TY - JOUR
AB - Regularization is used in many different areas of optimization when solutions
are sought which not only minimize a given function, but also possess a certain
degree of regularity. Popular applications are image denoising, sparse
regression and machine learning. Since the choice of the regularization
parameter is crucial but often difficult, path-following methods are used to
approximate the entire regularization path, i.e., the set of all possible
solutions for all regularization parameters. Due to their nature, the
development of these methods requires structural results about the
regularization path. The goal of this article is to derive these results for
the case of a smooth objective function which is penalized by a piecewise
differentiable regularization term. We do this by treating regularization as a
multiobjective optimization problem. Our results suggest that even in this
general case, the regularization path is piecewise smooth. Moreover, our theory
allows for a classification of the nonsmooth features that occur in between
smooth parts. This is demonstrated in two applications, namely support-vector
machines and exact penalty methods.
AU - Gebken, Bennet
AU - Bieker, Katharina
AU - Peitz, Sebastian
ID - 27426
IS - 3
JF - Journal of Global Optimization
TI - On the structure of regularization paths for piecewise differentiable regularization terms
VL - 85
ER -
TY - JOUR
AU - Alhaddad, Samer
AU - Förstner, Jens
AU - Grynko, Yevgen
ID - 43018
JF - Journal of Quantitative Spectroscopy and Radiative Transfer
KW - tet_topic_scattering
SN - 0022-4073
TI - Numerical study of light backscattering from layers of absorbing irregular particles larger than the wavelength
VL - 302
ER -
TY - CONF
AU - Hoffmann, Max
AU - Biehler, Rolf
ED - Trigueros, Marı́a
ED - Barquero, Berta
ED - Hochmuth, Reinhard
ED - Peters, Jana
ID - 31849
KW - Teaching and learning of specific topics in university mathematics
KW - Transition to
KW - across and from university mathematics
KW - Student Teachers
KW - Geometry
KW - Congruence
KW - Double Discontinuity.
T2 - Proceedings of the Fourth Conference of the International Network for Didactic Research in University Mathematics (INDRUM 2022, 19-22 October 2022)
TI - Student Teachers ’ Knowledge of Congruence before a University Course on Geometry
ER -
TY - CONF
AU - Florensa, Ignasio
AU - Hoffmann, Max
AU - Romo Vázquez, Avenilde
AU - Zandieh, Michelle
AU - Martínez-Planell, Rafael
ED - Trigueros, Marı́a
ED - Barquero, Berta
ED - Hochmuth, Reinhard
ED - Peters, Jana
ID - 43097
T2 - Proceedings of the Fourth Conference of the International Network for Didactic Research in University Mathematics (INDRUM 2022, 19-22 October 2022)
TI - Innovations in university teaching based on mathematic education research
ER -
TY - GEN
AU - Süßmann, Johannes
ID - 43186
TI - Pantheon
ER -
TY - JOUR
AB - Lightweight design is a common approach to reduce energy demand in the use stage of vehicles. The production of lightweight materials is usually associated with an increase in energy demand, so the environmental impacts of lightweight structures need to be assessed holistically using a life cycle assessment. To estimate the life cycle environmental impacts of a product in its developmental stage, for example, by life cycle engineering, future changes in relevant influencing factors must be considered. Prospective life cycle assessment provides methods for integrating future scenarios into life cycle assessment studies. However, approaches for integrating prospective life cycle assessment into product development are limited. The objective of this work is to provide the methodological foundation for integrating future scenarios of relevant influencing factors in the development of lightweight structures. The applicability of the novel methodology is demonstrated by a case study of a structural component in a steel, aluminium, and hybrid design. The results show that appropriate decarbonisation measures can reduce the life cycle greenhouse gas emissions by up to 95 percent until 2050. We also found that shifts in the environmentally optimal design are possible in future scenarios. Therefore, the methodology and data provided contribute to improved decision-making in product development.
AU - Ostermann, Moritz
AU - Grenz, Julian
AU - Triebus, Marcel
AU - Cerdas, Felipe
AU - Marten, Thorsten
AU - Tröster, Thomas
AU - Herrmann, Christoph
ID - 43464
IS - 8
JF - Energies
KW - Life Cycle Engineering
KW - Life Cycle Assessment
KW - Lightweight Design
KW - Prospective LCA
KW - Future-oriented LCA
KW - Energy System
KW - Material production
KW - Sustainable production
SN - 1996-1073
TI - Integrating Prospective Scenarios in Life Cycle Engineering: Case Study of Lightweight Structures
VL - 16
ER -
TY - JOUR
AB - A relatively small body of research has been conducted on the near- and long-term effects of study abroad (SA) to date. This existing research suggests that SA effects on language skills tend to be volatile, while the impact on various aspects of learners’ personal, academic, and professional development may be longer-lasting. Yet, learner perspectives on the dynamics and durability of such effects, in particular in the context of short-term SA programs, remain largely unexplored. This study hence investigates the near-term impact of short-term SA programs as experienced by students within the first months and years following their sojourns. A qualitative case-study design is employed to examine the accounts of four American students of German, who studied abroad in Austria for four weeks and were interviewed repeatedly over a period of up to 40 months after their sojourns. The results suggest that, from the students’ perspective, many effects deteriorate in the near term, although the overall sojourn experience still appears influential.
Abstract in German
Nur wenige Forschungsvorhaben haben sich bislang den mittel- bis langfristigen Auswirkungen studentischer Auslandsaufenthalte gewidmet; die bisherige Datenlage deutet jedoch darauf hin, dass die Auswirkungen auf sprachliche Kompetenzen eher unbeständig sind, wohingegen die persönliche, studiums- und berufsbezogene Entwicklung der Lernenden länger von einem Auslandsaufenthalt beeinflusst wird. Die Dynamik und Beständigkeit derartiger Auswirkungen wurden jedoch kaum mit Blick auf kurze Auslandsaufenthalte (≤ acht Wochen) sowie aus der Perspektive der Studierenden erforscht, was die vorliegende Studie insbesondere hinsichtlich mittelfristiger Effekte fokussiert. Mittels eines qualitativen Fallstudiendesigns werden die Interviewdaten vier amerikanischer Deutschlernender untersucht, die sich vier Wochen in Österreich aufhielten und in einem Zeitraum von bis zu 40 Monaten nach ihrem Aufenthalt wiederholt befragt wurden. Die Ergebnisse zeigen, dass viele Auswirkungen eines solchen Aufenthalts aus studentischer Perspektive mittelfristig verblassen, auch wenn der Auslandsaufenthalt im Gesamten weiterhin als einflussreiche Erfahrung wahrgenommen wird.
AU - Müller, Mareike
ID - 44058
IS - 1
JF - Frontiers: The Interdisciplinary Journal of Study Abroad
SN - 2380-8144
TI - Near-Term Effects of Short-Term Study Abroad: A Longitudinal Examination of Learner Perceptions
VL - 35
ER -
TY - JOUR
AB - Die Wirtschaftlichkeit von Wärmemotoren wird maßgeblich durch die Rückführung von Wärme in Rekuperatoren beeinflusst. Beim isobaren Expansionsmotor vom Bush-Typ, einem Wärmemotor, welcher bereits mit Wärmequellen ab 60°C betrieben werden kann, steigt der thermische Wirkungsgrad durch den Einsatz von Rekuperatoren signifikant. Gleichzeitig wirken sich das Fluidvolumen des Wärmeübertragers sowie der beim Betrieb auftretende Druckverlust negativ auf den thermischen Wirkungsrad aus. In dieser Arbeit wird der Zusammenhang von Totvolumen, Druckverlust und Wärmerückgewinnung untersucht und Empfehlungen für den Betrieb von Rekuperatoren am isobaren Expansionsmotor gegeben.
AU - Mügge, Nils
AU - Kronberg, Alexander
AU - Glushenkov, Maxim
AU - Kenig, Eugeny Y.
ID - 42252
IS - 5
JF - Chemie Ingenieur Technik
KW - Isobarer Expansionsmotor
KW - Dynamische Wärmeübertragungsmodellierung
KW - Phasenwechsel
KW - dichte Arbeitsmedien
TI - Untersuchung überlagerter Effekte von Druckverlust und Totvolumen durch Rekuperation am isobaren Expansionsmotor
VL - 95
ER -
TY - JOUR
AB - AbstractThe use of structured measuring systems to prevent wall slip is a common approach to obtain absolute rheological values. Typically, only the minimum distance between the measuring surfaces is used for further calculation, implying that no flow occurs between the structural elements. But this assumption is misleading, and a gap correction is necessary. To determine the radius correction $$\Delta r$$
Δ
r
for specific geometries, we conducted investigations on three Newtonian fluids (two silicon oils and one suspension considered to be Newtonian in the relevant shear rate range). The results show that $$\Delta r$$
Δ
r
is not only shear- and material-independent, but geometry-dependent, providing a Newtonian flow behaviour in a similar viscosity range. Therefore, a correction value can be determined with only minute deviations in different Newtonian fluids. As the conducted laboratory measurements are very time-consuming and expensive, a CFD-approach with only very small deviations was additionally developed and compared for validation purposes. Therefore, simulation is an effective and resource-efficient alternative to the presented laboratory measurements to determine $$\Delta r$$
Δ
r
for the correction of structured coaxial geometries even for non-Newtonian fluids in the future.
AU - Josch, Sebastian
AU - Jesinghausen, Steffen
AU - Dechert, Christopher
AU - Schmid, Hans-Joachim
ID - 36983
JF - Rheologica Acta
KW - rheology
KW - rheometry
KW - suspension
KW - coaxial
KW - correction
SN - 0035-4511
TI - Experimental and simulative determination and correction of the effective gap extension in structured coaxial measuring systems
ER -
TY - CONF
AB - We present an approach for guaranteed constraint satisfaction by means of data-based optimal control, where the model is unknown and has to be obtained from measurement data. To this end, we utilize the Koopman framework and an eDMD-based bilinear surrogate modeling approach for control systems to show an error bound on predicted observables, i.e., functions of the state. This result is then applied to the constraints of the optimal control problem to show that satisfaction of tightened constraints in the purely data-based surrogate model implies constraint satisfaction for the original system.
AU - Schaller, Manuel
AU - Worthmann, Karl
AU - Philipp, Friedrich
AU - Peitz, Sebastian
AU - Nüske, Feliks
ID - 30125
IS - 1
T2 - IFAC-PapersOnLine
TI - Towards reliable data-based optimal and predictive control using extended DMD
VL - 56
ER -
TY - JOUR
AB -
AU - Heck, Tamara
AU - Steinhardt, Isabel
AU - Rahal, Rima-Maria
AU - Schubotz, Moritz
AU - Scholl, Dominik
AU - Behrens, Sarah
ID - 43094
JF - Research Ideas and Outcomes
KW - Open Science
SN - 2367-7163
TI - Bootstrapping the Open Science culture: The fellowship approach
VL - 9
ER -
TY - GEN
ED - Meine, Sabine
ED - Otto, Arnold
ED - Süßmann, Johannes
ID - 35062
SN - 978-3-8260-7218-5
TI - Musiklandschaften zwischen Rhein und Weser. Pluralisierung und Verflechtung entlang des Hellwegs in der Frühen Neuzeit. Unter Mitarbeit v. Markus Lauert
VL - 13
ER -
TY - JOUR
AB - High-contrast slab waveguide Bragg gratings with 1D periodicity are investigated. For specific oblique excitation by semi-guided waves at sufficiently high angles of incidence, the idealized structures do not exhibit any radiative losses, such that reflectance and transmittance for the single port mode add strictly up to one. We consider a series of symmetric, fully and partly etched finite gratings, for parameters found in integrated silicon photonics. These can act as spectral filters with a reasonably flattop response. Apodization can lead to more box shaped reflectance and transmittance spectra. Together with a narrowband Fabry–Perot filter, these configurations are characterized by reflection bands, or transmittance peaks, with widths that span three orders of magnitude.
AU - Hammer, Manfred
AU - Farheen, Henna
AU - Förstner, Jens
ID - 43245
IS - 4
JF - Journal of the Optical Society of America B
KW - tet_topic_waveguide
SN - 0740-3224
TI - How to suppress radiative losses in high-contrast integrated Bragg gratings
VL - 40
ER -
TY - GEN
AU - Meier, Torsten
AU - Grisard, S.
AU - Trifonov, A.V.
AU - Rose, Hendrik
AU - Reichhardt, R.
AU - Reichelt, Matthias
AU - Schneider, C.
AU - Kamp, M.
AU - Höfling, S.
AU - Bayer, M.
AU - Akimov, I.A
ID - 43132
T2 - arxiv:2302.02480
TI - Temporal sorting of optical multi-wave-mixing processes in semiconductor quantum dots
ER -
TY - JOUR
AB - We present strong enhancement of third harmonic generation in an amorphous silicon metasurface consisting of elliptical nano resonators. We show that this enhancement originates from a new type of multi-mode Fano mechanism. These ‘Super-Fano’ resonances are investigated numerically in great detail using full-wave simulations. The theoretically predicted behavior of the metasurface is experimentally verified by linear and nonlinear transmission spectroscopy. Moreover, quantitative nonlinear measurements are performed, in which an absolute conversion efficiency as high as ηmax ≈ 2.8 × 10−7 a peak power intensity of 1.2 GW cm−2 is found. Compared to an unpatterned silicon film of the same thickness amplification factors of up to ~900 are demonstrated. Our results pave the way to exploiting a strong Fano-type multi-mode coupling in metasurfaces for high THG in potential applications.
AU - Hähnel, David
AU - Golla, Christian
AU - Albert, Maximilian
AU - Zentgraf, Thomas
AU - Myroshnychenko, Viktor
AU - Förstner, Jens
AU - Meier, Cedrik
ID - 44097
IS - 1
JF - Light: Science & Applications
KW - tet_topic_meta
SN - 2047-7538
TI - A multi-mode super-fano mechanism for enhanced third harmonic generation in silicon metasurfaces
VL - 12
ER -
TY - BOOK
AU - Bauer, Anna Brigitte
ID - 44083
SN - 978-3-8325-5625-9
TI - Experimentelle Kompetenz Physikstudierender. Entwicklung und erste Erprobung eines performanzorientierten Kompetenzstrukturmodells unter Nutzung qualitativer Methoden
VL - 352
ER -
TY - GEN
AU - Schürmann, Patrick
ID - 43374
TI - A Formal Comparison of Advanced Digital Signature Primitives
ER -
TY - JOUR
AB - Microcellular wood fiber reinforced polymers offer the possibility to reduce the use of fossil raw materials. In particular, thick-walled structures with thicknesses greater than 6 mm offer a high potential for weight savings. This study investigates the cell structures and mechanical properties of injection-molded test specimens. The influence of different thicknesses (6–10 mm) along with different chemical blowing agents (endothermic, exothermic) with varying dosages (0–2 wt%) is analyzed. The investigations reveal that exothermic chemical blowing agents form finer cells consistently to thin-walled structures than endothermic ones. Higher foaming agent content leads to higher pore fractions, with many small cells coalescing into a large open-pore cell network. The mechanical properties depend mainly on the pore content of the sample. The specific tensile properties deteriorate with the use of chemical blowing agents (CFA), whereas the sandwich structure produced with compact edge layers has a positive influence on the specific flexural properties.
AU - Moritzer, Elmar
AU - Flachmann, Felix
ID - 42515
IS - 3
JF - Journal of Cellular Plastics
KW - Materials Chemistry
KW - Polymers and Plastics
KW - General Chemistry
SN - 0021-955X
TI - Morphological and mechanical properties of foamed thick-walled Wood-Plastic-Composite structures
VL - 59
ER -
TY - JOUR
AU - Burmeister, Sascha Christian
AU - Schryen, Guido
ID - 42179
JF - Energy Systems
TI - Distribution Network Optimization: Predicting computation times to design scenario analysis for network operators
ER -
TY - JOUR
AB - Abstract
The accessibility to rheological parameters for concrete is becoming more and more relevant. This is mainly related to the constantly emerging challenges, such as not only the development of high-strength concretes is progressing very fast but also the simulation of the flow behaviour is of high importance. The main problem, however, is that the rheological characterisation of fresh concrete is not possible via commercial rheometers. The so-called concrete rheometers provide valuable relative values for comparing different concretes, but they cannot measure absolute values. Therefore, we developed an adaptive coaxial concrete rheometer (ACCR) that allows the measurement of fresh concrete with particles up to
d
max
=
5.5
mm
{d}_{{\rm{\max }}}=5.5\hspace{.5em}{\rm{mm}}
. The comparison of the ACCR with a commercial rheometer showed very good agreement for selected test materials (Newtonian fluid, shear thinning fluid, suspension, and yield stress fluid), so that self-compacting concrete was subsequently measured. Since these measurements showed a very high reproducibility, the rheological properties of the fresh concrete could be determined with high accuracy. The common flow models (Bingham (B), Herschel–Bulkley, modified Bingham (MB) models) were also tested for their applicability, with the Bingham and the modified Bingham model proving to be the best suitable ones.
AU - Josch, Sebastian
AU - Jesinghausen, Steffen
AU - Schmid, Hans-Joachim
ID - 43034
IS - 1
JF - Applied Rheology
KW - Condensed Matter Physics
KW - General Materials Science
SN - 1617-8106
TI - Development of an adaptive coaxial concrete rheometer and rheological characterisation of fresh concrete
VL - 33
ER -
TY - CHAP
AB - State education in honest tax payment can be understood as a facet of training in citizenship, i.e. as an attempt by the modern state to standardize the behavior of its citizens and to prevent deviations. Based on this Foucauldian understanding, this exploratory article examines tax education in the United States, Spain, and West Germany from the mid-1940s to the late 1980s. During this period, the USA asserted itself as the champion of tax education and Spain consistently tried to emulate this example, albeit with more modest means and different semantic strategies from as early as the 1960s, when it was still under a autoritarian regime. The FRG, however, completely discontinued its few early attempts at tax education from the mid-1950s onwards. Even during the economic crises and tax scandals of the 1970s, there was no relaunch of the programs. The article locates the reasons for this highly uneven development in the different ideal images of the citizen in the three states.
AU - Schönhärl, Korinna
AU - Düll, Nasrin
AU - Ramírez Lugo , Nadya Melina
ED - Sébastien, Guex
ED - Hadrien, Buclin
ID - 44249
T2 - Tax Evasion and Tax Havens since the Nineteenth Century
TI - Tax Education After WWII: How Spain, the USA, and West Germany Tried to Make Their Citizens Pay Honestly
ER -
TY - JOUR
AU - Neumann, Phillip
ID - 44321
IS - 5
JF - Zeitschrift für Heilpädagogik
KW - Inklusion
KW - Sonderpädagogik
KW - Bildung
KW - Bildungsstudien
KW - Integration
SN - 0513-9066
TI - Studien zu Schulleistungen und ihre Aufbereitung
VL - 74
ER -
TY - CHAP
AU - Meine, Sabine
AU - Otto, Arnold
AU - Süßmann, Johannes
ID - 35063
SN - 978-3-8260-7218-5
T2 - Musiklandschaften zwischen Rhein und Weser. Pluralisierung und Verflechtung entlang des Hellwegs in der Frühen Neuzeit. Unter Mitarbeit v. Markus Lauert
TI - Musiklandschaften zwischen Rhein und Weser – Einführung
ER -
TY - CONF
AU - Gharibian, Sevag
AU - Watson, James
AU - Bausch, Johannes
ID - 20841
T2 - Proceedings of the 40th International Symposium on Theoretical Aspects of Computer Science (STACS)
TI - The Complexity of Translationally Invariant Problems beyond Ground State Energies
VL - 254
ER -
TY - GEN
AB - For open world applications, deep neural networks (DNNs) need to be aware of
previously unseen data and adaptable to evolving environments. Furthermore, it
is desirable to detect and learn novel classes which are not included in the
DNNs underlying set of semantic classes in an unsupervised fashion. The method
proposed in this article builds upon anomaly detection to retrieve
out-of-distribution (OoD) data as candidates for new classes. We thereafter
extend the DNN by $k$ empty classes and fine-tune it on the OoD data samples.
To this end, we introduce two loss functions, which 1) entice the DNN to assign
OoD samples to the empty classes and 2) to minimize the inner-class feature
distances between them. Thus, instead of ground truth which contains labels for
the different novel classes, the DNN obtains a single OoD label together with a
distance matrix, which is computed in advance. We perform several experiments
for image classification and semantic segmentation, which demonstrate that a
DNN can extend its own semantic space by multiple classes without having access
to ground truth.
AU - Uhlemeyer, Svenja
AU - Lienen, Julian
AU - Hüllermeier, Eyke
AU - Gottschalk, Hanno
ID - 44512
T2 - arXiv:2305.00983
TI - Detecting Novelties with Empty Classes
ER -
TY - JOUR
AB - With enhancing digitalization, condition monitoring is used in an increasing number of application fields across various industrial sectors. By its application, increased reliability as well as reduced risks and costs can be achieved. Based on different approaches, technical systems are monitored and measured data is analyzed to enable condition-based or predictive maintenance. To this end, machine learning approaches are usually implemented to diagnose the health states or predict the health index of the monitored system. However, these trained models are often black-box models, not intuitively explainable for a human. To overcome this shortcoming, a model-based approach based on physics is developed for piezoelectric bending actuators. Such a model enables a transparent representation of the system. Moreover, the model-based approach is extended by a parameter-estimation to account for sudden changes in behavior e. g. caused by occurring cracks.
AU - Bender, Amelie
ID - 44672
JF - Sensors and Actuators A: Physical
KW - Condition Monitoring
KW - Model-based approach Diagnostics
KW - Varying conditions
KW - Explainability
KW - Piezoelectric bending actuators
SN - 0924-4247
TI - Model-based condition monitoring of piezoelectric bending actuators
VL - 357
ER -
TY - CONF
AU - Ahmed, Qazi Arbab
AU - Awais, Muhammad
AU - Platzner, Marco
ID - 44194
T2 - The 24th International Symposium on Quality Electronic Design (ISQED'23), San Francisco, Califorina USA
TI - MAAS: Hiding Trojans in Approximate Circuits
ER -
TY - JOUR
AB - Dispersion is present in every optical setup and is often an undesired effect, especially in nonlinear-optical experiments where ultrashort laser pulses are needed. Typically, bulky pulse compressors consisting of gratings or prisms are used
to address this issue by precompensating the dispersion of the optical components. However, these devices are only able to compensate for a part of the dispersion (second-order dispersion). Here, we present a compact pulse-shaping device that uses plasmonic metasurfaces to apply an arbitrarily designed spectral phase delay allowing for a full dispersion control. Furthermore, with specific phase encodings, this device can be used to temporally reshape the incident laser pulses into more complex pulse forms such as a double pulse. We verify the performance of our device by using an SHG-FROG measurement setup together with a retrieval algorithm to extract the dispersion that our device applies to an incident laser pulse.
AU - Geromel, René
AU - Georgi, Philip
AU - Protte, Maximilian
AU - Lei, Shiwei
AU - Bartley, Tim
AU - Huang, Lingling
AU - Zentgraf, Thomas
ID - 44044
IS - 8
JF - Nano Letters
KW - Mechanical Engineering
KW - Condensed Matter Physics
KW - General Materials Science
KW - General Chemistry
KW - Bioengineering
SN - 1530-6984
TI - Compact Metasurface-Based Optical Pulse-Shaping Device
VL - 23
ER -
TY - JOUR
AB - Hydrothermal carbonization (HTC) is an efficient thermochemical method for the conversion of organic feedstock to carbonaceous solids. HTC of different saccharides is known to produce microspheres (MS) with mostly Gaussian size distribution, which are utilized as functional materials in various applications, both as pristine MS and as a precursor for hard carbon MS. Although the average size of the MS can be influenced by adjusting the process parameters, there is no reliable mechanism to affect their size distribution. Our results demonstrate that HTC of trehalose, in contrast to other saccharides, results in a distinctly bimodal sphere diameter distribution consisting of small spheres with diameters of (2.1 ± 0.2) μm and of large spheres with diameters of (10.4 ± 2.6) μm. Remarkably, after pyrolytic post-carbonization at 1000 °C the MS develop a multimodal pore size distribution with abundant macropores > 100 nm, mesopores > 10 nm and micropores < 2 nm, which were examined by small-angle X-ray scattering and visualized by charge-compensated helium ion microscopy. The bimodal size distribution and hierarchical porosity provide an extraordinary set of properties and potential variables for the tailored synthesis of hierarchical porous carbons, making trehalose-derived hard carbon MS a highly promising material for applications in catalysis, filtration, and energy storage devices.
AU - Wortmann, Martin
AU - Keil, Waldemar
AU - Diestelhorst, Elise
AU - Westphal, Michael
AU - Haverkamp, René
AU - Brockhagen, Bennet
AU - Biedinger, Jan
AU - Bondzio, Laila
AU - Weinberger, Christian
AU - Baier, Dominik
AU - Tiemann, Michael
AU - Hütten, Andreas
AU - Hellweg, Thomas
AU - Reiss, Günter
AU - Schmidt, Claudia
AU - Sattler, Klaus
AU - Frese, Natalie
ID - 44837
IS - 21
JF - RSC Advances
KW - General Chemical Engineering
KW - General Chemistry
SN - 2046-2069
TI - Hard carbon microspheres with bimodal size distribution and hierarchical porosity via hydrothermal carbonization of trehalose
VL - 13
ER -
TY - CONF
AU - Dreiling, Dmitrij
AU - Itner, Dominik
AU - Hetkämper, Tim
AU - Birk, Carolin
AU - Gravenkamp, Hauke
AU - Henning, Bernd
ID - 45205
SN - 978-3-9819376-8-8
T2 - SMSI 2023 Conference
TI - Improved determination of viscoelastic material parameters using a pulse-echo measurement setup
ER -
TY - GEN
AU - Koch, Angelina
ID - 43375
TI - Privacy-Preserving Collection and Evaluation of Log Files
ER -
TY - JOUR
AU - Schryen, Guido
AU - Sperling, Martina
ID - 44361
IS - September
JF - Computers & Operations Research
TI - Literature Reviews in Operations Research: A New Taxonomy and a Meta Review
VL - 157
ER -
TY - JOUR
AB - Dielectric metasurfaces provide a unique platform for efficient harmonic generation and optical wavefront manipulation at the nanoscale. Tailoring phase and amplitude of a nonlinearly generated wave with a high emission efficiency using resonance-based metasurfaces is a challenging task that often requires state-of-the-art numerical methods. Here, we propose a simple yet effective approach combining a sampling method with a Monte Carlo approach to design the third-harmonic wavefront generated by all-dielectric metasurfaces composed of elliptical silicon nanodisks. Using this approach, we theoretically demonstrate the full nonlinear 2π phase control with a uniform and highest possible amplitude in the considered parameter space, allowing us to design metasurfaces operating as third harmonic beam deflectors capable of steering light into a desired direction with high emission efficiency. The TH beam deflection with a record calculated average conversion efficiency of 1.2 × 10–1 W–2 is achieved. We anticipate that the proposed approach will be widely applied as alternative to commonly used optimization algorithms with higher complexity and implementation effort for the design of metasurfaces with other holographic functionalities.
AU - Hähnel, David
AU - Förstner, Jens
AU - Myroshnychenko, Viktor
ID - 45596
JF - ACS Photonics
KW - tet_topic_meta
SN - 2330-4022
TI - Efficient Modeling and Tailoring of Nonlinear Wavefronts in Dielectric Metasurfaces
ER -
TY - CHAP
AU - Freymuth, Nina
ED - Balz, HHans-Jürgen
ED - Huneke, Annika
ED - Kuhlmann, Carola
ED - Römisch, Kathrin
ID - 45606
T2 - Diskriminierungsprozesse und Teilhabeperspektiven - Herausforderungen für die Praxis der Inklusion. Ausgewählte Master-Thesen 2018-2022 des Masterstudiengangs "Soziale Inklusion: Gesundheit und Bildung" der Evangelischen Hochschule Rheinland-Westfalen-Lippe
TI - Alternative für alle? Inklusionsspezifische Analyse der AfD und ihrer Wähler*innen
ER -
TY - JOUR
AU - Dieter, Peter
AU - Caron, Matthew
AU - Schryen, Guido
ID - 44383
IS - 1
JF - European Journal of Operational Research (EJOR)
TI - Integrating driver behavior into last-mile delivery routing: Combining machine learning and optimization in a hybrid decision support framework
VL - 311
ER -
TY - JOUR
AU - Meier, Jana
AU - Janzen, Thomas
AU - Wotschel, Philipp
AU - Vogelsang, Christoph
ID - 45672
JF - die hochschullehre
TI - Rollenspielbasierte Simulationen als Übungs- und Prüfungsformate im Lehramtsstudium. Eine explorative Studie zu Erfahrungen und Einschätzungen aus Studierendensicht.
VL - 9
ER -
TY - CONF
AU - Hotegni, Sedjro Salomon
AU - Mahabadi, Sepideh
AU - Vakilian, Ali
ID - 45695
KW - Fair range clustering
T2 - Proceedings of the 40th International Conference on Machine Learning, Honolulu, Hawaii, USA. PMLR 202, 2023.
TI - Approximation Algorithms for Fair Range Clustering
ER -
TY - CONF
AU - Hebrok, Sven Niclas
AU - Nachtigall, Simon
AU - Maehren, Marcel
AU - Erinola, Nurullah
AU - Merget, Robert
AU - Somorovsky, Juraj
AU - Schwenk, Jörg
ID - 43060
T2 - 32nd USENIX Security Symposium
TI - We Really Need to Talk About Session Tickets: A Large-Scale Analysis of Cryptographic Dangers with TLS Session Tickets
ER -
TY - JOUR
AB - Faradaic reactions including charge transfer are often accompanied with diffusion limitation inside the bulk. Conductive two-dimensional frameworks (2D MOFs) with a fast ion transport can combine both - charge transfer and fast diffusion inside their porous structure. To study remaining diffusion limitations caused by particle morphology, different synthesis routes of Cu-2,3,6,7,10,11-hexahydroxytriphenylene (Cu3(HHTP)2), a copper-based 2D MOF, are used to obtain flake- and rod-like MOF particles. Both morphologies are systematically characterized and evaluated for redox-active Li+ ion storage. The redox mechanism is investigated by means of X-ray absorption spectroscopy, FTIR spectroscopy and in situ XRD. Both types are compared regarding kinetic properties for Li+ ion storage via cyclic voltammetry and impedance spectroscopy. A significant influence of particle morphology for 2D MOFs on kinetic aspects of electrochemical Li+ ion storage can be observed. This study opens the path for optimization of redox active porous structures to overcome diffusion limitations of Faradaic processes.
AU - Wrogemann, Jens Matthies
AU - Lüther, Marco Joes
AU - Bärmann, Peer
AU - Lounasvuori, Mailis
AU - Javed, Ali
AU - Tiemann, Michael
AU - Golnak, Ronny
AU - Xiao, Jie
AU - Petit, Tristan
AU - Placke, Tobias
AU - Winter, Martin
ID - 44116
IS - 26
JF - Angewandte Chemie International Edition
KW - General Chemistry
KW - Catalysis
SN - 1433-7851
TI - Overcoming Diffusion Limitation of Faradaic Processes: Property‐Performance Relationships of 2D Conductive Metal‐Organic Framework Cu3(HHTP)2 for Reversible Lithium‐Ion Storage
VL - 62
ER -
TY - GEN
ED - Eckel, Julia
ED - Ernst, Christoph
ED - Schröter, Jens
ID - 36842
IS - 1
KW - tech demo
KW - technology demonstration
KW - demo or die
SN - 1619-1641
T2 - Navigationen - Zeitschrift für Medien- und Kulturwissenschaften
TI - Navigationen: Tech | Demo
VL - 23
ER -
TY - CONF
AU - Abbas, Nilab
AU - Bauer, Anna Brigitte
AU - Reinhold, Peter
ED - van Vorst, Helena
ID - 45759
T2 - Lernen, Lehren und Forschen in einer digital geprägten Welt
TI - PSΦ: Entwicklung von Unterstützungsmaßnahmen für Theoretische Physik
ER -
TY - CONF
AU - Bauer, Anna Brigitte
AU - Reinhold, Peter
ED - van Vorst, Helena
ID - 45758
T2 - Lernen, Lehren und Forschen in einer digital geprägten Welt
TI - PSФ: Entwicklung einer abgestimmten Studieneingangsphase (Physik)
ER -
TY - JOUR
AB - A series of new organic donor–π–acceptor dyes incorporating a diquat moiety as a novel electron-acceptor unit have been synthesized and characterized. The analytical data were supported by DFT calculations. These dyes were explored in the aerobic thiocyanation of indoles and pyrroles. Here they showed a high photocatalytic activity under visible light, giving isolated yields of up to 97 %. In addition, the photocatalytic activity of standalone diquat and methyl viologen through formation of an electron donor acceptor complex is presented.
AU - Meier, Armin
AU - Badalov, Sabuhi
AU - Biktagirov, Timur
AU - Schmidt, Wolf Gero
AU - Wilhelm, René
ID - 43827
IS - 22
JF - Chemistry – A European Journal
KW - General Chemistry
KW - Catalysis
KW - Organic Chemistry
SN - 0947-6539
TI - Diquat Based Dyes: A New Class of Photoredox Catalysts and Their Use in Aerobic Thiocyanation
VL - 29
ER -
TY - JOUR
AB - As a benchmark, the structural, electronic and optical properties of the three main phases of TiO$\rm{_2}$ crystals have been calculated using Hubbard U correction and hybrid functional methods in density-functional theory. These calculations are compared concerning the available experimental observations on pristine TiO$\rm{_2}$ crystals. Modified hybrid functionals, particularly the PBE0 functional with 11.4% fraction of exact exchange, are shown to provide highly accurate atomic structures and also accurate electronic structure data, including optical excitation energies. With $\rm{DFT+U}$, accurate optical spectra are also possible, but only if the Hubbard U is applied on the O $\rm2p$ electrons exclusively. Furthermore, both methods, the 11.4%-PBE0 hybrid functional and the $\rm{DFT+U_p}$ scheme have been used to study TiO$\rm{_2}$ amorphous ultra-thin films, confirming the agreement of the two methods even with respect to small details of the optical spectra. Our results show that the proposed $\rm{DFT+U_p}$ methodology is computationally efficient, but still accurate. It can be applied to well-ordered TiO$\rm{_2}$ polymorphs as well as to amorphous TiO$\rm{_2}$ and will allow for the calculations of complex titania-based structures.
AU - Badalov, Sabuhi
AU - Bocchini, Adriana
AU - Wilhelm, Rene
AU - Kozub, A. L.
AU - Gerstmann, Uwe
AU - Schmidt, Wolf Gero
ID - 45764
JF - Materials Research Express
TI - Rutile, anatase, brookite and titania thin film from Hubbard corrected and hybrid DFT
ER -
TY - JOUR
AB - The development of automotive components with reduced greenhouse gas (GHG) emissions is needed to reduce overall vehicle emissions. Life Cycle Engineering (LCE) based on Life Cycle Assessment (LCA) supports this by providing holistic information and improvement potentials regarding eco-efficient products. Key factors influencing LCAs of automotive components, such as material production, will change in the future. First approaches for integrating future scenarios for these key factors into LCE already exist, but they only consider a limited number of parameters and scenarios. This work aims to develop a method that can be practically applied in the industry for integrating prospective LCAs (pLCA) into the LCE of automotive components, considering relevant parameters and consistent scenarios. Therefore, pLCA methods are further developed to investigate the influence of future scenarios on the GHG emissions of automotive components. The practical application is demonstrated for a vehicle component with different design options. This paper shows that different development paths of the foreground and background system can shift the ecological optimum of design alternatives. Therefore, future pathways of relevant parameters must be considered comprehensively to reduce GHG emissions of future vehicles. This work contributes to the methodological and practical integration of pLCA into automotive development processes and provides quantitative results.
AU - Grenz, Julian
AU - Ostermann, Moritz
AU - Käsewieter, Karoline
AU - Cerdas, Felipe
AU - Marten, Thorsten
AU - Herrmann, Christoph
AU - Tröster, Thomas
ID - 45782
IS - 13
JF - Sustainability
KW - prospective LCA
KW - life cycle engineering (LCE)
KW - lightweight design
KW - automotive components
KW - body parts
KW - circular economy
KW - steel
KW - aluminum
KW - hybrid materials
KW - fiber metal laminates
SN - 2071-1050
TI - Integrating Prospective LCA in the Development of Automotive Components
VL - 15
ER -
TY - CONF
AB - The notion of neural collapse refers to several emergent phenomena that have been empirically observed across various canonical classification problems. During the terminal phase of training a deep neural network, the feature embedding of all examples of the same class tend to collapse to a single representation, and the features of different classes tend to separate as much as possible. Neural collapse is often studied through a simplified model, called the unconstrained feature representation, in which the model is assumed to have "infinite expressivity" and can map each data point to any arbitrary representation. In this work, we propose a more realistic variant of the unconstrained feature representation that takes the limited expressivity of the network into account. Empirical evidence suggests that the memorization of noisy data points leads to a degradation (dilation) of the neural collapse. Using a model of the memorization-dilation (M-D) phenomenon, we show one mechanism by which different losses lead to different performances of the trained network on noisy data. Our proofs reveal why label smoothing, a modification of cross-entropy empirically observed to produce a regularization effect, leads to improved generalization in classification tasks.
AU - Nguyen, Duc Anh
AU - Levie, Ron
AU - Lienen, Julian
AU - Kutyniok, Gitta
AU - Hüllermeier, Eyke
ID - 31880
T2 - International Conference on Learning Representations, ICLR
TI - Memorization-Dilation: Modeling Neural Collapse Under Noise
ER -
TY - GEN
AB - Label noise poses an important challenge in machine learning, especially in
deep learning, in which large models with high expressive power dominate the
field. Models of that kind are prone to memorizing incorrect labels, thereby
harming generalization performance. Many methods have been proposed to address
this problem, including robust loss functions and more complex label correction
approaches. Robust loss functions are appealing due to their simplicity, but
typically lack flexibility, while label correction usually adds substantial
complexity to the training setup. In this paper, we suggest to address the
shortcomings of both methodologies by "ambiguating" the target information,
adding additional, complementary candidate labels in case the learner is not
sufficiently convinced of the observed training label. More precisely, we
leverage the framework of so-called superset learning to construct set-valued
targets based on a confidence threshold, which deliver imprecise yet more
reliable beliefs about the ground-truth, effectively helping the learner to
suppress the memorization effect. In an extensive empirical evaluation, our
method demonstrates favorable learning behavior on synthetic and real-world
noise, confirming the effectiveness in detecting and correcting erroneous
training labels.
AU - Lienen, Julian
AU - Hüllermeier, Eyke
ID - 45814
T2 - arXiv:2305.13764
TI - Mitigating Label Noise through Data Ambiguation
ER -
TY - CONF
AB - Many applications require explainable node classification in knowledge graphs. Towards this end, a popular ``white-box'' approach is class expression learning: Given sets of positive and negative nodes, class expressions in description logics are learned that separate positive from negative nodes. Most existing approaches are search-based approaches generating many candidate class expressions and selecting the best one. However, they often take a long time to find suitable class expressions. In this paper, we cast class expression learning as a translation problem and propose a new family of class expression learning approaches which we dub neural class expression synthesizers. Training examples are ``translated'' into class expressions in a fashion akin to machine translation. Consequently, our synthesizers are not subject to the runtime limitations of search-based approaches. We study three instances of this novel family of approaches based on LSTMs, GRUs, and set transformers, respectively. An evaluation of our approach on four benchmark datasets suggests that it can effectively synthesize high-quality class expressions with respect to the input examples in approximately one second on average. Moreover, a comparison to state-of-the-art approaches suggests that we achieve better F-measures on large datasets. For reproducibility purposes, we provide our implementation as well as pretrained models in our public GitHub repository at https://github.com/dice-group/NeuralClassExpressionSynthesis
AU - KOUAGOU, N'Dah Jean
AU - Heindorf, Stefan
AU - Demir, Caglar
AU - Ngonga Ngomo, Axel-Cyrille
ED - Pesquita, Catia
ED - Jimenez-Ruiz, Ernesto
ED - McCusker, Jamie
ED - Faria, Daniel
ED - Dragoni, Mauro
ED - Dimou, Anastasia
ED - Troncy, Raphael
ED - Hertling, Sven
ID - 33734
KW - Neural network
KW - Concept learning
KW - Description logics
T2 - The Semantic Web - 20th Extended Semantic Web Conference (ESWC 2023)
TI - Neural Class Expression Synthesis
VL - 13870
ER -
TY - GEN
AB - Label noise poses an important challenge in machine learning, especially in
deep learning, in which large models with high expressive power dominate the
field. Models of that kind are prone to memorizing incorrect labels, thereby
harming generalization performance. Many methods have been proposed to address
this problem, including robust loss functions and more complex label correction
approaches. Robust loss functions are appealing due to their simplicity, but
typically lack flexibility, while label correction usually adds substantial
complexity to the training setup. In this paper, we suggest to address the
shortcomings of both methodologies by "ambiguating" the target information,
adding additional, complementary candidate labels in case the learner is not
sufficiently convinced of the observed training label. More precisely, we
leverage the framework of so-called superset learning to construct set-valued
targets based on a confidence threshold, which deliver imprecise yet more
reliable beliefs about the ground-truth, effectively helping the learner to
suppress the memorization effect. In an extensive empirical evaluation, our
method demonstrates favorable learning behavior on synthetic and real-world
noise, confirming the effectiveness in detecting and correcting erroneous
training labels.
AU - Lienen, Julian
AU - Hüllermeier, Eyke
ID - 45244
T2 - arXiv:2305.13764
TI - Mitigating Label Noise through Data Ambiguation
ER -
TY - JOUR
AB - Perfect vector vortex beams (PVVBs) have attracted considerable interest due to their peculiar optical features. PVVBs are typically generated through the superposition of perfect vortex beams, which suffer from the limited number of topological charges (TCs). Furthermore, dynamic control of PVVBs is desirable and has not been reported. We propose and experimentally demonstrate hybrid grafted perfect vector vortex beams (GPVVBs) and their dynamic control. Hybrid GPVVBs are generated through the superposition of grafted perfect vortex beams with a multifunctional metasurface. The generated hybrid GPVVBs possess spatially variant rates of polarization change due to the involvement of more TCs. Each hybrid GPVVB includes different GPVVBs in the same beam, adding more design flexibility. Moreover, these beams are dynamically controlled with a rotating half waveplate. The generated dynamic GPVVBs may find applications in the fields where dynamic control is in high demand, including optical encryption, dense data communication, and multiple particle manipulation.
AU - Ahmed, Hammad
AU - Ansari, Muhammad Afnan
AU - Li, Yan
AU - Zentgraf, Thomas
AU - Mehmood, Muhammad Qasim
AU - Chen, Xianzhong
ID - 45868
IS - 1
JF - Nature Communications
KW - General Physics and Astronomy
KW - General Biochemistry
KW - Genetics and Molecular Biology
KW - General Chemistry
KW - Multidisciplinary
SN - 2041-1723
TI - Dynamic control of hybrid grafted perfect vector vortex beams
VL - 14
ER -
TY - CHAP
AU - Götte, Thorsten
AU - Knollmann, Till
AU - Meyer auf der Heide, Friedhelm
AU - Scheideler, Christian
AU - Werthmann, Julian
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45875
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Capabilities and Limitations of Local Strategies in Dynamic Networks
VL - 412
ER -
TY - CHAP
AU - Karl, Holger
AU - Maack, Marten
AU - Meyer auf der Heide, Friedhelm
AU - Pukrop, Simon
AU - Redder, Adrian
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45895
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - On-The-Fly Compute Centers II: Execution of Composed Services in Configurable Compute Centers
VL - 412
ER -
TY - CHAP
AU - Blömer, Johannes
AU - Bobolz, Jan
AU - Eidens, Fabian
AU - Jager, Tibor
AU - Kramer, Paul
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45901
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Practical Cryptograhic Techniques for Secure and Privacy-Preserving Customer Loyalty Systems
VL - 412
ER -
TY - CHAP
AU - Boschmann, Alexander
AU - Clausing, Lennart
AU - Jentzsch, Felix
AU - Ghasemzadeh Mohammadi, Hassan
AU - Platzner, Marco
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45899
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Flexible Industrial Analytics on Reconfigurable Systems-On-Chip
VL - 412
ER -
TY - CHAP
AU - Wehrheim, Heike
AU - Platzner, Marco
AU - Bodden, Eric
AU - Schubert, Philipp
AU - Pauck, Felix
AU - Jakobs, Marie-Christine
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45888
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Verifying Software and Reconfigurable Hardware Services
VL - 412
ER -
TY - CHAP
AU - Gottschalk, Sebastian
AU - Vorbohle, Christian
AU - Kundisch, Dennis
AU - Engels, Gregor
AU - Wünderlich, Nacy V.
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45897
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Architectural Management of OTF Computing Markets
VL - 412
ER -
TY - CHAP
AU - Blömer, Johannes
AU - Eidens, Fabian
AU - Jager, Tibor
AU - Niehues, David
AU - Scheideler, Christian
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45891
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Robustness and Security
VL - 412
ER -
TY - CHAP
AU - Bäumer, Frederik Simon
AU - Chen, Wei-Fan
AU - Geierhos, Michaela
AU - Kersting, Joschka
AU - Wachsmuth, Henning
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45882
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Dialogue-based Requirement Compensation and Style-adjusted Data-to-text Generation
VL - 412
ER -
TY - CHAP
AU - Hanselle, Jonas Manuel
AU - Hüllermeier, Eyke
AU - Mohr, Felix
AU - Ngonga Ngomo, Axel-Cyrille
AU - Sherif, Mohamed
AU - Tornede, Alexander
AU - Wever, Marcel Dominik
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45884
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Configuration and Evaluation
VL - 412
ER -
TY - CHAP
AU - Haake, Claus-Jochen
AU - Hehenkamp, Burkhard
AU - Polevoy, Gleb
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45878
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - The Market for Services: Incentives, Algorithms, Implementation
VL - 412
ER -
TY - CHAP
AU - Wehrheim, Heike
AU - Hüllermeier, Eyke
AU - Becker, Steffen
AU - Becker, Matthias
AU - Richter, Cedric
AU - Sharma, Arnab
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45886
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Composition Analysis in Unknown Contexts
VL - 412
ER -
TY - GEN
AB - Label noise poses an important challenge in machine learning, especially in
deep learning, in which large models with high expressive power dominate the
field. Models of that kind are prone to memorizing incorrect labels, thereby
harming generalization performance. Many methods have been proposed to address
this problem, including robust loss functions and more complex label correction
approaches. Robust loss functions are appealing due to their simplicity, but
typically lack flexibility, while label correction usually adds substantial
complexity to the training setup. In this paper, we suggest to address the
shortcomings of both methodologies by "ambiguating" the target information,
adding additional, complementary candidate labels in case the learner is not
sufficiently convinced of the observed training label. More precisely, we
leverage the framework of so-called superset learning to construct set-valued
targets based on a confidence threshold, which deliver imprecise yet more
reliable beliefs about the ground-truth, effectively helping the learner to
suppress the memorization effect. In an extensive empirical evaluation, our
method demonstrates favorable learning behavior on synthetic and real-world
noise, confirming the effectiveness in detecting and correcting erroneous
training labels.
AU - Lienen, Julian
AU - Hüllermeier, Eyke
ID - 45911
T2 - arXiv:2305.13764
TI - Mitigating Label Noise through Data Ambiguation
ER -
TY - CHAP
AU - Elrich, Alina
AU - Kaimann, Daniel
AU - Fahr, René
AU - Kundisch, Dennis
AU - Mir Djawadi, Behnud
AU - Müller, Michelle
AU - Poniatowski, Martin
AU - Schäfers, Sabrina
AU - Frick, Bernd
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45880
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Empirical Analysis in Markets for OTF Services
VL - 412
ER -
TY - JOUR
AB - Intending to counteract Klein’s second discontinuity in teacher education, we explored and applied the innovation of “interface ePortfolio” in the context of a geometry course for preservice teachers (PSTs). The tool offers the possibility of implementing the design principle of profession orientation. In the article, we theoretically clarify what we understand by this principle and locate our innovative concept against this theoretical background. We empirically investigate the extent to which counteraction against the second discontinuity is successful by analyzing reflection texts created in the interface ePortfolio, focusing on PSTs’ perspectives. Our qualitative content analysis shows that most of them perceive the innovation as helpful in the intended sense and indicates that the course concept, in general, and the interface ePortfolio, in particular, have helped establish relevant links between the course content and their later work as teachers.
AU - Hoffmann, Max
AU - Biehler, Rolf
ID - 45786
JF - ZDM – Mathematics Education
KW - General Mathematics
KW - Education
SN - 1863-9690
TI - Implementing profession orientation as a design principle for overcoming Klein’s second discontinuity – preservice teacher’s perspectives on interface activities in the context of a geometry course
ER -
TY - JOUR
AU - Dieter, Peter
AU - Stumpe, Miriam
AU - Ulmer, Marlin Wolf
AU - Schryen, Guido
ID - 45816
JF - Transportation Research Part D
TI - Anticipatory Assignment of Passengers to Meeting Points for Taxi-Ridesharing
VL - 121
ER -
TY - GEN
AU - Leineweber, Jonas
ID - 46102
TI - Tagungsbericht: 10/20 Jahre UNESCO-Konvention zum Erhalt des Immateriellen Kulturerbes – Auftaktveranstaltung zum Doppeljubiläum
ER -
TY - CHAP
AU - Janzen, Thomas
AU - Gabel, Stephan
AU - Gampert, Martha
AU - Matz, Frauke
AU - Reckermann, Julia
ED - Mrohs, Lorenz
ED - Hess, Miriam
ED - Lindner, Konstantin
ED - Schlüter, Julia
ED - Overhage, Sven
ID - 46154
T2 - Digitalisierung in der Hochschullehre – Perspektiven und Gestaltungsoptionen
TI - Das DigitELE Tutorial: Eine digitale Lernumgebung in der Englischdidaktik
ER -
TY - JOUR
AB - While FPGA accelerator boards and their respective high-level design tools are maturing, there is still a lack of multi-FPGA applications, libraries, and not least, benchmarks and reference implementations towards sustained HPC usage of these devices. As in the early days of GPUs in HPC, for workloads that can reasonably be decoupled into loosely coupled working sets, multi-accelerator support can be achieved by using standard communication interfaces like MPI on the host side. However, for performance and productivity, some applications can profit from a tighter coupling of the accelerators. FPGAs offer unique opportunities here when extending the dataflow characteristics to their communication interfaces.
In this work, we extend the HPCC FPGA benchmark suite by multi-FPGA support and three missing benchmarks that particularly characterize or stress inter-device communication: b_eff, PTRANS, and LINPACK. With all benchmarks implemented for current boards with Intel and Xilinx FPGAs, we established a baseline for multi-FPGA performance. Additionally, for the communication-centric benchmarks, we explored the potential of direct FPGA-to-FPGA communication with a circuit-switched inter-FPGA network that is currently only available for one of the boards. The evaluation with parallel execution on up to 26 FPGA boards makes use of one of the largest academic FPGA installations.
AU - Meyer, Marius
AU - Kenter, Tobias
AU - Plessl, Christian
ID - 38041
JF - ACM Transactions on Reconfigurable Technology and Systems
KW - General Computer Science
SN - 1936-7406
TI - Multi-FPGA Designs and Scaling of HPC Challenge Benchmarks via MPI and Circuit-Switched Inter-FPGA Networks
ER -
TY - CHAP
AU - Hansmeier, Tim
AU - Kenter, Tobias
AU - Meyer, Marius
AU - Riebler, Heinrich
AU - Platzner, Marco
AU - Plessl, Christian
ED - Haake, Claus-Jochen
ED - Meyer auf der Heide, Friedhelm
ED - Platzner, Marco
ED - Wachsmuth, Henning
ED - Wehrheim, Heike
ID - 45893
T2 - On-The-Fly Computing -- Individualized IT-services in dynamic markets
TI - Compute Centers I: Heterogeneous Execution Environments
VL - 412
ER -
TY - CONF
AU - Opdenhövel, Jan-Oliver
AU - Plessl, Christian
AU - Kenter, Tobias
ID - 46190
T2 - Proceedings of the 13th International Symposium on Highly Efficient Accelerators and Reconfigurable Technologies
TI - Mutation Tree Reconstruction of Tumor Cells on FPGAs Using a Bit-Level Matrix Representation
ER -
TY - CONF
AU - Faj, Jennifer
AU - Kenter, Tobias
AU - Faghih-Naini, Sara
AU - Plessl, Christian
AU - Aizinger, Vadym
ID - 46188
T2 - Proceedings of the Platform for Advanced Scientific Computing Conference
TI - Scalable Multi-FPGA Design of a Discontinuous Galerkin Shallow-Water Model on Unstructured Meshes
ER -
TY - CONF
AU - Prouveur, Charles
AU - Haefele, Matthieu
AU - Kenter, Tobias
AU - Voss, Nils
ID - 46189
T2 - Proceedings of the Platform for Advanced Scientific Computing Conference
TI - FPGA Acceleration for HPC Supercapacitor Simulations
ER -
TY - JOUR
AU - Demir, Caglar
AU - Ngonga Ngomo, Axel-Cyrille
ID - 46243
JF - ECML-PKDD
TI - Clifford Embeddings – A Generalized Approach for Embedding in Normed Algebras
ER -
TY - JOUR
AU - Demir, Caglar
AU - Ngonga Ngomo, Axel-Cyrille
ID - 46251
JF - International Joint Conference on Artificial Intelligence
TI - Neuro-Symbolic Class Expression Learning
ER -
TY - JOUR
AB - The non-orthogonal local submatrix method applied to electronic structure–based molecular dynamics simulations is shown to exceed 1.1 EFLOP/s in FP16/FP32-mixed floating-point arithmetic when using 4400 NVIDIA A100 GPUs of the Perlmutter system. This is enabled by a modification of the original method that pushes the sustained fraction of the peak performance to about 80%. Example calculations are performed for SARS-CoV-2 spike proteins with up to 83 million atoms.
AU - Schade, Robert
AU - Kenter, Tobias
AU - Elgabarty, Hossam
AU - Lass, Michael
AU - Kühne, Thomas
AU - Plessl, Christian
ID - 45361
JF - The International Journal of High Performance Computing Applications
KW - Hardware and Architecture
KW - Theoretical Computer Science
KW - Software
SN - 1094-3420
TI - Breaking the exascale barrier for the electronic structure problem in ab-initio molecular dynamics
ER -
TY - THES
AU - Tornede, Alexander
ID - 45780
TI - Advanced Algorithm Selection with Machine Learning: Handling Large Algorithm Sets, Learning From Censored Data, and Simplyfing Meta Level Decisions
ER -
TY - CONF
AB - The article shows how to learn models of dynamical systems from data which are governed by an unknown variational PDE. Rather than employing reduction techniques, we learn a discrete field theory governed by a discrete Lagrangian density $L_d$ that is modelled as a neural network. Careful regularisation of the loss function for training $L_d$ is necessary to obtain a field theory that is suitable for numerical computations: we derive a regularisation term which optimises the solvability of the discrete Euler--Lagrange equations. Secondly, we develop a method to find solutions to machine learned discrete field theories which constitute travelling waves of the underlying continuous PDE.
AU - Offen, Christian
AU - Ober-Blöbaum, Sina
ED - Nielsen, F
ED - Barbaresco, F
ID - 42163
KW - System identification
KW - discrete Lagrangians
KW - travelling waves
T2 - Geometric Science of Information
TI - Learning discrete Lagrangians for variational PDEs from data and detection of travelling waves
VL - 14071
ER -
TY - JOUR
AB - The principle of least action is one of the most fundamental physical principle. It says that among all possible motions connecting two points in a phase space, the system will exhibit those motions which extremise an action functional. Many qualitative features of dynamical systems, such as the presence of conservation laws and energy balance equations, are related to the existence of an action functional. Incorporating variational structure into learning algorithms for dynamical systems is, therefore, crucial in order to make sure that the learned model shares important features with the exact physical system. In this paper we show how to incorporate variational principles into trajectory predictions of learned dynamical systems. The novelty of this work is that (1) our technique relies only on discrete position data of observed trajectories. Velocities or conjugate momenta do not need to be observed or approximated and no prior knowledge about the form of the variational principle is assumed. Instead, they are recovered using backward error analysis. (2) Moreover, our technique compensates discretisation errors when trajectories are computed from the learned system. This is important when moderate to large step-sizes are used and high accuracy is required. For this,
we introduce and rigorously analyse the concept of inverse modified Lagrangians by developing an inverse version of variational backward error analysis. (3) Finally, we introduce a method to perform system identification from position observations only, based on variational backward error analysis.
AU - Ober-Blöbaum, Sina
AU - Offen, Christian
ID - 29240
JF - Journal of Computational and Applied Mathematics
KW - Lagrangian learning
KW - variational backward error analysis
KW - modified Lagrangian
KW - variational integrators
KW - physics informed learning
SN - 0377-0427
TI - Variational Learning of Euler–Lagrange Dynamics from Data
VL - 421
ER -
TY - JOUR
AB - The numerical solution of an ordinary differential equation can be interpreted as the exact solution of a nearby modified equation. Investigating the behaviour of numerical solutions by analysing the modified equation is known as backward error analysis. If the original and modified equation share structural properties, then the exact and approximate solution share geometric features such as the existence of conserved quantities. Conjugate symplectic methods preserve a modified symplectic form and a modified Hamiltonian when applied to a Hamiltonian system. We show how a blended version of variational and symplectic techniques can be used to compute modified symplectic and Hamiltonian structures. In contrast to other approaches, our backward error analysis method does not rely on an ansatz but computes the structures systematically, provided that a variational formulation of the method is known. The technique is illustrated on the example of symmetric linear multistep methods with matrix coefficients.
AU - McLachlan, Robert
AU - Offen, Christian
ID - 29236
IS - 1
JF - Journal of Geometric Mechanics
KW - variational integrators
KW - backward error analysis
KW - Euler--Lagrange equations
KW - multistep methods
KW - conjugate symplectic methods
TI - Backward error analysis for conjugate symplectic methods
VL - 15
ER -
TY - JOUR
AB - Recently, Hamiltonian neural networks (HNN) have been introduced to incorporate prior physical knowledge when
learning the dynamical equations of Hamiltonian systems. Hereby, the symplectic system structure is preserved despite
the data-driven modeling approach. However, preserving symmetries requires additional attention. In this research, we
enhance the HNN with a Lie algebra framework to detect and embed symmetries in the neural network. This approach
allows to simultaneously learn the symmetry group action and the total energy of the system. As illustrating examples,
a pendulum on a cart and a two-body problem from astrodynamics are considered.
AU - Dierkes, Eva
AU - Offen, Christian
AU - Ober-Blöbaum, Sina
AU - Flaßkamp, Kathrin
ID - 37654
IS - 6
JF - Chaos
SN - 1054-1500
TI - Hamiltonian Neural Networks with Automatic Symmetry Detection
VL - 33
ER -
TY - THES
AB - Ever increasing demands on the performance of microchips are leading to ever more complex semiconductor technologies with ever shrinking feature sizes. Complex applications with high demands on safety and reliability, such as autonomous driving, are simultaneously driving the requirements for test and diagnosis of VLSI circuits. Throughout the life cycle of a microchip, uncertainties occur that affect its timing behavior. For example, weak circuit structures, aging effects, or process variations can lead to a change in the timing behavior of the circuit. While these uncertainties do not necessarily lead to a change of the functional behavior, they can lead to a reliability problem.
With modular and hybrid compaction two test instruments are presented in this work that can be used for X-tolerant test response compaction in the built-in Faster-than-At-Speed Test (FAST) which is used to detect uncertainties in VLSI circuits. One challenge for test response compaction during FAST is the high and varying X-rate at the outputs of the circuit under test. By dividing the circuit outputs into test groups and separately compacting these test groups using stochastic compactors, the modular compaction is able to handle these high and varying X-rates.
To deal with uncertainties on logic interconnects, a method for distinguishing crosstalk and process variation is presented. In current semiconductor technologies, the number of parasitic coupling capacitances between logic interconnects is growing. These coupling capacitances can lead to crosstalk, which causes increased current flow in the logic interconnects, which in turn can lead to increased electromigration. In the presented method, delay maps describing the timing behavior of the circuit outputs at different operating points are used to train artificial neural networks which classify the tested circuits into fault-free and faulty.
AU - Sprenger, Alexander
ID - 46482
KW - Testantwortkompaktierung
KW - Prozessvariation
KW - Silicon Lifecycle Management
TI - Testinstrumente und Testdatenanalyse zur Verarbeitung von Unsicherheiten in Logikblöcken hochintegrierter Schaltungen
ER -
TY - CONF
AU - Baci, Alkid
AU - Heindorf, Stefan
ID - 46575
T2 - CIKM
TI - Accelerating Concept Learning via Sampling
ER -
TY - GEN
AB - The Koopman operator has become an essential tool for data-driven analysis, prediction and control of complex systems, the main reason being the enormous potential of identifying linear function space representations of nonlinear
dynamics from measurements. Until now, the situation where for large-scale systems, we (i) only have access to partial observations (i.e., measurements, as is very common for experimental data) or (ii) deliberately perform coarse
graining (for efficiency reasons) has not been treated to its full extent. In this paper, we address the pitfall associated with this situation, that the classical EDMD algorithm does not automatically provide a Koopman operator approximation for the underlying system if we do not carefully select the number of observables. Moreover, we show that symmetries in the system dynamics can be carried over to the Koopman operator, which allows us to massively increase the model efficiency. We also briefly draw a connection to domain decomposition techniques for partial differential equations and present numerical evidence using the Kuramoto--Sivashinsky equation.
AU - Peitz, Sebastian
AU - Harder, Hans
AU - Nüske, Feliks
AU - Philipp, Friedrich
AU - Schaller, Manuel
AU - Worthmann, Karl
ID - 46579
T2 - arXiv:2307.15325
TI - Partial observations, coarse graining and equivariance in Koopman operator theory for large-scale dynamical systems
ER -
TY - JOUR
AU - Karakaya, Yasin
AU - Somnitz, H.
AU - Hermsen, A.
AU - Gonchikzhapov, Munko
AU - Kasper, Tina
ID - 45602
JF - Applications in Energy and Combustion Science
KW - Metastable particles
KW - Nanomaterials
KW - Quartz-crystal-microbalance
KW - Molecular-beam mass spectrometry
KW - Tetramethylsilane
KW - Reaction kinetics
SN - 2666-352X
TI - Revisiting the initial reaction rates for TMS combustion and a new evidence for metastable silica nanoparticles in the gas-phase synthesis
VL - 14
ER -
TY - JOUR
AB - The Koopman operator has become an essential tool for data-driven approximation of dynamical (control) systems in recent years, e.g., via extended dynamic mode decomposition. Despite its popularity, convergence results and, in particular, error bounds are still quite scarce. In this paper, we derive probabilistic bounds for the approximation error and the prediction error depending on the number of training data points; for both ordinary and stochastic differential equations. Moreover, we extend our analysis to nonlinear control-affine systems using either ergodic trajectories or i.i.d.
samples. Here, we exploit the linearity of the Koopman generator to obtain a bilinear system and, thus, circumvent the curse of dimensionality since we do not autonomize the system by augmenting the state by the control inputs. To the
best of our knowledge, this is the first finite-data error analysis in the stochastic and/or control setting. Finally, we demonstrate the effectiveness of the proposed approach by comparing it with state-of-the-art techniques showing its superiority whenever state and control are coupled.
AU - Nüske, Feliks
AU - Peitz, Sebastian
AU - Philipp, Friedrich
AU - Schaller, Manuel
AU - Worthmann, Karl
ID - 23428
JF - Journal of Nonlinear Science
TI - Finite-data error bounds for Koopman-based prediction and control
VL - 33
ER -
TY - GEN
AB - Different conflicting optimization criteria arise naturally in various Deep
Learning scenarios. These can address different main tasks (i.e., in the
setting of Multi-Task Learning), but also main and secondary tasks such as loss
minimization versus sparsity. The usual approach is a simple weighting of the
criteria, which formally only works in the convex setting. In this paper, we
present a Multi-Objective Optimization algorithm using a modified Weighted
Chebyshev scalarization for training Deep Neural Networks (DNNs) with respect
to several tasks. By employing this scalarization technique, the algorithm can
identify all optimal solutions of the original problem while reducing its
complexity to a sequence of single-objective problems. The simplified problems
are then solved using an Augmented Lagrangian method, enabling the use of
popular optimization techniques such as Adam and Stochastic Gradient Descent,
while efficaciously handling constraints. Our work aims to address the
(economical and also ecological) sustainability issue of DNN models, with a
particular focus on Deep Multi-Task models, which are typically designed with a
very large number of weights to perform equally well on multiple tasks. Through
experiments conducted on two Machine Learning datasets, we demonstrate the
possibility of adaptively sparsifying the model during training without
significantly impacting its performance, if we are willing to apply
task-specific adaptations to the network weights. Code is available at
https://github.com/salomonhotegni/MDMTN.
AU - Hotegni, Sedjro Salomon
AU - Peitz, Sebastian
AU - Berkemeier, Manuel Bastian
ID - 46649
T2 - arXiv:2308.12243
TI - Multi-Objective Optimization for Sparse Deep Neural Network Training
ER -
TY - JOUR
AU - Gonchikzhapov, Munko
AU - Kasper, Tina
ID - 46637
JF - Applications in Energy and Combustion Science
KW - Nanoparticle synthesis
KW - Flame spray pyrolysis
KW - SpraySyn burner
KW - Flame structure
KW - Species distribution
KW - Temperature distribution
SN - 2666-352X
TI - Thermal and chemical structure of ethanol and 2-ethylhexanoic acid/ethanol SpraySyn flames
VL - 15
ER -
TY - BOOK
AB - In the proposal for our CRC in 2011, we formulated a vision of markets for
IT services that describes an approach to the provision of such services
that was novel at that time and, to a large extent, remains so today:
„Our vision of on-the-fly computing is that of IT services individually and
automatically configured and brought to execution from flexibly combinable
services traded on markets. At the same time, we aim at organizing
markets whose participants maintain a lively market of services through
appropriate entrepreneurial actions.“
Over the last 12 years, we have developed methods and techniques to
address problems critical to the convenient, efficient, and secure use of
on-the-fly computing. Among other things, we have made the description
of services more convenient by allowing natural language input,
increased the quality of configured services through (natural language)
interaction and more efficient configuration processes and analysis
procedures, made the quality of (the products of) providers in the
marketplace transparent through reputation systems, and increased the
resource efficiency of execution through reconfigurable heterogeneous
computing nodes and an integrated treatment of service description and
configuration. We have also developed network infrastructures that have
a high degree of adaptivity, scalability, efficiency, and reliability, and
provide cryptographic guarantees of anonymity and security for market
participants and their products and services.
To demonstrate the pervasiveness of the OTF computing approach, we
have implemented a proof-of-concept for OTF computing that can run
typical scenarios of an OTF market. We illustrated the approach using
a cutting-edge application scenario – automated machine learning (AutoML).
Finally, we have been pushing our work for the perpetuation of
On-The-Fly Computing beyond the SFB and sharing the expertise gained
in the SFB in events with industry partners as well as transfer projects.
This work required a broad spectrum of expertise. Computer scientists
and economists with research interests such as computer networks and
distributed algorithms, security and cryptography, software engineering
and verification, configuration and machine learning, computer engineering
and HPC, microeconomics and game theory, business informatics
and management have successfully collaborated here.
AU - Haake, Claus-Jochen
AU - Meyer auf der Heide, Friedhelm
AU - Platzner, Marco
AU - Wachsmuth, Henning
AU - Wehrheim, Heike
ID - 45863
TI - On-The-Fly Computing -- Individualized IT-services in dynamic markets
VL - 412
ER -
TY - JOUR
AU - Wallscheid, Oliver
AU - Peitz, Sebastian
AU - Stenner, Jan
AU - Weber, Daniel
AU - Boshoff, Septimus
AU - Meyer, Marvin
AU - Chidananda, Vikas
AU - Schweins, Oliver
ID - 46784
IS - 89
JF - Journal of Open Source Software
KW - General Earth and Planetary Sciences
KW - General Environmental Science
SN - 2475-9066
TI - ElectricGrid.jl - A Julia-based modeling and simulationtool for power electronics-driven electric energy grids
VL - 8
ER -
TY - JOUR
AU - Höper, Lukas
AU - Schulte, Carsten
ID - 46186
IS - 4
JF - MNU journal
SN - 0025-5866
TI - Paradigmenwechsel vom klassischen zum datengetriebenen Problemlösen im Informatikunterricht
VL - 76
ER -
TY - CONF
AU - Blömer, Johannes
AU - Bobolz, Jan
AU - Bröcher, Henrik
ID - 35014
TI - On the impossibility of surviving (iterated) deletion of weakly dominated strategies in rational MPC
ER -
TY - CONF
AU - Blömer, Johannes
AU - Bobolz, Jan
AU - Porzenheim, Laurens Alexander
ID - 43458
TI - A Generic Construction of an Anonymous Reputation System and Instantiations from Lattices
ER -
TY - JOUR
AB - In this work, the influence of the filler–matrix adhesion on the tensile properties of laser-sintered parts built with Polyamide 613 filled with glass beads was investigated. For this purpose, dry blends of glass beads with and without organosilane coupling agents and polyamide powder were prepared and processed into tensile specimens on an EOS P396 laser sintering system. The samples were tested both in the dry state and after an accelerated conditioning in a climate chamber. Furthermore, finite element method (FEM) simulations were performed to model the extreme cases of optimum adhesion and no adhesion. By correlating the tensile tests with the simulation results and by analyzing the fracture surfaces, it was shown that the filler–matrix adhesion is sufficient in the dry state but is strongly degraded by conditioning. Even the presence of various organosilane thin films could not prevent a strong deterioration of the filler–matrix adhesion and the associated deterioration of the mechanical properties. Since a comparison with an injection-molded sample of the same polymer filler combination shows identical behavior after conditioning, it is assumed that this problem is not limited to additively manufactured parts.
AU - Kletetzka, Ivo
AU - Kosanke, Maren
AU - Meinderink, Dennis
AU - Neßlinger, Vanessa
AU - Grundmeier, Guido
AU - Schmid, Hans-Joachim
ID - 46815
JF - Progress in Additive Manufacturing
KW - Industrial and Manufacturing Engineering
SN - 2363-9512
TI - Influence of the filler–matrix adhesion and the effects of conditioning on tensile properties of laser-sintered parts built with polyamide–glass bead dry blends
ER -
TY - GEN
AB - Abstract
In this work, the influence of the filler matrix adhesion on the tensile properties of laser-sintered parts built with Polyamide 613 filled with glass beads was investigated. For this purpose, dry blends of glass beads with and without organosilane coupling agents and polyamide powder were prepared and processed into tensile specimens on an EOS P396. The samples were tested both in the dry state and after an accelerated conditioning in a climate chamber. Furthermore, FEM simulations were performed to model the limiting cases of optimum adhesion and no adhesion. By correlating the tensile tests with the simulation results and by analyzing the fracture surfaces, it was shown that the filler matrix adhesion is sufficient in the dry state but is strongly degraded by conditioning. Even the presence of various organosilane thin films could not prevent a strong deterioration of the filler-matrix adhesion and the associated deterioration of the mechanical properties. Since a comparison with an injection molded sample of the same polymer filler combination shows identical behavior after conditioning, it is assumed that this problem is not limited to additively manufactured parts.
AU - Kletetzka, Ivo
AU - Kosanke, Maren
AU - Meinderink, Dennis
AU - Neßlinger, Vanessa
AU - Grundmeier, Guido
AU - Schmid, Hans-Joachim
ID - 43049
TI - Influence of the filler matrix adhesion and the effects of conditioning on tensile properties of laser sintered parts built with polyamide glass bead dry blends
ER -
TY - JOUR
AB - In the laser sintering technology, the semi-crystalline polymer material is exposed to elevated temperatures during processing, which leads to serious material ageing for most materials. This has already been investigated intensively by various authors. However, the ageing of the material at ambient temperatures during shelf life has not been the focus so far. The need to analyse the shelf life can be derived from an ecological and economic point of view. This work is focusing on the shelf life of PA2200 (PA12). To reduce the potential influences of powder production fluctuations, two different powder batches stored for 5.5 years and 6.5 years are investigated and compared to a reference powder produced 0.5 years before these investigations. Multiple powder analyses and part characterisations have been performed. A significant yellowing and molecular chain length reduction can be derived from the measurement results. Whereas the influence on mechanical part performance was minor, the parts built with the stored powders are more yellowish. As it is most likely that this is due to the consumption of polyamide stabilisers, it can be assumed that these parts will be subject to significantly faster ageing. Therefore, it is still not recommended to use the stored powders for critical parts or light intense and humid environments.
AU - Klippstein, Sven Helge
AU - Kletetzka, Ivo
AU - Sural, Ilknur
AU - Schmid, Hans-Joachim
ID - 43046
JF - The International Journal of Advanced Manufacturing Technology
KW - Selective laser sintering
KW - Shelf life
KW - Polyamide 12
KW - powder
KW - PA2200
KW - material ageing
TI - Influence of a prolonged shelf time on PA12 laser sintering powder and resulting part properties
ER -
TY - JOUR
AB - »Über Geld spricht man nicht.« Diese Benimmregel erweist sich beim Blick in die Ver-
gangenheit als Illusion. Keineswegs war Geld grundsätzlich ein Tabuthema zwischen-
menschlicher Kommunikation. Ganz im Gegenteil: Mit dem Reden über Geld wird dieses
mit Bedeutung aufgeladen. Die Autor*innen dieses Themenheftes untersuch en Gelddis-
kurse und die Zuschreibungen von Bedeutung an Geld in der internationalen Geschichte.
AU - Schönhärl, Korinna
AU - Schotters, Frederike
AU - Thiemeyer, Guido
ID - 47155
JF - Werkstatt Geschichte
KW - Financial History
KW - Discourse Analysis
KW - History of Money
TI - Editorial
VL - 88
ER -
TY - CONF
AB - Modelling of dynamic systems plays an important role in many engineering disciplines. Two different approaches are physical modelling and data‐driven modelling, both of which have their respective advantages and disadvantages. By combining these two approaches, hybrid models can be created in which the respective disadvantages are mitigated, with discrepancy models being a particular subclass. Here, the basic system behaviour is described physically, that is, in the form of differential equations. Inaccuracies resulting from insufficient modelling or numerics lead to a discrepancy between the measurements and the model, which can be compensated by a data‐driven error correction term. Since discrepancy methods still require a large amount of measurement data, this paper investigates the extent to which a single discrepancy model can be trained for a physical model with additional parameter dependencies without the need for retraining. As an example, a damped electromagnetic oscillating circuit is used. The physical model is realised by a differential equation describing the electric current, considering only inductance and capacitance; dissipation due to resistance is neglected. This creates a discrepancy between measurement and model, which is corrected by a data‐driven model. In the experiments, the inductance and the capacity are varied. It is found that the same data‐driven model can only be used if additional parametric dependencies in the data‐driven term are considered as well.
AU - Wohlleben, Meike Claudia
AU - Muth, Lars
AU - Peitz, Sebastian
AU - Sextro, Walter
ID - 46813
KW - Electrical and Electronic Engineering
KW - Atomic and Molecular Physics
KW - and Optics
SN - 1617-7061
T2 - Proceedings in Applied Mathematics and Mechanics
TI - Transferability of a discrepancy model for the dynamics of electromagnetic oscillating circuits
ER -
TY - CONF
AB - This paper presents a comprehensive study on diagnosing a spacecraft propulsion system utilizing data provided by the Prognostics and Health Management (PHM) society, specifically obtained as part of the Asia-Pacific PHM conference’s data challenge 2023. The objective of the challenge is to identify and diagnose known faults as well as unknown anomalies in the spacecraft’s propulsion system, which is critical for ensuring the spacecraft’s proper functionality and safety. To address this challenge, the proposed method follows a systematic approach of feature extraction, feature selection, and model development. The models employed in this study are kMeans clustering and decision trees combined to ensembles, enriched with expert knowledge. With the method presented, our team was capable of reaching high accuracy in identifying anomalies as well as diagnosing faults, resulting in attaining the seventh place with a score of 93.08 %.
AU - Aimiyekagbon, Osarenren Kennedy
AU - Löwen, Alexander
AU - Bender, Amelie
AU - Muth, Lars
AU - Sextro, Walter
ID - 47116
IS - 1
KW - PHM
KW - Fault Diagnostics
KW - Multiple Fault Modes
KW - Expert-Informed Diagnostics
KW - Anomaly Detection
T2 - Proceedings of the Asia Pacific Conference of the PHM Society 2023
TI - Expert-Informed Hierarchical Diagnostics of Multiple Fault Modes of a Spacecraft Propulsion System
VL - 4
ER -
TY - CONF
AB -
The study investigates two different ways of guiding the addressee of an explanation - an explainee, through action demonstration: contrastive and non-contrastive. Their effect was tested on attention to specific action elements (goal) as well as on event memory. In an eye-tracking experiment, participants were shown different motion videos that were either contrastive or non-contrastive with respect to the segments of movement presentation. Given that everyday action demonstration is often multimodal, the stimuli were created with re- spect to their visual and verbal presentation. For visual presentation, a video combined two movements in a contrastive (e.g., Up-motion following a Down-motion) or non-contrastive way (e.g., two Up-motions following each other). For verbal presentation, each video was combined with a sequence of instruction descriptions in the form of negative (i.e., contrastive) or assertive (i.e., non-contrastive) guidance. It was found that a) attention to the event goal increased for this condition in the later time window, and b) participants’ recall of the event was facilitated when a visually contrastive motion was combined with a verbal contrast.
AU - Singh, Amit
AU - Rohlfing, Katharina J.
ID - 46067
KW - Attention
KW - negation
KW - contrastive guidance
KW - eye-movements
KW - action understanding
KW - event representation
T2 - Proceedings of the Annual Meeting of the Cognitive Science Society 45 (45)
TI - Contrastiveness in the context of action demonstration: an eye-tracking study on its effects on action perception and action recall
ER -
TY - CHAP
AU - Fuchs, Christian
ED - Güney, Selma
ED - Hille, Lina
ED - Pfeiffer, Juliane
ED - Porak, Laura
ED - Theine, Hendrik
ID - 47548
T2 - Eigentum, Medien, Öffentlichkeit: Verhandlungen des Netzwerks Kritische Kommunikationswissenschaft
TI - Zur Kritik der Politischen Ökonomie des Digitalen Kapitalismus: Die Aktualität von Manfred Knoches Beitrag zur Kritik der Politischen Ökonomie der Medien und der Kommunikation
ER -