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FD-Modellierung und Analyse der seismischen Wellenausbreitung am Vøring Plateau im Kontext der CO-Sequestrierung in Offshore-Basaltformationen
Get PDFIn the present bachelor’s thesis, a seismic survey at the Vøring Plateau is simulated and subsequently
analyzed. For this purpose, the viscoelastic wave propagation is modeled using the SOFI2D software
based on the finite-difference method. The subsurface model underlying the modeling is created
from borehole data of the ODP Hole 642.
This work is carried out in cooperation with the Geomar Helmholtz Centre for Ocean Research
Kiel (GEOMAR) within the PERBAS research project (Permanent sequestration of gigatons of
CO2 in continental margin basalt deposits). The project aims at developing CO2 storage in offshore
basalt formations as a future CCS technology. Such basalt formations are abundantly present at
the Vøring Plateau. More specifically, a nearly 800 m thick basalt series consisting of 120 individual
basaltic lava flows interbedded by sedimentary layers, drilled at ODP Hole 642, is at the core of this
study. The evaluation of the modeling results and, in particular, the elaboration of the characteristic
wave field properties will be used by GEOMAR to optimize the acquisition geometry of a marine
3D seismic survey at the Vøring Plateau.
First, a one-dimensional subsurface model of the physical parameters wave velocities vp and vs,
bulk density ρ, and intrinsic seismic attenuation Q is created from the data of ODP Hole 642.
In the modeling with SOFI2D, solving the two-dimensional viscoelastic wave equation, synthetic
seismograms, simulating the use of ocean-bottom seismometers, are generated. These are then
analyzed in detail using the basic seismic reflection and refraction method. Visual representations
of the calculated wave field propagation serve as a guiding tool. A detailed characterization of the
properties of the wave field is performed.
The basalt series causes both a reflected and guided wave field in the modeling. The former generates
stronger signal amplitudes (about an order of magnitude stronger for comparable ray paths) and
allows for the imaging of deeper structures throughout the basalt series, while the observed head
waves are generated exclusively within the upper 250 m. The highly variable velocity and density
structure of the basalt series create a complex wave field characterized by superimpositions. This
limits the horizontal distance over which coherent reflective signals form, to 500 m or at most 1000 m
for all deeper structures. The conversion between P- and S-waves also plays a role, resulting in
different types of signals which are classified in the study. Multiple reflections are observed, with
the strongest ones originating from the sea surface causing a quasi-periodic repetition of the seismic
response of the subsurface. However, they do not limit the maximum depth that can be explored
with primary reflections for small offsets.
The findings of this study provide qualitative insights into the wave field characteristics, but due to
the limitations of the one-dimensional model, quantitative deviations are to be expected depending
on the specific location of GEOMAR’s planned seismic survey. This could be addressed by a
continuation of this work using a two-dimensional subsurface model
On the Sobolev Stability Threshold for the 2D MHD Equations with Horizontal Magnetic Dissipation
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vMF-Contact: Uncertainty-aware Evidential Learning for Probabilistic Contact-grasp in Noisy Clutter
Get PDFGrasp learning in noisy environments, such as occlusions, sensor noise, and out-of-distribution (OOD) objects, poses significant challenges. Recent learning-based approaches focus primarily on capturing aleatoric uncertainty from inherent data noise. The epistemic uncertainty, which represents the OOD recognition, is often addressed by ensembles with multiple forward paths, limiting real-time application. In this paper, we propose an uncertainty-aware approach for 6-DoF grasp detection using evidential learning to comprehensively capture both uncertainties in real-world robotic grasping. As a key contribution, we introduce vMF-Contact, a novel architecture for learning hierarchical contact grasp representations with probabilistic modeling of directional uncertainty as von Mises-Fisher (vMF) distribution. To achieve this, we analyze the theoretical formulation of the second-order objective on the posterior parametrization, providing formal guarantees for the model\u27s ability to quantify uncertainty and improve grasp prediction performance. Moreover, we enhance feature expressiveness by applying partial point reconstructions as an auxiliary task, improving the comprehension of uncertainty quantification as well as the generalization to unseen objects. In the real-world experiments, our method demonstrates a significant improvement by 39% in the overall clearance rate compared to the baselines. The code is available under: https://github.com/YitianShi/vMF-Contact
Amtliche Bekanntmachung. Bekanntmachungen. 2025,22: Studien- und Prüfungsordnung des Karlsruher Instituts für Technologie (KIT) für den Bachelorstudiengang Geophysik vom 05.03.2025
Get PDFMaxwell equations with localized internal damping: strong and polynomial stability
Get PDFWe study the Maxwell system with localized conductivity and the boundary conditions of a perfect conductor on a simply connected domain , assuming that there are no electric charges off the support of . For matrix-valued permittivity and permeability we show strong stability of the underlying semigroup by checking the spectral criteria of the Arendt–Batty–Lyubich–Vũ Theorem. If , is the cube and supp contains a strip, the semigroup is polynomially stable of rate . To derive this result, we establish the resolvent estimate of the Borichev–Tomilov Theorem using an orthonormal basis of eigenfunctions of the Maxwell operator for
A data fusion approach for combined Terrestrial Radar Interferometry (TRI) and Robotic Total Station (RTS) monitoring
Get PDFPrediction of Residual Dipolar Couplings in analyte molecules aligned by Poly--benzyl-L-glutamate
No full textNuclear magnetic resonance (NMR) spectroscopy is an essential tool for the determination of molecular structures. However, due to the identical chemical environment of enantiomers and to a lesser extent diastereomers, the determination of relative and especially absolute configuration remains challenging. A promising method is the measurement of residual dipolar couplings (RDCs), which arise due to the partial alignment of analyte molecule orientations by an alignment medium. If the alignment of chiral analyte molecules is caused by a chiral alignment medium, the measured RDCs between the enantiomers differ. Previous studies showed that an approximate prediction of RDCs suitable for the determination of relative configuration is possible in some cases. In the case of the absolute configuration however, only tentative evidence exists that the assignment of enantiomers based on the prediction of RDCs is feasible.
In this thesis, I use atomistic approaches for the development of computational schemes to predict the RDCs in small analyte molecules aligned by the poly--benzyl-L-glutamate (PBLG) alignment medium in (deuterated) chloroform. This includes the detailed description of the interactions between the analyte molecules and PBLG, which lead to partial alignment. One approach are Molecular Dynamics (MD) simulations with explicit solvent, which provide detailed insights into the alignment interactions and, most importantly, indeed succeed in the correct assignment of enantiomers for molecules with hydrogen bond donors by comparing the differences between RDCs. For these molecules, hydrogen bonds to PBLG are essential for the alignment and the enantiodiscrimination. However, there are molecules whose RDCs by themselves do not agree with experiment and the MD simulations are computationally expensive. For this reason, I study the binding free energies to PBLG and evaluate different interaction models, including implicit solvation models. Using them in Monte Carlo (MC) calculations showed a pure Coulomb potential between PBLG and the analyte molecule to result in the best agreement with experiment. For the analyte molecules with O–H hydrogen bond donor, the agreement is also significantly better than with the MD simulations, although the strength of the alignment is severely overestimated. The difference between enantiomers in the MC simulations is very small however, showing the full MD simulations to be necessary for the determination of the absolute configuration.
The methods developed in this thesis are thus a significant step for the prediction of RDCs, which in the future may be used for the design of new alignment media. Additionally, the demonstrated theoretical approach can be already applied for the distinction of enantiomers if the differences of the RDCs are large enough
On the estimation of stratospheric age of air from correlations of multiple trace gases
Get PDFThe stratospheric circulation is an important element in the climate system, but observational constraints are prone to significant uncertainties due to the low circulation velocities and uncertainties in available trace gas measurements. Here, we propose a method to calculate mean age of air as a measure of the circulation from observations of multiple trace gas species which are reliably measurable by satellite instruments, like trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), chlorodifluoromethane (HCFC-22), methane (CH4), nitrous oxide (N2O), and sulfur hexafluoride (SF6), and we show that this method works well in most of the lower stratosphere up to a height of about 25km. The method is based on the compact correlations of these gases with mean age. Methodological uncertainties include effects of atmospheric variability, non-compactness of the correlation, and measurement related effects inherent for satellite instruments. The multi-species age calculation method is evaluated in a model environment and compared against the actual model age from an idealized clock tracer. We show that combination of the six chosen species reduces the resulting uncertainty of derived mean age to below 0.3 years throughout most regions in the lower stratosphere. Even small-scale, seasonal features in the global age distribution can be reliably diagnosed. The new correlation method is further applied to trace gas measurements with the balloon-borne Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA-B) instrument. The corresponding deduced mean age profiles agree reliably with SF6-based mean age below about 22km and show significantly lower uncertainty ranges. Comparison between observation-based and model-simulated mean ages indicates a slow-biased circulation in the ERA5 reanalysis. Overall, the proposed mean age calculation method shows promise to substantially reduce the uncertainty in mean age estimates from satellite trace gas observations