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.

/pdf/community-detection-in-graphs-34rogm3r6p.pdf

Community detection in graphs

Twitter has already become an important facet of the social Web, allowing users and organizations to share their ideas and subscribe to others' updates. Notably, it has been actively used during political events such as the recent elections in Iran, Spain and the USA, or the uprisings in the Middle East, to the extent that it is claimed that revolutions will be tweeted. However such claims are yet to be empirically established. In this work we study an extensive set of millions of tweets themed around the 2011 regional and local elections in Spain and their accompanying civil unrest. Our analysis shows that mainstream political entities were overshadowed on Twitter by grassroots movements discussing alternative points of view, at both regional and national levels. By tracking temporal trends we discover an explosion of interest in the Spanish protests following the establishment of the first protest camps in Madrid. The subsequent spontaneous setting up of similar camps in almost every town in Spain was widely reported at the time, and our spatial analysis quantitatively attests that the protests were indeed widely discussed in all parts of the country. Our results suggest that online social networks serve more as media for interactive engagement between grassroots peers, rather than as platforms for politicians to attract mass attention.

/pdf/los-twindignados-the-rise-of-the-indignados-movement-on-57v7jnn8z5.pdf

Los Twindignados: The Rise of the Indignados Movement on Twitter

Fact checking has been hard enough to do in traditional settings, but, as news consumption is moving on the Internet and sources multiply, it is almost unmanageable. To solve this problem, researchers have created applications that expose people to diverse opinions and, as a result, expose them to balanced information. The wisdom of this solution is, however, placed in doubt by this paper. Survey responses of 60 individuals in the UK and South Korea and in-depth structured interviews of 10 respondents suggest that exposure to diverse opinions would not always work. That is partly because not all individuals equally value opinion diversity, and mainly because the same individual benefits from it only at times. We find that whether one looks for diverse opinions largely depends on three factors--one's prior convictions, emotional state, and social context.

/pdf/why-individuals-seek-diverse-opinions-or-why-they-don-t-58oa071luj.pdf

Why individuals seek diverse opinions (or why they don't)

The concurrent use of multiple paths through a communications network has the potential to provide many benefits, including better utilisation of the network and increased robustness. A key part of a multipath network architecture is the ability for routing protocols to install multiple routes over multiple paths in the routing table. In this paper we propose changes to local BGP processing that allow a BGP router to use multiple paths concurrently without compromising loop-freeness.

/pdf/loop-freeness-in-multipath-bgp-through-propagating-the-1j16uzbmdx.pdf

Loop-Freeness in Multipath BGP through Propagating the Longest Path

For historical interest, this document captures the EF Design Team's proposed solution, preferred by the original authors of RFC 2598 but not adopted by the working group in December 2000. The original definition of EF was based on comparison of forwarding on an unloaded network. This experimental Delay Bound (DB) PHB requires a bound on the delay of packets due to other traffic in the network. At the Pittsburgh IETF meeting in August 2000, the Differentiated Services working group faced serious questions regarding RFC 2598 - the group's standards track definition of the Expedited Forwarding (EF) Per Hop Behavior (PHB). An 'EF Design Team' volunteered to develop a re-expression of RFC 2598, bearing in mind the issues raised in the DiffServ group. At the San Diego IETF meeting in December 2000 the DiffServ working group decided to pursue an alternative re-expression of the EF PHB.

A Delay Bound alternative revision of RFC 2598

The World Wide Web (WWW) is a global information system which is set to revolutionize the world of information search, retrieval and browsing via the Internet. This book serves as an authoritative introduction to concepts and design required to use the WWW. The book is intended for systems operators and managers, IT managers, computer science undergraduates, and general Internet users.

Jon Crowcroft

Papers

Los Twindignados: The Rise of the Indignados Movement on Twitter

Why individuals seek diverse opinions (or why they don't)

Loop-Freeness in Multipath BGP through Propagating the Longest Path

A Delay Bound alternative revision of RFC 2598

The World Wide Web: Beneath The Surf