Built-up structural steel sections as seismic metamaterials for surface wave attenuation with low frequency wide bandgap in layered soil medium

Background: A novel fault location method of HVDC transmission line based on a concentric relaxation principle is proposed in this paper. Methods: Due to the different position of fault, the instantaneous energy measured from rectifier and inverter are different, and the ratio k between them is the relationship to the fault location d. Through the analysis of amplitude-frequency characteristics, we found that the wave attenuation characteristic of low frequency in the traveling wave is stable, and the amplitude of energy is larger, so we get the instantaneous energy ratio by using the low-frequency data. By using the method of wavelet packet decomposition, the voltage traveling wave signal was decomposed. Results: Finally, calculate the value k. By using the data fitting, the relative function of k and d can be got, that is the fault location function. Conclusion: After an exhaustive evaluation process considering different fault locations, fault resistances, and noise on the unipolar DC transmission system, four-machine two-area AC/DC parallel system, and an actual complex grid, the method presented here showed a very accurate and robust behavior.

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Numerical Modelling and Optimization of Two-Dimensional Phononic Band Gaps in Elastic Metamaterials with Square Inclusions

Applied Sciences ◽

10.3390/app11073124 ◽

2021 ◽

Vol 11 (7) ◽

pp. 3124

Author(s):

Alya Alhammadi ◽

Jin-You Lu ◽

Mahra Almheiri ◽

Fatima Alzaabi ◽

Zineb Matouk ◽

...

Keyword(s):

Elastic Wave ◽

Tungsten Carbide ◽

Composite Structure ◽

Elastic Waves ◽

Wave Attenuation ◽

Low Frequency ◽

Filling Fraction ◽

Carbide Composite ◽

Elastic Metamaterials ◽

Tungsten Carbide Composite

A numerical simulation study on elastic wave propagation of a phononic composite structure consisting of epoxy and tungsten carbide is presented for low-frequency elastic wave attenuation applications. The calculated dispersion curves of the epoxy/tungsten carbide composite show that the propagation of elastic waves is prohibited inside the periodic structure over a frequency range. To achieve a wide bandgap, the elastic composite structure can be optimized by changing its dimensions and arrangement, including size, number, and rotation angle of square inclusions. The simulation results show that increasing the number of inclusions and the filling fraction of the unit cell significantly broaden the phononic bandgap compared to other geometric tunings. Additionally, a nonmonotonic relationship between the bandwidth and filling fraction of the composite was found, and this relationship results from spacing among inclusions and inclusion sizes causing different effects on Bragg scatterings and localized resonances of elastic waves. Moreover, the calculated transmission spectra of the epoxy/tungsten carbide composite structure verify its low-frequency bandgap behavior.

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A waveform inversion technique for measuring elastic wave attenuation in cylindrical bars

Geophysics ◽

10.1190/1.1443299 ◽

1992 ◽

Vol 57 (6) ◽

pp. 854-859 ◽

Cited By ~ 6

Author(s):

Xiao Ming Tang

Keyword(s):

Elastic Wave ◽

Wave Attenuation ◽

Waveform Inversion ◽

Finite Size ◽

Low Frequency ◽

Frequency Range ◽

Multiple Reflections ◽

Low Frequencies ◽

The Time Domain ◽

Attenuation Values

A new technique for measuring elastic wave attenuation in the frequency range of 10–150 kHz consists of measuring low‐frequency waveforms using two cylindrical bars of the same material but of different lengths. The attenuation is obtained through two steps. In the first, the waveform measured within the shorter bar is propagated to the length of the longer bar, and the distortion of the waveform due to the dispersion effect of the cylindrical waveguide is compensated. The second step is the inversion for the attenuation or Q of the bar material by minimizing the difference between the waveform propagated from the shorter bar and the waveform measured within the longer bar. The waveform inversion is performed in the time domain, and the waveforms can be appropriately truncated to avoid multiple reflections due to the finite size of the (shorter) sample, allowing attenuation to be measured at long wavelengths or low frequencies. The frequency range in which this technique operates fills the gap between the resonant bar measurement (∼10 kHz) and ultrasonic measurement (∼100–1000 kHz). By using the technique, attenuation values in a PVC (a highly attenuative) material and in Sierra White granite were measured in the frequency range of 40–140 kHz. The obtained attenuation values for the two materials are found to be reliable and consistent.

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Anelastic structure and evolution of the continental crust and upper mantle from seismic surface wave attenuation

Reviews of Geophysics ◽

10.1029/95rg02074 ◽

1995 ◽

Vol 33 (4) ◽

pp. 441 ◽

Cited By ~ 171

Author(s):

Brian J. Mitchell

Keyword(s):

Surface Wave ◽

Continental Crust ◽

Upper Mantle ◽

Wave Attenuation ◽

Crust And Upper Mantle

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Surface wave attenuation of seismic records with the co-core trace transform filter

Geophysics ◽

10.1190/geo2010-0010.1 ◽

2011 ◽

Vol 76 (6) ◽

pp. V115-V128 ◽

Cited By ~ 3

Author(s):

Ning Wu ◽

Yue Li ◽

Baojun Yang

Keyword(s):

Surface Wave ◽

Surface Waves ◽

Field Data ◽

Wave Attenuation ◽

Seismic Events ◽

Data Sets ◽

Transform Domain ◽

Recent Developments ◽

Seismic Records ◽

Trace Transform

To remove surface waves from seismic records while preserving other seismic events of interest, we introduced a transform and a filter based on recent developments in image processing. The transform can be seen as a weighted Radon transform, in particular along linear trajectories. The weights in the transform are data dependent and designed to introduce large amplitude differences between surface waves and other events such that surface waves could be separated by a simple amplitude threshold. This is a key property of the filter and distinguishes this approach from others, such as conventional ones that use information on moveout ranges to apply a mask in the transform domain. Initial experiments with synthetic records and field data have demonstrated that, with the appropriate parameters, the proposed trace transform filter performs better both in terms of surface wave attenuation and reflected signal preservation than the conventional methods. Further experiments on larger data sets are needed to fully assess the method.

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