Dominant Resonant Frequency Research Articles

Vibration properties of the Ostrich eggshell at impact

An experimental system has been used to generate the impact force, measure the response wave signal, and analyse the frequency spectrum for physical property of Ostrich eggshell. The effects of excitation point, detected point and impact intensity on the eggshell response to a light mechanical impact were analysed. The aim of this study consists in the evaluation of the main vibration properties which can be used for the detection of cracks in the eggshell. Four variables were investigated to determine if they are significant for classifying eggs by setting up relationship x- and y-coordinates, including the first dominant resonance frequency, the normalization average of the frequency domain, the average of the frequency domain, and the average x- and y-coordinates of the centroid for the frequency domain. The egg dynamic resonance frequency was obtained through the analysis of the dynamically measured frequency response of an egg excited by pendulum.

Electrically Small Eighth-Mode Substrate-Integrated Waveguide (EMSIW) Antenna With Different Resonant Frequencies Depending on Rotation of Complementary Split Ring Resonator

Electrically small antennas are proposed, based on a substrate-integrated waveguide (SIW) and a complementary split-ring resonator (CSRR). The antenna's electrical size is reduced by introducing both CSRR and the eight-mode substrate-integrated wave guide (EMSIW). A forward electromagnetic wave can be achieved with frequency below the characteristic waveguide cuff-off frequency due to the CSRR. The EMSIW occupies only 12.5% of the conventional SIW with the same dominant resonant frequency. In addition, by rotating the CSRR on the EMSIW, the resonant frequency of the antenna is varied, while maintaining the same radiation pattern and performance. The S-parameters and radiation patterns are investigated by a full-wave simulation and measurement. The resonant frequency is changed from 4.74 GHz to 5.07 GHz by varying the orientation of the CSRR from 0 to 360 degrees. Omnidirectional radiation patterns are observed, and the measured peak gains are 4.5-5.9 dBi.

Tunable Bandpass Filter With Independently Controllable Dual Passbands

This paper presents a two-pole dual-band tunable bandpass filter (BPF) with independently controllable dual passbands based on a novel tunable dual-mode resonator. This resonator principally comprises a λ/2 resonator and two varactor diodes. One varactor is placed at the center of the resonator to determine the dominant even-mode resonant frequency; the other is installed between two ends of the resonator to control the dominant odd-mode resonant frequency. These two distinct odd- and even-mode resonances can be independently generated, and they are used to realize the two separated passbands as desired. Detailed discussion is carried on to provide a set of closed-form design equations for determination of all of the elements involved in this tunable filter, inclusive of capacitively loaded quarter-wavelength or λ/2 resonators, external quality factor, and coupling coefficient. Finally, a prototype tunable dual-band filter is fabricated and measured. Measured and simulated results are found in good agreement with each other. The results show that the first passband can be tuned in a frequency range from 0.77 to 1.00 GHz with the 3-dB fractional-bandwidth of 20.3%-24.7%, whereas the second passband varies from 1.57 to 2.00 GHz with the 3-dB absolute-bandwidth of 120 ± 8 MHz.

상보적 분할 링 공진기를 이용한 전기적으로 작은 1/8 모드 기판 집적형 도파관 안테나

본 논문은 기판 집적형 도파관(SIW: Substrate Integrated Waveguide)와 상보적 분할링 공진기(CSRR: Complementary Split Ring Resonator)를 기반으로 한 전기적으로 작은 안테나를 제안한다. 안테나의 전기적 크기는 CSRR과 기존 SIW의 1/8크기인 Eighth-Mode Substrate Integrated Waveguide(EMSIW)를 적용하여 줄일 수 있었다. EMSIW는 기존의 SIW와 비교하였을 때 공진 주파수는 유지하면서 단지 12.5 %의 크기를 차지한다. 또한, EMSIW 안에 CSRR을 회전함으로써 안테나의 방사 특성을 유지하면서 공진 주파수를 바꿀 수 있었다. CSRR을 <TEX>$0^{\circ}$</TEX>부터 <TEX>$360^{\circ}$</TEX>까지 회전시켜 공진 주파수를 4.74 GHz에서 5.07 GHz까지 변화를 줄 수 있었다. 단향성 방사 패턴이 발생하며, 그 최대 이득은 4.5 dBi에서 5.92 dBi로 관측되었다. Based on a substrate integrated waveguide(SIW) and a complementary split ring resonator(CSRR), electrically small antennas are proposed in this paper. Antenna's electrical size is reduced by introducing both CSRR and the eighth-mode substrate integrated waveguide(EMSIW). The EMSIW occupies only 12.5 % of the conventional SIW at the same dominant resonant frequency. In addition, the resonant frequency of the antenna is varied by rotating the CSRR on the EMSIW while keeping the same radiation patterns. The resonant frequency is changed from 4.74 GHz to 5.07 GHz by varying orientation of the CSRR from 0 to 360 degree. Unidirectional radiation patterns are observed and the measured peak gains are from 4.50 to 5.92 dBi.

Electrically small complementary split‐ring resonator antenna on eighth‐mode substrate integrated waveguide

An electrically small substrate integrated waveguide (SIW) antenna is proposed at 5.22 GHz. Its electrical size is reduced by a complementary split-ring resonator which is loaded on the eighth-mode SIW (EMSIW). The EMSIW occupies only 12.5% of the conventional SIW with the same dominant resonant frequency. The S-parameters and radiation patterns are investigated by full-wave simulation and measurements. Results show the omnidirectional radiation pattern with a 4 dBi peak gain.

Empirical Formula of Cavity Dominant Mode Frequency for 60-GHz Cavity-Backed Wide Slot Antenna

An empirical formula of the dominant mode resonant frequency of the cavity which is used to back a wide slot antenna is presented. The antenna is formed by etching a wide slot onto the broad wall of a substrate integrated waveguide (SIW) cavity fed by an SIW through an inductive coupling window. The widely slotted cavity resonates at the dominant mode when the wide slot radiates. Based on the analysis of the field distribution in the slotted-cavity, an empirical formula is derived to determine the dominant mode resonant frequency of the cavity with respect to the width to length ratio (WLR) of the etched slot. The empirical formula is numerically verified at a 60-GHz band.

An experimental study of drive-by single channel time reversal using scaled targets and clutter

Previous results suggest that iterative single channel time reversal (TR) is a promising, simple and inexpensive technique to enhance the backscatter signature of elastic objects and to simultaneously focus on its dominant resonance frequency in the presence of noise and clutter (Pautet et al. 2005), (Waters et al. 2009). However, to the best of our knowledge, these and other studies have only considered the case when the sonar system, target, and clutter are fixed or stationary, i.e., not moving. This is an unrealistic assumption since the sonar platform is typically moving. In fact, motion and environmentally-induced clutter scintillations may actually be beneficial for TR when the dominant target resonance varies slowly with aspect in clutter-limited noise environments. Theoretical arguments in (Kirsteins et al. 2009) suggest TR provides additional signal-to-noise ratio (SNR) enhancements against clutter under these circumstances. To confirm this hypothesis, a drive-by TR experiment was conducted in a tank using scaled elastic targets/clutter sources with the platform motion simulated by rotating the target/clutter during each TR iteration. Quantitative analysis in regards to detecting the dominant resonance clearly shows that TR in drive-by mode provides SNR enhancements against clutter.

Age-specific mechanisms in an SSVEP-based BCI scenario: evidences from spontaneous rhythms and neuronal oscillators.

Utilizing changes in steady-state visual evoked potentials (SSVEPs) is an established approach to operate a brain-computer interface (BCI). The present study elucidates to what extent development-specific changes in the background EEG influence the ability to proper handle a stimulus-driven BCI. Therefore we investigated the effects of a wide range of photic driving on children between six and ten years in comparison to an adult control group. The results show differences in the driving profiles apparently in close communication with the specific type of intermittent stimulation. The factor age gains influence with decreasing stimulation frequency, whereby the superior performance of the adults seems to be determined to a great extent by elaborated driving responses at 10 and 11 Hz, matching the dominant resonance frequency of the respective background EEG. This functional interplay was only partially obtained in higher frequency ranges and absent in the induced driving between 30 and 40 Hz, indicating distinctions in the operating principles and developmental changes of the underlying neuronal oscillators.

Runtime Resonance Noise Reduction with Current Prediction Enabled Frequency Actuator

Power delivery network (PDN) is a distributed resistance-inductance-capacitance (RLC) network with its dominant resonance frequency in the low-to-middle frequency range. Though high-performance chips' working frequencies are much higher than this resonance frequency in general, chip runtime loading frequency is not. When a chip executes a chunk of instructions repeatedly, the induced current load may have harmonic components close to this resonance frequency, causing excessive power integrity degradation. Existing PDN design solutions are, however, mainly targeted at reducing high-frequency noise and not effective to suppress such resonance noise. In this work, we propose a novel approach to proactively suppress this type of noise. A method based on the high dimension generalized Markov process is developed to predict current load variation. Based on such prediction, a clock frequency actuator design is proposed to proactively select an optimal clock frequency to suppress the resonance. To the best of our knowledge, this is the first in-depth study on proactively reducing instruction loop induced PDN resonance noise at the runtime.

Pattern recognition of eggshell crack using PCA and LDA

The eggshell crack was detected with dynamic frequency response and an egg was excited by a light mechanical impact on different locations of the eggshell. The dominant resonance frequency can be observed using flexible piezoelectric film sensors. The results showed that some frequencies were higher for the cracked eggs, whereas the dominant frequency value was lower for the intact eggs. In normalized power spectrum, the first 10 or 20 features were extracted based on interval frequency (IFM), maximum magnitudes in turn (HVM) and frequencies by magnitudes in turn (MVF), and were used as input of pattern recognition algorithms The pattern recognition was conducted by Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA). Intact egg and cracked egg could be distinguished by LDA and PCA using HVM and MVF. More distinguishing effects were obtained based on LDA using 10 MVFs. The examination of cracks on eggshell was usually conducted by floodlighting before, but it gives eye fatigue, makes misjudgment and is not easy to detect hairline crack. The acoustic impulse response method was suggested in this research to measure hairline crack for eggshell using flexible piezoelectric film sensors. The result was found that the acoustic impulse response method can distinguish between intact egg and cracked egg. This research provides a technology detection of cracked egg.

Creep compensation in piezoelectric actuators for nanopositioning technology

Piezoelectric linear actuators are used in a wide variety of nanopositioning platforms. The nanopositioner platforms have undesired characteristics such as hysteresis, creep and dominant low resonant frequencies. These characteristics limit the open loop performance. Hence, the closed loop is necessary to obtain a superior performance and to achieve robust repeatable nanopositioning. This paper describes the development to control a single axis of a PI-734 nanopositioning platform. The linearised model is identified using frequency response in the literature. The closed loop controller consists of three parts: feed-forward compensator, resonant mode damper and integrator. The controller structure is sample based on PID classical control using linearised model of the system. The obtained simulation results affirmed the potential of the proposed control algorithm where the creep is eliminated and the resonant mode is damped. The position tracking error is reduced to sub-nanometers.

Frequency Response Analysis for Rolling-Bearing Damage Diagnosis

This paper deals with a new diagnosis method for detecting bearing faults (BFs) based on frequency response analysis. For non-rigid multi-mass systems with dominant mechanical resonance frequencies, the frequency response has to be calculated during the commissioning of the plant for reasons of safety and controlling. This task can be achieved by measuring two control variables of the drive which are both affected by BFs. This paper proposes that the measurement of the frequency response is a suitable strategy for detecting incipient BFs. In doing so, a two-channel analysis method for bearing damage diagnosis without additional sensors is developed. Deviations from the frequency response of the healthy state serve as indicators for a present BF. As the measurement of the two signals can be carried out during normal operation of the plant, online BF diagnosis is achieved. For the investigated two-inertia system, single-point bearing defects on the inner and outer raceways of rolling bearings and generalized roughness faults are within the scope of this paper.

Analysis of anti-vibration gloves mechanism and evaluation methods

The primary objectives of the current study are to enhance the understanding of the mechanisms of the anti-vibration gloves and to evaluate the methods for assessing their vibration isolation effectiveness through developing a mechanical-equivalent model of the glove-hand–arm system. The model is developed based on the measured driving-point mechanical impedances distributed at the fingers and the palm of the hand with and without a glove. Six subjects participated in the experiments with two types of anti-vibration gloves (air-bladder glove and gel-filled glove) for measuring the required impedance data. The proposed model is applied to predict the effectiveness of the glove in terms of vibration transmitted to the fingers-glove and palm-glove interfaces, the finger bones, and the wrist. The results show that the gloves could provide some attenuation of the palm-transmitted vibration at frequencies above the fundamental resonant frequency of the gloved hand–arm system, but only little reduction in the finger vibration below the dominant finger resonant frequency. The present standardized methodology based upon the transmissibility measurement at the palm alone would thus be inappropriate for characterizing the overall reduction of the vibration exposure by a glove. Moreover, the palm adapter could introduce some measurement errors because of its mass and misalignment effects and its interference with the glove-palm coupling relationship. Therefore, the standardized method may only be used for general screening tests. On the basis of the model results, several potential improvements in the current standardized methodologies for evaluations of gloves and glove material are proposed and discussed. The proposed model may also serve as a useful tool for further developments of anti-vibration gloves and other anti-vibration devices.

DESIGN OF BAND-PASS WAVEGUIDE FILTER USING FREQUENCY SELECTIVE SURFACES LOADED WITH SURFACE MOUNT CAPACITORS BASED ON SPLIT-FIELD UPDATE FDTD METHOD

A new band-pass narrow-band, miniaturized and single resonance within a wide range of frequency band frequency selective surface structure with lumped capacitors suitable for low frequency and narrowband waveguide filter applications is presented. The filter structure consists of five unit cells in one direction with notch square ring elements each consists of two lumped capacitors placed on the transverse plane of the rectangular waveguide. To reduce the simulation time in design procedure, split-field update FDTD method is used for the analysis of the unit cell of the analogous infinite frequency selective surface at different oblique incidence of plane waves to predict the FSS performance in the waveguide. As an application, a waveguide filter has been designed to be used in an easy to fabricate and inexpensive S-band band-pass filter. By using lumped capacitors, several undesirable higher order resonance frequencies near the dominant resonance frequency are eliminated and the waveguide filter dimensions are reduced considerably in one direction compared with the analogous waveguide filter without lumped capacitors.

Nonlinear dual-axis biodynamic response of the semi-supine human body during longitudinal horizontal whole-body vibration

The resonance frequencies in frequency response functions of the human body (e.g. apparent mass and transmissibility) decrease with increasing vibration magnitude. This nonlinear biodynamic response is found with various sitting and standing postures requiring postural control. The present study measured the apparent mass of the body in a relaxed semi-supine posture with two types of longitudinal horizontal vibration (in the z-axis of the semi-supine body): (i) continuous random excitation (0.25–20 Hz) at five magnitudes (0.125, 0.25, 0.5, 0.75 and 1.0 ms −2 rms); (ii) intermittent random excitation (0.25–20 Hz) alternately at 0.25 and 1.0 ms −2 rms. With continuous random vibration, the dominant primary resonance frequency in the median normalised apparent mass decreased from 3.7 to 2.4 Hz as the vibration magnitude increased from 0.125 to 1.0 ms −2 rms. A nonlinear response was apparent in both the horizontal ( z-axis) apparent mass and the vertical ( x-axis) cross-axis apparent mass. With intermittent random vibration, as the vibration magnitude increased from 0.25 to 1.0 ms −2 rms, the median resonance frequency of the apparent mass decreased from 3.2 to 2.5 Hz whereas, with continuous random vibration over the same range of magnitudes, the resonance frequency decreased from 3.4 to 2.4 Hz. The median change in the resonance frequency (between 0.25 and 1.0 ms −2 rms) was 0.6 Hz with the intermittent random vibration and 0.9 Hz with the continuous random vibration. With intermittent vibration, the resonance frequency was higher at the high magnitude and lower at the low magnitude than with continuous vibration at the same magnitudes. The responses were consistent with passive thixotropy being a primary cause of nonlinear biodynamic responses to whole-body vibration, although reflex activity of the muscles may also have an influence.

Nonlinear dual-axis biodynamic response of the semi-supine human body during vertical whole-body vibration

Nonlinear biodynamic responses are evident in many studies of the apparent masses of sitting and standing subjects in static postures that require muscle activity for postural control. In the present study, 12 male subjects adopted a relaxed semi-supine posture assumed to involve less muscle activity than during static sitting and standing. The supine subjects were exposed to two types of vertical vibration (in the x-axis of the semi-supine body): (i) continuous random vibration (0.25–20 Hz) at five magnitudes (0.125, 0.25, 0.5, 0.75, and 1.0 m s −2 rms); (ii) intermittent random vibration (0.25–20 Hz) alternately at 0.25 and 1.0 m s −2 rms. With continuous random vibration, the dominant primary resonance frequency in the median normalised apparent mass decreased from 10.35 to 7.32 Hz as the vibration magnitude increased from 0.125 to 1.0 m s −2 rms. This nonlinear response was apparent in both the vertical ( x-axis) apparent mass and in the horizontal ( z-axis) cross-axis apparent mass. As the vibration magnitude increased from 0.25 to 1.0 m s −2 rms, the median resonance frequency of the apparent mass with intermittent random vibration decreased from 9.28 to 8.06 Hz whereas, over the same range of magnitudes with continuous random vibration, the resonance frequency decreased from 9.62 to 7.81 Hz. The median change in the resonance frequency (between 0.25 and 1.0 m s −2 rms) was 1.37 Hz with the intermittent random vibration and 1.71 with the continuous random vibration. With the intermittent vibration, the resonance frequency was higher at the high magnitude and lower at the low magnitude than with continuous vibration of the same magnitudes. The response was typical of thixotropy that may be a primary cause of the nonlinear biodynamic responses to whole-body vibration.

Temporal evolution of long-period seismicity at Etna Volcano, Italy, and its relationships with the 2004–2005 eruption

Between December 2004 and August 2005, more than 50,000 long-period events (LP) accompanied by very-long period pulses (VLP) were recorded at Mt. Etna, encompassing the effusive eruption which started in September 2004. The observed activity can be explained by the injection of a gas slug formed within the magmatic column into an overlying cavity filled by either magmatic or hydrothermal fluids, thus triggering cavity resonance. Although a large number of LP events exhibit similar waveforms before the eruption, they change significantly during and after the eruption. We study the temporal evolution of the LP-VLP activity in terms of the source movement, change of the waveforms, temporal evolution of the dominant resonance frequencies and the source Q factor and changes in the polarization of the signal. The LP source locations before and after the eruption, respectively, do not move significantly, while a slight movement of the VLP source is found. The intensity of the LP events increases after the eruption as well as their dominant frequency and Q factor, while the polarization of the signals changes from predominantly transversal to pure radial motion. Although in previous studies a link between the observed LP activity and the eruption was not found, these observations suggest that such a link was established at the latter end of the eruptive sequence, most likely as a consequence of a reestablishment of the pressure balance in the plumbing system, after it was undermined due to the discharge of large amounts of resident magma during the eruption. Based on the polarization properties of the signal and geological setting of the area, a fluid-filled crack is proposed as the most likely source geometry. The spectral analysis based on the autoregressive-models (SOMPI) is applied to the signals in order to analyse the resonance frequencies and the source Q-factors. The results suggest water and basalt at low gas volume fraction as the most likely fluids involved in the source process. Using theoretical relations for the “slow waves” radiated from the fluid-filled crack, we also estimate the crack size for both fluids, respectively.

Photonic crystal defect mode cavity modelling: a phenomenological dimensional reduction approach

A phenomenological dimensional reduction approach (PDRA) for the cavity characteristics in defect mode based photonic crystal (PC) lasers is presented. Based on the fully vectorial three-dimensional finite-difference time-domain (3D FDTD) technique, simultaneous enhancement and suppression in spontaneous emission and absorption were obtained in an absorptive photonic crystal slab (PCS) cavity. Effective index perturbation (EIP) was proposed for fast and accurate determination of the effective index and the dominant resonant cavity frequency in a 3D PCS structure, with two-dimensional (2D) FDTD simulation. Further dimensional reduction from 2D to one-dimensional planar cavity enables phenomenological modelling of lasing characteristics via the effective reflectivity calculation and rate equation analysis. Very fast and accurate results have been achieved with this PDRA approach. A high spontaneous emission factor and cavity quality factor Q were obtained in a single defect cavity, which led to over an order reduction in lasing gain threshold. The model offers a fast and accurate tool for the design and modelling of PC defect mode cavity based devices and aids the research in the proposed novel defect mode based devices such as ultra-compact light sources on Si and spectrally resolved PC infrared photodetectors.

An ultra-small cavity resonator loaded with LHM and RHM layers

In this paper, an ultra-small cavity resonator (USCR) loaded with left-handed metamaterial (LHM) and right-handed material (RHM) layers is designed using a novel miniaturization approach. The resonant behavior is successfully observed, and the dimensions of the USCR are only 4.58 mm × 5.08 mm × 2.29 mm at the dominant resonance frequency of 10.3 GHz. Through the field distribution calculation, we confirmed that the miniaturization of the USCR arises from the left-handed property of the LHM. For a practical application, a miniaturized filter with overall length of 10.19 mm consisting of two USCRs is designed to confirm the frequency-selective characteristics. Results show that the filter has some narrow pass bands, which correspond to the resonant modes of the electromagnetic resonance in the USCR, and the insertion loss at the dominant resonance frequency of the USCR is as low as 0.65 dB. Moreover, the filtering characteristics of the filter can be controlled by changing its feeding loop positions in the USCR.

ACOUSTIC IMPULSE RESPONSE FOR MEASURING THE FIRMNESS OF MANDARIN DURING STORAGE

ABSTRACT The objective of this research was to evaluate the ability of acoustic impulse response for monitoring the mandarin firmness change during storage. The dominant resonant frequency, stiffness coefficient (SC) and elasticity coefficient (EC) decrease with storage time. A good correlation was established between the acoustic parameters (SC and EC) and fruit compression force, and the correlation coefficients were 0.88 and 0.92, respectively. Acoustic impulse response gives a good indication of firmness change for mandarin during storage. The change of EC was more prominent (greatest), and hence it can be a better index of mandarin firmness. The nondestructive acoustic test might replace conventional destructive test for mandarin to determine fruit firmness and expected shelf life.