Essai sur la corde vibrante et ses non-linéarités.

As soon as its elasticity is sollicitated, the Melde vibrating string exhibits a strong nonlinear behaviour even though it is made of a perfectly elastic material. When sinusoidally excited by means of an electric vibrator, the string's motion may become bistable, yielding hysteresis cycles. We propose a simple model accounting for these cycles, and bringing in a unique adjustable parameter gathering the wealth of dissipative processes that limit the string's oscillation amplitude

The adiabatic invariant of any harmonic oscillator : an unexpected application of Glauber's formalism

In this theoretical paper, we propose a general derivation of the adiabatic invariant of the n-degree-of-freedom harmonic oscillator, available whichever the physical nature of the oscillator and of the parametrical excitation it undergoes. This derivation is founded on the use of the classical Glauber variables and ends up with this simplest result: the oscillator's adiabatic invariant is just the sum of all the semiclassical quanta numbers associated with its different eigenmodes

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Theorie phenomenologique du transport dans les supraconducteurs de type II. Effet Joule de surface

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 78245 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Physique statistique

Maste

Physique des transports (théorie classique)

Chapitre 1 - IntroductionChapitre 2 - Transport dans les métauxChapitre 3 - Transport dans les fluidesChapitre 4 - Modèle de DrudeChapitre 5 - Théorie statistique du transportChapitre 6 - Théorie statistique classique du transport dans les métauxChapitre 7 - Théorie statistique du transport dans les fluidesMasterExposé de la physique des transports sous deux approches : thermodynamique et statistique (équation de Boltzmann)

L'oscillateur harmonique comme introduction pédagogique à la mécanique quantique

Stemming from the similar linearities of the Schrödinger equation in quantum mechanics on the one hand and of the harmonic oscillations in classical mechanics on the other hand, the idea that any N-degree-of-freedom harmonic oscillator (HON) is formally equivalent to a N-level quantum system is put forward. It is shown that the complex dynamic variables α introduced by R. J. Glauber can be regarded as the components of a state vector belonging to some N-dimension complex Hilbert space, and whose time-evolution is ruled by a Schrödinger-like equation. In case the classical HON is parametrically excited, the unitarity of the time-evolution of the associated quantum system is related to the Ehrenfest adiabaticity of the parametric excitation

L'oscillateur harmonique comme introduction pédagogique à la mécanique quantique

Stemming from the similar linearities of the Schrödinger equation in quantum mechanics on the one hand and of the harmonic oscillations in classical mechanics on the other hand, the idea that any N-degree-of-freedom harmonic oscillator (HON) is formally equivalent to a N-level quantum system is put forward. It is shown that the complex dynamic variables α introduced by R. J. Glauber can be regarded as the components of a state vector belonging to some N-dimension complex Hilbert space, and whose time-evolution is ruled by a Schrödinger-like equation. In case the classical HON is parametrically excited, the unitarity of the time-evolution of the associated quantum system is related to the Ehrenfest adiabaticity of the parametric excitation

Essai sur la corde vibrante et ses non-linéarités.

As soon as its elasticity is sollicitated, the Melde vibrating string exhibits a strong nonlinear behaviour even though it is made of a perfectly elastic material. When sinusoidally excited by means of an electric vibrator, the string's motion may become bistable, yielding hysteresis cycles. We propose a simple model accounting for these cycles, and bringing in a unique adjustable parameter gathering the wealth of dissipative processes that limit the string's oscillation amplitude

The two-degree-of-freedom parametric oscillator: A mechanical experimental implementation

We report the observation and quantitative measurements of the parametric resonance of a two-degree-of-freedom harmonic oscillator made of two coupled pendula. When varying the length of one of the pendula, we parametrically excite the whole set. The frequency of this excitation can be tuned and its depth ajusted, enabling us to draw a frequency-depth Cartesian diagram in which the oscillation behaviour, namely finiteness or exponential divergence, can be plotted. As in the well-known case of the one-degree-of-freedom oscillator, the stability and instability domains are demarcated by a tongue centred at twice the oscillator's free frequency. But in the two-degree-of-freedom oscillator case, this tongue has a three-tip fine structure, two tips corresponding to the free oscillator's eigenfrequencies and an extra tip corresponding to the average of both eigenfrequencies. This situation is unravelled theoretically using a classical adaptation of a formalism introduced in quantum optics by Glauber