Search results for "linéaire"
showing 10 items of 78 documents
Electronic implementation of a non-linear oscillator subjected to noise : application to the modeling of neuronal information coding
2011
We study the nonlinear FitzHugh-Nagumo model witch describes the dynamics of excitable neural element. It is well known that this system exhibits three different possible responses. Indeed, the system can be mono-stable, oscillatory or bistable. In the oscillatory regime, the system periodically responds by generating action potential. By contrast, in the mono-stable state the system response remains constant after a transient. Under certain conditions, the system can undergo a bifurcation between the stable and the oscillatory regime via the so called Andronov-Hopf bifurcation. In this Phd thesis, we consider the FitzHugh-Nagumo model in the stable state, that is set near the Andronov-Hopf…
Evaluation ex ante des conséquences de l'adoption de la production intégrée en grandes cultures à l'échelle de la Bourgogne
2015
The agriculture in France is under intense pressure. Farmers are asked to change their crop management, to evolve toward agroecology, to follow the principles of Integrated Pest Management (IPM) and to reduce pesticide use. However such an evolution toward an alternative agricultural model will be possible only if innovative cropping systems are able to maintain competitive and profitable farms.The aim of our work is to contribute to the debates about this issue, by evaluating ex ante the potential consequences of adopting the principles of IPM over one whole agricultural region, taking into account the diversity of production situations within this region. We considered the Burgundy region…
Statégie d'échantillonnage de la flore des bordures herbacées des parcelles cultivées
2012
National audience; 84 % des espèces cultivées en Europe et 80 % des espèces végétales dans le monde dépendent pour leur pollinisation des insectes pollinisateurs dont le déclin est actuellement avéré. La flore des bordures des champs pourrait jouer le rôle de réservoirs ou de ressources complémentaires en termes de nectar ou pollen pour les insectes pollinisateurs. Pour répondre à cette question, nous avons effectué des relevés de la production florale de la flore (espèces adventices et espèces rudérales) présente le long de ces bordures herbacées. Il existe actuellement différentes stratégies d’échantillonnages pour caractériser la flore intra‐parcellaire mais peu ou pas de stratégies ont …
Caractérisation d'une fibre optique ultra non-linéaire en verre de chalcogénure
2009
session orale 3 « Effets nonlinéaires » [Ma1.4], http://optiquelille2009.univ-lille1.fr/; National audience; Nous présentons les résultats expérimentaux concernant la caractérisation d'une fibre optique microstructurée en verre de chalcogénure de composition AsSe. Ces mesures concernent l'atténuation, la dispersion, l'aire effective et le coefficient non-linéaire du troisième ordre. Cette fibre présente un fort potentiel pour des applications non-linéaires avec un coefficient non-linéaire Kerr de 15 400 W-1m-1.
Microfibres for nonlinear optics
2011
In this thesis, I present my works on the fabrication, the characterization and the use of optical microfibres. Microfibres are optical fibres drawn down to sub-wavelength diameters by a temperature controlled process. Due to their small dimensions, microfibers have very special properties such as a high confinement of the electromagnetic field, a enhanced non-linear coefficient and a large evanescent tail. These properties are studied in the first chapter, after which a description of the techniques used for the drawing and manipulation of the microfibres is given. Next, we present our experiments on non-linear effects in silica microfibres. In particular, we show that it is possible to ge…
Observateur et contrôle optimal : améliorer l'efficacité de la conduite automobile avec Kalman et Pontryagin
2010
The PhD presents a combined approach to improving individual car efficiency. An optimal observer, the Extended Kalman Filter, is used to create an efficiency model for the car. Particular attention was paid to handling the asynchronous and redundant nature of the measurement data. A low-cost sensor suite developed to measure data is described. This sensor suite was installed on multiple vehicles to good success. It employsan accelerometer, gps, fuel injector timer, and Vss input to measure all the data necessary to reconstruct the car's state. This observer and sensor suite can be used as the base for any study which requires car efficiency maps, allowing research to proceed without manufac…
Etude des sources supercontinuum à fibres transparentes dans le moyen infrarouge
2012
The work reported in this thesis deals with the study of the supercontinuum generation in fibers transparent in the mid-infrared. To generate a supercontinuum between 3 and 5 µm we compare different glass families such as fluoride glasses, tellurite glasses and chalcogenide glasses. These fibers are pumped with fiber lasers emitting at 2 µm with nanosecond or picosecond pulse duration. This wavelength allows us to reach the zero dispersion wavelength of the chalcogenide tapered fibers. We report supercontinuum generation up to 3800 nm in a fluoride glass fiber. A connection with 75 % of transmission is made between a ZBLAN and a SiO2 fiber. We also measured absorption lines of the methane a…
Nouveaux systèmes de contrôle de la polarisation de la lumière par effets non lineaires dans les fibres optiques
2013
This thesis deals with the work the development of an all-optical device for the control of the polarization state of light. Actually, this feature of light remains so far an uncontrolled variable, which can degrade the performances of all-optical systems. Based on nonlinear interaction between two counterpropagating waves inside an optical fiber, this device called polarization attractor allows to control the polarization state of light without polarization dependent losses.In a first part, we carry out extensive studies of the polarization attractor properties leading to the control and the regeneration of the polarization state of the 10-Gb/s NRZ and RZ telecommunication signals. Then, t…
Nonlinear resonances and some of their applications to information processing
2021
The study of resonance phenomena in nonlinear dynamical systems has drawn considerable attention for years. The most studied nonlinear resonance is undoubtedly the famous stochastic resonance, which consists of perturbing a nonlinear system with an appropriate amount of noise to enhance the detection of a subthreshold input signal. Since the introduction of stochastic resonance in the context of climate dynamics, it was later observed that a deterministic high frequency perturbation can replace noise leading to vibrational resonance. Even if this latter resonance was investigated in many areas of science for more than two decades now, it is still receiving attentions. It is the subject of t…
High bit rate optical pulses sources generation and microstructured chalcogenide fibers characterizations
2011
This memory of thesis s' registered voter in the context of the FUTUR project financed by l'ANR and concerning the development of optical finctions fot the high bit-rate transmissions in the Network heart and carries on very high rates optical fibers sources generation and the optical chalcogenide microstructured fiber charaterization. For this purpose, we study the linear and non-linear characteristics of microstructured chalcogenide fibers conceived and realized in various collaborations within the framework of the ANR FUTUR project. For that a great number of characterizations methods were developed giving a comparison between a standard single mode fiber and there microstructured chalco…