Impulse Oscillation Research Articles

Study on pulse current auxiliary heating process of submerged arc welding

During the welding process, temperature filed distribution of weldment is one of the key factors which influence welding quality. In order to improve the mechanical properties of welding joint, a technology for heating process of weldment using auxiliary pulse current was proposed in this article. Firstly, through metallographic experiment, strength experiment and hardness experiment, it was proved that the auxiliary pulse current not only can refine grain size but also improves the mechanical property of the welding joint. Then the paper used ANSYS and its ANSYS Parametric Design Language parametric design language to simulate the welding process with assistant pulse current, and the temperature field, the pulse current density distribution and the time of effective pulse current in the welded joint were obtained. Quantitative analyses were undertaken on the influence laws of auxiliary pulse current parameters on weld temperature field, auxiliary pulse current density distribution and the time of effective pulse current. A new parameter was defined as time-current density (the time integral of current density) to demonstrate the change rule of auxiliary pulse current density distribution with time. Finally, analyzing the reasons for raising the welding quality. There were two reasons for such phenomenon: one was auxiliary pulse current change the state of heat distribution in the weld seam area, the other was that the impulse oscillation of the auxiliary pulse influences the nucleation process of melting region.

High-flow nasal cannula improves respiratory impedance evaluated by impulse oscillometry in chronic obstructive pulmonary disease patients: a randomised controlled trial

Non-pharmacological treatment with high-flow nasal cannula (HFNC) may play a vital role in treatment of patients with chronic obstructive pulmonary disease (COPD). To evaluate the efficacy of HFNC, impulse oscillation system (IOS) is a new noninvasive technique in measuring the impedance of different portions of lungs. It shows higher sensitivity in contrast to conventional pulmonary function tests (PFT). However, whether IOS is an appropriate technique to evaluate the efficacy of HFNC in improving the impedance of small airways or peripheral lung in patients with COPD is still unclear. We enrolled 26 stable COPD participants randomised into two groups receiving HFNC or nasal cannula (NC) for 10 min followed by a 4-week washout period and crossover alternatively. IOS was used to detect the difference of respiratory impedance after HFNC or NC interventions. IOS parameters, PFT results, transcutaneous partial pressure of carbon dioxide, peripheral oxygen saturation, body temperature, respiratory rate, pulse rate, and blood pressure at the time of pre-HFNC, post-HFNC, pre-NC, and post-NC, were collected and analysed using SPSS (version 25.0, IBM, Armonk, NY, USA). The IOS measurement indicated that HFNC significantly improved R5, R5% predicted, R5–R20, X5-predicted, and Fres compared with NC, whereas no significant difference was observed through the PFT measurement. The beneficial effect of HFNC in improving small airway resistance and peripheral lung reactance compared with that of NC in patients with stable COPD was confirmed through IOS measurement.Trial registration: ClinicalTrials.gov NCT05130112 22/11/2021.

Sex differences in body composition affect total airway resistance during puberty

BackgroundDuring puberty, changes in body composition due to sex hormones are associated with lung mechanics. However, little is known about the mediation effect of sex differences in body composition during puberty with total airway resistance.MethodsWe prospectively recruited 620 children (10–12 years old) from the general population and conducted a cross-sectional study. This study assessed pubertal status according to the five Tanner stages using a questionnaire, line drawings, and each subject’s blood sex hormone profile. Both the impulse oscillation system for total lung mechanics and multifrequency bioelectrical impedance for body composition analyses were conducted. The effects of puberty on body composition and subsequent total lung resistance were evaluated using mediation analysis.ResultsAmong the 503 children enrolled, there were 261 males (51.9%) and 242 females (48.1%). In males, higher testosterone levels corresponded with reduced total lung resistance (β = –0.13, 95% CI = –0.21 to –0.05, p < 0.001), and the proportion of the mediating effect through the muscle-fat ratio was 19% (95% CI = 4 to 59, p = 0.02). In contrast, in females, pubertal status reduced total lung resistance (β = –0.27, 95% CI = –0.58 to –0.05, p = 0.04), however, the proportion of the mediating effect through the body mass index was –51% (95% CI = –244 to –4%, p = 0.04).ConclusionThe muscle-fat ratio in adolescent males had a synergistic effect with testosterone on improving total airway resistance, whereas improvements in lung resistance by pubertal status were partially masked by body mass index in adolescent females. In conclusion, body composition changes during puberty between males and females have differing effects on total airway resistance.

Advances in the Diagnosis of Equine Respiratory Diseases: A Review of Novel Imaging and Functional Techniques.

Simple SummaryRespiratory problems are common in horses and are often diagnosed as a cause of poor athletic performance. The basic diagnostic techniques of the equine respiratory tract examination are not always sufficient for a complete diagnosis of the disease, its exacerbation, remission, or response to treatment. Therefore, advances have been introduced in the diagnosis of equine respiratory diseases. Among them, we can distinguish the high-resolution imaging modalities like computed tomography (CT) and magnetic resonance (MR) imaging. These techniques have revolutionized the capability of visualizing detailed anatomy of the upper respiratory tract, offering the practitioners an advanced view of airway pathology and allowing for appropriate management planning. On the other hand, the pulmonary function tests (PFTs), which provide sensitive assessment of small functional changes in the lungs, are able to comprehensively characterize the mechanics of the respiratory system. Spirometry and impulse oscillation system (IOS) analyze intra-breath respiratory mechanics, while electrical impedance tomography (EIT) measures changes in lung conductivity. These methods may be successfully applied to detect airway obstruction and mechanical inhomogeneity in breathing patterns. Presented advanced diagnostic techniques comply with owners’ and trainers’ requirements for accurate and early diagnosis of respiratory tract disorders. This paper reviews advantages, disadvantages, and clinical applications of the advanced diagnostic techniques of the equine respiratory tract.The horse, as a flight animal with a survival strategy involving rapid escape from predators, is a natural-born athlete with enormous functional plasticity of the respiratory system. Any respiratory dysfunction can cause a decline in ventilation and gas exchange. Therefore, respiratory diseases often lead to exercise intolerance and poor performance. This is one of the most frequent problems encountered by equine internists. Routine techniques used to evaluate respiratory tract diseases include clinical examination, endoscopic examination, radiographic and ultrasonographic imaging, cytological evaluation, and bacterial culture of respiratory secretions. New diagnostic challenges and the growing development of equine medicine has led to the implementation of advanced diagnostic techniques successfully used in human medicine. Among them, the use of computed tomography (CT) and magnetic resonance (MR) imaging significantly broadened the possibilities of anatomical imaging, especially in the diagnosis of upper respiratory tract diseases. Moreover, the implementation of spirometry, electrical impedance tomography (EIT), and impulse oscillation system (IOS) sheds new light on functional diagnostics of respiratory tract diseases, especially those affecting the lower part. Therefore, this review aimed to familiarize the clinicians with the advantages and disadvantages of the advanced diagnostic techniques of the equine respiratory tract and introduce their recent clinical applications in equine medicine.

HRCT quantitative analysis of airway remodeling and airway trapping in the small airway asthma phenotype and its correlation with pulmonary function

Objectives We aimed to explore whether large airway remodeling and small airway structural changes exist in subjects with small airway asthma phenotype and to evaluate the relationships between quantitative high-resolution computed tomography (qHRCT) parameters and lung function. Methods We enrolled 15 subjects with small airway asthma phenotype and 18 healthy controls. The two groups were matched by age, sex and body square area (BSA) with propensity score matching (PSM). Pulmonary function and qHRCT parameters [wall thickness (WT), wall area (WA), lumen area (LA), wall area percentage (WA%) of the 4th–6th generations in the right upper lobe apical segmental bronchus (RB1), adjusted by BSA, WT/BSA, WA/BSA, and LA/BSA, relative volume change −860 HU to −950 HU (RVC−860 to −950) and the expiration to inspiration ratio of mean lung density (MLDE/I)) were compared between the groups. Correlation analysis was employed to assess the relationship between qHRCT parameters and pulmonary function. Results The small airway asthma phenotype had significantly higher WA%, RVC−860 to −950 and MLDE/I and lower LA/BSA than the healthy control. Additionally, we found moderate to strong correlations between impulse oscillation (IOS) indices and WA6% and WT6/BSA. No significant correlation was found between bronchial parameters and air trapping parameters (p > 0.05). Conclusions Combining physiological tests with imaging approaches can lead to better evaluation of small airway disfunction (SAD) in asthmatic patients. Additionally, despite nonexistent airflow obstruction in patients with small airway asthma phenotype, large airway remodeling and small airway structural changes may appear simultaneously in the early stage of disease.

Effect of Adding Inhaled Corticosteroid to Long-Acting Muscarinic Antagonist/Long-Acting Beta-Agonist Therapy Among Patients With Chronic Obstructive Pulmonary Disease.

BackgroundThe role of inhaled corticosteroid (ICS) in chronic obstructive pulmonary disease (COPD) is unclear. Hence, this study aimed to evaluate the efficacy of ICS as an add-on to long-acting muscarinic antagonist (LAMA)/long-acting beta 2 agonist (LABA), which was assessed using the impulse oscillation system (IOS), in patients with COPD.MethodologyWe included patients with COPD whose treatment was changed from LAMA/LABA (≥four weeks) to ICS/LAMA/LABA between April 2019 and March 2021. To gain insight into the effect and safety of ICS-containing triple therapy for COPD, pulmonary function; Short-Form 36, St. George’s Respiratory Questionnaire, COPD Assessment Test, and modified Medical Research Council scores; and airway resistance assessed using the IOS from one week before LAMA/LABA was switched to ICS/LAMA/LABA therapy until more than eight but less than twelve weeks after switching were evaluated.ResultsIn total, 46 patients with COPD (mean age: 72.28 ± 7.81 years) were included in the study. None of the pulmonary function test parameters significantly changed from baseline values (mean difference in forced expiratory volume in one second [FEV1.0]: +0.032, P = 0.12; percentage FEV1.0 [FEV1.0%]/forced vital capacity [FVC]: −0.58, P = 0.42; and FVC: +0.087, P = 0.058). Meanwhile, the IOS showed that resonant frequency (mean difference from baseline: −2.12, P < 0.0001) and bodily pain scores in the St. George’s Respiratory Questionnaire (mean difference: −7.03, P = 0.031) significantly decreased.ConclusionsSwitching from LAMA/LABA to ICS/LAMA/LABA therapy reduces airway elasticity-to-inertial resistance ratios, which may lead to structural airway improvements in patients with COPD.

Periodic modes of group dominance in fully coupled neural networks

Nonlinear systems of differential equations with delay, which are mathematical models of fully connected networks of impulse neurons, are considered. Purpose of this work is to study the dynamic properties of one special class of solutions to these systems. Large parameter methods are used to study the existence and stability in сonsidered models of special periodic motions – the so-called group dominance or k-dominance modes, where k ∈ N. Results. It is shown that each such regime is a relaxation cycle, exactly k components of which perform synchronous impulse oscillations, and all other components are asymptotically small. The maximum number of stable coexisting group dominance cycles in the system with an appropriate choice of parameters is 2m − 1, where m is the number of network elements. Conclusion. Considered model with maximum possible number of couplings allows us to describe the most complex and diverse behavior that may be observed in biological neural associations. A feature of the k-dominance modes we have considered is that some of the network neurons are in a non-working (refractory) state. Each periodic k-dominance mode can be associated with a binary vector (α1, α2, . . . , αm), where αj = 1 if the j-th neuron is active and αj = 0 otherwise. Taking this into account, we come to the conclusion that these modes can be used to build devices with associative memory based on artificial neural networks.

ДОСЛІДЖЕННЯ СЕНСОРА ТЕМПЕРАТУРИ З ЧАСТОТНИМ ВИХОДОМ НА ОСНОВІ КВАНТОВОЇ ГЕТЕРОСТРУКТУРИ З ВІД’ЄМНИМ ДИФЕРЕНЦІЙНИМ ОПОРОМ

Physical processes in a quantum two-barrier heterostructure, which is the basis for the development of tunnel-resonant diodes, are considered. These studies have shown that tunnel resonance diodes can be used as temperature sensors with a frequency output signal. The use of devices with negative differential resistance makes it possible to significantly simplify the design of temperature sensors in the entire radio frequency range, at which, depending on the operating modes of the sensor, an output signal can be obtained both in the form of harmonic oscillations and in the form of impulse oscillations of a special form. The study of the characteristics of the sensor is based on the equivalent circuit of the tunnel-resonant diode, which takes into account its capacitive and inductive properties. The current-voltage characteristic of the sensor has a falling section, which is responsible for the appearance of a negative differential resistance in this section. The descending section arises due to a decrease in the current that flows through the double-barrier quantum heterostructure, with an increase in voltage. A decrease in the current occurs due to a decrease in the transparency coefficient of the potential barriers of the heterostructure. A mathematical model of the temperature sensor has been developed, on the basis of which the analytical dependences of the change in the elements of the equivalent circuit of the sensor on temperature, as well as the transformation function and sensitivity, have been determined. It is shown that the main contribution to changes in the conversion function and sensor sensitivity is made by the change in the negative differential resistance with a change in temperature. This, in turn, results in different readings of the instrument’s output frequency. The sensor sensitivity was varied from 480 kHz/0С to 220 kHz/0С in the temperature range from -150 0С to 50 0С.

Experimental Study on the Effect of Lightning Impulse Oscillation Frequency on Pressboard Flashover in Oil

In this work, effect of the oscillation frequency on the oil surface flashover characteristics under lightning impulse voltage is experimentally studied. Four lightning impulse (OLI) waves with different oscillation frequencies and 1.2/50 μs standard lightning impulse (SLI) wave are used in this study. The experiment results show that flashover voltages under OLI are larger than those under SLI and the flashover time lags under OLI are longer than those under SLI. Additionally, the flashover voltage tends to increase and the time lag tends to be shorter as the oscillation frequency increases. According to the experimental results and the discharge theory of liquids, we believe that the waveform oscillation frequency affects both the effective electron generation time lag and the formative time lag. This work provides a reference for the waveform selection of the on-site withstand voltage test and explains the physical mechanism of the oil flashover discharge from the perspective of impulse waveform oscillation.

Respiratory impedance measured using impulse oscillometry in a healthy urban population.

This study derives normative prediction equations for respiratory impedance in a healthy asymptomatic urban population using an impulse oscillation system (IOS). In addition, this study uses body mass index (BMI) in the equations to describe the effect of obesity on respiratory impedance.Data from an urban population comprising 472 healthy asymptomatic subjects that resided or worked in lower Manhattan, New York City were retrospectively analysed. This population was the control group from a previously completed case–control study of the health effects of exposure to World Trade Center dust. Since all subjects underwent spirometry and oscillometry, these previously collected data allowed a unique opportunity to derive normative prediction equations for oscillometry in an urban, lifetime non-smoking, asymptomatic population without underlying respiratory disease.Normative prediction equations for men and women were successfully developed for a broad range of respiratory oscillometry variables with narrow confidence bands. Models that used BMI as an independent predictor of oscillometry variables (in addition to age and height) demonstrated equivalent or better fit when compared with models that used weight. With increasing BMI, resistance and reactance increased compatible with lung and airway compression from mass loading.This study represents the largest cohort of healthy urban subjects assessed with an IOS device. Normative prediction equations were derived that should facilitate application of IOS in the clinical setting. In addition, the data suggest that modelling of lung function may be best performed using height and BMI as independent variables rather than the traditional approach of using height and weight.

New observations in Central Italy of groundwater responses to the worldwide seismicity

Chemical and physical responses of groundwater to seismicity have been documented for thousands of years. Among the waves produced by earthquakes, Rayleigh waves can spread to great distances and produce hydrogeological perturbations in response to their passage. In this work, the groundwater level, which was continuously recorded in a monitoring well in Central Italy between July 2014 and December 2019, exhibited evident responses to dynamic crustal stress. In detail, 18 sharp variations of the groundwater level due to worldwide Mw ≥ 6.5 earthquakes were observed. Apart from earthquakes that occurred in Papua New Guinea and those with a hypocentral depth > 150 km, all far away Mw ≥ 7.6 earthquakes produced impulsive oscillations of groundwater. As the earthquake magnitude decreased, only some earthquakes with 6.5 ≤ Mw < 7.6 caused groundwater level perturbations, depending on the data acquisition frequency and epicentral distance from the monitoring well. A clear correlation between earthquake distance and magnitude in hydrogeological responses was found. Our results shed light on the hydrosensitivity of the study site and on the characteristics of fractured aquifer systems. Detecting the water table variations induced by distant earthquakes is another step towards a correct identification of (preseismic) hydrogeological changes due to near-field seismicity.

Airway mechanics after withdrawal of a leukotriene receptor antagonist in children with mild persistent asthma: Double-blind, randomized, cross-over study.

To determine the response of airway mechanics and the changes in asthma symptoms to stepping down of leukotriene receptor antagonist (LTRA) therapy. Thirty children (mean age: 7.1 years) with mild, well-controlled, and persistent asthma who took LTRA as maintenance treatment were randomized into a double-blind, placebo-controlled, cross-over study. Each group received an LTRA (montelukast) or placebo daily for 2 weeks, followed by a 1-week washout period, and then the alternate treatment for 2 weeks. Spirometry and impulse oscillation system (IOS) measurements before and after four puffs of salbutamol inhalation, fractional exhaled nitric oxide (FeNO), and the childhood asthma control test (C-ACT) were evaluated at baseline, the end of placebo treatment, and the end of LTRA treatment. Changes of FEV1 /FVC (p = .113) and FEV1 (p = .109) from baseline to posttreatment did not differ significantly between the placebo and montelukast groups. In the placebo group, prebronchodilator (pre-) FEV1 /FVC was decreased (83% vs. 86%) and bronchodilator response (BDR) in FEV1 was diminished (10.7% vs. 6.4%) at posttreatment compared with baseline. However, the montelukast group had no significant changes in pre-FEV1 /FVC (p = .865) and BDR in FEV1 (p = .461). In addition, compared with the montelukast group, the placebo group showed no significant changes in Rrs5 (total airway resistance), Rrs5-20 (peripheral airway resistance), FeNO, and symptoms by the C-ACT. In children with well-controlled mild persistent asthma, changes in spirometry, IOS, FeNO, and C-ACT results did not differ between the placebo and montelukast groups within 2 weeks.

Time-resolved ion velocity measurements in a high-power Hall thruster using laser-induced fluorescence with transfer function averaging

We present time-resolved laser-induced fluorescence measurements of ion velocity distributions in a 12.5 kW Hall Effect Rocket with Magnetic Shielding (HERMeS) operating in both quasi-periodic and aperiodic oscillation regimes. Transfer function averaging in Fourier space is used to obtain useable signal-to-noise ratios and synchronize data traces taken at different laser wavelengths, measurement axes, and positions in the plasma, achieving a measurement bandwidth of ∼100 kHz. For breathing-mode like global oscillations, the results are shown to be robust to the choice of either discharge current Id(t) or cathode-to-ground voltage Vcg(t) as the reference waveform input to the transfer function. At discharge voltage Vd=600 V, a nearly periodic, impulsive oscillation in the acceleration zone position was accompanied by a ≳100 V peak-to-peak oscillation in the near-plume plasma potential. Smaller amplitude, aperiodic oscillations in the mean ion velocities were detected at Vd=300 V.

Stability of stochastic discrete-time piecewise homogeneous Markov jump systems with time delay and impulsive effects

This paper considers the stability of stochastic nonlinear discrete-time impulsive systems with time delay and Markov jumps. The transition probabilities of Markov jumps are finite piecewise homogeneous and the variations in the finite set are contingent on a higher-level transition probability matrix. By Lyapunov functional method and the discrete average impulsive interval approach, several novel stability criteria are obtained, which can loosen the constraint on impulsive intervals and thus reduce the conservativeness compared with previous results that take the upper/lower bound of all impulsive intervals. Also, our results are suitable for both stable impulses and unstable impulses. As illustrations, the obtained results are applied to stochastic impulsive neural networks and stochastic impulsive oscillator model, respectively. The simulations are also presented to support and validate the theoretical results.

Cyclostationary modeling for local fault diagnosis of planetary gear vibration signals

Owing to the rotation and reciprocation of mechanical equipment, their vibration signals inherently exhibit cyclic stationary characteristics. This paper provides a phenomenological signal model of the planetary gear vibrations under the cyclostationarity paradigm. The model is helpful to give comprehensive demodulation information which is the limit of classic spectral analysis of deterministic signals, so that the diagnosis of local faults in planetary gear sets can be more explicit. First, the effects of rotating speed fluctuation on periodic gear meshing vibrations are analyzed. It is shown that the stationary speed fluctuation will turn the periodicity of signals into second-order cyclostationarity. Next, an impulsive oscillation sequence with interval timing jitter is used to describe the dynamic response of the meshing stiffness change caused by local defects. Meanwhile, the influence of a vibration transfer path is also considered in the model. Based on the above analysis, the following procedure is utilized to analyze planetary gearbox vibrations: remove the periodic components by the self-adaptive noise cancellation method and then, apply the second-order frequency descriptor to reveal fault features of the signals. Both the simulation and experiment are used to validate the correctness of model derivation and the superiority of the cyclostationary analysis.

Fault Diagnosis of Brushless DC Motors Using Built-In Hall Sensors

In this paper, a method for fault detection of brushless direct current (BLDC) motors is proposed simply based on the hall sensors that exist in most of the BLDC motors. Two important faults in these motors are bearing faults and demagnetization fault. In the first step, the effects of bearing faults on the BLDC motor speed are studied. Then, using the discrete wavelet transform (DWT) and the continuous wavelet transform (CWT), a residual signal is extracted from the speed signal and analyzed in the time–frequency domain. It will be shown that the residual signal contains the main features of bearing faults such as bearing fault frequencies. In the second step, the effects of the demagnetization fault on the hall sensors outputs are studied. It is shown that the demagnetization fault leads to impulsive oscillations in the duty cycle signal of the hall sensors outputs. Using the kurtosis index of the duty cycle signal, the rotor condition is classified into either a healthy condition or a demagnetized condition. In the third step, using an experimental setup, the efficiency of the proposed methods is demonstrated. The proposed algorithms are simple and only use hall sensors for fault detection and hence lead to a simple and cheaper fault diagnosis system.

Dynamics of flexible plates and flow under impulsive oscillation

The induced flow and the dynamics of flexible plates under heaving characterized by impulsive acceleration patterns Π(t) were experimentally inspected for various Cauchy numbers Ca and fractions τa of the time under acceleration with respect to the period of oscillations T. Simultaneous measurements of the plate motion along their span and the surrounding flow were obtained with particle tracking velocimetry (PTV) and particle image velocimetry (PIV). The Π(t) function was imposed at the root of a low-aspect-ratio plate vertically submerged in a quiescent water tank. Results show that Ca and τa significantly modulated the plate dynamics as well as the induced flow and coherent motions. We developed a simple model to estimate the velocity difference Δu between the root and tip of the plates; it is based on the damped harmonic oscillator and exhibits good performance across the fifteen scenarios inspected (three Ca by five τa). In general, the plate dynamics and flow exhibited three distinctive patterns characterized by flapping-like motions, translation-like motions and another intermediate state. The type of motion was induced by the relative instant at the reverse direction within the forced Π(t)-heaving within one of three characteristic stages; two of them depending on the sign of Δu and the other when Δu→0, i.e., in the limit of pure translation.

Comparison of Forced and Impulse Oscillometry Measurements: A Clinical Population and Printed Airway Model Study

The use of commercialised forced oscillation (FOT) devices to assess impedance in obstructive diseases such as asthma has gained popularity. However, it has yet to be fully established whether resistance and reactance measurements are comparable across different FOT devices, particularly in disease. We compared two commercially available FOT devices: Impulse Oscillometry (IOS) and TremoFlo FOT (Thorasys) in a) clinical adult population of healthy controls (n = 14), asymptomatic smokers (n = 17) and individuals with asthma (n = 73) and b) a 3D printed CT-derived airway tree model resistance, as well as a 3 L standardised volume reactance. Bland-Altman Plots and linear regressions were used to evaluate bias between the devices. Resistance measurements at both 5 and 20 Hz were numerically higher with IOS compared to FOT, with evidence of small and statistically significant proportional systematic bias and a positive Bland-Altman regression slope at both 5 and 20 Hz. In contrast, the IOS device recorded reactances that were less negative at both 5 Hz and 20 Hz and significantly smaller reactance areas when compared to TremoFlo. Larger statistically significant proportional systematic biases were demonstrated with both reactance at 5 Hz and reactance area (AX) between the devices with a negative Bland-Altman regression slope. The printed airway resistance and standardised volume reactance confirmed the observations seen in patients. We have demonstrated that the impulse oscillation system and TremoFlo FOT demonstrate comparative bias, particularly when comparing airway reactance in patients. Our results highlight the need for further standardisation across FOT measurement devices, specifically using variable test loads for reactance standardisation.

A Novel Fault Diagnosis Method of Gearbox Based on Maximum Kurtosis Spectral Entropy Deconvolution

Minimum entropy deconvolution (MED) is widely used in the gearbox fault diagnosis because it can enhance the energy of the impact signal. However, it is sensitive to single abnormal impulsive oscillation. This is because it takes kurtosis as the objective function and solves the optimal filter by iteration. In addition, the filter length is not adaptive and needs to be determined artificially. This paper proposes a maximum kurtosis spectral entropy deconvolution (MKSED) method and applies it to bearing fault diagnosis. Considering that the kurtosis spectral entropy has the advantage of highlighting the continuous impact oscillation, the kurtosis spectral entropy is chosen as the objective function of deconvolution. At the same time, kurtosis spectral entropy is also used as the fitness function of improved local particle swarm optimization algorithm (LPSO), and the filter length is optimized by LPSO, which makes that MKSED adaptively determines the length of the filter while solving the deconvolution, so that it can accurately extract the continuous pulse signal. The results of the simulation signal analysis show that the proposed MKSED method is superior to MED, and the proposed method is applied to bearing fault diagnosis, which verifies its ability to extract continuous impact.

RESPONSES OF CONCRETE VERTICAL WALLS TO TSUNAMI WAVE PRESSURES AND DEBRIS IMPACT

By carrying out a set of experiments on the responses of vertical concrete/RC walls to tsunami impacts, the characteristics of the responses of concrete/RC walls to tsunami impacts were investigated. Experiments on both the responses of walls to only tsunami wave pressure and those to both tsunami wave pressure and debris collision were carried out. In experiments on the responses only to tsunami wave pressure, flexural failure at the base of the wall was observed when the bending moment at the base of the wall was greater than the predicted cracking moment. In experiments on the responses to both tsunami wave pressure and debris impact, flexural cracks and failure at the base of the wall were observed in some cases, and impulsive oscillations whose frequency immediately after debris collision depended on the debris material were observed.