Design trade-offs of bi-flyback and bi-forward AC/DC converters to comply low frequency harmonic regulation

2002 ◽  
Author(s):  
O. Garcia ◽  
C. Fernandez ◽  
R. Prieto ◽  
J.A. Cobos ◽  
J. Uceda
Keyword(s):  
Low Frequency ◽  
Trade Offs ◽  
Frequency Harmonic

Full-waveform inversion with borehole constraints for elastic VTI media

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. R553-R563
Author(s):  
Sagar Singh ◽  
Ilya Tsvankin ◽  
Ehsan Zabihi Naeini
Keyword(s):  
Objective Function ◽  
Reservoir Characterization ◽  
Waveform Inversion ◽  
Low Frequency ◽  
Rock Physics ◽  
Anisotropic Media ◽  
Full Waveform Inversion ◽  
Full Waveform ◽  
Trade Offs ◽  
Vti Media

The nonlinearity of full-waveform inversion (FWI) and parameter trade-offs can prevent convergence toward the actual model, especially for elastic anisotropic media. The problems with parameter updating become particularly severe if ultra-low-frequency seismic data are unavailable, and the initial model is not sufficiently accurate. We introduce a robust way to constrain the inversion workflow using borehole information obtained from well logs. These constraints are included in the form of rock-physics relationships for different geologic facies (e.g., shale, sand, salt, and limestone). We develop a multiscale FWI algorithm for transversely isotropic media with a vertical symmetry axis (VTI media) that incorporates facies information through a regularization term in the objective function. That term is updated during the inversion by using the models obtained at the previous inversion stage. To account for lateral heterogeneity between sparse borehole locations, we use an image-guided smoothing algorithm. Numerical testing for structurally complex anisotropic media demonstrates that the facies-based constraints may ensure the convergence of the objective function towards the global minimum in the absence of ultra-low-frequency data and for simple (even 1D) initial models. We test the algorithm on clean data and on surface records contaminated by Gaussian noise. The algorithm also produces a high-resolution facies model, which should be instrumental in reservoir characterization.

Filter for testing low-frequency harmonic analyzers S5-2 and S5-3

1974 ◽  
Vol 17 (4) ◽  
pp. 616-617
Author(s):  
A. S. Karavaev ◽  
L. V. Mishin
Keyword(s):  
Low Frequency ◽  
Frequency Harmonic

Vibration of otolithlike scatterers due to low frequency harmonic wave excitation in water.

2011 ◽  
Vol 129 (4) ◽  
pp. 2472-2472 ◽  
Author(s):  
Carl R. Schilt ◽  
Ted W. Cranford ◽  
Petr Krysl ◽  
Anthony D. Hawkins
Keyword(s):  
Harmonic Wave ◽  
Low Frequency ◽  
Wave Excitation ◽  
Frequency Harmonic

Localized Vibration Isolation Strategy for Low-Frequency Excitations in Membrane Space Structures

2006 ◽  
Vol 128 (6) ◽  
pp. 790-797 ◽  
Author(s):  
Hiraku Sakamoto ◽  
K. C. Park
Keyword(s):  
Vibration Isolation ◽  
Controller Design ◽  
Low Frequency ◽  
Space Structures ◽  
Membrane Structures ◽  
Low Frequency Vibration ◽  
And Control ◽  
Structural Mass ◽  
The Web ◽  
Frequency Harmonic

The present study explores both structural and controller design to attenuate vibration in large membrane space structures, especially due to low-frequency harmonic excitations. It is very difficult for membrane structures to suppress the low-frequency vibration induced by flexible support structures, because a lightly prestressed membrane has extremely low mode frequencies and little damping effect. The present study proposes the use of weblike perimeter cables around a membrane, and the application of simple and lightweight active controllers only along the web cables in order to isolate the membrane from vibration. This strategy successfully reduces the membrane vibration when the web-cable configuration is appropriately tailored. Both linear and nonlinear finite-element analyses exhibit a clear tradeoff between structural mass and control efficiency.

High-Frequency Harmonic Effects on Low-Frequency Iron Losses

2014 ◽  
Vol 50 (11) ◽  
pp. 1-4 ◽  
Author(s):  
Lucian Petrea ◽  
Cristian Demian ◽  
Jean Francois Brudny ◽  
Thierry Belgrand
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Iron Losses ◽  
High Frequency Harmonic ◽  
Frequency Harmonic

scholarly journals Scattering Attenuation of the Martian Interior through Coda-Wave Analysis

2021 ◽  
Author(s):  
Foivos Karakostas ◽  
Nicholas Schmerr ◽  
Ross Maguire ◽  
Quancheng Huang ◽  
Doyeon Kim ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Scattered Wave ◽  
Coda Wave ◽  
Very High Frequency ◽  
Scattering Layer ◽  
Scattering Attenuation ◽  
Trade Offs ◽  
Scattering Strength ◽  
Diffusive Layer

ABSTRACT We investigate the scattering attenuation characteristics of the Martian crust and uppermost mantle to understand the structure of the Martian interior. We examine the energy decay of the spectral envelopes for 21 high-quality Martian seismic events from sols 128 to 500 of InSight operations. We use the model of Dainty, Toksöz, et al. (1974) to approximate the behavior of energy envelopes resulting from scattered wave propagation through a single diffusive layer over an elastic half-space. Using a grid search, we mapped the layer parameters that fit the observed InSight data envelopes. The single diffusive layer model provided better fits to the observed energy envelopes for high-frequency (HF) and very-high-frequency (VF) than for the low-frequency and broadband events. This result is consistent with the suggested source depths (Giardini et al., 2020) for these families of events and their expected interaction with a shallow scattering layer. The shapes of the observed data envelopes do not show a consistent pattern with event distance, suggesting that the diffusivity and scattering layer thickness is nonuniform in the vicinity of InSight at Mars. Given the consistency in the envelope shapes between HF and VF events across epicentral distances and the trade-offs between the parameters that control scattering, the dimensions of the scattering layer remain unconstrained but require that scattering strength decreases with depth and that the rate of decay in scattering strength is the fastest near the surface. This is generally consistent with the processes that would form scattering structures in planetary lithospheres.

Sign in / Sign up

Export Citation Format

Share Document