Literatura académica sobre el tema "Système spatial distribué"
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Artículos de revistas sobre el tema "Système spatial distribué"
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Ray, Cyril. "Un système distribué pour la modélisation de flux de données spatiales désagrégées." Revue internationale de géomatique 13, no. 2 (2003): 201–24. http://dx.doi.org/10.3166/rig.13.201-224.
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Morin, Denis. "Allométrie du système urbain du Québec (1941-1971)." Cahiers de géographie du Québec 19, no. 46 (2005): 17–37. http://dx.doi.org/10.7202/021246ar.
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Ce travail contribue à la connaissance du phénomène de la croissance du système urbain québécois avec l'aide de techniques statistiques. Notre double objectif est le suivant : d'une part établir la pertinence des taux de croissance allométrique calculés à l'aide de six points de référence dans le temps, et d'autre part identifier et surtout mesurer les forces qui articulent la croissance du système urbain québécois. Tout d'abord, il a été possible de voir comment la croissance des agglomérations se distribue dans l'espace. L'analyse a fait ressortir très tôt la grande complexité de la croissance. C'est pourquoi nous avons eu recours à un large éventail de variables (56). La technique de l'analyse factorielle a rendu possible la réduction de la plus grande partie de notre information en treize facteurs avec une perte inférieure à 17%. L'âge humain et matériel, la position spatiale et sociale, le dynamisme ainsi que le découpage du pourtour des agglomérations constituent les dimensions fondamentales de la croissance du système urbain québécois.
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Fortin, J. P., R. Moussa, C. Bocquillon, and J. P. Villeneuve. "Hydrotel, un modèle hydrologique distribué pouvant bénéficier des données fournies par la télédétection et les systèmes d'information géographique." Revue des sciences de l'eau 8, no. 1 (2005): 97–124. http://dx.doi.org/10.7202/705215ar.
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Les processus hydrologiques variant dans l'espace et dans le temps en fonction de la variabilité spatio-temporelle des entrées météorologiques et de l'occupation du sol ainsi que de la variabilité spatiale de la topographie et de la nature du terrain, un modèle conçu pour bénéficier des données provenant de la télédétection et des SIG a été développé. Les principaux objectifs poursuivis étaient: l'application au plus grand nombre de bassins possible, une sélection d'algorithmes permettant de tenir compte des données disponibles, un minimum d'étalonnage, la facilité de transfert d'un bassin à l'autre, la programmation des algorithmes sur micro-ordinateur avec une interface très conviviale. La structure d'écoulement à l'intérieur d'un bassin versant est obtenue de manière informatisée à partir d'une discrétisation des altitudes rencontrées dans la zone d'intérêt, en mailles carrées de dimensions données, d'où l'on tire les pentes et les orientations de chaque maille, puis le bassin versant en amont de la maille identifiée comme exutoire, le réseau hydrographique, les sous-bassins versants et, finalement, les unités hydrologiques relativement homogènes (UHRH), définies sur la base de ces sous-bassins, en les regroupant ou les divisant au besoin. Un logiciel spécifique pour ce faire a été développé: PHYSITEL. Selon la conception très modulaire adoptée pour HYDROTEL, chaque sous-modèle offre généralement plus d'une option de simulation, afin de tenir compte des données disponibles sur le bassin versant traité. Les simulations peuvent être réalisées en considérant comme unité de simulation du bilan hydrologique vertical les mailles originales constituant le bassin ou les UHRH. Des exemples de simulation des débits à l'aide du modèle HYDROTEL sur divers bassins versants situés au Canada (Québec, Ontario, Colombie-Britannique) et dans le sud de la France sont présentés. Ces simulations indiquent que les différents algorithmes du modèle réagissent bien et qu'il est possible de considérer son application sur des bassins très divers situés sous des conditions climatiques variées. Des tests plus poussés sont en cours afin de mieux cerner la sensibilité des divers algorithmes aux données d'entrée ainsi que leur interchangeabilité.
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Smit, Izak. "Systems approach towards surface water distribution in Kruger National Park, South Africa." Pachyderm 53 (June 30, 2013): 91–98. http://dx.doi.org/10.69649/pachyderm.v53i.328.
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There was concerted effort, especially between the 1960s and 1990s, to increase the distribution of surface water in Kruger National Park (KNP). As a consequence, most of the park was within easy walking distance of a permanent water source for large, mobile herbivores during the peak of the water-for-game programme. This situation was unnatural and led to various unintended ecological effects. In reaction to this and in response to changing conservation and management paradigms, the water provision policy was revised in 1997. Since the policy change, about two-thirds of the more than 300 boreholes have been closed and many catchment dams have been breached in an ongoing process. This new approach towards water provision has a strong spatial focus and aims to recreate and mimic a more natural mosaic of spatio-temporal variability in surface water availability. KNP managers hope that the change in water provision will induce spatial and temporal variation in how elephants utilize landscapes, which is a key objective of the current KNP Elephant Management Plan. Although it seems unlikely that the reduced availability of water has had any numerical effects on the elephant population thus far, it did induce some spatial changes: elephants are now even more strongly attracted to the large river systems than before. More research is needed to ascertain whether surface water manipulation in KNP, where water is naturally relatively widely distributed, is effective in creating spatio-temporal refugia for biodiversity that are sensitive towards elephant impacts. L’on a vu des efforts concertés, surtout entre les années 1960 et 1990, d’augmenter la distribution de l’eau de surface dans le Parc National Kruger (PNK). En conséquence, la plus grande partie du parc se trouvait à une courte distance de marche d’une source d’eau permanente pour les grands herbivores mobiles lors du pic du programme de l’eau-pour-la-faune. Cette situation était anormale et a conduit à divers effets écologiques inattendus. En réaction à cela et en réponse à l’évolution des paradigmes de conservation et de gestion, la politique d’approvisionnement en eau a été révisée en 1997. Depuis le changement de politique, environ deux tiers des plus de 300 forages ont été fermés et de nombreux barrages de captage percés dans un processus continu. Cette nouvelle approche d’approvisionnement en eau a une forte concentration spatiale et vise à recréer et à imiter une mosaïque plus naturelle de variabilité spatio-temporelle de la disponibilité en eau de surface. Les gestionnaires du PNK espèrent que la variation de l’approvisionnement en eau va induire des variations spatiales et temporelles dans la façon dont les éléphants utilisent les paysages, ce qui est un objectif clé du plan actuel de gestion des éléphants du PNK. Bien qu’il semble peu probable que la disponibilité réduite de l’eau ait eu des effets numériques sur la population des éléphants à ce jour, elle a induit quelques changements spatiaux: les éléphants sont encore plus fortement attirés par les grands systèmes fluviaux qu’auparavant. Il faut plus de recherche pour déterminer si la manipulation des eaux de surface dans le PNK où l’eau est assez largement distribué naturellement, est efficace dans la création de refuges spatio-temporels de la biodiversité sensibles aux impacts des éléphants.
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Daghistani, Anas, Walid G. Aref, Arif Ghafoor, and Ahmed R. Mahmood. "SWARM: Adaptive Load Balancing in Distributed Streaming Systems for Big Spatial Data." ACM Transactions on Spatial Algorithms and Systems 7, no. 3 (2021): 1–43. http://dx.doi.org/10.1145/3460013.
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The proliferation of GPS-enabled devices has led to the development of numerous location-based services. These services need to process massive amounts of streamed spatial data in real-time. The current scale of spatial data cannot be handled using centralized systems. This has led to the development of distributed spatial streaming systems. Existing systems are using static spatial partitioning to distribute the workload. In contrast, the real-time streamed spatial data follows non-uniform spatial distributions that are continuously changing over time. Distributed spatial streaming systems need to react to the changes in the distribution of spatial data and queries. This article introduces SWARM, a lightweight adaptivity protocol that continuously monitors the data and query workloads across the distributed processes of the spatial data streaming system and redistributes and rebalances the workloads as soon as performance bottlenecks get detected. SWARM is able to handle multiple query-execution and data-persistence models. A distributed streaming system can directly use SWARM to adaptively rebalance the system’s workload among its machines with minimal changes to the original code of the underlying spatial application. Extensive experimental evaluation using real and synthetic datasets illustrate that, on average, SWARM achieves 2 improvement in throughput over a static grid partitioning that is determined based on observing a limited history of the data and query workloads. Moreover, SWARM reduces execution latency on average 4 compared with the other technique.
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Kacin, Melanie, Oakyoon Cha, and Isabel Gauthier. "The Relation between Ensemble Coding of Length and Orientation Does Not Depend on Spatial Attention." Vision 7, no. 1 (2022): 3. http://dx.doi.org/10.3390/vision7010003.
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Most people are good at estimating summary statistics for different features of groups of objects. For instance, people can selectively attend to different features of a group of lines and report ensemble properties such as the mean length or mean orientation and there are reliable individual differences in such ensemble judgment abilities. Our recent study found decisive evidence in support of a correlation between the errors on mean length and mean orientation judgments (r = 0.62). The present study investigates one possible mechanism for this correlation. The ability to allocate spatial attention to single items varies across individuals, and in the recent study, this variability could have contributed to both judgments because the location of lines was unpredictable. Here, we replicate this prior work with arrays of lines with fully predictable spatial locations, to lower the contribution of the ability to distribute attention effectively over all items in a display. We observed a strong positive correlation between errors on the length and orientation averaging tasks (r = 0.65). This provides evidence against individual differences in spatial attention as a common mechanism supporting mean length and orientation judgments. The present result aligns with the growing evidence for at least one ensemble-specific ability that applies across different kinds of features and stimuli.
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Cao, Kerang, Kwang-nam Choi, Hoekyung Jung, and Lini Duan. "Deep Learning for Facial Beauty Prediction." Information 11, no. 8 (2020): 391. http://dx.doi.org/10.3390/info11080391.
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Facial beauty prediction (FBP) is a burgeoning issue for attractiveness evaluation, which aims to make assessment consistent with human opinion. Since FBP is a regression problem, to handle this issue, there are data-driven methods for finding the relations between facial features and beauty assessment. Recently, deep learning methods have shown its amazing capacity for feature representation and analysis. Convolutional neural networks (CNNs) have shown tremendous performance on facial recognition and comprehension, which are proved as an effective method for facial feature exploration. Lately, there are well-designed networks with efficient structures investigated for better representation performance. However, these designs concentrate on the effective block but do not build an efficient information transmission pathway, which led to a sub-optimal capacity for feature representation. Furthermore, these works cannot find the inherent correlations of feature maps, which also limits the performance. In this paper, an elaborate network design for FBP issue is proposed for better performance. A residual-in-residual (RIR) structure is introduced to the network for passing the gradient flow deeper, and building a better pathway for information transmission. By applying the RIR structure, a deeper network can be established for better feature representation. Besides the RIR network design, an attention mechanism is introduced to exploit the inner correlations among features. We investigate a joint spatial-wise and channel-wise attention (SCA) block to distribute the importance among features, which finds a better representation for facial information. Experimental results show our proposed network can predict facial beauty closer to a human’s assessment than state-of-the-arts.
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Borges, Marco A., Paulo B. Lopes, and Leandro A. da Silva. "Network Optimization of Carbon Monoxide Sensor Nodes in the Metropolitan Region of São Paulo." Electronics 12, no. 22 (2023): 4647. http://dx.doi.org/10.3390/electronics12224647.
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Air pollution is one of the biggest problems affecting large urban areas. Better monitoring of regions suffering from this type of pollution is in the interest of public health. Although many cities employ sensors to monitor air pollution, a current concern is how to establish the ideal number of sensors to monitor a given geographical region. To address this concern, this research proposes a method to optimize the number of sensors in an air pollution monitoring network to cover a given region efficiently and precisely and uses the metropolitan region of São Paulo, Brazil, and CO sensors as an example. The model of Fragmentation into Groups via Routes is proposed to distribute sensors within micro-regions that display similar air pollution characteristics. A network of virtual sensors is created, and the output of each sensor is established using a method of spatial interpolation called IDW. To identify the optimum sensor configuration, a genetic algorithm is used to assess the topology with the lowest variance of data spread. A lesser number of sensor stations to be treated leads to faster responses to sudden changes in urban conditions. Therefore, municipality authorities can take quick measures to improve the population’s wellness.
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"Detection of False Data Injection Attacks in Smart-Grid Systems: Benchmarking Deep Learning Techniques." Journal of Electrical Electronics Engineering 2, no. 1 (2023). http://dx.doi.org/10.33140/jeee.02.01.05.
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In essence, smart grids are electrical networks that transmit and distribute electricity in a reliable, effective manner using information and communication technology (ICT). Trust and security are of the utmost importance. False data injection (FDI) attacks are one of the most serious new security problems, and they can drastically raise the price of the energy distribution process. However, rather than smart grid infrastructures, the majority of current research focuses on FDI defenses for conventional electricity networks. By utilizing spatial-temporal correlations between grid components, we create an effective and real-time technique to identify FDI attacks in smart grids called a deep learning framework. We show that the suggested method offers an accurate and dependable solution using realistic simulations based on the smart grid compared to the benchmarked techniques.
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Makanga, Prestige, and Julian Smit. "A Review of the Status of Spatial Data Infrastructure Implementation in Africa." South African Computer Journal 45 (August 3, 2010). http://dx.doi.org/10.18489/sacj.v45i0.36.
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Spatial data is a key resource for the development of a nation. There is a lot of economic potential that is locked away in spatial data collections and this potential is realised by making the data widely available. Spatial Data Infrastructures (SDI) provide a platform for spatial data users, producers and those that manage it, to distribute the data more efficiently. Governments all over the world are realising the value of National Spatial Data Infrastructures (NSDI), and therefore making major investments to establish them. However, in Africa, implementation of formal NSDI is being done at a seemingly slow pace. This paper presents an assessment of the status of NSDI activity in Africa. 29 countries were used in the survey and an assessment was made per region (South, West, East, North and Central Africa). The results show that generally, formal NSDI activity in most African countries is still in its infancy. The paper also gives recommendations of possible measures that can be taken to foster SDI implementation on the continent. In addition, it highlights potential areas for further SDI research.
Tesis sobre el tema "Système spatial distribué"
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Akopyan, Evelyne. "Fiabilité de l'architecture réseau des systèmes spatiaux distribués sur essaims de nanosatellites." Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSEP102.
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Le domaine de l’observation de l’Espace s’intéresse de près aux signaux très basse fréquence, car ils fournissent d’importantes informations quant à la naissance et aux premiers jours de l’Univers. A ce jour, les interféromètres observant ces signaux se situent à la surface de la Terre, dans des zones arides. Malheureusement, ces signaux sont très sensibles aux interférences terrestres ainsi qu’à l’ionosphère, et sont donc difficilement observables. Une solution à ce problème serait d’observer les signaux directement depuis l’Espace, en déployant un essaim de nanosatellites en orbite autour de la Lune. Cet essaim constitue un Système Spatial Distribué (DSS), fonctionnant en tant qu'interféromètre, dont l’orbite lunaire le préserve des interférences terrestres et de l’ionosphère. Cependant, la configuration de l’essaim de nanosatellites en interféromètre spatial est un défi de taille en termes de communication, notamment en raison de l’absence d’infrastructure dans l’Espace et du volume de données d’observation à propager au sein du système. L’objectif de la thèse est donc de définir une configuration d’architecture fiable, répondant aux contraintes conjointes d’un réseau MANET et d’un système distribué. La thèse commence par caractériser le réseau de l’essaim de nanosatellites et met en avant sa forte hétérogénéité. Ensuite, elle propose des algorithmes permettant de répartir équitablement la charge du réseau, en se basant sur des techniques de division de graphe, et compare les performances de ces algorithmes sur des critères d'équité. Enfin, elle évalue la sensibilité du système aux pannes en termes de robustesse (résistance aux pannes) et de résilience (maintien du fonctionnement en présence de pannes) et étudie l'impact de la division de graphe sur la fiabilité globale de l'essaim. Les algorithmes de division développés dans cette thèse devront garantir la Qualité de Service (QoS) essentielle au bon fonctionnement d'un interféromètre spatial. Pour atteindre cet objectif, des solutions de routage pertinentes devront être minutieusement étudiées et intégrées, afin de s'assurer qu'elles répondent aux exigences strictes de performance et de fiabilité de cette application avancée<br>The study of the low-frequency range is essential for Deep Space observation, as it extracts precious information from Dark Ages signals, which are signatures of the very early Universe. To this day, the majority of low-frequency radio interferometers are deployed in desertic regions on the surface of the Earth. However, these signals are easily distorted by radio-frequency interferences as well as the ionosphere, making them hardly observable when they are not completely masked. One solution to this problem would be to observe the low-frequency signals directly from Space, by deploying a nanosatellite swarm in orbit around the Moon. This swarm is defined as a Distributed Space System (DSS) operating as an interferometer, while being shielded by the Moon from terrestrial interferences and ionospheric distortions. However, the configuration of a nanosatellite swarm as a space observatory proves to be a challenging problem in terms of communication, mostly because of the lack of external infrastructure in Space, and the amount of observation data to propagate within the swarm. Thus, the objective of the thesis is to define a reliable network architecture that would comply with the requirements of a MANET and a distributed system, simultaneously. This thesis starts by characterizing the network of the nanosatellite swarm and highlights its strong heterogeneity. Then, it introduces a set of algorithms, based on graph division, to fairly distribute the network load among the swarm, and compares their performance in terms of fairness. Finally, it assesses the fault tolerance of the system in terms of robustness (capacity to resist faults) and resilience (capacity to maintain functionality when faults occur) and evaluates the impact of graph division on the overall reliability of the swarm. The division algorithms developped in this thesis should ensure the Quality of Service (QoS) necessary to the proper functioning of a Space interferometer. To this end, relevant routing protocols should be thoroughly studied and integrated, in order to meet the strict requirements of this advanced application in terms of performance and reliability
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Pontisso, Nadège. "Association cohérente de données dans les systèmes temps réel à base de composants - Application aux logiciels spatiaux." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2009. http://tel.archives-ouvertes.fr/tel-00459071.
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Les architectures distribuées des systèmes embarqués sont souvent décrites sous la forme de composants concurrents communiquant entre eux. De tels systèmes sont à la fois orientés flot de données pour leur description, et dirigés par le temps pour leur exécution. Cette thèse s'inscrit dans cette problématique et se concentre sur le contrôle de la compatibilité temporelle d'un ensemble de données interdépendantes utilisées par les composants du système. L'architecture d'un système modélisé par composants forme un graphe où plusieurs chemins peuvent relier deux composants, avec des caractéristiques temporelles hétérogènes, ce qui induit des temps de parcours disparates. Il est alors important que ces flots d'information soient assemblés de façon cohérente sur le composant destinataire, c'est-à-dire de telle manière que le composant utilise en entrée des données dépendant (directement ou indirectement) du même pas d'exécution du composant à l'origine de ces flots multiples. Dans un premier temps, ce principe d'association cohérente de données est identifié et formalisé. Une méthodologie est proposée afin de détecter, dans un graphe de composants, les configurations pouvant poser des problèmes d'association de données Dans un deuxième temps, différentes approches sont détaillées afin de gérer l'association cohérente des données dans des systèmes périodiques sans supposer de propriétés strictes sur l'ordonnancement des composants. Dans les systèmes où les composants partagent la même période et où les communications intra-périodiques sont interdites, l'association des données est gérée par un mécanisme de files permettant de rééquilibrer les temps de parcours des données sur les différents chemins. Dans le cas où les composants sont de périodes diverses, un mécanisme d'estampillage des données est utilisé afin de mémoriser les dépendances entre données. Associé à l'utilisation de files, cet estampillage permet aux composants de sélectionner, à chacune de leurs phases d'activation, des ensembles de données cohérents choisis parmi les données à leur disposition. La notion d'association cohérente est ensuite relâchée, permettant une utilisation de données approximativement cohérentes. Des files filtrantes, n'enregistrant qu'une donnée sur un certain nombre de données reçues, permettent de réduire la taille des files nécessaires. Par ailleurs, du fait de la liberté du modèle d'exécution choisi, il existe des situations où il est impossible de garantir la vivacité de l'association cohérente des données. D'autre part, une architecture particulière peut générer des contraintes de cohérence conflictuelles et aboutir à une impossibilité de gestion de la cohérence. Pour terminer, les résultats de ces travaux sont appliqués sur le logiciel applicatif d'un satellite d'observation terrestre détectant des points chauds.
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Salmon, Loïc. "Une approche holistique combinant flux temps-réel et données archivées pour la gestion et le traitement d'objets mobiles : application au trafic maritime." Thesis, Brest, 2019. http://www.theses.fr/2019BRES0006/document.
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La numérisation de nos espaces de vie et de mobilités s’est largement accentuée durant la dernière décennie. La multiplication des capteurs de toute nature permettant de percevoir et de mesurer notre espace physique en est le levier principal. L’ensemble de ces systèmes produit aujourd’hui de grands volumes de données hétérogènes sans cesse croissants, ce qui soulève de nombreux enjeux scientifiques et d'ingénierie en termes de stockage et de traitement pour la gestion et l’analyse de mobilités. Les travaux dans le domaine d’analyse des données spatio-temporelles ont largement été orientés soit vers la fouille de données historiques archivées, soit vers le traitement continu. Afin d’éviter les écueils de plus en plus prégnants dus à l’augmentation de ces volumes de données et de leur vélocité (temps de traitement trop long, modèles conceptuellement plus adaptés, analyse approximative des données), nous proposons la conception d’une approche hybride distribuée permettant le traitement combiné de flux temps-réel et de données archivées. L’objectif de cette thèse est donc de développer un nouveau système de gestion et de traitement distribué pour l’analyse des mobilités en particulier maritimes. La solution proposée répond principalement à des contraintes de temps-réel, les données archivées et les informations qui en sont extraites permettant d'améliorer la qualité de réponse. Une proposition de paradigme d'événements est également développée pour permettre ce traitement hybride mais aussi pour caractériser et identifier plus facilement des comportements types d'objets mobiles. Enfin, une requête appliquée sur des zones de couverture de signal pour des objets mobiles a été étudiée et testée sur des données maritimes mettant en exergue le besoin d'une approche hybride pour le traitement de trajectoires<br>Over the past few years, the rapid prolifération of sensors and devices recording positioning information regularly produces very large volumes of heterogeneous data. This leads to many research challenges as the storage, distribution, management,Processing and analysis of the large mobility data generated still needs to be solved. Current works related to the manipulation of mobility data have been directed towards either mining archived historical data or continuous processing of incoming data streams.The aim of this research is to design a holistic System whose objective is to provide a combined processing of real time data streams and archived data positions. The proposed solution is real-time oriented, historical data and informations extracted from them allowing to enhance quality of the answers to queries. A event paradigm is discussed to facilitate the hybrid approach and to identify typical moving objects behaviors. Finally, a query concerning signal coverage of moving objects has been studied and applied to maritime data showing the relevance of a hybrid approach to deal with moving object data processing
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Baumann, Hervé. "Diffusion décentralisée d'information dans les systèmes distribués." Paris 7, 2012. http://www.theses.fr/2012PA077076.
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Cette thèse porte sur la diffusion d'informations dans les réseaux. La diffusion consiste à transmettre une information à partir d'un nœud source vers tous les autres nœuds. Elle est très présente en informatique, aussi bien pour transmettre du contenu par internet que pour le calcul distribué ou parallèle. Dans les protocoles que nous considérons, chaque nœud informé participe à la diffusion d'information : dans l'inondation, un nœud informé transmet l'information à tous ses voisins en une seule étape de temps, et dans la diffusion 1-PORT chaque nœud informé communique, à chaque étape, avec un unique voisin. Notre première contribution porte sur l'étude du pire temps de diffusion 1-PoRT où un nœud n'appelle pas un voisin qu'il sait être informé. Nous étudions trois variantes. Dans la première, un nœud ne rappelle simplement pas un voisin auquel il a déjà envoyé l'information ; dans la deuxième, les voisins qu'un nœud sait être informés sont tous ceux avec lesquels il a déjà échangé de l'information (dans un sens ou dans l'autre) ; dans la troisième, chaque nœud sait exactement quels sont ses voisins informés. Nous montrons principalement que dans la première variante, il est possible de calculer en temps polynomial le pire temps de diffusion et un pire schéma correspondant. Pour les deux autres variantes, nous montrons que ce calcul est NP-difficile, en fait inapproximable en temps polynomial. Notre deuxième contribution concerne l'étude de la diffusion dans des réseaux dynamiques modélisés par des graphes à évolution arête-markovienne. Nous proposons une technique de réduction permettant de ramener le calcul du temps d'inondation au calcul du diamètre d'un graphe pondéré statique tiré aléatoirement. Cette technique nous permet de calculer le temps de diffusion par inondation dans les graphes dynamiques arête-markoviens. Nous avons également calculé le temps de diffusion probabiliste 1-PORT dans certains graphes à évolution arête-markovienne. Notre dernière contribution porte sur la diffusion spatiale où tous les nœuds peuvent communiquer les uns avec les autres. Les performances des protocoles de diffusion spatiale sont mesurées en fonction de l'éloignement des destinataires par rapport à la source. Nous décrivons un protocole de diffusion spatiale probabiliste généraliste, c'est-à-dire, valable pour toute métrique. Nous analysons sa vitesse de propagation dans les métriques de graphes et dans les métriques à densité uniforme<br>This thesis focuses on the broadcast of information in a network. Broadcasting is the disse¬mination of information from a source node to ail other nodes. It is very present in information technology, both to transmit content over the Internet and for distributed or parallel Computing. In the protocols we consider, each informed node take part in the dissemination of information : in flooding, an informed node disseminate the information to ail its neighbours in one time step, and in gossip (1-PORT) broadcasting each informed node communicates, at each time step, only with one of its neighbours. Our first contribution is the study of the worst broadcast time of a gossip protocol where a node does not call a neighbour he knows to be informed. We study three variants, in the first one, a node knows that a neighbour is informed only if it has sent it the information, in the second one, the neighbours a node knows to be informed are ail those with whom it has exchanged information (in one way or the other), and in the third one, each node knows exactly which of its neighbours are informed. We mainly show that in the first variant, it is possible to compute in polynomial time the worst broadcast time and a worse broadcast scheme. For the other two variants, we show that this calculation is NP-hard and even inapproximable in polynomial time. Our second contribution is the study of diffusion in dynamic networks modeled by edge-Markovian evolving graphs. We give a reduction technique that allows the computation of the time taken by the flooding to inform ail nodes of an edge-Markovian evolving graph to be reduced to the computation of the diameter of a static weighted random graph. We also compute the broadcast time of a random gossip protocol in some particular edge-Markovian evolving graphs. Our last contribution relates to spatial gossip where ail nodes can communicate with each other. The performances of spatial gossip protocols are measured in function of the targets' relative distance to the source. We describe a general random spatial gossip protocol, I. E. , valid for any metric. We analyze its propagation speed on graph metrics and on metrics of uniform density
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Pasqua, Roberto. "Inférence et modèles de données personnelles : mobilité sociale, proximité spatiale." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30195/document.
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La diffusion massive de dispositifs portables, de plus en plus utilisés pour le traitement et la communication de l'information, permet la collecte d'importantes masses de données liées à l'activité des utilisateurs sur des applications mobiles. Nous nous intéressons aux données de localisation (les traces de mobilité) qui sont issues de systèmes mobiles formés par un groupe d'utilisateurs. Les données de mobilité produites dans un système mobile sont étudiées suivant deux axes : - L'utilisation des modèles de mobilité est à la base du développement d'algorithmes de communication dédiés au systèmes mobiles. Les données de mobilité réelles concernant les utilisateurs vont nous permettre de comparer les données de mobilité synthétiques utilisées dans la simulation avec la réalité qu'ils sont censés décrire. - La manipulation des données de mobilité réelles implique une réflexion sur les conséquences que les informations extraites de ces données ont relativement à la protection de la vie privée des utilisateurs. Les contributions sur ces deux fronts sont les suivantes : - Une analyse fine des propriétés spatiales et sociales d'un ensemble de traces de mobilité réelles collecté expérimentalement à l'aide d'une plateforme à haute precision. - Une comparaison exploratoire entre des traces de mobilité réelles et des traces de mobilité synthétiques générées à partir de sept différents modèle de mobilité. - La conception et l'analyse d'un algorithme d'inférence par co-localisation décorrélée des informations sur la localisation des utilisateurs ciblés. - La quantification du potentiel des données de co-localisation non-déterministes sur la perte de protection de la vie privée d'un ensemble d'utilisateurs<br>The wide diffusion of smart portable devices allows the collection of a big amount of data concerning the activities of users from mobile apps. We focus our attention on location data, i.e. mobility traces, of a set of users in a crowd. Data collected from these mobile systems are studied following two axies: - Mobility models are used to simulate the behavior of users to develop opportunistic forwarding algorithms. We compare real and synthetic mobility traces to show the distance between the reality and the models. - Information on mobility may endanger the privacy of users. We analyze the impact of such information on privacy of users. The main contributions are: - We analyze the spatial and social properties of human motion from real traces collected by a highly accurate experimental localization system. - We compare the real traces with synthetic mobility traces generated from seven popular mobility models - We provide an inference algorithm based on co-location of users and we show its efficiency on different datasets. - We quantify the effect of probabilistic co-location information by means of a novel co-location attack
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Brahem, Mariem. "Optimisation de requêtes spatiales et serveur de données distribué - Application à la gestion de masses de données en astronomie." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV009/document.
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Les masses de données scientifiques générées par les moyens d'observation modernes, dont l’observation spatiale, soulèvent des problèmes de performances récurrents, et ce malgré les avancées des systèmes distribués de gestion de données. Ceci est souvent lié à la complexité des systèmes et des paramètres qui impactent les performances et la difficulté d’adapter les méthodes d’accès au flot de données et de traitement.Cette thèse propose de nouvelles techniques d'optimisations logiques et physiques pour optimiser les plans d'exécution des requêtes astronomiques en utilisant des règles d'optimisation. Ces méthodes sont intégrées dans ASTROIDE, un système distribué pour le traitement de données astronomiques à grande échelle.ASTROIDE allie la scalabilité et l’efficacité en combinant les avantages du traitement distribué en utilisant Spark avec la pertinence d’un optimiseur de requêtes astronomiques.Il permet l'accès aux données à l'aide du langage de requêtes ADQL, couramment utilisé.Il implémente des algorithmes de requêtes astronomiques (cone search, kNN search, cross-match, et kNN join) en exploitant l'organisation physique des données proposée.En effet, ASTROIDE propose une méthode de partitionnement des données permettant un traitement efficace de ces requêtes grâce à l'équilibrage de la répartition des données et à l'élimination des partitions non pertinentes. Ce partitionnement utilise une technique d’indexation adaptée aux données astronomiques, afin de réduire le temps de traitement des requêtes<br>The big scientific data generated by modern observation telescopes, raises recurring problems of performances, in spite of the advances in distributed data management systems. The main reasons are the complexity of the systems and the difficulty to adapt the access methods to the data. This thesis proposes new physical and logical optimizations to optimize execution plans of astronomical queries using transformation rules. These methods are integrated in ASTROIDE, a distributed system for large-scale astronomical data processing.ASTROIDE achieves scalability and efficiency by combining the benefits of distributed processing using Spark with the relevance of an astronomical query optimizer.It supports the data access using the query language ADQL that is commonly used.It implements astronomical query algorithms (cone search, kNN search, cross-match, and kNN join) tailored to the proposed physical data organization.Indeed, ASTROIDE offers a data partitioning technique that allows efficient processing of these queries by ensuring load balancing and eliminating irrelevant partitions. This partitioning uses an indexing technique adapted to astronomical data, in order to reduce query processing time
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Petit, Mathieu. "Approche spatiale pour la caractérisation du contexte d'exécution d'un système d'information ubiquitaire." Phd thesis, Paris, ENSAM, 2010. http://pastel.archives-ouvertes.fr/pastel-00511919.
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Les nouvelles technologies en matière d'accès à l'information, de communication sans-fil et de localisation d'informations ouvrent la voie à des innovations majeures dans l'utilisation des systèmes informatiques. Ces avancées permettent d'imaginer de nouveaux usages informatiques dont la mise en œuvre motive le développement de méthodes de conception appropriées. Plus particulièrement, l'informatique mobile combine désormais des enjeux conceptuels tels que l'accès à des services par un utilisateur en mobilité, la généralisation d'outils de localisation, la compréhension de systèmes complexes par un public non-expert ou l'importante variabilité des situations d'exécution. Cette thèse propose un cadre de conception qui adresse certains des enjeux pour la mobilité des systèmes d'information. Dans cette perspective, les attentes des utilisateurs et les contraintes technologiques inhérentes à la mobilité des constituants du système définissent un espace contextuel dont les dimensions sont prises en compte dès les premières étapes de la conception. Le modèle proposé établit comme point d'entrée une description de l'espace géographique du système pour différencier un ensemble de contextes d'exécution. L'énoncé de ces contextes permet de corréler les attentes des utilisateurs avec les capacités techniques de la plate-forme et d'offrir le niveau fonctionnel le plus acceptable dans une situation donnée. Dans un second temps, les différentes fonctionnalités et les données mises en œuvre dans chaque contexte d'exécution peuvent être ordonnées ou filtrées afin d'optimiser la présentation des informations aux utilisateurs. Ces recommandations sont produites par l'analyse conjointe des préférences d'utilisateurs selon leurs interactions et leurs comportements spatiaux. Deux cadres expérimentaux viennent illustrer les propositions du modèle. La conception d'un système mobile de suivi de compétition nautique prend en compte différents contextes d'exécution et adapte un niveau de service à des situations dégradées. Un système de documentation et de visite de campus illustre les algorithmes de recommandation et affine la présentation d'informations localement à chaque contexte d'exécution.
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Novaes, Tiago Fernandes de Athayde. "Processamento distribu?do da consulta espa?o textual top-k." Universidade Estadual de Feira de Santana, 2017. http://localhost:8080/tede/handle/tede/530.
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Previous issue date: 2017-07-17<br>With the popularization of databases containing objects with spatial and textual information (spatio-textual object), the interest in new queries and techniques for retrieving these objects have increased. In this scenario, the main query is the the top-k spatio-textual query. This query retrieves the k best spatio-textual objects considering the distance of the object to the query location and the textual similarity between the query keywords and the textual information of the objects. However, most the studies related to top-k spatio-textual query are performed in centralized environments, not addressing real world problems such as scalability. In this paper, we study different strategies for partitioning the data and processing the top-k spatio-textual query in a distributed environment. We evaluate each strategy in a real distributed environment, employing real datasets.<br>Com a populariza??o de bases de dados contendo objetos que possuem informa??o espacial e textual (objeto espa?o-textual), aumentou o interesse por novas consultas e t?cnicas capazes de recuperar esses objetos de forma eficiente. Uma das principais consultas para objetos espa?o-textuais ? a consulta espa?o-textual top-k. Essa consulta visa recuperar os k melhores objetos considerando a dist?ncia do objeto at? um local informado na consulta e a similaridade textual entre palavras-chave de busca e a informa??o textual dos objetos. No entanto, a maioria dos estudos para consultas espa?o-textual top-k assumem ambientes centralizados, n?o abordando problemas frequentes em aplica??es do mundo real como escalabilidade. Nesta disserta??o s?o estudadas diferentes formas de particionar os dados e o impacto destes particionamentos no processamento da consulta espa?o-textual top-k em um ambiente distribu?do. Todas as estrat?gias propostas s?o avaliadas em um ambiente distribu?do real, utilizando dados reais.
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Vu, Ngoc Minh Trang. "Approche hamiltonienne à ports pour la modélisation, la réduction et la commande des dynamiques des plasmas dans les tokamaks." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT067/document.
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L'objectif principal de la thèse est d'établir un modèle sous forme hamiltonienne à ports pour la dynamique du plasma dans les réacteurs de fusion de type tokamak, puis de démontrer le potentiel de cette approche pour aborder les problèmes d'intégration numérique et de commande non linéaire. Les bilans thermo-magnéto-hydrodynamiques, écrits sous forme hamiltonienne à ports à l'aide de structures Stokes-Dirac, conduisent à un modèle 3D “ multi-physique ” du plasma. Ensuite, un modèle 1D équivalent au modèle de diffusion résistive est obtenu en supposant les mêmes hypothèses d'équilibre quasi-statique et de symétries. Un schéma symplectique de réduction spatiale de ce modèle 1D qui préserve la structure du modèle et ses invariants est établi. Il ouvre la voie à des travaux ultérieurs de commande non linéaire fondés sur la structure géométrique d'interconnexion et les bilans du modèle. La commande IDA-PBC (Interconnection and Damping Assignment - Passivity Based Control) basée sur la passivité du modèle est d'abord synthétisée pour ce système en dimension finie. Finalement, une commande IDA-PBC associée avec la commande à la frontière est proposée pour le système en dimension infinie. Les controlleurs sont testés et validés avec les simulateurs des tokamak (METIS pour le Tore Supra de CEA/ Cadarache, et RAPTOR pour le TCV de l'EPFL Lausanne, Suisse)<br>The modelling and analysis of the plasma dynamics in tokamaks using the port-Hamiltonian approach is the main project purpose. Thermo-mMagnetohydrodynamics balances have been written in port-Hamiltonian form using Stokes-Dirac interconnection structures and 3D differential forms. A simplified 1D model for control has been derived using quasi-static and symmetry assumptions. It has been proved to be equivalent to a classical 1D control model: the resistive diffusion model for the poloidal magnetic flux. Then a geometric spatial integration scheme has been developped. It preserves both the symplecticity of the Dirac interconnection structure and physically conserved extensive quantities. This will allow coming works on energy-based approaches for the non linear control of the plasma dynamics.An Interconnection and Damping Assignment - Passivity Based Control (IDA-PBC) , the most general Port-Hamiltonian control, is chosen first to deal with the studied Tokamak system. It is based on a model made of the two coupled PDEs of resistive diffusion for the magnetic poloidal flux and of radial thermal diffusion. The used TMHD couplings are the Lorentz forces (with non-uniform resistivity) and the bootstrap current. The loop voltage at the plasma boundary, the total external current and the plasma heating power are considered as controller outputs. Due to the actuator constraints which imply to have a physically feasible current profile deposits, a feedforward control is used to ensure the compatibility with the actuator physical capability. Then, the IDA-PBC controllers, both finite-dimensional and infinite-dimensional, are designed to improve the system stabilization and convergence speed. The proposed works are validated against the simulation data obtained from the Tore-Supra WEST (CEA/Cadarache, France) test case and from RAPTOR code for the TCV real-time control system (CRPP/ EPFL, Lausanne, Switzerland)
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Wang, Peng. "Active vibration control in a specific zone of smart structures." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEC007/document.
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Cette recherche vise à résoudre un problème particulier du contrôle de vibration des structures intelligentes. Notre objectif est de réduire les vibrations dans une zone spécifique de la structure intelligente avec une perturbation qui couvre une large gamme de fréquences. De plus, dans cette zone spécifique, ni l'actionnement ni la détection ne sont possibles.Ici, nous faisons face à plusieurs défis principaux. Premièrement, nous devons contrôler les vibrations d’une zone spécifique de la structure, alors que nous n’avons accès aux mesures que dans d’autres zones. Deuxièmement, la large bande passante de la perturbation implique que nombreux modes doivent être contrôlés au même temps, ce qui nécessite l'utilisation de plusieurs actionneurs et capteurs. Cela conduit à un contrôleur MIMO difficile à obtenir avec les méthodes classiques de conception de contrôleur. Troisièmement, il faut éviter le problème de propagation, qui consiste à garantir la stabilité en boucle fermée lorsque le contrôleur basé sur un modèle est appliqué à la configuration réelle. Pour relever ces défis, nous étudions deux stratégies de contrôle: le contrôle centralisé et le contrôle distribué.Pour le contrôle centralisé, nous proposons une méthodologie qui nous permet d’obtenir un contrôleur MIMO simple permettant de relever ces défis. Tout d'abord, plusieurs techniques de modélisation et d’identification sont appliquées pour obtenir un modèle précis d'ordre faible de la structure intelligente. Ensuite, une méthode de synthèse basée sur le contrôle H_∞ avec un critère H_∞ particulièrement proposé est appliquée. Ce critère H_∞ intègre plusieurs objectifs de contrôle, y compris les défis principaux. En particulier, le problème de débordement se transforme en un problème de stabilité robuste et sera garanti en utilisant ce critère. Le contrôleur H_∞ obtenu est une solution standard du problème H_∞. Le contrôleur final est obtenu en simplifiant ce contrôleur H_∞ sans perdre la stabilité en boucle fermée ni dégrader les performances. Cette méthodologie est validée sur une structure de poutre avec des transducteurs piézoélectriques et la zone centrale est celle où les vibrations devraient être réduites. L'efficacité du contrôleur obtenu est validée par des simulations et des expériences.Pour le contrôle distribué, on considère la même structure de poutre et les mêmes objectifs de contrôle. Il existe des méthodes visant à concevoir des contrôleurs distribués pour les systèmes spatialement interconnectés. Cette recherche propose une méthode basée sur la FEM, associée à plusieurs techniques de réduction de modèle, permettant de discrétiser spatialement la structure de poutre et d'en déduire les modèles d’espace d'état des sous-systèmes interconnectés. La conception des contrôleurs distribués ne sera pas abordée dans cette recherche<br>This research aims at solving a particular vibration control problem of smart structures. We aim at reducing the vibration in a specific zone of the smart structure under the disturbance that covers a wide frequency band. Moreover, at this specific zone, neither actuation nor sensing is possible.Here we face several main challenges. First, we need to control the vibration of a specific zone of the structure while we only have access to measurements at other zones. Second, the wide bandwidth of the disturbance implies that numerous modes should be controlled at the same time which requires the use of multiple actuators and sensors. This leads to a MIMO controller which is difficult to obtain using classical controller design methods. Third, the so-called spillover problem must be avoided which is to guarantee the closed-loop stability when the model-based controller is applied on the actual setup. To tackle these challenges, we investigate two control strategies: the centralized control and the distributed control.For centralized control, we propose a methodology that allows us to obtain a simple MIMO controller that accomplishes these challenges. First, several modeling and identification techniques are applied to obtain an accurate low-order model of the smart structure. Then, an H_∞ control based synthesis method with a particularly proposed H_∞ criterion is applied. This H_∞ criterion integrates multiple control objectives, including the main challenges. In particular, the spillover problem is transformed into a robust stability problem and will be guaranteed using this criterion. The obtained H_∞ controller is a standard solution of the H_∞ problem. The final controller is obtained by further simplifying this H_∞ controller without losing the closed-loop stability and degrading the performance. This methodology is validated on a beam structure with piezoelectric transducers and the central zone is where the vibration should be reduced. The effectiveness of the obtained controller is validated by simulations and experiments.For distributed control, we consider the same beam structure and the same control objectives. There exist methods aiming at designing distributed controllers of spatially interconnected system. This research proposes a FEM based method, combined with several model reduction techniques, that allows to spatially discretize the beam structure and deduce the state-space models of interconnected subsystems. The design of distributed controllers will not be tackled in this research
Libros sobre el tema "Système spatial distribué"
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Shatkin, Gavin. Cities for Profit. Cornell University Press, 2018. http://dx.doi.org/10.7591/cornell/9781501709906.001.0001.
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In the past three decades, urban real estate megaprojects—massive, master planned, for profit urban developments—have captured the imagination of politicians and policy-makers across Asia. This book argues that state actors have been major drivers of these transformative projects, and have realized them through increasingly aggressive efforts to reclaim or acquire land, and to transfer land rights to corporate developers. State actors have specifically sought to monetize land as a strategy of state empowerment, a means to generate budget revenue, distribute patronage, and drive economic growth. This newly assertive state role in land markets constitutes the real estate turn in urban politics in the subtitle of the book. This real estate turn has significant implications for social, political, and ecological change in these societies. The book explores the varied spatial impacts of this real estate turn in three cities—Jakarta, Kolkata, and Chongqing—that differ in their systems of property rights and urban governance.
Capítulos de libros sobre el tema "Système spatial distribué"
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MOTTE-BAUMVOL, Benjamin. "Une mobilité inégalement distribuée, éclairage sur le Brésil." In Systèmes de mobilité urbaine dans le monde. ISTE Group, 2024. http://dx.doi.org/10.51926/iste.9154.ch2.
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Dans une société valorisant une forte mobilité, ce chapitre analyse le lien entre la faible mobilité, caractérisée par des distances courtes et un nombre réduit de déplacements, et les formes d'exclusion qui en découlent. Les effets de contexte sociaux et spatiaux sont étudiés en Europe, en Amérique du Nord et en Australie, puis confrontés au cas du Brésil, marqué par de fortes inégalités et une faible mobilité.
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Tsou, Ming-Hsiang, and Ick Hoi Kim. "Increasing Spatial Awareness by Integrating Internet Geographic Information Services (GIServices) with Real Time Wireless Mobile GIS Applications." In Wireless Technologies. IGI Global, 2012. http://dx.doi.org/10.4018/978-1-61350-101-6.ch308.
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Spatial awareness is one of the fundamental decision making capabilities for human beings. Two key information technologies, Internet Geographic Information Services (GIServices) and wireless mobile Geographic Information Systems (GIS) can enhance the spatial awareness of decision makers and facilitate more efficient and comprehensive decision making processes. Internet GIServices provide a collaborative communication environment for sharing data, information and knowledge among multiple decision makers and stakeholders. Wireless mobile GIS combines both geospatial information and Global Positional Systems (GPS) coordinates from remotely located field-based personnel to spatial decision support systems (SDSS). By adopting broadband wireless telecommunication technology for connecting Internet GIServices and mobile GIS devices, decision makers can gather near real time information from field personnel and equally quickly distribute updated information back to the field. Communicated via wireless devices and web applications, interactive and dynamic geographic information services will enhance spatial awareness of decision makers, field personnel (such as fire fighters and police officers), and the general public.
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Saltzman, W. Mark. "Controlled Drug Delivery Systems." In Drug Delivery. Oxford University Press, 2001. http://dx.doi.org/10.1093/oso/9780195085891.003.0015.
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In most forms of drug delivery, spatial localization and duration of drug concentration are constrained by organ physiology and metabolism. For example, drugs administered orally will distribute to tissues based on the principles of diffusion, permeation, and flow presented in Part II of this book. If the duration of therapy provided by a single administration is insufficient, the drug must be readministered. Localization of drug can be controlled by injection, but only within limited spatial constraints, and effectiveness after an injection is usually short-lived. Controlled-delivery systems offer an alternative approach to regulating both the duration and spatial localization of therapeutic agents. In controlled delivery, the active agent is combined with other (usually synthetic) components to produce a delivery system. Unlike drug modification, which results in new agents that are single molecules, or assemblies of a limited number of molecules, drug delivery systems are usually macroscopic. Like drug modification, controlled-delivery systems frequently involve combinations of active agents with inert polymeric materials. In this text, controlled-delivery systems are distinguished from “sustained-release” drug formulations. Sustained release is often achieved by mixing an active agent with excipients or binders that alter the agent’s rate of dissolution in the intestinal tract or adsorption from a local injection site. The distinction between sustained release (often achieved by drug formulation) and controlled delivery or controlled release is somewhat arbitrary. In our definition, controlled delivery systems must (1) include a component that can be engineered to regulate an essential characteristic (e.g., duration of release, rate of release, or targeting) and (2) have a duration of action longer than a day. Many polymeric materials are available for the development of drug delivery systems (see Appendix A). Non-degradable, hydrophobic polymers have been used the most extensively. Reservoir drug delivery devices, in which a liquid reservoir of drug is enclosed in a silicone elastomer tube, were first demonstrated to provide controlled release of small molecules several decades ago [1]. This discovery eventually led to clinically useful devices, including the Norplant® (Wyeth-Ayerst Laboratories) contraceptive delivery system, which provides reliable delivery of levonorgestrel for 5 years following subcutaneous implantation.
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Tang, Tengteng, Dylan Joralmon, and Xiangjia Li. "3D Printing of Biomimetic Functional Nanocomposites via Vat Photopolymerization." In Advances in 3D Printing [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.110413.
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The complex structures and functional material systems of natural organisms effectively cope with crisis-ridden living environments such as high temperature, drought, toxicity, and predator. Behind these excellent survival strategies evolved over hundreds of millions of years is a series of effective mechanical, optical, hydraulic, and electromagnetic properties. Bionic design and manufacturing have always attracted extensive attention, but the progress has been limited by the inability of traditional manufacturing techniques to reproduce microscopically complex structures and the lack of functional materials. Therefore, there is an urgent need for a fabrication technique with a high degree of fabrication freedom and using composites derived from biological materials. Vat photopolymerization, an emerging additive manufacturing (aka 3D printing) technology, exhibits high manufacturing flexibility in the integrated manufacturing of multi-material systems and multi-scale structures. Here, biomaterial-inspired heterogeneous material systems based on polymer matrices and nanofillers, and the introduction of magnetic and electric fields on the basis of conventional 3D printing systems to spatially and programmably distribute nanofillers are summarized, which provides a new strategy for fabricating anisotropic structures. The application of this versatile 3D printing system in fabricating mechanically reinforced structures, polymer/metal structures, self-actuating, and superhydrophobic structures is also elaborated.
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Tinker, Peter B., and Peter Nye. "Root System Architecture, Density, and Measurement." In Solute Movement in the Rhizosphere. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195124927.003.0013.
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The behaviour and properties of roots are central subjects in this book. A number of biochemical and physiological properties have already been described, for individual roots, in chapters 2, 5, 7, and 8. However, the macroscopic properties of root systems are of very great importance, to an extent that may not be immediately apparent from the point of view of the laboratory. These properties include the root/shoot ratio, the root system dimensions, its topological properties, and its distribution in the soil profile. The property of greatest practical importance is the way in which root length density (length per unit volume of soil) is distributed in the soil, because this defines the spatial limits to the efficiency of a root system in absorbing water and nutrients. For these reasons, we have collected material relating to root system properties here in a separate chapter. This may be particularly helpful to readers because there are very few single-part recent publications that deal with this subject. It appears logical to start with a discussion of how much root a plant possesses, its dependence upon the allocation of fixed carbon, and the efficiency with which this is used to form root tissue. Carbon is the basic currency of plants, and the way in which they distribute and use it is part of their growth strategy. The allocation of carbon in plants has been extensively researched within the above-ground part, but not the below-ground part, because of the difficult access to the root system, and the difficulty of separating the root, root surface and soil processes. It is important to understand the way in which carbon is allocated to both the root system as a whole, and then to the different parts of the root system, its symbiotic partners, exudates and other root products. Some broader issues are also relevant. Some of the carbon allocated to the root could be wasted, from the point of view of the plant or the farmer (Gregory 1994a).
Actas de conferencias sobre el tema "Système spatial distribué"
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Michalis, Krista, Donald Bliss, and Linda Franzoni. "Prediction and Modification of Broadband Interior Noise in Enclosures Using Energy-Intensity BEM and Absorption Scaling." In ASME 2008 Noise Control and Acoustics Division Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/ncad2008-73057.
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Enclosures with diffuse reflection boundaries are modeled with an energy-intensity boundary element method using uncorrelated broadband directional sources. Input power is assumed to enter the enclosure through the walls, which are also absorptive. An absorption-based perturbation analysis is used to analyze the spatial variation of the acoustic field, which is shown to obey certain scaling laws. A series expansion in terms of spatial-average absorption gives separate boundary integral problems at each order. For the primary spatial variation, the effects of the relative distributions of absorption and input power are linear and uncoupled. These distributions can be expressed in terms of constituent spatial modes corresponding to the ways absorption and input power can be distributed. These amplitudes can be adjusted to tailor the spatial variation subject to system constraints. Examples include how to distribute absorption to minimize sound levels in one location, or how to achieve a uniform interior field.
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Alawami, Rahmah L., Adan H. Tello Gomez, Ferney G. Moreno Sierra, and Imad Brohi. "Channel Characterization in Sandstone Formation Using Pressure Transient Analysis - A Practical Overview to Define Geological Attributes." In International Petroleum Technology Conference. IPTC, 2024. http://dx.doi.org/10.2523/iptc-24222-ms.
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Abstract Understanding reservoir systems is of significant importance in optimal exploitation, development plans and management strategies. Sandstone reservoirs consisting of stacked channel deposits are known for their heterogeneity and varying depositional facies adding to their complexity. This paper will focus on the characterization of sandstone reservoirs in channel environments using pressure transient analysis coupled with seismic attributes and stratigraphic features. Proper channel mapping and precise predications of the spatial distribution of sand bodies is a challenging process. Pressure transient analysis can identify the existence of channel features, reservoir properties, extent of formation properties, and boundary conditions. However, linear flow identified in well tests does not predict the direction of these channels. The proposal integrates both static and dynamic reservoir data along with regional geological interpretation which plays a vital role in the proper characterization and modeling of these channel systems. The findings of this study enrich a deeper reservoir understanding of the structural features’ extent, continuity and connection. Different pressure regimes were observed in both vertical and lateral directions showing the complex heterogeneity in between layers and irregular channel distribution patterns. This response is similarly exhibited in the reservoir flow capacity which resulted in abrupt shifts in reservoir characteristics as evident in the acquired pressure transient data. It is proposed to revise seismic attributes and the use of stratigraphic core data to validate the conceptual connections between this complex channel system. In addition, findings are used to re-distribute formation properties in order to improve future reservoir models. The combined use of dynamic and static data improves the regional interpretation of challenging sandstone systems. Adequate understanding of the spatial distribution of the sand facies and reservoir properties ensures effective well placement and development strategies.
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Zhang, Dan, and Lihui Wang. "On Performance Enhancement of Parallel Kinematic Machine." In ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-85034.
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This paper proposes a spatial three degrees of freedom parallel kinematic machine enhanced by a passive leg and a web-based remote control system. First, the geometric model of the three degrees of freedom parallel kinematic machine is addressed; in the mechanism, a fourth kinematic link — a passive link connecting the base center to the moving platform center — is introduced. This last link is used to constrain the motion of the tool (located in the moving platform) to only three degrees of freedom, as well as to enhance the global stiffness of the structure and distribute the torque from machining. With the kinematic model, a web-based remote control approach is then applied. The concept of the web-based remote manipulation approach is introduced and the principles behind the method are explored in detail. Finally, an example of remote manipulation is demonstrated to the proposed 3-DOF structure using web-based remote control concept before conclusions.
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Huang, Xindi, and Nadezhda Yudina. "MODELS DESCRIBING THE ENVIRONMENTAL EFFECTS OF POLLUTANT EMISSIONS BY ROAD TRANSPORT." In Modern aspects of modeling systems and processes. FSBE Institution of Higher Education Voronezh State University of Forestry and Technologies named after G.F. Morozov, 2021. http://dx.doi.org/10.34220/mamsp_167-173.
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Air pollution is the most serious environmental problem facing most industrial cities in the world and in China. The World Health Organization measured the concentration of sulfur dioxide, nitrogen dioxide and total suspended particulate matter in 272 cities in 53 countries around the world, listing the ten most severely polluted cities in the world. The spatial and temporal distribu-tion of air pollutants depends on various factors such as the meteorological field, the source of emissions, the complex bottom surface of the site, the interplay of physical and chemical processes, and has strong non-linear characteristics [5]. Air quality forecasting is commonly used in the field of statistical forecasting methods, according to long-term monitoring data, the creation of a statisti-cal forecasting model, the model is simple, easy to operate business, but no solid physical founda-tion, and another numerical forecasting model based on atmospheric physics and material transfer model although the physical foundation is solid, comprehensive forecast results, but the forecast results are not reliable. Already in the 1950s, the system of meteorology of air pollution was gradu-ally formed, the box model, the Gaussian model, the Lagrange model, the Euler model, the dense gas model and other five types of models appeared. The first Gaussian model allows one to obtain a diffusion model of a local small-scale space and make predictions, then, based on the Gaussian model of the study, a modified model is obtained for other reliefs and weather conditions. There-fore, the modeling accuracy and applicable conditions are difficult to cope with the needs of large-scale complex meteorological conditions of air quality models.
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Lin, Freddie, Eva M. Strzelecki, and William Liu. "Compact Crossbar Switch For Optical Interconnects." In Optical Computing. Optica Publishing Group, 1991. http://dx.doi.org/10.1364/optcomp.1991.me18.
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Optical crossbar switches are used in a variety of applications: in optical computing, optical communications, and optical interconnects in computers. High speed optical crossbars have been demonstrated for the use in communications such as waveguide electro-optic switches in LiNbO3 [1], semiconductor quantum well modulators [2]. For applications in optical computing it is important to have very large switching arrays to utilize the massively parallel capability of optical signal processing. This has been achieved using spatial light modulators (SLM) which are available in large arrays, such as liquid crystal TVs and ferroelectric liquid crystal devices [3], and high speed, such as PLZT [4] or quantum well modulators [2]. Many systems based on SLMs utilize the vector-matrix multiplication configuration to realize crossbar networks, linear algebra operations, iterative vector-matrix multiplication, and optical neural networks. Crossbars based on this configuration, though suffer from fan-out losses, are very versitile, offer broadcasting capability needed in optical interconnects, and can easily form large array sizes. Most SLM based systems, which use bulk optics, lenslet arrays, and fiber optic couplers [5], are bulky and require tedious alignment. In this paper we describe a compact vector-matrix mulitplier in which waveguides with arrays of grating couplers are used to distribute and collect light signals.
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Lee, Sing H. "Recent advances in computer-generated hologram applications." In OSA Annual Meeting. Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.tue2.
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Computer-generated holograms (CGHs) have traditionally been employed mostly for optical testing of aspherics. Their applications have recently been expanding to many new areas where the equivalent optical holograms are difficult to make. For example, in wavefront/beam conversion, CGHs can convert Gaussian beams to uniform beams or uniform beams to nondiffracting beams. For pattern recognition, CGHs are designed to make geometric transformations or to perform synthetic spatial filtering functions. For optical interconnects, CGHs are synthesized to distribute clock signals to various parts of a VLSI wafer, to power up an array of multiple-quantum-well optical bistable devices, or to facilitate intercommunication among multiprocessors and shared memories for optical digital computing. Furthermore, CGHs can be fabricated to combine the functions of multiple optical elements to reduce the size and weight of optical pickup heads for improved access speed in optical storage systems. CGHs can be fabricated on the flat surfaces of refractive optics to reduce aberrations and broaden their spectral responses, consequently reducing the number of refractive elements in achromatic optical systems. They can also be produced on the posterior surface of an intraocular lens to provide bifocal vision. Many of these recent advances have been facilitated by improved fabrication tools such as the electron beam writer and the reactive ion beam miller, and by improved CGH design procedures.
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Caglayan, Alper, Laura Cassani, Tim Clark, et al. "Semantic Enrichment and Reasoning for Mobile Data Collection of Socio-Cultural Data." In Applied Human Factors and Ergonomics Conference. AHFE International, 2019. http://dx.doi.org/10.54941/ahfe100190.
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Leveraging the widespread adoption of mobile devices, we have developed a semantic knowledge management, mobile data collection, and situational awareness capability that enables the automatic semantic annotation and fusion of mobile collected data. The major components of our semantic knowledge management system consist of form management; data collection, aggregation, and storage; and spatially aware semantic analysis. Our research transforms the analysis of large amounts of data collected from mobile devices from an unstructured process to a structured approach leveraging semantic technology and automated tagging. Semantic technology is used to author, publish, and distribute forms to mobile devices. When submitted from the mobile device, the structured form is mapped to a semantic form to automatically generate semantic annotations from the mobile collected data for semantic enrichment. The semantic representation of the data enables users to organize, analyze, visualize, and create custom information products from the aggregated data.
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Owechko, Yuri. "Programmable optical neural networks." In OSA Annual Meeting. Optica Publishing Group, 1992. http://dx.doi.org/10.1364/oam.1992.md2.
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We have developed an optical neurocomputer for implementing neural networks based on real-time holography in photorefractive materials. Optical techniques show great promise for implementing neural network models because of the parallelism, connectivity, and high storage capacity of optics. It is generally agreed that optics will most likely be used for implementing very large neural networks that are impractical to simulate or implement electronically. In our system weighted connections between neurons are recorded in barium titanate as photorefractive holograms. We have virtually eliminated distortion and crosstalk between holograms by using beam fanning to distribute each connection weight among many angularly and spatially distributed photorefractive gratings. We have successfully demonstrated several optical neural networks including the Perceptron Bidirectional Associative Memory (BAM) and back propagation with a single hidden layer. All of these networks were implemented on the same hardware using a single crystal and SLM by simply changing the software. We have demonstrated networks with up to 7,000 neurons, 800,000 weights, and PC bus-limited learning rates of up to 106 connection updates per second.
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Hu, Xin, and Po Hsun Wang. "Virtual Reality in Museum: Exploring the User Experience of Exhibition Narrative." In Intelligent Human Systems Integration (IHSI 2024) Integrating People and Intelligent Systems. AHFE International, 2024. http://dx.doi.org/10.54941/ahfe1004530.
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The exhibition narrative of traditional museums is “artifact- centered”, while the modern virtual museum is “people- centered”. The paper first analyzes the current typical VR narrative cases, summarizes the relevant elements and basic characteristics of virtual space narrative, and finds that there are many similarities with the narrative methods in traditional movies, but the relationship between storytelling in the virtual world and the audience The interactive relationship is closer. How to attract the audience's attention to the exhibits to enhance the VR exhibition experience is particularly important in the narrative design of virtual exhibitions. As we all know, the audience's line of sight in the three-dimensional space is not restricted because the audience has the freedom to distribute the line of sight.This research first confirmed the categories of points of interest that affect attention through expert interviews, including the physical layer, behavioral layer, and application layer of the VR system. Through 57 questionnaires, the behavioral characteristics, and psychological needs of audience for VR exhibition narratives were collected, Sample analyses were also conducted for this. Taking the design of China's virtual cultural relics exhibition as an example, the author mainly uses clues of points of interest in the design space to guide the audience to focus or distract their attention. During the narrative process of the exhibits, it was discovered that the connections between the points of interest are not isolated but have Continuous. Based on the narrative theory of "story and discourse", 7 points of interest were selected to explore the feasibility of point-of-interest narratives from three aspects: type combination, spatial arrangement, and interaction method. By comparing the attention-guiding effects of two different sets of interest points in linear narratives and non-linear narratives in two testing groups, a contextual correspondence between the audience's attention selection and points of interest was established. Through evaluation tests, we found that narrative methods that use points of interest to guide the audience's attention are feasible. Non-linear narratives have more opportunities than single-line narratives, such as increasing the application of interactive methods that guide the audience's attention. The conclusions have certain implications for the narrative design of VR exhibition.
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Yang, Chen, Manish Boorugu, Andrew Dopp, and Howon Lee. "Lightweight Microlattice With Tunable Mechanical Properties Using 3D Printed Shape Memory Polymer." In ASME 2018 13th International Manufacturing Science and Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/msec2018-6562.
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Metamaterials are architected artificial materials engineered to exhibit properties not typically found in natural materials. Increasing attention has recently been given to mechanical metamaterials with unprecedented mechanical properties including high stiffness, strength, or/and resilience even at extremely low density. These unusual mechanical performances emerge from the three-dimensional (3D) spatial arrangement of the micro-structural elements designed to effectively distribute mechanical loads. Recent advances in additive manufacturing in micro-/nano-scale have catalyzed the growing interest in this field. This work presents a new lightweight microlattice with tunable and recoverable mechanical properties using a three-dimensionally architected shape memory polymer (SMP). SMP microlattices were fabricated utilizing our micro additive manufacturing technique called projection micro-stereolithography (PμSL), which uses a digital micro-mirror device (DMD™) as a dynamically reconfigurable photomask. We use a photo-crosslinkable and temperature-responsive SMP which can retain its large deformation until heated for spontaneous shape recovery. In addition, it exhibits remarkable elastic modulus changes during this transition. We demonstrate that mechanical responses of the micro 3D printed SMP microlattice can be reversibly tuned by temperature control. Mechanical testing result showed that stiffness of a SMP microlattice changed by two orders of magnitude by a moderate temperature shift by 60°C. Furthermore, the shape memory effect of the SMP allows for full restitution of the original shape of the microlattice upon heating even after substantial mechanical deformation. Mechanical metamaterials with lightweight, reversibly tunable properties, and shape recoverability can potentially lead to new smart structural systems that can effectively react and adapt to varying environments or unpredicted loads.
Informes sobre el tema "Système spatial distribué"
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Pelletier, Austin, Amanda Hohner, Idil Deniz Akin, et al. Bench-scale Electrochemical Treatment of Co-contaminated Clayey Soil. Illinois Center for Transportation, 2021. http://dx.doi.org/10.36501/0197-9191/21-018.
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Industrial soil contamination is frequently unearthed by transportation agencies during construction within the right-of-way. As a result, transportation agencies may experience construction delays. Soils co-contaminated with high-molecular-weight polycyclic aromatic hydrocarbons (HMW-PAHs) and metals are commonly encountered in Illinois and exhibit recalcitrance towards conventional treatment technologies. This issue is exacerbated in the fine-grained soils common to Illinois, where low-permeability and immense sorption capacity increase treatment complexity, cost, and duration. Contaminated sites are spatially and temporally restrictive and require rapid in situ treatments, whereas conventional soil remediation requires 1 to 3 years on average. Consequently, transportation agencies typically pursue excavation and off-site disposal for expediency. However, this solution is expensive, so a comparatively expeditious and affordable treatment alternative is needed to combat the increasing cost of hazardous waste disposal. The objective of this work was to develop an accelerated in situ treatment approach adaptable for use at any construction site to cost-effectively remove HMW-PAHs and metals from clayey soil. It was hypothesized that an in situ electrochemical treatment which augments electrokinetics with H2O2 could remediate both HMW-PAHs and metals in less than a month. Bench-scale reactors resemblant of field-scale in situ electrokinetic systems were designed and fabricated to assess the electrochemical treatment of clayey soils contaminated with HMW-PAHs and metals. Pyrene, chromium, and manganese were used as model contaminants, spiked into kaolinite as a model clay. Electrokinetics were imposed by a low-intensity electrical field distributed by graphite rods. Electrolytic H2O2 systems were leveraged to distribute electrical current and facilitate contaminant removal. Average contaminant removals of 100%, 42.3%, and 4.5% were achieved for pyrene, manganese, and chromium, respectively. Successful development of this bench-scale treatment approach will serve to guide transportation agencies in field-scale implementation. The results from this work signify that electrochemical systems that leverage eco-friendly oxidant addition can replace excavation and disposal as a means of addressing clayey soils co-contaminated with HMW-PAHs and metals.