Publications related to Skywave

Toward Metantennas: Metamaterial-Based Antennas for Wireless Communications

Antennas have historically been the most common electromagnetic (EM) technology for wireless communication systems. Antenna as hardware is entirely dependent on the EM properties of the materials used, mostly related to the permittivity and permeability. I ...

Ieee-Inst Electrical Electronics Engineers Inc2023

Lightning interaction with the ionosphere

Farhad Rachidi-Haeri, Marcos Rubinstein, Dongshuai Li

Lightning discharges, including cloud-to-ground (CG) and intracloud (IC) lightning, are known to emit electromagnetic pulses (EMPs) in a wide frequency band ranging from few Hz up to hundreds MHz [1]. During the breakdown and ionization processes (mostly f ...

IET2023

Artificial Neural Network Training on an Optical Processor via Direct Feedback Alignment

Florent Gérard Krzakala, Julien Marcel Daniel Emmanuel Launay

Artificial Neural Networks (ANN) are habitually trained via the back-propagation (BP) algorithm. This approach has been extremely successful: Current models like GPT-3 have O(10 11 ) parameters, are trained on O(10 11 ) words and produce awe-inspiring resu ...

IEEE2023

Scalable angular spectrum propagation

Felix Wechsler

Coherent field propagation is an essential computational tool in optics with applications ranging from computational optics and optical design to iterative field reconstructions. An improvement in the computational speed of current propagation methods is t ...

Optica Publishing Group2023

Generation of OAM-carrying space-time wave packets with time-dependent beam radii using a coherent combination of multiple LG modes on multiple frequencies

Tobias Kippenberg, Maxim Karpov, Zhe Zhao, Hao Song, Xinzhou Su

Space-time (ST) wave packets, in which spatial and temporal characteristics are coupled, have gained attention due to their unique propagation characteristics, such as propagation invariance and tunable group velocity in addition to their potential ability ...

Optica Publishing Group2022

Theoretical Efficiency and Dosimetry of Buffered On-body Transmitter Antennas for Wireless Powering of In-body Devices

Anja Skrivervik, Denys Nikolayev

The viable and safe application of wireless power transfer for powering bioelectronic implants requires understanding the wave propagation in heterogeneous and dispersive media, the electromagnetic exposure assessment, and the optimum design of the system ...

IEEE2022

Reduced basis methods for numerical room acoustic simulations with parametrized boundaries

Jan Sickmann Hesthaven, Hermes Sampedro Llopis

The use of model-based numerical simulations of wave propagation in rooms for engineering applications requires that acoustic conditions for multiple parameters are evaluated iteratively, which is computationally expensive. We present a reduced basis metho ...

ACOUSTICAL SOC AMER AMER INST PHYSICS2022

Partial discharge localization in power transformers using acoustic time reversal

Farhad Rachidi-Haeri, Marcos Rubinstein, Mohammad Azadifar, Hamidreza Karami, Florent Quentin Aviolat

The localization of partial discharges (PD) is important to monitor the conditioning of high voltage insulator materials. One of the key components in power grids is the high power transformer. Localization of PDs in these pieces of equipment can increase ...

Elsevier2022

Uncertainty Quantification by Multilevel Monte Carlo and Local Time-Stepping for Wave Propagation

Fabio Nobile

Because of their robustness, efficiency, and non intrusiveness, Monte Carlo methods are probably the most popular approach in uncertainty quantification for computing expected values of quantities of interest. Multilevel Monte Carlo (MLMC) methods signific ...

2022

A Correlation-Based Electromagnetic Time Reversal Technique to Locate Indoor Transient Radiation Sources

Farhad Rachidi-Haeri, Marcos Rubinstein, Zhaoyang Wang, Qi Li

To overcome the multipath interference in locating transient electromagnetic (EM) radiation sources in an indoor environment, we propose a criterion that calculates the correlation between back-propagated signals from observation points, to be used in EM t ...

Institute of Electrical and Electronics Engineers2021

Enhancing visual motion discrimination by desynchronizing bifocal oscillatory activity

Friedhelm Christoph Hummel, Estelle Emeline Raffin, Roberto Felipe Salamanca Giron, Sarah Bernardina Zandvliet, Martin Seeber

Visual motion discrimination involves reciprocal interactions in the alpha band between the primary visual cortex (V1) and mediotemporal areas (V5/MT). We investigated whether modulating alpha phase synchronization using individualized multisite transcrani ...

2021

The Polarity Reversal of Lightning‐Generated Sky Wave

Farhad Rachidi-Haeri, Marcos Rubinstein, Mohammad Azadifar, Wenhao Hou

The polarity reversal of the lightning‐generated first sky wave as a function of the observation distance is studied using a novel approach combining the finite‐difference time domain (FDTD) method and the superposition principle of electromagnetic waves. ...

2020

A Subwavelength Microwave Bandpass Filter Based on a Chiral Waveguide

Romain Christophe Rémy Fleury, Maliheh Khatibi Moghaddam

Wave manipulation at a subwavelength scale has recently attracted significant interest, especially for low-frequency wave propagation, from acoustic to microwave devices. Recently, a few methods achieving subwavelength routing using locally resonant metama ...

IEEE Xplore2020

Effective Models and Numerical Homogenization for Wave Propagation in Heterogeneous Media on Arbitrary Timescales

Timothée Noé Pouchon, Assyr Abdulle

A family of effective equations for wave propagation in periodic media for arbitrary timescales O(epsilon-alpha), where epsilon MUCH LESS-THAN1 is the period of the tensor describing the medium, is proposed. The well-posedness of the effective equations of ...

SPRINGER2020

Nature of Crack Path Instabilities in Thin Sheets Cut by Blunt Objects

Iryna Sivak

Cutting a brittle thin sheet with a blunt object leaves an oscillating crack that seemingly violates the principle of local symmetry for fracture. We experimentally find that at a critical value of a well chosen control parameter the straight propagation i ...

AMER PHYSICAL SOC2020

Measurement and Modeling of Both Distant and Close Electric Fields of an M‐Component in Rocket‐Triggered Lightning

Farhad Rachidi-Haeri, Marcos Rubinstein, Mohammad Azadifar, Amirhossein Mostajabi, Qi Li, Mi Zhou

Simultaneous measurements of current and multiple‐station electric fields associated with a 5.4‐kA‐peak M‐component in rocket‐triggered lightning are presented in this study. A close‐range electric field measurement site was located northeast of the trigge ...

2020

Radiation Limitations for Small Implanted Antennas

Anja Skrivervik, Zvonimir Sipus

Medical implants with communication capability are becoming increasingly popular with today’s trends to continuously monitor patient’s condition. This is a major challenge for antenna designers since the implants are inherently small and placed in a commun ...

IEEE2019

Fundamental Limits for Implanted Antennas: Maximum Power Density Reaching Free Space

Anja Skrivervik, Zvonimir Sipus

Medical implants with communication capability are becoming increasingly popular with today’s trends to continuously monitor patient’s condition. This is a major challenge for antenna designers since the implants are inherently small and placed in a commun ...

2019

Effect of bed roughness on tsunami-like waves and induced loads on buildings

Anton Schleiss, Michael Pfister, Davide Wüthrich

Tsunami, impulse-waves and dam-break waves afflict humanity with casualties and damages. An insight into the flow mechanisms of these waves is important to provide safety and reduce reconstruction costs. This experimental study focuses on the effect of bed ...

2019

Time intermittency in nondiffusive transport regimes of suprathermal ions in turbulent plasmas

Ambrogio Fasoli, Ivo Furno, Paolo Ricci, Marcelo Baquero Ruiz, Oulfa Chellaï, Fabian Manke

Intermittent phenomena have long been studied in the context of nondiffusive transport across a variety of fields. In the TORPEX device, the cross-field spreading of an injected suprathermal ion beam by electrostatic plasma turbulence can access different ...

AMER PHYSICAL SOC2019