Dissertations / Theses on the topic 'Réseaux compacts'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 30 dissertations / theses for your research on the topic 'Réseaux compacts.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
Todeschini, Fabien. "Dimensionnement énergétique de réseaux de capteurs ultra-compacts autonomes en énergie." Thesis, Supélec, 2014. http://www.theses.fr/2014SUPL0008/document.
Wireless sensors have a bright future so their development is causing a lot of research.However, their autonomy is still an issue.This work focuses on this problem : find a strategy for the sensors to be autonomous.The energy required to power the sensor, whatever its working mode, must indeed be harvestedfrom the environment wherein the sensor is located. Moreover, in case of absence ora lack of available energy, the sensor has to keep working. Additionnaly the state-of-chargehas to be known in real time in order to extend the sensor lifetime. Finally, the energy managementhas to give the highest efficiency.This study led to the design and the test of a circuit in CMOS 90nm technology. Thiscircuit was integrated in wireless sensors for networks under development. Finally, a methodto estimate the level of energy in the sensor has been developed and will allow to design anew circuit of power management for wireless sensor network
Akale, Yao. "Compétitions inter-standards : modélisation des dynamiques de réseaux complexes interorganisationnels." Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL12005/document.
Throughout this thesis we’ve attempted to explain standard competitions through the interorganizationalnetworks built by the protagonists. Based on the synthesis of theories derived from three main academic fields(economy of the standards and network industries, networks analysis and strategic management), the thesiselaborates proposals which make it possible to build a model network of comprehension of these competitions. Ituses a single case study, chooses a critical realistic epistemological positioning and bases itself on the empiricalsituation of competition between Blu-Ray and HD DVD technologies for the emergence of the secondgeneration standard DVD. The entire trend of the thesis is justified by a postulate of a methodological andtheoretical proximity of the interorganizational network of sponsors of a given standard and the installed base ofthat standard. This postulate made it possible to state that the interorganizational network made it possible notonly to generate the ideal installed base to win the competition, but also to impact all the others components(reliability and technical superiority, availability of complements, lock-in the consumers by the switching costs,timing of entry to the market, etc.). By mobilizing some concepts of “growth” and “resilience” of complexnetworks approaches, (Albert & Barabasi 2002, Newman, 2003a) and those of “potential power ” and “use ofpower” of authors in management (Brass & Burkhardt, 1993, Mintzberg 1983 etc.), we concluded that thesuccess in a competition between standards lies in building up a growing and resilient interorganizationalnetwork, the potential of which must actually be used on the industrial and commercial ground
Tounou, Charles. "Contribution à l’étude de systèmes à diversité d’antennes sur terminaux compacts : mesures de performances en environnement réel." Limoges, 2008. https://aurore.unilim.fr/theses/nxfile/default/0662821a-fd19-48bc-9e75-2c3ce2be923e/blobholder:0/2008LIMO4042.pdf.
Wireless communication performances are improved by using multiple antennas or multiple access systems: this is the antenna diversity principle. Diversity studies, its analysis and some measurement results are depicted in this PhD thesis. First, numerical tools that allow the calculation of diversity parameters are developed. These tools are highly efficient since they are independent of any assumption. Second, a preliminary study of the relationships between mutual coupling and diversity parameters is done. The results demonstrated that mutual coupling and correlation coefficients should be preferably low. This conclusion is used to design and optimize a compact terminal that consists of two printed monopole antennas working in the WiMax 3. 4-3. 6GHz band by a slot insertion for decoupling. Next, measurements took place in a modes stirred reverberation chamber (MSRC) using two different test-beds. The first one used a network analyzer which delivers a constant wave in the chamber. The second one is constituted by two independent digital communication modules (transmission and reception). This latest test-bed allows also measurements in indoor and indoor to outdoor environments. Finally, an analytical study proves that antenna diversity and radiation pattern synthesis are equivalent
Touhami, Abdellah. "Optimisation multi-objectif d'antennes superdirectives compactes à balayage de faisceau pour des passerelles domestiques 5G sans fil." Electronic Thesis or Diss., Université de Rennes (2023-....), 2024. http://www.theses.fr/2024URENS002.
The evolution of wireless communication impose the need for more sophisticated antenna architectures, combined with antenna diversity and beamforming techniques. This type of antenna offers new possibilities for wireless applications in terms of spectral efficiency, radio link reliability, reduced environmental impact and increased communications system capacity. However, conventional beamforming techniques often lead to a significant increase in antenna size. As a result, the integration of such systems into small wireless devices is relatively limited. Compact, superdirective antenna arrays offer an innovative and attractive solution for both beamforming needs and integration in small volumes. However, they exhibits multiple drawbacks, including low radiation efficiency, low gain and narrow bandwidth. These drawbacks limit the usefulness of superdirective arrays to meet the needs of new-generation wireless technologies. In this thesis, we propose new multi-objectives optimization methods, based on network characteristic mode theory (NCM), array factor theory as well as artificial neural networks (ANN), for the design and the development of new compact, superdirective, efficient and wideband antenna architectures for 5G applications
Debard, Alexandre. "Analyse et optimisation d'antennes réseaux compactes superdirectives." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALT058.
The purpose of this thesis is to study and seek improvement of the superdirective antenna array technology. This technology has been recently re-examined in the literature since it can bring some interesting functionalities in the future telecommunication applications. The examination of this type of antenna is thus conducted through the use of Spherical Wave Expansion which allows for the general study of directivity limits as well as gain limits, considering lossy antennas. The classical theory of end-fire array antennas is also reviewed, in the case of uniformly spaced tapered arrays, providing theoretical evaluation of efficiency and sensitivity to source feeding precision.Infinitesimal dipoles and Huygens sources are considered in a proposed development that links array theory and Spherical Wave Expansion. This contribution provides a formal proof for the directivity limit of Huygens-source-based end-fire arrays as well as an upper bound for the directivity of dipole-based arrays, when the inter-element spacing tends to zero. Moreover, it is shown how classical array theory can also be used to derive excitation coefficients that maximize gain rather than directivity, when loss resistances are considered. An examination over antenna size is also made to demonstrate which conditions are most favorable for the use of such supergain or superdirective end-fire array optimization.In a second part, practical implementations of superdirective antennas are surveyed, focusing on Huygens sources and compact end-fire array designs. The chosen implementation architecture of parasitic element arrays is then detailed and studied, in order to minimize the requirement for negative or positive resistive loads. This lead to the design and measurement of five prototypes that aim at achieving the maximum possible gain or directivity for a limited radiator size, with two-, three- and four-dipole end-fire arrays
Halftermeyer, Pierre. "Connexité dans les Réseaux et Schémas d’Étiquetage Compact d’Urgence." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0140/document.
We aim at assigning each vertex x of a n-vertices graph G a compact O(log n)-bit label L(x) in order to :1. construct, from the labels of the vertices of a forbidden set X C V (G), a datastructure S(X)2. decide, from S(X), L(u) and L(v), whether two vertices u and v are connected in G n X.We give a solution to this problem for the family of 3-connected graphs whith bounded genus.— We obtain O(g log n)-bit labels.— S(X) is computed in O(Sort([X]; n)) time.— Connection between vertices is decided in O(log log n) optimal time.We finally extend this result to H-minor-free graphs. This scheme requires O(polylog n)-bit labels
Dourisboure, Yon. "Routage compact et longueur arborescente." Bordeaux 1, 2003. http://www.theses.fr/2003BOR12760.
In a network, the ability to construct efficent routing schemes is crucial. Each unit, with its local knowledge of the network, has to be able to decide in which direction to forward the message. In the first part of this thesis, we construct compact routing schemes for chordal graphs and for graphs which admit tree-decomposition with small diameter bags. In this work, it appeared to us that, to construct additive streched routing schemes, it seems more judicious to consider the diameter of the bags rather than their cardinality (the tree-width), the diameter of a bag is the longest distance between two of its vertices. In this way, we introdice a new invariant fo graphs : the tree-length, with complete the notion of tree-width. In the second part, we sho tha this new parameter is useful in the construction of routing schemes, of distance labellings, and of sparse spanners. Then we compute the tree-length of any outer-planer graphs and of any grid. We show that it is not possible to minimize both length and width in a same tréé-decomposition. Finally we study two algrorithms and we propose a heuristic, all three of wich approximate the tree-length of any graph
Martin, Loïc. "Conception d’une antenne compacte de station de base pour réseaux cellulaires." Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4009/document.
Cellular networks undergo majors changes in the world. Several standards have been deployed since 1980. The enthusiasm of the general public quickly saturated the first generations and the number of services increases for every standard. Development of a new one is the occasion to find new ways to simplify the radio architecture in order to relieve consumers high quality of service. Today, this radio architecture has been simplified but base station antennas have become more and more critical for their size and create problems in towns specially. Moreover, constraints from the government and consumers associations contest deployment of new base station. Works of the thesis are focused on increasing base station antenna gain based on two different technologies. Then, conception of compact radiating elements was developed and presented through a small array. Good results open new perspectives to realize a compact multiband base station antenna thanks to new compact radiating element sized in others frequency bands
Linot, Fabrice. "Apport des Surfaces à Haute Impédance à la conception d'antennes réseaux compactes et d'antennes réseaux à très large bande passante." Phd thesis, Télécom ParisTech, 2011. http://pastel.archives-ouvertes.fr/pastel-00617270.
Halnaut, Adrien. "Méthodes et outils d’analyse visuelle pour la compréhension, l’optimisation et l’élaboration de modèles de réseaux de neurones profonds." Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0042.
Deep‐learning methods are widely used in a variety of research and industrial domains, especially in the data classification task. However, this technology is often notoriously compared to a “black box”. The user can understand input and output data of the network, but has little to no knowledge about its internal processing. This aspect of neural networks makes difficult to justify their predictions. Explainability and Interpretability of deep neural networks is a research domain merging with a variety of scientific communities. Its goal is to make easier the understanding of neural networks for both users and experts. Information visualization is one of the techniques used to answer this need. It consists in building tools which make easier the understanding and the analysis of usually high dimensional datasets, using visual abstractions and interactions. In this thesis, we make use of data extracted from the output of each layer of the neural network to interpret the model decisions using visualization methods. First, we show it is possible to visualize groups of samples processed similarly by the network using a Sankey diagram. This method asks for large data processing, which we enable by using machine clusters infrastructures used in BigData operations. In order to study more complex scenarios, involving larger datasets and heavier network architectures, we develop compact data visualization methods. We propose two approaches: the first one implies representation of data proximities using data reduction to the ℕ space, the other one implies post‐processing to ℝ�� → ℝ2 data projections to build compact grids of data. In order to evaluate the performances of these projection methods, we propose a user study protocol. Its goal is to measure the suitability of visualization methods in tasks related to the understanding of high‐dimensional data. Finally, we carry out an evaluation following this protocol to compare the efficiency between compact data visualization and scatter plot visualization. This evaluation is conducted using state of the art methods t‐SNE and Self‐Sorting Maps
Morère, Olivier André Luc. "Deep learning compact and invariant image representations for instance retrieval." Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066406.
Image instance retrieval is the problem of finding an object instance present in a query image from a database of images. Also referred to as particular object retrieval, this problem typically entails determining with high precision whether the retrieved image contains the same object as the query image. Scale, rotation and orientation changes between query and database objects and background clutter pose significant challenges for this problem. State-of-the-art image instance retrieval pipelines consist of two major steps: first, a subset of images similar to the query are retrieved from the database, and second, Geometric Consistency Checks (GCC) are applied to select the relevant images from the subset with high precision. The first step is based on comparison of global image descriptors: high-dimensional vectors with up to tens of thousands of dimensions rep- resenting the image data. The second step is computationally highly complex and can only be applied to hundreds or thousands of images in practical applications. More discriminative global descriptors result in relevant images being more highly ranked, resulting in fewer images that need to be compared pairwise with GCC. As a result, better global descriptors are key to improving retrieval performance and have been the object of much recent interest. Furthermore, fast searches in large databases of millions or even billions of images requires the global descriptors to be compressed into compact representations. This thesis will focus on how to achieve extremely compact global descriptor representations for large-scale image instance retrieval. After introducing background concepts about supervised neural networks, Restricted Boltzmann Machine (RBM) and deep learning in Chapter 2, Chapter 3 will present the design principles and recent work for the Convolutional Neural Networks (CNN), which recently became the method of choice for large-scale image classification tasks. Next, an original multistage approach for the fusion of the output of multiple CNN is proposed. Submitted as part of the ILSVRC 2014 challenge, results show that this approach can significantly improve classification results. The promising perfor- mance of CNN is largely due to their capability to learn appropriate high-level visual representations from the data. Inspired by a stream of recent works showing that the representations learnt on one particular classification task can transfer well to other classification tasks, subsequent chapters will focus on the transferability of representa- tions learnt by CNN to image instance retrieval…
Capet, Nicolas. "Amélioration du découplage inter-éléments par surface haute impédance pour des antennes réseaux GNSS compactes." Toulouse 3, 2010. http://thesesups.ups-tlse.fr/1291/.
This thesis addresses the problem of mutual coupling reduction between the elements of a compact GNSS array - using High Impedance Surfaces (HIS) - to improve Controlled Reception Pattern Antenna (CRPA) performances. We first design a HIS, which elementary cell size is smaller than lambda0/14. Its Electromagnetic Band Gap (EBG) properties are characterised numerically and experimentally. A patch antenna is chosen as the elementary antenna of the CRPA. Ideal HIS are proposed to study different array configurations in order to define the elementary antenna. Resonant mechanisms occurring at the frequencies of the band gap in the HIS are then studied in detail. As a result, we propose the use of new compact HIS like resonators. Finally, different prototypes are designed and built. They consist of cavity backed patch elements surrounded or not by the proposed HIS like resonators. Numerical and experimental results demonstrate the mutual coupling drastic reduction achieved with these structures
Morère, Olivier André Luc. "Deep learning compact and invariant image representations for instance retrieval." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066406.
Image instance retrieval is the problem of finding an object instance present in a query image from a database of images. Also referred to as particular object retrieval, this problem typically entails determining with high precision whether the retrieved image contains the same object as the query image. Scale, rotation and orientation changes between query and database objects and background clutter pose significant challenges for this problem. State-of-the-art image instance retrieval pipelines consist of two major steps: first, a subset of images similar to the query are retrieved from the database, and second, Geometric Consistency Checks (GCC) are applied to select the relevant images from the subset with high precision. The first step is based on comparison of global image descriptors: high-dimensional vectors with up to tens of thousands of dimensions rep- resenting the image data. The second step is computationally highly complex and can only be applied to hundreds or thousands of images in practical applications. More discriminative global descriptors result in relevant images being more highly ranked, resulting in fewer images that need to be compared pairwise with GCC. As a result, better global descriptors are key to improving retrieval performance and have been the object of much recent interest. Furthermore, fast searches in large databases of millions or even billions of images requires the global descriptors to be compressed into compact representations. This thesis will focus on how to achieve extremely compact global descriptor representations for large-scale image instance retrieval. After introducing background concepts about supervised neural networks, Restricted Boltzmann Machine (RBM) and deep learning in Chapter 2, Chapter 3 will present the design principles and recent work for the Convolutional Neural Networks (CNN), which recently became the method of choice for large-scale image classification tasks. Next, an original multistage approach for the fusion of the output of multiple CNN is proposed. Submitted as part of the ILSVRC 2014 challenge, results show that this approach can significantly improve classification results. The promising perfor- mance of CNN is largely due to their capability to learn appropriate high-level visual representations from the data. Inspired by a stream of recent works showing that the representations learnt on one particular classification task can transfer well to other classification tasks, subsequent chapters will focus on the transferability of representa- tions learnt by CNN to image instance retrieval…
Moreschi, Vincent. "Etude et optimisation de la compacité de poudres inorganiques." Valenciennes, 2008. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/f830d09f-ec45-45a3-b44e-a1f6c3394d6e.
This work falls within the framework of an industrial process of inorganic powders cold compression. These powders are deposited on a continuous steel strip, which is distorted by mechanical profiling in order to create a cylindrical wire. This study aims to optimise the condition of compaction of six different inorganic powders for this particular process of shaping. The micrographic analyses of these wires indicate various compaction mechanisms depending on the nature of the powder. These characterisations reveal a main mechanism governing the process: the granular fragmentation. The improvement of aerated and taped compaction states of these various powder is then considered using two: modelling methods of the response, one by the design of experiments, the second by an artificial neural networks. The modelling by design of experiments was used to determine the optimal mixture of three size classes. It highlights some specific granular mixtures which conduct to some higher packing densities. The prediction by the design of experiments of the behaviour of taped and aerated compaction states and of the compressibility index is on the whole positive. As a result, for some of the considered powders, significant improvements up to 12% are obtained. An approach based on artificial neural networks is experimented to study the influence of the relative proportions of twenty three size classes on taped compaction state. This approach permit to fit very closely the response area
Guérin, Nicolas. "Etude théorique et numérique de la diffraction des réseaux bipérodiques en électromagnétisme : application aux cristaux photoniques et aux antennes directives compactes." Aix-Marseille 3, 2003. http://www.theses.fr/2003AIX30026.
We describe a theoretical and numerical study for the diffraction by biperiodic gratings of wires. We use an integral method based on the Harrington formalism. The development of a fast biperiodic Green's function allows us to reduce the unknowns to the first cell. We investigate then structures made of a source surrounded by a biperiodic metallic photonic crystal above a ground plane. The field diffracted by the source is expanded in a plane waves packet using FFT, then we solve a grating problem for each plane wave. Theses structures are employed to carry out directive compact antennas in the domain of microwave telecommunications (KU band). We investigate and compare two solutions : the first one is based on a Fabry-Perot like planar resonant cavity, the second solution uses the ultrarefractive properties of a metallic photonic crystal at the band edge (metamaterial). The results are confirmed by experiments in an anechoic chamber
Gavoille, Cyril. "Complexité mémoire du routage dans les réseaux distribués." Lyon, École normale supérieure (sciences), 1996. http://www.theses.fr/1996ENSL0015.
Gueye, Mamadou Bamba. "Définition, conception (modélisation) et réalisation d'une antenne compacte en ondes millimétriques (71GHz - 86GHz) pour des liaisons haut débit numérique." Paris 10, 2014. http://www.theses.fr/2014PA100002.
The objective of this thesis is the design of an ultra-directive planar antenna for 71-86 GHz band. The antenna is designed in waveguide technology (or metamaterials, in parallel with the LEME-OMS laboratory) using low cost plastic materials. Work will focus on the specification, analysis, design and implementation and testing of a prototype planar antenna waveguide. The work of this thesis fit into the framework of the project ELI-IAN * and more particularly in SP4 sub-project on the development of a new generation compact antenna. *The project ELHAN (E band Digital High Speed Link) belong to the competitiveness cluster SYSTEM@TIC of the Ile de France region (FUI7 / FEDER2) aims to develop electronic components and modules for future telecommunication applications at very high speed E band (60-90 GHz). This project was born from a need to cover new bands, strongly motivated by the saturation of the electromagnetic spectrum of current commercial bands. Indeed, it is crucial to explore the higher frequency in particular those still free to meet the surge demands broadband connections, including mobile communications and data transfers. The first chapter introduces: 1/ The ELI-IAN project, the context of the study and associate partners. 2/ The literature review for directional antennas, millimeter band technologies capable to meet the specifications. Chapter II is divided into several parts. 1/ Modeling and design of the various individual elements of the antenna waveguide. 2 / Elements specifications, definition of requirements and constraints related to technology. 3 / configuring an antenna array to reduce the side lobes to meet the templates required by the FCC or ETSI standards. We’ll adopt a configuration called polarization "slant 45°” or diamond position. It allows, in particular palliate the application of Taylor or Tchebychev weighting, reducing the side lobes level. 4 / Selecting feeding network associated with the antenna and the splitter architecture implemented for the distribution of energy. We present the problems encountered in using standards waveguides and the choice of innovative solutions to overcome them. A model of <> waveguide was adopted for <> to reduce the size of standard guides while maintaining their performance. The third and final chapter is an opportunity to validate the proposed concept of the array antenna. It discusses the implementation and measurements on the basic components of the antenna. A prototype of waveguide planar antenna in 80 GHz has been realized and tested. Similarly, all the individual elements (horn element, power divider, and sub-array 4 x 4 elements. . . ) has been made. We spend the last part of this chapter for the measurements and the experimental validations for all the antenna modules and comparing the results of the numerical study. We were able to validate the array planar antenna waveguide in the millimeter frequency band (80 GHz). We finished this memoir by the conclusions and perspectives
Chateau, Nicolas. "Modélisation et caractérisation de réseaux holographiques ; étude de composants optiques holographiques en gélatine bichromatée." Phd thesis, Université Paris Sud - Paris XI, 1993. http://pastel.archives-ouvertes.fr/pastel-00715993.
Lorho, Nina. "Etude et conception d'une antenne compacte ultra large bande à diversité de polarisation : application à la radiogoniométrie." Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4062/document.
Radio direction finding (DF) allows for the measurement of the direction of arrival of incoming electromagnetic signals. Its main applications include spectrum monitoring and electronic warfare. DF antennas and arrays are subject to new problematics (bandwidth, compactness and polarization diversity) while DF algorithms have kept on improving. Previous works have initiated the design of such antennas and arrays. This work aims at designing an antenna with reduced dimensions for the VHF and UHF frequency bands and with a polarization diversity. This antenna shall then be integrated in a functional DF array. For this purpose, a planar antenna has been designed and measured in the 500-3000 MHz frequency band. Its final dimensions are 150mm x 150mm (λ/4 x λ/4). This antenna has then been integrated in the final DF array whose accuracy on the same frequency band is of the order of 2° for a final size of 260mm (diameter) x 150mm (height), that is λ/2,3 x λ/4. This study has also allowed for the design of a low-profile absorber (with a height of 25mm, that is λ/24 at its lowest frequency of operation). An increase of 10dB in the front to back ratio of the proposed antenna has been enabled by this absorber on its whole frequency band
Hoang, Thi Quynh Van. "Maillage cartésien non-conforme pour la méthode TLM : application à la conception de rectennas compactes." Nice, 2012. http://www.theses.fr/2012NICE4045.
The work presented in this thesis is divided into two parts. The first part is devoted to the development of a computational electromagnetic code based on the TLM method (Transmission Line Matrix) to simulate structures with multi-scale aspects, requiring multigrids-subgrids locally refined. This leads to solve a simultaneous spatial and time domain coupling problem. As it was proved to be very effective for spatial domain coupling, the technique using transformers introduced by Wlodarczyk is implemented. Actual work is focussed on the time domain coupling to allow using the maximum time step in each sub grid. Interpolation techniques such as Taylor second order and cubic Spline and also a prediction technique inspired from the Prony-Pisarenko method for power spectral density estimation were implemented and evaluated. The second part is devoted to the design of rectennas. Such non linear and multi-scale structures, integrating Schottky diodes, are key elements of wireless power transmission or energy harvesting systems. It is demonstrated that modelling rectennas with a global circuit-electromagnetic simulation tool in time domain as with TLM provides a substantial advantage compared to commercial simulation softwares that requires various experimental adjustments, rendering complex the design process. It becomes then possible to accurately predict the conversion efficiency of an entire rectenna. The design and complete experimental characterization of two compact rectennas operating at 2. 45GHz are finally presented
Bennett, Christopher H. "Apprentissage local avec des dispositifs de mémoire hautement analogiques." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS037/document.
In the next era of distributed computing, brain-based computers that perform operations locally rather than in remote servers would be a major benefit in reducing global energy costs. A new generation of emerging nonvolatile memory devices is a leading candidate for achieving this neuromorphic vision. Using theoretical and experimental work, we have explored critical issues that arise when physically realizing modern artificial neural network (ANN) architectures using emerging memory devices (“memristors”). In our experimental work, we showed organic nanosynapses adapting automatically as logic gates via a companion digital neuron and programmable logic cell (FGPA). In our theoretical work, we also considered multilayer memristive ANNs. We have developed and simulated random projection (NoProp) and backpropagation (Multilayer Perceptron) variants that use two crossbars. These local learning systems showed critical dependencies on the physical constraints of nanodevices. Finally, we examined how feed-forward ANN designs can be modified to exploit temporal effects. We focused in particular on improving bio-inspiration and performance of the NoProp system, for example, we improved the performance with plasticity effects in the first layer. These effects were obtained using a silver ionic nanodevice with intrinsic plasticity transition behavior
Vernier, Eric. "Non compact conformal field theories in statistical mechanics." Thesis, Paris, Ecole normale supérieure, 2015. http://www.theses.fr/2015ENSU0005/document.
The critical points of statistical mechanical systems in 2 dimensions or quantum mechanical systems in 1+1 dimensions (this also includes non interacting systems in 2+1 dimensions) are effciently tackled by the exact methods of conformal fieldtheory (CFT) and integrability, which have witnessed a spectacular progress during the past 40 years. Several problems have however escaped an exact understanding so far, among which the plateau transition in the Integer Quantum Hall Effect,the main reason for this being that such problems are usually associated with non unitary, logarithmic conformal field theories, the tentative classification of which leading to formidable mathematical dificulties. Turning to a lattice approach, andin particular to the quest for integrable, exactly sovable representatives of these problems, one hits the second dificulty that the associated CFTs are usually of the non compact type, or in other terms that they involve a continuum of criticalexponents. The connection between non compact field theories and lattice models or spin chains is indeed not very clear, and in particular it has long been believed that the former could not arise as the continuum limit of discrete models built out of acompact set of degrees of freedom, which are the only ones allowing for a systematic construction of exact solutions.In this thesis, we show that the world of compact lattice models/spin chains with a non compact continuum limit is much bigger than what could be expected from the few particular examples known up to this date. More precisely we propose an exact Bethe ansatz solution of an infinite family of models (the so-called $a_n^{(2)}$ models, as well as some results on the $b_n^{(1)}$ models), and show that all of these models allow for a regime described by a non compact CFT. Such models include cases ofgreat physical relevance, among which a model for two-dimensional polymers with attractive interactions and loop models involved in the description of coupled Potts models or in a tentative description of the quantum Hall plateau transition by somecompact geometrical truncation. We show that the existence of an unsuspected non compact continuum limit for such models can have dramatic practical effects, for instance on the output of numerical determination of the critical exponents or ofMonte-Carlo simulations. We put our results to use for a better understanding of the controversial theta transition describing the collapse of polymers in two dimensions, and draw perspectives on a possible understanding of the quantum Hall plateautransition by the lattice approach
Dieng, Youssou. "Décomposition arborescente des graphes planaires et routage compact." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13855/document.
In a network, it is crucial to know how to construct an efficent routing scheme. It is fundamental for each entity with its local knowledge of the network, to be able to decide on which link to forward messages. Thus, it is important to sutdy the underlying network topology in order to design routing schemes. In the first part of this thesis, we construct a new tree-decomposition for planar graphs. In fact, as in many graph problems, the study of the graph structure leads to do a tree-decomposition for exploiting structural propertys of the graphs. In second part, we studied the structure of H-minor free graphs, in particular whenever H = K_{2,r}. Our results improve upon previous known bounds about the tree-width of K_{2,r}-minor free graphs. At last, we treat the problème of compact routing scheme. More precisely, we are interested in shortest-path routing schemes that use O(\log n) bits for addresses, headers and routing tables, where n is the number of vertices in the graph. We propose such a routing scheme for a large family of weighted graphs including outerplanar graphs
Juanals, Brigitte. "Mutations de l'accès à l'information, du livre aux dispositifs hypermédias en réseau sur l'internet : une approche comparative appliquée à l'évolution des encyclopédies : du livre au disque compact, jusqu'aux outils de recherche et aux flux de données en réseau." Paris 3, 2001. http://www.theses.fr/2001PA030063.
Villemaud, Guillaume. "Etude d'antennes ruban tridimentionnelles compactes pour liaison de proximité : Application à des systèmes de télémesure et de localisation de téléphones cellulaires." Limoges, 2002. http://www.theses.fr/2002LIMO0029.
This thesis takes place in short range wireless communication systems. In such a field, the major challenge for antennas is to combine size reduction and good matching and radiating characteristics to satisfy the required specifications. Thanks to numerical (FDTD) and experimental tools, the study of strip antennas based on quarter wavelength resonators folded in three dimensions and fed via a coupling gap has been performed. This study was particularly dedicated to achieve spherical or hemispherical radiation patterns offering a flawless coverage of the entire space. Several developments are exposed, some of them allowing a wider bandwidth
Couvreur, Romain. "Geometric lattice models and irrational conformal field theories." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS062.
In this thesis we study several aspects of two-dimensional lattice models of statistical physics with non-unitary features. This bottom-up approach, starting from discrete lattice models, is helpful to understand the features of the associated conformal field theories. They are non-unitary and often irrational, logarithmic or even non-compact. First, we study the problem of the entanglement entropy in non-unitary spin chains and its interpretation in loop models. We discuss the role of the effective central charge, a relevant quantity to study the next problems in this thesis. We then address two problems related to the Chalker-Coddington model, an infinite-dimensional supersymmetric chain important for the study of the plateau transition in the integer quantum Hall effect. Since the model has an infinite number of degrees of freedom, it has been proposed to study it with a series of truncations. We present new results based on this approach and extend this methodology to the case of Brownian motion in its supersymmetric formulation. Next, a new model is proposed to interpolate between class A and class C. The Chalker-Coddington model is a particular realisation of class A whereas class C, describing the physics of the spin quantum Hall effect, can be related to a model of percolation. This interpolating model provides an example of a RG-flow between a non-compact CFT and compact one. The last part of this thesis deals with the problem of classifying observables in lattice models with discrete symmetries. The process is illustrated on the Potts model and its symmetry under the group of permutations and previous results are extended for non-scalar operators. This approach is important to study indecomposability of non-unitary models and can be used to study models such as percolation in higher dimensions
Hniki, Saâdia. "Contribution à la modélisation des dispositifs MOS haute tension pour les circuits intégrés de puissance ("Smart Power")." Toulouse 3, 2010. http://thesesups.ups-tlse.fr/1162/.
In recent decades, power integrated circuits have experienced very significant growth. Today the regulation and distribution of electrical energy are crucial. The reduction of the dimensions and the need for power highlighted the need for efficient structures. Technology "smart power" has been developed to meet these demands. This technology uses high voltage devices, offering new solutions through its unique characteristics at high voltages and currents. The behavior of these devices is accompanied by the appearance of many phenomena. An accurate modeling of these phenomena is needed to replicate its physical behavior. The objective of this thesis is to improve modeling and to establish a good method of extracting physical parameters related to HV MOS. This thesis has been mainly devoted to modeling the phenomenon of self-heating: development of test structure, modeling of thermal coupling between the sources of transistor, development tool for generating the thermal network. This thesis also looks at the definition of a method for extracting RF noise in the high-voltage transistor including extrinsic gate resistance and capacity Cgs and Cgd. Finally, the last part of the thesis presents a brief assessment of compact HiSIM_HV dedicated to HV MOS and compares it with the macro model used by STMicroelectronics. The results presented in this thesis have been validated by comparison with different measures on SOI technology and solid substrate
Hniki, Saadia. "Contribution à la modélisation des dispositifs MOS haute tension pour les circuits intégrés de puissance ("Smart Power")." Phd thesis, Université Paul Sabatier - Toulouse III, 2010. http://tel.archives-ouvertes.fr/tel-00581114.
Rosenbaum, Tommy. "Performance prediction of a future silicon-germanium heterojunction bipolar transistor technology using a heterogeneous set of simulation tools and approaches." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0550/document.
Bipolar complementary metal-oxide-semiconductor (BiCMOS) processescan be considered as the most general solution for RF products, as theycombine the mature manufacturing tools of CMOS with the speed and drivecapabilities of silicon-germanium (SiGe) heterojunction bipolar transistors(HBTs). HBTs in turn are major contenders for partially filling the terahertzgap, which describes the range in which the frequencies generated bytransistors and lasers do not overlap (approximately 0.3THz to 30 THz). Toevaluate the capabilities of such future devices, a reliable prediction methodologyis desirable. Using a heterogeneous set of simulation tools and approachesallows to achieve this goal successively and is beneficial for troubleshooting.Various scientific fields are combined, such as technology computer-aided design(TCAD), compact modeling and parameter extraction.To create a foundation for the simulation environment and to ensure reproducibility,the used material models of the hydrodynamic and drift-diffusionapproaches are introduced in the beginning of this thesis. The physical modelsare mainly based on literature data of Monte Carlo (MC) or deterministicsimulations of the Boltzmann transport equation (BTE). However, the TCADdeck must be calibrated on measurement data too for a reliable performanceprediction of HBTs. The corresponding calibration approach is based onmeasurements of an advanced SiGe HBT technology for which a technology specific parameter set of the HICUM/L2 compact model is extracted for thehigh-speed, medium-voltage and high-voltage transistor versions. With thehelp of the results, one-dimensional transistor characteristics are generatedthat serve as reference for the doping profile and model calibration. By performingelaborate comparisons between measurement-based reference dataand simulations, the thesis advances the state-of-the-art of TCAD-based predictionsand proofs the feasibility of the approach.Finally, the performance of a future technology in 28nm is predicted byapplying the heterogeneous methodology. On the basis of the TCAD results,bottlenecks of the technology are identified
Bipolare komplementäre Metall-Oxid-Halbleiter (BiCMOS) Prozesse bietenhervorragende Rahmenbedingungen um Hochfrequenzanwendungen zurealisieren, da sie die fortschrittliche Fertigungstechnik von CMOS mit derGeschwindigkeit und Treiberleistung von Silizium-Germanium (SiGe) Heterostruktur-Bipolartransistoren (HBTs) verknüpfen. Zudem sind HBTs bedeutendeWettbewerber für die teilweise Überbrückung der Terahertz-Lücke, derFrequenzbereich zwischen Transistoren (< 0.3 THz) und Lasern (> 30 THz).Um die Leistungsfähigkeit solcher zukünftigen Bauelemente zu bewerten, isteine zuverlässige Methodologie zur Vorhersage notwendig. Die Verwendungeiner heterogenen Zusammenstellung von Simulationstools und Lösungsansätzenerlaubt es dieses Ziel schrittweise zu erreichen und erleichtert die Fehler-_ndung. Verschiedene wissenschaftliche Bereiche werden kombiniert, wie zumBeispiel der rechnergestützte Entwurf für Technologie (TCAD), die Kompaktmodellierungund Parameterextraktion.Die verwendeten Modelle des hydrodynamischen Simulationsansatzes werdenzu Beginn der Arbeit vorgestellt, um die Simulationseinstellung zu erläuternund somit die Nachvollziehbarkeit für den Leser zu verbessern. Die physikalischenModelle basieren hauptsächlich auf Literaturdaten von Monte Carlo(MC) oder deterministischen Simulationen der Boltzmann-Transportgleichung(BTE). Für eine zuverlässige Vorhersage der Eigenschaften von HBTs muss dieTCAD Kon_guration jedoch zusätzlich auf der Grundlage von Messdaten kalibriertwerden. Der zugehörige Ansatz zur Kalibrierung beruht auf Messungeneiner fortschrittlichen SiGe HBT Technologie, für welche ein technologiespezifischer HICUM/L2 Parametersatz für die high-speed, medium-voltage undhigh-voltage Transistoren extrahiert wird. Mit diesen Ergebnissen werden eindimensionaleTransistorcharakteristiken generiert, die als Referenzdaten fürdie Kalibrierung von Dotierungspro_len und physikalischer Modelle genutztwerden. Der ausführliche Vergleich dieser Referenz- und Messdaten mit Simulationengeht über den Stand der Technik TCAD-basierender Vorhersagenhinaus und weist die Machbarkeit des heterogenen Ansatzes nach.Schlieÿlich wird die Leistungsfähigkeit einer zukünftigen Technologie in28nm unter Anwendung der heterogenen Methodik vorhergesagt. Anhand derTCAD Ergebnisse wird auf Engpässe der Technologie hingewiesen
Mattioli, Pasqual Alexander. "Sound Directivity Control in a 3-D Space by a Compact Spherical Loudspeaker Array." Phd thesis, 2010. http://tel.archives-ouvertes.fr/tel-00530855.