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We present a new method for the generation of atmospheric turbulence phase screens based on the frequency shift property of the Fourier transform. This method produces low spatial frequency distortions without additional computation time…

Optics · Physics 2020-01-08 Daniel A. Paulson , Chensheng Wu , Christopher C. Davis

Unique Word-orthogonal frequency division multiplexing (UW-OFDM) is known to provide various performance benefits over conventional cyclic prefix (CP) based OFDM. Most important, UW-OFDM features excellent spectral sidelobe suppression…

Signal Processing · Electrical Eng. & Systems 2024-11-05 Christian Hofbauer , Werner Haselmayr , Hans-Peter Bernhard , Mario Huemer

We introduce the concept of fractured stochastic orbitals (FSOs), short vectors that sample a small number of space points and enable an efficient stochastic sampling of any general function. As a first demonstration, FSOs are applied in…

Computational Physics · Physics 2018-08-15 Vojtěch Vlček , Wenfei Li , Roi Baer , Eran Rabani , Daniel Neuhauser

In this article, we propose an index modulation system suitable for optical communications, based on jointly driving the time and frequency of the signal: an index-time frequency hopping (I-TFH) system. We analyze its performance from the…

Signal Processing · Electrical Eng. & Systems 2020-02-27 Francisco J. Escribano , Alexandre Wagemakers , Georges Kaddoum , Joao V. C. Evangelista

ITER coil tolerances are re-evaluated using the modern understanding of coupling to least-stable plasma modes and an updated center-line-traced model of ITER's coil windings. This reassessment finds the tolerances to be conservative through…

Plasma Physics · Physics 2024-12-05 Matthew Pharr , Nikolas Logan , Carlos Paz-Soldan , Jong-Kyu Park , Chistopher Hansen

The probabilistic approach to turbulence is applied to investigate density fluctuations in supersonic turbulence. We derive kinetic equations for the probability distribution function (PDF) of the logarithm of the density field, $s$, in…

Astrophysics of Galaxies · Physics 2018-10-24 Liubin Pan , Paolo Padoan , Åke Nordlund

One of the methods to find the natural frequencies of rotating systems is the application of the transfer matrix method. In this method the rotor is modeled as several elements along the shaft which have their own mass and moment of…

The commonly accepted description of transition to turbulence in shear flows requires the presence of an external source of disturbances that get amplified by an essentially linear mechanism up to the point where breakdown to turbulence…

Fluid Dynamics · Physics 2008-04-15 Paolo Luchini

This paper deals with the weak error estimates of the exponential Euler method for semi-linear stochastic partial differential equations (SPDEs). A weak error representation formula is first derived for the exponential integrator scheme in…

Numerical Analysis · Mathematics 2015-06-23 Xiaojie Wang

Monitoring turbulence parameters is crucial in high-angular resolution astronomy for various purposes, such as optimising adaptive optics systems or fringe trackers. The former are present at most modern observatories and will remain…

Instrumentation and Methods for Astrophysics · Physics 2023-10-25 Nuno Morujão , Carlos Correia , Paulo Andrade , Julien Woillez , Paulo Garcia

Information-theoretic metrics to analyze optical fiber communications systems with binary and nonbinary soft-decision FEC are reviewed. The numerical evaluation of these metrics in both simulations and experiments is also discussed.…

Information Theory · Computer Science 2020-06-05 Alex Alvarado

The ECMWF ensemble weather forecasts are generated by perturbing the initial conditions of the forecast using a subset of the singular vectors of the linearised propagator. Previous results show that when creating probabilistic forecasts…

Atmospheric and Oceanic Physics · Physics 2007-05-23 Stephen Jewson , Maarten Ambaum , Christine Ziehmann

Recently, Portelli et al (2003) have semi-numerically obtained a functional form of the probability distribution of fluctuations in the total energy flow in a model for fluid turbulence. This follows earlier work suggesting that…

Statistical Mechanics · Physics 2007-05-23 S. C. Chapman , G. Rowlands , N. W. Watkins

This paper presents a semi-analytical approximation of Symbol Error Rate (SER) for the well known LoRa Internet of Things (IoT) modulation scheme in the following two scenarios: 1) in multi-path frequency selective fading channel with…

Signal Processing · Electrical Eng. & Systems 2022-01-12 Clement Demeslay , Philippe Rostaing , Roland Gautier

Turbulence is a complex, irregular flow phenomenon ubiquitous in natural processes and engineering applications. The Reynolds-averaged Navier-Stokes (RANS) method, owing to its low computational cost, has become the primary approach for…

Fluid Dynamics · Physics 2026-02-10 Ziqi Ji , Penghao Duan , Gang Du

Isothermal fluid turbulence simulations have been performed in the edge and scrape-off-layer (SOL) of an analytic stellarator configuration with an island divertor, thereby providing numerical insight into edge turbulence in regions around…

Plasma Physics · Physics 2024-03-28 Brendan Shanahan , David Bold , Ben Dudson

Combining a generalized current in the set of Maxwell's equations offers a useful framework to address the complex phenomena of electromagnetic turbulence. The fluidic-electromagnetic analogy implies that diffraction is the analog…

Classical Physics · Physics 2022-02-15 Mario J. Pinheiro

While the thermodynamics for bosonic systems with weak $s$-wave interactions has been known for decades, a general and systematic extension to higher partial waves has not yet been reported. We provide closed-form expressions for the…

Quantum Gases · Physics 2024-09-16 Xin-Yuan Gao , D. Blume , Yangqian Yan

For high contrast imaging systems, the time delay is one of the major limiting factors for the performance of the extreme adaptive optics (AO) sub-system and, in turn, the final contrast. The time delay is due to the finite time needed to…

Instrumentation and Methods for Astrophysics · Physics 2019-04-08 Maaike van Kooten , Niek Doelman , Matthew Kenworthy

Weak measurement with a coherent state pointer and in combination with an orthogonal postselection can lead to a surprising amplification effect, and we give a fire-new physical mechanism about the weak measurement in order to understand…

Quantum Physics · Physics 2015-09-03 Gang Li , Ming-Yong Ye , Xiu-Min Lin , He-Shan Song