Resonance Frequencies Of Modes Research Articles

Attenuation of bulk waves using locally resonant soil-coupled metabarriers

Abstract Low frequency ground-borne vibrations generated by transport infrastructure are one of the most serious causes of disturbance to the general population. One possibility to reduce this problem is to use the wave filtering properties of elastic metamaterials. However, their integration in the soil complicates the prediction of their response, and the influence of soil-structure interaction needs to be correctly evaluated for an efficient design. The aim of this work is to experimentally evaluate the efficiency of metamaterial trench barriers set in soil in attenuating vibrations, using low-frequency local resonance mechanisms. A lab scale model is proposed comprising different resonating structures and a cylindrical encasement is adopted to couple the structure to the soil. The influence of various parameters is evaluated, such as metamaterial structure, geometrical characteristics of the resonator, and constituent materials. Finite Element simulations are used to develop a suitable design, analysing mode shapes and resonance frequencies of structures with and without the surrounding encasement. Experimental modal analysis is then performed on the corresponding fabricated samples, providing both model validation and out-of-soil mechanical characterization. Finally, vibration transmission loss measurements are performed in a setup in which different resonant metamaterial barriers are embedded into the soil sample, allowing the evaluation of barrier performance. Results indicate that the metamaterial structures provide good attenuation of vibrations in selected intervals in the low to high frequency range (1–5 kHz), demonstrating the feasibility of the approach in a scaled sample. Preliminary data regarding the structures providing preferable design characteristics is also obtained. These results can be useful for the design of trench barriers scaled to large dimensions in more realistic applicative settings.

Continuous broadband Rydberg receiver using AC Stark shifts and Floquet states

We demonstrate the continuous broadband microwave receivers based on AC Stark shifts and Floquet states of Rydberg levels in a cesium atomic vapor cell. The resonant transition frequency of two adjacent Rydberg states 78 S1/2 and 78 P1/2 is tuned based on AC Stark effect of 70 MHz radio frequency (RF) field that is applied outside the vapor cell. The use of the j=1/2 Rydberg states ensures that only a single mj sublevel is involved. The generated Rydberg Floquet states act to enhance the sensitivity of the AC-Stark-tuned states when the frequency is matched and further extend the bandwidths. We achieve microwave field measurements with over 1.172 GHz continuous frequency tuning and a sensitivity ranging from 280.2 nVcm−1Hz−1/2 to 14.6 μ Vcm−1Hz−1/2. The achieving of continuous frequency and high sensitivity microwave detection will promote the application of Rydberg receivers in the radar technique and wireless communication.

Design and Modelling of MEMS Vibrating Internal Ring Gyroscopes for Harsh Environments.

This paper presents a design, model, and comparative analysis of two internal MEMS vibrating ring gyroscopes for harsh environmental conditions. The proposed design investigates the symmetric structure of the vibrating ring gyroscopes that operate at the identical shape of wine glass mode resonance frequencies for both driving and sensing purposes. This approach improves the gyroscope's sensitivity and precision in rotational motion. The analysis starts with an investigation of the dynamic behaviour of the vibrating ring gyroscope with the detailed derivation of motion equations. The design geometry, meshing technology, and simulation results were comprehensively evaluated on two internal vibrating ring gyroscopes. The two designs are distinguished by their support spring configurations and internal ring structures. Design I consists of eight semicircular support springs and Design II consists of sixteen semicircular support springs. These designs were modelled and analyzed using finite element analysis (FEA) in Ansys 2023 R1 software. This paper further evaluates static and dynamic performance, emphasizing mode matching and temperature stability. The results reveal that Design II, with additional support springs, offers better mode matching, higher resonance frequencies, and better thermal stability compared to Design I. Additionally, electrostatic, modal, and harmonic analyses highlight the gyroscope's behaviour under varying DC voltages and environmental conditions. Furthermore, this study investigates the impact of temperature fluctuations on performance, demonstrating the robustness of the designs within a temperature range from -100 °C to 100 °C. These research findings suggest that the internal vibrating ring gyroscopes are highly suitable for harsh conditions such as high temperature and space applications.

Magnetic tuning with minimal thermal drift in high-Q microspheres coated with magnetorheological polydimethylsiloxane.

Integration of whispering-gallery-mode (WGM) resonators with high-quality factors (Q) into advanced timing, oscillator, and sensing systems demands a platform that enables precise resonance frequency modulation. This study investigates the tuning characteristics of magnetorheological polydimethylsiloxane (MR-PDMS) coated microspheres (µ-spheres) employed as magnetic microresonators, achieving a Q value of 107 at the 1550 nm wavelength. Magnetic WGM resonators not only endow the device with magnetic adjustability but also markedly improve thermal resistance. Experimental findings reveal that the magnetic µ-sphere demonstrates a sensitivity of -32.53 MHz/mT, outperforming conventional magnetic WGM resonators. Furthermore, analysis of the temperature dependence shows a reduction in fluctuation to -2.85 MHz/K, thereby greatly enhancing the sensor's practical detection limit.

The influence of AuNs on the optical properties of GaAs/AlGaAs tunnel-coupled quantum well

Using a numerical approach, we investigated a GaAs/AlGaAs tunnel-coupled quantum well (TCQW) to examine the interplay between electromagnetic waves and gold nanospheres (AuNs) in the presence of an extra SiO2 layer and surface roughness. Our findings demonstrated that the optical efficiency of the response of AuNs was increased in the presence of the SiO2 layer. The extinction cross-section also increased in the presence of surface roughness. Furthermore, we discovered that the orientation of AuNs on the rough surface of TCQW can give rise to a new mode of resonant frequency in the near infrared range. This new mode is advantageous for the TCQW as it is usually seen in AuNs only in the visible range. Lastly, the energy level and wave function of electrons in the TCQW intersubband could be adjusted by an electric field produced by the presence of AuNs. Therefore, this theoretical study could be applied to improve output efficiency and the tuning of performances of optical devices such as solar cells and tunable wavelength photoemitters.

A study of the spatial non-uniformity of reverberation time at low frequencies

This paper presents a study of the spatial non-uniformity of low-frequency reverberation time estimates. Using measured and simulated data, it is demonstrated that the reverberation times estimated from band-limited impulse responses vary as a function of space at low frequencies. The origin of this spatial dependency is investigated using a one-dimensional finite element model. It is shown that the Q-factor and reverberation time at the resonant frequency of a particular mode are spatially dependent and that the spatial dependency is related to the mode shapes. The ranges of the reverberation time estimates as a function of third-octave frequency bands in simulated and measured rooms are presented. An additional finding is that modal damping constants (obtained via eigenvalue analysis) quantify the decay of uncoupled modes but not necessarily the reverberation time. These observations have implications for measurements and simulations of reverberation time at low frequencies. When measuring a spatially averaged reverberation time, the choice of source and receiver positions is important. A guideline is proposed that defines a set of preferred measurement positions based on the mode shapes, from which estimates of the spatially averaged reverberation time can be obtained.

Data-driven prediction of rail neutral temperature for continuously welded rails using impulse-based vibration frequencies

Continuously welded rails (CWR) are prone to the development of high thermal-induced load along the axial direction. Excessive levels of load lead to risk of rail buckling and potential for derailment. Knowledge of the in situ rail axial load in CWRs is therefore important to ensure safe rail management. Field-deployable, nondestructive evaluation techniques for measuring the rail load, or a widely adopted alternative called rail neutral temperature (RNT), are desired. This study uses a data-driven approach to investigate if rail dynamic response data, collected in a non-destructive fashion, can be used to predict RNT. The study is based on a data set comprising rail equivalent strain, temperature and vibration resonance frequencies that was collected from a revenue-service rail over a period of nearly two years. All excited vibration resonance peaks are identified from other peaks caused by noise using spectral amplitude variance. Among these resonance peaks, potentially useful resonances are identified with respect to stacked spectra collected across a testing day using an assumed temperature-frequency relation. A subset of the identified useful resonances is then identified based on their consistent appearance across both testing locations and all testing days, strong correlation to effective strain, and strong correlation to each other. Three particular vibration resonances (or vibration modes -- these terms will be used interchangeably throughout this paper unless specified otherwise. The term mode does not necessarily indicate mode shapes or mode families.) emerge from this process as best candidates. A classic feature selection technique, Lasso linear regression, is then employed to identify critical power combinations of the three resonant mode frequencies. Two power combinations exhibit unique correlation to the measured equivalent axial strain at both test locations across all testing days, and thus show particular ability to predict RNT. The RNT is predicted at one test location using different models based on the power combination data from the other location, and vice versa, where the predictions satisfy standard RNT measurement accuracy expectations.

Asymmetric-Backed Multi-Frequency Ultrasonic Transducer for Conformal Tumor Ablation.

Minimally invasive ultrasound ablation transducers have been widely studied. However, conventional designs are limited by the single working frequency, restricting their conformal ablation ability (i.e., ablation size and shape controllability). New multi-frequency ultrasonic transducer design method is proposed based on the asymmetric backing layer, which divides the transducer into non-backing-layer region (i.e., front-piezoelectric region) and backing-layer region (i.e., front-piezoelectric-backing region) with multiple local thickness mode resonant frequencies. Ablation zone can be controlled by exciting the local resonance within or between the regions, and its control flexibility is further enhanced by driven under a frequency modulation signal. Experiments and calculations are combined for verifying the proposal. The fabricated transducer with a Y-direction asymmetric backing layer shows five resonances, with two in each region and one resonance excited in both regions. Spatial ultrasound emission is demonstrated by acoustic measurements. Tissue ablation experiments verified spatial ablation zone control, and frequency modulation driving method enables the spatial transition of ablation zone from one region to the other, generating different ablation sizes and shapes. Finally, patient-specific simulations verified the effectiveness of conformal ablation. The proposed transducer enables flexible control of ablation zone. This study demonstrates a new method for conformal tumor ablation.

Resonant Frequencies of TE0mn modes in multilayered resonators containing uniaxial anisotropic dielectrics with complex shapes

Resonant Frequencies of TE0mn modes in multilayered resonators containing uniaxial anisotropic dielectrics with complex shapes

Properties of observable mixed inertial and gravito-inertial modes in gamma Doradus stars

The space missions Kepler and TESS provided a large number of highly detailed time series for main-sequence stars, including gamma Doradus stars. Additionally, numerous gamma Doradus stars are to be observed in the near future thanks to the upcoming PLATO mission. In gamma Doradus stars, gravito-inertial modes in the radiative zone and inertial modes in the convective core can interact resonantly, which translates into the appearance of dip structures in the period spacing of modes. Those dips are information-rich, as they are related to the star core characteristics. Our aim is to characterise these dips according to stellar properties and thus to develop new seismic diagnostic tools to constrain the internal structure of gamma Doradus stars, especially their cores. We used the two-dimensional oscillation code TOP to compute sectoral prograde and axisymmetric dipolar modes in gamma Doradus stars at different rotation rates and evolutionary stages. We then characterised the dips we obtained by their width and location on the period spacing diagram. We found that the width and the location of the dips depend quasi-linearly on the ratio of the rotation rate and the Brunt-Väisälä frequency at the core interface. This allowed us to determine empirical relations between the width and location of dips as well as the resonant inertial mode frequency in the core and the Brunt-Väisälä frequency at the interface between the convective core and the radiative zone. We propose an approximate theoretical model to support and discuss these empirical relations. The empirical relations we established could be applied to dips observed in data, which would allow for the estimation of frequencies of resonant inertial modes in the core and of the Brunt-Väisälä jump at the interface between the core and the radiative zone. As those two parameters are both related to the evolutionary stage of the star, their determination could lead to more accurate estimations of stellar ages.

Compact and miniaturized wideband bandpass filter based on substrate integrated waveguide and microstrip line

In this work, we present a simple design of a compact and miniaturized wideband bandpass filter (BPF) based on substrate integrated waveguide (SIW) and microstrip line. Through the order extension, the filtering effect and the order of the Chebyshev response of the designed BPF can be indirectly controlled by preserving square notches (SNs) on the SIW. By introducing one or two SNs in the SIW structure, the resonance frequencies of different modes can be controlled, thus achieving dual- and tri-mode BPFs with wideband and low insert loss. The working principle of the designed BPFs was illustrated by modal analysis, field distribution, and equivalent circuit theory. Based on this, the dual- and tri-mode BPFs with center frequencies of 6.8 and 7 GHz were designed and demonstrated numerically. Further experimental results indicate that the proposed tri-mode BPF has low insertion loss (0.25 dB), compact size (0.27λg2), and wideband bandwidth (60%). In addition, the tri-mode BPF achieves a broadband out-of-band rejection of 1.5f0 (f0 is the center resonance frequency) below the −10 dB level, making it highly promising for various applications in related fields.

Transient behavior of a plate partially immersed in the fluid subjected to impact loadings: Theoretical analysis and experimental measurements

This study aimed to investigate the transient behavior of a rectangular plate partially in contact with fluid subjected to a dynamic external force. To this purpose, a theoretical model was developed to analyze vibration characteristics and transient wave propagation. Based on superposition method, the dry mode shapes and natural frequencies of the plate under vacuum could be obtained. The dry mode shapes were treated as the fundamental function to construct the wet mode that describes the vibration behavior of the fluid-plate coupled system. The velocity potential and fluid pressure within a finite tank due to the plate deflection were derived using an equation governing the incompressible fluid. Based on the relationship between dry mode shape and wet mode shape, the fluid-plate coupled system's wet mode shape and resonant frequency could be determined from the frequency response function. Applying the normal mode method, the transient displacement of plate and fluid pressure can be obtained by solving a system of non-homogeneous differential equations. The theoretical predictions were verified by finite element method (FEM) and experimental measurements. Experiments were conducted using piezoelectric film sensors (polyvinylidene fluoride, PVDF) to measure the force history induced by a steel ball impact to quantitatively analyze the transient response. The comparison results proved that the theoretical predictions and experiments were in good agreement, including the transient responses of the displacement and in-plane strain of a plate partially submerged in the fluid. The results indicate that changes in water depth can induce resonance frequency shifts and wet mode shape distortions, which also illustrate that the vibrational properties of wet modes affect transient behavior. The proposed transient solution demonstrates an analytical approach that connects the physical significance of the dynamic behavior of the fluid-plate coupled system in time and frequency domains; it provides a connection between the transient behaviors and vibration characteristics.

Multi-fold geometric phase metasurface with versatile operations for transmission and reflection

We propose a high efficiency wideband three-fold geometric phase metasurface for versatile operation of transmission and reflection. The transmission coefficient as high as 87 % is achieved in the frequency range of f1 (15.4–15.8 GHz), while equal transmission and reflection are achieved in two frequency bands represented by f2 (14.6–15.2 GHz & 16–17 GHz) with maximum coefficient reaches 49 %. With geometric rotation, the phase shifts of the cross-polarized transmission and co-polarized reflection are six times the rotation angle within the frequency range of 14.6–17 GHz. Furthermore, by elaborately breaking the mirror symmetry while preserving rotational symmetry, interesting features of resonance frequency shift and mode splitting are observed, offering a more fruitful approach for versatile operations. To substantiate the proposed design, a metasurface prototype for vortex beam generation is fabricated and verified by microwave measurement.

Harmonic impedance optimization scheme for multi‐resonance systems to suppress resonance

AbstractHarmonic resonance is caused by harmonic source matching resonance frequency and presents the characteristics of decentralization and whole network in modern grids. The current resonance suppression methods mainly focus on reducing the harmonic source, and are suitable for single‐site and small‐scale grids. This paper presents a new method for suppressing parallel resonance at system level. The holistic harmonic resonance is suppressed by reducing the harmonic impedance. In addition, new resonances are prevented by weakening the coupling between resonance and non‐resonance frequencies. The resonance modal analysis and resonance frequency shift (RFS) are employed to optimize harmonic impedance. Simulation results indicate that the capacitance parameter has higher sensitivity and is theoretically more suitable for RFS. Considering the accuracy of modal frequency sensitivity, a variable‐limit genetic algorithm for iteration is proposed. The validity of the proposed method was verified using an IEEE 14‐bus test network.

Stimulated magneto-optics with different detunings for plasma local diagnostics

The polarization plane stimulated rotation angle of a probe signal in an intense laser field in plasma is calculated for arbitrary detunings of intense and weak laser waves compared with the resonant transition frequency of the medium. Estimates of the residual gas local density in a cesium plasma have been found based on the Faraday, Cotton–Mouton effects and on the effect of stimulated rotation of the polarization plane of the probe signal in an intense laser field. It is shown that the rotation in the medium has a complex structure consisting of the sum of only the influence of the magnetic field, only the influence of the intense laser field and the interfering part of the magnetic and intense laser fields.

On the nonlinear energy interactions in vibro-impacting cantilever

The nonlinear energy interactions are an intriguing aspect of nonlinear oscillators, such as vibro-impacting cantilevers (VICs). Despite extensive research, the domain of energy interactions in nonlinear oscillators still requires further exploration. The motivation arises from the complex and captivating dynamics as well as the vast array of potential applications. This paper presents a comprehensive investigation of various energy interaction mechanisms within the resonance realms of the first and second mode resonance frequencies of harmonically base-excited VICs. These energy interactions are of paramount importance as they give rise to the captivating response of the VIC, characterized by multi- and quasi-periodicity, energy amplification, combination resonances, amplitude modulation, and other intriguing features. This paper introduces the phenomenon termed “Harmonic Resonance Energy Stimulation (HRES)” and extensively investigates its role in generating the secondary jump in the frequency response. Moreover, the present study discovers and reports the non-resonant energy interactions and resulting modulating, quasi-periodic response in the VIC. Various illustrative plots obtained from the theoretical investigation, relying on the mathematical model, have been utilized to facilitate a comprehensive investigation. The results hold immense significance as they contribute valuable knowledge to the nonlinear dynamics of VIC, which is of great importance in research advancements and practical applications.

A Compact Millimeter-Wave Multilayer Patch Antenna Array Based on a Mixed CPW-Slot-Couple Feeding Network.

A compact Ka-band antenna array has been proposed to realize broadband and high gain for millimeter-wave applications. The antenna array is divided into a multilayer composed of a driven slot patch layer and a parasitic patch array layer, which is excited by a mixed CPW-Slot-Couple feeding network layer. According to characteristic mode analysis, a pair of narrow coupling slots are introduced in the driven patch to move the resonant frequency of characteristic mode 3 to the resonant frequency of characteristic mode 2 for enhanced bandwidth. In this article, a 1to4 CPW-Slot-Couple feeding network for a 2 × 2 driven slot patch array is implemented, and then each driven slot patch excites a 2 × 2 parasitic patch array. Finally, a proposed 4 × 4 × 3 (row × column × layer) Ka-band antenna array is fabricated to verify the design concepts. The measured results show that the frequency bandwidth of the antenna array is 25 GHz to 32 GHz, and the relative bandwidth is 24.5%. The peak gain is 20.1 dBi. Due to its attractive properties of miniaturization, broadband, and high gain, the proposed antenna array could be applied to millimeter-wave wireless communication systems.

Temporal dynamics of surface phonon polaritons in polar dielectric nanoparticles with nonlocality

Surface phonon polaritons (SPhPs) supported by polar dielectrics have been a promising platform for nanophotonics in mid-infrared spectral range. In this work, the temporal dynamic behavior of polar dielectric nanoparticles without (or with) spatial dispersion/nonlocality driven by the ultrashort Gaussian pulses is carried out. We demonstrate that three possible scenarios for the temporal evolutions of the dipole moment including ultrafast oscillations with the decay, exponential decay, and keeping a Gaussian shape exist, when the pulse duration of the incident field is much shorter than, similar to, and much longer than the localized SPhP lifetime. Once the nonlocal effect is considered, the oscillation period becomes large slightly, and the exponential decay turns fast. Furthermore, nonlocality-induced novel temporal behavior is found such as the decay with long-period oscillations when the center frequency of the incident pulse lies at the frequency of adjacent longitudinal resonant modes. The positive and negative time-shifts of the dielectric response reveal that the excitation of the dipole moment will be delayed or advanced. These temporal evolutions can pave the way towards potential applications in the modulation of ultrafast signals for the mid-infrared optoelectronic nanodevices.

The effect of busbar structure on Q factor enhancement and spurious mode suppression in Lamb wave resonators

Lamb wave resonators (LWRs) exhibiting high-quality factors and clean spectra demonstrate promising applications in RF communication and sensing. This paper discusses the relationship between the spurious mode, the quality factor, and the effective electromechanical coupling factor of resonators. When the resonant frequency of the spurious mode is slightly below the parallel resonant frequency (fp), the quality factor at fp (Qp) decreases dramatically. To enhance Qp and suppress the spurious mode, the LWRs with busbars including only the top electrode (non-overlap busbars) and the LWRs with busbars incorporating both top and bottom electrodes (overlap busbars) are designed and fabricated. The LWR with 12 μm-wide overlap busbars exhibits a notable enhancement in Qp, elevating it from 553.76 to 1488.17 and suppresses the spurious mode simultaneously. This research introduces a promising approach to suppress the spurious mode and enhance the quality factor of Lamb wave resonators, thereby holding great potential for applications in sensors and mobile communication.

Resonant Frequencies of TE0mn modes in multilayered dielectric-ferrite resonators with complex shapes

The method of evaluating the resonant frequencies of multilayered resonator containing demagnetized ferrites is presented. The detailed solution of Maxwell's equations for such a structure by means of the radial modes matching method for TE0mn modes is given. The results of calculations using developed and launched computer program are given. Results of calculations are compared with those obtained by other method using CST simulator. These results are in close agreement, which proves the correctness of the method. The developed solution, and the software program can be used to measure the initial permeability of ferrites.