Measured Resonance Frequencies Research Articles

Farm wide sensitivity assessments of resonant frequencies of integrated offshore wind turbine finite element models

To date, despite advancements in the design of offshore wind turbines, the as-designed and identified as-built natural frequencies of offshore wind turbines still show discrepancies. These discrepancies are partially rooted in modelling uncertainties, as well as uncertain input parameters, related to e.g. aero-, fluid- or soil-structure interaction. The first objective of this article is to present a wind farm wide comparison of the first and second, modelled and identified, fore-aft natural frequencies for turbines in parked conditions for a wind farm located in the Belgian north sea. Secondly, the effect of different model parameters on the computed natural frequencies will be assessed using wind farm wide sensitivity studies, with the aim to describe the potential of each considered parametrization in reducing the discrepancy between modelled and measured resonance frequencies. The in-depth considered parametrizations are aimed at assessing the effect of the linearization of the p-y curves, soil stiffness, local scour as well as the mass of the rotor nacelle assembly, whereas results for wall thickness, marine growth, added mass coefficient and sea water level variations will be presented without further discussion. In order to perform this study, turbine specific finite element models have been prepared and verified based on detailed design documents; subsequently updated best-estimate soil data has been used to model the foundation for two different design scenarios. Furthermore, modal parameters have been identified for each turbine, based on vibration data collected in parked condition and state of the art operational modal analysis tools. The results show that the discrepancies between the modelled and identified first fore-aft natural frequencies could potentially be bridged by adjusting combination of the investigated parameters, whereas the discrepancies observed on the second natural frequency cannot be bridged by making changes to the investigated parameters. As such, future work will entail a more detailed investigation on modelling uncertainties.

Embroidered wearable Antenna-based sensor for Real-Time breath monitoring

In this paper we present the design and the validation of a novel fully embroidered meander dipole antenna-based sensor integrated into a commercially available T-shirt for real-time breathing monitoring using the technique based on chest well movement analysis. The embroidered antenna-based sensor is made of a silver-coated nylon thread. The proposed antenna-sensor is integrated into a cotton T-shirt and placed on the middle of the human chest. The breathing antenna-based sensor was designed to operate at 2.4 GHz. The sensing mechanism of the system is based on the resonant frequency shift of the meander dipole antenna-sensor induced by the chest expansion and the displacement of the air volume in the lungs during breathing. The resonant frequency shift was continuously measured using a Vector Network Analyzer (VNA) to a remote PC via LAN interface in real-time. A program was developed via Matlab to collect respiration data information using a PC host via LAN interface to be able to transfer data with instrumentation over TCP/IP. The measurements were carried out to monitor the breathing of a female volunteer for various positions (standing and sitting) with different breathing patterns: eupnea (normal respiration), apnea (absence of breathing), hypopnea (shallow breathing) and hyperpnea (deep breathing). The measured resonance frequency shift to 2.98 GHz, 3.2 GHz and 2 GHz for standing position and 2.84 GHz, 2.95 GHz and 2.15 GHz for sitting position, for eupnea, hyperpnea and hypopnea, respectively. The area of the textile sensor is 45 × 4.87 mm2, reducing the surface consumption significatively with regard to other reported breath wearable sensors for health monitoring.

Detection of globular and fibrillar proteins by quartz crystal microbalance sensor coated with a functionalized diamond thin film

This study presents a sensor based on quartz crystal microbalance (QCM) coated with nanocrystalline diamond (NCD) thin film, functionalization method and novel application of such sensor. Diamond-coated QCMs (DQCMs) were superficially terminated by hydrogen and oxygen (H-NCD and O-NCD) to control its surface dipole/potential. Two protein solutions were tested: bovine serum albumin (BSA) and fibronectin (FN). We performed reference measurements of serial resonant frequency (SRF) of clean QCMs loaded with protein and compared them with SRF shifts DQCMs loaded with proteins. In order to investigate the influence of the deposited NCD thin film on QCM measuring capabilities, additional FEM analysis was performed. The simulation results showed that QCM sensors maintain the sensing capabilities with a rigid thin film of NCD on its surface. The shift of SRF was demonstrably caused by the weight of protein adhered to the diamond film's surface. We compared masses estimated from the Sauerbrey equation to characterize the adhesive properties of the studied proteins. Comparing bare QCM and DQCM, we discovered diamonds enhance the sensing performance for proteins. At the same time, it saturates quickly with phosphate buffer saline used as a diluent solution for proteins. Results showed a significant increase in protein adhesion confirmed by the increase of the mass for both oxygen and hydrogen-terminated DQCMs. Moreover, a different time-dependent behaviour (i.e. different adsorption rate, degrees of physisorption and/or preference of the diamond surface functionalization) of the O-NCD and H-NCD QCMs was observed for BSA and FN proteins. In this meaning, we propose aschematic model which describes the detection principle of BSA and FN proteins on H- and O-terminated DQCM sensors. Finally, a simple proof of concept for using the functionalized diamond-coated sensors with current stimulation and EQCM (Electrochemical Quartz Crystal Microbalance) is also proposed.

Development of MEMS Acoustic Sensor With Microtunnel for High SPL Measurement

The fabrication of piezoelectric ZnO-based micro-electro-mechanical systems (MEMS) acoustic sensor has been reported. The sensor structure consists of a piezoelectric ZnO film deposited between two Al electrodes on a thin silicon diaphragm. A microtunnel is fabricated in the sensor structure using novel approach. This microtunnel is used to protect the diaphragm and determine the lower cut-off frequency of device. The approach presented in this paper completely removed a serious problem of microtunnel blockages during fabrication of sensors. In the developed process, the acoustic sensor fabricated using silicon-on-insulator and the Pyrex glass wafers are diced separately with same chip dimensions. Finally, both Pyrex glass and acoustic sensor chips are fitted in a jig for alignment and then anodically bonded. In reference to microtunnel blockages, the yield of the present technique is obtained as almost 100%. Also, the technique will serve as a cost-effective alternative to the present practice. The developed technique can also be used in manufacturing of similar devices where the microtunnels or microchannels are required in device structure. The technological development is supported by extensive atomic force microscopy (AFM), field emission scanning electron microscopy, Raman spectroscopy, and X-ray diffraction studies of ZnO film; glass-to-silicon bond strength measurement; resonance frequency measurement by laser doppler vibrometer; response characterization of the fabricated sensor, and scanning electron microscopy of microtunnel mouth to demonstrate the feasibility and yield of the process.

Measurement of the 2S_{1/2}-8D_{5/2} Transition in Hydrogen.

We present a measurement of the hydrogen 2S_{1/2}-8D_{5/2} transition performed with a cryogenic atomic beam. The measured resonance frequency is ν=770649561570.9(2.0) kHz, which corresponds to a relative uncertainty of 2.6×10^{-12}. Combining our result with the most recent measurement of the 1S-2S transition, we find a proton radius of r_{p}=0.8584(51) fm and a Rydberg constant of R_{∞}=10973731.568332(52) m^{-1}. This result has a combined 3.1σ disagreement with the Committee on Data for Science and Technology (CODATA) 2018 recommended value.

Theoretical and Empirical Verification of Electrical Impedance Matching Method for High-Power Transducers

In our prior study, a systematic approach was used to devise Langevin transducers for high-power applications where the energy efficiency was not considered in the design criteria. In this paper, the impedance matching methods are thus proposed to evaluate what matching topology is appropriate for their use. Both the series inductor scheme and low pass filter composed of a series inductor and shunt capacitor are examined as matching circuits. According to MATLAB simulation, the resonance frequency is seen at 36.79 kHz due to a series L circuit, and its associated impedance is reduced by 70.45% from that of its non-matching condition. The measured resonance frequency is 36.77 kHz and the corresponding impedance is decreased by 59.52%. Furthermore, the acoustic pressure is measured to determine the effect of the matching circuit on the transducer’s actual behavior. The transducer with a series L circuit shows more efficient matching results, 2.28 kPa of positive acoustic pressure is emitted without matching and 3.35 kPa is emitted with a series L element, respectively. As a result, this study demonstrates how to evaluate the influence of matching circuits by using our customized approach rather than commercial SPICE programs, as well as how to experimentally verify the acoustic behavior of high-power Langevin transducers.

Analysis and Treatment of Flue Duct Vibration of 1000MW Generator Set with High Load

In view of the serious flue duct vibration problem of the outlet of a 1000MW unit with a load of 80%BRL and above, combined the vibration test with the calculation of the acoustic standing wave frequency, the cause of the flue duct vibration was analyzed and determined. A modification plan is proposed to install clapboards to change the standing wave frequency of the flue duct and keep it away from the measured resonance frequency. After the clapboards are installed, the flue duct vibration frequency of the induced draft fan outlet is dispersed from the two main frequencies of 61.3Hz and 61.4Hz before the clapboards were installed to 6.88Hz~204Hz; the maximum amplitude of the flue duct is reduced from 105.0μm to 12.6μm, and the problem of the flue duct vibration is fundamentally solved. This case provides a new idea for solving the problem of vibration of the flue duct in the large-scale power station boiler.

Digital guides to facilitate retained root removal and simultaneous implant placement

The aim of this study was to report the use of digital guides to locate impacted residual roots (IRR) (location guide) and to simultaneously insert dental implants (surgical guide). This case series included five patients. The IRR was first removed through a lateral window approach using the digital location guide, then the implant was placed simultaneously with the implant surgical guide. Definitive restorations were completed after a 6-month healing period. An average of 13.0 ± 3.1 minutes was required to locate the IRR. The implant stability quotient (ISQ) was obtained during surgery and before digital coping using a non-invasive resonance frequency measurement. The average ISQ during surgery for the five dental implants was 60.2 ± 6.3, and the value increased to 66.6 ± 4.8 before final restoration. The average deviations at the implant neck and root apex were 0.48 ± 0.25 mm and 0.74 ± 0.46 mm, respectively. The average angular deviation was 3.5 ± 1.4°. Bone resorption at the implant neck was a mean 0.072 ± 0.041 mm before final restoration. All implants functioned well at 1 year after final restoration. The application of surgical guides in the extraction of IRR enabled crestal bone preservation and simultaneous implant placement.

Thermoresponsive Gelatin/Chitosan Hydrogel Films for a Degradable Capacitor.

Ingestible electronic devices are tools for exploring the condition of the gastrointestinal tract and adjacent organs without a burden on the patients. Making them safe requires that they be fabricated with harmless materials. In this study, we developed a capacitor using food materials for a wireless sensing component. As a safer approach, gelatin, an ingredient responsive to external stimuli, was selected as a substrate for deforming the device at the desired time. Gelatin experiences sol-gel changes near body temperature; however, it is instantly dissolved and is not suitable for long-term use in the body. Thus, to maintain its thermal responsiveness, we used a tangle of gel networks created by mixing gelatin and chitosan without cross-linking agents. Our search for the appropriate gel mixing ratio provided insights into the criteria for achieving slow sol-gel changes and how to improve the thermal durability. We transferred a sputtered gold film onto the gel films to produce electrodes and then made a capacitor by sandwiching a naturally dried sodium polyacrylate film between the electrodes. The resonance frequency measurement of RLC circuits in combination with commercial plane coils showed that the capacitor worked in the megahertz band and that it collapsed when immersed in hot water. Gastric acid detection was also achieved with this capacitor. This electronic part will contribute to the development of implanted or ingestible medical devices and a wide range of environmental sensors composed of natural ingredients.

Thermal Modeling of Resonant Scatterers and Reflectometry Approach for Remote Temperature Sensing

Thermal modeling of different transmission lines (TLs) based on resonant scatterers is presented. The coplanar strip (CPS) and microstrip (MS) TLs are used to model resonators and to introduce the thermal dependence. A reflectometry approach is employed to validate the model by detecting the scatterers’ resonance frequency and comparing it with analytical expressions. The observable shift in the resonance frequency of the scatterers with temperature variations is due to the thermal expansion of metals and temperature dependence of the substrate permittivity. Since all the measurements are done remotely with no direct line of sight, it is shown how such a reflectometry approach can be used for remote temperature sensing using a passive label composed of resonators. Unlike previous works in this domain where the thermal dependence is considered empirically, the introduced model is used to take into account all thermal effects affecting the resonant scatterers allowing to link rigorously the variations of the measured resonance frequency with the temperature without any lookup table. Temperature sensing using very simple TLs based on resonant scatterers was demonstrated in a real environment. A temperature error of less than 3 °C is obtained. Once the temperature has been determined, it is possible to go back to the TL parameters, such as the effective permittivity and the physical length.

Design evaluation of microwave transmission properties of YBa2Cu3O7-based kinetic inductance detectors

We designed, fabricated, and characterized microwave transmission properties with rewound strip structures for YBa2Cu3O7 (YBCO)-based kinetic inductance detectors (KIDs). The superconducting rewound strip serves as a microwave resonator and as a broadband terahertz-wave antenna. To predict the microwave resonance characteristics before fabrication, the line-width (w) and space (s) dependence of the spiral resonators were analyzed using an electromagnetic simulator; the resonance frequency increased, and the quality factor decreased with increasing w and s from 10 to 40 μm. YBCO-based KID arrays with different w (10 and 40 μm) were fabricated on 10 mm-square MgO substrates, cooled to 3 K using a 4He refrigerator, and evaluated using a vector network analyzer to verify the result of the simulation experimentally. The measured resonance frequency ratio of 1.11 times (5.04 → 5.59 GHz) agreed with the simulated ones of 1.10 times (4.84 → 5.33 GHz) between w = 10 and 40 μm. The other resonance characteristics, such as transmission coefficient and quality factor, have a similar w dependence with the simulation.

A strategy for correcting errors in automated formant extraction

Sociophonetic vowel analysis relies heavily on measurements of resonant frequencies, particularly of the first and second formants. Automated formant estimation using linear predictive coding (LPC) algorithms in software like Praat greatly increases efficiency compared to hand measurements and allows researchers to analyze more data than was possible before this technological advancement. However, LPC analysis is prone to certain types of errors (e.g., Di Paolo et al., 2011; Harrison, 2013; Labov et al., 2006; Strelluf, 2019; Styler, 2017). In one common error, which I call “faulty low F2” (FLF2), LPC identifies a spectral peak between F1 and F2 as an F2 measurement. In automated extraction, the real F2 is then recorded as F3. Manually correcting these errors is time-consuming, potentially erasing the gains made by automated extraction. However, a systematic error suggests the possibility of a systematic solution. This presentation describes a method for identifying and correcting FLF2 errors using a script in R. The script identifies possible errors based on expected ranges and trajectories, determines whether the recorded F3 at the measurement point meets the criteria for a legitimate F2, and makes substitutions where appropriate. Results of tests with real data are presented. [Work supported by NSF #XXXXXXX.]

Enhanced resonant ultrasound spectroscopy for multi-material characterization

Resonant ultrasound spectroscopy (RUS) is a non-destructive technique to describe the elastic tensor of a material through inversion of a sample’s measured resonance frequencies. The original RUS approach is limited to simple geometries as it uses a semi-analytical method to simulate the vibrational response. We modified this approach by combining the finite-element method with genetic algorithm. The new approach is applicable to systems with composite materials, complex geometries, and misaligned material and geometry axes. We present recent work focused on the response of a graphite-TZM composite system. We find composite material properties only vary a few percent from results from single-material RUS. Results from varied geometries and materials suggest further optimizations to enhanced RUS.

Self-Temperature-Compensated Air-Filled Substrate Integrated Waveguide (AFSIW) Quasi-Elliptic Filters

Patented single-slab self-temperature-compensated air-filled substrate integrated waveguide (AFSIW) cavities and quasi-elliptic filters are proposed and demonstrated in this article. Such components are of high interest for the design of thermally stable circuits and systems on substrate meeting the size, weight, power, and cost (SWaP-C) reduction expected for future systems, especially for space applications. First, a theoretical multiphysics model is presented for the synthesis of single-slab self-temperature-compensated AFSIW cavities. It is demonstrated from theory that by properly choosing the dielectric slab material and dimensions, perfect temperature compensation can be achieved. This extended technique allows the implementation of temperature compensation in any type of cavity, filter, and multiplexer configuration. For demonstration purposes, a single-slab self-temperature-compensated in-line folded seventh-order quasi-elliptic AFSIW filter operating at 12 GHz with a 250-MHz (2.27%) −3-dB bandwidth is designed and fabricated. It achieves a measured unload <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor of 992 at ambient temperature (23 °C) and a measured resonance frequency thermal stability as low as 0.58 ppm/°C at −20 °C and 0.89 ppm/°C at 70 °C compared with its temperature-uncompensated counterpart achieving a thermal stability of −15.5 ppm/°C at −20 °C and −17.73 ppm/°C at 70 °C. Furthermore, it is demonstrated in this article that transmission zeros (TZs) created by cross-couplings in the in-line folded configuration of the self-temperature-compensated quasi-elliptic filter achieve a thermal stability of 2.55 ppm/°C and 2.3 ppm/°C (2.34 ppm/°C and 4.37 ppm/°C) at −20 °C (70 °C), in the lower and upper bands, respectively.

Real-Time Detection and Control of Microchannel Resonance Frequency in Acoustic Trapping Systems by Monitoring Amplifier Supply Currents.

The utilization of bulk acoustic waves from a piezoelectric transducer for selective particle trapping under flow in a microchannel is limited by the high sensitivity of the resonance frequency to tolerances in device geometry, drift during trapping, and variations in the local flow or sample conditions in each channel. This is addressed by detecting the resonance condition based on the impedance minimum obtained by monitoring the amplitude of the stimulation voltage across the piezo transducer and utilizing real-time feedback to control the stimulation frequency. However, this requires an overlap in the frequency bandwidth of the detection and the stimulation system and is also limited by the decline in the acoustic trapping power when the stimulation and resonance frequency measurement are conducted simultaneously. Instead, we present a novel circuit implementation for on-chip real-time resonance frequency measurement and feedback control based on monitoring the current drawn from the amplifier used to stimulate the piezo transducer, since the need for high measurement sensitivity in this mode does not lower the power available for stimulation of the transducer. The enhanced level of control of acoustic trapping utilizing this current mode is validated for various localized channel perturbations, including drift, wash steps, and buffer swaps, as well as for selective sperm cell trapping from a heterogeneous sample that includes lysed epithelial cells.

Fundamental limits and optimal estimation of the resonance frequency of a linear harmonic oscillator

All physical oscillators are subject to thermodynamic and quantum perturbations, fundamentally limiting measurement of their resonance frequency. Analyses assuming specific ways of estimating frequency can underestimate the available precision and overlook unconventional measurement regimes. Here we derive a general, estimation-method-independent Cramer Rao lower bound for a linear harmonic oscillator resonance frequency measurement uncertainty, seamlessly accounting for the quantum, thermodynamic and instrumental limitations, including Fisher information from quantum backaction- and thermodynamically driven fluctuations. We provide a universal and practical maximum-likelihood frequency estimator reaching the predicted limits in all regimes, and experimentally validate it on a thermodynamically limited nanomechanical oscillator. Low relative frequency uncertainty is obtained for both very high bandwidth measurements (≈10−5 for τ = 30 μs) and measurements using thermal fluctuations alone (<10−6). Beyond nanomechanics, these results advance frequency-based metrology across physical domains.

MEMS-Based Cantilever Sensor for Simultaneous Measurement of Mass and Magnetic Moment of Magnetic Particles

This study presents a measurement approach suitable for the simultaneous determination of both the mass mp and magnetic moment µp of magnetic particles deposited on a micro electro mechanical system (MEMS) resonant cantilever balance, which is operated in parallel to an external magnetic field-induced force gradient F′(z). Magnetic induction B(z) and its second spatial derivative δ2B/δz2 is realized, beforehand, through the finite element method magnetics (FEMM) simulation with a pair of neodymium permanent magnets configured in a face-to-face arrangement. Typically, the magnets are mounted in a magnet holder assembly designed and fabricated in-house. The resulting F′ lowers the calibrated intrinsic stiffness k0 of the cantilever to k0-F′, which can, thus, be obtained from a measured resonance frequency shift of the cantilever. The magnetic moment µp per deposited particle is determined by dividing F′ by δ2B/δz2 and the number of the attached monodisperse particles given by the mass-induced frequency shift of the cantilever. For the plain iron oxide particles (250 nm) and the magnetic polystyrene particles (2 µm), we yield µp of 0.8 to 1.5 fA m2 and 11 to 19 fA m2 compared to 2 fA m2 and 33 fA m2 nominal values, respectively.

Parametric Analysis of the Edge Capacitance of Uniform Slots and Application to Frequency-Variation Permittivity Sensors

This paper presents a parametric analysis relative to the effects of the dielectric constant of the substrate, substrate thickness and slot width on the edge capacitance of a slot-based resonator. The interest is to find the conditions (ranges of the previously cited parameters) compatible with the presence of a quasi-magnetic wall in the plane of the slot (or plane of the metallization). If such magnetic wall is present (or roughly present), the electric field in the plane of the slot is tangential (or quasi-tangential) to it and the edge capacitance can be considered to be the parallel combination of the capacitances at both sides of the slot. Moreover, variations in one of such capacitances, e.g., caused by a change in the material on top of the slot, or by a modification of the dielectric constant of the substrate do not affect the opposite capacitance. Under the magnetic wall approximation, the capacitance of certain electrically small slot-based resonators can be easily linked to the dielectric constant of the material present on top of it. The consequence is that such resonators can be used as sensing elements in a permittivity sensor and the dielectric constant of the so-called material under test (MUT) can be determined from the measured resonance frequency and a simple analytical expression. In this paper, the results of this parametric analysis are validated by considering several sensing structures based on dumbbell defect ground structure (DB-DGS) resonators of different dimensions.

Computation and experimental considerations on dynamic testing of cement mortar

Non-destructive tests to assess the dynamic characteristics of the materials are important for both in-situ and laboratory situations. Elastic modulus, rigidity modulus and Poisson ratio can be determined through dynamic testing, by employing resonant frequency measurements. The ASTM C-215 standard contains the necessary information for the experimental set-up and subsequent computation using the longitudinal, transversal and torsional frequencies, for both prismatic and cylindrical specimens. Nevertheless, some experimental particularities are not explained and their influence on the final results might prove important. In this paper, the experimental and computational insights on performing the dynamic Young modulus test for cement mortar prismatic samples, with emphasis on the importance of interpretation of the results are presented. The type of specimen support and the actual data manipulation, when extracting results, are taken into consideration. The results may prove important for the correct employment of dynamic testing.

RETRACTED] An Approach to Optimize the Design of Ultrasonic Transducer for Food Dehydration

==========================================================Available online: 30 June 2021This article has been retracted by International Journal on Advanced Science, Engineering and Information Technology Editorial team, following clear correspondence and confirmation with authors.The article contained redundant material, the editor investigated and found that the paper published in Computational Intelligence Methods for Green Technology and Sustainable Development. GTSD 2020. Advances in Intelligent Systems and Computing, vol 1284. Springer, Cham. DOI: https://doi.org/10.1007/978-3-030-62324-1_35, URL: https://link.springer.com/chapter/10.1007/978-3-030-62324-1_35, entitled "An Approach to Optimize the Design of Ultrasonic Transducer for Food Dehydration".The paper is retracted from 30 November 2021.==========================================================Ultrasound-assisted air-drying is considered a useful method to reduce drying time and ensure some agricultural food products' quality. In this study, a practical design method of an Ultrasonic Transducer (UT), which is in the form of a circular stepped-plate, was developed by using Particle Swarm Optimization (PSO) algorithm and Finite Element Analysis (FEA). The numerical calculation is carried out for two different geometric dimensions of the stepped-plate. Based on the obtained results, the smaller UT dimensions were chosen, and its prototypes were fabricated. The prototype's measured resonance frequency is 19.927 kHz compared to calculations getting an error of 0.073 kHz (0.37%). Also, to evaluate the effects of ultrasound on a drying process, the UT is integrated into a heat-pump drying machine for drying foods. The experiments were carried out on Codonopsis javanica using heat-pump drying method at air temperature 45 ± 0.5 °C, air humidity 18-20 %, air velocity 0.5 ± 0.1 m/s with and without ultrasonic intensity while keeping all other conditions and parameters constant. The results showed that the total drying time was reduced in the range of 25% to 42% depending on ultrasonic intensity, compared to heat-pump drying without ultrasonic intensity. The color of the dried products is also considered to testify the quality of the product when using UT in drying processes. The obtained results prove the effectiveness of the proposed approach in design of the UT for food dehydration.