Waveform inversion using spectral decomposed signal with a single frequency component

2015 ◽  
Author(s):  
Jiho Ha* ◽  
Wookeen Chung ◽  
Sungryul Shin ◽  
Changsoo Shin
Keyword(s):  
Waveform Inversion ◽  
Frequency Component ◽  
Single Frequency

Full waveform inversion using a decomposed single frequency component from a spectrogram

2018 ◽  
Vol 153 ◽  
pp. 154-167 ◽  
Author(s):  
Jiho Ha ◽  
Seongpil Kim ◽  
Namhyung Koo ◽  
Young-Ju Kim ◽  
Nam-Sub Woo ◽  
...  
Keyword(s):  
Waveform Inversion ◽  
Frequency Component ◽  
Single Frequency ◽  
Full Waveform Inversion ◽  
Full Waveform

Laplace-domain full-waveform inversion of seismic data lacking low-frequency information

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. R199-R206 ◽  
Author(s):  
Wansoo Ha ◽  
Changsoo Shin
Keyword(s):  
Seismic Data ◽  
Field Data ◽  
Waveform Inversion ◽  
Low Frequency ◽  
Single Frequency ◽  
Frequency Content ◽  
Laplace Domain ◽  
Frequency Information ◽  
Velocity Models ◽  
Gaussian Source

The lack of the low-frequency information in field data prohibits the time- or frequency-domain waveform inversions from recovering large-scale background velocity models. On the other hand, Laplace-domain waveform inversion is less sensitive to the lack of the low frequencies than conventional inversions. In theory, frequency filtering of the seismic signal in the time domain is equivalent to a constant multiplication of the wavefield in the Laplace domain. Because the constant can be retrieved using the source estimation process, the frequency content of the seismic data does not affect the gradient direction of the Laplace-domain waveform inversion. We obtained inversion results of the frequency-filtered field data acquired in the Gulf of Mexico and two synthetic data sets obtained using a first-derivative Gaussian source wavelet and a single-frequency causal sine function. They demonstrated that Laplace-domain inversion yielded consistent results regardless of the frequency content within the seismic data.

scholarly journals Classification of metallic targets using a single frequency component of the magnetic polarisability tensor

2013 ◽  
Vol 450 ◽  
pp. 012038 ◽  
Author(s):  
J Makkonen ◽  
L A Marsh ◽  
J Vihonen ◽  
A Visa ◽  
A Järvi ◽  
...  
Keyword(s):  
Frequency Component ◽  
Single Frequency ◽  
Polarisability Tensor

Study of the effect of strain amplitude ratio at two-frequency cyclic loading

2018 ◽  
Vol 84 (12) ◽  
pp. 50-60 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Amplitude Ratio ◽  
Low Frequency ◽  
Frequency Component ◽  
Single Frequency ◽  
High Frequency Component ◽  
Dual Frequency ◽  
Operating Modes ◽  
Cyclic Durability ◽  
Cycle Loading

The operating modes of loading elements of machines and structures exhibit, as a rule, more complicated character of their loading cycles compared to sinusoidal used in the practice of calculations and experiments. It is noted that in a number of cases the actual conditions of load changing can be schematized by dual-frequency loading modes with superposition of the high-frequency component of the main workload attributed to the effects of vibrations, aero- and hydrodynamic impacts, regulation of the working process, etc. Testing of three steel samples which differ in their cyclic properties has shown that such two-frequency regimes lead to a decrease in the durability in comparison with single-frequency loading, equal in the amplitude of maximum stresses. This reduction depends on the parameters of the basic low-frequency and imposed high-frequency loads. Evaluation of this reduction can be performed both i) using the laws of summation of the damage expressed in the strain terms, and ii) using an analytical expression considered below, which includes calculated or experimentally determined durability for single-frequency loading with the maximum (total) amplitude of the effective stress and durability coefficient, characteristic of each type of material and determined by the ratio of amplitudes and hours of low- and high stresses. A computational-experimental analysis of the effect of the amplitude of low-frequency and superimposed high-frequency loading under two-frequency modes of stress change on the cyclic durability showed that the imposition of the high-frequency component of cyclic deformation on the main low-cycle loading process leads to a significant decrease in the cyclic durability, the level of the decrease correlates with the level of amplitudes and frequencies ratios of the summarized harmonic processes of load application.

scholarly journals Fundamental Frequency Suppression for the Detection of Broken Bar in Induction Motors at Low Slip and Frequency

2020 ◽  
Vol 10 (12) ◽  
pp. 4160 ◽  
Author(s):  
Daivd A. Elvira-Ortiz ◽  
Daniel Morinigo-Sotelo ◽  
Angel L. Zorita-Lamadrid ◽  
Roque A. Osornio-Rios ◽  
Rene de J. Romero-Troncoso
Keyword(s):  
Fundamental Frequency ◽  
Induction Motors ◽  
Frequency Component ◽  
Point Of View ◽  
Single Frequency ◽  
The Common ◽  
Preprocessing Technique ◽  
Complete Frequency ◽  
Operation Frequency ◽  
Fundamental Frequency Component

Broken rotor bar (BRB) is one of the most common failures in induction motors (IMs) these days; however, its identification is complicated since the frequencies associated with the fault condition appear near the fundamental frequency component (FFC). This situation gets worse when the IM slip or the operation frequency is low. In these circumstances, the common techniques for condition monitoring may experience troubles in the identification of a faulty condition. By suppressing the FFC, the fault detection is enhanced, allowing the identification of BRB even at low slip conditions. The main contribution of this work consists of the development of a preprocessing technique that estimates the FFC from an optimization point of view. This way, it is possible to remove a single frequency component instead of removing a complete frequency band from the current signals of an IM. Experimentation is performed on an IM operating at two different frequencies and at three different load levels. The proposed methodology is compared with two different approaches and the results show that the use of the proposed methodology allows to enhance the performance delivered by the common methodologies for the detection of BRB in steady state.

scholarly journals Nonlinear Maximization of the Sum-Frequency Component from Two Ultrasonic Signals in a Bubbly Liquid

Sensors ◽  
2019 ◽  
Vol 20 (1) ◽  
pp. 113
Author(s):  
María Teresa Tejedor Sastre ◽  
Christian Vanhille
Keyword(s):  
Numerical Model ◽  
Nonlinear Resonance ◽  
Frequency Component ◽  
Nonlinear Propagation ◽  
Single Frequency ◽  
Bubbly Liquid ◽  
Higher Harmonics ◽  
Sum Frequency ◽  
Bubbly Liquids ◽  
Oscillating Bubbles

Techniques based on ultrasound in nondestructive testing and medical imaging analyze the response of the source frequencies (linear theory) or the second-order frequencies such as higher harmonics, difference and sum frequencies (nonlinear theory). The low attenuation and high directivity of the difference-frequency component generated nonlinearly by parametric arrays are useful. Higher harmonics created directly from a single-frequency source and the sum-frequency component generated nonlinearly by parametric arrays are attractive because of their high spatial resolution and accuracy. The nonlinear response of bubbly liquids can be strong even at relatively low acoustic pressure amplitudes. Thus, these nonlinear frequencies can be generated easily in these media. Since the experimental study of such nonlinear waves in stable bubbly liquids is a very difficult task, in this work we use a numerical model developed previously to describe the nonlinear propagation of ultrasound interacting with nonlinearly oscillating bubbles in a liquid. This numerical model solves a differential system coupling a Rayleigh–Plesset equation and the wave equation. This paper performs an analysis of the generation of the sum-frequency component by nonlinear mixing of two signals of lower frequencies. It shows that the amplitude of this component can be maximized by taking into account the nonlinear resonance of the system. This effect is due to the softening of the medium when pressure amplitudes rise.

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