scholarly journals Center Impedance Method for Estimating Complex Modulus with Wide Frequency Range and Large Loss Factors

2021 ◽  
Vol 2021 ◽  
pp. 1-23
Author(s):  
Ryuzo Horiguchi ◽  
Yoshiro Oda ◽  
Keito Sato ◽  
Hiroto Kozuka ◽  
Takao Yamaguchi
Keyword(s):  
Loss Factor ◽  
Wide Frequency Range ◽  
Frequency Function ◽  
Single Frequency ◽  
Impedance Method ◽  
Frequency Range ◽  
Simple Method ◽  
Large Loss ◽  
Mobility Data ◽  
Loss Factors

A simple method for determining viscoelasticity over a wide frequency range using the frequency response function (FRF) mobility obtained by the center impedance method is presented. As user data comprise the FRF between the velocity of the excitation rod and excitation force, it is challenging to separate the signal and noise. Our proposed method is based on the FRF obtained from the analytical solution of the equation of motion of the viscoelastic beam and relationship between the complex wavenumber (real wavenumber and attenuation constant) of flexural wave and viscoelasticity. Furthermore, a large loss factor can be handled over a wide frequency range without using the half-power bandwidth. In this study, actual FRF mobility data containing noise were processed using preprocessing, inverse calculation, and postprocessing. Preprocessing removed low-coherence data, compensates for the effects of instrument gain, and transformed the FRF into its dimensionless equivalent. Then, inverse calculations were used to solve the mobility equation and determine the complex wavenumber. In postprocessing, the complex wavenumber obtained by the inverse calculation was curve fitted using functions with mechanical significance. Consequently, the storage modulus based on the curve-fitted complex wavenumber was a monotonically increasing frequency function. The loss factor had a smooth frequency dependence such that it has the maximum value at a single frequency. The proposed method can be applied to composite materials, where the application of time-temperature superposition is challenging. We utilized the measured FRF mobility data obtained over a duration of several seconds, and this method can also be applied to materials with large loss factors of 1 or more.

Dielectric Properties of Eucalyptus urophylla Under an Ultra-Wide Frequency Range

2020 ◽  
Vol 12 (8) ◽  
pp. 1236-1241
Author(s):  
He Xia ◽  
Wang Yong ◽  
Li Yunyan ◽  
Wei Yanqiang ◽  
Quan Peng ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Dielectric Loss ◽  
Dielectric Permittivity ◽  
Loss Factor ◽  
Wide Frequency Range ◽  
Dielectric Loss Factor ◽  
Regression Equations ◽  
Eucalyptus Urophylla ◽  
Frequency Range ◽  
Tangential Directions

Dielectric properties of Eucalyptus urophylla wood were measured by using a network analyzer over an ultrawide frequency range between 0.2 GHz and 20 GHz. The effects of moisture content (MC), temperature and frequency on the dielectric permittivity and the dielectric loss factor of Eucalyptus urophylla were investigated along different grain directions. The results showed that the dielectric permittivity along with the dielectric loss factor increased significantly with the elevation in MC. At the frequency of 2380 MHz with the MC increasing from 0% to 100%, the dielectric permittivity along different grain directions (including longitudinal, radial and tangential directions) increased by 180%, 110% and 112%, respectively, while the loss factor along these three directions increased by 1642%, 3703% and 5058%, respectively. In addition, the increase in dielectric properties of Eucalyptus urophylla wood was determined with the temperature elevating. When the temperature elevated from 20 °C to 140 °C, the dielectric permittivity at 2380 MHz along the longitudinal, radial and tangential directions, increased by 19%, 14% and 15%, respectively, while the loss factor increased by 133% at most. As the radio frequency increased, the dielectric permittivity of wood decreased. Regression equations satisfactorily described the dielectric properties of wood along different grain directions with different moisture contents.

Investigation of Room Temperature Mössbauer Spectroscopy and Initial Permeability Properties of Al3+ Substituted Cobalt Ferrites

SPIN ◽  
2018 ◽  
Vol 08 (01) ◽  
pp. 1840005
Author(s):  
Rabia Pandit ◽  
Pawanpreet Kaur ◽  
K. K. Sharma ◽  
Mohd. Hashim ◽  
Ravi Kumar
Keyword(s):  
Loss Factor ◽  
Room Temperature ◽  
Magnetic Hyperfine Field ◽  
Initial Permeability ◽  
Wide Frequency Range ◽  
Ion Concentration ◽  
Frequency Range ◽  
High Frequencies ◽  
Relative Loss ◽  
Cobalt Ferrites

In the present work, Al[Formula: see text] substituted cobalt ferrites (CoFe[Formula: see text]AlxO4, [Formula: see text], 0.4, 0.6, 0.8) have been synthesized via standard solid-state reaction technique. The incorporation of Al[Formula: see text] ions in cobalt ferrite has been shown to play an important role in modifying the magnetic properties. The room temperature (300[Formula: see text]K) [Formula: see text]Fe Mössbauer spectra reveals that the studied samples show two characteristic ferromagnetic zeeman sextets at A and B-sites at lower Al[Formula: see text] ion concentration (i.e., up to [Formula: see text]). However, a paramagnetic relaxation has been noted for higher Al[Formula: see text] substitution (for [Formula: see text] and 0.8) samples. The dependence of the Mössbauer parameters such as isomer shift, quadrupole splitting, line width and magnetic hyperfine field on Al[Formula: see text] ion concentration has also been noted. The variations in initial permeability over a wide frequency range (125[Formula: see text]kHz to 30[Formula: see text]MHz) at 300[Formula: see text]K have been recorded. The fairly constant values of initial permeability and the low values of the relative loss factor of the order of 10[Formula: see text] to 10[Formula: see text] over the wide frequency range are the important findings of the present work. The observed low values of relative loss factor at high frequencies suggest that the studied ferrites are promising materials to be used in microwave applications.

scholarly journals Investigation of Mechanical and Damping Performances of Cylindrical Viscoelastic Dampers in Wide Frequency Range

Actuators ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 71
Author(s):  
Teng Ge ◽  
Xing-Huai Huang ◽  
Ying-Qing Guo ◽  
Ze-Feng He ◽  
Zhong-Wei Hu
Keyword(s):  
Mechanical Properties ◽  
Energy Consumption ◽  
Loss Factor ◽  
Dynamic Mechanical Properties ◽  
Wide Frequency Range ◽  
Equivalent Stiffness ◽  
Frequency Range ◽  
Viscoelastic Damper ◽  
Equivalent Damping ◽  
Viscoelastic Dampers

This paper aims to develop viscoelastic dampers, which can effectively suppress vibration in a wide frequency range. First, several viscoelastic materials for damping performance were selected, and different batches of cylindrical viscoelastic dampers were fabricated by overall vulcanization. Second, the dynamic mechanical properties of the cylindrical viscoelastic dampers under different amplitudes and frequencies are tested, and the hysteretic curves under different loading conditions are obtained. Finally, by calculating the dynamic mechanical properties of the cylindrical viscoelastic dampers, the energy dissipation performance of these different batches of viscoelastic dampers is compared and analyzed. The experimental results show that the cylindrical viscoelastic damper presents a full hysteretic curve in a wide frequency range, in which the maximum loss factor can reach 0.57. Besides, the equivalent stiffness, storage modulus, loss factor, and energy consumption per cycle of the viscoelastic damper raise with the frequency increasing, while the equivalent damping decreases with the increase of frequency. When the displacement increases, the energy consumption per cycle of the viscoelastic damper rises rapidly, and the equivalent stiffness, equivalent damping, storage modulus, and loss factor change slightly.

Wide Frequency Characterization of Magnetic Properties of Commercial LTCC Ferrite Material

2011 ◽  
Vol 2011 (CICMT) ◽  
pp. 000224-000231
Author(s):  
Nelu Blaž ◽  
Andrea Marić ◽  
Goran Radosavljević ◽  
Nebojša Mitrović ◽  
Ibrahim Atassi ◽  
...  
Keyword(s):  
Dispersion Model ◽  
Low Frequency ◽  
Hysteresis Loops ◽  
Wide Frequency Range ◽  
Complex Permeability ◽  
Frequency Range ◽  
Dispersion Parameters ◽  
Simple Method ◽  
Microwave Engineering ◽  
Characterization Procedure

Complex magnetic permeability and hysteresis characteristic are key parameters that determine properties of ferrite components. This paper offers effective, accurate and simple method for complex permeability determination of LTCC (Low Temperature Co-fired Ceramic) ferrite sample at wide frequency range (up to 1 GHz). Presented research can be found to be of importance in fields of ferrite components design and application, as well as RF and microwave engineering. The characterization sample is a stack of LTCC tapes forming a toroidal shape structure. Commercially available ferrite tape ESL 40012 was used and standard LTCC processing applied for the sample fabrication. Permeability is determined in the frequency range from 10 kHz to 1 GHz and characterization procedure is divided in two segments - for low and high frequencies. Low frequency measurements (from 10 kHz to 1000 kHz) are performed using LCZ meter and discrete turns of wire, while a short coaxial sample holder and Vector Network Analyzer were used for the higher frequency range (from 1000 kHz to 1 GHz). Hysteresis properties of this material are also determined. B-H hysteresis loops were measured with BROCKHAUS Tester MPG 100D system using the maximum excitation of 2 kA/m and frequencies of 50 Hz, 500 Hz and 1000 Hz. In addition, we presented another important factor in the practical design, the temperature variation of the permeability dispersion parameters. Obtained results show good agreement with datasheet values given by the manufacturer at lower frequencies and are in good correlation with results extracted from developed dispersion model at higher frequencies.

Impedance Spectroscopy and Hall Measurements on CdTe Thin Polycrystalline Films

2001 ◽  
Vol 668 ◽  
Author(s):  
A.S. Gilmore ◽  
V. Kaydanov ◽  
T.R. Ohno ◽  
D. Grecu ◽  
D. Rose
Keyword(s):  
Impedance Spectroscopy ◽  
Grain Boundary ◽  
Carrier Concentration ◽  
Bulk Material ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Mobility Data ◽  
Thin Polycrystalline ◽  
Grain Bulk ◽  
Expected Increase

ABSTRACTMeasurements of film impedance in a wide frequency range (impedance spectroscopy, IS) were used to evaluate the grain boundary (GB) and the bulk material (B) resistance. Undoped films demonstrated very low carrier concentration and negligible GB resistance, both due to depletion of the bulk material by the GB deep states. Doping the film with Cu led to a significant increase in the GB resistance, in addition to the expected increase in carrier concentration. Illumination of doped films reduced GB resistance by orders of magnitude. This effect was used for the analysis of Hall concentration and Hall mobility data, aimed at exclusion of GB influence on measured parameters, and was used to determine the carrier concentration and mobility in the grain bulk. Hall studies on undoped films under illumination were also used to estimate the lifetime of the photogenerated carriers.

scholarly journals Active Absorption of Perforated Plate Based on Airflow

2005 ◽  
Vol 24 (3) ◽  
pp. 171-180 ◽  
Author(s):  
Zhu Congyun ◽  
Huang Qibai ◽  
Zhao Ming ◽  
Wang Yong
Keyword(s):  
Numerical Calculation ◽  
Absorption Coefficient ◽  
Sound Wave ◽  
Perforated Plate ◽  
Rigid Wall ◽  
Wide Frequency Range ◽  
Single Frequency ◽  
Frequency Range ◽  
Low Frequencies ◽  
Active Absorption

The theory of active absorption of a perforated plate is considered in this paper. The perforated plate is the material of active absorption and the frequency of the incident sound wave is measured. According to this frequency the depth of the cavity between the perforated plate and the rigid wall, is moved in order that resonance occurs so that the absorption coefficient is maximal. According to the numerical calculation, when the perforated plate is resonant, the distance moved is large at low frequencies and the absorption coefficient is low in some conditions. It is effective for a single frequency of incident sound wave, yet it is difficult for a wide frequency range. Hence active absorption based on airflow is considered and calculations and experiments an carried out. The results denote that this method of active absorption is practical.

scholarly journals Dielectric Properties of Switchgrass and Corn Stover in the Radio Frequency Range

2021 ◽  
Vol 64 (1) ◽  
pp. 243-252
Author(s):  
Augusto M. Souza ◽  
Stuart J. Birrell ◽  
Brian L. Steward
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Moisture Content ◽  
Radio Frequency ◽  
Corn Stover ◽  
Loss Factor ◽  
Prediction Models ◽  
Dielectric Constants ◽  
Frequency Range ◽  
Loss Factors

HighlightsDielectric permittivities of switchgrass and corn stover in the radio frequency range were calculated.Prediction models achieved R2 > 0.9, except for the switchgrass loss factor for the material in motion.The loss factors were different when static and in motion, but the dielectric constants were similar.Abstract. The dielectric properties of biological materials are relevant when developing moisture content sensors. However, little is known about the permittivities of switchgrass and corn stover in a wider frequency range. The goal of this research was to determine their dielectric constants and loss factors at different moisture contents across a frequency range of 5 Hz to 13 MHz and with the material static and in motion inside a sample container. The permittivity of these materials was calculated by measuring their admittance in a test fixture using an impedance analyzer at three different moisture levels (9.0% to 30.5%). Overall, the materials’ dielectric properties increased with moisture but decreased with frequency. Prediction models were developed using the data in a frequency range of 10 kHz to 5 MHz. Model coefficients of determination were higher than 0.90 in general, except for the model measuring the loss factor of switchgrass in motion. Additionally, the dielectric constant was not different with the materials static or in motion, but the loss factor values were distinct. This work can be used for the development of electrical moisture content sensors for switchgrass and corn stover. Keywords: Corn stover, Dielectric constant, Loss factor, Moisture content, Permittivity, Switchgrass.

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