Particules indiscernables

Résumé

Les particules indiscernables ou particules identiques sont des particules qui ne peuvent être différenciées l'une de l'autre, même en principe. Ce concept prend tout son sens en mécanique quantique, où les particules n'ont pas de trajectoire bien définie qui permettrait de les distinguer l'une de l'autre. Les particules indiscernables peuvent être soit des particules élémentaires telles que l'électron ou le photon, ou des particules composites - neutron, proton - ayant le même état interne. Le théorème spin-statistique permet de classer les particules en deux grandes familles : les bosons, de spin entier, et les fermions, de spin demi-entier. Lors de l'échange de deux particules identiques, l'état quantique global d'un ensemble de bosons indiscernables n'est pas modifié alors que l'état d'un ensemble de fermions est changé en son opposé. En conséquence, deux fermions identiques (par exemple deux électrons) ne peuvent se trouver dans le même état, ce qui est connu comme le principe d'

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

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L'objectif de ce cours est de familiariser l'étudiant avec les concepts, les méthodes et les conséquences de la physique quantique. En particulier, le moment cinétique, la théorie de perturbation, les systèmes à plusieurs particules, les symétries, et les corrélations quantique seront traité

Wave physics, Introduction to quantum mechanics.

Following an introduction of the main plasma properties, the fundamental concepts of the fluid and kinetic theory of plasmas are introduced. Applications concerning laboratory, space, and astrophysical plasmas are discussed throughout the course.

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Influence of consecutive sediment replenishment on channel bed morphology

Elena Battisacco, Lena Bösch, Mário Jorge Rodrigues Pereira Da Franca, Anton Schleiss

Dams interrupt the longitudinal connectivity of a river as they store water and trap sediment. When transport capacity downstream of dams exceeds sediment supply, water becomes hungry and channel incision, bed armouring and reduction of morphological diversity are the consequences. Sediment replenishment is an increasingly common measure to restore the sediment regime of such disturbed river reaches. In the present study the influence on channel bed morphology of different geometrical configuration of replenishments and of consecutive gravel augmentation is assessed by means of systematically laboratory experiments. The typical features of a straight armoured alpine gravel channel are reproduced on the model in terms of slope, cross section and bed grain size. The total amount of replenished sediment is deposited in four identical volumes following two different geometrical configurations (parallel and alternating). The reaction of the channel bed is analysed on image and laser data. Persistency of the first replenishment is high and it covers a large portion of the channel bed, which consequently decreases channel bed roughness remarkably. The persistency of the second replenishment is low and the effect on the depositional pattern established after the first replenishment only minor. This is explained by the smoothing of the channel bed during the first replenishment, resulting in higher transport capacities. For the alternating configuration an increase in the deposition heights in the very downstream channel reach can be observed due to the second replenishment. Thus it is assumed that consecutive replenishment can increase the impact length of restoration projects. The parallel configuration results in very spread depositions, while for the alternating configuration a clear bed form pattern could be observed with a wavelength of depositions corresponding to the length of the replenished volumes. These depositions are understood as mounds, forming the initial condition of alternating bars. Thus in order to enhance channel bed topography of an armoured layer downstream a dam, sediment replenishment added by the alternating configuration is most favourable and effective.

2016

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Similarity conditions and cube model tests of snow drift and precipitation preferential deposition patterns

Michael Lehning, Borui Zhang, Qingwen Zhang

We explore the process of modeling aeolian snow transport around buildings by proposing a set of similarity requirements on simulating a single snow fall event with drifting. The similarity criteria are used to guide our wind tunnel tests from the particle selection to the simulation set-up, including the determination of test wind speed, snowfall intensity and transported snow profile. In parallel, a specific field experiment on snow precipitation and drift around a 1-m prototype cube was achieved in Harbin to serve as the reference for the subsequent test validation. After reproducing a target wind and snow environment with a scale of 1:4 versus that of the prototype measurement, two verification tests were put forward using snow and substitution particles, which can mimic the effects of changing wind directions on the snow distribution. Herein, the wind tunnel and outside prototype results show good qualitative agreement in our limited range of length scales and particle properties. In future work, the range of scales and range of parameter values should be increased.

ELSEVIER2021

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Following the analytic approach to thermodynamics developed by Stuckelberg, we study the evolution equations of a closed thermodynamic system consisting of point particles in a fluid. We obtain a system of coupled differential equations describing the mechanical and the thermal evolution of the system. The coupling between these evolution equations is due to the action of a viscous friction term. Finally, we apply our coupled evolution equations to study the thermodynamics of an isolated system consisting of identical point particles interacting through a harmonic potential.

MDPI AG2011

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Influence of consecutive sediment replenishment on channel bed morphology

Elena Battisacco, Lena Bösch, Mário Jorge Rodrigues Pereira Da Franca, Anton Schleiss

2016