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hp-DG-QTT solution of high-dimensional degenerate diffusion equations
(2012)SAM Research ReportWe consider the discretization of degenerate, time-inhomogeneous Fokker-Planck equations for diffusion problems in high-dimensional domains. Well-posedness of the problem in time-weighted Bochner spaces is established. Analytic regularity of the time-dependence of the solution in countably normed, weighted Sobolev spaces is established. Time discretization by the hp-discontinuous Galerkin method is shown to converge exponentially. The ...Report -
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Phosphate nutrition of crops in lixisols from semi-arid West Africa
(2012)Annual report 2011 North-South CentreReport -
A Time-Splitting for the Semiclassical Schrödinger Equation
(2012)SAM Research ReportWe propose a new algorithm for solving the semiclassical time–dependent Schr¨odinger equation. The algorithm is based on semiclassical wavepackets. Convergence is proved to be quadratic in the time step and linear in the semiclassical parameter !. To the the authors’ best knowledge, all earlier algorithms had errors that grew as the semiclassical parameter was decreased.Report -
Evaluating User Privacy in Bitcoin
(2012)Cryptology ePrint ArchiveBitcoin is quickly emerging as a popular digital payment system. However, in spite of its reliance on pseudonyms, Bitcoin raises a number of privacy concerns due to the fact that all of the transactions that take place are publicly announced in the system. In this paper, we investigate the privacy guarantees of Bitcoin in the setting where Bitcoin is used as a primary currency for the daily transactions of individuals. More specifically, ...Report -
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Fukushima und die Grenzen der Risikoanalyse
(2012)CSS Risk and Resilience ReportsWas können Risikoanalysen erfassen und was nicht, wie vertrauenswürdig können sie sein, und was für Aussagen über die Zukunft können aus ihnen hergeleitet werden? Dieses Factsheet thematisiert die Grenzen der Risikoanalyse. Anhand verschiedener Beispiele aus dem Kernenergiebereich untersucht es, wie die Definition von Risiken, die Methodologie ihrer Erfassung sowie die Interpretation von Resultaten in der probabilistischen Risikoanalyse ...Report -
Fast Private Set Operations with SEPIA
(2012)TIK ReportPrivate set operations allow correlation of sensitive data from multiple data owners. Although intensely researched, current solutions still exhibit limited scalability in terms of the supported maximum set size and number of sets. To address these issues, we propose a new approach to private set operations based on a combination of efficient secure multiparty computation and bloom filters, a space-efficient probabilistic data structure ...Report -
DTN-Meteo: Forecasting the Performance of DTN Protocols under Heterogeneous Mobility
(2012)TIK ReportOpportunistic or Delay Tolerant Networks (DTNs) may be used to enable communication in case of failure or lack of infrastructure (disaster, censorship, remote areas) and to complement existing wireless technologies (cellular, WiFi). Wireless peers communicate when in contact, forming an impromptu network, whose connectivity graph is highly dynamic and only partly connected. In this harsh environment, communication algorithms are mostly ...Report -
Classifying Internet One-way Traffic
(2012)TIK ReportInternet background radiation (IBR) is a very interesting piece of Internet traffic as it is the result of attacks and misconfigurations. Previous work has primarily analyzed IBR traffic to large unused IP address blocks called network telescopes. In this work, we build new techniques for monitoring one-way traffic in live networks with the main goals of 1) expanding our understanding of this interesting type of traffic towards live ...Report