Resonant Behavior Research Articles

One-To-One-To-One Internal Resonance Analysis of a Double-Cable-Stayed Flexible Beam-Structure Mounted with a Manipulator System

This paper deals with the theoretical studies to investigate the in-plane eigenvalue problems and the one-to-one-to-one internal resonance behaviors of a double-cable-stayed flexible beam-structure mounted with a manipulator system (DCFBMS) under constant rotational speed. A more precise and rigorous dynamic model with proper boundary conditions has been developed in which geometric nonlinearity and coupling nonlinearity of cables and beam are considered while the manipulator has been modeled as a rigid link. The in-plane eigenvalue problem of the model considering the boundary and continuous conditions has been evaluated and graphically demonstrated. Then, the ordinary differential equations (ODEs) are obtained by Galerkin’s method and multiple scales method has been employed to further analyze the vibration attributes of steady-state responses and their stability under internal resonance condition. The nonlinear response, stability and bifurcations for one-to-one-to-one internal resonance have also been investigated by varying system parameters. Analytically obtained results have been verified by Runge–Kutta method and found to be in good agreement. The present theoretical results deliver a useful insight into the nonlinear dynamic behavior and operational stability of DCFBMS.

Investigation of diffraction grating in photothermal cavity

The photothermal effects in an optical cavity driven by a strong control field and a weak probe field have recently been shown to generate an induced transparency phenomenon (Ma et al., 2020). This phenomenon, referred to as photothermally induced transparency (PTIT), arises from the nonlinear behavior of an optical resonator caused by optical heating of the its mirrors. In this study, we investigate the manipulation of PTIT by substituting the strong coupling field in the PTIT scheme with a spatially periodic standing wave (SW) coupling field, resulting in the diffraction of the weak probe field into high-order diffractions. The resulting structure, termed the photothermally induced grating (PTIG), can be effectively controlled by adjusting various system parameters, including the coupling strength, effective detuning, interaction length, and photothermal coefficient. By carefully optimizing the coupling strength, we demonstrate that a significant portion of the probe field energy can be efficiently transferred to the third-order diffraction grating. The introduction of a spatially periodic standing wave coupling field opens up new possibilities for designing and manipulating photothermally induced gratings with enhanced functionalities.

Efficiently spatial field localization enabled second-harmonic and sum-frequency generation in an etchless LiNbO3 layer by guided resonant quasi-bound states in the continuum

High-Q resonances on metasurfaces have yielded a feasible approach for nonlinear frequency conversion in recent years. In this work, we propose a highly efficient nonlinear metasurface based on an etchless lithium niobate (LiNbO3) layer by combining periodic silicon nanodisks. These nanodisks introduce two kinds of capabilities for achieving ultra-sharp spectral lineshapes owing to the high-Q resonances of bound states in the continuum and simultaneously attain a significantly enhanced spatial field localization within the LiNbO3 cavity owing to guided resonant behaviors. This distinctive mode engineering yielded a total efficiency of conversion of 2.8% in the second-harmonic generation and 1% for sum-frequency generation when the peak intensity of the fundamental pump was as low as 1 MW/cm2. Our method eliminates challenges to the manufacture of etched LiNbO3 thin films and allows for the efficient conversion of frequency. It is suitable for various applications, such as integrated, nonlinear nanophotonic chips, and high-speed communication.

How Quantum is the Resonance Behavior in Vibrational Polariton Chemistry?

Recent experiments in polariton chemistry have demonstrated that reaction rates can be modified by vibrational strong coupling to an optical cavity mode. Importantly, this modification occurs only when the frequency of the cavity mode is tuned to closely match a molecular vibrational frequency. This sharp resonance behavior has proved to be difficult to capture theoretically. Only recently did Lindoy et al. [ Nat. Commun. 2023, 14, 2733] report the first instance of a sharp resonant effect in the cavity-modified rate simulated in a model system using exact quantum dynamics. We investigate the same model system with a different method, ring-polymer molecular dynamics (RPMD), which captures quantum statistics but treats dynamics classically. We find that RPMD does not reproduce this sharp resonant feature at the well frequency, and we discuss the implications of this finding for future studies of vibrational polariton chemistry.

Effects of the Librationally Induced Flow in Mercury’s Fluid Core with an Outer Stably Stratified Layer

Observational constraints on Mercury’s thermal evolution and magnetic field indicate that the top part of the fluid core is stably stratified. Here we compute how a stable layer affects the core flow in response to Mercury’s main 88 day longitudinal libration, assuming various degrees of stratification, and study whether the core flow can modify the libration amplitude through viscous and electromagnetic torques acting on the core–mantle boundary (CMB). We show that the core flow strongly depends on the strength of the stratification near the CMB but that the influence of core motions on libration is negligible with or without a stably stratified layer. A stably stratified layer at the top of the core can, however, prevent resonant behavior with gravito-inertial modes by impeding radial motions and promote a strong horizontal flow near the CMB. The librationally driven flow is likely turbulent and might produce a nonaxisymmetric induced magnetic field with a strength of the order of 1% of Mercury’s dipolar field.

Design of single‐layer bandstop fractal frequency selective surface based on WLAN applications

AbstractIn this letter, we present a new frequency selective surface (FSS) for shielding 2.4–2.5 and 4.98–5.825 GHz wireless local area network (WLAN) bands. This FSS structure is based on the traditional Sierpinski octagon and we improve it. Compared with the traditional structure, the improved one has a smaller element size and better angular stability. The design is realized on float glass with a relative permittivity () of 8, and the unit cell size is 0.1152λ0 × 0.1152λ0 (λ0 is the free space wavelength at the first resonant frequency). Wide rejection bandwidths (−10 dB) of 910 and 1630 MHz are obtained at 2.4–2.5 and 4.98–5.825 GHz, respectively. The surface current distribution and the equivalent circuit model are illustrated to explain the resonance behavior of the proposed FSS. Furthermore, this FSS exhibits stable frequency response to incident angles of 0°–80° under transverse electric and transverse magnetic polarizations. Finally, this FSS structure was fabricated and measured. The measured results demonstrate that this FSS structure has good performance in WLAN applications.

Wind/Wave Testing of a 1:70-Scale Performance-Matched Model of the IEA Wind 15 MW Reference Wind Turbine with Real-Time ROSCO Control and Floating Feedback

Experimental results from the Floating Offshore-wind and Controls Advanced Laboratory (FOCAL) experimental program, which tested a performance-matched model of the IEA Wind 15 MW Reference Turbine on a 1:70 scale floating semisubmersible platform, are compared with OpenFAST simulations. Four experimental campaigns were performed, and data from the fourth campaign, which focused on wind and wave testing of the scaled floating wind turbine system, are considered. Simulations of wave-only, wind-only, and wind/wave environments are performed in OpenFAST, and results for key metrics are compared with the experiment. Performance of the real-time Reference OpenSource COntroller (ROSCO) in above-rated wind conditions, including the effects of the floating feedback loop, are investigated. Results show good agreement in mean values for key metrics, and hydrodynamic effects are matched well. Differences in the surge resonant behavior of the platform are identified and discussed. The effect of the controller and floating feedback loop is evident in both the experiment and OpenFAST, showing significant reduction in platform pitch response and tower base bending load near the platform pitch natural frequency.

Resonance theory and quantum dynamics simulations of vibrational polariton chemistry.

We present numerically exact quantum dynamics simulations using the hierarchical equation of motion approach to investigate the resonance enhancement of chemical reactions due to the vibrational strong coupling (VSC) in polariton chemistry. The results reveal that the cavity mode acts like a "rate-promoting vibrational mode" that enhances the ground state chemical reaction rate constant when the cavity mode frequency matches the vibrational transition frequency. The exact simulation predicts that the VSC-modified rate constant will change quadratically as the light-matter coupling strength increases. When changing the cavity lifetime from the lossy limit to the lossless limit, the numerically exact results predict that there will be a turnover of the rate constant. Based on the numerical observations, we present an analytic rate theory to explain the observed sharp resonance peak of the rate profile when tuning the cavity frequency to match the quantum transition frequency of the vibrational ground state to excited states. This rate theory further explains the origin of the broadening of the rate profile. The analytic rate theory agrees with the numerical results under the golden rule limit and the short cavity lifetime limit. To the best of our knowledge, this is the first analytic theory that is able to explain the sharp resonance behavior of the VSC-modified rate profile when coupling an adiabatic ground state chemical reaction to the cavity. We envision that both the numerical analysis and the analytic theory will offer invaluable theoretical insights into the fundamental mechanism of the VSC-induced rate constant modifications in polariton chemistry.

Stochastic resonance in a model of a periodically driven DNA: Multiple transitions, scaling, and sequence dependence.

We numerically study stochastic resonance in the unzipping of a model double-stranded DNA by a periodic force. We observe multiple peaks in stochastic resonance in the output signal as the driving force frequency is varied for different force amplitudes, temperature, chain length, and chain heterogeneity. Multiple peaks point to the existence of multiple stable and metastable states, which correspond to dynamical states of partially zipped and unzipped conformations and transitions between them. We quantify such transitions by looking at the time evolution of the fraction of bound base pairs. We obtain phase diagrams in the force amplitude-temperature plane both in the resonance frequency of the primary peak and the output signal at the peak value. We further obtain an excellent scaling behavior of the output signal for changing lengths of the DNA. Resonance behavior is also affected by chain heterogeneity as it depends strongly on which base pair the periodic forcing is applied.

Free Vibration Analysis of Isotropic and Orthotropic Cylindrical Shells using Finite Element Method

The understanding of fundamental natural frequencies and mode shapes is crucial for assessing the resonant behavior of structures. Numerous scholars have investigated the free vibration properties of circular cylindrical shells. These cylindrical shell configurations find applications in diverse engineering fields such as aviation, rocketry, missiles, electric motors, and locomotive engines. Within this paper, an analytical solution is derived using the "first order shear deformation theory" to determine the frequency characteristics of free vibrations in symmetric laminated circular cylindrical composite shells. The outcomes are juxtaposed against classical and higher order theories. The central aim of this research is to scrutinize the influence of various parameters on the frequency traits of laminated composite shells. Furthermore, the analysis extends to laminated composite shells employing diverse stiffening methods, with their free vibration behavior explored through the utilization of FEA software ANSYS. Keywords: Cylindrical shell, free vibration, frequencies, mode shapes, laminated composites.

Dynamic error fields derivation by inverting a validated interpretative perturbations model

The need for a model able to provide the dynamic evolution of the intrinsic magnetic error fields amplitude in tokamaks is of a significant importance in order to develop strategies to correct its destabilizing effect. The present paper specifically aims to deliver this kind of model and adjacent code. A previously built direct perturbations interpretative model (Miron (JET Contributors) 2021 Nucl. Fusion 61 106016) is used to calculate the plasma instabilities amplitude and frequency aiming to match the same quantities provided by the device diagnostics data analysis specific code for various discharges at JET. The mentioned good match ensures our model validity against the experimental results. Based on its proven structural validity, our model considering the error field quantities is inverted. This time the initial direct model output results, namely the plasma perturbations amplitude and frequency, become input data for our inverse model aiming to solve the corresponding error field modes system of equations searched as unknowns. The error fields basically satisfy the same outer plasma perturbed equations as the plasma perturbations do (vacuum/wall/plasma column external structures). Obviously they do not satisfy the perturbed plasma equations. A clear and explicit dynamic error field solution is finally provided. It has been demonstrated that whenever the error fields are responsible for the mode locking effect and plasma rotation damping, the calculated error fields shows its expected disruptive resonant behavior during various discharges at JET.

Photoinduced valley-dependent equal-spin Andreev reflection in Ising superconductor junction

The Ising spin–orbit coupling could give rise to the spin-triplet Cooper pairs and equal-spin Andreev reflection (AR) in Ising superconductors. Here we theoretically study the valley-dependent equal-spin AR in a ferromagnet/Ising superconductor junction with a circularly polarized light applied to the ferromagnet. Because of the spin-triplet Cooper pairs and the optical irradiation, eight kinds of AR processes appear in the junction, including equal-spin AR and normal AR, the strengths and properties of which strongly depend on the valley degree of freedom. The AR probabilities for the incident electron from the two valleys exhibit certain symmetry with respect to the magnetization angle and the effective energy of light. The equal-spin AR and normal AR present different features and resonant behaviors near the superconducting gap edges. Due to equal-spin-triplet Cooper pairs, not only charge supercurrent but also spin supercurrent can transport in the Ising superconductors. The differential spin conductance for electron injecting from the two valleys can be controlled by the circularly polarized light.

A high frequency SiC nanobeam resonator with ultra-sensitivity

Nanomechanical resonator based on nanomaterials has great potential for high sensitive, high resolution and negligible energy consumed sensing devices. In this work, high frequency SiC nanobeam resonators with a diameter of ∼100 nm and with lengths of tens of micrometers were designed and demonstrated, which was produced based on the high quality monocrystal 3C-SiC nanowire material with high aspect ratio characteristics. The resonance behaviors of the nanobeam resonator was studied using an integrated mixing circuit measurement system with the pressure from 10−3 to 10−1 Torr. It was observed that the resonant frequency was up to 9.16 MHz, which was a distinguished essential feature for high sensitivity detection. The tunability of SiC nanobeam resonators was about 22%, which can be conveniently controlled by adjusting DC voltage on the gate. It was examined that the detection value of the SiC nanobeam resonator can be as low as zeptogram, which indicated its ultra-sensitive mass detection behaviors. The results show that the SiC nanobeam resonator has high resonant frequency, large tunability and high sensitivity, which is expected to be a high-performance device for biosensing and mechanical sensing.

Fluid resonance in the narrow gap for a ship close to the vertical caisson on impermeable and permeable beds

The behavior of fluid resonance in the narrow gap between a ship and a vertical caisson on impermeable and permeable beds is investigated. A two-dimensional viscous numerical flume with the permeable module is established, where the influence of impermeable and permeable beds on resonant behavior is focused. Numerical studies show that the existence of foundation bed decreases the resonant amplitude in the gap; while the resonant amplitude further decreases when considering the permeable effect of bed. This is mainly due to the fluid that can flow out of the box-wall system through the permeable bed. The increased influence of impermeable and permeable beds can be observed with the increase of box draft and gap breadth. Larger bed thicknesses and smaller incident wave amplitudes can also lead to more significant foundation bed effects. Finally, the influence of permeable foundation bed can also decrease the wave amplitude at the low-frequency range.

AutoHVSR: A machine-learning-supported algorithm for the fully-automated processing of horizontal-to-vertical spectral ratio measurements

The horizontal-to-vertical spectral ratio (HVSR) has seen widespread use as a tool for measuring a site’s resonant behavior. However, the processing of HVSR with traditional methods can be tedious and time-consuming when the HVSR is complex and exhibits multiple resonances. This work proposes the AutoHVSR algorithm that allows for fully-automated processing of HVSR measurements, including those with zero, one, or multiple clear resonances. The AutoHVSR algorithm accepts microtremor or earthquake recordings and user-defined HVSR processing parameters as input and returns the computed HVSR from each time window or earthquake record, the mean/median HVSR curve, and statistics on each automatically identified HVSR resonance in terms of frequency and amplitude. The AutoHVSR algorithm integrates robust signal processing and computational methods with state-of-the-art machine-learning models trained using a diverse dataset of 1108 HVSR measurements. The AutoHVSR algorithm demonstrates excellent performance by correctly determining the number of HVSR resonances for 1098 of the 1108 HVSR measurements (>99%) and predicting the mean resonant frequency of the correctly identified resonances with a root mean square error (RMSE) of 0.05 Hz. Furthermore, the AutoHVSR algorithm was able to produce these predictions in 13 min (including HVSR processing time) compared to the 30 h required for traditional processing (a speed up of 138). The AutoHVSR algorithm is further demonstrated on a challenging dataset from Canterbury, New Zealand that included many HVSR curves with multiple and/or ambiguous resonances. Despite the challenging nature of the Canterbury dataset, the AutoHVSR algorithm was capable of correctly determining the number of HVSR resonances for 113 of the 129 HVSR measurements (>87%) and predicting the mean resonant frequency of the correctly identified resonances with a RMSE of 0.10 Hz. The AutoHVSR algorithm produced these predictions under 2 min (including HVSR processing time) compared to the 4 h required for traditional processing (a speed up of 120). Finally, while the AutoHVSR algorithm was developed using microtremor measurements where the horizontal components were combined using the geometric mean, it is shown to extend without modification to microtremor HVSR measurements where the two horizontal components are rotated azimuthally and to HVSR measurements from earthquake recordings. The AutoHVSR algorithm has been made publicly available in v0.3.0 of HVSRweb, it can be accessed at https://hvsrweb.designsafe-ci.org/.

Synthesis and characterization of liposomes encapsulating silver nanoprisms obtained by millifluidic-based production for drug delivery

Silver nanoprisms (SNPs) have attracted significant attention due to their surface plasmon resonance behaviour, which is strongly dependent on their size and shape. The enhanced light absorption and scattering capacity of SNPs, make them a promising candidate system for non-invasive imaging and drug delivery in nanoparticle-assisted diagnostics and therapy. However, systemic administration of silver nanoparticles (AgNPs) at high concentrations may result in toxic side-effects, arising from non-targeted bio-distribution. These drawbacks could be mitigated by employing liposomes as carriers for AgNPs. However, there is a lack of systematic studies on production and subsequent physico-chemical characterisation of liposomal systems encapsulating SNPs. The present study therefore investigated the synthesis of liposomes encapsulating SNPs (Lipo/SNPs) using a continuous-flow millimetre-scale reactor, whereby liposome formation was governed by a solvent exchange mechanism. An aqueous phase and an ethanolic lipid phase were conveyed through two separate inlet channels, and subsequently travelled through a serpentine-shaped channel where mixing between the two phases took place. The synthesis process was optimised by varying both liposome formulation and the operating fluidic parameters, including the ratio between inlet flow rates (or flow rate ratio) and the total flow rate. The obtained Lipo/SNPs were characterised for their size and electrostatic charge, using a dynamic light scattering apparatus. Liposome morphology and encapsulation efficiency of SNPs within liposomes were determined by transmission electron microscopy (TEM) imaging. The synthesised negatively charged Lipo/SNP samples were found to have an average size of ∼150 nm (size dispersity < 0.3). The AgNPs encapsulation efficiency was equal to 77.48%, with mostly single SNPs encapsulated in liposomes. By using a multiangle TEM imaging approach, quasi-3D images were obtained, further confirming the encapsulation of nanoparticles within liposomes. Overall, the formulation and production technique developed in the present study has potential to contribute towards mitigating challenges associated with AgNP-mediated drug delivery and diagnostics.

Study of mechanical properties of sustainable biocomposite panels using Jute-PLA and Sisal-PLA

In recent years, bio composites have experienced significant growth and have found applications in various sectors, like domestic use, aerospace, circuit boards, and automotive industries. Extensive research has been conducted on natural fibres to develop it as composite materials so that can compete with synthetic fibre composites. Jute and sisal fibres with Polylactic acid (PLA) means fully biodegradable and recyclable, offer an environmentally friendly solution. The fabrication of the bio-composite specimen involved the utilization of a hot press moulding machine. The maximum strength and bending properties, including ductility, were assessed through flexural and tensile tests following ASTM standards. Free vibration analysis was conducted to determine important characteristics like damping frequency, damping ratio, and natural frequency of the bio composites. The resonant set obtained for Sisal/PLA is inferior to Jute/PLA composites, which clearly demonstrates the influence of fibre in resonant behaviour of the composites. Further Sisal/PLA composites show 20% rise in damping performance at first two resonant sets and 30% in the third resonant. This free vibration characterization of most widely used to composites provides valuable insights into the practical usage under suitable environment conditions.

A semi-analytic method for the computation of the effective properties of composites of two isotropic constituent materials

We develop a computational framework for the semi-analytic representation of the effective transport properties of two-component composite materials, in the spirit of Bergman’s spectral representation. The components of the effective permittivity (or conductivity) tensor are expanded as power series in a contrast parameter between the two phases. The coefficients (the moments of a spectral measure) of these expansions are determined recursively through the numerical evaluations of integrals defined solely on the boundary between the constituent phases, and discretized by high-order (possibly exponentially converging) quadrature schemes. The high precision reached by these coefficients allows the series representation to be recast into Padé approximants (or continued fractions) to provide analytical expressions valid over large (possibly infinite) regions of the parameter complex plane. Examples, thus far limited to two-dimensional rhombic unit cells, demonstrate that the method is reliable for microgeometries and material parameters for which other methods are far less dependable. The analytical representations are particularly useful to study the optical or electrostatic resonant behaviour of some composite materials.

A Microwave Voyage into Swelling Phenomenon: Investigation of Polydimethylsiloxane and VOCs Interaction.

When exposed to specific gases, polymers undergo swelling, leading to physiochemical changes that can significantly affect their performance. Monitoring this swelling phenomenon requires innovative approaches. This study focuses on investigating the real-time resonant microwave behavior of two polydimethylsiloxane (PDMS) structures (solid and porous) in interaction with tetrahydrofuran (THF) and acetone, which are primary swelling agents. A microwave measurement method is proposed using an 8.63 GHz planar split ring resonator (SRR). The device's resonant frequency downshifts to 7.75 and 8.42 GHz when solid and porous PDMS blocks are placed on the split ring gap. Interaction of the solid PDMS and porous PDMS with target gases caused a change in PDMS structure resulting in alterations in the dielectric properties of the PDMS/gas system, as evidenced by the resonator's transmission amplitude and resonant frequency shifts. The magnitude of these shifts depends on the type and concentration of the solvent gas. The PDMS-integrated SRR exhibits a sensitivity of 25.3 MHz/1 ppt THF and 7 MHz/1 ppt acetone. Additionally, the solid block demonstrates response times of 6800 and 4200 s for swelling and deswelling, respectively, when in exposure to 25 ppt concentrations of THF and acetone. Overall, this study underscores the substantial potential of microwave resonators as versatile tools for investigating the physical changes in polymers during their interaction with gases, contributing to the understanding of polymer-gas interactions and opening avenues for further research and diverse applications.

Synergistic Effects of Localized Surface Plasmon Resonance, Surface Plasmon Polariton, and Waveguide Plasmonic Resonance on the Same Material: A Promising Hypothesis to Enhance Organic Solar Cell Efficiency.

This work explores the utilization of plasmonic resonance (PR) in silver nanowires to enhance the performance of organic solar cells. We investigate the simultaneous effect of localized surface plasmon resonance (LSPR), surface plasmon polariton (SPP), and waveguide plasmonic mode on silver nanowires, which have not been thoroughly explored before. By employing finite-difference time-domain (FDTD) simulations, we analyze the plasmonic resonance behavior of a ZnO/Silver nanowires/ZnO (ZAZ) electrode structure. Our investigations demonstrate the dominance of LSPR, leading to intense electric fields inside the nanowire and their propagation into the surrounding medium. Additionally, we observe the synergistic effects of SPP and waveguide plasmonic mode, contributing to enhanced light absorption within the active layer of the organic solar cell. This leads to an improvement in photovoltaic performance, as demonstrated by our previous work, showing an approximate 20% increase in photocurrent and overall power conversion efficiency of the organic solar cell. The incorporation of metallic nanostructures exhibiting these multiple plasmonic modes opens up new opportunities for improving light absorption and overall device efficiency. Our study highlights the potential of these combined plasmonic effects for the design and optimization of organic solar cells.