Combining attenuation by Q and spherical divergence

Geophysics ◽  
1987 ◽  
Vol 52 (6) ◽  
pp. 740-744 ◽  
Author(s):  
William P. Iverson
Keyword(s):  
Seismic Data ◽  
High Frequency ◽  
Dynamic Range ◽  
Wave Attenuation ◽  
Theoretical Calculations ◽  
Propagation Distance ◽  
Seismic Surveys ◽  
Total Attenuation ◽  
Order Of Magnitude ◽  
Spherical Divergence

A general correlation of cross‐well seismic data and surface seismic data is attempted simply by examining a combination of the two major mechanisms of seismic wave attenuation, anelastic Q, and spherical divergence. High‐frequency cross‐well seismology can be hindered by the assumption that an order of magnitude increase in frequency is accompanied by an order of magnitude decrease in propagation distance such that the anelastic attenuation (described by quality factor Q) remains constant. Such a comparison, however, neglects the effects of geometrical spreading, which is independent of frequency. Through the consideration of both Q and spherical divergence, it is demonstrated that the total attenuation of 2 000 Hz energy at a distance of 613 m is equivalent to the total attenuation of 20 Hz energy at a distance of 7 000 m. Applications of kilohertz cross‐well seismic surveys between wells spaced by over 600 m could be possible with present dynamic‐range capabilities in seismic recording systems. Such applications would allow the use of high‐resolution cross‐well seismic surveys between wells drilled on a 40 acre spacing. One example of cross‐well seismic data is shown to demonstrate the high‐frequency content (kilohertz) which can be obtained. Theoretical calculations indicate that kilohertz energy could be recorded at distances up to 1 km. The assumptions are that present surface seismology measurements define the dynamic‐range capabilities of recording instruments, and that Q with spherical divergence accounts for all attenuation. All calculations neglect the problems of miniaturization required for downhole applications. The goal is that omission of extremely low Q regions near the surface and the noise‐free borehole environment can overcome the miniaturization problems.

Ultrasonic studies of the electronic structure of hexagonal metal crystals III. Shear wave attenuation in magnesium, zinc and cadmium

1975 ◽  
Vol 343 (1635) ◽  
pp. 537-560 ◽  
Keyword(s):  
Electronic Structure ◽  
Fermi Surface ◽  
Shear Wave ◽  
Basal Plane ◽  
High Frequency ◽  
Wave Attenuation ◽  
Theoretical Calculations ◽  
Strong Anisotropy ◽  
Surface Geometry ◽  
Frequency Limit

Measurements have been made of the electronic attenuation x of shear waves in pure magnesium, zinc and cadmium crystals. In the high-frequency limit x is proportional to the frequency of the sound v and values of N = lim (x/v) for propagation along the <1120> and <1010> directions, with the polarization vectors also in the basal plane, were obtained. These agreed well with theoretical calculations based on the Fermi surface geometry; a striking feature was the strong anisotropy in zinc and cadmium, but not in magnesium.

scholarly journals High-frequency rectifiers based on type-II Dirac fermions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Libo Zhang ◽  
Zhiqingzi Chen ◽  
Kaixuan Zhang ◽  
Lin Wang ◽  
Huang Xu ◽  
...  
Keyword(s):  
High Frequency ◽  
Dynamic Range ◽  
High Sensitivity ◽  
High Dynamic Range ◽  
Anisotropy Ratio ◽  
Dirac Fermions ◽  
Topological States ◽  
Topological Semimetals ◽  
Polarized Surface ◽  
Symmetry Protected

AbstractThe advent of topological semimetals enables the exploitation of symmetry-protected topological phenomena and quantized transport. Here, we present homogeneous rectifiers, converting high-frequency electromagnetic energy into direct current, based on low-energy Dirac fermions of topological semimetal-NiTe2, with state-of-the-art efficiency already in the first implementation. Explicitly, these devices display room-temperature photosensitivity as high as 251 mA W−1 at 0.3 THz in an unbiased mode, with a photocurrent anisotropy ratio of 22, originating from the interplay between the spin-polarized surface and bulk states. Device performances in terms of broadband operation, high dynamic range, as well as their high sensitivity, validate the immense potential and unique advantages associated to the control of nonequilibrium gapless topological states via built-in electric field, electromagnetic polarization and symmetry breaking in topological semimetals. These findings pave the way for the exploitation of topological phase of matter for high-frequency operations in polarization-sensitive sensing, communications and imaging.

Study of wave attenuation in concrete

1993 ◽  
Vol 8 (9) ◽  
pp. 2344-2353 ◽  
Author(s):  
J-M. Berthelot ◽  
Souda M. Ben ◽  
J.L. Robert
Keyword(s):  
Experimental Study ◽  
Plane Wave ◽  
Wave Attenuation ◽  
Plane Waves ◽  
Propagation Distance ◽  
Experimental Results ◽  
The Other ◽  
Wave Frequency ◽  
Concrete Composition ◽  
Analytical Expression

The experimental study of wave attenuation in concrete has been achieved in the case of the propagation of plane waves in concrete rods. Different mortars and concretes have been investigated. A transmitter transducer coupled to one of the ends of the concrete rod generates the propagation of a plane wave in the rod. The receiver transducer, similar to the previous one, is coupled to the other end of the rod. The experimental results lead to an analytical expression for wave attenuation as function of the concrete composition, the propagation distance, and the wave frequency.

Infrared spectra, rotational correlation functions, and intermolecular mean squared torques in compressed gaseous methane

1968 ◽  
Vol 46 (11) ◽  
pp. 1331-1340 ◽  
Author(s):  
R. L. Armstrong ◽  
S. M. Blumenfeld ◽  
C. G. Gray
Keyword(s):  
Correlation Functions ◽  
Theoretical Calculations ◽  
Dominant Contribution ◽  
Dispersion Interactions ◽  
Fundamental Vibration ◽  
Order Of Magnitude ◽  
The Mean ◽  
Vibration Rotation ◽  
Experimental Values ◽  
Rotational Correlation

Extensive measurements of the methane ν3 and ν4 fundamental vibration–rotation bands in CH4–He mixtures and the ν3 band in CH4–He, CH4–N2, and CD4–He mixtures have been carried out in infrared absorption at 295 °K to pressures of 3000 atm. Some profiles of the ν3 band in CH4–Ar mixtures and in pure CH4 have also been obtained. Rotational correlation functions, band moments, and intermolecular mean squared torques have been determined from the ν3 band profiles. Theoretical calculations of the mean squared torque due to anisotropic multipolar, induction and dispersion interactions have been carried out. The theoretical and experimental torques are in order-of-magnitude agreement for the CH4–N2 and CH4–CH4 systems; for CH4–He, CD4–He, and CH4–Ar the theoretical values are two to three orders of magnitude too small to account for the experimental values, indicating that in these cases the dominant contribution to the torques is given by the anisotropic overlap forces.

Clock signal requirement for high-frequency, high dynamic range acquisition systems

2005 ◽  
Vol 76 (11) ◽  
pp. 115103 ◽  
Author(s):  
Ivo Viščor ◽  
Josef Halámek ◽  
Marco Villa
Keyword(s):  
High Frequency ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Clock Signal ◽  
High Dynamic

scholarly journals MicroED Structures from Micrometer Thick Protein Crystals

2017 ◽  
Author(s):  
Michael W. Martynowycz ◽  
Calina Glynn ◽  
Jennifer Miao ◽  
M. Jason de la Cruz ◽  
Johan Hattne ◽  
...  
Keyword(s):  
Theoretical Calculations ◽  
Protein Structures ◽  
Atomic Resolution ◽  
Proteinase K ◽  
Protein Crystals ◽  
Molecular Replacement ◽  
Varying Thickness ◽  
Order Of Magnitude ◽  
Human Prion Protein ◽  
Do So

AbstractTheoretical calculations suggest that crystals exceeding 100 nm thickness are excluded by dynamical scattering from successful structure determination using microcrystal electron diffraction (MicroED). These calculations are at odds with experimental results where MicroED structures have been determined from significantly thicker crystals. Here we systematically evaluate the influence of thickness on the accuracy of MicroED intensities and the ability to determine structures from protein crystals one micrometer thick. To do so, we compare ab initio structures of a human prion protein segment determined from thin crystals to those determined from crystals up to one micrometer thick. We also compare molecular replacement solutions from crystals of varying thickness for a larger globular protein, proteinase K. Our results indicate that structures can be reliably determined from crystals at least an order of magnitude thicker than previously suggested by simulation, opening the possibility for an even broader range of MicroED experiments.SummaryAtomic resolution protein structures can be determined by MicroED from crystals that surpass the theoretical maximum thickness limit by an order of magnitude.

scholarly journals Обнаружение высокочастотных альфвеновских колебаний в омических разрядах сферического токамака Глобус-М2

2021 ◽  
Vol 47 (12) ◽  
pp. 17
Author(s):  
И.М. Балаченков ◽  
Ю.В. Петров ◽  
В.К. Гусев ◽  
Н.Н. Бахарев ◽  
В.И. Варфоломеев ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Standing Wave ◽  
High Frequency ◽  
Low Density ◽  
Frequency Range ◽  
High Frequency Oscillations ◽  
Model Predictions ◽  
Mode Excitation ◽  
Order Of Magnitude ◽  
Frequency Chirping

In Globus-M2 ohmic discharges with low density, by means of Mirnov coils array, magnetic field oscillations with frequencies in 1 MHz range were detected. Frequency range of these oscillations significantly exceed the range of TAE and RSAE frequencies, which were previously observed on Globus-M and Globus-M2 tokamaks, and their amplitude, contrary, turned out to be up to an order of magnitude lower. It was found that high frequency oscillations are interrelated with suprathermal electron fraction. At the same time the observed instability seems to have Alfvenic nature, since its frequency correlates well with Alfven frequency scaling. It was also found that magnetic perturbation always forms standing wave with predominantly low toroidal wavenumbers, including n = 0 structure, which makes gap (e.g. TAE) mode excitation impossible. Frequency chirping during single bursts with δω ~ √t is consistent with hole-clump model predictions.

A 108km2 Compressive Sensing Processing Trial

2021 ◽  
Author(s):  
Dustin Blymyer ◽  
Klaas Koster ◽  
Graeme Warren
Keyword(s):  
Compressive Sensing ◽  
Surface Waves ◽  
Seismic Data ◽  
High Frequency ◽  
Quality Data ◽  
Low Velocity ◽  
Conventional Design ◽  
Seismic Acquisition ◽  
Similar Cost ◽  
Station Density

Abstract Summary Compressive sensing (CS) of seismic data is a new style of seismic acquisition whereby the data are recorded on a pseudorandom grid rather than along densely sampled lines in a conventional design. A CS design with a similar station density will generally yield better quality data at a similar cost compared to a conventional design, whereas a CS design with a lower station density will reduce costs while retaining quality. Previous authors (Mosher, 2014) have shown good results from CS surveys using proprietary methods for the design and processing. In this paper we show results obtained using commercially available services based on published algorithms (Lopez, 2016). This is a necessary requirement for adoption of CS by our industry. This report documents the results of a 108km2 CS acquisition and processing trial. The acquisition and processing were specifically designed to establish whether CS can be used for suppression of backscattered, low velocity, high frequency surface waves. We demonstrate that CS data can be reconstructed by a commercial contractor and that the suppression of backscattered surface waves is improved by using CS receiver gathers reconstructed to a dense shot grid. We also show that CS acquisition is a reliable alternative to conventional acquisition from which high-quality subsurface images can be formed.

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