Universität Stuttgart
Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1
Browse
Search Results
Item Open Access Rigorous compilation for near-term quantum computers(2024) Brandhofer, Sebastian; Polian, Ilia (Prof.)Quantum computing promises an exponential speedup for computational problems in material sciences, cryptography and drug design that are infeasible to resolve by traditional classical systems. As quantum computing technology matures, larger and more complex quantum states can be prepared on a quantum computer, enabling the resolution of larger problem instances, e.g. breaking larger cryptographic keys or modelling larger molecules accurately for the exploration of novel drugs. Near-term quantum computers, however, are characterized by large error rates, a relatively low number of qubits and a low connectivity between qubits. These characteristics impose strict requirements on the structure of quantum computations that must be incorporated by compilation methods targeting near-term quantum computers in order to ensure compatibility and yield highly accurate results. Rigorous compilation methods have been explored for addressing these requirements as they exactly explore the solution space and thus yield a quantum computation that is optimal with respect to the incorporated requirements. However, previous rigorous compilation methods demonstrate limited applicability and typically focus on one aspect of the imposed requirements, i.e. reducing the duration or the number of swap gates in a quantum computation. In this work, opportunities for improving near-term quantum computations through compilation are explored first. These compilation opportunities are included in rigorous compilation methods to investigate each aspect of the imposed requirements, i.e. the number of qubits, connectivity of qubits, duration and incurred errors. The developed rigorous compilation methods are then evaluated with respect to their ability to enable quantum computations that are otherwise not accessible with near-term quantum technology. Experimental results demonstrate the ability of the developed rigorous compilation methods to extend the computational reach of near-term quantum computers by generating quantum computations with a reduced requirement on the number and connectivity of qubits as well as reducing the duration and incurred errors of performed quantum computations. Furthermore, the developed rigorous compilation methods extend their applicability to quantum circuit partitioning, qubit reuse and the translation between quantum computations generated for distinct quantum technologies. Specifically, a developed rigorous compilation method exploiting the structure of a quantum computation to reuse qubits at runtime yielded a reduction in the required number of qubits of up to 5x and result error by up to 33%. The developed quantum circuit partitioning method optimally distributes a quantum computation to distinct separate partitions, reducing the required number of qubits by 40% and the cost of partitioning by 41% on average. Furthermore, a rigorous compilation method was developed for quantum computers based on neutral atoms that combines swap gate insertions and topology changes to reduce the impact of limited qubit connectivity on the quantum computation duration by up to 58% and on the result fidelity by up to 29%. Finally, the developed quantum circuit adaptation method enables to translate between distinct quantum technologies while considering heterogeneous computational primitives with distinct characteristics to reduce the idle time of qubits by up to 87% and the result fidelity by up to 40%.Item Open Access Science planning for the DESTINY+ Dust Analyzer : leveraging the potential of a space exploration instrument(2024) Sommer, Maximilian; Srama, Ralf (Apl. Prof. Dr.-Ing.)The DESTINY+ Dust Analyzer (DDA) is a highly sophisticated planetary science instrument to provide cutting-edge in-situ characterization of individual cosmic dust grains, with respect to their composition, as well as their physical and dynamical properties. As such, it constitutes a critical component of the upcoming JAXA mission DESTINY+, which is scheduled to launch in 2025. After a three-year cruise phase, the spacecraft will perform a flyby of the target asteroid 3200 Phaethon, with the goal of observing the enigmatic Geminids parent body with two camera instruments, and sampling particles released from its surface with the DDA. Until that flyby, DESTINY+ will execute a highly diverse, ion-engine-driven flight plan that allows DDA to extensively study the dust environments of the Earth, Moon, and interplanetary space - a breadth of science opportunities that is unique to this mission and instrument. This dissertation provides a comprehensive study of the dust types and phenomena possibly encountered by DDA during its journey to Phaethon and applies the principles and methods of science planning to prepare for the operational phase of the mission. The work synthesizes technical considerations and scientific analyses of relevant cosmic dust populations, aiming to optimize DDA’s scientific potential. Detailed examinations of spacecraft and instrument factors, such as the dynamic spacecraft attitude during the near-Earth phase or the instrument’s two-axis pointing mechanism, lay the groundwork for the scientific planning. The thorough analysis of known (and lesser known) dust populations in the inner solar system and of previous relevant measurements by other dust instruments form the core of the study. Finally, the findings are consolidated into a draft science activity plan for the entire mission, as well as exemplary pointing timelines to be executed by the instrument for optimal scientific return. The latter is accomplished with the DOPE tool, which aids in intuitive and efficient planning of DDA observations, having been developed in the scope of this project. The presented work builds the foundation for the scientific operations of DDA, setting it up for a successful and scientifically impactful mission. The findings of this study also provide a valuable perspective for other ventures of in-situ dust astronomy to the inner solar system and contribute to the field of cosmic dust as a whole.Item Open Access Investigation of the impact of different scale-up dependent stimuli on metabolism and population heterogeneity in Corynebacterium glutamicum(2024) Eilingsfeld, Adrian; Takors, Ralf (Prof. Dr.-Ing.)This thesis investigates the impact of elevated carbon dioxide levels on population heterogeneity in Corynebacterium glutamicum, a widely used industrial production host. Through a series of experiments involving cultivation at varying CO2 partial pressures, flow cytometry, and analysis of DNA content, the research reveals that increased CO2 exerts significant selection pressure, affecting growth rates and cell aggregation tendencies. Key findings indicate that higher growth rates speed up DNA replication levels, while elevated CO2 levels slow them down. The results contribute to understanding how CO2 influences population dynamics, providing insights for optimizing industrial bioprocesses and support Corynebacterium glutamicum as a robust production strain.Item Open Access Über die Lösung der Navier-Stokes-Gleichungen mit Hilfe der Moore-Penrose-Inversen des Laplace-Operators im Vektorraum der Polynomkoeffizienten(2024) Große-Wöhrmann, Bärbel; Resch, Michael (Prof. Dr.-Ing.)Die bekannten numerischen Standard-Verfahren zur Lösung partieller Differentialgleichungen basieren auf einer räumlichen Diskretisierung des Berechnungsgebiets. Ihre Performance und Skalierbarkeit auf modernen massiv-parallelen Höchstleistungsrechnern ist von der Verfügbarkeit effizienter numerischer Verfahren zur Lösung linearer Gleichungssysteme abhängig. Angesichts grundlegender Herausforderungen erscheint die Entwicklung neuer Lösungsansätze sinnvoll. Ich stelle in dieser Arbeit einen Polynomansatz zur Lösung partieller Differentialgleichungen vor, der nicht auf einer räumlichen Diskretisierung beruht und mit Hilfe der Moore-Penrose-Inversen des Laplace-Operators die Entkopplung der Navier-Stokes-Gleichungen ermöglicht. Dabei ist der Grad der Polynome nicht grundsätzlich beschränkt, so dass eine hohe räumliche Auflösung erreicht werden kann.Item Open Access Development and investigation of protonic ceramic cells for hydrogen production at intermediate temperatures(2024) Zheng, Haoyu; Thess, André (Prof. Dr.)Item Open Access Biophysical validity of reduced soft tissue modelling in neuro-musculoskeletal simulations(Stuttgart : Institut für Modellierung und Simulation Biomechanischer Systeme, Computational Biophysics and Biorobotics, 2024) Hammer, Maria; Schmitt, Syn (Prof. Dr. rer. nat.)In the past decades, neuro-musculoskeletal simulations have become a key technology in biomechanical research, and are increasingly utilised to support clinical decision-making processes, evaluate occupational safety, and facilitate the design of assistive devices. The importance of precise and physiologically valid simulations cannot be emphasised enough across all application fields. However, achieving this accuracy becomes particularly challenging when developing reduced descriptions of soft tissue compartments, where the degrees of freedom and structural complexity are condensed into predominantly phenomenological or homogenised sub-models. Furthermore, it necessitates a deep understanding of the dynamic interplay among different soft tissue elements in the body, which, in turn, requires a high level of reliability and confidence in the employed underlying model. In order to ensure the usefulness of the models, it is crucial to strike a balance between the level of detail and the limitations arising from simplifications. This involves considering various possibilities to validate the mechanical behaviour of each sub-model individually and the overall model as a whole. The scientific aim of this dissertation is to investigate the load sharing of soft tissue compartments at the example of the human lumbar spine during active motions by using predictive simulations. To set the basis for this kind of research, the main objective is to create, calibrate, verify and validate a detailed neuro-musculoskeletal model, which gives rise to three research questions that guide this thesis: (1) How can (and should) common approaches for reduced single tissue models be improved to increase the level of biomechanical validity and physical verification of both the sub-models themselves, and the multibody models composed of them? (2) Which sub-structures are of biomechanical relevance for estimating internal forces and torques on a full-body scale? (3) Which validation methods need to be considered during the development of a physiological spine model, and how can the corresponding simulation results be assessed? This thesis encompasses five journal articles studies, contributing to the different aspects of the three research questions. More precisely, Contribution I addresses research questions (1) and (3) regarding how to enhance biomechanical validity of muscle routing in multibody models by introducing a novel algorithm for redirecting muscle paths. With this method, the physiological accuracy of muscle length and moment arm representations within Hill-type models can be refined, particularly for muscles spanning multiple joints with multiple degrees of freedom. Contribution II focuses on the intuitive assessment of the relative motion between two vertebral bodies. Using a newly developed method for graphical representation of finite helical axes, which fully encapsulates the information about rotation and translation of the relative motion between two vertebral bodies, extensive data sets were effectively presented through clustering methods. This work, thereby, contributes to research question (3) since the finite helical axis can serve as measure for model validation. Contribution III presents a comprehensive simulation study and introduces a detailed generic model of the human thoracolumbar spine. This generic model includes several hundred muscle and ligament strands, along with intervertebral joints modelled as free joints constrained only by intervertebral discs. Notably, the model is able to balance gravity in an upright position without additional constraints and with only a physiologically low level of muscle stimulation. The description of model development and validation significantly contributes to research question (3). Moreover, the analysis of load sharing among the three soft tissue sub-structures, namely ligaments, muscles, and intervertebral discs, revealed an almost equal distribution of bending moment during forward flexion, offering insights for research question (2). Additionally, this paper introduces a workflow for geometric individualisation of the generic model based on landmark data obtained from computed-tomography scans. The investigation of subject-specific forces and torques exhibits significant inter- and intrapersonal differences in the lumbar load distribution. These findings deepen the biomechanical understanding of complex interactions within the spine. Contribution IV explores the influence of neglecting entire passive tissue groups, precisely intervertebral discs and ligaments, which is common practice in many spine models. Using an inverse dynamic approach, this study contributes to research questions (2) and (3) by providing cross-platform validation. The examination of kinematic models that exclude ligament and intervertebral disc tissues reveals a tendency for highly overestimated muscle forces. These findings highlight the importance of considering all relevant soft tissue structures in computational models to ensure accurate muscle force estimations. Lastly, the Contribution V directly addresses research question (1) by tackling the challenge of incorporating energy conservation in surrogate models representing the elastic mechanical responses of intervertebral discs. It introduces a novel approach that surpasses currently used elastic models in terms of precision, coupling of different degrees of freedom, and nonlinear behaviour. This advancement increases the accuracy and physical validity while also enabling the individualisation of the mechanical behaviour of subject- and level-specific intervertebral disc geometry. In order to achieve the aforementioned aims and answer the research questions, a multibody simulation framework has been extended by the novel algorithms developed within the scope of this thesis. These algorithms improve the geometric quality of soft tissue representations and refine accuracy of predicted internal forces and torques while preserving basic physical principles. Furthermore, a pre-processor typically used to scale population-based models has been modified to serve two additional purposes. On the one hand, the existing code was advanced to create geometrically individualised models based on landmark positions derived from computed-tomography scans. On the other hand, the functionality to generate models compatible with another widely used multibody simulation tool was included. Having identical models facilitates cross-platform validation, and allows to test muscle, ligament and intervertebral disc sub-models, and whole thoracolumbar spine models in different scenarios. In summary, this thesis enhances existing methods and provides new approaches to create more accurate neuro-musculoskeletal models capable of predicting internal forces and kinematics. The detailed spine model developed during this thesis serves as a valuable foundation for future investigations, including subject-specific, non-invasive implant testing, and exploration of the rotation axes in complex movements and post-surgical scenarios.Item Open Access Experiments on laminar separation bubbles under inflow conditions of atmospheric turbulence(2024) Greiner, Michael; Krämer, Ewald (Prof. Dr.-Ing.)Natural laminar flow (NLF) airfoils have been largely responsible for the performance advances of today's general aviation aircraft and wind turbines. In the design of these airfoils, atmospheric turbulence has received little attention, although specific atmospheric conditions are often present during their operation. One reason for this is that the effect of atmospheric turbulence on the boundary layer, and in particular on laminar separation bubbles (LSB), has only been possible to be estimated from experience. This study addresses this issue based on the example of sailplanes. In the first part of this work, the inflow conditions during typical cross-country flights of sailplanes are studied. Avoiding laminar separation bubbles at high lift coefficients is one of the challenges in the design of NLF airfoils. Therefore, the focus is on circling in thermals and thus on the convective boundary layer of the atmosphere. Continuous measurements of free-stream turbulent velocity fluctuations have been made during cross-country flights, with resolutions well into the dissipation range of the turbulence spectrum. The second part studies the effect of free-stream turbulence on mid-chord laminar separation bubbles that may appear on the upper surface of low speed NLF airfoils typically used in general aviation or wind turbines. For this purpose, the relevant conditions found in the first part were transferred to the Laminar Wind Tunnel (Re = 880,000, Tu = 0.01%-0.38%) for detailed experimental investigation. A distinction is made between small-scale turbulence, which acts via the classical vortex receptivity, and large-scale turbulence, which corresponds to inflow angle fluctuations and acts on the evolution of the boundary layer via the transient change in stability properties. The insights gained in flight permit the modelling of the free stream turbulence to be expected in flight through the convective atmosphere. The results of the wind tunnel experiments allow to better regard these turbulent conditions during the design of NLF airfoils.Item Open Access From stress to acclimation : a systems biology look on the life of Saccharomyces cerevisiae in industrial bioreactors(2024) Minden, Steven; Takors, Ralf (Prof. Dr.-Ing.)Carbon limitation is a fundamental feeding strategy in commercial fermentations guaranteeing efficient substrate-to-product conversion. However, industrial reaction volumes often prevent a microbe from performing optimally. One common source of interference is insufficient mixing resulting in the formation of concentration gradients. For instance, faster microbial consumption versus convective supply depletes the highly diluted limiting substrate locally. The industrial workhorse Saccharomyces cerevisiae (S. cerevisiae) naturally possesses adaptive mechanisms to cope with substrate depletion. Whether triggered response mechanisms benefit strain performance is doubtful, given that enough substrate is present in an industrial carbonlimited process on average. On the contrary, unnecessary or futile adaptation mechanisms often cause unexpected microbial behavior on large scales. Exploring and elucidating this behavior is the focal point of this thesis. The presented case study employs a stimulus-response approach mimicking a baker’s yeast fermentation snapshot featuring non-ideal starvation zones. In brief, glucose-limited chemostats with two-minute intervals of stopped feeding induce transitions between limitation and starvation. Metabolomic and transcriptomic measurements enable a systems biology analysis of either non-adapted or stimulus-adapted yeasts. One part of this study investigates the haploid laboratory strain CEN.PK113-7D under aerobic conditions. Another part reports gene expression dynamics of the diploid industrial strain Ethanol RedTM under anaerobic conditions. Both strains display robust growth under the tested conditions at the cost of tactic and strategic investments. The laboratory yeast responds to a 110 μmol·L-1 glucose gradient with a modified energy and redox homeostasis. Non-adapted cells perceive this stimulus as a threat, as evidenced by a futile triggering of the environmental stress response causing transient growth rate reduction and increased maintenance demand. Complete adaptation evokes a distinct ‘bioreactor phenotype’ characterized by increased growth capacities and repressed stress response. Results obtained with Ethanol RedTM confirm this stress defense-growth trade-off to be a conserved implication in bioprocesses with fluctuating carbon supply. Altogether, the findings presented in this thesis contribute to a fundamental understanding of how S. cerevisiae operates in heterogeneous commercial-scale fermentations. Finally, the gained knowledge reveals optimization targets for both strain engineering and bioprocess development.Item Open Access Extracting thermodynamic information from local composition fluctuations in solids : extended theory and its application to simulated and experimental atom probe data(2024) Zheng, Jianshu; Schmitz, Guido (Prof. Dr. Dr. h.c.)In case of liquids, thermodynamic fluctuation theory has been applied for decades to obtain direct thermodynamic information (e.g. miscibility gap, mixing/demixing tendencies, critical solution temperature) from local composition fluctuations. Recently, this theory has been extended to solids by introducing an additional elastic work term between the evaluated sub-system and the entire system, which does not arise in liquids. This extended theory has been verified via atomistic simulations in an exemplary Cu-Ni embedded-atom system using Monte Carlo simulations at a fixed temperature over the entire composition range. Composition fluctuations in the system that are represented by the relative variance of the composition histogram are tracked in various-sized subvolumes over time, revealing a systematic dependence on the size of the evaluation volume due to interface effects. Nonetheless, these surface effects can be excluded by extrapolation to an infinitely large subvolume, leading to perfect agreement with the prediction by the extended theory. Thus, the recovery of the Gibbs free energy of mixing from evaluation of the fluctuations is possible also in the case of solids. Atom Probe Tomography (APT) delivers combined high-resolution chemical and sub nanometric three-dimensional (3D) spatial information, and is therefore the perfect technique to determine local composition fluctuations by using spatial frequency distribution analysis in practical applications. In this work, the applicability of the extended theory is tested on the Cu-Ni alloy and ionic CuO systems via frequency distribution analysis on simulated and experimental atom probe data, and eventually compared to available phase diagram data, thereby proving the validity of extracting the Gibbs free energy from local composition fluctuations in solids. In the first part of this work, the spatial frequency distribution analysis is applied to simulated crystals of long-range ordered L12 and monoclinic structures numerically modeled disregarding thermodynamic interaction between atoms. The relative variance displays an evaluation size dependence, but goes to zero (i.e. no composition fluctuations) if extrapolated to sufficiently large evaluation size. This result meets the expectation as no composition fluctuations should be found in perfectly ordered materials. In the second part, this approach is applied to simulated alloys including thermodynamic interactions. Cu-Ni alloys of various compositions are firstly equilibrated using a Monte Carlo simulation with an embedded-atom potential. Afterwards, the alloys are numerically field-evaporated by the evaporation simulation package TAPSim and the 3D coordinates of the field-evaporated sample are recovered through the usual reconstruction algorithm. Throughout this process, two practical considerations related to the atom probe technique have been effectively addressed: i) The newly developed model tackles the challenges associated with the limited detection efficiency and allows the reconstruction of the relative variance for the bulk system from limited atom probe data scaled by detection efficiency; ii) An additional correction term which is proportional to the evaluation size and magnitude of composition inhomogeneity is introduced. It enables the separation of thermodynamic fluctuations from artificial composition variations inherent in the experimental method based on their different size dependence, so that the extrapolation still recovers the intrinsic thermodynamic composition fluctuations. In the third part, this approach is finally applied to experimental atom probe data. The Cu-Ni alloys are prepared by induction melting of pure Cu and Ni and CuO thin films are prepared via ion beam sputtering. After sufficient equilibration by heat treatment, Cu-Ni and CuO specimens for the APT measurement are fabricated via focused ion beam cutting. By experimentally conducting the same approach as developed theoretically, local composition fluctuations are obtained for both Cu-Ni and CuO systems. After the elastic work term correction, the CALPHAD-style parametrization of the Gibbs free energy is obtained by linking it to the measured local composition fluctuations. In this way, the Cu-Ni miscibility gap is successfully reconstructed from data measured at elevated temperature (800 K), and the resulting phase diagram is in agreement with the CALPHAD results in literature. The frequency distribution analysis of the reconstructed CuO tends to approach the binomial distribution (i.e. behavior of random alloys), since field evaporation of molecules (e.g. CuO, Cu2O) but not only single ions destroys the long-range order structure and deteriorates the resolution in the reconstruction. This effect indicates the partial limitation of this method on ionic compounds. In summary, the present work has systematically extended and proven the application of the composition fluctuation theory to metallic alloys, and makes it possible to directly access thermodynamic information from local composition fluctuations. APT is demonstrated as a new technique to extract direct thermodynamic information, and a general route from the APT measurement to the Gibbs free energy is presented. Given that the composition fluctuation is a local property and only a substantially short diffusion length for equilibration is required, this represents an efficient methodology especially for systems where slow diffusion hinders the establishment of large scale thermodynamic equilibrium. APT, as a sub-nanometric resolution technique, promises to extract more accurate thermodynamic information in a wider temperature composition range. Besides, this study advances our understanding of the size dependence in the traditional frequency distribution analysis. It is pointed out that potential misinterpretation could happen and is presented in literature, if a sample evaluation size in the frequency distribution analysis is arbitrarily chosen. Only the bulk relative variance obtained via extrapolation to infinitely large sub-system is thermodynamically meaningful.Item Open Access Synthese von Tosyl-Samroiyotmycin und Samroiyotmycin-Derivaten : biologische Eigenschaften und neue Wege zum Aufbau der (2E,4E)-Dienon-Einheit(2024) Kolb, Benedikt; Laschat, Sabine (Prof. Dr.)