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

Experimental activities play a vital role in the deployment and development of novel radio access networks. In particular the movement from 3G to 4G poses new challenges, which need to be solved using practical approaches such as testbeds. This paper presents a testbed that can be regarded as an early attempt to build a 4G system. It fully integrates heterogeneous wireless technologies using a loosely-coupled architecture. Also, experimental results are included to show the possibilities of this setup.

/pdf/a-practical-approach-for-4g-systems-deployment-of-overlay-99u3bzuwhx.pdf

A practical approach for 4G systems: deployment of overlay networks

In this paper we present a new technique called Optimised Batch Patching with Classes of Service(OBP with CoS) which can be used to leverage the benefits of multicast within the context of 'near' video-on-demand systems in IP networks. OBP with CoS builds on an earlier scheme, known as Optimised Patching, but is different in two respects. Firstly, in OBP with CoS, the server artificially delays requests in order to increase the probability of accumulating duplicates, thereby allowing greater exploitation of multicast compared to Optimised Patching albeit at the expense of higher latency until commencement of service. Secondly, the client is able to request a latency class of service which reflects how long the client is prepared to wait until playout of the video. The server scheduling algorithm attempts to minimise network bandwidth consumption within the constraints imposed by the class of each request. We present analysis and simulations of our scheme in order to validate its effectiveness.

Optimised batch patching with classes of service

Unikernel specializes a minimalistic LibOS and a target application into a standalone single-purpose virtual machine (VM) running on a hypervisor, which is referred to as (virtual) appliance. Compared to traditional VMs, Unikernel appliances have smaller memory footprint and lower overhead while guaranteeing the same level of isolation. On the downside, Unikernel strips off the process abstraction from its monolithic appliance and thus sacrifices flexibility, efficiency, and applicability. This paper examines whether there is a balance embracing the best of both Unikernel appliances (strong isolation) and processes (high flexibility/efficiency). We present KylinX, a dynamic library operating system for simplified and efficient cloud virtualization by providing the pVM (process-like VM) abstraction. A pVM takes the hypervisor as an OS and the Unikernel appliance as a process allowing both page-level and library-level dynamic mapping. At the page level, KylinX supports pVM fork plus a set of API for inter-pVM communication (IpC). At the library level, KylinX supports shared libraries to be linked to a Unikernel appliance at runtime. KylinX enforces mapping restrictions against potential threats. KylinX can fork a pVM in about 1.3 ms and link a library to a running pVM in a few ms, both comparable to process fork on Linux (about 1 ms). Latencies of KylinX IpCs are also comparable to that of UNIX IPCs.

/pdf/kylinx-a-dynamic-library-operating-system-for-simplified-and-14y6hq9zfj.pdf

KylinX: A Dynamic Library Operating System for Simplified and Efficient Cloud Virtualization.

We discuss the use of interleaving as a bandwidth efficient means of protecting audio streams from the effects of packet loss on the Internet. The adverse effects of interleaving on IP/UDP/RTP header compression are noted and a number of schemes which remedy this problem are discussed.

/pdf/effects-of-interleaving-on-rtp-header-compression-4invpr5taz.pdf

Effects of interleaving on RTP header compression

Inter-domain routing is an important component to allow interoperation among heterogeneous network domains operated by different organizations. Although interdomain routing has been extensively studied in the Internet, it remains relatively unexplored in the Mobile Ad Hoc Networks (MANETs) space. In MANETs, the inter-domain routing problem is challenged by: (1) dynamic network topology, and (2) diverse intra-domain ad hoc routing protocols. In this paper, we propose a networking protocol called IDRM (Inter-Domain Routing Protocol for MANETs) to enable interoperation among MANETs. IDRM can handle the dynamic nature of MANETs and support policy-based routing similarly to BGP. We first discuss the design challenges for inter-domain routing in MANETs, and then present the design of IDRM with illustrative examples. Finally, we present a simulation-based study to understand the operational effectiveness of inter-domain routing and show that the overhead of IDRM is moderate.

/pdf/idrm-inter-domain-routing-protocol-for-mobile-ad-hoc-4jaoymzhcp.pdf

Jon Crowcroft

Papers

A practical approach for 4G systems: deployment of overlay networks

Optimised batch patching with classes of service

KylinX: A Dynamic Library Operating System for Simplified and Efficient Cloud Virtualization.

Effects of interleaving on RTP header compression

IDRM: Inter-Domain Routing Protocol for Mobile Ad Hoc Networks