TY - CONF
AU - Hetkämper, Tim
AU - Claes, Leander
AU - Henning, Bernd
ID - 31331
SN - 978-3-8007-5836-4
T2 - ITG-Fachbericht 303 - Sensoren und Messsysteme - Beiträge der 21. ITG/GMA-Fachtagung
TI - Schlieren imaging with fractional Fourier transform to visualise ultrasonic fields
ER -
TY - GEN
AB - Given a geometrically finite hyperbolic surface of infinite volume it is a
classical result of Patterson that the positive Laplace-Beltrami operator has
no $L^2$-eigenvalues $\geq 1/4$. In this article we prove a generalization of
this result for the joint $L^2$-eigenvalues of the algebra of commuting
differential operators on Riemannian locally symmetric spaces $\Gamma\backslash
G/K$ of higher rank. We derive dynamical assumptions on the $\Gamma$-action on
the geodesic and the Satake compactifications which imply the absence of the
corresponding principal eigenvalues. A large class of examples fulfilling these
assumptions are the non-compact quotients by Anosov subgroups.
AU - Weich, Tobias
AU - Wolf, Lasse Lennart
ID - 31189
T2 - arXiv:2205.03167
TI - Absence of principal eigenvalues for higher rank locally symmetric spaces
ER -
TY - BOOK
ED - Tophinke, Doris
ID - 30946
TI - Konjunktiv gebrauchen
ER -
TY - JOUR
AB - Optical geometric phase encoded by in-plane spatial orientation of microstructures has promoted the rapid development of numerous functional meta-devices. However, pushing the concept of the geometric phase toward the acoustic community still faces challenges. In this work, we utilize two acoustic nonlocal metagratings that could support a direct conversion between an acoustic plane wave and a designated vortex mode to obtain the acoustic geometric phase, in which an orbital angular momentum conversion process plays a vital role. In addition, we realize the acoustic geometric phases of different orders by merely varying the orientation angle of the acoustic nonlocal metagratings. Intriguingly, according to our developed theory, we reveal that the reflective acoustic geometric phase, which is twice the transmissive one, can be readily realized by transferring the transmitted configuration to a reflected one. Both the theoretical study and experimental measurements verify the announced transmissive and reflective acoustic geometric phases. Moreover, the reconfigurability and continuous phase modulation that covers the 2π range shown by the acoustic geometric phases provide us with the alternatives in advanced acoustic wavefront control.
AU - Liu, Bingyi
AU - Zhou, Zhiling
AU - Wang, Yongtian
AU - Zentgraf, Thomas
AU - Li, Yong
AU - Huang, Lingling
ID - 31480
IS - 21
JF - Applied Physics Letters
KW - Physics and Astronomy (miscellaneous)
SN - 0003-6951
TI - Experimental verification of the acoustic geometric phase
VL - 120
ER -
TY - JOUR
AU - Baswana, Surender
AU - Gupta, Shiv
AU - Knollmann, Till
ID - 31479
JF - Algorithmica
KW - Applied Mathematics
KW - Computer Science Applications
KW - General Computer Science
SN - 0178-4617
TI - Mincut Sensitivity Data Structures for the Insertion of an Edge
ER -
TY - GEN
AU - Kramer, Paul
ID - 31485
TI - On Transforming Lattice-Based Cryptography to the Ring Setting
ER -
TY - JOUR
AB - Carbon fiber reinforced plastics (CFRPs) gained high interest in industrial applications because of their excellent strength and low specific weight. The stacking sequence of the unidirectional plies forming a CFRP laminate, and their thicknesses, primarily determine the mechanical performance. However, during manufacturing, defects, e.g., pores and residual stresses, are induced, both affecting the mechanical properties. The objective of the present work is to accurately measure residual stresses in CFRPs as well as to investigate the effects of stacking sequence, overall laminate thickness, and the presence of pores on the residual stress state. Residual stresses were measured through the incremental hole-drilling method (HDM). Adequate procedures have been applied to evaluate the residual stresses for orthotropic materials, including calculating the calibration coefficients through finite element analysis (FEA) based on stacking sequence, laminate thickness and mechanical properties. Using optical microscopy (OM) and computed tomography (CT), profound insights into the cross-sectional and three-dimensional microstructure, e.g., location and shape of process-induced pores, were obtained. This microstructural information allowed for a comprehensive understanding of the experimentally determined strain and stress results, particularly at the transition zone between the individual plies. The effect of pores on residual stresses was investigated by considering pores to calculate the calibration coefficients at a depth of 0.06 mm to 0.12 mm in the model and utilizing these results for residual stress evaluation. A maximum difference of 46% in stress between defect-free and porous material sample conditions was observed at a hole depth of 0.65 mm. The significance of employing correctly calculated coefficients for the residual stress evaluation is highlighted by mechanical validation tests.
AU - Wu, Tao
AU - Kruse, Roland
AU - Tinkloh, Steffen
AU - Tröster, Thomas
AU - Zinn, Wolfgang
AU - Lauhoff, Christian
AU - Niendorf, Thomas
ID - 31496
IS - 5
JF - Journal of Composites Science
KW - Engineering (miscellaneous)
KW - Ceramics and Composites
SN - 2504-477X
TI - Experimental Analysis of Residual Stresses in CFRPs through Hole-Drilling Method: The Role of Stacking Sequence, Thickness, and Defects
VL - 6
ER -
TY - JOUR
AB - High-speed forming processes such as electromagnetic forming (EMF) and electrohydraulic forming (EHF) have a high potential for producing lightweight components with complex geometries, but the forming zone is usually limited to a small size for equipment-related reasons. Incremental strategies overcome this limit by using a sequence of local deformations to form larger component areas gradually. Hence, the technological potential of high-speed forming can be exploited for large-area components too. The target-oriented process design of such incremental forming operations requires a deep understanding of the underlying electromagnetic and electrohydraulic forming processes. This article therefore analyzes and compares the influence of fundamental process parameters on the acting loads, the resulting course of deformation, and the forming result for both technologies via experimental and numerical investigations. Specifically, it is shown that for the EHF process considered, the electrode distance and the discharge energy have a significant influence on the resulting forming depth. In the EHF process, the largest forming depth is achieved directly below the electrodes, while the pressure distribution in the EMF depends on the fieldshaper used. The energy requirement for the EHF process is comparatively low, while significantly higher forming speeds are achieved with the EMF process.
AU - Heggemann, Thomas
AU - Psyk, Verena
AU - Oesterwinter, Annika
AU - Linnemann, Maik
AU - Kräusel, Verena
AU - Homberg, Werner
ID - 30885
IS - 4
JF - Metals
SN - 2075-4701
TI - Comparative Analysis of Electrohydraulic and Electromagnetic Sheet Metal Forming against the Background of the Application as an Incremental Processing Technology
VL - 12
ER -
TY - JOUR
AB - In this paper we give an overview over some aspects of the modern mathematical theory of Ruelle resonances for chaotic, i.e. uniformly hyperbolic, dynamical systems and their implications in physics. First we recall recent developments in the mathematical theory of resonances, in particular how invariant Ruelle distributions arise as residues of weighted zeta functions. Then we derive a correspondence between weighted and semiclassical zeta functions in the setting of negatively curved surfaces. Combining this with results of Hilgert, Guillarmou and Weich yields a high frequency interpretation of invariant Ruelle distributions as quantum mechanical matrix coefficients in constant negative curvature. We finish by presenting numerical calculations of phase space distributions in the more physical setting of 3-disk scattering systems.
AU - Schütte, Philipp
AU - Barkhofen, Sonja
AU - Weich, Tobias
ID - 31057
IS - 24
JF - Journal of Physics A: Mathematical and Theoretical
TI - Semiclassical formulae For Wigner distributions
VL - 55
ER -
TY - GEN
AU - Elit, Stefan
ID - 31506
T2 - Arbitrium 40
TI - Friedrich Gottlieb Klopstock: Handexemplar der „Oden“. Kritische Edition, hg. v. Marit Müller, Göttingen 2020 (edition Text 18)
ER -
TY - BOOK
AU - Egidi, Margreth
ID - 31508
TI - Höfische Liebe: Entwürfe der Sangspruchdichtung. Literarische Verfahrensweisen von Reinmar von Zweter bis Frauenlob
ER -
TY - JOUR
AU - Mattiolo, Davide
AU - Steffen, Eckhard
ID - 26408
IS - 3
JF - Journal of Graph Theory
SN - 0364-9024
TI - Edge colorings and circular flows on regular graphs
VL - 99
ER -
TY - JOUR
AU - Kobecki, Michal
AU - Scherbakov, Alexey V.
AU - Kukhtaruk, Serhii M.
AU - Yaremkevich, Dmytro D.
AU - Henksmeier, Tobias
AU - Trapp, Alexander
AU - Reuter, Dirk
AU - Gusev, Vitalyi E.
AU - Akimov, Andrey V.
AU - Bayer, Manfred
ID - 31541
IS - 15
JF - Physical Review Letters
KW - General Physics and Astronomy
SN - 0031-9007
TI - Giant Photoelasticity of Polaritons for Detection of Coherent Phonons in a Superlattice with Quantum Sensitivity
VL - 128
ER -
TY - GEN
AB - Knowledge graph embedding research has mainly focused on learning continuous representations of entities and relations tailored towards the link prediction problem. Recent results indicate an ever increasing predictive ability of current approaches on benchmark datasets. However, this effectiveness often comes with the cost of over-parameterization and increased computationally complexity. The former induces extensive hyperparameter optimization to mitigate malicious overfitting. The latter magnifies the importance of winning the hardware lottery. Here, we investigate a remedy for the first problem. We propose a technique based on Kronecker decomposition to reduce the number of parameters in a knowledge graph embedding model, while retaining its expressiveness. Through Kronecker decomposition, large embedding matrices are split into smaller embedding matrices during the training process. Hence, embeddings of knowledge graphs are not plainly retrieved but reconstructed on the fly. The decomposition ensures that elementwise interactions between three embedding vectors are extended with interactions within each embedding vector. This implicitly reduces redundancy in embedding vectors and encourages feature reuse. To quantify the impact of applying Kronecker decomposition on embedding matrices, we conduct a series of experiments on benchmark datasets. Our experiments suggest that applying Kronecker decomposition on embedding matrices leads to an improved parameter efficiency on all benchmark datasets. Moreover, empirical evidence suggests that reconstructed embeddings entail robustness against noise in the input knowledge graph. To foster reproducible research, we provide an open-source implementation of our approach, including training and evaluation scripts as well as pre-trained models in our knowledge graph embedding framework.
AU - Demir, Caglar
AU - Lienen, Julian
AU - Ngonga Ngomo, Axel-Cyrille
ID - 31545
T2 - arXiv:2205.06560
TI - Kronecker Decomposition for Knowledge Graph Embeddings
ER -
TY - JOUR
AU - Hanke, Marcel
AU - Dornbusch, Daniel
AU - Hadlich, Christoph
AU - Rossberg, Andre
AU - Hansen, Niklas
AU - Grundmeier, Guido
AU - Tsushima, Satoru
AU - Keller, Adrian
AU - Fahmy, Karim
ID - 31547
JF - Computational and Structural Biotechnology Journal
KW - Computer Science Applications
KW - Genetics
KW - Biochemistry
KW - Structural Biology
KW - Biophysics
KW - Biotechnology
SN - 2001-0370
TI - Anion-specific structure and stability of guanidinium-bound DNA origami
VL - 20
ER -
TY - GEN
AB - In semi-supervised learning, the paradigm of self-training refers to the idea of learning from pseudo-labels suggested by the learner itself. Across various domains, corresponding methods have proven effective and achieve state-of-the-art performance. However, pseudo-labels typically stem from ad-hoc heuristics, relying on the quality of the predictions though without guaranteeing their validity. One such method, so-called credal self-supervised learning, maintains pseudo-supervision in the form of sets of (instead of single) probability distributions over labels, thereby allowing for a flexible yet uncertainty-aware labeling. Again, however, there is no justification beyond empirical effectiveness. To address this deficiency, we make use of conformal prediction, an approach that comes with guarantees on the validity of set-valued predictions. As a result, the construction of credal sets of labels is supported by a rigorous theoretical foundation, leading to better calibrated and less error-prone supervision for unlabeled data. Along with this, we present effective algorithms for learning from credal self-supervision. An empirical study demonstrates excellent calibration properties of the pseudo-supervision, as well as the competitiveness of our method on several benchmark datasets.
AU - Lienen, Julian
AU - Demir, Caglar
AU - Hüllermeier, Eyke
ID - 31546
T2 - arXiv:2205.15239
TI - Conformal Credal Self-Supervised Learning
ER -
TY - CONF
AU - Çavdar, Serkan
AU - Meschut, Gerson
ID - 31540
T2 - 45th Annual Meeting of The Adhesion Society
TI - Stress-based fatigue lifetime prediction of adhesively bonded joints with hyperelastic deformation behavior
ER -
TY - THES
AB - Mehrzieloptimierung behandelt Probleme, bei denen mehrere skalare Zielfunktionen simultan optimiert werden sollen. Ein Punkt ist in diesem Fall optimal, wenn es keinen anderen Punkt gibt, der mindestens genauso gut ist in allen Zielfunktionen und besser in mindestens einer Zielfunktion. Ein notwendiges Optimalitätskriterium lässt sich über Ableitungsinformationen erster Ordnung der Zielfunktionen herleiten. Die Menge der Punkte, die dieses notwendige Kriterium erfüllen, wird als Pareto-kritische Menge bezeichnet. Diese Arbeit enthält neue Resultate über Pareto-kritische Mengen für glatte und nicht-glatte Mehrzieloptimierungsprobleme, sowohl was deren Berechnung betrifft als auch deren Struktur. Im glatten Fall erfolgt die Berechnung über ein Fortsetzungsverfahren, im nichtglatten Fall über ein Abstiegsverfahren. Anschließend wird die Struktur des Randes der Pareto-kritischen Menge analysiert, welcher aus Pareto-kritischen Mengen kleinerer Subprobleme besteht. Schlussendlich werden inverse Probleme betrachtet, bei denen zu einer gegebenen Datenmenge ein Zielfunktionsvektor gefunden werden soll, für den die Datenpunkte kritisch sind.
AU - Gebken, Bennet
ID - 31556
TI - Computation and analysis of Pareto critical sets in smooth and nonsmooth multiobjective optimization
ER -
TY - JOUR
AB - We model negative polarization, which is observed for planetary regoliths at backscattering, solving a full wave problem of light scattering with a numerically exact Discontinuous Galerkin Time Domain (DGTD) method. Pieces of layers with the bulk packing density of particles close to 0.5 are used. The model particles are highly absorbing and have irregular shapes and sizes larger than the wavelength of light. This represents a realistic analog of low-albedo planetary regoliths. Our simulations confirm coherent backscattering mechanism of the origin of negative polarization. We show that angular profiles of polarization are stabilized if the number of particles in a layer piece becomes larger than ten. This allows application of our approach to the negative polarization modeling for planetary regoliths.
AU - Grynko, Yevgen
AU - Shkuratov, Yuriy
AU - Alhaddad, Samer
AU - Förstner, Jens
ID - 31574
JF - Icarus
KW - tet_topic_scattering
SN - 0019-1035
TI - Negative polarization of light at backscattering from a numerical analog of planetary regoliths
VL - 384
ER -
TY - GEN
AU - Strauß, Sara
ID - 31598
T2 - European Journal of Life Writing
TI - "Elizabeth Grubgeld, Disability and Life Writing in Post-Independence Ireland", Book Review
VL - 11
ER -