High Frequency Resonance Peaks Research Articles

Dynamic susceptibility in torus nanoring with canted external DC magnetic field

The dynamic susceptibility spectra of torus nanoring with a perpendicular or canted external DC magnetic field are studied by means of micromagnetic simulation. Due to the shape anisotropy of the torus nanoring, the system has a vortex spin structure when there is no external DC magnetic field, and the imaginary part of the dynamic susceptibility shows a single resonance peak. With the increase of DC magnetic field which is perpendicular to the plane of the ring, the resonant frequency decreases firstly and then increases monotonically. When the angle between the direction of the DC magnetic field and the center axis of the nanoring increases, the imaginary part of the magnetic susceptibility gradually shows one low frequency and three high frequency resonance peaks. By calculating the dynamic magnetic susceptibility of different parts of the nanoring, the corresponding region of each resonance mode is determined. Finally, we also discuss the effect of size on the magnetic susceptibility of the torus nanoring.

Averaging analysis on a semi-active inerter–based suspension system with relative-acceleration–relative-velocity control

The semi-active inerter–based suspension system with a semi-active inerter is proposed in this article to improve the dynamic performance of the passive one. The fluid inerter is used to implement the semi-active inerter and has two adjustable inertances: the maximum and minimum inertances. Based on the relative acceleration and relative velocity between the unsprung mass and sprung mass of the suspension system, and combined with the mechanical property of the semi-active inerter, the relative-acceleration–relative-velocity control strategy is proposed and has two different types: relative-acceleration–relative-velocity+− and relative-acceleration–relative-velocity−+ control strategies, respectively. The relative-acceleration–relative-velocity+− control strategy means adjusting the inertance of the semi-active inerter to the maximum one when the signs of relative acceleration and relative velocity are the same, and to the minimum one when the signs are the opposite, and the meaning of relative-acceleration–relative-velocity−+ control strategy does the reverse. The dynamic response of the semi-active inerter–based suspension system with the relative-acceleration–relative-velocity control strategy is obtained using the averaging method, and its dynamic performance is evaluated using three performance indices: vehicle body acceleration, dynamic tire load, and suspension system stroke. The results show that the semi-active inerter–based suspension system with the relative-acceleration–relative-velocity+− control strategy can have a better dynamic performance for the dynamic tire load and suspension system stroke in which the low-frequency and high-frequency resonance peaks can be smaller, but is poor for the vehicle body acceleration in which the high-frequency resonance peak can be significantly larger; whereas the relative-acceleration–relative-velocity−+ control strategy does the reverse. For smaller maximum and minimum inertances, the relative-acceleration–relative-velocity+− and relative-acceleration–relative-velocity−+ control strategies can achieve the corresponding better performance indices, with a small degeneration for the other performance indices.

Unfound Associated Resonant Model and Its Impact on Response of a Quartz Crystal Microbalance in the Liquid Phase.

Quartz crystal microbalance (QCM) is an important tool to detect in real time the mass change at the nanogram level. However, for a QCM operated in the liquid phase, the Sauerbrey equation is usually disturbed by the changes in liquid properties and the longitudinal wave effect. Herein, we report another unfound associated high-frequency resonance (HFR) model for the QCM, with the intensity 2 orders of magnitude higher than that of the fundamental peak in the liquid phase. The HFR model exhibits obvious impact on the response of QCM in the thickness-shear model (TSM), especially for overtones. The frequency of HFR peak is decreased dramatically with increasing conductivity or permittivity of the liquid phase, resulting in considerable additional frequency shifts in the TSM as baseline drift. Compared to that with a faraway HFR peak, the overlapping of HFR peak to a TSM overtone results in the frequency shifts of ±50-70 kHz with its intensity enhancement by 3 orders of magnitude in the later. The HFR behavior is explained by an equivalent circuit model including leading wire inductance, liquid inductance, and static capacitance of QCM. Taking into account the HFR model, the positive frequency shifts of the QCM at high overtones during the cell adhesion process is understandable. Combining the TSM and HFR is an effective way to improve the stability of QCM and provides more reliable information from the responses of QCM. The HFR may have potential application in chemical and biological sensors.

Dynamic micromagnetic simulation of permalloy antidot array film

Dynamic magnetic susceptibilities of permalloy antidot array film were studied using three-dimensional (3D) object oriented micromagnetic framework (OOMMF) code with two dimensional periodic boundary condition (2DPBC) extension. Two major resonance peaks associated with different regions were found in the investigated systems. Both resonance frequencies decrease with increasing inter-hole distance. The frequency corresponding to lower resonance peak increases with increasing film thickness for t<20 nm, and then the resonance frequency varies weakly with the thickness. High frequency resonance peak increases with decreasing inner radius, and disappears when the inner radius is below 10 nm. Low resonance frequency varies from 1.72 to 6.4 GHz when inner radius changes from 5 to 40 nm.

NUMERICAL MODELLING OF THE SOUND FIELD NEAR A TALL BUILDING WITH BALCONIES NEAR A ROAD

A two-dimensional, boundary element numerical model is used to study the sound field in the region of balconies in a tall building close to a roadway. The sound pressure level relative to the free field level is calculated within the balconies on the first four floors, and at positions 1 m outside the external facade. The effects of shielding of the source by the balcony wall are found to be largely cancelled by the strong reflected sound from the ceiling and rear wall of the balcony. The insertion loss resulting from eight different applications of an efficient sound absorbing material to the building surfaces is calculated. It is found that treatment of the ceiling or the rear wall of the balcony is the most efficient in terms of noise reduction, producing values of between about 5 and 8 dB for a broad band spectrum characteristic of A-weighted road traffic noise. The maximum effects obtained for a combination of surface treatments is 10 dB. Spectra of the sound pressure level relative to the free field level are compared for a receiver position in one balcony and it is observed that the main effect of an absorbent is to reduce the high frequency resonance peaks.