Resonant Vibration Research Articles

Synthesis, Structural Analysis and Antibacterial Properties of a Novel β-Aminoenone.

(Z)-3-butylamino-4,4,4-trifluoro-1-(2-hydroxyphenyl)but-2-en-1-one (1), a new β-aminoenone, has been investigated in terms of its intra- and intermolecular interactions. Vibrational, electronic and nuclear magnetic resonance spectroscopies were used for the characterization, while X-ray diffraction methods afforded the determination of the crystal structure. The compound is arranged in the crystal lattice as centre-symmetric H-bonded dimeric aggregates (C2/c monoclinic space group). Both experimental (infrared, Raman, ultraviolet-visible transitions and X-ray diffraction data) and theoretical (Quantum Theory of Atoms in Molecules and Natural Bond Orbital approaches, calculated spectra and conformational analysis) methods were used to obtain a deep insight into the intra- and intermolecular contacts. The interactions were quali- and quantitatively analysed and the data compared with closely related compounds. In vitro experiments were carried out in this work to evaluate the antibacterial activity of 1 against Gram-positive and Gram-negative bacteria, particularly Pseudomonas aeruginosa (ATCC 27853) and Staphylococcus aureus (6538). Compound 1 demonstrated a discernible suppression of biofilm formation and quorum sensing of both bacterial strains, indicating that it may be developed as an antibacterial candidate to reduce bacterial resistance and persistence on surfaces across a range of industries.

Modified ADRC based on optimized repetitive control for low-frequency vibration and harmonic disturbance suppression: Design and application to inertially stabilized platforms

Mechanical vibrations in low-frequency resonance and harmonic modes severely affect the closed-loop performance of inertially stabilized platforms (ISPs). This article proposes a new vibration control scheme capable of suppressing low-frequency vibration with large amplitude and harmonic disturbances in application to an ISP. Concretely, we first design an optimized repetitive control (ORC) framework with a plug-in optimization function, where the ORC retains the suppression effect of vibration in tip-tilt modes and mitigates the waterbed effect. To enhance vibration suppression, by introducing the ORC-based inner calibration network (ICN), a modified ADRC framework with the reduced-order extended state observer (ESO) design is established. Subsequently, substantial comparison experiments have been verified on an ISP to evaluate the superiorities of the proposed method, and the experiment results verify the effectiveness of the hybrid vibration control method, attenuating vibration in resonance mode to −51.94 dB.

Vibrational resonance in the FitzHugh-Nagumo neuron model under state-dependent time delay.

We propose a nonlinear FitzHugh-Nagumo neuronal model with an asymmetric potential driven by both a high-frequency signal and a low-frequency signal. Our numerical analysis focuses on the influence of a state-dependent time delay on vibrational resonance and delay-induced resonance phenomena. The response amplitude at the low-frequency signal is explored to characterize the vibrational resonance and delay-induced resonance. Our results show that for smaller values of the amplitude of the state-dependent time-delay velocity component, vibrational resonance and multi-resonance occur in the neuronal model. For large values of the high-frequency excitation amplitude, vibrational resonance appears with one peak. Furthermore, we observe a change in the response when the amplitude of the state-dependent time-delay velocity component increases. In addition, we analyze how the state-dependent time-delay position and velocity components can give birth to delay-induced resonance for separate and together. The key findings of this work demonstrate that the state-dependent time-delay velocity component plays a crucial role in both phenomena. Specifically, the delay parameter serves as a critical control factor, capable of triggering the onset of the two resonances.

Using mode shape residuals for model updating of a nonlinear structure featuring 1:1 internal resonance

Internal resonance isa unique phenomenon in nonlinear structures. It can lead to pronounced energy transfer between vibrating modes, causing unexpected stress concentrations in local areas and posing a risk to structural integrity. This paper presents a general model updating procedure for nonlinear structures with such internal resonances using experimentally measured data. The test involves using multiple amplitudes of sinusoidal excitations to drive the structure to several required vibration amplitudes, enabling the underlying linear dynamics, uncoupled nonlinear dynamics, and internal resonances to be activated individually. The underlying linear system, uncoupled nonlinear terms, and cross-coupling terms in the dynamic equation are updated sequentially, with updating the cross-coupling terms being the most challenging task. Unlike conventional practices that heuristically pre-assume a model for the cross-coupling force terms, this paper minimises their number by using the coupling potential energies and identifies their type via an interaction map. A novel mode shape residual is then proposed to tune the coefficients of the cross-coupling terms, which allows energy transfer between coupled modes to be captured quantitatively. A diesis-like structure featuring 1:1 bending-torsion coupling was experimentally investigated using multi-level stepped-sine excitations to demonstrate the proposed model updating procedure. The vibrations of its first resonance veered from a bending-dominant motion to a bending-torsion coexisting motion as the driving forces increased, indicating strong amplitude-dependent mode shapes on the occurrence of internal resonance. The experimental data also showed that the softening and hardening trend of the torsional mode was dependent on the vibration amplitude of the bending mode, a peculiar vibration phenomenon seldom reported for realistic structures in the literature. Using the proposed model updating procedure, a two-mode coupled nonlinear model was identified from the frequency response functions and validated by comparing the backbone curves and amplitude-dependent mode shapes. Results showed that the updated model could predict the resonant vibration patterns of the structure away from and around its internal resonance with sufficient accuracy. It was also revealed that the softening and hardening behaviours of the torsional mode were attributed to different branches of Nonlinear Normal Modes (NNMs).

Mos2 2D nanoparticles as inducers of changes in liposomes formation and their spectroscopic properties

Liposomes, due to their biocompatible and flexible lipid bilayer, serve as ideal model structures to study the biophysical properties and physiological functions of cell membranes. To investigate the impact of 2D nanoparticles on liposomes formation, methods of dynamic light scattering, optical and SEM microscopy were used to determine the size of liposomes, along with Raman, IR spectroscopy and quantum-chemistry calculations for structural study. Optical microscopy study confirmed feasibility of the preparation method and liposomes size redistribution, depending on the nanoparticles. SEM data and EDS analysis provided insides on the morphological structures of the nanopowder, nanoplatelets, liposomes, and its elemental composition. Sizes of the liposomes increase up to 12% with addition of 2D MoS2 nanoparticles. Analysis of IR spectra showed a change in the spectral properties of liposomes with particles in comparison with unloaded liposomes in the region of stretching C = O and CH vibration, bending OH. Changes in H-bonds redistribution, contribution from = C–H stretching ring vibrations at 3035 cm–1 and disappearance of the band at 3006 cm–1 in IR spectrum together with the virtual disappearance of Raman bands of liposomes seems to be a marker for particle entry into the liposome. Quenching of luminescence in Raman spectra is observed in liposomes with nanoparticles compared to unloaded liposomes which is weaker in the case of liposome preparation together with nanoparticles. Enhancement of intensity of vibration modes in IR spectra for nanoparticles introduced after liposome preparation from 34% (powder) to 52% (platelets) and covered the liposome surface is observed and could be liposome particle coating marker.

Development of a Basilar Membrane-Inspired Mechanical Spectrum Analyzer Using Metastructures for Enhanced Frequency Selectivity

This study introduces a mechanical spectrum analyzer (MSA) inspired by the tonotopic organization of the basilar membrane (BM), designed to achieve two critical features. First, it replicates the traveling-wave behavior of the BM, characterized by energy dissipation without reflections at the boundaries. Second, it enables the physical encoding of the wave energy into distinct spectral components. Moving beyond the conventional focus on metamaterial design, this research investigates wave propagation behavior and energy dissipation within metastructures, with particular attention to how individual unit cells absorb energy. To achieve these objectives, a metastructural design methodology is employed. Experimental characterization of metastructure samples with varying numbers of unit cells is performed, with reflection and absorption coefficients used to quantify energy absorption and assess bandgap quality. Simulations of a basilar membrane-inspired structure incorporating multiple sets of dynamic vibration resonators (DVRs) demonstrate frequency selectivity akin to the natural BM. The design features four types of DVRs, resulting in stepped bandgaps and enabling the MSA to function as a frequency filter. The findings reveal that the proposed MSA effectively achieves frequency-selective wave propagation and broad bandgap performance. The quantitative analysis of energy dissipation, complemented by qualitative demonstrations of wave behavior, highlights the potential of this metastructural approach to enhance frequency selectivity and improve sound processing. These results lay the groundwork for future exploration of 2D metastructures and applications such as energy harvesting and advanced wave filtering.

Dynamic tuning of terahertz atomic lattice vibration via cross-scale mode coupling to nanomechanical resonance in WSe2 membranes

Nanoelectromechanical systems (NEMS) based on atomically-thin tungsten diselenide (WSe2), benefiting from the excellent material properties and the mechanical degree of freedom, offer an ideal platform for studying and exploiting dynamic strain engineering and cross-scale vibration coupling in two-dimensional (2D) crystals. However, such opportunity has remained largely unexplored for WSe2 NEMS, impeding exploration of exquisite physical processes and realization of novel device functions. Here, we demonstrate dynamic coupling between atomic lattice vibration and nanomechanical resonances in few-layer WSe2 NEMS. Using a custom-built setup capable of simultaneously detecting Raman and motional signals, we accomplish cross-scale mode coupling between the THz crystal phonon and MHz structural vibration, achieving GHz frequency tuning in the atomic lattice modes with a dynamic gauge factor of 61.9, the best among all 2D crystals reported to date. Our findings show that such 2D NEMS offer great promises for exploring cross-scale physics in atomically-thin semiconductors.

Measurement of dynamic characteristics of a steel-spring floating slab track and a monolithic roadbed track in a subway tunnel

ABSTRACT Dynamic characteristics including wheel–rail interactions and vibration-damping effects of a steel-spring floating slab track were measured and compared with those of a monolithic roadbed track. These two tracks are in the same subway tunnel, and with similar conditions. Measuring results show that the vertical and transverse wheel-rail forces on the floating slab track were separately 8% and 47% larger than those on the monolithic roadbed track. Due to the increased quasi-static wheel-rail forces, vertical and transverse rail deformations on the floating slab track were separately 2.5 and 4 times larger than those of the monolithic roadbed track. Based on the measured acceleration vibration levels, the vertical and transverse vibrations of the tunnel wall of floating slab track were 5 dB smaller than those of the monolithic roadbed track. Meanwhile, the vibrations of the floating slab were 10 dB larger than those of the monolithic roadbed. Therefore, the floating slab effectively blocked vertical and transverse energy transmissions. Based on the measured frequency-division vibration levels, vertical and transverse resonant vibrations of the tunnel wall of floating slab track were 15–22 dB smaller than those of monolithic roadbed track. However, low-frequency wheel-rail forces increased vibrations from 1 to 20 hz, which may have a negative influence on soil ground vibrations.

Electronic-decay-process spectra including nuclear degrees of freedom

In the field of chemistry, where nuclear motion has traditionally been a focal point, we now explore the ultrarapid electronic motion spanning attoseconds to femtoseconds, demonstrating that it is equally integral and relevant to the discipline. The advent of ultrashort attosecond pulse technology has revolutionized our ability to directly observe electronic rearrangements in atoms and molecules, offering a time-resolved insight into these swift processes. Prominent examples include Auger-Meitner decay and interparticle Coulombic decay. However, the real challenge lies in interpreting these observations, where theoretical models are indispensable. Building upon the analytical framework introduced by Fasshauer and Madsen [], which analyzed the spectra of electrons emitted during electronic decay processes from a purely electronic perspective, we extend this theoretical base to include nuclear dynamics, utilizing the Born-Oppenheimer approximation to deepen our understanding of the intricate interaction between electronic and nuclear motion in these processes. We illustrate the impact of incorporating nuclear degrees of freedom in several theoretical cases characterized by different numbers of vibrational bound states in both the electronic resonance and the electronic final state. This approach not only clarifies complex spectral features and unusual peak shapes but also demonstrates a method for extracting the energy differences between multiple vibrational resonance states through their distinctive interference patterns. Published by the American Physical Society 2025

Spike propagation by synchronization and vibrational resonance in feedforward Izhikevich neural network

Spike propagation by synchronization and vibrational resonance in feedforward Izhikevich neural network

Photoelectron Imaging and Photodetachment Spectroscopy for the Cryogenically Cooled Cyanocyclopentadienide Anion.

The cyano-cyclopentadiene molecule (CN-C5H5) has attracted significant interest since its detection in the interstellar medium, but the radical (CN-C5H4) and anionic (CN-C5H4-) forms of cyano-cyclopentadiene have not been studied. The cyano-cyclopentadienyl radical (CN-Cp) has a strong dipole moment, rendering it an ideal system for vibrational and rotational spectroscopy. We report an investigation of the cryogenically cooled cyano-cyclopentadienide anion (CN-Cp-) using high-resolution photoelectron imaging, photodetachment spectroscopy, and resonant photoelectron imaging. The electron affinity of the CN-Cp radical is measured accurately to be 2.7741 ± 0.0003 eV (22,375 ± 2 cm-1). A low-lying excited state is observed for the CN-Cp neutral radical at 151 cm-1 above the ground state. The overlap and vibronic coupling of the ground and low-lying electronic states give rise to complicated and congested photoelectron spectra. A dipole-bound state is observed for the CN-Cp- anion with a binding energy of 94 cm-1, along with 15 vibrational Feshbach resonances. Resonant photoelectron spectra via the vibrational resonances yield well-resolved spectra, allowing 26 vibronic levels to be identified for CN-Cp. The rich spectroscopic information will be valuable to compare with theoretical studies to unravel the vibronic coupling and nonadiabatic effects in the CN-Cp radical.

Tuning of a Viscous Inerter Damper: How to Achieve Resonant Damping Without a Damper Resonance

Inerter dampers are effectively employed to mitigate and dampen structural vibrations in slender or high-rise buildings. The simple viscous inerter damper, with a viscous dashpot placed in series with an inerter, is designed to create resonant vibration damping, although the damper itself is without an internal resonance. The apparent resonant behavior is instead obtained by increasing the damper inertance until the two lowest modes of the considered building model interact, whereafter the viscous coefficient is adjusted until the desired response mitigation is achieved. The present modal interaction tuning requires that the reduced-order single-mode dynamic model of the building includes both inertia and flexibility from the (other) modes otherwise discarded by the model reduction. While the inertia correction adjusts the modal mass of the inerter damper, the corresponding flexibility introduces the apparent damper stiffness that creates the desired damper resonance. Thus, the accurate representation of other modes is essential for the design and resonant tuning of the simple viscous inerter damper. The resonant damper performance by the non-resonant viscous inerter damper is illustrated by a numerical example with a 20-story building model, for which the desired resonant modal interaction requires an inertance of almost ten times the entire translational building mass.

Exploring the resonant vibration of a cello with the finite element method

Violins are precisely crafted to present their brilliant quality in sound that dates from 16th century Italy. The wood component’s Young’s modulus (E), the soundpost, and the bass bar play significant roles in the instrument’s sound production. Yet, current acoustic research mostly focuses on violins. Therefore, this research aimed to investigate resonant vibration using a cello model. We hypothesized the structural changes in the soundpost and bass bar would lead to different eigenfrequencies, in which the original structure yields the highest value compared to the rest. To accurately reveal the secrets of cellos’ acoustics, we conducted numerical and graphical simulations with the finite element method. We utilized the simulation tool to calculate the eigenfrequencies of altered structures with varying Young’s modulus and positions of the soundpost, with or without the bass bar. We identified specific vibration mode shapes across all structures and found that Young’s modulus had the greatest influence on the eigenfrequencies while removing the bass bar had the least impact. Yet, our hypothesis was not fully supported: not in all mode shapes did the original structure have the highest eigenfrequency value. Within the investigated components, we concluded that the factor affecting resonant vibration frequencies the most is Young’s modulus, then soundpost, and, finally, the bass bar. Future research extension with physical experiments should be conducted to understand and quantify the result accuracy.

Theoretical modeling and modal analysis of multi-element coupled transducers.

Low-frequency transducers are considerably smaller than the wavelength. When multiple low-frequency transducers are closely packed, they couple with the surrounding water and form a transducer-water-transducer coupling structure called multi-element coupled transducers (MCT). This study presents a theoretical model of the MCT based on radiation and mutual radiation theory and analyzes it under multiple resonance frequencies and vibration modes. The MCT comprising N single-degree-of-freedom elements possesses N resonance frequencies and corresponding vibration modes, and the resonance frequency varies with the spacing between elements. Additionally, the elements have different vibration amplitudes, with the phases of vibration among the elements manifesting as different combinations of in-phase and anti-phase in different vibration modes. Validation is performed through finite element analysis (FEA) and measurements of binary and ternary coupled transducer prototypes. The prototypes comprise bender transducers closely packed in a vertical configuration. The theoretical predictions agree with the FEA and measurement results. Thus, the theoretical model contributes to enhancing the understanding of acoustic transducer behavior in coupled configurations and optimizing the design of low-frequency acoustic arrays.

Synthesis, single crystal culture, activation energy calculation and HMBC spectrum of 1-methyl-1,2,4-triazole-3-carboxylic acid methyl ester and its positional isomers

Ensitrelvir is a 3CLpro inhibitor developed by SHIONOGI & CO., Ltd. of Japan for the treatment of COVID-19 and was approved for marketing in Japan on November 1, 2022. Various research results show that compared with Pfizer's Paxlovid and Merck's molnupiravir, Ensitrelvir is currently the most effective, safest and longest-lasting drug in the world! The synthesis of ensitrevir can be divided into four segments, and the docking of these four segments. Among them, the challenging segments are the triazole and indole segments due to the issue of methylation selectivity. In this study, DFT theory was primarily employed to investigate the activation energy of 1-methyl-1,2,4-triazole-3-carboxylic acid methyl ester and its positional isomers under different solvent conditions. Through experimental screening, selective methylation of 1H-1,2,4-triazole-3-carboxylic acid methyl ester was achieved. Subsequently, single crystals of the main product were cultivated, and calculations of electron density, nuclear magnetic resonance vibrations, etc., were performed for the three products to study the differences in the properties of various methylation products. Further structural confirmation of the three compounds was carried out using HMBC two-dimensional spectra.

Vibrational resonance and chaos control in the canonical Chua’s circuit with a smooth nonlinear resistor

Vibrational resonance and chaos control in the canonical Chua’s circuit with a smooth cubic nonlinear resistor is investigated by an analog circuit experiment and a dynamical model. By adjusting the amplitude and frequency of the high-frequency signal while keeping other parameters constant, the system exhibits a resonant peak in its response to the weak low-frequency signal. Notably, when the amplitude of the high-frequency signal exceeds the critical threshold, the system undergoes a transition from a single-scroll chaotic attractor to a double-scroll chaotic attractor, marking the emergence of vibrational resonance. In particular, the maximum of the system’s response amplitude is insusceptible when the frequency of the high-frequency signal varies over a broad range, which indicates the strong robustness of the vibrational resonance in the present system. The experimental results are coincident with the numerical simulations. This research has potential applications in chaos control and weak signal detection.

Microstructure Embossing Patterning Using Resonated Droplets Dynamic Behavior Induced by Vertical Vibration

AbstractThis paper introduces a novel, ecofriendly, and cost‐effective method to create deformation patterns on vertically vibrating thin film surfaces using resonant sessile droplets. The key findings emphasize the critical role of resonant frequency and vibration velocity in the formation of these deformations. Through theoretical and experimental investigations on aluminum thin film, it is validated that the deformations are influenced by the energy distribution within the resonant droplets. Specifically, higher‐order resonant frequencies produce a more concentrated energy distribution at the droplet's center due to internal top‐down flow behaviors, resulting in various deformation states. By observing regularities in deformation width patterns, the underlying phenomena are elucidated, and derive related empirical formulas. This method demonstrates significant potential for surface microstructure fabrication. The ability to control deformation shapes by adjusting vibration parameters is crucial for optimizing microfabrication processes.

Spectroscopy and Dynamics of the Dipole-Bound States of ortho-, meta-, and para-Methylphenolate Anions.

A photodetachment and photoelectron spectroscopic study by employing a cryogenically cooled ion trap combined with a velocity-map imaging setup has been carried out to unravel the vibrational structures and autodetachment dynamics of the dipole-bound states (DBSs) of o-, m-, and p-methylphenolate anions (o-, m-, and p-CH3PhO-). The electron binding energy of the DBS increases monotonically with the increase of the neutral dipole moment to give respective values of 66 ± 15, 123 ± 18, or 154 ± 14 cm-1 for the o-, m-, or p-isomer. The different electron-donating effects of the methyl moieties in the three geometrically different isomers seem to be reflected in the experiment. Mode-specific DBS dynamics of the o-, m-, and p-CH3PhO- complexes have been interrogated by using picosecond time-resolved photoelectron velocity-map imaging spectroscopy. Autodetachment lifetimes of the DBS vibrational Feshbach resonances have been measured and discussed quantitatively using Fermi's golden rule, especially in comparison with those of the phenoxide anion to get insights into the methyl substitution effect on the electron binding dynamics of the metastable DBS.

Psychological health in health care workers: features of the formation of professional burnout, prevention opportunities

Introduction. The working conditions in medical workers are characterized by high tension, which leads to a violation of the psycho-emotional state in health care workers, including professional burnout, the features of which depend on the neurophysiological type of personality, the severity of chronic stress, and the level of commitment to a healthy lifestyle. The purpose is to identify risk factors for professional burnout and evaluate the effectiveness of preventing professional burnout in medical workers in conditions of increased work intensity. Materials and methods. The study included medical workers with indices of the intensity of the labour process of class 3.1 and 3.2. The questionnaire method was used to determine: the features of the formation of professional burnout, characteristics of the type of nervous system, the index of adherence to a healthy lifestyle, stress level, subjective assessment of the psychological state. The analysis of the trend in indices of professional burnout and psychological state after group psychosomatic correction sessions was carried out. Results. The structure of professional burnout in medical workers was dominated by high rates of reduction of professional achievements (53.8%), the frequency of emotional exhaustion was 25.6%, depersonalization – 30.8%. The probability of developing emotional exhaustion in persons with an average strength of the nervous system was 3.8 times higher than in persons with a strong type of nervous system. A lack of commitment to a healthy lifestyle is associated with an increased frequency of emotional exhaustion. The positive trend in indices of professional burnout and subjective assessment of the psychological state after the preventive program of resonant acoustic vibrations has been achieved. Limitations. The subjects were employees of a medical institution working under conditions of exposure to the intensity of the labour process exceeding hygienic standards. The data is limited to voluntary study participants. Conclusions. The features of the formation of professional burnout in medical workers are determined. The effectiveness of the program for the prevention of professional burnout with the use of group psychosomatic correction has been confirmed.

Single-Path Supercontinuum Near- to Mid-Infrared Correlation Spectroscopy of Aqueous Samples.

Combining near-infrared (NIR) and mid-infrared (MIR) spectroscopy to cover both the fundamental and overtone combination molecular vibrational resonances allows more robust analytical methods to be used, such as two-dimensional correlation spectroscopy. However, due to the strong differences in molar absorption coefficients and transparency of the optical material, it is inherently difficult to perform NIR and MIR spectroscopy on aqueous samples using a single instrument. Combining spectra from different instruments and sample presentations can result in unwanted spectral variations, which can influence the prediction models and mitigate the advantages of the combination approaches. In this work, a more consistent instrument response is achieved by combining a single supercontinuum (SC) laser spanning from 1000 to 4000 nm as the light source, with an attenuated total reflection crystal and a transmission cuvette in a single-path configuration. Using this approach, NIR-MIR correlation spectroscopy is demonstrated using a set of 22 aqueous samples with varying concentrations of ethanol, sucrose, and ʟ-proline.