There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Imagined communities: Reflections on the origin and spread of nationalism

The modern science of networks has brought significant advances to our understanding of complex systems. One of the most relevant features of graphs representing real systems is community structure, or clustering, i. e. the organization of vertices in clusters, with many edges joining vertices of the same cluster and comparatively few edges joining vertices of different clusters. Such clusters, or communities, can be considered as fairly independent compartments of a graph, playing a similar role like, e. g., the tissues or the organs in the human body. Detecting communities is of great importance in sociology, biology and computer science, disciplines where systems are often represented as graphs. This problem is very hard and not yet satisfactorily solved, despite the huge effort of a large interdisciplinary community of scientists working on it over the past few years. We will attempt a thorough exposition of the topic, from the definition of the main elements of the problem, to the presentation of most methods developed, with a special focus on techniques designed by statistical physicists, from the discussion of crucial issues like the significance of clustering and how methods should be tested and compared against each other, to the description of applications to real networks.

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Community detection in graphs

Because of the increasing number of diverse routing protocols proposed to deal with the network dynamics in mobile ad hoc networks (MANETs), the heterogeneity of MANETs has increased dramatically. While many of these extant proposals only concern enhancing routing in a single domain, little attention has been given to the interoperations among heterogeneous MANETs. Moreover, the existing inter-domain routing protocols (i.e., BGP) that have been designed for the Internet cannot cope with the new challenges derived from the MANETs, such as (1) the rapid dynamic changes of network topology due to mobility, and (2) the larger diversity in intra-domain ad hoc routing protocols. In this chapter, the authors address some of the major challenges and identify new directions to the development of seamless inter-domain routing for enabling end-to-end communications over heterogeneous MANET domains. © 2010, IGI Global.

Inter-Domain Routing in Mobile Ad Hoc Networks : Challenges and New Directions

TreacleWell: Unraveling the magic "Black box" of the network

This paper explores the extension of a model for the operation of an ad hoc mobile network to more general providerless networks, such as peer-to-peer systems. The model incorporates incentives for users to act as transit nodes on multi-hop paths and to be rewarded with their own ability to send traffic. The paper explores some of the trust questions that arise in this problem space and conjectures that the very structure of a peer organisation may have some hidden benefits for trust re-enforcement, that have not been previously explored (to our knowledge).

Providing incentives in providerless networks

Enhancing DSR maintenance with power awareness

This is a paper about pricing the Internet. The focus is the use of pricing for usage of the infrastructure for transmitting and receiving IP packets, rather than of services such as WWW, FTP, Archie, Gopher, etc. In this we propose subscription based pricing, and a mechanism based on dynamic host address allocation drawn from a set of separately routed addresses to give priority levels. The idea of subscriptions here is not that all service pricing should be achieved through subscriptions per se. They are seen as a way of policing priority access to service bottlenecks, and thus can be deployed incrementally at weak interconnection points in a network, or between ISPs. Users of these subscriptions could easily be entire organisations (represented by network numbers, or CIDRized collections of network numbers, or ASs and so on). These organisations could employ refinement techniques to provide more usage oriented charging if needed.

Jon Crowcroft

Papers

Inter-Domain Routing in Mobile Ad Hoc Networks : Challenges and New Directions

TreacleWell: Unraveling the magic "Black box" of the network

Providing incentives in providerless networks

Enhancing DSR maintenance with power awareness

Pricing the Internet