Resonance Frequency Values Research Articles

The effect of Mg:Ti ratio on the phase composition and microwave dielectric properties of MgTiO3 ceramics prepared by one synthetic process

In this paper, MgO–CaO–TiO2 based ceramics was prepared by solid-state reaction technique and the effect of Mg:Ti ratio (0.873–1.057) on the phase, microstructure and microwave dielectric properties were investigated. Only two phases MgTiO3 and CaTiO3 appeared in the sample with Mg:Ti = 0.955, and MgTi2O5 and Mg2TiO4 appeared in the sample with Mg:Ti ratio lower and higher than 0.955 respectively. The microstructure showed the dark MgTiO3 grains and the bright grains with three elements Mg, Ca and Ti in the triangle grain boundary. As increasing the ratio of Mg:Ti, the dielectric constant (er) displayed down trend from 21.2 to 20.6, and the Q × f value first increased from 76,300 to 80,000 GHz, thereafter, it declined to 75,000 GHz. Meanwhile, the temperature coefficient of resonant frequency (τf) value first varied from −3.8 to 1.2 ppm/°C and then maintained unchanged. At last, our MgO–CaO–TiO2 based ceramics with Mg:Ti = 0.955 sintered at 1,310 °C for 4 h showed good microwave dielectric properties: er = 21.1, Q × f = 79,915 GHz and τf = 1.2 ppm/°C.

Birdcage coils: Equivalent capacitance and equivalent inductance

ABSTRACTBirdcage coil is extensively used in MR systems thanks to its possibility to provide high signal‐to‐ noise ratio and high radiofrequency magnetic field homogeneity that guarantee a large field of view. This work describes how to schematize the birdcage coil in terms of an equivalent inductance and an equivalent capacitance, whose knowledge can be useful for coil design and characterization. In particular, the knowledge of equivalent capacitance and equivalent inductance permits to estimate theoretically coil resonant frequency, quality factors and matching circuit capacitor values in a quick way, while workbench tests permit to estimate coil resistance and sample‐induced resistance. The presented theory is validated for both lowpass and highpass birdcage coils.by using literature data. © 2014 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 44B: 32–38, 2014

Fast Extraction of Resonant Frequency of Square Ring Micro-strip antenna using Neural Network Approach

This paper presents an efficient approach based on neural network to design a square ring micro-strip antenna. Traditional techniques used to design a square ring antenna are based on EM field simulations like IE3D which is highly CPU intensive and requires lot of time for simulation. Neural networks can be used to map the complex relationship between physical and electrical parameters of ring antenna in an efficient manner. The model once developed can be used with minimal CPU resources and enables fast extraction of output parameter such as resonant frequency. The typical resonant frequency values are first obtained through IE3D and then from samples obtained from IE3D are used to train the neural network .The results obtained by the use of neural networks have been proved to be faster than comparison with IE3D software.

To the Problems of Determination of Dynamic Elasticity Modules of Calcium Silicate Bricks by Means of Resonance Method

Modulus of elasticity of building materials can be determined in a static way (loading in a press) or by means of non-destructive test methods (ultrasonic pulse method and resonance method); the parameter is most frequently determined for concrete and both methods of determining elasticity modulus are codified in Standards. Elasticity characteristics of calcium silicate bricks were determined by means of resonance test method. Because the shape of calcium silicate bricks (a block with oblong foot) is different from the shape of test specimens for concrete (usually blocks with square foot), expected frequencies for verification of accuracy of measurement by resonance method were determined. Moisture content of calcium silicate bricks (water absorbing capacity is up to 12-14%) has influence on the value of resonance frequency. Difference between dynamic Young's modulus of elasticity from fundamental longitudinal and transverse resonant frequency is on average 2.8%.

Effect of TiO2 Ratio on the Phase and Microwave Dielectric Properties of Li2ZnTi3+x O8+2x Ceramics

Low-loss materials Li2ZnTi3+xO8+2x (LZT) (x = 0, 0.10, 0.17, 0.25, 1.00) were prepared by the conventional solid-state route. The effect of TiO2 ratio on phase composition, microstructure, and the microwave dielectric properties of Li2ZnTi3+xO8+2x ceramics were investigated using x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and Vector Network Analyzer. The results revealed that a two-phase system Li2ZnTi3O8-TiO2 was formed. The appropriate content of TiO2 ratio can effectively adjust the temperature coefficient of the resonant frequency (τf) value from −14.5 to 0 ppm/ °C without obvious degradation of the microwave dielectric properties. The microwave dielectric properties of the Li2ZnTi3+xO8+2x materials were characterized at microwave frequencies. Typically, the Li2ZnTi3+xO8+2x (x = 0.17) ceramic sintered at 1,160 °C for 5 h showed excellent microwave dielectric properties with er = 28.51, Q × f = 58,511 GHz, and τf = + 2.3 ppm/ °C.

Anodic bonding using SOI wafer for fabrication of capacitive micromachined ultrasonic transducers

In medical ultrasound imaging, mostly piezoelectric crystals are used as ultrasonic transducers. Capacitive micromachined ultrasonic transducers (CMUTs) introduced around 1994 have been shown to be a good alternative to conventional piezoelectric transducers in various aspects, such as sensitivity, transduction efficiency or bandwidth. This paper focuses on a fabrication process for CMUTs using anodic bonding of a silicon on insulator wafer on a glass wafer. The processing steps are described leading to a good control of the mechanical response of the membrane. This technology makes possible the fabrication of large membranes and can extend the frequency range of CMUTs to lower frequencies of operation. Silicon membranes having radii of 50, 70, 100 and 150 µm and a 1.5 µm thickness are fabricated and electromechanically characterized using an auto-balanced bridge impedance analyzer. Resonant frequencies from 0.6 to 2.3 MHz and an electromechanical coupling coefficient around 55% are reported. The effects of residual stress in the membranes and uncontrolled clamping conditions are clearly responsible for the discrepancies between experimental and theoretical values of the first resonance frequency. The residual stress in the membranes is determined to be between 90 and 110 MPa. The actual boundary conditions are between the clamped condition and the simply supported condition and can be modeled with a torsional stiffness of 2.10−7 Nm rad–1 in the numerical model.

Development of Gas Sensors on Microstrip Disk Resonators

Abstract Here it is reported about the development of microwave disk resonators and their employment as transducers in gas sensing devices. The sensors were developed by designing, modeling and realizing microstrip resonators on several microwave substrates, and by depositing sensing films on the disk. The transduction mechanism can be explained through the change in the permittivity value, in a low thickness of the sensing film, due to the interaction with the gas target. Furthermore, due to the microwave penetration on the sensing material, the response depends on volume effect, not only on surface one. These devices own intrinsic stability due to the fact that the resonance frequency value is related to the physical dimensions.

Residual Stress in Capacitive Micromachined Ultrasonic Transducers Fabricated with Anodic Bonding Using SOI Wafer

This paper focuses on a fabrication process for CMUTs using anodic bonding of a silicon on insulator wafer on a glass wafer. This technology makes possible the fabrication of large membranes and can extend the frequency range of CMUTs to lower frequencies of operation. Silicon membranes having radii of 50, 70, 100 and 150 μm and a 1.5 μm thickness are fabricated and electromechanically characterized. Resonant frequencies from 0.6 to 2.3 MHz and an electromechanical coupling coefficient around 58% are reported. The discrepancies between experimental and theoretical values of the first resonance frequency can be explained by a combined effect of a tensile residual stress (between 90 and 110 MPa) in the membranes and experimental boundary conditions that can be modeled by a torsional stiffness of 2.10−7 N.m.rad–1 instead of a perfectly clamped ring.

Normal işiten yetişkinlerde orta kulak rezonans frekansı normatif değerleri

This study aims to determine the normative values of middle ear resonance frequency in healthy adults. Sixty adult volunteers (32 females, 28 males; mean age 31.8±7.1 years; range 21 to 46 years) with normal otoscopic examination, audiometry and electroacoustic immitancemetry findings were enrolled in the study. The middle ear resonance frequencies were calculated by multifrequency tympanometry. The mean resonance frequency for all volunteers was 999.6±134.9 Hz. The mean resonance frequency was 1020.8±140.6 Hz for the right ear, and 978.3±180.5 Hz for the left ear. The mean resonance frequencies for the right- and left-side were 1023.2±146.9 Hz and 912.5±177.8 Hz in males, and 1018.8±137.2 Hz and 1035.9±164.7 Hz in females, respectively. There was no statistically significant difference in the mean resonance frequency of the right ears between the males and females (p=0.9), whereas the mean resonance frequency of the left ears was statistically significantly higher in females (p=0.007). The middle ear resonance frequency values may vary according to the side of the ear or gender.

Piezoelectric excited millimeter sized cantilever sensors for measuring gas density changes

Rapid, in-situ measurement of gas density is valuable for monitoring industrial processes. We show that piezoelectric-excited millimeter-sized cantilever (PEMC) sensors exhibit precision for measuring gas density changes as small as 0.088g/l with sensitivity equivalent to 0.049g/(lHz). PEMC sensors were fabricated by bonding 127μm thick piezoelectric layer (lead zirconate titanate) to a base 160μm thick silica layer. Gases (He, N2, Ar) were passed continuously through an isothermally maintained flow cell, in which the PEMC sensors were mounted and the steady state resonant frequency values were monitored. The changes in observed resonant frequencies were collected and compared in multiple experiments with well-established theory for the frequency response of a dynamic cantilever surrounded by an inviscid fluid and were found to be in reasonable agreement. A finite element model of the PEMC sensor showed good agreement with the measured resonant frequency values.

Ca(Zn1/3Nb2/3−xVx)O3 solid solution: Microstructural evolution, optimized sintering behavior and microwave dielectric properties

Microwave dielectric ceramics with the composition of Ca(Zn1/3Nb2/3−xVx)O3 (CZNV, 0≤x≤0.02) were prepared by the solid-state reaction method. The sintering behavior, phase structure, and microwave dielectric properties of CZNV ceramics were investigated. All samples sintered at 1125–1225°C for 3h remained a single phase. However, the grain shape changed from equiaixed to rectangle with increasing x. The dielectric properties of CZNV solid solution exhibited a significant dependence on the sintering condition, microstructure and composition. The Q×f value and temperature coefficient of resonant frequency (τf) can be improved with substituting V for Nb. As x=0.005, Ca(Zn0.333Nb0.662V0.005)O3 ceramic sintered at 1200°C for 3h in air exhibited good microwave dielectric properties with εr=34.3, Q×f=16,420GHz, and τf=−17.6ppm/°C.

An Application of Artificial Neural Network to Compute the Resonant Frequency of E–Shaped Compact Microstrip Antennas

Abstract An application of artificial neural network (ANN) based on multilayer perceptrons (MLP) to compute the resonant frequency of E-shaped compact microstrip antennas (ECMAs) is presented in this paper. The resonant frequencies of 144 ECMAs with different dimensions and electrical parameters were firstly determined by using IE3D(tm) software based on the method of moments (MoM), then the ANN model for computing the resonant frequency was built by considering the simulation data. The parameters and respective resonant frequency values of 130 simulated ECMAs were employed for training and the remaining 14 ECMAs were used for testing the model. The computed resonant frequencies for training and testing by ANN were obtained with the average percentage errors (APE) of 0.257% and 0.523%, respectively. The validity and accuracy of the present approach was verified on the measurement results of an ECMA fabricated in this study. Furthermore, the effects of the slots loading method over the resonant frequency were investigated to explain the relationship between the slots and resonant frequency.

Modeling of Nonlinear Stiffness of Micro-Resonator in Silicon Resonant Accelerometer

Nonlinearities of the resonator in silicon resonant accelerometer (SRA) limit the ultimate short term frequency stability. In SRA, this stability is a measure of the achievable resolution. This paper discusses the nonlinear vibration phenomenon of micro-resonator considering the impact of the entire structure of SRA and builds a model to calculate the micro-resonator nonlinear stiffness K3,eff of the SRA prototype. The dies of SRA were fabricated by Silicon on Insulator (SOI) process. The equivalent model of the micro-resonator is built and the analytical value of the elastic constraint stiffness Ka of micro-resonator is derived as 8.91×104 N/m. It is calculated that K3,eff is equal to 5×1011 N/m3,and as a comparison, the simulation result is 5.026×1011 N/m3. The error between them is 0.52%. The nonlinear vibration experiments show that the maximum error between the theoretical and experimental value of resonance frequency is 2.1%. The prediction for the nonlinear stiffness contributes to further research on nonlinear vibration of the resonant beam. The model in this paper could also provide guidance and reference for optimal design of SRA.

A noncontact resonance frequency detection technique for the assessment of the interfacial bone defect around a dental implant

This study employed a noncontact resonance frequency (RF) detection technique that was developed by our group to evaluate the interfacial bone in in vitro implant-bone models. Based on our method, the implant-bone structure was excited by the acoustic energy of a loudspeaker, and its vibration response was acquired with a capacitance sensor. The spectral analysis was used to characterize the first RF value. Two types of in vitro defect models, Buccal-Lingual (BL) and Mesial-Distal (MD), were constructed for the verification. The measurements of the RF for a defect model clamped at four different heights (9, 10, 11, and 12mm) were performed in two sensing directions (BL and MD). Moreover, each model was also analyzed using an Osstell Mentor. The obtained two parameters, RF and ISQ (Implant Stability Quotient), were statistically analyzed through one-way analysis of variance (ANOVA) and linear regression analysis for comparisons. The RF and the ISQ values obtained for all of the defect models at the four clamp heights decreased significantly (p<0.05) with an increase in the severity of the defect. The two parameters for each imperfection increase significantly (p<0.05) with an increase in the clamp height. Additionally, the RFs of all of the defect models are linearly correlated with their corresponding ISQs for the four clamp heights and the two measuring orientations. Therefore, our developed technique is feasible for the assessment of the postoperative healing around a dental implant.

Researching into the methodology for the evaluation of deformed soft furniture upholstery

PurposeThe main aim of this work is to evaluate upholstery deformation by using resonant vibrations of separate zones of the soft part.Design/methodology/approachProvided methodology allows assessing the upholstery deformation of separate parts of soft furniture by exciting resonant vibrations in it.FindingsBy recording the value of resonant frequency at separate points of the plane, it becomes possible to obtain the graph of deformation distribution. It is compared to the graph that demonstrates how rigidity distributes itself in different directions within the upholstery fabric. This enables the authors to evaluate the unevenness of upholstery deformation that is present in different directions.Originality/valueProvided methodology allows assessing the quality of soft furniture assembly and predicting the exploitation time for its upholstery.

Underwater sound transmission through thin soft elastomers containing arrays of pancake voids: Measurements and modeling

Measurement of underwater sound transmission through thin (~750 micron) layers of the soft elastomer polydimethylsiloxane (PDMS) containing microfabricated arrays of pancake-shaped cavities is presented. Cavities are 120 microns in diameter and 5 microns in height with a nominal lattice spacing of 300 microns. A sound transmission minimum is found at 282 kHz which agrees with predictions of a finite-element model of the array and the value for monopole resonance frequency of an air-filled single pancake cavity in unbounded PDMS. This resonance is a factor of 0.62 lower than the null that would occur for spherical cavities of equivalent volume. The width of the null is also significantly broader than that which would be obtained with spherical voids. Modeling results incorporate careful measurements of attenuation for both shear and compression waves in PDMS done in a separate effort. Acoustic transmission variation as a function of lattice spacing and the number of layers is discussed. [Work sponsored by the Office of Naval Research]

Complex Conductivity of YBCO Films in Normal and Superconducting States Probed by Microwave Measurements

We report on microwave frequency characterization of yttrium barium copper oxide (YBCO) thin films in both normal and superconducting states. A microwave single-post dielectric resonator technique using two different resonators was used for the complex conductivity determination of YBCO samples deposited on dielectric substrates. The intrinsic complex conductivity of YBCO films was determined from the measured resonator quality factor Q and resonant frequency values employing rigorous electromagnetic modeling of the resonant structures with the mode-matching and Rayleigh-Ritz techniques. Such approach allowed us to determine the intrinsic properties of the films (conductivity, permittivity, and penetration depth) without any simplifications and errors associated with approximate modeling employing perturbation theory. We describe the superconducting material only through its intrinsic material properties, such as the complex conductivity, which does not depend on the thickness of the sample and other parameters. From both simulations and experimental results, we show that the proposed method of intrinsic complex conductivity determination is particularly useful for the characterization of very thin YBCO layers. To support the novelty of our approach, it is shown that significant differences appear between the rigorous and perturbation computations for thin superconducting films (below 50 nm).

Microstructures and dielectric properties of Ba[(Co0.7Zn0.3)1/3Nb2/3]O3-based ceramics prepared by aqueous gelcasting-assisted solid-state method

The aqueous gelcasting-assisted solid-state method (AGAS) and traditional solid-state reaction method (TSSR) were used to prepare Ba[(Co0.7Zn0.3)1/3Nb2/3]O3 (BCZN)-based ceramics. The effects of different powder-preparation methods on the microstructures and dielectric properties of the BCZN-based ceramics were investigated. X-ray diffraction analysis showed completely the same phase compositions regardless of the preparation method adopted. The relative permittivity (e r) did not significantly vary between the two methods. However, BCZN with CeO2-added ceramics prepared by AGAS had higher and more uniform density (6.374 g/cm3) and high quality factor of resonant frequency (Q × f) value (75,843 GHz) than those prepared by TSSR because of the more uniform microstructures, as shown by scanning electron microscopy images. The temperature coefficients of resonant frequency (τ f = 7.4 ppm/°C) of the ceramics prepared by AGAS were also closer to zero than those prepared by TSSR.

Well-designed rectangular cavity resonator for FMR experiment

The unloaded quality factor of the cavity resonator is the ratio between the stored energy of the cavity resonator to the power loses in the cavity resonator. The homemade rectangular cavity resonator in X-band shows higher unloaded quality factor compare with standard cavity resonator in the TE102 mode. Because the inner walls of rectangular cavity resonator are treated through high quality polishing and high purity Au plating. Also the inner walls are made by printed circuit board which has thin Cu foil, two problems such as mechanical vibration and thermal expansion can be solved by minimizing unwanted eddy current. Through the ferromagnetic resonance measurement by using our rectangular cavity resonator, we can be obtained reasonable values of resonance frequency and linewidth by using NiFe thin film. As a result, the Gilbert damping constant from the experimental result is in good agreement with the typical value of damping parameter of the NiFe thin film.

Researching into the methodology for the evaluation of deformed soft furniture upholstery

PurposeThe purpose of this paper is to evaluate upholstery deformation by using resonant vibrations of separate zones of the soft part.Design/methodology/approachBy recording the value of resonant frequency at separate points of the plane, it becomes possible to obtain the graph of deformation distribution. It is compared to the graph that demonstrates how rigidity distributes itself in different directions within the upholstery fabric. This enables the evaluation of unevenness of upholstery deformation that is present in different directions.FindingsThe provided methodology allows assessing the quality of soft furniture assembly and predicting the exploitation time for its upholstery.Originality/valueThe test results obtained using the original methodology enable the assessment of manufacturing defects existing in various directions (for example, the shape of different parts during the cutting process, the unevenness of seam width and others), as well as the quality of furniture during the production and exploitation process.