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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
Réseaux Mobile Ad hoc : modélisation, simulation et applications de diffusion.
No full textOver the last few years, personal communication devices have invaded most developed countries and today, the majority of the population owns a mobile phone and most people use personal digital assistants, mobile computers, etc. This tendency is reinforced and occurs at the same time with a new trend: most of these devices get equipped with one or several wireless networking interfaces. Practically, Wi-Fi or/and Bluetooth-enabled devices become of frequent use. More than allowing the connection to some access point (which can be found in airports, train stations, city-centers, restaurants, etc), these interfaces also permit to interconnect directly with one another in a decentralized way and hence to self-organize into “ad hoc networks”.A mobile ad hoc network is a set of mobile nodes able to communicate with other nodes in their surroundings. These wireless communications happen in a peer-to-peer manner, without relying on any predefined infrastructure. Today, mobile ad hoc networks are mainly used for sensing, gaming and military purposes. But the steadily wider adoption of wireless technologies in daily life let one foresee the next generation of mobile ad hoc network applications: environmental and medical monitoring, groupware, customer-to- customer applications, risk management, entertainment, advertising, etc. In this document we will consider a subclass of mobile ad hoc network called “delay tolerant networks”. In such network, the mobility is hardly predictable and the disruption of connection is a common and normal phenomenon.In order to enable the development and spreading of these applications, a number of issues have to be solved. First, in such networks, end-to-end connectivity cannot be guaranteed. Indeed mobile ad hoc networks may be partitioned and nodes may be spo- radically present in the network. As such, mobile ad hoc networks can be considered as Delay Tolerant Networks (DTN). Second, the topology of the network changes over time because of the mobility of the stations. Then, the way the communication primitives were implemented in the context of wired networks is no longer applicable. It is hence necessary to propose new algorithms to take those primitives into account, like broadcasting that serves as a basic pattern for the design of many mobile ad hoc network applications.The design and implementation of such communication schemes, and more generally of mobile ad hoc network applications, can be achieved using two different ways: either by building a real network, or by resorting to modelling and simulation. Theoretical approaches failed at modeling the inherent complexity of mobile ad hoc networks in a comprehensive manner. Indeed, ad hoc networks are decentralised systems which are ruled by a variety of elements including radio signal, network traffic, mobility, collaborative behavior, etc. If theoretical approaches certainly are useful for represent one or the other elements, they do not suit the modelling of a system as a whole. In the context of this work, where city-scale environment were considered, simulation was hence unavoidable.The development of such simulators took place at the crossroad of some projects in relation to complex system modelling, optimization and middleware design for mobile ad hoc networks, and conducted in several European countries.This diversity led to the design of a custom simulator called Madhoc. Indeed the mobile ad hoc simulators which are already available on the market most often are designed in such a way they allow the simulation of specific applications. They also generally suffer from a complex architecture (often poorly documented) that make them hardly adaptable to other applications. Consequently, none of them apparently turn out to be flexible enough so as it would have met our diverse needs. Madhoc captures the major characteristics of DTNs, by providing an extendable set of mobility models as well as a framework for the definition of new applications.By looking at the State of Art protocols for mobile ad hoc networks and delay tolerant networks, it appeared that the broadcast issue had not yet been solved in a satisfactory manner. Indeed none of the protocols proposed so far proceed nicely in specific conditions of delay tolerant networking. Madhoc was then primarily used for the investigation of the broadcasting issue. In this specific context, networks composed of thousands devices using a variety of wireless technologies were considered. These networks are partitioned and ex- hibit heterogeneous densities. This led to the design of a bandwidth-efficient broadcasting protocol called DFCN.Au cours des dernières années, l'utilisation de téléphones mobiles, d'ordinateurs portables et, dans une moindre mesure, d'assistants personnels a explosé. Le phénomène est tel que dans les pays industrialisés, la quasi-totalité de la population utilise un téléphone mobile. Dans le même temps, la majorité de ces équipements se voit associée à une interface pour réseau mobile, en particulier Wi-Fi et/ou Bluetooth. En plus de permettre la connection à Internet par le biais de points d'accès, ces technologies permettent aux machines mobiles de se connecter de façon décentralisée et par là même de s'auto-organiser en ``réseaux mobiles ad hoc''.Un réseau mobile ad hoc est un ensemble de n\oeuds mobiles capables de communiquer avec les n\oeuds présents à proximité géographique. Ces communications sans-fil opèrent en mode pair-à-pair : elles se passent d'infrastructure de télécommunication. A l'heure à laquelle ces lignes sont écrites, les réseaux mobiles ad hoc sont principalement utilisés dans le cadre de réseaux de capteurs, pour les applications de jeux et les applications militaires. Cependant, l'adoption croissante des technologies de réseau sans-fil par le grand public permet d'entrevoir les applications futures : surveillance environnementale et médicale, travail en équipe, applications entre particuliers, gestion du risque industriel, publicité, etc.Pourtant, afin que ces applications soient réalisables, un certain nombre de problèmes doivent toujours être solutionnés. En premier lieu, dans les réseaux mobile ad hoc, il n'est pas possible de garantir qu'il existe un chemin entre deux n\oeuds donnés. En effet le réseau peut être partitionné et la présence des n\oeuds est sporadique. En second lieu, à cause de la mobilité des n\oeuds, la topologie du réseau change au cours du temps. De ce fait, les implémentations courantes des primitives réseau ne sont plus utilisables. Il est nécessaire de proposer de nouveaux algorithmes permettant l'utilisation de ces primitives dans le cadre contraint des réseaux mobiles ad hoc. Ces primitives incluent la diffusion, qui est une pierre de base de nombreuses applications pour réseaux ad hoc.L'expérimentation de services (ou plus généralement d'applications) pour réseaux mobiles ad hoc peut être effectuée soit sur des réseaux dédiés (appelés testbeds), soit sur des simulateurs logiciels. Dans le cadre des travaux présentés dans cette thèse, pour lesquels un environement de type urbain est considéré, la simulation s'est avérée inévitable.Le développement d'un tel simulateur s'est opéré dans le cadre de plusieurs projets liés aux systèmes complexes, à l'optimisation et à la conception d'intergiciel. Ces projets impliquent des universités de différents pays d'Europe.Cette diversité des besoins a conduit à la conception d'un simulateur dédié, appelé MADHOC. MADHOC considère un certain nombre de caractéristiques des réseaux mobiles ad hoc en proposant un ensemble de modèles de mobilité ainsi qu'une interface de programmation pour la définition de nouvelles applications.MADHOC a été initialement utilisé pour l'expérimentation de protocoles de diffusion dans le cadre de réseaux hétérogènes de grande taille (réseaux impliquant plusieurs milliers de n\oeuds, et plusieurs technologies réseaux). Ces réseaux sont généralement partitionnés et ont des densités non-homogènes. Ceci nous a amené au développement de DFCN: un protocole de diffusion efficace en terme de bande passante utilisée
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
Towards Better Middleware for Distributed Computing
No full textNew middleware for distributed system is frequently released by computer science laboratories. Each new proposal comes with specific models of strategies to solve particular problems related to distributed computations. In our lab, pratical studies on a variety of networks configurations (i.e. in clusters, edge, IoT, etc) led us think about the design of a middleware that would be practicable in the worst conditions: high dynamics/mobility, heterogeneity, low security, reliability, etc. Because less is more, such middleware could then be used in any application setting. This paper describes the inventive collection of intricate models for application architecture, communication, computation, dynamics management, etc which can be found in the Idawi Open Source Java implementation
Idawi
No full textInternational audienceAs years pass, the number and the variety of computing devices and networking technologies is steadily growing. Today, super-computers meet mobile devices in dynamic networks known as the IoT, the fog, the edge, etc. Building applications for such networks is challenging especially asmost middleware solutions for distributed computing are tailored to managed grids and clusters, so they lacks the elasticity needed to deal with the difficult conditions brought by mobility, heterogeneity, untrustability, etc. To solve this, several decentralised middleware were released, each proposing adequate solutions to many problems, but none of them meet right out-of-the-box the requirements of the scientific projects involving distributed computing we conduct in the lab. This paper introduces Idawi, a new Open Source middleware for distributed computing in the IoT/fog/edge. From the beginning, its design has been driven by the real-world needs of scientific experiments, such as automatised deployment, good scalability, ability to handle streams of data, interoperability with other tools, etc. To this purpose, on top of a fully decentralized multi-paradigm architecture, an application model in the style of SOA, and collective communication and computation models, it features effective solutions to the problems aforementioned
A Service-Oriented Middleware Enabling Decentralised Deployment in Mobile Multihop Networks
Get PDFInternational audienceThe number of computing devices, mostly smartphones is tremendous. The potential for distributed computing on them is no less huge. But developing applications for such networks is challenging especially as most middleware solutions for distributed computing are tailored to managed grids and clusters, so they lacks the elasticity needed to deal with the difficult conditions brought by multi-hops, mobility, heterogeneity, untrustability, etc. To solve this, several middleware were released, but none of them feature workable deployment solutions. This paper presents the deployment service of the Idawi middleware, which implements a fully decentralized and automatised deployment strategy into a Open Source middleware tailored to enabling distributed computing in difficult networking conditions like in the IoT/fog/edge
Idawi: a middleware for distributed applications in the IOT, the fog and other multihop dynamic networks
No full textAs technology improves, new kind of devices are given the ability to interconnect to others, thereby shaping today’s networks. Sensors, smartphones, tablets, laptops, desktops, servers, be they organized or not, altogether form the Internet of Things (IoT), the cloud, and the glue between them. All these devices are heterogeneous in terms of hardware (CPUs, memory type and size, network interfaces, etc), software (Unix, Windows, Android, etc) and behavior (mobility, reliability). However they all have in common the ability to perform computations. But in this context of extreme heterogeneity, distributed computing has become even harder, and the tools we use for clusters, grids and clouds cannot be used. A few middleware solutions to distributed computing this is difficult environment have been proposed recently, but these tools address only a limited number of issues, and they can hardly be coupled together to a single usable solution. As a consequence, Researchers most often opt for developing their own solution, or resorting to simulation. At I3S we also did that. Through several Research projects which implied many aspects of cluster computing and IoT, we built a codebase of successful solutions to many problems we faced along the years. Revamped and generalized into the most consistent, efficient and cleanest possible middleware, we now expose it to the Research communities as Idawi: an Open Source Java message/queue/service/object-oriented decentralized overlay network of components designed to meet the conceptual and practical needs of Researchers working on distributed algorithms
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