Maximum Amplitude Frequency Research Articles

The δ Scuti stars of the Cep–Her Complex – I. Pulsator fraction, rotation, asteroseismic large spacings, and the νmax relation

ABSTRACT We identify delta Scuti ($\delta$ Sct) pulsators amongst members of the recently discovered Cep–Her Complex using light curves from the Transiting Exoplanet Survey Satellite (TESS). We use Gaia colours and magnitudes to isolate a subsample of provisional Cep–Her members that are located in a narrow band on the colour–magnitude diagram compatible with the zero-age main sequence. The $\delta$ Sct pulsator fraction amongst these stars peaks at 100 per cent and we describe a trend of higher pulsator fractions for younger stellar associations. We use four methods to measure the frequency of maximum amplitude or power, $\nu _{\rm max}$, to minimize methodological bias, and we demonstrate their sound performance. The $\nu _{\rm max}$ measurements display a correlation with effective temperature, but with a scatter that is too large for the relation to be useful. We find two ridges in the $\nu _{\rm max}$–$T_{\rm eff}$ diagram, one of which appears to be the result of rapid rotation causing stars to pulsate in low-order modes. We measure the $\nu _{\rm max}$ values of $\delta$ Sct stars in four other clusters or associations of similar age (Trumpler 10, the Pleiades, NGC 2516, and Praesepe) and find similar behaviour with $T_{\rm eff}$. Using échelle diagrams, we measure the asteroseismic large spacing, $\Delta \nu$, for 70 stars, and find a correlation between $\Delta \nu$, rotation, and luminosity that allows rapid rotators seen at low inclinations to be distinguished from slow rotators. We find that rapid rotators are more likely than slow rotators to pulsate, but they do so with less regular pulsation patterns. We also investigate the reliability of Gaia’s vbroad measurement for A-type stars, finding that it is mostly accurate but underestimates $v\sin i$ for slow rotators ($v\sin i \lt 50$ km s−1) by 10–15 per cent.

Vocalisation in wild-living mountain gazelles (Gazella gazella): structure and context of acoustical signals

Abstract Describing vocalisations of species in the wild is an important step to understanding their function. A wild-living population of mountain gazelles (Gazella gazella) was monitored in Israel, using camera traps, thereby providing a first detailed description of the acoustic repertoire. We described six acoustical signals that were either reported by previous authors or that were hitherto not reported. Acoustic signals were categorised according to behavioural context as alarm calls, courtship calls or threat calls and — if possible — characterised by four acoustic variables, i.e., duration, maximum amplitude frequency, three power quartiles and fundamental frequency. Vocalisations were illustrated as spectrograms supplemented by full video sequences to show the acoustical signal in its environmental, social, and behavioural context. Given the rather inconspicuous character of many acoustic signals, we proposed further in-depth studies of vocalisation in mountain gazelles and other Antilopine species to unravel new insights into their behaviour and social organisation.

The Frequency Characteristics of Vibration Events in an Underground Coal Mine and Their Implications on Rock Burst Monitoring and Prevention

The main frequency of microseismic signals has recently been identified as a dominant indicator for characterizing vibration events because it reflects the energy level of these events. Frequency information directly determines whether effective signals can be collected, which has a significant impact on the accuracy of predicting rock burst disasters. In this study, we adopted a characterizing method and developed a monitoring system for capturing rock failure events at various strata in an underground coal mine. Based on the rock break mechanism and energy release level, three types of rock failure events, namely, high roof breaking, low roof breaking, and coal fracture events, were evaluated separately using specific sensors and monitoring systems to optimize the monitoring accuracy and reduce the general cost. The captured vibration signals were processed and statistically analyzed to characterize the main frequency features for different rock failure events. It was found that the main frequency distribution ranges of low roof breaking, high roof breaking, and coal fracture events are 20–400 Hz, 1–180 Hz, and 1–800 Hz, respectively. Therefore, these frequency ranges are proposed to monitor different vibration events to improve detection accuracy and reduce the test and analysis times. The failure mechanism in a high roof is quite different from that of low roof failure and coal fracturing, with the main frequency and amplitude clustering in a limited zone close to the origin. Coal fracturing and lower roof failure show a synergistic effect both in the maximum amplitude and main frequency, which could be an indicator to distinguish failure locations in the vertical direction. This result can support the selection and optimization of the measurement range and main frequency parameters of microseismic monitoring systems. This study also discussed the distribution law of the maximum amplitude and main frequency of different events and the variation in test values with the measurement distance, which are of great significance in expanding the application of optimized microseismic monitoring systems for rock burst monitoring and prevention.

A study on vortex-induced vibration of a long flexible catenary cable in perpendicular flow

In this paper, a numerical model based on Euler-Bernoulli beam theory and a single van der Pol wake oscillator model is proposed to study the vortex-induced vibration of a long flexible catenary cable with a low mass ratio. The wake model uses only one oscillator to describe the in-line and cross-flow vibration with consideration of their nonlinear coupling. An experiment on a flexible cable model in perpendicular flow is carried out to validate the proposed numerical model. Numerical results and experimental measurements are compared on the vortex-induced vibration responses including the maximum amplitude, axial tension, and vibration frequency. A sensitivity analysis of the parameters used in the numerical model has been carried out. Numerical simulations by the proposed numerical model with properly selected parameters have demonstrated that the vibration frequency and the axial tension can be well predicted, and the variation of the vibration amplitudes can also be properly captured. The lock-in phenomena and the axial tension variation of the long flexible catenary cable in perpendicular flow have been carefully studied both numerically and experimentally.

Effect of Menstrual Cycle on Neuromuscular Efficiency and Muscular Strength in Runners

PURPOSE: The aim of this study was to examine the influence of the menstrual cycle (MC) stages on neuromuscular efficiency and muscular strength in female runners. METHODS: Three runners (females) underwent testing using a BIODEX isokinetic dynamometer concurrently with a BioPac EMG, during which peak torque, peak torque/body weight, time to peak torque, mean amplitude, median amplitude, minimum amplitude, maximum amplitude, frequency, and the p-p value were collected throughout the test. During the test, the performance variables were assessed on the quadriceps (rectus femoris) muscle and collected at speeds of 60 degrees/second and 180 degrees/second. STATISTICAL ANALYSIS: A paired-sample t-test was used to determine the correlation between neuromuscular efficiency and peak torque of the quadriceps during extension in the two MC phases. A paired-sample t-test was also used to determine the difference in neuromuscular efficiency between the MC phases, as well as peak torque between the MC phases. RESULTS: Muscular strength testing did not reveal statistical significance between neuromuscular efficiency and peak torque of the quadriceps during MC phases. Furthermore, there was no statistical significance between the differences in peak torque of the MC phases. Maximum amplitude at 60 degrees/second on the left leg between the MC phases revealed statistical significance (p = 0.026). EMG wave frequency at 60 degrees/second on the right leg between the MC phases revealed statistical significance (p = 0.007). CONCLUSION: Results show a significant difference in maximum amplitude and wave frequency at 60 degrees/second during knee extension between the MC phases.

Electrochemical oscillation behaviors of gold during its recovery from waste printed circuit boards through slurry electrolysis

Slurry electrolysis is an effective technology for recovering gold from waste printed circuit boards (WPCBs). However, electrochemical oscillation during the gold recovery process is a potential factor affecting power consumption. As a result, the potential oscillation behaviors of gold dissolution at a constant current were studied. These results showed that the periodic formation and dissolution of the Au-OH passive film on the anode induced electrochemical oscillation. The amplitude and frequency of electrochemical oscillation were affected by hydrochloric acid concentration, current intensity, electrode spacing, and sodium chloride concentration, among which the concentration of sodium chloride had a significant inhibitory effect. Under the following conditions: hydrochloric acid concentration of 8 mol/L, current of 0.03 A, and electrode spacing of 1.5 cm, the obtained maximum amplitude potential and frequency were 1.17 V and 0.56 Hz, respectively. The phase space reconstruction results showed that the systems evolved between the near-linear equilibrium region and the periodic oscillation region. Different factors induced two oscillation modes: top-down and bottom-up. The top-down and bottom-up oscillations induced by current intensity, hydrochloric acid concentration, and electrode spacing reduced the relative power consumption by 11.8, 17.2, and 11.8 %, respectively, and increased the relative power consumption by 14.3, 21.2, and 30.1 %, respectively. A critical value was obtained, which varied oscillation patterns and gained a region of lower power consumption. The addition of trisodium citrate and PVP can improve gold recovery rate and current efficiency by regulating process of electrochemical oscillation. This work will provide theoretical support for recovering valuable metals from WPCBs with reduced energy consumption by controlling the external conditions to switch the oscillation mode.

Time-delayed Duffing oscillator in an active bath.

During recent decades active particles have attracted an incipient attention as they have been observed in a broad class of scenarios, ranging from bacterial suspension in living systems to artificial swimmers in nonequilibirum systems. The main feature of these particles is that they are able to gain kinetic energy from the environment, which is widely modeled by a stochastic process due to both (Gaussian) white and Ornstein-Uhlenbeck noises. In the present work, we study the nonlinear dynamics of the forced, time-delayed Duffing oscillator subject to these noises, paying special attention to their impact upon the maximum oscillations amplitude and characteristic frequency of the steady state for different values of the time delay and the driving force. Overall, our results indicate that the role of the time delay is substantially modified with respect to the situation without noise. For instance, we show that the oscillations amplitude grows with increasing noise strength when the time delay acts as a damping term in absence of noise, whereas the trajectories eventually become aperiodic when the oscillations are sustained by the time delay. In short, the interplay among the noises, forcing, and time delay gives rise to a rich dynamics: a regular and periodic motion is destroyed or restored owing to the competition between the noise and the driving force depending on time delay values, whereas an erratic motion insensitive to the driving force emerges when the time delay makes the motion aperiodic. Interestingly, we also show that, for a sufficient noise strength and forcing amplitude, an approximately periodic interwell motion is promoted by means of stochastic resonance.

A novel vortex-induced vibration model for a circular cylinder in the vicinity of a plane wall

A novel vortex-induced vibration (VIV) model is proposed to predict the transverse responses of an elastically mounted circular cylinder in the proximity of the wall. Firstly, flow characteristics and hydrodynamic loads on a near-wall stationary circular cylinder are summarized and analyzed based on the existing experimental results, and then the Strouhal shedding frequency and the empirical correlations of the mean lift coefficient and oscillating lift coefficient are established. Subsequently, by introducing the empirical correlations of fluid loads to the equations of structure vibration, a novel VIV model for the near-wall circular cylinder is proposed to describe more precisely the effect of the plane wall. The accuracy, stability, and adaptability are validated by employing experimental VIV results. Compared to existing models, the novel model has advantages in achieving acceptable accuracy in various scenarios. Finally, using the proposed VIV model, the dynamic features of a near-wall circular cylinder to the reduced velocity and gap ratio are studied in detail, including the time-averaged displacements, lock-in regime, maximum amplitude, and dominant frequency. The results obtained are valuable for understanding the VIV characteristics of the near-wall cylinder, and the semi-empirical VIV model proposed could be applied in engineering prediction in the future.

Numerical study on the VIVs of two side-by-side elastically coupled cylinders under different Re and natural frequencies

Vortex-induced vibration (VIV) is very significant in influencing the structural safety of many practical engineering applications. However, the VIV mechanism of multiple elastically coupled cylinders is poorly understood. In this paper, the VIVs of two elastically coupled cylinders in a side-by-side arrangement is numerically studied under different effects, including the stiffness ratio of the two springs (K2/K1), the diameter ratio of the two cylinders (D2/D1), and the Reynolds number. The mass ratio of the two cylinders is 1.92. K2/K1 and D2/D1 have a significant impact on the maximum vibration amplitude and vibration frequency of the two-cylinder system. Furthermore, unlike the resonance of a single cylinder, no frequency-locking phenomenon occurs. When the Reynolds number is constant, it is found that the changes in K2/K1 and D2/D1 change the natural frequency of the system, and the lift force coefficient (CL) of the cylinders and the phase between the lift force and displacement (φ) change accordingly. The maximum vibration amplitude of a cylinder is proportional to the parameter CLsinφ. Under certain frequency conditions, the amplitude of one cylinder is significantly suppressed. In addition, when the natural frequency of the system is fixed, the Reynolds number also changes the CL and φ of the cylinders. Therefore, the method of suppressing the vibration of one cylinder by coupling the other cylinder in parallel is severely restricted by the Reynolds number. The conclusion of this study has certain guiding significance for the structural design of dual submerged floating tunnels with elastic connections.

Uncovering the Mechanism of the Role of Fly Ash in the Self-Healing Ability of Mortar with Different Curing Ages.

As an admixture of cement-based materials, the reaction of fly ash (FA) usually takes place in the late age of curing, so FA will affect the self-healing ability of long-age cement-based materials. The self-healing potential and the characteristics of self-healing products of cementitious materials before and after crack healing were analyzed by microscopic tests, and the mechanism of the effect of fly ash on the self-healing performance of cementitious materials was revealed. The results showed that the increase in fly ash content promoted the improvement of the self-repair performance of cracked specimens at 28 d, especially when the fly ash dosage was 40%, the crack opened after 30 d of healing in water was completely closed, the UPV value after recovery was close to 3000 m/s, the self-repair efficiency of maximum amplitude and main frequency amplitude was up to more than 60%, and the recovery rate of compressive strength was increased to more than 30%. However, the increase in fly ash content was not conducive to the self-repair of cracked samples at 210 d, and with the increase in fly ash content, the crack closure effect weakened, the UPV value after recovery decreased, the crack repair rate based on ultrasonic transmission decreased to about 20%, and the compressive strength recovery rate increased slightly. In addition, calcium carbonate precipitation was the main repair product of crack filling and healing, including calcite and spherulite. With the increase in fly ash content, the content of element C in the self-repair products of 28-day-old specimens gradually increased, and the size of calcium carbonate crystals gradually decreased, but the filling was denser, whereas the calcium carbonate crystals in the self-repair products of 210 d specimens gradually became fine and loose.

Effects of PAR2 Gene Knockout on Visceral Sensitivity, Stress Behaviors, and Colonic Electrical Activities in Irritable Bowel Syndrome.

Irritable bowel syndrome (IBS) could seriously affect the patient's health quality by its recurrence. There is a great medical and social need to explore the mechanisms and new treatment strategies of IBS. To explore the influence of protease-activated receptor 2 (PAR2) gene knockout on IBS visceral sensitivity, stress behaviors, and colonic electrical activities. The PAR2 gene knockout and IBS model rats were generated and divided into PAR2+/+ wild control (WC) group, PAR2+/+ wild IBS model (WM) group, PAR2-/- knockout control (KC) group and PAR2-/- knockout IBS model (KM) group. The stress behaviors scores, minimum rectal fluid injection capacity threshold value of abdominal withdrawal reflex (AWR) = 3, and the colonic electrical activities indexes were recorded and the experimental results were analyzed statistically. (1) PAR2 gene deletion and IBS models were successfully generated. (2) The scores of aggressive and exploratory behaviors in WM and KM groups were higher than WC and KC groups (p < 0.05). The grooming behavior scores in WC and KC groups were higher than the WM and KM groups (p < 0.05). WM group had the highest aggressive and exploratory behavior scores; WC group had the highest grooming behavior scores. (3) The minimum rectal fluid injection capacity threshold value of AWR = 3 in WM and KM groups were lower than WC and KC groups (p < 0.05); WM group had the lowest value. (4) The maximum amplitude and wave frequency of colonic fast and slow waves in WM and WC groups were greater than in the KM and KC groups, respectively (p < 0.05). The amplitude index and number of colonic contraction waves in WM and KM groups were greater than the WC and KC groups (p < 0.05). Colonic electrical activity indexes were highest in the WM group. The PAR2 gene deletion could have a beneficial effect on visceral sensitivity, stress behaviors and colonic electrical activities in rats with IBS.

Wake flow characteristics and unsteady performance of a pump-jet propulsor under hull condition

The propulsor is one of the main noise sources of an underwater vehicle. The pump-jet operating under hull condition is in a typical non-uniform strong anisotropic turbulent flow field. In this paper, the wake flow characteristics and unsteady performance of a pump-jet propulsor under hull condition are numerically investigated. Reynolds-averaged Navier–Stokes (RANS) method and large eddy simulation (LES) method are used to evaluate and compare the ability of solving vortex structure, pressure distribution and unsteady force. LES method can capture the interaction between different vortex systems, and the vortex shedding process of the stator wake and appendage wake. These lead to that the frequency spectra of fluctuation pressure have peaks in the low-frequency range for LES method. For unsteady force spectrum, the frequency of maximum amplitude of a single blade is mainly affected by relative intensities of the stator wake and appendage wake. “Humps” appear near the blade passing frequency and its multiples for unsteady force spectrum of the rotor for LES method. The blade passing frequency in the rotor force spectrum is generated by the phase cancelation between different blades. The completeness of rotor blade phase cancelation is mainly affected by the intensity of the non-stationarity in the flow field. Overall, it is sufficient to clarify the hydrodynamic performance and the characteristics of fluctuation pressure distribution of the pump-jet with RANS method. The LES method is necessary to obtain reasonable transient characteristics of the unsteady force and vortex system interaction for the pump-jet under hull condition.

Experimental Study on the Transient Disturbance Characteristics and Influence Factors of Pantograph–Catenary Discharge

The transient electromagnetic disturbance generated by arcing discharge between the pantograph and catenary can pose a significant risk to the safe operation of electrified railways. In order to better comprehend its properties, a pantograph–catenary discharge generating device is designed to simulate the discharge phenomenon with moving electrodes in this experimental investigation. The effects of the applied voltage, the gap distance, and the relative motion between the pantograph and catenary on the time- and frequency-domain features of the discharge current and electromagnetic field are investigated. The variation trends of pulse peak current, rise time, pulse repetition frequency, maximum amplitude, and characteristic frequency in the radiation spectrum are retrieved under varying experimental settings, and the effect mechanisms are derived from the physics of gas discharge. A dynamic discharge test is conducted in this study in order to further understand the effect of electrodes’ relative motion on discharge characteristics. The results indicate that lateral sliding motion of the pantograph along the track has a negligible effect on the transient discharge, whereas a faster vertical approaching motion between the pantograph and catenary generates a larger pulse current peak, a steeper rise front-edge, and a higher radiation intensity.

Modified Laplace Based Variational Iteration Method for the Mechanical Vibrations and its Applications

Abstract In this paper, we are putting forward the periodic solution of non-linear oscillators by means of variational iterative method (VIM) using Laplace transform. Here, we present a comparative study of the new technique based on Laplace transform and the previous techniques of maximum minimum approach (MMA) and amplitude frequency formulation (AFF) for the analytical results. For the non-linear oscillators, MMA, AFF and VIM by Laplace transform give the same analytical results. Comparison of analytical results of VIM by Laplace transform with numerical results by fourth-order Runge–Kutta (RK) method conforms the soundness of the method for solving non-linear oscillators as well as for the time and boundary conditions of the non-linear oscillators.

A Fast and Accurate Frequency Tracking Method for Ultrasonic Cutting System via the Synergetic Control of Phase and Current.

Ultrasonic cutting is a superior machining process for brittle materials, owing to its capability to reduce the cutting force and improve the surface quality. To avoid the destructive instability of ultrasonic vibration induced by the cutting force, the excitation frequency of the ultrasonic system must reliably track its resonance frequency. However, it remains challenging for the conventional frequency tracking methods via one parameter to simultaneously achieve both high response rate and high tracking accuracy. This study proposes that more than one parameter could be coupled to get advantages from each parameter. A frequency tracking method via the synergetic control of circuit phase and current of the ultrasonic system was proposed as an example. This method utilizes the phase to responsively determine the tracking direction and uses the characteristic current as the endpoint frequency to ensure accuracy. Theoretical analyses and numerical simulations were conducted to demonstrate that the proposed method can accurately track the frequency of maximum vibration amplitude with a higher response rate than conventional methods. Moreover, ultrasonic cutting tests were performed on Nomex composites to evaluate the machining performance of the ultrasonic system with the proposed method. The experimental results verify that the proposed frequency tracking method enables the ultrasonic system to reach a stable state with a shorter response time, which is beneficial for the reduction of cutting-induced defects.

Vibration characteristics analysis and structural improvement of natural gas venting ignition pipeline

In order to study the flow-induced vibration characteristics of the natural gas vent pipeline under the internal flow field, taking the gas transmission station pipeline as an example, the ANSYS Workbench software was used to establish models under two working conditions, uncoupling and fluid-solid coupling, for modal analysis, and analyze and compare the calculation results and propose a structural improvement plan. The results show that the maximum amplitude of the first three modes under the two working conditions is concentrated on the riser mouth, and the amplitude under the fluid-solid coupling condition is slightly larger than that of no coupling; the inner diameter of the pipe elbow is large and the pressure is small, and the outside diameter is small and the pressure is small. Large, this instability will increase the air pulsation of the flow field. In the improved scheme, adding a restriction on the top to increase the rigidity of the pipeline can significantly reduce the maximum amplitude of the gas pipeline; adding an orifice to eliminate air flow pulsation has a certain effect on reducing the maximum amplitude and natural frequency, and the combination of the two can make the pipeline more stable. The research results of this paper can provide improved ideas for vibration reduction at the natural gas venting operation site.

Effects of toluene-di-isocyanate microcapsules on the frost resistance and self-repairing capability of concrete under freeze-thaw cycles

Concrete buildings used in severe cold regions are susceptible to freeze-thaw damage, resulting in internal cracking and surface spalling of concrete. Microcapsules can self-repair concrete cracks and improve the durability of concrete. This paper focuses on the effects of toluene-di-isocyanate (TDI) microcapsules on the frost resistance and self-repairing capability of concrete under freeze-thaw cycles. The mass and mechanical properties of concrete were measured before and after freeze-thaw cycles. The pore size distribution and microstructure of the concrete were characterized using nuclear magnetic resonance and scanning electron microscopy (SEM). The mechanical properties and permeability of freeze-thaw damaged concrete were assessed by compressive strength tests and rapid chloride migration (RCM) tests after self-repairing. The frost resistance and self-repairing capability of concrete containing microcapsules were also evaluated by ultrasonic test. The results showed that the concrete containing nano-SiO2/paraffin/PE wax encapsulated TDI microcapsules (CON3) had better frost resistance and self-repairing capability than the concrete containing other microcapsules. After 100 freeze-thaw cycles, the mass loss rate and compressive strength loss rate of CON3 were only 1.63% and 13.6%, respectively. After 7 d of self-repairing, SEM images showed that repairing products with network structure appeared in the pores of CON3, which improved the microstructure of concrete. The harmful pores proportion, compressive strength recovery rate, chloride diffusion coefficient recovery rate, maximum amplitude and dominant frequency maximum amplitude of CON3 were 47.8%, 96.9%, 84.6%, 77.99 mV and 8.37 mV, respectively.

Fundamental properties of stars from Kepler and Gaia data: parallax offset and revised scaling relations

ABSTRACT Data from the space missions Gaia, Kepler, CoRoT and TESS, make it possible to compare parallax and asteroseismic distances. From the ratio of two densities ρsca/ρπ, we obtain an empirical relation fΔν between the asteroseismic large frequency separation and mean density, which is important for more accurate stellar mass and radius. This expression for main-sequence (MS) and subgiant stars with K-band magnitude is very close to the one obtained from interior MS models by Yıldız, Çelik &amp; Kayhan. We also discuss the effects of effective temperature and parallax offset as the source of the difference between asteroseismic and non-asteroseismic stellar parameters. We have obtained our best results for about 3500 red giants (RGs) by using 2MASS data and model values for fΔν from Sharma et al. Another unknown scaling parameter $f_{\nu _{\rm max}}$ comes from the relationship between the frequency of maximum amplitude and gravity. Using different combinations of $f_{\nu _{\rm max}}$ and the parallax offset, we find that the parallax offset is generally a function of distance. The situation where this slope disappears is accepted as the most reasonable solution. By a very careful comparison of asteroseismic and non-asteroseismic parameters, we obtain very precise values for the parallax offset and $f_{\nu _{\rm max}}$ for RGs of –0.0463 ± 0.0007 mas and 1.003 ± 0.001, respectively. Our results for mass and radius are in perfect agreement with those of APOKASC-2: the mass and radius of ∼3500 RGs are in the range of about 0.8–1.8 M⊙ (96 per cent) and 3.8–38 R⊙, respectively.

Accurate identification of microseismic waveforms based on an improved neural network model

Microseismic waveform identification is the basis of rock burst risk assessment and rock burst warning in metal mines. This paper presents a method combining a genetic algorithm and neural network algorithm to classify the signals collected by a microseismic monitoring system during the mining process. After the analysis of the characteristics of the signals, six parameters, the duration time (DT), rise time (RT), ring number (RN), ring number of rise time (RRN), maximum amplitude (MA), and main frequency (MF), are selected for waveform recognition, that is, these six parameters are taken as the inputs of the waveform classification model. After establishing a fitness function, the numbers of the nodes in the two hidden layers were determined by a genetic algorithm. A 6–79-1 neural network waveform identification model was established, including one input layer, two hidden layers and one output layer. Only one blasting vibration waveform was misjudged as a rock mass fracture waveform when 114 samples were tested. Compared to the unordered multiple classification logistic regression method (UMCLRM), the improved neural network (INN) model had a higher classification accuracy. This model can effectively classify microseismic waveforms, mechanical vibration waveforms, electrical noise waveforms and blasting vibration waveforms. Additionally, the accuracy of waveform recognition is likely to be improved by using a two-layer hidden layer structure instead of by using a one-layer hidden layer structure. However, the complexity of the model increases. The waveform recognition model proposed in this paper is of great help to reduce the amount of manual work required to perform waveform recognition.

Data-Driven Modelling of Damage Prediction of Granite Using Acoustic Emission Parameters in Nuclear Waste Repository

Evaluating the quantitative damage to rocks through acoustic emission (AE) has become a research focus. Most studies mainly used one or two AE parameters to evaluate the degree of damage, but several AE parameters have been rarely used. In this study, several data-driven models were employed to reflect the combined features of AE parameters. Through uniaxial compression tests, we obtained mechanical and AE-signal data for five granite specimens. The maximum amplitude, hits, counts, rise time, absolute energy, and initiation frequency expressed as the cumulative value were selected as input parameters. The result showed that gradient boosting (GB) was the best model among the support vector regression methods. When GB was applied to the testing data, the root-mean-square error and R between the predicted and actual values were 0.96 and 0.077, respectively. A parameter analysis was performed to capture the parameter significance. The result showed that cumulative absolute energy was the main parameter for damage prediction. Thus, AE has practical applicability in predicting rock damage without conducting mechanical tests. Based on the results, this study will be useful for monitoring the near-field rock mass of nuclear waste repository.