1,721,006 research outputs found
Interoperability of communication technologies in vehicular networks in the smart city
No full textUn réseau véhiculaire est un réseau sans fil dynamique. Les véhicules composant ce réseau peuvent être équipés de différentes technologies de communication. Les échanges d'information peuvent donc avoir lieu avec une ou plusieurs de ces technologies. Dans cette seconde possibilité, le choix de la technologie de communication influe sur le débit disponible.Dans cette thèse, nous étudions l'équilibrage des charges afin de maximiser le débit. Nous proposons différentes approches algorithmiques pour optimiser la répartition des charges par le choix des technologies de communication. Le problème est d'abord modélisé avec la théorie des graphes et formalisé. L'analyse en terme de complexité montre l'existence ou l'inexistence de solution à la fois rapide (en temps polynomial par rapport à la taille de l'entrée) et exacte (D'après "Combinatorial optimization : algorithms and complexity", de A.Papadimitriou, H. Christos datant de 1998). De ce fait, les solutions rapides proposées dans cette thèse sont soit associées à des résultats non exactes (ou approchés), soit associées à des contraintes de scénarios simplificatrices.Les approches algorithmiques proposées s'appuient dans un premier temps sur une infrastructure de supervision et sont donc centralisées. Les performances insuffisantes observées avec cette première approche nous ont dans un second temps conduit à proposer un algorithme complètement distribué, qui s'est montré bien plus performant. Les performances ont été améliorées dans une dernière approche par la prise en compte de la stabilité des liens sans fil.Vehicular networks are dynamic wireless networks. The vehicles that make up this network can be equipped with different communication technologies. Information exchanges can therefore take place on one or more of these technologies. In this second possibility, the choice of the communication technology influences the available throughput, especially when the communication technology is shared between several users.In this thesis, we study load balancing to maximize throughput. We propose different algorithmic approaches to optimize load balancing through the choice of communication technologies. For each proposed approach, we study its algorithmic complexity and provide time and performance guarantees. The problem is first modeled with graph theory and formalized. The analysis in terms of complexity shows the existence or non-existence of a solution that is both fast (in polynomial time with respect to the size of the input) and exact (from "Combinatorial optimization: algorithms and complexity", by A.Papadimitriou, H. Christos dating from 1998). Therefore, the fast solutions proposed in this thesis are either associated with non-exact (or approximate) results, or associated with simplifying scenario constraints.The proposed algorithmic approaches are initially based on a supervision infrastructure and are therefore centralized. The insufficient performances observed with this first approach led us to propose a completely distributed algorithm, which proved to be much more efficient. Its performance was improved by taking into account the stability of wireless links
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Optimization of routing in vehicular networks by link break prediction link break prediction
No full textLes réseaux véhiculaires appelés aussi Vehicular Ad hoc NETworks (VANET) sont des réseaux mobiles concernant des véhicules. Les réseaux VANET se distinguent des autres types de réseaux ad hoc par certaines caractéristiques et propriétés particulières. En effet, la topologie change constamment en raison de la vitesse élevée des véhicules ainsi qu'en fonction des voies de circulation. La communication (canal de transmission) devient donc instable du fait de la présence de nombreux obstacles notamment en milieu urbain (bâtiments, véhicules, etc.). L'une des problématiques dans ce type de réseau concerne le routage. En effet, les véhicules ou nœuds, ne peuvent pas communiquer directement entre eux sauf s'ils sont voisins. Dans ce cas, lorsqu'un nœud veut envoyer un message à un autre nœud, il utilise des nœuds relais. Dans cette thèse, la problématique d'optimisation du routage est abordé en utilisant une détection de rupture de lien. Afin de détecter la rupture de lien, un indicateur prédictif appelé Link Breakage Forecasting Indicateur (LBFI) basé sur les erreurs de décodage Orthogonal Frequency Division Multiplexing (OFDM) est développé. Le processus de détection de rupture est fondé sur l'application de la théorie des fonctions de croyance basés sur différents paramètres dont les erreurs de décodage OFDM. L'indicateur est ensuite intégré au protocole de routage AODV en remplaçant le mécanisme de détection de rupture de lien traditionnel de AODV par LBFI. Lorsqu'une rupture de lien est détecté, une recherche de route est enclenchée tout en continuant l'utilisation de la route actuelle permettant ainsi l'optimisation du routage. Ces travaux sont évalués sur un simulateur de réseaux intégrant notamment une émulation de la couche physique IEEE802.11p intégrant la couche OFDM. L'évaluation des performances du protocole ainsi obtenu montre une amélioration du taux de réception de paquet, des délais de bout en bout et une meilleure stabilité des routes notamment par rapport à AODV mais aussi par rapport à un autre protocole de détection de rupture de lien.Vehicular Ad hoc NETworks (VANET) are mobile networks involving vehicles. VANET networks are distinguished fromother types of ad hoc networks by certain specific characteristics and properties. Indeed, the topology is constantly changing due to the high speed of vehicles and according to the traffic lanes. Thus, communication (transmission channel) becomes unstable due to the presence of many obstacles, especially in urban areas (buildings, vehicles, etc.). One of the challenges in this kind of network concerns routing. In fact, vehicles or nodes cannot communicate directly with each other unless they are neighbors. In this case, when a node wants to send a message to another node, it uses relay nodes. In this thesis, the problem of routing optimization is addressed by using link failure detection. In order to detect link failure, a predictive indicator called Link Breakage Forecasting Indicator (LBFI) based on Orthogonal Frequency Division Multiplexing (OFDM) decoding errors is developed. The process of detecting a link failure is based on the application of belief function theory to various parameters including OFDM decoding errors. The indicator is the nintegrated into the AODV routing protocol by replacing AODV's traditional link failure detection mechanism with LBFI. When a link failure is detected, a route search is initiated while continuing to use the current route, thus optimizin grouting. This work is evaluated using a network simulator that integrates an emulation of the IEEE802.11p physical layer with the OFDM layer. The performance assessment of the protocol shows an improvement in the packet reception rate,end-to-end delays and better route stability, particularly compared to AODV but also compared to another link break detection protocol
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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