speci cations in their code via annotations. Actual monitoring code is automatically synthesized from these annotations before compilation and integrated at appropriate places in the program, according to user-dened conguration attributes. This way, the specication is checked at runtime against

Hiermit versichere ich, die vorliegende Diplomarbeit selbstständig und unter ausschliesslicher Verwendung der angegebenen Quellen und Hilfsmittel angefertigt zu haben. Diese Arbeit hat in gleicher oder ähnlicher Form noch keiner Prüfungsbehörde vorgelegen. Darmstadt, 14. Februar 2006

criterion, a very simple Iterative Thresholding & K (signed) Means algorithm (ITKM), which has complexity O(dKN) in each iteration, is presented and its local efficiency is demonstrated in several experiments. Index Terms dictionary learning, dictionary identification, sparse coding, sparse component

pages 156–175, 2013. [2] Johannes Buchmann, Denise Demirel, and Jeroen van de Graaf. Towards a publicly-verifiable mix-net providing everlasting privacy. In Financial Cryptog-raphy, pages 197–204, 2013. [3] Denise Demirel, Jeroen van de Graaf, and Roberto Araùjo. Improving helios

This thesis presents CraneTracker, a multi-modal sensing and communication system for monitoring migratory species at the continental level. By exploiting the robust and extensive cellular infrastructure across the continent, traditional mobile wireless sensor networks can be extended to enable reliable, low-cost monitoring of migratory species. The developed multi-tier architecture yields ecologists with unconventional behavior in-formation not furnished by alternative tracking systems at such a large scale and for a low-cost. The simulation, development and implementation of the CraneTracker soft-ware system is presented. The system is shown effective through multiple proxy deploy-

Existing file-system reliability methods, such as checksums, redundancy, or transactional updates, provide limited defenses against file-system bugs that cause disk corruption. The existing workarounds, based on using backups or repairing the file system, are painfully slow. Worse, the recovery

ii Internet broadcasting techniques are wide spread and have been the focus off many research projects. Due to high transmission delays these systems often lack interactivity. This thesis introduces a new streaming system to deliver real-time video and audio data with low-delays across the Internet. Packet loss, jitter and changing bandwidth availability describe the challenges that have to be handled by the system, since the Internet is a best effort network and does not guarantee quality of service. To lower bit-rates audio and video data are usually compressed in formats like MPEG-4. The high compression nearly eliminates redundancy in the audio and video data. A resultant loss of transmitted data and transmission errors can have big impact on the quality of the received stream. MPEG-4 video uses inter frame prediction, so errors propagate between frames. We will argue that retransmission of lost or invalid data is not feasible for low-delay communication due to high control loop delays.

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First, I would like to thank to Dimka Karastoyanova and Mariano Cilia for all the fruitful discussions, their guidance and support through the course of this project. Thanks also to Prof. Alejandro Buchmann who sponsored my stay at Technische Universität Darmstadt during the spring of 2004. The special thanks go to my advisor, Mariano Cilia, who has made all this possible. Finally, I’d like to thank to my family for all these years of support.

for the network implementation, thus the game is the first real application using CUSP. Finally the game Planet π4 is integrated with the CUSP network simulator, allowing to run the whole game in a simulated network without the need for modification of its core components. Kurzfassung Massen