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Concept

Velocity factor

Publications associées (26)

The dynamics of unsteady frictional slip pulses

Fabian Barras, Thibault Didier Roch

Self-healing slip pulses are major spatiotemporal failure modes of frictional systems, featuring a characteristic size L(t) and a propagation velocity c(p)(t) (t is time). Here, we develop a theory of slip pulses in realistic rate- and state-dependent fric ...

National Academy of Sciences2023

Fluid flow through microcracked and fractured granitic reservoirs

Marie Estelle Solange Violay, Michael Heap, Lucille Jocelyne Nadine Carbillet

The permeability of crustal rocks and rock-masses dictates the efficiency of hydrothermal circulation and therefore the productivity of geothermal resources. In this study, we find by monitoring P-wave velocity that thermal microcracking in Lanhélin granit ...

2023

Low-Loss Anisotropic Image Polaritons in van der Waals Crystal alpha-MoO3

Sergejs Boroviks

Orthorhombic molybdenum trioxide (alpha-MoO3), a newly discovered polaritonic van der Waals crystal, is attracting significant attention due to its strongly anisotropic mid-infrared phonon-polaritons. At the same time, coupling of polariton with its mirror ...

WILEY-V C H VERLAG GMBH2022

Ultimate Limit for Optical Losses in Gold, Revealed by Quantitative Near-Field Microscopy

Sergejs Boroviks

We report thorough measurements of surface plasmon polaritons (SPPs) running along nearly perfect air-gold interfaces formed by atomically flat surfaces of chemically synthesized gold monocrystals. By means of amplitude-and phase-resolved near-field micros ...

AMER CHEMICAL SOC2022

Study on the Performances of AlScN based SAW/BAW Hybrid Resonators A Parametric Analysis of Acoustic Wave Resonators with Large Figure of Merit

Luis Guillermo Villanueva Torrijo, Soumya Yandrapalli

In this study, we analyze a 3rd type of FBAR's fundamental mode by finite element method. We show the importance of the substrate's wave velocity and conductivity on the electromechanical coupling efficiency. Then we demonstrate that etching traditional SA ...

IEEE2021

An Extension of the Guided Wave M‐Component Model Taking Into Account the Presence of a Tall Strike Object

Farhad Rachidi-Haeri, Marcos Rubinstein, Mohammad Azadifar, Quanxin Li

We present in this paper an extension of the guided-wave M-component model of Rakov et al. considering the presence of a vertically elevated strike object. The tall object is represented as a lossless, uniform transmission line. Expressions for the current ...

2021

Simulation of High-Frequency Transients in Overhead Lines Including Frequency-Dependent Soil Parameters: an FDTD Aproach

Farhad Rachidi-Haeri, Rafael Silva Alipio

This paper investigates the effect of frequency-dependent soil parameters on the simulation of electromagnetic transients on overhead lines, based on the application of the FDTD method to solve the telegrapher’s equations. The ground return impedance is ca ...

2021

Origin of the Co‐Seismic Variations of Elastic Properties in the Crust: Insight From the Laboratory

Marie Estelle Solange Violay, François Xavier Thibault Passelègue, Mateo Alejandro Acosta, Federica Paglialunga

Seismological observations highlighted that earthquakes are often followed by changes in elastic properties around the fault zone. Here, we studied the origin of these variations using stick-slip experiments on saw-cut granite samples presenting different ...

2021

Pressure on obstacles induced by granular snow avalanches

Michael Lukas Kyburz

The increasing population and the consequential demand for dwelling and recreation areas lead to more frequent conflicts between humans and natural hazards. In mountainous regions snow avalanches are, therefore, still a major threat to humans and infrastru ...

EPFL2021

Mechanical and hydraulic transport properties of transverse-isotropic Gneiss deformed under deep reservoir stress and pressure conditions

Marie Estelle Solange Violay, Mateo Alejandro Acosta

In central Europe, many geo-energy reservoirs have revealed to be hosted in transverse isotropic crystalline rock, where the rock's mechanical and hydraulic transport properties are poorly constrained. Here, we performed triaxial experiments on Cresciano G ...

2020

Crack front waves: A 3D dynamic response to a local perturbation of tensile and shear cracks

Jean-François Molinari, Fabian Barras, Damien Spielmann

Crack front waves are long-lived perturbations propagating along the crack front. They are triggered by heterogeneities on the crack plane, as for instance tough asperities, which disturb the crack front shape. Crack front waves are thought to leave a trac ...

PERGAMON-ELSEVIER SCIENCE LTD2020

Seismic and Microseismic Signatures of Fluids in Rocks: Bridging the Scale Gap

Lucas Xan Pimienta

The aim of this collection is to record a snapshot of our current state of understanding of the impact of fluids on the evolution and monitorability of subsurface rock formations during anthropogenic fluid injection/withdrawal operations, accounting for sc ...

AMER GEOPHYSICAL UNION2019

Force measurement of a gas-assisted atomization using an impulse probe

Farzad Vakili Farahani

The main objective of this study was to develop further insight into the mass flux characterization of an effervescent atomization. The spray is injected through an industrial effervescent nozzle, and is measured using a newly developed coupled PDPA + IS m ...

PERGAMON-ELSEVIER SCIENCE LTD2019

Electromagnetic Fields Associated With the M‐Component Mode of Charge Transfer

Marcos Rubinstein, Mohammad Azadifar, Davide Pavanello, Lixia He

In upward flashes, charge transfer to ground largely takes place during the initial continuous current (ICC) and its superimposed pulses (ICC pulses). ICC pulses can be associated with either M-component or leader/return-stroke like modes of charge transfe ...

2019

Anomalous Vp/Vs ratios at seismic frequencies might evidence highly damaged rocks in subduction zones

Marie Estelle Solange Violay, Lucas Xan Pimienta

Unusually high compressional (P) to shear (S) wave velocity ratios (V-p/V-s) were measured at different subduction zones and interpreted as fluid-pressurized regions. Because no laboratory data reported such high values in isotropic rocks, mineralogical or ...

2018

Flow field in a reservoir subject to pumped-storage operation - in situ measurement and numerical modeling

Anton Schleiss, Giovanni De Cesare, Michael Müller

In pumped-storage reservoirs, turbulent kinetic energy input from plant operation can be considerably high. Flow velocities were measured by Acoustic Doppler Current Profilers near the intake/outlet structure to describe flow patterns induced by pumped-sto ...

2018

Investigation of the Propagation Length of Bloch Surface Waves on One Dimensional Photonic Crystals

Hans Peter Herzig, Nicolas Maxime André Descharmes, Babak Vosoughi Lahijani, Gaël David Osowiecki

A 1D photonic crystal structure sustaining optical surface waves is investigated. The propagation length of the surface mode is studied both using an eigenmode model and a rigorous time domain solver. The two models show good convergence. Our results demon ...

IEEE2018

Estimation of wave propagation velocity on a channel with smooth and rough bed

Anton Schleiss, Michael Pfister, Davide Wüthrich

Natural hazards such as tsunamis, impulse waves and dam-break waves are rare, but extremely destructive. In recent times, more importance was given to structures that could withstand such events, however, uncertainties still exist in the estimation of wave ...

2017

Demographic stochasticity and resource autocorrelation control biological invasions in heterogeneous landscapes

Andrea Rinaldo, Andrea Giometto, Florian Altermatt

Mounting theoretical evidence suggests that demographic stochasticity, environmental heterogeneity and biased movement of organisms individually affect the dynamics of biological invasions and range expansions. Studies of species spread in heterogeneous la ...

Wiley2017

Experimental investigation of the propagation properties of Bloch surface waves on dielectric multilayer platform

Hans Peter Herzig, Elsie Barakat, Richa Dubey

Background: The periodic dielectric multilayers sustaining Bloch surface waves have been proposed as a platformfor the sensing applications and the two dimensional integrated optics. In this paper, we present the experimental and theoretical investigation ...

2017