Lunettes

Résumé

vignette|Une paire de lunettes. Les lunettes sont un instrument permettant de pallier les défauts visuels ou de protéger les yeux. Une paire de lunettes est constituée d'une monture sur laquelle sont fixés des verres correcteurs ou protecteurs et reposant sur le nez et sur les oreilles par deux branches (80 % du poids des lunettes reposant sur le nez). Description et typologie vignette|Moine aux lunettes, sculpture de la cathédrale de Meaux. Les verres correcteurs sont enchâssés sur une monture reposant sur le nez. La monture est une armature composée de la face et de deux branches. La face est constituée de deux cercles et d'un pont muni de plaquettes, appelé aussi nez. Les branches, posées sur les oreilles, assurent la stabilité des lunettes : équipées de charnières pour être repliées, elles sont munies à leur extrémité d'un embout ou manchon formant le crochet (partie recourbée et flexible) destiné à protéger la peau derrière l'oreille. Dans une monture plastique, la

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https://fr.wikipedia.org/wiki/Lunettes

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Séances de cours associées (29)

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Local excitations in amorphous solids

Wencheng Ji

Amorphous solids are structurally disordered. They are very common and include glasses, colloids, and granular materials, but are far less understood than crystalline solids. Key aspects of these materials are controlled by the presence of excitations in which a group of particles rearranges. This motion can be triggered by (a) quantum fluctuations associated with two-level systems (TLS), which dominate the low temperature properties of conventional glasses and have practical importance on superconducting qubits; by (b) thermal fluctuations associated with activations, which are related to the famous and challenging

glass transition'' problem; or by (c) exerting an external stress or strain associated with shear transformations, which control the plasticity. Hence, it is important to understand how temperature and system preparation determines the density and geometry of these excitations. The possible unification of these excitations into a common description is also a fundamental problem.  These local excitations are thought to have a close relationship with

Quasi-localised modes (QLMs)'' which are present in the low-frequency vibrational spectrum in amorphous solids. Understanding the properties of QLMs and clarifying the relation between QLMs and these local excitations are important to the study of the latter. In this thesis: (1) we provide a theory for the QLMs, D_L(omega) ~ omega^alpha, that establishes the link between QLMs and shear transformations for systems under quasi-static loading. It predicts two regimes depending on the density of shear transformations P(x)~ x^theta (with x the additional stress needed to trigger a shear transformation). If theta>1/4, alpha=4 and a finite fraction of quasi-localised modes form shear transformations, whose amplitudes vanish at low frequencies. If theta

EPFL2021

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Interactive Mobile Robotic Drinking Glasses

Michele Leidi, Francesco Mondada, François Rey

The central idea behind this attempt is to merge common objects and robotics to obtain a new type of interactive artefact, we call robjects. Robjects provide services to everyday life and can be controlled by the user in a very intuitive way. Robjects take rarely the initiative, have few decisional autonomy. Most of their activity is centered and controlled by the interaction with the user. To test this concept in a concrete experimentwe decided to include mobile robotic technology into drinking glasses to improve their service on a table. Making them mobile and interactive brings a new dimension to the table, simplifies service and improves security. The system works in the following manner : when a user starts filling a glass, the other empty glasses come closer to get filled too and then go back to their initial position. Owners of the glasses can refuse to fill their glasses by simply bringing back the glass on its initial position as soon as the glass starts to move. The system has been prototyped and tested. The analysis of the interaction of some users shows strengths in interactivity and weaknesses in the speed of the system and in reliability of the actual prototype.

Springer2009

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Marginal Stability in Structural, Spin, and Electron Glasses

Markus Müller, Matthieu Wyart

We revisit the concept of marginal stability in glasses and determine its range of applicability in the context of an avalanche-type response to slow external driving. We argue that there is an intimate connection between a pseudogap in the distribution of local fields and crackling in systems with long-range interactions. We classify glassy systems according to the presence or absence of marginal stability, providing a unifying perspective on the phenomenology of systems as diverse as spin and electron glasses, hard spheres, pinned elastic interfaces, and soft amorphous solids undergoing plastic deformation. © 2015 by Annual Reviews.

2015

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