scholarly journals Study of railway curve squeal in the time domain using a high-frequency vehicle/track interaction model

2018 ◽  
Vol 431 ◽  
pp. 177-191 ◽  
Author(s):  
J. Giner-Navarro ◽  
J. Martínez-Casas ◽  
F.D. Denia ◽  
L. Baeza
Keyword(s):  
Time Domain ◽  
High Frequency ◽  
Interaction Model ◽  
The Time Domain ◽  
Curve Squeal

scholarly journals Development of a vehicle–track interaction model to predict the vibratory benefits of rail grinding in the time domain

2015 ◽  
Vol 23 (3) ◽  
pp. 189-201 ◽  
Author(s):  
Julia Irene Real ◽  
Clara Zamorano ◽  
José Luis Velarte ◽  
Antonio Enrique Blanco
Keyword(s):  
Time Domain ◽  
Interaction Model ◽  
Rail Grinding ◽  
The Time Domain

scholarly journals Approximating spheroid inductive responses using spheres

Geophysics ◽  
2006 ◽  
Vol 71 (2) ◽  
pp. G21-G25 ◽  
Author(s):  
J. Torquil Smith ◽  
H. Frank Morrison
Keyword(s):  
Magnetic Fields ◽  
Time Domain ◽  
High Frequency ◽  
Transverse Direction ◽  
High Permeability ◽  
Frequency Limit ◽  
Aspect Ratios ◽  
Oblate Spheroids ◽  
Prolate Spheroids ◽  
The Time Domain

Spheroid responses are important as limiting cases when modeling inductive responses of isolated metallic objects such as unexploded military ordnance. The response of high-permeability ([Formula: see text] ≥ 50) conductive spheroids of moderate aspect ratios (0.25–4) to excitation by uniform magnetic fields in the axial or transverse direction is approximated by the response of spheres of appropriate diameters, of the same conductivity and permeability, with magnitude rescaled based on the differing volumes, dc magnetizations, and high-frequency limit responses of the spheres and modelled spheroids. In the frequency domain, the scaled sphere responses agree within 5% of complex magnitudes for prolate spheroids and within 7% for oblate spheroids. The approximation is more accurate for source magnetic fields in the spheroid's shorter direction than in the spheroid's longer direction. In the time domain, the approximation describes spheroid responses over five decades of time after transmitter shutoff, with a maximum discrepancy of 20%.

Time domain waveform inversion—A frequency domain view: How well we need to match waveforms?

1991 ◽  
Vol 81 (6) ◽  
pp. 2351-2370
Author(s):  
Zoltan A. Der ◽  
Robert H. Shumway ◽  
Michael R. Hirano
Keyword(s):  
Time Domain ◽  
High Frequency ◽  
Waveform Inversion ◽  
Quantitative Measure ◽  
Domain Modeling ◽  
Low Frequencies ◽  
Waveform Modeling ◽  
Time Domain Modeling ◽  
Frequency Components ◽  
The Time Domain

Abstract Waveform modeling in the time domain matches the various frequency components of seismic signals unevenly; the agreement is better at low frequencies and becomes progressively worse towards higher frequencies. The net effect of this kind of time-domain modeling is that the resolution in the spatial details of the source is less than optimal since the high-frequency components of the signal with their short wavelengths to resolve finer details do not fit the data. These problems are demonstrated by numerical simulations and by the reanalysis of some aspects of the El Golfo earthquake in using a new seismic imaging technique based on a generalization of an f-k algorithm. This procedure computes a statistic that can be used to derive confidence limits of the parameters sought in the inversion, thus providing a quantitative measure of the uncertainties in the results.

Development of High Frequency Virtual Thermocouples

2017 ◽  
Author(s):  
James Braun ◽  
Shengqi Lu ◽  
Guillermo Paniagua
Keyword(s):  
Frequency Response ◽  
Time Domain ◽  
High Frequency ◽  
Conjugate Heat Transfer ◽  
Numerical Procedure ◽  
Navier Stokes ◽  
Digital Compensation ◽  
Fine Wire ◽  
The Time Domain ◽  
Thermocouple Probe

This paper presents a numerical procedure to enhance the frequency response of temperature probes equipped with two thermocouple junctions of different diameter. The output of the two thermocouples exposed to the same flow transient can be used to predict the output of a virtual smaller thermocouple, which cannot be physically realized. The approach is demonstrated numerically, with the aid of conjugate heat transfer simulations performed with 3D Unsteady Reynolds Averaged Navier-Stokes. The dual junction thermocouple with wire diameters of 50 μm, 25 μm were exposed to several inlet temperatures and pressures to analyze the overall recovery factor. Then multiple unsteady tests were performed. The analysis of those transient tests was used to determine the transfer function in the time domain between the two wires and to perform a digital compensation to predict the performance of a much thinner wire thermocouple. This method was assessed by recovering the theoretical response of the 12.5 μm thermocouple with our dual-junction thermocouple probe for several pressures and wall temperatures. Finally, the procedure was applied to a virtual fine wire thermocouple of 6 μm and a frequency response around 700 Hz.

Experimental and Numerical Investigation of the Stabilizing Effects of a Water-Entrapment Plate on a Deepwater Minimal Floating Platform

2005 ◽  
Author(s):  
Christian A. Cermelli ◽  
Dominique G. Roddier
Keyword(s):  
Time Domain ◽  
Laboratory Experiments ◽  
Interaction Model ◽  
Coupled Analysis ◽  
Diffraction Radiation ◽  
Floating Platform ◽  
Ship Model ◽  
Testing Facility ◽  
Radiation Theory ◽  
The Time Domain

The stabilizing effects of a water-entrapment plate at the keel of a small three-legged semi-submersible platform are determined using laboratory experiments and time-domain simulations. Motion predictions were carried out in the time-domain using coupled-analysis between the vessel and its mooring, linear diffraction-radiation theory, and an empirical wave-viscous interaction model. Model tests were conducted at the U.C. Berkeley Ship Model Testing Facility to determine the validity of the numerical model.

A Fast ECG Diagnosis by Using Non-Uniform Spectral Analysis and the Artificial Neural Network

2021 ◽  
Vol 2 (3) ◽  
pp. 1-21
Author(s):  
Kun-chih (Jimmy) Chen ◽  
Po-Chen Chien ◽  
Zi-Jie Gao ◽  
Chi-Hsun Wu
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Spectral Analysis ◽  
Power Consumption ◽  
Time Domain ◽  
High Frequency ◽  
Heart Diseases ◽  
Ecg Signal ◽  
Computing Power ◽  
The Time Domain

The electrocardiogram (ECG) has been proven as an efficient diagnostic tool to monitor the electrical activity of the heart and has become a widely used clinical approach to diagnose heart diseases. In a practical way, the ECG signal can be decomposed into P, Q, R, S, and T waves. Based on the information of the features in these waves, such as the amplitude and the interval between each wave, many types of heart diseases can be detected by using the neural network (NN)-based ECG analysis approach. However, because of a large amount of computing to preprocess the raw ECG signal, it is time consuming to analyze the ECG signal in the time domain. In addition, the non-linear ECG signal analysis worsens the difficulty to diagnose the ECG signal. To solve the problem, we propose a fast ECG diagnosis approach based on spectral analysis and the artificial neural network. Compared with the conventional time-domain approaches, the proposed approach analyzes the ECG signal only in the frequency domain. However, because most of the noises in the raw ECG signal belong to high-frequency signals, it is necessary to acquire more features in the low-frequency spectrum and fewer features in the high-frequency spectrum. Hence, a non-uniform feature extraction approach is proposed in this article. According to less data preprocessing in the frequency domain than the one in the time domain, the proposed approach not only reduces the total diagnosis latency but also reduces the computing power consumption of the ECG diagnosis. To verify the proposed approach, the well-known MIT-BIH arrhythmia database is involved in this work. The experimental results show that the proposed approach can reduce ECG diagnosis latency by 47% to 52% compared with conventional ECG analysis methods under similar diagnostic accuracy of heart diseases. In addition, because of less data preprocessing, the proposed approach can achieve lower area overhead by 22% to 29% and lower computing power consumption by 29% to 34% compared with the related works, which is proper for applying this approach to portable medical devices.

The influence of economic policy uncertainty on PIIGS tourism: Evidence from three-dimensional wavelet analyses

2020 ◽  
Author(s):  
Yu-Yu Wu
Keyword(s):  
Economic Policy ◽  
Time Domain ◽  
High Frequency ◽  
Three Dimensional ◽  
Policy Uncertainty ◽  
Economic Policy Uncertainty ◽  
The Time Domain ◽  
Changes Over Time ◽  
The Relationship ◽  
Wavelet Analyses

This paper aims to examine the relationship between Economic Policy Uncertainty (EPU) and tourism activities in Portugal, Ireland, Italy, Greece and Spain (PIIGS) using wavelet transform context structures. The results indicate that the relationships among the variables evolve through time and frequencies. From the time-domain view, we show strong evidence of the relationships between these variables. From the frequency-domain view, we uncover significant wavelet coherences and strong lead-lag interrelationships changes over time, displaying low to high frequency cycles over the whole sample period.

Sign in / Sign up

Export Citation Format

Share Document