This work is part of the innovative "Active Generator" (AG) project. AG is a concept that suggests a new arrangement of the turbine-generator line of a high power utility (a few hundred of MW) in order to de-synchronize the rotation speed of the turbine-generator group from the fixed grid frequency (50 Hz or 60 Hz). This de-synchronization has essentially two advantages. First, the variable speed of the group enables the operation of the turbine at...

One of the key trends in computing over the past two decades has been increased distribution, both at the processor level, where multi-core architectures are now the norm, and at the system level, where many key services are currently distributed overmultiple machines. Thus, understanding the power and limitations of computing in a concurrent, distributed setting is one of the major challenges in Computer Science. In this thesis, we analyze the complexity of implementing concurrent data...

Symmetric cryptographic primitives such as block and stream ciphers are the building blocks in many cryptographic protocols. Having such blocks which provide provable security against various types of attacks is often hard. On the other hand, if possible, such designs are often too costly to be implemented and are usually ignored by practitioners. Moreover, in RFID protocols or sensor networks, we need lightweight and ultra-lightweight algorithms. Hence, cryptographers often search for a fair trade-off between...

This thesis is concerned with the algebraic theory of hermitian forms. It is organized in two parts. The first, consisting of the first two chapters, deals with some descent properties of unimodular hermitian forms over central simple algebras with involution. The second, which consists of the last two chapters, generalizes several classical properties of unimodular hermitian forms over rings with involution to the setting of sesquilinear forms in hermitian categories. The original results established in...

Among the many challenges of Alpine flood prediction is describing complex, meteo-hydrological processes in a simplified, robust manner that can be easily integrated into operational forecasting. In this dissertation, improved methods to characterize these processes are developed and integrated into the hydrological modeling component of an operational flood forecasting system used in the Swiss Alps. Detailed studies are conducted to improve hydrological model inputs, processes and outputs. Improvements, detailed in four chapters of this thesis,...

The topic of this thesis is the study of several stochastic control problems motivated by sailing races. The goal is to minimize the travel time between two locations, by selecting the fastest route in face of randomly changing weather conditions, such as wind direction. When a sailboat is travelling upwind, the key is to decide when to tack. Since this maneuver slows down the yacht, it is natural to model this time lost by a...

Silicon technology has advanced through the past four decades at exponential rate both in performance and productivity. Along with the miniaturization, the power demand grew also exponentially. New technologies are studied in order to develop switches that commute faster and, in the near future, we might see an increasing number of hybrid approaches to overcome the limitations CMOS performance. The ferroelectric thin layers have been studied for memory applications, one transistor memory cell, and recently...

A sound field on a line or in a plane has an effectively limited spatial bandwidth determined by the temporal frequency. Similar can be said for sound fields from far-field sources when analyzed on circular and spherical apertures. Namely, for a given frequency and aperture size, a sound field is effectively composed of a finite number of circular or spherical harmonic components. Based on these two observations, it follows that if adequately sampled, sound fields...

Modern data storage systems are extremely large and consist of several tens or hundreds of nodes. In such systems, node failures are daily events, and safeguarding data from them poses a serious design challenge. The focus of this thesis is on the data reliability analysis of storage systems and, in particular, on the effect of different design choices and parameters on the system reliability. Data redundancy, in the form of replication or advanced erasure codes,...

The septation initiation network (SIN) in Schizosaccharomyces pombe regulates cytokinesis. Cdc7p encodes the first kinase in the core SIN pathway. In this study, I performed a genetic screen to identify novel regulators of the SIN pathway by isolating spontaneous revertants of cdc7-24 that displayed a cold-sensitive phenotype. The screen yielded a cold-sensitive allele of ppa2, the major PP2A catalytic subunit, and a mutant in ypa2, one of the two S. pombe PTPA orthologues. I characterised...

In the first place the behavior of (online) traders on markets is analyzed and modeled, and it is shown that the average investor behaves as a mean-variance optimizer in finance. Within this description, transaction costs play a key role in explaining observed investment patterns and in particular an important uncovered relation between average investment and portfolio value. As online investors take into account transaction costs in their investment strategy, they are also sensitive to high...

The earth's surface is permanently exposed to the atmosphere and accordingly to strong wind forces in many regions. Aerodynamic entrainment, transport and redeposition of sand, soil or snow are able to considerably reshape the surface morphology and influence the environment in areas ranging from deserts to polar regions. Even in moderate climate zones, entrainment and transport of dust, particulate matter and pollen or seeds by wind may have a strong impact on the local atmosphere...

Mammalian cell cultures have become a major topic of research in the biopharmaceutical industry. This kind of cells requires specific conditions to grow. In this thesis, we study the hydrodynamics of orbitally shaken reactors (OSR), a recently introduced kind of bioreactors for mammalian cell cultures that represents a simple to operate and cheap alternative to commonly used reactors such as stirred tanks. OSRs can provide suitable conditions for small scale cell cultures, however a deeper...

Landslides belong to the most important natural hazards in all mountainous regions. It is wellknown that water is one of the major triggers of landslides. Numerous landslide studies discuss different effects that water may have on slope stability: decreasing suction, rising groundwater table and subsequent increasing pore water pressure, groundwater exfiltration from the bedrock, seepage erosion, hydraulic uplift pressure from below the landslide, and influence of water on the plasticity of the landslide. Geological and...

The goal of this thesis is to study an anisotropic adaptive algorithm for transonic compressible viscous flow around an airwing. A convection-diffusion model problem is considered, an anisotropic a posteriori error estimator for the H1 semi-norm of the error is derived. The equivalence between the error and the estimator is proved, which provides the efficiency and the reliability of this estimator. A goal oriented anisotropic a posteriori error estimator is introduced. The equivalence with the...

Cryptographic hash functions are used in many cryptographic applications, and the design of provably secure hash functions (relative to various security notions) is an active area of research. Most of the currently existing hash functions use the Merkle-Damgård paradigm, where by appropriate iteration the hash function inherits its collision and preimage resistance from the underlying compression function. Compression functions can either be constructed from scratch or be built using well-known cryptographic primitives such as a...

In this thesis work we investigate the heat transfer through the electrical insulation of superconducting cables cooled by super fluid helium. The cable insulation constitutes the most severe barrier for heat extraction from the superconducting magnets of the CERN Large Hadron Collider (LHC). We performed an experimental analysis, a theoretical modeling and a fundamental research to characterize the present LHC insulation and to develop new ideas of thermally enhanced insulations. The outcome of these studies...

The shortage of natural resources, rising energy demands and global warming have created an urgent need for more efficient energy conversion devices and different energy resources to achieve a more sustainable and efficient economy. Solid Oxide Fuel Cells (SOFC) are one of the most promising devices for the direct conversion from chemical to electrical energy in conjunction with high system efficiencies. Micro-tubular SOFC have been investigated since roughly 15 years. In contrast to planar systems,...

MicroRNAs (miRNAs) are small non-coding RNAs involved in post-transcriptional regulation of gene expression. The first miRNA was discovered less than 20 years ago in the context of studying Caenorabditis elegans development. The discovery of the second miRNA only 10 years ago led to knowledge that these small regulatory RNAs are widely expressed in eukaryotic organisms and involved in almost all cellular processes. It is generally believed that miRNAs predominantly bind to complementary sequences within the...