Response Waveform Research Articles

Depth detection of void defect in sandwich-structured immersed tunnel using elastic wave and decision tree

Void defects seriously threaten the overall force of the Sandwich-structured immersed tunnel (SSIT). Accurately identifying the location and evaluating the severity of the void defect through non-destructive testing methods to determine the overall structural health status can provide meaningful information for the grouting reinforcement repair of the immersed tunnel structure. This research has developed a method to identify void defects in SSIT by combining impact elastic wave technology with machine learning algorithms. Eleven eigenvalues including the waveform characteristics, frequency spectrum characteristics and structural location attributes of the impulse response waveform were integrated, and the different characteristics of the void defect area and the dense area were analyzed. Based on the full-size model experimental data, a sample database was established for model training and verification. The average accuracy of void-defect identification was 90.83%. The results show that this method has great potential for the detection and evaluation of void defects in SSIT structures.

Pre-Stack Seismic Data-Driven Pre-Salt Carbonate Reef Reservoirs Characterization Methods and Application

Carbonate reservoirs have significant reserves globally, but the substantial heterogeneity brings intractable difficulties to exploration. In the work area, the thick salt rock reduces the resolution of pre-salt seismic signals and increases the difficulty of reservoir characterization. Therefore, this paper proposes to utilize wavelet frequency decomposition technology to depict the seismic blank reflection area’s signal and improve the pre-salt signal’s resolution. The high-precision pre-stack inversion based on Bayesian theory makes full use of information from various angles and simultaneously inverts multiple elastic parameters, effectively depicting reservoirs with substantial heterogeneity. Integrating the high-precision inversion results and the Kuster-Toksöz model, a porosity prediction method is proposed. The inversion results are consistent with the drilling rock samples and well-logging porosity results. Moreover, the reef’s accumulation and growth, which conform to the geological information, proves the accuracy of the above methods. This paper also discusses the seismic reflection characteristics of reefs and the influence of different lithological reservoirs on the seismic waveform response characteristics through forward modeling, which better proves the rationality of porosity inversion results. It provides a new set of ideas for future pre-salt carbonate reef reservoirs’ prediction and characterization methods.

Changes in pulse waveforms in response to intraocular pressure elevation determined by laser speckle flowgraphy in healthy subjects

BackgroundThe influences of intraocular pressure (IOP) elevations on the pulse waveform in the optic nerve head (ONH) were evaluated using laser speckle flowgraphy (LSFG) in normal subjects.MethodsThis prospective cross-sectional study was conducted at the Nagoya University Hospital. An ophthalmodynamometer was pressed on the sclera to increase the IOP by 20 mmHg or 30 mmHg for 1 min (experiment 1, 16 subjects) and by 30 mmHg for 10 min (experiment 2, 10 subjects). The mean blur rate (MBR) and the eight pulse waveform parameters determined using LSFG were measured before, immediately after and during an IOP elevation, and after the IOP returned to the baseline pressure.ResultsA significant elevation in the IOP and a significant reduction in the ocular perfusion pressure (OPP) were found after applying the ophthalmodynamometer (both, P < 0.001). The blowout score (BOS) reduced significantly (P < 0.001), and the flow acceleration index (FAI; P < 0.01) and resistivity index (RI; P < 0.001) increased significantly immediately after increasing the IOP by 20 or 30 mmHg (experiment 1). The BOS reduced significantly (P < 0.001), and the FAI (P < 0.01) and RI (P < 0.001) increased significantly after the IOP elevation by 30 mmHg in both experiment 2 and 1. However, the BOS and RI recovered significantly at time 10 compared to that in time 0 (immediately after IOP elevation) during the 10-min IOP elevation (P < 0.001 and P = 0.008, respectively).ConclusionsIn conclusion, the BOS, FAI, and RI of the pulse waveforms changed significantly with an acute elevation in the IOP. The change should be related to the larger difference between the maximum and minimum MBRs during the IOP elevation.

Simulation Analysis of Void Defect Detection in Sandwich-Structured Immersed Tunnel Using Elastic Wave

Void defects can be easily generated between a steel plate and concrete joint due to the complicated internal structure of a sandwich-structured immersed tunnel (SSIT), which affect the overall bearing capacity of the main structure of the immersed tube tunnel. A prototype experiment was conducted to study the application of impact imaging method in the nondestructive detection of void defects in SSITs. The detection criterion for the impact imaging method was established based on the features of the waveform data. Nevertheless, the influence of steel plate thickness, material properties, void location, and structure on the detection accuracy of the impact imaging method is unclear. Therefore, numerical simulation was applied to study the influencing factors by establishing a different condition model. Good agreement between the experimental and numerical results was observed for the response waveform collected from the inspection area. Using the calculation model and identified material parameters validated in the active prototype experiment, numerical simulations of several sets, which considered all influencing factors, were performed. The application scope and sensitivity of the impact image method were recommended to reduce misjudgement in practical applications and improve detection accuracy.

Prevalence of electronegative electroretinograms in a healthy adult cohort

ObjectiveAn electronegative electroretinogram (ERG) can indicate important ocular or systemic disease. This study explored the prevalence of electronegative responses to dark-adapted stimuli in a largely healthy cohort.Methods and Analysis211 participants...

Finite element modeling of buildings with structural and foundation rocking on dry sand

AbstractAllowing structures to rock during an earthquake can effectively provide base isolation at a relatively small cost. Rocking limits the base shear demand and provides self‐centering, but the rocking response depends on energy dissipation caused by interaction with the soil and impacts during re‐centering. This paper addresses the computational modeling of buildings that have either been designed to rock on the soil beneath their foundation (foundation rocking) or at the foundation–structure interface (structural rocking). Within OpenSees, foundation and structural rocking were modeled using a beam‐on‐a‐nonlinear‐Winkler‐foundation model (BNWF) combined with flat‐slider elements for footing–soil and superstructure–footing interactions, respectively. The modified with flat‐slider elements BNWF model (mBNWF) involves an uplift‐dependent stiffness and viscous damping for both vertical and horizontal directions, and a friction–vertical force coupling. The proposed computational model was used to simulate an extensive set of centrifuge tests involving both structural rocking and foundation rocking with sequential excitations. Generally, the proposed modeling approach, without calibration of built‐in parameters, adequately captured the response observed in centrifuge experiments. More specifically, the modeling captured the response amplitude and waveform of story accelerations and building rocking angle in most cases, but including potential nonlinear behavior caused by previous ground excitations was in some cases critical to obtain reasonable predictions. This was more profound for foundation rocking due to its inherent dependency on the soil strength and energy dissipation; for structural rocking previous nonlinear response primarily affected the transition time between full contact and rocking, but had a smaller effect on the prediction of maximum response.

Analysis of waveform and amplitude of mouse rod and cone flash responses.

Most vertebrate eyes have rod and cone photoreceptors, which use a signal transduction pathway consisting of many biological processes to transform light into an electrical response. We dissect and quantify the contribution of each of these processes to the photoreceptor light response by using a novel method of analysis that provides an analytical solution for the entire time course of the dim-flash light response. We find that the shape of the light response is exclusively controlled by deactivation parameters. Activation parameters scale this shape and alter the response amplitude. We show that the rising phase of the response depends on Ca2+ feedback, and we identify the deactivation parameters that control the recovery phase of the response. We devise new methods to extract values for deactivation and activation parameters from a separate analysis of response shape and response amplitude. Vertebrate eyes have rod and cone photoreceptors, which use a complex transduction pathway comprising many biological processes to transform the absorption of light into an electrical response. A fundamental question in sensory transduction is how these processes contribute to the response. To study this question, we use a well-accepted phototransduction model, which we analyse with a novel method based on the log transform of the current. We derive an analytical solution that describes the entire time course of the photoreceptor response to dim flashes of light. We use this solution to dissect and quantify the contribution of each process to the response. We find that the entire dim-flash response is proportional to the flash intensity. By normalizing responses to unit amplitude, we define a waveform that is independent of the light intensity and characterizes the invariant shape of dim-flash responses. We show that this waveform is exclusively determined by deactivation rates; activation rates only scale the waveform and affect the amplitude. This analysis corrects a previous assumption that the rising phase is determined entirely by activation rates. We further show that the rising phase depends on Ca2+ feedback to the cyclase, contrary to current belief. We identify the deactivation rates that control the recovery phase of the response, and we devise new methods to extract activation and deactivation rates from an analysis of response shape and response amplitude. In summary, we provide a comprehensive understanding of how the various transduction processes produce the cellular response.

Nonlinear electromechanical modeling and robustness of soft robotic fish-like energy harvester: insights and possible issues

This work investigates the possible integration of an energy harvester in a bioinspired fish-like aquatic unmanned vehicle. The defined fish-like system utilizes a reduced complexity prescribed motion as the representation for energy harvester to be subjected to. Nonlinear electromechanical modeling is performed by considering the geometric and piezoelectric nonlinearities. A convergence analysis is carried out in order to determine the required modes in the Galerkin discretization due to the presence of nonlinear interactions between the prescribed and relative motions. The utilization of higher-order modeling for the strain and material leads to the identification of impactful prescribed motions terms that can activate the nonlinearities in the system, results in more harmonics to consider, and leads to the presence parametric excitation terms. Considering a reduced-complex model by decreasing the value of the quadratic constraint envelope that the fish-like system would be forced with, the soft-robotic system behaves more with a base excitation characteristic. Small damping would allow this prescribed motion with reduced quadratic envelope forcing still induces a hardening behavior, but the other harmonics and parametric resonance seen are greatly reduced. Considering this reduced complexity system, the interaction between the prescribed and base excitations is also investigated to demonstrate that when the two excitations are of similar nature constructive and destructive build of the response waveform can occur when looking at near the first natural resonance. It is shown that the quenching phenomenon can take place which may result in a destructive response of the piezoelectric energy harvester. The results show that the robustness of the fish-like robot is directly dependent on the design parameters including the damping of the structure, importance of the undulatory motion, and activation of the resonances.

A comfortable steady state visual evoked potential stimulation paradigm using peripheral vision

Objective. Steady-state visual evoked potential (SSVEP)-brain–computer interfaces (BCIs) can cause much visual discomfort if the users use the SSVEP-BCIs for a long time. As an alternative scheme to reduce users’ visual fatigue, this study proposes a new stimulation paradigm (termed as steady state peripheral visual evoked potential, abbreviated as SSPVEP) which makes full use of peripheral vision. The electroencephalography (EEG) signals are classifiable which means this proposed stimulation paradigm can be used in BCI system with the aid of the latest hybrid signal processing approach. Approach. Under the SSPVEP stimulation paradigm, 20 targets are mounted on 20 frequencies and other targets are set between two targets with flicker stimuli coding. In order to ensure the classification accuracy of SSPVEP signal detection under the proposed stimulation paradigm, two optimization schemes are proposed for the detection stage of the conventional ensemble task-related component analysis (ETRCA) algorithm. The first optimization scheme uses nonlinear correlation coefficient at the detection part for the first time to improve the classification accuracy of the system. The second optimization scheme uses γ correction to enhance the time domain features of the SSPVEP signals, and uses Manhattan distance for the final detection. Main results. According to the response waveforms of the EEG signals generated under the SSPVEP stimulation paradigm and the results of the questionnaire on user’s comfort level to the two stimulation paradigms (SSPVEP paradigm and conventional SSVEP paradigm), the proposed stimulation paradigm brings less visual fatigue. The comparison results indicate that the proposed detection methods (ETRCA + γ correction + Manhattan distance, ETRCA + Spearman correlation) can greatly improve the classification accuracy compared with the individual template canonical correlation analysis method and conventional ETRCA method based on Pearson correlation. Significance. The SSPVEP stimulation paradigm reduces users’ visual fatigue via using peripheral vision, which provides a new design idea for SSVEP stimulation paradigm aimed at visual comfort.

Influence of the input frequency for soundness evaluation of concrete structure based on waveform analysis

In the soundness evaluation method based on waveform analysis in time domain, the response waveforms that are measured while the target is in sound condition is indispensable. Therefore, it is expected that this method is for the evaluation of precast concrete products because the state of the products is almost identical and it is able to measure the response waveforms before using the products. On the other hand, although there are difficulties to apply this method for the evaluation of the existing structures because the response waveform is not measured before using, it is expected that this method can be applied to the evaluation of the existing structures by making the response waveform on the basis of the numerical simulation. The computational conditions should be set properly based on the actual measurement conditions for the numerical simulation. Among the computational conditions, the input frequency is determined based on the diameter of the steel ball and contact time if the excitation is given by making an impact with the steel ball by using the theory proposed by Sansalone et al. However, Kubo et al. reported that the measured contact time is different from the theoretical value and the difference reaches maximum twice. The influence of the difference would not be negligible for the soundness evaluation and should be considered carefully to perform the soundness evaluation accurately. Therefore, in this study, the response waveforms are computed on a numerical model with excitations of various input frequencies, and the influence of the input frequency to the response waveform is discussed by comparing the computed response waveforms.

Rapid Measurement of Yeast Status using the Phase Angles of Harmonics in the Electrical Response Waveform

Rapid Measurement of Yeast Status using the Phase Angles of Harmonics in the Electrical Response Waveform

Seismic Observations of Four Thunderstorms Using an Underground Fiber-Optic Array

Abstract Thunderstorms are a common atmospheric phenomenon that cause abundant acoustic disturbances, which can interact with the ground surface, creating a link between atmospheric and solid Earth processes. This article reports seismological observations of four thunderstorms through the spring and summer of 2019, as recorded by the distributed acoustic sensing fiber-optic array (4.9 km) on the Penn State campus in State College, Pennsylvania. With a dense sensor array in the local region, we are able to construct the seismic full waveform response of the thunderstorm events (hereafter referred to as thunderquakes) and track the wave propagation across the array. We use a time-domain grid search to obtain the back azimuth and slowness of the waves, and a modified Geiger’s method to pinpoint source locations of the thunderquakes. Correlated with the time of the recorded signal, this data allows reconstruction of thunderstorm movement as well as offering measurements of the seismic velocity.

Shaping the Temporal Waveform of Tri‐Photon with Double‐Dressing

AbstractHere, a method to generate and shape the tri‐photon entanglement in the temporal domain via simplified single step of six‐wave mixing processes of hot atomic gas media is proposed. The effect of dressing fields on shaping the tri‐photon temporal waveform is discussed. Cascade double dressing fields will reduce the width of rectangular profile of tri‐photon waveform when compared to the single dressing field. Conversely, nested double dressing fields will widen the width of rectangular profile of tri‐photon waveform. The double dressing field will affect the coherence time of linear optical response. The relationship between phase matching bandwidth and electromagnetically induced transparency bandwidth will decide the shape of temporal waveform and coherence time in linear optical response. The transition of nonlinear optical response to linear optical response can be completed by regulating the dressing fields. The results of this proposed study have potential impact on long‐distance quantum communication, high‐dimensional entanglement, and photon storage.

Humidity Effect on Dynamic Electromechanical Properties of Polyacrylic Dielectric Elastomer: An Experimental Study.

In this research, by utilizing the Very-High-Bond (VHB) 4905 elastomer, we carry out an experimental examination on the humidity effect on dynamic electromechanical performances of dielectric elastomers, including the dynamic response and viscoelastic creeping. Firstly, we experimentally analyze effects of the pre-stretch, peak voltage, waveform and frequency of the dynamic response of VHB 4905 elastomer under several ambient humidities. In general, the amplitude of dynamic deformation gradually adds up with the increasing humidity. Besides, it is found that the amplitude affected by different parameters shows diverse sensitivity to humidity. Subsequently, effect of humidity on the viscoelastic creeping of VHB 4905 is explored. The results demonstrate that, subject to different ambient humidities, the viscoelastic creeping under Alternating Current (AC) voltage is similar to that under Direct Current (DC) voltage. Furthermore, the equilibrium position of dynamic viscoelastic creep enlarges gradually with the humidity, regardless of voltage waveforms. For the dielectric elastomer with a pre-stretch ratio of 3, when the humidity increases from 20% to 80%, the increase of average equilibrium position of dynamic viscoelastic creep is larger than 1599%.

On the Use of Machine Learning for Classifying Auditory Brainstem Responses: A Scoping Review

Recent advances in machine learning have led to a surge of interest in classification of the auditory brainstem response. In this work, we conducted a search in the PubMed, Google Scholar, SpringerLink, ScienceDirect, and Scopus databases, and identified twelve studies that explored the use of machine learning to classify the auditory brainstem response as a complementary and objective method to (a) help clinicians better diagnose hearing impairment by discerning between healthy and pathological auditory brainstem response waveforms, (b) present a neural marker for potential applications in hearing aid tuning, and (c) provide a biometric marker for discriminating between subjects. A comparison between the studies presented in this review is not possible as they used different test subjects, group sizes, and stimuli, and evaluated auditory brainstem response differently. Instead, the result of these studies will be presented and their limitations as well as their potential applications will be discussed. Overall, the findings of these studies suggest that ABR classification using machine learning is a promising tool for assessing patients with hearing loss, optimizing technologies for tuning hearing aids, and discriminating between subjects.

Identification of non-dimensional density distribution in concrete by convolutional neural network using impact response waveforms

Identification of non-dimensional density distribution in concrete by convolutional neural network using impact response waveforms

Surrogate modeling of waveform response using singular value decomposition and Bayesian optimization

Surrogate modeling of waveform response using singular value decomposition and Bayesian optimization

Effects of frost-damaged reinforced concrete beams on their impact resistance behavior

Impact loading experiments were conducted to clarify the impact resistance behavior of frost-damaged reinforced concrete (RC) beams. The load-bearing performance and their response deflections were evaluated based on the energy conservation concept. The experimental results indicated that 1) when frost deterioration occurred on the top face, the compressive failure of the top concrete was significant; and the response deflection increased, and 2) when frost deterioration occurred at the bottom face, the response waveform was almost identical to that generated when no deterioration occurred; however, the bottom cover concrete peeled off during elastic stress wave propagation.

Ensuring both velocity and spatial responses robust to field inhomogeneities for velocity-selective arterial spin labeling through dynamic phase-cycling.

To evaluate both velocity and spatial responses of velocity-selective arterial spin labeling (VS-ASL), using velocity-insensitive and velocity-compensated waveforms for control modules, as well as a novel dynamic phase-cycling approach, at different B0 / field inhomogeneities. In the presence of imperfect refocusing, the mechanism of phase-cycling the refocusing pulses through four dynamics was first theoretically analyzed with the conventional velocity-selective saturation (VSS) pulse train. Numerical simulations were then deployed to compare the performance of the Fourier-transform based velocity-selective inversion (FT-VSI) with these three different schemes in terms of both velocity and spatial responses under various B0 / conditions. Phantom and human brain scans were performed to evaluate the three methods at scales of 0.8, 1.0, and 1.2. The simulations of FT-VSI showed that, under nonuniform B0 / conditions, the scheme with velocity-insensitive control was susceptible to DC bias of the static spins as systematic error, while the scheme with velocity-compensated control had deteriorated velocity-selective labeling profiles and, thus, reduced labeling efficiency. Through numerical simulation, phantom scans, and brain perfusion measurements, the dynamic phase-cycling method demonstrated considerable improvements over these issues. The proposed dynamic phase-cycling approach was demonstrated for the velocity-selective label and control modules with both velocity and spatial responses robust to a wide range of B0 and field inhomogeneities.

Target detection in healthy 4-week old piglets from a passive two-tone auditory oddball paradigm

BackgroundPassive auditory oddball tests are effort independent assessments that evaluate auditory processing and are suitable for paediatric patient groups. Our goal was to develop a two-tone auditory oddball test protocol and use this clinical assessment in an immature large animal model. Event-related potentials captured middle latency P1, N1, and P2 responses in 4-week old (N = 16, female) piglets using a custom piglet 32- electrode array on 3 non-consecutive days. The effect of target tone frequency (250 Hz and 4000 Hz) on middle latency responses were tested in a subset of animals.ResultsResults show that infrequent target tone pulses elicit greater N1 amplitudes than frequent standard tone pulses. There was no effect of day. Electrodes covering the front of the head tend to elicit greater waveform responses. P2 amplitudes increased for higher frequency target tones (4000 Hz) than the regular 1000 Hz target tones (p < 0.05).ConclusionsTwo-tone auditory oddball tests produced consistent responses day-to-day. This clinical assessment was successful in the immature large animal model.