation. Stripe flexural vibration modes are generated on the plate, radiating sound waves into the air between the plate and the object. The radiation angle of these sound waves is dependent on the driving frequency, resulting in a change in the sound field and the electrical admittance characteristics. The sensing performance is examined using two resonant vibration modes. The sensor can determine the position of an object uniquely within a two-dimensional area, and the lower resonant mode gave a wider measurable range. The sensitivity is improved six-fold over that of our conventional sensor using the same sensing mechanism.

How to fix an ultrasonic variable-focus liquid crystal lens for substrate-mountable applications

This paper proposed a board-mounted ultrasonic variable-focus liquid crystal (LC) lens. The lens controls the focus using the acoustic radiation force generated by the resonant flexural vibration mode. The LC lens was fixed to an aluminum substrate with a hole whose aperture corresponded to the inner diameter of the transducer. The part of the LC lens attached to the substrates functioned as a fixed condition, and the flexural vibration mode was successfully generated. The fixed lens exhibited a gradual focal change with current, confirming that fixing the condition affected the rate of focal change.

Dynamic behavior of earth dams under different kinematic impacts

The paper provides a detailed analysis of the current state of the problem. A mathematical model is presented to determine the dynamic behavior of earth dams, considering the viscoelastic properties of soil, using the hereditary Boltzmann-Volterra theory with the A.R. Rzhanitsyn kernel under periodic kinematic impacts. To solve the problems considered, the finite element method and complex arithmetics were used to reduce integrodifferential equations to a high-order complex algebraic equation. The accuracy of the methods was verified by solving test problems. Steadystate forced vibrations of the Pskem earth dam 195 m high are studied considering the real geometry and soil properties under resonant vibration modes. It was stated that the largest stress amplitudes in the body of the dam occur not only under the first resonance, but they can occur under other dense spectra of the eigenfrequencies of the dam, due to the interaction between close natural modes of vibration. The strength of various sections of the dam body was tested under kinematic impact using the Coulomb- Mohr theory of strength; the most dangerous sections of the dam were identified in terms of the highest stress.

Investigation of thermal control in phase-changing ABO3 perovskites via first-principles predictions: general mechanism of emittance.

Phase-change thermal control has recently seen increased interest due to its significant potential for use in smart windows, building insulation, and optoelectronic devices in spacecraft. Tunable variation in infrared emittance can be achieved by thermally controlling the phase transitions of materials at different temperatures. A high emittance in the mid-infrared region is usually caused by resonant phonon vibrational modes. However, the fundamental mechanism of emittance variation during the phase-change process remains elusive. In this work, the electronic bandgaps, phononic structures, optical-spectrum properties, and formation energies of 76 kinds of phase-changing ABO3 perovskites were predicted based on first-principles calculations in the mid-infrared region. The variation in emittance between two phases of a single material was found to have an exponential correlation with the bandgap difference (R2 ∼ 0.92). Furthermore, a strong linear correlation (R2 ∼ 0.92) was found between the emittance variation and the formation-energy difference, and the emittance variation was also strongly correlated with the volume-distortion rate (R2 ∼ 0.90). Finally, it was concluded that a large lattice vibrational energy, a high formation energy, and a small cell volume are conducive to high emittance. This work provides a strong dataset for training machine-learning models, and it paves the way for further use of this novel methodology to seek efficient phase-change materials for thermal control.

드릴링 가공을 위한 초음파 유닛 설계

With the development of new alloys and composites, existing drilling techniques have technical constraints for machining difficult-to-cut materials. To overcome these constraints, researchers have developed various drilling methods, including ultrasonic-assisted drilling (UAD). An ultrasonic spindle with a 30 kHz resonant frequency was designed to apply UAD to hole processing. The resonance frequency and vibration mode were predicted using the finite element method (FEM), and a vibration nodal plane was selected. The resonance frequency and impedance characteristics of the ultrasonic spindle were determined using an impedance analyzer, and an error of approximately 1.9% was predicted using the FEM. Next, the vibration characteristics of the ultrasonic spindle were analyzed using a laser displacement system. The vibration displacement tests showed amplitudes of 39.7 and 0.5 μm at the end of the drilling tool and the nodal plane, respectively. The design validity of the manufactured ultrasonic spindle was demonstrated based on experimental drilling results.

The Effect of Stem on the Bryan's Factor of a Hemispherical Resonator

• Bryan's factor of a hemispherical shell with stem is analytically investigated • Revised formulation of the Bryan's factor is presented with corrected shape functions considering the effect of stem • Existing values for the Bryan's factor are updated • Bryan's factor depends on the boundary condition at the interface between the stem and hemispherical shell • Stem/shell interface area of a HRG resonator should be cautiously designed to obtain high sensitivity • The effect of stem on the Bryan's factor is more significant as the non-dimensional stem size increases, especially for up-to-date MEMS or small-sized HRG HRG (Hemispherical Resonator Gyroscope) is a resonator gyroscope sensor which utilizes Coriolis effect for the resonant vibrational modes of a hemispherical shell-type resonator. HRG has a resonator that is composed of an axisymmetric hemispherical shell and a column structure that support the shell, usually called a stem. This paper investigates the effect of the stem on Bryan's factor of a hemispherical resonator. When a resonating structure is installed on a platform, which is under rotational motion, the vibrating pattern of the resonator rotates by the angle proportional to the rotational angle of the platform with respect to the rotating frame of reference. The Bryan's factor is the proportional constant, and so fundamental and important because it determines the physical sensitivity for the HRG to measure the rotational motion of the platform. Most of the previous studies on Bryan's factor have dealt with the hemispherical resonator without the stem for simplicity of mathematics or approximately neglecting the effect of the stem. Some of them considered the stem, however, used incorrect solutions for deflection shape function of the operational vibration mode. In this paper, the effect of the stem on the Bryan's factor is newly investigated by correctly deriving the deflection shape functions based on the thin shell theory and inextensional Rayleigh's mode assumptions. Then, the Bryan's factors are calculated with different non-dimensional diametrical sizes of the stem for various boundary conditions. This paper provides more correct and complete formulation for the Bryan's factor of a hemispherical resonator shell with considering the effect of stem, which could be a more solid foundation for the development of the HRG sensor.

Achieving Low Lattice Thermal Conductivity in Half‐Heusler Compound LiCdSb via Zintl Chemistry

Half‐Heusler compounds usually possess ultrahigh power factors, while the large thermal conductivity hinders the further optimization of their thermoelectric properties. Herein, from the perspective of material design, a new half‐Heusler lattice with low lattice thermal conductivity by using Zintl chemistry based on the composition of LiCdSb is rationally constructed. The weak bonding within the polyanions combined with the resonance vibration modes of Li+ contributes to the small lattice thermal conductivity of pristine LiCdSb as low as 3.2 W m−1 K−1 at 303 K and 0.85 W m−1 K−1 at 573 K. Ag doping is further conducted for boosting the electronic quality factor BE from 2.5 to 5.2 μW cm−1 K−2 due to the energy band modulation. As a result, a high power factor up to 21.35 μW cm−1 K−2 at 393 K is achieved in LiCd0.94Ag0.06Sb. In view of the low thermal conductivity, the figure of merit zT reaches 0.79 at 633 K. Herein, it is demonstrated that the half‐Heusler compound LiCdSb is a competitive thermoelectric parent, and low thermal conductivity can indeed be realized in half‐Heusler compounds through Zintl chemistry.

Nanodiamond/cellulose nanocrystals composite-based acoustic humidity sensor

This paper fabricated a high-performance nanodiamond (ND)/cellulose nanocrystal (CNC) composite-based acoustic humidity sensor. First, the effects of changes in both mass and viscosity of humidity-sensitive films on the resonance displacement, vibration modes, and impedance characteristics of the quartz crystal microbalance (QCM) were discussed using the finite element simulation software COMSOL Multiphysics. Then, the surface morphology and elemental composition of ND/CNC composites were characterized by TEM and EDS. Next, the humidity-sensing properties of ND/CNC composites, including response sensitivity, humidity hysteresis, dynamic characteristics, and stability, were tested at a relative humidity range from 11.3 % to 97.3 % RH combined with QCM transducers. In addition, the humidity-sensing performance of the QCM sensors with different ratios of composites was compared. The best ND/CNC-based QCM humidity sensors exhibited high sensitivity (54.1 Hz/%RH), low humidity hysteresis (3.2%RH), and fast response/recovery times. Then the adsorption process and sensitivity mechanism of water molecules on ND/CNC composites were analyzed using Langmuir isothermal adsorption model. Finally, the potential application of ND/CNC composite-based QCM humidity sensor was illustrated with respiration monitoring as an example.