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91.
Das Internet ist heute eine globale Infrastruktur, deren st?ndige Verfügbarkeit mehr oder weniger als gegeben angenommen wird.
Die Einführung neuer Technologien (z. B. Multicast, IPv6) in diese Infrastruktur erweist sich aus unterschiedlichen Gründen
als schwierig. Vielmehr haben sich Overlay-Netze in diesem Kontext als Innovationsmotor etabliert. Diese werden von Endger?ten
am Netzrand aufgespannt, ben?tigen somit keine neuen Komponenten in der Netzinfrastruktur und lassen sich selbstorganisierend
sowie skalierbar einsetzen. Interessant sind diese Eigenschaften auch für den Overlay-basierten Aufbau und Betrieb von Kommunikationsnetzen
an sich, mit dem Ziel, unbeeinflusst von Mobilit?t, Multi-Homing und Heterogenit?t der Protokolle und Zugangsnetze nahtlose
Konnektivit?t zwischen Endger?ten herzustellen. Dieser Artikel zeigt anhand von Beispielen auf, wie Overlays die Entwicklung
neuer Dienste im Internet vorantreiben k?nnen. Als Beispiel für eine Overlay-basierte Netzarchitektur, welche die Realisierung
neuer Dienste und Anwendungen erm?glicht, wird die Architektur zur Realisierung von Spontanen Virtuellen Netzen (SpoVNet) und deren Netzabstraktionsschicht ariba detailliert vorgestellt. 相似文献
92.
Anselm Grundhöfer Daniel Kurz Sebastian Thiele Oliver Bimber 《The Visual computer》2010,26(9):1167-1176
In this article we show how temporal backdrops that alternately change their color rapidly at recording rate can aid chroma
keying by transforming color spill into a neutral background illumination. Since the chosen colors sum up to white, the chromatic
(color) spill component is neutralized when integrating over both backdrop states. The ability to separate both states additionally
allows to compute high-quality alpha mattes. Besides the neutralization of color spill, our method is invariant to foreground
colors and supports applications with real-time demands. In this article, we explain different realizations of temporal backdrops
and describe how keying and color spill neutralization are carried out, how artifacts resulting from rapid motion can be reduced,
and how our approach can be implemented to be compatible with common real-time post-production pipelines. 相似文献
93.
Rupert Wegerif Bruce M. McLaren Marian Chamrada Oliver Scheuer Nasser Mansour Jan Mikšátko Mriga Williams 《Computers & Education》2010
This paper reports on an aspect of the EC funded Argunaut project which researched and developed awareness tools for moderators of online dialogues. In this study we report on an investigation into the nature of creative thinking in online dialogues and whether or not this creative thinking can be coded for and recognized automatically such that moderators can be alerted when creative thinking is occurring or when it has not occurred after a period of time. We outline a dialogic theory of creativity, as the emergence of new perspectives from the interplay of voices, and the testing of this theory using a range of methods including a coding scheme which combined coding for creative thinking with more established codes for critical thinking, artificial intelligence pattern-matching techniques to see if our codes could be read automatically from maps and ‘key event recall’ interviews to explore the experience of participants. Our findings are that: (1) the emergence of new perspectives in a graphical dialogue map can be recognized by our coding scheme supported by a machine pattern-matching algorithm in a way that can be used to provide awareness indicators for moderators; (2) that the trigger events leading to the emergence of new perspectives in the online dialogues studied were most commonly disagreements and (3) the spatial representation of messages in a graphically mediated synchronous dialogue environment such as Digalo may offer more affordance for creativity than the much more common scrolling text chat environments. All these findings support the usefulness of our new account of creativity in online dialogues based on dialogic theory and demonstrate that this account can be operationalised through machine coding in a way that can be turned into alerts for moderators. 相似文献
94.
95.
Oliver Schreer Ingo Feldmann Isabel Alonso Mediavilla Pedro Concejero Abdul H. Sadka Mohammad Rafiq Swash Sergio Benini Riccardo Leonardi Tijana Janjusevic Ebroul Izquierdo 《Multimedia Tools and Applications》2010,48(1):23-49
Multimedia analysis and reuse of raw un-edited audio visual content known as rushes is gaining acceptance by a large number
of research labs and companies. A set of research projects are considering multimedia indexing, annotation, search and retrieval
in the context of European funded research, but only the FP6 project RUSHES is focusing on automatic semantic annotation,
indexing and retrieval of raw and un-edited audio-visual content. Even professional content creators and providers as well
as home-users are dealing with this type of content and therefore novel technologies for semantic search and retrieval are
required. In this paper, we present a summary of the most relevant achievements of the RUSHES project, focusing on specific
approaches for automatic annotation as well as the main features of the final RUSHES search engine. 相似文献
96.
Jürgen Bernard Jan Brase Dieter Fellner Oliver Koepler Jörn Kohlhammer Tobias Ruppert Tobias Schreck Irina Sens 《International Journal on Digital Libraries》2010,11(2):111-123
Digital Library support for textual and certain types of non-textual documents has significantly advanced over the last years.
While Digital Library support implies many aspects along the whole library workflow model, interactive and visual retrieval
allowing effective query formulation and result presentation are important functions. Recently, new kinds of non-textual documents
which merit Digital Library support, but yet cannot be fully accommodated by existing Digital Library technology, have come
into focus. Scientific data, as produced for example, by scientific experimentation, simulation or observation, is such a
document type. In this article we report on a concept and first implementation of Digital Library functionality for supporting
visual retrieval and exploration in a specific important class of scientific primary data, namely, time-oriented research
data. The approach is developed in an interdisciplinary effort by experts from the library, natural sciences, and visual analytics
communities. In addition to presenting the concept and to discussing relevant challenges, we present results from a first
implementation of our approach as applied on a real-world scientific primary data set. We also report from initial user feedback
obtained during discussions with domain experts from the earth observation sciences, indicating the usefulness of our approach. 相似文献
97.
With the advent of multi-core processors, desktop application developers must finally face parallel computing and its challenges.
A large portion of the computational load in a program rests within iterative computations. In object-oriented languages these
are commonly handled using iterators which are inadequate for parallel programming. This paper presents a powerful Parallel
Iterator concept to be used in object-oriented programs for the parallel traversal of a collection of elements. The Parallel
Iterator may be used with any collection type (even those inherently sequential) and it supports several scheduling schemes
which may even be decided dynamically at run-time. Some additional features are provided to allow early termination of parallel
loops, exception handling and a solution for performing reductions. With a slight contract modification, the Parallel Iterator
interface imitates that of the Java-style sequential iterator. All these features combine together to promote minimal, if
any, code restructuring. Along with the ease of use, the results reveal negligible overhead and the expected inherent speedup. 相似文献
98.
W. Clark K. Logan R. Luckin A. Mee & M. Oliver 《Journal of Computer Assisted Learning》2009,25(1):56-69
99.
Moritz Steiner Damiano Carra Ernst W. Biersack 《Peer-to-Peer Networking and Applications》2010,3(2):115-128
We analyze in detail the content retrieval process in kad. kad implements content search (publish and retrieval) functions that use the Kademlia Distributed Hash Table for content routing. Node churn is quite common in peer-to-peer systems and results in information loss and stale routing table entries. To deal
with node churn, kad issues parallel route requests and publishes multiple redundant copies of each piece of information. We identify the key
design parameters in kad and present an analytical model to evaluate the impact of changes in the values of these parameters on the overall lookup
latency and message overhead. Extensive measurements of the lookup performance using an instrumented client allow us to validate
the model. The overall lookup latency is in most cases 5 s or larger. We elucidate the cause for such high lookup latencies
and propose an improved scheme that significantly decreases the overall lookup latency without increasing the overhead. 相似文献
100.
Oliver Baur 《Computers & Geosciences》2009,35(3):548-556
Least-squares (LS) problems occur in almost every scientific and engineering discipline. Basically, they are generated by providing more observations than unknown parameters to be resolved. Appropriate LS solvers depend on both quality and computational issues. With regard to the latter, this paper focuses on the tailored parallel implementation of two LS solvers: the iterative LSQR method (substitutional for any Krylov-space method) and the “brute-force” inversion approach. Both implementations demonstrate very good scaling results in a parallel processing environment. Even so, the present investigations show that, from the computational and hardware point of view, iterative solvers outperform the “brute-force” approach. LSQR not only provides superior speed-up values; but, in addition, source code portability and hardware requirements are much more convenient for the iterative solver. These conclusions are drawn in the context of state-of-the-art terrestrial geopotential recovery with regard to the forthcoming Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission. 相似文献