Letteratura scientifica selezionata sul tema "Consensus distribué"
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Articoli di riviste sul tema "Consensus distribué"
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Chen, Yingwen, Bowen Hu, Hujie Yu, Zhimin Duan e Junxin Huang. "A Threshold Proxy Re-Encryption Scheme for Secure IoT Data Sharing Based on Blockchain". Electronics 10, n. 19 (27 settembre 2021): 2359. http://dx.doi.org/10.3390/electronics10192359.
Testo completoAbstract (sommario):
The IoT devices deployed in various application scenarios will generate massive data with immeasurable value every day. These data often contain the user’s personal privacy information, so there is an imperative need to guarantee the reliability and security of IoT data sharing. We proposed a new encrypted data storing and sharing architecture by combining proxy re-encryption with blockchain technology. The consensus mechanism based on threshold proxy re-encryption eliminates dependence on the third-party central service providers. Multiple consensus nodes in the blockchain network act as proxy service nodes to re-encrypt data and combine converted ciphertext, and personal information will not be disclosed in the whole procedure. That eliminates the restrictions of using decentralized network to store and distribute private encrypted data safely. We implemented a lot of simulated experiments to evaluate the performance of the proposed framework. The results show that the proposed architecture can meet the extensive data access demands and increase a tolerable time latency. Our scheme is one of the essays to utilize the threshold proxy re-encryption and blockchain consensus algorithm to support IoT data sharing.
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Wuthishuwong, Chairit, e Ansgar Traechtler. "Distributed control system architecture for balancing and stabilizing traffic in the network of multiple autonomous intersections using feedback consensus and route assignment method". Complex & Intelligent Systems 6, n. 1 (9 novembre 2019): 165–87. http://dx.doi.org/10.1007/s40747-019-00125-3.
Testo completoAbstract (sommario):
Abstract Autonomous and intelligent system show a remarkable step in urban traffic management. Autonomous Intersection Management (AIM) is an outstanding example of using an autonomous vehicle and wireless communication technology. The traffic performance of a single AIM system has been proved in many works however, traffic in the network of multiple AIMs is waiting for an implementation. Coordination of traffic between intersections in the network is an important step of managing the overall networked traffic throughput. The authors modeled the traffic network with the multi-agents concept and used the discrete consensus algorithm to coordinate between autonomous agents and implemented the rerouting algorithm in order to distribute the excessive traffics to neighbored intersections with the optimal condition. Our target is to have a balance traffic in each intersection and reaches the equilibrium where the stability has been not compromised. The results show that reaching consensus condition will bring the networked traffic to an equilibrium state where a peak traffic will not be happened. In addition, this method shows that when traffic in a network reached consensus, it will also converge to the Nash equilibrium in the finite time.
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Yu, Zhuo, Gang Wang, Emanuel Goldman, Barbara Zangerl, Ning Xie, Yanhong Cao, Jingyu Chen et al. "COVID-19 vaccine: Call for employees in international transportation industries and international travelers as the first priority in global distribution". Open Medicine 16, n. 1 (1 gennaio 2021): 134–38. http://dx.doi.org/10.1515/med-2021-0210.
Testo completoAbstract (sommario):
Abstract While countries are in a hurry to obtain SARS-CoV-2 vaccine, we are concerned with the availability of vaccine and whether a vaccine will be available to all in need. We predicted three possible scenarios for vaccine distributions and urge an international united action on the worldwide equitable access. In case the international community does not reach a consensus on how to distribute the vaccine to achieve worldwide equitable access, we call for a distribution plan that includes the employees in international transportation industries and international travelers to halt the disease transmission and promote the recovery of the global economy.
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Durand, Marie-Anne, Michelle D. Dannenberg, Catherine H. Saunders, Anik M. C. Giguere, Brian S. Alper, Tammy Hoffmann, Lily Perestelo-Pérez, Stephen T. Campbell e Glyn Elwyn. "Modified Delphi survey for the evidence summarisation of patient decision aids: Study protocol". BMJ Open 9, n. 3 (marzo 2019): e026701. http://dx.doi.org/10.1136/bmjopen-2018-026701.
Testo completoAbstract (sommario):
IntroductionInformation included in a patient decision aid (PDA) can significantly influence patients’ decisions and is, therefore, expected to be evidence-based and rigorously selected and summarised. PDA developers have not yet agreed on a standardised process for the selection and summarisation of the supporting evidence. We intend to generate consensus on a process (and related steps and criteria) for selecting and summarising evidence for PDAs using a modified Delphi survey.Methods and analysisWe will develop an evidence summarisation process specific to PDA development by using a consensus-based Delphi approach, surveying international experts and stakeholders with two to three rounds. To increase generalisability and acceptability, we will distribute the survey to the following stakeholder groups: PDA developers, researchers with expertise in shared decision making, PDA development and evidence summarisation, members of the International Patient Decision Aids Standards (IPDAS) collaboration, policy makers with expertise in PDA certification and patient stakeholder groups. For each criterion, if at least 80% of survey participants rank the criterion as most important/least important, we will consider that consensus has been achieved.Ethics and disseminationIt is critical for PDAs to have accurate and trustworthy evidence-based information about the risks and benefits of health treatments and tests, as these decision aids help patients make important choices. We want to generate consensus on an approach for selecting and summarising the evidence included in PDAs, which can be widely implemented by PDA developers. Dartmouth College’s Committee for the Protection of Human Subjects approved this protocol. We will publish our results in a peer reviewed journal.
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Yan, Pengpeng, Yonghua Fan, Ruifan Liu e Mingang Wang. "Distributed target-encirclement guidance law for cooperative attack of multiple missiles". International Journal of Advanced Robotic Systems 17, n. 3 (1 maggio 2020): 172988142092914. http://dx.doi.org/10.1177/1729881420929140.
Testo completoAbstract (sommario):
The target-encirclement guidance problem for many-to-one missile-target engagement scenario is studied, where the missiles evenly distribute on a target-centered circle during the homing guidance. The proposed distributed target-encirclement guidance law can achieve simultaneous attack of multiple missiles in different line-of-sight directions. Firstly, the decentralization protocols of desired line-of-sight angles are constructed based on the information of neighboring missiles. Secondly, a biased proportional navigation guidance law that can arbitrarily designate the impact angle is cited. The missiles can achieve all-aspect attack on the target in an encirclement manner by combining the biased proportional navigation guidance law and dynamic virtual targets strategy. Thirdly, the consensus protocol of simultaneous attack is designed, which can guarantee that all missiles’ time-to-go estimates achieve consensus asymptotically, and the convergence of the closed-loop system is proved strictly via the Lyapunov stability theory. Finally, numerical simulation results demonstrate the performance and feasibility of the proposed distributed target-encirclement guidance law in different engagement situations.
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Araujo, Erin. "Consensus and activism through collective exchanges: a focus on El Cambalache, Mexico". International Journal of Sociology and Social Policy 36, n. 11/12 (10 ottobre 2016): 741–55. http://dx.doi.org/10.1108/ijssp-12-2015-0134.
Testo completoAbstract (sommario):
Purpose The purpose of this paper is to explore how consensus decision making serves as a foundation for organizing an alternative economy while the agency of the economic project itself organizes participants because it serves to distribute resources as people need them and foment a community of sharing based on the concept that as individuals we are lacking but as a community we have enough. The paper asserts that as activists looking to foment change, alternative economic projects in themselves are actors in organizing community building and resistance to capitalism. Design/methodology/approach El Cambalache (The Swap in English), located in San Cristobal de las Casas, Chiapas, Mexico, is an exchange-based money-less economy that trades unwanted items as well as knowledge, abilities and skills that one wants to share. The project receives anything; specifically used, broken and/or unwanted electronics as well as just about anything else that one might possess. In exchange people provide laptop maintenance classes, language exchange, land to be worked, rooms, gardening services, objects, stories, etc. The rules in this money-less non-capitalist economy organize participation through one exchange or many. Findings Consensus decision making is an effective method for engaging in non-hierarchical research projects. Originality/value This project contributes to research in heterodox economies by presenting an original project with a new suggestion for exchange value as an inclusive process of exchange among participants in the economy. It also provides evidence that consensus decision making can be a useful and productive method for research.
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Wang, Xianbing, Yong Meng Teo e Jiannong Cao. "Corrigendum to “Message and time efficient consensus protocols for synchronous distributed systems” [J. Parallel Distrib. Comput. 68 (2008) 641–654]". Journal of Parallel and Distributed Computing 68, n. 6 (giugno 2008): 876. http://dx.doi.org/10.1016/j.jpdc.2008.04.005.
Testo completo
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Gettler, Brian. "En espèce ou en nature ? Les présents, l’imprévoyance et l’évolution idéologique de la politique indienne pendant la première moitié du XIXe siècle1". Revue d’histoire de l’Amérique française 65, n. 4 (3 gennaio 2014): 409–37. http://dx.doi.org/10.7202/1021048ar.
Testo completoAbstract (sommario):
Cet article porte sur la distribution des présents aux Premières Nations du Canada par l’État impérial britannique pendant la première moitié du XIXe siècle. En analysant les débats entourant une proposition de remplacer des biens matériels distribués en tant que présents par de l’argent, l’auteur observe le développement d’un consensus au sein des autorités métropolitaines et coloniales, mais qui est également partagé par les philanthropes et même par certains Autochtones, selon lequel les Amérindiens, à l’instar des pauvres du milieu urbain, sont imprévoyants par nature. Ces mêmes acteurs croient que les Autochtones ont besoin de la direction et du soutien de l’État paternel, une conviction qui demeure au coeur même de la politique indienne canadienne jusqu’à nos jours. L’article affirme que le discours prônant la « civilisation » des Premières Nations, tenu par les fonctionnaires et les philanthropes, s’appuie sur cette conviction et ainsi participe à former l’idéologie justifiant l’intervention étatique dans les communautés autochtones et la mise en tutelle de ces dernières.
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Toroev, A. S., e A. B. Sizonenko. "ANALYSIS OF THE EFFECTIVENESS OF CONSENSUS-BUILDING ALGORITHMS IN DISTRIBUTED DATA PROCESSING SYSTEMS BASED ON BLOCKCHAIN TECHNOLOGY". Vestnik komp'iuternykh i informatsionnykh tekhnologii, n. 197 (novembre 2020): 13–22. http://dx.doi.org/10.14489/vkit.2020.11.pp.013-022.
Testo completoAbstract (sommario):
The authors of the article consider consensus-building algorithms that are central to the life cycle of transactional exchange between nodes of a DDPS (Distributed Data Processing System) based on blockchain technology. The term under consideration is formally defined. It is proved that when developing these algorithms, it is necessary to choose the main indicators and methods for calculating them, which can be used to evaluate their effectiveness. The process of false forking is described in detail, and the probability of its occurrence is calculated in order to assess the security of data stored in the distributed ledger. When analyzing existing consensus-building algorithms based on statistical data, it is shown that the Byzantine Fault Tolerance Delegated Proof-of-Stake (BFT-DPoS) algorithm has a higher level of efficiency not only in terms of security, but also in terms of performance compared to other algorithms. There is a lack of comprehensive evaluation of candidates for winning Registrar nodes that generate (mining) blocks and distribute them to verifier nodes. It is concluded that the elimination of the above-mentioned drawback would provide a more correct construction of the distributed ledger, since most of the existing algorithms are focused on applicability only in cryptocurrency systems and are not universal. To solve this problem, we propose the need to synthesize the BFT-DPoS and Proof-of-Importance algorithms in order to make it applicable to any type of DDPS using distributed ledger technology (blockchain).
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Toroev, A. S., e A. B. Sizonenko. "ANALYSIS OF THE EFFECTIVENESS OF CONSENSUS-BUILDING ALGORITHMS IN DISTRIBUTED DATA PROCESSING SYSTEMS BASED ON BLOCKCHAIN TECHNOLOGY". Vestnik komp'iuternykh i informatsionnykh tekhnologii, n. 197 (novembre 2020): 13–22. http://dx.doi.org/10.14489/vkit.2020.11.pp.013-022.
Testo completoAbstract (sommario):
The authors of the article consider consensus-building algorithms that are central to the life cycle of transactional exchange between nodes of a DDPS (Distributed Data Processing System) based on blockchain technology. The term under consideration is formally defined. It is proved that when developing these algorithms, it is necessary to choose the main indicators and methods for calculating them, which can be used to evaluate their effectiveness. The process of false forking is described in detail, and the probability of its occurrence is calculated in order to assess the security of data stored in the distributed ledger. When analyzing existing consensus-building algorithms based on statistical data, it is shown that the Byzantine Fault Tolerance Delegated Proof-of-Stake (BFT-DPoS) algorithm has a higher level of efficiency not only in terms of security, but also in terms of performance compared to other algorithms. There is a lack of comprehensive evaluation of candidates for winning Registrar nodes that generate (mining) blocks and distribute them to verifier nodes. It is concluded that the elimination of the above-mentioned drawback would provide a more correct construction of the distributed ledger, since most of the existing algorithms are focused on applicability only in cryptocurrency systems and are not universal. To solve this problem, we propose the need to synthesize the BFT-DPoS and Proof-of-Importance algorithms in order to make it applicable to any type of DDPS using distributed ledger technology (blockchain).
Tesi sul tema "Consensus distribué"
1
Mansouri, Imen. "Contrôle distribué pour les systèmes multi-cœurs auto-adaptatifs". Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20087.
Testo completoAbstract (sommario):
Les architectures régulières intégrant plusieurs cœurs de traitement sont davantage utilisées dans les systèmes embarqués. Dans cette thèse, on s'intéresse aux mécanismes d'optimisation d'énergie dans des architectures avec une dimension étendue; pour faire face aux problèmes de variabilité technologique et aux changements du contexte applicatif, le processus d'optimisation se déroule en temps réel. Des capteurs in-situ détectent le degré de dégradation du circuit. Quant a la variabilité applicative, des moniteurs d'activité sont insérés sur un niveau architectural pour estimer la charge de travail engendrée par l'application en cours et la consommation qui en découle. Nous avons développé une méthode systématique pour l'intégration de ces capteurs avec un moindre coût en surface. Leurs sorties alimentent un processus d'optimisation basé sur la théorie de consensus et dupliqué dans chaque cœur. Ce contrôle vise à fixer la meilleure configuration locale à chaque cœur permettant d'optimiser la consommation globale du système tout en respectant les contraintes temps réel de l'application en cours. Ce schéma opère d'une manière complètement distribuée afin de garantir la scalabilité de notre solution, et donc sa faisabilité, compte tenu de la complexité des circuits actuels et futursRegular architectures embedding several processing elements are increasingly used in embedded systems. They require careful design to avoid high power consumption and to improve their flexibility. This thesis work deals with optimization mechanisms of large scale architectures; to meet variability issues, optimization is processed at run-time. The target design implements in-situ features to collect physical information about its yield and to monitor application workload and generated consumption. As for workload monitoring, we use activity counters connected at architecture level to a set of critical signals. We developed an automated method to optimally place these features with a minimal area overhead. The collected information are used further jointly with a power model to estimate the dissipated power and then driven appropriate optimization process. Optimal frequency for each core is set by means of a distributed controller based on consensus theory. The resulting settings aim to reduce the whole system power while fulfilling application constraints. The scheme needs to be fully distributed to garantee the control scalability, and so feasibility, as the number of cores scales
2
Tran-The, Hung. "Problème du Consensus dans le Modèle Homonyme". Phd thesis, Université Paris-Diderot - Paris VII, 2013. http://tel.archives-ouvertes.fr/tel-00925941.
Testo completoAbstract (sommario):
So far, the distributed computing community has either assumed that all the processes of a distributed system have distinct identifiers or, more rarely, that the processes are anonymous and have no identifiers. These are two extremes of the same general model: namely, n processes use l different identifiers, where 1 l n. We call this model homonymous model. To determine the power of homonymous model as well as the importance of identifiers in distributed computing, this thesis studies the consensus problem, one of the most famous distributed computing problem. We give necessary and sufficient conditions on the number of identifiers for solving consensus in a distributed system with t faulty processes in the synchronous case. We show that in crash, send omission and general omission failures model, the uniform consensus is solvable even if processes are anonymous. Thus, identifiers are not useful in that case. However identifiers become important in Byzantine failures model: 3t + 1 identifiers is necessary and sufficient for Byzantine agreement. Surprisingly the number of identifiers must be greater than n+3t 2 in presence of three facets of uncertainty: partial synchrony, Byzantine failures and homonyms. This demonstrates two differences from the classical model (which has l = n): there are situations where relaxing synchrony to partial synchrony renders agreement impossible, and, in the partially synchronous case, increasing the number of correct processes can actually make it harder to reach agreement.
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Travers, Corentin. "Derrière le consensus : coordination faiblement contrainte dans les systèmes distribués asynchrones". Phd thesis, Université Rennes 1, 2007. http://tel.archives-ouvertes.fr/tel-00485704.
Testo completoAbstract (sommario):
L'informatique moderne est distribuée. La distribution du calcul résulte parfois d'un besoin applicatif lorsque l'objectif est de connecter des ordinateurs distants. Parfois, elle naît du besoin de tolérer des défaillances. En effet, pour éviter qu'une application ne soit à la merci de la défaillance d'une machine, le calcul est dupliqué sur plusieurs machines. Au coeur de tout calcul réparti repose une forme de coordination. Le fait même que des ordinateurs aient une tâche commune implique un besoin de se concerter avant d'accomplir certaines tâches. Nous étudions les problèmes de coordination dans le modèle asynchrone, sans hypothèses sur des bornes de vitesse d'exécution des processeurs ou de transmission des messages. Les processus peuvent défaillir à n'importe quel moment. Le degré de coordination qui peut être atteint en fonction du degré d'incertitude du système est la question principale de cette thèse. Trois formes de coordination sont considérées : l'accord ensembliste, le renommage et le consensus simultané. Dans un premier temps, nous proposons différentes réductions algorithmiques entre ces problèmes, afin de prouver dans quelles conditions une solution à l'un de ces problèmes permet d'obtenir une solution à un autre problème. Nous étudions ensuite des hypothèses nécessaires et suffisantes sur la détection de défaillances permettant de résoudre les problèmes d'accord. Le formalisme utilisé ici est celui des détecteurs de défaillances. Enfin, nous proposons un autre point de vue sur les détecteur de défaillances. Nous caractérisons la puissance de calcul amenée par ces détecteurs par une restriction des exécutions du modèle itéré de Gafni.
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Hu, Wei. "Identification de paramètre basée sur l'optimisation de l'intelligence artificielle et le contrôle de suivi distribué des systèmes multi-agents d'ordre fractionnaire". Thesis, Ecole centrale de Lille, 2019. http://www.theses.fr/2019ECLI0008/document.
Testo completoAbstract (sommario):
Cette thèse traite de l'identification des paramètres du point de vue de l'optimisation et du contrôle de suivi distribué des systèmes multi-agents d'ordre fractionnaire (FOMASs) en tenant compte des retards, des perturbations externes, de la non-linéarité inhérente, des incertitudes des paramètres et de l'hétérogénéité dans le cadre d'une topologie de communication fixe non dirigée / dirigée. Plusieurs contrôleurs efficaces sont conçus pour réaliser avec succès le contrôle de suivi distribué des FOMASs dans différentes conditions. Plusieurs types d'algorithmes d'optimisation de l'intelligence artificielle et leurs versions modifiées sont appliquées pour identifier les paramètres inconnus des FOMASs avec une grande précision, une convergence rapide et une grande robustesse. Il est à noter que cette thèse fournit un lien prometteur entre la technique d'intelligence artificielle et le contrôle distribuéThis thesis deals with the parameter identification from the viewpoint of optimization and distributed tracking control of fractional-order multi-agent systems (FOMASs) considering time delays, external disturbances, inherent nonlinearity, parameters uncertainties, and heterogeneity under fixed undirected/directed communication topology. Several efficient controllers are designed to achieve the distributed tracking control of FOMASs successfully under different conditions. Several kinds of artificial intelligence optimization algorithms andtheir modified versions are applied to identify the unknown parameters of the FOMASs with high accuracy, fast convergence and strong robustness. It should be noted that this thesis provides a promising link between the artificial intelligence technique and distributed control
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Hanna, Fouad. "Etude et développement du nouvel algorithme distribué de consensus FLC permfettant de maintenir la cohérence des données partagées et tolérant aux fautess". Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2051.
Testo completoAbstract (sommario):
De nos jours, le travail collaboratif a pris une place très importante dans plusieurs domaines, et notamment dans le domaine du télédiagnostic médical. Et la cohérence des données partagées est un enjeu primordial dans ce type d'application. De plus, pour garantir la cohérence des données, l'utilisation d'un algorithme de consensus est un élément indispensable dans les plateformes collaboratives. Nous présentons ici un nouvel algorithme de consensus, nommé FLC, permettant de garantir la cohérence des données partagées dans les systèmes distribués collaboratifs complètement asynchrones. Notre algorithme est tolérant aux pannes et a pour objectif d'améliorer la performance de consensus et notamment lorsque les processus participants tombent en panne. Ce nouvel algorithme utilise l'oracle leader Omega pour contourner le résultat d'impossibilité du théorème FLP. L'algorithme est décentralisé et adopte le modèle de pannes crash-stop. L'algorithme FLC s'appuie sur deux idées principales. La première propose de réaliser, au début de chaque cycle d'exécution, une phase simple d'élection de processus leader garantissant l'existence d'un seul leader par cycle. La deuxième bénéficie de la stabilité du système et plus particulièrement du fait que le processus leader ne tombe pas en panne d'un consensus à l'autre. Les performances de notre algorithme ont été analysées et comparées à celles des algorithmes les plus connus dans le domaine. Les résultats obtenus par simulation en utilisant la plateforme Neko ont montré que notre algorithme donne les meilleures performances lorsque le réseau utilisé est un réseau multicast et qu'aucun processus ne tombent en panne ainsi que pour les situations dans lesquelles l'algorithme de consensus subit une ou plusieurs pannes de processus coordinateurs/leadersNowadays, collaborative work took a very important place in many fields and particularly in the medicaltelediagnosis field. The consistency of shared data is a key issue in this type of applications. Moreover, itis essential to use a consensus algorithm to ensure data consistency in collaborative platforms. We presenthere our new consensus algorithm FLC that helps to ensure data consistency in asynchronous collaborativedistributed systems. Our algorithm is fault tolerant and aims to improve the performance of consensus ingeneral and particularly in the case of process crashes. The new algorithm uses the leader oracle tocircumvent the impossibility result of the FLP theorem. It is decentralized and considers the crash-stop failuremodel. The FLC algorithm is based on two main ideas. The first is to perform, at the beginning of eachround, a simple election phase guaranteeing the existence of only one leader per round. The second is totake advantage of system stability and more particularly of the fact that the leader does not crash betweentwo consecutive consensus runs. The performance of our algorithm was analyzed and compared to the mostknown algorithms in the domain. The results obtained by simulation, using the Neko platform, demonstratedthat our algorithm gave the best performance when using a multicast network in the best case scenario and insituations where the algorithm undergoes one or more crashes of coordinators/leaders processes
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Nguyen, Le-Duy-Lai. "Contrôle distribué multi-couche des systèmes complexes avec contraintes de communication : application aux systèmes d'irrigation". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT108/document.
Testo completoAbstract (sommario):
Cette thèse présente une contribution sur les problèmes de contrôle de réseaux d'irrigations en tenant compte des contraintes de communication grâce à une approche multicouches d’intelligence distribuée. Les analyses détaillées de chaque couche avec les résultats analytiques et les simulations seront décrites dans les différents chapitres. Ils mettent l'accent sur l'intérêt de l'approche multicouches, plus précisément sur son efficacité et sa fiabilité pour la supervision, l'optimisation multi-objectifs et le contrôle coopératif distribué sur des systèmes complexes de transport d'eau.La première couche analysé est le réseau hydraulique composé de canaux d’écoulements à surface libre, de sous-réseaux maillés de tuyaux sous pression et des structures hydrauliques (pompes vannes, ..). En intégrant les équations de Saint-Venant pour décrire l’écoulement physique des fluides en surface libre et la méthode Lattice Boltzmann pour la simulation du fluide, nous obtenons un modèle non linéaire discret pour les canaux à surface libre. Les structures hydrauliques sont généralement traitées comme des limites internes des biefs (tronçons) et modélisées par des relations entre les variables de flux et de pression.Permettant l'échange d'informations entre les éléments du système de contrôle, le réseau de communication sera considéré comme la deuxième couche. La résolution des problèmes d’hétérogénéités des systèmes et des communications (par exemple les retards de diffusion dans le réseau, la perte de paquets, la consommation d'énergie) sera étudié en introduisant une architecture de réseau hybride avec un routage dynamique basé sur les exigences de Qualité de Service (QoS) des applications de contrôle. Pour le routage dynamique dans le réseau, une composition pondérée de certaines métriques standards est proposée afin que le protocole de routage utilisant cette métrique composite converge sans boucle avec une « route » optimum. Grâce à différents scénarios de simulation, plusieurs critères de performance du réseau ont été évalués. La comparaison des résultats de simulation permet de valider l'intérêt de cette approche de composition pour le routage dynamique.Une troisième couche propose un système de contrôle réactif optimal développé pour la régulation du réseau d'irrigation dans un modèle étendue à grande échelle : Distributed Cooperative Model Predictive Control (DCMPC). Cette partie aborde la mise en œuvre de différentes stratégies de contrôle (centralisées, décentralisées et distribuées) et intègre la communication coopérative entre les contrôleurs MPC locaux afin d’améliorer les performances global es du système. La gestion de la divergence dans l'échange d'informations entre les contrôleurs est considérée comme un problème de consensus et résolue en utilisant un protocole de consensus asynchrone. Cette approche du contrôle distribué basée sur le paradigme des systèmes multi-agents, fournit une solution garantissant que tous les contrôleurs aient une vue cohérente de certaines valeurs des données nécessaires pour le calcul de décision. Un cas d’application sur un canal d'irrigation est étudié dans les simulations. La comparaison des résultats de simulations valide les avantages de l'approche du contrôle distribué coopératif par rapport aux autres stratégies de contrôleThis thesis presents control problems of irrigation network with communication constraints and a multi-layer approach to solve these problems in a distributed manner. Detailed discussions of each layer with analytical and simulation results are described throughout several chapters. They emphasize the potential interest of the multi-layer approach, more precisely its efficiency and reliability for supervision, multi-objective optimization and distributed cooperative control of complex water transport systems. Conventionally, the first layer to be considered is the hydraulic network composed of free-surface channels, hydraulic structures and mesh subnetwork of pressurized pipes. By coupling the Saint-Venant equations for describing the physics of free-surface fluid and the Lattice Boltzmann method for the fluid simulation, a discrete-time nonlinear model is obtained for channel reaches. The hydraulic structures are usually treated as internal boundaries of reaches and modeled by algebraic relationships between the flow and pressure variables. To enable the exchange of information among the control system’s components, a communication network is considered in the second layer. Solving challenging problems of heterogeneous devices and communication issues (e.g., network delay, packet loss, energy consumption) is investigated in this thesis by introducing a hybrid network architecture and a dynamic routing design based on Quality of Service (QoS) requirements of control applications. For network routing, a weighted composition of some standard metrics is proposed so that the routing protocol using the composite metric achieves convergence, loop-freeness and path-optimality properties. Through extensive simulation scenarios, different network performance criteria are evaluated. The comparison of simulation results can validate the interest of this composition approach for dynamic routing. Finally, the third layer introduces an optimal reactive control system developed for the regulatory control of large-scale irrigation network under a Distributed Cooperative Model Predictive Control (DCMPC) framework. This part discusses the implementation of different control strategies (e.g., centralized, decentralized, and distributed strategies) and how the cooperative communication among local MPC controllers can be included to improve the performance of the overall system. Managing divergent (or outdated) information exchange among controllers is considered in this thesis as a consensus problem and solved by an asynchronous consensus protocol. This approach based on the multi-agent system paradigm to distributed control requires each controller to agree with its neighbors on some data values needed during action computation. For simulations, a particular benchmark of an irrigation channel is considered. The comparison of simulation results validate the benefits of the distributed cooperative control approach over other control strategies
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Auvolat, Alex. "Probabilistic methods for collaboration systems in large-scale trustless networks". Thesis, Rennes 1, 2021. http://www.theses.fr/2021REN1S125.
Testo completoAbstract (sommario):
Internet est un outil formidable pour l'éducation, la communication et la collaboration, mais ses usages majoritaires sont actuellement sous monopole de grandes multinationales (GAFAM), ce qui a des conséquences sur le respect des droits humains et des libertés individuelles. Cette thèse propose des outils pour le développement d'applications décentralisées : des applications sur Internet qui fournissent des fonctionnalités similaires aux plateformes des GAFAM, mais de manière décentralisée, afin de rendre le pouvoir aux utilisateur pour décider démocratiquement de leur fonctionnement et de leurs usages. Nous nous concentrons sur les algorithmes épidémiques qui sont particulièrement adaptés dans le cadre de réseaux ouverts à large échelle. Nous proposons des contributions sur la diffusion causale de messages tolérante aux nœuds Byzantins, la diffusion causale épidémique à l'aide d'un stockage d'événements synchronisé par anti-entropie, l'échantillonnage aléatoire de pairs résistants aux attaques Byzantines et aux attaques Sybil, ainsi qu'un nouvel algorithme épidémique de diffusion totalement ordonnée qui tolère les nœuds malicieux et fournit un débit de messages élevéThe Internet is a formidable tool for education, communication and collaboration, however it is currently being monopolized by large corporations (GAFAM), which has consequences for many social issues such as respect of human rights and individual freedoms. This thesis focuses on ways to build decentralized applications: Internet applications that provide levels of functionality similar to those provided by the GAFAM, but that function in a decentralized manner, empowering the users to democratically decide of their functioning and their uses. We focus on epidemic algorithms, which are particularly suited to the context of very large open networks. We make contributions on causal broadcast in presence of Byzantine nodes, epidemic causal broadcast using an event store synchronized with an anti-entropy algorithm, random peer sampling in presence of Byzantine nodes and Sybil attacks, as well as a new epidemic total order broadcast which is tolerant to malicious nodes and provides high throughput message delivery
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Bellachehab, Anass. "Pairwise gossip in CAT(k) metric spaces". Thesis, Evry, Institut national des télécommunications, 2017. http://www.theses.fr/2017TELE0017/document.
Testo completoAbstract (sommario):
Cette thèse adresse le problème du consensus dans les réseaux. On étudie des réseaux composés d'agents identiques capables de communiquer entre eux, qui ont une mémoire et des capacités de calcul. Le réseau ne possède pas de nœud central de fusion. Chaque agent stocke une valeur qui n'est pas initialement connue par les autres agents. L'objectif est d'atteindre le consensus, i.e. tous les agents ont la même valeur, d'une manière distribuée. De plus, seul les agents voisins peuvent communiquer entre eux. Ce problème a une longue et riche histoire. Si toutes les valeurs appartiennent à un espace vectoriel, il existe plusieurs protocoles pour résoudre le problème. Une des solutions connues est l'algorithme du gossip qui atteint le consensus de manière asymptotique. C'est un protocole itératif qui consiste à choisir deux nœuds adjacents à chaque itération et de les moyenner. La spécificité de cette thèse est dans le fait que les données stockées par les agents n'appartiennent pas nécessairement à un espace vectoriel, mais à un espace métrique. Par exemple, chaque agent stocke une direction (l'espace métrique est l'espace projectif) ou une position dans un graphe métrique (l'espace métrique est le graphe sous-jacent). Là, les protocoles de gossip mentionnés plus haut n'ont plus de sens car l'addition qui n'est plus disponibles dans les espaces métriques. Cependant, dans les espaces métriques les points milieu ont du sens dans certains cas. Et là ils peuvent se substituer aux moyennes arithmétiques. Dans ce travail, on a compris que la convergence du gossip avec les points milieu dépend de la courbure. On s'est focalisés sur le cas où l'espace des données appartient à une classe d'espaces métriques appelés les espaces CAT(k). Et on a pu démontrer que si les données initiales sont suffisamment "proches" dans un sens bien précis, alors le gossip avec les points milieu - qu'on a appelé le Random Parwise Midpoints- converge asymptotiquement vers un consensusThis thesis deals with the problem of consensus on networks. Networks under study consists of identical agents that can communicate with each other, have memory and computational capacity. The network has no central node. Each agent stores a value that, initially, is not known by other agents. The goal is to achieve consensus, i.e. all agents having the same value, in a fully distributed way. Hence, only neighboring agents can have direct communication. This problem has a long and fruitful history. If all values belong to some vector space, several protocols are known to solve this problem. A well-known solution is the pairwise gossip protocol that achieves consensus asymptotically. It is an iterative protocol that consists in choosing two adjacent nodes at each iteration and average them. The specificity of this Ph.D. thesis lies in the fact that the data stored by the agents does not necessarily belong to a vector space, but some metric space. For instance, each agent stores a direction (the metric space is the projective space) or position on a sphere (the metric space is a sphere) or even a position on a metric graph (the metric space is the underlying graph). Then the mentioned pairwise gossip protocols makes no sense since averaging implies additions and multiplications that are not available in metric spaces: what is the average of two directions, for instance? However, in metric spaces midpoints sometimes make sense and when they do, they can advantageously replace averages. In this work, we realized that, if one wants midpoints to converge, curvature matters. We focused on the case where the data space belongs to some special class of metric spaces called CAT(k) spaces. And we were able to show that, provided initial data is "close enough" is some precise meaning, midpoints-based gossip algorithm – that we refer to as Random Pairwise Midpoints - does converge to consensus asymptotically. Our generalization allows to treat new cases of data spaces such as positive definite matrices, the rotations group and metamorphic systems
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Lavault, Christian. "Algorithmique et complexité distribuées : applications à quelques problèmes fondamentaux de complexité, protocoles distribués à consensus, information globale, problèmes distribués d'élection et de routage". Paris 11, 1987. http://www.theses.fr/1987PA112392.
Testo completoAbstract (sommario):
Présentation d'un cadre général pour l'étude et l'analyse des algorithmes répartis et résolution de plusieurs problèmes de fond relatifs à la complexité dans les systèmes répartis. Développement de divers outils d'analyse en moyenne de la complexite en messages de protocoles généraux à consensus. Résolution par l'analyse mathématique d'un problème ouvert sur les performances comparées des anneaux uni et bidirectionnels pour la complexité en moyenne en messages d'algorithmes d'élection déterministes. Un algorithme probabiliste de construction d'un arbre couvrant sur un système distribué anonyme et quelconque est développé. Deux théorèmes sont proposés qui bornent la faille des messages en fonction de la complexite en messages des algorithmes distribués asynchrones du point de vue de la quantité d'information.
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Wen, Guoguang. "Distributed cooperative control for multi-agent systems". Phd thesis, Ecole Centrale de Lille, 2012. http://tel.archives-ouvertes.fr/tel-00818774.
Testo completoAbstract (sommario):
Cette thèse considère principalement trois problèmes dans le domaine du contrôle distribué coopératif des systèmes multi-agents(SMA): le consensus, la navigation en formation et le maintien en formation d'un groupe d'agents lorsqu'un agent disparait. Nous proposons 3 algorithmes pour résoudre le problème du calcul distribué d'un consensus à partir de l'approche leadeur-suiveur dans le contexte SMA à dynamique non-linéaire. La référence est définie comme un leader virtuel dont on n'obtient, localement, que les données de position et de vitesse. Pour résoudre le problème du suivi par consensus pour les SMA à dynamique non-linéaire, nous considérons le suivi par consensus pour SMA de premier ordre. On propose des résultats permettant aux suiveurs de suivre le leadeur virtuel en temps fini en ne considérant que les positions des agents. Ensuite, nous considérons le suivi par consensus de SMA de second. Dans le cas de la planification de trajectoire et la commande du mouvement de la formation multi-agents. L'idée est d'amener la formation, dont la dynamique est supposée être en 3D, d'une configuration initiale vers une configuration finale (trouver un chemin faisable en position et orientation) en maintenant sa forme tout le long du chemin en évitant les obstacles. La stratégie proposée se décompose en 3 étapes. Le problème du Closing-Rank se traduit par la réparation d'une formation rigide multi-agents "endommagée" par la perte de l'un de ses agents. Nous proposons 2 algorithmes d'autoréparation systématique pour récupérer la rigidité en cas de perte d'un agent. Ces réparations s'effectuent de manière décentralisée et distribuée n'utilisant que des informations de voisinage.
Libri sul tema "Consensus distribué"
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Targeting funding: A new look at setting priorities : apply criteria to data on needs, develop consensus on priorities, distribute funds. Alexandria, Va. (701 N. Fairfax St., Alexandria 22314-2045): United Way of America, Community Problem Solving and Fund Distribution Division, 1985.
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Hanisch, Markus. Co-operatives and the Transformation of the German Energy Sector. A cura di Jonathan Michie, Joseph R. Blasi e Carlo Borzaga. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199684977.013.22.
Testo completoAbstract (sommario):
Over the last decades, the discussion on climate change, together with catastrophic events in the power sector, has raised global interest for radical policy changes. Since the year 2000, Germany´s Renewable Energy Sources Act (EEG) has been a forerunner in triggering large-scale decentralized deployment of renewable energy. Although built on a relatively large social consensus, the consequences of the German ‘Energiewende’ have also raised conflicts between communities and investor-oriented project developers. This chapter reviews the increasing role of energy co-operatives as means to involve civil society, mitigate conflicts in planning, and distribute subsidies more evenly among a variety of often rural stakeholders.
Capitoli di libri sul tema "Consensus distribué"
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Daniels, Norman. "Reasonableness and its definition in the provision of health care". In Oxford Textbook of Medicine, 54–58. Oxford University Press, 2010. http://dx.doi.org/10.1093/med/9780199204854.003.020402.
Testo completoAbstract (sommario):
Two central goals of health policy are to improve population health as much as possible and to distribute the improvements fairly. These goals will often conflict. Reasonable people will disagree about how to resolve these conflicts, which take the form of various unsolved rationing problems. The conflict is also illustrated by the ethical controversy that surrounds the use of cost-effectiveness analysis. Because there is no consensus on principles to resolve these disputes, a fair process is needed to assure outcomes that are perceived to be fair and reasonable. One such process, accountability for reasonableness, assures transparency, involves stakeholders in deliberating about relevant rationales, and requires that decisions be revised in light of new evidence and arguments. It has been influential in various contexts including developed countries such as Canada, the United Kingdom, New Zealand, and Sweden, and developing countries, such as Mexico....
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Kannan, P. K., Eva Guterres e Barbara Kline Pope. "Pricing Strategies for Digital Books". In Internet Marketing Research, 47–60. IGI Global, 2001. http://dx.doi.org/10.4018/978-1-878289-97-1.ch003.
Testo completoAbstract (sommario):
While the World Wide Web has impacted many industries significantly, none of them have been affected as dramatically as the publishing industry. The ability to deliver electronic content online and to distribute it in various forms instantaneously using the Web have opened up technological possibilities and consumer expectations that have left the industry grappling for new business models. Most of those running publishing businesses have finally come to a consensus about the importance of the Web to the future of the industry and are embracing the new technologies but with little guidance on how to best use the medium. They are aware of the pressing need to adapt to the much speedier efficiencies, strategies, and requirements of the digital channel while balancing them with non-digital strategies that continue to work but are looking for some guidance on how to move forward. In this chapter, we first describe some of the key trends and challenges faced by book publishers with the emergence of the digital arena. We then focus on the issue of pricing electronic books distributed online, especially in conjunction with books distributed through traditional channels. We outline some of the possible strategies that book publishers could adopt and examine the pros and cons of the different strategies in light of the features of the product marketed and consumer segments targeted.
Atti di convegni sul tema "Consensus distribué"
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Yiming, Wu, He Xiongxiong e Ou Xianhua. "Distribute consensus for multi-agent systems with attacks and delays". In 2015 34th Chinese Control Conference (CCC). IEEE, 2015. http://dx.doi.org/10.1109/chicc.2015.7260817.
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Pedroso Junior, Carlos Alberto, Yan Uehara De Moraes, Michele Nogueira De Lima e Aldri Luiz Dos Santos. "Atribuições Cooperativas de Tarefas de Sensoriamento Baseada em Consenso Relacional para Redes IIoT". In XXV Workshop de Gerência e Operação de Redes e Serviços. Sociedade Brasileira de Computação, 2020. http://dx.doi.org/10.5753/wgrs.2020.12461.
Testo completoAbstract (sommario):
Entre os atuais serviços IoT destacam-se os voltados a indústrias, que muitas vezes exigem que os objetos desempenhem mais de uma tarefa. Entretanto, o crescimento exponencial dos objetos na IoT impõe o desafio de distribuir e gerenciar a alocação de tarefas entre os objetos. Um dos principais objetivos da alocação de tarefas é melhorar a qualidade das informações e a maximização de tarefas a serem executadas. Embora existam abordagens que otimizem e gerenciem a dinamicidade dos nós, nem todas consideram a relação de similaridade a alocação distribuída sobre o serviço de agrupamento. Este trabalho propõe um mecanismo chamado CONTASKI para alocação de tarefas em redes IIoT, a fim de distribuir as tarefas entre os objetos. Ele baseia-se em estratégias de consenso relacional para alocar as tarefas e de similaridade de capacidades para determinar quais objetos podem atuar na realização dessas tarefas. O CONTASKI foi avaliado no NS-3 gerenciando um ambiente IIoT e obteve uma eficiência de cerca de 98% de tarefas alocadas na maioria dos cenários avaliados e mais de 80% dos agrupamentos IIoT aptos a executá-las.
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Ugueto C., Gustavo A., Paul T. Huckabee e Mathieu M. Molenaar. "Challenging Assumptions About Fracture Stimulation Placement Effectiveness Using Fiber Optic Distributed Sensing Diagnostics: Diversion, Stage Isolation and Overflushing". In SPE Hydraulic Fracturing Technology Conference. SPE, 2015. http://dx.doi.org/10.2118/spe-173348-ms.
Testo completoAbstract (sommario):
Abstract The connection of the wellbore to the hydrocarbon resource volumes via effective fracture stimulation is a critical factor in unconventional reservoir completions. Various well construction and dynamic placement methods are used to distribute treatment volumes into targeted sections of the wellbore. This paper provides some insights into the effectiveness of hydraulic fracture stimulation process using Fiber Optics (FO): distributed acoustic sensing (DAS) and distributed temperature sensing (DTS). This paper reviews examples from multiple wells where FO has been used to gain a better understanding of three highly debated fracture stimulation distribution topics: Diversion, Stage Isolation and Overflushing. Diversion is increasingly being used as a way to improve the efficiency of hydraulic fracture stimulation distributions. The effectiveness of the diversion techniques has traditionally been judged on the basis of surface pressure response during treatment and ultimately, from production comparisons to reference wells. Unfortunately, getting clear answers from production performance takes significant time. FO allows for monitoring of the diversion process in real-time. Analysis of DAS and DTS responses is used to quantify diversion efficiency in re-directing hydraulic fracture stimulation from dominant perforation clusters to those not being stimulated. Lack of isolation between stages has frequently been observed in wells with diagnostics. There is consensus amongst the completion community that communication between stages is highly undesirable because the energy and materials of the stimulation are partially or totally misdirected from the target interval to other portions of the wellbore. The analysis of DAS and DTS not only can help determine the frequency of occurrence of communication between stages in cemented and uncemented horizontal wells but also can provide insights about the different communication paths. Fiber Optic distributed sensing in conjunction with complementary diagnostics is also being used to investigate if connections are being maintained at the end of the treatment between the newly created fracs and the wellbore. The use of integrated diagnostics allows evaluation of the frequency in which overflushing (over-displacement) occurs in both vertical and horizontal wells and its impact on well inflow performance where production profiling data is available.