Search results for "Instability"
showing 10 items of 724 documents
Rayleigh-instability-driven dewetting of thin Au and Ag films on indium-tin-oxide surface under nanosecond laser irradiations
2013
Investigations have been carried out on laser-beam-induced nanoparticle (NP) formation in thin (5 nm) Au and Ag films on indium-tin-oxide substrate. After the irradiation the films were observed to break-up into NPs through a dewetting mechanism. This mechanism was investigated as a Rayleigh-instability- driven process. In fact, for each used laser fluence, the resulting Au and Ag NPs' mean size and surface-to-surface mean distance were quantified and correlated between them in the framework of the Rayleigh-instability theory showing an excellent agreement. © The Institution of Engineering and Technology 2013.
Rotational effects on the oscillation frequencies of newly born proto-neutron stars
2003
In this paper we study the effects of rotation on the frequencies of the quasi-normal modes of a proto-neutron star (PNS) born in a gravitational collapse during the first minute of life. Our analysis starts a few tenths of seconds after the PNS formation, when the stellar evolution can be described by a sequence of equilibrium configurations. We use the evolutionary models developed by Pons et al. (1999; 2001) that describe how a non rotating star cools down and contracts while neutrino diffusion and thermalization processes dominate the stellar dynamics. For assigned values of the evolution time, we set the star into slow rotation and integrate the equations of stellar perturbations in th…
Understanding the health care pattern of homeless children through their residential journey
2021
En Île-de-France, l’hôtel social est souvent mobilisé par les associations pour héberger des familles, principalement migrantes et accompagnées d’enfants de moins de 6 ans. À cet âge, l’enfant nécessite un suivi de soins régulier auprès des professionnels pédiatriques. Nous supposons que ce suivi est dépendant de la mobilité résidentielle inhérente au système d’hébergement hôtelier. Cet article a pour objectif de reconstituer le parcours résidentiel des familles et le parcours de soins de leurs enfants et de saisir comment ces derniers s’influencent. La démonstration repose sur 18 entretiens biographiques spatialisés réalisés entre 2013 et 2016 auprès des familles sans logement hébergées en…
Limits to Arbitrage and Interest Rates: a Debate Between Keynes, Hawtrey and Hicks
2018
International audience; This paper deals with a debate between Hawtrey, Hicks and Keynes concerning the capacity of the central bank to influence the short-term and the long-term rates of interest. Both Hawtrey and Keynes considered the central bank’s ability to influence short-term rates of interest. However, they do not put the same emphasis on the study of the long-term rates of interest. According to Keynes, long-term rates are influenced by future expected short-term rates (1930, 1936), whereas for Hawtrey (1932, 1937, 1938), long-term rates are more dependent on the business cycle. Short-term rates do not have much effect on long-term rates according to Hawtrey. In 1939, Hicks enters …
Liquid aluminum particle effects on propagation of waves in solid rocket motor internal flow
2007
Aluminum-droplet effects on propagation of acoustic waves in the internal flow of a solid propellant rocket motor are analysed. Changes of the multiphase flow compressibility are calculated by taking into account both the translational and the pulsational motions of the aluminum droplets in consequence of the acoustic waves. Chemical reactions are not included in the analysis to avoid the complications arising from the non-isothermal and non-chemical-uniform combustion of aluminum in the chamber. Some corrections in current metalized propellant rocket instability calculations accounting for the results of the analysis are proposed.
Hétérogénéité spatiale : principes et méthodes
2004
Spatial Heterogeneity : Principles and Methods This article has a dual purpose . First , it describes the main econometric specifications which can be used to represent spatial heterogeneity , reflected in an instability of parameters in space and / or a heteroscedasticity of error terms . Only the specifications valid in cross-section are examined . Second , it explains the links between spatial heterogeneity and autocorrelation , the other major feature of localised data , defined by the absence of independence between geographical observations . In particular , we look at the extent to which traditional tests of heteroscedasticity or instability need to be amended to take account of spat…
Recurrent lumbar disc herniation: Is there a correlation with the surgical technique? A multivariate analysis
2019
Purpose: The recurrence of a lumbar disc herniation (LDH) is a common cause of poor outcome following lumbar discectomy. The aim of this study was to assess a potential relationship between the incidence of recurrent LDH and the surgical technique used. Furthermore, we tried to define the best surgical technique for the treatment of recurrent LDH to limit subsequent recurrences. Materials and Methods: A retrospective study was conducted on 979 consecutive patients treated for LDH. A multivariate analysis tried to identify a possible correlation between (1) the surgical technique used to treat the primary LDH and its recurrence; (2) technique used to treat the recurrence of LDH and the secon…
Three-dimensional skyrmions in spin-2 Bose–Einstein condensates
2017
We introduce topologically stable three-dimensional skyrmions in the cyclic and biaxial nematic phases of a spin-2 Bose-Einstein condensate. These skyrmions exhibit exceptionally high mapping degrees resulting from the versatile symmetries of the corresponding order parameters. We show how these structures can be created in existing experimental setups and study their temporal evolution and lifetime by numerically solving the three-dimensional Gross-Pitaevskii equations for realistic parameter values. Although the biaxial nematic and cyclic phases are observed to be unstable against transition towards the ferromagnetic phase, their lifetimes are long enough for the skyrmions to be imprinted…
Theoretical and Experimental Study of Polarization Modulation Instability in All-Normal Dispersion Photonic Crystal Fibers
2018
Experimental observation of polarization modulation instability in all-normal dispersion photonic crystal fibers is reported. Stokes and anti-Stokes sidebands with spectral shift of 40 nm were observed when the fiber was pumped at 1064 nm. Experimental results are baked by a vectorial four-wave mixing model.
On Stability of a Concentrated Fiber Suspension Flow
2014
Linear stability analysis of a fiber suspension flow in a channel domain is performed using a modified Folgar-Tucker equation. Two kinds of potential instability are identified: one is associated with overcritical Reynolds number and another is associated with certain perturbations in fiber orientation field and is present for any Reynolds numbers. The second type of instability leads to initially growing transient perturbations in the microstructure. It is shown that both types of instability lead to instability of the bulk velocity field. As for the perturbed Orr-Sommerfeld eigenvalues, the presence of fibers increases the stability region; the stability region increases with growing C i …