Dominant Frequency Range Research Articles

Study on subway resilient wheel's influence on noise inside the vehicle and in the bogie area through the in-situ measurements

Based on a new type of resilient wheel installed on a subway train, a measurement campaign is devised to evaluate the effectiveness of the resilient wheel in reducing noise. For reference, the same series of tests are carried out on another train of the same type but fitted with conventional wheels. The measurements involve the noise of various parts of the vehicle-track system which are used to investigate the sources of wheel-rail rolling noise, the noise inside the vehicle, and the noise close to the wheels. The series of tests are conducted on the normal-conditioned and corrugated track on which the two sets of trains pass through at difference speeds. It is found that the decrease of interior noise measured on the corrugated track is within the range of 0.2~10.5 dB(A), which is greater than on normal conditioned track after using the resilient wheels. This attributes to the frequency range available for vibration reduction by using the resilient wheel covers the dominant frequency range of the excitation from corrugation.

Surface wave isolation by variable depth infilled trenches

Excessive environmental vibrations generated by urban traffic pose adverse effects on nearby structures and residents. These vibrations are predominantly carried by surface waves, which are localized within the surface layer of soil. The isolation of surface waves through the embedding of periodic wave barriers in soils between the source and the receiver has gained significant attention in recent years. In this paper, a novel approach is proposed for isolating surface waves induced by urban traffic through the use of variable depth infilled trenches. This innovative design not only achieves efficient surface wave isolation but also minimizes the consumption of structural materials. Based on the measured dominant frequency range of rail transit and the available soil parameters, variable depth infilled trenches are designed with suitable dimensions. The eigenvalue equation is solved using the finite element method to derive the dispersion relations and bandgap of identical regularly spaced trenches. To study the efficacy of the proposed structure, a finite element model of the soil-infilled trench system is developed using COMSOL. The mechanism underlying the isolation of surface wave is elucidated, and the effect of variable angle α on the isolation efficiency within 40–50 Hz η40−50Hz of surface waves is studied. The results of this study reveal that for variable angle α of 15°, the surface wave isolation efficiency within 40–50 Hz η40−50Hz is 90.9 % and 92.5 % for uniformly increasing depth infilled trenches and uniformly decreasing depth infilled trenches, respectively. Although the surface wave isolation efficiencies predicted for the variable depth infilled trench arrangements are only 93.8 % and 95.5 % of those predicted for the regularly spaced identical infilled trenches, the variable depth arrangements result in a remarkable 34 % reduction in material usage. These findings highlight the potential of the proposed variable depth infilled trenches as a cost-effective and efficient solution for surface wave isolation.

Triaxial failure behavior and microfracture source time–frequency characteristics of marble under in situ stress conditions at different depths considering engineering disturbance

The safety of the surrounding rock in deep underground engineering is crucial. To understand the surrounding rock hazards at different depths of the Jinping underground cavern, triaxial compression tests were conducted, and the acoustic emission (AE) of Jinping marble samples was monitored while considering the influence of engineering disturbances and in situ stress conditions at different burial depths (100 m, 1000 m, 1400 m, 1800 m, and 2400 m). The results revealed that the AE events were dominated by small and medium-sized energy releases of magnitude 0–2, accounting for approximately 90 % of all AE events. The dominant frequency range of the microfracture sources was 0–450 kHz. As the burial depth increases, the AE frequency band aggregation time tended to stabilise at the average frequency during the loading process, and the failure mode trended towards ductile failure. This study offers theoretical support for assessing the operational security of deep underground caverns.

Chaos control in cardiac dynamics: terminating chaotic states with local minima pacing.

Current treatments of cardiac arrhythmias like ventricular fibrillation involve the application of a high-energy electric shock, that induces significant electrical currents in the myocardium and therefore involves severe side effects like possible tissue damage and post-traumatic stress. Using numerical simulations on four different models of 2D excitable media, this study demonstrates that low energy pulses applied shortly after local minima in the mean value of the transmembrane potential provide high success rates. We evaluate the performance of this approach for ten initial conditions of each model, ten spatially different stimuli, and different shock amplitudes. The investigated models of 2D excitable media cover a broad range of dominant frequencies and number of phase singularities, which demonstrates, that our findings are not limited to a specific kind of model or parameterization of it. Thus, we propose a method that incorporates the dynamics of the underlying system, even during pacing, and solely relies on a scalar observable, which is easily measurable in numerical simulations.

Influence of Immersion Time on the Frequency Domain Characteristics of Acoustic Emission Signals in Clayey Mineral Rocks.

The frequency domain characteristics of acoustic emission can reflect issues such as rock structure and stress conditions that are difficult to analyze in time domain parameters. Studying the influence of immersion time on the mechanical properties and acoustic emission frequency domain characteristics of muddy mineral rocks is of great significance for comprehensively analyzing rock changes under water-rock coupling conditions. In this study, uniaxial compression tests and acoustic emission tests were conducted on sandstones containing montmorillonite under dry, saturated, and different immersion time conditions, with a focus on analyzing the effect of immersion time on the dominant frequency of rock acoustic emission. The results indicated that immersion time had varying degrees of influence on compressive strength, the distribution characteristics of dominant acoustic emission frequencies, the frequency range of dominant frequencies, and precursor information of instability failure for sandstones. After initial saturation, the strength of the rock sample decreased from 53.52 MPa in the dry state to 49.51 MPa, and it stabilized after 30 days of immersion. Both dry and initially saturated rock samples exhibited three dominant frequency bands. After different immersion days, a dominant frequency band appeared between 95 kHz and 110 kHz. After 5 days of immersion, the dominant frequency band near 0 kHz gradually disappeared. After 60 days of immersion, the dominant frequency band between 35 kHz and 40 kHz gradually disappeared, and with increasing immersion time, the dominant frequency of the acoustic emission signals increased. During the loading process of dry rock samples, the dominant frequency of acoustic emission signals was mainly concentrated between 0 kHz and 310 kHz, while after saturation, the dominant frequencies were all below 180 kHz. The most significant feature before the rupture of dry rock samples was the frequent occurrence of high frequencies and sudden changes in dominant frequencies. Before rupture, the characteristics of precursor events for initially saturated and immersed samples for 5, 10, and 30 days were the appearance and rapid increase in sudden changes in dominant frequencies, as well as an enlargement of the frequency range of dominant frequencies. After 60 days of immersion, the precursor characteristics of rock sample rupture gradually disappeared, and sudden changes in dominant frequencies frequently occurred at various stages of sample loading, making it difficult to accurately predict the rupture of specimens based on these sudden changes.

A Robust Model Order Reduction Scheme for Lithium-Ion Batteries in Control-Oriented Vehicle Models

The role of batteries in electrification of vehicles is eminent; thus, a dynamic model that represents the physics-based phenomena of the battery system at a minimum computational cost is essential in the model-based design of electrified vehicle control systems. Furthermore, robustness of the reduced-order battery model when maintaining the dominant physics-based phenomena governing the dynamic behavior of the battery system is crucial. Characterization of the power signal applied to the lithium-ion battery in the energy management controller of a plug-in hybrid electric vehicle shows that there is a dominant frequency range in the input signal to the battery. This key feature can be considered as a basis to construct a reduced-order model in which the training input is different from the original power signal. The original idea in this paper is to generate the training input by applying a low-pass filter to the white-noise random signal to maintain the same dominant frequency range observed in the original power signal. Response of the reduced-order model, constructed using the proper orthogonal decomposition, compared to the high-fidelity battery model shows promising results; a maximum relative error of 1% was obtained for the battery state of charge while simulation time was reduced by 42.9%.

Analysis and intelligent prediction of subway train-induced vibration in the building with pile foundation

The rapid development of subway construction inevitably leads to the subway lines traversing through or adjoining the buildings. However, current research primarily focuses on the train-induced ground-borne or building with shallow foundation vibrations, with a relatively limited investigation into the vibration pertaining to the building with pile foundation. A vibration analysis model of a building with pile foundation adjacent to a subway is established in this study using the finite element method, and the effects of various factors on the vibration of the building are analyzed, then the prediction of building vibration characteristics is also carried out by combining artificial intelligence methods. The results show that the building floor has an amplifying effect on the vibration acceleration level and Z-vibration level in the high frequency range, and the vibration energy attenuation at high frequencies is faster in the building with pile foundation compared to the building with shallow foundation. In the meantime, it shows that the GA-BP model is capable of effectively capturing the vibration characteristics of the building with pile foundation within the dominant frequency range. and the vibration of the building with pile foundation can be predicted not only by parameters such as train speed, soil and structure parameters but also by train-induced ground-borne vibration, which provides the possibility of simplifying the process of vibration prediction process and enhancing the practical application.

The link between the acoustic characteristics of worship spaces and their emotional impact.

The emotional impact of sound depends on its characteristics. Given that such characteristics can be modified when the sound is played in a room, it is crucial to examine how the acoustic characteristic of a room can impact the emotional experience. Researchers have investigated the links between the acoustic parameters of concert halls and the emotional impact; however, the applicability of such links to other building types, such as worship spaces, needs to be studied. In a previous study, the author analyzed the emotional response to the acoustic environments of worship spaces using self-report and physiological indicators. This paper builds on the previous work by analyzing the acoustic parameters of the buildings from the previous study and establishing links between such parameters and the emotional response indicators. It also analyzes the frequency domain to study the role of the interaction between the room and sound source in enhancing the emotional experience and introduces resonance quality (Q) and resonance width (Δf) as important parameters to consider in room acoustics. The results showed the significance of considering frequencies < 1000 Hz in analyzing the acoustics of the studied worship spaces and demonstrated that amplifying the dominant frequency range of the sound source was linked to enhancing the emotional experience.

Hazard analysis of earthquake in Pleret, Bantul Regency, Yogyakarta Special Region based on microtremor data

Pleret, one of the sub-districts in Bantul Regency, Yogyakarta, is prone to earthquakes. This area is traversed by an active fault system known as the Opak fault, with a maximum magnitude of 6.6 Mw. The local geological conditions can be determined based on microtremor data from 43 measurement points. The purpose of this research is to understand the dynamic characteristics of the local geological conditions, including the dominant frequency (f0), shear wave velocity (Vs30), peak ground acceleration (PGA), and to map the earthquake impacts on the population and structures. Microtremor measurements were conducted for approximately 20 minutes, revealing a dominant frequency range of 0.61-10.85 Hz. The HVSR curve inversion revealed the Vs30 range 213 to 826 m/s distribution. Peak Ground Acceleration (PGA) values varied from 0.16 to 0.26 g. Using InaSAFE software, the estimated affected population reached 49,052 people, with over 23,176 structures affected. The results of this mapping are expected to be utilized as a step towards enhancing disaster preparedness.

Research on Vibration Characteristics of a Flexible Vehicle-Ladder Track System

As a means of vibration reduction, the ladder track has seen broad implementation in urban rail transit. However, issues such as increased vibration noise, rail corrugation, and fastener failure have been observed in certain sections of the ladder track during later operation. To investigate the mechanisms behind these phenomena and provide comprehensive insights into the system's response to various operational conditions, this study employed vehicle-track coupled dynamic theory to establish a three-dimensional finite element model of the flexible vehicle-ladder track system. The vibration transmission and dynamic response characteristics of the vehicle-ladder track system were analyzed. The findings revealed that the vehicle-track resonance and anti-resonance phenomena were more prominent in the medium- to low-frequency range. At specific frequencies, the wheelset exhibited various vibration modes, and the fastener force was found to closely correlate with the ladder vibration mode. Furthermore, the influence of speed on diverse components of the vehicle-ladder track system, in terms of maximum vibration and the dominant vibration frequency range, differed considerably. This study provides a more comprehensive and reasonable exploration of the modeling and dynamic behavior of vehicle-ladder track systems.

Seismic Microzonation Map of Chiang Mai Basin, Thailand

The seismic site effect which is controlled by local geological conditions is a key parameter of seismic hazards analysis. This paper presents an observational study of microtremor data to investigate the dynamic characteristics of soil in the Chiang Mai basin (Chiang Mai and Lumphun province), Northern Thailand. The Chiang Mai basin was formed on terrace sediments and alluvium sediments. The horizontal vertical spectral ratio (HVSR) analyses of ambient noise data at 101 sites in the basin were analyzed for an average smoothed HVSR curve to estimate the amplification factor and fundamental resonance frequency of each observation point. We also evaluated the shear wave velocity using the HVSR inversion technique based on the diffuse field assumption. Tests undertaken include a comparison of the HVSR of a significant earthquake that was detected at stations in the basin and a nearby bedrock site. The results indicate that the resonance frequency ranges between 0.15 - 0.4 Hz at sites having large thicknesses of soft sediments. The lowest resonance frequencies occur in the center of the basin, whereas higher resonance frequencies were observed in the areas of the shallowest bedrock in the west and east of the basin. It can be inferred that the western margin of the Chiang Mai basin is a steep slope, while the eastern margin of the basin is a low-angle west-dipping basement. The amplification factor ranges between 3 - 5 times, in the middle of the basin. Most of the Chiang Mai basin area is classified as site D soil (stiff soil) relative to alluvium sediments, and a region of class C soil (very dense soil) conforms to the terrace sediments located on the eastern edge of the basin. The soil classification is based on shear wave velocity (Vs30) determined by HVSR inversion. HIGHLIGHTS HVSR analysis and inversion of HVSR from 101 survey points in Chiang Mai basin The Chiang Mai basin area is at high risk from seismic amplification that amplifies a ground motion between 3 - 5 times in the middle of the basin at a dominant frequency range from 0.15 - 0.4 Hz The lowest Vs30 values location is in the middle of the basin classified as site class E (soft soil), while most of the basin area is classified as site D soil (stiff soil) corresponding to alluvium sediments. The class C soil (very dense soil) area conforms to the terrace sediments located on the eastern edge of the basin GRAPHICAL ABSTRACT

Determinatioan Of Sediment Thickness By Using Microtremor Data In Kadia Sub-District, Kendari City

This study aims to determine the value of the distribution of sediment layer thickness. This research was conducted in the Kadia District area, Kendari City, with data collection carried out at 16 measurement points with intervals for each point varying from 400 to 600 meters with a sampling frequency of 100 Hz. The data obtained from this study is in the form of ground vibration data which is then downloaded software DataPro.exe East-Westhorizontal component, the North-South vertical component Up-Down. The downloaded microtremor data is then processed using a device software Geopsy 4.3.2 to obtain the H/V curve. The dominant frequency value (f0) is obtained from the H/V curve with a dominant frequency range of 1.247 Hz to 4.955 Hz and the shear (VS30) is obtained from the website www.USGS.gov with a VS30 of 276 m/s up to 301 m/s. Based on the data that has been obtained, the distribution value of the sediment layer thickness (h) will be determined. The value of the thickness of the sediment layer (h) in the study area ranged from 13,016 meters to 59,473 meters.

A comparative characterization of recording devices for vibration signals on the example of &lt;i&gt;Heterocerus fenestratus&lt;/i&gt; (Thunberg, 1784) (Coleoptera: Heteroceridae)

Works on vibration communication for Orthoptera and Hemiptera are widely known in Russian literature. Basically, the piezoelectric adapter GZK-661 or the electromagnetic transducer GZM-105 are used for recording this communication. The use of these devices does not give satisfactory results when recording insects smaller than 1 cm. In this paper we consider a comparative characteristic of recording devices based on the piezoelectric transducer GZK-661, electromagnetic transducer GZM-105 and electrodynamic head eas15s02m when recording vibration communication of near-water rigid-winged Heterocerus fenestratus (Thunberg, 1784) (Coleoptera: Heteroceridae). A comparative analysis of the efficiency of the three transducers considered in this paper shows that the transducer based on the electrodynamic loudspeaker head used as a signal source (reverse mode of operation) has the best characteristics. In addition, the shielded magnetic system of the dynamic head provides high magnetic induction in the working gap and insensitivity to inductions from external electromagnetic fields. 176 stress signals were recorded for males and 189 for females. The range of dominant frequencies ranged from 857,29 to 1002,01 Hz for males and from 898,04 to 1189,12 Hz for females.

Seismic Signal Characteristics and Numerical Modeling Analysis of the Xinmo Landslide

Due to the high elevation and huge potential energy of high-level landslides, they are extremely destructive and have prominent kinetic-hazard effects. Studying the kinetic-hazard effects of high-level landslides is very important for landslide risk prevention and control. In this paper, we focus on the high-level landslide that occurred in Xinmo on 24 June 2017. The research is carried out based on a field geological survey, seismic signal analysis, and the discrete element method. Through ensemble empirical mode decomposition (EEMD) and Fourier transformation, it is found that the seismic signals of the Xinmo landslide are mainly located at low frequencies of 0–10 Hz, and the dominant frequency range is 2–8 Hz. In addition, the signal time-frequency analysis and numerical simulation calculation results reveal that the average movement distance of the sliding body was about 2750 m, and the average movement speed was about 22.9 m/s. The movement process can be divided into four main stages: rapid start, impact loading, fragmentation and migration, and scattered accumulation stages. We also provide corresponding suggestions for the zoning of high-level landslide geological hazards.

A Rapid Learning Model based on Selected Frequency Range Spectral Subtraction for the Data-Driven Fault Diagnosis of Manufacturing Systems

Limited amount of training dataset is often a critical problem in developing a diagnosis model or computational intelligence of mechanical failures. In this paper, we propose a Selected Frequency Range Critical Information Map (SFCIM)-based data-driven diagnosis method for detecting mechanical system failure with a relatively small amount of available dataset. The algorithm determines whether there is a failure with reference to normal condition signals using the spectral subtraction method. In this process, time-domain synchronization and time-frequency representation are applied. In addition, the dominant frequency range is selected based on Fisher’s scores for the more efficient calculation. We designed this algorithm to provide users with time-frequency domain information about system failure through SFCIM instead of the only simple decision of diagnosis. The usefulness of our method has been checked with the following problems of the small amount of available dataset: diagnoses of (1) the IMS bearing faults, (2) input gear faults of a manipulator driving system, and (3) a driving system of an industrial robot by load current signals. From these case studies, we also confirmed that the proposed method was practical and useful for fault diagnosis regardless of signal types, such as stationary, non-stationary, accelerometer-based vibration, or current signal.

Performance evaluation of different micro vortex generators in controlling a flare-induced shock–boundary layer interaction

This study evaluates the ability of five micro vortex generator (MVG) geometries in attenuating the flow separation induced by an axisymmetric compression corner. Experimental and computational investigations were carried out at Mach 2 on a cone–cylinder–flare model, with a flow deflection angle of 24° at the cylinder/flare juncture. The MVG shapes considered were baseline ramp, trapezoidal ramp, split ramp, thick vanes and ramped vanes. A circumferential array of these MVGs having a device height (h) of 1.4 mm and an inter-device spacing of 10.5 mm (7.5 h) was introduced 50 mm upstream of the compression corner. Streamwise counter-rotating vortex pairs that originated from these devices created alternate bands of upwash and downwash regions in the incoming boundary layer, which resulted in suitable three-dimensional alterations of the separation region’s size. Furthermore, surface streamline visualizations showed that the vortices induced profound topological transformations in the separated flow structure. In the absence of MVGs, spectral analysis of the pressure signal obtained from the separation shock’s intermittent region revealed a relatively broadband dominant frequency range of 0.55 kHz–0.9 kHz. The MVGs did not cause any significant change in the dominant frequency, but made the bandwidth slightly narrower. Among the different MVG designs that were studied, the ramped vanes (RV) induced the most momentum augmentation in the near wall region and thereby caused the maximum downstream shift in the separation shock’s position.

Acoustic Emission Source Characterisation during Fatigue Crack Growth in Al 2024-T3 Specimens.

While acoustic emission (AE) testing can be used as a valuable technique in structural health monitoring and non-destructive testing, little research has been conducted to establish its sources, particularly in 2024-T3 aluminium alloys. The major contribution of this work is that it provides a method to obtain a better linear relationship of count rate with crack growth rate based on waveform. This paper aims to characterise AE sources by synchronising the AE waveforms with load levels and then to propose possible dominant frequency ranges. The AE waveforms during fatigue crack growth in edge-notched 2024-T3 aluminium specimens, from an initial crack length of 10 mm to 70 mm, were collected at two different load ratios R = 0.125 and 0.5. At the same time, the crack growth rate was determined using thermal imaging and associated control software. The AE waveforms obtained were processed using the fast Fourier transform. It was shown that a significantly higher AE count rate was recorded at R = 0.125 compared to R = 0.5 when the maximum load was kept the same. This means that the R-ratio would affect the total amount of AE activities collected. It was also found that the dominant frequency range of the AE waveforms directly related to crack growth was 152-487 kHz, and the ranges due to crack closure were likely to be 310 kHz-316 kHz and 500-700 kHz. Based on the proposed frequency ranges, waveform selection was conducted and a better linear relationship between count rate and crack growth rate was observed. This study provides a better understanding of the AE sources and waveforms for future structural health monitoring applications.

Subinertial Variability in Four Southeast Greenland Fjords in Realistic Numerical Simulations

AbstractWe identified the nature and driving mechanisms of subinertial variability (variability at a time scale of several days) in four fjords in Southeast Greenland, in three high‐resolution numerical simulations. We find two dominant frequency ranges in along‐fjord velocity, volume transport of Atlantic Water, and along‐fjord heat transport: one around 2–4 days and one around 10 days. The higher frequency is most prominent in the two smaller fjords (Sermilik Fjord and Kangerdlugssuaq Fjord), while the lower frequency peak dominates in the larger fjords (Scoresby Sund and King Oscar Fjord). The cross‐fjord structure of variability patterns is determined by the fjord's dynamic width, while the vertical structure is determined by the stratification in the fjord. The dominant frequency range is a function of stratification and fjord length, through the travel time of resonant internal Kelvin waves. We find that the subinertial variability is the imprint of Coastal Trapped Waves, which manifest as Rossby‐type waves on the continental shelf and as internal Kelvin‐type waves inside the fjords. Between 50% and 80% of the variability in the fjord is directly forced by Coastal Trapped Waves propagating in from the shelf, with an additional role played by alongshore wind forcing on the shelf.

Noise from above: A summary of studies regarding the perceived annoyance due to impact sounds

To support efforts of introducing an impact sound requirement into the National Building Code of Canada (NBCC), the National Research Council of Canada has initiated a long-term research project. In cooperation with the Hochschule Duesseldorf in Germany and Kangwon National University in Korea, several listening tests were performed to investigate the annoyance due to impact sound as it is perceived by building occupants, and how this annoyance relates to the results of standardized laboratory measurements. In this contribution, the different listening test setups will be described and compared. Tests were performed in the laboratory using loudspeakers, headphones, and also with a Virtual Reality headset. In addition, an online listening test was launched to expand the reach of such studies to the general population. The results will be summarized and discussed regarding appropriate rating methods. The goal of these studies is to gain a better understanding of the relevant factors that affect the perceived annoyance, such as the impact source type and the dominant frequency range, but also how the test environment influences the results.

Deep learning-based noise robust flexible piezoelectric acoustic sensors for speech processing

Flexible piezoelectric acoustic sensors (f-PAS) have attracted significant attention as a promising component for voice user interfaces (VUI) in the era of artificial intelligence of things (AIoT). The signal distortion issue of highly sensitive biomimetic f-PAS is one of the most challenging obstacle for real-life application, due to the fundamental difference compared with the conventional microphones. Here, a noise-robust flexible piezoelectric acoustic sensor (NPAS) is demonstrated by designing the multi-resonant bands outside the noise dominant frequency range. Broad voice coverage up to 8 kHz is achieved by adopting an advanced piezoelectric membrane (Nb-doped PZT; PNZT) with the optimized polymer ratio. Deep learning-based speech processing of multi-channel NPAS is demonstrated to show the outstanding improvement in speaker recognition and speech enhancement compared to a commercial microphone. Finally, the NPAS filtered the crowd condition noises, showing independent speaker’s speeches can be identified and digitalized simultaneously.