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11th European Conference on Pattern Languages of Programs, EuroPLoP 2006

作者： Harrison, Neil B. Avgeriou, Paris Zdun, Uwe Department of Computer Science and Engineering Utah Valley State College Orem UT United States Department of Mathematics and Computing Science University of Groningen Groningen Netherlands Distributed Systems Group Information Systems Institute Vienna University of Technology Vienna Austria

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Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

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Physical Review B 2007年第17期75卷 174515-174515页

作者： Ph. Vanderbemden Z. Hong T. A. Coombs S. Denis M. Ausloos J. Schwartz I. B. Rutel N. Hari Babu D. A. Cardwell A. M. Campbell SUPRATECS and Department of Electrical Engineering and Computer Science B28 Sart-Tilman B-4000 Liège Belgium Centre for Advanced Photonics and Electronics Engineering Department University of Cambridge 9 JJ Thomson Avenue Cambridge CB3 0FA United Kingdom SUPRATECS Communication Information Systems & Sensors (CISS) Department Royal Military Academy of Belgium 30 avenue de la Renaissance B-1000 Bruxelles Belgium SUPRATECS and Physics Institute B5 University of Liège Sart-Tilman B-4000 Liège Belgium National High Magnetic Field Laboratory Florida State University 1800 E. Paul Dirac Drive Tallahassee Florida 32310 USA IRC in Superconductivity University of Cambridge Madingley Road Cambridge CB3 OHE United Kingdom

Crossed-magnetic-field effects on bulk high-temperature superconductors have been studied both experimentally and numerically. The sample geometry investigated involves finite-size effects along both (crossed-)magnetic-field directions. The experiments were carried out on bulk melt-processed Y-Ba-Cu-O single domains that had been premagnetized with the applied field parallel to their shortest direction (i.e., the c axis) and then subjected to several cycles of the application of a transverse magnetic field parallel to the sample ab plane. The magnetic properties were measured using orthogonal pickup coils, a Hall probe placed against the sample surface, and magneto-optical imaging. We show that all principal features of the experimental data can be reproduced qualitatively using a two-dimensional finite-element numerical model based on an E−J power law and in which the current density flows perpendicularly to the plane within which the two components of magnetic field are varied. The results of this study suggest that the suppression of the magnetic moment under the action of a transverse field can be predicted successfully by ignoring the existence of flux-free configurations or flux-cutting effects. These investigations show that the observed decay in magnetization results from the intricate modification of current distribution within the sample cross section. The current amplitude is altered significantly only if a field-dependent critical current density Jc(B) is assumed. Our model is shown to be quite appropriate to describe the cross-flow effects in bulk superconductors. It is also shown that this model does not predict any saturation of the magnetic induction, even after a large number (∼100) of transverse field cycles. These features are shown to be consistent with the experimental data.

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Synchronizing without locks is inherently expensive

Synchronizing without locks is inherently expensive

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25th Annual ACM Symposium on Principles of distributed Computing 2006

作者： Attiya, Hagit Hendler, Danny Guerraoui, Rachid Kouznetsov, Petr Department of Computer Science Technion Israel Faculty of Industrial Engineering and Management Technion Israel Computer Science and Artificial Intelligence Laboratory School of Computer and Communication Sciences MIT Switzerland Max Planck Institute for Software Systems Germany

ISBN: (纸本)1595933840

It has been considered bon ton to blame locks for their fragility, especially since researchers identified obstruction-freedom: a progress condition that precludes locking while being weak enough to raise the hope for good performance. This paper attenuates this hope by establishing lower bounds on the complexity of obstruction-free implementations in contention-free executions: those where obstruction-freedom was precisely claimed to be effective. Through our lower bounds, we argue for an inherent cost of concurrent computing without locks. We first prove that obstruction-free implementations of a large class of objects, using only overwriting or trivial primitives in contention-free executions, have Ω(n) space complexity and Ω(log2 n) (obstruction-free) step complexity. These bounds apply to implementations of many popular objects, including variants of fetch&add, counter, compare&swap, and LL/SC. When arbitrary primitives can be applied in contention-free executions, we show that, in any implementation of binary consensus, or any perturbable object, the number of distinct base objects accessed and memory stalls incurred by some process in a contention free execution is Ω(√n). All these results hold regardless of the behavior of processes after they become aware of contention. We also prove that, in any obstruction-free implementation of a perturbable object in which processes are not allowed to fail their operations, the number of memory stalls incurred by some process that is unaware of contention is Ω(n). Copyright 2006 ACM.

关键词： Security systems

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CAM05-1: Impact of Unprotected Multi-Failures in Resilient SPM Networks: a Capacity Dimensioning Approach

CAM05-1: Impact of Unprotected Multi-Failures in Resilient S...

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IEEE Globecom 2006

作者： Michael Menth Ruediger Martin Ulrich Spoerlein Department of Distributed Systems Institute of Computer Science University of Wurzburg Germany

Restoration or protection switching mechanisms protect traffic in packet-switched networks against local outages by deviating it around the failure location. This assures connectivity, but sufficient backup capacity is also needed to maintain quality of service (QoS) for the duration of the outage. To that end, sufficient capacity must be provided on the links so that the network can survive a set of protected failure scenarios without congestion due to redirected traffic. The self- protecting multipath (SPM) is a protection switching mechanism for which the required backup capacity can be minimized by linear optimization methods. However, unprotected multi-failures may lead to congestion in such "resilient networks" since backup capacity may be missing. In this paper, we quantify and compare the impact of unprotected double failures on the QoS for the optimized SPM, single shortest path routing (SSP), and equal- cost multipath (ECMP) routing.

关键词： Scanning probe microscopy Telecommunication traffic Routing Protection switching Costs Quality of service Load management computer science Optimization methods Aggregates

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A P2P-based framework for distributed Network Management

A P2P-based framework for Distributed Network Management

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2nd International Workshop of the EURO-NGI Network of Excellence

作者： Binzenhöfer, Andreas Tutschku, Kurt Auf Dem Graben, Björn Fiedler, Markus Arlos, Patrik Department of Distributed Systems Institute of Computer Science University of Würzburg Am Hubland 97074 Würzburg Germany Dept. of Telecommunication Systems School of Engineering Blekinge Institute of Technology 371 79 Karlskrona Sweden

ISBN: (纸本)3540340254

In this paper we present a novel framework supporting distributed network management using a self-organizing peer-to-peer over-lay network. The overlay consists of several distributed Network Agents which can perform distributed tests and distributed monitoring for fault and performance management. In that way, the concept is able to over-come disadvantages that come along with a central management unit, like lack of scalability and reliability. So far, little attention has been payed to the quality of service experienced by the end user. Our self-organizing management overlay provides a reliable and scalable basis for distributed tests that incorporate the end user. The use of a distributed, self-organizing software will also reduce capital and operational expenditures of the operator since fewer entities have to be installed and operated. © Springer-Verlag Berlin Heidelberg 2006.

关键词： Telecommunication networks

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Motor adptation to dynamic environments in arm reaching motions

Motor adptation to dynamic environments in arm reaching moti...

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18th IMEKO World Congress 2006: Metrology for a Sustainable Development

作者： Ito, Koji Imai, Tsutomu Kondo, Toshiyuki Department of Computational Intelligence and Systems Science Tokyo Institute of Technology Yokohama Japan Department of Computer Information and Communication Sciences Tokyo University of Agriculture and Technology Tokyo Japan

ISBN: (纸本)9781622766468

In daily life, humans must compensate for the resultant forces arising form interaction with the physical environment. Recent studies have shown that humans can acquire a neural representation of the relation between motor command and movement, i.e. learn an internal model of the environment dynamics. The present paper discusses whether humans can identify one side of dynamics from the mixed environment dynamics in the case where humans have experienced either of them.

关键词： Dynamic environment Force field Internal model Motor adaptation Reaching motion

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Displacement Whiplash PCR: Optimized architecture and experimental validation 1

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12th International Meeting on DNA Computing

作者： Rose, John A. Komiya, Ken Yaegashi, Satsuki Hagiya, Masami Institute of Information Communication Technology Ritsumeikan Asia Pacific University Department of Computer Science and UPBSB The University of Tokyo Japan Science and Technology Agency-CREST Dept. of Computational Intelligence and Systems Science Tokyo Institute of Technology

ISBN: (数字)9783540684237

ISBN: (纸本)9783540490241

Whiplash PCR-based methods of biomolecular computation (BMC), while highly-versatile in principle, are well-known to suffer from a simple but serious form of self-poisoning known as back-hybridization. In this work, an optimally re-engineered WPCR-based architecture, Displacement Whiplash PCR (DWPCR) is proposed and experimentally validated. DWPCR's new rule protect biostep, which is based on the primer-targeted strand-displacement of back-hybridized hairpins, renders the most recently implemented rule-block of each strand unavailable, abolishing back-hybridization after each round of extension. In addition to attaining a near-ideal efficiency, DWPCR's ability to support isothermal operation at physiological temperatures eliminates the need for thermal cycling, and opens the door for potential biological applications. DWPCR should also be capable of supporting programmable exon shuffling, allowing XWPCR, a proposed method for programmable protein evolution, to more closely imitate natural evolving systems. DWPCR is expected to realize a highly-efficient, versatile platform for routine and efficient massively parallel BMC.

关键词： Biology

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Vishwa: A reconfigurable P2P middleware for Grid Computations

Vishwa: A reconfigurable P2P middleware for Grid Computation...

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International Conference on Parallel Processing (ICPP)

作者： M. Venkateswara Reddy A. Vijay Srinivas Tarun Gopinath D. Janakiram Department of Computer Science & Engineering Distributed and Object Systems Laboratory Chennai India

The abundant computing resources available on the Internet has made grid computing over the Internet a viable solution, to scientific problems. The dynamic nature of the Internet necessitates dynamic reconfigurability of applications to handle failures and varying loads. Most of the existing grid solutions handle reconfigurability to a limited extent. These systems lack appropriate support to handle the failure of key-components, like coordinators, essential for the computational model. We propose a two layered peer-to-peer middleware, Vishwa, to handle reconfiguration of the application in the face of failure and system load. The two-layers, task management layer and reconfiguration layer, are used in conjunction by the applications to adapt and mask node failures. We show that our system is able to handle the failures of the key-components of a computation model. This is demonstrated in the case studies of two computational models, namely bag of tasks and connected problems, with an appropriate example for each

关键词： Middleware Grid computing Peer to peer computing Internet Computational modeling computer networks IP networks Scalability Routing computer architecture

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Performance modelieg of a bottleneck node in an IEEE 802.11 ad-hoc network

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5th International Conference on Ad-Hoc, Mobile, and Wireless Networks, ADHOC-NOW 2006

作者： Van Den Berg, Hans Mandjes, Michel Roijers, Frank TNO Information and Communication Technology Netherlands Department of Design and Analysis of Communication Systems University of Twente Netherlands Centre for Mathematics and Computer Science Netherlands Korteweg-de Vries Institute University of Amsterdam Netherlands

ISBN: (纸本)3540372466

The IEEE 802.11 MAC-protocol, often used in ad-hoc networks, has the tendency to share the capacity equally amongst the active nodes, irrespective of their loads. An inherent drawback of this fair-sharing policy is that a node that serves as a relay-node for multiple flows is likely to become a bottleneck. This paper proposes a flow-level performance model of such a bottleneck node using fluid-flow analysis. Assuming Poisson initiations of new flow transfers at the bottleneck node, we obtain insightful, robust, and explicit expressions for characteristics related to the overall flow transfer time, the buffer occupancy, and the packet delay at the bottleneck node. The analysis is enabled by a translation of the behavior of the bottleneck node and the source nodes in terms of an M/G/1 queueing model. We conclude the paper by an assessment of the impact of alternative capacity sharing amongst source nodes and the bottleneck in order to improve the performance of the bottleneck. © Springer-Verlag Berlin Heidelberg 2006.

关键词： Telecommunication networks

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On the use of DVB-H for satellite multimedia networks

On the use of DVB-H for satellite multimedia networks

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2006 IEEE 17th International Symposium on Personal, Indoor and Mobile Radio communications, PIMRC

作者： Cioni, S. Corazza, G.E. Neri, M. Vanelli-Coralli, A. Advanced Research Center on Electronic Systems for Information and Communication Technologies Department of Electronics Computer Science and Systems University of Bologna Via V. Toffano 2/2 40125 Bologna Italy

ISBN: (纸本)1424403294

In all short-medium term business/market forecasts, the efficient provision of digital multimedia broadcasting (DMB) services in mobile systems appears to be of key importance for mobile operators and broadcasters. Several DMB systems are being developed around the world, with several proposed competing standards. In this framework, the DVB (Digital Video Broadcasting) forum is working to define a new air interface, identified as DVB-SSP, to deliver satellite services to portable devices, and several possibilities are being considered as viable options, including the use of DVB-H (Handheld). A critical factor to be considered is the resilience to non linear distortion effects. In fact, DVB-H signals are obtained through an OFDM modulation, which traditionally was considered unfit for satellite communications. Recently [3], it has been proved that the adoption of strong channel coding techniques in conjunction with the use of non-linear distortion compensation techniques can lead to good OFDM performance even when operating close to amplifier saturation. Following this avenue, this paper investigates the adaptation of the DVB-H physical layer to the satellite environment, and validates the improved robustness of the proposed scheme to non linear distortion. © 2006 IEEE.

关键词： Orthogonal frequency division multiplexing

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