Bøger udgivet af Karlsruher Institut Fur Technologie

The object-based stochastic approach in facies modelling is important in the construction of geologically consistent 3-D reservoir models and in constraining the distribution of petrophysical properties. Tortuosity factor, facies, porosity and cementation factor constitute major uncertainties in the generated 3-D static model of the Niger Delta Basin. Reservoir quality in the Dahomey Basin is mainly controlled by detrital matrix, carbonate cement, and iron oxide and iron oxyhydroxide cements.

This study systematically investigates the representation of warm conveyor belts (WCBs) in large reforecast data sets of different numerical weather prediction models and evaluates the role of WCBs for the onset and life cycle of Atlantic-European weather regimes. The results emphasize the importance of accurate forecast of WCBs for sub-seasonal prediction on time scales beyond two weeks and tie the low forecast skill of blocked weather regimes over Europe to misrepresented WCBs.

Modern production systems have become more flexible and agile. For them, a suitable control and planning method is needed. Agent-based systems offer the required characteristics. The contributions of these work are a remodeling of the Shifting Bottleneck heuristic to include limited buffers, the development of a decentralized multi-agent system for production planning, and the adaptation of the heuristic to the agent system. It concludes with evaluations of real-world production systems.

In this work a process simulation model identifies the most profitable German biogas plant types and sizes. Small manure and large-scale biowaste plants are currently the most economically attractive installations whereas the valorization of energy crops turns out to be unprofitable. Future developments are assessed with the help of a regional optimization model under constraints. Capacity expansion concerns small-scale manure and biowaste installations rather than plants based on energy crops.

An early detection and diagnosis of atrial fibrillation sets the course for timely intervention to prevent potentially occurring comorbidities. Electrocardiogram data resulting from electrophysiological cohort modeling and simulation can be a valuable data resource for improving automated atrial fibrillation risk stratification with machine learning techniques and thus, reduces the risk of stroke in affected patients.

Photonic integrated circuits (PIC) become increasingly important for numerous applications. Mass production of PIC has become widely available, but large-volume low-cost photonic packaging still represents a challenge. Additive micro-fabrication of free-form optical coupling structures is discussed as a concept to overcome this technology gap. Multi-photon 3D-lithography is used to fabricate dielectric waveguides ("photonic wire bonds", PWB) as well as facet-attached microlenses (FaML).

Materials of industrial interest often show a complex microstructure which directly influences their macroscopic material behavior. For simulations on the component scale, multi-scale methods may exploit this microstructural information. This work is devoted to a multi-scale approach for brittle materials. Based on a homogenization result for free discontinuity problems, we present FFT-based methods to compute the effective crack energy of heterogeneous materials with complex microstructures.

Computational homogenization permits to capture the influence of the microstructure on the cyclic mechanical behavior of polycrystalline metals. In this work we investigate methods to compute Laguerre tessellations as computational cells of polycrystalline microstructures, propose a new method to assign crystallographic orientations to the Laguerre cells and use Bayesian optimization to find suitable parameters for the underlying micromechanical model from macroscopic experiments.

Proposed in the early 1990s, the enhanced assumed strain (EAS) method is one of the probably most successful mixed finite element methods for solid mechanics. This cumulative dissertation gives a comprehensive overview of previous publications on that method and covers recent improvements for EAS elements. In particular, we describe three key issues of standard EAS elements and develop corresponding solutions.

Warm conveyor belts (WCBs) are weather systems that substantially modulate the large-scale extratropical circulation. As they can amplify forecast errors and project them onto the Rossby wave pattern, they are of high relevance for numerical weather prediction. This work elaborates on two aspects of WCBs in the context of ensemble forecasts: (1) sensitivities of WCBs to the representation of initial condition and model uncertainties, and (2) the role of WCBs for forecast error growth.

Hybrid perovskite photovoltaics could play a vital role in future¿s renewable energy production. However, there are still severe challenges when scaling the technology. In this work, perovskite solution films drying in laminar and slot-jet air flows are investigated extensively by optical in situ characterization. The main results are a quantitative model of perovskite drying dynamics and a novel in situ imaging technique ¿ yielding valuable predictions for large-scale perovskite fabrication.

This work proposes a new numerical approach for analyzing the behavior of fiber-reinforced materials, which have gained popularity in various applications. The approach combines theories and methods to model the fracture behavior of the polymeric matrix and the embedded fibers separately, and includes a modified plasticity model that considers the temperature-dependent growth of voids. Tests are conducted to explore different types and sequences of failure in long fiber-reinforced polymers.

Complementary to scattering techniques, scanning tunnelling microscopy provides atomic-scale real space information about a material's electronic state of matter. State-of-the-art designs of a scanning tunnelling microscope (STM) allow measurements at millikelvin temperatures with unprecedented energy resolution. Therefore, this instrument excels in probing the superconducting state at low temperatures and especially its local quasiparticle excitations as well as bosonic degrees of freedom.

Ein wellenleiterbasierter Sensorchip wird demonstriert, der für Point-of-Care-Anwendungen geeignet ist. Der Biosensor wird mit Hilfe eines mathematischen Modells entworfen, mit dem die Sensitivität der Wellenleiter untersucht wird. Für die Lichteinkopplung in die Wellenleiter wird erstmalig eine neue Klasse von integrierten Laserquellen für sichtbare Wellenlängen untersucht. Die Funktionsfähigkeit des wellenleiterbasierten Biosensorchips durch Detektionsexperimente erfolgreich nachgewiesen. A waveguide-based sensor chip is demonstrated that is suitable for point-of-care applications. The biosensor is designed using a mathematical model to investigate the sensitivity of the waveguides. A new class of integrated laser sources for visible wavelengths is being investigated for the first time for light coupling into the waveguides. The functionality of the waveguide-based biosensor chip is successfully demonstrated by detection experiments.

This work presents three advances to scale SNSPDs from few-pixel devices to large detector arrays: atomic layer deposition for the fabrication of uniform superconducting niobium nitride films of few-nanometer thickness, a frequency-multiplexing scheme to operate multiple detectors with a reduced number of lines, and the integration of SNSPDs with free-form polymer structures to achieve efficient optical coupling onto the active area of the detectors.

Effective mechanical properties of fiber-reinforced composites strongly depend on the microstructure, including the fibers' orientation. Studying this dependency, we identify the variety of fiber orientation tensors up to fourth-order using irreducible tensors and material symmetry. The case of planar fiber orientation tensors, relevant for sheet molding compound, is presented completely. Consequences for the reconstruction of fiber distributions and mean field homogenization are presented.

Business processes and information systems evolve constantly and affect each other in non-trivial ways. Aligning security requirements between both is a challenging task. This work presents an automated approach to extract access control requirements from business processes with the purpose of transforming them into a) access permissions for role-based access control and b) architectural data flow constraints to identify violations of access control in enterprise application architectures.

Microwave-assisted alkaline hydrolysis of PET can be 20 times faster and at lower temperatures. This work presents a novel industrial microwave applicator at 2.45 GHz with homogeneous distribution to support this reaction, which allows an efficient and continuous operation. In addition, an innovative dielectric and calorimetric measurements setup is presented. Furthermore, the modelling of the reaction kinetics based on the measured dielectric parameters is presented.

This work presents the development of a new sub-THz source for the generation of trains of coherent high-power ultra-short pulses at 263 GHz via passive mode-locking of two coupled helical gyro-TWTs. For the first time, it is shown that the operation of such passive mode-locked helical gyro-TWTs in the hard excitation regime is of particular importance to reach the optimal coherency of the generated pulses. This could be of particular interest for some new time-domain DNP-NMR methods.

A Flywheel Energy Storage System (FESS) can rapidly inject or absorb high amounts of active power in order to support the grid, following abrupt changes in the generation or in the demand, with no concern over its lifetime. The work presented in this book studies the grid integration of a high-speed FESS in low voltage distribution grids from several perspectives, including optimal allocation, sizing, modeling, real-time simulation, and Power Hardware-in-the-Loop testing.

With the further development of automated driving, the functional performance increases resulting in the need for new and comprehensive testing concepts. This doctoral work aims to enable the transition from quantitative mileage to qualitative test coverage by aggregating the results of both knowledge-based and data-driven test platforms. The validity of the test domain can be extended cost-effectively throughout the software development process to achieve meaningful test termination criteria.

This work presents model-based algorithmic approaches for interference-invariant time delay estimation, which are specifically suited for the estimation of small time delay differences with a necessary resolution well below the sampling time. Therefore, the methods can be applied particularly well for transit-time ultrasonic flow measurements, since the problem of interfering signals is especially prominent in this application.