Heterodyne interferometry for calibration of standard accelerometers in high frequency regime

2006 ◽  
Author(s):  
Alexandre Cabral ◽  
José Manuel Rebordão ◽  
Vitor Oliveira ◽  
Maria Isabel Godinho ◽  
Mário Costanzo Nunes
Keyword(s):  
High Frequency ◽  
Heterodyne Interferometry ◽  
Frequency Regime

scholarly journals A comparison of coarse spaces for Helmholtz problems in the high frequency regime

2021 ◽  
Vol 98 ◽  
pp. 239-253
Author(s):  
Niall Bootland ◽  
Victorita Dolean ◽  
Pierre Jolivet ◽  
Pierre-Henri Tournier
Keyword(s):  
High Frequency ◽  
Frequency Regime

The high-frequency regime

2012 ◽  
pp. 334-374
Author(s):  
C. J. Joachain ◽  
N. J. Kylstra ◽  
R. M. Potvliege
Keyword(s):  
High Frequency ◽  
Frequency Regime

NONCOMMUTATIVE DESCRIPTION OF SPIN HALL EFFECT

2009 ◽  
Vol 06 (02) ◽  
pp. 343-360 ◽  
Author(s):  
AHMED JELLAL ◽  
RACHID HOUÇA
Keyword(s):  
Magnetic Field ◽  
Quantum Mechanics ◽  
Hall Effect ◽  
High Frequency ◽  
Hall Conductivity ◽  
Spin Hall Effect ◽  
Harmonic Oscillators ◽  
Frequency Regime ◽  
Basic Features ◽  
Noncommutative Plane

We propose an approach based on a generalized quantum mechanics to deal with the basic features of the intrinsic spin Hall effect. This can be done by considering two decoupled harmonic oscillators on the noncommutative plane and evaluating the spin Hall conductivity. Focusing on the high frequency regime, we obtain a diagonalized Hamiltonian. After getting the corresponding spectrum, we show that there is a Hall conductivity without an external magnetic field, which is noncommutativity parameter θ-dependent. This allows us to make contact with the spin Hall effect and also give different interpretations. Fixing θ, one can recover three different approaches dealing with the phenomenon.

scholarly journals Greybody Factors for Schwarzschild Black Holes: Path-Ordered Exponentials and Product Integrals

Universe ◽  
2018 ◽  
Vol 4 (9) ◽  
pp. 93 ◽  
Author(s):  
Finnian Gray ◽  
Matt Visser
Keyword(s):  
Black Holes ◽  
High Frequency ◽  
Low Frequency ◽  
Intermediate Frequency ◽  
General Context ◽  
Matrix Formalism ◽  
Barrier Penetration ◽  
Frequency Regime ◽  
Transfer Matrix Formalism ◽  
Numerical Approaches

In earlier work concerning the sparsity of the Hawking flux, we found it necessary to re-examine what is known regarding the greybody factors of black holes, with a view to extending and expanding on some old results from the 1970s. Focusing specifically on Schwarzschild black holes, we have re-calculated and re-assessed the greybody factors using a path-ordered-exponential approach, a technique which has the virtue of providing a pedagogically useful semi-explicit formula for the relevant Bogoliubov coefficients. These path-ordered-exponentials, being based on a variant of the “transfer matrix” formalism, are closely related to so-called “product integrals”, leading to quite straightforward and direct numerical evaluation, while side-stepping any need for numerically solving the relevant ordinary differential equations. Furthermore, while considerable analytic information is already available regarding both the high-frequency and low-frequency asymptotics of these greybody factors, numerical approaches seem better adapted to finding suitable “global models” for these greybody factors in the intermediate frequency regime, where most of the Hawking flux is actually concentrated. Working in a more general context, these path-ordered-exponential techniques are also likely to be of interest for generic barrier-penetration problems.

scholarly journals Numerical Eulerian method for linearized gas dynamics in the high frequency regime

2013 ◽  
Vol 127 (4) ◽  
pp. 641-683
Author(s):  
Youness Noumir ◽  
François Dubois ◽  
Olivier Lafitte
Keyword(s):  
High Frequency ◽  
Gas Dynamics ◽  
Eulerian Method ◽  
Frequency Regime

scholarly journals Precorrected-FFT Accelerated Singular Boundary Method for High-Frequency Acoustic Radiation and Scattering

Mathematics ◽  
2022 ◽  
Vol 10 (2) ◽  
pp. 238
Author(s):  
Weiwei Li ◽  
Fajie Wang
Keyword(s):  
High Frequency ◽  
Acoustic Radiation ◽  
Low Frequency ◽  
Singular Boundary ◽  
Cpu Time ◽  
Interpolation Matrix ◽  
Collocation Points ◽  
Boundary Method ◽  
Frequency Regime ◽  
Singular Boundary Method

This paper presents a precorrected-FFT (pFFT) accelerated singular boundary method (SBM) for acoustic radiation and scattering in the high-frequency regime. The SBM is a boundary-type collocation method, which is truly free of mesh and integration and easy to program. However, due to the expensive CPU time and memory requirement in solving a fully-populated interpolation matrix equation, this method is usually limited to low-frequency acoustic problems. A new pFFT scheme is introduced to overcome this drawback. Since the models with lots of collocation points can be calculated by the new pFFT accelerated SBM (pFFT-SBM), high-frequency acoustic problems can be simulated. The results of numerical examples show that the new pFFT-SBM possesses an obvious advantage for high-frequency acoustic problems.

scholarly journals Standing shock prevents propagation of sparks in supersonic explosive flows

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Jens von der Linden ◽  
Clare Kimblin ◽  
Ian McKenna ◽  
Skyler Bagley ◽  
Hsiao-Chi Li ◽  
...  
Keyword(s):  
Radio Frequency ◽  
High Frequency ◽  
Fluid Dynamic ◽  
Supersonic Jet ◽  
Explosive Eruptions ◽  
Jet Flows ◽  
Frequency Content ◽  
Frequency Regime ◽  
High Frequency Content ◽  
Volcanic Jet

AbstractVolcanic jet flows in explosive eruptions emit radio frequency signatures, indicative of their fluid dynamic and electrostatic conditions. The emissions originate from sparks supported by an electric field built up by the ejected charged volcanic particles. When shock-defined, low-pressure regions confine the sparks, the signatures may be limited to high-frequency content corresponding to the early components of the avalanche-streamer-leader hierarchy. Here, we image sparks and a standing shock together in a transient supersonic jet of micro-diamonds entrained in argon. Fluid dynamic and kinetic simulations of the experiment demonstrate that the observed sparks originate upstream of the standing shock. The sparks are initiated in the rarefaction region, and cut off at the shock, which would limit their radio frequency emissions to a tell-tale high-frequency regime. We show that sparks transmit an impression of the explosive flow, and open the way for novel instrumentation to diagnose currently inaccessible explosive phenomena.

scholarly journals On the Effectiveness of Low Frequency Perturbations

2019 ◽  
Author(s):  
Yash Sharma ◽  
Gavin Weiguang Ding ◽  
Marcus A. Brubaker
Keyword(s):  
High Frequency ◽  
State Of The Art ◽  
Low Frequency ◽  
Human Perception ◽  
Search Space ◽  
Frequency Space ◽  
Performance Improvements ◽  
Frequency Regime ◽  
Frequency Components ◽  
Norm Constraint

Carefully crafted, often imperceptible, adversarial perturbations have been shown to cause state-of-the-art models to yield extremely inaccurate outputs, rendering them unsuitable for safety-critical application domains. In addition, recent work has shown that constraining the attack space to a low frequency regime is particularly effective. Yet, it remains unclear whether this is due to generally constraining the attack search space or specifically removing high frequency components from consideration. By systematically controlling the frequency components of the perturbation, evaluating against the top-placing defense submissions in the NeurIPS 2017 competition, we empirically show that performance improvements in both the white-box and black-box transfer settings are yielded only when low frequency components are preserved. In fact, the defended models based on adversarial training are roughly as vulnerable to low frequency perturbations as undefended models, suggesting that the purported robustness of state-of-the-art ImageNet defenses is reliant upon adversarial perturbations being high frequency in nature. We do find that under L-inf-norm constraint 16/255, the competition distortion bound, low frequency perturbations are indeed perceptible. This questions the use of the L-inf-norm, in particular, as a distortion metric, and, in turn, suggests that explicitly considering the frequency space is promising for learning robust models which better align with human perception.

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