Experimental Resonance Frequencies Research Articles

Spectral properties of superconducting microwave photonic crystals modeling Dirac billiards

We determined experimentally the eigenvalues of two rectangular quantum billiards that contain circular scatterers forming a triangular grid, so-called Dirac billiards. For this we performed measurements of unprecedented accuracy using superconducting macroscopic-size microwave billiards that enclose a photonic crystal. The objective was the investigation of the peculiar features of the density of the eigenvalues (DOE), which resemble that of a graphene flake, and of their fluctuation properties. We identified in the measured resonance spectra Dirac points and in their adjacent bands the van Hove singularities (VHSs), that show up as sharp peaks in the DOE. The analysis of the experimental resonance frequencies and of the band structure, which was computed with a tight-binding model, revealed that the VHSs divide the associated band into regions where the system is governed by the nonrelativistic Schr\"odinger equation of the quantum billiard and the Dirac equation of the graphene billiard of corresponding shape, respectively. Furthermore, we demonstrate that Dirac billiards are most suitable for the modeling of idealized graphene. Indeed, the DOEs of both systems are well described by a finite tight-binding model which includes first-, second-, and third-nearest-neighbor couplings.

Shape oscillation and detachment conditions for a droplet on a vibrating flat surface

In this study, we obtain experimental understanding of the mode characteristics of a droplet placed on a flat surface under periodic forced vibrations. The detachment conditions for the droplet on the surface were also studied. In order to estimate the resonance frequency of a droplet placed on a hydrophobic surface, theoretical modelling was combined with experimental approaches. Two high speed cameras were used to observe droplet characteristics, including mode shape, detachment, occurrence of secondary droplet breakup, and horizontal torsional motion. Two cameras were installed to the right above the droplet and at the side of the droplet. There was no more than an 18% discrepancy between the theoretical and experimental resonance frequencies. This discrepancy was likely caused by several factors such as contact line friction, nonlinear wall adhesion, and experimental uncertainty. When applying a relatively low voltage to a speaker, the contact line of a droplet was pinned and shape oscillations of the droplet appeared in a bilaterally symmetric way. In contrast, at higher voltages, the contact line depinned and the shape oscillations became more active. For excitation frequencies identical to the mode frequency, the lobe size of the droplet was relatively larger than that at neighbouring frequencies. The experimental results also indicate that the generation and complete detachment of small-scale droplets occur only at the 2nd mode.

Mechanics of filled carbon nanotubes

Abstract The benefits of filling carbon nanotubes (CNTs) with assorted molecular and crystalline substances have been investigated for the past two decades. Amongst the study of new structural phases, defects, chemical reactions and varied types of host–guest interactions, there is one fundamental characterisation aspect of these systems that continues to be overlooked: the mechanical behaviour of filled CNTs. In contrast to their empty counterparts, the mechanics of filled CNTs is a subject where reports appear far and apart, this despite being key to the application of these materials in technological devices. In the following paragraphs, we review the work that has been carried out up to the present on the mechanics of filled CNTs. The studies discussed range from experimental resonant frequency essays performed within electron microscopes to modelling, via molecular dynamics, of three-point bending of nanotubes filled with gases.

Controllable resonance frequency in Ni/Pb(Zr,Ti)O3/FeCo cylindrical composites

Magnetoelectric (ME) Ni/Pb(Zr,Ti)O3/FeCo cylindrical layered composites with a negative magnetostrictive/piezoelectric/positive magnetostrictive structure have been prepared by electroless deposition. The magnetostrictive layers are in direct contact with the piezoelectric layer. The ME effect was measured by applying both constant and alternating magnetic fields parallel and perpendicular to the cylinder’s axis direction. The ME voltage coefficient increases, and the resonance frequency decreases as the cylinder diameter increases. The experimental resonance frequency is very close to the calculated ones. This characteristic of resonance frequency can be applied to design a kind of ME composites with the controllable resonance ME coupling.

Modeling, Fabrication and Characterization of Piezoelectric ZnO-Based Micro-Sensors and Micro-Actuators

In this study, capabilities of zinc oxide (ZnO) thin films in sensing and actuating were investigated using micromachined micro-cantilevers. A heterogeneous piezoelectric cantilever was modeled to study its response under voltage and/or external mechanical loading. A ZnO thin-film micro-cantilever was designed based on the developed theoretical model. Simulated tip deflections of the micro-cantilever were on the nanometer level under typical electrical and mechanical input. A prototype was fabricated with microfabrication techniques. The ZnO thin film was sputtered at room temperature and demonstrated good compatibility with common chemicals and processes in micromachining. The fabricated micro-cantilever was experimentally characterized for its actuating and sensing performance. For actuator characterization tip deflection of the micro-cantilever was detected by a laser Doppler vibrometer, while for sensor characterization the micro-cantilever was calibrated as an acceleration sensor using a reference accelerometer. The experimental resonant frequency, actuating and sensing sensitivities agreed well the design specifications.

Nonlinear dynamics of adhesive micro-spherical particles on vibrating substrates

The coupled (rocking and out-of-plane) vibrational dynamics of micro-spherical particles on vibrating flat substrates is studied experimentally, analytically, and computationally. In the experimental spectral responses of some of vibrating particles, in addition to their predicted rocking resonance frequencies, extra resonance peaks at the doubles of these predicted frequencies have been previously observed and reported. To understand and explain the rocking resonance frequency doubling effect, a two-dimensional mathematical model describing the coupled dynamics of a micro-spherical particle in the out-of-plane and rocking coordinates is developed and reported. Previously, the doubling effect was leading to ambiguity in adhesion characterization. It is determined that the frequency doubling observed in the spectral domain responses of particles is caused by nonlinear coupling between the out-of-plane and in-plane modes of motion while the particle is experiencing a whirling-like motion taking place around a nearly stationary axis tilted with respect to the substrate normal (as opposed to the substrate normal itself). In current study, the leaning angles of the rocking motion with whirling of a set of polystyrene latex particles are approximated by utilizing the coupled dynamic model. Also, the work-of-adhesion values extracted from the experimental resonance frequencies of a set of particles using the developed model are compared to those reported in the literature and a good agreement is found. The detection and analysis of the reported motion is relevant to adhesion bond characterization and particle manipulation.

Accurate resonant frequency of isosceles right‐angled triangular patch antenna

AbstractDue to high quality factor compared to other regular well known shaped resonators, triangular resonators, and/or radiators attract much attention recently. The development of triangular geometry (except equilateral) is still in its early stages of research due to lack of proper theory. In this article, an isosceles right‐angled triangular microstrip antenna (TMA) is analyzed theoretically using well known cavity model. Internal field components are derived. An expression for predicting resonant frequency is obtained. Results are compared with published results to show the correctness of our theory. A simple expression for computing effective side length of isosceles right‐angled TMA is provided. A prototype is also fabricated to verify this theory. The error between theoretical and experimental resonant frequency is 0.0773%. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1306–1308, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27536

Doubling of rocking resonance frequency of an adhesive microparticle vibrating on a surface

For some spherical micro-particles on a vibrating flat substrate, in addition to their predicted rocking resonance frequencies, other resonance peaks at their doubles are observed. Here, a mathematical model and experimental results are presented for explaining this observation. It is determined that the frequency doubling is caused by nonlinear coupling between the out-of-plane and rocking modes of motion, and whirling-like motion that must be present for the presence of doubling effect. It is also found that the work-of-adhesion values extracted from the experimental resonance frequencies of a set of particles using the developed model are in good agreement with those reported in the literature.

Frequency-dependent resonance and asymmetric droplet oscillation under ac electrowetting on coplanar electrodes

Sessile droplet oscillations in electrowetting on dielectric with a coplanar-electrode configuration are studied experimentally under the actuation of ac voltage with different frequencies. It was found that the experimental resonance frequencies and the number of lobes at different resonance modes agree reasonably well with a previous linear analysis. Oscillations of contact width and droplet height are in-phase at resonance modes P2n+2 while out-of-phase at P2n with n = 2, 4, 6,…. At certain critical frequencies, the droplet oscillations are very weak and switch from in-phase (out-of-phase) to out-of-phase (in-phase). For the oscillations after resonance frequency but before critical frequency, at low frequency, the large amplitude oscillation of the contact line deforms it from a circle to having lobes; the number of lobes increases with the frequency and their position alternates in the azimuthal direction, through periodical droplet spreading and receding. For the oscillations after critical frequency but before resonance frequency, the droplet oscillation demonstrates droplet waggling with an obvious contact line at normal and abnormal stops, due to the contact line pinning at low frequency, or the transportation of lobes on the droplet surface from one end to the other at high frequency. These asymmetric oscillations will produce a more chaotic fluid flow inside the droplets than symmetric oscillations and could be used purposely to enhance mixing in droplet-based micro-fluidics.

A new technique to detect defect size and depth in composite structures using digital shearography and unconstrained optimization

Advanced composite materials are finding increasing application in aerospace, marine and many other industries due to their performance and structural efficiency. Maintenance inspection of these light-weight structures is a relatively new and difficult task for Non-Destructive Testing (NDT), which need robust methods to be applicable in industrial environments. In this paper, a new numerical–experimental procedure to detect size and depth of flat bottom holes in metallic and laminated composite structures by digital shearography (DISH) is proposed. The flaw detection capabilities of DISH have been evaluated by measuring the dynamic response of defects to applied stresses. Vibration dynamic loading is used to reveal flat bottom holes made with different sizes and placed at different depths in CFRP laminates. The shearographic methodology is based on the recognition of the (0 1) resonance mode per defect. A simplified model of thin circular plate, idealized above each flaw position, is used to calculate the natural frequency of vibrating defects. Then, the numerical difference between experimental resonance frequencies and those computationally obtained is minimized using an unconstrained optimization algorithm in order to calculate the defect depth. Considering the simplicity and rapidity of this technique, the laser shearography methodology is evaluated reliable as NDT method.

High frequency magnetic properties of Bi and Si oxides-doped NiCuZn ferrite

We developed Bi2O3 and SiO2-doped NiCuZn ferrite for noise-suppression parts or near-field wireless communication parts. Bi and Si reacted selectively by means of sintering at approximately 900 °C, which created the Bi4(SiO4)3 phase. It consisted of two-phase structure of NiCuZn ferrite and Bi4(SiO4)3, which was sintered densely while suppressing the grain growth of NiCuZn ferrite. As a result, this ferrite had a high saturation magnetization and showed excellent frequency response. This paper shows, furthermore, that the experimental spin resonance frequency was in good agreement with the theoretical ones, whereby the density of NiCuZn ferrite approached the theoretical bulk density.

Theoretical investigation of electronic structure, electric field gradients, and photoemission of PuCoGa5and PuRhGa5superconductors

We report electronic structure calculations of PuCoGa${}_{5}$ and PuRhGa${}_{5}$ superconductors. The band structure, electric field gradients, and Fermi surface topologies were investigated using two methods of correlated band theory, namely the conventional static mean-field LDA$+$$U$ and the local density matrix approximation (LDMA). The latter is based on the Hubbard-I approximation and includes intra-atomic dynamical correlations in a self-consistent manner. Our results show that although LDA$+$$U$ and LDMA calculations do not significantly modify the Fermi surface topologies compared to LDA, they do lead to a substantial reduction of the $f$ character of the electronic states at the Fermi energy. The calculations indicate presence of a pseudogap in the electronic spectrum. We achieve a good agreement between calculated and experimental nuclear quadrupolar resonance frequencies and a fairly good agreement between calculated and experimental photoemission spectra. Our findings can be important for the theory of superconductivity in PuCoGa${}_{5}$ and related compounds.

Analytical and numerical modelling of AlGaN/GaN/AlN heterostructure based cantilevers for mechanical sensing in harsh environments

Some industrial areas as oil, automotive and aerospace industries, require electromechanical systems working in harsh environments. An elegant solution is to use III–V materials alloys having semiconductor, piezoelectric and pyroelectric properties. These materials, particularly nitrides such as GaN or AlN, enable design of advanced devices suitable for harsh environment. A cantilever structure based on AlGaN/GaN/AlN heterostructures coupled with a High Electron Mobility Transistor (HEMT) can act as an electromechanical device suited for sensing applications. In this article, we present the mechanical modelling of such a structure. An analytical and a numerical model have been developed to obtain the electrical charge distribution in the structure in response to mechanical stress. A theoretical electromechanical sensitivity of 3.5μCm−2 was achieved for the cantilever free end displacement of several hundreds of nanometres. Both models show good agreement, presenting less than 5% deviation in almost the whole structure. The differences between the two models that are pronounced near the clamped area can be explained by particular boundary conditions of the numerical model. The topological characterization and numerical modelling allowed the estimation of the equivalent intrinsic residual stress in the structure and the stress distribution within each layer. Finally, the dynamic mechanical characterization of fabricated cantilevers using laser interferometry is presented and compared to numerical modal analysis with less than 10% deviation between theoretical and experimental resonant frequencies. The obtained results enable the use of the analytical model for further study of the electromechanical coupling with the HEMT structure.

Impact Damage Detection in a Stiffened Composite Wing Panel Using Digital Shearography and Thermosonics

There has been a growing interest in the use of composites especially in structural application ranging from aerospace to automotive and marine sectors. However, their performances under impact loading represent one of the major concerns as impacts may occur during manufacture, normal operations and maintenance. This paper presents two novel NDT techniques, thermosonics and digital shearography (DISH) to detect and assess barely visible impact damage (BVID) produced on a stiffened composite wing panel by unknown low energy impacts. Thermosonics is based on synchronized infrared imaging and ultrasonic excitation. Despite the apparent simplicity of the experimental setup, thermosonics involves a number of factors, e.g. acoustic horn location, horn crack proximity, horn-sample coupling etc., that significantly tend to influence both the degree and the period of the excitation. Then, a numerical-experimental procedure for the assessment of the size and depth of delamination by digital shearography (DISH) is proposed. The flaw detection capabilities of DISH have been evaluated by measuring the dynamic response of the delaminated area to applied stresses. The shearographic methodology is based on the recognition of the (0 1) resonance mode per defect. A simplified model of thin circular plate, idealized above each impacted area, is used to calculate the natural frequency of vibrating delamination. The numerical difference between experimental resonance frequencies and those computationally obtained is minimized using an unconstrained optimization algorithm in order to calculate the delamination depth. The results showed that thermosonics is a quick and effective method to detect and localize BVID damage while the combined shearography and optimization methodology was able to size and localize delamination due to low velocity impacts.

Experimental investigation of resonant frequency of multilayered rectangular and circular microstrip antennas

This article presents the experimental results and verification of design expressions of multilayer rectangular and circular microstrip patch. Three rectangular and circular microstrip patch of different dimension have been fabricated on substrates er2 = 4.3, thickness 1.53 mm and er2 = 2.2, thickness 0.787 mm. The measurements have been carried out for simple microstrip patch, covered microstrip patch, space dielectric patch and microtrip patch with two superstrate. The experimental results obtained have been compared with reported design expression of multilayer rectangular and circular Microstrip patch in (Kumar and Malathi, Microwave Opt Technol Lett (2007), 2946-2950; Microwave Opt Technol Lett 40 (2008), 3206-3212). The experimental resonant frequency is in close agreement with the calculated resonant frequency. Such experimental validation and results may prove to be more useful for design engineers and further investigation. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:352–356, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25735

Multidomain ferroelectric actuator.

An improved performance of a multidomain PZT actuator compared to a single domain actuator is demonstrated. The multidomain actuator is fabricated out of a 650‐μm‐thick single domain plate. The internal electric field is inverted by applying 1 kV/mm external electric field to 1/3 of the plate area. The remaining 2/3 of the area is left with the original internal electric field. The actuator is excited by applying 1 kV ac voltage to the electrodes deposited on the top and bottom surfaces of the plate. The amplitude of acoustical displacement at the tip of the actuator is calculated with the aid of a finite element model developed for the piezoelectric plate. In an experiment, the amplitude of tip vibration is measured under the microscope. The experimental resonance frequencies are consistent with the calculations. At the second order resonance, the calculations predict 25% higher amplitude of vibrations for the multidomain actuator than for the single domain actuator. The results for several actuators with different configurations of ferroelectric domains are compared to the single domain actuator.

Microwave Magnetic Properties and Natural Resonance of ∊-Co Nanoparticles

Owing to the novel crystal structure, ∊-Co nanoparticles with an average diameter of 12nm are synthesized and the microwave magnetic properties of the epoxy resin composite with 50vol% ∊-Co particles are measured in the frequency range 0.1–7 GHz. The experimental resonance frequency (4.7 GHz) matches well with the values obtained by the theoretical calculation with the Kittel equation and fitting the experimental permeability dispersion curve via the Landau–Lifshitz equation. Hence the resonance peak is attributed to natural resonance mode. This work is believed to be beneficial for further understanding microwave applications of the novel ∊-Co nanoparticles.

Proton resonance for oscillating field of the order of static magnetic field

A spin decoupling method in nuclear quadrupole resonance spin echo experiment is used to detect the proton magnetic resonance absorption spectrum. The behavior of proton resonance in α phase of polycrystalline p-dichlorobenzene as a function of the intensity of the proton decoupling oscillating field ( H 2) is measured. Good agreement between the experimental resonance frequency and Shirley’s theory for a non-interacting 1/2 spin system is observed. To our knowledge this is the first time the NMR proton frequency dependence on linear polarized excitation field intensity for H 2/ H o as high as 1.8 is measured.

Modeling, fabrication and stress compensation of an epitaxial thin film piezoelectric microscale energy scavenging device

This paper focuses on a renewable power source for wireless sensor nodes via energy scavenging using thin film piezoelectrics. The novelty of this research is the growth of epitaxial PZT on a Si platform. The films were grown with good consistency using pulsed laser deposition. Using the optimized piezoelectric film properties, an analytical model was generated to predict the output power for a single cantilever, 5.5 nW/beam. Further, if arrays of the cantilevers were packed into a cubic centimeter, the output power would be 80–200 µW cm−3. A microfabrication technique was developed to manufacture the cantilevers using standard low-temperature procedures. As the devices demonstrated a significant residual stress upon release, an analytical model was created to predict the residual stress in the films from the high-temperature growth step. A neutral argon bombardment technique was then established to compensate for these stresses and to develop a planar usable device. The initial device fabrication was successful and testing was done to determine resonant frequency, quality factor and output power. The experimental resonant frequency response compared well with what was determined by the model, but the quality factor was 95, which was lower than expected. The output power per cantilever was 24.5 pW over a 510 MΩ load operating over an input vibration of 10 m s−2 and at resonant frequency (976 Hz).

Determining Elastic Constants of Material Using Optimization Method and Vibration Test

This paper proposes an inverse method to obtain the elastic properties of material. The sum of the squared differences between the experimental resonance frequencies and calculated resonance frequencies from the finite element method is chosen as the objective function. The proposed method presents an optimization method, Hybrid Genetic /Simulated Annealing algorithm, to determine the elastic properties. When the objective function reaches its minimum value, its corresponding design variables are the elastic constants of the material. The inverse method is applied to determine the elastic constants of aluminum plate, Glass/PP laminate, and double coated steel plate .The results indicate that for few elastic constants as an aluminum plate, Hybrid Genetic /Simulated Annealing algorithm has no apparent improvement, but more calculation time in comparison method. While simulated annealing while for Glass/PP laminate and double coated steel plate with more elastic constants, Hybrid Genetic /Simulated Annealing algorithm is superior to the traditional simulated annealing method.