20 research outputs found
Random phononic crystals
No full textAu début des années 1990, une nouvelle discipline de la physique est apparue à travers l'étude des cristaux phononiques. Ce travail s'intéresse aux cristaux phononiques, cristaux artificiels dont les propriétés physiques peuvent être modulées par la nature et/ou la géométrie de leurs composants. Ces matériaux ont ainsi permis la manipulation et le contrôle des ondes élastiques avec des structurations d'inclusions dans l'ordre de grandeur de la longueur d'onde excitatrice. Avec les années 2000, les métamatériaux acoustiques ouvrent de nouvelles perspectives, basées sur le concept physique de milieu effectif aux grandes longueurs d'onde. L'origine des métamatériaux acoustique s'appuie alors sur le concept physique de la résonance propre des inclusions et offrent ainsi de nouvelles applications comme la réfraction négative, le cloaking ou l'hyperfocalisation. Ce travail est une première approche sur l'effet du désordre dans des métamatériaux acoustiques. Pour cela, nous étudions une structure de métamatériau acoustique formée de cylindres sur un substrat semi-infini. Les effets des matériaux et de la géométrie constitutifs des cylindres et de la surface sur les ondes acoustiques de surface seront étudiés. Nous étudions alors le couplage entre piliers et la possibilité de propagation le long d'une chaine. Nous mettons en évidence l'effet de couplage élastique entre piliers à partir du mode de compression et la possibilité de propagation et de contrôle des ondes acoustiques dans les milieux sub-longueur d'onde. L'étude est étendue à une surface à deux dimensions et une distribution périodique, hyperuniforme et aléatoire de la position des piliers.In the early 1990s, a new discipline of physics appeared through the study of phononic crystals. This work focuses on phononic crystals, artificial crystals whose physical properties can be modulated by the nature and/or the geometry of their components. These materials have allowed the manipulation and control of elastic waves with inclusion structures in the order of magnitude of the exciting wavelength. With the 2000's, acoustic metamaterials open new perspectives, based on the physical concept of effective medium at long wavelengths. The origin of acoustic metamaterials is based on the physical concept of eigen resonance of inclusions and thus offer new applications such as negative refraction, cloaking or hyperfocusing. This work is a first approach on the effect of disorder in acoustic metamaterials. For this purpose, we study an acoustic metamaterial structure formed by cylinders on a semi-infinite substrate. The effects of material and geometry of both the cylinders and the surface on the surface acoustic waves is studied. We then study the coupling between pillars and the possibility of propagation along a chain. We highlight the effect of elastic coupling between pillars from the compression mode and the possibility of propagation and control of acoustic waves in sub-wavelength regime. The study is then extended to a two-dimensional surface with a periodic, hyperuniform, and random distribution of the position of the pillars
Cristaux phononiques aléatoires
No full textIn the early 1990s, a new discipline of physics appeared through the study of phononic crystals. This work focuses on phononic crystals, artificial crystals whose physical properties can be modulated by the nature and/or the geometry of their components. These materials have allowed the manipulation and control of elastic waves with inclusion structures in the order of magnitude of the exciting wavelength. With the 2000's, acoustic metamaterials open new perspectives, based on the physical concept of effective medium at long wavelengths. The origin of acoustic metamaterials is based on the physical concept of eigen resonance of inclusions and thus offer new applications such as negative refraction, cloaking or hyperfocusing. This work is a first approach on the effect of disorder in acoustic metamaterials. For this purpose, we study an acoustic metamaterial structure formed by cylinders on a semi-infinite substrate. The effects of material and geometry of both the cylinders and the surface on the surface acoustic waves is studied. We then study the coupling between pillars and the possibility of propagation along a chain. We highlight the effect of elastic coupling between pillars from the compression mode and the possibility of propagation and control of acoustic waves in sub-wavelength regime. The study is then extended to a two-dimensional surface with a periodic, hyperuniform, and random distribution of the position of the pillars.Au début des années 1990, une nouvelle discipline de la physique est apparue à travers l'étude des cristaux phononiques. Ce travail s'intéresse aux cristaux phononiques, cristaux artificiels dont les propriétés physiques peuvent être modulées par la nature et/ou la géométrie de leurs composants. Ces matériaux ont ainsi permis la manipulation et le contrôle des ondes élastiques avec des structurations d'inclusions dans l'ordre de grandeur de la longueur d'onde excitatrice. Avec les années 2000, les métamatériaux acoustiques ouvrent de nouvelles perspectives, basées sur le concept physique de milieu effectif aux grandes longueurs d'onde. L'origine des métamatériaux acoustique s'appuie alors sur le concept physique de la résonance propre des inclusions et offrent ainsi de nouvelles applications comme la réfraction négative, le cloaking ou l'hyperfocalisation. Ce travail est une première approche sur l'effet du désordre dans des métamatériaux acoustiques. Pour cela, nous étudions une structure de métamatériau acoustique formée de cylindres sur un substrat semi-infini. Les effets des matériaux et de la géométrie constitutifs des cylindres et de la surface sur les ondes acoustiques de surface seront étudiés. Nous étudions alors le couplage entre piliers et la possibilité de propagation le long d'une chaine. Nous mettons en évidence l'effet de couplage élastique entre piliers à partir du mode de compression et la possibilité de propagation et de contrôle des ondes acoustiques dans les milieux sub-longueur d'onde. L'étude est étendue à une surface à deux dimensions et une distribution périodique, hyperuniforme et aléatoire de la position des piliers
Cristaux phononiques aléatoires
No full textIn the early 1990s, a new discipline of physics appeared through the study of phononic crystals. This work focuses on phononic crystals, artificial crystals whose physical properties can be modulated by the nature and/or the geometry of their components. These materials have allowed the manipulation and control of elastic waves with inclusion structures in the order of magnitude of the exciting wavelength. With the 2000's, acoustic metamaterials open new perspectives, based on the physical concept of effective medium at long wavelengths. The origin of acoustic metamaterials is based on the physical concept of eigen resonance of inclusions and thus offer new applications such as negative refraction, cloaking or hyperfocusing. This work is a first approach on the effect of disorder in acoustic metamaterials. For this purpose, we study an acoustic metamaterial structure formed by cylinders on a semi-infinite substrate. The effects of material and geometry of both the cylinders and the surface on the surface acoustic waves is studied. We then study the coupling between pillars and the possibility of propagation along a chain. We highlight the effect of elastic coupling between pillars from the compression mode and the possibility of propagation and control of acoustic waves in sub-wavelength regime. The study is then extended to a two-dimensional surface with a periodic, hyperuniform, and random distribution of the position of the pillars.Au début des années 1990, une nouvelle discipline de la physique est apparue à travers l'étude des cristaux phononiques. Ce travail s'intéresse aux cristaux phononiques, cristaux artificiels dont les propriétés physiques peuvent être modulées par la nature et/ou la géométrie de leurs composants. Ces matériaux ont ainsi permis la manipulation et le contrôle des ondes élastiques avec des structurations d'inclusions dans l'ordre de grandeur de la longueur d'onde excitatrice. Avec les années 2000, les métamatériaux acoustiques ouvrent de nouvelles perspectives, basées sur le concept physique de milieu effectif aux grandes longueurs d'onde. L'origine des métamatériaux acoustique s'appuie alors sur le concept physique de la résonance propre des inclusions et offrent ainsi de nouvelles applications comme la réfraction négative, le cloaking ou l'hyperfocalisation. Ce travail est une première approche sur l'effet du désordre dans des métamatériaux acoustiques. Pour cela, nous étudions une structure de métamatériau acoustique formée de cylindres sur un substrat semi-infini. Les effets des matériaux et de la géométrie constitutifs des cylindres et de la surface sur les ondes acoustiques de surface seront étudiés. Nous étudions alors le couplage entre piliers et la possibilité de propagation le long d'une chaine. Nous mettons en évidence l'effet de couplage élastique entre piliers à partir du mode de compression et la possibilité de propagation et de contrôle des ondes acoustiques dans les milieux sub-longueur d'onde. L'étude est étendue à une surface à deux dimensions et une distribution périodique, hyperuniforme et aléatoire de la position des piliers
De la Lecture comme mélange
Get PDFBased on the theory of Roland Barthes Pleasure of the text, this article dives into the work of Charif Majdalani, a French-writing Lebanese author as it questions the contemporary novelistic concept. The ’’récits de filiation’’ of Majdalani’s body of work are studied through their narratology and its effects on the reader. This article also questions the collapse of the sacred trilogy, writer, story-teller and main character, trademark of this 21st century’s literature. The objective here is also to highlight the correlation between the storytelling and the course of History in the Lebanese novel: this double movement allows then the fiction to fill in the voids of the reality
La Recette du roman populaire, façon Alexandre Dumas
No full textThe popular novel is often considered to be second-class literature, orbiting around the Fine Literature. The blame is on the consumerism of its readers that forces the authors to follow a certain style of writing. However, some authors, like Alexandre Dumas, managed to avoid this contempt by getting the acknowledging of the French nation. For this prolific writer, recognition saw the light in the dark alleys of the Pantheon, unlike his works that remain snubbed.The aim of this thesis is to prove that Dumas’ work is a heavy-weight of literature due to the high appeal it has over the masses. Two works grab our attention as they are known to all, but not necessarily read by all: The Count of Monte Cristo and The Three Musketeers. In the first place, we will observe the double reception of each of these novels, before analyzing their imaginary (characters, spaces and genre scenes) on the one hand and narration structure (morphology, narrator and narration) on the other. Through this slow dissection, in the second and third part, we will try to understand how Dumas’ pen casts his spell over the big mass of readers.It thus leads us to specific ingredients that are the signature of the author. Nevertheless, we are compelled to note that this recipe is shared by other writers. It allows popular literature to regain its stripes and its legitimacy.Le roman populaire est souvent associé à une littérature de seconde zone, gravitant autour des Lettres nobles. C’est surtout son public qui est décrié puisqu’il s’agit d’un lectorat de consommation qui impose à l’auteur un mode d’écriture particulier. Toutefois, certains auteurs comme Alexandre Dumas ont réussi à dépasser ce mépris en étant reconnus par la nation française. Pour cet écrivain prolifique, la reconnaissance voit le jour dans les couloirs sombres du Panthéon. Ses oeuvres, elles, demeurent sur le parvis !Ce travail a l’ambition de montrer que l’écriture dumasienne détient un poids littéraire des plus considérables à travers sa sollicitation par les foules. Deux oeuvres retiennent notre attention vu qu’elles sont connues de tous mais pas nécessairement lues par tous : Le Comte de Monte-Cristo et Les Trois Mousquetaires. Après un constat premier sur la réception double accordée à ces romans, nous analyserons leur imaginaire (personnages, espaces et scènes de genre) d’une part et leur structure narratologique (morphologie, narrateur et narration) d’autre part. Cette lente dissection tentera de comprendre, à partir de sa deuxième et de sa troisième partie, le mécanisme de l’attrait exercé par la plume de Dumas sur la grande masse des lecteurs.L’on aboutit ainsi à des ingrédients particuliers qui sont la signature de l’auteur. Néanmoins, force nous est de constater que cette recette est partagée par d’autres écrivains. Elle permet à la littérature populaire de regagner ses galons et d’affirmer sa légitimité
The popular novel recipe – The Alexandre Dumas way
No full textLe roman populaire est souvent associé à une littérature de seconde zone, gravitant autour des Lettres nobles. C’est surtout son public qui est décrié puisqu’il s’agit d’un lectorat de consommation qui impose à l’auteur un mode d’écriture particulier. Toutefois, certains auteurs comme Alexandre Dumas ont réussi à dépasser ce mépris en étant reconnus par la nation française. Pour cet écrivain prolifique, la reconnaissance voit le jour dans les couloirs sombres du Panthéon. Ses œuvres, elles, demeurent sur le parvis! Ce travail a l’ambition de montrer que l’écriture dumasienne détient un poids littéraire des plus considérables à travers sa sollicitation par les foules. Deux œuvres retiennent notre attention vu qu’elles sont connues de tous mais pas nécessairement lues par tous : Le Comte de Monte-Cristo et Les Trois Mousquetaires. Après un constat premier sur la réception double accordée à ces romans, nous analyserons leur imaginaire (personnages, espaces et scènes de genre) d’une part et leur structure narratologique (morphologie, narrateur et narration) d’autre part. Cette lente dissection tentera de comprendre, à partir de sa deuxième et de sa troisième partie, le mécanisme de l’attrait exercé par la plume de Dumas sur la grande masse des lecteurs. L’on aboutit ainsi à des ingrédients particuliers qui sont la signature de l’auteur. Néanmoins, force nous est de constater que cette recette est partagée par d’autres écrivains. Elle permet à la littérature populaire de regagner ses galons et d’affirmer sa légitimité.The popular novel is often considered to be second-class literature, orbiting around the Fine Literature. The blame is on the consumerism of its readers that forces the authors to follow a certain style of writing. However, some authors, like Alexandre Dumas, managed to avoid this contempt by getting the acknowledging of the French nation. For this prolific writer, recognition saw the light in the dark alleys of the Pantheon, unlike his works that remain snubbed.The aim of this thesis is to prove that Dumas’ work is a heavy-weight of literature due to the high appeal it has over the masses. Two works grab our attention as they are known to all, but not necessarily read by all : The Count of Monte Cristo and The Three Musketeers. In the first place, we will observe the double reception of each of these novels, before analyzing their imaginary (characters, spaces and genre scenes) on the one hand and narration structure (morphology, narrator and narration) on the other. Through this slow dissection, in the second and third part, we will try to understand how Dumas’ pen casts his spell over the big mass of readers. It thus leads us to specific ingredients that are the signature of the author. Nevertheless, we are compelled to note that this recipe is shared by other writers. It allows popular literature to regain its stripes and its legitimacy
Strong Acousto-Plasmonic Coupling in Film-Coupled Nanoparticles Mediated by Surface Acoustic Waves
No full textInternational audienceThe interaction between phonons and localized plasmons in film-coupled nanoparticles designs can be exploited both for modulating the scattered electromagnetic field and the understanding of the mechanical vibrations at nanoscale. In this paper, we show by finite element numerical analysis an enhanced optomechanical interaction in a film-coupled gold nanoridges or pillars mediated by surface acoustic waves. The metallic nanoparticles are placed atop a multilayer structure consisting of a thin dielectric spacer covering a gold film layer on a silicon dioxide/or silicon substrate. Optical simulations reveal the existence of surface localized plasmons in the infrared range confined under the nanoparticles in the dielectric spacer and/or in between such particles. Optomechanical coupling between the plasmonic modes and localized phonons is evaluated from the shift in the plasmon eigenfrequency. It is found that the compressional, the in-phase compressional and the out-of-phase flexural modes, yield the highest coupling rates. Such phonons are excited by means of SAW launched from the system inlet in front of the particles. The findings in this paper could help design new generation of acousto-optic modulators monitored by fast coherent surface acoustics
Evanescent coupling between aluminum pillars
No full textposterInternational audienceWe theoretically investigate, with the help of the finite element method, the interaction between aluminum pillars erected on top of a semi-infinite substrate of silicon in the low frequency range. Our interest is to control and manipulate the propagation of the surface acoustic waves through a linear chain of pillars for frequencies in the [0, 2] GHz range. We show that two pillars can interact together in near field through the excitation of their resonant compressional eigen mode. We will then investigate the resonant modes of a finite linear chain of N pillars, in order to analyze the possibility of propagation along the chain. To reach this objective and to relax the numerical stresses, we have considered a periodicity in the direction perpendicular to the propagation where the lattice parameter is significantly higher to avoid any interaction between two adjacent lines of pillars
Enhanced phonon-plasmon interaction in film-coupled dimer nanoridges mediated by surface acoustic waves
No full textInternational audienceThe interaction between phonons and localized plasmons in coupled nanoparticles can be exploited both for modulating the scattered electromagnetic field and the understanding of the mechanical vibrations at nanoscale. In this paper, we demonstrate by numerical analysis an enhanced optomechanical interaction in a film-coupled gold dimer nanoparticles mediated by surface acoustic waves. Two gold nanoridges are placed atop a multilayer structure consisting of a thin dielectric spacer covering a gold film layer on a silicon dioxide substrate. Numerical simulations of the optical properties reveal the existence of three surface localized plasmons in the infrared range with enhanced scattering and narrower linewidths than with a single nanoridge. The physical origin of such modes as well as their tunability as function of key geometrical parameters are successfully captured with a simple model based on effective Metal-Insulator-Metal (MIM)-like plasmonic cavity. We calculate the optomechanic coupling rates between the GHz localized mechanical modes and plasmonic modes of the dimer, finding that the strongest coupling is observed for the in-phase compressional mode followed by the out-of-phase flexural mode. Both such modes can be excited by launching a surface acoustic wave (Sezawa wave) at the inlet in front of the dimer structure. It is also found that the flexural mode which is inactive optomechanically in case of a monomer becomes active due to dimer coupling, with a significant phonon-plasmon coupling rate. The findings in this work may facilitate design of new optomechanical components monitored with fast coherent acoustics, leading to new generation of light acousto-optic modulators where strong optomechanical interactions are required
Surface acoustic waves-localized plasmon interaction in pillared phononic crystals
No full textInternational audienceWe study numerically the interaction of surface acoustic waves propagating at the surface of a multilayer structure (the so-called Sezawa waves) with localized surface plasmons at the bottom of metallic pillars deposited on the substrate. The pillars are made of gold and the multilayer structure is constituted by a layer of gold on a silicon substrate and covered by a thin spacer of dielectric material. We are interested in localized plasmons, which are the analog of metal-dielectric-metal surface plasmons. The physical characteristics of these plasmons, such as their eigenvalues and absorption or reflection spectra, are modulated by surface acoustic waves due to deformation of the structure in the vicinity of the pillars. The surface waves are generated in the area in front of the pillars deposited on the substrate. Two types of acoustic modes are envisioned to interact with the localized plasmons, namely, confined modes associated with the local resonances of the pillars and the propagating Sezawa modes that deform the structure in the vicinity of the surface. We discuss the efficiency of phonon-plasmon coupling for both types of modes and select those that can be useful for an experimental realization based on this platform. Also, we show that, besides the plasmon frequency, the phonon-plasmon coupling magnitude strength is sensitive to the distance between the pillars, which reveals the role of interactions between the pillars on the coupling. The geometrical parameters are chosen such that the acoustic waves are in the sub-GHz range and the plasmons are around the telecommunication wavelength of 1.55 mu m. This work may help with the design of optomechanical devices that can be controlled by fast coherent acoustics and facilitate applications involving enhanced sound-light interactions, such as light modulation
