Measured Resonance Frequencies Research Articles

Resonant ultrasound spectroscopy for textured materials

Resonant ultrasound spectroscopy (RUS) is a method in which the least-squares fitting of a sample's measured resonance frequencies is used to determine the sample material's elastic constants. Difficulties arise when RUS is applied to textured materials, which are composed of crystallites that are neither completely aligned nor randomly oriented; such materials would have effective elastic tensors with 21 independent elastic constants, and this would overburden the conventional RUS analysis process. In any case, the elastic nature of some textured materials may be represented as the weighted average of the elastic tensors of the constituent crystalline material rotated in the directions of the individual crystallites. The collection of weights is the orientation distribution function (ODF). Now the least-squares fitting of a sample's measured resonance frequencies may be used to determine not the sample's elastic constants but instead its ODF. This is not trivial since the weights must be positive and sum to one, but it may be done with a simple modification of the conventional RUS software.

Resonant ultrasound spectroscopy experimental design and optimization

Resonant Ultrasound Spectroscopy (RUS) is a nondestructive material characterization technique that utilizes solid body resonances to estimate elastic moduli. This method is advantageous over traditional mechanical testing due to the significantly lower number of required samples to estimate the same number of moduli. The goal of this project is to develop a high-throughput RUS system capable of measuring experimental resonances and mode shapes in a fraction of the time of traditional RUS measurements. A new system was designed which leverages data/image analysis algorithms to aid in sample alignment and data collection. A standardized sample geometry was also analyzed by performing a geometric sensitivity study and optimizing the aspect ratio of lengths of a parallelepiped. The results show that the optimized sample geometry is consistent between materials with varying elastic properties. In order to validate the design of the new RUS system a comparative study to an existing system was conducted. The results show that the newly designed system produces comparable resonant frequency and mode shape measurements.

Noise and thermal performance of a sub-attofarad capacitance sensor for precision measurements, with applications in gravitational wave detectors.

We describe the design principles, fabrication, and characterization of a precision AC resonant capacitance bridge (RCB) sensor, based on a resonant differential planar printed circuit board transformer with a solid (ungapped) MnZn ferrite core, demonstrating a short-term sensitivity at 293K of 0.225 ± 0.005 aF/√Hz at around 120kHz resonance frequency and 1Hz Fourier measurement frequency. At 120K, the RCB short term noise sensitivity is 0.118 ± 0.005 aF/√Hz. We compare the ungapped configuration to five different RCBs: three with a core gap of 65 μm and two with a core gap of 130 μm. Their average room temperature short term noise sensitivities are 0.30 ± 0.01 and 0.45 ± 0.01 aF/√Hz, while the cryogenic operation of these transformers at 120K resulted in averaged sensitivities of 0.23 ± 0.01 and 0.36 ± 0.01 aF/√Hz, respectively. Multi-hour room temperature runs, with one core of each of the three gap types, proved the stability of their long-term sensitivities of 0.234 ± 0.005, 0.338 ± 0.009, and 0.435 ± 0.010 aF/√Hz for the ungapped (40-h duration) and the 65 and 130 μm (28-h duration) cores, respectively. At 0.1mHz, a critical frequency for space gravitational wave detectors, the respective sensitivities are 0.25 ± 0.02, 0.35 ± 0.02, and 0.53 ± 0.07 aF/√Hz. Measurements with the ungapped transformer configuration for temperatures from 325 to 349K further validate the dependence of the noise model on temperature and permeability. The performance of our RCB with an ungapped core matches the calculated performance value and shows an improvement in signal-to-noise ratio of two or more compared with capacitance bridges developed for similar applications. A further factor of about two noise reductions is achieved by cooling to 120K.

First-in-Human Pilot Study to Assess Methodology for Using a Mineral-Organic Bone Adhesive for Optimization of Primary Stability and Implant Success for Implants Glued into Immediate Extraction Sockets and Immediately Temporized: Pilot Study.

To assess the handling properties and clinical function of a new class of material, a so-called mineral-organic bone adhesive (Tetranite; TN), which as yet has no precedent in orthopedic or oral and maxillofacial surgery, for clinically unstable implants placed in immediate extraction sockets and immediately temporized in the anterior maxilla. A cohort of up to 15 patients requiring between one and four immediate dental implants placed into maxillary extraction sockets from canine to canine were eligible for inclusion. Implants had to be unstable with an insertion torque of < 15 Ncm. Implants were then stabilized using TN, which was allowed to set before reassessing stability using both torque and resonance frequency measurements. Implant stability quotients (ISQs) taken after TN setting were compared to ISQs taken prior to its application, and the implants had to demonstrate resistance to a forward torque of 20 Ncm to be considered stable. ISQs were monitored at 1 week and 1, 3, 7, and 12 months postplacement. In addition, peri-implant tissue health was monitored, adverse events were recorded, and implant success was determined at 1 year postplacement. Eleven patients received a total of 14 implants. Three out of the first six implants failed within 1 month (50%), and thus a protocol amendment was made to remove steps considered potentially destructive to the bonding process. As a result of these amendments, only one further failure was experienced for the next eight implants placed (12.5%). Mean ISQ data averaged for buccolingual and mesiodistal measurements demonstrated a baseline value before TN application of 59.1 Ncm (SD: ± 9.7; range: 40.5 to 73.0). After final setting of the TN, mean ISQ measured 71.9 Ncm (± 6.5; 56.0 to 80.0). At 3 months, just prior to restoration placement, mean ISQ measured 71.0 Ncm (± 6.6; 57.0 to 78.0). Thereafter, the mean ISQ continued to increase at both the 7- and 12-month follow-ups with scores of 78.9 (± 4.6; 72.0 to 84.5) and 80.3 (± 3.8; 74.5 to 85.0), respectively. The surviving 10 implants went on to be fully restored and remained in function beyond the end of the study period to yield a final success rate of 71.4%. The purpose of a first-in-human study is to demonstrate an extrapolation of preclinical data into the controlled human clinical arena. It is an opportunity to learn what does and does not translate well from experimental data. In that regard, the current pilot study can be deemed a complete success. The implant survival rate of 71.4%, while disappointing, should be considered in light of the protocol amendments identified, the user handling experience learned, and the opportunity to modify the material to better perform in the human patient, as all represent important lessons learned. The notable increase in ISQ sheds light on the nature by which the glue was substituted for bone to yield a stable implant by the end of the study period.

Compact Micro-Coriolis Mass-Flow Meter with Optical Readout.

This paper presents the first nickel-plated micro-Coriolis mass-flow sensor with integrated optical readout. The sensor consists of a freely suspended tube made of electroplated nickel with a total length of 60 mm, an inner diameter of 580 µm, and a wall thickness of approximately 8 µm. The U-shaped tube is actuated by Lorentz forces. An optical readout consisting of two LEDs and two phototransistors is used to detect the tube motion. Mass-flow measurements were performed at room temperature with water and isopropyl alcohol for flows up to 200 g/h and 100 g/h, respectively. The measured resonance frequencies were 1.67 kHz and 738 Hz for water and 1.70 kHz and 752 Hz for isopropyl alcohol for the twist and swing modes, respectively. The measured phase shift between the two readout signals shows a linear response to mass flow with very similar sensitivities for water and isopropyl alcohol of 0.41mdegg/h and 0.43 mdegg/h, respectively.

Designing an omnidirectional horizontally polarized circular patch antenna implementing unequal open‐circuited stubs

AbstractA novel method of designing an omnidirectional horizontally polarized (OHP) patch antenna with omnidirectionality in the H‐plane is proposed in this letter. The three pairs of unequal arch slots with three open radial slots are etched on the ground, which is equivalent to three pairs of open‐circuited unequal stubs that excite the TM1.5,1 patch mode and produce two resonance frequencies with circulating in‐phase current on the patch and the ground. Additionally, three pairs of open‐circuited unequal stubs are generated to enhance bandwidth and generate extra resonance frequencies by sequentially printing unequal arch and open radial slots on the top patch. The proposed antenna's 10 dB impedance bandwidth, including all resonance frequencies of TM1.5,1 patch mode, is 10.20%, covering the 2.326–2.576 GHz Wi‐Fi band. The patch and ground diameter are 0.31λ0 and 0.387λ0, respectively, with a real gain of 1.84–1.98 dBi over the operating band, and a gain variation is within 1.3 dB in the H‐plane at two measured resonance frequencies.

Assessing Asphalt Pavement Pre-Compaction with Paver Screed Frequency Measurements

The quality and longevity of an asphalt road depends on the accurate compaction of the asphalt pavement. Particular emphasis should be placed on the pre-compaction process involving the paver’s screed. Inadequate or excessive pre-compaction can result in paving errors and inhomogeneities within the pavement, which even expert roller operation cannot rectify. In practical paving, however, the degree of pre-compaction is rarely determined, so that one is dependent on the empirical knowledge and assessments of the paving personnel. Within the context of the research initiative, InfraROB (Grant Agreement No.: 955337), an innovative system was devised to infer the extent of pre-compaction by leveraging the resonance frequency of the paver’s screed. This system comprises a rugged, enclosed acceleration sensor capable of capturing high-speed accelerations and a Wi-Fi-enabled control unit for data storage and processing. To validate this system, a series of test pavements were constructed using an asphalt binder mix (AC 16 BS), deliberately varying the speed of the tamper compaction unit in four steps from 0 rpm up to 1500 rpm. Half of the test lanes were longitudinally compacted with rollers, allowing for the examination of the asphalt pavement in its partially pre-compacted state. To achieve this, drill cores were extracted, and their density was assessed in the laboratory. Through the application of Fast Fourier Transformation, the measured resonance frequency data was analysed and subsequently correlated with the outcomes of the drill core inspections. This analysis revealed a strong logarithmic relationship between the average peak acceleration and the bulk densities measured, with a high coefficient of determination exceeding 0.9. The presented method enables real-time assessment of the pre-compaction status of asphalt pavement, offering support to paving personnel, optimising roller usage, and enhancing asphalt pavement quality.

Resonance frequency measurement to identify stiffness variations based on photoacoustic imaging.

Linear assumption on the level of stiffness in a tissue shows a significant correlation with disease. Photoacoustic imaging techniques that are non-contact by design have been developed in this study to detect differences in phantom (soft tissue mimicking materials) stiffness. This study aims to detect differences in phantom stiffness based on the results of image reconstruction at the resonance frequency. Four phantom agars with differing concentrations were made to achieve different stiffnesses. The position of each phantom agar's highest photoacoustic signal amplitude is identified by a frequency modulation sweep. The characterization results show an increase in resonance frequency along with an increase in phantom stiffness. The image difference can be detected because the intensity of the photoacoustic image in samples that have a resonance frequency with laser modulation is comparatively higher than in other samples.

Wideband acoustic absorbance and resonance frequency measurements in Ménière’s disease – case series

Wideband acoustic absorbance and resonance frequency measurements in Ménière’s disease – case series

Variability in measured resonance frequencies and loss factors of a bolted panel structure

Structural bolted joints are not perfectly contiguous or rigid. Instead, the joint stiffness, mass, and damping depend on many parameters including the joint thickness, number and size of bolts, the bolt preload, and the motion of the jointed region. Also, damping can vary with motion type (stick-slip for friction and impact for joint opening and closing) and amplitude. Finally, all joint dynamic parameters vary from installation to installation. We measured the variability of bolted joint stiffness and damping for four low-order modes of a bolted Aluminum panel structure - two flexural modes and two twisting/torsional modes. While a large portion of the bolted joint literature features a lap joint or an assembly of two beams, there are few studies dealing with flanged connections of plates. Two flanged rectangular panels were bolted together with two cap screws threaded into one of the flanges. Modal resonance frequencies and loss factors were tracked throughout a decaying vibration response induced by hammer impacts on the structure. Measurements were made for three bolt torques and two flange thicknesses, three impact force strengths, and three repeated assemblies (the panel was unbolted and bolted together again). Relative motion at the joint with respect to mode shape determines whether the joint primarily adds stiffness or mass, as well as the amount of added damping. Not surprisingly, reducing bolt preload reduces resonance frequencies. Only minor variability in resonance frequency and loss factor were observed for most conditions, except for cases with low bolt preload. In these cases mild nonlinearity is evident in the response, where resonance frequency decreases and loss factor increases with increasing vibration amplitude. Also, variability of resonance frequencies and loss factors between installations often exceeds that due to variability in preload and vibration amplitude.

Magnetic haptic device using miniature SmFeN powder magnets in PCB-on-MEMS system

This paper reports a magnetic microactuator for haptic applications. The actuator consists of a Si chip and two printed circuit boards (PCBs), and the total size of the device is 7.8 mm × 7.8 mm × 2.4 mm. A tiny magnet is embedded into the Si chip and actuated by a current flowing in the PCBs. The mechanical and electrical parts are separated on the Si chip and the PCBs, respectively, and there is no electrical connection between them, allowing simple fabrication and assembly. The magnet, made from a mixture of SmFeN magnetic powder and wax, exhibits a large magnetic field of 0.4 T. The magnet is supported by soft springs of parylene, enabling a large displacement amplitude, a low resonance frequency, and high mechanical robustness. The measured resonance frequency and amplitude are 139 Hz and 62 µm, respectively. The rise and fall times of the vibration of the device at 100 mA drive are 19 ms and 52 ms, respectively. Sensory analysis revealed that the haptic device created the haptic sensation on a scale of three, weak, medium, and strong intensity, with input currents from 50 mA to 200 mA.

Evaluation of elastic constants of particle accelerator cavity materials with Resonant Ultrasound Spectroscopy

European Spallation Source is a multi-nation, interdisciplinary research facility based on the world’s most powerful neutron source that will operate with high standards of availability and reliability minimizing downtime periods. In order to meet these goals, critical component’s performance and ageing need to be constantly monitored and assessed. Resonant Ultrasound Spectroscopy (RUS) is a highly versatile non-destructive technique for the definition of elasticity matrix of materials through the measurement of resonance frequencies. RUS could benefit the characterization of particle accelerator cavity materials exposed to challenging operational environments during project’s design and commissioning phases. This paper demonstrates the methodology and the first results on the implementation of this technique on Radio-Frequency Quadrupole (RFQ) structural copper. Rectangular parallelepiped samples of polycrystal, oxygen free, high purity Cu-OF copper were prepared and RUS measured on a designed experimental set-up. The obtained resonance frequencies were used as an input for the solution of the inverse eigenvalue problem using open-source objective function minimization software. The obtained results are compared with commercially available Finite Element Method (FEM) software defining a repeatable methodology for material property and defect characterization.

Strain, Young’s modulus, and structural transition of EuTiO3 thin films probed by micro-mechanical methods

EuTiO3 (ETO) is a well-known complex oxide mainly investigated for its magnetic properties and its incipient ferro-electricity. In this work, we demonstrate the realization of suspended micro-mechanical structures, such as cantilevers and micro-bridges, from 100 nm-thick single-crystal epitaxial ETO films deposited on top of SrTiO3(100) substrates. By combining profile analysis and resonance frequency measurements of these devices, we obtain the Young’s modulus, strain, and strain gradients of the ETO thin films. Moreover, we investigate the ETO anti-ferro-distortive transition by temperature-dependent characterizations, which show a non-monotonic and hysteretic mechanical response. The comparison between experimental and literature data allows us to weight the contribution from thermal expansion and softening to the tuning slope, while a full understanding of the origin of such a wide hysteresis is still missing. We also discuss the influence of oxygen vacancies on the reported mechanical properties by comparing stoichiometric and oxygen-deficient samples.

An Estimation Formula for Resonance Frequency Using Sex and Height for Healthy Individuals and Patients with Incurable Cancers

Resonance frequency breathing is a technique that involves breathing that maximizes heart rate variability. It is specific to individuals and is determined through a procedure taking approximately 30 min, using a procedure that is often best carried out at specialized medical institutions. This is a physical and time-consuming burden because of hospital visits and measurements, particularly for patients with cancer. Therefore it would be beneficial if a procedure can be found to determine resonance frequency from the patient’s physical characteristics, without the need for special assessment procedures. This exploratory cross-sectional study examined the correlation between individual characteristics and resonance frequency in healthy volunteers. Multiple regression analysis was performed with the measured resonance frequency as the target variable and individual characteristic parameters as explanatory variables. The study aims to build an estimation formula for resonance frequency with some of these parameters and assess its validity. In addition, the validity of the formula’s applicability to patients with incurable cancers is assessed. A total of 122 healthy volunteers and 32 patients with incurable cancers were recruited as participants. The median resonance frequency of 154 participants was six breaths per min. Sex and height were selected as explanatory variables associated with the measured resonance frequency in the volunteers. The estimation formula for resonance frequency using individual characteristics was 17.90—0.07 × height for men and 15.88—0.06 × height for women. Adjusted R-squared values were 0.55 for men and 0.47 for women. When the measured resonance frequency in patients with incurable cancers was six breaths per minute or less, the resonance frequency estimated by this formula was slightly larger than the measured ones. Information on individual characteristics, such as sex and height, which can be easily obtained, was useful to construct an estimation formula for resonance frequency.

Validation of Photoplethysmography Using a Mobile Phone Application for the Assessment of Heart Rate Variability in the Context of Heart Rate Variability-Biofeedback.

Heart rate variability-biofeedback (HRV-BF) is an effective intervention to reduce stress and anxiety and requires accurate measures of real-time HRV. HRV can be measured through photoplethysmography (PPG) using the camera of a mobile phone. No studies have directly compared HRV-BF supported through PPG against classical electrocardiogram (ECG). The current study aimed to validate PPG HRV measurements during HRV-BF against ECG. Fifty-seven healthy participants (70% women) with a mean (standard deviation) age of 26.70 (9.86) years received HRV-BF in the laboratory. Participants filled out questionnaires and performed five times a 5-minute diaphragmatic breathing exercise at different paces (range, ~6.5 to ~4.5 breaths/min). Four HRV indices obtained through PPG, using the Happitech software development kit, and ECG, using the validated NeXus apparatus, were calculated and compared: RMSSD, pNN50, LFpower, and HFpower. Resonance frequency (i.e., optimal breathing pace) was also compared between methods. All intraclass correlation coefficient values of the five different breathing paces were "near perfect" (>0.90) for all HRV indices: lnRMSSD, lnpNN50, lnLFpower, and lnHFpower. All Bland-Altman analyses (with just three incidental exceptions) showed good interchangeability of PPG- and ECG-derived HRV indices. No systematic evidence for proportional bias was found for any of the HRV indices. In addition, correspondence in resonance frequency detection was good with 76.6% agreement between PPG and ECG. PPG is a potentially reliable and valid method for the assessment of HRV. PPG is a promising replacement of ECG assessment to measure resonance frequency during HRV-BF.

Mitigating self-desiccation of cement composites via cellulose microfibers: Evidence of the microscopic behavior

Water-saturated cellulose microfibers (CMFs) incorporated into fresh cement composites can mitigate microcracking induced by self-desiccation during drying. This study utilized a nonlinear impact resonance acoustic spectroscopy (NIRAS) technique to elucidate the mechanism underlying the CMF-driven mitigation of self-desiccation. The hysteresis nonlinearity parameter (α) from the NIRAS was used to quantify the microstructural changes in three different mixtures (0 0.3 and 1% dosages of CMFs). Computed tomography (CT) compression tests and periodic measurements of mass and resonance frequency were performed to obtain more insights into mitigating self-desiccation. Supported by the collected data the results show a remarkable reduction in α over time confirming high sensitivity of α to the microstructural change. Furthermore the trend of α was consistent with the pore size distribution estimated by the CT test which provides quantitative evidence to support the mitigation of self-desiccation promoted by CMFs. We envision that these findings can be used as guidelines for enhancing the durability of cement composites facilitated by CMFs.

On the utility of linear and nonlinear ultrasound for evaluating microstructure-property relationships in laser powder bed fusion 316 L stainless steel

Given the complexity and potential for variability in components fabricated with metal additive manufacturing, the need for efficient, reliable, and nondestructive quality assurance is imperative for advancing its utilization in industry. Here, linear and nonlinear ultrasonic testing is used to nondestructively link microscale features and mechanical properties of 21 distinctly-printed AISI 316 L stainless steel samples manufactured by laser powder bed fusion. Groups of samples were heat-treated to induce microstructural changes under as-built, 600 ℃, 900 ℃, and 1100 ℃ conditions. While a linear ultrasonic parameter, wave speed, could not completely differentiate the evolution of microstructure and mechanical properties during heat treatment, the relative acoustic nonlinearity parameter β′ measured with second harmonic generation demonstrated sensitivity to incremental changes in heat treatment temperature, ultimate tensile strength, yield strength, dislocation density, and presence of oxide inclusions. Precise resonance frequency measurements were obtained using a fully noncontact configuration, and shifts in resonance frequency with heat treatment were connected to changes in average grain area and partial recrystallization. The large number of samples and high volume of ultrasonic testing in this study provides insight into part and measurement variability, which is key in demonstrating the feasibility of ultrasonic evaluation as the nondestructive solution for additively manufactured parts qualification.

Structural design and analytical study of a new polysilicon tunable microactuator for measurement of different resonance frequencies

This paper presents a novel MEMS tunable resonator that draws inspiration from the folded beam structure in its comb drive resonator design. Conventional electrostatic comb-drive resonators commonly employ folded-beam suspensions to achieve linearity and reduce system stiffness. The proposed design incorporates eight zigzag-shaped meander springs to support the comb finger structure, featuring two central anchors. The objective of this design is to introduce zigzag-shaped nested-folded beam suspensions to the comb parts, thereby reducing the tuning voltage and sensor size. The governing equations are provided to calculate the support springs’ stiffness, and a comparative analysis is conducted to evaluate the stiffness of the proposed design against other parameters. The mathematical analysis demonstrates that Zigzag Nested-Folded beams result in a decreased resonance frequency and a softened electrostatic spring under applied DC voltage. The integration of zigzag-shaped nested-folded beam flexures enables MEMS resonator devices to exhibit reduced stiffness, leading to a lower pull-in voltage. The resonator design and simulation are performed using Intellisuite and SolidWorks software. Results indicate that the resonant frequency of the proposed tunable comb-drive resonator, equipped with 26 finger pairs and a movable part displacement of 21 μm, is reduced by 66% from the original frequency of 2.420 kHz when a tuning voltage of 59 V is applied. Simultaneously, the corresponding effective stiffness decreases by 66% from the initial value of 0.72 N m−1. This compact resonator occupies an area of approximately 1.058×278 (μm)2, demonstrating a smaller size compared to previous works.

A statistical and reliability approach to vibration-based health monitoring in composite structures

In this paper, a novel statistical vibration-based damage detection method is developed considering uncertainties in measured resonance frequencies. The proposed method is based on the application of resonance frequencies as the most accurate and easiest measurable vibration feature. For proof of efficiency of the proposed method, case studies were undertaken using two identical composite plates, one delaminated and the other pristine. In this respect, the frequency response functions (FRFs) were measured and used as the main input to the Resonance Detection Algorithm as the proposed method. Applying these FRFs to a Resonance Detector Function can determine the resonant frequencies and their statistical distribution. Through the statistical distributions of the corresponding resonant frequencies, their reliability of detecting damage has been obtained via the beta distribution. By observing the damage detection reliability of the two sets of corresponding resonant frequencies, it has been determined that the changes in natural frequencies are due to structural changes and not random errors through measurement.

Quartz tuning fork-based biosensor for the direct detection of human cytomegalovirus

Human cytomegalovirus (HCMV) possess great threat to immunocompromised patients and pregnant women since It can cause disability if left untreated. Especially for unborn babies, if the virus was not detected at early stages, it can cause disabilities as the baby develops. Furthermore, the virus can be asymptomatic, hence, low-cost and rapid detection techniques are desirable. Currently available detection techniques of the virus are labor intensive and demand experienced technicians. For these reasons, new detection techniques are needed to overcome the current challenges associated with conventional techniques. In this work, quartz tuning fork (QTF)-based biosensor was developed for the detection of UL83-antigen of HCMV for the first time. Firstly, QTF coated with gold was functionalized with cysteamine and glutaraldehyde for UL83-antibody immobilization at the QTF surface. Then, the biosensor was tested against a variety of UL83-antigen concentrations. As the UL83-antigen concentration increased, the measured resonance frequency decreased due to increased mass loading at the QTF surface. The sensitivity of the biosensor is 15.91 Hz/ln(ng/mL). Whereas the limit of detection is 0.36 ng/mL. The biosensor showed comparable biosensing performances to those available in the literature. Furthermore, the biosensor demonstrated its selectivity towards UL83-antigen when tested against samples containing a mixture of biomarkers. The reported work demonstrates a platform for the direct and low-cost mass screening of diseases.