Auswahl der wissenschaftlichen Literatur zum Thema „Atténuation différentielle des modes“
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Zeitschriftenartikel zum Thema "Atténuation différentielle des modes":
Huteau, Michel, und Jacques Aubret. „L'activité du service de recherche de l'I.N.E.T.O.P. et du laboratoire de psychologie différentielle (1980-1987)“. L’Orientation scolaire et professionnelle 17, Nr. 4 (1988): 271–308. http://dx.doi.org/10.3406/binop.1988.1676.
Blayo, Chantal. „La condition d'homogénéité en analyse démographique et en analyse statistique des biographies“. Population Vol. 50, Nr. 6 (01.06.1995): 1501–17. http://dx.doi.org/10.3917/popu.p1995.50n6.1517.
Schmitt, A., und B. Bizot. „Retour d'expériences sur l'étude de trois assemblages osseux issus de sépultures collectives néolithiques“. Bulletins et Mémoires de la Société d'Anthropologie de Paris 28, Nr. 3-4 (29.03.2016): 190–201. http://dx.doi.org/10.1007/s13219-016-0156-7.
Goffin, Roger. „Interlinguistique et Terminologie : un bref regard en arrière“. Meta 55, Nr. 1 (30.04.2010): 119–26. http://dx.doi.org/10.7202/039606ar.
Dissertationen zum Thema "Atténuation différentielle des modes":
Bsaibes, Maroun. „Vers une meilleure compréhension des mécanismes de pertes et de couplages de modes dans les fibres optiques légèrement multimodes“. Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILR004.
Numerous technological research initiatives have been conducted in recent years to propose solutions to the upcoming saturation of the capacity of single-mode optical fiber-based telecommunications networks. In these conditions, while information multiplexing is already based on the simultaneous use of several physical dimensions (wavelength, polarization, phase, and time), the addition of a new dimension, namely space, seems to be the most promising solution. Space division multiplexing (SDM) of the data is then possible through the use of multicore fibers (MCF) or few-mode fibers (FMF) and the capacity then becomes proportional to the number of spatial channels available. In the case of FMF, this is known as mode division multiplexing (MDM), with the channels corresponding to the spatial modes guided in the fiber core. However, there are many challenges to overcome in order to achieve low error rate transmissions over respectable distances. Thus, the reduction of the differential mode attenuation (DMA) and the coupling between modes are two obstacles to overcome before considering transposing such a technology to the field.The first objective of this thesis was to identify and quantify the contribution of the different loss sources to the total attenuation of each mode in FMFs with different index profiles but supporting the same number of modes. The second objective was to establish and analyze the suspected link between some attenuation mechanisms, in this case, those related to light scattering, and the coupling between modes. At 1550 nm, it is known that light scattering represents the largest source of attenuation in silica fibers. It is a combination of two factors: Rayleigh scattering which depends on the physico-chemical properties of the material used to create the fiber, and SALS (small angle light scattering), less documented in the literature, which results from fluctuations of the refractive index in the waveguide. In this thesis, the Rayleigh and SALS scattering coefficients were quantified by measuring the angular distribution of the scattered intensity of different modes. In addition, the absorption attenuation (infrared and OH) has also been quantified. On the other hand, a simple method based on optical reflectometry (OTDR) has been applied to compare the Rayleigh coefficient of the same modes propagating in two different FMFs. In parallel, theoretical models have been developed to analyze the obtained results, in particular in the case of SALS. The modal dependencies of the SALS scattering coefficients of different fibers have been qualitatively reproduced. This work provides crucial information for the understanding of the impact of the FMF index profile on the mode attenuation coefficients, leading to a better understanding of the limitations of FMFs and the improvements that can be made to guide their design
Harder, Thomas. „Atténuation des instabilités paramétriques basée sur la pression de radiation dans les détecteurs d’ondes gravitationnelles“. Thesis, Université Côte d'Azur, 2022. http://www.theses.fr/2022COAZ4005.
Direct detection of Gravitational Waves was demonstrated for the first time in 2015 with km-scale Michelson interferometers. In order to reduce the shot noise at high frequency of these detectors high optical power in the arm cavities is needed. At that high circulating power a nonlinear optomechanical phenomenon called parametric instability (PI) may occur that induce the amplification of mirror’s eigenmodes. It limits the optical power and can cause the loss of the interferometer’s control if notmitigated.Several PI mitigation strategies have been proposed and already implemented in current gravitational wave detectors. These schemes keep them working without PI at the current optical power level in the cavities but they are not adapted to PI involving any kind of mechanical mirror modes, which needs to be considered when the optical circulation power is increased further. Next generation detectors aim at increasing their sensitivity of a factor of ten compared to current detectors. This can be achieved, inter alia, through the increase of the optical power in the arm cavities which will imply more PI.In this thesis an active and flexible PI mitigation strategy based on radiation pressure of a movable laser beam is proposed. The idea is to apply a damping force to mitigate PI. Fast beam steering is required to point at different positions of the cavity mirror with a small laser spot during one period of the mechanical mode with frequencies in the kHz-range. A sensitive sensing method is required to detect PI at the level ofthermal excitation.First experimental studies of a table-top setup are presented: rapid beam deflection based on acousto-optic modulators is investigated. A final configuration with 2D arbitrary beam steering with a maximal deflection rate of 10 MHz is demonstrated for a maximal optical power of 3.6 W, corresponding to a radiation pressure force of 24 nN. It satisfies the requirements of the laser beam that should be used as radiation pressure force for our proposed PI damping scheme.Sensing of mechanical mirror modes is investigated with the 2D beam steering system based on a Michelson interferometer. A sensitivity corresponding to a differential arm length change of δL = 4.8 · 10^-14 m/√Hz is achieved for a fixed beam position on the mirror. It is around one order of magnitude higher than the expected displacement of the mirror due to thermally excited mirror modes. Propositions are given to improve the sensitivity of the interferometer and to use the same setup to investigate active damping of mirror modes via radiation pressure
Durand, Stéphanie. „L'atténuation sismique dans le manteau terrestre“. Thesis, Lyon, École normale supérieure, 2012. http://www.theses.fr/2012ENSL0754.
This thesis is devoted to various aspects of seismic attenuation in the Earth's mantle and the consequences on the mantle structure. The challenge is to better understand the attenuation mechanisms, as well as the measurements that can be done, in order to improve the published radial profiles of attenuation and in fine the interpretation of tomographic models.I focus on two examples of attenuation mechanisms, belonging to two kinds of attenuation: the intrinsic attenuation related to the absorption by the medium of a part of the seismic energy then irreversibly dissipated as heat, and the extrinsic attenuation related to the dispersion of the seismic energy by the medium. In the first case, I investigate the effect of phase transitions upon seismic attenuation. Applying the thermo-mechanical model developped by Ricard et al., 2012, to calculate the attenuation of seismic waves due to the phase transition only and comparing the obtained values to published measurements, I succeed in constraining the kinetics of a mantle phase transition. In the second case, I test the seismic anisotropy as a mechanism of extrinsic attenuation, the aim being to find a statistical distribution of anisotropy orientation and layer thicknesses that can reproduce the observed quasi-frequency independence of Q in seismology and laboratory experiments (Knopoff, 1964), and which is, today, only explained by an ad-hoc model (Liu, 1976).Finally, I was interested in measuring the seismic attenuation on real seismograms. After having tested the method of the instantaneous frequency (Ford et al., 2012), I applied it to seismic records sampling the mantle below Central America and Alaska. These measurements are then inverted for a radial profile of shear attenuation which reveals the existence of an attenuating zone in the lower mantle. I also show that these attenuation anomalies are likely to be of chemical origin
Huber, Olivier. „Analyse et implémentation du contrôle par modes glissants en temps discret“. Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT042.
Sliding Mode Control is a control technique with a long history, with research efforts dating back to the 50's. The basic idea is to define the control input as a discontinuous function of the sliding variable, which solely depends on the state, and to constraint the system to evolve on a manifold, hence the term sliding. Over the years a strong theory was build around this technique, but only in continuous time. In our context, this means that control input value can change value at any time. The discrete-time case is when the control input can only change at isolated time instants and the dynamical system on which the control is still a continuous-time process. The control input is therefore a step function. This case appears when the controller is digitally implemented, for instance with the help of a microcontroller. This kind of setup is nowadays ubiquitous in benchmarks and industrial applications. One of the main limitation of the applicability of sliding mode control is the chattering phenomenon that is witnessed when this control technique is applied in practice, but already in simulations. In contrast to previous approaches, we single out the chattering that is already witnessed in simulation, even with no disturbance and with perfect knowledge of the dynamics. This is called the numerical chattering and one of its distinct feature is the constant chattering, or high-frequency bang-bang behavior, of the control input. This naturally induces a chattering of the sliding variable. The claim that this type of chattering is usually predominant and that it is due to a bad discretization of the signum multifunction. The approach developed in this work was inspired by the research effort in the nonsmooth mechanical to properly simulate some systems like those with dry friction and/or unilateral constraints. The main point is to discretize the signum in an implicit fashion, that is its argument is the value of the sliding variable at the end of the next sampling period. With this change, the numerical chattering can be removed in the simplest cases, largely attenuated. The research effort was focused on classical sliding mode controller, rather than the higher order ones. The frameworks used to perform the analysis are convex analysis and variational inequalities. This discrete-time controller enjoys several interesting theoretical properties. First it is finite-time Lyapunov stable: the sliding variable goes to 0 in finite-time. The discrete-time control input converges to the continuous-time one as the sampling period goes to 0. The control action also attenuates the effect of matched perturbations. Also the increase of the gain of the controller does not affect the performances when the system is sliding. The twisting controller can be discretized in the same way and is also finite-time Lyapunov stable. This good theoretical properties have been verified in simulations, but also on experimental setups. Two tests were conducted: the first one on an electropneumatic system, where both the classical first-order sliding mode controller and the twisting algorithm were tested. The objective was to track a reference trajectory. The second one was an inverted pendulum on a cart with only the classical SMC. The goal was to stabilize the system at the unstable equilibrium. The analysis from the data collected during those experiments shows that the proposed controllers perform better than the their explicitly discretized versions. The performances are better and the chattering is effectively reduced
Millot-Langet, Raphaële. „Modélisation des modes propres et des sismogrammes longue-période d' une Terre anélastique en rotation : vers une tomographie anélastique du manteau“. Paris, Institut de physique du globe, 2004. http://www.theses.fr/2004GLOB0009.
The elastic structure of the Earth is relatively well known to seismologists today, but its three-dimensional anelastic structure is still poorly constraint. Using the HOPT perturbation method, we can compute the normal modes of 3D elastic Earth, with the recent addition of the effect of ratation and ellipticity, and a 3D anelastic structure. These modes are then used to compute realistic synthetic seismograms, that show a strong non-linearity between the influence of elastic and anelastic structures. We perform synthetic tests for a joint inversion of the elastic and anelastic parameters, based on the exploration method of the neighbourhood algorithm. These tests are encouraging and give us hope in bringing new constraints on the anelastic structure of the whole mantle, by using real low frequency normal mode
Félix, Simon. „Propagation acoustique dans les guides d'ondes courbes et Problème avec source dans un écoulement cisaillé“. Phd thesis, Université du Maine, 2002. http://tel.archives-ouvertes.fr/tel-00007890.
Pour un guide courbe à deux ou trois dimensions, une formulation multimodale de la propagation acoustique est mise en place et validée, et des équations différentielles matricielles sont établies pour la pression et la vitesse longitudinale, ainsi qu'une équation de Riccati pour la matrice impédance. Si les caractéristiques du coude (section, admittance aux parois) sont constantes, un calcul algébrique de la matrice de diffusion est possible, qui permet l'étude des propriétés de diffusion de ce coude et de tout système complexe composé de conduits droits et courbes. Une comparaison de cette approche, ondulatoire, et d'une matrice de diffusion construite par la méthode des rayons montre une très grande similitude entre ces résultats à haute fréquence. L'atténuation dans un coude traité en parois par un matériau absorbant est enfin étudiée dans le cadre de l'approche multimodale et nous mettons en évidence plusieurs propriétés des conduits courbes traités.
La seconde partie de ces travaux concerne le problème de la propagation acoustique dans un guide droit siège d'un écoulement parallèle cisaillé, en présence d'une source. La fonction de Green de l'équation de Pridmore-Brown est calculée dans un premier temps. Par transformée de Fourier spatiale inverse, les pôles de la fonction de Green font apparaître les modes acoustiques perturbés par l'écoulement, dont il est alors possible de calculer l'amplitude. La présence d'un spectre continu dû à la singularité de l'équation de Pridmore-Brown est également mise en évidence, et la contribution du continuum de modes hydrodynamiques correspondant est étudiée et décrite.
Gaussiat, Nicolas. „Mesure du contenu en eau et en glace des nuages en phase mixte par radars multifréquences“. Toulouse 3, 2002. http://www.theses.fr/2002TOU30216.
Amat, Amandine. „Le changement climatique de la simulation aux modes d'existence : étude de trajectoires climatiques de villes et d'entreprises en Alsace“. Electronic Thesis or Diss., Strasbourg, 2016. http://www.theses.fr/2016STRAG023.
This thesis focuses on the ultimatum imposed by the climate change phenomenon in contemporary Western society : changing the model of society or risk collapse (Diamonds, 2006). The major ordealt hat is required was that of otherwise inhabit the Earth around another project : the fight against climate change. Many publications (Aykut, 2012 ; Dahan, 2015 ; Latour, 2015 ; Roques, 2013 ;Stengers, 2009) describe the inability of state institutions to build a common project to respond to climate challenges. In this situation, the "critical" studies note the important place that has taken the simulation at the expense of concrete and sustainable action. Climate modelling, political and economic simulations, sociological diagnoses, literary fiction, climate change is largely invested by the narrative. Our field immersions have shown that other scales of action are already actively seized ofthe climate deal. Cities and businesses are in fact more likely to take a position in the energy and climate challenge. It follows that some statements, by their position mediators had given way to concrete experiments. Taking a pragmatic approach, inspired by the l’Enquête sur les modes d’existence proposed by Latour, and enriched by the model of Économies de la Grandeur of Boltanski and Thevenot, this thesis attempts to describe the various modes of existence of the climate problem from territorial collectives. We also assuming the rear of influence cultural plans and attachments in producing climate strategies by local actors
Amat, Amandine. „Le changement climatique de la simulation aux modes d'existence : étude de trajectoires climatiques de villes et d'entreprises en Alsace“. Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAG023/document.
This thesis focuses on the ultimatum imposed by the climate change phenomenon in contemporary Western society : changing the model of society or risk collapse (Diamonds, 2006). The major ordealt hat is required was that of otherwise inhabit the Earth around another project : the fight against climate change. Many publications (Aykut, 2012 ; Dahan, 2015 ; Latour, 2015 ; Roques, 2013 ;Stengers, 2009) describe the inability of state institutions to build a common project to respond to climate challenges. In this situation, the "critical" studies note the important place that has taken the simulation at the expense of concrete and sustainable action. Climate modelling, political and economic simulations, sociological diagnoses, literary fiction, climate change is largely invested by the narrative. Our field immersions have shown that other scales of action are already actively seized ofthe climate deal. Cities and businesses are in fact more likely to take a position in the energy and climate challenge. It follows that some statements, by their position mediators had given way to concrete experiments. Taking a pragmatic approach, inspired by the l’Enquête sur les modes d’existence proposed by Latour, and enriched by the model of Économies de la Grandeur of Boltanski and Thevenot, this thesis attempts to describe the various modes of existence of the climate problem from territorial collectives. We also assuming the rear of influence cultural plans and attachments in producing climate strategies by local actors
Tilhac, Cyrille. „Développement d’architectures de filtres à base de résonateurs à ondes acoustiques de volume et contribution à l’intégration dans une technologie avancée silicium industrielle pour des applications radio-fréquences“. Limoges, 2007. http://aurore.unilim.fr/theses/nxfile/default/80d92337-b229-40e2-a75a-1b8eb28464c8/blobholder:0/2007LIMO4012.pdf.
For reasons of cost, consumption, and volume, the complete integration of communication systems seems a subject carrying for the micro-electronic industry. That is why, new resonators with bulk acoustic waves (BAW) are developed. One of the advantages of these resonators is the possibility of integrating them in a complete system on silicon substrate for filtering applications. On the other band, there are variations in the manufacturing process which make that the thicknesses of the deposited materials fluctuate slightly. That directly impacts the resonance frequency of the resonators and it is necessary to compensate these variations if one wishes to carry out an integrated system. The thesis work subject deals with the study and the realization of new filters architectures allowing the use of tuneable BAW resonators