Tesis sobre el tema "Détection de courbure"
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Prevost, Coline. "Déformation membranaire et détection de courbure par des protéines à domaine I-BAR". Paris 7, 2014. http://www.theses.fr/2014PA077145.
Texto completoBiological membranes display a vast array of shapes. These shapes result in particular from the binding of proteins with characteristic curvature, or carrying motifs able to insert into the bilayer, or both. Moreover these shapes often provide geometrical cues, "informing" the cell on the stage of a budding reaction for instance. The detection of this peculiar signal again requires specialized proteins, and a current question is whether the same proteins or protein motifs are involved in performing both tasks in vivo. Additionally, cellular membranes may either bend toward or away from the cytoplasm, so that cytosolic proteins may either face the convex (of "positive" curvature) or concave (of "negative" curvature) side of the membrane. We quantitatively characterized the I-BAR domain of the protein IRSp53, which displays a convex membrane-binding interface, and therefore interacts preferentially with negative curvature. We used an in vitro assay in which the I-BAR is first encapsulated inside giant liposomes of practically zero curvature. A membrane nanotube is then pulled out of a single liposome, creating a negatively-curved interface for the encapsulated I-BAR. We measured the redistribution of the I-BAR, and how it affects the tube mechanics, as a function of tube curvature and protein area coverage on the membrane. We observe a continuous behavior where the I-BAR mostly detects curvature at low coverage, and imposes a preferred curvature at higher coverage. We have also studied the I-BAR domain of ABBA, which is similar to IRSp53 I-BAR, but additionally displays an amphipathic helix, a motif usually associated with the generation and detection of positive curvature
Mérigot, Quentin. "Détection de structure géométrique dans les nuages de points". Phd thesis, Université de Nice Sophia-Antipolis, 2009. http://tel.archives-ouvertes.fr/tel-00443038.
Texto completoTremblais, Benoît. "De la résolution numérique des EDP à l'extraction de caractéristiques linéiques dans les images : application à la détection multi-échelles d'un arbre vasculaire". Poitiers, 2002. http://www.theses.fr/2002POIT2316.
Texto completoWu, Zhi-Qian. "Caveolin in membrane nanotubes : curvature sensing and bulge formation". Electronic Thesis or Diss., Université Paris sciences et lettres, 2024. http://www.theses.fr/2024UPSLS007.
Texto completoCaveolin is one of the major protein components of caveolae, which are small cup-shaped invaginations in the plasma membrane. It is synthesized in the endoplasmic reticulum in a signal recognition particle-dependent manner and transported to the Golgi apparatus via COPII-coated vesicles. At the trans-Golgi network (TGN), caveolin 8S complexes further oligomerize into 70S complexes with the facilitation of cholesterol. They are then sorted intotransport carriers through an unknown mechanism and transported to the plasma membrane. The conventional structural model of caveolin might suggest it is a curvature-sensing protein based on its hairpin molecular shape. However, a recently discovered structure model of the caveolin 8S complex in detergent micelles based on cryo-electron microscopy, which exhibits a flat disc geometry, raises questions about its curvature sensitivity.Furthermore, cavins, another major protein component of caveolae that cooperate with caveolins in bending the membrane to form caveolae, do not associate with caveolins at the TGN. Given that no other known candidate, apart from cavins, can cooperate with caveolin to form transport carriers at the TGN, it becomes unclear how these carriers for caveolin are formed there. Therefore, in this project, we aimed to elucidate the curvaturesensitivity and induction of caveolin. We addressed these issues by reconstituting caveolin-1 (Cav1) into the membrane of giant unilamellar vesicles (GUVs) and by performing tube-pulling experiments. The results showed that caveolin is indeed a curvature-sensing protein, with caveolin 8S complexes exhibiting approximately a 5 degree tilt from the horizontal, which endows them with curvature sensitivity. Furthermore, we showed that caveolin 8S complexes can collectively generate membrane curvature at low tension and form scaffolds on the tubes at high tension. In summary, our results showed that caveolin is a curvature-sensing and -inducing protein, suggesting the possibility of its sorting into transport carriers at the TGN based on these properties. Interestingly, we observed that above a certain membrane tension Tt that depends on Cav1 density, nanotubes pulled from Cav1-GUVs no longer exhibit a constant radius and that caveolins form bulges on the tube. To explore how Cav1 form these bulges, we first observed that on average, bulges' size decreases with an increase in membrane tension. We found that the bulge size is proportional to the total amount of caveolin in the bulge, suggesting a constant Cav1 density in the bulges. Additionally, higher density of caveolin in the membrane favors bulge formation and lowers Tt. These results suggest that when the tube radius decreases, caveolin might induce formation of bulges to relax mechanicalconstraints due to the tubular geometry, but a model and high resolution imaging are now needed to explain these observations
Walter, Nicolas. "Détection de primitives par une approche discrète et non linéaire : application à la détection et la caractérisation de points d'intérêt dans les maillages 3D". Phd thesis, Université de Bourgogne, 2010. http://tel.archives-ouvertes.fr/tel-00808216.
Texto completoMahmoudi, Saïd. "Indexation de formes planes : application à la reconnaissance multi-vues de modèles 3D". Lille 1, 2003. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2003/50376-2003-291.pdf.
Texto completoChristoff, Vesselinova Nicole. "Détection et caractérisation d'attributs géométriques sur les corps rocheux du système solaire". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0565/document.
Texto completoOne of the challenges of planetary science is the age determination of the surfaces of the different celestial bodies in the solar system, to understand their formation and evolution processes. An approach relies on the analysis of the crater impact density and size. Due to the huge quantity of data to process, automatic approaches have been proposed for automatically detecting impact craters in order to facilitate this dating process. They generally use the color values from images or the elevation values from Digital Elevation Model (DEM). In this PhD thesis, we propose a new approach for detecting craters rims. The main idea is to combine curvature analysis with Neural Network based classification. This approach contains two main steps: first, each vertex of the mesh is labeled with the value of the minimal curvature; second, this curvature map is injected into a neural network to automatically detect the shapes of interest. The results show that detecting forms are more efficient using a two-dimensional map based on the computation of discrete differential estimators, than by the value of the elevation at each vertex. This approach significantly reduces the number of false negatives compared to previous approaches based on topographic information only. The validation of the method is performed on DEMs of Mars, acquired by a laser altimeter aboard NASA’s Mars Global Surveyor spacecraft and combined with a database of manually identified craters
El, Guedri Mabrouka. "Caractérisation aveugle de la courbe de charge électrique : Détection, classification et estimation des usages dans les secteurs résidentiel et tertiaire". Phd thesis, Université Paris Sud - Paris XI, 2009. http://tel.archives-ouvertes.fr/tel-00461671.
Texto completoAziz, Usama. "Détection des défauts des éoliennes basée sur la courbe de puissance : Comparaison critique des performances et proposition d'une approche multi-turbines". Thesis, Université Grenoble Alpes, 2020. https://tel.archives-ouvertes.fr/tel-03066125.
Texto completoSince wind turbines are electricity generators, the electrical power produced by a machine is a relevant variable for monitoring and detecting possible faults. In the framework of this thesis, an in-depth literature review was first performed on fault detection methods for wind turbines using the electrical power produced. It showed that, although many methods have been proposed in the literature, it is very difficult to compare their performance in an objective way due to the lack of reference data, allowing to implement and evaluate all these methods on the basis of the same data.To address this problem, as a first step, a new realistic simulation approach has been proposed in this thesis. It allows to create simulated data streams, coupling the power output, wind speed and temperature, in normal conditions and in fault situations, in an infinite way. The defects that can be simulated are those that impact the shape of the power curve. The simulated data are generated from real data recorded on several French wind farms, located on different geographical sites. In a second step, a method for evaluating the performance of fault detection methods using the power produced has been proposed.This new simulation method was implemented on 4 different fault situations affecting the power curve, using data from 5 geographically remote wind farms. A total of 1875 years of 10-minute SCADA data was generated and used to compare the detection performance of 3 fault detection methods proposed in the literature. This allowed a rigorous comparison of their performance.In the second part of this research, the proposed simulation method was extended to a multi-turbine configuration. Indeed, several multi-turbine strategies have been published in the literature, with the objective of reducing the impact of environmental conditions on the performance of fault detection methods using temperature as a variable. In order to evaluate the performance gain that a multi-turbine strategy could bring, a hybrid mono-multi-turbine implementation of fault detection methods based on the power curve was first proposed. Then, the simulation framework proposed to evaluate mono-turbine methods was extended to multi-turbine approaches and a numerical experimental analysis of the performance of this hybrid mono-multi-turbine implementation was performed
Tremblais, Benoit. "De la résolution numérique des EDP à l'extraction de caractéristiques linéiques dans les images : application à la détection multi-échelles d'un arbre vasculaire". Phd thesis, Université de Poitiers, 2002. http://tel.archives-ouvertes.fr/tel-00349464.
Texto completoDi, Martino Jean Claude. "Intégration de connaissances dans des systèmes distribués pour l'extraction de raies spectrales dans des images sonar". Nancy 1, 1995. http://www.theses.fr/1995NAN10008.
Texto completoFadhel, Siwar. "Efficacité énergétique et surveillance d’un microgrid à courant continu alimenté par des panneaux photovoltaïques". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS001.
Texto completoPhotovoltaic (PV) systems are frequently subjected to several faults leading to costly production losses. The proposed work focuses on the improvement of the energy efficiency of a DC micro-grid by minimizing the losses related to the occurrence of PV faults. First, we presented a state of the art on the most recurrent faults and their diagnosis methods. The literature review has led us to adopt a data-driven diagnosis approach. Then, the Principal Component Analysis (PCA) method was proposed for PV shading fault detection and classification for a PV module of 250 Wp. The PCA was first performed using the entire I(V) curve obtained under real climatic conditions. A minimum classification success rate of 87.38% is obtained in the training step and 97% is obtained in the validation step. PCA was then applied using only the MPP coordinates to detect the shading fault. The data is discriminated with a classification rate of 100%.Linear Discriminant Analysis (LDA) was opted to predict the new MPP outdoor measurements’classes. Finally, a faults effects analysis study was carried out for three typical faults on the scale of a PV array of 250 kWp. The study was based on the simulated I(V) curves, considering differents severities of each fault. The sensitivity of the I(V) curve of the whole PV plant was observed for both the contact degradation between PV strings and the partiel shading starting from a severity of 10%. The short-ciruit fault of the PV modules has considerably more effect on the strings’ I(V) curves
Jhaidri, Mohamed Amine. "Techniques de synchronisation à très faible SNR pour des applications satellites". Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2017. http://www.theses.fr/2017IMTA0038/document.
Texto completoIn deep space communication systems, the long distance between the spacecraft and the ground station along with the limited capacity of the on-board power generator result a very low signal to noise ratio (SNR). However, such transmission still possible by using near Shannon limit error correction codes (Turbo code and LDPC code). Nevertheless, to take advantage of this coding gain, the coherent demodulation is mandatory, and the carrier phase synchronization must be reliable at more restrictive SNR. At very low SNR, current synchronization systems are limited and unable to provide the required performances. Our goal is to improve the reliability of the receiver synchronization stage under very difficult conditions of a very low SNR, a variable Doppler effect (Doppler rate) and a blind transmission. This thesis deals with the problem of carrier phase synchronization for the downlink of a Deep Space transmission. After the study of the existing solutions, we selected the phase locked loop (Phase Locked Loop: PLL). In an industrial context, PLL offers the best trade-off between complexity and performance. Several phase detectors based on the maximum likelihood criterion were considered and characterized by their S-curves. Based on the equivalent models, we have developed a new study of the non-linear acquisition phase of a second-order PLL with a semi-sinusoidal phase error detector. The second part of the thesis was dedicated to the antennas combining techniques. These methods aim to improve the link budget of the transmission and offer more flexibility. At the end of this part, we proposed a new antennas combining scheme that improves the operating threshold of existing systems
Falade, Joannes Chiderlos. "Identification rapide d'empreintes digitales, robuste à la dissimulation d'identité". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMC231.
Texto completoBiometrics are increasingly used for identification purposes due to the close relationship between the person and their identifier (such as fingerprint). We focus this thesis on the issue of identifying individuals from their fingerprints. The fingerprint is a biometric data widely used for its efficiency, simplicity and low cost of acquisition. The fingerprint comparison algorithms are mature and it is possible to obtain in less than 500 ms a similarity score between a reference template (enrolled on an electronic passport or database) and an acquired template. However, it becomes very important to check the identity of an individual against an entire population in a very short time (a few seconds). This is an important issue due to the size of the biometric database (containing a set of individuals of the order of a country). Thus, the first part of the subject of this thesis concerns the identification of individuals using fingerprints. Our topic focuses on the identification with N being at the scale of a million and representing the population of a country for example. Then, we use classification and indexing methods to structure the biometric database and speed up the identification process. We have implemented four identification methods selected from the state of the art. A comparative study and improvements were proposed on these methods. We also proposed a new fingerprint indexing solution to perform the identification task which improves existing results. A second aspect of this thesis concerns security. A person may want to conceal their identity and therefore do everything possible to defeat the identification. With this in mind, an individual may provide a poor quality fingerprint (fingerprint portion, low contrast by lightly pressing the sensor...) or provide an altered fingerprint (impression intentionally damaged, removal of the impression with acid, scarification...). It is therefore in the second part of this thesis to detect dead fingers and spoof fingers (silicone, 3D fingerprint, latent fingerprint) used by malicious people to attack the system. In general, these methods use machine learning techniques and deep learning. Secondly, we proposed a new presentation attack detection solution based on the use of statistical descriptors on the fingerprint. Thirdly, we have also build three presentation attacks detection workflow for fake fingerprint using deep learning. Among these three deep solutions implemented, two come from the state of the art; then the third an improvement that we propose. Our solutions are tested on the LivDet competition databases for presentation attack detection
Dosso, Fangan Yssouf. "Contribution de l'arithmétique des ordinateurs aux implémentations résistantes aux attaques par canaux auxiliaires". Electronic Thesis or Diss., Toulon, 2020. http://www.theses.fr/2020TOUL0007.
Texto completoThis thesis focuses on two currently unavoidable elements of public key cryptography, namely modular arithmetic over large integers and elliptic curve scalar multiplication (ECSM). For the first one, we are interested in the Adapted Modular Number System (AMNS), which was introduced by Bajard et al. in 2004. In this system of representation, the elements are polynomials. We show that this system allows to perform modular arithmetic efficiently. We also explain how AMNS can be used to randomize modular arithmetic, in order to protect cryptographic protocols implementations against some side channel attacks. For the ECSM, we discuss the use of Euclidean Addition Chains (EAC) in order to take advantage of the efficient point addition formula proposed by Meloni in 2007. The goal is to first generalize to any base point the use of EAC for ECSM; this is achieved through curves with one efficient endomorphism. Secondly, we propose an algorithm for scalar multiplication using EAC, which allows error detection that would be done by an attacker we detail