ACKNOWLEDGMENTS I would like to give many thanks to Dr. Shengli Fu and Dr. Yan Huang as my advi-

Traditionally, link quality estimation (LQE) has been viewed as an a priori step in sensor network routing protocols because it filters out unreliable links before data transmission. Recent results, however, show that protocols can perform well without a priori LQE. Because getting rid of LQE seems rather counter-intuitive, the aim of this work is to look deeper into the behavior of LQE-free protocols. Our results, based on one of the stateof-the-art LQE-free protocols, show two interesting insights. First, LQEfree protocols manage to choose links that are slightly better than the ones obtained with a priori LQE methods. Second, in traditional protocols, the effort needed to identify good links accounts for 40 % to 60 % of the energy consumption of nodes. By eliminating this overhead, LQE-free protocols can save a significant amount of energy compared to standard approaches. On the other hand, clear downsides of LQE-free operation are the longer paths and the worse load balance. The latter poses a higher transmission burden on some nodes.

A particularly important sector for the stability of financial systems is the banking sector. Banks play a central role in the money creation process and in the payment system. Moreover, bank credit is an important factor in the financing of investment and growth. Faltering banking systems have

Abstract-The ion microprobe has been used to determine the concentrations of a number oftrace elements (including all 14 stable rare earth elements) and the isotopic compositions of Ca and Mg in seven hibonite-rich refractory inclusions. Hibonite in every inclusion analyzed shows the effect of RAZE partitioning with other solid or liquid phases, in which hibonite is enriched in light over heavy REE compared to other existing phases. This partitioning causes Cl chondrite-normalized enrichments to drop by factors of 4 to 22 from lanthanum to lutetium. Fractionations due to gas-solid partitioning of REE are sometimes uperimposed on the pattern produced by partitioning between condensed phases. Two inclusions, HAL and DH-H 1, show evidence for formation in extremely oxidizing environments and their Ca is mass fm~ionat ~ in favor of the heavy isotopes by 7 and 12~/~u, reape&vely. Two ~~ndurn-hi~nite inclu~ons show evidence of extremely high temperature gas-solid fractionation, such that the more volatile tight REE are depleted as a group relative to the more refractory heavy REE. These inciusions both have Ca that is mass fractionated in favor of the light isotopes. Hibonite preserves the largest nuclear isotope anomalies inTi found to date (FAHEY ef al., 198Sa; HINTON et al., 1987b), but there does not seem to be a simple relationship between chemical composition, isotopic mass fractionation and the sign and magnitude of nuclear isotopic anomalies in hibonite-rich inclusions. One possibility for producing a variety of chemical compositions and degrem of mass fractionation while preserving nuclear isotope anomalies is by multiple cycles of condensation and evaporation in a turbulent protoplanetary accretion disk (MORL~LL,

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I first thank my thesis advisors Thiemo Voigt and Adam Dunkels for being my excellent advisors, and also for being the great colleagues you still are. Thiemo and Adam have complemented each other superbly, giving me feedback, perspectives, insights, and having made every single new venture truly fun. My deepest thanks also go to my professor Per Gunningberg, Uppsala University. Per has in a seemingly easy way spotted erroneous assumptions, has valued my research contributions, and has connected my own work with another broader world of research. I want to thank all colleagues in the Networked Embedded Systems group:

Algebraic algorithms deal with numbers, vectors, matrices, polynomials, for-mal power series, exponential and differential polynomials, rational functions, algebraic sets, curves and surfaces. In this vast area, manipulation with matri-ces and polynomials is fundamental for modern computations in Sciences and

This is a preliminary version of a Chapter on Algebraic Algorithms in the up-

I would like to thank some people who were involved in the creation of this thesis: • Berry Schoenmakers of TU Eindhoven for introducing me to the topic of cryptographic voting protocols. • Evangelos Karatsiolis for his work in guiding me through the process of writing this thesis and his constant motivation. • Roberto Samarone Araujo for hours of discussing various protocols with Evengelos and me. • Warren D. Smith for providing with a preliminary version of his upcoming book »How Mathematics can Improve Democracy«. • Ute Günther and Christian Burgmann for their proof-reading. Nonetheless, any remaing errors shall be blamed on me. • Andrea Peter for her love and for cheering me up when I was down. • Last but not least my parents, Jacqueline Herrnkind and Hans Peter Klink – without their love and continuous support, this thesis would never have been written.

Wireless sensor networks are used to collect sensor data in different applications such as environmental monitoring, smart building control, and health care applications. Wireless sensor nodes used are typically small, low-cost, and battery powered. The nodes are often hard to access after deployment, for example when they are in remote locations. Another property of wireless sensor networks is that their operation is dependent on the environment they operate in, both due to the specific sensor readings but also due to the effects on communication by factors such as fading and radio interference. This makes it important to evaluate a wireless sensor network in its intendent target environment before final deployment. To enable experiments with wireless sensor networks in their target environment, we have designed and implemented a testbed called Sensei-UU. It is designed to allow WSN experiments to be repeated in different locations, thus exposing effects caused by the environment. To allow this, the testbed is designed to be easily moved between experimental sites. One type of WSN applications Sensei-UU is aimed to evaluate is protocols where nodes are mobile. Mobile testbed nodes are low-cost robots which follow a tape track on the floor. The localization accuracy of the robot approach is evaluated and is accurate enough to expose a