Harmonic Resonance Frequencies Research Articles

Current-driven domain-wall dynamics in curved ferromagnetic nanowires

The current-induced motion of a domain wall in a semicircle nanowire with applied Zeeman field is investigated. Starting from a micromagnetic model we derive an analytical solution which characterizes the domain-wall motion as a harmonic oscillation. This solution relates the micromagnetic material parameters with the dynamical characteristics of a harmonic oscillator, i.e., domain-wall mass, resonance frequency, damping constant, and force acting on the wall. For wires with strong curvature the dipole moment of the wall as well as its geometry influence the eigenmodes of the oscillator. Based on these results we suggest experiments for the determination of material parameters which otherwise are difficult to access. Numerical calculations confirm our analytical solution and show its limitations.

Wide-stopband microstrip bandpass filters using dissimilar quarter-wavelength stepped-impedance resonators

Wide-stopband and compact microstrip bandpass filters (BPFs) are proposed using various dissimilar quarter-wavelength (/spl lambda//4) stepped-impedance resonators (SIRs) for multiple spurious suppression. The use of /spl lambda//4 SIRs is essential in widening the filter stopband and reducing the circuit size. By properly arranging the individual /spl lambda//4 SIR, which has the same fundamental resonance frequency f/sub 0/, but has different spurious (harmonic) resonance frequencies, and also carefully misaligning the maximum current density nodes, several higher order spurious resonances may be suppressed so that a BPF with wide stopband may be realized. In this study, the basic concept of multiple spurious suppression is demonstrated by thoroughly investigating the spurious characteristics of the fourth-order interdigital BPFs, which consist of two different types of /spl lambda//4 SIRs. To widen the rejection bandwidth, the fourth-order coupled-resonator BPFs based on three and four different types of /spl lambda//4 SIRs are implemented and carefully examined. Specifically, a very wide-stopband microstrip BPF composed of four dissimilar /spl lambda//4 SIRs is realized and its stopband is extended even up to 11.4f/sub 0/ with a rejection level better than 27.5 dB.

Theoretical aspects of the harmonic performance of subsea AC transmission systems for offshore power generation schemes

An analytical investigation of harmonic phenomena in power cables designed for use in AC subsea transmission systems is presented. Methods for calculating the frequency response of the subsea cables and for determining the harmonic resonance frequencies are presented. Mathematical models have been developed to quantify the harmonic resistances and harmonic inductances and also to predict the harmonic resonant frequencies for a range of commercially available AC cable designs. The influence of the HVAC transmission system arrangements upon harmonic performance when a static VAR compensator is employed is also presented. The paper concludes by comparing and contrasting the harmonic performance of various subsea AC transmission arrangements and demonstrates that the subsea cable has a significant impact upon the harmonic response in offshore power transmission systems.

Determination of the electromechanical coupling factor of gallium orthophosphate (GaPO/sub 4/) and its influence on resonance-frequency temperature dependencies

The quartz homeotype gallium orthophosphate (GaPO4) is a representative of piezoelectric single crystals of large electromechanical coupling factor. It is known that its coupling factor kappa26 associated with the resonators vibrating in the thickness-shear mode is approximately two times greater than that of quartz. This property increases the spacing between the series and parallel resonance frequencies of resonators, as well as the difference between the resonance frequency temperature dependencies of the fundamental and harmonic resonance frequencies of resonators vibrating in the thickness-shear mode. In this paper, the methods for determination of the coupling factor kappa26 are presented, and the computed values are compared with the measured ones. The influence of the coupling factor to the resonance-frequency temperature dependencies of the fundamental and third harmonics of selected rotated Y-cut GaPO4 resonators vibrating in the thickness-shear mode is presented. The purely elastic case for a laterally unbounded plate, which corresponds closely to the limiting case of high harmonic resonance frequency-temperature behavior was assumed for the calculations. The computed temperature coefficients for the Y-cut orientation and calculated turnover point temperatures TTP for different (YX1) orientations are presented.

A novel relative humidity sensor based on microwave resonators and a customized polymeric film

This paper reports a new relative humidity (RH) sensor for monitoring operating environment of a radio frequency (RF) system. The proposed RH sensor is based on two different microwave resonators in its structure, a coplanar waveguide (CPW)-to-slotline ring resonator and a microstrip patch antenna, and a customized polyimide film for humidity sensing material. To integrate a humidity sensor without making a RF system complex, first harmonic resonant frequency of the resonators are designed to be 3.375 and 5.0GHz for the CPW-to-slotline ring resonator and the microstrip patch antenna, respectively. For high sensitivity of the polyimide film to RH change, it was synthesized from oxidianiline (ODA), m-pyromellitic dianhydride (m-PMDA), and N-methly-2-pyrrolidone (NMP) in which any hydrophobic elements are not included. This results in enhancement of water sorption characteristic of the polyimide film which serves as a dielectric layer of the microwave resonators. Calibration of the microwave RH sensors was carried out in terms of sensitivity, hysteresis and stability. These characteristics were analyzed through change in first harmonic resonant frequency of the resonators against various RH levels. Sensitivity of the RH sensor using the CPW-to-slotline ring resonator was −181kHz/%RH and 4.95mdB/%RH in terms of its resonant frequency and insertion loss, respectively. Hysteresis was 0.0013%, and average-percent-deviation from an average resonant frequency was 0.002%. Sensitivity of the antenna RH sensor was −108kHz/%RH and 5.50mdB/%RH in terms of resonant frequency and return loss, respectively.

Frequency-tuning for control of parametrically resonant mass sensors

Parametric resonance based mass sensing leads to increased sensitivity over other resonant methods. In this work, we present a frequency-tuning approach to measure mass change in an ultra-sensitive mass sensor. This scheme drives the oscillator using an electrical signal with fixed frequency and tunes the parametric resonance frequency to match the driving frequency by feeding back a dc offset to the sensor. Instead of monitoring frequency shift of the oscillation in a micro-oscillator, mass change in the sensor can be detected by measuring the shift in dc offset, making the sensor amenable to closed-loop control. This scheme and the prototype mass sensor with a mass of ∼30ng and a first mode harmonic resonance frequency of ∼83kHz has been built and experimentally characterized. Good correlation between parametric resonance frequency and dc offset has been shown and the noise floor is less than 1 pg. The sensor is used to track water content variation in a humidity-testing chamber and shows increased effi...

Novel SIS resonators waveguide filters

A novel stepped-impedance slot (SIS) resonator waveguide band-pass filter with quarter-wave couplings is investigated. SIS resonators have been studied in order to increase the stopband width between the fundamental and spurious harmonic resonant frequencies. They have been employed in the design of waveguide band-pass filters with good harmonic suppression.

Viscosity Measurements in Liquid Using Transversal Effects of Piezoceramic Disk-Type PZT Transducer in the Frequency Range of 70–430 kHz

Transversal effects of a piezoceramic disk-type Pb(Zr,Ti)O3 (PZT) transducer are newly introduced in the measurement of dynamic viscosity of liquid. The fundamental resonance (75 kHz) and the higher harmonic resonant frequencies (195, 310, 424 kHz) of the transducer are used in the experiments. The resonant resistance Rr and the resonant frequency shift Δfr of transducer are measured with a water-glycerin mixtures (viscosity ηL:3∼490 mPa·s) and silicone oil (ηL:10 ∼1000 mPa·s) as the sample liquids. From the experimental results, it is gathered that 1) the resonant resistance Rr has a linear relationship to ηL1/2, 2) the resonant frequency shift Δfr does not show a linearity in the high viscosity range larger than 100 mPa·s. The viscosity measurement in the frequency range of 75∼424 kHz, which has not been explored previously, was successfully accomplished by our method.

Modeling of a novel vibrospring particle‐size distribution analyzer

AbstractThe design and modeling of a novel technique for particle‐size distribution analysis are described. In its most basic form, the unit comprises a horizontally held closed‐coil helical spring that is partly filled with the test powder and sinusoidally vibrated in the transverse direction. Particle‐size distribution data are obtained by stretching the spring to known lengths and measuring the mass of the powder discharged from the spring resonant frequency. The spring's vibration characteristics, including the dynamic vibration profile as well as its first harmonic resonant frequency, are predicted using a viscoelastic model, which is in turn validated by comparison with experimental data. Particle‐size distribution data are reported in conjunction with a variety of powders including glass Ballotini, grit stone, sand, and sawdust in the size range 30–800 μm. A typical reproducibility is ±4%.

Effects of tube shape on nonlinear resonant oscillations of interior gas

An investigation is conducted to get an outline of designing the tube shape for a sonic compressor with high efficiency. When a closed tube oscillates with its resonant frequency, the interior acoustic properties such as density, velocity, and pressure undergo very large perturbation with nonlinear patterns. In order to analyze the nonlinear acoustic phenomena such as harmonic generation, shock formation, and resonant frequency shift, two-dimensional axisymmetric governing equations are derived and solved numerically. Numerical simulations are performed to investigate the effect of the tube shape that gives us maximum possible pressure. Results show that the resonant frequency and patterns of pressure waves strongly depend on not only the tube shape but also the amplitude of driving acceleration. The degree of nonlinearity of pressure signals is measured by the newly defined nonlinear energy ratio of the signals. The nonlinear energy ratio well describes not only the energy transfer to higher harmonics but also the compression efficiency, so that it can be a good measure for designing tube shape.

The magnetized plasma permittivity tensor

An alternative form of the nonrelativistic permittivity tensor for a homogeneous magnetized plasma in thermal equilibrium is derived in the linear approximation. The derivation follows the lines of Trubnikov’s derivation of the relativistic permittivity tensor and is restricted to a collisionless electron plasma. In the case of a Maxwellian equilibrium distribution, the final form is equivalent to Gordeev’s integral form of the permittivity tensor. The analysis is, with minor modification, applicable to plasma comprised of multiple particle species. Unlike the standard formulas, the alternative formula presented in this article yields the components of the permittivity tensor by means of partial derivatives of a scalar kernel integral. Besides the cyclotron harmonic resonance frequencies, where the permittivities in the nonrelativistic approximation become singular, the alternative formula is manifestly valid for all wave frequencies without any restrictions on the wave vector and the thermal energy.

The multiphoton AC Stark effect

We study the interaction of a two-level atom with two intense lasers: a strong laser of Rabi frequency 2Ω on resonance with the atomic transition, and a weaker laser detuned by 2Ω/n, i.e. by a subharmonic of the Rabi frequency of the first. The second laser “dresses” the dressed states created by the first in an n-photon process. We calculate the energy levels and eigenstates of this “doubly-dressed” atom, and find a new phenomenon: the splitting of the energy levels due to an n-photon coupling between them, resulting in a multiphoton AC Stark effect. We illustrate this effect in the fluorescence spectrum, and show that the spectrum contains triplets at the subharmonic as well as harmonic resonance frequencies with a clear dependence on the order n of the resonance and the ratio α of the Rabi frequencies of the lasers

Spectral response of asymmetrical random oscillators

An analytical procedure to estimate the power spectral density (PSD) response of a weakly damped oscillator with a nonlinear asymmetrical restoring force under external stochastic wide-band excitation is presented. An equivalent linear system with random parameters is derived, from which the PSD is deduced. The use of corrective terms yields an approximation of the PSD in the region of the second and third harmonic resonant frequencies (as well as at higher harmonics). In the same way, the PSD of the reaction force is also reported. The method is applied to an impact oscillator with asymmetrical clearances and asymmetrical elastic stops.

Piezoelectric thickness resonance of aromatic polyurea films prepared by vapor deposition polymerization

Abstract By vapor deposition of a diisocyanate monomer (MDI) and a diamine monomer (MDA or MeMDA) onto a polyimide substrate, thin two-layer films of aromatic polyurea, P(MDA/MDI) or P(MeMDA/MDI), and polyimide were prepared. The polyurea layers acquired piezoelectric activity after poling treatment. The electric admittance of the films was measured as a function of frequency. Piezoelectric resonance and antiresonance were observed at the frequency of thickness mode resonance of the polyurea layer and at side-band frequencies corresponding to the harmonic thickness resonance frequencies of the polyimide layer. Theoretical analysis yielded the electromechanical coupling factor kt = 12%, the piezoelectric constant e 33 = 60 mC/m2, and the elastic constant C 33 = 6.87 GN/m2 for P(MDA/MDI). MDI: 4,4'-diphenyl methane diisocyanate, MDA: 4,4'-diamino diphenyl methane MeMDA: 4,4'-diamino-3,3'-dimethyl diphenyl-methane.

Performance of toroidally wide-separation loop antennae for JT-60U ICRF experiments

Abstract The performance of two array antennae of phased 2 × 2 loops for JT-60U is presented in the initial operation for higher harmonic ion cyclotron resonant frequency (ICRF) experiments. The array antenna is designed so as to have a sharp coupled power spectrum of n  peak ≈ 3 with Δn  ≈ 2.5 when out of phase with toroidally adjacent loop currents ((π, 0) phasing) at 116 MHz by separating the loops widely by 0.44 m. The maximum coupled power up to the present is 6.4 MW with (π, 0) phasing at Bt = 4 T, which corresponds to the power density of about 6.1 MW m−2. Anomalous antenna breakdown is observed during combined neutral beam injection (NBI) and ICRF heating for the particular magnetic field strength Bt = 3.0 T at which an ion cyclotron resonance layer of 7ωcD is located near the antennae. A fairly large antenna loading resistance is obtained, i.e. 4 Ω for (π, 0) phasing at 0.13 m of the distance δSF between the separatrix and the Faraday shield, and 5 Ω for in-phase ((0, 0) phasing) at very large distances of more than 0.33 m. results show the decrease in the loading resistance at the L to H transition is about 30%, from 5 to 3.7 Ω with (0, 0) phasing at δSF = 0.32 m. The ratio of the incremental radiation loss to ICRF power decreases with increasing ICRF power and is saturated at small values less than 10% at power levels more than 4 MW. The increase in the radiation loss seems to be mainly caused by the light impurities from the first wall.

The Power Spectral Density Of Response For A Strongly Non-linear Random Oscillator

An oscillator with a non-linear restoring force and a small linear damping under wide-band random excitation is considered. A modified Van Der Pol transformation with a suitable amplitude dependent frequency, is used to transform the original system into a first order vector system to which the stochastic averaging method (SAM) and its higher approximations apply, despite the presence of a large non-linear term. The averaged equations are derived in the Appendix by using a two-timescale approach after performing a random time change which depends on the solution. An efficient equivalent linear system with random coefficients is then proposed from which the power spectral density (PSD) is deduced. The use of corrective terms yields to an approximation of the PSD in the region of the third harmonic resonant frequency (as well as at higher harmonics). The analytical results are in excellent agreement with numerical simulations.

Resonance response of scanning force microscopy cantilevers

A variational method is used to calculate the deflection and the fundamental and harmonic resonance frequencies of commercial V-shaped and rectangular atomic force microscopy cantilevers. The effective mass of V-shaped cantilevers is roughly half that calculated for the equivalent rectangular cantilevers. Damping by environmental gases, including air, nitrogen, argon, and helium, affects the frequency of maximum response and to a much greater degree the quality factor Q. Helium has the lowest viscosity, resulting in the highest Q, and thus provides the best sensitivity in noncontact force microscopy. Damping in liquids is dominated by an increase in effective mass of the cantilever due to an added mass of the liquid being dragged with that cantilever.

Harmonic analysis for industrial customers

A power flow program is developed to analyze the harmonic distortion of a power system with various types of harmonic loads. The proposed program can be applied to solve the harmonic current flow, voltage harmonic distortion factor, resonance frequency, and current amplification factor at every bus in the system. In this study, a large metal factory is selected for the harmonic power flow analysis. The current waveforms at every bus are measured and analyzed to determine various orders of harmonic components. These harmonic currents are used in the computer simulation to determine the harmonic voltage distortion factor at the buses of the system, and the variations of resonance impedance and amplification factor with frequencies are investigated. Finally, the program is used to calculate the harmonic load flow when the metal factory is expanded by including a new plant in the power system, and proper filters are designed to alleviate the harmonic problems. >

Principles and recent developments in ultrasound contrast agents

The behaviour of gas bubbles and gas encapsulated spheres as echographic contrast agents is reviewed. Compared with rigid spheres, gas bubbles are superior scattering agents and they offer a number of useful properties which can be exploited in a variety of ways. The analysis of their velocity of sound, back-scatter intensity, second harmonic emission and resonant frequency opens up new perspectives in the development of contrast agents for echocardiographic research with potential clinical applications.

Dynamic Stresses and Strains in a Buoy Cable System Subjected to Longitudinal Excitation Using a Continuum Approach

This paper deals with the analysis of the stresses and displacements in a buoy cable system subjected to longitudinal excitation when one-dimensional wave effects are taken into account. The cable is considered as a distributed mass with external linear damping due to fluid viscosity and internal damping simulating viscoelastic behavior of the cable material. The payload mass is attached to a rigid foundation by an elastic spring and a dashpot. The results are presented in terms of parameters common to a discrete single degree of freedom (df) system so that comparisons could be made showing the effects of cable distributed mass and cable external damping. Numerical results are presented for the case of a sinusoidal displacement at the upper end of an externally damped elastic cable and payload damping at the lower end. The results show that the cable stress in the low-frequency range can be higher for a system with cable damping than the stress value obtained in the case of a system with no damping. External damping, however, does reduce the stress in the vicinity of the resonant frequencies. It is also shown that the cable stress increases significantly at the higher harmonic resonant frequencies. Comparisons of the analysis of a distributed mass system with the one corresponding to a lumped parameter system using an effective cable mass of one-third its actual mass in a single (df) discrete system indicates fairly good agreement below the first fundamental frequency. The largest difference occurs in the vicinity of resonance where the continuum approach yields higher amplification factors. Better agreement over the fundamental-frequency range is obtained using a two-parameter lumped system. The case of a two-material cable system is also analyzed and experimental verification of the linear mathematical model is presented. Future research will consider improvement of some of the simplifications introduced in the analysis: nonlinear versus linear external damping, finite versus infinitesimal deformations, etc.