Resonant Behavior Research Articles

Arrest behavior of local resonators connected by nonlocal interaction in elastic wave metamaterials with machine learning prediction

Arrest behavior of local resonators connected by nonlocal interaction in elastic wave metamaterials with machine learning prediction

Investigation on flow–acoustic resonance behaviors inside ducts with tandem cavities using a high-order spectral/hp element method

This study numerically investigates the flow–acoustic resonance behaviors inside ducts with tandem cavities, containing the flow-excited acoustic eigenmodes and elevated flow dynamics under self-sustained acoustic forcing. An advanced high-order spectral/hp element method integrated with implicit large-eddy simulations was utilized to solve the nonlinear compressible Navier–Stokes equations, which effectively identified the fully coupled self-sustained flow–acoustic resonance fields. The benchmark shallow cavity configuration with a length-to-depth (L/D) ratios of 2 was motivated by the experimental findings from Shaaban and Ziada [“Fully developed building unit cavity source for long multiple shallow cavity configurations,” Phys. Fluids 30, 086105 (2018)], in which the intensive flow–acoustic resonance was occurred at a Reynolds number of 1.3×105, and we further investigated three deeper cavity configurations with L/D of 1, 2/3, and 1/2 for numerical validation and further comparison. Subsequently, aeroacoustic characteristics were assessed by analyzing the wall pressure fluctuations, indicating broader resonance regions and augmented pressure pulsation amplitudes extending from main duct to local cavity volumes with larger cavity depths. As feedback, the intensified acoustic forcing can modulate the cavity flow dynamics into stronger fluctuation levels. Furthermore, the spectral proper orthogonal decomposition analysis was conducted on the pressure fields and velocity fields, respectively. The significant fluctuations in acoustic pressure were linked to transitional acoustic modes that were present as global modes in the main duct and local modes in tandem cavities. As for velocity analysis, coherent vortex structures were extracted along the cavity entrances. These vortex structures caused progressively amplified velocity fluctuations and classified the shear layers into two dynamic motions, i.e., a flapping motion in shallow cavities and a rolling-up motion in deep cavities.

Nonlinear simultaneous resonance behaviors of a shallow arch model under the moving load

By applying a moving load with the uniform velocity, this paper investigates nonlinear behaviors of a shallow arch model allowing for describing the effects of the initial configuration of the structure. Two different cases are taken into account, namely, simultaneous primary resonances of the first and third modes; simultaneous resonances of the first mode for two-term excitations. First, nonlinear ordinary differential equations (ODEs) of the shallow arch are derived by using Galerkin method. Through introducing different time scales, the ODEs are solved based on the widely utilized method of multiple time scales (MMTS). In this way, the modulation equations for the two cases are derived, on the basis of which the steady state frequency- and force-response curves are obtained. Meanwhile, phase portraits, power spectra and two-parameter bifurcation diagram are also given to assist in analysis on nonlinear behaviors. The results show that the large vibration of the shallow arch under the moving load may occur and primary resonance peaks of the different modes are located in distinct positions.

In Situ Deprotection-Free Synthesis of Silver/Graphdiyne with a High Raman Sensing Effect for Detection of Polychlorophenols and Microplastics.

Since the first synthesis of graphdiyne (GDY), it has been widely receiving a lot of attention and has great application prospects in many fields, such as energy storage, catalysis, and sensing. However, the complex deprotection treatment and long reaction time limit its mass production and applications. Here, we present a strategy for the silver-catalyzed deprotection-free rapid synthesis of GDY. Crystalline GDY was synthesized in 8 h at room temperature and atmospheric pressure, and after the reaction, Ag nanoparticles with an ultrathin diameter of 2-3 nm were formed in situ inside and on the surface of GDY. This Ag/GDY composite exhibits a high specific surface area of 672.3 m2 g-1 and strong surface plasmon resonance behavior, showing a strong surface-enhanced Raman scattering effect. The enhancement factor and the lowest detection limit for rhodamine 6G are 3.54 × 108 and 1 × 10-14 M, respectively. The Ag/GDY achieves the simultaneous enrichment and detection of polychlorophenols and ultrafine nanoplastics.

Utilization of the Resonance Behavior of a Tendon-Driven Continuum Joint for Periodic Natural Motions in Soft Robotics

Continuum joints use structural elastic deformations to enable joint motion, and their intrinsic compliance and inherent mechanical robustness are envisioned for applications in which the robot, the human, and the environment need to be safe during interaction. In particular, the intrinsic compliance makes continuum joints a competitor to soft articulated joints, which require additional integrated spring elements. For soft articulated joints incorporating rigid and soft parts, natural motions have been investigated in robotics research to exploit this energy-efficient motion property for cyclic motions, e.g., locomotion. To the best of the author’s knowledge, there is no robotic system to date that utilizes the natural motion of a continuum joint under periodic excitation. In this paper, the resonant behavior of a tendon-driven continuum joint under periodic excitation of the torsional axis is experimentally investigated in a functional sense. In the experiments, periodic inputs are introduced on the joint side of a tendon driven continuum joint with four tendons. By modulating the pretension of the tendons, both the resonant frequency and the gain can be shifted, from 3 to 4.3 Hz and 2.8 to 1.4, respectively, in the present experimental setup. An application would be the rotation of a humanoid torso, where gait frequencies are synchronized with the resonant frequency of the continuum joint.

Nonlinear harmonic resonant behaviors and bifurcation in a Two Degree-of-Freedom Duffing oscillator coupled system of Tension Leg Platform type Floating Offshore Wind Turbine

The surge-heave coupled motion model of a Tension Leg Platform type Floating Offshore Wind Turbine (TLP FOWT) is first established. By taking the tendons stretching and platform set-down motion into consideration, the nonlinear model is a Duffing oscillator coupled system. We analyze the nonlinear feature in the surge-heave coupled motions by the semi-analytical algorithms in nonlinear dynamics. The harmonic balance method is applied to obtain the analytical solutions of the nonlinear system under wind and wave excitations. The analytical solution verifies the excellent accuracy. To further achieve the heave motion response, we organize the bifurcation analysis and discuss the effects of the dynamic parameters on the heave responses. The results reveal the multi components of heave motion, which consist of constant, primary harmonic resonate and higher order harmonic resonate. In addition, the change of dynamic parameters has various effects on the response. The increment of wave load leads to the expansion of heave response, and an instantaneous expansion appear. Both linear surge and heave damping only affect the amplitudes of heave motion. The nonlinear surge stiffness and heave stiffness can barely affect the primary harmonic resonance amplitudes, but they present different effects on the higher order harmonic resonance component.

Ultrabroadband and >93% Microwave Absorption Enabled by "Doped" Water Meta-Atom Lattice with Subwavelength Thickness.

Perfect microwave absorbers, which absorb electromagnetic waves completely, play pivotal roles in electromagnetic shielding, and stealth technologies. Existing microwave absorber technologies rely on either electromagnetic properties of absorptive materials, the resonance behavior of meta-atoms, or a combination of both. So far, achieving simultaneous broadband absorption, high efficiency, and compact sizes remains a great challenge. Inspired by atomic doping techniques employed in conventional optical materials to broaden spectral bandwidths, a single-layer microfluidic metasurface microwave absorber is proposed with the assembly of two distinct types of water meta-atoms. By manipulating electromagnetic resonances of these water meta-atoms, the metasurface maintains impedance matching over a broad working range. A microwave absorber design with a thickness equivalent to 0.2 times the central wavelength is showcased, measuring over 93% absorption across both K and Ka bands (17.5-40.0GHz). The results highlight unprecedented superiorities of microwave absorbers based on a 2D doped water meta-atom lattice when compared to previously reported metasurface absorbers utilizing identical meta-atoms. This absorber has advantages including small thickness, broad bandwidth, and cost-effectiveness, making it promising for applications in electromagnetic shielding, camouflage, and multi-spectral stealth.

Metal-free ultrathin terahertz absorber with independently tunable dual narrow bands

Abstract A technique is introduced to precisely control the resonance behaviour of a metal-free graphene-based terahertz absorber by independently tuning dual resonant peaks. The proposed ultrathin absorber features a multilayer configuration, with two isolated resonator layers of patterned graphene on dielectric (SiO2) substrates, and a thin graphite sheet at the bottom serving as a reflector. The stacked arrangement enables independent tunability of the high-absorptivity resonant peaks at 7.33THz and 9.34THz. The structure, with a thickness of just λ/15 of the free-space wavelength, offers a compact design suitable for space-constrained applications. Its symmetrical geometry ensures polarization insensitivity and stable performance for incident angles up to 60°. Simulated results, analysed via CST Studio and validated with an Equivalent Circuit Model (ECM), demonstrate excellent thermal stability. Furthermore, the narrowband response of the proposed absorber improves its sensitivity for refractive index variations induced by biomolecular interactions validating its suitability in biosensing applications. The absorber demonstrates peak absorption across both the resonant frequencies with an analyte optimised at 1.5μm thickness. Sensitivity levels of 1.1THz/RIU and 1.05THz/RIU along with figure-of-merit (FOM) values of 2.11 and 2.23. are recorded for the lower and upper bands, respectively. The absorber offers enhanced selectivity owing to low values of full-width at half maximum (FWHM). High Q-factors of 12.85 and 19.3, confirm its strong potential for refractive index sensing. 

Beam halo studies of double-periodic focusing structures at the low-energy end of superconducting linac

This paper presents a comprehensive study on the beam halo evolution in the low-energy end of high-current superconducting linear accelerators (SLAs) with double-period focusing structures. The structure consists of cryogenic cooling modules (macro-period structures) and focusing units composed of RF cavities and solenoids within each module (micro-period structures). We utilized a three-dimensional particle-core model based on an ellipsoidal bunch to study the mechanism of halo formation with greater realism and reference value.Numerical simulations indicate that, in line with envelope instability theory, maintaining the zero current phase advance (σ0s) below 90° is critical for the formation of halo structures. Using 90° as the demarcation line, the resonance behavior between particles and the core shows significant differences. Fourier analysis of the envelope oscillation spectrum reveals that when the σ0s of each micro-period structure is less than 90°, the resonance types differ between emittance-dominated beams and space-charge-dominated beams. 2:1 resonance occurs between particles and the 3rd harmonic of the envelope oscillation in space-charge-dominated beams; while 4:1 resonance occurs in emittance-dominated beams. As σ0s increases, the influence of lower harmonics in the resonance becomes more significant. When σ0s is slightly greater than 90°, 4:1 resonance form with higher harmonics of the envelope oscillation (specifically related to the number of micro-period structures in each module). When σ0s reaches 110° or higher, 1:1 resonance form with the 2nd harmonic of the envelope oscillation. Unlike most previous studies based on two-dimensional particle-core models, we found that the longitudinal envelope significantly alters the charge density distribution of the core, leading to halo formation. This finding highlights the importance of three-dimensional effects in beam dynamics, especially under high current conditions.Additionally, we analyzed the impact of the number of micro-period structures within a module and their envelope modulation. Specifically, fewer micro-period structures within a module result in the envelope oscillation spectrum power to be concentrated at lower frequencies, making resonance with low harmonics more likely. Finally, we provide guidelines for the beam matching design at the low-energy end. By adjusting the focusing parameters of the matching structures, the likelihood of beam halo formation can be effectively suppressed.In summary, this study not only reveals the key mechanisms of halo formation in double-period focusing structures but also provides an effective approach to optimizing beam quality by adjusting structural parameters and matching methods. These findings offer clear guidance for beam design in the low-energy end of SLAs.

Chaotic dynamics of flexible graphene electronic membranes with variable density in motion

With advancements in artificial intelligence and wearable technology, flexible electronic devices characterized by their flexibility and extensibility have found widespread applications in fields such as information technology, healthcare, and military. Printing technology can accurately print a circuit diagram onto a flexible membrane substrate by the pressure transfer of a conductive ink, which makes the large-scale printing of flexible graphene electronic membranes possible. However, during the roll-to-roll printing process used to prepare flexible graphene electron membranes, the density of electron membranes is variable due to the uneven distribution of inkjet-printed circuits, which limits the printing speed of flexible graphene electron membranes. Hence, investigating the dynamic properties of flexible graphene electron materials with different densities is of paramount importance to improve the production efficiency and quality of flexible graphene electron membranes. This paper takes roll-to-roll intelligent graphene electronic membranes as the research object. According to Hamilton’s principle, nonlinear vibration partial differential equations for the motion of flexible graphene electron membranes with varying densities were established and subsequently discretized using the assumed displacement function and the Bubnov–Galerkin method. Through numerical calculations, the simulation results obtained based on the fourth-order Runge–Kutta method and the multiscale algorithm were compared, and the multiscale algorithm was verified to be more correct and effective. The primary resonance amplitude–parameter characteristic curve, along with phase-plane portraits, Poincaré maps, power spectrum, time history plots, and bifurcation diagrams, for the nonlinear behavior of the membrane was obtained. The impacts of the density coefficient, velocity, damping ratio, excitation force, and detuning parameters on the nonlinear primary resonance and chaotic behavior of the moving graphene electron membrane were determined, and the stable operational region was identified, laying a theoretical foundation for the development of flexible graphene electronic membranes.

Generalised eigenfunction expansion and singularity expansion methods for canonical time-domain wave scattering problems

The generalised eigenfunction expansion method (GEM) and the singularity expansion method (SEM) are applied to solve the canonical problem of wave scattering on an infinite stretched string in the time domain. The GEM, which is shown to be equivalent to d’Alembert’s formula when no scatterer is present, is also derived in the case of a point-mass scatterer coupled to a spring. The discrete GEM, which generalises the discrete Fourier transform, is shown to reduce to matrix multiplication. The SEM, which is derived from the Fourier transform and the residue theorem, is also applied to solve the problem of scattering by the mass–spring system. The GEM and SEM are also used to solve the problem of wave scattering by a mass positioned a fixed distance from an anchor point, which supports more complicated resonant behavior.

A data-driven approach to analyze bubble deformation in turbulence

Bubble deformation and breakup from turbulence is present in many engineering applications and in nature, yet the physical mechanisms still remain poorly understood. Depending on the local turbulence intensity or Weber number, a bubble may either deform without breakup, suffer a violent breakup, or exhibit a resonant behavior, where the turbulent eddies excite the bubble's natural frequencies. Recent studies have used spherical harmonic decomposition to analyze bubble interaction with turbulence, quantifying the deformation energy of each eigenmode. However, this approach is only applicable for small levels of deformation (linear regime), while the bubble shape remains close to a sphere. In the present work, we present a novel data-driven approach combining large deformation diffeomorphic metric mapping and proper orthogonal decomposition, which is more robust for large deformations. The method is tested on a set of validation cases and applied to turbulent bubble deformation cases obtained from direct numerical simulations data.

Seismic evaluation of frequency influence and resonant behavior for lead rubber bearing isolated rigid rectangular liquid tanks

Seismic evaluation of frequency influence and resonant behavior for lead rubber bearing isolated rigid rectangular liquid tanks

An ultrathin ultralight electromagnetic absorber based on shortcut glass-coated amorphous magnetic Fiber/Salisbury-like screen

A structural design methodology is proposed for an ultrathin, ultralight, and absorption-adjustable electromagnetic absorber. The proposed absorber (SFSL) consists of an absorbing layer with shortcut glass-coated amorphous magnetic fiber and a substrate layer with transmitting material. This absorber features a Salisbury-like screen structure and incorporates multiple loss mechanisms. By investigating the influence of fiber distribution, length, content, and substrate layer thickness on absorption performance, it has been determined that the weight per square meter and thickness of a single-layer SFSL can be lowered within 50 g/m2 and 1.5 mm respectively. Furthermore, the absorption intensity and bandwidth can be adjusted by manipulating these parameters. The SFSL exhibits resonant behavior similar to that of a metamaterial absorber; however, SFSL with randomly distributed fibers demonstrates broader and stronger absorption characteristics in the frequency range from 2 to18 GHz. Additionally, the thicknesses of the substrate layer and surface covering affect the electromagnetic response characteristics. This work provides a simple strategy for constructing an ultrathin and ultralight composite to achieve efficient absorption of electromagnetic waves.

Inherent Temporal Metamaterials with Unique Time-Varying Stiffness and Damping.

Time-varying metamaterials offer new degrees of freedom for wave manipulation and enable applications unattainable with conventional materials. In these metamaterials, the pattern of temporal inhomogeneity is crucial for effective wave control. However, existing studies have only demonstrated abrupt changes in properties within a limited range or time modulation following simple patterns. This study presents the design, construction, and characterization of a novel temporal elastic metamaterial with complex time-varying constitutive parameters induced by self-reconfigurable virtual resonators (VRs). These VRs, achieved by simulating the resonating behavior of mechanical resonators in digital space, function as virtualized meta-atoms. The autonomously time-varying VRs cause significant temporal variations in both the stiffness and loss factor of the metamaterial. By programming the time-domain behavior of the VRs, the metamaterial's constitutive parameters can be modulated according to desired periodic or aperiodic patterns. The proposed time-varying metamaterial has demonstrated capabilities in shaping the amplitudes and frequency spectra of waves in the time domain. This work not only facilitates the development of materials with sophisticated time-varying properties but also opens new avenues for low-frequency signal processing in future communication systems.

Manipulating conductivity and noise for transitioning between stochastic and inverse stochastic resonances in liquid–crystal electroconvection

Noise can play a constructive role in nature and various engineering systems. Over the past four decades, noise-induced stochastic resonances (SRs) have been extensively documented, showing enhancement in system performance. Additionally, inverse SR has been observed in various systems. Typically, these resonances were studied independently. A transition between these resonances was recently observed in an alternating current-driven liquid–crystal electroconvection (EC) system using combined amplitude and phase noises. This study uses internal (material) and external (noise) parameters to demonstrate the control of this transition. Specifically, the nonmonotonic threshold voltage behavior of the EC system, indicative of the resonances, was numerically examined using additional parameters. Experimental tests were conducted to confirm the effects of these parameters. The findings reveal that the transition between these resonances can be systematically controlled to meet specific needs, whether desirable or undesirable system performances. Notably, this study illustrates how to modify the behavior of both resonances in colored noise by adjusting its cutoff frequency and steepness and phase noise, which is often overlooked. Moreover, this study provides valuable insights for various noise-related applications.

Numerical simulations of a low-pressure electrodeless ion source intended for air-breathing electric propulsion

Abstract Air breathing electric propulsion (ABEP) systems offer a promising solution to extend the lifetime of very low earth orbit (VLEO) missions by using residual atmospheric particles as propellants. Such systems would operate in very low-pressure environments where plasma ignition and confinement prove challenging. In this contribution, we present results of a global plasma model (GPM) of a plasma ignited in a very low-pressure air mixture. The results are validated against experimental measurements acquired using a laboratory electrodeless ion source utilizing a resonator for plasma ignition. The device is specifically designed to operate within low-pressure environments as it holds potential applications in ABEP systems for VLEO missions. Parametric studies are carried out via GPM to investigate the resonant behavior and its implications. The potential of the model serving as a predictive tool is assessed through experimental validation against measured data, mainly investigating the extracted ion current dependency on operational pressure and external magnetic field strength. The verified model is further utilized to extrapolate additional information about the resonant plasma such as ion composition or a degree of ionization.

Relevance of surface characterization of <i>Bambusa vulgaris</i> (l.) leaf extract doped iron nanoparticle

In the present study, green nano scaled zero-valent irons (nZVI) were synthesized from Bambusa vulgaris leaf extract at room temperature. The plant extract was evaluated for the presence of reducing agents (bioactive compounds) phytochemically using standard methods. nZVI was systematically characterized using Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Ultraviolet-Visible (UV-Vis), and Fourier Transform Infra-Red (FT-IR) techniques. The SEM and XRD results showed that after the reduction process for 4 hr at 25oC, the iron powder obtained was a single phase of lamellar or platy α-Fe crystals with the presence of medium nanoparticles (10-100 nm) having crystal size, L ranging from 40-46 nm (42.2 nm) and particle size, D ranging from 53-70 nm (56.1 nm) for both 0.3 M and 0.9 M B. vulgaris-nZVI. It has been demonstrated that B. vulgaris leaf extract was capable of producing iron nanoparticles that shows good stability in solution and under the UV-Visible wavelength, nanoparticles exhibited quite good surface plasmon resonance behavior in the range of 220-740 nm. The FT-1R spectra revealed that the vibrational bands at 3722.76 cm-1 and 3706.4 cm-1 represented the O-H stretching due to the presence of polyphenol as a functional group in addition to tannins, saponins, and others which may be responsible for the eduction of ferrous ion (Fe3+) to zero-valent iron (Feo). This study reveals that B. vulgaris-nZVI possessing short-time synthesis protocol, anisotropism, and eco-benignity could be promising lowcost matrix for remediation (both soil and water), adsorption, catalysis, and other applications.

MURCA driven bulk viscosity in neutrino trapped baryonic matter

We examine bulk viscosity, taking into account trapped neutrinos in baryonic matter, in the context of binary neutron star mergers. Following the merging event, the binary star can yield a remnant compact object with densities up to 5 nuclear saturation density and temperature up to 50 MeV resulting in the retention of neutrinos. We employ two relativistic mean field models, NL3 and DDME2, to describe the neutrino-trapped baryonic matter. The dissipation coefficient is determined by evaluating the Modified URCA interaction rate in the dense baryonic medium, and accounting for perturbations caused by density oscillations. We observe the resonant behavior of bulk viscosity as it varies with the temperature of the medium. The bulk viscosity peak remains within the temperature range of ∼13\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim 13$$\\end{document}–50 MeV, depending upon the underlying equation of states and lepton fractions. This temperature range corresponds to the relevant domain of binary neutron star mergers. We also note that in presence of neutrinos in the medium the bulk viscosity peak shifts towards higher temperature and the peak value of bulk viscosity also changes. The time scale of viscous dissipation is dictated by the beta-off-equilibrium susceptibilities derived from the nuclear equation of state. The resulting viscous decay time scale ranges from 32–100 ms, which aligns with the order of magnitude of the post-merger object’s survival time in some specific scenarios.

An insight on local defect resonance based on modal decomposition analysis: A two-dimensional case

The resonance behaviors of defects, specifically local defect resonance (LDR), are useful for defect detection in structures. However, there is a lack of intuitive elucidation regarding the underlying mechanisms governing defect resonance. This study aims to analyze the LDR of a horizontal crack in a plate activated by Lamb waves using the modal decomposition method (MDM). The MDM involves an approximate decomposition of the wavefield into finite constituent Lamb wave modes, including propagating, non-propagating, and inhomogeneous modes. The amplitude of each mode is determined according to the continuous boundary conditions of displacement and stress between the damaged zone and the intact zone. Analytical results reveal specific frequencies at which the damaged zone exhibits significantly stronger vibrations than the intact zone, indicating the emergence of LDR. The corresponding wavefields exhibit various resonance patterns, encompassing both in-plane LDR and out-of-plane LDR types. In contrast to finite element simulations and experimental observations, the MDM unveils the dominant constituents of resonance patterns: out-of-plane LDR results from the combination of reflected and transmitted A0 and A1 modes within the damaged zone, while in-plane LDR is formed by the superposition of reflected and transmitted A0, A1, and S0 modes.