Resonance Curves Research Articles

Characteristics of partially filled Helmholtz resonators

In this work we have developed a technique for the measurement of the resonance curve of Helmholtz resonators as a function of filling with beads and sands of different sizes, and water as the reference. Our measurements allowed us to observe very different behaviors of resonance frequencies and resonance half-widths as a function of the size of the sand grains and the beads. By comparing results for beads and water we were able to prove that the sound penetrates the interstitial space between the beads. This was confirmed by measurements of the resonance properties in resonators filled with spherical beads whose experimentally determined filling factor is close to the random filling factor of about 0.54. The similar behavior of the frequency and half-width of resonance of sand-filled resonators of three different sizes allowed us to suggest that sound penetrates the sand in the same way as it does the beads.

Исследование магнитных наночастиц оксида железа, покрытых оксидом кремния, методом ферромагнитного резонанса

Magnetic nanoparticles of magnetite with a size of ~8 nm synthesized with a different type of coating were studied by ferromagnetic resonance in the temperature range from 7 to 300 K. The features of the experimental temperature dependences of the parameters of the ferromagnetic resonance curve (the magnitude of the resonant field, line width and intensity) and their approximation allowed us to estimate the values of characteristic temperatures. Firstly, the value of the Vervey temperature and the dependence of its value on the type of coating were determined. Secondly, the temperature of transition of nanoparticles to the superparamagnetic state (blocking temperature) and the temperature range within which the magnetic structure of the outer shell of the magnetic nanoparticle is in the spin glass state are established

Dynamical Stability of a 3-DOF Auto-Parametric Vibrating System

PurposeThis article concentrates on the oscillating movement of an auto-parametric dynamical system comprising of a damped Duffing oscillator and an associated simple pendulum in addition to a rigid body as main and secondary systems, respectively.MethodsAccording to the system generalized coordinates, the controlling equations of motion are derived utilizing Lagrange's approach. These equations are solved applying the perturbation methodology of multiple scales up to higher orders of approximation to achieve further precise unique outcomes. The fourth-order Runge–Kutta algorithm is employed to obtain numerical outcomes of the governing system.ResultsThe comparison between both solutions demonstrates their high level of consistency and highlights the great accuracy of the adopted analytical strategy. Despite the conventional nature of the applied methodology, the obtained results for the studied dynamical system are considered new.ConclusionsIn light of the solvability criteria, all resonance scenarios are classified, in which two of the fundamental exterior resonances are examined simultaneously with one of the interior resonances. Therefore, the modulation equations are achieved. The conditions of Routh–Hurwitz are employed to inspect the stability/instability regions and to analyze them in accordance with the solutions in the steady-state case. For various factors of the examined structure, the temporary history solutions, the curves of resonance in terms of the adjusted amplitudes and phases, and the stability zones are graphically presented and discussed.ApplicationsThe results of the current study will be of interest to wide range experts in the fields of mechanical and aerospace technology, as well as those working to reduce rotors dynamical vibrations and attenuate vibration caused by swinging structures.

DESIGN OF METHOD FOR NONLINEAR SHEAR MODULUS MEASURING IN GEL-LIKE MEDIUM BY APPLYING AN ADDITIONAL STATIC STRESS TO AN ACOUSTIC RESONATOR

Measurements of the nonlinear parameter of a gel-like medium were carried out in an acoustical resonator fixed without slipping between two solid-state boundaries. A sample of thickness L is fixed on an oscillating plate (x = 0). The other plate of finite mass on the free surface of the sample (x = L) moves together with this surface. By changing the mass of the plate (x = L), it is possible to achieve additional static deformation of the resonator up to 65%. The dynamic method assumes measuring resonance curves at various static deformations. Nonlinear properties appear at deformations of more than 20%. The nonlinear parameter and shear modulus measured dynamically were compared to static measurements where the dependence becomes nonlinear at strains greater than 30%. The static values of the shear modulus and the nonlinear parameter correspond to the values obtained in the dynamic method within an error.

Analysis on the mechanism and characteristics of nanofluid imbibition in low permeability sandstone core pore surface: Application in reservoir development engineering

In this work, the mechanism of nanofluid imbibition in the development of low permeability reservoirs is studied. Firstly, by analyzing nuclear magnetic resonance (NMR) curves and imaging maps, the imbibition displacement effects of low-permeability reservoirs in water and different nanofluids are compared. Subsequently, the influence characteristics of rock modification mechanism of nanofluid on imbibition displacement are analyzed by three-phase contact angle experiments. Finally, the attraction forces between oil and rock surfaces with different properties are measured by atomic force microscopy (AFM) experiments, and the influence of wetting inversion of nanofluids on the adsorption between oil and reservoir rocks is evaluated. The results show that the relaxation time map area of the core treated with nanofluid is smaller than that of the core treated with water, and the NMR images show that the nanofluid has a higher sweep efficiency, indicating that nanofluid can improve the oil displacement efficiency of low-permeability reservoirs. The higher the nanoparticle concentration of fluid, the more significant the effect. In addition, the effect of nanofluids on oil displacement efficiency in small pores and large pores of the reservoir is obvious, and the increase amplitude is 30 % and 50 %, respectively. Scanning electron microscope (SEM) images show that nanoparticles adsorbed on the reservoir inner wall exert a wetting inversion effect, leading to changes in reservoir wettability and promoting imbibition oil displacement, which is also reflected in the NMR maps. Contact angle experiments show that nanofluids convert the lipophilicity of rock surface into hydrophilicity, and the contact area between oil and rock shrinks due to the change of wettability and the decrease of interface energy, which weakens the adsorption between the two, promotes capillary imbibition of fluid and oil displacement. The AFM experiment confirms that nanoparticles reduce the microscopic adsorption force between oil and rock through wetting inversion and interface energy reduction. It is less difficult for the fluid to peel oil from the reservoir rock, which promotes the oil displacement. The studies show that nanofluid imbibition has advantages in the field of low permeability reservoir development.

Stabilization of Copper-Based Biochips with Alumina for Biosensing Application

Surface plasmon resonance devices typically rely on the use of gold-coated surfaces, but the use of more abundant metals is desirable for the long-term development of plasmonic biochips. As a substitute for gold, thin copper films have been deposited on glass coverslips by thermal evaporation. As expected, these films immersed in a water solution initially exhibit an intense plasmonic resonance comparable to gold. However, without protection, an angle-resolved optical analysis shows a rapid degradation of the copper, characterized by a continuous angular shift of the plasmonic resonance curve. We show that copper films protected with a thin layer of aluminum oxide of a few nanometers can limit the oxidation rate for a sufficient time to perform some standard measurements. As the process is simple and compatible with the current biochip production technique, such an approach could pave the way for the production of alternative and more sustainable biochips.

Analyzing the motion of a forced oscillating system on the verge of resonance

In this paper, a nonlinear vibrating dynamical system of two degrees-of-freedom is examined. By virtue of the generalized coordinates, the controlling system of motion is constructed using Lagrange’s equations. Among other perturbation approaches, the technique of multiple scales (TMS) is utilized to get the required solutions analytically of this system till the third approximation. These solutions allow us to discuss the system’s behavior and realize both the solvability requirements and the modulation equations in the context of the system’s resonance scenarios. The resonance curves and solution diagrams are drawn to demonstrate the influence of the various parameters of the behavior of the considered system. The stability and instability of the gained possible fixed points are examined. The used method is considered traditional, but it is applied to a certain specified model. Therefore, the obtained outcomes are considered novel. The importance of this work is represented in its various applications in practical life, such as the motion of railway vehicles, for transporting goods in ports, and for facilitating the movement of passengers’ baggage at airports.

Energy Analysis and the Determination of the Resonant Frequency of a Custom-Designed Scientific Oscillating Body

This paper computes the resonant frequency and energy curves of a harmonically oscillating pendulum. The apparatus was customized in design, and could also be used for demonstrating and validating other oscillatory phenomena with extreme accuracy. The determined resonant frequencies of three pendula of length 21.10 cm, 23.84 cm, and 33 cm, used in this work are 1.07 Hz, 1.0 Hz, and 0.86 Hz respectively, which were found to be close to theoretically calculated values, i.e., the natural frequency of the pendulum. The error analysis of the determined resonant frequencies validated the consistency of the designed laboratory apparatus with the minute errors of 0.009, 0.019, and 0.011 respectively. The potential and kinetic energy calculated for the bob positions ranging from -5.30 cm to +5.30 cm showed an inverse relationship between the two with a total energy of 115.17 J for all the experimental positions of the bob. As an annexure of the study, the paper also determined the g (acceleration due to gravity) value of 9.78 m/s2 from the experiment, which is very close to its standard value, 9.8 m/s2.

New method for fitting complex resonance curve to study nonlinear superconducting resonators

We present a new fitting method that can robustly and accurately fit the complex transmission curve of a superconducting resonator in the nonlinear regime. This method takes into account the varying internal current in the resonator at different frequencies and the nonlinear dependence of the inductance on the internal current , where is a characteristic current. We demonstrate using this method to retrieve important resonator parameters, such as the quality factor and the resonance frequency, from resonators driven below, near, and above bifurcation. We further use this method to retrieve for lumped-element TiN resonators with various inductor designs. By fitting the resonance frequency shift at different readout powers of each resonator, we can determine the characteristic current , which is found to be linearly related to the cross-sectional area of the narrow inductor strip. Our method has wide applications in superconducting detector, superconducting qubit and parametric amplifier data analysis where the resonator is driven in the nonlinear regime.

Assessment of magnetoelastic resonance parameters retrieval for sensor applications

Magnetoelastic resonance sensors have been widely used for several sensing applications, as their resonance behavior is very sensitive to different external factors and they can be operated remotely. Nevertheless, under some working conditions, such as when the sensor signal is low, has considerable noise, or the medium viscosity causes damping of the signal, the accuracy in obtaining the parameters that characterize the resonance response of these sensors by direct methods can decrease. The aim of this work is to improve the performance of magnetoelastic sensors through the use of numerical fittings of the resonance curves to obtain accurately the resonance parameters used for detection. The capability of these numerical fittings to retrieve the parameters when signals present different levels of noise is evaluated, and the accuracy of this fitting method is compared with the precision of classical direct methods.

A parametric study on the subharmonic isolas in a bistable dielectric elastomer actuator

Resonant actuation of dielectric elastomer actuators (DEAs) greatly improves their output power densities and energy efficiencies. However, their outstanding performance usually accompanies complex dynamics which hinder the robust applications of DEAs. Isolated frequency responses, or isolas, are branches of resonant curves that are isolated from the main frequency response curve, hence can be easily overlooked during the dynamic analyses of DEAs. Once triggered, however, isolas can lead to dramatic changes in frequency responses, which pose great threats to system stability. As a critical step towards controlling the isolas within DEAs, this work adopts a bistable cone DEA (BCDEA) configuration and conducts dedicated numerical and experimental parametric studies on its isolas to uncover the physical mechanisms that create them. The effects of potential barriers, equilibrium positions and excitation level on the evolutions of isolas are studied with the aim of finding the critical parameters that determine their evolutions. The outcomes of this paper help to gain more insights into the complex isola phenomena in BCDEAs, which may offer guidelines for eliminating undesired isolas within BCDEAs or for exploiting isolas for applications in, e.g. energy harvesting, soft robotic locomotion and vibro-tactile feedbacks.

Modeling and analyzing the motion of a 2DOF dynamical tuned absorber system close to resonance

This work investigates the planar motion of a dynamical model with two degrees-of-freedom (DOF) consisting of a connected tuned absorber with a simple pendulum. It is taken into account that the pendulum’s pivot moves in a Lissajous trajectory with stationary angular velocity in the presence of a harmonic excitation moment. In terms of the model’s generalized coordinates, Lagrange’s equations are used to derive the motion’s controlling system. The approximate solutions of this system, up to a higher order of approximation, are achieved utilizing the approach of multiple scales (AMS). Resonance cases are all classified, in which two of them are examined simultaneously to gain the corresponding equations of modulation. The solutions at the steady-state are studied in terms of solvability conditions. According to the Routh-Hurwitz criteria, all potential fixed points at steady and unsteady states are determined and graphed. The dynamical behavior of the motion's time-histories and the curves of resonance are drawn. Regions of stability are examined by inspecting their graphs in order to assess the favorable impact of various parameters on the motion. The achieved outcomes are regarded as novel because the used methodology is applied to a specific dynamical system. The importance of this model under study can be seen from its numerous applications in disciplines like engineering and physics. Furthermore, pendulum vibration absorbers are commonly employed to reduce the vibrations in engineering constructions such as chimneys, bridges, television towers, high buildings, auto-balancing shafts, and antennas.

Application of resonance functions in estimating the parameters of interwell zones

It is shown that the use of force resonance leads to the effect of “shaking” the formation, followed by breaking up the film oil and involving it in the further filtration process. For the first time in oilfield geophysics, the concept of passive noise-metering method is justified for monitoring oil and gas deposit development by measuring the quality factor of the contours in the point areas of formation development channels in interwell zones. It is established that determining the depth of modulation for the reactive substitution parameter of the linear FDC chain is crucial not only for determining the parametric excitation in FDC attenuation systems, but also without attenuation in the metrological support for the analysis of petrophysical properties of rock samples from the wells. It is shown that based on the method of complex amplitudes (for formation pressure current, differential flow rates, impedance), different families of resonance curves can be plotted: displacement amplitudes (for differential flow rates on the piezocapacity of the studied formation section), velocities (amplitudes of formation pressure current) and accelerations (amplitudes of differential flow rates on the linear piezoinductivity of the FDC section). The use of predicted permeability and porosity properties of the reservoir with its continuous regulation leads to increased accuracy of isolation in each subsequent sub-cycle of new segment formation in the FDC trajectories, which contributes to a more complete development of productive hydrocarbon deposits and increases the reliability of prediction for development indicators.

Highly Sensitive Plasmonic Biosensors with Precise Phase Singularity Coupling on the Metastructures.

In this paper, we demonstrated the ability of a plasmonic metasensor to detect ultra-low refractive index changes (in the order of ∆n = 10−10 RIU), using an innovative phase-change material, vanadium dioxide (VO2), as the sensing layer. Different from current cumbersome plasmonic biosensing setups based on optical-phase-singularity measurement, our phase signal detection is based on the direct measurement of the phase-related lateral position shift (Goos–Hänchen) at the sensing interface. The high sensitivity (1.393 × 108 μm/RIU for ∆n = 10−10 RIU), based on the Goos–Hänchen lateral shift of the reflected wave, becomes significant when the sensor is excited at resonance, due to the near-zero reflectivity dip, which corresponds to the absolute dark point (lower than 10−6). GH shifts in the order of 2.997 × 103 μm were obtained using the optimal metasurface configuration. The surface plasmon resonance (SPR) curves (reflectivity, phase, GH) and electromagnetic simulations were derived using the MATLAB programming algorithm (by the transfer matrix method) and Comsol modeling (by finite element analysis), respectively. These results will provide a feasible way for the detection of cancer biomarkers.

Enhanced tetracycline removal using membrane-like air-cathode with high flux and anti-fouling performance in flow-through electro-filtration system

The membrane-like air-cathodes modified with different polyaniline were prepared using phase inversion method, which possessed dual functions of interception and electrochemical degradation, and showed good conductivity (15.9±0.4 to 25.7±0.5 mS cm-1) and porosity (77.0±0.1 to 87.8±0.1%) compared to the unmodified control one (13.2±0.5 mS cm-1, and 63.1±0.7%). At tetracycline 50mg L-1, the cathode with 25 wt% polyaniline exhibited the highest rejection rate and final removal (71.1% and 92.9%, 35.9% and 31.4% higher than the control), the highest water flux recovery (97.9%), and the lowest attenuation of porosity and conductivity. The modified cathode also showed an autocatalytic effect on H2O2, an obvious ·OH peak appeared on the electron paramagnetic resonance curves. It also had good anti-fouling performance because it exhibited a high durability (the final removal was decreased by 4.0% after 15 cycles) with a long service life of 124 periods (372h, 15.5 d). The tetracycline (0.5mg L-1) removal in the river background was near 100%, and the chemical oxygen demand removal was 91.9%, supporting that it was suitable for treating antibiotics in natural water without adding agents but only for electricity consumption.

Vibration Control of Coupled Wind Tower–Nacelle–Blade System

Wind turbines are slender and flexible structures which can undergo large amplitude vibrations when subjected to external loads and, an important way to reduce these excessive vibrations is to apply structural control. In this work, the vibration control of the coupled wind tower–blade system subjected to external lateral loads and rotating blade is studied. To model the tower and blade, the nonlinear Euler–Bernoulli beam theory was applied, and the structural control device considered is a nonlinear inverted tuned mass damper pendulum (ITMDP), located at the top of the tower. The Rayleigh–Ritz method, together with Hamilton’s principle, is applied to obtain a set of coupled nonlinear ordinary differential equations of motion which are in turn solved by the Runge–Kutta method. First, the dynamic instability of the system is studied by considering the variation of the natural frequencies of the tower, as a function of the speed of rotation of the blade and the veering phenomenon is observed. The optimum parameters for the ITMDP are obtained and, a nonlinear dynamic analysis is performed to evaluate the influence of the tuned mass damper (TMD) in the nonlinear regime, by obtaining the time responses, resonance curves, Poincaré maps and basins of attraction. The obtained results show the importance of considering the coupled system and the good performance of the structural control in the dynamic behavior of the system.

Dynamics and integrability of the swinging Atwood machine generalisations

This paper studies the dynamics and integrability of two generalisations of a 3D Swinging Atwood’s Machine with additional Coulomb’s interactions and Hooke’s law of elasticity. The complexity of these systems is presented with the help of Poincaré cross sections, phase-parametric diagrams and Lyapunov exponents spectrums. Amazingly, such systems possess both chaotic and integrable dynamics. For the integrable cases we find additional first integrals and we construct general solutions written in terms of elliptic functions. Moreover, we present bifurcation diagrams for the integrable cases and we find resonance curves, which give families of periodic orbits of the systems. In the absence of the gravity, both models are super-integrable.

Resonant curves of geo-centric satellite under the gravitational effect of the Earth-Moon-Sun system including Earth’s equatorial ellipticity and resistive force using unperturbed solutions

This research article presents the effect of the Earth’s equatorial ellipticity and the resistive force on a geocentric satellite’s resonant curves. The resonance occurs in the motion of the satellite due to the frequencies, the angular velocity of the satellite, the rate of change of Earth’s equatorial ellipticity parameter (γ̇), the steady-state angular velocity of the Moon around the Earth (ϑ0̇), and the steady-state angular velocity of barycenter (Θ̇) around the Sun. We express the equations of motion of the satellite in a spherical coordinate system by using the Earth’s potential. By applying the unperturbed solution, we reduced the system of equations into a second-order differential equation and obtained its solution. From the solution it is observed that the resonance appears between the frequencies δs0̇,γ̇,Θ0̇ and ϑ0̇ at ten resonant points. We analyze the resonant curves corresponding to the resonant points and show the effect of resistive force and latitude of a satellite. Also, We show the effect of eccentricity (e) and semi-major axis (a) on the oscillatory amplitudes (Ai), for i=1,2,3…21.

The stability of 3-DOF triple-rigid-body pendulum system near resonances

In this article, the motion of three degree-of-freedom (DOF) dynamical system consisting of a triple rigid body pendulum (TRBP) in the presence of three harmonically external moments is studied. In view of the generalized coordinates of the system, Lagrange's equations are used to obtain the governing system of equations of motion (EOM). The analytic approximate solutions are gained up to the third approximation utilizing the approach of multiple scales (AMS) as novel solutions. The solvability conditions are determined in accordance with the elimination of secular terms. Therefore, the arising various resonances cases have been categorized and the equations of modulation have been achieved. The temporal histories of the obtained approximate solutions, as well as the resonance curves, are visually displayed to reveal the positive effects of the various parameters on the dynamical motion. The numerical results of the governing system are achieved using the fourth-order Runge–Kutta method. The visually depicted comparison of asymptotic and numerical solutions demonstrates high accuracy of the employed perturbation approach. The criteria of Routh–Hurwitz are used to investigate the stability and instability zones, which are then analyzed in terms of steady-state solutions. The strength of this work stems from its uses in engineering vibrational control applications which carry the investigated system a huge amount of importance.

Bilayered soft/hard magnetic nanowires as in-line writing heads

Multi-segmented cylindrical nanowires (NWs) are the most promising systems for 3D racetrack memory devices, where information is stored as in-line magnetic domains. However, reading and writing information is still a challenge, as external reading/writing heads have to be implemented near the tracks. The writing component should be made of a bilayered soft/hard coupled magnetic system, so that information could be easily written by external magnetic fields. Here, we demonstrate the feasibility of using a Ni90Cu10/Fe20Co80 segmented NW as the writing element, in which magnetic information is written by applying external magnetic fields. Using low-cost template-assisted electrodeposition methods, single, bi- and multi-segmented NW hexagonal arrays of NiCu and FeCo/Au were fabricated. A throughout magnetic characterization using magnetic hysteresis loops, ferromagnetic resonance and first-order reversal curves (FORCs) revealed that the soft segment (NiCu) induced the reversal of the hard segment (FeCo) in a two-step process, reducing its coercive and effective anisotropy fields when coupled. Finally, micromagnetic simulations certified the experimental observations of a multi-step reversal process. This work demonstrates the important role of interface interactions for the future implementation of an in-line writing component in a 3D racetrack memory device, enhancing their potential applicability.