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

A major contribution to global warming has been the number of new workshops publishing proceedings with the prefix hot. In this article, I propose that we counter this trend in an attempt to remain carbon neutral with a set of 'anti-workshops' on cold topics.We suggest a number of heuristics for detecting when a topic has gone cold, and give some examples of the application of these heuristics. Of course, some cold topics warm up again, and so there is a risk of over dampening in our heuristic. Over a long period, dynamic equilibrium should be assured, but from time to time, our scheme may prejudice against surprising results in boring areas of communications research. Nevertheless, it may leave room for more surprising results in interesting areas of research, which cannot be a bad thing

http://ccr.sigcomm.org/online/files/p45-v38n1k-crowcroftA.pdf

Cold topics in networking

The Internet is inherently a multipath network---for an underlying network with only a single path connecting various nodes would have been debilitatingly fragile. Unfortunately, traditional Internet technologies have been designed around the restrictive assumption of a single working path between a source and a destination. The lack of native multipath support constrains network performance even as the underlying network is richly connected and has redundant multiple paths. Computer networks can exploit the power of multiplicity to unlock the inherent redundancy of the Internet. This opens up a new vista of opportunities promising increased throughput (through concurrent usage of multiple paths) and increased reliability and fault-tolerance (through the use of multiple paths in backup/ redundant arrangements). There are many emerging trends in networking that signify that the Internet's future will be unmistakably multipath, including the use of multipath technology in datacenter computing; multi-interface, multi-channel, and multi-antenna trends in wireless; ubiquity of mobile devices that are multi-homed with heterogeneous access networks; and the development and standardization of multipath transport protocols such as MP-TCP. 
The aim of this paper is to provide a comprehensive survey of the literature on network-layer multipath solutions. We will present a detailed investigation of two important design issues, namely the control plane problem of how to compute and select the routes, and the data plane problem of how to split the flow on the computed paths. The main contribution of this paper is a systematic articulation of the main design issues in network-layer multipath routing along with a broad-ranging survey of the vast literature on network-layer multipathing. We also highlight open issues and identify directions for future work.

/pdf/exploiting-the-power-of-multiplicity-a-holistic-survey-of-43a6rufy62.pdf

Exploiting the power of multiplicity: a holistic survey of network-layer multipath

Cryptocurrencies are notorious for their exchange rate high volatility, and are often tools of wild speculation rather than decentralised value exchange. This is especially true for Bitcoin, still, nowadays, the most popular cryptocurrency. This paper presents an analysis to detect the influence of a set of topological properties of the Bitcoin Users Graph on Bitcoin's exchange rate. 1 1. In the rest of this paper we will use the terms “Bitcoin price” and “Bitcoin's exchange rate” interchangeably to represent the amount of fiat currency (USD) needed to buy one Bitcoin at a given time. We consider, besides classical properties, a novel notion of Trustful Transaction Graph introduced to describe partial Users Graphs derived by chains of 0-confirmation transactions. We present a temporal analysis of the evolution of a set of features with a single day granularity. Afterwards, we applied autoregressive distributed-lag linear regression to assess whether and with which strength and duration a change in the considered features is likely to influence the exchange rate up to a prespecified number of days (fifteen) in the future. The results show that some of the considered features significantly influence the exchange rate up to several days, and that such relationships are likely not to be spurious, since we found that those features contribute significantly to decrease the error in predicting the exchange rate.

Leveraging the Users Graph and Trustful Transactions for the Analysis of Bitcoin Price

In recent years, much work has been done on attempting to scale multicast data transmission to hundreds or thousands of receivers. There are, however, many situations where an application might involve transmission to just ten or twenty sites. The European Space Agency, for example, carry out regular multi-gigabyte bulk data transfers to a handful of destinations.Using multicast for this type of application can provide significant benefits including reduced load on the transmitter, an overall reduction in network traffic, and consequently shorter data transfer times.In this paper we take a fresh look at the problem of deploying reliable multicast. So far, there has been no convincing solution to achieve this. We present a simple hybrid solution which has not been proposed before. The approach taken is to combine unicast with multicast by modifying TCP to support multicast transfers, and run this modified TCP engine over UDP as a userspace transport protocol.Our goal is clear: reliable bulk data delivery to a moderate number of sites. Unlike some other multicast protocols, our work is complete: we have designed, implemented, deployed and evaluated a protocol which meets this goal.

Hybrid reliable multicast with TCP-XM

We describe the EpiMap project, in which mobile phones and sensors record the proximity of other devices, to gather information on human interactions within the rural communities of developing countries. Collected information will be used to develop improved mathematical models of the spread of infectious diseases, such as measles, tuberculosis and pneumococcal diseases. Modelling will be complemented by the use of surveys to aid in the understanding of living conditions in these villages. EpiMap is an extension of the FluPhone project, which we carried out in 2010. FluPhone collected data on human interaction, by using mobile phones to record information such as locality and user symptoms. Delay tolerant opportunistic networks such as the Haggle framework [5] were used as a basis for communication. We introduce the EpiMap vision for a system of opportunistic networks combined with satellite communication, designed to face the challenges posed by weak power and communications infrastructure in the rural regions of developing countries in Asia, Africa and South America. We aim to use a delay-tolerant small satellite for data transfer between developing countries and Europe and North America. Data collected through EpiMap can be used to help design more efficient vaccination strategies and equitable control programmes.

/pdf/epimap-towards-quantifying-contact-networks-and-modelling-50v8mfhkq2.pdf

Jon Crowcroft

Papers

Cold topics in networking

Exploiting the power of multiplicity: a holistic survey of network-layer multipath

Leveraging the Users Graph and Trustful Transactions for the Analysis of Bitcoin Price

Hybrid reliable multicast with TCP-XM

EpiMap: towards quantifying contact networks and modelling the spread of infections in developing countries