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

Data communications networks have traditionally been divided into local area networks and wide area networks. This division actually represents two ends of a range of a number of parameters for a network:

Metropolitan area network (MAN)

Creating a division between inter-domain and intradomain routing is expected to assist in meeting the challenges of future MANET deployments in terms of heterogeneity and administrative separation. Previous research in MANET routing and security has focussed on the intra-domain context. This paper discusses the problems encountered in inter-domain routing security, and the security requirements that arise from interactions between multiple management domains. It identifies the ways in which inter-domain routing for MANETs requires a different trust model to that of intra-domain MANET routing. Additionally, it discusses the way in which its requirements differ from inter-domain routing security in the Internet due to the more dynamic topological environment found in MANETs. The paper identifies how domain ownership and relationships between domain owners influence the security problem.

Security across Disparate Management Domains in MANETs

Some Lessons Learned from Various ALF and ILP Applications.

In this document we study the application of weighted proportional fairness to data flows in the Internet. We let the users set the weights of their connections in order to maximise the utility they get from the network. When combined with a pricing scheme where connections are billed by weight and time, such a system is known to maximise the total utility of the network. Our study case is a national Web cache server connected to long distance links. We propose two ways of weighting TCP connections by manipulating some parameters of the protocol and present results from simulations and prototypes. We finally discuss how proportional fairness could be used to implement an Internet with differentiated services.

Differentiated End-to-End Internet Services using a Weighted Proportional Fair Sharing TCP

Is the temporal dimension alone sufficient to characterize contacts in opportunistic networks? Several studies analyze the temporal aspect of contacts with significant results concerning contact and inter-contact distributions. Nevertheless, only the temporal dimension does not give a complete overview of contact characterization. In this paper, we propose the surround indicator as a metric to exhibit the contact's surrounding environment in opportunistic networks. We evaluate the surround indicator on two existing datasets and show that contacts have too heterogeneous and too unstable surrounds to be considered only in terms of duration. Besides a large variability of the surrounding environment within the duration of a single contact, it is frequent to observe contacts of identical duration that exhibit differences in their surrounds of more than a hundred times.

/pdf/contact-surround-in-opportunistic-networks-4mcz2otkzq.pdf

Jon Crowcroft

Papers

Metropolitan area network (MAN)

Security across Disparate Management Domains in MANETs

Some Lessons Learned from Various ALF and ILP Applications.

Differentiated End-to-End Internet Services using a Weighted Proportional Fair Sharing TCP

Contact surround in opportunistic networks