Amplitude Measurements Research Articles

Nonembedded measurement method based on amplitude correction for unsteady surface pressure estimation in a high-subsonic compressor cascade

Unsteady surface pressure (USP) is a crucial physical quantity for studying blade loads and boundary layer flow. However, the unique characteristics of high-load compressor cascades, including thin walls, narrow passages, and significant geometric deflection angles, pose considerable challenges for USP measurements. The primary innovation of this study lies in proposing a nonembedded measurement method based on amplitude correction for USP measurement, which can provide frequency and amplitude information of dynamic pressure on measured surface. Unlike existing methods that rely on theoretical models for amplitude correction, the proposed method establishes amplitude correction transfer models using Gaussian process regression (GPR) based on pre-calibration data. This innovation overcomes the constraints faced by theoretical models when dealing with high-speed complex geometries, such as those found in compressor blades, which are limited by geometric and Reynolds number considerations. The principle of this method is to perform indirect measurement by leading the airflow out of the measured surface through an air tube and correcting the amplitudes through transfer models. An acoustic calibration system was developed for amplitude calibration and measurement verification. The results demonstrate that the developed method accurately provides the dynamic pressure frequencies in the range of 1–10 kHz with a tube length of ≤ 55 mm and from 1 to 7 kHz with the tube length of 80 mm. Verification results proof that the GPR statistical model can reasonably estimate amplitude attenuation. Ultimately, the developed method was successfully applied to unsteady pressure measurement in a high-subsonic compressor cascade and showed highly encouraging results.

Optical coherence elastography and its applications for the biomechanical characterization of tissues.

The biomechanical characterization of the tissues provides significant evidence for determining the pathological status and assessing the disease treatment. Incorporating elastography with optical coherence tomography (OCT), optical coherence elastography (OCE) can map the spatial elasticity distribution of biological tissue with high resolution. After the excitation with the external or inherent force, the tissue response of the deformation or vibration is detected by OCT imaging. The elastogram is assessed by stress-strain analysis, vibration amplitude measurements, and quantification of elastic wave velocities. OCE has been used for elasticity measurements in ophthalmology, endoscopy, and oncology, improving the precision of diagnosis and treatment of disease. In this article, we review the OCE methods for biomechanical characterization and summarize current OCE applications in biomedicine. The limitations and future development of OCE are also discussed during its translation to the clinic.

Real-time Stokes polarimetry using a polarization camera.

This Lab Note introduces the "Stokes Camera," a simple experimental arrangement for real-time measurement of spatial amplitude and polarization and thus spatially resolved Stokes parameters. It uses a polarization sensitive camera and a fixed quarter-wave plate, providing a one-shot, digital solution for polarization measurement that is only limited by the frame rate of the camera and the computation speed of the provided code. The note also provides background information on relevant polarization theory and vector vortex beams, which are used as a demonstration of the device.

Rock ‘n’ roll solutions to the Hubble tension

Local measurements of the Hubble parameter are increasingly in tension with the value inferred from a ΛCDM fit to the cosmic microwave background (CMB) data. In this paper, we construct scenarios in which evolving scalar fields significantly ease this tension by adding energy to the Universe around recombination in a narrow redshift window. We identify solutions with scalar field potential V∝ϕ2n that have simple asymptotic behavior, both oscillatory (rocking) and rolling. These solutions consistently describe both the field evolution and its fluctuations without approximation. Our findings differ qualitatively from some of the existing literature, which rely upon a coarse-grained fluid description. Combining CMB data with low-redshift measurements, the best fit model has n=2 with a significantly higher value of the Hubble constant as compared to a ΛCDM fit to the same data. Future measurements of the late-time amplitude of matter fluctuations and of the reionization history could help distinguish these models from competing solutions.

Manipulation of affective speech and hemoglobin changes: A case study

Despite the wide use of functional near-infrared spectroscopy (fNIRS) in various cognitive research, it is under-investigated whether fNIRS can offer neural evidence of emotion vocalization, especially in older adults. In this study, an 74-year-old male participant without a cognitive or physical difficulty completed two speech tasks while an fNIRS device recorded Changes in Oxy-hemoglobin (HbO) and total hemoglobin (HbT) levels in the pre-frontal cortex. The three speech tasks were (1) affective speech (i.e., talking about happy and sad life events) and (2) neutral speech (i.e., explaining how to make a peanut butter and jelly sandwich). The speech tasks were audio recorded which was acoustically analyzed using Praat for frequency and amplitude measures. In general, the frequency measures were highest when talking about sad life event while amplitude measures were highest when producing neutral speech. The HbO and HbT levels were positive and highest during the happy speech manipulation. During the other two speech tasks, the HbO levels were all negative with neutral being the lowest. The HbT levels showed a more complex change. More data are needed to confirm the pre-frontal lobe (de)activation associated with manipulation of affective prosody. This case study will facilitate future research in this line.

“Do I sound happy?” Acoustic characteristics of affective prosody in older adults

It is known that older adults have difficulty comprehending affective prosody. However, it is unclear how well they manipulate affective prosody to express emotion. Five older adults were recorded when they completed three speech tasks: (1) Talking about happy and sad life events; (2) Describing the Refused Umbrella pictures; (3) Explaining how to make a peanut butter and jelly sandwich. Two independent investigators listened to the recordings and parsed them into utterances considering pauses and connectivity. Afterwards, the investigators identified the primary emotion (i.e., happy, sad, neutral) in each utterance. The recordings were acoustically analyzed using Pratt for rate, pitch, and amplitude measures. The rate measures included speech and articulation rates and the pitch/amplitude measures contained initial, final, minimum, maximum f0/dB and the difference between the maximum and minimum f0/dB. Multivariate ANOVAs with Tukey post-hoc test were conducted to analyze the acoustic data. Among the acoustic measures, all rate and pitch measures were significantly different across the three emotions. However, none of the amplitude measures differed significantly. Research on production of affective prosody in healthy older adults has been scarce and this study may serve as a catalyst for further exploration in this area.

Исследование амплитудной и фазовой ошибок датчика-опоры при ультразвуковой сварке пластмасс

The paper presents a technique making it possible to evaluate amplitude and phase errors of the magnetoelastic support sensor used in the plastics ultrasonic welding. Measurement of the support sensor vibration amplitude allows monitoring alterations in the basic physical properties of the polymer being welded, i.e. its temperature and thickness. The support sensor operation dynamic mode is described. It is established that evaluating measurement errors with the proposed method in manufacture of any support sensor of different design makes it possible to accurately determine its performance with parameters of the polymer material ultrasonic welding process. The problem of evaluating accuracy of the magnetoelastic support sensor operation used in the welding process was considered. The support sensor amplitude and phase errors during ultrasonic welding were studied. A magnetoelastic sensor was designed and developed ensuring improved accuracy in measuring the support vibrations amplitude during the polymer material ultrasonic welding. The experiments carried out confirmed clear relationship between the support vibrations amplitude and heating of the welded samples, their thickness and properties during the ultrasonic welding.

Enhanced Reservoir Description via Areal Data Integration and Reservoir Fluid Geodynamics: A Case Study From Deepwater Gulf of Mexico

Accurate reservoir characterization is vital for effective decisions made throughout the life cycle of an oilfield reservoir, including management and development. Of all the components of reservoir description, hydraulic connectivity carries the highest amount of uncertainty, where inaccurate connectivity evaluation often results in production underperformance. Shortcomings are faced when applying conventional approaches of connectivity assessment. Seismic surveys are not always sufficient to evaluate lateral connectivity as detected faults can be transmissive or partially transmissive, while some faults are below the detection limits of seismic amplitude measurements. Vertical connectivity represents another uncertainty, where pressure measurements and well logs are often either unable to detect the baffles along oil columns or cannot assess whether detected baffles are relevant seals or flow diverters. Although conventional downhole fluid analysis (DFA) workflows have proven effective in delineating reservoir connectivity, enough DFA data are not always available, and with added complexity, uncertainties arise. Additionally, while equilibrated asphaltene gradients, measured through DFA probes, imply connectivity, ongoing reservoir fluid geodynamics (RFG) processes, such as current hydrocarbon charging, can preclude equilibration in a connected reservoir. Thus, a comprehensive assessment approach, that utilizes all available data streams, is needed to overcome the significant spatial complexity associated with moderately and heavily faulted reservoirs. In this paper, we employed our recently introduced interpretation workflow to evaluate the connectivity of a heavily faulted reservoir in the deepwater Gulf of Mexico. The field was divided into five investigation areas penetrated by 12 wells. Areal downhole fluid analysis (ADFA) was applied to assess local connectivity leading to reservoir-scale connectivity. Through integrating fluid/dynamic and rock/static data, each data type provided insights that were pieced together to enhance consistency and reduce uncertainty. Analyzed data included pressure-volume-temperature (PVT) reports, pressure surveys, well logs, and geochemistry. The study resulted in a verifiable connectivity description where faults, previously regarded as sealing, were classified into sealing or partially transmissive faults; unresolved faults were detected. Fault-block migration was detected, and fault throw was estimated; asphaltenes behavior was used to deduce original field structures prior to faulting. We also examined RFG processes to investigate oil biodegradation, where an asphaltene clustering trend was observed, causing high oil viscosities toward the bottom of one sandstone. A correlation was then derived and successfully implemented to estimate oil viscosity.

A single session of hip abductors resistance exercise until failure changes shank muscle activation during landing tasks

BACKGROUND: Weakness in the hip abductors can lead to lower limb misalignment and an elevated risk of injury. This can result in compensatory mechanisms at the ankle to maintain stability. AIM: To verify the effects of a single session of hip abductors resistance exercise until failure on the foot pronation and EMG amplitude of shank muscles (peroneus longus - PL; tibialis anterior - TA) during landing tasks. METHOD: Seventeen participants completed single-leg and double-leg landings both before and after a single session of hip abductors resistance exercise until failure. The exercise consisted of four sets of 10 repetitions maximum, with a 2-minute rest interval between each set. Measurements of PL and TA EMG amplitude and degree of foot pronation were performed during landings. RESULTS: We observed a greater degree of supination of the foot during single-leg compared to double-leg landing (p=0.006), without effect of exercise. Regarding TA EMG amplitude, there was no exercise effect (p=0.951), with a higher amplitude observed in double-leg compared to single-leg landing (p=0.001). EMG amplitude of PL was higher during single-leg compared to double-leg landing (p=0.003) and the exercise significantly reduced its activation in both tasks (p=0.032). CONCLUSION: Single-leg and double-leg landings exhibited variations in mechanics and activation patterns of the distal muscles. Following a single session of hip abductors resistance exercise until failure, there was a reduction in PL activation during landing tasks. This suggests that there were neuromuscular compensations occurring distally due to alterations in the hip abductor muscles.

Vehicle-Mounted Pavement Health Monitoring System Based on a Spring-Guide-Assisted Triboelectric Sensor.

The present pavement health monitoring is limited by a professional staff patrol. Herein, a vehicle-mounted pavement health monitoring system (VPHMS) based on a spring-guide-assisted triboelectric sensor (S-TES) is proposed, which uses the vibration generated by vehicles passing through uneven pavements to monitor the pavement damage. The VPHMS consists of S-TES, the integration module, and the terminal display module. The designed S-TES has high stability and can achieve a high linear vibration amplitude measurement within 90 mm. Moreover, the integration module is used to process signals and transmit wireless data transmission. The terminal display module is used to receive signals and display the measurement results on the screen. When a vehicle equipped with VPHMS is driven over uneven pavements, the system can accurately monitor the potholes and upheavals on the pavement in real time. This work has significant application value in fields such as pavement health monitoring and intelligent transportation.

Auditory evoked potentials in adolescents with autism: An investigation of brain development, intellectual impairment, and neural encoding.

Limited research has evaluated neural encoding of sounds from a developmental perspective in individuals with autism (ASD), especially among those with intellectual disability. We compared auditory evoked potentials (AEPs) in autistic adolescents with a wide range of intellectual abilities (n = 40, NVIQ 30-160) to both age-matched cognitively able neurotypical adolescent controls (NT-A, n = 37) and younger neurotypical children (NT-C, n = 27) to assess potential developmental delays. In addition to a classic measure of peak amplitude, we calculated a continuous measure of intra-class correlation (ICC) between each adolescent participant's AEP and the age-normative, average AEP waveforms calculated from NT-C and NT-A to study differences in signal morphology. We found that peak amplitudes of neural responses were significantly smaller in autistic adolescents compared to NT-A. We also found that the AEP morphology of autistic adolescents looked more like NT-A peers than NT-C but was still significantly different from NT-A AEP waveforms. Results suggest that AEPs of autistic adolescents present differently from NTs, regardless of age, and differences cannot be accounted for by developmental delay. Nonverbal intelligence significantly predicted how closely each adolescent's AEP resembled the age-normed waveform. These results support an evolving theory that the degree of disruption in early neural responses to low-level inputs is reflected in the severity of intellectual impairments in autism.

Locating tectonic tremors with uncertainty estimates: time- and amplitude-difference optimization, wave propagation-based quality control and Bayesian inversion

SUMMARY The accurate location of tectonic tremors helps improve understanding of their underlying physical processes. However, current location methods often do not statistically evaluate uncertainties to a satisfactory degree and do not account for potential biases due to subsurface structures not included in the model. To address these issues, we propose a novel three-step process for locating tectonic tremors. First, the measured time- and amplitude differences between station pairs are optimized to obtain station-specific relative time and amplitude measurements with uncertainty estimates. Secondly, the time– and amplitude–distance relationships in the optimized data are used to roughly estimate the propagation speed (i.e. shear wave velocity) and attenuation strength. Linear regression is applied to each event, and the resulting velocity and attenuation strength are used for quality control. Finally, the tremor location problem is formulated within a Bayesian framework where the model parameters include the source locations, local site delay/amplification factors, shear wave velocity and attenuation strength. The Markov chain Monte Carlo algorithm is used to sample the posterior probability and is augmented by a parallel tempering scheme for an efficient global search. We tested the proposed method on ocean-bottom data indicating an intense episode of tectonic tremors in Kumano-nada within the Nankai Trough subduction zone. The results show that the range of the 95 per cent confidence interval is typically <7 km horizontally and <10 km vertically. A series of experiments with different inversion settings reveals that adopting amplitude data and site correction factors help reduce random error and systematic bias, respectively. Probabilistic sampling allows us to spatially map the probability of a tremor occurring at a given location. The probability map is used to identify lineaments of tremor sources, which provides insights into structural factors that favour tremor activity.

Evolution of coupled weakly driven waves in a dissipative plasma

The nonlinear collisional dynamics of coupled driven plasma waves in the presence of background dissipation is studied analytically within kinetic theory. Sufficiently near marginal stability, phase space correlations are poorly preserved and time delays become unimportant. The system is then shown to be governed by two first-order coupled autonomous differential equations of cubic order for the wave amplitudes and two complementary first-order equations for the evolution of their phases. That system of equations can be decoupled and further simplified to a single second-order differential equation of Liénard's type for each amplitude. Numerical solutions for this equation are obtained in the general case, while analytic solutions are obtained for special cases in terms of parameters related to the spacing of the resonances of the two waves in frequency space, e.g., wave lengths and oscillation frequencies. These parameters are further analyzed to find classes of quasi-steady saturation and pulsating scenarios. To classify equilibrium points, local stability analysis is applied, and bifurcation conditions are determined. When the two waves saturate at similar amplitude levels, their combined signal is shown to invariably exhibit amplitude beating and phase jumps of nearly π. The obtained analytical results can be used to benchmark simulations and to interpret eigenmode amplitude measurements in fusion experiments.

Two neurosubtypes of ADHD different from the clinical phenotypes

Clinical and etiological variability of attention deficit hyperactivity disorder (ADHD) presents an obstacle to understand the disorder. The aim of this study was to disentangle the heterogeneity of ADHD using neuroimaging and a semi-supervised machine learning algorithm. We collected brain structural and functional magnetic resonance imaging (MRI) data and clinical profiles of 183 children with ADHD and 396 neurotypical controls from 7 independent sites. We also used an external validation set with 750 subjects. We adopted a semi-supervised clustering method to subtype ADHD by regional volumetric measures of gray matter, white matter, and fractional amplitude of low frequency fluctuation (fALFF). In addition, split sample test, leave-one-site-out test and external validation were applied to evaluate the reproducibility and stability of ADHD subtypes. Two stable and reproducible neurosubtypes of ADHD were disclosed, which were proved by the split-sample test and leave-one-site-out validation. The structural and functional patterns of ADHD subtypes were also stable in the external validation set. The current two neurosubtypes differed in clinical manifestations and volumetric gray matter, white matter volume and fALFF patterns. The current neurosubtypes of ADHD which were different from clinical phenotypes could facilitate understanding the underlying neuropathological and neurobiological mechanism of the disorder.

Changes in the electrical impedance of goat meat in the process of autolysis

The data on the development of meat goat breeding are presented and the prospects of this sub-branch of animal husbandry in obtaining meat products are shown. The dynamics of electrical impedance of goat meat during autolysis is presented. For carrying out of researches the electrophysical method is offered, allowing on the basis of measurement of amplitude of a signal on a sample, phase shift between fluctuations of current and voltage in a circuit to calculate active and reactive components of impedance of a sample of meat and then, according to the equivalent electric scheme of a sample, to find parameters of this scheme - values of electric resistances and capacitances. The object of the study was the longest muscle of the back of goat meat, which has a special value for the production of meat food products, including functional purpose. Measurements were carried out in the frequency range of 10-100000 Hz. It was found that the modulus of complex resistance of muscle tissue samples decreases during storage time, and the phase angle dependence on frequency at frequencies 10 - 500 Hz shifts towards higher frequencies with time, with the value of the extremum at frequencies around 50000 Hz decreasing. Analysis of the dependence of the parameters of the equivalent circuit of the sample on the time of autolysis shows that these changes are associated with the synthesis of adenosine triphosphoric acid in the first hours after slaughter and an increase in the permeability of cell membranes. The results of the analysis have similarity with indicators in the study of microstructure and changes in the hydrogen index of meat during autolysis. The presented data can be used as a basis for the creation of electrophysical express-method of autolysis control and prediction of functional and technological properties of systems of animal origin.

A Computer Program for Assessing Histoanatomical Morphometrics in Ultra-High-Frequency Ultrasound Images of the Bowel Wall in Children: Development and Inter-Observer Variability.

Ultra-high-frequency ultrasound (UHFUS) has a reported potential to differentiate between aganglionic and ganglionic bowel wall, referred to as histoanatomical differences. A good correlation between histoanatomy and UHFUS of the bowel wall has been proven. In order to perform more precise and objective histoanatomical morphometrics, the main research objective of this study was to develop a computer program for the assessment and automatic calculation of the histoanatomical morphometrics of the bowel wall in UHFUS images. A computer program for UHFUS diagnostics was developed and presented. A user interface was developed in close collaboration between pediatric surgeons and biomedical engineers, to enable interaction with UHFUS images. Images from ex vivo bowel wall samples of 23 children with recto-sigmoid Hirschsprung's disease were inserted. The program calculated both thickness and amplitudes (image whiteness) within different histoanatomical bowel wall layers. Two observers assessed the images using the program and the inter-observer variability was evaluated. There was an excellent agreement between observers, with an intraclass correlation coefficient range of 0.970-0.998. Bland-Altman plots showed flat and narrow distributions. The mean differences ranged from 0.005 to 0.016 mm in thickness and 0 to 0.7 in amplitude units, corresponding to 1.1-3.6% and 0.0-0.8% from the overall mean. The computer program enables and ensures objective, accurate and time-efficient measurements of histoanatomical thicknesses and amplitudes in UHFUS images of the bowel wall. The program can potentially be used for several bowel wall conditions, accelerating research within UHFUS diagnostics.

Atmospheric waves disturbances from the solar terminator according to the VLF radio stations data

The perturbations from the solar terminator in the range of acoustic-gravity waves (AGWs) periods from 5 min to 1 h were analysed with the use of measurements of VLF radio signals amplitudes on the European radio path GQD–A118 (Great Britain–France). These observations provide information on the propagation of waves at altitudes near the mesopause (∼90 km), where VLF radio waves are reflected. On the considered radio path a systematic increase in fluctuations in the amplitudes of radio waves was observed within a few hours after the passage of the evening terminator. For April, June, October 2020 and February 2021 events, the distribution of the number of wave perturbations with large amplitudes over AGWs time periods has been studied. Our results show that the evening terminator for different seasons is dominated by waves in the range of periods of 15–20 min. The amplitudes of the AGWs from the terminator at the heights of the mesosphere (fluctuations in the concentration of neutral particles, velocity components and vertical displacement of the volume element) are approximately determined by the fluctuations of the amplitudes of the VLF radio signals. The amplitudes of the AGWs on the terminator are 12–14% in relative concentration fluctuations, which correspond to the vertical displacement of the atmospheric gas volume of 1.1–1.3 km. Based on the analysis of the AGW energy balance equation, it was concluded that the waves predominantly propagate in a quasi-horizontal direction at the terminator. The possibility of studying the long-term changes in the mesosphere parameters using fluctuations in the amplitudes of VLF radio waves at the terminator is shown.

Fringe-to-pulse counting demodulation of a laser interferometer for primary vibration calibration

A high accuracy and real-time amplitude-phase demodulation method based on the pulse counting of optical fringes is proposed for a laser interferometer to realize amplitude and phase measurement of the vibration in primary vibration calibration. The two orthogonally analog signals with high frequency are converted into two digital signals through the comparison module instead of a high-speed data acquisition device. Then one displacement increment during a quarter period of the digital signal can be obtained by the high-frequency clock through comparing the four states of two orthogonally digital signals. The actual output rate of the demodulation data will be decreased by subsample with the vibration frequency. The results of experiment illustrated the deviations were within the limits and the displacement waves were well reconstructed, not only for homodyne interferometer but also for heterodyne interferometer. The proposed method involves less complicated hardware equipment and algorithm, so it is sufficient for real-time and high-precision demodulation of the laser interference signals to realize vibration measurements in primary vibration calibration.

Two-aperture measurements for GEO-feeder adaptive optics pre-compensation optimization.

We present a method to estimate the pre-compensation phase of ground-to-geostationary orbit (GEO) optical links based on downlink phase and log-amplitude measurements from two ground apertures. This method allows us to reduce the point-ahead anisoplanatism that currently limits the telecom performance of GEO-feeder links. It is shown to reduce the anisoplanatic phase variance by 50%, hence improving the statistics of the coupled flux aboard the satellite. It also outperforms the one-aperture estimation method for very severe atmospheric conditions. Besides, only low-resolution amplitude measurements are required on the second aperture to reach the performance of the novel estimator.

Hydrocarbon exploration technique based on the ratio coefficient measurement of two-frequency amplitudes

The paper presents a hydrocarbon field exploration technique based on the ratio coefficient measurement of two-frequency amplitudes. The study establishes electronic plasma resonance frequencies. The anomalous measurement values show a large range when receiving the reflected signal at the station line measurement points. The technique test proved an increase in the accuracy of hydrocarbon field boundaries by 20-30 %. The findings can be implemented in prospecting geophysics to improve the accuracy of hydrocarbon boundaries applying the ratio coefficient measurement of two-frequency amplitudes within a wide frequency range. The study also proved that it is possible to increase the deposits location resolution using the coefficient measurement ratio of three-frequency amplitudes of the range covered.