scholarly journals Study of the Static and Microwave Magnetic Properties of Nanostructured BaFe12−xTixO19

Coatings ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 789
Author(s):  
Polina A. Zezyulina ◽  
Dmitry A. Petrov ◽  
Konstantin N. Rozanov ◽  
Denis A. Vinnik ◽  
Sergey S. Maklakov ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Resonance Frequency ◽  
Electromagnetic Interference ◽  
Low Frequency ◽  
Frequency Range ◽  
Functional Coatings ◽  
Nano Structure ◽  
Substitution Level ◽  
Resonance Frequencies ◽  
Ferrite Composites

The effect of Ti substitution on the microwave and magnetostatic properties of nanostructured hexagonal BaFe12−xTixO19 ferrite composites is studied. The microwave permeability is measured in the frequency range of 0.1–22 GHz by a coaxial technique. An analysis of the magnetostatic data is made by the law of approach to saturation. The ferrimagnetic resonance frequencies calculated from the magnetostatic data are consistent with those obtained from the microwave measurements. The natural ferrimagnetic resonance frequencies are located in the frequency range of 15 to 22 GHz, depending on the substitution level x. An increase in the amount of substitution elements results in a low-frequency shift of the ferrimagnetic resonance frequency for samples with x < 1. With x rising from 1 to 2.5, the resonance frequency increases. The results of the study demonstrate that the tailored optimization of the nano-structure of a functional material is a robust tool to fine-tune its microwave magnetic properties. The ferrites under study are promising materials to be applied as functional coatings intended to control electromagnetic interference in microwave devices.

Bandgap Properties of Two-Layered Locally Resonant Phononic Crystals

2020 ◽  
Vol 12 (07) ◽  
pp. 2050075
Author(s):  
Hongyun Wang ◽  
Heow Pueh Lee ◽  
Wei Xu
Keyword(s):  
Coating Thickness ◽  
Low Frequency ◽  
Phononic Crystals ◽  
Formation Mechanisms ◽  
Frequency Range ◽  
The Third ◽  
Resonance Frequencies ◽  
Rubber Coating ◽  
Lower Frequency Range ◽  
Mass Spring

Multi-layered locally resonant phononic crystals (LRPCs) with wider and multiple bandgaps (BGs) in low frequency range and small size of the unit cell have promising applications in noise and vibration controls. In this paper, a 2D two-layered ternary LRPC consisting of a periodical array of cylindrical inclusions embedded in an epoxy matrix is investigated by the finite element method (FEM), where the inclusion is comprised of two coaxial cylindrical steel cores with rubber coating. It is found that the size of the inclusion of the 2D two-layered ternary LRPC has significant effects on the BG properties. With the increase of the core radius and coating thickness, the first BG would shift to lower frequency range with its width decreasing, and the second BG width would become wider until the third BG appears. Especially, with the increase of the coating thickness, more bands and BGs would appear in the lower frequency range. Based on the formation mechanisms of the BGs, several mass-spring models to predict the frequencies of the first two BG edges are developed. The results calculated by these mass-spring models are in good agreement with those by the FEM except for the upper edge frequency of the second BG when the rubber coating thickness exceeds a certain value and the third BG is opened up. These proposed mass-spring models would allow for quick pre-estimation of the resonance frequencies, and facilitate the selection of possible parameters for the wider and lower frequency BGs to obtain the desired attenuation bands. The studies would also benefit the design of multiple BGs for some device applications.

Hybrid processing and properties of Ni0.8Zn0.2Fe2O4/Ba0.6Sr0.4TiO3 magnetodielectric composites

2010 ◽  
Vol 25 (9) ◽  
pp. 1803-1811 ◽  
Author(s):  
Haibo Yang ◽  
Hong Wang ◽  
Li Shui ◽  
Li He
Keyword(s):  
Magnetic Properties ◽  
Dielectric Properties ◽  
Electromagnetic Interference ◽  
High Frequency ◽  
Processing Route ◽  
High Frequency Range ◽  
Frequency Range ◽  
Low Loss ◽  
High Permittivity ◽  
Interference Filters

Ni0.8Zn0.2Fe2O4/Ba0.6Sr0.4TiO3 (NZO/BST) composites with high permittivity and low loss were synthesized via the hybrid processing route. The composites possess very dense and homogenous microstructure. The NZO/BST composites show good dielectric properties and magnetic properties with low loss in high frequency range. This indicates that this kind of magnetodielectric composites can be used in high-frequency communications for the capacitor-inductor integrating devices such as electromagnetic interference filters and antennas. The permittivities of the composites were also fitted using the combination of Maxwell–Wagner polarization and modified Curie–Weiss law.

scholarly journals Analysis of inertial amplification mechanism with smart spring-damper for attenuation of beam vibrations

2018 ◽  
Vol 157 ◽  
pp. 03002 ◽  
Author(s):  
Mateusz Barys ◽  
Robert Zalewski
Keyword(s):  
Complex Systems ◽  
Real Time ◽  
Active Control ◽  
Smart Materials ◽  
Low Frequency ◽  
Frequency Range ◽  
Longitudinal Vibrations ◽  
The Real ◽  
Resonance Frequencies ◽  
Amplification Mechanism

In this paper an inertial amplification mechanism with an embedded smart spring-damper device for attenuation of longitudinal vibrations in continuous structures is analyzed. The complex systems are the extension of the already investigated inertial mechanism, here additionally equipped with the vacuum controlled spring-damper device which shows features of smart materials. This allows the semi-active control to affect different frequency vibration ranges in the real time. The fea.tures of the basic inertia amplification mechanism are preserved as a possibility to generate two neighbouring anti-resonance frequencies between resonance peaks in the low frequency range.

Dynamic analysis and vibration reduction of articulated silicone gel column with varying geometry

2021 ◽  
pp. 1-13
Author(s):  
Ji-Hou Yang ◽  
Xiao-Dong Yang ◽  
Qing-Kai Han ◽  
Jinguo Liu
Keyword(s):  
Frequency Band ◽  
Vibration Reduction ◽  
Low Frequency ◽  
Vibration Absorber ◽  
Frequency Range ◽  
Dynamic Vibration Absorber ◽  
Dynamic Vibration ◽  
Silicone Gel ◽  
Resonance Frequencies ◽  
Reduction Effect

Abstract To improve vibration reduction effect in low-frequency band of dynamic vibration absorber (DVA), a novel type of articulated silicone gel column (SGC) is introduced in the design of the tuned dynamic vibration absorber. The nonlinear variation of frequency of SGC with varying geometry is obtained by both finite element simulation and experiments. The most sensitive mode is located, which has wider frequency range by varying the geometry. The polynomial fitting is used to describe nonlinear relation between frequency and geometry. By tuning the geometry, the equivalent stiffness and then resonance frequencies can be manipulated to behave as an active vibration absorber. The vibration reduction experiment of SGC vibration absorbers is investigated. It is found that SGC has better vibration reduction effect in low-frequency band. The experimental results in the current design demonstrate that the vibration reduction effect can reach 94.03% when tuning SCG to the first order main resonance. The dimensions and material parameters of SGC should be altered for specific frequency range and vibration strength.

Bending Vibrations of the Femur and the Oscillatory Behavior of a Cemented Femoral Hip Endoprosthesis

2000 ◽  
Vol 122 (4) ◽  
pp. 416-422
Author(s):  
M. Thomsen ◽  
A. Go¨rtz ◽  
U. V. Na¨gerl ◽  
D. Kubein-Meesenburg ◽  
W. Go¨rtz ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Low Frequency ◽  
Oscillatory Behavior ◽  
Measuring System ◽  
Frequency Range ◽  
Entire Frequency Range ◽  
Bending Vibrations ◽  
Low Frequencies ◽  
Hip Endoprosthesis ◽  
Resonance Frequencies

The paper presents a novel method for recording amplitude and phase of 6D-vibrations of a spatial pendulum over a wide frequency range (10 Hz up to 20 kHz). The six degrees of freedom of the pendulum mass were monitored by three electrodynamic stereo pickups. At rest, the tips of the needles and the pendulum’s center of mass defined the reference system with respect to which the oscillations of the mass were recorded in terms of their amplitudes and phases. Its small dimensions, constant transfer characteristics, linearity, high dynamics, and virtual lack of reaction onto the moving system over the entire frequency range provided the advantages of the measuring system. This method was used to analyze the spatial 6D-vibrations of the head of a cemented femoral hip endoprosthesis when the femur was stimulated to bending vibrations. The head of the prosthesis carried out axial rotational vibrations at every frequency used to stimulate the femur. The amplitudes of the axial rotations of the cortical bone were small in comparison to the ones of the prosthesis head, indicating that axial rotational vibrations following femur bending vibrations mainly stressed the spongiosa and the cement layer. This was observed over the entire frequency range, including at the low frequencies relevant for gait. Over the low-frequency range, as well as at some of the higher resonance frequencies, stationary instantaneous helical axes characterized the vibrations. The measurements suggest the mechanism that the interface “implant-bone” may already be stressed by axial torsional loads when the femur is loaded by bending impacts that are known to occur during walking. [S0148-0731(00)01604-6]

scholarly journals Control the Frequency Response of a Loudspeaker by Changing Its Enclosure

2021 ◽  
Vol 4 (2) ◽  
Author(s):  
Pavlo Olehovych Riabokon
Keyword(s):  
Resonant Frequency ◽  
Resonance Frequency ◽  
Frequency Response ◽  
Rock Music ◽  
Low Frequency ◽  
Total Quality ◽  
Frequency Range ◽  
Low Frequencies ◽  
Frequency Components ◽  
Internal Volume

This article analyzes how to control frequency response of a loudspeaker by changing the volume of its closed-box enclosure. The calculation is performed by the method of  Thiele-Small on the basic of a pre-calculated loudspeaker, the parameters of which are given in third section. This became possible because of the simplification of the circuit on figure 1 to the form of circuit on figure 2. This allowed us to consider it as a second order filter (presence of two reactive elements). Obtained results are compared with corresponding characteristics of open-box enclosure of the same loudspeaker, that was pre-calculated by the author too. Results are presented graphically in figure 3 and 4. As can be seen from them, the resonant frequency of the loudspeaker in the closed-box enclosure is higher than the resonant frequency of the loudspeaker in the open box. The result in the form of a ratio  is listed in table 2. Analyzing the obtained data, it can be noticed that with the change of the internal volume of the closed box (and hence its total quality factor), it is possible to affect both the resonance frequency and the peak amplitude values in these frequencies by changing the FR. The result shown in figure 3 and 4 is achieved by taking into account effect of radiation only on the one side of the driver (in the case of open-box enclosure). Closed box was calculating by taking into account both sides radiation of the driver. Shifting the resonance frequency of the system towards higher frequencies and increasing the sound pressure on the resonance generally worsens the FR of the loudspeaker (reduces the reproduction of low-frequency components of sound and increases the unevenness of the frequency). However, certain variants of this group of frequency characteristics may be useful depending on the reproducible frequency range and need of emphasize the low-frequency components (for example, in rock music). If you need a smoothed low-frequency sound, it is appropriate to use systems with low overall quality and increased internal volume or open-box enclosure. Therefore, the volume of the closed-box enclosure significantly affects the resonant frequency and the shape of the frequency response of the loudspeaker. Reducing the volume of the enclosure of the loudspeaker leads to a decrease in its frequency range due to low frequencies and at the same time increase in the unevenness of the frequency response. The change in the resonant frequency of the system as the volume of the closed-box enclosure decreases, the less the volume of the closed-box.

scholarly journals Black-Box Modelling of Low-Switching-Frequency Power Inverters for EMC Analyses in Renewable Power Systems

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3413
Author(s):  
Lu Wan ◽  
Abduselam Hamid Beshir ◽  
Xinglong Wu ◽  
Xiaokang Liu ◽  
Flavia Grassi ◽  
...  
Keyword(s):  
Power Systems ◽  
Electromagnetic Interference ◽  
Low Frequency ◽  
Black Box ◽  
Switching Frequency ◽  
Frequency Range ◽  
Negative Sequence ◽  
Renewable Power ◽  
Zero Sequence ◽  
Power Inverters

Electromagnetic interference (EMI) from renewable power systems to the grid attracts more attention especially in the low-frequency range, due to the low switching frequency of high-power inverters. It is significantly important to derive EMI models of power inverters as well as to develop strategies to suppress the related conducted emissions. In this work, black-box modelling is applied to a three-phase inverter system, by implementing an alternative procedure to identify the parameters describing the active part of the model. Besides, two limitations of black-box modelling are investigated. The first regards the need for the system to satisfy the linear and time-invariant (LTI) assumption. The influence of this assumption on prediction accuracy is analysed with reference to the zero, positive and negative sequence decomposition. It is showing that predictions for the positive/negative sequence are highly influenced by this assumption, unlike those for the zero sequence. The second limitation is related to the possible variation of the mains impedance which is not satisfactorily stabilized at a low frequency outside the operating frequency range of standard line impedance stabilization networks.

Résonance quadripolaire nucléaire du brome dans des composés organomagnésiens

1977 ◽  
Vol 55 (9) ◽  
pp. 1515-1520 ◽  
Author(s):  
Jacky Kress ◽  
Lucien Guibé
Keyword(s):  
Resonance Frequency ◽  
Nuclear Quadrupole Resonance ◽  
Ionic Character ◽  
Frequency Range ◽  
Resonance Frequencies ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole

Bromine nuclear quadrupole resonance signals corresponding to both isotopes 79Br and 81Br have been observed, at 77 °K, in some crystallized organomagnesium bromides of formula RMgBr•nR′2O, and in MgBr2•nEt2O. The low value of the resonance frequencies, of about 33 MHz-to be compared to 220 MHz for a typical [Formula: see text] bond, bond, shows the ionic character of the Mg—Br bond. The fact that the resonance frequencies are found within a restricted frequency range, between 30 and 42 MHz, shows that the Mg—Br bond is only slightly affected by the nature of the radicals R and R′ through the series studied; However the variation of the bromine resonance frequency in this series may be interpreted in terms of the nature of R and R′.

EXPERIMENT AND MODELING OF SEATED HUMAN BODY EXPOSED TO LARGE-MAGNITUDE VIBRATION IN SIX SINGLE DIRECTIONS

2019 ◽  
Vol 19 (05) ◽  
pp. 1950037
Author(s):  
SHUANG LUO ◽  
HONGYU SHU ◽  
XIANBAO CHEN
Keyword(s):  
Test Bench ◽  
Low Frequency ◽  
Biomechanical Model ◽  
Frequency Range ◽  
Large Magnitude ◽  
Damping Coefficients ◽  
Sensitivity Tests ◽  
Resonance Frequencies ◽  
Series Of Experiments ◽  
Insight Into

This paper is to perform experiment, modeling and parameter identification for the seated human bodies to provide insight into transmissibilities to the thigh and the chest, and estimate the indistinct spring and damping constants at human-seat interface. A test bench was designed, and a series of experiments was conducted with 15-seated subjects exposed to low-frequency and large-magnitude vibrations individually in roll, pitch, yaw, fore-and-aft, lateral and vertical axes. Transmissibilities were measured for each subject over the frequency range 0.5–8[Formula: see text]Hz. A 12-degree-of-freedom (DOF) biomechanical model was proposed and was subsequently simplified to six 2-DOF models to describe the experimental results in the corresponding directions. Translational and rotational spring and damping coefficients in six directions were identified via a genetic algorithm. Sensitivity tests were carried out and the influences of the spring and damping coefficients on the principal resonance frequencies and the peak moduli of the transmissibilities were exhibited.

Sign in / Sign up

Export Citation Format

Share Document