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

In the near future mobile devices with several interfaces will become commonplace. Most of the peripheral networks using the Internet will therefore employ wireless technology. To provide support for these devices, this paper proposes a new framework which encompasses the functions of both peripheral and core networks. The framework is called Y-Comm and is defined in a layered manner like the OSI model.

https://www.mdx.ac.uk/__data/assets/pdf_file/0019/50266/wicon_extended.pdf

Y-Comm: a global architecture for heterogeneous networking

In this paper we consider the problem of efficient data gathering in sensor networks for arbitrary sensor node deployments. The efficiency of the solution is measured by a number of criteria: total energy consumption, total transport capacity, latency and quality of the transmissions. We present a number of different constructions with various tradeoffs between aforementioned parameters. We provide theoretical performance analysis for our approaches, present their distributed implementation and discuss the different aspects of using each. We show that in many cases our output-sensitive approximation solution performs better than the currently known best results for sensor networks. Our simulation results validate the theoretical findings. © 2014 IEEE.

https://www.cs.bgu.ac.il/~segal/infocom2014.pdf

Improved Structures for Data Collection in Wireless Sensor Networks

Do-It-Yourself (DIY) networks are decentralised networks built by an (often) amateur community. As DIY networks do not rely on the need for backhaul Internet connectivity, these networks are mostly a mix of both offline and online networks. Although DIY networks have their own homegrown services, the current Internet-based cloud services are often useful, and access to some services could be beneficial to the community. Considering that most DIY networks have challenged Internet connectivity, migrating current service virtualisation instances could face great challenges. Service Centric Networking (SCN) has been recently proposed as a potential solution to managing services more efficiently using Information Centric Networking (ICN) principles. In this position paper, we present our arguments for the need for a resilient SCN architecture, propose a strawman SCN architecture that combines multiple transmission technologies for providing resilient SCN in challenged DIY networks and, finally, identify key challenges that need to be explored further to realise the full potential of our architecture.

/pdf/scandex-service-centric-networking-for-challenged-j31vam5zoe.pdf

SCANDEX: Service Centric Networking for Challenged Decentralised Networks

Developing protocols and applications for opportunistic networking can represent a daunting task given the many aspects that must be taken into consideration, such as intermittent connectivity, smart choice among multiple interfaces and intelligent data storage. The implementation of these protocols can be based on generic layer-less communication frameworks that provide programming abstractions for the extraction and analysis of social, colocation and mobility information and allows data exchange by means of heterogeneous devices. We propose Gently, a novel fully implemented solution which combines techniques of context awareness and social knowledge to concretely solve issues related to opportunistic forwarding. More precisely, Gently is born as the combination of the Context-aware Adaptive Routing (CAR) and the socially aware LABEL protocol. We discuss the implementation of our solution on top of the layer-less Haggle framework presenting the key design choices and the lessons learnt.

/pdf/writing-on-the-clean-slate-implementing-a-socially-aware-27kbi3xmql.pdf

Writing on the clean slate: Implementing a socially-aware protocol in Haggle

Delivering data to on-line game participants requires the game data to be “customized” in real-time to each participant's characteristics. Using multicast in such an environment might sound contradictory. But multicast is a very efficient communication paradigm to minimize the transmission delays. Also, multicast reduces the workload at the sender. Content delivery according to receiver interest can be achieved by group management in multicast. But the natural dynamics of the application results in numerous delays because of join/leave latencies. In this paper, we propose the Router Level Filtering as a solution to the above problem.RLF relies on an extension to the current IP multicast service model. It introduces “filters” in the router forwarding process thereby providing a simple effective mechanism to customize the data delivered to a multicast session receiver while minimizing the number of groups and the related management cost. Contrary to other router filtering proposals, the filter semantics is determined by the application. The paper discusses protocol specification and implementation details of RLF, and shows how it may be implemented in routers.

/pdf/router-level-filtering-for-receiver-interest-delivery-mxereubxa6.pdf

Jon Crowcroft

Papers

Y-Comm: a global architecture for heterogeneous networking

Improved Structures for Data Collection in Wireless Sensor Networks

SCANDEX: Service Centric Networking for Challenged Decentralised Networks

Writing on the clean slate: Implementing a socially-aware protocol in Haggle

Router level filtering for receiver interest delivery