Order Resonant Frequencies Research Articles

EFFECTS OF SIMPLIFIED METHODS FOR HYDRODYNAMIC FORCE ON TRANSFER FUNCTION OF CIRCULAR PIER

The rigid-structure method, Morison method and a method based on approximation of fundamental frequency are applicable simplified methods for the hydrodynamic force of incompressible non-viscous water. To investigate the differences of the above methods, the responsesof elastic cantilever circular piers were compared in the form of frequency domain transfer function, with the exact solutions which based on the radiation theory of incompressible non-viscous water considering structural deformation. Two kinds of size parameters were selected and 84 different sizes of piers were designed. By inputting impulse excitation, the transfer functions of displacement at the bottom, the transfer function of shear force and bending moment at the top were obtained. Then the first two order resonance-peak amplitude and resonance frequency were extracted for error analysis. Through the analysis of the range and variation trend of errors, it is found that:the resonance peak amplitude obtained by the rigid-structure method is more accurate, the resonance period obtained by the method based on approximation of fundamental-frequency is more accurate, and the error of the Morison method is significantly affected by the parameters. In addition, the amplitude of formant obtained by the fundamental frequency approximation is mostly smaller, while the amplitude and period obtained by the Morrison method are mostly larger.

Tuning Techniques for Piezoelectric and Electromagnetic Vibration Energy Harvesters

This paper is focused on resonant vibration energy harvesters (RVEHs). In applications involving RVEHs the maximization of the extraction of power is of fundamental importance and a very crucial aspect of such a task is represented by the optimization of the mechanical resonance frequency. Mechanical tuning techniques (MTTs) are those techniques allowing the regulation of the value of RVEHs mechanical resonance frequency in order to make it coincident with the vibration frequency. A very great number of MTTs has been proposed in the literature and this paper is aimed at reviewing, classifying and comparing the main of them. In particular, some important classification criteria and indicators are defined and are used to put in evidence the differences existing among the various MTTs and to allow the reader an easy comparison of their performance. Finally, the open issues concerning MTTs for RVEHs are identified and discussed.

Structure design and analysis of tracking frame for horizontal telescope

针对某700 mm口径地平式望远镜系统，提出了一种U型跟踪架的结构设计方案。跟踪架结构中方位轴系采用双排密珠球轴承，轴承设计为双排轴向止推钢珠及双排径向钢珠结构，滚珠的密集及均化作用可保证轴系具有高回转精度。俯仰轴系设计采用一端固定、一端游动的结构方式，以补偿机械误差及热变形对回转精度的影响。对望远镜跟踪架进行有限元建模，分析得出其一阶谐振频率可达到47.6 Hz，说明它具有良好的模态特性。使用电子水平仪及自准直仪分别对方位轴及俯仰轴进行定量检测，方位轴轴系晃动优于1.3″，俯仰轴轴系晃动优于1.8″。通过仿真分析及实验测试，证明设计的望远镜跟踪架结构具有高刚度及高回转精度，为同类跟踪架的结构设计提供了一定的参考价值。

타이어 저압감지를 위한 타이어 공진 주파수 추정

Indirect tire pressure monitoring system(i-TPMS) monitors the inflation pressures in pneumatic tires by using wheel speed signals acquired from the anti-lock braking system(ABS). Frequency analysis and wheel radius analysis are performed at the same time in order to monitor the tire pressures indirectly. The resonance frequency of the tire torsional vibration decreases as the tire pressure decreases. It is necessary to estimate the resonance frequency in order to detect a reduction in tire pressure. This paper discusses the method of estimating the resonance frequency with the rotational wheel speed signal. First, the toothed wheel error of the wheel speed sensor and the wheel speed corrected with the toothed wheel error are calculated from the wheel speed signals. The engine noise caused by the explosion in the four-stroke of engine is eliminated by the notch filter, which is designed by using the engine rotational speed. Finally, the resonance frequency is evaluated via model parameter estimation based on the autoregressive(AR) model. Vehicle tests have been conducted in order to evaluate the proposed estimation method of resonance frequency. The findings of the vehicle test have shown that the proposed method provides satisfactory performance for the warning indication of tire pressure loss.

Metamaterial‐inspired miniaturized antenna loaded with IDC and meander line inductor using partial ground plane

In this article, a novel omnidirectional compact dual band metamaterial-inspired antenna with CPW feed has been proposed for application of GSM 1800 (1.71-1.785 GHz/1.805-1.879 GHz), GSM 1900 (1.85-1.91 GHz/1.93-1.99 GHz), UMTS (1.92-2.17 GHz), WLAN/Wi Fi (4.9, 5, 5.9 GHz), HiperLAN1 (5.15-5.3 GHz), and HiperLAN2 (5.47-5.72 GHz) using a combination of meander line inductor and interdigital capacitor (IDC). The antenna consists of complimentary right/left handed (CRLH) transmission line on both sides of patch to excite zeroth order mode (n = 0). The rectangular slotted stubs act as a virtual ground for the structure using a short circuit condition at the end of the IDC. The zeroth order resonance (ZOR) frequency is mainly controlled by IDC and partially with the meander line inductor. The designed antenna operates from 1.72 to 2.22 GHz and 4.25 to 5.88 GHz with radiating size of 0.56λo × 0.35λo (32 × 20 mm2), where λo is the free-space wavelength at ZOR frequency of 5.27 GHz. The proposed antenna offers measured impedance bandwidth (|S11| <−10 dB) of 25.3 and 18.7% at 1.95 and 5.28 GHz and covers the targeted frequency bands. The proposed structure offers omnidirectional radiation patterns are congruous throughout the working band.

Effect of heat transfer optimization on brake noise characteristics of automotive disc brake

Heat effect is one of the most important factors affecting the brake noise level. The finite element model for transient heat transfer analysis of disc brake is established based on heat transfer control equation and heat dissipation boundary conditions of dynamic convection. According to the NVH test and modal calculation, the brake noise characteristics are tested and analyzed. Meanwhile, the heat transfer simulation is verified and shows high accuracy. The discrete data for the response surface function are obtained by the Central Composite Design method with the peak temperature and mass as the target variables. The error of regression function is judged by fitting decision coefficient, correcting decision coefficient and root mean square error. By the optimizing mathematical model, the brake disc temperature peak can be greatly reduced and the heat transfer ability is obviously optimized without mass increasing, the time with temperature above 120 °C can be reduced by 46 %. Through the comparison of brake noise level before and after optimization, it can be known that the noise level can be significantly decreased after structural optimization, except the first order resonance frequency. The optimization result has good social and economic value.

A Metamaterial Inspired ZOR Antenna Using IDC and Spiral Inductor with Partial Ground Plane for WLAN Application

In this article, an open-ended metamaterial antenna structure is designed for WLAN application. The antenna comprises of an interdigital capacitor (IDC) and spiral inductor with a partial ground plane. The IDC (shunt element) act as a varying parameter to control the zeroth-order resonance (ZOR) frequency, whereas spiral inductor (series element) is used to form a first negative order resonance frequency at 2.29 GHz. The ZOR mode has been excited at 4.53 GHz by employing complimentary right/left handed transmission line model in the structure and the first positive order resonance (FPOR) frequency is obtained at 4.9 GHz. A rectangular shaped stub has been used to act as a virtual ground for IDC. The proposed antenna design has total foot-print size of 0.29λ0 × 0.27λ0 × 0.024λ0. The fractional bandwidth of 20.41% (4.36–5.35 GHz) is achieved due to the merging of ZOR and FPOR mode respectively. In addition, it also exhibits a measured peak gain of 2.12 dB and 2 dB with a radiation efficiency of 77.76% and 87.62% at ZOR and FPOR frequencies respectively. A prototype of the proposed antenna structure has been fabricated and simulation results are experimentally rectified. A good agreement between simulation and measured results are obtained.

Application Status of Left and Right Handed Transmission Lines in Dual/Multi-Band Antenna Units

The advent of dual/multi-band antennas has met the need for diversification of modern wireless communication functions. The left and right hand transmission lines have positive, zero and negative order resonant frequencies, and based on this characteristic, dual/multiple frequency antennas can be realized. This paper summarizes the application of the left and right hand transmission lines in the dual/multi-frequency antenna unit.

A broadband E-shaped piezoelectric energy harvester based on vortex-shedding induced vibration from low velocity liquid flow

This letter presents an E-shaped piezoelectric energy harvester (PEH) based on vortex-shedding induced vibration (VSIV) for achieving broadband and enhanced energy capture from the liquid flow with low velocities. The PEH is realized by introducing two symmetrical vice piezoelectric beams to a traditional structure consisting of a drive sheet and a main piezoelectric beam. By changing the mass blocks on the sheet and vice beams, the first two order resonance frequencies can be tuned to be close enough to obtain a wide bidirectional tunable operating bandwidth. Experimental results demonstrate that the proposed harvester can adapt to a wider fluid velocity spectrum and bring out higher output performances than the conventional PEH. Under the excitation of vortexes from the liquid flow with low velocities (0.15m/s–0.7m/s), the maximum increase in power, efficiency and velocity spectrum over 20μW can be 70%, 326% and 60%, respectively, compared to its conventional counterpart. The total size of the E-shaped harvester is L×W×H = 90 mm×70 mm×5 mm.

Extended-Doublet Half-Mode Substrate Integrated Waveguide Bandpass Filter With Wide Stopband

A half-mode substrate integrated waveguide (HSIW) filter incorporated with co-planar waveguide (CPW) and co-planar strip (CPS) is proposed. Quarter-wavelength CPW and half-wavelength CPS resonators etched on the top metal layer are used to realized extended-doublet topology. Meanwhile, wide stopband characteristic is obtained, which is due to different higher order resonant frequencies of HSIW, CPS, and CPW. Finally, an HSIW filter is designed and measured, good agreements are achieved between measured and simulated S-parameters.

Nonlinear air-coupled thermosonics for fatigue micro-damage detection and localisation

Over the years, traditional active infrared thermography has played a pivotal role in ensuring that a component is free of any damage. However, whilst optical thermography is still not sufficiently sensitive to the presence of material micro-flaws, current vibro-thermography requires inspection solutions that are not always feasible, such as the use of coupling materials between the sensing probe and the monitored structure. This paper presents a valid alternative to current thermographic systems by developing and experimentally validating nonlinear air-coupled thermosonics for a contactless, rapid and accurate detection of fatigue micro-cracks in an aero-engine turbine blade. The proposed thermographic method combines the high sensitivity to micro-damage of nonlinear ultrasonic techniques with non-contact air-coupled ultrasonic transducers and thermographic equipment. Narrowband frequency sweeps were performed to identify local damage resonance frequencies in order to generate large vibrational amplitudes at the damage location and compensate for signal losses caused by the high acoustic impedance mismatch between the air and the sample. An infrared camera was then used to acquire the thermal response generated by frictional heat at the crack interfaces. Moreover, an image processing method based on a combination of morphological opening and a Savitzky-Golay smoothing filter was employed to enhance the quality of thermal images affected by anisotropic heating and thermal noise effects. Nonlinear air-coupled thermosonics experiments were validated with laser Doppler vibrometry scan measurements and compared with both flash and pulsed phase thermography. Thermal imaging results showed that the proposed nonlinear air-coupled thermosonics was the only thermographic technique able to detect fatigue micro-cracks, thus demonstrating its potential as an efficient and sensitive inspection tool for micro-damage detection in geometrically complex components.

A compact CPW-based dual-band filter using modified complementary split ring resonator

In this paper, a compact coplanar waveguide (CPW) based dual-band bandpass filter has been proposed. The modified complementary split ring resonator (CSRR) structure at CPW ground plane is investigated for designing of dual-band bandpass filter with minimum insertion loss. The zeroth order resonance (ZOR) frequency depends on shunt parameter due to open ended boundary condition. The dual-band bandpass filter with return loss 21 and 20 dB, insertion loss 0.5 and 0.4 dB at 1.8 and 3.2 GHz, respectively, are simulated and measured. The measured 3 dB fractional bandwidths are 92.7% and 18.8% with respect to their centre frequencies of passbands. The simulated and measured results are showing good agreement in the passband. The electrical size of designed filter is 0.10λ0 × 0.09λ0 × 0.007λ0, where λ0 is the free space wavelength at the resonance frequency of first pass band. It is suitable for a global system for mobile (GSM) and long term evolution (LTE) in different service bands of 900, 1800, 1900 and 2300 MHz wireless communication applications.

CPW fed miniaturized dual-band short-ended metamaterial antenna using modified split-ring resonator for wireless application

A miniaturized dual-band metamaterial (MTM) antenna has been designed in this article. The designed coplanar waveguide fed antenna has composed of inner split-ring resonator and an outer open ring resonator with rectangular stub. The series parameter of the antenna is used to determine the zeroth order resonance frequency due to short-ended boundary condition. The whole size of proposed structure is 20 × 25.5 mm2. This MTM antenna exhibits dual-band operation at 3.17 GHz (3.1–3.22 GHz) and 5.39 GHz (5.27–5.47 GHz). The proposed MTM structure achieves measured peak gain of 0.71 and 1.89 dB at 3.17 and 5.39 GHz, respectively. The proposed antenna can be used for recent radio communication in form of S-band application and Wi-MAX.

Dynamics of solid alanine by means of nuclear magnetic resonance relaxometry.

1H nuclear magnetic resonance relaxometry was applied to investigate the dynamics of l-alanine in the solid phase (powder). The experimental studies were carried out in a very broad frequency range, covering four orders of magnitude-from 4 kHz to 40 MHz (referring to the 1H resonance frequency) in order to probe motional processes of much different time scales by a single experiment. To get access to the dynamics of different proton groups of alanine, the 1H spin-lattice relaxation measurements were performed for non-deuterated and partially deuterated alanine. The experiments were carried out in the temperature range of 293 K-370 K (non-deuterated alanine) and 318 K-370 K (partially deuterated alanine). As a result of a thorough theoretical analysis of the extensive set of experimental results, three motional processes occurring on different time scales are identified and quantitatively described. The slowest process occurs on a time scale of μs and it is attributed to the collective dynamics of a 3D hydrogen bond network of alanine, while the intermediate, attributed to the dynamics of the NH3 group, corresponds to the range of tenths of ns. The fast process describes the rotation of the CH3 group.

Frequency Sweep Test and Modal Analysis of Watermelon during Transportation

Abstract Determining the natural frequency of watermelon is important to reduce loss by vibration during transportation. The purpose of frequency sweep test is to determine the tolerance of watermelon to vibration within a certain frequency range and to search the resonant frequency of watermelon in a certain frequency range. Frequency sweep test of Xinong No.8 watermelon cultivar was conducted, and the acceleration transmissibility curve was obtained. Furthermore, the 1st and 2nd order natural frequencies of watermelon were determined as 35.125 Hz and 71.034 Hz respectively from the acceleration transmissibility curve. Based on Geometric and mechanical parameters of Xinong No.8 watermelon cultivar, a finite element analysis model was developed and modal analysis of watermelon was carried out to obtain its natural frequencies and mode shapes. Since the value of 1st and 2nd order resonance frequency were the same or similar to the value of 3rd, 4th, and 5th order resonance frequency, this study only focused on 1st and 2nd order modes. The 1st order and 2nd order natural frequency test data fit to the corresponding simulation data well which validated the FEA model. This study demonstrated the feasibility of detecting the resonant frequency of watermelon vibration during transportation using FEA methods and provided a theoretical basis for watermelon transportation device design to reduce damage by avoiding resonant frequency.

Design and optimization of the CFRP mirror components

As carbon fiber reinforced polymer (CFRP) material has been developed and demonstrated as an effective material in lightweight telescope reflector manufacturing recently, the authors of this article have extended to apply this material on the lightweight space camera mirror design and fabrication. By CFRP composite laminate design and optimization using finite element method (FEM) analysis, a spherical mirror with φ316 mm diameter whose core cell reinforcement is an isogrid configuration is fabricated. Compared with traditional ways of applying ultra-low-expansion glass (ULE) on the CFRP mirror surface, the method of nickel electroplating on the surface effectively reduces the processing cost and difficulty of the CFRP mirror. Through the FEM analysis, the first order resonance frequency of the CFRP mirror components reaches up to 652.3 Hz. Under gravity affection coupling with +5°C temperature rising, the mirror surface shape root-mean-square values (RMS) at the optical axis horizontal state is 5.74 nm, which meets mechanical and optical requirements of the mirror components on space camera.

Optical fiber grating vibration sensor for vibration monitoring of hydraulic pump

In view of the existing electrical vibration monitoring traditional hydraulic pump vibration sensor, the high false alarm rate is susceptible to electromagnetic interference and is not easy to achieve long-term reliable monitoring, based on the design of a beam of the uniform strength structure of the fiber Bragg grating (FBG) vibration sensor. In this paper, based on the analysis of the vibration theory of the equal strength beam, the principle of FBG vibration tuning based on the equal intensity beam is derived. According to the practical application of the project, the structural dimensions of the equal strength beam are determined, and the optimization design of the vibrator is carried out. The finite element analysis of the sensor is carried out by ANSYS, and the first order resonant frequency is 94.739 Hz. The vibration test of the sensor is carried out by using the vibration frequency of 35 Hz and the vibration source of 50 Hz. The time domain and frequency domain analysis results of test data show that the sensor has good dynamic response characteristics, which can realize the accurate monitoring of the vibration frequency and meet the special requirements of vibration monitoring of hydraulic pump under specific environment.

Implementation of Resonance Tracking for Assuring Reliability in Resonance Enhanced Photothermal Infrared Spectroscopy and Imaging.

Photothermal-induced resonance (PTIR) is a method for optical spectroscopy that allows for infrared (IR) chemical imaging at spatial resolution below the limit of diffraction. By using the mechanical resonance of the cantilever for amplification the technique has been shown to allow sensitivity down to single monolayers. In this work, we discuss the challenges that must be overcome for performing stable resonant PTIR measurements and how imprecise experimental procedures can lead to irreproducible or even erroneous results. We also present a controller design that continuously readjusts the excitation frequency of a PTIR setup back to the resonance frequency in order to allow for accurate resonance-enhanced PTIR measurements. This controller can be used together with a broad range of atomic force microscopes. Schematics and program code for the controller are made freely available.

Effects of multilayered porous sediment on earthquake-induced hydrodynamic response in reservoir

Sediment in a reservoir can be inhomogeneous and layered due to the natural sedimentation process, which highly complexes the hydrodynamic response in the reservoir. Based on an extended transmission and reflection matrix (TRM) method developed in this study, an analytical solution to hydrodynamic response of a water-multilayered porous sediment-bedrock system due to SV wave incident from the bedrock is presented. The uniqueness of the method is that it not only can well accommodate porous sediment with multiple layers, but also is convenient to implement compared to global matrix method. Thus the method is able to reasonably reflect the effects of sediment heterogeneity. The analytical solution is effectively verified against the solution proposed by Wang et al. [28]. Comprehensive parametric study is conducted to investigate the effects of sediment heterogeneity and wave characteristics on the hydrodynamic response in reservoir. Resonant frequencies exist and change with incident angle. Sediment heterogeneity highly influences the hydrodynamic response of the system, especially when the sediment is unsaturated. For sediment with relatively low degree of saturation, the sediment heterogeneity in terms of consolidation level significantly affects the hydrodynamic response at higher order resonant frequencies. Sediment can be divided into numerous layers to reflect the sediment heterogeneity with depth. With the increase of frequency, the needed layer number to precisely describe the sediment heterogeneity increases.

Design of Dual-Band Bandpass Filter With High Isolation and Wide Stopband

A simple and effective method to design a dual-band bandpass filter with high isolation and wide stopband is presented and validated using symmetric open-circuited stub-loaded resonators. By adjusting the electric length and the ratio of characteristic admittance of the resonators, the first two resonant frequencies are identical, but the higher order resonant frequencies dispersed in the upper stopband to extent the bandwidth of stopband. Two transmission zeros are introduced to obtain high isolation and selectivity between the two passbands by placing them in the appropriate position. Proper feeding position is selected to further improve the attenuation of stopband. The measured results highly agree with the simulated one. Measured results demonstrate the isolation level of 40 dB, attenuation of larger than 28 dB, and a wide stopband.